Rat cytochromes P450 (CYP) specifically contribute to the reductive bioactivation of AQ4N, an alkylaminoanthraquinone-di-N-oxide anticancer prodrug

S M Raleigh, E Wanogho, M D Burke, L H Patterson

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Abstract

1. The bioreductive activation of the alkylaminoanthraquinone di-N-oxide prodrug AQ4N has been characterized in rat hepatic tissue using HPLC. 2. AQ4N was shown to be metabolized to two products, namely AQM, the two electron reduced mono-N-oxide, and AQ4, the four electron reduced active cytotoxic agent. 3. Metabolism was shown to occur in microsomes with an apparent Km = 30.29 microM and Vmax = 1.05 nmol/mg/min. 4. Bioreduction was dependent on anaerobic conditions and the presence of the reduced cofactor NADPH. Ketoconazole (100 microM) and carbon monoxide both inhibited AQ4N metabolism inferring a role for cytochrome P450 (CYP). 5. Microsomes from phenobarbitone and isoniazid-pretreated animals significantly (p < 0.05) enhanced the formation of AQ4 from AQ4N indicating a role for CYP2B and 2E respectively. The involvement of both CYP2B and 2E was confirmed by the use of CYP-specific inhibitors. 6. In conclusion, the involvement of rat hepatic CYP in the reductive bioactivation of the novel antitumour prodrug AQ4N has been established in detail for the first time. These findings highlight an important interspecies difference between the metabolism of AQ4N in rat and man which was shown earlier to be mediated by CYP3A enzymes. The pharmacological significance of this is discussed.

Original languageEnglish
Pages (from-to)1115-1122
Number of pages8
JournalXenobiotica; the fate of foreign compounds in biological systems
Volume29
Issue number11
DOIs
Publication statusPublished - Nov 1999

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Prodrugs
Cytochrome P-450 Enzyme System
Oxides
Rats
Metabolism
Microsomes
Electrons
Cytochrome P-450 CYP3A
Ketoconazole
Liver
Isoniazid
Cytotoxins
Carbon Monoxide
Phenobarbital
NADP
AQ4N
Animals
Chemical activation
High Pressure Liquid Chromatography
Pharmacology

Keywords

  • Animals
  • Anthraquinones
  • Antineoplastic Agents
  • Biotransformation
  • Chromatography, High Pressure Liquid
  • Cytochrome P-450 Enzyme System
  • Kinetics
  • Male
  • Oxidation-Reduction
  • Prodrugs
  • Proteins
  • Rats
  • Rats, Sprague-Dawley
  • Subcellular Fractions
  • Journal Article
  • Research Support, Non-U.S. Gov't

Cite this

@article{18fbd4d1a1974d46ab3a3140b277e380,
title = "Rat cytochromes P450 (CYP) specifically contribute to the reductive bioactivation of AQ4N, an alkylaminoanthraquinone-di-N-oxide anticancer prodrug",
abstract = "1. The bioreductive activation of the alkylaminoanthraquinone di-N-oxide prodrug AQ4N has been characterized in rat hepatic tissue using HPLC. 2. AQ4N was shown to be metabolized to two products, namely AQM, the two electron reduced mono-N-oxide, and AQ4, the four electron reduced active cytotoxic agent. 3. Metabolism was shown to occur in microsomes with an apparent Km = 30.29 microM and Vmax = 1.05 nmol/mg/min. 4. Bioreduction was dependent on anaerobic conditions and the presence of the reduced cofactor NADPH. Ketoconazole (100 microM) and carbon monoxide both inhibited AQ4N metabolism inferring a role for cytochrome P450 (CYP). 5. Microsomes from phenobarbitone and isoniazid-pretreated animals significantly (p < 0.05) enhanced the formation of AQ4 from AQ4N indicating a role for CYP2B and 2E respectively. The involvement of both CYP2B and 2E was confirmed by the use of CYP-specific inhibitors. 6. In conclusion, the involvement of rat hepatic CYP in the reductive bioactivation of the novel antitumour prodrug AQ4N has been established in detail for the first time. These findings highlight an important interspecies difference between the metabolism of AQ4N in rat and man which was shown earlier to be mediated by CYP3A enzymes. The pharmacological significance of this is discussed.",
keywords = "Animals, Anthraquinones, Antineoplastic Agents, Biotransformation, Chromatography, High Pressure Liquid, Cytochrome P-450 Enzyme System, Kinetics, Male, Oxidation-Reduction, Prodrugs, Proteins, Rats, Rats, Sprague-Dawley, Subcellular Fractions, Journal Article, Research Support, Non-U.S. Gov't",
author = "Raleigh, {S M} and E Wanogho and Burke, {M D} and Patterson, {L H}",
year = "1999",
month = "11",
doi = "10.1080/004982599237994",
language = "English",
volume = "29",
pages = "1115--1122",
journal = "Xenobiotica",
issn = "0049-8254",
publisher = "Taylor & Francis",
number = "11",

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TY - JOUR

T1 - Rat cytochromes P450 (CYP) specifically contribute to the reductive bioactivation of AQ4N, an alkylaminoanthraquinone-di-N-oxide anticancer prodrug

AU - Raleigh, S M

AU - Wanogho, E

AU - Burke, M D

AU - Patterson, L H

PY - 1999/11

Y1 - 1999/11

N2 - 1. The bioreductive activation of the alkylaminoanthraquinone di-N-oxide prodrug AQ4N has been characterized in rat hepatic tissue using HPLC. 2. AQ4N was shown to be metabolized to two products, namely AQM, the two electron reduced mono-N-oxide, and AQ4, the four electron reduced active cytotoxic agent. 3. Metabolism was shown to occur in microsomes with an apparent Km = 30.29 microM and Vmax = 1.05 nmol/mg/min. 4. Bioreduction was dependent on anaerobic conditions and the presence of the reduced cofactor NADPH. Ketoconazole (100 microM) and carbon monoxide both inhibited AQ4N metabolism inferring a role for cytochrome P450 (CYP). 5. Microsomes from phenobarbitone and isoniazid-pretreated animals significantly (p < 0.05) enhanced the formation of AQ4 from AQ4N indicating a role for CYP2B and 2E respectively. The involvement of both CYP2B and 2E was confirmed by the use of CYP-specific inhibitors. 6. In conclusion, the involvement of rat hepatic CYP in the reductive bioactivation of the novel antitumour prodrug AQ4N has been established in detail for the first time. These findings highlight an important interspecies difference between the metabolism of AQ4N in rat and man which was shown earlier to be mediated by CYP3A enzymes. The pharmacological significance of this is discussed.

AB - 1. The bioreductive activation of the alkylaminoanthraquinone di-N-oxide prodrug AQ4N has been characterized in rat hepatic tissue using HPLC. 2. AQ4N was shown to be metabolized to two products, namely AQM, the two electron reduced mono-N-oxide, and AQ4, the four electron reduced active cytotoxic agent. 3. Metabolism was shown to occur in microsomes with an apparent Km = 30.29 microM and Vmax = 1.05 nmol/mg/min. 4. Bioreduction was dependent on anaerobic conditions and the presence of the reduced cofactor NADPH. Ketoconazole (100 microM) and carbon monoxide both inhibited AQ4N metabolism inferring a role for cytochrome P450 (CYP). 5. Microsomes from phenobarbitone and isoniazid-pretreated animals significantly (p < 0.05) enhanced the formation of AQ4 from AQ4N indicating a role for CYP2B and 2E respectively. The involvement of both CYP2B and 2E was confirmed by the use of CYP-specific inhibitors. 6. In conclusion, the involvement of rat hepatic CYP in the reductive bioactivation of the novel antitumour prodrug AQ4N has been established in detail for the first time. These findings highlight an important interspecies difference between the metabolism of AQ4N in rat and man which was shown earlier to be mediated by CYP3A enzymes. The pharmacological significance of this is discussed.

KW - Animals

KW - Anthraquinones

KW - Antineoplastic Agents

KW - Biotransformation

KW - Chromatography, High Pressure Liquid

KW - Cytochrome P-450 Enzyme System

KW - Kinetics

KW - Male

KW - Oxidation-Reduction

KW - Prodrugs

KW - Proteins

KW - Rats

KW - Rats, Sprague-Dawley

KW - Subcellular Fractions

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1080/004982599237994

DO - 10.1080/004982599237994

M3 - Article

VL - 29

SP - 1115

EP - 1122

JO - Xenobiotica

JF - Xenobiotica

SN - 0049-8254

IS - 11

ER -