Identification of a novel human constitutive androstane receptor (CAR) agonist and its use in the identification of CAR target genes.
The orphan nuclear constitutive androstane receptor (CAR) is proposed to play a central role in the response to xenochemical stress. Identification of CAR target genes in humans has been limited by the lack of a selective CAR agonist. We report the identification of 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime (CITCO) as a novel human CAR agonist with the following characteristics: (a) potent activity in an in vitro fluorescence-based CAR activation assay; (b) selectivity for CAR over other nuclear receptors, including the xenobiotic pregnane X receptor (PXR); (c) the ability to induce human CAR nuclear translocation; and (d) the ability to induce the prototypical CAR target gene CYP2B6 in primary human hepatocytes. Using primary cultures of human hepatocytes, the effects of CITCO on gene expression were compared with those of the PXR ligand rifampicin. The relative expression of a number of genes encoding proteins involved in various aspects of steroid and xenobiotic metabolism was analyzed. Notably, CAR and PXR activators differentially regulated the expression of several genes, demonstrating that these two nuclear receptors subserve overlapping but distinct biological functions in human hepatocytes.
Maglich
Jodi M
JM
Nuclear Receptor Discovery Research, GlaxoSmithKline, Research Triangle Park, North Carolina 27709, USA.
Parks
Derek J
DJ
Moore
Linda B
LB
Collins
Jon L
JL
Goodwin
Bryan
B
Billin
Andrew N
AN
Stoltz
Catherine A
CA
Kliewer
Steven A
SA
Lambert
Millard H
MH
Willson
Timothy M
TM
Moore
John T
JT
D002478:Cells, Cultured; D000090702:Constitutive Androstane Receptor; D005786:Gene Expression Regulation / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D010091:Oximes / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013844:Thiazoles / Q000494:pharmacology*; D014157:Transcription Factors / Q000819:agonists* / Q000502:physiology
D000090702:Constitutive Androstane Receptor; D010091:Oximes; D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D014157:Transcription Factors; C475093:6-(4-chlorophenyl)imidazo(2,1-b)(1,3)thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime