MiR-146a mediates TLR-4 signaling pathway to affect myocardial fibrosis in rat constrictive pericarditis model

BACKGROUND: Myocardial fibrosis (MF) is thought to be associated with constrictive pericarditis (CP). miR-146a has been reported to be related to the survival of myocardial fibroblasts and related signal transduction pathways. The aim of this study was to investigate the expression of miR-146a in CP with MF and the activation of the Toll-like receptor 4 (TLR-4) signaling pathway, to understand the molecular mechanism of MF involvement in CP. METHODS: Thirty rats with different disease duration were randomly divided into three groups: an 8-week model group (CP-8W group), a 16-week model group (CP-16W group) model, and a normal control group (N group). After the CP model was established in the rats, the myocardial tissues were collected. The expression of miR-146a, the key factors of TLR-4 signaling pathway, including IL-1 receptor-associated kinase 1 (IRAK1), tumor necrosis factor receptor-associated factor 6 (TRAF6), nuclear factor-κB (NF-κB) and p-NF-κB, and the MF indicator α-SMA in myocardial tissue were detected. After treatment with lipopolysaccharide (LPS), primary cultured rat cardiac fibroblasts (CFs) were transfected with miR-146a. RT-PCR and western blot were used to detect the expression of downstream effectors to further verify the function of miRNA-146a in regulating MF via the TLR-4 signaling pathway. RESULTS: miR-146a was increased in the CP-8W group but not in the CP-16W group. IRAK1 and TRAF6 in the CP-16W group were found to be higher than in the N group and CP-8W group. α-SMA in the model groups was higher than in the N group. Compared with the CP-8W group, α-SMA in the CP-16W model group was further increased. In the experiments using CFs, the expression of IRAK1, TRAF6, p-NF-κB and α-SMA increased in the LPS-treated group compared with the N group. After transfection of CFs with the miR-146a mimics, the expression of IRAK1, TRAF6, p-NF-κB and α-SMA decreased compared with the LPS-treated group. Following transfection of CFs with miR-146a inhibitors, the expression of IRAK1, TRAF6, p-NF-κB and α-SMA increased compared with the LPS-treated group. CONCLUSIONS: The expression of miR-146a demonstrated a dynamic change in the CP model; it was increased at the early time point (CP-8W) and then decreased at the 16W time point. miR-146a suppressed MF by inhibiting the target genes TRAF6 and IRAK1 via the TLR-4 signaling pathway.