Effect of rapamycin on the balance of T helper cell subsets in rats with pulmonary fibrosis / 中国中西医结合急救杂志

ABSTRACT

Objective To study the effect of rapamycin on the balance of T helper cell subsets in rats with pulmonary fibrosis. Methods Fifteen male Sprague-Dawley (SD) rats were randomly divided into control group, model group and rapamycin group, with 5 rats in each group. Pulmonary fibrosis model was reproduced by using the method of intratracheal instillation of bleomycin (5 mg/kg). Control group was treated by intratracheal instillation of saline (1.25 mL/kg) to obtain the negative control. The rats of the rapamycin group were given rapamycin (1 mg·kg-1·d-1) by gastric perfusion for consecutive 10 days beginning on the 3rd day after intratracheal instillation of bleomycin. On the 28th day all rats were sacrificed, and the peripheral blood and the lung tissues were harvested. The lung tissue was observed. And the severity of pulmonary fibrosis in rats was assessed by Ashcroft score. The lung tissues were performed using immunohistochemical staining to detect the expression ofγ-interferon (IFN-γ) and interleukins (IL-4, IL-17). Flow cytometry was used to detect the percentages of CD4+ T cells and CD8+ T cells. Results The severity of pulmonary fibrosis was improved in rats of rapamycin group compared with that of model group, and the Ashcroft score was decreased (2.92±0.64 vs. 5.76±1.76, F = 16.276, P = 0.080). The expression levels of IL-4 and IL-17 (A value) in model group were the highest (4 789.0±1 014.6, 19 139.0±2 433.3), followed by those of the rapamycin group (3 547.0±953.8, 10 380.0±2 352.4), and the least was found in the control group (1 627.0±914.8, 4 419.0±923.6). The expression levels of IFN-γ (A value) in control group were the highest (9 956.0±1 172.6), followed by those of the rapamycin group (7 487.0±998.4), and the least was found in the model group (6 054.0±1 045.2). There were significantly differences in above parameters among three groups (all P<0.01). Compared with the control group and model group, the percentages of CD4+CD25+Foxp3+T cells in CD4+CD25+, CD4+cells, and lymphocytes were significantly increased in rapamycin group [(57.36±8.84)% vs. (41.28±5.91)%, (34.52±4.56)%; (4.77±0.48)% vs. (3.15±0.37)%, (3.14±0.28)%;(1.97±0.22)%vs. (1.24±0.17)%, (1.44±0.21)%, all P<0.05], and the percentages of CD8+CD25+Foxp3+T cells in CD8+CD25+, CD8+cells, and lymphocytes were also significantly increased in rapamycin group [(73.92±7.69)% vs. (33.44±4.46)%, (49.14±11.38)%; (1.73±1.05)% vs. (0.46±0.15)%, (0.71±0.42)%;(0.31±0.20)% vs. (0.09±0.04)%, (0.14±0.09)%, all P < 0.05]. The percentage of CD8+CD25+Foxp3+ T cells in CD8+CD25+in model group was significantly higher than that in control group [(49.14±11.38)% vs. (33.44±4.46)%, P < 0.05]. Conclusions T helper cell subsets are imbalanced in pulmonary fibrosis rats. Rapamycin can prevent bleomycin-induced pulmonary fibrosis, and its antifibrotic effect maybe the promotion of proliferation and function of regulatory T cells and imbalance regulation of T helper cell subsets.