The convergence of fibrosis and immune pathways: 5-HT2 and 5-HT2B antagonists attenuate profibrotic phenotype in human pancreatic stellate cells by modulating signal transducer and activator of transcription 3 phosphorylation

Abstract

Background: Immune mechanisms are believed to play an important role in the pathogenesis of pancreatic inflammation and fibrosis. Transforming growth factor β1-mediated mechanisms are well known; however, an effective treatment option is yet not available. Serotonin (5-HT) is known to induce fibrosis in carcinoid tumors and diseases such as scleroderma and blocking 5-HT has shown promise in the attenuation of fibrosis in animal models of scleroderma. Herein, we evaluated the role of 5-HT in pancreatic fibrosis and its reversal with antagonists of 5-HT. Methodology: Pancreatic stellate cells (PSCs) were cultured from the two patients of pancreatic cancer undergoing pancreaticoduodenectomy. PSCs were cultured in the presence of 5-HT and as per the disease mimicking strategy (PSCs cultured with 5-HT first followed by 5-HT antagonist (terguride) and 5-HT2Bantagonist (SB204741) for 24 h and pretreatment strategy, PSCs treated with 5-HT antagonists first followed by 5-HT. mRNA expression of profibrotic genes (col1A1, Col1A2, ACTA-2, and CTGF) and Western blot analysis of signal transducer and activator of transcription 3 (STAT-3) and Smad-3 proteins was carried out. Results: 5-HT-induced profibrotic genes mRNA expression in PSCs was significantly reversed by 5-HT antagonists, terguride and SB204741, to a large extent. Pretreatment strategy was more effective in the amelioration of profibrotic potential. SB204741, 5-HT2Bantagonist was more effective than terguride. 5-HT antagonists mediated their effect by reducing the phosphorylation of noncanonical pathway mediator pSTAT3 more significantly then canonical pathway mediator pSmad-3. Conclusion: 5-HT induces profibrotic potential in human PSCs and inhibitors of 5-HT receptors, Terguride and SB 204,741 ameliorate it by reducing the phosphorylation of STAT-3 and Smad-3, more so in pretreatment strategy. 5-HT inhibitors may have a potential to ameliorate fibrosis in pancreas.