Glutathione and glutathione peroxidase in sputum samples of adult patients with cystic fibrosis

Abstract

Background: Reduced glutathione (GSH) is a major antioxidant in the lung. In cystic fibrosis (CF) patients, extracellular GSH levels of lower airways, obtained by bronchoalveolar lavage (BAL), were reported to be lower than non-CF individuals. Methods: Upper airway secretions of stable adult CF patients (29 spontaneous and 13 induced sputum) and non-CF individuals (14 healthy and 12 asthmatics; all induced sputum) were analyzed for total glutathione (i.e. the sum of reduced, GSH, and oxidized, GSSG, forms), GSH and GSSG levels by enzymatic kinetic assay. Results: In CF, both spontaneous and induced sputum samples were comparable in total glutathione levels which were surprisingly high (median concentration of 9.2 (range 1.4–65.2) and 11.6 (1.1–69.8) μM, respectively). In non-CF individuals, total glutathione levels were significantly lower (healthy 2.8 (1.0–12.3), asthmatics (5.3 (1.3–19.2) μM; p<0.001, both vs. CF). In CF, more than 90% of total glutathione was represented by GSH, whereas in non-CF controls, GSH made up less than 50% of total glutathione ( p<0.001). Conclusions: In contrast to BAL, CF sputum contains high levels of GSH. Sputum induction is a potentially useful procedure to monitor antioxidant levels in upper airways of CF patients.