Oxidative stress and its determinants in the airways of children with asthma

BACKGROUND: There is ample evidence for the existence of a systemic oxidative stress in childhood asthma but relatively little information on the oxidant stress in the airways. OBJECTIVE: To determine the extent of oxidant/antioxidant imbalance and describe its determinants in the airways of asthmatic children including asthma severity and the genotype of the antioxidant enzymes. METHODS: One hundred and ten children with mild asthma, 30 children with moderate asthma and 191 healthy controls were included in the study. Exhaled breath condensate (EBC) was collected from all children with EcoScreen. Levels of malondialdehyde were measured as the indicator of oxidative stress, and of reduced glutathione as the indicator of antioxidant defense. Children were genotyped for the presence of null variants of glutathione S transferase (GST) T1 and GSTM1, and ile105val variant of GSTP1. Risk factors were analyzed with multivariate logistic regression. RESULTS: EBC contained significantly higher levels of malondialdehyde and lower levels of reduced glutathione in asthmatic children compared with healthy controls (P < 0.001 for each), whereas there was no difference between mild and moderate asthmatics. Multivariate logistic regression identified asthma as the only independent factor contributing to oxidative stress. Genotypes of the antioxidant enzymes had no effect on the oxidative burden. CONCLUSIONS: Asthma is associated with an extremely powerful oxidative stress not only in the systemic circulation but also in the airways.