脑缺血后SIRT3对神经元及血管内皮细胞的保护作用及机制的研究

The research about brain protection after stroke and injury is in predicament because of a series of recent failures. It is urgent and necessary to re-consider the fundamental mechanisms underlying the brain injury caused by cerebral ischemia. The disturbances of energy metabolism and mitochondrial functions are the most early and significant events after cerebral ischemia, which induce a series of injury events such as production of free radical, calcium overload et al., directly or indirectly, resulting in neurons and endothelial cells injury and death. SIRT3, a member of Sirtuins which are NAD+ dependent histone/non-histone deacetylases, is located in mitochondria and plays a central role in energy metabolism and mitochondrial functions. SIRT3 is a major determinant of oxidative damage in cells and is critical for cell survival. Our studies demonstrate that SIRT3 is down-regulated in brain after cerebral ischemia; knockdown of SIRT3 by shRNA lentivirus results in increased death of neurons in oxygen and glucose deprivation assays. Based on these observations, this project will systematically demonstrate the protective roles of SIRT3 for cerebral ischemia and reperfusion, by using mice model of middle cerebral artery occlusion, in vitro oxygen and glucose deprivation assays. In vivo gene manipulation techniques will be introduced to knockdown or overexpress SIRT3 in mice brain, and integrated in vivo and in vitro technologies will be used to investigate the roles and mechanisms of the protective effects of SIRT3 for neurons and vascular endothelial cells in cerebral ischemia.The project will provide foundations for developing novel treatments targeting SIRT3 and shed light on possible avenues to walk out from the predicament of brain protection research.

近年来脑保护研究陷入了困境，促使我们不得不重新审视隐藏在脑缺血再灌注损伤背后的核心机制。线粒体能量代谢紊乱是脑缺血再灌注后改变最早和最显著的环节，直接或间接引起自由基产生、钙超载等一系列反应，造成神经元和血管内皮细胞损伤和死亡。SIRT3定位于线粒体，属Sirtuins家族NAD依赖的组蛋白/非组蛋白去乙酰化酶，参与能量代谢和线粒体功能的中心环节。SIRT3是调节自由基产生的关键分子，且与细胞生存密切相关。我们研究发现，脑缺血后脑组织中SIRT3表达降低；慢病毒shRNA抑制SIRT3可加重氧糖剥夺实验中神经元死亡。基于这些发现，本项目将利用小鼠大脑中动脉阻断模型及离体缺血缺氧模型，引入在体基因沉默和过表达技术，综合运用体内、外基因调控手段，系统阐明SIRT3参与脑缺血中对神经元和血管内皮细胞保护效应的机制，为开辟脑保护研究新思路，寻找基于SIRT3的新干预措施奠定基础。

本项目利用离体及在体缺血缺氧模型，引入在体基因沉默和过表达技术，综合运用体内、外基因调控手段，系统阐明Sirt3 参与脑缺血中对神经元和血管内皮细胞保护效应，并探索其调控氧化应激反应和线粒体功能的具体机制，为寻找基于 Sirt3的新干预措施奠定基础。经过深入研究，我们证实：1. Sirt3可通过保护线粒体功能在脑缺血后发挥脑保护作用，其作用机制与减轻线粒体损伤、抑制氧化应激反应有关；2.Sirt1-Sirt3信号轴调控缺血性脑损伤后血脑屏障通透性，其下游分子机制与AMPK-PGC1信号途径有关。本项目取得的研究成果主要为Sirt3 参与脑缺血中对神经元和血管内皮细胞保护效应提供了新的理论基础，并丰富了脑缺血后氧化应激反应和线粒体功能的调控机制，后续进一步研究有望发现新的脑卒中治疗干预靶点和干预策略。