NITRIC-OXIDE DONOR PREVENTS HYDROGEN PEROXIDE-MEDIATED ENDOTHELIAL-CELL INJURY

Because nitric oxide is being used to treat acute lung injury and beca use it may either reduce or potentiate oxidant-mediated vascular injur y, we studied the effect of the nitric oxide donor S-nitroso-N-acetyl- D-penicillamine (SNAP) on hydrogen peroxide (H2O2)-induced injury to c ultured rat lung microvascular endothelial cells (RLMVC). Cells were e xposed to H2O2 through its enzymatic generation by glucose and glucose oxidase or by its direct application. Glucose oxidase exposure causes a concentration- and time-dependent increase in (51)chromium (Cr-51) release from RLMVC. Catalase, dimethylthiourea or deferoxamine protect s against this oxidant injury. SNAP (100 mu M) prevents the increase i n Cr-51 release resulting from glucose oxidase or direct application o f H2O2. N-acetyl-D-penicillamine is ineffective. Photo-decayed SNAP sl ightly decreases the Cr-51 release caused by glucose oxidase but not t he injury produced by directly adding H2O2. Treatment with the guanosi ne 3',5'-cyclic monophosphate (cGMP) analogue 8-BrcGMP (1-10 mM) provi des no protection. SNAP decreases in vitro the net oxidation of ferrou s to ferric iron by H2O2, the iron-catalyzed consumption of H2O2 in Fe nton's reaction, the iron-mediated generation of hydroxyl radicals, an d the Fe2+-H2O2-catalyzed peroxidation of Lipid membranes. Providing e xogenous nitric oxide dramatically prevents H2O2-mediated endothelial injury, likely by reducing iron-mediated oxidant generation and subseq uent lipid peroxidation.