Spironolactone Regulates HCN Protein Expression Through MiRNA-1 In Rats With Myocardial Infarction

Objective:Many studies have found that ventricular arrhythmias after myocardial infarction (MI) are closely related to abnormal hyperpolarization-activated cyclic nucleotide-gated channel (HCN) gene expression in the ventricular myocardium. Emerging evidence has shown that aldosterone blockers (ABs) reduced the incidence of ventricular arrhythmias in patients with MI. However, the mechanism remains unknown. In this study, we investigated the mechanism by which spironolactone regulates HCN protein expression in ischemic rat myocardium after MI, so as to provide a theoretical basis for the effect of ABs in the anti-ventricular arrhythmias treatment after MI.Methods:The MI model was established by ligation of the left anterior descending coronary artery of Sprague-Dawley rats. Eighteen rats surviving 24 h after MI were randomly assigned into three groups:MI, Spironolactone, and Spironolactone+Antagomir-1. Six Sham-operated rats had a suture loosely tied around the left coronary artery, without ligation. The border zone of the MI was collected from MI rats at 1 week after MI, and the corresponding myocardium was collected in sham-operated rats. HCN2, HCN4 mRNA and miRNA-1 levels were measured using qRT-PCR. HCN2 and HCN4 protein levels were measured using Western blot.Results:Spironolactone significantly increased miRNA-1 levels and down-regulated HCN2 and HCN4 protein and mRNA levels. miRNA-1 suppression with antagomir-1 increased HCN2 and HCN4 protein levels; however, HCN2 and HCN4 mRNA levels were not affected.Conclusion:Spironolactone could increase miRNA-1 expression in ischemic rat myocardium after MI and that the up-regulation of miRNA-1 expression partially contributed to the post-transcriptional repression of HCN protein expression. This may be the one of mechanisms of spironolactone reduce the incidence of MI-associated ventricular arrhythmias.