Role of carnitine acetyl transferase in regulation of nitric oxide signaling in pulmonary arterial endothelial cells.
Congenital heart defects with increased pulmonary blood flow (PBF) result in pulmonary endothelial dysfunction that is dependent, at least in part, on decreases in nitric oxide (NO) signaling. Utilizing a lamb model with left-to-right shunting of blood and increased PBF that mimics the human disease, we have recently shown that a disruption in carnitine homeostasis, due to a decreased carnitine acetyl transferase (CrAT) activity, correlates with decreased bioavailable NO. Thus, we undertook this study to test the hypothesis that the CrAT enzyme plays a major role in regulating NO signaling through its effect on mitochondrial function. We utilized the siRNA gene knockdown approach to mimic the effect of decreased CrAT activity in pulmonary arterial endothelial cells (PAEC). Our data indicate that silencing the CrAT gene disrupted cellular carnitine homeostasis, reduced the expression of mitochondrial superoxide dismutase-and resulted in an increase in oxidative stress within the mitochondrion. CrAT gene silencing also disrupted mitochondrial bioenergetics resulting in reduced ATP generation and decreased NO signaling secondary to a reduction in eNOS/Hsp90 interactions. Thus, this study links the disruption of carnitine homeostasis to the loss of NO signaling observed in children with CHD. Preserving carnitine homeostasis may have important clinical implications that warrant further investigation.
Pulmonary Vascular Disease Program, Vascular Biology Center, 1459 Laney Walker Blvd, Georgia Health Sciences University, Augusta, GA 30912, USA. shsharma@georgiahealth.edu.
Shruti
S
Sharma
Xutong
X
Sun
Saurabh
S
Agarwal
Ruslan
R
Rafikov
Sridevi
S
Dasarathy
Sanjiv
S
Kumar
Stephen M
SM
Black
D000818:Animals; D002332:Carnitine O-Acetyltransferase / Q000378:metabolism*; D042783:Endothelial Cells / Q000201:enzymology / Q000378:metabolism*; D004734:Energy Metabolism; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006706:Homeostasis; D008928:Mitochondria / Q000473:pathology; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D018384:Oxidative Stress; D011485:Protein Binding; D011651:Pulmonary Artery / Q000166:cytology*; D034741:RNA, Small Interfering / Q000378:metabolism; D012756:Sheep; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000378:metabolism; D000099156:Superoxide Dismutase 2
D002332:Carnitine O-Acetyltransferase; D018841:HSP90 Heat-Shock Proteins; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D034741:RNA, Small Interfering; D013482:Superoxide Dismutase; D000099156:Superoxide Dismutase 2