Identification and characterization of the major DNA adduct formed chemically and in vitro from the environmental genotoxin 3-nitrofluoranthene

Comparison of the mutational specificity induced by environmental genotoxin nitrated polycyclic aromatic hydrocarbons in Salmonella typhimurium his genes

Mutagenicity of 15 nitrated polycyclic aromatic hydrocarbons (nitro PAHs), which were detected in ambient air particles and/or combustion source emissions, were examined using a set of six Salmonella typhimurium tester strains (TA7001 to TA7006), and the mutational specificity was characterized by the comparison of the mutagenic potencies of nitro-PAHs in the tester strains. Each strain carries a unique missense mutation in the histidine operon and is reverted by only one specific base-substitution out of six possible changes. All nitro-PAHs tested were mutagenic in multiple strains, and were classified into four categories based on the strains predominantly reverted. 1-Nitropyrene (1-NPy), 2,7-dinitrofluoren-9-one and 1,3-, 1,6- and 1,8-dinitropyrene isomers exerted the highest mutagenicity in strain TA7005 (C.G-->A.T transversion) followed by strain TA7006 (C.G-->G.C transversion). 2- And 3-nitrofluoren-9-one isomers, 2-NPy and 2,7-dinitrophenanthrene were also markedly mutagenic in strain TA7005 but not in strain TA7006. For 2-, 3- and 9-nitrophenanthrene isomers, 2-nitrofluoranthene (2-NFT) and 4-NPy, TA7004 (G.C-->A.T transition) was the most responsive strain. 3-NFT was unique, showing the highest mutagenicity in strain TA7002 (T.A-->A.T transversion). All nitro-PAHs tested induced C.G-->A.T transversion, which is observed as the most frequent base-substitution mutation of p53 tumor suppressor gene in human lung cancer.

Differentiation of isomeric C8- and N (2)-deoxyguanosine adducts of 2-acetylaminofluorene by fast-atom bombardment and tandem mass spectrometry

Product-ion studies of source-produced ions corresponding to acetylated and nonacetylated N (2)- and C8-substituted aminofluorene adducts of deoxyguanosine were conducted to identify specific fragmentation pathways differentiating the isomers and to determine the influence of the acetyl group on the fragmentation of the arylamide modified deoxyguanosine adducts. The collision-induced dissociation spectra of the BHZ 2 (+) ion and other significant source-produced ions showed no evidence to suggest that ketene loss (deacetylation) resulted in significant alteration of the structure of the adducts. However, other significant ion formation processes, particularly loss of water from the N (2)-substituted arylamide did appear to require rearrangement, likely involving bond formation between the carcinogen moiety (acetyl group) and the N1 or N2 position of the guanine base. The combined loss of ketene and water constitute a fragmentation pattern specific for the N (2)-arylamide, 3-(deoxyguanosin-N (2)-yl)-2-acetylaminofluorene.

Identification of deoxynucleoside-polyaromatic hydrocarbon adducts by capillary zone electrophoresis-Continuous Flow-fast atom bombardment mass spectrometry

Capillary zone electrophoresis coupled to continuous flow-fast atom bombardment mass spectrometry is shown to have utility for the detection and characterization of adducts formed by the covalent attachment of four polyaromatic hydrocarbon (PAH) and amino-PAH compounds to deoxyguanosine. Normal scanning provided structural information for a 1.3 ng injection of a model adduct, while 1.3 ng of each of a mixture of adducts was sufficient to determine their molecular weights by monitoring the constant neutral loss of deoxyribose. Exploitation of this loss in the multiple reaction monitoring mode resulted in the detection of low picogram amounts of target adducts in mixtures.

The kinetics of 1-nitropyrene and 3-nitrofluoranthene metabolism using bovine liver xanthine oxidase

The cytosolic molybdoflavoprotein xanthine oxidase has been shown to catalyze the reduction of exocyclic nitro groups to the corresponding nitroso, hydroxylamino and amino derivatives for a wide variety of xenobiotics including the nitrated polycyclic aromatic hydrocarbons 1-nitropyrene and 3-nitrofluoranthene. Using commercially available bovine liver xanthine oxidase, we have studied the kinetics of the metabolism of 1-nitropyrene and 3-nitrofluoranthene. The nitroreduction of these nitro compounds in the presence of xanthine oxidase is dependent on the presence of hypoxanthine or xanthine and the absence of oxygen. This nitroreduction is independent of added flavins (FMN and FAD), unlike the related molybdoflavoprotein aldehyde oxidase. Xanthine oxidase has a Km of 0.7 microM and Vmax of 0.06 nmol/min per unit enzyme for 1-nitropyrene and a Km of 8.6 microM and Vmax of 0.7 nmol/min per unit enzyme for 3-nitrofluoranthene. The importance of these kinetic constants in evaluating the cytosolic metabolism of 1-nitropyrene and 3-nitrofluoranthene are discussed.