Mechanisms of age-dependent nigral neuron loss in PINK1 knockout rats

PINK1 基因敲除大鼠年龄依赖性黑质神经元丢失的机制

• 批准号: 8988874
• 负责人: Matthew S Goldberg
• 金额: $ 22.89万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2017-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8988874
• 关键词: Mechanisms; age; dependent; nigral; neuron

DESCRIPTION (provided by applicant): Parkinson's disease (PD) is a frequent cause of neurodegeneration, disability and premature mortality in older adults. Loss of dopaminergic neurons in the substantia nigra is the primary neuropathological hallmark of PD. There are currently no treatments proven to slow down the progressive nigral cell loss in PD, which causes increasing severity of the clinical symptoms. The recent linking of human mutations in genes such as Parkin, DJ-1, and PINK1 to recessively inherited forms of PD provides new opportunities to discover pathogenic mechanisms and to develop and test neuroprotective therapies in animal models with nigral cell loss based on mechanisms physiologically relevant to human parkinsonism. We have pursued this strategy for over a decade using knockout (KO) mice. For unknown reasons, Parkin KO, DJ-1 KO and PINK1 KO mice do not reproduce the nigral cell loss that occurs in humans bearing loss-of-function mutations in these genes. We and others identified mitochondrial dysfunction (respiratory chain defects) in KO mice, Drosophila and cultured cells, suggesting that this is a common and perhaps early event in the mechanism by which loss-of-function mutations in these genes cause nigral cell loss. However, the lack of nigral cell loss precludes using nigral cell loss as an outcome measure to directly test this and other potential key pathogenic mechanisms in Parkin KO, DJ-1 KO or PINK1 KO mice. Recently developed PINK1 KO rats show age-dependent nigral cell loss beginning at age 6 months and reaching 50% by age 8 months. The age-dependent nigral neuron loss in PINK1 KO rats makes it possible for the first time to test the leading candidate pathogenic mechanisms such as mitochondrial impairment and diminished Parkin-mediated mitochondrial autophagy directly in a mammalian brain that reproduces this central neuropathological feature of PD. We propose to use PINK1 KO rats to achieve the following interrelated specific aims which have been chosen because of their significance for therapeutic development: 1) To identify mechanisms by which PINK1 deficiency leads to nigral cell loss in the rat; 2) To characterize Parkin as an inhibitor of age-dependent nigral cell loss in PINK1 KO rats; 3) To stimulate the mitochondrial respiratory chain as a potential therapy for PD. We expect to contribute a systematic characterization of PINK1 KO rats as an apt test bed for therapeutic development by testing the principal hypothesis that PINK1 deficiency diminishes Parkin-mediated degradation of impaired mitochondria and the second main hypothesis that respiratory chain stimulation via dietary intake of methylene blue is neuroprotective in PINK1 KO rats. We have previously shown that methylene blue prevents neurodegeneration in the rotenone rat PD model. The use of this novel rat model of nigral cell loss is innovative and the proposal will significantly impact the understanding of PD by shifting emphasis to disease mechanisms present in PD brain tissue selected for their strong therapeutic potential. We also expect that what will be learned will be broadly applicable to diseases associated with mitochondrial dysfunction and neurodegeneration.

描述（由申请人提供）：帕金森病 (PD) 是老年人神经退行性变、残疾和过早死亡的常见原因。黑质中多巴胺能神经元的丧失是 PD 的主要神经病理学标志。目前尚无任何治疗方法被证明可以减缓帕金森病中黑质细胞的进行性丧失，从而导致临床症状日益严重。最近，人类 Parkin、DJ-1 和 PINK1 等基因突变与隐性遗传的帕金森病形式之间存在联系，这为发现致病机制以及基于与人类帕金森病生理相关的机制在黑质细胞丧失的动物模型中开发和测试神经保护疗法提供了新的机会。十多年来，我们一直在使用基因敲除 (KO) 小鼠来推行这一策略。由于未知原因，Parkin KO、DJ-1 KO 和 PINK1 KO 小鼠无法重现携带这些基因功能丧失突变的人类中发生的黑质细胞损失。我们和其他人在 KO 小鼠、果蝇和培养细胞中发现了线粒体功能障碍（呼吸链缺陷），表明这是这些基因的功能丧失突变导致黑质细胞损失的机制中的常见且可能是早期事件。然而，由于缺乏黑质细胞损失，无法使用黑质细胞损失作为结果指标来直接测试 Parkin KO、DJ-1 KO 或 PINK1 KO 小鼠中的这一机制和其他潜在的关键致病机制。最近开发的 PINK1 KO 大鼠表现出年龄依赖性黑质细胞损失，从 6 个月大开始，到 8 个月大时达到 50%。 PINK1 KO 大鼠中年龄依赖性黑质神经元损失使得首次有可能直接在哺乳动物大脑中测试主要候选致病机制，例如线粒体损伤和 Parkin 介导的线粒体自噬减少，从而再现 PD 的这种中枢神经病理学特征。我们建议使用 PINK1 KO 大鼠来实现以下相互关联的具体目标，之所以选择这些目标是因为它们对治疗开发的重要性：1）确定 PINK1 缺陷导致大鼠黑质细胞损失的机制； 2) 将Parkin描述为抑制剂 PINK1 KO 大鼠中年龄依赖性黑质细胞损失； 3) 刺激线粒体呼吸链作为帕金森病的潜在治疗方法。我们希望通过测试主要假设（PINK1 缺乏会减少 Parkin 介导的受损线粒体降解）和第二个主要假设（通过膳食摄入亚甲蓝刺激呼吸链对 PINK1 KO 大鼠具有神经保护作用），对 PINK1 KO 大鼠进行系统表征，作为治疗开发的合适试验台。我们之前已经证明，亚甲蓝可以预防鱼藤酮大鼠帕金森病模型中的神经变性。这种新型黑质细胞丢失大鼠模型的使用具有创新性，该提案将重点转移到帕金森病脑组织中存在的疾病机制，因为这些组织具有强大的治疗潜力，因此将极大地影响对帕金森病的理解。我们还期望所学到的知识将广泛适用于与线粒体功能障碍和神经变性相关的疾病。