title: Depletion of pre-beta-high density lipoprotein by human chymase impairs ATP-binding cassette transporter A1- but not scavenger receptor class B type I-mediated lipid efflux to high density lipoprotein.
abstract: The ATP-binding cassette transporter A1 (ABCA1) mediates the efflux of cellular unesterified cholesterol and phospholipid to lipid-poor apolipoprotein A-I. Chymase, a protease secreted by mast cells, selectively cleaves pre-beta-migrating particles from high density lipoprotein (HDL)(3) and reduces the efflux of cholesterol from macrophages. To evaluate whether this effect is the result of reduction of ABCA1-dependent or -independent pathways of cholesterol efflux, in this study we examined the efflux of cholesterol to preparations of chymase-treated HDL(3) in two types of cell: 1) in J774 murine macrophages endogenously expressing low levels of scavenger receptor class B, type I (SR-BI), and high levels of ABCA1 upon treatment with cAMP; and 2) in Fu5AH rat hepatoma cells endogenously expressing high levels of the SR-BI and low levels of ABCA1. Treatment of HDL(3) with the human chymase resulted in rapid depletion of pre-beta-HDL and a concomitant decrease in the efflux of cholesterol and phospholipid (2-fold and 3-fold, respectively) from the ABCA1-expressing J774 cells. In contrast, efflux of free cholesterol from Fu5AH to chymase-treated and to untreated HDL(3) was similar. Incubation of HDL(3) with phospholipid transfer protein led to an increase in pre-beta-HDL contents as well as in ABCA1-mediated cholesterol efflux. A decreased cholesterol efflux to untreated HDL(3) but not to chymase-treated HDL(3) was observed in ABCA1-expressing J774 with probucol, an inhibitor of cholesterol efflux to lipid-poor apoA-I. Similar results were obtained using brefeldin and gliburide, two inhibitors of ABCA1-mediated efflux. These results indicate that chymase treatment of HDL(3) specifically impairs the ABCA1-dependent pathway without influencing either aqueous or SR-BI-facilitated diffusion and that this effect is caused by depletion of lipid-poor pre-beta-migrating particles in HDL(3). Our results are compatible with the view that HDL(3) promotes ABCA1-mediated lipid efflux entirely through its lipid-poor fraction with pre-beta mobility.
authors.affiliation: Department of Pharmacological and Biological Sciences, and Applied Chemistry, University of Parma, Italy.
authors.forename: Elda
authors.initials: E
authors.lastname: Favari
authors.forename: Miriam
authors.initials: M
authors.lastname: Lee
authors.forename: Laura
authors.initials: L
authors.lastname: Calabresi
authors.forename: Guido
authors.initials: G
authors.lastname: Franceschini
authors.forename: Francesca
authors.initials: F
authors.lastname: Zimetti
authors.forename: Franco
authors.initials: F
authors.lastname: Bernini
authors.forename: Petri T
authors.initials: PT
authors.lastname: Kovanen
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D002460:Cell Line; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D053818:Chymases; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015180:Electrophoresis, Gel, Two-Dimensional; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D050356:Lipid Metabolism; D008075:Lipoproteins, HDL / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D010743:Phospholipids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D013997:Time Factors
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D008075:Lipoproteins, HDL; D010743:Phospholipids; D011994:Recombinant Proteins; D020126:Brefeldin A; D002784:Cholesterol; D000242:Cyclic AMP; D012697:Serine Endopeptidases; D053818:Chymases; D005905:Glyburide