PARG- Mediated Cell Death: Biochemical Mechanisms

描述(申请人提供)：中风是美国主要的死亡和残疾原因之一。关于缺血性神经元死亡的机制和新的中风治疗策略迫切需要新的信息。先前的研究表明，在脑缺血和其他几种衰弱疾病中，过度激活多聚(ADP-核糖)聚合酶-1(PARP-1)在氧化性细胞死亡中起着关键作用。最近美国和其他实验室的研究提供了直接的证据表明，PARP-1通过耗尽NAD+而诱导细胞死亡，从而导致线粒体通透性转变(MPT)和凋亡诱导因子的核移位。我们还提供了首次证据表明，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前途的治疗靶点。然而，与快速增长的关于PARP-1在细胞死亡中的信息相反，PARG在细胞死亡中的作用机制尚不清楚。本研究的主要目的是探讨PARG抑制产生的神经保护作用的机制。这项研究的信息可能提供关于介导PARG/PARP-1细胞毒性的下游事件的基本信息，并建议在延迟的时间点减少缺血性脑损伤的新策略。本研究的具体目的1是验证PARG抑制可以通过防止NAD+耗竭来减少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的凋亡变化的假说，以及PARG抑制可以防止遗传毒剂诱导的星形胶质细胞线粒体通透性转变(MPT)的假说。

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.