Environmental and genetic influences on atherosclerosis

Thesis

Background: Atherosclerosis is the underlying cause of coronary artery disease (CAD), which remains a major cause of death worldwide. It is a complex disease influenced by multiple environmental factors acting on different cell types and at different stages of pathogenesis. Genetic variants at more than 160 loci have been associated with CAD, but for the majority the causal molecular mechanisms remain unknown.

Aims: I aim to improve our understanding of the cellular response to environmental influences on atherosclerosis, and to identify molecular mechanisms of heritable disease risk. Specifically, I aim to characterise the responses of human macrophages to high glucose, of human aortic endothelial cells to laminar shear stress, and of single human macrophages to oxidised low-density lipoprotein.

Methods: I developed primary human cell models of atherosclerotic disease processes and applied high-throughput sequencing (HTS) methods to study changes in transcriptional regulation. RNA-seq and ATAC-seq were used to characterise responses to known environmental atherosclerosis risk factors at the molecular level. Resulting genome-wide maps were integrated with publicly available GWAS data to identify SNPs located in dynamic regulatory elements. In addition, I used single-cell RNA-seq to study heterogeneity in human macrophages exposed to atherogenic lipid.

Key results: Human macrophages express CD28 at the cell surface, and expression is downregulated by high glucose. Laminar shear stress induces widespread changes in endothelial cell chromatin accessibility. Newly accessible regions are enriched for AP-1 and KLF transcription factor binding motifs, as well as for GWAS SNPs associated with CAD. Colocalisation of these features reveals candidate genetic mechanisms for disease risk. Human macrophages are heterogeneous in vitro and consist of subtypes with gene expression reflecting the full range of macrophage functions.

Conclusions: HTS methods are valuable tools for studying the intersection of environmental and genetic influences on atherosclerosis. Discovery of novel disease mechanisms could lead to the development of therapeutic strategies for cardiovascular disease.

Authors: Hiron, TK

• DOI: 10.5287/ora-vyazrdqgb
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English