Effects of SP600125 or PD98059 on IL-1β-induced IL-6 release. Cultured cells were pretreated with various concentrations of SP600125 (A) or PD98059 (B) for 60 min, and then stimulated with 10 ng/ml IL-1β (closed circle) or vehicle (open circle) for 36 h in the presence of SP600125 or PD98059. Each value represents the mean ± SD of triplicate independent determinations of a representative experiment carried out three times. Similar results were obtained with two additional and different cell preparations. *P < 0.05 in comparison to the value of IL-1β alone.