UGT1A3

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 158924361 Experts worldwide ranked by ideXlab platform

Nobumitsu Hanioka - One of the best experts on this subject based on the ideXlab platform.

  • Glucuronidation of mono(2-ethylhexyl) phthalate in humans: roles of hepatic and intestinal UDP-glucuronosyltransferases.
    Archives of Toxicology, 2016
    Co-Authors: Nobumitsu Hanioka, Yu Kinashi, Toshiko Tanaka-kagawa, Takashi Isobe, Hideto Jinno
    Abstract:

    Mono(2-ethylhexyl) phthalate (MEHP) is an active metabolite of di(2-ethylhexyl) phthalate (DEHP), which is an endocrine-disrupting chemical. In the present study, MEHP glucuronidation in humans was studied using recombinant UDP-glucuronosyltransferases (UGTs) and microsomes of the liver and intestine. Among the recombinant UGTs examined, UGT1A3, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B4, and UGT2B7 glucuronidated MEHP. The kinetics of MEHP glucuronidation by UGT1A3, UGT1A7, UGT1A8, UGT1A10, UGT2B4, and UGT2B7 followed the Michaelis–Menten model, whereas that by UGT1A9 fit the negative allosteric model. CLint values were in the order of UGT1A9 > UGT2B7 > UGT1A7 > UGT1A8 ≥ UGT1A10 > UGT1A3 > UGT2B4. The kinetics of MEHP glucuronidation by liver microsomes followed the Michaelis–Menten model. Diclofenac (20 µM) and raloxifene (20 µM) decreased CLint values to 43 and 36 % that of native microsomes, respectively. The kinetics of MEHP glucuronidation by intestine microsomes fit the biphasic model. Diclofenac (150 and 450 µM) decreased CLint values to 32 and 13 % that of native microsomes for the high-affinity phase, and to 28 and 21 % for the low-affinity phase, respectively. Raloxifene (2.5 and 7.0 µM) decreased CLint values to 35 and 4.1 % that of native microsomes for the high-affinity phase, and to 48 and 53 % for the low-affinity phase, respectively. These results suggest that MEHP glucuronidation in humans is catalyzed by UGT1A3, UGT1A9, UGT2B4, and/or UGT2B7 in the liver, and by UGT1A7, UGT1A8, UGT1A9, UGT1A10, and/or UGT2B7 in the intestine, and also that these UGT isoforms play important and characteristic roles in the detoxification of DEHP.

  • raloxifene glucuronidation in liver and intestinal microsomes of humans and monkeys contribution of ugt1a1 ugt1a8 and ugt1a9
    Xenobiotica, 2016
    Co-Authors: Naoki Kishi, Akane Takasuka, Yuki Kokawa, Maho Taguchi, Masato Shigeyama, Manabu Suno, Takashi Isobe, Mikio Murata, Nobumitsu Hanioka
    Abstract:

    Abstract1. Raloxifene is an antiestrogen that has been marketed for the treatment of osteoporosis, and is metabolized into 6- and 4′-glucuronides by UDP-glucuronosyltransferase (UGT) enzymes. In this study, the in vitro glucuronidation of raloxifene in humans and monkeys was examined using liver and intestinal microsomes and recombinant UGT enzymes (UGT1A1, UGT1A8 and UGT1A9).2. Although the Km and CLint values for the 6-glucuronidation of liver and intestinal microsomes were similar between humans and monkeys, and species differences in Vmax values (liver microsomes, humans > monkeys; intestinal microsomes, humans   UGT1A8 >UGT1A9 for humans, and UGT1A8 > UGT1A1 > UGT1A9 for monkeys. The activities of 4′-glucuronidation were UGT1...

  • Effect of aflatoxin B1 on UDP-glucuronosyltransferase mRNA expression in HepG2 cells.
    Chemosphere, 2012
    Co-Authors: Nobumitsu Hanioka, Yuko Nonaka, Keinosuke Okamoto, Hiroyuki Kataoka, Tomoe Negishi, Keita Saito, Shizuo Narimatsu
    Abstract:

    Aflatoxin B1 (AFB1) is a potent mycotoxin that induces hepatocellular carcinoma in many animal species, including humans. In this study, we examined the effects of AFB1 on UDP-glucuronosyltransferase (UGT) mRNA expression in HepG2 cells (human hepatocellular carcinoma cell line). The cells were treated with AFB1 for 48 h at a concentration of 10 μM, and their viability (87%) was not significantly different from that of control cells. Reverse transcription polymerase chain reaction (RT-PCR) analysis demonstrated that the mRNAs of four UGT1As (UGT1A1, UGT1A3, UGT1A4 and UGT1A9) and seven UGT2Bs (UGT2B4, UGT2B7, UGT2B10, UGT2B11, UGT2B15, UGT2B17 and UGT2B28) are expressed in HepG2 cells. The mRNAs of aryl hydrocarbon receptor (AhR), pregnane X receptor (PXR), retinoid X receptor (RXR) and glucocorticoid receptor (GR) as transcriptional regulators were also detected. AFB1 significantly increased mRNA levels of UGT1A3, UGT2B10, UGT2B15 and UGT2B17 in HepG2 cells to 2.5-, 2.0-, 1.9- and 1.5-fold, respectively, whereas the mRNA levels of transcriptional regulators were hardly affected by AFB1. These findings suggest that AFB1 induces UGT2B isoforms rather than UGT1A isoforms in HepG2 cells, and that the change may closely contribute to the toxicity of AFB1.

  • Human UDP-glucuronosyltransferase isoforms involved in bisphenol A glucuronidation.
    Chemosphere, 2008
    Co-Authors: Nobumitsu Hanioka, Takanori Naito, Shizuo Narimatsu
    Abstract:

    Bisphenol A (BPA) is one of a number of potential endocrine disruptors which may affect normal hormonal function. In this study, human UDP-glucuronosyltransferase (UGT) isoforms involved in BPA glucuronidation were studied by kinetic analyses using human liver microsomes and recombinant human UGTs expressed in insect cells (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B4, UGT2B7, UGT2B15 and UGT2B17). BPA glucuronidation was catalyzed by UGT1A1, UGT1A3, UGT1A9, UGT2B4, UGT2B7 and UGT2B15 as well as by human liver microsomes. Among these UGTs, UGT2B15 showed the highest activity of BPA glucuronidation at low- (1.0 μM) and high- (20 μM) substrate concentrations. Kinetic analyses of BPA glucuronidation were performed by constructing Michaelis–Menten and Eadie–Hofstee plots. The kinetic profile of BPA glucuronidation by pooled human liver microsomes and UGT2B15 was monophasic, the Km and Vmax values were 6.39 μM and 4250 pmol min−1 mg−1 protein for pooled human liver microsomes, and 8.68 μM and 873 pmol min−1 mg−1 protein for UGT2B15, respectively. The Km values for BPA glucuronidation by pooled human liver microsomes and UGT2B15 were similar. These findings demonstrate that BPA is mainly glucuronidated by UGT2B15 in human liver microsomes, and suggest that this UGT isoform plays important roles in the detoxification and elimination of BPA.

  • Human liver UDP-glucuronosyltransferase isoforms involved in the glucuronidation of 7-ethyl-10-hydroxycamptothecin
    Xenobiotica; the fate of foreign compounds in biological systems, 2001
    Co-Authors: Nobumitsu Hanioka, Hideto Jinno, Shogo Ozawa, M. Ando, Yoshiro Saito, Jun-ichi Sawada
    Abstract:

    1. The human liver UDP-glucuronosyltransferase (UGT) isoforms involved in the glucuronidation of 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan (CPT-11), have been studied using microsomes from human liver and insect cells expressing human UGTs (1A1, 1A3, 1A4, 1A6, 1A9, 2B7, 2B15). 2. The glucuronidation of SN-38 was catalysed by UGT1A1, UGT1A3, UGT1A6 and UGT1A9 as well as by liver microsomes. Among these UGT isoforms, UGT1A1 showed the highest activity of SN-38 glucuronidation at both low (1 µM) and high (200 µM) substrate concentrations. The ranking in order of activity at low and high substrate concentrations was UGT1A1 > UGT1A9 > UGT1A6> UGT1A3 and UGT1A1 > UGT1A3 > UGT1A6 ≥ UGT1A9, respectively. 3. The enzyme kinetics of SN-38 glucuronidation were examined by means of Lineweaver-Burk analysis. The activity of the glucuronidation in liver microsomes exhibits a monophasic kinetic pattern, with an apparent K m and V max of 35.9 µM and 134pmol min -1 mg -1 protein, respectiv...

Yoshihiro Takeuchi - One of the best experts on this subject based on the ideXlab platform.

  • effect of d256n and y483d on propofol glucuronidation by human uridine 5 diphosphate glucuronosyltransferase ugt1a9
    Basic & Clinical Pharmacology & Toxicology, 2008
    Co-Authors: Hiroko Takahashi, Yoshihiro Maruo, Asami Mori, Masaru Iwai, Hiroshi Sato, Yoshihiro Takeuchi
    Abstract:

    Uridine 5 ' -diphosphate glucuronosyltransferases (UGTs) are part of a major elimination pathway for endobiotics and xenobiotics. UGT1A9 is a UGT that catalyses the conjugation of endogenous oestrogenic and thyroid hormones, aceta- minophen, SN-38 (an active metabolite of irinotecan) and phenols. UGT1A9 is the only isoform that catalyses the glucuronidation of propofol (2,6-diisopropylphenol) in the liver. In the present study, we analysed polymorphisms of UGT1A9 in 100 healthy adult Japanese volunteers. A transversion of 766G > A resulting in the amino acid substitution of D256N was detected in exon 1. The allele frequency of D256N is 0.005. We investigated the effects of D256N and Y483D, which is located on the common exon of UGT1 , on propofol glucuronidation by an in vitro expression study. The K m of wild-type, D256N and Y483D for propofol glucuronidation were 111.2, 43.6 and 64.5 µ M, respectively. The V max of D256N and Y483D were 8.1% and 28.8%, and the efficiencies ( V max / K m ) were 19.1% and 57.1% of the wild-type, respectively. For mycophenolic acid, 1-naphthol and naringenin, the D256N variant lowered glucuronidation activity considerably, compared to Y483D. The V max value of D256N variant for mycophenolic acid was only 9.5% of the wild-type. This study shows the importance of D256N in differences between individuals concerning adverse effects of drugs that are catalysed primarily by UGT1A9. Carriers of D256N may be at risk of suffering adverse effects of propofol and other substrates that are primarily metabolized by UGT1A9. Uridine 5 ' -diphosphate glucuronosyltransferases (UGTs) are phase II drug metabolizing enzymes that catalyse the glucuro- nidation of a wide variety of endogenous and exogeneous compounds, including hormones, drugs, carcinogens and other natural substances. The UGT family is divided into two sub- families, UGT1 and UGT2 (1). UGT1 is located on chromosome 2 and has a unique gene structure (2). UGT1 has 13 different exons 1 from UGT1A1 to UGT1A13P , whereas exons 2-5 are common to all mRNAs expressed by the gene. The UGT1 family contains four pseudo-exons 1: 1A2P, 1A11P, 1A12P and 1A13P. UGT1 mRNAs are processed by differential splicing (3). UGT1A9 conjugates many endogenous and exogenous substrates, including oestrogens and thyroid hormones, acetaminophen, SN-38 (an active metabolite of irinotecan) and phenols (4-8). The cDNA of UGT1A9 was first cloned by Wooster et al . (9). This gene is expressed in the liver, kidney, small intestine, colon and reproductive organs such as the testis and ovary (3,4,10). UGT1A9 activity in the liver is greater than in extrahepatic organs (11). We have previously reported polymorphisms of UGT1A1, UGT1A3 and UGT1A4 in the Japanese population; the analyses have found considerable differences in the polymorphic muta- tions of each UGT isoform between ethnic groups (12-14). Propofol (2,6-diisopropylphenol) is widely used as an intravenous anaesthetic agent. Direct glucuronidation of propofol is its major route of elimination (15). Although UGT1A7, UGT1A8 and UGT1A10 conjugate propofol in

  • Effect of D256N and Y483D on Propofol Glucuronidation by Human Uridine 5′-diphosphate Glucuronosyltransferase (UGT1A9)
    Basic & Clinical Pharmacology & Toxicology, 2008
    Co-Authors: Hiroko Takahashi, Yoshihiro Maruo, Asami Mori, Masaru Iwai, Hiroshi Sato, Yoshihiro Takeuchi
    Abstract:

    Uridine 5 ' -diphosphate glucuronosyltransferases (UGTs) are part of a major elimination pathway for endobiotics and xenobiotics. UGT1A9 is a UGT that catalyses the conjugation of endogenous oestrogenic and thyroid hormones, aceta- minophen, SN-38 (an active metabolite of irinotecan) and phenols. UGT1A9 is the only isoform that catalyses the glucuronidation of propofol (2,6-diisopropylphenol) in the liver. In the present study, we analysed polymorphisms of UGT1A9 in 100 healthy adult Japanese volunteers. A transversion of 766G > A resulting in the amino acid substitution of D256N was detected in exon 1. The allele frequency of D256N is 0.005. We investigated the effects of D256N and Y483D, which is located on the common exon of UGT1 , on propofol glucuronidation by an in vitro expression study. The K m of wild-type, D256N and Y483D for propofol glucuronidation were 111.2, 43.6 and 64.5 µ M, respectively. The V max of D256N and Y483D were 8.1% and 28.8%, and the efficiencies ( V max / K m ) were 19.1% and 57.1% of the wild-type, respectively. For mycophenolic acid, 1-naphthol and naringenin, the D256N variant lowered glucuronidation activity considerably, compared to Y483D. The V max value of D256N variant for mycophenolic acid was only 9.5% of the wild-type. This study shows the importance of D256N in differences between individuals concerning adverse effects of drugs that are catalysed primarily by UGT1A9. Carriers of D256N may be at risk of suffering adverse effects of propofol and other substrates that are primarily metabolized by UGT1A9. Uridine 5 ' -diphosphate glucuronosyltransferases (UGTs) are phase II drug metabolizing enzymes that catalyse the glucuro- nidation of a wide variety of endogenous and exogeneous compounds, including hormones, drugs, carcinogens and other natural substances. The UGT family is divided into two sub- families, UGT1 and UGT2 (1). UGT1 is located on chromosome 2 and has a unique gene structure (2). UGT1 has 13 different exons 1 from UGT1A1 to UGT1A13P , whereas exons 2-5 are common to all mRNAs expressed by the gene. The UGT1 family contains four pseudo-exons 1: 1A2P, 1A11P, 1A12P and 1A13P. UGT1 mRNAs are processed by differential splicing (3). UGT1A9 conjugates many endogenous and exogenous substrates, including oestrogens and thyroid hormones, acetaminophen, SN-38 (an active metabolite of irinotecan) and phenols (4-8). The cDNA of UGT1A9 was first cloned by Wooster et al . (9). This gene is expressed in the liver, kidney, small intestine, colon and reproductive organs such as the testis and ovary (3,4,10). UGT1A9 activity in the liver is greater than in extrahepatic organs (11). We have previously reported polymorphisms of UGT1A1, UGT1A3 and UGT1A4 in the Japanese population; the analyses have found considerable differences in the polymorphic muta- tions of each UGT isoform between ethnic groups (12-14). Propofol (2,6-diisopropylphenol) is widely used as an intravenous anaesthetic agent. Direct glucuronidation of propofol is its major route of elimination (15). Although UGT1A7, UGT1A8 and UGT1A10 conjugate propofol in

Tsuyoshi Yokoi - One of the best experts on this subject based on the ideXlab platform.

  • preparation of a specific monoclonal antibody against human udp glucuronosyltransferase ugt 1a9 and evaluation of ugt1a9 protein levels in human tissues
    Drug Metabolism and Disposition, 2012
    Co-Authors: Miki Nakajima, Masahiko Hatakeyama, Tatsuki Fukami, Tsuyoshi Yokoi
    Abstract:

    Glucuronidation is a major detoxification pathway of drugs and xenobiotics that are catalyzed by the UDP-glucuronosyltransferase (UGT) superfamily. Determination of the protein levels of the individual UGT isoforms in human tissues is required for the successful extrapolation of in vitro metabolic data to in vivo clearance. Most previous studies evaluating UGT isoform expression were limited to the mRNA level because of the high degree of amino acid sequence homology between UGT isoforms that has hampered the availability of isoform-specific antibodies. In this study, we generated a peptide-specific monoclonal antibody against human UGT1A9. We demonstrated that this antibody does not cross-react with the other UGT1A isoforms including UGT1A7, UGT1A8, and UGT1A10 and shows a high degree of amino acid sequence similarity with UGT1A9. Using this antibody, we found that UGT1A9 protein is expressed in the kidney and the liver but not in the jejunum or the ileum, consistent with previous reports of mRNA expression. In a panel of 20 individual human livers, the UGT1A9 protein levels exhibited 9-fold variability. It is noteworthy that the relative UGT1A9 protein levels were not correlated with the UGT1A9 mRNA level ( r = −0.13), like other UGT isoforms reported previously, suggesting the importance of evaluating UGT isoform expression at protein levels. In conclusion, we generated a specific monoclonal antibody against UGT1A9 and evaluated the distribution and relative expression levels of the UGT1A9 protein in human tissues. This antibody may serve as a useful tool for further studies of UGT1A9 to evaluate its physiological, pharmacological, and toxicological roles in human tissues.

  • Quantitative analysis of UDP-glucuronosyltransferase (UGT) 1A and UGT2B expression levels in human livers.
    Drug Metabolism and Disposition, 2009
    Co-Authors: Takeshi Izukawa, Masataka Takamiya, Tatsuki Fukami, Miki Nakajima, Toshiyuki Sakaki, Shin Ichi Ikushiro, Hiroyuki Yamanaka, Ryoichi Fujiwara, Yasuhiro Aoki, Tsuyoshi Yokoi
    Abstract:

    UDP-glucuronosyltransferases (UGTs) catalyze glucuronidation of a variety of xenobiotics and endobiotics. UGTs are divided into two families, UGT1 and UGT2. The purpose of this study was to estimate the absolute expression levels of each UGT isoform in human liver and to evaluate the interindividual variability. Real-time reverse transcriptase-polymerase chain reaction analysis was performed to determine the copy numbers of nine functional UGT1A isoforms and seven UGT2B isoforms. We noticed that not only primers but also templates as a standard for quantification should prudently be selected. Once we established appropriate conditions, the mRNA levels of each UGT isoform in 25 individual human livers were determined. UGT1A1 (0.9–138.5), UGT1A3 (0.1–66.6), UGT1A4 (0.1–143.3), UGT1A6 (1.0–70.4), UGT1A9 (0.3–132.4), UGT2B4 (0.3–615.0), UGT2B7 (0.2–97.4), UGT2B10 (0.7–253.2), UGT2B15 (0.3–107.8), and UGT2B17 (0.5–157.1) were substantially expressed (×104 copy/μg RNA) with large interindividual variability. Abundant isoforms were UGT2B4 and UGT2B10, followed by UGT1A1, UGT2B15, and UGT1A6. The sum of the UGT2B mRNA levels was higher than that of UGT1A mRNA levels. It is interesting to note that the mRNA levels normalized with glyceraldehyde-3-phosphate dehydrogenase mRNA for almost UGT isoforms that are substantially expressed in liver showed significant correlations to each other. Western blot analysis was performed using antibodies specific for UGT1A1, UGT1A4, UGT1A6, or UGT2B7. Correlation between the protein and mRNA levels was observed in only UGT1A1 ( r = 0.488; p < 0.01). In conclusion, this study comprehensively determined the absolute values of mRNA expression of each UGT isoform in human livers and found considerable interindividual variability.

  • stereoselective glucuronidation of 5 4 hydroxyphenyl 5 phenylhydantoin by human udp glucuronosyltransferase ugt 1a1 ugt1a9 and ugt2b15 effects of ugt ugt interactions
    Drug Metabolism and Disposition, 2007
    Co-Authors: Miki Nakajima, Miki Katoh, H Yamanaka, Ryoichi Fujiwara, Tsuyoshi Yokoi
    Abstract:

    5-(4′-Hydroxyphenyl)-5-phenylhydantoin (4′-HPPH), a major metabolite of phenytoin in human, is exclusively metabolized to a glucuronide. 4′-HPPH has a chiral center. ( S )-4′-HPPH is a predominant form produced from phenytoin in humans, and ( R )-4′-HPPH is an extremely toxic form with respect to gingival hyperplasia. In the present study, we investigated stereoselective 4′-HPPH O -glucuronide formation in human liver microsomes. Human liver microsomes predominantly formed ( S )-4′-HPPH O -glucuronide rather than ( R )-4′-HPPH O -glucuronide from racemic 4′-HPPH. Among human UDP-glucuronosyltransferase (UGT) enzymes, UGT1A1, UGT1A9, and UGT2B15 showed 4′-HPPH O -glucuronide formation. Interestingly, UGT1A1 stereoselectively formed ( R )-4′-HPPH O -glucuronide, whereas UGT1A9 and UGT2B15 stereoselectively formed ( S )-4′-HPPH O -glucuronide from racemic 4′-HPPH. By using UGT1A double-expression systems in HEK293 cells that we previously established, the effects of UGT-UGT interactions on 4′-HPPH O -glucuronide formation were investigated. It was demonstrated that coexpression of UGT1A4 increased the V max values of ( S )- and ( R )-4′-HPPH O -glucuronide formation catalyzed by UGT1A1 but decreased the V max values of ( S )- and ( R )-4′-HPPH O -glucuronide formation catalyzed by UGT1A9. Coexpression of UGT1A6 increased the S 50 values and decreased the V max values of ( S )- and ( R )-4′-HPPH glucuronide formation catalyzed by UGT1A1 and UGT1A9. However, the interaction did not alter the stereoselectivity. In conclusion, we found that 4′-HPPH O -glucuronide formation in human liver microsomes is catalyzed by UGT1A1, UGT1A9, and UGT2B15 in a stereoselective manner, being modulated by interaction with other UGT1A isoforms.

  • Stereoselective Glucuronidation of 5-(4′-Hydroxyphenyl)-5-phenylhydantoin by Human UDP-Glucuronosyltransferase (UGT) 1A1, UGT1A9, and UGT2B15: Effects of UGT-UGT Interactions
    Drug Metabolism and Disposition, 2007
    Co-Authors: Miki Nakajima, Miki Katoh, H Yamanaka, Ryoichi Fujiwara, Tsuyoshi Yokoi
    Abstract:

    5-(4′-Hydroxyphenyl)-5-phenylhydantoin (4′-HPPH), a major metabolite of phenytoin in human, is exclusively metabolized to a glucuronide. 4′-HPPH has a chiral center. ( S )-4′-HPPH is a predominant form produced from phenytoin in humans, and ( R )-4′-HPPH is an extremely toxic form with respect to gingival hyperplasia. In the present study, we investigated stereoselective 4′-HPPH O -glucuronide formation in human liver microsomes. Human liver microsomes predominantly formed ( S )-4′-HPPH O -glucuronide rather than ( R )-4′-HPPH O -glucuronide from racemic 4′-HPPH. Among human UDP-glucuronosyltransferase (UGT) enzymes, UGT1A1, UGT1A9, and UGT2B15 showed 4′-HPPH O -glucuronide formation. Interestingly, UGT1A1 stereoselectively formed ( R )-4′-HPPH O -glucuronide, whereas UGT1A9 and UGT2B15 stereoselectively formed ( S )-4′-HPPH O -glucuronide from racemic 4′-HPPH. By using UGT1A double-expression systems in HEK293 cells that we previously established, the effects of UGT-UGT interactions on 4′-HPPH O -glucuronide formation were investigated. It was demonstrated that coexpression of UGT1A4 increased the V max values of ( S )- and ( R )-4′-HPPH O -glucuronide formation catalyzed by UGT1A1 but decreased the V max values of ( S )- and ( R )-4′-HPPH O -glucuronide formation catalyzed by UGT1A9. Coexpression of UGT1A6 increased the S 50 values and decreased the V max values of ( S )- and ( R )-4′-HPPH glucuronide formation catalyzed by UGT1A1 and UGT1A9. However, the interaction did not alter the stereoselectivity. In conclusion, we found that 4′-HPPH O -glucuronide formation in human liver microsomes is catalyzed by UGT1A1, UGT1A9, and UGT2B15 in a stereoselective manner, being modulated by interaction with other UGT1A isoforms.

  • effects of coexpression of ugt1a9 on enzymatic activities of human ugt1a isoforms
    Drug Metabolism and Disposition, 2007
    Co-Authors: Ryoichi Fujiwara, Akiko Nakamura, Miki Katoh, H Yamanaka, Miki Nakajima, Toshiyuki Sakaki, Shin Ichi Ikushiro, Tsuyoshi Yokoi
    Abstract:

    We established stable HEK293 cell lines expressing double isoforms, UGT1A1 and UGT1A9, UGT1A4 and UGT1A9, or UGT1A6 and UGT1A9, as well as stable cell lines expressing each single isoform. To analyze the protein-protein interaction between the UGT1As, we investigated the thermal stability and resistance to detergent. UGT1A9 uniquely demonstrated thermal stability, which was enhanced in the presence of UDP-glucuronic acid (>90% of control), and resistance to detergent. Interestingly, UGT1A1, UGT1A4, and UGT1A6 acquired thermal stability and resistance to detergent by the coexpression of UGT1A9. An immunoprecipitation assay revealed that UGT1A6 and UGT1A9 interact in the double expression system. Using the single expression systems, it was confirmed that estradiol 3-O-glucuronide, imipramine N-glucuronide, serotonin O-glucuronide, and propofol O-glucuronide formations are specific for UGT1A1, UGT1A4, UGT1A6, and UGT1A9, respectively. By kinetic analyses, we found that the coexpressed UGT1A9 significantly affected the kinetics of estradiol 3-O-glucuronide formation (decreased Vmax), imipramine N-glucuronide formation (increased Km and Vmax), and serotonin O-glucuronide formation (decreased Vmax) catalyzed by UGT1A1, UGT1A4, and UGT1A6, respectively. On the other hand, the coexpressed UGT1A1 increased Km and decreased the Vmax of the propofol O-glucuronide formation catalyzed by UGT1A9. The coexpressed UGT1A4 and UGT1A6 also increased the Vmax of the propofol Oglucuronide formation by UGT1A9. This is the first study showing that human UGT1A isoforms interact with other isoforms to change the enzymatic characteristics.

Shizuo Narimatsu - One of the best experts on this subject based on the ideXlab platform.

  • Effect of aflatoxin B1 on UDP-glucuronosyltransferase mRNA expression in HepG2 cells.
    Chemosphere, 2012
    Co-Authors: Nobumitsu Hanioka, Yuko Nonaka, Keinosuke Okamoto, Hiroyuki Kataoka, Tomoe Negishi, Keita Saito, Shizuo Narimatsu
    Abstract:

    Aflatoxin B1 (AFB1) is a potent mycotoxin that induces hepatocellular carcinoma in many animal species, including humans. In this study, we examined the effects of AFB1 on UDP-glucuronosyltransferase (UGT) mRNA expression in HepG2 cells (human hepatocellular carcinoma cell line). The cells were treated with AFB1 for 48 h at a concentration of 10 μM, and their viability (87%) was not significantly different from that of control cells. Reverse transcription polymerase chain reaction (RT-PCR) analysis demonstrated that the mRNAs of four UGT1As (UGT1A1, UGT1A3, UGT1A4 and UGT1A9) and seven UGT2Bs (UGT2B4, UGT2B7, UGT2B10, UGT2B11, UGT2B15, UGT2B17 and UGT2B28) are expressed in HepG2 cells. The mRNAs of aryl hydrocarbon receptor (AhR), pregnane X receptor (PXR), retinoid X receptor (RXR) and glucocorticoid receptor (GR) as transcriptional regulators were also detected. AFB1 significantly increased mRNA levels of UGT1A3, UGT2B10, UGT2B15 and UGT2B17 in HepG2 cells to 2.5-, 2.0-, 1.9- and 1.5-fold, respectively, whereas the mRNA levels of transcriptional regulators were hardly affected by AFB1. These findings suggest that AFB1 induces UGT2B isoforms rather than UGT1A isoforms in HepG2 cells, and that the change may closely contribute to the toxicity of AFB1.

  • Human UDP-glucuronosyltransferase isoforms involved in bisphenol A glucuronidation.
    Chemosphere, 2008
    Co-Authors: Nobumitsu Hanioka, Takanori Naito, Shizuo Narimatsu
    Abstract:

    Bisphenol A (BPA) is one of a number of potential endocrine disruptors which may affect normal hormonal function. In this study, human UDP-glucuronosyltransferase (UGT) isoforms involved in BPA glucuronidation were studied by kinetic analyses using human liver microsomes and recombinant human UGTs expressed in insect cells (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B4, UGT2B7, UGT2B15 and UGT2B17). BPA glucuronidation was catalyzed by UGT1A1, UGT1A3, UGT1A9, UGT2B4, UGT2B7 and UGT2B15 as well as by human liver microsomes. Among these UGTs, UGT2B15 showed the highest activity of BPA glucuronidation at low- (1.0 μM) and high- (20 μM) substrate concentrations. Kinetic analyses of BPA glucuronidation were performed by constructing Michaelis–Menten and Eadie–Hofstee plots. The kinetic profile of BPA glucuronidation by pooled human liver microsomes and UGT2B15 was monophasic, the Km and Vmax values were 6.39 μM and 4250 pmol min−1 mg−1 protein for pooled human liver microsomes, and 8.68 μM and 873 pmol min−1 mg−1 protein for UGT2B15, respectively. The Km values for BPA glucuronidation by pooled human liver microsomes and UGT2B15 were similar. These findings demonstrate that BPA is mainly glucuronidated by UGT2B15 in human liver microsomes, and suggest that this UGT isoform plays important roles in the detoxification and elimination of BPA.

Moon Kyo In - One of the best experts on this subject based on the ideXlab platform.

  • Inhibition of cytochrome P450 and uridine 5′-diphospho-glucuronosyltransferases by MAM-2201 in human liver microsomes
    Archives of Pharmacal Research, 2017
    Co-Authors: Tae Yeon Kong, Soon-sang Kwon, Jae Chul Cheong, Moon Kyo In
    Abstract:

    MAM-2201, a synthetic cannabinoid, is a potent agonist of the cannabinoid receptors and is increasingly used as an illicit recreational drug. The inhibitory effects of MAM-2201 on major drug-metabolizing enzymes such as cytochrome P450s (CYPs) and uridine 5′-diphospho-glucuronosyltransferases (UGTs) have not yet been investigated although it is widely abused, sometimes in combination with other drugs. We evaluated the inhibitory effects of MAM-2201 on eight major human CYPs (CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4) and six UGTs (UGTs 1A1, 1A3, 1A4, 1A6, 1A9, and 2B7) of pooled human liver microsomes; we thus explored potential MAM-2201-induced drug interactions. MAM-2201 potently inhibited CYP2C9-catalyzed diclofenac 4′-hydroxylation, CYP3A4-catalyzed midazolam 1′-hydroxylation, and UGT1A3-catalyzed chenodeoxycholic acid 24-acyl-glucuronidation, with K _i values of 5.6, 5.4 and 5.0 µM, respectively. MAM-2201 exhibited mechanism-based inhibition of CYP2C8-catalyzed amodiaquine N -de-ethylation with K _i and k _inact values of 1.0 µM and 0.0738 min^−1, respectively. In human liver microsomes, MAM-2201 (50 µM) negligibly inhibited CYP1A2, CYP2A6, CYP2B6, CYP2C19, CYP2D6, UGT1A1, UGT1A4, UGT1A6, UGT1A9, and UGT2B7. Based on these in vitro results, we conclude that MAM-2201 has the potential to trigger in vivo pharmacokinetic drug interactions when co-administered with substrates of CYP2C8, CYP2C9, CYP3A4, and UGT1A3.

  • AM-2201 Inhibits Multiple Cytochrome P450 and Uridine 5′-Diphospho-Glucuronosyltransferase Enzyme Activities in Human Liver Microsomes
    Molecules, 2017
    Co-Authors: Soon-sang Kwon, Tae Yeon Kong, Jae Chul Cheong, Moon Kyo In
    Abstract:

    AM-2201 is a synthetic cannabinoid that acts as a potent agonist at cannabinoid receptors and its abuse has increased. However, there are no reports of the inhibitory effect of AM-2201 on human cytochrome P450 (CYP) or uridine 5′-diphospho-glucuronosyltransferase (UGT) enzymes. We evaluated the inhibitory effect of AM-2201 on the activities of eight major human CYPs (1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4) and six major human UGTs (1A1, 1A3, 1A4, 1A6, 1A9, and 2B7) enzymes in pooled human liver microsomes using liquid chromatography–tandem mass spectrometry to investigate drug interaction potentials of AM-2201. AM-2201 potently inhibited CYP2C9-catalyzed diclofenac 4′-hydroxylation, CYP3A4-catalyzed midazolam 1′-hydroxylation, UGT1A3-catalyzed chenodeoxycholic acid 24-acyl-glucuronidation, and UGT2B7-catalyzed naloxone 3-glucuronidation with IC50 values of 3.9, 4.0, 4.3, and 10.0 μM, respectively, and showed mechanism-based inhibition of CYP2C8-catalyzed amodiaquine N-deethylation with a Ki value of 2.1 μM. It negligibly inhibited CYP1A2, CYP2A6, CYP2B6, CYP2C19, CYP2D6, UGT1A1, UGT1A4, UGT1A6, and UGT1A9 activities at 50 μM in human liver microsomes. These in vitro results indicate that AM-2201 needs to be examined for potential pharmacokinetic drug interactions in vivo due to its potent inhibition of CYP2C8, CYP2C9, CYP3A4, UGT1A3, and UGT2B7 enzyme activities.