Epithelial-mesenchymal transition in injured bronchial epithelial cells and regulation by transforming growth factor-β1

Objective To study phenotypic,ultrastructural changes,and releasing of endothelin-1(ET-1)and transforming growth factor-β1(TGF-β1)following bronchial epithelial injury,and to investigate the regulation of epithelial-mesenchymal transition(EMT)during epithelial restitution by TGF-β1.Methods Bronchial epithelial injury was induced by poly-L-arginine(PA)in 16HBE-140 cell line.ET-1,TGF-β1,lactate dehydrogenase(LDH)content in conditioned culture medium,phenotypic and uhrastructural changes were monitored dynamically along with the regulation of EMT during epithelial repair by TGF-β1.Results PA elicited epithelial injury in 16HBE-14o cells with elevation of LDH,increased releasing of ET-1 and TGF-β1by injured epithelial cells.Transient EMT occurred during epithelial restitution,evidenced by emergence of spindle-shaped,α smooth actin immunostaining cells with stress microfilaments and enriched rough endoplasmic reticulum as well as newly-secreted collagen fibers.Co-incubation with 50 μg/L TGF-β1 promoted EMT whereas TGF-β1 neutralizing antibody abrogated the transition.ET-1 stimulated epithelial release of TGF-β1,which was completely blocked by ET-1 receptor A antagonist,bq123.Conclusions There was overexpression of ET-1,TGF-β1 and transient EMT following bronchial epithelial injury.EMT was driven by TGF-β1 in autocrine/paracrine pattern.ET-1 possibly participated in EMT through stimulating epithelial release of TGF-β1.Epithelial activation and EMT following epithelial injury might play crucial roles in the pathogenesis of airway remodeling in bronchial asthma. Key words: Epithelial injury; Myofibroblast; Transforming growth factor-β1; Endothelin