title: LXR/RXR activation enhances basolateral efflux of cholesterol in CaCo-2 cells.
abstract: Regulation of gene expression of ATP-binding cassette transporter (ABC)A1 and ABCG1 by liver X receptor/retinoid X receptor (LXR/RXR) ligands was investigated in the human intestinal cell line CaCo-2. Neither the RXR ligand, 9-cis retinoic acid, nor the natural LXR ligand 22-hydroxycholesterol alone altered ABCA1 mRNA levels. When added together, ABCA1 and ABCG1 mRNA levels were increased 3- and 7-fold, respectively. T0901317, a synthetic non-sterol LXR agonist, increased ABCA1 and ABCG1 gene expression 11- and 6-fold, respectively. ABCA1 mass was increased by LXR/RXR activation. T0901317 or 9-cis retinoic acid and 22-hydroxycholesterol increased cholesterol efflux from basolateral but not apical membranes. Cholesterol efflux was increased by the LXR/RXR ligands to apolipoprotein (apo)A-I or HDL but not to taurocholate/phosphatidylcholine micelles. Actinomycin D prevented the increase in ABCA1 and ABCG1 mRNA levels and the increase in cholesterol efflux induced by the ligands. Glyburide, an inhibitor of ABCA1 activity, attenuated the increase in basolateral cholesterol efflux induced by T0901317. LXR/RXR activation decreased the esterification and secretion of cholesterol esters derived from plasma membranes. Thus, in CaCo-2 cells, LXR/RXR activation increases gene expression of ABCA1 and ABCG1 and the basolateral efflux of cholesterol, suggesting that ABCA1 plays an important role in intestinal HDL production and cholesterol absorption.
authors.affiliation: Department of Veterans Affairs and Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA. shubha-murthy@uiowa.edu
authors.forename: Shubha
authors.initials: S
authors.lastname: Murthy
authors.forename: Ella
authors.initials: E
authors.lastname: Born
authors.forename: Satya N
authors.initials: SN
authors.lastname: Mathur
authors.forename: F Jeffrey
authors.initials: FJ
authors.lastname: Field
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D000077556:Alitretinoin; D000924:Anticholesteremic Agents / Q000494:pharmacology; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D016764:Cell Polarity; D002784:Cholesterol / Q000378:metabolism* / Q000494:pharmacology; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation / Q000187:drug effects; D006023:Glycoproteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D006801:Humans; D006845:Hydrocarbons, Fluorinated; D008024:Ligands; D000071518:Liver X Receptors; D008823:Micelles; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D047488:Retinoid X Receptors; D013449:Sulfonamides; D014157:Transcription Factors / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology; D005466:Fluorocarbons; D000096926:Benzenesulfonamides
chemical_list: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D000077556:Alitretinoin; D000924:Anticholesteremic Agents; D002784:Cholesterol; D004268:DNA-Binding Proteins; D006023:Glycoproteins; D006845:Hydrocarbons, Fluorinated; D008024:Ligands; D000071518:Liver X Receptors; D008823:Micelles; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D013449:Sulfonamides; D014157:Transcription Factors; D014212:Tretinoin; C577836:ABCA1 protein, human; C423915:T0901317; D005466:Fluorocarbons; D000096926:Benzenesulfonamides