Anticoagulant properties of the anti-inflammatory cytokine IL-10 in a factor Xa-activated human monocyte model

Background: Monocytes and factor Xa (FXa) are procoagulant agents implicated in the physiopathological processes of atherosclerosis and thrombosis. Objective: we evaluated the anticoagulant effect of the anti-inflammatory cytokine IL-10 on an FXa-activated human monocyte (Hu-monocyte) procoagulant phenotype. Methods: Hu-monocytes were purified by elutriation and activated by FXa. The effect of IL-10 was assessed by means of a 2 h pre-incubation step with recombined human IL-10 (0.5 and 1 ng/mL). Real-time RT-PCR and Western blotting were used to evaluate the effect of IL-10 on tissue factor (TF) mRNA and protein synthesis. A thrombin generation (TG) assay was used as a functional test to assess the effect of IL-10 on TF-dependent TG. Results: we showed that IL-10 inhibited both TF mRNA and TF protein expression in a dose-dependant manner. We showed, as a functional consequence, that IL-10 inhibited Hu-monocyte-triggered TG and that this inhibition was concentration-dependant, and significant for all TG phases. The rate index of the propagation phase (rate index) was the most sensitive parameter while the endpoint of TG decay (S-tail) and the endogenous thrombin potential (ETP) were the least sensitive (inhibition of 80, 40 and 30% respectively). The IL-10 pattern of TG inhibition was similar to TF-Ab-induced inhibition: IC50 were not reached by ETP and S-tail, and the lowest IC50 values were reached by the rate index (0.61 +/- 0.12 ng/mL and 1.87 +/- 0.35 mu g/mL respectively). Conclusion: the anticoagulant effect of the anti-inflammatory cytokine IL-10 in an FXa-activated Hu-monocyte model is an additional illustration of the cross-talk between inflammation and coagulation, opening new approaches in the field of arteriosclerosis and thrombosis.