Biomonitoring studies and susceptibility markers for acrolein congeners and allylic and benzyl compounds.

The importance of genotoxic acrolein congeners and allylic and benzyl compounds as industrial compounds, ubiquitous environmental pollutants, and naturally occurring substances necessitates the availability of adequate biomonitoring techniques. Endogenously formed acrolein congeners are considered to play an important role in carcinogenesis. Our studies have demonstrated that acrolein congeners react with DNA components and form adducts with the guanine moiety. We have identified and characterized cyclic 1,N2-deoxyguanosine adducts, cyclic 7,8-guanine adducts, linear 7-guanine adducts, 1,N2,7,8-bis-cyclic adducts, and 1,N2-cyclic, 7-linear bis adducts. Both the reactivity of the acroleins toward nucleosides and their mutagenicity in S. typhimurium TA100 decrease with increasing degree of alkyl substitution. Adducts are now available as reference substances for developing sensitive detection methods. Of the biomonitoring methods investigated for allylic and benzyl compounds, the detection of cysteine and histidine adducts isolated from hemoglobin seems to be the most sensitive. Gas chromatography with electron capture detection of heptafluorobutyric acid derivatives allows a detection limit in the femtomole range, HPLC-fluorescence detection of O-phthalic dialdehyde derivatives allows a limit in the picomole range, and detection of 9-fluorenylmethyl-chlorofomiate derivatives allows a limit in the femtomole range.

Molecular mechanisms of DNA damage initiated by alpha, beta-unsaturated carbonyl compounds as criteria for genotoxicity and mutagenicity.

alpha, beta-Unsaturated carbonyl compounds are important not only from a theoretical but also a practical standpoint. These ubiquitous compounds can interact with DNA through various mechanisms. The predominant interaction is the formation of cyclic 1,N2-deoxyguanosine adducts; 7,8-cyclic guanine adducts are also found. We have synthesized and characterized the stereoisomers of adducts formed by about 20 alpha, beta-unsaturated carbonyl compounds. The different types of adducts and the mutagenic and genotoxic response can be explained by the molecular structures of the agents. Compounds forming saturated cyclic adducts are mutagenic in S. typhimurium strain TA100 and to a lesser extent in TA1535. Substances with a leaving group at the C-3 position form unsaturated conjugated cyclic adducts and are mutagenic only in the His D3052 frameshift strains with an intact excision repair system (no urvA mutation). Metabolic epoxidation of the double bond and other metabolic activation, e.g., activation of the nitrogroups via nitroreductases, were also found to contribute to genotoxic and mutagenic activities. Our results have further elucidated the genotoxic mechanisms of these compounds; however, additional investigations are required for a complete understanding of the genotoxic activity of this class of compounds.

The possible role of alpha, beta-unsaturated carbonyl compounds in mutagenesis and carcinogenesis.

alpha, beta-Unsaturated carbonyl compounds are industrially important compounds, ubiquitous in the environment and are formed endogenously. They interact with proteins and enzymes. Genotoxicity was found in eucaryotic cells and some compounds were carcinogenic. Unsaturated carbonyl compounds are considered to play an important role in human cancer. Insufficient and contradictory results were reported on mutagenicity. We demonstrated a clear mutagenic potential for these compounds and have shown interference of their bacterial toxicity with an adequate testing. Structure-mutagenicity relationships were confirmed by the results of the SOS-chromotest. The compounds induce DNA-strand breaks. However, we did not find indications for cross linking. With mutagenic alpha, beta-unsaturated carbonyl compounds we isolated and characterized 1,N2-cyclic deoxyguanosine adducts, 7,8-cyclic and 7-linear guanine adducts as well as 1,N2-7,8-biscyclic adducts and 1,N2-cyclic, 7-linear bisadducts. Reactivity of these compounds towards nucleosides runs in parallel with their mutagenic potential. Mutagenic and carcinogenic activities most probably depend on these reactions with DNA, and DNA adducts can be utilized as indicators for the role of these compounds in human carcinogenicity.

Risk assessment for mutagenic and carcinogenic activities of alpha,beta-unsaturated carbonyl compounds by a screening strategy based on structure-activity relationships.

alpha,beta-Unsaturated compounds are ubiquitous and are formed endogenously. They form DNA adducts and are a constant source of DNA damage. A speedy screening strategy based on structure-activity relationships and a battery of prescreening tests for a rapid and reliable assessment of the role of these compounds in mutagenesis and carcinogenesis is presented and discussed. In this screening strategy, time-consuming and expensive animal tests are replaced by in vitro test with bacteria and cell cultures. The results of the mutagenicity and genotoxicity tests, as well as the results of the binding studies of alpha,beta-unsaturated carbonyl compounds with DNA components, and the corresponding structure-activity relationships, are presented.