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Ke T, Rajoo A, Tinkov AA, Skalny AV, Tizabi Y, Rocha JBT, Bowman AB, Aschner M. Intestinal microbiota protects against methylmercury-induced neurotoxicity. Biometals 2024; 37:561-576. [PMID: 37973679 DOI: 10.1007/s10534-023-00554-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 10/14/2023] [Indexed: 11/19/2023]
Abstract
Methylmercury (MeHg) remains a global public health issue because of its frequent presence in human food sources obtained from the water. The excretion of MeHg in humans occurs slowly with a biological half-time of 32-47 days. Short-term MeHg exposure may cause long-lasting neurotoxicity. The excretion through feces is a major route in the demethylation of MeHg. Accumulating evidence suggests that the intestinal microbiota plays an important role in the demethylation of MeHg, thereby protecting the host from neurotoxic effects. Here, we discuss recent developments on the role of intestinal microbiota in MeHg metabolism, based on in vitro cell culture experiments, experimental animal studies and human investigations. Demethylation by intestinal bacteria is the rate-limiting step in MeHg metabolism and elimination. The identity of bacteria strains responsible for this biotransformation is currently unknown; however, the non-homogenous distribution of intestinal microbiota may lead to different demethylation rates in the intestinal tract. The maintenance of intestinal barrier function by intestinal microbiota may afford protection against MeHg-induced neurotoxicity, which warrant future investigations. We also discuss studies investigating the effects of MeHg exposure on the population structural stability of intestinal microbiota in several host species. Although this is an emerging area in metal toxicity, current research suggests that a change in certain phyla in the intestinal microbiota may indicate MeHg overexposure.
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Affiliation(s)
- Tao Ke
- Department of Biological Sciences, University of Delaware, Newark, DE, 19716, USA
| | - André Rajoo
- Stiles-Nicholson Brain Institute, Florida Atlantic University, Jupiter, FL, 33458, USA
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL, 33431, USA
| | - Alexey A Tinkov
- IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia, 119991
- Yaroslavl State University, Yaroslavl, Russia, 150003
- Institute of Cellular and Intracellular Symbiosis, Russian Academy of Sciences, Orenburg, Russia, 460000
| | - Anatoly V Skalny
- IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia, 119991
- Department of Medical Elementology, Peoples' Friendship University of Russia (RUDN University), Moscow, Russia, 117198
| | - Yousef Tizabi
- Department of Pharmacology, Howard University College of Medicine, Washington, DC, 20059, USA
| | - Joao B T Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, 97105900, RS, Brazil
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN, 47907-2051, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue Forchheimer Building, Room 209, Bronx, NY, 10461, USA.
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Barbosa NV, Aschner M, Tinkov AA, Farina M, da Rocha JBT. Should ebselen be considered for the treatment of mercury intoxication? A minireview. Toxicol Mech Methods 2024; 34:1-12. [PMID: 37731353 PMCID: PMC10841883 DOI: 10.1080/15376516.2023.2258958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 09/09/2023] [Indexed: 09/22/2023]
Abstract
Mercury is a ubiquitous environmental contaminant and can be found in inorganic (Hg0, Hg+ and Hg2+) and organic forms (chiefly CH3Hg+ or MeHg+). The main route of human, mammals and bird exposure occurs via predatory fish ingestion. Occupational exposure to Hg0 (and Hg2+) can also occur; furthermore, in gold mining areas the exposure to inorganic Hg can also be high. The toxicity of electrophilic forms of Hg (E+Hg) is mediated by disruption of thiol (-SH)- or selenol (-SeH)-containing proteins. The therapeutic approaches to treat methylmercury (MeHg+), Hg0 and Hg2+ are limited. Here we discuss the potential use of ebselen as a potential therapeutic agent to lower the body burden of Hg in man. Ebselen is a safe drug for humans and has been tested in clinical trials (for instance, brain ischemia, noise-induce hearing loss, diabetes complications, bipolar disorders) at doses varying from 400 to 3600 mg per day. Two clinical trials with ebselen in moderate and severe COVID are also approved. Ebselen can be metabolized to an intermediate with -SeH (selenol) functional group, which has a greater affinity to electrophilic Hg (E+Hg) forms than the available thiol-containing therapeutic agents. Accordingly, as observed in vitro and rodent models in vivo, Ebselen exhibited protective effects against MeHg+, indicating its potential as a therapeutic agent to treat MeHg+ overexposure. The combined use of ebselen with thiol-containing molecules (e.g. N-acetylcysteine and enaramide)) is also commented, because they can have synergistic protective effects against MeHg+.
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Affiliation(s)
- Nilda V. Barbosa
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Alexey A. Tinkov
- Yaroslavl State University, Yaroslavl, Russia
- Center of Bioelementology and Human Ecology, IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
| | - Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - João Batista Teixeira da Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil
- Departamento de Bioquímica, Instituto Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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De Marco G, Billè B, Brandão F, Galati M, Pereira P, Cappello T, Pacheco M. Differential Cell Metabolic Pathways in Gills and Liver of Fish (White Seabream Diplodus sargus) Coping with Dietary Methylmercury Exposure. TOXICS 2023; 11:181. [PMID: 36851056 PMCID: PMC9961322 DOI: 10.3390/toxics11020181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 02/10/2023] [Accepted: 02/12/2023] [Indexed: 06/18/2023]
Abstract
Mercury (Hg) is a dangerous and persistent trace element. Its organic and highly toxic form, methylmercury (MeHg), easily crosses biological membranes and accumulates in biota. Nevertheless, understanding the mechanisms of dietary MeHg toxicity in fish remains a challenge. A time-course experiment was conducted with juvenile white seabreams, Diplodus sargus (Linnaeus, 1758), exposed to realistic levels of MeHg in feed (8.7 μg g-1, dry weight), comprising exposure (E; 7 and 14 days) and post-exposure (PE; 28 days) periods. Total Hg levels increased with time in gills and liver during E and decreased significantly in PE (though levels of control fish were reached only for gills), with liver exhibiting higher levels (2.7 times) than gills. Nuclear magnetic resonance (NMR)-based metabolomics revealed multiple and often differential metabolic changes between fish organs. Gills exhibited protein catabolism, disturbances in cholinergic neurotransmission, and changes in osmoregulation and lipid and energy metabolism. However, dietary MeHg exposure provoked altered protein metabolism in the liver with decreased amino acids, likely for activation of defensive strategies. PE allowed for the partial recovery of both organs, even if with occurrence of oxidative stress and changes of energy metabolism. Overall, these findings support organ-specific responses according to their sensitivity to Hg exposure, pointing out that indications obtained in biomonitoring studies may depend also on the selected organ.
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Affiliation(s)
- Giuseppe De Marco
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, 98166 Messina, Italy
| | - Barbara Billè
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, 98166 Messina, Italy
| | - Fátima Brandão
- Centre for Environmental and Marine Studies (CESAM) and Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Mariachiara Galati
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, 98166 Messina, Italy
| | - Patrícia Pereira
- Centre for Environmental and Marine Studies (CESAM) and Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Tiziana Cappello
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, 98166 Messina, Italy
| | - Mário Pacheco
- Centre for Environmental and Marine Studies (CESAM) and Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal
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Akiyama M, Shinkai Y, Yamakawa H, Kim YG, Kumagai Y. Potentiation of methylmercury toxicity by combined metal exposure: In vitro and in vivo models of a restricted metal exposome. CHEMOSPHERE 2022; 299:134374. [PMID: 35318019 DOI: 10.1016/j.chemosphere.2022.134374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 03/05/2022] [Accepted: 03/17/2022] [Indexed: 06/14/2023]
Abstract
Methylmercury (MeHg) is a prevalent toxic metal that readily modifies protein thiols. Reactive persulfides that play a role in redox homeostasis are able to inactivate this metal through sulfur adduct formation. Although humans are exposed to other metals that could consume reactive persulfides on a daily basis, the health effects of combined exposure to MeHg and other metals remain unexplored. This study aimed to examine potential MeHg toxicity during exposure to MeHg with other metals capable of consuming reactive persulfides. We designed a simple system to assess the risk of combined exposure to metals based on reactivity to reactive persulfides and mercury accumulation. Among the metals examined in a cell-free system, copper, cadmium, nickel, and MeHg consumed Na2S2, used as a model of reactive persulfides, whereas zinc, iron, lithium, strontium, tin, and aluminum did not. In HepG2 cells, binary exposure to MeHg and copper, but not aluminum, increased the consumption of extracellular reactive persulfides. Binary exposure exacerbated MeHg-induced cytotoxicity by promoting the modification of intracellular proteins by MeHg. In a mouse model, binary exposure to MeHg and copper resulted in elevated mercury accumulation in the fetuses and placenta of pregnant mice, as well as the brain and liver of non-pregnant mice. Our study suggests that MeHg sensitivity can be increased by combined exposure with other electrophilic metals. In particular, binary exposure to MeHg and copper during pregnancy exacerbated mercury accumulation in offspring.
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Affiliation(s)
- Masahiro Akiyama
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan; Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University, Tokyo, 105-8512, Japan
| | - Yasuhiro Shinkai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan; Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan
| | - Hiroto Yamakawa
- Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan
| | - Yun-Gi Kim
- Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University, Tokyo, 105-8512, Japan
| | - Yoshito Kumagai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan; Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan.
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5
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Horai S, Abiko Y, Unoki T, Shinkai Y, Akiyama M, Nakata K, Kunisue T, Kumagai Y. Concentrations of nucleophilic sulfur species in small Indian mongoose (Herpestes auropunctatus) in Okinawa, Japan. CHEMOSPHERE 2022; 295:133833. [PMID: 35120952 DOI: 10.1016/j.chemosphere.2022.133833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 01/27/2022] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
Reactive sulfur species (RSS), such as hydrogen per (poly)sulfide, cysteine per (poly)sulfide, glutathione per (poly)sulfide, and protein-bound per (poly)sulfides, can easily react with environmental electrophiles such as methylmercury (MeHg), because of their high nucleophilicity. These RSS are produced by enzymes such as cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) and are found in mammalian organs. Organs of wildlife have not been analyzed for hydrogen sulfide, cysteine, glutathione, and RSS. In this study, low molecular weight nucleophilic sulfur substances, including RSS, were quantified by stable isotope dilution assay-based liquid chromatography-mass spectrometry using β-(4-hydroxyphenyl)ethyl iodoacetamide to capture the target chemicals in the small Indian mongoose which species possesses high mercury content as same as some marine mammals. Western blotting revealed that the mongoose organs (liver, kidney, cerebrum, and cerebellum) contained proteins that cross-reacted with anti-CBS and CSE antibodies. The expression patterns of these enzymes were similar to those in mice, indicating that mongoose organs contain CBS and CSE. Moreover, bis-methylmercury sulfide (MeHg)2S, which is a low toxic compound in comparison to MeHg, was found in the liver of this species. These results suggest that the small Indian mongoose produces RSS and monothiols associated with detoxification of electrophilic organomercury. The animals which have high mercury content in their bodies may have function of mercury detoxification involved not only Se but also RSS interactions.
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Affiliation(s)
- Sawako Horai
- Environmental Health Section, Department of Environment and Public Health, National Institute for Minamata Disease, 4058-18 Hama, Minamata, Kumamoto, 867-0008, Japan.
| | - Yumi Abiko
- Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan.
| | - Takamitsu Unoki
- Hygienic Chemistry Section, Department of Basic Medical Sciences, National Institute for Minamata Disease, 4058-18 Hama, Minamata, Kumamoto, 867-0008, Japan.
| | - Yasuhiro Shinkai
- Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan.
| | - Masahiro Akiyama
- Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University, 1-5-30 Shibakoen, Minato-ku, Tokyo, 105-8512, Japan.
| | - Katsushi Nakata
- Nansei Environmental Laboratory Co., Ltd., 4-4 Agarizaki, Nishihara, Okinawa, 903-0105, Japan.
| | - Tatsuya Kunisue
- Center for Marine Environmental Studies, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime, 790-8577, Japan.
| | - Yoshito Kumagai
- Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan.
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6
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Unoki T, Akiyama M, Shinkai Y, Kumagai Y, Fujimura M. Spatio-temporal distribution of reactive sulfur species during methylmercury exposure in the rat brain. J Toxicol Sci 2022; 47:31-37. [PMID: 34987139 DOI: 10.2131/jts.47.31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Brain susceptibility to methylmercury (MeHg) is developmentally and regionally specific in both humans and rodents, but the mechanism is not well clarified. Reactive sulfur species (RSS) with high nucleophilicity can react with MeHg, leading to the formation of a less toxic metabolite bismethylmercury sulfide, thus exerting cytoprotection. In this study, we assessed the variation of RSS content in the rat brain and evaluated its relevance in sensitivity to MeHg. Analyses of fetal/juvenile rat brains showed low RSS levels in early developmental stages. Site-specific analysis of adult rat brains revealed that cerebellar RSS levels were lower than those of the hippocampus. Microscopically, RSS levels of the granular cell layer were lower than those of the molecular layer in the cerebellum. Thus, low RSS levels corresponded with age and site of the brain that is vulnerable to MeHg. Taken together with the finding that brain RSS were consumed during MeHg exposure, these results indicate that RSS is a factor that defines the specificity of MeHg vulnerability in the brain.
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Affiliation(s)
- Takamitsu Unoki
- Department of Basic Medical Sciences, National Institute for Minamata Disease
| | - Masahiro Akiyama
- Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University
| | - Yasuhiro Shinkai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba
| | - Yoshito Kumagai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba
| | - Masatake Fujimura
- Department of Basic Medical Sciences, National Institute for Minamata Disease
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Martins AC, Ke T, Bowman AB, Aschner M. New insights on mechanisms underlying methylmercury-induced and manganese-induced neurotoxicity. CURRENT OPINION IN TOXICOLOGY 2021; 25:30-35. [PMID: 33898886 PMCID: PMC8061890 DOI: 10.1016/j.cotox.2021.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Toxic and essential elements are widely distributed in the Earth's crust and individuals may be exposed to several of them. Indeed, exposure to toxic elements such as mercury (Hg) can be a potential health risk factor of health, mainly by ingestion of fish containing methylmercury (MeHg). On the other hand, essential elements such as manganese (Mn) play an important role in physiological process in human body. However, Mn overexposure may cause toxic effects. In this respect, the neurotoxic effects of MeHg and Mn on the developing brain are well recognized. Therefore, in this critical review, we address the effects of MeHg and Mn on cell signaling pathways which may contribute to molecular mechanisms involved in MeHg- and Mn-induced neurotoxicity.
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Affiliation(s)
- Airton C Martins
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Tao Ke
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
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Seki N, Akiyama M, Yamakawa H, Hase K, Kumagai Y, Kim YG. Adverse effects of methylmercury on gut bacteria and accelerated accumulation of mercury in organs due to disruption of gut microbiota. J Toxicol Sci 2021; 46:91-97. [PMID: 33536393 DOI: 10.2131/jts.46.91] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Methylmercury (MeHg), an environmental electrophile, binds covalently to the cysteine residues of proteins in organs, altering protein function and causing cytotoxicity. MeHg has also been shown to alter the composition of gut microbes. The gut microbiota is a complex community, the disturbance of which has been linked to the development of certain diseases. However, the relationship between MeHg and gut bacteria remains poorly understood. In this study, we showed that MeHg binds covalently to gut bacterial proteins via cysteine residues. We examined the effects of MeHg on the growth of selected Lactobacillus species, namely, L. reuteri, L. gasseri, L. casei, and L. acidophilus, that are frequently either positively or negatively correlated with human diseases. The results revealed that MeHg inhibits the growth of Lactobacillus to varying degrees depending on the species. Furthermore, the growth of L. reuteri, which was inhibited by MeHg exposure, was restored by Na2S2 treatment. By comparing mice with and without gut microbiota colonization, we found that gut bacteria contribute to the production of reactive sulfur species such as hydrogen sulfide and hydrogen persulfide in the gut. We also discovered that the removal of gut bacteria accelerated accumulation of mercury in the cerebellum, liver, and lungs of mice subsequent to MeHg exposure. These results accordingly indicate that MeHg is captured and inactivated by the hydrogen sulfide and hydrogen persulfide produced by intestinal microbes, thereby providing evidence for the role played by gut microbiota in reducing MeHg toxicity.
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Affiliation(s)
- Natsumi Seki
- Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University
- Division of Biochemistry, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University
| | - Masahiro Akiyama
- Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba
| | - Hiroto Yamakawa
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba
| | - Koji Hase
- Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University
- Division of Biochemistry, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University
| | - Yoshito Kumagai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba
| | - Yun-Gi Kim
- Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University
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Sakamoto M, Kakita A, Sakai K, Kameo S, Yamamoto M, Nakamura M. Methylmercury exposure during the vulnerable window of the cerebrum in postnatal developing rats. ENVIRONMENTAL RESEARCH 2020; 188:109776. [PMID: 32592939 DOI: 10.1016/j.envres.2020.109776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/02/2020] [Accepted: 06/02/2020] [Indexed: 06/11/2023]
Abstract
The developing brain is known to be sensitive to the toxic effects of methylmercury (MeHg). The effects of toxic levels of MeHg exposure during the most seemingly vulnerable window of the cerebrum are not well studied. In this study, we aimed to examine the specific effects of toxic levels of MeHg on neurobehavior, neurodegeneration, and selenoenzyme activity in the cerebrum of infant rats. Male Wistar rats (n = 8/group) were orally treated with MeHg at an acute toxic dose (8 mg Hg/kg/day) for 10 consecutive days starting on postnatal day 14 (P14). The MeHg-exposed rats showed a significant reduction in body weight after day 8 and severe neurological symptoms similar to dystonia on day 12 (P25). Motor coordination deficits determined using the rotarod performance test and short-term memory impairment determined using the Y-maze task were observed in the MeHg-exposed rats on day 11 (P24). The MeHg-exposed rats sacrificed on day 12 showed severe cerebral neuronal degeneration, reactive astrocytosis, and TUNEL-positive apoptotic nuclei, with the cerebral Hg concentration of 15.0 ± 1.6 μg/g. Furthermore, the activities of glutathione peroxidase and thioredoxin reductase in the cerebrum in MeHg-exposed rats were lower than those in control. These results indicate that MeHg exposure to infant rats will be useful to predict the effects of MeHg at the cerebral growth spurt in humans.
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Affiliation(s)
| | - Akiyoshi Kakita
- Brain Research Institute, Niigata University, Niigata, Japan
| | - Kazuo Sakai
- Japan Institute for the Control of Aging, Nikken SEIL Co., Ltd., Japan
| | - Satomi Kameo
- Department of Public Health, Graduate School of Medicine, Gunma University, Japan; Department of Nutrition, Koshien University, Hyogo, Japan
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