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von Hellfeld R, Hastings A. An approach to assessing subsea pipeline-associated mercury release into the North Sea and its potential environmental and human health impact. ROYAL SOCIETY OPEN SCIENCE 2024; 11:230943. [PMID: 38481980 PMCID: PMC10935551 DOI: 10.1098/rsos.230943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 12/19/2023] [Accepted: 02/05/2024] [Indexed: 04/26/2024]
Abstract
Mercury is a naturally occurring heavy metal that has also been associated with anthropogenic sources such as cement production or hydrocarbon extraction. Mercury is a contaminant of concern as it can have a significant negative impact on organismal health when ingested. In aquatic environments, it bioaccumulates up the foodweb, where it then has the potential to impact human health. With the offshore hydrocarbon platforms in the North Sea nearing decommissioning, they must be assessed as a potential source for the environmental release of mercury. International treaties govern the handling of materials placed in the ocean. Studies have assessed the ecologic and economic benefits of (partial) in situ abandonment of the infrastructure as artificial reefs. This can be applied to pipelines after substantial cleaning to remove mercury accumulation from the inner surface. This work outlines the application of an approach to modelling marine mercury bioaccumulation for decommissioning scenarios in the North Sea. Here, in situ decommissioning of cleaned pipelines was unlikely to have a negative impact on the North Sea food web or human health. However, significant knowledge gaps have been determined, which must be addressed before all negative impacts on ecosystems and organismal health can be excluded.
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Affiliation(s)
- Rebecca von Hellfeld
- School of Biological Sciences, University of Aberdeen, 23 St Machar Drive, AberdeenAB24 3UL, UK
- National Decommissioning Centre, Main Street, NewburghAB41 6AA, UK
| | - Astley Hastings
- School of Biological Sciences, University of Aberdeen, 23 St Machar Drive, AberdeenAB24 3UL, UK
- National Decommissioning Centre, Main Street, NewburghAB41 6AA, UK
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2
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Azevedo LF, Karpova N, Rocha BA, Barbosa Junior F, Gobe GC, Hornos Carneiro MF. Evidence on Neurotoxicity after Intrauterine and Childhood Exposure to Organomercurials. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:1070. [PMID: 36673825 PMCID: PMC9858833 DOI: 10.3390/ijerph20021070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/03/2023] [Accepted: 01/04/2023] [Indexed: 06/17/2023]
Abstract
Although the molecular mechanisms underlying methylmercury toxicity are not entirely understood, the observed neurotoxicity in early-life is attributed to the covalent binding of methylmercury to sulfhydryl (thiol) groups of proteins and other molecules being able to affect protein post-translational modifications from numerous molecular pathways, such as glutamate signaling, heat-shock chaperones and the antioxidant glutaredoxin/glutathione system. However, for other organomercurials such as ethylmercury or thimerosal, there is not much information available. Therefore, this review critically discusses current knowledge about organomercurials neurotoxicity-both methylmercury and ethylmercury-following intrauterine and childhood exposure, as well as the prospects and future needs for research in this area. Contrasting with the amount of epidemiological evidence available for methylmercury, there are only a few in vivo studies reporting neurotoxic outcomes and mechanisms of toxicity for ethylmercury or thimerosal. There is also a lack of studies on mechanistic approaches to better investigate the pathways involved in the potential neurotoxicity caused by both organomercurials. More impactful follow-up studies, especially following intrauterine and childhood exposure to ethylmercury, are necessary. Childhood vaccination is critically important for controlling infectious diseases; however, the safety of mercury-containing thimerosal and, notably, its effectiveness as preservative in vaccines are still under debate regarding its potential dose-response effects to the central nervous system.
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Affiliation(s)
- Lara Ferreira Azevedo
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Nina Karpova
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Bruno Alves Rocha
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Fernando Barbosa Junior
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Glenda Carolyn Gobe
- Kidney Disease Research Group, School of Medicine, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, QLD 4102, Australia
| | - Maria Fernanda Hornos Carneiro
- Department of Pharmacy, Faculty of Chemistry and Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
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3
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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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4
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Sakamoto M, Haraguchi K, Tatsuta N, Nakai K, Nakamura M, Murata K. Plasma and red blood cells distribution of total mercury, inorganic mercury, and selenium in maternal and cord blood from a group of Japanese women. ENVIRONMENTAL RESEARCH 2021; 196:110896. [PMID: 33640495 DOI: 10.1016/j.envres.2021.110896] [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: 12/10/2020] [Revised: 01/20/2021] [Accepted: 02/15/2021] [Indexed: 06/12/2023]
Abstract
Fetuses are a high-risk group for methylmercury (MeHg) exposure. The main objective of this study was to compare the characteristic profiles of total mercury (THg), inorganic mercury (IHg), MeHg, and selenium in plasma and red blood cells (RBCs) between maternal and cord blood at parturition collected from a group of Japanese women. Furthermore, correlations of THg in RBCs, which is a biomarker of MeHg, and THg in plasma, which is an IHg exposure biomarker, were examined in maternal and cord blood. Fifty-five pairs of maternal and cord blood samples obtained at parturition were collected from pregnant women in Fukuoka, Japan. THg in RBCs and plasma were significant correlated between maternal and cord blood. THg in RBCs was 13.9 ng/mL for cord and 9.16 ng/mL for maternal blood, with a cord:maternal RBCs ratio for THg of 1.58, suggesting that MeHg is actively transferred from the mother to the fetus via the placenta. THg in plasma showed a positive correlation with THg in RBCs for maternal and cord blood. This result suggests that measuring THg in plasma can overestimate the exposure level to IHg in fish-eating populations. The percentages of IHg in cord plasma and RBCs were 31% and 1.7%, respectively, and those in maternal plasma and RBCs were 46% and 5.9%, respectively. These results suggest that cord blood is rich in MeHg and can easily transfer to the fetal brain. Selenium in cord plasma was 67 ng/mL and that in maternal plasma was 97 ng/mL, with a cord:maternal plasma ratio for Se of 0.69, suggesting that the protective effects of Se against MeHg toxicity in fetuses may be weaker than those expected in adult mothers.
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Affiliation(s)
- Mineshi Sakamoto
- National Institute for Minamata Disease, 4058-18 Hama, Minamata City, Kumamoto, 867-0008, Japan.
| | - Koichi Haraguchi
- National Institute for Minamata Disease, 4058-18 Hama, Minamata City, Kumamoto, 867-0008, Japan
| | - Nozomi Tatsuta
- Development and Environmental Medicine, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Kunihiko Nakai
- Development and Environmental Medicine, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Masaaki Nakamura
- National Institute for Minamata Disease, 4058-18 Hama, Minamata City, Kumamoto, 867-0008, Japan
| | - Katsuyuki Murata
- Department of Environment and Public Health, Akita University School Graduate School of Medicine, 1-1 Hondo, Akita, 010-8543, Japan
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5
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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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6
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Kern JK, Geier DA, Homme KG, Geier MR. Examining the evidence that ethylmercury crosses the blood-brain barrier. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2020; 74:103312. [PMID: 31841767 DOI: 10.1016/j.etap.2019.103312] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 12/06/2019] [Accepted: 12/06/2019] [Indexed: 06/10/2023]
Abstract
Scientific research can provide us with factual, repeatable, measurable, and determinable results. As such, scientific research can provide information that can be used in the decision-making process in the care of patients and in public policy. Although it has been suggested that ethylmercury (C2H5Hg+)-containing compounds do not cross the blood-brain barrier (BBB), this review examines the literature that addresses the question as to whether ethylmercury-containing compounds cross the BBB. The review will begin with cellular studies that provide evidence for the passive and active transport of mercury species across the BBB. Then, animal and clinical studies will be presented that specifically examine whether mercury accumulates in the brain after exposure to ethylmercury-containing compounds or Thimerosal (an ethylmercury-containing compound used as a preservative in vaccines and other drugs that metabolizes or degrades to ethylmercury-containing compounds and thiosalicylate). The results indicate that ethylmercury-containing compounds are actively transported across membranes by the L (leucine-preferring)-amino acid transport (LAT) system, the same as methylmercury-containing compounds. Further, 22 studies from 1971 to 2019 show that exposure to ethylmercury-containing compounds (intravenously, intraperitoneally, topically, subcutaneously, intramuscularly, or intranasally administered) results in accumulation of mercury in the brain. In total, these studies indicate that ethylmercury-containing compounds and Thimerosal readily cross the BBB, convert, for the most part, to highly toxic inorganic mercury-containing compounds, which significantly and persistently bind to tissues in the brain, even in the absence of concurrent detectable blood mercury levels.
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Affiliation(s)
- Janet K Kern
- Institute of Chronic Illnesses, Inc, Silver Spring, MD, USA; CoMeD, Inc, Silver Spring, MD, USA; CONEM US Autism Research Group, Allen, TX, USA.
| | - David A Geier
- Institute of Chronic Illnesses, Inc, Silver Spring, MD, USA; CoMeD, Inc, Silver Spring, MD, USA
| | - Kristin G Homme
- International Academy of Oral Medicine and Toxicology, ChampionsGate, FL, USA
| | - Mark R Geier
- Institute of Chronic Illnesses, Inc, Silver Spring, MD, USA; CoMeD, Inc, Silver Spring, MD, USA
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7
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Sakamoto M, Tatsuta N, Chan HM, Domingo JL, Murata K, Nakai K. Brain methylmercury uptake in fetal, neonate, weanling, and adult rats. ENVIRONMENTAL RESEARCH 2018; 167:15-20. [PMID: 30005196 DOI: 10.1016/j.envres.2018.06.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 06/15/2018] [Accepted: 06/18/2018] [Indexed: 06/08/2023]
Abstract
Fetuses and neonates are known to be highly susceptible to methylmercury (MeHg) toxicity, but little is known about the relative uptake of MeHg from blood to the developing brain. We measured time-course changes in mercury (Hg) concentrations in the brain of fetal, neonate, weanling, and adult rats after an injection of 0.08 μg (0.4 nmol) Hg/g MeHg. In the prenatal experiment, MeHg was subcutaneously injected to pregnant dams on embryonic days 17, 18, 18.5, 19, 19.5, or 20, and Hg concentrations in tissues were measured in both mothers and fetuses on embryonic day 21 (1 day before parturition). Brain Hg levels in fetuses peaked 2 days after injection and were approximately 1.5 times higher than in mothers. In the postnatal experiment, the same MeHg dose was injected subcutaneously to male rats on postnatal days 1 (neonates), 35 (weanlings), or 56 (adults). Mercury concentrations in tissues were measured 1, 2, 3, 4, 5, or 6 days after the injection. Brain Hg levels peaked most rapidly in neonates, and were approximately 1.5 times higher than levels in weanlings or adults. Throughout the examined period, peak Hg levels in the brain and the Hg brain/blood ratio 24 h after injection were highest in fetuses, followed by the levels in neonates, and decreased with life stage. These findings suggest that relatively higher brain MeHg uptake is an important factor in the vulnerability of fetuses and neonates to MeHg exposure.
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Affiliation(s)
- Mineshi Sakamoto
- Department of Environment and Public Health, National Institute for Minamata Disease, 4058-18 Hama, Kumamoto 867-0008, Japan; Development and Environmental Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.
| | - Nozomi Tatsuta
- Development and Environmental Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Hing Man Chan
- Center for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - José L Domingo
- Laboratory of Toxicology and Environmental Health, School of Medicine, IISPV, Universitat "Rovira I Virgili", Reus, Spain
| | - Katsuyuki Murata
- Department of Environmental Health Sciences, Akita University School of Medicine, Akita, Japan
| | - Kunihiko Nakai
- Development and Environmental Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
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Impact of glutamine on the effect of neopterin in methyl mercury-exposed neurons. Pteridines 2018. [DOI: 10.1515/pteridines-2018-0011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
Exposure to methyl mercury (MeHg), induces blood-brain barrier damage leading to non-selective influx of cytotoxic agents, besides the entrance of inflammatory cells into the brain. However, there is no data available regarding the effects of co-treatment of neopterin and interferon-gamma (IFN-gamma) in MeHgexposed SH-SY5Y dopaminergic neurons. MeHg-exposed SH-SY5Y human neuroblastoma cells were treated with neopterin and IFN-gamma in the presence and absence of L-Glutamine. Cell viability was determined by MTT assay. Oxidative stress intensity coefficient was calculated by taking into consideration the amount of nitric oxide production per viable neuron. 5μM MeHg was found to be more toxic than 1μM or 2μM doses of MeHg for SH-SY5Y cells in glutamine-containing medium. Furthermore, 0.1μM neopterin supplementation significantly increased the neuronal cell viability while, oxidative stress significantly decreased. Glutamine supplementation in culture medium, not only enhanced the MeHg toxicity, but also supported the antioxidant effect of neopterin. These results indicate that neopterin has a protective effect on MeHg toxicity in SH-SY5Y neurons. Neopterin was more effective in improving the total mitochondrial metabolic activity of cells exposed to 5μM MeHg in comparison to IFN-gamma. Although IFN-gamma supplementation alone partially improved 5μM MeHg toxicity on neurons, it weakened the protective effect of neopterin.
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9
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Health Impacts and Biomarkers of Prenatal Exposure to Methylmercury: Lessons from Minamata, Japan. TOXICS 2018; 6:toxics6030045. [PMID: 30081479 PMCID: PMC6161157 DOI: 10.3390/toxics6030045] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 07/26/2018] [Accepted: 07/31/2018] [Indexed: 12/03/2022]
Abstract
The main chemical forms of mercury are elemental mercury, inorganic divalent mercury, and methylmercury, which are metabolized in different ways and have differing toxic effects in humans. Among the various chemical forms of mercury, methylmercury is known to be particularly neurotoxic, and was identified as the cause of Minamata disease. It bioaccumulates in fish and shellfish via aquatic food webs, and fish and sea mammals at high trophic levels exhibit high mercury concentrations. Most human methylmercury exposure occurs through seafood consumption. Methylmercury easily penetrates the blood-brain barrier and so can affect the nervous system. Fetuses are known to be at particularly high risk of methylmercury exposure. In this review, we summarize the health effects and exposure assessment of methylmercury as follows: (1) methylmercury toxicity, (2) history and background of Minamata disease, (3) methylmercury pollution in the Minamata area according to analyses of preserved umbilical cords, (4) changes in the sex ratio in Minamata area, (5) neuropathology in fetuses, (6) kinetics of methylmercury in fetuses, (7) exposure assessment in fetuses.
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Sakamoto M, Chan HM, Domingo JL, Koriyama C, Murata K. Placental transfer and levels of mercury, selenium, vitamin E, and docosahexaenoic acid in maternal and umbilical cord blood. ENVIRONMENT INTERNATIONAL 2018; 111:309-315. [PMID: 29150340 DOI: 10.1016/j.envint.2017.11.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 10/27/2017] [Accepted: 11/02/2017] [Indexed: 06/07/2023]
Abstract
Methylmercury (MeHg) is a neurotoxicant known to affect the developing fetal brain as a sensitive target organ. As most mercury (Hg) in blood is MeHg, total mercury (THg) levels in blood are used to estimate the body burden of MeHg. The nutrients selenium (Se), vitamin E, and docosahexaenoic acid (DHA) are protective against MeHg toxicity. We compared maternal and cord blood concentrations of biochemical substances, THg and Se, vitamin E, DHA, and other elements, fatty acids, and amino acids in 54 Japanese mother-newborn pairs to elucidate the fetal risk of MeHg toxicity. Cord blood had higher hematocrit and amino acid values and lower concentrations of lipid components, including fatty acids compared with maternal blood. THg levels in cord blood (7.26ng/g) were 1.9 times higher than levels in maternal blood (3.79ng/g). Se concentrations in cord blood (176ng/g) were slightly higher than concentrations in maternal blood (156ng/g). Levels of vitamin E (0.31mg/dL) and DHA (58.8μg/mL) in cord blood were much lower than levels in maternal blood (1.38mg/dL and 147μg/mL, respectively). The ratios of Se/THg, vitamin E/THg, and DHA/THg in cord blood were lower than ratios in maternal blood. These results suggest that fetuses are at higher risk to MeHg toxicity.
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Affiliation(s)
- Mineshi Sakamoto
- Environmental Health Section, Department of Environmental Science and Epidemiology, National Institute for Minamata Disease, Minamata, Japan; Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
| | - Hing Man Chan
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - José L Domingo
- Laboratory of Toxicology and Environmental Health, School of Medicine, IISPV, Universitat "Rovira i Virgili", Reus, Spain
| | - Chihaya Koriyama
- Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Katsuyuki Murata
- Department of Environmental Health Sciences, Akita University Graduate School of Medicine, Akita, Japan
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11
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Oliveira VA, Favero G, Stacchiotti A, Giugno L, Buffoli B, de Oliveira CS, Lavazza A, Albanese M, Rodella LF, Pereira ME, Rezzani R. Acute mercury exposition of virgin, pregnant, and lactating rats: Histopathological kidney and liver evaluations. ENVIRONMENTAL TOXICOLOGY 2017; 32:1500-1512. [PMID: 27726300 DOI: 10.1002/tox.22370] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 09/09/2016] [Accepted: 09/15/2016] [Indexed: 06/06/2023]
Abstract
This work investigated the effects of mercury chloride (HgCl2 ) acute exposure on virgin, pregnant and lactating rats by determination of renal and hepatic morphological and ultrastructural parameters and the expression of oxidative stress and stress tolerance markers, due to kidney and liver are the organs that more accumulate inorganic mercury. Adult Wistar rats virgin (90 days old), pregnant (18th gestation day) and lactating (7th lactation day) were injected once with HgCl2 (5 mg/kg) or saline (controls). We observed that HgCl2 exposure of virgin rats caused significant inflammatory infiltration and severe morphological variations, like glomeruli atrophy, dilatation of Bowman's capsule, tubular degeneration and hepatocytes alteration. Moreover, virgin rats presented mitochondrial modification, important oxidative stress and increase in stress tolerance proteins at both kidney and liver level, compared with virgin controls. In detail, virgin rats exposed to HgCl2 presented significantly elevated level of inducible nitric oxide synthase, heat shock protein 27 and glucose regulated proteins 75 expressions at both renal tubular and hepatocytes level, respect untreated virgin rats. Interestingly, pregnant and lactating rats exposed to HgCl2 presented weak renal and liver morphological alterations, showing weak inflammatory infiltration and no significant difference in structural mitochondrial transmembrane protein, oxidative stress markers and stress tolerance proteins expressions respect controls (virgin, pregnant and lactating rats). Although, both control and HgCl2 -exposed pregnant and lactating rats showed renal glomeruli greater in diameter respect virgin rats. In conclusion, we believe that virgin rats are more sensitive to HgCl2 toxicity respect pregnant and lactating rats. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1500-1512, 2017.
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Affiliation(s)
- Vitor Antunes Oliveira
- Anatomy and Physiopathology Division, Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa 11, Brescia, 25123, Italy
- Department of Biochemistry and Molecular Biology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Gaia Favero
- Anatomy and Physiopathology Division, Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa 11, Brescia, 25123, Italy
| | - Alessandra Stacchiotti
- Anatomy and Physiopathology Division, Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa 11, Brescia, 25123, Italy
- Interdipartimental University Center of Research "Adaption and Regeneration of Tissues and Organs- (ARTO)", University of Brescia, Italy
| | - Lorena Giugno
- Anatomy and Physiopathology Division, Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa 11, Brescia, 25123, Italy
| | - Barbara Buffoli
- Anatomy and Physiopathology Division, Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa 11, Brescia, 25123, Italy
- Interdipartimental University Center of Research "Adaption and Regeneration of Tissues and Organs- (ARTO)", University of Brescia, Italy
| | - Claudia Sirlene de Oliveira
- Department of Biochemistry and Molecular Biology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Antonio Lavazza
- OIE Reference Laboratory for RHD, Istituto Zooprofilattico Sperimentale della Lombardia e Emilia Romagna, Brescia, Italy
| | - Massimo Albanese
- Department of Oral and Maxillofacial Surgery, University of Verona, Verona, Italy
| | - Luigi Fabrizio Rodella
- Anatomy and Physiopathology Division, Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa 11, Brescia, 25123, Italy
- Interdipartimental University Center of Research "Adaption and Regeneration of Tissues and Organs- (ARTO)", University of Brescia, Italy
| | - Maria Ester Pereira
- Department of Biochemistry and Molecular Biology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Rita Rezzani
- Anatomy and Physiopathology Division, Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa 11, Brescia, 25123, Italy
- Interdipartimental University Center of Research "Adaption and Regeneration of Tissues and Organs- (ARTO)", University of Brescia, Italy
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12
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Exploring cross-talk between oxidative damage and excitotoxicity and the effects of riluzole in the rat cortex after exposure to methylmercury. Neurotox Res 2014; 26:40-51. [PMID: 24519665 DOI: 10.1007/s12640-013-9448-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 11/07/2013] [Accepted: 12/05/2013] [Indexed: 12/22/2022]
Abstract
Methylmercury (MeHg) is a ubiquitous environmental toxin that causes neurologic and developmental diseases. Oxidative damage and excitotoxicity are putative mechanisms, which underlie MeHg-induced neurotoxicity. In this study, the cross-talk between the oxidative damage and excitotoxicity pathways and the protective effects of riluzole in the rat cortex were explored. Rats were injected with MeHg and/or riluzole, and cold vapor atomic fluorescence spectrometry, hematoxylin and eosin staining, flow cytometry, fluorescence assays, spectrophotometry, real-time PCR, and Western blotting were used to evaluate neurotoxicity. The present study showed that (1) MeHg accumulated in the cerebral cortex and caused pathology. (2) MeHg caused oxidative damage by inducing glutathione (GSH) depletion, reactive oxygen species (ROS) production, inhibition of antioxidant enzyme activity, and alteration of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. (3) MeHg disrupted the glutamate transporters (GluTs), glutamate-glutamine cycle, and N-methyl-D-aspartate receptor expression and induced excitotoxicity. (4) Excitotoxicity resulted in disruption of GSH synthesis, calcium overloading, oxidative damage, and excessive ROS production. (5) Pretreatment with riluzole antagonized MeHg neurotoxicity by down regulating cross-talk between the oxidative damage and excitotoxicity pathways. In conclusion, the cross-talk between the oxidative damage and excitotoxicity pathways caused by MeHg exposure was linked by GluTs and calcium and inhibited by riluzole treatment.
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Zimmermann LT, dos Santos DB, Colle D, dos Santos AA, Hort MA, Garcia SC, Bressan LP, Bohrer D, Farina M. Methionine stimulates motor impairment and cerebellar mercury deposition in methylmercury-exposed mice. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2014; 77:46-56. [PMID: 24555646 DOI: 10.1080/15287394.2014.865582] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Methylmercury (MeHg) is a highly toxic environmental contaminant that produces neurological and developmental impairments in animals and humans. Although its neurotoxic properties have been widely reported, the molecular mechanisms by which MeHg enters the cells and exerts toxicity are not yet completely understood. Taking into account that MeHg is found mostly bound to sulfhydryl-containing molecules such as cysteine in the environment and based on the fact that the MeHg-cysteine complex (MeHg-S-Cys) can be transported via the L-type neutral amino acid carrier transport (LAT) system, the potential beneficial effects of L-methionine (L-Met, a well known LAT substrate) against MeHg (administrated as MeHg-S-Cys)-induced neurotoxicity in mice were investigated. Mice were exposed to MeHg (daily subcutaneous injections of MeHg-S-Cys, 10 mg Hg/kg) and/or L-Met (daily intraperitoneal injections, 250 mg/kg) for 10 consecutive days. After treatments, the measured hallmarks of toxicity were mostly based on behavioral parameters related to motor performance, as well as biochemical parameters related to the cerebellar antioxidant glutathione (GSH) system. MeHg significantly decreased motor activity (open-field test) and impaired motor performance (rota-rod task) compared with controls, as well as producing disturbances in the cerebellar antioxidant GSH system. Interestingly, L-Met administration did not protect against MeHg-induced behavioral and cerebellar changes, but rather increased motor impairments in animals exposed to MeHg. In agreement with this observation, cerebellar levels of mercury (Hg) were higher in animals exposed to MeHg plus L-Met compared to those only exposed to MeHg. However, this event was not observed in kidney and liver. These results are the first to demonstrate that L-Met enhances cerebellar deposition of Hg in mice exposed to MeHg and that this higher deposition may be responsible for the greater motor impairment observed in mice simultaneously exposed to MeHg and L-Met.
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Affiliation(s)
- Luciana T Zimmermann
- a Departamento de Bioquímica, Centro de Ciências Biológicas , Universidade Federal de Santa Catarina , Florianópolis , Santa Catarina , Brazil
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Farina M, Rocha JBT, Aschner M. Mechanisms of methylmercury-induced neurotoxicity: evidence from experimental studies. Life Sci 2011; 89:555-63. [PMID: 21683713 DOI: 10.1016/j.lfs.2011.05.019] [Citation(s) in RCA: 291] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 04/22/2011] [Accepted: 05/13/2011] [Indexed: 02/08/2023]
Abstract
Neurological disorders are common, costly, and can cause enduring disability. Although mostly unknown, a few environmental toxicants are recognized causes of neurological disorders and subclinical brain dysfunction. One of the best known neurotoxins is methylmercury (MeHg), a ubiquitous environmental toxicant that leads to long-lasting neurological and developmental deficits in animals and humans. In the aquatic environment, MeHg is accumulated in fish, which represent a major source of human exposure. Although several episodes of MeHg poisoning have contributed to the understanding of the clinical symptoms and histological changes elicited by this neurotoxicant in humans, experimental studies have been pivotal in elucidating the molecular mechanisms that mediate MeHg-induced neurotoxicity. The objective of this mini-review is to summarize data from experimental studies on molecular mechanisms of MeHg-induced neurotoxicity. While the full picture has yet to be unmasked, in vitro approaches based on cultured cells, isolated mitochondria and tissue slices, as well as in vivo studies based mainly on the use of rodents, point to impairment in intracellular calcium homeostasis, alteration of glutamate homeostasis and oxidative stress as important events in MeHg-induced neurotoxicity. The potential relationship among these events is discussed, with particular emphasis on the neurotoxic cycle triggered by MeHg-induced excitotoxicity and oxidative stress. The particular sensitivity of the developing brain to MeHg toxicity, the critical role of selenoproteins and the potential protective role of selenocompounds are also discussed. These concepts provide the biochemical bases to the understanding of MeHg neurotoxicity, contributing to the discovery of endogenous and exogenous molecules that counteract such toxicity and provide efficacious means for ablating this vicious cycle.
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Affiliation(s)
- Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
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15
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Methylmercury exposure and health effects from rice and fish consumption: a review. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2010; 7:2666-91. [PMID: 20644695 PMCID: PMC2905572 DOI: 10.3390/ijerph7062666] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 06/04/2010] [Accepted: 06/08/2010] [Indexed: 12/02/2022]
Abstract
Methylmercury (MeHg) is highly toxic, and its principal target tissue in humans is the nervous system, which has made MeHg intoxication a public health concern for many decades. The general population is primarily exposed to MeHg through consumption of contaminated fish and marine mammals, but recent studies have reported high levels of MeHg in rice and confirmed that in China the main human exposure to MeHg is related to frequent rice consumption in mercury (Hg) polluted areas. This article reviews the progress in the research on MeHg accumulation in rice, human exposure and health effects, and nutrient and co-contaminant interactions. Compared with fish, rice is of poor nutritional quality and lacks specific micronutrients identified as having health benefits (e.g., n-3 long chain polyunsaturated fatty acid, selenium, essential amino acids). The effects of these nutrients on the toxicity of MeHg should be better addressed in future epidemiologic and clinical studies. More emphasis should be given to assessing the health effects of low level MeHg exposure in the long term, with appropriate recommendations, as needed, to reduce MeHg exposure in the rice-eating population.
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Sakamoto M, Kubota M, Murata K, Nakai K, Sonoda I, Satoh H. Changes in mercury concentrations of segmental maternal hair during gestation and their correlations with other biomarkers of fetal exposure to methylmercury in the Japanese population. ENVIRONMENTAL RESEARCH 2008; 106:270-276. [PMID: 18054904 DOI: 10.1016/j.envres.2007.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 08/21/2007] [Accepted: 10/04/2007] [Indexed: 05/25/2023]
Abstract
Methylmercury (MeHg) is one of the most hazardous substances that affects the fetus through fish consumption. The objective of this study was to evaluate the changes in the level of exposure to MeHg by assessing the mercury (Hg) concentrations of the segmental hair at parturition and 3 months after parturition, and to study their correlations with the total Hg concentrations of maternal and cord red blood cells (RBCs) and neonatal hair as biomarkers of fetal exposure to MeHg at parturition. In total, 40 paired samples of maternal hair from the scalp, maternal and cord RBCs, and 21 samples of neonatal hair from the scalp were collected at parturition. In addition, 19 samples of maternal hair from the scalp were collected at 3 months after parturition. The maternal hair samples were cut into 1cm segments from the scalp end toward the tip. The geometric mean of the Hg concentrations in cord RBCs was approximately 1.6 times higher than that in the maternal RBCs, and a strong correlation coefficient (r=0.91) was found between them. The increase or decrease in the Hg concentrations of the segmental hair during gestation differed largely among individuals. The correlation coefficients between the Hg concentrations of the segmental hair and cord RBCs were the strongest (r=0.90) in the hair segment 1cm from the scalp and decreased gradually with the distance from the scalp. The correlation coefficients between the Hg concentrations of the segmental hair collected at 3 months after parturition and maternal RBCs were over 0.9 in the hair segments 5 and 6 cm from the scalp, suggesting that the time required for the incorporation of Hg from the blood into a growing hair was very short. The geometric mean of Hg concentrations in the neonatal hair at parturition was similar to that in the maternal hair 1cm from the scalp at parturition, and they exhibited a strong correlation (r=0.95). The findings of this study indicate that maternal hair close to the scalp at parturition and neonatal hair are useful biomarkers of fetal exposure to MeHg at parturition. In addition, the segmental maternal hair throughout gestation is essential to obtain important information on MeHg exposure during the different sensitive windows or bolus MeHg exposure during gestation.
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Affiliation(s)
- Mineshi Sakamoto
- Department of Epidemiology, National Institute for Minamata Disease, Kumamoto 867-0008, Japan.
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17
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Attenuation by methyl mercury and mercuric sulfide of pentobarbital induced hypnotic tolerance in mice through inhibition of ATPase activities and nitric oxide production in cerebral cortex. Arch Toxicol 2007; 82:343-53. [DOI: 10.1007/s00204-007-0255-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2007] [Accepted: 10/16/2007] [Indexed: 12/15/2022]
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Coluccia A, Borracci P, Giustino A, Sakamoto M, Carratù MR. Effects of low dose methylmercury administration during the postnatal brain growth spurt in rats. Neurotoxicol Teratol 2007; 29:282-7. [PMID: 17141469 DOI: 10.1016/j.ntt.2006.10.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 10/17/2006] [Accepted: 10/17/2006] [Indexed: 11/16/2022]
Abstract
Male Sprague-Dawley rats from eight litters were orally administered 0.75 mg/kg/day methylmercury (MeHg) chloride from postnatal day (PD) 14 to PD 23. One male pup per litter from eight different litters per treatment group was used. Each pup was used only for a single behavioral test and tested once. The MeHg dose level resulted in Hg brain concentrations of 0.82+/-0.05 microg/g tissue (n=4). Locomotor behavior was studied in the Opto-Varimex apparatus by testing rats (n=8) weekly from PD 24 to PD 45. Performance of rats (n=8) on learning paradigm was analysed on PD 90. MeHg treatment induced a significant reduction in the number of rearings without altering the distance travelled, the resting time and the time spent in the central part of the arena. Results of conditioned avoidance task showed that, unlike control rats, MeHg-treated animals did not show improvement over blocks and never reached a level of performance that would indicate significant learning had taken place. The present results show that low level exposure to MeHg during late brain growth spurt induces subtle and persistent motor and learning deficits, further underlining the serious potential hazard for the exposed children.
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Affiliation(s)
- Addolorata Coluccia
- Department of Pharmacology and Human Physiology, Medical School, University of Bari, Policlinico, Piazza G. Cesare 11, 70124 Bari, Italy
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Sakamoto M, Kaneoka T, Murata K, Nakai K, Satoh H, Akagi H. Correlations between mercury concentrations in umbilical cord tissue and other biomarkers of fetal exposure to methylmercury in the Japanese population. ENVIRONMENTAL RESEARCH 2007; 103:106-11. [PMID: 16650842 DOI: 10.1016/j.envres.2006.03.004] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Revised: 03/10/2006] [Accepted: 03/15/2006] [Indexed: 05/08/2023]
Abstract
Methylmercury (MeHg) is one of the most risky substances to affect humans through fish consumption, and the fetus is known to be in the most susceptible group. Our objective in this study is to examine the relationships of total mercury (THg) and MeHg concentrations between umbilical cord tissue and other tissues as biomarkers of fetal exposure to MeHg in the Japanese population. In total, 116 paired samples were collected in three Japanese districts, the Tsushima Islands, Fukuoka City, and Katsushika ward of metropolitan Tokyo. THg was measured for hair and THg and MeHg were measured in cord tissues, maternal blood, and cord blood. The relationships among tissues in Hg concentrations were similar among districts. Therefore, we analyzed the relationships using all the samples. More than 90% of Hg in cord tissue, cord blood, and maternal blood was MeHg. THg and MeHg in cord blood was about two times higher than in maternal blood. A strong correlation was found between THg and MeHg in cord tissue. The cord tissue THg and MeHg showed a strong correlation with cord blood Hg, which is recognized as the best biomarker for fetal exposure to MeHg. The findings of this study indicate the significance of cord tissue THg and MeHg as biomarkers for fetal exposure to MeHg at parturition.
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Affiliation(s)
- Mineshi Sakamoto
- Department of Epidemiology, National Institute for Minamata Disease, Kumamoto 867-0008, Japan.
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Kakita A, Wakabayashi K, Su M, Piao YS, Takahashi H. Experimentally induced leptomeningeal glioneuronal heterotopia and underlying cortical dysplasia of the lateral limbic area in rats treated transplacentally with methylmercury. J Neuropathol Exp Neurol 2001; 60:768-77. [PMID: 11487051 DOI: 10.1093/jnen/60.8.768] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Leptomeningeal glioneuronal heterotopia (LGH) is a developmental anomaly sometimes observed at the surface of human brains with severe malformations. We experimentally induced LGH in brains of rat pups by transplacental exposure to methylmercury. Histopathological profiles of the induced LGH, including the spatio-temporal predominance of the manifestation, suggest some aspects of the histogenesis of this malformation. Pregnant rats on embryonic day 8 (E8), E11, E13, E16, E18 or E21 were treated orally with a single administration of 20 mg/kg methylmercury chloride, and the brains of their delivered offspring were examined on postnatal day 7 (P7) and P28. The incidence of LOH varied significantly according to the treatment day: it was almost exclusively restricted to individuals treated on E13. Furthermore, all the induced LGH was confined to the subarachnoid space dorsal to the rhinal fissure, unilaterally or bilaterally. A part of the nest was connected to the underlying cortical surface of the lateral limbic area, where glia limitans and basal lamina were disrupted. Narrow stripes of disarrangement of cortical neurons underlying the bridges were observed. The P7 LGHs consisted mainly of neurons, some of which were GABA-immunolabeled. and a small number of astrocytes as well as endogenous blood vessels and fibroblasts. LGHs in P28 brains consisted mainly of GFAP-positive astrocyte processes. An additional experiment with double administrations of 5-bromo-2-deoxyuridine (BrdU) and methylmercury on E13 disclosed an abnormally widespread distribution of labeled neurons throughout all cortical layers underlying the LGH in P28 brains. Thus, cerebral LGH would be induced if a developing brain were insulted at the early stage of neurogenesis. accompanied by cortical dysplasia.
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Affiliation(s)
- A Kakita
- Department of Pathology, Brain Research Institute, Niigata University, Japan
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21
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Chapman L, Chan HM. The influence of nutrition on methyl mercury intoxication. ENVIRONMENTAL HEALTH PERSPECTIVES 2000; 108 Suppl 1:29-56. [PMID: 10698722 PMCID: PMC1637774 DOI: 10.1289/ehp.00108s129] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
This article reviews progress in the research of methyl mercury (MeHg) and nutrient interactions during the past two decades. Special emphasis is placed on the following three major areas: a) effects on kinetics, b) effects on toxicity, and c) possible mechanisms. Dietary information is not usually collected in most epidemiologic studies examining of the effects of MeHg exposure. However, inconsistency of the MeHg toxicity observed in different populations is commonly attributed to possible effects of dietary modulation. Even though the mechanisms of interaction have not been totally elucidated, research in nutritional toxicology has provided insights into the understanding of the effects of nutrients on MeHg toxicity. Some of this information can be readily incorporated into the risk assessment of MeHg in the diets of fish-eating populations. It is also clear that there is a need for more studies designed specifically to address the role of nutrition in the metabolism and detoxification of MeHg. It is also important to collect more detailed dietary information in future epidemiologic studies of MeHg exposure.
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Affiliation(s)
- L Chapman
- Center for Indigenous Peoples' Nutrition and the Environment and the School of Dietetics and Human Nutrition, Macdonald Campus at McGill University, Quebec, Canada
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22
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Haykal-Coates N, Shafer TJ, Mundy WR, Barone S. Effects of gestational methylmercury exposure on immunoreactivity of specific isoforms of PKC and enzyme activity during post-natal development of the rat brain. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1998; 109:33-49. [PMID: 9706389 DOI: 10.1016/s0165-3806(98)00039-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Protein kinase C (PKC)-mediated phosphorylation has been implicated in neuronal growth and differentiation [R.S. Turner, R.L. Mazzei, G.J. Raynor, P.R. Girard, J.F. Kuo, Proc. Natl. Acad. Sci. U.S.A., 81 (1984) 3143-3147.]. We examined effects of gestational exposure to the neurotoxicant, methylmercury (CH3Hg), on the developmental profile of immunoreactivity (IR) for alpha, beta, gamma and epsilon PKC isoforms and cytosolic PKC activity. Long-Evans dams were dosed on gestational days (GD)6-15 (p.o.) with 0, 1, or 2 mg kg-1 day-1 CH3Hg dissolved in saline. Pups were sacrificed and perfused with buffered paraformaldehyde on post-natal days (PND) 1, 4, 10, 21, 45 and 85. The brains were sectioned sagittally, stained immunohistochemically, and examined throughout the medial to lateral extent. IR in neuronal cell bodies for PKC isoforms alpha, beta, gamma, and epsilon was densest in the olfactory bulb, hippocampus, shell of the inferior colliculus, pons, cerebral, piriform, and cerebellar cortex, whereas axonal staining was prominent in the brainstem, internal capsule, corpus callosum, anterior commissure, fornix and olfactory tract. In controls, the PKC alpha and epsilon IR was highest on PND1-4, decreased dramatically by PND10, and decreased further by PND21. In the neonate, the regional and cellular distributions of alpha and epsilon IR were similar. The PKC gamma IR was greater at post-weaning ages (PND21-85) with the greatest regional density apparent in the hippocampus, cortex, and cerebellum. Only the highest dose of CH3Hg (2 mg kg-1 day-1; GD6-15) produced a persistent decrease in regional alpha and epsilon, but not beta or gamma IR during the post-natal period. These regional and time-dependent changes in PKC isoforms were complemented by the examination of PKC activity in cortex, olfactory bulb, cerebellum and brainstem. Cytosolic PKC activity increased from PND1 to 10 in cortex, olfactory bulb, and cerebellum. On PND21, PKC activity decreased in the cortex and olfactory bulb, but remained high in the cerebellum. By contrast, PKC activity in the brainstem was highest on PND1 and 4 and decreased dramatically by PND21. CH3Hg (2 mg kg-1 day-1) significantly decreased PKC activity on PND1 and 4 in the cortex. The present results characterize the cellular and regional ontogeny of PKC isoenzymes alpha, beta, gamma and epsilon, and indicate that developmental exposure to CH3Hg can alter the ontogeny of specific isoforms and regional PKC activity.
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Affiliation(s)
- N Haykal-Coates
- National Health Effects and Ecological Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA
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23
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Su M, Wakabayashi K, Kakita A, Ikuta F, Takahashi H. Selective involvement of large motor neurons in the spinal cord of rats treated with methylmercury. J Neurol Sci 1998; 156:12-7. [PMID: 9559981 DOI: 10.1016/s0022-510x(98)00030-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mercury is thought to be a possible epidemiological factor for the pathogenesis of motor neuron disease, since it has been reported that metallic, inorganic and organic mercury causes a syndrome clinically resembling amyotrophic lateral sclerosis. We administered 10 mg/kg/day methylmercury chloride to adult rats for 10 consecutive days. The hind-limbs became flaccid and atrophic, and 14 out of the 34 rats had died by the 18th day after methylmercury treatment began. Light microscopical examination of the large motor neurons in the spinal anterior horn revealed cytoplasmic vacuolation and loss of Nissl substance on the 14th day, and neuronophagia appeared on the 16th day. On the 18th day, the loss of large motor neurons was almost complete, whereas small to medium-sized neurons were preserved. Silver acetate autometallography to detect mercury revealed the selective accumulation of mercury in the large motor neurons. These findings suggest that although a high dose is required, organic mercury can cause the definite loss of large spinal motor neurons in rats.
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Affiliation(s)
- M Su
- Department of Pathology, Brain Research Institute, Niigata University, Japan
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Wakabayashi K, Kakita A, Sakamoto M, Su M, Iwanaga K, Ikuta F. Variability of brain lesions in rats administered methylmercury at various postnatal development phases. Brain Res 1995; 705:267-72. [PMID: 8821758 DOI: 10.1016/0006-8993(95)01208-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The effect of methylmercury chloride (MMC) on the developing rat nervous system was studied by light microscopy. Rats on postnatal day 2 (P2), P15 and P60 were administered 10 mg/kg/day MMC orally for 10 days. In newborn (after P2) rats, there was no abnormal activity or body weight loss. Young (after P15) rats showed weight loss on the 9th day after starting MMC, and subsequently unsteadiness, gait disturbance and paroxysmal convulsions appeared. In adult rats, weight loss began on the 6th day after starting MMC, and the hind-limb crossing phenomenon was induced on the 13th day. Histopathologically, minimal damage was found in the hippocampus and brainstem in newborn rats. In young rats, widespread neuronal degeneration was observed in the cerebral neocortex, CA3 and CA4 regions of the hippocampus, neostriatum, red nucleus, and various brainstem nuclei. In adult rats, neuronal damage was most extensive in the cerebellum and spinal dorsal nerve roots. These findings indicate that neuronal vulnerability to MMC exposure differs depending on the postnatal developmental stage and the brain region in the rat.
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Affiliation(s)
- K Wakabayashi
- Department of Pathology, Brain Research Institute, Niigata University, Japan
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25
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Affiliation(s)
- B H Choi
- Department of Pathology, University of California, Irvine 92717
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Aschner M, Clarkson TW. Mercury 203 distribution in pregnant and nonpregnant rats following systemic infusions with thiol-containing amino acids. TERATOLOGY 1987; 36:321-8. [PMID: 3424221 DOI: 10.1002/tera.1420360308] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Near-term pregnant (gestational day 17) and nonpregnant Long-Evans female rats were continuously infused into the external jugular vein with 0.1 mmole/hour L-cysteine, 0.1 mmole/hour L-leucine, or saline. At 24, 48, and 72 hours, 50 mumole/hour [203Hg]-MeHgCl was administered over 1 hour. Total 203Hg body burden, brain, kidney, liver, and blood 203Hg concentrations were determined at 96 hours by gamma scintillation spectrometry. Despite significantly greater 203Hg whole body retention in the pregnant animals 203Hg concentrations in blood, brain, kidney, and liver were higher in nonpregnant rats. In addition, brain 203Hg concentrations in both pregnant and virgin rats were significantly higher in L-cysteine-treated rats compared with controls. These results suggest that the fetus may act as a "sink" for MeHg, thus decreasing 203Hg concentrations in maternal blood, brain, kidney, and liver. Furthermore, the data indicate that brain uptake of methylmercury in both pregnant and nonpregnant rats is enhanced by chronic L-cysteine infusion, lending support to the hypothesis that methylmercury in the rat may be translocated across the blood-brain barrier by the neutral amino acid carrier transport system.
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Affiliation(s)
- M Aschner
- Environmental Health Sciences Center, School of Medicine and Dentistry, University of Rochester, New York 14642
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