IL-1β inhibits isoproterenol (ISO)-induced relaxation of cultured human airway smooth muscle (HASM) cells. The purpose of this study was to determine whether IL-1β can also suppress ISO-induced cAMP response element (CRE)-dependent gene expression. ISO (10 μM) caused a marked increase in CRE-binding protein (CREB) phosphorylation, which was attenuated by IL-1β (2 ng/ml). This effect of IL-1β was abolished by the cyclooxygenase (COX) inhibitor indomethacin. To examine CRE-driven gene expression, we transiently transfected HASM cells with a construct containing CRE upstream of a luciferase reporter gene. ISO (6 h) caused a sixfold increase in luciferase activity. IL-1β (24 h) alone also increased luciferase activity, although to a lesser extent (2-fold). However, the ability of ISO to elicit luciferase expression was markedly reduced in cells treated with IL-1β. Indomethacin, the MEK and p38 inhibitors U-0126 and SB-203580, the protein kinase A inhibitor H-89, and dexamethasone each completely abolished the ability of IL-1β to induce CRE-driven gene expression but only slightly increased the ability of ISO to induce CRE-driven gene expression in IL-1β-treated cells. IL-1β also attenuated dibutyryl cAMP-induced CRE-driven gene expression, but not dibutyryl cAMP-induced CREB phosphorylation. Tumor necrosis factor-α (10 ng/ml) also attenuated ISO-induced CRE-driven gene expression, even though it was without effect on ISO-induced cAMP formation or ISO-induced CREB phosphorylation. The results suggest that IL-1β and tumor necrosis factor-α may attenuate the ability of β-agonists to induce expression of genes with CRE in their regulatory regions at least in part through events downstream of CREB phosphorylation.
Tumor Necrosis Factor- α Enhances mRNA Expression and Secretion of Interleukin-6 in Cultured Human Airway Smooth Muscle Cells