Altered carnitine homeostasis is associated with decreased mitochondrial function and altered nitric oxide signaling in lambs with pulmonary hypertension

• Published in: American journal of physiology. Lung cellular and molecular physiology 2008-01, Vol.294 (1), p.L46-L56
• Main Authors: Sharma, Shruti, Sud, Neetu, Wiseman, Dean A, Carter, A. Lee, Kumar, Sanjiv, Hou, Yali, Rau, Thomas, Wilham, Jason, Harmon, Cynthia, Oishi, Peter, Fineman, Jeffrey R, Black, Stephen M
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Carnitine - metabolism; Carnitine O-Acetyltransferase - metabolism; Carnitine O-Palmitoyltransferase - metabolism; Correlation analysis; Delivery, Obstetric; Disease Models, Animal; Female; Homeostasis; HSP90 Heat-Shock Proteins - physiology; Hypertension; Hypertension, Pulmonary - enzymology; Hypertension, Pulmonary - physiopathology; Metabolism; Mitochondria - physiology; Nitric oxide; Nitric Oxide - physiology; Nitric Oxide Synthase - metabolism; Pregnancy; Pulmonary Circulation - physiology; Regional Blood Flow; Respiratory diseases; Sheep; Signal Transduction - physiology
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00247.2007

1 Program in Pulmonary Vascular Disease, Vascular Biology Center, and 2 Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia; 3 Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, Montana; and 4 Department of Pediatrics and 5 Cardiovascular Research Institute, University of California, San Francisco, California Submitted 28 June 2007 ; accepted in final form 13 November 2007 Utilizing aortopulmonary vascular graft placement in the fetal lamb, we have developed a model (shunt) of pulmonary hypertension that mimics congenital heart disease with increased pulmonary blood flow. Our previous studies have identified a progressive development of endothelial dysfunction in shunt lambs that is dependent, at least in part, on decreased nitric oxide (NO) signaling. The purpose of this study was to evaluate the possible role of a disruption in carnitine metabolism in shunt lambs and to determine the effect on NO signaling. Our data indicate that at 2 wk of age, shunt lambs have significantly reduced expression ( P < 0.05) of the key enzymes in carnitine metabolism: carnitine palmitoyltransferases 1 and 2 as well as carnitine acetyltransferase (CrAT). In addition, we found that CrAT activity was inhibited due to increased nitration. Furthermore, free carnitine levels were significantly decreased whereas acylcarnitine levels were significantly higher in shunt lambs ( P < 0.05). We also found that alterations in carnitine metabolism resulted in mitochondrial dysfunction, since shunt lambs had significantly decreased pyruvate, increased lactate, and a reduced pyruvate/lactate ratio. In pulmonary arterial endothelial cells cultured from juvenile lambs, we found that mild uncoupling of the mitochondria led to a decrease in cellular ATP levels and a reduction in both endothelial NO synthase-heat shock protein 90 (eNOS-HSP90) interactions and NO signaling. Similarly, in shunt lambs we found a loss of eNOS-HSP90 interactions that correlated with a progressive decrease in NO signaling. Our data suggest that mitochondrial dysfunction may play a role in the development of endothelial dysfunction and pulmonary hypertension and increased pulmonary blood flow. carnitine metabolism; oxidative stress Address for reprint requests and other correspondence: S. M. Black, Vascular Biology Center, 1459 Laney Walker Blvd., CB3210B, Medical College of Georgia, Augusta, GA 30912 (e-mail: sblack{at}mcg.edu )