Induction of Socs-3 by IL-25 relies on p38 Map kinase activity. (A) CD14⁺ cells were preincubated with SB202190 (a p38 inhibitor) or vehicle (DMSO) and then treated with IL-25, LPS, or both as indicated in “Methods.” *P = .001. (B) CD14⁺ cells were cultured with or without IL-25 for the indicated time points, and both p-p38 and total p38 were then evaluated by Western blotting of total extracts. (C) CD14⁺ cells were cultured with or without IL-25 for 30 minutes and then either left unstimulated or stimulated with LPS for the indicated times. Lower insets in both panels B and C show the quantitative analysis of p-p38/total p38 protein ratio, as measured by densitometry scanning of Western blots. Values are expressed in arbitrary units (a.u.). (D) Representative Western blots showing p-Ser-MKP-1 and β-actin in CD14⁺ cells cultured in the presence or absence of IL-25 (50 ng/mL) for the indicated time points. (E) Preincubation of cells with SB202190 prevents the negative regulation of IL-25 on the cytokine response induced by LPS. Cells were cultured as indicated in “Methods,” and RNA was then extracted and analyzed for the indicated cytokines by real-time PCR. *P < .01.