Localization of gamma-glutamylcysteine synthetase messenger RNA expressionin lungs of smokers and patients with chronic obstructive pulmonary disease

Cigarette smoking results in an oxidant/antioxidant imbalance in the lungs and inflammation, which are considered to be key factors in the pathogenesi s of chronic obstructive pulmonary disease (COPD). Glutathione (GSH) is an important protective antioxidant in lung epithelial cells and epithelial li ning fluid. De novo GSH synthesis in cells occurs by a two-enzyme process. The rate-limiting enzyme is gamma-glutamylcysteine synthetase (gamma-GCS), in which the heavy subunit (HS) constitutes most of its catalytic activity. The localization and expression of gamma-GCS-HS in specific lung cells as well as possible differences in its expression between smokers with and wit hout COPD have not yet been studied. The purpose of this study was to inves tigate gamma-GCS-HS expression using messenger RNA in situ hybridization in peripheral lung tissue. We studied 23 current or ex-smokers with similar s moking histories with (n = 11; forced expiratory volume in 1 s [FEV1] < 75% predicted) or without COPD (n = 12; FEV1 < 84% predicted). We assessed the relations between pulmonary gamma-GCS-HS expression, FEV1 and transforming growth factor-beta 1 (TGF beta(1)), because TGF beta(1) can modulate gamma -GCS-HS expression in lung epithelial cells. Gamma-GCS-HS is predominantly expressed by airway and alveolar epithelial cells, alveolar CD68+ cells (ma crophages), and endothelial cells of both arteries and veins. In subjects w ith COPD, semiquantitative analysis revealed higher levels of gamma-GCS-HS messenger RNA in alveolar epithelium (1.5 times, p < .04) and a trend for a higher expression in bronchiolar epithelium (1.3 times, p = .075) compared with subjects without COPD. We did not observe a significant correlation b etween airway and alveolar epithelial gamma-GCS-HS expression and TGF beta( 1) expression (r = .20), FEV1 percentage predicted (r = .18), or FEV1/force d vital capacity ratio (r = .14; p > .05). Our results show that gamma-GCS- HS is localized, particularly in lung epithelium, and shows higher expressi on in smokers with COPD. This suggests a specific role for enhanced GSH syn thesis as a mechanism to provide an adaptive response against oxidative str ess in patients with COPD.(C) 2000 Elsevier Science Inc.