T Watabe

Toyama Medical and Pharmaceutical University, Тояма, Toyama, Japan

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Publications (129)407.83 Total impact

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    ABSTRACT: Thirty samples of Indonesian medicinal plants were analyzed for their capacity to inhibit in vitro metabolism by human cytochrome P450 3A4 (CYP3A4) and CYP2D6 with a radiometric assay. The MeOH-soluble fractions of 25 samples, prepared from water extracts, demonstrated inhibitory activity more than 50% on the metabolism mediated by CYP3A4, and 21 samples on the metabolism mediated by CYP2D6. Among the MeOH-soluble fractions, Piper nigrum leaf showed the highest inhibitory activity against CYP3A4 (91.7%), and Punica granatum against CYP2D6 (98.1%). The water extracts of which MeOH-soluble fraction showed inhibitory activity more than 70% were fractionated with EtOAc. From the EtOAc-soluble fractions, Curcuma heyneana (67.0%), Pi. cubeba (75.0%), Pi. nigrum fruit (84.0%), Pi. nigrum leaf (85.8%), and Zingiber aromaticum (75.3%) demonstrated inhibitory activity more than 50% on the metabolism mediated by CYP3A4, but only Pi. nigrum fruit (72.8%) and Pi. nigrum leaf (69.1%) showed strong inhibitory activity against CYP2D6. For samples that showed more than 70% inhibition, their IC(50) values were determined. The most potent inhibitory activity against CYP3A4 (IC(50) value of 25 microg/ml) was found for the extract of Pi. nigrum leaf, while that of Catharanthus roseus showed the most potent inhibitory effect against CYP2D6 (IC(50) value of 11 microg/ml). These results should indicate once more the possibility of potential medicinal plant-drug interactions.
    Phytomedicine 02/2006; 13(1-2):67-73. · 2.97 Impact Factor
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    ABSTRACT: Tamoxifen (TAM) is used as the standard endocrine therapy for breast cancer patients and as a chemopreventive agent for women at high risk for this disease. Unfortunately, treatment of TAM increases the incidence of endometrial cancer; this may be due to the genotoxic damage induced by TAM metabolites. Formation of TAM-DNA adducts in rat liver correlates with the development of hepatocarcinoma. TAM-DNA adducts are proposed to be formed through O-sulfonation and/or O-acetylation of alpha-hydroxylated TAM and its metabolites. However, the role of O-sulfonation and O-acetylation in the formation of TAM-DNA adducts has not been extensively investigated. Rat or human hydroxysteroid sulfotransferases (HST), acetyltransferases, and liver cytosol were incubated with calf thymus DNA, alpha-OHTAM, and either 3'-phosphoadenosine 5'-phosphosulfate (PAPS) or acetyl coenzyme A (acetyl-CoA) as a cofactor and analyzed for TAM-DNA adduct formation, using 32P postlableling/polyacrylamide gel electrophoresis analysis. TAM-DNA adduct was formed when PAPS, not acetyl-CoA, was used. No TAM-DNA adducts were produced using human N-acetyltransferase I and II. HST antibody inhibited approximately 90% of TAM-DNA adduct formation generated by the cytosol or HST, suggesting that HST is primarily involved in the formation of TAM-DNA adducts. The formation of TAM-DNA adducts with rat liver cytosol and HST was much higher than that of human liver cytosol and HST. Our results indicate that TAM-DNA adducts are formed via O-sulfonation, not O-acetylation, of alpha-hydroxylated TAM and its metabolites.
    Drug Metabolism and Disposition 12/2005; 33(11):1673-8. · 3.36 Impact Factor
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    ABSTRACT: The MeOH-soluble fraction of the water extract of Catharanthus roseus from Indonesia, having shown potent inhibitory activity on the metabolism mediated by CYP2D6, was subjected to activity-guided isolation to yield two triterpenes, ursolic acid (1) and oleanolic acid (2), and three alkaloids, vindoline (3), ajmalicine (4), and serpentine (5). The isolated compounds were tested for their inhibitory activity on the metabolism mediated by CYP3A4 or CYP2D6 using [N-methyl-14C]erythromycin or [O-methyl-14C]dextromethorphan as a substrate, respectively. Ajmalicine (4) and serpentine (5) showed very potent inhibitory activity against CYP2D6 with IC50 values of 0.0023 and 3.51 microM, respectively. All isolated compounds showed weak or no inhibition against CYP3A4. On time-, concentration-, and NADPH-dependent assay, serpentine (5) appear to be the mechanism-based inhibitor for CYP2D6 enzyme in which the inhibition was irreversible and driven by catalytic process. K(I) and k(inact) values for serpentine (5) were 0.148 microM and 0.090 min-1, respectively. On the other hand, ajmalicine (4) showed no time-dependent inhibition or reversible inhibition, and thus appear to be not mechanism-based inhibitor.
    Biological & Pharmaceutical Bulletin 07/2005; 28(6):1021-4. · 1.85 Impact Factor
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    ABSTRACT: Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme catalyzing the metabolic degradation of the anticancer drug 5-fluorouracil (5-FU). Population studies of DPD activity in peripheral blood mononuclear cells (PBMC) were reported in healthy volunteers and cancer patients. Although these studies were done in mainly Caucasian and African American populations, only a little information is available for a Japanese population. One hundred fifty healthy Japanese volunteers were screened for a population distribution of PBMC-DPD activity. Genetic analysis of a volunteer with very low DPD activity was carried out by reverse transcriptase-PCR and genomic sequencing. Bacterially expressed recombinant mutant DPD proteins were purified and characterized. Mean and median values of PBMC-DPD activity for 5-FU reduction in the study population were 0.173 and 0.166 nmol/min/mg protein, respectively. A 57-year-old female volunteer (proband in this study) had very low DPD activity (0.014 nmol/min/mg protein) with a very low level of expression of DPD protein. Two novel nucleotide substitutions, at nucleotide positions 1097 (1097G > C) and 2303 (2303C > A), resulting in amino acid substitutions at positions 366 (G366A) and 768 (T768K), respectively, were identified. The G366A mutation caused not only a marked decrease in the affinity of the enzyme to cofactor NADPH but also reduced Vmax for 5-FU-reducing activity to approximately 0.5. T768K mutant lost its activity much faster than did wild DPD. We found one healthy volunteer (0.7% of the population) with very low PBMC-DPD activity due to heterozygosity for a mutant allele of the DPYD gene in a population of 150 Japanese.
    Clinical Cancer Research 07/2005; 11(14):5104-11. · 7.84 Impact Factor
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    ABSTRACT: Five methylenedioxyphenyl lignans, (-)-clusin (1), (-)-dihydroclusin (2), (-)-yatein (3), (-)-hinokinin (4), and (-)-dihydrocubebin (5), were isolated from Piper cubeba as potent and selective inhibitors against cytochrome P450 3A4 (CYP3A4). In this study, we investigated the mechanism of inhibition of CYP3A4 by these lignans and the possibility of their mechanism-based inhibition. Using [N-methyl-14C]erythromycin as a substrate, all lignans appear to be showed mixed-type of inhibition with apparent Ki of 1.96-4.07 microM. Furthermore, all lignans (1-5) inhibited CYP3A4 in a time-, concentration-, and NADPH-dependent manners and thus appear to be the mechanism-based inhibitors of CYP3A4. The apparent inactivation parameter, K(I) for these compounds were in the range of 0.054-0.373 microM, whereas the k(inact) values were 0.225-0.320 min-1. Among them, (-)-clusin (1) and (-)-dihydroclusin (2) were found to be the most potent CYP3A4 inactivator with apparent K(I) and k(inact) values of 0.082, 0.054 microM and 0.253, 0.310 min-1, respectively. Spectral scanning of microsomes with these lignans yielded an absorbance at 455 nm, suggesting that all of them appear to inactivate the cytochrome P450 via the formation of a metabolite intermediate complex. This pattern is consistent with the metabolism of the methylenedioxyphenyl compounds. These results indicate that (-)-clusin (1), (-)-dihydroclusin (2), (-)-yatein (3), (-)-hinokinin (4), and (-)-dihydrocubebin (5) are effective mechanism-based inhibitors of CYP3A4.
    Life Sciences 05/2005; 76(20):2381-91. · 2.56 Impact Factor
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    ABSTRACT: Pretreatment of Hep G2 cells with beta-naphthoflavone (BNF 1-25microM) significantly increased cytosolic sulfation activities of 4-hydroxypropranolol (4-OH-PL) racemate. The profile was similar to those of sulfations towards dopamine and triiodothyronine in the same cytosolic fractions. Kinetic studies of 4-OH-PL sulfation in Hep G2 cytosolic fractions revealed that V(max) values increased but apparent K(m) values remained unchanged following the BNF pretreatment. Among five recombinant human SULT isoforms (SULT1A1, -1A3, -1B1, -1E1 and -2A1) examined, only SULT2A1 did not show 4-OH-PL sulfation activities under the conditions used. SULT1A3 and -1E1 exhibited an enantioselectivity of 4-OH-R-PL sulfation>4-OH-S-PL sulfation, which agreed with that of BNF-pretreated Hep G2 cells as well as of nontreated cells, whereas SULT1A1 and -1B1 showed a reversed enantioselectivity (R<S). In kinetic studies of 4-OH-PL sulfations by four kinds of human SULT isoforms, apparent K(m) values for SULT1A3 were the lowest, and the parameters were close to those of Hep G2 cytosolic fractions. Real time RT-PCR using TaqMan probes demonstrated that the mRNA levels of SULT1A3 increased following BNF pretreatment, which paralleled the results from Western blotting showing the elevated levels of SULT1A3 proteins. These results suggest that the induction of SULT1A3 is mainly responsible for the elevated 4-OH-PL sulfation activities following the pretreatment of Hep G2 cells with BNF.
    Biochemical Pharmacology 04/2005; 69(6):941-50. · 4.58 Impact Factor
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    ABSTRACT: Sixteen compounds isolated from Zingiber aromaticum and showing concentration-dependent inhibition with IC50 values less than 100 microM, were analyzed for their possibility of time-, concentration-, and NADPH-dependent inhibition of CYP3A4 and four were analyzed for CYP2D6. All seven kaempferol glycosides and two kaempferol derivatives (4, 5, 8-14) appear to be the mechanism-based inhibitors of CYP3A4 enzyme in which the inhibition is irreversible and driven by the catalytic process. The other compounds showed no NADPH-dependent inhibition or reversible inhibition, and thus do not appear to be mechanism-based inhibitors. K(I) values for compounds 4, 5, 8-14 were in the range of 2.21-27.01 microM, whereas the k(inact) values were 0.23-0.65 min(-1). Kaempferol-3-O-(2,3,4-tri-O-acetyl-alpha-L-rhamnopyranoside) (5) was found to be the most potent CYP3A4 inactivator with K(I) and k(inact) values of 2.21 microM and 0.45 min(-1), respectively.
    Biological & Pharmaceutical Bulletin 04/2005; 28(3):495-9. · 1.85 Impact Factor
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    ABSTRACT: Evodia fruit (Evodiae Fructus) is used as a herbal medicine prepared from the matured fruit of the Evodia rutaecarpa Bentham or Evodia officinalis Dode, of the Rutaceae plant family. An extract of Evodia fruit in the presence of NADPH was shown to inhibit human liver microsomal erythromycin N-demethylation activity, mediated by cytochrome P450 3A4 (CYP3A4), in a preincubation-time dependent manner. The present study was conducted to identify components of Evodia fruit extract having preincubation-time dependent inhibitory effects on CYP3A4 by analyzing human liver microsomal erythromycin N-demethylation activity. Rutaecarpine, a major component of Evodia fruit, and limonin caused the most dramatic decrease in residual CYP3A4 activity (IC50 before and after 20 min preincubation with: rutaecarpine, >100 microM and 1.4 microM; limonin, 23.5 microM and 1.8 microM, respectively). Furthermore, rutaecarpine and limonin were identified as mechanism-based inhibitors of CYP3A4 from the following observations: 1) The inhibitory effects of rutaecarpine and limonin on CYP3A4 activity were dependent on the preincubation time, 2) The inhibition required NADPH, 3) The inhibition was depressed in the presence of the competitive CYP3A4 inhibitor, ketoconazole, 4) Dialysis resulted in no recovery of CYP3A4 activity. The kinetic parameters for inactivation k(inact) and K(I) were: 0.387 min-1 and 107.7 microM for rutaecarpine, 0.266 min-1 and 23.2 microM for limonin, respectively. These results indicate that rutaecarpine and limonin are mechanism-based inhibitors of CYP3A4.
    Drug Metabolism and Pharmacokinetics 03/2005; 20(1):34-45. · 2.07 Impact Factor
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    ABSTRACT: The EtOAc-soluble fraction of the water extract of Piper cubeba, having shown potent inhibitory activity on the metabolism mediated by CYP3A4, was subjected to activity-guided isolation to yield two new lignans, (8R,8'R)-4-hydroxycubebinone (1) and (8R,8'R,9'S)-5-methoxyclusin (2), and two new sesquiterpenes, (5 alpha,8 alpha)-2-oxo-1(10),3,7(11)-guaiatrien-12,8-olide (3) and (1 alpha,2 beta,5 alpha,8 alpha 10 alpha)-1,10-epoxy-2-hydroxy-3,7(11)-guaiadien-12,8-olide (4), along with 16 known compounds (5-20). The structures of the isolated compounds were elucidated on the basis of spectroscopic and chemical analyses. The isolated compounds were tested for their inhibitory activity on the metabolism mediated by CYP3A4 or CYP2D6 using [N-methyl-(14)C]erythromycin or [O-methyl-(14)C]dextromethorphan as a substrate, respectively. The compounds (8R,8'R,9'S)-5-methoxyclusin (2), (-)-clusin (10), (-)-yatein (13), ethoxyclusin (15), and (-)-dihydroclusin (17), having one methylenedioxyphenyl moiety in their structures, showed very potent and selective inhibitory activity against CYP3A4 with IC(50) values (0.44-1.0 microM) identical to that of the positive control, ketoconazole (IC(50), 0.72 microM).
    Journal of Natural Products 02/2005; 68(1):64-8. · 3.29 Impact Factor
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    ABSTRACT: Schisandra fruit, a Schisandraceae family herb, is used as a component in Kampo medicines (developed from Chinese medicines, but established in Japan). It can act as a sedative and antitussive, improve hepatic function, and give a general tonic effect. An extract of Schisandra fruit has been shown with a potent inhibitory effect on human liver microsomal erythromycin N-demethylation activity mediated by cytochrome P450 3A4 (CYP3A4). The present study was conducted to identify Schisandra fruit components having inhibitory effects on CYP3A4 by surveying the effect on human liver microsomal erythromycin N-demethylation activity. Known components of Schisandra fruit, gomisins B, C, G, and N and gamma-shizandrin, showed inhibitory effects on N-demethylation activity. Among these components, gomisin C displayed the most potent and competitive inhibitory effect, with a Ki value of 0.049 microM. Furthermore, the inhibitory effect of gomisin C was stronger than that of ketoconazole (Ki = 0.070 microM), a known potent CYP3A4 inhibitor. Gomisin C, however, inhibited CYP1A2-, CYP2C9-, CYP2C19-, and CYP2D6-dependent activities only to a limited extent (IC50 values >10 microM). Moreover, gomisin C inactivated human liver microsomal erythromycin N-demethylation activity in a time- and concentration-dependent manner. The inactivation kinetic parameters k(inact) and K(I) were 0.092 min(-1) and 0.399 microM, respectively. The human liver microsomal erythromycin N-demethylation activity inactivated by gomisin C did not recover on dialysis of the microsomes. Spectral scanning of CYP3A4 with gomisin C yielded an absorbance at 455 nm, suggesting that gomisin C inactivated the cytochrome P450 via the formation of a metabolite intermediate complex. This pattern is consistent with the metabolism of the methylenedioxy substituent in gomisin C. These results indicate that gomisin C is a mechanism-based inhibitor that not only competitively inhibits but irreversibly inactivates CYP3A4.
    Drug Metabolism and Disposition 01/2005; 32(12):1351-8. · 3.36 Impact Factor
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    ABSTRACT: Three new sesquiterpenes, (2R,3S,5R)-2,3-epoxy-6,9-humuladien-5-ol-8-one (1), (2R,3R,5R)-2,3-epoxy-6,9-humuladien-5-ol-8-one (2), and (5R)-2,6,9-humulatrien-5-ol-8-one (3), and two new flavonol glycosides, kaempferol-3-O-(2,3-di-O-acetyl-alpha-l-rhamnopyranoside) (4) and kaempferol-3-O-(2,3,4-tri-O-acetyl-alpha-l-rhamnopyranoside) (5), were isolated from the EtOAc-soluble fraction of the water extract of Zingiber aromaticum, along with 13 known compounds (6-18). The structures of the isolated compounds were elucidated on the basis of spectroscopic and chemical analyses. The isolated compounds were tested for their inhibitory activity on the metabolism mediated by CYP3A4 or CYP2D6 using [N-methyl-(14)C]erythromycin or [O-methyl-(14)C]dextromethorphan as a substrate, respectively. Kaempferol-3-O-(2,3,4-tri-O-acetyl-alpha-l-rhamnopyranoside) (5) showed the most potent inhibitory activity (IC(50), 14.4 microM) on the metabolism mediated by CYP3A4, and kaempferol-3-O-methyl ether (14) inhibited CYP2D6 most potently (IC(50), 4.63 microM).
    Journal of Natural Products 08/2004; 67(7):1079-83. · 3.29 Impact Factor
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    ABSTRACT: Regioselective sulfation of the phytoestrogens daidzein (DZ, 7,4'-dihydroxyisoflavone) and genistein (GS, 5,7,4'-trihydroxyisoflavone) was investigated using human liver cytosol and purified recombinant human sulfotransferase (SULT) isoforms, SULT1A1, SULT1A3, SULT2A1, and SULT1E1. 7-Position-preferential sulfation of DZ and GS was observed in human hepatic cytosols from 3 male and 3 female subjects. Average ratios for 7- to 4'-sulfate formation were 4.5:1 from DZ and 8.4:1 from GS in these human liver cytosols. Apparent K(m) values for the 7- and 4'-sulfation of DZ and GS by these cytosols were similar and in a range from 0.46 to 0.66 microM. All recombinant human SULTs had activity for 7- and 4'-sulfation of these phytoestrogens except for 7-sulfating activity of SULT1A3. SULT1A1 and SULT1E1 exhibited much higher catalytic efficiency, k(cat)/K(m), for 7- and 4'-sulfation of these substrates than did the other two, SULT1A3 and SULT2A1. SULT1A1 showed K(m) values of 0.47 and 0.52 microM for the mono-sulfation of DZ and GS, respectively, which were very similar to those of human cytosol. The observed k(cat)/K(m) indicated that SULT1A1 catalyzed 7-sulfation of DZ and GS at rates 4.4- and 8.8-fold higher, respectively, than such 4'-sulfation. However, with SULT1E1, catalytic efficiency was very similar for the sulfation of both positions. These data strongly suggest that SULT1A1 plays a major role in monosulfation of the phytoestrogens and determines the regioselectivity of sulfation in human hepatic cytosol. A kinetic study for 7,4'-disulfate formation of DZ and GS from their 7- and 4'-monosulfates indicated that SULT1E1 most efficiently catalyzed both reactions among human SULTs.
    Drug Metabolism and Pharmacokinetics 07/2004; 19(3):216-26. · 2.07 Impact Factor
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    ABSTRACT: rights: 本文データは学協会の許諾に基づきCiNiiから複製したものである The inhibitory effects of 78 herbal extracts on cytochrome P450 3A4 (CYP3A4) and P450 2D6 (CYP2D6) activity were investigated using human liver microsomes. The incubation mixture contained a methanol soluble fraction prepared from the powder of each herbal water extract (equivalent to 1.65 mg of extract powder per mL). Thirty-one herbal extracts inhibited over 50% of human liver microsomal erythromycin N-demethylation, a marker reaction of CYP3A4 activity. Among the 31 herbal extracts, 8 of them (Angelica Dahurica Root, Cassia Bark, Clove, Incised Notopterygium Rhizome, Moutan Bark, Rhubarb, Sappan Wood, Schisandra Fruit) inhibited N-demethylation by over 90%. Among the herbal extracts examined, the strongest inhibition of CYP3A4 was noted with Sappan Wood, which had an IC_<50> value of 43 mg/mL. Rhubarb, Schisandra Fruit, Incised Notopterygium Rhizome, and Angelica Dahurica Root had IC_<50> values of 77, 127, 144, and 185 μg/mL, respectively. Further, 28 of the herbal extracts inhibited over 50% of human liver microsomal dextromethorphan O-demethylation, which is a marker of CYP2D6 activity. Among the 28 herbal extracts, 13 (Cassia Bark, Clove, Coptis Rhizome, Ephedra Herb, Gambir Plant, Incised Notopterygium Rhizome, Magnolia Bark, Moutan Bark, Phellodendron Bark, Rhubarb, Sappan Wood, Sinomenium Stem, Zanthoxylum Fruit) inhibited O-demethylation by over 90%. The strongest inhibition of CYP2D6 was noted with Phellodendron Bark, which had an IC_<50> value of 4 μg/mL. Coptis Rhizome, Sinomenium Stem, Sappan Wood, and Rhubarb showed IC_<50> values of 14, 40, 52, and 64 μg/mL, respectively. These results indicate that many herbal extracts have an inhibitory effect on CYP3A4 and CYP2D6. 78種の生薬エキスについて,ヒト薬物代謝酵素シトクロムP450 3A4(CYP3A4)およびP450 2D6(CYP2D6)に対する阻害作用を調べた。生薬エキス粉末からメタノール可溶性画分を調製し,添加量1.65mg/mLで反応を行った。CYP3A4の指標として用いたヒト肝ミクロソーム中のエリスロマイシンN-脱メチル化活性に対して50%以上の阻害を示した生薬は31種であり,その中の8種(白芷,桂皮,丁子,羌活,牡丹皮,大黄,蘇木,五味子)が阻害率90%以上を示した。CYP3A4活性に対する阻害の強さは,蘇木,大黄,五味子,羌活,白芷の順であり,IC_<50>値は,それぞれ43,77,127,144および185μg/mLであった。一方,CYP2D6の指標として用いたヒト肝ミクロソーム中のデキストロメトルファンO-脱メチル化活性に対して50%以上の阻害を示した生薬は28種であり,その中の13種(桂皮,丁子,黄連,麻黄,釣藤鈎,羌活,厚朴,牡丹皮,黄柏,大黄,蘇木,防巳,山椒)が阻害率90%以上を示した。CYP2D6活性に対する阻害の強さは,黄柏,黄連,防巳,蘇木,大黄の順であり,IC_<50>値は各々4,14,40,52および64μg/mLであった。これらの結果から,CYP3A4あるいはCYP2D6に対する阻害活性を示す生薬が複数存在することが明らかとなった。 21st Century COE Program, Toyama Medical and Pharmaceutical University
    01/2004;
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    Journal of Health Science - J HEALTH SCI. 01/2003; 49(4):292-297.
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    ABSTRACT: In 1993, there were 18 acute deaths in Japanese patients who had the viral disease herpes zoster and were treated with the new antiviral drug sorivudine (SRV, 1-beta-D-arabinofuranosyl-(E)-5-(2-bromovinyl)uracil). All the dead patients had received a 5-fluorouracil (5-FU) prodrug as anticancer chemotherapy concomitant with SRV administration. Studies on toxicokinetics in rats and on hepatic dihydropyrimidine dehydrogenase (DPD), a rate-limiting enzyme for 5-FU catabolism in rats and humans, strongly suggested that in the patients who received both SRV and the 5-FU prodrug, tissue levels of highly toxic 5-FU markedly increased as a result of irreversible inactivation of DPD in the presence of NADPH by 5-(2-bromovinyl)uracil (BVU), a metabolite formed from SRV by gut flora in rats and humans. Recombinant human (h) DPD was also irreversibly inactivated by [14C] BVU in the presence of NADPH. MALDI-TOF MS analysis of radioactive tryptic fragments from the radiolabeled and inactivated hDPD demonstrated that a Cys residue located at position 671 in the pyrimidine-binding domain of hDPD was modified with an allyl bromide type of reactive metabolite, dihydro-BVU. Thus artificial DPD deficiency caused by BVU from SRV led to patient deaths when coadministered with the 5-FU prodrug. Human population studies using healthy volunteers have demonstrated that there are poor and extensive 5-FU metabolizers who have very low and high DPD activities, respectively. Administration of a clinical dose of 5-FU or its prodrug to poor 5-FU metabolizers may cause death unless DPD activity is determined using their peripheral blood mononuclear cells prior to the administration of the anticancer drug.
    Yakugaku zasshi journal of the Pharmaceutical Society of Japan 09/2002; 122(8):527-35. · 0.46 Impact Factor
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    ABSTRACT: The phenolic active metabolites, cis-4-hydroxytamoxifen (cis-HO-TAM) and trans-4-hydroxytamoxifen (trans-HO-TAM), of the anti-breast-cancer drug, trans-tamoxifen (TAM), were geometrically selectively glucuronidated in the manner of cis>trans by microsomes and sulfated in the manner of trans>cis by cytosol from the liver of 10 human subjects (7 females and 3 males). There was a large individual difference in the microsomal glucuronidation of cis-HO-TAM, which correlated well with glucuronidation of 4-hydroxybiphenyl by human liver microsomes. However, there was only a slight correlation between the glucuronidation of cis-HO-TAM and trans-HO-TAM or 4-nitrophenol (NP). A small individual difference was observed for the human liver cytosolic sulfation of trans-HO-TAM, which correlated well with the sulfation of NP. Recombinant human UDP-glucuronosyltransferase (UGT)2B15 catalyzed the cis-selective glucuronidation of geometrical isomers of HO-TAM. UGTs1A1, 1A4, 1A9 and 2B7 had weak activity toward HO-TAMs with a much smaller cis-selectivity than did UGT2B15. UGTs1A3 and 1A6 had no detectable activity toward these substrates. Among the four known major sulfotransferases (SULTs) occurring in the human liver, SULT1A1 was strongly suggested to play the most important role in the hepatic cytosolic trans-selective sulfation of HO-TAM isomers. A good correlation was observed between the hepatic cytosolic sulfation of trans-HO-TAM and NP, a standard substrate for SULT1A1. SULT1E1 had slight activity toward the HO-TAMs. SULTs1A3 and 2A1 had no detectable activity toward HO-TAMs.
    Biochemical Pharmacology 06/2002; 63(10):1817-30. · 4.58 Impact Factor
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    ABSTRACT: Twenty-one water-soluble acid dyes, including eleven azo, five triphenylmethane four xanthene, one naphthol derivatives, used at practical concentrations for food coloration, were quantitatively extracted from water and various carbonated beverages into a 0.1 M quinine-chloroform solution in the presence of 0.5 M boric acid by brief shaking. Quantitative extraction of these dyes was also accomplished by the 0.1 M quinine-chloroform solution made conveniently from chloroform, quinine hydrochloride, and sodium hydroxide added successively to water or beverages containing boric acid. Quinine acted as a countercation on the dyes having sulfonic and/or carboxylic acid group(s) to form chloroform-soluble ion-pair complexes. The diacidic base alkaloid interacted with each acid group of mono-, di-, tri-, and tetrasulfonic acid dyes approximately in the ratio 0.8-0.9 to 1. The dyes in the chloroform solution were quantitatively concentrated into a small volume of sodium hydroxide solution also by brief shaking. The convenient quinine-chloroform method was applicable to the quantitative extraction of a mixture of 12 dyes from carbonated beverages, which are all currently used for food coloration. A high-pressure liquid chromatographic method is also presented for the systematic separation and determination of these 12 dyes following their concentration into the aqueous alkaline solution. The chromatogram was monitored by double-wavelength absorptiometry in the visible and ultraviolet ray regions.
    Analytical Chemistry - ANAL CHEM. 04/2002; 58(14).
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    ABSTRACT: It is known that in humans taking soy food, the phytoestrogens, daidzein (DZ) and genistein (GS), exist as sulfates and glucuronides in the plasma and are excreted as conjugates in urine. To investigate which human sulfotransferase (SULT) isoforms participate in the sulfation of these phytoestrogens, the four major cytosolic SULTs, SULT1A1, SULT1A3, SULT1E1, and SULT2A1, occurring in the human liver were bacterially expressed as His-tagged proteins and chromatographically purified to homogeneity in the presence of Tween 20 and glycerol as highly efficient agents for stabilizing the recombinant enzymes. All the SULTs showed sulfating activity toward both DZ and GS. However, k(cat)/K(m) values observed indicated that these phytoestrogens were sulfated predominantly by SULT1A1 and SULT1E1 with K(m) values of 0.3 and 0.7 microM for GS and 1.9 and 3.4 microM for DZ, respectively. DZ and GS strongly inhibited the sulfation of the endogenous substrate, beta-estradiol, by SULT1E1 in a non-competitive manner with K(i) values of 14 and 7 microM, respectively, suggesting that these phytoestrogens might affect tissue levels of beta-estradiol in the human. The phenolic endocrine-disrupting chemicals, bisphenol A (BPA), 4-n-nonylphenol (NP), and 4-t-octylphenol (t-OP), were used as substrates to investigate the possible participation of human SULTs in their metabolism for excretion. High k(cat)/K(m) values were observed for the sulfation of BPA by SULT1A1, NP by SULT1A1 and SULT1E1, and t-OP by SULT1E1 and SULT2A1.
    Drug Metabolism and Pharmacokinetics 02/2002; 17(3):221-8. · 2.07 Impact Factor
  • Yakugaku Zasshi-journal of The Pharmaceutical Society of Japan - YAKUGAKU ZASSHI-J PHARM SOC J. 01/2002; 122(8):527-535.
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    ABSTRACT: In guinea-pig liver cytosol, racemic 4-hydroxy-2(E)-nonenal (HNE), a reactive and highly toxic product released from biomembranes by lipid peroxidation, was detoxified (S)-preferentially by GSH conjugation mediated by glutathione S-transferases (GSTs) and (R)-preferentially by NAD(+)-dependent oxidation mediated by aldehyde dehydrogenase (ALDH). The GST-mediated detoxification of the HNE enantiomers proceeded at much higher rates than that mediated by ALDH in guinea-pig liver cytosol. All the major guinea-pig GSTs, A1-1, M1-1, M1-2 and M1-3*, isolated from guinea-pig liver cytosol also catalysed the (S)-preferential conjugation of the HNE enantiomers. The liver and other major tissues of guinea-pigs had no immunologically detectable level of a putative GSTA4-4 orthologue, which exists as a minor GST protein in rat, mouse and human livers and exhibits extremely high catalytic activity towards HNE. All the hepatic rat GSTs, A1-1(2), A1-3, A4-4, M1-1, M1-2 and M2-2, also catalysed the (S)-preferential conjugation of HNE enantiomers.
    Biochemical Journal 05/2001; 355(Pt 1):237-44. · 4.65 Impact Factor

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1k Citations
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Institutions

  • 2004–2005
    • Toyama Medical and Pharmaceutical University
      Тояма, Toyama, Japan
  • 1995–2002
    • Tokyo University of Pharmacy and Life Science
      • School of Pharmacy
      Tokyo, Tokyo-to, Japan
  • 1994
    • Showa University
      • Department of Internal Medicine
      Shinagawa, Tōkyō, Japan
  • 1990–1991
    • Hatano Research Institute, Food and Drug Safety Center
      Hatano, Kanagawa, Japan
  • 1989
    • The University of Tokyo
      Edo, Tōkyō, Japan
    • Setsunan University
      • Faculty of Pharmaceutical Sciences
      Ōsaka-shi, Osaka-fu, Japan
  • 1982
    • Institute of Public Health
      Bengalūru, Karnātaka, India