Interferon-γ enhances the antifibrotic effects of pirfenidone by attenuating IPF lung fibroblast activation and differentiation

Background: Idiopathic pulmonary fibrosis (IPF) pathogenesis involves multiple pathways, and combined antifibrotic therapy is needed for future IPF therapy. Inhaled interferon-gamma (IFN-gamma) was recently shown to be safe and without systemic effects in patients with IPF. Aim: To examine the in vitro effects of individual and combined treatment with IFN-gamma and pirfenidone (PFD) on normal and IPF fibroblast activation and extracellular matrix remodeling after TGF-beta 1 and PDGF-BB stimulation. Methods: IPF and normal human lung fibroblasts (NHLF) were treated with IFN-gamma, PFD or a combination of both drugs in the presence of either TGF-beta 1 or PDGF-BB. The effects of TGF-beta 1 and PDGF-BB treatment on cell viability, proliferation, differentiation and migration were examined. The expression of collagen 1, matrix metalloproteinases (MMPs) and tissue inhibitors of MMP (TIMPs) was analyzed using qPCR, Western blotting and gelatin zymography. Total collagen content in conditioned media was also measured using a Sircol assay. Results: Compared to that of PFD, the effect of IFN-gamma in downregulating normal and IPF lung fibroblast differentiation to myofibroblasts in response to TGF-beta 1 was more potent. Importantly, the combination of IFN-gamma and PFD had a possibly synergistic/additive effect in inhibiting the TGF-beta 1- and PDGF-BB-induced proliferation, migration and differentiation of normal and IPF lung fibroblasts. Furthermore, both drugs reversed TGF-beta 1-induced effects on MMP-1, -2, -3, -7, and -9, while only PFD promoted TIMP-1 and-2 expression and release. Conclusions: Our findings demonstrate that the antifibrotic effects of IFN-gamma and PFD on normal and IPF lung fibroblasts are different and complementary. Combination therapy with inhaled IFN-gamma and PFD in IPF is promising and should be further explored in IPF clinical trials.