DNA adduct formation and mutation induction by nitropyrenes in Salmonella and Chinese hamster ovary cells: relationships with nitroreduction and acetylation.

Abstract

Nitrated pyrenes are environmental pollutants and potent mutagens in the Salmonella reversion assay. In this study reversion induction by 1-nitropyrene and 1,8-dinitropyrene in Salmonella typhimurium TA1538 and mutation induction by 1-nitropyrene in Chinese hamster ovary (CHO) cells were related to the extent of metabolism and DNA adduct formation. In suspension cultures of Salmonella typhimurium TA1538, 1,8-dinitropyrene was up to 40-fold more mutagenic than 1-nitropyrene, although both compounds were metabolized at similar rates with nitroreduction being the major pathway. The major metabolite formed from 1-nitropyrene after 2 hr of incubation was 1-nitrosopyrene, while 1-amino-8-nitropyrene was the major metabolite formed from 1,8-dinitropyrene. 1-Nitrosopyrene and 1-nitro-8-nitrosopyrene elicited mutation values consistent with their being intermediates in the activation pathways. However, subsequent to nitroreduction, 1,8-dinitropyrene appeared to be further activated by acetylation, while 1-nitropyrene was not. Each nitrated pyrene produced a major DNA adduct substituted at the C8-position of deoxyguanosine. Although 1,8-dinitropyrene was more mutagenic than 1-nitropyrene, both compounds induced a similar number of revertants per adduct. Incubation of 1-nitrosopyrene with CHO cells produced a rapid concentration-and time-dependent induction of mutations and the conversion of 1-nitrosopyrene to 1-aminopyrene. In contrast, 1-nitropyrene did not induce mutations and was not converted to 1-aminopyrene. Both compounds produced the same major adduct, but adduct formation by 1-nitropyrene was much lower than by 1-nitrosopyrene. These data indicate that nitroreduction and C8 deoxyguanosine adduct formation are strongly associated with mutation induction by 1-nitropyrene in Salmonella and CHO cells. With 1,8-dinitropyrene, however, mutation induction in Salmonella is dependent upon both nitroreduction and esterification

Disubstituted amino‐, nitroso‐, and nitrofluorenes: A physicochemical basis for structure‐activity relationships in salmonella typhimurium

“…Since most nitroso compounds are more mutagenic in TA98NR than TA98 and most nitro compounds are more mutagenic in TA98 than in TA98NR (Table I), it is tempting to speculate that the classical nitroreductase catalyzes sequential 1 ereductions while the alternate nitroreductase may catalyze concerted 2e-reductions. It is not clear from the data presented here and elsewhere [Heflich et al, 1985b;Fifer et al, 19861 which reduction is rate limiting. Since 2-NOF is much more mutagenic than 2-NF (Table I) it would seem that reduction of the nitroso group proceeds faster than the nitro group.…”

Role of nitroreduction in the synergistic mutational response induced by mixtures of 1‐ and 3‐ nitrobenzo[a]pyrene in Salmonella typhimurium

“…In addition, based on studies with TA98NR, 1-NP and 1-and 3-nitro-BaP are all reduced to mutagens by the classical nitroreductase [Mermelstein et al, 1981;Pitts et al, 1984;Chou et al, 1985, 19861. The amounts of 1-NP metabolized to 1-AP by the cultures after 1 hr of incubation were similar to the amounts reported by Heflich et al [1985] using strain TA1538. Even a 1% increase in the conversion of nitro-BaPs to nitroso-BaPs could account for the synergistic mutational responses observed, although in one case treatment with a mixture resulted in only a 9% increase in metabolite formation compared with treatment with pure compounds.…”

Formation of reactive 1-nitropyrene metabolites by lung microsomes and isolated lung cells

“…In contrast to the strain TA 98, TA 98NR is not able to carry out the initial metabolic step to form 1-nitrosopyrene, whereas both strains can perform the next reductive step to form N-hydroxy-l-nitropyrene, believed to be the reactive 1-NP intermediate (McCoy et al, 1984;Heflich et al, 1985;Filer et al, 1986a). Figure 1 shows the mutagenicity of purified 1-NP with microsomal preparations from lung and liver of rabbit, rat and hamster.…”

“…Nitroarenes are activated to mutagenic species in bacteria in the absence of mammalian metabolism systems (Rosenkranz and Mermelstein, 1983). Whereas nitroreduction by bacterial enzymes to form a C8 deoxyguanosine DNA adduct is strongly associated with mutation induction for 1-NP, the intermediate reduction products derived from compounds such as dinitropyrenes are further activated by acetylation (Bryant et al, 1984;Heflich et al, 1985;Fifer et al, 1986a).…”