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Ke T, Tinkov AA, Skalny AV, Santamaria A, Rocha JBT, Bowman AB, Chen W, Aschner M. Epigenetics and Methylmercury-Induced Neurotoxicity, Evidence from Experimental Studies. TOXICS 2023; 11:toxics11010072. [PMID: 36668798 PMCID: PMC9860901 DOI: 10.3390/toxics11010072] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/08/2023] [Accepted: 01/10/2023] [Indexed: 05/14/2023]
Abstract
MeHg is an environmental neurotoxin that can adversely affect the development of the nervous system. The molecular integrity of chromatin in the nucleus is an important target of MeHg. Low levels of MeHg trigger epigenetic mechanisms that may be involved in long-lasting and transgenerational neurotoxicity after exposure. Emerging evidence has shown that these mechanisms include histone modification, siRNA, and DNA methylation. The MeHg-induced inhibition of neurodifferentiation and neurogenesis are mechanistically associated with epigenetic alterations in critical genes, such as neurotrophin brain-derived neurotrophic factor (BDNF). Further, MeHg exposure has been shown to alter the activity and/or expression of the upstream regulators of chromatin structure, including histone deacetylases (HDACs) and DNA methyltransferase (DNMTs), which may trigger permanent alterations in histone modifications and DNA methylation. MeHg-exposure also alters several species of miRNA that are associated with neurodevelopment. Genetic studies in the C. elegans model of MeHg-induced toxicity proposes a potential interplay between exogenous RNAi and antioxidant defense. In this review, we discuss the molecular basis for MeHg exposure-induced alterations in chromatin structure and the roles of histone modifications, siRNA, and DNA methylation in MeHg-induced neurotoxic effects.
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Affiliation(s)
- Tao Ke
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Correspondence: (T.K.); (M.A.)
| | - Alexey A. Tinkov
- World-Class Research Center “Digital Biodesign and Personalized Healthcare”, IM Sechenov First Moscow State Medical University (Sechenov University), 119435 Moscow, Russia
- Laboratory of Ecobiomonitoring and Quality Control, Yaroslavl State University, 150003 Yaroslavl, Russia
- Department of Medical Elementology, RUDN University, 117198 Moscow, Russia
| | - Anatoly V. Skalny
- World-Class Research Center “Digital Biodesign and Personalized Healthcare”, IM Sechenov First Moscow State Medical University (Sechenov University), 119435 Moscow, Russia
- Department of Medical Elementology, RUDN University, 117198 Moscow, Russia
| | - Abel Santamaria
- Laboratorio de Aminoácidos Excitadores/Laboratorio de Neurofarmacología Molecular y Nanotecnología, Instituto Nacional de Neurología y Neurocirugía, Mexico City 14269, Mexico
| | - Joao B. T. Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria 97105-900, RS, Brazil
| | - Aaron B. Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Wen Chen
- Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Toxicology, School of Public Health, Sun Yat-sen University, Guangzhou 510080, China
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Correspondence: (T.K.); (M.A.)
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EPA and DHA confer protection against deoxynivalenol-induced endoplasmic reticulum stress and iron imbalance in IPEC-1 cells. Br J Nutr 2022; 128:161-171. [PMID: 34519265 DOI: 10.1017/s0007114521003688] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
This study assessed the molecular mechanism of EPA or DHA protection against intestinal porcine epithelial cell line 1 (IPEC-1) cell damage induced by deoxynivalenol (DON). The cells were divided into six groups, including the CON group, the EPA group, the DHA group, the DON group, the EPA + DON group and the DHA + DON group. RNA sequencing was used to investigate the potential mechanism, and qRT-PCR was employed to verify the expression of selected genes. Changes in ultrastructure were used to estimate pathological changes and endoplasmic reticulum (ER) injury in IPEC-1 cells. Transferrin receptor 1 (TFR1) was tested by ELISA. Fe2+ and malondialdehyde (MDA) contents were estimated by spectrophotometry, and reactive oxygen species (ROS) was assayed by fluorospectrophotometry. RNA sequencing analysis showed that EPA and DHA had a significant effect on the expression of genes involved in ER stress and iron balance during DON-induced cell injury. The results showed that DON increased ER damage, the content of MDA and ROS, the ratio of X-box binding protein 1s (XBP-1s)/X-box binding protein 1u (XBP-1u), the concentration of Fe2+ and the activity of TFR1. However, the results also showed that EPA and DHA decreased the ratio of XBP-1s/XBP-1u to relieve DON-induced ER damage of IPEC-1 cells. Moreover, EPA and DHA (especially DHA) reversed the factors related to iron balance. It can be concluded that EPA and DHA reversed IPEC-1 cell damage induced by DON. DHA has the potential to protect IPEC-1 cells from DON-induced iron imbalance by inhibiting ER stress.
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Yang CY, Liu SH, Su CC, Fang KM, Yang TY, Liu JM, Chen YW, Chang KC, Chuang HL, Wu CT, Lee KI, Huang CF. Methylmercury Induces Mitochondria- and Endoplasmic Reticulum Stress-Dependent Pancreatic β-Cell Apoptosis via an Oxidative Stress-Mediated JNK Signaling Pathway. Int J Mol Sci 2022; 23:ijms23052858. [PMID: 35270009 PMCID: PMC8910963 DOI: 10.3390/ijms23052858] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 02/21/2022] [Accepted: 03/01/2022] [Indexed: 12/21/2022] Open
Abstract
Methylmercury (MeHg), a long-lasting organic pollutant, is known to induce cytotoxic effects in mammalian cells. Epidemiological studies have suggested that environmental exposure to MeHg is linked to the development of diabetes mellitus (DM). The exact molecular mechanism of MeHg-induced pancreatic β-cell cytotoxicity is still unclear. Here, we found that MeHg (1-4 μM) significantly decreased insulin secretion and cell viability in pancreatic β-cell-derived RIN-m5F cells. A concomitant elevation of mitochondrial-dependent apoptotic events was observed, including decreased mitochondrial membrane potential and increased proapoptotic (Bax, Bak, p53)/antiapoptotic (Bcl-2) mRNA ratio, cytochrome c release, annexin V-Cy3 binding, caspase-3 activity, and caspase-3/-7/-9 activation. Exposure of RIN-m5F cells to MeHg (2 μM) also induced protein expression of endoplasmic reticulum (ER) stress-related signaling molecules, including C/EBP homologous protein (CHOP), X-box binding protein (XBP-1), and caspase-12. Pretreatment with 4-phenylbutyric acid (4-PBA; an ER stress inhibitor) and specific siRNAs for CHOP and XBP-1 significantly inhibited their expression and caspase-3/-12 activation in MeHg-exposed RIN-mF cells. MeHg could also evoke c-Jun N-terminal kinase (JNK) activation and reactive oxygen species (ROS) generation. Antioxidant N-acetylcysteine (NAC; 1mM) or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox; 100 μM) markedly prevented MeH-induced ROS generation and decreased cell viability in RIN-m5F cells. Furthermore, pretreatment of cells with SP600125 (JNK inhibitor; 10 μM) or NAC (1 mM) or transfection with JNK-specific siRNA obviously attenuated the MeHg-induced JNK phosphorylation, CHOP and XBP-1 protein expression, apoptotic events, and insulin secretion dysfunction. NAC significantly inhibited MeHg-activated JNK signaling, but SP600125 could not effectively reduce MeHg-induced ROS generation. Collectively, these findings demonstrate that the induction of ROS-activated JNK signaling is a crucial mechanism underlying MeHg-induced mitochondria- and ER stress-dependent apoptosis, ultimately leading to β-cell death.
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Affiliation(s)
- Ching-Yao Yang
- Department of Surgery, National Taiwan University Hospital, Taipei 100, Taiwan;
- Department of Surgery, College of Medicine, National Taiwan University, Taipei 100, Taiwan
| | - Shing-Hwa Liu
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei 100, Taiwan;
| | - Chin-Chuan Su
- Department of Otorhinolaryngology, Head and Neck Surgery, Changhua Christian Hospital, Changhua County 500, Taiwan;
| | - Kai-Min Fang
- Department of Otolaryngology, Far Eastern Memorial Hospital, New Taipei City 220, Taiwan;
| | - Tsung-Yuan Yang
- Department of Internal Medicine, Chung Shan Medical University Hospital, Taichung 402, Taiwan;
- School of Medicine, Institute of Medicine, Chung-Shan Medical University, Taichung 402, Taiwan
| | - Jui-Ming Liu
- Department of Urology, Taoyuan General Hospital, Ministry of Health and Welfare, Taoyuan 330, Taiwan;
- Department of Obstetrics and Gynecology, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan
| | - Ya-Wen Chen
- Department of Physiology, School of Medicine, College of Medicine, China Medical University, Taichung 404, Taiwan;
| | - Kai-Chih Chang
- Center for Digestive Medicine, Department of Internal Medicine, China Medical University Hospital, Taichung 404, Taiwan;
| | - Haw-Ling Chuang
- Department of Emergency, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung 427, Taiwan;
| | - Cheng-Tien Wu
- Department of Nutrition and Master Program of Food and Drug Safety, China Medical University, Taichung 40402, Taiwan;
| | - Kuan-I Lee
- Department of Emergency, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung 427, Taiwan;
- Correspondence: (K.-I.L.); (C.-F.H.)
| | - Chun-Fa Huang
- School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung 404, Taiwan
- Department of Nursing, College of Medical and Health Science, Asia University, Taichung 413, Taiwan
- Correspondence: (K.-I.L.); (C.-F.H.)
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p62/sequestosome 1 attenuates methylmercury-induced endoplasmic reticulum stress in mouse embryonic fibroblasts. Toxicol Lett 2021; 353:93-99. [PMID: 34678407 DOI: 10.1016/j.toxlet.2021.10.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 09/29/2021] [Accepted: 10/14/2021] [Indexed: 01/07/2023]
Abstract
Methylmercury (MeHg) is a hazardous environmental pollutant that causes serious toxicity in humans and animals, as well as proteotoxic stress. In our previous study, we found that MeHg induces the expression of p62/sequestosome 1 (p62) that selectively targets ubiquitinated proteins for degradation via autophagy, and that p62 might protect cells against MeHg toxicity. To further investigate the role of p62 in MeHg-induced stress responses, we evaluated the role of p62 in MeHg-induced endoplasmic reticulum (ER) stress in p62 knockout (p62KO) mouse embryonic fibroblasts (MEFs). Treatment of wild-type (WT) MEFs were treated with MeHg (1 μM) increased mRNA levels of Chop encoding C/EBP homologous protein, Trib3 encoding Tribbles homolog 3, and Dnajb9 encoding DnaJ heat-shock protein family (Hsp40) member B9 increased, suggesting that ER stress is elicited by MeHg stress. Additionally, p62KO MEFs treated with MeHg showed a higher mRNA expression of Chop and Trib3 relative to that in WT MEFs. Furthermore, knock-in of GFP-p62 to p62KO cells diminished the Chop and Trib3 induction responses to MeHg stress and resulted in a higher cell viability than that of p62KO MEFs. These results suggest that the protective role of p62 against MeHg toxicity is partly mediated by suppressing the ER stress response.
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Zhang H, Wang S, Wang Y, Lu A, Hu C, Yan C. DHA ameliorates MeHg‑induced PC12 cell apoptosis by inhibiting the ROS/JNK signaling pathway. Mol Med Rep 2021; 24:558. [PMID: 34109428 PMCID: PMC8188641 DOI: 10.3892/mmr.2021.12197] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 03/24/2021] [Indexed: 12/28/2022] Open
Abstract
Recent studies have reported that methylmercury (MeHg) induces neuronal apoptosis, which is accompanied by abnormal neurological development. Despite the important role of docosahexaenoic acid (DHA) in maintaining the structure and function of the brain, as well as improving neuronal apoptosis induced by MeHg, the exact mechanism remains unknown. The present study hypothesized that the reactive oxygen species (ROS)-mediated JNK signaling pathway may be associated with the protective effect of DHA against MeHg-induced PC12 cell apoptosis. Cell Counting Kit-8, TUNEL staining, flow cytometry, ROS detection, PCR and western blot analysis were performed. The results demonstrated that MeHg inhibited the activity of PC12 cells, causing oxidative damage and promoting apoptosis; however, DHA significantly attenuated this effect. Mechanistic studies revealed that MeHg increased intracellular ROS levels and JNK protein phosphorylation, and decreased the expression levels of the anti-apoptotic protein Bcl-2, whereas DHA reduced ROS levels and JNK phosphorylation, and increased Bcl-2 expression. In addition, the ROS inhibitor N-acetyl-l-cysteine (NAC) was used to verify the experimental results. After pretreatment with NAC, expression levels of Bcl-2, Bax, phosphorylated-JNK and JNK were assessed. Bcl-2 protein expression was increased and the Bcl-2/Bax ratio was increased. Moreover, the high expression levels of phosphorylated-JNK induced by MeHg were significantly decreased. Based on the aforementioned results, the present study indicated that the effects of DHA against MeHg-induced PC12 cell apoptosis may be mediated via the ROS/JNK signaling pathway.
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Affiliation(s)
- Hong Zhang
- Ministry of Education‑Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, P.R. China
| | - Susu Wang
- School of Public Health, Shanghai Jiao Tong University, Shanghai 200025, P.R. China
| | - Yaqian Wang
- School of Public Health, Shanghai Jiao Tong University, Shanghai 200025, P.R. China
| | - Anxin Lu
- Ministry of Education‑Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, P.R. China
| | - Chunping Hu
- School of Public Health, Shanghai Jiao Tong University, Shanghai 200025, P.R. China
| | - Chonghuai Yan
- Ministry of Education‑Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, P.R. China
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DHA and Its Metabolites Have a Protective Role against Methylmercury-Induced Neurotoxicity in Mouse Primary Neuron and SH-SY5Y Cells. Int J Mol Sci 2021; 22:ijms22063213. [PMID: 33809931 PMCID: PMC8004243 DOI: 10.3390/ijms22063213] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 03/16/2021] [Accepted: 03/18/2021] [Indexed: 02/06/2023] Open
Abstract
The consumption of fish now involves a risk of methylmercury (MeHg) exposure but also provides the benefit of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) such as docosahexaenoic acid (DHA). Some epidemiological studies have suggested that the intake of DHA can alleviate the neurotoxicity of MeHg, but the underlying mechanism is not known. Herein, we observed that pretreatment with 0.1–1 µM DHA suppressed MeHg-induced cytotoxicity in human neuroblastoma (SH-SY5Y) cells and mouse primary neuronal cells. These effects of DHA were canceled in the presence of the retinoid X receptor (RXR) antagonist UVI3003. An RXR agonist, bexarotene, suppressed the cytotoxicity of MeHg. DHA also suppressed the MeHg-induced production of reactive oxygen species (ROS) via an induction of antioxidant genes (catalase and SOD1). Pretreatment with DHA did not change the incorporation of MeHg. We showed previously that in the brain, the intake of DHA increased the level of 19,20-DHDP, which is the metabolite produced by cytochrome P450 and soluble epoxide hydrolase from DHA. In the present study, we observed that 19,20-DHDP also suppressed neurotoxicity from MeHg. These results indicate that DHA and its metabolites have a protective role in MeHg-induced neurotoxicity.
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Kang GJ, Kim EJ, Lee CH. Therapeutic Effects of Specialized Pro-Resolving Lipids Mediators on Cardiac Fibrosis via NRF2 Activation. Antioxidants (Basel) 2020; 9:antiox9121259. [PMID: 33321955 PMCID: PMC7764646 DOI: 10.3390/antiox9121259] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/09/2020] [Accepted: 12/09/2020] [Indexed: 12/19/2022] Open
Abstract
Heart disease is the number one mortality disease in the world. In particular, cardiac fibrosis is considered as a major factor causing myocardial infarction and heart failure. In particular, oxidative stress is a major cause of heart fibrosis. In order to control such oxidative stress, the importance of nuclear factor erythropoietin 2 related factor 2 (NRF2) has recently been highlighted. In this review, we will discuss the activation of NRF2 by docosahexanoic acid (DHA), eicosapentaenoic acid (EPA), and the specialized pro-resolving lipid mediators (SPMs) derived from polyunsaturated lipids, including DHA and EPA. Additionally, we will discuss their effects on cardiac fibrosis via NRF2 activation.
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Affiliation(s)
- Gyeoung Jin Kang
- Lillehei Heart Institute, University of Minnesota, Minneapolis, MN 55455, USA; (G.J.K.); (E.J.K.)
| | - Eun Ji Kim
- Lillehei Heart Institute, University of Minnesota, Minneapolis, MN 55455, USA; (G.J.K.); (E.J.K.)
- College of Pharmacy, Dongguk University, Seoul 04620, Korea
| | - Chang Hoon Lee
- College of Pharmacy, Dongguk University, Seoul 04620, Korea
- Correspondence: ; Tel.: +82-31-961-5213
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Li R, Liu T, Shi J, Luan W, Wei X, Yu J, Mao H, Liu P. ROR2 induces cell apoptosis via activating IRE1α/JNK/CHOP pathway in high-grade serous ovarian carcinoma in vitro and in vivo. J Transl Med 2019; 17:428. [PMID: 31878941 PMCID: PMC6933631 DOI: 10.1186/s12967-019-02178-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 12/12/2019] [Indexed: 12/15/2022] Open
Abstract
Background Epithelial ovarian cancer (EOC) is the most lethal cancer in female genital tumors. New disease markers and novel therapeutic strategies are urgent to identify considering the current status of treatment. Receptor tyrosine kinases family plays critical roles in embryo development and disease progression. However, ambivalent research conclusions of ROR2 make its role in tumor confused and the underlying mechanism is far from being understood. In this study, we sought to clarify the effects of ROR2 on high-grade serous ovarian carcinoma (HGSOC) cells and reveal the mechanism. Methods Immunohistochemistry assay and western-blot assay were used to detect proteins expression. ROR2 overexpression adenovirus and Lentivirus were used to create ROR2 overexpression model in vitro and in vivo, respectively. MTT assay, colony formation assay and transwell assay were used to measure the proliferation, invasion and migration ability of cancer cells. Flow cytometry assay was used to detect cell apoptosis rate. Whole transcriptome analysis was used to explore the differentially expressed genes between ROR2 overexpression group and negative control group. SiRNA targeted IRE1α was used to knockdown IRE1α. Kira6 was used to inhibit phosphorylation of IRE1α. Results Expression of ROR2 was significantly lower in HGSOC tissues compared to normal fallopian tube epithelium or ovarian surface epithelium tissues. In HGSOC cohort, patients with advanced stages or positive lymph nodes were prone to express lower ROR2. Overexpression of ROR2 could repress the proliferation of HGSOC cells and induce cell apoptosis. RNA sequencing analysis indicated that ROR2 overexpression could induce unfold protein response. The results were also confirmed by upregulation of BIP and phosphorylated IRE1α. Furthermore, pro-death factors like CHOP, phosphorylated JNK and phosphorylated c-Jun were also upregulated. IRE1α knockdown or Kira6 treatment could reverse the apoptosis induced by ROR2 overexpression. Finally, tumor xenograft experiment showed ROR2 overexpression could significantly repress the growth rate and volume of transplanted tumors. Conclusions Taken together, ROR2 downregulation was associated with HGSOC development and progression. ROR2 overexpression could repress cell proliferation and induce cell apoptosis in HGSOC cells. And the underlying mechanism might be the activation of IRE1α/JNK/CHOP pathway induced by ROR2.
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Affiliation(s)
- Rui Li
- Department of Gynecology and Obstetrics, Qilu Hospital of Shandong University, 107 Wenhua Xi Road, Jinan, 250012, Shandong, People's Republic of China
| | - Tianfeng Liu
- Department of Gynecology and Obstetrics, Linyi People's Hospital, 27 Jiefang Road, Linyi, 276003, Shandong, People's Republic of China
| | - Juanjuan Shi
- Department of Gynecology and Obstetrics, Affiliated Tengzhou Center People's Hospital of Jining Medical University, 181 Xing Tan Road, Tengzhou, 277599, Shandong, People's Republic of China
| | - Wenqing Luan
- Department of Gynecology and Obstetrics, Qilu Hospital of Shandong University, 107 Wenhua Xi Road, Jinan, 250012, Shandong, People's Republic of China
| | - Xuan Wei
- Department of Gynecology and Obstetrics, Qilu Hospital of Shandong University, 107 Wenhua Xi Road, Jinan, 250012, Shandong, People's Republic of China
| | - Jiangtao Yu
- Department of Gynecology and Obstetrics, Qilu Hospital of Shandong University, 107 Wenhua Xi Road, Jinan, 250012, Shandong, People's Republic of China
| | - Hongluan Mao
- Department of Gynecology and Obstetrics, Qilu Hospital of Shandong University, 107 Wenhua Xi Road, Jinan, 250012, Shandong, People's Republic of China.
| | - Peishu Liu
- Department of Gynecology and Obstetrics, Qilu Hospital of Shandong University, 107 Wenhua Xi Road, Jinan, 250012, Shandong, People's Republic of China.
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Chung YP, Yen CC, Tang FC, Lee KI, Liu SH, Wu CC, Hsieh SS, Su CC, Kuo CY, Chen YW. Methylmercury exposure induces ROS/Akt inactivation-triggered endoplasmic reticulum stress-regulated neuronal cell apoptosis. Toxicology 2019; 425:152245. [PMID: 31330229 DOI: 10.1016/j.tox.2019.152245] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/06/2019] [Accepted: 07/15/2019] [Indexed: 12/13/2022]
Abstract
Epidemiological studies have positively linked mercury exposure and neurodegenerative diseases (ND). Methylmercury (MeHg), an organic form of mercury, is a ubiquitous and potent environmental neurotoxicant that easily crosses the blood-brain barrier and causes irreversible injury to the central nervous system (CNS). However, the molecular mechanisms underlying MeHg-induced neurotoxicity remain unclear. Here, the present study found that Neuro-2a cells underwent apoptosis in response to MeHg (1-5 μM), which was accompanied by increased phosphatidylserine (PS) exposure on the outer cellular membrane leaflets, caspase-3 activity, and the activation of caspase cascades and poly (ADP-ribose) polymerase (PARP). Exposure of Neuro-2a cells to MeHg also triggered endoplasmic reticulum (ER) stress, which was identified via several key molecules (including: glucose-regulated protein (GRP)78, GRP94, C/EBP homologous protein (CHOP) X-box binding protein(XBP)-1, protein kinase R-like ER kinase (PERK), eukaryotic initiation factor 2α (eIF2α), inositol-requiring enzyme(IRE)-1, activation transcription factor(AFT)4, and ATF6. Transfection with GRP78-, GRP94-, CHOP-, and XBP-1-specific small interfering (si)RNA significantly suppressed the expression of these proteins, and attenuated cytotoxicity and caspase-12, -7, and -3 activation in MeHg-exposed cells. Furthermore, MeHg dramatically decreased Akt phosphorylation, and the overexpression of activation of Akt1 (myr-Akt1) could significantly prevent MeHg-induced Akt inactivation, as well as apoptotic and ER stress-related signals. Pretreatment with the antioxidant N-acetylcysteine (NAC) effectively prevented MeHg-induced neuronal cell reactive oxygen species (ROS) generation, apoptotic and ER stress-related signals, and Akt inactivation. Collectively, these results indicate that MeHg exerts its cytotoxicity in neurons by inducing ROS-mediated Akt inactivation up-regulated ER stress, which induces apoptosis and ultimately leads to cell death.
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Affiliation(s)
- Yao-Pang Chung
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei 100, Taiwan; Department of Occupational Safety and Health, College of Health Care and Management, Chung Shan Medical University, Taichung, 402, Taiwan
| | - Cheng-Chieh Yen
- Department of Occupational Safety and Health, College of Health Care and Management, Chung Shan Medical University, Taichung, 402, Taiwan; Department of Occupational Medicine, Chung Shan Medical University Hospital, Taichung, 402, Taiwan
| | - Feng-Cheng Tang
- Department of Occupational Medicine, Changhua Christian Hospital, Changhua County, 500, Taiwan; Department of Leisure Services Management, Chaoyang University of Technology, Taichung, 413, Taiwan
| | - Kuan-I Lee
- Department of Emergency, Taichung Tzuchi Hospital, The Buddhist Tzuchi Medical Foundation, Taichung, 427, Taiwan
| | - Shing-Hwa Liu
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei 100, Taiwan
| | - Chin-Ching Wu
- Department of Public Health, China Medical University, Taichung, 404, Taiwan
| | - Shang-Shu Hsieh
- Department of Emergency, Taichung Tzuchi Hospital, The Buddhist Tzuchi Medical Foundation, Taichung, 427, Taiwan
| | - Chin-Chuan Su
- Department of Otorhinolaryngology, Head and Neck Surgery, Changhua Christian Hospital, Changhua County 500, Taiwan
| | - Chun-Ying Kuo
- Department of Otorhinolaryngology, Head and Neck Surgery, Changhua Christian Hospital, Changhua County 500, Taiwan
| | - Ya-Wen Chen
- Department of Physiology and Graduate Institute of Basic Medical Science, School of Medicine, College of Medicine, China Medical University, Taichung 404, Taiwan.
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