TWEAK/Fn14 promotes pro-inflammatory cytokine secretion in hepatic stellate cells via NF-κB/STAT3 pathways
Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor fibroblast growth factor-inducible 14 (Fn14) have been associated with liver disease. Hepatic stellate cells (HSCs) play a critical role in the hepatic wound-healing response after liver injury, but there is little information available on the role of the TWEAK/Fn14 pathway in human HSCs. In this study, we explored the role of TWEAK/Fn14 in activated human HSCs. The LX-2 cells were treated with TWEAK, and the expression of pro-inflammatory cytokines was assayed by enzyme-linked immunosorbent assay (ELISA) and real-time PCR (RT-PCR). Western blotting and RT-PCR were performed to evaluate the expression of Fn14 after TWEAK stimulation. Total and phosphorylated of inhibitor-κB (I-κB), nuclear factor kappa B (NF-κB), Janus kinase 2 (JAK2), and signal transducers and activators of transcription 3 (STAT3) were examined by western blotting after TWEAK stimulation and small interfering RNA (siRNA) transfection. The result showed that TWEAK upregulated the expression of Fn14 and pro-inflammatory factors interleukin-8 (IL-8), interleukin-6 (IL-6), regulated upon activation normal T cell expressed and secreted (RANTES), and monocyte chemotactic protein-1 (MCP-1). In LX-2 cells, the pro-inflammatory cytokine secretion was closely related to the activation of the NF-κB and STAT3 pathways. Furthermore, our research showed that STAT3 and NF-κB could interact with each other, which resulted in a significant increase of pro-inflammatory cytokine secretion. The activation of NF-κB and STAT3 signalling-dependent pro-inflammatory cytokine expression may be responsible for such a novel principle and new therapeutic targets in chronic liver disease.