Full length articlePirfenidone prevents radiation-induced intestinal fibrosis in rats by inhibiting fibroblast proliferation and differentiation and suppressing the TGF-β1/Smad/CTGF signaling pathway
Graphical abstract
Introduction
Radiation-induced intestinal fibrosis (RIF) is a chronic toxicity of pelvic radiation. It is characterized by transmural accumulation of extracellular matrix within intestinal layers, which induces loss of intestinal compliance, and might leads to strictures formation requiring surgical resection (Larsen et al., 2007). Currently, there is no reliable clinical or laboratory marker available for RIF; progressive fibrosis and consequent intestinal strictures are not often diagnosed until irreversible. Moreover, current drug therapies have limited effect on fibrotic development, making surgery the only practical option for severe symptomatic intestinal fibrosis (Hamama et al., 2012, Henson et al., 2012). Bear in mind that excessive synthesis and deposition of collagens are the main pathological process of fibrotic diseases and the pathogenesis of fibrosis often shares common signaling pathways, it is of great value to learn from other fibrotic diseases in terms of pathogenesis and treatment (Urban et al., 2015).
Pirfenidone (5-methyl-N-phenyl-2- (1H)-pyridone), a promising anti-fibrotic agent, has exhibited remarkable antifibrotic properties in various clinical and animal-based experimental studies (Azuma et al., 2005, Di Sario et al., 2002, Duan et al., 2015, Hewitson et al., 2001, Rodríguez-Castellanos et al., 2015, Shi et al., 2011). In vitro studies have shown that pirfenidone inhibits proliferation and/or activation of a variety of fibroblasts responsible for the pathogenesis of fibrosis (Hewitson et al., 2001, Lin et al., 2009, Shi et al., 2011). Due to its great efficacy and safety, pirfenidone has been approved for the treatment of idiopathic pulmonary fibrosis in Europe and Japan (Cottin, 2013, Takeda et al., 2014). Recently, pirfenidone has been reported to inhibit the proliferation and secretory activities of fibroblasts isolated from patients with Crohn's disease (Kadir et al., 2016). In addition, this agent also showed promising antifibrotic effects in a newly developed mouse model of intestinal fibrosis, suggesting that pirfenidone might be used as an antifibrotic agent for intestinal fibrosis (Meier et al., 2016).
In the present study, we explored whether pirfenidone could protect against RIF in a rat model. Additionally, primary rat intestinal fibroblasts were incubated with transforming growth factor-β1 (TGF-β1) to possibly mimic in vivo situation, and we investigated the inhibitory effects of pirfenidone on critical fibrotic process, such as fibroblast proliferation as well as TGF-β1-induced myofibroblasts differentiation and fibrogenic activities. We also evaluated pirfenidone effects on the TGF-β1/Smad/CTGF signaling pathways underlying these antifibrotic activities both in vivo and in vitro.
Section snippets
Animal experiments
Six-week-old male Sprague–Dawley (SD) rats weighing 180–200 g were purchased from the Laboratory Animal Center, Fujian Medical University (Fuzhou, China). Rats were maintained in a controlled environment (23 ± 3 °C and 12 h light/dark illumination cycle) and fed with a standard chow diet and water. Experimental protocols were approved by Institutional Animal Care and Use Committee of Fujian Medical University.
After acclimatization for one week, rats were randomly divided into four groups (n =
Pirfenidone attenuates radiation-induced intestinal fibrosis in rats
The first symptom of RIF in rats is body weight loss. A gradual body weight loss was observed in the radiation group compared with the control group, but the extent of weight loss was decreased after treatment with pirfenidone (P< 0.01, Fig. 1A). One rat in the radiation group died from acute radiation injury at week 3, and four rats developed remarkable chronic bowel obstruction due to stenosis of the irradiated intestines (Fig. 1B). The remaining 5 rats also developed intestinal strictures of
Discussion
Radiation-induced intestinal fibrosis is a chronic toxicity after pelvic radiation, which is considered progressive and irreversible the majority of clinicians (Barcellos-Hoff and Costes, 2006). Currently, effective drug therapy for RIF is still lacking. In the present study, we explored the role of pirfenidone, a safe and well-tolerated drug, in the prevention or treatment of RIF. We found that pirfenidone attenuated RIF both in vivo and in vitro by inhibiting TGF-β1/Smad/CTGF signaling
Conclusion
The present study demonstrated that pirfenidone protected against the progression of RIF both in vivo and in vitro by inhibiting the proliferation and differentiation of intestinal fibroblasts and suppressing TGF-β1/Smad/CTGF signaling pathways. Further studies are needed to translate pirfenidone into the treatment of intestinal fibrosis in patients following pelvic radiation.
Acknowledgement
This study was supported by National Clinical Key Specialty Construction Project (General Surgery) of China (Grant no. 2012-649), guiding key project of social development by the Fujian Provincial Science and Technology Department (Grant no. 2015Y0058), and National Natural Science Fund for Young Scholars of China (Grant no. 81602798). We thank Dr. Ben-Hua Xu and Wen-Yao Li at the radiotherapy department of the Fujian Medical University Union Hospital for pelvic irradiation of rat models.
Conflict of interest
The authors declare that they have no conflict of interest.
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