© 1998 American Heart Association, Inc.
Original Contributions |
Lipoprotein-like Phospholipid Particles Inhibit the Smooth Muscle Cell Cytotoxicity of Lysophosphatidycholine and Platelet-Activating Factor
From King Gustaf V Research Institute, Department of Medicine, Karolinska Hospital (J.N., B.D., M.A., J.W.), and the Department of Cell and Molecular Biology, Karolinska Institute (A.H.N.), Stockholm, Sweden; and the Division of Cardiology, Cedars-Sinai Medical Center, Los Angeles, Calif (B.C., P.K.S.).
Correspondence to Jan Nilsson, King Gustaf V Research Institute, Karolinska Hospital, S-171 76 Stockholm, Sweden.
Abstract—Oxidation of LDL is associated with degradation of phosphatidylcholine into platelet-activating factor (PAF)–like phospholipids and lysophosphatidylcholine (LPC). Exposure of cultured human smooth muscle cells to PAF and LPC in a concentration of 25 µmol/L was found to result in complete cell death, as assessed by the MTT cytotoxicity assay and cell counting. Addition of 50 µg/mL apolipoprotein A-I– and apolipoprotein A-IMilano–containing phospholipid particles completely inhibited this cytotoxicity. Phospholipid complexes alone were almost as effective, whereas free apolipoprotein A-IMilano and albumin were without effect, suggesting that the effect was phospholipid dependent. Experiments using [14C]LPC demonstrated that apolipoprotein A-I– and apolipoprotein A-IMilano–containing phospholipid particles effectively bind LPC. The results show that HDL-like phospholipid particles effectively inhibit the toxic effect of phospholipids and other lipid-soluble factors. The ability of HDL to inhibit the proinflammatory and toxic effects of phospholipids generated during oxidation of LDL may be responsible for part of the antiatherogenic properties of HDL.
Key Words: smooth muscle cell • apoptosis • cell death • phospholipids
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