Low density lipoprotein receptor-related protein is required for macrophage-mediated oxidation of low density lipoprotein by 12/15-lipoxygenase.
The oxidative modification of low density lipoprotein (LDL) has been implicated in the early stage of atherosclerosis through multiple potential pathways, and 12/15-lipoxygenase is suggested to be involved in this oxidation process. We demonstrated previously that the 12/15-lipoxygenase overexpressed in mouse macrophage-like J774A.1 cells was required for the cell-mediated LDL oxidation. However, the mechanism of the oxidation of extracellular LDL by the intracellular 12/15-lipoxygenase has not yet been elucidated. In the present study, we found that not only the LDL receptor but also LDL receptor-related protein (LRP), both of which are cell surface native LDL-binding receptors, were down-regulated by the preincubation of the cells with cholesterol or LDL and up-regulated by lipoprotein-deficient serum. Moreover, 12/15-lipoxygenase-expressing cell-mediated LDL oxidation was decreased by the preincubation of the cells with LDL or cholesterol and increased by the preincubation with lipoprotein-deficient serum. Heparin-binding protein 44, an antagonist of the LDL receptor family, also suppressed the cell-mediated LDL oxidation in a dose-dependent manner. The cell-mediated LDL oxidation was dose-dependently blocked by an anti-LRP antibody but not by an anti-LDL receptor antibody. Furthermore, antisense oligodeoxyribonucleotides against LRP reduced the cell-mediated LDL oxidation under the conditions in which the expression of LRP was decreased. The results taken together indicate that LRP was involved essentially for the cell-mediated LDL oxidation by 12/15-lipoxygenase expressed in J774A.1 cells, suggesting an important pathophysiological role of this receptor-enzyme system as the initial trigger of the progression of atherosclerosis.
Xu
W
W
Department of Molecular Pharmacology, Kanazawa University Graduate School of Medicine, Kanazawa 920-8640, Japan.
Takahashi
Y
Y
Sakashita
T
T
Iwasaki
T
T
Hattori
H
H
Yoshimoto
T
T
D000818:Animals; D000906:Antibodies / Q000378:metabolism; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism*; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006023:Glycoproteins / Q000378:metabolism; D006493:Heparin / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D026563:LDL-Receptor Related Protein-Associated Protein; D008024:Ligands; D008077:Lipoproteins, LDL / Q000378:metabolism; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008264:Macrophages / Q000201:enzymology* / Q000378:metabolism*; D051379:Mice; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000378:metabolism* / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine; D017392:Thiobarbituric Acid Reactive Substances; D015854:Up-Regulation
D000906:Antibodies; D002352:Carrier Proteins; D018076:DNA, Complementary; D006023:Glycoproteins; D026563:LDL-Receptor Related Protein-Associated Protein; D008024:Ligands; D008077:Lipoproteins, LDL; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D016376:Oligonucleotides, Antisense; D011971:Receptors, Immunologic; D017392:Thiobarbituric Acid Reactive Substances; D006493:Heparin; D002784:Cholesterol; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase; D010100:Oxygen