Effect of ozone on allergic airway inflammation.

Abstract

Exposure to ozone (O3) is associated with increased risk of exacerbations of asthma, but the underlying mechanisms are not well studied. We sought to determine whether O3 exposure would enhance airway inflammatory responses to allergen and the GSTM1-null genotype would modulate this enhancement. In a crossover design, 10 asthmatic participants (5 with GSTM1-null genotype) who had specific sensitization to Dermatophagoides pteronyssinus (DP) were exposed to 160 ppb O3 or filtered air (FA) control for 4 hours on 2 separate days at least 3 weeks apart. At 20 hours after exposure, endobronchial challenge with DP allergen, and sham normal saline (NS) instillation, were performed in separate bronchi. Six hours later, a second bronchoscopy was performed to collect bronchoalveolar lavage (BAL) from the DP- and NS-challenged segments for analyses of inflammatory biomarkers. Linear regression compared cell and cytokine responses across the 4 exposure groups (FA-NS, O3-NS, FA-DP, O3-DP). Effect modification by GSTM1 genotype was assessed in stratified regressions. BAL eosinophil counts were increased in segments challenged with DP compared to sham-challenged segments (P < .01). DP challenge compared to sham also caused a significant increase in BAL concentrations of the TH2 cytokines IL-4, IL-5, IL-10, and IL-13 (P < .03 for all comparisons). O3 exposure did not significantly affect BAL cells or cytokine after DP challenge. Compared to GSTM1-present participants, GSTM1-null participants had significantly lower eosinophil (P < .041) and IL-4 (P < .014) responses to DP challenge after O3 exposure. While O3 did not cause a clear differential effect on airway inflammatory responses to allergen challenge, those responses did appear to be modulated by the antioxidant enzyme, GSTM1.