Effects of mechanical stretch preconditioning on pathological stretch-induced activation of NF-κB and STAT3 signaling pathways in human type II alveolar epithelial cells

Abstract

Objective To evaluate the effects of mechanical stretch preconditioning on pathological stretch-induced activation of nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) signaling pathways in human type Ⅱ alveolar epithelial cells. Methods Human type Ⅱ alveolar epithelial cell line A549 cells cultured in vitro were randomly divided into 3 groups (n=24 each) using a random number table: control group (groupⅠ), pathological stretch group (group Ⅱ), and mechanical stretch preconditioning group (group Ⅲ). In groupⅠ, A549 cells were cultured routinely without receiving pathological stretch.In group Ⅱ, A549 cells were exposed to 20% cyclic stretch at 0.3 Hz for 6 h. In group Ⅲ, A549 cells were exposed to 5% cyclic stretch at 0.3 Hz for 60 min, and then exposed to 20% cyclic stretch at 0.3 Hz for 6 h. After the end of the treatment, the cells were collected for determination of the cell viability (by methyl thiazolyl tetrazolium assay) and lactate dehydrogeuase (LDH) release(by colorimetric method). The concentrations of tumor necrosis factor-alpha (TNF-α), interleukin-8 (IL-8) and high mobility group box 1 (HMGB1) in the culture medium were detected using enzyme linked immunosorbent assay.The expression of total NF-κB, phosphorylated NF-κB, total STAT3 and phosphorylated STAT3 was detected using Western blot.The ratios of phosphorylated NF-κB to total NF-κB and phosphorylated STAT3 to total STAT3 were calculated to reflect the activation. Results Compared with group Ⅰ, the cell viability was significantly decreased, the amount of LDH released was increased, and the concentrations of TNF-α, IL-8 and HMGB1, and activation of NF-κB and STAT3 were increased in Ⅱ and Ⅲ groups.Compared with group Ⅱ, the cell viability was significantly increased, the amount of LDH released was decreased, and the concentrations of TNF-α, IL-8 and HMGB1, and activation of NF-κB and STAT3 were decreased in group Ⅲ. Conclusion The mechanism by which mechanical stretch preconditioning attenuates pathological stretch-induced damage to human type Ⅱ alveolar epithelial cells is related to inhibited activation of NF-κB and STAT3 signaling pathways. Key words: Biomechanics; Ischemic preconditioning; Epithelial cells; Pulmonary alveoli; NF-kappa B; STAT3 transcription factor