Mitochondrial miR-762 regulates apoptosis and myocardial infarction by impairing ND2

Kaowen Yan,Mei Zhai,Jian Zhang,Yan Huang,Rongcheng Zhang,Jing Liu,Kun Wang,Tao Wang,Yuhui Zhang,Qi Wang,Tao An,Yunhong Wang

doi:10.1038/s41419-019-1734-7

Abstract

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.

Highlights

Cardiovascular diseases are considered the main causes of human mortality worldwide[1]
MiR-762 predominantly translocates into the mitochondria and is upregulated upon A/R treatment Myocardial apoptosis mediated by mitochondrial dysfunction is an important mechanism for the initiation and progression of heart failure[15]
Since miR-762 is located on chromosome 7, to confirm whether translocation of miR-762 into the mitochondria was mediated by Ago[2], RNA immunoprecipitation (RIP) experiment with Ago[2] was performed in cardiomyocytes (Fig. 1e)

Summary

Introduction

Cardiovascular diseases are considered the main causes of human mortality worldwide[1]. Mitochondrial-based disturbances in energy supply, calcium homeostasis, reactive oxygen species generation and cell death have. The human mitochondrial DNA (mtDNA) consists of a circular molecule of 16,569 bp encoding 13 proteins, which is required for oxidative phosphorylation (OXPHOS)[3,4]. The OXPHOS system contains five multiple subunit enzyme complexes, including complexes I, II, III, IV, and V, and one or more of the core subunits for the NADH-ubiquinone oxidoreductase (Complex I) is encoded by mtDNA, such as the mitochondrial NADH dehydrogenase subunit 2 (ND2) protein, which is a core assembly subunit of the mitochondrial respiratory chain. Yan et al Cell Death and Disease (2019)10:500 complex I and is essential for catalyzing NADH dehydrogenation and electron transfer to ubiquinone to produce ATP5. The molecular mechanism of ND2 in myocardial infarction remains to be fully elucidated

Methods

Results

Conclusion