Cellular detachment and deformation induce IL-8 gene expression in human bronchial epithelial cells

Neutrophil elastase (NE) is known to be one of the most potent proteases capable of deforming and detaching human bronchial epithelial cells (BECs) and inducing IL-8 gene expression. However, mechanisms of NE-induced IL-8 gene expression are unclear, especially with respect to how they relate to cellular detachment. To elucidate these mechanisms, effects of cell detachment and deformation following mechanical injury or pharmacologic stimuli on IL-8 gene expression were examined by Northern analyses. When BET-1A cells from a human bronchial epithelial cell line were incubated with NE (100 nM), trypsin (0.5 mg/ml), EGTA (7 mM), or EDTA (0.7 mM) to induce deformation and detachment, IL-8 mRNA transcript levels were up-regulated, as demonstrated in a case of mechanical detachment from the culture plate using a cell scraper. This IL-8 gene expression was inhibited by pretreatment with 5 microM taxol, a microtubule-stabilizing agent. Colchicine or vinblastine, microtubule-disrupting agents, induced IL-8 gene expression, which was also inhibited by taxol treatment. These data suggest that structural changes, including deformation of the cytoskeleton, especially microtubules, may contribute to IL-8 gene expression in human BECs. Since detachment and cellular deformation of BECs caused by proteases have been observed frequently in a variety of inflammatory airway diseases, our findings provide evidence that detached or deformed BECs potentially enhance production of inflammatory mediators in the pathogenesis of airway inflammation.