Figure 2.

Reduced fibroblast PPARβ/δ expression increases IL-1β activation of TAK1 and up-regulation of AP-1–controlled mitogenic target genes. (A) Expression of mitogenic factor mRNAs in 2-wk old OTC F_PPARβ/δ and F_CTRL treated with PPARβ/δ agonist (500 nM GW501516 for 24 h) or vehicle. The expression levels of the indicated mitogenic factors were analyzed by qPCR and normalized to control ribosomal protein P0. Results are represented in fold induction as compared with OTC F_CTRL. (B) Immunoblot analysis of phosphorylated c-Jun from F_PPARβ/δ and F_CTRL extracted from K_CTRL/F_PPARβ/δ and K_CTRL/F_CTRL OTCs (n = 2), respectively. Total c-Jun and TAK1 protein expression level, which remains unchanged, showed equal loading and transfer. (C) Immunoblot analysis of IL-1β and TNF-α activation of TAK1 in F_CTRL or F_PPARβ/δ. Cells were treated with either vehicle (DMSO) or 800 nM GW501516 for 24 h prior to exposure to 10 ng/ml IL-1β (top) or TNF-α (bottom). At the indicated time points, total cell lysates were extracted. Equal amounts of total protein (50 µg) were resolved, electrotransferred, and probed for phosphorylated TAK1 (Thr184/187), total TAK1, and β-tubulin. Values below each band represent the mean fold differences (n = 3) in expression level with respect to vehicle-treated F_CTRL at 5 min, which was assigned the value of one. Data are mean ± SEM, n = 3.