Knockdown expression and hepatic deficiency reveal an atheroprotective role for SR-BI in liver and peripheral tissues
Thierry Huby, … , M. John Chapman, Philippe Lesnik
Thierry Huby, … , M. John Chapman, Philippe Lesnik
Published October 2, 2006
Citation Information: J Clin Invest. 2006;116(10):2767-2776. https://doi.org/10.1172/JCI26893.
View: Text | PDF
Research Article Cardiology

Knockdown expression and hepatic deficiency reveal an atheroprotective role for SR-BI in liver and peripheral tissues

Abstract

Scavenger receptor SR-BI has been implicated in HDL-dependent atheroprotective mechanisms. We report the generation of an SR-BI conditional knockout mouse model in which SR-BI gene targeting by loxP site insertion produced a hypomorphic allele (hypomSR-BI). Attenuated SR-BI expression in hypomSR-BI mice resulted in 2-fold elevation in plasma total cholesterol (TC) levels. Cre-mediated SR-BI gene inactivation of the hypomorphic SR-BI allele in hepatocytes (hypomSR-BI–KOliver) was associated with high plasma TC concentrations, increased plasma free cholesterol/TC (FC/TC) ratio, and a lipoprotein-cholesterol profile typical of SR-BI–/– mice. Plasma TC levels were increased 2-fold in hypomSR-BI and control mice fed an atherogenic diet, whereas hypomSR-BI–KOliver and SR-BI–/– mice developed severe hypercholesterolemia due to accumulation of FC-rich, VLDL-sized particles. Atherosclerosis in hypomSR-BI mice was enhanced (2.5-fold) compared with that in controls, but to a much lower degree than in hypomSR-BI–KOliver (32-fold) and SR-BI–/– (48-fold) mice. The latter models did not differ in either plasma lipid levels or in the capacity of VLDL-sized lipoproteins to induce macrophage cholesterol loading. However, reduced atherosclerosis in hypomSR-BI–KOliver mice was associated with decreased lesional macrophage content as compared with that in SR-BI–/– mice. These data imply that, in addition to its major atheroprotective role in liver, SR-BI may exert an antiatherogenic role in extrahepatic tissues.

Authors

Thierry Huby, Chantal Doucet, Christiane Dachet, Betty Ouzilleau, Yukihiko Ueda, Veena Afzal, Edward Rubin, M. John Chapman, Philippe Lesnik

×

Figure 4

Analysis of the distribution of plasma lipoprotein cholesterol in female mice fed an atherogenic diet.

Options: View larger image (or click on image) Download as PowerPoint
Analysis of the distribution of plasma lipoprotein cholesterol in female...
(A) Lipoprotein cholesterol profiles. Fasting plasma samples were prepared from female mice fed an atherogenic (HFC) diet for 11 weeks. For each genotype, plasma samples from individual mice were pooled and loaded on Superose 6 columns, and cholesterol was measured in collected fractions. (B) Electrophoretic mobilities of plasma lipoproteins. Plasma samples (10 μl) were subjected to agarose gel electrophoresis and lipoproteins revealed by Sudan black staining. (C) Apolipoprotein composition of lipoprotein fractions. Lipoproteins were first isolated from pooled plasmas (n = 5–10) by ultracentrifugation at a density of 1.21 g/ml and then fractionated by size-exclusion chromatography. Collected fractions were pooled as indicated in A (I, II, III, and IV), concentrated, and subjected (20–30 μg protein loaded per lane) to SDS-PAGE on gradient gels. Proteins were visualized by Coomassie blue staining. Bands corresponding to apoAI, apoE, and apoAIV, as confirmed by immunoblotting (data not shown), are indicated.