NF-κB Activation Plays a Role in Superoxide-Mediated Cerebral Endothelial Dysfunction After Hypoxia/Reoxygenation

Abstract

Background and Purpose-Cerebral vascular injury occurs in response to hypoxia/reoxygenation (H/R). However, the cellular signaling pathways that regulate this event remain unclear. The present study was designed to determine whether reactive oxygen species (ROS) mediate endothelial dysfunction after H/R in cerebral resistance arteries and, if so, the relative contribution of ROS, NADPH oxidase, and a nuclear factor-B (NF-B) pathway. Methods-Arterial diameter and intraluminal pressure were simultaneously measured on rat posterior cerebral arteries (PCA). Superoxide was measured by 5-mol/L lucigenin-enhanced chemiluminescence. Results-Hypoxia/reoxygenation selectively inhibited cerebral vasodilation to the endothelium-dependent agonist acetylcholine (Ach) (0.01 to 10 mol/L) by Ϸ50%. Impaired vasodilation after H/R was reversed by 2,2,6,6-tetramethylpiperidine-N-oxyl (Tempo) (100 mol/L), a cell-permeable superoxide dismutase mimetic, and partially by ebselen (10 mol/L), a peroxynitrite scavenger. H/R-impaired vasodilation to Ach was also preserved by apocynin (1 mmol/L), a specific inhibitor for NADPH oxidase. Correspondingly, H/R significantly increased lucigenin-detectable superoxide, which was reduced by either Tempo or apocynin, but not by allopurinol (10 mol/L), an inhibitor of xanthine oxidase. Finally, the NF-B inhibitors helenalin (10 mol/L) and MG-132 (1 mol/L) independently antagonized H/R-impaired Ach-induced vasodilation without affecting dilator response to sodium nitroprusside, an endothelium-independent vasodilator. Conclusions-These results indicate that superoxide mediates cerebral endothelial dysfunction after hypoxia/reoxygenation largely via activation of NADPH oxidase and possibly activation of NF-B pathway.

Vascular effects of a common gene variant of extracellular superoxide dismutase in heart failure

“…Ebselen is not only a peroxynitrite scavenger (3,18,28) but also a glutathione peroxidase mimetic (22). Gene transfer of ecSOD increases hydrogen peroxide in vessels from rats with heart failure (11), but we found that ebselen did not reduce luminol-enhanced chemiluminescence, levels of superoxide, or responses to acetylcholine after gene transfer of ecSOD to rats with heart failure (data not shown).…”

“…Gene transfer of ecSOD increases hydrogen peroxide in vessels from rats with heart failure (11), but we found that ebselen did not reduce luminol-enhanced chemiluminescence, levels of superoxide, or responses to acetylcholine after gene transfer of ecSOD to rats with heart failure (data not shown). These results suggest that the dose of ebselen that we used may reduce levels of peroxynitrite but not other mediators of oxidative stress in this setting (28).…”

“…In some aortic rings, responses to acetylcholine were examined after 30 min incubation with ebselen (5 M), a scavenger of peroxynitrite (28)…”

“…Peroxynitrite, which is formed by the combination of NO and superoxide, is a marker of oxidative stress and also has adverse vascular effects (3,18,28). Vascular effects of peroxynitrite in heart failure are not known.…”

Hyperglycemia in Acute Ischemic Stroke: A Vascular Perspective

“…On reperfusion, oxygenrich blood returns to the ischemic tissue, providing abundant oxygen substrate for production of vascular superoxide by NAD(P)H oxidase (Xie et al, 2005), and perhaps uncoupled eNOS as well as xanthine oxidase (Beetsch et al, 1998). Reactive oxygen species production increases in both normoglycemic and hyperglycemic animals, though the increase is more dramatic in hyperglycemic animals (Wei and Quast, 1998).…”