Investigation of cysteinyl protein adducts of benzene diolepoxide

Metabolism of benzene is fairly complex yielding several reactive metabolites that could form adducts with macromolecules such as DNA and proteins. Systemic availability of these reactive species can be estimated by measuring the corresponding adducts of these species with serum albumin or hemoglobin. We have shown previously that serum albumin adducts of benzene oxide and 1,4-benzoquinone increased in a dose-dependent manner in rodents and humans exposed to benzene. However, formation of macromolecular adducts of other reactive metabolites, such as benzene diolepoxide and E,E-muconaldehyde, has not received much attention despite the demonstrated mutagenicity and/or carcinogenicity of these metabolites. We studied the reaction of isomers of benzene diolepoxide, namely syn-((±)BDE1) and anti-BDE ((±)BDE2), with sulfhydryl groups in vitro. The half-life of BDE2 in 0.1 M ammonium acetate buffer (pH 7.6) was (5.46 h) longer that that in serum albumin in the same buffer (3.83 h) indicating the reaction of BDE with nucleophilic sites on albumin. Reaction products between these and l-cysteine, and GSH were identified and characterized by mass spectrometry in an attempt to develop an assay to quantify these adducts in serum albumin.