Submitted on April 13, 2007
Accepted on August 25, 2008
Progressive dysfunction of nitric oxide synthase in a lamb model of chronically increased pulmonary blood flow: a role for oxidative stress
Peter E Oishi1, Dean A Wiseman2, Shruti Sharma2, Sanjiv Kumar2, Yali Hou2, Sanjeev A Datar1, Anthony Azakie3, Michael J Johengen1, Cynthia Harmon1, Sohrab Fratz4, Jeffrey R. Fineman5, and Stephen M Black2*
1 Pediatrics, University of California San Francisco, San Francisco, California, United States
2 Vascular Biology Center, Medical College of Georgia, Augusta, Georgia, United States
3 Surgery, University of California San Francisco, San Francisco, California, United States
4 Department of Pediatric Cardiology and Congenital Heart Disease, German Heart Center, Munich, Germany
5 Pediatrics, University of California, San Francisco, 505 Parnassus Ave., San Francisco, California, 94143-0106, United States; Cardiovascular Research Institute , University of California San Francisco, San Francisco, California, United States
* To whom correspondence should be addressed. E-mail: Sblack{at}mail.mcg.edu.
Cardiac defects with increased pulmonary blood flow result in pulmonary vascular dysfunction that may relate to a decreased bioavailable nitric oxide (NO). An 8mm graft (shunt) was placed between the aorta and pulmonary artery in 30 fetal lambs; 27 fetal lambs underwent a sham procedure. Hemodynamic responses to acetylcholine (ACh, 1µg/kg) and inhaled NO (40 ppm) were assessed at 2, 4, and 8 weeks of age. Lung tissue NOS activity, eNOS, nNOS, iNOS, and HSP90 protein, lung tissue and plasma NOX, and lung tissue superoxide anion and nitrated eNOS levels were determined. In shunted lambs, ACh decreased pulmonary artery pressure at 2 weeks (P<0.05), but not at 4 and 8 weeks. Inhaled NO decreased pulmonary artery pressure at each age (P<0.05). In control lambs, ACh and inhaled NO decreased pulmonary artery pressure at each age (P<0.05). Total NOS activity did not change from 2 to 8 weeks in control lambs but increased in shunted lambs (ANOVA, P<0.05). NOX levels relative to NOS activity were lower in shunted lambs than controls at 4 and 8 weeks (P<0.05). Superoxide levels increased from 2 to 8 weeks in control and shunted lambs (ANOVA, P<0.05), and were greater in shunted lambs than controls at all ages (P<0.05). Nitrated eNOS levels were greater in shunted lambs than controls at each age (P<0.05). We conclude that increased pulmonary blood flow results in progressive impairment of basal and agonist-induced NOS function, in part secondary to oxidative stress that decreases bioavailable NO.
