Roles of NAMPT and NAD+ in hypoxic conditioning-induced neurovascular protection in subarachnoid hemorrhage

项目总结/摘要 动脉瘤性蛛网膜下腔出血（SAH）是一种高度病态的疾病，在很大程度上是由于继发性脑出血。 早期脑损伤（EBI）和迟发性脑缺血（DCI）。EBI发生在发作后1-3天， 其特征在于血脑屏障破坏、神经炎症和神经元细胞死亡。DCI发生4-12 发作后30天，由大动脉血管痉挛和微循环缺陷共同引起。给定 EBI和DCI是由广泛的神经血管缺陷引起的，我们相信有效的SAH治疗将 需要多种保护作用以最大化功效的机会。因此，我们采用了一种强大的 具有已知多效性效应的保护策略-基于条件反射的治疗-对实验模型 SAH。条件反射是一个概念，即大脑对损伤的固有抵抗力可以通过暴露来增强 无害的压力刺激。以前，我们发现低氧条件反射在蛛网膜下腔出血（SAH）之前启动（低氧条件反射）， 预处理）以eNOS依赖的方式提供针对DCI的鲁棒保护。最近，我们扩展了 结果表明：1）SAH后3 h开始出现低氧条件反射 （hypothermia Post-Conditioning; HPostC）也产生了强大的神经血管保护作用; 2）我们表明， NAD+依赖性脱乙酰酶，Sirtuin 1（SIRT 1），是这种保护的关键介质; 3）我们发现， 初步认为烟酰胺磷酸核糖基转移酶（NAMPT）可能是一个关键的上游分子， HPostC提供的神经血管保护。NAMPT是NAD+补救途径中的限速酶 将烟酰胺（NAM）转化为烟酰胺单核苷酸（NMN），从而能够生物合成NAD+， 是SIRT 1的重要辅因子，导致其活化。 在本研究中，我们将检验我们的中心假设，即NAMPT驱动的NAD+产生是一种因果关系， HPostC在SAH中提供的神经血管保护中的作用，并且这种保护是部分或 完全由SIRT 1介导。具体目的是：（1）检验NAMPT对于 HPostC在SAH中提供的EBI和DCI保护;（2）检验治疗策略设计的假设， 为了增强NAMPT活性或增加NAD+水平，模拟HPostC提供的EBI和DCI保护， SAH;如果是，确定这种保护是否是部分或完全SIRT 1介导的;以及（3）确定SAH的保护机制。 靶向NAMPT和NAD+的治疗策略的翻译潜力，通过评估其对长 SAH后的长期认知障碍。使用的方法包括：（a）SAH的两种互补小鼠模型;（B） 评估NAMPT、NAD+和SIRT 1水平;（c）评估神经炎症、神经元细胞死亡、 血管痉挛、微循环缺陷以及短期和长期神经行为缺陷;（d）药理学和 NAMPT和SIRT 1的遗传抑制;和（e）NAMPT或NAD+的药理学和遗传增强。 总的来说，目前资助的工作有可能为癌症患者确定一种全新的治疗方法。 脑动脉瘤破裂患者的治疗- NAMPT激活或NAD+增强。如果成功， 这些研究将使人们更好地了解HPostC的广度、机制和可持续性， 诱导SAH中的神经血管保护，并确定NAMPT-和NAD+-定向的 治疗学

Project Summary/Abstract Aneurysmal subarachnoid hemorrhage (SAH) is a highly morbid condition, in large part due to secondary brain injury from Early Brain Injury (EBI) and Delayed Cerebral Ischemia (DCI). EBI occurs 1-3 days after ictus and is characterized by blood brain barrier breakdown, neuroinflammation, and neuronal cell death. DCI occurs 4-12 days after ictus and results from a combination of large artery vasospasm and microcirculatory deficits. Given that EBI and DCI are caused by wide-ranging neurovascular deficits, we believe that effective SAH therapy will require a multiplicity of protective effects to maximize the chance of efficacy. We therefore applied a powerful protection strategy with known pleiotropic effects – Conditioning-based therapy – to experimental models of SAH. Conditioning is a concept whereby the brain's inherent resistance to injury can be enhanced by exposure to non-harmful stress stimuli. Previously, we showed that hypoxic conditioning initiated before SAH (Hypoxic Preconditioning) provides robust protection against DCI in an eNOS-dependent manner. Recently, we extended upon these results in three important ways: 1) We showed that hypoxic conditioning initiated 3h after SAH (Hypoxic Post-Conditioning; HPostC) also produces robust neurovascular protection; 2) We showed that the NAD+-dependent deacetylase, Sirtuin 1 (SIRT1), is a key mediator of this protection; and 3) We showed preliminarily that Nicotinamide phosphoribosyltransferase (NAMPT) is likely a key upstream molecule driving the neurovascular protection afforded by HPostC. NAMPT is the rate-limiting enzyme in the NAD+ salvage pathway that converts nicotinamide (NAM) to nicotinamide mononucleotide (NMN) enabling biosynthesis of NAD+, which is an essential co-factor of SIRT1 leading to its activation. In the present grant, we will test our central hypothesis is that NAMPT-driven NAD+ production plays a causal role in the neurovascular protection afforded by HPostC in SAH, and that this protection is either partially or completely SIRT1-mediated. The Specific Aims are (1) Test the hypothesis that NAMPT is necessary for the EBI and DCI protection afforded by HPostC in SAH; (2) Test the hypothesis that therapeutic strategies designed to augment NAMPT activity or increase NAD+ levels mimic the EBI and DCI protection afforded by HPostC in SAH; and if so, determine if this protection is partially or completely SIRT1-mediated; and (3) Determine the translational potential of therapeutic strategies targeting NAMPT and NAD+ by assessing their impact on long- term cognitive deficits after SAH. Methods used include: (a) Two complementary mouse models of SAH; (b) Assessment of NAMPT, NAD+, and SIRT1 levels; (c) Assessment of neuroinflammation, neuronal cell death, vasospasm, microcirculatory deficits, and short- and long-term neurobehavioral deficits; (d) Pharmacologic and genetic inhibition of NAMPT and SIRT1; and (e) Pharmacologic and genetic augmentation of NAMPT or NAD+. Overall, the work proposed in the present grant has the potential to identify an entirely new therapies for the treatment of patients with ruptured brain aneurysms – NAMPT activation or NAD+ augmentation. If successful, these studies will result in an improved understanding of the breadth, mechanism, and sustainability of HPostC- induced neurovascular protection in SAH and determine the translatability of NAMPT- and NAD+-directed therapeutics.