Influence of TNFα and cigarette smoke on endothelial dysfunction : interplay between shear stress and risk factors

• Main Author: Teasdale, Jack Edward
• Published: University of Bristol 2015
• Subjects: 616.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682679

I have developed a model in which to examine factors that may affect endothelial erosion, a pathology that is responsible for approximately 25% of myocardial infarctions. Cigarette smoking is a risk factor for erosion; and long-term, heavy smokers have increased circulating markers of inflammation; therefore I have studied the interaction of cigarette smoke extract (CSE) and the inflammatory mediator tumour necrosis factor-alpha (TNFα) on endothelial dysfunction. Endothelial cells are mechanosensitive, with Kruppel-like factor (KLF) 2/4 and Nuclear response erythroid 2-like 2 (Nrf) Nrf2 mediating a large part of the atherop~otective effect of laminar shear stress in endothelial cells. I therefore studied endothelial dysfunction in oscillatory, normal laminar and elevated laminar shear stress in human coronary artery endothelial cells (HCAEC). TNFα robustly increased nuclear factor kappa-B (NFKB) responsive gene expression, which was suppressed with increasing magnitude of laminar shear stress. CSE did not activate the expression of NFKB responsive genes, but inhibited TNFα induction of NFKB regulated genes. CSE strongly increased the expression of Nrf2-regulated gene expression, which was further increased by the addition of TNFα; however, Nrf2 was not responsible for the reduction in NFKB signalling. Despite the reduction in NFKB gene expression, HCAECs under laminar shear stress lost adherence when treated with both TNFα and CSE a process that appears to be independent of MMP activity, apoptosis or necrosis. Treatment with Nrf2 agonists increased rather than protected against cell loss raising the possibility that uncontrolled Nrf2 expression is detrimental. In summary, I have for the first time created an in vitro model that utilizes risk factors for endothelial erosion and can mimic endothelial cell loss when combining CSE and TNFα. A reduction in inflammatory gene expression was not associated with increased cell survival, rather Nrf2 hyperactivation contributed to endothelial erosion.