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Li S, Li Z, Wu M, Zhou Y, Tang W, Zhong H. Mercury transformations in algae, plants, and animals: The occurrence, mechanisms, and gaps. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 911:168690. [PMID: 38000748 DOI: 10.1016/j.scitotenv.2023.168690] [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: 10/16/2023] [Revised: 11/16/2023] [Accepted: 11/16/2023] [Indexed: 11/26/2023]
Abstract
Mercury (Hg) is a global pollutant showing potent toxicity to living organisms. The transformations of Hg are critical to global Hg cycling and Hg exposure risks, considering Hg mobilities and toxicities vary depending on Hg speciation. Though currently well understood in ambient environments, Hg transformations are inadequately explored in non-microbial organisms. The primary drivers of in vivo Hg transformations are far from clear, and the impacts of these processes on global Hg cycling and Hg associated health risks are not well understood. This hinders a comprehensive understanding of global Hg cycling and the effective mitigation of Hg exposure risks. Here, we focused on Hg transformations in non-microbial organisms, particularly algae, plants, and animals. The process of Hg oxidation/reduction and methylation/demethylation in organisms were reviewed since these processes are the key transformations between the dominant Hg species, i.e., elemental Hg (Hg0), divalent inorganic Hg (IHgII), and methylmercury (MeHg). By summarizing the current knowledge of Hg transformations in organisms, we proposed the potential yet overlooked drivers of these processes, along with potential challenges that hinder a full understanding of in vivo Hg transformations. Knowledge summarized in this review would help achieve a comprehensive understanding of the fate and toxicity of Hg in organisms, providing a basis for predicting Hg cycles and mitigating human exposure.
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Affiliation(s)
- Shouying Li
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China
| | - Zhuoran Li
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China
| | - Mengjie Wu
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China
| | - Yang Zhou
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China
| | - Wenli Tang
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China.
| | - Huan Zhong
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China.
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2
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Tang W, Bai X, Zhou Y, Sonne C, Wu M, Lam SS, Hintelmann H, Mitchell CPJ, Johs A, Gu B, Nunes L, Liu C, Feng N, Yang S, Rinklebe J, Lin Y, Chen L, Zhang Y, Yang Y, Wang J, Li S, Wu Q, Ok YS, Xu D, Li H, Zhang XX, Ren H, Jiang G, Chai Z, Gao Y, Zhao J, Zhong H. A hidden demethylation pathway removes mercury from rice plants and mitigates mercury flux to food chains. NATURE FOOD 2024; 5:72-82. [PMID: 38177223 DOI: 10.1038/s43016-023-00910-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 12/01/2023] [Indexed: 01/06/2024]
Abstract
Dietary exposure to methylmercury (MeHg) causes irreversible damage to human cognition and is mitigated by photolysis and microbial demethylation of MeHg. Rice (Oryza sativa L.) has been identified as a major dietary source of MeHg. However, it remains unknown what drives the process within plants for MeHg to make its way from soils to rice and the subsequent human dietary exposure to Hg. Here we report a hidden pathway of MeHg demethylation independent of light and microorganisms in rice plants. This natural pathway is driven by reactive oxygen species generated in vivo, rapidly transforming MeHg to inorganic Hg and then eliminating Hg from plants as gaseous Hg°. MeHg concentrations in rice grains would increase by 2.4- to 4.7-fold without this pathway, which equates to intelligence quotient losses of 0.01-0.51 points per newborn in major rice-consuming countries, corresponding to annual economic losses of US$30.7-84.2 billion globally. This discovered pathway effectively removes Hg from human food webs, playing an important role in exposure mitigation and global Hg cycling.
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Affiliation(s)
- Wenli Tang
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Xu Bai
- Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yang Zhou
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Christian Sonne
- Department of Ecoscience, Arctic Research Centre, Aarhus University, Roskilde, Denmark.
- Sustainability Cluster, School of Engineering, University of Petroleum and Energy Studies, Dehradun, India.
| | - Mengjie Wu
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Su Shiung Lam
- Higher Institution Centre of Excellence (HICoE), Institute of Tropical Aquaculture and Fisheries (AKUATROP), Universiti Malaysia Terengganu, Kuala Nerus, Malaysia
- Center for Global Health Research (CGHR), Saveetha Institute of Medical and Technical Sciences (SIMATS), Saveetha University, Chennai, India
| | - Holger Hintelmann
- Department of Chemistry and School of the Environment, Trent University, Peterborough, Ontario, Canada
| | - Carl P J Mitchell
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Scarborough, Ontario, Canada
| | - Alexander Johs
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Luís Nunes
- Faculty of Sciences and Technology, Civil Engineering Research and Innovation for Sustainability Center, University of Algarve, Faro, Portugal
| | - Cun Liu
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China
| | - Naixian Feng
- College of Life Science and Technology, Jinan University, Guangzhou, China
| | - Sihai Yang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Jörg Rinklebe
- School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, University of Wuppertal, Wuppertal, Germany
| | - Yan Lin
- Tianjin Key Laboratory of Environmental Technology for Complex Trans-Media Pollution, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Long Chen
- Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographic Sciences, East China Normal University, Shanghai, China
| | - Yanxu Zhang
- School of Atmospheric Sciences, Nanjing University, Nanjing, China
| | - Yanan Yang
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Jiaqi Wang
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Shouying Li
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Qingru Wu
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China
- State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing, China
| | - Yong Sik Ok
- Korea Biochar Research Center, APRU Sustainable Waste Management Program and Division of Environmental Science and Ecological Engineering, Korea University, Seoul, Republic of Korea
| | - Diandou Xu
- Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China
| | - Hong Li
- Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China
| | - Xu-Xiang Zhang
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Hongqiang Ren
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Guibin Jiang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
| | - Zhifang Chai
- Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China
- State Key Laboratory of Radiation Medicine and Protection, Soochow University, Suzhou, China
| | - Yuxi Gao
- Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China.
| | - Jiating Zhao
- Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China.
- Department of Environmental Science, Zhejiang University, Hangzhou, China.
| | - Huan Zhong
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China.
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3
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Takanezawa Y, Ishikawa K, Nakayama S, Nakamura R, Ohshiro Y, Uraguchi S, Kiyono M. Conversion of methylmercury into inorganic mercury via organomercurial lyase (MerB) activates autophagy and aggresome formation. Sci Rep 2023; 13:19958. [PMID: 37968352 PMCID: PMC10651920 DOI: 10.1038/s41598-023-47110-y] [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: 06/16/2023] [Accepted: 11/09/2023] [Indexed: 11/17/2023] Open
Abstract
Methylmercury (MeHg) is converted to inorganic mercury (iHg) in several organs; however, its impact on tissues and cells remains poorly understood. Previously, we established a bacterial organomercury lyase (MerB)-expressing mammalian cell line to overcome the low cell permeability of iHg and investigate its effects. Here, we elucidated the cytotoxic effects of the resultant iHg on autophagy and deciphered their relationship. Treatment of MerB-expressing cells with MeHg significantly increases the mRNA and protein levels of LC3B and p62, which are involved in autophagosome formation and substrate recognition, respectively. Autophagic flux assays using the autophagy inhibitor chloroquine (CQ) revealed that MeHg treatment activates autophagy in MerB-expressing cells but not in wild-type cells. Additionally, MeHg treatment induces the accumulation of ubiquitinated proteins and p62, specifically in MerB-expressing cells. Confocal microscopy revealed that large ubiquitinated protein aggregates (aggresomes) associated with p62 are formed transiently in the perinuclear region of MerB-expressing cells upon MeHg exposure. Meanwhile, inhibition of autophagic flux decreases the MeHg-induced cell viability of MerB-expressing cells. Overall, our results imply that cells regulate aggresome formation and autophagy activation by activating LC3B and p62 to prevent cytotoxicity caused by iHg. These findings provide insights into the role of autophagy against iHg-mediated toxicity.
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Affiliation(s)
- Yasukazu Takanezawa
- Department of Public Health, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Kouhei Ishikawa
- Department of Public Health, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Shunsuke Nakayama
- Department of Public Health, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Ryosuke Nakamura
- Department of Public Health, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Yuka Ohshiro
- Department of Public Health, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Shimpei Uraguchi
- Department of Public Health, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Masako Kiyono
- Department of Public Health, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan.
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4
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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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5
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Azevedo LF, Karpova N, Rocha BA, Barbosa Junior F, Gobe GC, Hornos Carneiro MF. Evidence on Neurotoxicity after Intrauterine and Childhood Exposure to Organomercurials. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:1070. [PMID: 36673825 PMCID: PMC9858833 DOI: 10.3390/ijerph20021070] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/03/2023] [Accepted: 01/04/2023] [Indexed: 06/17/2023]
Abstract
Although the molecular mechanisms underlying methylmercury toxicity are not entirely understood, the observed neurotoxicity in early-life is attributed to the covalent binding of methylmercury to sulfhydryl (thiol) groups of proteins and other molecules being able to affect protein post-translational modifications from numerous molecular pathways, such as glutamate signaling, heat-shock chaperones and the antioxidant glutaredoxin/glutathione system. However, for other organomercurials such as ethylmercury or thimerosal, there is not much information available. Therefore, this review critically discusses current knowledge about organomercurials neurotoxicity-both methylmercury and ethylmercury-following intrauterine and childhood exposure, as well as the prospects and future needs for research in this area. Contrasting with the amount of epidemiological evidence available for methylmercury, there are only a few in vivo studies reporting neurotoxic outcomes and mechanisms of toxicity for ethylmercury or thimerosal. There is also a lack of studies on mechanistic approaches to better investigate the pathways involved in the potential neurotoxicity caused by both organomercurials. More impactful follow-up studies, especially following intrauterine and childhood exposure to ethylmercury, are necessary. Childhood vaccination is critically important for controlling infectious diseases; however, the safety of mercury-containing thimerosal and, notably, its effectiveness as preservative in vaccines are still under debate regarding its potential dose-response effects to the central nervous system.
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Affiliation(s)
- Lara Ferreira Azevedo
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Nina Karpova
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Bruno Alves Rocha
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Fernando Barbosa Junior
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Glenda Carolyn Gobe
- Kidney Disease Research Group, School of Medicine, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, QLD 4102, Australia
| | - Maria Fernanda Hornos Carneiro
- Department of Pharmacy, Faculty of Chemistry and Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
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6
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Bjørklund G, Antonyak H, Polishchuk A, Semenova Y, Lesiv M, Lysiuk R, Peana M. Effect of methylmercury on fetal neurobehavioral development: an overview of the possible mechanisms of toxicity and the neuroprotective effect of phytochemicals. Arch Toxicol 2022; 96:3175-3199. [PMID: 36063174 DOI: 10.1007/s00204-022-03366-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 08/17/2022] [Indexed: 11/25/2022]
Abstract
Methylmercury (MeHg) is a global environmental pollutant with neurotoxic effects. Exposure to MeHg via consumption of seafood and fish can severely impact fetal neurobehavioral development even when MeHg levels in maternal blood are as low as about 5 μg/L, which the mother tolerates well. Persistent motor dysfunctions and cognitive deficits may result from trans-placental exposure. The present review summarizes current knowledge on the mechanisms of MeHg toxicity during the period of nervous system development. Although cerebellar Purkinje cells are MeHg targets, the actions of MeHg on thiol components in the neuronal cytoskeleton as well as on mitochondrial enzymes and induction of disturbances of glutamate signaling can impair extra-cerebellar functions, also at levels well tolerated by adult individuals. Numerous herbal substances possess neuroprotective effects, predominantly represented by natural polyphenolic molecules that might be utilized to develop natural drugs to alleviate neurotoxicity symptoms caused by MeHg or other Hg compounds.
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Affiliation(s)
- Geir Bjørklund
- Council for Nutritional and Environmental Medicine, Toften 24, 8610, Mo i Rana, Norway.
| | | | | | | | - Marta Lesiv
- Ivan Franko National University of Lviv, Lviv, Ukraine
| | - Roman Lysiuk
- Danylo Halytsky Lviv National Medical University, Lviv, Ukraine
- CONEM Ukraine Life Science Research Group, Danylo Halytsky Lviv National Medical University, Lviv, Ukraine
| | - Massimiliano Peana
- Department of Chemical, Physics, Mathematics and Natural Sciences, University of Sassari, Sassari, Italy
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7
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Revisiting Astrocytic Roles in Methylmercury Intoxication. Mol Neurobiol 2021; 58:4293-4308. [PMID: 33990914 DOI: 10.1007/s12035-021-02420-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 05/04/2021] [Indexed: 02/06/2023]
Abstract
Intoxication by heavy metals such as methylmercury (MeHg) is recognized as a global health problem, with strong implications in central nervous system pathologies. Most of these neuropathological conditions involve vascular, neurotransmitter recycling, and oxidative balance disruption leading to accelerated decline in fine balance, and learning, memory, and visual processes as main outcomes. Besides neurons, astrocytes are involved in virtually all the brain processes and perform important roles in neurological response following injuries. Due to astrocytes' strategic functions in brain homeostasis, these cells became the subject of several studies on MeHg intoxication. The most heterogenous glial cells, astrocytes, are composed of plenty of receptors and transporters to dialogue with neurons and other cells and to monitor extracellular environment responding tightly through fluctuation of cytosolic ions. The overall toxicity of MeHg might be determined on the basis of the balance between MeHg-mediated injury to neurons and protective responses from astrocytes. Although the role of neurons in MeHg intoxication is relatively well-established, the role of the astrocytes is only beginning to be understood. In this review, we update the information on astroglial modulation of the MeHg-induced neurotoxicity, providing remarks on their protective and deleterious roles and insights for future studies.
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8
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Li M, Juang CA, Ewald JD, Yin R, Mikkelsen B, Krabbenhoft DP, Balcom PH, Dassuncao C, Sunderland EM. Selenium and stable mercury isotopes provide new insights into mercury toxicokinetics in pilot whales. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 710:136325. [PMID: 31927288 DOI: 10.1016/j.scitotenv.2019.136325] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 12/16/2019] [Accepted: 12/23/2019] [Indexed: 05/12/2023]
Abstract
High exposures of mammalian species to inorganic mercury (HgII) and methylmercury (MeHg) have been associated with adverse effects on behavior and reproduction. Different mammalian species exhibit varying responses to similar external exposure levels, reflecting potential differences in Hg toxicokinetics. Here, we use Hg stable isotopes, total Hg, MeHg and selenium (Se) concentrations measured in multiple tissues of North Atlantic pilot whales (Globicephala melas) to investigate processes affecting the distribution and accumulation of HgII and MeHg. We find that simple mixing of two distinct isotopic end-members: MeHg (1.4‰) and HgII (-1.6‰) can explain the observed variability of δ202Hg in brain tissue. A similar isotopic composition for the MeHg end-member in the brain, muscle, heart, and kidney suggests efficient exchange of MeHg in blood throughout the body. By contrast, the Hg isotopic composition of the liver of adult whales is different from younger whales and other tissues that follow the two-end member mixing model. Measured Se:Hg ratios are lowest in adult whales with the highest levels of MeHg exposure. In these individuals, Se availability is likely reduced by complexation with demethylated HgII. We speculate that this results in a higher fraction of labile HgII eliminated from the liver of adult whales compared to young whales and subsequent redistribution to other tissues, potentially affecting toxicity.
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Affiliation(s)
- Miling Li
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States; Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115, United States.
| | - C Alicia Juang
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States
| | - Jessica D Ewald
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States; Faculty of Agricultural and Environmental Sciences, Macdonald Campus, McGill University Ste-Anne-de-Bellevue, Quebec H9X 3V9, Canada
| | - Runsheng Yin
- Department of Civil and Environmental Engineering, University of Wisconsin, Madison, WI, United States
| | - Bjarni Mikkelsen
- The Faroese Museum of Natural History, V. U. Hammershaimbsgøta 13, FO-100 Tórshavn, Faroe Islands
| | | | - Prentiss H Balcom
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States
| | - Clifton Dassuncao
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States; Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115, United States
| | - Elsie M Sunderland
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States; Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115, United States
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9
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Corrêa MG, Bittencourt LO, Nascimento PC, Ferreira RO, Aragão WAB, Silva MCF, Gomes-Leal W, Fernandes MS, Dionizio A, Buzalaf MR, Crespo-Lopez ME, Lima RR. Spinal cord neurodegeneration after inorganic mercury long-term exposure in adult rats: Ultrastructural, proteomic and biochemical damages associated with reduced neuronal density. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 191:110159. [PMID: 31962214 DOI: 10.1016/j.ecoenv.2019.110159] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 12/28/2019] [Accepted: 12/31/2019] [Indexed: 06/10/2023]
Abstract
Mercury chloride (HgCl2) is a chemical pollutant widely found in the environment. This form of mercury is able to promote several damages to the Central Nervous System (CNS), however the effects of HgCl2 on the spinal cord, an important pathway for the communication between the CNS and the periphery, are still poorly understood. The aim of this work was to investigate the effects of HgCl2 exposure on spinal cord of adult rats. For this, animals were exposed to a dose of 0.375 mg/kg/day, for 45 days. Then, they were euthanized, the spinal cord collected and we investigated the mercury concentrations in medullary parenchyma and the effects on oxidative biochemistry, proteomic profile and tissue structures. Our results showed that exposure to this metal promoted increased levels of Hg in the spinal cord, impaired oxidative biochemistry by triggering oxidative stress, mudulated antioxidant system proteins, energy metabolism and myelin structure; as well as caused disruption in the myelin sheath and reduction in neuronal density. Despite the low dose, we conclude that prolonged exposure to HgCl2 triggers biochemical changes and modulates the expression of several proteins, resulting in damage to the myelin sheath and reduced neuronal density in the spinal cord.
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Affiliation(s)
- Márcio Gonçalves Corrêa
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil
| | - Leonardo Oliveira Bittencourt
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil
| | - Priscila Cunha Nascimento
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil
| | - Railson Oliveira Ferreira
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil
| | - Walessa Alana Bragança Aragão
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil
| | - Marcia Cristina Freitas Silva
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil
| | - Walace Gomes-Leal
- Laboratory of Experimental Neuroprotection and Neuroregeneration, Institute of Biological Sciences, Federal University of Pará, Belém, PA, Brazil
| | - Mileni Silva Fernandes
- Department of Biological Sciences, Bauru Dental School, University of São Paulo, Bauru, SP, Brazil
| | - Aline Dionizio
- Department of Biological Sciences, Bauru Dental School, University of São Paulo, Bauru, SP, Brazil
| | - Marília Rabelo Buzalaf
- Department of Biological Sciences, Bauru Dental School, University of São Paulo, Bauru, SP, Brazil
| | - Maria Elena Crespo-Lopez
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil
| | - Rafael Rodrigues Lima
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil.
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10
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Ehnert-Russo SL, Gelsleichter J. Mercury Accumulation and Effects in the Brain of the Atlantic Sharpnose Shark (Rhizoprionodon terraenovae). ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2020; 78:267-283. [PMID: 31760438 DOI: 10.1007/s00244-019-00691-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 11/14/2019] [Indexed: 06/10/2023]
Abstract
Few published studies have examined whether the elevated concentrations of the nonessential toxic metal mercury (Hg) often observed in shark muscle also occur in the shark brain or whether Hg accumulation affects shark neurophysiology. Therefore, this study examined accumulation and distribution of Hg in the shark brain, as well as effects of Hg on oxidative stress in the shark central nervous system, with particular focus on the Atlantic sharpnose shark (Rhizoprionodon terraenovae). Sharks were collected along the southeastern U.S. coast throughout most of this species' U.S. geographical range. Total Hg (THg) concentrations were measured in and compared between shark muscle and brain, whereas known biomarkers of Hg-induced neurological effects, including glutathione depletion, lipid peroxidation, and concentrations of a protein marker of glial cell damage (S100b), were measured in shark cerebrospinal fluid. Brain THg concentrations were correlated with muscle THg levels but were significantly lower and did not exceed most published thresholds for neurological effects, suggesting limited potential for detrimental responses. Biomarker concentrations supported this premise, because these data were not correlated with brain THg levels. Hg speciation also was examined. Unlike muscle, methylmercury (MeHg) did not comprise a high percentage of THg in the brain, suggesting that differential uptake or loss of organic and inorganic Hg and/or demethylation of MeHg may occur in this organ. Although Hg accumulation in the shark brain generally fell below toxicity thresholds, higher THg levels were measured in the shark forebrain compared with the midbrain and hindbrain. Therefore, there is potential for selective effects on certain aspects of shark neurophysiology if brain Hg accumulation is increased.
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Affiliation(s)
- S L Ehnert-Russo
- University of North Florida, 1 UNF Dr, Jacksonville, FL, 32224, USA
| | - J Gelsleichter
- University of North Florida, 1 UNF Dr, Jacksonville, FL, 32224, USA.
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11
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Chang J, Yang B, Zhou Y, Yin C, Liu T, Qian H, Xing G, Wang S, Li F, Zhang Y, Chen D, Aschner M, Lu R. Acute Methylmercury Exposure and the Hypoxia-Inducible Factor-1α Signaling Pathway under Normoxic Conditions in the Rat Brain and Astrocytes in Vitro. ENVIRONMENTAL HEALTH PERSPECTIVES 2019; 127:127006. [PMID: 31850806 PMCID: PMC6957278 DOI: 10.1289/ehp5139] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Revised: 11/07/2019] [Accepted: 11/18/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND As a ubiquitous environmental pollutant, methylmercury (MeHg) induces toxic effects in the nervous system, one of its main targets. However, the exact mechanisms of its neurotoxicity have not been fully elucidated. Hypoxia-inducible factor- 1 α (HIF- 1 α ), a transcription factor, plays a crucial role in adaptive and cytoprotective responses in cells and is involved in cell survival, proliferation, apoptosis, inflammation, angiogenesis, glucose metabolism, erythropoiesis, and other physiological activities. OBJECTIVES The aim of this study was to explore the role of HIF- 1 α in response to acute MeHg exposure in rat brain and primary cultured astrocytes to improve understanding of the mechanisms of MeHg-induced neurotoxicity and the development of effective neuroprotective strategies. METHODS Primary rat astrocytes were treated with MeHg (0 - 10 μ M ) for 0.5 h . Cell proliferation and cytotoxicity were assessed with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl diphenyltetrazolium bromide (MTT) assay and a lactate dehydrogenase (LDH) release assay, respectively. Reactive oxygen species (ROS) levels were analyzed to assess the level of oxidative stress using 2',7'-dichlorofluorescin diacetate (DCFH-DA) fluorescence. HIF- 1 α , and its downstream proteins, glucose transporter 1 (GLUT-1), erythropoietin (EPO), and vascular endothelial growth factor A (VEGF-A) were analyzed by means of Western blotting. Real-time PCR was used to detect the expression of HIF- 1 α mRNA. Pretreatment with protein synthesis inhibitor (CHX), proteasome inhibitor (MG132), or proline hydroxylase inhibitor (DHB) were applied to explore the possible mechanisms of HIF- 1 α inhibition by MeHg. To investigate the role of HIF- 1 α in MeHg-induced neurotoxicity, cobalt chloride (CoC l 2 ), 2-methoxyestradiol (2-MeOE2), small interfering RNA (siRNA) transfection and adenovirus overexpression were used. Pretreatment with N-acetyl-L-cysteine (NAC) and vitamin E (Trolox) were used to investigate the putative role of oxidative stress in MeHg-induced alterations in HIF- 1 α levels. The expression of HIF- 1 α and related downstream proteins was detected in adult rat brain exposed to MeHg (0 - 10 mg / kg ) for 0.5 h in vivo. RESULTS MeHg caused lower cell proliferation and higher cytotoxicity in primary rat astrocytes in a time- and concentration-dependent manner. In comparison with the control cells, exposure to 10 μ M MeHg for 0.5 h significantly inhibited the expression of astrocytic HIF- 1 α , and the downstream genes GLUT-1, EPO, and VEGF-A (p < 0.05 ), in the absence of a significant decrease in HIF- 1 α mRNA levels. When protein synthesis was inhibited by CHX, MeHg promoted the degradation rate of HIF- 1 α . MG132 and DHB significantly blocked the MeHg-induced decrease in HIF- 1 α expression (p < 0.05 ). Overexpression of HIF- 1 α significantly attenuated the decline in MeHg-induced cell proliferation, whereas the inhibition of HIF- 1 α significantly increased the decline in cell proliferation (p < 0.05 ). NAC and Trolox, two established antioxidants, reversed the MeHg-induced decline in HIF- 1 α protein levels and the decrease in cell proliferation (p < 0.05 ). MeHg suppressed the expression of HIF- 1 α and related downstream target proteins in adult rat brain. DISCUSSION MeHg induced a significant reduction in HIF- 1 α protein by activating proline hydroxylase (PHD) and the ubiquitin proteasome system (UPS) in primary rat astrocytes. Additionally, ROS scavenging by antioxidants played a neuroprotective role via increasing HIF- 1 α expression in response to MeHg toxicity. Moreover, we established that up-regulation of HIF- 1 α might serve to mitigate the acute toxicity of MeHg in astrocytes, affording a novel therapeutic target for future exploration. https://doi.org/10.1289/EHP5139.
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Affiliation(s)
- Jie Chang
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Bobo Yang
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Yun Zhou
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Changsheng Yin
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
- Institute of Life Sciences, Jiangsu University, Zhenjiang, China
| | - Tingting Liu
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Hai Qian
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Guangwei Xing
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Suhua Wang
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Fang Li
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Yubin Zhang
- Department of Occupational Health and Toxicology, School of Public Health, Fudan University, Shanghai, China
| | - Da Chen
- School of Environment, Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou, China
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Rongzhu Lu
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, China
- Center for Experimental Research, Kunshan Hospital Affiliated to Jiangsu University, Kunshan, China
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12
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Takanezawa Y, Nakamura R, Matsuda H, Yagi T, Egawa Z, Sone Y, Uraguchi S, Adachi T, Kiyono M. Intracellular Demethylation of Methylmercury to Inorganic Mercury by Organomercurial Lyase (MerB) Strengthens Cytotoxicity. Toxicol Sci 2019; 170:438-451. [DOI: 10.1093/toxsci/kfz094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Abstract
Some methylmercury (MeHg) is converted to inorganic mercury (Hg2+) after incorporation into human and animal tissues, where it can remain for a long time. To determine the overall toxicity of MeHg in tissues, studies should evaluate low concentrations of Hg2+. Although demethylation is involved, the participating enzymes or underlying mechanisms are unknown; in addition, the low cell membrane permeability of Hg2+ makes these analyses challenging. We established model cell lines to assess toxicities of low concentrations of Hg2+ using bacterial organomercury lyase (MerB). We engineered MerB-expressing HEK293 and HeLa cell lines that catalyze MeHg demethylation. These cells were significantly more sensitive to MeHg exposure compared to the parental cells. MeHg treatment remarkably induced metallothioneins (MTs) and hemeoxygenase-1 (HMOX-1) mRNAs and modest expression of superoxide dismutase 1, whereas catalase and glutathione peroxidase 1 mRNAs were not up-regulated. merB knockdown using small interfering RNA supported the induction of MT and HMOX-1 mRNA by MerB enzymatic activity. Pretreatment with Trolox, a water-soluble vitamin E analog, did not inhibit MeHg-induced elevation of MT-Ix and HMOX-1 mRNAs in MerB-expressing cells, suggesting that Hg2+ works independently of reactive oxygen species generation. Similar results were obtained in cells expressing MerB, suggesting that high MTs and HMOX-1 induction and cytotoxicity are common cellular responses to low intracellular Hg2+ concentrations. This is the first study to establish cell lines that demethylate intracellular MeHg to Hg2+ using bacterial MerB for overcoming the low membrane permeability of Hg2+ and exploring the intracellular responses and toxicities of low Hg2+ concentrations.
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Affiliation(s)
- Yasukazu Takanezawa
- Department of Public Health, School of Pharmacy, Kitasato University, Minato-ku, Tokyo 108-8641
| | - Ryosuke Nakamura
- Department of Public Health, School of Pharmacy, Kitasato University, Minato-ku, Tokyo 108-8641
| | - Haruki Matsuda
- Department of Public Health, School of Pharmacy, Kitasato University, Minato-ku, Tokyo 108-8641
| | - Tomomi Yagi
- Department of Public Health, School of Pharmacy, Kitasato University, Minato-ku, Tokyo 108-8641
| | - Zen Egawa
- Department of Public Health, School of Pharmacy, Kitasato University, Minato-ku, Tokyo 108-8641
| | - Yuka Sone
- Department of Public Health, School of Pharmacy, Kitasato University, Minato-ku, Tokyo 108-8641
| | - Shimpei Uraguchi
- Department of Public Health, School of Pharmacy, Kitasato University, Minato-ku, Tokyo 108-8641
| | - Tatsumi Adachi
- Faculty of Pharmacy, Chiba Institute of Science, Choshi, Chiba 288-0025, Japan
| | - Masako Kiyono
- Department of Public Health, School of Pharmacy, Kitasato University, Minato-ku, Tokyo 108-8641
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Pamphlett R, Bishop DP, Kum Jew S, Doble PA. Age-related accumulation of toxic metals in the human locus ceruleus. PLoS One 2018; 13:e0203627. [PMID: 30231068 PMCID: PMC6145836 DOI: 10.1371/journal.pone.0203627] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 08/23/2018] [Indexed: 12/28/2022] Open
Abstract
Damage to the locus ceruleus has been implicated in the pathogenesis of a number of neurological conditions. Locus ceruleus neurons accumulate toxic metals such as mercury selectively, however, the presence of toxic metals in locus ceruleus neurons of people of different ages, and with a variety of disorders, is not known. To demonstrate at what age toxic metals are first detectable in the locus ceruleus, and to evaluate whether their presence is more common in certain clinicopathological conditions, we looked for these metals in 228 locus ceruleus samples. Samples were taken at coronial autopsies from individuals with a wide range of ages, pre-existing conditions and causes of death. Paraffin sections of pons containing the locus ceruleus were stained with silver nitrate autometallography, which indicates inorganic mercury, silver and bismuth within cells (termed autometallography-detected toxic metals, or AMG™). No locus ceruleus AMG neurons were seen in 38 individuals aged under 20 years. 47% of the 190 adults (ie, aged 20 years and over) had AMG locus ceruleus neurons. The proportion of adults with locus ceruleus AMG neurons increased during aging, except for a decreased proportion in the 90-plus years age group. No differences were found in the proportions of locus ceruleus AMG neurons between groups with different neurological, psychiatric, or other clinicopathological conditions, or among various causes of death. Elemental analysis with laser ablation-inductively coupled plasma-mass spectrometry was used to cross-validate the metals detected by AMG, by looking for silver, gold, bismuth, cadmium, chromium, iron, mercury, nickel, and lead in the locus ceruleus of ten individuals. This confirmed the presence of mercury in locus ceruleus samples containing AMG neurons, and showed cadmium, silver, lead, iron, and nickel in the locus ceruleus of some individuals. In conclusion, toxic metals stained by AMG (most likely inorganic mercury) appear in locus ceruleus neurons in early adult life. About half of adults in this study had locus ceruleus neurons containing inorganic mercury, and elemental analysis found a range of other toxic metals in the locus ceruleus. Locus ceruleus inorganic mercury increased during aging, except for a decrease in advanced age, but was not found more often in any single clinicopathological condition or cause of death.
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Affiliation(s)
- Roger Pamphlett
- Discipline of Pathology, Sydney Medical School, Brain and Mind Centre, The University of Sydney, New South Wales, Australia
- Department of Neuropathology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - David P. Bishop
- Elemental Bio-imaging Facility, University of Technology, Sydney, New South Wales, Australia
| | - Stephen Kum Jew
- Discipline of Pathology, Sydney Medical School, Brain and Mind Centre, The University of Sydney, New South Wales, Australia
| | - Philip A. Doble
- Elemental Bio-imaging Facility, University of Technology, Sydney, New South Wales, Australia
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14
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Chan MC, Bautista E, Alvarado-Cruz I, Quintanilla-Vega B, Segovia J. Inorganic mercury prevents the differentiation of SH-SY5Y cells: Amyloid precursor protein, microtubule associated proteins and ROS as potential targets. J Trace Elem Med Biol 2017; 41:119-128. [PMID: 28209268 DOI: 10.1016/j.jtemb.2017.02.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 01/16/2017] [Accepted: 02/05/2017] [Indexed: 10/20/2022]
Abstract
Exposure to mercury (Hg) occurs through different pathways and forms including methylmecury (MeHg) from seafood and rice, ethylmercury (EtHg), and elemental Hg (Hg0) from dental amalgams and artisanal gold mining. Once in the brain all these forms are transformed to inorganic Hg (I-Hg), where it bioaccumulates and remains for long periods. Hg is a well-known neurotoxicant, with its most damaging effects reported during brain development, when cellular key events, such as cell differentiation take place. A considerable number of studies report an impairment of neuronal differentiation due to MeHg exposure, however the effects of I-Hg, an important form of Hg found in brain, have received less attention. In this study, we decided to examine the effects of I-Hg exposure (5, 10 and 20μM) on the differentiation of SH-SY5Y cells induced by retinoic acid (RA, 10μM). We observed extension of neuritic processes and increased expression of neuronal markers (MAP2, tubulin-βIII, and Tau) after RA stimulation, all these effects were decreased by the co-exposure to I-Hg. Interestingly, I-Hg increased the levels of reactive oxygen species (ROS) and nitric oxide (NO) accompanied with increased levels of inducible nitric oxide synthase (iNOS) and, dimethylarginine dimethylaminohydrolase 1 (DDHA1). Remarkably I-Hg decreased levels of nitric oxide synthase neuronal (nNOS). Moreover I-Hg reduced the levels of tyrosine hydroxylase (TH) and amyloid precursor protein (APP) a protein recently involved in neuronal differentiation. These data suggest that the exposure to I-Hg impairs cell differentiation, and point to new potential targets of Hg toxicity such as APP and NO signaling.
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Affiliation(s)
- Miguel Chin Chan
- Departmento de Toxicología, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, 07360, Mexico; Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Campeche, Campeche 4039, Mexico
| | - Elizabeth Bautista
- Departmento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, 07360, Mexico; Facultad de Ciencias de la Salud, Universidad Anáhuac Norte, 52786, Huixquilucan, Mexico
| | - Isabel Alvarado-Cruz
- Departmento de Toxicología, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, 07360, Mexico
| | - Betzabet Quintanilla-Vega
- Departmento de Toxicología, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, 07360, Mexico
| | - José Segovia
- Departmento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, 07360, Mexico.
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15
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Pan S, Feng C, Lin J, Cheng L, Wang C, Zuo Y. Occurrence and photodegradation of methylmercury in surface water of Wen-Rui-Tang River network, Wenzhou, China. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:11289-11298. [PMID: 28299570 DOI: 10.1007/s11356-017-8708-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 02/27/2017] [Indexed: 06/06/2023]
Abstract
The spatial distribution and seasonal variations of methylmercury (MeHg) in Wen-Rui-Tang (WRT) River network were investigated by monitoring the MeHg concentrations in surface water samples collected from 30 sites across the river network over four seasons. Detection frequencies and concentrations of MeHg were generally higher in January, indicating that low sunlight irradiation, wind speed, and temperature conditions might enhance the persistence of MeHg in surface water. The MeHg levels varied with sampling locations, with the highest concentrations being observed in the industrial area especially around wastewater outfall, revealing that the mercury contamination in WRT River mainly comes from the industrial wastewater. Photodegradation of MeHg in WRT River surface water and the effects of natural constituents such as fulvic acid (FA), ferric ions (Fe3+), nitrate (NO3-), and dissolved oxygen on the MeHg photodegradation in aqueous solutions were studied under the simulated sunlight. The experimental data indicated that the indirect photodecomposition of MeHg occurred in WRT River surface water. Photodegradation of MeHg in FA solution was initiated by triplet 3FA* or MeHg-FA* via electron transfer interaction under light irradiations. The Fe3+ and NO3- can absorb light energy to produce ·OH and enhance the photochemical degradation of MeHg. The MeHg photodecompositions in FA, nitrate, and Fe3+ solutions were markedly accelerated after removing the dissolved oxygen.
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Affiliation(s)
- Shuihong Pan
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Chuchu Feng
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Jialu Lin
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Lidong Cheng
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Chengjun Wang
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China.
| | - Yuegang Zuo
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, 02747, USA.
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16
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Bonnineau C, Scaion D, Lemaire B, Belpaire C, Thomé JP, Thonon M, Leermaker M, Gao Y, Debier C, Silvestre F, Kestemont P, Rees JF. Accumulation of neurotoxic organochlorines and trace elements in brain of female European eel (Anguilla anguilla). ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2016; 45:346-355. [PMID: 27376663 DOI: 10.1016/j.etap.2016.06.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 06/04/2016] [Accepted: 06/07/2016] [Indexed: 06/06/2023]
Abstract
Xenobiotics such as organochlorine compounds (OCs) and metals have been suggested to play a significant role in the collapse of European eel stocks in the last decades. Several of these pollutants could affect functioning of the nervous system. Still, no information is so far available on levels of potentially neurotoxic pollutants in eel brain. In present study, carried out on female eels caught in Belgian rivers and canals, we analyzed brain levels of potentially-neurotoxic trace elements (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Hg, MeHg, Mn, Ni, Pb, Sn, Sb, Zn) and OCs (Polychlorinated biphenyls, PCBs; Hexachlorocyclohexanes, HCHs; Dichlorodiphenyltrichloroethane and its metabolites, DDTs). Data were compared to levels in liver and muscle tissues. Eel brain contained very high amounts of OCs, superior to those found in the two other tissues. Interestingly, the relative abundance of PCB congeners markedly differed between tissues. In brain, a predominance of low chlorinated PCBs was noted, whereas highly chlorinated congeners prevailed in muscle and liver. HCHs were particularly abundant in brain, which contains the highest amounts of β-HCH and ϒ-HCH. p,p'-DDTs concentration was similar between brain and muscle (i.e., about twice that of liver). A higher proportion of p,p'-DDT was noticed in brain. Except for Cr and inorganic Hg, all potentially neurotoxic metals accumulated in brain to levels equal to or lower than hepatic levels. Altogether, results indicate that eel brain is an important target for organic and, to a lesser extent, for inorganic neurotoxic pollutants.
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Affiliation(s)
- C Bonnineau
- Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud, 2/L7.05.08, B-1348 Louvain-la-Neuve, Belgium
| | - D Scaion
- Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud, 2/L7.05.08, B-1348 Louvain-la-Neuve, Belgium
| | - B Lemaire
- Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud, 2/L7.05.08, B-1348 Louvain-la-Neuve, Belgium
| | - C Belpaire
- Research Institute for Nature and Forest (INBO), Duboislaan 14, 1560 Hoeilaart, Belgium
| | - J-P Thomé
- Laboratoire d'Ecologie animale et d'Ecotoxicologie, Institut de Zoologie, Université de Liège, Quai Van Beneden 22, 4020 Liège, Belgium
| | - M Thonon
- Laboratoire d'Ecologie animale et d'Ecotoxicologie, Institut de Zoologie, Université de Liège, Quai Van Beneden 22, 4020 Liège, Belgium
| | - M Leermaker
- Analytical and Environmental Chemistry, Department of Chemistry, Faculty of Science, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Belgium
| | - Y Gao
- Analytical and Environmental Chemistry, Department of Chemistry, Faculty of Science, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Belgium
| | - C Debier
- Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud, 2/L7.05.08, B-1348 Louvain-la-Neuve, Belgium
| | - F Silvestre
- Unité de Recherche en Biologie Environnementale et Evolutive (URBE), Université de Namur, Rue de Bruxelles 61, B-5000, Namur, Belgium
| | - P Kestemont
- Unité de Recherche en Biologie Environnementale et Evolutive (URBE), Université de Namur, Rue de Bruxelles 61, B-5000, Namur, Belgium
| | - J-F Rees
- Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud, 2/L7.05.08, B-1348 Louvain-la-Neuve, Belgium.
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17
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Methylmercury alters glutathione homeostasis by inhibiting glutaredoxin 1 and enhancing glutathione biosynthesis in cultured human astrocytoma cells. Toxicol Lett 2016; 256:1-10. [PMID: 27180086 DOI: 10.1016/j.toxlet.2016.05.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 04/28/2016] [Accepted: 05/11/2016] [Indexed: 02/08/2023]
Abstract
Methylmercury (MeHg) is a neurotoxin that binds strongly to thiol residues on protein and low molecular weight molecules like reduced glutathione (GSH). The mechanism of its effects on GSH homeostasis particularly at environmentally relevant low doses is not fully known. We hypothesized that exposure to MeHg would lead to a depletion of reduced glutathione (GSH) and an accumulation of glutathione disulfide (GSSG) leading to alterations in S-glutathionylation of proteins. Our results showed exposure to low concentrations of MeHg (1μM) did not significantly alter GSH levels but increased GSSG levels by ∼12-fold. This effect was associated with a significant increase in total cellular glutathione content and a decrease in GSH/GSSG. Immunoblot analyses revealed that proteins involved in glutathione synthesis were upregulated accounting for the increase in cellular glutathione. This was associated an increase in cellular Nrf2 protein levels which is required to induce the expression of antioxidant genes in response to cellular stress. Intriguingly, we noted that a key enzyme involved in reversing protein S-glutathionylation and maintaining glutathione homeostasis, glutaredoxin-1 (Grx1), was inhibited by ∼50%. MeHg treatment also increased the S-glutathionylation of a high molecular weight protein. This observation is consistent with the inhibition of Grx1 and elevated H2O2 production however; contrary to our original hypothesis we found few S-glutathionylated proteins in the astrocytoma cells. Collectively, MeHg affects multiple arms of glutathione homeostasis ranging from pool management to protein S-glutathionylation and Grx1 activity.
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Mailloux RJ, Yumvihoze E, Chan HM. Superoxide produced in the matrix of mitochondria enhances methylmercury toxicity in human neuroblastoma cells. Toxicol Appl Pharmacol 2015; 289:371-80. [DOI: 10.1016/j.taap.2015.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 10/28/2015] [Accepted: 11/02/2015] [Indexed: 01/08/2023]
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19
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Mailloux RJ, Yumvihoze E, Chan HM. Superoxide anion radical (O2(-)) degrades methylmercury to inorganic mercury in human astrocytoma cell line (CCF-STTG1). Chem Biol Interact 2015; 239:46-55. [PMID: 26111762 DOI: 10.1016/j.cbi.2015.06.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 06/11/2015] [Accepted: 06/19/2015] [Indexed: 10/23/2022]
Abstract
Methylmercury (MeHg) is a global pollutant that is affecting the health of millions of people worldwide. However, the mechanism of MeHg toxicity still remains somewhat elusive and there is no treatment. It has been known for some time that MeHg can be progressively converted to inorganic mercury (iHg) in various tissues including the brain. Recent work has suggested that cleavage of the carbon-metal bond in MeHg in a biological environment is facilitated by reactive oxygen species (ROS). However, the oxyradical species that actually mediates this process has not been identified. Here, we provide evidence that superoxide anion radical (O2(-)) can convert MeHg to iHg. The calculated second-order rate constant for the degradation of 1μM MeHg by O2(-) generated by xanthine/xanthine oxidase was calculated to be 2×10(5)M(-1)s(-1). We were also able to show that this bioconversion can proceed in intact CCF-STTG1 human astrocytoma cells exposed to paraquat (PQ), a O2(-) generating viologen. Notably, exposure of cells to increasing amounts of PQ led to a dose dependent increase in both MeHg and iHg. Indeed, a 24h exposure to 500μM PQ induced a ∼13-fold and ∼18-fold increase in intracellular MeHg and iHg respectively. These effects were inhibited by superoxide dismutase mimetic MnTBAP. In addition, we also observed that a 24h exposure to a biologically relevant concentration of MeHg (1μM) did not induce cell death, oxidative stress, or even changes in cellular O2(-) and H2O2. However, co-exposure to PQ enhanced MeHg toxicity which was associated with a robust increase in cell death and oxidative stress. Collectively our results show that O2(-) can bioconvert MeHg to iHg in vitro and in intact cells exposed to conditions that simulate high intracellular O2(-) production. In addition, we show for the first time that O2(-) mediated degradation of MeHg to iHg enhances the toxicity of MeHg by facilitating an accumulation of both MeHg and iHg in the intracellular environment.
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Affiliation(s)
- Ryan J Mailloux
- University of Ottawa, Department of Biology, Center for Advanced Research in Environmental Genomics, Ottawa, ON K1N 6N5, Canada
| | - Emmanuel Yumvihoze
- University of Ottawa, Department of Biology, Center for Advanced Research in Environmental Genomics, Ottawa, ON K1N 6N5, Canada
| | - Hing Man Chan
- University of Ottawa, Department of Biology, Center for Advanced Research in Environmental Genomics, Ottawa, ON K1N 6N5, Canada.
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20
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Claveau J, Monperrus M, Jarry M, Baudrimont M, Gonzalez P, Cavalheiro J, Mesmer-Dudons N, Bolliet V. Methylmercury effects on migratory behaviour in glass eels (Anguilla anguilla): an experimental study using isotopic tracers. Comp Biochem Physiol C Toxicol Pharmacol 2015; 171:15-27. [PMID: 25797033 DOI: 10.1016/j.cbpc.2015.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Revised: 03/07/2015] [Accepted: 03/11/2015] [Indexed: 01/19/2023]
Abstract
The effect of methylmercury (MeHg) on glass eels' propensity to migrate, mitochondrial activity and antioxidative defence systems was investigated. Marine glass eels were first sorted in an experimental flume according to their response to dusk. Fish responding to the decrease in light intensity by ascending in the water column and moving with or against the flow were considered as having a high propensity to migrate (migrant). Glass eels still sheltering at the end of the 24 h catching period were considered as having a low propensity to migrate and were called non-migrant. Migrant and non-migrant glass eels were then individually tagged and exposed to isotopically enriched (201)MeHg (50 ng L(-1)) for 11 days. The effect of contamination was studied on muscle fibre structure, and the expression level of genes involved in mitochondrial activity and antioxidative defence systems. To investigate the effect of MeHg on glass eel behaviour, migrant and non-migrant glass eels were sorted again and the bioaccumulation of (201)MeHg and its demethylation product ((201)Hg(II)) were determined for each individual. MeHg exposure increased activity in non-migrant glass eels but not migratory behaviour. Contamination affected mitochondrial structure and metabolism and suggests a higher oxidative stress and activation of antioxidative defence systems in non-migrant glass eels. Overall, our results suggest that exposure to MeHg might induce an increase in energy expenditure and a higher vulnerability to predation in non-migrant glass eels in the wild.
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MESH Headings
- Anguilla/physiology
- Animal Migration/drug effects
- Animals
- Atlantic Ocean
- Biotransformation
- Energy Metabolism/drug effects
- France
- Gene Expression Regulation, Enzymologic/drug effects
- Mercury Isotopes
- Methylmercury Compounds/metabolism
- Methylmercury Compounds/toxicity
- Mitochondria, Muscle/drug effects
- Mitochondria, Muscle/metabolism
- Mitochondria, Muscle/ultrastructure
- Models, Biological
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/ultrastructure
- Oxidants/pharmacokinetics
- Oxidants/toxicity
- Oxidative Stress
- Oxidoreductases/chemistry
- Oxidoreductases/genetics
- Oxidoreductases/metabolism
- Phototrophic Processes/drug effects
- Tissue Distribution
- Toxicokinetics
- Water Pollutants, Chemical/metabolism
- Water Pollutants, Chemical/toxicity
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Affiliation(s)
- Julie Claveau
- INRA, UMR 1224 Ecobiop, Aquapôle, 64310 Saint Pée sur Nivelle, France; Université de Pau et des Pays de L'Adour, UMR 1224 Ecobiop, UFR Sciences et Techniques Côte Basque, Anglet, France.
| | - Mathilde Monperrus
- Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux, UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Hélioparc Pau Pyrénées, 2 av. P. Angot, 64053 9 Pau cedex 9, France.
| | - Marc Jarry
- INRA, UMR 1224 Ecobiop, Aquapôle, 64310 Saint Pée sur Nivelle, France; Université de Pau et des Pays de L'Adour, UMR 1224 Ecobiop, UFR Sciences et Techniques Côte Basque, Anglet, France.
| | - Magalie Baudrimont
- Université de Bordeaux, UMR 5805 EPOC, Team Aquatic Ecotoxicology, Place du Dr Peyneau, 33120 Arcachon, France.
| | - Patrice Gonzalez
- Université de Bordeaux, UMR 5805 EPOC, Team Aquatic Ecotoxicology, Place du Dr Peyneau, 33120 Arcachon, France.
| | - Joana Cavalheiro
- Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux, UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Hélioparc Pau Pyrénées, 2 av. P. Angot, 64053 9 Pau cedex 9, France.
| | - Nathalie Mesmer-Dudons
- Université de Bordeaux, UMR 5805 EPOC, Team Aquatic Ecotoxicology, Place du Dr Peyneau, 33120 Arcachon, France.
| | - Valérie Bolliet
- INRA, UMR 1224 Ecobiop, Aquapôle, 64310 Saint Pée sur Nivelle, France; Université de Pau et des Pays de L'Adour, UMR 1224 Ecobiop, UFR Sciences et Techniques Côte Basque, Anglet, France.
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21
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Krey A, Ostertag SK, Chan HM. Assessment of neurotoxic effects of mercury in beluga whales (Delphinapterus leucas), ringed seals (Pusa hispida), and polar bears (Ursus maritimus) from the Canadian Arctic. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 509-510:237-247. [PMID: 24958011 DOI: 10.1016/j.scitotenv.2014.05.134] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Revised: 05/19/2014] [Accepted: 05/27/2014] [Indexed: 06/03/2023]
Abstract
Marine mammals are indicator species of the Arctic ecosystem and an integral component of the traditional Inuit diet. The potential neurotoxic effects of increased mercury (Hg) in beluga whales (Delphinapterus leucas), ringed seals (Pusa hispida), and polar bears (Ursus maritimus) are not clear. We assessed the risk of Hg-associated neurotoxicity to these species by comparing their brain Hg concentrations with threshold concentrations for toxic endpoints detected in laboratory animals and field observations: clinical symptoms (>6.75 mg/kg wet weight (ww)), neuropathological signs (>4 mg/kg ww), neurochemical changes (>0.4 mg/kg ww), and neurobehavioral changes (>0.1mg/kg ww). The total Hg (THg) concentrations in the cerebellum and frontal lobe of ringed seals and polar bears were <0.5mg/kg ww, whereas the average concentration in beluga whale brain was >3mg/kg ww. Our results suggest that brain THg levels in polar bears are below levels that induce neurobehavioral effects as reported in the literature, while THg concentrations in ringed seals are within the range that elicit neurobehavioral effects and individual ringed seals exceed the threshold for neurochemical changes. The relatively high THg concentration in beluga whales exceeds all of the neurotoxicity thresholds assessed. High brain selenium (Se):Hg molar ratios were observed in all three species, suggesting that Se could protect the animals from Hg-associated neurotoxicity. This assessment was limited by several factors that influence neurotoxic effects in animals, including: animal species; form of Hg in the brain; and interactions with modifiers of Hg-associated toxicity, such as Se. Comparing brain Hg concentrations in wildlife with concentrations of appropriate laboratory studies can be used as a tool for risk characterization of the neurotoxic effects of Hg in Arctic marine mammals.
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Affiliation(s)
- Anke Krey
- Natural Resources and Environmental Studies, University of Northern British Columbia, 3333 University Way, Prince George, BC V2N 4Z9, Canada.
| | - Sonja K Ostertag
- Natural Resources and Environmental Studies, University of Northern British Columbia, 3333 University Way, Prince George, BC V2N 4Z9, Canada.
| | - Hing Man Chan
- Center for Advanced Research in Environmental Genomics, University of Ottawa, 20 Marie-Curie, Ottawa, ON K1N 6N5, Canada.
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22
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Chin-Chan M, Segovia J, Quintanar L, Arcos-López T, Hersh LB, Chow KM, Rodgers DW, Quintanilla-Vega B. Mercury Reduces the Enzymatic Activity of Neprilysin in Differentiated SH-SY5Y Cells. Toxicol Sci 2015; 145:128-37. [PMID: 25673500 DOI: 10.1093/toxsci/kfv037] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Levels of amyloid beta (Aβ) in the central nervous system are regulated by the balance between its synthesis and degradation. Neprilysin (NEP) is associated with Alzheimer's disease (AD) by its ability to degrade Aβ. Some studies have involved the exposure to mercury (Hg) in AD pathogenesis; therefore, our aim was to investigate the effects on the anabolism and catabolism of Aβ in differentiated SH-SY5Y cells incubated with 1-20 μM of Hg. Exposure to 20 µM of Hg induced an increase in Aβ-42 secretion, but did not increase the expression of the amyloid precursor protein (APP). Hg incubation (10 and 20 µM) increased NEP protein levels; however, it did not change NEP mRNA levels nor the levels of the amyloid intracellular domain peptide, a protein fragment with transcriptional activity. Interestingly, Hg reduced NEP activity at 10 and 20 µM, and circular dichroism analysis using human recombinant NEP showed conformational changes after incubation with molar equivalents of Hg. This suggests that the Hg-induced inhibition of NEP activity may be mediated by a conformational change resulting in reduced Aβ-42 degradation. Finally, the comparative effects of lead (Pb, 50 μM) were evaluated. We found a significant increase in Aβ-42 levels and a dramatic increase in APP protein levels; however, no alteration in NEP levels was observed nor in the enzymatic activity of this metalloprotease, despite the fact that Pb slightly modified the rhNEP conformation. Overall, our data suggest that Hg and Pb increase Aβ levels by different mechanisms.
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Affiliation(s)
- Miguel Chin-Chan
- *Department of Toxicology, Ave. IPN 2508, Colonia Zacatenco, Mexico City 07360, Department of Physiology, Biophysics and Neuroscience, Department of Chemistry, CINVESTAV, Mexico City 07360 and Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Biomedical Biological Sciences Research Building, 741 South Limestone St., Lexington, Kentucky 40536-0509
| | - José Segovia
- *Department of Toxicology, Ave. IPN 2508, Colonia Zacatenco, Mexico City 07360, Department of Physiology, Biophysics and Neuroscience, Department of Chemistry, CINVESTAV, Mexico City 07360 and Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Biomedical Biological Sciences Research Building, 741 South Limestone St., Lexington, Kentucky 40536-0509
| | - Liliana Quintanar
- *Department of Toxicology, Ave. IPN 2508, Colonia Zacatenco, Mexico City 07360, Department of Physiology, Biophysics and Neuroscience, Department of Chemistry, CINVESTAV, Mexico City 07360 and Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Biomedical Biological Sciences Research Building, 741 South Limestone St., Lexington, Kentucky 40536-0509
| | - Trinidad Arcos-López
- *Department of Toxicology, Ave. IPN 2508, Colonia Zacatenco, Mexico City 07360, Department of Physiology, Biophysics and Neuroscience, Department of Chemistry, CINVESTAV, Mexico City 07360 and Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Biomedical Biological Sciences Research Building, 741 South Limestone St., Lexington, Kentucky 40536-0509
| | - Louis B Hersh
- *Department of Toxicology, Ave. IPN 2508, Colonia Zacatenco, Mexico City 07360, Department of Physiology, Biophysics and Neuroscience, Department of Chemistry, CINVESTAV, Mexico City 07360 and Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Biomedical Biological Sciences Research Building, 741 South Limestone St., Lexington, Kentucky 40536-0509
| | - K Martin Chow
- *Department of Toxicology, Ave. IPN 2508, Colonia Zacatenco, Mexico City 07360, Department of Physiology, Biophysics and Neuroscience, Department of Chemistry, CINVESTAV, Mexico City 07360 and Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Biomedical Biological Sciences Research Building, 741 South Limestone St., Lexington, Kentucky 40536-0509
| | - David W Rodgers
- *Department of Toxicology, Ave. IPN 2508, Colonia Zacatenco, Mexico City 07360, Department of Physiology, Biophysics and Neuroscience, Department of Chemistry, CINVESTAV, Mexico City 07360 and Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Biomedical Biological Sciences Research Building, 741 South Limestone St., Lexington, Kentucky 40536-0509
| | - Betzabet Quintanilla-Vega
- *Department of Toxicology, Ave. IPN 2508, Colonia Zacatenco, Mexico City 07360, Department of Physiology, Biophysics and Neuroscience, Department of Chemistry, CINVESTAV, Mexico City 07360 and Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Biomedical Biological Sciences Research Building, 741 South Limestone St., Lexington, Kentucky 40536-0509
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23
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Yuntao F, Chenjia G, Panpan Z, Wenjun Z, Suhua W, Guangwei X, Haifeng S, Jian L, Wanxin P, Yun F, Cai J, Aschner M, Rongzhu L. Role of autophagy in methylmercury-induced neurotoxicity in rat primary astrocytes. Arch Toxicol 2014; 90:333-45. [PMID: 25488884 DOI: 10.1007/s00204-014-1425-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 11/25/2014] [Indexed: 11/30/2022]
Abstract
Autophagy is an evolutionarily conserved process in which cytoplasmic proteins and organelles are degraded and recycled for reuse. There are numerous reports on the role of autophagy in cell growth and death; however, the role of autophagy in methylmercury (MeHg)-induced neurotoxicity has yet to be identified. We studied the role of autophagy in MeHg-induced neurotoxicity in astrocytes. MeHg reduced astrocytic viability in a concentration- and time-dependent manner, and induced apoptosis. Pharmacological inhibition of autophagy with 3-methyladenine or chloroquine, as well as the silencing of the autophagy-related protein 5, increased MeHg-induced cytotoxicity and the ratio of apoptotic astrocytes. Conversely, rapamycin, an autophagy inducer, along with as N-acetyl-L-cysteine, a precursor of reduced glutathione, decreased MeHg-induced toxicity and the ratio of apoptotic astrocytes. These results indicated that MeHg-induced neurotoxicity was reduced, at least in part, through the activation of autophagy. Accordingly, modulation of autophagy may offer a new avenue for attenuating MeHg-induced neurotoxicity.
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Affiliation(s)
- Fang Yuntao
- Department of Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Guo Chenjia
- Department of Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Zhang Panpan
- Department of Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Zhao Wenjun
- Department of Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Wang Suhua
- Department of Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Xing Guangwei
- Department of Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Shi Haifeng
- Institute of Life Sciences, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Lu Jian
- Department of Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Peng Wanxin
- Department of Biology, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Feng Yun
- Department of Pharmacology, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Jiyang Cai
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, TX, 77550-1106, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Lu Rongzhu
- Department of Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
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24
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Krey A, Kwan M, Chan HM. In vivo and in vitro changes in neurochemical parameters related to mercury concentrations from specific brain regions of polar bears (Ursus maritimus). ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2014; 33:2463-2471. [PMID: 25264143 DOI: 10.1002/etc.2685] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 02/27/2014] [Accepted: 07/11/2014] [Indexed: 06/03/2023]
Abstract
Mercury (Hg) has been detected in polar bear brain tissue, but its biological effects are not well known. Relationships between Hg concentrations and neurochemical enzyme activities and receptor binding were assessed in the cerebellum, frontal lobes, and occipital lobes of 24 polar bears collected from Nunavik (Northern Quebec), Canada. The concentration-response relationship was further studied with in vitro experiments using pooled brain homogenate of 12 randomly chosen bears. In environmentally exposed brain samples, there was no correlative relationship between Hg concentration and cholinesterase (ChE) activity or muscarinic acetylcholine receptor (mAChR) binding in any of the 3 brain regions. Monoamine oxidase (MAO) activity in the occipital lobe showed a negative correlative relationship with total Hg concentration. In vitro experiments, however, demonstrated that Hg (mercuric chloride and methylmercury chloride) can inhibit ChE and MAO activities and muscarinic mAChR binding. These results show that Hg can alter neurobiochemical parameters but the current environmental Hg exposure level does have an effect on the neurochemistry of polar bears from northern Canada.
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Affiliation(s)
- Anke Krey
- Natural Resources and Environmental Studies, University of Northern British Columbia, Prince George, British Columbia, Canada
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25
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Kong HK, Wong MH, Chan HM, Lo SCL. Chronic exposure of adult rats to low doses of methylmercury induced a state of metabolic deficit in the somatosensory cortex. J Proteome Res 2013; 12:5233-45. [PMID: 23984759 DOI: 10.1021/pr400356v] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Because of the ever-increasing bioaccumulation of methylmercury (MeHg) in the marine food chain, human consumers are exposed to low doses of MeHg continually through seafood consumption. Epidemiological studies strongly suggest that chronic prenatal exposure to nanomolar of MeHg has immense negative impacts on neurological development in neonates. However, effects of chronic exposure to low doses (CELDs) of MeHg in adult brains on a molecular level are unknown. The current study aims to investigate the molecular effects of CELD of MeHg on adult somatosensory cortex in a rat model using proteomic techniques. Young adult rats were fed with a low dose of MeHg (40 μg/kg body weight/day) for a maximum of 12 weeks. Whole proteome expression of the somatosensory cortex (S1 area) of normal rats and those with CELD to MeHg were compared. Levels of MeHg, total calcium, adenosine triphosphate (ATP), and pyruvate were also measured. Comparative proteomic studies of the somatosensory cortexes revealed that 94 proteins involved in the various metabolic processes (including carbohydrate metabolism, generation of precursors for essential metabolites, energy, proteins, cellular components for morphogenesis, and neurotransmission) were down-regulated. Consequently, levels of important end products of active metabolism including ATP, pyruvate, and total calcium were also found to be significantly reduced concomitantly. Our results showed that CELD of MeHg induced a state of metabolic deficit in the somatosensory cortex of adult rats.
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Affiliation(s)
- Hang-Kin Kong
- Food Safety and Technology Research Centre, The Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University , Room Y810, Lee Shau Kee Building (Block Y), Hung Hom, Hong Kong, China
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Jebbett NJ, Hamilton JW, Rand MD, Eckenstein F. Low level methylmercury enhances CNTF-evoked STAT3 signaling and glial differentiation in cultured cortical progenitor cells. Neurotoxicology 2013; 38:91-100. [PMID: 23845766 DOI: 10.1016/j.neuro.2013.06.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 06/26/2013] [Accepted: 06/28/2013] [Indexed: 01/18/2023]
Abstract
Although many previous investigations have studied how mercury compounds cause cell death, sub-cytotoxic levels may affect mechanisms essential for the proper development of the nervous system. The present study investigates whether low doses of methylmercury (MeHg) and mercury chloride (HgCl2) can modulate the activity of JAK/STAT signaling, a pathway that promotes gliogenesis. We report that sub-cytotoxic doses of MeHg enhance ciliary neurotrophic factor (CNTF) evoked STAT3 phosphorylation in human SH-SY5Y neuroblastoma and mouse cortical neural progenitor cells (NPCs). This effect is specific for MeHg, since HgCl2 fails to enhance JAK/STAT signaling. Exposing NPCs to these low doses of MeHg (30-300nM) enhances CNTF-induced expression of STAT3-target genes such as glial fibrillary acidic protein (GFAP) and suppressors of cytokine signaling 3 (SOCS3), and increases the proportion of cells expressing GFAP following 2 days of differentiation. Higher, near-cytotoxic concentrations of MeHg and HgCl2 inhibit STAT3 phosphorylation and lead to increased production of superoxide. Lower concentrations of MeHg effective in enhancing JAK/STAT signaling (30nM) do not result in a detectable increase in superoxide nor increased expression of the oxidant-responsive genes, heme oxygenase 1, heat shock protein A5 and sirtuin 1. These findings suggest that low concentrations of MeHg inappropriately enhance STAT3 phosphorylation and glial differentiation, and that the mechanism causing this enhancement is distinct from the reactive oxygen species-associated cell death observed at higher concentrations of MeHg and HgCl2.
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Affiliation(s)
- Nathan J Jebbett
- University of Vermont, Department of Neurological Sciences, Burlington, VT, United States
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27
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Ostertag SK, Stern GA, Wang F, Lemes M, Chan HM. Mercury distribution and speciation in different brain regions of beluga whales (Delphinapterus leucas). THE SCIENCE OF THE TOTAL ENVIRONMENT 2013; 456-457:278-286. [PMID: 23624002 DOI: 10.1016/j.scitotenv.2013.03.106] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 03/29/2013] [Accepted: 03/30/2013] [Indexed: 06/02/2023]
Abstract
The toxicokinetics of mercury (Hg) in key species of Arctic ecosystem are poorly understood. We sampled five brain regions (frontal lobe, temporal lobe, cerebellum, brain stem and spinal cord) from beluga whales (Delphinapterus leucas) harvested in 2006, 2008, and 2010 from the eastern Beaufort Sea, Canada, and measured total Hg (HgT) and total selenium (SeT) by inductively coupled plasma mass spectrometry (ICP-MS), mercury analyzer or cold vapor atomic absorption spectrometry, and the chemical forms using a high performance liquid chromatography ICP-MS. At least 14% of the beluga whales had HgT concentrations higher than the levels of observable adverse effect (6.0 mg kg(-1) wet weight (ww)) in primates. The concentrations of HgT differed between brain regions; median concentrations (mgkg(-1) ww) were 2.34 (0.06 to 22.6, 81) (range, n) in temporal lobe, 1.84 (0.12 to 21.9, 77) in frontal lobe, 1.84 (0.05 to 16.9, 83) in cerebellum, 1.25 (0.02 to 11.1, 77) in spinal cord and 1.32 (0.13 to 15.2, 39) in brain stem. Total Hg concentrations in the cerebellum increased with age (p<0.05). Between 35 and 45% of HgT was water-soluble, of which, 32 to 41% was methyl mercury (MeHg) and 59 to 68% was labile inorganic Hg. The concentration of MeHg (range: 0.03 to 1.05 mg kg(-1) ww) was positively associated with HgT concentration, and the percent MeHg (4 to 109%) decreased exponentially with increasing HgT concentration in the spinal cord, cerebellum, frontal lobe and temporal lobe. There was a positive association between SeT and HgT in all brain regions (p<0.05) suggesting that Se may play a role in the detoxification of Hg in the brain. The concentration of HgT in the cerebellum was significantly associated with HgT in other organs. Therefore, HgT concentrations in organs that are frequently sampled in bio-monitoring studies could be used to estimate HgT concentrations in the cerebellum, which is the target organ of MeHg toxicity.
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Affiliation(s)
- Sonja K Ostertag
- Natural Resources and Environmental Studies, University of Northern British Columbia, Prince George, British Columbia, V2N 4Z9, Canada.
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28
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Affiliation(s)
- Michael Aschner
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN 37232, United States.
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29
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Krey A, Kwan M, Chan HM. Mercury speciation in brain tissue of polar bears (Ursus maritimus) from the Canadian Arctic. ENVIRONMENTAL RESEARCH 2012; 114:24-30. [PMID: 22406289 DOI: 10.1016/j.envres.2012.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Revised: 01/03/2012] [Accepted: 01/31/2012] [Indexed: 05/31/2023]
Abstract
Methylmercury (MeHg) is a neurotoxicant that has been found at elevated concentrations in the Arctic ecosystem. Little is known about its internal dose in wildlife such as polar bears. We measured concentrations of mercury (Hg) in three different brain regions (cerebellum, frontal lobe and brain stem) of 24 polar bears collected from the Nunavik, Canada between 2000 and 2003. Speciation of Hg was measured by High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectroscopy (HPLC-ICP-MS). Concentrations of mean total Hg in brain tissue were up to 625 times lower (0.28 ± 0.07 mg kg(-1) dry weight (dw) in frontal lobe, 0.23 ± 0.07 mg kg(-1) dw in cerebellum and 0.12 ± 0.0 3mg kg(-1) dw in brain stem) than the mean total Hg concentration previously reported in polar bear liver collected from Eastern Baffin Island. Methylmercury (MeHg) accounted for 100% of the Hg found in all three brain regions analyzed. These results suggest that polar bear might reduce the toxic effects of Hg by limiting the uptake into the brain and/or decrease the rate of demethylation so that Hg can be excreted from the brain more easily. The toxicokinetics and the blood-brain-barrier mechanisms of polar bears are still unknown and further research is required.
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Affiliation(s)
- Anke Krey
- Natural Resources and Environmental Studies, University of Northern British Columbia, Prince George, BC, Canada
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Bassett T, Bach P, Chan HM. Effects of methylmercury on the secretion of pro-inflammatory cytokines from primary microglial cells and astrocytes. Neurotoxicology 2011; 33:229-34. [PMID: 22037494 DOI: 10.1016/j.neuro.2011.10.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 10/10/2011] [Accepted: 10/13/2011] [Indexed: 10/16/2022]
Abstract
Glial cells, including oligodendrocytes, astrocytes and microglia are important to proper central nervous system (CNS) function. Deregulation or changes to CNS populations of astrocytes and microglia in particular are expected to play a role in many neurodegenerative diseases, including Parkinson's disease, amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD). Previous studies have reported methylmercury (MeHg) induced changes in glial cell function; however, the effects of MeHg on these cells remains poorly understood. This study aims to examine the effect of MeHg on the secretion of pro-inflammatory cytokines from microglia and astrocytes. The impact of the microglia/astrocyte ratio on cytokine secretion was also examined. Microglia and astrocytes were cultured from the brains of neo-natal BALB/C mice and dosed with MeHg (0-1 μM) and stimulated with PAM(3)CSK(4) (PAM(3)), a toll-like receptor (TLR) ligand. After this, the secretion of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α) and interleukin-1-beta (IL-1β) was measured by ELISA. MeHg reduced the secretion of IL-6 in a dose dependant manner but did not effect the secretion of TNF-α. No change in IL-1β was observed in any treatments, indicating that PAM(3) cannot induce the secretion of this cytokine from glial cells. Additionally, the ratio of microglia/astrocyte had an effect on the secretion of IL-6 but not TNF-α. These results indicate that MeHg can modify the response of glial cells and the interactions with astrocytes can affect the response of the microglia cells in culture. These results are significant in understanding the potential relationship with MeHg and neurodegenerative diseases and for the interpretation of results of future in vitro studies using monoculture.
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Affiliation(s)
- Tyler Bassett
- Community Health Sciences Program, University of Northern British Columbia, Prince George, BC, Canada
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Black P, Niu L, Sachdeva M, Lean D, Poon R, Bowers WJ, Chan HM, Arnason JT, Pelletier G. Modulation of the effects of methylmercury on rat neurodevelopment by co-exposure with Labrador Tea (Rhododendron tomentosum ssp. subarcticum). Food Chem Toxicol 2011; 49:2336-42. [DOI: 10.1016/j.fct.2011.06.035] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 06/14/2011] [Accepted: 06/15/2011] [Indexed: 02/07/2023]
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Amoli JS, Barin A, Ebrahimi-Rad M, Sadighara P. Cell damage through pentose phosphate pathway in fetus fibroblast cells exposed to methyl mercury. J Appl Toxicol 2011; 31:685-9. [DOI: 10.1002/jat.1628] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 07/03/2010] [Accepted: 10/08/2010] [Indexed: 11/08/2022]
Affiliation(s)
- Jamileh Salar Amoli
- Department of Toxicology; Veterinary Faculty; Tehran University; Tehran; Iran
| | - Abbas Barin
- Department of Clinical Pathology; Veterinary Faculty; Tehran University; Tehran; Iran
| | | | - Parisa Sadighara
- Department of Toxicology; Veterinary Faculty; Tehran University; Tehran; Iran
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Helmcke KJ, Aschner M. Hormetic effect of methylmercury on Caenorhabditis elegans. Toxicol Appl Pharmacol 2010; 248:156-64. [PMID: 20691719 DOI: 10.1016/j.taap.2010.07.023] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 07/23/2010] [Accepted: 07/27/2010] [Indexed: 10/19/2022]
Abstract
Research has demonstrated the toxic effects of methylmercury (MeHg), yet molecular mechanisms underlying its toxicity are not completely understood. Caenorhabditis elegans (C. elegans) offers a unique biological model to explore mechanisms of MeHg toxicity given many advantages associated with its ease of use and genetic power. Since our previous work indicated neurotoxic resistance of C. elegans to MeHg, the present study was designed to examine molecular mechanisms associated with this resistance. We hypothesized MeHg would induce expression of gst, hsp or mtl in vivo since glutathione (GSH), heat shock proteins (HSPs), and metallothioneins (MTs) have shown involvement in MeHg toxicity. Our studies demonstrated a modest, but significant increase in fluorescence in gst-4::GFP and mtl-1::GFP strains at an acute, low L1 MeHg exposure, whereas chronic L4 MeHg exposure induced expression of gst-4::GFP and hsp-4::GFP. Knockout gst-4 animals showed no alterations in lethality sensitivity compared to wildtype animals whereas mtl knockouts displayed increased sensitivity to MeHg exposure. GSH levels were increased by acute MeHg treatment and depleted with chronic exposure. We also demonstrate that MeHg induces hormesis, a phenotype whereby a sublethal exposure to MeHg rendered C. elegans resistant to subsequent exposure to the organometal. The involvement of gst-4, hsp-4, mtl-1, and mtl-2 in hormesis was examined. An increase in gst-4::GFP expression after a low-dose acute exposure to MeHg indicated that gst-4 may be involved in this response. Our results implicate GSH, HSPs, and MTs in protecting C. elegans from MeHg toxicity and show a potential role of gst-4 in MeHg-induced hormesis.
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Affiliation(s)
- Kirsten J Helmcke
- Pharmacology Department and Center in Molecular Toxicology, Vanderbilt University, Nashville, TN 37232, USA.
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Nagano M, Yasutake A, Miura K. Demethylation of Methylmercury in Human Neuroblastoma, Glioblastoma and Liver Cells. ACTA ACUST UNITED AC 2010. [DOI: 10.1248/jhs.56.326] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Masaaki Nagano
- Biochemistry Section, National Institute for Minamata Disease
- Water and Soil Environmental Division, National Institute for Environmental Studies
| | - Akira Yasutake
- Biochemistry Section, National Institute for Minamata Disease
| | - Kyoko Miura
- Department of Environmental Sciences, Wako University
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Fonnum F, Mariussen E. Mechanisms involved in the neurotoxic effects of environmental toxicants such as polychlorinated biphenyls and brominated flame retardants. J Neurochem 2009; 111:1327-47. [DOI: 10.1111/j.1471-4159.2009.06427.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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