Activation of innate immunity in patients with venous thrombosis: the Leiden Thrombophilia Study

Background: Previous studies have suggested that levels of inflammatory mediators are risk indicators for venous thrombotic disease. We have Sought to confirm and extend these findings by measuring plasma tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, IL-8, IL-10 and IL-12p70 levels in a case-control study for venous thrombotic disease. Methods:: The plasma levels of these inflammatory mediators were measured by flow cytometric analysis using a multiplexed bead assay. Patient and control samples came from the Leiden Thrombophilia Study (474 controls and 474 patients). Results: In a subset of patients and controls inflammatory mediators are detectable in plasma. The crude odds ratios (ORs) associated with the presence of detectable markers were 2.1 [TNF-alpha, 95% confidence interval (CI) 1.1, 3.9], 1.7 (IL-1beta, 95% CI 1.1, 2.9) 2.4 (IL-6, 95% CI 1.9, 5.3), 2.8 (IL-8, 95%) (CI 1.8, 4.4) 0.8 (IL-10, 95% CI 0.3, 1.8). and 1.3 (IL-12p70, 95% CI 0.9, 2.0). Adjustment for putative confounders did not influence the risk estimates. Conclusion: TNF-alpha, IL-6. and IL-8 levels are risk determinants for venOLIS thrombosis. Individuals with detectable levels of either of these mediators in plasma have an OR of about 2. In line with these findings, the odds for the anti-inflammatory cytokine IL-10 tend to be <1. These results add further evidence for the contention that there is an inflammatory component to venous thrombotic disease and may explain why anti-inflammatory agents Such as aspirin may be effective for preventio

Reversal Agents for the Direct Factor Xa Inhibitors: Biochemical Mechanisms of Current and Newly Emerging Therapies

The direct oral anticoagulants targeting coagulation factor Xa or thrombin are widelyused as alternatives to vitamin K antagonists in the management of venous thromboembolismand nonvalvular atrial fibrillation. In case of bleeding or emergency surgery,reversal agents are helpful to counteract the anticoagulant therapy and restorehemostasis. While idarucizumab has been established as an antidote for the directthrombin inhibitor dabigatran, reversal strategies for the direct factor Xa inhibitorshave been a focal point in clinical care over the past years. In the absence of specificreversal agents, the off-label use of (activated) prothrombin complex concentrate andrecombinant factor VIIa have been suggested as effective treatment options duringinhibitor-induced bleeding complications. Meanwhile, several specific reversal agentshave been developed. In this review, an overview of the current state of nonspecific andspecific reversal agents for the direct factor Xa inhibitors is provided, focusing on thebiochemistry and mechanism of action and the preclinical assessment of newlyemerging therapies.Thrombosis and Hemostasi

Hawking radiation in different coordinate settings: Complex paths approach

We apply the technique of complex paths to obtain Hawking radiation in different coordinate representations of the Schwarzschild space-time. The coordinate representations we consider do not possess a singularity at the horizon unlike the standard Schwarzschild coordinate. However, the event horizon manifests itself as a singularity in the expression for the semiclassical action. This singularity is regularized by using the method of complex paths and we find that Hawking radiation is recovered in these coordinates indicating the covariance of Hawking radiation as far as these coordinates are concerned.Comment: 18 pages, 2 figures, Uses IOP style file; final version; accepted in Class. Quant. Gra

Elevated anti-human factor Xa activity in rabbit and rodent plasma: implications for preclinical assessment of human factor X in animal models of hemostasis

A wide variety of animal models on thrombosis and hemostasis are used in thrombosis and hemostasis research for the preclinical assessment of hemostatic agents. While the vertebrate coagulome is highly conserved, human and animal plasmas differ considerably when evaluated in coagulation assays such as prothrombin time (PT), activated partial thromboplastin time (APTT), and calibrated automated thrombography (CAT). Here, we have aimed to provide a reference framework for the evaluation of coagulation assays and inhibition of activated human FXa (hFXa) in various animal plasmas. To do so, a side-by-side evaluation of the extrinsic and intrinsic pathway of coagulation was performed by means of PT, APTT, and CAT measurements on (diluted) pooled plasmas from goats, pigs, rabbits, rats, mice, and humans. Plasma anti-FXa activity was assessed by determining the rate of recombinant hFXa inhibition through chromogenic activity analyses and immunoblotting. In general, rabbit, rat, and mouse plasmas exhibited robust clotting upon stimulation of both the extrinsic and intrinsic pathway, produced more thrombin during CAT upon plasma dilution, and displayed relatively high hFXa inhibitory activities. By comparison, goat, porcine, and human plasma displayed a similar profile in PT and APTT assays, produced less thrombin during CAT upon plasma dilution, and displayed comparable hFXa inhibitory activities. In conclusion, the observed differences in clotting parameters and anti-hFXa activity point to a higher anticoagulant threshold in plasma from rabbits, rats, and particularly in mice relative to human, goat, and porcine plasma. Finally, rat plasma was found to be more relevant to the preclinical assessment of human FX(a) in comparison to murine plasma.Thrombosis and Hemostasi

Evolutionary Adaptations in Pseudonaja Textilis Venom Factor X Induce Zymogen Activity and Resistance to the Intrinsic Tenase Complex

The venom of the Australian snake Pseudonaja textilis comprises powerful prothrombinactivators consisting of factor X (v-ptFX)- and factor V-like proteins. While all vertebrateliver-expressed factor X (FX) homologs, including that of P. textilis, comprise anactivation peptide of approximately 45 to 65 residues, the activation peptide of vptFXis significantly shortened to 27 residues. In this study, we demonstrate thatexchanging the human FX activation peptide for the snake venom ortholog impedesproteolytic cleavage by the intrinsic factor VIIIa–factor IXa tenase complex. Furthermore,our findings indicate that the human FX activation peptide comprises anessential binding site for the intrinsic tenase complex. Conversely, incorporation ofFX into the extrinsic tissue factor–factor VIIa tenase complex is completely dependenton exosite-mediated interactions. Remarkably, the shortened activation peptide allowsfor factor V-dependent prothrombin conversion while in the zymogen state. Thisindicates that the active site of FX molecules comprising the v-ptFX activation peptidepartially matures upon assembly into a premature prothrombinase complex. Takentogether, the shortened activation peptide is one of the remarkable characteristics of vptFXthat has been modified from its original form, thereby transforming FX into apowerful procoagulant protein. Moreover, these results shed new light on thestructural requirements for serine protease activation and indicate that catalyticactivity can be obtained without formation of the characteristic Ile16–Asp194 saltbridge via modification of the activation peptide.Thrombosis and Hemostasi

Engineered factor Xa variants retain procoagulant activity independent of direct factor Xa inhibitors

Thrombosis and Hemostasi