Time Course of Hepatic 1-Methylpyrene DNA Adducts in Rats Determined by Isotope Dilution LC-MS/MS and P-32-Postlabeling

Department of Toxicology, German Institute of Human Nutrition (DIfE), 14558 Nuthetal, Germany.
Chemical Research in Toxicology (Impact Factor: 3.53). 10/2008; 21(10):2017-25. DOI: 10.1021/tx800217d
Source: PubMed


The alkylated polycyclic aromatic hydrocarbon 1-methylpyrene is a carcinogen in rodents and has been detected in various environmental matrices and foodstuffs. It is activated metabolically by benzylic hydroxylation to 1-hydroxymethylpyrene followed by sulfoconjugation to yield electrophilic 1-sulfooxymethylpyrene (1-SMP) that is prone to form DNA adducts. An LC-MS/MS method using multiple reaction monitoring (MRM) of fragment ions has been developed for specific detection and quantification of N (2)-(1-methylpyrenyl)-2'-deoxyguanosine (MP-dGuo) and N (6)-(1-methylpyrenyl)-2'-deoxyadenosine (MP-dAdo) formed in DNA in the presence of 1-SMP. DNA samples were spiked with stable isotope internal standards, [ (15)N 5, (13)C 10]MP-dGuo and [ (15)N 5]MP-dAdo, followed by enzymatic digestion to 2'-deoxynucleosides and solid-phase extraction to remove unmodified 2'-deoxynucleosides prior to analysis by LC-MS/MS. The limits of detection were 10 fmol of MP-dGuo and 2 fmol of MP-dAdo or three molecules of MP-dGuo and 0.6 molecules of MP-dAdo per 10 (8) 2'-deoxynucleosides using 100 mug of herring sperm DNA as the sample matrix. The method was validated with herring sperm DNA reacted with 1-SMP in vitro. Hepatic DNA was analyzed from rats that were dosed intraperitoneally with 9.3 mg 1-SMP per kg body weight and killed after various time periods. Levels of MP-dGuo and MP-dAdo in rat liver were found to increase, reaching their maxima at approximately 3 h, and then decrease over time. A good correlation was observed between the results obtained using LC-MS/MS and MRM and those from (32)P-postlabeling. MRM allowed the more precise quantification of specific 1-MP adducts, in addition to a time reduction of the analysis when compared with (32)P-postlabeling.

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    • "The mass spectrometric collision-induced dissociation showed the expected fragmentation patterns (Fig. 2): the cleavage of the 2-methylfuran cation (m/z = 348.1 → 81.0), the neutral loss of the ribose unit (m/z = 348.1 → 216.1) and the release of the positively charged N 6 -methylated adenine (m/z = 348.1 → 148.0). The 1 H-NMR spectrum (Supplementary Material Fig. S4) corroborated the expected structure of N 6 -MF-A to consist of the ribonucleoside with a single 2-methylfuran moiety attached to the exocyclic nitrogen of the adenine, a structural scaffold that has been observed previously for many 2′-deoxyadeno- sine adducts of SULT-activated hydrocarbons (Herrmann et al. 2012; Monien et al. 2008, 2011, 2012). For the quantification of N 6 -MF-A by UPLC-MS/MS MRM in incubation mixtures containing SULTs and FFA, we synthesized the isotopelabeled reference compound [ 15 N 5 ]N 6 -MF-A. "
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    ABSTRACT: 5-Hydroxymethylfurfural (HMF) and furfuryl alcohol (FFA) are moderately potent rodent carcinogens that are present in thermally processed foodstuffs. The carcinogenic effects were hypothesized to originate from sulfotransferase (SULT)-mediated bioactivation yielding DNA-reactive and mutagenic sulfate esters, a confirmed metabolic pathway of HMF and FFA in mice. It is known that orthologous SULT forms substantially differ in substrate specificity and tissue distribution. This could influence HMF- and FFA-induced carcinogenic effects. Here, we studied HMF and FFA sulfoconjugation by 30 individual SULT forms of humans, mice and rats. The catalytic efficiencies (k cat/K M) of HMF sulfoconjugation of human SULT1A1 (13.7 s−1 M−1), mouse Sult1a1 (15.8 s−1 M−1) and 1d1 (4.8 s−1 M−1) and rat Sult1a1 (5.3 s−1 M−1) were considerably higher than those of all other SULT forms investigated (≤0.73 s−1 M−1). FFA sulfoconjugation was monitored using adenosine as a nucleophilic scavenger for the reactive 2-sulfoxymethylfuran (t 1/2 = 20 s at 37 °C). The resulting adduct N 6-((furan-2-yl)methyl)-adenosine (N 6-MF-A) was quantified by isotope-dilution UPLC-MS/MS. The rates of N 6-MF-A formation showed that hSULT1A1 and its orthologues in mice and rats were also the most important contributors to FFA sulfoconjugation in each of the species. Taken together, the catalytic capacity of hSULT1A1 is comparable to that of mSult1a1 in mice, the species in which carcinogenic effects of HMF and FFA were detected. This is of primary concern due to the expression of hSULT1A1 in many different tissues.
    Archive für Toxikologie 11/2014; DOI:10.1007/s00204-014-1392-6 · 5.98 Impact Factor
    • "MePyr is also present in sediments from PAH-affected areas (Notar et al. 2001). MePyr proved to be bioaccumulable in various aquatic species including teleost fish (Pancirov and Brown 1977) and is considered to be genotoxic and a potent carcinogen in mammals (Glatt et al. 2008; Monien et al. 2008), but to our knowledge, no study is available on the effects of MePyr in fish ELS. "
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    ABSTRACT: Japanese medaka (Oryzias latipes) embryos were exposed to sediments spiked with environmental concentrations (300 and 3,000 ng/g dry weight) of pyrene (Pyr) and methylpyrene (MePyr) throughout their development. Embryotoxicity, teratogenicity, and transcriptional responses (qRT-PCR) were analyzed in embryos and newly hatched larvae. The genotoxicity of the two polycyclic aromatic hydrocarbons (PAHs) was also tested in prolarvae using the comet assay. Exposure to each compound had a clear impact on embryonic development and resulted in several teratogenic effects, including cardiovascular injuries, reduced absorption of yolk sac reserves, and jaw and spinal deformities. Interestingly, the overall toxic effects of Pyr and MePyr considerably overlapped those induced following dioxin exposure. qRT-PCR analysis revealed the transcriptional induction of genes involved in mitochondrial energetic metabolism (coxI), xenobiotic biotransformation (cyp1a), and cell cycle regulation (wnt1) by the two PAHs. MePyr also activated cell cycle arrest (p53), oxidative DNA damage repair (ogg1), and retinoid-mediated (raldh2 and rarα1) gene transcription. DNA damage was not found to be significantly increased following Pyr and MePyr exposure. The lack of significant genotoxic effect in comparison to the control might be the consequence of the efficient onset of DNA damage repair mechanisms as suggested by ogg1 gene transcription upregulation. Results reported in the present study have brought new insights into the modes of action of Pyr, and the effects of MePyr exposure have been investigated in fish ELS for the first time.
    Environmental Science and Pollution Research 04/2014; 21(24). DOI:10.1007/s11356-014-2895-7 · 2.83 Impact Factor
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