Mechanisms of Neuronal Death in Parkinson's Disease

描述（由申请人提供）：氧化应激是帕金森病（PD）的主要因素。多巴胺（DA）本身容易被氧化成醌衍生物和活性氧（ROS），其损害能量代谢并与蛋白质如突触核蛋白形成加合物。由于动物模型中DA的药理学消耗受到非特异性外周和中枢神经系统作用的混淆，因此DA氧化在黑质细胞死亡中的作用以前无法解决。因此，在这一领域的一个关键的未回答的假设是，DA氧化是一个主要的贡献者在PD多巴胺能神经元的死亡。拟议的研究解决了这一假设的几个方面，包括已知的环境因素在触发DA氧化的相互作用。具体而言，假设帕金森病诱导药物MPP+的DA释放潜力是由于其与DA交换和/或降低细胞内pH梯度的能力，将使用新衍生的表达来自多巴胺能基因座的增强型绿色荧光蛋白（TH+/eGFP）的小鼠来解决。来自这些动物的原代培养物以及来自多巴胺能终末场的纯化的突触体和囊泡制剂将与荧光和放射性探针组合使用，以确定响应于毒素处理的DA释放、细胞内膜变化、ROS形成、ATP损失等的时间方面。此外，DA氧化导致多巴胺能细胞死亡的假设将使用经基因工程改造具有不同DA产生水平的动物在体内直接进行测试。行为，氧化和免疫细胞化学标准将被用来建立DA在急性和慢性MPTP模型的PD的作用。为了测试DA消耗是否阻止ROS，将使用一组针对硝基酪氨酸、硝化的α-突触核蛋白等的抗体来使用原位检测ROS的新方法，以暂时评估DA缺陷型和野生型动物中急性或慢性MPTP施用后的ROS形成。总之，拟议的研究将确定DA氧化是否在DA合成细胞的死亡中起核心作用，并提供从标准动物模型中无法获得的见解。了解DA诱导的自由基形成的来源和级联事件将有助于回答围绕使用多巴胺替代疗法的风险-获益争议，并促进PD发病机制中新药和/或治疗策略的开发。

DESCRIPTION (provided by applicant): Oxidative stress is a major factor in Parkinson's Disease (PD). Dopamine (DA) itself is easily oxidized to quinone derivatives and reactive oxygen species (ROS) that impair energy metabolism and form adducts with proteins such as upsilon-synuclein. Because pharmacological depletion of DA in animal models is confounded by non-specific peripheral and central nervous system effects, the role of DA oxidation in nigral cell death has been previously impossible to address. Thus a key unanswered hypothesis in this field is that DA oxidation is a major contributor to the death of dopaminergic neurons in PD. The proposed studies address several aspects of this hypothesis including the interaction of known environmental factors in triggering DA oxidation. Specifically, the hypothesis that the DA-releasing potential of the parkinsonism-inducing drug, MPP+, is due to its ability to exchange with DA and/or to reduce intracellular pH gradients will be addressed using newly derived mice expressing enhanced green fluorescent protein from a dopaminergic locus (TH+/eGFP). Primary cultures derived from these animals as well purified synaptosomal and vesicular preparations from dopaminergic terminal fields will be used in combination with fluorescent and radioactive probes to determine the temporal aspects of DA release, intracellular membrane changes, ROS formation, ATP loss, etc in response to toxin treatment. In addition, the hypothesis that DA oxidation contributes to the death of dopaminergic cells will be directly tested in vivo using animals genetically engineered to have different levels of DA production. Behavioral, oxidative and immunocytochemical criteria will be used to establish the role of DA in both the acute and chronic MPTP model of PD. To test whether DA depletion prevents ROS, new methodologies to detect in situ ROS will be used with a battery of antibodies directed against nitrotyrosine, nitrated alpha-synuclein, etc. to temporally evaluate ROS formation following acute or chronic MPTP administration in DA deficient and wild type animals. Taken together, the proposed studies will determine whether DA oxidation plays a central role in the death of DA synthesizing cells and provide insights impossible to obtain from standard animal models. Knowledge of the source and cascade of events surrounding DA-induced free radical formation will help answer risk-benefit controversies surrounding the use of dopamine replacement therapies as well as facilitate the development of new drugs and/or treatment strategies in the pathogenesis of PD.