The overall objective of this proposal is to define the effect of two common endocrine-disrupting compounds (EDCs) on cardiac function in healthy and high-risk subjects, and to establish the potential applicability of these findings to humans. The ubiquitous nature of plastics has raised concerns pertaining to continuous exposure to plastic additives and human health risks. Of particular concern is the use of EDCs in plastic production, including bisphenol A (BPA) and di-2-ethylhexylphthalate (DEHP). Despite the popularity of BPA-free and phthalate-free plastics, these compounds are found in many consumer products, including food and beverage containers, children's toys and medical devices. As a result, exposure to these EDCs has become virtually continuous and essentially unavoidable, a fact that is highlighted by human biomonitoring studies. Recently, human epidemiological and animal experimental studies have associated EDC exposure with cardiovascular disorders. However, their toxicity remains hotly debated, mainly because 1) epidemiological studies are useful in identifying associations and not causal links, and 2) animal research studies frequently employ high exposure doses that impede extrapolation to humans. Consequently, there is a need on behalf of the public, scientific, medical and regulatory communities to resolve the direct effect of EDCs on cardiac physiology and to understand the risks to both general and vulnerable patient populations. The proposed project will address this need by utilizing a comprehensive set of models (acute in situ, chronic in vivo, prenatal exposure, heart failure model) to thoroughly investigate the cardia processes altered by EDCs while mimicking human exposure. This is significant, as examining the effect of clinically relevant concentrations using an in situ model will allow one to quantify direct effects on the heart, while an in vivo model takes into account the indirect effects between organ systems and the impact of the metabolic system. Specifically, the effect of EDCs will be quantified on cardiac electrical and mechanical function and a determination of whether the presence of blood negates these effects will be employed. These in situ studies will be accomplished by acutely exposing hearts to clinically-relevant doses of BPA and DEHP. Next, an examination of the in vivo effect of EDCs on the cardiovascular system, and a determination of whether such effects are exacerbated in those with pre-existing heart conditions and other high-risk populations will be performed. To accomplish these studies, the principal investigator will compare and contrast the chronic effect(s) of BPA and DEHP exposure between healthy, prenatally exposed, and heart failure animals. Modifications in cardiovascular function will be assessed using a telemetry implant system that monitors heart rate, temperature, and ECG parameters in freely moving animals. Finally, the principal investigator will investigate the applicability of the findings to human cells and identify potential mechanisms of EDC cardiac toxicity. To complete these studies, human cardiomyocyte networks will be exposed to BPA and DEHP to measure modifications in cardiac function, and identify genomic and non-genomic mechanisms of toxicity. The later will be accomplished using DNA microarrays, miRNA expression analysis, and pharmacological assays. During the K99 phase, the principal investigator will receive extensive training in surgical techniques (nonsurvival: heart excision, annulation, LV pressure; survival: telemetry transmitter implantation, radiofrequency cardiac ablation), epicardial optical mapping and signal processing, human embryonic stem cell maintenance and cardiac differentiation, and miRNA expression profiling. At the end of the K99 mentored phase, the principal investigator will possess the tools necessary to become an independent investigator with expertise in cardiovascular toxicity that encompasses multiple disciplines and models (cell layers, whole heart organ, live animal physiology, prenatal exposure, and heart injury and stem cell models). The principal investigator will apply this new training to her overall study design during the R00 phase of this award, which aims to address significant gaps in the current understanding of EDC cardiac toxicity. The expertise gained during the K99 phase, together with the principal investigator's molecular biology and genomics background, will allow the principal investigator to develop an integrated research program designed to assess how environmental toxins affect cardiovascular function at the molecular, cellular, tissue and organism level. This multidisciplinary experience will allow the principal investigator to investigate the effect of environmental toxins on cardiovascular disease etiology and progression, and also the mechanistic explanation for these effects (e.g., signal transduction pathways, gene, protein, miRNA expression). Completion of this proposal will advance the cardiovascular and environmental health sciences by providing mechanistic insight into a highly controversial topic, i.e., the negative impact of endocrine disruptors on cardiovascular function. Results of this proposal will provide a foundation for objective decision making by the public, scientific, medical and regulatory communities. This proposal will also bridge the gap between clinical observations published from the NHANES surveys with the underlying pathophysiology of EDCs. If adverse outcomes are observed in the proposed studies, it will pinpoint additional variables to investigate in future human epidemiological studies. Finally, at the conclusion of this award, the Principal Investigator will be well positiond to develop an independent multifaceted research program, which will investigate how environmental toxins contribute to cardiovascular disease, and identify risk factors that influence cardiac disease susceptibility.
The use of EDCs, including BPA and DEHP, in plastic production is a source of concern for human health. Human and animal studies have shown a link between exposure to these toxins and adverse health outcomes. However, the direct effect of BPA and DEHP on the cardiovascular system is relatively unknown and the cardiac risk to vulnerable populations has not been established.
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