Role of cyclo‐oxygenase‐2 induction in interleukin‐1β induced attenuation of cultured human airway smooth muscle cell cyclic AMP generation in response to isoprenaline

Airway smooth muscle (ASM) in human asthma shows reduced relaxation and cyclic AMP generation in response to beta-adrenoceptor agonists. IL-beta attenuates cyclic AMP generation but the underlying mechanism is unclear. We have reported that IL-1beta induces cyclo-oxygenase-2 (COX-2) in human ASM cells and results in a marked increase in prostanoid generation with PGE2 and PGI2 as the major products. We investigated the role of COX-2 induction and prostanoid release (measured as PGE2) in IL-1beta induced attenuation of cyclic AMP generation in response to the beta-adrenoceptor agonist isoprenaline (ISO). Pre-treatment of human ASM cells with IL-1beta significantly attenuated cyclic AMP generation in response to high concentrations of ISO (1.0-10.0 microM) in a time- and concentration-dependent manner. The effect was accompanied by a high concentration of PGE2 release. The non-selective COX inhibitor indomethacin (Ind), the selective COX-2 inhibitor NS-398, the protein synthesis inhibitors cycloheximide (CHX) and actinomycin D and the steroid dexamethasone (Dex) all abolished the PGE2 release and prevented the attenuated cyclic AMP generation. COX substrate arachidonic acid time- and concentration-dependently mimicked IL-1beta induced attenuation and the effect was prevented by the non-selective COX inhibitors Ind and flurbiprofen, but not by NS-398, CHX and Dex. In contrast to IL-1beta, TNFalpha and IFNgamma, which are ineffective in inducing COX-2 and releasing PGE2 from human ASM cells, did not affect the cyclic AMP formation. Our study demonstrates that COX-2 induction and the consequent release of prostanoids plays a crucial role in IL-1beta induced attenuation of human ASM cell cyclic AMP response to ISO.