Mechanosensory signalling interactions in the vascular endothelium and their impact on atherosclerosis development

Thesis

The vascular endothelium plays a dynamic role in regulating vessel physiology by responding to environmental signals. Damage to the endothelial layer leads to endothelial dysfunction, which triggers inflammatory signalling and promotes atherosclerotic plaque formation. This process is promoted by oscillatory shear stress (OSS) in regions of vessel curvature or bifurcation, resulting in localised plaque development. Specialised mechanosensors on the endothelial surface respond to forces from blood flow by activating intracellular signalling pathways. However, the process by which endothelial cells diRerentiate between physiological and pathological signalling remains poorly understood. Despite the importance of mechanical forces in atherosclerosis, current therapies overlook mechanosensory signalling, making it a crucial area for research.

This thesis aims to address this knowledge gap by exploring how endothelial cells integrate signals from diRerent mechanosensory sites to produce a coordinated response to blood flow. I first focus on the role of the adaptor protein Shc, which associates with various endothelial mechanosensors in response to fluid shear stress. I identify phosphorylation at the Y239/240 residue of Shc as a critical signalling event regulated by OSS, acting as a molecular switch that triggers inflammatory endothelial signalling. This phosphorylation may facilitate the convergence of signals from multiple mechanosensors, resulting in a unified inflammatory response to pathological flow.

Additionally, I explore the interaction between two mechanosensors, Plxnd1 and Piezo1. Through co-immunoprecipitation and biolayer interferometry, I reveal a direct interaction between their extracellular domains. Given their established roles in driving pathological flow signalling and atherosclerosis, examining this interaction as a potential therapeutic target is a promising avenue for future research.

Finally, I explore therapeutic strategies targeting pathological flow signalling by developing monoclonal antibodies that inhibit PLXND1's mechanosensory function. These antibodies show promise in blocking flow-mediated inflammatory signalling in vitro, laying the foundation for future preclinical studies and potential treatments for atherosclerosis.

Authors: Aitken, C

• DOI: 10.5287/ora-rdn5ebmkd
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: endothelial; mechanotransduction; vascular; shear stress; atherosclerosis; blood flow
• Subjects: Vascular endothelial cells; Atherosclerosis; Cellular signal transduction; Shear flow