Objective To explore the effect and mechanism of microRNA (miR)-155-5p on myocardial pyroptosis in rats with myocardial ischemia-reperfusion injury (IRI).

Methods Sixty SD rats were randomly divided into sham group, IRI group, agomir-NC group, miR-155-5p agomir group, antagomir-NC group, and miR-155-5p antagomir group, with 10 rats in each group. Echocardiography was used to measure the left ventricular enddiastolic diameter (LVEDD), left ventricular endsystolic diameter (LVESD), left ventricular ejection fraction (LVEF), and left ventricular fractional shortening (LVFS) of rats. Enzyme-linked immune absorbent assay (ELISA) was used to detect the levels of creatine kinase isoenzyme (CK-MB), lactate dehydrogenase (LDH), and cardiac troponin T (cTnT) in serum, as well as the levels of interleukin (IL)-1β, IL-6, IL-18, and tumor necrosis factor (TNF)-α in myocardial tissue of rats. Hematoxylin-eosin staining was used to observe pathological changes in rat myocardial tissue. Real-time fluorescent quantitative polymerase chain reaction was used to detect the expression levels of miR-155-5p and silent information regulator 1 (SIRT1) messenger RNA (mRNA) in myocardial tissue of rats. Dual-luciferase reporter gene assay was used to verify the targeting relationship between miR-155-5p and SIRT1. Western blot was used to detect the expression levels of SIRT1, NOD-like receptor protein 3 (NLRP3), cleaved-cysteine aspartate specific protease-1 (Cleaved-Caspase-1), and gasdermin D (GSDMD) proteins in myocardial tissue of rats.

Results Compared with the sham group, the LVEDD and LVESD of rats in the IRI group were increased, LVEF and LVFS were decreased, serum levels of CK-MB, LDH, and cTnT were increased, IL-1β, IL-6, IL-18 and TNF-α levels in myocardial tissue were increased, myocardial tissue structure was severely damaged, myocardial fibers were disordered, relative expression of miR-155-5p, NLRP3, Cleaved-Caspase-1, and GSDMD proteins were increased, and the relative expression of SIRT1 protein was decreased (all P<0.05/5). Compared with the IRI group, the rats in the miR-155-5p agomir group had increased LVEDD and LVESD, decreased LVEF and LVFS, increased serum levels of CK-MB, LDH, and cTnT, increased myocardial tissue levels of IL-1β, IL-6, IL-18, TNF-α, aggravated myocardial tissue lesions, increased relative expression of miR-155-5p, NLRP3, Cleaved-Caspase-1, and GSDMD proteins, and decreased relative expression of SIRT1 protein, and the rats in the miR-155-5p antagomir group had decreased LVEDD and LVESD, increased LVEF and LVFS, decreased serum levels of CK-MB, LDH, and cTnT, decreased myocardial tissue levels of IL-1β, IL-6, IL-18, TNF-α, reduced myocardial tissue lesions, decreased relative expression of miR-155-5p, NLRP3, Cleaved-Caspase-1, and GSDMD proteins, and increased relative expression of SIRT1 protein (all P<0.05/5). miR-155-5p was negatively correlated with the expression levels of SIRT1 in rat myocardial tissue, and SIRT1 was a target gene of miR-155-5p.

Conclusions miR-155-5p may participate in the regulation of myocardial IRI in rats by targeting the downregulation of SIRT1 and promoting NLRP3-mediated myocardial pyroptosis.