Pirfenidone inhibits PDGF isoforms in bleomycin hamster model of lung fibrosis at the translational level

Pirfenidone (PD) is known for its antifibrotic effects in the bleomycin (BL) hamster model of lung fibrosis. We evaluated whether pretreatment of hamsters with PD could influence the effects of BL-induced overexpression of platelet-derived growth factor (PDGF)-A and PDGF-B genes and proteins in the same model of lung fibrosis. We demonstrate elevated levels of PDGF-A and PDGF-B mRNAs in bronchoalveolar lavage (BAL) cells from lungs of BL-treated compared with saline control hamsters by RT-PCR analysis. However, these levels were not altered in BAL cells obtained from BL-treated hamsters on diets containing 0.5% PD. Western blot analysis of BAL fluid for PDGF isoforms demonstrated that PD treatment inhibited the synthesis of both PDGF-A and PDGF-B isoforms. PD treatment also decreased the mitogenic activity in the BAL fluid from BL-treated hamster lungs. Taken together, these data provide evidence that the protective effects of PD against BL-induced lung fibrosis may be mediated by a reduction in PDGF isoforms produced by lung macrophages.