Superfund Research Program
Integrated Response to Toxic Perturbation
Arsenic action. This team has studied effects on proteins in human epidermal cells treated with arsenic concentrations in the range of human exposure causing health problems at sites around the world. In a survey of approximately 300 proteins, they found that nearly half were altered at least two-fold in amount within a day and remained altered during treatment for 9 days. An overall change in protein oxidation state (free sulfhydryl groups) was not detected, but stress related (heat shock) proteins and enzymes in the glycolysis pathway were altered greatly in amount. The results are consistent with targeting of protein chaperones and the oxidative phosphorylation pathway. Identification of such macromolecular targets, clarifying the mechanism of arsenic action, promises to assist in setting exposure standards.
Proteomic approaches to lung toxicity. Proteins adducted by reactive naphthalene and 1-nitronaphthalene metabolites in susceptible rodent species have been identified and compared with those adducted in rhesus macaques. Nearly 50 protein adducts were identified in these studies, and substantial overlap was found among proteins adducted in rodent and rhesus airways. These findings are being used as the basis for development of biomarkers that can be applied to human nasal swipes. To accomplish this task, proteins were separated by 2D gel electrophoresis and quantitated by fluorescence imaging. The project investigators have established and validated new methods for these analyses by incorporating a fluorescent internal standard, which stabilizes and normalizes the variance in the analyses. In the processes of these analyses, they have discovered that one of the commercial software packages adds substantially to the variability in the data and likely yields information that is not accurate.
Gene coordination inferred from DNA microarray results. A major area in need of development is tracing how gene expression changes detected by microarray result in effects on growth and differentiation pathways. This translation will be greatly assisted by knowledge of protein-protein interactions. As a foundation for treatment with xenobiotics, airway mucous cells were treated with retinoic acid, a modulator of toxic response. From time course experiments, and with reference to known protein interactions among homologues in other species, at least 6 groups of genes have been identified that are important for mucus cells differentiation induced by vitamin A and that could be targeted by xenobiotics.