(a) The effect of AAT1 knockdown on the SO2/AAT1 pathway. (b) The effect of AAT1 knockdown and SB431542 on collagen remodeling and the TGF-β1/Smad2/3 pathway. *P < 0.05, data are presented as mean ± SD (n = 5) and ANOVA followed by post-hoc analysis was used. AAT1sh: AAT1 knockdown. SB431542: a TGF-β1/Smad2/3 inhibitor, concentration of 5 μmol/L.