Extracellular signal-regulated kinase 1/2 (ERK1/2) pathway and nitric oxide synthase 2 (NOS2) expression induced by interferon-γ (IFN-γ) and/or interleukin-17 (IL-17) in RAW 264.7 cells. (A-a) Representative western blot analysis of p-ERK1/2 in RAW 264.7 cells treated with indicated cytokines for 30 min. (B-a, C-a and D-a) Representative western blot analysis of NOS2, IκBα degradation and p-p38 in RAW 264.7 cells pretreated with p-ERK1/2 inhibitor PD98059 for 30 min prior to cytokine exposure for 24 h, 4 h or 5 min. β-actin was used as a loading control. (A-b, B-b, C-b and D-b) Average quantification obtained by densitometric analysis for western blot analysis. Data are expressed as the density ratio of target protein to its non-treated level in arbitrary units. Data are presented as the means ± SD from three independent experiments. **p<0.01.