miR-202-5p protects rat against myocardial ischemia reperfusion injury by downregulating the expression of Trpv2 to attenuate the Ca 2+ overload in cardiomyocytes.

BACKGROUND: This study was aimed to unveil micro RNA (miRNA) expression profiles in myocardial ischemia-reperfusion (MI/R) rats and explore whether and how dysregulated miRNAs were involved in the initiation and progression of MI/R in a calcium-dependent manner. METHOD AND RESULTS: Rat model of MI/R was established and cardiomyocytes isolated from neonatal rats cardiomyocytes were induced. Both miRNA and messenger RNA expression profiles were analyzed by Microarray. Quantitative reverse-transcription polymerase chain reaction, immunoblotting, bioinformatics analysis, dual-luciferase reporter gene assay, hematoxylin and eosin, Evans blue, and triphenyl tetrazolium chloride were also used in this study. Serum concentrations of myocardial enzymes (phosphocreatine kinase [CK], creatine kinase [CK-MB], lactate dehydrogenase [LDH]), cardiomyocytes loadage of Ca2+ , as well as the expression level of inositol 1,4,5-trisphosphate receptors (IP3R) and sarcoplasmic reticulum Ca2+ -ATPase 2a (SERCA2a) were measured, respectively. Effects of upregulation or downregulation of miR-202-5p or Trpv2 on these indicators were investigated in vivo and in vitro. In MI/R rats and hypoxia/reoxygenation-induced NCMs, miR-202-5p was downregulated, while Trpv2 was upregulated. Trpv2 was a promising target of miR-202-5p and negatively regulated by miR-202-5p. Upregulation of miR-202-5p or downregulation of Trpv2 significantly reduced the serum concentration of myocardial enzymes, as well as cardiomyocyte-produced reactive oxygen species, but inhibition of miR-202-5p or overexpression of Trpv2 brought the worsening situation for these indicators. Besides, upregulation of miR-202-5p upregulation or downregulation of Trpv2 also inhibited Ca2+ overload in cardiomyocytes, accompanied with the increase of SERCA2a and suppression of IP3R. The reduced damage degree and infarct size in myocardial tissue were contrarily worsened by miR-202-5p inhibitor. CONCLUSION: Overexpression of miR-202-5p or downregulation of its downstream Trpv2 presented the cardioprotective effects to MI/R rats.