Figure 4

Inhibition of p38, JNK1–3, ERK1/2 and NF-κB attenuates poly-IC induced release of IL-26. Primary bronchial epithelial cells were pre-incubated (1 h) with MAP kinase inhibitors for p38 (SB203580), JNK1–3 (SP600125), ERK1/2 (AZD6244) as well as combined (p38 plus ERK1/2, p38 plus JNK1–3 and JNK1’3 plus ERK1/2). Cells were preincubated for 5 h with the NF-κB inhibitor (SC17741). Cells were then stimulated with poly-IC (0.05 µg/mL) for another 24 h. Figure panels show the different concentrations of each inhibitor used during poly-IC stimulation. Extracellular concentrations of IL-26 in cell-free conditioned media as well as intracellular levels were measured using ELISA and western blot respectively and mRNA expression by real time. Panels show IL-26 concentrations after the inhibition of (A) p38, (B) JNK1–3, (C) ERK1/2, (D) p38 plus JNK1–3, (E) p38 plus ERK1/2 and (F) JNK1–3 plus ERK1/2 and (G) NF-κB (n = 7 for all panels). (C) Intracellular IL-26 (representative western blot) and (D) the average protein levels (fold difference) in response to poly-IC (1 µg/mL) in the presence of the MAP kinase or NF-κB inhibitors (n = 5). The p values indicated are according to Student paired t test and p < 0.05 is considered significant.