Hypoxia diminishes the detoxification of the environmental mutagen benzo[a]pyrene

M.A.C. Schults, K. Sanen, R.W. Godschalk, J. Theys, F.J. van Schooten, R.K. Chiu

Research output: Contribution to journalArticleAcademicpeer-review

4 Citations (Scopus)

Abstract

Hypoxia promotes genetic instability and is therefore an important factor in carcinogenesis. We have previously shown that activation of the hypoxia responsive transcription factor HIFalpha can enhance the mutagenic phenotype induced by the environmental mutagen benzo[a]pyrene (BaP). To further elucidate the mechanism behind the ability of hypoxia to increase mutagenicity of carcinogens, we examined the activation and detoxification of BaP under hypoxic conditions. To this end, the human lung carcinoma cell line A549 was treated with BaP under 20%, 5% or 0.2% oxygen for 18h and alterations in BaP metabolism were assayed. First, BaP-induced expression of key metabolic enzymes was analysed; expression levels of the activating CYP1A1 and CYP1B1 were increased, while the detoxifying enzymes UGT1A6 and UGT2B7 were significantly reduced by hypoxia. To evaluate whether these changes had an effect on metabolism, levels of BaP and several of its metabolites were determined. Cells under hypoxia have a reduced capacity to metabolise BaP leaving more of the parent molecule intact. Additionally, BaP-7,8-dihydrodiol, the pre-cursor metabolite of the reactive metabolite BaP-7,8-dihydroxy-9,10-epoxide (BPDE), was formed in higher concentrations. Finally, under hypoxia, DNA adducts accumulated over a period of 168 h, whereas adducts were efficiently removed in 20% oxygen conditions. The delayed detoxification kinetics resulted in a 1.5-fold increase in DNA adducts. These data indicate that the metabolism under hypoxic conditions has shifted towards increased activation of BaP instead of detoxification and support the idea that modulation of carcinogen metabolism is an important additional mechanism for the observed HIF1 mediated genetic instability.
Original languageEnglish
Pages (from-to)481-487
Number of pages7
JournalMutagenesis
Volume29
Issue number6
DOIs
Publication statusPublished - Nov 2014

Keywords

  • DNA ADDUCT LEVELS
  • HYDROCARBON HYDROXYLASE-ACTIVITY
  • INDUCIBLE FACTOR
  • LUNG-CANCER
  • GENETIC INSTABILITY
  • FACTOR 1-ALPHA
  • KNOCKOUT MICE
  • FACTOR-1
  • BINDING
  • UBIQUITYLATION

Cite this

Schults, M.A.C. ; Sanen, K. ; Godschalk, R.W. ; Theys, J. ; van Schooten, F.J. ; Chiu, R.K. / Hypoxia diminishes the detoxification of the environmental mutagen benzo[a]pyrene. In: Mutagenesis. 2014 ; Vol. 29, No. 6. pp. 481-487.
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title = "Hypoxia diminishes the detoxification of the environmental mutagen benzo[a]pyrene",
abstract = "Hypoxia promotes genetic instability and is therefore an important factor in carcinogenesis. We have previously shown that activation of the hypoxia responsive transcription factor HIFalpha can enhance the mutagenic phenotype induced by the environmental mutagen benzo[a]pyrene (BaP). To further elucidate the mechanism behind the ability of hypoxia to increase mutagenicity of carcinogens, we examined the activation and detoxification of BaP under hypoxic conditions. To this end, the human lung carcinoma cell line A549 was treated with BaP under 20{\%}, 5{\%} or 0.2{\%} oxygen for 18h and alterations in BaP metabolism were assayed. First, BaP-induced expression of key metabolic enzymes was analysed; expression levels of the activating CYP1A1 and CYP1B1 were increased, while the detoxifying enzymes UGT1A6 and UGT2B7 were significantly reduced by hypoxia. To evaluate whether these changes had an effect on metabolism, levels of BaP and several of its metabolites were determined. Cells under hypoxia have a reduced capacity to metabolise BaP leaving more of the parent molecule intact. Additionally, BaP-7,8-dihydrodiol, the pre-cursor metabolite of the reactive metabolite BaP-7,8-dihydroxy-9,10-epoxide (BPDE), was formed in higher concentrations. Finally, under hypoxia, DNA adducts accumulated over a period of 168 h, whereas adducts were efficiently removed in 20{\%} oxygen conditions. The delayed detoxification kinetics resulted in a 1.5-fold increase in DNA adducts. These data indicate that the metabolism under hypoxic conditions has shifted towards increased activation of BaP instead of detoxification and support the idea that modulation of carcinogen metabolism is an important additional mechanism for the observed HIF1 mediated genetic instability.",
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Hypoxia diminishes the detoxification of the environmental mutagen benzo[a]pyrene. / Schults, M.A.C.; Sanen, K.; Godschalk, R.W.; Theys, J.; van Schooten, F.J.; Chiu, R.K.

In: Mutagenesis, Vol. 29, No. 6, 11.2014, p. 481-487.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Hypoxia diminishes the detoxification of the environmental mutagen benzo[a]pyrene

AU - Schults, M.A.C.

AU - Sanen, K.

AU - Godschalk, R.W.

AU - Theys, J.

AU - van Schooten, F.J.

AU - Chiu, R.K.

PY - 2014/11

Y1 - 2014/11

N2 - Hypoxia promotes genetic instability and is therefore an important factor in carcinogenesis. We have previously shown that activation of the hypoxia responsive transcription factor HIFalpha can enhance the mutagenic phenotype induced by the environmental mutagen benzo[a]pyrene (BaP). To further elucidate the mechanism behind the ability of hypoxia to increase mutagenicity of carcinogens, we examined the activation and detoxification of BaP under hypoxic conditions. To this end, the human lung carcinoma cell line A549 was treated with BaP under 20%, 5% or 0.2% oxygen for 18h and alterations in BaP metabolism were assayed. First, BaP-induced expression of key metabolic enzymes was analysed; expression levels of the activating CYP1A1 and CYP1B1 were increased, while the detoxifying enzymes UGT1A6 and UGT2B7 were significantly reduced by hypoxia. To evaluate whether these changes had an effect on metabolism, levels of BaP and several of its metabolites were determined. Cells under hypoxia have a reduced capacity to metabolise BaP leaving more of the parent molecule intact. Additionally, BaP-7,8-dihydrodiol, the pre-cursor metabolite of the reactive metabolite BaP-7,8-dihydroxy-9,10-epoxide (BPDE), was formed in higher concentrations. Finally, under hypoxia, DNA adducts accumulated over a period of 168 h, whereas adducts were efficiently removed in 20% oxygen conditions. The delayed detoxification kinetics resulted in a 1.5-fold increase in DNA adducts. These data indicate that the metabolism under hypoxic conditions has shifted towards increased activation of BaP instead of detoxification and support the idea that modulation of carcinogen metabolism is an important additional mechanism for the observed HIF1 mediated genetic instability.

AB - Hypoxia promotes genetic instability and is therefore an important factor in carcinogenesis. We have previously shown that activation of the hypoxia responsive transcription factor HIFalpha can enhance the mutagenic phenotype induced by the environmental mutagen benzo[a]pyrene (BaP). To further elucidate the mechanism behind the ability of hypoxia to increase mutagenicity of carcinogens, we examined the activation and detoxification of BaP under hypoxic conditions. To this end, the human lung carcinoma cell line A549 was treated with BaP under 20%, 5% or 0.2% oxygen for 18h and alterations in BaP metabolism were assayed. First, BaP-induced expression of key metabolic enzymes was analysed; expression levels of the activating CYP1A1 and CYP1B1 were increased, while the detoxifying enzymes UGT1A6 and UGT2B7 were significantly reduced by hypoxia. To evaluate whether these changes had an effect on metabolism, levels of BaP and several of its metabolites were determined. Cells under hypoxia have a reduced capacity to metabolise BaP leaving more of the parent molecule intact. Additionally, BaP-7,8-dihydrodiol, the pre-cursor metabolite of the reactive metabolite BaP-7,8-dihydroxy-9,10-epoxide (BPDE), was formed in higher concentrations. Finally, under hypoxia, DNA adducts accumulated over a period of 168 h, whereas adducts were efficiently removed in 20% oxygen conditions. The delayed detoxification kinetics resulted in a 1.5-fold increase in DNA adducts. These data indicate that the metabolism under hypoxic conditions has shifted towards increased activation of BaP instead of detoxification and support the idea that modulation of carcinogen metabolism is an important additional mechanism for the observed HIF1 mediated genetic instability.

KW - DNA ADDUCT LEVELS

KW - HYDROCARBON HYDROXYLASE-ACTIVITY

KW - INDUCIBLE FACTOR

KW - LUNG-CANCER

KW - GENETIC INSTABILITY

KW - FACTOR 1-ALPHA

KW - KNOCKOUT MICE

KW - FACTOR-1

KW - BINDING

KW - UBIQUITYLATION

U2 - 10.1093/mutage/geu034

DO - 10.1093/mutage/geu034

M3 - Article

VL - 29

SP - 481

EP - 487

JO - Mutagenesis

JF - Mutagenesis

SN - 0267-8357

IS - 6

ER -