Superfund Research Program
Urinary Protein Biomarkers for Assessing the Potential Toxicity of Naphthalene in Humans
Project Leader: Alan R. Buckpitt
Grant Number: P42ES004699
Funding Period: 2010-2015
Naphthalene causes dose-dependent cytotoxicity to murine airway epithelial cells but a link between exposure and human pulmonary disease has not been established. Naphthalene toxicity in rodents depends on P450 metabolism; subsequent biotransformation results in urinary elimination of several conjugated metabolites. Numerous studies have been published on human naphthalene exposure using deconjugated urinary naphthols as a measure of internal exposure. This research team’s work in animals suggested that the glucuronides and sulfate conjugates were not the major urinary metabolites and that metabolites derived from glutathione were quantitatively more important. Work conducted in the past year focused on the development of quantitative LC/MS methods for measuring all of the major metabolites of naphthalene including glucuronide and sulfate conjugates of naphthols, the N-acetyl glutathione derivative and mercapturic acid from naphthalene epoxide. Application of the method to urine collected from mice exposed to naphthalene at 15 ppm (4 hrs) showed that glutathione-derived metabolites accounted for 60-70% of the total measured metabolites and sulfate and glucuronide conjugates were eliminated in equal amounts. The method is robust and directly measures several major naphthalene metabolites including those derived from glutathione conjugation of naphthalene epoxide. The assays do not require enzymatic deconjugation, extraction or derivatization thus simplifying sample work up.