title: Specific gene expression of ATP-binding cassette transporters and nuclear hormone receptors in rat liver parenchymal, endothelial, and Kupffer cells.
abstract: Hepatic cholesterol(ester) uptake from serum coupled to intracellular processing and biliary excretion are important features in the removal of excess cholesterol from the body. ATP-binding cassette (ABC) transporters play an important role in hepatic cholesterol transport. The liver consists of different cell types, and ABC transporters may exert different physiological functions dependent on the individual cell type. Therefore, in the current study, using real time PCR we compared the mRNA expression of ABC transporters and genes involved in the regulation of cholesterol metabolism in liver parenchymal, endothelial, and Kupffer cells. It appears that liver parenchymal cells contain high expression levels compared with endothelial and Kupffer cells of scavenger receptor class BI ( approximately 3-fold), peroxisome proliferator-activated receptor (PPAR)alpha and PPARgamma (8-20-fold), cholesterol 7alpha-hydroxylase A1 (>100-fold), and ABCG5/G8 ( approximately 5-fold). Liver endothelial cells show a high expression of cholesterol 27-hydroxylase, liver X receptor (LXR)beta, PPARdelta, and ABCG1, suggesting a novel specific role for these genes in endothelial cells. In Kupffer cells, the expression level of LXRalpha, ABCA1, and in particular ABCG1 is high, leading to an ABCG1 mRNA expression level that is 70-fold higher than in parenchymal cells. It can be calculated that 51% of the total liver ABCG1 expression resides in Kupffer cells and 24% in endothelial cells, suggesting an intrahepatic-specific role for ABCG1 in Kupffer and endothelial cells. Because of a specific stimulation of ABCG1 in parenchymal cells by a high cholesterol diet, the contribution of parenchymal cells to the total liver increased from 25 to 60%. Our data indicate that for studies of the role of ABC transporters and their regulation in liver, their cellular localization should be taken into account, allowing proper interpretation of metabolic changes, which are directly related to their (intra)cellular expression level.
authors.affiliation: Division of Biopharmaceutics, Leiden Amsterdam Center for Drug Research, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, Leiden, Zuid-Holland 2300 RA, The Netherlands. Hoekstra@LACDR.Leidenuniv.nl
authors.forename: Menno
authors.initials: M
authors.lastname: Hoekstra
authors.forename: J Kar
authors.initials: JK
authors.lastname: Kruijt
authors.forename: Miranda
authors.initials: M
authors.lastname: Van Eck
authors.forename: Theo J C
authors.initials: TJ
authors.lastname: Van Berkel
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D018955:CD36 Antigens / Q000096:biosynthesis; D053493:Cholestanetriol 26-Monooxygenase; D002784:Cholesterol / Q000378:metabolism; D002790:Cholesterol 7-alpha-Hydroxylase / Q000096:biosynthesis; D004268:DNA-Binding Proteins; D004727:Endothelium / Q000166:cytology / Q000378:metabolism*; D007728:Kupffer Cells / Q000378:metabolism*; D008074:Lipoproteins / Q000096:biosynthesis; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D000071518:Liver X Receptors; D008297:Male; D008565:Membrane Proteins; D057093:Orphan Nuclear Receptors; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis / Q000378:metabolism*; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051122:Scavenger Receptors, Class B; D013250:Steroid Hydroxylases / Q000096:biosynthesis
chemical_list: C577836:ABCA1 protein, human; C419353:ABCG1 protein, human; C416945:ABCG5 protein, human; C416946:ABCG8 protein, human; D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters; D018955:CD36 Antigens; D004268:DNA-Binding Proteins; D008074:Lipoproteins; D000071518:Liver X Receptors; D008565:Membrane Proteins; C000605213:NR1H3 protein, human; C000605214:Nr1h3 protein, mouse; C000605215:Nr1h3 protein, rat; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D000255:Adenosine Triphosphate; D002784:Cholesterol; D013250:Steroid Hydroxylases; D002790:Cholesterol 7-alpha-Hydroxylase; C506831:CYP27A1 protein, human; D053493:Cholestanetriol 26-Monooxygenase; C506832:Cyp27a1 protein, mouse