The Nrf2 activator oltipraz also activates the constitutive androstane receptor.
Oltipraz (OPZ) is a well known inducer of NAD(P)H:quinone oxidoreductase (NQO1) along with other enzymes that comprise the nuclear factor E2-related factor 2 (Nrf2) battery of detoxification genes. However, OPZ treatment also induces expression of CYP2B, a gene regulated by the constitutive androstane receptor (CAR). Therefore, this study was designed to determine whether OPZ induces gene expression in the mouse liver through activation of CAR in addition to Nrf2. OPZ increased the mRNA expression of both Cyp2b10 and Nqo1 in C57BL/6 mouse livers. As expected, in livers from Nrf2-/- mice, OPZ induction of Nqo1 was reduced, indicating Nqo1 induction is dependent on Nrf2 activation, whereas Cyp2b10 induction was unchanged. The robust induction of Cyp2b10 by OPZ in wild-type mice was completely absent in CAR-/- mice, revealing a CAR-dependent induction by OPZ. OPZ also induced transcription of the human CYP2B6 promoter-reporter containing the phenobarbital (PB) responsive element in mouse liver using an in vivo transcription assay. Additionally, OPZ induced in vivo nuclear accumulation of CAR at 3 h but, as with PB, was unable to reverse androstanol repression of mouse CAR constitutive activity in transiently transfected HepG2 cells. In summary, OPZ induces expression of Cyp2b10 and Nqo1 via the activation of CAR and Nrf2, respectively.
Merrell
Matthew D
MD
Department of Pharmacology and Toxicology, University of Arizona, Tucson, AZ 85721, USA.
Jackson
Jonathan P
JP
Augustine
Lisa M
LM
Fisher
Craig D
CD
Slitt
Angela L
AL
Maher
Jonathan M
JM
Huang
Wendong
W
Moore
David D
DD
Zhang
Youcai
Y
Klaassen
Curtis D
CD
Cherrington
Nathan J
NJ
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D000090702:Constitutive Androstane Receptor; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis; D004790:Enzyme Induction; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016660:NAD(P)H Dehydrogenase (Quinone); D009252:NADPH Dehydrogenase / Q000096:biosynthesis; D051267:NF-E2-Related Factor 2 / Q000819:agonists* / Q000235:genetics / Q000502:physiology; D011719:Pyrazines / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists*; D013871:Thiones; D013876:Thiophenes; D014157:Transcription Factors / Q000819:agonists*; D014158:Transcription, Genetic
D000090702:Constitutive Androstane Receptor; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D011719:Pyrazines; D018160:Receptors, Cytoplasmic and Nuclear; D013871:Thiones; D013876:Thiophenes; D014157:Transcription Factors; C026209:oltipraz; D003577:Cytochrome P-450 Enzyme System; D016660:NAD(P)H Dehydrogenase (Quinone); C491732:Nqo1 protein, mouse; D009252:NADPH Dehydrogenase