title: Carbonyl reduction of triadimefon by human and rodent 11β-hydroxysteroid dehydrogenase 1.
abstract: 11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1) catalyzes the conversion of inactive 11-oxo glucocorticoids (endogenous cortisone, 11-dehydrocorticosterone and synthetic prednisone) to their potent 11β-hydroxyl forms (cortisol, corticosterone and prednisolone). Besides, 11β-HSD1 accepts several other substrates. Using rodent liver microsomes and the unspecific inhibitor glycyrrhetinic acid, it has been proposed earlier that 11β-HSD1 catalyzes the reversible conversion of the fungicide triadimefon to triadimenol. In the present study, recombinant human, rat and mouse enzymes together with a highly selective 11β-HSD1 inhibitor were applied to assess the role of 11β-HSD1 in the reduction of triadimefon and to uncover species-specific differences. To further demonstrate the role of 11β-HSD1 in the carbonyl reduction of triadimefon, microsomes from liver-specific 11β-HSD1-deficient mice were employed. Molecular docking was applied to investigate substrate binding. The results revealed important species differences and demonstrated the irreversible 11β-HSD1-dependent reduction of triadimefon. Human liver microsomes showed 4 and 8 times higher activity than rat and mouse liver microsomes. The apparent Vmax/Km of recombinant human 11β-HSD1 was 5 and 15 times higher than that of mouse and rat 11β-HSD1, respectively, indicating isoform-specific differences and different expression levels for the three species. Experiments using inhibitors and microsomes from 11β-HSD1-deficient mice indicated that 11β-HSD1 is the major if not only enzyme responsible for triadimenol formation. The IC50 values of triadimefon and triadimenol for cortisone reduction suggested that exposure to these xenobiotica unlikely impairs the 11β-HSD1-dependent glucocorticoid activation. However, elevated glucocorticoids during stress or upon pharmacological administration likely inhibit 11β-HSD1-dependent metabolism of triadimefon in humans.
authors: Swiss Center for Applied Human Toxicology and Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland.
authors: Arne
authors: A
authors: Meyer
authors: Anna
authors: A
authors: Vuorinen
authors: Agnieszka E
authors: AE
authors: Zielinska
authors: Thierry
authors: T
authors: Da Cunha
authors: Petra
authors: P
authors: Strajhar
authors: Gareth G
authors: GG
authors: Lavery
authors: Daniela
authors: D
authors: Schuster
authors: Alex
authors: A
authors: Odermatt
mesh_terms: D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2 / Q000378:metabolism; D000818:Animals; D003348:Cortisone / Q000378:metabolism; D005659:Fungicides, Industrial / Q000737:chemistry / Q000493:pharmacokinetics*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008862:Microsomes, Liver / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D014227:Triazines / Q000737:chemistry / Q000493:pharmacokinetics*; D014230:Triazoles / Q000737:chemistry / Q000378:metabolism
chemical_list: D005659:Fungicides, Industrial; D014227:Triazines; D014230:Triazoles; C539456:tradimefon; C032910:triadimefon; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2; D003348:Cortisone