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Study on the inhibitory effect of furafylline and troleandomycin in the 7-methoxyresorufin-O-demethylase and nifedipine oxidase activities in hepatic microsomes from four poultry species using high-performance liquid chromatography coupled with fluorescence and ultraviolet detection. J Pharm Biomed Anal 2018; 164:148-154. [PMID: 30390556 DOI: 10.1016/j.jpba.2018.10.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 10/16/2018] [Accepted: 10/17/2018] [Indexed: 10/28/2022]
Abstract
The present study reports the in vitro studies with furafylline and troleandomycin (TAO) as specific inhibitors of activities 7-methoxyresorufin-O-demethylase (MROD) and nifedipine oxidase, catalyzed by cytochrome P450 1 A2 (CYP1 A2) and 3A4 human enzymes, respectively, in hepatic microsomes of quail, duck, turkey and chicken. The results suggest that in chicken and quail the MROD activity is carried out by orthologs CYP1 A4 and 1 A5, meanwhile in duck and turkey by a CYP1 A5 ortholog. The nifedipine oxidase activity is carried out by orthologs of the CYP3A family in the four bird species. The use of furafylline and TAO significantly decreased these activities (P < 0.05) and suggested that the biotransformation of resorufin methyl ether (RME) may be related to more than one avian ortholog.
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2
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Kamenickova A, Anzenbacherova E, Pavek P, Soshilov AA, Denison MS, Anzenbacher P, Dvorak Z. Pelargonidin activates the AhR and induces CYP1A1 in primary human hepatocytes and human cancer cell lines HepG2 and LS174T. Toxicol Lett 2013; 218:253-9. [PMID: 23419638 PMCID: PMC3644221 DOI: 10.1016/j.toxlet.2013.01.020] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/24/2013] [Accepted: 01/25/2013] [Indexed: 10/27/2022]
Abstract
We examined the effects of anthocyanidins (cyanidin, delphinidin, malvidin, peonidin, petunidin, pelargonidin) on the aryl hydrocarbon receptor (AhR)-CYP1A1 signaling pathway in human hepatocytes, hepatic HepG2 and intestinal LS174T cancer cells. AhR-dependent reporter gene expression in transfected HepG2 cells was increased by pelargonidin in a concentration-dependent manner at 24h. Similarly, pelargonidin induced the expression of CYP1A1 mRNA up to 5-fold in HepG2 and LS174T cells relative to the induction by 5 nM 2,3,7,8-tetrachlorodibenzodioxin (TCDD), the most potent activator of AhR. CYP1A1 and CYP1A2 mRNAs were also increased by pelargonidin in three primary human hepatocytes cultures (approximately 5% of TCDD potency) and the increase in CYP1A1 protein in HepG2 and LS174T cells was comparable to the increase in catalytic activity of CYP1A1 enzyme. Ligand binding analysis demonstrated that pelargonidin was a weak ligand of AhR. Enzyme kinetic analyses using human liver microsomes revealed inhibition of CYP1A1 activity by delphinidin (IC50 78 μM) and pelargonidin (IC50 33 μM). Overall, although most anthocyanidins had no effects on AhR-CYP1A1 signaling, pelargonidin can bind to and activate the AhR and AhR-dependent gene expression, and pelargonidin and delphinidin inhibit the CYP1A1 catalytic activity.
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Affiliation(s)
- Alzbeta Kamenickova
- Department of Cell Biology and Genetics, Faculty of Science, Palacky University, Slechtitelu 11, 783 71 Olomouc, Czech Republic
| | - Eva Anzenbacherova
- Institute of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, 775 15 Olomouc, Czech Republic
| | - Petr Pavek
- Department of Pharmacology and Toxicology, Charles University in Prague, Faculty of Pharmacy in Hradec Kralove, Heyrovskeho 1203, Hradec Kralove 50005, Czech Republic
| | - Anatoly A. Soshilov
- Department of Environmental Toxicology, University of California, Meyer Hall, One Shields Avenue, Davis, CA 95616-8588, USA
| | - Michael S. Denison
- Department of Environmental Toxicology, University of California, Meyer Hall, One Shields Avenue, Davis, CA 95616-8588, USA
| | - Pavel Anzenbacher
- Institute of Pharmacology, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, 775 15 Olomouc, Czech Republic
| | - Zdenek Dvorak
- Department of Cell Biology and Genetics, Faculty of Science, Palacky University, Slechtitelu 11, 783 71 Olomouc, Czech Republic
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Diaz GJ, Murcia HW, Cepeda SM. Cytochrome P450 enzymes involved in the metabolism of aflatoxin B1 in chickens and quail. Poult Sci 2010; 89:2461-9. [PMID: 20952710 DOI: 10.3382/ps.2010-00864] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
A study was conducted to identify the cytochrome P450 (CYP, CYP450) enzyme orthologs involved in the bioactivation of aflatoxin B(1) (AFB(1)) into the highly toxic metabolite known as aflatoxin-8,9-epoxide (AFBO) in quail and chicken hepatic microsomes. The strategies used included the use of specific CYP450 inhibitors and the correlation of prototype substrate activities with AFBO production. Additionally, the presence of the enzymes was qualitatively determined using an immunoblotting technique. The results showed that both quail and chicken microsomes have CYP1A1, CYP1A2, CYP2A6, and CYP3A4 enzymatic activity. A strong relationship between CYP1A1 and CYP2A6 activities and AFB(1) bioactivation was found in both species. Inhibition studies provided more evidence for the role of CYP2A6 in the bioactivation of AFB(1). The immunoblot results showed clear bands for the CYP2A6 and CYP3A4 orthologs in both species. The results of the present study indicate that CYP2A6 and, to a lesser extent, CYP1A1 are responsible for the bioactivation of AFB(1) into AFBO in both quail and chicken hepatic microsomes.
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Affiliation(s)
- G J Diaz
- Laboratorio de Toxicología, Facultad de Medicina Veterinaria y de Zootecnia, Universidad Nacional de Colombia, Bogotá, D.C. Colombia.
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Diaz G, Murcia H, Cepeda S. Bioactivation of aflatoxin B1 by turkey liver microsomes: responsible cytochrome P450 enzymes. Br Poult Sci 2010; 51:828-37. [DOI: 10.1080/00071668.2010.528752] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Diaz GJ, Murcia HW, Cepeda SM, Boermans HJ. The role of selected cytochrome P450 enzymes on the bioactivation of aflatoxin B1 by duck liver microsomes. Avian Pathol 2010; 39:279-85. [DOI: 10.1080/03079457.2010.495109] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Reperfusion does not induce oxidative stress but sustained endoplasmic reticulum stress in livers of rats subjected to traumatic-hemorrhagic shock. Shock 2010; 33:289-98. [PMID: 19503022 DOI: 10.1097/shk.0b013e3181aef322] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Oxidative stress is believed to accompany reperfusion and to mediate dysfunction of the liver after traumatic-hemorrhagic shock (THS). Recently, endoplasmic reticulum (ER) stress has been suggested as an additional factor. This study investigated whether reperfusion after THS leads to increased oxidative and/or ER stress in the liver. In a rat model, including laparotomy, bleeding until decompensation, followed by inadequate or adequate reperfusion phase, three time points were investigated: 40 min, 3 h, and 18 h after shock. The reactive oxygen and nitrogen species and its scavenging capacity (superoxide dismutase 2), the nitrotyrosine formation in proteins, and the lipid peroxidation together with the status of endogenous antioxidants (alpha-tocopherylquinone-alpha-tocopherol ratio) were investigated as markers for oxidative or nitrosylative stress. Mitochondrial function and cytochrome P450 isoform 1A1 activity were analyzed as representatives for hepatocyte function. Activation of the inositol-requiring enzyme 1/X-box binding protein pathway and up-regulation of the 78-kDa glucose-regulated protein were recorded as ER stress markers. Plasma levels of alanine aminotransferase and Bax/Bcl-XL messenger RNA (mRNA) ratio were used as indicators for hepatocyte damage and apoptosis induction. Oxidative or nitrosylative stress markers or representatives of hepatocyte function were unchanged during and short after reperfusion (40 min, 3 h after shock). In contrast, ER stress markers were elevated and paralleled those of hepatocyte damage. Incidence for sustained ER stress and subsequent apoptosis induction were found at 18 h after shock. Thus, THS or reperfusion induces early and persistent ER stress of the liver, independent of oxidative or nitrosylative stress. Although ER stress was not associated with depressed hepatocyte function, it may act as an early trigger of protracted cell death, thereby contributing to delayed organ failure after THS.
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Pegolo S, Merlanti R, Giantin M, Dacasto M, Montesissa C, Capolongo F. High performance liquid chromatography determination of cytochrome P450 1A and 2C activities in bovine liver microsomes. Vet J 2010; 183:81-88. [DOI: 10.1016/j.tvjl.2008.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 07/24/2008] [Accepted: 08/07/2008] [Indexed: 10/21/2022]
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Guo F, An T, Rein KS. The algal hepatoxoxin okadaic acid is a substrate for human cytochromes CYP3A4 and CYP3A5. Toxicon 2009; 55:325-32. [PMID: 19699225 DOI: 10.1016/j.toxicon.2009.08.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Revised: 08/11/2009] [Accepted: 08/14/2009] [Indexed: 11/28/2022]
Abstract
The hepatotoxin okadaic acid (OA) was incubated with nine human recombinant cytochrome P450s (1A1, 1A2, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4 and 3A5). Both CYP3A4 and CYP3A5 converted OA to a mixture of the same four metabolites, but incubation with CYP3A4 resulted in higher levels of conversion. Michaelis-Menten parameters, K(m) (73.4 microM) and V(max) (7.23 nmol of metabolitesnmol(-1)min(-1)) for CYP3A4 were calculated by analyzing double-reciprocal plots. LC-MS(n) analysis and chemical interconversion indicate that metabolites 2 and 3 are the 11S-hydroxy and 11R-hydroxy okadaic acid respectively, while metabolite 4 is 11-oxo okadaic acid. LC-MS(n) analysis of metabolite 1 shows a molecular ion which corresponds to an addition of 16 amu to OA, also suggesting hydroxylation, but the specific site has not been identified. The same four metabolites were produced upon incubation of okadaic acid with pooled human liver microsomes. This transformation could be completely inhibited with ketokonazole, and inhibitor of the CYP3A family of enzymes. The metabolites were determined to be only slightly less potent inhibitors of serine threonine protein phosphatase 2A (PP2A) when compared to OA. As PP2A is the principle molecular target for OA, these oxidative transformations may not effectively detoxify OA.
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Affiliation(s)
- Fujiang Guo
- Department of Chemistry and Biochemistry, Florida International University, 11200 SW 8th St., Miami, FL 33199, USA
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Kozlov AV, Duvigneau JC, Miller I, Nürnberger S, Gesslbauer B, Kungl A, Ohlinger W, Hartl RT, Gille L, Staniek K, Gregor W, Haindl S, Redl H. Endotoxin causes functional endoplasmic reticulum failure, possibly mediated by mitochondria. Biochim Biophys Acta Mol Basis Dis 2009; 1792:521-30. [PMID: 19327397 DOI: 10.1016/j.bbadis.2009.03.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 02/25/2009] [Accepted: 03/11/2009] [Indexed: 10/21/2022]
Abstract
Inflammatory response has recently been shown to induce endoplasmic reticulum (ER) stress and the unfolded protein response (UPR), which either recovers proper ER function or activates apoptosis. Here we show that endotoxin (lipopolysaccharide = LPS) can lead to functional ER failure tentatively via a mitochondrion-dependent pathway in livers of rats. Histological examination did not reveal significant damage to liver in form of necroses. Electron microscopy displayed transparent rings appearing around morphologically unchanged mitochondria, which were identified as dilated ER. The spliced mRNA variant of X-box protein-1 (XBP1) and also the mRNA of 78 kDa glucose-regulated protein (GRP78) were up-regulated, both typical markers of ER stress. However, GRP78 was down-regulated at the protein level. A pro-apoptotic shift in the bax/bcl-XL mRNA ratio was not accompanied by translocation of apoptosis inducing factor (AIF) to the nucleus, suggesting that the cells entered a pre-apoptotic state, but apoptosis was not executed. Monooxygenase activity of p450, representing the detoxification system in ER, was decreased after administration of endotoxin. Biochemical analysis of proteins important for ER function revealed the impairment of protein folding, transport, and detoxification suggesting functional ER failure. We suggest that functional ER failure may be a reason for organ dysfunction upon excessive inflammatory response mediated by endotoxin.
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Affiliation(s)
- Andrey V Kozlov
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology in the AUVA Research Center, Donaueschingenstr. 13, 1200 Vienna, Austria.
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Mosadeghi S, Furnes B, Matsuo AYO, Schlenk D. Expression and characterization of cytochrome P450 2X1 in channel catfish (Ictalurus punctatus). Biochim Biophys Acta Gen Subj 2007; 1770:1045-52. [PMID: 17459590 DOI: 10.1016/j.bbagen.2007.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Revised: 02/20/2007] [Accepted: 03/08/2007] [Indexed: 11/25/2022]
Abstract
Previous studies in channel catfish identified a novel cDNA encoding the cytochrome P450 isoform, CYP2X1. To characterize the substrate specificity of CYP2X1, the 57 kDa protein was expressed in Sf9 cells. Microsomes from Sf9 cells transfected with CYP2X1 demonstrated a maximum carbon monoxide-reduced difference spectrum at 450 nm and catalyzed aminopyrine and benzphetamine demethylase activity with catalytic efficiency (Vmax/Km) values of 0.82 pmol/nmol P450/min and 4.39 pmol/nmol P450/min, respectively. However, enzymatic activity was not observed following incubation with p-nitrophenol, benzyloxyresorufin or pentoxyresorufin. Expression of CYP2X1 transcription was significantly elevated in the gills and liver relative to that detected in brain, kidney and heart. In the brain, liver and heart, intraperitoneal injections with clofibric acid, ethanol, pyridine and rifampin failed to alter expression of CYP2X1 mRNA. In kidney, pyridine significantly suppressed the expression of CYP2X1 transcription (p < or = 0.05). These results indicate CYP2X1 displays minimal catalytic activities consistent with other piscine CYP2 isoforms, and unique tissue expression and regulation patterns in juvenile channel catfish.
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Affiliation(s)
- Sasan Mosadeghi
- Department of Environmental Sciences, University of California, Riverside, CA 92521-0144, USA
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Fraga H, Fernandes D, Novotny J, Fontes R, Esteves da Silva JCG. Firefly luciferase produces hydrogen peroxide as a coproduct in dehydroluciferyl adenylate formation. Chembiochem 2006; 7:929-35. [PMID: 16642538 DOI: 10.1002/cbic.200500443] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Firefly luciferase catalyzes the synthesis of H2O2 from the same substrates as the bioluminescence reaction: ATP and luciferin (D-LH2). About 80% of the enzyme-bound intermediate D-luciferyl adenylate (D-LH2-AMP) is oxidized into oxyluciferin, and a photon is emitted during this reaction. The enzyme pathway responsible for the generation of H2O2 is a side reaction in which D-LH2-AMP is oxidized into dehydroluciferyl adenylate (L-AMP). Like the bioluminescence reaction, the luciferase-catalyzed synthesis of H2O2 and L-AMP is a stereospecific process, involving only the natural D enantiomer. However, the intramolecular electron transfer postulated as essential to the light emission process is not involved in this side reaction.
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Affiliation(s)
- Hugo Fraga
- Centro de Investigação em Química, Departamento de Química, Faculdade de Ciências, Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal
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12
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Magnusson MO, Karlsson MO, Sandström R. A mechanism-based integrated pharmacokinetic enzyme model describing the time course and magnitude of phenobarbital-mediated enzyme induction in the rat. Pharm Res 2006; 23:521-32. [PMID: 16525862 DOI: 10.1007/s11095-005-9571-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2005] [Accepted: 11/21/2005] [Indexed: 11/26/2022]
Abstract
PURPOSE To characterize the magnitude, time course, and specificity of phenobarbital (PB)-mediated enzyme induction, and further, to develop an integrated pharmacokinetic (PK)-enzyme model describing the changes in the activities of CYP enzymes as well as in the PK of PB. METHODS PB plasma concentrations and in vitro activities of several CYP enzymes were measured in rats treated with PB between 0 and 14 days. A PB PK-enzyme induction model was developed using the program NONMEM: . RESULTS PB treatment both induces and reduces the activity of CYP enzymes by stimulating the enzymes' formation or elimination rates. Certain CYP enzymes affected the PB PK through autoinduction. The half-life of the induction process was estimated to be 2 days for CYP1A2, CYP3A1/2, and CYP2B1/2, and 3 days for androstenedione producing enzymes. The CYP2C11 activity was rapidly reduced by PB treatment. A lag time for the PB autoinduction was observed. This lag time is explained by the rate difference between induction and reduction in CYP activities. CONCLUSION To our knowledge, this is the first example of an induction model that simultaneously describes plasma PK and in vitro data. It does so by integrating the bidirectional interaction between drug and enzymes in a mechanistic manner.
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Affiliation(s)
- Mats O Magnusson
- Division of Pharmacokinetics and Drug Therapy, Department of Pharmaceutical Biosciences, Uppsala University, Box 591, SE-751 24, Uppsala, Sweden.
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Meng Y, High K, Antonello J, Washabaugh MW, Zhao Q. Enhanced sensitivity and precision in an enzyme-linked immunosorbent assay with fluorogenic substrates compared with commonly used chromogenic substrates. Anal Biochem 2006; 345:227-36. [PMID: 16137635 DOI: 10.1016/j.ab.2005.07.026] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 07/18/2005] [Accepted: 07/20/2005] [Indexed: 11/25/2022]
Abstract
Quantitative enzyme-linked immunosorbent assay (ELISA) is a widely used tool for analyzing biopharmaceutical and vaccine products. The superior sensitivity of the ELISA format is conferred by signal amplification through the enzymatic oxidation or hydrolysis of substrates to products with enhanced color or fluorescence. The extinction coefficient for a colored product or the quantum yield of a fluorescent product, coupled with the efficiency of the immobilized enzyme, is the determining factor for the sensitivity and precision of a given ELISA. The enhancement of precision and sensitivity using fluorogenic substrates was demonstrated in a direct-binding ELISA in a low-analyte concentration range compared with commonly used chromogenic substrates. The enhancement in precision was demonstrated quantitatively with lower coefficients of variation in measurements of signal intensities, approximately a five- to six-fold enhancement in signal-to-noise ratio at a given analyte concentration with fluorogenic substrates. Similarly, the amplitude of the enhancement in sensitivity, as reflected by relative limits of detection or quantitation, is approximately two- to five-fold when compared with commonly used chromogenic substrates. Additional advantages of a fluorescence-based ELISA format include the continuous monitoring of initial rates of enzymatic reactions, the measurement of fluorescence changes in the presence of particulate materials, the absence of a quench step, and a larger quantifiable analyte range.
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Affiliation(s)
- Yuan Meng
- Department of Bioprocess and Bioanalytical Research, Merck Research Laboratories, West Point, PA 19486, USA
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Hanada K, Ogawa R, Son K, Sasaki Y, Kikkawa A, Ichihara S, Ogata H. Effects of Indoxylsulfate on the in vitro Hepatic Metabolism of Various Compounds Using Human Liver Microsomes and Hepatocytes. ACTA ACUST UNITED AC 2006; 103:p179-86. [PMID: 16645322 DOI: 10.1159/000092919] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Accepted: 02/03/2006] [Indexed: 11/19/2022]
Abstract
BACKGROUND Alterations of hepatic drug metabolism in patients with renal failure are poorly understood. In this study, the effects of uremic substances that can be removed by hemodialysis on in vitrohepatic drug metabolism were studied using human liver microsomes and hepatocytes. METHODS The metabolism of various compounds that undergo oxidation and glucuronidation in the liver was studied using human liver microsomes and hepatocytes in the presence of 11 uremic substances removable by hemodialysis. RESULTS The formation of resorufin from ethoxyresorufin was inhibited by 3-indoxylsulfate and 3-indoleacetic acid. The formation of 6beta-hydroxytestosterone from testosterone was inhibited only by 3-indoxylsulfate. These uremic substances reduced the maximum metabolic rate but not the affinity, suggesting that the inhibitory mechanism was noncompetitive. The inhibition of formation of resorufin and 6beta-hydroxytestosterone by 3-indoxylsulfate was also observed in human hepatocytes. The elimination of nicardipine in liver microsomes was decreased significantly in the presence of 3-indoxylsulfate and 3-indoleacetic acid. CONCLUSION The hepatic metabolism of certain drugs may be inhibited directly by uremic substances such as 3-indoxylsulfate that accumulate in the plasma in patients with chronic renal failure.
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Affiliation(s)
- Kazuhiko Hanada
- Department of Biopharmaceutics, Meiji Pharmaceutical University, Kiyose, Tokyo, Japan.
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Tachibana S, Fujimaki Y, Yokoyama H, Okazaki O, Sudo KI. IN VITRO METABOLISM OF THE CALMODULIN ANTAGONIST DY-9760e (3-[2-[4-(3-CHLORO-2-METHYLPHENYL)-1-PIPERAZINYL]ETHYL]-5,6-DIMETHOXY-1-(4-IMIDAZOLYLMETHYL)-1H-INDAZOLE DIHYDROCHLORIDE 3.5 HYDRATE) BY HUMAN LIVER MICROSOMES: INVOLVEMENT OF CYTOCHROMES P450 IN ATYPICAL KINETICS AND POTENTIAL DRUG INTERACTIONS. Drug Metab Dispos 2005; 33:1628-36. [PMID: 16049129 DOI: 10.1124/dmd.105.004903] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human cytochrome P450 (P450) isozyme(s) responsible for metabolism of the calmodulin antagonist 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate (DY-9760e) and kinetic profiles for formation of its six primary metabolites [M3, M5, M6, M7, M8, and DY-9836 (3-[2-[4-(3-chloro-2-methylphenyl)piperazinyl]ethyl]-5,6-dimethoxyindazole)] were identified using human liver microsomes and recombinant P450 enzymes. In vitro experiments, including an immunoinhibition study, correlation analysis, and reactions with recombinant P450 enzymes, revealed that CYP3A4 is the primary P450 isozyme responsible for the formation of the DY-9760e metabolites, except for M5, which is metabolized by CYP2C9. Additionally, at clinically relevant concentrations, CYP2C8 and 2C19 make some contribution to the formation of M3 and M5, respectively. The formation rates of DY-9760e metabolites except for M8 by human liver microsomes are not consistent with a Michaelis-Menten kinetics model, but are better described by a substrate inhibition model. In contrast, the enzyme kinetics for all metabolites formed by recombinant CYP3A4 can be described by an autoactivation model or a mixed model of autoactivation and biphasic kinetics. Inhibition of human P450 enzymes by DY-9760e in human liver microsomes was also investigated. DY-9760e is a very potent competitive inhibitor of CYP2C8, 2C9 and 2D6 (Ki 0.25-1.7 microM), a mixed competitive and noncompetitive inhibitor of CYP2C19 (Ki 2.4 microM) and a moderate inhibitor of CYP1A2 and 3A4 (Ki 11.4-20.1 microM), suggesting a high possibility for human drug-drug interaction.
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Affiliation(s)
- Shuko Tachibana
- Drug Metabolism & Physicochemistry Research Laboratories, R&D Division, Daiichi Pharmaceutical Co., Ltd., Toky, Japan.
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Iwata H, Tezuka Y, Kadota S, Hiratsuka A, Watabe T. IDENTIFICATION AND CHARACTERIZATION OF POTENT CYP3A4 INHIBITORS IN SCHISANDRA FRUIT EXTRACT. Drug Metab Dispos 2004; 32:1351-8. [PMID: 15342469 DOI: 10.1124/dmd.104.000646] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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.
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Affiliation(s)
- Hiroshi Iwata
- Division of Natural Products Chemistry, Institute of Natural Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama, 930-0194, Japan
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Murayama N, Soyama A, Saito Y, Nakajima Y, Komamura K, Ueno K, Kamakura S, Kitakaze M, Kimura H, Goto YI, Saitoh O, Katoh M, Ohnuma T, Kawai M, Sugai K, Ohtsuki T, Suzuki C, Minami N, Ozawa S, Sawada JI. Six Novel NonsynonymousCYP1A2Gene Polymorphisms: Catalytic Activities of the Naturally Occurring Variant Enzymes. J Pharmacol Exp Ther 2003; 308:300-6. [PMID: 14563787 DOI: 10.1124/jpet.103.055798] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Six novel nonsynonymous nucleotide alterations were found in the cytochrome P450 1A2 gene in a Japanese population, which resulted in the following amino acid substitutions: T83M, E168Q, F186L, S212C, G299A, and T438I. These individuals were heterozygous for the amino acid substitutions. The potential functional alterations caused by the amino acid substitutions were characterized by a cDNA-mediated expression system using Chinese hamster V79 cells. Among the six CYP1A2 variants, F186L showed the most profound and statistically significant reduction in O-deethylation of phenacetin and 7-ethoxyresorufin. Kinetic analyses performed for the ethoxyresorufin O-deethylation revealed that the Vmax of the F186L variant was approximately 5% of that of the CYP1A2 wild type, despite a 5-fold lower Km value of the variant, the consequence of which was reduced enzymatic activity toward the substrate. Thus, for the first time, phenylalanine at residue 186 is suggested to be a critical amino acid for catalytic activity.
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Affiliation(s)
- Norie Murayama
- Project Team for Pharmacogenetics, National Institute of Health Sciences, Tokyo, Japan
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Hanioka N, Tatarazako N, Jinno H, Arizono K, Ando M. Determination of cytochrome P450 1A activities in mammalian liver microsomes by high-performance liquid chromatography with fluorescence detection. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2000; 744:399-406. [PMID: 10993529 DOI: 10.1016/s0378-4347(00)00278-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A sensitive method for the determination of cytochrome P450 (P450 or CYP) 1A activities such as ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-demethylase (MROD) in liver microsomes from human, monkey, rat and mouse by high-performance liquid chromatography with fluorescence detection is reported. The newly developed method was found to be more sensitive than previous methods using a spectrofluorimeter and fluorescence plate reader. The detection limit for resorufin (signal-to-noise ratio of 3) was 0.80 pmol/assay. Intra-day and inter-day precisions (expressed as relative standard deviation) were less than 6% for both enzyme activities. With this improved sensitivity, the kinetics of EROD and MROD activities in mammalian liver microsomes could be determined more precisely. EROD activities in human and monkey liver microsomes, and MROD activities in liver microsomes from all animal species exhibited a monophasic kinetic pattern, whereas the pattern of EROD activities in rat and mouse liver microsomes was biphasic. In addition, the method could determine the non-inducible and 3-methylcholanthrene-inducible activities of EROD and MROD in rat and mouse liver microsomes under the same assay conditions. Therefore, this method is applicable to in vivo and in vitro studies on the interaction of xenobiotic chemicals with cytochrome CYP1A isoforms in mammals.
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Affiliation(s)
- N Hanioka
- Division of Environmental Chemistry, National Institute of Health Sciences, Tokyo, Japan.
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