Anti-fibrotic effects of theophylline on lung fibroblasts

Theophylline has been used in the management of bronchial asthma and chronic obstructive pulmonary disease for over 50 years. It has not only a bronchodilating effect, but also an anti-inflammatory one conducive to the inhibition of airway remodeling, including subepithelial fibrosis. To date however, whether theophylline has a direct inhibitory effect on airway fibrosis has not been established. To clarify this question, we examined whether theophylline affected the function of lung fibroblasts. Theophylline suppressed TGF-β-induced type I collagen (COL1) mRNA expression in lung fibroblasts and also inhibited fibroblast proliferation stimulated by FBS and TGF-β-induced α-SMA protein. A cAMP analog also inhibited TGF-β-induced COL1 mRNA expression in lung fibroblasts. A PKA inhibitor reduced the inhibitory effect of theophylline on TGF-β-induced COL1 mRNA expression. These results indicate that theophylline exerts anti-fibrotic effects, at least partly, through the cAMP-PKA pathway.