Project Summary/Abstract Naphthalene (NA), a simple polycyclic aromatic hydrocarbon, is persistently present in the environment as a byproduct of combustion of fossil fuels and burning of tobacco and other products. Its ubiquitous presence results in widespread exposure to the general population. Certain occupational groups, such as firefighters, have elevated levels of exposure. Firefighters also have increased incidences of certain types of cancer. NA is currently classified by the International Agency for Research on Cancer (IARC) as a Class 2B Carcinogen. There is direct evidence of tumor formation in mice and rats but no direct evidence of carcinogenecity of NA in humans at this time. The pathogenesis of tumor formation in mice and rats after exposure to NA is unclear; cytotoxic and genotoxic mechanisms are both proposed in the current literature. NA metabolism results in the generation of reactive intermediates such as 1,2-epoxide and reactive metabolites such as 1,4- and 1,2- naphthoquinone (NAQ). Reactive quinone and epoxide metabolites of similar compounds, such as benzo[a]pyrene, have been shown to enact their carcinogenecity through DNA adduct formation. Published ex vivo and in vitro data have demonstrated that NA metabolites can form adducts with DNA. The objective of this study is to identify and quantify NA-DNA adducts in mouse lung as well as mouse and human blood to enable assessment of potential genotoxicity in firefighters. Several hypotheses will be tested: 1) Circulating reactive NA metabolites, particularly NAQs, will form stable as well as depurinating adducts with DNA in both lung tissue and blood leukocytes in vivo; 2) the types and abundances of NA-DNA adducts in circulating leukocytes will at least partly reflect adduct formation in the lung; 3) the types of NA-DNA adducts detected in circulating leukocytes from exposed mice and firefighters will be similar; and 4) exposure to fire smoke will increase NA- DNA adduct levels in firefighters. These hypotheses will be tested through the application of 3 Specific Aims. In Aim 1, I will Identify and quantitate NA-DNA adducts formed in wild-type (WT) mice following NA inhalation exposure, with use of mass spectrometry methods. In Aim 2, I will dissect metabolic pathways responsible for NA-DNA adduct formation in the lung and circulating leukocytes of NA-exposed mice, with use of unique transgenic mouse models (liver-Cpr-null, liver-Ephx1-null, and Cyp2abfgs-null). In Aim 3, I will characterize NA-DNA adducts in blood specimens from firefighters and control donors. This project will provide direct evidence for the formation of NA-DNA adducts in vivo, lay the foundation for future studies of the genotoxicity of NA, obtain evidence to support more extensive assessments of the carcinogenic risks of NA to firefighters, and could have direct implications for the general population. Through the execution of this project and the help of this fellowship, I will be fully trained in scie...