Correlation between Bilirubin Glucuronidation and Estradiol-3-Gluronidation in the Presence of Model UDP-Glucuronosyltransferase 1A1 Substrates/Inhibitors

Zhou, Jiaqi; Tracy, Timothy S.; Remmel, Rory P.

doi:10.1124/dmd.110.035030

Cited by 60 publications

(49 citation statements)

References 32 publications

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“…The resulting ES3-G product formation displayed atypical kinetics (curved Eadie-Hofstee plot) and best fit the Hill equation, which is consistent with previous literature (Fisher et al, 2000). The mean Hill coefficient value (n), which gives an indication of the degree of sigmoidicity of the curve, ranged from 1.8 to 2.7 for all incubation conditions (Table 3; Tables 3 and 4. is in agreement with apparent S 50 values previously reported for HLM ranging from 17 to 61 M (Fisher et al, 2000;Alkharfy and Frye, 2002;Williams et al, 2002;Soars et al, 2003;Itäaho et al, 2008) and 8.7 to 23 M for rUGT1A1 (Soars et al, 2003;Lépine et al, 2004;Fujiwara et al, 2007;Zhou et al, 2011).…”

Section: Ugt Inhibition Assayssupporting

confidence: 80%

Optimized Assays for Human UDP-Glucuronosyltransferase (UGT) Activities: Altered Alamethicin Concentration and Utility to Screen for UGT Inhibitors

Walsky

Bauman²,

Bourcier³

et al. 2012

Drug Metab Dispos

133

146

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ABSTRACT:The measurement of the effect of new chemical entities on human UDP-glucuronosyltransferase (UGT) marker activities using in vitro experimentation represents an important experimental approach in drug development to guide clinical drug-interaction study designs or support claims that no in vivo interaction will occur. Selective high-performance liquid chromatography-tandem mass spectrometry functional assays of authentic glucuronides for five major hepatic UGT probe substrates were developed: ␤-estradiol-3-glucuronide (UGT1A1), trifluoperazine-N-glucuronide (UGT1A4), 5-hydroxytryptophol-O-glucuronide (UGT1A6), propofol-O-glucuronide (UGT1A9), and zidovudine-5-glucuronide (UGT2B7). High analytical sensitivity permitted characterization of enzyme kinetic parameters at low human liver microsomal and recombinant UGT protein concentration (0.025 mg/ml), which led to a new recommended optimal universal alamethicin activation concentration of 10 g/ml for microsomes. Alamethicin was not required for recombinant UGT incubations. Apparent enzyme kinetic parameters, particularly for UGT1A1 and UGT1A4, were affected by nonspecific binding. Unbound intrinsic clearance for UGT1A9 and UGT2B7 increased significantly after addition of 2% bovine serum albumin, with minimal changes for UGT1A1, UGT1A4, and UGT1A6. Eleven potential UGT and cytochrome P450 inhibitors were evaluated as UGT inhibitors, resulting in observation of nonselective UGT inhibition by chrysin, mefenamic acid, silibinin, tangeretin, ketoconazole, itraconazole, ritonavir, and verapamil. The pan-cytochrome P450 inhibitor, 1-aminobenzotriazole, minimally inhibited UGT activities and may be useful in reaction phenotyping of mixed UGT and cytochrome P450 substrates. These methods should prove useful in the routine assessments of the potential for new drug candidates to elicit pharmacokinetic drug interactions via inhibition of human UGT activities and the identification of UGT enzymeselective chemical inhibitors.

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Section: Ugt Inhibition Assayssupporting

confidence: 80%

Optimized Assays for Human UDP-Glucuronosyltransferase (UGT) Activities: Altered Alamethicin Concentration and Utility to Screen for UGT Inhibitors

Walsky

Bauman²,

Bourcier³

et al. 2012

Drug Metab Dispos

133

146

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“…3,21,31) The kinetics of E-3OH glucuronidation by human liver microsomes and recombinant UGT1A1s (hUGT1A1 and mpUGT1A1) fitted the Hill equation, indicating substrate activation, and agreed with the previous report of Fisher et al 32) and our previous report 25) ; however, the kinetics of MPlM appeared to follow a typical MichaelisMenten model. Fisher et al 32) have also suggested that E-3OH glucuronidation by human liver microsomes exhibited atypical kinetics.…”

Section: Discussionsupporting

confidence: 78%

cDNA Cloning and Functional Analysis of Minipig Uridine Diphosphate-Glucuronosyltransferase 1A1

Miyake

Mayumi

Jinno

et al. 2013

Biological & Pharmaceutical Bulletin

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Uridine diphosphate (UDP)-glucuronosyltransferase 1A1 (UGT1A1) plays important roles in the glucuronidation of various drugs and endogenous substances. Minipigs have been used as experimental animals in pharmacological and toxicological studies, because many of their physiological characteristics are similar to those of humans. In this study, the similarities and differences in enzymatic properties of UGT1A1 between humans and minipigs were precisely identified. Minipig UGT1A1 (mpUGT1A1) cDNA was firstly cloned by the rapid amplification of cDNA ends (RACE) method, and the corresponding protein as well as human UGT1A1 (hUGT1A1) enzyme was expressed in insect cells. Then the kinetics of estradiol at 3-hydroxy position (E-3OH) and 7-ethyl-10-hydroxycamptothecin (SN-38) glucuronidation by recombinant UGT1A1s as well as human and minipig liver microsomes were analyzed. The homology between mpUGT1A1 and hUGT1A1 at the amino acid level was 80.9%. E-3OH and SN-38 glucuronidation by recombinant hUGT1A1 and mpUGT1A1 showed allosteric sigmoidal kinetics. The CL max value (29.1 µL/min/mg protein) for E-3OH glucuronidation of mpUGT1A1 was significantly higher (1.4-fold) than that of hUGT1A1, whereas the CL max value (0.83 µL/min/mg protein) for SN-38 glucuronidation was significantly lower (27%) than that of hUGT1A1; however, the kinetic models and parameter levels for E-3OH and SN-38 glucuronidation by human and minipig liver microsomes did not parallel those in the respective species. These findings suggest that the enzymatic properties of UGT1A1 are considerably different between humans and minipigs. The information on species differences in UGT1A1 function gained in this study should help with in vivo extrapolation of xenobiotic metabolism and toxicity.Key words uridine diphosphate-glucuronosyltransferase (UGT); UGT1A1; minipig; estradiol at 3-hydroxy position; 7-ethyl-10-hydroxycamptothecin Glucuronidation is important for the detoxification and elimination of various lipophilic endogenous substances (e.g. bile acids, bilirubin and steroids) and xenobiotics (e.g. drugs, environmental chemicals and dietary constituents) in mammals.1) This reaction is catalyzed by a multigenic family of uridine diphosphate (UDP)-glucuronosyltransferases (UGTs) that are localized in the endoplasmic reticulum membrane. 2-4)The human UGT superfamily comprises two families (UGT1 and UGT2) and three subfamilies (UGT1A, UGT2A, and UGT2B).2) The UGT1A gene is localized on chromosome 2q37 and codes proteins with unique N-terminal domains and identical C-terminal domains, which are formed from the alternate mRNA splicing of unique first exons with common exons 2-5. In contrast, UGT2A and UGT2B genes are clustered on chromosome 4q13 and individual UGT proteins are coded by unique genes with six exons. 5,6) In addition, each UGT has been demonstrated to exhibit unique substrate and tissue specificities. 3,4,7) UGT1A1 is expressed in the liver, small intestine and colon, and is exclusively involved in the metabolism of bilirubin. 4,8,9) UGT1A1 has b...

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“…38 Estrogen could influence the production of bilirubin by inhibiting the uridine 5'-diphospho-glucuronosyltransferase 1A1-catalyzed bilirubin glucuronidation. 39,40 In addition, a recent study confirmed that there was an association between the uridine 5'-diphospho-glucuronosyltransferase 1A1 and TC and LDL-C levels in women with different hormonal status. 41 Similarly, a negative correlation between TB and blood pressure was only found in women.…”

Section: Discussionmentioning

confidence: 74%

Decreased Serum Bilirubin Is Associated With Silent Cerebral Infarction

Cao

Zhang

et al. 2014

ATVB

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946S ilent cerebral infarction (SCI) is a cerebral infarction that is evident on brain imaging but is not associated with a clinical symptom. In most cases, SCI is found as a lacunar infarction, that is, a small, deep cerebral infarct caused by occlusion of small penetrating cerebral arteries. Recent studies demonstrated that the presence of SCI predicts transient ischemia attack, clinically overt stroke, cardiovascular disease, and dementia. 1-3 See accompanying editorial on page 702A large body of evidence has highlighted a role for oxidative stress in atherosclerosis. Oxidative stress is induced by increased production of reactive oxygen species or decreased antioxidant capacity of endogenous antioxidant systems. Bilirubin is an effective antioxidant molecule that suppresses the oxidation of lipids and prevents the formation of plaque. 4 In several cross-sectional studies, bilirubin levels were found to be decreased in carotid intima-media thickness, cardiovascular disease, stroke, and peripheral arterial disease.5-8 A meta-analysis further confirmed that bilirubin levels were reduced in coronary artery disease. 9 To the best of our knowledge, the relationship between bilirubin levels and SCI has not yet been reported. We, therefore, conducted this study to assess the bilirubin levels in general population. Materials and MethodsMaterials and Methods are available in the online-only Supplement. ResultsClinical and laboratory data of participants with and without SCI are shown in Table 1. Of the 2865 participants enrolled, 1831 (63.91%) were men and 1034 (36.09%) were women. Median (interquartile range) of total bilirubin (TB) concentration was 10.5 (7.8-13.8; range, 2.1-33.4) μmol/L in the whole cohort of individuals. Three hundred forty-three participants (11.97%; 274 men and 69 women) presented SCI. The patients with SCI were older and had higher body mass index (BMI), systolic blood pressure, diastolic blood pressure (DBP), total cholesterol (TC), triglyceride, low-density lipoprotein cholesterol (LDL-C), fasting plasma glucose (FPG), and brachial-ankle pulse wave velocity (baPWV) levels and reduced TB, indirect bilirubin, direct bilirubin, estimated glomerular filtration rate (eGFR), and high-density lipoprotein cholesterol levels compared with the subjects without SCI. However, the levels of aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transpeptidase, and current use of statins and calcium channel blocker drugs in the 2 groups had no difference. Male sex, smoking, alcohol consumption, type 2 diabetes mellitus (DM), hypertension, and current use of angiotensin-converting enzyme inhibitor/angiotensin II receptor antagonist, aspirin, and hypoglycemic drugs had a higher prevalence in SCI group.The demographic and biochemical characteristics of the study population according to TB quartiles are shown in Table 2 FPG, triglyceride, LDL-C, FPG, aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transpeptidase, and baPWV decreased gradually as TB increased. Also, the percentage ...

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Correlation between Bilirubin Glucuronidation and Estradiol-3-Gluronidation in the Presence of Model UDP-Glucuronosyltransferase 1A1 Substrates/Inhibitors

Cited by 60 publications

References 32 publications

Optimized Assays for Human UDP-Glucuronosyltransferase (UGT) Activities: Altered Alamethicin Concentration and Utility to Screen for UGT Inhibitors

Optimized Assays for Human UDP-Glucuronosyltransferase (UGT) Activities: Altered Alamethicin Concentration and Utility to Screen for UGT Inhibitors

cDNA Cloning and Functional Analysis of Minipig Uridine Diphosphate-Glucuronosyltransferase 1A1

Decreased Serum Bilirubin Is Associated With Silent Cerebral Infarction

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