Background: Chronic alcoholism is associated with an elevated risk for pulmonary infection and a 3-fold chance for incidence and mortality of acute respiratory distress syndrome with critical injury. Limited sampling of the alveolar lining fluid has restricted clinical studies of the role of glutathione (GSH) redox balance in pulmonary function and diseased states. Non-invasive sampling in the exhaled breath condensate (EBC) to monitor alveolar GSH would facilitate research in pulmonary oxidative stress.
Methods: EBC was collected from otherwise healthy subjects with and without a history of alcohol abuse. Reduced and oxidized EBC glutathione (GSH and GSSG, respectively), pH, and hydrogen peroxide were measured.
Results: GSH was statistically decreased in alcohol abusers only when normalized to protein (4.7nmol/mg protein [0.75, 11.4] vs. 13.4 [7.8, 26.4], p=0.03). In contrast, GSSG was significantly elevated in the EBC from alcohol abusers when compared to controls, 5.62 [0.45, 8.94] vs. 0.50nM [0.38, 0.80], p=0.03. Thus, a greater percentage was in the oxidized GSSG form when subjects abused alcohol (35.3% [11.8, 58.1] vs. 5.2 [3.6, 6.1], p<0.001). These concentrations represented a 40mV shift in GSH redox state towards a more oxidized state.
Conclusions: Proper sample preparation was essential to prevent GSH loss and artificial oxidation. The shift in redox potential or %GSSG, which were not affected by dilution, may serve as better markers of pulmonary oxidative stress. Furthermore, these data suggested that the oxidant stress observed in the lavage fluid of otherwise healthy alcoholics could be measured non-invasively in the EBC.