Commentary: Macrophage IL-1β-positive microvesicles exhibit thrombo-inflammatory properties and are detectable in patients with active juvenile idiopathic arthritis

Rigor and reproducibility in biomedical science are the cornerstones to ensure the quality and reproducibility of preclinical research. Concerns raised about the use of antibodies in common laboratory applications led the International Working Group for Antibody Validation to establish several recommendation for the use of antibodies. They suggested that investigators use at least one of five strategies for validation of antibodies for western blotting. The best way to demonstrate that an antibody is correctly recognizing its target is to eliminate or reduce expression of the target protein using genome editing or RNA interference. Unfortunately, most investigators do not independently validate commercial antibodie

Expression of factor V by resident macrophages boosts host defense in the peritoneal cavity

Macrophages resident in different organs express distinct genes, but understanding how this diversity fits into tissue-specific features is limited. Here, we show that selective expression of coagulation factor V (FV) by resident peritoneal macrophages in mice promotes bacterial clearance in the peritoneal cavity and serves to facilitate the well-known but poorly understood macrophage disappearance reaction. Intravital imaging revealed that resident macrophages were nonadherent in peritoneal fluid during homeostasis. Bacterial entry into the peritoneum acutely induced macrophage adherence and associated bacterial phagocytosis. However, optimal control of bacterial expansion in the peritoneum also required expression of FV by the macrophages to form local clots that effectively brought macrophages and bacteria in proximity and out of the fluid phase. Thus, acute cellular adhesion and resident macrophage-induced coagulation operate independently and cooperatively to meet the challenges of a unique, open tissue environment. These events collectively account for the macrophage disappearance reaction in the peritoneal cavity

Microvesicle Tissue Factor Activity and Interleukin-8 Levels are Associated with Mortality in Patients with Influenza A/H1N1 Infection

To identify plasma biomarkers that can be early predictors of mortality in critically ill patients with primary influenza A/H1N1

Procoagulant Microparticles in Dogs with Immune-Mediated Hemolytic Anemia

BACKGROUND: Studies of some human prothrombotic diseases suggest that phosphatidylserine-positive (PS+) and tissue factor-positive (TF+) microparticles (MPs) might play a role in the pathogenesis of thrombosis or serve as biomarkers of thrombotic risk. HYPOTHESIS/OBJECTIVES: To determine if circulating levels of PS+MP and procoagulant activity (PCA) associated with PS+MPs and TF+ MPs are increased in dogs with IMHA. ANIMALS: Fifteen dogs with primary or secondary IMHA and 17 clinically healthy dogs. METHODS: Prospective case-controlled observational study. Circulating PS+MPs were measured by flow cytometry. PCA associated with PS+MPs and TF+MPs was measured by thrombin and Factor Xa generating assays, respectively. RESULTS: Circulating numbers of PS+MPs were not significantly higher in dogs with IMHA [control median 251,000/μL (36,992-1,141,250/μL); IMHA median 361,990/μL (21,766-47,650,600/μL) P = .30]. However, PS+MP PCA [control median 2.2 (0.0-16.8) nM PS eq; IMHA median 8.596, (0-49.33 nM PS eq) P = .01] and TF+MP PCA [control median 0.0, (0.0-0.0 pg/mL); IMHA median 0.0; (0-22.34 pg/mL], P = .04) were increased. Intravascular hemolysis, which we showed might increase PS+ and TF+MP PCA, was evident in 3 of 5 dogs with PS+MP PCA and 2 of 4 dogs with TF+MP PCA higher than controls. Underlying disease in addition to IMHA was detected in 1 of 5 dogs with PS+PCA and 3 of 4 dogs with TF+MP PCA higher than controls. CONCLUSIONS AND CLINICAL IMPORTANCE: TF+ and PS+MP PCA is increased in some dogs with IMHA. Further studies that determine if measuring TF+ and PS+ MP PCA can help identify dogs at risk for thrombosis are warranted

Role of Coagulation Factors in Cerebral Venous Sinus and Cerebral Microvascular Thrombosis

Thrombus formation can occur in both macroscopic and microscopic blood vessels. In the brain, cerebral venous sinus thrombosis (CVST) and focal cortical infarctions can result from the formation of thrombi in these different sized vessels. In this study we define the relative contributions of three major pro- and anti-coagulation pathways (heparin-antithrombin, protein C, and tissue factor (TF)) in the thrombogenic responses that occur in large and small vessels of the brain

Critical Review of Mouse Models of Venous Thrombosis

Deep vein thrombosis and pulmonary embolism are a significant health care concern, representing a major source of mortality and morbidity. In order to understand the pathophysiology of thrombogenesis and thrombus resolution, animal models are necessary. Mouse models of venous thrombosis contribute to our understanding of the initiation, propagation, and resolution of venous thrombus, as well as allow for the evaluation of new pharmaceutical approaches to prophylaxis and treatment of deep vein thrombosis. In this work we review the ferric chloride model, the inferior vena cava ligation model, the inferior vena cava stenosis models, and the electrolytic inferior vena cava model and compare their advantages and disadvantages

Protective Roles for Fibrin, Tissue Factor, Plasminogen Activator Inhibitor-1, and Thrombin Activatable Fibrinolysis Inhibitor, but Not Factor XI, during Defense against the Gram-Negative Bacterium Yersinia enterocolitica

Septic infections dysregulate hemostatic pathways, prompting coagulopathy. Nevertheless, anticoagulant therapies typically fail to protect humans from septic pathology. The data reported here may help to explain this discrepancy by demonstrating critical protective roles for coagulation leading to fibrin deposition during host defense against the gram-negative bacterium Yersinia enterocolitica. After intraperitoneal inoculation with Y. enterocolitica, fibrinogen-deficient mice display impaired cytokine and chemokine production in the peritoneal cavity and suppressed neutrophil recruitment. Moreover, both gene-targeted fibrinogen-deficient mice and wild type mice treated with the anticoagulant coumadin display increased hepatic bacterial burden and mortality following either intraperitoneal or intravenous inoculation with Y. enterocolitica. Mice with low tissue factor (TF) activity succumb to yersiniosis with a phenotype similar to fibrin(ogen)-deficient mice, whereas factor XI (FXI)-deficient mice show wild type levels of resistance. Mice deficient in plasminogen activator inhibitor-1 (PAI-1) or thrombin activatable fibrinolysis inhibitor (TAFI) display modest phenotypes, but mice deficient in both PAI-1 and TAFI succumb to yersiniosis with a phenotype resembling fibrin(ogen)-deficient mice. These findings demonstrate critical protective roles for the TF-dependent extrinsic coagulation pathway during host defense against bacteria and caution that therapeutics targeting major thrombin-generating or anti-fibrinolytic pathways may disrupt fibrin-mediated host defense during gram-negative sepsis

Protease-Activated Receptor 2 Deficiency Reduces Cardiac Ischemia/Reperfusion Injury

Protease-activated receptor-2 (PAR-2) signaling enhances inflammation in different diseases. The effect of PAR-2 deficiency in cardiac ischemia/reperfusion (I/R) injury is unknown. We investigated the effect of PAR-2 deficiency on I/R injury-induced infarct size, inflammation, heart remodeling and cardiac function

Signal-dependent splicing of tissue factor pre-mRNA modulates the thrombogenecity of human platelets

Tissue factor (TF) is an essential cofactor for the activation of blood coagulation in vivo. We now report that quiescent human platelets express TF pre-mRNA and, in response to activation, splice this intronic-rich message into mature mRNA. Splicing of TF pre-mRNA is associated with increased TF protein expression, procoagulant activity, and accelerated formation of clots. Pre-mRNA splicing is controlled by Cdc2-like kinase (Clk)1, and interruption of Clk1 signaling prevents TF from accumulating in activated platelets. Elevated intravascular TF has been reported in a variety of prothrombotic diseases, but there is debate as to whether anucleate platelets—the key cellular effector of thrombosis—express TF. Our studies demonstrate that human platelets use Clk1-dependent splicing pathways to generate TF protein in response to cellular activation. We propose that platelet-derived TF contributes to the propagation and stabilization of a thrombus