Center for Developmental Cardiology, Institute for Translational Medicine, College of Medicine, Qingdao University, 266021, Qingdao, China.
State Key Laboratory of Cardiovascular Disease, Heart Failure center, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences, Peking Union Medical College, 100037, Beijing, China.
Cell Death Dis. 2019 Jun 24;10(7):500. doi: 10.1038/s41419-019-1734-7.
Mitochondrial dysfunction plays a major role in the pathogenesis of cardiovascular diseases. MicroRNAs (miRNAs) are small RNAs that act as negative regulators of gene expression, but how miRNAs affect mitochondrial function in the heart is unclear. Using a miRNA microarray assay, we found that miR-762 predominantly translocated in the mitochondria and was significantly upregulated upon anoxia/reoxygenation (A/R) treatment. Knockdown of endogenous miR-762 significantly attenuated the decrease in intracellular ATP levels, the increase in ROS levels, the decrease in mitochondrial complex I enzyme activity and the increase in apoptotic cell death in cardiomyocytes, which was induced by A/R treatment. In addition, knockdown of miR-762 ameliorated myocardial ischemia/reperfusion (I/R) injury in mice. Mechanistically, we showed that enforced expression of miR-762 dramatically decreased the protein levels of endogenous NADH dehydrogenase subunit 2 (ND2) but had no effect on the transcript levels of ND2. The luciferase reporter assay showed that miR-762 bound to the coding sequence of ND2. In addition, knockdown of endogenous ND2 significantly decreased intracellular ATP levels, increased ROS levels, reduced mitochondrial complex I enzyme activity and increased apoptotic cell death in cardiomyocytes, which was induced by A/R treatment. Furthermore, we found that the inhibitory effect of miR-762 downregulation was attenuated by ND2 knockdown. Thus, our findings suggest that miR-762 participates in the regulation of mitochondrial function and cardiomyocyte apoptosis by ND2, a core assembly subunit of mitochondrial complex I. Our results revealed that mitochondrial miR-762, as a new player in mitochondrial dysfunction, may provide a new therapeutic target for myocardial infarction.
线粒体功能障碍在心血管疾病的发病机制中起着重要作用。microRNAs（miRNAs）是作为基因表达负调节剂的小 RNA，但 miRNAs 如何影响心脏中线粒体的功能尚不清楚。使用 miRNA 微阵列分析，我们发现 miR-762 主要在线粒体中转录，在缺氧/复氧（A/R）处理后显著上调。内源性 miR-762 的敲低显著减轻了 A/R 处理诱导的心肌细胞内 ATP 水平降低、ROS 水平升高、线粒体复合物 I 酶活性降低和细胞凋亡死亡增加。此外，miR-762 的敲低减轻了小鼠心肌缺血/再灌注（I/R）损伤。在机制上，我们表明强制表达 miR-762 显著降低了内源性 NADH 脱氢酶亚单位 2（ND2）的蛋白水平，但对 ND2 的转录水平没有影响。荧光素酶报告基因检测表明 miR-762 与 ND2 的编码序列结合。此外，内源性 ND2 的敲低显著降低了心肌细胞内 ATP 水平，增加了 ROS 水平，降低了线粒体复合物 I 酶活性，并增加了 A/R 处理诱导的细胞凋亡死亡。此外，我们发现 ND2 敲低减弱了 miR-762 下调的抑制作用。因此，我们的研究结果表明，miR-762 通过线粒体复合物 I 的核心组装亚基 ND2 参与调节线粒体功能和心肌细胞凋亡。我们的研究结果表明，作为线粒体功能障碍的新参与者，线粒体 miR-762 可能为心肌梗死提供新的治疗靶点。
