Abstract 16948: Cholesterol-enriched Macrophages Excrete Cholesterol into Unique Extracellular Deposits
Introduction: Atherosclerotic plaques contain cholesterol in both intracellular and extracellular forms. However, the origin and fate of extracellular cholesterol in atherosclerosis is far less understood compared with intracellular cholesterol.
Methods and Results: Using a Mab that detects ordered cholesterol arrays, we have identified unesterified cholesterol microdomains that accumulate in the extracellular space of atherosclerotic plaques. In vitro studies have shown that cholesterol-enriched macrophages form these cholesterol microdomains mostly within the extracellular matrix, but also in focal regions of the macrophage plasma membrane. ABCA1 and ABCG1 mediate excretion of the cholesterol microdomains, which can be mobilized by HDL and ApoA-I. We have isolated the cholesterol microdomains from the extracellular matrix and determined that their cholesterol content is entirely unesterified. Although appearing spherical at the resolution of the standard fluorescence microscope, the cholesterol microdomains are actually irregularly shaped deposits of varying size when viewed by high-resolution fluorescence microscopy (a) and immunoelectron microscopy (b).
Conclusion: We have discovered that a novel type of cholesterol deposit is functioning in cellular cholesterol metabolism and reverse cholesterol transport. These findings are important because, to date, cholesterol in discoidal and vesicular forms have been the focus of research on macrophage excretion of unesterified cholesterol.
Figure legend: (a) Cholesterol microdomains in the extracellular matrix (which surrounded a cholesterol-enriched cultured macrophage) were immunolabeled with the cholesterol microdomain Mab, and imaged by high-resolution fluorescence microscopy. (b) Cholesterol microdomains isolated from the extracellular matrix were immunogold labeled with the cholesterol microdomain Mab, and imaged by electron microscopy.
Author Disclosures: X. Jin: None. Y. Liu: None. C.A. Combs: None. J. Chang: None. N. Varsano: None. L. Addadi: None. H.S. Kruth: None.
- © 2016 by American Heart Association, Inc.