Glucuronidation of Nicotine and Cotinine by UGT2B10: Loss of Function by the UGT2B10 Codon 67 (Asp>Tyr) Polymorphism

Abstract

Nicotine, the major addicting agent in tobacco and tobacco smoke, undergoes a complex metabolic pathway, with f22% of nicotine urinary metabolites in the form of phase II N-glucuronidated compounds. Recent studies have shown that UGT2B10 is a major enzyme involved in the N-glucuronidation of several tobacco-specific nitrosamines. In the present study, microsomes of UGT2B10-overexpressing HEK293 cells exhibited high N-glucuronidation activity against both nicotine and cotinine with apparent K M 's that were 37-and 3-fold lower than that observed for microsomes of UGT1A4-overexpressing cells against nicotine and cotinine, respectively. The K M of microsomes from wild-type (WT) UGT2B10-overexpressing cells for nicotine and cotinine was similar to that observed for human liver microsomes (HLM) against both substrates. The level of glucuronidated nicotine or cotinine in 112 HLM samples was correlated with UGT2B10 genotype; the levels of nicotine-and cotinine-glucuronide were 21% to 30% lower in specimens from subjects with the UGT2B10 (*1/*2) genotype compared with specimens from subjects with the WT UGT2B10 (*1/*1) genotype; a 5-and 16-fold lower level of nicotine-and cotinine-glucuronide formation, respectively, was observed in HLM from subjects with the UGT2B10 (*2/*2) genotype. In contrast to the relatively high activity observed for cells overexpressing WT UGT2B10 in vitro, little or no glucuronidation was observed for microsomes from cells overexpressing the UGT2B10*2 variant against either nicotine or cotinine. These data suggest that UGT2B10 is the major hepatic enzyme involved in nicotine/cotinine glucuronidation and that the UGT2B10*2 variant significantly reduces nicotineand cotinine-N-glucuronidation formation and plays an important role in nicotine metabolism and elimination.

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

“…Previously reported K m and V max values for cotinine N-glucuronidation by HLM range from 0.93 to 5.43 mM and 643 to 696 pmol/min.mg, respectively (Ghosheh and Hawes, 2002;Nakajima et al, 2002;Chen et al, 2007;Kaivosaari et al, 2007), whereas K m values of 0.47 and 1.0 mM have been reported for cotinine N-glucuronidation by recombinant UGT2B10 (Chen et al, 2007;Kaivosaari et al, 2007). The mean K m (2.78 mM) and V max (297 pmol/mg.min) values for human liver microsomal cotinine N-glucuronidation determined in this study tended to be higher and lower, respectively, than previously reported values.…”

“…Previous studies have shown that the TCAs amitriptyline, clomipramine, imipramine, and trimipramine and the atypical antipsychotic olanzapine are substrates and/or inhibitors of UGT2B10 (Chen et al, 2007;Zhou et al, 2010;Guo et al, 2011;Kato et al, 2013). As noted in the Introduction, antidepressant and antipsychotic drugs typically contain an amine functional group.…”

“…Although initially considered an orphan enzyme, more recent studies have shown that UGT2B10, like UGT1A4, catalyzes the N-glucuronidation of a number of xenobiotics that incorporate an aliphatic tertiary amine or aromatic N-heterocyclic group (Kaivosaari et al, 2011). Known substrates are nicotine and its oxidation product cotinine (Chen et al, 2007;Kaivosaari et al, 2007); desloratadine (Kazmi et al, 2015a); medetomidine (Kaivosaari et al, 2008); the tricyclic antidepressants (TCAs) amitriptyline, clomipramine, imipramine, and trimipramine (Chen et al, 2007;Zhou et al, 2010;Kato et al, 2013); several tobacco-specific nitrosamines (Chen et al, 2008); RO5263397 (Fowler et al, 2015); and miscellaneous drugs that include diphenhydramine, ketoconazole, ketotifen, midazolam, olanzapine, pizotifen, and tamoxifen (Erickson-Ridout et al, 2011;Kato et al, 2013). Consistent with the known selectivity of UGT1A4 for N-glucuronidation (Kubota et al, 2007), most, if not all, UGT2B10 substrates are additionally glucuronidated by UGT1A4 and biphasic kinetics are frequently observed when human liver microsomes (HLM) are used as the enzyme source (Kaivosaari et al, 2011;Kato et al, 2013).…”

Regio- and Stereospecific N-Glucuronidation of Medetomidine: The Differences between UDP Glucuronosyltransferase (UGT) 1A4 and UGT2B10 Account for the Complex Kinetics of Human Liver Microsomes

“…Until recently, UGT1A4 was assumed to be the only enzyme that specializes in N-glucuronidation. This concept changed last year with the simultaneous discoveries, both in our laboratory and by Chen and coworkers, of the high N-glucuronidation activities of UGT2B10 (Kaivosaari et al, 2007;Chen et al, 2007).…”

Prediction of Deleterious Non-synonymous Single-Nucleotide Polymorphisms of Human Uridine Diphosphate Glucuronosyltransferase Genes

“…Only two variant alleles of the human UGT2 mRNAs have been confirmed in the UGT2 gene family, which are Asp67Tyr and Asp85Tyr (60,61). Hyperbilirubinemia can be caused by a number of reasons including liver disease and hemolysis (62).…”