title: Acute effects of oxidized low density lipoprotein on metabolic responses in macrophages.
abstract: The immediate effects of oxidized low density lipoprotein (OxLDL) on the metabolic activity of cultured macrophages (RAW 264.7) were studied using a microphysiometer. Administration of OxLDL acutely induced a concentration-dependent increase in metabolic activity, with an EC50 of 16 +/- 3 microg/ml OxLDL and a maximal effect of 35% +/- 4% (mean +/- SEM; n=5). A biphasic response was measured after administration of 75 or 100 microg/ml OxLDL consisting of an initial sharp increase, followed by the induction of a long-lasting hypoactivity of 80% of the control value. Incubation of cells with polyinosinic acid (polyI; 100 microg/ml) for 30 min prior to OxLDL administration could completely block the effect of 25 microg/ml OxLDL. In addition, polyI acted as a full antagonist on the decrease of the biphasic response of cells generated by 75 and 100 microg/ml OxLDL. Macrophages used in this study possessed a specific binding site for OxLDL, with a dissociation constant (KD) of 9 +/- 2 microg/ml and a maximal binding of 610 +/- 32 ng 125I-OxLDL/mg cell protein. Binding of 125I-OxLDL to macrophages could be completely competed for by unlabeled OxLDL, by polyI for 58%, and by AcLDL for 46%. In conclusion, OxLDL can acutely activate the metabolic state of macrophages by a receptor-mediated process in a concentration-dependent fashion, which could be antagonized by polyI. Metabolic responses to OxLDL may underlie the changes observed in macrophages in the early atherosclerotic plaque.
authors.affiliation: Division of Biopharmaceutics, Leiden/Amsterdam Center for Drug Research, University of Leiden, The Netherlands. e.vries@lacdr.LeidenUniv.nl
authors.forename: H E
authors.initials: HE
authors.lastname: De Vries
authors.forename: E
authors.initials: E
authors.lastname: Ronken
authors.forename: J H
authors.initials: JH
authors.lastname: Reinders
authors.forename: B
authors.initials: B
authors.lastname: Buchner
authors.forename: T J
authors.initials: TJ
authors.lastname: Van Berkel
authors.forename: J
authors.initials: J
authors.lastname: Kuiper
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006863:Hydrogen-Ion Concentration; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008244:Lysophosphatidylcholines / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D010084:Oxidation-Reduction; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000378:metabolism; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B
chemical_list: D008077:Lipoproteins, LDL; D008244:Lysophosphatidylcholines; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; C099252:oxidized low density lipoprotein