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Eva Frei - One of the best experts on this subject based on the ideXlab platform.
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The Anticancer Drug Ellipticine Induces Cytochromes P450 1A1, 1A2 and 3A, Cytochrome b5 and NADPH:Cytochrome
2015Co-Authors: P Oxidoreductase, Rat Liver, Iveta Vranová, Michaela Moserová, Petr Hodek, Rene Kizek, Eva Frei, Marie StiborováAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, the pharmacological efficiency of which is dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation in target tissues. Using the Western blotting, we found that this compound increases protein expression of cytochrome b5, CYP1A1, 1A2, 3A and NADPH:CYP oxidoreductase (POR) in livers, lungs and kidneys of rats treated (i.p.) with ellipticine. The ellipticine-mediated induction of these enzymes resulted in an increase in their enzymatic activities and ellipticine oxidation to 7-hydroxy-, 9-hydroxy-, 12-hydroxy-and 13-hydroxyellipticine, the metabolites that are both detoxication products (7-hydroxy-, 9-hydroxyellipticine) and metabolites responsible for generation ellipticine-derived DNA adducts (12-hydroxy- and 13-hydroxyellipticine). The results demonstrate that by inducing CYP1A1/2, 3A, POR and cytochrome b5, ellipticine increases its own metabolism in rats, thereby modulating its own pharmacological and/or genotoxic potential
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Electrochemical Determination of Enzymes Metabolizing Ellipticine in Thyroid Cancer Cells- a Tool to Explain the Mechanism of Ellipticine Toxicity to these Cells
2015Co-Authors: Jitka Poljaková, Rene Kizek, Eva Frei, Tomas Eckschlager, Jindřich Činátl, Marie StiborováAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, the pharmacological efficiency of which is dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation to species forming DNA adducts in target tissues. Here, we found that this compound is cytotoxic to human BHT-101, B-CPAP and 8505-C thyroid cancer cells and blocks one or more phases of cell cycle in these cancer cells. Ellipticine toxicity to the thyroid cancer cells corresponded to levels of DNA adducts generated by the CYP- and/or peroxidase-mediated ellipticine metabolites, 12-hydroxy- and 13-hydroxyellipticine, in these cells. Cultivation of all tested cells under hypoxic conditions (1 % oxygen) led to a decrease in ellipticine toxicity. Such a lower sensitivity of cells to ellipticine correlates with a decrease in the formation of ellipticine-derived DNA adducts in these cells. Using Western blotting, the expression of CYP1A1, 1B1, 3A4, thyroid peroxidase (TPO), cyclooxygenase-1 (COX-1) an
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cytochrome b5 increases cytochrome p450 3a4 mediated activation of anticancer drug ellipticine to 13 hydroxyellipticine whose covalent binding to dna is elevated by sulfotransferases and n o acetyltransferases
Chemical Research in Toxicology, 2012Co-Authors: Marie Stiborová, Michaela Moserová, Rene Kizek, Radek Indra, Věra Cerna, Martina Rupertova, Vaclav Martinek, Tomas Eckschlager, Eva FreiAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (P450)- and/or peroxidase-mediated activation in target tissues. The P450 3A4 enzyme oxidizes ellipticine to five metabolites, mainly to 13-hydroxy- and 12-hydroxyellipticine, the metabolites responsible for the formation of ellipticine-13-ylium and ellipticine-12-ylium ions that generate covalent DNA adducts. Cytochrome b5 alters the ratio of ellipticine metabolites formed by P450 3A4. While the amounts of the detoxication metabolites (7-hydroxy- and 9-hydroxyellipticine) were not changed with added cytochrome b5, 12-hydroxy- and 13-hydroxyellipticine, and ellipticine N2-oxide increased considerably. The P450 3A4-mediated oxidation of ellipticine was significantly changed only by holo-cytochrome b5, while apo-cytochrome b5 without heme or Mn-cytochrome b5 had no such effect. The change in amounts of metabolites resulted in an increased formation of covalent ellipticine-DNA adducts, o...
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Cytochrome b5 Increases Cytochrome P450 3A4-Mediated Activation of Anticancer Drug Ellipticine to 13-Hydroxyellipticine Whose Covalent Binding to DNA Is Elevated by Sulfotransferases and N,O-Acetyltransferases
2012Co-Authors: Marie Stiborová, Radek Indra, Tomas Eckschlager, Michaela Moserová, Věra Černá, Martina Rupertová, Václav Martínek, René Kizek, Eva FreiAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (P450)- and/or peroxidase-mediated activation in target tissues. The P450 3A4 enzyme oxidizes ellipticine to five metabolites, mainly to 13-hydroxy- and 12-hydroxyellipticine, the metabolites responsible for the formation of ellipticine-13-ylium and ellipticine-12-ylium ions that generate covalent DNA adducts. Cytochrome b5 alters the ratio of ellipticine metabolites formed by P450 3A4. While the amounts of the detoxication metabolites (7-hydroxy- and 9-hydroxyellipticine) were not changed with added cytochrome b5, 12-hydroxy- and 13-hydroxyellipticine, and ellipticine N2-oxide increased considerably. The P450 3A4-mediated oxidation of ellipticine was significantly changed only by holo-cytochrome b5, while apo-cytochrome b5 without heme or Mn-cytochrome b5 had no such effect. The change in amounts of metabolites resulted in an increased formation of covalent ellipticine-DNA adducts, one of the DNA-damaging mechanisms of ellipticine antitumor action. The amounts of 13-hydroxy- and 12-hydroxyellipticine formed by P450 3A4 were similar, but more than 7-fold higher levels of the adduct were formed by 13-hydroxyellipticine than by 12-hydroxyellipticine. The higher susceptibility of 13-hydroxyellipticine toward heterolytic dissociation to ellipticine-13-ylium in comparison to dissociation of 12-hydroxyellipticine to ellipticine-12-ylium, determined by quantum chemical calculations, explains this phenomenon. The amounts of the 13-hydroxyellipticine-derived DNA adduct significantly increased upon reaction of 13-hydroxyellipticine with either 3′-phosphoadenosine-5′-phosphosulfate or acetyl-CoA catalyzed by human sulfotransferases 1A1, 1A2, 1A3, and 2A1, or N,O-acetyltransferases 1 and 2. The calculated reaction free energies of heterolysis of the sulfate and acetate esters are by 10–17 kcal/mol more favorable than the energy of hydrolysis of 13-hydroxyellipticine, which could explain the experimental data
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Cytochrome P450- and peroxidase-mediated oxidation of anticancer Alkaloid ellipticine dictates its anti-tumor efficiency.
Biochimica et biophysica acta, 2010Co-Authors: Marie Stiborová, Martina Rupertova, Eva FreiAbstract:An Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation in target tissues. The aim of this review was to summarize our knowledge on the molecular mechanisms of ellipticine action in the cancer cells. The CYP-mediated ellipticine metabolites 9-hydroxy- and 7-hydroxyellipticine and the product of ellipticine oxidation by peroxidases, the ellipticine dimer, are the detoxication metabolites of this compound. In contrast, two carbenium ions, ellipticine-13-ylium and ellipticine-12-ylium, derived from two activation ellipticine metabolites, 13-hydroxyellipticine and 12-hydroxyellipticine, generate two major deoxyguanosine adducts in DNA found in the human breast adenocarcinoma MCF-7 cells, leukemia HL-60 and CCRF-CEM cells, neuroblastoma IMR-32, UKF-NB-3, and UKF-NB-4 cells and glioblastoma U87MG cells in vitro and in rat breast carcinoma in vivo. Formation of these covalent DNA adducts by ellipticine is the predominant mechanism of its cytotoxicity and anti-tumor activity to these cancer cell lines. Ellipticine is also an inducer of CYP1A, 1B1, and 3A4 enzymes in the cancer cells and/or in vivo in rats exposed to this compound, thus modulating its own pharmacological efficiencies. The study forms the basis to further predict the susceptibility of human cancers to ellipticine and suggests that this Alkaloid for treatment in combination with CYP and/or peroxidase gene transfer increasing the anticancer potential of this prodrug. It also suggests ellipticine reactive metabolites 13-hydroxyellipticine and 12-hydroxyellipticine to be good candidates for targeting to tumors absent from the CYP and peroxidase activation enzymes.
Marie Stiborová - One of the best experts on this subject based on the ideXlab platform.
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The Anticancer Drug Ellipticine Induces Cytochromes P450 1A1, 1A2 and 3A, Cytochrome b5 and NADPH:Cytochrome
2015Co-Authors: P Oxidoreductase, Rat Liver, Iveta Vranová, Michaela Moserová, Petr Hodek, Rene Kizek, Eva Frei, Marie StiborováAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, the pharmacological efficiency of which is dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation in target tissues. Using the Western blotting, we found that this compound increases protein expression of cytochrome b5, CYP1A1, 1A2, 3A and NADPH:CYP oxidoreductase (POR) in livers, lungs and kidneys of rats treated (i.p.) with ellipticine. The ellipticine-mediated induction of these enzymes resulted in an increase in their enzymatic activities and ellipticine oxidation to 7-hydroxy-, 9-hydroxy-, 12-hydroxy-and 13-hydroxyellipticine, the metabolites that are both detoxication products (7-hydroxy-, 9-hydroxyellipticine) and metabolites responsible for generation ellipticine-derived DNA adducts (12-hydroxy- and 13-hydroxyellipticine). The results demonstrate that by inducing CYP1A1/2, 3A, POR and cytochrome b5, ellipticine increases its own metabolism in rats, thereby modulating its own pharmacological and/or genotoxic potential
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Electrochemical Determination of Enzymes Metabolizing Ellipticine in Thyroid Cancer Cells- a Tool to Explain the Mechanism of Ellipticine Toxicity to these Cells
2015Co-Authors: Jitka Poljaková, Rene Kizek, Eva Frei, Tomas Eckschlager, Jindřich Činátl, Marie StiborováAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, the pharmacological efficiency of which is dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation to species forming DNA adducts in target tissues. Here, we found that this compound is cytotoxic to human BHT-101, B-CPAP and 8505-C thyroid cancer cells and blocks one or more phases of cell cycle in these cancer cells. Ellipticine toxicity to the thyroid cancer cells corresponded to levels of DNA adducts generated by the CYP- and/or peroxidase-mediated ellipticine metabolites, 12-hydroxy- and 13-hydroxyellipticine, in these cells. Cultivation of all tested cells under hypoxic conditions (1 % oxygen) led to a decrease in ellipticine toxicity. Such a lower sensitivity of cells to ellipticine correlates with a decrease in the formation of ellipticine-derived DNA adducts in these cells. Using Western blotting, the expression of CYP1A1, 1B1, 3A4, thyroid peroxidase (TPO), cyclooxygenase-1 (COX-1) an
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cytochrome b5 increases cytochrome p450 3a4 mediated activation of anticancer drug ellipticine to 13 hydroxyellipticine whose covalent binding to dna is elevated by sulfotransferases and n o acetyltransferases
Chemical Research in Toxicology, 2012Co-Authors: Marie Stiborová, Michaela Moserová, Rene Kizek, Radek Indra, Věra Cerna, Martina Rupertova, Vaclav Martinek, Tomas Eckschlager, Eva FreiAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (P450)- and/or peroxidase-mediated activation in target tissues. The P450 3A4 enzyme oxidizes ellipticine to five metabolites, mainly to 13-hydroxy- and 12-hydroxyellipticine, the metabolites responsible for the formation of ellipticine-13-ylium and ellipticine-12-ylium ions that generate covalent DNA adducts. Cytochrome b5 alters the ratio of ellipticine metabolites formed by P450 3A4. While the amounts of the detoxication metabolites (7-hydroxy- and 9-hydroxyellipticine) were not changed with added cytochrome b5, 12-hydroxy- and 13-hydroxyellipticine, and ellipticine N2-oxide increased considerably. The P450 3A4-mediated oxidation of ellipticine was significantly changed only by holo-cytochrome b5, while apo-cytochrome b5 without heme or Mn-cytochrome b5 had no such effect. The change in amounts of metabolites resulted in an increased formation of covalent ellipticine-DNA adducts, o...
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Cytochrome P450- and peroxidase-mediated oxidation of anticancer Alkaloid ellipticine dictates its anti-tumor efficiency.
Biochimica et biophysica acta, 2010Co-Authors: Marie Stiborová, Martina Rupertova, Eva FreiAbstract:An Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation in target tissues. The aim of this review was to summarize our knowledge on the molecular mechanisms of ellipticine action in the cancer cells. The CYP-mediated ellipticine metabolites 9-hydroxy- and 7-hydroxyellipticine and the product of ellipticine oxidation by peroxidases, the ellipticine dimer, are the detoxication metabolites of this compound. In contrast, two carbenium ions, ellipticine-13-ylium and ellipticine-12-ylium, derived from two activation ellipticine metabolites, 13-hydroxyellipticine and 12-hydroxyellipticine, generate two major deoxyguanosine adducts in DNA found in the human breast adenocarcinoma MCF-7 cells, leukemia HL-60 and CCRF-CEM cells, neuroblastoma IMR-32, UKF-NB-3, and UKF-NB-4 cells and glioblastoma U87MG cells in vitro and in rat breast carcinoma in vivo. Formation of these covalent DNA adducts by ellipticine is the predominant mechanism of its cytotoxicity and anti-tumor activity to these cancer cell lines. Ellipticine is also an inducer of CYP1A, 1B1, and 3A4 enzymes in the cancer cells and/or in vivo in rats exposed to this compound, thus modulating its own pharmacological efficiencies. The study forms the basis to further predict the susceptibility of human cancers to ellipticine and suggests that this Alkaloid for treatment in combination with CYP and/or peroxidase gene transfer increasing the anticancer potential of this prodrug. It also suggests ellipticine reactive metabolites 13-hydroxyellipticine and 12-hydroxyellipticine to be good candidates for targeting to tumors absent from the CYP and peroxidase activation enzymes.
Martina Rupertova - One of the best experts on this subject based on the ideXlab platform.
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cytochrome b5 increases cytochrome p450 3a4 mediated activation of anticancer drug ellipticine to 13 hydroxyellipticine whose covalent binding to dna is elevated by sulfotransferases and n o acetyltransferases
Chemical Research in Toxicology, 2012Co-Authors: Marie Stiborová, Michaela Moserová, Rene Kizek, Radek Indra, Věra Cerna, Martina Rupertova, Vaclav Martinek, Tomas Eckschlager, Eva FreiAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (P450)- and/or peroxidase-mediated activation in target tissues. The P450 3A4 enzyme oxidizes ellipticine to five metabolites, mainly to 13-hydroxy- and 12-hydroxyellipticine, the metabolites responsible for the formation of ellipticine-13-ylium and ellipticine-12-ylium ions that generate covalent DNA adducts. Cytochrome b5 alters the ratio of ellipticine metabolites formed by P450 3A4. While the amounts of the detoxication metabolites (7-hydroxy- and 9-hydroxyellipticine) were not changed with added cytochrome b5, 12-hydroxy- and 13-hydroxyellipticine, and ellipticine N2-oxide increased considerably. The P450 3A4-mediated oxidation of ellipticine was significantly changed only by holo-cytochrome b5, while apo-cytochrome b5 without heme or Mn-cytochrome b5 had no such effect. The change in amounts of metabolites resulted in an increased formation of covalent ellipticine-DNA adducts, o...
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Cytochrome P450- and peroxidase-mediated oxidation of anticancer Alkaloid ellipticine dictates its anti-tumor efficiency.
Biochimica et biophysica acta, 2010Co-Authors: Marie Stiborová, Martina Rupertova, Eva FreiAbstract:An Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation in target tissues. The aim of this review was to summarize our knowledge on the molecular mechanisms of ellipticine action in the cancer cells. The CYP-mediated ellipticine metabolites 9-hydroxy- and 7-hydroxyellipticine and the product of ellipticine oxidation by peroxidases, the ellipticine dimer, are the detoxication metabolites of this compound. In contrast, two carbenium ions, ellipticine-13-ylium and ellipticine-12-ylium, derived from two activation ellipticine metabolites, 13-hydroxyellipticine and 12-hydroxyellipticine, generate two major deoxyguanosine adducts in DNA found in the human breast adenocarcinoma MCF-7 cells, leukemia HL-60 and CCRF-CEM cells, neuroblastoma IMR-32, UKF-NB-3, and UKF-NB-4 cells and glioblastoma U87MG cells in vitro and in rat breast carcinoma in vivo. Formation of these covalent DNA adducts by ellipticine is the predominant mechanism of its cytotoxicity and anti-tumor activity to these cancer cell lines. Ellipticine is also an inducer of CYP1A, 1B1, and 3A4 enzymes in the cancer cells and/or in vivo in rats exposed to this compound, thus modulating its own pharmacological efficiencies. The study forms the basis to further predict the susceptibility of human cancers to ellipticine and suggests that this Alkaloid for treatment in combination with CYP and/or peroxidase gene transfer increasing the anticancer potential of this prodrug. It also suggests ellipticine reactive metabolites 13-hydroxyellipticine and 12-hydroxyellipticine to be good candidates for targeting to tumors absent from the CYP and peroxidase activation enzymes.
Tomas Eckschlager - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical Determination of Enzymes Metabolizing Ellipticine in Thyroid Cancer Cells- a Tool to Explain the Mechanism of Ellipticine Toxicity to these Cells
2015Co-Authors: Jitka Poljaková, Rene Kizek, Eva Frei, Tomas Eckschlager, Jindřich Činátl, Marie StiborováAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, the pharmacological efficiency of which is dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation to species forming DNA adducts in target tissues. Here, we found that this compound is cytotoxic to human BHT-101, B-CPAP and 8505-C thyroid cancer cells and blocks one or more phases of cell cycle in these cancer cells. Ellipticine toxicity to the thyroid cancer cells corresponded to levels of DNA adducts generated by the CYP- and/or peroxidase-mediated ellipticine metabolites, 12-hydroxy- and 13-hydroxyellipticine, in these cells. Cultivation of all tested cells under hypoxic conditions (1 % oxygen) led to a decrease in ellipticine toxicity. Such a lower sensitivity of cells to ellipticine correlates with a decrease in the formation of ellipticine-derived DNA adducts in these cells. Using Western blotting, the expression of CYP1A1, 1B1, 3A4, thyroid peroxidase (TPO), cyclooxygenase-1 (COX-1) an
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cytochrome b5 increases cytochrome p450 3a4 mediated activation of anticancer drug ellipticine to 13 hydroxyellipticine whose covalent binding to dna is elevated by sulfotransferases and n o acetyltransferases
Chemical Research in Toxicology, 2012Co-Authors: Marie Stiborová, Michaela Moserová, Rene Kizek, Radek Indra, Věra Cerna, Martina Rupertova, Vaclav Martinek, Tomas Eckschlager, Eva FreiAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (P450)- and/or peroxidase-mediated activation in target tissues. The P450 3A4 enzyme oxidizes ellipticine to five metabolites, mainly to 13-hydroxy- and 12-hydroxyellipticine, the metabolites responsible for the formation of ellipticine-13-ylium and ellipticine-12-ylium ions that generate covalent DNA adducts. Cytochrome b5 alters the ratio of ellipticine metabolites formed by P450 3A4. While the amounts of the detoxication metabolites (7-hydroxy- and 9-hydroxyellipticine) were not changed with added cytochrome b5, 12-hydroxy- and 13-hydroxyellipticine, and ellipticine N2-oxide increased considerably. The P450 3A4-mediated oxidation of ellipticine was significantly changed only by holo-cytochrome b5, while apo-cytochrome b5 without heme or Mn-cytochrome b5 had no such effect. The change in amounts of metabolites resulted in an increased formation of covalent ellipticine-DNA adducts, o...
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Cytochrome b5 Increases Cytochrome P450 3A4-Mediated Activation of Anticancer Drug Ellipticine to 13-Hydroxyellipticine Whose Covalent Binding to DNA Is Elevated by Sulfotransferases and N,O-Acetyltransferases
2012Co-Authors: Marie Stiborová, Radek Indra, Tomas Eckschlager, Michaela Moserová, Věra Černá, Martina Rupertová, Václav Martínek, René Kizek, Eva FreiAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (P450)- and/or peroxidase-mediated activation in target tissues. The P450 3A4 enzyme oxidizes ellipticine to five metabolites, mainly to 13-hydroxy- and 12-hydroxyellipticine, the metabolites responsible for the formation of ellipticine-13-ylium and ellipticine-12-ylium ions that generate covalent DNA adducts. Cytochrome b5 alters the ratio of ellipticine metabolites formed by P450 3A4. While the amounts of the detoxication metabolites (7-hydroxy- and 9-hydroxyellipticine) were not changed with added cytochrome b5, 12-hydroxy- and 13-hydroxyellipticine, and ellipticine N2-oxide increased considerably. The P450 3A4-mediated oxidation of ellipticine was significantly changed only by holo-cytochrome b5, while apo-cytochrome b5 without heme or Mn-cytochrome b5 had no such effect. The change in amounts of metabolites resulted in an increased formation of covalent ellipticine-DNA adducts, one of the DNA-damaging mechanisms of ellipticine antitumor action. The amounts of 13-hydroxy- and 12-hydroxyellipticine formed by P450 3A4 were similar, but more than 7-fold higher levels of the adduct were formed by 13-hydroxyellipticine than by 12-hydroxyellipticine. The higher susceptibility of 13-hydroxyellipticine toward heterolytic dissociation to ellipticine-13-ylium in comparison to dissociation of 12-hydroxyellipticine to ellipticine-12-ylium, determined by quantum chemical calculations, explains this phenomenon. The amounts of the 13-hydroxyellipticine-derived DNA adduct significantly increased upon reaction of 13-hydroxyellipticine with either 3′-phosphoadenosine-5′-phosphosulfate or acetyl-CoA catalyzed by human sulfotransferases 1A1, 1A2, 1A3, and 2A1, or N,O-acetyltransferases 1 and 2. The calculated reaction free energies of heterolysis of the sulfate and acetate esters are by 10–17 kcal/mol more favorable than the energy of hydrolysis of 13-hydroxyellipticine, which could explain the experimental data
Radek Indra - One of the best experts on this subject based on the ideXlab platform.
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cytochrome b5 increases cytochrome p450 3a4 mediated activation of anticancer drug ellipticine to 13 hydroxyellipticine whose covalent binding to dna is elevated by sulfotransferases and n o acetyltransferases
Chemical Research in Toxicology, 2012Co-Authors: Marie Stiborová, Michaela Moserová, Rene Kizek, Radek Indra, Věra Cerna, Martina Rupertova, Vaclav Martinek, Tomas Eckschlager, Eva FreiAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (P450)- and/or peroxidase-mediated activation in target tissues. The P450 3A4 enzyme oxidizes ellipticine to five metabolites, mainly to 13-hydroxy- and 12-hydroxyellipticine, the metabolites responsible for the formation of ellipticine-13-ylium and ellipticine-12-ylium ions that generate covalent DNA adducts. Cytochrome b5 alters the ratio of ellipticine metabolites formed by P450 3A4. While the amounts of the detoxication metabolites (7-hydroxy- and 9-hydroxyellipticine) were not changed with added cytochrome b5, 12-hydroxy- and 13-hydroxyellipticine, and ellipticine N2-oxide increased considerably. The P450 3A4-mediated oxidation of ellipticine was significantly changed only by holo-cytochrome b5, while apo-cytochrome b5 without heme or Mn-cytochrome b5 had no such effect. The change in amounts of metabolites resulted in an increased formation of covalent ellipticine-DNA adducts, o...
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Cytochrome b5 Increases Cytochrome P450 3A4-Mediated Activation of Anticancer Drug Ellipticine to 13-Hydroxyellipticine Whose Covalent Binding to DNA Is Elevated by Sulfotransferases and N,O-Acetyltransferases
2012Co-Authors: Marie Stiborová, Radek Indra, Tomas Eckschlager, Michaela Moserová, Věra Černá, Martina Rupertová, Václav Martínek, René Kizek, Eva FreiAbstract:The Antineoplastic Alkaloid ellipticine is a prodrug, whose pharmacological efficiency is dependent on its cytochrome P450 (P450)- and/or peroxidase-mediated activation in target tissues. The P450 3A4 enzyme oxidizes ellipticine to five metabolites, mainly to 13-hydroxy- and 12-hydroxyellipticine, the metabolites responsible for the formation of ellipticine-13-ylium and ellipticine-12-ylium ions that generate covalent DNA adducts. Cytochrome b5 alters the ratio of ellipticine metabolites formed by P450 3A4. While the amounts of the detoxication metabolites (7-hydroxy- and 9-hydroxyellipticine) were not changed with added cytochrome b5, 12-hydroxy- and 13-hydroxyellipticine, and ellipticine N2-oxide increased considerably. The P450 3A4-mediated oxidation of ellipticine was significantly changed only by holo-cytochrome b5, while apo-cytochrome b5 without heme or Mn-cytochrome b5 had no such effect. The change in amounts of metabolites resulted in an increased formation of covalent ellipticine-DNA adducts, one of the DNA-damaging mechanisms of ellipticine antitumor action. The amounts of 13-hydroxy- and 12-hydroxyellipticine formed by P450 3A4 were similar, but more than 7-fold higher levels of the adduct were formed by 13-hydroxyellipticine than by 12-hydroxyellipticine. The higher susceptibility of 13-hydroxyellipticine toward heterolytic dissociation to ellipticine-13-ylium in comparison to dissociation of 12-hydroxyellipticine to ellipticine-12-ylium, determined by quantum chemical calculations, explains this phenomenon. The amounts of the 13-hydroxyellipticine-derived DNA adduct significantly increased upon reaction of 13-hydroxyellipticine with either 3′-phosphoadenosine-5′-phosphosulfate or acetyl-CoA catalyzed by human sulfotransferases 1A1, 1A2, 1A3, and 2A1, or N,O-acetyltransferases 1 and 2. The calculated reaction free energies of heterolysis of the sulfate and acetate esters are by 10–17 kcal/mol more favorable than the energy of hydrolysis of 13-hydroxyellipticine, which could explain the experimental data
