Time course characterization of the induction of cytochrome P-450 2E1 by pyrazole and 4-methylpyrazole.
Cytochrome P-450 (P-450) 2E1 is under transcriptional and post-transcriptional control. Well-defined time courses were carried out to compare the effect of pyrazole and 4-methylpyrazole on catalytic activities, apo-P-450 2E1 levels and mRNA levels to evaluate whether induction of P-450 2E1 is preceded by altered mRNA levels. Two days of treatment with pyrazole or three days of treatment with 4-methylpyrazole resulted in significant induction of P-450 2E1, as assessed by Western blots and by oxidation of dimethylnitrosamine or p-nitrophenol. No changes in mRNA levels were detected with either inducer. Within 2 h of the second treatment with pyrazole, maximal induction of P-450 2E1 was observed, however, a 8-12 h time-dependent period was required after the third treatment with 4-methylpyrazole for maximal induction. Irrespective of the time period, increased catalytic activity and P-450 2E1 appears to reflect a post-transcriptional mechanism. A single treatment with 4-methylpyrazole increased P-450 2B1/B2 levels and oxidation of pentoxyresorufin about 2- to 3-fold. No change in mRNA levels for 2B1/B2 was observed. Although significant, the induction of 2B1/B2 by 4-methylpyrazole is more than an order of magnitude less than that by phenobarbital. Pyrazole did not induce 2B1/B2. It appears that, similar to acetone and ethanol, 4-methylpyrazole may increase several P-450 isozymes, whereas pyrazole is more specific for induction of P-450 2E1.
Winters
D K
DK
Department of Biochemistry, Mount Sinai School of Medicine, New York, NY 10029.
Cederbaum
A I
AI
D000818:Animals; D001483:Base Sequence; D019392:Cytochrome P-450 CYP2E1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004128:Dimethylnitrosamine / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D000077604:Fomepizole; D015151:Immunoblotting; D008297:Male; D008969:Molecular Sequence Data; D009596:Nitrophenols / Q000378:metabolism; D015345:Oligonucleotide Probes; D010078:Oxazines / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000096:biosynthesis*; D011720:Pyrazoles / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D009596:Nitrophenols; D015345:Oligonucleotide Probes; D010078:Oxazines; D011720:Pyrazoles; D012333:RNA, Messenger; C031280:pyrazole; D000077604:Fomepizole; C044943:pentoxyresorufin; D003577:Cytochrome P-450 Enzyme System; D019392:Cytochrome P-450 CYP2E1; D010089:Oxidoreductases, N-Demethylating; D004128:Dimethylnitrosamine; C024836:4-nitrophenol