Inhibiting miR-155 protects against myocardial ischemia/reperfusion injury via targeted regulation of HIF-1α in rats

The aim of this study was to identify the role of miR-155 in the myocardial ischemia/reperfusion (I/R) injury through targeting hypoxia-inducible factor 1-alpha (HIF-1α). We constructed rat models with myocardial I/R injury and H9C2 cell models with hypoxia/reoxygenation (H/R) damage. Anti-miR-155 and HIF-1α short hairpin RNA (shRNA) were used to treat rats and H9C2 cells to measure infarct area (IA) by TTC staining, determine creatine kinase (CK) and lactate dehydrogenase (LDH) activities by automatic biochemical analyzer, cardiac troponin T (cTnT) and cardiac troponin I (cTnI) levels by ELISA, and detect apoptosis-related proteins by Western blotting. TUNEL staining and flowcytometry were employed to evaluate the apoptosis, JC-1 staining to detect mitochondrial membrane potential (MMP), and MTT assay to determine H9C2 cell viability. After I/R and H/R, significant elevations were observed in IA, apoptosis, CK, LDH, cTnT, cTnI, and miR-155 levels with reduced HIF-1α. Besides, H/R-induced H9C2 cells presented decreases in MMP and Bcl-2/Bax, but increases in cytosolic/mitochondrial ratio of cytochrome C (Cyt-C) and expressions of cleaved caspase-3 and cleaved caspase-9. However, both rats and H9C2 cells showed an opposite tendency concerning the above after anti-miR-155 treatment. Nevertheless, HIF-1α shRNA effectively reversed protective effects of anti-miR-155 on alleviating I/R- and H/R- induced injury. Inhibiting miR-155 could reduce myocardial infarct size, suppress I/R-induced cardiomyocyte apoptosis, and maintain the MMP to alleviate I/R-induced injury via specific regulation of HIF-1α.