Mechanisms of protection against age-dependent nigral neuron loss in DJ-1 KO rats

描述（由申请人提供）：帕金森病（PD）是老年人神经变性、残疾和过早死亡的常见原因。黑质多巴胺能神经元的丧失是帕金森病的主要神经病理学标志。目前还没有证实的治疗方法可以减缓PD患者的进行性神经细胞丢失，这导致临床症状的严重程度增加。最近将Parkin、DJ-1和PINK1等基因突变与隐性遗传形式的PD联系起来，为发现致病机制以及基于与人类帕金森病相关的生理机制开发和测试神经保护疗法的动物模型提供了新的机会。十多年来，我们一直在使用基因敲除（KO）小鼠来追求这一策略。由于未知的原因，没有进一步的伤害，Parkin KO， DJ-1 KO和PINK1 KO小鼠不会复制在这些基因中发生功能丧失突变的人类中发生的黑细胞损失。在Parkin KO、DJ-1 KO或PINK1 KO小鼠中，缺乏黑质细胞损失排除了将黑质细胞损失作为直接测试潜在致病机制和神经保护策略的结果测量。最近开发的DJ-1 KO大鼠在4个月和6个月时显示出年龄依赖性的神经细胞丢失，多巴胺神经元完全补充，但在8个月时损失超过50%。DJ-1 KO大鼠的年龄依赖性神经神经元丢失使得首次在再现PD中枢神经病理特征的哺乳动物大脑中直接测试候选致病机制成为可能。我们建议使用DJ-1 KO大鼠来实现以下具体目标，我们选择这些目标是因为它们对治疗发展的重要性：1)确定需要DJ-1来防止大鼠黑质多巴胺神经元年龄依赖性丧失的细胞和分子机制；2)确定应激激活蛋白激酶c-jun- n-末端激酶（JNK）或p38抑制剂是否能预防DJ-1缺乏引起的黑质多巴胺神经元的年龄依赖性丧失。我们希望通过验证DJ-1缺乏导致应激激活激酶信号通路增加的主要假设和DJ-1需要半胱氨酸106来防止DJ-1 KO大鼠的黑质细胞损失的第二个主要假设，为DJ-1 KO大鼠提供系统的表征，作为治疗开发的合适试验平台。使用这种新的大鼠神经细胞损失模型是一种创新，这一提议将显著影响对帕金森病的理解，因为它将重点转移到帕金森病脑组织中存在的疾病机制上，因为它们具有强大的治疗潜力。我们期望我们的发现将广泛适用于家族性和散发性PD以及其他神经退行性疾病的神经保护疗法的开发。

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, without further insult, 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. The lack of nigral cell loss precludes using nigral cell loss as an outcome measure to directly test potential pathogenic mechanisms and neuroprotective strategies in Parkin KO, DJ-1 KO or PINK1 KO mice. Recently developed DJ-1 KO rats show age-dependent nigral cell loss with a full complement of dopamine neurons at ages 4 months and 6 months but greater than 50% loss by age 8 months. The age-dependent nigral neuron loss in DJ-1 KO rats makes it possible for the first time to test candidate pathogenic mechanisms directly in a mammalian brain that reproduces this central neuropathological feature of PD. We propose to use DJ-1 KO rats to achieve the following specific aims that we have chosen because of their significance for therapeutic development: 1) To define the cellular and molecular mechanisms by which DJ-1 is required to prevent age-dependent loss of nigral dopamine neurons in rats; 2) To determine whether inhibitors of the stress activated protein kinases c-jun-N-terminal kinase (JNK) or p38 prevent age-dependent loss of nigral dopamine neurons caused by DJ-1 deficiency. We expect to contribute a systematic characterization of DJ-1 KO rats as an apt test bed for therapeutic development by testing the principal hypothesis that DJ-1 deficiency causes increased signaling of stress-activated kinase pathways and the second main hypothesis that cysteine 106 is required for DJ-1 to prevent nigral cell loss in DJ-1 KO rats. The use of this novel rat model of nigral cell loss is innovative and the proposal will significantly impact the understanding of PD b shifting emphasis to disease mechanisms present in PD brain tissue selected for their strong therapeutic potential. We expect that our findings will be broadly applicable to the development of neuroprotective therapies for familial and sporadic PD as well as other neurodegenerative diseases.