title: Human UDP-Glucuronosyltransferase (UGT) 2B10: Validation of Cotinine as a Selective Probe Substrate, Inhibition by UGT Enzyme-Selective Inhibitors and Antidepressant and Antipsychotic Drugs, and Structural Determinants of Enzyme Inhibition.
abstract: Although there is evidence for an important role of UGT2B10 in the N-glucuronidation of drugs and other xenobiotics, the inhibitor selectivity of this enzyme is poorly understood. This study sought primarily to characterize the inhibition selectivity of UGT2B10 by UDP-glucuronosyltransferase (UGT) enzyme-selective inhibitors used for reaction phenotyping, and 34 antidepressant and antipsychotic drugs that contain an amine functional group. Initial studies demonstrated that cotinine is a highly selective substrate of human liver microsomal UGT2B10. The kinetics of cotinine N-glucuronidation by recombinant UGT and human liver microsomes (± bovine serum albumin) were consistent with the involvement of a single enzyme. Of the UGT enzyme-selective inhibitors employed for reaction phenotyping, only the UGT2B4/7 inhibitor fluconazole reduced recombinant UGT2B10 activity to an appreciable extent. The majority of antidepressant and antipsychotic drugs screened for effects on UGT2B10 inhibited enzyme activity with IC50 values <100 µM. The most potent inhibition was observed with the tricyclic antidepressants amitriptyline and doxepin and the tetracyclic antidepressant mianserin, and the structurally related compounds desloratadine and loratadine. Molecular modeling using a ligand-based approach indicated that hydrophobic and charge interactions are involved in inhibitor binding, whereas spatial features influence the potency of UGT2B10 inhibition. Respective mean Ki,u (± S.D.) values for amitriptyline, doxepin, and mianserin inhibition of human liver microsomal UGT2B10 were 0.61 ± 0.05, 0.95 ± 0.18, and 0.43 ± 0.01 µM. In vitro-in vivo extrapolation indicates that these drugs may perpetrate inhibitory drug-drug interactions when coadministered with compounds that are cleared predominantly by UGT2B10.
authors.affiliation: Department of Clinical Pharmacology (A.P., P.C.N., A.R., J.O.M.) and Flinders Centre for Innovation in Cancer (A.R., P.C.N., J.O.M.), Flinders University School of Medicine, Adelaide, Australia.
authors.forename: Attarat
authors.initials: A
authors.lastname: Pattanawongsa
authors.affiliation: Department of Clinical Pharmacology (A.P., P.C.N., A.R., J.O.M.) and Flinders Centre for Innovation in Cancer (A.R., P.C.N., J.O.M.), Flinders University School of Medicine, Adelaide, Australia.
authors.forename: Pramod C
authors.initials: PC
authors.lastname: Nair
authors.affiliation: Department of Clinical Pharmacology (A.P., P.C.N., A.R., J.O.M.) and Flinders Centre for Innovation in Cancer (A.R., P.C.N., J.O.M.), Flinders University School of Medicine, Adelaide, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Rowland
authors.affiliation: Department of Clinical Pharmacology (A.P., P.C.N., A.R., J.O.M.) and Flinders Centre for Innovation in Cancer (A.R., P.C.N., J.O.M.), Flinders University School of Medicine, Adelaide, Australia john.miners@flinders.edu.au.
authors.forename: John O
authors.initials: JO
authors.lastname: Miners
mesh_terms: D000639:Amitriptyline / Q000494:pharmacology; D000929:Antidepressive Agents, Tricyclic / Q000494:pharmacology*; D014150:Antipsychotic Agents / Q000494:pharmacology*; D002460:Cell Line; D003367:Cotinine / Q000494:pharmacology*; D004347:Drug Interactions / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015725:Fluconazole / Q000494:pharmacology; D014453:Glucuronosyltransferase / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D017336:Loratadine / Q000031:analogs & derivatives / Q000494:pharmacology; D008862:Microsomes, Liver / Q000378:metabolism
chemical_list: D000929:Antidepressive Agents, Tricyclic; D014150:Antipsychotic Agents; D004791:Enzyme Inhibitors; D000639:Amitriptyline; D017336:Loratadine; D015725:Fluconazole; C552162:UGT2B10 protein, human; D014453:Glucuronosyltransferase; C121345:desloratadine; D003367:Cotinine