Interaction of endothelial microparticles with monocytic cells in vitro induces tissue factor-dependent procoagulant activity.
In the present study we investigated whether endothelial microparticles (EMPs) can bind to monocytic THP-1 cells and modulate their procoagulant properties. Using flow cytometry, we demonstrated that EMPs express adhesive receptors similar to those expressed by activated endothelial cells. Expression of endothelial antigens by THP-1 cells incubated with EMP was shown by immunoperoxidase staining and flow cytometry using antibodies directed against E-selectin, VCAM-1, and endoglin. EMP binding to THP-1 cells was time- and concentration- dependent, reached a plateau at 15 minutes, and had an EMP-to-monocyte ratio of 50:1. EMP binding was not affected by low temperature and was not followed by the restoration of phosphatidylserine asymmetry, suggesting that adhesion was not followed by fusion. A 4-hour incubation of THP-1 cells with EMP led to an increase in procoagulant activity as measured by clotting assay. Concomitantly, THP-1 exhibited increased levels of tissue factor (TF) antigen and TF mRNA compared to control cells. The ability of EMP to induce THP-1 procoagulant activity was significantly reduced when THP-1 cells were incubated with EMP in the presence of blocking antibodies against ICAM-1 and beta2 integrins. These results demonstrate that EMPs interact with THP-1 cells in vitro and stimulate TF-mediated procoagulant activity that is partially dependent on the interaction of ICAM-1 on EMP and its counterreceptor, beta2 integrins, on THP-1 cells. Induction of procoagulant activity was also demonstrated using human monocytes, suggesting a novel mechanism by which EMP may participate in the dissemination and amplification of procoagulant cellular responses.
Sabatier
Florence
F
INSERM EMI 00-19, Laboratoire d'Hématologie et d'Immunologie, UFR de Pharmacie, Université de la Méditerranée, Marseilles, France.
Roux
Veronique
V
Anfosso
Francine
F
Camoin
Laurence
L
Sampol
José
J
Dignat-George
Françoise
F
D001779:Blood Coagulation Factors / Q000032:analysis / Q000096:biosynthesis*; D002448:Cell Adhesion; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000502:physiology*; D006801:Humans; D009000:Monocytes / Q000502:physiology*; D011994:Recombinant Proteins / Q000494:pharmacology; D013925:Thromboplastin / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014471:Umbilical Veins
D001779:Blood Coagulation Factors; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; C045071:leukocyte procoagulant activity; D013925:Thromboplastin