Glutathione in induced sputum of healthy individuals and patients with asthma

Abstract

BACKGROUND Glutathione is central to the antioxidant defences of the lung. The aim of this study was to determine whether sputum induction can be used for the measurement of glutathione in the respiratory tract. METHODS Saliva and induced sputum (3% NaCl, 20 minutes) samples were collected from 10 healthy individuals and 10 patients with stable asthma receiving treatment with inhaled corticosteroids. Samples were chilled on ice and dispersed by dilution with ice cold phosphate buffered saline and pipetting. Cell-free supernatants were obtained by centrifugation of samples and filtration of supernatants and analysed for total glutathione, glutathione disulfide, and albumin content. The cells were treated with dithiothreitol and cell numbers, cell viability, and differential cell patterns were determined. RESULTS As judged by cell viability and percentage of non-squamous cells, adequate sputum samples were obtained from nine healthy and nine asthmatic subjects. The salivary total glutathione content was low (median concentration 1.2 μM (range 0.8–1.5) in healthy subjects and 0.9 μM (0.7–1.2) in asthmatic subjects). The sputum total glutathione content of both healthy and asthmatic subjects was within the same range (3.9 (1.0–12.3) μM and 6.4 (1.3–19.2) μM, respectively; p=0.35). Surprisingly, and in marked contrast to results obtained with bronchoalveolar lavage, sputum levels of glutathione disulfide represented more than 50% of the total glutathione in both groups (50.9% (range 24.6–83.1) and 72.3% (range 36.5–97.4), respectively; p=0.2). CONCLUSIONS The results of this study indicate that sputum induction can be used to measure the glutathione content of bronchial secretions. Sputum glutathione levels of stable asthmatic patients did not differ significantly from healthy controls.