Environmental Mitochondrial Toxicants Cause LRRK2 Activation in Parkinson's Disease

摘要 特发性帕金森病（PD）的病因尚不清楚，然而，有重要证据表明， 遗传易感性和环境因素之间的相互作用是PD的主要病因。 引起线粒体功能障碍的环境毒物，如有机农药鱼藤酮， 常见除草剂百草枯与帕金森病风险升高相关（OR 2.5，95% CI：0.1.3-4.7; OR 2.5，95% CI： 1.4-4.7;分别）。大量使用的工业溶剂三氯乙烯（TCE）也会导致线粒体 有毒，是美国地下水中最常见的有机污染物。TCE暴露是 与PD的发生相关（OR 6.1，95% CI：1.2-3.3），TCE暴露的啮齿动物模型显示 黑质纹状体多巴胺神经元变性我们实验室的最新证据表明鱼藤酮 (ROT)百草枯（PQ）和三氯乙烯与PD易感基因相互作用，特别是引起LRRK 2的激活 在野生型（WT）人胚肾（HEK）细胞中，其可被选择性LRRK 2抑制剂阻断 （GNE-7915）。由于LRRK 2是与家族性PD相关的最常见的遗传突变，这一证据 表明LRRK 2与线粒体毒物之间存在基因-环境相互作用。在功能上， LRRK 2激活导致多种下游细胞病理学，例如囊泡运输的破坏， 自噬缺陷、α-突触核蛋白磷酸化和神经炎症;所有这些都是机制 假设在PD中多巴胺神经元变性之前。这项建议的基础是调查 LRRK 2激活和环境致多巴胺神经元变性前机制 线粒体毒物为达致这个目标，我们会致力达致以下的具体目标： 确定环境线粒体毒物是否在WT神经元中诱导LRRK 2活性的基础，以及 如果LRRK 2突变加剧了线粒体功能障碍后的病理学。目标2（R 00）将进一步 在TCE暴露的动物模型中表征LRRK 2活化，并确定LRRK 2抑制是否 保护TCE。目标3（R 00）将描述受以下因素影响的另一种退变前机制 环境线粒体毒物和LRRK 2，线粒体抗原呈递（MitAP）。MitAP涉及 线粒体蛋白质从内腔运输到细胞表面MHC分子，导致选择性 免疫细胞杀死多巴胺神经元。我们测量了多巴胺神经元中的MitAP， 在大鼠中暴露于ROT，表明这是对线粒体毒性的早期反应。我们将确定是否 ROT、PQ和TCE诱导多巴胺能神经元中的MitAP。由于LRRK 2活性影响囊泡运输，我们 提出N27细胞系中的LRRK 2突变影响MitAP对线粒体毒物暴露的反应， 并且用LRRK 2抑制剂治疗可以在体内对MitAP具有保护作用。这些目标将提供创新 环境因素导致LRRK 2活化，从而导致多巴胺能神经元变性的证据。 总的来说，这一建议可能会导致新的治疗途径，特发性和遗传性PD。

Abstract The cause of idiopathic Parkinson’s disease (PD) remains unknown, however, significant evidence suggests that interaction between genetic susceptibility and environmental factors is the predominant etiology of PD. Environmental toxicants that cause mitochondrial dysfunction, such as the organic pesticide rotenone, and the common herbicide paraquat, are associated with elevated PD risk (OR 2.5, 95% CI: 0.1.3-4.7; OR 2.5, 95% CI: 1.4-4.7; respectively). A heavily used industrial solvent, trichloroethylene (TCE), also causes mitochondrial toxicity, and is the most frequently reported organic contaminant found in US groundwater. TCE exposure is linked to the development of PD (OR 6.1, 95% CI: 1.2-3.3), and rodent models of TCE exposure display dopamine neuron degeneration from the nigrostriatal tract. Recent evidence from our lab indicates that rotenone (ROT), paraquat (PQ), and TCE interact with PD susceptibility genes, notably, causing the activation of LRRK2 in wildtype (WT) human embryonic kidney (HEK) cells, which could be blocked by a selective LRRK2 inhibitor (GNE-7915). As LRRK2 is the most commonly inherited mutation associated with familial PD, this evidence suggests that a gene-environment interaction exists between LRRK2 and mitochondrial toxicants. Functionally, LRRK2 activation leads to multiple downstream cellular pathologies, such as disruption of vesicular trafficking, deficits in autophagy, the phosphorylation of α-synuclein, and neuroinflammation; all of which are mechanisms hypothesized to precede dopamine neuron degeneration in PD. The basis of this proposal is to investigate LRRK2 activation and pre-degenerative mechanisms in dopamine neurons caused by environmental mitochondrial toxicants. To achieve this, we will pursue the following specific aims: Aim 1 (K99) will build a foundation to identify if LRRK2 activity is induced in WT neurons by environmental mitochondrial toxicants, and if LRRK2 mutations exacerbate this pathology following mitochondrial dysfunction. Aim 2 (R00) will further characterize LRRK2 activation in an animal model of TCE exposure, and determine whether LRRK2 inhibition is protective against TCE. Aim 3 (R00) will characterize another pre-degenerative mechanism influenced by environment mitochondrial toxicants and LRRK2, mitochondrial antigen presentation (MitAP). MitAP involves the trafficking of mitochondrial proteins from the inner lumen to cell surface MHC molecules, causing the selective killing of dopamine neurons by immune cells. We have measured MitAP in dopamine neurons following a single exposure to ROT in rats, suggesting this is an early response to mitochondrial toxicity. We will identify whether ROT, PQ, and TCE induce MitAP in dopaminergic neurons. As LRRK2 activity affects vesicular trafficking, we propose that LRRK2 mutations in N27 cell lines influences MitAP in response to mitochondrial toxicant exposure, and treatment with a LRRK2 inhibitor may be protective against MitAP in vivo. These aims will provide innovative evidence for LRRK2 activation by environmental factors that contributes to dopaminergic neuron degeneration. Collectively, this proposal may lead to new therapeutic treatment avenues for idiopathic and inherited PD.