[Mechanisms of bronchial hyperreactivity. Role of the epithelium]

Bronchial epithelial cells are present all along the airways. They play a role of barrier and protect the airways against inhaled pollutants. However it is known to day that they could play an active role, through synthesis and release of mediators which modulate the airway muscles, the epithelium permeability and the vascular tone. Shedding of the epithelium is a constant feature of the asthmatic airways as can be observed directly on the bronchial biopsies and indirectly through and increased number of epithelial cells in the bronchoalveolar lavage fluid. The epithelial shedding is well correlated to the bronchial hyperreactivity. In vitro, bronchial epithelial cells release higher quantities of 15 HETE, endothelin and PGE2 in asthmatics than in normal control subjects. They express HLA-DR and ICAM-1 in higher quantities in asthmatic patients. Bronchial epithelial cells might play an important role in inflammatory lesions which are observed in asthmatic patients. They could be a good target for new therapeutic approaches in asthma.