Identification of Adducts Formed by Pyridyloxobutylation of Deoxyguanosine and DNA by 4-(Acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone, a Chemically Activated Form of Tobacco Specific Carcinogens

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• 作者：Mingyao Wang ; Guang Cheng ; Shana J. Sturla ; Yongli Shi ; Edward J. McIntee ; Peter W. Villalta ; Pramod Upadhyaya ; and Stephen S. Hecht
• 刊名：Chemical Research in Toxicology
• 出版年：2003
• 出版时间：May 2003
• 年：2003
• 卷：16
• 期：5
• 页码：616 - 626
• 全文大小：263K
• 年卷期：v.16,no.5(May 2003)
• ISSN：1520-5010

文摘

The tobacco specific carcinogens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) andN'-nitrosonornicotine (NNN) are metabolically activated to 4-oxo-4-(3-pyridyl)-1-butanediazohydroxide (7), which is known to pyridyloxobutylate DNA. A substantial proportion of theadducts in this DNA releases 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB, 11) under varioushydrolysis conditions, including neutral thermal hydrolysis. These HPB-releasing DNA adductshave been detected in target tissues of animals treated with NNK and NNN as well as in lungtissue from smokers. Although their presence in pyridyloxobutylated DNA was conclusivelydemonstrated 15 years ago, their structures have not been previously determined. Weinvestigated this question in the present study by determining the structures of products formedin reactions with dGuo and DNA of 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone(NNKCH₂OAc, 3), a stable precursor to 7. Reaction mixtures from NNKCH₂OAc and dGuowere analyzed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) with selected ion monitoring at m/z 415. A major peak was detected and identified as7-[4-oxo-4-(3-pyridyl)but-1-yl]dGuo (37) by its ESI-MS fragmentation pattern and by neutralthermal hydrolysis, which converted it to 11 and 7-[4-oxo-4-(3-pyridyl)but-1-yl]Gua (26). Thelatter was identified by comparison to synthetic 26 using LC-ESI-MS with selected ionmonitoring at m/z 299, M + 1 of 26. Further evidence was obtained by NaBH₄ reduction of 26to 7-[4-hydroxy-4-(3-pyridyl)but-1-yl]Gua, which was also matched with a standard. Adduct37 was similarly identified in enzyme hydrolysates of DNA reacted with NNKCH₂OAc,accounting for 30-35% of the HPB-releasing adducts in this DNA. Several other adductsresulting from pyridyloxobutylation of the N²- and O⁶-positions of Gua were also identified asproducts in the dGuo or DNA reactions by comparison to standards; their concentrations wereconsiderably less than that of 37. These adducts were N²-[4-oxo-4-(3-pyridyl)but-1-yl]dGuo (23),N²-[4-oxo-4-(3-pyridyl)but-2-yl]dGuo (25), N²-[2-(3-pyridyl)tetrahydrofuran-2-yl]dGuo (31a) (orits open chain tautomer 31b), and O⁶-[4-oxo-4-(3-pyridyl)but-1-yl]dGuo (10). Adducts 23, 25,and 10 did not release HPB upon neutral thermal hydrolysis. The results of this study providethe first structural identification of an HPB-releasing DNA adduct of the tobacco specificnitrosamines NNK and NNN.