The phagocytosis-associated respiratory burst in human monocytes is associated with increased uptake of glutathione

During the phagocytic respiratory burst, oxygen is converted to potent cyto toxic oxidants, Monocytes and macrophages are potentially long-lived, and w e have hypothesized that protective mechanisms against oxidant stress are v aried and fully expressed in these cells. We report here that the respirato ry burst in monocytes is accompanied by an increase in the uptake of [S-35] glutathione ([S-35]GSH) after 20-30 min to levels up to 10-fold greater tha n those at baseline. By 30 min, 49% of the cell-associated radioactivity wa s in the cytosol, 41% was in membrane, and 10% was associated with the nucl ear fraction. GSH uptake was inhibited by catalase, which removes hydrogen peroxide (H2O2), and micromolar H2O2 stimulated GSH uptake effectively in m onocytes and also lymphocytes, Oxidation of GSH to glutathione disulfide wi th H2O2 and glutathione peroxidase prevented uptake. Acivicin, which inhibi ts GSH breakdown by gamma -glutamyl transpeptidase (GGT), had no effect on the enhanced uptake seen during the respiratory burst. Uptake of cysteine o r cystine, possible products of GGT activity, stayed the same or decreased during the respiratory burst. These results suggest that a GGT-independent mechanism is responsible for the enhanced GSH uptake seen during the respir atory burst. We describe here a sodium-independent, methionine-inhibitable transport system with a K-m (8.5 muM) for GSH approximating the plasma GSH concentration. These results suggest that monocytes have a specific GSH tra nsporter that is triggered by the release of H2O2 during the respiratory bu rst and that induces the uptake of GSH into the cell. Such a mechanism has the potential to protect the phagocyte against oxidant damage.