AP collagen peptides recover cortisol-dependent inhibition of TGF-β signaling. HDFs were treated with various concentrations of cortisol (0, 10 and 100 nM) and cultured for 24 h. (A) Culture media were harvested and TGF-β levels were determined using a specific ELISA kit. HDFs were treated with cortisol (100 nM) in the presence of APCP (1 μg/mL) or GR inhibitor (1 μM) and cultured for 8 h and 24 h. (B) Culture media from cells cultured for 24 h were harvested and TGF-β levels were detected using a specific ELISA kit. (C,D) Cell lysates from cells cultured for 8 h were subjected to immunoblot analysis to assess the phosphorylation of Smad2 (Ser465/Ser467) and Smad2 (Ser465/Ser467) / 3 (Ser423/425). All data represent the mean ± SD of three independent experiments. Significant differences: # p < 0.05, ## p < 0.01, ### p < 0.005 compared with the control; * p < 0.05, ** p < 0.01, *** p < 0.005 compared with cortisol-treated control.