Role of tight junction derangement in the endothelial dysfunction elicited by exogenous and endogenous peroxynitrite and poly(ADP-ribose) synthetase

DNA single-strand breakage and activation of the nuclear enzyme poly(ADP-ribose) synthetase (PARS) triggers an energy consuming, inefficient repair cycle, which contributes to peroxynitrite-induced cellular injury. Here, we investigated whether peroxynitrite and PARS activation are involved in tight junctions (tight junction) derangement in the endothelial dysfunction in cells exposed to peroxynitrite and in vascular rings of animals subjected to zymosan non-septic shock. In human umbilical vein endothelial cells (HUVEC) in vitro, peroxynitrite caused a dose-dependent suppression of mitochondrial respiration, as measured by the mitochondrial-dependent conversion of the dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide to formazan. Moreover, peroxynitrite caused activation of PARS. Inhibition of PARS by 3-aminobenzamide (3-AB; 1 mM) reduced the peroxynitrite-induced suppression of mitochondrial respiration in HUVECs. Vascular rings exposed to peroxynitrite exhibited reduced endothelium-dependent relaxant responses in response to acetylcholine. Peroxynitrite incubation also caused a significant derangement of zonula occludens (ZO)-1, which was significantly affected by pharmacological inhibition of PARS. 3-AB ameliorated the development of this peroxynitrite-induced endothelial dysfunction. In vascular rings obtained from the zymosan-treated rats, there was a marked suppression of the endothelium-dependent relaxation ex vivo, which was reduced by, in vivo 3-AB treatment. A significant derangement of ZO-1 was observed in vascular rings from zymosan-treated rats. Tight junction alteration was significantly reduced by in vivo 3-AB treatment. Thus, activation of PARS by exogenous and endogenous peroxynitrite may be involved in the tight junction derangement associated with endothelial dysfunction. Inhibition of PARS may be a novel pharmacological approach to preserve endothelial tight junction function in shock and inflammation.