Abstract: Objective To investigate the mechanism of miR-146a on the level of serum myocardial enzyme, Toll-like receptor 4 (TLR4) genes and apoptosis of myocardial cells in rats with myocardial ischemia-reperfusion injury (MI/RI). Methods Thirty-six rats were divided into sham operation group (sham), model group (model), miR-146a NC group (transfected with miR-146a-NC after ligation) and miR-146a agomir group (transfected with miR-146a-a agomir after ligation).Myocardial infarct size was measured by TTC staining, the mRNA expression of miR-146a/TLR4 in myocardial tissue was detected by RT-qPCR and cardiomyocyte apoptosis was microscopied by TUNEL staining.The activity of lactate dehydrogenase (LDH), troponin (cTnT) and creatine kinase isoenzyme (CK-MB) in serum was determined by colorimetry.TLR4 protein expression in myocardial tissue was detected by Western blot. Results Compared with sham operation group, the area of myocardial infarction (white) in model group was increased (P＜0.05). While the area of myocardial infarction (white) in miR-146a agomir group decreased (P＜0.05), and the mRNA expression of miR-146a in the model group was decreased (P＜0.05), the miR-146a mRNA expression was increased in miR-146a agomir group (P＜0.05);Compared with the sham operation group, the myocardial muscle fibers were broken and swollen, the interstitial hyperemia was obvious, the structure disappeared, and the boundary of multiple cell necroses was not clear.Compared with the model group, the myocardial tissues of miR-146a agomir group were neatly arranged, and pathology such as edema was improved, the activities of LDH, cTnT and CK-MB, the apoptosis rate of myocardial cells and the protein expressions of TLR4, tumor necrosis factor-α (TNF-α) and nuclear factor-κB (NF-κB) in serum of the model group were increased (P＜0.05).Compared with model group, the above indexes in miR-146a agomir group were decreased (P＜0.05). Conclusions The expression of miR-146a is low in the myocardial tissue of MI/RI, and over-expression can reduce the activity of serum myocardial enzyme spectrum and TLR4 expression, thereby reducing the apoptosis of cardiomyocytes and protecting the heart.

Key words: myocardial ischemia-reperfusion, myocardial enzyme spectrum, apoptosis, myocardial tissue