Airway Epithelial Changes in Smokers but Not in Ex-Smokers with Asthma

Abstract

Smoking has detrimental effects on asthma outcome, such as increased cough, wheezing, sputum production, and frequency of asthma attacks. This results in accelerated lung function decline. The underlying pathological process of smoke-induced deterioration of asthma is unknown. To compare bronchial inflammation and remodeling in never-smokers, ex-smokers, and current smokers with asthma. A total of 147 patients with asthma (66 never-smokers, 46 ex-smokers, and 35 current smokers) were investigated. Lung function, exhaled nitric oxide levels, and symptom questionnaires were assessed, and induced sputum and bronchial biopsies were obtained for determination of airway inflammation and remodeling. Smokers with asthma had lower FEV(1) and alveolar and bronchial nitric oxide levels than never-smokers. Smokers also had more goblet cells and mucus-positive epithelium, increased epithelial thickness, and a higher proliferation rate of intact and basal epithelium than ex-smokers and never-smokers. Smokers had higher numbers of mast cells and lower numbers of eosinophils than never-smokers. Ex-smokers had similar goblet cell numbers and mucus-positive epithelium, epithelial thickness, epithelial proliferation rate, and mast cell numbers as never-smokers. Smokers with asthma have epithelial changes that are associated with increased asthma symptoms, such as shortness of breath and phlegm production. The fact that epithelial characteristics in ex-smokers are similar to those in never-smokers suggests that the smoke-induced changes can be reversed by smoking cessation.