衰老心肌自噬障碍触发缺血心肌程序性坏死

Cell survival and death are the basic problems of life sciences. Autophagy and Necroptosis are major biological events that determine the fate of cardiomyocytes. However the regulatory mechanism between autophagy and necroptosis remains unclear. We have confirmed that autophagic dysfunction and increased vulnerability in aging hearts. In the recent exploration, we found that①abnormal accumulation of p62 / SQSTM1 in myocardium and autophagy and lysosomal vesicle fusion disorder in aged mice hearts; ②cardiac necroptosis was significantly increased after myocardial ischemia and reperfusion (MI/R) in aged hearts, but the mechanism was unknown; ③It is known that the RIP1 and RIP3 complex (necrosome) is the key signal of necroptosis. For the first time, our in vivo data demonstrated that p62 had a direct interaction with RIP1 and RIP3 in hearts. The levels of p62 / RIP1 / RIP3 protein complex in aged heart during MI/R were significantly higher than those in young hearts. Therefore, we hypothesis that aging related myocardial autophagy dysfunction triggers ischemic myocardial necroptosis, p62 accumulation promotes RIP1 / RIP3 to form necrosome. The present study intends to explore the new mechanism of myocardial aging and injury through the study of model animal and function research. It is expected to realize the new strategy of intervention or regulation of autophagy to programmed necrosis. This study will provide new ideas for elucidating the common mechanism of senescence and degenerative diseases.

自噬（autophagy）和程序性坏死（Necroptosis）都是决定心肌细胞命运的重大生物学事件，但两者之间的联系机制有待阐明。衰老心肌自噬功能减退和易损性增加，加剧心肌细胞的死亡倾向。我们在探索中发现①衰老小鼠心肌自噬体与溶酶体囊泡融合障碍，出现p62/SQSTM1的异常堆积；②衰老心肌缺血再灌注后Necroptosis程度显著加重，但机制不明；③已知RIP1与RIP3结合形成necrosome是Necroptosis的关键信号，我们首次在in vivo衰老心肌中发现p62与程序性坏死通路关键分子RIP1和RIP3存在直接的互作关系。在缺血再灌注过程中衰老心肌中p62/RIP1/RIP3蛋白复合物水平较成年心肌显著升高。据此我们提出：衰老心肌自噬障碍触发缺血心肌程序性坏死，p62蓄积促进RIP1/RIP3形成坏死复合物。本研究拟探讨自噬到程序性坏死的联动干预和调控新策略。

细胞生存与死亡是生命科学的基本问题。自噬（autophagy）和程序性坏死（Necroptosis）都是决定心肌细胞命运的重大生物学事件。我们的前期研究证实衰老心肌自噬功能减退和缺血易损性增加，加剧心肌细胞的死亡倾向，但是两者之间的联系机制有待阐明。此外，二甲双胍作为一种潜在的抗衰老相关损伤药物，其与心肌程序性坏死的相互作用机制尚不清楚。本研究以3 ~ 4月龄(成年)、22 ~ 24月龄(老年)的雄性C57BL/6小鼠和Ripk3敲除(RIP3 KO)小鼠为研究对象，通过离体实验和整体动物实验研究发现：衰老心肌缺血再灌注（I/R）中自噬流发生功能障碍，自噬底物蛋白p62大量堆积。p62可结合necroptosis关键蛋白RIP1与RIP3，促进RIP1-RIP3坏死复合体形成，并进一步促进RIP3与MLKL的磷酸化激活，造成I/R后心肌坏死加重，心肌缺血易损性增加。本研究发现了p62 蓄积促进RIP1/RIP3 形成坏死复合物的衰老心肌“Autophagy-Necroptosis机制”。进而发现，二甲双胍治疗可有效抑制p62-RIP1-RIP3复合体，并有效减轻I/R诱导的衰老心肌程序性坏死，最终改善衰老心肌I/R后收缩舒张功能，显著提高I/R衰老小鼠的生存率。本研究通过模式动物及机能研究探讨了心肌衰老与损伤之间的新机制，为衰老心肌自噬障碍触发缺血心肌程序性坏死提供了直接的分子生物学证据。本研究的相关成果可望实现从自噬到程序性坏死联动的心肌干预和调控新策略，并为阐明细胞衰老的共性机制及心血管系统退行性疾病的发生、发展进程提供新思考。