Department of Second Gastroenterology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, Henan Province, China.
World J Gastroenterol. 2019 Jun 28;25(24):3044-3055. doi: 10.3748/wjg.v25.i24.3044.
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-κB (NF-κB) 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.
To investigate the role of NLRC5 in the activation and reversion of HSCs induced with transforming growth factor-β (TGF-β) and MDI, and to explore its relationship with liver fibrosis.
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 and treated with TGF-β1 and MDI. Real-time quantitative PCR (qPCR) and Western blot were used to analyze the expression levels of NLRC5, α-smooth muscle actin (α-SMA), and collagen type I alpha1 (Col1a1) in each group. The activity of NF-κB in each group of cells transfected with NLRC5-siRNA was detected.
Compared with the normal mice, the expression level of NLRC5 increased significantly ( < 0.01) in the fibrosis group, but decreased significantly in the recovery group ( < 0.01). In experiments, the content of NLRC5 was enhanced after TGF-β1 stimulation and decreased to a lower level when treated with MDI ( < 0.01). The expression of α-SMA and Col1a1 proteins and mRNAs in TGF-β1-mediated cells was suppressed by transfection with NLRC5-siRNA ( < 0.01). Western blot analysis showed that the expression of NF-κB p65 protein and phosphorylated IκBα (p-IκBα) was increased in the liver of mice in the fibrosis group but decreased in the recovery group ( < 0.01), and the protein level of nuclear p65 and p-IκBα was significantly increased after treatment with NLRC5-siRNA ( < 0.01).
NLRC5 may play a key role in the development and reversal of hepatic fibrosis through the NF-κB signaling pathway, and it is expected to be one of the clinical therapeutic targets.
肝纤维化的形成主要是由肝星状细胞（HSCs）的激活和细胞外基质（ECM）产生和降解的失衡引起的。肝纤维化的治疗主要包括去除病因、抑制 HSCs 的激活和抑制炎症。NOD 样受体（NLR）家族、半胱氨酸天冬氨酸蛋白酶激活和募集结构域（CARD）结构域包含 5/NOD27/CLR16.1（NLRC5）是 NLR 家族的一个高度保守成员，通过调节核因子-κB（NF-κB）信号等各种信号通路参与炎症和免疫反应。已经发现 NLRC5 在肝纤维化中起着重要作用，但它的具体作用和可能的机制仍有待充分阐明。
研究 NLRC5 在转化生长因子-β（TGF-β）和 MDI 诱导的 HSCs 激活和逆转中的作用，并探讨其与肝纤维化的关系。
将 24 只雄性 C57BL/6 小鼠随机分为正常、纤维化和恢复三组。在建立肝纤维化和自发性逆转模型 24 小时后，处死小鼠并进行肝组织病理学检查，观察各组肝纤维化程度。培养 LX-2 细胞并给予 TGF-β1 和 MDI 处理。实时定量 PCR（qPCR）和 Western blot 用于分析各组 NLRC5、α-平滑肌肌动蛋白（α-SMA）和胶原 I 型α1（Col1a1）的表达水平。检测各组转染 NLRC5-siRNA 后 NF-κB 的活性。
与正常小鼠相比，纤维化组 NLRC5 的表达水平显著升高（<0.01），但在恢复组显著降低（<0.01）。在实验中，TGF-β1 刺激后 NLRC5 的含量增加，用 MDI 处理后降低到较低水平（<0.01）。NLRC5-siRNA 转染后 TGF-β1 介导的细胞中 α-SMA 和 Col1a1 蛋白和 mRNA 的表达受到抑制（<0.01）。Western blot 分析表明，纤维化组小鼠肝组织中 NF-κB p65 蛋白和磷酸化 IκBα（p-IκBα）的表达增加，但在恢复组中降低（<0.01），用 NLRC5-siRNA 处理后核 p65 和 p-IκBα 的蛋白水平显著增加（<0.01）。
NLRC5 可能通过 NF-κB 信号通路在肝纤维化的发生和逆转中发挥关键作用，有望成为临床治疗靶点之一。
