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Doroudian M, Thibault ME, Gailer J. N-Acetylcysteine Displaces Glutathionyl-Moieties from Hg 2+ and MeHg + to Form More Hydrophobic Complexes at Near-Physiological Conditions. Molecules 2023; 28:6762. [PMID: 37836605 PMCID: PMC10574133 DOI: 10.3390/molecules28196762] [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: 08/19/2023] [Revised: 09/19/2023] [Accepted: 09/19/2023] [Indexed: 10/15/2023] Open
Abstract
The anthropogenic release of Hg is associated with an increased human exposure risk. Since Hg2+ and MeHg+ have a high affinity for thiols, their interaction with L-glutathione (GSH) within mammalian cells is fundamentally involved in their toxicological chemistry and excretion. To gain insight into the interaction of these mercurials with multiple small molecular weight thiols, we have investigated their competitive interactions with GSH and N-acetylcysteine (NAC) at near-physiological conditions, using a liquid chromatographic approach. This approach involved the injection of each mercurial onto a reversed-phase (RP)-HPLC column (37 °C) using a PBS buffer mobile phase containing 5.0 mM GSH to simulate cytosolic conditions with Hg being detected in the column effluent by an inductively coupled plasma atomic emission spectrometer (ICP-AES). When the 5.0 mM GSH mobile phase was amended with up to 10 mM NAC, gradually increasing retention times of both mercurials were observed. To explain this behavior, the experiment with 5.0 mM NAC and 5.0 mM GSH was replicated using 50 mM Tris buffer (pH 7.4), and the Hg-containing fractions were analyzed by electrospray ionization mass spectrometry. The results revealed the presence of Hg(GS)(NAC) and Hg(NAC)2 for Hg2+ and MeHg(GS) and MeHg(NAC) for MeHg+, which suggests that the coordination/displacement of GS-moieties from each mercurial by the more hydrophobic NAC can explain their retention behavior. Since the biotransformations of both mercurials were observed at near-physiological conditions, they are of toxicological relevance as they provide a biomolecular explanation for some results that were obtained when animals were administered with each mercurial and NAC.
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Affiliation(s)
| | | | - Jürgen Gailer
- Department of Chemistry, University of Calgary, Calgary, AB T2N 1N4, Canada; (M.D.); (M.E.T.)
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Sasaki S, Negishi T, Tsuzuki T, Yukawa K. Methylmercury-induced reactive oxygen species-dependent and independent dysregulation of MAP kinase-related signaling pathway in cultured normal rat cerebellar astrocytes. Toxicology 2023; 487:153463. [PMID: 36813253 DOI: 10.1016/j.tox.2023.153463] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 02/17/2023] [Accepted: 02/17/2023] [Indexed: 02/22/2023]
Abstract
Methylmercury (MeHg), a global environmental pollutant, could seriously damage the central nervous system (CNS) and cause neurological disorders such as cerebellar symptoms. Although numerous studies have revealed detailed toxicity mechanisms of MeHg in neurons, toxicity in astrocytes is barely known. Here, we tried to shed light on the toxicity mechanisms of MeHg exposure in cultured normal rat cerebellar astrocytes (NRA), focusing on the involvement of reactive oxygen species (ROS) in MeHg toxicity by assessing the effects of major antioxidants Trolox, a free-radical scavenger, N-acetyl-L-cysteine (NAC), a potent thiol-containing antioxidant, and glutathione (GSH), an endogenous thiol-containing antioxidant. Exposure to MeHg at just approximately 2 µM for 96 h increased cell viability, which was accompanied by the increase in intracellular ROS level and at ≥ 5 µM induced significant cell death and lowered ROS level. Trolox and NAC suppressed 2 µM MeHg-induced increases in cell viability and ROS level corresponding to control, although GSH with 2 µM MeHg induced significant cell death and ROS increase. On the contrary, against 4 µM MeHg-induced cell loss and ROS decrease, NAC inhibited both cell loss and ROS decrease, Trolox inhibited cell loss and further enhanced ROS decrease, and GSH moderately inhibited cell loss and increased ROS level above the control level. MeHg-induced oxidative stress was suggested by increases in the protein expression levels of heme oxygenase-1 (HO-1), Hsp70, and Nrf2, except for the decrease in SOD-1 and no change in catalase. Furthermore, MeHg exposure dose-dependently induced increases in the phosphorylation of MAP kinases (ERK1/2, p38MAPK, and SAPK/JNK) and phosphorylation and/or expression levels of transcription factors (CREB, c-Jun, and c-Fos) in NRA. NAC successfully suppressed 2 µM MeHg-induced alterations in all of the above-mentioned MeHg-responsive factors, whereas Trolox suppressed some MeHg-responsive factors but failed to suppress MeHg-induced increases in the protein expression levels of HO-1 and Hsp70 and increase in p38MAPK phosphorylation. Protein expression analyses in NRA exposed to 2 µM MeHg and GSH were excluded because of devastating cell death. These results suggested that MeHg could induce aberrant NRA activation, and ROS must be substantially involved in the toxicity mechanism of MeHg in NRA; however, other factors should be assumed.
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Affiliation(s)
- Shoto Sasaki
- Department of Physiology, Graduate School of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya-shi, Aichi 468-8503, Japan
| | - Takayuki Negishi
- Department of Physiology, Graduate School of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya-shi, Aichi 468-8503, Japan; Department of Physiology, Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya-shi, Aichi 468-8503, Japan.
| | - Takamasa Tsuzuki
- Department of Physiology, Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya-shi, Aichi 468-8503, Japan
| | - Kazunori Yukawa
- Department of Physiology, Graduate School of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya-shi, Aichi 468-8503, Japan; Department of Physiology, Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya-shi, Aichi 468-8503, Japan
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3
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Takanezawa Y, Sakai K, Nakamura R, Ohshiro Y, Uraguchi S, Kiyono M. Inhibition of p38 Mitogen-Activated Protein Kinases Attenuates Methylmercury Toxicity in SH-SY5Y Neuroblastoma Cells. Biol Pharm Bull 2023; 46:1203-1210. [PMID: 37661399 DOI: 10.1248/bpb.b23-00014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Methylmercury (MeHg) is a toxic metal that causes irreversible damage to the nervous system, making it a risk factor for neuronal degeneration and diseases. MeHg activates various cell signaling pathways, particularly the mitogen-activated protein kinase (MAPK) cascades, which are believed to be important determinants of stress-induced cell fate. However, little is known about the signaling pathways that mitigate the neurotoxic effects of MeHg. Herein, we showed that pretreatment with a p38 MAPK-specific inhibitor, SB203580, attenuates MeHg toxicity in human neuroblastoma SH-SY5Y cells, whereas pretreatment with the extracellular signaling-regulated kinase inhibitor U0126 and the c-Jun N-terminal kinase inhibitor SP600125 does not. Specifically, we quantified the levels of intracellular mercury (Hg) and found that pretreatment with SB203580 reduced Hg levels compared to MeHg treatment alone. Further analysis showed that pretreatment with SB203580 increased multidrug resistance-associated protein 2 (MRP2) mRNA levels after MeHg treatment. These results indicate that detoxification of MeHg by p38 MAPK inhibitors may involve an efflux function of MeHg by inducing MRP2 expression.
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Affiliation(s)
| | - Kazuma Sakai
- Department of Public Health, School of Pharmacy, Kitasato University
| | - Ryosuke Nakamura
- Department of Public Health, School of Pharmacy, Kitasato University
| | - Yuka Ohshiro
- Department of Public Health, School of Pharmacy, Kitasato University
| | - Shimpei Uraguchi
- Department of Public Health, School of Pharmacy, Kitasato University
| | - Masako Kiyono
- Department of Public Health, School of Pharmacy, Kitasato University
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4
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Nascimento TS, Pinto DV, Dias RP, Raposo RS, Nunes PIG, Roque CR, Santos FA, Andrade GM, Viana JL, Fostier AH, Sussulini A, Alvarez-Leite JI, Fontes-Ribeiro C, Malva JO, Oriá RB. Chronic Methylmercury Intoxication Induces Systemic Inflammation, Behavioral, and Hippocampal Amino Acid Changes in C57BL6J Adult Mice. Int J Mol Sci 2022; 23:13837. [PMID: 36430321 PMCID: PMC9697706 DOI: 10.3390/ijms232213837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 10/24/2022] [Accepted: 10/26/2022] [Indexed: 11/12/2022] Open
Abstract
Methylmercury (MeHg) is highly toxic to the human brain. Although much is known about MeHg neurotoxic effects, less is known about how chronic MeHg affects hippocampal amino acids and other neurochemical markers in adult mice. In this study, we evaluated the MeHg effects on systemic lipids and inflammation, hippocampal oxidative stress, amino acid levels, neuroinflammation, and behavior in adult male mice. Challenged mice received MeHg in drinking water (2 mg/L) for 30 days. We assessed weight gain, total plasma cholesterol (TC), triglycerides (TG), endotoxin, and TNF levels. Hippocampal myeloperoxidase (MPO), malondialdehyde (MDA), acetylcholinesterase (AChE), amino acid levels, and cytokine transcripts were evaluated. Mice underwent open field, object recognition, Y, and Barnes maze tests. MeHg-intoxicated mice had higher weight gain and increased the TG and TC plasma levels. Elevated circulating TNF and LPS confirmed systemic inflammation. Higher levels of MPO and MDA and a reduction in IL-4 transcripts were found in the hippocampus. MeHg-intoxication led to increased GABA and glycine, reduced hippocampal taurine levels, delayed acquisition in the Barnes maze, and poor locomotor activity. No significant changes were found in AChE activity and object recognition. Altogether, our findings highlight chronic MeHg-induced effects that may have long-term mental health consequences in prolonged exposed human populations.
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Affiliation(s)
- Tyciane S. Nascimento
- Neuroscience and Behavior Laboratory, Drug Research and Development Center, Federal University of Ceará, Fortaleza 60430-275, Brazil
| | - Daniel V. Pinto
- Laboratory of Tissue Healing, Ontogeny, and Nutrition, Department of Morphology and Institute of Biomedicine, School of Medicine, Federal University of Ceará, Fortaleza 60430-270, Brazil
| | - Ronaldo P. Dias
- Laboratory of Tissue Healing, Ontogeny, and Nutrition, Department of Morphology and Institute of Biomedicine, School of Medicine, Federal University of Ceará, Fortaleza 60430-270, Brazil
| | - Ramon S. Raposo
- Experimental Biology Core, Health Sciences Center, University of Fortaleza, Fortaleza 60812-020, Brazil
| | - Paulo Iury G. Nunes
- Natural Products Laboratory, Department of Physiology and Pharmacology, Federal University of Ceará, Fortaleza 60430-270, Brazil
| | - Cássia R. Roque
- Laboratory of Tissue Healing, Ontogeny, and Nutrition, Department of Morphology and Institute of Biomedicine, School of Medicine, Federal University of Ceará, Fortaleza 60430-270, Brazil
| | - Flávia A. Santos
- Natural Products Laboratory, Department of Physiology and Pharmacology, Federal University of Ceará, Fortaleza 60430-270, Brazil
| | - Geanne M. Andrade
- Neuroscience and Behavior Laboratory, Drug Research and Development Center, Federal University of Ceará, Fortaleza 60430-275, Brazil
| | - José Lucas Viana
- Department of Analytical Chemistry, Institute of Chemistry, University of Campinas—UNICAMP, Campinas 13083-862, Brazil
| | - Anne H. Fostier
- Department of Analytical Chemistry, Institute of Chemistry, University of Campinas—UNICAMP, Campinas 13083-862, Brazil
| | - Alessandra Sussulini
- Department of Analytical Chemistry, Institute of Chemistry, University of Campinas—UNICAMP, Campinas 13083-862, Brazil
| | - Jacqueline I. Alvarez-Leite
- Laboratory of Atherosclerosis and Nutritional Biochemistry, Federal University of Minas Gerais, Belo Horizonte 31270-901, Brazil
| | - Carlos Fontes-Ribeiro
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Institute of Pharmacology and Experimental Therapeutics and Center for Innovative Biomedicine and Biotechnology (CIBB), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - João O. Malva
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Institute of Pharmacology and Experimental Therapeutics and Center for Innovative Biomedicine and Biotechnology (CIBB), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Reinaldo B. Oriá
- Laboratory of Tissue Healing, Ontogeny, and Nutrition, Department of Morphology and Institute of Biomedicine, School of Medicine, Federal University of Ceará, Fortaleza 60430-270, Brazil
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Horai S, Abiko Y, Unoki T, Shinkai Y, Akiyama M, Nakata K, Kunisue T, Kumagai Y. Concentrations of nucleophilic sulfur species in small Indian mongoose (Herpestes auropunctatus) in Okinawa, Japan. CHEMOSPHERE 2022; 295:133833. [PMID: 35120952 DOI: 10.1016/j.chemosphere.2022.133833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 01/27/2022] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
Reactive sulfur species (RSS), such as hydrogen per (poly)sulfide, cysteine per (poly)sulfide, glutathione per (poly)sulfide, and protein-bound per (poly)sulfides, can easily react with environmental electrophiles such as methylmercury (MeHg), because of their high nucleophilicity. These RSS are produced by enzymes such as cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) and are found in mammalian organs. Organs of wildlife have not been analyzed for hydrogen sulfide, cysteine, glutathione, and RSS. In this study, low molecular weight nucleophilic sulfur substances, including RSS, were quantified by stable isotope dilution assay-based liquid chromatography-mass spectrometry using β-(4-hydroxyphenyl)ethyl iodoacetamide to capture the target chemicals in the small Indian mongoose which species possesses high mercury content as same as some marine mammals. Western blotting revealed that the mongoose organs (liver, kidney, cerebrum, and cerebellum) contained proteins that cross-reacted with anti-CBS and CSE antibodies. The expression patterns of these enzymes were similar to those in mice, indicating that mongoose organs contain CBS and CSE. Moreover, bis-methylmercury sulfide (MeHg)2S, which is a low toxic compound in comparison to MeHg, was found in the liver of this species. These results suggest that the small Indian mongoose produces RSS and monothiols associated with detoxification of electrophilic organomercury. The animals which have high mercury content in their bodies may have function of mercury detoxification involved not only Se but also RSS interactions.
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Affiliation(s)
- Sawako Horai
- Environmental Health Section, Department of Environment and Public Health, National Institute for Minamata Disease, 4058-18 Hama, Minamata, Kumamoto, 867-0008, Japan.
| | - Yumi Abiko
- Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan.
| | - Takamitsu Unoki
- Hygienic Chemistry Section, Department of Basic Medical Sciences, National Institute for Minamata Disease, 4058-18 Hama, Minamata, Kumamoto, 867-0008, Japan.
| | - Yasuhiro Shinkai
- Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan.
| | - Masahiro Akiyama
- Research Center for Drug Discovery, Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University, 1-5-30 Shibakoen, Minato-ku, Tokyo, 105-8512, Japan.
| | - Katsushi Nakata
- Nansei Environmental Laboratory Co., Ltd., 4-4 Agarizaki, Nishihara, Okinawa, 903-0105, Japan.
| | - Tatsuya Kunisue
- Center for Marine Environmental Studies, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime, 790-8577, Japan.
| | - Yoshito Kumagai
- Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan.
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6
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Bridle TG, Kumarathasan P, Gailer J. Toxic Metal Species and 'Endogenous' Metalloproteins at the Blood-Organ Interface: Analytical and Bioinorganic Aspects. Molecules 2021; 26:molecules26113408. [PMID: 34199902 PMCID: PMC8200099 DOI: 10.3390/molecules26113408] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 05/19/2021] [Accepted: 06/01/2021] [Indexed: 01/15/2023] Open
Abstract
Globally, human exposure to environmental pollutants causes an estimated 9 million deaths per year and it could also be implicated in the etiology of diseases that do not appear to have a genetic origin. Accordingly, there is a need to gain information about the biomolecular mechanisms that causally link exposure to inorganic environmental pollutants with distinct adverse health effects. Although the analysis of blood plasma and red blood cell (RBC) cytosol can provide important biochemical information about these mechanisms, the inherent complexity of these biological matrices can make this a difficult task. In this perspective, we will examine the use of metalloentities that are present in plasma and RBC cytosol as potential exposure biomarkers to assess human exposure to inorganic pollutants. Our primary objective is to explore the principal bioinorganic processes that contribute to increased or decreased metalloprotein concentrations in plasma and/or RBC cytosol. Furthermore, we will also identify metabolites which can form in the bloodstream and contain essential as well as toxic metals for use as exposure biomarkers. While the latter metal species represent useful biomarkers for short-term exposure, endogenous plasma metalloproteins represent indicators to assess the long-term exposure of an individual to inorganic pollutants. Based on these considerations, the quantification of metalloentities in blood plasma and/or RBC cytosol is identified as a feasible research avenue to better understand the adverse health effects that are associated with chronic exposure of various human populations to inorganic pollutants. Exposure to these pollutants will likely increase as a consequence of technological advances, including the fast-growing applications of metal-based engineering nanomaterials.
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Affiliation(s)
- Tristen G. Bridle
- Department of Chemistry, 2500 University Drive NW, University of Calgary, Calgary, AB T2N 1N4, Canada;
| | - Premkumari Kumarathasan
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON K1A 0K9, Canada;
| | - Jürgen Gailer
- Department of Chemistry, 2500 University Drive NW, University of Calgary, Calgary, AB T2N 1N4, Canada;
- Correspondence:
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Spiller HA, Hays HL, Casavant MJ. Rethinking treatment of mercury poisoning: the roles of selenium, acetylcysteine, and thiol chelators in the treatment of mercury poisoning: a narrative review. TOXICOLOGY COMMUNICATIONS 2021. [DOI: 10.1080/24734306.2020.1870077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Affiliation(s)
- Henry A. Spiller
- Central Ohio Poison Center, Nationwide Children’s Hospital, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Hannah L. Hays
- Central Ohio Poison Center, Nationwide Children’s Hospital, Columbus, OH, USA
- Departments of Emergency Medicine and Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Marcel J. Casavant
- Central Ohio Poison Center, Nationwide Children’s Hospital, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
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8
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Muniroh M. Methylmercury-induced pro-inflammatory cytokines activation and its preventive strategy using anti-inflammation N-acetyl-l-cysteine: a mini-review. REVIEWS ON ENVIRONMENTAL HEALTH 2020; 35:233-238. [PMID: 32710722 DOI: 10.1515/reveh-2020-0026] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 06/09/2020] [Indexed: 06/11/2023]
Abstract
The exposure of methylmercury (MeHg) has become a public health concern because of its neurotoxic effect. Various neurological symptoms were detected in Minamata disease patients, who got intoxicated by MeHg, including paresthesia, ataxia, gait disturbance, sensory disturbances, tremors, visual, and hearing impairments, indicating that MeHg could pass the blood-brain barrier (BBB) and cause impairment of neurons and other brain cells. Previous studies have reported some expected mechanisms of MeHg-induced neurotoxicity including the neuroinflammation pathway. It was characterized by the up-regulation of numerous pro-inflammatory cytokines expression. Therefore, the use of anti-inflammatories such as N-acetyl-l-cysteine (NAC) may act as a preventive compound to protect the brain from MeHg harmful effects. This mini-review will explain detailed information on MeHg-induced pro-inflammatory cytokines activation as well as possible preventive strategies using anti-inflammation NAC to protect brain cells, particularly in in vivo and in vitro studies.
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Affiliation(s)
- Muflihatul Muniroh
- Department of Physiology, Faculty of Medicine Diponegoro University, Semarang, Central Java, 50275, Indonesia
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Evaluation of Renal Anionic Secretion Following Living-donor and Deceased-donor Renal Transplantation: A Clinical Pharmacokinetic Study of Cefoxitin Microdosing. Transplant Direct 2020; 6:e561. [PMID: 33062845 PMCID: PMC7531749 DOI: 10.1097/txd.0000000000001001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 03/19/2020] [Indexed: 11/25/2022] Open
Abstract
Renal transplantation is the treatment of choice for patients with end-stage renal disease. Because kidneys are the primary excretory organs for various drugs/drug metabolites, changes in renal graft function would significantly alter the clearance and exposure of renally secreted drugs. Renal allografts from living and deceased donors normally undergo numerous insults, including injuries associated with prolonged cold ischemic time, reperfusion, and nephrotoxicity due to calcineurin inhibitors. These physiologic and pharmacologic stresses can alter the expression and functional capacity of renal organic anionic transporters (OATs). Methods The objectives of this study were to assess the longitudinal changes in renal anionic secretion in kidney transplant patients, to study the effect of prolonged cold ischemic time on OAT secretion in kidney transplant patients (living- versus deceased-donor recipients), and to compare OAT secretory capacity of renal transplant recipients with healthy volunteers. Cefoxitin was used as a probe drug to assess OAT secretion. Cefoxitin pharmacokinetics was studied in 15 de novo renal transplant recipients following intravenous administration of 200 mg cefoxitin within 14 d and beyond 90 d posttransplantation. Results No longitudinal changes in real OAT secretion in early posttransplant period were observed, and there were no differences in renal OAT secretion between living- and deceased-donor renal transplant recipients. Overall, cefoxitin exposure was 2.6-fold higher and half-life increased by 2.2-fold in renal transplant recipients when compared with historical healthy controls. Conclusions These results suggest that OAT system is functioning well, but renal transplant recipients would need significantly lower dosage of drugs that are primarily secreted via the OAT system compared with normal subjects.
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Rand MD, Vorojeikina D, Peppriell A, Gunderson J, Prince LM. Drosophotoxicology: Elucidating Kinetic and Dynamic Pathways of Methylmercury Toxicity in a Drosophila Model. Front Genet 2019; 10:666. [PMID: 31447878 PMCID: PMC6695472 DOI: 10.3389/fgene.2019.00666] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 06/25/2019] [Indexed: 01/18/2023] Open
Abstract
The risks of methylmercury (MeHg) toxicity are greatest during early life where it has long been appreciated that the developing nervous system is an especially sensitive target. Yet, understanding the discrete mechanisms of MeHg toxicity have been obscured by the wide variation in the nature and severity of developmental outcomes that are typically seen across individuals in MeHg exposed populations. Some insight has come from studies aimed at identifying a role for genetic background as a modifier of MeHg toxicity, which have predominantly focused on factors influencing MeHg toxicokinetics, notably, polymorphisms in genes related to glutathione (GSH) metabolism. For example, variants in genes encoding the catalytic and modifier subunits of glutamyl-cysteine ligase (GCLc and GCLm), the rate limiting enzyme for GSH synthesis, have been reported to associate with Hg body burden (Hg levels in blood or hair) in humans. However, GSH can facilitate both toxicokinetics and toxicodynamics of MeHg by forming MeHg-GSH conjugates, which are readily transported and excreted, and by acting indirectly as an anti-oxidant. In this study, we refine a model to distinguish kinetic and dynamic traits of MeHg toxicity using a paradigm of Drosophotoxicolgy. First, we identify that the pupal stage is selectively sensitive to MeHg toxicity. Using a protocol of larval feeding, measurements of Hg body burden, and assays of development to adulthood (pupal eclosion), we identify strain-dependent variation in MeHg elimination as a potential kinetic determinant of differential tolerance to MeHg. We also find that global upregulation of GSH levels, with GCLc trans-gene expression, can induce MeHg tolerance and reduce Hg body burden. However, we demonstrate that MeHg tolerance can also be achieved independently of reducing Hg body burden, in both wild-derived strains and with targeted expression of GCLc in developing neuronal and muscle tissue, pointing to a robust toxicodynamic mechanism. Our findings have important implications for understanding variation in MeHg toxic potential on an individual basis and for informing the process of relating a measurement of Hg body burden to the potential for adverse developmental outcome.
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Affiliation(s)
- Matthew D Rand
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Daria Vorojeikina
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Ashley Peppriell
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Jakob Gunderson
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Lisa M Prince
- School of Human Health Sciences, Purdue University, West Lafayette, IN, United States
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Nakamura R, Shirahata T, Konishi N, Takanezawa Y, Sone Y, Uraguchi S, Kobayashi Y, Kiyono M. Oleanolic acid 3-glucoside, a synthetic oleanane-type saponin, alleviates methylmercury toxicity in vitro and in vivo. Toxicology 2019; 417:15-22. [PMID: 30776458 DOI: 10.1016/j.tox.2019.02.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 01/20/2019] [Accepted: 02/11/2019] [Indexed: 02/07/2023]
Abstract
Methylmercury (MeHg) is one of the most toxic environmental pollutants, presenting a serious health hazard worldwide. In this study, we examined the potential of derivatives of oleanolic acid (OA), such as OA 3-glucoside, OA 28-glucoside, and OA 3,28-diglucoside, to mitigate MeHg toxicity in vitro and in vivo. We found that OA 3-glucoside suppressed the cellular MeHg uptake by 63.4% compared with that of the control and improved the cell viability from 75.4% to 107.9% upon exposure to cytotoxic MeHg in Caco-2 cells. To verify the anti-MeHg activity of OA 3-glucoside, mice were orally administered MeHg (0, 1.0, or 5.0 mg kg-1·d-1), with or without OA 3-glucoside, and then mercury accumulation was measured in various organs of the mice. The mice co-treated with MeHg and OA 3-glucoside showed significantly lower mercury content in organs such as the cerebrum, cerebellum, liver, kidney, and spleen, with 83.1%, 68.7%, 71.7%, 82.1%, and 18.2% of those in the OA 3-glucoside-untreated group, respectively. This suggested OA 3-glucoside had the potential as an anti-MeHg compound, owing to its ability to suppress the distribution of MeHg into organs. Supporting this hypothesis, the mice treated with MeHg and OA 3-glucoside showed a tendency to survive one day longer than the control mice. Our findings suggest OA 3-glucoside administration alleviates the toxicity of MeHg by suppressing MeHg accumulation in organs.
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Affiliation(s)
- Ryosuke Nakamura
- School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Tatsuya Shirahata
- School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Naruki Konishi
- School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Yasukazu Takanezawa
- School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Yuka Sone
- School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Shimpei Uraguchi
- School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Yoshinori Kobayashi
- School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Masako Kiyono
- School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8641, Japan.
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Nogara PA, Oliveira CS, Schmitz GL, Piquini PC, Farina M, Aschner M, Rocha JBT. Methylmercury's chemistry: From the environment to the mammalian brain. Biochim Biophys Acta Gen Subj 2019; 1863:129284. [PMID: 30659885 DOI: 10.1016/j.bbagen.2019.01.006] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 12/14/2018] [Accepted: 01/09/2019] [Indexed: 02/06/2023]
Abstract
Methylmercury is a neurotoxicant that is found in fish and rice. MeHg's toxicity is mediated by blockage of -SH and -SeH groups of proteins. However, the identification of MeHg's targets is elusive. Here we focus on the chemistry of MeHg in the abiotic and biotic environment. The toxicological chemistry of MeHg is complex in metazoans, but at the atomic level it can be explained by exchange reactions of MeHg bound to -S(e)H with another free -S(e)H group (R1S(e)-HgMe + R2-S(e)H ↔ R1S(e)H + R2-S(e)-HgMe). This reaction was first studied by professor Rabenstein and here it is referred as the "Rabenstein's Reaction". The absorption, distribution, and excretion of MeHg in the environment and in the body of animals will be dictated by Rabenstein's reactions. The affinity of MeHg by thiol and selenol groups and the exchange of MeHg by Rabenstein's Reaction (which is a diffusion controlled reaction) dictates MeHg's neurotoxicity. However, it is important to emphasize that the MeHg exchange reaction velocity with different types of thiol- and selenol-containing proteins will also depend on protein-specific structural and thermodynamical factors. New experimental approaches and detailed studies about the Rabenstein's reaction between MeHg with low molecular mass thiol (LMM-SH) molecules (cysteine, GSH, acetyl-CoA, lipoate, homocysteine) with abundant high molecular mass thiol (HMM-SH) molecules (albumin, hemoglobin) and HMM-SeH (GPxs, Selenoprotein P, TrxR1-3) are needed. The study of MeHg migration from -S(e)-Hg- bonds to free -S(e)H groups (Rabenstein's Reaction) in pure chemical systems and neural cells (with special emphasis to the LMM-SH and HMM-S(e)H molecules cited above) will be critical to developing realistic constants to be used in silico models that will predict the distribution of MeHg in humans.
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Affiliation(s)
- Pablo A Nogara
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Cláudia S Oliveira
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Gabriela L Schmitz
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Paulo C Piquini
- Departamento de Física, CCNE, Universidade Federal de Santa Maria (UFSM), Santa Maria, RS, Brazil
| | - Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - João B T Rocha
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil.
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Spiller HA, Hays HL, Burns G, Casavant MJ. Severe elemental mercury poisoning managed with selenium and N-acetylcysteine administration. TOXICOLOGY COMMUNICATIONS 2017. [DOI: 10.1080/24734306.2017.1392076] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Henry A. Spiller
- Department of Pediatrics, Central Ohio Poison Center, Nationwide Children's Hospital, The Ohio State University College of Medicine, Columbus, OH, U.S.A
| | - Hannah L. Hays
- Department of Pediatrics, Central Ohio Poison Center, Nationwide Children's Hospital, The Ohio State University College of Medicine, Columbus, OH, U.S.A
| | - Glenn Burns
- Department of Emergency Medicine & Division of Pediatric Critical Care, Wright State University Boonshoft School of Medicine/Dayton Children's Hospital, Dayton, OH, U.S.A
| | - Marcel J Casavant
- Department of Pediatrics, Central Ohio Poison Center, Nationwide Children's Hospital, The Ohio State University College of Medicine, Columbus, OH, U.S.A
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14
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Orr SE, Bridges CC. Chronic Kidney Disease and Exposure to Nephrotoxic Metals. Int J Mol Sci 2017; 18:ijms18051039. [PMID: 28498320 PMCID: PMC5454951 DOI: 10.3390/ijms18051039] [Citation(s) in RCA: 200] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 04/26/2017] [Indexed: 12/26/2022] Open
Abstract
Chronic kidney disease (CKD) is a common progressive disease that is typically characterized by the permanent loss of functional nephrons. As injured nephrons become sclerotic and die, the remaining healthy nephrons undergo numerous structural, molecular, and functional changes in an attempt to compensate for the loss of diseased nephrons. These compensatory changes enable the kidney to maintain fluid and solute homeostasis until approximately 75% of nephrons are lost. As CKD continues to progress, glomerular filtration rate decreases, and remaining nephrons are unable to effectively eliminate metabolic wastes and environmental toxicants from the body. This inability may enhance mortality and/or morbidity of an individual. Environmental toxicants of particular concern are arsenic, cadmium, lead, and mercury. Since these metals are present throughout the environment and exposure to one or more of these metals is unavoidable, it is important that the way in which these metals are handled by target organs in normal and disease states is understood completely.
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Affiliation(s)
- Sarah E Orr
- Mercer University School of Medicine, Division of Basic Medical Sciences, 1550 College St., Macon, GA 31207, USA.
| | - Christy C Bridges
- Mercer University School of Medicine, Division of Basic Medical Sciences, 1550 College St., Macon, GA 31207, USA.
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15
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Bridges CC, Zalups RK. The aging kidney and the nephrotoxic effects of mercury. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2017; 20:55-80. [PMID: 28339347 PMCID: PMC6088787 DOI: 10.1080/10937404.2016.1243501] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Owing to advances in modern medicine, life expectancies are lengthening and leading to an increase in the population of older individuals. The aging process leads to significant alterations in many organ systems, with the kidney being particularly susceptible to age-related changes. Within the kidney, aging leads to ultrastructural changes such as glomerular and tubular hypertrophy, glomerulosclerosis, and tubulointerstitial fibrosis, which may compromise renal plasma flow (RPF) and glomerular filtration rate (GFR). These alterations may reduce the functional reserve of the kidneys, making them more susceptible to pathological events when challenged or stressed, such as following exposure to nephrotoxicants. An important and prevalent environmental toxicant that induces nephrotoxic effects is mercury (Hg). Since exposure of normal kidneys to mercuric ions might induce glomerular and tubular injury, aged kidneys, which may not be functioning at full capacity, may be more sensitive to the effects of Hg than normal kidneys. Age-related renal changes and the effects of Hg in the kidney have been characterized separately. However, little is known regarding the influence of nephrotoxicants, such as Hg, on aged kidneys. The purpose of this review was to summarize known findings related to exposure of aged and diseased kidneys to the environmentally relevant nephrotoxicant Hg.
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Affiliation(s)
- Christy C Bridges
- a Mercer University School of Medicine , Division of Basic Medical Sciences , Macon , Georgia , USA
| | - Rudolfs K Zalups
- a Mercer University School of Medicine , Division of Basic Medical Sciences , Macon , Georgia , USA
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16
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Toyama T, Abiko Y, Katayama Y, Kaji T, Kumagai Y. S-Mercuration of ubiquitin carboxyl-terminal hydrolase L1 through Cys152 by methylmercury causes inhibition of its catalytic activity and reduction of monoubiquitin levels in SH-SY5Y cells. J Toxicol Sci 2016; 40:887-93. [PMID: 26558469 DOI: 10.2131/jts.40.887] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Methylmercury (MeHg) is an environmental electrophile that covalently modifies cellular proteins. In this study, we identified proteins that undergo S-mercuration by MeHg. By combining two-dimensional SDS-PAGE, atomic absorption spectrometry and ultra performance liquid chromatography mass spectrometry (UPLC/MS/MS), we revealed that ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) is a target for S-mercuration in human neuroblastoma SH-SY5Y cells exposed to MeHg (1 µM, 9 hr). The modification site of UCH-L1 by MeHg was Cys152, as determined by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. MeHg was shown to inhibit the catalytic activity of recombinant human UCH-L1 in a concentration-dependent manner. Knockdown of UCH-L1 indicated that this enzyme plays a critical role in regulating mono-ubiquitin (monoUb) levels in SH-SY5Y cells and exposure of SH-SY5Y cells to MeHg caused a reduction in the level of monoUb in these cells. These observations suggest that UCH-L1 readily undergoes S-mercuration by MeHg through Cys152 and this covalent modification inhibits UCH-L1, leading to the potential disruption of the maintenance of cellular monoUb levels.
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17
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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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18
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Mercury toxicokinetics of the healthy human term placenta involve amino acid transporters and ABC transporters. Toxicology 2016; 340:34-42. [DOI: 10.1016/j.tox.2015.12.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 12/10/2015] [Accepted: 12/23/2015] [Indexed: 11/18/2022]
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Yoshida E, Abiko Y, Kumagai Y. Glutathione adduct of methylmercury activates the Keap1-Nrf2 pathway in SH-SY5Y cells. Chem Res Toxicol 2014; 27:1780-6. [PMID: 25271560 DOI: 10.1021/tx5002332] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Methylmercury (MeHg) reacts readily with GSH, leading to the formation of a MeHg-SG adduct that is excreted into extracellular space through multidrug-resistance-associated protein (MRP), which is regulated by the transcription factor Nrf2. We previously reported that MeHg covalently modifies Keap1 and activates Nrf2 in human neuroblastoma SH-SY5Y cells. In the study presented here, we examined whether the MeHg-SG adduct could also modulate the Keap1-Nrf2 pathway because the formation of the Hg-S bond is believed to be reversible in the presence of a nucleophile. SH-SY5Y cells exposed to the synthetic ethyl monoester of the MeHg-SG adduct (which is hydrolyzed by cellular esterase(s) to give the MeHg-SG adduct) exhibited a concentration-dependent cellular toxicity that was enhanced by pretreatment with a specific MRP inhibitor. As expected, the MeHg-SG adduct was able to modify cellular proteins in the SH-SY5Y cells and purified Keap1. We also found that this prodrug, as well as MeHg, causes the cellular Keap1 in the cells to be modified, resulting in Nrf2 activation and, thereby, the upregulation of the downstream genes. These results suggest that the MeHg-SG adduct is not electrophilic but that it modifies protein thiols (including Keap1) through S-transmercuration and that rapid Nrf2-dependent excretion of the MeHg-SG adduct is essential in decreasing the cytotoxicity of MeHg.
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Affiliation(s)
- Eiko Yoshida
- Doctoral Program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
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20
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Bouchet S, Björn E. Analytical developments for the determination of monomethylmercury complexes with low molecular mass thiols by reverse phase liquid chromatography hyphenated to inductively coupled plasma mass spectrometry. J Chromatogr A 2014; 1339:50-8. [DOI: 10.1016/j.chroma.2014.02.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/12/2014] [Accepted: 02/16/2014] [Indexed: 11/29/2022]
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21
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VanDuyn N, Nass R. The putative multidrug resistance protein MRP-7 inhibits methylmercury-associated animal toxicity and dopaminergic neurodegeneration in Caenorhabditis elegans. J Neurochem 2013; 128:962-74. [PMID: 24266639 DOI: 10.1111/jnc.12515] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 10/17/2013] [Accepted: 10/28/2013] [Indexed: 10/26/2022]
Abstract
Parkinson's disease (PD) is the most prevalent neurodegenerative motor disorder worldwide, and results in the progressive loss of dopamine (DA) neurons in the substantia nigra pars compacta. Gene-environment interactions are believed to play a significant role in the vast majority of PD cases, yet the toxicants and the associated genes involved in the neuropathology are largely ill-defined. Recent epidemiological and biochemical evidence suggests that methylmercury (MeHg) may be an environmental toxicant that contributes to the development of PD. Here, we report that a gene coding for the putative multidrug resistance protein MRP-7 in Caenorhabditis elegans modulates whole animal and DA neuron sensitivity to MeHg. In this study, we demonstrate that genetic knockdown of MRP-7 results in a twofold increase in Hg levels and a dramatic increase in stress response proteins associated with the endoplasmic reticulum, golgi apparatus, and mitochondria, as well as an increase in MeHg-associated animal death. Chronic exposure to low concentrations of MeHg induces MRP-7 gene expression, while exposures in MRP-7 genetic knockdown animals results in a loss of DA neuron integrity without affecting whole animal viability. Furthermore, transgenic animals expressing a fluorescent reporter behind the endogenous MRP-7 promoter indicate that the transporter is expressed in DA neurons. These studies show for the first time that a multidrug resistance protein is expressed in DA neurons, and its expression inhibits MeHg-associated DA neuron pathology.
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Affiliation(s)
- Natalia VanDuyn
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, USA
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22
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Yamashita M, Yamashita Y, Suzuki T, Kani Y, Mizusawa N, Imamura S, Takemoto K, Hara T, Hossain MA, Yabu T, Touhata K. Selenoneine, a novel selenium-containing compound, mediates detoxification mechanisms against methylmercury accumulation and toxicity in zebrafish embryo. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2013; 15:559-70. [PMID: 23709046 PMCID: PMC3742965 DOI: 10.1007/s10126-013-9508-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Accepted: 03/19/2013] [Indexed: 05/15/2023]
Abstract
The selenium (Se)-containing antioxidant selenoneine (2-selenyl-N α,N α,N α-trimethyl-L-histidine) has recently been discovered to be the predominant form of organic Se in tuna blood. Although dietary intake of fish Se has been suggested to reduce methylmercury (MeHg) toxicity, the molecular mechanism of MeHg detoxification by Se has not yet been determined. Here, we report evidence that selenoneine accelerates the excretion and demethylation of MeHg, mediated by a selenoneine-specific transporter, organic cations/carnitine transporter-1 (OCTN1). Selenoneine was incorporated into human embryonic kidney HEK293 cells transiently overexpressing OCTN1 and zebrafish blood cells by OCTN1. The K m for selenoneine uptake was 13.0 μM in OCTN1-overexpressing HEK293 cells and 9.5 μM in zebrafish blood cells, indicating high affinity of OCTN1 for selenoneine in human and zebrafish cells. When such OCTN1-expressing cells and embryos were exposed to MeHg-cysteine (MeHgCys), MeHg accumulation was decreased and the excretion and demethylation of MeHg were enhanced by selenoneine. In addition, exosomal secretion vesicles were detected in the culture water of embryos that had been microinjected with MeHgCys, suggesting that these may be responsible for MeHg excretion and demethylation. In contrast, OCTN1-deficient embryos accumulated MeHg, and MeHg excretion and demethylation were decreased. Furthermore, Hg accumulation was decreased in OCTN1-overexpressing HEK293 cells, but not in mock vector-transfected cells, indicating that selenoneine and OCTN1 can regulate MeHg detoxification in human cells. Thus, the selenoneine-mediated OCTN1 system regulates secretory lysosomal vesicle formation and MeHg demethylation.
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Affiliation(s)
- Michiaki Yamashita
- National Research Institute of Fisheries Science, 2-12-4 Fukuura, Yokohama, Kanagawa, 236-8648, Japan.
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23
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The role of the Keap1/Nrf2 pathway in the cellular response to methylmercury. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:848279. [PMID: 23878621 PMCID: PMC3710591 DOI: 10.1155/2013/848279] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 05/26/2013] [Accepted: 06/03/2013] [Indexed: 12/26/2022]
Abstract
Methylmercury (MeHg) is an environmental electrophile that covalently modifies cellular proteins with reactive thiols, resulting in the formation of protein adducts. While such protein modifications, referred to as S-mercuration, are thought to be associated with the enzyme dysfunction and cellular damage caused by MeHg exposure, the current consensus is that (1) there is a cellular response to MeHg through the activation of NF-E2-related factor 2 (Nrf2) coupled to S-mercuration of its negative regulator, Kelch-like ECH-associated protein 1 (Keap1), and (2) the Keap1/Nrf2 pathway protects against MeHg toxicity. In this review, we introduce our findings and discuss the observations of other workers concerning the S-mercuration of cellular proteins by MeHg and the importance of the Keap1/Nrf2 pathway in protection against MeHg toxicity in cultured cells and mice.
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Jalilehvand F, Parmar K, Zielke S. Mercury(ii) complex formation with N-acetylcysteine. Metallomics 2013; 5:1368-76. [DOI: 10.1039/c3mt00173c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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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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26
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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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27
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Falluel-Morel A, Lin L, Sokolowski K, McCandlish E, Buckley B, DiCicco-Bloom E. N-acetyl cysteine treatment reduces mercury-induced neurotoxicity in the developing rat hippocampus. J Neurosci Res 2012; 90:743-50. [PMID: 22420031 DOI: 10.1002/jnr.22819] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Mercury is an environmental toxicant that can disrupt brain development. However, although progress has been made in defining its neurotoxic effects, we know far less about available therapies that can effectively protect the brain in exposed individuals. We previously developed an animal model in which we defined the sequence of events underlying neurotoxicity: Methylmercury (MeHg) injection in postnatal rat acutely induced inhibition of mitosis and stimulated apoptosis in the hippocampus, which later resulted in intermediate-term deficits in structure size and cell number. N-acetyl cysteine (NAC) is the N-acetyl derivative of L-cysteine used clinically for treatment of drug intoxication. Here, based on its known efficacy in promoting MeHg urinary excretion, we evaluated NAC for protective effects in the developing brain. In immature neurons and precursors, MeHg (3 μM) induced a >50% decrease in DNA synthesis at 24 hr, an effect that was completely blocked by NAC coincubation. In vivo, injection of MeHg (5 μg/g bw) into 7-day-old rats induced a 22% decrease in DNA synthesis in whole hippocampus and a fourfold increase in activated caspase-3-immunoreactive cells at 24 hr and reduced total cell numbers by 13% at 3 weeks. Treatment of MeHg-exposed rats with repeated injections of NAC abolished MeHg toxicity. NAC prevented the reduction in DNA synthesis and the marked increase in caspase-3 immunoreactivity. Moreover, the intermediate-term decrease in hippocampal cell number provoked by MeHg was fully blocked by NAC. Altogether these results suggest that MeHg toxicity in the perinatal brain can be ameliorated by using NAC, opening potential avenues for therapeutic intervention.
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Affiliation(s)
- Anthony Falluel-Morel
- Department of Neuroscience and Cell Biology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
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28
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Yoshida E, Toyama T, Shinkai Y, Sawa T, Akaike T, Kumagai Y. Detoxification of Methylmercury by Hydrogen Sulfide-Producing Enzyme in Mammalian Cells. Chem Res Toxicol 2011; 24:1633-5. [DOI: 10.1021/tx200394g] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Eiko Yoshida
- Doctoral Program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Takashi Toyama
- Doctoral Program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
- Japan Society for the Promotion of Science, 1-8 Chiyoda-ku, Tokyo 102-8472, Japan
| | - Yasuhiro Shinkai
- Doctoral Program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Tomohiro Sawa
- Department of Microbiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan
| | - Takaaki Akaike
- Department of Microbiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan
| | - Yoshito Kumagai
- Doctoral Program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
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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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30
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Toyama T, Shinkai Y, Sumi D, Kumagai Y. Carbon monoxide derived from heme oxygenase-2 mediates reduction of methylmercury toxicity in SH-SY5Y cells. Toxicol Appl Pharmacol 2010; 249:86-90. [DOI: 10.1016/j.taap.2010.08.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 08/17/2010] [Accepted: 08/21/2010] [Indexed: 11/16/2022]
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Jemnitz K, Heredi-Szabo K, Janossy J, Ioja E, Vereczkey L, Krajcsi P. ABCC2/Abcc2: a multispecific transporter with dominant excretory functions. Drug Metab Rev 2010; 42:402-36. [PMID: 20082599 DOI: 10.3109/03602530903491741] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
ABCC2/Abcc2 (MRP2/Mrp2) is expressed at major physiological barriers, such as the canalicular membrane of liver cells, kidney proximal tubule epithelial cells, enterocytes of the small and large intestine, and syncytiotrophoblast of the placenta. ABCC2/Abcc2 always localizes in the apical membranes. Although ABCC2/Abcc2 transports a variety of amphiphilic anions that belong to different classes of molecules, such as endogenous compounds (e.g., bilirubin-glucuronides), drugs, toxic chemicals, nutraceuticals, and their conjugates, it displays a preference for phase II conjugates. Phenotypically, the most obvious consequence of mutations in ABCC2 that lead to Dubin-Johnson syndrome is conjugate hyperbilirubinemia. ABCC2/Abcc2 harbors multiple binding sites and displays complex transport kinetics.
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Affiliation(s)
- Katalin Jemnitz
- Chemical Research Center, Institute of Biomolecular Chemistry, HAS, Budapest, Hungary
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32
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Gundacker C, Gencik M, Hengstschläger M. The relevance of the individual genetic background for the toxicokinetics of two significant neurodevelopmental toxicants: mercury and lead. Mutat Res 2010; 705:130-140. [PMID: 20601101 DOI: 10.1016/j.mrrev.2010.06.003] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 06/07/2010] [Accepted: 06/10/2010] [Indexed: 11/25/2022]
Abstract
The heavy metals mercury and lead are well-known and significant developmental neurotoxicants. This review summarizes the genetic factors that modify their toxicokinetics. Understanding toxicokinetics (uptake, biotransformation, distribution, and elimination processes) is a key precondition to understanding the individual health risks associated with exposure. We selected candidate susceptibility genes when evidence was available for (1) genes/proteins playing a significant role in mercury and lead toxicokinetics, (2) gene expression/protein activity being induced by these metals, and (3) mercury and lead toxicokinetics being affected by gene knockout/knockdown or (4) by functional gene polymorphisms. The genetic background is far better known for mercury than for lead toxicokinetics. Involved are genes encoding L-type amino acid transporters, organic anion transporters, glutathione (GSH)-related enzymes, metallothioneins, and transporters of the ABC family. Certain gene variants can influence mercury toxicokinetics, potentially explaining part of the variable susceptibility to mercury toxicity. Delta-aminolevulinic acid dehydratase (ALAD), vitamin D receptor (VDR) and hemochromatosis (HFE) gene variants are the only well-established susceptibility markers of lead toxicity in humans. Many gaps remain in our knowledge about the functional genomics of this issue. This calls for studies to detect functional gene polymorphisms related to mercury- and lead-associated disease phenotypes, to demonstrate the impact of functional polymorphisms and gene knockout/knockdown in relation to toxicity, to confirm the in vivo relevance of genetic variation, and to examine gene-gene interactions on the respective toxicokinetics. Another crucial aspect is knowledge on the maternal-fetal genetic background, which modulates fetal exposure to these neurotoxicants. To completely define the genetically susceptible risk groups, research is also needed on the genes/proteins involved in the toxicodynamics, i.e., in the mechanisms causing adverse effects in the brain. Studies relating the toxicogenetics to neurodevelopmental disorders are lacking (mercury) or very scarce (lead). Thus, the extent of variability in susceptibility to heavy metal-associated neurological outcomes is poorly characterized.
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Affiliation(s)
- Claudia Gundacker
- Institute of Medical Genetics, Medical University of Vienna, Währinger Strasse 10, A-1090 Vienna, Austria.
| | - Martin Gencik
- Praxis fur Humangenetik, Brünnlbadgasse 15, A-1090 Vienna, Austria
| | - Markus Hengstschläger
- Institute of Medical Genetics, Medical University of Vienna, Währinger Strasse 10, A-1090 Vienna, Austria
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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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Detoxification of mercury species—an in vitro study with antidotes in human whole blood. Anal Bioanal Chem 2009; 395:1929-35. [DOI: 10.1007/s00216-009-3105-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2009] [Revised: 08/24/2009] [Accepted: 08/25/2009] [Indexed: 10/20/2022]
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Effect of DMPS and DMSA on the placental and fetal disposition of methylmercury. Placenta 2009; 30:800-5. [PMID: 19615742 DOI: 10.1016/j.placenta.2009.06.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 06/22/2009] [Accepted: 06/23/2009] [Indexed: 11/22/2022]
Abstract
Methylmercury (CH3Hg+) is a serious environmental toxicant. Exposure to this metal during pregnancy can cause serious neurological and developmental defects in a developing fetus. Surprisingly, little is known about the mechanisms by which mercuric ions are transported across the placenta. Although it has been shown that 2,3-dimercaptopropane-1-sulfonate (DMPS) and 2,3-dimercaptosuccinic acid (DMSA) are capable of extracting mercuric ions from various organs and cells, there is no evidence that they are able to extract mercury from placental or fetal tissues following maternal exposure to CH3Hg+. Therefore, the purpose of the current study was to evaluate the ability of DMPS and DMSA to extract mercuric ions from placental and fetal tissues following maternal exposure to CH3Hg+. Pregnant Wistar rats were exposed to CH3HgCl, containing [203Hg], on day 11 or day 17 of pregnancy and treated 24 h later with saline, DMPS or DMSA. Maternal organs, fetuses, and placentas were harvested 48 h after exposure to CH3HgCl. The disposition of mercuric ions in maternal organs and tissues was similar to that reported previously by our laboratory. The disposition of mercuric ions in placentas and fetuses appeared to be dependent upon the gestational age of the fetus. The fetal and placental burden of mercury increased as fetal age increased and was reduced by DMPS and DMSA, with DMPS being more effective. The disposition of mercury was examined in liver, total renal mass, and brain of fetuses harvested on gestational day 19. On a per gram tissue basis, the greatest amount of mercury was detected in the total renal mass of the fetus, followed by brain and liver. DMPS and DMSA reduced the burden of mercury in liver and brain while only DMPS was effective in the total renal mass. The results of the current study are the first to show that DMPS and DMSA are capable of extracting mercuric ions, not only from maternal tissues, but also from placental and fetal tissues following maternal exposure to CH3Hg+.
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Zalups RK, Bridges CC. MRP2 involvement in renal proximal tubular elimination of methylmercury mediated by DMPS or DMSA. Toxicol Appl Pharmacol 2008; 235:10-7. [PMID: 19063911 DOI: 10.1016/j.taap.2008.11.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Revised: 11/06/2008] [Accepted: 11/10/2008] [Indexed: 11/28/2022]
Abstract
2, 3-Dimercaptopropane-1-sulfonic acid (DMPS) and meso-2, 3-Dimercaptosuccinic acid (DMSA) are dithiols used to treat humans exposed to methylmercury (CH(3)Hg(+)). After treatment, significant amounts of mercury are eliminated rapidly from the kidneys and are excreted in urine. In the present study, we extended our previous studies by testing the hypothesis that MRP2 mediates the secretion of DMPS or DMSA S-conjugates of CH(3)Hg(+). To test this hypothesis, the disposition of mercury was assessed in control and Mrp2-deficient (TR(-)) rats exposed intravenously to a 5.0-mg/kg dose of CH(3)HgCl. Twenty-four and 28 h after exposure, groups of four control and four TR(-) rats were injected with saline, DMPS, or DMSA. Tissues were harvested 48 h later. Renal and hepatic contents of mercury were greater in saline-injected TR(-) rats than in controls. In contrast, the amounts of mercury excreted in urine and feces by TR(-) rats were less than those by controls. DMPS and DMSA significantly reduced the renal and hepatic content of mercury in both groups of rats, with the greatest reduction in controls. A significant increase in urinary and fecal excretion of mercury (which was greater in the controls) was also observed. Our findings in inside-out membrane vesicles prepared from hMRP2-transfected Sf9 cells show that uptake of DMPS and DMSA S-conjugates of CH(3)Hg(+) was greater in the vesicles containing hMRP2 than in control vesicles. Overall, these dispositional findings indicate that MRP2 does play a role in DMPS- and DMSA-mediated elimination of mercury from the kidney.
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Affiliation(s)
- Rudolfs K Zalups
- Division of Basic Medical Sciences, Mercer University School of Medicine, 1550 College St., Macon, GA 31207, USA.
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Aremu DA, Madejczyk MS, Ballatori N. N-acetylcysteine as a potential antidote and biomonitoring agent of methylmercury exposure. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:26-31. [PMID: 18197295 PMCID: PMC2199271 DOI: 10.1289/ehp.10383] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2007] [Accepted: 10/16/2007] [Indexed: 05/25/2023]
Abstract
BACKGROUND Many people, by means of consumption of seafood or other anthropogenic sources, are exposed to levels of methylmercury (MeHg) that are generally considered to be quite low, but that may nevertheless produce irreversible brain damage, particularly in unborn babies. The only way to prevent or ameliorate MeHg toxicity is to enhance its elimination from the body. OBJECTIVES Using N-acetylcysteine (NAC), we aimed to devise a monitoring protocol for early detection of acute exposure or relatively low MeHg levels in a rodent model, and to test whether NAC reduces MeHg levels in the developing embryo. RESULTS NAC produced a transient, dose-dependent acceleration of urinary MeHg excretion in rats of both sexes. Approximately 5% of various MeHg doses was excreted in urine 2 hr after injection of 1 mmol/kg NAC. In pregnant rats, NAC markedly reduced the body burden of MeHg, particularly in target tissues such as brain, placenta, and fetus. In contrast, NAC had no significant effect on urinary MeHg excretion in preweanling rats. CONCLUSIONS Because NAC causes a transient increase in urinary excretion of MeHg that is proportional to the body burden, it is promising as a biomonitoring agent for MeHg in adult animals. In view of this and because NAC is effective at enhancing MeHg excretion when given either orally or intravenously, can decrease brain and fetal levels of MeHg, has minimal side effects, and is widely available in clinical settings, NAC should be evaluated as a potential antidote and biomonitoring agent in humans.
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Affiliation(s)
| | | | - Nazzareno Ballatori
- Address correspondence to N. Ballatori, Department of Environmental Medicine, University of Rochester School of Medicine, 575 Elmwood Ave., Box EHSC, Rochester, NY 14642 USA. Telephone: (585) 275-0262. Fax: (585) 256-2591. E-mail:
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Toyama T, Sumi D, Shinkai Y, Yasutake A, Taguchi K, Tong KI, Yamamoto M, Kumagai Y. Cytoprotective role of Nrf2/Keap1 system in methylmercury toxicity. Biochem Biophys Res Commun 2007; 363:645-50. [PMID: 17904103 DOI: 10.1016/j.bbrc.2007.09.017] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Accepted: 09/06/2007] [Indexed: 11/27/2022]
Abstract
Human exposure to methylmercury (MeHg) from contaminated fish is a potential health risk. Because of its chemical properties as a soft electrophile, we investigated the participation of Nrf2 in the cellular response to and protection against MeHg with SH-SY5Y cells and with primary mouse hepatocytes from Nrf2- and Keap1-deficient mice. Exposure of SH-SY5Y cells to MeHg activated Nrf2 through the binding of MeHg and Keap1. Nrf2 overexpression attenuated MeHg-induced cytotoxicity in SH-SY5Y cells. In addition, primary mouse hepatocytes extracted from Nrf2-deficient mouse was susceptible, and hepatocyte-specific conditional Keap1-deficient mouse was resistant to MeHg-induced cytotoxicity. Consistent with this data, MeHg was accumulated by Nrf2 deficiency and reduced by Keap1 deficiency. Our findings indicate that MeHg activates Nrf2 and the activation of Nrf2 is essential for reduction of MeHg toxicity by facilitating its excretion into extracellular space.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Adaptor Proteins, Signal Transducing/physiology
- Animals
- Blotting, Western
- Cell Line, Tumor
- Cell Survival/drug effects
- Cells, Cultured
- Cytoskeletal Proteins/genetics
- Cytoskeletal Proteins/metabolism
- Cytoskeletal Proteins/physiology
- Dose-Response Relationship, Drug
- Hepatocytes/cytology
- Hepatocytes/drug effects
- Hepatocytes/metabolism
- Humans
- Kelch-Like ECH-Associated Protein 1
- Luciferases/genetics
- Luciferases/metabolism
- Methylmercury Compounds/metabolism
- Methylmercury Compounds/toxicity
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- NF-E2-Related Factor 2/genetics
- NF-E2-Related Factor 2/metabolism
- NF-E2-Related Factor 2/physiology
- Protein Binding
- RNA, Small Interfering/genetics
- Recombinant Fusion Proteins/metabolism
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Affiliation(s)
- Takashi Toyama
- Master's Program in Environmental Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8572, Japan
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