Effects of mechanical stretch preconditioning on endotoxin-induced damage to human type II alveolar epithelial cells

Abstract

Objective To evaluate the effects of mechanical stretch preconditioning on endotoxin-induced damage to human type Ⅱ alveolar epithelial cells. Methods Human type Ⅱ alveolar epithelial cell line A549 cells at the logarithmic growth phase were seeded in 96-well plates at a density of 0.5×106 cells/ml (2 ml/well). The cells were randomly divided into 3 groups: control group (group C, n = 12); lipopolysaccharide (LPS) group (n = 36) and 5% CS + LPS group (n = 48). The 5% CS + LPS group was further divided into 4 subgroups, and A549 cells were exposed to 5% cyclic stretch for 15, 30, 60 and 120 min in the 4 subgroups, respectively. LPS with the final concentration of 1 μg/ml was added after the end of mechanical stretch in the 4 subgroups, and A549 cells were incubated for 4 h. The apoptosis in cells was detected using flow cytometry and apoptosis rate was calculated. F-actin expression was determined using immunofluorescence. Results Compared with group C, the early and late apoptosis rates were significantly increased in LPS and 5%CS + LPS groups. Compared with the value at 4 h of LPS incubation in group LPS, the early and late apoptosis rates were significantly decreased, and the reconstruction of F-actin was reduced in 5%CS + LPS group. Conclusion Preconditioning with 5% cyclic stretch (15-120 min) can mitigate endotoxin-induced damage to human type Ⅱ alveolar epithelial cells. Key words: Stress, mechanical; Pulmonary alveoli; Epithelial cells; Endotoxemia