ABSTRACT
@#<b>Objective</b> To investigate the role of complement in radiation-induced lung injury in mice after chest irradiation with <sup>60</sup>Co γ-rays at a single dose of 20 Gy. <b>Methods</b> C57BL/6 mice underwent chest irradiation with <sup>60</sup>Co γ-rays at a single dose of 20 Gy, followed by observation for the inflammatory reaction of the lung tissue in the early stage (within 15 d) and pulmonary fibrosis in the later stage (30 and 180 d). Enzyme-linked immunosorbent assay was used to measure the levels of C2, C3a, C4, and C5b-9 in the lung tissues at 1, 3, 7, 15, 30, and 180 d after irradiation. The expression of complement mRNA in BEAS-2B cells after irradiation was determined using RT-PCR. <b>Results</b> Radiation-induced lung injury in micepresented as inflammatory response in the early stage and fibrosis in the late stage. Complement C2, C4, and C5b-9 complexes were increased in the early period (3 or 7 d) after irradiation (<i>P</i> < 0.05), which might be associated with the inflammatory response induced by irradiation. During 3 to 180 d, complement C3a was significantly higher in the irradiated mice than in the control mice, suggesting a close relationship between C3a and radiation-induced lung injury. The irradiated cells showed increased mRNA expression of C2 and C3, with no changes in the mRNA levels of C4 and C5. <b>Conclusion</b> Different complement proteins have varying responses to radiation-induced lung injury, among which C3a is closely related to radiation-induced lung injury, suggesting that regulating C3a and its receptors may be a new way to prevent and treat radiation-induced lung injury.