title: Estradiol attenuates high glucose-induced endothelial nitrotyrosine: role for neuronal nitric oxide synthase.
abstract: Hyperglycemia in diabetes causes increased oxidative stress in the vascular endothelium with generation of free radicals such as superoxide. Peroxynitrite, a highly reactive species generated from superoxide and nitric oxide (NO), induces proinflammatory tyrosine nitration of intracellular proteins under such conditions. The female sex hormone estrogen appears to exert protective effects on the nondiabetic endothelium. However, several studies show reduced vascular protection in women with diabetes, suggesting alterations in estrogen signaling under high glucose. In this study, we examined the endothelial effects of estrogen under increasing glucose levels, focusing on nitrotyrosine and peroxynitrite. Human umbilical vein endothelial cells were incubated with normal (5.5 mM) or high (15.5 or 30.5 mM) glucose before addition of estradiol (E2, 1 or 10 nM). Selective NO synthase (NOS) inhibitors were used to determine the role of specific NOS isoforms. Addition of E2 significantly reduced high glucose-induced increase in peroxynitrite and consequently, nitrotyrosine. The superoxide levels were unchanged, suggesting effects on NO generation. Inhibition of neuronal NOS (nNOS) reduced high glucose-induced nitrotyrosine, demonstrating a critical role for this enzyme. E2 increased nNOS activity under normal glucose while decreasing it under high glucose as determined by its phosphorylation status. These data show that nNOS contributes to endothelial peroxynitrite and subsequent nitrotyrosine generation under high glucose, which can be attenuated by E2 through nNOS inhibition. The altered regulation of nNOS by E2 under high glucose is a potential therapeutic target in women with diabetes.
authors.affiliation: Department of Obstetrics and Gynecology, Women and Children's Health Research Institute, Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Subhadeep
authors.initials: S
authors.lastname: Chakrabarti
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Cheung
authors.forename: Sandra T
authors.initials: ST
authors.lastname: Davidge
mesh_terms: D003920:Diabetes Mellitus / Q000378:metabolism* / Q000473:pathology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D005947:Glucose / Q000009:adverse effects* / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D030421:Peroxynitrous Acid / Q000009:adverse effects; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000037:antagonists & inhibitors / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D013481:Superoxides; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D004958:Estradiol; C496320:NOS1 protein, human; C496314:NOS3 protein, human; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; D005947:Glucose