title: 13-cis retinoic acid exerts its specific activity on human sebocytes through selective intracellular isomerization to all-trans retinoic acid and binding to retinoid acid receptors.
abstract: Despite its potent biologic effect on human sebocytes, 13-cis retinoic acid exhibits low binding affinity for cellular retinoic acid binding proteins and nuclear retinoid receptors. Hence, 13-cis retinoic acid may represent a pro-drug possibly acting through all-trans isomerization. In this study, marked isomerization of 13-cis retinoic acid has been confirmed in cultured SZ95 sebocytes showing 2- to 15-fold higher levels of all-trans retinoic acid at 12-72 h, as measured by high performance liquid chromatography. In contrast, only low amounts of all-trans retinoic acid were converted intracellularly to its 13-cis isoform. 9-cis retinoic acid was not detected after either 13-cis retinoic acid or all-trans retinoic acid treatment. The rapid isomerization of 13-cis retinoic acid to high levels of all-trans retinoic acid was a sebocyte-specific event, as no significant isomerization of 13-cis retinoic acid to all-trans retinoic acid occurred in HaCaT keratinocytes. De novo mRNA expression of cytochrome P450 1A1, a major xenobiotic metabolizing enzyme, in SZ95 sebocytes was induced by all-trans retinoic acid, but not by 13-cis retinoic acid. In addition, mRNA levels of cellular retinoic acid-binding protein II, which is supposed to regulate the concentration of intracellular all-trans retinoic acid, rapidly increased under all-trans retinoic acid treatment (30 min-6 h), whereas the 13-cis retinoic acid effect was markedly weaker and delayed. Both 13-cis retinoic acid and all-trans retinoic acid suppressed mRNA expression of cytochrome P450 1A2. In parallel experiments, 13-cis retinoic acid significantly reduced SZ95 sebocyte proliferation at 10-7 M, show- ing 30-40% inhibition after 9 d. All-trans retinoic acid and 9-cis retinoic acid exhibited similar anti-proliferative effects. AGN 193109, a pan-antagonist of the retinoic acid receptors, antagonized the anti-proliferative activity of all retinoic acid isomers tested in a concentration-dependent manner with complete abolishment at ratios of 1:10 13-cis retinoic acid and 1:1 all-trans retinoic acid. Coincubation of SZ95 sebocytes with 13-cis retinoic acid and AGN 193109 did not alter the intracellular concentration of 13-cis retinoic acid and its isomerization profile. In contrast, the retinoid X receptor antagonist CD 3507 did not affect the inhibition of SZ95 sebocyte proliferation induced by retinoic acids. Our findings indicate: (i) a selective 13-cis retinoic acid isomerization to all-trans retinoic acid in the intracellular compartment of SZ95 sebocytes; (ii) a reduced all-trans retinoic acid inactivation process after 13-cis retinoic acid treatment as compared with treatment with all-trans retinoic acid; and (iii) a retinoic acid receptor-mediated inhibition of SZ95 sebocyte proliferation. These data explain the sebocyte-specific activity of 13-cis retinoic acid and support a pro-drug/drug relation between 13-cis retinoic acid and all-trans retinoic acid.
authors.affiliation: Department of Dermatology, University Medical Center Benjamin Franklin, The Free University of Berlin, Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Tsukada
authors.forename: M
authors.initials: M
authors.lastname: Schröder
authors.forename: T C
authors.initials: TC
authors.lastname: Roos
authors.forename: R A
authors.initials: RA
authors.lastname: Chandraratna
authors.forename: U
authors.initials: U
authors.lastname: Reichert
authors.forename: H F
authors.initials: HF
authors.lastname: Merk
authors.forename: C E
authors.initials: CE
authors.lastname: Orfanos
authors.forename: C C
authors.initials: CC
authors.lastname: Zouboulis
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D004355:Drug Stability; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D007536:Isomerism; D015474:Isotretinoin / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D015603:Keratinocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D012629:Sebum / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D014212:Tretinoin / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; C082927:retinoic acid binding protein I, cellular; D014212:Tretinoin; D019363:Cytochrome P-450 CYP1A1; D015474:Isotretinoin