title: Involvement of Vitamin D receptor in the intestinal induction of human ABCB1.
abstract: ABCB1 (P-glycoprotein) is an efflux transporter that limits the cellular uptake levels of various drugs in intestine, brain, and other tissues. The expression of human ABCB1 has recently been reported to be under the control of nuclear receptor NR1I subfamily members, pregnane X receptor (PXR, NR1I2) and constitutive androstane receptor (CAR, NR1I3). Here, we have investigated the involvement of another NR1I member, vitamin D receptor (VDR, NR1I1), in ABCB1 expression. In the human colorectal adenocarcinoma cell line LS174T, which abundantly expresses VDR, both 1alpha,25-dihydroxyvitamin D(3) (1,25-VD3) and lithocholic acid (LCA) increased ABCB1 mRNA levels. Reporter gene assays in LS174T cells with constructs containing various lengths of the ABCB1 regulatory region revealed that the region containing multiple nuclear receptor binding motifs located at -7.8 kilobases [termed nuclear receptor-responsive module (NURREM)], to which PXR and CAR also bind, is essential for the VDR-mediated ABCB1 transactivation. Further reporter assays with constructs containing truncated NURREM and gel shift assays suggested simultaneous binding of multiple VDR/retinoid X receptor alpha heterodimers to NURREM. Furthermore, knockdown of VDR expression in LS174T cells blocked the LCA- and the 1,25-VD3-induced transcription of ABCB1 reporter genes. In human hepatoma HepG2 cells, in contrast with LS174T cells, 1,25-VD3 activated the ABCB1 transcription only in the presence of ectopically expressed VDR. These results suggest that the NR1I subfamily members regulate the ABCB1 expression sharing the binding sites within NURREM and that the physiologically produced LCA and 1,25-VD3 may modulate the ABCB1 expression in human intestines, possibly associated with interindividual variations of ABCB1 expression.
authors.affiliation: Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, Miyagi, Japan. yamazoe@mail.tains.tohoku.ac.jp
authors.forename: Shuko
authors.initials: S
authors.lastname: Tachibana
authors.forename: Kouichi
authors.initials: K
authors.lastname: Yoshinari
authors.forename: Tsubasa
authors.initials: T
authors.lastname: Chikada
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Toriyabe
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nagata
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yamazoe
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000469:Alkaline Phosphatase; D000951:Antigens, Neoplasm / Q000378:metabolism; D001665:Binding Sites; D045744:Cell Line, Tumor; D002762:Cholecalciferol / Q000031:analogs & derivatives* / Q000378:metabolism; D003110:Colonic Neoplasms / Q000378:metabolism; D000090702:Constitutive Androstane Receptor; D024202:Electrophoretic Mobility Shift Assay; D058851:GPI-Linked Proteins; D017930:Genes, Reporter; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000201:enzymology; D008024:Ligands; D008095:Lithocholic Acid / Q000378:metabolism*; D008113:Liver Neoplasms / Q000378:metabolism; D055503:Protein Multimerization; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid; D047490:Retinoid X Receptor alpha / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D015854:Up-Regulation
chemical_list: C116777:1,25-dihydroxy-16,23-diene vitamin D3; C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000951:Antigens, Neoplasm; D000090702:Constitutive Androstane Receptor; D058851:GPI-Linked Proteins; D008024:Ligands; C000716327:NR1I3 protein, human; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D047490:Retinoid X Receptor alpha; D002762:Cholecalciferol; D008095:Lithocholic Acid; C063088:ALPI protein, human; D000469:Alkaline Phosphatase