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Kang B, Wang J, Guo S, Yang L. Mercury-induced toxicity: Mechanisms, molecular pathways, and gene regulation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 943:173577. [PMID: 38852866 DOI: 10.1016/j.scitotenv.2024.173577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/01/2024] [Accepted: 05/25/2024] [Indexed: 06/11/2024]
Abstract
Mercury is a well-known neurotoxicant for humans and wildlife. The epidemic of mercury poisoning in Japan has clearly demonstrated that chronic exposure to methylmercury (MeHg) results in serious neurological damage to the cerebral and cerebellar cortex, leading to the dysfunction of the central nervous system (CNS), especially in infants exposed to MeHg in utero. The occurrences of poisoning have caused a wide public concern regarding the health risk emanating from MeHg exposure; particularly those eating large amounts of fish may experience the low-level and long-term exposure. There is growing evidence that MeHg at environmentally relevant concentrations can affect the health of biota in the ecosystem. Although extensive in vivo and in vitro studies have demonstrated that the disruption of redox homeostasis and microtube assembly is mainly responsible for mercurial toxicity leading to adverse health outcomes, it is still unclear whether we could quantitively determine the occurrence of interaction between mercurial and thiols and/or selenols groups of proteins linked directly to outcomes, especially at very low levels of exposure. Furthermore, intracellular calcium homeostasis, cytoskeleton, mitochondrial function, oxidative stress, neurotransmitter release, and DNA methylation may be the targets of mercury compounds; however, the primary targets associated with the adverse outcomes remain to be elucidated. Considering these knowledge gaps, in this article, we conducted a comprehensive review of mercurial toxicity, focusing mainly on the mechanism, and genes/proteins expression. We speculated that comprehensive analyses of transcriptomics, proteomics, and metabolomics could enhance interpretation of "omics" profiles, which may reveal specific biomarkers obviously correlated with specific pathways that mediate selective neurotoxicity.
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Affiliation(s)
- Bolun Kang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Jinghan Wang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Shaojuan Guo
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Lixin Yang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China.
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Zakharova MN, Bakulin IS, Abramova AA. Toxic Damage to Motor Neurons. NEUROCHEM J+ 2021. [DOI: 10.1134/s1819712421040164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Abstract—Amyotrophic lateral sclerosis (ALS) is a multifactor disease in the development of which both genetic and environmental factors play a role. Specifically, the effects of organic and inorganic toxic substances can result in an increased risk of ALS development and the acceleration of disease progression. It was described that some toxins can induce potentially curable ALS-like syndromes. In this case, the specific treatment for the prevention of the effects of the toxic factor may result in positive clinical dynamics. In this article, we review the main types of toxins that can damage motor neurons in the brain and spinal cord leading to the development of the clinical manifestation of ALS, briefly present historical data on studies on the role of toxic substances, and describe the main mechanisms of the pathogenesis of motor neuron disease associated with their action.
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Koski L, Ronnevi C, Berntsson E, Wärmländer SKTS, Roos PM. Metals in ALS TDP-43 Pathology. Int J Mol Sci 2021; 22:12193. [PMID: 34830074 PMCID: PMC8622279 DOI: 10.3390/ijms222212193] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 11/03/2021] [Accepted: 11/09/2021] [Indexed: 11/16/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS), Alzheimer's disease, Parkinson's disease and similar neurodegenerative disorders take their toll on patients, caregivers and society. A common denominator for these disorders is the accumulation of aggregated proteins in nerve cells, yet the triggers for these aggregation processes are currently unknown. In ALS, protein aggregation has been described for the SOD1, C9orf72, FUS and TDP-43 proteins. The latter is a nuclear protein normally binding to both DNA and RNA, contributing to gene expression and mRNA life cycle regulation. TDP-43 seems to have a specific role in ALS pathogenesis, and ubiquitinated and hyperphosphorylated cytoplasmic inclusions of aggregated TDP-43 are present in nerve cells in almost all sporadic ALS cases. ALS pathology appears to include metal imbalances, and environmental metal exposure is a known risk factor in ALS. However, studies on metal-to-TDP-43 interactions are scarce, even though this protein seems to have the capacity to bind to metals. This review discusses the possible role of metals in TDP-43 aggregation, with respect to ALS pathology.
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Affiliation(s)
- Lassi Koski
- Institute of Environmental Medicine, Karolinska Institutet, 171 77 Stockholm, Sweden;
| | | | - Elina Berntsson
- Department of Biochemistry and Biophysics, Stockholm University, 106 91 Stockholm, Sweden;
- Department of Chemistry and Biotechnology, Tallinn University of Technology, 12616 Tallinn, Estonia
| | | | - Per M. Roos
- Institute of Environmental Medicine, Karolinska Institutet, 171 77 Stockholm, Sweden;
- Capio St. Göran Hospital, 112 19 Stockholm, Sweden;
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Eiró LG, Ferreira MKM, Bittencourt LO, Aragão WAB, Souza MPCD, Silva MCF, Dionizio A, Buzalaf MAR, Crespo-López ME, Lima RR. Chronic methylmercury exposure causes spinal cord impairment: Proteomic modulation and oxidative stress. Food Chem Toxicol 2020; 146:111772. [DOI: 10.1016/j.fct.2020.111772] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 09/18/2020] [Accepted: 09/21/2020] [Indexed: 12/19/2022]
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Colón-Rodríguez A, Colón-Carrión NM, Atchison WD. AMPA receptor contribution to methylmercury-mediated alteration of intracellular Ca 2+ concentration in human induced pluripotent stem cell motor neurons. Neurotoxicology 2020; 81:116-126. [PMID: 32991939 DOI: 10.1016/j.neuro.2020.09.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 09/21/2020] [Accepted: 09/22/2020] [Indexed: 12/28/2022]
Abstract
α motor neurons (MNs) are a target of the environmental neurotoxicant methylmercury (MeHg), accumulating MeHg and subsequently degenerating. In mouse spinal cord MN cultures, MeHg increased intracellular Ca2+ [Ca2+]i; the AMPA receptor (AMPAR) antagonist CNQX delayed the increase in [Ca2+]i, implicating the role of AMPARs in this response. Here we used human induced pluripotent stem cell-derived MNs (hiPSC-MNs), to characterize the role of MN AMPARs in MeHg neurotoxicity. Acute exposure to MeHg (0.1, 0.2, 0.5, 1 and 1.5 μM), fura-2 microfluorimetry, and a standard cytotoxicity assay, were used to examine MN regulation of [Ca2+]i, and cytotoxicity, respectively. Contribution of Ca2+-permeable and impermeable AMPARs was compared using either CNQX, or the Ca2+-permeable AMPAR antagonist N-acetyl spermine (NAS). MeHg-induced cytotoxicity was evaluated following a 24 h delay subsequent to 1 h exposure of hiPSC-MNs. MeHg caused a characteristic biphasic increase in [Ca2+]i, the onset of which was concentration-dependent; higher MeHg concentrations hastened onset of both phases. CNQX significantly delayed MeHg's effect on onset time of both phases. In contrast, NAS significantly delayed only the 2nd phase increase in fura-2 fluorescence. Exposure to MeHg for 1 h followed by a 24 h recovery period caused a concentration-dependent incidence of cell death. These results demonstrate for the first time that hiPSC-derived MNs are highly sensitive to effects of MeHg on [Ca2+]i, and cytotoxicity, and that both Ca2+-permeable and impermeable AMPARs contribute the elevations in [Ca2+]i.
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Affiliation(s)
- Alexandra Colón-Rodríguez
- Department of Pharmacology and Toxicology, College of Veterinary Medicine, Michigan State University, 1355 Bogue St., B338 Life Science Bldg., East Lansing, MI 48824, United States; Institute for Integrative Toxicology, College of Veterinary Medicine, Michigan State University, 1355 Bogue St., B338 Life Science Bldg., East Lansing, MI 48824, United States; Comparative Medicine and Integrative Biology Program, College of Veterinary Medicine, Michigan State University, 1355 Bogue St., B331 Life Science Bldg., East Lansing, MI 48824, United States.
| | - Nicole M Colón-Carrión
- Department of Pharmacology and Toxicology, College of Veterinary Medicine, Michigan State University, 1355 Bogue St., B338 Life Science Bldg., East Lansing, MI 48824, United States.
| | - William D Atchison
- Department of Pharmacology and Toxicology, College of Veterinary Medicine, Michigan State University, 1355 Bogue St., B338 Life Science Bldg., East Lansing, MI 48824, United States; Institute for Integrative Toxicology, College of Veterinary Medicine, Michigan State University, 1355 Bogue St., B338 Life Science Bldg., East Lansing, MI 48824, United States; Comparative Medicine and Integrative Biology Program, College of Veterinary Medicine, Michigan State University, 1355 Bogue St., B331 Life Science Bldg., East Lansing, MI 48824, United States.
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6
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Sceniak MP, Spitsbergen JB, Sabo SL, Yuan Y, Atchison WD. Acute neurotoxicant exposure induces hyperexcitability in mouse lumbar spinal motor neurons. J Neurophysiol 2020; 123:1448-1459. [PMID: 32159428 DOI: 10.1152/jn.00775.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Spinal motor neurons (MNs) are susceptible to glutamatergic excitotoxicity, an effect associated with lumbar MN degeneration in amyotrophic lateral sclerosis (ALS). MN susceptibility to environmental toxicant exposure, one prospective contributor to sporadic ALS, has not been systematically studied. The goal of this study was to test the ability of a well-known environmental neurotoxicant to induce hyperexcitability in mouse lumbar MNs. Methylmercury (MeHg) causes neurotoxicity through mechanisms involving elevated intracellular Ca2+ concentration ([Ca2+]i), a hallmark of excitotoxicity. We tested whether acute exposure to MeHg induces hyperexcitability in MNs by altering synaptic transmission, using whole cell patch-clamp recordings of lumbar spinal MNs in vitro. Acute MeHg exposure (20 μM) led to an increase in the frequency of both spontaneous excitatory postsynaptic currents (EPSCs) and miniature EPSCs. The frequency of inhibitory postsynaptic currents (IPSCs) was also increased by MeHg. Action potential firing rates, both spontaneous and evoked, were increased by MeHg, despite increases in both EPSCs and IPSCs, indicating a shift toward hyperexcitability. Also consistent with hyperexcitability, fluo 4-AM microfluorimetry indicated that MeHg exposure induced an increase in [Ca2+]i. Spinal cord hyperexcitability is partially mediated by Ca2+-permeable AMPA receptors, as MeHg-dependent increases in EPSCs were blocked by 1-napthyl spermine. Therefore, spinal MNs appear highly susceptible to MeHg exposure, leading to significant increases in spontaneous network excitability and disruption of normal function. Prolonged hyperexcitability could lead to eventual neurodegeneration and loss of motor function as observed in spinal cord after MeHg exposure in vivo and may contribute to MeHg-induced acceleration of ALS symptoms.NEW & NOTEWORTHY Spinal motor neurons (MN) are susceptible to glutamatergic excitotoxicity, an effect associated with lumbar MN degeneration in amyotrophic lateral sclerosis (ALS). This study investigated MN susceptibility to environmental toxicant exposure, one prospective contributor to sporadic ALS. Spinal MNs appear highly susceptible to methylmercury exposure, leading to significant increases in spontaneous network excitability and disruption of normal function. Prolonged hyperexcitability could lead to neurodegeneration and loss of motor function as observed in ALS spinal cord symptoms.
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Affiliation(s)
- Michael P Sceniak
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan.,Department of Biology, Central Michigan University, Mount Pleasant, Michigan
| | - Jake B Spitsbergen
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Shasta L Sabo
- Department of Biology, Central Michigan University, Mount Pleasant, Michigan
| | - Yukun Yuan
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - William D Atchison
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
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Bailey JM, Colón-Rodríguez A, Atchison WD. Evaluating a Gene-Environment Interaction in Amyotrophic Lateral Sclerosis: Methylmercury Exposure and Mutated SOD1. Curr Environ Health Rep 2017; 4:200-207. [PMID: 28397096 DOI: 10.1007/s40572-017-0144-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
PURPOSE OF REVIEW Gene-environment (GxE) interactions likely contribute to numerous diseases, but are often difficult to model in the laboratory. Such interactions have been widely hypothesized for amyotrophic lateral sclerosis (ALS); recent controlled laboratory studies are discussed here and hypotheses related to possible mechanisms of action are offered. Using methylmercury exposure and mutated SOD1 to model the impacts of such an interaction, we interpret evidence about their respective mechanisms of toxicity to interrogate the possibility of additive (or synergistic) effects when combined. RECENT FINDINGS Recent work has converged on mechanisms of calcium-mediated glutamate excitotoxicity as a likely contributor in one model of a gene-environment interaction affecting the onset and progression of ALS-like phenotype. The current experimental literature on mechanisms of metal-induced neuronal injury and their relevant interactions with genetic contributions in ALS is sparse, but we describe those studies here and offer several integrative hypotheses about the likely mechanisms involved.
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Affiliation(s)
- Jordan M Bailey
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, 48824-1317, USA.,Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, 48824-1317, USA
| | - Alexandra Colón-Rodríguez
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, 48824-1317, USA.,Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, 48824-1317, USA.,Comparative Medicine and Integrative Biology Program, Michigan State University, East Lansing, MI, 48824-1317, USA
| | - William D Atchison
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, 48824-1317, USA. .,Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, 48824-1317, USA. .,Comparative Medicine and Integrative Biology Program, Michigan State University, East Lansing, MI, 48824-1317, USA. .,, Life Science Building, 1355 Bogue St. Room B331A, East Lansing, MI, 48824-1317, USA.
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8
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Colón-Rodríguez A, Hannon HE, Atchison WD. Effects of methylmercury on spinal cord afferents and efferents-A review. Neurotoxicology 2017; 60:308-320. [PMID: 28041893 PMCID: PMC5447474 DOI: 10.1016/j.neuro.2016.12.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 12/21/2016] [Accepted: 12/21/2016] [Indexed: 10/20/2022]
Abstract
Methylmercury (MeHg) is an environmental neurotoxicant of public health concern. It readily accumulates in exposed humans, primarily in neuronal tissue. Exposure to MeHg, either acutely or chronically, causes severe neuronal dysfunction in the central nervous system and spinal neurons; dysfunction of susceptible neuronal populations results in neurodegeneration, at least in part through Ca2+-mediated pathways. Biochemical and morphologic changes in peripheral neurons precede those in central brain regions, despite the fact that MeHg readily crosses the blood-brain barrier. Consequently, it is suggested that unique characteristics of spinal cord afferents and efferents could heighten their susceptibility to MeHg toxicity. Transient receptor potential (TRP) ion channels are a class of Ca2+-permeable cation channels that are highly expressed in spinal afferents, among other sensory and visceral organs. These channels can be activated in numerous ways, including directly via chemical irritants or indirectly via Ca2+ release from intracellular storage organelles. Early studies demonstrated that MeHg interacts with heterologous TRP channels, though definitive mechanisms of MeHg toxicity on sensory neurons may involve more complex interaction with, and among, differentially-expressed TRP populations. In spinal efferents, glutamate receptors of the N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and possibly kainic acid (KA) classes are thought to play a major role in MeHg-induced neurotoxicity. Specifically, the Ca2+-permeable AMPA receptors, which are abundant in motor neurons, have been identified as being involved in MeHg-induced neurotoxicity. In this review, we will describe the mechanisms that could contribute to MeHg-induced spinal cord afferent and efferent neuronal degeneration, including the possible mediators, such as uniquely expressed Ca2+-permeable ion channels.
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Affiliation(s)
- Alexandra Colón-Rodríguez
- Department of Pharmacology and Toxicology, 1355 Bogue Street, Life Sciences Building Rm. B440, Michigan State University, East Lansing, MI, United States; Institute for Integrative Toxicology, 1129 Farm Lane, Food Safety and Toxicology Rm. 165, Michigan State University, East Lansing, MI, United States; Comparative Medicine and Integrative Biology Program, 784 Wilson Road, Veterinary Medical Center Rm. G-100, Michigan State University, East Lansing, MI, United States.
| | - Heidi E Hannon
- Department of Pharmacology and Toxicology, 1355 Bogue Street, Life Sciences Building Rm. B440, Michigan State University, East Lansing, MI, United States; Institute for Integrative Toxicology, 1129 Farm Lane, Food Safety and Toxicology Rm. 165, Michigan State University, East Lansing, MI, United States; Comparative Medicine and Integrative Biology Program, 784 Wilson Road, Veterinary Medical Center Rm. G-100, Michigan State University, East Lansing, MI, United States.
| | - William D Atchison
- Department of Pharmacology and Toxicology, 1355 Bogue Street, Life Sciences Building Rm. B440, Michigan State University, East Lansing, MI, United States; Institute for Integrative Toxicology, 1129 Farm Lane, Food Safety and Toxicology Rm. 165, Michigan State University, East Lansing, MI, United States; Comparative Medicine and Integrative Biology Program, 784 Wilson Road, Veterinary Medical Center Rm. G-100, Michigan State University, East Lansing, MI, United States.
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Ramanathan G, Atchison WD. Ca2+ entry pathways in mouse spinal motor neurons in culture following in vitro exposure to methylmercury. Neurotoxicology 2011; 32:742-50. [PMID: 21839771 DOI: 10.1016/j.neuro.2011.07.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Revised: 06/06/2011] [Accepted: 07/13/2011] [Indexed: 12/29/2022]
Abstract
Methylmercury (MeHg) is a widespread environmental toxicant with major actions on the central nervous system. Among the neurons reportedly affected in cases of Hg poisoning are motor neurons; however, the direct cellular effects of MeHg on motor neurons have not been reported. Ratiometric fluorescence imaging, using the Ca(2+)-sensitive fluorophore fura-2, was used to examine the effect of MeHg on Ca(2+) homeostasis in primary cultures of mouse spinal motor neurons. In vitro MeHg exposure at concentrations (0.1-2 μM) known to affect other neurons in culture differentially, induced a biphasic rise in fura-2 fluorescence ratio indicating an increase in [Ca(2+)](i). The time-to-onset of these fura-2 fluorescence ratio changes was inversely correlated with MeHg concentration. TPEN (20 μM), a non-Ca(2+), divalent cation chelator, reduced the amplitude of the increase in fura-2 fluorescence induced by MeHg in the first phase, indicating that both Ca(2+) and non-Ca(2+) divalent cations contribute to the MeHg-induced effect. When examining various Ca(2+) entry pathways as possible targets contributing to Ca(2+) influx, we found that excitatory amino acid receptor blockers MK-801 (15 μM), and AP-5 (100 μM)-both NMDA receptor-operated ion channel blockers, CNQX (20 μM), a non-NMDA receptor blocker, and the voltage-dependent Ca(2+) channel blockers nifedipine (1 μM) and ω-conotoxin-GVIA (1 μM) all significantly delayed the development of increased Ca(2+) caused by MeHg. The voltage-dependent Na(+) channel blocker tetrodotoxin (TTX, 1 μM) did not alter the MeHg-induced increases in fura-2 fluorescence ratio. Thus, MeHg alters Ca(2+) homeostasis in mouse spinal motor neurons through excitatory amino acid receptor-mediated pathways, and nifedipine and ω-conotoxin-GVIA-sensitive pathways. Spinal motor neurons are highly sensitive to this effect of acute exposure to MeHg.
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Affiliation(s)
- Gunasekaran Ramanathan
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824, USA
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Toyama T, Shinkai Y, Yasutake A, Uchida K, Yamamoto M, Kumagai Y. Isothiocyanates reduce mercury accumulation via an Nrf2-dependent mechanism during exposure of mice to methylmercury. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:1117-22. [PMID: 21382770 PMCID: PMC3237354 DOI: 10.1289/ehp.1003123] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Accepted: 03/07/2011] [Indexed: 05/20/2023]
Abstract
BACKGROUND Methylmercury (MeHg) exhibits neurotoxicity through accumulation in the brain. The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) plays an important role in reducing the cellular accumulation of MeHg. OBJECTIVES We investigated the protective effect of isothiocyanates, which are known to activate Nrf2, on the accumulation of mercury after exposure to MeHg in vitro and in vivo. METHODS We used primary mouse hepatocytes in in vitro experiments and mice as an in vivo model. We used Western blotting, luciferase assays, atomic absorption spectrometry assays, and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assays, and we identified toxicity in mice based on hind-limb flaccidity and mortality. RESULTS The isothiocyanates 6-methylsulfinylhexyl isothiocyanate (6-HITC) and sulforaphane (SFN) activated Nrf2 and up-regulated downstream proteins associated with MeHg excretion, such as glutamate-cysteine ligase, glutathione S-transferase, and multidrug resistance-associated protein, in primary mouse hepatocytes. Under these conditions, intracellular glutathione levels increased in wild-type but not Nrf2-deficient primary mouse hepatocytes. Pretreatment with 6-HITC and SFN before MeHg exposure suppressed cellular accumulation of mercury and cytotoxicity in wild-type but not Nrf2-deficient primary mouse hepatocytes. In comparison, in vivo administration of MeHg to Nrf2-deficient mice resulted in increased sensitivity to mercury concomitant with an increase in mercury accumulation in the brain and liver. Injection of SFN before administration of MeHg resulted in a decrease in mercury accumulation in the brain and liver of wild-type, but not Nrf2-deficient, mice. CONCLUSIONS Through activation of Nrf2, 6-HITC and SFN can suppress mercury accumulation and intoxication caused by MeHg intake.
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Affiliation(s)
- Takashi Toyama
- Doctoral Programs in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan
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Gagliardi S, Ogliari P, Davin A, Corato M, Cova E, Abel K, Cashman JR, Ceroni M, Cereda C. Flavin-containing monooxygenase mRNA levels are up-regulated in als brain areas in SOD1-mutant mice. Neurotox Res 2010; 20:150-8. [PMID: 21082301 DOI: 10.1007/s12640-010-9230-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 10/07/2010] [Accepted: 11/03/2010] [Indexed: 12/12/2022]
Abstract
Flavin-containing monooxygenases (FMOs) are a family of microsomal enzymes involved in the oxygenation of a variety of nucleophilic heteroatom-containing xenobiotics. Recent results have pointed to a relation between Amyotrophic Lateral Sclerosis (ALS) and FMO genes. ALS is an adult-onset, progressive, and fatal neurodegenerative disease. We have compared FMO mRNA expression in the control mouse strain C57BL/6J and in a SOD1-mutated (G93A) ALS mouse model. Fmo expression was examined in total brain, and in subregions including cerebellum, cerebral hemisphere, brainstem, and spinal cord of control and SOD1-mutated mice. We have also considered expression in male and female mice because FMO regulation is gender-related. Real-Time TaqMan PCR was used for FMO expression analysis. Normalization was done using hypoxanthine-guanine phosphoribosyl transferase (Hprt) as a control housekeeping gene. Fmo genes, except Fmo3, were detectably expressed in the central nervous system of both control and ALS model mice. FMO expression was generally greater in the ALS mouse model than in control mice, with the highest increase in Fmo1 expression in spinal cord and brainstem. In addition, we showed greater Fmo expression in males than in female mice in the ALS model. The expression of Fmo1 mRNA correlated with Sod1 mRNA expression in pathologic brain areas. We hypothesize that alteration of FMO gene expression is a consequence of the pathological environment linked to oxidative stress related to mutated SOD1.
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Affiliation(s)
- Stella Gagliardi
- Lab of Experimental Neurobiology, IRCCS National Neurological Institute C. Mondino, Via Mondino, 2, 27100, Pavia, Italy.
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Dietary selenium protects against selected signs of aging and methylmercury exposure. Neurotoxicology 2010; 31:169-79. [PMID: 20079371 DOI: 10.1016/j.neuro.2010.01.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 12/24/2009] [Accepted: 01/06/2010] [Indexed: 01/01/2023]
Abstract
Acute or short-term exposure to high doses of methylmercury (MeHg) causes a well-characterized syndrome that includes sensory and motor deficits. The environmental threat from MeHg, however, comes from chronic, low-level exposure, the consequences of which are poorly understood. Selenium (Se), an essential nutrient, both increases deposition of mercury (Hg) in neurons and mitigates some of MeHg's neurotoxicity in the short term, but it is unclear whether this deposition produces long-term adverse consequences. To investigate these issues, adult Long-Evans rats were fed a diet containing 0.06 or 0.6 ppm of Se as sodium selenite. After 100 days on these diets, the subjects began consuming 0.0, 0.5, 5.0, or 15 ppm of Hg as methylmercuric chloride in their drinking water for 16 months. Somatosensory sensitivity, grip strength, hindlimb cross (clasping reflex), flexion, and voluntary wheel-running in overnight sessions were among the measures examined. MeHg caused a dose- and time-dependent impairment in all measures. No effects appeared in rats consuming 0 or 0.5 ppm of Hg. Somatosensory function, grip strength, and flexion were among the earliest signs of exposure. Selenium significantly delayed or blunted MeHg's effects. Selenium also increased running in unexposed animals as they aged, a novel finding that may have important clinical implications. Nerve pathology studies revealed axonal atrophy or mild degeneration in peripheral nerve fibers, which is consistent with abnormal sensorimotor function in chronic MeHg neurotoxicity. Lidocaine challenge reproduced the somatosensory deficits but not hindlimb cross or flexion. Together, these results quantify the neurotoxicity of long-term MeHg exposure, support the safety and efficacy of Se in ameliorating MeHg's neurotoxicity, and demonstrate the potential benefits of Se during aging.
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Lukács M, Vécsei L, Beniczky S. Large motor units are selectively affected following a stroke. Clin Neurophysiol 2008; 119:2555-8. [PMID: 18809353 DOI: 10.1016/j.clinph.2008.08.005] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2008] [Revised: 08/06/2008] [Accepted: 08/13/2008] [Indexed: 10/21/2022]
Abstract
OBJECTIVE Previous studies have revealed a loss of functioning motor units in stroke patients. However, it remained unclear whether the motor units are affected randomly or in some specific pattern. We assessed whether there is a selective loss of the large (high recruitment threshold) or the small (low recruitment threshold) motor units following a stroke. METHODS Forty-five stroke patients and 40 healthy controls participated in the study. Macro-EMG was recorded from the abductor digiti minimi muscle at two levels of force output (low and high). The median macro motor unit potential (macro-MUP) amplitude on the paretic side was compared with those on the unaffected side and in the controls. RESULTS In the control group and on the unaffected side, the macro-MUPs were significantly larger at the high force output than at the low one. However, on the paretic side the macro-MUPs at the high force output had the same amplitude as those recorded at the low force output. These changes correlated with the severity of the paresis. CONCLUSIONS Following a stroke, there is a selective functional loss of the large, high-threshold motor units. These changes are related to the severity of the symptoms. SIGNIFICANCE Our findings furnish further insight into the pathophysiology of the motor deficit following a stroke.
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Affiliation(s)
- M Lukács
- Department of Neurology, Miskolc Health Center, Kórház u. 1, H-3520 Miskolc, Hungary.
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14
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Mori F, Tanji K, Wakabayashi K. Thiophene, a sulfur‐containing heterocyclic hydrocarbon, causes widespread neuronal degeneration in rats. Neuropathology 2008. [DOI: 10.1111/j.1440-1789.2000.00348.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fumiaki Mori
- Department of Neuropathology, Institute of Brain Science, Hirosaki University School of Medicine, Hirosaki, Japan
| | - Kunikazu Tanji
- Department of Neuropathology, Institute of Brain Science, Hirosaki University School of Medicine, Hirosaki, Japan
| | - Koichi Wakabayashi
- Department of Neuropathology, Institute of Brain Science, Hirosaki University School of Medicine, Hirosaki, Japan
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15
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Praline J, Guennoc AM, Limousin N, Hallak H, de Toffol B, Corcia P. ALS and mercury intoxication: A relationship? Clin Neurol Neurosurg 2007; 109:880-3. [PMID: 17719172 DOI: 10.1016/j.clineuro.2007.07.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Revised: 07/12/2007] [Accepted: 07/13/2007] [Indexed: 12/13/2022]
Abstract
We report the case of an 81-year-old woman in whom clinical signs and features of electromyographic activity patterns were consistent with amyotrophic lateral sclerosis (ALS). Increased blood level and massive urinary excretion of mercury proved mercury intoxication. Despite a chelation treatment with Meso 2-3 dimercaptosuccininc acid (DMSA), she died after 17 months. The pathophysiology of sporadic ALS remains unclear. However, the role of environmental factors has been suggested. Among some environmental factors, exposure to heavy metals has been considered and ALS cases consecutive to occupational intoxication and accidental injection of mercury have been reported. Although no autopsy was performed, we discuss the role of mercury intoxication in the occurrence of ALS in our case, considering the results of experimental studies on the toxicity of mercury for motor neuron.
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Affiliation(s)
- Julien Praline
- Department of Neurology and Neurophysiology, CHRU, Tours, France.
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16
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Day JJ, Reed MN, Newland MC. Neuromotor deficits and mercury concentrations in rats exposed to methyl mercury and fish oil. Neurotoxicol Teratol 2005; 27:629-41. [PMID: 16024222 DOI: 10.1016/j.ntt.2005.03.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2004] [Revised: 03/01/2005] [Accepted: 03/02/2005] [Indexed: 11/26/2022]
Abstract
It has been suggested that docosahexaenoic acid (DHA) or other n-3 polyunsaturated fatty acids (PUFAs) may prevent or ameliorate methyl mercury's neurotoxicity. To examine interactions between PUFAs and methyl mercury exposure, sixty-six female Long-Evans rats were exposed to methyl mercury continuously via drinking water from fifteen weeks of age. Water included methyl mercury concentrations of 0, 0.5, and 5.0 ppm, creating estimated intakes of about 0, 40, and 400 microg/kg/day across exposure groups. An additional fifty-eight female offspring were exposed to methyl mercury only during gestation. Rats consumed one of two diets, each based on AIN-93 formulation, providing a 2 (generation) X 2 (diet) X 3 (methyl mercury exposure) factorial experimental design. A "coconut oil" diet (1/3 of fats were provided by coconut oil) was marginally adequate in n-3 PUFAs and contained no DHA. A "fish oil" diet was rich in n-3 fatty acids, including DHA. The diets were approximately equal in n-6 fatty acids. Forelimb grip strength declined with age for all groups, but the decline was greatest for those exposed chronically to 400 microg/kg/day of methyl mercury. This high-dose group also displayed hind limb crossing, gait disorders, and diminished running wheel activity. Dietary n-3 fatty acids did not influence these effects. Chronic exposure to 400 microg/kg/day of methyl mercury resulted in blood and brain concentrations of about 70 and 10 ppm, respectively, approximately 50-fold higher than concentrations seen in rats exposed to 40 microg/kg/day. Rats that became ill and died before the experiment ended had higher concentrations of mercury than their cohorts who survived to the end. Organic mercury was highly correlated with total mercury in these rats but inorganic mercury remained approximately constant. Some deaths were due to urolithiasis (kidney or bladder stones) associated with a dietary contaminant and that was eventually fatal to 22% of the females in the colony. Neurobehavioral effects are reported on rats that did not become ill.
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Affiliation(s)
- Jeremy J Day
- Department of Psychology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
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17
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Mori F, Tanji K, Wakabayashi K. Thiophene, a sulfur-containing heterocyclic hydrocarbon, causes widespread neuronal degeneration in rats. Neuropathology 2000; 20:283-8. [PMID: 11211052 DOI: 10.1046/j.1440-1789.2000.00348.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Thiophene is a sulfur-containing heterocyclic hydrocarbon that has been detected in a number of environmental sources as various derivatives. Previous studies with rats have shown that thiophene induces selective degeneration of granule cells in the cerebellum, as observed with methyl mercury. To study the neurotoxicity of thiophene, Wistar rats received daily intramuscular injections of 0.2 mL thiophene for 3 days. Ataxia and convulsions were noted in all animals within 24 h after the final dose. Histologically, multiple foci of necrosis were observed in the cerebellum, predominantly in the granular layer. Neuronal damage was also found in the cerebral cortex, inferior colliculus and inferior olive. These findings suggest that thiophene causes widespread neuronal degeneration in rats and that the regional distribution of brain lesions induced by thiophene is different from that caused by methyl mercury poisoning.
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Affiliation(s)
- F Mori
- Department of Neuropathology, Institute of Brain Science, Hirosaki University School of Medicine, Japan.
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18
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Mori F, Tanji K, Wakabayashi K. Widespread calcium deposits, as detected using the alizarin red S technique, in the nervous system of rats treated with dimethyl mercury. Neuropathology 2000; 20:210-5. [PMID: 11132937 DOI: 10.1046/j.1440-1789.2000.00341.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It has been reported that the alizarin red S technique may be used to visualize both intracellular and extracellular calcium deposits. Using this method histologic observations of the nervous system were made in rats that were given dimethyl mercury at 5 mg/kg per day for 12 consecutive days, and killed on days 1, 4, 7, 10, 12, 24, 32, 49, 100 and 140 (day 0 was the day that the final dose was administered). Neuronal degeneration with calcium deposition was found in the nervous system from day 4 onward. In the cerebellum alizarin red S-positive granules became gradually larger with time after dimethyl mercury administration, and large calcospherites were observed from day 32 onward. In contrast, the visualization of calcium deposits in the cerebral cortex was restricted to days 10-12. Calcium deposits were found in the ascending axons of the dorsal root ganglion neurons (dorsal fascicles of the spinal cord), but not in their perikarya. These findings suggest that widespread calcium deposition could occur in the nervous system following dimethyl mercury exposure, and that in the rat the mechanism of calcium deposition differs depending upon the brain region.
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Affiliation(s)
- F Mori
- Department of Neuropathology, Institute of Brain Science, Hirosaki University School of Medicine, Japan.
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