Autocrine loop between TGF-β1 and IL-1β through Smad3- and ERK-dependent pathways in rat pancreatic stellate cells

Pancreatic stellate cells ( PSCs) are activated during pancreatitis and promote pancreatic fibrosis by producing and secreting ECMs such as collagen and fibronectin. IL-1 beta has been assumed to participate in pancreatic fibrosis by activating PSCs. Activated PSCs secrete various cytokines that regulate PSC function. In this study, we have examined IL-1 beta secretion from culture-activated PSCs as well as its regulatory mechanism. RT-PCR and ELISA have demonstrated that PSCs express IL-1 beta mRNA and secrete IL-1 beta peptide. Inhibition of TGF-beta(1) activity secreted from PSCs by TGF-beta(1)-neutralizing antibody attenuated IL-1 beta secretion from PSCs. Exogenous TGF-beta(1) increased IL-1 beta expression and secretion by PSCs in a dose-dependent manner. Adenovirus-mediated expression of dominant-negative ( dn) Smad2/3 expression reduced both basal and TGF-beta(1)-stimulated IL-1 beta expression and secretion by PSCs. Coexpression of Smad3 with dnSmad2/3 restored IL-1 beta expression and secretion by PSCs, which were attenuated by dnSmad2/3 expression. In contrast, coexpression of Smad2 with dnSmad2/3 did not alter them. Furthermore, inhibition of IL-1 beta activity secreted from PSCs by IL-1 beta-neutralizing antibody attenuated TGF-beta(1) secretion from PSCs. Exogenous IL-1 beta enhanced TGF-beta(1) expression and secretion by PSCs. IL-1 beta activated ERK, and PD-98059, a MEK1 inhibitor, blocked IL-1 beta enhancement of TGF-beta(1) expression and secretion by PSCs. We propose that an autocrine loop exists between TGF-beta(1) and IL-1 beta in activated PSCs through Smad3- and ERK-dependent pathways.