DNA Adducts from Nitroreduction of 2,7-Dinitrofluorene, a Mammary Gland Carcinogen, Catalyzed by Rat Liver or Mammary Gland Cytosol
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- 作者：Clare L. Ritter ; Sandra J. Culp ; James P. Freeman ; M. Matilde Marques ; Frederick A. Beland ; and Danuta Malejka-Giganti
- 刊名：Chemical Research in Toxicology
- 出版年：2002
- 出版时间：April 2002
- 年：2002
- 卷：15
- 期：4
- 页码：536 - 544
- 全文大小：121K
- 年卷期：v.15,no.4(April 2002)
- ISSN：1520-5010
文摘
Nitrofluorenes are mutagenic and carcinogenic environmental pollutants arising chiefly fromcombustion of fossil fuels. Nitro aromatic compounds undergo nitroreduction to N-hydroxyarylamines that bind to DNA directly or after O-esterification. This study analyzes the DNAbinding and adducts from the in vitro nitroreduction of 2,7-dinitrofluorene (2,7-diNF), a potentmammary carcinogen in the rat. Potential adduct(s) of 2,7-diNF was (were) generated byreduction of 2-nitroso-7-NF with ascorbate/H+ in the presence of calf thymus DNA. The majoradduct was characterized by HPLC/ESI/MS and 1H NMR spectrometry as N-(deoxyguanosin-8-yl)-2-amino-7-NF, and a minor one was determined by HPLC/ESI/MS to be a deoxyadenosineadduct of 2-amino-7-NF. Products from enzymatic nitroreduction were monitored by HPLCand DNA adduct formation by 32P-postlabeling. Xanthine oxidase/hypoxanthine-catalyzednitroreduction of 2,7-diNF, 2-nitrofluorene (2-NF), and 1-nitropyrene (1-NP) yielded therespective amines to similar extents (30-50%). However, the level of the major adducts (~0.15/106 nucleotides) from 2-NF [N-(deoxyguanosin-8-yl)-2-aminofluorene] and 2,7-diNF [N-(deoxyguanosin-8-yl)-2-amino-7-NF] was 
2% that from 1-NP. In the presence of acetyl CoA,nitroreduction of 2-NF catalyzed by rat liver cytosol/NADH yielded the same adduct at a levelof 2.2/106 nucleotides. Liver or mammary gland cytosol with acetyl CoA yielded mainlyN-(deoxyguanosin-8-yl)-2-amino-7-NF from 2,7-diNF at >30 adducts/106 nucleotides, levelscomparable to those from 1,6-dinitropyrene and 4- or 49-fold greater than the respective levelswithout acetyl CoA. Recovery of 2-nitroso-7-NF and 2-amino-7-NF from cytosol-catalyzedreduction of 2,7-diNF indicated nitroreduction and an N-hydroxy arylamine intermediate.Likewise, the presence of 2-acetylamino-7-NF indicated that reactivity with acyltransferase(s)was not prevented by the nitro group at C7. These data are consistent with activation of 2,7-diNF via nitroreduction to the N-hydroxy arylamine and acetyl CoA-dependent O-acetylationof the latter to bind to DNA. Enzymatic nitroreduction of 2,7-diNF was greatly enhanced by9-oxidation. The nitroreduction of either 9-oxo-2,7-diNF or 9-hydroxy-2,7-diNF catalyzed byliver cytosol with acetyl CoA yielded two adducts (>2/106 nucleotides). Differences in the TLCmigration of these adducts, compared to those from 2,7-diNF, and the lack of 2,7-diNF formationin the incubations suggested retention of the C9-oxidized groups. The relative ratios of theamine to amide from nitroreductions of 9-oxo-2,7-diNF and 2,7-diNF catalyzed by liver cytosolsuggested that the 9-oxo group decreased reactivity with acyltransferase and, thus, the amountof N-acetoxy arylamine that binds to DNA. The mammary gland tumorigenicity of 2,7-diNFand the extent of its activation by the tumor target tissue shown herein suggest relevance ofthis environmental pollutant for breast cancer.
2% that from 1-NP. In the presence of acetyl CoA,nitroreduction of 2-NF catalyzed by rat liver cytosol/NADH yielded the same adduct at a levelof 2.2/106 nucleotides. Liver or mammary gland cytosol with acetyl CoA yielded mainlyN-(deoxyguanosin-8-yl)-2-amino-7-NF from 2,7-diNF at >30 adducts/106 nucleotides, levelscomparable to those from 1,6-dinitropyrene and 4- or 49-fold greater than the respective levelswithout acetyl CoA. Recovery of 2-nitroso-7-NF and 2-amino-7-NF from cytosol-catalyzedreduction of 2,7-diNF indicated nitroreduction and an N-hydroxy arylamine intermediate.Likewise, the presence of 2-acetylamino-7-NF indicated that reactivity with acyltransferase(s)was not prevented by the nitro group at C7. These data are consistent with activation of 2,7-diNF via nitroreduction to the N-hydroxy arylamine and acetyl CoA-dependent O-acetylationof the latter to bind to DNA. Enzymatic nitroreduction of 2,7-diNF was greatly enhanced by9-oxidation. The nitroreduction of either 9-oxo-2,7-diNF or 9-hydroxy-2,7-diNF catalyzed byliver cytosol with acetyl CoA yielded two adducts (>2/106 nucleotides). Differences in the TLCmigration of these adducts, compared to those from 2,7-diNF, and the lack of 2,7-diNF formationin the incubations suggested retention of the C9-oxidized groups. The relative ratios of theamine to amide from nitroreductions of 9-oxo-2,7-diNF and 2,7-diNF catalyzed by liver cytosolsuggested that the 9-oxo group decreased reactivity with acyltransferase and, thus, the amountof N-acetoxy arylamine that binds to DNA. The mammary gland tumorigenicity of 2,7-diNFand the extent of its activation by the tumor target tissue shown herein suggest relevance ofthis environmental pollutant for breast cancer.