Mechanisms of Methylmercury Induced Neuronal Toxicity

甲基汞诱导神经元毒性的机制

• 批准号: 7227713
• 负责人: Michael Aschner
• 金额: $ 34万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-03-01 至 2009-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7227713
• 关键词: Affect; Affinity; Antioxidants; Arginine; Astrocytes; Binding; Biological; Biological Assay; Biological Availability; Brain; Brain region; Carrier Proteins; Cell Death; Cell physiology; Cell-Free System; Cells; Citrulline; Client; Co-Immunoprecipitations; Coculture Techniques; Complex; Condition; Confocal Microscopy; Cyclic GMP; Cysteine; Cytoplasm; Cytosolic Phospholipase A2; Development; Dinoprostone; Disulfides; Drug Formulations; Electron Transport; Enzyme Immunoassay; Ethidium; Excitatory Amino Acids; Fluorescence; Food Chain; Funding; Geldanamycin; Generations; Glutamates; Glutathione; HTATIP gene; Heat shock proteins; Heat-Shock Proteins 90; Homeostasis; Homidium Bromide; In Vitro; Interferons; Label; Lead; Ligands; Light; Lipopolysaccharides; Measures; Mediating; Methylmercury Compounds; Mitochondria; Modality; Molecular Chaperones; NOS1 protein, human; Neuraxis; Neurodegenerative Disorders; Neurons; Neurotoxins; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Oxidants; Oxidases; Oxidation-Reduction; Oxidative Stress; PLA2G4A gene; Pathway interactions; Phospholipase A2; Play; Post-Translational Protein Processing; Production; Prostaglandin-Endoperoxide Synthase; Prostaglandins; Protein Biochemistry; Protein Isoforms; Proteins; Rattus; Reactive Oxygen Species; Regulation; Research Personnel; Role; Rotenone; Series; Signal Transduction; Solutions; Stress; Sulfhydryl Compounds; Superoxides; Time; Toxic effect; Work; aqueous; brain tissue; complex IV; cyclooxygenase 1; cytochrome c; human NOS3 protein; human PLA2G4A protein; in vivo; inhibitor/antagonist; innovation; insight; mitochondrial dysfunction; monorden; neurotoxic; neurotoxicity; novel; pollutant; programs; prostaglandin E synthase; stress protein; transport inhibitor

DESCRIPTION (provided by applicant): Methylmercury (MeHg) is a global pollutant and potent neurotoxin whose abundance in the food chain mandates additional studies on the consequences and mechanisms of its CNS toxicity. Formulation of our new hypotheses was predicated on our appreciation for (a) the remarkable affinity of mercurials for the anionic form of sulfhydryl (-SH) groups, (b) the essential role of thiols in protein biochemistry, and (c) the role of molecular chaperone proteins, such as heat shock protein 90 (Hsp90), in the regulation of protein redox status by facilitating the formation and breakage of disulfide bridges. Given the high affinity of MeHg for thiols, we hypothesized that MeHg interferes with Hsp90 chaperone function resulting in altered cellular homeostasis and neurotoxicity. Among the client proteins known to bind to Hsp90 are type I (neuronal) nitric oxide synthase (NOS), and cytosolic prostaglandin E synthase (cPGESIp23). Additionally, Hsp90 reduces the mitochondrial electron transport protein, cytochrome c (cyt c). The specific aims are to [1] demonstrate that MeHg physically binds to Hsp90, altering Hsp90 chaperone function. [2] Determine whether MeHg increases the activity of the cPLA2-cyclooxygenase-1 (COX-1)-PGES enzymatic pathway resulting in enhanced prostaglandin E2 (PGE2) production by altering the binding of Hsp90 to PGES/p23. [3] Demonstrate that by altering the association between Hsp90 and neuronal NOS (nNOS) MeHg uncouples nNOS activity, resulting in NOS-derived superoxide (-O2) production and reduced NO bioavailability. [4] Determine whether MeHg-induced oxidant stress occurs via inhibition of the mitochondrial electron transport chain, causing increased -O2 production and reduced levels of the intracellular antioxidant, glutathione. The experimental approach includes cell-free lysates, rat-derived in vitro astrocyte, neuron, and astrocyte/neuron co-cultures, as well as in vivo corroborative studies in the rat. MeHg-mediated alterations in Hsp90/client protein interactions offers an innovative and unifying mechanism integrating the known propensity of MeHg to form complexes with -SH-containing ligands and MeHg-induced oxidant stress, mitochondrial dysfunction and CNS toxicity. The results of these studies will shed new light on meaningful mechanisms of MeHg-induced neurotoxicity, and pave the way for new pharmacological modalities for treatment. Additionally, studies on altered post-translational modification of Hsp90 client proteins might offer new mechanistic insight into other neurodegenerative disorders, and therefore they have broad biological implications

描述（由申请人提供）：甲基汞 (MeHg) 是一种全球污染物和强效神经毒素，其在食物链中的丰富程度需要对其中枢神经系统毒性的后果和机制进行进一步研究。我们新假设的制定基于我们对以下方面的认识：(a) 汞与阴离子形式的巯基 (-SH) 基团的显着亲和力，(b) 硫醇在蛋白质生物化学中的重要作用，以及 (c) 分子伴侣蛋白，例如热休克蛋白 90 (Hsp90)，通过促进 二硫桥的形成和断裂。鉴于 MeHg 对硫醇的高亲和力，我们假设 MeHg 干扰 Hsp90 伴侣功能，导致细胞稳态改变和神经毒性。已知与 Hsp90 结合的客户蛋白包括 I 型（神经元）一氧化氮合酶 (NOS) 和胞质前列腺素 E 合酶 (cPGESIp23)。此外，Hsp90 还可减少线粒体电子传递蛋白细胞色素 c (cyt c)。具体目标是 [1] 证明 MeHg 与 Hsp90 物理结合，改变 Hsp90 伴侣功能。 [2] 确定 MeHg 是否会通过改变 Hsp90 与 PGES/p23 的结合来增加 cPLA2-环加氧酶-1 (COX-1)-PGES 酶途径的活性，从而增强前列腺素 E2 (PGE2) 的产生。 [3] 证明通过改变 Hsp90 和神经元 NOS (nNOS) 之间的关联，MeHg 可以解偶联 nNOS 活性，导致 NOS 衍生的超氧化物 (-O2) 产生并降低 NO 生物利用度。 [4] 确定甲基汞诱导的氧化应激是否通过抑制线粒体电子传递链而发生，从而导致 -O2 产量增加和细胞内抗氧化剂谷胱甘肽水平降低。实验方法包括无细胞裂解物、大鼠体外星形胶质细胞、神经元和星形胶质细胞/神经元共培养物，以及大鼠体内的确证研究。 MeHg 介导的 Hsp90/客户蛋白相互作用的改变提供了一种创新且统一的机制，整合了已知的 MeHg 与含 -SH 配体形成复合物的倾向以及 MeHg 诱导的氧化应激、线粒体功能障碍和 CNS 毒性。这些研究的结果将为甲基汞引起的神经毒性的有意义的机制提供新的线索，并为新的药理学治疗方式铺平道路。此外，对 Hsp90 客户蛋白翻译后修饰改变的研究可能为其他神经退行性疾病提供新的机制见解，因此具有广泛的生物学意义