title: Liarozole inhibits human epidermal retinoic acid 4-hydroxylase activity and differentially augments human skin responses to retinoic acid and retinol in vivo.
abstract: Metabolic inactivation of all-trans retinoic acid to 4-hydroxy retinoic acid occurs via a cytochrome P-450 enzyme. We investigated the effects of liarozole on the retinoic acid 4-hydroxylase activity of human epidermis and its ability to modify in vivo human skin responses to retinoic acid and all-trans retinol. Retinoic acid 4-hydroxylase activity induced in vivo by 4 d treatment with retinoic acid (0.1%) was inhibited in vitro by liarozole in a concentration-dependent manner. Comparable micromolar concentrations of liarozole were extracted from stratum corneum-free epidermis treated with 3% liarozole. Retinoic acid levels in liarozole-treated skin increased to 19 +/- 5 ng/g wet wt (mean +/- SEM, p < 0.002, n = 17) at 18 h and to 6 +/- 2 ng/g wet wt (p = 0.38, n = 17) at 48 h as compared to vehicle (not detectable). At 48 h, retinoic acid 4-hydroxylase activity was induced 9-fold over vehicle (p < 0.03, n = 8). At 96 h, no significant erythema or increased epidermal thickness was found when either retinoic acid (0.001%), all-trans retinol (0.0250%), or liarozole (3%) was applied individually, but when 0.001% retinoic acid and 3% liarozole were applied together, both erythema and increased epidermal thickness occurred. In contrast, 0.025% all-trans retinol and 3% liarozole together caused increased epidermal thickness but no erythema. These data demonstrate that, at doses used here, liarozole, although an effective inhibitor of retinoic acid 4-hydroxylase, cannot function alone like a retinoid in vivo, probably because of retinoic acid 4-hydroxylase induction. In the presence of a low dose retinoic acid or all-trans retinol, however, liarozole can amplify human skin responses to each retinoid in a manner characteristic of the retinoid at a higher dose (erythema and hyperplasia with retinoic acid; no erythema but hyperplasia with all-trans retinol).
authors: Department of Dermatology, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0528, U.S.A.
authors: S
authors: S
authors: Kang
authors: E A
authors: EA
authors: Duell
authors: K J
authors: KJ
authors: Kim
authors: J J
authors: JJ
authors: Voorhees
mesh_terms: D000726:Androgen Antagonists / Q000494:pharmacology; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004817:Epidermis / Q000201:enzymology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D000072516:Retinoic Acid 4-Hydroxylase; D012867:Skin / Q000187:drug effects* / Q000201:enzymology*; D014212:Tretinoin / Q000494:pharmacology*; D014801:Vitamin A / Q000494:pharmacology*
chemical_list: D000726:Androgen Antagonists; D065607:Cytochrome P-450 Enzyme Inhibitors; D007093:Imidazoles; D014801:Vitamin A; D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; D000072516:Retinoic Acid 4-Hydroxylase; C061121:liarozole