Vascular endothelial growth factor levels in induced sputum and emphysematous changes in smoking asthmatic patients

Background Although asthmatic patients frequently smoke cigarettes, the effect of smoking on asthmatic lungs has not been extensively studied. Vascular endothelial growth factor (VEGF) has been suggested to play a role in the pathogenesis of asthma and emphysema. Objective To determine whether the level of airway VEGF might be related to emphysematous lung changes in asthmatic patients with a history of smoking. Methods Pulmonary function tests and volumetric computed tomography (CT) of the lungs were performed in 10 ex-smoking and 15 nonsmoking asthmatic patients. Levels of VEGF were evaluated in the supernatants of induced sputum using an enzyme-linked immunosorbent assay method in these 25 asthmatic patients and in 10 healthy nonsmoking controls. Associations among sputum VEGF levels, emphysema indices on CT, and clinical variables were analyzed. Results Ex-smoking asthmatic patients showed a higher emphysema index on volumetric CT and a decreased mean forced expiratory volume in 1 second to forced vital capacity ratio compared with nonsmoking asthmatic patients. Sputum VEGF levels in asthmatic patients with a history of smoking were significantly lower than those in nonsmoking asthmatic patients but remained higher than those in control subjects. Furthermore, the emphysema index was significantly correlated with sputum VEGF levels in asthmatic patients. Conclusion Lower VEGF levels in the airway might be a surrogate marker for emphysematous changes in the lungs, especially in asthmatic patients with a history of smoking.