title: Evidence for endogenous formation of the hepatocarcinogen N-nitrosodihydrouracil in rats treated with dihydrouracil and sodium nitrite: a potential source of human hepatic DNA carboxyethylation.
abstract: An earlier study demonstrated that hydrolysates of all human liver DNA samples analyzed contain the DNA adduct 7-(2'-carboxyethyl)guanine (7-CEGua) with an average level of 74.6 adducts per 10(9) nucleotides. One possible source of this DNA adduct would be endogenous nitrosation of the normal pyrimidine metabolites dihydrouracil (DHU) and β-ureidopropionic acid (β-UPA), yielding the corresponding nitroso compounds N-nitrosodihydrouracil, a potent hepatocarcinogen, and N-nitroso-β-ureidopropionic acid. Another potential source would be reaction of endogenously formed acrylic acid with DNA. We tested these hypotheses in a study in which rats were treated with NaNO2 in the drinking water, alone, or in combination with dietary DHU or β-UPA, or with acrylic acid in the drinking water, for either 2 or 4 weeks. Hepatic DNA from these rats was analyzed for 7-CEGua, using liquid chromatography-tandem mass spectrometry-selected reaction monitoring with confirmation by high resolution mass spectrometry. The results demonstrated consistent statistically significant increases of 7-CEGua in hepatic DNA of the rats treated with the combination of NaNO2 and DHU compared to the corresponding controls, while the other treatments gave variable results. These results support the hypothesis that endogenous nitrosation of DHU could be a major source of 7-CEGua in human hepatic DNA. Development of methodology for analysis of 7-CEGua in human leukocyte DNA is also reported, which will allow testing of this hypothesis in epidemiologic and clinical studies.
authors.affiliation: Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Mingyao
authors.initials: M
authors.lastname: Wang
authors.forename: Guang
authors.initials: G
authors.lastname: Cheng
authors.forename: Samir S
authors.initials: SS
authors.lastname: Khariwala
authors.forename: Dipankar
authors.initials: D
authors.lastname: Bandyopadhyay
authors.forename: Peter W
authors.initials: PW
authors.lastname: Villalta
authors.forename: Silvia
authors.initials: S
authors.lastname: Balbo
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Hecht
mesh_terms: D000818:Animals; D004247:DNA / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D018736:DNA Adducts / Q000032:analysis; D006147:Guanine / Q000031:analogs & derivatives / Q000032:analysis; D006801:Humans; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D015394:Molecular Structure; D009603:Nitroso Compounds / Q000737:chemistry; D051381:Rats; D011916:Rats, Inbred F344; D012977:Sodium Nitrite / Q000494:pharmacology*; D014498:Uracil / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology
chemical_list: D018736:DNA Adducts; C585160:N-nitrosodihydrouracil; D009603:Nitroso Compounds; C007419:dihydrouracil; D014498:Uracil; D006147:Guanine; C034100:7-carboxymethylguanine; D004247:DNA; D012977:Sodium Nitrite
keywords: 7-(2′-carboxyethyl)guanine; Acrylic acid; Dihydrouracil; Endogenous nitrosation; N-Nitrosodihydrouracil; β-Ureidopropionic acid
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