title: Endothelial dysfunction in small arteries of essential hypertensive patients: role of cyclooxygenase-2 in oxidative stress generation.
abstract: Essential hypertensive patients show a reduced nitric oxide availability secondary to oxidative stress generation in peripheral microcirculation. Cyclooxygenase (COX) contributes to reduce nitric oxide availability. We assessed the possible vascular sources of oxidative stress, including COX-1, COX-2, and nicotinamide adenine dinucleotide phosphate oxidase, as determinants of endothelial dysfunction in small arteries isolated from essential hypertensive patients or normotensive controls. Small arteries were dissected after subcutaneous fat biopsies and evaluated on a pressurized micromyograph. Endothelium-dependent vasodilation was assessed by acetylcholine, repeated under NG-nitro-l-arginine methyl ester, SC-560 (COX-1 inhibitor), DuP-697 (COX-2 inhibitor), ascorbic acid, or the nicotinamide adenine dinucleotide phosphate oxidase inhibitors apocynin or diphenylene iodonium. Vascular oxidative stress generation (fluorescent dihydroethidium), COX-1 and COX-2 expression (Western blot), and localization (immunohistochemistry) were also assessed. In controls, response to acetylcholine was blunted by NG-nitro-l-arginine methyl ester (P<0.001) and unmodified by SC-560, DuP-697, or ascorbic acid. In hypertensive patients, relaxation to acetylcholine was blunted, resistant to NG-nitro-l-arginine methyl ester or SC-560, and enhanced (P<0.01) by DuP-697, apocynin, or diphenylene iodonium (P<0.05). Furthermore, in hypertensive patients, response to acetylcholine was normalized by ascorbic acid or apocynin+DuP-697. Intravascular oxidative stress generation was enhanced in hypertensive patients, decreased (P<0.01) by DuP-697, partly attenuated by apocynin or diphenylene iodonium, and prevented by ascorbic acid. Enhanced COX-2 expression and localization in the vascular media of hypertensive patients were also detected. In small resistance arteries of essential hypertensive patients, COX-2 is overexpressed and reduces nitric oxide availability. COX-2 represents a major source of oxidative stress generation, whereas nicotinamide adenine dinucleotide phosphate oxidase plays a minor, but significant, role in promoting superoxide generation.
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Via Roma 67, 56100 Pisa, Italy. agostino.virdis@med.unipi.it
authors.forename: Agostino
authors.initials: A
authors.lastname: Virdis
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bacca
authors.forename: Rocchina
authors.initials: R
authors.lastname: Colucci
authors.forename: Emiliano
authors.initials: E
authors.lastname: Duranti
authors.forename: Matteo
authors.initials: M
authors.lastname: Fornai
authors.forename: Gabriele
authors.initials: G
authors.lastname: Materazzi
authors.forename: Chiara
authors.initials: C
authors.lastname: Ippolito
authors.forename: Nunzia
authors.initials: N
authors.lastname: Bernardini
authors.forename: Corrado
authors.initials: C
authors.lastname: Blandizzi
authors.forename: Giampaolo
authors.initials: G
authors.lastname: Bernini
authors.forename: Stefano
authors.initials: S
authors.lastname: Taddei
mesh_terms: D000328:Adult; D001158:Arteries / Q000503:physiopathology; D051546:Cyclooxygenase 2 / Q000032:analysis / Q000502:physiology*; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D019255:NADPH Oxidases / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D050151:Subcutaneous Fat / Q000098:blood supply; D013481:Superoxides / Q000378:metabolism; D014664:Vasodilation
chemical_list: D017382:Reactive Oxygen Species; D013481:Superoxides; D009569:Nitric Oxide; D051546:Cyclooxygenase 2; D019255:NADPH Oxidases
keywords: endothelium; microcirculation; nitric oxide; oxidative stress