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Rustom NY, Reynolds JN. Developmental exposure to methylmercury alters GAD67 immunoreactivity and morphology of endothelial cells and capillaries of midbrain and hindbrain regions of adult rat offspring. Neurotoxicol Teratol 2024; 101:107320. [PMID: 38199312 DOI: 10.1016/j.ntt.2024.107320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 01/05/2024] [Accepted: 01/07/2024] [Indexed: 01/12/2024]
Abstract
INTRODUCTION Methylmercury (MeHg) is an environmental contaminant that is of particular concern in Northern Arctic Canadian populations. Specifically, organic mercury compounds such as MeHg are potent toxicants that affect multiple bodily systems including the nervous system. Developmental exposure to MeHg is a major concern, as the developing fetus and neonate are thought to be especially vulnerable to the toxic effects of MeHg. The objective of this study was to examine developmental exposure to low doses of MeHg and effects upon the adult central nervous system (CNS). The doses of MeHg chosen were scaled to be proportional to the concentrations of MeHg that have been reported in human maternal blood samples in Northern Arctic Canadian populations. METHOD Offspring were exposed to MeHg maternally where pregnant Sprague Dawley rats were fed cookies that contained MeHg or vehicle (vehicle corn oil; MeHg 0.02 mg/kg/body weight or 2.0 mg/kg/body weight) daily, throughout gestation (21 days) and lactation (21 days). Offspring were not exposed to MeHg after the lactation period and were euthanized on postnatal day 450. Brains were extracted, fixed, frozen, and sectioned for immunohistochemical analysis. A battery of markers of brain structure and function were selected including neuronal GABAergic enzymatic marker glutamic acid decarboxylase-67 (GAD67), apoptotic/necrotic marker cleaved caspase-3 (CC3), catecholamine marker tyrosine hydroxylase (TH), immune inflammatory marker microglia (Cd11b), endothelial cell marker rat endothelial cell antigen-1 (RECA-1), doublecortin (DCX), Bergmann glia (glial fibrillary acidic protein (GFAP)), and general nucleic acid and cellular stains Hoechst, and cresyl violet, respectively. Oxidative stress marker lipofuscin (autofluorescence) was also assessed. Both male and female offspring were included in analysis. Two-way analysis of variance (ANOVA) was utilized where sex and treatment were considered as between-subject factors (p* <0.05). ImageJ was used to assess immunohistochemical results. RESULTS In comparison with controls, adult rat offspring exposed to both doses of MeHg were observed to have (1) increased GAD67 in the cerebellum; (2) decreased lipofuscin in the locus coeruleus; and (3) decreased GAD67 in the anterior CA1 region. Furthermore, in the substantia nigra and periaqueductal gray, adult male offspring consistently had a larger endothelial cell and capillary perimeter in comparison to females. The maternal high dose of MeHg influenced RECA-1 immunoreactivity in both the substantia nigra and periaqueductal gray of adult rat offspring, where the latter neuronal region also showed statistically significant decreases in RECA-1 immunoreactivity at the maternal low dose exposure level. Lastly, males exposed to high doses of MeHg during development exhibited a statistically significant increase in the perimeter of endothelial cells and capillaries (RECA-1) in the cerebellum, in comparison to male controls. CONCLUSION Findings suggest that in utero and early postnatal exposure to MeHg at environmentally relevant doses leads to long-lasting and selective changes in the CNS. Exposure to MeHg at low doses may affect GABAergic homeostasis and vascular integrity of the CNS. Such changes may contribute to neurological disturbances in learning, cognition, and memory that have been reported in epidemiological studies.
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Affiliation(s)
- Nazneen Y Rustom
- Centre for Neuroscience Studies and Department of Biomedical and Molecular Sciences, Queen's University, Botterell Hall, 18 Stuart Street, Kingston, ON K7L 3N6, Canada
| | - James N Reynolds
- Centre for Neuroscience Studies and Department of Biomedical and Molecular Sciences, Queen's University, Botterell Hall, 18 Stuart Street, Kingston, ON K7L 3N6, Canada.
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Ishida K, Takeda K, Takehara Y, Takabayashi T, Miyara M, Sanoh S, Kawai H, Ohta S, Kotake Y. Methylmercury Decreases AMPA Receptor Subunit GluA2 Levels in Cultured Rat Cortical Neurons. Biol Pharm Bull 2023; 46:292-300. [PMID: 36724957 DOI: 10.1248/bpb.b22-00744] [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: 02/03/2023]
Abstract
Methylmercury (MeHg) is a well-known environmental pollutant that has harmful effects on the central nervous systems of humans and animals. The molecular mechanisms of MeHg-induced neurotoxicity at low concentrations are not fully understood. Here, we investigated the effects of low-concentration MeHg on the cell viability, Ca2+ homeostasis, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA2 levels, which determine Ca2+ permeability of AMPA receptors, in rat primary cortical neurons. Exposure of cortical neurons to 100 and 300 nM MeHg for 7 d resulted in a decrease in GluA2 levels, an increase in basal intracellular Ca2+ concentration, increased phosphorylation levels of extracellular signal-regulated kinase (ERK)1/2 and p38, and decreased cell viability. Moreover, glutamate stimulation exacerbated the decrease in cell viability and increased intracellular Ca2+ levels in MeHg-treated neurons compared to control neurons. MeHg-induced neuronal cell death was ameliorated by 1-naphthyl acetyl spermine, a specific antagonist of Ca2+-permeable, GluA2-lacking AMPA receptors. Our findings raise the possibility that decreased neuronal GluA2 levels and the subsequent increase in intracellular Ca2+ concentration may contribute to MeHg-induced neurotoxicity.
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Affiliation(s)
- Keishi Ishida
- Graduate School of Biomedical and Health Sciences, Hiroshima University
| | - Kazuki Takeda
- Graduate School of Biomedical and Health Sciences, Hiroshima University
| | - Yuki Takehara
- Graduate School of Biomedical and Health Sciences, Hiroshima University
| | | | - Masatsugu Miyara
- Graduate School of Biomedical and Health Sciences, Hiroshima University
| | - Seigo Sanoh
- Graduate School of Biomedical and Health Sciences, Hiroshima University.,Wakayama Medical University
| | - Hidehiko Kawai
- Graduate School of Biomedical and Health Sciences, Hiroshima University
| | - Shigeru Ohta
- Graduate School of Biomedical and Health Sciences, Hiroshima University.,Wakayama Medical University
| | - Yaichiro Kotake
- Graduate School of Biomedical and Health Sciences, Hiroshima University
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Ralston NVC. Concomitant selenoenzyme inhibitor exposures as etiologic contributors to disease: Implications for preventative medicine. Arch Biochem Biophys 2023; 733:109469. [PMID: 36423662 DOI: 10.1016/j.abb.2022.109469] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 11/16/2022] [Accepted: 11/16/2022] [Indexed: 11/23/2022]
Abstract
The physiological activities of selenium (Se) occur through enzymes that incorporate selenocysteine (Sec), a rare but important amino acid. The human genome includes 25 genes coding for Sec that employ it to catalyze challenging reactions. Selenoenzymes control thyroid hormones, calcium activities, immune responses, and perform other vital roles, but most are devoted to preventing and reversing oxidative damage. As the most potent intracellular nucleophile (pKa 5.2), Sec is vulnerable to binding by metallic and organic soft electrophiles (E*). These electron poor reactants initially form covalent bonds with nucleophiles such as cysteine (Cys) whose thiol (pKa 8.3) forms adducts which function as suicide substrates for selenoenzymes. These adducts orient E* to interact with Sec and since Se has a higher affinity for E* than sulfur, the E* transfers to Sec and irreversibly inhibits the enzyme's activity. Organic electrophiles have lower Se-binding affinities than metallic E*, but exposure sources are more abundant. Individuals with poor Se status are more vulnerable to the toxic effects of high E* exposures. The relative E*:Se stoichiometries remain undefined, but the aggregate effects of multiple E* exposures are predicted to be additive and possibly synergistic under certain conditions. The potential for the combined Se-binding effects of common pharmaceutical, dietary, or environmental E* require study, but even temporary loss of selenoenzyme activities would accentuate oxidative damage to tissues. As various degenerative diseases are associated with accumulating DNA damage, defining the effects of complementary E* exposures on selenoenzyme activities may enhance the ability of preventative medicine to support healthy aging.
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Affiliation(s)
- Nicholas V C Ralston
- Earth System Science and Policy, University of North Dakota, Grand Forks, ND, USA.
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Costa F, Coelho JP, Baptista J, Martinho F, Pereira E, Pardal MA. Lifelong mercury bioaccumulation in Atlantic horse mackerel (Trachurus trachurus) and the potential risks to human consumption. MARINE POLLUTION BULLETIN 2021; 173:113015. [PMID: 34628345 DOI: 10.1016/j.marpolbul.2021.113015] [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: 03/15/2021] [Revised: 09/21/2021] [Accepted: 09/28/2021] [Indexed: 06/13/2023]
Abstract
Atlantic horse mackerel is one of the most commercially important species in Europe. It can reach a longevity of 30 years, with potential implications in lifespan mercury contamination. This study conducted along the Portuguese coast aimed at evaluating the total Hg content and tissue distribution, to determine the annual mercury bioaccumulation patterns and the associated risk for consumption. The T-Hg accumulation patterns observed followed the order: muscle (0.34) > liver (0.28) > heart (0.19) > gills (0.11) > brain (0.041 mg kg-1). Significant differences between tissues reflect the role of the different tissues in storage and redistribution. Significant relationships observed between age and T-Hg for all tissues highlight the continuous nature of the bioaccumulation process. European food safety guidelines signalled significant risk of consumption in about 30% of the samples. Still, there was an overall low risk from the consumption of this species, which can be further minimized through consumer options to avoid health issues.
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Affiliation(s)
- Filipe Costa
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
| | - João P Coelho
- Department of Biology, CESAM, ECOMARE, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
| | - Joana Baptista
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
| | - Filipe Martinho
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
| | - Eduarda Pereira
- Department of Chemistry, REQUIMTE, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
| | - Miguel A Pardal
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
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Song X, Wu J, Pang J, Wu Y, Huang X. Task specific monolith for magnetic field-reinforced in-tube solid phase microextraction of mercury species in waters prior to online HPLC quantification. JOURNAL OF HAZARDOUS MATERIALS 2021; 411:125141. [PMID: 33485231 DOI: 10.1016/j.jhazmat.2021.125141] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 12/30/2020] [Accepted: 01/11/2021] [Indexed: 06/12/2023]
Abstract
In this study, a novel sorbent based on task specific monolith doped with Fe3O4 was in situ fabricated in capillary and acted as the extraction medium of magnetic field-reinforced in-tube solid phase microextraction (MFR/IT-SPME) to trap and preconcentrate mercury species which were coordinated with dithizone to form chelates. Various characterization technologies evidenced that the obtained monolithic adsorbent presented porous and super paramagnetic properties, and possessed abundant functional groups. Results evidenced that the implementation of magnetic field during extraction stages enhanced the extraction efficiency of studied Hg chelates from 48.5% to 75.3% to 69.9-94.4%. Under the optimized extraction parameters, the introduced MFR/IT-SPME was online coupled to HPLC/DAD to quantify mercury species at ultra-trace levels in various water samples. Limits of detection varied from 0.0067 μg/L to 0.016 μg/L, and the RSDs for precision were below 7.5%. Additionally, related extraction mechanism was deduced and revealed multiple forces co-contributed to the enrichment. The reliability and accuracy of suggested online approach for speciation analysis of mercury was well proved by confirmatory experiments.
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Affiliation(s)
- Xiaochong Song
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, College of the Environment and Ecology, Xiamen University, Xiamen 361005, PR China
| | - Jiangyi Wu
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, College of the Environment and Ecology, Xiamen University, Xiamen 361005, PR China
| | - Jinling Pang
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, College of the Environment and Ecology, Xiamen University, Xiamen 361005, PR China
| | - Yuanfei Wu
- College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, PR China
| | - Xiaojia Huang
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, College of the Environment and Ecology, Xiamen University, Xiamen 361005, PR China.
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Ferrer B, Prince LM, Tinkov AA, Santamaria A, Bowman AB, Aschner M. Chronic exposure to methylmercury disrupts ghrelin actions in C57BL/6J mice. Food Chem Toxicol 2020; 147:111918. [PMID: 33301842 DOI: 10.1016/j.fct.2020.111918] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 12/02/2020] [Accepted: 12/03/2020] [Indexed: 01/06/2023]
Abstract
Methylmercury (MeHg) is a neurotoxic pollutant widely present in the environment. Initial symptoms of MeHg may include loss of body weight. However, the mechanisms by which MeHg induces body weight changes have yet to be fully elucidated. Body weight is regulated by multiple mechanisms. Whereas multiple peripheral peptides lead to food intake cessation, ghrelin is the only recognized peripheral hormone that stimulates food intake. It exerts its action on Neuropeptide Y/Agouti-related peptide neurons in the hypothalamus. To test if MeHg affects ghrelin signaling C57BL/6J mice (males and females) were exposed to 5 ppm MeHg via drinking water during a month. On days 15 and 30 of MeHg exposure ghrelin was administered intraperitoneally and changes in body weight and food intake were recorded. In addition, changes in ghrelin-induced signaling pathways in hypothalamus were also analyzed. Here, we show that in males, MeHg enhanced ghrelin-induced body weight gain by activating the AMP-activated Kinase (AMPK)/Uncoupled protein 2 (UCP2) signaling pathway. In contrast, in females, MeHg inhibited ghrelin-induced mTOR signaling activation and decreased Npy mRNA expression, thus mitigating the ghrelin-induced weight gain. Combined, our novel results demonstrate, for the first time, that MeHg disrupts the physiological functions of ghrelin differently in males and females.
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Affiliation(s)
- Beatriz Ferrer
- Department of Molecular Pharmacology, Neuroscience, and Pediatrics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, 10461, Bronx, NY, USA.
| | - Lisa M Prince
- School of Health Sciences, Purdue University, West Lafayette, IN, USA.
| | - Alexey A Tinkov
- IM Sechenov First Moscow State Medical University, Moscow, Russia; Institute of Cellular and Intracellular Symbiosis, Russian Academy of Sciences, Orenburg, Russia; Yaroslavl State University, Yaroslavl, Russia; Federal Research Centre of Biological Systems and Agro-technologies of the Russian Academy of Sciences, Orenburg, Russia.
| | - Abel Santamaria
- Laboratorio de Aminoácidos Excitadores, Instituto Nacional de Neurología y Neurocirugía, 14269, Mexico City, Mexico.
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN, USA.
| | - Michael Aschner
- Department of Molecular Pharmacology, Neuroscience, and Pediatrics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, 10461, Bronx, NY, USA; IM Sechenov First Moscow State Medical University, Moscow, Russia; Institute of Cellular and Intracellular Symbiosis, Russian Academy of Sciences, Orenburg, Russia.
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7
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Gustin K, Barman M, Stråvik M, Levi M, Englund-Ögge L, Murray F, Jacobsson B, Sandberg AS, Sandin A, Wold AE, Vahter M, Kippler M. Low-level maternal exposure to cadmium, lead, and mercury and birth outcomes in a Swedish prospective birth-cohort. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 265:114986. [PMID: 32585550 DOI: 10.1016/j.envpol.2020.114986] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/26/2020] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
Observational studies have indicated that low-to-moderate exposure to cadmium (Cd), lead (Pb), and mercury (Hg) adversely affects birth anthropometry, but results are inconclusive. The aim of this study was to elucidate potential impact on birth anthropometry of exposure to Cd, Pb, and Hg in pregnant women, and to identify the main dietary sources. In the NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment) birth-cohort in northern Sweden, blood and urine were collected from pregnant women in early third trimester. Cd, Pb and Hg were measured in erythrocytes (n = 584), and Cd also in urine (n = 581), by inductively coupled plasma mass spectrometry. Dietary data were collected through a semi-quantitative food frequency questionnaire administered in mid-third trimester. Birth anthropometry data were extracted from hospital records. In multivariable-adjusted spline regression models, a doubling of maternal erythrocyte Cd (median: 0.29 μg/kg) above the spline knot of 0.50 μg/kg was associated with reduced birth weight (B: -191 g; 95% CI: -315, -68) and length (-0.67 cm; -1.2, -0.14). The association with birth weight remained when the analysis was restricted to never-smokers. Likewise, a doubling of erythrocyte Hg (median 1.5 μg/kg, mainly MeHg) above 1.0 μg/kg, was associated with decreased birth weight (-59 g; -115, -3.0), and length (-0.29 cm; -0.54, -0.047). Maternal Pb (median 11 μg/kg) was unrelated to birth weight and length. Erythrocyte Cd was primarily associated with intake of plant derived foods, Pb with game meat, tea and coffee, and Hg with fish. The results indicated that low-level maternal Cd and Hg exposure were associated with poorer birth anthropometry. Further prospective studies in low-level exposed populations are warranted.
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Affiliation(s)
- Klara Gustin
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Malin Barman
- Food and Nutrition Science, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Mia Stråvik
- Food and Nutrition Science, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Michael Levi
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Linda Englund-Ögge
- Department of Obstetrics and Gynecology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Fiona Murray
- Odontology/Cariology, Umeå University, Umeå, Sweden; Sunderby Research Unit, Region Norrbotten, Luleå, Sweden
| | - Bo Jacobsson
- Department of Obstetrics and Gynecology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Institute of Clinical Sciences, Department of Obstetrics and Gynecology, Sahlgrenska University Hospital, Gothenburg, Sweden; Department of Genetics and Bioinformatics, Domain of Health Data and Digitalisation, Institute of Public Health Oslo, Norway
| | - Ann-Sofie Sandberg
- Food and Nutrition Science, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Anna Sandin
- Department of Clinical Sciences, Unit of Pediatrics, Sunderby Research Unit, Umeå University, Umeå, Sweden
| | - Agnes E Wold
- Institute of Biomedicine, Dept, of Infectious Diseases, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Marie Vahter
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Maria Kippler
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
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Akiyama M, Unoki T, Yoshida E, Ding Y, Yamakawa H, Shinkai Y, Ishii I, Kumagai Y. Repression of mercury accumulation and adverse effects of methylmercury exposure is mediated by cystathionine γ-lyase to produce reactive sulfur species in mouse brain. Toxicol Lett 2020; 330:128-133. [PMID: 32413476 DOI: 10.1016/j.toxlet.2020.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 04/02/2020] [Accepted: 05/07/2020] [Indexed: 01/16/2023]
Abstract
Reactive sulfur species (RSS), such as hydropersulfides and hydropolysulfides with high nucleophilicity, contain mobilized sulfur that readily captures xenobiotic electrophiles, leading to their sulfur adducts. We have previously reported that RSS produced by cystathionine γ-lyase (CSE) captures the electrophilic metal methylmercury (MeHg) to form inert sulfur adducts, which in turn play a critical role in the protection against MeHg-induced motor impairment in mice. However, the mechanism underlying this neuroprotective effect is not fully understood. Here, we addressed this using CSE-knockout mice. The cerebellum of CSE-knockout mice was more susceptible to MeHg than that of wild type mice. Moreover, these CSE-deficient mice exhibited a higher level of mercury accumulation in the brain. However, co-treatment with sodium tetrasulfide, an RSS able to capture MeHg, leading to the formation of its sulfur adducts, blocked the increased accumulation of mercury, motor dysfunction and mortality caused by CSE deficiency. Our findings suggest that capturing MeHg by RSS in association with its sulfur adduct formation is involved in the repression of the brain distribution and deleterious effects of MeHg.
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Affiliation(s)
- Masahiro Akiyama
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Takamitsu Unoki
- Department of Basic Medical Sciences, National Institute for Minamata Disease, Minamata, Kumamoto 867-0008, Japan
| | - Eiko Yoshida
- Department of Environmental Health, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba 278-0022, Japan
| | - Yunjie Ding
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan; Doctoral Program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Hiroto Yamakawa
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan; Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Yasuhiro Shinkai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Isao Ishii
- Laboratory of Health Chemistry, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan
| | - Yoshito Kumagai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
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Ben Bacha A, Norah AO, Al-Osaimi M, Harrath AH, Mansour L, El-Ansary A. The therapeutic and protective effects of bee pollen against prenatal methylmercury induced neurotoxicity in rat pups. Metab Brain Dis 2020; 35:215-224. [PMID: 31625070 DOI: 10.1007/s11011-019-00496-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Accepted: 09/12/2019] [Indexed: 12/14/2022]
Abstract
The current study evaluated the protective and therapeutic potency of bee pollen in ameliorating the toxic effects of methylmercury (MeHg), by measuring certain biochemical parameters related to neurotransmission, neuroinflammation, apoptosis, and glutamate excitotoxicity in the male neonate brain. Healthy, pregnant female rats (N = 40) were randomly divided into 5 groups, each comprising10 male neonates, as follows: (i) neonates delivered by control mothers; (ii) neonates delivered by MeHg-treated mothers who received 0.5 mg/kg BW/day MeHg via drinking water from gestational day 7 till postnatal day 7; (iii) neonates delivered by bee pollen treated mothers who received 200-mg/kg BW bee pollen from postnatal day 0 for 4 weeks; (iv) protective group of neonates delivered by MeHg and bee pollen-treated mothers, who continued to receive bee pollen until day 21 at the same dose, and (v) therapeutic group of neonates delivered by MeHg- treated mothers followed by bee pollen treatment, wherein they received 200-mg/kg BW bee pollen from postnatal day 0 for 4 weeks. Selected biochemical parameters in brain homogenates from each group were measured. MeHg-treated groups exhibited various signs of brain toxicity, such as a marked reduction in neurotransmitters (serotonin (5-HT), nor-adrenalin (NA), dopamine (DA)) and gamma aminobutyric acid (GABA) and elevated levels of interferon gamma (IFN-γ), caspase-3, and glutamate (Glu). Bee pollen effectively reduced the neurotoxic effects of MeHg. Minimal changes in all measured parameters were observed in MeHg-treated animals compared to the control group. Therefore, bee pollen may safely improve neurotransmitter defects, inflammation, apoptosis, and glutamate excitotoxicity.
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Affiliation(s)
- Abir Ben Bacha
- Biochemistry Department, Science College, King Saud University, P.O Box 22452, Riyadh, 11495, Saudi Arabia.
- Laboratory of Plant Biotechnology Applied to Crop Improvement, Faculty of Science of Sfax, University of Sfax, Sfax, Tunisia.
| | - Al-Orf Norah
- Biochemistry Department, Science College, King Saud University, P.O Box 22452, Riyadh, 11495, Saudi Arabia
- The Materials Science Research Institute, King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia
| | - May Al-Osaimi
- Biochemistry Department, Science College, King Saud University, P.O Box 22452, Riyadh, 11495, Saudi Arabia
| | - Abdel Halim Harrath
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Lamjed Mansour
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Afaf El-Ansary
- Central Laboratory, King Saud University, Riyadh, Saudi Arabia
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Cabezas-Sanchez P, Rainieri S, Conlledo N, Barranco A, Sanz-Landaluze J, Camara C, Luque-Garcia JL. Impact of selenium co-administration on methylmercury exposed eleutheroembryos and adult zebrafish (Danio rerio): Changes in bioaccumulation and gene expression. CHEMOSPHERE 2019; 236:124295. [PMID: 31319311 DOI: 10.1016/j.chemosphere.2019.07.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 06/10/2023]
Abstract
Mercury still represents one of the most hazardous threats for the aquatic ecosystem due to its high toxicity, and the fact that it can be easily incorporated into the food chain by accumulation in fish as MeHg. On the other hand, selenium is a micronutrient that is part of different antioxidant enzymes that regulate the cellular redox state, and whose complex interaction with Hg has been extensively studied from a toxicological point of view. In order to evaluate the protective effect of Se(IV) co-administration against MeHg accumulation and toxicity, we have selected an in-vivo model at two developmental stages: zebrafish eleutheroembryos and adult fish. Embryos were exposed during 48 h to MeHg (5 or 25 μg/l) and a concentration of Se (IV) representing a molar ratio close to one (2.5 or 12.5 μg/l), while adult zebrafish were exposed during 72 h to either 25 μg/l of MeHg alone or co-exposed with 12.5 μg/l of Se (IV). A significant decrease in MeHg bioaccumulation factor was observed in eleutheroembryos co-exposed to Se(IV). A time-dependent accumulation of MeHg was observed in all the analyzed organs and tissues of adult fish, which was significantly reduced in the muscular tissue and the intestine by Se(IV) co-administration. However, such protection against MeHg bioaccumulation was not maintained in the brain and liver. The data derived from the gene expression analysis also demonstrated the protective effect of Se(IV) against MeHg-induced oxidative stress and the activation of different defense mechanisms by Se(IV) co-administration.
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Affiliation(s)
- Pablo Cabezas-Sanchez
- Department of Analytical Chemistry, Faculty of Chemistry, Complutense University of Madrid, Ciudad Universitaria, 28040, Madrid, Spain
| | - Sandra Rainieri
- Food Research Division, AZTI, Parque Tecnológico de Bizkaia, Astondo Bidea 609, 48160, Derio, Spain
| | - Nadia Conlledo
- Food Research Division, AZTI, Parque Tecnológico de Bizkaia, Astondo Bidea 609, 48160, Derio, Spain
| | - Alejandro Barranco
- Food Research Division, AZTI, Parque Tecnológico de Bizkaia, Astondo Bidea 609, 48160, Derio, Spain
| | - Jon Sanz-Landaluze
- Department of Analytical Chemistry, Faculty of Chemistry, Complutense University of Madrid, Ciudad Universitaria, 28040, Madrid, Spain
| | - Carmen Camara
- Department of Analytical Chemistry, Faculty of Chemistry, Complutense University of Madrid, Ciudad Universitaria, 28040, Madrid, Spain
| | - Jose L Luque-Garcia
- Department of Analytical Chemistry, Faculty of Chemistry, Complutense University of Madrid, Ciudad Universitaria, 28040, Madrid, Spain.
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11
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Ishihara Y, Itoh K, Oguro A, Chiba Y, Ueno M, Tsuji M, Vogel CFA, Yamazaki T. Neuroprotective activation of astrocytes by methylmercury exposure in the inferior colliculus. Sci Rep 2019; 9:13899. [PMID: 31554907 PMCID: PMC6761145 DOI: 10.1038/s41598-019-50377-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 09/11/2019] [Indexed: 11/17/2022] Open
Abstract
Methylmercury (MeHg) is well known to induce auditory disorders such as dysarthria. When we performed a global analysis on the brains of mice exposed to MeHg by magnetic resonance imaging, an increase in the T1 signal in the inferior colliculus (IC), which is localized in the auditory pathway, was observed. Therefore, the purpose of this study is to examine the pathophysiology and auditory dysfunction induced by MeHg, focusing on the IC. Measurement of the auditory brainstem response revealed increases in latency and decreases in threshold in the IC of mice exposed to MeHg for 4 weeks compared with vehicle mice. Incoordination in MeHg-exposed mice was noted after 6 weeks of exposure, indicating that IC dysfunction occurs earlier than incoordination. There was no change in the number of neurons or microglial activity, while the expression of glial fibrillary acidic protein, a marker for astrocytic activity, was elevated in the IC of MeHg-exposed mice after 4 weeks of exposure, indicating that astrogliosis occurs in the IC. Suppression of astrogliosis by treatment with fluorocitrate exacerbated the latency and threshold in the IC evaluated by the auditory brainstem response. Therefore, astrocytes in the IC are considered to play a protective role in the auditory pathway. Astrocytes exposed to MeHg increased the expression of brain-derived neurotrophic factor in the IC, suggesting that astrocytic brain-derived neurotrophic factor is a potent protectant in the IC. This study showed that astrogliosis in the IC could be an adaptive response to MeHg toxicity. The overall toxicity of MeHg might be determined on the basis of the balance between MeHg-mediated injury to neurons and protective responses from astrocytes.
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Affiliation(s)
- Yasuhiro Ishihara
- Program of Biomedical Science, Graduate School of Integrated Sciences for Life, Hiroshima University, Hiroshima, 739-8521, Japan. .,Center for Health and the Environment, University of California, Davis, CA, 95616, USA.
| | - Kouichi Itoh
- Laboratory for Pharmacotherapy and Experimental Neurology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Kagawa, 769-2193, Japan
| | - Ami Oguro
- Program of Biomedical Science, Graduate School of Integrated Sciences for Life, Hiroshima University, Hiroshima, 739-8521, Japan
| | - Yoichi Chiba
- Department of Pathology and Host Defense, Faculty of Medicine, Kagawa University, Kagawa, 761-0793, Japan
| | - Masaki Ueno
- Department of Pathology and Host Defense, Faculty of Medicine, Kagawa University, Kagawa, 761-0793, Japan
| | - Mayumi Tsuji
- Department of Environmental Health, University of Occupational and Environmental Health, Fukuoka, 807-8555, Japan
| | - Christoph F A Vogel
- Center for Health and the Environment, University of California, Davis, CA, 95616, USA.,Department of Environmental Toxicology, University of California, Davis, CA, 95616, USA
| | - Takeshi Yamazaki
- Program of Life and Environmental Sciences, Graduate School of Integrated Sciences for Life, Hiroshima University, Hiroshima, 739-8521, Japan
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12
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Man Y, Yin R, Cai K, Qin C, Wang J, Yan H, Li M. Primary amino acids affect the distribution of methylmercury rather than inorganic mercury among tissues of two farmed-raised fish species. CHEMOSPHERE 2019; 225:320-328. [PMID: 30884293 DOI: 10.1016/j.chemosphere.2019.03.058] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 02/16/2019] [Accepted: 03/10/2019] [Indexed: 05/25/2023]
Abstract
The distributions of primary amino acids, MeHg and IHg in body tissues of two commonly farm-raised fish species (common carp: Cyprinus carpio; grass carp: Ctenopharyngodon idellus) in Guizhou Province, SW China, were investigated to understand the effects of primary amino acids on MeHg and IHg metabolism in farm-raised fish. The primary amino acids were classified into four groups: (1) essential and polar amino acids; (2) essential and non-polar amino acids; (3) non-essential and polar amino acids; and (4) non-essential and non-polar amino acids. For both fish species, groups (1, 2 and 3) were enriched in muscle and kidney, whereas group (4) was enriched in scale. The two fish species showed low MeHg concentrations (grass carp: 0.5-3.9 ng/g; common carp:1.0-7.4 ng/g) and low MeHg proportions (grass carp: 2-45%; common carp: 6-37%) in their tissues, which are mainly due to the simple food web structures and the fast growth of the farm-raised fish. Positive correlations (r = 0.342 to 0.472; p < 0.01; n = 78) were observed between MeHg and several primary amino acids (cysteine, threonine, phenylalanine, leucine, valine, glutamate serine and tyrosine) in fish tissues, which may be driven by the formation of MeHg-Cys complexes within fish body. However, no significant correlations were observed between IHg and any primary amino acids, indicating the metabolic processes of IHg and MeHg are different. This study advances our understanding that cysteine and its related/derived amino acids may be an important driving force for MeHg distribution and translocation in fish.
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Affiliation(s)
- Yi Man
- State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou Province, China; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou Province, China; University of Chinese Academic of Sciences, Beijing, China
| | - Runsheng Yin
- State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou Province, China.
| | - Kai Cai
- Guizhou Academy of Tobacco Science, Guiyang, Guizhou Province, China
| | - Chongyang Qin
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou Province, China; University of Chinese Academic of Sciences, Beijing, China
| | - Jianxu Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou Province, China
| | - Haiyu Yan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou Province, China.
| | - Miling Li
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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13
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Jia X, Zhao J, Ren H, Wang J, Hong Z, Zhang X. Zwitterion-functionalized polymer microspheres-based solid phase extraction method on-line combined with HPLC–ICP-MS for mercury speciation. Talanta 2019; 196:592-599. [DOI: 10.1016/j.talanta.2019.01.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 12/25/2018] [Accepted: 01/02/2019] [Indexed: 10/27/2022]
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14
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Ferrer B, Peres TV, Dos Santos AA, Bornhorst J, Morcillo P, Gonçalves CL, Aschner M. Methylmercury Affects the Expression of Hypothalamic Neuropeptides That Control Body Weight in C57BL/6J Mice. Toxicol Sci 2019; 163:557-568. [PMID: 29850906 DOI: 10.1093/toxsci/kfy052] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Methylmercury (MeHg) is an environmental pollutant that affects primarily the central nervous system (CNS), causing neurological alterations. An early symptom of MeHg poisoning is the loss of body weight and appetite. Moreover, the CNS has an important role in controlling energy homeostasis. It is known that in the hypothalamus nutrient and hormonal signals converge to orchestrate control of body weight and food intake. In this study, we investigated if MeHg is able to induce changes in the expression of key hypothalamic neuropeptides that regulate energy homeostasis. Thus, hypothalamic neuronal mouse cell line GT 1-7 was treated with MeHg at different concentrations (0, 0.5, 1, and 5 µM). MeHg induced the expression of the anorexigenic neuropeptide pro-omiomelanocortin (Pomc) and the orexigenic peptide Agouti-related peptide (Agrp) in a concentration-dependent manner, suggesting deregulation of mechanisms that control body weight. To confirm these in vitro observations, 8-week-old C57BL/6J mice (males and females) were exposed to MeHg in drinking water, modeling the most prevalent exposure route to this metal. After 30-day exposure, no changes in body weight were detected. However, MeHg treated males showed a significant decrease in fat depots. Moreover, MeHg affected the expression of hypothalamic neuropeptides that control food intake and body weight in a gender- and dose-dependent manner. Thus, MeHg increases Pomc mRNA only in males in a dose-dependent way, and it does not have effects on the expression of Agrp mRNA. The present study shows, for first time, that MeHg is able to induce changes in hypothalamic neuropeptides that regulate energy homeostasis, favoring an anorexigenic/catabolic profile.
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Affiliation(s)
- Beatriz Ferrer
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Tanara Vieira Peres
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
| | | | - Julia Bornhorst
- Department of Food Chemistry, Institute of Nutritional Science, University of Potsdam, 14558 Nuthetal, Germany
| | - Patricia Morcillo
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Cinara Ludvig Gonçalves
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
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15
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Ralston NV. Effects of soft electrophiles on selenium physiology. Free Radic Biol Med 2018; 127:134-144. [PMID: 30053507 DOI: 10.1016/j.freeradbiomed.2018.07.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 07/18/2018] [Accepted: 07/23/2018] [Indexed: 12/12/2022]
Abstract
This review examines the effects of neurotoxic electrophiles on selenium (Se) metabolism. Selenium-dependent enzymes depend on the unique and elite functions of selenocysteine (Sec), the 21st proteinogenic amino acid, to perform their biochemical roles. Humans possess 25 selenoprotein genes, ~ half of which are enzymes (selenoenzymes) required for preventing, controlling, or reversing oxidative damage, while others participate in regulating calcium metabolism, thyroid hormone status, protein folding, cytoskeletal structure, Sec synthesis and Se transport. While selenoproteins are expressed in tissue dependent distributions and levels in all cells of all vertebrates, they are particularly important in brain development, health, and functions. As the most potent intracellular nucleophile, Sec is subject to binding by mercury (Hg) and other electron poor soft neurotoxic electrophiles. Epidemiological and environmental studies of the effects of exposures to methyl-Hg (CH3Hg+), elemental Hg (Hg°), and/or other metallic/organic neurotoxic soft electrophiles need to consider the concomitant effects of all members of this class of toxicants in relation to the Se status of their study populations. The contributions of individual electrophiles' discrete and cooperative rates of Se sequestration need to be evaluated in relation to tissue Se reserves of the exposed populations to identify sensitive subgroups which may be at accentuated risk due to poor Se status. Additional study is required to examine possibilities of inherited, acquired, or degenerative neurological disorders of Se homeostasis that may influence vulnerability to soft electrophile exposures. Investigations of soft electrophile toxicity will be enhanced by considering the concomitant effects of combined exposures on tissue Se-availability in relation to pathological consequences during fetal development or in relation to etiologies of neurological disorders and neurodegenerative diseases. Since selenoenzymes are molecular "targets" of soft electrophiles, concomitant evaluation of aggregate exposures to these toxicants in relation to dietary Se intakes will assist regulatory agencies in their goals of improving and protecting public health.
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Affiliation(s)
- Nicholas Vc Ralston
- Earth System Science and Policy, University of North Dakota, Grand Forks, ND, USA.
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16
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Ke T, Gonçalves FM, Gonçalves CL, Dos Santos AA, Rocha JBT, Farina M, Skalny A, Tsatsakis A, Bowman AB, Aschner M. Post-translational modifications in MeHg-induced neurotoxicity. Biochim Biophys Acta Mol Basis Dis 2018; 1865:2068-2081. [PMID: 30385410 DOI: 10.1016/j.bbadis.2018.10.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 10/16/2018] [Accepted: 10/19/2018] [Indexed: 12/29/2022]
Abstract
Mercury (Hg) exposure remains a major public health concern due to its widespread distribution in the environment. Organic mercurials, such as MeHg, have been extensively investigated especially because of their congenital effects. In this context, studies on the molecular mechanism of MeHg-induced neurotoxicity are pivotal to the understanding of its toxic effects and the development of preventive measures. Post-translational modifications (PTMs) of proteins, such as phosphorylation, ubiquitination, and acetylation are essential for the proper function of proteins and play important roles in the regulation of cellular homeostasis. The rapid and transient nature of many PTMs allows efficient signal transduction in response to stress. This review summarizes the current knowledge of PTMs in MeHg-induced neurotoxicity, including the most commonly PTMs, as well as PTMs induced by oxidative stress and PTMs of antioxidant proteins. Though PTMs represent an important molecular mechanism for maintaining cellular homeostasis and are involved in the neurotoxic effects of MeHg, we are far from understanding the complete picture on their role, and further research is warranted to increase our knowledge of PTMs in MeHg-induced neurotoxicity.
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Affiliation(s)
- Tao Ke
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States.
| | - Filipe Marques Gonçalves
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | - Cinara Ludvig Gonçalves
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | | | - João B T Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97105900 Santa Maria, RS, Brazil
| | - Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, 88040900 Florianópolis, SC, Brazil
| | - Anatoly Skalny
- Yaroslavl State University, Sovetskaya St., 14, Yaroslavl 150000, Russia; Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklaya St., 6, Moscow 105064, Russia; Orenburg State University, Pobedy Ave., 13, Orenburg 460352, Russia
| | - Aristidis Tsatsakis
- Center of Toxicology Science & Research, Medical School, University of Crete, Heraklion, Crete, Greece
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN, United States.
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States.
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17
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Antunes Dos Santos A, Ferrer B, Marques Gonçalves F, Tsatsakis AM, Renieri EA, Skalny AV, Farina M, Rocha JBT, Aschner M. Oxidative Stress in Methylmercury-Induced Cell Toxicity. TOXICS 2018; 6:toxics6030047. [PMID: 30096882 PMCID: PMC6161175 DOI: 10.3390/toxics6030047] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 08/03/2018] [Accepted: 08/07/2018] [Indexed: 02/06/2023]
Abstract
Methylmercury (MeHg) is a hazardous environmental pollutant, which elicits significant toxicity in humans. The accumulation of MeHg through the daily consumption of large predatory fish poses potential health risks, and the central nervous system (CNS) is the primary target of toxicity. Despite well-described neurobehavioral effects (i.e., motor impairment), the mechanisms of MeHg-induced toxicity are not completely understood. However, several lines of evidence point out the oxidative stress as an important molecular mechanism in MeHg-induced intoxication. Indeed, MeHg is a soft electrophile that preferentially interacts with nucleophilic groups (mainly thiols and selenols) from proteins and low-molecular-weight molecules. Such interaction contributes to the occurrence of oxidative stress, which can produce damage by several interacting mechanisms, impairing the function of various molecules (i.e., proteins, lipids, and nucleic acids), potentially resulting in modulation of different cellular signal transduction pathways. This review summarizes the general aspects regarding the interaction between MeHg with regulators of the antioxidant response system that are rich in thiol and selenol groups such as glutathione (GSH), and the selenoenzymes thioredoxin reductase (TrxR) and glutathione peroxidase (Gpx). A particular attention is directed towards the role of the PI3K/Akt signaling pathway and the nuclear transcription factor NF-E2-related factor 2 (Nrf2) in MeHg-induced redox imbalance.
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Affiliation(s)
| | - Beatriz Ferrer
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Filipe Marques Gonçalves
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Aristides M Tsatsakis
- Laboratory of Toxicology, Medical School, University of Crete, 71003 Heraklion, Greece.
| | - Elisavet A Renieri
- Laboratory of Toxicology, Medical School, University of Crete, 71003 Heraklion, Greece.
| | - Anatoly V Skalny
- Department of Medical Elementology, Peoples' Friendship University of Russia (RUDN University), Moscow 150000, Russia.
- Laboratory of Biotechnology and Applied Bioelementology, Yaroslavl State University, Yaroslavl 150014, Russia.
- All-Russian Research Institute of Medicinal and Aromatic Plants (VILAR), Moscow 150000, Russia.
| | - Marcelo Farina
- Department of Biochemistry, Federal University of Santa Catarina, Florianopolis 88040-900, Santa Catarina, Brazil.
| | - João B T Rocha
- Department of Biochemistry, Federal University of Santa Maria, Santa Maria 97105-900, Rio Grande do Sul, Brazil.
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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18
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Zhang Y, Miró M, Kolev SD. A novel on-line organic mercury digestion method combined with atomic fluorescence spectrometry for automatic mercury speciation. Talanta 2018; 189:220-224. [PMID: 30086909 DOI: 10.1016/j.talanta.2018.06.083] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 06/26/2018] [Indexed: 11/30/2022]
Abstract
A novel on-line digestion method was developed based on organic mercury (Org-Hg) oxidation at ambient temperature using potassium permanganate in the presence of sulphide. The digestion of Org-Hg was instantaneous and quantitative. Consequently, a simple mercury speciation method was developed to differentiate inorganic mercury (In-Hg) and Org-Hg in water samples with a sequential injection analytical system in conjunction with atomic fluorescence spectrometric detection by using Hg2+ as the sole standard for calibration. In-Hg was determined after acidification and decomposition of the organic matter in the sample matrix with KMnO4, while total mercury (T-Hg) was determined after online Org-Hg digestion, and Org-Hg was calculated as the difference between T-Hg and In-Hg. The operational parameters were optimized and the possible role that sulphide played in the digestion of Org-Hg was discussed. A detection limit (3σ criterion) of 3 ng L-1 Hg was achieved, which is far below the guideline value of Hg in drinking water set by WHO, viz., 1 μg L-1. The method was applied to the analysis of lake water samples for the determination of In-Hg and Org-Hg. Relative recoveries of 94-97% for In-Hg and 93.5-94.5% for T-Hg with relative standard deviations of 1.1-3.1% were obtained in real samples spiked with 100 ng L-1 Hg2+ and 100 ng L-1 Org-Hg, respectively, indicating the feasibility of the automatic method for the determination of Hg species at the low ng L-1 level.
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Affiliation(s)
- Yanlin Zhang
- Centre for Aquatic Pollution Identification and Management (CAPIM), School of Chemistry, The University of Melbourne, Victoria 3010, Australia
| | - Manuel Miró
- FI-TRACE group, Department of Chemistry, Faculty of Science, University of the Balearic Islands, Carretera de Valldemossa km 7.5, E-07122 Palma de Mallorca, Spain.
| | - Spas D Kolev
- Centre for Aquatic Pollution Identification and Management (CAPIM), School of Chemistry, The University of Melbourne, Victoria 3010, Australia.
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Bjørklund G, Dadar M, Mutter J, Aaseth J. The toxicology of mercury: Current research and emerging trends. ENVIRONMENTAL RESEARCH 2017; 159:545-554. [PMID: 28889024 DOI: 10.1016/j.envres.2017.08.051] [Citation(s) in RCA: 237] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 08/27/2017] [Accepted: 08/30/2017] [Indexed: 05/16/2023]
Abstract
Mercury (Hg) is a persistent bio-accumulative toxic metal with unique physicochemical properties of public health concern since their natural and anthropogenic diffusions still induce high risk to human and environmental health. The goal of this review was to analyze scientific literature evaluating the role of global concerns over Hg exposure due to human exposure to ingestion of contaminated seafood (methyl-Hg) as well as elemental Hg levels of dental amalgam fillings (metallic Hg), vaccines (ethyl-Hg) and contaminated water and air (Hg chloride). Mercury has been recognized as a neurotoxicant as well as immunotoxic and designated by the World Health Organization as one of the ten most dangerous chemicals to public health. It has been shown that the half-life of inorganic Hg in human brains is several years to several decades. Mercury occurs in the environment under different chemical forms as elemental Hg (metallic), inorganic and organic Hg. Despite the raising understanding of the Hg toxicokinetics, there is still fully justified to further explore the emerging theories about its bioavailability and adverse effects in humans. In this review, we describe current research and emerging trends in Hg toxicity with the purpose of providing up-to-date information for a better understanding of the kinetics of this metal, presenting comprehensive knowledge on published data analyzing its metabolism, interaction with other metals, distribution, internal doses and targets, and reservoir organs.
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Affiliation(s)
- Geir Bjørklund
- Council for Nutritional and Environmental Medicine, Toften 24, 8610 Mo i Rana, Norway.
| | - Maryam Dadar
- Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
| | | | - Jan Aaseth
- Innlandet Hospital Trust and Inland Norway University of Applied Sciences, Elverum, Norway
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20
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Uchikawa T, Kanno T, Maruyama I, Mori N, Yasutake A, Ishii Y, Yamada H. Demethylation of methylmercury and the enhanced production of formaldehyde in mouse liver. J Toxicol Sci 2017; 41:479-87. [PMID: 27432234 DOI: 10.2131/jts.41.479] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Methylmercury (MeHg) is gradually changed to inorganic Hg after demethylation in animal tissues, and a selective quantification of inorganic Hg in the tissues is necessary to detect the reaction. We detected inorganic Hg formation in liver and kidney of mouse as early as 24 hr after MeHg injection. As an example of biological demethylation, the cytochrome P450 (P450)-mediated N-demethylation of drugs has been well documented, and formaldehyde was detected as a reaction product. Here we incubated mouse liver homogenate with added MeHg and observed a dose-dependent production of formaldehyde, as well as inorganic Hg formation. Since the amount of formaldehyde was approx. 500 times higher than that of the inorganic Hg that formed, the formaldehyde production would be stimulated by inorganic Hg formed from MeHg. We observed that inorganic Hg caused formaldehyde production, and it was enhanced by L-methionine and sarcosine. Thus, some biomolecules with S-methyl and N-methyl groups may function as methyl donors in the reaction. Using subcellular fractions of mouse liver, we observed that microsomal P450 did not participate in the demethylation of MeHg, but the greatest activity was located in the mitochondria-rich fraction. The addition of superoxide anion in the reaction mixture significantly enhanced the formaldehyde production, whereas Mn-superoxide dismutase depressed the reaction. Our present findings demonstrated that inorganic Hg formed by MeHg demethylation in mouse liver stimulated the endogenous formaldehyde production, and we observed that MeHg demethylation could be estimated by a formaldehyde analysis. Our results also suggested that superoxide anion is involved in the reaction.
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Affiliation(s)
- Takuya Uchikawa
- Graduate School of Pharmaceutical Sciences, Kyushu University
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21
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Bridges K, Venables B, Roberts A. Effects of dietary methylmercury on the dopaminergic system of adult fathead minnows and their offspring. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2017; 36:1077-1084. [PMID: 27677528 DOI: 10.1002/etc.3630] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Revised: 09/04/2016] [Accepted: 09/27/2016] [Indexed: 06/06/2023]
Abstract
Mercury (Hg) is a ubiquitous environmental contaminant and potent neurotoxin, which may be transformed by bacteria in aquatic ecosystems to methylmercury (MeHg), an organic form which bioaccumulates and biomagnifies. Consequently, long-lived organisms at the top of the food web are at risk of dietary MeHg exposure, which can be actively transferred from mother to offspring. Exposure during neurodevelopment can lead to serious, irreversible neurological dysfunction, associated with a variety of cognitive and motor abnormalities. At low dietary concentrations, MeHg exposure has been associated with deficits in attention and hyperactivity in multiple species. Pathways associated with cognitive function and motor activity are primarily associated with the dopaminergic system. The present study used a model fish species, Pimephales promelas, to examine the effects of MeHg exposure on dopamine concentrations and monoamine oxidase activity in embryos and adult brains. Adult fatheads were exposed for 30 d to either a control or a treated diet (0.72 ppm Hg). Embryonic and larval exposures were a result of maternal transfer of dietary MeHg. The authors confirmed hyperactive behaviors in embryos and detected significant changes in embryonic dopamine concentrations. Similar effects on dopamine concentrations were seen in the telencephalon of adult brains. Exposure to MeHg also corresponded with a significant decrease in monoamine oxidase activity in both embryos and brain tissue. Collectively, these results suggest that current exposure scenarios in North America are sufficient to induce alterations to this highly conserved neurochemical pathway in offspring, which may have adverse effects on fish behavior and cognition. Environ Toxicol Chem 2017;36:1077-1084. © 2016 SETAC.
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Affiliation(s)
- Kristin Bridges
- Department of Biological Sciences and Institute of Applied Sciences, University of North Texas, Denton, Texas, USA
| | - Barney Venables
- Department of Biological Sciences and Institute of Applied Sciences, University of North Texas, Denton, Texas, USA
| | - Aaron Roberts
- Department of Biological Sciences and Institute of Applied Sciences, University of North Texas, Denton, Texas, USA
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22
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Farina M, Aschner M. Methylmercury-Induced Neurotoxicity: Focus on Pro-oxidative Events and Related Consequences. ADVANCES IN NEUROBIOLOGY 2017; 18:267-286. [DOI: 10.1007/978-3-319-60189-2_13] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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23
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Antunes Dos Santos A, Appel Hort M, Culbreth M, López-Granero C, Farina M, Rocha JBT, Aschner M. Methylmercury and brain development: A review of recent literature. J Trace Elem Med Biol 2016; 38:99-107. [PMID: 26987277 PMCID: PMC5011031 DOI: 10.1016/j.jtemb.2016.03.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 03/02/2016] [Indexed: 02/02/2023]
Abstract
Methylmercury (MeHg) is a potent environmental pollutant, which elicits significant toxicity in humans. The central nervous system (CNS) is the primary target of toxicity, and is particularly vulnerable during development. Maternal exposure to MeHg via consumption of fish and seafood can have irreversible effects on the neurobehavioral development of children, even in the absence of symptoms in the mother. It is well documented that developmental MeHg exposure may lead to neurological alterations, including cognitive and motor dysfunction. The neurotoxic effects of MeHg on the developing brain have been extensively studied. The mechanism of toxicity, however, is not fully understood. No single process can explain the multitude of effects observed in MeHg-induced neurotoxicity. This review summarizes the most current knowledge on the effects of MeHg during nervous system development considering both, in vitro and in vivo experimental models. Considerable attention was directed towards the role of glutamate and calcium dyshomeostasis, mitochondrial dysfunction, as well as the effects of MeHg on cytoskeletal components/regulators.
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Affiliation(s)
| | - Mariana Appel Hort
- Institute of Biological Sciences, Federal University of Rio Grande, Campus Carreiros, Rio Grande do Sul, Brazil
| | - Megan Culbreth
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Caridad López-Granero
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Marcelo Farina
- Department of Biochemistry, Federal University of Santa Catarina, Florianopolis, Santa Catarina, Brazil
| | - Joao B T Rocha
- Department of Biochemistry, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA.
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Puga S, Pereira P, Pinto-Ribeiro F, O'Driscoll NJ, Mann E, Barata M, Pousão-Ferreira P, Canário J, Almeida A, Pacheco M. Unveiling the neurotoxicity of methylmercury in fish (Diplodus sargus) through a regional morphometric analysis of brain and swimming behavior assessment. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2016; 180:320-333. [PMID: 27780124 DOI: 10.1016/j.aquatox.2016.10.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 10/11/2016] [Accepted: 10/14/2016] [Indexed: 06/06/2023]
Abstract
The current study aims to shed light on the neurotoxicity of MeHg in fish (white seabream - Diplodus sargus) by the combined assessment of: (i) MeHg toxicokinetics in the brain, (ii) brain morphometry (volume and number of neurons plus glial cells in specific brain regions) and (iii) fish swimming behavior (endpoints associated with the motor performance and the fear/anxiety-like status). Fish were surveyed for all the components after 7 (E7) and 14 (E14) days of dietary exposure to MeHg (8.7μgg-1), as well as after a post-exposure period of 28days (PE28). MeHg was accumulated in the brain of D. sargus after a short time (E7) and reached a maximum at the end of the exposure period (E14), suggesting an efficient transport of this toxicant into fish brain. Divalent inorganic Hg was also detected in fish brain along the experiment (indicating demethylation reactions), although levels were 100-200 times lower than MeHg, which pinpoints the organic counterpart as the great liable for the recorded effects. In this regard, a decreased number of cells in medial pallium and optic tectum, as well as an increased hypothalamic volume, occurred at E7. Such morphometric alterations were followed by an impairment of fish motor condition as evidenced by a decrease in the total swimming time, while the fear/anxiety-like status was not altered. Moreover, at E14 fish swam a greater distance, although no morphometric alterations were found in any of the brain areas, probably due to compensatory mechanisms. Additionally, although MeHg decreased almost two-fold in the brain during post-exposure, the levels were still high and led to a loss of cells in the optic tectum at PE28. This is an interesting result that highlights the optic tectum as particularly vulnerable to MeHg exposure in fish. Despite the morphometric alterations reported in the optic tectum at PE28, no significant changes were found in fish behavior. Globally, the effects of MeHg followed a multiphasic profile, where homeostatic mechanisms prevented circumstantially morphometric alterations in the brain and behavioral shifts. Although it has become clear the complexity of matching brain morphometric changes and behavioral shifts, motor-related alterations induced by MeHg seem to depend on a combination of disruptions in different brain regions.
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Affiliation(s)
- Sónia Puga
- Life and Health Sciences Research Institute (ICVS), School of Medicine, Campus of Gualtar, University of Minho, 4750-057 Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Patrícia Pereira
- Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
| | - Filipa Pinto-Ribeiro
- Life and Health Sciences Research Institute (ICVS), School of Medicine, Campus of Gualtar, University of Minho, 4750-057 Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Nelson J O'Driscoll
- Department of Earth and Environmental Science, Center for Analytical Research on the Environment, K.C. Irving Center, Acadia University, Wolfville, Nova Scotia, Canada
| | - Erin Mann
- Department of Earth and Environmental Science, Center for Analytical Research on the Environment, K.C. Irving Center, Acadia University, Wolfville, Nova Scotia, Canada
| | - Marisa Barata
- IPMA - Aquaculture Research Station, 8700-005 Olhão, Portugal
| | | | - João Canário
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Armando Almeida
- Life and Health Sciences Research Institute (ICVS), School of Medicine, Campus of Gualtar, University of Minho, 4750-057 Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Mário Pacheco
- Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal
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Affiliation(s)
- Eva M. Krupp
- University of Aberdeen; Chemistry Department; Meston Walk Aberdeen AB24 3UE UK
| | - Zuzana Gajdosechova
- University of Aberdeen; Chemistry Department; Meston Walk Aberdeen AB24 3UE UK
| | - Tanja Schwerdtle
- University of Potsdam, Institute of Nutritional Science; Department of Food Chemistry; Arthur-Scheunert-Allee 114-116 14558 Nuthetal Germany
| | - Hanna Lohren
- University of Potsdam, Institute of Nutritional Science; Department of Food Chemistry; Arthur-Scheunert-Allee 114-116 14558 Nuthetal Germany
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Arantes LP, Peres TV, Chen P, Caito S, Aschner M, Soares FAA. Guarana ( Paullinia cupana Mart.) attenuates methylmercury-induced toxicity in Caenorhabditis elegans. Toxicol Res (Camb) 2016; 5:1629-1638. [PMID: 28316775 DOI: 10.1039/c6tx00161k] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The influence of routine guarana (Paullinia cupana) consumption on apparent tolerance to mercury intoxication has been proposed. The present study investigated this hypothesis in Caenorhabditis elegans, a suitable experimental model for studies in toxicology. Wild type (WT) and skn-1 (ok2315) worm strains were pretreated with guarana ethanolic extract (GEE) from larvae 1 (L1) to L4 stage and then exposed for 6 hours to methylmercury (MeHg). The analyses included evaluation of GEE's effects on lethality, developmental delay, feeding, locomotion, gene expression (sod-3, gst-4, sir-2.1, hsf-1, snn-1, mtl-1, mtl-2, aat-1, aat-2 and aat-3) and antioxidant activity. GEE pre-treatment had no aberrant effects on WT worms exposed to MeHg, and protected skn-1 (ok2315) worms, which are more susceptible to environmental stresses. Protective effects of GEE might be dependent on modulation of genes other than those directly involved in antioxidant activity. GEE increased the expression of genes involved in metal transport (aat-2), metal detoxification (mtl-1 and mtl-2) and antioxidant responses (sir-2.1 and sod-3). Thus, routine consumption of guarana might be beneficial in protecting against MeHg-induced toxicity.
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Affiliation(s)
- Leticia Priscilla Arantes
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Tanara Vieira Peres
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, United States
| | - Pam Chen
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, United States
| | - Samuel Caito
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, United States
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, United States
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Mechanisms involved in the transport of mercuric ions in target tissues. Arch Toxicol 2016; 91:63-81. [PMID: 27422290 DOI: 10.1007/s00204-016-1803-y] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 07/07/2016] [Indexed: 01/16/2023]
Abstract
Mercury exists in the environment in various forms, all of which pose a risk to human health. Despite guidelines regulating the industrial release of mercury into the environment, humans continue to be exposed regularly to various forms of this metal via inhalation or ingestion. Following exposure, mercuric ions are taken up by and accumulate in numerous organs, including brain, intestine, kidney, liver, and placenta. In order to understand the toxicological effects of exposure to mercury, a thorough understanding of the mechanisms that facilitate entry of mercuric ions into target cells must first be obtained. A number of mechanisms for the transport of mercuric ions into target cells and organs have been proposed in recent years. However, the ability of these mechanisms to transport mercuric ions and the regulatory features of these carriers have not been characterized completely. The purpose of this review is to summarize the current findings related to the mechanisms that may be involved in the transport of inorganic and organic forms of mercury in target tissues and organs. This review will describe mechanisms known to be involved in the transport of mercury and will also propose additional mechanisms that may potentially be involved in the transport of mercuric ions into target cells.
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Abstract
SIGNIFICANCE Mitochondria are structurally and biochemically diverse, even within a single type of cell. Protein complexes localized to the inner mitochondrial membrane synthesize ATP by coupling electron transport and oxidative phosphorylation. The organelles produce reactive oxygen species (ROS) from mitochondrial oxygen and ROS can, in turn, alter the function and expression of proteins used for aerobic respiration by post-translational and transcriptional regulation. RECENT ADVANCES New interest is emerging not only into the roles of mitochondria in disease development and progression but also as a target for environmental toxicants. CRITICAL ISSUES Dysregulation of respiration has been linked to cell death and is a major contributor to acute neuronal trauma, peripheral diseases, as well as chronic neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. FUTURE DIRECTIONS Here, we discuss the mechanisms underlying the sensitivity of the mitochondrial respiratory complexes to redox modulation, as well as examine the effects of environmental contaminants that have well-characterized mitochondrial toxicity. The contaminants discussed in this review are some of the most prevalent and potent environmental contaminants that have been linked to neurological dysfunction, altered cellular respiration, and oxidation.
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Affiliation(s)
- Samuel W Caito
- Department of Molecular Pharmacology, Albert Einstein College of Medicine , Bronx, New York
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine , Bronx, New York
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Takemoto T, Ishihara Y, Ishida A, Yamazaki T. Neuroprotection elicited by nerve growth factor and brain-derived neurotrophic factor released from astrocytes in response to methylmercury. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2015; 40:199-205. [PMID: 26143513 DOI: 10.1016/j.etap.2015.06.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 06/05/2015] [Accepted: 06/06/2015] [Indexed: 06/04/2023]
Abstract
The protective roles of astrocytes in neurotoxicity induced by environmental chemicals, such as methylmercury (MeHg), are largely unknown. We found that conditioned medium of MeHg-treated astrocytes (MCM) attenuated neuronal cell death induced by MeHg, suggesting that astrocytes-released factors can protect neuronal cells. The increased expression of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) was observed in MeHg-treated astrocytes. NGF and BDNF were detected in culture media as homodimers, which are able to bind specific tyrosine kinase receptors, tropomyosin related kinase (Trk) A and TrkB, respectively. The TrkA antagonist and TrkB antagonist abolished the protective effects of MCM in neuronal cell death induced by MeHg. Taken together, astrocytes synthesize and release NGF and BDNF in response to MeHg to protect neurons from MeHg toxicity. This study is considered to show a novel defense mechanism against MeHg-induced neurotoxicity.
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Affiliation(s)
- Takuya Takemoto
- Laboratory of Molecular Brain Science, Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan
| | - Yasuhiro Ishihara
- Laboratory of Molecular Brain Science, Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan.
| | - Atsuhiko Ishida
- Laboratory of Molecular Brain Science, Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan
| | - Takeshi Yamazaki
- Laboratory of Molecular Brain Science, Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan
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Protective actions of 17β-estradiol and progesterone on oxidative neuronal injury induced by organometallic compounds. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2015:343706. [PMID: 25815107 PMCID: PMC4359856 DOI: 10.1155/2015/343706] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Accepted: 02/06/2015] [Indexed: 01/10/2023]
Abstract
Steroid hormones synthesized in and secreted from peripheral endocrine glands pass through the blood-brain barrier and play a role in the central nervous system. In addition, the brain possesses an inherent endocrine system and synthesizes steroid hormones known as neurosteroids. Increasing evidence shows that neuroactive steroids protect the central nervous system from various harmful stimuli. Reports show that the neuroprotective actions of steroid hormones attenuate oxidative stress. In this review, we summarize the antioxidative effects of neuroactive steroids, especially 17β-estradiol and progesterone, on neuronal injury in the central nervous system under various pathological conditions, and then describe our recent findings concerning the neuroprotective actions of 17β-estradiol and progesterone on oxidative neuronal injury induced by organometallic compounds, tributyltin, and methylmercury.
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Lohren H, Bornhorst J, Galla HJ, Schwerdtle T. The blood–cerebrospinal fluid barrier – first evidence for an active transport of organic mercury compounds out of the brain. Metallomics 2015; 7:1420-30. [DOI: 10.1039/c5mt00171d] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hg strongly transfers across the blood–CSF barrier towards the blood side after incubation with organic Hg compounds.
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Affiliation(s)
- Hanna Lohren
- Department of Food Chemistry
- Institute of Nutritional Science
- University of Potsdam
- 14558 Nuthetal, Germany
| | - Julia Bornhorst
- Department of Food Chemistry
- Institute of Nutritional Science
- University of Potsdam
- 14558 Nuthetal, Germany
| | | | - Tanja Schwerdtle
- Department of Food Chemistry
- Institute of Nutritional Science
- University of Potsdam
- 14558 Nuthetal, Germany
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32
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Osuna CE, Grandjean P, Weihe P, El-Fawal HAN. Autoantibodies associated with prenatal and childhood exposure to environmental chemicals in Faroese children. Toxicol Sci 2014; 142:158-66. [PMID: 25124724 DOI: 10.1093/toxsci/kfu163] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Methylmercury, polychlorinated biphenyls (PCBs), and perfluorinated compounds (PFCs) are ubiquitous and persistent environmental chemicals with known or suspected toxic effects on the nervous system and the immune system. Animal studies have shown that tissue damage can elicit production of autoantibodies. However, it is not known if autoantibodies similarly will be generated and detectable in humans following toxicant exposures. Therefore, we conducted a pilot study to investigate if autoantibodies specific for neural and non-neural antigens could be detected in children at age 7 years who have been exposed to environmental chemicals. Both prenatal and age-7 exposures to mercury, PCBs, and PFCs were measured in 38 children in the Faroe Islands who were exposed to widely different levels of these chemicals due to their seafood-based diet. Concentrations of IgM and IgG autoantibodies specific to both neural (neurofilaments, cholineacetyltransferase, astrocyte glial fibrillary acidic protein, and myelin basic protein) and non-neural (actin, desmin, and keratin) antigens were measured and the associations of these autoantibody concentrations with chemical exposures were assessed using linear regression. Age-7 blood-mercury concentrations were positively associated with titers of multiple neural- and non-neural-specific antibodies, mostly of the IgM isotype. Additionally, prenatal blood-mercury and -PCBs were negatively associated with anti-keratin IgG and prenatal PFOS was negatively associated with anti-actin IgG. These exploratory findings demonstrate that autoantibodies can be detected in the peripheral blood following exposure to environmental chemicals. The unexpected association of exposures with antibodies specific for non-neural antigens suggests that these chemicals may have toxicities that have not yet been recognized.
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Affiliation(s)
- Christa E Osuna
- Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02215 Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
| | - Philippe Grandjean
- Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02215 Department of Environmental Medicine, Institute of Public Health, University of Southern Denmark, Winsloewparken 17, DK-5000 Odense, Denmark
| | - Pál Weihe
- Department of Occupational Medicine and Public Health, Faroese Hospital System, Tórshavn, Faroe Islands
| | - Hassan A N El-Fawal
- Neurotoxicology Laboratory, Albany College of Pharmacy and Health Sciences, Albany, New York 12208
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Ngu-Schwemlein M, Lin X, Rudd B, Bronson M. Synthesis and ESI mass spectrometric analysis of the association of mercury(II) with multi-cysteinyl peptides. J Inorg Biochem 2013; 133:8-23. [PMID: 24413258 DOI: 10.1016/j.jinorgbio.2013.12.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Revised: 12/17/2013] [Accepted: 12/17/2013] [Indexed: 01/21/2023]
Abstract
In order to gain more insight into the associations of mercury(II) with cysteinyl peptides, we investigated the effect of increasing cysteinyl residues on complex type formations. Three series of di-, tri-, and tetra-cysteinyl peptides, D[CGD]nCG (CP 2A, CP 3A, and CP 4A), E[CEG]nCG (CP 2B, CP 3B, and CP 4B) and E[CDG]nCG (CP 2C, CP 3C, and CP 4C), where n=1, 2, or 3, were prepared by microwave-assisted solid phase peptide synthesis. Complexes formed in different relative ratios of mercury(II) to cysteinyl peptides were characterized by electrospray orbitrap mass spectrometry utilizing complex specific mercury isotopic patterns. In equimolar mercury(II) to peptide ratio, all three series of di-, tri-, and tetra-cysteinyl peptides form predominantly the 1:1Hg(peptide) complex type, indicating that the intervening amino acid residues do not elicit preferential complex type formation. However, in non-equivalent mercury(II) to peptide ratio, the number of cysteinyl residues has a significant effect on the Hg:peptide stoichiometry in the complex formed. For example, in four times excess peptide, the 1:2Hg(peptide)2 and 1:1Hg(peptide) complexes are formed for di-cysteinyl peptides but not for the tri- and tetra-cysteinyl peptides. In contrast, the 2:1Hg2(peptide) and 1:1Hg(peptide) complexes are formed for the tri- and tetra-cysteinyl peptides. In excess mercury(II), CP 4C formed exclusively the 2:1Hg2(peptide) complex. The exact number of deprotonations observed for each complex could be derived from its signature mercury isotope pattern and monoisotopic peak mass. These multi-cysteinyl peptides present an attractive option for mercury chelation or environmental heavy metal remediation.
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Affiliation(s)
- Maria Ngu-Schwemlein
- Department of Chemistry, Winston-Salem State University, Winston-Salem, NC 27110, USA.
| | - Xiuli Lin
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Brent Rudd
- Department of Chemistry, Winston-Salem State University, Winston-Salem, NC 27110, USA
| | - Matthew Bronson
- Department of Chemistry, Winston-Salem State University, Winston-Salem, NC 27110, USA
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In-vivo evaluation of the permeability of the blood–brain barrier to arsenicals, molybdate, and methylmercury by use of online microdialysis–packed minicolumn–inductively coupled plasma mass spectrometry. Anal Bioanal Chem 2013; 406:239-47. [DOI: 10.1007/s00216-013-7429-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 10/06/2013] [Accepted: 10/09/2013] [Indexed: 02/06/2023]
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Caito SW, Zhang Y, Aschner M. Involvement of AAT transporters in methylmercury toxicity in Caenorhabditis elegans. Biochem Biophys Res Commun 2013; 435:546-50. [PMID: 23669041 DOI: 10.1016/j.bbrc.2013.04.090] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 04/17/2013] [Indexed: 10/26/2022]
Abstract
Methylmercury (MeHg) is a potent neurotoxin that enters mammalian cells as a conjugate with L-cysteine through L-type large neutral amino acid transporter, LAT1, by a molecular mimicry mechanism by structurally resembling L-methionine. Caenorhabditis elegans (C. elegans) has been increasingly used to study the neurotoxic effects of MeHg, but little is known about uptake and transport of MeHg in the worm. This study examined whether MeHg uptake through LAT1 is evolutionarily conserved in nematodes. MeHg toxicity in C. elegans was blocked by pre-treatment of worms with l-methionine, suggesting a role for amino acid transporters in MeHg transport. Knockdown of aat-1, aat-2, and aat-3, worm homologues to LAT1, increased the survival of C. elegans following MeHg treatment and significantly attenuated MeHg content following exposure. These results indicate that MeHg is transported in the worm by a conserved mechanism dependent on functioning amino acid transporters.
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Affiliation(s)
- Samuel W Caito
- Division of Clinical Pharmacology and Pediatric Toxicology, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN 37232-0414, USA
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36
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Dórea JG, Farina M, Rocha JBT. Toxicity of ethylmercury (and Thimerosal): a comparison with methylmercury. J Appl Toxicol 2013; 33:700-11. [PMID: 23401210 DOI: 10.1002/jat.2855] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 12/10/2012] [Accepted: 12/11/2012] [Indexed: 12/18/2022]
Abstract
Ethylmercury (etHg) is derived from the metabolism of thimerosal (o-carboxyphenyl-thio-ethyl-sodium salt), which is the most widely used form of organic mercury. Because of its application as a vaccine preservative, almost every human and animal (domestic and farmed) that has been immunized with thimerosal-containing vaccines has been exposed to etHg. Although methylmercury (meHg) is considered a hazardous substance that is to be avoided even at small levels when consumed in foods such as seafood and rice (in Asia), the World Health Organization considers small doses of thimerosal safe regardless of multiple/repetitive exposures to vaccines that are predominantly taken during pregnancy or infancy. We have reviewed in vitro and in vivo studies that compare the toxicological parameters among etHg and other forms of mercury (predominantly meHg) to assess their relative toxicities and potential to cause cumulative insults. In vitro studies comparing etHg with meHg demonstrate equivalent measured outcomes for cardiovascular, neural and immune cells. However, under in vivo conditions, evidence indicates a distinct toxicokinetic profile between meHg and etHg, favoring a shorter blood half-life, attendant compartment distribution and the elimination of etHg compared with meHg. EtHg's toxicity profile is different from that of meHg, leading to different exposure and toxicity risks. Therefore, in real-life scenarios, a simultaneous exposure to both etHg and meHg might result in enhanced neurotoxic effects in developing mammals. However, our knowledge on this subject is still incomplete, and studies are required to address the predictability of the additive or synergic toxicological effects of etHg and meHg (or other neurotoxicants).
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Affiliation(s)
- José G Dórea
- Department of Nutrition, Faculty of Health Sciences, Universidade de Brasilia, 70919-970, Brasilia, DF, Brazil.
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Huang SSY, Strathe AB, Fadel JG, Lin P, Liu TY, Hung SSO. Absorption, distribution, and elimination of graded oral doses of methylmercury in juvenile white sturgeon. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2012; 122-123:163-171. [PMID: 22819805 DOI: 10.1016/j.aquatox.2012.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 06/11/2012] [Accepted: 06/19/2012] [Indexed: 06/01/2023]
Abstract
Mercury (Hg) is toxic and is released into the environment from a wide variety of anthropogenic sources. Methylmercury (MeHg), a product of microbial methylation, enables rapid Hg bioaccumulation and biomagnification in the biota. Methylmercury is sequestered and made available to the rest of the biota through the benthic-detrital component leading to the high risk of exposure to benthic fish species, such as white sturgeon (Acipenser transmontanus). In the present study, a combined technique of stomach intubation, dorsal aorta cannulation, and urinary catheterization was utilized to characterize the absorption, distribution, and elimination of Hg in white sturgeon over a 48h exposure. Mercury, as methylmercury chloride, at either 0, 250, 500, or 1000 μg Hg/kg body weight, was orally intubated into white sturgeon, in groups of five. The blood was repeatedly sampled and urine collected from the fish over the 48h post intubation period, and at 48h, the fish were sacrificed for Hg tissue concentration and distribution determinations. The fractional rate of absorption (K), blood Hg concentration (μg/ml), tissue concentration (μg/g dry weight) and distribution (%), and urinary Hg elimination flux (μg/kg/h) are significantly different (p<0.05) among the MeHg doses. Complete blood uptake of Hg was observed in all MeHg treated fish by 12h. The maximal observed blood Hg concentration peaks are 0.56±0.02, 0.70±0.02, and 2.19±0.07 μg/ml (mean±SEM) for the 250, 500, and 1000 μgHg/kg body weight dose groups, respectively. Changes in blood Hg profiles can be described by a monomolecular function in all of the MeHg treated fish. The Hg concentration asymptote (A) and K are dose dependent. The relationship between A and the intubation dose, however, is nonlinear. Mercury levels in certain tissues are comparable to field data and longer-term study, indicating that the lower doses used in the current study are ecologically relevant for the species. Tissue Hg concentrations are in the following decreasing order: gastro-intestinal tract>kidney>spleen>gill>heart>liver>brain>white muscle and remaining whole body. At 48h, Hg was found to be preferentially distributed to metabolically active tissues. Digestibility is highest at the lowest MeHg dose. Measurable urinary Hg was observed in the fish treated with the highest MeHg dose, and a significant increase in the elimination flux was observed between 3 and 12h post intubation.
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Bridges CC, Joshee L, Zalups RK. Placental and fetal disposition of mercuric ions in rats exposed to methylmercury: role of Mrp2. Reprod Toxicol 2012; 34:628-34. [PMID: 23059061 DOI: 10.1016/j.reprotox.2012.10.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 09/14/2012] [Accepted: 10/01/2012] [Indexed: 12/24/2022]
Abstract
Methylmercury is a prevalent environmental toxicant that can have deleterious effects on a developing fetus. Previous studies indicate that the multidrug resistance-associated protein 2 (Mrp2) is involved in renal and hepatic export of mercuric ions. Therefore, we hypothesize that Mrp2 is also involved in export of mercuric ions from placental trophoblasts and fetal tissues. To test this hypothesis, we assessed the disposition of mercuric ions in pregnant Wistar and TR(-) (Mrp2-deficient) rats exposed to a single dose of methylmercury. The amount of mercury in renal tissues (cortex and outer stripe of outer medulla), liver, blood, amniotic fluid, uterus, placentas and fetuses was significantly greater in TR(-) rats than in Wistar rats. Urinary and fecal elimination of mercury was greater in Wistar dams than in TR(-) dams. Thus, our findings suggest that Mrp2 may be involved in the export of mercuric ions from maternal and fetal organs following exposure to methylmercury.
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Affiliation(s)
- Christy C Bridges
- Mercer University School of Medicine, Division of Basic Medical Sciences, Macon, GA 31207, United States.
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Syversen T, Kaur P. The toxicology of mercury and its compounds. J Trace Elem Med Biol 2012; 26:215-26. [PMID: 22658719 DOI: 10.1016/j.jtemb.2012.02.004] [Citation(s) in RCA: 231] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 02/07/2012] [Indexed: 12/27/2022]
Abstract
A concentrated review on the toxicology of inorganic mercury together with an extensive review on the neurotoxicology of methylmercury is presented. The challenges of using inorganic mercury in dental amalgam are reviewed both regarding the occupational exposure and the possible health problems for the dental patients. The two remaining "mysteries" of methylmercury neurotoxicology are also being reviewed; the cellular selectivity and the delayed onset of symptoms. The relevant literature on these aspects has been discussed and some suggestions towards explaining these observations have been presented.
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Affiliation(s)
- Tore Syversen
- Norwegian University of Science and Technology, Department of Neuroscience, Trondheim, Norway.
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Wang Y, Zalups RK, Barfuss DW. Luminal transport of thiol S-conjugates of methylmercury in isolated perfused rabbit renal proximal tubules. Toxicol Lett 2012; 213:203-10. [PMID: 22800651 DOI: 10.1016/j.toxlet.2012.07.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 07/05/2012] [Accepted: 07/07/2012] [Indexed: 10/28/2022]
Abstract
Lumen-to-cell transport, cellular accumulation, and toxicity of L-cysteine (Cys), glutathione (GSH) and N-acetylcysteine (NAC) S-conjugates of methylmercury (CH(3)Hg(+)) were evaluated in isolated, perfused rabbit proximal tubular segments. When these conjugates were perfused individually through the lumen of S(2) segments of the proximal tubule it was found that Cys-S-CH(3)Hg and GSH-S-CH(3)Hg were transported avidly, while NAC-S-CH(3)Hg was transported minimally. In addition, 95% of the (203)Hg taken up by the tubular cells was associated with precipitable proteins of the tubule, while very little was found in the acid-soluble cytosol. No visual cellular pathological changes were observed during 30min of study. Luminal uptake of Cys-S-CH(3)Hg was temperature-dependent and inhibited significantly by the amino acids L-methionine and l-cystine. Rates of luminal uptake of GSH-S-CH(3)Hg were twice as great as that of Cys-S-CH(3)Hg and uptake was inhibited significantly (74%) by the presence of acivicin. When 2,3-bis(sulfanyl)propane-1-sulfonate (DMPS) was added to the bathing or luminal fluid, luminal uptake of Cys-S-CH(3)Hg was diminished significantly. Overall, our data indicate that Cys-S-CH(3)Hg is likely a transportable substrate of one or more amino acid transporters (such as system B(0,+) and system b(0,+)) involved in luminal absorption of L-methionine and L-cystine along the renal proximal tubule. In addition, GSH-S-CH(3)Hg appears to be degraded enzymatically to Cys-S-CH(3)Hg, which can then be taken up at the luminal membrane. By contrast NAC-S-CH(3)Hg and Cys-S-CH(3)Hg (in the presence of DMPS) are not taken up avidly at the luminal membrane of proximal tubular cells, thus promoting the excretion of CH(3)Hg(+) into the urine.
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Affiliation(s)
- Yanhua Wang
- Department of Biology, Georgia State University, Atlanta, GA 30303, United States.
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Fretham SJ, Caito S, Martinez-Finley EJ, Aschner M. Mechanisms and Modifiers of Methylmercury-Induced Neurotoxicity. Toxicol Res (Camb) 2012; 1:32-38. [PMID: 27795823 DOI: 10.1039/c2tx20010d] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The neurotoxic consequences of methylmercury (MeHg) exposure have long been known, however a complete understanding of the mechanisms underlying this toxicity is elusive. Recent epidemiological and experimental studies have provided many mechanistic insights, particularly into the contribution of genetic and environmental factors that interact with MeHg to modify toxicity. This review will outline cellular processes directly and indirectly affected by MeHg, including oxidative stress, cellular signaling and gene expression, and discuss genetic, environmental and nutritional factors capable of modifying MeHg toxicity.
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Affiliation(s)
- Stephanie Jb Fretham
- Department of Pediatrics and Department of Pharmacology, and the Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Samuel Caito
- Department of Pediatrics and Department of Pharmacology, and the Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Ebany J Martinez-Finley
- Department of Pediatrics and Department of Pharmacology, and the Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Michael Aschner
- Department of Pediatrics and Department of Pharmacology, and the Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, Nashville, TN, USA
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Owens SE, Summar ML, Ryckman KK, Haines JL, Reiss S, Summar SR, Aschner M. Lack of association between autism and four heavy metal regulatory genes. Neurotoxicology 2011; 32:769-75. [PMID: 21798283 PMCID: PMC3206176 DOI: 10.1016/j.neuro.2011.07.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 07/07/2011] [Accepted: 07/08/2011] [Indexed: 11/29/2022]
Abstract
Autism is a common neurodevelopmental disorder with genetic and environmental components. Though unproven, genetic susceptibility to high mercury (Hg) body burden has been suggested as an autism risk factor in a subset of children. We hypothesized that exposure to "safe" Hg levels could be implicated in the etiology of autism if genetic susceptibility altered Hg's metabolism or intracellular compartmentalization. Genetic sequences of four genes implicated in the transport and response to Hg were screened for variation and association with autism. LAT1 and DMT1 function in Hg transport, and Hg exposure induces MTF1 and MT1a. We identified and characterized 74 variants in MT1a, DMT1, LAT1 and MTF1. Polymorphisms identified through screening 48 unrelated individuals from the general and autistic populations were evaluated for differences in allele frequencies using Fisher's exact test. Three variants with suggestive p-values <0.1 and four variants with significant p-values <0.05 were followed-up with TaqMan genotyping in a larger cohort of 204 patients and 323 control samples. The pedigree disequilibrium test was used to examine linkage and association. Analysis failed to show association with autism for any variant evaluated in both the initial screening set and the expanded cohort, suggesting that variations in the ability of the four genes studied to process and transport Hg may not play a significant role in the etiology of autism.
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Affiliation(s)
- Sarah E. Owens
- Department of Pediatric Toxicology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Marshall L. Summar
- Center for Human Genetics Research, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Kelli K. Ryckman
- Center for Human Genetics Research, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Jonathan L. Haines
- Center for Human Genetics Research, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Sara Reiss
- Center for Human Genetics Research, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Samantha R. Summar
- Center for Human Genetics Research, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Michael Aschner
- Department of Pediatric Toxicology, Vanderbilt University School of Medicine, Nashville, TN, USA
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Comparative study on the efficacy of Allium sativum (garlic) in reducing some heavy metal accumulation in liver of wistar rats. Food Chem Toxicol 2011; 50:222-6. [PMID: 22101063 DOI: 10.1016/j.fct.2011.11.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 10/27/2011] [Accepted: 11/03/2011] [Indexed: 01/08/2023]
Abstract
SCOPE Heavy metals are known to cause damage through indirect oxidative effects. This study was undertaken to compare the therapeutic efficacy and protective ability of garlic extracts on reducing toxicity induced by mercury, lead and cadmium in the liver. METHODS AND RESULTS Rats were fed with rat chow mixed with raw garlic (7% w/w) while mercury (10ppm), cadmium (200ppm) and lead (100ppm) were given in drinking water. Garlic was administered either at the same time with the metals (group 2), a week after exposure to heavy metals (group 3) or a week before heavy metal exposure (group 4) for 6weeks. The heavy metal accumulations in the liver were determined using AAS. The percentage protection showed a time-dependent effect and was significantly (P<0.01) higher for cadmium compared to mercury and lead-treated groups. Analysis between the groups showed that garlic treatment after exposure had a significantly (P<0.05) higher percentage protection when compared with other modes. CONCLUSION These results suggest that garlic offered more hepatoprotective effect to cadmium followed by mercury and least protection to lead at the selected dose of each metal in this study through the processes of uptake, assimilation and elimination of these metals.
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Quantum chemical studies on the role of water microsolvation in interactions between group 12 metal species (Hg2+, Cd2+, and Zn2+) and neutral and deprotonated cysteines. Theor Chem Acc 2011. [DOI: 10.1007/s00214-011-0975-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Nwokocha CR, Owu DU, Ufearo CS, Iwuala MOE. Comparative study on the efficacy of Garcinia kola in reducing some heavy metal accumulation in liver of Wistar rats. JOURNAL OF ETHNOPHARMACOLOGY 2011; 135:488-491. [PMID: 21458555 DOI: 10.1016/j.jep.2011.03.049] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Revised: 03/14/2011] [Accepted: 03/23/2011] [Indexed: 05/30/2023]
Abstract
Garcinia kola is regarded as an antidote and anti-hepatotoxic agent. We examined its protection ability against mercury (Hg), lead (Pb) and cadmium (Cd) accumulation in the liver. The ground seed was mixed with rat feed (5%, w/w) and fed to rats while Hg (10 ppm), Cd (200 ppm) and Pb (100 ppm) was given in drinking water. Garcinia kola was administered either at the same time with the metals (group 2), a week after exposure to heavy metals (group 3) or given a week before heavy metal exposure (group 4) for six weeks. The heavy metal accumulations in the liver were determined using AAS. Garcinia kola could not reverse the weight reduction in the heavy metal exposed groups although it offers more protection and aid greater elimination of heavy metals from the liver. There was a significant (P<0.01) increase in protection by Garcinia kola to Cd (72.4%) and Pb (56.2%) accumulation when compared to Hg (40%) at week 2 which was significantly (P<0.01) decreased at week 4 when compared to week 2. At week 6, the percentage protection to both Hg (64.2%) and Cd (62.2%) were comparable to each other while protection to Pb (49.9%) accumulation was significantly (P<0.01) reduced. The percentage protection was time-dependent in some groups but treatment during and after the exposure provided a greater protection. Garcinia kola has the highest hepatoprotective effect to Cd followed by Hg and least protection against Pb toxicity in rats and its administration is beneficial in reducing heavy metal accumulation in the liver.
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Affiliation(s)
- C R Nwokocha
- Department of Basic Medical Sciences, University of the West Indies, Mona Campus, Kingston 7, Jamaica.
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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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Bridges CC, Zalups RK. Transport of inorganic mercury and methylmercury in target tissues and organs. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2010; 13:385-410. [PMID: 20582853 PMCID: PMC6943924 DOI: 10.1080/10937401003673750] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Owing to the prevalence of mercury in the environment, the risk of human exposure to this toxic metal continues to increase. Following exposure to mercury, this metal accumulates in numerous organs, including brain, intestine, kidneys, liver, and placenta. Although a number of mechanisms for the transport of mercuric ions into target organs were proposed in recent years, these mechanisms have not been characterized completely. This review summarizes the current literature related to the transport of inorganic and organic forms of mercury in various tissues and organs. This review identifies known mechanisms of mercury transport and provides information on additional mechanisms that may potentially play a role in the transport of mercuric ions into target cells.
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Affiliation(s)
- Christy C Bridges
- Division of Basic Medical Sciences, Mercer University School of Medicine, Macon, Georgia 31207, USA.
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da Conceição Nascimento Pinheiro M, do Nascimento JLM, de Lima Silveira LC, da Rocha JBT, Aschner M. Mercury and Selenium - A Review on Aspects Related to the Health of Human Populations in the Amazon. ACTA ACUST UNITED AC 2009; 4:222-245. [PMID: 31485199 DOI: 10.1080/15555270903143440] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Mercury (Hg) toxicity is governed by cellular thiol compounds and its capacity to generate reactive oxygen radicals and oxidative stress. Selenium (Se) plays a key role in the prevention of the toxic effects of Hg by modulating the activity of several Se-dependent enzymes, including glutathione peroxidase (GSH-Px). In addition, dietary Se can reduce Hg toxicity by directly interacting with either Hg(II) or methylmercury (MeHg) to form inert products, such as HgSe complexes.. Although experimental and environmental data have indicated a protective role for selenium against Hg toxicity, human data are more limited and somewhat conroversial In the Amazon Region of Brazil, Hg pollution is rampant as a result of gold (Au) mining and other anthropogenic factors, leading to pervasive release of large quantities of metallic Hg0 into the environment. Exposure to Hg in this region is associated with direct occupational exposure in the gold mining industry, as well as consumption by in inhabitants of riverside communities of a diet rich in MeHg-contaminated fish. Human exposure to MeHg in the Amazon through the diet has been monitored by measuring Hg and MeHg in hair samples. In this paper, we review the environmental contamination of Hg in the Amazon and detail human exposures in populations of this region. We conclude with a brief synopsis on Se levels in the Amazon population and provide a brief review of data available on the interaction between Hg and Se in this region. Overall, the literature supports the notion that low environmental Se is linked to susceptibility to Hg toxicity and that Se levels could be used as a bioindicator to monitor the health of Hg exposed subjects. However, in light of the limited human data on this subject, further epidemiological studies are needed to clarify how changes in Se levels modify the toxicity of environmental Hg.
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Affiliation(s)
| | | | - Luiz Carlos de Lima Silveira
- Núcleo de Medicina Tropical, Universidade Federal do Pará, Belém, Pará Brazil.,Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil
| | | | - Michael Aschner
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Heggland I, Kaur P, Syversen T. Uptake and efflux of methylmercury in vitro: Comparison of transport mechanisms in C6, B35 and RBE4 cells. Toxicol In Vitro 2009; 23:1020-7. [DOI: 10.1016/j.tiv.2009.06.018] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Revised: 06/10/2009] [Accepted: 06/15/2009] [Indexed: 10/20/2022]
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50
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Bellum S, Thuett KA, Taylor RJ, Abbott LC. Assessment of Mercury Concentrations in Mouse Brain Using Different Routes of Administration and Different Tissue Preparations. Toxicol Mech Methods 2008; 17:165-73. [DOI: 10.1080/15376510601091368] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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