Synergistic effect of pro-inflammatory TNFα and IL-17 in periostin mediated collagen deposition: Potential role in liver fibrosis

Background: The pro-inflammatory cytokines, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-17, have been implicated in the pathogenesis of liver fibrosis. In this study, we investigated the role of TNF alpha and IL-17 toward induction of profibrotic factor, periostin. Methods: HepG2 cells were cultured and treated with inflammatory cytokines, TNFa and IL-17. Computational promoter sequence analysis of the periostin promoter was performed to define the putative binding sites for transcription factors. Transcription factors were analyzed by Western blot and Chromatin Immunoprecipitation. Periostin and transcription factor expression analysis was performed by RT-PCR, Western blot, and fluorescence microscopy. Type I collagen expression from fibroblast cultures was analyzed by Western blot and Sircol soluble collagen assay. Results: Activation of HepG2 Cells with TNF alpha and IL-17 enhanced-the expression of periostin (3.5 and 4.4 fold, respectively p<0.05) compared to untreated cells. However, combined treatment with both TNF alpha and IL-17 at similar concentration demonstrated a 13.3 fold increase in periostin (p < 0.01), thus suggesting a synergistic role of these cytokines. Periostin promoter analysis and specific siRNA knock-down revealed that TNFa induces periostin through cJun, while IL-17 induced periostin via STAT-3 signaling mechanisms. Treatment of the supernatant from the cytokine activated HepG2 cells on fibroblast cultures induced enhanced expression of type I collagen (>9.1 fold, p < 0.01), indicative of a direct fibrogenic effect of TNF alpha and IL-17. Conclusion: TNF alpha and IL-17 induced fibrogenesis through dun and STAT-3 mediated expression of profibrotic biomarker, periostin. Therefore, periostin might serve as a novel biomarker in early diagnosis of liver fibrosis. (C) 2014 Elsevier Ltd. All rights reserved.