p38 MAP kinase regulates IL-1 beta responses in cultured airway smooth muscle cells

We have previously reported that interleukin (IL)-1 beta causes beta -adren ergic hyporesponsiveness in cultured human airway smooth muscle (HASM) cell s by increasing cyclooxygenase (COX)-2 expression. The purpose of this stud y was to determine whether p38 mitogen-activated protein (MAP) kinase is in volved in these events. IL-1 beta (2 ng/ml for 15 min) increased p38 phosph orylation fourfold. The p38 inhibitor SB-203580 (3 muM) decreased IL-1 beta -induced COX-2 by 70 +/- 7% (P < 0.01). SB-203580 had no effect on PGE(2) release in control cells but caused a significant (70-80%) reduction in PGE (2) release in IL-1<beta>-treated cells. IL-1 beta increased the binding of nuclear proteins to the oligonucleotides encoding the consensus sequences for activator protein (AP)-1 and nuclear factor (NF)-kappaB, but SB-203580 did not affect this binding, suggesting that the mechanism of action of p38 was not through AP-1 or NF-kappaB activation. The NF-kappaB inhibitor MG-1 32 did not alter IL-1 beta -induced COX-2 expression, indicating that NF-ka ppaB activation is not required for IL-1 beta -induced COX-2 expression in HASM cells. IL-1 beta attenuated isoproterenol-induced decreases in HASM st iffness as measured by magnetic twisting cytometry, and SB-203580 abolished this effect. These results are consistent with the hypothesis that p38 is involved in the signal transduction pathway through which IL-1 beta induces COX-2 expression, PGE(2) release, and beta -adrenergic hyporesponsiveness.