Expression of Bcl-xl/Bid and apoptosis in epithelial cells of pulmonary fibrosis rats

Abstract

Objective To investigate the expressions of Bcl-2 family,which leads to apoptotic cell of the pulmonary fibrosis rats.Methods Fouty-eight Sprague-Dawley (SD) rats were randomly divided into four groups:control group,model group 7 d,14 d,28 d.The model group were induced to produce pulmonary fibrosis with bleomycin endotracheally while the control group was given with normal saline instead in the same condition.Eight rats in each group were sacrificed on 7,14,and 28 days respectively after intratracheal instillation.Pathological changes in the lungs were evaluated by HE stain.The mRNA expressions of Bid and Bcl-xl were evaluated by RT-PCR quantitative analysis,and the immunohistochemical method was used to investigate the change of Bid and Bcl-xl protein.TUNEL was used to detect the change of cell apoptosis.Results The percentage of cell apoptosis in alveolar and bronachial epithelial cells of pulmonary fibrosis rats was higher than that in normal control group.The result of immunohistochemistry and RT-PCR suggested that the expressions of Bid mRNA and Bid protein in model groups were higher than those in normal control group.The expressions of Bcl-xl mRNA and Bcl-xl protein in model groups were lower than those in normal control group ( P ＜ 0.01).The.expressions of Bid protein and mRNA also increased after 7 d by treated with bleomycin,increased on the 14th day and further increased on the 28th day.The expression of Bcl-xl protein and mRNA also decreased after 7 d by treated with bleomycin,reaches the trough in the 28th day.There was significant correlation between TUNEL results and the expression of Bid/Bcl-xl mRNA.Conclusions Higher expression of apoptosis in alveolar epithelial cells and bronchial cells of pulmonary fibrosis rats can contribute to fibrogenesis.The apoptosis index of lung cells may be related to the expression imbalance of Bcl-2 family protein. Key words: Pulmonary fibrosis ; Apoptosis; Bid; Bcl-xl; Rat