Increased superoxide generation is associated with pulmonary hypertension in fetal lambs: a role for NADPH oxidase.
Ligation of the ductus arteriosus in utero produces pulmonary hypertension and vascular remodeling in fetal and newborn lambs. However, the mechanisms producing these vascular changes are not well defined. Because reactive oxygen species (ROS) have been implicated as mediators of smooth muscle cell proliferation, we hypothesized that increased formation of ROS may be involved in the pathophysiology of pulmonary hypertension after in utero ductal ligation. Using ethidium fluorescence, we demonstrated an increase in superoxide levels after 9 days of ductal ligation compared with control lungs (P<0.05) that was localized to the adventitia and smooth muscle cells of hypertensive vessels. SOD-1 and SOD-2 protein levels and activities in lung, vein, and artery of hypertensive lambs were unchanged relative to controls after 2 days of ductal ligation. However, after 9 days, superoxide dismutase (SOD) activity was significantly decreased in arteries from ligated lambs without associated changes in SOD protein expression (P<0.05). Examination of NADPH oxidase expression as a potential source of the superoxide production indicated that the levels of p67phox, a subunit of the NADPH oxidase complex, were significantly increased in the pulmonary arteries, but not veins, from the ligated lung as early as 2 days (P<0.05). Functional analyses demonstrated that reducing superoxide levels significantly increased the NO-mediated relaxation of pulmonary arteries isolated after 9 days, but not 2 days, of ductal ligation (P<0.05). These results suggest that increased NADPH oxidase expression may increase levels of superoxide in persistent pulmonary hypertension of the newborn lung tissue, and that increased superoxide blunts vascular relaxations to exogenous NO while stimulating smooth muscle cell growth.
Brennan
Lisa A
LA
Department of Pediatrics, Northwestern University, Ward 12-191, 303 E Chicago Ave, Chicago, Ill 60611-3008, USA.
Steinhorn
Robin H
RH
Wedgwood
Stephen
S
Mata-Greenwood
Eugenia
E
Roark
Everett A
EA
Russell
James A
JA
Black
Stephen M
SM
D000818:Animals; D046508:Culture Techniques; D005333:Fetus / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D018832:Molecular Chaperones / Q000032:analysis; D019255:NADPH Oxidases / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010547:Persistent Fetal Circulation Syndrome / Q000201:enzymology / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D010750:Phosphoproteins / Q000032:analysis; D011651:Pulmonary Artery / Q000187:drug effects / Q000503:physiopathology; D012756:Sheep; D013482:Superoxide Dismutase / Q000032:analysis; D013481:Superoxides / Q000378:metabolism*; D014664:Vasodilation
C114678:CCS protein, human; D018832:Molecular Chaperones; D020030:Nitric Oxide Donors; D010750:Phosphoproteins; C110881:S-nitro-N-acetylpenicillamine; C079789:neutrophil cytosol factor 67K; D013481:Superoxides; D013482:Superoxide Dismutase; D019255:NADPH Oxidases; D010396:Penicillamine