To investigate the effects of microRNA-29a (miR-29a) on myocardial ischemia-reperfusion (I/R) injury and its specific mechanisms, we used H9C2 myocardial cells to establish a myocardial ischemia model by hypoxia/reoxygenation (H/R), and microRNA-29a inhibitor was interfered. Annexin V/propidium iodide and flow cytometry were used to detect the effects of cell death. C57 mice were used to establish were used to establish the I/R injury model, and H&E staining was used to detect pathologic damage to heart tissues. The expressions of miR-29a silent information regulator factor 2-related enzyme 1 (SIRT1) and nucleotide-binding oligomerization domain like receptor protein 3 (NLRP3), as well as pyroptosis-related proteins were determined by quantitative reverse-transcription polymerase chain reaction and Western blot analysis. The serum levels of 2-hydroxybutyrate dehydrogenase (HBDH), lactate dehydrogenase-1 (LDH), creatine kinase (CK), creatine kinase MB activity (CK-MB), IMA, and inflammatory factors in I/R rats were significantly up-regulated. In the I/R group, the expression of miR-29a was significantly up-regulated while SIRT1 was remarkably down-regulated. Dual luciferase reporter assay showed SIRT1 was a direct target of miR-29a. Inhibition of miR-29a significantly up-regulated the expression of peroxisome proliferator-activated receptor gamma coactivator-1a/nuclear respiratory factor-2 and endothelial nitric oxide synthase while remarkably down-regulating levels of inducible nitric oxide synthase and malondialdehyde in I/R. The oxidative stress that was induced by I/R injury was also suppressed by inhibition of miR-29a. All these effects of miR-29a inhibition were reversed by small interfering SIRT1. The in vitro H/R results showed that NLRP3caspase-1-mediated pyroptosis was activated in H/R but was significantly inhibited by the inhibition of miR-29a. Inhibition of miR-29a improved myocardial I/R injury by targeting SIRT1 through suppressing oxidative stress and NLRP3-mediated pyroptosis. SIGNIFICANCE STATEMENTIn this study, we showed for the first time that miR-29a could improve myocardial I/R injury through inhibition of pyroptosis.

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Syringic acid (SA), a naturally occur-ring O‑methy-lated trihydroxybenzoic acid monomer extracted from Dendrobium nobile Lindl., has been demonstrated to attenuate renal ischemia‑reperfusion (I/R) injury. However, the role of SA in myocardial I/R injury is unclear. The present study aimed to clarify the cardioprotective effect of SA in myocardial I/R injury in vitro and explore the potential molecular mechanisms. In the present study, it was revealed that pretreatment with SA increased the viability and inhibited oxidant stress in H9c2 cardiomyocytes that had suffered hypoxia/reoxygenation (H/R). SA also markedly downregulated B‑cell lymphoma 2 (Bcl‑2) expression and inhibited the expression of Bcl‑2‑like protein 4 (Bax) and cleaved caspase‑3 in H9c2 cardiomyocytes induced by H/R. In addition, SA significantly alleviated H/R-induced the phosphorylation of p38 mitogen‑activated protein kinase (p38MAPK) and c‑Jun N‑terminal kinase (JNK) in H9c2 cardiomyocytes. In conclusion, the present study demonstrated that SA inhibits the apoptosis of H9c2 cardiomyocytes following H/R injury via reduced activation of the p38MAPK and JNK signaling pathways. The results support the therapeutic usage of SA in the treatment of myocardial infarction.