PARS ACTIVATION AFTER TBI

聚（ADP-核糖）合成酶（PARS），也称为聚（ADP-核糖）聚合酶或PARP，是一种普遍存在的核蛋白，其在消耗NAD和ATP的过程中促进DNA链断裂的修复。在非神经元细胞中的几项体外研究支持“PARS激活的自杀理论”，其中活性PARS导致能量衰竭和通过坏死的细胞死亡。我们的初步研究提供了证据表明，PARS被激活后，创伤性脑损伤（TBI）。PARS缺陷的小鼠表现出明显的由TBI通常产生的功能缺陷，这表明TBI后PARS激活是有害的。我们的假设是，过氧亚硝酸盐产生的氧化性DNA损伤激活PARS，干扰细胞能量，损伤线粒体，并导致坏死细胞死亡。解决这一假设的具体目标包括测试过氧亚硝酸盐诱导的PARS激活对氧化DNA损伤，细胞能量学，线粒体功能，以及使用药理学PARS抑制剂在体外神经元中的凋亡坏死和总细胞死亡的影响。通过首先表征TBI后小鼠、大鼠和人样品中的PARS活化，然后使用药理学抑制剂或遗传破坏（PARS敲除小鼠）测试PARS活化对NAD储存、线粒体损伤、脑水肿和脑血流量、凋亡性坏死和总细胞死亡以及TBI后神经病理学结果的影响，来确定TBI后PARS的作用。通过抑制PARS来保护细胞能量储存可能代表治疗TBI的关键策略。重要的是，PARS抑制可以靶向坏死性神经元死亡，这在以前被认为是不可操纵的。然而，PARS也可能在TBI后通过参与基因组完整性的维持而发挥有益的作用。在实施针对急性脑损伤后PARS的临床治疗策略之前，需要仔细研究TBI后PARS的潜在双重作用。创伤性脑损伤是在没有任何警告的情况下发生的，是成人和儿童发病和死亡的主要原因。细胞能量衰竭和坏死性神经元死亡导致发病率和死亡率，目前只有少数非特异性治疗可用。拟议的实验解决了关键问题，即过亚硝酸盐产生的氧化应激是否会在体外和体内TBI后引发PARS介导的线粒体损伤、能量衰竭和神经元死亡？针对TBI后能量衰竭和坏死的新的和临床相关的药理学策略的开发可能被证明是治疗TBI的强大而有效的药物。

Poly(ADP-ribose) synthetase (PARS), also termed poly (ADP- ribose)polymerase or PARP, is a ubiquitous nuclear protein that facilitates repair of DNA strand breaks in a process that consumes NAD and ATP. Several in vitro studies in non-neuronal cells support a "suicide theory of PARS activation" where active PARS leads to energy failure and cell death by necrosis. Our preliminary studies provide evidence that PARS is activated after traumatic brain injury (TBI). Mice deficient in PARS showed dramatic from functional deficits typically produced by TBI, suggesting that in toto PARS activation is detrimental after TBI. Our hypothesis is that oxidative DNA damage produced by peroxynitrite activates PARS, disturbs cellular energetics, injures mitochondria, and contributes to necrotic cell death. Specific aims to address this hypothesis include testing the effects of peroxynitrite-induced PARS activation on oxidative DNA damage, cellular energetics, mitochondrial function, and apoptotic necrotic and total cell death in neurons in vitro using pharmacologic PARS inhibitors. The role of PARS after TBI will be established by first characterizing PARS activation in mice, rats, and human samples after TBI; then testing the effects of PARS activation on NAD stores, mitochondrial injury, brain edema and cerebral blood flow, apoptotic necrotic, and total cell death, and neuropathologic outcome after TBI using pharmacologic inhibitors or genetic disruption (PARS knockout mice). Preserving cellular energy stores by inhibiting PARS may represent a key strategy for the treatment of TBI. Importantly, PARS inhibition may target necrotic neuronal death which has been previously felt to be unmanipulable. However, PARS may also play a beneficial role after TBI by participating in the maintenance of genomic integrity. The potential dual-role of PARS after TBI needs to be carefully addressed prior to implementation of clinical treatment strategies targeting PARS after acute brain injury. TBI strikes without warning and is a major cause of morbidity and mortality in adults and children. Cellular energy failure and necrotic neuronal death contribute to morbidity and mortality and currently only few non-specific therapies are available. The proposed experiments address the key question, does oxidative stress produced by peroxynitrite trigger PARS-mediated mitochondrial damage, energy failure, and neuronal death in vitro and after TBI in vivo? The development of novel and clinically-relevant pharmacologic strategies that target energy failure and necrosis after TBI may prove to be powerful and efficacious agents for the treatment of TBI.