Mitochondrial Oxidative Stress and Protection in Pesticide-induced Neurotoxicity

描述（申请人提供）：帕金森病（PD）的病因涉及基因/环境相互作用。虽然大多数已确定的基因突变会影响泛素-蛋白酶体系统（UPS），但流行病学研究和临床病例报告强烈表明农药暴露与PD发病率增加之间存在关联。在动物模型中，全身暴露于鱼藤酮和百草枯后，黑质纹状体多巴胺能神经元发生选择性毒性。氧化应激是农药神经毒性的一种常见介质。它有助于PD相关的病理变化，如α-突触核蛋白聚集体的形成和蛋白酶体功能的抑制。然而，氧化损伤的分子靶点还没有明确的定义和线粒体之间的机制联系!蛋白酶体功能障碍仍有待确定。在我们的初步研究中，我们已经表明，线粒体硫氧还蛋白（mtTrx; Trx2）是特别容易氧化诱导的各种环境毒物，包括过氧化物，鱼藤酮，MPP+和百草枯。亚微摩尔浓度的鱼藤酮诱导持续氧化的mtTrx和重新分配的mtTrx的细胞质。慢性暴露于纳摩尔浓度的鱼藤酮导致mtTrx蛋白降低。过表达mtTrx保护细胞免受氧化剂诱导的凋亡，并抑制慢性鱼藤酮毒性引起的α-突触核蛋白聚集。线粒体硫氧还蛋白还原酶（TrxR2）的下调导致成熟mtTrx减少，而其前体形式增加.此外，我们确定，mtTrx与线粒体热休克蛋白60，这是一个关键组成部分的线粒体蛋白加工机制。基于这些发现，我们推测，选择性靶向的mtTrx的农药和确保氧化的mtTrx导致受损的线粒体蛋白输入。将以两个具体目标来检验这一假设。具体目标1是确定是否氧化还原状态和表达水平的mtTrx控制的敏感性，农药诱导的毒性培养的神经细胞。具体目标2是确定农药诱导的氧化是否抑制mtTrx和其他核DMA编码的线粒体蛋白的输入。这些研究的结果将定义新的蛋白质靶点的氧化损伤，并将促进我们对与PD相关的环境毒性的分子机制的理解。

DESCRIPTION (provided by applicant): 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.