title: Oxidative tyrosylation of high density lipoproteins impairs cholesterol efflux from mouse J774 macrophages: role of scavenger receptors, classes A and B.
abstract: Studies were designed to test whether tyrosylation of high-density lipoprotein (HDL(T)) modifies its metabolic features. HDL(T) was less effective than native HDL in promoting cholesterol efflux from J774-AI macrophages. Cell association with fluorescent HDL(T)-apolipoprotein and the uptake of HDL(T)-[(3)H]cholesteryl hexadecyl ether were enhanced by 50% in comparison with native HDL. In addition, neutral cholesterol ester hydrolase (nCEH) activity in J774-AI, which controls the hydrolysis of cholesteryl ester stores to provide free cholesterol for cellular release, declined in the presence of HDL(T). In vitro displacement experiments revealed the ability of HDL(T) to compete with oxidized and acetylated LDL, known as ligands of scavenger receptor (SR) class B type I/II. Similarly, treatment with a blocking antibody to SR-BI/II reduced the cell association of HDL(T) and native HDL by 50%. The addition of polyinosinic acid, an inhibitor of SR class A, reduced the cell association of HDL(T) without affecting that of native HDL. These findings provide evidence that HDL(T) can compete with modified LDL, bind SR-BI/BII and internalize cholesterol ester. Furthermore, the impaired capacity of HDL(T) in promoting cholesterol efflux from J774-AI was accompanied by diminished nCEH and enhanced recognition by SR-AI/II, which appears to involve the transport of cholesterol into cells.
authors.affiliation: Centre de Recherche, Hôpital Sainte-Justine, Department of Nutrition, Université de Montréal, Montréal, Québec, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Suc
authors.forename: Sylvain
authors.initials: S
authors.lastname: Brunet
authors.forename: Grant
authors.initials: G
authors.lastname: Mitchell
authors.forename: Georges-Etienne
authors.initials: GE
authors.lastname: Rivard
authors.forename: Emile
authors.initials: E
authors.lastname: Levy
mesh_terms: D000818:Animals; D000906:Antibodies; D001053:Apolipoproteins / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D018955:CD36 Antigens / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D008078:Cholesterol, LDL / Q000378:metabolism; D003324:Coronary Artery Disease / Q000378:metabolism* / Q000503:physiopathology; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D011069:Poly I / Q000494:pharmacology; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051117:Scavenger Receptors, Class A; D051122:Scavenger Receptors, Class B; D002787:Sterol Esterase / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000906:Antibodies; D001053:Apolipoproteins; D018955:CD36 Antigens; D008078:Cholesterol, LDL; D008075:Lipoproteins, HDL; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051117:Scavenger Receptors, Class A; D051122:Scavenger Receptors, Class B; C035237:3-O-(1-hexadecyl)cholesterol; D011069:Poly I; D014443:Tyrosine; D002784:Cholesterol; D002787:Sterol Esterase