Involvement of urokinase in cigarette smoke extract-induced epithelial-mesenchymal transition in human small airway epithelial cells.

Urokinase-type plasminogen activator (uPA) augments inflammation and tissue remodeling during lung injury and repair. The uPA expression in small airway epithelium of chronic obstructive pulmonary disease (COPD) increases. Epithelial-mesenchymal transition (EMT) is important in the small airway fibrosis of COPD. This study shows the uPA regulation in cigarette smoke extract (CSE)-induced EMT in human small airway epithelial cell lines (HSAEpiCs). uPA is overexpressed in the small airway epithelium of COPD patients and CSE-treated cell lines. Furthermore, uPA expression correlated with vimentin expression in the small airway epithelium of COPD patients. uPA inhibition blocks CSE-induced EMT by reversing E-cadherin and α-catenin expression and retarding the induction of N-cadherin and vimentin, resulting in reduction in migration. uPA overexpression in HSAEpiC cells also promotes EMT and migration. EMT is partly reversed in uPA-overexpressing HSAEpiC cells through the silencing expression of uPA receptor. In conclusion, this study provides new insights into the contribution of uPA upregulation to EMT associated with small airway remodeling in COPD.