Nitric oxide donor-induced hyperpermeability of cultured intestinal epithelial monolayers: role of superoxide radical, hydroxyl radical, and peroxynitrite

Many of the cytopathic effects of nitric oxide (NO.) are mediated by peroxynitrite (PN), a product of the reaction between NO. and superoxide radical (O-2(.-)). In the present study, we investigated the role of PN, O-2(.-) and hydroxyl radical (OH.) as mediators of epithelial hyperpermeability induced by the NO. donor, S-nitroso-N-acetylpenicillamine (SNAP), and the PN generator, 3-morpholinosydnonimine (SIN-1). Caco-2(BBe) enterocytic monolayers were grown on permeable supports in bicameral chambers. Epithelial permeability, measured as the apical-to-basolateral flux of fluorescein disulfonic acid, increased after 24 h of incubation with 5.0 mM SNAP or SIN-1. Addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylidazoline-1- oxyl-3-oxide, an NO. scavenger, or Tiron, an O-2(.-) scavenger, reduced the increase in permeability induced by both donor compounds. The SNAP-induced increase in permeability was prevented by allopurinol, an inhibitor of xanthine oxidase (a source of endogenous O-2(.-)). Diethyldithiocarbamate, a superoxide dismutase inhibitor, and pyrogallol, an O-2(.-) generator, potentiated the increase in permeability induced by SNAP. Addition of the PN scavengers deferoxamine, urate, or glutathione, or the OH. scavenger mannitol, attenuated the increase in permeability induced by both SNAP and SIN-1. Both donor compounds decreased intracellular levels of glutathione and protein-bound sulfhydryl groups, suggesting the generation of a potent oxidant. These results support a role for PN, and possibly OH., in the pathogenesis of NO. donor-induced intestinal epithelial hyperpermeability. (C) 1998 Elsevier Science B.V. All rights reserved.