Project 4: Urinary Protein Biomarkers for Assessing the Potential Toxicity

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Lung diseases are a significant cause of morbidity and mortality in the US population. Exposure to chemicals in air, water and food contributes to these diseases. A number of chemicals undergo bioactivation to produce selective lung injury in rodents. This project focuses on naphthalene (NA) and 1-nitronaphthalene (NN), which are present in superfund waste sites and which represent a class of environmentally important compounds. Both chemicals undergo metabolism to electrophilic intermediates which become bound covalently to proteins in target cells. Protein binding is a key component of cytotoxicity. We have demonstrated that the proteins targeted are similar in rodents and primate nasal epithelium. This underscores the need to develop biomarkers which are tightly tied to toxicity. The central hypothesis is: /the formation of key protein adducts with reactive metabolites of NA/NN in target respiratory tissue is causally related to cytotoxicity; measurement of adducted peptides/proteins in urine and nasal brushings provides a highly sensitive molecular signature of exposure and effect./ The proposed work builds on recent findings showing 1) high specific activity adducts in urine of NA-treated mice, and 2) numerous identified protein adducts in lungs and nasal cavity of mice, rats and monkeys. The proposed studies will utilize antibodies from project 3 to trap and concentrate adducted peptides from the urine and to evaluate adduct levels in animal model systems. These approaches will be validated for their ability to assess adduct levels following exposures to small amounts of 14C-NA by accelerator mass spectrometry (Core A), will utilize the mass spectrometry facilities of cores A and B for analysis of adducted peptides and will depend heavily on the proteomics services offered by Core B. Overall, these studies are expected to: 1) yield fundamental information on how adducted proteins, formed in respiratory tissues, are handled in the whole animal, 2) explore concentration-response relationships at environmentally relevant concentrations, 3) provide methods which can be applied to exposed human populations, which will be useful-with modification-for assessing risk of other metabolically activated chemicals and 4) provide methods which can clarify the importance of genetic polymorphisms in genes responsible for the biodisposition of chemicals like NA and NN.