Published online before print April 21, 2005, doi: 10.1161/01.ATV.0000166616.86723.d0
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© 2005 American Heart Association, Inc.
Atherosclerosis and Lipoproteins |
Knockdown of Hepatic ABCA1 by RNA Interference Decreases Plasma HDL Cholesterol Levels and Influences Postprandial Lipemia in Mice
From the Institute for Biochemistry and Molecular Biology II, Molecular Cell Biology (S.R., A.N., A.L., U.B., J.H.), and the Departments of Orthopedics (A.N.) and Internal Medicine (B.L., M.M.), University Hospital Hamburg-Eppendorf, Hamburg, Germany.
Correspondence to Dr Joerg Heeren, IBM II, Molecular Cell Biology, University Hospital Hamburg-Eppendorf Martinistrasse 52 D-20246 Hamburg, Germany. E-mail heeren{at}uke.uni-hamburg.de
Objective— To investigate the impact of hepatic ABCA1 on systemic lipoprotein metabolism in vivo by an adenovirus-mediated RNA interference approach.
Methods and Results— Efficiency of plasmid-based small interference RNA (siRNA)-induced knockdown of cotransfected murine ATP binding cassette transporter A1 (mABCA1) in HEK-293 cells was judged by RT-polymerase chain reaction, immunofluorescence, and Western blot analysis. The most effective plasmid was used to generate a recombinant adenovirus as a tool to selectively downregulate ABCA1 expression in mouse liver (C57BL/6). In comparison to controls, Western blot analysis from liver membrane proteins of Ad-anti-ABCA1 infected mice resulted in an 
50% reduction of endogenous ABCA1 and a clear upregulation of apolipoprotein E. Fast protein liquid chromatography analysis of plasma revealed that hepatic ABCA1 protein reduction was associated with an 40% decrease of HDL cholesterol and a reduction of HDL-associated apolipoprotein A-I and E. In the fasted state, other lipoprotein classes were not affected. To analyze the influence of ABCA1 downregulation on postprandial lipemia, infected mice were given a gastric load of radiolabeled trioleate in olive oil. In Ad-anti-ABCA1 infected mice, the postprandial increase of chylomicrons and chylomicron-associated apolipoproteins B and E was significantly reduced as compared with controls.
Conclusion— Hepatic ABCA1 contributes to HDL plasma levels and influences postprandial lipemia.
Here we describe the application of RNA interference in vivo by using an adenoviral vector to elucidate the liver-specific role of ABCA1 with regard to its influence on systemic lipoprotein metabolism. Knockdown of hepatic ABCA1 leads to a reduction of both plasma HDL levels and postprandial lipemia.
Key Words: ATP binding cassette transporter A1 • high-density lipoproteins • RNA interference • apolipoprotein E • postprandial lipemia
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