title: Endothelial nitric oxide synthase activation leads to dilatory H2O2 production in mouse cerebral arteries.
abstract: OBJECTIVE
  Hydrogen peroxide (H2O2) produced by the vascular endothelium is a signaling molecule regulating vascular tone. We hypothesized that H2O2 derived from eNOS activity could play a physiological role in endothelium-dependent dilation of mouse cerebral arteries.
  
  
  METHODS
  Simultaneous endothelium-dependent dilation and fluorescence-associated free radical (DCF-DA) or NO (DAF-2) production were recorded in isolated and pressurized (60 mm Hg) cerebral artery of C57Bl/6 male mice.
  
  
  RESULTS
  Without synergism, N-nitro-L-arginine (L-NNA) or the H2O2 scavengers catalase, PEG-catalase and pyruvate reduced (P < 0.05) by 50% the endothelium-dependent dilation induced by acetylcholine (ACh). Simultaneously with the dilation, H2O2--but not NO--production, sensitive to either L-NNA or catalase, was detected. In cerebral arteries from C57Bl/6.eNOS-/- mice, catalase had no effect on ACh-induced dilation and no H2O2-associated fluorescence was observed. In C57Bl/6 mice, silver diethyldithiocarbamate (DETC), a superoxide dismutase (SOD) inhibitor, but not the specific NO scavenger 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl3-oxide (PTIO), prevented ACh-induced dilation and H2O2 production suggesting that eNOS-derived superoxide is an intermediate in the production of H2O2. The catalase-sensitive ACh-induced dilation was restored by the eNOS cofactor tetrahydrobiopterin (BH4). This reversal was associated with a NO-associated fluorescence sensitive to PTIO but not to catalase. Soluble guanylate cyclase inhibition with 1H-[1,2,4]-oxadiazole-4,3-aquinoxalin-1-one (ODQ) prevented the dilation induced by ACh and by exogenous H2O2. Lastly, L-NNA, PTIO and ODQ--but not DETC, catalase or pyruvate--increased the pressure-dependent myogenic tone, suggesting that eNOS produces NO at rest, but leads to H2O2 during muscarinic stimulation.
  
  
  CONCLUSIONS
  H2O2-dependent dilation in mouse cerebral arteries appears to be a physiological eNOS-derived mechanism.
authors.affiliation: Université de Montréal, Department of Surgery and Research Center, Institut de Cardiologie de Montréal, Montréal, Québec, Canada.
authors.forename: Annick
authors.initials: A
authors.lastname: Drouin
authors.forename: Nathalie
authors.initials: N
authors.lastname: Thorin-Trescases
authors.forename: Edith
authors.initials: E
authors.lastname: Hamel
authors.forename: John R
authors.initials: JR
authors.lastname: Falck
authors.forename: Eric
authors.initials: E
authors.lastname: Thorin
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D002478:Cells, Cultured; D002536:Cerebral Arteries; D042783:Endothelial Cells; D004730:Endothelium, Vascular / Q000201:enzymology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000032:analysis / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000494:pharmacology; D019289:Pyruvic Acid / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D014665:Vasodilator Agents; C070295:catalase-polyethylene glycol; D019335:Nitroarginine; D009569:Nitric Oxide; D011092:Polyethylene Glycols; D019289:Pyruvic Acid; D006861:Hydrogen Peroxide; D002374:Catalase; D052250:Nitric Oxide Synthase Type III; D006162:Guanylate Cyclase; D000109:Acetylcholine; D001920:Bradykinin