Overexpression of miR‐503‐5p exacerbates hypoxia/reoxygenation injury in H9C2 cardiomyocytes

Abstract

Acute myocardial infarction (MI) is a leading cause of death worldwide, and the most effective therapy for reducing acute myocardial ischemic injury is myocardial reperfusion, while reperfusion itself can lead to further cardiomyocyte death, called ischemia/reperfusion injury (IRI). A number of microRNAs have been shown to be involved in IRI, however, the role of miR‐503‐5p, which is implicated in cancers, diabetes mellitus or pulmonary arterial hypertension, remains unknown in myocardial IRI. This study was aimed to investigate the effects of miR‐503‐5p in myocardial IRI. Cardiac miR‐503‐5p expression was measured in mice subjected to myocardial IRI achieved by occlusion of left anterior descending artery for 30 minutes followed by reperfusion for 2 hours. H9C2 cardiomyocytes hypoxia/reoxygenation (H/R) was achieved by exposing the cells to glucose deprivation and hypoxia for 10 hours followed by reoxygenation 6 hours. We found that cardiac miR‐503 expression level was down‐regulated after induction of IRI compared with control, and it was also down‐regulated in H9C2 cells after exposure to H/R. In vitro, cell viability was decreased after H/R treatment, and lactate dehydrogenase (LDH) activity was increased. Administration of an agomir designed to overexpress miR503‐5p in cells before inducing H/R further reduced cell viability and elevated LDH activity. Moreover, proapoptotic Bax protein showed no significant change after overexpression of miR‐503‐5p in both normal and H/R states, while anti‐apoptotic Bcl protein decreased significantly. We analyzed putative miR‐503 targets using the TargetScan software, and found that the phosphoinositide‐3‐kinase regulatory subunit 1(PI3K p85) was one of the target genes. After overexpression of miR‐503‐5p, we found that PI3K p85 was decreased in both normal and H/R states. In addition, Akt1 and Akt2 as well as Phospho‐Akt were decreased in H/R state, and were further decreased after miR‐503‐5p overexpressed. Furthermore, we also found that prosurvival protein phosphorylation of signal transducer and activator of transcription (STAT3) was decreased after exposure to H/R, and declined further after overexpression of miR‐503‐5p. It is concluded that miR‐503‐5p regulates H9C2 cardiomyocyte injury during H/R, and exacerbates cell injury by inhibiting the activation of prosurvival protein Akt and STAT3.Support or Funding InformationSupported by Hong Kong RGC(17158616 M) and HMRF (05161826)grants.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.