Pirfenidone (5-methyl-1-phenyl-2-[1 H]-pyridone) is known to inhibit pulmonary fibrosis progression in animal models40 as well as in clinical trials41–45, at least in part by inhibiting TGF-β signalling (Fig. 5a). Pre-treating HBECs with 1 mg/ml of pirfenidone had no effect on Smad3 (Fig. 5b left), but decreased HSP-27 phosphorylation 1 h after cigarette smoke exposure (Fig. 5b right). This evidence concerns the gene SMAD3 and pulmonary fibrosis.