title: Cloning of rat cytochrome P450RAI (CYP26) cDNA and regulation of its gene expression by all-trans-retinoic acid in vivo.
abstract: A novel retinoic acid (RA)-inducible cytochrome P450 (P450 RAI or CYP26), previously cloned from human, zebra fish, and mouse, functions in the metabolism of all-trans-RA to polar metabolites including 4-hydroxy-RA and 4-oxo-RA. To further study CYP26 in the rat model, we first cloned rat CYP26 cDNA. The nucleotide sequence predicts a 497-amino-acid protein whose sequence is 95% identical to mouse and 91% homologous to human CYP26. Animal studies showed that CYP26 mRNA expression is very low (0.01+/-0.008;P<0.05) in vitamin-A-deficient rats compared to pair-fed vitamin-A-sufficient rats (defined as 1.0). In a kinetic study, vitamin-A-deficient rats were treated with approximately 100 microg of all-trans-RA and liver was collected after 3-72 h for analysis of CYP26 mRNA by quantitative real-time PCR. Liver CYP26 mRNA increased to nearly 10-fold above control after 3 h (P<0.01), reaching a peak of about 2000-fold greater around 10 h (P<0.001) and then decreased rapidly. The CYP26 dose response to RA was nearly linear (R(2)=0.9638). Additionally, significant regulation of CYP26 gene expression was observed in the vitamin-A-deficient, control, and RA-treated condition in lung, testis, and small intestine. We conclude that CYP26 mRNA expression is dynamically regulated in vivo by diet and RA in hepatic and extrahepatic tissues. The long-term down-regulation of CYP26 in retinoid deficiency may be critical for conserving RA, while the acute up-regulation of CYP26 may be important for preventing a deleterious overshoot of RA derived from either dietary or exogenous sources.
authors.affiliation: Program in Integrative Biosciences, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Yuanping
authors.initials: Y
authors.lastname: Wang
authors.forename: Reza
authors.initials: R
authors.lastname: Zolfaghari
authors.forename: A Catharine
authors.initials: AC
authors.lastname: Ross
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D008099:Liver / Q000201:enzymology; D008297:Male; D051379:Mice; D006899:Mixed Function Oxygenases / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D000072516:Retinoic Acid 4-Hydroxylase; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014212:Tretinoin / Q000494:pharmacology; D014802:Vitamin A Deficiency / Q000201:enzymology / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C000607080:Cyp26a1 protein, mouse; D000072516:Retinoic Acid 4-Hydroxylase