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Bone marrow-derived multidrug resistance protein ABCB4 protects against atherosclerotic lesion development in LDL receptor knockout mice

  1. Marieke Penningsa,*,
  2. Reeni B. Hildebranda,
  3. Dan Yea,
  4. Cindy Kunneb,
  5. Theo J.C. Van Berkela,
  6. Albert K. Groenb and
  7. Miranda Van Ecka
  1. aDivision of Biopharmaceutics, Leiden/Amsterdam Center for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
  2. bDepartment of Medical Biochemistry, Amsterdam Medical Center, Meibergdreef 15, 1105 BK Amsterdam, The Netherlands
  1. *
    Corresponding author. Einsteinweg 55, 2333 CC Leiden, The Netherlands. Tel.: +31 715276213; fax: + 31 715276032. pennings{at}lacdr.leidenuniv.nl
  • Received November 16, 2006.
  • Revision requested May 9, 2007.
  • Accepted May 11, 2007.

Abstract

Objective Several members of the ATP binding cassette (ABC)-transporter super family expressed in macrophages protect against atherosclerosis by promoting macrophage cholesterol and phospholipid efflux. Systemic disruption of ABCB4 in mice results in a virtual absence of phospholipids in bile and a strongly impaired biliary cholesterol secretion, indicating that ABCB4 plays an essential role in cellular lipid efflux. The aim of the current study was to determine the role of bone marrow-derived ABCB4 in atherosclerotic lesion development.

Methods Chimeras were created that specifically lack ABCB4 in bone marrow-derived cells, including macrophages, by performing a bone marrow transplantation on LDL receptor knockout (LDLr−/−) mice. Atherosclerotic lesion development was induced by feeding a high-cholesterol diet (15% fat and 0.25% cholesterol).

Results Serum cholesterol levels were significantly lower in mice reconstituted with ABCB4 knockout bone marrow as a result of reduced VLDL and LDL cholesterol levels. Despite the lower serum cholesterol levels, ABCB4 deficiency in bone marrow-derived cells resulted in a 1.8-fold (p=0.005) increase in lesion size. In vitro foam cell formation, induced with acetylated LDL (AcLDL) in peritoneal macrophages, was increased in the absence of ABCB4, possibly due to a 2-fold (p<0.05) increased association of AcLDL, while the efflux of cholesterol was unaffected.

Conclusion Bone marrow-derived ABCB4 has an important anti-atherosclerotic function, probably by limiting macrophage foam cell formation.

Keywords

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