FIG. 4.

Activation of MAP kinase p38 by NTHI SCF is required for IL-8 up-regulation. (A) HM3 cells were pretreated with SB 203580 or dimethyl sulfoxide, the solvent for SB 203580, for 1.5 h and were then incubated with NTHI SCF for 4 h before being lysed for luciferase assays. Activities associated with SB 203580-treated cells are significantly different from control (P ≤ 0.005). (B) HM3 cells were cotransfected with IL-8-Luc and a dominant-negative form of either p38α (p38α DN) or p38β (p38β DN). Forty-two hours after transfection, cells were treated with NTHI SCF for 4 h and then assayed for luciferase activity. Cells transfected with the vector alone served as a control. The activities in p38α- and p38β-cotransfected cells are significantly lower than that of the vector control (P ≤ 0.05). Data are presented as means ± standard deviations of three individual treatments. Results are representative of three separate experiments.