title: Chemical and biological evidence for base propenals as the major source of the endogenous M1dG adduct in cellular DNA.
abstract: The endogenous DNA adduct, M(1)dG, has been shown to arise in vitro in reactions of dG with malondialdehyde (MDA), a product of both lipid peroxidation and 4'-oxidation of deoxyribose in DNA, and with base propenals also derived from deoxyribose 4'-oxidation. We now report the results of cellular studies consistent with base propenals, and not MDA, as the major source of M1dG under biological conditions. As a foundation for cellular studies, M1dG, base propenals, and MDA were quantified in purified DNA treated with oxidizing agents known to produce deoxyribose 4'-oxidation. The results revealed a consistent pattern; Fe2+-EDTA and gamma-radiation generated MDA but not base propenals or M1dG, whereas bleomycin and peroxynitrite (ONOO-) both produced M1dG as well as base propenals with no detectable MDA. These observations were then assessed in Escherichia coli with controlled membrane levels of polyunsaturated fatty acids (PUFA). ONOO- treatment (2 mm) of cells containing no PUFA (defined medium with 18:0/stearic acid) produced 6.5 M1dG/10(7) deoxynucleotides and no detectable lipid peroxidation products, including MDA, as compared with 3.8 M1dG/10(7) deoxynucleotides and 0.07 microg/ml lipid peroxidation products with control cells grown in a mixture of fatty acids (0.5% PUFA) mimicking Luria-Bertani medium. In cells grown with linoleic acid (18:2), the level of PUFA rose to 54% and the level of MDA rose to 0.14 microg/ml, whereas M1dG fell to 1.4/10(7) deoxynucleotides. Parallel studies with gamma-radiation revealed levels of MDA similar to those produced by ONOO- but no detectable M1dG. These results are consistent with base propenals as the major source of M1dG in this model cell system.
authors.affiliation: Biological Engineering Division and Center for Environmental Health Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Xinfeng
authors.initials: X
authors.lastname: Zhou
authors.forename: Koli
authors.initials: K
authors.lastname: Taghizadeh
authors.forename: Peter C
authors.initials: PC
authors.lastname: Dedon
mesh_terms: D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D018736:DNA Adducts / Q000737:chemistry / Q000378:metabolism*; D003855:Deoxyribose / Q000378:metabolism; D004926:Escherichia coli; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D015227:Lipid Peroxidation / Q000502:physiology; D008315:Malondialdehyde / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D030421:Peroxynitrous Acid / Q000378:metabolism; D011684:Purine Nucleosides / Q000737:chemistry / Q000378:metabolism*; D011687:Purines / Q000378:metabolism; D011743:Pyrimidines / Q000378:metabolism
chemical_list: C491625:3-(2'-deoxy-beta-D-erythro-pentofuranosyl)pyrimido(1,2-alpha)purin-10(3H)-one; D018736:DNA Adducts; D005231:Fatty Acids, Unsaturated; D016877:Oxidants; D011684:Purine Nucleosides; D011687:Purines; D011743:Pyrimidines; D030421:Peroxynitrous Acid; D008315:Malondialdehyde; D003855:Deoxyribose; D004247:DNA