title: Both all-trans retinoic acid and cytochrome P450 (CYP26) inhibitors affect the expression of vitamin A metabolizing enzymes and retinoid biomarkers in organotypic epidermis.
abstract: The biosynthesis of retinoic acid (RA) from retinol is controlled by several enzymes, e.g. dehydrogenases (RalDH2, RoDH-4) and retinol-esterifying enzyme (LRAT), whereas its degradation mainly involves CYP26 enzymes. In keratinocytes, RA activates the nuclear retinoid-receptors inducing the transcription of many genes. Here, we examined the effects of RA and the CYP26 inhibitors, liarozole and talarozole, on retinoid metabolism and RA-regulated genes in organotypic epidermis. RA induced the expression of CYP26 enzymes already after 8 h, whereas LRAT exhibited a later response and peaked at 48 h, indicating a feedback induction of retinol esterification. In line with a reduced biosynthesis of RA from retinol after exogenous RA, the expression of RDH16 reduced 80% in response to exogenous RA. The mRNA expression of RA-regulated genes (KRT2, KRT4, CRABPII and HBEGF) was altered within 24 h after RA exposure. In contrast, the CYP26 inhibitors caused only minor effects, except for a clear-cut induction of CYP26A1 only when combined with minute amounts of exogenous RA. Cellular accumulation of exogenous [3H]RA was higher after talarozole than after liarozole, probably indicating a greater CYP26-inhibitory potency of the former drug. The present study shows that CYP26A1 expression is extremely sensitive to both exogenous RA and increased endogenous RA levels, i.e. due to CYP26 inhibition, and thus an excellent biomarker for retinoid signalling in organotypic epidermis.
authors.affiliation: Department of Medical Sciences, Dermatology and Venereology, Uppsala University, 751 85 Uppsala, Sweden.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Pavez Loriè
authors.forename: Jean Christopher
authors.initials: JC
authors.lastname: Chamcheu
authors.forename: Anders
authors.initials: A
authors.lastname: Vahlquist
authors.forename: Hans
authors.initials: H
authors.lastname: Törmä
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000726:Androgen Antagonists / Q000494:pharmacology; D052160:Benzothiazoles / Q000494:pharmacology; D015415:Biomarkers / Q000378:metabolism; D002478:Cells, Cultured; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004817:Epidermis / Q000378:metabolism* / Q000473:pathology; D025461:Feedback, Physiological; D015971:Gene Expression Regulation, Enzymologic; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D053557:Keratin-2 / Q000235:genetics / Q000378:metabolism; D053527:Keratin-4 / Q000235:genetics / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism; D050697:Retinal Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D000072516:Retinoic Acid 4-Hydroxylase; D014212:Tretinoin / Q000378:metabolism / Q000494:pharmacology*; D014230:Triazoles / Q000494:pharmacology; D014801:Vitamin A / Q000378:metabolism
chemical_list: D000726:Androgen Antagonists; D052160:Benzothiazoles; D015415:Biomarkers; D065607:Cytochrome P-450 Enzyme Inhibitors; C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D007093:Imidazoles; D036341:Intercellular Signaling Peptides and Proteins; C089241:KRT2 protein, human; D053557:Keratin-2; D053527:Keratin-4; D018168:Receptors, Retinoic Acid; D014230:Triazoles; C082928:retinoic acid binding protein II, cellular; D014801:Vitamin A; D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; D000429:Alcohol Oxidoreductases; C113992:trans-retinol dehydrogenase; D000072516:Retinoic Acid 4-Hydroxylase; D050697:Retinal Dehydrogenase; D000217:Acyltransferases; C061121:liarozole; C406527:R 115866