opposing roles of stat1 and stat3 in cox-2 protein expression in human follicular dendritic cells

Prostaglandins (PGs) are the lipid mediators of inflammatory responses and acknowledged also as the mediators of immune inflammation. We have explored the role of PGs and their production mechanisms using follicular dendritic cell (FDC)-like cells. In the course of our recent study of the regulation mechanisms of PG production, we observed the involvement of JAK-STAT molecules in the IL-1β-induced PG production. In the current study, we aimed to elucidate the role of JAK and STAT proteins in the expression of COX-2 protein, the responsible enzyme for PG production. COX-2 protein level and PG production were assessed using immunoblotting and EIA, respectively. The intracellular target proteins were detected by a confocal microscopy. STAT1 knockdown resulted in an increase of COX-2 expression, while STAT3 knockdown led to a reduction in the COX-2 induction by IL-1β. IL-1β induced phosphorylation of both STAT1 and STAT3 at the S727 sites, rather than at Y701 or Y705. The phosphorylation and nuclear translocation of pSTAT1 and pSTAT3 were confirmed by a confocal microscopy. Based on these findings, we maintain that STAT1 may play an inhibitory role in COX-2 induction, while STAT3 acts as a promoter, via fine tuning of phosphorylation levels. The current study may enhance our understanding of the precise roles of these STAT proteins in COX-2 induction and PG production and suggests that these molecules could be potential targets for the treatment of immune inflammatory disorders.