Advertisement

Cytochrome P450 dependent xenobiotic activation by physiological hydroperoxides in intact hepatocytes

  • M. R. Anari
  • S. Khan
  • S. D. Jatoe
  • P. J. O’Brien
Article

Summary

Xenobiotic metabolic activation by intact hepatocytes was recently shown to be enhanced by the addition of nontoxic concentrations oft-butyl hydroperoxide and prevented by cytochrome P450 inhibitors (1). Furthermore, H2O2 (Km=103 μM) was found to be highly effective in supporting the human microsomal CYP1A2 catalyzed metabolic activation of the heterocyclic aromatic amine 2-amino-3-methylimidazo (4,5-f) quinoline (IQ) to mutagenic metabolites and the DNA adduct formed was the same as that formed by the mixed-function oxidase catalyzed activation system (2). In the following, it is shown that the cytotoxicity of other xenobiotics including carcinogenic arylamines and their N-hydroxyarylamine metabolites were markedly enhanced by hydroperoxide addition but not in the presence of cytochrome P450 inhibitors. The CYP1A2 dependent O-demethylation of methoxyresorufin in 3-methylcholanthrene induced hepatocytes was also markedly enhanced when intracellular H2O2 was generated by the mitochondrial monoamine oxidase (MAO) substrates tyramine or kynurenamine. Linoleic acid hydroperoxide also dramatically enhanced the cytotoxicity of phenelzine towards isolated hepatocytes and the microsomal metabolism of phenelzine to form ethylbenzene. The P450 inhibitors phenylimidazole, benzylimidazole prevented the metabolic activation of phenelzine but not lipid peroxidation. These results suggest that linoleic acid hydroperoxide can activate hydrazines via a cytochrome P450 peroxidase catalyzed one electron oxidation to form highly cytotoxic reactive intermediates. Furthermore, increased hydrogen peroxide formation, e.g. as a result of oxidative stress, would also be expected to enhance the metabolic activation of carcinogenic arylamines via the peroxygenase function of CYP1A2.

Keywords

Cytochrome P450 peroxidase hydrazines amines carcinogens 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Anari M.R., Khan S., Liu Z.C., O’Brien P.J. (1995): Cytochrome P450 peroxidase/peroxygenase mediated xenobiotic metabolic activation and cytotoxicity in isolated hepatocytes. Chem. Res. Toxicol., 8, 997–1004.CrossRefPubMedGoogle Scholar
  2. 2.
    Anari M.R., Josephy P.D., Henrey T., O’Brien P.J. (1997): Hydrogen peroxide supports human and rat cytochrome P450 1A2-catalyzed 2-amino-3-methyl imidazo [4,5-f] quinoline bioactivation to mutagenic metabolites: significance of cytochrome P450 peroxygenase. Chem. Res. Toxicol., 10, 528–534.CrossRefGoogle Scholar
  3. 3.
    O’Brien P.J. (1978): Hydroperoxides and superoxides in microsomal oxidations. Pharmacol. Ther., A2, 517–537.Google Scholar
  4. 4.
    Hycay E.G., O’Brien P.J. (1971): Cytochrome P450 as a microsomal peroxidase utilizing a lipid peroxide substrate. Arch. Biochem. Biophys., 147, 14–27.CrossRefGoogle Scholar
  5. 5.
    Estabrook R.W., Martin-Wixtrom C., Saeki Y., Renneberg R., Hildebrandt A., Werringloer J. (1994): The peroxidatic function of liver microsomal cytochrome P450: comparison of hydrogen peroxide and NADPH catalysed N-demethylation reactions. Xenobiotica, 14, 87–104.CrossRefGoogle Scholar
  6. 6.
    Penneberg R., Scheller F., Ruckpaul K., Pirritz J., Mohr P. (1978): NADPH and H2O2-dependent reactions of cytochrome P450LM compared with peroxidase catalysis. FEBS Lett., 96, 349–353.CrossRefGoogle Scholar
  7. 7.
    Coon M.J., Vaz A.D.N., Bestervelt L.L. (1996): Peroxidative reactions of diversozymes. FASEB J., 10, 428–434.PubMedGoogle Scholar
  8. 8.
    Hecker M., Ullrich V. (1989): On the mechanism of prostacyclin and thromoboxane A2 biosynthesis. J. Biol. Chem., 264, 141–150.PubMedGoogle Scholar
  9. 9.
    Song W.C., Brash A.R. (1991): Purification of an allene oxide synthase and identification of the enzyme as a cytochrome P450. Science, 253, 731–734.CrossRefGoogle Scholar
  10. 10.
    Matsui K., Shibutari M., Hase T., Kajurara T. (1996): Fatty acid hydroperoxide lyase is a cytochrome P450 (CYP74B). FEBS Lett., 394, 21–24.CrossRefPubMedGoogle Scholar
  11. 11.
    Shimizu T., Murakami Y., Hatano T. (1994): Gln and Thr mutation of cytochrome P450 1A2 remarkably enhance homolytic O−O cleavage of alkyl hydroperoxides. J. Biol. Chem., 269, 13296–13304.PubMedGoogle Scholar
  12. 12.
    Reed C.J., DeMatteis F. (1989): Cumene hydroperoxide-dependent oxidation of tetramethyl phenylenediamine and 7-ethoxycoumarin by cytochrome P-450. Biochem. J., 261, 793–800.PubMedGoogle Scholar
  13. 13.
    Jatoe S.D., Khan S., O’Brien P.J. (1991): Molecular cytotoxic mechanisms of carcinogenic arylamines. Prog. Pharmacol. Clin. Pharmacol., 8, 245–253.Google Scholar
  14. 14.
    Moldeus P., Hogberg J., Orrenius S. (1978): Isolation and use of liver cells. Methods Enzymol., 52, 60–70.CrossRefPubMedGoogle Scholar
  15. 15.
    Kreamer B.L., Staecker J.L., Saurada N., Sattler G.L., Hsia M.T.S., Pitot H.C. (1986): Use of speed, isodensity Percoll centrifugation method to increase the viability of isolated rat hepatocyte preparations. In vitro cell. Dev. Biol., 22, 201–211.CrossRefGoogle Scholar
  16. 16.
    Reed D.J., Balson J.R., Beaty B.W., Brodie N., Potter D.W. (1980): High performance liquid chromatography analysis of nanomole levels of glutathione, glutathione disulfide, and related thiols and disulfides. Anal. Biochem., 106, 55–62.CrossRefPubMedGoogle Scholar
  17. 17.
    Ortiz de Montellano P.R., Augusto O., Viola F., Kunze K.L. (1983): Carbon radicals in the metabolism of alkyl hydrazines. J. Biol. Chem., 258, 8623–8629.PubMedGoogle Scholar
  18. 18.
    Hanioka N., Jinno H., Takahashi A., Nakano K., Yoda R., Nishimura T.M. (1995): Interaction of tetrachloroethylene with rat hepatic microsomal P450-dependent monooxygenases. Xenobiotica, 25, 151–165.CrossRefPubMedGoogle Scholar
  19. 19.
    Hammons G.J., Milton D., Stepps K. Guengerich F.P., Tukey R.H., Kadlubar F.F. (1997): Metabolism of carcinogenic heterocyclic and aromatic amines by recombinant human cytochrome P450 enzymes. Carcinogenesis, 18, 851–854.CrossRefPubMedGoogle Scholar
  20. 20.
    Albano E., Comoglio A., Clot P., Iannone A., Ingelman Sundberg M. (1995): Activation of alkylhydrazines for free radical intermediates by ethanol-inducible cytochrome P-4502E1 (CYP2E1). Biochim. Biophys. Acta, 1243, 414–420.PubMedGoogle Scholar
  21. 21.
    Ortiz de Montellano P.R., Watanabe M.D. (1986): Free radical pathways in the in vitro hepatic metabolism of phenelzine. Mol. Pharmacol., 31, 213–219.Google Scholar
  22. 22.
    Wener P., Cohen G. (1991): Intramitochondrial formation of oxidised glutathione during the oxidation of benzylamine by monoamine oxidases. FEBS Lett., 280, 44–46.CrossRefGoogle Scholar
  23. 23.
    Jones D.P., Eklow L., Thor H., Orrenius S. (1981): Metabolism of hydrogen peroxide in isolated hepatocytes: relative contributions of catalase and glutathione peroxidase in decomposition of endogenously generated H2O2. Arch. Biochem. Biophys., 210, 505–516.CrossRefPubMedGoogle Scholar

Copyright information

© Springer-Verlag 1997

Authors and Affiliations

  • M. R. Anari
    • 1
  • S. Khan
    • 1
  • S. D. Jatoe
    • 1
  • P. J. O’Brien
    • 1
  1. 1.Faculty of PharmacyUniversity of TorontoTorontoCanada

Personalised recommendations