Epigenic effects of environmental toxicants on cellular communication pathways

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Chemicals, such as PCB's, PBB's, TCDD, DDT, peroxisomes, proliferators, etc., which have been associated with birth defects, cancer, reproductive and neuro-behavioral dysfunctions in experimental animals, work by "epigenetic", not by genotoxic mechanisms [They all have been demonstrated to inhibit gap junctional intercellular communication (GJIC)]. The goal of the interdisciplinary project is to use an in vitro human neuron cell line with stem cell-like potential, to study the molecular (altered gene expression), biochemical (various mitogenetic/differentiation, signal transducing systems) and cellular (GFIC), cell proliferation, cell differentiation, apoptosis] mechanisms that might be affected by exposure to environmental toxicants prior to, or post, biological or chemical remediation processes. The proposal contains both an extension of our collaboration in the previous Superfund Program Project with Dr. Susan and Dr. W. Weber to assess the efficacy of their remediation techniques using our rat liver epithelial GJIC assay, as well as a new project to study the relationship of the modulation of GJIC in human neurons cells to chemically-induced signal transduction, to alterations in gene expression. The working hypothesis will be to determine if the blockage of GJIC by toxic chemicals is mediated by specific signal transduction mechanisms which might alter the expression of specific battery of genes which, in turn, could affect the cell's ability to regulate proliferation, cell differentiation or apoptosis. Three specific aims are proposed: Aim 1: To use known model toxicants with known structure/function relations to identify specific intracellular signaling associated with alterations of cell behavior; Aim : To study the signaling pathways, as in Aim 1, with the remediated mixtures to screen the efficacy of various remediation strategies; Aim 3: To test if the new DNA microarray technology can be used to identify altered gene expression associated with the altered GJIC and cellular endpoint studies of Aims 1 and 2. The significance is to provide validation of the inhibition of GJIC as a predictive endpoint of chemicals that can be toxic via their ability to trigger various signal transduction mechanisms that alter gene expression controlling either cell proliferation, cell differentiation, apoptosis or adaptive response of differentiated cells. In addition, using DNA microarray technology on a human in vitro system where many confounding factors can be controlled, identification of those genes associated with chemical-induced signal transduction systems and their associated biological effects might be easier and more relevant to the extrapolation of risk assessment in human beings, than the use of tissues from animal systems.