The effect of deuterium and fluorine substitution upon the mutagenicity of N-hydroxy-2,6-dimethylaniline

Characterization of N-(2,6-dimethylphenyl)hydroxylamine adducts of 2'-deoxyguanosine under weakly basic conditions

Aromatic amines are a class of chemical carcinogens that are activated by cytochrome P450 enzymes to form arylhydroxylamines that are conjugated to form N-acetoxyarylamines or N-sulfonyloxyarylamines. These conjugates undergo N-O bond cleavage to become reactive nitrenium ions that may form DNA adducts. Numerous studies in the past using N-acetoxyarylamines to investigate DNA adduct formation were conducted, however, less is known in regard to DNA adduct formation directly from arylhydroxylamines - especially under conditions that mimic the physiological conditions of cells such as weakly basic conditions. In this study, 2'-deoxyguanosine (dG) was exposed to N-(2,6-dimethylphenyl)hydroxylamine (2,6-DMPHA) and N-phenylhydroxylamine (PHA) at pH 7.4 without enzymes and analyzed by liquid chromatography high resolution mass spectrometry (LC-HRMS). 2,6-DMPHA exposure resulted in the production of relatively low amounts of adducts however the identities of at least six different adducts that were formed through reactions with carbon, nitrogen and oxygen of 2'-deoxyguanosine were proposed based upon different analytical approaches including HRMS CID fragmentation and NMR analyses. Contrastively, PHA exposure under identical conditions resulted in one adduct at the C8 position. It was concluded from these results and results of theoretical calculations that nitrenium ions produced from 2,6-DMPHA were relatively more stable resulting in longer nitrenium ion lifetimes which ultimately led to greater potential for 2,6-DMPHA nitrenium ions to react with multiple sites on dG.

Influence of structural and functional modifications of selected genotoxic carcinogens on metabolism and mutagenicity - a review

Alterations in molecular structure are responsible for the differential biological response(s) of a chemical inside a biosystem. Structural and functional parameters that govern a chemical's metabolic course and determine its ultimate outcome in terms of mutagenic/carcinogenic potential are extensively reviewed here. A large number of environmentally-significant organic chemicals are addressed under one or more broadly classified groups each representing one or more characteristic structural feature. Numerous examples are cited to illustrate the influence of key structural and functional parameters on the metabolism and DNA adduction properties of different chemicals. It is hoped that, in the event of limited experimental data on a chemical's bioactivity, such knowledge of the likely roles played by key molecular features should provide preliminary information regarding its bioactivation, detoxification and/or mutagenic potential and aid the process of screening and prioritising chemicals for further testing.

Highlights of the eighth international conference on carcinogenic/mutagenic N-substituted aryl compounds

Research in the 20th century initially identified arylamines as causative factors in occupational carcinogenesis, especially bladder cancer, and subsequently identified arylamines as a major class of mutagens/carcinogens in the environment and diet that are potential risk factors in a variety of human cancers. Current research focuses on understanding of mechanisms of arylamine carcinogenesis, such as the role of metabolic processing, DNA adduct formation, and mutagenesis, and learning more about the molecular alterations in carcinomas induced by these compounds. Furthermore, research to identify human exposures, including developing more sensitive methods for analyzing environmental samples and identifying suitable biomarkers are important aspects of contemporary investigations. In addition, better evaluation of the risk of these compounds in human cancer especially with regard to the impact of genetic polymorphisms is a major focus of research in this field. Although current population studies have sometimes been described as equivocal, improved tools for epidemiology, refined human biomonitoring methods and collaborative endeavors to study multiple population groups now provide a better means to ultimately define the role of arylamines in human carcinogenesis. The purpose of the Eighth International Conference on Carcinogenic/Mutagenic N-Substituted Aryl Compounds, held in Washington, DC, 12-14 November 2001, was to explore the current scope of studies on arylamine carcinogenesis among scientists in basic research and epidemiology and to discuss future research priorities. With the intent of providing a view to the current field of research on aromatic amines, this review presents a synopsis of the Proceedings of the Eighth International Conference and highlights the manuscripts contained in this special issue of Mutation Research.