[Modulation of respiratory smooth muscle reactivity by epithelial factors]

The epithelium of the pulmonary airways plays a complex role in the modulation of bronchial smooth muscle reactivity thanks to the metabolic properties and the mobilisation of contractant and relaxant factors which may issue directly from the epithelial cells or surrounding cells. The expression of these epithelial factors varies along the length of the tracheo-bronchial tree and with the species of animal being considered. Neuronal cells and inflammatory cells may equally intervene and interfere with relaxant and contractant factors depending on the epithelium. But the greatest difficulty in characterising these epithelial factors residues in the functional antagonism between relaxant and contractant factors when they are jointly expressed. Amongst factors depending on the respiratory epithelium prostaglandin E2 would be one of the relaxing factors and Calcitonin Gene-Related Peptide (CGRP), one of the contracting factors.