Inhibition of microRNA-346 inhibits myocardial inflammation and apoptosis after myocardial infarction via targeting NFIB.

Abstract

Acute myocardial infarction (AMI) is a sudden cardiovascular event that endangers human life. MicroRNA is considered to be an important participant in the pathophysiology of myocardial infarction (MI). This article aim was to study the function and mechanisms of microRNA-346 (miR-346) on myocardium after MI. To study the role of miR-346 in MI, we established H2O2-induced H9c2 cell injury model and rat MI model. Real-time polymerase chain reaction (RT-PCR) was used to detect miR-346 expression. Western blot was utilized to measure the expression of Bcl-2, Bax, TNF-α, IL-6 and NFIB. Apoptosis of H9c2 cells was detected by TUNEL staining and flow cytometry. Enzyme-linked immunosorbent assay (ELISA) assay was utilized to measure the levels of TNF-α and IL-6 in supernatant. Assessment of left ventricular function in rats was performed using echocardiography. MiR-346 was significantly upregulated in H2O2-treated H9c2 cells and ischemic myocardium. In the H9c2 cell injury model, the expressions of Bax, TNF-α, and IL-6 were greatly increased while Bcl-2 expression was decreased, and the number of TUNEL-positive cells and apoptosis rate were also significantly increased. At the same time, the levels of TNF-α and IL-6 in the cell supernatant were markedly increased. However, after miR-346 expression was suppressed, these results were reversed. The expression of Bcl-2 increased, while the expression of Bax, TNF-α, and IL-6 decreased. The contents of TNF-α and IL-6 in the cell supernatant also decreased significantly. Both the number of TUNEL-positive cells and the apoptosis rate were markedly reduced. After injecting antagomir-346 into the myocardium of rats to silence miR-346, the cardiac function of MI rats was remarkably improved, and the LDH content in the serum of rats also decreased significantly. Using computational predictions tools, Western blotting and Luciferase activity assay, we found that nuclear factor I/B (NFIB) was targeted by miR-346. The expression of miR-346 was increased in H9c2 cells and ischemic myocardium of MI rats. Silencing miR-346 can significantly inhibit the inflammatory response and the apoptosis of cardiomyocytes by targeting NFIB.