Apixaban is a new oral anticoagulant with a specific inhibitory action on FXa. No information is available on the reversal of the antihemostatic action of apixaban in experimental or clinical settings. We have evaluated the effectiveness of different factor concentrates at reversing modifications of hemostatic mechanisms induced by moderately elevated concentrations of apixaban (200 ng/ml) added in vitro to blood from healthy donors (n = 10). Effects on thrombin generation (TG) and thromboelastometry (TEM) parameters were assessed. Modifications in platelet adhesive, aggregating and procoagulant activities were evaluated in studies with blood circulating through damaged vascular surfaces, at a shear rate of 600 s⁻¹. The potential of prothrombin complex concentrates (PCCs; 50 IU/kg), activated prothrombin complex concentrates (aPCCs; 75 IU/kg), or activated recombinant factor VII (rFVIIa; 270 μg/kg), at reversing the antihemostatic actions of apixaban, were investigated. Apixaban interfered with TG kinetics. Delayed lag phase, prolonged time to peak and reduced peak values, were improved by the different concentrates, though modifications in TG patterns were diversely affected depending on the activating reagents. Apixaban significantly prolonged clotting times (CTs) in TEM studies. Prolongations in CTs were corrected by the different concentrates with variable efficacies (rFVIIa≥aPCC>PCC). Apixaban significantly reduced fibrin and platelet interactions with damaged vascular surfaces in perfusion studies (p<0.05 and p<0.01, respectively). Impairments in fibrin formation were normalized by the different concentrates. Only rFVIIa significantly restored levels of platelet deposition. Alterations in hemostasis induced by apixaban were variably compensated by the different factor concentrates investigated. However, effects of these concentrates were not homogeneous in all the tests, with PCCs showing more efficacy in TG, and rFVIIa being more effective on TEM and perfusion studies. Our results indicate that rFVIIa, PCCs and aPCCs have the potential to restore platelet and fibrin components of the hemostasis previously altered by apixaban.

There is endothelial activation and damage in hematopoietic stem cell transplantation (HSCT). The impact of the conditioning and type of HSCT on endothelial dysfunction in the early phases of HSCT has been evaluated. Plasma samples were obtained before and at different times after autologous and allogeneic HSCT with and without early complications. Changes in soluble markers of endothelial damage (VWF, ADAMTS-13, sVCAM-1, sICAM-1, and sTNFRI) were measured. There were changes in all markers evaluated that followed different patterns in auto and allo settings. For VWF and sTNRI, progressive increases from day Pre to day 14 and to day 21 were observed in the auto and the allo group, respectively. ADAMTS-13 activity correlated inversely with VWF levels. Levels of sVCAM-1 decreased until day 7, and raised significantly to day 14 and to day 21 in the auto and the allo HSCT, respectively. No significant changes were detected for sICAM-1. Our results confirm that there is endothelial damage at the early phases of HSCT, apparently induced by the consecutive effects of the conditioning, the proinflammatory agents used during transplantation, the translocation of endotoxins across the damaged gastrointestinal tract, and the engraftment. However, the comparative analysis between patients with and without complications suggests that none of these markers has diagnostic or prognostic value.

Chronic kidney disease (CKD) patients have an accelerated atherosclerosis, increased risk of thrombotic-ischemic complications, and excessive mortality rates when compared with the general population. There is also evidence of an endothelial damage in which the proinflammatory state, the enhanced oxidative stress, or the accumulation of toxins due to their reduced renal clearance in uremia play a role. Further, there is evidence that uremic endothelial cells are both involved in and victims of the activation of the innate immunity. Uremic endothelial cells produce danger associated molecular patterns (DAMPS), which by binding to specific pattern recognition receptors expressed in multiple cells, including endothelial cells, induce the expression of adhesion molecules, the production of proinflammatory cytokines and an enhanced production of reactive oxygen species in endothelial cells, which constitute a link between immunity and inflammation. The connection between endothelial damage, inflammation and defective immunity in uremia will be reviewed here.

Circulating tissue factor (TF) has been linked to thrombus propagation. Our group demonstrated that platelets possess mechanisms to capture TF-rich microvesicles (TF-MVs). Serotonin facilitates the development of platelets with increased procoagulant activity. An enhanced platelet serotonin uptake has been identified with increased cardiovascular risk. We have investigated the involvement of serotonergic mechanisms facilitating the interaction of human platelets with TF-MVs. Inhibitory strategies aimed at blocking serotonin and coagulation mechanisms were also studied. Standard aggregometry, flow cytometry, electron microscopy, and thrombin generation assays were performed. TF-MVs induced platelet aggregation in heparinized platelet-rich plasma (PRP) samples; this aggregation was further accelerated by serotonin. In washed platelets, serotonin enhanced platelet aggregation to TF-MVs with a maximum peak of 55.9 ± 1.8 vs. 48.7 ± 2.1% (P < 0.05). Inhibitory strategies with a selective serotonin re-uptake inhibitor and with lepirudin decreased these aggregations. Ultrastructural analysis revealed that serotonin induced platelet pseudopodia formation, thus facilitating the engulfment of TF-MVs. In general, serotonin significantly enhanced (P < 0.05) thrombin generation and the expression of activation markers and procoagulant activity in platelets measured for TF-MVs alone. Serotonin enhances the interaction of platelets with TF-MVs, increases platelet activation, and potentiates their overall procoagulant activity. The present results could have significant implications in thrombus formation and in the thrombogenic profile of pathological situations with increased cardiovascular risk.

There is a link between depression, cardiovascular events and inflammation. We have explored this connection through endothelial dysfunction, using in vivo and in vitro approaches. We evaluated circulating biomarkers of endothelial dysfunction in patients with major depression at their diagnosis (MD-0) and during antidepressant treatment with the selective serotonin reuptake inhibitor escitalopram, for 8 and 24 weeks (MD-8 and MD-24). Results were always compared with matched healthy controls (CON). We measured in vivo circulating endothelial cells (CECs) and endothelial progenitor cells (EPCs) in blood samples, and assessed plasma levels of soluble von Willebrand factor (VWF) and vascular cell adhesion molecule-1 (VCAM-1). CEC counts, soluble VWF and VCAM-1 were statistically elevated in MD-0 (P<0.01 versus CON) and gradually decreased during treatment. Conversely, EPC levels were lower in MD-0, tending to increase throughout treatment. In vitro studies were performed in human endothelial cells cultured in the presence of sera from each study group. Elevated expression of the inflammation marker intercellular adhesion molecule-1 and oxidative stress, with lower presence of endothelial nitric oxide synthase and higher reactive oxygen species production, were found in cells exposed to MD-0 sera (P<0.05 versus CON). These results were normalized in cells exposed to MD-24 sera. Thrombogenicity of extracellular matrices generated by these cells, measured as expression of VWF, tissue factor and platelet reactivity, showed non-significant differences. We provide a model of cultured endothelial cells reproducing endothelial dysfunction in naive patients with major depression, demonstrating endothelial damage and inflammation at diagnosis, and recovering with selective serotonin reuptake inhibitor treatment for 24 weeks.