Proliferation and activation of bronchial epithelial cells in corticosteroid-dependent asthma

Abstract

Background: Structural and functional characteristics of bronchial epithelial cells in corticosteroid-dependent asthma are unknown. Objective: In bronchial biopsy specimens from 16 control, 9 untreated asthmatic, 9 inhaled corticosteroid-treated asthmatic, and 19 corticosteroid-dependent asthmatic subjects, we evaluated epithelium morphology and patterns of cell apoptosis, proliferation, and activation. Methods: We used the terminal deoxynucleotidyl-mediated dUTP nick end labeling (TUNEL) technique to study apoptosis. Immunohistochemistry was used to evaluate the expression of molecules related to apoptosis (such as Bcl-2 and P53), cell proliferation (PCNA), and cell activation (NFκB and CD40/CD40-L). Results: Epithelium thickness was higher in corticosteroid-dependent asthmatic and control subjects than in inhaled corticosteroid-treated and untreated asthmatic subjects (P < .0001 and P < .0003). Very few TUNEL-positive epithelial cells were found in the 4 groups. Bcl-2 expression was higher in all groups of asthmatic subjects than in controls (P < .001). In corticosteroid-dependent asthmatic subjects, PCNA, NFκB, and CD40-L expression was higher than in inhaled corticostetold-treated asthmatic (P < .001), untreated asthmatic (P < .001 and P < .04), and control (P < .01) subjects. CD40 expression was greater in corticosteroid-dependent asthmatic and untreated asthmatic subjects than in inhaled corticosteroid-treated asthmatic subjects (P < .0001 and P < .0006) and controls (P < .02 and P < .03). In corticosteroid-dependent asthma, PCNA expression was correlated with the epithelium thickness (P < .007). Conclusion: This study shows that in bronchial epithelial cells of corticosteroid-dependent asthma, markers of cell survival and proliferation are coexpressed with markers of cells activation, suggesting that in this disease epithelium repair is associated with a persistent activation state of epithelial cells.