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Title: Vascular protection during systemic inflammation : investigation of the relationship between PKC epsilon and heme oxygenase-1
Author: Mylroie, Hayley
ISNI:       0000 0004 2729 132X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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Background: Patients with chronic inflammatory diseases including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) demonstrate endothelial dysfunction. The inflammatory response triggered by endothelial injury leads to reduced NO biosynthesis, while increasing superoxide generation, monocyte adhesion and endothelial cell (EC) apoptosis. Apoptosis occurs preferentially at atherosclerosis prone sites, where endothelial erosion increases the risk of thrombosis and plaque development. Thus, chronic endothelial injury is a significant factor in the accelerated atherosclerosis associated with SLE and RA. Identifying the mechanisms underlying vascular injury and understanding innate cytoprotective pathways are essential for novel therapy development. Results: Known to play a role in cardiomyocyte ischemic preconditioning, protein kinase C (PKC) ε co-precipitates with stress-activated proteins and induces anti-apoptotic genes. We have now identified PKCε as an important regulator of cytoprotective responses in the vascular endothelium. We have shown that activation of PKCε induces expression of the cytoprotective enzyme HO-1 in human umbilical vein EC, using qRT-PCR and immunoblotting. This response is dependent upon gene transcription and de novo protein synthesis. A combined siRNA and immunohistochemical approach revealed a role for CREB and Nrf2 in PKCε-mediated HO-1 induction via a novel mechanism, which may involve positive feedback mechanisms and the dimerization of these two transcription factors. PKCε- dependent HO-1 expression is inducible by angiotensin II and able to protect against apoptosis and TNF-α- induced ICAM-1 upregulation. Furthermore, analysis of cardiac EC isolated from PKCε-/- and wild-type mice demonstrated altered expression of HO-1 in PKCε-/- EC and increased generation of reactive oxygen species. Conclusion: We have demonstrated a regulatory role for PKCε in the expression of the cytoprotective enzyme HO-1 in the vascular endothelium, and unearthed a novel signalling pathway involving CREB and Nrf2. The ultimate aim of this work is to identify novel therapeutic targets for treatment of endothelial dysfunction in systemic inflammatory diseases.
Supervisor: Mason, Justin ; Evans, Paul Sponsor: Arthritis Research UK
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral