Pesticide-Mediated Generation of a Toxic Neurotransmitter Metabolite

项目摘要。接触有机氯狄氏剂会使人容易患帕金森氏症 疾病（PD）;然而，与疾病暴露相关的机制未知。狄氏剂可干扰DA 稳态，但单独可能不足以使多巴胺（DA）神经元丧失，神经变性可能 需要一个额外的“打击”。几种动物模型已经证明，改变DA稳态， 代谢和/或运输，产生DA神经元的进行性损失;因此， DA代谢可能是一个额外的“打击”，具有毒性协同农药暴露。DA中断 稳态产生毒性中间体如ROS和醛（3，4-二羟基苯乙醛， DOPAL），通过单胺氧化酶。与帕金森病类似，有证据表明狄氏剂是阿尔茨海默病的危险因素 疾病（AD）。有人提出NE稳态的改变与有毒物质的产生有关 以及与AD相关的细胞损伤。与DA一样，NE通过单胺氧化酶生物转化为醛（3，4-二氢呋喃）。 二羟基苯基乙醇醛，DOPEGAL），其是高度蛋白质反应性和毒性的。早期AD 神经病理学发生在蓝斑（LC）中，蓝斑是脑中NE神经支配的主要部位， 蛋白Tau在被天冬酰胺蛋白酶（AEP）切割后的神经元缠结。最近 报道表明NE代谢物DOPEGAL激活AEP以切割Tau并诱导Tau 聚合来细胞外基质（ECM）的调节被认为对于AD病理学是重要的，并且可能 影响LC动力学和NE代谢。我们假设NE代谢/运输是狄氏剂的靶点， 产生升高水平的DOPEGAL，其影响Tau加工并产生Tau聚集。此外，本发明还提供了一种方法， 我们认为ECM的调节是影响细胞对狄氏剂反应的第二次“打击”。的 建议的工作是高度相关的AD神经发病机制，并建立在以前资助的申请。 本补充的目的是阐明AD的环境风险因素的潜在机制， 特别关注农药狄氏剂与神经元中NE代谢的相互作用以及 ECM。中心假设是狄氏剂靶向NE代谢和/或神经元中的运输， 启动毒性途径的反应性代谢物的积累，如tau蛋白的固定，损伤神经元， 依赖ECM的方式。将完成两个具体目标：1）阐明农药/狄氏剂的成果 暴露于去甲肾上腺素能细胞产生毒性物质多巴酚丁胺。2)确定的贡献 ECM对杀虫剂和DOPEGAL介导的细胞损伤的影响。这些具体目标将建立在以前的基础上。 致力于解决AD的关键机制问题，即关键的细胞相互作用产生的脆弱性， 神经元到杀虫剂这些创新的研究对于确定关键的机制目标具有重要意义。 神经毒性农药和鉴定处于发展AD风险中的个体的潜在生物标志物。

PROJECT SUMMARY. Exposure to the organochlorine dieldrin predisposes individuals to Parkinson's Disease (PD); however, the mechanisms linking exposure to disease unknown. Dieldrin can disrupt DA homeostasis but alone may be insufficient for loss of dopamine (DA) neurons, and neurodegeneration may require an additional “hit”. Several animal models have demonstrated that altering DA homeostasis, metabolism and/or trafficking, yields progressive loss of DA neurons; therefore, a genetic variation modifying DA metabolism may be an additional “hit” that has toxic synergy with pesticide exposure. Disruption of DA homeostasis generates toxic intermediates such as ROS and aldehydes (3,4-dihydroxyphenylacetaldehyde, DOPAL), via monoamine oxidase. Similar to PD, there is evidence that dieldrin is a risk factor for Alzheimer's Disease (AD). It has been proposed that altered NE homeostasis is linked to the production of toxic species and cell injury relevant to AD. As with DA, NE is biotransformed via monoamine oxidase to an aldehyde (3,4- dihydroxyphenylglycolaldehyde, DOPEGAL), which is highly protein reactive and toxic. Early AD neuropathology occurs in the locus coeruleus (LC), a major site of NE innervation in the brain, and involves neurofibrillary tangles of the protein Tau, following its cleavage by an asparagine proteinase (AEP). Recent reports demonstrated that the NE metabolite, DOPEGAL, activates AEP to cleave Tau and induce Tau aggregation. Modulation of the extracellular matrix (ECM) is thought to be important for AD pathology and may influence LC dynamics and NE metabolism. We hypothesize NE metabolism/trafficking as a target for dieldrin, producing elevated levels of DOPEGAL which affects Tau processing and yields Tau aggregation. In addition, we posit that modulation of ECM as the second “hit” that influences cellular responses to dieldrin. The proposed work is highly relevant to AD neuropathogenesis and builds upon the previously funded application. The goal of this supplement is to elucidate mechanisms underlying environmental risk factors for AD, specifically focusing on the interaction of the pesticide dieldrin with NE metabolism in neurons and the role of the ECM. The central hypothesis is that dieldrin targets NE metabolism and/or trafficking in neurons, yielding build-up of reactive metabolites that initiate toxic pathways, such as tau fibrillization, injuring neurons in an ECM-dependent manner. Two specific aims will be completed: 1) Elucidate the outcomes of pesticide/dieldrin exposure on noradrenergic cells for production of the toxic species DOPEGAL. 2) Determine the contribution of the ECM to pesticide- and DOPEGAL-mediated cellular injury. These Specific Aims will build upon previous work to address key mechanistic questions for AD regarding critical cellular interactions yielding vulnerability of neurons to pesticides. These innovative studies are significant to identifying key mechanistic targets of neurotoxic pesticides and to identifying potential biomarkers for individuals at risk for developing AD.