研究者データベース

池中 良徳(イケナカ ヨシノリ)
獣医学研究院 獣医学部門 環境獣医科学分野
准教授

基本情報

所属

  • 獣医学研究院 獣医学部門 環境獣医科学分野

職名

  • 准教授

学位

  • 博士(理学)(信州大学)

ホームページURL

J-Global ID

研究キーワード

  • 環境汚染   シトクロムP450   野生動物   アフリカ   アフリカ地域   免疫抑制   サイトカイン   感染症   Pyrene   化学物質感受性   免疫かく乱   環境化学物質   重金属   第II相抱合反応   飼育動物   環境汚染バイオマーカー   アフリカ諸国   メタロチオネイン   インターロイキン   異物代謝系   種差   生態系影響評価   産業動物   グルクロン酸転移酵素   獣医学   プレデター   化学発癌   硫酸転移酵素   グルタチオン転移酵素   センシング   GIS   

研究分野

  • 環境・農学 / 化学物質影響
  • 環境・農学 / 放射線影響
  • 環境・農学 / 環境政策、環境配慮型社会
  • 環境・農学 / 環境影響評価
  • 環境・農学 / ランドスケープ科学
  • 環境・農学 / 環境農学

職歴

  • 2015年12月 - 現在 北海道大学 (連合)獣医学研究科 准教授
  • 2011年01月 - 2015年11月 北海道大学(連合)獣医学研究科 講師
  • 2009年04月 - 2009年07月 北海道大学(連合)獣医学研究科 博士研究員
  • 2008年04月 - 2009年03月 北海道大学 日本学術振興会 特別研究員(PD)
  • 2007年04月 - 2008年03月 信州大学 日本学術振興会 特別研究員(DC2)

学歴

  • 2005年04月 - 2008年03月   信州大学   大学院総合工学系研究科
  • 2003年04月 - 2005年03月   信州大学   大学院工学系研究科
  • 1999年04月 - 2003年03月   信州大学   理学部   物質循環学科

研究活動情報

論文

  • Yared B. Yohannes, Shouta M. M. 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 mu g/dL and 7.9 mu g/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.
  • 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.
  • Kraisiri Khidkhan, Hazuki Mizukawa, Yoshinori Ikenaka, Shouta M M Nakayama, Kei Nomiyama, Nozomu Yokoyama, Osamu Ichii, Mitsuyoshi Takiguchi, Shinsuke Tanabe, Mayumi Ishizuka
    The Journal of veterinary medical science 82 7 978 - 982 2020年07月31日 [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.
  • 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 2020年06月18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. 26.5% 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.
  • Rio Doya, Shouta Mm 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 & technology 2020年06月03日 [査読有り][通常論文]
     
    We investigated the potential effects of different land use and other environment 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 distance from the contaminant source, while those in lizards living in green fields were lower than expected. In addition, lead concentration of lungs were higher than that of 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.
  • 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.
  • 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.
  • 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01日 [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.
  • John Yabe, Shouta M. M. 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 mu g/dL, with residents from Kasanda (mean 45.7 mu g/dL) recording the highest BLL while Hamududu residents recorded the lowest (mean 3.3 mu g/dL). Of the total number of children sampled (n = 562), 23% exceeded the 45 mu g/dL, the threshold required for chelation therapy. A few children (5) exceeded the 100 mu g/dL whereas none of the parents exceeded the 100 mu g/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. (C) 2019 Elsevier Ltd. All rights reserved.
  • 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.
  • Tadashi Takada, Naoki Yoneda, Tetsushi Hirano, Kanoko Onaru, Youhei Mantani, Toshifumi Yokoyama, Hiroshi Kitagawa, Yoshiaki Tabuchi, Colins Nimako, Mayumi Ishizuka, Yoshinori Ikenaka, Nobuhiko Hoshi
    The Journal of veterinary medical science 2020年01月27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.
  • 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.
  • 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.
  • Tetsushi Hirano, Satsuki Minagawa, Yukihiro Furusawa, Tatsuya Yunoki, Yoshinori Ikenaka, Toshifumi Yokoyama, Nobuhiko Hoshi, Yoshiaki Tabuchi
    Toxicology and applied pharmacology 383 114777 - 114777 2019年11月15日 [査読有り][通常論文]
     
    Neonicotinoids are one of most widely used pesticides targeting nicotinic acetylcholine receptors (nAChRs) of insects. Recent epidemiological evidence revealed increasing amounts of neonicotinoids detected in human samples, raising the critical question of whether neonicotinoids affect human health. We investigated the effects of a neonicotinoid pesticide clothianidin (CTD) on human neuroblastoma SH-SY5Y cells as in vitro models of human neuronal cells. Cellular and functional effects of micromolar doses of CTD were evaluated by changes in cell growth, intracellular signaling activities and gene expression profiles. We examined further the effects of CTD on neuronal differentiation by measuring neurite outgrowth. Exposure to CTD (1-100 μM) significantly increased the number of cells within 24 h of culture. The nAChRs antagonists, mecamylamine and SR16584, inhibited this effect, suggesting human α3β4 nAChRs could be targets of neonicotinoids. We observed a transient intracellular calcium influx and increased phosphorylation of extracellular signal-regulated kinase 1/2 shortly after exposure to CTD. Transcriptome analysis revealed that CTD down-regulated genes involved in neuronal function (e.g., formation of filopodia and calcium ion influx) and morphology (e.g., axon guidance signaling and cytoskeleton signaling); these changes were reflected by a finding of increased neurite length during neuronal differentiation. These findings provide novel insight into the potential risks of neonicotinoids to the human nervous system.
  • 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.
  • 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.
  • Takahashi Keisuke, Tsurumi Tatsuya, Inami Moe, Li Zui, Kusakabe Taichi, Kikkawa Shoko, Azumaya Isao, Tominaga Nobuaki, Ikenaka Yoshinori, Arizono Koji, Kato Keisuke
    CHEMISTRYSELECT 4 24 7343 - 7345 2019年06月28日 [査読有り][通常論文]
  • Uno Y, Takahira R, Murayama N, Onozeki S, Kawamura S, Uehara S, Ikenaka Y, Ishizuka M, Ikushiro S, Yamazaki H
    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.
  • Kawai YK, Shinya S, Ikenaka Y, Saengtienchai A, Kondo T, Darwish WS, Nakayama SMM, Mizukawa H, Ishizuka M
    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.
  • A. Shoji, K. H. Elliott, S. Aris-Brosou, H. Mizukawa, S. M.M. Nakayama, Y. Ikenaka, M. Ishizuka, T. Kuwae, K. Watanabe, J. Escoruela Gonzalez, Y. Watanuki
    Environmental Toxicology and Chemistry 38 1 106 - 114 2019年01月 [査読有り][通常論文]
     
    © 2018 SETAC 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.
  • Uno Yasuhiro, Takahira Rika, Murayama Norie, Ishii Yu, Ikenaka Yoshinori, Ishizuka Mayumi, Yamazaki Hiroshi, Ikushiro Shinichi
    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.
  • Ishibashi Hiroshi, Uchida Masaya, Yoshimoto Keisuke, Imamura Yuta, Yamamoto Ryoko, Ikenaka Yoshinori, Kawai Masahito, Ichikawa Nobuhiro, Takao Yuji, Tominaga Nobuaki, Ishibashi Yasuhiro, Arizono Koji
    ENVIRONMENTAL POLLUTION 239 281 - 288 2018年08月 [査読有り][通常論文]
     
    In this study, we determined the concentration of equine estrogens, such as equilin (Eq) and equilenin (Eqn), in the river water collected from nine research stations in Hokkaido, Japan. The LC-MS/MS analysis revealed that Eq concentrations were 2.7 ± 6.7, 0.22 ± 0.12, and 1.2 ± 0.64 ng/L in Sep 2015, Feb 2016, and Jul 2016, respectively. Eqn had concentration levels similar to those of Eq. Comparison of the concentrations at nine research stations showed that seasonal variation was observed in the detected Eq and Eqn concentration levels. This study was the first to show the occurrences and seasonal variation of Eq and Eqn in the river water of Japan. We further investigated the reproductive and transgenerational effects of Eq in Japanese medaka (Oryzias latipes) exposed to 10, 100, and 1000 ng/L for 21 days and assessed the transcriptional profiles of the estrogen-responsive genes in the livers of both sexes. The reproduction assay demonstrated that 1000 ng/L of Eq adversely affected the reproduction (i.e. fecundity) in the F0 generation and that the hatching of F1 generation fertilized eggs was reduced in the 100 and 1000 ng/L treatment groups. Our qRT-PCR assay revealed that the mRNA expression levels of hepatic vitellogenin 1 and 2, choriogenin L and H, and estrogen receptor α were significantly up-regulated in males exposed to 100 and/or 1000 ng/L of Eq. In contrast, the transcriptional levels of several genes, such as pregnane X receptor and cytochrome P450 3A, were down-regulated in the livers of males after the 21-d exposure. These results suggest that Eq has endocrine-disrupting potential such as reproductive and transgenerational effects by the modulation of hepatic estrogen-responsive genes expression on medaka.
  • Pheiffer Wihan, Wolmarans Nico J, Gerber Ruan, Yohannes Yared B, Ikenaka Yoshinori, Ishizuka Mayumi, Smit Nico J, Wepener Victor, Pieters Rialet
    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.
  • 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.
  • 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.
  • 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.
  • 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.
  • Kawai YK, Ikenaka Y, Ishizuka M, Kubota A
    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.
  • ポリ塩化ビフェニル(PCBs)がネコの甲状腺機能に及ぼす影響
    水川 葉月, 高居 名菜, 野見山 桂, 高口 倖暉, 横山 望, 市居 修, 滝口 満喜, 池中 良徳, 中山 翔太, 石塚 真由美
    環境ホルモン学会研究発表会要旨集 20回 78 - 78 環境ホルモン学会(日本内分泌撹乱化学物質学会) 2017年12月 [査読有り][通常論文]
  • 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.
  • 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03日 [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 (Barking, Essex : 1987) 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 (∑OHPAHs) were significantly higher from urban sites compared to the control site. Geometric mean concentrations adjusted by specific gravity, GMSG, 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 ∑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.
  • Takamitsu Kondo, Yoshinori Ikenaka, Shouta M M Nakayama, Yusuke K Kawai, Hazuki Mizukawa, Yoko Mitani, Kei Nomiyama, Shinsuke Tanabe, Mayumi Ishizuka
    Toxicological sciences : an official journal of the Society of Toxicology 158 1 90 - 100 2017年07月01日 [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 Vmax/Km 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.
  • ネコの甲状腺機能に対するポリ塩化ビフェニル(PCBs)の影響評価 甲状腺ホルモンの脱ヨード化と代謝能の解析
    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, 中山 翔太, Sainnoxoi Tsend-ayush, 田辺 信介, 石塚 真由美
    The Journal of Toxicological Sciences 42 Suppl. S236 - S236 (一社)日本毒性学会 2017年06月 [査読有り][通常論文]
  • Chihiro Ishii, Yoshinori Ikenaka, Shouta M M Nakayama, Hazuki Mizukawa, Yared Beyene Yohannes, Yutaka Watanuki, Masaaki Fukuwaka, Mayumi Ishizuka
    The Journal of veterinary medical science 79 4 807 - 814 2017年04月20日 [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 (δ15N) and carbon (δ13C) 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 δ15N 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.
  • Lesa A Thompson, Wageh Sobhy Darwish, Yoshinori Ikenaka, Shouta M M Nakayama, Hazuki Mizukawa, Mayumi Ishizuka
    The Journal of veterinary medical science 79 4 751 - 764 2017年04月08日 [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.
  • 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.
  • 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.
  • 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 [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
    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.
  • Saengtienchai A, Ikenaka Y, Bortey-Sam N, Jermnark U, Mizukawa H, Kawai YK, Nakayama SM, Ishizuka M
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 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-1-glucuronide, pyrene-1-sulfate, and pyrenediol-sulfate, and excreted in the urine. Pyrene-1-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 O-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 β-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.
  • Bortey-Sam N, Ikenaka Y, Akoto O, Nakayama SM, Marfo J, Saengtienchai A, Mizukawa H, Ishizuka M
    Environmental pollution (Barking, Essex : 1987) 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), GMSG, 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, 2-3-OHFlu, 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.
  • Nishiyama Y, Nakayama SM, Watanabe KP, Kawai YK, Ohno M, Ikenaka Y, Ishizuka M
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science 78 4 675 - 80 2016年05月03日 [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.
  • Gerber R, Smit NJ, Van Vuren JH, Nakayama SM, Yohannes YB, Ikenaka Y, Ishizuka M, Wepener V
    The Science of the total environment 550 522 - 533 2016年04月15日 [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) are exposed to by use of OCPs in the catchments outside the KNP and how this exposure relates to human health. Tigerfish (Hydrocynus vittatus) are 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.
  • Mahmoud AF, Ikenaka Y, Yohannes YB, Darwish WS, Eldaly EA, Morshdy AE, Nakayama SM, Mizukawa H, Ishizuka M
    Chemosphere 144 1365 - 71 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 γ-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 ≅ 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.
  • Darwish WS, Ikenaka Y, Morshdy AE, Eldesoky KI, Nakayama S, Mizukawa H, Ishizuka M
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science 78 2 351 - 4 2016年02月 [査読有り][通常論文]
     
    The aim of this study was to estimate total carotenoids, β-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 β-carotene. Unexpectedly, sheep was the highest accumulator of retinol with a mean concentration of 203 ± 23.34 µg/g, while the least accumulator was buffalo, having a mean value of 58.28 ± 13.77 µg/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.
  • Mizukawa H, Nomiyama K, Nakatsu S, Iwata H, Yoo J, Kubota A, Yamamoto M, Ishizuka M, Ikenaka Y, Nakayama SM, Kunisue T, Tanabe S
    Environmental science & technology 50 1 444 - 52 2016年01月05日 [査読有り][通常論文]
     
    There are growing concerns about the increase in hyperthyroidism in pet cats due to exposure to organohalogen 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 (6OH-/MeO-BDE47 and 2'OH-/MeO-BDE68) from marine organisms. In particular, higher concentrations of 6OH-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 6OH-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 6OH-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.
  • Hokuto Nakata, Shouta M M Nakayama, John Yabe, Allan Liazambi, Hazuki Mizukawa, Wageh Sobhy Darwish, Yoshinori Ikenaka, Mayumi Ishizuka
    Environmental pollution (Barking, Essex : 1987) 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 μg/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 μg/dL of Pb-B in goats.
  • Darwish WS, Ikenaka Y, Nakayama SM, Mizukawa H, Ishizuka M
    Journal of food science 81 1 T275-81 - 81 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 β-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 β-carotene (10 μM) 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.
  • Gerber R, Smit NJ, van Vuren JH, Nakayama SM, Yohannes YB, Ikenaka Y, Ishizuka M, Wepener V
    Environmental science and pollution research international 22 24 19971 - 89 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.
  • Teraoka H, Okamoto E, Kudo M, Nakayama SM, Ikenaka Y, Ishizuka M, Endo T, Kitazawa T, Hiraga T
    Ecotoxicology and environmental safety 122 557 - 64 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.
  • Darwish WS, Ikenaka Y, Nakayama S, Mizukawa H, Ishizuka M
    The Japanese journal of veterinary research 63 4 173 - 82 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.
  • Saengtienchai A, Ikenaka Y, Darwish WS, Nakayama SM, Mizukawa H, Ishizuka M
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science 77 10 1261 - 7 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-sulfate (PYOS), pyrene-1-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.
  • Kakehi M, Ikenaka Y, Nakayama SM, Kawai YK, Watanabe KP, Mizukawa H, Nomiyama K, Tanabe S, Ishizuka M
    Toxicological sciences : an official journal of the Society of Toxicology 147 2 360 - 9 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.
  • 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 (Barking, Essex : 1987) 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, 0.17-4.35 μg/kg, dry-wt) and Pb (90-2710 μg/kg) levels in blood were generally high, suggesting human exposure to Cd through livestock consumption and Pb poisoning among pigs (2600 μg/kg) and cattle (354 μg/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.
  • Bortey-Sam N, Nakayama SM, Akoto O, Ikenaka Y, Baidoo E, Mizukawa H, Ishizuka M
    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.
  • Bortey-Sam N, Nakayama SM, Akoto O, Ikenaka Y, Fobil JN, Baidoo E, Mizukawa H, Ishizuka M
    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.
  • Bortey-Sam N, Nakayama SM, Ikenaka Y, Akoto O, Baidoo E, Mizukawa H, Ishizuka M
    Environmental monitoring and assessment 187 7 397 - 397 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 (μg/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.
  • Darwish WS, Nakayama SM, Itotani Y, Ohno M, Ikenaka Y, Ishizuka M
    Journal of food science 80 7 T1627-32 - 32 2015年07月 [査読有り][通常論文]
     
    UNLABELLED: 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.
  • Bortey-Sam N, Ikenaka Y, Akoto O, Nakayama SM, Yohannes YB, Baidoo E, Mizukawa H, Ishizuka M
    Environmental science and pollution research international 22 13 9658 - 67 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 1:2 v/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.
  • Ikenaka Y, Nakayama SM, Oguri M, Saengtienchai A, Mizukawa H, Kobayashi J, Darwish WS, Ishizuka M
    Environmental toxicology and pharmacology 39 3 1148 - 53 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.
  • Marfo JT, Fujioka K, Ikenaka Y, Nakayama SM, Mizukawa H, Aoyama Y, Ishizuka M, Taira K
    PloS one 10 11 e0142172  2015年 [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.
  • Bortey-Sam N, Nakayama SM, Ikenaka Y, Akoto O, Baidoo E, Yohannes YB, Mizukawa H, Ishizuka M
    Ecotoxicology and environmental safety 111 160 - 7 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 (μg/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.
  • 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.
  • Bortey-Sam N, Ikenaka Y, Nakayama SM, Akoto O, Yohannes YB, Baidoo E, Mizukawa H, Ishizuka M
    The Science of the total environment 496 471 - 478 2014年10月15日 [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.
  • Fujisawa N, Nakayama SM, Ikenaka Y, Ishizuka M
    Archives of toxicology 88 9 1739 - 1748 9 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.
  • Saengtienchai A, Ikenaka Y, Nakayama SM, Mizukawa H, Kakehi M, Bortey-Sam N, Darwish WS, Tsubota T, Terasaki M, Poapolathep A, Ishizuka M
    Environmental toxicology and chemistry / SETAC 33 9 2062 - 9 9 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.
  • 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.
  • Sutjarit S, Nakayama SM, Ikenaka Y, Ishizuka M, Banlunara W, Rerkamnuaychoke W, Kumagai S, Poapolathep A
    Toxicology letters 229 1 292 - 302 1 2014年08月17日 [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.
  • 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.
  • Mizukawa H, Ikenaka Y, Nakayama SM, Sakamoto KQ, Fujita S, Ishizuka M
    The Japanese journal of veterinary research 62 3 107 - 15 3 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.
  • Ishii C, Ikenaka Y, Nakayama SM, Suzuki Y, Watanuki Y, Watanabe Y, Yohannes YB, Mizukawa H, Ishizuka M
    The Japanese journal of veterinary research 62 3 143 - 9 3 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.
  • Darwish WS, Ikenaka Y, Nakayama SM, Ishizuka M
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science 76 6 789 - 97 6 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.
  • Hironobu Yasui, Ryo Takeuchi, Masaki Nagane, Shunsuke Meike, Yoshinari Nakamura, Tohru Yamamori, Yoshinori Ikenaka, Yasuhiro Kon, Hiroki Murotani, Motoi Oishi, Yukio Nagasaki, Osamu Inanami
    CANCER LETTERS 347 1 151 - 158 2014年05月 [査読有り][通常論文]
     
    High atomic number molecules, such as gold and platinum, are known to enhance the biological effect of X-irradiation. This study was aimed to determine the radiosensitizing potential of PEGylated nanogel containing gold nanoparticles (GNG) and the cellular mechanism involved. GNG pretreatment increased the levels of reproductive cell death and apoptosis induced by X-irradiation. GNG accumulated in cytoplasm and increased the expression of endoplasmic reticulum (ER) stress-related protein. GNG suppressed the repair capacity of DNA after X-irradiation by down-regulating DNA repair-related proteins. Our results suggest that GNG radiosensitized cells by enhancing apoptosis and impairing DNA repair capacity via ER stress induction. (C) 2014 Elsevier Ireland Ltd. All rights reserved.
  • Darwish WS, Ikenaka Y, Nakayama S, Ishizuka M
    Biological trace element research 158 2 243 - 8 2 2014年05月 [査読有り][通常論文]
     
    Copper (Cu(2+)) is an essential element that plays important roles in physiological functions of the body. However, high Cu(2+) levels can have toxic implications. This study aims to investigate the constitutive response to Cu(2+) exposure of xenobiotic-metabolizing enzymes in cultured rat liver (H4-II-E) cell lines. Rat cells were exposed to copper sulfate (0-500 μM) for 24 h. The effects of Cu(2+) 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 Cu(2+). 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 Cu(2+); however, CYP1A1 and CYP1A2 mRNA expressions were significantly downregulated at higher Cu(2+) concentrations. These effects corresponded with expression of aryl hydrocarbon receptor mRNA. The mRNA expressions of phase II enzymes were reduced upon exposure to Cu(2+). In conclusion, phase I and II enzyme expressions were significantly modulated upon Cu(2+) exposure. These results indicated that Cu(2+) exposure had toxicological implications for cultured H4-II-E cells.
  • Saengtienchai T, Poapolathep S, Isariyodom S, Ikenaka Y, Ishizuka M, Poapolathep A
    Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association 66 307 - 12 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 1mg/kg 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 24h and 48h after iv and po administration, respectively, and the concentration of NIV was detected up to 12h after both types of administration. The Cp(0) of FX was 580.28 ± 140.81 ng/ml after iv administration. The values of t1/2β, Vss and Foral 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 24h 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 3h following po administration. In vitro of liver postmitochondrial fractions with FX demonstrated that the liver and kidney are capable of FX-to-NIV metabolism.
  • 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]
  • Kensuke P. Watanabe, Yusuke K. Kawai, Minami Kawata, Shouta M. M. Nakayama, Yoshinori Ikenaka, Mayumi Ishizuka
    DRUG METABOLISM REVIEWS 45 92 - 92 2014年01月 [査読有り][通常論文]
  • Fujisawa N, Kawai YK, Nakayama SM, Ikenaka Y, Yamamoto H, Ishizuka M
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science 75 12 1577 - 83 12 2013年12月30日 [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.
  • 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.
  • Sasaki Nobuo, Matumoto Tomoyuki, Ikenaka Yoshinori, Nakayama Shouta M. M, Ishizuka Mayumi, Kazusaka Akio, Fujita Shoichi
    JOURNAL OF VETERINARY MEDICAL SCIENCE 75 11 1497 - 502 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.
  • Kawai YK, Watanabe KP, Ishii A, Ohnuma A, Sawa H, Ikenaka Y, Ishizuka M
    Comparative biochemistry and physiology. Part D, Genomics & proteomics 8 3 201 - 8 3 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.
  • Ikenaka Y, Oguri M, Saengtienchai A, Nakayama SM, Ijiri S, Ishizuka M
    Environmental toxicology and pharmacology 36 2 567 - 578 2 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.
  • Nakayama SM, Ikenaka Y, Hamada K, Muzandu K, Choongo K, Yabe J, Umemura T, Ishizuka M
    Environmental monitoring and assessment 185 6 4907 - 18 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.
  • Darwish WS, Eldaly EA, El-Abbasy MT, Ikenaka Y, Nakayama S, Ishizuka M
    The Japanese journal of veterinary research 61 Suppl S13-22 - 22 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.
  • Darwish WS, Ikenaka Y, Ishizuka M
    The Japanese journal of veterinary research 61 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.
  • Mahmoud AF, Darwish WS, Morshdy AE, Eldaly EA, Ikenaka Y, Ishizuka M
    The Japanese journal of veterinary research 61 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.
  • Marfo JT, Akoto O, Nakayama SM, Baidoo E, Ikenaka Y, Ishizuka M
    The Japanese journal of veterinary research 61 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.
  • Bortey-Sam N, Akoto O, Ikenaka Y, Nakayama SM, Ishizuka M
    The Japanese journal of veterinary research 61 Suppl S72-4 - 4 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.
  • Ishii C, Ikenaka Y, Nakayama SM, Suzuki Y, Watanuki Y, Watanabe Y, Fukuwaka MA, Yohannes YB, Kawai YK, Ishizuka M
    The Japanese journal of veterinary research 61 Suppl S75-6 - 6 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.
  • Oroszlany B, Ikenaka Y, Saengtiengchan A, Oguri M, Nakayama SM, Ishizuka M
    The Japanese journal of veterinary research 61 Suppl S77-8 - 8 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.
  • Nakayama SM, Ikenaka Y, Muzandu K, Choongo K, Yabe J, Umemura T, Ishizuka M
    The Japanese journal of veterinary research 61 Suppl S79-81 - 81 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.
  • Hayami A, Darwish WS, Ikenaka Y, Nakayama SM, Ishizuka M
    The Japanese journal of veterinary research 61 Suppl S82-4 - 4 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.
  • Ikenaka Y, Sakamoto M, Nagata T, Takahashi H, Miyabara Y, Hanazato T, Ishizuka M, Isobe T, Kim JW, Chang KH
    The Journal of toxicological sciences 38 1 131 - 6 1 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. LC(50) of B[a]P for C. reticulata and D. magna was 4.3 and 4.7 µg/l, respectively. However, individuals fed with Chlorella showed higher LC(50), 6.1 µg/l for C. reticulata and 8.0 µg/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 µg/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 µg/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.
  • 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.
  • Tanaka Kazuyuki D, Kawai Yusuke K, Ikenaka Yoshinori, Harunari Tsunehito, Tanikawa Tsutomu, Fujita Shoichi, Ishizuka Mayumi
    JOURNAL OF VETERINARY MEDICAL SCIENCE 75 2 135 - 9 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 µM. The Vmax 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 Km values of resistant rats (47 ± 32 µM) were similar to those of sensitive rats (59 ± 18 µM). Warfarin-sensitive rats exhibited enzyme efficiencies (Vmax/Km) 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.
  • Nakayama SM, Ikenaka Y, Muzandu K, Choongo K, Yabe J, Muroya T, Ijiri S, Minagawa M, Umemura T, Ishizuka M
    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
  • Watanabe KP, Kawai YK, Ikenaka Y, Kawata M, Ikushiro S, Sakaki T, Ishizuka M
    PloS one 8 9 e75689  9 2013年 [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.
  • Mureithi D, Darwish WS, Ikenaka Y, Kanja L, Ishizuka M
    The Japanese journal of veterinary research 60 4 205 - 10 4 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.
  • Ikenaka Y, Nakayama SM, Muroya T, Yabe J, Konnai S, Darwish WS, Muzandu K, Choongo K, Mainda G, Teraoka H, Umemura T, Ishizuka M
    Environmental toxicology and chemistry / SETAC 31 10 2300 - 5 10 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-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), 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-α, IL-1β, and iNOS, similar to those found in vivo. These results indicate the possibility of immune system modulations in cattle from the Kabwe area.
  • M'kandawire E, Syakalima M, Muzandu K, Pandey G, Simuunza M, Nakayama SM, Kawai YK, Ikenaka Y, Ishizuka M
    Gene 506 2 310 - 6 2 2012年09月15日 [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 183bp, 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.
  • 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 - 9 2012年08月15日 [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 caffer), 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.
  • Nakayama SM, Ikenaka Y, Muzandu K, Choongo K, M'kandawire E, Yasuda J, Ishizuka M
    Ecotoxicology and environmental safety 80 333 - 8 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.
  • Ohno M, Ikenaka Y, Ishizuka M
    Biochemical and biophysical research communications 417 1 484 - 9 1 2012年01月06日 [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 RARα. 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.
  • Ohno M, Ikenaka Y, Ishizuka M
    Journal of biochemical and molecular toxicology 26 1 16 - 22 1 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 µM 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.
  • Ueda H, Ikenaka Y, Nakayama SM, Tanaka-Ueno T, Ishizuka M
    Aquatic toxicology (Amsterdam, Netherlands) 105 3-4 337 - 43 3-4 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.
  • 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
  • Ohno M, Darwish WS, Ikenaka Y, Miki W, Ishizuka M
    Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association 49 6 1285 - 91 6 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 I 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.
  • Nakayama SM, Ikenaka Y, Hamada K, Muzandu K, Choongo K, Teraoka H, Mizuno N, Ishizuka M
    Environmental pollution (Barking, Essex : 1987) 159 1 175 - 181 1 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.
  • Darwish WS, Ikenaka Y, Ohno M, Eldaly EA, Ishizuka M
    Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association 48 11 3201 - 8 11 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 β-carotene, with both EROD activity and CYP1A protein expression. These correlations were negative with the accumulated retinoids, such as retinol. The β-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.
  • 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.
  • Darwish Wageh Sobhy, Kawai Yusuke, Ikenaka Yoshinori, Yamamoto Hideaki, Muroya Tarou, Ishizuka Mayumi
    JOURNAL OF VETERINARY MEDICAL SCIENCE 72 9 1237 - 41 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.
  • Nakayama SM, Ikenaka Y, Muzandu K, Choongo K, Oroszlany B, Teraoka H, Mizuno N, Ishizuka M
    Archives of environmental contamination and toxicology 59 2 291 - 300 2 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).
  • Takiguchi M, Darwish WS, Ikenaka Y, Ohno M, Ishizuka M
    Toxicological sciences : an official journal of the Society of Toxicology 116 1 79 - 91 1 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.
  • Watanabe KP, Saengtienchai A, Tanaka KD, Ikenaka Y, Ishizuka M
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP 152 1 114 - 9 1 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 (11.3+/-2.5 microM and 0.64+/-0.39 microM, respectively). Interestingly, the ostrich K(i) was similar to the values for rats (0.28+/-0.09 microM). 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.
  • Kawai YK, Ikenaka Y, Fujita S, Ishizuka M
    Mammalian genome : official journal of the International Mammalian Genome Society 21 5-6 320 - 9 5-6 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 phytochemicals 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.
  • Darwish WS, Ikenaka Y, Eldaly EA, Ohno M, Sakamoto KQ, Fujita S, Ishizuka M
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science 72 5 561 - 6 5 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.
  • 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.
  • Darwish WS, Morshdy AE, Ikenaka Y, Ibrahim ZS, Fujita S, Ishizuka M
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science 72 2 221 - 4 2 2010年02月 [査読有り][通常論文]
     
    In this study, we determined a partial sequence of CYP1A1 in the camel and its phylogenetic position. The deduced amino acid sequence of camel CYP1A1 showed the highest identity 94% with those of sheep and cattle CYP1A1. In a phylogenetic analysis, the camel CYP1A1 isoform was located beside sheep and cattle CYP1A1. When we studied the distribution of camel CYP1A1 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 CYP1A1 mRNA, and this may indicate exposure to ligands of aryl hydrocarbon receptor such as environmental pollutants or flavonoids.
  • 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.
  • El BK, Hashimoto Y, Muzandu K, Ikenaka Y, Ibrahim ZS, Kazusaka A, Fujita S, Ishizuka M
    The Japanese journal of veterinary research 57 2 109 - 18 2 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.
  • Sasaki N, Sakai N, Ikenaka Y, Kamiya T, Heewon M, Sakamoto KQ, Ishizuka M, Fujita S
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science 70 3 223 - 6 3 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.
  • Ikenaka Y, Ishizaka M, Eun H, Miyabara Y
    Biochemical and biophysical research communications 360 2 490 - 5 2 2007年08月24日 [査読有り][通常論文]
     
    We found that aquatic crustaceans, decapoda; atyidae (Caridina multidentata, Neocaridina denticulate, and Paratya compressa), metabolize pyrene to a new conjugation product. The results of deconjugation treatments indicated that glucose and sulfate combined with 1-hydroxypyrene. Further analysis by LC/ESI-MS/MS showed that the molecular weight of the product was 460 (m/z 459; deprotonated ion), and that it has a glucose-sulfate moiety (m/z 241; fragment ion). These results indicated that the new metabolite was the glucose-sulfate conjugate of 1-hydroxypyrene. The glucose-sulfate conjugate is a phase II product that has not been reported previously from any organism. Several studies have demonstrated that sulfation is an important pathway for metabolism of xenobiotics in aquatic invertebrates. Thus, glucose-sulfate conjugates may add an important signal for excretion or sequestration of xenobiotics for aquatic invertebrates.
  • Ikenaka Y, Eun H, Ishizaka M, Miyabara Y
    Aquatic toxicology (Amsterdam, Netherlands) 80 2 158 - 65 2 2006年11月16日 [査読有り][通常論文]
     
    The aquatic crustacean Daphnia magna is an important species for ecotoxicological study, and is often used as a test organism for environmental risk assessment. However, the mechanism of xenobiotic metabolism by this species has not been studied in detail. In the present study, pyrene was used as model substance to investigate the mechanism of xenobiotic metabolism in D. magna. The results of 24-h exposure experiments showed that D. magna could metabolize pyrene and biotransform it into water-soluble metabolites. On the other hand, the metabolism of pyrene was significantly inhibited by SKF-525A as the cytochrome P450 (CYP) inhibitor. These observations indicated that oxidation by CYP participated in the biotransformation of pyrene by D. magna. We also identified the pyrene metabolites formed by D. magna by HPLC with an electrospray ionization triple quadrupole mass spectrometry detector (LC/ESIMS/MS) and de-conjugation by sulfatase, beta-glucuronidase, and beta-glucosidase. One of the metabolites was ionized in ESI negative mode and formed a dominant mass of m/z 297 (MS) with the product ion of m/z 217 (MS2). Furthermore, this metabolite formed 1-hydroxypyrene on treatment with sulfatase. This metabolite was considered to be a sulfate conjugate of oxidized pyrene (1-hydroxypyrenesulfate). Furthermore, we quantified the deconjugated 1-hydroxypyrene formed by the above enzyme treatment. It showed that 52% of the total metabolized pyrene was biotransformed into 1-hydroxypyrene-sulfate, and more than 73% was biotransformed into oxidized pyrene conjugate. These results indicated that CYP and several conjugation enzymes participate in its biotransformation, and sulfation is important in D. magna for metabolism and elimination of xenobiotics.
  • Ikenaka Y, Eun H, Watanabe E, Kumon F, Miyabara Y
    Environmental pollution (Barking, Essex : 1987) 138 3 529 - 37 3 2005年12月 [査読有り][通常論文]
     
    To elucidate the historical changes in polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), coplanar polychlorinated biphenyl (co-PCB), and polycyclic aromatic hydrocarbon (PAH) inflows in Lake Suwa, their concentrations in the sediment core were analyzed in 5 cm interval. The maximum concentrations (depth cm) of PCDDs/DFs, co-PCBs, and PAHs were 25.2 ng/g dry (30-35 cm), 19.0 ng/g dry (30-35 cm), and 738, 795 ng/g dry (50-55 cm, 30-35 cm), respectively. Age and sedimentation rate of the sediment were estimated from the vertical changes in apparent density. Deposition rate of dioxins and PAHs were calculated from the concentration and sedimentation rate of the sediment. The results indicate that large amounts of dioxins and PAHs flowed into the lake in flood stage compared to normal stage.

その他活動・業績

  • 佐藤裕, 石井千尋, 中山翔太, 一瀬貴大, 齊藤慶輔, 渡邊有希子, 小笠原浩平, 鳥本亮太, 小林篤史, 木村享史, 池中良徳, 石塚真由美 日本獣医学会学術集会講演要旨集 162nd 504 2019年08月20日 [査読無し][通常論文]
  • 川合佑典, 新屋惣, 中山翔太, 池中良徳, 石塚真由美, 久保田彰 日本進化学会大会プログラム・講演要旨集(Web) 21st 116 (WEB ONLY) 2019年08月07日 [査読無し][通常論文]
  • 井上 裕美子, 佐々木 東, 池中 良徳, 一瀬 貴大, 笹岡 一慶, 大菅 辰幸, 中山 翔太, 森下 啓太郎, 大田 寛, 石塚 真由美, 滝口 満喜 日本獣医学会学術集会講演要旨集 162回 470 -470 2019年08月 [査読無し][通常論文]
  • 鈴木 智裕, 池中 良徳, 中山 翔太, 水川 葉月, 一瀬 貴大, 佐々木 東, 笹岡 一慶, 石塚 真由美 日本獣医学会学術集会講演要旨集 162回 501 -501 2019年08月 [査読無し][通常論文]
  • 白尾 大樹, 池中 良徳, 一瀬 貴大, 中山 翔太, 佐々木 東, 永田 矩之, 水川 葉月, 滝口 満喜, 石塚 真由美 日本獣医学会学術集会講演要旨集 162回 470 -470 2019年08月 [査読無し][通常論文]
  • 大井真里奈, 丸橋孝昭, 吉村久仁子, 栗原祐太朗, 長田真由子, 池中良徳, 石塚真由美, 浅利靖 中毒研究 32 (2) 239 2019年07月20日 [査読無し][通常論文]
  • 本平航大, 池中良徳, 池中良徳, BEYENE Yared, 中山翔太, WEPENER Victor, SMIT Nico, VAN VUREN Johan, 江口哲史, SOUSA Ana Catarina, 石塚真由美 環境化学討論会要旨集(CD-ROM) 28th ROMBUNNO.2A‐06 2019年06月11日 [査読無し][通常論文]
  • 中田北斗, 中山翔太, YABE John, MUZANDU Kaampwe, 豊巻治也, BEYENE Yared, KATABA Andrew, KATABA Andrew, ZYAMBO Golden, CHOONGO Kennedy, 池中良徳, 石塚真由美 環境化学討論会要旨集(CD-ROM) 28th ROMBUNNO.1C‐18 2019年06月11日 [査読無し][通常論文]
  • 水川葉月, NGYUEN Hoa Thanh, 岩田久人, 野見山桂, 池中良徳, 中山翔太, 横山望, 市居修, 滝口満喜, KHIDKHAN Kraisiri, 田辺信介, 石塚真由美 環境化学討論会要旨集(CD-ROM) 28th ROMBUNNO.1C‐08 2019年06月11日 [査読無し][通常論文]
  • 田中厚資, 綿貫豊, 高田秀重, 石塚真由美, 山下麗, 水川薫子, 水川葉月, 池中良徳, 中山翔太 環境化学討論会要旨集(CD-ROM) 28th ROMBUNNO.P‐031 2019年06月11日 [査読無し][通常論文]
  • 白尾大樹, 池中良徳, 一瀬貴大, 中山翔太, 佐々木東, 永田矩之, 水川葉月, 滝口満善, 石塚真由美 環境化学討論会要旨集(CD-ROM) 28th ROMBUNNO.1A‐10 2019年06月11日 [査読無し][通常論文]
  • 池中良徳, 池中良徳, 一瀬貴大, NIMAKO Collins, 市川剛, 野見山桂, 長谷川浩, 中山翔太, 星信彦, 平久美子, 石塚真由美 環境化学討論会要旨集(CD-ROM) 28th ROMBUNNO.2B‐05 2019年06月11日 [査読無し][通常論文]
  • 田中啓介, 野見山桂, 水川葉月, 水川葉月, 高口倖暉, 田上瑠美, 横山望, 市居修, 滝口満喜, 笹岡一慶, 中山翔太, 池中良徳, 石塚真由美, 国末達也, 田辺信介 環境化学討論会要旨集(CD-ROM) 28th ROMBUNNO.1C‐09 2019年06月11日 [査読無し][通常論文]
  • 一瀬貴大, 池中良徳, 池中良徳, 三津橋嵩史, 中山翔太, SAENGTIENCHAI Aksorn, 野見山桂, 田上瑠美, 石塚真由美 環境化学討論会要旨集(CD-ROM) 28th ROMBUNNO.P‐106 2019年06月11日 [査読無し][通常論文]
  • 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 2019年06月 [査読無し][通常論文]
  • 打田茉由果, 石塚真由美, 池中良徳, 水川葉月, 中山翔太, 坂東武治, 田村力, 小西健志, 鈴木一平, 三谷曜子 日本水産学会大会講演要旨集 2019 162 2019年03月26日 [査読無し][通常論文]
  • 池中 良徳, 平 久美子, 有薗 幸司, 星 信彦, 藤岡 一俊, 石塚 真由美, 一瀬 貴大, Collins NIMAKO, 中山 翔太, 平野 哲史, 市川 剛, 加藤 恵介, 高橋 圭介, 長谷川 浩 日本毒性学会学術年会 46 (0) S7 -2 2019年 [査読無し][通常論文]
     

    ネオニコチノイド(NNs)は、現在世界で最も使用されている殺虫剤の一つである。特に日本では、果物や野菜における残留基準値が諸外国と比べ高く設定され、かつ複数種が使用されるため、全体的にNNsの摂取量が多いと考えられる。

    そこで本研究では、日本人におけるNNs曝露実態を明らかにする事を目的に、新生児、幼児を含む延べ数百人から尿を採取し、尿中に含まれる7種のNNs(アセタミプリド、イミダクロプリド、チアメトキサム、チアクロプリド、ニテンピラム、クロチアニジン、ジノテフラン)及び代謝物(N-デスメチルアセタミプリド)をLC/MS/MSで定量した。更に、得られた尿中データより、推定摂取量を算出し、一日摂取許容量(ADI)と比較した。

    分析の結果、日本人の尿から何らかのNNsが検出され、特に、N-デスメチルアセタミプリド(90%)、クロチアニジン(50%)、ジノテフラン(50%)の検出頻度が高かった。一方、尿中濃度から推定した各NNs摂取量は、10~50 µg/dayであり、ADIに比べアセタミプリドで最大1%程度、他のNNsは1%未満であった。更に本研究では、生後48時間以内の新生児の尿も分析した。その尿中濃度は‹LOD~0.7 ng/mLと極めて低かったが、分析した57サンプルのうち14サンプルから検出された。

    本研究の結果、多くの日本人は胎児を含めNNsの曝露を受けていることが明らかにされた。NNsの慢性低濃度曝露の健康影響については、胎児移行のメカニズムや神経発達を含む毒性に不明な点が多いが、最近の報告においてNNsは現在のNOAELの1/10程度の曝露でも実験動物に対し不安などの情動認知行動に影響を与える事が示されている。

    NNsの毒性について、再度リスク評価を実施した上で、継続的なモニタリングを行う必要がある。

  • 高本 亜希子, 石橋 弘志, 石塚 真由美, 有薗 幸司, 池中 良徳, 杉本 真夕, 岩野 まな美, 福島 聡, 一瀬 貴大, 中山 翔太, 高橋 圭介, 加藤 恵介 日本食品化学学会誌 26 (1) 17 -27 2019年 [査読無し][通常論文]
     
    In this study, we determined the concentration of seven neonicotinoid insecticides and 13 of their metabolites in 46 bottled greenteabeverages, and estimated the daily intake of neonicotinoids in adults and children from these drinks. Liquid chromatographycoupled with electrospray ionization tandem mass spectrometry (LC–ESI/MS/MS) analysis revealed that six neonicotinoidsand two metabolites were detected in bottled green-tea beverages, and the 50th percentile concentration indicated dinotefuran > thiacloprid > clothianidin > imidacloprid > thiamethoxam > acetamiprid > N-desmethyl-acetamiprid > thiacloprid-amide. Theconcentration and composition profile of neonicotinoids in bottled green-tea beverages were different between brands; however,no significant differences were observed among manufacturing sites. The concentration of acetamiprid in bottled green-teabeverages was significantly correlated with that of N-desmethyl-acetamiprid. A significant relationship between concentrations ofthiamethoxam and clothianidin in bottled green-tea beverages was also observed, suggesting those neonicotinoids are metabolizedduring the tea leaves cultivation period. The daily intake for neonicotinoids in both adults and children from consumption ofbottled green-tea beverages was < 2.1% when compared with the acceptable daily intake (ADI) of neonicotinoids.
  • 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.
  • 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.
  • 大野周嗣, 大成果乃子, 久保静花, 坂田奈那美, 平野哲史, 万谷洋平, 横山俊史, 石塚真由美, 池中良徳, 星信彦 日本内分泌かく乱化学物質学会研究発表会要旨集 21st 79 2018年12月 [査読無し][通常論文]
  • 杉田晄佑, 高田匡, 万谷洋平, 横山俊史, 石塚真由美, 池中良徳, 星信彦 日本内分泌かく乱化学物質学会研究発表会要旨集 21st 82 2018年12月 [査読無し][通常論文]
  • Nico J. Wolmarans, Louis H. Du Preez, Louis H. Du Preez, Yared Beyene Yohannes, Yoshinori Ikenaka, Yoshinori Ikenaka, Mayumi Ishizuka, Nico J. Smit, Victor Wepener Ecotoxicology 27 (9) 1203 -1216 2018年11月 [査読有り][通常論文]
     
    © 2018, Springer Science+Business Media, LLC, part of Springer Nature. 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 Müller’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.
  • W. Pheiffer, N. Bortey-Sam, Y. Ikenaka, Y. Ikenaka, S. M.M. Nakayama, H. Mizukawa, M. Ishizuka, N. J. Smit, R. Pieters African Journal of Aquatic Science 43 305 -312 2018年09月25日 [査読無し][通常論文]
     
    © 2018, © 2018 NISC (Pty) Ltd. The concentrations of selected hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) were determined in the bile of the African sharptooth catfish Clarias gariepinus from impoundments in the urban impacted Klip River system in Soweto, South Africa. Fish were sampled from three impoundments (Lenasia, Fleurhof, and Orlando dams) during the early high-flow season (September/October) of 2013. Biliary OH-PAHs were analysed using a high-pressure liquid chromatograph coupled to a tandem mass spectrometer (HPLC-MS/MS). Seven of the thirteen targeted metabolites were present in the fish of Soweto. The ΣOH-PAHs ranged between 0.1 and 1 876 ng ml−1, with greatest ΣOH-PAH mean at Orlando (947 ng ml−1) followed by Fleurhof (371 ng ml−1). The most dominant metabolite in the sampling area was 2–,3–OH fluorene, ranging between not detected and 1 429 ng ml−1, with the greatest mean at Orlando (709 ng ml−1). PAH metabolites quantified in C. gariepinus most likely originated from the sediments. The hepatosomatic index of the C. gariepinus increased proportionally with the biliary OH-PAH concentrations. To the authors’ knowledge this data on biliary OH-PAH for fish is the first for South Africa.
  • 庄子晶子, ELLIOTT K, ARIS‐BROSOU S, 水川葉月, 中山翔太, 池中良徳, 石塚真由美, 桑江朝比呂, 渡辺謙太, 綿貫豊 日本鳥学会大会講演要旨集 2018 97 2018年09月14日 [査読無し][通常論文]
  • 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.
  • XAFSを用いたザンビア鉛汚染地域の生物及び環境試料における鉛の化学形態の解明
    豊巻治也, 中山翔太, 中田北斗, 藤森崇, 塩田憲司, Yabe John, Muzandu Kaampwe, Beyene Yared, 池中良徳, 水川葉月, 石塚真由美 第21回XAFS討論会 2018年09月 [査読無し][通常論文]
  • 佐野花澄, 池中良徳, 近藤誉充, 川合佑典, 中山翔太, 水川葉月, 石塚真由美 日本獣医学会学術集会講演要旨集 161st 469 2018年08月21日 [査読無し][通常論文]
  • 大野周嗣, 大成果乃子, 久保静花, 坂田奈那美, 杉田晄佑, 宮田結佳, 高田匡, 平野哲史, 万谷洋平, 横山俊史, 石塚真由美, 池中良徳, 星信彦 日本獣医学会学術集会講演要旨集 161st 467 2018年08月21日 [査読無し][通常論文]
  • 山田尚輝, 中山翔太, 水川葉月, 小笠原浩平, 渡邊有希子, 齊藤慶輔, 伊藤真輝, 大澤夏生, 竹中康進, 小松謙之, 千葉茜, 内田義崇, 池中良徳, 石塚真由美 日本獣医学会学術集会講演要旨集 161st 469 2018年08月21日 [査読無し][通常論文]
  • 三津橋嵩史, 池中良徳, 池中良徳, 中山翔太, 水川葉月, 一瀬貴大, SAENGTIENCHAI Aksorn, 河合正人, 南保泰雄, 石塚真由美 日本獣医学会学術集会講演要旨集 161st 467 2018年08月21日 [査読無し][通常論文]
  • R. Gerber, N. J. Smit, Johan H.J. van Vuren, Y. Ikenaka, Victor Wepener Ecotoxicology and Environmental Safety 157 307 -317 2018年08月15日 [査読無し][通常論文]
     
    Studies have shown high levels of contamination of both metals and organochlorine pesticides (OCPs) in aquatic systems of the world renowned Kruger National Park, South Africa. With effects evident in top predators, including, unexplained Crocodylus niloticus deaths and organ level and histological changes in Hydrocynus vittatus. A suite of biomarkers reflecting exposure and were selected to evaluate biological responses of H. vittatus to anthropogenic stressors as well as to evaluate whether the chosen suite of biomarkers could successfully distinguish between the different pollution profiles present in the selected rivers. During this study a clear relationship was found between exposure to environmental contaminants and the concomitant responses of H. vittatus to these stressors. The ensuing biomarker responses indicated that there is a physiological attempt to deal with, and mitigate the deleterious effects that metals and OCPs may induce. In the Luvuvhu River there is a clear indication in H. vittatus of the stimulation of anti-oxidant protective mechanisms in response to internal OCP exposure. This is reflected by the increasing cytochrome P-450, superoxide dismutase, and more specifically reduced glutathione, which resulted in decreased lipid and protein breakdown (reflected in decreased lipid peroxidation and protein carbonyl levels). Consequently H. vittatus populations of the Luvuvhu River are under greater cumulative stress and this is reflected in the lower energy budgets. Our results further show the integrated application value of the current suite of biomarkers in assessing responses of subtropical fish to metal and OCP exposure as the entire suite of biomarkers when used in conjunction were able to explain 100% of the variation in the data.
  • 武田 一貴, 池中 良徳, 田中 和之, 中山 翔太, 谷川 力, 水川 葉月, 石塚 真由美 日本毒性学会学術年会 45 (0) P -71 2018年08月10日 [査読無し][通常論文]
     
    <p> 野生げっ歯類はレプトスピラやハンタウイルス感染症、ペストなど種々の人獣共通感染症を媒介するため殺鼠剤による駆除は不可欠である。しかしワルファリン(Wf)など殺鼠剤に対し抵抗性を有する個体群が殺鼠剤使用頻度の高い世界各地の都市に出現している。現在抵抗性ラットに有効な防除策は乏しく、抵抗性獲得機序の解明と新規防除策の提案は急務である。</p><p> これまでWf抵抗性の原因はWfの標的分子ビタミンKエポキシド還元酵素の遺伝子変異だと考えられてきたが、発表者が東京の殺鼠剤抵抗性ラットでWf肝灌流試験を実施した所、肝臓でのWf代謝が亢進していた。このため、抵抗性にWfの代謝・排泄も寄与することが示唆された。また、肝臓から薬物代謝酵素シトクロムP450(CYPs)を含む酵素画分を調製しWf代謝試験を実施すると、ミクロソームへNADPHを添加した所CYPsの酵素活性に大きな差は認められなかったが、S9画分へNADP+を添加するとCYPsによる代謝活性が抵抗性群で大きく上昇した。このため、肝灌流で確認された高代謝能はCYPs自体の変化ではなく、その活性に必要なNADPH産生能に起因するということが示唆された。また、実際に抵抗性ラットS9画分ではNADPHの産生が亢進していた。</p><p> このため、抵抗性ラットで確認された高NADPH産生能の責任分子を特定するため、肝臓でNADPH産生を主に担うペントースリン酸経路のNADPH産生酵素、グルコース6リン酸脱水素酵素(G6PD)について、シークエンス解析とウェスタンブロットによる発現量の定量を行った。しかしG6PD発現量自体には有意な差は認められず、アミノ酸配列においても変化は認められなかった。</p>
  • 中山 翔太, ジアンボ ゴルデン, 栗谷 豪, 中川 光弘, 水川 葉月, 石塚 真由美, ヤベ ジョン, 池中 良徳, ムザンド カアンプウェ, チョーンゴ ケネディ, 中田 北斗, 豊巻 治也, ベイエネ ヤレド, カタバ アンドリュー 日本毒性学会学術年会 45 (0) P -35 2018年08月10日 [査読無し][通常論文]
     
    <p>発表者らは、2008年よりアフリカのザンビア共和国カブウェ市における鉛汚染問題に関わる研究を進めてきた。当該の鉛・亜鉛鉱床地域では、1900年頃から鉱床活動が行われているが、低効率の精錬技術による多くの不純物を含む鉱さいの排出および不適切な廃棄により、地質中の鉛やカドミウムが環境に拡散している。我々の先行研究により、家畜(ニワトリ、ヤギ、ウシ)およびイヌ、野生ラットなどの動物における血中・臓器中の高濃度の鉛蓄積を確認した。さらに、鉱床周辺に住む子供300名の血中鉛濃度は、対象のほぼ全員が研究当時の基準値である5 µg/dLを超過する深刻な状況であることを解明した。この研究結果を受けて、特に子供における治療や地域の環境汚染レベルの低減を目的としたプロジェクト(<u>KA</u>bwe <u>M</u>ine <u>P</u>ollution <u>A</u>melioration <u>I</u>nitiative ~KAMPAI Project~)を2016年より実施している。本発表では、より広範囲のエリアにおける汚染状況の解明や、鉛の暴露経路解明を目的としたプロジェクトの一部結果を発表する。</p><p>ザンビア大学、ザンビア国保健省および所属機関における研究倫理許可を取得し、鉱床付近およびそれ以外のエリアも対象とした約500世帯(父、母、子供)の合計1250名における血液・血漿・尿および子供の糞便試料を採取した。血中鉛濃度は、オンサイトで測定可能なLeadCareⅡを用いて、現地クリニックにおいて測定し、鉛汚染の広がっている範囲の概要を掴むことができた。予想に反して、鉱床から離れた地域でも高濃度の血中鉛が検出される対象者の存在も明らかになった。今後は、血液や糞便における金属濃度および鉛安定同位体比解析により鉛の人への暴露経路を解明し、環境改善手法を検討する。さらに、100年間以上にも及ぶ長期慢性暴露により、動物や人におけるゲノム・エピゲノム修飾、腸内細菌叢コミュニティ変化などの可能性を予想している。近年では、鉛の毒性発現には閾値を設定できないとされているが、長期慢性暴露に伴う毒性発現メカニズムを解明し、効果的な予防法・治療法開発に貢献したい。</p>
  • 近藤 誉充, 池中 良徳, 中山 翔太, 水川 葉月, 三谷 曜子, 野見山 桂, 田辺 信介, 石塚 真由美 日本毒性学会学術年会 45 (0) P -60 2018年08月10日 [査読無し][通常論文]
     
    <p>アザラシやネコ科を含む食肉目動物は生態系高次栄養段階に位置し、食物連鎖を介した生物濃縮により残留性の高い有機化合物が高濃度で生体内に蓄積している。化学物質代謝酵素はこれら化学物質の解毒を担う酵素である。その中でも特に第II相抱合酵素はCytochrome P450等の代謝を受けた化学物質をさらに代謝する酵素であり、発がん性物質を含む多くの化学物質がP450の代謝を受けた後に代謝的活性化を示すため、第II相酵素は特に解毒に重要な酵素である。しかし多くの食肉目動物で第II相抱合酵素の情報は皆無であり、特に基本的情報である遺伝的性状や酵素活性の種差の情報が欠如している。そこで本研究は主要な第II相抱合酵素であるグルクロン酸転移酵素(UGT)および硫酸転移酵素(SULT)の遺伝子性状およびin vitro酵素活性の解明を目的とした。遺伝的性状解析では遺伝子データベースやシークエンス解析による遺伝子情報から系統解析、および遺伝子コード領域の種差を解明した。In vitro活性解析ではネコ、イヌ、ラット、および鰭脚類(カスピカイアザラシ、ゼニガタアザラシ、トド、キタオットセイ)の肝ミクロソームおよびサイトゾルを用いて種々の分子種特異的な基質(Lorazepam:UGT2B分子種, Estradiol:SULT1E1等)に対する酵素活性を測定した。UGTに関して、系統解析の結果から食肉目で特に重要と推定される2B31分子種の存在が明らかとなった。また、食肉目の中でもイヌでは3つのUGT2B31を持つのに対して、ネコ科動物では2B分子種が存在せず、鰭脚類でも1つの分子種しか持たないことが明らかとなった。さらにin vitro活性もイヌと比較してネコ及びアザラシ科で非常に低い活性が確認された。SULTに関しては、鰭脚類でエストロゲン代謝に重要なSULT1E1分子種が遺伝的に欠損しており、in vitro活性も低いことが解明された。これらの結果から食肉目動物の中でもとくに鰭脚類やネコ科動物では第II相抱合酵素による解毒能が弱く、種々の化学物質に対して感受性が強い可能性が示唆された。</p>
  • 中山翔太, 森田鮎子, 池中良徳, 石井千尋, 水川葉月, 武田一貴, 川合佑典, 齊藤慶輔, 渡邊有希子, 大澤夏生, 伊藤真輝, 石塚真由美 日本野生動物医学会大会・講演要旨集 24th 150 2018年08月 [査読無し][通常論文]
  • 近藤誉充, 池中良徳, 中山翔太, 水川葉月, 三谷曜子, 田辺信介, 野見山桂, 石塚真由美 日本野生動物医学会大会・講演要旨集 24th 151 2018年08月 [査読無し][通常論文]
  • 石井千尋, 池中良徳, 池中良徳, 中山翔太, 齊藤慶輔, 渡辺有希子, 小笠原浩平, 水川葉月, 石塚真由美 日本野生動物医学会大会・講演要旨集 24th 114 2018年08月 [査読無し][通常論文]
  • 中山翔太, 池中良徳, 石井千尋, 水川葉月, 川合佑典, 平野なぎ沙, 齊藤慶輔, 渡邊有希子, 大澤夏生, 伊藤真輝, 中村亮平, 石塚真由美 日本野生動物医学会大会・講演要旨集 24th 138 2018年08月 [査読無し][通常論文]
  • 佐々木 東, 中山 翔太, 大田 寛, 大菅 辰幸, 森下 啓太郎, 水川 葉月, 池中 良徳, 石塚 真由美, 滝口 満喜 日本獣医学会学術集会講演要旨集 161回 429 -429 2018年08月 [査読無し][通常論文]
  • 中山翔太, YABE John, 池中良徳, MUZANDU Kaampwe, CHOONGO Kennedy, 中田北斗, 豊巻治也, BEYENE Yared, KATABA Andrew, ZYAMBO Golden, 栗谷豪, 中川光弘, 水川葉月, 石塚真由美 Journal of Toxicological Sciences 43 (Supplement) S226 2018年06月 [査読無し][通常論文]
  • 近藤誉充, 池中良徳, 中山翔太, 水川葉月, 三谷曜子, 野見山桂, 田辺信介, 石塚真由美 Journal of Toxicological Sciences 43 (Supplement) S238 2018年06月 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 池中良徳, 田中和之, 中山翔太, 谷川力, 水川葉月, 石塚真由美 Journal of Toxicological Sciences 43 (Supplement) S244 2018年06月 [査読無し][通常論文]
  • 一瀬貴大, 池中良徳, 池中良徳, SAENGTIENCHAI Aksorn, 中山翔太, 水川葉月, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.P‐086 2018年05月11日 [査読無し][通常論文]
  • 池中良徳, THOMPSON Lesa, DARWISH Wageh, YOHANNES Yared, VAN VUREN Johan, SMIT Nico, WEPENER Victor, 中山翔太, 水川葉月, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.2A‐04 2018年05月11日 [査読無し][通常論文]
  • 豊巻治也, YABE John, 中山翔太, YARED Beyene, MUZANDU Kaampwe, 水川葉月, 池中良徳, 中田北斗, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.3C‐06(PA‐54) 2018年05月11日 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 池中良徳, 田中和之, 中山翔太, 谷川力, 水川葉月, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.2B‐01(PA‐22) 2018年05月11日 [査読無し][通常論文]
  • 近藤誉充, 池中良徳, 中山翔太, 水川葉月, 三谷曜子, 田辺信介, 野見山桂, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.2A‐09(PA‐18) 2018年05月11日 [査読無し][通常論文]
  • 島崎真琴, 野見山桂, 水川葉月, SAENGTIENCHAI Aksorn, NGAMCHIRTTAKUL Araya, PENCHAREE Disdanai, 星野光希, 山本恭央, 高口倖暉, 石塚真由美, 池中良徳, 中山翔太, 国末達也, 田辺信介 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.2A‐03(PA‐14) 2018年05月11日 [査読無し][通常論文]
  • 池中良徳, 一瀬貴大, NIMAKO Collins, 市川剛, 水川葉月, 中山翔太, 有薗幸司, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.1C‐16 2018年05月11日 [査読無し][通常論文]
  • 野見山桂, 江口哲史, 西川博之, 水川葉月, 山本恭央, 滝口満喜, 中山翔太, 池中良徳, 石塚真由美, 田辺信介 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.2A‐11 2018年05月11日 [査読無し][通常論文]
  • 銅谷理緒, 中山翔太, 中田北斗, 豊巻治也, YABE John, MUZANDU Kaampwe, BEYENE Yared, KATABA Andrew, ZYAMBO Golden, 水川葉月, 池中良徳, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.3C‐05(PA‐53) 2018年05月11日 [査読無し][通常論文]
  • 中山翔太, 豊巻治也, YABE John, MUZANDU Kaampwe, 中田北斗, 栗谷豪, 中川光弘, 水川葉月, 池中良徳, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.3C‐08 2018年05月11日 [査読無し][通常論文]
  • 水川葉月, KHIDKHAN Kraisiri, 高口倖暉, 横山望, 市居修, 滝口満喜, 笹岡一慶, 池中良徳, 池中良徳, 中山翔太, TSEND‐AYUSH Sainnoxoi, 野見山桂, 田辺信介, 石塚真由美 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.2A‐10 2018年05月11日 [査読無し][通常論文]
  • 田中啓介, 野見山桂, 水川葉月, 高口倖暉, 田上瑠美, 横山望, 市居修, 滝口満喜, 笹岡一慶, 中山翔太, 池中良徳, 石塚真由美, 国末達也, 田辺信介 環境化学討論会要旨集(CD-ROM) 27th ROMBUNNO.1A‐03(PA‐13) 2018年05月11日 [査読無し][通常論文]
  • L. A. Thompson, Y. Ikenaka, Y. B. Yohannes, T. Ichise, G. Ito, N. Bortey-Sam, J. J. van Vuren, V. Wepener, N. J. Smit, W. S. Darwish, S. M.M. Nakayama, H. Mizukawa, M. Ishizuka Bulletin of Environmental Contamination and Toxicology 100 (5) 672 -676 2018年05月01日 [査読無し][通常論文]
     
    Many countries with incidence of malaria, including those surrounding Maputo Bay, use dichloro-diphenyl-trichloroethane (DDT) to reduce mosquitoes. This study is the first to estimate the human health risk associated with consumption of marine fish from Maputo Bay contaminated with DDTs. The median for ∑DDTs was 3.8 ng/g ww (maximum 280.9 ng/g ww). The overall hazard ratio for samples was 1.5 at the 75th percentile concentration and 28.2 at the 95th percentile. These calculations show increased potential cancer risks due to contamination by DDTs, data which will help policy makers perform a risk–benefit analysis of DDT use in malaria control programs in the region.
  • C Ishii, Y Ikenaka, O Ichii, S M M Nakayama, S-I Nishimura, T Ohashi, M Tanaka, H Mizukawa, M Ishizuka Poultry science 97 (5) 1722 -1729 2018年05月01日 [査読無し][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.
  • 打田茉由果, 鈴木一平, 石塚真由美, 池中良徳, 中山翔太, 水川葉月, 田村力, 坂東武治, 小西健志, 三谷曜子 日本水産学会大会講演要旨集 2018 44 2018年03月26日 [査読無し][通常論文]
  • 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.
  • 武田一貴, 池中良徳, 池中良徳, 田中和之, 中山翔太, 谷川力, 石塚真由美 日本分子生物学会年会プログラム・要旨集(Web) 41st ROMBUNNO.3P‐0628 (WEB ONLY) 2018年 [査読無し][通常論文]
  • 石塚真由美, 池中良徳, 中山翔太 日本環境化学会講演会予稿集 60th 8 2018年 [査読無し][通常論文]
  • 高口 倖暉, 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, 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 日本毒性学会学術年会 45 (0) P -72 2018年 [査読無し][通常論文]
     

    近年、ペット動物に対するポリ塩化ビフェニル(PCBs)および水酸化代謝物(OH-PCBs)の曝露による甲状腺ホルモン(THs)の恒常性への影響が注目されている。本研究ではPCBs曝露がペット動物のTHs恒常性に及ぼす影響を明らかにするため、イヌ・ネコのPCBs投与試験を実施し、PCBs曝露に伴う血清中THs濃度の変化を解析した。

    PCBs投与後から5日間、継続的に血清を採取し、THs濃度の変化を解析した結果、ネコ血清中THs濃度は、総THs、遊離型THsともに対照群と投与群の間に有意な変化は認められなかった。一方、イヌ血清中総THs濃度は投与群において、総L-サイロキシン(T4)と総3,5,3'-トリヨード-L-サイロニン(T3)の減少傾向がみられ、総PCBs濃度は総T4、総T3濃度と有意な負の相関を示した(p < 0.01)。一方、遊離型T4、遊離型T3濃度では、対照群と投与群の間に経時的な変化は認められなかったが、曝露後48、96時間目で有意に増加した(p < 0.05)。加えて、遊離型T4濃度は総OH-PCBs濃度と正の相関を示し(p < 0.01)、異性体別ではT4様構造の高塩素化OH-PCBsで同様の傾向が認められた。上記の結果および先行研究から、PCBs曝露によるイヌ血清中THsへの影響を推察した。PCBsがT4様構造のOH-PCBsへ代謝されてTHs輸送タンパクに競合結合し、結合できない遊離型T4が血中に増加することで、THsの臓器・組織への取り込み量が増加したと予測される。その結果、イヌ肝臓中のTHs濃度は増加し、PCBs曝露により肝臓中のAhR・CARが過剰に誘導されることで、UGTおよびSULTが誘導され、THsの抱合化を促進することで体外排泄量が増加し、血清中総T4、T3が減少したものと推察された。

  • 池中良徳, 宮原裕一, 一瀬貴大, 中山翔太, 水川葉月, 市川剛, 遠山千春, 石塚真由美 日本内分泌かく乱化学物質学会研究発表会要旨集 20th 44 2017年12月 [査読無し][通常論文]
  • 中山 翔太, 水川 葉月, 池中 良徳, 石塚 真由美 日本野生動物医学会誌 = Japanese journal of zoo and wildlife medicine 22 (4) 69 -72 2017年12月 [査読無し][通常論文]
  • 石塚真由美, 中山翔太, 水川葉月, 池中良徳 Endocrine Disrupter News Letter 20 (3) 4 2017年12月 [査読無し][通常論文]
  • 水川葉月, 高居名菜, 野見山桂, 高口倖暉, 横山望, 市居修, 滝口満喜, 池中良徳, 池中良徳, 中山翔太, 石塚真由美 日本内分泌かく乱化学物質学会研究発表会要旨集 20th 78 -78 2017年12月 [査読無し][通常論文]
  • 石井千尋, 池中良徳, 川合佑典, 市居修, 中山翔太, 水川葉月, 石塚真由美 日本鳥学会大会講演要旨集 2017 100 2017年09月15日 [査読無し][通常論文]
  • 庄子晶子, ELLIOTT K, ARIS‐BROSOU S, 水川葉月, 中山翔太, 池中良徳, 石塚真由美, 桑江朝比呂, 渡辺謙太, 綿貫豊 日本鳥学会大会講演要旨集 2017 70 2017年09月15日 [査読無し][通常論文]
  • 新屋惣, 池中良徳, 中山翔太, 水川葉月, 伊藤真輝, 高江洲昇, 齊藤慶輔, 渡邉有希子, 石塚真由美 日本鳥学会大会講演要旨集 2017 105 2017年09月15日 [査読無し][通常論文]
  • 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.
  • 池中 良徳 環境化学 = Journal of environmental chemistry 27 (3) 98 -100 2017年09月 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 田中和之, 中山翔太, 谷川力, 水川葉月, 石塚真由美 日本獣医学会学術集会講演要旨集 160th 504 2017年08月30日 [査読無し][通常論文]
  • 佐々木 東, 中山 翔太, 森下 啓太郎, 中村 健介, 大田 寛, 水川 葉月, 池中 良徳, 石塚 真由美, 滝口 満喜 日本獣医学会学術集会講演要旨集 160回 461 -461 2017年08月 [査読無し][通常論文]
  • 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 環境化学討論会要旨集(CD-ROM) 26th ROMBUNNO.2A‐01 2017年06月05日 [査読無し][通常論文]
  • 高口倖暉, 野見山桂, 西川博之, 水川葉月, 田上瑠美, 芳之内結加, 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 環境化学討論会要旨集(CD-ROM) 26th ROMBUNNO.2A‐02 2017年06月05日 [査読無し][通常論文]
  • 水川葉月, 野見山桂, 池中良徳, 池中良徳, 中山翔太, SAENGTIENCHAI Aksorn, SAINNOXOI Tsendayush, 横山望, 笹岡一慶, 市居修, KHIDKHAN Kraisiri, 高居名菜, 滝口満喜, 田辺信介, 石塚真由美 環境化学討論会要旨集(CD-ROM) 26th ROMBUNNO.2A‐03 2017年06月05日 [査読無し][通常論文]
  • 池中良徳, 池中良徳, 宮原裕一, 一瀬貴大, 八木橋美緒, 中山翔太, 水川葉月, 遠山千春, 石塚真由美 環境化学討論会要旨集(CD-ROM) 26th ROMBUNNO.3C‐03 2017年06月05日 [査読無し][通常論文]
  • 野見山桂, 西川博之, 水川葉月, 高口倖暉, SAINNOXOI Tsend‐ayush, 横山望, 市居修, 滝口満喜, 石塚真由美, 池中良徳, 中山翔太, 江口哲史, 国末達也, 田辺信介 環境化学討論会要旨集(CD-ROM) 26th ROMBUNNO.2A‐05 2017年06月05日 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 田中和之, 中山翔太, 谷川力, 水川葉月, 石塚真由美 環境化学討論会要旨集(CD-ROM) 26th ROMBUNNO.P‐218 2017年06月05日 [査読無し][通常論文]
  • 一瀬貴大, 池中良徳, 池中良徳, 藤岡一俊, 平久美子, 中山翔太, 水川葉月, 八木橋美緒, 有薗幸司, 加藤恵介, 高橋圭介, 石塚真由美 環境化学討論会要旨集(CD-ROM) 26th ROMBUNNO.P‐093 2017年06月05日 [査読無し][通常論文]
  • 田中啓介, 野見山桂, 水川葉月, 高口倖暉, 田上瑠美, SAENGTIENCHAI Aksorn, SAINNOXOI Tsend‐ayush, 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, 田辺信介 環境化学討論会要旨集(CD-ROM) 26th ROMBUNNO.2A‐04 2017年06月05日 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 田中和之, 中山翔太, 谷川力, 水川葉月, 石塚真由美 Journal of Toxicological Sciences 42 (Supplement) S219 2017年06月 [査読無し][通常論文]
  • 水川葉月, 野見山桂, 田辺信介, 池中良徳, 池中良徳, 中山翔太, 石塚真由美 Journal of Toxicological Sciences 42 (Supplement) S36 2017年06月 [査読無し][通常論文]
  • 打田茉由果, 伊藤慶造, 石塚真由美, 池中良徳, 中山翔太, 水川葉月, 坂東武治, 田村力, 小西健志, 鈴木一平, 三谷曜子 日本水産学会大会講演要旨集 2017 24 2017年03月26日 [査読無し][通常論文]
  • DARWISH Wageh Sobhy, IKENAKA Yoshinori, NAKAYAMA Shouta M.M, MIZUKAWA Hazuki, ISHIZUKA Mayumi 日本毒性学会学術年会 44 (0) O -15 2017年 [査読無し][通常論文]
     
    Polycyclic aromatic hydrocarbons (PAHs) are wide spread as environmental pollutants, which can be generated during the preparation of food. Food is the main source of exposure to PAHs for people who do not smoke. Epidemiological studies indicate that diets rich in fruits and vegetables can be associated with lower risks of numerous diseases and cancers. However, the exact mechanisms behind these effects are still unclear. The objectives of this study were firstly to estimate PAHs contents in some heat-treated meat samples collected from different localities in Egypt. Secondly, to investigate the mutagenic activities for some of the formed PAHs. Finally, to investigate the protective effects and mechanism of action of some micronutrients against the adverse effects of PAHs. <br> Polycyclic aromatic hydrocarbons were measured in heat-treated meat collected from different localities in Egypt using HPLC. Mutagenic activities of some formed PAHs were examined using Ames Salmonella typhimurium mutagenicity assay. Human HepG2 cells were exposed to environmental-relevant concentrations of some formed PAHs. Modulation of xenobiotic metabolizing enzymes (XMEs) mRNA expressions was investigated using real-time qPCR.<br> The results of this study indicated the formation of different PAHs in heat-treated meat with variable concentrations. Some of the formed PAHs had clear mutagenic activities such as benzo[a]pyrene. Obtained results declare the protective effects of carotenoids like β-carotene and retinoids like retinol against B[a]P induced adverse effects. Modulation of XMEs is proposed to be a possible mechanism for this protection. In conclusion, consumption of β-carotene and retinol in the areas of high PAH pollution is recommended.
  • 水川 葉月, 中山 翔太, Tsend-ayush SAINNOXOI, 田辺 信介, 石塚 真由美, 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 日本毒性学会学術年会 44 (0) P -55 2017年 [査読無し][通常論文]
     
    有機ハロゲン化合物の一種であるポリ塩化ビフェニル(PCBs)は甲状腺ホルモン(THs)の恒常性かく乱が懸念されており、実際、ヒトやげっ歯類においてはPCBs暴露により血中THs濃度の低下が認められている。ヒトの身近な動物であるネコは餌などを介してPCBsに暴露していると懸念され、THs恒常性に何らかの悪影響をもたらすことが予想される。本研究では、ネコの甲状腺機能に対するPCBsの影響を解析するため、in vivo投与試験したネコを用いて甲状腺機能への影響を解析した。血中のTHs濃度(総T4、総T3、遊離T4、遊離T3、リバースT3)を解析した結果、対照群と暴露群の間に有意な差は見られなかった。また、THsの恒常性に関与する遺伝子(甲状腺ホルモン受容体αおよびβ、脱ヨード酵素type1)の肝臓中発現量やTHs代謝に関わる酵素であるグルクロン酸抱合酵素(UGT1A1)の活性を調べたところ、対照群と暴露群の間に有意な差は見られなかった。
    本実験結果では、ネコにおいてPCBs短期暴露によるTHsへの影響が認められなかったが、日本のペットネコにおけるモニタリング調査では、血中のTHs濃度とPCBs濃度との間に負の相関が見られており、有機ハロゲン化合物によるTHsかく乱が懸念されている。また、本研究試料のメタボローム解析結果では酸化ストレスの発現、抗酸化物質、電子伝達物質の生産阻害などが示唆されており、PCBsや水酸化代謝物による内分泌撹乱作用が心配される。THsの恒常性は非常に複雑な機構のもと維持されていることが知られており、負のフィードバック機構に加え、THsの活性化や代謝、排泄の調整にも多くの遺伝子やトランスポーター、酵素など様々な要因が関わっていることから、ネコは長期的かつ慢性的に化学物質に暴露されることで、甲状腺機能などへの悪影響が現れると考えられ、内分泌撹乱作用の作用機序について解析を進めることが重要である。
  • 池中 良徳, 加藤 恵介, 遠山 千春, 石塚 真由美, 宮原 裕一, 一瀬 貴大, 八木橋 美緒, 中山 翔太, 水川 葉月, 平 久美子, 有薗 幸司, 高橋 圭介 日本毒性学会学術年会 44 (0) O -20 2017年 [査読無し][通常論文]
     
    ネオニコチノイド系殺虫剤は、哺乳類における体内蓄積性は短く、昆虫とヒトのニコチン受容体に対する親和性の違いから、ヒトに対する毒性は相対的に低いため、一定の基準以下であれば、日常生活においてその毒性は無視できると考えられている。しかし、日本では諸外国と比べ数倍~数十倍と果物や野菜、茶葉における食品残留基準値が高く設定されていること、また、記憶・学習などの脳機能に及ぼす影響をはじめ、発達神経毒性には不明な点が多いことなどから、健康に及ぼす懸念が払拭できていない。とりわけ、感受性が高いこどもたちや化学物質に過敏な人々の健康へのリスクを評価するためには、ネオニコチノイドが体内にどの程度取り込まれているかを把握することがまず必要である。そこで本調査では、長野県上田市の松くい虫防除が行われている地域の住民のうち、感受性が高いと考えられる小児(3歳~6歳)から尿を採取し、尿中のネオニコチノイドおよびその代謝物を測定することで、曝露評価を行う事を目的とした。当該調査では、松枯れ防止事業に用いる薬剤(エコワン3フロワブル、主要成分:Thiacloprid)の散布時期の前後に、46人の幼児から提供された尿試料中のネオニコチノイドとその代謝産物を測定した。また、同時に大気サンプルもエアーサンプラーを用いて採取し、分析に供した。分析した結果、Thiaclopridは検出頻度が30%程度であり、濃度は
  • 石井 千尋, 中山 翔太, 水川 葉月, 池中 良徳, 石塚 真由美 The Japanese journal of clinical toxicology = 中毒研究 : 日本中毒学会機関誌 30 (4) 363 -367 2017年 [査読無し][通常論文]
  • 水川 葉月, 中山 翔太, Tsend-ayush SAINNOXOI, 田辺 信介, 石塚 真由美, 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 日本毒性学会学術年会 44 (0) P -55 2017年 [査読無し][通常論文]
     
    有機ハロゲン化合物の一種であるポリ塩化ビフェニル(PCBs)は甲状腺ホルモン(THs)の恒常性かく乱が懸念されており、実際、ヒトやげっ歯類においてはPCBs暴露により血中THs濃度の低下が認められている。ヒトの身近な動物であるネコは餌などを介してPCBsに暴露していると懸念され、THs恒常性に何らかの悪影響をもたらすことが予想される。本研究では、ネコの甲状腺機能に対するPCBsの影響を解析するため、in vivo投与試験したネコを用いて甲状腺機能への影響を解析した。血中のTHs濃度(総T4、総T3、遊離T4、遊離T3、リバースT3)を解析した結果、対照群と暴露群の間に有意な差は見られなかった。また、THsの恒常性に関与する遺伝子(甲状腺ホルモン受容体αおよびβ、脱ヨード酵素type1)の肝臓中発現量やTHs代謝に関わる酵素であるグルクロン酸抱合酵素(UGT1A1)の活性を調べたところ、対照群と暴露群の間に有意な差は見られなかった。
    本実験結果では、ネコにおいてPCBs短期暴露によるTHsへの影響が認められなかったが、日本のペットネコにおけるモニタリング調査では、血中のTHs濃度とPCBs濃度との間に負の相関が見られており、有機ハロゲン化合物によるTHsかく乱が懸念されている。また、本研究試料のメタボローム解析結果では酸化ストレスの発現、抗酸化物質、電子伝達物質の生産阻害などが示唆されており、PCBsや水酸化代謝物による内分泌撹乱作用が心配される。THsの恒常性は非常に複雑な機構のもと維持されていることが知られており、負のフィードバック機構に加え、THsの活性化や代謝、排泄の調整にも多くの遺伝子やトランスポーター、酵素など様々な要因が関わっていることから、ネコは長期的かつ慢性的に化学物質に暴露されることで、甲状腺機能などへの悪影響が現れると考えられ、内分泌撹乱作用の作用機序について解析を進めることが重要である。
  • 石井千尋, 中山翔太, 池中良徳, ANDREW Kataba, 齊藤慶輔, 渡辺有希子, 槇納好岐, 松川岳久, 久保田章乃, 横山和仁, 水川葉月, 平田岳史, 石塚真由美 日本野生動物医学会大会・講演要旨集 23rd 81 2017年 [査読無し][通常論文]
  • 新屋惣, 池中良徳, 中山翔太, 石井千尋, 水川葉月, 伊藤真輝, 高江洲昇, 大澤夏生, 綿貫豊, 石塚真由美 日本野生動物医学会大会・講演要旨集 23rd 125 2017年 [査読無し][通常論文]
  • 石塚真由美, 中山翔太, 水川葉月, 池中良徳 日本薬学会年会要旨集(CD-ROM) 137th ROMBUNNO.S45‐4 2017年 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 池中良徳, 田中和之, 中山翔太, 谷川力, 水川葉月, 石塚真由美 日本生化学会大会(Web) 90th ROMBUNNO.3AT12‐14(3P‐0236) (WEB ONLY) 2017年 [査読無し][通常論文]
  • L. A. Thompson, Y. Ikenaka, Y. B. Yohannes, J. J. van Vuren, V. Wepener, N. J. Smit, W. S. Darwish, S. M. M. Nakayama, H. Mizukawa, M. Ishizuka FOOD ADDITIVES AND CONTAMINANTS PART A-CHEMISTRY ANALYSIS CONTROL EXPOSURE & RISK ASSESSMENT 34 (11) 1959 -1969 2017年 [査読無し][通常論文]
     
    Organochlorine pesticides such as dichlorodiphenyltrichloroethane (DDT) have been used in agriculture and for disease control purposes over many decades. Reports suggest that DDT exposure may result in a number of adverse effects in humans. In the KwaZulu-Natal Province of South Africa, DDT is sprayed annually in homes (indoor residual spraying) to control the mosquito vector of malaria. In the northern part of the Province, samples of free-range chicken meat (n=48) and eggs (n=13), and commercially produced chicken meat (n=6) and eggs (n=11), were collected and analysed. Of the free-range chicken meat samples, 94% (45/48) contained DDTs (sigma DDTs median 6.1ng/g wet weight [ww], maximum 79.1ng/g ww). Chicken egg contents were also contaminated (sigma DDTs in free-range eggs median 9544ng/g ww, maximum 96.666ng/g ww; and in commercial eggs median 1.3ng/g ww, maximum 4.6ng/g ww). The predominant DDT congener detected was p,p'-DDE in both free-range meat (>63%) and eggs (>66%), followed by p,p'-DDT and then p,p'-DDD. Based on estimated daily intake values, calculated human risk ratio (carcinogenic) values were >1 for DDTs detected in both free-range chicken products. Consumption of free-range eggs poses a particularly high health risk.
  • R. Gerber, G. M. Wagenaar, W. Smith, Y. Ikenaka, N. J. Smit ECOLOGICAL INDICATORS 72 530 -544 2017年01月 [査読無し][通常論文]
     
    There is a need for sensitive bio-monitoring and indicator tools in toxicant impact assessment to show the effect on fish health. Histopathological assessment of fish tissue is a bio-monitoring tool allowing for early warning signs of disease and detection of long term injury in cells, tissues or organs. The aims of this study were firstly to determine and compare the health status of the tigerfish (Hydrocynus vittatus) from two lowland rivers in Kruger National Park (KNP), secondly to attempt to explain the histological changes observed, through the application of a suite of multivariate statistics to relate changes to biotic levels of selected metals and organochlorine pesticides (OCP5) and thirdly to determine the suitability of H. vittatus as a bio-indicator of riverine health. Tigerfish were caught using rod and reel from the Olifants (n = 37) and Luvuvhu Rivers (n = 34) between 2009 and 2011. The histology-based fish health assessment (liver, kidney, gills and gonads) indicated that fish were in relatively good health. Even though fish were considered to be healthy, the general fish health in both rivers improved over time, corresponding to an overall decrease in river pollution, most notably in terms of metals. The incorporation of multiple lines of evidence in tigerfish, including histopathological changes and organ and whole organism indices, proved to be a valuable tool in using a bio-indicator approach toward river monitoring. These histopathological changes serve as an early warning system to more serious health concerns arising if the pollution in the rivers of the KNP is not dealt with. The use of a suite of uni- and multivariate statistics proved helpful in determining the links between fish health and river contamination and further proved to be a valuable tool in assessing spatial and temporal differences in river pollution and the effects thereof on the selected bioindicator. (C) 2016 Elsevier Ltd. All rights reserved.
  • 水川 葉月, 池中 良徳, 筧 麻友, 中山 翔太, 石塚 真由美 薬学雑誌. 乙号 137 (3) 257 -263 2017年 [査読無し][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.
  • 高本亜希子, 池中良徳, 吉本圭佑, 福島聡, 石塚真由美, 石橋康弘, 有薗幸司 日本内分泌かく乱化学物質学会研究発表会要旨集 19th 76 2016年12月 [査読無し][通常論文]
  • 山本久美子, 池中良徳, 一瀬貴大, 石塚真由美, 安井博宣, 平岡和佳子, 鵜飼光子, 山盛徹, 稲波修 電子スピンサイエンス学会年会講演要旨集 55th 156‐157 2016年11月10日 [査読無し][通常論文]
  • Kazuki Takeda, Yoshinori Ikenaka, 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]
     
    © 2016 Elsevier B.V.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.
  • S. M. M. Nakayama, Y. Ikenaka, A. Hayami, H. Mizukawa, W. S. Darwish, K. P. Watanabe, Y. K. Kawai, M. Ishizuka JOURNAL OF VETERINARY PHARMACOLOGY AND THERAPEUTICS 39 (5) 478 -487 2016年10月 [査読無し][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.
  • 石塚真由美, 中山翔太, 水川葉月, 池中良徳 日本哺乳類学会大会プログラム・講演要旨集 2016 56 2016年09月23日 [査読無し][通常論文]
  • 池中良徳 Endocrine Disrupter News Letter 19 (2) 5 2016年09月 [査読無し][通常論文]
  • 石塚真由美, 中山翔太, 水川葉月, 池中良徳 日本獣医学会学術集会講演要旨集 159th 293 2016年08月30日 [査読無し][通常論文]
  • 近藤誉充, 池中良徳, 中山翔太, 水川葉月, SAENGTIENCHAI Aksorn, BEYENE Yared, 坂本健太郎, 和田昭彦, 服部薫, 三谷曜子, 田辺信介, 野見山桂, 石塚真由美 日本獣医学会学術集会講演要旨集 159th 493 2016年08月30日 [査読無し][通常論文]
  • 栂尾正雄, 中山翔太, YABE John, 池中良徳, 中田北斗, 石井千尋, 水川葉月, BEYENE Yared, SAENGTIENCHAI Aksorn, 石塚真由美 日本獣医学会学術集会講演要旨集 159th 494 2016年08月30日 [査読無し][通常論文]
  • 稲波修, 山本久美子, 池中良徳, 一瀬貴大, 石塚真由美, 安井博宣, 鵜飼光子, 山盛徹 日本酸化ストレス学会学術集会プログラム・抄録集 69th 142 2016年08月30日 [査読無し][通常論文]
  • 山本久美子, 池中良徳, 一瀬貴大, 石塚真由美, 安井博宣, 鵜飼光子, 山盛徹, 稲波修 日本獣医学会学術集会講演要旨集 159th 474 2016年08月30日 [査読無し][通常論文]
  • 池中良徳, 池中良徳, 藤岡一俊, 平久美子, 中山翔太, 水川葉月, 一瀬貴大, MARFO Jemima Tiwaa, 有薗幸司, 加藤恵介, 石坂真澄, 馬場浩司, 川上智規, 石塚真由美 環境化学討論会要旨集(CD-ROM) 25th ROMBUNNO.1A‐07 2016年06月06日 [査読無し][通常論文]
  • 有薗幸司, 石橋弘志, 内田雅也, 吉本圭佑, 山元涼子, 池中良徳, 河合正人, 高尾雄二, 一川暢宏, 冨永伸明, 石橋康弘 環境化学討論会要旨集(CD-ROM) 25th ROMBUNNO.P‐075 2016年06月06日 [査読無し][通常論文]
  • 西川博之, 野見山桂, 水川葉月, 横山望, 市居修, 滝口満喜, 石塚真由美, 池中良徳, 中山翔太, 江口哲史, 国末達也, 田辺信介 環境化学討論会要旨集(CD-ROM) 25th ROMBUNNO.1A‐12 2016年06月06日 [査読無し][通常論文]
  • 野見山桂, 山本恭央, 水川葉月, 江口哲史, 滝口満喜, 中山翔太, 池中良徳, 石塚真由美, 国末達也, 田辺信介 環境化学討論会要旨集(CD-ROM) 25th ROMBUNNO.1A‐14 2016年06月06日 [査読無し][通常論文]
  • 宮原裕一, 吉田知可, 一瀬貴大, 池中良徳, 石塚真由美 環境化学討論会要旨集(CD-ROM) 25th ROMBUNNO.P‐173 2016年06月06日 [査読無し][通常論文]
  • 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 環境化学討論会要旨集(CD-ROM) 25th ROMBUNNO.1A‐13 2016年06月06日 [査読無し][通常論文]
  • 本平航大, 池中良徳, DARWICH Wageh S, 中山翔太, 水川葉月, 石塚真由美 Journal of Toxicological Sciences 41 (Supplement) S255 2016年06月 [査読無し][通常論文]
  • 池中良徳, 石塚真由美 Journal of Toxicological Sciences 41 (Supplement) S150 2016年06月 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 田中和之, 谷川力, 中山翔太, 水川葉月, 石塚真由美 Journal of Toxicological Sciences 41 (Supplement) S257 2016年06月 [査読無し][通常論文]
  • 石塚真由美, 中山翔太, 水川葉月, 池中良徳 Journal of Toxicological Sciences 41 (Supplement) S106 2016年06月 [査読無し][通常論文]
  • Yutaka Watanuki, Ai Yamashita, Mayumi Ishizuka, Yoshinori Ikenaka, Shouta M. M. Nakayama, Chihiro Ishii, Takashi Yamamoto, Motohiro Ito, Tomohiro Kuwae, Philip N. Trathan MARINE ECOLOGY PROGRESS SERIES 546 263 -269 2016年03月 [査読有り][通常論文]
     
    We measured mercury concentration ([Hg]) and nitrogen stable isotope values (delta N-15) in tail feathers that were replaced during the non-breeding period of streaked shearwaters Calonectris leucomelas that bred on 3 islands in Japan. The birds' year-round movements were tracked and their breeding status was monitored. [Hg] was greater in males than in females, and was greatest in those birds spending their non-breeding period in the South China Sea (3.1 +/- 1.5 mu g g(-1) dry weight), moderate in birds in the Arafura Sea (1.5 +/- 0.7 mu g g(-1)), and lowest in birds in the Pacific Ocean north of New Guinea (0.8 +/- 0.4 mu g g(-1)). Adverse effects of feather [Hg] on breeding status were not observed. This regional variation in feather [Hg] might partly reflect differences in the intake of Hg between these non-breeding areas in addition to accumulation during the late breeding period and the southward migration period.
  • 石井千尋, 池中良徳, 市居修, 中山翔太, 西村紳一郎, 大橋哲, 田中誠一, 齊藤慶輔, 渡邊有希子, 水川葉月, 石塚真由美 日本野生動物医学会大会・講演要旨集 22nd 123 2016年 [査読無し][通常論文]
  • 新屋惣, 池中良徳, 中山翔太, 石井千尋, 水川葉月, 齊藤慶輔, 渡邊有希子, 伊藤真輝, 高江洲昇, 石塚真由美 日本野生動物医学会大会・講演要旨集 22nd 97 2016年 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 田中和之, 中山翔太, 谷川力, 水川葉月, 石塚真由美 日本分子生物学会年会プログラム・要旨集(Web) 39th ROMBUNNO.3LBA‐070 (WEB ONLY) 2016年 [査読無し][通常論文]
  • 水川 葉月, 高口 倖暉, 田辺 信介, 石塚 真由美, 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 日本毒性学会学術年会 43 (0) P -6 2016年 [査読無し][通常論文]
     
    ポリ塩化ビフェニル(PCBs)の水酸化代謝物であるOH-PCBsは、肝臓内で薬物代謝酵素より生成され、その後体外へ排泄される。しかしながら、一部の水酸化代謝物は甲状腺ホルモン(TH)と類似の構造をもつため、THの恒常性を撹乱することが危惧されている。これまでに、多様な陸棲哺乳類の血中OH-PCBsを分析したところ、種間でOH-PCBsの組成に差異が認められ、中でも、ネコのOH-PCBs残留パターンは他種と大きく異なることから、本種は特異な代謝機能を有することが示唆された。しかし、ネコの異物代謝能の研究は僅かであり、化学物質暴露による毒性影響も不明な点が多い。本研究では、ネコにおけるPCBs in vivo暴露試験を実施し、体内動態および代謝に関与する酵素活性や遺伝子を解析するとともに、化学物質の暴露評価に繋がる基盤的情報の収集を目的とした。
    コーン油に溶解した12異性体のPCBsを腹腔内投与し、経時採血した血清中PCBsおよびOH-PCBs濃度について同条件で実施したイヌのin vivo試験と比較した結果、異性体の残留パターンや体内動態にイヌとネコで種差が観察された。とくにネコでは低塩素化体の残留が顕著であった。また、代謝酵素活性および遺伝子解析の結果、PCBs暴露によりEROD、MROD、PROD活性は上昇するものの、第2相抱合酵素(UGTやSULT)活性は変化せず、PCBs暴露による抱合酵素活性への影響もみられなかった。また、CYP1A1およびCYP1A2遺伝子の発現量の上昇も認められた。
    本研究により、ネコのPCBs吸収・代謝・排泄能はイヌと異なることが示唆され、とくに低塩素化OH-PCBsの毒性リスクは高いことが予想された。低塩素化OH-PCBsは血中でTH輸送タンパクとの競合結合や、THの硫酸抱合排泄の阻害、TH起因性遺伝子の転写抑制などが報告されており、ネコの甲状腺機能障害が懸念される。
  • 池中 良徳, 石塚 真由美 日本毒性学会学術年会 43 (0) W3 -3 2016年 [査読無し][通常論文]
     
    近年、ネオニコチノイドによる暴露が原因とされる野生動物、特に鳥類への被害に関する報告が後を絶たない。更に、ネオニコチノイドは、哺乳動物に対して蓄積性はなく、毒性は無視できると言われて来たが、使用量急増による亜急性・慢性曝露の実体、又は健康影響に関する調査はまだまだ不足している。<br>ここで、ヒトへの曝露実態の解明には非侵襲的に採取できるサンプルである尿がしばしば使用される。即ち、尿中に排泄されるネオニコチノイドおよびその代謝産物を測定することにより曝露量を概算することが可能となる。一方で、ネオニコチノイドは極めて代謝されやすいため、親化合物のみでなく代謝産物も対象としたスクリーニングが必要である。そこで、当該研究では、主要ネオニコチノイド7種(ジノテフラン、ニテンピラム、チアメトキサム、クロチアニジン、イミダクロプリド、アセタミプリド、チアクロプリド)に加え、その代謝産物について一斉分析法を確立し、LC-ESI/MS/MSによる分析を行った。<br>群馬県の尿サンプルを85検体採取し、分析した結果、ニテンピラム(n = 4)、クロチアニジン(n = 1)、チアメトキサム(n = 7)は親化合物が尿中から検出された。一方、アセタミプリドについて、親化合物は検出されなかったのに対し、その代謝産物であるNデスメチル体が14サンプルで検出された。<br>当該結果は、ヒトにおけるネオニコチノイドの曝露評価において、代謝産物を含めたスクリーニングが重要である事を示唆するものであった。
  • 武田 一貴, 池中 良徳, 田中 和之, 谷川 力, 中山 翔太, 水川 葉月, 石塚 真由美 日本毒性学会学術年会 43 (0) P -89 2016年 [査読無し][通常論文]
     
    ワルファリンは抗凝血作用を示す化学物質であり、その薬効はビタミンK依存性血液凝固因子合成に不可欠なビタミンKエポキシド還元酵素 (VKOR)の阻害により発揮される。ワルファリンを含む種々の抗凝血薬は殺鼠剤として広く用いられているが、世界中の都市部でワルファリンに対し抵抗性を持つ野生齧歯類の棲息が確認されており、東京では棲息数の80%を占める地域すら存在する。これら野生齧歯類は重篤な人獣共通感染症を媒介するため、抵抗性獲得機序の解明は急務であるといえる。抵抗性の原因としてワルファリンの標的分子:VKORに遺伝子変異が生じ、それに伴いVKORのワルファリン感受性が低下する事が報告されている。しかしVKOR変異が生体レベルでどの程度抵抗性へ寄与するか不明な点も多くVKOR以外の抵抗性獲得機序が疑われている。そこでVKOR変異以外の要因を探索するため、筆者らは東京由来ワルファリン抵抗性野生クマネズミクローズドコロニーを確立し、その個体群を用いワルファリン経口投与後体内薬物動態解析を行った。その結果、抵抗性群ではワルファリン投与後のAUC(血漿中濃度-時間曲線下面積)、肝臓腎臓中蓄積濃度が感受性群に比べ有意に低く、一方で消失速度を示すクリアランスは有意に高かった。またワルファリンの代謝産物である水酸化ワルファリンの血漿中濃度は、抵抗性群において投与後1時間と非常に迅速に最高濃度に達し(感受性群では投与後6時間前後)、尿中への排泄量も水酸化体の一分子種(4’水酸化体)で有意に増加していた。このワルファリン代謝を担っているシトクロムP450分子種の肝ミクロソーム中タンパク発現量は抵抗性群では有意に高かった。<br>これらの結果は東京のワルファリン抵抗性個体群ではワルファリンの代謝・排泄能が亢進している事を示唆し、それによる迅速な解毒が抵抗性に寄与しているものと考えられる。
  • 石塚 真由美, 中山 翔太, 水川 葉月, 池中 良徳 日本毒性学会学術年会 43 (0) S16 -4 2016年 [査読無し][通常論文]
     
    外来性化学物質代謝の第II相反応では、第I相反応の代謝物の極性をさらに増加させるグルクロン酸抱合(UGT)や硫酸抱合(SULT)、グルタチオン抱合酵素などの抱合反応が主要な代謝となっている。化学物質の代謝能力は、生物の化学物質に対する感受性を決定する重要なファクターである。我々はこれまでの研究から、魚類から哺乳類まで、P450および第II相反応の抱合に大きな動物種差があることを報告してきた。<br>哺乳類ではUGT1ファミリーは、主に内因性物質を代謝するビリルビングループ(1A1-1A5)と外因性物質を代謝するフェノールグループ(UGT1A6-1A10)に大別される。我々は、食肉目を中心とした哺乳類におけるUGT1ファミリーの遺伝子解析を行ったところ、鰭脚類は外因性物質であるアセトアミノフェン及び1-ヒドロキシピレンに対するUGT活性がネコと同程度に低く、中でもトドおよびキタオットセイではUGT1A6の偽遺伝子化が明らかになった。またUGT1ファミリーの系統解析及びシンテニー解析の結果、哺乳類のUGT1ファミリーは内因性物質代謝を担うUGT1A1相同遺伝子及び外因性物質代謝を担うUGT1A6相同遺伝子がそれぞれ遺伝子重複した後、動物種ごとに独自に遺伝子重複/欠損が起き、UGT1A2-1A5及びUGT1A7-1A10遺伝子が形成されたことが示唆された。一方、UGTと基質特異性が一部重複するSULTに関しては、これまで教科書的にブタで活性が欠損しているとされてきたが、ブタの肝臓ミクロソームのKm/Vmaxによる酵素効率の比較では他の動物種と大きな差はないことや、新たに硫酸抱合酵素が低活性である哺乳類を同定した<br>そこで、今回、動物が有する化学物質代謝の種差と毒性発現の違いを、UGTを中心に紹介したい。
  • 本平 航大, 池中 良徳, ワギ ダルウィシュ, 中山 翔太, 水川 葉月, 石塚 真由美 日本毒性学会学術年会 43 (0) P -84 2016年 [査読無し][通常論文]
     
    【はじめに】AhR(芳香族炭化水素受容体)はシトクロムP450をはじめとした種々の薬物代謝酵素を誘導することで異物の代謝に関与する受容体として研究が進められてきた。近年、従来主要な役割であると考えられてきた異物の代謝に加え、成長因子、抗酸化因子、炎症物質などを誘導するといった新たな生体内での役割が注目を集めている。AhRは肝臓や肺といった異物代謝活性が高い組織で活性が高く、上記に挙げた新たなAhRの働きの研究がなされているのに対し、薬物の「蓄積」という特徴的な応答を示す脂肪組織における反応は未知の部分が多い。そこで本研究では脂肪組織におけるAhRの働きを探求するとともに他組織との比較を試みた。<br>【方法】脂肪組織としてヒト脂肪由来幹細胞、肝臓組織としてヒト肝癌由来細胞を用い、AhRのリガンドと考えられているβ-naphthoflavoneを含む複数の化学物質を暴露した。これらの暴露細胞から抽出、精製したcDNAを用いて比較リアルタイムPCR法により各組織における異物代謝酵素と成長因子をはじめとした異物代謝とは直積関与するわけではない遺伝子の発現量を暴露-被暴露間、肝-脂肪細胞間で比較した。<br>【結果と考察】AhRリガンド暴露の結果、ヒト脂肪由来幹細胞、ヒト肝癌細胞の何れの細胞においてもCYP1A1や成長因子である繊維芽細胞増殖因子(fgf2など)の発現量の増加が確認された。種々の遺伝子で脂肪由来幹細胞と肝癌細胞の間で反応性や遺伝子発現量に違いが確認された。この結果から一般的に肝臓で誘導が認められている遺伝子に関して、脂肪組織でも誘導されていることが明らかになった。また今回観察を行った繊維芽細胞増殖因子では複数のサブファミリーがAhRリガンドにより誘導されており、繊維芽細胞増殖因子の全てのサブファミリーがAhRの支配を受けていることが示唆された。本研究の結果、種々の遺伝子で脂肪由来幹細胞-肝癌細胞間に反応性や遺伝子発現量に差が見られ、これが脂肪組織におけるAhRの他組織における働きとの違いと推測出来た。
  • 水川 葉月, 高口 倖暉, 田辺 信介, 石塚 真由美, 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 日本毒性学会学術年会 43 (0) P -6 2016年 [査読無し][通常論文]
     
    ポリ塩化ビフェニル(PCBs)の水酸化代謝物であるOH-PCBsは、肝臓内で薬物代謝酵素より生成され、その後体外へ排泄される。しかしながら、一部の水酸化代謝物は甲状腺ホルモン(TH)と類似の構造をもつため、THの恒常性を撹乱することが危惧されている。これまでに、多様な陸棲哺乳類の血中OH-PCBsを分析したところ、種間でOH-PCBsの組成に差異が認められ、中でも、ネコのOH-PCBs残留パターンは他種と大きく異なることから、本種は特異な代謝機能を有することが示唆された。しかし、ネコの異物代謝能の研究は僅かであり、化学物質暴露による毒性影響も不明な点が多い。本研究では、ネコにおけるPCBs in vivo暴露試験を実施し、体内動態および代謝に関与する酵素活性や遺伝子を解析するとともに、化学物質の暴露評価に繋がる基盤的情報の収集を目的とした。
    コーン油に溶解した12異性体のPCBsを腹腔内投与し、経時採血した血清中PCBsおよびOH-PCBs濃度について同条件で実施したイヌのin vivo試験と比較した結果、異性体の残留パターンや体内動態にイヌとネコで種差が観察された。とくにネコでは低塩素化体の残留が顕著であった。また、代謝酵素活性および遺伝子解析の結果、PCBs暴露によりEROD、MROD、PROD活性は上昇するものの、第2相抱合酵素(UGTやSULT)活性は変化せず、PCBs暴露による抱合酵素活性への影響もみられなかった。また、CYP1A1およびCYP1A2遺伝子の発現量の上昇も認められた。
    本研究により、ネコのPCBs吸収・代謝・排泄能はイヌと異なることが示唆され、とくに低塩素化OH-PCBsの毒性リスクは高いことが予想された。低塩素化OH-PCBsは血中でTH輸送タンパクとの競合結合や、THの硫酸抱合排泄の阻害、TH起因性遺伝子の転写抑制などが報告されており、ネコの甲状腺機能障害が懸念される。
  • アクソルン サエンティエンチャイ, 池中 良徳, ネスタ サム, ウスマ ジャムナーク, 水川 葉月, 中山 翔太, 石塚 真由美 日本毒性学会学術年会 43 (0) P -237 2016年 [査読無し][通常論文]
     
    African hedgehog, <i>Atalerix albiventris</i>, is a spiny mammal which becomes famous exotic pet in many counties. In order to elucidate xenobiotic metabolisms ability of hedgehogs, pyrene, one of the typical polycyclic aromatic hydrocarbon were exposed. From in vivo exposure study, pyrene was biotransformed to glucuronide and sulfate conjugates such as pyrene-1-glucuronide, pyrene-1-sulfate, and pyrenediol-sulfate and excreted to urine. Pyrene-1-glucuronide was main metabolite and limited excretion of sulfate conjugates were observed. Based on the results of in vivo exposure study, in vitro enzymatic kinetic experiments were performed by using various substrate and compare to rat and pig. Enzyme efficiency of cytochrome P450 (CYP) mediated Ethoxyresorufin <i>O</i>-deethylase activity, and warfarin 4'-, 6-, and 8-hydroxylation activity in hedgehogs were lower than that of rats. Furthermore, UDP-glucuronosyltransferase activities in hedgehogs were also lower <i>Km</i> than that of rats. Interestingly, the enzymatic efficiency of sulfation in hedgehogs was significantly lower than that of rats, whereas hedgehogs had similar sulfation ability as in pigs. Sulfation of hedgehogs may be limit activity in xenobiotic metabolism.
  • 池中良徳 日本内分泌かく乱化学物質学会講演会テキスト 30th 21‐30 2016年 [査読無し][通常論文]
  • 森田鮎子, 池中良徳, 中山翔太, 石井千尋, 水川葉月, 渡邉研右, 齊藤慶輔, 渡邊有希子, 伊藤真輝, 高江洲昇, 石塚真由美 日本獣医学会学術集会講演要旨集 158th 433 2015年08月30日 [査読無し][通常論文]
  • 中山翔太, 水川葉月, 池中良徳, 石塚真由美 日本野生動物医学会大会・講演要旨集 21st 22 2015年07月01日 [査読無し][通常論文]
  • 池中良徳 衛生動物 66 (2) 48 2015年06月25日 [査読無し][通常論文]
  • 池中良徳, 筧麻友, 中山翔太, 川合佑典, 渡邊研右, 水川葉月, 野見山桂, 田辺信介, 石塚真由美 環境化学討論会要旨集(CD-ROM) 24th ROMBUNNO.3A‐06 2015年06月17日 [査読無し][通常論文]
  • 綿貫豊, 山下愛, 石塚真由美, 池中良徳, 中山翔太, 石井千尋, 山本誉士, 山本誉士, 伊藤元裕, 桑江朝比呂, 鈴木裕也, 新妻靖彰, MEATHREL C.E, TRATHAN P.N, PHILLIPS R.A 環境化学討論会要旨集(CD-ROM) 24th ROMBUNNO.P‐146 2015年06月17日 [査読無し][通常論文]
  • 寺岡宏樹, 岡本絵梨佳, 久道萌, 中山翔太, 池中良徳, 石塚真由美, 北澤多喜雄 環境化学討論会要旨集(CD-ROM) 24th ROMBUNNO.P‐145 2015年06月17日 [査読無し][通常論文]
  • 武田一貴, 池中良徳, 田中和之, 中山翔太, 谷川力, 水川葉月, 石塚真由美 環境化学討論会要旨集(CD-ROM) 24th ROMBUNNO.3A‐07 2015年06月17日 [査読無し][通常論文]
  • 水川葉月, 中山翔太, 池中良徳, 速水秋, DARWISH Wageh Sobhy, 渡邊研右, 川合佑典, 石塚真由美 環境化学討論会要旨集(CD-ROM) 24th ROMBUNNO.P‐030 2015年06月17日 [査読無し][通常論文]
  • 石井千尋, 中山翔太, 池中良徳, 水川葉月, 中田北斗, 森田鮎子, 齊藤慶輔, 渡邊有希子, 神和夫, 田辺信介, 野見山桂, 林光武, 増田泰, 坂本健太郎, 石塚真由美 環境化学討論会要旨集(CD-ROM) 24th ROMBUNNO.3D‐05 2015年06月17日 [査読無し][通常論文]
  • 高平梨可, 宇野泰広, 池中良徳, 石塚真由美, 西川美宇, 榊利之, 生城真一 Journal of Toxicological Sciences 40 (Supplement) S187 2015年06月 [査読無し][通常論文]
  • 池中良徳, SAENGTIENCHAI Aksorn, SAENGTIENCHAI Aksorn, 筧麻友, DARWISH Wageh Sobhy, DARWISH Wageh Sobhy, 水川葉月, 中山翔太, 石塚真由美 Journal of Toxicological Sciences 40 (Supplement) S68 2015年06月 [査読無し][通常論文]
  • 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 [査読無し][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.
  • 山田綾子, 堀本高矩, 石塚真由美, 池中良徳, 中山翔太, 水川葉月, 三谷曜子, 宮下和士 日本水産学会大会講演要旨集 2015 49 2015年03月27日 [査読無し][通常論文]
  • 高平梨可, 西川美宇, 宇野泰広, 池中良徳, 石塚真由美, 榊利之, 生城真一 日本農芸化学会大会講演要旨集(Web) 2015 2F22P02 (WEB ONLY) 2015年03月05日 [査読無し][通常論文]
  • DARWISH Wageh Sobhy, IKENAKA Yoshinori, NAKAYAMA Shouta, MIZUKAWA Hazuki, ISHIZUKA Mayumi 日本毒性学会学術年会 42 (0) O -20 2015年 [査読無し][通常論文]
     
    Benzo[a]pyeren (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. B[a]P is confirmed to be pro-mutagenic and pro-carcinogenic to animals and humans in many studies. <br>Carotenoids such asβ-carotene and its metabolites like retinol and retinoic acids have a confirmed antioxidant activities through their radical scavenging roles. <br>The aim of this study, was firstly to estimate the B[a]P levels in fresh and heat treated meats. Additionally, B[a]P induced mutagenicity was studied using Salmonella mutagenicity assay. Moreover, B[a]P induced oxidative stress was examined using human hepatoma cell line (HepG2) cells after exposure to the relevant concentrations of B[a]P formed in heat-treated foods. In addition, the protective effects of carotenoids and retinoids against these harmful effects were also examined. The mechanisms behind these effects were also investigated.<br>The obtained results confirmed that carotenoids and retinoids have clear protective effects against B[a]P induced mutagenicity and oxidative stress, probably through their ability of induction of phase II and III enzymes and interference with the induction of phase I enzymes.
  • 池中 良徳, Aksorn SAENGTIENCHAI, 筧 麻友, Wageh Sobhy, DARWISH, 水川 葉月, 中山 翔太, 石塚 真由美 日本毒性学会学術年会 42 (0) S9 -3 2015年 [査読無し][通常論文]
     
    化学物質に対する最も基本的な生体防御機構は異物代謝系である。一方、これら異物代謝系の動物種差が、各動物の化学物質に対する感受性に強く寄与することが知られている。各生物が持つ異物代謝系には大きな種差があることが報告されている。例えば、異物代謝・第II相抱合反応において、ネコではグルクロン酸抱合、イヌではアセチル抱合およびブタでは硫酸抱合遺伝子が欠損していることが獣医学領域の研究から明らかになっており、投薬時に注意を要する。しかし、これら異物代謝系の動物種差に関する知見は、一部の実験動物を除くとほとんどの生物種で十分に解明されていない。<br>我々の研究グループでは、野生動物を含む様々な動物の異物代謝・第II相抱合反応を解明するため、in vivo、in vitroレベルおよびゲノム情報を用いた評価法の構築を行った。その結果、グルクロン酸抱合活性が低いと言われているネコ科動物以外にも、フェレットやトド、北オットセイ等の野生動物でもその活性が低いことが明らかになってきた。一方、硫酸抱合活性が低いと言われてきたブタでは、その活性は代表的な実験動物であるラットと変化が無いことが明らかになった。
  • 高平 梨可, 宇野 泰広, 池中 良徳, 石塚 真由美, 西川 美宇, 榊 利之, 生城 真一 日本毒性学会学術年会 42 (0) O -25 2015年 [査読無し][通常論文]
     
    【目的】抱合酵素であるUDP-グルクロン酸転移酵素(UGT)は、医薬品、環境汚染物質、食品成分などの生体異物に対するグルクロン酸抱合を触媒する。遺伝子ファミリーを形成しているUGT分子種は、複数の分子種の存在により動物種間において多様な基質及び部位特異性を示す。生体異物に対する毒性評価においてヒト代替動物を用いた代謝解析ではグルクロン酸抱合能に寄与するUGT分子種の機能解析は重要である。本発表では出芽酵母発現系を用いてカニクイザル(<i>Macaca fascicularis</i>, mf)由来UGT分子種の異物抱合能の代謝解析を行った。<br>【方法】自律複製型発現ベクターpGYRにmfUGT1A分子種のcDNAをそれぞれ組込み、出芽酵母AH22に酢酸リチウム法を用いて遺伝子導入した。それぞれの形質転換体よりミクロソーム膜画分を調製し、ウェスタンブロット法によってタンパク発現を確認した。また、UDP-グルクロン酸供給系との同時発現によるグルクロン酸抱合能を有する酵母株の構築もそれぞれの分子種について行った。種々の基質に対する抱合能解析はC18逆相カラムを用いたHPLCにより分離定量を行った。<br>【結果・考察】C末端共通領域に対するペプチド抗体を用いたウェスタンブロット解析により、ミクロソーム膜画分およびグルクロン酸抱合能を有する菌体株においてUGT1A分子種の発現を確認した。いずれの分子種もモデル基質であるスコポレチンに対してグルクロン酸抱合能を示し、ビスフェノールAや1-ヒドロキシピレンなどの異物に対しても代謝能が確認された。このことから酵母を用いたin vitroでのUGT抱合能解析が可能であり、抱合体調製系としても有用であることが示された。以上より、出芽酵母発現系を用いたmfUGT分子種の機能解析により、カニクイザルにおけるグルクロン酸抱合能をUGT分子種レベルで理解することが可能となった。
  • W. S. Darwish, W. S. Darwish, M. A. Hussein, K. I. El-Desoky, Y. Ikenaka, S. Nakayama, H. Mizukawa, M. Ishizuka International Food Research Journal 22 1719 -1726 2015年01月01日 [査読無し][通常論文]
     
    Environmental pollution by heavy metals is a serious problem worldwide. This study aimed to investigate comparisons between concentrations of toxic metals (cadmium and lead) in the liver, kidneys, and muscle of Egyptian cattle and sheep. The effect of animal age on levels of toxic metal residues as well as results of a public health risk assessment is also reported. The results show that both cadmium and lead levels exceeded Food and Agriculture Organization and World Health Organization permissible limits in the liver and kidneys. These parts had higher concentrations of toxic metals compared with muscle in the two animal species examined. Age had a significant influence on toxic metal accumulation in both species. The hazard index indicates that consuming the livers and kidneys of these animals might pose a health risk.
  • 石塚真由美, 中山翔太, 水川葉月, 池中良徳 日本毒性病理学会講演要旨集 31st (JA)44,(EN)116 2015年 [査読無し][通常論文]
  • 平久美子, MARFO Jemima, 池中良徳, 藤岡一俊, 青山美子 日本公衆衛生学会総会抄録集 73rd 268 2014年10月15日 [査読無し][通常論文]
  • 安井博宣, 武内亮, 永根大幹, 山盛徹, 池中良徳, 昆泰寛, 室谷憲紀, 大石基, 長崎幸夫, 稲波修 日本放射線影響学会大会講演要旨集 57th 109 2014年09月17日 [査読無し][通常論文]
  • 中田北斗, 中山翔太, 水川葉月, 池中良徳, 石井千尋, YARED YB, YABE John, 今内覚, 石塚真由美 日本獣医学会学術集会講演要旨集 157th 533 2014年08月11日 [査読無し][通常論文]
  • 石井千尋, 中山翔太, 池中良徳, 水川葉月, 中谷北斗, 齊藤慶輔, 渡邊有希子, 田辺信介, 野見山桂, 林光武, 増田泰, 坂本健太郎, 石塚真由美 日本獣医学会学術集会講演要旨集 157th 533 2014年08月11日 [査読無し][通常論文]
  • 渡辺有希子, 角田真穂, 石井千尋, 池中良徳, 石塚真由美, 齊藤慶輔 北海道獣医師会雑誌 58 (8) 389 2014年08月10日 [査読無し][通常論文]
  • 中田北斗, 中山翔太, 水川葉月, 池中良徳, 石井千尋, YOHANNES Yared B, 今内覚, 石塚真由美 J Toxicol Sci 39 (Supplement) S336 -187 2014年07月 [査読無し][通常論文]
     
    ケニア共和国の首都ナイロビ市内の大規模ゴミ集積場・ダンドラ地域は、世界第二位の巨大・高密度スラム街であり、地域内の子供の半数はWHO基準(100 μg/kg)以上の血中Pb濃度であることが報告されているが、家畜の汚染や生体への曝露源に関する報告はない。本研究では、ダンドラおよび対照区として同国・ナクル地域に生息するヤギ、ヒツジ、ブタおよびウシの血中金属類(10元素)濃度およびPb安定同位体比をICP-MSにより、PCBsおよび有機塩素系農薬(OCPs)濃度をGC-MSとGC-ECDにより測定した。<br> その結果、全てのサンプルでCr, Mn, Ni, Cu, Zn, As, Mo, Agの高濃度蓄積は認められず、PCBsおよびOCPsは検出限界以下であった。Pb濃度はナクルに比べてダンドラで高い蓄積傾向を示し、ヤギおよびヒツジでは有意差が認められた。ブタの平均Pb濃度はダンドラ(2600 μg/kg, dry wt:dw)がナクル(73 μg/kg, dw)の約35倍の高値を示した。ダンドラのウシからは、ヘム合成に関与するアミノレブリン酸脱水酵素活性が低下するとされる値(100μg/kg)と同程度のPb濃度(91 μg/kg以上)が検出され、血液毒性等の中毒症状の蔓延が示唆された。Cd濃度の地域差および種差は認められなかったが、総じて高値(570±460 ng/kg, dw)を示し、ウシの摂食によるヒトのCd曝露が示唆された。Pb安定同位体比は地域および動物種により異なる傾向を示し、地域内に複数の曝露源があること、動物種により主要な曝露源が異なることが示唆された。<br> 本研究より、両地域に生息する家畜には高濃度のPb, Cdが蓄積し、特にPb汚染はダンドラで深刻なレベルであり、その曝露源が複数存在することが示唆された。家畜と生活環境を共にするヒトへの同様の汚染も強く示唆された。
  • 石井千尋, 中山翔太, 池中良徳, 水川葉月, 中田北斗, 齊藤慶輔, 渡邊有希子, 田辺信介, 野見山桂, 林光武, 増田泰, 坂本健太郎, 石塚真由美 J Toxicol Sci 39 (Supplement) S336 -188 2014年07月 [査読無し][通常論文]
     
    【はじめに】北海道では、猛禽類において鉛弾摂取による鉛中毒が問題となっている。現在は鉛弾の使用規制が設けられているものの、未だに被害個体が発見されている。また、本州など他地域でも鉛中毒個体が発見されているが、北海道を除く地域における汚染実態調査は極僅かであり、鉛弾使用規制も不十分である。そこで、本研究では北海道、本州、四国において死亡した猛禽類の鉛濃度と鉛安定同位体比を測定し、鉛汚染状況と汚染源の解明を試みた。<br>【方法】試料は、1993年から2014年に北海道、本州、四国で死亡したイヌワシ、トビ、オオワシ、オオタカ、フクロウ、オジロワシ、オオハヤブサ、クマタカ、サシバ、ハイタカ、ツミ、チョウゲンボウの計49個体の肝臓を採取し、誘導結合プラズマ質量分析計で鉛濃度と鉛安定同位体比(<sup>207</sup>Pb/<sup>206</sup>Pb、<sup>208</sup>Pb/<sup>206</sup>Pb)を分析した。<br>【結果と考察】本研究の結果、1999‐2014年に北海道で死亡した4羽のオオワシにおいて、鉛中毒が疑われる値(11.0-29.5 mg/kg、湿重量)が検出された。北海道では2004年に大型獣の狩猟における鉛弾使用が禁止されているが、2013、2014年に採取されたオオワシにおいても高濃度の鉛蓄積が検出され、このうち1羽からはレントゲン撮影と剖検で胃内に鉛弾の破片が認められた。また岩手県で死亡したイヌワシからも高濃度の鉛蓄積(2.0 mg/kg)が認められた。さらに鉛安定同位体比を分析した結果、高濃度の鉛蓄積個体の鉛安定同位体比の値が同程度であった。このうち1羽から鉛弾が検出されたことを考慮すると、これらの高濃度蓄積個体の汚染源は鉛ライフル弾であると考えられた。<br> 上記の結果から、猛禽類の鉛弾摂取による中毒が未だに問題となっていることが明らかとなった。従って、北海道以外の地域における調査、また日本全国における鉛弾流通の完全禁止など規制強化の検討が必要であると考えられた。
  • 筧麻友, 中山翔太, 水川葉月, 池中良徳, 渡邊研右, 坂本健太郎, 和田昭彦, 服部薫, 田辺信介, 野見山桂, 石塚真由美 J Toxicol Sci 39 (Supplement) S281 -78 2014年07月 [査読無し][通常論文]
     
    【目的】グルクロン酸抱合酵素(UGT)は、生体外異物代謝の第Ⅱ相抱合反応を担い、各動物の化学物質感受性決定に関与することが報告されている。食肉目ネコ亜目(Feliformia)では環境化学物質や薬物等の代謝に関与するUGT1A6の偽遺伝子化が報告されており、この偽遺伝子化に伴いアセトアミノフェン等の薬物の毒性作用が強いことが知られている。一方、食肉目に属する鰭脚類(Pinnipedia)では、環境化学物質の高濃度蓄積が報告されているが、感受性に関与するUGTについての研究はほとんど行われていない。そこで、鰭脚類を中心とした食肉目において、肝臓でのUGT活性の測定と系統解析を行った。<br>【方法】食肉目に属するネコ(<i>Felis catus</i>)、イヌ(<i>Canis familiaris</i>)、鰭脚類であるトド(<i>Eumetopias jubatus</i>)、キタオットセイ(<i>Callorhinus ursinus</i>)、カスピカイアザラシ(<i>Phoca caspica</i>)及び対照としてラット(<i>Rattus norvegicus</i>)の肝臓ミクロソームを作成し、1-ヒドロキシピレン(UGT1A6、UGT1A7、UGT1A9)、アセトアミノフェン(UGT1A1、UGT1A6、UGT1A9)、セロトニン(UGT1A6)を基質としてUGT活性を測定した。また、NCBIのデータベースからUGT1A領域の系統解析およびシンテニー解析を行った。<br>【結果及び考察】1-ヒドロキシピレン、アセトアミノフェン、セロトニンに対するUGT抱合活性を測定した結果、ラットに比べ食肉目では極めて低い活性を示した。また、系統解析及びシンテニー解析より、解析した全ての食肉目において、UGT1A分子種は特徴的な2遺伝子であるUSP40 とMROH2の間に保存されていることが明らかになった。さらに、食肉目は齧歯目に比べUGT1A領域が短く、UGT1A分子種数が少ないことが確認された。以上の結果から、鰭脚類を含めた食肉目はUGTによる異物代謝能が低く、環境化学物質に対する感受性が高い可能性が考えられた。
  • 筧麻友, 池中良徳, 中山翔太, 水川葉月, 渡邊研右, 坂本健太郎, 和田昭彦, 服部薫, 田辺信介, 野見山桂, 石塚真由美 J Toxicol Sci 39 (Supplement) S223 -9 2014年07月 [査読無し][通常論文]
     
    【目的】グルクロン酸抱合酵素(UGT)は、異物代謝の第Ⅱ相抱合反応を担い、各動物の化学物質感受性決定に関与することが報告されている。食肉目ネコ亜目(<i>Feliformia</i>)では環境化学物質や薬物等の代謝に関与するUGT1A6の偽遺伝子化が報告されており、この偽遺伝子化によりアセトアミノフェン等の薬物の毒性作用が強く表れることが知られている。一方、食肉目に属する鰭脚類(<i>Pennipedia</i>)では、PCB、DDTなどの残留性有機汚染物質の高濃度蓄積が報告されているが、感受性に関与するUGTについての研究がほとんど行われていない。そこで、鰭脚類を中心とした食肉目において、UGTの機能解析及び系統解析を行い、種差を明らかにすることを目的とした。<br>【方法】食肉目に属するネコ(<i>Felis catus</i>)、イヌ(<i>Canis familiaris</i>)、鰭脚類であるトド(<i>Eumetopias jubatus</i>)、キタオットセイ(<i>Callorhinus ursinus</i>)、カスピカイアザラシ(<i>Phoca caspica</i>)及び対照としてラット(<i>Rattus norvegicus</i>)の肝臓ミクロソームを調整した。この肝臓ミクロソームを用いて、1-ヒドロキシピレンを基質としてUGT活性を測定した。さらに食肉目UGT1A遺伝子について、他の哺乳類と比較し、系統解析を行った。<br>【結果及び考察】1-ヒドロキシピレンを基質として用いたところ、イヌはラットと同程度のUGT活性を示したが、鰭脚類3種およびネコのUGT活性はラットの3分の1以下だった。また、UGT1A遺伝子は一般に2-10程度のホモログが近接して染色体上に存在しているが、系統解析及びシンテニー解析より、食肉目は齧歯目に比べUGT1A領域が短くUGT1A分子種数が少ないことが確認された。さらに、トドおよびキタオットセイでは、UGT1A6のエクソン1領域に2塩基挿入によるストップコドンが生じ、偽遺伝子化していることが明らかになった。以上の結果より、鰭脚類は、UGTによる異物代謝能が低く、環境化学物質に対する感受性が高い可能性が考えられた。
  • 水川葉月, 池中良徳, 野見山桂, 田辺信介, 宇根有美, 伊藤真輝, 高江洲昇, 長野靖子, 中山翔太, 石塚真由美 環境化学討論会要旨集(CD-ROM) 23rd ROMBUNNO.3B-14 2014年05月14日 [査読無し][通常論文]
  • 吉田知可, 池中良徳, 宮原裕一 環境化学討論会要旨集(CD-ROM) 23rd ROMBUNNO.P-179 2014年05月14日 [査読無し][通常論文]
  • 石井千尋, 池中良徳, 中山翔太, 水川葉月, 齊藤慶輔, 渡邊有希子, 田辺信介, 野見山桂, 林光武, 増田泰, 坂本健太郎, 石塚真由美 環境化学討論会要旨集(CD-ROM) 23rd ROMBUNNO.3D-03 2014年05月14日 [査読無し][通常論文]
  • 池中良徳, YOHANNES Yared Beyene, 中山翔太, 水川葉月, VAN VUREN Johannes J, WEPENER Victor, SMIT Nico J, WYNAND Vlok, 石塚真由美 環境化学討論会要旨集(CD-ROM) 23rd ROMBUNNO.2A-08 2014年05月14日 [査読無し][通常論文]
  • 中田北斗, 中山翔太, 水川葉月, 池中良徳, 石井千尋, YOHANNES Yared B, 今内覚, 石塚真由美 環境化学討論会要旨集(CD-ROM) 23rd ROMBUNNO.3D-01 2014年05月14日 [査読無し][通常論文]
  • 高平梨可, 宇野泰広, 池中良徳, 石塚真由美, 西川美宇, 榊利之, 生城真一 日本生化学会大会(Web) 87th 3P-182 (WEB ONLY) 2014年 [査読無し][通常論文]
  • 筧麻友, 池中良徳, 中山翔太, 水川葉月, 渡邉研右, 坂本健太郎, 和田昭彦, 服部薫, 田辺信介, 野見山桂, 石塚真由美 日本野生動物医学会大会・講演要旨集 20th 75 2014年 [査読無し][通常論文]
  • 筧麻友, 池中良徳, 中山翔太, 水川葉月, 渡邉研右, 坂本健太郎, 和田昭彦, 服部薫, 田辺信介, 野見山桂, 石塚真由美 日本分子生物学会年会プログラム・要旨集(Web) 37th 3P-0853 (WEB ONLY) 2014年 [査読無し][通常論文]
  • 綿貫豊, 山下愛, 保科賢司, 鈴木優也, 山本誉士, 石塚真由美, 池中良徳, 中山翔太, 石井千尋, 新妻靖章, MEATHREL C, PHILLIPS R. A 日本鳥学会大会講演要旨集 2013 53 2013年09月13日 [査読無し][通常論文]
  • 速水秋, DARWISH Wageh, 池中良徳, 中山翔太, 石塚真由美 日本獣医学会学術集会講演要旨集 156th 388 2013年08月30日 [査読無し][通常論文]
  • 宇野泰広, 池中良徳, 石塚真由美 日本獣医学会学術集会講演要旨集 156th 388 2013年08月30日 [査読無し][通常論文]
  • N. Fujisawa, W. S. Darwish, Y. Ikenaka, E. Kim, J. Lee, H. Iwata, S. Nakayama, M. Ishizuka POULTRY SCIENCE 92 (7) 1921 -1929 2013年07月 [査読無し][通常論文]
     
    A 1,000-fold difference has been reported in dioxin sensitivity between avian species. This difference is because the 2 amino acids in the type 1 aryl hydrocarbon receptor (AhR1), at positions 325 and 381, correspond to Leu324 and Ser380 in chickens. The chicken had been reported to be the only avian species to possess a sensitive form of AhR1. This is the first study to reveal that the ostrich (Struthio camelus), a nonchicken species, also has a pair of amino acids (Ile-325 and Ser-381) that show high ligand affinity. However, the alignment of the AhR1 cDNA sequence showed that the AhR sequence in the ostrich was different than that of other avian species even though the critical amino acids were observed at positions 325 and 381. Ostrich AhR1 was also evaluated in a heterologous expression study. Ostrich AhR1 showed very high transcriptional activity of the cytochrome P450 1A5 (CYP1A5) gene in African Green Monkey Cercopithecus aethiops kidney cells (COS-7) treated with Sudan III. In primary cultures of ostrich kidney cells, CYP1A5 expression was induced by Sudan III at a lower (or almost identical) concentration to that observed in the chicken. The present study revealed a new AhR ligand sensitive avian species (i.e., the ostrich).
  • 石井千尋, 池中良徳, 中山翔太, 鈴木優也, 綿貫豊, 渡邊雄児, 福若雅章, YOHANNES Yared B, 川合佑典, 石塚真由美 環境化学討論会要旨集(CD-ROM) 22nd ROMBUNNO.1-1B-1-1 2013年07月 [査読無し][通常論文]
  • 大谷豪, 池中良徳, 中山翔太, AKOTO Osei, APAU Joseph, BAIDOO Elvis, 石塚真由美 環境化学討論会要旨集(CD-ROM) 22nd ROMBUNNO.1-1B-2-2 2013年07月 [査読無し][通常論文]
  • 池中良徳, 田中和之, 中山翔太, 春成常仁, 谷川力, 水川葉月, 石塚真由美 環境化学討論会要旨集(CD-ROM) 22nd ROMBUNNO.3-2D-6-3 2013年07月 [査読無し][通常論文]
  • 苅和 宏明, 尾崎 由佳, 真田 崇弘, 池中 良徳, 石塚 真由美, 坪田 敏男, 好井 健太朗, 吉松 組子, 有川 二郎, 高島 郁夫 獣医畜産新報 66 (4) 262 -264 2013年04月 [査読無し][通常論文]
     
    ハンタウイルスはげっ歯類媒介性の人獣共通感染症の病原体で、腎症候性出血熱(HFRS)またはハンタウイルス肺症候群(HPS)を引き起こす。近年の日本におけるげっ歯類のハンタウイルス感染状況を明らかにするために、1994年から2010年にかけて国内の様々な地域で捕獲された1658匹のげっ歯類の血清について、抗ハンタウイルス抗体の検出を行った。840例のRattus属げっ歯類(ドブネズミとクマネズミ)は全て抗体陰性であった。北海道以外の地域で捕獲された野生げっ歯類113例はいずれも抗体陰性であったのに対し、北海道で捕獲された705例の野性げっ歯類のうち、エゾヤチネズミの7.4%(26/352)とアカネズミの1.2%(2/168)が抗体を保有していた。(著者抄録)
  • 綿貫豊, 山下愛, 石塚真由美, 池中良徳, 中山翔太, 石井千尋, 山本誉士, 伊藤元裕, 桑江朝比呂 日本生態学会大会講演要旨集 60th 118 2013年03月05日 [査読無し][通常論文]
  • 池中良徳 日本獣医学会学術集会講演要旨集 155th 166 2013年03月04日 [査読無し][通常論文]
  • 石井千尋, 池中良徳, 中山翔太, 鈴木優也, 綿貫豊, 渡邊雄児, 福若雅章, YARED Yohannes Beyene, 川合佑典, 石塚真由美 日本獣医学会学術集会講演要旨集 155th 260 2013年03月04日 [査読無し][通常論文]
  • OROSZLANY Balazs, IKENAKA Yoshinori, SAENGTIENGCHAN Aksorn, OGURI Mami, NAKAYAMA Shouta, ISHIZUKA Mayumi 日本毒性学会学術年会 40 (0) 2013年 [査読無し][通常論文]
     
    Introduction : Reptile populations all around the world are decreasing. The dominant stressors are decrease of habitats, targeted harvesting and climate change. Environmental pollution could be a common factor weakening populations, yet we know little about the effect of xenobiotics on reptiles. Pyrene, as a representative of polycyclic aromatic hydrocarbons (PAHs), was choosen to study the metabolism in freshwater turtles, as disasters involving PAHs (oil spills) are one of the main causes of health and reproductive problems in water-living organism. <br>Materials and Methods:Red-eared sliders (<i>Trachemys scripta elegans</i>), Chinese pond turtles (<i>Mauremys reevesii</i>) and Chinese softshell turtles (<i>Pelodiscus sinensis</i>) were used. Pyrene exposure occurred thorugh oral feeding (4 mg/kg pyrene, dissolved in corn oil) or through water (250 &mu;g/l). Exposed water was filtered, passed through a solid-phase cartridge, and eluded with methanol. Metabolites were determined by HPLC with FD equipped with an ODS column, and identified by an MS/MS system. Liver subcellular fractions were isolated from fresh samples, protein concentration were measured by BCA protein assay. EROD, UGT and SULT activity were measured.<br>Results and Discussion:Distinct metabolite distributions were measured for each species. The dominant metabolite in all three species was pyrene-1-sulfate. All enzyme activities were low compared to mammals (rat). Sulfate conjugation was the dominant phase II metabolic pathway in all three species.
  • DARWISH Wageh Sobhy, IKENAKA Yoshinori, NAKAYAMA Shouta, ISHIZUKA Mayumi 日本毒性学会学術年会 40 (0) 2013年 [査読無し][通常論文]
     
    <b>[Introduction]</b> <br> In our previous work, positive correlations between CYP1A- dependent activities, protein expression and &beta;-carotene (BC) accumulation in the ungulates were observed, however these cross-talks were poorly understood. Additionally, the regulatory effects of carotenoids on xenobiotics metabolizing enzymes (XMEs) had received little attention. Thus, the aim of the current study is to deeply investigate the constitutive response of AhR gene battery to the exposure to BC under various doses in the human hepatoma cell line (HEPG2) cells. Moreover, the possible regulatory mechanisms of these cross-talks between AhR and BC will be declared.<br> <b>[Materials and Methods]</b> <br> HEPG2 cell lines were treated with different concentrations of BC (0-10 &micro;M) for 12-24h. The mRNA expression for phase I (CYP1A1 and 1A2), Phase II (UGT1A6 and NQO1) enzymes and AhR were examined using Real-Time PCR. Protein expression of AhR was investigated using western blotting. Rat H4IIE cells were transfected with h-XRE luciferase reporter plasmid and exposed to BC for 24h and dual- luciferase reporter assay was performed.<br> <b>[Results and Discussion]</b> <br> BC differentially modulated XMEs (Phase I and II enzymes) expression in dose-dependent fashion. In parallel, BC induced AhR mRNA, protein expression and luciferase activity. Thus, &beta;-carotene differentially modulated AhR gene battery.
  • 河田みなみ, 池中良徳, 渡邉研右, AKSORN Saengtienchai, 大野円実, 石塚真由美 日本獣医学会学術集会講演要旨集 154th 349 2012年08月31日 [査読無し][通常論文]
  • YABE John, NAKAYAMA Shouta M.M, IKENAKA Yoshinori, MUZANDU Kaampwe, CHOONGO Kennedy, ISHIZUKA Mayumi, UMEMURA Takashi 環境化学討論会要旨集(CD-ROM) 21st ROMBUNNO.1B-12 2012年07月10日 [査読無し][通常論文]
  • YARED B. Yohannes, IKENAKA Yoshinori, WATANABE Kensuke, SAENGTIENCHAI Aksorn, NAKAYAMA Shouta, ISHIZUKA Mayumi 環境化学討論会要旨集(CD-ROM) 21st ROMBUNNO.1B-06 2012年07月10日 [査読無し][通常論文]
  • 池中良徳, SAENGTIENCHAI Aksorn, 川合佑典, 石塚真由美 環境化学討論会要旨集(CD−ROM) 21st ROMBUNNO.1D-10 2012年07月10日 [査読無し][通常論文]
  • 池中良徳, 上田春樹, SAENGTIENCHAI Aksorn, 石塚真由美 環境化学討論会要旨集(CD−ROM) 21st ROMBUNNO.P-210 2012年07月10日 [査読無し][通常論文]
  • 池中良徳, 河田みなみ, 渡辺研右, SAENGTIENCHAI Aksorn, 大野円美, 石塚真由美 環境化学討論会要旨集(CD−ROM) 21st ROMBUNNO.P-211 2012年07月10日 [査読無し][通常論文]
  • 小栗真美, 池中良徳, SAENGTIENCHAI Aksorn, 石塚真由美 環境化学討論会要旨集(CD−ROM) 21st ROMBUNNO.3C-04 2012年07月10日 [査読無し][通常論文]
  • 渡邉研右, 河田みなみ, 川合佑典, 池中良徳, 石塚真由美 J Toxicol Sci 37 (Supplement 1) S238 -163 2012年07月 [査読無し][通常論文]
     
    【背景と目的】鳥類では、ミクロソームを用いたシトクロムP450(CYP)によるワルファリン代謝活性について、ニワトリと比べ他種鳥類では活性が低く、数十倍の種差があることが明らかになっている。しかし、これまでにゲノムプロジェクトが終了しているニワトリにおいてもCYP分子種ごとの発現解析や機能解析が行われておらず、異物代謝上重要と考えられる分子種やそれぞれの機能が明らかになっていない。そのため、これまでに報告されている鳥類種間での異物代謝能の種差が、どの分子種に帰属されるのかも明らかでない。そこで、本研究では、鳥類の異物代謝において重要と考えられる分子種の特定と、その種差を明らかにすることを目的とした。【方法と結果】ニワトリの肝臓を用い、CYP分子種ごとのmRNAコピー数を比較したところ、肝臓においてCYP1A5、2C23、2C45が多く発現していることが明らかになった。一方で、ニワトリなどの家禽で研究が進められているCYP3A37は大きな発現量を示さなかった。また、哺乳類でCYP2Bや3Aを誘導するフェノバルビタールを投与した場合においても、CYP2C、3Aが受ける誘導は同程度だった。そこで、これまでに機能解析がほとんど行われていないCYP2C23について8種の鳥類からcDNAクローニングを行い、鳥類種間で保存されているアミノ酸領域に対する抗ペプチド抗体の作製を行った。各鳥類種の肝臓ミクロソームについて、この抗体を用いたウェスタンブロット法を行った結果、すべての鳥類種でCYP2C23特異的に交差反応が見られ、CYP2C23タンパク質を定量することができた。【考察】mRNAコピー数比較から、鳥類ではCYP2Cサブファミリーが多く発現し、重要な分子種であると考えられた。そこで、鳥類CYP2C23特異的抗体を用いたタンパク質発現量比較を行ったが、その発現量には大きな種差が見られなかった。以上の結果より、鳥類種間で見られる活性の種差はタンパク質発現量の違いによるものではなく、酵素の機能的な違いによるものであると考えられた。
  • 新海秀史, 春成常仁, 田中和之, 谷川力, 池中良徳, 石塚真由美 生理学技術研究会報告 2012 (34) 57-59 -59 2012年06月25日 [査読無し][通常論文]
  • Kazuyuki D. Tanaka, Yusuke K. Kawai, Yoshinori Ikenaka, Tsunehito Harunari, Tsutomu Tanikawa, Shima Ando, Hee Won Min, Fumie Okajima, Shoichi Fujita, Mayumi Ishizuka PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 103 (2) 144 -151 2012年06月 [査読無し][通常論文]
     
    Warfarin is commonly used worldwide as a rodenticide. It inhibits blood coagulation by inhibiting vitamin K 2,3-epoxide reductase (VKOR) activity leading to hemorrhage. However, it has been reported that repeated or long-term treatment with warfarin results in resistance emerging in wild rodents. Such resistance may explain why it is difficult to control rodents in many regions in Japan. In this report, we studied mutations in the VKOR gene (including the VKOR complex subunit 1 (VKORC1)), while also analyzing VKOR and clotting factor activity in black rats (Rattus rattus) in order to understand better the mechanism of warfarin resistance in this species. We sequenced the VKORC1 gene from 275 rats living in the wild in Japan. We found several types of novel base substitutions, some of which conferred warfarin resistance. There was no difference in coagulation times between warfarin-sensitive and resistant rats measured under physiological conditions. However, after warfarin administration, no effect was noted in warfarinresistant rats, although a prolonged coagulation time was noted in warfarin-sensitive rats. We also determined the kinetic differences in hepatic microsomal VKOR-dependent activity between warfarin-resistant and sensitive rats. Warfarin-resistant rats showed 2-3-fold lower VmaxIK values than did sensitive rats. In addition, we report that resistant rats found in the Tokyo area had a VKOR activity which was poorly inhibited by warfarin. Finally, we conclude that reduced VKOR activity and warfarin resistance in the Japanese black rat might be due to mutations in the VKORC1 gene. However, further study is needed to clarify how such rats can maintain adequate vitamin K-dependent clotting factor levels, while simultaneously exhibiting low VKOR activity and warfarin resistance. (C) 2012 Elsevier Inc. All rights reserved.
  • S. Suzuki, S. Konnai, T. Okagawa, N. W. Githaka, E. Kariuki, F. Gakuya, E. Kanduma, T. Shirai, R. Ikebuchi, Y. Ikenaka, M. Ishizuka, S. Murata, K. Ohashi INTERNATIONAL JOURNAL OF IMMUNOGENETICS 39 (2) 170 -182 2012年04月 [査読無し][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-?, and Th2 cytokines IL-4 and IL-10. The cloned cDNA of IL-2, IL-4, IL-10 and IFN-? 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-? 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.
  • 上田春樹, 中山翔太, 川合佑典, 田中(上野)寛子, 池中良徳, 石塚真由美 は虫両棲類学会報 2012 (1) 89 2012年03月31日 [査読無し][通常論文]
  • 河田みなみ, 池中良徳, 渡邉研右, 大野円実, 上田春樹, 西山義広, 石塚真由美 日本獣医学会学術集会講演要旨集 153rd 265 2012年03月01日 [査読無し][通常論文]
  • Nozomi Fujisawa, Yoshinori Ikenaka, Eun-Young Kim, Jin-Seon Lee, Hisato Iwata, Mayumi Ishizuka EUROPEAN JOURNAL OF WILDLIFE RESEARCH 58 (1) 167 -175 2012年02月 [査読無し][通常論文]
     
    Some wild populations of fish-eating birds and raptors are exposed to high concentrations of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) and related compounds such as other 2,3,7,8-substituted polychlorinated dibenzop- dioxins and polychlorinated dibenzofurans and coplanar polychlorinated biphenyls, resulting in accumulation in their tissues. It has been demonstrated that TCDD-like chemicals cause toxic effects via aryl hydrocarbon receptor (AHR)-mediated signaling pathways. The aim of this study was to characterize the AHR from the peregrine falcon (Falco peregrines) to predict its sensitivity to TCDD-like chemicals. The AHR1, AHR2, and AHR nuclear translocator 1 of the peregrine falcon are more similar in amino acid sequence to avian species less sensitive to TCDD-like chemicals such as the cormorant (95%) than to more sensitive species such as the chicken (90%). From the amino acid sequence, it is likely that the ligand-binding affinity of peregrine falcon AHR1 and AHR2 would be very low compared with the chicken or other sensitive species, and it was actually proved by an in vitro reporter gene assay. We concluded that the peregrine falcon, one of raptor species, may be relatively resistant to TCDD-like chemicals.
  • Marumi Ohno, Wageh Sobhy Darwish, Yoshinori Ikenaka, Wataru Miki, Shoichi Fujita, Mayumi Ishizuka FOOD CHEMISTRY 130 (2) 356 -361 2012年01月 [査読無し][通常論文]
     
    The xanthophyll, astaxanthin (Ax), strongly induces cytochrome P450 (CYP) 1A-dependent activity in rats and mice, via increased transcription of Cyp1a1 mRNA through an undetermined mechanism. In this study, we have investigated how aryl hydrocarbon receptor (AhR)-related events are affected by the addition of Ax-rich crude extract from Haematococcus pluvialis in H4IIE rat hepatoma cells. The expression of Cyp 1a1 mRNA was significantly increased by exposure to H. pluvialis extract (100 mu mol/l, 17.6-fold). The highest level of Cyp1a1 mRNA was observed after a 6-h exposure to H. pluvialis extract (25-fold), but 12- and 24-h exposures resulted in lower levels of induction. Green fluorescence protein-tagged AhR was translocated into the nucleus in COS-7 cells after a 10 min exposure to Ax. Moreover, H. pluvialis extract containing Ax activated the human CYP1A1 enhancer region in a luciferase assay, and a gel shift assay showed that nuclear proteins stimulated by H. pluvialis extract can interact specifically with xenobiotic responsive elements (XREs) in the CYP1A1 promoter. Together these results indicate the possibility that Ax, contained in H. pluvialis extract, caused the induction of Cyp1a1 mRNA through the activation and translocation of an XRE-binding form of AhR. (C) 2011 Elsevier Ltd. All rights reserved.
  • A. Saengtienchai, Y. Ikenaka, K. Watanabe, T. Ishida, M. Ishizuka POULTRY SCIENCE 90 (12) 2775 -2781 2011年12月 [査読無し][通常論文]
     
    Warfarin, a coumarin rodenticide, is commonly used worldwide for rodent control, and is often reported as the cause for poisoning accidents in nontarget animals, in particular bird species. However, the metabolism of warfarin in birds is still unclear. In a previous study, we found an unknown warfarin metabolite in chicken cytosolic fractions. In the present study, we aimed to clarify the cytosolic warfarin metabolites in chickens compared with those in rats. The cytosol fractions of both chicken and rat livers showed the metabolic activity of 2 diastereomers and 2 enantiomers of warfarin alcohol. In chicken cytosol, we found that the production level of (S)-warfarin-(S)-alcohol was markedly higher (32-fold) than that in rat cytosol. From the results of the inhibition assay, we finally suggest that aldehyde oxidase may mainly contribute to the warfarin alcohol products in chicken cytosol.
  • 石塚真由美, 池中良徳 衛生薬学・環境トキシコロジー講演要旨集 2011 104 2011年10月05日 [査読無し][通常論文]
  • 岡本絵梨佳, 久道萌, 水野直治, 古賀公也, 志村良治, 中山翔, 池中良徳, 石塚真由美, 北澤多喜雄, 井上雅子, 百瀬邦和, 正富宏之, 寺岡宏樹 日本鳥学会大会講演要旨集 2011 63 2011年09月13日 [査読無し][通常論文]
  • 岡本絵梨佳, 久道萌, 水野直治, 古賀公也, 志村良治, 中山翔, 池中良徳, 石塚真由美, 北澤多喜雄, 井上雅子, 百瀬邦和, 正富宏之, 寺岡宏樹, 寺岡宏樹 日本鳥学会大会講演要旨集 2011 63 2011年09月13日 [査読無し][通常論文]
  • 西山義広, 池中良徳, 大野円実, 渡邊研右, 川合佑典, 中山翔太, 田中和之, 石塚真由美 日本獣医学会学術集会講演要旨集 152nd 335 2011年08月31日 [査読無し][通常論文]
  • 糸谷悠美, 池中良徳, 大野円実, 中山翔太, SOBHY Wageh, 石塚真由美 日本獣医学会学術集会講演要旨集 152nd 335 2011年08月31日 [査読無し][通常論文]
  • 尾崎 由佳, 萩谷 友洋, 真田 崇弘, 瀬戸 隆弘, Taylor Kyle, 吉川 佳佑, Ivanov Leonid I., 好井 健太朗, 坪田 敏男, 池中 良徳, 石塚 真由美, 吉松 組子, 有川 二郎, 苅和 宏明 北海道獣医師会雑誌 55 (8) 415 -415 2011年08月 [査読無し][通常論文]
  • 尾崎 由佳, 萩谷 友洋, 真田 崇弘, 瀬戸 隆弘, Kyle Taylor, 吉川 佳佑, Leonid Ivanov, 好井 健太朗, 坪田 敏男, 池中 良徳, 石塚 真由美, 吉松 組子, 有川 二郎, 苅和 宏明 日本獣医学会学術集会講演要旨集 152回 256 -256 2011年08月 [査読無し][通常論文]
  • YARED Beyene, IKENAKA Yoshinori, WATANABE Kensuke, SAENGTIENCHAI Aksorn, NAKAYAMA Shouta, ISHIZUKA Mayumi 環境化学討論会要旨集(CD-ROM) 20th ROMBUNNO.2E-01 2011年07月01日 [査読無し][通常論文]
  • NAKAYAMA Shouta M.M, IKENAKA Yoshinori, MUZANDU Kaampwe, CHOONGO Kennedy, YABE John, MUROYA Taro, UMEMURA Takashi, ISHIZUKA Mayumi 環境化学討論会要旨集(CD-ROM) 20th ROMBUNNO.2E-09 2011年07月01日 [査読無し][通常論文]
  • 大谷豪, 池中良徳, 中山翔太, AKOTO Osei, APAU Joseph, BAIDOO Elvis, 石塚真由美 環境化学討論会要旨集(CD-ROM) 20th ROMBUNNO.P-214 2011年07月01日 [査読無し][通常論文]
  • Nobuo Sasaki, Tomoyuki Matsumoto, Yoshinori Ikenaka, Akio Kazusaka, Mayumi Ishizuka, Shoichi Fujita PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 100 (2) 135 -139 2011年06月 [査読無し][通常論文]
     
    The nitrofuran antibacterial agent furazolidone (FZ) is still used in veterinary medicine in some countries in the Middle and Far East. The present study aimed to show the effect of FZ on the activity of microsomal enzymes that metabolize FZ, and to identify the enzyme that contributes to FZ metabolism in chickens. Wistar rats and White Leghorn chickens were administered FZ once a day for four consecutive days. FZ metabolism was accelerated by FZ administration in chickens, but not in rats. The elevation of FZ metabolism coincided with the induction of NADPH cytochrome P450 reductase (CPR) activity in chickens, but such induction was not observed in rats. FZ metabolizing activities were inhibited in the presence of a CPR inhibitor (diphenylene iodonium chloride) but not by the addition of archetypal cytochrome P450 inhibitors (CO or n-octylamine). The preset study concluded that FZ accelerated its own metabolism in the chicken by induction of the activity of CPR. (C) 2011 Elsevier Inc. All rights reserved.
  • 小栗真美, 池中良徳, AKSORN Saengtienchai, 上田春樹, 石塚真由美 J Toxicol Sci 36 (Supplement) S119 2011年06月 [査読無し][通常論文]
  • 池中 良徳, 石塚 真由美 安全工学 50 (2) 80 -84 2011年04月15日 [査読無し][通常論文]
     
    <p>野生動物は環境化学物質に汚染された環境下で棲息をしており,常にこれらの化学物質に曝露されている.本節では,野生動物の化学物質感受性と生体防御機構について,外来化学物質を代謝する主要酵素シトクロムP450 を中心に概説する.また,汚染環境下で棲息する野生の動物が,環境に適応する為にどのような変化を示すのか,野生のドブネズミを例に最近の研究を報告する.</p>
  • 糸谷悠美, 池中良徳, 大野円実, 中山翔太, WAGEH Sobhy, 石塚真由美 日本獣医学会学術集会講演要旨集 151st 271 2011年03月01日 [査読無し][通常論文]
  • 西山義広, 田中和之, 大野円実, 渡邊研右, 川合佑典, 中山翔太, 谷川力, 春成常仁, 池中良徳, 石塚真由美 日本獣医学会学術集会講演要旨集 151st 270 2011年03月01日 [査読無し][通常論文]
  • 田中和之, 春成常仁, 谷川力, 渡邉研右, 池中良徳, 石塚真由美 日本獣医師会獣医学術学会年次大会講演要旨集 2010 170 2011年01月31日 [査読無し][通常論文]
  • W. S. Darwish, Y. Ikenaka, W. R. El-Ghareeb, M. Ishizuka ANIMAL 4 (12) 2023 -2029 2010年12月 [査読無し][通常論文]
     
    The objective of this study was to investigate the tissue-specific mRNA expression of different cytochrome P450 (CYP) isoforms, UDP glucuronsyl transferase 1A1 (UGT1A1) and glutathione-S-transferase (GSTA1) in the different tissues (liver, mammary gland, lungs, spleen, kidney cortex, heart, masseter muscle and tongue) of cattle, using quantitative real-time polymerase chain reaction (qPCR). CYP1A1-like mRNA was expressed in all of the tissues examined, including the liver, with the highest expression level in the kidney. CYP1A2-, 2E1- and 3A4-like mRNAs were only expressed hepatically. Interestingly, significant expression of CYP2B6-like mRNA was recorded in the lung tissue, while CYP2C9-like mRNA was expressed in the liver and kidney tissues of the cattle examined. UGT1A1- and GSTA1-like mRNAs were expressed in all of the examined tissues, except the mammary glands, and the highest expression levels were recorded in the kidney. The high expression of UGT1A1 in the lung tissue and GSTA1 in the liver tissue was unique to cattle; this has not been reported for rats or mice. The findings of this study strongly suggest that the liver, kidneys and lungs of cattle are the major organs contributing to xenobiotics metabolism.
  • Ikenaka Yoshinori, Nakayama Shouta M. M, Muzandu Kaampwe, Choongo Kennedy, Teraoka Hiroki, Mizuno Naoharu, Ishizuka Mayumi African Journal of Environmental Science and Technology 4 (11) 729 -739 2010年11月 [査読無し][通常論文]
     
    Heavy metal pollution is one of the most important problems in Zambia and causes serious effects to humans and animals. The aim of the present study was to evaluate the spatial distribution of heavy metals in main areas of Zambia and understand the characteristics of the pollution in each area. River and lake sediments and soil samples were collected from a large area of Zambia and analyzed for ten heavy metals (Cr, Co, Ni, Cu, Zn, As, Cd, Pb, Sr and Hg). The results indicate that heavy metal pollution in Zambia has strong regional differences. Using cluster analysis, the patterns of heavy metal pollution were divided into three major clusters: (1) Kabwe, (2) Copperbelt and (3) Lusaka and other areas. Heavy metals in the Copperbelt area are transported to downstream areas by the Kafue River. Pollution was also detected in national parks, and Lake Itezhi-tezhi has been polluted with high concentrations of Cu, possibly from mining activities in the upper reaches of the river. However, areas geographically distant from mining beds had only moderate or low heavy metal concentrations, although the concentrations of Pb and Zn were highly correlated with the populations of each town. Our findings indicate that heavy metal pollution in Zambia is still increasing, due to human activities, especially mining.
  • 池中良徳, 中山翔太, 石塚真由美 北海道獣医師会雑誌 54 (10) 569 -575 2010年10月10日 [査読無し][通常論文]
  • 室谷太郎, 池中良徳, 中山翔太, YABE John, MUZANDU Kaampwe, CHOONGO Kennedy, 今内覚, 梅村孝司, 石塚真由美 日本獣医学会学術集会講演要旨集 150th 323 2010年09月01日 [査読無し][通常論文]
  • OROSZLANY Balazs, 池中良徳, 谷川力, 春成常仁, 田中和之, 中山翔太, 石塚真由美 日本獣医学会学術集会講演要旨集 150th 323 2010年09月01日 [査読無し][通常論文]
  • 濱田泰平, 池中良徳, 中山翔太, MUZANDU Kaampwe, CHOONGO Kennedy, 寺岡宏樹, 石塚真由美 日本獣医学会学術集会講演要旨集 150th 323 2010年09月01日 [査読無し][通常論文]
  • 田中和之, 春成常仁, 谷川力, 川合佑典, 渡邉研右, バラージュ オロスラーニュ, 池中良徳, 石塚真由美 北海道獣医師会雑誌 54 (8) 478 2010年08月10日 [査読無し][通常論文]
  • 藤澤希望, 池中良徳, 山本秀明, KIM Eun‐Young, LEE Jin‐Seon, 岩田久人, 石塚真由美 北海道獣医師会雑誌 54 (8) 477 2010年08月10日 [査読無し][通常論文]
  • W. Darwish, Y. Ikenaka, E. Eldaly, M. Ishizuka FOOD AND CHEMICAL TOXICOLOGY 48 (8-9) 2526 -2531 2010年08月 [査読無し][通常論文]
     
    The mutagenic activation activity of hepatic microsomes from three meat-producing animals (cattle, deer and horses) was compared with those of rats as a reference species. In the Ames Salmonella typhimurium TA98 assay, the liver microsomes of all examined animals mutagenically activated benzo[a]pyrene, an ideal promutagens, in terms of production of histidine-independent revertant colonies. The microsomes of horses had the highest ability to produce revertant colonies of the examined animals under both low and high substrate concentrations. Inhibition of this mutagenic activity using alpha-naphthoflavone, anti-rat CYP1A1, CYP3A2 and CYP2E1 antibodies suggests that this activity was mainly because of CYP1A1 in these animals as well as in rats. The addition of co-factors for two phase II enzymes, microsomal UDP glucoronosyl transferase and cytosolic glutathione-S-transferase, reduced the production of the revertant colonies in a concentration-dependent manner. Interestingly, horses had the highest reduction rate among the examined animals, suggesting that phase II enzymes play a great role in producing a state of balance between the bioactivation and detoxification of xenobiotics in these meat-producing animals. This report is the first to investigate the mutagenic activation activity of the hepatic microsomes and the role of phase II enzymes against this activity in meat-producing animals. (C) 2010 Elsevier Ltd. All rights reserved.
  • OROSZLANY Balazs, IKENAKA Yoshinori, TANIKAWA Tsutomu, HARUNARI Tsunehito, TANAKA Kazuyuki, NAKAYAMA Shouta, ISHIZUKA Mayumi 環境化学討論会講演要旨集 19th 802 -803 2010年06月20日 [査読無し][通常論文]
  • 中山翔太, 池中良徳, MUZANDU Kaampwe, CHOONGO Kennedy, 濱田恭平, 室谷太郎, 寺岡宏樹, 水野直治, 石塚真由美 環境化学討論会講演要旨集 19th 314 -315 2010年06月20日 [査読無し][通常論文]
  • 室谷太郎, 中山翔太, 池中良徳, YABE John, MUZANDU Kaampwe, CHOONGO Kennedy, 今内覚, 梅村孝司, 石塚真由美 環境化学討論会講演要旨集 19th 816 -817 2010年06月20日 [査読無し][通常論文]
  • 藤澤希望, 池中良徳, 山本秀明, KIM Eun‐Young, LEE Jin‐Seon, 岩田久人, 石塚真由美 J Toxicol Sci 35 (Supplement) S132 2010年05月 [査読無し][通常論文]
  • 渡邉研右, 田中和之, 池中良徳, 石塚真由美 J Toxicol Sci 35 (Supplement) S231 2010年05月 [査読無し][通常論文]
  • 上田春樹, 中山翔太, 池中良徳, 石塚真由美 J Toxicol Sci 35 (Supplement) S196 2010年05月 [査読無し][通常論文]
  • 濱田恭平, 中山翔太, 池中良徳, KAAMPWE Muzandu, KENNEDY Choongo, 水野直治, 寺岡宏樹, 石塚真由美 日本獣医学会学術集会講演要旨集 149th 308 2010年 [査読無し][通常論文]
  • 田中 和之, 常仁 春成, 谷川 力, 池中 良徳, 石塚 真由美 環境毒性学会誌 12 (2) 61 -70 2009年12月30日 [査読無し][通常論文]
     
    Warfarin is commonly used worldwide as a rodenticide. Warfarin inhibits blood coagulation, and continuous intake of warfarin causes potentially fatal hemorrhages. However, warfarin-resistant roof rats(Rattus rattus)are found in Japan, especially in the Tokyo area. Recently, warfarin-resistant brown rats(Rattus norvegicus)were discovered in rural areas of Japan. Warfarin-resistant house mice have not been reported, but it is highly possible that resistant mice will be also found in our country. Warfarin-resistant rats, which have acquired resistance to anticoagulant rodenticides, are called &lquot;super rats&rquot;. Rodenticide-resistant roof rats, brown rats, and house mice have been also reported in the United States and European countries, e.g., Britain, France, Denmark, and Germany. In addition, warfarin-resistant rodents may be widespread in other countries that have not been investigated yet. The warfarin target molecule is vitamin K epoxide reductase(VKOR).Warfarin inhibits the function of VKOR, which recycles vitamin K to activate blood coagulant factors, and causes hemorrhage. Substitutions in the VKORC1 gene were reported in warfarin-resistant rodents. Moreover, the metabolism of warfarin is accelerated in warfarin-resistant rats due to the elevation of cytochrome P450-dependent xenobiotic metabolizing activities. The combination of a VKOR mutation and P450 acceleration causes warfarin resistance in wild rodents, which is an evolutionary adaptation to the pesticide-polluted environment. After the appearance of warfarin-resistant rodents, a second-generation rodenticide was developed and replaced warfarin in Europe and America. In Japan, difethialone is the only the second-generation rodenticide that can be used in public buildings. In Japan, a critical zoonosis infection has not yet spread on a large scale through wild rodents. However, it is necessary to consider how to prevent serious infestation by house rodents in the industrial, administrative, and academic sectors before such infestation occurs.
  • IKENAKA Yoshinori, NAKAYAMA Shouta M.M, MUZANDU Kaampwe, CHOONGO Kennedy, SAKAMOTO Kentaro Q, TERAOKA Hiroki, MIZUNO Naoharu, ISHIZUKA Mayumi 環境化学討論会講演要旨集 18th 134 -135 2009年06月09日 [査読無し][通常論文]
  • 渡邉研右, 田中和之, 池中良徳, 藤田正一, 石塚真由美 日本獣医学会学術集会講演要旨集 148th 293 2009年 [査読無し][通常論文]
  • 滝口真美, SOBHY Wageh, 池中良徳, 藤田正一, 石塚真由美 日本獣医学会学術集会講演要旨集 148th 293 2009年 [査読無し][通常論文]
  • 池中 良徳, 伊藤 有希, 殷 煕洙, 渡邉 栄喜, 宮原 裕一 環境化学 : journal of environmental chemistry 18 (3) 341 -352 2008年09月24日 [査読無し][通常論文]
     
    The purpose of the present study was to elucidate the characteristic accumulation patterns of the Polycyclic Aromatic Hydrocarbons (PAHs) in various organisms inhabited in the typical eutrophic lake "Lake Suwa". We also calculated the Biota Sediment Accumulation Factors (BSAF) of each organism to estimate the difference in the pattern of PAHs accumulation among their tropic levels or habitat.<BR>We showed that the concentrations of Σ<SUB>11</SUB>PAHs was highest in phytoplankton (mainly Aphanizomenon sp.) (36,900±2,800 ng/g-lipid), followed by chironomid (3, 130±380 ng/g-lipid), catfish (1,720±1,360 ng/g-lipid), zooplankton (mainly Bosmina sp.) (890±170 ng/g-lipid), cherry salmon (270±70 ng/g-lipid), freshwater prawn (240±70 ng/g-lipid), largemouth bass(130±20 ng/g-lipid), Japanese smelt (140±30 ng/g-lipid), crucian carp (120±4 ng/g-lipid), and common carp (50±16 ng/g-lipid). We also analyzed dioxins (DXNs) in largemouth bass.The concentration of polychlorinated dibenzo-<I>p</I>-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), non-<I>ortho</I> dioxin like-PCBs, and mono-<I>ortho</I>-substituted dioxin-like PCBs (dioxin-like PCBs) were 7±1, 3±1, 117±13 ,and 3,770±930 ng/g-lipid, respectively. Based on these data, we calculated the BSAF of each organism. Σ<SUB>11</SUB>PAHs BSAF exceeded 1.0 only in phytoplankton (18.7 g-ignition loss/g-lipid) and chironomid (1.6 g-ignition loss/g-lipid), and other organisms, especially fish, were below 1.0. These results indicated that PAHs were the substances mainly accumulated in primary consumers but not in higher tropic level consumers. On the other hand, BSAF of PAHs and dioxin like-PCBs in largemouth bass had large difference. This may due to the high metabolic rate of PAHs compared to dioxin like-PCBs. These results indicated that ability to metabolize PAHs is important to estimate accumulation pattern of PAHs.<BR>From our results, different accumulation pattern of PAHs in invertebrate and fish were observed. Invertebrates accumulate high Kow PAHs compared to fish. These results may also due to the difference in the ability to metabolize PAHs between fish and invertebrates.
  • 佐々木 信夫, 酒井 紀彰, 池中 良徳, 神谷 知未, 閔 姫源, 坂本 健太郎, 石塚 真由美, 藤田 正一 The journal of veterinary medical science 70 (3) 223 -226 2008年03月 [査読無し][通常論文]
     
    フラゾリドン(ニトロフラン剤,FZ)はその変異原性と発疹性のため,先進諸国では食用動物に対する使用が禁止されているが,発展途上国並びに一部ヒトの医療分野における使用が報告されている.FZの連続投与は肝薬物代謝酵素活性に影響を与えることが報告されているが,FZ投与により誘導されるCYP分子種を特定した報告はない.我々はFZ(125mg/kg)を3日間連続経口投与したラット肝S-9を用い,Ames testを行ったところ,有意にエチジウムブロマイドによる変異原性が増強することを確認した.ついでこの変異原性に寄与していると考えられるCYPの分子種をWestem blot法によって検討して,FZ投与群においてCYP1A1が明らかに増加すること,他方CYP1A2およびCYP2E1は変化しないことを明らかにした.さらにCYP1A1mRNAレベルについてRT-PCR分析を行った結果,FZ投与群でのCYP1A1mRNAが有意に増加していることが分かり,これによりCYP1A1が転写レベルで誘導されていることが明らかになった.
  • 池中 良徳, 伊藤 有希, 殷 煕洙, 渡邉 栄喜, 宮原 裕一 Journal of Environmental Chemistry 18 (3) 341 -352 2008年 [査読無し][通常論文]
     
    The purpose of the present study was to elucidate the characteristic accumulation patterns of the Polycyclic Aromatic Hydrocarbons (PAHs) in various organisms inhabited in the typical eutrophic lake "Lake Suwa". We also calculated the Biota Sediment Accumulation Factors (BSAF) of each organism to estimate the difference in the pattern of PAHs accumulation among their tropic levels or habitat.<BR>We showed that the concentrations of Σ<SUB>11</SUB>PAHs was highest in phytoplankton (mainly Aphanizomenon sp.) (36,900±2,800 ng/g-lipid), followed by chironomid (3, 130±380 ng/g-lipid), catfish (1,720±1,360 ng/g-lipid), zooplankton (mainly Bosmina sp.) (890±170 ng/g-lipid), cherry salmon (270±70 ng/g-lipid), freshwater prawn (240±70 ng/g-lipid), largemouth bass(130±20 ng/g-lipid), Japanese smelt (140±30 ng/g-lipid), crucian carp (120±4 ng/g-lipid), and common carp (50±16 ng/g-lipid). We also analyzed dioxins (DXNs) in largemouth bass.The concentration of polychlorinated dibenzo-<I>p</I>-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), non-<I>ortho</I> dioxin like-PCBs, and mono-<I>ortho</I>-substituted dioxin-like PCBs (dioxin-like PCBs) were 7±1, 3±1, 117±13 ,and 3,770±930 ng/g-lipid, respectively. Based on these data, we calculated the BSAF of each organism. Σ<SUB>11</SUB>PAHs BSAF exceeded 1.0 only in phytoplankton (18.7 g-ignition loss/g-lipid) and chironomid (1.6 g-ignition loss/g-lipid), and other organisms, especially fish, were below 1.0. These results indicated that PAHs were the substances mainly accumulated in primary consumers but not in higher tropic level consumers. On the other hand, BSAF of PAHs and dioxin like-PCBs in largemouth bass had large difference. This may due to the high metabolic rate of PAHs compared to dioxin like-PCBs. These results indicated that ability to metabolize PAHs is important to estimate accumulation pattern of PAHs.<BR>From our results, different accumulation pattern of PAHs in invertebrate and fish were observed. Invertebrates accumulate high Kow PAHs compared to fish. These results may also due to the difference in the ability to metabolize PAHs between fish and invertebrates.
  • 宮原 裕一, 池中 良徳 環境化学 : journal of environmental chemistry 17 (4) 649 -658 2007年12月25日 [査読無し][通常論文]
     
    In the present study, we estimated inflow and effluent load of Polycyclic Aromatic Hydrocarbons (PAHs) in Lake Suwa, Japan. Estimation of PAHs inflow and effluent load were performed by measuring changes in stream flow and concentration of suspended solids (SS) in the lake and river water. Results showed that the concentration of SS increased with stream flow. Annual (March 2004 to February 2005) inflow and effluent load of SS at the lake were calculated as 8.9×10<sup>6</sup> kg and 7.6×10<sup>6</sup> kg, respectively. The mass balance between inflow and effluent load indicated that 1.3×10<sup>6</sup> kg of SS were sedimentated to the lake. The total amount of Σ<sub>9</sub>PAHs (Phenanthrene, Pyrene, Chrysene, Benzo[e]pyrene, Benzo[b]fluoranthene, Benzo[k]fluoranthene, Benzo[a]pyrene, Dibenz[a,h]anthracene, Benzo[ghi]perylene) in lake SS varied by 230±120 g/lake (average±SD); the maximum amount exceeded 500 g/lake, which was observed in May and October 2004. Specifically, for Benzo[a]pyrene the total amount in lake SS was 14±7 g/lake. Estimation of total Σ<sub>9</sub>PAHs flowing into Lake Suwa and out through Kamaguchi Gate indicated Σ<sub>9</sub>PAHs values of 8.6 and 3.5 kg/yr, respectively. The mass balance between Σ<sub>9</sub>PAHs inflow and outflow indicated that approximately 5.1 kg/yr of Σ<sub>9</sub>PAHs were sedimentated with SS to the lake. The annual flux of PAHs in Lake Suwa calculated in the present study agreed with the deposition flux of PAHs in a previous study estimated from sediment cores (4 kg/yr) (Ikenaka et al.: Environ. Pollut., 138, 530-538 (2005)). Inflow loads of PAHs markedly increased in May 21, October 9, and October 21 when heavy rains occurred, occupying approximately 27 % of the annual inflow. These results indicated that large quantities of PAHs flowed into the lake when river flow increased by heavy rain.
  • 池中 良徳, 館野 覚俊, 宮原 裕一 環境化学 17 (2) 217 -226 2007年06月28日 [査読無し][通常論文]
  • 池中良徳, EUN Heesoo, 石坂真澄, 宮原裕一 環境化学討論会講演要旨集 16th 650 -651 2007年06月19日 [査読無し][通常論文]
  • 宮原裕一, 犬塚良平, 池中良徳 信州大学環境科学年報(Web) (29) WEB ONLY 24-28 2007年03月 [査読無し][通常論文]
  • 宮原 裕一, 池中 良徳 Journal of Environmental Chemistry 17 (4) 649 -658 2007年 [査読無し][通常論文]
     
    In the present study, we estimated inflow and effluent load of Polycyclic Aromatic Hydrocarbons (PAHs) in Lake Suwa, Japan. Estimation of PAHs inflow and effluent load were performed by measuring changes in stream flow and concentration of suspended solids (SS) in the lake and river water. Results showed that the concentration of SS increased with stream flow. Annual (March 2004 to February 2005) inflow and effluent load of SS at the lake were calculated as 8.9×106 kg and 7.6×106 kg, respectively. The mass balance between inflow and effluent load indicated that 1.3×106 kg of SS were sedimentated to the lake. The total amount of Σ9PAHs (Phenanthrene, Pyrene, Chrysene, Benzo[e]pyrene, Benzo[b]fluoranthene, Benzo[k]fluoranthene, Benzo[a]pyrene, Dibenz[a,h]anthracene, Benzo[ghi]perylene) in lake SS varied by 230±120 g/lake (average±SD); the maximum amount exceeded 500 g/lake, which was observed in May and October 2004. Specifically, for Benzo[a]pyrene the total amount in lake SS was 14±7 g/lake. Estimation of total Σ9PAHs flowing into Lake Suwa and out through Kamaguchi Gate indicated Σ9PAHs values of 8.6 and 3.5 kg/yr, respectively. The mass balance between Σ9PAHs inflow and outflow indicated that approximately 5.1 kg/yr of Σ9PAHs were sedimentated with SS to the lake. The annual flux of PAHs in Lake Suwa calculated in the present study agreed with the deposition flux of PAHs in a previous study estimated from sediment cores (4 kg/yr) (Ikenaka et al.: Environ. Pollut., 138, 530-538 (2005)). Inflow loads of PAHs markedly increased in May 21, October 9, and October 21 when heavy rains occurred, occupying approximately 27 % of the annual inflow. These results indicated that large quantities of PAHs flowed into the lake when river flow increased by heavy rain.
  • 池中 良徳, 館野 覚俊, 宮原 裕一 Journal of Environmental Chemistry 17 (2) 217 -226 2007年 [査読無し][通常論文]
     
    In the present study, we investigated the Polycyclic Aromatic Hydrocarbons (PAHs) at the representative eutrophic lake "Lake Suwa", which has drastically eutrophicated since 1960s by inflow of domestic and industrial effluents. We also investigated PAHs in river sediments, road dusts, suspended solids and air particles of the catchment area of Lake Suwa.We showed that the concentrations of Σ17PAHs in the lake sediments and river sediments were 364±129 ng/g-dry and 157±194 ng/g-dry, respectively. On the other hand, the concentrations of Σ17PAHs in sediments were relatively high in the northeast part of Lake Suwa.One of the major PAHs in the sediment of Lake Suwa was perylene. It would be mainly produced from precursor substances (such as perylenequinone) in anoxic lake sediment. On the other hand, the major sources of other PAHs (except perylene) were considered to be both petrogenic and pyrogenic source as diesel exhaust matter and asphalt. They entered the Lake Suwa through rivers and finally precipitated to lake sediment.
  • 宮原裕一, 池中良徳, 犬塚良平, 館野覚俊, 内山隆文 日本陸水学会甲信越支部会報 (32) 72 2006年12月 [査読無し][通常論文]
  • 坂本正樹, 花里孝幸, 池中良徳, 宮原裕一 日本陸水学会大会講演要旨集 71st (0) 138 -4 2006年09月05日 [査読無し][通常論文]
  • 池中良徳, 伊藤有希, 宮原裕一 環境化学討論会講演要旨集 15th 100 -101 2006年06月19日 [査読無し][通常論文]
  • 武田隼一, 池中良徳, 宮原裕一 環境化学討論会講演要旨集 15th 646 -647 2006年06月19日 [査読無し][通常論文]
  • 館野覚俊, 池中良徳, 宮原裕一 環境化学討論会講演要旨集 15th 96 -97 2006年06月19日 [査読無し][通常論文]
  • 宮原裕一, 池中良徳, 犬塚良平, 花里孝幸 信州大学環境科学年報 (28) 39 -46 2006年03月31日 [査読無し][通常論文]
  • 池中 良徳, 石坂 真澄, 殷 熙洙, 宮原 裕一 日本陸水学会 講演要旨集 71 (0) 6 -6 2006年 [査読無し][通常論文]
  • 池中良徳, 石塚真由美, 藤田正一, 坂本健太郎, 渡邉肇, 宮原裕一 日本陸水学会甲信越支部会報 (31) 57 2005年12月 [査読無し][通常論文]
  • Y Ikenaka, H Eun, E Watanabe, Y Miyabara BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 75 (5) 915 -921 2005年11月 [査読無し][通常論文]
  • 中村剛也, 池中良徳, 宮原裕一, 朴虎東 日本陸水学会大会講演要旨集 70th 114 2005年09月10日 [査読無し][通常論文]
  • 池中良徳, 石坂真澄, EUN Heesoo, 宮原裕一 環境化学討論会講演要旨集 14th 288 -289 2005年06月15日 [査読無し][通常論文]
  • 宮原裕一, 池中良徳 環境化学討論会講演要旨集 14th 698 -699 2005年06月15日 [査読無し][通常論文]
  • 公文 富士夫, 池中 良徳 第14回環境地質学シンポジウム論文集 14th 323 -328 2004年12月06日 [査読無し][通常論文]
     
    Sedimentation of Lake Suwa is much affected by flood sediments even in the center of the lake. The concentrations of dioxins and PAHs are diluted by such event sediment composed mainly of inorganic,non-contaminated materials. Flood sediment layers dated on 10 June 1950, 29 June 1961 and 28 September 1983 are confirmed in the cored sediments from Lake Suwa. Although the persistent organic pollutants are low in the floodsediments compared with the normal sediments below and above, the total amount of pollutants deposited in one flood is much larger than the annual amount of normal sediments....
  • 齊藤玲子, 池中良徳, 宮原裕一 日本陸水学会甲信越支部会報 (30) 10 2004年11月 [査読無し][通常論文]
  • 池中良徳, 宮原裕一 日本陸水学会甲信越支部会報 (30) 43 2004年11月 [査読無し][通常論文]
  • 池中良徳, 渡辺栄喜, EUN H, 宮原裕一 環境化学討論会講演要旨集 13th 162 -163 2004年07月05日 [査読無し][通常論文]
  • 宮原裕一, 池中良徳, 犬塚良平, 上沢春香, 牛原阿海, 笠井由香, 角田紗代子 日本内分泌かく乱化学物質学会研究発表会要旨集 6th 149 2003年12月02日 [査読無し][通常論文]
  • 池中良徳, 渡邊栄喜, 殷煕洙, 宮原裕一 日本陸水学会甲信越支部会報 (29) 62 2003年12月 [査読無し][通常論文]
  • 上沢春香, 池中良徳, 宮原裕一 日本陸水学会甲信越支部会報 (29) 32 2003年12月 [査読無し][通常論文]
  • 池中良徳, 渡辺栄喜, EUN H, 宮原裕一 環境化学討論会講演要旨集 12th 92 -93 2003年06月25日 [査読無し][通常論文]

共同研究・競争的資金等の研究課題

  • 殺虫剤の「生物学的モニタリングに基づく適応的リスク評価法」の開発と実践
    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 : 2019年04月 -2022年03月 
    代表者 : 星 信彦, 横山 俊史, 池中 良徳, 平野 哲史, 市川 剛
  • アフリカにおける新興・再興の環境汚染のフィールドベースの毒性メカニズム解析
    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。2018年度は、これらの国との共同研究を実施し、ザンビアにおいて鉛汚染、南アフリカではDDT、ガーナではネオニコチノイドなどに関する共同研究を推進した。このうち、ザンビアおよび南アフリカは現地に渡航し、また南アフリカの研究者を日本に招聘した。ガーナに関しては共同研究に関するMOUの作成およびガーナの倫理機関において申請手続きを行い、試料採集を実施した。
  • mlAOPコンセプトによる化学物質感受性多様性評価と殺虫剤中毒解明に向けた応用
    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, 加藤 恵介, 宮原 裕一, 市川 剛, 岡松 優子, 中山 翔太, 平野 哲史
     
    本年度は研究実施計画通り、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。特にゼブラフィッシュは行動試験を実施するための基盤設備を整備した。また、同時に各系統について胎児への移行量を含む、ADME(吸収・分布・代謝・排泄)を求め、基本的なToxico Kinetics/Dynamics を明らかにした。 ・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、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が、未だ検出に至っていない。対象化学物質の検出のための、各種条件検討が必要である。 ・細胞・分子レベルでの評価: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: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。その結果、日本人は新生児から曝露を受けている事、その摂取源は飲食物である事が明らかになった。
  • イオン性環境汚染物質がもたらす神経伝達物質への影響の理解と評価法の開発
    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 : 2019年06月 -2021年03月 
    代表者 : 野見山 桂, 水川 葉月, 池中 良徳
  • 「カクテル型」コンセプトによる「猛禽類対応型」新世代殺鼠剤の開発
    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
     
    野生齧歯類は35種以上の人獣共通感染症を媒介する。また、野生ラットは繁殖力の強さから離島へ生息域を広げ外来動物として 生態系を攪乱している。齧歯類の駆除方策として、殺鼠剤ワルファリンなど抗凝血系化学物質が比較的安全性が高いため広く利用された。一方、度重なる使用により抵抗性を持つ個体群が世界各地に出現している。その対策に欧米では致死性の高い第二世 代抗凝血系殺鼠剤が用いられている。しかしながら、これらは毒性が強く駆除対象外生物の二次被害が絶えない。一方、選択性の高い新規殺鼠剤の開発は、感受性種差に関する毒性学的知見も服なく、困難である。当該研究は、in silicoシミュレーショ ンによるサンプル入手が困難な抵抗性ラット・鳥類種における殺鼠剤感受性評価法の確立を目的とする。 今年度は、ビタミンKエポキシド還元酵素(VKOR)やシトクロムP450(CYPs)について研究を進めた。殺鼠剤の標的生物であるラットにおける抵抗性メカニズムについて、分析を行った。電子伝達系に関して抵抗性個体ではこの機構が明らかに高活性であることを明らかにし、これが抵抗性獲得の一因であることが予測された。この研究を進める際に、ビタミンKエポキシド還元酵素活性の新たな分析方法も構築して実験を進めた。殺鼠剤を投与し、血中濃度や血液凝固時間を測定したところ、対象動物であるラットなど齧歯類に比して、比較的感受性が低いことが分かった。 上記の試験系により同定した抵抗性獲得因子をターゲットとする新規殺鼠剤を作成することを目的として、シトクロムP450阻害剤と殺鼠剤との併用によるin vivo試験を実施した。海産物から得られた天然素材を用いた試験では想定した効果は得られなかったが、CYPの典型的な阻害剤を併用投与したラットでは血中の殺鼠剤濃度が上昇し、一定の効果が出ることがわかった。
  • 高次の動物種における化学物質感受性の種差と適応進化の解明
    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
     
    動物はヒトと同じく多くの環境化学物質に曝露されており、環境化学物質による集団死は野生動物では世界的にも恒常的に起こっている。また、日常的な化学物 質曝露は野生動物に病態を引き起こしていることがこれまでの 研究により明らかになりつつある。一方で、動物の化学物質の感受性の種差や個体差に関する研究 は少なく、化学物質のリスク管理を難しくし、また、野生動物のケミカルハザード(化学物質の有害性による被害)を引き起こ す原因となっている。本研究では 野生動物、とくに生態系で高次に立つ野生哺乳類と野生鳥類の化学物質感受性 に関して種差や個体差を引き起こしているその要因を明らかにし、データベースの 構築を行うと同時に、環境適 応への分子進化過程を高等動物で初めて明らかにすることを目的とした。 平成29年度では、下記の研究を進め、成果を得た。
    1)哺乳類について、UGT1ファミリーおよびUGT2ファミリーの動物種差について明らかにした。特に食肉目の動物に関して、UGTの特徴を明らかにすることができた。また、同時に、雑食性動物や草食動物などに関して、ゲノム上でのUGTの特徴について、in silico解析から明らかにすることができた。 2)鳥類について、UGTファミリーの分布とそのゲノム構造について明らかにした。 3)哺乳類、鳥類について食性とUGT活性との関係性について明らかにした。 4)殺鼠剤をモデル化合物として、その感受性に関する新規のメカニズムを提唱した。
  • 野生動物iHep細胞の作成とトッププレデターのMetabolism評価法の開発
    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
     
    化学物質の感受性の差は種により数千倍に及ぶこともあり、実験動物を用いた毒性試験の結果を野生動物にそのまま外挿することは難しい。特に希少トッププレデターでは、化学物質の影響を直接観察できるin vivo実験は実質困難であり、それゆえ化学物質感受性の“種差”を適切に評価できる実験系は未だ存在していない。そこで、本研究では、化学物質感受性決定因子である薬物代謝“Metabolism”を、野生動物の皮膚線維芽細胞より作成した誘導性肝臓様細胞(iHep)を用いて評価することを試みた。 2018年度は2017年度に引き続き、①野生動物の皮膚線維芽細胞の培養およびiHep細胞への誘導因子の選定および、②肉食動物の薬物代謝第II相抱合酵素活性、特に硫酸抱合酵素(SULT)の評価を実施した。 先ず、①の実験では、野生動物の線維芽細胞として、エゾヒグマおよびツシマヤマネコの保存に成功し、その後のiHep誘導実験に供試した。ただ、いくつかの誘導因子を導入し、誘導を試みたが、成功には至らなかった。 ②の実験では、野生動物の中で、鰭足類動物において、エストロゲン代謝に重要な分子種であるSULT1E1が遺伝的に欠損している事を明らかにし、多くの化学物質に対して高感受性を示す可能性を示唆する知見が得られた。
  • 亜急性・慢性ネオニコチノイド中毒の診断法の開発と病態発生機序の解明
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2015年04月 -2019年03月 
    代表者 : 平 久美子, 池中 良徳, 中山 翔太
     
    ヒトのネオニコチノイド(NN)曝露指標となりうる尿中代謝物を同定し分析法を確立しフィールドレベルでの検出を確認した。またNNがヒト血漿中で代謝されないことを確認した。 ①主要代謝物の同定:ウサギにNN7種を投与し、12―48時間後の尿を採取し、LC-TOF/MSと代謝物のスクリーニングソフトMetabolite Pilotを用い網羅的解析を行った。イミダクロプリドで水酸化物IMI-5OHなど5種、アセタミプリドで脱メチルアセタミプリド1種、ニテンピラムで脱メチル体など6種、チアクロプリドでTHI-4OHやそのグルクロン酸抱合体など7種が検出、クロチアニジンで脱メチル体、チアメトキサムから、クロチアニジン他2種、ジノテフランから脱メチル体など5種が検出された。 ②代謝物の生体試料分析法の確立:主要代謝物の構造解析とその有機合成を行い、LC-ESI/MS/MSを用いた高感度分析法を開発し、親化合物7種、内部標準物質7種に加え代謝産物21種の定量が、尿など液体試料と、組織や全血などマトリクスの多い試料において可能となった。 ③様々な集団での尿中NNおよび代謝物分析:②を用いフィールドレベルで随時尿を収集し分析した。日本で3-6歳の幼児46人の尿を分析し、90%で同時に2種以上のNNまたは脱メチルアセタミプリドを検出した。スリランカの住民96人の尿を分析し、イミダクロプリド、クロチアニジン、チアメトキサム、脱メチルアセタミプリド、脱メチルニテンピラム、5-OHイミダクロプリド、4OHイミダクロプリドを検出した。また近年急激にNNの使用量が増加しているガーナの成人300人の尿を分析し、NN5種と脱メチルアセタミプリドを検出した。 ④血漿画分を用いた代謝試験: NNは細胞内Cytochrome P450により代謝を受けることが報告されている。本試験で血漿酵素による代謝は認められなかった。
  • 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 : 川上 智規, 平 久美子, 池中 良徳, 袋布 昌幹
     
    カドミウム、鉛、クロム、ヒ素はCKDuの原因物質ではないと明確に結論付けることができた。CKDu患者の症状はネオニコチノイド中毒による症状と矛盾しなかったが、ネオニコチノイドがCKDuに関わっていると判断するには至らなかった。アヌラダプラに炭素電極電解法によるフッ素除去装置を設置した。フッ素濃度を2.1 mg/Lから0.4 mg/L程度にまで低下させることができ、スリランカの飲料水基準である1 mg/Lを下回る水質を得ることができた。炭素電極電解法の後段に鳥骨炭フィルターを設置したハイブリッド方式のフッ素除去装置を2カ所設置し、フッ素濃度を0 mg/Lにまで下げることができた。
  • 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 : 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 : 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 挑戦的萌芽研究
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 池中 良徳, 水川 葉月, 中山 翔太
     
    当該研究では、比較生物学・系統解析により、脊椎動物におけるグルクロン酸抱合酵素(UGT)の種差を明らかにする事で、その生体内での役割と分子メカニズムについて解明することを試みた。その結果、UGT1A6活性が低いと報告されていたネコ以外にも、鰭脚類で極めてその活性が低い事が明らかになった。更に、ネコやアザラシではUGT1Aに加えUGT2B活性が低く、偽遺伝子化している事が示唆された。この結果から、グルクロン酸抱合は哺乳動物にとって極めて重要な解毒反応であると共に、欠損している動物では化学物質にとってのハイリスクアニマルであることが示唆された。
  • 日本学術振興会:科学研究費助成事業 基盤研究(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 基盤研究(A)
    研究期間 : 2012年04月 -2016年03月 
    代表者 : 石塚 真由美, 池中 良徳, 坪田 敏男, 今内 覚
     
    産業動物について、第I相反応であるシトクロムP450、第II相反応であるグルクロン酸抱合および硫酸抱合酵素について種差を明らかにした。哺乳類の尿におけるグルクロン酸抱合と硫酸抱合体比を比較し、その特徴を明らかにした。また、国内外の産業動物に蓄積する環境化学物質を分析し、ウシなどについては、重金属蓄積性が比較的高いことを見出した。鳥類について家禽を中心にトランスクリプトーム解析を行い、肝臓に発現する第I相反応酵素および第II相反応酵素の網羅的解析を行った。以上の研究により、産業動物の化学物質に対する防御機構を、異物代謝酵素を中心に明らかにした。
  • 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 基盤研究(B)
    研究期間 : 2012年04月 -2015年03月 
    代表者 : 石塚 真由美, 池中 良徳
     
    アフリカはすでに、急激な開発による「副作用」を受け、化学物質の汚染は生態系の浄化作用では対処できない地域が顕在化している。我々の予備調査では、食肉や魚類の有害金属やDDTの濃度はWHO基準を超えており、アフリカ諸国の食の化学物質汚染の現状の把握は喫緊の問題となっている。本研究では、ザンビア、南アフリカ、ガーナ、エジプト、エチオピアにおける家畜を中心とした環境汚染の影響を明らかにし、環境汚染が食の安全やヒトの健康に及ぼすリスクについて報告した。
  • 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 : 2011年 -2012年 
    代表者 : 池中 良徳
     
    当該研究では希少な生態系が成り立つアフリカを中心に、野生動物と環境試料の採集を行い、環境毒性研究を展開した。まず、野生動物に対する異物代謝系の種差を主に第II相抱合反応に注目し明らかにした。11種の哺乳類の尿を用いたスクリーニングでは、現在まで硫酸抱合活性が低いと考えられてきたブタで硫酸抱合化Pyreneが検出された。また、カイネティックス解析の結果、ブタの酵素効率はラットよりも高いことが明らかになった。一方、アフリカで行った調査では、両生類、哺乳類、鳥類の尿及び臓器を採取した。これらの試料について、重金属類や農薬類を中心に化学分析を行った結果、一部の地域からきわめて高濃度の化学物質が検出され、特に鳥類において他の生物種に比べ高い濃度で化学物質を蓄積している傾向が観察された。
  • 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 : 2009年 -2010年 
    代表者 : 池中 良徳
     
    当該研究では、「化学物質を起因とする野生動物の病態」の中で、特に「免疫抑制」に焦点をあて、その現状をフィールドレベルで調査・研究を行った。調査地域であるザンビア共和国では、鉱業活動の影響により、家畜であるウシやげっ歯類において、炎症性サイトカインや酸化ストレスマーカーの変動が明らかになり、重金属への曝露が免疫応答に影響を与えている可能性が示唆された。これら得られた免疫かく乱の結果と土壌中重金属濃度のGISの結果を併せて解析した結果、土壌の汚染分布と生物中蓄積濃度やMT発現量との間に相関は見られず、摂餌などのその他の要因の影響が強いことが示唆された。
  • 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 : 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。
  • 甲殻類が持つ生体外異物に対する受容・応答の分子基盤と新規代謝機構の解明
    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 : 2007年 -2008年 
    代表者 : 池中 良徳
     
    化学物質の代謝能は,各生物種により非常に多様である。その結果,生物種間で化学物質の蓄積特性に違いが生じ,その化学物質耐性にまで影響がおよぶ。一方,化学物質の生態系への影響は未だ不明な点が多い。その原因の一つとして,化学物質の毒性メカニズムや代謝メカニズムの研究が主に魚類や哺乳類など,脊椎動物を対象としたものであり,地球上に生息する動物のうち95%を占めると言われている無脊椎動物についてほとんど注目されてこなかったことが挙げられる。そこで本研究では,無脊椎動物の中でも,水圏において特にバイオマスの大きい甲殻類に注目し,その異物代謝第一相反応の主要な酵素群であるシトクロムP450と異物代謝第二相反応のcharacterizationを行った。その結果,甲殻類は,脊椎動物や昆虫類を含む他の無脊椎動物とは異なる独自の異物代謝反応を行っていることが明らかになった。 これまで,脊椎動物や昆虫類などの無脊椎動物で生成される抱合体は,グルコース抱合体,グルクロン酸抱合体,および硫酸抱合体であることが報告されてきた。しかし,甲殻類ではこれら抱合体の他に,グルコースに対し更に硫酸が負荷した「グルコース-硫酸抱合体」を生成していた。一方、本研究によりフィールドレベルで行った調査により、魚類と甲殻類では明らかに多環芳香族炭化水素類(PAHs)の蓄積特性が異なった。本研究で明らかにした甲殻類の特徴的な代謝反応が、フィールドで実際に観察された化学物質の蓄積特性に影響を与えたと考えられる。 本研究により、化学物質の蓄積特性・感受性の種差に対する、異物代謝系の新たなメカニズムを解明できた。

教育活動情報

主要な担当授業

  • 獣医科学・感染症学基礎科目 研究機器演習
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 国際感染症学院
  • 基礎毒性学・環境毒性学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 獣医学部
    キーワード : 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
  • 専門獣医科学特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 環境衛生学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 獣医学部
    キーワード : 環境破壊、環境汚染、化学汚染物質、生体防御、規制
  • ケミカルハザード対策専門特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 毒性学実習
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 獣医学部
    キーワード : 化学物質 毒性発現目がニズム 毒性試験法 体内動態 環境動態
  • 獣医科学基礎科目B 研究機器演習
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 獣医科学基礎科目B 環境毒性学特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 獣医科学基礎科目 研究機器演習
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • 獣医科学基礎科目 環境獣医科学特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • 先端獣医科学科目 環境毒性学演習
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • ケミカルハザード対策専門特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • 専門獣医科学特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • 毒性学演習
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 獣医学部


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