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Title: Effects of shear stress on NF-κB transcription factors in vascular endothelium
Author: Cuhlmann, Simon
ISNI:       0000 0004 2699 6280
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2011
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Atherosclerosis, a chronic inflammatory disease of arteries, occurs predominantly at regions of the arterial system that are exposed to disturbed patterns of blood flow. Blood flow influences the atherosclerosis by exerting shear stress on endothelial cells (ECs). Although the signalling pathways that activate pro-inflammatory NF-κB transcription factors are well defined, the regulation and physiological significance of differential NF-κB subunit expression is poorly understood. In this thesis, we demonstrate that RelA NF-κB sub-unit expression is positively regulated in ECs via c-Jun N-terminal kinase (JNK) and the transcription factor ATF2. This pathway promoted focal arterial inflammation as genetic deletion of JNK1 reduced RelA expression and macrophage accumulation at an athero-susceptible site. Furthermore, JNK signalling to RelA is controlled by mechanical forces as en face immunostaining revealed that disturbed flow patterns (generated by a constrictive cuff) elevated RelA expression in murine carotid arteries via JNK1. Positron emission tomography and en face staining revealed that disturbed flow enhanced 18F-fluorodeoxyglucose uptake (a marker of inflammation) and accumulation of CD68-positive inflammatory cells in arteries via JNK1. We conclude that disturbed flow promotes arterial inflammation via a novel JNK-NF-κB cross-talk. The duration of RelA nuclear localisation is an important determinant of the magnitude and specificity of target gene expression. En face staining revealed that RelA rapidly accumulated in the nucleus upon LPS stimulation in ECs at both athero-protected and athero-susceptible sites. RelA was exported from the nucleus to the cytoplasm in response to prolonged stimulation in the athero-protected region but not in the athero-susceptible region. The duration of RelA nuclear localisation was suppressed by histone deacetylases which displayed higher activity at the protected site compared to the susceptible site. Overall, our findings reveal that ECs at athero-susceptible sites are primed for inflammatory activation via complementary mechanisms that enhance both the expression and the activity of NF-κB transcription factors.
Supervisor: Evans, Paul ; Krams, Rob Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral