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氏病(PD)的风险因素。具体地说，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，其潜在机制仍有待确定。一条潜在的途径涉及氧化应激。狄氏剂与帕金森病的发病有关，已被证明是导致这种损害的原因。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定的多巴胺能毒性。一种被提议的机制涉及3，4-二羟基苯乙醛(DOPAL)，一种来自多巴胺(DA)的神经毒素。DA被代谢成有毒的中间体DOPAL，后者在辅因子NAD的作用下通过线粒体醛脱氢酶(MALDH)氧化成3，4-二羟基苯乙酸(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，环境因素引起的细胞应激可能会抑制DOPAL代谢，产生高水平的DA衍生醛。此外，在农药中也观察到负责产生线粒体NAD的复合体I的损伤，这种损伤也会降低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4HNE和狄氏剂均可抑制DOPAL的线粒体代谢；此外，DA衍生的醛对蛋白质具有高度的反应性。根据先前的研究和在本应用中提供的初步数据，假设有机氯狄氏剂抑制DOPAL的细胞代谢，产生这种内源性乙醛神经毒素的异常水平和随后的蛋白质修饰。为了检验这一假设，将完成三个具体目标。具体目标1将检测狄氏剂对多巴胺能细胞中DOPAL代谢的影响，并阐明其抑制机制。特定目标2将展示在狄氏剂处理的细胞中DA衍生的醛对蛋白质的加合作用。具体目标3将确定DOPAL在体内对狄氏剂慢性给药小鼠模型的蛋白质修饰程度。本申请中提出的工作具有重大意义和创新性，将为未来旨在确定环境暴露在帕金森病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.