Copyright © 2006, European Society of Cardiology
Endothelial nitric oxide synthase activation leads to dilatory H2O2 production in mouse cerebral arteries
aUniversité de Montréal, Department of Surgery and Research Center, Institut de Cardiologie de Montréal, Montréal, Québec, Canada
bInstitut Neurologique de Montréal, McGill University, Montréal, Québec, Canada
cDepartment of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, U.S.A.
* Corresponding author. Institut de Cardiologie de Montréal, centre de recherche, 5000, rue Bélanger, Montréal, Québec, Canada, H1T 1C8. Tel.: +1 514 376 3330; fax: +1 514 376 1355. Email address: eric.thorin{at}umontreal.ca
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.
Conclusion: H2O2-dependent dilation in mouse cerebral arteries appears to be a physiological eNOS-derived mechanism.
KEYWORDS Endothelial function; Nitric oxide; Microcirculation; Oxygen radicals
Time for primary review 30 days
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