In vivo oxidative metabolism of a major peroxidation-derived DNA adduct, M1dG
Michael B Otteneder1, Charles G Knutson, J Scott Daniels
1Memorial Laboratory for Cancer Research, Department of Biochemistry, Vanderbilt Institute of Chemical Biology, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA.
Abstract:
3-(2-Deoxy-beta-D-erythro-pentofuranosyl)pyrimido[1,2-alpha]purin-10(3H)-one (M1dG) is a DNA adduct arising from the reaction of 2-deoxyguanosine with the lipid peroxidation product, malondialdehyde, or the DNA peroxidation product, base propenal. M1dG is mutagenic in bacteria and mammalian cells and is present in the genomic DNA of healthy human beings. It is also detectable, albeit at low levels, in the urine of healthy individuals, which may make it a useful biomarker of DNA damage linked to oxidative stress. We investigated the possibility that the low urinary levels of M1dG reflect metabolic conversion to derivatives. M1dG was rapidly removed from plasma (t(1/2) = 10 min) after i.v. administration to rats. A single urinary metabolite was detected that was identified as 6-oxo-M1dG by MS, NMR spectroscopy, and independent chemical synthesis. 6-Oxo-M1dG was generated in vitro by incubation of M1dG with rat liver cytosols, and studies with inhibitors suggested that xanthine oxidase and aldehyde oxidase are involved in the oxidative metabolism. M1dG also was metabolized by three separate human liver cytosol preparations, indicating 6-oxo-M1dG is a likely metabolite in humans. This represents a report of the oxidative metabolism of an endogenous DNA adduct and raises the possibility that other endogenous DNA adducts are metabolized by oxidative pathways. 6-Oxo-M1dG may be a useful biomarker of endogenous DNA damage associated with inflammation, oxidative stress, and certain types of cancer chemotherapy.
Insights
This study identifies 6-oxo-M1dG as a urinary metabolite of the DNA adduct M1dG in rats and humans, suggesting a role in oxidative stress and DNA damage biomarkers.
Area of Science:
- Biochemistry
- Toxicology
- Molecular Biology
Background:
- 3-(2-Deoxy-beta-D-erythro-pentofuranosyl)pyrimido[1,2-alpha]purin-10(3H)-one (M1dG) is a mutagenic DNA adduct found in human DNA and urine.
- Low urinary M1dG levels suggest potential metabolic conversion.
Purpose of the Study:
- To investigate the metabolic fate of M1dG in vivo and in vitro.
- To identify potential urinary metabolites of M1dG.
- To explore the utility of M1dG derivatives as biomarkers of DNA damage.
Main Methods:
- Intravenous administration of M1dG to rats and analysis of plasma and urine.
- Identification of urinary metabolites using mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy.
- In vitro metabolism studies using rat and human liver cytosols with enzyme inhibitors.
Main Results:
- M1dG was rapidly cleared from rat plasma.
- A single urinary metabolite, 6-oxo-M1dG, was identified.
- 6-Oxo-M1dG was formed in vitro by rat and human liver cytosols, involving xanthine oxidase and aldehyde oxidase.
Conclusions:
- Oxidative metabolism of the endogenous DNA adduct M1dG produces 6-oxo-M1dG.
- 6-Oxo-M1dG is a likely human metabolite of M1dG.
- 6-Oxo-M1dG may serve as a biomarker for DNA damage linked to oxidative stress, inflammation, and cancer chemotherapy.
