Interleukin-1β-induced cyclooxygenase-2 expression is mediated through activation of p42/44 and p38 MAPKS, and NF-κB pathways in canine tracheal smooth muscle cells

Interleukin-β (IL-1β) was found to induce inflammatory responses in the airways, which exerted a potent stimulus for PG synthesis. This study was to determine the mechanisms of IL-1β-enhanced cyclooxygenase (COX)-2 expression associated with PGE₂ synthesis in tracheal smooth muscle cells (TSMCs). IL-1β markedly increased COX-2 expression and PGE₂ formation in a time- and concentration-dependent manner in TSMCs. Both COX-2 expression and PGE₂ formation in response to IL-1β were attenuated by a tyrosine kinase inhibitor, genistein, a phosphatidylcholine-phospholipase C inhibitor, D609, a phosphatidylinositol-phospholipase C inhibitor, U73122, protein kinase C inhibitors, GF109203X and staurosporine, removal of Ca²⁺ by addition of BAPTA/AM plus EGTA, and phosphatidylinositol 3-kinase (PI3-K) inhibitors, LY294002 and wortmannin. IL-1β-induced activation of NF-κB correlated with the degradation of IκB-α in TSMCs. IL-1β-induced NF-κB activation, COX-2 expression, and PGE₂ synthesis were inhibited by the dominant negative mutants of NIK and IKK-α, but not by IKK-β. IL-1β-induced COX-2 expression and PGE₂ synthesis were completely inhibited by PD98059 (an inhibitor of MEK1/2) and SB203580 (an inhibitor of p38 inhibitor), but these two inhibitors had no effect on IL-1β-induced NF-κB activation, indicating that activation of p42/44 and p38 MAPK and NF-κB signalling pathways were independently required for these responses. These findings suggest that the increased expression of COX-2 correlates with the release of PGE₂ from IL-1β-challenged TSMCs, at least in part, independently mediated through MAPKs and NF-κB signalling pathways in canine TSMCs. IL-1β-mediated responses were modulated by PLC, Ca²⁺, PKC, tyrosine kinase, and PI3-K in these cells.