Increasing sputum levels of gamma-glutamyltransferase may identify cystic fibrosis patients who do not benefit from inhaled glutathione

Glutathione (GSH) is decreased in cystic fibrosis (CF) airways, thus its resupply by inhalation has been employed to restore antioxidant defense. CF airways present however increased activity of gamma-glutamyltransferase (GGT), the enzyme specifically capable of degrading GSH, and thus inhaled GSH might be promptly catabolized. In addition, prooxidant reactions are known to originate during GGT-mediated GSH catabolism. We determined levels of GGT in the sputum samples obtained from a previously published trial of GSH inhalation treatment, and analyzed their correlations with inflammatory markers and FEV1% values. Results indicate that differentiating patients with increasing vs. decreasing GGT activity – as measured in sputum before and after the six months duration of the study – may discriminate subjects more likely profiting from inhaled GSH, as opposed to those with increasing GGT in which these treatments might even produce aggravation of the damage.