Transcriptional induction of the cytochrome P4501A1 gene by a thiazolium compound, YH439.
The molecular mechanism of induction of cytochromes P4501A1/2 (CYP1A1/2) by a synthetic compound YH439 was studied in rodents as well as in cultured hepatoma cells. CYP1A1-mediated ethoxyresorufin-O-deethylase activity and amounts of its immunoreactive protein were increased in a time- and concentration-dependent manner after a single dose of YH439 (150 mg/kg). Northern blot analyses revealed that YH439 rapidly increased (< or = 2 hr) the levels of CYP1A1/2 mRNAs, resulting in an increase in CYP1A protein level by > 6-fold at 8 hr after injection. After YH439 administration, the levels of CYP1A1 and CYP1A2 mRNAs peaked at 8 hr and 16 hr, respectively, before returning to control levels at 16 and 24 hr. The CYP1A protein level, on the other hand, reached a maximum at 24 hr after YH439 treatment and returned to near-control levels at 72 hr. Nuclear run-on analyses revealed that YH439 induces CYP1A1/2 gene transcription as early as 2 hr after YH439 treatment. Cytosolic electrophoretic mobility shift assays suggested that YH439 activates the CYP1A1/2 genes through the aryl hydrocarbon (Ah) receptor and the xenobiotic response elements. The dependency on the Ah receptor for the induction of CYP1A1/2 by YH439 was confirmed by the lack of CYP1A1/2 induction in the Ah receptor knock-out mice (Ahr-1-) as well as in murine hepatoma cells without a functional Ah receptor. Molecular structural analysis of YH439 and several other compounds indicated that the planarity and size of a molecule are important in its interaction with the Ah receptor and subsequent CYP1A1/2 induction. YH439 is a thiazolium compound with little aromaticity and with a two-dimensional structure different from that of the Ahs. Therefore, it represents a new class of Ah receptor ligand and CYP1A inducer.
Lee
I J
IJ
Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA. ijlee@dicbr.niaaa.nih.gov
Jeong
K S
KS
Roberts
B J
BJ
Kallarakal
A T
AT
Fernandez-Salguero
P
P
Gonzalez
F J
FJ
Song
B J
BJ
D000818:Animals; D001483:Base Sequence; D019388:Cytochrome P-450 CYP1A2; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004586:Electrophoresis; D004790:Enzyme Induction / Q000187:drug effects; D006801:Humans; D008297:Male; D008314:Malonates / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000096:biosynthesis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018336:Receptors, Aryl Hydrocarbon / Q000502:physiology; D013844:Thiazoles / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D008314:Malonates; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D013844:Thiazoles; C098009:YH 439; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019388:Cytochrome P-450 CYP1A2; C024808:diisopropyl 1,3-dithiol-2-ylidenemalonate