Peroxynitrite increases iNOS through NF- B and decreases prostacyclin synthase in endothelial cells

Cooke, Christy-Lynn M., and Sandra T. Davidge. Peroxynitrite increases iNOS through NFB and decreases prostacyclin synthase in endothelial cells. Am J Physiol Cell Physiol 282: C395–C402, 2002. First published October 10, 2001; 10.1152/ajpcell.00295.2001.—Peroxynitrite, a marker of oxidative stress, is elevated in conditions associated with vascular endothelial cell dysfunction, such as atherosclerosis, preeclampsia, and diabetes. However, the effects of peroxynitrite on endothelial cell function are not clear. The endothelium-derived enzymes nitric oxide synthase (NOS) and prostaglandin H synthase (PGHS) mediate vascular reactivity and contain oxidant-sensitive isoforms (iNOS and PGHS-2) that can be induced by nuclear factor (NF)B activation. We investigated the effect(s) of peroxynitrite on NOS and PGHS pathways in endothelial cells. We hypothesized that peroxynitrite will increase levels of iNOS and PGHS-2 through activation of NFB. Western immunoblots of endothelial cells show that 3-morpholinosydnonimine (SIN-1; 0.5 mM), a peroxynitrite donor, increased iNOS protein mass, which can be inhibited by pyrroline dithiocarbamate (an NFB inhibitor) (167 24.2 vs. 78 19%, P 0.05, n 6). SIN-1 treatment also significantly increased NFB translocation into endothelial cell nuclei (135 10%, P 0.05). Endothelial NOS, PGHS-1, and PGHS-2 protein levels were not altered by SIN-1. However, prostacyclin synthase protein mass, but not mRNA, was significantly reduced in SIN-1treated endothelial cells (78 8.9%, P 0.05). Our results illustrate novel mechanisms through which peroxynitrite may modulate vascular endothelial function.