Aims/hypothesis: Chemokines recruit activated immune cells to sites of inflammation and are important mediators of insulitis. Activation of the pro-apoptotic receptor Fas leads to apoptosis-mediated death of the Fas-expressing cell. The pro-inflammatory cytokines IL-1beta and IFN-gamma regulate the transcription of genes encoding the Fas receptor and several chemokines. We have previously shown that suppressor of cytokine signalling (SOCS)-3 inhibits IL-1beta- and IFN-gamma-induced nitric oxide production in a beta cell line. The aim of this study was to investigate whether SOCS-3 can influence cytokine-induced Fas and chemokine expression in beta cells.
Methods: Using a beta cell line with inducible Socs3 expression or primary neonatal rat islet cells transduced with a Socs3-encoding adenovirus, we employed real-time RT-PCR analysis to investigate whether SOCS-3 affects cytokine-induced chemokine and Fas mRNA expression. The ability of SOCS-3 to influence the activity of cytokine-responsive Fas and Mcp-1 (also known as Ccl2) promoters was measured by reporter analysis.
Results: IL-1beta induced a time-dependent increase in Mcp-1 and Mip-2 (also known as Cxcl2) mRNA expression after 6 h of stimulation in insulinoma (INS)-1 and neonatal rat islet cells. This induction was inhibited when Socs3 was expressed in the cells. In INS-1 cells, IL-1beta + IFN-gamma induced a tenfold and eightfold increase of Fas mRNA expression after 6 and 24 h, respectively. This induction was inhibited at both time-points when expression of Socs3 was induced. In promoter studies SOCS-3 significantly inhibited the cytokine-induced activity of Mcp-1 and Fas promoter constructs.
Conclusions/interpretation: SOCS-3 inhibits the expression of cytokine-induced chemokine and death-receptor Fas mRNA.