Synthesis,Characterization,and ~(32)P-Postlabeling Analysis of DNA Adducts Derived from the Environmental Contaminant 3-Nitrobenzanthrone

摘要

3-Nitrobenzanthrone (3-NBA) is a potent mutagen and potential human carcinogen identified in diesel exhaust and ambient air particulate matter.3-NBA forms DNA adducts in rodent tissues that arise principally through reduction to N-hydroxy-3-aminobenzanthrone (N-OH-ABA),esterification to its acetate or sulfate ester,and reaction of this activated ester with DNA.We detected 3-NBA-derived DNA adducts in rodent tissues by ~(32)P-postlabeling and generated them chemically by acid-catalyzed reaction of N-OH-ABA with DNA,but their structural identification has not yet been reported.We have now prepared 3-NBA-derived adducts by reaction of a possible reactive metabolite,N-acetoxy-N-acetyl-3-aminobenzanthrone (N-Aco-N-Ac-ABA),with purine nucleosides and nucleotides,characterized them,and have shown that they are present in DNA treated with this 3-NBA derivative.Three of these adducts have been characterized as the C-C adduct N-acetyl-3-amino-2-(2'-deoxyguanosin-8-yl)-benzanthrone,the C-N adduct N-acetyl-N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone,and an unusual 3-acetylaminobenzanthrone adduct of deoxyadenosine,which involves a double linkage between adenine and benzanthrone (N1 to Cl,N~6 to C11b),creating a five-membered imidazo type ring system.According to IUPAC fused ring conventions,we propose the following systematic name for this adduct:(9'-(2"-deoxyribofuranosyl))purino[6',1':2,3]imidazo[5,4-p]-(1,11b-dihydro-(Nacetyl-3-amino))benzanthrone.The 3'-phosphates of these novel adducts could be 5'-postlabeled using [gamma-~(32)P]ATP,although the efficiency of labeling was found to be low (less than 20%).However,none of these adducts could be detected in DNA from 3-NBA-treated rats by ~(32)P-postlabeling.Two of these synthetic adducts were treated with alkali to generate nonacetylated adducts,and these were also shown by HPLC to differ from those adducts found in rat DNA.Therefore,a different approach to the synthesis of authentic standards is needed for the structural characterization of 3-NBA-derived DNA adducts formed in vivo.