PhIP-induced neurodegeneration: mechanisms and relevance to Parkinson's disease

描述(申请人提供)：大多数帕金森氏病(PD)病例的病因不明(~90%是散发性的)，而~10%是纯遗传因素。长期以来，人们一直怀疑环境因素，但还没有令人信服的毒物被确定。许多不同类别的化合物，包括杀虫剂和溶剂，都与帕金森病有关。这项建议测试的假设是：暴露于杂环胺，2-氨基-1-甲基-6-苯基咪唑[4，5-b]吡啶(PhIP)，一种已知的啮齿动物致癌物质，复制了人类帕金森病(PD)的关键特征。目前，关于慢性PHIP的神经学影响的初步数据很少。然而，四个关键因素导致了PhIP在帕金森病相关神经退行性变中的作用。1)我们小组成员的一项初步研究显示，小鼠存在与帕金森病相关的运动缺陷2)公布了结构上相关的杂环胺对大鼠的多巴胺能效应3)人类高水平消费的潜力。PhIP是从熟肉(高达15ug/kg生肉)的外壳中分离出的最丰富的氨基咪唑氮芳烃，4)PhIP和PhIP代谢产物穿过血脑屏障，因此可能对不同的神经元核有直接影响。这项建议的主要目标是：1)确定长期给予PhIP是否在大鼠体内繁殖 帕金森病的关键特征和2)使用体外方法确定潜在的毒性机制。在这项提案中，将实现以下目标：目标1.确定慢性PhIP治疗是否复制了PD的关键特征。目的2.利用中脑原代培养系统鉴定PhIP的神经毒性机制。这一提议的成功将导致帕金森病研究的至少三个主要进展。1.确定可能的致病因素。PhIP是肉类加工中产生的一种常见毒物，可单剂量、高剂量食用，与大多数罕见的多巴胺能毒物相比，可长期服用。这一提议的成功可能会促使流行病学研究。此外，肉类准备中的变化是可用的，减少了PhIP的形成和潜在的PD相关暴露。2.发展了一种新的局部放电模型。PD模型有很多种，每一种都有优缺点。没有一个人充分考虑到饮食因素。目前的模型也未能预测临床试验的成功，而一个新的模型可能被证明更成功。3.新的PD机制。如果PhIP暴露再现了帕金森病的关键特征，机制研究将有望确定可能成为治疗靶点的新的致病途径。总之，使用体内和体外系统，我们将仔细描述PhIP暴露后的神经退化特征，并初步确定与影响黑质纹状体多巴胺系统相关的毒性机制。

DESCRIPTION (provided by applicant): The causes of most Parkinson's disease (PD) cases are unknown (~90% are "sporadic"), while ~10 % are due to purely inherited factors. Environmental factors have long been suspected, but no toxicant has been convincingly identified. Numerous diverse classes of compounds, including pesticides and solvents have been linked to PD. This proposal tests the hypothesis that: exposure to the heterocyclic amine, 2-amino-1-methyl-6- phenylimidazo[4,5-b]pyridine (PhIP), a known carcinogen in rodents, replicates key features of human Parkinson's disease (PD). Currently, there are little preliminary data on the neurological effects of chronic PhIP. However, four key factors have led to proposing a role for PhIP in PD-relevant neurodegeneration. 1) A preliminary study from members of our group showing PD-relevant motor deficits in mice 2) Published dopaminergic effects of structurally related heterocylic amines in rats 3) Potential for high-level human consumption. PhIP is the most abundant amino-imidazoazaarene isolated from the crust of cooked meat (up to 15ug/kg uncooked meat) and 4) PhIP and PhIP metabolites cross the blood-brain barrier and, therefore, may have direct effects on distinct neuronal nuclei. The major goals of this proposal are to: 1) Determine if chronic administration of PhIP in the rat reproduces the key features of PD and 2) Identify potential mechanisms of toxicity using in vitro approaches. In this proposal, the following aims will be carried out: Aim 1. To determine if chronic PhIP administration replicates the key features of PD. Aim 2. To identify mechanisms of neurotoxicity of PhIP using a primary midbrain culture system. Success of this proposal would lead to at least three major advances in PD research. 1. Identification of a possible causative factor. PhIP is a common toxicant produced in meat preparation and may be consumed in single high doses and chronically vs. most rarely encountered dopaminergic toxicants. Success of this proposal would likely prompt epidemiological studies. Further, alterations in meat preparation are available, reducing PhIP formation and a potential PD-relevant exposure. 2. Development of a new PD model. There are numerous PD models, each with advantages/ disadvantages. None have adequately considered dietary factors. Current models have also failed to predict clinical trial successes and a novel model may prove to be more successful. 3. New PD mechanisms. If PhIP exposure reproduces the key PD features, mechanistic studies would be expected to identify novel pathogenic pathways that may be therapeutic targets. In summary, using both in vivo and in vitro systems we will carefully characterize neurodegeneration after PhIP exposure and preliminarily identify mechanisms of toxicity relevant to effects on the nigrostriatal dopamine system.