Endothelial cell oxidant production: effect of NADPH oxidase inhibitors

The effects of known leukocyte NADPH oxidase inhibitors on general cellular oxidant production in cultured human endothelial cells (EC) has been investigated. EC were stimulated with 10 nM phorbol 12-myristate 13-acetate and cellular oxidant production measured in the presence and absence of inhibitors that act on various substituents of the oxidase complex and its activation pathways. The effects of the cytosolic oxidase subunit translocation inhibitors, catechols (3,4-dihydroxybenzaldehyde, caffeic acid, and protocatechuic acid), ortho-methoxy-substituted catechols (apocynin, vanillin, and 4-nitroguaiacol), and quinone, 1,4-naphthoquinone; flavoprotein inhibitors, diphenylene iodonium and quinacrine; haem ligands, imidazole and pyridine; directly acting thiol reagents, disulfiram and penicillamine; NADPH analogue, Cibacron Blue; redox active inhibitors, quercetin and esculetin; intracellular calcium antagonist, TMB-8; and calmodulin antagonists, W-7 and trifluoperazine, were determined. All compounds reduced oxidant production in stimulated EC. These findings add to previous observations suggesting the presence of a functionally active NADPH oxidase in EC. Identifying the major cellular reactive oxygen species source in perturbed EC will provide new insights into our understanding of endothelial dysfunction, which has been hypothesized to be a major contributing factor in the pathogenesis of atherosclerosis.