Characterization of urinary protein/peptide adducts as markers of reactive naphthalene metabolite formation

Naphthalene (NA) is a volatile polycyclic aromatic hydrocarbon generated during combustion and is ubiquitous in the environment. The toxicity of the NA is believed to be mediated by the generation of electrophilic species that subsequently bind to biological proteins following chemical metabolism in rodents. However the potential human health effects from NA exposure remain uncertain. 1,2-naphthalene epoxide, naphthalene diol epoxide, 1,2-naphthoquinone, and 1,4-napthoquinone have all been identified as reactive metabolites of interest, yet the role of each in overall covalent protein adduction and subsequent cytotoxicity remains to be established. Accordingly, to better understand the chemical species produced when naphthalene metabolites react with proteins and peptides, model systems were developed. Products were studied using collision-induced dissociation (CID) high resolution mass spectrometry (HRMS). The results from the model system studies assisted in data interpretation from ongoing work to detect protein/peptide adducts as biomarkers of biologic effect. Subsequently this lead to the development of a new methodology to identify protein adducts generated in target tissues and eliminated in the urine after NA exposure as potential biomarkers for the assessment of critical steps leading to cytotoxicity. Findings from this new methodology has opened the possibility of using the urinary adductome as a biomarker to evaluate processes intimately linked to the mechanisms of cytotoxicity and applicable across species from rodent models where toxicities are well established to exposed human populations.