dc.contributor.author | Churchman, Adrian Thomas | |
dc.date.accessioned | 2014-08-07T08:12:20Z | |
dc.date.available | 2014-08-07T08:12:20Z | |
dc.date.issued | 2005 | |
dc.identifier.uri | http://hdl.handle.net/2299/14269 | |
dc.description.abstract | Endothelial cell apoptosis is an important process during vasculature remodelling,
angiogenesis and inflammation. Medical interest in endothelial cell apoptosis as a
target for arthritis and solid tumour treatment has prompted biochemical and
pharmacological investigation into the mechanisms controlling endothelial cell survival
and angiogenesis. In recent years it has been hypothesised that control of endothelial
cell apoptosis and the induction of angiogenesis may in part be due to the enzyme
cyclooxygenase (COX)-2.
COX-2 is involved in the metabolism of arachidonic acid to prostaglandins in
mammals. This pathway has been implicated in controlling inflammation and
angiogenesis through prostaglandin (PG) production and more recently has been shown
to inhibit endothelial cell death. It was the aim of this study to investigate endothelial
cell apoptosis and angiogenesis focussing on the role of COX-2, prostaglandins and
endogenous apoptotic inhibitors in these pathways.
Endothelial cell apoptosis was assessed by chromatin condensation, DNA fragmentation
and caspase activation. Angiogenesis was investigated by examining capillary-like
tubule formation. Endothelial cell apoptosis induction and angiogenesis inhibition was
observed using the selective COX-2 inhibitor 5-bromo-2-(4-fluorophenyl)-3-
(methylsulfonyl) thiophene (DuP-697) at a concentration 100 times lower than has
previously been reported. Apoptosis was confirmed by induction of caspases 8, 9 and 3
over 8 hr and DNA fragmentation and condensation over 24 hr. The effects observed
may be due to a selective inhibition of COX-2 as apoptosis induction and angiogenic
inhibition only occurred when COX-2 was inhibited by selective and non-selective
COX inhibitors.
Induction of endothelial cell death was induced by treatment with two natural products
that inhibit COX-2, namely curcumin and 6-shogaol (from turmeric and ginger
respectively) although only at concentrations higher than were required to inhibit COX-
2. Both compounds induced chromatin condensation in endothelial cells and lurkat
E6.1 cells with no DNA laddering or caspase induction.
Further examination of the mechanisms of endothelial cell survival were investigated by
assessing the endogenous expression of the apoptosis repressor with a caspase
recognition domain (ARC) protein through examining reverse transcriptase CRT) - peR,
native protein expression and transgenic over-expression in the endothelial cells.
Endogenous expression of ARC was found in endothelial cells. However this
expression declined during in vitro culture. Transgenic expression of ARC was found
to increase levels of ARC in vitro. However it had no effect on apoptosis inhibition
after 24 hr.
The underlying mechanisms of cell death induction may be compound dependent in
endothelial cells. Pharmacological inhibition of COX-2 and possibly PGE2 generation
has detrimental effects on angiogenesis and endothelial cell survival. However
inhibition of COX-2 by natural products at low concentrations may be advantageous in
preventing tumour angiogenesis with no apoptosis induction. | en_US |
dc.language.iso | en | en_US |
dc.publisher | University of Hertfordshire | en_US |
dc.rights | info:eu-repo/semantics/openAccess | en_US |
dc.title | Endothelial cell apoptosis | en_US |
dc.type | info:eu-repo/semantics/doctoralThesis | en_US |
dc.identifier.doi | 10.18745/th.14269 | |
dc.identifier.doi | 10.18745/th.14269 | |
dc.type.qualificationlevel | Doctoral | en_US |
dc.type.qualificationname | PhD | en_US |
herts.preservation.rarelyaccessed | true | |