Genetic polymorphism of GSTM1 and antioxidant supplementation influence lung function in relation to ozone exposure in asthmatic children in Mexico City

Background: We recently reported that antioxidant supplementation with vitamins C and E mitigated ozone related decline in forced expiratory flow (FEF25–75) in 158 asthmatic children in an area with high ozone exposure in Mexico City. Methods: A study was undertaken to determine whether deletion of glutathione S-transferase M1 (GSTM1 null genotype), a gene involved in response to oxidative stress, influences ozone related decline in FEF25–75 and the benefit of antioxidant supplementation. Results: GSTM1 null children receiving placebo had significant ozone related decrements in FEF25–75 (percentage change per 50 ppb of ozone 2.9 (95% CI -5.2 to -0.6), p = 0.01); GSTM1 positive children did not. Conversely, the effect of antioxidants was stronger in children with the GSTM1 null genotype. Conclusions: Asthmatic children with a genetic deficiency of GSTM1 may be more susceptible to the deleterious effects of ozone on the small airways and might derive greater benefit from antioxidant supplementation.