Increased formation of hepatic N2 -ethylidene-2′-deoxyguanosine DNA adducts in aldehyde dehydrogenase 2-knockout mice treated with ethanol

Graduate School of Global Environmental Studies, Kyoto University, Kyoto 606-8501, Japan.
Carcinogenesis (Impact Factor: 5.33). 12/2007; 28(11):2363-6. DOI: 10.1093/carcin/bgm057
Source: PubMed


N2-ethylidene-2'-deoxyguanosine (N2-ethylidene-dG) is a major DNA adduct induced by acetaldehyde. Although it is unstable in the nucleoside form, it is relatively stable when present in DNA. In this study, we analyzed three acetaldehyde-derived DNA adducts, N2-ethylidene-dG, N2-ethyl-2'-deoxyguanosine (N2-Et-dG) and alpha-methyl-gamma-hydroxy-1,N2-propano-2'-deoxyguanosine (alpha-Me-gamma-OH-PdG) in the liver DNA of aldehyde dehydrogenase (Aldh)-2-knockout mice to determine the influence of alcohol consumption and the Aldh2 genotype on the levels of DNA damage. In control Aldh2+/+ mice, the level of N2-ethylidene-dG adduct in liver DNA was 1.9 +/- 0.7 adducts per 10(7) bases and was not significantly different than that of Aldh2+/- and -/- mice. In alcohol-fed mice (20% ethanol for 5 weeks), the adduct levels of Aldh2+/+, +/- and -/- mice were 7.9 +/- 1.8, 23.3 +/- 4.0 and 79.9 +/- 14.2 adducts per 10(7) bases, respectively, and indicated that adduct level was alcohol and Aldh2 genotype dependent. In contrast, an alcohol- or Aldh2 genotype-dependent increase was not observed for alpha-Me-gamma-OH-PdG, and N2-Et-dG was not detected in any of the analyzed samples. In conclusion, the risk of formation of N2-ethylidene-dG in model animal liver in vivo is significantly higher in the Aldh2-deficient population and these results may contribute to our understanding of in vivo adduct formation in humans.

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Available from: Katsumaro Tomokuni, Feb 05, 2014
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    • ". Among them, N 2 -ethylidene-dG is the most abundant DNA adduct derived from acetaldehyde [15] [17]. Matsuda et al. reported that the N 2 -ethylidene-dG level in the liver or stomach is elevated by ethanol consumption in experimental mouse models [16] [17]. Thus, quantification of acetaldehyde-derived DNA adducts provide an index of direct DNA damage caused by acetaldehyde [15-18]. "
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    ABSTRACT: Ethanol and its metabolite, acetaldehyde, are the definite carcinogens for esophageal squamous cell carcinoma (ESCC), and reduced catalytic activity of aldehyde dehydrogenase 2 (ALDH2), which detoxifies acetaldehyde, increases the risk for ESCC. However, it remains unknown whether the ALDH2 genotype influences the level of acetaldehyde-derived DNA damage in the esophagus after ethanol ingestion. In the present study, we administered ethanol orally or intraperitoneally to Aldh2-knockout and control mice, and we quantified the level of acetaldehyde-derived DNA damage, especially N(2) -ethylidene-2'-deoxyguanosine (N(2) -ethylidene-dG), in the esophagus. In the model of oral ethanol administration, the esophageal N(2) -ethylidene-dG level was significantly higher in Aldh2-knockout mice compared with control mice. Similarly, in the model of intraperitoneal ethanol administration, in which the esophagus is not exposed directly to the alcohol solution, the esophageal N(2) -ethylidene-dG level was also elevated in Aldh2-knockout mice. This result indicates that circulating ethanol-derived acetaldehyde causes esophageal DNA damage, and that the extent of damage is influenced by knockout of Aldh2. Taken together, our findings strongly suggest the importance of acetaldehyde-derived DNA damage which is induced in the esophagus of individuals with ALDH2 gene impairment. This provides a physiological basis for understanding alcohol-related esophageal carcinogenesis.
    Full-text · Article · Jun 2014 · American Journal of Cancer Research
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    • "Acetaldehyde reacts with DNA at primarily the N 2 position of deoxyguanosine (dG) and forms the N 2 -ethylidene-dG adduct, which can be reduced to N 2 -ethyl-dG following reaction with a strong reducing agent (Fig. 1) (Hecht et al., 2001a, b; Wang et al., 2000). Acetaldehyde can also react twice with dG to form the 1,N focusing on the formation of the adduct following ingestion of ethanol in humans or rodents (Chen et al., 2007; Fang and Vaca, 1997; Matsuda et al., 2007; Nagayoshi et al., 2009; Oyama et al., 2010; Vaca et al., 1998). Recent studies monitoring the formation of DNA adducts following [ 13 C 2 ]-acetaldehyde exposures in a human lung fibroblast cell line (IMR-90) have shown the formation of exogenous 1,N 2 -propano-dG along with the N 2 -ethylidene-dG adducts though no values for the N 2 ethylidene-dG adduct were reported (Garcia et al., 2011). "
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    ABSTRACT: The dose-response relationship for biomarkers of exposure (N(2)-ethylidene-dG adducts) and effect (cell survival and micronucleus formation) was determined across 4.5 orders of magnitude (50 nM - 2 mM) using [(13)C(2)]-acetaldehyde exposures to human lymphoblastoid TK6 cells for 12 hours. There was a clear increase in exogenous N(2)-ethylidene-dG formation at exposure concentrations ≥ 1 µM while the endogenous adducts remained nearly constant across all exposure concentrations with an average of 3.0 adducts/10(7) dG. Exogenous adducts were lower than endogenous adducts at concentrations ≤ 10 µM and greater than endogenous at concentrations ≥ 250 µM. When the endogenous and exogenous adducts were summed together, statistically significant increases in total adduct formation over the endogenous background occurred at 50 µM. Cell survival and micronucleus formation were monitored across the exposure range and statistically significant decreases in cell survival and increases in micronucleus formation occurred at ≥1000 µM. This research supports the hypothesis that endogenously produced reactive species, including acetaldehyde, are always present, and constitute the majority of the observed biological effects following very low exposures to exogenous acetaldehyde. These data can replace default assumptions of linear extrapolation to very low doses of exogenous acetaldehyde for risk prediction.
    Full-text · Article · Feb 2013 · Toxicological Sciences
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    • "N 2 -Et-dG in human liver could be detected a few hundredfold by undergoing this process [7]. This method was used to show that the content of hepatic and gastric N 2 -ethylidene-dG is much higher in ethanol-treated aldehyde dehydrogenase-2-knock- out mice than in control mice [8] [9]. However, the biochemical properties of N "
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    ABSTRACT: Acetaldehyde (AA) derived from alcoholic beverages is a confirmed carcinogen for esophageal and head and neck cancers. AA forms various DNA adducts and is thought to play a crucial role in carcinogenesis. Transient DNA adducts are usually repaired, but the stability of AA-derived DNA adducts has not been elucidated. We investigated the stability of N(2)-ethylidene-2'-deoxyguanosine (N(2)-ethylidene-dG), a major AA-derived DNA adduct, in cultured cells. First, to determine the optimal concentration of AA for detecting N(2)-ethylidene-dG in cell culture, a dose-response study was performed using HL60 cells of the human promyelocytic leukemia cell line. An AA concentration ≥ 0.01% (1.8 mM) was required to detect N(2)-ethylidene-dG in vitro. We next examined the stability of N(2)-ethylidene-dG. After a 1 or 2h exposure to 0.01% of AA in a tightly sealed bottle, N(2)-ethylidene-dG content was measured by sensitive liquid chromatography tandem mass spectrometry immediately, 24h, and 48 h after exposure. After the 1h exposure, the mean (± SD) N(2)-ethylidene-dG contents were 12.1 ± 1.28, 8.20 ± 0.64, and 6.70 ± 0.52 adducts per 10(7) bases at each postexposure time. After the 2h exposure, N(2)-ethylidene-dG content increased to 21.4 ± 7.50, 10.5 ± 3.61, and 9.83 ± 3.90 adducts per 10(7) bases at each postexposure time. The half-life of this adduct was calculated as ∼35 h in independent experiments. These results indicate that AA exposure from daily alcohol consumption may cause DNA damage and may increase the risk of alcohol-related carcinogenesis.
    Full-text · Article · Jun 2012 · Biochemical and Biophysical Research Communications
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