Effect of NLRC5 on activation and reversion of hepatic stellate cells by regulating the nuclear factor-κB signaling pathway

BACKGROUND The formation of liver fibrosis is mainly caused by the activation of hepatic stellate cells (HSCs) and the imbalance of extracellular matrix (ECM) production and degradation. The treatment of liver fibrosis mainly includes removing the cause, inhibiting the activation of HSCs, and inhibiting inflammation. NOD-like receptor (NLR) family, caspase activation and recruitment domain (CARD) domain containing 5/NOD27/CLR16.1 (NLRC5) is a highly conserved member of the NLR family and is involved in inflammation and immune responses by regulating various signaling pathways such as nuclear factor-kappa B (NF-kappa B) signaling. It has been found that NLRC5 plays an important role in liver fibrosis, but its specific effect and possible mechanism remain to be fully elucidated. AIM To investigate the role of NLRC5 in the activation and reversion of HSCs induced with transforming growth factor-beta (TGF-beta) and MDI, and to explore its relationship with liver fibrosis. METHODS A total of 24 male C57BL/6 mice were randomly divided into three groups, including normal, fibrosis, and recovery groups. Twenty-four hours after a liver fibrosis and spontaneous reversion model was established, the mice were sacrificed and pathological examination of liver tissue was performed to observe the degree of liver fibrosis in each group. LX-2 cells were cultured in vitro and treated with TGF-beta 1 and MDI. Real-time quantitative PCR (qPCR) and Western blot were used to analyze the expression levels of NLRC5, alpha-smooth muscle actin (alpha-SMA), and collagen type I alpha1 (Col1a1) in each group. The activity of NF-kappa B in each group of cells transfected with NLRC5-siRNA was detected. RESULTS Compared with the normal mice, the expression level of NLRC5 increased significantly (P < 0.01) in the fibrosis group, but decreased significantly in the recovery group (P < 0.01). In in vitro experiments, the content of NLRC5 was enhanced after TGF-beta 1 stimulation and decreased to a lower level when treated with MDI (P < 0.01). The expression of alpha-SMA and Col1a1 proteins and mRNAs in TGF-beta 1-mediated cells was suppressed by transfection with NLRC5-siRNA (P < 0.01). Western blot analysis showed that the expression of NF-kappa B p65 protein and phosphorylated I kappa B alpha (p-I kappa B alpha) was increased in the liver of mice in the fibrosis group but decreased in the recovery group (P < 0.01), and the protein level of nuclear p65 and p-I kappa B alpha was significantly increased after treatment with NLRC5-siRNA (P < 0.01). CONCLUSION NLRC5 may play a key role in the development and reversal of hepatic fibrosis through the NF-kappa B signaling pathway, and it is expected to be one of the clinical therapeutic targets.