Abstract: Objective To study the effect of Fangxian Decoction on lung tissue pathology, lung surface active substance binding protein and inflammatory factors of rats with radiation pneumonia, and to explore the efficacy and mechanism of Fangxian Decoction in the treatment of radiation pneumonia. Methods Ninety SPF male SD rats were randomly divided into blank group, model group and 3 treatment groups(low-dose group, middle-dose group and high-dose group), and 6mV X-rays with the total dose of being 20 Gy were used to irradiate the whole chest of rats in the treatment groups and model group to build the model of the rats with radiation pneumonia. The treatment groups were given Fangxian Decoction by gavage, and the model group and the blank group were given the same amount of normal saline by gavage. Gavage medication on the first day of irradiation until 6 weeks after irradiation. Six rats were selected from each group in the second, fourth, and eighth week after irradiation to observe the pathological changes of lung tissue under HE staining light microscope, detect the levels of interleukin-3(IL-3), interleukin-6(IL-6), interleukin-7(IL-7), tumor necrosis factor-α(TNF-α), transforming growth factor-β(TGF-β), C-reactive protein(CRP), and lung surfactant binding protein(SP-A, SP-D)by immunohistochemical method, and make correlation analysis. Results Compared with the model group, the rats in the treatment groups had less or no pulmonary congestion and edema, inflammatory cell infiltration, and collagen fiber proliferation in the interstitium. Compared with the blank group, the IL-3, IL-6, IL-7, TNF-α, TGF-β, and CRP levels in the model group and treatment groups were significantly increased(medium-dose treatment for 4 weeks, P values were 0.012, 0.033, 0.027, 0.018, 0.024, and 0.009, respectively), SP-A and SP-D levels were significantly reduced(middle dose treatment for 4 weeks, P values were 0.004 and 0.005, respectively). Compared with the model group, IL-3, IL-6, IL-7, TNF-α, TGF-β, CRP levels were significantly reduced(P<0.05), and SP-A and SP-D levels were significantly increased(P<0.05)in treatment groups. Analysis of the correlation results showed that IL-6 was strongly negatively correlated with SP-A and SP-D, IL-3 and IL-7 were negatively correlated with SP-A and SP-D, and TNF-α and TGF-β were weakly positively correlated with SP-A and SP-D. The effects of different doses of treatment groups on the pathology of rat lung tissue and the detected humoral factors were dose-dependent. Conclusion Fangxian Decoction has a clear effect on improving the inflammatory degree of radiation lung injury. The changes of SP-A and SP-D are related to IL-3, IL-6, IL-7, TNF-α and TGF-β. It is speculated that the mechanism of Fangxian Decoction is through up-regulation of SP-A and SP-D levels and inhibiting the release of inflammatory factors IL-3, IL-6, and IL-7.

Key words: Fangxian Decoction, Radiation Pneumonia, Histopathology, Mechanism of action, Rat