Organochlorine-Mediated Generation of a Dopamine Derived Neurotoxin

描述（由申请人提供）：暴露于环境化学品是帕金森病（PD）的风险因素。具体而言，农业中使用的农药，如有机氯狄氏剂，与PD发病率有关;然而，暴露与疾病之间的联系尚不清楚，其潜在机制仍有待确定。一个潜在的途径涉及氧化应激。与PD发病率相关的狄氏剂已被证明可诱导这种损伤性疾病。然而，目前尚不清楚环境暴露引起的一般氧化应激如何转化为特异性多巴胺能毒性。一种解释这一点的机制涉及3，4-二羟基苯乙醛（DOPAL），一种多巴胺（DA）衍生的神经毒素。DA代谢为毒性中间体DOPAL，DOPAL使用辅因子NAD通过线粒体醛脱氢酶（mALDH）氧化为3，4-二羟基苯基乙酸（DOPAC）。通过氧化应激产生的醛，例如，4-羟基壬烯醛（4 HNE）是mALDH的有效抑制剂;因此，由环境因素引起的细胞应激可抑制DOPAL代谢，产生高水平的DA衍生醛。此外，已经观察到杀虫剂对负责线粒体NAD产生的复合物I的损害，并且这种损害也会降低mALDH代谢DOPAL的能力。本申请中提供的初步数据表明，氧化应激产物4 HNE和狄氏剂均抑制DOPAL的线粒体代谢;此外，DA衍生的醛对蛋白质具有高度反应性。基于先前的研究和本申请中提供的初步数据，假设有机氯狄氏剂抑制DOPAL的细胞代谢，产生异常水平的这种内源性醛神经毒素和随后的蛋白质修饰。为了验证这一假设，将完成三个具体目标。具体目标1将检查狄氏剂损害多巴胺能细胞中DOPAL代谢的能力，并阐明抑制机制。具体目标2将证明在用狄氏剂处理的细胞中DA衍生的醛的蛋白加合。具体目标3将在慢性狄氏剂给药的小鼠模型中确定DOPAL体内蛋白质修饰的程度。本申请中提出的工作是重要的和创新的，并将作为未来研究的基础，旨在确定金属暴露在PD发病机制中的作用。

DESCRIPTION (provided by applicant): Exposure to environmental chemicals is a risk factor for Parkinson's Disease (PD). Specifically, pesticides used in agriculture, such as the organochlorine dieldrin, are associated with PD incidence; however, the link between exposure and disease is not known, and the underlying mechanisms remain to be determined. A potential pathway involves oxidative stress. Dieldrin, which is associated with PD incidence, has been shown to induce this injurious condition. However, it is not known how general oxidative stress, resulting from environmental exposure, can translate into specific dopaminergic toxicity. A proposed mechanism to account for this involves 3,4-dihydroxyphenylacetaldehyde (DOPAL), a dopamine (DA) derived neurotoxin. DA is metabolized to the toxic intermediate, DOPAL, which is oxidized via mitochondrial aldehyde dehydrogenase (mALDH) to 3,4-dihydroxyphenyl acetic acid (DOPAC) using the cofactor NAD. Aldehydes generated via oxidative stress, e.g., 4-hydroxynonenal (4HNE), are potent inhibitors of mALDH; therefore, cellular stress resulting from environmental agents may inhibit DOPAL metabolism yielding high levels of the DA-derived aldehyde. Furthermore, impairment of complex I, responsible for generation of mitochondrial NAD, has been observed for pesticides, and such an insult would also decrease the ability of mALDH to metabolize DOPAL. Preliminary data presented in this application demonstrate that both the oxidative stress product 4HNE and dieldrin yield inhibition of mitochondrial metabolism of DOPAL; furthermore, the DA-derived aldehyde is highly reactive toward proteins. Based on previous studies and preliminary data presented in this application, it is hypothesized that the organochlorine dieldrin inhibits cellular metabolism of DOPAL, yielding aberrant levels of this endogenous aldehyde neurotoxin and subsequent protein modification. To test the hypothesis, three specific aims will be completed. Specific Aim 1 will examine the ability of dieldrin to impair DOPAL metabolism in dopaminergic cells and elucidate the mechanism of inhibition. Specific Aim 2 will demonstrate protein adduction by the DA-derived aldehyde in cells treated with dieldrin. Specific Aim 3 will determine the extent of protein modification by DOPAL in vivo in a mouse model of chronic dieldrin dosing. The work proposed in this application is significant and innovative and will serve as a foundation for future research aimed at determining the role of environmetal exposure in PD pathogenesis.