title: Estrogen induces nitric oxide production via nitric oxide synthase activation in endothelial cells.
abstract: BACKGROUND
  17β-estradiol (E2) has been found to induce vasodilation in the cardiovascular system and at physiological levels, resulting in prevention of cerebral vasospasm following subarachnoid hemorrhage (SAH) in animal models. The goal of this study was to analyze the cellular mechanism of nitric oxide (NO) production and its relation to E2, in vitro in brain and peripheral endothelial cells.
  
  
  METHODS
  Human umbilical endothelial cells (HUVEC) and brain endothelial cells (bEnd.3) were treated with estradiol (E2, 0.1, 10, 100, and 1,000 nM), and supernatant was collected at 0, 5, 15, 30, 60, and 120 min for nitric oxide metabolome (nitrite, NO₂) measurements. Cells were also treated with E2 in the presence of 1400W, a potent eNOS inhibitor, and ICI, an antagonist of estradiol receptors (ERs). Effects of E2 on eNOS protein expression were assessed with Western blot analysis.
  
  
  RESULTS
  E2 significantly increased NO2 levels irrespective of its concentration in both cell lines by 35 % and 42 % (p < 0.05). The addition of an E2 antagonist, ICI (10 μM), prevented the E2-induced increases in NO2 levels (11 % p > 0.05). The combination of E2 (10 nM) and a NOS inhibitor (1400W, 5 μM) inhibited NO2 increases in addition (4 %, p > 0.05). E2 induced increases in eNOS protein levels and phosphorylated eNOS (eNOS(p)).
  
  
  CONCLUSIONS
  This study indicates that E2 induces NO level increases in cerebral and peripheral endothelial cells in vitro via eNOS activation and through E2 receptor-mediated mechanisms. Further in vivo studies are warranted to evaluate the therapeutic value of estrogen for the treatment of SAH-induced vasospasm.
authors.affiliation: Department of Neurosurgery, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: Edin
authors.initials: E
authors.lastname: Nevzati
authors.forename: Maziar
authors.initials: M
authors.lastname: Shafighi
authors.forename: Kamran D
authors.initials: KD
authors.lastname: Bakhtian
authors.forename: Hannes
authors.initials: H
authors.lastname: Treiber
authors.forename: Javier
authors.initials: J
authors.lastname: Fandino
authors.forename: Ali Reza
authors.initials: AR
authors.lastname: Fathi
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004958:Estradiol / Q000378:metabolism* / Q000494:pharmacology; D047629:Estrogen Receptor beta / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism / Q000494:pharmacology; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*
chemical_list: D047629:Estrogen Receptor beta; D004967:Estrogens; D009569:Nitric Oxide; D004958:Estradiol; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse