Mitochondrial Oxidative Stress and Protection in Pesticide-induced Neurotoxicity

帕金森病(PD)的病因学涉及基因和环境的相互作用。而大多数已确认的 基因突变影响泛素-蛋白酶体系统(UPS)、流行病学研究和临床病例 有报道强烈表明，接触杀虫剂与帕金森病发病率增加之间存在关联。 在动物模型中，全身暴露后，黑质纹状体多巴胺能神经元发生选择性毒性。 鱼藤酮和百草枯。氧化应激是农药所致神经毒性的常见介体。它 参与帕金森病相关的病理变化，如a-突触核蛋白聚集体的形成和抑制 蛋白酶体功能。然而，氧化损伤的分子靶点还没有明确定义。 以及线粒体之间的机械联系！蛋白酶体功能障碍仍有待确定。在……里面 我们的初步研究表明，线粒体硫氧还蛋白(mtTrx；Trx2)特别是 易受各种环境毒物的氧化，包括过氧化氢、鱼藤酮、 MPP+和百草枯。亚微摩尔浓度鱼藤酮诱导mtTrx和 MtTrx重新分布到细胞质。长期接触纳摩尔浓度的鱼藤酮导致 MtTrx蛋白减少。MtTrx过表达保护细胞免受氧化剂诱导的细胞凋亡和 抑制慢性鱼藤酮中毒引起的α-突触核蛋白聚集。线粒体的下调 硫氧还蛋白还原酶(TrxR2)导致成熟mtTrx减少，而其前体形式增加。 此外，我们还发现mtTrx与线粒体热休克蛋白60相互作用，这是一个关键 线粒体蛋白质加工机械的组成部分。基于这些发现，我们假设 杀虫剂选择性靶向mtTrx和确保mtTrx的氧化导致损害 线粒体蛋白进口。这一假设将通过两个具体目标进行检验。具体目标1是 确定mtTrx的氧化还原状态和表达水平是否控制对农药诱导的敏感性 对培养的神经细胞的毒性。具体目标2是确定农药诱导的氧化 抑制mtTrx和其他核DMA编码的线粒体蛋白的输入。来自这些的结果 研究将确定氧化损伤的新蛋白质靶点，并将有助于我们理解 与PD相关的环境毒性的分子机制。

The etiology of Parkinson's disease (PD) involves gene/environment interaction. While most of the identified genetic mutations affect the ubiquitin-proteasome system (UPS), epidemiological studies and clinical case reports have strongly suggested the association between pesticide exposure and increased incidence of PD. In animal models, selective toxicities to the nigrostriatal dopaminergic neurons occur after systemic exposure to rotenone and paraquat. Oxidative stress is a common mediator of pesticide-induced neurotoxicity. It contributes to PD-related pathological changes such as formation of a-synuclein aggregates and inhibition of proteasomal function. However, the molecular targets of oxidative damage have not been clearly defined and the mechanistic link between mitochondria! and proteasomal dysfunction remains to be determined. In our preliminary studies, we have shown that mitochondrial thioredoxin (mtTrx; Trx2) is particularly susceptible to oxidation induced by a variety of environmental toxicants, including peroxides, rotenone, MPP+ and paraquat. Submicromolar concentrations of rotenone induced persistent oxidation of mtTrx and redistribution of mtTrx to the cytoplasm. Chronic exposure to nanomolar concentrations of rotenone resulted in decreased mtTrx protein. Overexpression of mtTrx protected cells from oxidant-induced apoptosis and inhibited a-synuclein aggregation caused by chronic rotenone toxicity. Downregulation of the mitochondrial thioredoxin reductase (TrxR 2) led to decreased mature mtTrx while increased its precursor form. Furthermore, we identified that mtTrx interacted with mitochondrial heat shock protein 60 which is a key component of the mitochondrial protein processing machinery. Based on these findings, we hypothesize that selective targeting of mtTrx by pesticides and the ensuring oxidation of mtTrx lead to impaired mitochondrial protein import. The hypothesis will be tested with two specific aims. Specific aim 1 is to determine whether the redox status and expression level of mtTrx control the sensitivity to pesticide-induced toxicity in cultured neuronal cells. Specific aim 2 is to determine whether the pesticide-induced oxidation inhibits the import of mtTrx and other nuclear DMA-encoded mitochondrial proteins. Results from these studies will define novel protein targets of oxidative injury and will facilitate our understanding towards the molecular mechanisms of environmental toxicities associated with PD.