Fig. 9.

ERK and c-RAF phosphorylation are required for S100 calcium-binding protein A9 (S100A9) induction of cytokines and proteases in lung fibroblasts. A: fibroblasts from nonsmoker (NS) individuals were grown in media supplemented with the ERK inhibitor LY3214996 or the c-RAF inhibitor GW5074, and toxicity assays were performed by measuring lactate dehydrogenase (LDH) release. Real-time PCR analysis was performed on these cells to examine levels of monocyte chemoattractant protein-1 (MCP-1), IL-6, IL-8, matrix metalloproteinase-3 (MMP-3), and matrix metalloproteinase-9 (MMP-9). B: immunoblots subsequent to densitometry analysis were performed in fibroblasts following silencing of Toll-like receptor 4 (TLR4), advanced glycosylation end product-specific receptor (AGER), and sasigin (BSG), and ERK and c-RAF phosphorylation were determined. Data are represented as means ± SE, where each measurement was performed with n ≥ 4 subjects per group. P values shown when comparing both treatments connected by a line were determined by two-way ANOVA with Bonferroni posttests or by Student’s t tests. C: possible signaling mechanism following age- and cigarette smoke-induced S100A9 signaling.