Background: Several studies have confirmed the role of microRNAs in regulating ischemia/reperfusion-induced cardiac injury (I/R-I). MiR-17-5p has been regarded as an oncomiR in the development of cancer. However, its potential role in cardiomyocytes has not been exploited. The aim of this study is to investigate the role of miR-17-5p in I/R-I and the underlying mechanism through targeting Stat3, a key surviving factor in cardiomyocytes.

Methods: MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide) assay was used to detect the cell viability. ELISA and TUNEL were performed to measure apoptosis of neonatal rat ventricular cardiomyocytes (NRVCs). Infarct area was estimated by TTC (triphenyltetrazolium chloride) and Evans blue staining. Western blot analysis was employed to detect the Stat3 and p-Stat3 levels and real-time RT-PCR was used to quantify miR-17-5p level.

Results: The miR-17-5p level was significantly up-regulated in I/R-I mice and in NRVCs under oxidative stress. Overexpression of miR-17-5p aggravated cardiomyocyte injury with reduced cell viability and enhanced apoptotic cell death induced by H2O2, whereas inhibition of miR-17-5p by its antisense AMO-17-5p abrogated the deleterious changes. Moreover, the locked nucleic acid-modified antisense (LNA-anti-miR-17-5p) markedly decreased the infarct area and apoptosis induced by I/R-I in mice. Furthermore, overexpression of miR-17-5p diminished the p-Stat3 level in response to H2O2. The results from Western blot analysis and luciferase reporter gene assay confirmed Stat3 as a target gene for miR-17-5p.

Conclusion: Upregulation of miR-17-5p promotes apoptosis induced by oxidative stress via targeting Stat3, accounting partially for I/R-I.