The respiratory tract is an important target for environmental agents, which require P450 dependent metabolism to ellicit toxicity. Naphthalene (NA) and close structural congeners produce injury to airway Clara cells which is species selective. Human exposure to naphthalenes occurs from a variety of sources including cigarette smoke and polluted air. Nitronaphthalenes (NN)(and structural congeners) are generated in the atmosphere from NA and are a direct byproduct of diesel exhaust but do not show species selective toxicity. The overarching goal of work outlined in this application is to identify biochemical and metabolic mechanisms for the toxicity of these agents in animals with the aim of determining the relevance of these mechanisms in humans. The following hypotheses will be tested: 1) epoxides generated from the parent hydrocarbons are proximate intermediates in both toxicity and protein adduct formation, 2) these electrophiles interact irreversibly with a number of proteins involved in antioxidant protection and protein folding (protein disulfide isomerase, peroxiredoxin, heat shock proteins and glutathione transferase) 3) by depleting glutathione these electrophiles enhance the redox sensitivity of these same proteins, 4) glutathione transferase pi plays a key role in the inactivation of toxic metabolites generated from both compounds and 5) the liver plays a role in generating metabolites which are released to the circulation and enhance the susceptibility of the lung to metabolites generated in situ. These studies will use a number of mouse models in which key enzymes involved in the detoxication of the epoxides (epoxide hydrolase, glutathione transferase pi), a key enzyme in quinone redox cycling (NADPH quinone oxidoreductase) and the redox partner for CYP450 in the liver have been genetically disrupted. Adducts with, and loss of sulfhydryls on individual proteins will be measured using 2D electrophoresis. These studies are expected to identify appropriate biomarker targets and metabolic proteins where polymorphisms could be important in altering individual susceptibility.
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