解偶联蛋白UCP3在缺血性心力衰竭进程中对线粒体自噬和融合分裂的作用及机制

Myocardial ischemia caused by coronary artery disease is the main cause that lead to heart failure. The disorder of dynamic balance among mitochondrial ATP critically contributes to the development of myocardial dysfunction and cell death. A growing body of research suggests that autophagy including mitophagy and mitochondrial dynamics play an essential role in mitochondrial quality control, but their exact functions and underlying mechanisms in ischemic heart failure remain largely unknown. Our study synergy with other research demonstrated that mitochondrial uncoupling protein 3 (UCP3) confer cardioprotective effects during ischemic heart failure, however its precise mechanisms remain largely unknown. Recently, we found that UCP3 expression was downregulated during ischemic stress and its overexpression reverses ischemia-induced loss of mitochondrial inner membrane potential and reactive ROS burst, resulting in the improvement of cardiomyocyte survival and postischemic cardiac performance. These protective effects are critically related to the interaction of UCP3 with the component, adenine nucleotide translocator (ANT) of mitochondrial permeability transition pore (mPTP), and partially related to the activation of PI3K/Akt pathway. In contrast, UCP3 knockdown has the opposite effects. Furthermore, UCP3 overexpression activates Parin/PINK1-mediated mitophagy, regulates abundance of key proteins related to mitochondrial fusion and fission, and reduces hypoxia- or myocardial infarction-induced cell death. We thus hypothesize that UCP3 may play an important beneficial role during the ischemic heart failure via regulating mitochondrial dynamics and mitophagy through affecting the mitochondrial membrane potential and ATP level. To test it, in the present study, we are going to i) determine the role of UCP3 during ischemic heart failure; ii) investigate the effect, molecular mechanisms, and impact of UCP3 on mitochondrial dynamics and mitophagy during ischemic heart failure; and iii) explore the strategy and methods targeting at the intervention of progression of ischemic heart failure by regulating UCP3-related mechanisms. The findings will provide the new insight into the importance and regulatory mechanisms of mitochondrial dynamics and mitophagy during ischemic heart failure and will provide laboratory data to help for the development of the new strategy against ischemic heart failure.

线粒体结构和功能紊乱是缺血性心力衰竭(心衰)细胞死亡和功能异常的重要因素，线粒体自噬和融合分裂在其进程中是双刃剑，但其确切作用和机制未明。线粒体解耦联蛋白UCP3具心肌保护作用，但在缺血性心衰中的重要性和机制不清。我们发现UCP3与心肌细胞mPTP组分结合；在心肌缺血时下调；而过表达逆转心肌缺血/复灌后线粒体膜电位异常、维持线粒体功能稳态，改善心功能和心梗面积；UCP3下调/敲除则反之；并发现过表达UCP3进一步升高缺氧及心梗后心肌细胞线粒体自噬、调节线粒体分裂融合蛋白表达，故推测UCP3可能通过调控线粒体自噬和融合分裂干预缺血性心衰进程。为验证此，本项目拟探讨1)UCP3在缺血性心衰进程中的作用；2)UCP3对缺血性心衰进程中线粒体自噬和融合分裂的作用、分子机制；3)调控UCP3干预心衰进程的方式。研究发现将揭示线粒体自噬和融合分裂在缺血性心衰中的作用、调控新机制和干预心衰的潜在靶点。

如何延缓和减轻心肌缺血导致的心力衰竭（心衰）进程、改善缺血/复灌后心功能对于降低心梗病人死亡率、提高其生活质量至关重要。线粒体作为心肌细胞重要的能量供给和分子信号调控中心，对其结构和功能的保护在缺血性心衰和压力负荷性心衰的干预中发挥至关重要的作用。线粒体自噬和融合分裂对维持线粒体正常功能至关重要，但具体的机制尚有待阐明。研究组前期工作发现线粒体解耦联蛋白3（Uncoupling protein 3, UCP3）具有心肌保护作用，但在缺血性心衰和压力负荷性心衰中的作用和机制不清。本项目主要研究发现：1）通过构建诱导型心肌特异性UCP3敲除和过表达小鼠，结合缺血性心衰和压力负荷性心衰模型，揭示了UCP3在缺血性心衰和压力负荷性心衰进程中发挥保护心肌作用； 2）揭示促进自噬小体清除和mTOR信号抑制对减轻心肌缺血/复灌损伤的重要性，丰富了对自噬及线粒体质量控制在缺血性和压力负荷心衰中的地位和调控机制的认识；并为解析UCP3的作用和机制提供了实验体系和理论支持；3）通过建立心肌缺血/复灌不同时程模型，我们发现线粒体分裂在复灌早期被激活进而引起线粒体自噬，而UCP3通过调控线粒体融合蛋白和线粒体自噬蛋白，进而促进心肌缺血/复灌后的线粒体分裂和线粒体自噬，维持线粒体正常功能并发挥心肌保护作用；4）筛选得到调控UCP3干预心衰进程的关键因子，并发现了新型抗心肌肥厚的天然化合物衍生物QF84139。以上研究发现进一步明确了UCP3在缺血性和压力负荷型心衰中的保护作用，揭示其调控线粒体自噬和融合分裂的分子机制，为发展心衰干预手段提供重要实验依据。