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Serum albumin adducts, DNA adducts and micronuclei frequency measured in benzo[a]pyrene-exposed mice for estimation of genotoxic potency

Motwani, Hitesh V. ; Westberg, Emelie ; Lindh, Christian LU ; Abramsson-Zetterberg, Lilianne and Törnqvist, Margareta (2020) In Mutation Research - Genetic Toxicology and Environmental Mutagenesis 849.
Abstract

The environmental and food contaminant, benzo[a]pyrene {B[a]P, a polycyclic aromatic hydrocarbon (PAH)}, is classified as a human carcinogen by the International Agency for Research on Cancer. The carcinogenicity of B[a]P is linked to the formation of electrophilic metabolites, namely B[a]P-diol epoxides (BPDEs) occurring as stereoisomers. In this work, we quantified the metabolic formation of BPDE isomers and the genotoxic effect in B[a]P-exposed mice, with an aim to estimate the genotoxic potency of B[a]P per in vivo dose of its most potent metabolite [i.e. (+)-anti-BPDE]. The increase in frequency of micronuclei (fMN) in erythrocytes was measured as a biomarker for genotoxic effect. Covalent adducts to serum albumin (SA) and those to... (More)

The environmental and food contaminant, benzo[a]pyrene {B[a]P, a polycyclic aromatic hydrocarbon (PAH)}, is classified as a human carcinogen by the International Agency for Research on Cancer. The carcinogenicity of B[a]P is linked to the formation of electrophilic metabolites, namely B[a]P-diol epoxides (BPDEs) occurring as stereoisomers. In this work, we quantified the metabolic formation of BPDE isomers and the genotoxic effect in B[a]P-exposed mice, with an aim to estimate the genotoxic potency of B[a]P per in vivo dose of its most potent metabolite [i.e. (+)-anti-BPDE]. The increase in frequency of micronuclei (fMN) in erythrocytes was measured as a biomarker for genotoxic effect. Covalent adducts to serum albumin (SA) and those to DNA from the BPDEs were analysed using liquid chromatography tandem mass spectrometry (LC–MS/MS), as adducts to histidine (BPDE-His-Pro) and deoxyguanosine (BPDE-dG), respectively. For the first time in animal experiments it was possible to resolve adducts to SA from (+)-anti-, (-)-anti- and (±)-syn-BPDE isomers by LC–MS/MS. The adduct levels in the protein were about 16 fmol/mg SA, which was orders of magnitude lower than that in the nucleic acid, 28 pmol/mg DNA, in mice exposed to 100 mg B[a]P per kg body weight (bw). Using SA adduct levels, the in vivo dose of (+)-anti-BPDE was calculated to be approximately 50 nM·h per mg B[a]P per kg bw. This allowed to make a preliminary estimate of the genotoxic potency as 2‰ fMN per μM·h of (+)-anti-BPDE. This estimate was compared to that from another food toxicant, glycidol, studied with similar methods, which indicated that the BPDE has several orders of magnitude higher genotoxic potency. The demonstrated approach on integrating biomarkers of internal dose of a causative agent and that of genotoxic effect for assessing genotoxic potency, using B[a]P as a model, has a potential for improving cancer risk assessment procedures for PAHs.

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type
Contribution to journal
publication status
published
subject
keywords
Adducts, Cancer risk, Genotoxic metabolites, Internal dose, Polycyclic aromatic hydrocarbons
in
Mutation Research - Genetic Toxicology and Environmental Mutagenesis
volume
849
article number
503127
publisher
Elsevier
external identifiers
  • scopus:85075532033
ISSN
1383-5718
DOI
10.1016/j.mrgentox.2019.503127
language
English
LU publication?
yes
id
defb9fef-3a4e-4523-b1df-b47d42be238f
date added to LUP
2019-12-04 12:41:38
date last changed
2019-12-05 02:22:15
@article{defb9fef-3a4e-4523-b1df-b47d42be238f,
  abstract     = {<p>The environmental and food contaminant, benzo[a]pyrene {B[a]P, a polycyclic aromatic hydrocarbon (PAH)}, is classified as a human carcinogen by the International Agency for Research on Cancer. The carcinogenicity of B[a]P is linked to the formation of electrophilic metabolites, namely B[a]P-diol epoxides (BPDEs) occurring as stereoisomers. In this work, we quantified the metabolic formation of BPDE isomers and the genotoxic effect in B[a]P-exposed mice, with an aim to estimate the genotoxic potency of B[a]P per in vivo dose of its most potent metabolite [i.e. (+)-anti-BPDE]. The increase in frequency of micronuclei (fMN) in erythrocytes was measured as a biomarker for genotoxic effect. Covalent adducts to serum albumin (SA) and those to DNA from the BPDEs were analysed using liquid chromatography tandem mass spectrometry (LC–MS/MS), as adducts to histidine (BPDE-His-Pro) and deoxyguanosine (BPDE-dG), respectively. For the first time in animal experiments it was possible to resolve adducts to SA from (+)-anti-, (-)-anti- and (±)-syn-BPDE isomers by LC–MS/MS. The adduct levels in the protein were about 16 fmol/mg SA, which was orders of magnitude lower than that in the nucleic acid, 28 pmol/mg DNA, in mice exposed to 100 mg B[a]P per kg body weight (bw). Using SA adduct levels, the in vivo dose of (+)-anti-BPDE was calculated to be approximately 50 nM·h per mg B[a]P per kg bw. This allowed to make a preliminary estimate of the genotoxic potency as 2‰ fMN per μM·h of (+)-anti-BPDE. This estimate was compared to that from another food toxicant, glycidol, studied with similar methods, which indicated that the BPDE has several orders of magnitude higher genotoxic potency. The demonstrated approach on integrating biomarkers of internal dose of a causative agent and that of genotoxic effect for assessing genotoxic potency, using B[a]P as a model, has a potential for improving cancer risk assessment procedures for PAHs.</p>},
  author       = {Motwani, Hitesh V. and Westberg, Emelie and Lindh, Christian and Abramsson-Zetterberg, Lilianne and Törnqvist, Margareta},
  issn         = {1383-5718},
  language     = {eng},
  publisher    = {Elsevier},
  series       = {Mutation Research - Genetic Toxicology and Environmental Mutagenesis},
  title        = {Serum albumin adducts, DNA adducts and micronuclei frequency measured in benzo[a]pyrene-exposed mice for estimation of genotoxic potency},
  url          = {http://dx.doi.org/10.1016/j.mrgentox.2019.503127},
  doi          = {10.1016/j.mrgentox.2019.503127},
  volume       = {849},
  year         = {2020},
}