MicroRNA-421 improves ischemia/reperfusion injury via regulation toll-like receptor 4 pathway

OBJECTIVES: The objective was to investigate the effects of microRNA-421 against myocardial ischemia/reperfusion injury in C57BL/6 mice. METHODS: Male C57BL/6 mice (n = 27) were randomly divided into three groups: normal control (NC) group (sham-treated); I/R model group, which underwent the I(30min)/R(24h) model (ischemia for 30 minutes followed by reperfusion for 24 hours); and the miRNA group, which were injected with miR-421. Pathology was assessed by hematoxylin and eosin staining and myocardial infarct size was measured by triphenyltetrazolium chloride staining. The apoptosis rate was measured by TUNEL assay, and relative expression of toll-like receptor-4 (TLR4), Janus kinase 2 (JAK2), and signal transducer and activator of translation 3 (STAT3) was evaluated by immunohistochemistry. Interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-10, and high mobility group protein B1 (HMGB1) serum concentrations were measured by ELISA. RESULTS: Compared with the NC group, in the model group, the myocardial infarction was large; inflammatory cell infiltration was severe; apoptosis was enhanced; expression of TLR4, JAK2, and STAT3 was increased; and serum concentrations of IL-6, TNF-α, IL-10, and HMGB1 were significantly increased. In the miRNA group, the ischemia/reperfusion injury was significantly improved. CONCLUSIONS: Overexpression of miRNA-421 could reduce ischemia/reperfusion inflammatory response, perhaps via inactivation of TLR4, JAK2, and STAT3.