Tissue factor expressed by adherent cells contributes to hemodialysis-membrane thrombogenicity.

End-stage renal patients present a high risk of thrombosis and bleeding. Consequently, it is challenging to prevent clotting during hemodialysis. If a contact system induces thrombin generation in the extra corporeal circuit, recent data suggest a role of tissue factor (TF) in hemodialysis-associated thrombosis. Using a method of elution, we collected adhering cells to an acrylonitrile membrane layered by polythyleneimine (AN69-ST). Using optic microscopy and flow cytometry, we observed that adherent cells were mainly constituted by activated polymorphonuclear neutrophils (PMNs). Using a sensitive fluorogenic method of thrombin generation, we found that adhering cells triggered thrombin generation in a TF-dependent manner. We next identified the presence of TF mRNA (Q-PCR) in adhering cells. Using immunofluorescence, we observed the presence of TF in PMNs and of TF-decorated neutrophil extracellular traps (NETs). As TF triggers thrombin generation after binding to serine protease FVIIa, we evaluated the effect of an inactivated human recombinant factor VIIa (hrFVIIai) in a sheep model of hemodialysis (HD). One single bolus of hrFVIIai maintained the full patency of the hemodialysis circuit without any measurable systemic anticoagulant effect. TF is a promising target for preventing thrombosis during HD.

IL-10 modulates fondaparinux inhibition of monocyte-induced thrombin generation.

In addition to its established immuno-regulating capacity, the anti-inflammatory cytokine interleukin (IL)-10 exerts direct effects on coagulation. IL-10 down regulates the expression of tissue factor (TF) and thrombin generation (TG). Thus, we hypothesised that IL-10 could enhance the effect of anticoagulants. To evaluate in vitro the potential additive effect of IL-10 on fondaparinux-induced anticoagulation. Human monocytes were purified by elutriation, and were activated by factor Xa (FXa). Real-time RT-PCR and Western blotting were used to evaluate FXa-induced TF synthesis. TG test was used as a functional test to assess TF-dependent monocyte procoagulation, and to evaluate the effects of IL-10 (200 and 500 pg/ml) and fondaparinux (0.0, 0.1, 0.4, 0.7 and 1.2 µg/ml), separately and in combination. We confirmed that FXa induced TF mRNA and protein synthesis by monocyte in a concentration dependent manner. We showed that FXa-activated monocytes triggered TG via TF expression. We reported that IL-10 inhibited TG with a marginal effect seen at 200 pg/ml. Results with fondaparinux showed a concentration-dependent TG inhibition. The combination of IL-10 and fondaparinux effects demonstrated that IL-10: (i) potentiates the inhibitory effect of fondaparinux on TG by 10-30%, and (ii) dramatically modifies fondaparinux IC50 for each TG parameter. IL-10 enhances in vitro the extent of anticoagulation induced by fondaparinux.