2-nitroanisole OR C005328 Dotaz Zobrazit nápovědu
- MeSH
- financování organizované MeSH
- Publikační typ
- abstrakty MeSH
- MeSH
- financování organizované MeSH
- Publikační typ
- abstrakty MeSH
OBJECTIVES: 2-Nitrophenol (2-NP) is the major detoxification metabolite of an important industrial pollutant and a potent carcinogen, 2-nitroanisole (2-NA). Characterization of the products of 2-NP metabolism by rat hepatic microsomes containing cytochromes P450 (CYPs) and identification of the major CYP enzymes participating in this process are aims of this study. METHODS: HPLC with UV detection was employed for the separation and characterization of 2-NP metabolites. Inducers and inhibitors of CYPs and rat recombinant CYPs were used to characterize the enzymes participating in 2-NP oxidation. RESULTS: Rat hepatic microsomes oxidize 2-NP to its hydroxylated metabolite, 2,5-dihydroxynitrobenzene (2,5-DNB). No nitroreductive metabolism leading to the formation of o-aminophenol was evident when using rat hepatic microsomes. Selective CYP inhibitors and hepatic microsomes of rats pre-treated with specific CYP inducers were used to characterize CYPs oxidizing 2-NP in rat livers. Based on these studies, we attribute most of 2-NP oxidation in rat liver to CYP2E1 and 3A, followed by CYP2D and 2C. Among recombinant rat CYP enzymes tested in this study, CYP2E1 and 2C11 were the most effective enzymes oxidizing 2-NP. Oxidation of 2-NP by rat CYP2E1 exhibits the Michaelis-Menten kinetics, having the Km value of 0.35 mM. CONCLUSION: The results found in this study, the first report on the metabolism of 2-NP by rat hepatic microsomes and rat CYP enzymes, demonstrate that CYP2E1 is the major enzyme oxidizing this compound in rat liver.
- MeSH
- anisoly metabolismus MeSH
- inhibiční koncentrace 50 MeSH
- inhibitory cytochromu P450 MeSH
- jaterní mikrozomy enzymologie metabolismus MeSH
- kinetika MeSH
- krysa rodu rattus MeSH
- lidé MeSH
- nitrofenoly metabolismus MeSH
- oxidace-redukce MeSH
- rekombinantní proteiny antagonisté a inhibitory metabolismus MeSH
- systém (enzymů) cytochromů P-450 metabolismus MeSH
- ultrafialové záření MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- karcinogeny chemie MeSH
2-Nitrophenol (2-NP) is the major detoxification metabolite of an important industrial pollutant and a potent carcinogen, 2-nitroanisole (2-NA). Here, we characterized the product of 2-NP metabolism catalyzed by human, rat, rabbit and mouse hepatic microsomes containing cytochromes P450 (CYPs) and identified the major human CYP enzymes participating in this process. The 2-NP metabolite was characterized by mass spectrometry and co-chromatography on HPLC with a synthetic standard, 2,5-dihydroxynitrobenzene (2,5-DNB) to be 2,5-DNB. No nitroreductive metabolism leading to the formation of N-(2-hydroxyphenyl)hydroxylamine or o-aminophenol was evident by all tested hepatic microsomes. Likewise, no DNA binding of 2-NP metabolite(s) measured with the 32P-postlabeling technique was detectable in hepatic microsomes. Therefore, hepatic microsomal CYP enzymes participate in 2-NP metabolism that does not lead to its activation to species binding to DNA. Selective inhibitors of human CYPs were used to characterize CYPs oxidizing 2-NP in human livers. Based on these inhibitory studies, we attribute most of 2-NP oxidation in human liver to CYP2E1, 3A4, 2A6, 2C and 2D6. Among recombinant human CYP enzymes tested in this study, CYP2E1, 2A6 and 2B6 were the most effective enzymes oxidizing 2-NP. Oxidation of 2-NP by human CYP2E1 exhibits the Michaelis-Menten kinetics, having the Km value of 0.21 mM. The results found in this study, the first report on the metabolism of 2-NP by human hepatic microsomes and human CYP enzymes, demonstrate that CYP2E1 is the major enzyme oxidizing this compound in human.
- MeSH
- cytosol analýza MeSH
- dusíkaté sloučeniny metabolismus toxicita MeSH
- hodnocení rizik MeSH
- játra enzymologie metabolismus MeSH
- karcinogeny životního prostředí MeSH
- látky znečišťující životní prostředí MeSH
- lidé MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- srovnávací studie MeSH
N-(2-Methoxyphenyl)hydroxylamine is a component in the human metabolism of two industrial and environmental pollutants and bladder carcinogens, viz. 2-methoxyaniline (o-anisidine) and 2-methoxynitrobenzene (o-nitroanisole), and it is responsible for their genotoxicity. Besides its capability to form three deoxyguanosine adducts in DNA, N-(2-methoxyphenyl)-hydroxylamine is also further metabolized by hepatic microsomal enzymes. To investigate its metabolism by human hepatic microsomes and to identify the major microsomal enzymes involved in this process are the aims of this study. N-(2-Methoxyphenyl)hydroxylamine is metabolized by human hepatic microsomes predominantly to o-anisidine, one of the parent carcinogens from which N-(2-methoxyphenyl)hydroxylamine is formed, while o-aminophenol and two N-(2-methoxyphenyl)hydroxylamine metabolites, whose exact structures have not been identified as yet, are minor products. Selective inhibitors of microsomal CYPs, NADPH:CYP reductase and NADH:cytochrome-b(5) reductase were used to characterize human liver microsomal enzymes reducing N-(2-methoxyphenyl)hydroxylamine to o-anisidine. Based on these studies, we attribute the main activity for this metabolic step in human liver to CYP3A4, 2E1 and 2C (more than 90%). The enzymes CYP2D6 and 2A6 also partake in this N-(2-methoxyphenyl)hydroxylamine metabolism in human liver, but only to ∼6%. Among the human recombinant CYP enzymes tested in this study, human CYP2E1, followed by CYP3A4, 1A2, 2B6 and 2D6, were the most efficient enzymes metabolizing N-(2-methoxyphenyl)hydroxylamine to o-anisidine. The results found in this study indicate that genotoxicity of N-(2-methoxyphenyl)hydroxylamine is dictated by its spontaneous decomposition to nitrenium/carbenium ions generating DNA adducts, and by its susceptibility to metabolism by CYP enzymes.
- MeSH
- adukty DNA metabolismus MeSH
- aniliny metabolismus MeSH
- anisoly metabolismus MeSH
- hydroxylaminy metabolismus MeSH
- jaterní mikrozomy metabolismus MeSH
- karcinogeny metabolismus MeSH
- krysa rodu rattus MeSH
- látky znečišťující životní prostředí metabolismus MeSH
- lidé MeSH
- potkani Wistar MeSH
- systém (enzymů) cytochromů P-450 metabolismus MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- lidé MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
OBJECTIVES: N-(2-methoxyphenyl)hydroxylamine is a human metabolite of two industrial and environmental pollutants and bladder carcinogens 2-methoxyaniline (o-anisidine) and 2-methoxynitrobenzene (o-nitroanisole). Metabolism of N-(2-methoxyphenyl)hydroxylamine by rat hepatic microsomes and identification of the major microsomal enzymes participating in this process are aims of this study. METHODS: HPLC with UV detection was employed for the separation of N-(2-methoxyphenyl)hydroxylamine metabolites. Inducers and inhibitors of microsomal enzymes and rat recombinant CYPs were used to characterize the enzymes participating in N-(2-methoxyphenyl)hydroxylamine metabolism. RESULTS: N-(2-methoxyphenyl)hydroxylamine is metabolized by rat hepatic microsomes predominantly to o-anisidine, the parent carcinogen from which N-(2-methoxyphenyl)hydroxylamine is formed, while o-aminophenol and two N-(2-methoxyphenyl)hydroxylamine metabolites, whose exact structures have not been identified as yet, are minor products. Selective inhibitors of microsomal CYPs, NADPH:CYP reductase and NADH:cytochrome b5 reductase and hepatic microsomes of rats pre-treated with specific inducers of CYPs and NADPH:CYP reductase were used to characterize rat liver microsomal enzymes reducing N-(2-methoxyphenyl)hydroxylamine to o-anisidine. Based on these studies, we attribute most of N-(2-methoxyphenyl)hydroxylamine metabolism to o-anisidine in rat liver to CYP2C, followed by CYP2E1, 2D and 2A. Among recombinant rat CYP enzymes tested in this study, rat CYP2C11 and 2E1, followed by CYP2A2, 2D1/2, 2C12, 3A1/2 and 1A1/2 were the most efficient enzymes metabolizing N-(2-methoxyphenyl)hydroxylamine to o-anisidine. CONCLUSION: The results found in this study, the first report on the reduction of N-(2-methoxyphenyl)hydroxylamine by rat CYP enzymes, demonstrate that CYP2C, followed by CYP2E1, 2D and 2A are the major enzymes participating in this process in rat liver.
- MeSH
- aniliny metabolismus MeSH
- anisoly metabolismus MeSH
- aromatické hydroxylasy fyziologie MeSH
- cytochrom P-450 CYP2E1 fyziologie MeSH
- hydroxylamin metabolismus MeSH
- jaterní mikrozomy metabolismus MeSH
- karcinogeny metabolismus MeSH
- krysa rodu rattus MeSH
- látky znečišťující životní prostředí metabolismus MeSH
- modely u zvířat MeSH
- oxidace-redukce MeSH
- potkani Wistar MeSH
- steroidhydroxylasy fyziologie MeSH
- systém (enzymů) cytochromů P-450 fyziologie MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- adukty DNA MeSH
- anisoly škodlivé účinky MeSH
- cytosol enzymologie MeSH
- DNA metabolismus MeSH
- finanční podpora výzkumu jako téma MeSH
- izotopy fosforu diagnostické užití MeSH
- karcinogeny farmakokinetika farmakologie škodlivé účinky MeSH
- lidé MeSH
- xanthinoxidasa metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
