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

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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; Abramsson-Zetterberg, Lilianne; Törnqvist, Margareta.

In: Mutation Research - Genetic Toxicology and Environmental Mutagenesis, Vol. 849, 503127, 2020.

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T1 - Serum albumin adducts, DNA adducts and micronuclei frequency measured in benzo[a]pyrene-exposed mice for estimation of genotoxic potency

AU - Motwani, Hitesh V.

AU - Westberg, Emelie

AU - Lindh, Christian

AU - Abramsson-Zetterberg, Lilianne

AU - Törnqvist, Margareta

PY - 2020

Y1 - 2020

N2 - 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.

AB - 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.

KW - Adducts

KW - Cancer risk

KW - Genotoxic metabolites

KW - Internal dose

KW - Polycyclic aromatic hydrocarbons

U2 - 10.1016/j.mrgentox.2019.503127

DO - 10.1016/j.mrgentox.2019.503127

M3 - Article

VL - 849

JO - Mutation Research - Genetic Toxicology and Environmental Mutagenesis

JF - Mutation Research - Genetic Toxicology and Environmental Mutagenesis

SN - 1383-5718

M1 - 503127

ER -