Endothelial microparticle reseach is currently a very novel and exciting topic in the field of
haemosistasis and thrombosis. The role of microparticles in inflammatory and thrombotic
disorders is however not fully understood. Dysfunction of endothelial cells is hypothesized to
be a trigger of microparticle formation. In inflammatory disorders like sepsis and thrombotic
disorders like atherosclerosis and thrombotic thrombocytopenic purpura, endothelial
microparticle formation is altered and the numbers thereof may increase or decrease. It is
not known if microparticles are the cause or the consequence of these disorders.
To understand the role of endothelial microparticles in inflammation and thrombosis, the
effect of inflammatory cytokines and coagulation stimuli was studied as well as combinations
thereof on endothelial microparticle formation and on microparticle VWF and its regulating
protease, ADAMTS-13 in HUVEC.
In this study, the formation of microparticles in cultured human umbilical vein endothelial
cells (HUVEC) was stimulated by different inflammatory agents: IL-6 (100 ng/ml), IL-8 (100
ng/ml) and TNF-α (100 ng/ml), coagulation stimuli: TF (2 U/ml) and thrombin (2 U/ml) and
combinations thereof. The number of endothelial microparticles that formed was determined
using flow cytometry. VWF and ADAMTS-13 levels of the microparticles were assessed by
ELISAs and microparticle thrombin generation was measured by thrombin generation
assays. VWF multimers were visualized by a Western Blot technique.
IL-6 did not have any effect on HUVEC-derived microparticles due to the lack of the receptor
for IL-6 on these cells. IL-8 only slightly increased effect on microparticle VWF and
ADAMTS-13 levels. TNF-α had a significant effect on microparticle numbers and
contributed to almost 80% of thrombin generated by the microparticles. It has however
almost no effect on VWF levels. The coagulation stimulus TF, on the other hand, induced
the highest increase in microparticle VWF levels and increased microparticle numbers
impressively. Yet, it had no effect on the thrombin generation by the microparticles. TF in
combination with TNF-α also induced an increase in microparticle VWF and a small
decrease in ADAMTS-13 levels. So, TF may contribute to the increased VWF levels that are
commonly found in TTP patients where inflammation and thrombosis occur.
Interestingly, thrombin had a protective effect on the intact HUVEC by preventing
microparticle formation. The combination stimuli of thrombin and inflammatory agents also had a protective effect on HUVEC. This highlighted the regulatory role of thrombin in intact
endothelial cells and also the protection that it provides against thrombosis in extremely
inflammatory environments.
Endothelial microparticles can therefore be detrimental or beneficial, depending on the
different stimuli and different environments. Inflammatory and coagulation stimuli may still
pose a significant risk of clotting by altering microparticle quantity and content. This study
contributes to understand the role that endothelial microparticles play in inflammation and
thrombosis.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-11202013-151011 |
| Date | 20 November 2013 |
| Creators | le Roux, Elzette |
| Contributors | Prof MJ Coetzee, Prof SM Meiring |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-11202013-151011/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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