INTERACTIVE ROLE OF NITRIC-OXIDE AND SUPEROXIDE ANION IN NEUTROPHIL-MEDIATED ENDOTHELIAL-CELL INJURY

This study addresses the interactive role of nitric oxide (NO) and rea ctive oxygen intermediates (ROI) by direct quantitation of NO and supe roxide (O-2(-)) in human neutrophil (PMN)-endothelial cell (EC) co-cul ture during PMN-mediated EC injury. The results directly demonstrate a n inverse correlation between NO and ROI levels in PMN-EC co-culture, which significantly alters the PMN-EC adhesion and PMN-mediated EC kil ling. N-formyl-methionyl-leucyl-phenylalanine (fMLF)-stimulated PMN ad hesion to cytokine-treated ED was decreased (> 25%) in the presence of S-nitroso-N-penicillamine, a NO donor. NO also inhibited EC killing b y stimulated PMN,suggesting its cytoprotective role. In addition, a si gnificant decrease in NO levels was observed in the PMN-EC co-culture compared with the EC cultured alone (422.45 +/- 35.76 vs. 800.79 +/- 4 1.69 pmol). The reduced NO levels were restored by the addition of sup eroxide dismutase, a scavenger of O-2(-), suggesting that PMN-derived O-2(-) is involved in the neutralization of NO in the co-culture. The results indicate an inverse correlation between NO and O-2(-) in PMN-E C interactions and suggest the need for a critical balance between the se two radicals in the regulation of PMN-mediated tissue injury.