Exposure profiling of reactive compounds in complex mixtures

Abstract

Humans are constantly exposed to mixtures, such as tobacco smoke, exhaust from diesel, gasoline or new bio-fuels, containing several thousand compounds, including many known human carcinogens. Covalent binding of reactive compounds or their metabolites to DNA and formation of stable adducts is believed to be the causal link between exposure and carcinogenesis. DNA and protein adducts are well established biomarkers for the internal dose of reactive compounds or their metabolites and are an integral part of science-based risk assessment. However, technical limitations have prevented comprehensive detection of a broad spectrum of adducts simultaneously. Therefore, most studies have focused on measurement of abundant individual adducts. These studies have produced valuable insight into the metabolism of individual carcinogens, but they are insufficient for risk assessment of exposure to complex mixtures. To overcome this limitation, we present herein proof-of-principle for comprehensive exposure assessment, using N-terminal valine adduct profiles as a biomarker. The reported method is based on our previously established immunoaffinity liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with modification to enrich all N-terminal valine alkylated peptides. The method was evaluated using alkylated peptide standards and globin reacted in vitro with alkylating agents (1,2-epoxy-3-butene, 1,2:3,4-diepoxybutane, propylene oxide, styrene oxide, N-ethyl-N-nitrosourea and methyl methanesulfonate), known to form N-terminal valine adducts. To demonstrate proof-of-principle, the method was successfully applied to globin from mice treated with four model compounds. The results suggest that this novel approach might be suitable for in vivo biomonitoring.

Evaluation of time-dependent toxicity and combined effects for a series of mono-halogenated acetonitrile-containing binary mixtures

“…Via exposure profiling of reactive mixtures [1], docking-based receptor library [2] or toxicogenomics [3] studies, or examining aquatic toxicity [4], mammalian reproductive effects [5] or endocrine disruptors [6] such research efforts can improve the ability to predict mixture toxicity. Assessments of toxicity in binary [7], ternary [8] or complex chemical mixtures [9] have been common, with such toxicity having been evaluated for metals [10], pesticides [11], polycyclic aromatic hydrocarbons [12], [13], and micropollutants [14].…”

Time-dependence in mixture toxicity prediction

“…Such research has included in vitro and in vivo studies (Boyd et al, 2013; Cedergreen et al, 2012; Coors et al, 2012), toxicity assessment using combined effects models (Crépet et al, 2013; Hertzberg et al, 2013; Moser et al, 2012; Rider et al, 2008; Webster, 2013), evaluating stressor impacts environmentally (Allan et al, 2012; Florian et al., 2013; Løkke 2010), risk assessment studies (Johnson et al, 2013; Løkke et al, 2013; Meek, 2013; Moore and Teed, 2013) and examining chemical reactivity within complex mixtures (Goel et al, 2013). Although the specifics of such research vary, the common goal is improving the ability to predict the effects of exposure to chemical mixtures.…”

In vivo doses of butadiene epoxides as estimated from in vitro enzyme kinetics by using cob(I)alamin and measured hemoglobin adducts: An inter-species extrapolation approach

“…This concerns the exposure dose estimates, which are explained by uncertainties in the measured exposure levels and duration, and because of varying exposure conditions, e.g. simultaneous exposures to other compounds (Goel et al, 2013;Sathiakumar et al, 2007). The Hb adduct level increments could be afflicted with uncertainties, particularly when the measured adduct levels are close to the LOQ of the analytical method or close to background adduct levels from other sources as measured in the controls (this particularly concerns the adduct from DEB in humans).…”