title: Apocynin improves oxygenation and increases eNOS in persistent pulmonary hypertension of the newborn.
abstract: NADPH oxidase is a major source of superoxide anions in the pulmonary arteries (PA). We previously reported that intratracheal SOD improves oxygenation and restores endothelial nitric oxide (NO) synthase (eNOS) function in lambs with persistent pulmonary hypertension of the newborn (PPHN). In this study, we determined the effects of the NADPH oxidase inhibitor apocynin on oxygenation, reactive oxygen species (ROS) levels, and NO signaling in PPHN lambs. PPHN was induced in lambs by antenatal ligation of the ductus arteriosus 9 days prior to delivery. Lambs were treated with vehicle or apocynin (3 mg/kg intratracheally) at birth and then ventilated with 100% O(2) for 24 h. A significant improvement in oxygenation was observed in apocynin-treated lambs after 24 h of ventilation. Contractility of isolated fifth-generation PA to norepinephrine was attenuated in apocynin-treated lambs. PA constrictions to NO synthase (NOS) inhibition with N-nitro-l-arginine were blunted in PPHN lambs; apocynin restored contractility to N-nitro-l-arginine, suggesting increased NOS activity. Intratracheal apocynin also enhanced PA relaxations to the eNOS activator A-23187 and to the NO donor S-nitrosyl-N-acetyl-penicillamine. Apocynin decreased the interaction between NADPH oxidase subunits p22(phox) and p47(phox) and decreased the expression of Nox2 and p22(phox) in ventilated PPHN lungs. These findings were associated with decreased superoxide and 3-nitrotyrosine levels in the PA of apocynin-treated PPHN lambs. eNOS protein expression, endothelial NO levels, and tetrahydrobiopterin-to-dihydrobiopterin ratios were significantly increased in PA from apocynin-treated lambs, although cGMP levels did not significantly increase and phosphodiesterase-5 activity did not significantly decrease. NADPH oxidase inhibition with apocynin may improve oxygenation, in part, by attenuating ROS-mediated vasoconstriction and by increasing NOS activity.
authors.affiliation: Deparment of Pediatrics, Northwestern University, Chicago, Illinois, USA. s-wedgwood@northwestern.edu
authors.forename: Stephen
authors.initials: S
authors.lastname: Wedgwood
authors.forename: Satyan
authors.initials: S
authors.lastname: Lakshminrusimha
authors.forename: Kathryn N
authors.initials: KN
authors.lastname: Farrow
authors.forename: Lyubov
authors.initials: L
authors.lastname: Czech
authors.forename: Sylvia F
authors.initials: SF
authors.lastname: Gugino
authors.forename: Fernando
authors.initials: F
authors.lastname: Soares
authors.forename: James A
authors.initials: JA
authors.lastname: Russell
authors.forename: Robin H
authors.initials: RH
authors.lastname: Steinhorn
mesh_terms: D000098:Acetophenones / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001708:Biopterins / Q000031:analogs & derivatives / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000503:physiopathology*; D006976:Hypertension, Pulmonary / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism / Q000503:physiopathology; D008168:Lung / Q000378:metabolism / Q000503:physiopathology; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012756:Sheep; D013481:Superoxides / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects
chemical_list: D000098:Acetophenones; D020030:Nitric Oxide Donors; D017382:Reactive Oxygen Species; D013481:Superoxides; D001708:Biopterins; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; C017226:7,8-dihydrobiopterin; C056165:acetovanillone; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D019255:NADPH Oxidases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C003402:sapropterin; D006152:Cyclic GMP; D009638:Norepinephrine