A pathway-dependent on ApoE, ApoAI, and ABCA1 determines formation of buoyant high-density lipoprotein by macrophage foam cells

Patricia G. Yancey, Hong Yu, MacRae F. Linton, Sergio Fazio

Research output: Contribution to journalArticle

43 Scopus citations

Abstract

OBJECTIVE - ABCA1-dependent and ABCA1-independent pathways may operate in high-density lipoprotein formation by macrophages secreting apolipoprotein (apo) E. We examined the impact of ABCA1 on apoE-mediated efflux from cholesterol-enriched macrophages. METHODS AND RESULTS - Without acceptors, wild-type, ABCA1, and apoE macrophages released 5.7%±0.3%, 1.8%±0.1%, and 2.3%±0.2% of their cholesterol, and the LXR agonist, TO-901317, enhanced efflux by 137%, 10%, and 20%. Although similar amounts of apoE were secreted from ABCA1 and wild-type cells, apoE from ABCA1 cells was only partially phospholipidated and floated at density >1.21g/mL, whereas apoE from wild-type cells floated at density of 1.09 to 1.17g/mL and paralleled the density of cholesterol. With apoAI, LXR stimulation increased efflux by 139% and 86% from wild-type and apoE cells, resulting in a large difference in efflux (29.5%±0.2% versus 17.0%±0.5%). The density of apoE and cholesterol from wild-type cells did not change with apoAI, and most apoAI floated at density ≥1.17g/mL. In apoE cells, apoAI and cholesterol floated at similar density, but the peak fraction only contained 4 μg cholesterol/mg protein versus 18 in WT cells. CONCLUSIONS - Macrophage apoE requires ABCA1 for formation of high-density lipoprotein. ApoAI facilitates association of apoE with more buoyant high-density lipoprotein, suggesting that apoE, plasma apoAI, and ABCA1 operate together to optimize mobilization of macrophage cholesterol, a process critical to limiting plaque development.

Original languageEnglish (US)
Pages (from-to)1123-1131
Number of pages9
JournalArteriosclerosis, thrombosis, and vascular biology
Volume27
Issue number5
DOIs
StatePublished - May 2007
Externally publishedYes

Keywords

  • ABCA1
  • Apolipoprotein AI
  • Cholesterol efflux
  • Endogenous apolipoprotein E
  • LXR stimulation
  • Macrophage foam cell
  • Nascent high-density lipoprotein

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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