Epigenic effects of environmental toxicants on cellular communication pathways

与实验动物的出生缺陷、癌症、生殖和神经行为障碍有关的化学物质，如多氯联苯、多溴联苯、三氯二苯、滴滴涕、过氧化物体、增殖物等，通过“表观遗传”发挥作用，而不是通过遗传毒性机制[它们都已被证明抑制缝隙连接细胞间通讯(GJIC)]。该跨学科项目的目标是利用具有干细胞样潜能的体外人类神经元细胞系，研究在生物或化学修复过程之前或之后暴露于环境毒物可能影响的分子(基因表达改变)、生化(各种有丝分裂/分化、信号转导系统)和细胞(GFIC)、细胞增殖、细胞分化、凋亡[机制]。该提案既包括我们与Susan博士和W.Weber博士在之前的超级基金计划项目中的合作的扩展，以使用我们的大鼠肝上皮GJIC检测来评估他们的补救技术的有效性，也包括一个新的项目，研究GJIC在人类神经元细胞中的调制与化学诱导的信号转导和基因表达变化的关系。工作假设是确定有毒化学物质对GJIC的阻断是否由特定的信号转导机制介导，这些机制可能会改变特定基因的表达，进而影响细胞调节增殖、细胞分化或凋亡的能力。提出了三个具体的目标：目标1：使用已知结构/功能关系的模型毒物来确定与细胞行为改变相关的特定细胞内信号转导；目的：研究与目标1相同的信号通路，与修复的混合物一起，以筛选各种补救策略的效果；目的3：测试新的DNA微阵列技术是否可以用于鉴定与改变的GJIC相关的基因表达变化以及AIMS 1和2的细胞终点研究。其意义在于验证GJIC的抑制是化学物质的预测终点，这些化学物质可能是有毒的，其能力是通过触发各种信号转导机制来改变控制细胞增殖、细胞分化、细胞凋亡或分化细胞适应性反应的基因表达。此外，在人类体外系统中使用DNA微阵列技术，在其中许多混杂因素可以控制，识别那些与化学诱导的信号转导系统相关的基因及其相关的生物效应可能比使用动物系统的组织更容易和更相关地推断人类的风险评估。

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.