Cigarette smoke irreversibly modifies glutathione in airway epithelial cells

In patients with chronic obstructive pulmonary disease ( COPD), an imbalance between oxidants and antioxidants is acknowledged to result in disease development and progression. Cigarette smoke ( CS) is known to deplete total glutathione (GSH + GSSG) in the airways. We hypothesized that components in the gaseous phase of CS may irreversibly react with GSH to form GSH derivatives that cannot be reduced (GSX), thereby causing this depletion. To understand this phenomenon, we investigated the effect of CS on GSH metabolism and identified the actual GSX compounds. CS and H2O2 (control) deplete reduced GSH in solution [Delta-54.1 +/- 1.7 mu M (P < 0.01) and -39.8 +/- 0.9 mu M (P < 0.01), respectively]. However, a significant decrease of GSH + GSSG was observed after CS (Delta=-75.1 +/- 7.6 mu M, P < 0.01), but not after H2O2. Exposure of A549 cells and primary bronchial epithelial cells to CS decreased free sulfhydryl (-SH) groups (Delta=-64.2 +/- 14.6 mu M/mg protein, P < 0.05) and irreversibly modified GSH + GSSG (Delta=-17.7 +/- 1.9 mu M, P < 0.01) compared with nonexposed cells or H2O2 control. Mass spectrometry (MS) showed that GSH was modified to glutathione-aldehyde derivatives. Further MS identification showed that GSH was bound to acrolein and crotonaldehyde and another, yet to be identified, structure. Our data show that CS does not oxidize GSH to GSSG but, rather, reacts to nonreducible glutathione-aldehyde derivatives, thereby depleting the total available GSH pool.