Inhibitory effect of tranilast on radiation-induced pneumonitis in C57BL/6 mouse

Tranilast is an anti-allergic drug clinically used because it inhibits the release of chemical mediators from mast cells and of cytokines from macrophages. Tranilast is also shown to cure or prevent keloids and hypertrophic scars. Thus, to observe whether tranilast can prevent radiation pneumonitis and fibrosis that are caused by radiation-induced cytokines, we examined the effect of tranilast on the release of transforming growth factor-beta-1 (TGF-beta1), collagen I and III that are induced by ionizing radiation (RT) in C57BL/6 mouse lung. In mice treated with tranilast after lung irradiation, there were no inflammatory reaction, collagen deposition or septal thickness, and the protein level of TGF-beta1, collagen I and III was much more reduced than that of irradiated mice. These results suggest that tranilast can prevent the radiation pneumonitis and fibrosis.