Glutathione oxidation by hypochlorous acid in endothelial cells produces glutathione sulfonamide as a major product but not glutathione disulfide

Treatment of cells with hypochlorous acid (HOCl) at sublethal doses causes a concentration-dependent loss in reduced glutathione (GSH) levels. We have investigated the products of the reaction of HOCl with GSH in human umbili cal vein endothelial cells. Despite a complete loss of GSH, there were only very small increases in intracellular and extracellular glutathione disulf ide and glutathione sulfonic acid after exposure to HOCl. S-35 labeling of the GSH pool showed only a minimal increase in protein-bound GSH, suggestin g that S-thiolation was not a major contributor to HOCl-mediated loss of GS H in endothelial cells. Rather, the products of the reaction were mostly ex ported from cells and included a peak that co-eluted with the cyclic sulfon amide that is a product of the reaction of GSH with reagent HOCl. Evidence of this species in endothelial cell supernatants after HOCl treatment was a lso obtained using electrospray mass spectrometry. In conclusion, expo sure to HOCl causes the irreversible loss of cellular GSH with the formation of novel products that are rapidly exported from the cell, and resynthesis of GSH will be required to restore levels. The loss of GSH would alter the re dox state of the cell and compromise its defenses against further oxidative stress.