Abstract
BACKGROUND: There is evidence that the bronchial microcirculation has the potential to contribute to the pathophysiological mechanisms of exercise induced bronchoconstriction (EIB) in asthmatic subjects. Vascular endothelial growth factor (VEGF), which is highly expressed in asthmatic airways, increases vascular permeability. The relationship between VEGF levels in induced sputum and the severity of EIB in asthmatic subjects was studied. METHODS: The concentration of VEGF in induced sputum was examined in 23 asthmatic subjects and 11 normal controls. The asthmatic subjects performed an exercise test and the % maximal fall in forced expiratory volume in 1 second (FEV(1)) was measured. Beclomethasone dipropionate (BDP) 400 micro g twice daily was administered to the asthmatic subjects for 8 weeks and the exercise test and sputum induction were repeated. RESULTS: The concentration of VEGF in induced sputum was significantly higher in asthmatic subjects than in normal controls. There was a significant correlation between the concentration of VEGF and the % maximal fall in FEV(1) (r=0.826, p=0.0001) and between the concentration of VEGF and airway vascular permeability index (r=0.621, p=0.0037). After treatment with inhaled BDP there was a significant decrease in the concentration of VEGF in the asthmatic subjects (before treatment: 7051 (2361) pg/ml, after treatment: 4498 (2135) pg/ml, p<0.0001). The change in the concentration of VEGF was significantly correlated with the change in the % maximal fall in FEV(1) (r=0.463, p=0.031). CONCLUSIONS: Excessive production of VEGF in asthmatic airways may contribute to the pathogenesis of EIB via increased airway vascular permeability.