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Updated: Jun 23, 2026
Cholesterol Efflux Assay
Published on: March 6, 2012
Reduced ABCA1-mediated cholesterol efflux and accelerated atherosclerosis in apolipoprotein E-deficient mice lacking
Yan Ru Su1, Dwayne E Dove, Amy S Major
1Atherosclerosis Research Unit, Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, Tenn 37232-6300, USA. Yan.Ru.Su@vanderbilt.edu
Insights
Macrophage ACAT1 deletion accelerates atherosclerosis in apoE-/- mice unless macrophage apoE corrects cholesterol levels. ACAT1 deficiency impairs cholesterol efflux, increasing inflammation and apoptosis.
Area of Science:
- Cardiovascular Biology
- Atherosclerosis Research
- Macrophage Biology
Background:
- Macrophage ACAT1 and apoE regulate cholesterol homeostasis and foam cell formation.
- ACAT1 or apoE deletion increases atherosclerosis in hyperlipidemic mice.
- This study investigates ACAT1 deletion effects on atherogenesis in apoE-deficient mice.
Purpose of the Study:
- To determine the role of macrophage ACAT1 in atherogenesis in apoE-deficient mice.
- To assess the impact of ACAT1 deletion with or without macrophage apoE restoration.
- To elucidate the mechanisms underlying ACAT1's influence on cholesterol metabolism and inflammation.
Main Methods:
- Bone marrow transplantation to create apoE-/- mice with four macrophage genotypes (wild type, ACAT1-/-, apoE-/-, and 2KO).
- Analysis of plasma cholesterol, atherosclerosis, and aortic apoptosis.
- Assessment of cholesterol efflux to apoA-I and ABCA1 expression in macrophages.
- Microarray analysis of gene expression in ACAT1-/- macrophages.
Main Results:
- Macrophage ACAT1 deficiency accelerated atherosclerosis in apoE-/- mice when macrophage apoE was absent.
- Plasma cholesterol normalized and ACAT1 deficiency had no significant effect when macrophage apoE was present.
- ACAT1 deficiency reduced cholesterol efflux to apoA-I and altered ABCA1 expression, increasing pro-inflammatory and pro-collagen genes.
Conclusions:
- Macrophage ACAT1 deficiency exacerbates atherosclerosis in hypercholesterolemic apoE-/- mice, but this is mitigated by macrophage apoE expression.
- ACAT1 deletion impairs ABCA1-mediated cholesterol efflux independently of apoE expression.
- ACAT1 deficiency influences macrophage membrane stability, apoptosis, and inflammatory responses, contributing to accelerated atherosclerosis.
Background:
Macrophage acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT1) and apolipoprotein E (apoE) have been implicated in regulating cellular cholesterol homeostasis and therefore play critical roles in foam cell formation. Deletion of either ACAT1 or apoE results in increased atherosclerosis in hyperlipidemic mice, possibly as a consequence of altered cholesterol processing. We have studied the effect of macrophage ACAT1 deletion on atherogenesis in apoE-deficient (apoE-/-) mice with or without the restoration of macrophage apoE.
Methods And Results:
We used bone marrow transplantation to generate apoE-/- mice with macrophages of 4 genotypes: apoE+/+/ACAT1+/+ (wild type), apoE+/+/ACAT1-/- (ACAT-/-), apoE-/-/ACAT1+/+ (apoE-/-), and apoE-/-/ACAT1-/- (2KO). When macrophage apoE was present, plasma cholesterol levels normalized, and ACAT1 deficiency did not have significant effects on atherogenesis. However, when macrophage apoE was absent, ACAT1 deficiency increased atherosclerosis and apoptosis in the proximal aorta. Cholesterol efflux to apoA-I was significantly reduced (30% to 40%; P<0.001) in ACAT1-/- peritoneal macrophages compared with ACAT1+/+ controls regardless of apoE expression. 2KO macrophages had a 3- to 4-fold increase in ABCA1 message levels but decreased ABCA1 protein levels relative to ACAT1+/+ macrophages. Microarray analyses of ACAT1-/- macrophages showed increases in proinflammatory and procollagen genes and decreases in genes regulating membrane integrity, protein biosynthesis, and apoptosis.
Conclusions:
Deficiency of macrophage ACAT1 accelerates atherosclerosis in hypercholesterolemic apoE-/- mice but has no effect when the hypercholesterolemia is corrected by macrophage apoE expression. However, ACAT1 deletion impairs ABCA1-mediated cholesterol efflux in macrophages regardless of apoE expression. Changes in membrane stability, susceptibility to apoptosis, and inflammatory response may also be important in this process.
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