Clonorchis sinensis ESPs enhance the activation of hepatic stellate cells by a cross-talk of TLR4 and TGF-β/Smads signaling pathway

Excretory/Secretory products (ESPs) from Clonorchis sinensis-a fluke dwelling on the biliary ducts-promote the activation of hepatic stellate cells (HSCs) and lead to hepatic fibrosis ultimately, although the mechanisms that are responsible for CsESPs-induced activation of HSCs are largely unknown. In the present study, we investigated the underlying mechanism of TLR4 in the regulation of the activation of HSCs caused by CsESPs. We found that the expression of TLR4 was significantly increased in the HSCs with CsESPs for 24 h, compared to the control group. However, the activation of HSCs induced by CsESPs was inhibited by interfering with TGF-β/Smad pathway using a TGF-β receptor I inhibitor LY2157299, indicating that TGF-β induced signaling pathway was involved in CsESPs-caused the activation of HSCs. In addition, the activation of HSCs caused by CsESPs was remarkably inhibited by a TLR4 specific inhibitor (VIPER), and phosphorylation of Smad2/3 was significantly attenuated but the expression of the pseudoreceptor of TGF-β-type I receptor (BAMBI) was obviously increased when TLR4 signaling pathway was blocked. The results of the present study demonstrate that activation of HSCs caused by CsESPs is mediated by a cross-talk between TLR4 and TGF-β/Smads signaling pathway, and may provide a potential treatment strategy to interrupt the process of liver fibrosis caused by C. sinensis.