SMAD2 and pulmonary fibrosis: In a previous bleomycin-induced pulmonary fibrosis model, NIH 3T3 fibroblasts and primary lung fibroblasts were treated with andrographolide and there was a reduction in TGF-β1-induced Smad2/3 phosphorylation in both cell types, suggesting its regulation by andrographolide decreases pulmonary fibrosis [24].