Cytotoxic cellular cholesterol is selectively removed by apoA-I via ABCA1

Atherosclerosis. 2003 Dec;171(2):235-43. doi: 10.1016/j.atherosclerosis.2003.08.024.


Excess intracellular free cholesterol (FC) is cytotoxic. This study examines prevention of FC-induced cytotoxicity in J774 macrophage foam cells by incubation with apolipoprotein AI (apoA-I). J774 were cholesterol enriched using acetylated low-density lipoprotein and FC/phospholipid (PL) dispersions. Treatment with an acyl coenzyme-A:cholesterol acyltransferase (ACAT) inhibitor, in the absence of extracellular acceptors, produced hydrolysis of stored esterified cholesterol (EC) and FC-induced cytotoxicity. Incubation of cells with ACAT inhibitor plus apoA-I resulted in FC efflux (0.39 +/- 0.02%/h) along with a reduction in cytotoxicity (26.30 +/- 5.80%), measured by adenine release. Small unilamellar vesicles (SUV) caused greater FC efflux (0.53 +/- 0.02%/h, P = 0.001), but a modest reduction in cytotoxicity (8.40 +/- 2.70%, P = 0.008). Co-incubation of ACAT inhibitor plus the cholesterol transport inhibitor U18666A or the antioxidant Probucol reduced efflux to apoA-I, but not to SUV. Pre-treatment of J774 foam cells with CTP-cAMP upregulates hormone sensitive lipase (HSL) and further upregulates ATP binding cassette A1 (ABCA1). Using mouse serum as a cholesterol acceptor, CTP-cAMP caused greater protection against FC-induced cytotoxicity compared to cells without pre-treatment, suggesting a role of ABCA1 in removal of cytotoxic FC. We conclude that a cytotoxic pool of FC is located in the plasma membrane, is readily available for efflux to apoA-I, and removal of cytotoxic cholesterol may involve ABCA1.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters / metabolism
  • Animals
  • Apolipoprotein A-I / metabolism*
  • Apolipoprotein A-I / pharmacology
  • Binding Sites
  • Biological Transport
  • Blotting, Western
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Cholesterol / metabolism*
  • Culture Media, Conditioned
  • Cytidine Triphosphate / metabolism
  • Drug Interactions
  • Foam Cells / metabolism
  • Macrophages / drug effects
  • Macrophages / metabolism*
  • Mice
  • Phospholipids / metabolism*
  • Phospholipids / pharmacology
  • Probability
  • Probucol / pharmacology
  • Sterol O-Acyltransferase / analysis
  • Sterol O-Acyltransferase / metabolism*


  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters
  • Apolipoprotein A-I
  • Culture Media, Conditioned
  • Phospholipids
  • Cytidine Triphosphate
  • Cholesterol
  • Sterol O-Acyltransferase
  • Probucol