Functional characteristics of bronchial epithelium obtained by brushing from asthmatic and normal subjects

Airways epithelial cells may be involved in the pathogenesis of asthma, but their role remains to be determined. Epithelial cells can release large amounts of 15-hydroxy-eicosatetranoic acid (15-HETE) and smaller amounts of prostaglandin E2 (PGE2) as well as fibronectin, a mediator involved in epithelial repair after injury. Epithelial cells obtained after bronchial brushing of 16 asthmatic (age 38 +/- 5 yr) and 11 normal subjects (age 36 +/- 5 yr) were studied. The percentage of epithelial cells was assessed by immunocytochemistry using an anti-cytokeratin antibody. The viability of the cells was assessed by trypan blue exclusion. The release of 15-HETE PGE2 and fibronectin was studied in resting cells and after A23187 calcium ionophore stimulation. Epithelial cells always comprised more than 86% of cells recovered, and the viability of epithelial cells was significantly (p < 0.001, Mann-Whitney U test) greater in normal subjects (54 +/- 5%) compared with asthmatic subjects (13 +/- 1%). The release of 15-HETE and fibronectin by resting epithelial cells was significantly greater in asthmatics (p < 0.05, Mann-Whitney U test) than in normal subjects. A23187 significantly (p < 0.05, Wilcoxon W test) increased the release of 15-HETE and fibronectin. There was no significant difference in the release of PGE2 by resting cells from either asthmatics or normal subjects, but challenge with A23187 induced a significant (p < 0.03, Wilcoxon W test) increase in PGE2 from cells of asthmatics but not from cells of normal subjects. This study shows that epithelial cells are activated and less viable in asthma and suggests a role for these cells in asthma.