Analysis of chromatin accessibility changes in endothelial cells exposed to plastic contaminants

Degradation products from everyday plastic products are known to bioaccumulate and have also been shown to contaminate drinking water and food sources. BPA and phthalates are endocrine disrupting chemicals and plastic components that have previously been associated with endothelial cell dysfunction, atherosclerotic and other adverse cardiovascular events. However, there is a limited understanding of the mechanisms underlying these associations, such as genome-wide chromatin accessibility changes in endothelial cells exposed to these compounds. The purpose of this study is to explore genome-wide changes in chromatin accessibility associated with plastic exposure, as well as the discovery of transcription factor binding motifs dysregulated by plastic exposure. Human umbilical vein endothelial cells (HUVECs) were exposed for 6 or 24 hours to monobutyl phthalate (MBP), bisphenol A (BPA), or a vehicle control and were then processed by Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq). After peak calling, three different read counting strategies, which include percent in peaks (PIC), chromVar, and Rsubread, were evaluated for quantifying chromatin accessibility of peaks. PIC was determined to be superior in terms of robustness to outliers caused by transposition artifacts, and had better pairwise correlations between untreated controls. This research will serve as the basis to subsequently identify differentially accessible regions (DARs) of chromatin associated to MBP and BPA exposure. This study will also provide deeper insight into endothelial gene regulatory pathways that are altered as a result of this exposure, and will be integrated with genes associated with cardiovascular disease that are modulated by plastic exposure in endothelial cells.