© 2003 by European Society of Cardiology
Copyright © 2003, European Society of Cardiology
Formation of apolipoprotein AI–phosphatidylcholine core aldehyde Schiff base adducts promotes uptake by THP-1 macrophages
aDepartment of Pathology and Laboratory Medicine, University of Louisville Medical Center, Louisville, KY 40202, USA
bBanting and Best Department of Medical Research, University of Toronto, Toronto, Canada
cJ. Alick Little Lipid Research Laboratory, St. Michael's Hospital, 38 Shuter Street, Room 1004 WA, Toronto, Ontario M5B 1A6, Canada
dDepartment of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
eDepartment of Biochemistry, University of Toronto, Toronto, Canada
fDepartment of Medicine, University of Toronto, Toronto, Canada
connellyp{at}smh.toronto.on.ca
* Corresponding author. Tel.: +1-416-864-6023; fax: +1-416-864-5870.
Objective: High-density lipoprotein (HDL) is believed to protect against development of atherosclerosis by inhibiting the accumulation of oxidized lipids in low-density lipoprotein (LDL). Paradoxically, HDL lipid is more susceptible to oxidation than LDL lipid. In the present study, we examined the effect of oxidized phospholipids on the uptake of HDL by macrophages. Methods and results: Oxidation of HDL increased formation of phosphatidylcholine core aldehydes that was paralleled by increased covalent binding of phospholipids to HDL protein from 0.96±0.44 to 8.5±1.76 phosphorus/HDL protein (mol/mol). Incubation of apolipoprotein AI with synthetically prepared phosphatidylcholine core aldehydes, 1-palmitoyl-2-[5-oxo]valeroyl-sn-glycero-3-phosphocholine or 1-palmitoyl-2-[9-oxo] nonanoyl-sn-glycero-3-phosphocholine, significantly increased the phosphorus:apolipoprotein AI ratio from 1.1±0.5 to 7.2±2.0 and from 0.9±0.6 to 8.5±0.8, respectively. The binding and uptake of phosphatidylcholine core aldehyde–apolipoprotein AI proteoliposomes, by THP-1 macrophages, was similar to that observed for oxidized HDL and oxidized LDL. Conclusion: We conclude that oxidation of HDL increased formation of phosphatidylcholine core aldehyde–apolipoprotein AI Schiff base adducts and enhanced uptake of oxidized HDL by THP-1 macrophages.
KEYWORDS ApoAI, apolipoprotein AI; DiI, 1,1'-dioctadecyl-3,3,3'3'tetramethyl-indocarbocyanine perchlorate; DiO, 3,3'dihexadecyloxacarbocyanine perchlorate; DMPC, dimyristoyl phosphatidylcholine; HDL, high-density lipoproteins; LDL, low-density lipoproteins; PC, phosphatidylcholine; POVPC, 1-palmitoyl-2-[5-oxo]valeroyl-sn-glycero-3-phosphocholine; LC–ESI-MS, liquid chromatography–electrospray ionization-mass spectrometry; PONPC, 1-palmitoyl-2-(9-oxo)nonanoyl-sn-glycero-3-phosphocholine; SDS– PAGE, sodium dodecyl sulfate–polyacrylamide gel electrophoresis
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