LDL Inhibits the Mediation of Cholesterol Efflux From Macrophage Foam Cells by ApoA‐I‐Containing LipoproteinsA Putative Mechanism for Foam Cell Formation
作者:
Rie,
Nakamura Takao,
Ohta Yoichiro,
Ikeda Ichiro,
期刊:
Arteriosclerosis and Thrombosis: A Journal of Vascular Biology
(OVID Available online 1993)
卷期:
Volume 13,
issue 9
页码: 1307-1316
ISSN:1049-8834
年代: 1993
出版商: OVID
关键词: reverse cholesterol transport;lipoprotein A-I;lipoprotein A-I/A-II;HDL;LDL;foam cells;atherosclerosis;lecithimcholesterol acyltransferase
数据来源: OVID
摘要:
Although the accumulation of cholesterol in macrophages appears to be an initial step in atherogenesis, low-density lipoprotein (LDL), a major risk factor for atherosclerosis, does not promote cholesterol accumulation in macrophages in its native form. On the other hand, apolipoprotein (apo) A-I-containing lipoprotein removes cholesterol from cholesterol-loaded macrophages (foam cells) and prevents cholesterol from accumulating in the cells. We examined the effect of LDL on cholesterol removal by two species of apoA-I-containing lipoproteins, one containing only apoA-I (LpA-I) and the other containing apoA-I and apoA-II (LpA-1/A-II). When foam cells were incubated with LpA-I or LpA-I/A-H, cellular cholesterol mass was reduced. In contrast, when LDL was added, the cholesterol-reducing capacities of these lipoproteins were dose-dependently inhibited by LDL. In the presence of LDL, LpA-I and LpA-I/A-II removed free cholesterol preferentially from LDL rather than from the plasma membrane of foam cells. In addition, a fair amount of cellular cholesterol was directly moved to LDL rather than to LpA-I or LpA-I/A-II. The cellular cholesterol that moved to LDL was completely compensated for by the cholesterol influx from LDL to foam cells. Thus, net cholesterol efflux (a combination of influx and efflux) from foam cells was inhibited by LDL. These results, taken together, indicate that LDL may accelerate foam cell formation by inhibiting cholesterol removal from the cells and that elevated levels of plasma LDL may become a risk factor for atherosclerosis by inhibiting the function of LpA-I and LpA-I/A-II at the cellular level.
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