Pirfenidone prevents radiation-induced intestinal fibrosis in rats by inhibiting fibroblast proliferation and differentiation and suppressing the TGF-ß1/Smad/CTGF signaling pathway.

Radiation-induced intestinal fibrosis (RIF) is a chronic toxicity following radiation, and can be very difficult to treat. Pirfenidone is a promising anti-fibrotic agent that inhibits fibrosis progression in various clinical and experimental studies. This study was aimed to explore whether pirfenidone could protect against RIF, and to evaluate the underlying mechanism. An animal model of RIF was induced by exposure of a single dose of 20 Gy to the pelvis. Rats were orally administered with pirfenidone (200, 400 md/kg/d) for 12 weeks. Primary rat intestinal fibroblasts were cultured to determine the effects of pirfenidone on TGF-ß1-induced (5 ng/ml) proliferation and transdifferentiation of fibroblasts. The expression of collagen I, α-SMA, and TGF-ß1/Smad/CTGF pathway proteins were analyzed by qRT-PCR and/or western blot analysis. The cell proliferation rate was determined by CCK-8 assay. The results indicated that pirfenidone significantly attenuated fibrotic lesion in irradiated intestines and reduced collagen deposition by inhibiting TGF-ß1/Smad/CTGF pathway in rat models. Moreover, in primary rat intestinal fibroblasts, pirfenidone decreased the up-regulation of TGF-ß1-induced collagen I and α-SMA by suppressing TGF-ß1/Smad/CTGF signaling pathway. Altogether, our findings suggested that pirfenidone attenuated RIF by inhibiting the proliferation and differentiation of intestinal fibroblasts and suppressing the TGF-ß1/Smad/CTGF signaling pathway.

Effect of pirfenidone on proliferation, TGF-ß-induced myofibroblast differentiation and fibrogenic activity of primary human lung fibroblasts.

Pirfenidone is an orally active small molecule that has been shown to inhibit the progression of fibrosis in animal models and in patients with idiopathic pulmonary fibrosis. Although pirfenidone exhibits well documented antifibrotic and antiinflammatory activities, in vitro and in vivo, its molecular targets and mechanisms of action have not been elucidated. In this study, we investigated the effects of pirfenidone on proliferation, TGF-ß-induced differentiation and fibrogenic activity of primary human lung fibroblasts (HLFs). Pirfenidone reduced fibroblast proliferation and attenuated TGF-ß-induced α-smooth muscle actin (SMA) and pro-collagen (Col)-I mRNA and protein levels. Importantly, pirfenidone inhibited TGF-ß-induced phosphorylation of Smad3, p38, and Akt, key factors in the TGF-ß pathway. Together, these results demonstrate that pirfenidone modulates HLF proliferation and TGF-ß-mediated differentiation into myofibroblasts by attenuating key TGF-ß-induced signaling pathways.