MiR-134-5p targeting XIAP modulates oxidative stress and apoptosis in cardiomyocytes under hypoxia/reperfusion-induced injury.

MicroRNA-134-5p (MiR-134-5p) has been proposed as a promising novel biomarker for the diagnosis of acute myocardial infarction (AMI). However, the biological role of miR-134-5p in ischemic cardiomyocytes has been little disclosed yet. Expression of miR-134-5p and X-linked inhibitor of apoptosis protein (XIAP) was detected using RT-qPCR and western blot. Oxidative stress and cell apoptosis were determined by enzyme-linked immunosorbent assays, 3-(4, 5-dimethylthiazole-2-y1)-2, 5-biphenyl tetrazolium bromide assay, flow cytometry, western blot, and terminal-deoxynucleoitidyl transferase-mediated nick end labeling (TUNEL). The interaction between miR-134-5p and XIAP was confirmed by luciferase reporter assay. Expression of miR-134-5p was upregulated in serum of AMI patients and hypoxia/reoxygenation (H/R)-induced cardiomyocytes (AC16 and HCM). MiR-134-5p downregulation could inhibit H/R-mediated release of lactic dehydrogenase enzyme (LDH) and malondialdehyde (MDA), and promote superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) levels. Meanwhile, cell viability was increased, while the apoptosis rate and TUNEL positive cells were inhibited by miR-134-5p downregulation in H/R-treated AC16 and HCM cells. Mechanically, XIAP was downregulated and targeted by miR-134-5p in H/R-induced cardiomyocytes in vitro. Overexpression of XIAP inhibited oxidative stress and cell apoptosis in H/R-treated AC16 and HCM cells, which was similar to miR-134-5p knockdown. Moreover, downregulation of XIAP could partially reverse the effect of miR-134-5p knockdown in H/R-induced cardiomyocytes. Knockdown of miR-134-5p protected cardiomyocytes from H/R-induced oxidative stress and apoptosis in vitro through targeting XIAP.