[Suppression by methylprednisolone of the expression of LFA-1 by alveolar macrophages in irradiated rat lungs].

A common side effect of radiotherapy is the development of fibrosis in the irradiated tissue. To study the effects of methylprednisolone on acute radiation-induced lung injury, we counted neutrophils, lymphocytes, and macrophages, and measured the expression on alveolar macrophages of lymphocyte function associated molecule-1 (LFA-1) in bronchoalveolar lavage fluid recovered from irradiated rat lungs. Twenty 10-week-old male Wistar rats were divided into 4 groups of 5 rats each: (1) a radiation group (R), which received 20 Gy of radiation from 60Co to the left hemithorax in one fraction; (/) a methylprednisolone treatment group (RS), which received the same dose of radiation as the R group, along with 2.0 mg x kg-1 of methylprednisolone (6 alpha methylprednisolone 21-acetate) by intramuscular injection 6 hours before and every 48 hours after irradiation; (3) an untreated control group (C); and (4) a methylprednisolone control group (S), which received the same dosage of methylprednisolone as the RS group. Rats were kept under specific-pathogen-free conditions. Bronchoalveolar lavage of the left lung was done in all 4 groups 2 week after irradiation. The number of neutrophils in the recovered fluid was significantly higher in the R and RS groups than in the C and S groups. The expression of LFA-1 on alveolar macrophages was significantly higher in the R group than in the RS, C, and S groups. The number of neutrophils in bronchoalveolar lavage fluid and the expression of LFA-1 on alveolar macrophages were significantly higher in the R group than in the RS groups. These results suggest that the increase in the expression of LFA-1 on alveolar macrophages and the increase in the number of neutrophils in bronchoalveolar lavage fluid are related to acute radiation-induced lung injury. Methylprednisolone suppressed the expression of LFA-1 on alveolar macrophages and the increase in the number of neutrophils measured in bronchoalveolar lavage fluid 2 weeks after irradiation.