Transgenerational epigenetic effects of PCBs on neuroendocrine systems

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DESCRIPTION (provided by applicant): This application addresses broad Challenge Area (15): Translational Science and specific Challenge Topic, 15- ES-101*: Effects of Environmental Exposures on Phenotypic Outcomes Using Non-human Models. The overall goal of this research proposal is to study transgenerational, epigenetic effects of endocrine- disrupting chemicals (EDCs) on neuroendocrine function. Environmental EDC exposures can result in permanent dysfunctions in reproductive development, impaired fertility, and hormonally-related disease states. Developing organisms, particularly fetuses and infants, are especially vulnerable to endocrine disruption. During these early life periods, hormones are responsible for normal development of the hypothalamus, the brain region that regulates endocrine and hormonal systems and is responsible for the control of adult reproductive physiology and behavior. Disruptions of these systems by environmental EDCs can interfere with the acquisition and maintenance of these processes, resulting in aberrant neuroendocrine development and a compromised adult phenotype. We propose that EDCs such as polychlorinated biphenyls (PCBs) can effect these changes in the fetally exposed (F1) individuals through actions on steroid hormone receptor gene and protein expression in the hypothalamus. Additionally, effects may be transmitted to future generations (F2, F3) through transgenerational, epigenetic mechanisms. The proposed studies seek to understand the mechanisms by which fetal exposures to PCBs cause permanent imprinting changes on gene expression in the hypothalamus to cause adult dysfunction. We will also investigate how these effects are transmitted to subsequent generations. Our goals in the fetally-exposed (F1) generation are to measure effects of expression of genes for steroid hormone receptors in the hypothalamus of PCB vs. control animals (Aim 1); and to explore and identify how PCBs may cause epigenetic modifications to these genes through analyses of DNA methylation and histone modifications (Aim 2). Then, comparisons will be made among the F1, F2 and F3 generations of rats to determine the manifestation of transgenerational, epigenetic effects and to ascertain the mechanism for transmission (Aim 3). As a whole, these experiments are designed to provide mechanistic insight into endocrine disruption of hypothalamic function during critical developmental life stages, the latent manifestation of a disrupted adult phenotype, and the transmission of this trait to subsequent generations. PUBLIC HEALTH RELEVANCE: The proposed studies on endocrine disruption are highly relevant to humans. The EDC chosen for the current proposal, PCBs are a persistent and continuing problem, as virtually all living humans have a detectable body burden of PCBs. Therefore, understanding the transgenerational epigenetic effects of PCBs in a rat model can provide information about public policy, prevention, and medical interventions in humans.