Prostanoids mediate IL-1β-induced β-adrenergic hyporesponsiveness in human airway smooth muscle cells

Abstract

We have previously reported that pretreatment of cultured human airway smooth muscle (HASM) cells with interleukin-1beta (IL-1beta) results in decreased beta-adrenergic responsiveness. The purpose of this study was to determine whether prostanoids released as a result of cyclooxygenase-2 (COX-2) induction by IL-1beta contribute to this effect of the cytokine. Confluent serum-deprived HASM cells were studied in passages 4-7. IL-1beta (20 ng/ml for 22 h) reduced the ability of the beta-agonist isoproterenol (Iso) to decrease stiffness of HASM cells as measured by magnetic twisting cytometry. The effect of IL-1beta on Iso-induced changes in cell stiffness was abolished by nonselective [indomethacin (Indo), 10(-6) M] and selective (NS-398, 10(-5) M) COX-2 inhibitors. Indo and NS-398 also inhibited both the increased basal cAMP and the decreases in Iso-stimulated cAMP production induced by IL-1beta. IL-1beta (20 ng/ml for 22 h) caused an increase in both basal (15-fold) and arachidonic acid (AA)-stimulated (10-fold) PGE2 release. Indo blocked basal and AA-stimulated PGE2 release in both control and IL-1beta-treated cells. NS-398 also markedly reduced basal and AA-stimulated PGE2 release in IL-1beta-treated cells but had no significant effect on AA-stimulated PGE2 release in control cells. Western blot analysis confirmed the induction of COX-2 by IL-1beta. Exogenously administered PGE2 (10(-7) M, 22 h) caused a significant reduction in the ability of Iso to decrease cell stiffness, mimicking the effects of IL-1beta. Cycloheximide (10 microg/ml for 24 h), an inhibitor of protein synthesis, also abolished the effects of IL-1beta on Iso-induced cell stiffness changes and cAMP formation. In summary, our results indicate that IL-1beta significantly increases prostanoid release by HASM cells as a result of increased COX-2 expression. The prostanoids appear to contribute to beta-adrenergic hyporesponsiveness, perhaps by heterologous desensitization of the beta2 receptor.