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

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.

Mitochondrial MiRNA in Cardiovascular Function and Disease

“…Bioinformatics analysis showed that mitochondria enriched miR-696, miR-532, miR-690, and miR-345-3p at the early stage of the failing heart, and these miRNAs were associated with energy metabolism and oxidative stress pathways [33]. More recently, in hypoxic/reoxygenated cardiomyocytes, miR-762, miR-744, miR-92a, miR-1892, miR-150, miR-669a, miR-296-3p, miR-711, and miR-450a-3p were found to translocate into the mitochondria, whereas miR-362-5p, miR-532-5p, miR-31, miR-139-5p, miR-330, and miR-379 were decreased in the mitochondria [47]. Among them, miR-762 was demonstrated to decrease intracellular ATP levels and to increase ROS levels in cardiomyocytes [47].…”

“…More recently, in hypoxic/reoxygenated cardiomyocytes, miR-762, miR-744, miR-92a, miR-1892, miR-150, miR-669a, miR-296-3p, miR-711, and miR-450a-3p were found to translocate into the mitochondria, whereas miR-362-5p, miR-532-5p, miR-31, miR-139-5p, miR-330, and miR-379 were decreased in the mitochondria [47]. Among them, miR-762 was demonstrated to decrease intracellular ATP levels and to increase ROS levels in cardiomyocytes [47]. Although other nuclear-encoded miRNAs may also regulate mitochondrial signaling and function [48], mitomiRs play a crucial role in post-transcriptional regulation of gene expression related to mitochondrial function (e.g., energetics and apoptosis).…”

“…MiR-1 has been demonstrated to regulate the mitochondrial electron transport chain (ETC) by targeting the mitochondrial gene cytochrome c oxidase subunit 1 (mt-COX1), and the mitochondrial gene NADH dehydrogenase subunit 1 (mt-ND1) in the ETC networks in the heart [44]. MiR-762 was recently found to largely translocate to the mitochondria and was markedly upregulated by hypoxia/reoxygenation in cardiomyocytes [47]; this directly decreased ND2 translation to decrease mitochondrial complex I enzyme activity, decrease intracellular ATP levels, increase ROS levels, and increase apoptosis in cardiomyocytes [47]. Also, knockdown of miR-762 attenuated myocardial ischemia/reperfusion injury in mice [47].…”

“…MiR-762 was recently found to largely translocate to the mitochondria and was markedly upregulated by hypoxia/reoxygenation in cardiomyocytes [47]; this directly decreased ND2 translation to decrease mitochondrial complex I enzyme activity, decrease intracellular ATP levels, increase ROS levels, and increase apoptosis in cardiomyocytes [47]. Also, knockdown of miR-762 attenuated myocardial ischemia/reperfusion injury in mice [47]. Mechanistically, we showed that enforced expression of miR-762 dramatically decreased the protein levels of endogenous ND2 but had no effect on the transcript levels of ND2.…”

Critical roles of microRNA-141-3p and CHD8 in hypoxia/reoxygenation-induced cardiomyocyte apoptosis

“…Increasing number of miRNAs, such as miR-25 and miR-762 modulate the expression of key molecular associated with apoptosis in myocardial I/R injury [37,38]. Previous studies have shown that miR-141-3p alters the expression of p53 as a reason of promoting glioblastoma progression and temozolomide resistance [16].…”