Radiotherapy is commonly used to treat thoracic malignancies, but often causes severe lung injury. Currently there are no effective protective strategies against radiation-induced lung injury (RILI). This study aimed to evaluate the ability of an angiogenesis antagonist, Endostar, against RILI, and the underlying mechanism in a mouse model. A total of 108 C57BL/6 female mice were randomized into 4 groups (n=27): i) control group; ii) Endostar group, animals were administered 7.75 ml/kg Endostar through intraperitoneal injection; iii) irradiation group, RILI was induced by exposing the animals to a single external irradiation on the thoraces (6 MV X-ray, 12 Gy); and iv) irradiation plus Endostar group, animals were subjected to Endostar treatment and irradiation as in groups 2 and 3. A total of 3 animals from each of the 4 groups were sacrificed at 1, 6, 12, 24 and 72 h and at 2, 4, 8 and 24 weeks following treatment. Clinical signs and pathology of RILI were examined. The expression of transforming growth factor-β 1 (TGF-β1) in lungs was analyzed by real-time quantitative polymerase chain reaction (RT-QPCR) and immunohistochemistry. Compared with the control group, irradiation induced evident interstitial edema and a significant increase in inflammatory cells in the lungs (P<0.05). Correlated with these changes, a notable increase in TGF-β1 mRNA level and a robust increase in TGF-β1 immunoreactivity were observed in lung tissues in a time-dependent manner following irradiation (P<0.05). Endostar administration effectively attenuated the magnitude of the increase in inflammatory cells as well as the elevation of TGF-β1 expression in lung tissues after RILI (P<0.05). In conclusion, radiation induced an increased expression of the inflammatory mediator TGF-β1 and the associated pathogenesis in the lung, while Endostar was able to at least partially attenuate RILI through downregulating the expression of TGF-β1 in mice. Our findings suggest that Endostar may be a novel protective agent against RILI.
Keywords: radiation-induced lung injury; transforming growth factor-β1; Endostar; radiation protection.