Article

Formation of N-7-(2-carbamoyl-2-hydroxyethyl)guanine in DNA of the mouse and the rat following intraperitoneal administration of [14C]acrylamide.

Center for Nutrition and Toxicology, Karolinska Institute, Novum, Huddinge, Sweden.
Carcinogenesis (Impact Factor: 5.64). 06/1995; 16(5):1161-5. DOI: 10.1093/carcin/16.5.1161
Source: PubMed

ABSTRACT Acrylamide is an alkylating agent which reacts very slowly in direct reactions with DNA and is negative in the Ames test, but is carcinogenic in mice and rats. In order to explain the cancer-initiating properties of acrylamide we have studied DNA adduct formation in vitro with a metabolizing system and in vivo in mice and rats following i.p. administration of 14C-labeled acrylamide. A major adduct found in both species was N-7-(2-carbamoyl-2-hydroxy-ethyl)guanine, formed by reaction of the DNA with the epoxide metabolite glycidamide. The levels of this adduct were similar in the different organs of the two rodent species, which supports the notion that glycidamide is relatively evenly distributed among tissues and that the organ-specificity in acrylamide carcinogenesis cannot be explained by a selective accumulation of the DNA-reactive metabolite in target organs.

0 Bookmarks
 · 
106 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Thiotepa (N,N′,N″-triethylenethiophosphoramide) and its major metabolite (Tepa) as trifunctional alkylating agents has recently been used in cancer therapy. In vivo and vitro studies show the possible pathways of alkylation of DNA by Thiotepa and Tepa. Two pathways are suggested, but the main pathway of mechanism remains unclear. In pathway 1, forming cross-links with DNA molecules can be carried out via two different mechanisms. In first mechanism, these agents undergo the ring opening reaction which is initiated by protonating aziridine, which then becomes the main target of nucleophilic attack by the N7-Guanine of DNA. The second probable mechanism is ring opening of aziridyl group by nucleophilic attack of N7-Guanine without initial protonation. Thiotepa and Tepa in pathway 2, act as a cell penetrating carrier for aziridine, which is released via hydrolysis. The released aziridine can form a cross-link with N7-Guanine. In this study, we calculated the activation free energy and kinetic rate constant for alkylating the Guanine via the first pathway to determine the most precise mechanism by applying density functional theory using B3LYP method. We carried out geometrical optimizations with the conductor-like polarizable continuum model to account for the solvent effect, and the results were compared with those in the gas phase. Hyperconjugation stabilization factors that affect on stability of generated transition state were investigated by natural bond order analysis. Furthermore, quantum theory of atoms in molecules analysis was performed to extract the bond critical points properties because the electron densities can be considered as a good description of the strength of different types of interactions.
    Structural Chemistry 01/2013; 24(1). · 1.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Acrylamide (AA) is a well-known industrial chemical classified as a probable human carcinogen. Benign and malignant tumours at different sites, including the mammary gland, have been reported in rodents exposed to AA. This xenobiotic is also formed in many carbohydrate-rich foods prepared at high temperatures. For this reason, AA is an issue of concern in terms of human cancer risk. The epoxide glycidamide (GA) is thought to be the ultimate genotoxic AA metabolite. Despite extensive experimental and epidemiological data focused on AA-induced breast cancer, there is still lack of information on the deleterious effects induced by GA in mammary cells. The work reported here addresses the characterisation and modulation of cytotoxicity, generation of reactive oxygen species, formation of micronuclei (MN) and quantification of specific GA-DNA adducts in human MCF10A epithelial cells exposed to GA. The results show that GA significantly induces MN, impairs cell proliferation kinetics and decreases cell viability at high concentrations by mechanisms not involving oxidative stress. KU55933, an inhibitor of ataxia telangiectasia mutated kinase, enhanced the cytotoxicity of GA (P < 0.05), supporting a role of this enzyme in regulating the repair of GA-induced DNA lesions. Moreover, even at low GA levels, N7-GA-Gua adducts were generated in a linear dose-response manner in MCF10A cells. These results confirm that human mammary cells are susceptible to GA toxicity and reinforce the need for additional studies to clarify the potential correlation between dietary AA exposure and breast cancer risk in human populations.
    Mutagenesis 11/2013; 28(6):721-9. · 3.50 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The goal of this work was to show the possibility of removing acrylamide from real foods using bacterial enzymes at relatively high temperatures. Cell-free extracts from Ralstonia eutropha AUM-01 isolated from soil collected from leaf litter on Picnic Point on the UW-Madison campus and a thermophilic strain, Geobacillus thermoglucosidasius AUT-01 isolated from soil collected from hot spring area in Montana, were used to remove acrylamide from coffee. Coffee was chosen because ~39 % of the acrylamide that people consumed is from coffee. Cell extracts containing acrylamide-degrading enzymes, which hydrolyze acrylamide to acrylic acid, were directly applied to coffee. Although acrylamide was not totally degraded at higher concentrations of coffee in water, it was totally disappeared in 100 mg coffee/10 mL ddH20, which ordinary people drink. This is the first approach for applying bacterial enzymes to real food for the removal of acrylamide.
    European Food Research and Technology 03/2013; 236(3). · 1.39 Impact Factor