Effects Of MiR-17-5p On Cardiac Ischemia/Reperfusion Injury And The Underlying Mechanism In Mice

Background and PurposeMicroRNA-17-5p（miR-17-5p）has been demonstrated to play criticial roles in the development of mutiple cancers.However,its potential role in cardiomyocyte injury has not been exploited.The aim of this study is to investigate the role of miR-17-5p in ischemia/reperfusion injury（I/R-I）of mouse and the underlying mechanism.MethodsThe mouse model of myocardial I/R-I was established by ligating the left anterior descending artery for 30 min,followed by 24 h of reperfusion.Primary neonatal rat ventricular myocytes（NRVCs）were used to establish the cellular model of oxidative stress by H₂O₂.Cardiac infarct area was measured by 2,3,5-triphenyl-2H-tetrazolium chloride（TTC）and evans blue staining.The cell viability was evaluated by 3-（4,5）-dimethylthiahiazo（-z-y1）-3,5-di-phenytetrazoliumromide（MTT）assay.Terminal deoxynucleotidyl transferase-mediated d UTP nick end labeling（TUNEL）and enzyme-linked immunosorbent assay（ELISA）were performed to measure cardiomyocytes apoptosis.Western blot analysis was employed to detect the STAT3 and p-STAT3 levels and quantitative real-time PCR（q RT-PCR）was used to quantify miR-17-5p level.Luciferase reporter assay was performed to confirm the interaction between miR-17-5p and STAT3.ResultsMiR-17-5p was significantly upregulated and STAT3 downregulated in mouse cardiac tissue after cardiac I/R.Administration of LNA-17-5p through tail vein significantly reduced cardiomyocytes apoptosis and infarct area,improved cardiac injury in I/R mice,which was associated with donwnregulation of miR-17-5p.The cardiomyocytes that survived from apoptotic insults induced by H₂O₂ had markedly higher level of miR-17-5p and lower level of STAT3.Application of miR-17-5p alone to NRVCs failed to affect cell viability.But this maneuver remarkably aggravated the apoptosis induced by H₂O₂.Application of the anti-miRNA oligonucleotide（AMO）to miR-17-5p（AMO-17-5p）was able to reverse H₂O₂ induced cardiomyocyte apoptosis.Transfection of miR-17-5p alone to NRVCs significantly inhibited expression of STAT3,which was abrogated by co-transfection of AMO-17-5p.The reduced luciferase reporter activity by transfection of miR-17-5p demonstrated that STAT3 was a direct target of miR-17-5p.Moreover,the level of p-STAT3 was significantly reduced by transfection of miR-17-5p in the presence of H₂O₂,indicating p-STAT3 involved in the regulation of miR-17-5p on myocardial I/R-I.ConclusionsUpregulation of miR-17-5p promotes apoptosis induced by myocardial I/R-I via targeting STAT3,accounting partially for I/R-I.LNA-17-5p exerts anti-apoptotic action by inhibiting expression of miR-17-5p.Thus,miR-17-5p may become a new therapeutic target for cardiac I/R-I.