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Absence of acrylamide-induced genotoxicity in CYP2E1-null mice: evidence consistent with a glycidamide-mediated effect. Mutat Res

Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, P.O. Box 12233, Research Triangle Park, NC 27709, USA.
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis (Impact Factor: 4.44). 10/2005; 578(1-2):284-97. DOI: 10.1016/j.mrfmmm.2005.05.004
Source: PubMed

ABSTRACT Acrylamide, an animal carcinogen and germ cell mutagen present at low (ppm) levels in heated carbohydrate-containing foodstuffs, is oxidized by cytochrome P4502E1 (CYP2E1) to the epoxide glycidamide, which is believed to be responsible for the mutagenic and carcinogenic activity of acrylamide. We recently reported a comparison of the effects of acrylamide on the genetic integrity of germ cells of male wild-type and CYP2E1-null mice [B.I. Ghanayem, K.L. Witt, L. El-Hadri, U. Hoffler, G.E. Kissling, M.D. Shelby, J.B. Bishop, Comparison of germ-cell mutagenicity in male CYP2E1-null and wild-type mice treated with acrylamide: evidence supporting a glycidamide-mediated effect, Biol. Reprod. 72 (2005) 157-163]. In those experiments, dose-related increases in dominant lethal mutations were detected in uterine contents of female mice mated to acrylamide-treated wild-type males but not CYP2E1-null males, clearly implicating CYP2E1-mediated formation of glycidamide in the induction of genetic damage in male germ cells. We hypothesized that acrylamide-induced somatic cell damage is also caused by glycidamide. Therefore, to examine this hypothesis, female wild-type and CYP2E1-null mice were administered acrylamide (0, 25, 50mg/kg) by intraperitoneal injection once daily for 5 consecutive days. Twenty-four hours after the final treatment, blood and tissue samples were collected. Erythrocyte micronucleus frequencies were determined using flow cytometry and DNA damage was assessed in leukocytes, liver, and lung using the alkaline (pH>13) single cell gel electrophoresis (Comet) assay. Results were consistent with the earlier observations in male germ cells: significant dose-related increases in micronucleated erythrocytes and DNA damage in somatic cells were induced in acrylamide-treated wild-type but not in the CYP2E1-null mice. These results support the hypothesis that genetic damage in somatic and germ cells of mice-treated with acrylamide is dependent upon metabolism of the parent compound by CYP2E1. This dependency on metabolism has implications for the assessment of human risks resulting from occupational or dietary exposure to acrylamide. CYP2E1 polymorphisms and variability in CYP2E1 activity associated with, for example, diabetes, obesity, starvation, and alcohol consumption, may result in altered metabolic efficiencies leading to differential susceptibilities to acrylamide toxicities in humans.

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    • "Glycidamide, the reactive metabolite of acrylamide, forms adducts on reaction with DNA and is thought to be involved in the genotoxicity of acrylamide, and may lead to the carcinogenicity of acrylamide (Dearfield et al., 1988, 1995; Doerge et al., 2005; Ghanayem et al., 2005; Segerbä ck et al., 1995; Von Tungeln et al., 2012; Zeiger et al., 2009). The extent of AAVal adduct formation is associated with the area under the curve for acrylamide in blood, which is dependent on the dose administered, and the extent of metabolism (Calleman et al., 1993; Fennell et al., 2005). "
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    ABSTRACT: Acrylamide is an industrial chemical used to manufacture polymers, and is produced in foods during cooking at high heat. Hemoglobin adducts provide a long-lived dosimeter for acrylamide and glycidamide. This study determined acrylamide and glycidamide hemoglobin adducts (AAVal and GAVal) during a lifetime carcinogenesis bioassay. Exposure to acrylamide in drinking water began in utero in pregnant rats on gestation day (GD) 6. Dams were administered acrylamide until weaning, and male and female F1 rats were exposed for a further 104 weeks. Acrylamide concentration in drinking water was adjusted to provide a constant dose of 0.5, 1.5, and 3 mg/kg/day. Blood was collected from animals euthanized at 2, 60, 90 and 120 days and 53, 79, and 104 weeks after weaning. Low levels of AAVal and GAVal at postnatal day (PND) 24 suggested that little exposure to acrylamide occurred by placental or lactational transfer, and extensive metabolism to glycidamide occurred with a GAVal:AAVal ratio of 4. Adduct levels varied somewhat from 60 days - 2 years, with a GAVal:AAVal ratio of approximately 1. Adduct formation/day estimated at each timepoint at 3 mg/kg/day for AAVal was 1293 ± 220 and 1096 ± 338 fmol/mg/day for male and female rats, respectively. Adduct formation per day estimated at each timepoint at 3 mg/kg/day for GAVal was 827 ± 78 fmol/mg/day for male rats, and 982 ± 222 fmol/mg/day for female rats. The study has provided estimates of linearity for dose response, and variability in internal dose throughout an entire 2-year bioassay, including the early phases of pregnancy and lactation. © The Author 2015. Published by Oxford University Press on behalf of the Society of Toxicology.
    Toxicological Sciences 07/2015; DOI:10.1093/toxsci/kfv104 · 4.48 Impact Factor
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    • "The genotoxicity and carcinogenicity of AA is attributed to the three mechanisms a) Radical mediated polymerisation b) Michael reactivity i.e., the addition of carban ions to α−β−unsaturated chemicals and c) oxidation to GA by cytochrome P450 enzymes (Dearfield et al., 1995). Ghanayem et al., (2005b) have investigated the role of cytochrome P450 in the metabolism of AA using mice differing in CYP2EI expression (wild type CYP2EI +/-and CYP2EI-/-m knockout mice). Additionally Ghanayem et al. (2005a) also confirmed that the AA to GA transformation leads to the formation of GA-DNA adducts in liver, lung and testes. "
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    ABSTRACT: ABSTRACT The micronucleus test is an effective method for determination of the evolution of genotoxic or clastogenic agents of physical and chemical functions. The micronuclei are formed due to the condensation lagging off of acentric chromosomes, chromatid fragments or entire chromosomes and also due to non introduction of them in main daughter nuclei during metaphase or anaphase of cell division. Formation of micronuclei reflects chromosome damage and thus provide a marker for carcinogenesis analysis. Acrylamide is an important industrial chemical used in waste water treatment, adhesives and grout, cosmetics and also in laboratories. It is genotoxic, in in vitro and in vivo, in both somatic and germ cells. Acrylamide induces chromosomal aberrations, micronuclei formation, sister chromatid exchanges, SS-DNA breaks, polyploidy, aneuploidy and other mitotic disturbances, dominant lethal and specific locus mutations. Therefore a study was made on micronuclei assay to evaluate the degree of genotoxicity of acrylamide and its toxicologic effects on rat’s reproductive system after intraperitoneal injection of different doses of acrylamide. The Acrylamide treatment to rats caused damage not only to peripheral blood cells and reticulocytes but also to spermatids. The formation of micronuclei was evidence in our present study though acrylamide may not be used directly. The indirect consumption of acrylamide definitely causes damage to almost all type of cells in the rats.
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    • "The genotoxicity and carcinogenicity of AA is attributed to the three mechanisms a) Radical mediated polymerisation b) Michael reactivity i.e., the addition of carban ions to α−β−unsaturated chemicals and c) oxidation to GA by cytochrome P450 enzymes (Dearfield et al., 1995). Ghanayem et al., (2005b) have investigated the role of cytochrome P450 in the metabolism of AA using mice differing in CYP2EI expression (wild type CYP2EI +/-and CYP2EI-/-m knockout mice). Additionally Ghanayem et al. (2005a) also confirmed that the AA to GA transformation leads to the formation of GA-DNA adducts in liver, lung and testes. "
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