Aflatoxin-Guanine
DNA Adducts and Oxidatively Induced
DNA Damage in Aflatoxin-Treated Mice in Vivo as Measured
by Liquid Chromatography-Tandem Mass Spectrometry with Isotope Dilution
posted on 2018-12-11, 00:00authored byErdem Coskun, Pawel Jaruga, Vladimir Vartanian, Onur Erdem, Patricia A. Egner, John D. Groopman, R. Stephen Lloyd, Miral Dizdaroglu
Dietary exposure to aflatoxin B1 (AFB1) is
a significant contributor to the incidence of hepatocellular carcinomas
globally. AFB1 exposure leads to the formation of AFB1-N7-guanine (AFB1-N7-Gua)
and two diastereomers of the imidazole ring-opened 8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin
B1 (AFB1-FapyGua) in DNA. These adducts lead
to G → T transversion mutations with the ring-opened adduct
being more mutagenic than the cationic species. Accurate measurement
of these three adducts as biomarkers in DNA and urine will help identify
dietary exposure to AFB1 as a risk factor in the development
of hepatocellular carcinoma worldwide. Herein, we report an improved
methodology for the measurement of AFB1-N7-Gua
and the two diastereomers of AFB1-FapyGua using liquid
chromatography-tandem mass spectrometry with isotope dilution. We
measured the levels of these compounds in liver DNA of six control
mice and six AFB1-treated mice. Levels varying from 1.5
to 45 lesions/106 DNA bases in AFB1-treated
mice were detected depending on the compound and animal. No background
levels of these adducts were detected in control mice. We also tested
whether the AFB1 treatment caused oxidatively induced DNA
base damage using gas chromatography-tandem mass spectrometry with
isotope dilution. Although background levels of several pyrimidine-
and purine-derived lesions were detected, no increases in these levels
were found upon AFB1 treatment of mice. On the other hand,
significantly increased levels of (5′R)- and
(5′S)-8,5′-cyclo-2′-deoxyadenosines
were observed in liver DNA of AFB1-treated mice. The impact
of this work is expected to achieve the accurate measurement of three
AFB1-DNA adducts and oxidatively induced DNA lesions as
biomarkers of AFB1 exposure as germane to investigations
designed for the prevention of aflatoxin-related hepatocellular carcinomas
and for determining the effects of genetic deficiencies in human populations.