Comparative metabolism of the tobacco-related carcinogens benzo[a]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol, and N'-nitrosonornicotine in human hepatic microsomes

Marianne E. Staretz, Sharon E. Murphy, Christopher J. Patten, Maria G. Nunes, Werner Koehl, Shantu Amin, Leeann A. Koenig, F. Peter Guengerich, Stephen S. Hecht

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Abstract

We compared the metabolism in human hepatic microsomes of three tobacco smoke carcinogens believed to be involved in the induction of cancer in humans: benzo[a]pyrene (BaP),4-(methylnitrosamino)-1(3-pyridyl)-1-butanone (NNK), and N'-nitrosonomicotine (NNN). The metabolism of 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a major metabolite of NNK, was also investigated. Although the metabolism of some of these compounds by human enzymes or tissue preparations has been previously examined in some studies, they have never been compared in the same human hepatic samples. Moreover, there have been no previous reports of NNAL metabolism by human tissues or enzymes. The tritium-labeled carcinogens (3 μM) were incubated with 10 different human hepatic microsomal preparations and cofactors for 10-20 min, and the products were analyzed by radioflow HPLC. NNN was the best substrate for oxidative metabolism, with the 5'- hydroxylation pathway being the predominant one observed (mean ± SD = 31 ± 17 pmol/min/mg protein). α-Hydroxylation of NNK by the methylene and methyl hydroxylation metabolic activation pathways was the next fastest reaction, with rates of 3.1 ± 1.9 and 3.3 ± 1.1 pmol/min/mg protein, respectively. Metabolism of BaP resulted in the formation of dihydrodiols and phenols; trans-7,8-dihydro-7,8-dihydroxy-BaP, its major proximate carcinogen, was formed at a rate of 1.1 ± 0.61 pmol/min/mg protein. α-Hydroxylation of NNAL proceeded at a rate of 0.53 ± 0.26 pmol/min/mg protein. The results of this study demonstrate that human hepatic microsomes metabolize all of these tobacco carcinogens resulting in a substantial stream of electrophilic intermediates capable of binding to DNA. The relative rates of oxidative metabolism to electrophiles or their precursors were NNN > NNK > BaP > NNAL. Correlation studies indicated involvement of cytochrome P4502A6 in the 5'- hydroxylation of NNN and cytochrome P4503A4 in the α-methylene hydroxylation and pyridine-N-oxidation of NNK and NNAL. The results of this study provide the first data on the comparative metabolism of these important carcinogens in human hepatic microsomes.

Original languageEnglish (US)
Pages (from-to)154-162
Number of pages9
JournalDrug Metabolism and Disposition
Volume25
Issue number2
StatePublished - Feb 1 1997

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N'-nitrosonornicotine
Benzo(a)pyrene
Microsomes
Carcinogens
Tobacco
Hydroxylation
Liver
Cytochromes
Proteins
Tritium
4-(methylnitrosamino)-1-(3-pyridyl)-1-butan-1-ol
4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone
Phenols
Enzymes
Metabolic Networks and Pathways

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Pharmaceutical Science

Cite this

Staretz, Marianne E. ; Murphy, Sharon E. ; Patten, Christopher J. ; Nunes, Maria G. ; Koehl, Werner ; Amin, Shantu ; Koenig, Leeann A. ; Guengerich, F. Peter ; Hecht, Stephen S. / Comparative metabolism of the tobacco-related carcinogens benzo[a]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol, and N'-nitrosonornicotine in human hepatic microsomes. In: Drug Metabolism and Disposition. 1997 ; Vol. 25, No. 2. pp. 154-162.
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abstract = "We compared the metabolism in human hepatic microsomes of three tobacco smoke carcinogens believed to be involved in the induction of cancer in humans: benzo[a]pyrene (BaP),4-(methylnitrosamino)-1(3-pyridyl)-1-butanone (NNK), and N'-nitrosonomicotine (NNN). The metabolism of 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a major metabolite of NNK, was also investigated. Although the metabolism of some of these compounds by human enzymes or tissue preparations has been previously examined in some studies, they have never been compared in the same human hepatic samples. Moreover, there have been no previous reports of NNAL metabolism by human tissues or enzymes. The tritium-labeled carcinogens (3 μM) were incubated with 10 different human hepatic microsomal preparations and cofactors for 10-20 min, and the products were analyzed by radioflow HPLC. NNN was the best substrate for oxidative metabolism, with the 5'- hydroxylation pathway being the predominant one observed (mean ± SD = 31 ± 17 pmol/min/mg protein). α-Hydroxylation of NNK by the methylene and methyl hydroxylation metabolic activation pathways was the next fastest reaction, with rates of 3.1 ± 1.9 and 3.3 ± 1.1 pmol/min/mg protein, respectively. Metabolism of BaP resulted in the formation of dihydrodiols and phenols; trans-7,8-dihydro-7,8-dihydroxy-BaP, its major proximate carcinogen, was formed at a rate of 1.1 ± 0.61 pmol/min/mg protein. α-Hydroxylation of NNAL proceeded at a rate of 0.53 ± 0.26 pmol/min/mg protein. The results of this study demonstrate that human hepatic microsomes metabolize all of these tobacco carcinogens resulting in a substantial stream of electrophilic intermediates capable of binding to DNA. The relative rates of oxidative metabolism to electrophiles or their precursors were NNN > NNK > BaP > NNAL. Correlation studies indicated involvement of cytochrome P4502A6 in the 5'- hydroxylation of NNN and cytochrome P4503A4 in the α-methylene hydroxylation and pyridine-N-oxidation of NNK and NNAL. The results of this study provide the first data on the comparative metabolism of these important carcinogens in human hepatic microsomes.",
author = "Staretz, {Marianne E.} and Murphy, {Sharon E.} and Patten, {Christopher J.} and Nunes, {Maria G.} and Werner Koehl and Shantu Amin and Koenig, {Leeann A.} and Guengerich, {F. Peter} and Hecht, {Stephen S.}",
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Comparative metabolism of the tobacco-related carcinogens benzo[a]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol, and N'-nitrosonornicotine in human hepatic microsomes. / Staretz, Marianne E.; Murphy, Sharon E.; Patten, Christopher J.; Nunes, Maria G.; Koehl, Werner; Amin, Shantu; Koenig, Leeann A.; Guengerich, F. Peter; Hecht, Stephen S.

In: Drug Metabolism and Disposition, Vol. 25, No. 2, 01.02.1997, p. 154-162.

Research output: Contribution to journalArticle

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T1 - Comparative metabolism of the tobacco-related carcinogens benzo[a]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol, and N'-nitrosonornicotine in human hepatic microsomes

AU - Staretz, Marianne E.

AU - Murphy, Sharon E.

AU - Patten, Christopher J.

AU - Nunes, Maria G.

AU - Koehl, Werner

AU - Amin, Shantu

AU - Koenig, Leeann A.

AU - Guengerich, F. Peter

AU - Hecht, Stephen S.

PY - 1997/2/1

Y1 - 1997/2/1

N2 - We compared the metabolism in human hepatic microsomes of three tobacco smoke carcinogens believed to be involved in the induction of cancer in humans: benzo[a]pyrene (BaP),4-(methylnitrosamino)-1(3-pyridyl)-1-butanone (NNK), and N'-nitrosonomicotine (NNN). The metabolism of 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a major metabolite of NNK, was also investigated. Although the metabolism of some of these compounds by human enzymes or tissue preparations has been previously examined in some studies, they have never been compared in the same human hepatic samples. Moreover, there have been no previous reports of NNAL metabolism by human tissues or enzymes. The tritium-labeled carcinogens (3 μM) were incubated with 10 different human hepatic microsomal preparations and cofactors for 10-20 min, and the products were analyzed by radioflow HPLC. NNN was the best substrate for oxidative metabolism, with the 5'- hydroxylation pathway being the predominant one observed (mean ± SD = 31 ± 17 pmol/min/mg protein). α-Hydroxylation of NNK by the methylene and methyl hydroxylation metabolic activation pathways was the next fastest reaction, with rates of 3.1 ± 1.9 and 3.3 ± 1.1 pmol/min/mg protein, respectively. Metabolism of BaP resulted in the formation of dihydrodiols and phenols; trans-7,8-dihydro-7,8-dihydroxy-BaP, its major proximate carcinogen, was formed at a rate of 1.1 ± 0.61 pmol/min/mg protein. α-Hydroxylation of NNAL proceeded at a rate of 0.53 ± 0.26 pmol/min/mg protein. The results of this study demonstrate that human hepatic microsomes metabolize all of these tobacco carcinogens resulting in a substantial stream of electrophilic intermediates capable of binding to DNA. The relative rates of oxidative metabolism to electrophiles or their precursors were NNN > NNK > BaP > NNAL. Correlation studies indicated involvement of cytochrome P4502A6 in the 5'- hydroxylation of NNN and cytochrome P4503A4 in the α-methylene hydroxylation and pyridine-N-oxidation of NNK and NNAL. The results of this study provide the first data on the comparative metabolism of these important carcinogens in human hepatic microsomes.

AB - We compared the metabolism in human hepatic microsomes of three tobacco smoke carcinogens believed to be involved in the induction of cancer in humans: benzo[a]pyrene (BaP),4-(methylnitrosamino)-1(3-pyridyl)-1-butanone (NNK), and N'-nitrosonomicotine (NNN). The metabolism of 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a major metabolite of NNK, was also investigated. Although the metabolism of some of these compounds by human enzymes or tissue preparations has been previously examined in some studies, they have never been compared in the same human hepatic samples. Moreover, there have been no previous reports of NNAL metabolism by human tissues or enzymes. The tritium-labeled carcinogens (3 μM) were incubated with 10 different human hepatic microsomal preparations and cofactors for 10-20 min, and the products were analyzed by radioflow HPLC. NNN was the best substrate for oxidative metabolism, with the 5'- hydroxylation pathway being the predominant one observed (mean ± SD = 31 ± 17 pmol/min/mg protein). α-Hydroxylation of NNK by the methylene and methyl hydroxylation metabolic activation pathways was the next fastest reaction, with rates of 3.1 ± 1.9 and 3.3 ± 1.1 pmol/min/mg protein, respectively. Metabolism of BaP resulted in the formation of dihydrodiols and phenols; trans-7,8-dihydro-7,8-dihydroxy-BaP, its major proximate carcinogen, was formed at a rate of 1.1 ± 0.61 pmol/min/mg protein. α-Hydroxylation of NNAL proceeded at a rate of 0.53 ± 0.26 pmol/min/mg protein. The results of this study demonstrate that human hepatic microsomes metabolize all of these tobacco carcinogens resulting in a substantial stream of electrophilic intermediates capable of binding to DNA. The relative rates of oxidative metabolism to electrophiles or their precursors were NNN > NNK > BaP > NNAL. Correlation studies indicated involvement of cytochrome P4502A6 in the 5'- hydroxylation of NNN and cytochrome P4503A4 in the α-methylene hydroxylation and pyridine-N-oxidation of NNK and NNAL. The results of this study provide the first data on the comparative metabolism of these important carcinogens in human hepatic microsomes.

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