线粒体代谢酶去乙酰化修饰调控能量代谢保护复苏后心功能

Postresuscitation myocardial dysfunction has been implicated as one of the leading causes of early death for patients initially resuscitated from sudden cardiac arrest. Currently the pathophysiological mechanisms of postresuscitation myocardial dysfunction remain uncertain. Our previous investigation revealed that impaired mitochondrial energy metabolism plays a pivotal role in the development of postresuscitation myocardial function. However, the mechanism responsible for the metabolic disorder of myocardial mitochondria is unknown. Recent evidences suggested that the catalytic activities of mitochondrial metabolic enzymes are covalently regulated by mitochondrial protein acetylation/deacetylation. Our preliminary study also found that the protein expresssion level of SIRT3, a major mitochondrial deacetylase, was significantly downregulated following successful resuscitation. On the basis of our work and others, we test the hypothesis that 1) the imbalance between acetylation and deacetylation of metabolic enzymes appears to contribute to the postresuscitation metabolic disorder of myocardial mitochondria; 2) enhancing the catalytic activities of mitochondrial metabolic enzymes via increasing the protein expression of the deacetylase SIRT3, will ameliorate the impairment of mitochondrial energy metabolism, subsequently improve the postresuscitation myocardial function. The present study is thus performed to 1) investigate the relationship between the extent of deacetylation of mitochondrial enzymes and the severity of impaired mitochondrial energy metabolism; 2) furthermore, observe the effect of upregulation or downregulation of SIRT3 expression on the catalytic activities of mitochondrial metabolic enzymes, and subsequently postresuscitation myocardial dysfunction. The present investigation will give further insight into the pathophysiological mechanism of the postresuscitation myocardial dysfunction, and will provide evidence in support of the effectiveness of therapeutic strategy targeting at correcting the mitochondrial metabolic disorder.

复苏后心功能不全是导致初始复苏成功的病人早期死亡的主要原因，其病理生理机制尚未阐明。我们前期研究提示线粒体能量代谢障碍是复苏后心功能不全的核心环节，但线粒体能量代谢障碍的具体病理生理机制尚不明确。有证据表明线粒体代谢酶活性主要受乙酰化/去乙酰化共价调控，我们前期亦发现复苏后心肌线粒体蛋白的主要去乙酰化酶SIRT3表达水平下降。由此设想：线粒体代谢酶乙酰化/去乙酰化失衡是复苏后心肌能量代谢障碍的重要机制；通过提高SIRT3表达水平，增强线粒体代谢酶活性可以改善能量代谢障碍，从而改善复苏后心功能。本研究拟于在体和细胞水平，利用免疫沉淀等技术，研究复苏后心肌线粒体代谢酶去乙酰化程度与能量代谢障碍之间的关系；进而通过正向负向调控SIRT3表达，观察其对线粒体代谢酶活性和复苏后心功能的影响。本研究将进一步明确复苏后心功能不全的病理生理机制，为以改善心肌能量代谢障碍为治疗靶点的保护策略提供理论依据。

复苏后心功能不全是导致初始复苏成功的病人早期死亡的主要原因，其病理生理机制尚未阐明。我们前期研究提示线粒体能量代谢障碍是复苏后心功能不全的核心环节，但线粒体能量代谢障碍的具体病理生理机制尚不明确。有证据表明线粒体代谢酶活性主要受乙酰化/去乙酰化共价调控，由此设想：线粒体代谢酶乙酰化/去乙酰化失衡是复苏后心肌能量代谢障碍的重要机制。本课题首先建立了慢性心力衰竭模型，初步探讨慢性心衰动物发生心搏骤停，心肺复苏后恢复自主循环的可行性、以及复苏后心功能不全和存活预后情况。再从高质量的心肺复苏角度出发，研究其对心脏、脑的线粒体呼吸功能、能量代谢、超微结构病理学的影响，证实有效的高质量心肺复苏，在一定程度上能有效地减轻线粒体氧化磷酸化损伤的严重程度。项目实施过程，增加了近年来业内研究热点亚低温治疗干预措施，研究其在心肺复苏期间和恢复自主循环后对心肌线粒体氧化磷酸化功能的影响，证明低温治疗可以保护心肺复苏期间和复苏后线粒体呼吸功能，并改善复苏后心肌能量代谢障碍。上述研究为进一步开展后续复苏后心肌能量代谢障碍病理生理机制的研究奠定基础。再以复苏后糖代谢关键限速酶活性变化为切入点，检测复苏后心肌组织糖代谢关键限速酶活性变化以及线粒体代谢酶乙酰化/去乙酰化状态，提出并证实复苏后心肌组织糖代谢关键限速酶的广泛乙酰化修饰导致代谢酶活性下降是能量代谢障碍的重要原因之一。同时研究心肌组织线粒体去乙酰化酶SIRT3的表达与代谢酶乙酰化程度及酶活性的相关关系，证实去乙酰化酶SIRT3调控心肌组织线粒体关键限速酶乙酰化/去乙酰化失衡在复苏后心肌能量代谢障碍及复苏后心功能不全中的作用。本项目的实施，进一步明确复苏后心功能不全的病理生理机制，为以改善心肌能量代谢障碍为治疗靶点的保护策略提供了切实可行的理论依据。