microRNA-210 is upregulated in hypoxic cardiomyocytes through Akt- and p53-dependent pathways and exerts cytoprotective effects

Abstract

microRNA-210 (miR-210) is upregulated in hypoxia, but its function in cardiomyocytes and its regulation in response to hypoxia are not well characterized. The purpose of this study was to identify upstream regulators of miR-210, as well as to characterize miR-210's function in cardiomyocytes. We first showed miR-210 is upregulated through both hypoxia-inducible factor (HIF)-dependent and -independent pathways, since aryl hydrocarbon nuclear translocator (ARNT) knockout mouse embryonic fibroblasts (MEF), lacking intact HIF signaling, still displayed increased miR-210 levels in hypoxia. To determine the mechanism for HIF-independent regulation of miR-210, we focused on p53 and protein kinase B (Akt). Overexpression of p53 in wild-type MEFs induced miR-210, whereas p53 overexpression in ARNT knockout MEFs did not, suggesting p53 regulates miR-210 in a HIF-dependent mechanism. Akt inhibition reduced miR-210 induction by hypoxia, whereas Akt overexpression increased miR-210 levels in both wild-type and ARNT knockout MEFs, indicating Akt regulation of miR-210 is HIF-independent. We then studied the effects of miR-210 in cardiomyocytes. Overexpression of miR-210 reduced cell death in response to oxidative stress and reduced reactive oxygen species (ROS) production both at baseline and after treatment with antimycin A. Furthermore, downregulation of miR-210 increased ROS after hypoxia-reoxygenation. To determine a mechanism for the cytoprotective effects of miR-210, we focused on the predicted target, apoptosis-inducing factor, mitochondrion-associated 3 (AIFM3), known to induce cell death. Although miR-210 reduced AIFM3 levels, overexpression of AIFM3 in the presence of miR-210 overexpression did not reduce cellular viability either at baseline or after hydrogen peroxide treatment, suggesting AIFM3 does not mediate miR-210's cytoprotective effects. Furthermore, HIF-3α, a negative regulator of HIF signaling, is targeted by miR-210, but miR-210 does not modulate HIF activity. In conclusion, we demonstrate a novel role for p53 and Akt in regulating miR-210 and demonstrate that, in cardiomyocytes, miR-210 exerts cytoprotective effects, potentially by reducing mitochondrial ROS production.

MiR-1246: A new link of the p53 family with cancer and Down syndrome

“…6 These miRNAs have also been shown to play a role in controlling cell growth, apoptosis, senescence and autophagy in a p53-dependent fashion ( Table 1). [7][8][9][10][11][12][13][14][15][16][17][18][19][20] Recently, we identified miR-1246 as another novel p53 target miRNA. Interestingly, this miRNA regulates the expression of DYRK1A, a Down syndrome-associated kinase, 21 which inactivates a nuclear transcriptional factor called NFAT1C by phosphorylating it and preventing it from nuclear import.…”

Function and clinical potential of microRNAs in hepatocellular carcinoma

“…A direct target of miR210 in human HCC cells is apoptosis-inducing factor M3 (AIFM3), also referred to as AIF-like, as it is a gene homolog of AIF. AIFM3 is mainly present in mitochondria, resulting in cytochrome c release and apoptosis in a caspase-dependent manner (96,97). AIFM3 downregulation by small interfering RNA-impaired radiation-induced apoptosis in human HCC cells was associated with reduced miR210 expression.…”

RNAs that make a heart beat

“…Overexpression and loss-of function studies have revealed roles for individual miRNAs in heart disease (31,39,40). For example, miR-208 is expressed from the intron of myosin heavy chain 6 and is expressed specifically in cardiac and slow skeletal muscle (41).…”