Extracellular cholesterol-rich microdomains generated by human macrophages and their potential function in reverse cholesterol transport.
Previous studies have shown that cholesterol in atherosclerotic plaques is present in both intracellular and extracellular forms. In the current study, we investigated a mechanism for extracellular cholesterol accumulation and examined the capacity of this pool of cholesterol to be removed by cholesterol acceptors, a step in reverse cholesterol transport. Human monocyte-derived macrophages differentiated with macrophage-colony stimulating factor were incubated with acetylated LDL to allow cholesterol enrichment and processing. These macrophages were subsequently labeled with a monoclonal antibody that specifically detects ordered cholesterol arrays, revealing the presence of unesterified cholesterol-rich microdomains on the cell surfaces and in the extracellular matrix. Similar unesterified cholesterol-rich microdomains were present in human atherosclerotic plaques. Actin microfilaments functioned in microdomain deposition or maintenance, and Src family kinases regulated transfer of these microdomains from the cell surface onto the extracellular matrix. Mediators of reverse cholesterol transport, apolipoprotein A-I (apoA-I), and HDL were capable of removing these extracellular un-esterified cholesterol-rich microdomains. However, apoA-I removed the microdomains only when macrophages were present. ApoA-I removal of microdomains was blocked by glyburide and inhibitor of ATP-binding cassette transporter A1 (ABCA1) function. In summary, cultures of cholesterol-enriched human monocyte-derived macrophages generate extracellular unesterified cholesterol-rich microdomains, which can subsequently be removed by cholesterol acceptors and therefore potentially function in reverse cholesterol transport.
Ong
Daniel S
DS
Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1422, USA.
Anzinger
Joshua J
JJ
Leyva
Francisco J
FJ
Rubin
Noa
N
Addadi
Lia
L
Kruth
Howard S
HS
D000906:Antibodies / Q000378:metabolism; D001011:Aorta / Q000166:cytology; D016632:Apolipoprotein A-I / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002454:Cell Differentiation; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D004951:Esterification; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D008075:Lipoproteins, HDL / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D008264:Macrophages / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology; D015398:Signal Transduction; D019061:src-Family Kinases / Q000378:metabolism
D000906:Antibodies; D016632:Apolipoprotein A-I; D008075:Lipoproteins, HDL; D016173:Macrophage Colony-Stimulating Factor; D002784:Cholesterol; D019061:src-Family Kinases; D005905:Glyburide