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 inves tigated. EC were stimulated with 10 nM phorbol 12-myristate 13-acetate and cellular oxidant production measured in the presence and absence of inhibit ors that act on various substituents of the oxidase complex and its activat ion pathways. The effects of the cytosolic oxidase subunit translocation in hibitors, catechols (3,4-dihydroxybenzaldehyde, caffeic acid, and protocate chuic 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 analogu e, Cibacron Blue; redox active inhibitors, quercetin and esculetin; intrace llular calcium antagonist, TMB-8; and calmodulin antagonists, W-7 and trifl uoperazine, were determined. All compounds reduced oxidant production in st imulated EC, These findings add to previous observations suggesting the pre sence of a functionally active NADPH oxidase in EC. Identifying the major c ellular reactive oxygen species source in perturbed EC will provide new ins ights into our understanding of endothelial dysfunction, which has been hyp othesized to be a major contributing factor in the pathogenesis of atherosc lerosis.