Influence of nitric oxide on the intracellular reduced glutathione pool: Different cellular capacities and strategies to encounter nitric oxide-mediated stress

Different cell types exhibit huge differences towards the cytotoxic action of NO. In search for an explanation, we used subtoxic concentrations of the NO-donors S-nitrosocysteine (SNOC) for short-term challenge and of (Z)-1- [N-(2-aminoethyl)-N-(2-ammonioethyl)amino] diazen-1-ium-1,2-diolate (DETA/N O) for longer periods of exposure, respectively, and subtoxic concentration s of the oxidant H2O2 to determine the impact on intracellular reduced glut athione (GSH) concentrations. We find that GSH concentrations are always de creased, but that different cell types show different responses. Incubation of the relatively NO-sensitive murine lymphocytes with both NO-donors, but not with H2O2, resulted in a nearly complete loss of intracellular GSH. Sh ort-term NO-treatment of P815 mastocytoma cells, also sensitive to NO-media ted cell death, decreased GSH to a similar extent only if either glutathion e reductase (GSHR) activity or gamma-glutamylcysteine synthetase (gamma GCS ) activity were inhibited concomitantly by specific inhibitors. Longterm NO -treatment of P815 cells, however, resulted in a significant decrease of GS H that could be further enhanced by inhibiting gamma GCS activity. In contr ast, neither short-term nor long-term NO-exposure nor H2O2-treatment affect ed intracellular GSH levels of L929 fibroblasts, which were previously show n to be extremely resistent towards NO, whereas concomitant gamma GCS inhib ition, but not GSHR inhibition, completely decreased GSH concentrations. Th ese results show that different cell types use different pathways trying to maintain glutathione concentrations to cope with nitrosative stress, and t he overall capability to maintain a critical amount of GSH correlates with susceptibility to NO-induced cell death. (C) 1999 Elsevier Science Inc.