A comprehensive evaluation of the enzymatic and nonenzymatic antioxidant systems in childhood asthma

Background: Even though there is ample evidence on the oxidative stress in asthma, there is limited information on the antioxidant defense systems. Objectives: To conduct a comprehensive evaluation of various components of both enzymatic and nonenzymatic antioxidants in a large group of children with asthma. Methods: A total of 164 children with mild asthma and 173 healthy children were included in the study. Levels of the enzymes glutathione peroxidase and superoxide dismutase were measured by using ELISA, whereas reduced glutathione, ascorbic acid, alpha-tocopherol, lycopene, beta-carotene, amino acids participating in glutathione synthesis, and amino acids susceptible to oxidation were measured by HPLC. All comparisons were adjusted for atopy, body mass index, smoke exposure, and pet ownership. Results: Levels of the enzymes glutathione peroxidase and superoxide dismutase and of the nonenzymatic components of the antioxidant system including reduced glutathione, ascorbic acid, alpha-tocopherol, lycopene, and beta-carotene were significantly lower in children with asthma compared with healthy controls (P <.001 for each). Of the amino acids contributing to glutathione synthesis, glycine and glutamine were significantly lower in children with asthma (P <.001). The majority of the amino acid susceptible to oxidative stress displayed lower levels in children with asthma (P <.05). Conclusion: Childhood asthma is associated with significant decreases in various components of both enzymatic and nonenzymatic antioxidant defenses.