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Xu X, Wang SS, Zhang L, Lu AX, Lin Y, Liu JX, Yan CH. Methylmercury induced ferroptosis by interference of iron homeostasis and glutathione metabolism in CTX cells. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 335:122278. [PMID: 37517642 DOI: 10.1016/j.envpol.2023.122278] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 07/20/2023] [Accepted: 07/26/2023] [Indexed: 08/01/2023]
Abstract
Environmental methylmercury (MeHg) exposure has gained global attention owing to its serious health hazards, especially neurotoxicity. Ferroptosis is a novel form of programmed cell death characterized by lipid peroxidation and iron overload. However, the occurrence of ferroptosis and its underlying mechanisms have not been fully elucidated in the methylmercury-induced neurotoxicity and the role of Nrf2 in MeHg-induced ferroptosis remains unexplored. In this study, we verified that MeHg decreased cell viability in a dose- and time-dependent manner in the Rat Brain Astrocytes cells (CTX cells). MeHg (3.5 μmol/L) exposure induced CTX cells to undergo ferroptosis, as evidenced by glutathione (GSH) depletion, lipid peroxidation, and iron overload, which was significantly rescued by the ferroptosis-specific inhibitors Ferrostatin-1 and Deferoxamine. MeHg directly disrupted the process of GSH metabolism by downregulating of SLC7A11 and GPX4 and interfered with intracellular iron homeostasis through inhibition of iron storage and export. Simultaneously, the expression of Nrf2 was upregulated by MeHg in CTX cells. Hence, the inhibition of Nrf2 activity further downregulated the levels of GPX4, SLC7A11, FTH1, and SLC40A1, which aggravated MeHg-induced ferroptosis to a greater extent. Overall, our findings provided evidence that ferroptosis played a critical role in MeHg-induced neurotoxicity, and suppressing Nrf2 activity further exacerbated MeHg-induced ferroptosis in CTX cells.
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Affiliation(s)
- Xi Xu
- Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Su-Su Wang
- Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lin Zhang
- Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - An-Xin Lu
- Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yin Lin
- Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jun-Xia Liu
- Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chong-Huai Yan
- Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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Kendricks DR, Bhattacharya S, Reed MN, Newland MC. Impacts of Neonatal Methylmercury on Behavioral Flexibility and Learning in Spatial Discrimination Reversal and Visual Signal Detection Tasks. Neurotoxicology 2022; 93:9-21. [PMID: 36055519 DOI: 10.1016/j.neuro.2022.08.013] [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: 06/14/2022] [Revised: 08/19/2022] [Accepted: 08/22/2022] [Indexed: 11/19/2022]
Abstract
Early postnatal development in rodents is sensitive to neurotoxic effects of the environmental contaminant, methylmercury. While juvenile and adolescent exposure also produce long-term impairments in behavior, the outcome of neonatal exposure is less understood. Neural development during the neonatal period in rodents is akin to that seen in humans during the third trimester of pregnancy but methylmercury exposure occurring during the neonatal period has not been modeled, partly because breast milk is a poor source of bioavailable methylmercury. To examine this developmental period, male Long-Evans rats were exposed to 0, 80, or 350µg/kg/day methylmercuric chloride from postnatal days 1 to 10, the rodent neonatal period. As adults, behavioral flexibility, attention, memory, and expression of the dopamine transporter in these rats was assessed. Rats exhibited changes in behavioral flexibility assessed in a spatial discrimination reversal procedure. Those rats exposed to the highest dose of methylmercury displayed subtly altered patterns of perseveration compared to control animals. During acquisition of the attention/memory procedure, rats exposed to this dose also had slower acquisition, and achieved lower overall accuracy during training, compared to controls despite neither attention nor memory being affected once the task was acquired. Finally, dopamine transporter expression in the striatum, prefrontal cortex, and hippocampus was unchanged in these adult rats. The results of this study replicate the trend of findings seen with exposure during gestation or during adolescence.
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Affiliation(s)
- Dalisa R Kendricks
- Department of Psychological Sciences, Auburn University, Auburn, AL, USA
| | - Subhrajit Bhattacharya
- Keck Graduate Institute, School of Pharmacy and Health Sciences, Claremont Colleges, Claremont, CA, USA
| | - Miranda N Reed
- Department of Drug Discovery and Development, Auburn University, Auburn, AL, USA; Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
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Ke T, Santamaria A, Junior FB, Rocha JBT, Bowman AB, Aschner M. Methylmercury exposure-induced reproductive effects are mediated by dopamine in Caenorhabditis elegans. Neurotoxicol Teratol 2022; 93:107120. [PMID: 35987454 DOI: 10.1016/j.ntt.2022.107120] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 08/09/2022] [Accepted: 08/11/2022] [Indexed: 11/28/2022]
Abstract
Methylmercury (MeHg) is a neurotoxicant that exists in the natural environment, which level can be greatly increased because of human activity. MeHg exposures have the risk of being detrimental to the development of the nervous system. Studies on MeHg toxicity have largely focused on the mechanisms of its neurotoxicity following developmental exposures. Additionally, reproductive toxicity of developmental MeHg exposures has been noted in rodent models. The model organism Caenorhabditis elegans (C. elegans) is a self-fertilizing animal which has a short lifespan around 20 days. Most C. elegans are hermaphrodites that can generate both sperm and oocytes. To investigate the effects of developmental MeHg exposures on the reproduction in C. elegans, larvae stage 1 worms were exposed to MeHg (0, 0.01 or 0.05 μM) for 24 h. The laid eggs and oocytes were compared during each day at adult stages for 6 days. We showed that MeHg exposure significantly induced an increased number of eggs in day 1 adults without an effect on the timing of egg laying or the total number of eggs or oocytes over the 6-day period. The expression of dat-1 and cat-2 and dopamine levels were increased in worms exposed to MeHg. Supplementation with 100 μM dopamine recapitulated the effect of MeHg on the number of eggs present in day 1 adults. Furthermore, the effect of MeHg on the number of eggs was abrogated in the cat-2 mutant worms CB1112. The number of oocytes in the 6-day adult stages was decreased by MeHg in the dat-1 mutant RM2702. MeHg exposures did not change the mating rate or the number of offspring from mating. Combined, these novel findings show that developmental exposure to low levels of MeHg has limited effects on the reproduction in C. elegans. Furthermore, our data support a modulatory role of dopamine in MeHg-induced effects on reproduction in this model system.
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Affiliation(s)
- Tao Ke
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | - Abel Santamaria
- Laboratorio de Aminoácidos Excitadores/Laboratorio de Neurofarmacología Molecular y Nanotecnología, Instituto Nacional de Neurología y Neurocirugía, 14269 Mexico City, Mexico
| | - Fernando Barbosa Junior
- Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP 14040-900, Brazil
| | - João B T Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97105900 Santa Maria, RS, Brazil
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN 47907-2051, United States
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States.
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Kendricks DR, Boomhower SR, Newland MC. Adolescence as a sensitive period for neurotoxicity: Lifespan developmental effects of methylmercury. Pharmacol Biochem Behav 2022; 217:173389. [PMID: 35452710 DOI: 10.1016/j.pbb.2022.173389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 04/04/2022] [Accepted: 04/11/2022] [Indexed: 10/18/2022]
Abstract
Neurotoxicity resulting from the environmental contaminant, methylmercury (MeHg), is a source of concern for many human populations that rely heavily on the consumption of fish and rice as stable ingredients in the diet. The developmental period of exposure is important both to the qualitative effects of MeHg and to the dose required to produce those effects. MeHg exposure during the sensitive prenatal period causes deleterious and long-lasting changes in neurodevelopment at particularly low doses. The effects include a wide host of cognitive and behavioral outcomes expressed in adulthood and sometimes not until aging. However, neurotoxic outcomes of methylmercury when exposure occurs during adolescence are only recently revealing impacts on human populations and animal models. This review examines the current body of work and showcases the sensitivity of adolescence, a period that straddles early development and adulthood, to methylmercury neurotoxicity and the implications such toxicity has in our understanding of methylmercury's effects in human populations and animal models.
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Affiliation(s)
- Dalisa R Kendricks
- Department of Psychology, Auburn University, Auburn, AL, United States of America.
| | - Steven R Boomhower
- Gradient, Boston, MA, United States of America; Harvard Division of Continuing Education, Harvard University, Cambridge, MA, United States of America
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Ke T, Tinkov AA, Skalny AV, Bowman AB, Rocha JBT, Santamaria A, Aschner M. Developmental exposure to methylmercury and ADHD, a literature review of epigenetic studies. ENVIRONMENTAL EPIGENETICS 2021; 7:dvab014. [PMID: 34881051 PMCID: PMC8648069 DOI: 10.1093/eep/dvab014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/20/2021] [Accepted: 11/08/2021] [Indexed: 06/13/2023]
Abstract
Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that affects the competence of academic performance and social wellness in children and adults. The causes of ADHD are unclear. Both genetic and environmental factors contribute to the development of ADHD. The behavioral impairments in ADHD are associated with epigenetic changes in genes that are important for neurodevelopment. Among environmental causes of ADHD, the neurotoxin methylmercury (MeHg) is associated with an increased risk for ADHD. Developing children are susceptible to neurotoxic effects of prenatal MeHg exposure. Human epidemiology studies have shown that prenatal MeHg exposure could invoke epigenetic changes in genes that are involved in ADHD. In addition, the pathogenesis of ADHD involves dopaminergic system, which is a target of developmental MeHg exposure. MeHg-induced alterations in the dopaminergic system have a profound impact on behavioral functions in adults. As a trace level of MeHg (around nM) can induce long-lasting behavioral alterations, potential mechanisms of MeHg-induced functional changes in the dopaminergic system may involve epigenetic mechanisms. Here, we review the relevant evidence on developmental MeHg exposures and the risk for ADHD. We also point out research gaps in understanding environmental causes of ADHD.
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Affiliation(s)
- Tao Ke
- **Correspondence address. Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Forchheimer Building, Room 209, Bronx, NY 10461, USA. Tel: +1 718 430 4047; Fax: +1 718 430 8922; E-mail:
| | - Alexey A Tinkov
- World-Class Research Center “Digital Biodesign and Personalized Healthcare”, IM Sechenov First Moscow State Medical University (Sechenov University), Moscow 119435, Russia
- Laboratory of Ecobiomonitoring and Quality Control, Yaroslavl State University, Yaroslavl 150003, Russia
| | - Antoly V Skalny
- World-Class Research Center “Digital Biodesign and Personalized Healthcare”, IM Sechenov First Moscow State Medical University (Sechenov University), Moscow 119435, Russia
- Laboratory of Medical Elementology, K.G. Razumovsky Moscow State University of Technologies and Management, Moscow 109004, Russia
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN 47907-2051, USA
| | - Joao B T Rocha
- Department of Biochemistry and Molecular Biology, Federal University of Santa Maria, Santa Maria, RS 97105-900, Brazil
| | - Abel Santamaria
- Laboratorio de Aminoácidos Excitadores, Instituto Nacional de Neurología y Neurocirugía, Mexico City 14269, Mexico
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Forchheimer Building, Room 209, Bronx, NY 10461, USA
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Kendricks DR, Newland MC. Selective dopaminergic effects on attention and memory in male mice exposed to Methylmercury during adolescence. Neurotoxicol Teratol 2021; 87:107016. [PMID: 34274440 DOI: 10.1016/j.ntt.2021.107016] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 06/06/2021] [Accepted: 07/08/2021] [Indexed: 01/22/2023]
Abstract
Gestational exposure to methylmercury disrupts dopamine-mediated behavior and produces heightened sensitivity to monoamine agonists later in life. This has been reported and replicated following both pre- and post-natal exposure. Impacts of methylmercury when exposure occurs during the sensitive period of adolescence, a key period of dopaminergic development, remain underexplored. There have been variable results thus far in studies investigating links between adolescent exposure to methylmercury and alterations in executive function and altered sensitivity to monoamine agonists. The current study was designed to investigate adolescent exposure by exposing male mice to 0, 0.3, or 3 ppm methylmercury during adolescence and training them in a hybrid task to assess two executive functions, attention and memory, in adulthood. Behavior in these animals was probed with a range of doses of the dopamine agonist, d-amphetamine, and the norepinephrine agonist, desipramine. Attention and memory in these mice were sensitive to disruption by d-amphetamine and interacted with methylmercury exposure. Choice latencies were also longer in the MeHg-exposed mice. Desipramine did not affect behavior in these animals nor did it interact with methylmercury. It is concluded that methylmercury-related inhibition of behavior observed in this study were differentially sensitive to acute disruption in dopamine, but not norepinephrine, neurotransmission.
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Affiliation(s)
- Dalisa R Kendricks
- Department of Psychological Science, Auburn University, Auburn, AL, United States of America.
| | - M Christopher Newland
- Department of Psychological Science, Auburn University, Auburn, AL, United States of America
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Martins AC, Ke T, Bowman AB, Aschner M. New insights on mechanisms underlying methylmercury-induced and manganese-induced neurotoxicity. CURRENT OPINION IN TOXICOLOGY 2021; 25:30-35. [PMID: 33898886 PMCID: PMC8061890 DOI: 10.1016/j.cotox.2021.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Toxic and essential elements are widely distributed in the Earth's crust and individuals may be exposed to several of them. Indeed, exposure to toxic elements such as mercury (Hg) can be a potential health risk factor of health, mainly by ingestion of fish containing methylmercury (MeHg). On the other hand, essential elements such as manganese (Mn) play an important role in physiological process in human body. However, Mn overexposure may cause toxic effects. In this respect, the neurotoxic effects of MeHg and Mn on the developing brain are well recognized. Therefore, in this critical review, we address the effects of MeHg and Mn on cell signaling pathways which may contribute to molecular mechanisms involved in MeHg- and Mn-induced neurotoxicity.
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Affiliation(s)
- Airton C Martins
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Tao Ke
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
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