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Pajarillo E, Digman A, Nyarko-Danquah I, Son DS, Soliman KFA, Aschner M, Lee E. Astrocytic transcription factor REST upregulates glutamate transporter EAAT2, protecting dopaminergic neurons from manganese-induced excitotoxicity. J Biol Chem 2021; 297:101372. [PMID: 34756885 PMCID: PMC8626589 DOI: 10.1016/j.jbc.2021.101372] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 10/18/2021] [Accepted: 10/27/2021] [Indexed: 11/25/2022] Open
Abstract
Chronic exposure to high levels of manganese (Mn) leads to manganism, a neurological disorder with similar symptoms to those inherent to Parkinson's disease. However, the underlying mechanisms of this pathological condition have yet to be established. Since the human excitatory amino acid transporter 2 (EAAT2) (glutamate transporter 1 in rodents) is predominantly expressed in astrocytes and its dysregulation is involved in Mn-induced excitotoxic neuronal injury, characterization of the mechanisms that mediate the Mn-induced impairment in EAAT2 function is crucial for the development of novel therapeutics against Mn neurotoxicity. Repressor element 1-silencing transcription factor (REST) exerts protective effects in many neurodegenerative diseases. But the effects of REST on EAAT2 expression and ensuing neuroprotection are unknown. Given that the EAAT2 promoter contains REST binding sites, the present study investigated the role of REST in EAAT2 expression at the transcriptional level in astrocytes and Mn-induced neurotoxicity in an astrocyte–neuron coculture system. The results reveal that astrocytic REST positively regulates EAAT2 expression with the recruitment of an epigenetic modifier, cAMP response element-binding protein–binding protein/p300, to its consensus binding sites in the EAAT2 promoter. Moreover, astrocytic overexpression of REST attenuates Mn-induced reduction in EAAT2 expression, leading to attenuation of glutamate-induced neurotoxicity in the astrocyte–neuron coculture system. Our findings demonstrate that astrocytic REST plays a critical role in protection against Mn-induced neurotoxicity by attenuating Mn-induced EAAT2 repression and the ensuing excitotoxic dopaminergic neuronal injury. This indicates that astrocytic REST could be a potential molecular target for the treatment of Mn toxicity and other neurological disorders associated with EAAT2 dysregulation.
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Affiliation(s)
- Edward Pajarillo
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA
| | - Alexis Digman
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA
| | - Ivan Nyarko-Danquah
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA
| | - Deok-Soo Son
- Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, Tennessee, USA
| | - Karam F A Soliman
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA; Laboratory of Molecular Nutrition of the Institute for Personalized Medicine, Sechenov First Moscow State Medical University, Moscow, Russia
| | - Eunsook Lee
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA.
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Critical Involvement of Glial Cells in Manganese Neurotoxicity. BIOMED RESEARCH INTERNATIONAL 2021; 2021:1596185. [PMID: 34660781 PMCID: PMC8514895 DOI: 10.1155/2021/1596185] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 09/16/2021] [Accepted: 09/21/2021] [Indexed: 12/13/2022]
Abstract
Over the years, most of the research concerning manganese exposure was restricted to the toxicity of neuronal cells. Manganese is an essential trace element that in high doses exerts neurotoxic effects. However, in the last two decades, efforts have shifted toward a more comprehensive approach that takes into account the involvement of glial cells in the development of neurotoxicity as a brain insult. Glial cells provide structural, trophic, and metabolic support to neurons. Nevertheless, these cells play an active role in adult neurogenesis, regulation of synaptogenesis, and synaptic plasticity. Disturbances in glial cell function can lead to neurological disorders, including neurodegenerative diseases. This review highlights the pivotal role that glial cells have in manganese-induced neurotoxicity as well as the most sounding mechanisms involved in the development of this phenomenon.
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Li ZC, Wang F, Li SJ, Zhao L, Li JY, Deng Y, Zhu XJ, Zhang YW, Peng DJ, Jiang YM. Sodium Para-aminosalicylic Acid Reverses Changes of Glutamate Turnover in Manganese-Exposed Rats. Biol Trace Elem Res 2020; 197:544-554. [PMID: 31838737 DOI: 10.1007/s12011-019-02001-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 12/03/2019] [Indexed: 01/26/2023]
Abstract
Sodium para-aminosalicylic acid (PAS-Na) has been used to treat patients with manganism, a neurological disease caused by manganese (Mn) toxicity, although the exact molecular mechanisms are yet unclear. The present study aims to investigate the effect of PAS-Na on glutamate (Glu) turnover of Mn-exposed rats. The results showed that Mn concentrations in the hippocampus, thalamus, striatum, and globus pallidus were increased in Mn-exposed rats. Moreover, the results also demonstrated that subacute Mn exposure (15 mg/kg for 4 weeks) interrupted the homeostasis of Glu by increasing Glu levels but decreasing glutamine (Gln) levels in the hippocampus, thalamus, striatum, and globus pallidus in male Sprague-Dawley rats. These effects lasted even after Mn exposure had been ceased for a period of 6 weeks. Meanwhile the main Glu turnover enzymes [Gln synthetase (GS) and phosphate-activated glutaminase (PAG)] and transporters [Glu/aspartate transporter (GLAST) and Glu transporter-1 (GLT-1)] were also affected by Mn treatment. Additionally, PAS-Na treatment recovered the aforementioned changes induced by Mn. Taken together, these results indicate that Glu turnover might be involved in Mn-induced neurotoxicity. PAS-Na treatment could promote Mn excretions and recover the changes in Glu turnover induced by Mn, and a prolonged PAS-Na treatment may be more effective.
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Affiliation(s)
- Zhao-Cong Li
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China
| | - Fang Wang
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Institute of Toxicology, Guangxi Center for Disease Prevention and Control, Nanning, 530028, China
| | - Shao-Jun Li
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China
| | - Lin Zhao
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China
| | - Jun-Yan Li
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China
| | - Yue Deng
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China
| | - Xiao-Juan Zhu
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China
| | - Yu-Wen Zhang
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China
| | - Dong-Jie Peng
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China
| | - Yue-Ming Jiang
- Department of Toxicology, School of Public Health, Guangxi Medical University, No. 22, Shuang-yong Rd, Nanning, 530021, Guangxi, China.
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, Nanning, China.
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Medeiros RDCN, Moraes JO, Rodrigues SDC, Pereira LM, Aguiar HQDS, de Cordova CAS, Yim Júnior A, de Cordova FM. Thiamine Deficiency Modulates p38 MAPK and Heme Oxygenase-1 in Mouse Brain: Association with Early Tissue and Behavioral Changes. Neurochem Res 2020; 45:940-955. [PMID: 31989470 DOI: 10.1007/s11064-020-02975-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/11/2020] [Accepted: 01/22/2020] [Indexed: 12/18/2022]
Abstract
Thiamine deficiency (TD) produces severe neurodegenerative lesions. Studies have suggested that primary neurodegenerative events are associated with both oxidative stress and inflammation. Very little is known about the downstream effects on intracellular signaling pathways involved in neuronal death. The primary aim of this work was to evaluate the modulation of p38MAPK and the expression of heme oxygenase 1 (HO-1) in the central nervous system (CNS). Behavioral, metabolic, and morphological parameters were assessed. Mice were separated into six groups: control (Cont), TD with pyrithiamine (Ptd), TD with pyrithiamine and Trolox (Ptd + Tr), TD with pyrithiamine and dimethyl sulfoxide (Ptd + Dmso), Trolox (Tr) and DMSO (Dmso) control groups and treated for 9 days. Control groups received standard feed (AIN-93M), while TD groups received thiamine deficient feed (AIN-93DT). All the groups were subjected to behavioral tests, and CNS samples were collected for cell viability, histopathology and western blot analyses. The Ptd group showed a reduction in weight gain and feed intake, as well as a reduction in locomotor, grooming, and motor coordination activities. Also, Ptd group showed a robust increase in p38MAPK phosphorylation and mild HO-1 expression in the cerebral cortex and thalamus. The Ptd group showed a decreased cell viability, hemorrhage, spongiosis, and astrocytic swelling in the thalamus. Groups treated with Trolox and DMSO displayed diminished p38MAPK phosphorylation in both the structures, as well as attenuated thalamic lesions and behavioral activities. These data suggest that p38MAPK and HO-1 are involved in the TD-induced neurodegeneration in vivo, possibly modulated by oxidative stress and neuroinflammation.
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Affiliation(s)
- Rita de Cássia Noronha Medeiros
- Programa de Pós-Graduação em Sanidade Animal e Saúde Pública nos Trópicos, Universidade Federal do Tocantins, BR-153, km 112, Araguaína, TO, 77804-970, Brazil
| | - Juliana Oliveira Moraes
- Programa de Pós-Graduação em Sanidade Animal e Saúde Pública nos Trópicos, Universidade Federal do Tocantins, BR-153, km 112, Araguaína, TO, 77804-970, Brazil
| | | | - Leidiano Martins Pereira
- Curso de Medicina Veterinária, Universidade Federal do Tocantins, BR-153, km 112, Araguaína, TO, 77804-970, Brazil
| | - Helen Quézia da Silva Aguiar
- Curso de Medicina Veterinária, Universidade Federal do Tocantins, BR-153, km 112, Araguaína, TO, 77804-970, Brazil
| | | | - Alberto Yim Júnior
- Curso de Medicina Veterinária, Universidade Federal do Tocantins, BR-153, km 112, Araguaína, TO, 77804-970, Brazil
| | - Fabiano Mendes de Cordova
- Programa de Pós-Graduação em Sanidade Animal e Saúde Pública nos Trópicos, Universidade Federal do Tocantins, BR-153, km 112, Araguaína, TO, 77804-970, Brazil.
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Mn Inhibits GSH Synthesis via Downregulation of Neuronal EAAC1 and Astrocytic xCT to Cause Oxidative Damage in the Striatum of Mice. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:4235695. [PMID: 30228854 PMCID: PMC6136513 DOI: 10.1155/2018/4235695] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 06/24/2018] [Accepted: 07/12/2018] [Indexed: 11/17/2022]
Abstract
Excessive manganese (Mn) can accumulate in the striatum of the brain following overexposure. Oxidative stress is a well-recognized mechanism in Mn-induced neurotoxicity. It has been proven that glutathione (GSH) depletion is a key factor in oxidative damage during Mn exposure. However, no study has focused on the dysfunction of GSH synthesis-induced oxidative stress in the brain during Mn exposure. The objective of the present study was to explore the mechanism of Mn disruption of GSH synthesis via EAAC1 and xCT in vitro and in vivo. Primary neurons and astrocytes were cultured and treated with different doses of Mn to observe the state of cells and levels of GSH and reactive oxygen species (ROS) and measure mRNA and protein expression of EAAC1 and xCT. Mice were randomly divided into seven groups, which received saline, 12.5, 25, and 50 mg/kg MnCl2, 500 mg/kg AAH (EAAC1 inhibitor) + 50 mg/kg MnCl2, 75 mg/kg SSZ (xCT inhibitor) + 50 mg/kg MnCl2, and 100 mg/kg NAC (GSH rescuer) + 50 mg/kg MnCl2 once daily for two weeks. Then, levels of EAAC1, xCT, ROS, GSH, malondialdehyde (MDA), protein sulfhydryl, carbonyl, 8-hydroxy-2-deoxyguanosine (8-OHdG), and morphological and ultrastructural features in the striatum of mice were measured. Mn reduced protein levels, mRNA expression, and immunofluorescence intensity of EAAC1 and xCT. Mn also decreased the level of GSH, sulfhydryl, and increased ROS, MDA, 8-OHdG, and carbonyl in a dose-dependent manner. Injury-related pathological and ultrastructure changes in the striatum of mice were significantly present. In conclusion, excessive exposure to Mn disrupts GSH synthesis through inhibition of EAAC1 and xCT to trigger oxidative damage in the striatum.
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Affiliation(s)
- Jiao Li
- Department of Hygiene Toxicology, School of Public Health, Zunyi Medical College, Zunyi, P.R. China
- The second people’s Hospital of Qixingguan District, Bijie, Guizhou, P.R. China
| | - Yuyan Cen
- Department of Hygiene Toxicology, School of Public Health, Zunyi Medical College, Zunyi, P.R. China
| | - Yan Li
- Department of Hygiene Toxicology, School of Public Health, Zunyi Medical College, Zunyi, P.R. China
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Abstract
Manganese (Mn) is an essential trace element, serving as a cofactor for several enzymes involved in various cellular and biochemical reactions in human body. However, chronic overexposure to Mn from occupational or environmental sources induces a neurological disorder, characterized by psychiatric, cognitive, and motor abnormalities, referred to as manganism. Mn-induced neurotoxicity is known to target astrocytes since these cells preferentially accumulate Mn. Astrocytes are the most abundant non-neuronal glial cells in the brain, and they play a critical role in maintaining the optimal glutamate levels to prevent excitotoxic death. The fine regulation of glutamate in the brain is accomplished by two major glutamate transporters - glutamate transporter-1 (GLT-1) and glutamate aspartate transporter (GLAST) that are predominantly expressed in astrocytes. Excitotoxic neuronal injury has been demonstrated as a critical mechanism involved in Mn neurotoxicity and implicated in the pathological signs of multiple neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Recent evidences also establish that Mn directly deregulates the expression and function of both astrocytic glutamate transporters by decreasing mRNA and protein levels of GLT-1 and GLAST. Herein, we will review the mechanisms of Mn-induced gene regulation of glutamate transporters at the transcriptional level and their role in Mn toxicity.
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Inflammatory Activation of Microglia and Astrocytes in Manganese Neurotoxicity. ADVANCES IN NEUROBIOLOGY 2017; 18:159-181. [PMID: 28889267 DOI: 10.1007/978-3-319-60189-2_8] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neurotoxicity due to excessive exposure to manganese (Mn) has been described as early as 1837 (Couper, Br Ann Med Pharm Vital Stat Gen Sci 1:41-42, 1837). Extensive research over the past two decades has revealed that Mn-induced neurological injury involves complex pathophysiological signaling mechanisms between neurons and glial cells. Glial cells are an important target of Mn in the brain, both for sequestration of the metal, as well as for activating inflammatory signaling pathways that damage neurons through overproduction of numerous reactive oxygen and nitrogen species and inflammatory cytokines. Understanding how these pathways are regulated in glial cells during Mn exposure is critical to determining the mechanisms underlying permanent neurological dysfunction stemming from excess exposure. The subject of this review will be to delineate mechanisms by which Mn interacts with glial cells to perturb neuronal function, with a particular emphasis on neuroinflammation and neuroinflammatory signaling between distinct populations of glial cells.
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Sulforaphane Prevents Methylmercury-Induced Oxidative Damage and Excitotoxicity Through Activation of the Nrf2-ARE Pathway. Mol Neurobiol 2016; 54:375-391. [PMID: 26742517 DOI: 10.1007/s12035-015-9643-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 12/16/2015] [Indexed: 12/29/2022]
Abstract
Methylmercury (MeHg) is a prominent environmental neurotoxicant, which induces oxidative damage and an indirect excitotoxicity caused by altered glutamate (Glu) metabolism. However, the interaction between oxidative damage and excitotoxicity in MeHg-exposed rats has not been fully recognized. Here, we explored the interaction between oxidative damage and excitotoxicity and evaluated the preventive effects of sulforaphane (SFN) on MeHg-induced neurotoxicity in rat cerebral cortex. Seventy-two rats were randomly assigned to four groups: control group, MeHg-treated groups (4 and 12 μmol/kg), and SFN pretreatment group. After treatment (28 days), the rats were killed and the cerebral cortex was analyzed. Then, Hg, glutathione (GSH), malondialdehyde (MDA), protein sulfhydryl, protein carbonyl, 8-hydroxy-2-deoxyguanosine (8-OHdG), and the levels of reactive oxygen species (ROS) and apoptosis were examined. Glu and glutamine (Gln) levels, glutamine synthetase (GS), phosphate-activated glutaminase (PAG), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), Na+-K+-ATPase and Ca2+-ATPase activities, intracellular Ca2+ levels, and the mRNA and protein expressions of Nrf2, Nrf2-regulated gene products, and N-methyl-D-aspartate receptors (NMDARs) were investigated in rat cerebral cortex. In our study, MeHg exposure not only induced Hg accumulation, apoptosis, ROS formation, GSH depletion, inhibition of antioxidant enzyme activities, and activation of Nrf2-ARE pathway signaling but also caused lipid, protein, and DNA peroxidative damage in a dose-dependent manner in rat cerebral cortex. Moreover, MeHg treatment significantly altered Gln/Glu cycling and NMDAR expression and resulted in calcium overloading. Furthermore, the present study also indicated that SFN pretreatment significantly reinforced the activation of the Nrf2-ARE pathway, which could prevent the toxic effects of MeHg exposure. Collectively, MeHg initiates multiple additive or synergistic disruptive mechanisms that lead to oxidative damage and excitotoxicity in rat cerebral cortex; pretreatment with SFN might prevent the MeHg-induced neurotoxicity by reinforcing the activation of the Nrf2-ARE pathway and then downregulating the interaction between oxidative damage and excitotoxicity pathways.
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Manganese-Disrupted Interaction of Dopamine D1 and NMDAR in the Striatum to Injury Learning and Memory Ability of Mice. Mol Neurobiol 2015; 53:6745-6758. [PMID: 26660110 DOI: 10.1007/s12035-015-9602-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 12/01/2015] [Indexed: 10/22/2022]
Abstract
Manganese (Mn) is widely regarded as a neurotoxic heavy metal that causes learning and memory deficits. Recently, it has been proved that the striatum is related to memory and learning ability. However, no previous study focused on the effect of Mn-induced learning and memory deficits on the striatum. This study aims to investigate the probable interaction of dopamine D1 receptor (DR1) and N-methyl-D-aspartate receptor (NMDAR), two cognition-related receptors in the striatum during Mn exposure. Mice are randomly divided into four groups, including control group, 12.5 mg/kg MnCl2 group, 25 mg/kg MnCl2 group, and 50 mg/kg MnCl2 group. The mice receive intraperitoneal injections of 0, 12.5, 25, and 50 mg/kg MnCl2 once daily for 2 weeks. Then, learning and memory ability, pathological changes, expression, and interaction of DR1 and NMDAR are determined. It has been found that Mn disrupted spatial learning and memory ability of mice by Morris water maze test and the passive avoidance test. Pathological and ultrastructure were injured. Mn decreased the immunohistochemical activities, protein levels, and messenger RNA (mRNA) expression of DR1, NR1, and NR2A. Mn exposure inhibited interaction between DR1 and NMDAR in striatum by double immunofluorescent staining and co-immunoprecipitation. In conclusion, our study illustrated that Mn caused learning and memory dysfunction via injury of striatum and inhibition of interaction between DR1 and NMDAR in striatum.
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Kim HN, Jang JY, Choi BT. A single fraction from Uncaria sinensis exerts neuroprotective effects against glutamate-induced neurotoxicity in primary cultured cortical neurons. Anat Cell Biol 2015; 48:95-103. [PMID: 26140220 PMCID: PMC4488647 DOI: 10.5115/acb.2015.48.2.95] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 01/13/2015] [Accepted: 02/17/2015] [Indexed: 01/16/2023] Open
Abstract
We identified a neuroprotective single fraction among 62 ones of hexane extract from Uncaria sinensis (JGH43IA) and investigated its effects and mechanisms in primary cortical neurons. Pretreatment with JGH43IA showed a significantly increase cell viability in a dose-dependent manner with a decrease in the lactate dehydrogenase release. When we performed morphological assay and flow cytometry to determination of the type of cell death, pretreatment with JGH43IA showed a significant reduction of glutamate-induced apoptotic cell death. Then we explored the downstream signaling pathways of N-methyl-D-aspartate receptor (NMDAR) with calpain activation to elucidate possible pathways of neuroprotection by JGH43IA. Pretreatment with JGH43IA exhibited a significant attenuation of NMDAR GluN2B subunit activation and a decrease in active form of calpain 1 leading to subsequent cleavage of striatal-enriched protein tyrosine phosphatase (STEP). In addition, pretreatment with JGH43IA showed a marked increase of cAMP responsive element binding protein. These results suggest that JGH43IA may have neuroprotective effects through down-regulation of NMDAR GluN2B subunit and calpain 1 activation, and subsequent alleviation of STEP cleavage. This single fraction from U. sinensis might be a useful therapeutic agent for brain disorder associated with glutamate injury.
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Affiliation(s)
- Ha Neui Kim
- Department of Korean Medicine, School of Korean Medicine, Pusan National University, Yangsan, Korea
| | - Ji Yeon Jang
- Division of Meridian and Structural Medicine, School of Korean Medicine, Pusan National University, Yangsan, Korea
| | - Byung Tae Choi
- Department of Korean Medicine, School of Korean Medicine, Pusan National University, Yangsan, Korea. ; Division of Meridian and Structural Medicine, School of Korean Medicine, Pusan National University, Yangsan, Korea
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Abstract
Metals are frequently used in industry and represent a major source of toxin exposure for workers. For this reason governmental agencies regulate the amount of metal exposure permissible for worker safety. While essential metals serve physiologic roles, metals pose significant health risks upon acute and chronic exposure to high levels. The central nervous system is particularly vulnerable to metals. The brain readily accumulates metals, which under physiologic conditions are incorporated into essential metalloproteins required for neuronal health and energy homeostasis. Severe consequences can arise from circumstances of excess essential metals or exposure to toxic nonessential metal. Herein, we discuss sources of occupational metal exposure, metal homeostasis in the human body, susceptibility of the nervous system to metals, detoxification, detection of metals in biologic samples, and chelation therapeutic strategies. The neurologic pathology and physiology following aluminum, arsenic, lead, manganese, mercury, and trimethyltin exposures are highlighted as classic examples of metal-induced neurotoxicity.
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Affiliation(s)
- Samuel Caito
- Division of Clinical Pharmacology and Pediatric Toxicology, Vanderbilt University Medical Center, Nashville, TN, USA; The Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, Nashville, TN, USA.
| | - Michael Aschner
- Division of Clinical Pharmacology and Pediatric Toxicology, Vanderbilt University Medical Center, Nashville, TN, USA; The Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, Nashville, TN, USA; Center in Molecular Toxicology, Vanderbilt University Medical Center, Nashville, TN, USA; Center for Molecular Neuroscience, Vanderbilt University Medical Center, Nashville, TN, USA
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Liu W, Xu Z, Deng Y, Xu B, Yang H, Wei Y, Feng S. Excitotoxicity and oxidative damages induced by methylmercury in rat cerebral cortex and the protective effects of tea polyphenols. ENVIRONMENTAL TOXICOLOGY 2014; 29:269-283. [PMID: 22223486 DOI: 10.1002/tox.21755] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 11/28/2011] [Accepted: 12/03/2011] [Indexed: 05/31/2023]
Abstract
Methylmercury (MeHg) is a highly neurotoxic environmental pollutant that has a high appetency to the central nervous system. The underlying mechanisms of MeHg-induced neurotoxicity have not been elucidated clearly until now. Therefore, to explore the mechanisms contribute to MeHg-induced neurotoxicity, rats were exposed to different dosage of methylmercury chloride (CH3 ClHg) (0, 4, and 12 μmol kg(-1)) for 4 weeks to evaluate the neurotoxic effects of MeHg. In addition, considering the antioxidative properties of tea polyphenols (TP), 1 mmol kg(-1) TP was pretreated to observe the possible protective effects on MeHg-induced neurotoxicity. Then Hg, glutamate (Glu) and glutamine (Gln) levels, glutamine synthetase (GS), phosphate-activated glutaminase (PAG), Na(+)-K(+)-ATPase, and Ca(2+)-ATPase activities, intracellular Ca(2+) level were examined, glutathione (GSH), malondialdehyde (MDA), protein sulfhydryl, carbonyl, 8-hydroxy-2-deoxyguanosine (8-OHdG), and reactive oxygen species (ROS) levels, N-methyl-D-aspartate receptors (NMDARs) mRNA and protein expressions, apoptosis level and morphological changes in the cerebral cortex were also investigated. Study results showed that compared with those in control, exposure to CH3 ClHg resulted in excitotoxicity in a concentration-dependent manner, which was shown by the Glu-Gln cycle disruption and intracellular Ca(2+) homeostasis disturbance. On the other hand, CH3 ClHg exposure resulted in oxidative damages of brain, which were supported by the significant changes on GSH, MDA, sulfhydryl, carbonyl, 8-OHdG, and ROS levels. Moreover, apoptosis rate increased obviously and many morphological changes were found after CH3 ClHg exposure. Furthermore, this research indicated that TP pretreatment significantly mitigated the toxic effects of MeHg. In conclusion, findings from this study indicated that exposure to MeHg could induce excitotoxicity and oxidative damage in cerebral cortex while TP might antagonize the MeHg-induced neurotoxicity.
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Affiliation(s)
- Wei Liu
- Department of Environmental Health, School of Public Health, China Medical University, North 2nd Road 92, Heping Ward, Shenyang 110001, Liaoning Province, People's Republic of China
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Hernández RB, Farina M, Espósito BP, Souza-Pinto NC, Barbosa F, Suñol C. Mechanisms of Manganese-Induced Neurotoxicity in Primary Neuronal Cultures: The Role of Manganese Speciation and Cell Type. Toxicol Sci 2011; 124:414-23. [DOI: 10.1093/toxsci/kfr234] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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Aschner M, Erikson KM, Herrero Hernández E, Hernández EH, Tjalkens R. Manganese and its role in Parkinson's disease: from transport to neuropathology. Neuromolecular Med 2009; 11:252-66. [PMID: 19657747 PMCID: PMC4613768 DOI: 10.1007/s12017-009-8083-0] [Citation(s) in RCA: 216] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Accepted: 07/24/2009] [Indexed: 01/03/2023]
Abstract
The purpose of this review is to highlight recent advances in the neuropathology associated with Mn exposures. We commence with a discussion on occupational manganism and clinical aspects of the disorder. This is followed by novel considerations on Mn transport (see also chapter by Yokel, this volume), advancing new hypotheses on the involvement of several transporters in Mn entry into the brain. This is followed by a brief description of the effects of Mn on neurotransmitter systems that are putative modulators of dopamine (DA) biology (the primary target of Mn neurotoxicity), as well as its effects on mitochondrial dysfunction and disruption of cellular energy metabolism. Next, we discuss inflammatory activation of glia in neuronal injury and how disruption of synaptic transmission and glial-neuronal communication may serve as underlying mechanisms of Mn-induced neurodegeneration commensurate with the cross-talk between glia and neurons. We conclude with a discussion on therapeutic aspects of Mn exposure. Emphasis is directed at treatment modalities and the utility of chelators in attenuating the neurodegenerative sequelae of exposure to Mn. For additional reading on several topics inherent to this review as well as others, the reader may wish to consult Aschner and Dorman (Toxicological Review 25:147-154, 2007) and Bowman et al. (Metals and neurodegeneration, 2009).
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Affiliation(s)
- Michael Aschner
- Departments of Pediatrics and Pharmacology and the Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, 2215-B Garland Avenue, 11425 MRB IV, Nashville, TN, 37232-0414, USA.
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