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Kang B, Wang J, Guo S, Yang L. Mercury-induced toxicity: Mechanisms, molecular pathways, and gene regulation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 943:173577. [PMID: 38852866 DOI: 10.1016/j.scitotenv.2024.173577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/01/2024] [Accepted: 05/25/2024] [Indexed: 06/11/2024]
Abstract
Mercury is a well-known neurotoxicant for humans and wildlife. The epidemic of mercury poisoning in Japan has clearly demonstrated that chronic exposure to methylmercury (MeHg) results in serious neurological damage to the cerebral and cerebellar cortex, leading to the dysfunction of the central nervous system (CNS), especially in infants exposed to MeHg in utero. The occurrences of poisoning have caused a wide public concern regarding the health risk emanating from MeHg exposure; particularly those eating large amounts of fish may experience the low-level and long-term exposure. There is growing evidence that MeHg at environmentally relevant concentrations can affect the health of biota in the ecosystem. Although extensive in vivo and in vitro studies have demonstrated that the disruption of redox homeostasis and microtube assembly is mainly responsible for mercurial toxicity leading to adverse health outcomes, it is still unclear whether we could quantitively determine the occurrence of interaction between mercurial and thiols and/or selenols groups of proteins linked directly to outcomes, especially at very low levels of exposure. Furthermore, intracellular calcium homeostasis, cytoskeleton, mitochondrial function, oxidative stress, neurotransmitter release, and DNA methylation may be the targets of mercury compounds; however, the primary targets associated with the adverse outcomes remain to be elucidated. Considering these knowledge gaps, in this article, we conducted a comprehensive review of mercurial toxicity, focusing mainly on the mechanism, and genes/proteins expression. We speculated that comprehensive analyses of transcriptomics, proteomics, and metabolomics could enhance interpretation of "omics" profiles, which may reveal specific biomarkers obviously correlated with specific pathways that mediate selective neurotoxicity.
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Affiliation(s)
- Bolun Kang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Jinghan Wang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Shaojuan Guo
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Lixin Yang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China.
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2
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Tam LM, Rand MD. Review: myogenic and muscle toxicity targets of environmental methylmercury exposure. Arch Toxicol 2024; 98:1645-1658. [PMID: 38546836 PMCID: PMC11105986 DOI: 10.1007/s00204-024-03724-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 02/29/2024] [Indexed: 05/01/2024]
Abstract
A number of environmental toxicants are noted for their activity that leads to declined motor function. However, the role of muscle as a proximal toxicity target organ for environmental agents has received considerably less attention than the toxicity targets in the nervous system. Nonetheless, the effects of conventional neurotoxicants on processes of myogenesis and muscle maintenance are beginning to resolve a concerted role of muscle as a susceptible toxicity target. A large body of evidence from epidemiological, animal, and in vitro studies has established that methylmercury (MeHg) is a potent developmental toxicant, with the nervous system being a preferred target. Despite its well-recognized status as a neurotoxicant, there is accumulating evidence that MeHg also targets muscle and neuromuscular development as well as contributes to the etiology of motor defects with prenatal MeHg exposure. Here, we summarize evidence for targets of MeHg in the morphogenesis and maintenance of skeletal muscle that reveal effects on MeHg distribution, myogenesis, myotube formation, myotendinous junction formation, neuromuscular junction formation, and satellite cell-mediated muscle repair. We briefly recapitulate the molecular and cellular mechanisms of skeletal muscle development and highlight the pragmatic role of alternative model organisms, Drosophila and zebrafish, in delineating the molecular underpinnings of muscle development and MeHg-mediated myotoxicity. Finally, we discuss how toxicity targets in muscle development may inform the developmental origins of health and disease theory to explain the etiology of environmentally induced adult motor deficits and accelerated decline in muscle fitness with aging.
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Affiliation(s)
- Lok Ming Tam
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave, Rochester, NY, 14642, USA.
- Clinical and Translational Science Institute, University of Rochester Medical Center, 601 Elmwood Ave, Rochester, NY, 14642, USA.
| | - Matthew D Rand
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave, Rochester, NY, 14642, USA
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3
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Xu S, Liu H, Wang C, Deng Y, Xu B, Yang T, Liu W. Study of ATF4/CHOP axis-mediated mitochondrial unfolded protein response in neuronal apoptosis induced by methylmercury. Food Chem Toxicol 2023; 182:114190. [PMID: 37967789 DOI: 10.1016/j.fct.2023.114190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 10/18/2023] [Accepted: 11/08/2023] [Indexed: 11/17/2023]
Abstract
Methylmercury (MeHg) is a widely distributed environmental pollutant that can easily cross the blood-brain barrier and accumulate in the brain, thereby damaging the central nervous system. Studies have shown that MeHg-induced mitochondrial damage and apoptosis play a crucial role in its neurotoxic effects. Mitochondrial unfolded protein response (UPRmt) is indispensable to maintain mitochondrial protein homeostasis and ensure mitochondrial function, and the ATF4/CHOP axis is one of the signaling pathways to activate UPRmt. In this study, the role of the ATF4/CHOP axis-mediated UPRmt in the neurotoxicity of MeHg has been investigated by C57BL/6 mice and the HT22 cell line. We discovered that mice exposed to MeHg had abnormal neurobehavioral patterns. The pathological section showed a significant decrease in the number of neurons. MeHg also resulted in a reduction in mtDNA copy number and mitochondrial membrane potential (MMP). Additionally, the ATF4/CHOP axis and UPRmt were found to be significantly activated. Subsequently, we used siRNA to knock down ATF4 or CHOP and observed that the expression of UPRmt-related proteins and the apoptosis rate were significantly reduced. Our research showed that exposure to MeHg can over-activate the UPRmt through the ATF4/CHOP axis, leading to mitochondrial damage and ultimately inducing neuronal apoptosis.
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Affiliation(s)
- Si Xu
- Department of Environmental Health, School of Public Health, China Medical University, China
| | - Haihui Liu
- Department of Environmental Health, School of Public Health, China Medical University, China
| | - Chen Wang
- Department of Environmental Health, School of Public Health, China Medical University, China
| | - Yu Deng
- Department of Environmental Health, School of Public Health, China Medical University, China
| | - Bin Xu
- Department of Environmental Health, School of Public Health, China Medical University, China
| | - Tianyao Yang
- Department of Environmental Health, School of Public Health, China Medical University, China.
| | - Wei Liu
- Department of Environmental Health, School of Public Health, China Medical University, China.
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Park SY, Liu S, Carbajal EP, Wosczyna M, Costa M, Sun H. Hexavalent chromium inhibits myogenic differentiation and induces myotube atrophy. Toxicol Appl Pharmacol 2023; 477:116693. [PMID: 37742872 PMCID: PMC10591800 DOI: 10.1016/j.taap.2023.116693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 09/12/2023] [Accepted: 09/14/2023] [Indexed: 09/26/2023]
Abstract
Hexavalent chromium [Cr(VI)] is extensively used in many industrial processes. Previous studies reported that Cr(VI) exposures during early embryonic development reduced body weight with musculoskeletal malformations in rodents while exposures in adult mice increased serum creatine kinase activity, a marker of muscle damage. However, the impacts of Cr(VI) on muscle differentiation remain largely unknown. Here, we report that acute exposures to Cr(VI) in mouse C2C12 myoblasts inhibit myogenic differentiation in a dose-dependent manner. Exposure to 2 μM of Cr(VI) resulted in delayed myotube formation, as evidenced by a significant decrease in myotube formation and expression of muscle-specific markers, such as muscle creatine kinase (Mck), Myocyte enhancer factor 2 (Mef2), Myomaker (Mymk) and Myomixer (Mymx). Interestingly, exposure to 5 μM of Cr(VI) completely abolished myotube formation in differentiating C2C12 cells. Moreover, the expression of key myogenic regulatory factors (MRFs) including myoblast determination protein 1 (MyoD), myogenin (MyoG), myogenic factor 5 (Myf5), and myogenic factor 6 (Myf6) were significantly altered in Cr(VI)-treated cells. The inhibitory effect of Cr(VI) on myogenic differentiation was further confirmed in freshly isolated mouse satellite cells, a stem cell population essential for adult skeletal muscle regeneration. Furthermore, Cr(VI) exposure to fully differentiated C2C12 myotubes resulted in a decrease in myotube diameter, which was exacerbated upon co-treatment with dexamethasone. Together, our results demonstrate that Cr(VI) inhibits myogenic differentiation and induces myotube atrophy in vitro.
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Affiliation(s)
- Sun Young Park
- Division of Environmental Medicine, Department of Medicine, NYU Grossman School of Medicine, New York, NY 10010, United States of America
| | - Shan Liu
- Division of Environmental Medicine, Department of Medicine, NYU Grossman School of Medicine, New York, NY 10010, United States of America
| | - Edgar Perez Carbajal
- Department of Orthopedic Surgery, NYU Grossman School of Medicine, New York, NY 10010, United States of America
| | - Michael Wosczyna
- Department of Orthopedic Surgery, NYU Grossman School of Medicine, New York, NY 10010, United States of America
| | - Max Costa
- Division of Environmental Medicine, Department of Medicine, NYU Grossman School of Medicine, New York, NY 10010, United States of America
| | - Hong Sun
- Division of Environmental Medicine, Department of Medicine, NYU Grossman School of Medicine, New York, NY 10010, United States of America.
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Go S, Masuda H, Tsuru M, Inden M, Hozumi I, Kurita H. Exposure to a low concentration of methylmercury in neural differentiation downregulates NR4A1 expression with altered epigenetic modifications and inhibits neuronal spike activity in vitro. Toxicol Lett 2023; 374:68-76. [PMID: 36565944 DOI: 10.1016/j.toxlet.2022.12.010] [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: 04/01/2022] [Revised: 10/31/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
Methylmercury (MeHg) is a well-known developmental neurotoxin. Our previous research showed that the inhibition of neurite extension by exposure to a low level of MeHg (1 nM) was attributed to the decrease of acetylation of histone H3 and the increase of DNA methylation. However, the target molecules responsible for the neurological dysfunctions caused by MeHg exposure have not been identified. This study focused on a nuclear receptor subfamily 4 group A member 1 (NR4A1), which is reported to be related to synaptic plasticity and neurite extension. LUHMES cells, which are derived from human fetal brain, were treated with 0.1 and 1 nM MeHg beginning at two days of differentiation and continued for 6 consecutive days. The present study showed that exposure to a 1 nM MeHg during neural differentiation inhibited neuronal spike activity and neurite extension. Furthermore, MeHg exposure increased DNA methylation, and altered histone modifications for transcriptional repression in the NR4A1 promoter region to decrease the levels of NR4A1 expression. In addition, MeHg exposure inhibited the mobilization of cAMP response element-binding protein (CREB) and CREB binding protein (CBP) in the NR4A1 promoter region. These results suggest that MeHg inhibits the recruitment of the CREB-CBP complex to the NR4A1 promoter region and impairs neuronal functions associated with NR4A1 repression via a decrease in acetylation of histone H3 lysine 14 levels. Conclusively, this study demonstrated that MeHg exposure during neuronal differentiation could induce neurological dysfunctions even at a low concentration in vitro. These dysfunctions could be associated with the transcriptional repression of NR4A1 by the dissociation of CREB and CBP from the NR4A1 promoter region due to the alterations of epigenetic modifications.
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Affiliation(s)
- Suzuna Go
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu city, Gifu, 501-1196, Japan
| | - Haruka Masuda
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu city, Gifu, 501-1196, Japan
| | - Mizuki Tsuru
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu city, Gifu, 501-1196, Japan
| | - Masatoshi Inden
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu city, Gifu, 501-1196, Japan
| | - Isao Hozumi
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu city, Gifu, 501-1196, Japan.
| | - Hisaka Kurita
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu city, Gifu, 501-1196, Japan.
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Camacho J, de Conti A, Pogribny IP, Sprando RL, Hunt PR. Assessment of the Effects of Organic vs. Inorganic Arsenic and Mercury in Caenorhabditis elegans. Curr Res Toxicol 2022; 3:100071. [PMID: 35602005 PMCID: PMC9118485 DOI: 10.1016/j.crtox.2022.100071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 03/26/2022] [Accepted: 04/20/2022] [Indexed: 01/03/2023] Open
Abstract
Similar developmental delays and oxidative stress with 20x DMA relative to NaAsO2. Dissimilar gene expression and locomotion with organic vs. inorganic mercury. Dissimilar unfolded protein responses for organic vs. inorganic arsenic and mercury. Across phyla, methylation has opposite effects on arsenic vs. mercury toxicity.
Exposures to mercury and arsenic are known to pose significant threats to human health. Effects specific to organic vs. inorganic forms of these toxic elements are less understood however, especially for organic dimethylarsinic acid (DMA), which has recently been detected in pups of rodent dams orally exposed to inorganic sodium (meta)arsenite (NaAsO2). Caenorhabditis elegans is a small animal alternative toxicity model. To fill data gaps on the effects of DMA relative to NaAsO2, C. elegans were exposed to these two compounds alongside more thoroughly researched inorganic mercury chloride (HgCl2) and organic methylmercury chloride (meHgCl). For timing of developmental milestone acquisition in C. elegans, meHgCl was 2 to 4-fold more toxic than HgCl2, and NaAsO2 was 20-fold more toxic than DMA, ranking the four compounds meHgCl > HgCl2 > NaAsO2 ≫ DMA for developmental toxicity. Methylmercury induced significant decreases in population locomotor activity levels in developing C. elegans. DMA was also associated with developmental hypoactivity, but at >100-fold higher concentrations than meHgCl. Transcriptional alterations in native genes were observed in wild type C. elegans adults exposed to concentrations equitoxic for developmental delay in juveniles. Both forms of arsenic induced genes involved in immune defense and oxidative stress response, while the two mercury species induced proportionally more genes involved in transcriptional regulation. A transgenic bioreporter for activation of conserved proteosome specific unfolded protein response was strongly activated by NaAsO2, but not DMA at tested concentrations. HgCl2 and meHgCl had opposite effects on a bioreporter for unfolded protein response in the endoplasmic reticulum. Presented experiments indicating low toxicity for DMA in C. elegans are consistent with human epidemiologic data correlating higher arsenic methylation capacity with resistance to arsenic toxicity. This work contributes to the understanding of the accuracy and fit-for-use categories for C. elegans toxicity screening and its usefulness to prioritize compounds of concern for further testing.
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Affiliation(s)
- Jessica Camacho
- Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Applied Research and Safety Assessment, 8301 Muirkirk Road, Laurel, MD 20708, United States
| | - Aline de Conti
- Food and Drug Administration, National Center for Toxicological Research, 3900 NCTR Rd, Jefferson, AR 72079, United States
| | - Igor P. Pogribny
- Food and Drug Administration, National Center for Toxicological Research, 3900 NCTR Rd, Jefferson, AR 72079, United States
| | - Robert L. Sprando
- Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Applied Research and Safety Assessment, 8301 Muirkirk Road, Laurel, MD 20708, United States
| | - Piper Reid Hunt
- Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Applied Research and Safety Assessment, 8301 Muirkirk Road, Laurel, MD 20708, United States
- Corresponding author.
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7
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Gunderson JT, Peppriell AE, Krout IN, Vorojeikina D, Rand MD. Neuroligin-1 Is a Mediator of Methylmercury Neuromuscular Toxicity. Toxicol Sci 2021; 184:236-251. [PMID: 34546366 DOI: 10.1093/toxsci/kfab114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Methylmercury (MeHg) is a developmental toxicant capable of eliciting neurocognitive and neuromuscular deficits in children with in utero exposure. Previous research in Drosophila melanogaster uncovered that developmental MeHg exposure simultaneously targets the developing musculature and innervating motor neuron in the embryo, along with identifying Drosophila neuroligin 1 (nlg1) as a gene associated with developmental MeHg sensitivity. Nlg1 and its transsynaptic partner neurexin 1 (Nrx1) are critical for axonal arborization and NMJ maturation. We investigated the effects of MeHg exposure on indirect flight muscle (IFM) morphogenesis, innervation, and function via flight assays and monitored the expression of NMJ-associated genes to characterize the role of Nlg1 mediating the neuromuscular toxicity of MeHg. Developmental MeHg exposure reduced the innervation of the IFMs, which corresponded with reduced flight ability. In addition, nlg1 expression was selectively reduced during early metamorphosis, whereas a subsequent increase was observed in other NMJ-associated genes, including nrx1, in late metamorphosis. Developmental MeHg exposure also resulted in persistent reduced expression of most nlg and nrx genes during the first 11 days of adulthood. Transgenic modulation of nlg1 and nrx1 revealed that developing muscle is particularly sensitive to nlg1 levels, especially during the 20-36-h window of metamorphosis with reduced nlg1 expression resulting in adult flight deficits. Muscle-specific overexpression of nlg1 partially rescued MeHg-induced deficits in eclosion and flight. We identified Nlg1 as a muscle-specific, NMJ structural component that can mediate MeHg neuromuscular toxicity resulting from early life exposure.
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Affiliation(s)
- Jakob T Gunderson
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | - Ashley E Peppriell
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | - Ian N Krout
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | - Daria Vorojeikina
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | - Matthew D Rand
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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Caito SW, Newell-Caito J, Martell M, Crawford N, Aschner M. Methylmercury Induces Metabolic Alterations in Caenorhabditis elegans: Role for C/EBP Transcription Factor. Toxicol Sci 2021; 174:112-123. [PMID: 31851340 DOI: 10.1093/toxsci/kfz244] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Methylmercury (MeHg) is a well-known neurotoxicant; however, its role in metabolic diseases has been gaining wider attention. We have previously shown that MeHg causes metabolic alterations in Caenorhabditis elegans, leading to decreased nicotinamide adenine dinucleotide cofactor, mitochondrial dysfunction, and oxidative stress. We were, therefore, interested in whether MeHg also affects nutrient metabolism, particularly lipid homeostasis, which may contribute to the development of metabolic conditions such as obesity or metabolic syndrome (MS). RNA from wild-type worms exposed to MeHg was collected immediately after treatment and used for gene expression analysis by DNA microarray. MeHg differentially regulated 215 genes, 17 genes involved in lipid homeostasis, and 12 genes involved in carbohydrate homeostasis. Of particular interest was cebp-1, the worm ortholog to human C/EBP, a pro-adipogenic transcription factor implicated in MS. MeHg increased the expression of cebp-1 as well as pro-adipogenic transcription factors sbp-1 and nhr-49, triglyceride synthesis enzyme acl-6, and lipid transport proteins vit-2 and vit-6. Concurrent with the altered gene expression, MeHg increased triglyceride levels, lipid storage, and feeding behaviors. Worms expressing mutant cebp-1 were protected from MeHg-induced alterations in lipid content, feeding behaviors, and gene expression, highlighting the importance of this transcription factor in the worm's response to MeHg. Taken together, our data demonstrate that MeHg induces biochemical, metabolic, and behavioral changes in C. elegans that can lead to metabolic dysfunction.
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Affiliation(s)
- Samuel W Caito
- Department of Basic Pharmaceutical Sciences, Husson University School of Pharmacy, Bangor, Maine
| | | | - Megan Martell
- Department of Basic Pharmaceutical Sciences, Husson University School of Pharmacy, Bangor, Maine
| | - Nicole Crawford
- Department of Basic Pharmaceutical Sciences, Husson University School of Pharmacy, Bangor, Maine
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York
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Peppriell AE, Gunderson JT, Vorojeikina D, Rand MD. Methylmercury myotoxicity targets formation of the myotendinous junction. Toxicology 2020; 443:152561. [PMID: 32800841 PMCID: PMC7530093 DOI: 10.1016/j.tox.2020.152561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 07/24/2020] [Accepted: 08/09/2020] [Indexed: 12/12/2022]
Abstract
Methylmercury (MeHg) is a ubiquitous environmental contaminant and developmental toxicant known to cause a variety of persistent motor and cognitive deficits. While previous research has focused predominantly on neurotoxic MeHg effects, emerging evidence points to a myotoxic role whereby MeHg induces defects in muscle development and maintenance. A genome wide association study for developmental sensitivity to MeHg in Drosophila has revealed several conserved muscle morphogenesis candidate genes that function in an array of processes from myoblast migration and fusion to myotendinous junction (MTJ) formation and myofibrillogenesis. Here, we investigated candidates for a role in mediating MeHg disruption of muscle development by evaluating morphological and functional phenotypes of the indirect flight muscles (IFMs) in pupal and adult flies following 0, 5, 10, and 15 μM MeHg exposure via feeding at the larval stage. Developmental MeHg exposure induced a dose-dependent increase in muscle detachments (myospheres) within dorsal bundles of the IFMs, which paralleled reductions eclosion and adult flight behaviors. These effects were selectively phenocopied by altered expression of kon-tiki (kon), a chondroitin sulfate proteoglycan 4/NG2 homologue and a central component of MTJ formation. MeHg elevated kon transcript expression at a crucial window of IFM development and transgene overexpression of kon could also phenocopy myosphere phenotypes and eclosion and flight deficits. Finally, the myosphere phenotype resulting from 10 μM MeHg was partially rescued in a background of reduced kon expression using a targeted RNAi approach. Our findings implicate a component of the MTJ as a MeHg toxicity target which broaden the understanding of how motor deficits can emerge from early life MeHg exposure.
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Affiliation(s)
- Ashley E Peppriell
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Jakob T Gunderson
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Daria Vorojeikina
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Matthew D Rand
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States.
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10
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Gunderson JT, Peppriell AE, Vorojeikina D, Rand MD. Tissue-specific Nrf2 signaling protects against methylmercury toxicity in Drosophila neuromuscular development. Arch Toxicol 2020; 94:4007-4022. [PMID: 32816092 DOI: 10.1007/s00204-020-02879-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Accepted: 08/12/2020] [Indexed: 02/07/2023]
Abstract
Methylmercury (MeHg) can elicit cognitive and motor deficits due to its developmental neuro- and myotoxic properties. While previous work has demonstrated that Nrf2 antioxidant signaling protects from MeHg toxicity, in vivo tissue-specific studies are lacking. In Drosophila, MeHg exposure shows greatest developmental toxicity in the pupal stage resulting in failed eclosion (emergence of adults) and an accompanying 'myosphere' phenotype in indirect flight muscles (IFMs). To delineate tissue-specific contributions to MeHg-induced motor deficits, we investigated the potential of Nrf2 signaling in either muscles or neurons to moderate MeHg toxicity. Larva were exposed to various concentrations of MeHg (0-20 µM in food) in combination with genetic modulation of the Nrf2 homolog cap-n-collar C (CncC), or its negative regulator Keap1. Eclosion behavior was evaluated in parallel with the morphology of two muscle groups, the thoracic IFMs and the abdominal dorsal internal oblique muscles (DIOMs). CncC signaling activity was reported with an antioxidant response element construct (ARE-GFP). We observed that DIOMs are distinguished by elevated endogenous ARE-GFP expression, which is only transiently seen in the IFMs. Dose-dependent MeHg reductions in eclosion behavior parallel formation of myospheres in the DIOMs and IFMs, while also increasing ARE-GFP expression in the DIOMs. Modulating CncC signaling via muscle-specific Keap1 knockdown and upregulation gives a rescue and exacerbation, respectively, of MeHg effects on eclosion and myospheres. Interestingly, muscle-specific CncC upregulation and knockdown both induce lethality. In contrast, neuron-specific upregulation of CncC, as well as Keap1 knockdown, rescued MeHg effects on eclosion and myospheres. Our findings indicate that enhanced CncC signaling localized to either muscles or neurons is sufficient to rescue muscle development and neuromuscular function from a MeHg insult. Additionally, there may be distinct roles for CncC signaling in myo-morphogenesis.
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Affiliation(s)
- Jakob T Gunderson
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Ashley E Peppriell
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Daria Vorojeikina
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Matthew D Rand
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
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Akiyama M, Unoki T, Yoshida E, Ding Y, Yamakawa H, Shinkai Y, Ishii I, Kumagai Y. Repression of mercury accumulation and adverse effects of methylmercury exposure is mediated by cystathionine γ-lyase to produce reactive sulfur species in mouse brain. Toxicol Lett 2020; 330:128-133. [PMID: 32413476 DOI: 10.1016/j.toxlet.2020.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 04/02/2020] [Accepted: 05/07/2020] [Indexed: 01/16/2023]
Abstract
Reactive sulfur species (RSS), such as hydropersulfides and hydropolysulfides with high nucleophilicity, contain mobilized sulfur that readily captures xenobiotic electrophiles, leading to their sulfur adducts. We have previously reported that RSS produced by cystathionine γ-lyase (CSE) captures the electrophilic metal methylmercury (MeHg) to form inert sulfur adducts, which in turn play a critical role in the protection against MeHg-induced motor impairment in mice. However, the mechanism underlying this neuroprotective effect is not fully understood. Here, we addressed this using CSE-knockout mice. The cerebellum of CSE-knockout mice was more susceptible to MeHg than that of wild type mice. Moreover, these CSE-deficient mice exhibited a higher level of mercury accumulation in the brain. However, co-treatment with sodium tetrasulfide, an RSS able to capture MeHg, leading to the formation of its sulfur adducts, blocked the increased accumulation of mercury, motor dysfunction and mortality caused by CSE deficiency. Our findings suggest that capturing MeHg by RSS in association with its sulfur adduct formation is involved in the repression of the brain distribution and deleterious effects of MeHg.
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Affiliation(s)
- Masahiro Akiyama
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Takamitsu Unoki
- Department of Basic Medical Sciences, National Institute for Minamata Disease, Minamata, Kumamoto 867-0008, Japan
| | - Eiko Yoshida
- Department of Environmental Health, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba 278-0022, Japan
| | - Yunjie Ding
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan; Doctoral Program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Hiroto Yamakawa
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan; Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Yasuhiro Shinkai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Isao Ishii
- Laboratory of Health Chemistry, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan
| | - Yoshito Kumagai
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
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12
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Culbreth M, Rand MD. Methylmercury modifies temporally expressed myogenic regulatory factors to inhibit myoblast differentiation. Toxicol In Vitro 2019; 63:104717. [PMID: 31706035 DOI: 10.1016/j.tiv.2019.104717] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 10/20/2019] [Accepted: 11/04/2019] [Indexed: 11/29/2022]
Abstract
Methylmercury (MeHg) is a pervasive environmental toxicant, with known detrimental effects on neurodevelopment. Despite a longstanding paradigm of neurotoxicity, where motor deficits are prevalent among those developmentally exposed, consideration of muscle as a MeHg target has received minimal investigation. Recent evidence has identified muscle-specific gene networks that modulate developmental sensitivity to MeHg toxicity. One such network is muscle cell differentiation. Muscle cell differentiation is a coordinated process regulated by the myogenic regulatory factors (MRFs): Myf5, MyoD, MyoG, and MRF4. A previous study demonstrated that MeHg inhibits muscle cell differentiation in vitro, concurrent with reduced MyoG expression. The potential for MeHg to modify the temporal expression of the MRFs to alter differentiation, however, has yet to be fully explored. Using the C2C12 mouse myoblast model, we examined MRF expression profiles at various stages subsequent to MeHg exposure to proliferating myoblasts. MeHg was seen to persistently alter myoblast differentiation capacity, as myod, myog, and mrf4 gene expression were all affected. Myog exhibited the most robust changes in expression across the various culture conditions, while myf5 was unaffected. Following MeHg exposure to myoblasts, where elevated p21 expression indicated departure from proliferation, cells failed to subsequently differentiate, even in the absence of MeHg, as reflected by a concurrent reduction in MRF4 and myosin heavy chain (MHC), markers of terminal differentiation. Our results indicate that within a brief window of exposure MeHg can disrupt the intrinsic myogenic differentiation program of proliferative myoblasts.
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Affiliation(s)
- Megan Culbreth
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States of America
| | - Matthew D Rand
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States of America.
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13
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Ke T, Gonçalves FM, Gonçalves CL, Dos Santos AA, Rocha JBT, Farina M, Skalny A, Tsatsakis A, Bowman AB, Aschner M. Post-translational modifications in MeHg-induced neurotoxicity. Biochim Biophys Acta Mol Basis Dis 2018; 1865:2068-2081. [PMID: 30385410 DOI: 10.1016/j.bbadis.2018.10.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 10/16/2018] [Accepted: 10/19/2018] [Indexed: 12/29/2022]
Abstract
Mercury (Hg) exposure remains a major public health concern due to its widespread distribution in the environment. Organic mercurials, such as MeHg, have been extensively investigated especially because of their congenital effects. In this context, studies on the molecular mechanism of MeHg-induced neurotoxicity are pivotal to the understanding of its toxic effects and the development of preventive measures. Post-translational modifications (PTMs) of proteins, such as phosphorylation, ubiquitination, and acetylation are essential for the proper function of proteins and play important roles in the regulation of cellular homeostasis. The rapid and transient nature of many PTMs allows efficient signal transduction in response to stress. This review summarizes the current knowledge of PTMs in MeHg-induced neurotoxicity, including the most commonly PTMs, as well as PTMs induced by oxidative stress and PTMs of antioxidant proteins. Though PTMs represent an important molecular mechanism for maintaining cellular homeostasis and are involved in the neurotoxic effects of MeHg, we are far from understanding the complete picture on their role, and further research is warranted to increase our knowledge of PTMs in MeHg-induced neurotoxicity.
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Affiliation(s)
- Tao Ke
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States.
| | - Filipe Marques Gonçalves
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | - Cinara Ludvig Gonçalves
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | | | - João B T Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97105900 Santa Maria, RS, Brazil
| | - Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, 88040900 Florianópolis, SC, Brazil
| | - Anatoly Skalny
- Yaroslavl State University, Sovetskaya St., 14, Yaroslavl 150000, Russia; Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklaya St., 6, Moscow 105064, Russia; Orenburg State University, Pobedy Ave., 13, Orenburg 460352, Russia
| | - Aristidis Tsatsakis
- Center of Toxicology Science & Research, Medical School, University of Crete, Heraklion, Crete, Greece
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN, United States.
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States.
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14
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Algarve TD, Assmann CE, Aigaki T, da Cruz IBM. Parental and preimaginal exposure to methylmercury disrupts locomotor activity and circadian rhythm of adult Drosophila melanogaster. Drug Chem Toxicol 2018; 43:255-265. [PMID: 30033776 DOI: 10.1080/01480545.2018.1485689] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Methylmercury (MeHg) is a well-known toxic pollutant. However, little is known about the effects of this toxic agent in an adult as a consequence of a parental or preimaginal exposure. This study used Drosophila melanogaster to investigate whether a parental or a preimaginal (eggs-larvae-pupae stages) exposure could impact parameters as viability, locomotor activity, and sleep patterns of fruit flies. Thus, we performed two exposure protocols. One where just parents were exposed to MeHg (0-12 µM) during 24 h, then flies were transferred to lay eggs in a healthy medium (without MeHg). In the other, flies were set to lay eggs in a MeHg medium, same concentrations, and discarded after this (preimaginal exposure). Viability was evaluated from egg to adult flies. F1 progeny was collected within 24 h and transferred to a fresh healthy medium. Sleep behavior analysis was performed using Drosophila Active Monitoring System (DAMS), and the locomotor activity was evaluated by climbing assay. Results have shown that the parental exposure had a significant impact on F1 progeny reducing viability and locomotor activity performance, but no significant circadian rhythm alterations. Whereas the preimaginal exposure had a stronger effect decreasing viability and locomotor activity, it also disrupted sleep patterns. MeHg preimaginal exposure showed a longer sleep duration and lower daily activity. Results corroborate the hypothesis that low MeHg exposure could trigger subclinical symptoms related to a 'neurotoxicological development effect'. Complementary investigations could clarify the underlying mechanisms of MeHg effects in neural functions due to parental and early development exposure to this toxicant.
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Affiliation(s)
- Thaís Doeler Algarve
- Graduate Program in Biological Sciences: Toxicological Biochemistry, Federal University of Santa Maria, Santa Maria, Brazil.,Department of Morphology, Laboratory of Biogenomics, Federal University of Santa Maria, Santa Maria, Brazil.,Department of Biological Sciences, Cellular Genetics Laboratory, Tokyo Metropolitan University, Tokyo, Japan
| | - Charles Elias Assmann
- Graduate Program in Biological Sciences: Toxicological Biochemistry, Federal University of Santa Maria, Santa Maria, Brazil.,Department of Morphology, Laboratory of Biogenomics, Federal University of Santa Maria, Santa Maria, Brazil
| | - Toshiro Aigaki
- Department of Biological Sciences, Cellular Genetics Laboratory, Tokyo Metropolitan University, Tokyo, Japan
| | - Ivana Beatrice Mânica da Cruz
- Graduate Program in Biological Sciences: Toxicological Biochemistry, Federal University of Santa Maria, Santa Maria, Brazil.,Department of Morphology, Laboratory of Biogenomics, Federal University of Santa Maria, Santa Maria, Brazil
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