title: Diethylstilbestrol can effectively accelerate estradiol-17-O-glucuronidation, while potently inhibiting estradiol-3-O-glucuronidation.
abstract: This in vitro study investigates the effects of diethylstilbestrol (DES), a widely used toxic synthetic estrogen, on estradiol-3- and 17-O- (E2-3/17-O) glucuronidation, via culturing human liver microsomes (HLMs) or recombinant UDP-glucuronosyltransferases (UGTs) with DES and E2. DES can potently inhibit E2-3-O-glucuronidation in HLM, a probe reaction for UGT1A1. Kinetic assays indicate that the inhibition follows a competitive inhibition mechanism, with the Ki value of 2.1±0.3μM, which is less than the possible in vivo level. In contrast to the inhibition on E2-3-O-glucuronidation, the acceleration is observed on E2-17-O-glucuronidation in HLM, in which cholestatic E2-17-O-glucuronide is generated. In the presence of DES (0-6.25μM), Km values for E2-17-O-glucuronidation are located in the range of 7.2-7.4μM, while Vmax values range from 0.38 to 1.54nmol/min/mg. The mechanism behind the activation in HLM is further demonstrated by the fact that DES can efficiently elevate the activity of UGT1A4 in catalyzing E2-17-O-glucuronidation. The presence of DES (2μM) can elevate Vmax from 0.016 to 0.81nmol/min/mg, while lifting Km in a much lesser extent from 4.4 to 11μM. Activation of E2-17-O-glucuronidation is well described by a two binding site model, with KA, α, and β values of 0.077±0.18μM, 3.3±1.1 and 104±56, respectively. However, diverse effects of DES towards E2-3/17-O-glucuronidation are not observed in liver microsomes from several common experimental animals. In summary, this study issues new potential toxic mechanisms for DES: potently inhibiting the activity of UGT1A1 and powerfully accelerating the formation of cholestatic E2-17-O-glucuronide by UGT1A4.
authors.affiliation: The Centre for Drug and Food Safety Evaluation, School of Life Science, Anqing Normal University, Anqing 246011, China.
authors.forename: Liangliang
authors.initials: L
authors.lastname: Zhu
authors.affiliation: The Centre for Drug and Food Safety Evaluation, School of Life Science, Anqing Normal University, Anqing 246011, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Xiao
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Yangliu
authors.initials: Y
authors.lastname: Xia
authors.affiliation: College of Pharmacy, Liaoning University of Traditional Chinese Medicine, Dalian 116600, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Zhou
authors.affiliation: The Centre for Drug and Food Safety Evaluation, School of Life Science, Anqing Normal University, Anqing 246011, China.
authors.forename: Huili
authors.initials: H
authors.lastname: Wang
authors.affiliation: The Centre for Drug and Food Safety Evaluation, School of Life Science, Anqing Normal University, Anqing 246011, China.
authors.forename: Minyi
authors.initials: M
authors.lastname: Huang
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China. Electronic address: geguangbo@dicp.ac.cn.
authors.forename: Guangbo
authors.initials: G
authors.lastname: Ge
authors.affiliation: The Centre for Drug and Food Safety Evaluation, School of Life Science, Anqing Normal University, Anqing 246011, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wu
authors.affiliation: The Centre for Drug and Food Safety Evaluation, School of Life Science, Anqing Normal University, Anqing 246011, China.
authors.forename: Ganlin
authors.initials: G
authors.lastname: Wu
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China. Electronic address: yling@dicp.ac.cn.
authors.forename: Ling
authors.initials: L
authors.lastname: Yang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002478:Cells, Cultured; D004054:Diethylstilbestrol / Q000633:toxicity*; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D020719:Glucuronides / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008862:Microsomes, Liver / Q000187:drug effects* / Q000378:metabolism*; D008875:Middle Aged; D051381:Rats; D017207:Rats, Sprague-Dawley; D055815:Young Adult
chemical_list: D020719:Glucuronides; D004958:Estradiol; D004054:Diethylstilbestrol
keywords: Diethylstilbestrol; Estradiol glucuronidation; UGT1A1; UGT1A4