Organochlorine-Mediated Generation of a Dopamine Derived Neurotoxin

描述（由申请人提供）：暴露于环境化学物质是帕金森病（PD）的危险因素。具体来说，农业中使用的农药，如有机氯狄氏剂，与帕金森病的发病率有关；然而，暴露与疾病之间的联系尚不清楚，潜在的机制仍有待确定。一个潜在的途径涉及氧化应激。Dieldrin与PD发病率相关，已被证明可诱发这种损伤性疾病。然而，尚不清楚由环境暴露引起的一般氧化应激如何转化为特定的多巴胺能毒性。一种提出的机制涉及3,4-二羟基苯乙醛（DOPAL），一种多巴胺（DA）衍生的神经毒素。DA被代谢为有毒的中间体DOPAL， DOPAL通过线粒体醛脱氢酶（mALDH）通过辅助因子NAD氧化为3,4-二羟基苯基乙酸（DOPAC）。氧化应激产生的醛，如4-羟基壬烯醛（4HNE），是mALDH的有效抑制剂；因此，由环境因素引起的细胞应激可能抑制DOPAL代谢，产生高水平的da衍生的醛。此外，已经观察到农药对线粒体NAD生成的复合物I的损害，这种损害也会降低mALDH代谢DOPAL的能力。本应用的初步数据表明，氧化应激产物4HNE和狄氏剂均能抑制DOPAL的线粒体代谢；此外，da衍生的醛对蛋白质有很高的反应性。根据先前的研究和本申请提供的初步数据，我们假设有机氯狄氏剂抑制DOPAL的细胞代谢，产生异常水平的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。特异性目的1将研究狄氏剂对多巴胺能细胞多巴代谢的影响，并阐明其抑制机制。特异性目标2将证明在用狄氏剂处理的细胞中，da衍生的醛可以内聚蛋白质。特异性Aim 3将在慢性狄氏剂给药小鼠模型中确定DOPAL在体内对蛋白质的修饰程度。本应用程序中提出的工作具有重要意义和创新性，并将为未来旨在确定环境暴露在PD发病机制中的作用的研究奠定基础。

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.