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In vitro generation of endothelial microparticles and possible prothrombotic activity in patients with lupus
V Combes1, A C Simon, G E Grau
1Laboratory of Hematology and Immunology, UPRES EA 2195, UFR de Pharmacie, 13385 Marseille, France.
Abstract:
Microparticles (MPs) resulting from vesiculation of platelets and other blood cells have been extensively documented in vitro and have been found in increased numbers in several vascular diseases, but little is known about MPs of endothelial origin. The aim of this study was to analyze morphological, immunological, and functional characteristics of MPs derived from human umbilical vein endothelial cells (HUVECs) stimulated by TNF, and to investigate whether these MPs are detectable in healthy individuals and in patients with a prothrombotic coagulation abnormality. Electron microscopy evidenced bleb formation on the membrane of TNF-stimulated HUVECs, leading to increased numbers of MPs released in the supernatant. These endothelial microparticles (EMPs) expressed the same antigenic determinants as the corresponding cell surface, both in resting and activated conditions. MPs derived from TNF-stimulated cells induced coagulation in vitro, via a tissue factor/factor VII-dependent pathway. The expression of E-selectin, ICAM-1, alphavbeta3, and PECAM-1 suggests that MPs have an adhesion potential in addition to their procoagulant activity. In patients, labeling with alphavbeta3 was selected to discriminate EMPs from those of other origins. We provide evidence that endothelial-derived MPs are detectable in normal human blood and are increased in patients with a coagulation abnormality characterized by the presence of lupus anticoagulant. Thus, MPs can be induced by TNF in vitro, and may participate in vivo in the dissemination of proadhesive and procoagulant activities in thrombotic disorders.
Insights
Endothelial microparticles (EMPs) from TNF-stimulated cells are procoagulant and adhesive. These EMPs are detectable in healthy individuals and increased in patients with coagulation disorders, suggesting a role in thrombotic conditions.
Area of Science:
- Vascular Biology
- Hematology
- Cell Biology
Background:
- Microparticles (MPs) from platelets and blood cells are known, but endothelial-derived MPs (EMPs) are less understood.
- Vascular diseases are associated with increased MPs, yet the specific role of EMPs remains unclear.
Purpose of the Study:
- To characterize the morphological, immunological, and functional properties of EMPs.
- To determine if EMPs are detectable in humans and elevated in prothrombotic conditions.
Main Methods:
- Human umbilical vein endothelial cells (HUVECs) were stimulated with TNF to induce EMP release.
- Electron microscopy, immunophenotyping (e.g., alphavbeta3), and coagulation assays were performed.
- EMPs were quantified in healthy individuals and patients with coagulation abnormalities.
Main Results:
- TNF stimulation increased EMP release from HUVECs, characterized by bleb formation.
- EMPs expressed cell surface antigens and demonstrated procoagulant activity via a tissue factor/factor VII pathway.
- EMPs showed adhesion potential (E-selectin, ICAM-1, alphavbeta3, PECAM-1) and were detected in normal blood, elevated in patients with lupus anticoagulant.
Conclusions:
- Endothelial microparticles can be induced by TNF and possess both procoagulant and adhesive properties.
- EMPs are detectable in human circulation and may contribute to the pathogenesis of thrombotic disorders.
- EMPs may serve as biomarkers for thrombotic conditions, particularly those involving coagulation abnormalities.
