Several classes of environmental and therapeutic chemicals are recognized for their capacity to modulate expression of batteries of mammalian genes, in particular, genes encoding biotransformation enzymes catalyzing the detoxification of xenobiotic agents. The cytochrome P450s constitute a superfamily of core metabolizing enzymes participating in the oxidative metabolism of many exogenous substances in animals, plants, and bacteria. It is noteworthy that individual P450 genes are differentially and distinctly inducible by common contaminants of Superfund waste sites. In this renewal application, we will continue to develop and explore the utility of P450 gene expression markers in human cells as biomonitors of chemical exposure and effect. Ib addition, we will continue to probe the potential linkage of certain P450 genotypes with disease susceptibility in human populations. in past funding periods, we have developed a series of probes enabling assessment of mRNA levels (via RT/PCR), immunoreactive protein, and enzymological assays enabling extremely sensitive and highly specific detection of several P450 gene products. These methods will continue to be used and validated for human exposure applications. The primary hypothesis to be tested with the proposed research is that animal and human exposure to various classes of chemicals can be ascertained by composite measure of expression patterns for key P450 genes in peripheral cells. P450 CYP2D6 genetic analyses also have been performed in relation to Parkinson's disease susceptibility and these avenues will be continued to test a second hypothesis, that P450, genotype is a marker of Parkinson's disease susceptibility.
Specific aims of the current proposal are: 1) to use human cell lines in culture, and isolated blood cells from human volunteers to assess P450 expression patterns as a function of a) chemical exposure, b) cell type, and c) differentiation status of the cells; 2) with human tissue samples accumulated since the last submission, correlate P450 expression composites across liver, lung and blood cell types within the same individuals; 3) in collaboration with project 11, use genetic diagnostic approaches to assess the association of CYP2D6 genotype with Parkinson's disease incidence; 4) a) in collaboration with project 10, assess CYP2E1 genotype and gene expression patterns in alkylbenzene-exposed human volunteers to test the association of these markers with clearance rates in vivo; 4) b) in collaboration with project 7, develop mouse CYP2E1 immunochemical and mRNA hybridization biomarkers to examine the effects of trichloroethylene exposures on CYP2E1 expression levels in sensitive sentinel species (deermice) inhabiting Superfund hazardous waste sites. The results of these investigations should allow expanded use of the P450 system as bioindicator of chemical exposure, biological effect, and risk susceptibility in humans exposed to xenobiotic agents.
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