Abstract
dc:description.abstractFOXO3a is a pro-apoptotic transcription factor which shows increased activation in vascular smooth muscle cells (VSMCs) of advanced atherosclerotic plaques, specifically within the intimal layer. Since VSMC apoptosis plays a crucial role in the pathophysiology of atherosclerosis, we investigated the mechanisms underlying FOXO3a-mediated cell death in this particular cell type. We aimed to characterise a novel VSMC system (FOXO3aA3ERTM) and use these cells to validate MMP-13 and TIMP3 as new FOXO3a target genes. Also, we sought to determine the mechanisms of FOXO3aA3ERTM-mediated VSMC apoptosis, particularly regarding MMP-13 and TIMP3, potential MMP-13 substrates in the extracellular matrix and the precise apoptotic signalling involved. Furthermore, we aimed to investigate whether VSMC-specific activation of FOXO3aA3ERTM in mouse affects vascular remodelling during injury and whether this is reliant on MMP-13. Lastly, we aimed to address if endogenous FOXO3a upregulates MMP-13 in mouse and human VSMCs. Our laboratory has created a transgenic rat VSMC line which stably expresses an inducible FOXO3a mutant allele known as FOXO3aA3ERTM and previous microarray experiments identified matrix metalloproteinase 13 (MMP-13) as a potential novel FOXO3a target gene. Initially, we described several key features of the FOXO3aA3ERTM VSMCs used throughout this thesis, and subsequently demonstrated that MMP-13 is a bona fide target whose expression is rapidly upregulated upon FOXO3a activation, leading to markedly higher levels of protein, cleavage and proteolytic capacity. This induction of MMP-13 was responsible for the vast majority of FOXO3a-mediated apoptosis which was accompanied by prominent degradation of fibronectin, a glycoprotein found in the extracellular matrix. However, we could not identify a terminal apoptotic pathway. FOXO3a also downregulated the endogenous MMP inhibitor TIMP3, the recombinant protein of which reduced both MMP-13 proteolysis and FOXO3a-mediated apoptosis. Activation of FOXO3aA3ERTM in the VSMCs of medium and large arteries in mice resulted in heightened expression of MMP-13 in the vessel wall, which contributed to enhanced neointimal formation during carotid ligation. Finally, endogenous FOXO3a activation leads to increased MMP-13 expression in human VSMCs, but not mouse. Overall, we have shown that FOXO3a promotes VSMC apoptosis through MMP-13 both in vitro and in vivo, a novel pathway that has important implications for the pathogenesis and treatment of vascular disease.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2018
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Fellows, Adam Lee
- Advisor dc:contributor.advisor
-
- Bennett, Martin
Subjects
dc:subject × 4Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.22947
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/275687