Ozone, but not nitrogen dioxide, exposure decreases glutathione peroxidases in epithelial lining fluid of human lung

Antioxidants, such as glutathione peroxidases (GPxs), in epithelial lining fluid (ELF) protect against health effects of oxidant pollutants, which includes O₃ or NO₂. We hypothesized that GPxs concentration in ELF is responsive to O₃ or NO₂ exposure. Subjects underwent two 4-h exposures to O₃ (0.22 ppm) and one to air. In another experiment, subjects underwent 3-h exposures to air and NO₂ (0.6 and 1.5 ppm). Bronchoalveolar lavage (BAL) was performed immediately or 18 h after O₃ exposure and 3.5 h after each NO₂ exposure. GPx activity and extracellular GPx (eGPx) protein concentrations were determined in ELF, and their relationships to markers of lung function, inflammation, and epithelial permeability were examined. Although the total amounts were not changed, basal (air) GPx activity (223.6 ± 24.4 mU/ml), basal eGPx protein concentration (2.62 ± 0.25 μg/ml), and basal ELF dilution factor (152.3 ± 8.4) decreased 40% immediately after O₃ exposure and remained 30% decreased 18 h after exposure (p = 0.0001). No effect of NO₂ exposure on GPxs concentration was detected. There was an inverse correlation between baseline ELF eGPx protein concentration and the change in PMN 18 h after O₃ exposure (p = 0.04). Thus, O₃, a strong oxidant, decreases both GPx activity and eGPx protein in ELF, whereas NO₂, a weaker oxidant, does not. eGPx in ELF may protect against O₃-induced airway inflammation.