NLRC5 silencing ameliorates cardiac fibrosis by inhibiting the TGF-β1/Smad3 signaling pathway

The proliferation of cardiac fibroblasts (CFs) and excessive deposition of extracellular matrix are the predominant pathological characteristics of cardiac fibrosis. As the largest member of the nucleotide-binding domain and leucine-rich repeat (NLR) family, NLRC5 has been shown to be pivotal in the development of hepatic fibrosis. However, whether NLRC5 is involved in the pathogenesis of cardiac fibrosis remains to be elucidated. The present study aimed to investigate the role of NLRC5 and its mechanisms in regulating cardiac fibrosis. CFs were stimulated with transforming growth factor (TGF)-beta 1 for various times and the mRNA and protein expression of NLRC5 was assessed using reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. In addition, CFs were transfected with small interfering (si) RNA targeting NLRC5 or scramble siRNA for 24 h and then stimulated with TGF-beta 1 for 24 h. Subsequently, cell proliferation was measured using an MTT assay, whereas cell migration was evaluated using a Transwell migration assay. The protein expression levels of a-smooth muscle actin, collagen I, connective tissue growth factor, phosphorylated-Smad3 and Smad3 were measured using western blot analysis. The results demonstrated that NLRC5 was upregulated in TGF-beta 1-induced CFs. The knockdown of NLRC5 significantly inhibited cell proliferation and migration, and suppressed myofibroblast differentiation and the expression of pro-fibrotic molecules in TGF-beta 1-treated CFs. Furthermore, the knockdown of NLRC5 attenuated TGF-beta 1-induced phosphorylation of small mothers against decapentaplegic (Smad) 3 in the CFs. The results of the present study indicated that NLRC5 acted as a key regulator of pathological cardiac fibrosis, and NLRC5 silencing ameliorated cardiac fibrosis by inhibiting the TGF-beta 1/Smad3 signaling pathway. These results suggested that NLRC5 may be a novel target for attenuating cardiac fibrosis.