Environmental Mitochondrial Toxicants Cause LRRK2 Activation in Parkinson's Disease

摘要 特发性帕金森氏病(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的相互作用是帕金森病的主要病因。 导致线粒体功能障碍的环境毒物，如有机杀虫剂鱼藤酮和 常见除草剂百草枯与帕金森病风险增加相关(OR 2.5，95%CI：0.1.3-4.7；OR 2.5，95%CI： 分别为1.4-4.7)。一种大量使用的工业溶剂三氯乙烯(TCE)也会导致线粒体 毒性，是在美国地下水中发现的最常见的有机污染物。TCE暴露是 与PD(OR 6.1，95%CI：1.2-3.3)和TCE暴露展示的啮齿动物模型的发展有关 黑质纹状体束中的多巴胺神经元变性。我们实验室的最新证据表明，鱼藤酮 腐胺(ROT)、百草枯(PQ)和三氯乙烯(TCE)与帕金森病易感基因相互作用，特别是导致LRRK2激活 野生型(WT)人胚胎肾(HEK)细胞，可被选择性LRRK2抑制剂阻断 (GNE-7915)。由于LRRK2是与家族性帕金森病相关的最常见的遗传性突变，这一证据 提示LRRK2与线粒体毒物之间存在基因-环境相互作用。在功能上， LRRK2激活导致多种下游细胞病理，如囊泡运输中断， 自噬、α-突触核蛋白磷酸化和神经炎症的缺陷；所有这些都是机制 推测可能先于帕金森病患者的多巴胺神经元变性。这项建议的基础是调查 环境致多巴胺神经元LRRK2激活及其预变性机制 线粒体毒物。为此，我们将实现以下具体目标：目标1(K99)将建立一个 确定环境线粒体毒物是否诱导WT神经元LRRK2活性的基础，以及 如果LRRK2突变在线粒体功能障碍后加剧了这种病理。Aim 2(R00)将进一步 在三氯乙烯暴露的动物模型中表征LRRK2的激活，并确定LRRK2的抑制是否 对三氯乙烯的防护。目标3(R00)将描述受以下因素影响的另一种预退化机制 环境线粒体毒物与LRRK2、线粒体抗原提呈(MITAP)。Mitap涉及到 线粒体蛋白从内腔到细胞表面MHC分子的运输，导致选择性 免疫细胞杀死多巴胺神经元。我们已经测量了多巴胺神经元中的Mitap 暴露在老鼠身上的腐烂，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可诱导多巴胺能神经元MITAP。由于LRRK2活性影响囊泡运输，我们 提示n27细胞系LRRK2突变影响线粒体毒物暴露后的Mitap反应， 在体内，用LRRK2抑制剂治疗可能对Mitap具有保护作用。这些目标将提供创新 环境因素激活LRRK2导致多巴胺能神经元退化的证据。 总的来说，这项建议可能会为特发性和遗传性帕金森病带来新的治疗途径。

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.