miR-135a Mediates Mitochondrial Oxidative Respiratory Function through SIRT1 to Regulate Atrial Fibrosis

This study aimed to explore the function of miR-135a in the progress of atrial fibrosis, and the mechanism of miR-135a/SIRT1(Sirtuin 1,SIRT1) in human cardiac fibroblasts and mouse cardiac fibroblasts mediating the regulation of atrial fibrosis by mitochondrial oxidative respiration function.Using Ang II(Angiotensin II,Ang II) to induce fibrosis in HCFs(humancornealfibroblasts,HCFs) and MCF(Michigan Cancer Foundation, MCF ) cells in vitro, the miRNA-seq sequencing results of previous studies were validated. Proliferative and invasive ability of HCFs and MCFs were detected by Cell counting kit-8 assay (CCK-8) and scratch experiment after over-expressing miR-135a in HCFs and MCF cells. Protein and mRNA expression were tested using western blot and qPCR. The target of miR-135a was verified as SIRT1 by a luciferase reporter assay and the activities of the mitochondrial respiratory enzyme complexes I, II, III, and IV were determined colorimetrically. The activities of malondialdehyde (MDA), reactive oxygen species (ROS) and superoxide dismutase (SOD) in cells were detected with enzyme linked immunosorbent assay(ELISA).miR-135a expression was elevated in HCFs and MCFs cells in the Ang II group than control group. Overexpression of miR-135a could promote the proliferation, migration, oxidative stress, as well as fibrosis of cardiac fibroblasts, and suppresses mitochondrial activity. In addition, we found SIRT1 was a target gene of miR-135a. What's more, the findings showed miR-135a promoted fibrosis in HCFs and MCFs cells acting through regulation of SIRT1.miR-135a mediate mitochondrial oxidative respiratory function through SIRT1 to regulate atrial fibrosis.