Microparticles derived from stimulation of human umbilical endothelium

["Thrombosis -- Treatment","Blood -- Coagulation","Blood coagulation disorders","Inflammation -- Treatment","Cytokines","Dissertation (M.Med.Sc. (Haematology and Cell Biology))--University of the Free State, 2013"]

Le Roux, Elzette ; ["Meiring, S. M.","Coetzee, M. J."]

University of the Free State

Others  :  http://scholar.ufs.ac.za/xmlui/bitstream/11660/1193/1/LeRouxE.pdf

瑞士|英语

来源: University of Iowa

【 摘 要 】

English: Endothelial microparticle reseach is currently a very novel and exciting topic in the field ofhaemosistasis and thrombosis. The role of microparticles in inflammatory and thromboticdisorders is however not fully understood. Dysfunction of endothelial cells is hypothesized tobe a trigger of microparticle formation. In inflammatory disorders like sepsis and thromboticdisorders like atherosclerosis and thrombotic thrombocytopenic purpura, endothelialmicroparticle formation is altered and the numbers thereof may increase or decrease. It isnot known if microparticles are the cause or the consequence of these disorders.To understand the role of endothelial microparticles in inflammation and thrombosis, theeffect of inflammatory cytokines and coagulation stimuli was studied as well as combinationsthereof on endothelial microparticle formation and on microparticle VWF and its regulatingprotease, ADAMTS-13 in HUVEC.In this study, the formation of microparticles in cultured human umbilical vein endothelialcells (HUVEC) was stimulated by different inflammatory agents: IL-6 (100 ng/ml), IL-8 (100ng/ml) and TNF-α (100 ng/ml), coagulation stimuli: TF (2 U/ml) and thrombin (2 U/ml) andcombinations thereof. The number of endothelial microparticles that formed was determinedusing flow cytometry. VWF and ADAMTS-13 levels of the microparticles were assessed byELISAs and microparticle thrombin generation was measured by thrombin generationassays. 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 receptorfor IL-6 on these cells. IL-8 only slightly increased effect on microparticle VWF andADAMTS-13 levels. TNF-α had a significant effect on microparticle numbers andcontributed to almost 80% of thrombin generated by the microparticles. It has howeveralmost no effect on VWF levels. The coagulation stimulus TF, on the other hand, inducedthe highest increase in microparticle VWF levels and increased microparticle numbersimpressively. Yet, it had no effect on the thrombin generation by the microparticles. TF incombination with TNF-α also induced an increase in microparticle VWF and a smalldecrease in ADAMTS-13 levels. So, TF may contribute to the increased VWF levels that arecommonly found in TTP patients where inflammation and thrombosis occur.Interestingly, thrombin had a protective effect on the intact HUVEC by preventingmicroparticle formation. The combination stimuli of thrombin and inflammatory agents also had a protective effect on HUVEC. This highlighted the regulatory role of thrombin in intactendothelial cells and also the protection that it provides against thrombosis in extremelyinflammatory environments.Endothelial microparticles can therefore be detrimental or beneficial, depending on thedifferent stimuli and different environments. Inflammatory and coagulation stimuli may stillpose a significant risk of clotting by altering microparticle quantity and content. This studycontributes to understand the role that endothelial microparticles play in inflammation andthrombosis.