The induction of human UDP-glucuronosyltransferase 1A1 mediated through a distal enhancer module by flavonoids and xenobiotics.
We identified the UDP-glucuronosyltransferase (UGT) 1A1 5'-upstream region that confers UGT1A1 induction by various agents, including flavonoids, on a luciferase reporter gene and has the properties of a transcriptional enhancer. Chrysin- and rifampicin-response activities were traced to the same element as a 290-bp distal enhancer module (-3483/-3194), in which the reporter activities were enhanced by activators of nuclear receptors [constitutive androstane receptor (CAR) and pregnane X receptor (PXR)] and transcription factor [aryl hydrocarbon receptor (AhR)]. Utilizing transactivation experiments with the UGT1A1 290-bp reporter gene, we assessed UGT1A1 induction by various flavonoids. 5,7-Dihydroxyflavones with varying substituents in the B-ring and gallocatechin dimers increased the reporter activity in a time- and dose-dependent manner. The treatment of HepG2 cells with the flavonoids for 24 hr elevated the expression of mRNAs and proteins of UGT1A1 and CYP1A1, while the mRNA levels of CYP2B6, CYP3A4, CAR, PXR and AhR was not altered. Chrysin and rifampicin induced the activation of the wild-type reporter gene and T-3263G-mutated gene to a similar extent in HepG2 cells cotransfected with expression vectors of CAR and PXR. Mutation of the AhR core binding region most prominently suppressed the activation of the 290-bp reporter gene by chrysin and baicalein, while mutations of four putative nuclear receptor motifs (DR4 element, PXRE, CARE and DR3 element) partly decreased its activation. Taken together, the results indicate that UGT1A1 was induced in response to flavonoids and xenobiotics through the transactivation of the 290-bp reporter gene, that was a multi-component enhancer containing CAR, PXR and AhR motifs.
Sugatani
Junko
J
Department of Pharmaco-Biochemistry and COE 21, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan.
Yamakawa
Kasumi
K
Tonda
Eri
E
Nishitani
Shinichi
S
Yoshinari
Kouichi
K
Degawa
Masakuni
M
Abe
Ikuro
I
Noguchi
Hiroshi
H
Miwa
Masao
M
D000704:Analysis of Variance; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins; D001564:Benzo(a)pyrene / Q000494:pharmacology; D044946:Biflavonoids; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002392:Catechin / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000187:drug effects / Q000502:physiology; D004790:Enzyme Induction / Q000187:drug effects; D005136:Eye Proteins; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D017930:Genes, Reporter; D014453:Glucuronosyltransferase / Q000096:biosynthesis* / Q000235:genetics; D051597:Hippocalcin; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D008074:Lipoproteins; D008968:Molecular Conformation; D016296:Mutagenesis; D009419:Nerve Tissue Proteins; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics / Q000378:metabolism; D000077297:Pregnane X Receptor; D044945:Proanthocyanidins; D011794:Quercetin / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism; D051603:Recoverin; D014162:Transfection; D014407:Tumor Cells, Cultured; D015262:Xenobiotics / Q000737:chemistry / Q000494:pharmacology*; D000099148:UGT1A1 Enzyme
D001189:Aryl Hydrocarbon Hydroxylases; D051792:Basic Helix-Loop-Helix Proteins; D001564:Benzo(a)pyrene; D044946:Biflavonoids; D002135:Calcium-Binding Proteins; D002392:Catechin; D019363:Cytochrome P-450 CYP1A1; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System; D005136:Eye Proteins; D005419:Flavonoids; D014453:Glucuronosyltransferase; D051597:Hippocalcin; D006873:Hydroquinones; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; D010089:Oxidoreductases, N-Demethylating; D000077297:Pregnane X Receptor; D044945:Proanthocyanidins; D011794:Quercetin; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D051603:Recoverin; D015262:Xenobiotics; D000099148:UGT1A1 Enzyme; C111235:AHR protein, human; C496731:RCVRN protein, human; C043561:chrysin; C017674:procyanidin; C018855:2-tert-butylhydroquinone; C585599:CYP2B6 protein, human; C104464:CYP3A protein, human; C510163:CYP3A4 protein, human