NITRIC-OXIDE INHIBITS PEROXIDE-MEDIATED ENDOTHELIAL TOXICITY

Background. Oxidant molecules and nitric oxide (NO) have each been imp licated as mediators of endothelial cell damage, but the biologic effe ct of these molecules acting in concert is incompletely understood. Ma terials and methods. We studied the effects of an NO donor, S-nitroso- acetyl-D,L-penicillamine (SNAP), in combination with the peroxidants t ert-butyl hydroperoxide (TBH) and hydrogen peroxide (H2O2) on rabbit a ortic endothelial cells in culture, Cell viability was assessed using Alamar blue, a nontoxic dye indicator of cell metabolism, Lipid peroxi dation was assessed using a chemiluminescent single-photon counting te chnique. Results. After 90 min exposure to test reagents, there was co ncentration-dependent cytotoxicity for both TBH and H2O2. Peroxidant-i nduced cytotoxicity was significantly ameliorated by SNAP (10(-4) - 10 (-3) M). N-Acetylpenicillamine and NO-depleted SNAP failed to demonstr ate a cytoprotective effect against peroxidant cellular injury, thus i mplicating NO as the agent responsible for the protective effect. SNAP reduced lipid peroxidation caused by 10(-3) M TBH in a dose-dependent manner. Preincubation of cells with SNAP before exposure to peroxidan ts alone had no effect on toxicity. Conclusions. NO is cytoprotective to the endothelium in the presence of peroxidants through a reduction of lipid peroxidation. (C) 1998 Academic Press.