MicroRNA­221­3p contributes to cardiomyocyte injury in H2O2­treated H9c2 cells and a rat model of myocardial ischemia­reperfusion by targeting p57.

ABSTRACT

Myocardial ischemia­reperfusion (I/R) injury is a major cause of cardiovascular disease worldwide, and microRNAs have been implicated in the regulation of pathological and physiological processes in myocardial I/R injury. The present study aimed to investigate the role of microRNA (miR)­221­3p in myocardial I/R injury. Cell death and lactate dehydrogenase (LDH) activity were increased in hydrogen peroxide (H2O2)­treated H9c2 cells, as measured by flow cytometry and an LDH detection kit. The expression of miR­221­3p was elevated in H2O2­incubated cells and in remote areas of the rat I/R model, examined using reverse transcription­quantitative polymerase chain reaction analysis. The overexpression of miR­221­3p enhanced the number of propidium iodide (PI)+ cells and the activity of LDH in H2O2­treated cells. In I/R­induced rats, the overexpression of miR­221­3p promoted the number of myosin+ cells and inhibited the fractional shortening of left ventricular diameter (FSLVD%). The results showed that the expression of p57 at the gene and protein levels was decreased in H9c2 cells incubated with H2O2 and in rats subjected to I/R surgery; the expression of p57 decreased following the overexpression of miR­221­3p. Subsequently, the hypothesis that p57 was the direct target of miR­221­3p was confirmed by performing a dual­luciferase reporter assay. Finally, to examine the function of p57 in myocardial impairment, p57 was transfected into H9c2 cells and administered to the rats prior to undergoing H2O2 treatment and I/R surgery, respectively. The results indicated that p57 attenuated the number of PI+ cells and the activity of LDH in H2O2­treated cells, whereas p57 downregulated the number of myosin+ cells and upregulated FSLVD% in the I/R­treated rats. Therefore, these findings suggested that miR­221­3p exacerbated the H2O2­induced myocardial damage in H9c2 cells and myocardial I/R injury in the rat model by modulating p57.