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Last Updated :2024/11/15

研究者情報

マスター

アカウント（マスター）

  • 氏名

    石塚　真由美(イシヅカ　マユミ), イシヅカ　マユミ

所属（マスター）

  • 獣医学研究院　獣医学部門　環境獣医科学分野

所属（マスター）

  • 獣医学研究院　獣医学部門　環境獣医科学分野

独自項目

syllabus

  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, ケミカルハザード、食の安全、毒性学、環境汚染、シェルターメディスン、リスクアセスメント、GIS、生態学、薬理学、病理学、免疫毒性学、分子毒性学、地球規模課題、リスクアナリシス、コンピューターシミュレーション、R、ドッキングシミュレーション、分析化学、環境化学
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, conservation medicine, Africa
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, conservation medicine, Africa, Japanese culture, Japanese language
  • 2021, 大学院共通授業科目（一般科目）：複合領域, Inter-Graduate School Classes(General Subject):Inter-Disciplinary Sciences, 修士課程, 大学院共通科目, One Health、Student Free Design Activities、海外活動、国際会議運営、フィールドサンプリング、感染症、環境汚染、保健衛生、途上国、保全医学
  • 2021, 大学院共通授業科目（一般科目）：複合領域, Inter-Graduate School Classes(General Subject):Inter-Disciplinary Sciences, 修士課程, 大学院共通科目, 保全医学、鉱山、環境汚染、感染症、SDGs
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, ケミカルハザード、毒性学、環境汚染、GIS、保健科学、経済学、工学、農業、地球環境科学
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, 金属汚染、モニタリング手法
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, 金属暴露、毒性学的影響評価
  • 2021, 大学院共通授業科目（一般科目）：複合領域, Inter-Graduate School Classes(General Subject):Inter-Disciplinary Sciences, 修士課程, 大学院共通科目, One Health、感染症、環境汚染、地球環境問題、保全医学、多分野融合、国際機関
  • 2021, 大学院共通授業科目（一般科目）：複合領域, Inter-Graduate School Classes(General Subject):Inter-Disciplinary Sciences, 修士課程, 大学院共通科目, One Health、国際的リーダー、国際機関、異分野連携、異分野コミュニケーション、課題解決能力、地球規模課題
  • 2021, 生物統計学特論, Advanced Lecture on Biostatistics, 博士後期課程, 国際感染症学院
  • 2021, インターンシップ, Internships, 博士後期課程, 獣医学院
  • 2021, 環境毒性学演習, Advanced Seminar on Environmental Toxicology, 博士後期課程, 獣医学院, 化学物質、毒性発現、細胞毒性、臓器毒性、毒性試験
  • 2021, ケミカルハザード対策専門特論, Advanced and Comprehensive Studies on Chemical Hazard Control, 博士後期課程, 獣医学院, ケミカルハザード、食の安全、毒性学、環境汚染、シェルターメディスン、リスクアセスメント、GIS、生態学、薬理学、病理学、免疫毒性学、分子毒性学、地球規模課題、リスクアナリシス、コンピューターシミュレーション、R、ドッキングシミュレーション、分析化学、環境化学
  • 2021, 研究機器演習（総合成績）, Advanced Seminar on Analytical Machines(Intergraded Grade), 博士後期課程, 国際感染症学院
  • 2021, 研究機器演習（総合成績）, Advanced Seminar on Analytical Machines(Intergraded Grade), 博士後期課程, 獣医学院
  • 2021, 環境獣医科学特論, Advanced Lecture on Environmental Veterinary Sciences, 博士後期課程, 獣医学院
  • 2021, 基礎毒性学, Basic Toxicology, 学士課程, 獣医学部, 公害、薬害、毒性発現、異物代謝、排泄、動態、用量-反応、毒性試験、環境汚染物質、リスクアセスメント
  • 2021, 環境毒性学・環境衛生学, Environmental Toxicology ･ Environmental Hygiene, 学士課程, 獣医学部, 環境毒性、環境破壊、環境汚染、化学汚染物質、生体防御、規制、衛生動物
  • 2021, 獣医倫理・動物福祉, Veterinary Ethics･Animal Welfare, 学士課程, 獣医学部, 生命倫理、獣医倫理、動物福祉、伴侶動物、産業動物、実験動物、展示動物、野生動物
  • 2021, 獣医英語演習, Seminar in Veterinary English, 学士課程, 獣医学部, 獣医学、英語演習
  • 2021, 生物科学基礎演習（ＰＢＬ）, Elementary Seminar in Biosciences(PBL), 学士課程, 獣医学部, 獣医学、獣医療、自学自習、PBL学習
  • 2021, 研究スタートアップ演習, Seminar in Research Start-up, 学士課程, 獣医学部, 獣医学、解剖学、生理学、生化学、薬理学、放射線学、実験動物学、毒性学、野生動物学、獣医内科学、獣医外科学、比較病理学、繁殖学、動物分子医学、微生物学、感染症学、寄生虫学、公衆衛生学、衛生学
  • 2021, 獣医法規, Veterinary Lows and Regulations, 学士課程, 獣医学部, 法規、獣医学、獣医師、獣医療、獣医業、薬事、公衆衛生、食品衛生、動物衛生、環境衛生
  • 2021, 応用毒性学, Applied Toxicology, 学士課程, 獣医学部, 化学物質、毒性発現、細胞毒性、臓器毒性、毒性試験
  • 2021, 毒性学実習, Practice in Toxicology, 学士課程, 獣医学部, 化学物質，毒性発現メカニズム，毒性試験法，体内動態，環境動態

PositionHistory

  • 教育改革室室員, 2019年4月1日, 2020年9月30日
  • 教育改革室室員, 2020年10月12日, 2022年3月31日
  • 教育改革室室員, 2022年4月1日, 2024年3月31日
  • 教育研究評議会評議員, 2021年4月1日, 2023年3月31日
  • 経営戦略室室員, 2019年4月1日, 2020年9月30日
  • 経営戦略室室員, 2020年10月12日, 2021年3月31日
  • 経営戦略室室員, 2017年10月26日, 2019年3月31日
  • 大学院獣医学院長, 2021年4月1日, 2023年3月31日
  • 大学院獣医学研究科副研究科長, 2013年4月1日, 2015年3月31日
  • 大学院獣医学研究科副研究科長, 2015年4月1日, 2017年3月31日
  • 大学院獣医学院長, 2023年4月1日, 2025年3月31日
  • 総長補佐, 2017年4月1日, 2019年3月31日
  • 総長補佐, 2019年4月1日, 2020年9月30日
  • 総長補佐, 2020年10月12日, 2022年3月31日
  • 総長補佐, 2022年4月1日, 2024年3月31日

researchmap

プロフィール情報

学位

  • 獣医学博士（北海道大学）

プロフィール情報

  • 姓

    石塚, イシヅカ

  • 名

    真由美, マユミ

  • ID各種

    201201005548429868

対象リソース

業績リスト

研究キーワード

  • シトクロムP450   環境化学物質   エストロゲン   野生動物   マイクロアレイ   アフリカ   ルシフェラーゼ   neonatal imprinting   レポーターアッセイ   アロマターゼ   レポーター   トランスジェニック   トキシコロジー   in vivoイメージング   ERE   インプリンティング   視床下部   環境汚染   ステロイドホルモン   環境ホルモン   ビスフェノールA   ダイオキシン受容体   PPAR   フタル酸エステル   バイオマーカー   環境汚染物質   ダイオキシン類   CYP1A   海棲哺乳類   ドブネズミ   

研究分野

  • 環境・農学 / ランドスケープ科学
  • 環境・農学 / 環境農学
  • 環境・農学 / 化学物質影響
  • 環境・農学 / 放射線影響
  • ライフサイエンス / 応用分子細胞生物学
  • ライフサイエンス / 衛生学、公衆衛生学分野：実験系を含まない
  • ライフサイエンス / 衛生学、公衆衛生学分野：実験系を含む
  • ライフサイエンス / 医療管理学、医療系社会学
  • ライフサイエンス / 獣医学

経歴

  • 2011年 - 2012年 北海道大学 (連合)獣医学研究科 教授

委員歴

  • - 現在   日本毒性学会   評議員
  • - 現在   食品安全委員会   専門委員（動物用医薬品、添加物）
  • - 現在   日本環境化学会   理事
  • - 現在   日本獣医学会   理事
  • - 現在   日本学術会議   会員

受賞

  • 2020年 日本環境化学会 学術賞
  • 2015年 ソロプチミスト日本財団 女性研究者賞
     
    受賞者: 石塚真由美
  • 2015年 北海道大学 研究総長賞（優秀賞）
     
    受賞者: 石塚真由美
  • 2009年 文部科学省 科学技術分野の文部科学大臣表彰・若手科学者賞
     野生動物のシトクロムP450と汚染環境適応能力解明の研究 
    受賞者: 石塚真由美
  • 2007年 日本農学会 日本農学進歩賞
     環境化学物質が野生動物に引き起こす毒性と適応 
    受賞者: 石塚真由美
  • 2007年 日本トキシコロジー学会 奨励賞
     野生生物のシトクロムP450と汚染環境への適応機構に関する研究 
    受賞者: 石塚真由美

論文

  • Yasuhiro Uno, Kyoko Tsukiyama-Kohara, Mayumi Ishizuka, Hazuki Mizukawa, Norie Murayama, Hiroshi Yamazaki
    Drug Metabolism and Disposition 52 9 1009 - 1019 2024年09月01日 
    Pigs are sometimes used in preclinical drug metabolism studies, with growing interest, and thus their drug-metabolizing enzymes, including the cytochromes P450 (P450 or CYP; EC 1.14.14.1), need to be examined. In the present study, novel CYP4A cDNAs were isolated and characterized, namely, pig CYP4A23 and CYP4A90; cat CYP4A37 and CYP4A106; and tree shrew CYP4A11a, CYP4A11d, CYP4A11e, CYP4A11f, and CYP4A11g. For comparison, the following known CYP4A cDNAs were also analyzed: pig CYP4A21 and dog CYP4A37, CYP4A38, and CYP4A39. These CYP4A cDNAs all contained open reading frames of 504–513 amino acids and had high amino acid sequence identity (74%–80%) with human CYP4As. Phylogenetic analysis of amino acid sequences revealed that these CYP4As were clustered in each species. All CYP4A genes contained 12 coding exons and formed a gene cluster in the corresponding genomic regions. A range of tissue types were analyzed, and these CYP4A mRNAs were preferentially expressed in liver and/or kidney, except for pig CYP4A90, which showed preferential expression in lung and duodenum. CYP4A enzymes, heterologously expressed in Escherichia coli, preferentially catalyzed lauric acid 12-hydroxylation and arachidonic acid 20-hydroxylation, just as human CYP4A11 does, with the same regioselectivity (i.e., at the x-position of fatty acids). These results imply that dog, cat, pig, and tree shrew CYP4As have functional characteristics similar to those of human CYP4A11, with minor differences in lauric acid 12-hydroxylation.
  • Anri Hirai, Chitoku Toda, Yared Beyene Yohannes, Nimako Collins, Mai Tamba, Kei Nomiyama, Akifumi Eguchi, Nobuhiko Hoshi, Tetsushi Hirano, Shouta M M Nakayama, Mayumi Ishizuka, Yoshinori Ikenaka
    Toxicology 153839 - 153839 2024年05月21日 [査読有り]
     
    Neonicotinoid (NN) pesticides have been linked to increased brain dysfunction in mammals, such as anxiety-like behavior; this is thought to involve monoamines (MA), neurotransmitters that control behavior, memory, and learning. However, the mechanism by which NNs affect the central nervous system is not fully understood. In this study, we aimed to investigate whether MAs affect NNs-induced anxiety-like behavior. Mice were orally administered acetamiprid (ACE), an NN, at the no observed adverse effect level (NOAEL) of mouse (20mg/kg body mass) set by the Food Safety Commission of Japan, and the elevated zero-maze (EZM) test was performed 30min after administration. After behavioral analysis, levels of four MA (dopamine, 3-MT, serotonin, and histamine) in selected brain regions were determined by liquid chromatography mass spectrometry (LC/MS/MS). In the exposed group, a trend toward increased anxiety-like behavior was observed, and at least one MA concentration was significantly increased in each region. Further, significant correlations were found between behavioral test results and hippocampal serotonin and striatal dopamine concentrations, as well as between dopamine and serotonin concentrations, in the exposed group. As anxiety can influence activity in the behavioral tests, the activity of neurons in the raphe nuclei (RN), a brain region greatly involved in anxiety via the serotonergic system, was examined by staining with anti-serotonin antibodies, and increased serotonergic activity was observed. Taken together, these results suggest that ACE regulates MA levels, notably serotonin levels in the hippocampus and that RN plays an important role in ACE-induced anxiety-like behavior.
  • Faustin Pascal Tsagué Manfo, Collins Nimako, Edouard Akono Nantia, Christian Fusi Suh, Shu Policap Chenwi, Fidelis Cho-Ngwa, Paul Fewou Moundipa, Shouta M M Nakayama, Mayumi Ishizuka, Yoshinori Ikenaka
    Environmental toxicology and chemistry 43 5 952 - 964 2024年05月 [査読有り]
     
    Pesticides, especially the newly developed neonicotinoids, are increasingly used in many countries around the world, including Cameroon, to control pests involved in crop destruction or disease transmission. Unfortunately, the pesticides also pose tremendous environmental problems because a predominant amount of their residues enter environmental matrices to affect other nontargeted species including humans. This therefore calls for continuous biomonitoring of these insecticides in human populations. The present study sought to assess the neonicotinoid insecticide exposures in two agrarian regions of Cameroon, the South-West region and Littoral region. The study involved 188 men, including 125 farmers and 63 nonfarmers. Spot urine samples were obtained from these subjects and subjected to liquid chromatographic-tandem mass spectrometric analysis for concentrations of neonicotinoid compounds, including acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, nitenpyram, thiamethoxam, and N-dm-acetamiprid. Neonicotinoid compounds were detected in all study participants, and residues of all the screened pesticides were detected among participants. N-dm-Acetamiprid and imidacloprid were the most prevalent among the subjects (100.0% and 93.1%, respectively), whereas nitenpyram was less common (3.2%). The median values of imidacloprid and total urinary neonicotinoid concentrations were elevated among farmers (0.258 vs. 0.126 µg/L and 0.829 vs. 0.312 µg/L, respectively). Altogether the findings showed that both the farmer and nonfarmer study populations of Cameroon were exposed to multiple residues of neonicotinoids, with relatively higher levels of pesticides generally recorded among farmers. Although exposure levels of the neonicotinoids were generally lower than their respective reference doses, these results warrant further research on the health risk evaluation of multiple residues of the pesticides and reinforcement of control measures to minimize the exposure risks, especially among farmers. Environ Toxicol Chem 2024;43:952-964. © 2024 SETAC.
  • Mizuki Maruyama, Nana Ushine, Yukiko Watanabe, Chihiro Ishii, Keisuke Saito, Hidefumi Sakai, Takeshi Kuritani, Rio Doya, Kohei Ogasawara, Yoshinori Ikenaka, Yared Beyene Yohannes, Mayumi Ishizuka, Shouta M M Nakayama
    Environmental pollution (Barking, Essex : 1987) 123907 - 123907 2024年04月04日 [査読有り]
     
    Although lead (Pb) poisoning in wild birds has been considered a serious problem in Japan for over 30 years, there is little information about Pb exposure and its sources throughout Japan except for Hokkaido. Furthermore, to identify and effectively prioritize the conservation needs of highly vulnerable species, differences in sensitivity to Pb exposure among avian species need to be determined. Therefore, we investigated the current situation of Pb exposure in raptors (13 species, N = 82), waterfowl (eight species, N = 44) and crows (one species, N = 6) using concentration and isotope analysis. We employed blood or tissue samples collected in various Japanese facilities mainly in 2022 or 2023. We also carried out a comparative study of blood δ-ALAD sensitivity to in vitro Pb exposure using blood of nine avian species. Pb concentrations in the blood or tissues displayed increased levels (>0.1 μg/g blood) in two raptors (2.4%), ten waterfowl (23%) and one crow (17%). Among them, poisoning levels (>0.6 μg/g blood) were found in one black kite and one common teal. The sources of Pb isotope ratios in ten blood samples with high Pb levels were determined as deriving from shot pellets (N = 9) or rifle bullets (N = 1). In the δ-ALAD study, red-crowned crane showed the highest sensitivity among the nine tested avian species and was followed in order by five Accipitriformes species (including white-tailed and Steller's sea eagle), Blakiston's fish owl, Muscovy duck and chicken, suggesting a genetically driven variance in susceptibility. Further studies on contamination conditions and exposure sources are urgently needed to inform strict regulations on the usage of Pb ammunition. Furthermore, detailed examinations of δ-ALAD sensitivity, interspecific differences, and other factors involved in the variability in sensitivity to Pb are required to identify and prioritize highly sensitive species.
  • Nyein Chan Soe, Yared Beyene Yohannes, Takamitsu Ohigashi, Hokuto Nakata, Chikae Tatsumi, Yoshitaka Uchida, Walubita Mufalo, Mayumi Ito, Tsutomu Sato, Toshifumi Igarashi, Yoshinori Ikenaka, Mayumi Ishizuka, Shouta M. M. Nakayama
    Journal of Soils and Sediments 2024年03月13日 [査読有り]
  • So Shinya, Mariko Sashika, Miku Minamikawa, Tetsuji Itoh, Tsutomu Tanikawa, Kazuyuki D. Tanaka, Shouta M. M. Nakayama, Mayumi Ishizuka, Yoshinori Ikenaka
    Environmental Toxicology and Chemistry 2024年03月05日 [査読有り]
     
    Abstract Pesticides, which are vital for agriculture, pose a significant threat to wildlife in transformed Japanese landscapes. Despite global reports of pesticide poisoning in animals, limited studies have examined current wildlife exposure in croplands or metropolitan areas in the region. Using liquid chromatography–tandem mass spectrometry (LC–MS/MS) and gas chromatography–tandem mass spectrometry (GC–MS/MS), our study aimed to assess the contamination status of 368 commonly used pesticides. The stomach contents of raccoons living in croplands contained 13 pesticides, including six herbicides and 11 fungicides. Neonicotinoid insecticides, some fungicides, and previously banned insecticides (benzene hexachloride and dichlofenthion) were most frequently detected and found at the highest concentrations, suggesting direct soil–plant transfer and direct consumption by crop‐eating species. In masked palm civets living in metropolitan areas, four insecticides and six fungicides were detected, indicating urban wildlife exposure from raided dustbins, urban gardens, and lumber from houses. Although the maximum measured concentrations of all pesticides were lower than the acceptable daily intake for humans, it remains unclear whether these concentrations may have toxic or adverse health effects on the species evaluated in these transformed landscapes. Our study is the first to examine recent pesticide exposures in wild mammals in Japan. Application of the method we developed will lay the foundation for the examination of pesticides in other wildlife species to assist conservation management efforts in the region. Environ Toxicol Chem 2024;00:1–9. © 2024 SETAC
  • Tetsushi Hirano, Shuji Ohno, Yoshinori Ikenaka, Kanoko Onaru, Shizuka Kubo, Yuka Miyata, Mizuki Maeda, Youhei Mantani, Toshifumi Yokoyama, Collins Nimako, Yared Beyene Yohannes, Shouta M M Nakayama, Mayumi Ishizuka, Nobuhiko Hoshi
    Toxicology and applied pharmacology 116847 - 116847 2024年02月07日 [査読有り]
     
    Neonicotinoids (NNs) are commonly used pesticides that have a selective agonistic action on insect nicotinic acetylcholine receptors. Recent evidence has shown that NNs have adverse effects in the next generation of mammals, but it remains unclear how NNs transferred from dams to fetuses are distributed and accumulated in fetal tissues. Here, we aimed to clarify the tissue distribution and accumulation properties of the NN clothianidin (CLO) and its 6 metabolites in 7 tissues and blood in both dams and fetuses of mice administered CLO for a single day or for 9 consecutive days. The results showed that the total concentrations of CLO-related compounds in the brain and kidney were higher in fetuses than in dams, whereas in the liver, heart, and blood they were lower in fetuses. The multi-day administration increased the total levels in heart and blood only in the fetuses of the single administration group. In addition, dimethyl metabolites of CLO showed fetus/dam ratios >1 in some tissues, suggesting that fetuses have higher accumulation property and are thus at higher risks of exposure to CLO-related compounds than dams. These findings revealed differences in the tissue-specific distribution patterns of CLO and its metabolites between dams and fetuses, providing new insights into the assessment of the developmental toxicity of NNs.
  • Walubita Mufalo, Takahiko Arima, Toshifumi Igarashi, Mayumi Ito, Tsutomu Sato, Shingo Tomiyama, Imasiku Nyambe, Carlito Baltazar Tabelin, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Environmental Geochemistry and Health 46 2 2024年02月06日 [査読有り]
  • Mayuko Otsuki, Monica Ogawa, Watanuki Yutaka, Yoko Mitani, Mayumi Ishizuka, Yoshinori Ikenaka, Jean-Baptiste Thiebot
    Polar Science 2024年02月
  • Takashi Fujimori, Haruya Toyomaki, Kenji Shiota, Hokuto Nakata, John Yabe, Kaampwe Muzandu, Kenneth Chawinga, Rio Doya, Nyein Chan Soe, Mayumi Ishizuka, Shouta M.M. Nakayama
    Science of The Total Environment 908 168297 - 168297 2024年01月
  • Takahiko ARIMA, Kenta NOTO, Walubita MUFALO, Toshifumi IGARASHI, Mayumi ITO, Tsutomu SATO, Hokuto NAKATA, Shouta NAKAYAMA, Mayumi ISHIZUKA
    Resources Processing 70 3 141 - 150 2024年
  • Kei NOMIYAMA, Fuka SATO, Makoto SHIMASAKI, Hazuki MIZUKAWA, Kraisiri KHIDKHAN, Yoshinori IKENAKA, Mayumi ISHIZUKA
    Environmental Monitoring and Contaminants Research 4 38 - 54 2024年 [査読有り]
  • Kraisiri Khidkhan, Fuyu Yasuhira, Aksorn Saengtienchai, Chaiyan Kasorndorkbua, Ratiwan Sitdhibutr, Kohei Ogasawara, Hikaru Adachi, Yukiko Watanabe, Keisuke Saito, Hidefumi Sakai, Kazuo Horikoshi, Hajime Suzuki, Yusuke K. Kawai, Kazuki Takeda, Yared B. Yohannes, Yoshinori Ikenaka, Barnett A. Rattner, Mayumi Ishizuka, Shouta M.M. Nakayama
    Environmental Pollution 122837 - 122837 2023年11月 [査読有り]
  • Kohei Ogasawara, Naoki Yamada, Shouta Mm Nakayama, Yukiko Watanabe, Keisuke Saito, Akane Chiba, Yoshitaka Uchida, Kaoru Ueda, Yasunori Takenaka, Kentaro Kazama, Mami Kazama, Junya Yamagishi, Hazuki Mizukawa, Yoshinori Ikenaka, Mayumi Ishizuka
    The Journal of veterinary medical science 2023年10月31日 [査読有り]
     
    The composition of the gut microbiome varies due to dietary habits. We investigated influences of diet on the composition of the gut microbiome using the feces of 11 avian species, which consumed grain-, fish- and meat-based diets. We analyzed gut microbiome diversity and composition by next-generation sequencing (NGS) of 16S ribosomal RNA. The grain-diet group had higher gut microbiome diversity than the meat- and fish-diet group. The ratio of Bacteroidetes and Firmicutes phyla was higher in the grain-diet group than in the meat- and fish-diet groups. The grain-diet group had a higher ratio of Veillonellaceae than the meat-diet group and a higher ratio of Eubacteriaceae than the fish-diet habit group. To clarify the influence of diet within the same species, white-tailed eagles (Haliaeetus albicilla, n=6) were divided into two groups, and given only deer meat or fish for approximately one month. The composition of the gut microbiome of individuals in both groups were analyzed by NGS. There were indications of fluctuation in the levels of some bacteria (Lactobacillus, Coriobacteriales, etc.) in each diet group. Moreover, one individual for each group which switched each diet in last week changed to each feature of composition of bacterial flora. The above results show that the composition of the gut microbiome differ depending on diet, even within the same species.
  • Ruan Gerber, Lizaan de Necker, Johan H J van Vuren, Yoshinori Ikenaka, Shouta M M Nakayama, Mayumi Ishizuka, Victor Wepener, Nico J Smit
    Journal of fish biology 2023年07月27日 [査読有り]
     
    Stable isotope analyses, specifically δ13 C and δ15 N, are useful tools increasingly used to understand ecosystem function, food web structures and consumer diets. Although the iconic tigerfish, Hydrocynus vittatus, is regarded as an apex predator in southern African freshwater systems, little information is available regarding their feeding behaviour and how this may change with growth or differ between ecosystems with most information stemming from stomach content analyses (SCA). The aim of the present study was to address this lack of information through a baseline study of the diet of large and small tigerfish in various lentic and lotic ecosystems in South Africa using stable isotope methods. Fish and various food web components and food sources were collected from two river and two lake ecosystems from the Lower Phongolo River floodplain, SA. The δ13 C and δ15 N values for all samples were determined and multivariate analyses and Bayesian analytical techniques applied to determine the feeding ecology of H. vittatus and how this may differ with size and habitat type. Analyses revealed a substantial difference in the type and abundance of food sources contributing to the diet of H. vittatus between ecosystems, most prominently between the lotic systems, where less dietary specialisation was observed, and lentic systems where more specialisation was observed. Furthermore, there was a distinct difference in diet between small and large tigerfish, especially in the lotic system, indicating an ontogenetic diet shift as tigerfish grow and further supporting previous SCA studies. This is the first study of its kind on the African continent for H. vittatus and the findings illustrate the value of stable isotope analysis in providing in-depth information into the feeding ecology of consumers and how this may differ between size classes and habitat types. This article is protected by copyright. All rights reserved.
  • Nana, Makoto Ozawa, Shouta, Mayumi Ishizuka, Takuya Kato, Shin-ichi Hayama
    Animals 2023年07月 [査読有り]
  • Kanami Watanabe, Mitsuki Kondo, Yoshinori Ikenaka, Shouta M M Nakayama, Mayumi Ishizuka
    Animals : an open access journal from MDPI 13 12 2023年06月09日 [査読有り]
     
    Cytochrome P450 is an important enzyme that metabolizes a variety of chemicals, including exogenous substances, such as drugs and environmental chemicals, and endogenous substances, such as steroids, fatty acids, and cholesterol. Some CYPs show interspecific differences in terms of genetic variation. As little is known about the mechanisms of elephant metabolism, we carried out a comparative genomic and phylogenetic analysis of CYP in elephants. Our results suggest that elephant CYP genes have undergone independent duplication, particularly in the CYP2A, CYP2C, and CYP3A genes, a unique cluster specific to elephant species. However, while CYP2E and CYP4A were conserved in other Afrotheria taxa, their decay in elephants resulted in genetic dysfunction (pseudogene). These findings outline several remarkable characteristics of elephant CYP1-4 genes and provide new insights into elephant xenobiotic metabolism. Further functional investigations are necessary to characterize elephant CYP, including expression patterns and interactions with drugs and sensitivities to other chemicals.
  • Nana Ushine, Shouta MM Nakayama, Mayumi Ishizuka, Takuya Kato, Shin-ichi Hayama
    Japanese Journal of Environmental Toxicology 26 25 - 37 2023年06月 [査読有り]
  • Walubita Mufalo, Pawit Tangviroon, Takahiko Arima, Toshifumi Igarashi, Mayumi Ito, Tsutomu Sato, Kenta Noto, Takeshi Kawashima, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Journal of Geochemical Exploration 249 107209 - 107209 2023年06月 [査読有り]
  • Andrew Kataba, Yared Beyene Yohannes, Hokuto Nakata, John Yabe, Haruya Toyomaki, Kaampwe Muzandu, Golden Zyambo, Yoshinori Ikenaka, Kennedy Choongo, Mayumi Ishizuka, Shouta M M Nakayama
    International journal of environmental research and public health 20 8 2023年04月20日 [査読有り]
     
    Lead (Pb) poisoning remains a great public health challenge globally known to induce a wide range of ailments in both children and adults. The current study investigated the association of chronic environmental Pb exposure and immunomodulatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8) in adult males and females living in Kabwe, Zambia. The standard human cytokine/chemokine Milliplex assay was used to quantify plasma cytokines from four groups categorized as low (<10 μg/dL) and high (>10 μg/dL) blood lead level (BLL) groups, namely, low BLL female (n = 47; BLL = 3.76 μg/dL), low BLL Male (n = 43; BLL = 4.13 μg/dL), high BLL female (n = 21; BLL = 23.5 μg/dL), and high BLL male (n = 18; BLL = 23.7 μg/dL), respectively. The low BLL group was associated with increased TNF-α levels, and the high BLL group was associated with reduced TNF-α levels in female subjects. No associations between BLL and the levels of IL-8 and TNF-α cytokines were observed in either females or males, respectively. A negative correlation between BLL and TNF-α was found in female subjects, suggesting that an increase in BLL accompanied by a reduction in TNF-α. The reduced levels of circulating TNF-α in female subjects suggest that chronic Pb exposure could predispose females to immune and inflammation-related disorders than their male counterparts. Further studies are recommended to ascertain the impact of chronic Pb exposure on immunomodulatory cytokines, especially in females.
  • Yuko Kihara, Yohsuke Makino, Masaaki Yokoyama, Fumiko Chiba, Aki Tanaka, Shouta M M Nakayama, Shin-Ichi Hayama, Mayumi Ishizuka, Kurt B Nolte, Hirotaro Iwase
    Legal medicine (Tokyo, Japan) 63 102257 - 102257 2023年04月11日 [査読有り]
     
    In forensic pathology, it is important to detect and recover as evidence residual metal particles and projectiles when evaluating potential gunshot wounds. This process can be challenging when the bullets are fragmented. This report presents our experience using multiple modalities to analyze the wound of an illegally killed Japanese serow (Capricornis crispus) found in a mountainous region without its head and hind limbs. We performed postmortem computed tomography (PMCT) and necropsy that showed a distant-range gunshot wound of the neck likely created by a centerfire rifle. A postmortem cut through the neck and absent head precluded a complete evaluation. To determine the composition of the metal-like fragments in the neck, sampling and metal analysis were performed in two ways. Samples extracted from the exposed wound surface without CT guidance were analyzed directly using inductively coupled plasma mass spectrometry (ICP-MS). Samples from the bone, muscles, and cervical cord extracted under CT guidance were analyzed using x-ray analytic microscopy (XGT-9000, HORIBA, Kyoto, Japan). In wound surface samples, silicon and iron were detected as the main components on ICP-MS, suggesting that the materials were gravel. The samples taken under CT guidance and analyzed with XGT-9000 revealed that the high-density CT areas were mainly composed of lead. Combining CT-guided sample extraction and XGT-9000 can be useful for retrieving true projectile fragments and avoiding the confusion created by erroneously sampling non-projectile surface materials.
  • So Shinya, Devinda S. Muthusinghe, Nobuo Koizumi, Kumiko Yoshimatsu, Shouta M. M. Nakayama, Mayumi Ishizuka, Yoshinori Ikenaka
    Toxics 11 4 2023年04月11日 [査読有り]
     
    Wild rodents are natural hosts of Leptospira spp. and are exposed to various pesticides, some of which are immunotoxic. Rodent urine is an important source of infection for humans and other animals. We evaluated the effects of pesticide exposure on Leptospira growth in mice. Diazinon, at doses of 0.2, 1, and 5 mg/kg/day, was orally administered continuously to mice infected with Leptospira interrogans serogroup Hebdomadis for 32 days. The numbers of L. interrogans in urine and kidney tissues were significantly lower in mice exposed to 5 mg/kg/day diazinon than in unexposed mice (p < 0.05). The urinary concentration of 2-isopropyl-6-methyl-4-pyrimidinol, the metabolite of diazinon, was comparable with the concentration at which viability of L. interrogans was decreased in in vitro assay, suggesting that it had toxic effects on L. interrogans in the proximal renal tubules. Diazinon exposure reinforced Leptospira-induced expression of inflammatory cytokine genes in kidney tissues, and an enhanced immune system might suppress Leptospira growth. These results suggest that diazinon exposure may not increase the risk of Leptospira transmission to humans through mice. This novel study evaluated the relationship between pesticide exposure and Leptospira infection in mice, and the results could be useful for risk assessment of leptospirosis.
  • So Shinya, Fumiya Nishibe, Yared Beyene Yohannes, Mayumi Ishizuka, Shouta M Nakayama, Yoshinori Ikenaka
    Aquatic toxicology (Amsterdam, Netherlands) 257 106437 - 106437 2023年04月 [査読有り]
     
    Pesticide exposure is considered to be one important factor responsible for declining amphibian populations worldwide. The usage of neonicotinoid insecticides (NNIs) has markedly increased in recent years, and there are concerns regarding the effects of NNI-induced toxicity on the development and behavior of amphibians. However, there have been few reports on the metabolism, distribution, and neurotoxicity of NNIs in amphibians. In this study, we exposed the Western clawed frog (Silurana tropicalis) to clothianidin (CLT) in water. After 24 h of exposure, the highest concentrations were detected in the skin, indicating that frogs are at a high risk of absorbing CLT through their skin along with water. Excretion of CLT was estimated based on the concentrations of CLT metabolites in the water until 48 h of exposure. The findings showed that frogs had higher CLT metabolic ability than zebrafish. Serotonin levels in the brain were lower in the high-concentration CLT exposure group than in the control group, although the difference was not statistically significant. This suggested that catecholamine-related effects of CLT on the brain cannot be disregarded. In addition, quantitative analyses of NNI residue in wild frogs, soil, and water in agricultural areas in Hokkaido, Japan, were performed and four NNIs were detected. These results indicated the possible risk of NNI-induced toxicity in frogs. This is the first report of the characteristics of tissue distribution and metabolism of NNIs in frogs, which may facilitate the design of appropriate conservation programs for amphibians.
  • So Shinya, Yusuke Kawai, Mitsuki Kondo, Shouta M M Nakayama, Mayumi Ishizuka, Yoshinori Ikenaka
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 265 109537 - 109537 2023年03月 [査読有り]
     
    Soricidae spp. (shrews) play an essential role in soil ecosystems and, due to their habitat and behavior, are exposed to soil pollutants, such as pesticides. Still, toxicity risk in Soricidae spp. has not been appropriately assessed. In this study, the musk shrew (Suncus murinus) was used as a model organism for toxicity assessment in Soricidae. Considering their carnivorous diet, it is reasonable to assume that the musk shrew has unique metabolic traits that are different from those of other common experimental models. This study describes the cytochrome P450 (CYP)-dependent metabolism affected by acetamiprid (ACP), a neonicotinoid insecticide. Pharmacokinetics analysis, an in vitro metabolic assay, and genetic analysis of CYP were performed and compared with data from mice and rats. Through phylogenetic and syntenic analyses, three families of CYP were identified in the musk shrew. Pharmacokinetic analysis showed that the blood concentration of ACP decreased more quickly in musk shrews than in mice. Moreover, the in vitro metabolic assay suggested more efficient metabolic responses toward ACP in musk shrews than in mice or rats. One of the CYP2A isoforms in musk shrews might be linked to a better ACP metabolism. From the results above, we describe novel metabolic traits of the musk shrew. Future research on recombinant CYP enzymes is necessary to fully understand CYP-dependent metabolism of xenobiotics in musk shrews.
  • Daichi Yamada, Masato Hiwatari, Daiju Narita, Peter Hangoma, Bona Chitah, Hokuto Nakata, Shouta M.M. Nakayama, John Yabe, Mayumi Ito, Toshifumi Igarashi, Mayumi Ishizuka, Golden Zyambo
    Science of The Total Environment 865 161281 - 161281 2023年03月 [査読有り]
  • Kodai Motohira, Yared Beyene Yohannes, Yoshinori Ikenaka, Akifumi Eguchi, Shouta Mm Nakayama, Victor Wepener, Nico J Smit, Johan Hj VAN Vuren, Mayumi Ishizuka
    The Journal of veterinary medical science 85 2 236 - 243 2023年01月02日 [査読有り]
     
    Dichlorodiphenyltrichloroethane (DDT) is an organochlorine insecticide used worldwide. Several studies have reported the toxic effects of DDT and its metabolites on steroid hormone biosynthesis; however, its environmental effects are not well understood. This study examined wild rats collected in DDT-sprayed areas of South Africa and quantified plasma metabolites using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS). Fold change analysis of the metabolome revealed the effect of DDT on bile acid biosynthesis. Gene expression of the related enzyme in rat liver samples was also quantified. Significant association was found between DDT and gene expression levels related to constitutive androstane receptor mediated enzymes, such as Cyp2b1 in rat livers. However, our results could not fully demonstrate that enzymes related to bile acid biosynthesis were strongly affected by DDT. The correlation between DDT concentration and gene expression involved in steroid hormone synthesis in testis was also evaluated; however, no significant correlation was found. The disturbance of metabolic enzymes occurred in rat liver in the target area. Our results suggest that DDT exposure affects gene expression in wild rats living in DDT-sprayed areas. Therefore, there is a need for DDT toxicity evaluation in mammals living in DDT-sprayed areas. We could not find an effective biomarker that could reflect the mechanism of DDT exposure; however, this approach can provide new insights for future research to evaluate DDT effects in sprayed areas.
  • NIMAKO Collins, NAKAYAMA Shouta M. M., YOHANNES Yared Beyene, IKENAKA Yoshinori, ISHIZUKA Mayumi
    Environmental Monitoring and Contaminants Research 3 69 - 91 2023年 [査読有り]
     
    Neonicotinoid insecticides are exclusively used for insect control in many parts of the globe. Since early 1992, various neonicotinoid active compounds have been used for pest control in Japan. At present, all seven major neonicotinoid active compounds, imidacloprid, acetamiprid, dinotefuran, clothianidin, thiamethoxam, thiacloprid, and nitenpyram, are used in Japan, and the total shipment amount of these chemicals in the country was estimated 337.9 tons in 2022. Due to the massive neonicotinoid application in Japan, concerns have been raised about their potential infiltrations into nontarget ecosystems and their effects on human and ecological species. These concerns have inspired several studies, extensively investigating the environmental contamination levels and exposure tendencies in humans and several other invertebrate species. The current status report harmonized the up-to-date data on neonicotinoids in Japan and identified the incoherencies or knowledge gaps existing in the neonicotinoid literature reported in Japan. The report further summarized extensive neonicotinoid publications globally to illustrate the distributions of various neonicotinoid compounds in agricultural soils and surface waters and their exposures in humans and nontarget animal species. This report represents a few perspectives with detailed data from Japan into perspective.
  • Kazuki Takeda, Keita Shimizu, Miyu Sato, Masafumi Katayama, Shouta MM Nakayama, Kotaro Tanaka, Yoshinori Ikenaka, Takuma Hashimoto, Ryuichi Minato, Yusuke Oyamada, Kazuyuki D. Tanaka, Goro Kimura, Tsutomu Tanikawa, Keisuke Kato, Taichi Kusakabe, Mayumi Ishizuka, Ryo Kamata
    2023年
  • Khidkhan K, Mizukawa H, Ikenaka Y, Nakayama SMM, Nomiyama K, Yokoyama N, Ichii O, Takiguchi M, Tanabe S, Ishizuka M
    PLOS ONE 18 1 e0277689  2023年01月 [査読有り]
     
    As an animal familiar to humans, cats are considered to be sensitive to chemicals; cats may be exposed to polychlorinated biphenyls (PCBs) and decabromodiphenyl ether (BDE-209) from indoor dust, household products, and common pet food, leading to adverse endocrine effects, such as thyroid hormone dysfunction. To elucidate the general biological effects resulting from exposure of cats to PCBs and PBDEs, cats were treated with a single i.p. dose of a principal mixture of 12 PCBs and observed for a short-term period. Results revealed that the testis weight, serum albumin, and total protein of the treated group decrease statistically in comparison with those in the control group. The negative correlations suggested that the decrease in the total protein and albumin levels may be disturbed by 4'OH-CB18, 3'OH-CB28 and 3OH-CB101. Meanwhile, the serum albumin level and relative brain weight decreased significantly for cats subjected to 1-year continuous oral administration of BDE-209 in comparison to those of control cats. In addition, the subcutaneous fat as well as serum high-density lipoprotein (HDL) and triglycerides (TG) levels increased in cats treated with BDE-209 and down-regulation of stearoyl-CoA desaturase mRNA expression in the liver occurred. These results suggested that chronic BDE-209 treatment may restrain lipolysis in the liver, which is associated with lipogenesis in the subcutaneous fat. Evidence of liver and kidney cell damage was not observed as there was no significant difference in the liver enzymes, blood urea nitrogen and creatinine levels between the two groups of both experiments. To the best of our knowledge, this is the first study that provides information on the biochemical effects of organohalogen compounds in cats. Further investigations on risk assessment and other potential health effects of PCBs and PBDEs on the reproductive system, brain, and lipid metabolism in cats are required.
  • Mitsuki Kondo, Yoshinori Ikenaka, Shouta M M Nakayama, Yusuke K Kawai, Hazuki Mizukawa, Yoko Mitani, Kei Nomyama, Shinsuke Tanabe, Mayumi Ishizuka
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 263 109476 - 109476 2023年01月 
    Wild carnivorans are one of the most important species due to their high positions in the food chain. They are also highly affected by numerous environmental contaminants through bioaccumulation and biomagnification. Xenobiotic metabolism is a significant chemical defense system from xenobiotics because it degrades the activity of a wide range of chemicals, generally into less active forms, resulting in their deactivation. Sulfotransferases (SULTs) are one of the most important xenobiotic metabolic enzymes, which catalyze the sulfonation of a variety of endogenous and exogenous chemicals, such as hormones, neurotransmitters, and a wide range of xenobiotic compounds. Although SULTs are of such high importance, little research has focused on these enzymes in wild carnivorans. In this study, we clarified the genetic properties of SULTs in a wide range of mammals, focusing on carnivorans, using in silico genetic analyses. We found genetic deficiencies of SULT1E1 and SULT1D1 isoforms in all pinnipeds analyzed and nonsense mutations in SULT1Cs in several carnivorans including pinnipeds. We further investigated the enzymatic activity of SULT1E1 in vitro using liver cytosols from pinnipeds. Using a SULT1E1 probe substrate, we found highly limited estradiol sulfonation in pinnipeds, whereas other mammals had relatively high sulfation. These results suggest that pinnipeds have severely or completely absent SULT1E1 activity, which importantly catalyzes the metabolism of estrogens, drugs, and environmental toxins. This further implies a high susceptibility to a wide range of xenobiotics in these carnivorans, which are constantly exposed to environmental chemicals throughout their lifetime.
  • Makoto Shimasaki, Hazuki Mizukawa, Kohki Takaguchi, Aksorn Saengtienchai, Araya Ngamchirttakul, Disdanai Pencharee, Kraisiri Khidkhan, Yoshinori Ikenaka, Shouta M. M. Nakayama, Mayumi Ishizuka, Kei Nomiyama
    Animals 12 24 3520 - 3520 2022年12月13日 [査読有り][招待有り]
     
    In this study, we analyzed serum samples of pet cats from Thailand and estimated the contribution to organohalogen compounds (OHCs) exposure through cat food and house dust intake. BDE-209 was predominant in cat sera and accounted for 76% of all polybrominated diphenyl ethers (PBDEs). Decabromodiphenyl ether (BDE-209) is a major contaminant in dry cat food and house dust, which has been estimated to be a source of exposure for Thai pet cats. BDE-209 is a major contaminant of OHCs in dry cat food and house dust, which was estimated to be a source of exposure for Thai pet cats. On the other hand, the level of contamination by PCBs was lower than in other countries. Analysis of pet foods suggested that BDE-209 in pet cat serum was attributable to the consumption of dry cat food. On the other hand, house dust also contained high concentrations of BDE-209. Thus, high levels of BDE-209 in pet cat sera can be attributed to the consumption of dry cat food and house dust. These results suggest that pet cats are routinely exposed to non-negligible levels of OHCs.
  • Bayartogtokh Bataa, Kodai Motohira, Delgermurun Dugar, Tsend-Ayush Sainnokhoi, Lkhamjav Gendenpil, Tserenchimed Sainnokhoi, Bolormaa Pelden, Yared Beyene Yohannes, Sumiya Ganzorig, Shouta M M Nakayama, Mayumi Ishizuka, Yoshinori Ikenaka
    Toxics 10 12 2022年12月10日 [査読有り]
     
    The Mongolian economy is supported by rich deposits of natural resources, such as copper, coal, and gold. However, the risk of heavy metal pollution to livestock and human have been recently discussed. This research collected various samples from soil and animal (sheep, goat, horse, cow, and camel), blood and organs (kidney and liver) in the Mongolian countryside. These samples were processed, and the concentration of metals was quantified using inductively coupled plasma-mass spectrometry (ICP/MS). As previously reported, arsenic was found at high levels of accumulation in soil. Selenium is another concern, as median concentration in one area exceeded the maximum allowable level. Cadmium and selenium were found to be highly accumulated in animal kidney. This research revealed the current pollution level in Mongolia based on evaluation of soil and animals. The concentration in animals could not indicate that animals had severe effects because of heavy metal exposure. However, kidney is eaten in Mongolia, and so there is a direct connection to human health, and this research suggested the possible risks posed by each edible animal. In particular, evaluation of metals in livestock is rare in Mongolia. This result can contribute to animal and human health in Mongolian communities.
  • Yared Beyene Yohannes, Shouta M M Nakayama, John Yabe, Haruya Toyomaki, Andrew Kataba, Hokuto Nakata, Kaampwe Muzandu, Chihiro Miyashita, Yoshinori Ikenaka, Kennedy Choongo, Mayumi Ishizuka
    Epigenetics 17 13 2377 - 2388 2022年12月 [査読有り]
     
    Lead (Pb) exposure has adverse health effects and altered DNA methylation may contribute to Pb toxicity. LINE-1 is an interspersed repeated DNA that is used as a surrogate marker for estimating genomic DNA methylation levels, and GSTP1 is an isozyme that detoxifies xenobiotics like Pb, and its expression is inhibited by methylation. Thus, to assess the effects of Pb exposure on global hypomethylation and gene-specific promoter hypermethylation, we examined DNA methylation at LINE-1 repetitive elements and the GSTP1 promoter region. Blood samples were obtained from children (N = 123) living in Pb-polluted areas (as exposed children) and children (N = 63) living in Pb-unpolluted areas (as control children) in Kabwe, Zambia. ICP-MS was used to determine blood lead levels (BLLs), and pyrosequencing and a fluorescence-based polymerase chain reaction assay were used to determine levels of LINE-1 methylation and GSTP1 promoter methylation, respectively. Inverse association was found between BLLs and LINE-1 methylation (β = - 0.046, p = 0.006). The highest quartile of BLL had significant hypomethylation of LINE-1 (p for trend = 0.03), suggesting the higher the BLL, the lower LINE-1 methylation. GSTP1 methylation levels did not differ significantly between the two areas (p = 0.504), nor was it associated with Pb poisoning risk (OR = 1.03, p = 0.476), indicating GSTP1 methylation may not be a reliable biomarker of Pb exposure in healthy people. Therefore, Pb-related health problems could result from global DNA methylation changes due to high BLLs.
  • Anri Hirai, Ryo Yamazaki, Atsushi Kobayashi, Takashi Kimura, Kei Nomiyama, Shuichi Shimma, Shouta M M Nakayama, Mayumi Ishizuka, Yoshinori Ikenaka
    Toxics 10 11 2022年11月17日 [査読有り]
     
    Monoamine neurotransmitters (MAs), including dopamine (DA) and serotonin (5-HT), regulate brain functions such as behavior, memory, and learning. Neonicotinoids are pesticides that are being used more frequently. Neonicotinoid exposure has been observed to produce neurological symptoms, such as altered spontaneous movements and anxiety-like behaviors, which are suspected to be caused by altered MA levels. However, current neurotoxicity tests are not sufficiently sensitive enough to make these determinations. In this study, we performed some behavior tests, and derivatization reagents to improve the ionization efficiency, which was applied to liquid chromatography mass spectrometry (LC-MS/MS) to reveal the effect of neonicotinoid administration on MAs in the brain. We orally administered the neonicotinoid imidacloprid (0, 10, and 50 mg/kg body weight) to C57BL/6NCrSlc mice. In the behavior tests, a decrease in activity was observed. The LC-MS/MS quantification of MAs in various brain regions showed a decrease in some MA levels in the olfactory bulb and the striatum. These results showed, for the first time, that even a low dose of imidacloprid could alter MA levels in various parts of the brain.
  • So Shinya, Yared Beyene Yohannes, Yoshinori Ikenaka, Shouta Mm Nakayama, Mayumi Ishizuka, Shoichi Fujita
    The Journal of veterinary medical science 84 12 1665 - 1672 2022年11月02日 [査読有り]
     
    Wildlife is exposed to a wide range of xenobiotics in the natural environment. In order to appropriately assess xenobiotic-induced toxicity in wildlife, it is necessary to understand metabolic capacities. Carnivores, in general, have low metabolic abilities, making them vulnerable to a variety of chemicals. Raccoons (Procyon lotor) in the wild have been found to have high levels of xenobiotics. However, little is known about the metabolic capacity of the cytochrome P450 (CYP) enzymes in this species. Thus, this study used liver samples to investigate the characteristics of CYP enzymes in wild raccoons. In 22 wild raccoons, CYP concentrations in hepatic microsomes were examined. To better understand the properties of CYP-dependent metabolism, in vitro metabolic activity studies were performed using ethoxyresorufin, pentoxyresorufin and testosterone as substrates. In addition, three raccoons were fed commercial dog food in the laboratory for one week, and the effects on CYP-dependent metabolism were investigated. In comparison to other mammalian species, raccoons had very low concentrations of CYP in their livers. In an in vitro enzymatic analysis, raccoons' ethoxyresorufin O-deethylase (EROD) and pentoxyresorufin O-depentylase (PROD) metabolic capacities were less than one-fifth and one-tenth of rats', respectively. These results indicate the possible high risk in raccoons if exposed to high levels of environmental xenobiotics because of their poor CYP activity. In this study, the features of CYP-dependent metabolism in wild raccoons are described for the first time.
  • Mitsuki Kondo, Yoshinori Ikenaka, Shouta M M Nakayama, Yusuke K Kawai, Mayumi Ishizuka
    Animals : an open access journal from MDPI 12 21 2022年10月27日 [査読有り]
     
    UDP-glucuronosyltransferases (UGTs) are one of the most important enzymes for xenobiotic metabolism or detoxification. Through duplication and loss of genes, mammals evolved the species-specific variety of UGT isoforms. Among mammals, Carnivora is one of the orders that includes various carnivorous species, yet there is huge variation of food habitat. Recently, lower activity of UGT1A and 2B were shown in Felidae and pinnipeds, suggesting evolutional loss of these isoforms. However, comprehensive analysis for genetic or evolutional features are still missing. This study was conducted to reveal evolutional history of UGTs in Carnivoran species. We found specific gene expansion of UGT1As in Canidae, brown bear and black bear. We also found similar genetic duplication in UGT2Bs in Canidae, and some Mustelidae and Ursidae. In addition, we discovered contraction or complete loss of UGT1A7-12 in phocids, some otariids, felids, and some Mustelids. These studies indicate that even closely related species have completely different evolution of UGTs and further imply the difficulty of extrapolation of the pharmacokinetics and toxicokinetic result of experimental animals into wildlife carnivorans.
  • Mitsuki Kondo, Yoshinori Ikenaka, Shouta M M Nakayama, Yusuke K Kawai, Mayumi Ishizuka
    Animals : an open access journal from MDPI 12 20 2022年10月18日 [査読有り]
     
    Cytochrome P450s are among the most important xenobiotic metabolism enzymes that catalyze the metabolism of a wide range of chemicals. Through duplication and loss events, CYPs have created their original feature of detoxification in each mammal. We performed a comprehensive genomic analysis to reveal the evolutionary features of the main xenobiotic metabolizing family: the CYP1-3 families in Carnivora. We found specific gene expansion of CYP2Cs and CYP3As in omnivorous animals, such as the brown bear, the black bear, the dog, and the badger, revealing their daily phytochemical intake as providing the causes of their evolutionary adaptation. Further phylogenetic analysis of CYP2Cs revealed Carnivora CYP2Cs were divided into CYP2C21, 2C41, and 2C23 orthologs. Additionally, CYP3As phylogeny also revealed the 3As' evolution was completely different to that of the Caniformia and Feliformia taxa. These studies provide us with fundamental genetic and evolutionary information on CYPs in Carnivora, which is essential for the appropriate interpretation and extrapolation of pharmacokinetics or toxicokinetic data from experimental mammals to wild Carnivora.
  • Shizuka Kubo, Tetsushi Hirano, Yuka Miyata, Shuji Ohno, Kanoko Onaru, Yoshinori Ikenaka, Shouta M M Nakayama, Mayumi Ishizuka, Youhei Mantani, Toshifumi Yokoyama, Nobuhiko Hoshi
    Toxicology and applied pharmacology 456 116283 - 116283 2022年10月14日 [査読有り]
     
    Although neonicotinoids are among the major classes of pesticides that affect mammalian nervous systems, little is known about sex differences in their effects. This study aimed to examine whether the neurobehavioral effects of a neonicotinoid, clothianidin (CLO), differed between sexes. Male and female C57BL/6 N mice were orally administered CLO (5 or 50 mg/kg) at or below the chronic no-observed-adverse-effect-level (NOAEL) and subjected to behavioral tests of emotional and learning functions. Changes in neuroactivity in several brain regions and the concentrations of CLO and its metabolites in blood and urine were measured. Acute CLO exposure caused sex-related behavioral effects; decreases in locomotor activities and elevation of anxiety-like behaviors were more apparent in males than in females. In addition, male-specific impairment of short- and long-term learning memory by CLO exposure was observed in both the novel recognition test and the Barnes maze test. Male-dominant increases in the number of c-fos positive cells were observed in the paraventricular thalamic nucleus in the thalamus and in the dentate gyrus in the hippocampus, which are related to the stress response and learning function, respectively. The concentrations of CLO and most metabolites in blood and urine were higher in males. These results support the notion that male mice are more vulnerable than females to the neurobehavioral effects of CLO and provide novel insights into the risk assessment of neonicotinoids in mammalian neuronal function.
  • Kazuki Takeda, Kosuke Manago, Ayuko Morita, Yusuke K. Kawai, Nobuaki Yasuo, Masakazu Sekijima, Yoshinori Ikenaka, Takuma Hashimoto, Ryuichi Minato, Yusuke Oyamada, Kazuo Horikoshi, Hajime Suzuki, Mayumi Ishizuka, Shouta M.M. Nakayama
    Ecotoxicology and Environmental Safety 243 113971 - 113971 2022年09月 [査読有り]
  • Lizaan de Necker, Luc Brendonck, Ruan Gerber, Pieter Lemmens, David X Soto, Yoshinori Ikenaka, Mayumi Ishizuka, Victor Wepener, Nico J Smit
    The Science of the total environment 834 155338 - 155338 2022年08月15日 [査読有り]
     
    Climate change and associated droughts threaten the ecology and resilience of natural saline lakes globally. There is a distinct lack of research regarding their ecological response to climatic events in the Global South. This region is predicted to experience climatic events such as El Niño-Southern Oscillation (ENSO) more often and with greater severity with the potential to alter the structure and functioning of aquatic ecosystems significantly. From 2015 to 2016 South Africa experienced one of the most severe country-wide droughts as a result of a strong ENSO event. Our study aimed to investigate the effect of this supra-seasonal drought on the trophic structure of fish communities in a naturally saline shallow lake of a Ramsar wetland using stable isotope techniques. Fishes and potential basal sources were collected from the lake, during predrought conditions in 2010 and after severe drought (recovery phase; 2017). The δ13C and δ15N values of food web elements were determined and analysed using Bayesian mixing models and Bayesian Laymen metrics to establish the proportional contribution of C3 and C4 basal sources to the fish (consumer) diets, and examine the fish community in terms of isotopic niche and trophic structure, respectively. Fish consumers relied predominantly on C3 basal sources in the predrought and shifted to greater reliance on C4 basal sources, decreased isotopic niche space use and a reduction in trophic length in the recovery phase. Drought altered the type and abundance of the basal sources available by limiting sources to those that are more drought-tolerant, reducing the trophic pathways of the food web with no significant alterations in the fish community. These results demonstrate the resilience and biological plasticity of Lake Nyamithi and its aquatic fauna, highlighting the importance of freshwater inflow to saline lakes with alterations thereof posing a significant threat to their continued functioning.
  • Hokuto Nakata, Shouta M.M. Nakayama, John Yabe, Kaampwe Muzandu, Andrew Kataba, Atsuko Ikeda-Araki, Marie-Noel Brune Drisse, Lesley Jayne Onyon, Julia Gorman, Poudel Kritika, Hisanori Fukunaga, Yoshinori Ikenaka, Reiko Kishi, Mayumi Ishizuka
    Science of The Total Environment 157833 - 157833 2022年08月 [査読有り]
  • Chihiro Ishii, Yusuke K Kawai, Yoshinori Ikenaka, Naoya Maekawa, Osamu Ichii, Shouta M M Nakayama, Mayumi Ishizuka
    Poultry science 101 9 102011 - 102011 2022年06月16日 
    Bird death is often caused by renal lesions induced by chemicals. The avian kidney has a renal portal system with significant blood flow that is sensitive to many chemicals. However, early avian biomarkers for kidney injury are yet to be identified. This study aimed to identify novel renal biomarkers. Acute kidney injury (AKI) can be divided into acute interstitial nephritis (AIN) and acute tubular necrosis (ATN). A chicken model of kidney damage was created by an injection of diclofenac or cisplatin, which caused either AIN or ATN, respectively. Microarray analysis was performed to profile the gene expression patterns in the chickens with nephropathy. A gene enrichment analysis suggested that the genes related to responses to external stimuli showed expression changes in both AIN and ATN. However, hierarchical clustering analyses suggested that gene expression patterns differed between AIN and ATN, and the number of biomarkers relating to renal damage was low. To identify early biomarkers for nephropathy, we focused on genes that were induced at various levels of renal damage. The gene, vanin-1 (VNN1) was highly induced in the early stages of renal damage. A quantitative real-time PCR analysis supported this finding. These results suggest VNN1 could be a useful early biomarker of kidney injury in avian species.
  • Yasuhiro Uno, Norie Murayama, Moe Ijiri, Hiroaki Kawaguchi, Osamu Yamato, Mitsuya Shiraishi, Atsushi Asano, Hiroki Teraoka, Hazuki Mizukawa, Shouta M M Nakayama, Yoshinori Ikenaka, Mayumi Ishizuka, Hiroshi Yamazaki
    Drug metabolism and disposition: the biological fate of chemicals 50 11 1434 - 1441 2022年06月14日 [査読有り]
     
    Cytochromes P450 (P450 or CYP) have been identified and analyzed in dogs and pigs, species that are often used in preclinical drug studies. Moreover, P450s are clinically important for drug therapy not only in humans but also in species under veterinary care, including dogs and cats. In the present study, seven P450s homologous to human CYP2J2, namely, dog CYP2J2; cat CYP2J2; and pig CYP2J33, CYP2J34, CYP2J35, CYP2J91, and CYP2J93, were newly identified and characterized. The cDNAs of these CYP2Js contained open reading frames of 502 amino acids, except for CYP2J35 (498 amino acids), and shared high sequence identity (77-80%) with human CYP2J2. Phylogenetic analysis revealed that dog and cat CYP2J2 were closely related, whereas pig CYP2Js formed a cluster. All seven CYP2J genes contain nine coding exons and are located in corresponding genomic regions, with the pig CYP2J genes forming a gene cluster. These CYP2J2 mRNAs were predominantly expressed in small intestine with additional expression in kidney and brain for dog CYP2J2 and pig CYP2J91 mRNAs, respectively. All seven CYP2Js metabolized human CYP2J2 substrates terfenadine, ebastine, and astemizole, indicating that they are functional enzymes. Dog CYP2J2 and pig CYP2J34 and CYP2J35 efficiently catalyzed ebastine primary hydroxylation and secondary carebastine formation at low substrate concentrations, just as human CYP2J2 does. Velocity-versus-substate plots exhibited sigmoidal relationships for dog CYP2J2, cat CYP2J2, and pig CYP2J33, indicating allosteric interactions. These results suggest that dog, cat, and pig CYP2Js have similar functional characteristics to human CYP2J2, with slight differences in ebastine and astemizole oxidations. Significance Statement New dog cytochrome P450 2J2 (CYP2J2); cat CYP2J2; and pig CYP2J33, CYP2J34, CYP2J35, CYP2J91, and CYP2J93, homologous to human CYP2J2, were identified and characterized by sequence, phylogenetic, and genomic structure analyses. Intestinal expression patterns of CYP2J mRNAs were characteristic in dogs, cats, and pigs. Dog, cat, and pig CYP2Js likely play roles as drug-metabolizing enzymes in small intestine, similar to human CYP2J2.
  • Yasuhiro Uno, Makiko Shimizu, Yurie Ogawa, Miaki Makiguchi, Hiroaki Kawaguchi, Osamu Yamato, Mayumi Ishizuka, Hiroshi Yamazaki
    Biochemical pharmacology 202 115125 - 115125 2022年06月08日 [査読有り]
     
    Flavin-containing monooxygenases (FMOs) are drug-oxygenating enzymes that are present in the human genome as FMO1-5 and FMO6P. Among pig, dog, and cat FMOs, pig and dog FMO1 and FMO3 have been partly characterized, but other FMOs have not been systematically identified. In this study, orthologous FMO cDNAs were isolated from pig, dog, and cat livers and evaluated by sequence and phylogenetic analyses, tissue expression, and catalytic function. The amino acid sequences of pig, dog, and cat FMO1-5 shared high sequence identities (83-89%) with human FMO1-5 and were closely clustered in a phylogenetic tree. The gene structure and genomic organization of FMO1-5 were conserved across these species. Dog and pig FMO6P contained insertions of 1 and 83 bases, respectively, and are possibly pseudogenes similar to human FMO6P. Among the tissue types analyzed, pig FMO1 mRNA was abundant in liver, kidney, and lung; dog FMO3, FMO2, and FMO5 mRNAs were abundant in liver, lung, and kidney, respectively; cat FMO1 and FMO3 mRNAs were abundant in kidney and liver, respectively. Recombinant pig and dog FMO1-5 and cat FMO1-6 all mediated benzydamine and trimethylamine N-oxygenations and methyl p-tolyl sulfoxide S-oxygenation. The selective human FMO3 substrate trimethylamine was predominantly metabolized by pig FMO1, dog FMO3, and cat FMO3. Cat FMO6 was also active toward trimethylamine. These results suggest some similarities in the drug-metabolizing capabilities of FMO3 in dogs, cats, and humans and that dog and cat FMO3 generally have molecular and functional characteristics similar to human FMO3, being the major FMO in human liver.
  • Hiroshi Sato, Chihiro Ishii, Shouta M M Nakayama, Takahiro Ichise, Keisuke Saito, Yukiko Watanabe, Kohei Ogasawara, Ryota Torimoto, Atsushi Kobayashi, Takashi Kimura, Yukiko Nakamura, Junya Yamagishi, Yoshinori Ikenaka, Mayumi Ishizuka
    Environmental pollution (Barking, Essex : 1987) 308 119580 - 119580 2022年06月06日 [査読有り]
     
    Among wild birds, lead (Pb) exposure caused by ingestion of ammunition is a worldwide problem. We aimed to reveal the behavior and toxic effect of Pb caused by ingesting Pb shots in waterfowl. Four male, eight-week old Muscovy ducks (Cairina moschata) were given three Pb shots (approximately 240 mg in total) orally and then fed for 29 days after exposure, simulating a low-dose Pb exposure in wild waterfowl. During the breeding period, blood samples were collected 10 times, and fecal samples every day. Additionally, 22 fresh tissue and 6 bone samples were obtained from each duck through the dissection. Although there were no gross abnormalities, the maximum blood Pb concentration of each duck ranged from 0.6 to 3.7 mg/L, reaching a threshold concentration indicative of clinical symptoms (>0.5 mg/L). δ-aminolevulinic acid dehydratase declined one day after exposure and remained low throughout the feeding period. Hematocrit also tended to decrease, indicating signs of anemia. The highest Pb accumulation was observed in the bones, followed by the kidneys, intestinal tracts, and liver. High Pb accumulation in the bones, which are known to have a long Pb half-life, suggested that Pb would remain in the body and possibly affect bird health beyond 28 days after exposure. Gene expression analysis showed a significant increase in the expression of the toll-like receptor-3 gene, which is involved in virus discrimination in the liver, suggesting a disruption of the immune system. Microbiota analyses showed a correlation between the blood Pb concentration and the abundances of Lachnospiraceae and Ruminococcaceae, suggesting that Pb affects lipid metabolism. These results provide fundamental data on Pb exposure in wild birds and a new perspective on the damage such exposure causes.
  • 野見山桂, 山本恭央, 江口哲史, 西川博之, 水川葉月, 横山望, 市居修, 滝口満喜, 中山翔太, 池中良徳, 石塚真由美, 国末達也
    環境ホルモン学会研究発表会プログラム・要旨集 842 156490 - 156490 2022年06月03日 [査読有り]
     
    Companion animals are in close contact with the human surroundings, and there is growing concern about the effects of harmful substances on the health of pet cats. In this study, we investigated the potential health effects of organohalogen compounds (OHCs) on thyroid hormone (TH) homeostasis and metabolomics in Japanese pet cats. There was a significant negative correlation between concentrations of several contaminants, such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hydroxylated PCBs (OH-PCBs), hydroxylated PBDEs (OH-PBDEs), and THs in cat serum samples. These results suggested that exposure to OHCs causes a decrease in serum TH levels in pet cats. In this metabolomics study, each exposure level of parent compounds (PCBs and PBDEs) and their hydroxylated compounds (OH-PCBs and OH-PBDEs) were associated with their own unique primary metabolic pathways, suggesting that parent and phenolic compounds exhibit different mechanisms of action and biological effects. PCBs were associated with many metabolic pathways, including glutathione and purine metabolism, and the effects were replicated in in-vivo cat PCB administration studies. These results demonstrated that OHC exposure causes chronic oxidative stress in pet cats. PBDEs were positively associated with alanine, aspartate, and glutamate metabolism. Due to the chronic exposure of cats to mixtures of these contaminants, the combination of their respective metabolic pathways may have a synergistic effect.
  • Shinsaku Nakamura, Toshifumi Igarashi, Yoshitaka Uchida, Mayumi Ito, Kazuyo Hirose, Tsutomu Sato, Walubita Mufalo, Meki Chirwa, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Minerals 12 5 2022年05月 [査読有り]
     
    Effects of the water content of ground surface on windborne lead (Pb) dispersion from the zinc (Zn) leach residue site at the Kabwe mine, Zambia, were simulated. The Pb-bearing Zn plant leach residue site was selected as the source of the dispersion, and water conditions of the surface of the source were evaluated by the modified normalized difference water index (MNDWI) under the actual weather conditions in the year 2019. The MNDWI was calculated based on Sentinel-2 datasets, which were acquired in the year 2019. The index was used for monitoring the surface condition of the source necessary for simulating Pb dispersion, because the higher surface water content reduces the intensity of windborne source. The results showed that the wind speeds and directions had huge impacts on Pb dispersion when the MNDWI had negative values, and that the dispersion was inhibited when the MNDWI had positive values. These indicate that the water content of the surface is sensitive to dispersion, and that MNDWI is an effective parameter that expresses the source strength.
  • Given Moonga, Moses N Chisola, Ursula Berger, Dennis Nowak, John Yabe, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka, Stephan Bose-O'Reilly
    Environmental research 207 112646 - 112646 2022年05月01日 [査読有り]
     
    BACKGROUND: Communities around Kabwe, Zambia are exposed to lead due to deposits from an old lead (Pb) and zinc (Zn) mining site. Children are particularly more vulnerable than adults, presenting with greatest risk of health complications. They have increased oral uptake due to their hand to mouth activities. Spatial analysis of childhood lead exposure is useful in identifying specific areas with highest risk of pollution. The objective of the current study was to use a geospatial approach to investigate spatial clustering and hotspots of blood lead levels in children within Kabwe. METHODS: We analysed existing data on blood lead levels (BLL) for 362 children below the age of 15 from Kabwe town. We used spatial autocorrelation methods involving the global Moran's I and local Getis-Ord Gi*statistic in ArcMap 10.5.1, to test for spatial dependency among the blood lead levels in children using the household geolocations. RESULTS: BLL in children from Kabwe are spatially autocorrelated with a Moran's Index of 0.62 (p < 0.001). We found distinct hotspots (mean 51.9 μg/dL) in communities close to the old lead and zinc-mining site, lying on its western side. Whereas coldspots (mean 7 μg/dL) where observed in areas distant to the mine and traced on the eastern side. This pattern suggests a possible association between observed BLL and distance from the abandoned lead and zinc mine, and prevailing winds. CONCLUSION: Using geocoded data for households, we found clustering of childhood blood lead and identified distinct hotspot areas with high lead levels for Kabwe town. The geospatial approach used is especially valuable in resource-constrained settings like Zambia, where the precise identification of high risk locations allows for the initiation of targeted remedial and treatment programs.
  • So Shinya, Mariko Sashika, Miku Minamikawa, Tetsuji Itoh, Yared Beyene Yohannes, Shouta M M Nakayama, Mayumi Ishizuka, Collins Nimako, Yoshinori Ikenaka
    Environmental toxicology and chemistry 41 8 1865 - 1874 2022年04月22日 [査読有り]
     
    Toxicological effects of neonicotinoid insecticides (NNIs) have been reported for mammals, such as humans, rats, and mice. However, there are limited reports on their toxic effects on wild mammals. To predict NNI-induced toxic effects on wild mammals, it is necessary to determine the exposure levels and metabolic ability of these species. We considered that raccoons could be an animal model for evaluating NNI-induced toxicities on wildlife because they live near agricultural fields and eat crops treated with NNIs. The objective of the present study was to estimate the effects of NNI exposure on wild raccoons. Urinary concentrations of NNI compounds (n = 59) and cytochrome P450-dependent metabolism of NNIs (n = 3) were evaluated in wild raccoons captured in Hokkaido, Japan, in 2020. We detected either one of the six NNIs or one metabolite, including acetamiprid, imidacloprid, clothianidin, dinotefuran, thiacloprid, thiamethoxam, and desmethyl-acetamiprid in 90% of raccoons (53/59); the average cumulative concentration of the seven NNI compounds was 3.1 ng/ml. The urinary concentrations were not much different from those reported previously for humans. Furthermore, we performed an in vitro assessment of the ability of raccoons to metabolize NNIs using hepatic microsomes. The amounts of NNI metabolites were measured using liquid chromatography-electrospray ionization-tandem mass spectrometry and compared with those in rats. Raccoons showed much lower metabolic ability; the maximum velocity/Michaelis-Menten constant (Vmax /Km ) values for raccoons were one-tenth to one-third of those for rats. For the first time, we show that wild raccoons could be frequently exposed to NNIs in the environment, and that the cytochrome P450-dependent metabolism of NNIs in the livers of raccoons might be low. Our results contribute to a better understanding of the effects of NNIs on raccoons, leading to better conservation efforts for wild mammals. Environ Toxicol Chem 2022;00:1-10. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
  • Golden Zyambo, John Yabe, Kaampwe Muzandu, Ethel M'kandawire, Kennedy Choongo, Andrew Kataba, Kenneth Chawinga, Allan Liazambi, Shouta M M Nakayama, Hokuto Nakata, Mayumi Ishizuka
    International journal of environmental research and public health 19 8 2022年04月14日 [査読有り]
     
    Lead (Pb) contamination in the environment affects both humans and animals. Chronic exposure to Pb via dietary intake of animal products such as milk from contaminated areas poses a health risk to consumers; therefore, the present study investigated Pb contamination in cow milk and its health risk impact on humans through consumption of milk from cattle reared in the proximity of a Pb-Zn mine in Kabwe, Zambia. Fresh milk samples were collected from cows from Kang'omba (KN), Kafulamse (KF), Mpima (MP), Mukobeko (MK), and Munga (MN) farming areas. Pb determination was performed using Graphite Flame Absorption Atomic Spectrophotometry (GFAAS). Cow milk Pb levels showed different concentration patterns according to season, distance, and location of the farms from the Pb-Zn mine. The overall mean Pb levels were ranged 0.60-2.22 µg/kg and 0.50-4.24 µg/kg in the wet and dry seasons, respectively. The mean Pb concentration, chronic daily intake (CDIs), target hazard quotients (THQs), and incremental lifetime cancer risk (ILCR) results obtained were all within the permissible limits of 20 µg/kg, 3 and 12.5 µg/kg-BW/day, <1 and 10-4 to10-6, respectively. In conclusion, although Pb was detected in milk from cows reared in Kabwe, the health risk effects of Pb exposure associated with the consumption of milk in both adults and children were negligible.
  • Kazuhiro Toyoda, Shota Nakano, Shunitz Tanaka, Kawawa Banda, Imasiku A. Nyambe, Tsuyoshi Ishikawa, Shouta Nakayama, Mayumi Ishizuka
    Applied Geochemistry 139 2022年04月 [査読有り]
     
    The town of Kabwe has been exposed to the most severe lead pollution due to mining activities in the 20th century. A large tailing (slag) hill containing over 1% of Pb is still standing within the mine's licensed area. We analysed the chemical composition and lead isotope ratios in seventeen shallow wells, five deep wells in the inhabitants' area, three ponds and three borehole wells in the area of the mine, and in the surrounding areas, we examined two samples from the soil's surface and nineteen 1-m deep core samples at each of the 15 sites. We found low dissolved Pb (<0.04 μg/L) but high particulate Pb concentrations (2–100 μg/L) in seventeen shallow groundwater samples (aquifer depth of ca. 10 meters). Five shallow wells exceeded the World Health Organization (WHO) guideline (10 μg/L) for total-Pb concentration. However, three of the five shallow wells had low dissolved Zn and sulphate ion concentrations (<1 μg/L; <50 mg/L), suggesting a low amount of Pb transfers through the aquifer. The isotopic water and soil samples data clarified that the Pb pollution in the shallow groundwaters is derived from the tailings deposit. Most of the shallow groundwater samples had negative cerium (Ce) anomaly in the rare earth element (REE) pattern, indicating contributions of colloidal transport from the dolomite aquifer in this area. However, PHREEQC modelling shows that migration by hydroxide colloids from the mining area does not explain the high particulate lead concentrations in the well water. The positive correlation between Pb/Ce and Pb/Al ratios in the particulates exhibited that the lead pollutants were derived from the aluminosilicates on the land. The estimated Pb contents in particulates in most shallow-well water were 700–2800 mg/L, and they distributed geographically similar to the Pb bulk concentration contour map of the surface soil. The analysis of the grain-size fractions in a 2-km transect soil demonstrated that Pb was eight times enriched in the silt fraction (<53 μm) than a very coarse sand fraction (1–2 mm). Therefore, we hypothesized that the particulates in the well water were mainly derived from the aeolian dust (>0.45 μm) at the well site. Further studies are required to examine the hypothesis.
  • Marthias Silwamba, Mayumi Ito, Naoki Hiroyoshi, Carlito Baltazar Tabelin, Ryota Hashizume, Tomoki Fukushima, Ilhwan Park, Sanghee Jeon, Toshifumi Igarashi, Tsutomu Sato, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Minerals 12 4 2022年04月 [査読有り]
     
    Zinc plant leach residues (ZPLRs), particularly those produced using old technologies, have both economic importance as secondary raw materials and have environmental impacts because they contain hazardous heavy metals that pose risks to human health and the environment. Therefore, the extraction and recovery of these metals from ZPLRs has both economic and environmental benefits. In this study, we investigated the removal of lead (Pb) and zinc (Zn) from ZPLRs by alkaline (NaOH) leaching and the concurrent cementation of dissolved Pb and Zn using aluminum (Al) metal powder. The effects of the leaching time, NaOH concentration, solid-to-liquid ratio (S/L), and dosage of Al metal powder on the extraction of Pb and Zn were investigated. Pb and Zn removal efficiencies increased with increasing NaOH concentrations and decreasing S/Ls. The Pb and Zn removal efficiencies were 62.2% and 27.1%, respectively, when 2.5 g/50 mL (S/L) of ZPLRs were leached in a 3 M NaOH solution for 30 min. The extraction of Pb and Zn could be attributed to the partitioning of these metals in relatively more mobile phases—water-soluble, exchangeable, and carbonate phases— in ZPLRs. Around 100% of dissolved Pb and less than 2% of dissolved Zn were cemented in leaching pulp when Al metal powder was added. Minerals in the solid residues, particularly iron oxides minerals, were found to suppress the cementation of extracted Zn in leaching pulp, and when they were removed by filtration, Zn was recovered by Al metal powder via cementation.
  • Collins Nimako, Takahiro Ichise, Hiroshi Hasegawa, Osei Akoto, Nathaniel O Boadi, Kumiko Taira, Kazutoshi Fujioka, Norikazu Isoda, Shouta M M Nakayama, Mayumi Ishizuka, Yoshinori Ikenaka
    Environment international 162 107169 - 107169 2022年04月 [査読有り]
     
    Neonicotinoid insecticides (NNIs) are a popular class of insecticides used in various pest management regimens worldwide. Biomonitoring studies continuously report high exposure rates of NNIs in various human populations across the globe. Yet, there is no validated countermeasure for combating the recent exponential rise in NNI exposure rates observed in human populations. The current study assessed the impacts of organic dietary interventions on NNI exposure rates in a Japanese population. A total of 103 volunteers were recruited into the study. Subjects were either served with Organic diets for 5 and 30 days or conventional diets. A total of 919 repeated urine samples were collected from the participants and then subjected to LC-MS/MS analysis to determine urinary concentrations of 7 NNIs parent compounds and an NNI metabolite. Eight NNIs were detected; with a decreasing detection frequency (%Dfs) pattern; desmethyl-acetamiprid (dm-ACE) (64.96%) > dinotefuran (52.12%), imidacloprid (39.61%) > clothianidin (33.95%) > thiamethoxam (28.51%) > acetamiprid (12.62%) > nitenpyram (5.33%) > thiacloprid (2.83%). Dinotefuran, dm-ACE, and clothianidin recorded the highest concentrations in the subjects. The %Df of NNIs in the 5-days or 30-days organic diet group were lower than those of the conventional diet consumers. The organic diet group showed lower rates of multiple NNI exposures than those of the conventional diet consumers. The mean and median cumulative levels of NNIs (median IMIeq) were significantly lower in the organic diet group than the conventional diet group (p < 0.0001). The estimated daily intakes (EDIs) of NNIs were higher in adults than children, but less than 1% of NNI cRfDs, except for clothianidin, which exhibited a %cRfD of 1.32 in children. Compared to the conventional diet group, the 5- and 30-day organic dietary intervention showed drastic reductions in NNI EDIs. Findings from the present study give credence to organic dietary interventions as potential ameliorative strategies for NNI exposure rates in human populations.
  • Anri Hirai, Shouta Sugio, Collins Nimako, Shouta M M Nakayama, Keisuke Kato, Keisuke Takahashi, Koji Arizono, Tetsushi Hirano, Nobuhiko Hoshi, Kazutoshi Fujioka, Kumiko Taira, Mayumi Ishizuka, Hiroaki Wake, Yoshinori Ikenaka
    Scientific reports 12 1 5114 - 5114 2022年03月24日 [査読有り]
     
    Neonicotinoid pesticides are a class of insecticides that reportedly have harmful effects on bees and dragonflies, causing a reduction in their numbers. Neonicotinoids act as neuroreceptor modulators, and some studies have reported their association with neurodevelopmental disorders. However, the precise effect of neonicotinoids on the central nervous system has not yet been identified. Herein, we conducted in vivo Ca2+ imaging using a two-photon microscope to detect the abnormal activity of neuronal circuits in the brain after neonicotinoid application. The oral administration of acetamiprid (ACE) (20 mg/kg body weight (BW) in mature mice with a quantity less than the no-observed-adverse-effect level (NOAEL) and a tenth or half of the median lethal dose (LD50) of nicotine (0.33 or 1.65 mg/kg BW, respectively), as a typical nicotinic acetylcholine receptor (nAChR) agonist, increased anxiety-like behavior associated with altered activities of the neuronal population in the somatosensory cortex. Furthermore, we detected ACE and its metabolites in the brain, 1 h after ACE administration. The results suggested that in vivo Ca2+ imaging using a two-photon microscope enabled the highly sensitive detection of neurotoxicant-mediated brain disturbance of nerves.
  • Hiroshi Ishikawa, Mayuko Otsuki, Tsutomu Tamura, Kenji Konishi, Takaharu Bando, Mayumi Ishizuka, Yoshinori Ikenaka, Shouta M.M. Nakayama, Yoko Mitani
    Polar Science 31 2022年03月 [査読有り]
     
    The Antarctic minke whale (Balaenoptera bonaerensis) is a seasonal migrator that feeds mainly on Antarctic krill at higher latitudes during the summer and travels to lower latitudes to breed in winter. A previous study using δ13C and δ15N values of baleen plates showed that pregnant Antarctic minke whales feed on Antarctic krill in the foraging season, with less feeding during the breeding season. However, long-term changes in the habitat use and diet of males remain unknown. In this study, we estimated the foraging habits of nine mature male Antarctic minke whales using the stable isotope signatures of baleen plates. From Bayesian stable isotope mixing models, it was found that Antarctic krill was the predominant prey of male whales, and prey species in lower latitudes were rarely incorporated into the baleen plates. This result is consistent with that of female Antarctic minke whales. Eight whales showed at least one oscillation in δ13C and δ15N values, whereas one whale (AM246) showed no variation in δ15N values. This possibly indicates that AM246 remained in the Antarctic water year-round. Our results suggest multiple migration patterns of male Antarctic minke whales.
  • Andrew Kataba, Tarryn L Botha, Shouta M M Nakayama, Yared B Yohannes, Yoshinori Ikenaka, Victor Wepener, Mayumi Ishizuka
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 252 109215 - 109215 2022年02月 [査読有り]
     
    Early developmental stages of aquatic organisms including fish are inherently vulnerable to lead (Pb) and other water metal contaminants. However, reports on the deleterious effects of environmentally relevant Pb levels are limited. To this end, we exposed 2.5 h post fertilization (hpf) old zebrafish (Danio rerio) embryos to a range of Pb concentrations encompassing environmentally relevant levels (1, 10, 25, 50 and 100 μg/L Pb) until 96 hpf. Exposure negatively impacted the development and survival of zebrafish embryos by inducing embryo coagulation related mortalities in a concentration-dependent manner. At 24 hpf, the highest level of exposure (100 μg/L Pb) had impaired embryo activity characterized by reduced burst activity and the number of movements per minute made by embryos. At 72 hpf, newly hatched larvae exhibited adverse cardiovascular effects (100 μg/L Pb group) and neuromuscular effects (50 and 100 μg/L Pb groups). The antioxidant system dysregulation evidenced by downregulation of catalase, and upregulation of mRNA expression of glutathione S-transferase and cytochrome oxidase subunit I were observed. The pro-apoptotic tumour protein P53 (TP53) and the anti-apoptotic B cell lymphoma -2 (Bcl-2) mRNA expression levels were also affected. The former was downregulated across exposed groups and the latter was upregulated and downregulated in the groups with Pb concentrations less than 50 μg/L Pb and downregulated in 50 μg/L Pb, respectively. These findings suggest that Pb within environmentally relevant levels may be deleterious to developing zebrafish.
  • Hokuto Nakata, Akifumi Eguchi, Shouta M M Nakayama, John Yabe, Kaampwe Muzandu, Yoshinori Ikenaka, Chisato Mori, Mayumi Ishizuka
    International journal of environmental research and public health 19 1 2022年01月04日 [査読有り]
     
    Lead poisoning is often considered a traditional disease; however, the specific mechanism of toxicity remains unclear. The study of Pb-induced alterations in cellular metabolic pathways is important to understand the biological response and disorders associated with environmental exposure to lead. Metabolomics studies have recently been paid considerable attention to understand in detail the biological response to lead exposure and the associated toxicity mechanisms. In the present study, wild rodents collected from an area contaminated with lead (N = 18) and a control area (N = 10) were investigated. This was the first ever experimental metabolomic study of wildlife exposed to lead in the field. While the levels of plasma phenylalanine and isoleucine were significantly higher in a lead-contaminated area versus the control area, hydroxybutyric acid was marginally significantly higher in the contaminated area, suggesting the possibility of enhancement of lipid metabolism. In the interregional least-absolute shrinkage and selection operator (lasso) regression model analysis, phenylalanine and isoleucine were identified as possible biomarkers, which is in agreement with the random forest model. In addition, in the random forest model, glutaric acid, glutamine, and hydroxybutyric acid were selected. In agreement with previous studies, enrichment analysis showed alterations in the urea cycle and ATP-binding cassette transporter pathways. Although regional rodent species bias was observed in this study, and the relatively small sample size should be taken into account, the present results are to some extent consistent with those of previous studies on humans and laboratory animals.
  • Collins NIMAKO, Anri HIRAI, Takahiro ICHISE, Shouta M.M. NAKAYAMA, Mayumi ISHIZUKA, Yoshinori IKENAKA
    日本毒性学会学術年会 49.1 P-108  日本毒性学会 2022年 
    Organic farming practices are generally considered potential countermeasures against pesticide exposure in human populations. However, little is known if current organic interventional measures adopted in Japan can mitigate neonicotinoid (NNI) exposures or otherwise. The current validates the efficacies of organic dietary interventions in ameliorating NNIs exposures within the Japanese population. Firstly, 103 Japanese volunteers were recruited and fed strictly with either organic diets for 5 or 30 days or with conventional diets. Then the exposure rates of 8 NNIs were determined in the population, by LC-MS/MS analysis. After analysis, 8 NNIs were detected in the target population; but the detection rates were far lower in the organic diet consumers compared to conventional diet consumers. The organic dietary intervention drastically reduced the cumulative levels and the daily intake rates of NNIs in the Japanese population. Subsequently, the residual levels of NNIs were determined in organic and conventional green tea leaves produced in Japan. Seven NNIs compounds and one NNI metabolite were detected in tea leaves cultivated by strict organic farming methods. However, the detection rates of NNIs were relatively lower in organic tea leaves than conventional tea leaves. Moreover, the daily exposure rates of NNIs through green tea consumption were far lower for organic tea leaves than conventional tea leaves. These findings ultimately show that the adoption of organic farming interventions may offer optimum ameliorative outcomes on NNI exposure rates Japanese population.
  • Nana Ushine, Osamu Kurata, Yoshikazu Tanaka, Shouta M.M Nakayama, Mayumi Ishizuka, Takuya Kato, Shin-Ichi Hayama
    Avian Conservation and Ecology 17 2 2022年
  • Yoshikazu Furuta, Fumihito Miura, Takahiro Ichise, Shouta M M Nakayama, Yoshinori Ikenaka, Tuvshinzaya Zorigt, Mai Tsujinouchi, Mayumi Ishizuka, Takashi Ito, Hideaki Higashi
    PloS one 17 3 e0265225  2022年 [査読有り]
     
    5-Methylcytosine is one of the major epigenetic marks of DNA in living organisms. Some bacterial species possess DNA methyltransferases that modify cytosines on both strands to produce fully-methylated sites or on either strand to produce hemi-methylated sites. In this study, we characterized a DNA methyltransferase that produces two sequences with different methylation patterns: one methylated on both strands and another on one strand. M.BatI is the orphan DNA methyltransferase of Bacillus anthracis coded in one of the prophages on the chromosome. Analysis of M.BatI modified DNA by bisulfite sequencing revealed that the enzyme methylates the first cytosine in sequences of 5'-GCAGC-3', 5'-GCTGC-3', and 5'-GCGGC-3', but not of 5'-GCCGC-3'. This resulted in the production of fully-methylated 5'-GCWGC-3' and hemi-methylated 5'-GCSGC-3'. M.BatI also showed toxicity when expressed in E. coli, which was caused by a mechanism other than DNA modification activity. Homologs of M.BatI were found in other Bacillus species on different prophage like regions, suggesting the spread of the gene by several different phages. The discovery of the DNA methyltransferase with unique modification target specificity suggested unrevealed diversity of target sequences of bacterial cytosine DNA methyltransferase.
  • Fernando Capela E Silva, Ana Catarina Sousa, Manuel Ramiro Pastorinho, Hazuki Mizukawa, Mayumi Ishizuka
    Frontiers in veterinary science 9 891483 - 891483 2022年 [査読有り]
  • Kumiko Taira, Tomonori Kawakami, Sujithra Kaushaliya Weragoda, H M Ayala S Herath, Yoshinori Ikenaka, Kazutoshi Fujioka, Madhubhani Hemachandra, Nirmalie Pallewatta, Yoshiko Aoyama, Mayumi Ishizuka, Jean-Marc Bonmatin, Makiko Komori
    Scientific reports 11 1 22484 - 22484 2021年11月18日 [査読有り]
     
    Neonicotinoids are systemic insecticides used since the 1990's , that possess renal tubular toxicity. We conducted a field-based descriptive study in the North Central Dry-zone of Sri Lanka, where chronic kidney disease (CKD) of unknown etiology has been increasing since the 1990's. To elucidate the relationship between renal tubular dysfunctions and urinary neonicotinoids concentrations, we collected spot urine samples from15 CKD patients, 15 family members, and 62 neighbors in 2015, analyzed two renal tubular biomarkers, Cystatin-C and L-FABP, quantified seven neonicotinoids and a metabolite N-desmethyl-acetamiprid by LC-MS/MS; and we investigated their symptoms using a questionnaire. Cystatin-C and L-FABP had a positive correlation (p < 0.001). N-Desmethyl-acetamiprid was detected in 92.4% of the urine samples, followed by dinotefuran (17.4%), thiamethoxam (17.4%), clothianidin (9.8%), thiacloprid and imidacloprid. Dinotefuran and thiacloprid have never been registered in Sri Lanka. In High Cystatin-C group (> 70 μg/gCre, n = 7), higher urinary concentration of dinotefuran (p = 0.009), and in Zero Cystatin-C group (< LOQ, n = 7), higher N-desmethyl-acetamiprid (p = 0.013), dinotefuran (p = 0.049), and thiacloprid (p = 0.035), and more complaints of chest pains, stomachache, skin eruption and diarrhea (p < 0.05) were found than in Normal Cystatin-C group (n = 78). Urinary neonicotinoids may be one of the potential risk factors for renal tubular dysfunction in this area.
  • Walubita Mufalo, Pawit Tangviroon, Toshifumi Igarashi, Mayumi Ito, Tsutomu Sato, Meki Chirwa, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Toxics 9 10 2021年10月04日 [査読有り]
     
    Zambia's Kabwe mine wastes (KMWs) are responsible for contaminating the surrounding soil and dust in the Kabwe district. Unfortunately, these wastes arise from the historical mining activities of lead (Pb) and Zinc (Zn), which lacked adequate waste management strategies. As a result, potentially toxic elements (PTEs) (Pb and Zn) spread across the Kabwe district. To assess the soil pollution derived from previous mining activities, we studied topsoil samples (n = 8) from the school playground soils (SPs). In this study, the degree of contamination, geochemical partitioning, and leachability, coupled with the release and retention of Pb and Zn, were studied. The SPs were classified as extremely enriched (EF > 40) and contaminated with Pb (Igeo > 5). On average, Pb (up to 89%) and Zn (up to 69%) were bound with exchangeable, weak acid-soluble, reducible and oxidizable phases, which are considered as 'geochemically mobile' phases in the environment. The leachates from the soils (n = 5) exceeded the Zambian standard (ZS: 190:2010) for Pb in potable drinking water (Pb < 0.01 mg/L). Furthermore, the spatial distribution of Pb and Zn showed a significant reduction in contents of Pb and Zn with the distance from the mine area.
  • Jumpei Yamazaki, Haruya Toyomaki, Shouta M.M. Nakayama, John Yabe, Kaampwe Muzandu, Jaroslav Jelinek, Shoko Yokoyama, Yoshinori Ikenaka, Mitsuyoshi Takiguchi, Mayumi Ishizuka
    Environmental Pollution 286 117229 - 117229 2021年10月01日 [査読有り]
     
    Lead (Pb) is a heavy metal that has been proven to be toxic to both animals and humans. Genom-wide DNA methylation in domestic dogs exposed to high levels of Pb in Kabwe, Zambia was analyzed in this study. Using next-generation sequencing on samples from 20 domestic dogs (mean blood Pb concentration: 43.6 μg/dL and 7.2 μg/dL in the high and low exposure groups), a digital restriction enzyme analysis of methylation was performed to identify the genomic locations of differentially methylated CpG sites. A validation study on an additional 20 dogs followed (blood Pb concentration: 4.9–29.7 μg/dL). The cluster analysis resolved two broad clusters indicating high and low Pb exposure. The study identified 827 (1.2%) CpG sites with differences in methylation (101 CpG sites were hypermethylated in the low exposure group and 726 were hypermethylated in the high exposure group). The sites corresponded to 26 genes with differentially methylated CpG sites at their promoter regions, including the NGF gene. The methylation of four CpG sites was validated using bisulfite pyrosequencing. The results indicate that aberrant hypermethylation is prevalent in dogs exposed to Pb. The altered DNA methylation of the genes identified in this study contributes to a greater understanding of the epigenetic changes caused by Pb exposure and highlights novel biomarker discoveries across species.
  • Haruya Toyomaki, John Yabe, Shouta M.M. Nakayama, Yared B. Yohannes, Kaampwe Muzandu, Tiza Mufune, Hokuto Nakata, Yoshinori Ikenaka, Takeshi Kuritani, Mitsuhiro Nakagawa, Kennedy Choongo, Mayumi Ishizuka
    Environmental Pollution 286 117456 - 117456 2021年10月01日 [査読有り]
     
    Lead (Pb) poses a serious public health concern. Breastmilk may be a possible source of Pb exposure in infants, as Pb can be transferred from the maternal blood to breastmilk. The present study was undertaken to determine the Pb exposure and the contribution of lactation as one of the exposure pathways to infants in a Pb mining area, Kabwe, Zambia. Blood, breastmilk and infants' feces were collected from 418 pairs of infants and mothers. The Pb concentrations, isotope ratios in the samples, and biochemistry in mothers' plasma were analyzed. The overall mean of blood lead levels (BLLs) in infants and mothers were 18.0 and 11.3 μg/dL, respectively. High Pb concentration in breastmilk (range: 0.4–51.9, mean: 5.3 μg/L) above the WHO acceptable level between 2 and 5 μg/L were found and could be one of the sources of Pb exposure in infants. The Pb isotope ratios in infants’ feces were the most similar to Pb ratios in the soil samples. The results suggest that infants are also exposed to Pb from the environment. Pb exposure in infants through breastfeeding and soil ingestion could potentially exceed daily intake of Pb which causes neurodevelopmental toxicity. In contrast to the high BLLs in mothers, the plasma biochemical profiles of most analyzed parameters were interestingly within, or close to, the standard reference values. Our data suggest that environmental remediation is urgently needed to reduce the Pb exposure in infants and mothers from the environment in Kabwe in parallel with chelation therapy.
  • Noboru Sasaki, Thandar Oo, Yoshikazu Yasuda, Takahiro Ichise, Noriyuki Nagata, Nozomu Yokoyama, Kazuyoshi Sasaoka, Keitaro Morishita, Shouta Mm Nakayama, Mayumi Ishizuka, Kensuke Nakamura, Mitsuyoshi Takiguchi, Yoshinori Ikenaka
    The Journal of veterinary medical science 83 11 1634 - 1642 2021年09月17日 [査読有り]
     
    We developed an analytical method using an on-line column-switching liquid chromatography with triple quadrupole mass spectrometry (LC/MS/MS) for quantifying multiple steroids in serum. Using the developed method, we evaluated the serum concentration of nine steroids (cortisol, corticosterone, cortisone, 11-deoxycortisol, 21-deoxycortisol, deoxycorticosterone, progesterone, 17α-OH-progesterone and aldosterone) in dogs with hyperadrenocorticism (HAC). Serum was mixed with stable isotope internal standards and thereafter purified by the automated column-switching system. The limit of detection ranged 2-16 pg/ml for nine steroids. In the baseline samples, five steroids (cortisol, corticosterone, cortisone, 11-deoxycortisol, and 17α-OH-progesterone) were detected in all dogs. The concentrations of cortisone, 11-deoxycortisol, and 17α-OH-progesterone in dogs with HAC (n=19) were significantly higher those in dogs without HAC (n=15, P<0.02). After the adrenocorticotropic hormone stimulation test, six steroids (cortisol, corticosterone, cortisone, 11-deoxycortisol, 17α-OH-progesterone, and deoxycorticosterone) were above the limit of quantification in all dogs. Cortisol, corticosterone, cortisone, and deoxycorticosterone concentrations of dogs with HAC were significantly higher than those of dogs without HAC (P<0.02). In addition, 11-deoxycortisol and 17α-OH-progesterone concentration was higher in dogs with HAC than in dogs without HAC (P=0.044 and P=0.048, respectively). The on-line column-switching LC/MS/MS would be feasible for measuring multiple steroids in dog serum. The results suggest that cortisone, 11-deoxycortisol, and 17α-OH-progesterone would be related to HAC. Further studies are warranted to assess the clinical feasibility of steroid profile in dogs with HAC.
  • Andrew Kataba, Shouta M M Nakayama, Yared Beyene Yohannes, Haruya Toyomaki, Hokuto Nakata, Yoshinori Ikenaka, Mayumi Ishizuka
    The Journal of veterinary medical science 83 11 1674 - 1685 2021年09月16日 [査読有り]
     
    Lead (Pb) exposure occurs together with other metals including zinc (Zn). This study investigated the impact of Zn on Pb tissue accumulation and Pb-induced toxicities. Animals (n = 6 rats per group) were exposed to lead acetate (PbAc) or a combination of PbAc and zinc acetate (ZnAc) under the following groups: control (deionized water), low PbAc [12 mg/kg PbAc (3 mg PbAc/rat/day)], low PbAc-ZnAc [12 mg/kg PbAc (3 mg PbAc/rat/day) + 0.2 mg ZnAc/rat/48 hr], high PbAc [120 mg/kg (30 mg PbAc/rat/day)], and high PbAc-ZnAc [120 mg/kg (30 mg PbAc/rat/day) + 1 mg ZnAc/rat/48 hr] for 8 weeks. A significant reduction in body weight gain was observed in the high PbAc group relative to the control group. Muscles and testes both had reduced and increased Pb uptake in low PbAc-ZnAc and high PbAc-ZnAc groups compared to PbAc only groups, respectively. Bone Pb levels in the high PbAc-ZnAc group were lower than the high PbAc group. Zinc co-administration attenuated Pb-induced inhibition of delta aminolaevulinic acid dehydratase enzyme and enhanced catalase enzyme activity at a high level of exposure. Moreover, ZnAc seems to have minimized the effects of Pb-induced mRNA dysregulation in antioxidant and antiapoptotic enzymes encoding genes. Heme oxygenase-1 was downregulated in the kidney and brain in the low PbAc group. Liver glutathione peroxidase and thioredoxin reductase-1 were downregulated in the high PbAc group. These findings suggest that zinc co-administration with lead may partially mitigate against Pb-induced toxicities.
  • Hokuto Nakata, Harukazu Tohyama, Wakako Fujita, Shouta M.M. Nakayama, Mayumi Ishizuka, John Yabe, Nosiku S. Munyinda, Doreen Sakala, Kennedy Choongo, Shojiro Yamasaki, Natsumi Nagai, Takahiko Yoshida, Takeshi Saito
    Chemosphere 279 130490 - 130490 2021年09月 [査読有り]
     
    Kabwe is a mining town in Zambia that has been ranked among “the ten most polluted places in the world” with previous findings of serious lead (Pb) pollution. In this study, we aim to examine the impact of childhood Pb poisoning on the health-related quality of life (HRQoL) of mothers in Kabwe. The HRQoL was assessed using the Short-Form 36 survey for 404 mothers coming from residences in 40 randomly selected standard enumeration areas (SEAs). Blood lead levels (BLLs) of the household members including the mothers themselves were measured. We found a significant positive correlation between the BLLs of the mothers and their children (R = 0.6385, p < 0.0001), while the BLLs of preschool-aged and school-aged children were significantly higher than those of their mothers and fathers. Using the data sets containing the BLLs of the household members, the age of the mothers, the household income, and the household SEA, we performed stepwise multiple linear regression analyses. The results showed significant negative associations between the representative BLL of household children and the BLL of preschool-aged children with the vitality and mental health scores of their mothers. Additionally, the BLL of school-aged children was only significantly associated with the mental health score of their mothers. By contrast, there was a significant negative association between the BLLs of the mothers with the social role functioning score. This suggests that elevated BLLs in children have a negative impact on the mental health conditions of their mothers regardless of the mothers’ BLL.
  • Akiko Shoji, Kyle H. Elliott, Yutaka Watanuki, Niladri Basu, Shannon Whelan, Joshua Cunningham, Scott Hatch, Hazuki Mizukawa, Shouta M.M. Nakayama, Yoshinori Ikenaka, Mayumi Ishizuka, Stéphane Aris-Brosou
    Environmental Pollution 284 117035 - 117035 2021年09月01日 [査読有り]
     
    Seabirds are widely used as indicators of marine pollution, including mercury (Hg), because they track contaminant levels across space and time. However, many seabirds are migratory, and it is difficult to understand the timing and location of their Hg accumulation. Seabirds may obtain Hg thousands of kilometers away, during their non-breeding period, and deposit that Hg into their terrestrial breeding colonies. We predicted that Hg concentration in rectrices reflects exposure during the previous breeding season, in body feathers reflects non-breeding exposure, and in blood collected during breeding reflects exposure during current breeding. To test this hypothesis, we measured total Hg concentration in these three tissues, which reflect different timepoints during the annual cycle of rhinoceros auklets (Cerorhinca monocerata) breeding on both sides of the North Pacific (Middleton Island in Alaska and Teuri Island in Hokkaido), and tracked their wintering movement patterns with biologging devices. We (i) identify the wintering patterns of both populations, (ii) examine Hg levels in different tissues representing exposure at different time periods, (iii) test how environmental Hg exposure during the non-breeding season affects bird contamination, and (iv) assess whether variation in Hg levels during the non-breeding season influences levels accumulated in terrestrial plants. Individuals from both populations followed a figure-eight looping migration pattern. We confirm the existence of a pathway from environmental Hg to plant roots via avian tissues, as Hg concentrations were higher in plants within the auklet colonies than at control sites. Hg concentrations of breast feathers were higher in Alaskan than in Japanese auklets, but Hg concentrations in rectrices and blood were similar. Moreover, we found evidence that tissues with different turnover rates could record local anthropogenic Hg emission rates of areas visited during winter. In conclusion, Hg was transported across thousands of kilometers by seabirds and transferred to local plants.
  • Collins Nimako, Yoshinori Ikenaka, Osei Akoto, Kazutoshi Fujioka, Kumiko Taira, Koji Arizono, Keisuke Kato, Keisuke Takahashi, Shouta M.M. Nakayama, Takahiro Ichise, Mayumi Ishizuka
    Journal of Chromatography A 1652 462350 - 462350 2021年08月30日 [査読有り]
     
    This study aimed to (i) develop a sensitive method for simultaneous detection and quantification of imidacloprid (IMI) and seven of its metabolites in tissue specimens, and to (ii) determine the biodistribution of the IMI compounds in tissues of C57BL/6J male mice; after exposure to 0.6 mg/kg bw/day of IMI (10% of no observable adverse effect level of IMI) through a powdered diet for 24 weeks. We successfully developed a method which was accurate (recoveries were ≥ 70% for most compounds), sensitive (LODs ≤ 0.47 ng/mL and LOQs ≤ 1.43 ng/mL were recorded for all detected compounds, R2 ≥ 0.99) and precise (RSDs ≤ 20%) for routine analysis of IMI and seven of its metabolites in blood and various tissue matrices. After bio-distributional analysis, IMI and five of its metabolites were detected in mice. Brain, testis, lung, kidney, inguinal white adipose tissue and gonadal white adipose tissue mainly accumulated IMI, blood and mesenteric white adipose tissue mainly accumulated IMI-olefin; liver mainly accumulated desnitro-IMI; pancreas predominately accumulated 4-hydroxy-IMI. The desnitro-dehydro-IMI and the desnitro-IMI metabolites recorded tissue-blood concentration ratios ≥ 1.0 for testis, brain, lung and kidney. The cumulative levels of the six detected IMI compounds (Σ6 IMI compounds) were found in the decreasing order: blood > testis > brain > kidney > lung > iWAT > gWAT > mWAT > liver > pancreas. Altogether, this study provided essential data needed for effective mechanistic elucidation of compound-specific adverse outcomes associated with chronic exposures to IMI in mammalian species.
  • Yared Beyene Yohannes, Shouta M M Nakayama, John Yabe, Haruya Toyomaki, Andrew Kataba, Hokuto Nakata, Kaampwe Muzandu, Yoshinori Ikenaka, Kennedy Choongo, Mayumi Ishizuka
    Environmental science and pollution research international 29 5 6622 - 6632 2021年08月28日 [査読有り]
     
    Interindividual genetic variations determine human's susceptibility to heavy metal-induced toxicity. Thus, we analyzed blood concentrations of lead (Pb) and cadmium (Cd) in 140 lead-exposed children. Genotyping of the glutathione S-transferase (GST) genes, GSTM1, GSTT1, and GSTP1 genes, was carried out to investigate their possible association with heavy metal concentrations and the risk of susceptibility to Pb toxicity. Exposure to both heavy metals was prevalent among the children. The blood Pb level ranged from 3.30 to 74.0 μg dL-1 with an average value of 26.8 μg dL-1 that is five times above its reference level. The average Cd level (0.22 μg L-1) was below its reference level. The metal-gene interaction showed positive correlation between GSTT1 null genotype and Pb and Cd levels (β = 0.11; p = 0.02 and β = 0.10; p = 0.01, respectively). More pronounced effects (β = 0.19; p < 0.01 and β = 0.25; p = 0.04) were found for the mixture of the three putative genes with blood Pb concentration. The susceptibility analysis using 10 μg dL-1 as blood Pb cutoff level showed a high risk of Pb toxicity (OR = 2.54; 95% CI: 1.02-6.32, p = 0.04) for children carrying the GSTP1 Ile/Val genotype. Further, the combined effect of GSTP1 Ile/Val with GSTT1 null genotype was more pronounced and showed an increased risk of susceptibility to Pb toxicity (OR = 11.7; 95% CI: 1.36-102.1, p = 0.02). In summary, this study suggests that GSTT1 null and GSTP1 Ile/Val genotypes are the main genetic factors, and individual and specific combinations of GSTP1 Ile/Val with GSTM1 and GSTT1 GST polymorphisms are associated with susceptibility to Pb toxicity.
  • Ryu Miura, Atsuko Ikeda-Araki, Toru Ishihara, Kunio Miyake, Chihiro Miyashita, Tamie Nakajima, Sumitaka Kobayashi, Mayumi Ishizuka, Takeo Kubota, Reiko Kishi
    Science of the Total Environment 783 147035 - 147035 2021年08月20日 [査読有り]
     
    Prenatal exposure to phthalates negatively affects the offspring's health. In particular, epigenetic alterations, such as DNA methylation, may connect phthalate exposure with health outcomes. Here, we evaluated the association of di-2-ethylhexyl phthalate (DEHP) exposure in utero with cord blood epigenome-wide DNA methylation in 203 mother-child pairs enrolled in the Hokkaido Study on Environment and Children's Health, using the Illumina HumanMethylation450 BeadChip. Epigenome-wide association analysis demonstrated the predominant positive associations between the levels of the primary metabolite of DEHP, mono(2-ethylhexyl) phthalate (MEHP), in maternal blood and DNA methylation levels in cord blood. The genes annotated to the CpGs positively associated with MEHP levels were enriched for pathways related to metabolism, the endocrine system, and signal transduction. Among them, methylation levels of CpGs involved in metabolism were inversely associated with the offspring's ponderal index (PI). Further, clustering and mediation analyses suggested that multiple increased methylation changes may jointly mediate the association of DEHP exposure in utero with the offspring's PI at birth. Although further studies are required to assess the impact of these changes, this study suggests that differential DNA methylation may link phthalate exposure in utero to fetal growth and further imply that DNA methylation has predictive value for the offspring's obesity.
  • Ryouta Torimoto, Chihiro Ishii, Hiroshi Sato, Keisuke Saito, Yukiko Watanabe, Kohei Ogasawara, Ayano Kubota, Takehisa Matsukawa, Kazuhito Yokoyama, Atsushi Kobayashi, Takashi Kimura, Shouta M.M. Nakayama, Yoshinori Ikenaka, Mayumi Ishizuka
    Environmental Pollution 283 117086 - 117086 2021年08月15日 [査読有り]
     
    Lead poisoning of wild birds by ingestion of lead ammunition occurs worldwide. Histopathological changes in organs of lead-intoxicated birds are widely known, and lead concentration of each organ is measurable using mass spectrometry. However, detailed lead localization at the suborgan level has remained elusive in lead-exposed birds. Here we investigated the detailed lead localization in organs of experimentally lead-exposed ducks and kites by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In both the ducks and kites, lead accumulated diffusely in the liver, renal cortex, and brain. Lead accumulation was restricted to the red pulp in the spleen. With regard to species differences in lead distribution patterns, it is noteworthy that intensive lead accumulation was observed in the arterial walls only in the kites. In addition, the distribution of copper in the brain was altered in the lead-exposed ducks. Thus, the present study shows suborgan lead distribution in lead-exposed birds and its differences between avian species for the first time. These findings will provide fundamental information to understand the cellular processes of lead poisoning and the mechanisms of species differences in susceptibility to lead exposure.
  • Shinsaku Nakamura, Toshifumi Igarashi, Yoshitaka Uchida, Mayumi Ito, Kazuyo Hirose, Tsutomu Sato, Walubita Mufalo, Meki Chirwa, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Minerals 11 8 2021年08月 
    Dispersion of lead (Pb) in mine wastes was simulated for reproducing Pb contamination of soil in Kabwe District, Zambia. Local weather data of year 2019 were monitored in situ and used for the simulations. The plume model, weak puff model, and no puff model were adopted for calculation of Pb dispersion under different wind conditions. The results showed that Pb dispersion from the Kabwe mine was directly affected by wind directions and speeds in the dry season, although it was not appreciably affected in the rainy season. This may be because the source strength is lower in the rainy season due to higher water content of the surface. This indicates that Pb dispersion patterns depend on the season. In addition, the distribution of the amount of deposited Pb-bearing soils around the mine corresponded to the distribution of Pb contents in soils. These results suggest that Pb contamination in soils primarily results from dispersion of fine mine wastes.
  • Collins Nimako, Yoshinori Ikenaka, Osei Akoto, Nesta Bortey-Sam, Takahiro Ichise, Shouta M.M. Nakayama, Kwadwo A. Asante, Kazutoshi Fujioka, Kumiko Taira, Mayumi Ishizuka
    Environmental Toxicology and Chemistry 40 8 2306 - 2318 2021年08月 [査読有り]
     
    Neonicotinoid insecticides (NNIs) are now popular in many agricultural systems across Africa; however, the extent of human exposures to NNIs in African countries is scarcely reported. The present study evaluates neonicotinoid exposures in the consumer population of Kumasi, a cosmopolitan city in Ghana. A total of 75 human urine samples were collected from healthy volunteers (nonfarmers, aged 13–80 yr) and analyzed with a liquid chromatography electrospray ionization tandem mass spectrometry system. Seven NNIs and 3 NNI metabolites were detected in the following pattern (frequency, median concentration, maximum concentration): N-dm-acetamiprid (94.7%, 0.41 µg/L, 8.79 µg/L) > imidacloprid (70.7%, 0.15 µg/L, 211.62 µg/L) > N-(6-chloro-3-pyridylmethyl)-N-ethyl-N′-methylformamidine (62.2%, 0.43 µg/L, 53.85 µg/L) > 2-[N-(6-chloro-3-pyridylmethyl)-N-ethylamino]-2-(methylimino)acetic acid (56.8%, 0.10 µg/L, 3.53 µg/L) > clothianidin (40%, >limit of quantification [LOQ], 0.45 µg/L) > nitenpyram (18.7%, >LOQ, 0.14 µg/L) ≈ thiamethoxam (18.7%, >LOQ, 0.21 µg/L) > dinotefuran (12.0%, >LOQ, 1.01 µg/L) > acetamiprid (2.7%, >LOQ, 0.08 µg/L) ≈ thiacloprid (2.7%, >LOQ, 0.14 µg/L). Approximately 92% of the subjects were found to be exposed to multiple neonicotinoids simultaneously. The mean, median, and maximum imidacloprid equivalent of the relative potency factor of NNIs were found to be 1.6, 0.5, and 22.52, respectively. The median estimated daily intakes of acetamiprid, imidacloprid, and nitenpyram were 0.47, 1.27, and 0.02 µg/kg/d for females and 0.91, 0.66, and 0.08 µg/kg/d for males, respectively. The maximum daily intakes of all the NNIs were <1% of their chronic reference doses (cRfDs), except for imidacloprid and thiacloprid which recorded maximum daily intakes corresponding to 17.97 and 8.28% of cRfDs, respectively. To the best of our knowledge, the present study is the first biomonitoring report on neonicotinoid insecticides in Africa. Environ Toxicol Chem 2021;40:2306–2318. © 2021 SETAC.
  • 二光子顕微鏡を用いた、ニコチン性アセチルコリン受容体アゴニストによる脳機能障害の検出
    平井 杏梨, 杉尾 翔太, Nimako Collins, 中山 翔太, 加藤 恵介, 高橋 圭介, 有薗 幸司, 平野 哲史, 星 信彦, 藤岡 一俊, 平 久美子, 石塚 真由美, 和氣 弘明, 池中 良徳
    The Journal of Toxicological Sciences 46 Suppl. S102 - S103 2021年07月
  • Nico J. Wolmarans, Lieven Bervoets, Ruan Gerber, Yared Beyene Yohannes, Shouta MM Nakayama, Yoshinori Ikenaka, Mayumi Ishizuka, Patrick Meire, Nico J. Smit, Victor Wepener
    Chemosphere 274 129956 - 129956 2021年07月 [査読有り]
     
    The threat to wildlife from chemical exposure exists regardless of the presence of conservation boundaries. An issue exacerbated by the use of environmentally persistent insecticides for vector control and long-range transport of legacy persistent organic pollutants. In this comparative study between two important conservation regions in South Africa, Kruger National Park (KNP) and Ndumo Game Reserve (NGR), we assessed organochlorine pesticide (OCP) accumulation in several anuran species collected from within the conservation regions. The two conservation regions differ in size and subsequent proximity of collection sites to OCP input sources. Detectable concentrations of OCPs were present in ∼ half the frogs analysed from KNP and ∼all frogs from NGR and total OCP loads were similar between regions, where measured in the same species. The OCP profiles in KNP frogs were representative of legacy pesticides likely introduced via long-range transport, whereas NGR profiles showed influence of current use of DDT consistent with close proximity to sources. This indicates amphibians can accumulate OCPs within conservation regions and that the exposure of non-target organisms inside conservation regions to current use pesticides has a strong association with proximity to sources. These results serve to inform conservation management decision making with regard to the non-target organism effects of chemical interventions such as vector control pesticide use in and around conservation regions.
  • Tomohiro Suzuki, Anri Hirai, Kraisiri Khidkhan, Collins Nimako, Takahiro Ichise, Kazuki Takeda, Hazuki Mizukawa, Shouta M.M. Nakayama, Kei Nomiyama, Nobuhiko Hoshi, Mizuki Maeda, Tetsushi Hirano, Kazuyoshi Sasaoka, Noboru Sasaki, Mitsuyoshi Takiguchi, Mayumi Ishizuka, Yoshinori Ikenaka
    Pesticide Biochemistry and Physiology 175 104847 - 104847 2021年06月 [査読有り]
     
    Fipronil is a phenylpyrazole insecticide that is widely used as a pesticide and a veterinary drug, although studies suggest that it could be toxic to mammals. The objectives of this study were to examine the pharmacokinetic profile of fipronil in mice, dogs, and cats, and to evaluate its effects on emotional and cognitive behaviors of dogs and cats using the data obtained from mice. The assessment of in vivo kinetics of fipronil was conducted in mice and dogs. We also performed behavioral tests (elevated plus-maze and Y-maze) and measured the levels of neurotransmitters in mice exposed to fipronil. In addition, the in vitro metabolism of fipronil were evaluated using liver microsomes of rats, mice, dogs, and cats. The results revealed that fipronil is distributed throughout the body (blood, brain, adipose tissue, and liver) of mice after dermal application. It was metabolized to fipronil sulfone primarily in the liver. The data on kinetics show that both fipronil and fipronil sulfone have a longer half-life in dogs and cats than in mice. The behavioral tests indicated that fipronil and fipronil sulfone could affect emotional and cognitive behaviors and alter the levels of neurotransmitters (dopamine in the striatum and serotonin in the hippocampus) in mice. Furthermore, we found that dogs and cats have a low ability to metabolize fipronil than mice and rats. However, further comprehensive studies are needed to determine whether fipronil affects the emotional and cognitive behaviors when administered to dogs and cats. To the best of our knowledge, this is the first study to examine the pharmacokinetic data and verify the effects of fipronil on emotional and cognitive behaviors of dogs and cats using the data obtained from mice.
  • Tetsushi Hirano, Yuka Miyata, Shizuka Kubo, Shuji Ohno, Kanoko Onaru, Mizuki Maeda, Sayaka Kitauchi, Misaki Nishi, Yoshiaki Tabuchi, Yoshinori Ikenaka, Takahiro Ichise, Shouta M.M. Nakayama, Mayumi Ishizuka, Koji Arizono, Keisuke Takahashi, Keisuke Kato, Youhei Mantani, Toshifumi Yokoyama, Nobuhiko Hoshi
    Toxicology Letters 342 95 - 103 2021年05月15日 [査読有り]
     
    Neonicotinoids, which act as agonists of the nicotinic acetylcholine receptors of insects, are widely used pesticides worldwide. Although epidemiological studies revealed that the detection amounts of neonicotinoids in urine are higher in the elderly population than other age-groups, there is no available information regarding the risks of neonicotinoids to older mammals. This study was aimed to investigate aging-related differences in the behavioral effects of the neonicotinoid pesticide clothianidin (CLO). We acutely administered a sub-NOAEL level (5 mg/kg) of CLO to adult (12-week-old) and aging (90-week-old) mice and conducted four behavioral tests focusing on the emotional behavior. In addition, we measured the concentrations of CLO and its metabolites in blood, brain and urine. There were age-related changes in most parameters in all behavioral tests, and CLO significantly decreased the locomotor activity in the open field test and elevated plus-maze test in the aging group, but not in the adult group. The concentrations of most CLO and its metabolites were significantly higher in the blood and brain and were slightly lower in the urine in the aging group compared to the adult group. These findings should contribute to our understanding of age-related differences in the adverse effects of neonicotinoids in mammals.
  • Hokuto Nakata, Shouta M.M. Nakayama, John Yabe, Kaampwe Muzandu, Haruya Toyomaki, Yared Beyene Yohannes, Andrew Kataba, Golden Zyambo, Yoshinori Ikenaka, Kennedy Choongo, Mayumi Ishizuka
    Chemosphere 271 129832 - 129832 2021年05月 [査読有り]
     
    The LeadCare® testing system, which utilizes anodic stripping voltammetry (ASV) methodology, has been widely used worldwide for cost-effective blood lead level (BLL) screening. However, some concerns have recently been issued regarding inaccurate results obtained using LeadCare®. Hence, we aimed to evaluate the accuracy of BLL measured by LeadCare® II (BLLLC) by comparison with ICP-MS (BLLIM) by the Passing–Bablok regression, Deming regression, and Bland–Altman analyses by using 994 venous blood samples. BLLLC ranged from 3.3 to 162.3 μg/dL, while BLLIM ranged from 0.8 to 154.8 μg/dL. Although BLLLC and BLLIM exhibited a strong and positive correlation, BLLLC values were generally greater than BLLIM values, indicative of the overestimation of the LeadCare® analysis. A large positive bias of 19.15 ± 8.26 μg/dL and 29.25 ± 14.04 μg/dL for BLLLC compared with BLLIM were recorded in the BLLLC range of 45.0–64.9 μg/dL and for ≥65.0 μg/dL, respectively. In contrast, a bias of ≤0.3 μg/dL was observed at a BLLLC of less than 10.0 μg/dL. Blood copper, cadmium, and iron levels did not exhibit an effect on the bias of BLLLC, indicative of the minimal potential interferences of the metals; these interferences are a cause for concern with the ASV method. In conclusion, LeadCare® analysis is thought to be a good tool for screening purposes at a lower BLL around the reference level of 5 μg/dL in the initial stage; however, conversion or retesting using a laboratory analyzer is recommended at a higher BLL for appropriate clinical evaluation and research.
  • Yoshiya Yamamura, Kazuki Takeda, Yusuke K. Kawai, Yoshinori Ikenaka, Chiyo Kitayama, Satomi Kondo, Chiho Kezuka, Mari Taniguchi, Mayumi Ishizuka, Shouta M.M. Nakayama
    Aquatic Toxicology 233 105792 - 105792 2021年04月 [査読有り]
     
    Although anticoagulant rodenticides (ARs) are effectively used for the control of invasive rodents, nontarget species are also frequently exposed to ARs and secondary poisonings occur widely. However, little data is available on the effects of ARs, especially on marine organisms. To evaluate the effects of ARs on marine wildlife, we chose green sea turtles (Chelonia mydas), which are one of the most common marine organisms around the Ogasawara islands, as our primary study species. The sensitivity of these turtles to ARs was assessed using both in vivo and in vitro approaches. We administered 4 mg/kg of warfarin sodium either orally or intravenously to juvenile green sea turtles. The turtles exhibited slow pharmacokinetics, and prolongation of prothrombin time (PT) was observed only with intravenous warfarin administration. We also conducted an in vitro investigation using liver microsomes from green sea turtles, and two other turtle species (softshell turtle and red-eared slider) and rats. The cytochrome P450 metabolic activity in the liver of green sea turtles was lower than in rats. Additionally, vitamin K epoxide reductase (VKOR), which is the target enzyme of ARs, was inhibited by warfarin in the turtles at lower concentration levels than in rats. These data indicate that turtles may be more sensitive to ARs than rats. We expect that these findings will be helpful for sea turtle conservation following accidental AR-broadcast incidents.
  • Mayuka Uchida, Ippei Suzuki, Keizo Ito, Mayumi Ishizuka, Yoshinori Ikenaka, Shouta M.M. Nakayama, Tsutomu Tamura, Kenji Konishi, Takeharu Bando, Yoko Mitani
    Polar Biology 44 3 621 - 629 2021年03月 [査読有り]
     
    Antarctic minke whales (Balaenoptera bonaerensis) are migratory capital breeders that experience intensive summer feeding on Antarctic krill (Euphausia superba) in the Southern Ocean and winter breeding at lower latitudes, but their prey outside of the Antarctic is unknown. Stable isotope analyses were conducted on δ13C and δ15N from the baleen plates of ten pregnant Antarctic minke whales to understand the growth rate of the baleen plate and their diet in lower latitudes. Two to three oscillations along the length of the edge of the baleen plate were observed in δ15N, and the annual growth rate was estimated to be 75.2 ± 20.4 mm, with a small amplitude (0.97 ± 0.21 ‰). Bayesian stable isotope mixing models were used to understand the dominant prey that contributed to the isotopic component of the baleen plate using Antarctic krill from the stomach contents and reported values of Antarctic coastal krill (Euphausia crystallorophias), Antarctic silver fish (Pleuragramma antarcticum), Australian krill spp., and Australian pelagic fish spp. The models showed that the diet composition of the most recent three records from the base of the baleen plates (model 1) and the highest δ15N values in each baleen plate (model 2) were predominantly Antarctic krill, with a contribution rate of approximately 80%. The rates were approximately 10% for Antarctic coastal krill and less than 2.0% for the two Australian prey groups in both models. These results suggest that pregnant Antarctic minke whales did not feed on enough prey outside of the Antarctic to change the stable isotope values in their baleen plates.
  • Kazuki Takeda, Yoshinori Ikenaka, Denis Fourches, Kazuyuki D. Tanaka, Shouta M.M. Nakayama, Dhoha Triki, Xinhao Li, Manabu Igarashi, Tsutomu Tanikawa, Mayumi Ishizuka
    Pesticide Biochemistry and Physiology 173 104774 - 104774 2021年03月 [査読有り]
     
    Well-known 4-hydroxycoumarin derivatives, such as warfarin, act as inhibitors of the vitamin K epoxide reductase (VKOR) and are used as anticoagulants. Mutations of the VKOR enzyme can lead to resistance to those compounds. This has been a problem in using them as medicine or rodenticide. Most of these mutations lie in the vicinity of potential warfarin-binding sites within the ER-luminal loop structure (Lys30, Phe55) and the transmembrane helix (Tyr138). However, a VKOR mutation found in Tokyo in warfarin-resistant rats does not follow that pattern (Leu76Pro), and its effect on VKOR function and structure remains unclear. We conducted both in vitro kinetic analyses and in silico docking studies to characterize the VKOR mutant. On the one hand, resistant rats (R-rats) showed a 37.5-fold increased IC50 value to warfarin when compared to susceptible rats (S-rats); on the other hand, R-rats showed a 16.5-fold lower basal VKOR activity (Vmax/Km). Docking calculations exhibited that the mutated VKOR of R-rats has a decreased affinity for warfarin. Molecular dynamics simulations further revealed that VKOR-associated warfarin was more exposed to solvents in R-rats and key interactions between Lys30, Phe55, and warfarin were less favored. This study concludes that a single mutation of VKOR at position 76 leads to a significant resistance to warfarin by modifying the types and numbers of intermolecular interactions between the two.
  • Hokuto Nakata, Shouta M.M. Nakayama, Andrew Kataba, Yared Beyene Yohannes, Yoshinori Ikenaka, Mayumi Ishizuka
    Journal of Functional Foods 77 2021年02月 [査読有り]
     
    The current study aimed to validate the possible ameliorative effects of Spirulina (Arthrospira platensis) on lead poisoning and obesity using C57BL/6J mice. After a treatment period, we performed metal analyses, as well as hematocrit and plasma biochemical parameter measurements, and assayed oxidative stress markers and erythrocyte δ-aminolevulinic acid dehydratase (ALAD) activity. Our results highlighted the effectiveness of Spirulina in improving anemia status with the normalization of hematocrit levels and ALAD activity ratios, even in mice that exhibited obesity in addition to lead poisoning. Spirulina treatment also decreased epididymal white adipose tissue weight and increased plasma high-density lipoprotein levels, which are normally reduced after lead exposure. However, most of the studied plasma biochemical parameters and oxidative stress markers did not show large changes after treatment, likely because of the short duration of treatment. Further studies with longer-term exposures are required to validate the usefulness of Spirulina suggested in the present study.
  • Yared B. Yohannes, Shouta M.M. Nakayama, John Yabe, Haruya Toyomaki, Andrew Kataba, Hokuto Nakata, Kaampwe Muzandu, Yoshinori Ikenaka, Kennedy Choongo, Mayumi Ishizuka
    Meta Gene 27 2021年02月 [査読有り]
     
    Lead is a ubiquitous environmental pollutant that poses serious health problems to humans, especially to children. However, genetic variability in individuals varies their susceptibility to lead poisoning. One possible factor is genetic polymorphism. Thus, this study aimed to investigate the association between blood lead level (BLL), and polymorphisms in the delta-aminolevulinic acid dehydratase (ALAD) MspI (rs1800435) and vitamin D receptor (VDR) FokI (rs19735810), BsmI (rs15444410), ApaI (rs7975232) and TaqI (rs731236) genes in children exposed to lead. A total of 140 children (aged 2–10 years) were recruited in areas living closer to and far away from an abandoned lead‑zinc mine in Kabwe, Zambia. Blood samples were collected from each child for BLLs and polymorphisms analysis. All children were homozygous for the ALAD 1 allele, indicating there might be bioavailable lead in the children's blood which can transfer to the soft tissues and the brain. The distribution of the VDR gene polymorphisms showed major alleles prevalence's of 81%, 80%, 68%, and 75% for FokI, BsmI, ApaI, and TaqI polymorphisms, respectively. The aa genotype of VDR ApaI showed significantly higher BLL compared to other genotypes of the VDRs polymorphism. The TaqI - TT genotype was associated with an increase of lead exposure risk in female children (OR = 2.06; 95% CI:1.04–4.06, p = 0.03). The haplotype analysis showed 10 haplotypes with a frequency above 1%, and the FbAt haplotype showed a protective role against lead toxicity. In conclusion, the children, especially female children, which exposed to lead mainly from the abandoned lead‑zinc mine might be at a higher risk of developing lead poisoning. Further, larger scale sample sizes are needed to corroborate the role of ALAD and VDR genetic variants on the implications of lead toxicity in the general population, particularly in children.
  • Ruan Gerber, Hindrik Bouwman, Danny Govender, Mayumi Ishizuka, Yoshinori Ikenaka, Yared B. Yohannes, Nico J. Smit, Victor Wepener
    Chemosphere 264 Pt 1 128368 - 128368 2021年02月 [査読有り]
     
    Mass Nile crocodile (Crocodylus niloticus) deaths in Africa's premier conservation area, the Kruger National Park (KNP), prompted numerous studies to determine possible causes of the sudden die-offs. The majority highlighted the involvement of the anthropocene to crocodile mass mortalities. One of the potential causative agents was identified as legacy compounds such as organochlorine pesticides (OCPs) present in the various aquatic ecosystems of the KNP. Thus, this study aimed to quantify OCP levels in wild crocodiles from the aquatic systems associated with the KNP. As part of a larger study, muscle tissue samples were collected from tails of 12 wild crocodiles. Results indicated that eight of the 19 OCPs analysed for were quantifiable. These included DDTs (2130–167968 ng/g lw), chlordanes (BD – 7583 ng/g lw) and cyclodeines (BD – 872 ng/g lw). Measured concentrations indicated spatial- and sex-related differences in accumulation patterns. DDT and its metabolites, paricularly p,p’-DDE accumulated to the highest concentrations of the OCP groups. Levels of the different groups of OCPs were the highest recorded in recent history from any crocodilian tissue. The different measured OCP residues were between 2.5 and 120 times higher than levels reported in literature, depending on the compound. These results are of ecotoxicological significance and have several management implications. In view of individuals being sampled from a conservation area it emphasizes the fact that pollutants know no boundaries and that premier conservation areas such as the world renowned KNP may be some of the most contaminated areas of the world.
  • Andrew Kataba, Shouta M.M. Nakayama, Hokuto Nakata, Haruya Toyomaki, Yared B. Yohannes, John Yabe, Kaampwe Muzandu, Golden Zyambo, Ayano Kubota, Takehisa Matsukawa, Kazuhito Yokoyama, Yoshinori Ikenaka, Mayumi Ishizuka
    International Journal of Environmental Research and Public Health 18 2 1 - 15 2021年01月02日 [査読有り]
     
    Lead (Pb) is a metal toxicant of great public health concern. The present study investigated the applicability of the rat incisor in Pb exposure screening. The levels of lead in teeth (Pb-T) in the crown and root of incisors in laboratory Pb-exposed Sprague Dawley rats were quantified using inductively coupled plasma mass spectrometry (ICP-MS). The crown accumulated much Pb-T than the root of the Sprague Dawley rat incisor. The levels of lead in blood (Pb-B) were positively correlated with the Pb-T in the crown and root incisors of the Sprague Dawley rats. As an application of the Pb-T crown results in experimental rats, we subsequently analyzed the Pb-T in the crown incisors of Pb-exposed wild rats (Rattus rattus) sampled from residential sites within varying distances from an abandoned lead–zinc mine. The Pb-T accumulation in the crown of incisors of R. rattus rats decreased with increased distance away from the Pb–Zn mine. Furthermore, the Pb-T was strongly correlated (r = 0.85) with the Pb levels in the blood. Laser ablation ICP-MS Pb-T mappings revealed a homogenous distribution of Pb in the incisor with an increased intensity of Pb-T localized in the tip of the incisor crown bearing an enamel surface in both Sprague Dawley and R. rattus rats. These findings suggest that Pb-T in the crown incisor may be reflective of the rat’s environmental habitat, thus a possible indicator of Pb exposure.
  • Collins NIMAKO, Yoshinori IKENAKA, Osei AKOTO, Kazutoshi FUJIOKA, Kumiko TAIRA, Koji ARIZONO, Keisuke KATO, Keisuke TAKAHASHI, Shouta M.M. NAKAYAMA, Takahiro ICHISE, Mayumi ISHIZUKA
    日本毒性学会学術年会 48.1 P-154E  日本毒性学会 2021年 
    The present study aimed to (i) develop a sensitive LC-MS/MS-based technique for simultaneous detection and quantification of Imidacloprid (IMI) and its metabolites in tissue specimens, and to (ii) determine the specific bioaccumulation trends of the IMI compounds in organs of C57BL/6J male mice; after exposure to 0.6 mg/kg bw/day of IMI (10% of NOAEL) through a powdered diet for 24 weeks. We successfully developed a method which was accurate (recoveries were ≥ 70% for most compounds), sensitive (LODs ≤ 0.47 ng/mL, LOQs ≤ 1.43 ng/mL and R2 ≥ 0.99) and precise (RSDs ≤ 20%) for routine analysis of IMI and seven of its metabolites in in blood and various tissues of mice. Upon biodistribution analysis, IMI and five of its metabolites were detected in various organs within mice. Blood, liver, mesenteric white adipose tissue and pancreas mainly accumulated IMI-olefin; brain, testis, inguinal white adipose tissue and gonadal white adipose tissue mainly accumulated IMI, whereas the kidney mainly accumulated 4-hydroxy-IMI. The N-desnitro-IMI metabolite showed unique accumulation in brain and testis by recording brain-blood and testis-blood detection ratios of 8.4 and 7.6, respectively. Cumulative levels of the six detected IMI compounds (Σ6 IMI compounds) were found in the decreasing order; blood > testis > iWAT > kidney > brain > gWAT > mWAT > pancreas > liver. The current study provides essential data needed for effective mechanistic elucidation of compound-specific adverse outcomes associated with chronic exposures to IMI in mammalian species.
  • 本平 航大, Dugar Delgermurun, 池中 良徳, 中山 翔太, Pelden Bolormaa, Gendenpil Lkhamjav, 石塚 真由美
    日本科学教育学会年会論文集 45 563 - 564 一般社団法人 日本科学教育学会 2021年 
    発表者は北海道大学のJICAを通じたプロジェクトの一環で２０１９年に青年海外協力隊（獣医師）としてモンゴル生命科学大学獣医学部に短期派遣され、約１か月の研究支援を実施した。モンゴル国では残留抗生物質の検査体制の拡大が望まれており、発表者の活動により、日本から大学研究レベルの検査手法の開発とその研究プロセスの伝達、共有が実現された。帰国後も、現在に至るまでFacebook Messengerなどのツールを利用し、追加の検査手法開発に向けた継続的な研究協力関係を構築した。結果として、国際会議における科学的成果発表など、今回の活動により一定の進展があったことを社会に報告できた。しかし、専門性の高い研究レベルの支援を遠隔で実施する過程で双方、難点を抱える場面があった。本発表により発表者が実施した研究支援を踏まえ、開発途上国に対する大学研究レベルの支援の一例紹介、またその課題を共有する。
  • Collins Nimako, Anri Hirai, Takahiro Ichise, Osei Akoto, Shouta M M Nakayama, Kumiko Taira, Kazutoshi Fujioka, Mayumi Ishizuka, Yoshinori Ikenaka
    Toxicology reports 8 1657 - 1664 2021年 [査読有り]
     
    The current study sought to assess the residual levels of neonicotinoid insecticides (NEO) in organic and conventional green tea leaves produced in Japan. A total of 103 tea leaves (thus, 42 organic and 61 conventional), were sampled from grocery stores in Japan. Concentrations of NEOs in the tea leaves were quantified using LC-MS/MS; and the data was used to estimate maximum daily intakes of NEOs within the Japanese population. Seven native NEO compounds and one NEO metabolite were detected in both organic and conventional tea leaves. Detection frequencies (%Dfs) of NEOs in the tea samples (n = 103) were found in the decreasing order; thiacloprid (84.47 %) > dinotefuran (74.76 %) > imidacloprid (69.90 %) ≈ clothianidin (69.90 %) > dm-acetamiprid (63.11 %) > thiamethoxam (58.25 %) > acetamiprid (4.85 %) > nitenpyram (1.94 %). About 94.20 % of the tea leaves contained two or more NEO compounds simultaneously. The %Dfs of NEOs were relatively lower in organic tea leaves, compared to the conventional tea leaves. Various percentile concentrations of NEOs were far lower in organic tea leaves, compared to the conventional tea leaves. The maximum daily intakes of NEOs through consumption of tea (MDIgt) were also lower for organic tea leaves, compared to the conventional tea samples.
  • Collins Nimako, Yoshinori Ikenaka, Yuko Okamatsu-Ogura, Jussiaea V. Bariuan, Atsushi Kobayashi, Ryo Yamazaki, Kumiko Taira, Nobuhiko Hoshi, Tetsushi Hirano, Shouta M.M. Nakayama, Mayumi Ishizuka
    Journal of Veterinary Medical Science 83 3 487 - 500 2021年 [査読有り]
     
    Hepatic steatosis is known to precede a continuum of events that lead to hepatic metabolic dysfunction, inflammation and carcinogenesis. Recently, studies have linked xenobiotic exposures to hepatic steatogenesis and its associated metabolic disorders; however, the underlying mechanisms remain elusive. This study aimed to elucidate the mechanistic role of imidacloprid in the prevalence of high fat diet (HFD)-induced liver steatosis, using a C57BL/6J mice model. Mice (3 weeks old) were fed with HFD and treated with 0.6 mg/kg bw/day (one-tenth of the NOAEL) of imidacloprid through water or diet, for 24 weeks. In a controlled group, mice were fed with only HFD. At the end of the study, imidacloprid treatment significantly potentiated HFD-induced body weight gain in mice. Also, imidacloprid increased the liver weights of mice, with complimentary reductions in mesenteric and gonadal white adipose tissue weights. Histopathological analysis of liver revealed a drastic steatosis in imidacloprid treated mice. Following a real-time qPCR analysis, imidacloprid upregulated transcriptions of hepatic fatty acid biosynthesis-related transcription factors and genes. Imidacloprid also induced hepatic expression of the gene encoding pregnane X receptor; but had no significant effect on hepatic expressions of liver X receptor and aryl hydrocarbon receptor. The imidacloprid treatment further enhanced serum alanine aminotransferase levels but downregulated hepatic antioxidant mRNA expressions. Ultimately, this study suggested an imidacloprid-potentiation effects on prevalence of HFD-induced liver steatosis via transcriptional modulations of the hepatic FA biosynthesis pathway.
  • Noboru Sasaki, Yoshinori Ikenaka, Yumiko Inoue, Takahiro Ichise, Noriyuki Nagata, Mayumi Ishizuka, Syouta M.M. Nakayama, Kensuke Nakamura, Mitsuyoshi Takiguchi
    Journal of Veterinary Medical Science 83 4 648 - 655 2021年 [査読有り]
     
    Measurement of urinary metanephrines in spot samples is used for the diagnosis of canine pheochromocytoma (PC). We describe a simple analytical method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) for measuring free metanephrine (MN) and normetanephrine (NMN) in spot urine samples. Using the developed method, we evaluated the stability of urinary free-MN and free-NMN at various storing conditions. In addition, we assessed the feasibility of urinary free-MN and-NMN measurement for diagnosing PC. Urine samples were mixed with stable isotope internal standards and thereafter purified by ultrafiltration. The purified samples were analyzed by LC-MS/MS in the multiple reaction monitoring mode after separation on a multimode octa decyl silyl column. The coefficient of variation of free-MN and-NMN measurement was 7.6% and 5.5%, respectively. The linearity range was 0.5–10 µg/l for both analytes. Degradation was less than 10% for both analytes under any of the storage conditions. The median free-NMN ratio to creatinine of 9 PC dogs (595, range 144–47,961) was significantly higher (P<0.05) than that of 13 dogs with hypercortisolism (125, range 52–224) or 15 healthy dogs (85, range 50–117). The developed method is simple and may not require acidification of spot urine. The results of this preliminary retrospective study suggest that the measurement of urinary free metanephrines is a promising tool for diagnosing canine PC.
  • Kraisiri Khidkhan, Yoshinori Ikenaka, Takahiro Ichise, Shouta M.M. Nakayama, Hazuki Mizukawa, Kei Nomiyama, Hisato Iwata, Koji Arizono, Keisuke Takahashi, Keisuke Kato, Mayumi Ishizuka
    Comparative Biochemistry and Physiology Part - C: Toxicology and Pharmacology 239 108898 - 108898 2021年01月 [査読有り]
     
    Neonicotinoid insecticides are used for agricultural and non-agricultural purposes worldwide. Pets are directly exposed to neonicotinoids in veterinary products and through environmental contamination. Cytochrome P450 (CYP) is among the most significant xenobiotic metabolizing enzymes that oxidizes several chemicals, including neonicotinoids. However, CYP activities and metabolite compositions of neonicotinoid metabolites are unknown in most domesticated pet species. Our objectives were to reveal the differences in metabolites of neonicotinoids (imidacloprid, clothianidin, and acetamiprid) and CYP activities among common pet species (cats and dogs), humans, and rats. The results indicated that the CYP-mediated neonicotinoid metabolism was different depending on species and each neonicotinoid. Among these four species, the kinetics of imidacloprid metabolism indicated that rats have the highest rate of oxidation of imidacloprid to 4OH-imidacloprid, while the greatest enzyme kinetics of imidacloprid metabolism to 5OH-imidacloprid were found in rats and humans. Clothianidin was rapidly metabolized to 1-methyl-3-nitroguanidine and dm-clothianidin in rats, but cats and humans showed the lowest formation of dm-clothianidin. CYP activities in metabolism of acetamiprid to dm-acetamiprid and N-acetyl-acetamiprid were determined to be significantly higher in humans compared to other species. However, further studies should be targeted at identifying the differences in hepatic metabolism of neonicotinoids in these species using recombinant CYP enzymes.
  • Hokuto Nakata, Shouta M.M. Nakayama, John Yabe, Kaampwe Muzandu, Haruya Toyomaki, Yared Beyene Yohannes, Andrew Kataba, Golden Zyambo, Yoshinori Ikenaka, Kennedy Choongo, Mayumi Ishizuka
    Chemosphere 262 127788 - 127788 2021年01月 [査読有り]
     
    Lead (Pb) interferes with various bodily functions. Although high blood Pb (Pb–B) levels in residents from Kabwe, Zambia have been reported, the accumulation pattern of other metals remains unknown. The study was designed to determine the Pb–B, blood cadmium (Cd–B), and zinc (Zn–B) values of 504 representative samples from Kabwe, as well as the potential associated adverse health effects. The Pb–B level ranged from 0.79 to 154.75 μg/dL and generally increased in areas near the mine. A significant elevation of Cd–B was observed in two areas (0.37 ± 0.26 and 0.32 ± 0.30 μg/L) where the two highest mean Pb–B levels were recorded. By contrast, the Zn–B values did not differ greatly with respect to area. Some blood biochemical parameters relating to hepatic and renal functions were out of the normal range in approximately 20–50% of studied adult participants. The δ-aminolevulinic acid dehydratase (δ-ALAD) activity was significantly inhibited in the two areas contaminated by Pb and Cd. A significant negative relationship was observed between metal levels and clinical parameters, e.g., between Pb–B and δ-ALAD for all the age categories and between Cd–B and the estimated glomerular filtration rate for all the age categories except 0–4 years. The elevated Cd–B in areas near the mine relative to the other areas suggested the potential adverse health effects of Cd and/or the interaction of Pb and Cd. A significant association of metal levels with clinical parameters also indicated the effects of metal exposure on hematopoietic, hepatic, and renal systems.
  • Daichi Yamada, Masato Hiwatari, Peter Hangoma, Daiju Narita, Chrispin Mphuka, Bona Chitah, John Yabe, Shouta M.M. Nakayama, Hokuto Nakata, Kennedy Choongo, Mayumi Ishizuka
    Scientific Reports 10 1 15092 - 15092 2020年12月01日 [査読有り]
     
    This study quantitatively assessed the population-wide lead poisoning conditions in Kabwe, Zambia, a town with severe lead pollution. While existing data have reported concerning blood lead levels (BLLs) of residents in pollution hotspots, the data representing the entire population are lacking. Further, selection bias is a concern. Given the lack of compulsory testing schemes, BLLs have been observed from voluntary participants in blood sampling surveys, but such data can represent higher or lower BLLs than the population average because of factors simultaneously affecting participation and BLLs. To illustrate the lead poisoning conditions of the population, we expanded the focus of our surveys and then econometrically estimated the BLLs of individuals representing the population, including those not participating in blood sampling, using background geographic, demographic, and socioeconomic information. The estimated population mean BLL was 11.9 μg/dL (11.6–12.1, 95% CI), lower than existing data because of our wide focus and correction of selection bias. However, the scale of lead poisoning remained immense and 74.9% of residents had BLLs greater than 5 μg/dL, the standard reference level for lead poisoning. Our estimates provide a deeper understanding of the problem and a foundation for policy intervention designs.
  • Wilson Mwandira, Kazunori Nakashima, Satoru Kawasaki, Allison Arabelo, Kawawa Banda, Imasiku Nyambe, Meki Chirwa, Mayumi Ito, Tsutomu Sato, Toshifumi Igarashi, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Scientific Reports 10 1 21189 - 21189 2020年12月 [査読有り]
     
    The present study investigated biosorption of Pb (II) and Zn (II) using a heavy metal tolerant bacterium Oceanobacillus profundus KBZ 3-2 isolated from a contaminated site. The effects of process parameters such as effect on bacterial growth, pH and initial lead ion concentration were studied. The results showed that the maximum removal percentage for Pb (II) was 97% at an initial concentration of 50 mg/L whereas maximum removal percentage for Zn (II) was at 54% at an initial concentration of 2 mg/L obtained at pH 6 and 30 °C. The isolated bacteria were found to sequester both Pb (II) and Zn (II) in the extracellular polymeric substance (EPS). The EPS facilitates ion exchange and metal chelation-complexation by virtue of the existence of ionizable functional groups such as carboxyl, sulfate, and phosphate present in the protein and polysaccharides. Therefore, the use of indigenous bacteria in the remediation of contaminated water is an eco-friendly way of solving anthropogenic contamination.
  • Patricia N. Mwilola, Ikabongo Mukumbuta, Victor Shitumbanuma, Benson H. Chishala, Yoshitaka Uchida, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    International Journal of Environmental Research and Public Health 17 23 1 - 15 2020年12月01日 [査読有り]
     
    Health risks due to heavy metal (HM) contamination is of global concern. Despite concerns of high levels of HMs in soils near Kabwe mine in Zambia, edible crop production is common, posing potential health risks. This study assessed the potential of chicken manure (CM), triple superphosphate (TSP) and a blended fertilizer (BF; consisting of Nitrogen, Phosphorous and Potassium (NPK) fertilizer and composted chicken manure) to reduce lead (Pb), zinc (Zn) and cadmium (Cd) in soils and their accumulation in maize grown near the Kabwe mine. Maize was grown to maturity and its HM concentrations and associated health risk indices were calculated. All soil amendments decreased bioavailable soil Pb concentrations by 29–36%, but only CM decreased Zn, while the amendments increased or had no effect on Cd concentrations compared to the control. The amendments reduced Pb (>25%) and Zn concentrations (>18%) in the maize stover and grain. However, Cd concentrations in maize grain increased in the BF and TSP treatments. Bioaccumulation factors showed that Cd had the highest mobility from the soil into maize stover and grain, indicating the need for greater attention on Cd in Kabwe despite its apparently lower soil concentration compared to Pb and Zn. The hazard quotients for Pb and Cd were much greater than one, indicating a high risk of possible exposure to toxic levels by people consuming maize grain grown in this area. This study demonstrated the significant potential of manure and phosphate-based amendments to reduce Pb and Zn, and to some extent Cd, uptake in maize grain and consequently reduce associated health risks.
  • Rio Doya, Shouta M.M. Nakayama, Hokuto Nakata, Haruya Toyomaki, John Yabe, Kaampwe Muzandu, Yared B. Yohannes, Andrew Kataba, Golden Zyambo, Takahiro Ogawa, Yoshitaka Uchida, Yoshinori Ikenaka, Mayumi Ishizuka
    Environmental Science and Technology 54 22 14474 - 14481 2020年11月17日 [査読有り][通常論文]
     
    We investigated the potential effects of different land use and other environmental factors on animals living in a contaminated environment. The study site in Kabwe, Zambia, is currently undergoing urban expansion, while lead contamination from former mining activities is still prevalent. We focused on a habitat generalist lizards (Trachylepis wahlbergii). The livers, lungs, blood, and stomach contents of 224 lizards were analyzed for their lead, zinc, cadmium, copper, nickel, and arsenic concentrations. Habitat types were categorized based on vegetation data obtained from satellite images. Multiple regression analysis revealed that land use categories of habitats and three other factors significantly affected lead concentrations in the lizards. Further investigation suggested that the lead concentrations in lizards living in bare fields were higher than expected based on the distance from the contaminant source, while those in lizards living in green fields were lower than expected. In addition, the lead concentration of lungs was higher than that of the liver in 19% of the lizards, implying direct exposure to lead via dust inhalation besides digestive exposure. Since vegetation reduces the production of dust from surface soil, it is plausible that dust from the mine is one of the contamination sources and that vegetation can reduce exposure to this.
  • Yui Yoshii, Isabell von Rein, Kabenuka Munthali, Mukuka Mwansa, Hokuto Nakata, Shota Nakayama, Mayumi Ishizuka, Yoshitaka Uchida
    SOUTH AFRICAN JOURNAL OF PLANT AND SOIL 37 5 351 - 360 2020年11月 [査読有り]
     
    High levels of lead (Pb) in the soil is a serious issue in the city of Kabwe, Zambia. Phytoremediation is an effective approach to revive the life-supporting functions of the soils. Locally available soil amendments, such as chicken manure, can strengthen phytoremediation. This study aims to find an appropriate combination of a locally available Pb hyperaccumulator, lemongrass (Cymbopogon citratus (DC.) Stapf.), and soil amendments, to minimize the Pb pollution. After a short-term (78 day) pot experiment with lemongrass and three soil amendments (chicken manure, biochar of chicken manure, and urea) on a Pb-contaminated soil in Kabwe, an edible crop, dent corn (Zea mays var. indentata (Sturtev.) L.H.Bailey), was grown for two weeks. Chicken manure combined with lemongrass had the most beneficial impact, reducing the Pb level in dent corn by 19%, compared to the Pb in dent corn grown on the control soil. By growing lemongrass in the Kabwe soil with chicken manure, the exchangeable soil Pb was reduced by 70%. The growth of lemongrass without chicken manure reduced the exchangeable soil Pb by 20%. In conclusion, lemongrass successfully reduced Pb levels, in combination with chicken manure. Soil amendments must be chosen carefully by considering the soil properties and environmental conditions for an optimized Pb reduction.
  • Andrew Kataba, Tarryn L. Botha, Shouta M.M. Nakayama, Yared B. Yohannes, Yoshinori Ikenaka, Victor Wepener, Mayumi Ishizuka
    Aquatic Toxicology 227 105607 - 105607 2020年10月 [査読有り]
     
    The ubiquitous contamination of environmental lead (Pb) remains a worldwide threat. Improper Pb mine waste disposal from an abandoned lead-zinc mine has recently unearthed widespread Pb poisoning in children in Kabwe Zambia. Although the adverse effects of Pb on human health have begun to receive attention, the ecotoxicological effects on aquatic vertebrates still need further investigation. In addition, there is paucity in the knowledge on the behavioural and molecular subcellular responses in larval zebrafish exposed to Pb within the range of environmental relevant concentration (average 3 μg/L with maximum of 94 μg/L) on aquatic organisms such as zebrafish. The adverse effects of environmentally relevant levels of Pb on larval zebrafish was evaluated by measuring swimming behaviour under alternating dark and light conditions. Larval zebrafish acutely exposed to environmentally relevant Pb exhibited neuro-behavioural alteration including enhanced hyperactivity under light conditions evidenced by increased distanced covered and speed compared to the control. The alteration of entire behavioral profiles was further associated with the disturbed expression patterns of mRNA level of key genes associated with antioxidant (HO-1, Ucp-2 and CoxI), proapoptotic gene (TP53), and antiapoptotic gene (Bcl-2). To our knowledge, this is the first report on the effects of environmentally relevant Pb levels from Kabwe, Zambia and their adverse neurobehavioural effects and subcellular molecular oxidative responses in larval zebrafish acutely exposed within a 30 min period. The current results would be beneficial in our understanding of the effects of low Pb levels acutely discharged into an aquatic environment and the life of aquatic organisms.
  • Pawit Tangviroon, Kenta Noto, Toshifumi Igarashi, Takeshi Kawashima, Mayumi Ito, Tsutomu Sato, Walubita Mufalo, Meki Chirwa, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Minerals 10 9 1 - 16 2020年09月 [査読有り]
     
    Massive amount of highly contaminated mining residual materials (MRM) has been left unattended and has leached heavy metals, particularly lead (Pb) and zinc (Zn) to the surrounding environments. Thus, the performance of three immobilizers, raw dolomite (RD), calcined dolomite (CD), and magnesium oxide (MO), was evaluated using batch experiments to determine their ability to immobilize Pb and Zn, leached from MRM. The addition of immobilizers increased the leachate pH and decreased the amounts of dissolved Pb and Zn to different extents. The performance of immobilizers to immobilize Pb and Zn followed the following trend: MO > CD > RD. pH played an important role in immobilizing Pb and Zn. Dolomite in RD could slightly raise the pH of the MRM leachate. Therefore, the addition of RD immobilized Pb and Zn via adsorption and co-precipitation, and up to 10% of RD addition did not reduce the concentrations of Pb and Zn to be lower than the effluent standards in Zambia. In contrast, the presence of magnesia in CD and MO significantly contributed to the rise of leachate pH to the value where it was sufficient to precipitate hydroxides of Pb and Zn and decrease their leaching concentrations below the regulated values. Even though MO outperformed CD, by considering the local availability of RD to produce CD, CD could be a potential immobilizer to be implemented in Zambia.
  • Yared B. Yohannes, Shouta MM Nakayama, John Yabe, Hokuto Nakata, Haruya Toyomaki, Andrew Kataba, Kaampwe Muzandu, Yoshinori Ikenaka, Kennedy Choongo, Mayumi Ishizuka
    Environmental Research 188 109759 - 109759 2020年09月 [査読有り][通常論文]
     
    Background: Lead (Pb) is a well-known toxic heavy metal which can have serious public health hazards. As of today, there is no safe threshold for Pb exposure, especially for children. Lead exposure has been associated with adverse health outcomes involving epigenetic mechanisms, such as aberrant DNA methylation. The objective of the present study was to elucidate the associations between blood lead levels (BLLs) and gene-specific promoter DNA methylation status in environmental Pb-exposed children from Kabwe, Zambia. Methods: A cross-sectional study was conducted using 2 to 10-year-old children from high Pb exposed area (N = 102) and low Pb exposed area (N = 38). We measured BLLs using a LeadCare II analyzer and investigated the methylation status of the ALAD and p16 gene promoters by methylation–specific PCR. Results: The mean BLLs were 23.7 μg/dL and 7.9 μg/dL in high Pb exposed and low Pb exposed children, respectively. Pb exposure was correlated with increased methylation of the ALAD and p16 genes. The promoter methylation rates of ALAD and p16 in high Pb exposed children were 84.3% and 67.7%, and 42.1% and 44.7% in low Pb exposed children, respectively. Significantly increased methylation was found in both genes in high Pb exposed children compared with low Pb exposed children (p < 0.05). Children with methylated ALAD and p16 genes showed an increased risk of Pb poisoning (odd ratio >1) compared to the unmethylated status. Conclusions: This study for the first time tries to correlate promoter methylation status of the ALAD and p16 genes in environmental Pb-exposed children from Kabwe, Zambia as a representative. The result suggests that Pb exposure increases aberrations in ALAD and p16 gene methylation, which may be involved in the mechanism of Pb toxicity.
  • Nana Ushine, Shouta M M Nakayama, Mayumi Ishizuka, Tatsuo Sato, Yoshihiro Kurahashi, Emu Wakayama, Natsuko Sugiura, Shin-Ichi Hayama
    The Journal of veterinary medical science 82 8 1124 - 1129 2020年08月19日 [査読有り]
     
    Few studies have evaluated immunosuppression due to lead accumulation below the overt toxicity threshold. If low levels of lead accumulation cause immunosuppression in birds, those birds could become more susceptible to pathogens. We aimed to determine if low levels of lead accumulation lead to immunosuppression in Black-headed gulls (Chroicocephalus ridibundus). Gulls were captured in Tokyo-bay and Mikawa-bay from January to April 2019. Their blood samples were analyzed for eight items. The data were analyzed to evaluate the correlation between lead concentrations and the variables from each bay. Lead was positively correlated with the percentage of heterophils and heterophil and lymphocyte ratio and negatively with lymphocytes. Thus, low lead accumulation levels may induce changes in percentage of the heterophils and lymphocyte.
  • Chihiro Ishii, Yoshinori Ikenaka, Shouta M M Nakayama, Takeshi Kuritani, Mitsuhiro Nakagawa, Keisuke Saito, Yukiko Watanabe, Kohei Ogasawara, Manabu Onuma, Atsushi Haga, Mayumi Ishizuka
    The Journal of veterinary medical science 82 8 1118 - 1123 2020年08月19日 [査読有り][通常論文]
     
    Birds of a number of species have died as a result of lead (Pb) poisoning, including many Steller's sea eagles (Haliaeetus pelagicus) and white-tailed sea eagles (Haliaeetus albicilla) in Hokkaido, the northernmost island of Japan. To address this issue, the use of any type of Pb ammunition for hunting of large animals was prohibited in Hokkaido in 2004. However, Pb poisoning is still being reported in this area, and there are few regulations regarding the use of Pb ammunition in other parts of Japan, where it has been reported that eagles and water birds have been exposed to Pb. This study was performed to accurately determine the current level of Pb exposure of birds found dead in the field or dead in the wild bird centers in Japan (June 2015-May 2018) and to identify the sources of Pb. Pb exposure was found to still be occurring in raptors and water birds in various parts of Japan. Twenty-six point five % and 5.9% of the recorded deaths of Steller's sea eagles and white-tailed sea eagles, respectively, were found to have been poisoned by Pb. In addition, Pb isotope ratio analysis showed that both Pb rifle bullets and Pb shot pellets cause Pb exposure in birds, and these endangered eagles are also exposed to Pb in Hokkaido due to the illegal use of Pb ammunition. Changing to Pb-free ammunition, such as copper (Cu) rifle bullets, steel shot pellets, or bismuth shot pellets, will be essential for the conservation of avian species in Japan.
  • Anja Erasmus, Yoshinori Ikenaka, Shouta M.M. Nakayama, Mayumi Ishizuka, Nico J. Smit, Victor Wepener
    Marine Pollution Bulletin 157 111309 - 111309 2020年08月 [査読有り][通常論文]
     
    Tsitsikamma and Sheffield Beach are two relatively pristine sites along the South African east coast representing warm temperate and subtropical biogeographic rocky shore intertidal ecosystems, respectively. Stable isotopes (δ15N and δ13C), metals and organochlorine pesticides (OCPs) were measured in 38 intertidal components to study biomagnification or biodilution of metals and OCPs in these marine food webs. Comparison of the four species common to both sites revealed that the highest Al, Fe and OCP concentrations were measured in intertidal organisms from Sheffield Beach and was attributed to diffuse input into the nearshore marine environment sources via estuaries and groundwater. All other metals were higher in intertidal organisms from Tsitsikamma and were attributed to the metal-rich phytoplankton blooms during upwelling events. There was no correlation between metal and OCP accumulation and dietary source (δ13C) or trophic level (δ15N). The application of trophic magnification factors (TMFs) using a relatively short benthic food chain indicated biomagnification for As, Cd, Cu, Se and Zn and biodilution of OCPs at both sites. Since these food chains represent only a small portion of the intertidal ecosystems we found limited evidence of biomagnification or biodilution of metals and OCPs across species. This was attributed to different dietary sources in the same food web and similar trophic levels being occupied by the same species in different food chains. We found that food web composition rather than temperature-based biogeographical distribution influenced trophic transfer of metals and OCPs.
  • Marthias Silwamba, Mayumi Ito, Naoki Hiroyoshi, Carlito Baltazar Tabelin, Tomoki Fukushima, Ilhwan Park, Sanghee Jeon, Toshifumi Igarashi, Tsutomu Sato, Imasiku Nyambe, Meki Chirwa, Kawawa Banda, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Journal of Environmental Chemical Engineering 8 4 104197 - 104197 2020年08月 [査読有り][通常論文]
     
    Zinc plant leach residues (ZPLRs) are hazardous solid wastes generated from zinc metal production owing to their substantial contents of lead (Pb), a toxic heavy metal. This study investigated the detoxification of historic ZPLRs from Kabwe, Zambia by removing Pb using a coupled extraction-cementation method in chloride media. For the coupled extraction-cementation method, micro-scale zero-valent iron (mZVI) was added during ZPLRs leaching in acidified chloride solution. Cemented Pb on the surface of mZVI was recovered easily from the leaching pulp by magnetic separation. Pb removal was evaluated in different solution compositions (NaCl:1-5.13M, HCl: 0-0.1M) with and without the addition of mZVI. The addition of mZVI during ZPLRs leaching (i.e., coupled extraction-cementation) increased Pb removal from 3% to 24%, 1.3% to 27.5%, 5.2% to 34.9%, and 6.5% to 55.8% when NaCl concentration was fixed at 0.86M and HCl concentrations were 0M, 0.01M, 0.05M and 0.1M, respectively. When NaCl concentration was increased above 3.42M and HCl maintained at 0.1M HCl, Pb removal increased to 80%. Analysis of the Pb-loaded mZVI (magnetic fraction) by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray photoelectron spectroscopy (XPS) revealed that Pb was recovered during leaching via cementation as Pb°. The toxicity characteristic leaching procedure (TCLP) and in vitro solubility and bioavailability research consortium gastric phase (SBRC-G) tests for Pb of ZPLRs before and after treatment decreased drastically from 11.3 to 3.5mg/L (below 5mg/L threshold) and 12 300 to 2 840mg/Kg, respectively.
  • Kraisiri Khidkhan, Hazuki Mizukawa, Yoshinori Ikenaka, Shouta M.M. Nakayama, Kei Nomiyama, Nozomu Yokoyama, Osamu Ichii, Mitsuyoshi Takiguchi, Shinsuke Tanabe, Mayumi Ishizuka
    Journal of Veterinary Medical Science 82 7 978 - 982 2020年07月 [査読有り][通常論文]
     
    The knowledge of cytochrome P450 (CYP) expression involved in chemical exposure are necessary in clinical applications for the medication and prediction of adverse effects. The aim of this study was to evaluate the mRNA expression of CYP1–CYP3 families in cats exposed to BDE-209 for one year. All selected CYP isoforms showed no significant difference in mRNA expressions between control and exposure groups, however, CYP3A12 and CYP3A131 revealed tend to be two times higher in the exposure group compared to control group. The present results indicate that the chronic exposure of BDE209 could not alter CYP expression in the liver of cats. This result considered caused by the deficiency of CYP2B subfamily which is major metabolism enzyme of polybrominated diphenyl ethers (PBDEs) in cat.
  • エジプシャンルーセットオオコウモリ(Rousettus aegyptiacus)における抗血液凝固系殺鼠剤の薬物動態学/薬力学的解析
    武田 一貴, 真砂 皓大, 中山 翔太, 川合 佑典, 池中 良徳, 石塚 真由美
    The Journal of Toxicological Sciences 45 Suppl. S181 - S182 (一社)日本毒性学会 2020年06月
  • Kazuki Takeda, Ayuko Morita, Yoshinori Ikenaka, Shouta M.M. Nakayama, Mayumi Ishizuka
    Veterinary and Animal Science 9 100095 - 100095 2020年06月 [査読有り][通常論文]
     
    Vitamin K epoxide reductase (VKOR) is a target enzyme for anticoagulants, such as warfarin, that are used as medicines or rodenticides. Assessing VKOR activity is required to ensure the proper usage of these drugs. Dithiothreitol (DTT) is a typical disulfide reductant that is used as a substrate for in vitro VKOR assays. However, DTT is considered problematic because of its side effects. Tris(3-hydroxypropyl)phosphine (THP) has been found to be a reliable alternative to DTT, as shown by kinetic analyses of the VKOR with them. THP showed significantly lower Vmax and Km values than those of DTT; however, there was no significant difference in their Vmax/Km and IC50 for warfarin.
  • L. De Necker, A. Manfrin, Y. Ikenaka, M. Ishizuka, L. Brendonck, J. H.J. Van Vuren, B. Sures, V. Wepener, N. J. Smit
    African Zoology 55 1 79 - 92 2020年05月 [査読有り]
     
    Southern Africa has one of the highest densities of temporary pools and some of the most understudied temporary wetlands in the world. Additionally, the eastern African annual killifishes (Nothobranchius spp.) are rare in southern Africa and found exclusively in temporary habitats. There is a notable lack of literature regarding the diet of these fish, as well as the foodweb structures of temporary ecosystems. The current study aimed to address this paucity in literature by assessing the foodweb of a temporary pool located in the Ndumo Game Reserve (NGR) in northern Kwa-Zulu Natal using stable isotopes analysis. In addition, Bayesian mixing models were used to assess the diet of the spotted killifish Nothobranchius orthonotus over two seasons (dry and wet seasons). The foodweb consisted of only three trophic levels and comprised different foodweb items between the two seasons. Stable isotope analysis indicated significant increases in δ15N from the dry to wet season. It further revealed the diet of N. orthonotus to be more varied and omnivorous with primary producers contributing a much greater percentage toward their diet than previous studies have reported. This study contributes valuable information to the paucity of knowledge regarding foodweb structure and food-chain length of temporary pools in South Africa, as well as new insights into the extended diet of N. orthonotus. The analytical techniques used in this study could also be utilised as part of future research in ecological assessments of temporary pools and other aquatic ecosystems in Africa and globally.
  • Haruya Toyomaki, John Yabe, Shouta M.M. Nakayama, Yared B. Yohannes, Kaampwe Muzandu, Allan Liazambi, Yoshinori Ikenaka, Takeshi Kuritani, Mitsuhiro Nakagawa, Mayumi Ishizuka
    Chemosphere 247 125884 - 125884 2020年05月 [査読有り][通常論文]
     
    Lead (Pb)-poisoning is a serious public health concern and dogs have been useful as a sentinel-animal for Pb exposure of humans. In the present study, the blood Pb concentrations (BLC), isotope ratios (208 Pb/206 Pb and 207 Pb/206 Pb), and biochemistry of 120 domestically owned dogs living around a Pb mining area, in Kabwe, Zambia were analyzed to determine factors associated with Pb exposure. The overall mean value of Pb in dog blood in the present study was 271.6 μg/L. The BLC in the dogs from sites near the mine were significantly higher than those in the dogs from a site 4 km from the mine (352.9 ± 205.1 μg/L versus 28.0 ± 13.9 μg/L). BLC significantly decreased with both increasing age of the dogs and distance from the mine. The Pb isotope ratios in the dog that resided near the mine showed values similar to those reported at the galena mine in Kabwe, which is considered to be the source of Pb exposure. In contrast to the high metal exposure that was determined in these dogs, the mean values of most analyzed parameters in the blood biochemical analysis were surprisingly within or close to the standard reference values. Moreover, none of the dogs showed overt signs of Pb-poisoning or other clinical symptoms. The results of analysis of Pb exposure of the dogs obtained in the present study, which are similar to the previously reported results in human in this location, suggest that dogs could be useful as a sentinel animal for Pb exposure of humans in Kabwe.
  • Marthias Silwamba, Mayumi Ito, Naoki Hiroyoshi, Carlito Baltazar Tabelin, Ryota Hashizume, Tomoki Fukushima, Ilhwan Park, Sanghee Jeon, Toshifumi Igarashi, Tsutomu Sato, Meki Chirwa, Kawawa Banda, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama, Mayumi Ishizuka
    Metals 10 4 531 - 531 2020年04月 [査読有り][通常論文]
     
    Zinc plant leach residues (ZPLRs) contain significant amounts of metal compounds of lead (Pb), zinc (Zn), iron (Fe), etc., hence, they are considered as a secondary source of metals. On the other hand, ZPLRs are regarded as hazardous materials because they contain heavy metals that pollute the environment. Resources and environmental concerns of ZPLRs were addressed in this study by removing/recovering Pb and Zn using a concurrent dissolution and cementation technique. To cement the dissolved Pb and Zn in leaching pulp, zero-valent aluminum (ZVAl) was added during ZPLRs leaching in the hydrochloric (HCl)-sodium chloride (NaCl) solution. The resulting cemented metals were agglomerated and separated by sieving. Lead removal increased with increasing both NaCl and HCl concentrations. However, when ZVAl was added, significant Pb removal was achieved at a low concentration. Zinc was not cemented out of the pulp using ZVAl and its recovery from ZPLRs was dependent on the HCl concentration only. By applying a concurrent dissolution and cementation technique, both Pb and Zn were removed using a low concentration of NaCl, and most importantly Pb-the most toxic metal in ZPLRs-was captured and separated before the solid-liquid separation, hence, eliminating the need for extensive washing of the generated residues to remove the inherent residual solution.
  • Shuji Ohno, Yoshinori Ikenaka, Kanoko Onaru, Shizuka Kubo, Nanami Sakata, Tetsushi Hirano, Youhei Mantani, Toshifumi Yokoyama, Keisuke Takahashi, Keisuke Kato, Koji Arizono, Takahiro Ichise, Shouta M.M. Nakayama, Mayumi Ishizuka, Nobuhiko Hoshi
    Toxicology Letters 322 32 - 38 2020年04月 [査読有り][通常論文]
     
    Neonicotinoids (NNs), a widely used class of systemic pesticides, are regarded as exhibiting selective toxicity in insects. However, NNs are suspected of exerting adverse effects on mammals as well, including humans. To date, only adult male animal models have been subjected to general toxicity studies of NNs; fetuses have yet to be considered in this context. Here, we focused on the NN clothianidin (CLO) for the first quantitative LC–MS/MS analysis of maternal-to-fetal transfer and residual property of once-daily (single or multiple days), orally administered CLO and its metabolites in mice. The results revealed the presence of CLO and its five metabolites at approximately the same respective blood levels in both dams and fetuses. In the dams, CLO showed a peak value 1 h after administration, after which levels rapidly decreased at 3 and 6 h. In the fetuses of each group, levels of CLO were almost the same as those observed in the corresponding dams. The present results clearly demonstrated rapid passage of CLO through the placental barrier. However, metabolite-dependent differences observed in blood pharmacokinetics and residual levels. This is the first quantitative demonstration of the presence of CLO and its metabolites in fetal mouse blood.
  • Tadashi Takada, Naoki Yoneda, Tetsushi Hirano, Kanoko Onaru, Youhei Mantani, Toshifumi Yokoyama, Hiroshi Kitagawa, Yoshiaki Tabuchi, Collins Nimako, Mayumi Ishizuka, Yoshinori Ikenaka, Nobuhiko Hoshi
    The Journal of veterinary medical science 82 3 350 - 359 2020年03月24日 [査読有り][通常論文]
     
    Dinotefuran (DIN) belongs to the neonicotinoids (NNs), a class of globally applied pesticides originally developed to exhibit selective toxicity in insects. However, several reports have suggested that NNs also exert neurotoxic effects in mammals. We previously demonstrated neurobehavioral effects of DIN on mice under non-stressful conditions. For further toxicity assessments in the present study, we investigated the effects of DIN on mice exposed to stressful conditions. After subacutely administering a no-observed-effect-level (NOEL) dose of DIN and/or chronic unpredictable mild stress (CUMS) to mice, we conducted three behavioral tests (i.e., open field test [OFT], tail suspension test [TST] and forced swimming test [FST]). In addition, serotonin (5-HT) and tryptophan hydroxylase 2 (TPH2) of the dorsal raphe nuclei (DRN) and median raphe nuclei (MRN) and tyrosine hydroxylase (TH) of the ventral tegmental area and substantia nigra (SN) were evaluated immunohistochemically. A NOEL dose of DIN or CUMS alone increased of the total distance in OFT, decreased or increased the immobility time in TST or FST, respectively, and increased the positive intensity of 5-HT and TPH2 in the DRN/MRN, and TH in the SN. These changes were suppressed under the conditions of combined exposure to DIN and CUMS, though the blood corticosterone level was increased depending on the blood DIN values and the presence of CUMS. The present study suggests the multifaceted toxicity of the neurotoxin DIN.
  • John Yabe, Shouta MM Nakayama, Hokuto Nakata, Haruya Toyomaki, Yared B. Yohannes, Kaampwe Muzandu, Andrew Kataba, Golden Zyambo, Masato Hiwatari, Daiju Narita, Daichi Yamada, Peter Hangoma, Nosiku Sipilanyambe Munyinda, Tiza Mufune, Yoshinori Ikenaka, Kennedy Choongo, Mayumi Ishizuka
    Chemosphere 243 125412 - 125412 2020年03月 [査読有り][通常論文]
     
    Childhood lead (Pb) poisoning has devastating effects on neurodevelopment and causes overt clinical signs including convulsions and coma. Health effects including hypertension and various reproductive problems have been reported in adults. Historical Pb mining in Zambia's Kabwe town left a legacy of environmental pollution and childhood Pb poisoning. The current study aimed at establishing the extent of Pb poisoning and exposure differences among family members in Kabwe as well as determining populations at risk and identify children eligible for chelation therapy. Blood samples were collected in July and August 2017 from 1190 household members and Pb was measured using a portable LeadCare-II analyser. Participants included 291 younger children (3-months to 3-years-old), 271 older children (4-9-years-old), 412 mothers and 216 fathers from 13 townships with diverse levels of Pb contamination. The Blood Lead Levels (BLL) ranged from 1.65 to 162 μg/dL, with residents from Kasanda (mean 45.7 μg/dL) recording the highest BLL while Hamududu residents recorded the lowest (mean 3.3 μg/dL). Of the total number of children sampled (n = 562), 23% exceeded the 45 μg/dL, the threshold required for chelation therapy. A few children (5) exceeded the 100 μg/dL whereas none of the parents exceeded the 100 μg/dL value. Children had higher BLL than parents, with peak BLL-recorded at the age of 2-years-old. Lead exposure differences in Kabwe were attributed to distance and direction from the mine, with younger children at highest risk. Exposure levels in parents were equally alarming. For prompt diagnosis and treatment, a portable point-of-care devise such as a LeadCare-II would be preferable in Kabwe.
  • Kosuke Tanaka, Yutaka Watanuki, Hideshige Takada, Mayumi Ishizuka, Rei Yamashita, Mami Kazama, Nagako Hiki, Fumika Kashiwada, Kaoruko Mizukawa, Hazuki Mizukawa, David Hyrenbach, Michelle Hester, Yoshinori Ikenaka, Shouta M M Nakayama
    Current biology : CB 30 4 723 - 728 2020年02月24日 [査読有り][通常論文]
     
    Plastic debris is ubiquitous and increasing in the marine environment [1]. A wide range of marine organisms ingest plastic, and its impacts are of growing concern [2]. Seabirds are particularly susceptible to plastic pollution because of high rates of ingestion [3]. Because marine plastics contain an array of hazardous compounds, the chemical impacts of ingestion are concerning. Several studies on wild seabirds suggested accumulation of plastic-derived chemicals in seabird tissues [4-7]. However, to date, the evidence has all been indirect [4-7], and it is unclear whether plastic debris is the source of these pollutants. To obtain direct evidence for the transfer and accumulation of plastic additives in the tissues of seabirds, we conducted an in vivo plastic feeding experiment. Environmentally relevant exposure of plastics compounded with one flame retardant and four ultraviolet stabilizers to streaked shearwater (Calonectris leucomelas) chicks in semi-field conditions resulted in the accumulation of the additives in liver and adipose fat of 91 to 120,000 times the rate from the natural diet. Additional monitoring of six seabird species detected these chemical additives only in those species with high plastic ingestion rates, suggesting that plastic debris can be a major pathway of chemical pollutants into seabirds. These findings provide direct evidence of seabird exposure to plastic additives and emphasize the role of marine debris ingestion as a source of chemical pollution in marine organisms.
  • Shouta M M Nakayama, Ayuko Morita, Yoshinori Ikenaka, Yusuke K Kawai, Kensuke P Watanabe, Chihiro Ishii, Hazuki Mizukawa, Yared B Yohannes, Keisuke Saito, Yukiko Watanabe, Masaki Ito, Natsuo Ohsawa, Mayumi Ishizuka
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 228 108635 - 108635 2020年02月 [査読有り][通常論文]
     
    Worldwide use of anticoagulant rodenticides (ARs) for rodents control has frequently led to secondary poisoning of non-target animals, especially raptors. In order to suggest some factors that may help considering the mechanism of the incidents, this study focused on the avian vitamin K 2, 3-epoxide reductase (VKOR) that is the target protein of ARs. We addressed the interspecific differences in VKOR activity and inhibition related to amino acid sequence and mRNA expression of VKORC1 and VKORC1-like1 (VKORC1L1). Poultry have been considered to be more tolerant to ARs than mammals. However, VKOR activity of owls, hawks, falcon and surprisingly, canaries, was lower and inhibited by warfarin more easily than that of chickens and turkeys. The amino acid sequence of VKORC1 and VKORC1L1 implied that the value of Ki for VKOR activity to ARs could depend on the amino acid at position 140 in the TYX warfarin-binding motif in VKORC1, and other amino acid mutations in VKORC1L1. The mRNA expression ratio of VKORC1:VKORC1L1 differed between turkey (8:1) and chicken (2:3) liver. VKORC1L1 has been reported to be resistant to warfarin compared to VKORC1. Hence, both the Ki of specific VKORC1 and VKORC1L1, and the mRNA expression ratio would cause avian interspecific difference of the VKOR inhibition. Our study also suggested the high inhibition of VKOR activities in raptors and surprisingly that in canaries as well. These factors are the most likely to contribute to the high sensitivity to ARs found in raptors.
  • 平井 杏梨, 杉尾 翔太, 池中 良徳, Nimako COLLINS, 中山 翔太, 星 信彦, 和氣 弘明, 石塚 真由美
    日本毒性学会学術年会 47.1 P-4S  日本毒性学会 2020年 
    一部の化学物質は脳内の受容体に作用する事で細胞内、細胞間における情報伝達を攪乱する“シグナル毒性”を示し、予期せぬ影響を引き起こす。特に脳機能は神経細胞やグリア細胞間の複雑なシグナルネットワークが形成されており、このネットワークの攪乱は、シグナル毒性のクリティカルなエンドポイントになり得ると考えられる。しかし、シグナル毒性を起因とする“脳機能の攪乱”は、細胞死やそれに伴う脳組織変性を伴わない場合が多く、現行の神経毒性試験法では検出不可能である。そこで、本研究では、ニコチン性アセチルコリン受容体 (nAChR)のアゴニストであるネオニコチノイド(NNs)およびニコチンをモデル化合物とし、体性感覚野における神経細胞の活動変化を2光子顕微鏡で検出する事で、シグナル毒性に伴う脳機能の攪乱を検出する事を目的とした。 まず、C57BL/6Nマウスを用い、アセタミプリド(ACE)をマウスの最小毒性量である20 mg/kgとなるように経口投与し、経時的に採血を行い、LC/MSを用いてACEおよびその代謝産物の血中濃度を定量した。また、ACEを20 mg/kgおよび7.1 mg/kgとなるように経口投与し、投与1時間後にオープンフィールド試験および高架式十字迷路試験をそれぞれ行った。さらに、C57BL/6JマウスにACEを30 mg/kgおよび典型的なnAChRアゴニストであるニコチンをLD50の半分の濃度（1.6 mg/kg）となるように経口投与し、2光子顕微鏡を用いて、体性感覚野における神経細胞の活動を経時的に観察した。 結果について、ACEのTmaxは約25分で、主要な代謝産物であるdm-ACEでは約150分であった。ACE投与の1時間後には、マウスの活動性は抑制され、不安様行動が増加した。また、体性感覚野において、ACE投与1時間後および2時間半後に神経細胞の発火頻度が減少し、同期発火が増加した。ニコチン投与直後および30分後には、発火頻度が減少傾向を示し、同期発火が増加した。本結果は、脳神経活動の変化が行動の変化の原因であることを示唆する結果であった。
  • Taishi Kidaka, Sithumini M.W. Lokupathirage, Bungiriye Devinda Shameera Muthusinghe, Boniface Lombe Pongombo, Christida Estu Wastika, Zhouxing Wei, Shizuka Yoshioka, Mayumi Ishizuka, Yoshihiro Sakoda, Hiroaki Kariwa, Norikazu Isoda
    Japanese Journal of Veterinary Research 68 3 133 - 150 2020年 
    An outbreak of novel coronavirus infection occurred in China at the end of 2019, which was designated as coronavirus disease 2019 (COVID-19), and spread to regions across Asia and ultimately all over the world. As of 21 May 2020, a total of more than 5 million cases with more than 350 thousand deaths were reported worldwide. Evaluation of the pathogenicity of the disease and determining the efficacy of control measures are essential for rapid containment of the disease. However, the world is facing difficulties in controlling COVID-19 at both of the national and global levels due to variations in pathogenicity of infection by severe acute respiratory syndrome coronavirus 2, the causal agent of COVID-19, and to diverse measures applied in each country based on their control capacities and policies. In the present review, we summarize the basic information and findings related to the COVID-19 pandemic, including pathogen agent, epidemiology, disease transmission, and clinical manifestations. Diagnosis, treatment, and preventive measures applied or under development all over the world are also reviewed to provide the opportunity to establish a more effective scenario for disease containment. Humanity has progressed by developing countless great technologies and immense scientific theories, however it may be a fact that we cannot conquer all risks to humanity. New findings and challenges for the unprecedented pandemic at the global level, such as COVID-19, should also contribute to preparedness for unknown diseases in future, similar to the lessons learnt from severe acute respiratory syndrome and the pandemic A(H1N1)pdm09 influenza.
  • Masao Togao, Shouta M M Nakayama, Yoshinori Ikenaka, Hazuki Mizukawa, Yoshiki Makino, Ayano Kubota, Takehisa Matsukawa, Kazuhito Yokoyama, Takafumi Hirata, Mayumi Ishizuka
    Chemosphere 238 124581 - 124581 2020年01月 [査読有り][通常論文]
     
    Lead (Pb) pollution is one of the most serious environmental problems and has attracted worldwide attention. Pb causes hematological, central nervous system, as well as renal toxicity, and so on. Although many investigations about Pb in blood to evaluate pollution status and toxic effects have been reported, there are open question about biological behavior of Pb. In order to reveal any toxicological mechanisms or influences, we focused on the local distribution of Pb in mice organs. Lead acetate (100 mg/L and 1000 mg/L) in drinking water were given to the BALB/c mice (male, seven weeks of age, N = 24) for three weeks. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis revealed a homogenous distribution of Pb in the liver and inhomogeneous distribution in the kidney and brain. The hippocampus, thalamus, and hypothalamus had higher concentrations than other areas such as the white matter. Surprisingly, in the kidney, Pb tended to accumulate in the medulla rather than the cortex, strongly suggesting that high sensitivity areas and high accumulation areas differ. Moreover, distribution of stromal interacting protein 1 (STIM1) which is candidate gene of Pb pathway to the cells was homogenous in the liver and kidney whereas inhomogeneous in the brain. In contrast to our hypothesis, interestingly, Pb exposure under the current condition did not induce mRNA expressions for any candidate channel or transporter genes. Thus, further study should be conducted to elucidate the local distribution of Pb and other toxic metals, and pathway that Pb takes to the cells.
  • Kosuke Tanaka, Hideshige Takada, Yoshinori Ikenaka, Shouta M M Nakayama, Mayumi Ishizuka
    Marine pollution bulletin 150 110732 - 110732 2020年01月 [査読有り][通常論文]
     
    In the ocean, plastic debris containing chemical additives is fragmented into smaller pieces that can be ingested by a wide range of organisms, potentially exposing them to additives. However, the levels of additives retained in marine plastic fragments have rarely been assessed. In this study, 141 plastic fragments from a beach in Kauai were analyzed piece-by-piece for 12 compounds, including UV stabilizers and brominated flame retardants. UV stabilizers (UV-326, UV-328, UV-327, and BP-12) were found in 13% of "small" fragments (4-7 mm) with levels of up to 315 μg/g and in 33% of "large" fragments (15-80 mm) with levels of up to 1130 μg/g. This observation suggests that exhaustive leaching of additives does not occur during fragmentation and that significant levels of additives, comparable to those of the original products, can be retained in fragments of marine plastic, indicating their importance as a vector of chemical additive exposure.
  • 水川 葉月, 野見山 桂, 池中 良徳, 中山 翔太, 石塚 真由美, 高橋 真
    環境ホルモン学会研究発表会要旨集 22回 45 - 45 環境ホルモン学会(日本内分泌撹乱化学物質学会) 2019年12月
  • Kraisiri Khidkhan, Hazuki Mizukawa, Yoshinori Ikenaka, Shouta M M Nakayama, Kei Nomiyama, Nozomu Yokoyama, Osamu Ichii, Wageh Sobhy Darwish, Mitsuyoshi Takiguchi, Shinsuke Tanabe, Mayumi Ishizuka
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 226 108613 - 108613 2019年12月 [査読有り][通常論文]
     
    Cats have been known to be extremely sensitive to chemical exposures. To understand these model species' sensitivity to chemicals and their toxicities, the expression profiles of xenobiotic-metabolizing enzymes should be studied. Unfortunately, the characterization of cytochrome P450 (CYP), the dominant enzyme in phase I metabolism, in cats has not extensively been studied. Polychlorinated biphenyls (PCBs) are known as CYP inducers in animals, but the information regarding the PCB-induced CYP expression in cats is limited. Therefore, in the present study, we aimed to elucidate the mRNA expression of the CYP1-CYP3 families in the cat tissues and to investigate the CYP mRNA expression related to PCB exposure. In cats, the greatest abundance of CYP1-CYP3 (CYP1A2, CYP2A13, CYP2C41, CYP2D6, CYP2E1, CYP2E2, CYP2F2, CYP2F5, CYP2J2, CYP2U1, and CYP3A132) was expressed in the liver, but some extrahepatic isozymes were found in the kidney (CYP1A1), heart (CYP1B1), lung (CYP2B11 and CYP2S1) and small intestine (CYP3A131). In cats, CYP1A1, CYP1A2 and CYP1B1 were significantly upregulated in the liver as well as in several tissues exposed to PCBs, indicating that these CYPs were distinctly induced by PCBs. The strong correlations between 3,3',4,4'-tetrachlorobiphenyl (CB77) and CYP1A1 and CYP1B1 mRNA expressions were noted, demonstrating that CB77 could be a potent CYP1 inducer. In addition, these CYP isoforms could play an essential role in the PCBs biotransformation, particularly 3-4 Cl-PCBs, because a high hydroxylated metabolite level of 3-4 Cl-OH-PCBs was observed in the liver.
  • Kodai Motohira, Yoshinori Ikenaka, Yared Beyene Yohannes, Shouta M M Nakayama, Victor Wepener, Nico J Smit, Johan H J VAN Vuren, Ana Catarina Sousa, Alex Ajeh Enuneku, Emmanuel Temiotan Ogbomida, Mayumi Ishizuka
    The Journal of veterinary medical science 81 11 1575 - 1579 2019年11月14日 [査読有り][通常論文]
     
    Dichlorodiphenyltrichloroethane (DDT) is an organochlorine insecticide that has been used for indoor residual spraying for the control of mosquito-borne diseases including malaria. However, due to its toxicity and environmental persistence, there are concerns about its potential deleterious effects in humans and wildlife. Therefore, the current study aimed to monitor and estimate the level of DDTs in human communities. The accumulation of DDT and its metabolites was evaluated in house rat (as sentinel) livers collected in an area where DDT was sprayed. DDTs were measured using a gas chromatography / Electron Capture Detector. The results revealed high concentrations of DDTs in the rat livers and the levels of DDTs were similar to findings reported from the same area in 2014.
  • Lesa A Thompson, Yoshinori Ikenaka, Wageh Sobhy Darwish, Shouta M M Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    Environmental toxicology and pharmacology 72 103249 - 103249 2019年11月 [査読有り][通常論文]
     
    The organochlorine pesticide dichloro-diphenyl-trichloroethane (DDT) is persistent in the environment and leads to adverse human health effects. High levels in breast milk pose a threat to both breast tissue and nursing infants. The objectives of this study were to investigate DDT-induced transcriptomic alterations in enzymes and transporters involved in xenobiotic metabolism, immune responses, oxidative stress markers, and cell growth in a human breast cancer cell line. MCF-7 cells were exposed to both environmentally-relevant and previously-tested concentrations of p,p'-DDT in a short-term experiment. Significant up-regulation of metabolizing enzymes and transporters (ACHE, GSTO1, NQO1 and ABCC2) and oxidative stress markers (CXCL8, HMOX-1, NFE2L2 and TNF) was clearly observed. Conversely, UGT1A6, AHR and cell growth genes (FGF2 and VEGFA) were severely down-regulated. Identification of these genes helps to identify mechanisms of p,p'-DDT action within cells and may be considered as useful biomarkers for exposure to DDT contamination.
  • Kohki Takaguchi, Hiroyuki Nishikawa, Hazuki Mizukawa, Rumi Tanoue, Nozomu Yokoyama, Osamu Ichii, Mitsuyoshi Takiguchi, Shouta M M Nakayama, Yoshinori Ikenaka, Tatsuya Kunisue, Mayumi Ishizuka, Shinsuke Tanabe, Hisato Iwata, Kei Nomiyama
    The Science of the total environment 688 1172 - 1183 2019年10月20日 [査読有り][通常論文]
     
    Polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) might disrupt thyroid function. However, there is no clear evidence of PCB exposure disrupting thyroid hormone (TH) homeostasis in dogs and cats. The present study conducted in vivo experiments to evaluate the effects of a mixture of 12 PCB congeners (CB18, 28, 70, 77, 99, 101, 118, 138, 153, 180, 187 and 202, each congener 0.5 mg/kg BW, i.p. administration) on serum TH levels in male dogs (Canis lupus familiaris) and male cats (Felis silvestris catus). In PCB-exposed dogs, the time courses of higher-chlorinated PCBs and L-thyroxine (T4)-like OH-PCBs (4-OH-CB107 and 4-OH-CB202) concentrations were unchanged or tended to increase, whereas those of lower-chlorinated PCBs and OH-PCBs tended to decrease after 24 h. In PCB-exposed cats, concentrations of PCBs increased until 6 h and then remained unchanged. The levels of lower-chlorinated OH-PCBs including 4'-OH-CB18 increased until 96 h and then decreased. In PCB-exposed dogs, free T4 concentrations were higher than those in the control group at 48 and 96 h after PCB administration and positively correlated with the levels of T4-like OH-PCBs, suggesting competitive binding of T4 and T4-like OH-PCBs to a TH transporter, transthyretin. Serum levels of total T4 and total 3,3',5-triiodo-L-thyronine (T3) in PCB-exposed dogs were lower than in the control group at 24 and 48 h and negatively correlated with PCB concentrations, implying that PCB exposure enhanced TH excretion by increasing TH uptake and TH conjugation enzyme activities in the dog liver. In contrast, no obvious changes in TH levels were observed in PCB-exposed cats. This could be explained by the lower levels of T4-like OH-PCBs and lower hepatic conjugation enzyme activities in cats compared with dogs. Different effects on serum TH levels in PCB-exposed dogs and cats are likely to be attributable to species-specific PCB and TH metabolism.
  • C.M. Volschenk, R. Gerber, M.T. Mkhonto, Y. Ikenaka, Y.B. Yohannes, S. Nakayama, M. Ishizuka, J.H.J. van Vuren, V. Wepener, N.J. Smit
    Science of The Total Environment 685 1116 - 1126 2019年10月
  • Tarryn L Botha, Sarel J Brand, Yoshinori Ikenaka, Shouta M M Nakayama, Mayumi Ishizuka, Victor Wepener
    Aquatic toxicology (Amsterdam, Netherlands) 215 105287 - 105287 2019年10月 [査読有り][通常論文]
     
    Gold nanoparticles are used as drug delivery vectors based on the assumption that they have low toxicity. Literature has, however, produced conflicting results over the last few years. As such, this study aimed to investigate the toxicological effects of nanogold (nAu) on several indicators that range from subcellular to whole-organism level. Gene regulation, changes in oxidative stress biomarkers and swimming performance were assessed in Danio rerio (zebrafish) following exposures to nAu. Adult zebrafish were exposed in vivo to nAu for 96 h and swimming performance measured post-exposure. Liver tissue was collected for DNA microarray and Real-Time Polymerase Chain Reactions (RT-PCR) analyses to determine changes in gene expression (catalase, superoxide dismutase and metallothioneins) and protein biomarker analyses (catalase, superoxide dismutase, acetylcholine esterase, malondialdehyde, cellular energy allocation and metallothionein) were performed on whole-body samples. Swimming behaviour was assessed in 1.1 L Tecniplast™ tanks for a period of six hours and videos were analysed using Noldus EthoVision software. Critical swimming speed was measured in a Loligo® swimming tunnel. The DNA microarray revealed that fish exposed to 20 mg/L differed most from the control group. At 20 mg/L there was a significant increase in gene expression for all genes analysed but this didn't translate to significant responses in protein biomarker levels except for an increase in protein carbonyl formation. The behaviour results demonstrated significant changes in distance moved, swimming speed, acceleration bouts, zone alterations and time spent within the top zone - responses that are usually observed in fish responding to toxicological stress. Furthermore, the critical swimming speed of exposed fish was decreased significantly compared to the control. Since swimming performance and social interaction among zebrafish is essential to their survival, whole-organism behaviour that suggests a toxicological response after exposure to nAu is in agreement with the genetic responses measured in this study.
  • Shouta M M Nakayama, Hokuto Nakata, Yoshinori Ikenaka, John Yabe, Balazs Oroszlany, Yared B Yohannes, Nesta Bortey-Sam, Kaampwe Muzandu, Kennedy Choongo, Takeshi Kuritani, Mitsuhiro Nakagawa, Mayumi Ishizuka
    Environmental pollution (Barking, Essex : 1987) 252 Pt B 1267 - 1276 2019年09月 [査読有り][通常論文]
     
    Metal pollution has been associated with anthropogenic activities, such as effluents and emissions from mines. Soil could be exposure route of wild rats to metals, especially in mining areas. The aim of this study was to verify whether soil exposure under environmentally relevant circumstances results in metal accumulation and epigenetic modifications. Wistar rats were divided to three groups: 1) control without soil exposure, 2) low-metal exposure group exposed to soil containing low metal levels (Pb: 75 mg/kg; Cd: 0.4), and 3) high-metal exposure group exposed to soil (Pb: 3750; Cd: 6). After 1 year of exposure, the metal levels, Pb isotopic values, and molecular indicators were measured. Rats in the high-group showed significantly greater concentrations of Pb and Cd in tissues. Higher accumulation factors (tissue/soil) of Cd than Pb were observed in the liver, kidney, brain, and lung, while the factor of Pb was higher in the tibia. The obtained results of metal accumulation ratios (lung/liver) and stable Pb isotope ratios in the tissues indicated that the respiratory exposure would account for an important share of metal absorption into the body. Genome-wide methylation status and DNA methyltransferase (Dnmt 3a/3b) mRNA expressions in testis were higher in the high-group, suggesting that exposure to soil caused metal accumulation and epigenetic alterations in rats.
  • Ryu Miura, Atsuko Araki, Machiko Minatoya, Kunio Miyake, Mei-Lien Chen, Sumitaka Kobayashi, Chihiro Miyashita, Jun Yamamoto, Toru Matsumura, Mayumi Ishizuka, Takeo Kubota, Reiko Kishi
    Scientific reports 9 1 12369 - 12369 2019年08月26日 [査読有り][通常論文]
     
    Exposure to bisphenol A (BPA) in utero is associated with adverse health outcome of the offspring. Differential DNA methylation at specific CpG sites may link BPA exposure to health impacts. We examined the association of prenatal BPA exposure with genome-wide DNA methylation changes in cord blood in 277 mother-child pairs in the Hokkaido Study on Environment and Children's Health, using the Illumina HumanMethylation 450 BeadChip. We observed that a large portion of BPA-associated differentially methylated CpGs with p-value < 0.0001 was hypomethylated among all newborns (91%) and female infants (98%), as opposed to being hypermethylated (88%) among males. We found 27 and 16 CpGs with a false discovery rate (FDR) < 0.05 in the analyses for males and females, respectively. Genes annotated to FDR-corrected CpGs clustered into an interconnected genetic network among males, while they rarely exhibited any interactions in females. In contrast, none of the enrichment for gene ontology (GO) terms with FDR < 0.05 was observed for genes annotated to the male-specific CpGs with p < 0.0001, whereas the female-specific genes were significantly enriched for GO terms related to cell adhesion. Our epigenome-wide analysis of cord blood DNA methylation implies potential sex-specific epigenome responses to BPA exposure.
  • Wilson Mwandira, Kazunori Nakashima, Satoru Kawasaki, Mayumi Ito, Tsutomu Sato, Toshifumi Igarashi, Meki Chirwa, Kawawa Banda, Imasiku Nyambe, Shouta Nakayama, Hokuto Nakata, Mayumi Ishizuka
    Chemosphere 228 17 - 25 2019年08月 [査読有り][通常論文]
     
    Environmental impacts resulting from historic lead and zinc mining in Kabwe, Zambia affect human health due to the dust generated from the mine waste that contains lead, a known hazardous pollutant. We employed microbially induced calcium carbonate precipitation (MICP), an alternative capping method, to prevent dust generation and reduce the mobility of contaminants. Pb-resistant Oceanobacillus profundus KBZ 1-3 and O. profundus KBZ 2-5 isolated from Kabwe were used to biocement the sand that would act as a cover to prevent dust and water infiltration. Sand biocemented by KBZ 1-3 and KBZ 2-5 had maximum unconfined compressive strength values of 3.2 MPa and 5.5 MPa, respectively. Additionally, biocemented sand exhibited reduced water permeability values of 9.6 × 10-8 m/s and 8.9 × 10-8 m/s for O. profundus KBZ 1-3 and KBZ 2-5, respectively, which could potentially limit the entrance of water and oxygen into the dump, hence reducing the leaching of heavy metals. We propose that these isolates represent an option for bioremediating contaminated waste by preventing both metallic dust from becoming airborne and rainwater from infiltrating into the waste. O. profundus KBZ 1-3 and O. profundus KBZ 2-5 isolated form Kabwe represent a novel species that has, for the first time, been applied in a bioremediation study.
  • Zinc and Lead Biosorption by Oceanobacillus Profundus Kbz 3-2: a Bacterial Strain Resistant to Metals Isolated from Metal polluted Soils in Kabwe, Zambia
    Wilson Mwandira, Kazunori Nakashima, Satoru Kawasaki, Mayumi Ito, Tsutomu Sato, Toshifumi Igarashi, Meki Chirwa, Kawawa Banda, Imasiku Nyambe, Shouta Nakayama, Mayumi Ishizuka
    Proceedings of the 14th Asian Congress on Biotechnology (ACB2019) 2019年07月 [査読有り][通常論文]
  • ネオニコチノイド系殺虫剤と農薬の現状と今後の展望〜毒性学・農学・行政の視点から〜 ネオニコチノイド系殺虫剤の曝露実態の解明と毒性評価
    池中 良徳, 一瀬 貴大, Nimako Collins, 中山 翔太, 平野 哲史, 市川 剛, 加藤 恵介, 高橋 圭介, 長谷川 浩, 平 久美子, 有薗 幸司, 星 信彦, 藤岡 一俊, 石塚 真由美
    The Journal of Toxicological Sciences 44 Suppl. S53 - S53 (一社)日本毒性学会 2019年06月
  • H Bouwman, Y B Yohannes, S M M Nakayama, K Motohira, M Ishizuka, M S Humphries, V van der Schyff, M du Preez, A Dinkelmann, Y Ikenaka
    Chemosphere 225 647 - 658 2019年06月 
    DDT remains in use for malaria control in South Africa. We quantified DDTs in aquatic bird eggs from the highly biodiverse northern KwaZulu-Natal, a province of South Africa where DDT has been used for more than 80 years for malaria control. Pelican eggs had the highest ΣDDT concentration (7200 ng/g lipid mass; lm), Little Egret eggs had 6900 ΣDDT lm, African Openbill eggs had 3400 ng/g lm ΣDDT, and White-breasted Cormorant had 2400 ng/g lm. All species had non-significantly different mean concentrations of o,p'-DDT, p,p'-DDT, and ΣDDT, but with significant differences for p,p-DDE, o,p'-DDD, p,p'-DDD, %DDT, %DDD, and %lipid. The thinnest pelican eggshell (0.40 mm) had a ΣDDT concentration of 3300 ng/g lm.; the thickest shell (0.96 mm) had the lowest ΣDDT concentration at 29 ng/g lm; a 58% difference. Linear regressions of concentrations with shell thickness for the pelican eggs were significant for p,p'-DDE and p,p'-DDD, indicating risk of reproductive impairment. Compositional profiles indicate different food webs for the different species. DDT concentrations were lower than from another DDT-sprayed locality in South Africa, possible linked to differences in hydrology and rainfall. We conclude that significant ecotoxic threats associated with DDT remain in this area, and possibly threatens birds from less polluted areas. Our findings suggest continued negative human health and environmental impacts from DDT. There is an urgency to move away from DDT as quickly as possible; alternatively, to implement practices that prevent emissions of DDT to the environment while protecting human life.
  • C M Volschenk, Y Ikenaka, Y B Yohannes, S M Nakayama, M Ishizuka, E Smit, J H J van Vuren, R Greenfield
    Pesticide biochemistry and physiology 156 44 - 55 2019年05月 
    The use of 1,1'-(2,2,2-Trichloro-1,1-ethanediyl)bis(4-chlorobenzene) (DDT) as a pesticide for the control of insects vectors responsible for the spread of many life threatening diseases was officially banned in 1972 by the United States Environmental Protection Agency (USEPA). It was banned throughout the world, in most developed countries, because of the toxic effects it causes in wildlife, including birds and fish. However, DDT is still used in approximately 43 African countries, including South Africa, to control the spread of malaria. The lipophilic nature of DDT and therefore its persistence in the environment makes it extremely important for laboratory based studies to be conducted in an effort to evaluate the accumulation potential and possible physiological effects of DDT in aquatic organisms under controlled conditions. The aim of this study was to establish baseline bioaccumulation concentrations within Synodontis zambezensis following an acute exposure to 4,4'-DDT. The three metabolites analysed were 4,4'-DDE, 4,4'-DDD and 4,4'-DDT. None of the 2,4'-isomers were analysed in this study since the acute exposure used a solution of 98.7% pure 4,4'-DDT (Sigma-Aldrich PESTANAL®, Analytical Standard, CAS-No 50-29-3, Batch number SZBE057XV) and not a mixture of 4,4'-DDT and 2,4'-DDT as found in technical grade DDT. Soxhlet extraction of tissue samples and liquid/liquid extraction of water samples followed by analysis through Gas-chromatography mass-spectrophotometry was completed. Mean 4,4'-DDE, 4,4'-DDD and 4,4'-DDT concentrations ranged from 15.34 ng/g to 45.34 ng/g, 28.16 ng/g to 63.25 ng/g and 28.64 ng/g to 96.21 ng/g respectively. All of the accumulated concentrations fell within environmentally relevant concentrations with no input through the food web. The accumulated concentrations of 4,4'-DDT and its three metabolites resulted in oxidative stress responses within the gills and the liver tissue of S. zambezensis. Significant differences (p ≤ .05) were observed between malondialdehyde (MDA) and reduced glutathione (GSH) within the liver and in superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) in the gills.
  • Yasuhiro Uno, Rika Takahira, Norie Murayama, Shunsuke Onozeki, Shu Kawamura, Shotaro Uehara, Yoshinori Ikenaka, Mayumi Ishizuka, Shinichi Ikushiro, Hiroshi Yamazaki
    Biochemical pharmacology 163 335 - 344 2019年05月 [査読有り][通常論文]
     
    UDP-glucuronosyltransferases (UGTs) are essential enzymes metabolizing endogenous and exogenous chemicals. However, characteristics of UGTs have not been fully investigated in molecular levels of cynomolgus macaques, one of non-human primates widely used in preclinical drug metabolism studies. In this study, three UGT2A cDNAs (UGT2A1, 2A2, and 2A3) were isolated and characterized along with seven UGT2Bs previously identified in cynomolgus macaques. Several transcript variants were found in cynomolgus UGT2A1 and UGT2A2, like human orthologs. Cynomolgus UGT2A and UGT2B amino acid sequences were highly identical (87-96%) to their human counterparts. By phylogenetic analysis, all these cynomolgus UGT2s were more closely clustered with their human homologs than with dog, rat, or mouse UGT2s. Especially, UGT2As showed orthologous relationships between humans and cynomolgus macaques. All the cynomolgus UGT2 mRNAs were expressed in livers, jejunum, and/or kidneys abundantly, except that UGT2A1 and UGT2A2 mRNAs were predominantly expressed in nasal mucosa, like human UGT2s. UGT2A and UGT2B genes together form a gene cluster in the cynomolgus and human genome. Among the seven cynomolgus UGT2Bs heterologously expressed in yeast, UGT2B9 and UGT2B30 showed activities in estradiol 17-O-glucuronidation and morphine 3-O-glucuronidation but did not show activities in estradiol 3-O-glucuronidation, similar to human UGT2Bs. In liver microsomes, cynomolgus macaques showed higher estradiol 17-O-glucuronidase and morphine 3-O-glucuronidase activities than humans, suggesting functional activities of the responsible UGT2B enzymes in cynomolgus macaques. Therefore, cynomolgus UGT2s had overall molecular similarities to human UGT2s, but also showed some differences in UGT2B enzyme properties.
  • Wilson Mwandira, Kazunori Nakashima, Satoru Kawasaki, Mayumi Ito, Tsutomu Sato, Toshifumi Igarashi, Kawawa Banda, Meki Chirwa, Imasiku Nyambe, Shouta Nakayama, Mayumi Ishizuka
    Environmental science and pollution research international 26 15 15653 - 15664 2019年05月 [査読有り][通常論文]
     
    Biocementation of hazardous waste is used in reducing the mobility of contaminants, but studies on evaluating its efficacy have not been well documented. Therefore, to evaluate the efficacy of this method, physicochemical factors affecting stabilized hazardous products of in situ microbially induced calcium carbonate precipitation (MICP) were determined. The strength and leach resistance were investigated using the bacterium Pararhodobacter sp. Pb-contaminated kiln slag (KS) and leach plant residue (LPR) collected from Kabwe, Zambia, were investigated. Biocemented KS and KS/LPR had leachate Pb concentrations below the detection limit of < 0.001 mg/L, resisted slaking, and had maximum unconfined compressive strengths of 8 MPa for KS and 4 MPa for KS/LPR. Furthermore, biocemented KS and KS/LPR exhibited lower water absorption coefficient values, which could potentially reduce the water transportation of Pb2+. The results of this study show that MICP can reduce Pb2+ mobility in mine wastes. The improved physicochemical properties of the biocemented materials, therefore, indicates that this technique is an effective tool in stabilizing hazardous mine wastes and, consequently, preventing water and soil contamination.
  • Yusuke K Kawai, So Shinya, Yoshinori Ikenaka, Aksorn Saengtienchai, Takamitsu Kondo, Wageh Sobhy Darwish, Shota M M Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 217 5 - 14 2019年03月 [査読有り][通常論文]
     
    Birds are exposed to many xenobiotics during their lifetime. For accurate prediction of xenobiotic-induced toxic effects on avian species, it is necessary to understand metabolic capacities in a comprehensive range of bird species. However, there is a lack of information about avian xenobiotic metabolizing enzymes (XMEs), particularly in wild birds. Uridine diphosphate glucuronosyltransferase (UGT) is an XME that plays an important role in phase II metabolism in the livers of mammals and birds. This study was performed to determine the characteristics of UGT1E isoform in avian species, those are related to mammals UGT 1A. To understand the characteristics of avian UGT1E isoforms, in vitro metabolic activity and genetic characteristics were investigated. Furthermore, mRNA expression levels of all chicken UGT1E isoforms were measured. On in vitro enzymatic analysis, the white-tailed eagle, great horned owl, and Humboldt penguin showed lower UGT-dependent activity than domestic birds. In synteny analysis, carnivorous birds were shown to have fewer UGT1E isoforms than herbivorous and omnivorous birds, which may explain why they have lower in vitro UGT activity. These observations suggested that raptors and seabirds, in which UGT activity is low, may be at high risk if exposed to elevated levels of xenobiotics in the environment. Phylogenetic analysis suggested that avian UGT1Es have evolved independently from mammalian UGT1As. We identified the important UGT isoforms, such as UGT1E13, and suspected their substrate specificities in avian xenobiotic metabolism by phylogenetic and quantitative real-time PCR analysis. This is the first report regarding the genetic characteristics and interspecies differences of UGT1Es in avian species.
  • Shouta M M Nakayama, Ayuko Morita, Yoshinori Ikenaka, Hazuki Mizukawa, Mayumi Ishizuka
    The Journal of veterinary medical science 81 2 298 - 313 2019年02月28日 [査読有り][通常論文]
     
    Worldwide use of anticoagulant rodenticides (ARs) for rodents control has frequently led to secondary poisoning of non-target animals, especially raptors. In spite of the occurrence of many incidents of primary or secondary AR-exposure and poisoning of non-target animals, these incidents have been reported only for individual countries, and there has been no comprehensive worldwide study or review. Furthermore, the AR exposure pathway in raptors has not yet been clearly identified. The aim of this review is therefore to comprehensively analyze the global incidence of primary and secondary AR-exposure in non-target animals, and to explore the exposure pathways. We reviewed the published literature, which reported AR residues in the non-target animals between 1998 and 2015, indicated that various raptor species had over 60% AR- detection rate and have a risk of AR poisoning. According to several papers studied on diets of raptor species, although rodents are the most common diets of raptors, some raptor species prey mainly on non-rodents. Therefore, preying on targeted rodents does not necessarily explain all causes of secondary AR-exposure of raptors. Since AR residue-detection was also reported in non-target mammals, birds, reptiles and invertebrates, which are the dominant prey of some raptors, AR residues in these animals, as well as in target rodents, could be the exposure source of ARs to raptors.
  • Shoji A, Elliott KH, Aris-Brosou S, Mizukawa H, Nakayama SMM, Ikenaka Y, Ishizuka M, Kuwae T, Watanabe K, Escoruela Gonzalez J, Watanuki Y
    Environmental toxicology and chemistry 38 1 106 - 114 2019年01月 [査読有り][通常論文]
     
    Physical systems, such as currents and winds, have traditionally been considered responsible for transporting contaminants. Although evidence is mounting that animals play a role in this process through their movements, we still know little about how such contaminant biotransport occurs and the extent of effects at deposition sites. In the present study, we address this question by studying how rhinoceros auklets (Cerorhinca monocerata), a seabird that occurs in immense colonies (∼300 000 pairs at our study site, Teuri Island), affect contaminant levels at their colony and at nearby sites. More specifically, we hypothesize that contaminants are transported and deposited by seabirds at their colony and that these contaminants are passed on locally to the terrestrial ecosystem. To test this hypothesis, we analyzed the concentration of 9 heavy metal and metalloids, as well as δ 13 C and δ 15 N stable isotopes, in bird tissues, plants, and soil, both within and outside of the colony. The results show that rhinoceros auklets transport marine-derived mercury (Hg), possibly from their wintering location, and deposit Hg via their feces at their breeding site, thereby contaminating plants and soils within the breeding colony. The present study confirms not only that animals can transport contaminants from marine to terrestrial ecosystems, potentially over unexpectedly long distances, but also that bird tissues contribute locally to plant contamination. Environ Toxicol Chem 2019;38:106–114. © 2018 SETAC.
  • Yoshinori Ikenaka, Yuichi Miyabara, Takahiro Ichise, Shouta Nakayama, Collins Nimako, Mayumi Ishizuka, Chiharu Tohyama
    Environmental toxicology and chemistry 38 1 71 - 79 2019年01月 [査読有り][通常論文]
     
    Neonicotinoid insecticides that have been on the market since 1992 have been used globally including in Japan. Because they are sprayed over forests and agricultural areas, inadvertent toxicity in nontarget insects (especially honey bees) and humans is a matter of public concern. However, information on exposure levels and potential health impacts of neonicotinoids in children living around sprayed areas is scarce. Thus, we determined neonicotinoid exposure levels in children living in communities where thiacloprid was used to control pine wilt disease. A total of 46 children (23 males and 23 females) were recruited for the present study, and informed written consent was obtained from their guardians. Urine specimens were collected before, during, and after insecticide spraying events; and atmospheric particulate matter was also collected. Concentrations of thiacloprid and 6 other neonicotinoid compounds were determined in urine samples and in atmospheric particulate matter specimens using liquid chromatography-electrospray ionization-tandem mass spectrometry. In urine specimens, thiacloprid concentrations were <0.13 μg/L and were detectable in approximately 30% of all samples. Concentrations of the other neonicotinoids, N-dm-acetamiprid, thiamethoxam, dinotefuran, and clothianidin, were 18.7, 1.92, 72.3, and 6.02 µg/L, respectively. Estimated daily intakes of these neonicotinoids were then calculated from urinary levels; although the estimated daily intakes of the neonicotinoids were lower than current acceptable daily intake values, the children were found to be exposed to multiple neonicotinoids on a daily basis. Environ Toxicol Chem 2019;38:71-79. © 2018 SETAC.
  • Go Ichikawa, Ryota Kuribayashi, Yoshinori Ikenaka, Takahiro Ichise, Shouta M M Nakayama, Mayumi Ishizuka, Kumiko Taira, Kazutoshi Fujioka, Toshimi Sairenchi, Gen Kobashi, Jean-Marc Bonmatin, Shigemi Yoshihara
    PloS one 14 7 e0219208  2019年 [査読有り][通常論文]
     
    OBJECTIVES: Neonicotinoid insecticides are widely used systemic pesticides with nicotinic acetylcholine receptor agonist activity that are a concern as environmental pollutants. Neonicotinoids in humans and the environment have been widely reported, but few studies have examined their presence in fetuses and newborns. The objective of this study is to determine exposure to neonicotinoids and metabolites in very low birth weight (VLBW) infants. METHODS: An analytical method for seven neonicotinoids and one neonicotinoid metabolite, N-desmethylacetamiprid (DMAP), in human urine using LC-ESI/MS/MS was developed. This method was used for analysis of 57 urine samples collected within 48 hours after birth from VLBW infants of gestational age 23-34 weeks (male/female = 36/21, small for gestational age (SGA)/appropriate gestational age (AGA) = 6/51) who were admitted to the neonatal intensive care unit of Dokkyo Hospital from January 2009 to December 2010. Sixty-five samples collected on postnatal day 14 (M/F = 37/22, SGA/AGA = 7/52) were also analyzed. RESULTS: DMAP, a metabolite of acetamiprid, was detected in 14 urine samples collected at birth (24.6%, median level 0.048 ppb) and in 7 samples collected on postnatal day 14 (11.9%, median level 0.09 ppb). The urinary DMAP detection rate and level were higher in SGA than in AGA infants (both p<0.05). There were no correlations between the DMAP level and infant physique indexes (length, height, and head circumference SD scores). CONCLUSION: These results provide the first evidence worldwide of neonicotinoid exposure in newborn babies in the early phase after birth. The findings suggest a need to examine potential neurodevelopmental toxicity of neonicotinoids and metabolites in human fetuses.
  • Aksorn Saengtienchai, Yoshinori Ikenaka, Minami Kawata, Yusuke Kawai, Kazuki Takeda, Takamitsu Kondo, Nesta Bortey-Sam, Shouta M M Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 214 28 - 35 2018年12月 [査読有り][通常論文]
     
    There have been many reports regarding toxic chemicals in birds. Chemicals are mainly metabolized in the liver through phase I oxidation by cytochrome P450 (CYP) and phase II conjugation by conjugated enzymes, such as UDP-glucuronosyltransferase (UGT), sulfotransferase (SULT), glutathione-S-transferase (GST), etc. Xenobiotic metabolism differs among bird species, but little detailed information is available. In the present study, the four-ring polycyclic aromatic hydrocarbon (PAH), pyrene, was used as a model xenobiotic to clarify the characteristics of xenobiotic metabolism in birds compared with laboratory animals by in vivo and in vitro studies. Plasma, bile, and excreta (urine and feces) were collected after oral administration of pyrene and analyzed to clarify xenobiotic metabolism ability in chickens and quails. Interestingly, pyrenediol-glucuronide sulfate (PYDOGS) and pyrenediol-diglucuronide (PYDOGG) were present in chickens and quails but not in rats. In addition, the area under the curve (AUC), maximum plasma concentration (Cmax), and time to maximum plasma concentration (Tmax) of pyrene-1-sulfate (PYOS) were higher than those of the parent molecule, pyrene, while the elimination half-life (t1/2) and mean residence time (MRT) were faster than those of the parent pyrene. With regard to sulfation of 1-hydroxypyrene (PYOH), the maximum velocity (Vmax) and Michaelis constant (Km) of rat liver cytosol were greater than those of chicken and quail liver cytosol. Furthermore, Vmax/Km of UGT activity in rat liver microsomes was also greater than those of chicken and quail liver microsomes. Characterization of xenobiotic metabolism revealed species differences between birds and mammals, raising concerns about exposure to various xenobiotics in the environment.
  • Chihiro Ishii, Shouta M M Nakayama, Andrew Kataba, Yoshinori Ikenaka, Keisuke Saito, Yukiko Watanabe, Yoshiki Makino, Takehisa Matsukawa, Ayano Kubota, Kazuhito Yokoyama, Hazuki Mizukawa, Takafumi Hirata, Mayumi Ishizuka
    Chemosphere 212 994 - 1001 2018年12月 [査読有り][通常論文]
     
    Lead (Pb) poisoning in raptors and water birds is a serious problem in many countries. However, only a small fraction of Pb poisoning has been detected in birds. Bone specimens may be useful indices of Pb exposure because bones contain ∼90% of the total Pb body burden. The original purpose of this study was to comprehensively analyze Pb accumulation in various bone types using inductively coupled plasma-mass spectrometry (ICP-MS). Since our results showed that Pb accumulation differed greatly depending on bone type, a secondary objective was defined, aiming to investigate the fine Pb distribution and its relation to bone structure and bone marrow by using laser ablation (LA)-ICP-MS. Our findings suggested that bone samples (1) consisting of trabecular tissue and (2) those that contain bone marrow could accumulate high levels of Pb following acute exposure. The shorter turnover time of trabecular bone can cause a rapid accumulation of Pb, and bone marrow may have an important role for internal exposure of Pb to bone tissue. Pb is accumulated in bones via blood flow, and bone marrow receives blood from outside the bones. In conclusion, bone samples provide valuable information on Pb exposure and could be useful to investigate and understand mortalities related to suspected Pb poisoning.
  • Wolmarans NJ, Du Preez LH, Yohannes YB, Ikenaka Y, Ishizuka M, Smit NJ, Wepener V
    Ecotoxicology (London, England) 27 9 1203 - 1216 2018年11月 [査読有り][通常論文]
     
    Organochlorine pesticides are highly persistent in aquatic ecosystems. Amphibians, specifically anurans, play an intricate part in the aquatic food web, and have very permeable skin which makes them prone to bioaccumulation of persistent pollutants. In this study the bioaccumulation of various legacy organochlorine pesticides (OCPs)including dichlorodiphenyltrichloroethane (DDT), currently used for malaria vector control (MVC)was assessed along with a set of biomarker responses in Muller's clawed frog Xenopus muelleri collected from the lower Phongolo River floodplain in South Africa. Possible relationships between bioaccumulation and biomarkers (of exposure, oxidative stress biomarkers, and cellular energy allocation) alongside their temporal changes were investigated. The OCP concentrations showed a significant increase over time for the duration of the study. The increase correlated negatively with rainfall from the region. DDT levels were well below expected effects levels with p,p-DDE being the main contributing metabolite. The results of this study indicate OCPs actively accumulate at sub-lethal levels in aquatic frogs from the study area, while showing possible relations towards some of the biochemical stress responses measured. Most notable were negative relationships indicated between p,p-DDE and acetylcholinesterase, malondialdehyde, and carbohydrates and protein energy availability. Levels of DDT were not found to be significantly higher than other legacy pesticides in the frog tissue, although evidence of newly introduced DDT in the frog tissue was found. Further investigation about sub-lethal effects of these pesticides on anurans is required to gain better insight into their full impact on animal livelihood.
  • Yasuhiro Uno, Rika Takahira, Norie Murayama, Yu Ishii, Yoshinori Ikenaka, Mayumi Ishizuka, Hiroshi Yamazaki, Shinichi Ikushiro
    Biochemical pharmacology 155 172 - 181 2018年09月 [査読有り][通常論文]
     
    UDP-glucuronosyltransferases (UGTs) are drug-metabolizing enzymes essential for the metabolism of endogenous substrates and xenobiotics. Molecular characteristics of UGTs have been extensively investigated in humans, but in cynomolgus macaques, a non-human primate species widely used in drug metabolism studies, remain to be investigated. In this study, 12 UGT1A cDNAs (UGT1A1, 1A2, 1A4A, 1A4B, 1A5A, 1A5B, 1A5C, 1A6, 1A7, 1A8, 1A9, and 1A10) were isolated and characterized in cynomolgus macaques. UGT1A5C cDNA did not contain a complete coding region due to nonsense mutations, and was excluded from further analysis. Amino acid sequences of all 11 cynomolgus UGT1As had high sequence identities (92-95%) with human UGT1As and were phylogenetically close to human UGT1As. These cynomolgus UGT1A genes shared exons 2-5, and contained a variable exon 1 unique to each gene, similar to human UGT1A genes. Moreover, cynomolgus and human UGT1A gene clusters were located in corresponding regions in the genome. Among the 10 tissue types analyzed, cynomolgus UGT1A mRNAs were most abundantly expressed in the liver, jejunum, and/or kidney, the drug-metabolizing organs, similar to human UGT1As. Among these 11 cynomolgus UGT1A mRNAs, cynomolgus UGT1A2, UGT1A9, and UGT1A10 mRNAs were most abundantly expressed in the liver, kidney, and jejunum, respectively. Cynomolgus liver microsomes and UGT1A proteins catalyzed glucuronidation of the substrates human UGT1As catalyze, including 4-methylumbelliferone, 4-nitrophenol, estradiol, trifluoperazine, serotonin, and propofol, although trifluoperazine glucuronidation was not catalyzed by any cynomolgus UGT1A proteins. These results suggest that cynomolgus UGT1As are functional enzymes with molecular similarities to human UGT1As.
  • Osei Akoto, Nesta Bortey-Sam, Shouta M M Nakayama, Yoshinori Ikenaka, Elvis Baidoo, Joseph Apau, Jemima Tiwaa Marfo, Mayumi Ishizuka
    Journal of health & pollution 8 19 180902 - 180902 2018年09月 [査読有り][通常論文]
     
    Background: Soil contamination with heavy metals and metalloids has become an increasingly important issue in recent years. Objectives: The present study examines possible contamination of the environment with metals from gold mining activities in Obuasi, Ghana. Methods: Soil samples were collected from commercial and residential areas and tailing dams in Obuasi in order to investigate the extent of lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu), zinc (Zn), cobalt (Co), chromium (Cr), nickel (Ni) and arsenic (As) pollution, create thematic maps showing the extent of heavy metals pollution, identify the sources of pollution, and to assess risks to humans and the surrounding ecological system. Results: Mean concentrations of metals from the study were found in the order of As > Cu > Zn > Cr > Ni > Pb > Co > Hg > Cd. The results showed that all communities were severely polluted with As, and distribution maps highlighted two hot spots at the sulfite treatment plant and Pompura treatment plant tailings dams. Additionally, the levels of Pb, Cu and Zn were elevated around the city center where vehicular traffic is very dense. Principal component analysis indicated that mining activities may have significantly contributed to metal levels in Obuasi soils. The potential ecological risk (RI) indicated that soils in 41% of the communities pose very high risks to the surrounding ecological system, 50% pose considerable risk, and 9% pose a moderate risk. Arsenic and Hg contributed 73 and 15% of the RI, respectively. The average hazard quotient due to soil As exposure was 2.51 ± 1.23 and ingestion of soils in 95% of the communities in the study area could pose non-carcinogenic health risks to children. Moreover, the average cancer risk for children from the communities was 1.13 × 10-3. Based on the United States Environmental Protection Agency (USEPA) recommendation for cancer risk of 10-6 to 10-4, the cancer risk for children (> 10-3) was higher in 45% of the studied communities. Conclusions: The central part of the study area is polluted with Pb, Zn and Cu, and As pollution is severe in all of the studied communities. The RI from all study sites revealed very high risk to the ecological system, including mammals. There could be non-cancer and cancer risks to Obuasi residents due to ingestion of As-contaminated soils, and children are particularly vulnerable. Competing Interests: The author declares no competing financial interests.
  • Wihan Pheiffer, Nico J Wolmarans, Ruan Gerber, Yared B Yohannes, Yoshinori Ikenaka, Mayumi Ishizuka, Nico J Smit, Victor Wepener, Rialet Pieters
    The Science of the total environment 628-629 517 - 527 2018年07月01日 [査読有り][通常論文]
     
    Organochlorine pesticides (OCPs) in South Africa have for the most part been banned, except dichlorodiphenyltrichloroethane (DDT) which is still used as malaria vector control. The aim of this study was to determine OCP residues in the aquatic fauna of one of South Africa's most populated areas, Soweto. Risk to human health through OCP exposure via fish consumption was investigated. Clarias gariepinus was chosen as bioindicator because it is an apex predator that is in abundance, but is also a valued food source. Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and chlordanes (CHLs) were detected in the fish tissue with the DDTs being the most prevalent at all sites. Of the three locations, Fleurhof, Orlando, and Lenasia, the latter location's fish had the highest ΣOCP load, ranging between 81 and 1190ng/gwm. The DDTs were determined to be from historic use, whereas the CHL levels indicated more recent inputs. Although the possibility of illegal use cannot be excluded completely, the presence of OCPs outside of their allowed areas of use indicate that these compounds not only stay in the aquatic systems long term, but may be of concern in areas previously not considered high risk areas. The OCP residues in C. gariepinus from the study area pose an extremely high risk to human health when consumed, and has a cancer risk as high as 1 in 10. This potential problem should be kept in consideration when developing national health and conservation strategies.
  • John Yabe, Shouta M. M. Nakayama, Yoshinori Ikenaka, Yared B. Yohannes, Nesta Bortey-Sam, Abel Nketani Kabalo, John Ntapisha, Hazuki Mizukawa, Takashi Umemura, Mayumi Ishizuka
    CHEMOSPHERE 202 48 - 55 2018年07月 [査読有り][通常論文]
     
    Lead (Pb) and cadmium (Cd) are toxic metals that exist ubiquitously in the environment. Children in polluted areas are particularly vulnerable to metal exposure, where clinical signs and symptoms could be nonspecific. Absorbed metals are excreted primarily in urine and reflect exposure from all sources. We analyzed Pb and Cd concentrations in blood, feces and urine of children from polluted townships near a lead-zinc mine in Kabwe, Zambia, to determine concurrent childhood exposure to the metals. Moreover, the study determined the Pb and Cd relationships among urine, feces and blood as well as accessed the potential of urine and fecal analysis for biomonitoring of Pb and Cd exposure in children. Fecal Pb (up to 2252 mg/kg, dry weight) and urine Pb (up to 2914 mu g/L) were extremely high. Concentrations of Cd in blood (Cd-B) of up to 7.7 mu g/L, fecal (up to 4.49 mg/kg, dry weight) and urine (up to 18.1 mu g/L) samples were elevated. metal levels were higher in younger children (0-3 years old) than older children (4-7). Positive correlations were recorded for Pb and Cd among blood, urine and fecal samples whereas negative correlations were recorded with age. These findings indicate children are exposed to both metals at their current home environment. Moreover, urine and feces could be useful for biomonitoring of metals due to their strong relationships with blood levels. There is need to conduct a clinical evaluation of the affected children to fully appreciate the health impact of these metal exposure. (C) 2018 Published by Elsevier Ltd.
  • Yoshii K, Sato K, Ishizuka M, Kobayashi S, Kariwa H, Kawabata H
    The American journal of tropical medicine and hygiene 99 1 180 - 181 2018年07月 [査読有り][通常論文]
     
    Tick-borne encephalitis (TBE) is widely prevalent on the Eurasian continent, including Japan, but four cases of TBE have been reported in Japan. To inspect unconfirmed TBE cases in Japan, we conducted a retrospective seroepidemiological study of a total of 158 samples from 81 meningoencephalitis patients suspected as Lyme disease. Two serum samples from one patient showed neutralizing antibodies against TBE virus. The patient with severe and progressive encephalitis had a history of tick bite in Hokkaido in 2012. These results demonstrated that tick-borne encephalitis virus (TBEV) case was actually unconfirmed in Japan. Further seroepidemiological surveys are required to identify unconfirmed TBEV infections to consider the pros and cons of introducing specific countermeasures including vaccination in Japan.
  • Ryu Miura, Atsuko Araki, Chihiro Miyashita, Sumitaka Kobayashi, Sachiko Kobayashi, Shu-Li Wang, Chung-Hsing Chen, Kunio Miyake, Mayumi Ishizuka, Yusuke Iwasaki, Yoichi M. Ito, Takeo Kubota, Reiko Kishi
    Environment International 115 21 - 28 2018年06月01日 [査読有り][通常論文]
     
    Background: Prenatal exposure to perfluoroalkyl substances (PFASs) influences fetal development and later in life. Objective: To investigate cord blood DNA methylation changes associated with prenatal exposure to PFASs. Methods: We assessed DNA methylation in cord blood samples from 190 mother-child pairs from the Sapporo cohort of the Hokkaido Study (discovery cohort) and from 37 mother-child pairs from the Taiwan Maternal and Infant Cohort Study (replication cohort) using the Illumina HumanMethylation 450 BeadChip. We examined the associations between methylation and PFAS levels in maternal serum using robust linear regression models and identified differentially methylated positions (DMPs) and regions (DMRs). Results: We found four DMPs with a false discovery rate below 0.05 in the discovery cohort. Among the top 20 DMPs ranked by the lowest P-values for perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) exposure, four DMPs showed the same direction of effect and P-value < 0.05 in the replication assay: cg16242615 mapped to ZBTB7A, cg21876869 located in the intergenic region (IGR) of USP2-AS1, cg00173435 mapped to TCP11L2, and cg18901140 located in IGR of NTN1. For DMRs, we found a region associated with PFOA exposure with family-wise error rate < 0.1 located in ZFP57, showing the same direction of effect in the replication cohort. Among the top five DMRs ranked by the lowest P-values that were associated with exposure to PFOS and PFOA, in addition to ZFP57, DMRs in the CYP2E1, SMAD3, SLC17A9, GFPT2, DUSP22, and TCERG1L genes showed the same direction of effect in the replication cohort. Conclusion: We suggest that prenatal exposure to PFASs may affect DNA methylation status at birth. Longitudinal studies are needed to examine whether methylation changes observed are associated with differential health outcomes.
  • Kazuki Takeda, Yoshinori Ikenaka, Kazuyuki D Tanaka, Shouta M M Nakayama, Tsutomu Tanikawa, Hazuki Mizukawa, Mayumi Ishizuka
    Pesticide biochemistry and physiology 148 42 - 49 2018年06月 [査読有り][通常論文]
     
    Anti-blood coagulation rodenticides, such as warfarin, have been used all over the world. They inhibit vitamin K epoxide reductase (VKOR), which is necessary for producing several blood clotting factors. This inhibition by rodenticides results in lethal hemorrhage in rodents. However, heavy usage of these agents has led to the appearance of rodenticide-resistant rats. There are two major mechanisms underlying this resistance, i.e., mutation of the target enzyme of warfarin, VKOR, and enhanced metabolism of warfarin. However, there have been few studies regarding the hepatic metabolism of warfarin, which should be related to resistance. To investigate warfarin metabolism in resistant rats, in situ liver perfusion of warfarin was performed with resistant black rats (Rattus rattus) from Tokyo, Japan. Liver perfusion is an in situ methodology that can reveal hepatic function specifically with natural composition of the liver. The results indicated enhanced hepatic warfarin hydroxylation activity compared with sensitive black rats. On the other hand, in an in vitro microsomal warfarin metabolism assay to investigate kinetic parameters of cytochrome P450, which plays a major role in warfarin hydroxylation, the Vmax of resistant rats was slightly but significantly higher compared to the results obtained in the in situ study. These results indicated that another factor like electron donators may also contribute to the enhanced metabolism in addition to high expression of cytochrome P450.
  • Ishii C, Ikenaka Y, Ichii O, Nakayama SMM, Nishimura SI, Ohashi T, Tanaka M, Mizukawa H, Ishizuka M
    Poultry science 97 5 1722 - 1729 2018年05月 [査読有り][通常論文]
     
    Avian species have a unique renal structure and abundant blood flow into the kidneys. Although many birds die due to nephrotoxicity caused by chemicals, there are no early biomarkers for renal lesions. Uric acid level in blood, which is generally used as a renal biomarker, is altered when the kidney function is damaged by over 70%. Therefore, early biomarkers for kidney injury in birds are needed. In humans, glycomics has been at the forefront of biological and medical sciences, and glycans are used as biomarkers of diseases, such as carcinoma. In this study, a glycomics approach was used to screen for renal biomarkers in chicken. First, a chicken model of kidney damage was generated by injection of diclofenac or cisplatin, which cause acute interstitial nephritis (AIN) and acute tubular necrosis (ATN), respectively. The nephrotoxicity levels were determined by a blood chemical test and histopathological analysis. The plasma N-glycans were then analyzed to discover renal biomarkers in birds. Levels of 14 glycans increased between pre- and post administration in kidney-damaged chickens in the diclofenac group, and some of these glycans had the same presumptive composition as those in human renal carcinoma patients. Glycan levels did not change remarkably in the cisplatin group. It is possible that there are changes in glycan expression due to AIN, but they do not reflect ATN. Although further research is needed in other species of birds, glycans are potentially useful biomarkers for AIN in avian species.
  • Emmanuel Temiotan Ogbomida, Shouta M M Nakayama, Nesta Bortey-Sam, Balazs Oroszlany, Isioma Tongo, Alex Ajeh Enuneku, Ogbeide Ozekeke, Martins Oshioriamhe Ainerua, Iriagbonse Priscillia Fasipe, Lawrence Ikechukwu Ezemonye, Hazuki Mizukawa, Yoshinori Ikenaka, Mayumi Ishizuka
    Ecotoxicology and environmental safety 151 98 - 108 2018年04月30日 [査読有り][通常論文]
     
    The use of free range animals for monitoring environmental health offers opportunities to detect exposure and assess the toxicological effects of pollutants in terrestrial ecosystems. Potential human health risk of dietary intake of metals and metalloid via consumption of offal and muscle of free range chicken, cattle and goats by the urban population in Benin City was evaluated. Muscle, gizzard, liver and kidney samples were analyzed for Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb concentrations using inductively coupled plasma mass spectrometer (ICP-MS) while Hg was determined using Hg analyzer. Mean concentrations of metals (mg/kg ww) varied significantly depending upon the tissues and animal species. Human health risk estimations for children and adults showed estimated daily intake (EDI) values of tissues below oral reference dose (RfD) threshold for non essential metals Cd, As, Pb and Hg thus strongly indicating no possible health risk via consumption of animal based food. Calculated Hazard quotient (THQ) was less than 1 (< 1) for all the metals analyzed for both adult and children. However, Cd and As had the highest value of THQ suggestive of possible health risk associated with continuous consumption of Cd and As contaminated animal based foods. Hazard Index (HI) for additive effect of metals was higher in chicken liver and gizzard for children and chicken liver for adults. Thus, HI indicated that chicken liver and gizzard may contribute significantly to adult and children dietary exposure to heavy metals. Principal component analysis (PCA) showed a clear species difference in metal accumulation between chickens and the ruminants. This study provides baseline data for future studies and also valuable evidence of anthropogenic impacts necessary to initiate national and international policies for control of heavy metal and metalloid content in food items.
  • Nesta Bortey-Sam, Yoshinori Ikenaka, Osei Akoto, Shouta M M Nakayama, Kwadwo A Asante, Elvis Baidoo, Christian Obirikorang, Hazuki Mizukawa, Mayumi Ishizuka
    Environmental pollution (Barking, Essex : 1987) 235 163 - 170 2018年04月 [査読有り][通常論文]
     
    Heavy metals and metalloids contamination in soils, water, food and livers of wild rats have been studied in Kumasi, Ghana and despite the estimated risks to residents, there is no epidemiological study to ascertain these projections. In addition, the World Health Organization and International Agency for Research on Cancer have reported an increase in respiratory diseases and cancers, in Ghana. The study's purpose was therefore to explore the potential associations between metal exposure and occurrences of respiratory diseases, lipid peroxidation and/or DNA damage to different age groups and sexes in Kumasi. Human urine was collected from the general population in urban and control sites in Kumasi and nine metals were measured in each sample. Results showed that although Zn was the most abundant total urinary As concentration was higher in 83% of samples compared to reference values. Urinary concentrations of metals, malondialdehyde (MDA) and 8-hydroxy-2-deoxy-guanosine (8-OHdG) were higher in urban sites compared to the control site. Based on the results obtained, there was no significant correlation between urinary metals and age. However, urinary Cd and MDA were highest in age groups 61-85 and 3-20 years, respectively. Significantly higher levels of urinary Co, As and Cd were detected in female participants. The study revealed that exposure to As was significantly associated with increased odds of asthma (odds ratio (OR) = 2.76; CI: 1.11-6.83) and tachycardia (OR = 3.93; CI: 1.01-15.4). Significant association was observed between urinary metals and MDA and 8-OHdG indicating possibility of lipid peroxidation and/or DNA damage in Kumasi residents.
  • Nesta Bortey-Sam, Yoshinori Ikenaka, Osei Akoto, Shouta M M Nakayama, Jemima T Marfo, Aksorn Saengtienchai, Hazuki Mizukawa, Mayumi Ishizuka
    The Journal of veterinary medical science 80 2 375 - 381 2018年03月02日 [査読有り][通常論文]
     
    Industrialization, economic and population growth rates in Ghana have increased the release of contaminants including polycyclic aromatic hydrocarbons (PAHs) into the environment through which humans and animals are exposed. Cattle is reported to be exposed to high levels of PAHs through feed and inhalation. Once exposed, PAHs are metabolized and excreted in urine, feces or bile. In a previous study, cattle in Ghana was reported to excrete high levels of 1-hydroxypyrene (1-OHPyr) due to high exposure to the parent compound, pyrene. 1-OHPyr is further metabolized to glucuronide and sulfate conjugates. Thus, the aim of this study was to investigate the sex and site differences in urinary excretion of conjugated pyrene metabolites using cattle urine collected from rural and urban sites of the Ashanti region, Ghana. From the results, geometric mean concentration adjusted by specific gravity indicated that 1-OHPyreneGlucuronide (PyG) was the most abundant conjugate followed by PyrenediolSulfate (M3). The sum of conjugated pyrene metabolites and sum of both conjugated and deconjugated pyrene metabolites correlated significantly with PyG, PydiolSulfate (M2) and PydiolSulfate (M3). The study revealed no significant difference in urinary excretion of conjugated pyrene metabolites between rural and urban sites. This indicated that similar to urban sites, cattle in rural sites were exposed to high levels of pyrene. There was no significant difference in urinary concentrations of conjugated pyrene metabolites between sexes.
  • Darwish WS, Ikenaka Y, Nakayama S, Mizukawa H, Thompson LA, Ishizuka M
    Environmental science and pollution research international 25 7 6320 - 6328 2018年03月 [査読有り][通常論文]
     
    Benzo[a]pyrene (B[a]P) is one of the polycyclic aromatic hydrocarbons which is formed due to smoking of foods, incomplete combustion of woods, vehicle exhausts, and cigarettes smokes. B[a]P gets entry into human and animal bodies mainly through their diets. Metabolic activation of B[a]P is required to induce mutagenesis and carcinogenesis in animal and human studies. Carotenoids and retinoids are phytochemicals that if ingested have multiple physiological interferences in the human and animal bodies. In this study, we firstly investigated the protective effects of β-carotene, β-apo-8-carotenal, retinol, and retinoic acid against B[a]P-induced mutagenicity and oxidative stress in human HepG2 cells. Secondly, we tested the hypothesis of modulating xenobiotic metabolizing enzymes (XMEs) by carotenoids and retinoids as a possible mechanism of protection by these micronutrients against B[a]P adverse effects. The obtained results declared that β-carotene and retinol significantly reduced B[a]P-induced mutagenicity and oxidative stress. Tested carotenoids and retinoids reduced B[a]P-induced phase I XMEs and induced B[a]P reduced phase II and III XMEs. Thus, the protective effects of these micronutrients are probably due to their ability of induction of phase II and III enzymes and interference with the induction of phase I enzymes by the promutagen, B[a]P. It is highly recommended to consume foods rich in these micronutrients in the areas of high PAH pollution.
  • Kumiko Yamamoto, Yoshinori Ikenaka, Takahiro Ichise, Tomoki Bo, Mayumi Ishizuka, Hironobu Yasui, Wakako Hiraoka, Tohru Yamamori, Osamu Inanami
    FREE RADICAL RESEARCH 52 6 648 - 660 2018年 [査読有り][通常論文]
     
    To evaluate the metabolic responses in tumour cells exposed to ionizing radiation, oxygen consumption rate (OCR), cellular lipid peroxidation, cellular energy status (intracellular nucleotide pool and ATP production), and mitochondrial reactive oxygen species (ROS), semiquinone (SQ), and iron-sulphur (Fe-S) cluster levels were evaluated in human cervical carcinoma HeLa cells at 12 and 24h after X-irradiation. LC/MS/MS analysis showed that levels of 8-iso PGF(2 alpha) and 5-iPF(2 alpha)VI, lipid peroxidation products of membrane arachidonic acids, were not altered significantly in X-irradiated cells, although mitochondrial ROS levels and OCR significantly increased in the cells at 24h after irradiation. LC/UV analysis revealed that intracellular AMP, ADP, and ATP levels increased significantly after X-irradiation, but adenylate energy charge (adenylate energy charge (AEC) = [ATP + 0.5 x ADP]/[ATP +ADP + AMP]) remained unchanged after X-irradiation. In lowtemperature electron spin resonance (ESR) spectra of HeLa cells, the presence of mitochondrial SQ at g = 2.004 and Fe-S cluster at g = 1.941 was observed and X-irradiation enhanced the signal intensity of SQ but not of the Fe-S cluster. Furthermore, this radiation-induced increase in SQ signal intensity disappeared on treatment with rotenone, which inhibits electron transfer from Fe-S cluster to SQ in complex I. From these results, it was suggested that an increase in OCR and imbalance in SQ and Fe-S cluster levels, which play a critical role in the mitochondrial electron transport chain (ETC), o(cur after X-irradiation, resulting in an increase in ATP production and ROS leakage from the activated mitochondrial ETC.
  • Yoshinori Ikenaka, Kazutoshi Fujioka, Tomonori Kawakami, Takahiro Ichise, Nesta Bortey-Sam, Shouta M M Nakayama, Hazuki Mizukawa, Kumiko Taira, Keisuke Takahashi, Keisuke Kato, Koji Arizono, Mayumi Ishizuka
    Toxicology reports 5 744 - 749 2018年 [査読有り][通常論文]
     
    Tea is one of the world's most popular beverages due to health promoting effects. Despite these, there have been concerns about the adverse effects of tea contamination by neonicotinoid insecticides. Only a handful of studies on neonicotinoid insecticides in tea have been carried out and this study was therefore performed to determine the concentrations of seven neonicotinoid insecticides and 20 metabolites in Japanese green tea leaves, and black tea leaves from Sri Lanka; and assess the Maximum Daily Intake (MDI) of neonicotinoid insecticides. From the results, the seven parent compounds were detected in Japanese tea leaves and beverages. Dinotefuran (3004 ng/g) was found at the highest level in green tea leaves. Ten of the 20 metabolites were detected in Japanese tea products. Dinotefuran-urea (92%) and thiacloprid-amide (89%) were most frequently detected in Japanese tea leaves. Clothianidin-urea (100 ng/g) was found at the highest level in green tea leaves. Neonicotinoid insecticides and metabolites were not detected in Sri Lankan black tea leaves. The concentrations and MDI of neonicotinoid insecticides in tea leaves were below the Maximum Residual Levels (MRLs) and Acceptable Daily Intakes (ADIs), respectively.
  • Lesa A Thompson, Yoshinori Ikenaka, Wageh S Darwish, Yared B Yohannes, Johan J van Vuren, Victor Wepener, Nico J Smit, Atnafu G Assefa, Ahmed Tharwat, Walaa Fathy Saad Eldin, Shouta M M Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    PloS one 13 10 e0204400  2018年 [査読有り][通常論文]
     
    The objective of this study was to identify potential mRNA expression changes in chicken livers associated with environmental exposure to dichloro-diphenyl-trichloroethane (DDT) and its metabolites (DDTs). In particular, we focused on genes relating to the immune system and metabolism. We analyzed liver samples from free-ranging chickens in KwaZulu-Natal, South Africa, for contamination by DDTs. This area predominantly uses DDT in its malaria control program, and homes are sprayed annually with the pesticide. Genes relating to the immune system and metabolism were selected as potential genetic biomarkers that could be linked to higher contamination with DDTs. RT-qPCR analysis on 39 samples showed strong correlations between DDTs contamination and mRNA expression for the following genes: AvBD1, AvBD2, AvBD6 and AvBD7 (down-regulated), and CYP17, ELOVL2 and SQLE (up-regulated). This study shows for the first time interesting and significant correlations between genetic material collected from environmentally-exposed chickens and mRNA expression of several genes involved in immunity and metabolism. These findings show the usefulness of analysis on field samples from a region with high levels of environmental contamination in detecting potential biomarkers of exposure. In particular, we observed clear effects from DDT contamination on mRNA expression of genes involved in immune suppression, endocrine-disrupting effects, and lipid dysregulation. These results are of interest in guiding future studies to further elucidate the pathways involved in and clinical importance of toxicity associated with DDT exposure from contaminated environments, to ascertain the health risk to livestock and any subsequent risks to food security for people.
  • 高口倖暉, 野見山桂, 西川博之, 水川葉月, 田上瑠美, 草木桃子, 横山望, 市居修, 滝口満喜, 中山翔太, 池中良徳, 石塚真由美, 岩田久人, 国末達也, 田辺信介
    Journal of Toxicological Sciences 43 Supplement S245 - S245 (一社)日本毒性学会 2018年 [査読有り][通常論文]
  • Chinzei Kiyoyuki, Shimizu Akinobu, Mori Kensaku, Harada Kanako, Takeda Hideaki, Hashizume Makoto, Ishizuka Mayumi, Kato Nobumasa, Kawamori Ryuzo, Kyo Shunei, Nagata Kyosuke, Yamane Takashi, Sakuma Ichiro, Ohe Kazuhiko, Mitsuishi Mamoru
    ADVANCED BIOMEDICAL ENGINEERING 7 118 - 123 2018年 [査読無し][通常論文]
     
    © 2018, Japanese Society for Medical and Biological Engineering. All rights reserved. AI-based medical and healthcare devices and systems have unique characteristics including 1) plasticity causing changes in system performance through learning, and need of creating new concepts about the timing of learning and assignment of responsibilities for risk management; 2) unpredictability of system behavior in response to unknown inputs due to the black box characteristics precluding deductive output prediction; and 3) need of assuring the characteristics of datasets to be used for learning and evaluation. The Subcommittee on Artificial Intelligence and its Applications in Medical Field of the Science Board, the Pharmaceuticals and Medical Devices Agency (PMDA), Tokyo, Japan, examined “new elements specific to AI” not included in conventional technologies, thereby clarifying the characteristics and risks of AI-based technologies. This paper summarizes the characteristics and clinical positioning of AI medical systems and their applications from the viewpoint of regulatory science, and presents the issues related to the characteristics and reliability of data sets in machine learning.
  • Yusuke K Kawai, Yoshinori Ikenaka, Mayumi Ishizuka, Akira Kubota
    PloS one 13 10 e0205266  2018年 [査読有り][通常論文]
     
    UDP-glycosyltransferase (UGT) catalyzes the transfer of glycosyl groups (e.g., glucuronic acid) to exogenous or endogenous chemicals and plays an important role in conjugation reactions. In vertebrates, UGT genes are divided into 5 families: UGT1, UGT2, UGT3, UGT5, and UGT8. Among these UGT enzymes, UGT1 and UGT2 enzymes are known to be important xenobiotic metabolizing enzymes in mammals. However, little is known about UGT1 and UGT2 genes in avian species. In this study, we therefore aimed to classify avian UGT1 and UGT2 genes based on their evolutionary relationships. We also investigated the association between UGT molecular evolution and ecological factors, specifically feeding habits, habitat, and migration. By examining the genomes of 43 avian species with differing ecology, we showed that avian UGT1E genes are divided into 6 groups and UGT2 genes into 3 groups. Correlations between UGT gene count and ecological factors suggested that the number of UGT1E genes is decreasing in carnivorous species. Estimates of selection pressure also support the hypothesis that diet influenced avian UGT1E gene evolution, similar to mammalian UGT1A and UGT2B genes.
  • Chihiro Ishii, Shouta M. M. Nakayama, Yoshinori Ikenaka, Hokuto Nakata, Keisuke Saito, Yukiko Watanabe, Hazuki Mizukawa, Shinsuke Tanabe, Kei Nomiyama, Terutake Hayashi, Mayumi Ishizuka
    CHEMOSPHERE 186 367 - 373 2017年11月 [査読有り][通常論文]
     
    Lead (Pb) poisoning is widespread among raptors and water birds. In Japan, fragments of Pb ammunition are still found in endangered eagles although more than 10 years have passed since legislation regarding use of Pb ammunition was introduced. This study was performed to investigate Pb exposure in raptors from various locations in Japan. We measured hepatic and renal Pb concentrations and hepatic Pb isotope ratios of Steller's sea eagles (Haliaeetus pelagicus), white-tailed sea eagles (Haliaeetus albicilla), golden eagles (Aquila chrysaetos), and 13 other species (total 177 individuals) that were found dead, as well as blood samples from three eagles found in a weakened state during 1993-2015 from Hokkaido (northern part), Honshu (the main island), and Shikoku (a southern island) of japan. In the present study in Hokkaido, one quarter of the sea eagles showed a high Pb concentration, suggesting exposure to abnormally high Pb levels and Pb poisoning. Pb isotope ratios indicated that endangered Steller's sea eagle and white-tailed sea eagle were poisoned by Pb ammunition that was used illegally in Hokkaido. In other areas of Japan, both surveillance and regulations were less extensive than in Hokkaido, but Pb poisoning in raptors was also noted. Therefore, Pb poisoning is still a serious problem in raptors in various areas of Japan due to accidental ingestion of materials containing Pb, especially Pb ammunition. (C) 2017 Published by Elsevier Ltd.
  • Noboru Sasaki, Kazuhiro Ishi, Nobuki Kudo, Shouta M. M. Nakayama, Kensuke Nakamura, Keitaro Morishita, Hiroshi Ohta, Mayumi Ishizuka, Mitsuyoshi Takiguchi
    PLOS ONE 12 11 e0188093  2017年11月 [査読有り][通常論文]
     
    Non-muscle invasive bladder cancer is one of the most common tumors of the urinary tract. Despite the current multimodal therapy, recurrence and progression of disease have been challenging problems. We hereby introduced a new approach, ultrasound-assisted intravesical chemotherapy, intravesical instillation of chemotherapeutic agents and microbubbles followed by ultrasound exposure. We investigated the feasibility of the treatment for nonmuscle invasive bladder cancer. In order to evaluate intracellular delivery and cytotoxic effect as a function to the thickness, we performed all experiments using a bladder cancer mimicking 3D culture model. Ultrasound-triggered microbubble cavitation increased both the intracellular platinum concentration and the cytotoxic effect of cisplatin at the thickness of 70 and 122 mu m of the culture model. The duration of enhanced cytotoxic effect of cisplatin by ultrasound-triggered microbubble cavitation was approximately 1 hr. Based on the distance and duration of delivery, we further tested the feasibility of repetition of the treatment. Triple treatment increased the effective distance by 1.6-fold. Our results clearly showed spatial and temporal profile of delivery by ultrasound-triggered microbubble cavitation in a tumor-mimicking structure. Furthermore, we demonstrated that the increase in intracellular concentration results in the enhancement of the cytotoxic effect in a structure with the certain thickness. Repetition of ultrasound exposure would be treatment of choice in future clinical application. Our results suggest ultrasound-triggered microbubble cavitation can be repeatable and is promising for the local control of non-muscle invasive bladder cancer.
  • Hazuki Mizukawa, Kei Nomiyama, Susumu Nakatsu, Miyuki Yamamoto, Mayumi Ishizuka, Yoshinori Ikenaka, Shouta M. M. Nakayama, Shinsuke Tanabe
    ENVIRONMENTAL SCIENCE & TECHNOLOGY 51 19 11354 - 11362 2017年10月 [査読有り][通常論文]
     
    Present study determined concentrations and residue patterns of bromophenols (BPhs) in whole blood samples of pet cats and pet dogs collected from veterinary hospitals in Japan. BPhs concentrations were higher in cat blood than in dog blood, with statistically insignificant differences (p = 0.07). Among the congeners, 2,4,6-tribromophenol (TBPh) constituted the majority of BPhs (>90%) detected in both species. Analysis of commercial pet food to estimate exposure routes showed that the most abundant congener in all pet food samples was 2,4,6-TBPh, accounting for >99% of total BPhs. This profile is quite similar to the blood samples of the pets, suggesting that diet might be an important exposure route for BPhs in pets. After incubation in polybrominated diphenyl ether (PBDE) mixtures (BDE-47, BDE-99 and BDE-209), 2,4,5-TBPh was found in dog liver microsomes but not in cat liver microsomes, implying species-specific metabolic capacities for PBDEs. Formation of 2,4,5-TBPh occurred by hydroxylation at the 1' carbon atom of the ether bond of BDE-99 is similar to human study reported previously. Hydroxylated PBDEs were not detected in cats or dogs; therefore, diphenyl ether bond cleavage of PBDEs can also be an important metabolic pathway for BPhs formation in cats and dogs.
  • Yared Beyene Yohannes, Yoshinori Ikenaka, Gengo Ito, Shouta M. M. Nakayama, Hazuki Mizukawa, Victor Wepener, Nico J. Smit, Johan H. J. Van Vuren, Mayumi Ishizuka
    ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 24 30 23763 - 23770 2017年10月 [査読有り][通常論文]
     
    Ethiopia and South Africa are among the few countries to still implement indoor residual spraying with dichloro-diphenyl-trichloroethane (DDT) for malaria vector control. In this study, we investigated the levels and ecological risks of DDT and its metabolites in liver tissues of house rat, as a sentinel animal, for providing an early warning system for public health and wildlife intervention from Ethiopia and South Africa. The results showed that Sigma DDT concentration ranged from 127 to 9155 mu g/kg wet weight, and the distribution order of DDT and its metabolites in the analyzed liver samples was p,p'-DDD > p,p'-DDE >> p,p'-DDT, o,p'-DDT, and o,p'-DDD. The risk assessment indicated a potential adverse impact on humans, especially for pregnant women and children, because they spend majority of their time in a DDT-sprayed house. The ecological assessment also showed a concern for birds of prey and amphibians like frogs. This study is the first report on DDT contamination in liver tissues of house rats from Ethiopia and South Africa, and henceforth, the data will serve as a reference data for future studies.
  • Nesta Bortey-Sam, Yoshinori Ikenaka, Osei Akoto, Shouta M. M. Nakayama, Kwadwo A. Asante, Elvis Baidoo, Christian Obirikorang, Aksorn Saengtienchai, Norikazu Isoda, Collins Nimako, Hazuki Mizukawa, Mayumi Ishizuka
    ENVIRONMENTAL POLLUTION 228 311 - 320 2017年09月 [査読有り][通常論文]
     
    Studies of polycyclic aromatic hydrocarbons (PAHs) and its metabolites in PM10, soils, rat livers and cattle urine in Kumasi, Ghana, revealed high concentrations and cancer potency. In addition, WHO and IARC have reported an increase in cancer incidence and respiratory diseases in Ghana. Human urine were therefore collected from urban and control sites to: assess the health effects associated with PAHs exposure using malondialdehyde (MDA) and 8-hydroxy-2-deoxyguanosine (8-OHdG); identify any association between OH-PAHs, MDA, 8-OHdG with age and sex; and determine the relationship between PAHs exposure and occurrence of respiratory diseases. From the results, urinary concentrations of the sum of OH-PAHs (Sigma OHPAHs) were significantly higher from urban sites compared to the control site. Geometric mean concentrations adjusted by specific gravity, GM(SG), indicated 2-OHNaphthalene (2-OHNap) (6.01 +/- 4.21 ng/mL) as the most abundant OH-PAH, and exposure could be through the use of naphthalene-containing-mothballs in drinking water purification, insect repellent, freshener in clothes and/or "treatment of various ailments". The study revealed that exposure to naphthalene significantly increases the occurrence of persistent cough (OR = 2.68, CI: 1.43-5.05), persistent headache (OR = 1.82, CI: 1.02-3.26), tachycardia (OR = 3.36, CI: 1.39-8.10) and dyspnea (OR = 3.07, CI: 1.27-7.43) in Kumasi residents. Highest level of urinary 2-OHNap (224 ng/mL) was detected in a female, who reported symptoms of persistent cough, headache, tachycardia, nasal congestion and inflammation, all of which are symptoms of naphthalene exposure according to USEPA. The Sigma OHPAHs, 2-OHNap, 2-3-OHFluorenes, and -OHPhenanthrenes showed a significantly positive correlation with MDA and 4-OHPhenanthrene with 8-OHdG, indicating possible lipid peroxidation/cell damage or degenerative disease in some participants. MDA and 8-OHdG were highest in age group 21-60. The present study showed a significant sex difference with higher levels of urinary OH-PAHs in females than males. (C) 2017 Published by Elsevier Ltd.
  • Sumitaka Kobayashi, Fumihiro Sata, Chihiro Miyashita, Ryu Miura, Kaoru Azumi, Sachiko Kobayashi, Houman Goudarzi, Atsuko Araki, Mayumi Ishizuka, Takashi Todaka, Jumboku Kajiwara, Tsuguhide Hori, Reiko Kishi
    TOXICOLOGY 390 135 - 145 2017年09月 [査読有り][通常論文]
     
    Background: Associations between prenatal exposure to polychlorinated biphenyls (PCBs) and reduced birth size, and between DNA methylation of insulin-like growth factor-2 (IGF-2), HI 9 locus, and long interspersed nuclear element-1 (LINE-1) and reduced birth-size are well established. To date, however, studies on the associations between prenatal exposure to PCBs and alterations in methylation of IGF-2, H19, and LINE-1 are lacking. Thus, in this study, we examined these associations with infant-gender stratification. Methods: We performed a prospective birth cohort study using the Sapporo cohort from the previously described Hokkaido Birth Cohort Study on Environment and Children's Health conducted between 2002 and 2005 in Japan. In the final 169 study participants included in this study, we measured the concentrations of various non dioxin-like PCBs in maternal blood during pregnancy using high-resolution gas chromatography/high-resolution mass spectrometry. IGF-2, H19 and LINE-1 methylation levels in cord blood were measured using the bisulfite pyrosequencing methods Finally, we assessed the associations between prenatal exposure to various PCBs and the gene methylation levels using multiple regression models stratified by infant gender. Results: We observed a 0.017 (95% confidence interval [CI]: 0.003-0.031) increase in the log(10)-transformed H19 methylation levels (%) in cord blood for each ten-fold increase in the levels of decachlorinated biphenyls (decaCBs) in maternal blood among all infants. Similarly, a 0.005 (95% CI: 0.000-0.010) increase in the log(10)-transformed LINE-1 methylation levels (%) in cord blood was associated with each ten-fold increase in heptachlorinated biphenyls (heptaCBs) in maternal blood among all infants. In particular, we observed a dose-dependent association of the decaCB levels in maternal blood with the H19 methylation levels among female infants (P value for trend = 0.040); likewise a dose-dependent association of heptaCB levels was observed with LINE-I methylation levels among female infants (P value for trend = 0.015). Moreover, these associations were only observed among infants of primiparous women. Conclusion: Our results suggest that the dose-dependent association between prenatal exposure to specific non-dioxin-like PCBs and increases in the H19 and LINE-1 methylation levels in cord blood might be more predominant in females than in males.
  • Osei Akoto, Nesta Bortey-Sam, Yoshinori Ikenaka, Shouta M M Nakayama, Elvis Baidoo, Yared Beyene Yohannes, Mayumi Ishizuka
    Journal of health & pollution 7 15 28 - 39 2017年09月 [査読有り][通常論文]
     
    Background: Environmental contamination with heavy metals and metalloids due to industrial, smelting and mining activities have become common in large and growing cities. Kumasi is one of the most industrialized cities in Ghana and experiences metal pollution due to recent and past activities. Although metals are naturally abundant in the area, their accumulation in soils could potentially lead to adverse effects on local ecosystems. Objectives: The aims of this study were to determine the distribution, enrichment, geoaccumulation and sources of metals in Kumasi soils and to estimate the contamination factor (CF) and pollution load index (PLI) of these metals in soils. Methods: Concentrations of eight heavy metals and a metalloid were determined in 112 soil samples randomly collected from 31 sampling sites in the area. In addition, 5 soil samples were collected from a pristine site (Kwame Nkrumah University of Science and Technology Botanical Gardens) for data comparison, to determine the local background values for metal concentrations and to evaluate the extent of metal pollution in the study area. Results: Heavy metals such as zinc (Zn), lead (Pb), cadmium (Cd) and chromium (Cr) were enriched in 65, 32, 58 and 93% of the sampling sites, respectively, and geo-accumulation indexes for Cr, Zn, Cd, mercury (Hg) and Pb showed moderate to extreme contamination in 100, 97, 77, 65 and 45% of the sampling sites, respectively. Principal component and cluster analyses revealed that industrial activities including mining were the major sources of metals in Kumasi soils with high metal input in the community of Suame. Distribution maps revealed hotspots of Cd, nickel (Ni), arsenic (As), cobalt (Co), copper (Cu) and Pb in Suame. The highest CFs for Cu, Cd, Ni, As, Co and Pb highlighted anthropogenic inputs in Suame, while Hg was highest in Mbrom, Zn in Suntreso, and Cr in Aboabo. Conclusions: The PLI of metals revealed Suame as the most polluted study site, while Anomangye and Bomso were the least polluted.
  • Takamitsu Kondo, Yoshinori Ikenaka, Shouta M. M. Nakayama, Yusuke K. Kawai, Hazuki Mizukawa, Yoko Mitani, Kei Nomiyama, Shinsuke Tanabe, Mayumi Ishizuka
    TOXICOLOGICAL SCIENCES 158 1 90 - 100 2017年07月 [査読有り][通常論文]
     
    UDP-glucuronosyltransferases (UGTs) are among the most important xenobiotic metabolizing enzymes that conjugate a wide range of chemicals. Previous studies showed that Felidae and Pinnipedia species have very low UGT activities toward some phenolic compounds because of the UGT1A6 pseudogene and small numbers of UGT1A isozymes. In addition to the UGT1As, UGT2Bs isozymes also conjugate various endogenous (eg, estrogens, androgens, and bile acids) and exogenous compounds (opioids, non-steroidal anti-inflammatory drugs, and environmental pollutants). However UGT2B activity and genetic background are unknown in carnivore species. Therefore, this study was performed to elucidate the species differences of UGT2Bs. Using typical substrates for UGT2Bs, UGT activity was measured in vitro. In addition, UGT2B genetic features are analyzed in silico. Results of UGT activity measurement indicate marked species differences between dogs and other carnivores (cats, Northern fur seals, Steller sea lions, Harbor seals, and Caspian seals). Dogs have very high V-max/K-m toward estradiol (17-glucuronide), estrone, lorazepam, oxazepam, and temazepam. Conversely, cats and pinniped species (especially Caspian seals and Harbor seals) have very low activities toward these substrates. The results of genetic synteny analysis indicate that Felidae and pinniped species have very small numbers of UGT2B isozymes (one or none) compared with dogs, rodents, and humans. Furthermore, Felidae species have the same nonsense mutation in UGT2B, which suggests that Felidae UGT2B31-like is also a pseudogene in addition to UGT1A6. These findings of lower activity of UGT2B suggest that Felidae and some pinniped species have very low UGT activity toward a wide range of chemicals. These results are important for Felidae and Pinnipedia species that are frequently exposed to drugs and environmental pollutants.
  • Sachiko Kobayashi, Kaoru Azumi, Houman Goudarzi, Atsuko Araki, Chihiro Miyashita, Sumitaka Kobayashi, Sachiko Itoh, Seiko Sasaki, Mayumi Ishizuka, Hiroyuki Nakazawa, Tamiko Ikeno, Reiko Kishi
    JOURNAL OF EXPOSURE SCIENCE AND ENVIRONMENTAL EPIDEMIOLOGY 27 3 251 - 259 2017年05月 [査読有り][通常論文]
     
    Prenatal exposure to perfluoroalkyl acids (PFAAs) influences fetal growth and long-term health. However, whether PFAAs affect offspring DNA methylation patterns to influence health outcomes is yet to be evaluated. Here, we assessed effect of prenatal PFAA exposure on cord blood insulin-like growth factor 2 (IGF2), H19, and long interspersed element 1 (LINE1) methylation and its associations with birth size. Mother-child pairs (N = 177) from the Hokkaido Study on Environment and Children's Health were included in the study. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) levels in maternal serum were measured by liquid chromatography-tandem mass spectrometry. IGF2, H19, and LINE1 methylation in cord blood DNA was determined by pyrosequencing. After full adjustment in multiple linear regression models, IGF2 methylation showed a significant negative association with log-unit increase in PFOA (partial regression coefficient = -0.73; 95% confidence interval: -1.44 to -0.02). Mediation analysis suggested that reduced IGF2 methylation explained similar to 21% of the observed association between PFOA exposure and reduced ponderal index of the infant at birth. These results indicated that the effects of prenatal PFOA exposure could be mediated through DNA methylation. Further study will be required to determine the potential for long-term adverse health effects of reduced IGF2 methylation induced by PFOA exposure.
  • Lesa A. Thompson, Wageh Sobhy Darwish, Yoshinori Ikenaka, Shouta M. M. Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 79 4 751 - 764 2017年04月 [査読有り][通常論文]
     
    Organochlorine pesticides (OCPs) have been used worldwide, particularly in Africa, for several decades. Although many are banned, several African countries still use OCPs especially for the prevention and control of malaria. OCPs are characterized by their bio-accumulation in the environment, especially in the food chain, where they find their way into the human body. Despite no clear epidemiological studies confirming hazardous effects of these chemicals on human health, many studies have reported positive associations between the use of OCPs and neurological and reproductive disorders, and cancer risk. There is a clear gap in published reports on OCPs in Africa and their potential health hazards. Thus, the aim of this review is to summarize the incidence of OCP contamination in various foods in Africa, to demonstrate the potential transmission of these chemicals to people and to discuss their possible health hazards.
  • Chihiro Ishii, Yoshinori Ikenaka, Shouta M. M. Nakayama, Hazuki Mizukawa, Yared Beyene Yohannes, Yutaka Watanuki, Masaaki Fukuwaka, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 79 4 807 - 814 2017年04月 [査読有り][通常論文]
     
    Seabirds are marine top predators and accumulate high levels of metals and metalloids in their tissues. Contamination by metals in the highly productive offshore region has become a matter of public concern. It is home to 80% of the seabird population in the U.S.A., 95% of northern fur seals (Callorhinus ursinus), and major populations of Steller sea lions (Eumetopias jubatus), walruses (Odobenus rosmarus) and whales. Here, the concentrations of eight heavy metals (Hg, Cd, Cr, Co, Ni, Cu, Zn and Pb) and a metalloid (As) in the liver and kidneys of the northern fulmar (Fulmarus glacialis), thick-billed murre (Uria lomvia), short-tailed shearwater (Puffinus tenuirostris), tufted puffin (Fratercula cirrhata) and horned puffin (Fratercula corniculata) collected in the Bering Sea were measured. As proxies of trophic level and habitat, nitrogen (delta N-15) and carbon (delta C-13) stable isotope ratios of breast muscles were also measured. Hepatic Hg concentration was high in northern fulmar, whereas Cd level was high in tufted puffin and northern fulmar. The Hg concentration and d15N value were positively correlated across individual birds, suggesting that Hg uptake was linked to the trophic status of consumed prey. Furthermore, Hg concentration in our study was higher than those of the same species of seabirds collected in 1990.
  • Hazuki Mizukawa, Yoshinori Ikenaka, Mayu Kakehi, Shouta Nakayama, Mayumi Ishizuka
    YAKUGAKU ZASSHI-JOURNAL OF THE PHARMACEUTICAL SOCIETY OF JAPAN 137 3 257 - 263 2017年03月 [査読有り][通常論文]
     
    The ability to metabolize xenobiotics in organisms has a wide degree of variation among organisms. This is caused by differences in the pattern of xenobiotic bioaccumulation among organisms, which affects their tolerance. It has been reported in the veterinary field that glucuronidation (UGT) activity in cats, acetylation activity in dogs and sulfation (SULT) activity in pigs are sub-vital in these species, respectively, and require close attention when prescribing the medicine. On the other hand, information about species differences in xenobiotics metabolism remains insufficient, especially in non-experimental animals. In the present study, we tried to elucidate xenobiotic metabolism ability, especially in phase II UGT conjugation of various non-experimental animals, by using newly constructed in vivo, in vitro and genomic techniques. The results indicated that marine mammals (Steller sea lion, northern fur seal, and Caspian seal) showed UGT activity as low as that in cats, which was significantly lower than in rats and dogs. Furthermore, UGT1A6 pseudogenes were found in the Steller sea lion and Northern fur seal; all Otariidae species are thought to have the UGT1A6 pseudogene as well. Environmental pollutants and drugs conjugated by UGT are increasing dramatically in the modern world, and their dispersal into the environment can be of great consequence to Carnivora species, whose low xenobiotic glucuronidation capacity makes them highly sensitive to these compounds.
  • Yared Beyene Yohannes, Yoshinori Ikenaka, Shouta M. M. Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 98 2 172 - 177 2017年02月 [査読有り][通常論文]
     
    Concentrations of ten trace elements (Hg, As, Cd, Pb, Co, Cr, Cu, Ni, Se and Zn) were determined in different tissues (liver, kidney, muscle, heart and brain) of African sacred ibis (Threskiornis aethiopicus), Hamerkop (Scopus umbretta), marabou stork (Leptoptilos crumeniferus) and great white pelican (Pelecanus onocrotalus) inhabiting the Ethiopian Rift Valley region. There were differences in trace element patterns among the bird species. Significantly (p < 0.05) higher concentrations of Cd (5.53 A mu g/g dw +/- 2.94) in kidney and Hg (0.75 A mu g/g ww +/- 0.30) in liver were observed in the great white pelican compared to the other species, and liver concentrations of these two elements showed positive correlations with trophic level. Concentrations of toxic elements (As, Cd, Pb and Hg) in liver were below their respective toxicological thresholds, indicating that the data may provide baseline information for future studies.
  • Hokuto Nakata, Shouta M M Nakayama, Balazs Oroszlany, Yoshinori Ikenaka, Hazuki Mizukawa, Kazuyuki Tanaka, Tsunehito Harunari, Tsutomu Tanikawa, Wageh Sobhy Darwish, Yared B Yohannes, Aksorn Saengtienchai, Mayumi Ishizuka
    International journal of environmental research and public health 14 1 2017年01月10日 [査読有り][通常論文]
     
    Although Japan has been considered to have little lead (Pb) pollution in modern times, the actual pollution situation is unclear. The present study aims to investigate the extent of Pb pollution and to identify the pollution sources in Japan using stable Pb isotope analysis with kidneys of wild rats. Wild brown (Rattus norvegicus, n = 43) and black (R. rattus, n = 98) rats were trapped from various sites in Japan. Mean Pb concentrations in the kidneys of rats from Okinawa (15.58 mg/kg, dry weight), Aichi (10.83), Niigata (10.62), Fukuoka (8.09), Ibaraki (5.06), Kyoto (4.58), Osaka (4.57), Kanagawa (3.42), and Tokyo (3.40) were above the threshold (2.50) for histological kidney changes. Similarly, compared with the previous report, it was regarded that even structural and functional kidney damage as well as neurotoxicity have spread among rats in Japan. Additionally, the possibility of human exposure to a high level of Pb was assumed. In regard to stable Pb isotope analysis, distinctive values of stable Pb isotope ratios (Pb-IRs) were detected in some kidney samples with Pb levels above 5.0 mg/kg. This result indicated that composite factors are involved in Pb pollution. However, the identification of a concrete pollution source has not been accomplished due to limited differences among previously reported values of Pb isotope composition in circulating Pb products. Namely, the current study established the limit of Pb isotope analysis for source identification. Further detailed research about monitoring Pb pollution in Japan and the demonstration of a novel method to identify Pb sources are needed.
  • Reiko Kishi, Atsuko Araki, Machiko Minatoya, Tomoyuki Hanaoka, Chihiro Miyashita, Sachiko Itoh, Sumitaka Kobayashi, Yu Ait Bamai, Keiko Yamazaki, Ryu Miura, Naomi Tamura, Kumiko Ito, Houman Goudarzi, S. Sasaki, T. Ikeno, E. Okada, S. Nishihara, R. M. Ketema, T. Kita, I. Kashino, T. Baba, T. S. Braimoh, S. Minakami, K. Cho, N. Shinohara, K. Moriya, T. Mitsui, T. Saito, S. Suyama, T. Nomura, S. Konno, H. Matsuura, M. Ishizuka, T. Endo, T. Baba, F. Sata, K. Sengoku, Y. Saijo, E. Yoshioka, T. Miyamoto, M. Yuasa, J. Kajiwara, T. Hori, Y. Chisaki, T. Matsumura, F. Mizutani, J. Yamamoto, Y. Onoda, T. Kawai, T. Tsuboi
    Environmental Health and Preventive Medicine 22 1 2017年 
    The Hokkaido Study on Environment and Children's Health is an ongoing study consisting of two birth cohorts of different population sizes: the Sapporo cohort and the Hokkaido cohort. Our primary study goals are (1) to examine the effects of low-level environmental chemical exposures on birth outcomes, including birth defects and growth retardation; (2) to follow the development of allergies, infectious diseases, and neurobehavioral developmental disorders and perform a longitudinal observation of child development; (3) to identify high-risk groups based on genetic susceptibility to environmental chemicals; and (4) to identify the additive effects of various chemicals, including tobacco smoking. The purpose of this report is to update the progress of the Hokkaido Study, to summarize the recent results, and to suggest future directions. In particular, this report provides the basic characteristics of the cohort populations, discusses the population remaining in the cohorts and those who were lost to follow-up at birth, and introduces the newly added follow-up studies and case-cohort study design. In the Sapporo cohort of 514 enrolled pregnant women, various specimens, including maternal and cord blood, maternal hair, and breast milk, were collected for the assessment of exposures to dioxins, polychlorinated biphenyls, organochlorine pesticides, perfluoroalkyl substances, phthalates, bisphenol A, and methylmercury. As follow-ups, face-to-face neurobehavioral developmental tests were conducted at several different ages. In the Hokkaido cohort of 20,926 enrolled pregnant women, the prevalence of complicated pregnancies and birth outcomes, such as miscarriage, stillbirth, low birth weight, preterm birth, and small for gestational age were examined. The levels of exposure to environmental chemicals were relatively low in these study populations compared to those reported previously. We also studied environmental chemical exposure in association with health outcomes, including birth size, neonatal hormone levels, neurobehavioral development, asthma, allergies, and infectious diseases. In addition, genetic and epigenetic analyses were conducted. The results of this study demonstrate the effects of environmental chemical exposures on genetically susceptible populations and on DNA methylation. Further study and continuous follow-up are necessary to elucidate the combined effects of chemical exposure on health outcomes.
  • 水川葉月, 高居名菜, 横山望, 市居修, 滝口満喜, 野見山桂, 高口倖暉, 西川博之, 池中良徳, 池中良徳, 中山翔太, SAINNOXOI Tsend-Ayush, 田辺信介, 石塚真由美
    Journal of Toxicological Sciences 42 Supplement S236 - S236 (一社)日本毒性学会 2017年 [査読有り][通常論文]
  • Hokuto Nakata, Shouta M. M. Nakayama, Balazs Oroszlany, Yoshinori Ikenaka, Hazuki Mizukawa, Kazuyuki Tanaka, Tsunehito Harunari, Tsutomu Tanikawa, Wageh Sobhy Darwish, Yared B. Yohannes, Aksorn Saengtienchai, Mayumi Ishizuka
    INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 14 1 2017年01月 [査読有り][通常論文]
     
    Although Japan has been considered to have little lead (Pb) pollution in modern times, the actual pollution situation is unclear. The present study aims to investigate the extent of Pb pollution and to identify the pollution sources in Japan using stable Pb isotope analysis with kidneys of wild rats. Wild brown (Rattus norvegicus, n = 43) and black (R. rattus, n = 98) rats were trapped from various sites in Japan. Mean Pb concentrations in the kidneys of rats from Okinawa (15.58 mg/kg, dry weight), Aichi (10.83), Niigata (10.62), Fukuoka (8.09), Ibaraki (5.06), Kyoto (4.58), Osaka (4.57), Kanagawa (3.42), and Tokyo (3.40) were above the threshold (2.50) for histological kidney changes. Similarly, compared with the previous report, it was regarded that even structural and functional kidney damage as well as neurotoxicity have spread among rats in Japan. Additionally, the possibility of human exposure to a high level of Pb was assumed. In regard to stable Pb isotope analysis, distinctive values of stable Pb isotope ratios (Pb-IRs) were detected in some kidney samples with Pb levels above 5.0 mg/kg. This result indicated that composite factors are involved in Pb pollution. However, the identification of a concrete pollution source has not been accomplished due to limited differences among previously reported values of Pb isotope composition in circulating Pb products. Namely, the current study established the limit of Pb isotope analysis for source identification. Further detailed research about monitoring Pb pollution in Japan and the demonstration of a novel method to identify Pb sources are needed.
  • Yared Beyene Yohannes, Yoshinori Ikenaka, Shouta M. M. Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    SCIENCE OF THE TOTAL ENVIRONMENT 574 1389 - 1395 2017年01月 [査読有り][通常論文]
     
    Despite the presence of a wide variety and number of birds, there is exceedingly little data on organochlorine pesticide (OCP) residues in birds inhabiting in Africa. In the present study, concentrations of dichlorodiphenyl-trichloroethanes (DDTs), hexachlorocyclohexanes, drins, cyclodienes, and hexachlorobenzene were measured in liver, kidney, heart and brain of 4 bird species from the Rift Valley region, Ethiopia. Indoor residual spraying of DDT for malaria vector control, and indiscriminate and illegal use of pesticides underline the relevance of this study. Levels of Sigma OCPs ranged from 1.87 to 4586 ng/g wet weight, and the scavenger bird species Leptoptilos crumeniferus had the highest level in liver. In all tissues, contamination profiles of OCPs within the species were similar, with DDTs >> other OCPs. Among the DDTs, p,p'-DDE was the most abundant compound and had significantly a higher burden in all tissues. The risk characterization demonstrated potential risks to the studied birds associated with DDE exposure. Maximum hepatic levels of p,p'-DDE exceeded the levels reported to trigger adverse effects. The detection of p,p'-DDT in all bird tissues suggests the release of fresh DDT to the environment. This is the first study to assay OCPs in different tissues of birds from the Ethiopian Rift Valley region, and henceforth the data will serve as a reference data for future studies. (C) 2016 Elsevier B.V. All rights reserved.
  • Aksorn Saengtienchai, Yoshinori Ikenaka, Nesta Bortey-Sam, Usuma Jermnark, Hazuki Mizukawa, Yusuke K. Kawai, Shouta M. M. Nakayama, Mayumi Ishizuka
    COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C-TOXICOLOGY & PHARMACOLOGY 190 38 - 47 2016年12月 [査読有り][通常論文]
     
    The African hedgehog, Atelerix albiventris, is a spiny mammal that has become popular as an exotic pet in many countries. To elucidate the ability of hedgehogs to metabolize xenobiotics, the animals were exposed to polycyclic aromatic hydrocarbon, pyrene. The in vivo exposure study indicated that pyrene was biotransformed to glucuronide and sulfate conjugates, such as pyrene-l-glucuronide, pyrene-1-sulfate, and pyrenediol-sulfate, and excreted in the urine. Pyrene-l-glucuronide was the main metabolite, and limited sulfate conjugate excretion was observed. The main products excreted in feces were 1-hydroxypyrene and pyrene. Based on the results of the in vivo exposure study, in vitro enzymatic kinetic experiments were performed using various substrates and compared to rats and pigs. The enzyme efficiencies of cytochrome P450 (CYP)-mediated ethoxyresorufin 0-deethylase activity and warfarin 4 '-, 6-, and 8-hydroxylation activity in hedgehogs were lower than those of rats. Furthermore, UDP-glucuronosyltransferase activity in hedgehogs also had a lower Km value than that in pigs. Interestingly, the enzyme efficiencies of sulfation activity toward 1-hydroxypyrene and beta-estradiol in hedgehogs were significantly lower than those in pigs. These observations suggested that phenol and estrogen sulfotransferases may have limited roles in xenobiotic metabolism in hedgehogs. (C) 2016 Elsevier Inc. All rights reserved.
  • Nesta Bortey-Sam, Yoshinori Ikenaka, Osei Akoto, Shouta M. M. Nakayama, Jemima Marfo, Aksorn Saengtienchai, Hazuki Mizukawa, Mayumi Ishizuka
    ENVIRONMENTAL POLLUTION 218 331 - 337 2016年11月 [査読有り][通常論文]
     
    Previous studies of polycyclic aromatic hydrocarbons (PAHs) in particulate matter, soils and livers of wild rats indicated that the city centre of Kumasi, Ghana has been severely polluted with high cancer potency. Cattle urine were therefore collected from Kumasi (urban) and Offinso (rural), Ghana: to determine concentrations of urinary PAH metabolites (OH-PAHs); and find their association with sex; and to estimate exposure of cattle to PAHs from the different sites. From the results, geometric mean concentrations (adjusted by specific gravity), GM(SG), showed that 2-OHNaphthalene (2-OHNap) was the most abundant OH-PAH in cattle urine from all study sites, and naphthalene-containing-mothballs might have contributed significantly to the levels. There was no significant difference between urinary OH-PAHs concentrations in cattle from urban and rural sites except for 2-OHPhe and 4-OHPhe, and similar to urban areas, rural sites could also be polluted with PAHs. GMSG of 2-OHNap in cattle urine in Kokote (21.9 +/- 6.51 ng/mL; a rural area), was significantly higher compared to the other sites followed by Oforikrom (4.15 +/- 4.37 ng/mL; urban). The GMSG concentration (ng/mL) of the sum of OH-PAHs decreased in the order, Kokote (44.7) > Oforikrom (7.87) > Saboa (6.98) > Santasi (6.68) > and Twumasen Estate (5.23). The high concentrations of urinary 2-OHNap, 2-OHPhe, 3-OHPhe and 4-OHPhe in Kokote indicated high PAHs exposure to cattle in this area or different/specific source of PAHs exposure. GMSG of 2-OHNap was significantly higher in male cattle compared to females while 1-9-OHPhe was significantly higher in females. (C) 2016 Published by Elsevier Ltd.
  • Kazuki Takeda, Yoshinori Ikenaka, Tsutomu Tanikawa, Kazuyuki D. Tanaka, Shouta M. M. Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 134 1 - 7 2016年11月 [査読有り][通常論文]
     
    Roof rats (Rattus rattus) live mainly in human habitats. Heavy use of rodenticides, such as warfarin, has led to the development of drug resistance, making pest control difficult. There have been many reports regarding mutations of vitamin K epoxide reductase (VKOR), the target enzyme of warfarin, in resistant rats. However, it has been suggested there are other mechanisms of warfarin resistance. To confirm these possibilities, closed colonies of warfarin-susceptible roof rats (S) and resistant rats from Tokyo (R) were established, and the pharmacokinetics/ pharmacodynamics of warfarin in rats from both colonies was investigated. R rats had low levels of warfarin in serum and high clearance activity. These rats can rapidly metabolize warfarin by hydroxylation. The levels of accumulation in the organs were lower than those of S rats. R rats administered warfarin showed high expression levels of CYP2B, 2C, and 3A, which play roles in warfarin hydroxylation, and may explain the high clearance ability of R rats. The mechanism of warfarin resistance in roof rats from Tokyo involved not only mutation of VKOR but also high clearance ability due to high levels of CYP2B, 2C and 3A expression possibly induced by warfarin. (C) 2016 Elsevier Inc. All rights reserved.
  • Bortey Sam Nesta, M M Nakayama Shouta, Ikenaka Yoshinori, Akoto Osei, Baidoo Elvis, Mizukawa Hazuki, Ishizuka Mayumi
    Journal of Environmental Chemistry and Ecotoxicology 8 7 58 - 68 2016年07月31日
  • Yoshihiro Nishiyama, Shouta M. M. Nakayama, Kensuke P. Watanabe, Yusuke K. Kawai, Marumi Ohno, Yoshinori Ikenaka, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 78 4 675 - 680 2016年04月 [査読有り][通常論文]
     
    Rat cytochrome P450 (CYP) exhibits inter-strain differences, but their analysis has been scattered across studies under different conditions. To identify these strain differences in CYP more comprehensively, mRNA expression, protein expression and metabolic activity among Wistar (WI), Sprague Dawley (SD), Dark Agouti (DA) and Brown Norway (BN) rats were compared. The mRNA level and enzymatic activity of CYP1A1 were highest in SD rats. The rank order of Cyp3a2 mRNA expression mirrored its protein expression, i.e., DA>BN>SD>WI, and was similar to the CYP3A2-dependent warfarin metabolic activity, i.e., DA>SD>BN>WI. These results suggest that the strain differences in CYP3A2 enzymatic activity are caused by differences in mRNA expression. Cyp2b1 mRNA levels, which were higher in DA rats, did not correlate with its protein expression or enzymatic activity. This suggests that the strain differences in enzymatic activity are not related to Cyp2b1 mRNA expression. In conclusion, WI rats tended to have the lowest CYP1A1, 2B1 and 3A2 mRNA expression, protein expression and enzymatic activity among the strains. In addition, SD rats had the highest CYP1A1 mRNA expression and activity, while DA rats had higher CYP2B1 and CYP3A2 mRNA and protein expression. These inter-strain differences in CYP could influence pharmacokinetic considerations in preclinical toxicological studies.
  • Ruan Gerber, Nico J. Smit, Johan H. J. Van Vuren, Shouta M. M. Nakayama, Yared B. Yohannes, Yoshinori Ikenaka, Mayumi Ishizuka, Victor Wepener
    SCIENCE OF THE TOTAL ENVIRONMENT 550 522 - 533 2016年04月 [査読有り][通常論文]
     
    With the second highest gross domestic product in Africa, South Africa is known to have a high pesticide usage, including the highly persistent and banned group of organochlorine pesticides (OCPs). South Africa is also one of few countries to still actively spray DDT as malaria vector control. The aim of the study was to determine the degree to which aquatic biota in selected rivers of the world renowned Kruger National Park (KNP) arc exposed to by use of OCPs in the catchments outside the KNP and how this exposure relates to human health. Tigerfish (Hydrocynus vittatus) arc economically important apex predators and was selected as bioindicator for this study. Fish were sampled from the KNP sections of the Luvuvhu, Letaba and Olifants rivers during the high and low flow periods from 2010 to 2011 within the KNP and 19 OCPs were determined in muscle tissue using GC-ECD techniques. Significant flow related and spatial OCP bioaccumulation was observed. Tigerfish from the Luvuvhu River displayed the highest OCP bioaccumulation. Concentrations of the majority of the OCPs including the DDTs were the highest levels ever recorded from South African freshwater systems and in many cases the concentrations were higher than most contaminated areas from around the world. The concentrations found in H. vittatus muscle also exceeded maximum residue levels in edible fat as set by the European Union. The health risk assessment also demonstrated that the levels of OCPs pose very high cancer risks to the local populations consuming tigerfish, as high as 2 in 10 increased risk factor. This is of concern not only when managing the water resources of the conservation area but also for surrounding communities consuming freshwater fish. Contaminants enter the park from outside the borders and pose potential risks to the mandated conservation of aquatic biota within the KNP. (C) 2016 Elsevier B.V. All rights reserved.
  • Nakayama SM, Ikenaka Y, Hayami A, Mizukawa H, Darwish WS, Watanabe KP, Kawai YK, Ishizuka M
    Journal of veterinary pharmacology and therapeutics 39 5 478 - 487 2016年03月 [査読有り][通常論文]
     
    Research on drug metabolism and pharmacokinetics in large animal species including the horse is scarce because of the challenges in conducting in vivo studies. The metabolic reactions catalyzed by cytochrome P450s (CYPs) are central to drug pharmacokinetics. This study elucidated the characteristics of equine CYPs using diazepam (DZP) as a model compound as this drug is widely used as an anesthetic and sedative in horses, and is principally metabolized by CYPs. Diazepam metabolic activities were measured in vitro using horse and rat liver microsomes to clarify the species differences in enzyme kinetic parameters of each metabolite (temazepam [TMZ], nordiazepam [NDZ], p-hydroxydiazepam [p-OH-DZP], and oxazepam [OXZ]). In both species microsomes, TMZ was the major metabolite, but the formation rate of p-OH-DZP was significantly less in the horse. Inhibition assays with a CYP-specific inhibitors and antibody suggested that CYP3A was the main enzyme responsible for DZP metabolism in horse. Four recombinant equine CYP3A isoforms expressed in Cos-7 cells showed that CYP3A96, CYP3A94, and CYP3A89 were important for TMZ formation, whereas CYP3A97 exhibited more limited activity. Phylogenetic analysis suggested diversification of CYP3As in each mammalian order. Further study is needed to elucidate functional characteristics of each equine CYP3A isoform for effective use of diazepam in horses.
  • Abdallah Fikry A. Mahmoud, Yoshinori Ikenaka, Yared B. Yohannes, Wageh S. Darwish, Elsaid A. Eldaly, Alaa Eldin M. A. Morshdy, Shouta M. M. Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    CHEMOSPHERE 144 1365 - 1371 2016年02月 [査読有り][通常論文]
     
    Food consumption is an important route of human exposure to organochlorine pesticides (OCPs). In order to assess the potential human health risks associated with OCPs, edible cattle tissues (liver, kidney and tongue) were collected from three slaughter houses in Mansoura, Zagazig and Ismailia cities, Egypt. Levels of 22 OCPs such as hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), aldrin, dieldrin and endrin (Drins), chlordanes (CHLs), heptachlors (HPTs) and hexachlorobenzene (HCB) residues were investigated. Among the investigated OCPs, HCHs represented the most dominant group with high proportions of gamma-HCH isomer (53-91% of total HCHs). Mansoura city had the highest OCPs contamination load ranged from 0.1 to 2827 ng g(-1) lw (lipid weight). Surprisingly, tongue samples collected from Mansoura showed the highest concentration of HCHs (448 ng g(-1) lw) in comparison to liver (152 ng g(-1) lw) and kidney (266 ng g(-1) lw). Generally, contamination pattern of OCPs was in the order of HCHs > Drins > CHLs > DDTs congruent to HCB and HPTs. Estimated daily intakes (EDIs) through dietary consumption of cattle tissues were lower than the recommended acceptable daily intakes (ADIs) established by FAO/WHO. However, the hazard ratios (HRs) based on cancer risk were greater than 1.0 for HCHs based on the average and 95th centile concentrations, indicating carcinogenic effects to consumers through cattle tissues consumption. (C) 2015 Elsevier Ltd. All rights reserved.
  • Darwish WS, Ikenaka Y, Morshdy AE, Eldesoky KI, Nakayama S, Mizukawa H, Ishizuka M
    The Journal of veterinary medical science 78 2 351 - 354 2016年02月 [査読有り][通常論文]
     
    The aim of this study was to estimate total carotenoids, beta-carotene and retinol concentrations in the livers and muscles of some ungulates (cattle, buffalo, sheep, goats and horses) in comparison with the Wistar rats as a control. Cattle and horses had the highest contents of total carotenoids and beta-carotene. Unexpectedly, sheep was the highest accumulator of retinol with a mean concentration of 203 +/- 23.34 mu g/g, while the least accumulator was buffalo, having a mean value of 58.28 +/- 13.77 mu g/g. Livers had higher contents of the examined phytochemicals than muscles. Consumption of these tissues may provide human with some needs from these important phytochemicals, though ingestion of livers, especially that of the sheep, is not advisable for the pregnant women.
  • 水川葉月, 前原美咲, 横山望, 市居修, 滝口満喜, 野見山桂, 西川博之, 池中良徳, 中山翔太, 高口倖暉, 田辺信介, 石塚真由美
    Journal of Toxicological Sciences 41 Supplement S215 - S215 (一社)日本毒性学会 2016年 [査読有り][通常論文]
  • Hokuto Nakata, Shouta M. M. Nakayama, John Yabe, Allan Liazambi, Hazuki Mizukawa, Wageh Sobhy Darwish, Yoshinori Ikenaka, Mayumi Ishizuka
    ENVIRONMENTAL POLLUTION 208 Pt B 395 - 403 2016年01月 [査読有り][通常論文]
     
    Stable Pb isotope ratios (Pb-IRs) have been recognized as an efficient tool for identifying sources. This study carried out at Kabwe mining area, Zambia, to elucidate the presence or absence of Pb isotope fractionation in goat and chicken, to evaluate the reliability of identifying Pb pollution sources via analysis of Pb-IRs, and to assess whether a threshold for blood Pb levels (Pb-B) for biological fractionation was present The variation of Pb-IRs in goat decreased with an increase in Pb-B and were fixed at certain values close to those of the dominant source of Pb exposure at Pb-B > 5 mu g/dL. However, chickens did not show a clear relationship for Pb-IRs against Pb-B, or a fractionation threshold. Given these, the biological fractionation of Pb isotopes should not occur in chickens but in goats, and the threshold for triggering biological fractionation is at around 5 mu g/dL of Pb-B in goats. (C) 2015 Elsevier Ltd. All rights reserved.
  • Darwish WS, Ikenaka Y, Nakayama SM, Mizukawa H, Ishizuka M
    Journal of food science 81 1 T275 - T281 2016年01月 [査読有り][通常論文]
     
    Lead (Pb) is an environmental pollutant that can get entry into human body through contaminated foods, drinks, and inhaled air leading to severe biological consequences, and has been responsible for many deaths worldwide. The objectives of this study were 1st to investigate the modulatory effects of environmentally relevant concentrations of Pb on AhR gene battery, which is controlling xenobiotics metabolism. 2nd, trials to reduce Pb-induced adverse effects were done using some phytochemicals like beta-carotene or ascorbic acid. Human hepatoma (HepG2) cell lines were exposed to a wide range of Pb concentrations varying from physiological to toxic levels (0 to 10 mg/L) for 24 h. High Pb concentrations (1 to 10 mg/L) significantly reduced phase I (CYP1A1 and 1A2) and phase II (UGT1A6 and NQO1) xenobiotic metabolizing enzyme mRNA expression in a mechanistic manner through the AhR regulation pathway. Additionally, these Pb concentrations induced oxidative stress in HepG2 cells in terms of production of reactive oxygen species (ROS) and induced heme oxygenase-1 mRNA expression in a concentration-dependent phenomenon. Coexposure of HepG2 cells to physiological concentrations of some micronutrients, like beta-carotene (10 mu M) or ascorbic acid (0.1 mM), along with Pb (1 mg/L) for 24 h significantly reduced the levels of ROS production and recovered AhR mRNA expression into the normal levels. Thus, consumption of foods rich in these micronutrients may help to reduce the adverse effects of lead in areas with high levels of pollution.
  • Hazuki Mizukawa, Kei Nomiyama, Susumu Nakatsu, Hisato Iwata, Jean Yoo, Akira Kubota, Miyuki Yamamoto, Mayumi Ishizuka, Yoshinori Ikenaka, Shouta M. M. Nakayama, Tatsuya Kunisue, Shinsuke Tanabe
    ENVIRONMENTAL SCIENCE & TECHNOLOGY 50 1 444 - 452 2016年01月 [査読有り][通常論文]
     
    There are growing concerns about the increase in hyperthyroidism in pet cats due to exposure to organo-halogen contaminants and their hydroxylated metabolites. This study investigated the blood contaminants polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) and their hydroxylated and methoxylated derivatives (OH-PCBs, OH-PBDEs, and MeO-PBDEs), in pet dogs and cats. We also measured the residue levels of these compounds in commercially available pet foods. Chemical analyses of PCBs and OH-PCBs showed that the OH-PCB levels were 1 to 2 orders of magnitude lower in cat and dog food products than in their blood, suggesting that the origin of OH-PCBs in pet dogs and cats is PCBs ingested with their food. The major congeners of OH-/MeO-PBDEs identified in both pet food products and blood were natural products (60H-/MeO-BDE47 and 2'OH-/MeO-BDE68) from marine organisms. In particular, higher concentrations of 60H-BDE47 than 2'OH-BDE68 and two MeO-PBDE congeners were observed in the cat blood, although MeO-BDEs were dominant in cat foods, suggesting the efficient biotransformation of 60H-BDE47 from 6MeO-BDE47 in cats. We performed in vitro demethylation experiments to confirm the biotransformation of MeO-PBDEs to OH-PBDEs using liver microsomes. The results showed that 6MeO-BDE47 and 2'MeO-BDE68 were demethylated to 60H-BDE47 and 2'OH-BDE68 in both animals, whereas no hydroxylated metabolite from BDE47 was detected. The present study suggests that pet cats are exposed to MeO-PBDEs through cat food products containing fish flavors and that the OH-PBDEs in cat blood are derived from the CYP-dependent demethylation of naturally occurring MeO-PBDE congeners, not from the hydroxylation of PBDEs.
  • Ruan Gerber, Nico J. Smit, Johan H. J. van Vuren, Shouta M. M. Nakayama, Yared B. Yohannes, Yoshinori Ikenaka, Mayumi Ishizuka, Victor Wepener
    ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 22 24 19971 - 19989 2015年12月 [査読有り][通常論文]
     
    The physical and chemical characteristics of surface sediments from a leading conservation area, namely the Kruger National Park, were determined in order to identify potential stressors in the systems that may contribute to overall deterioration in sediment quality within the reserve, leading to potential threats to the aquatic biota conserved within these stretches of river. Sediment samples were collected during four surveys (two low flow and two high flow) from 2009 to 2011. Samples were analysed for organic content, grain size determination, metals and various organochlorine pesticides. Results indicated that the Olifants River sediments did not show any great improvement over the years and point towards the continued input of pollutants into this system. Sediment quality in the Luvuvhu and Letaba Rivers is better than that of sediments from the Olifants River in terms of metals, but metal concentrations are still comparable and point towards anthropogenic inputs of metals into these rivers. Even though the data indicate that these systems are being contaminated with both metals and organochlorine pesticides (OCPs), levels were still below contaminated sediments from around the globe. Sediment Quality Index scores showed that the sediment quality of these rivers is in a relatively good state. High metal concentrations were the drivers behind lowered sediment quality, and in some cases certain OCPs played a role. Both metals and OCP concentrations were highly correlated with finer grain sizes. Sediment assessments are not routinely applied in South Africa resulting in very little reference or background data available for the area. The metal concentrations for the study area were generally lower than those for other studies in more polluted regions. The study also contributes to the available knowledge on surrounding metal pollution in riverine sediments in South Africa.
  • Hiroki Teraoka, Erika Okamoto, Moe Kudo, Shouta M. M. Nakayama, Yoshinori Ikenaka, Mayumi Ishizuka, Tetsuya Endo, Takio Kitazawa, Takeo Hiraga
    ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 122 557 - 564 2015年12月 [査読有り][通常論文]
     
    The red-crowned (Japanese) crane Grus japonensis is native to east Hokkaido, Japan, in contrast to the East Asia mainland. Previously, we reported that red-crowned cranes in Hokkaido were highly contaminated with mercury in the 1990s and that the contamination rapidly decreased to a moderate level in the 2000s. In the present study, we determined levels of organic mercury (O-Hg) in the liver and kidney of cranes in east Hokkaido in comparison with levels of total mercury (T-Hg). T-Hg levels in the kidneys were higher than those in the livers in adults but not in subadults and juveniles; however, the reverse was the case for O-Hg even for adults. The ratio of O-Hg to T-Hg in both the liver and kidney decreased as T-Hg increased in the three developmental stages. While the ratios of O-Hg to T-Hg in the liver and kidney of adults were significantly lower than those of juveniles, the ratios were similar for adults and juveniles in a lower range of T-Hg. The ratio of selenium (Se) to T-Hg decreased as T-Hg increased in both the liver and kidney, irrespective of stages. Mercury burdens in feathers were about 59% and 67% of the total body burdens for juveniles and adults, respectively. Furthermore, ratios of carbon and nitrogen stable isotopes to T-Hg varied greatly, with no relation to mercury level in the liver. The results suggest slow accumulation of inorganic mercury in the kidney of red-crowned cranes in east Hokkaido, Japan. (C) 2015 Elsevier Inc. All rights reserved.
  • Jemima Tiwaa Mario, Kazutoshi Fujioka, Yoshinori Ikenaka, Shouta M. M. Nakayama, Hazuki Mizukawa, Yoshiko Aoyama, Mayumi Ishizuka, Kumiko Taira
    PLOS ONE 10 11 e0142172  2015年11月 [査読有り][通常論文]
     
    Neonicotinoid insecticides are nicotinic acetylcholine receptor agonists used worldwide. Their environmental health effects including neurotoxicity are of concern. We previously determined a metabolite of acetamiprid, N-desmethyl-acetamiprid in the urine of a patient, who exhibited some typical symptoms including neurological findings. We sought to investigate the association between urinary N-desmethyl-acetamiprid and the symptoms by a prevalence case-control study. Spot urine samples were collected from 35 symptomatic patients of unknown origin and 50 non-symptomatic volunteers (non-symptomatic group, NSG, 4-87 year-old). Patients with recent memory loss, finger tremor, and more than five of six symptoms (headache, general fatigue, palpitation/chest pain, abdominal pain, muscle pain/weakness/spasm, and cough) were in the typical symptomatic group (TSG, n = 19, 5-69 year-old); the rest were in the atypical symptomatic group (ASG, n = 16, 5-78 year-old). N-desmethyl-acetamiprid and six neonicotinoids in the urine were quantified by liquid chromatography-tandem mass spectrometry. The detection of N-desmethyl-acetamiprid was the most frequent and highest in TSG (47.4%, 6.0 ppb (frequency, maximum)), followed by in ASG (12.5%, 4.4 ppb) and in NSG (6.0%, 2.2 ppb), however acetamiprid was not detected. Thiamethoxam was detected in TSG (31.6%, 1.4 ppb), in ASG (6.3%, 1.9 ppb), but not in NSG. Nitenpyram was detected in TSG (10.5%, 1.2 ppb), in ASG (6.3%, not quantified) and in NSG (2.0%, not quantified). Clothianidin was only detected in ASG (6.3%, not quantified), and in NSG (2.0%, 1.6 ppb). Thiacloprid was detected in ASG (6.3%, 0.1 ppb). The cases in TSG with detection of N-desmethyl-acetamiprid and thiamethoxam were aged 5 to 62 years and 13 to 62 years, respectively. Detection of N-desmethyl-acetamiprid was associated with increased prevalence of the symptoms (odds ratio: 14, 95% confidence interval: 3.5-57). Urinary N-desmethyl-acetamiprid can be used as a biomarker for environmental exposure to acetamiprid. Further multi-centered clinical research in larger patients groups with more metabolites analysis is needed.
  • Wageh Sobhy Darwish, Yoshinori Ikenaka, Shouta Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 63 4 173 - 182 2015年11月 [査読有り][通常論文]
     
    Cooking of meat usually aims in producing microbiologically safe food suitable for human consumption. However, doing so at such high temperatures may produce some cooking toxicants or mutagens. The objectives of this study were to investigate the mutagenicity of modelled-heat-treated meat after different cooking methods (boiling, pan-frying and charcoal grilling) using Ames Salmonella typhimurium mutagenicity assay. In addition, the content of benzo[a]pyrene (B[a]P) in the meat extracts prepared under different cooking methods were measured using HPLC. In a trial to investigate the causes behind the mutagenicity of different meat extracts, HepG2 cell line was exposed to different modelled-heat-treated meat extracts. mRNA expression levels of various phase I and II xenobiotic metabolizing enzymes (XMEs) were examined using real time PCR. The results obtained declared that pan-fried and charcoal grilled-meat extracts significantly induced production of histidine+ revertants in the Ames mutagenicity assay. Grilled-meat extracts had the highest residual concentrations of B[a]P followed by pan-fried-meat, boiled meat and raw meat extracts, respectively. Induction of XMEs especially CYP1A1, CYP1A2 and NQO1 may contribute to the mutagenic ability of these extracts. It is highly advisable to control cooking temperature, time and method in order to reduce cooked-meat mutagens.
  • Kensuke P. Watanabe, Minami Kawata, Yoshinori Ikenaka, Shouta M. M. Nakayama, Chihiro Ishii, Wageh Sobhi Darwish, Aksorn Saengtienchai, Hazuki Mizukawa, Mayumi Ishizuka
    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 34 10 2328 - 2334 2015年10月 [査読有り][通常論文]
     
    Coumarin-derivative anticoagulant rodenticides used for rodent control are posing a serious risk to wild bird populations. For warfarin, a classic coumarin derivative, chickens have a high median lethal dose (LD50), whereas mammalian species generally have much lower LD50. Large interspecies differences in sensitivity to warfarin are to be expected. The authors previously reported substantial differences in warfarin metabolism among avian species; however, the actual in vivo pharmacokinetics have yet to be elucidated, even in the chicken. In the present study, the authors sought to provide an in-depth characterization of warfarin metabolism in birds using in vivo and in vitro approaches. A kinetic analysis of warfarin metabolism was performed using liver microsomes of 4 avian species, and the metabolic abilities of the chicken and crow were much higher in comparison with those of the mallard and ostrich. Analysis of in vivo metabolites from chickens showed that excretions predominantly consisted of 4-hydroxywarfarin, which was consistent with the in vitro results. Pharmacokinetic analysis suggested that chickens have an unexpectedly long half-life despite showing high metabolic ability in vitro. The results suggest that the half-life of warfarin in other bird species could be longer than that in the chicken and that warfarin metabolism may not be a critical determinant of species differences with respect to warfarin sensitivity. Environ Toxicol Chem 2015;34:2328-2334. (c) 2015 SETAC
  • Hokuto Nakata, Shouta M. M. Nakayama, Yoshinori Ikenaka, Hazuki Mizukawa, Chihiro Ishii, Yared B. Yohannes, Satoru Konnai, Wageh Sobhy Darwish, Mayumi Ishizuka
    ENVIRONMENTAL POLLUTION 205 8 - 15 2015年10月 [査読有り][通常論文]
     
    Nairobi city in Kenya produces 2000 tons/day of garbage, and most of it is dumped onto the Dandora dumping site, home to a quarter-million residents. This study was conducted (1) to assess the contamination levels of nine metals and a metalloid (arsenic) in the blood of pigs, goats, sheep and cattle from Dandora, and (2) to identify a possible source of lead (Pb) pollution. Cadmium (Cd, 0.17-435 mu g/kg, dry-wt) and Pb (90-2710 mu g/kg) levels in blood were generally high, suggesting human exposure to Cd through livestock consumption and Pb poisoning among pigs (2600 mu g/kg) and cattle (354 mu g/kg). Results of Pb isotope ratios indicated that the major exposure route might differ among species. Our results also suggested a possibility that the residents in Dandora have been exposed to the metals through livestock consumption. (C) 2015 Elsevier Ltd. All rights reserved.
  • Aksorn Saengtienchai, Yoshinori Ikenaka, Wageh Sobhy Darwish, Shouta M. M. Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 77 10 1261 - 1267 2015年10月 [査読有り][通常論文]
     
    Pyrene (PY) is a polycyclic aromatic hydrocarbon (PAH) that is often used as a biomarker for human and wildlife exposure to PAHs. As the metabolites of PAHs, similar to their parent compounds, pose public health risks, it is necessary to study their characteristics and tissue-specific distribution. The present study was performed to experimentally characterize PY metabolites and analyze the tissue-specific distribution of the conjugated metabolites after oral administration of PY to rats. PY metabolites, such as pyrenediol-disulfate (PYdiol-diS), pyrenediol-sulfate (PYdiol-S), pyrene-1-sufate (PYOS), pyrene-l-glucuronide (PYOG) and 1-hydroxypyrene (PYOH), were detected in rat urine. Although glucuronide conjugate was the predominant metabolite, the metabolite composition varied among tissues. Interestingly, the proportion of PYOH was high in the large intestine. Furthermore, PYOH was the only PY metabolite detected in feces.
  • Mayu Kakehi, Yoshinori Ikenaka, Shouta M. M. Nakayama, Yusuke K. Kawai, Kensuke P. Watanabe, Hazuki Mizukawa, Kei Nomiyama, Shinsuke Tanabe, Mayumi Ishizuka
    TOXICOLOGICAL SCIENCES 147 2 360 - 369 2015年10月 [査読有り][通常論文]
     
    There are various interspecies differences in xenobiotic-metabolizing enzymes. It is known that cats show slow glucuronidation of drugs such as acetaminophen and strong side effects due to the UGT1A6 pseudogene. Recently, the UGT1A6 pseudogene was found in the Northern elephant seal and Otariidae was suggested to be UGT1A6-deficient. From the results of measurements of uridine diphosphate-glucuronosyltransferase (UGT) activity using liver microsomes, the Steller sea lion, Northern fur seal, and Caspian seal showed UGT activity toward 1-hydroxypyrene and acetaminophen as low as in cats, which was significantly lower than in rat and dog. Furthermore, UGT1A6 pseudogenes were found in Steller sea lion and Northern fur seal, and all Otariidae species were suggested to have the UGT1A6 pseudogene. The UGT1 family genes appear to have undergone birth-and-death evolution based on a phylogenetic and synteny analysis of the UGT1 family in mammals including Carnivora. UGT1A2-1A5 and UGT1A7-1A10 are paralogous genes to UGT1A1 and UGTA6, respectively, and their numbers were lower in cat, ferret and Pacific walrus than in human, rat, and dog. Felidae and Pinnipedia, which are less exposed to natural xenobiotics such as plant-derived toxins due to their carnivorous diet, have experienced fewer gene duplications of xenobiotic-metabolizing UGT genes, and even possess UGT1A6 pseudogenes. Artificial environmental pollutants and drugs conjugated by UGT are increasing dramatically, and their elimination to the environment can be of great consequence to cat and Pinnipedia species, whose low xenobiotic glucuronidation capacity makes them highly sensitive to these compounds.
  • Nesta Bortey-Sam, Shouta M M Nakayama, Osei Akoto, Yoshinori Ikenaka, Elvis Baidoo, Hazuki Mizukawa, Mayumi Ishizuka
    International journal of environmental research and public health 12 9 11448 - 65 2015年09月11日 [査読有り][通常論文]
     
    Heavy metals and a metalloid in agricultural soils in 19 communities in Tarkwa were analyzed to assess the potential ecological risk. A total of 147 soil samples were collected in June, 2012 and analyzed for As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn. Mean concentrations (mg/kg dw) of heavy metals in the communities decreased in order of Zn (39) ˃ Cr (21) ˃ Pb (7.2) ˃ Cu (6.2) ˃ As (4.4) ˃ Ni (3.7) ˃ Co (1.8) ˃ Hg (0.32) ˃ Cd (0.050). Correlations among heavy metals and soil properties indicated that soil organic matter could have substantial influence on the total contents of these metals in soil. From the results, integrated pollution (C(deg)) in some communities such as, Wangarakrom (11), Badukrom (13) and T-Tamso (17) indicated high pollution with toxic metals, especially from As and Hg. Potential ecological risk (RI) indices indicated low (Mile 7) to high risks (Wangarakrom; Badukrom) of metals. Based on pollution coefficient (C(i)(f)), C(deg), monomial ecological risk (E(i)(r)) and RI, the investigated soils fall within low to high contamination and risk of heavy metals to the ecological system especially plants, soil invertebrates and/or mammalian wildlife. This represented moderate potential ecological risk in the study area, and mining activities have played a significant role.
  • Nesta Bortey-Sam, Shouta M. M. Nakayama, Osei Akoto, Yoshinori Ikenaka, Elvis Baidoo, Hazuki Mizukawa, Mayumi Ishizuka
    INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 12 9 11448 - 11465 2015年09月 [査読有り][通常論文]
     
    Heavy metals and a metalloid in agricultural soils in 19 communities in Tarkwa were analyzed to assess the potential ecological risk. A total of 147 soil samples were collected in June, 2012 and analyzed for As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn. Mean concentrations (mg/kg dw) of heavy metals in the communities decreased in order of Zn (39) ? Cr (21) ? Pb (7.2) ? Cu (6.2) ? As (4.4) ? Ni (3.7) ? Co (1.8) ? Hg (0.32) ? Cd (0.050). Correlations among heavy metals and soil properties indicated that soil organic matter could have substantial influence on the total contents of these metals in soil. From the results, integrated pollution (C-deg) in some communities such as, Wangarakrom (11), Badukrom (13) and T-Tamso (17) indicated high pollution with toxic metals, especially from As and Hg. Potential ecological risk (RI) indices indicated low (Mile 7) to high risks (Wangarakrom; Badukrom) of metals. Based on pollution coefficient (C-f(i)), C-deg, monomial ecological risk (E-r(i)) and RI, the investigated soils fall within low to high contamination and risk of heavy metals to the ecological system especially plants, soil invertebrates and/or mammalian wildlife. This represented moderate potential ecological risk in the study area, and mining activities have played a significant role.
  • Nesta Bortey-Sam, Shouta M. M. Nakayama, Osei Akoto, Yoshinori Ikenaka, Julius N. Fobil, Elvis Baidoo, Hazuki Mizukawa, Mayumi Ishizuka
    INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 12 8 8811 - 8827 2015年08月 [査読有り][通常論文]
     
    This study was carried out to assess the extent of heavy metals and metalloid accumulation from agricultural soils to foodstuffs (viz, M. esculenta (cassava) and Musa paradisiaca (plantain)) around thirteen neighboring communities within Tarkwa, Ghana; and to estimate the human health risk associated with consumption of these foodstuffs. Concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn were measured with an inductively coupled plasma-mass spectrometer and mercury analysis was done using a mercury analyzer. From the results, 30% of cassava samples collected, contained higher concentrations of Pb when compared to Codex Alimentarius Commission standard values. Bioconcentration factor indicated that Ni had higher capacity of absorption into food crops from soil than the other heavy metals. For both children and adults, the target hazard quotient (THQ) of Pb in cassava in communities such as Techiman, Wangarakrom, Samahu, and Tebe (only children) were greater than 1, which is defined as an acceptable risk value. This indicated that residents could be exposed to significant health risks associated with cassava consumption.
  • Nesta Bortey-Sam, Shouta M M Nakayama, Osei Akoto, Yoshinori Ikenaka, Julius N Fobil, Elvis Baidoo, Hazuki Mizukawa, Mayumi Ishizuka
    International journal of environmental research and public health 12 8 8811 - 27 2015年07月28日 [査読有り][通常論文]
     
    This study was carried out to assess the extent of heavy metals and metalloid accumulation from agricultural soils to foodstuffs (viz, M. esculenta (cassava) and Musa paradisiaca (plantain)) around thirteen neighboring communities within Tarkwa, Ghana; and to estimate the human health risk associated with consumption of these foodstuffs. Concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn were measured with an inductively coupled plasma-mass spectrometer and mercury analysis was done using a mercury analyzer. From the results, 30% of cassava samples collected, contained higher concentrations of Pb when compared to Codex Alimentarius Commission standard values. Bioconcentration factor indicated that Ni had higher capacity of absorption into food crops from soil than the other heavy metals. For both children and adults, the target hazard quotient (THQ) of Pb in cassava in communities such as Techiman, Wangarakrom, Samahu, and Tebe (only children) were greater than 1, which is defined as an acceptable risk value. This indicated that residents could be exposed to significant health risks associated with cassava consumption.
  • Yutaka Watanuki, Takashi Yamamoto, Ai Yamashita, Chihiro Ishii, Yoshinori Ikenaka, Shouta M. M. Nakayama, Mayumi Ishizuka, Yuya Suzuki, Yasuaki Niizuma, C. E. Meathrel, R. A. Phillips
    JOURNAL OF ORNITHOLOGY 156 3 847 - 850 2015年07月 [査読有り][通常論文]
     
    We measured mercury concentrations ([Hg]) and nitrogen stable isotope ratios (delta N-15) in the primary feathers of Short-tailed Shearwaters (Puffinus tenuirostris) that were tracked year-round. The [Hg] were highest in 14 birds that used the Okhotsk and northern Japan Seas during the non-breeding period (2.5 +/- A 1.4 mu g/g), lowest in nine birds that used the eastern Bering Sea (0.8 +/- A 0.2 mu g/g), and intermediate in five birds that used both regions (1.0 +/- A 0.5 mu g/g), with no effects of delta N-15. The results illustrate that samples from seabirds can provide a useful means of monitoring pollution at a large spatial scale.
  • Nesta Bortey-Sam, Yoshinori Ikenaka, Osei Akoto, Shouta M. M. Nakayama, Yared Beyene Yohannes, Elvis Baidoo, Hazuki Mizukawa, Mayumi Ishizuka
    ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 22 13 9658 - 9667 2015年07月 [査読有り][通常論文]
     
    Airborne particulate samples were collected on quartz filters to determine the concentrations, sources and health risks of polycyclic aromatic hydrocarbons (PAHs) in air in Kumasi, Ghana. A total of 32 air samples were collected in Kwame Nkrumah University of Science and Technology (KNUST) campus (pristine site) and city centre (CC). Samples were extracted with 1:2v/v acetone/hexane mixture prior to GC-MS analyses. The sum of concentrations of 17 PAHs in air ranged from 0.51 to 16 (KNUST) and 19-38 ng/m(3) (CC). The concentration of benzo[a]pyrene, BaP, ranged from below detection limit to 0.08 ng/m(3) (KNUST) and 1.6 to 5.6 ng/m(3) (CC). Chemical mass balance model showed that PAHs in air in Kumasi were mainly from fuel combustion. The total BaP equivalent concentration (BaPeq) in CC was 18 times higher compared to KNUST; based on the European Legislation and Swedish and UK Standards for BaP in air, CC could be classified as highly polluted. Estimated carcinogenicity of PAHs in terms of BaPeq indicated that BaP was the principal PAH contributor in CC (70 %). Health risk to adults and children associated with PAH inhalation was assessed by taking into account the lifetime average daily dose and corresponding incremental lifetime cancer risk (ILCR). The ILCR was within the acceptable range (10(-6) to 10(-4)), indicating low health risk to residents.
  • Nesta Bortey-Sam, Shouta M. M. Nakayama, Yoshinori Ikenaka, Osei Akoto, Elvis Baidoo, Hazuki Mizukawa, Mayumi Ishizuka
    ENVIRONMENTAL MONITORING AND ASSESSMENT 187 7 397 - 12 2015年07月 [査読有り][通常論文]
     
    Concentrations of heavy metals and metalloid in borehole drinking water from 18 communities in Tarkwa, Ghana, were measured to assess the health risk associated with its consumption. Mean concentrations of heavy metals (mu g/L) exceeded recommended values in some communities. If we take into consideration the additive effect of heavy metals and metalloid, then oral hazard index (HI) results raise concerns about the noncarcinogenic adverse health effects of drinking groundwater in Huniso. According to the US Environmental Protection Agency's (USEPA) guidelines, HI values indicating noncarcinogenic health risk for adults and children in Huniso were 0.781 (low risk) and 1.08 (medium risk), respectively. The cancer risk due to cadmium (Cd) exposure in adults and children in the sampled communities was very low. However, the average risk values of arsenic (As) for adults and children through drinking borehole water in the communities indicated medium cancer risk, but high cancer risk in some communities such as Samahu and Mile 7. Based on the USEPA assessment, the average cancer risk values of As for adults (3.65E-05) and children (5.08E-05) indicated three (adults) and five (children) cases of neoplasm in a hundred thousand inhabitants. The results of this study showed that residents in Tarkwa who use and drink water from boreholes could be at serious risk from exposure to these heavy metals and metalloid.
  • Wageh S. Darwish, Shouta M. M. Nakayama, Yuumi Itotani, Marumi Ohno, Yoshinori Ikenaka, Mayumi Ishizuka
    JOURNAL OF FOOD SCIENCE 80 7 T1627 - T1632 2015年07月 [査読有り][通常論文]
     
    Heterocyclic amines get entry into human body mainly through ingestion of pan-fried meats cooked at high temperatures. Exposure of the gastrointestinal tract (GIT) to ingested xenobiotics prior to delivery to the liver may lead to metabolic activation, which may explain the high incidence of GIT carcinogenesis. Therefore, this study investigated the mutagenic activation of 2 heterocyclic amines, 2-aminoanthracene (2-AA) and 3-amino-1-methyl-5H-prydo[4,3-b]indole (Trp-P-2), in the GIT of rats. In addition, the constitutive mRNA expression profiles of xenobiotic-metabolizing enzymes (XMEs) in the GIT of rats were examined. Metabolic activation of 2-AA was detected in all GIT tissues except the duodenum and rectum, and it was detected at high levels in the ileum and cecum. Furthermore, we revealed high metabolic activation of 2-AA and Trp-P-2 in the jejunum. The mRNA expression of phase I and II enzymes in rat GIT corresponded with their mutagenic activation ability. In conclusion, our results suggest that different expression levels of XME among GIT tissues may contribute to the tissue-specific differences in metabolic activation of xenobiotics such as heterocyclic amines in rats. Practical Application This study declares mutagenic activation of 2 heterocyclic amines namely 2-aminoanthracene (2-AA) and 3-amino-1-methyl-5H-prydo[4,3-b]indole (Trp-P-2), in the gastrointestinal tract (GIT) of rats. In addition, results obtained in this study suggest that GIT tissue-specific expression of xenobiotic metabolizing enzymes may contribute to the tissue-specific mutagenesis/carcinogenesis.
  • Yoshinori Ikenaka, Shouta M. M. Nakayama, Mami Oguri, Aksorn Saengtienchai, Hazuki Mizukawa, Jun Kobayashi, Wageh Sobhy Darwish, Mayumi Ishizuka
    ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 39 3 1148 - 1153 2015年05月 [査読有り][通常論文]
     
    Red gourami (Colisa labiosa) have previously been shown to have low levels of pyrene-metabolizing activity. In this study, other pharmacokinetic factors of pyrene in C. labiosa were compared to those in Japanese medaka (Oryzias latipes). Results indicated that the two species labiosa absorbed pyrene in similar amounts. However, excretion of pyrene metabolites from C. labiosa over an 8-day period was lower than those from O. latipes. These findings show that C. labiosa has low ability to metabolize pyrene and to excrete pyrene and its metabolites from the body, and is therefore considered an accumulator of these chemicals. C. labiosa has unique characteristics with regard to pyrene pharmacokinetics. Knowledge about interspecies differences in pharmacokinetics is crucial in determining the endangered species to xenobiotic exposure. (C) 2015 Elsevier B.V. All rights reserved.
  • K. P. Watanabe, Y. K. Kawai, S. M.M. Nakayama, Y. Ikenaka, H. Mizukawa, N. Takaesu, M. Ito, S. I. Ikushiro, T. Sakaki, M. Ishizuka
    Journal of Veterinary Pharmacology and Therapeutics 38 2 190 - 195 2015年04月01日 [査読有り][通常論文]
     
    Large interspecies differences in avian xenobiotic metabolism have been revealed by microsome-based studies, but specific enzyme isoforms in different bird species have not yet been compared. We have previously shown that CYP2C23 genes are the most induced CYP isoforms in chicken liver. In this study, we collected partial CYP2C23a gene sequences from eight avian species (ostrich, blue-eared pheasant, snowy owl, great-horned owl, Chilean flamingo, peregrin falcon, Humboldt penguin, and black-crowned night heron) selected to cover the whole avian lineage: Paleognathae, Galloanserae, and Neoaves. Genetic analysis showed that CYP2C23 genes of Galloanserae species (chicken and blue-eared pheasant) had unique characteristics. We found some duplicated genes (CYP2C23a and CYP2C23b) and two missing amino acid residues in Galloanserae compared to the other two lineages. The genes have lower homology than in other avian lineages, which suggests Galloanserae-specific rapid evolutionary changes. These genetic features suggested that the Galloanserae are not the most representative avian species, considering that the Neoaves comprise more than 95% of birds. Moreover, we succeeded in synthesizing an antipeptide polyclonal antibody against the region of CYP2C23 protein conserved in avians. However, comparative quantitation of CYP2C23 proteins in livers from six species showed that expression levels of these proteins differed no more than fourfold. Further study is needed to clarify the function of avian CYP2C23 proteins.
  • Hazuki Mizukawa, Kei Nomiyama, Tatsuya Kunisue, Michio X. Watanabe, Annamalai Subramanian, Hisato Iwata, Mayumi Ishizuka, Shinsuke Tanabe
    ENVIRONMENTAL RESEARCH 138 255 - 263 2015年04月 [査読有り][通常論文]
     
    The concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and their hydroxylated metabolites (OH-PCBs and OH-PBDEs) were measured in the blood of Eurasian wild pigs (Sus scrofa) from a municipal waste open dumping site (DS) and a reference site (RS) in South India. We showed that contamination with OH-PCBs was higher in female pigs from the DS than in all other adult pigs. The highest OH-PCB concentrations were found in piglets from the DS. Moreover, the hepatic expression levels of CYP1A and CYP2B were higher in piglets than in their dam, implying metabolism of PCBs by cytochrome P450 (CYP) enzymes. The OH-PCB congener profiles differed according to sex and collection sites, possibly because of variations in the expression levels of phase I and phase II enzymes among individual pigs, differences in the exposure sources, and maternal transfer of parent PCBs. The hepatic CYP1A expression levels were positively correlated with the blood concentrations of 4OH-CB107, 4OH-CB162, and 4OH-CB187, implying CYP1A-dependent formation of these OH-PCBs in the pig liver. We found no significant correlations between the blood concentrations of OH-PCBs and thyroid hormones (THs); however, the thyroxin (T-4) levels were lower in pigs from the DS than in pigs from the RS. Our limited dataset suggest that induced CYP enzymes accelerate the metabolism of xenobiotics and endogenous molecules in pigs. Thus, besides parental compounds, the risk of hydroxylated metabolites entering wildlife and humans living in and around municipal open waste dumping sites should be considered. (C) 2015 Elsevier Inc. All rights reserved.
  • John Yabe, Shouta M. M. Nakayama, Yoshinori Ikenaka, Yared B. Yohannes, Nesta Bortey-Sam, Balazs Oroszlany, Kaampwe Muzandu, Kennedy Choongo, Abel Nketani Kabalo, John Ntapisha, Aaron Mweene, Takashi Umemura, Mayumi Ishizuka
    CHEMOSPHERE 119 941 - 947 2015年01月 [査読有り][通常論文]
     
    Childhood lead poisoning is a serious public health concern worldwide. Blood lead levels exceeding 5 mu g dL(-1) are considered elevated. In Kabwe, the capital of Zambia's Central Province, extensive Pb contamination of township soils in the vicinity of a Pb-Zn mine and posing serious health risk to children has been reported. We investigated BLLs in children under the age of 7 years in townships around the mine; where blood samples were collected and analyzed using an ICP-MS. All of the sampled children had BLLs exceeding 5 mu g dL(-1). Children in these areas could be at serious risk of Pb toxicity as 18% of the sampled children in Chowa, 57% (Kasanda) and 25% (Makululu) had BLLs exceeding 65 mu g dL(-1). Eight children had BLLs exceeding 150 mu g dL(-1) with the maximum being 427.8 mu g dL(-1). We recommend that medical intervention be commenced in the children with BLL exceeding 45 mu g dL(-1). (C) 2014 Elsevier Ltd. All rights reserved.
  • Nesta Bortey-Sam, Shouta M. M. Nakayama, Yoshinori Ikenaka, Osei Akoto, Elvis Baidoo, Yared Beyene Yohannes, Hazuki Mizukawa, Mayumi Ishizuka
    ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 111 160 - 167 2015年01月 [査読有り][通常論文]
     
    Heavy metal and metalloid contamination in food resulting from mining is of major concern due to the potential risk involved. Food consumption is the most likely route of human exposure to metals. This study was therefore to assess metals in different organs and different animal species near gold mines used for human consumption (free-range chicken, goat and sheep) in Tarkwa, Ghana, and to estimate the daily intake and health risk. The concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb were measured with an inductively coupled plasma-mass spectrometer and Hg analysis was done using the mercury analyzer. Principal component analysis of the results showed a clear separation between chicken, grouped on one side, and the ruminants clustered on another side in both offal and muscle. Interestingly, As, Cd, Hg, Mn and Pb made one cluster in the offal of chicken. Chicken muscle also showed similar distribution with As, Hg and Pb clustered together. The daily intake of metals (mu g/kg body weight/day) were in the following ranges; As [0.002 (kidneys of goat and sheep)-0.19 (chicken gizzard)], Cd [0.003 (chicken muscle)-0.55 (chicken liver)], Hg [0.002 (goat muscle)-0.29 (chicken liver)], Pb [0.01 (muscles and kidneys of goat and sheep)-0.96 (chicken gizzard)] and Mn [0.13 (goat kidney)-8.92 (sheep liver)]. From the results, daily intakes of As, Cd, Hg, Pb and Mn in these food animals were low compared to the provisional tolerable daily intake guidelines. The THQs although less than one, indicated that contributions of chicken gizzard and liver to toxic metal exposure in adults and especially children could be significant. (C) 2014 Published by Elsevier Inc.
  • Nesta Bortey-Sam, Yoshinori Ikenaka, Shouta M. M. Nakayama, Osei Akoto, Yared Beyene Yohannes, Elvis Baidoo, Hazuki Mizukawa, Mayumi Ishizuka
    SCIENCE OF THE TOTAL ENVIRONMENT 496 471 - 478 2014年10月 [査読有り][通常論文]
     
    As a developing country, the economic and population growth rates in Ghana over the past few years have seen a tremendous increase. The growing rate of industrialization is gradually leading to contamination and deterioration of the environment and pollution is likely to reach disturbing levels. Surface soil samples were collected randomly from 36 communities in the Kumasi Metropolis, Ghana, to determine the concentrations, distribution, sources and toxic potential of emission of polycyclic aromatic hydrocarbons (PAHs) since no such comprehensive study had been conducted. The mean concentration of total PAHs in the surface soils in each community ranged from 14.78 at Ahinsan to 2084 ng/g dry weight at Adum with an average of 442.5 +/- 527.2 ng/g dry weight. Diagnostic ratios and chemical mass balance models of the results showed that PAHs in surface soil samples from the study area were mainly from fuel combustion. Carcinogenic potency of PAH load from the city centre was approximately 150 times higher as compared to a pristine site, Kwame Nkrumah University of Science and Technology's Botanical Garden. BaP, a human carcinogen, contributed 70% of the total PAHs toxicity level from the city centre of Kumasi. (C) 2014 Elsevier B.V. All rights reserved.
  • Fujisawa N, Nakayama SM, Ikenaka Y, Ishizuka M
    Archives of toxicology 88 9 1739 - 1748 2014年09月 [査読有り][通常論文]
     
    Halogenated aromatic hydrocarbons, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are known to cause severe heart defects in avian species. However, the mechanism of TCDD-induced chick cardiovascular toxicity is unclear. In this study, we investigated cyclooxygenase-2 (COX-2) as a possible mechanism of TCDD-induced cardiotoxicity. Fertile chicken eggs were injected with TCDD and a COX-2 selective inhibitor, NS398, and we investigated chick heart failure on day 10. We found that the chick heart to body weight ratio and atrial natriuretic factor mRNA expression were increased, but this increase was abolished with treatment of NS398. In addition, the morphological abnormality of an enlarged ventricle resulting from TCDD exposure was also abolished with co-treatment of TCDD and NS398. Our results suggested that TCDD-induced chick heart defects are mediated via the nongenomic pathway and that they do not require the genomic pathway.
  • Aksorn Saengtienchai, Yoshinori Ikenaka, Shouta M. M. Nakayama, Hazuki Mizukawa, Mayu Kakehi, Nesta Bortey-Sam, Wageh Sobhy Darwish, Toshio Tsubota, Masanori Terasaki, Amnart Poapolathep, Mayumi Ishizuka
    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 33 9 2062 - 2069 2014年09月 [査読有り][通常論文]
     
    Interspecific differences in xenobiotic metabolism are a key to determining relative sensitivities of animals to xenobiotics. However, information on domesticated livestock, companion animals, and captive and free-ranging wildlife is incomplete. The present study evaluated interspecific differences in phase II conjugation using pyrene as a nondestructive biomarker of polycyclic aromatic hydrocarbon (PAH) exposure. Polycyclic aromatic hydrocarbons and their metabolites have carcinogenic and endocrine-disrupting effects in humans and wildlife and can have serious consequences. The authors collected urine from 16 mammalian species and analyzed pyrene metabolites. Interspecific differences in urinary pyrene metabolites, especially in the concentration and composition of phase II conjugated metabolites, were apparent. Glucuronide conjugates are dominant metabolites in the urine of many species, including deer, cattle, pigs, horses, and humans. However, they could not be detected in ferret urine even though the gene for ferret Uridine 5'-diphospho-glucuronosyltransferase (UDP-glucuronosyltransferase, UGT) 1A6 is not a pseudogene. Sulfate conjugates were detected mainly in the urine of cats, ferrets, and rabbits. Interestingly, sulfate conjugates were detected in pig urine. Although pigs are known to have limited aryl sulfotransferase activity, the present study demonstrated that pig liver was active in 1-hydroxypyrene sulfation. The findings have some application for biomonitoring environmental pollution. (c) 2014 SETAC
  • Yared Beyene Yohannes, Yoshinori Ikenaka, Shouta M. M. Nakayama, Mayumi Ishizuka
    ENVIRONMENTAL POLLUTION 192 121 - 128 2014年09月 [査読有り][通常論文]
     
    Organochlorine pesticides (OCPs) and stable isotopes were measured in muscle from 4 bird and 5 fish species from the Ethiopian Rift Valley region where DDT is used for malaria control and vast agricultural activities are carried out. We investigated the bioaccumulation of OCPs such as DDTs, HCHs, chlordanes, and heptachlors between the species, and examined the potential risk posed by these compounds for bird species. Significant differences in contaminant profiles and levels were observed within the species. Levels of total OCPs ranged from 3.7 to 148.7 mu g/g lipid in bird and 0.04 to 10.9 mu g/g lipid in fish species. DDTs were the predominant contaminant, and a positive relationship between delta N-15 and Sigma DDT concentrations was found. The main DDT metabolite, p,p'-DDE was the most abundant and significantly greater concentrations in bird species (up to 138.5 mu g/g lipid), which could have deleterious effects on survival and/or reproduction of birds. (C) 2014 Elsevier Ltd. All rights reserved.
  • Zein Shaban Ibrahim, Mohamed Mohamed Ahmed, Samir Ahmed El-Shazly, Mayumi Ishizuka, Shoichi Fujita
    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 78 9 1550 - 1559 2014年09月 [査読有り][通常論文]
     
    Peroxisome proliferator activated receptor alpha (PPAR alpha) ligands, fibrates used to control hyperlipidemia. We demonstrated CYP2B induction by clofibric acid (CFA) however, the mechanism was not clear. In this study, HepG2 cells transfected with expression plasmid of mouse constitutive androstane receptor (CAR) or PPAR alpha were treated with CFA, phenobarbital (PB) or TCPOBOP. Luciferase assays showed that CFA increased CYP2B1 transcription to the same level as PB, or TCPOBOP in HepG2 transfected with mouse CAR But failed to induce it in PPAR alpha transfected cells. CYP2B expressions were increased with PB or CFA in Wistar female rats (having normal levels of CAR) but not in Wistar Kyoto female rats (having low levels of CAR). The induction of CYP2B by PB or CFA was comparable to nuclear CAR levels. CAR nuclear translocation was induced by CFA in both rat strains. This indicates that fibrates can activate CAR and that fibrates-insulin sensitization effect may occur through CAR, while hypolipidemic effect may operate through PPAR alpha.
  • Yoshinori Shimamoto, Kensuke Watanabe, Hiromi Ikadai, Masashi Okamura, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 76 8 1147 - 1151 2014年08月 [査読有り][通常論文]
     
    To examine the effect of Babesia infection on the level of the drug-metabolizing enzyme hepatic cytochrome P450 (CYP) 2D, we intraperitoneally inoculated Babesia microti into male ICR mice. CYP2D protein and CYP2D9 mRNA were significantly decreased at 12 days after infection with B. microti. The activity of bunitrolol 4-hydroxylase, which is catalyzed by CYP2D, was also significantly decreased. The mRNA levels of transcriptional regulators of CYP2D9, hepatocyte nuclear factor 4 alpha and signal transducer and activator of transcription 5b, were markedly suppressed. These results suggest that Babesia infection represses CYP2D expression in the mouse liver. The decline in CYP2D-dependent drug metabolism might be involved in the incidence of adverse drug reactions in patients with babesiosis.
  • Yared B. Yohannes, Yoshinori Ikenaka, Aksorn Saengtienchai, Kensuke P. Watanabe, Shouta M. M. Nakayam, Mayumi Ishizuka
    ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 106 95 - 101 2014年08月 [査読有り][通常論文]
     
    Fish consumption is known to have several health benefits for humans. However, the accumulation of organic pollutants, like organochlorine pesticides (OCPs) could pose health hazards. Thus, OCPs in edible fish species (Oreochromis niloticus, Tilapia zillii, Carassius spp., and Clarias gariepinus) from Lake Ziway, an Ethiopian Rift Valley Lake were investigated to assess the potential human health hazards of these contaminants. Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), chlordanes, and heptachlors were observed with Sigma OCPs concentration ranging from 1.41 to 63.8 ng g(-1) ww. DDTs were the predominant contaminants (0.9 to 61.9 ng g(-1) ww), followed by HCHs. The predominance of DDTs may be attributed to their current use in vector control and contamination from past usage. The estimated daily intakes (EDIs) of OCPs from all fish species were much lower than the acceptable daily intakes (ADIs), indicating that consumption of fish is at little risk to human health at present. However, the cancer risk estimates in the area of concern and the hazard ratios (HRs) of HCHs, DDTs, and heptachlors exceeded the threshold value of one, indicating daily exposure to these compounds is a potential concern. This may result in a lifetime cancer risk greater than of I in 10(6). (C) 2014 Elsevier Inc. All rights reserved.
  • Samak Sutjarit, Shota M. M. Nakayama, Yoshinori Ikenaka, Mayumi Ishizuka, Wijit Banlunara, Worawut Rerkamnuaychoke, Susumu Kumagai, Amnart Poapolathep
    TOXICOLOGY LETTERS 229 1 292 - 302 2014年08月 [査読有り][通常論文]
     
    Fusarenon-X (FX), a type B trichothecene mycotoxin, is mainly produced by Fusarium crookwellense, which occurs naturally in agricultural commodities, such as wheat and barley. FX has been shown to exert a variety of toxic effects on multiple targets in vitro. However, the embryonic toxicity of FX in vivo remains unclear. In the present study, we investigated FX-induced apoptosis and the relationship between the genetic regulatory mechanisms and FX-induced apoptosis in the developing mouse brain of FX-treated pregnant mice. Pregnant mice were orally administered FX (3.5 mg/kg b.w.) and were assessed at 0,12, 24 and 48 h after treatment (HAT). Apoptosis in the fetal brain was determined using hematoxylin and eosin staining, the TUNEL method, immunohistochemistry for PCNA and electron microscopy. Gene expressions were evaluated using microarray and real time-reverse transcription polymerase chain reaction (qRT-PCR). Histopathological changes showed that the number of apoptotic cells in the telencephalon of the mouse fetus peaked at 12 HAT and decreased at 24 and 48 HAT. FX induced the up-regulation of Bax, Trp53 and Casp9 and down-regulated Bcl2 but the expression levels of Fas and Casp8 mRNA remained unchanged. These data suggested that FX induces apoptosis in the developing mouse brain in FX-treated dams. Moreover, the genetic regulatory mechanisms of FX-induced apoptosis are regulated by Bax, Bcl2, Trp53 and Casp9 or can be defined via an intrinsic apoptotic pathway. (C) 2014 Elsevier Ireland Ltd. All rights reserved.
  • Hazuki Mizukawa, Yoshinori Ikenaka, Shouta M. M. Nakayama, Kentaro Q. Sakamoto, Shoichi Fujita, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 62 3 107 - 115 2014年08月 [査読有り][通常論文]
     
    Contamination levels of coplanar polychlorinated biphenyls (Co-PCBs), polycyclic aromatic hydrocarbons (PAHs), and dichlorodiphenyltrichloroethane (DDTs) were measured in the entire body of the large Japanese field mouse (Apodemus speciosus) collected from Hokkaido (Ishikari and Rankoshi) and Aomori prefecture (Takko) in Japan. Higher concentrations of PCBs including Co-PCBs, were observed in the mice collected from Ishikari than those from Rankoshi. The concentration of PAHs in the soil from Ishikari was also higher than that in the other sampling sites. The findings suggest that Ishikari is the most polluted area, probably because of human activities, depending on the population distribution. However, the observed contaminant levels were extremely lower compared to those in previous studies. The ratio of testis weight to body weight (TW/BW) was the lowest in the mice collected from Ishikari, which is the area contaminated with PAHs and p,p'-dichlorodiphenyldichloroethylene (DDE). However, the serum testosterone levels of mice from the Ishikari area were higher than those from the non-contaminated other areas although no significant differences. Previous studies have shown that a low-level exposure to dioxin related compounds (DRCs) disturbances in sexual function, resulting in the production of testosterone. This study showed that POPs exposure is one of the possibility of the high testosterone concentration in the mice of the Ishikari area in addition to a cause of biological and environmental factors such as habitat density, age, temperatures and/or food riches.
  • Chihiro Ishii, Yoshinori Ikenaka, Shouta M. M. Nakayama, Yuya Suzuki, Yutaka Watanuki, Yuji Watanabe, Yared Beyene Yohannes, Hazuki Mizukawa, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 62 3 143 - 149 2014年08月 [査読有り][通常論文]
     
    Teuri Island, Hokkaido in Japan is an important place for seabirds breeding. We measured the concentrations of heavy metals (Hg, Cd, Cr, Co, Ni, Cu, Zn, and Pb) and a metalloid (As) in rhinoceros auklet (Cerorhinca monocerata) (n = 7), thick-billed murre (Uria lomvia) (n = 2), spectacled guillemot (Cepphus carbo) (n = 6), slaty-backed gull (Larus schistisagus) (n = 15), jungle crow (Corvus macrorhynchos) (n = 3), Japanese anchovy (Engraulis japonica) (n = 6) and Atka mackerel (Pleurogrammus azonus) (n = 2). Spectacled guillemot had high As concentrations, with its source being their feeding habitat. Concentration of Hg in kidney of jungle crow was higher than other seabird species at Teuri.
  • Wageh Sobhy Darwish, Yoshinori Ikenaka, Shouta M. M. Nakayama, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 76 6 789 - 797 2014年06月 [査読有り][通常論文]
     
    Mycotoxins are fungal secondary metabolites that contaminate various feedstuffs and agricultural crops. The contamination of food by mycotoxins can occur before production, during storage, processing, transportation or marketing of the food products. High temperature, moisture content and water activity are among the predisposing factors that facilitate the production of mycotoxins in food. Aflatoxins, ochratoxins, fumonisins, deoxynivalenol and zearalenone are all considered the major mycotoxins produced in food and feedstuffs. In Africa, mycotoxin contamination is considered to be a major problem with implications that affect human and animal health and economy. Aflatoxin-related hepatic diseases are reported in many African countries. Ochratoxin and fumonisin toxicity in humans and animals is widespread in Africa. The available, updated information on the incidence of mycotoxin contamination, decontamination and its public health importance in Africa is lacking. The aim of this review is to highlight, update and discuss the available information on the incidence of mycotoxins in African countries. The public health implications and the recommended strategies for control of mycotoxins in food and agricultural crops are also discussed.
  • Wageh Sobhy Darwish, Yoshinori Ikenaka, Shouta Nakayama, Mayumi Ishizuka
    BIOLOGICAL TRACE ELEMENT RESEARCH 158 2 243 - 248 2014年05月 [査読有り][通常論文]
     
    Copper (Cu2+) is an essential element that plays important roles in physiological functions of the body. However, high Cu2+ levels can have toxic implications. This study aims to investigate the constitutive response to Cu2+ exposure of xenobiotic-metabolizing enzymes in cultured rat liver (H4-II-E) cell lines. Rat cells were exposed to copper sulfate (0-500 mu M) for 24 h. The effects of Cu2+ on the messenger RNA (mRNA) expressions of phase I and II enzymes and regulatory elements were examined using real-time PCR. Metallothionein mRNA expression was induced in a dose-dependent manner after treatment with Cu2+. mRNA expressions of phase I enzymes such as cytochrome P450 1A1 and 1A2 (CYP1A1 and CYP1A2) were slightly induced after exposure to low concentrations of Cu2+; however, CYP1A1 and CYP1A2 mRNA expressions were significantly downregulated at higher Cu2+ concentrations. These effects corresponded with expression of aryl hydrocarbon receptor mRNA. The mRNA expressions of phase II enzymes were reduced upon exposure to Cu2+. In conclusion, phase I and II enzyme expressions were significantly modulated upon Cu2+ exposure. These results indicated that Cu2+ exposure had toxicological implications for cultured H4-II-E cells.
  • Thanit Saengtienchai, Saranya Poapolathep, Supaporn Isariyodom, Yoshinori Ikenaka, Mayumi Ishizuka, Amnart Poapolathep
    FOOD AND CHEMICAL TOXICOLOGY 66 307 - 312 2014年04月 [査読有り][通常論文]
     
    Fusarenon-X (FX) is one of the trichothecene mycotoxins mainly produced by Fusarium crookwellense, which naturally occurs in agricultural commodities such as wheat and barley. To investigate the toxicokinetics of FX and its metabolite nivalenol (NIV), FX was then administered intravenously or orally to piglets at a dosage of 1 mg/1<g body weight. The concentrations of FX and NIV in the plasma and various tissues were measured using LC-MS/MS. The plasma concentrations of FX in the piglets were determined up to 24 h and 48 h after iv and po administration, respectively, and the concentration of NIV was detected up to 12 h after both types of administration. The C-p(0) of FX was 580.28 +/- 140.81 ng/ml after iv administration. The values of t(1/2 beta), V-ss and F-oral were 1.71 +/- 0.74 h, 0.009 +/- 0.002 ml and 74.40 +/- 18.96%, respectively. FX and NIV were detectable in the vital organs up to 24 h after po administration. The peak level of FX in the liver, the kidney, and the spleen, respectively, were 165.95 +/- 9.68 ng/g, 66.29 +/- 8.48 and 7.35 +/- 0.69 ng/g at 3 h following po administration. In vitro of liver postmitochondrial fractions with FX demonstrated that the liver and kidney are capable of FX-to-NIV metabolism. (C) 2014 Elsevier Ltd. All rights reserved.
  • Molecular Characterization and mRNA Expression of Cytochrome P450 1A1 and Cytochrome P450 3A in Liver of Kafue Lechwe (Kobus leche kafuensis) as Potential Biomarkers of Pollution of the Kafue River Basin, Zambia
    M'kandawire, Ethel, Syakalima, Michelo, Muzandu, Kaampwe, Pandey, Girja, Simuunza, Martin, Nakayama, Shouta M. M, Kawai, Yusuke K, Ikenaka, Yoshinori, Ishizuka, Mayumi
    Engineering 6 2 51 - 58 2014年02月 [査読有り][通常論文]
  • Yoshinori Ikenaka, Shouta M.M. Nakayama, Kaampwe Muzandu, Kennedy Choongo, Hiroki Teraoka, Naoharu Mizuno, Mayumi Ishizuka
    Heavy Metal Contamination of Water and Soil: Analysis, Assessment, and Remediation Strategies 109 - 128 2014年01月01日 
    Africa is a continent located in the southern hemisphere and known for its rich diversity of wildlife including birds, amphibians, reptiles and large mammals. However, in recent years, there have been concerns about significant environmental problems caused by the mining of rare and major metals and metallurgical activities in African countries by domestic and foreign corporations (Oelofse, 2008). Environmental pollution due to the rapid progress of economic development in Africa can cause various problems and heavy metals are some of the major contaminants in these countries (Akiwumi and Butler, 2008; Norman et al., 2007; Rashad and Barsoum, 2006). Humans and wildlife can be exposed to heavy metals by drinking water and inhaling air or soil contaminated by mining activities and the metal industry (Nakayama et al., 2010).
  • Watanabe Kensuke P, Kawai Yusuke K, Kawata Minami, Nakayama Shouta M. M, Ikenaka Yoshinori, Ishizuka Mayumi
    DRUG METABOLISM REVIEWS 45 92  2014年01月 [査読有り][通常論文]
  • Hiroshi Kitamura, Shunsuke Kimura, Yoshinori Shimamoto, Jun Okabe, Masatoshi Ito, Tomomi Miyamoto, Yoshinori Naoe, Chisato Kikuguchi, Bob Meek, Chitoku Toda, Shiki Okamoto, Katsushi Kanehira, Koji Hase, Hiroshi Watarai, Mayumi Ishizuka, Assam El-Osta, Osamu Ohara, Ichiro Miyoshi
    FASEB Journal 27 12 4940 - 4953 2013年12月 [査読有り][通常論文]
     
    Macrophages play a critical role in chronic inflammation and metabolic diseases. We identified a longer splice variant of ubiquitin specific protease (USP) 2-69 as a novel molecule that modulates pathways implicated in metabolic disorders. Expression levels of aP2/ FABP4 and PAI-1/SERPINE1 genes were increased by 4- and 1.8-fold, respectively, after short hairpin RNA-mediated knockdown (KD) of the USP2 gene, and such expression was alleviated by overexpression of USP2-69 in human myeloid cell lines. Supernatants derived from USP2-KD cells induced IL6 (6-fold) and SAA3 (15-fold) in 3T3-L1 adipocytes to suggest the anti-inflammatory properties of USP2. In addition, we observed a 30% decrease in the number of macrophages in mesenteric adipose tissue derived from USP2-69 transgenic mice fed a high-fat diet for 14 wk compared with that in their C57BL/6 littermates (P< 0.01), which was consistent with a 40% decrease in transcription of aP2 and PAI-1. The aP2 locus exhibited elevated chromatin accessibility (> 2.1-fold), methylation of histone H3 lysine 4 (> 4.5- fold), and acetylation of histone H4 (> 2.5-fold) in USP2-KD cells. Transfection of isopeptidase-mutated USP2-69 did not alter chromatin conformation on the aP2 locus in USP2-KD cells. Our results suggest that USP2-69 suppresses meta-inflammatory molecules involved in the development of type-2 diabetes.-Kitamura, H., Kimura, S., Shimamoto, Y., Okabe, J., Ito, M., Miyamoto, T., Naoe, Y., Kikuguchi, C., Meek, B., Toda, C., Okamoto, S., Kanehira, K., Hase, K., Watarai, H., Ishizuka, M., El-Osta, A., Ohara, O., Miyoshi, I. Ubiquitin-specific protease 2-69 in macrophages potentially modulates metainflammation. © FASEB.
  • Yared Beyene Yohannes, Yoshinori Ikenaka, Aksorn Saengtienchai, Kensuke P. Watanabe, Shouta M. M. Nakayama, Mayumi Ishizuka
    ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 20 12 8663 - 8671 2013年12月 [査読有り][通常論文]
     
    Dichlorodiphenyltrichloroethanes (DDTs) and heavy metals are ubiquitous contaminants with high bioaccumulation and persistence in the environment, which can have adverse effects on humans and animals. Although applications of DDTs have been banned in many countries, developing countries like Ethiopia are still using these for agricultural and medicinal purposes. In addition, heavy metals are naturally present in the aquatic environment and distributed globally. In this study, the occurrence, distribution, and ecological risk of DDTs and heavy metals in surface sediments from one of the Ethiopian rift valley lakes were studied. Twenty-five surface sediment samples from Lake Awassa, Ethiopia were collected and analyzed for DDTs and heavy metals. Results showed that concentrations of total DDTs ranged from 3.64 to 40.2 ng/g dry weight. High levels of DDTs were observed in the vicinity of inflow river side and coastal areas with agricultural activities. The heavy metals content were followed the order Zn > Ni > Pb > Cu > Cr > Co > As > Cd > Hg. Correlation analysis and principal components analysis demonstrated that heavy metals were originated from both natural and anthropogenic inputs. The levels of DDE and DDD in surface sediments exceeded the sediment quality guideline values, indicating that adverse effects may occur to the lake. A method based on toxic-response factor for heavy metals revealed that the calculated potential ecological risk indices showed low ecological risk for the water body.
  • Nozomi Fujisawa, Yusuke K. Kawai, Shouta M. M. Nakayama, Yoshinori Ikenaka, Hideaki Yamamoto, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 75 12 1577 - 1583 2013年12月 [査読有り][通常論文]
     
    There are two arylhydrocarbon receptor (AhR) isoforms in birds, AhR1 and AhR2. The varying sensitivity of AhR is reported to be related to two critical amino acids at positions 325 and 381 in the AhR1 ligand-binding domain. In this study, seven avian species whose in vivo dioxin sensitivity was known, and 13 species with no data regarding their in vivo dioxin sensitivity were examined. The two critical amino acids in the ligand-binding domain were investigated in avian species, and the results were compared with the taxonomy or phylogenetic trees for the bird AhR proteins. We found that the two critical amino acids did not correlate with the taxonomy or phylogeny of these proteins, suggesting that dioxin sensitivity was independent of taxonomy.
  • Hiroshi Kitamura, Shunsuke Kimura, Yoshinori Shimamoto, Jun Okabe, Masatoshi Ito, Tomomi Miyamoto, Yoshinori Naoe, Chisato Kikuguchi, Bob Meek, Chitoku Toda, Shiki Okamoto, Katsushi Kanehira, Koji Hase, Hiroshi Watarai, Mayumi Ishizuka, Assam El-Osta, Osamu Ohara, Ichiro Miyoshi
    FASEB JOURNAL 27 12 4940 - 4953 2013年12月 [査読有り][通常論文]
     
    Macrophages play a critical role in chronic inflammation and metabolic diseases. We identified a longer splice variant of ubiquitin specific protease (USP) 2-69 as a novel molecule that modulates pathways implicated in metabolic disorders. Expression levels of aP2/FABP4 and PAI-1/SERPINE1 genes were increased by 4- and 1.8-fold, respectively, after short hairpin RNA-mediated knockdown (KD) of the USP2 gene, and such expression was alleviated by overexpression of USP2-69 in human myeloid cell lines. Supernatants derived from USP2-KD cells induced IL6 (similar to 6-fold) and SAA3 (similar to 15-fold) in 3T3-L1 adipocytes to suggest the anti-inflammatory properties of USP2. In addition, we observed a 30% decrease in the number of macrophages in mesenteric adipose tissue derived from USP2-69 transgenic mice fed a high-fat diet for 14 wk compared with that in their C57BL/6 littermates (P<0.01), which was consistent with a similar to 40% decrease in transcription of aP2 and PAI-1. The aP2 locus exhibited elevated chromatin accessibility (>2.1-fold), methylation of histone H3 lysine 4 (>4.5-fold), and acetylation of histone H4 (>2.5-fold) in USP2-KD cells. Transfection of isopeptidase-mutated USP2-69 did not alter chromatin conformation on the aP2 locus in USP2-KD cells. Our results suggest that USP2-69 suppresses meta-inflammatory molecules involved in the development of type-2 diabetes.
  • Yoshinori Shimamoto, Hiroshi Kitamura, Kimie Niimi, Yasunaga Yoshikawa, Fumio Hoshi, Mayumi Ishizuka, Eiki Takahashi
    MOLECULAR BIOLOGY REPORTS 40 12 6747 - 6755 2013年12月 [査読有り][通常論文]
     
    The common marmoset (Callithrix jacchus) is increasingly being used as a non-human primate animal model in biomedical research. To perform accurate quantitative analysis of gene expression by quantitative reverse transcription polymerase chain reaction, reliable reference genes should be selected. In this study, we evaluated the expressions of 11 widely used reference genes: ACTB, ATP5F1, B2M, GAPDH, HPRT1, PGK1, PPIA, RN18S1, RPLP0, TBP and UBC in 12 tissues and five brain areas of healthy common marmosets. NormFinder and geNorm indicated that the most suitable reference genes for cross-sectional studies of the 17 tissues were RN18S1 and RPLP0. Conversely, ACTB and PPIA were the most suitable for analyzing brain samples; however, the expression of PGK1 fluctuated among brain areas. These results indicate that suitable reference genes differ between the tissues examined. This study provides fundamental information for gene expression studies of the common marmoset and highlights the importance of validating reference genes before quantification of target mRNAs.
  • Nobuo Sasaki, Tomoyuki Matumoto, Yoshinori Ikenaka, Shouta M. M. Nakayama, Mayumi Ishizuka, Akio Kazusaka, Shoichi Fujita
    JOURNAL OF VETERINARY MEDICAL SCIENCE 75 11 1497 - 1502 2013年11月 [査読有り][通常論文]
     
    The nitrofuran antimicrobial agent, furazolidone (FZ), is still used in veterinary medicine in some countries in the Middle and Far Eastern countries. The present study aimed to investigate the effects of successive bolus doses of FZ and its metabolite 3-amino-2-oxazolidinone (AOZ) on cytochrome P450 (CYP)-related activities in the livers of rats and chickens. Female Wistar rats and white Leghorn chickens were orally administered FZ once a day for 4 consecutive days. FZ-treated chickens showed an increase in multiple CYP-related activities, however, rats treated with FZ did not show these changes. In chickens, treatment with FZ also induced production of microsomal CYP2C6-like apoprotein. The present study demonstrated that FZ caused a multiple-type induction of CYP-related activities in chickens, but not in rats.
  • Yusuke K. Kawai, Kensuke P. Watanabe, Akihiro Ishii, Aiko Ohnuma, Hirofumi Sawa, Yoshinori Ikenaka, Mayumi Ishizuka
    COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 8 3 201 - 208 2013年09月 [査読有り][通常論文]
     
    The cytochrome P450 (CYP) 1-3 families are involved in xenobiotic metabolism, and are expressed primarily in the liver. Ostriches (Struthio camelus) are members of Palaeognathae with the earliest divergence from other bird lineages. An understanding of genes coding for ostrich xenobiotic metabolizing enzyme contributes to knowledge regarding the xenobiotic metabolisms of other Palaeognathae birds. We investigated CYP1-3 genes expressed in female ostrich liver using a next-generation sequencer. We detected 10 CYP genes: CYP1A5, CYP2C23, CYP2C45, CYP2D49, CYP2G19, CYP2W2, CYP2AC1, CYP2AC2, CYP2AF1, and CYP3A37. We compared the gene expression levels of CYP1A5, CYP2C23, CYP2C45, CYP2D49, CYP2G19, CYP2AF1, and CYP3A37 in ostrich liver and determined that CYP2G19 exhibited the highest expression level. The mRNA expression level of CYP2G19 was approximately 2-10 times higher than those of other CYP genes. The other CYP genes displayed similar expression levels. Our results suggest that CYP2G19, which has not been a focus of previous bird studies, has an important role in ostrich xenobiotic metabolism. (C) 2013 Elsevier Inc. All rights reserved.
  • Yoshinori Ikenaka, Mami Oguri, Aksorn Saengtienchai, Shouta M M Nakayama, Shigeho Ijiri, Mayumi Ishizuka
    Environmental toxicology and pharmacology 36 2 567 - 578 2013年09月 [査読有り][通常論文]
     
    Metabolic activity, particularly conjugation, was examined in fish by analyzing pyrene (a four-ring, polycyclic aromatic hydrocarbon) metabolites using high-performance liquid chromatography (HPLC) with fluorescence detector (FD), a mass spectrometry (MS) system, and kinetic analysis of conjugation enzymes. Fourteen fresh water fish species, including Danio rerio and Orizias latipes, were exposed to aqueous pyrene, and the resulting metabolites were collected. Identification of pyrene metabolites by HPLC/FD and ion-trap MS indicated that the major metabolites were pyrene glucuronide and pyrene sulfate in all 14 species. Differences were observed in pyrene glucuronide:pyrene sulfate ratio and in the total amount of pyrene conjugates excreted between fish species. Furthermore, a correlation was found between the amount of pyrene glucuronide present and the total amount of the pyrene metabolite eliminated. Kinetic analysis of conjugation by hepatic microsomes in vitro indicated that the differences in excreted metabolites reflected the differences in enzymatic activities.
  • Kensuke P. Watanabe, Yusuke K. Kawai, Yoshinori Ikenaka, Minami Kawata, Shin-Ichi Ikushiro, Toshiyuki Sakaki, Mayumi Ishizuka
    PLOS ONE 8 9 e75689  2013年09月 [査読有り][通常論文]
     
    Cytochrome P450 (CYP) of chicken and other avian species have been studied primarily with microsomes or characterized by cloning and protein expression. However, the overall existing isoforms in avian CYP1-3 families or dominant isoforms in avian xenobiotic metabolism have not yet been elucidated. In this study, we aimed to clarify and classify all of the existing isoforms of CYP1-3 in avian species using available genome assemblies for chicken, zebra finch, and turkey. Furthermore, we performed qRT-PCR assay to identify dominant CYP genes in chicken liver. Our results suggested that avian xenobiotic-metabolizing CYP genes have undergone unique evolution such as CYP2C and CYP3A genes, which have undergone avian-specific gene duplications. qRT-PCR experiments showed that CYP2C45 was the most highly expressed isoform in chicken liver, while CYP2C23b was the most highly induced gene by phenobarbital. Considering together with the result of further enzymatic characterization, CYP2C45 may have a dominant role in chicken xenobiotic metabolism due to the constitutive high expression levels, while CYP2C23a and CYP2C23b can be greatly induced by chicken xenobiotic receptor (CXR) activators. These findings will provide not only novel insights into avian xenobiotic metabolism, but also a basis for the further characterization of each CYP gene.
  • Shouta M. M. Nakayama, Yoshinori Ikenaka, Kyohei Hamada, Kaampwe Muzandu, Kennedy Choongo, John Yabe, Takashi Umemura, Mayumi Ishizuka
    ENVIRONMENTAL MONITORING AND ASSESSMENT 185 6 4907 - 4918 2013年06月 [査読有り][通常論文]
     
    The lead-zinc (Pb-Zn) mine in Kabwe City and the copper-cobalt (Cu-Co) mine in the Copperbelt Province are major mining areas in Zambia. To examine the effects of metal pollution on wildlife, wild black rats (Rattus rattus and Rattus tanezumi) were captured in Kabwe and Chingola (in the Copperbelt Province), and in Lusaka (a noncontaminated site). Wild black rats in Kabwe accumulated significantly higher concentrations of Pb and Cd in various organs than rats from Lusaka. In Chingola, significantly higher concentrations of Cu, Co, Pb, and Cd were accumulated in wild black rats than in rats from Lusaka. These results were in accordance with metal accumulation patterns in soil. From toxicological aspects, concentrations of Pb and Cd in rats were generally low. However, metallothionein-1 (MT-1) and metallothionein-2 (MT-2) mRNA expression levels in wild black rats from Kabwe were significantly higher than those in rats from Lusaka. A generalized linear model (GLM) showed that concentrations of Zn and Cu had positive effects on the MT-1 and MT-2 mRNA expression. These results suggest that wild black rats in Zambian mining sites were exposed to metals that accumulated in their organs, causing biological responses such as MT mRNA induction. GLM indicated that heme oxygenase-1 (HO-1) mRNA expression could be a marker for Cr exposure.
  • Yared Beyene Yohannes, Yoshinori Ikenaka, Shouta M. M. Nakayama, Aksorn Saengtienchai, Kensuke Watanabe, Mayumi Ishizuka
    CHEMOSPHERE 91 6 857 - 863 2013年05月 [査読有り][通常論文]
     
    The levels and bioaccumulation of organochlorine pesticides (OCPs) and heavy metals were studied in muscle and liver of three fish species, with two trophic levels, from Lake Awassa, Ethiopia. DDTs were the predominant organic pollutant in all species with a maximum level of 73.28 ng g(-1) wet weight (ww). p,p'-DDE was the predominate congener and showed a significant (p <0.001) relationship with delta N-15, which indicates that DDTs could biomagnified in the food web of the lake. Generally, high levels of heavy metals (Cd, Co, Cr, Cu, Ni, Pb, Zn and Hg) were found in liver samples as compared to muscles. The levels of Cd, Co, Cu, Ni, and Pb in liver samples showed negative correlation with delta N-15. They were found markedly higher in the lower trophic level fish species (p < 0.05) that indicates biodilution whereas; Zn level showed positive correlation with delta N-15. (C) 2013 Elsevier Ltd. All rights reserved.
  • Kazuyuki D. Tanaka, Yusuke K. Kawai, Yoshinori Ikenaka, Tsunehito Harunari, Tsutomu Tanikawa, Shoichi Fujita, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 75 2 135 - 139 2013年02月 [査読有り][通常論文]
     
    Warfarin is a rodenticide commonly used worldwide. It inhibits coagulation of blood by inhibiting vitamin K 2,3-epoxide reductase (VKOR) activity. An inadequate supply of vitamin K blocks the production of prothrombin and causes hemorrhage. Recently, warfarin-resistant brown rats (Rattus norvegicus) were found around the Aomori area of Japan. There is no significant difference in the metabolic activity of warfarin in sensitive and resistant brown rats. To clarify the mechanism underlying warfarin resistance, we cloned the VKORC1 gene from rats and identified a novel substitution of arginine to proline at position 33 of the VKORC1 amino acid sequence. Then, we determined the differences in kinetics of VKOR activity between warfarin-resistant and sensitive rats. Hepatic microsomal VKOR-dependent activity was measured over a range of vitamin K epoxide concentrations from 6.25 to 150 mu M. The V-max, values of resistant rats (0.0029 +/- 0.020 nmol/min/mg) were about one tenth of those of sensitive rats (0.29 +/- 0.12 nmol/min/mg). The K-m values of resistant rats (47 +/- 32 mu M) were similar to those of sensitive rats (59 +/- 18 mu M). Warfarin-sensitive rats exhibited enzyme efficiencies (V-max/K-m) which were ten-fold greater than those observed in resistant rats. It may mean that VKOR activity of warfarin-resistant Aomori rats is almost lost, because their enzymatic efficiencies are very low even without warfarin. Further studies are needed to clarify how these rats can survive with a markedly reduced VKOR activity and how they simultaneously exhibit warfarin resistance.
  • Yoshinori Ikenaka, Masaki Sakamoto, Takamaru Nagata, Hirokazu Takahashi, Yuichi Miyabara, Takayuki Hanazato, Mayumi Ishizuka, Tomohiko Isobe, Jun-Woo Kim, Kwang-Hyeon Chang
    JOURNAL OF TOXICOLOGICAL SCIENCES 38 1 131 - 136 2013年02月 [査読有り][通常論文]
     
    We estimated acute toxicity of benzo[a]pyrene (B[a]P) using two cladoceran species, Ceriodaphnia reticulata and Daphnia magna, and also analyzed its impact on zooplankton community throughout an exposure experiment using small-scale mesocosms. LC50 of B[a]P for C. reticulata and D. magna was 4.3 and 4.7 mu g/l, respectively. However, individuals fed with Chlorella showed higher LC50, 6.1 mu g/l for C. reticulata and 8.0 mu g/l for D. magna. In the exposure experiment, we examined the impact of B[a]P on zooplankton community using conceivable concentrations in the environment (5 and 10 mu g/l) using typical zooplankton community in eutrophicated systems. Despite the residence time of B[a]P in the water column was short as < 4 days, application of B[a]P induced decrease of zooplankton abundance. However, the recovery pattern was different among cladocerans and rotifers. Consequently, B[a]P showed insecticide-like impacts, suppressing cladoceran populations and inducing the dominance of rotifers particularly under high concentration (10 mu g/l). Results have suggested that, even such short duration of B[a] P in the water body can have impact on zooplankton abundance and community structure. Since B[a]P easily precipitate to the bottom and rapidly disappears from the water body, careful monitoring and further assessment of the potential toxicity of polycyclic aromatic hydrocarbons are necessary.
  • Wageh Sobhy Darwish, Elsaid A. Eldaly, Mohamed Tharwat E-Abbasy, Yoshinori Ikenaka, Shouta Nakayama, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 61 SUPPL. S13 - S22 2013年02月 [査読有り][通常論文]
     
    Antibiotics are substances either produced naturally by living organisms or synthetically in the laboratory, and they are able to kill or inhibit the growth of microorganisms. Antibiotics are also used as feed additives for the purpose of livestock health maintenance. Antibiotic residues in feedstuffs are currently a problem of some magnitude in different parts of the world, particularly due to associated public health concerns that include hypersensitivity reactions, antibiotic resistance, toxicity, teratogenicity, and carcinogenicity. In Africa, as in other parts of the world, antibiotic residues in animal-derived foods have been extensively recorded in many African countries; these residues have exceeded the WHO maximum residue levels in many cases. It has been reported that tetracyclines are the most predominantly prescribed antibiotics in Africa, and of all antibiotic-associated residues they represent 41% of cases, followed by beta-lactams at 18%. Great care should be taken to monitor antibiotic cessation periods before the release of animal-derived foods for human consumption. In addition, strict legislation should be implemented in order to minimize the abuse of antibiotics.
  • Wageh Sobhy Darwish, Yoshinori Ikenaka, Mayumi Ishizuka
    The Japanese journal of veterinary research 61 Suppl SUPPL. S48-53 - 53 2013年02月 [査読有り][通常論文]
     
    This study was undertaken to investigate the constitutive response of xenobiotic metabolizing enzymes (XMEs) to lead (Pb2+) exposure in cultured rat liver (H4IIE) cell lines. Phase I enzymes such as CYP1A1 and CYP1A2 had mRNA expressions that were slightly induced after exposure to low concentrations of Pb2+; however, under higher concentrations of Pb2+, the mRNA expressions of CYP1A1 and CYP1A2 were significantly down-regulated. These effects were in correspondence with AhR mRNA expression. Phase II enzymes had mRNA expressions that were reduced upon exposure to Pb2+. Metallothionein mRNA expression was induced after treatment with Pb2+ in a dose-dependent trend. In conclusion, Phase I and II enzymes were significantly modulated upon lead exposure indicating some toxicological implications for lead exposure in cultured H4IIE cells.
  • Abdallah Fikry A Mahmoud, Wageh Sobhy Darwish, Alaa Eldin M A Morshdy, Elsaid A Eldaly, Yoshinori Ikenaka, Mayumi Ishizuka
    The Japanese journal of veterinary research 61 Suppl SUPPL. S58-63 - 63 2013年02月 [査読有り][通常論文]
     
    Environmental contamination by OCPs has a great concern, since most of these pesticide compounds are very toxic and harmful to human and ecosystems. This study was conducted to determine the concentrations of OCPs residues in the edible offal (livers, kidneys and tongues) of Egyptian buffalo collected from three locations (Zagazig, Ismailia and Mansoura) in Egypt. Examined samples from Mansura city had the highest OCPs contamination load. Tongues had the highest concentration of these toxic residues in a comparison to livers and kidneys in the examined samples. The overall results showed that OCPs residues did not exceed the Egyptian maximum permissible limits in all of the samples analyzed from the three different locations.
  • Jemima T Marfo, Osei Akoto, Shouta M M Nakayama, Elvis Baidoo, Yoshinori Ikenaka, Mayumi Ishizuka
    The Japanese journal of veterinary research 61 Suppl SUPPL. S69-71 - 71 2013年02月 [査読有り][通常論文]
     
    All heavy metals are potentially harmful to most organisms at some level of exposure and absorption. Concentrations of Co, Cr, Cu, Ni, Zn, Hg, Cd, As, and Pb were determined by atomic absorption spectrophotometry (AAS) in three fish species (C. gariepinus, C. nigrodigitatus, and H. bidorsalis) from the Offin River in Dunkwa township, Ghana. In the fish species, gills, livers, and muscles were analyzed. The metal that recorded the highest concentration was Zn, which was highly accumulated in the liver of C. gariepinus, but had the lowest concentration in the muscles of C. nigrodigitatus.
  • Nesta Bortey-Sam, Osei Akoto, Yoshinori Ikenaka, Shouta M. M. Nakayama, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 61 SUPPL. S72 - S74 2013年02月 [査読有り][通常論文]
     
    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants produced from incomplete combustion of fuel or vegetation fires. Their presence in air deserves attention because they can produce carcinogenic and mutagenic effects. As an industrialized and economically significant city in Ghana, Kumasi has been subject to heavy anthropogenic influences due to rapid economic development and urbanization leading to a greater fuel combustion rate. Airborne particulate samples were collected on filters using a Sibata air sampler and analyzed by gas chromatography-mass spectrometry (GC-MS). Our results indicated that air from the city center can be classified as highly polluted with benzo[a] pyrene (B[a]P). The diagnostic ratios of the results showed that PAHs in the air samples were mainly from fuel combustion.
  • Chihiro Ishii, Yoshinori Ikenaka, Shouta M. M. Nakayama, Yuya Suzuki, Yutaka Watanuki, Yuji Watanabe, Masa-aki Fukuwaka, Yared B. Yohannes, Yusuke K. Kawai, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 61 SUPPL. S75 - S76 2013年02月 [査読有り][通常論文]
     
    It is reported that seabirds accumulate high levels of metals, prompting concerns regarding poisoning. The present study investigated the accumulation patterns of metals in tissues among four species of seabirds (Fratercula corniculata, Uria lomvia, Puffinus tenuirostris, and Fulmarus glacialis). Furthermore, we focused on Slaty-backed Gulls, which accumulated high levels of cadmium and mercury, and compared the areal differences. Geographic variation of metal levels could also contribute to differences in metal accumulation levels in these bird species. Therefore, the concentrations of metals in seabirds are considered to reflect their habitat. There are differences in the accumulation pattern among the seabird species. The high accumulation of metals could affect seabirds even if they do not show any symptoms.
  • Balazs Oroszlany, Yoshinori Ikenaka, Aksorn Saengtiengchan, Mami Oguri, Shouta M. M. Nakayama, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 61 SUPPL. S77 - S78 2013年02月 [査読有り][通常論文]
     
    Reptile population decrease is an alarming trend all around the world. Yet little is known about the role of xenobiotics in this decrease. In this study, we investigated the metabolism of pyrene in three freshwater turtle species (Red-EARED sliders (Trachemys scripta elegans), Chinese pond turtles (Mauremys reevesii) and Chinese softshell turtles (Pelodiscus sinensis). Compared to other vertebrates, all turtles showed an unique metabolite distribution, pyrene-1-sulfate being the main metabolite. The observed low phase II enzyme metabolic rates raises the question of the effect of long-time exposure.
  • Shouta M. M. Nakayama, Yoshinori Ikenaka, Kaampwe Muzandu, Kennedy Choongo, John Yabe, Takashi Umemura, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 61 SUPPL. S79 - S81 2013年02月 [査読有り][通常論文]
     
    In order to assess the effects of metal contamination on wildlife, we collected wild black rats (Rattus sp.) from mining areas (Kabwe and Chingola) and a control area (Lusaka) in Zambia and compared metal and metallothionein (MT) levels in their tissues. Furthermore, we exposed metal-contaminated soil from Kabwe to laboratory Wistar rats (Rattus norvegicus) for one year in order to determine the accumulation factors and effects of metals caused by soil exposure. Results of both the field and laboratory studies suggested that metal-contaminated soil caused accumulation and biological responses such as elevation of MT-2 mRNA expression levels in rats.
  • Aki Hayami, Wageh Sobhy Darwish, Yoshinori Ikenaka, Shouta M. M. Nakayama, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 61 SUPPL. S82 - S84 2013年02月 [査読有り][通常論文]
     
    There is little information about drug metabolism and pharmacokinetics in horses. Therefore, it is necessary to characterize the profiles of drug metabolites for the safe use of drugs. In this study, we focused on cytochrome P450 enzymes (CYPs), which represent an important enzyme group to determine pharmacological effects of drugs. We chose diazepam as the drug of choice for this study. The aim of this study was to elucidate the metabolic pathway of diazepam in horses in comparison with rats, and to clarify CYP subfamilies responsible for diazepam metabolism in horses. Our results showed temazepam was the major diazepam metabolite produced from microsomal reactions in horse liver, but horses produced drastically less p-hydroxydiazepam as compared with rats. Furthermore, CYP3A was a major contributor from the CYP subfamily of temazepam production.
  • Shouta M M Nakayama, Yoshinori Ikenaka, Kaampwe Muzandu, Kennedy Choongo, John Yabe, Taro Muroya, Shigeho Ijiri, Masao Minagawa, Takashi Umemura, Mayumi Ishizuka
    Archives of environmental contamination and toxicology 64 1 119 - 29 2013年01月 [査読有り][通常論文]
     
    The Copperbelt region, upstream of the Kafue River, including Lake Itezhi-tezhi (ITT), in Zambia has extensive copper (Cu) mines. In our field study, geographic information system analysis in lake sediment indicated that the northern part of the lake, i.e., the Copperbelt region, could be the source of Cu pollution. Concentrations of Cu in stomach contents between fish species were not significantly different. However, Oreochromis spp. liver showed significantly greater Cu concentrations than those in other fish species. Log liver [Cu], standard length, and nitrogen stable isotope ratio were positively correlated only in Oreochromis spp. In the laboratory study, O. niloticus and O. latipes were exposed to Cu for 4 days, and recovery phases ≤ 28 days were examined. O. niloticus showed significantly greater concentrations of Cu compared with O. latipes at all sampling points. Significantly greater concentrations of Hg in Schilbe intermedius liver than for other fish species were observed, whereas O. macrochir showed significantly greater concentrations of cadmium. In conclusion, the northern part of the lake could be the source of Cu pollution in Lake ITT. Diet may not be the reason for high Cu accumulation in Oreochromis spp. Results from both field and laboratory studies imply that Oreochromis spp. contain high concentrations of Cu under normal physiological conditions.
  • John Yabe, Shouta M. M. Nakayama, Yoshinori Ikenaka, Kaampwe Muzandu, Kennedy Choongo, Geoffrey Mainda, Matthew Kabeta, Mayumi Ishizuka, Takashi Umemura
    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 32 1 189 - 192 2013年01月 [査読有り][通常論文]
     
    Concentrations of Pb, Cd, and other metals in tissues of 17 free-range and 32 commercial broiler chickens from the Kabwe mining town in Zambia were determined. Mean concentrations of Pb and Cd exceeded maximum levels for human consumption in some organs including muscle (Pb only) in free-range chickens, in contrast to low levels in broiler chickens. Human consumers in Kabwe could be exposed to Pb and Cd in free-range chickens. Environ. Toxicol. Chem. 2013;32:189192. (c) 2012 SETAC
  • Dominic Mureithi, Wageh Sobhy Darwish, Yoshinori Ikenaka, Laetitia Kanja, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 60 4 205 - 210 2012年11月 [査読有り][通常論文]
     
    The cytochrome P450 (CYP) 3A family is involved in the elimination processes of almost 50% of commonly used drugs. CYP3A mRNA expressions in goat and rat gastrointestinal tracts in comparison to the liver were investigated using real-time PCR. In goats, the expression of CYP3A-like mRNAs was comparatively higher in the liver than in the gastrointestinal tract. The intestinal expression of CYP3A-like mRNA showed a gradual decrease from the duodenum to the ileum. In rats, the highest CYP3A62 mRNA expression was found in the duodenum followed by the liver. This study provides insights into the contribution of CYP3A enzymes to xenobiotic metabolism, especially in small ruminants such as goats.
  • John Yabe, Shouta M. M. Nakayama, Yoshinori Ikenaka, Kaampwe Muzandu, Mayumi Ishizuka, Takashi Umemura
    JOURNAL OF VETERINARY MEDICAL SCIENCE 74 10 1345 - 1347 2012年10月 [査読有り][通常論文]
     
    Intensive agricultural practices are recognized as significant sources of metal pollution in soils and pasture. This study investigated metal contamination in cattle offal from an agricultural area in Zambia, where inorganic fertilizers, agricultural lime, and pesticides are routinely applied. The highest median values (mg/kg, wet weight) of Cu (40.9), Zn (35.2), Cr (1.35) and Ni (0.594) were recorded in the liver, whereas the highest median values of Pb (0.061) and Cd (0.049) were found in kidneys. Maximum levels of Hg, As and Co were under 0.2 mg/kg in both organs. Pb and Cd did not exceed the benchmark values in cattle offal for human consumption and did not pose immediate health risks. Concentrations of Ni and Cr could present a public health concern. Monitoring of metal accumulations in offal of cattle, not only from well-known polluted environments but also agricultural areas, should be done regularly for the health of human consumers.
  • Yoshinori Ikenaka, Shouta M. M. Nakayama, Taro Muroya, John Yabe, Satoru Konnai, Wageh Sobhy Darwish, Kaampwe Muzandu, Kennedy Choongo, Geoffrey Mainda, Hiroki Teraoka, Takashi Umemura, Mayumi Ishizuka
    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 31 10 2300 - 2305 2012年10月 [査読有り][通常論文]
     
    The Republic of Zambia is rich in mineral resources, such as zinc (Zn) and lead (Pb), and mining is a key industry in Zambia. A previous study of Pb pollution in Kabwe, one of the main mining areas, found that soil was contaminated with high levels of toxic metals over a substantial area. In the present study, the authors focus on toxic metal pollution in cattle, one of the most important domestic animals in Zambia. Blood samples from cattle in Kabwe and a control area (Lusaka) were tested for toxic metal content. They also measured mRNA expression of metal-responsive proteins and cytokines in white blood cells using real-time reverse transcriptase polymerase chain reaction. In the present in vitro study, The authors cultured peripheral blood mononuclear cells (PBMCs) from cattle, exposing them to Pb acetate for 24?h and analyzing mRNA expression of metal-responsive proteins and selected cytokines. Lead concentrations in cattle blood from Kabwe were significantly greater than those from Lusaka, as were the mRNA expressions of metallothionein-2 (MT-2), tumor necrosis factor-a (TNF-a), interferon-? (IFN-?), interleukin-1 beta (IL-1 beta), IL-6, and inducible nitric oxide synthase (iNOS). The present in vitro study demonstrated that Pb exposure led to an increase in the expressions of MT-2, TNF-a, IL-1 beta, and iNOS, similar to those found in vivo. These results indicate the possibility of immune system modulations in cattle from the Kabwe area. Environ. Toxicol. Chem. 2012; 31: 23002305. (c) 2012 SETAC
  • Ethel M'kandawire, Michelo Syakalima, Kaampwe Muzandu, Girja Pandey, Martin Simuunza, Shouta M. M. Nakayama, Yusuke K. Kawai, Yoshinori Ikenaka, Mayumi Ishizuka
    GENE 506 2 310 - 316 2012年09月 [査読有り][通常論文]
     
    The study determined heavy metal concentrations and MT1 nucleotide sequence [phylogeny] in liver of the Kafue lechwe. Applicability of MT1 as a biomarker of pollution was assessed. cDNA-encoding sequences for lechwe MT1 were amplified by RT-PCR to characterize the sequence of MT1 which was subjected to BLAST searching at NCBI. Phylogenetic relationships were based on pairwise matrix of sequence divergences calculated by Clustal W. Phylogenetic tree was constructed by NJ method using PHILLIP program. Metals were extracted by acid digestion and concentrations of Cr, Co, Cu, Zn, Cd, Pb, and Ni were determined using an AAS. MT1 mRNA expression levels were measured by quantitative comparative real-time RT-PCR. Lechwe MT1 has a length of 183 bp, which encode for MT1 proteins of 61AA, which include 20 cysteines. Nucleotide sequence of lechwe MT1 showed identity with sheep MT (97%) and cattle MT1E (97%). Phylogenetic tree revealed that lechwe MT1 was clustered with sheep MT and cattle MT1E. Cu and Ni concentrations and MT1 mRNA expression levels of lechwe from Blue Lagoon were significantly higher than those from Lochinvar (p<0.05). Concentrations of Cd and Cu, Co and Cu, Co and Pb, Ni and Cu, and Ni and Cr were positively correlated. Spearman's rank correlations also showed positive correlations between Cu and Co concentrations and MT mRNA expression. PCA further suggested that MT mRNA expression was related to Zn and Cd concentrations. Hepatic MT1 mRNA expression in lechwe can be used as biomarker of heavy metal pollution. (C) 2012 Elsevier B.V. All rights reserved.
  • Tomohiro Okagawa, Satoru Konnai, Hirohisa Mekata, Naftaly Githaka, Saori Suzuki, Edward Kariuki, Francis Gakuya, Esther Kanduma, Tatsuya Shirai, Ryoyo Ikebuchi, Yoshinori Ikenaka, Mayumi Ishizuka, Shiro Murata, Kazuhiko Ohashi
    VETERINARY IMMUNOLOGY AND IMMUNOPATHOLOGY 148 3-4 373 - 379 2012年08月 [査読有り][通常論文]
     
    Theileria parva (T. parva) causes East Coast fever (ECF), which is of huge economic importance to Eastern and Southern African countries. In a previous bovine model, inflammatory cytokines were closely associated with disease progression in animals experimentally infected with T. parva. The African Cape buffalo (Syncerus coffer), the natural reservoir for T. parva, is completely resistant to ECF despite a persistently high parasitaemia following infection with T. parva. Characterizing basic immunological interactions in the host is critical to understanding the mechanism underlying disease resistance in the African Cape buffalo. In this study, the expression level of several cytokines was analyzed in T. parva-infected buffaloes. There were no significant differences in the expression profiles of inflammatory cytokines between the infected and uninfected animals despite a remarkably high parasitaemia in the former. However, the expression level of IL-10 was significantly upregulated in the infected animals. These results indicate a correlation between diminished inflammatory cytokines response and disease resistance in the buffalo. (c) 2012 Elsevier B.V. All rights reserved.
  • Tomohide Uno, Mayumi Ishizuka, Takao Itakura
    ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 34 1 1 - 13 2012年07月 [査読有り][通常論文]
     
    Cytochrome P450 (CYP) enzymes are members of the hemoprotein superfamily, and are involved in the mono-oxygenation reactions of a wide range of endogenous and exogenous compounds in mammals and plants. Characterization of CYP genes in fish has been carried out intensively over the last 20 years. In Japanese pufferfish (Takifugu rubripes), 54 genes encoding P450s have been identified. Across all species of fish, 137 genes encoding P450s have been identified. These genes are classified into 18 CYP families: namely, CYP1, CYP2, CYP3, CYP4, CYP5, CYP7, CYP8, CYP11, CYP17, CYP19, CYP20, CYP21, CYP24, CYP26, CYP27, CYP39, CYP46 and CYP51. We pinpointed eight CYP families: namely, CYP1, CYP2, CYP3, CYP4, CYP11, CYP17, CYP19 and CYP26 in this review because these CYP families are studied in detail. Studies of fish P450s have provided insights into the regulation of P450 genes by environmental stresses including water pollution. In this review, we present an overview of the CYP families in fish. (C) 2012 Elsevier B.V. All rights reserved.
  • Shouta M. M. Nakayama, Yoshinori Ikenaka, Kaampwe Muzandu, Kennedy Choongo, Ethel M'kandawire, Jun Yasuda, Mayumi Ishizuka
    ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 80 333 - 338 2012年06月 [査読有り][通常論文]
     
    Hippopotami (Hippopotamus amphibius L) are large semi-aquatic mammals that can be exposed to metals and metalloid from both terrestrial and aquatic environments. Therefore, knowledge of metal and metalloid accumulation characteristics in hippopotami living in the national park is important from ecotoxicological point of view. Levels of toxic metals (Cd, Pb and Hg) and metalloid (As) in hippopotami liver from the South Luangwa National Park in Zambia were far lower compared to the established values of toxic levels in cattle. No temporal variations of metal levels in hippopotami were observed, probably because of good management condition and the lack of anthropogenic activities around the national park. However, hippopotami liver accumulated significantly higher concentrations of Hg compared to soil, sediment and their food (plants), most likely due to a process of biomagnification throughout a trophic chain. Moreover, hippopotami liver and land plants showed significantly higher Cd levels than those of soil. These results strongly suggest that hippopotami liver accumulate higher levels of these metals if surrounding environment is contaminated. Levels of Cr and Ni in hippopotami liver were higher compared to other toxic metals. Since this is the first report to show the Cr and Ni levels and bio-accumulation characteristics of Hg and Cd in hippopotami, we concluded that continuous monitoring and evaluation of toxic effects of these metals on hippopotami should be conducted. (C) 2012 Elsevier Inc. All rights reserved.
  • K. Kawamoto, K. Otsuguro, M. Ishizuka, S. Ito
    British Journal of Pharmacology 166 2 788 - 800 2012年05月 
    Background and Purpose: Dopamine released from the endings of descending dopaminergic nerve fibres in the spinal cord may be involved in modulating functions such as locomotion and nociception. Here, we examined the effects of dopamine on spinal synaptic transmissions in rats. Experimental Approach: Spinal reflex potentials, monosynaptic reflex potential (MSR) and slow ventral root potential (sVRP), were measured in the isolated spinal cord of the neonatal rat. Dopamine release was measured by HPLC. Key Results: Dopamine at lower concentrations (<1 μM) depressed sVRP, which is a C fibre-evoked polysynaptic response and believed to reflect nociceptive transmission. At higher concentrations (>1 μM), in addition to a potent sVRP depression, dopamine depolarized baseline potential and slightly depressed MSR. Depression of sVRP by dopamine was partially reversed by dopamine D 1-like but not by D 2-like receptor antagonists. SKF83959 and SKF81297, D 1-like receptor agonists, and methamphetamine, an endogenous dopamine releaser, also caused the inhibition of sVRP. Methamphetamine also depressed MSR, which was inhibited by ketanserin, a 5-HT 2A/2C receptor antagonist. Methamphetamine induced the release of dopamine and 5-HT from spinal cords, indicating that the release of endogenous dopamine and 5-HT depresses sVRP and MSR respectively. Conclusion and Implications: These results suggested that dopamine at lower concentrations preferentially inhibited sVRP, which is mediated via dopamine D 1-like and other unidentified receptors. The dopamine-evoked depression is involved in modulating the spinal functions by the descending dopaminergic pathways. © 2011 The British Pharmacological Society.
  • Shimamoto Yoshinori, Watanabe Kensuke, Sasaki Mizuki, Ikadai Hiromi, Ishizuka Mayumi, Hoshi Fumio, Yokoyama Naoaki, Igarashi Ikuo, Kitamura Hiroshi
    FASEB JOURNAL 26 2012年04月 [査読有り][通常論文]
  • Suzuki S, Konnai S, Okagawa T, Githaka NW, Kariuki E, Gakuya F, Kanduma E, Shirai T, Ikebuchi R, Ikenaka Y, Ishizuka M, Murata S, Ohashi K
    Int J Immunogenet. 39 2 170 - 82 2012年04月 [査読有り][通常論文]
     
    The African buffalo (Syncerus caffer) has been implicated as the reservoir of several bovine infectious agents. However, there is insufficient information on the protective immune responses in the African buffalo, particularly in infected animals. In this study, we analysed Th1 cytokines IL-2 and IFN-γ, and Th2 cytokines IL-4 and IL-10. The cloned cDNA of IL-2, IL-4, IL-10 and IFN-γ contained an open reading frame of 468, 501, 408 and 540 nucleotides, encoding polypeptides of 155, 166, 135 and 179 amino acids, respectively. Nucleotide sequence homology of IL-2, IFN-γ and IL-4 was more than 98% between the African buffalo and cattle, which resulted in identical polypeptides. Meanwhile, IL-10 gene of African buffalo and cattle had 95% homology in nucleotide sequence, corresponding to thirteen amino acid residues substitution. Cysteine residues and potential glycosylation sites were conserved within the family Bovinae. Phylogenetic analyses including cytokines of the African buffalo placed them within a cluster comprised mainly of species belonging to the order Artiodactyla, including cattle, water buffalo, sheep, goat, pig and artiodactyl wildlife. A deeper understanding of the structure of these cytokines will shed light on their protective role in the disease-resistant African buffalo in comparison with other closely related species. © 2011 Blackwell Publishing Ltd.
  • Yoshinori Shimamoto, Mizuki Sasaki, Hiromi Ikadai, Mayumi Ishizuka, Naoaki Yokoyama, Ikuo Igarashi, Fumio Hoshi, Hiroshi Kitamura
    JOURNAL OF VETERINARY MEDICAL SCIENCE 74 2 241 - 245 2012年02月 [査読有り][通常論文]
     
    To investigate effects of Babesia infection on drug metabolism, we intraperitoneally inoculated B. microti into ICR mice and measured the expression and activity of hepatic cytochrome P450 (CYP) 3A, a major drug-metabolizing enzyme. Twelve days after infection, CYP3A11 mRNA, CYP3A protein and activity and mRNAs of nuclear receptors, which participate in CYP3A expression, were significantly reduced. These results suggest that B. microti infection suppresses CYP3A-dependent drug metabolism. Additionally, tumor necrosis factor (TNF)-alpha and nitric oxide synthase (NOS) 2 mRNAs were induced in the infected mouse liver. Since TNT-a is one of the potent mediators that induce NOS2 and repress CYP3A transcription, the possible involvement of TNF-alpha in this downregulation of CYP3A was discussed.
  • DARWISH Wageh S., IKENAKA Yoshinori, ISHIZUKA Mayumi
    日本毒性学会学術年会 39 O - 6 日本毒性学会 2012年 
    [Introduction] The growing exposure of the human and animals to heavy metal pollution generates modulation in xenobiotics-metabolizing enzymes (XMEs) response. In this study, the modulation of Ahr ligand-dependent toxicities by heavy metals and the molecular basis of this modulation were investigated.[Materials and Methods] Samples were collected from different edible offal of cattle slaughtered at Zagazig abattoir, Egypt. Different heavy metals were measured using atomic absorption spectrophotometer. Human and rat liver hepatoma cell lines (HEPG2 and H4IIE) were treated with Lead and Copper under different concentrations ranged between permissible and toxic doses. The effects of these treatments on various XMEs and regulatory elements were screened using the methods of qPCR and Western Blotting.[Results and Discussion] Liver, kidney and tongue showed the highest contents of the various heavy metal residues compared to other tissues. Lead, copper, cadmium, zinc and nickel exceeded the maximum permissible limits of Egyptian Standards and WHO. Interestingly, both copper and lead could induce CYP1A1 mRNA expression under low doses in the treated cell cultures. This expression level was markedly decreased under high concentrations. Effects of copper and lead on CYP1A1 expression was parallel to their effects on Ahr suggesting that those effects were in response to Ahr. All tested phase II enzymes were severely down regulated by exposure to lead in a concentration dependent manner. In conclusion, there were clear cross-talks between copper, lead and pase I, II enzymes and regulatory elements in the cultured cells.
  • WATANABE Kensuke P, KAWATA Minami, KAWAI Yusuke, IKENAKA Yoshinori, ISHIZUKA Mayumi
    日本毒性学会学術年会 39 AP - 223 日本毒性学会 2012年 
    [Background and aim]In wild bird species, the metabolic activity of warfarin by cytochrome P450 (CYP) was reported to be much lower compared to chicken. However, even the important CYP isoforms in avian xenobiotic metabolism have not been clarified due to the lack of information about the expression level and the function of each isoforms. Thus, the reported species difference of metabolic ability cannot be attributed to any isoform. In this study, we aimed to identify the isoform dominant in avian xenobiotic metabolism and to characterize the species difference of the isoform.[Method and result]We compared the mRNA copy number among CYP isoforms in chicken liver. CYP1A5, 2C23 and 2C45 were highly expressed in liver, while CYP3A37, which has been well studied in poultry species, showed lower expression level. Therefore, we focused on CYP2C23 of avian species. Partial sequences of CYP2C23 from 8 avian species were cloned and the anti-peptide antibody was synthesized against the conserved amino acid sequence among them. In immunoblot with the antibody and the microsomes of the avian species, we could detect CYP2C23s from all the avian species.[Discussion]With mRNA expression, CYP2C subfamily was assumed to be important isoforms in chicken xenobiotics metabolism. The expression levels of CYP2C23 proteins showed not as much difference among bird species as the metabolic activity. With all results above, the species difference of metabolic ability among bird species cannot be attributed to the protein expression levels, but the functional difference.
  • SAENGTIENCAHI Aksorn, IKENAKA Yoshinori, LEE Kyunglee, TSUBOTA Toshio, ISHIZUKA Mayumi
    日本毒性学会学術年会 39 P - 125 日本毒性学会 2012年 
    [Introduction] Polycyclic aromatic hydrocarbons (PAHs) distribute ubiquitously as complex mixtures in the environment. Pyrene is one of PAHs that is widely used as model of PAH contamination in environment. Pyrene is metabolized by cytochrome P450s in phase I reaction then conjugated in phase II metabolism, and excreted into urine and feces. Although their metabolites are available for use in human as indicator for PAH exposure, there are still less information in wildlife. In present study, we focus on the elucidation of pyrene metabolites in wild animals. [Materials and Methods] Urine of 10 male sika deer (Cervus nippon), 1 to 5 year olds were collected from Hokkaido, Japan. All samples were extracted by Oasis WAX cartridge and they were analyzed by High performance liquid chromatography with fluorescence detector. [Results and Discussions] We could detect pyrene-1-glucuronide largely in urine. Moreover, pyrene-1-sulfate, and 1-hydroxypyrene also detected. When we compared this results with other ruminant as cattle, pyrene-1-glucuronide was main metabolites same as sika deer. Pyrene conjugate compounds were easily detected in urine. Due to observe the amount of polluted chemical as PAHs in environment, we could suggest that not only elucidate PAH concentration, but also its metabolite as 1-hydroxypyrene, pyrene 1-glucuronide, and sulfate conjugates were important to establish the appropriate biomarker for the assessment for PAH exposures in various wildlife animal species in environment.
  • Marumi Ohno, Yoshinori Ikenaka, Mayumi Ishizuka
    BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 417 1 484 - 489 2012年01月 [査読有り][通常論文]
     
    Aryl hydrocarbon receptor (AHR) and AHR nuclear translocator (ARNT) are well-conserved transcription factors among species. However, there are a very limited number of reports on the physiological function of AHR, particularly on the regulation of AHR by endogenous compounds. We hence investigated the effects of all-trans retinoic acid (atRA) on cytochrome P450 (CYP)1A1 gene transcription as a model of AHR-regulated transcription mechanisms in HepG2 cells, a human hepatoma cell line. Treatment with atRA significantly reduced transactivation and expression of CYP1A1 mRNA to less than half of its control value, and this inhibitory effect was mediated by RAR alpha. The result of chromatin immunoprecipitation assay indicated that treatment with atRA at 1-100 nM drastically inhibited the recruitment of ARNT to DNA regions containing xenobiotic responsive elements. In conclusion, atRA at physiological concentrations could reduce AHR-mediated gene transcription via the inhibition of recruitment of ARNT to relevant DNA regions. (C) 2011 Elsevier Inc. All rights reserved.
  • Marumi Ohno, Yoshinori Ikenaka, Mayumi Ishizuka
    JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY 26 1 16 - 22 2012年01月 [査読有り][通常論文]
     
    Sudan dyes possess a high affinity to the aryl hydrocarbon receptor (AHR) and potently induce its target genes, such as cytochrome P450 (CYP) 1A1, through unknown mechanisms. We investigated a detailed event occurring in cells after binding of Sudan dye to AHR in HepG2 cells. Treatment with 10 mu M Sudan III caused rapid translocation of AHR into the nucleus and increased expression levels of human CYP1A1 mRNA by approximately 20-fold after 16 and 24 h. The transactivation was due to the activation of a region located at -1137 to +59 bp from CYP1A1, in particular, four xenobiotic responsive elements (XREs) existing in the region. AHR and the Ah receptor nuclear translocator interacted with XRE sequences in a gel shift assay using nuclear extract from Sudan III-treated HepG2 cells. Moreover, we suggest that constitutive androstane receptor could modify CYP1A1 transactivation by Sudan III. (C) 2012 Wiley Periodicals, Inc. J Biochem Mol Toxicol 26:16-22 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.20408
  • Haruki Ueda, Yoshinori Ikenaka, Shouta M. M. Nakayama, Tomoko Tanaka-Ueno, Mayumi Ishizuka
    AQUATIC TOXICOLOGY 105 3-4 337 - 343 2011年10月 [査読有り][通常論文]
     
    The present study examines amphibian metabolic activity - particularly conjugation - by analysis of pyrene (a four ring, polycyclic aromatic hydrocarbon) metabolites using high-performance liquid chromatography (HPLC) with fluorescence detector (FD), a mass spectrometry detector (MS) system and kinetic analysis of conjugation enzymes. Six amphibian species were exposed to pyrene (dissolved in water): African claw frog (Xenopus laevis); Tago's brown frog (Rana tagoi); Montane brown frog (Rana ornativentris); Wrinkled frog (Rana rugosa); Japanese newt (Cynops pyrrhogaster); and Clouded salamander (Hynobius nebulosus); plus one fish species, medaka (Oryzias latipes); and a fresh water snail (Clithon retropictus), and the resultant metabolites were collected. Identification of pyrene metabolites by HPLC and ion-trap MS system indicated that medaka mainly excreted pyrene-1-glucuronide (PYOG), while pyrene-1 -sulfate (PYOS) was the main metabolite in all amphibian species. Pyrene metabolites in amphibians were different from those in invertebrate fresh water snails. Inter-species differences were also observed in pyrene metabolism among amphibians. Metabolite analysis showed that frogs relied more strongly on sulfate conjugation than did Japanese newts and clouded salamanders. Furthermore, urodelan amphibians, newts and salamanders, excreted glucose conjugates of pyrene that were not detected in the anuran amphibians. Kinetic analysis of conjugation by hepatic microsomes and cytosols indicated that differences in excreted metabolites reflected differences in enzymatic activities. Furthermore, pyrenediol (PYDOH) glucoside sulfate was detected in the Japanese newt sample. This novel metabolite has not been reported previously to this report, in which we have identified unique characteristics of amphibians in phase II pyrene metabolism. (C) 2011 Elsevier B.V. All rights reserved.
  • John Yabe, Shouta M. M. Nakayama, Yoshinori Ikenaka, Kaampwe Muzandu, Mayumi Ishizuka, Takashi Umemura
    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 30 8 1892 - 1897 2011年08月 [査読有り][通常論文]
     
    Concentrations of lead, cadmium, and other metals in the liver and kidneys of cattle near a lead-zinc mine in Kabwe (Zambia), which is ranked among the 10 worst polluted places on earth, were compared with other Zambian towns. Metal concentrations were measured in the liver and kidneys of 51 cattle from Kabwe and other Zambian towns. The maximum metal concentrations, expressed in mg/kg and dry weight, in the liver or kidneys were 398.4 (Cu), 252.6 (Zn), 77.81 (Cr), 19.37 (Cd), 7.57 (Ni), 1.8 (Pb), 1.04 (Co), 0.112 (Hg), and 0.05 (As). Concentrations of Pb and Cd in Kabwe cattle were higher than levels in other Zambian towns. The mean concentration of Cd exceeded benchmark values in offal destined for human consumption. Levels of Ni and Cr may also pose public health concerns. Concentrations of Pb and Cr, Pb and Cu, Cd and Zn, Cd and Hg, Zn and Cu, Cu and Co, as well as Co and Ni were positively correlated. The present study also highlighted the dangers of exposure of animals and humans to a mixture of toxic metals. Environ. Toxicol. Chem. 2011;30:1892-1897. (C) 2011 SETAC
  • Marumi Ohno, Wageh S. Darwish, Yoshinori Ikenaka, Wataru Miki, Mayumi Ishizuka
    FOOD AND CHEMICAL TOXICOLOGY 49 6 1285 - 1291 2011年06月 [査読有り][通常論文]
     
    Astaxanthin (Ax), a xanthophyll carotenoid, is reported to induce cytochrome P450 (CYP) 1A-dependent activity. CYP1A is one of the most important enzymes participating in phase! metabolism for chemicals, and it can activate various mutagens. To investigate the effect of Ax on the metabolic activation of a typical promutagen, benzo[a]pyrene by CYP1A, we orally administrated Ax-containing oil (100 mg Ax/kg body weight/day for 3 days) to male Wistar rats. In the treated rat liver, expression of CYP1A1 mRNA, protein, and its activity were significantly increased (5.5-, 8.5-, and 2.5-fold, respectively). In contrast, the activities of phase II enzymes (glutathione S-transferase and glucuronosyl-transferase) were not modulated by Ax-containing oil. As a consequence, the mutagenicity of benzo[a]pyrene was more enhanced in Ax-treated rats, compared with controls in the Ames assay. On the other hand, NADPH P450 reductase activity was decreased in liver microsomes from the treated group. This result suggests the possibility that Ax inhibits the electron supply necessary for CYP catalytic activities and decreases CYP1A activity indirectly. In conclusion, Ax-containing oil intake can alter CYP1A-dependent activities through two different mechanisms: (1) induction of CYP1A1 mRNA, protein expression, and activity; and (2) inhibition of the electron supply for the enzyme. (C) 2011 Elsevier Ltd. All rights reserved.
  • Shouta M. M. Nakayama, Yoshinori Ikenaka, Kyohei Hamada, Kaampwe Muzandu, Kennedy Choongo, Hiroki Teraoka, Naoharu Mizuno, Mayumi Ishizuka
    ENVIRONMENTAL POLLUTION 159 1 175 - 181 2011年01月 [査読有り][通常論文]
     
    Metal (Cr, Co, Cu, Zn, Cd, Pb, Ni) and metalloid (As) accumulation was studied in roadside soil and wild rat (Rattus sp.) samples from near a Pb Zn mine (Kabwe, Zambia) and the capital city of Zambia (Lusaka). The concentrations of the seven metals and As in the soil samples and Pb in the rat tissue samples were quantified using atomic absorption spectroscopy. The concentrations of Pb, Zn, Cu, Cd, and As in Kabwe soil were much higher than benchmark values. Geographic Information System analysis indicated the source of metal pollution was mining and smelting activity. Interestingly, the area south of the mine was more highly contaminated even though the prevailing wind flow was westward. Wild rats from Kabwe had much higher tissue concentrations of Pb than those from Lusaka. Their body weight and renal Pb levels were negatively correlated, which suggests that mining activity might affect terrestrial animals in Kabwe. (C) 2010 Published by Elsevier Ltd.
  • Wageh S. Darwish, Yoshinori Ikenaka, Marumi Ohno, Elsaid A. Eldaly, Mayumi Ishizuka
    FOOD AND CHEMICAL TOXICOLOGY 48 11 3201 - 3208 2010年11月 [査読有り][通常論文]
     
    Ungulates (deer, cattle and horses) are reported as animal species which show extreme-accelerated metabolism of CYP1A substrates, such as ethoxyresorufin compared to rats. This study was undertaken to investigate whether accumulation of carotenoids is a possible cause for inter-species difference in CYP1A-dependent activity in this group of animals. The relationship between inter-species differences in CYP1A-dependent activity and the accumulated carotenoids and retinoids as candidates of dietary CYP1A inducers in ungulate species was clarified. Interestingly, there were positive correlations between the accumulated carotenoids, such as beta-carotene, with both EROD activity and CYP1A protein expression. These correlations were negative with the accumulated retinoids, such as retinol. The beta-carotene was major component of carotenoids in ungulates, and known as an inducer of CYP1A. On the other hand, the retinol is reported as the inhibitor of CYP1A. Other factors which affect CYP1A1 expression, such as polycyclic aromatic hydrocarbons, were also analyzed. To cancel the effects of inter-species difference in CYP1A induction signal cascade among these animals, the rat cell line (H4-II-cells) was treated with the extracted carotenoids from the examined animals. In conclusion, carotenoids and retinoids may have direct effects on the inter-species differences in CYP1A-dependent activity and protein expression. (C) 2010 Elsevier Ltd. All rights reserved.
  • John Yabe, Mayuni Ishizuka, Takashi Umemura
    Journal of Veterinary Medical Science 72 10 1257 - 1263 2010年10月 
    Studies of environmental pollution in Africa indicate that toxic metal pollution has reached unprecedented levels over the past decade. Human exposure to toxic metals has become a major health risk on the continent and is the subject of increasing attention from national and international environmentalists. This paper reviews data from the past decade on environmental pollution in Africa and highlights countries where most heavy metal pollutions have been reported. Characteristics of heavy metal pollution in North, West, East and Southern regions of Africa have been described, as have major sources of pollution in the different regions. This review summarizes the sites where most of the heavy metal pollution has been reported in Africa and, where applicable, presents reported levels of pollution in different environmental compartments in the context of internationally acceptable limits. Contaminations in fish and food animals as well as impacts of heavy metal pollution on humans are also described.
  • Wageh Sobhy Darwish, Yusuke Kawai, Yoshinori Ikenaka, Hideaki Yamamoto, Tarou Muroya, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 72 9 1237 - 1241 2010年09月 [査読有り][通常論文]
     
    As part of an ongoing effort to understand the biological response of wild and domestic ungulates to different environmental pollutants such as dioxin-like compounds, cDNAs encoding for CYP1A1 and CYP1A2 were cloned and characterized. Four novel CYP1A cDNA fragments from the livers of four wild ungulates (elephant, hippopotamus, tapir and deer) were identified. Three fragments from hippopotamus, tapir and deer were classified as CYP1A2, and the other fragment from elephant was designated as CYP1A1/2. The deduced amino acid sequences of these fragment CYP1As showed identities ranging from 76 to 97% with other animal CYP1As. The phylogenetic analysis of these fragments showed that both elephant and hippopotamus CYP1As made separate branches, while tapir and deer CYP1As were located beside that of horse and cattle respectively in the phylogenetic tree. Analysis of dN/dS ratio among the identified CYP1As indicated that odd toed ungulate CYP1A2s were exposed to different selection pressure.
  • Sata F, Kurahashi N, Ban S, Moriya K, Tanaka KD, Ishizuka M, Nakao H, Yahata Y, Imai H, Kakizaki H, Nonomura K, Kishi R
    The journal of sexual medicine 7 8 2729 - 2738 8 2010年08月 [査読有り][通常論文]
     
    Introduction. Hypospadias is a common congenital anomaly caused by incomplete fusion of urethral folds. Development of the urethra and external genital system in the male fetus is an androgen-dependent process. In this regard, enzymes 17 beta-hydroxvsteroid dehydrogenase type 3 (17 beta HSD3, encoded by HSD17B3) and steroid 5 alpha-reductase type 2 (encoded by SRD5A2) play crucial roles. Aim. To investigate the possible associations between common polymorphisms in HSD17B3 as well as well-known V89L polymorphism in SRD5A2 and risk of hypospadias. Methods. A case-control study was performed between 1999 and 2005. There were 89 Japanese boys with hypospadias and 291 newborn controls. We genotyped HSD17B3 -1999T>C, +10A>G, +20A>G, +139G>A (V31I), +913G>A (G289S), and SRD5A2 +336G>C (V89L) polvmorphisms by allelic discrimination assay. We measured mRNA expression of the wildtype G289 allele and the mutant S289 allele of the HSD17B3 gene in the transfected human fetal kidney HEK293 cells. Main Outcome Measures. Assessment of hypospadias including its severity and HSD17B3 and SRD5A2 genes using DNA blood samples: allele and genotype distribution of single nucleotide polymorphisms in these two genes in cases and controls. Results. In our study, the risk of hypospadias was significantly higher in subjects carrying homozygous HSD17133 +913A (289S) alleles (odds ratio [OR]: 3.06; 95% confidence interval [CI]: 1.38-6.76). The risk of severe hypospadias was much higher in these subjects (OR: 3.93; 95% CI: 1.34-11.49). The mRNA expression levels of HSD17B3 G289 were higher than those of IISD17B3 S289 mutant (P < 0.001). In addition, the risk of severe hypospadias increased in boys carrying the SRD5A2 +336C (89L) allele (OR: 3.19; 95% CI: 1.09-9.36). Conclusions. These results suggest that the HSD17B3 G289S polymorphism may be a potential risk modifier for hypospadias. Our findings provide evidence that a certain genotype related to androgen production may potentiate risk of hypospadias. Sata F, Kurahashi N, Ban S, Moriya K, Tanaka KD, Ishizuka M, Nakao H, Yahata Y, Imai H, Kakizaki H, Nonomura K, and Kishi R. Genetic polymorphisms of 17 beta-hydroxysteroid dehydrogenase 3 and the risk of hypospadias. J Sex Med 2010;7:2729-2738.
  • Shouta M. M. Nakayama, Yoshinori Ikenaka, Kaampwe Muzandu, Kennedy Choongo, Balazs Oroszlany, Hiroki Teraoka, Naoharu Mizuno, Mayumi Ishizuka
    ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 59 2 291 - 300 2010年08月 [査読有り][通常論文]
     
    We measured the level of heavy metal accumulation in lake sediments, herbivorous (Oreochromis niloticus) and carnivorous (Serranochromis thumbergi) fish, and crayfish (Cherax quadricarinatus) from Lake Itezhi-tezhi (ITT) and Lake Kariba. We used atomic absorption spectrophotometry to quantify the levels of seven heavy metals (Cr, Co, Cu, Zn, Cd, Pb, and Ni). The sediment and the herbivorous fish O. niloticus accumulated a very high concentration of Cu in Lake ITT, most likely due to the discharge of Cu waste from a mining area 450 km upstream. The aquatic species we sampled in Lake Kariba had higher concentrations of Cr, Ni, and Pb relative to those in Lake ITT. This is most likely due to anthropogenic activities, such as the use of leaded petrol and antifouling agents in marine paints. Interestingly, we observed a negative correlation between the coefficient of condition (K) and Ni concentration in the crayfish hepatopancreas. Both O. niloticus and the crayfish had much higher biota-sediment accumulation factors (BSAF) for Cu, Zn, and Cd relative to Cr, Co, Pb, and Ni. The rank of BSAF values for O. niloticus (Cu > Cd > Zn) and C. quadricarinatus (Zn > Cd > Cu) differed from the expected ranks based on the general order of affinity of metals (Cd >> Zn > Cu).
  • Mami Takiguchi, Wageh S. Darwish, Yoshinori Ikenaka, Marumi Ohno, Mayumi Ishizuka
    TOXICOLOGICAL SCIENCES 116 1 79 - 91 2010年07月 [査読有り][通常論文]
     
    Xenobiotic metabolism in oral tissues, especially in the tongue, has never been reported. In the present study, the metabolic activation/detoxification ability of promutagens in the tongue and the expression levels of related enzymes were investigated. Quantitative PCR analysis of rat tongue demonstrated constitutive messenger RNA (mRNA) expression of numerous drug-metabolizing enzymes. In particular, we detected mRNA, protein expression, and enzymatic activity of cytochrome P450 (CYP)1A1 in the tongue tissue. Metabolic activation of promutagens in the tongue was estimated using benzo[a]pyrene or heterocyclic amines (HCAs), found in cooked meat and tobacco products. Metabolic activation levels of HCAs in the tongue were comparable to those in the liver. In contrast, the expression levels of glutathione-S-transferase (GST) and uridine diphosphate-glucuronosyltransferase (UGT) in the tongue were considerably lower compared with those in the liver, and as a result, the mutagenic activity in the tongue was not decreased by GST- or UGT-dependent conjugation. Treatment of rats with sudan III, a typical inducer of CYP1A1, resulted in markedly increased CYP1A1 mRNA, protein expressions, and CYP1A-dependent enzymatic and mutagenic activities. In addition, CYP1A1 mRNA expression in carcinoma cells (SAS) was induced by sudan III exposure. In conclusion, mutagenic activation of xenobiotics and an increased risk of cancer in the tongue were observed in this study. Furthermore, ingestion of drug-metabolizing enzyme inducers has the potential to increase the metabolic activation in the tongue tissue and increase the risk of biomolecular attack by promutagens.
  • Kensuke P. Watanabe, Aksorn Saengtienchai, Kazuyuki D. Tanaka, Yoshinori Ikenaka, Mayumi Ishizuka
    COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C-TOXICOLOGY & PHARMACOLOGY 152 1 114 - 119 2010年06月 [査読有り][通常論文]
     
    Scattering coumarin derivative rodenticides in broad areas have caused primary- and secondary-poisoning incidents in non-target wild birds. In this study, we compared factors determining warfarin sensitivity between bird species and rats based on vitamin K 2,3-epoxide reductase (VKOR) kinetics, VKOR inhibition by warfarin and warfarin metabolism assays. In VKOR characterization, chickens and ostriches showed significantly lower enzymatic efficiencies than rats (one-sixth and one-third, respectively), suggesting bird species depend more on a non-VKOR vitamin K source. On the other hand, the inhibition constants (K-i) of VKOR for warfarin were significantly different between chickens and ostriches (113 +/- 2.5 mu M and 0.64 +/- 0.39 mu M, respectively). Interestingly, the ostrich K-i was similar to the values for rats (0.28 +/- 0.09 mu M). The K-i results reveal a surprising possibility that VKOR in some bird species are easily inhibited by warfarin. Warfarin metabolism assays also showed a large inter-species difference in bird species. Chickens and ostriches showed higher metabolic activity than that of rats, while mallards and owls showed only a slight ability to metabolize warfarin. In this study, we clarified the wide inter-species difference that exists among birds in xenobiotic metabolism and sensitivity to a rodenticide. (C) 2010 Elsevier Inc. All rights reserved.
  • Yusuke K. Kawai, Yoshinori Ikenaka, Shoichi Fujita, Mayumi Ishizuka
    MAMMALIAN GENOME 21 5-6 320 - 329 2010年06月 [査読有り][通常論文]
     
    Members of the cytochrome P450 family 1 (CYP1s) are involved in the detoxification and bioactivation of numerous environmental pollutants and phyto-chemicals such as polycyclic aromatic hydrocarbons (PAHs), aromatic amines, and flavonoids. The vertebrate CYP1 gene comprises four subfamilies: CYP1A, CYP1B, CYP1C, and CYP1D. Recently, the CYP1D gene was identified in fish, and subsequently in the platypus. These findings indicate the possibility that all vertebrates have a functional CYP1D subfamily. However, there is no information on the mammalian CYP1D gene. In this study we investigated the genomic location of CYP1D genes in mammals and other vertebrates in silico. We also performed phylogenetic analysis and calculated the identities and similarities of CYP1D sequences. The data from synteny and phylogenetic analyses of CYP1D genes demonstrated the evolutionary history of the CYP1 gene family. The results suggested that CYP1D became a nonfunctional pseudogene in human and bovine species; however, several other mammals possess functional CYP1D genes. The promoter regions of CYP1D genes were also examined. Unlike other CYP1 isoforms, few xenobiotic responsive element (XRE)-like sequences were found upstream of the CYP1D genes. Analysis of mammalian CYP1Ds also provided new insight into the relationship between CYP1 genes and the aryl hydrocarbon receptor.
  • Hye-Sook Chang, Miyan Ko, Mayumi Ishizuka, Shoichi Fujita, Akira Yabuki, Mohammad Alamgir Hossain, Osamu Yamato
    NUTRITION RESEARCH 30 6 435 - 440 2010年06月 [査読有り][通常論文]
     
    There is evidence that onions and garlic protect against cancer in humans. It has been suggested that this effect is partly due to the organosulfur compounds in Allium vegetables and that these substances act through induction of phase II detoxification enzymes. Here, we hypothesized that alk (en)yl thiosulfates, sodium n-propyl thiosulfate (NPTS), and sodium 2-propenyl thiosulfate (2PTS), which were identified in onions and garlic, respectively, may induce phase II enzymes. Therefore, rat hepatoma cells (H4IIE) were cultured with 1 to 100 mu mol/L of NPTS or 2PTS for 48 hours at 37 degrees C; and the activities and messenger RNA (mRNA) expression levels of phase II enzymes in H4IIE cells were investigated. The effects of diallyl trisulfide and tert-butylhydroquinone, known as phase 11 inducers, were also examined as positive controls and compared with the responses of NPTS and 2PTS. Quinone reductase (QR) activity and mRNA expression levels of QR and epoxide hydrolase 1 were significantly increased by 2PTS (P < .05-.005). In particular, QR activity was increased at a relatively low concentration of 2PTS (10 mu mol/L). However, glutathione S-transferase activity and mRNA expression levels of glutathione S-transferase A5 and uridine diphosphate glucuronosyl transferase 1A1 were not changed by 2PTS. In contrast, NPTS did not affect the activities and mRNA expression levels of these phase II enzymes. These results show that 2PTS can induce phase II enzymes, and its inductive effect is comparable or superior to that of diallyl trisulfide and tert-butylhydroquinone. (C) 2010 Elsevier Inc. All rights reserved.
  • Wageh Sobhy Darwish, Yoshinori Ikenaka, Elsaid Abozeid Eldaly, Marumi Ohno, Kentaro Q. Sakamoto, Shoichi Fujita, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 72 5 561 - 566 2010年05月 [査読有り][通常論文]
     
    The objective of this study was to investigate and characterize the metabolic activities of CYP1A in deer, cattle and horses in comparison to those of rats using ethoxyresorufin O-deethylation (EROD) and methoxyresorufin O-demethylation (MROD) assays. We performed an inhibition study for these activities using anti-rat CYP1A1 antibody and identified that these activities were due to the CYP1A subfamily. Interspecies differences in the CYP1A-dependent activities were highly observed in this study. In particular, we found that the horse had the highest EROD and MROD activities among the examined animal species. In the kinetic analysis, the horses showed the highest Vmax and catalytic efficiency (Vmax/Km), followed by the cattle, deer and rats.
  • Sakamoto KQ, Sato K, Kato A, Fukui D, Bando G, Naito Y, Habara Y, Ishizuka M, Fujita S
    Physiological and biochemical zoology : PBZ 83 2 232 - 238 2 2010年03月 [査読有り][通常論文]
     
    Prolonged abnormal vomiting causes metabolic alkalosis. Many seabirds are known to feed their chicks by regurgitation. We hypothesized that metabolic alkalosis occurs in seabirds even under natural conditions during the breeding season. Adelie penguins Pygoscelis adeliae feed their chicks by regurgitating food for 50-60 d until the chicks fledge. In this study, the concentrations of Cl(-), HCO(3)(-), Na(+), K(+), pH, and Pco(2) in the blood of breeding Adelie penguins were measured throughout the chick-rearing season. The pH of penguin venous blood shifted from 7.54 in the guarding period to 7.47 in the creche period. Decreasing Cl(-) and increasing HCO(3)(-) blood concentrations in parents were associated with increasing mass of their brood in the guarding period, the early phase of the rearing season, indicating that regurgitating to feed chicks causes loss of gastric acid and results in relative metabolic alkalosis. The inverse trend was observed during the creche period, the latter phase of the rearing season, when parents spent more time at sea and have fewer opportunities for gastric acid loss. This was assumed to be the recovery phase. These results indicate that regurgitation might cause metabolic alkalosis in breeding Adelie penguins. To our knowledge, this is the first report to indicate that seabirds exhibit metabolic alkalosis due to regurgitation to feed chicks under natural conditions.
  • Wageh Sobhy Darwish, Alaa Eldin Morshdy, Yoshinori Ikenaka, Zein Shaban Ibrahim, Shoichi Fujita, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 72 2 221 - 224 2010年02月 [査読有り][通常論文]
     
    In this study, we determined a partial sequence of CYPIA1 in the camel and its phylogenetic position. The deduced amino acid sequence of camel CYPIA1 showed the highest identity 94% with those of sheep and cattle CYPIA1. In a phylogenetic analysis, the camel CYPIA1 isoform was located beside sheep and cattle CYPIA1. When we studied the distribution of camel CYPIA1 mRNA in different tissues, we found that this isoform was expressed in all tissues except the hump. Interestingly, the lungs of all the camels and tongues of two of the three animals showed high expressions of CYPIA1 mRNA, and this may indicate exposure to ligands of aryl hydrocarbon receptor such as environmental pollutants or flavonoids.
  • Hyung-Sub Kim, Noriaki Sakai, Konomu Saito, Shoichi Fujita, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 72 1 7 - 11 2010年01月 [査読有り][通常論文]
     
    Previously, we have reported drastic strain differences of diazepam metabolism in the livers of a variety of rat strain. In this study, to characterize strain and sex differences of diazepam metabolism in the kidney, renal microsomal diazepam metabolic activities were determined in the Dark Agouti (DA), Sprague-Dawley (SD), Brown Norway (BN) and Wistar (WS) strains of rat. We found that the major pathway of diazepam metabolism in the kidney was diazepam N-demethylation, which is different from that in the liver, 3-hydroxylation. A Dose-course (12.5-200 mu M of diazepam) Study revealed that the DA and WS male rats had higher diazepam N-demethylation activity than the SD and BN rats. In contrast to the males, a lower activity of diazepam N-demethylation was observed in female BN rats. By Western blot analysis, constitutive protein expressions of cytochrome P450 (CYP) 2C11, which is responsible for diazepam N-demethylation, were detected in the 4 strain in both the male and female rats, and the BN rats had lower expression levels of CYP2C11 protein. However, we did not observe significant differences in the kinetic parameters of diazepam N-demethylation. Our results suggested that there was a strain difference in CYP-dependent diazepam N-demethylation in the rat kidney, which is different from the finding in liver microsomes.
  • Noriaki Sakai, Mayumi Ishizuka
    EXPERT OPINION ON DRUG METABOLISM & TOXICOLOGY 5 11 1421 - 1433 2009年11月 [査読有り][通常論文]
     
    Rats are an important tool in pharmacology and toxicology. The authors focus on rat P450s in relation to diazepam metabolism. In particular, considerable attention is devoted to the CYP2D subfamily, which is a group of highly polymorphic enzymes. First, the metabolic profiles of diazepam of humans and other animals are compared. In this review, the authors describe a novel genetic polymorphism of diazepam observed in commonly used rat strains and compare it to human genetic polymorphisms. The genetic basis underlying diazepam polymorphism in rats is also discussed. The authors conclude that the metabolic capacities and major metabolic pathways of diazepam are quite different among rat strains and in the Wistar strain due to CYP2D3 genetic polymorphism, which is independent of the debrisoquine polymorphism catalyzed by CYP2D2. The situation, in which major metabolites differ depending on animal strain, will be highly problematic not only in pharmacokinetic studies of test compounds, but also in pharmacological or toxicological tests. This may provide researchers who use experimental animals insights into important aspects of the genetic background of experimental animals. Thus, great caution must be taken in the choice of rat strains for studies of drug metabolism.
  • Shouta M. M. Nakayama, Tomoko Tanaka-Ueno, Kentaro Q. Sakamoto, Shoichi Fujita, Mayumi Ishizuka
    JOURNAL OF VETERINARY MEDICAL SCIENCE 71 10 1407 - 1411 2009年10月 [査読有り][通常論文]
     
    Novel cytochrome P450 1A(CYP1A) cDNA fragments were isolated from the liver of mile Japanese amphibian species using reverse transcription polymerase chain reaction (RT-PCR). Degenerate PCR primers were used to amplify 122-bp fragments of CYP1A cDNAs. Construction of a phylogenetic tree revealed that urodele and anuran amphibians formed two branches. Within the anuran species, three branches were formed: 1) Ranidae and Rhacophoridae, 2) Bufo japonicus formosus and Hyla japonica, and 3) Xenopus laevis. The cDNA nucleotide sequence of these CYP1A fragments showed identities ranging 72-98% (all), 72-78% (Anura vs, Urodela), 75 to 98% (Anura), 81% (Urodela), 74-80% (Xenopus laevis vs. nine Japanese amphibians).
  • Marumi Ohno, Kentaro Q. Sakamoto, Mayumi Ishizuka, Shoichi Fujita
    PHYTOTHERAPY RESEARCH 23 8 1134 - 1139 2009年08月 [査読有り][通常論文]
     
    Polyphenols have been shown to have potent antioxidant activity, and therefore, food containing polyphenols is expected to contribute to the prevention of cancer. However, food contains not only polyphenols but also various other constituents. We used the Ames test to investigate the effects of crude extracts of whole cacao products, which are known to be rich in polyphenols, on the mutagenicity of benzo[a]pyrene (B[a]P) in Salmonella typhimurium strain TA 98 and tert-butyl hydroperoxide (t-BuOOH) in S. typhimurium strain TA 102. B[a]P induces mutagenicity by metabolic activation and t-BuOOH induces it by generation of free radicals. While white chocolate did not modulate the numbers of revertant colonies produced by B[a]P treatment, milk chocolate and cacao powder extracts did. On the other hand, surprisingly, none of the cacao products tested affected the number of revertant colonies when t-BuOOH was used as the mutagen. At maximum concentration (13.25 mg cacao powder/ml), the crude cacao powder extract reduced ethoxyresorufin O-deethylase activity to 17.4% of the control, suggesting that whole cacao products inhibit cytochrome P450 (CYP) 1A activity. In conclusion, inhibition of CYP1A activity by cacao products may prevent DNA damage by reducing metabolic activation of carcinogens. Copyright (C) 2009 John Wiley & Sons, Ltd.
  • Noriaki Sakai, Kentaro Q. Sakamoto, Shoichi Fujita, Mayumi Ishizuka
    DRUG METABOLISM AND DISPOSITION 37 8 1703 - 1710 2009年08月 [査読有り][通常論文]
     
    Cytochrome P450 (P450) 2D2 (CYP2D2) enzyme is known to metabolize the majority of typical substrates of the human CYP2D6 enzyme, which is the most extensively characterized polymorphic drug-metabolizing enzyme. Despite its impact on drug metabolism in rats, the transcriptional regulation of CYP2D2 remains to be elucidated. We clarified the molecular mechanism of CYP2D2 gene expression. The CYP2D2 gene was positively regulated by the poly(C)-binding protein heterogeneous nuclear ribonucleoprotein K (hnRNP K) through a transcriptional regulatory element located in the 5'-flanking region from -94 to -113. To date, nothing is known about the potential role of hnRNP K in P450 gene regulation. Thus, this is the first report that hnRNP K protein is involved in CYP2D2 gene regulation. Furthermore, we elucidated the genetic basis of the extremely low expression of CYP2D2 mRNA in Dark Agouti (DA) rats. Because of its relatively low abundance, DA rats have been frequently used for the study of CYP2D substrate metabolism as the animal model of the poor metabolizer phenotype for CYP2D6 compared with Sprague-Dawley rats as an extensive metabolizer phenotype. We found a single substitution within the transcriptional regulatory element of the CYP2D2 gene in DA rats. The mutation was detected in the polypyrimidine sequence that is the preferred binding site for hnRNP K protein. The mutation within the transcriptional regulatory element attenuated the binding of hnRNP K protein. In conclusion, decreased recruitment of hnRNP K protein to the mutated sequence causes the low expression of CYP2D2 mRNA in DA rats.
  • Khlood M. El Bohi, Yoshiharu Hashimoto, Kaampwe Muzandu, Yoshinori Ikenaka, Zein Shaban Ibrahim, Akio Kazusaka, Shoichi Fujita, Mayumi Ishizuka
    JAPANESE JOURNAL OF VETERINARY RESEARCH 57 2 109 - 118 2009年08月 [査読有り][通常論文]
     
    Pleurotus cornucopiae (PC) mushrooms are found in the field and commonly known in Japan as Tamogidake mushrooms. The present study investigated the protective effects of an aqueous extract of PC on carbon tetrachloride (CCl4)-induced hepatotoxicity and the possible mechanism involved in this protection including cytochrome P450 (CYP) 2E1. Wistar rats were pretreated with aqueous extracts of PC (0, 100, 200, and 400 mg/kg) orally for 8 days prior to the intraperitoneal. administration of a single dose of CCl4 (0.5 ml/kg) or corn oil. Pretreatment with PC mushroom extract significantly prevented the increased serum enzyme activities of alanine and aspartate aminotransferases in a dose-dependent manner, and suppressed the expression of CYP2E1. PC mushroom extract also protected hepatocytes from the damage effects of CCl4 as remarked by histological and electromicroscopical findings. It was concluded that repeated daily doses of aqueous extracts of PC mushroom reduced the toxic effects exerted by CCl4 on the liver.
  • Kenzi Nakano, Mayumi Ishizuka, Kentaro Q. Sakamoto, Shoichi Fujita
    BIOMETALS 22 2 345 - 351 2009年04月 [査読有り][通常論文]
     
    Accumulating evidence, including experiments using cytochrome P450 1a2 (Cyp1a2) gene knock-out mice (Cyp1a2(-/-)), indicates that the development of chemically induced porphyria requires the expression of CYP1A2. It has also been demonstrated that iron enhances and expedites the development of experimental uroporphyria, but that iron alone without CYP1A2 expression, as in Cyp1a2(-/-) mice, does not cause uroporphyria. The role of iron in the development of porphyria has not been elucidated. We examined the in vivo effect of iron deficiency on hepatic URO accumulation in experimental porphyria. Mice were fed diets containing low (iron-deficient diet (IDD), 8.5 mg iron/kg) or normal (normal diet (ND), 213.7 mg iron/kg) levels of iron. They were treated with 3-methylcholanthrene (MC), an archetypal inducer of CYP1A, and 5-aminolevulinate (ALA), precursors of porphyrin and heme. We found that uroporphyrin (URO) levels and uroporphyrinogen oxidation (UROX) activity were markedly increased in ND mice treated with MC and ALA, while the levels were not raised in IDD mice with the same treatments. CYP1A2 levels and methoxyresorufin O-demethylase (MROD) activities, the CYP1A2-mediated reaction, were markedly induced in the livers of both ND and IDD mice treated with MC and ALA. UROX activity, supposedly a CYP1A2-dependent activity, was not enhanced in iron-deficient mice in spite of the fact of induction of CYP1A2. We showed that a sufficient level of iron is essential for the development of porphyria and UROX activity.
  • Kentaro Q. Sakamoto, Katsufumi Sato, Mayumi Ishizuka, Yutaka Watanuki, Akinori Takahashi, Francis Daunt, Sarah Wanless
    PLOS ONE 4 4 e5379  2009年04月 [査読有り][通常論文]
     
    An ethogram is a catalogue of discrete behaviors typically employed by a species. Traditionally animal behavior has been recorded by observing study individuals directly. However, this approach is difficult, often impossible, in the case of behaviors which occur in remote areas and/or at great depth or altitude. The recent development of increasingly sophisticated, animal-borne data loggers, has started to overcome this problem. Accelerometers are particularly useful in this respect because they can record the dynamic motion of a body in e. g. flight, walking, or swimming. However, classifying behavior using body acceleration characteristics typically requires prior knowledge of the behavior of free-ranging animals. Here, we demonstrate an automated procedure to categorize behavior from body acceleration, together with the release of a user-friendly computer application, "Ethographer''. We evaluated its performance using longitudinal acceleration data collected from a foot-propelled diving seabird, the European shag, Phalacrocorax aristotelis. The time series data were converted into a spectrum by continuous wavelet transformation. Then, each second of the spectrum was categorized into one of 20 behavior groups by unsupervised cluster analysis, using k-means methods. The typical behaviors extracted were characterized by the periodicities of body acceleration. Each categorized behavior was assumed to correspond to when the bird was on land, in flight, on the sea surface, diving and so on. The behaviors classified by the procedures accorded well with those independently defined from depth profiles. Because our approach is performed by unsupervised computation of the data, it has the potential to detect previously unknown types of behavior and unknown sequences of some behaviors.
  • Kentaro Q. Sakamoto, Katsufumi Sato, Yasuhiko Naito, Yoshiaki Habara, Mayumi Ishizuka, Shoichi Fujita
    JOURNAL OF VETERINARY MEDICAL SCIENCE 71 3 341 - 344 2009年03月 [査読有り][通常論文]
     
    We investigated the blood status of 9 Weddell seal mothers and 9 pups during the breeding season ill a field study conducted from November to December 2004 at a breeding colony in Antarctica. The blood glucose and total cholesterol concentrations were higher ill the Pups than in the mothers. On the other hand, the blood urea nitrogen concentration was lower in the pups than in the mothers. Growth-associated depletion of blood triglyceride was observed in the pups and may have been due to the post-weaning fast. The results characterize the blood status of Weddell seals in relation to physiological adaptations for breeding.
  • Noriaki Sakai, Konomu Saito, Kentaro Q. Sakamoto, Mayumi Ishizuka, Shoichi Fujita
    DRUG METABOLISM AND DISPOSITION 37 2 268 - 271 2009年02月 [査読有り][通常論文]
     
    Diazepam (7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one) is widely used as a sedative, hypnotic, and anti-anxiety drug. At low diazepam concentrations, p-hydroxylation is the major metabolic pathway in rat liver microsomes. However, there are marked (similar to 300-fold) inter-and intrastrain differences in the activity among Sprague-Dawley, Brown Norway, Dark Agouti, and Wistar rats. In our previous study, we determined that a deficiency of CYP2D3 protein, not CYP2D2, was responsible for the inter-and intrastrain differences in diazepam p-hydroxylation (Drug Metab Dispos 33:1657-1660, 2005). Quantitative real-time polymerase chain reaction (PCR) did not provide enough evidence to explain the inter-and intrastrain differences in the expression of CYP2D3 protein. Nucleotide sequence analysis revealed the insertion of a thymine in exon 8 of the CYP2D3 gene in the poor diazepam metabolizers. This single nucleotide mutation caused a shift in the reading frame and introduced a premature termination signal. It is noteworthy that the heme binding region, which is essential to maintain proper heme binding and active cytochrome P450 enzymes, was consequently deleted by the premature termination signal. In contrast, no mutation was detected in the CYP2D3 gene of extensive metabolizers. Thus, the truncated CYP2D3 must be a nonfunctional enzyme in poor metabolizers. In addition, we developed a convenient and specific genotyping assay using PCR-restriction, fragment-length polymorphism to distinguish homozygotes from heterozygotes. The genotyping gave results fully consistent with those of the inter-and intrastrain differences in diazepam p-hydroxylation.
  • Zein S. Ibrahim, Mayumi Ishizuka, Mohamed Soliman, Khlood ElBohi, Wageh Sobhy, Kaampwe Muzandu, Azza M. Elkattawy, Kentaro Q. Sakamoto, Shoichi Fujita
    JAPANESE JOURNAL OF VETERINARY RESEARCH 56 3 119 - 128 2008年11月 [査読有り][通常論文]
     
    Nigella sativa (family Ranunculaceae) is an annual plant that has been traditionally used on the Indian subcontinent and in Middle Eastern countries. In this study, we investigated the effect of N. sativa oil on the drug-metabolizing cytochrome P450 (CYP) enzymes and whether it has a protective effect against the acute hepatotoxicity Of CCl4. Intraperitoneal injection of rats with CCl4 drastically decreased CYP2E1, CYP2B, CYP3A2, CYP2C11, and CYP1A2 mRNA and protein expressions. Oral administration of 1 ml/kg N. sativa oil every day for one week prior to CCl4 injection alleviated CCl4-induced suppression of CYP2B, CYP3A2, CYP2C11, and CYP1A2. Moreover, CCl4 increased iNOS and TNF alpha mRNA, while N. sativa oil administration for one week prior to CCl4 injection downregulated the CCl4-induced iNOS mRNA and up-regulated IL-10 mRNA. These results indicate that N. sativa oil administration has a protective effect against the CCl4-mediated suppression of hepatic CYPs and that this protective effect is partly due to the downregulation of NO production and up-regulation of the anti-inflammatory IL-10.
  • Abu Daude NH, Kariwa H, Tkachenko E, Dzagurnova T, Medvedkina O, Tkachenko P, Ishizuka M, Seto T, Miyashita D, Sanada T, Nakauchi M, Yoshii K, Maeda A, Yoshimatsu K, Arikawa J, Takashima I
    The Japanese journal of veterinary research 56 3 151 - 165 3 2008年11月 [査読有り][通常論文]
     
    Puumala virus (PUUV), a causative agent of hemorrhagic fever with renal syndrome (HFRS), is prevalent in Europe and European Russia. No vaccine has been developed for PUUVassociated HFRS, primarily because of the low viral yield in cultured cells. A PUUV strain known as DTK/Ufa-97 was isolated in Russia and adapted for growth in Vero E6 cells maintained in serum-free medium. The DTK/Ufa-97 strain produced a higher viral titer in serumfreemedium, suggesting that it may prove useful in the development of an HFRS vaccine.When PUUV-infected Vero E6 cells were grown in serum-free medium, the DTK/Ufa-97 strain yielded more copies of intracellular viral RNA and a higher viral titer in the culture fluid than did the Sotkamo strain. Phylogenetic analysis revealed that PUUVs can be classified into multiple lineages according to geographical origin, and that the DTK/Ufa-97 strain is a member of the Bashkiria-Saratov lineage. The deduced amino acid sequences of the small, medium, and large segments of the DTK/Ufa-97 strain were 99.2% to 100%, 99.3% to 99.8%, and 99.8% identical, respectively, to those of the Bashkirian PUUV strains and 96.9%, 92.6%, and 97.4% identical, respectively, to those of the Sotkamo strain, indicating that the PUUVs are genetically diverse. However, DTK/Ufa-97 and other strains of PUUV exhibited similar patterns of binding to a panel of monoclonal antibodies against Hantaan virus. In addition, diluted antisera (i.e., ranging from 1:160 to 1:640) specific to three strains of PUUV neutralized both homologous and heterologous viruses. These results suggest that the DTK/Ufa-97 strain is capable of extensive growth and is antigenically similar to genetically distant strains of PUUV.
  • Mayumi Ishizuka, Kazutoshi Fujioka, Takayuki Shibamoto
    JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 56 15 6093 - 6096 2008年08月 [査読有り][通常論文]
     
    A recently developed headspace/solid-phase microextraction/gas chromatograph (GC) equipped with a nitrogen-phosphorus detector (NPD) (HS/SPME/GC/NPD) method was used to analyze acrylamide formed in an aqueous polyacrylamide solution (25%) treated by heat or photo-irradiation. Original polyacrylamide contained 0.43 +/- 0.11 mu g/mL of acrylamide. When polyacrylamide solution was heated at 70 degrees C for 16 h with 0.5% potassium persulfate, the amount of acrylamide increased to 1.02 +/- 0.11 mu g/mL. When polyacrylamide solution was irradiated by UV (lambda = 300 nm) for 16 h with 0.05% 2-anthraquinone sulfate sodium salt, the amount of acrylamide increased to 1.14 +/- 0.54 mu g/mL. Polyacrylamide has been used in cosmetic formulations. The present study, therefore, suggests that there is another route of acrylamide exposure to humans in addition to foods and beverages.
  • Mayumi Ishizuka, Tsutomu Tanikawa, Kazuyuki D. Tanaka, Min Heewon, Fumie Okajima, Kentaro Q. Sakamoto, Shoichi Fujita
    JOURNAL OF TOXICOLOGICAL SCIENCES 33 3 283 - 291 2008年08月 [査読有り][通常論文]
     
    Warfarin is commonly used worldwide as a rodenticide. It inhibits coagulation of blood by inhibiting vitamin K 2,3-epoxide reductase (VKOR) activity. An inadequate supply of vitamin K blocks the production of prothrombin and causes hemorrhage. It has been reported that repeated or long-term treatments with this drug cause resistance in wild rodents. However, the mechanism of warfarin resistance in rodents is still not known precisely. Recent studies reported and identified the function of the molecule, vitamin K epoxide reductase complex subunit 1 (VKORC1), which is the main unit of VKOR. An amino acid substitution in VKORC1 is one of the supposed mechanisms of warfarin resistance. An accelerated detoxification system involving cytochrome P450 (CYP) could also cause the rodenticide resistance. Administration of SKF-525A, a potent inhibitor for P450, increased the mortality due to reduction of warfarin metabolism in warfarin-resistant rats. Meanwhile, the appearance of warfarin-resistant rodents has led to the development of the more effective and toxic rodenticide superwarfarin, which is widely used in Europe and the USA. However, animals resistant to this second-generation rodenticide have already been reported in Europe. In this review, we focus on the mechanism and the pleiotropic effects of pesticide resistance in wild rodents.
  • Gihan G. Moustafa, Zein S. Ibrahim, Mohamed M. Ahmed, Mervat H. Ghoneim, Kentaro Q. Sakamoto, Mayumi Ishizuka, Shoichi Fujita
    JAPANESE JOURNAL OF VETERINARY RESEARCH 56 2 109 - 118 2008年08月 [査読有り][通常論文]
     
    The health hazards of individual organophosphorus insecticides have been characterized by their acute toxicity, mainly by investigating their cholinesterase inhibition. However, the chronic effects of most of these toxicants on the drug-metabolizing enzymes have not been investigated. Profenofos (O-4-bromo-2-chlorophenyl O-ethyl S-propyl phosphorothioate) is an organophosphorus pesticide widely used in cotton cultivation. In the present study, we investigated the effect of profenofos on male-specific cytochrome P450 (CYP) enzymes in adult Wistar rats. We orally administered 17.8 mg/kg body weight, twice weekly for 65 days. Profenofos downregulated levels of hepatic and testicular CYP2C11 and CYP3A2 mRNA and protein expression. Testicular aromatase (CYP19A) mRNA was decreased in the profenofos-treated rats compared to controls. Overall, the present study suggests that profenofos acts as an endocrine disruptor of male-specific CYP enzymes and affects testosterone concentration, which implicates its deleterious effects on animal or human males chronically exposed to organophosphorus pesticide.
  • Seiko Sasaki, Fumihiro Sata, Shizue Katoh, Yasuaki Saijo, Sonomi Nakajima, Noriaki Washino, Kanae Konishi, Susumu Ban, Mayumi Ishizuka, Reiko Kishi
    AMERICAN JOURNAL OF EPIDEMIOLOGY 167 6 719 - 726 2008年03月 [査読有り][通常論文]
     
    Maternal smoking during pregnancy can result in both pregnancy complications and reduced size of the fetus and neonate. Among women who smoke, genetic susceptibility to tobacco smoke also is a likely causative factor in adverse pregnancy outcomes. A prospective cohort study was conducted among 460 pregnant women who delivered live singletons in Sapporo, Japan, from 2002 to 2005. Multiple linear regression models were used to estimate associations of maternal smoking and polymorphisms in two genes encoding N-nitrosamine-metabolizing enzymes-NAD(P)H: quinone oxidoreductase 1 (NQO1) and cytochrome P-450 2E1 (CYP2E1)-with birth size. Among infants born to smokers with the NQO1 homozygous wild-type allele, birth weight, birth length, and birth head circumference were significantly reduced (p < 0.01 for each factor). For the homozygous wild-type CYP2E1 allele, birth weight was lower by an estimated 195 g (standard error, 55; p < 0.001) among smokers. These genotypes did not confer adverse effects among women who had never smoked or who quit smoking during the first trimester. The adverse effects of maternal smoking on infant birth size may be modified by maternal genetic polymorphisms in N-nitrosamine-metabolizing enzymes among Japanese subjects. These results may help in directing smoking cessation interventions during pregnancy, especially among susceptible women.
  • Nobuo Sasaki, Noriaki Sakai, Yoshinori Ikenaka, Tomomi Kamiya, Min Heewon, Kentaro Q. Sakamotoo, Mayumi Ishizuka, Shoichi Fujita
    JOURNAL OF VETERINARY MEDICAL SCIENCE 70 3 223 - 226 2008年03月 [査読有り][通常論文]
     
    Furazolidone (FZ), one of the nitrofuran fungicides, is used as a veterinary medicine in the Middle and Far Eastern countries. In this study, FZ (125 mg/kg) was administered orally to Wistar rats for 3 days. Results of the Ames test using the S-9 fraction of rats treated with FZ showed a significant increase in the number of revertant colonies. Western blot analysis of hepatic CYP isozymes induced by FZ, revealed a remarkable induction of CYP1A1 apoprotein, but CYP1A2 and CYP2E1 apoproteins were not altered. In addition, the expression of CYP1A1 mRNA level in rats treated with FZ by RT-PCR was significantly enhanced by FZ treatment. We concluded that FZ is apparently mutagenic and induces transcription of the CYP1A1 isozyme, which metabolically activates numerous promutagens, in hepatocytes.
  • Nahla A. G. Ahmed Refat, Zein Shaban Ibrahim, Gihan Gamal Moustafa, Kentaro Q. Sakamoto, Mayumi Ishizuka, Shoichi Fujita
    JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY 22 2 77 - 84 2008年 [査読有り][通常論文]
     
    Azo dyes form a major class of chemically related compounds that are ubiquitous in foods, paints, printing inks, cosmetics, and also used as biological stains in histological and histopathological laboratories and clinics. Sudan I, sudan III, and sudan IV have been classified as category 3 carcinogens by International Agency for Research on Cancer. In this study, we investigated the difference between these three sudan dyes in induction of CYP1A1. We intraperitoneally treated Wistar rats with each of the three sudan dyes (I, III, and IV) for 3 days. Treatment of Wistar rats with sudan I produced the highest induction of CYP1A1 protein and mRNA whereas treatment of Wistar rats with sudan III produced about two third of CYP1A1 protein and mRNA than induced by sudan I. Furthermore, treatment of Wistar rats with sudan IV produced the lowest induction of CYP1A1 protein and mRNA which is about two third of that induced with sudan III treatment. We further investigated the effect of these sudan dyes on CYP1A1 transcription through investigating the xenobiotic response element (XRE) reporter activity in HepG2. The XRE reporter activity study showed the same trend of activity of sudan dyes comparable to the effects on CYP1A1 mRNA and protein. Immunohistochemical study revealed a differential pattern of distribution of CYP1A1 protein in rat liver among the three sudan dyes, apparent in the centrilobular and midzonal region with sudan III, progressing to panlobular with sudan I, whereas sudan IV showed a reversal of pattern of induction with the most intense staining in the periportal region. Our results suggest that there is an inverse relationship between the molecular size of the three sudan dyes and their ability to induce CYP1A. (c) 2008 Wiley Periodicals, Inc.
  • Gihan Gamal Moustafa, Zein Shaban Ibrahim, Yoshiharu Hashimoto, M. Alkelch Alkelch, Kentaro Q. Sakamoto, Mayumi Ishizuka, Shoichi Fujita
    ARCHIVES OF TOXICOLOGY 81 12 875 - 881 2007年12月 [査読有り][通常論文]
     
    To investigate the effect of the phosphorothoate insecticide profenofos on male specific gene expression on rat testis, 16-week-old Wistar rats were orally administered at dose of 17.8 mg/kg twice weekly for 65 days. Gene expression in the testes was monitored by DNA microarray analysis and real-time RT-PCR, which revealed that genes related to steroidogenesis including cytochrome P450 17A1 (CYP17A1), steroidogenic acute regulatory protein (StAR) and CYP11A1 were significantly increased. Besides the testes were histopathologicaly examined, which revealed testicular destruction and degeneration represented by a layer of columnar epithelium, oedematous changes surrounding the seminiferous tubules besides vacuolated spermatogonial cells and more elongated Leydig cells. These data suggest that profenofos considered as one of the male reproductive toxicants. Furthermore, we propose that the above three steroidogenic-related genes and the gene of acrosomal reaction as potential biomarkers of testicular toxicity.
  • Ban S, Kondo T, Ishizuka M, Sasaki S, Konishi K, Washino N, Fujita S, Kishi R
    Fukuoka igaku zasshi = Hukuoka acta medica 98 5 208 - 214 5 2007年05月 [査読有り][通常論文]
     
    The field of molecular biology currently faces the need for a comprehensive method of evaluating individual differences derived from genetic variation in the form of single nucleotide polymorphisms (SNPs). SNPs in human genes are generally considered to be very useful in determining inherited genetic disorders, susceptibility to certain diseases, and cancer predisposition. Quick and accurate discrimination of SNPs is the key characteristic of technology used in DNA diagnostics. For this study, we first developed a DNA microarray and then evaluated its efficacy by determining the detection ability and validity of this method. Using DNA obtained from 380 pregnant Japanese women, we examined 13 polymorphisms of 9 genes, which are associated with the metabolism of environmental chemical compounds found in high frequency among Japanese populations. The ability to detect CYP1A1 I462V, CYP1B1 L432V, GSTP1 I105V and AhR R554K gene polymorphisms was above 98%, and agreement rates when compared with real time PCR analysis methods (kappa values) showed high validity: 0.98 (0.96), 0.97 (0.93), 0.90 (0.81), 0.90 (0.91), respectively. While this DNA microarray analysis should prove important as a method for initial screening, it is still necessary that we find better methods for improving the detection of other gene polymorphisms not part of this study.
  • Mayumi Ishizuka, Fumie Okajima, Tsutomu Tanikawa, Heewon Min, Kazuyuki D. Tanaka, Kentaro Q. Sakamoto, Shoichi Fujita
    DRUG METABOLISM AND DISPOSITION 35 1 62 - 66 2007年01月 [査読有り][通常論文]
     
    Wild roof rats (Rattus rattus) live in proximity to human habitats, and they may carry numerous pathogens of infectious diseases. Pest control is important for public health, and warfarin is a commonly used rodenticide worldwide. However, continual use of warfarin may cause drug resistance in rodents and lead to failure of their control, especially in urbanized areas. In warfarin-resistant rats, the warfarin level in plasma was significantly lower after oral administration than that in the control warfarin-sensitive rats. Warfarin is metabolized by cytochrome P450 (P450), and hydroxylation of warfarin by P450 isoforms was significantly higher in warfarin-resistant rats (2-fold). Western blot analysis indicated that the level of CYP3A2 expression in warfarin-resistant rats was significantly larger than in warfarin-sensitive rats. The NADPH-P450 reductase activities in resistant rats were 8-fold higher than those in sensitive rats. In vivo, the administration of the P450 potent inhibitor proadifen (SKF-525A) increased the mortality of warfarin in the warfarin-resistant roof rats. We concluded that the mechanism of warfarin resistance in Tokyo roof rats is caused by increased clearance of warfarin.
  • M. Ishizuka, S. Nagai, K. Q. Sakamoto, S. Fujita
    XENOBIOTICA 37 5 503 - 513 2007年 [査読有り][通常論文]
     
    Imatinib is a highly selective tyrosine kinase inhibitor, and is used for the treatment of chronic myeloid leukaemia (CML) and gastrointestinal stromal tumours (GISTs) in humans. The aim of this study is to determine the in vitro and in vivo pharmacokinetics of imatinib in dogs and which cytochrome P450 (CYPs) contribute to its metabolism. Imatinib was administered orally or intravenously to dogs and the time of the peak concentration (T-max) of imatinib was 4 - 9 h. The mean half-life was 622 +/- 368 min, and the AUC was 1256 +/- 809 mM * min after oral administration. The range of C0 of intravenously injected dogs was 12 - 24 mM. The half-life and AUC after intravenous injection were 206 +/- 112 min and 1026 +/- 371 mu M * min, respectively. Recombinant system of dog CYP3A12 and CYP2C21 showed that CYP3A12 contributed to the metabolism of imatinib. The inhibition of CYP3A-dependent activity using a rat anti-CYP3A antibody or ketoconazole revealed that CYP3A12 plays a major role in the metabolism of imatinib in dog liver microsomes.
  • Kaampwe Muzandu, Mayumi Ishizuka, Kentaro Q. Sakamoto, Zein Shaban, Khlood El Bohi, Akio Kazusaka, Shoichi Fujita
    TOXICOLOGY AND APPLIED PHARMACOLOGY 215 3 330 - 340 2006年09月 [査読有り][通常論文]
     
    Peroxynitrite formed by the reaction of superoxide and nitric oxide is a highly reactive species with a role in various pathological processes such as cancer, chronic inflammation, and cardiovascular and neurological diseases. In the present study, the effect of the carotenoids, lycopene and beta-carotene, on peroxynitrite-mediated modifications in plasmid DNA as well as cellular DNA and proteins were investigated. In pUC18 plasmid DNA, these carotenoids strongly inhibited DNA strand breaks caused by peroxynitrite generated from 3-morpholinosydnonimine (SIN-1). SIN-1 was also used to determine effects on DNA damage and protein tyrosine nitration in Chinese hamster lung fibroblasts. SIN-1 dose-dependently increased nitration of proteins in cells above basal levels as determined by Western blotting. This nitration was inhibited in the presence of the uric acid as well as lycopene. Physiological concentrations (0.31 - 10 mu M) of lycopene and beta-carotene also had protective effects on DNA damage, as measured by the comet assay. Lycopene significantly reduced DNA damage particularly, in the median range of concentrations (2.5 mu M). The protective effects of lycopene and beta-carotene could be due to their scavenging of reactive oxygen (ROS) and/or nitrogen species (RNS) as they reduce the amount of intracellular ROS/RNS produced following treatment with SIN-1 by as much as 47.5% and 42.4%, respectively. The results obtained in this study suggest that carotenoids may alleviate some of the deleterious effects of peroxynitrite and possibly other reactive nitrogen species as well in vivo. (c) 2006 Elsevier Inc. All rights reserved.
  • M. Ishizuka, J. J. Lee, M. Masuda, F. Akahori, A. Kazusaka, S. Fujita
    Veterinary Research Communications 30 5 505 - 512 2006年07月 [査読有り][通常論文]
     
    CYP2D-related drug metabolism in liver microsomes from animals of the Canoidea super family, i.e. mink (Mustela vison) , bears (Ursus arctos), foxes (Vulpes vulpes) and dogs, were investigated. Propranolol, bunitrolol and imipramine, which are typically substrates of CYP2D subfamilies, were used in the experiment. All the animals of the Canoidea superfamily that were tested lacked the ability to catalyse 7-hydroxylation of propranolol, which is one of the major metabolic pathways in rats. Stereoselectivity of propranolol metabolism was towards (S)-propranolol in all the reactions of the animals tested with the exception of mink, which showed a selective tendency towards (R)-propranolol in N-dealkylation. As far as metabolic patterns of (R)- and (S) -propranolol are concerned, bears, foxes and dogs are alike, but minks are somewhat different. Liver microsomes from mink showed, among the animals of the Canoidea superfamily, the lowest propranolol hydroxylase activity at 4- and 5-positions and imipramine 2-hydroxylation and N-demethylation activities. We could not detect bunitrolol 4-hydroxylation in mink liver microsomes at the low substrate concentration used. We conclude that mink have the lowest activity of CYP2D-related xenobiotic metabolism among the Canoidea superfamily. © Springer Science + Business Media, Inc. 2006.
  • S Sasaki, T Kondo, F Sata, Y Saijo, S Katoh, S Nakajima, M Ishizuka, S Fujita, R Kishi
    MOLECULAR HUMAN REPRODUCTION 12 2 77 - 83 2006年02月 [査読有り][通常論文]
     
    Genetic susceptibility to tobacco smoke might have relation to adverse pregnancy outcomes. To estimate the effects of maternal smoking and genetic polymorphisms on infant birth weight and length, we conducted a prospective cohort study of 293 women who delivered singleton live births in Sapporo, Japan. Birth weight and length were significantly lower among infants born to continuously smoking women having the aryl hydrocarbon receptor (AhR) wild type genotype (Arg/Arg; 211 g +/- 76 g; 1.2 cm +/- 0.4 cm, p < 0.01 and p < 0.01, respectively), the CYP1A1 variant genotype (m1/m2 + m2/m2; 170 g +/- 64 g, 0.8 cm +/- 0.3 cm, p < 0.01 and p < 0.05, respectively), or the GSTM1 null genotype (171 g +/- 58 g, 0.6 cm +/- 0.3 cm, p < 0.01 and p < 0.05, respectively). When combinations of these genotypes were considered, birth weight and length were significantly lower for infants of continuously smoking women in the AhR wild type + CYP1A1 variant group (315 g +/- 116 g; 1.7 cm +/- 0.6 cm, p < 0.01 and p < 0.01, respectively) and in the CYP1A1 variant + GSTM1 null group (237 g +/- 92 g; 1.3 cm +/- 0.5 cm, p < 0.05 and p < 0.01, respectively). These genotypes did not confer adverse effects among women who had never smoked; therefore, maternal smoking in combination with maternal AhR, CYP1A1 and GSTM1 genetic polymorphisms may adversely affect infant birth size.
  • A Jinno, Y Maruyama, M Ishizuka, A Kazusaka, A Nakamura, S Fujita
    JOURNAL OF STEROID BIOCHEMISTRY AND MOLECULAR BIOLOGY 98 1 48 - 55 2006年01月 [査読有り][通常論文]
     
    Equilenin is one of 10 kinds of estrogens that are found in pregnant mares' urine. lt has been used extensively for estrogen replacement therapy in postmenopausal women. Typical inducers of the cytochrome P4501A1 (CYP1A1), such as TCDD, benzo(a)pyrene (B(a)P) and 3-methylcholanthrene, have a planar molecular structure in common and bind to the aryl hydrocarbon receptor (AhR). The structure of equilenin differs from classic estrogens by the presence of two additional double bonds in ring B of the steroid nucleus, and it is planar. This structural similarity of equilenin to the typical AhR agonist prompted us to investigate the capability of equilenin to induce CYP1A1 expression. Administration of equilenin to two mouse strains (C57BL and DBA) that exhibit different degrees of responsiveness to an Ahreceptor agonist and showed that equilenin was capable of dose-dependently increasing both the ethoxyresorufin O-deethylase activity and CYP1a proteins in both strains of mice. Equilenin also induced CYP1A1 mRNA in treated HepG2 cell lines and transcriptional activity in an XRE-directed luciferase reporter gene. Competitive binding studies using C57BL AhR indicated equilenin weakly displaced 3 H-B(a)P from AhR. Together, these data show that equilenin, an equine steroid hormone, served as an AhR ligand in the present study. (c) 2005 Elsevier Ltd. All rights reserved.
  • N Sakai, K Saito, HS Kim, A Kazusaka, M Ishizuka, Y Funae, S Fujita
    DRUG METABOLISM AND DISPOSITION 33 11 1657 - 1660 2005年11月 [査読有り][通常論文]
     
    Diazepam was metabolized to three primary metabolites, 3-hydroxy-diazepam, N-desmethyl-diazepam, and p-hydroxy-diazepam. Our previous studies reported metabolic position-specific inter- or intrastrain differences in diazepam metabolism among Sprague-Dawley, Brown Norway, Dark Agouti, and Wistar rats. Especially, there were marked (similar to 300 fold) inter- or intrastrain differences in diazepam p-hydroxylation activity at low concentration of substrate. In this study, we investigated the enzyme that catalyzes diazepam p-hydroxylation. The activity toward diazepam p-hydroxylation was inhibited by anti-cytochrome P450 2D (CYP2D) antibody, suggesting that this activity was catalyzed by CYP2D isoforms. Comparing the expression levels of the CYP2D subfamily in liver microsomes from various strains of rats using anti-CYP2D2 antibody, we found that there was a band of protein that was consistent with the phenotype of diazepam p-hydroxylation. N-terminal amino acid sequences of the specific protein exactly corresponded to those of CYP2D3, indicating that CYP2D3 might be involved in diazepam p-hydroxylation. Moreover, using rat CYP2D isoforms expressed in yeast, we tested CYP2Ds to catalyze diazepam p-hydroxylation. CYP2D1 and CYP2D2 practically did not participate in diazepam metabolism. On the other hand, diazepam p-hydroxylation was catalyzed by CYP2D3. CYP2D4 had high activity toward diazepam N-desmethylation, but not p-hydroxylation. In conclusion, the polymorphic expression of CYP2D3 caused the inter- or intrastrain differences in diazepam p-hydroxylation among rat strains or intrastrain differences in diazepam p-hydroxylation among rat strains or individuals.
  • K Muzandu, Z Shaban, M Ishizuka, A Kazusaka, S Fujita
    FREE RADICAL RESEARCH 39 4 389 - 398 2005年04月 [査読有り][通常論文]
     
    Catechol estrogens (CEs), such as 4-hydroxyestradiol (4-OHE2), undergo redox cycling during which reactive oxygen species (ROS) such as superoxide (O-2(-)) and the chemically reactive estrogen semiquinone (CE-SQ) and quinone (CE-Q) intermediates are produced. The quinone's putative mutagenicity may be enhanced by ROS and/or reactive nitrogen species. High concentrations of nitric oxide (NO) present during inflammatory conditions may react with (O-2(-)) to form peroxynitrite (ONOO-), a potent oxidant implicated in many pathological conditions. In this study, the possible generation of peroxynitrite from the interaction of CEs and NO and its effect on plasmid DNA and intact cells were investigated. A combination of 4-OHE2 and NO increased the level of single strand breaks (SSB) in plasmid DNA by more than 60% compared to vehicle controls in a metal-free buffer system. 4-OHE2 alone or NO alone had no effect. Results obtained from use of different antioxidants and ROS scavengers suggested a role of peroxynitrite in oxidative stress. In cells, 4-OHE2 or NO alone induced dose-dependent DNA damage as assessed by single cell gel electrophoresis. Co-treatment with 4-OHE2 and NO had an additive effect at lower doses. Generation of intracellular ROS was measured by the oxidation of carboxy-2',7'-dichlorofluorescein diacetate to the fluorescent compound carboxy-2',7'-dichlorofluorescein. NO alone, in oxygenated media, generated little ROS whereas 4-OHE2 produced approximately 70% increase in fluorescence. When added together 4-OHE2 and NO, produced a 2-fold increase in ROS. The generation and involvement of peroxynitrite to this increase was implied since uric acid inhibited it. Generation of peroxynitrite was also observed by use of dihydrorhodamine 123. Therefore, we conclude that combined treatments with 4-OHE2 and NO generated peroxynitrite seen from increased fluorescence and its inhibition by uric acid or combined SOD and catalase treatments. Results reported here suggest a role of peroxynitrite in causing damage to biomolecules when CEs and NO are present simultaneously. This may have biological relevance as high concentrations of NO formed during inflammatory conditions may exacerbate cancers due to estrogens.
  • KM El Bohi, L Sabik, K Muzandu, Z Shaban, M Soliman, M Ishizuka, A Kazusaka, S Fujita
    JAPANESE JOURNAL OF VETERINARY RESEARCH 52 4 163 - 172 2005年02月 [査読有り][通常論文]
     
    Pleurotus cornucopiae (PC) mushroom with a brilliant yellow pileus is found in the field and known in Japan as Tamogi dake mushroom. The purpose of this paper is to investigate the mechanism of the antimutagenic effect of PC mushroom using both the Ames test and Comet assay. We have found a strong inhibitory effect of both aqueous and organic PC extracts on the mutagenicity elicited by benzo [a] pyrene (B [a] P). This inhibition was dose-dependent in reaction mixtures containing cytosolic and microsomal fractions (S-9) from untreated rat liver as well as in those containing S-9 from aryl hydrocarbon receptor (Ah) ligand of Sudan Ill-treated rats. Sudan III was a potent inducer of cytochrome P450 1A (CYP1A) activity. We treated rats with Sudan III to enhance the metabolic activation of B [a] P by the S-9 fraction. To explain whether this antimutagenicity was due to the inhibition of CYP1A activity that metabolically activates B [a] P, we tested the effects of the extracts on activities of CYP1A1 and CYP1A2, represented by ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-demethylase (MROD), respectively. Both aqueous and organic extracts inhibited EROD activity at all dose levels, while the inhibitory effect was only observed at high doses with regard to MROD activity. Furthermore, pre-treatment of Chinese hamster V79cells with PC extracts significantly reduced H2O2-induced-DNA damage, indicating that PC extracts provide a protective effect against oxidative DNA damage. These results indicate that whole-mushroom extracts contain compounds that may inhibit the metabolic activation of B [a] P by CYP1A1 as well as prevent oxidative DNA damage.
  • K Muzandu, K El Bohi, Z Shaban, M Ishizuka, A Kazusaka, S Fujita
    JAPANESE JOURNAL OF VETERINARY RESEARCH 52 4 173 - 184 2005年02月 [査読有り][通常論文]
     
    The consumption of fruits and vegetables is associated with a reduced risk of various ailments, including cancer and cardiovascular diseases. Carotenoids, such as lycopene and beta-carotene, are natural constituents of edible plants and may protect against disease. In this study, the influence of lycopene and beta-carotene on DNA damage caused by catechol-estrogens in vitro is examined. One possible mechanism by which catechol estrogens such as 4-hydroxyestradiol (4-OHE2) and 2-hydroxyestradiol, which cause DNA damage in naked plasmid DNA as well as in cells, contributing to the process of carcinogenesis, is through the generation of reactive oxygen species. It was found that both carotenoids at concentrations ranging from 0.25 to 10 mu M significantly inhibit strand breakage induced by 4-OHE2/copper sulphate by up to 90 %in plasmid DNA with beta-carotene being slightly more effective. No pro-oxidant or cytotoxic effects were observed at the concentrations tested. These carotenoids had a similar, though reduced effect on DNA damage as measured by the comet assay, in Chinese hamster lung fibroblasts. The results obtained show that both lycopene and beta-carotene, most probably and mainly through their potent antioxidant properties, are able to inhibit catechol-estrogen-mediated DNA damage.
  • S Nikaidou, M Ishizuka, Y Maeda, Y Hara, A Kazusaka, S Fujita
    JAPANESE JOURNAL OF VETERINARY RESEARCH 52 4 185 - 192 2005年02月 [査読有り][通常論文]
     
    Green tea contains catechins and caffeine as major constituents. Treatment of rats with green tea (2.5% w/v) significantly increased 7-ethoxycoumarin O-deethylase(7-ECOD), caffeine N-1 demethylase (CN1D) and UDP -glucuronyltransferase (UGT) activities. Treatment with caffeine similarly activated CYP1A2 and related monooxygenases as well as UGT, while treatment with catechins induced UGT activity but not 7-ECOD or CN1D activity. Numbers of benzo [a] pyrene (BP)-induced revertant colonies in an Ames test (mutation assay) with S. typhimurium TA98 as the test strain were markedly larger when BP was preincubated with the liver S-9 (9000 Xg supernatant of liver homogenate) from green tea-treated rats than when preincubated with that from control rats. In a modified Ames assay system in which UGT was activated by the addition of UDP-glucuronic acid to the preincubation mixture, the numbers of revertant colonies in the assay using liver S-9 from green tea-treated rats decreased to a similar level to that in the assay using S-9 from controls. The acceleration of two enzymatic reactions may contribute to the rapid elimination of BP; the first step, the formation of a metabolic intermediate (which is mutagenic) by CYP1A2 and the second, the conjugation of active metabolic intermediates by UGT. We speculated that green tea can reduce the amount of time carcinogens reside in the body and the chance that body tissues will be exposed to active metabolites of carcinogens thorough rapid elimination due to the simultaneous induction of CYP1A2 and UGT activities.
  • S Nikaidou, M Ishizuka, Y Maeda, Y Hara, A Kazusaka, S Fujita
    JOURNAL OF VETERINARY MEDICAL SCIENCE 67 1 137 - 138 2005年01月 [査読有り][通常論文]
     
    Green tea, one of the most popular beverages consumed in Asian countries, has been reported to possess anticarcinogenic and antimutagenic properties. The aim in this study is to test the radical scavenging effect of catechins and caffeine, which were major components of green tea, and if they really prevent oxygen radical-induced mutagenesis. We used TA102 strain of Salmonella typhimurium which is sensitive to hydroxyl radical in the Ames mutation assay. We found that caffeine did not show any effects on mutagenesis in this system, but catechin significantly reduced mutagenesis or genotoxicity caused by hydroxyl radical. This radical-scavenging action of catechins may indeed contribute to the anticarcinogenic activity of green tea as has been proposed.
  • Z Shaban, M Soliman, S El-Shazly, K El-Bohi, A Abdelazeez, K Kehelo, HS Kim, K Muzandu, M Ishizuka, A Kazusaka, S Fujita
    XENOBIOTICA 35 1 51 - 68 2005年01月 [査読有り][通常論文]
     
    The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates a spectrum of toxic and biological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin ( TCDD) and related compounds. The peroxisome proliferator-activated receptor alpha (PPAR alpha) is a member of the nuclear receptor super-family of ligand-activated transcription factors and it functions as an obligate heterodimer with retinoid X-receptor alpha RXR alpha. The aim was to investigate whether the negative cross-talk recently proposed by the present authors between AhR and PPAR alpha on CYP4A and CYP1A has any impact on other cytochrome P450 enzymes. Treatment of male Wistar rats with a PPAR alpha ligand clofibric acid (CA) induced CYP2B1/2 and CYP3A proteins, activities, and the mRNA expression of CYP2B1, CYP2B2, CYP3A1 and CYP3A2, and suppressed CYP2C11 protein, activities and mRNA expression. AhR ligand Sudan III (S.III) treatment decreased basal and CA-induced CYP2B, CYP3A and CYP2C11 protein, activities and mRNA expression. To the best of the authors' knowledge, this is the first study showing the presence of mutual effects of AhR and PPAR alpha on CYP2B and CYP3A and an additive inhibitory effect on CYP2C11 in the livers of male rats.
  • Z Shaban, S El-Shazly, S Abdelhady, Fattouh, I, K Muzandu, M Ishizuka, K Kimura, A Kazusaka, S Fujita
    JOURNAL OF VETERINARY MEDICAL SCIENCE 66 11 1377 - 1386 2004年11月 [査読有り][通常論文]
     
    Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates a spectrum of toxic and biological effects of 2,3,7,8-tetrachloro dibenzo-p-dioxin (TCDD) and related compounds. Peroxisome proliferator activated receptor alpha (PPARalpha) is a nuclear receptor involved in the maintenance of lipid and glucose homeostasis. In this study we hypothesized that one of the possible mechanisms for the effect of TCDD and its related chemicals on fat metabolism could be through down regulation of PPARalpha functions. We treated Wistar rats with an AhR ligand, Sudan III (S.III), and/or PPARalpha ligand, Clofibric Acid (CA), for 3 days. We analysed the expression of one of the PPARalpha-target gene products, CYP4A protein and its mRNA. We also tested HepG2 cells with the afore-mentioned treatments and evaluated their effects on PPARalpha and RXRalpha protein. Treatment of Wistar rats with S.III was found to down regulates CYP4A protein expression and reduced its induction with CA. It also decreased mRNA expressions of CYP4A1, CYP4A2, CYP4A3 and PPARalpha. In HepG2 cells, PPARalpha and RXRalpha protein expression was decreased by S.III treatment in a dose dependent manner. Our results suggest that AhR has an inhibitory effect on PPARa function and a new pathway by which AhR ligands could disturb lipid metabolism.
  • Z Shaban, S El-Shazly, M Ishizuka, K Kimura, A Kazusaka, S Fujita
    ARCHIVES OF TOXICOLOGY 78 9 496 - 507 2004年09月 [査読有り][通常論文]
     
    Fibrates, hypolipidemic drugs, have been reported to suppress the metabolic activities of cytochrome P450 1A1 and 1A2 in rats but the mechanism has not been elucidated. In the present study we tested the hypothesis that the inhibitory effect of fibrates on arylhydrocarbon receptor (AhR) function may be due to their stimulatory effects on PPARalpha. Sudan III (S.III) treatment induced CYP 1A1 and CYP 1A2 protein expression, mRNA and their metabolic activities, methoxyresorufin-O-demethylase (MROD) and ethoxyresorufin-O-deethylase (EROD), in Wistar rats higher than those in the control. Co-treatment of rats with S.III and clofibric acid (CA) caused a 40-50% decrease in the induced levels of CYP1A1 and CYP1A2 protein, mRNA expression and their metabolic activities and reduced AhR protein expression. When we treated HepG2 cells with S.III and/or CA, no suppressive effect on S.III-induced CYP1A1 protein expression due to CA was found. HepG2 cells were transiently transfected with increasing concentrations of PPARalpha mammalian expression vector and exposed to the same treatment. CA co-treatment with S.III decreased AhR protein and S.III-induced CYP1A1 protein expression with increasing dose of PPARalpha transfected into HepG2 cells. Our results demonstrate that the suppressive effect of fibrates on CYP1A is PPARalpha-dependent and suggest that PPARalphahas an inhibitory effect on AhR function.
  • K Saito, N Sakai, HS Kim, M Ishizuka, A Kazusaka, S Fujita
    DRUG METABOLISM AND DISPOSITION 32 9 959 - 965 2004年09月 [査読有り][通常論文]
     
    Knowledge of strain differences in drug metabolism is important for the selection of animals for pharmacokinetic, pharmacodynamic, and toxicological studies. Hepatic microsomes from Sprague-Dawley (SD) and Brown Norway (BN) rats had 300-fold higher diazepam p-hydroxylation activity than Dark Agouti (DA) and Wistar (W) rats at a low diazepam concentration (3 muM). Kinetic studies indicated that diazepam p-hydroxylation in SD and BN rats proceeded with lower K-m and higher V-max values than it did in DA and W rats. However, the expression levels of cytochrome P450 CYP2D1, the reported enzyme for diazepam p-hydroxylation, did not cosegregate with the activity. These results suggest the presence of a new high-affinity diazepam p-hydroxylation enzyme other than CYP2D1 in SD and BN rats. DA rats showed 3- and 2-fold higher diazepam 3-hydroxylation and N-desmethylation activities, respectively, than the other rat strains. In agreement with this, DA rat liver microsomes had a higher expression of CYP3A2, which is responsible for diazepam 3-hydroxylation and partly responsible for N-desmethylation. Values of CLint (V-max/K-m) indicated that p-hydroxy-diazepam is the major metabolite in SD and BN rats, whereas 3-hydroxy-diazepam is the major metabolite in DA and W rats. The sum of the CLint in each strain was in the order of DA > SD = BN >> W. Strain differences in the pharmacodynamics of diazepam between SD and DA rats may be due to these differences in diazepam metabolism. We found that both the rate of elimination of diazepam and the major metabolic pathways in diazepam metabolism differed among the different rat strains due to polymorphic expression of the two enzymes involved in diazepam metabolism.
  • HS Kim, M Ishizuka, A Kazusaka, S Fujita
    JOURNAL OF VETERINARY MEDICAL SCIENCE 66 9 1119 - 1124 2004年09月 [査読有り][通常論文]
     
    Di-(2-ethylhexyl) phthalate (DEHP), a peroxisome proliferator-activated receptor alpha (PPARalpha) ligand, alters the lipid composition of rat testis, yet the mechanism is unclear. In this study, we investigated the effect of DEHP on the synthesis and metabolism of arachidonic acid (AA), a precursor of eicosanoids, in the testis of prepubertal rats. DEHP (100 and 1,000 mg/kg, 5 days) administration caused a significant reduction in activity of cytosolic phospholipase A(2) (cPLA(2)), the rate-limiting enzyme in the AA and eicosanoid synthesis pathways. DEHP increased the expression of 12-lipoxygenase (12-LOX) in rat testis, whereas cyclooxygenase-2 (COX-2) expression was not altered. Cytochrome P450 4A1 (CYP4A1), a product of a PPARalpha-regulated gene, was markedly increased in the testis by DEHP administration. Taken together, DEHP suppresses cPLA(2) activity and induces the AA metabolizing enzymes such as 12-LOX and CYP4A1, resulting in the reduction of AA level. These data suggest that altered AA metabolic cascades may be related to the decrease of testosterone concentration in DEHP-induced testicular atrophy.
  • KQ Sakamoto, M Ishizuka, A Kazusaka, S Fujita
    JAPANESE JOURNAL OF VETERINARY RESEARCH 52 2 85 - 94 2004年08月 [査読有り][通常論文]
     
    In order to examine whether iodine supplements may have caused a global decline in sperm concentrations during the past several decades, the synchronicity of the decline in mean sperm counts and the introduction of iodine supplements was analyzed statistically. A positive correlation between the incidence of thyroid disease and sperm counts has been detected in Europe. In addition, it has been shown that sperm counts began falling around 1965 in the United States, 40years after iodine supplements were introduced. Mean sperm counts before and after 1965 were 111 x 10(6)/ml and 70 x 10(6)/ml, respectively, in calculations weighted by the number of subjects included in each individual publication. The timing of the declines coincided with the introduction of iodine supplements in the United States, France, and the United Kingdom. The implications are that the global decline in sperm concentrations may be caused by iodine intake. Geographical variation in the types of sperm count decline also appears to be present.
  • K Saito, HS Kim, N Sakai, M Ishizuka, A Kazusaka, S Fujita
    JOURNAL OF PHARMACEUTICAL SCIENCES 93 5 1271 - 1278 2004年05月 [査読有り][通常論文]
     
    We observed variations in the metabolism of diazepam in Wistar rats. We studied these variations carefully, and found that the variations are dimorphic and about 17% of male rats of Wistar strain we examined showed two times higher diazepam metabolic activities in their liver microsomes than the rest of animals at the substrate concentrations less than 5 muM. We classified them as extensive metabolizer (EM) and poor metabolizer (PM) of diazepam. No sex difference was observed in the frequency of appearance of EM. Activities of the primary metabolic pathways of diazepam were examined to elucidate the cause of this polymorphism in male Wistar rats. No significant differences were observed in activities of neither diazepam 3-hydroxylation or N-desmethylation between EM and PM rats, while activity of diazepam p-hydroxylation was markedly (more than 200 times) higher in EM rats, indicating that this reaction is responsible for the polymorphism of diazepam metabolism in Wistar rats. We examined the expression levels of CYP2D1, which was reported to catalyze diazepam p-hydroxylation in Wistar rats to find no differences in the expression levels of CYP2D1 between EM and PM rats. The kinetic study on diazepam metabolism in male Wistar rats revealed that EM rats had markedly higher V-max and smaller K-m in diazepam p-hydroxylation than those of PM rats, indicating the presence of high affinity high capacity p-hydroxylase enzyme in EM rats. As a consequence, at low concentrations of diazepam, major pathways of diazepam metabolism were p-hydroxylation and 3-hydroxylation in male EM rats, while in male PM rats, 3-hydroxylation followed byN-desmethylation. Due to this kinetic nature of p-hydroxylase activity, EM rats had markedly higher total CLint of diazepam than that of PM rats. Polymorphism in diazepam metabolism in humans is well documented, but this is the first report, revealing the presence of the polymorphism in diazepam metabolism in rats. The current results infer polymorphic expression of new diazepam p-hydroxylating enzyme with lower K-m than CYP2D1 in EM Wistar rats. (C) 2004Wiley-Liss, Inc. and the American Pharmacists Association.
  • KQ Sakamoto, K Nakai, T Aoto, A Yokoyama, R Ushikoshi, H Hirose, M Ishizuka, A Kazusaka, S Fujita
    CHEMOSPHERE 51 6 491 - 500 2003年05月 [査読有り][通常論文]
     
    Accumulations of polychlorinated dibenzo-p-dioxins, dibenzofurans and coplanar polychlorinated biphenyls were analyzed in common carp (Cyprinus carpio) collected in the Hikiji River, Kanagawa Prefecture, Japan in which dioxin contaminated effluent was released during the period starting from November 1992 to March 2000. Higher levels of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin toxic equivalents were observed in carps collected downstream to the dioxin release site (contaminated site) than the reference site. Modulations of cytochrome P450 (CYP) enzyme in liver; serum estrogen concentration and gonadal somatic index (GSI) were also measured as biomarkers for the contaminants. Total CYP content in livers was markedly higher in male and female carps from the contaminated site relative to the reference site fish. The expression level of the cytochrome P450 1A and Ethoxyresorufin 0-deethylase activity were significantly higher in female carps from the contaminated site than from the reference site. A lower level of plasma estrogen was observed in carps from the contaminated site. The GSI in female carps from the contaminated site was smaller than that recorded at the reference site. The present study indicates that dioxins released to the Hikiji River might induce the CYP enzyme and inhibit the reproductive functions in common carps dwelling downstream from the release site. (C) 2003 Elsevier Science Ltd. All rights reserved.
  • HS Kim, K Saito, M Ishizuka, A Kazusaka, S Fujita
    ARCHIVES OF TOXICOLOGY 77 8 446 - 451 2003年 [査読有り][通常論文]
     
    Exposure of pubertal rats to di-(2-ethylhexyl) phthalate (DEHP) for 14 days was reported to result in reduced testosterone (T) biosynthesis by altering androstenedione 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activity. However, our study indicated that shorter period exposure of DEHP (100 or 1000 mg/kg for 5 days) to 4-week-old male rats did not affect the activity of 17beta-HSD, the rate-limiting enzyme of T biosynthesis in the testis. Testosterone 5alpha-reductase (T5alpha-R) activity in the testis was significantly enhanced, while aromatase mRNA was significantly reduced by increasing doses of DEHP. The expressions of cytochrome P450 (CYP) isoforms, CYP2C11 and CYP3A, in the testis increased along with their enzymatic activities, T16alpha- and T6beta-hydroxylation, respectively. Thus, the current study clearly indicates that the short period exposure to DEHP alters T metabolism through altering activities of T5alpha-R, aromatase and CYP2C11/3A2 in the testis of prepubertal rats, and that they are more sensitive marker enzymes to the DEHP exposure than those of biosynthetic enzymes of T from androstenedione.
  • M Ishizuka, J Yonemoto, H Zaha, C Tohyama, H Sone
    JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY 17 5 278 - 285 2003年 [査読有り][通常論文]
     
    The cytochrome P450 (CYP) isoform CYP2C11 is specifically expressed in the liver of adult male rats, and 5alpha-reductase is specifically expressed in the liver of the adult female rats. The sexually dimorphic expressions of these hepatic enzymes are regulated by the sex-dependent profiles of the circulating growth hormone (GH). However, it is not well known whether hormonal imprinting or activation factors in the neonatal brain influence the sexually dimorphic expression patterns of hepatic enzymes. We therefore examined the effect of perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on sex-dependent expressions of hepatic enzymes. Pregnant rats were treated with TCDD at a dose of 0, 200, or 800 ng/kg on gestation day 15, exposing the pups to the chemical. Although the expression of CYP2C11 protein in the livers of male pups on postnatal day (PND) 49 was significantly higher than that of the controls, but the 5alpha-reductase activities in the livers of female pups were not altered by exposure to TCDD. Focusing on perinatal periods, testosterone and estrogen levels significantly increased in the brain of male pups on PND 2. The results suggest that the alteration of testosterone and estrogen levels affect hormonal imprinting in the neonatal brain of male pups, and thus induces a change in the level of male-specific hepatic CYP2C11. We conclude that perinatal exposure to TCDD at low doses may change the sexual differentiation of the neonatal brain in male rats. (C) 2003 Wiley Periodicals, Inc.
  • Hoshino, H, Fujita, S, Goto, Y, Isono, T, Ishinazaka, T, Sakurai, Y, Iwata, H, Kazusaka, A, Ishizuka, M, Tanabe, S
    Japanese Journal of Environmental Toxicology 6 1 1 - 10 2003年 [査読有り][通常論文]
  • Chiba, I, A Sakakibara, H Iwata, M Ishizuka, S Tanabe, F Akahori, A Kazusaka, S Fujita
    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 21 4 794 - 806 2002年04月 [査読有り][通常論文]
     
    From 16 largha seats (Phoca largha) and 15 ribbon seals (Phoca fasciata) in the coastal waters of Hokkaido, Japan, blubber chlorinated hydrocarbon (CHC) levels and hepatic cytochrome P450 (CYP) catalytic activities and their immunochemically detected protein content levels were measured. Concentrations of DDTs (2,2-bis(4-chlorophenyl)-1,1-dichloroethylene,p,p'-DDE; 2,2-bis(4-chlorophenyl)-1,1-dichloroethane,p,p'-DDD; dichlorodiphenyltrichloroethane, p,p'-DDT), polychlorinated biphenyl congeners (PCBs), and chlordane compounds (oxychlordane, chlordanes, and nonachlors) in both species were in the range of 290 to 5,300, 420 to 4,000, and 130 to 1,500 ng/g lipid weight, respectively. Aryl hydrocarbon receptor (AhR) agonists, non-ortho (IUPAC 77 and 126) and mono-ortho (IUPAC 105, 118, and 156) coplanar PCB congeners, were also detected, and the 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) toxic equivalents (TEQs) were 4.9 to 120 pg TEQ/g lipid weight. Cross-reactive proteins with polyclonal antibodies against rat CYP1A1 and CYP3A2 were notably detected in seal liver microsomes. Interestingly, a polyclonal antibody against rat CYP2B1 recognized proteins only at trace levels. In largha seals, both levels of alkoxyresorufin- (methoxy-, ethoxy-, pentoxy-, and benzyloxyresorufin) O-dealkylase (AROD) activities and proteins detected by polyclonal antibodies against rat CYP1A1 were significantly correlated with the concentrations of individual coplanar PCB congeners, total TEQs, and total PCBs. Threshold concentrations for TEQs in blubber of the largha seal to induce hepatic CYP1A protein and EROD activity were estimated to be 8.5 and 19 pg TEQ/g fat weight, respectively. In ribbon seals, similar correlations were not detected, although the TEQ levels were not significantly lower than those in largha seals. These results suggest that AROD activity and CYP1A1 protein in the liver of the largha seal could be a biomarker for the exposure to AhR agonists such as coplanar PCB congeners. This study also indicates differences in AhR-mediated responses to the CHC exposures between largha and ribbon seals.
  • KQ Sakamoto, T Kunisue, M Watanabe, Y Masuda, H Iwata, S Tanabe, F Akahori, M Ishizuka, A Kazusaka, S Fujita
    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 21 4 842 - 847 2002年04月 [査読有り][通常論文]
     
    Polychlorinated biphenyls (PCBs), including coplanar congeners, hexachlorocyclohexane isomers, chlordane-related compounds, and hexachlorobenzene, were found in the breast muscle of Steller's sea eagles (SSE) and white-tailed sea eagles (WSE) threatened species, collected in Hokkaido, Japan, during the two years from 1998 to 1999. Both PCBs and DDTs were the most notable compounds, with concentrations one to two orders of magnitude higher than the other compounds, that is, from 120 to 39,000 and from 68 to 15,000 ng/g wet weight, respectively. Non-ortho (International Union of Pure and Applied Chemistry [IUPAC] 77, 126, and 169) and mono-ortho (IUPAC 105, 118, and 156)-substituted coplanar PCB congeners amounted to 9.2 to 740 pg/g of 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents derived from the World Health Organization, Paris, France (WHO), toxic equivalent factors. The atmospheric PCBs and DDTs in eastern Siberian cities, such as Khabarovsk and Magadan, have been reported to be much higher than Hokkaido and the North Pacific. Thus, we speculated that the eagles might have been contaminated in these areas, where they spend most of the year except winter, which they spend in eastern Siberia. Adult eagles accumulated more PCBs and DDTs than younger ones. The patterns of PCB congeners were also found to change, depending on the age of the eagle examined; adult eagles showed relatively higher proportions of highly chlorinated PCBs than juvenile eagles did. This difference would be related to the efficiency of the excretion and the metabolism of each PCB congener in the eagles.
  • Mayumi Ishizuka, Yukio Yamamoto, Ayato Takada, Akio Kazusaka, Shoichi Fujita
    International Congress Series 1233 C 121 - 126 2002年 [査読有り][通常論文]
     
    In the previous study, we cloned two novel cytochrome P450 (CYP) cDNAs (CYP2D23 and CYP2D24) from a rabbit liver cDNA library. CYP2D23 and CYP2D24 were heterogeneously expressed in 293T cells. CYP2D24 effectively catalyzed the oxidation of bufuralol and bunitrolol, the archetypal substrates of the CYP2D subfamily, while CYP2D23 exhibited catalytic activity only toward bufuralol. Furthermore, in this study, we isolated the variant of CYP2D24, in which 473threonine was substituted with valine, and mutant CYP2D24 forms, in which 76lysine was replaced by proline. We determined the catalytic activities of the CYP2D24 forms and found that the mutants showed no activity related to drug metabolism. The computer-assisted analysis of the primary sequences of the CYP2D24 variant and mutant forms suggested that proline substitution results in alterations in the secondary structure and hydrophobicity of beta-Sheet 1, which was closed to Helix A, B and SRS-1, and was the proposed substrate-binding sites of P450. © 2002 Elsevier Science B.V.
  • Shoichi Fujita, Issei Chiba, Mayumi Ishizuka, Hidenobu Hoshi, Hisato Iwata, Akihito Sakakibara, Shinsuke Tanabe, Akio Kazusaka, Makihiko Masuda, Yasushi Masuda, Hajime Nakagawa
    Biomarkers 6 1 6(1): 19-25 - 25 2001年02月03日 [査読有り][通常論文]
     
    The impact of environmental pollution on selected animals was tested by monitoring the hepatic content of cytochromes P450 and their enzyme activities or by calculating TEQ values from the concentration of pollutants in the body. Fish-eating Stellars Sea Eagles, Haliaeetus pelagicus, found dead in the northern part of Hokkaido island accumulated high levels of PCBs and DDT and metabolites. The TEQ values calculated from the PCB concentration in the eagles were high enough to cause a significant toxic effect in other birds living in the same environment. Some of these birds were also contaminated with high concentrations of lead. Spotted seals, Phoca largha, captured along the coast-line of Hokkaido accumulated PCBs in their fat at about 100 million times the concentrations in the surface sea water. The levels of expressions of hepatic microsomal CYP 1A1 and related enzyme activities in these seals showed good correlation to the levels of PCBs accumulated in the fat. The fresh water crabs, Eriocheir japonicus, were captured from three different rivers with various degrees of pollution. The P450 content and the related enzyme activities showed good correlation to TEQ values obtained from the concentrations of PCBs and PCDDs in the crabs from the rivers. The wild rodents, Clethrionomys rufocanus, were captured from urban, agricultural, and forest areas in Hokkaido. Those from the forest area had the lowest CYP content and related enzyme activities, comparable to those in laboratory-raised animals. Those from the urban areas, presumably contaminated with PAHs from fuel combustion, showed increased CYP 1A1 content and related enzyme activities. Those from the agricultural areas showed increased levels of CYP 1A1, 2B, 2E1. Rats treated with some of the agrochemicals used in the area resulted in a similar pattern of induction. It is concluded that P450 can be a useful biomarker for assessing the environmental impact of chemical pollutants on wild animals.
  • H. Sone, Ying Jie Li, M. Ishizuka, Y. Aoki, M. Nagao
    Cancer Research 60 18 5080 - 5086 2000年09月15日 [査読有り][通常論文]
     
    The mutant strain Long-Evans Cinnamon (LEC) rat, which accumulates copper in the liver because of a mutation in the Atp7b gene, encoding a copper-ATPase, is a model of Wilson disease. It spontaneously develops hepatitis, and subsequently hepatocellular carcinoma and cholangiofibrosis. Excess intracellular copper has been thought to induce DNA damage through reactive oxygen species produced by Cu (II)/Cu (I) redox cycling, and also by direct interaction with DNA. We have developed lacI transgenic Wilson disease (WND-B) rats by mating LEC with Big Blue F344 rats carrying a lambda shuttle vector harboring the lacI gene. lacI mutations of the livers of C-B heterozygous (Atp7b w/m, lacI) and WND-B homozygous (Atp7b m/m, lacI) rats at 6, 24, and 40 weeks of ages were analyzed. Mutant frequencies in the WND-B rats were 2.0 ± 0.7 x 10-5, 5.3 ± 0.9 x 10-5, and 5.3 ± 1.0 x 10-5, respectively, significantly higher than those of C-B rats. Nucleotide sequence analysis revealed that the frequency of deletion mutations of more than two nucleotides were much higher, 15% in WND-B rats, but only 2% in C-B rats. In addition, the average size of deletion was larger in the former. Loss of oligonucleotide-repeat units was specific and relatively frequent in WND-B rats. This type of mutation might be implicated in the induction of DNA strand scissions by reactive oxygen species. These findings suggest that the increase in mutant frequencies and/or the specific type of mutation according to copper accumulation play a crucial role in hepatocarcinogenesis in LEC rats.
  • Nihar Ranjan Jana, Shubhashishi Sarkar, Mayumi Ishizuka, Junzo Yonemoto, Chiharu Tohyama, Hideko Sone
    Molecular Cell Biology Research Communications 4 3 174 - 180 2000年 [査読有り][通常論文]
     
    A study was conducted to investigate whether target hormones affect 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible gene expression, using as an experimental model system three human cancer cell lines, breast (MCF-7), uterine (RL95-2), and prostate (LNCaP). Exposure to TCDD induced the CYP1A1 gene in all three cell lines. MCF-7 and RL95-2 cells showed more than 15- and 10-fold induction of EROD (7-ethoxyresorufin O-deethylase) activity, respectively, compared with the less responsive LNCaP cells. Surprisingly, however, TCDD-induced reporter gene activity driven by a single XRE element was similar in RL95-2 and LNCaP cells. The steady-state levels of expression of aryl hydrocarbon receptor (AhR) and aryl hydrocarbon receptor nuclear translocator (ARNT) were similar in all three cell lines. Expression of the CYP1B1 and PAI-2 genes was induced by TCDD in MCF-7 and RL95-2, but not in LNCaP, cells. Transient coexpression of estradiol receptor-α (ER-α) with a TCDD-responsive reporter plasmid and subsequent TCDD treatment increased responsiveness to TCDD in RL95-2 and LNCaP cells. Treatment with AZA-C, a DNA methyltransferase inhibitor, enhanced responsiveness to TCDD, in terms of EROD activity in LNCaP cells, but not in MCF-7 and RL95-2 cells, suggesting that DNA methylation in the CpG dinucleotide within the XRE core sequence is another factor involved in silencing of CYP1A1 in LNCaP cells. TCDD markedly inhibited E2- or testosterone-induced reporter gene activities in all three cell lines. Conversely, these target hormones inhibited TCDD-induced EROD activity in the three cell lines. These findings suggest that TCDD and the target steroid hormones negatively regulate each other's activity. © 2001 Academic Press.
  • NR Jana, S Sarkar, M Ishizuka, J Yonemoto, C Tohyama, H Sone
    ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS 368 1 31 - 39 1999年08月 [査読有り][通常論文]
     
    The present study was conducted to investigate the mechanism of the response of human uterine endometrial carcinoma cells, RL95-2 and KLE, to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), RL95-2 cells were highly responsive to TCDD in terms of cytochrome P4501A1 (CYP1A1), cytochrome P4501B1 (CYP1B1), and plasminogen activator inhibitor-2 (PAI-2), whereas KLE cells showed little stimulatory effects only at high doses. Neither showed any growth inhibition upon exposure to TCDD. KLE cells expressed higher levels of aryl hydrocarbon receptor (AhR) than RL95-2 and gel mobility shift assay also identified more liganded AhR-ARNT complex bound to xenobiotic response elements (XRE), TCDD had no down-regulatory effects on the expression of either AhR or the estradiol receptor (ER). Though both cell types expressed ER-alpha almost equally, immunofluorescence demonstrated a defect in its nuclear translocation in KLE cells where ER-alpha was mainly cytoplasmic and estradiol-17 beta (E-2) was unable to translocate it to the nucleus. However, both cells were nonresponsive to E-2 in terms of transcriptional activation and transient expression of normal ER-alpha restored the E-2 responsiveness. Transient expression of ER-alpha in KLE cells also restored its responsiveness to TCDD on transcriptional activation. Collectively, these results indicate that ER-alpha acts as a positive modulator in regulation of the TCDD-inducible genes. (C) 1999 Academic Press.
  • ISHIZUKA M, SAKIYAMA T, IWATA H, FUKUSHIMA M, KAZUSAKA A, FUJITA S
    Environ. Toxicol. Chem. 17 8 1490 - 1498 1998年08月24日 [査読有り][通常論文]
     
    The hepatopancreases of freshwater crabs (Eriocheir japonicus) collected from three Japanese rivers (Barato, Shiribetsu, and Tone) were analyzed for planar halogenated aromatic hydrocarbons (HAHs), including polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs). The hepatic glutathione S-transferase (GST)-dependent enzyme activities in the crab hepatopancreas were also measured to examine their potential as biomarkers for the contaminants. Crabs from the Tone River, which runs through industrial, agricultural, and urban areas, have the highest concentrations of HAHs (4,100 pg/g fat weight), followed by those from the Barato River (2,430-2,970 pg/g fat weight), whereas crabs from the Shiribetsu River were relatively less contaminated (1,350-1,800 pg/g fat weight). Identification of numerous PCDD and PCDF congeners in crabs from all three rivers provided evidence that one of the major sources of PCDDs and PCDFs was waste incineration. In addition, crabs from the Barato and Shiribetsu Rivers were notably contaminated with 1,3,6,8- and 1,3,7,9-TeCDD congeners, which suggests that a possible source was chlornitrofen, which has been extensively used in paddy fields as herbicide. Calculation of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin toxic equivalents (TEQs) showed that the causal contaminants of higher TEQs in crabs from the Tone River (94.7 TEQ picograms per gram fat weight) were PCDDs and PCDFs, although the most important contributor to the total TEQs was coplanar PCBs (49.95%). The crab hepatopancreas appeared to have abilities to transfer glutathione to 1-chloro-2,4-nitrobenzene (CDNB) and 3,4-dichloronitrobenzene (DCNB). The crabs with the highest TEQ levels showed the highest GST activities. The current results and our previous data lead us to conclude that cytochrome P450 and GST-dependent enzyme activities (benzo[a]pyrene hydroxylation and CDNB and DCNB conjugation) in freshwater crab hepatopancreases are likely to be useful biomarkers for the contamination of planar aromatic hydrocarbons such as benzo[a]pyrene, PCDDs, PCDFs, and coplanar PCBs.
  • Yukio Yamamoto, Mayumi Ishizuka, Ayato Takada, Shoichi Fujita
    Journal of Biochemistry 124 3 503 - 508 1998年 [査読有り][通常論文]
     
    We cloned two novel cytochrome P450 cDNAs (CYP2D23 and CYP2D24) from a rabbit liver cDNA library. The open-reading frames of these cDNAs encode proteins that are each composed of 500 amino acids. The amino acid sequence identity of CYP2D23 with CYP2D24 is 91.6%, and the homology of these two isozymes with other known mammalian CYPs in the CYP2D subfamily range from 64.9 to 79.8%. Using RT-PCR, we determined the distribution of these two isozymes in 9 major organs, including brain tissue sections. CYP2D23 mRNA was abundantly expressed in the liver and small intestine, but only slightly in the brain sections, whereas CYP2D24 mRNA was expressed in the liver, small intestine, and stomach, CYP2D23 and CYP2D24 were heterogeneously expressed in 293T cells. CYP2D24 effectively catalyzed the oxidation of bufuralol and bunitrolol, the archetypal substrates of the CYP2D subfamily, while CYP2D23 exhibited catalytic activity only toward bufuralol. The results of this first study on rabbit CYP2D isozymes indicate that CYP2D23 and CYP2D24 are functionally expressed in rabbits, and have different organ distributions and metabolic properties.
  • ISHIZUKA M, IWATA H, KAZUSAKA A, HATAKEYAMA S, FUJITA S
    Xenobiotica 28 11 1029 - 1039 1998年01月01日 [査読無し][通常論文]
     
    1. The herbicides butachlor (2-chloro-2',6',diethyl-N-[buthoxymethyl acetanilide) and pretilachlor (2-chloro-2',6'-diethyl-N-[2-propoxyethyl] acetanilide) are widely used in Asia, South America, Europe and Africa. Isoprothioiane (diisopropyl-1,3-dithiolan-2-ylidenemalonate) is used as a fungicide and an insecticide in rice paddies. We administered these agrochemicals to the male rat and examined their effects on cytochrome P450 (P450), glutathione S-transferase (GST), UDP-glucuronosyltransferase (UDPGT), and NAD(P)H-quinone oxidoreductase 1 (NQO1)-related metabolism in the liver. 2. Administration of isoprothiolane, butachlor or pretilachlor to rat induced hepatic P4502B subfamily-dependent enzyme activities (pentoxyresorufin O-depentylation and testosterone 16 β-hydroxylation) up to 271-413% of control, which coincided with the increase in expression levels of the P4502B apoprotein. 3. Activities of GST toward 1-chloro-2,4-nitrobenzene and 3,4-dichloronitrobenzene were slightly induced (127-133% of control) in the liver of the rat treated with these pesticides. On the other hand, marked elevations of UDPGT activities toward p-nitrophenol (164-281% of control) were observed. NQO1-related metabolism (menadione reductase activity) was also induced (123-176% of control) in the liver of rat treated with these agrochemicals. 4. These results indicate that some of the agrochemicals currently in use are capable of inducing phase I and II xenobiotic-metabolizing enzyme activities in an isozyme selective manner. The induction of these activities may disrupt normal physiologic functions related to these enzymes in exposed animals.
  • ISHIZUKA M, YOSHINO S, YAMAMOTO Y, YAMAMOTO H, IMAOKA S, FUNAE Y, MASUDA M, IWATA H, FUJITA S
    Xenobiotica 27 9 923 - 931 1997年09月29日 [査読有り][通常論文]
     
    1. During liver regeneration in the male rat, the metabolic activities of imipramine were differentially affected depending on the specific metabolic pathways. Imipramine N-demethylation was markedly reduced whereas 2-hydroxylation showed only a moderate reduction following partial hepatectomy. 2. A slight decline was observed in the hepatic microsomal content of CYP2D apoprotein, whereas a substantial decrease occurred in CYP2C11 content during liver regeneration. Since imipramine 2-hydroxylation and N-demethylation are mediated by CYP2D and 2C11 respectively, metabolic pathway-specific alterations in the activities of imipramine metabolism are explained by the isozyme selective alteration in the levels of CYPs in regenerating liver. 3. No significant effect of regeneration was observed on expression of CYP2B1 and 2E1 apoproteins. CYP3A2 apoprotein, one of the male-specific CYP isoforms, was significantly suppressed in regenerating liver showing a similar pattern of alteration to the levels of CYP2C11. The alteration pattern of the CYP1A1 level was different to the above with a moderate decline at the first day post-operation and a marked rebound thereafter. 4. In the partially hepatectomized male rat, no significant increase in androslenedione 5-alpha reductase activity, an activity predominant in the female rat, was detected. It is concluded that the pattern of alterations of hepatic oxidative metabolism during liver regeneration was not related to the functional feminization of the liver.
  • Mayumi Ishizuka, Hidenobu Hoshi, Nobuyuki Minamoto, Makihiko Masuda, Akio Kazusaka, Shoichi Fujita
    Environmental Health Perspectives 104 7 774 - 778 1996年 [査読有り][通常論文]
     
    Eriocheir japonicus fresh-water crabs inhabiting rivers and estuaries in Japan, were investigated for cytochrome P450 (CYP)-dependent drug-metabolizing enzyme activities to see if these activities reflect the river pollution gradient. From the laboratory dose-response experiments, we found that the polycyclic aromatic hydrocarbon (PAH) 3-methylcholanthrene induced total CYP contents, ethoxycoumarin O-deethylase activity, and bunitrolol 4-hydroxylase activity in crab hepatopancreas. In the field studies, crabs collected from the river with the highest concentration of PAHs exhibited the highest levels of CYP, the highest activities of benzo[a]pyrene 3-hydroxylase, imipramine 2-hydroxylase, bunitrolol 4-hydroxylase, ethoxycoumarin O-deethylase, and the ability to metabolically activate benzo[a]pyrene, but erythromycin N-demethylase activity was not induced. The correlation between PAH levels and drug-metabolizing enzyme activities in female crabs were not as marked as in male crabs. The levels and acitivities of CYP did not appear to reflect the concentrations of organochlorines and polychlorinated biphenyl congeners (PCBs) studied in the fat of crab hepatopancreas.

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  • 日本野生動物医学会   環境ホルモン学会 [正式名称;日本内分泌撹乱化学物質学会]   日本環境化学会   日本獣医学会   日本毒性学会   

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2023年04月 -2027年03月 
    代表者 : 池中 良徳, 星 信彦, 野見山 桂, 杉尾 翔太, 石塚 真由美, 戸田 知得, 江口 哲史, 池中 建介, 平野 哲史
  • 日本学術振興会：科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B))
    研究期間 : 2022年10月 -2026年03月 
    代表者 : 石塚 真由美, 武田 一貴, 池中 良徳, 江口 哲史, 中山 翔太
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2021年04月 -2026年03月 
    代表者 : 石塚 真由美
     
    我々はこれまでの研究により、高次の動物が外来性の化学物質（Xenobiotics）への「適応」ために、化学物質の代謝や排泄など、解毒のカスケードに沿って薬物代謝酵素などの一連の多様性を発展させてきたとの仮説を立てた。化学物質感受性には多様性があり、解毒代謝酵素の解析から、この多様性獲得の主要因は食餌由来の化学物質である可能性を報告した。本研究では食性の観点および重度環境汚染域に棲息する動物を中心に、哺乳類が日常的に曝露される化学物質にどのように適応してきたのか、多様な種を用いてその進化を機能面から明らかにする。これまでの研究で構築してきた多様な動物試料を用いた研究体制を生かし、食性のユニークな動物種を対象としたウェットな実験や、データベースを用いた網羅的解析により、外来性の化学物質に対する動物の「適応」と「共存」メカニズムを明らかにする。
    今年度は、食肉目クマ科、スカベンジャー種（腐肉食類）等について、ゲノムデータベースを用いた遺伝子解析を行った。外来化学物質の代謝を担う第I相反応酵素シトクロムP450、第II相反応のグルクロン酸転移酵素や硫酸転移酵素について、種間比較を行い、食性との関連性について解析した。特に硫酸転移酵素についてはこれまで分子進化と食性に関するデータは少なく、研究成果については、現在論文を作成している。野生げっ歯類、トカゲ、一部の食肉性哺乳類について、次世代シークエンサーを用いて、エクソーム解析およびトランスクリプトームを行っている。また農薬や重金属の環境汚染地域に生活・棲息している野生げっ歯類及びヒトについてメタボローム解析を行った。現在データを解析中であるが、野生げっ歯類についてはDDT高濃度汚染域に棲息している野生げっ歯類のステロイド代謝への影響が認められた。現在、野生げっ歯類をDDT環境汚染レベル下で世代飼育し、フィールドデータの検証を行っている。
  • 日本学術振興会：科学研究費助成事業 挑戦的研究(開拓)
    研究期間 : 2022年06月 -2025年03月 
    代表者 : 池中 良徳, 野見山 桂, 新間 秀一, 杉尾 翔太, 石塚 真由美, 江口 哲史, 中山 翔太, 星 信彦, 平野 哲史
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2019年04月 -2024年03月 
    代表者 : 綿貫 豊, 依田 憲, 石塚 真由美, 力石 嘉人, 高田 秀重
     
    本研究では，海鳥をデバイスとする新しいアイデアで，生物多様性・資源保全に資する，広域スケールの汚染マップを作る。そのため，北太平洋西部において，①バイオロギング（動物装着型データロガー）により多数の外洋性海鳥（オオミズナギドリ）個体の移動を通年追跡して，集中度が高いホットスポットを抽出する，②全個体の血液・羽根など体組織の汚染物質濃度を，栄養段階に対して標準化し，体組織形成時期に対応する各個体の利用場所に関連付けることで，汚染度を地図化する，そして③体組織中のストレスマーカーで汚染物質の生体影響を知り，ホットスポットのリスクを評価する，の3つを達成する汎用性の高い手法を開発することを目的としている。R1年度は，新潟県粟島において、雛を育てている４０個体のオオミズナギドリに追跡装置（ジオロケーター：光強度を記録することで日の出日の入り時刻を知り、１年間の毎日の位置を推定する、超小型記録装置）を足輪にて装着した。一方で、繁殖期間中の採食場所と行動を調べるために、GPS・加速度データロガーを装着回収し、回収時にその胃内容を採取した。また，オオミズナギドリを中心とした既存の海鳥体組織標本（一部はes-BANKより資料提供）をつかって，さまざまな部位の羽や血液、体脂肪などの窒素・炭素安定同位体比、酸化ストレス指標やストレス関連ステロイドや汚染物質などの予備的化学分析を実施し、問題点について検討し、追跡個体の体組織の分析に備えた。
  • 日本学術振興会：科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B))
    研究期間 : 2018年10月 -2022年03月 
    代表者 : 石塚 真由美, 池中 良徳, 中山 翔太, 中田 北斗
     
    近年、アフリカ諸国では急速な資源開発がすすめられている。そのため急激な環境の汚染が顕在化しており、一部の国では生態 系や家畜・ヒトにおける健康被 害が報告されるようになった。化学物質は、食糧生産や感染症制圧には必要不可欠であるが、途上国では化学物質汚染によるリスクを度外視して使用している現 状がある。2018年度に発表された大気汚染度を国別で分析した データでは世界ワースト10のうち7か国はアフリカで占められている。化学物質による脅威（ケミ カルハザード）については、 目に見えにくい潜在的な性質のため、対策が後手に回される傾向が強い。本研究では、アフリカでもっとも問題となっている金属、農薬についてその現状を明ら かにすること、およびフィールドトキシコ ロジーの概念により、そのメカニズムと現象を結 びつけることを目的としてい る。当該研究では、ザンビア大学（金属）および南アフリカのノースウェスト大学（再興農薬）、ガーナのクワメエンクルマ科学技術大学（KNUST 、新興農薬）と共 同研究を計画した。
    ザンビアでは鉛による環境汚染がヒトおよび動物に及ぼす毒性学的影響について調査を行った。特に、イヌを歩哨動物とした汚染モニタリング方法について報告した。また、乳児における鉛汚染の状況について調査を行った。ガーナではヒト試料の最終に向けた準備を行うとともに、ネオニコチノイドが神経系や脂肪代謝等に及ぼす影響について動物を用いた実験を行った。南アフリカではDDTが引き起こす毒性学的影響について、家畜や野生動物を用いてオミクス解析を行い、バイオマーカーの探索を行った。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2018年04月 -2022年03月 
    代表者 : 池中 良徳, 星 信彦, 川合 佑典, 石塚 真由美, 小林 篤史, 久保田 彰, 水川 葉月, 有薗 幸司, 平野 哲史, 加藤 恵介, 宮原 裕一, 市川 剛, 岡松 優子, 中山 翔太
     
    本年度は昨年度に引き続き、研究実施計画通り、以下の項目について、実施した。 ・mlAOPの基礎データ取得に向けた、げっ歯類およびゼブラフィッシュを用いた各種行動試験の実施：個体レベルでの評価として、様々な系統及び種の動物でオープンフィールドテストや高架式十字迷路等の行動試験を実施した。特に、マウスでは、神経毒性試験の新たな評価法として、２光子顕微鏡を用いた実験および解析を導入し、in vivoにおける化学物質の脳神経系への影響の可視化にチャレンジした。 ・組織レベルでの評価のための、イメージング解析を実施：組織レベルでの評価として、昨年度に引き続き、特にイメージング技術を駆使して実施した。特に超高分解能質量顕微鏡（MALDI-FT-ICR-MS 型;Bruker Solarix XR）によるネオニコチノイドおよびその代謝産物の組織分布のイメージング解析を試みた。カテコールアミンに着目した解析では、DPPによる誘導体化により、ドパミンの検出に成功した。一方、現在は再現性の評価や他のニューロトランスミッターへの応用を検討している。 ・細胞・分子レベルでの評価：昨年度に引き続き、SH-SY5Y細胞をモデル神経細胞として用い、細胞増殖パラメーターなどの各種項目についてデータを取得した。また、マイクロアレイを実施し、投与により変動する遺伝子群を明らかにした。また、標的分子のリン酸化状態についても解析を実施した。 ・ヒト尿試料を用いたバイオモニタリング：昨年度に引き続き、ボランティアを募り、一般市民延べ約1000人から尿試料の採取を実施し、尿中のネオニコチノイド濃度を測定した。また、有機野菜を食べてもらう事による尿中ネオニコチノイド低減効果についても明らかにした。
  • 科学技術振興機構：国際的な科学技術共同研究などの推進 SATREPS
    研究期間 : 2015年 -2021年 
    代表者 : 石塚 真由美
     
    汚染除去法を最適化し、健康リスク評価に基づく経済効果を定量化 鉛汚染が深刻なザンビアにおいて生態系および人への汚染メカニズムとリスクを解明し、経済的損失を可視化することで、汚染防御対策や環境修復へと結びつける。リモートセンシングによる調査、地上調査による土壌や植物のキャラクテリゼーション、人の鉛汚染のメカニズム、健康ハザードと経済リスクの可視化、環境修復技術の確立と同時に、モニタリングシステムの構築とキャパシティビルディングによる各専門家の持続的育成を行う。 環境修復、健康・経済リスク評価をもとに、汚染低減に貢献! ザンビアの未来を担う人(特に幼児)の鉛レベルに低下が見られる。ザンビアにおける環境修復、健康リスク評価の新規プロトコルなどの政策に採用される。将来的には、アフリカを中心とした世界的に主要なハザードである金属汚染対策に貢献する。
  • 日本学術振興会：科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2018年06月 -2020年03月 
    代表者 : 石塚 真由美, 池中 良徳, 中山 翔太
     
    現在、殺鼠剤による猛禽類への二次被害が頻発している。このため、殺鼠剤抵抗性ラットに有効かつ安全な駆除方策は存在しない。これは抵抗獲得機序に対する研究の不足と野生動物における感受性評価法の欠如が原因である。本研究では、殺鼠剤抵抗性の獲得の原因を明らかにし、殺鼠剤の開発や非対象生物種への保全に資するデータを得ることを目的とした。本研究により、野生齧歯類の殺鼠剤への抵抗性の原因として、ビタミンKエポキシド還元酵素の結合ポケット内外の変異が抵抗性獲得に寄与する事を実証した他、NADPH産生の向上とそれに伴うシトクロムP450による殺鼠剤代謝能の活性化という新しい抵抗性獲得機序が明らかとなった。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2016年04月 -2020年03月 
    代表者 : 石塚 真由美, 池中 良徳, 中山 翔太, 水川 葉月
     
    哺乳類および鳥類について、肝臓における異物代謝の主要経路となるシトクロムP450（P450)、グルクロン酸転移酵素（UGT)、硫酸転移酵素（ST)についてクローニングを行い、その酵素学的特徴を明らかにした。UGTやSTが欠損もしくは極めて活性が低い動物種とその原因を明らかにした。また、現在、世界的に外来性の小型哺乳類の駆除には主に抗血液凝固系の殺鼠剤が使用されている。そこで、広範の動物種についての殺鼠剤感受性評価を行い、P450、UGTによる代謝能について、その種差を明らかにした。
  • 日本学術振興会：科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2017年06月 -2019年03月 
    代表者 : 池中 良徳, 川合 佑典, 鈴木 淳史, 三谷 曜子, 石塚 真由美, 水川 葉月, 中山 翔太
     
    本研究では、化学物質感受性のキーであるMetabolismの評価法を開発し、希少野生動物の感受性を明らかにする事である。この評価のためには、新鮮肝が必要であるが、希少種ではその入手が困難である。そこで、皮膚線維芽細胞からダイレクトリプログラミングにより肝臓様（iHep）細胞への誘導を試みた。先ずiHep作成に先立ち、本研究では数種のトッププレデターの線維芽細胞を入手し、その培養に成功した。培養した線維芽細胞を用い、iHep細胞への誘導を試みた結果、特定の因子を導入する事でアルブミンを発現する上皮細胞に変化する事を見出した。本研究を通じて、初めて野生動物iHep細胞の作成に成功した可能性が高い。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 野見山 桂, 水川 葉月, 国末 達也, 石塚 真由美, 岩田 久人
     
    ネコを対象にPCBs12異性体混合物の曝露試験を実施し、血液・肝臓・脳を対象にトランスクリプトームおよびメタボローム解析を実施した。 トランスクリプトームでは、21890遺伝子のうちPCBs曝露群で531遺伝子が有意に変動した。パスウェイ解析の結果、炎症や感染症関連経路への影響が認められ、PCBsによる免疫系への影響が示唆された。 血清を対象としたメタボローム解析では、122種のメタボロームが有意な変動を示した。パスウェイ解析の結果、ペントースリン酸回路、ヒスチジン代謝系等の中心炭素代謝に関連するメタボロームが減少しており、PCBs曝露に伴うこれらの代謝経路の抑制が示唆された。
  • 日本学術振興会：科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 石塚 真由美, 池中 良徳, 中山 翔太, 水川 葉月
     
    野生齧歯類は様々な感染症を媒介するため駆除する必要がある。駆除には殺鼠剤が用いられたがこれらに抵抗性を有す個体群が出現し駆除を困難にしている。従来抵抗性群は殺鼠剤の標的分子が変異し殺鼠剤が結合しにくい形になるのが原因と考えられてきた。本研究では殺鼠剤の解毒代謝機能を評価した。その結果、抵抗性群では肝で殺鼠剤を代謝し排泄する能力が向上しており、標的分子の変異と代謝能の向上という二つの機構を併せ持つことが判明した。
  • 日本学術振興会：科学研究費助成事業 若手研究(B)
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 中山 翔太, 石塚 真由美, 池中 良徳, 水川 葉月, 平田 岳史
     
    年間23万人が主に鉱床由来の鉛中毒により死亡し、60万人以上の子供の知的発達に影響を及ぼしているが、汚染源推定に有用な手法は確立されていない。本研究では鉛汚染源推定に有用な家畜・家禽種を解明することを目的とした。高精度鉛同位体比解析より、アフリカを含めた発展途上国で流通し、またヒトの食糧源としても用いられるヤギやニワトリを用いることで、鉛汚染源の推定が可能であることを明らかにした。LA-ICP-MS（レーザー照射型 誘導結合プラズマ質量分析法）により、マウスにおける鉛の臓器内局所分布を解析した。脳の海馬領域の高濃度蓄積や、特に、腎臓の髄質において皮質よりも高濃度の鉛蓄積が確認された。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 池中 良徳, 石塚 真由美, 水川 葉月, 中山 翔太
     
    本研究では、アフリカのベクターコントロール地域である南アフリカのKwaZulu-Natal州に注目し、その汚染状況の調査および生息する生物に対する毒性影響評価を実施した。 家禽に着目した調査の結果、肝臓中DDT濃度は中央値として920 ng/g ww、最大濃度で14,400 ng/g wwと非常に高い値を示した。リアルタイムRT-PCR法により遺伝子発現解析を実施した結果、脂質代謝や合成や性ステロイドホルモン合成に関与する遺伝子群に影響を与えている事が明らかになった。本研究結果は、DDTが生体に一定の影響を与えている事を示しており、今後より適切なベクターコントロールを実施する必要性を示唆する。
  • 日本学術振興会：科学研究費助成事業 若手研究(B)
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 水川 葉月, 石塚 真由美, 池中 良徳, 中山 翔太, 滝口 満善, 野見山 桂
     
    ネコにおけるPCBs短期投与試験およびBDE209長期投与試験を実施し、ネコにおける有機ハロゲン化合物の生体内動態（吸収、分布、代謝、排泄）の解明、甲状腺機能への影響評価、遺伝子解析やオミクス解析による毒性発現メカニズムの解明を目的とし、調査・研究を実施した。その結果、PCBsおよびBDE209曝露によって、甲状腺機能への影響のみならず酸化ストレスの増大やNADPHの生産の撹乱、脂質代謝機能や免疫機能のかく乱なども予想された。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 池中 良徳, 石塚 真由美, 中山 翔太, 水川 葉月, 櫻井 達也, 宮原 裕一, 下鶴 倫人, 中山 翔太, 水川 葉月
     
    WHOはハマダラカの駆除のためDDTの使用を推進しており、アフリカ等の途上国を中心に、室内残留散布として使用されている。一方、DDTは難分解性で環境中の長期間残留が知られ、発がんや内分泌撹乱などの生体影響も疑われている。当該研究では、南アフリカ共和国・クワズルナタール州をベクターコントロールモデル地域とし、DDT・IRSの潜在的な毒性リスク評価を行った。 ニワトリ、ラット、野生鳥類の卵のを採取し、その分析を行った結果、いずれの試料からも極めて高濃度のDDT蓄積が観察された。本研究結果は、環境負荷が小さいとされるDDT・IRSにおける、潜在的な毒性影響および環境リスクの存在を示唆していた。
  • 日本学術振興会：科学研究費助成事業 研究活動スタート支援
    研究期間 : 2013年08月 -2015年03月 
    代表者 : 水川 葉月, 石塚 真由美, 池中 良徳, 中山 翔太, 滝口 満善, 野見山 桂
     
    ペットのネコに着目し、研究報告例の少ない液体クロマトグラフタンデム質量分析計（LC-MS/MS）を用いた有機ハロゲン化合物であるポリ塩化ビフェニル（PCBs）およびポリ臭素化ジフェニルエーテル（PBDEs）の代謝物の分析法を開発した。さらに、第I相、第II相代謝活性を測定しネコにおける有機ハロゲン化合物に対する代謝能評価を試みた。
  • 日本学術振興会：科学研究費助成事業 特別研究員奨励費
    研究期間 : 2011年 -2013年 
    代表者 : 石塚 真由美, DARWISH Abdallah, DARWISH ABDALLAH
     
    シトクロムP450の分子種のひとつCYPIA1は様々な発がん物質や変異原物質を代謝的に活性化し、化学物質の毒性を決定する重要な異物代謝酵素である。CYPIA1はAhR(アリルハイドロカーボン受容体)によって転写調節を受けており、CYPIA1の上流域のXRE (Xenobiotic Response Element)に結合してその転写を活性化することが知られている。最近、我々はカロテノイド類がAhRの機能に影響を及ぼすことを見出しており、カロテノイドがCYPIA1の生理的な動態の決定因子の一つである可能性を見出している。そこで、本研究では、カロテノイド類がAhRに及ぼす影響、およびその他のシトクロムP450分子種を制御する転写調節因子とのクロストークを明らかにし、カロテノイド類の新たな機能を明らかにすることを目的とする。 本年度は、実際に産業動物などがどの程度の重金属類を蓄積しているのかを明らかにし、実施に環境中で人や動物が暴露されている範囲での金属暴露を細胞を用いて行った。H4IIE細胞、およびHepG2細胞を用いて実際に動物が暴露される可能性のある濃度で金属類及びカロテノイドの暴露が異物代謝酵素群にどのような影響を及ぼすのかについて調べた。金属類の曝露によりシトクロムP450、グルクロン酸抱合酵素等の発現量が減少した。メカニズムとして酸化ストレスの介在が考えられたが、同時に転写調節因子の発現量も減少していた。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2007年 -2010年 
    代表者 : 藤田 正一, 池中 良徳, 石塚 真由美, 坂本 健太郎, 石塚 真由美, 坂本 健太郎
     
    当該研究では、希少動物を含む生態系高次の動物について発がん物質の影響を調べるために、癌原物質を代謝的に活性化するシトクロムP450(CYP)1A1、及びその転写調節因子アリルハイドロカーボン受容体、活性代謝中間体を抱合する抱合酵素の種差を中心に調べ、その基質との親和性や分子進化について明らかにした。また、野生動物における発がん物質など環境汚染物質の蓄積とその影響について、野生げっ歯類を中心とした歩哨動物を用いて分析した。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2007年 -2009年 
    代表者 : 岸 玲子, 佐田 文宏, 吉岡 英治, 坂 晋, 中島 そのみ, 佐々木 成子, 室橋 春光, 神尾 陽子, 仙石 泰仁, 花岡 知之, 西條 泰明, 藤田 正一, 中澤 裕之, 梶原 淳睦, 湯浅 資之, 石塚 真由美
     
    妊婦514名とその児を対象とした1産院ベースコホートで、ベースライン時、1歳6ヵ月時、3歳6ヵ月時、7歳時の両親または児の食習慣・生活習慣・職業歴・居住環境・育児環境等を詳細に調べた。環境化学物質として母体血中ダイオキシン・PCB異性体類、母乳中ダイオキシン・PCB異性体類、母体血中PFOS/PFOAの測定した。小児の神経行動発達検査は、生後6ヵ月、1歳6ヵ月時にBSID-II、3歳6ヵ月時に日本語版K-ABC3歳7ヵ月時に日本版CBCLを終了した。
  • 日本学術振興会：科学研究費助成事業 萌芽研究
    研究期間 : 2007年 -2008年 
    代表者 : 藤田 正一, 石塚 真由美, 坂本 健太郎
     
    ホルムアルデヒドはシックハウス症候群の1原因物質としてその詳細が調べられてきた。しかし、長期曝露による神経毒性は、「神経変性」という観点からは不明であり、さらに、ホルムアルデヒドとドパミンの縮合によって合成されるノルサルソリノールに着目してその毒性やパーキンソン氏病との関連を研究した報告は殆どない。そこで、本研究では、上記仮説の検証を含め、ホルムアルデヒドの内因性の発生や消去能の低下、ホルムアルデヒドを発生させる環境化学物質への曝露が弧発性パーキンソン氏病の原因となりえるのかを究明することを目的とする。 本年度は、脳におけるホルムアルデヒドの解毒に重要なADH3のノックアウト(KO)マウスの繁殖を行い、材料採集と受容体発現の変化について調べた。また、行動を詳細に解析するために、データロガーを用いた毒性学的な行動解析方法を確立した。 一方、シトクロムP450の分子種のひとつCYP2Dの遺伝的多型がパーキンソン氏病の発症とかかわりがあるとの報告があることから、ドパミンの代謝へのCYP2Dの関与について同定を行った。CYP2Dを欠損するDAラットを用いてカテコールアミン濃度や代謝に対し、P450がどのように関与するのか、明らかにした。また、その過程ではDAラットにおけるCYP2D2mRNAの低発現は、CYP2D2遺伝子の転写調節領域内の一塩基置換により、hnRNP K蛋白質のDNA結合が低下する事が原因である事を初めて明らかにした。
  • 日本学術振興会：科学研究費助成事業 萌芽研究
    研究期間 : 2006年 -2007年 
    代表者 : 坂本 健太郎, 藤田 正一, 石塚 真由美
     
    チトクロームP450(CYP)は外来異物を主な基質とする事を特徴とする酵素である。天然物質としては植物性アルカロイドなどが基質として知られている。これは植物側が捕食されないための防衛手段として毒性のあるアルカロイドを産生し、草食動物がそれを解毒するための酵素を進化させたと考える事が出来る。従って、解素酵素を解析することによって、餌生物に関する情報を得る事が出来るのではないかと考えた。本研究の最終的な目標は、既に絶滅してしまったケナガマンモスのCYPの解析を通して、その種が生息していた環境に関する情報を得ることである。本年度は下記の成果を得た。 CYPの種間差を比較検討するために、哺乳類の12目、38種の試料採集を行った。このサンプルを元に、CYP1AのcDNAをクローニングし、その塩基配列について比較検討を行った。また、酵素活性と基質特異性について調べた。 哺乳動物目間の比較では、食肉目内で塩基配列の種差が比較的少ない傾向が明らかとなった。また、酵素活性を調べたところ、草食獣では他の食性をもつ動物種に比べ、酵素活性が高いことが明らかとなった。これらの草食獣では、肝臓におけるCYP1Aの発現レベルも高かったことから、草食性の動物ではCYPをより多く発現させることで酵素活性を高く保っていると考えられた。食性の違いで代謝の動物種差があることから、これらの傾向は動物の生息状況を反映している可能性が示唆された。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2003年 -2006年 
    代表者 : 藤田 正一, 石塚 真由美, 坂本 健太郎, 数坂 昭夫
     
    DNAマイクロアレイは多くの遺伝子変動を短時間でスクリーニングできる有効なツールである。しかし、塩基配列の違いから幅広い生物種間に応用することは極めて難しく、この手技を様々な階層の野生生物に用いる為には、各々の生物特有のアレイの開発が必要である。そこで、より簡便に広範囲の野生生物に対応する次世代環境影響評価システムを開発することを目的として基礎的研究を行った。 これまでに、マイクロアレイ法で野生動物を用いた研究報告はほとんどない。野生動物では、系統差や複合汚染の影響、生理的条件の差により、通常の実験動物や細胞を用いた網羅的解析が難しいことが考えられる。そこで、野生げっ歯類を捕獲し、体内に蓄積している汚染物質を同定し、濃度を調べ、それらの動物への影響を既存のマイクロアレイを用いた解析が可能かどうかについて検討し、解析方法として、マイクロアレイ法が有効であることを報告した。また、ヒトのサンプルを用いて、マイクロアレイを作成し、従来の各遺伝子の解析とマイクロアレイ法について、比較検討した。さらに、簡便な生態影響評価用DNAマイクロアレイの開発のために、アレイ上にのせるべきDNAを検討し、ダイオキシン類など、残留性有機汚染物質の汚染亢進域で捕獲したネズミから、肝臓で変動の大きいバイオマーカーとなり得る遺伝子群を抽出した。また、広範囲の野生動物の試料を採集し、異物代謝酵素を中心にその塩基配列や基質特異性などを同定した。100種類以上の野生動物や動物園飼育動物のサンプルを採集し、これまでに報告のない動物種を中心に解析を進め、そのホモロジーから、マイクロアレイでの解析がどの動物種間で可能か検討した。 さらに、生体機能を利用した生体影響スクリーニング用アレイ開発の為に、受容体への環境化学物質の結合および受容体活性化を利用したスクリーニングを検討した。環境汚染物質の中でも発がん性を持つ化学物質の受容体となるAhR(arylhydrocarbon receptor)と生体内の各核内受容体のクロストークを検討した。
  • 日本学術振興会：科学研究費助成事業 萌芽研究
    研究期間 : 2002年 -2003年 
    代表者 : 数坂 昭夫, 佐々木 一正, 石塚 真由美, 藤田 正一
     
    狂牛病を始めとするプリオン病研究において、PrPcからPrPScへの変性機序の解明と、それに基ずく発病機序の解明が重要と考え、幾つかの検討を行ってきた。その後、諸外国での研究成果の蓄積が多く重ねられている。それらの成果を考慮し本年は以下の研究を進めてきた。幾つかの成果を得た。 1.生体中で、変性によって生ずる異常タンパク質を高選択・高感度に検出するバイオセンサーの開発を試みた。 2.研究分担者が従来行ってきた、光ファイバセンシング・システムの改良を行い、目的達成を試みた。本システムでは、従来の蛍光発光の測定に加え、光屈折を利用する表面プラズモン測定を検出系とするシステム開発を継続中である。 3.光ファイバに先端にPrPScに特異的に反応する抗体を固定化し、高選択バイオセンサの作成を試みている。光ファイバ先端を金微粒子を含む高分子で加工することにより抗体を安定に固定化することが可能であることが明らかになった。金微粒子の調製と高分子の選択が現在の課題である。 4.タンパク質変性状態をより詳しく調べることを目的として、捕捉されたタンパク質のラマンスペクトル観測の有効性が期待される。その時、タンパク質に銀微粒子等を加えることにより、Surface enhanced ramanスペクトルの観測も期待され、高感度バイオセンサーへの拡張を今後の検討課題と考えている。
  • 日本学術振興会：科学研究費助成事業 特定領域研究
    研究期間 : 2001年 -2003年 
    代表者 : 藤田 正一, 昆 泰寛, 石塚 真由美, 数坂 昭夫
     
    環境汚染による野生動物への影響として、野生生物における個体数の減少、奇形の発生、性比のバランスの変化、繁殖能低下や行動異常が懸念されている。特に、PCBなどの有機塩素系化合物は、環境中において安定で脂溶性に富むため、食物連鎖の上位に立つ生物に高濃度の濃縮されることが知られている。当該研究では、アザラシやイルカ等の海棲哺乳類に、生物濃縮によって高濃度の有機塩素系化合物が蓄積されていることや、それらが内分泌系を撹乱している可能性を報告した。 前述の海棲哺乳類については残留性の高い環境汚染物質が高濃度に蓄積しているため、他にも多くの毒性学的データが得られている。しかし、一方で、陸棲哺乳類については、魚食性の海棲哺乳類に比べると汚染レベルも低いため、環境汚染物質曝露がこれらの生物にもたらす影響については報告が少ない。そこで、我々は本研究において、陸生野生げっ歯類(アカネズミ、エゾヤチネズミ、ドブネズミ)に関し、生体に蓄積する環境汚染物質(ダイオキシン類、そのほかの有機塩素系化合物、臭素系難燃剤)や、土壌など棲息環境の汚染(PCB、DDTなどの有機塩素系化合物、多環芳香族)の分析を行い、また、生殖行動を調節するステロイドホルモンに関して、生合成・代謝を行う代謝酵素シトクロムP450(P450、CYP)の発現や活性、生殖器の発現遺伝子プロファイルや病理的変化との関係について調べた。また、野生げっ歯類のモデルとして、ラットを用いて、環境化学物質がどのような影響をもたらす可能性があるのかについて明らかにした。
  • 日本学術振興会：科学研究費助成事業 萌芽研究
    研究期間 : 2001年 -2002年 
    代表者 : 岸 玲子, 佐田 文宏, 小橋 元, 本間 研一, 石塚 真由美
     
    「目的」近年、内分泌かく乱物質に関する問題が重要視され、スチレン、2-ブロモプロパンなどの有機溶剤曝露労働者での無月経、不正月経周期、不正出血、受精率の減少が報告されている。その作用機序を解明するために、内分泌かく乱物質も含めた環境化学物質曝露による神経内分泌物質の動態と、生殖毒性の発現について知見を得ることを目的とした。 「方法」産業分野での用途の広さ、また、日常的にも食品容器としての使用頻度の高さに伴い、取り扱い作業者の数も多いことから、内分泌かく乱作用の疑いのある有機溶剤スチレンモノマーを使用した。8週令オスラットに150ppm吸入曝露8時間/日で12日間行い、血漿中プロラクチン、成長ホルモン、甲状腺刺激ホルモンレベルをELISAにより測定した。また、精巣、血液を採取し、リアルタイムPCRによる精巣ステロイド合成酵素mRNAの定量と組織学的検討、RIAによる血中テストステロン濃度の検討を行った。 「結果と考察」曝露により、血漿中のプロラクチンがメスで、甲状腺刺激ホルモンがオスで有意に増加していた。精巣毒性の検討で、血漿中テストステロン濃度、精巣組織への曝露影響は見られなかった。また、ステロイド合成酵素であるP450scc,3-beta-hydroxysteroid dehydrogenase, CYP17,CYP19 mRNAの発現には、どれも有意な差は見られなかった。プロラクチンに関しては、労働者で有意に増加するという報告があることから、疫学的報告を裏付ける結果を得た。また、結果の雌雄差については、血中スチレン濃度に雌雄差があったことから、代謝能力の違いによるものと考えられる。生殖毒性に関しては、短期間曝露であったため影響が見られなかったと考えられるため、今後より高濃度、長期間曝露の検討が必要である。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 1999年 -2002年 
    代表者 : 藤田 正一, 星 英之, 石塚 真由美, 数坂 昭夫
     
    本研究では、様々な生物層から生物を採集して環境汚染およびその生体影響についての実態を把握し、そのメカニズムの解明することを目的とした。本研究では特に、魚食性生物に着目し、魚類、魚食性哺乳類、魚食性鳥類について、蓄積する環境汚染物質の化学分析を行い、P450発現やその他の生体影響について調べた。この過程で、北海道沿岸のゴマフアザラシに表層海水の一億倍の濃度のPCB、10億倍の濃度のDDTが蓄積していることを見出した。また、PCB蓄積レベルに相関してP450分子種であるCYP1ファミリーの発現量が増加していることも明らかにした。さらに、甲状腺ホルモンへの影響について検討したところ、PCB170やPCB180と血中の甲状腺ホルモンレベルは負の相関を示し、PCBによる野生生物の汚染が内分泌系を撹乱している可能性が考えられた。また、同じ魚食性生物で食物連鎖の頂点に立つオジロワシ、オオワシについて、その成長過程と生体に蓄積する環境汚染物質の残量パターンを解析し、PCB類、DDT類が高濃度で蓄積していることを示した。これらの烏獣の下位に立つ魚類については、ダイオキシン類汚染域棲息の雌コイでは、非汚染域棲息群に比べて、P450量、CYP1A発現量、CYP1A依存の代謝活性が増加していることや生殖腺重量や血中エストロゲン量が減少していることを見出した。一方で、海洋汚染物質の一つ、有機スズをラットに投与し、その影響を調べた。実際の汚染物質は低濃度で環境に存在するため、低濃度のトリブチルスズ(TBT)を妊娠ラットに曝露し、次世代への影響について調べたところ、胎仔・新生仔の脳グリア細胞のマーカー蛋白や細胞骨格蛋白の発現量を変動させ、さらに小脳の発達遅延を起こすことを初めて報告した。TBTの胎仔期・新生仔期曝露は、性成熟後も視床下部において神経細胞の分化・局在に影響することを明らかにした。他の重金属についても野生動物に高濃度で蓄積している事を明らかにした。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 1999年 -2002年 
    代表者 : 藤田 正一, 星 英之, 石塚 真由美, 数坂 昭夫
     
    本研究では、P450のバイオマーカーとしての有用性を確立し、これを利用した評価法の確立、環境浄化への利用を目的とした。対象生物として、食物連鎖の頂点にたち、海洋汚染の影響を受けやすい海生哺乳類に着目した。我々は、北海道沿岸の魚類を捕食するゴマフアザラシに表層海水の一億倍の濃度のPCB、10億倍の濃度のDDTが蓄積し、このPCB蓄積レベルに相関してP450分子種であるCYP1ファミリーの発現量が増加していることを明らかにした。そこで、P450のバイオマーカーとしての利用のために、海棲哺乳類からP450をクローニングし、その酵素の基質特異性などについて研究を行った。アザラシ2種、トド、イルカ2種、ミンククジラより、P450分子種であるCYP1A、CYP3AのcDNAを世界で初めて単離することに成功した。また、食物連鎖下位生物の魚類について、ダイオキシン類による汚染が問題となった藤沢市の引地川水域に棲息するコイを、環境省の安全宣言後に採集し、肝膵臓における異物代謝能や生殖腺への影響の有無を汚染水域の上流に棲息するコイとの比較から検討した。化学分析から、引地川の藤沢工場下流域より採集したコイではダイオキシン類が生体に高濃度に蓄積されていることが明らかとなった。汚染域棲息の雌コイでは、上流域棲息群に比べて、P450量、CYP1A発現量、CYP1A依存の代謝活性が増加していた。また、雌個体においては、生殖腺重量や血中エストロゲン量について、下流域のコイでは減少が見られた。エストロゲン及びCYP1A誘導の関係については、培養細胞を用いた研究から共役因子の関与などを明らかにした。以上の環境汚染物質の蓄積とP450との関係に関する研究は世界的にも高い評価を受け、1999年にNZで開かれたバイオマーカーシンポジウム、2000年に仙台で開かれた国際P450シンポジウム、2001年東京の日本獣医学会においてそれぞれ講演に招待された。

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