PARG- Mediated Cell Death: Biochemical Mechanisms

描述（由申请人提供）：在美国，中风是导致死亡和残疾的主要原因之一。关于缺血性神经元死亡机制的新信息和中风的新治疗策略是迫切需要的。先前的研究表明，过度的聚（adp -核糖）聚合酶-1 （PARP-1）激活在脑缺血和其他几种衰弱性疾病的氧化细胞死亡中起关键作用。我们和其他实验室最近的研究提供了直接证据，证明PARP-1通过耗尽NAD+诱导细胞死亡，从而导致线粒体通透性转移（MPT）和凋亡诱导因子的核易位。我们还提供了第一个证据，表明聚（adp -核糖）糖水解酶（PARG）是聚（adp -核糖）代谢中唯一的分解代谢酶，是氧化性和兴奋性毒性神经元死亡的重要介质。最近的研究进一步表明，PARG和PARP-1在体内和体外都是减少缺血性神经元死亡的有希望的治疗靶点。然而，与PARP-1在细胞死亡中的快速增长的信息相反，PARP-1在细胞死亡中的作用机制尚不清楚。本研究的主要目的是研究PARG抑制产生神经保护的机制。本研究的信息可能为下游事件介导PARG/PARP-1细胞毒性提供基础信息，并提出减少延迟时间点缺血性脑损伤的新策略。本研究的具体目的1是验证PARG抑制可通过阻止NAD+耗竭来降低氧化应激和其他遗传毒性药物诱导的神经元和星形胶质细胞凋亡变化的假设；特异性目的2是验证PARG抑制可以阻止遗传毒性物质诱导的星形胶质细胞线粒体通透性转变（MPT）的假设。

DESCRIPTION (provided by applicant): Stroke is one of the leading causes of death and disability in the U.S. New information regarding the mechanisms of ischemic neuronal death and new treatment strategies for stroke is urgently needed. Previous studies have indicated a key role of excessive poly (ADP-ribose) polymerase-1 (PARP-1) activation in oxidative cell death in cerebral ischemia and several other debilitating diseases. Recent studies by us and other laboratories have provided direct evidence demonstrating that PARP-1 induces cell death by depleting NAD+, which leads to mitochondria permeability transition (MPT) and nuclear translocation of apoptosis inducing factor. We have also provided the first evidence suggesting that poly(ADP-ribose) glycohydrolase (PARG), the sole catabolizing enzyme in poly(ADP-ribose) metabolism, is an important mediator of oxidative and excitotoxic neuronal death. Recent studies have further suggested that PARG and PARP-1 are promising therapeutic targets for decreasing ischemic neuronal death both in vivo and in vitro. However, in contrast to the rapidly growing information regarding PARP-1 in cell death, the mechanisms underlying the roles of PARG in cell death are unclear. The major objective of this study is to investigate the mechanisms underlying the PARG inhibition-produced neuroprotection. The information from this study may provide fundamental information regarding the downstream events mediating PARG/PARP-1 cytotoxicity, and suggest new strategies to decrease ischemic brain injury at delayed time points. Specific aim 1 of this study is to test the hypothesis that PARG inhibition can decrease apoptotic changes of neurons and astrocytes induced by oxidative stress and other genotoxic agents by preventing NAD+ depletion; and Specific aim 2 is to test the hypothesis that PARG inhibition can prevent genotoxic agent-induced mitochondrial permeability transition (MPT) of astrocytes.