scholarly journals Targeting coagulation factor XII provides protection from pathological thrombosis in cerebral ischemia without interfering with hemostasis

2006 ◽  
Vol 203 (3) ◽  
pp. 513-518 ◽  
Author(s):  
Christoph Kleinschnitz ◽  
Guido Stoll ◽  
Martin Bendszus ◽  
Kai Schuh ◽  
Hans-Ulrich Pauer ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Coagulation Factor ◽  
Artery Occlusion ◽  
Factor Xii ◽  
Intrinsic Pathway ◽  
Fibrin Formation ◽  
Vessel Injury ◽  
Normal Hemostasis ◽  
A Site

Formation of fibrin is critical for limiting blood loss at a site of blood vessel injury (hemostasis), but may also contribute to vascular thrombosis. Hereditary deficiency of factor XII (FXII), the protease that triggers the intrinsic pathway of coagulation in vitro, is not associated with spontaneous or excessive injury-related bleeding, indicating FXII is not required for hemostasis. We demonstrate that deficiency or inhibition of FXII protects mice from ischemic brain injury. After transient middle cerebral artery occlusion, the volume of infarcted brain in FXII-deficient and FXII inhibitor–treated mice was substantially less than in wild-type controls, without an increase in infarct-associated hemorrhage. Targeting FXII reduced fibrin formation in ischemic vessels, and reconstitution of FXII-deficient mice with human FXII restored fibrin deposition. Mice deficient in the FXII substrate factor XI were similarly protected from vessel-occluding fibrin formation, suggesting that FXII contributes to pathologic clotting through the intrinsic pathway. These data demonstrate that some processes involved in pathologic thrombus formation are distinct from those required for normal hemostasis. As FXII appears to be instrumental in pathologic fibrin formation but dispensable for hemostasis, FXII inhibition may offer a selective and safe strategy for preventing stroke and other thromboembolic diseases.

scholarly journals In vivo roles of factor XII

Blood ◽  
2012 ◽  
Vol 120 (22) ◽  
pp. 4296-4303 ◽  
Author(s):  
Thomas Renné ◽  
Alvin H. Schmaier ◽  
Katrin F. Nickel ◽  
Margareta Blombäck ◽  
Coen Maas
Keyword(s):  
Thrombus Formation ◽  
Coagulation Factor ◽  
Special Focus ◽  
Factor Xii ◽  
Excessive Bleeding ◽  
Charged Surfaces ◽  
Factor Xiia ◽  
Knockout Model

Abstract Coagulation factor XII (FXII, Hageman factor, EC = 3.4.21.38) is the zymogen of the serine protease, factor XIIa (FXIIa). FXII is converted to FXIIa through autoactivation induced by “contact” to charged surfaces. FXIIa is of crucial importance for fibrin formation in vitro, but deficiency in the protease is not associated with excessive bleeding. For decades, FXII was considered to have no function for coagulation in vivo. Our laboratory developed the first murine knockout model of FXII. Consistent with their human counterparts, FXII−/− mice have a normal hemostatic capacity. However, thrombus formation in FXII−/− mice is largely defective, and the animals are protected from experimental cerebral ischemia and pulmonary embolism. This murine model has created new interest in FXII because it raises the possibility for safe anticoagulation, which targets thrombosis without influence on hemostasis. We recently have identified platelet polyphosphate (an inorganic polymer) and mast cell heparin as in vivo FXII activators with implications on the initiation of thrombosis and edema during hypersensitivity reactions. Independent of its protease activity, FXII exerts mitogenic activity with implications for angiogenesis. The goal of this review is to summarize the in vivo functions of FXII, with special focus to its functions in thrombosis and vascular biology.

scholarly journals Contradictory functions of sulfatide in the blood coagulation system as coagulant and anticoagulant.

1998 ◽  
Vol 45 (2) ◽  
pp. 493-499 ◽  
Author(s):  
M Kyogashima ◽  
J Onaya ◽  
A Hara ◽  
T Taketomi
Keyword(s):  
Blood Coagulation ◽  
Thrombus Formation ◽  
Coagulation Factor ◽  
Coagulation System ◽  
Factor Xii ◽  
Blood Coagulation System ◽  
Coagulant Activity ◽  
J 13

Sulfatide (galactosylceramide I3 -sulfate) has been reported to activate blood coagulation factor XII (Hageman factor), which suggests that it exhibits coagulant activity (Fujikama et al., 1980 Biochemistry 19, 1322-1330) However, sulfatide administered into animals as a bolus shot without subsequent thrombus formation, prolonged conventional clotting times and bleeding time (Hara et al., 1996 Glycoconjugate J. 13, 187-194). These findings suggest that it may exhibit anticoagulant rather than coagulant activity. Following this suggestion we found in vitro that binding of sulfatide to fibrinogen resulted in disturbance of fibrin formation. To examine a possible pharmacological effect of sulfatide on blood coagulation in vivo we continuously infused sulfatide into rats through plastic cannulae and found formation of giant thrombi around the tips of the cannulae. These data suggest that sulfatide may exhibit contradictory functions in the blood coagulation system.

scholarly journals Coagulation factor XII in thrombosis and inflammation

Blood ◽  
2018 ◽  
Vol 131 (17) ◽  
pp. 1903-1909 ◽  
Author(s):  
Coen Maas ◽  
Thomas Renné
Keyword(s):  
Thrombus Formation ◽  
Coagulation Factor ◽  
Contact System ◽  
Inflammatory Disorder ◽  
Factor Xii ◽  
Kinin System ◽  
Disease States ◽  
Exciting Opportunity

Abstract Combinations of proinflammatory and procoagulant reactions are the unifying principle for a variety of disorders affecting the cardiovascular system. The factor XII–driven contact system starts coagulation and inflammatory mechanisms via the intrinsic pathway of coagulation and the bradykinin-producing kallikrein-kinin system, respectively. The biochemistry of the contact system in vitro is well understood; however, its in vivo functions are just beginning to emerge. Challenging the concept of the coagulation balance, targeting factor XII or its activator polyphosphate, provides protection from thromboembolic diseases without interfering with hemostasis. This suggests that the polyphosphate/factor XII axis contributes to thrombus formation while being dispensable for hemostatic processes. In contrast to deficiency in factor XII providing safe thromboprotection, excessive FXII activity is associated with the life-threatening inflammatory disorder hereditary angioedema. The current review summarizes recent findings of the polyphosphate/factor XII–driven contact system at the intersection of procoagulant and proinflammatory disease states. Elucidating the contact system offers the exciting opportunity to develop strategies for safe interference with both thrombotic and inflammatory disorders.

In Vivo Roles for Factor XII

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. SCI-19-SCI-19
Author(s):  
Thomas Renné
Keyword(s):  
Pulmonary Embolism ◽  
Conflicts Of Interest ◽  
Thrombus Formation ◽  
Coagulation Factor ◽  
Coagulation System ◽  
Factor Xii ◽  
Intrinsic Pathway ◽  
Inorganic Polyphosphate ◽  
Edema Formation

Abstract Abstract SCI-19 The coagulation system is critical for limiting blood loss at a site of injury (hemostasis), but may also contribute to thrombotic disease. The model of a coagulation balance represents these two sides of the same coin. Thrombosis may occur in the venous or arterial circulation, causing pulmonary embolism or myocardial infarction and stroke, collectively the most common causes of death in the developed world. Recent data from genetically altered mouse models have challenged the dogma of a coagulation balance. Deficiency of coagulation factor XII (Hageman factor), a serine protease, which initiates the intrinsic pathway of coagulation, severely impairs thrombus formation but is not associated with any excessive bleedings in humans or in mice. Targeting factor XII protects from occlusive disease in experimental animal models. Individuals with hereditary deficiency in the factor XII substrate factor XI are largely protected form ischemic stroke and deep-vein thrombosis. These findings indicate that fibrin-forming mechanisms, which operate during pathologic thrombus formation, involve pathways distinct from those proceeding during normal hemostasis. As the factor XII-driven contact system selectively contributes to thrombosis, but not to hemostasis, inhibition of the system offers novel anticoagulation strategies associated with minimal or no bleeding risk. In contrast to factor XII deficiency states, a single missense mutation (Thr328Lys) in the coagulation protein is associated with a life-threatening swelling disease, hereditary angioedema type III. Pharmacological factor XII inhibitors interfered both with pathological thrombosis and edema formation suggesting broad medical implications. Factor XII is activated in vivo by platelet-released inorganic polyphosphate, a linear polymer of 60–100 phosphate residues that directly bound to the coagulation factor. Polyphosphates-driven factor XII activation triggered release of the inflammatory mediator bradykinin. Polyphosphates increased vascular permeability and induced skin edema formation in mice and animals deficient in factor XII or bradykinin receptors were resistant to polyphosphates-induced leakage. Polyphosphates were procoagulant via the intrinsic pathway of coagulation. Ablation of intrinsic coagulation pathway proteases factors XII and XI protected mice from polyphosphate-triggered lethal pulmonary embolism. Targeting polyphosphates with phosphatases interfered with procoagulant activity of activated platelets and blocked platelet-induced thrombosis in mice. Addition of polyphosphates restored defective plasma clotting of Hermansky-Pudlak Syndrome patients, who platelet lack storage organelles for polyphosphates. The data identify polyphosphates as the endogenous activator of factor XII having fundamental roles in platelet-driven proinflammatory and procoagulant disorders. Disclosures: No relevant conflicts of interest to declare.

scholarly journals CpaA Is a Glycan-Specific Adamalysin-like Protease Secreted byAcinetobacter baumanniiThat Inactivates Coagulation Factor XII

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Ursula Waack ◽  
Mark Warnock ◽  
Andrew Yee ◽  
Zachary Huttinger ◽  
Sara Smith ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Defense Mechanisms ◽  
Thrombus Formation ◽  
Coagulation Factor ◽  
Factor Xii ◽  
Contact Activation ◽  
Extrinsic Pathway ◽  
Content Type

ABSTRACTAntibiotic-resistantAcinetobacter baumanniiis increasingly recognized as a cause of difficult-to-treat nosocomial infections, including pneumonia, wound infections, and bacteremia. Previous studies have demonstrated that the metalloprotease CpaA contributes to virulence and prolongs clotting time when added to human plasma as measured by the activated partial thromboplastin time (aPTT) assay. Here, we show that CpaA interferes with the intrinsic coagulation pathway, also called the contact activation system, in human as well as murine plasma, but has no discernible effect on the extrinsic pathway. By utilizing a modified aPTT assay, we demonstrate that coagulation factor XII (fXII) is a target of CpaA. In addition, we map the cleavage by CpaA to two positions, 279-280 and 308-309, within the highly glycosylated proline-rich region of human fXII, and show that cleavage at the 308-309 site is responsible for inactivation of fXII. At both sites, cleavage occurs between proline and an O-linked glycosylated threonine, and deglycosylation of fXII prevents cleavage by CpaA. Consistent with this, mutant fXII (fXII-Thr309Lys) from patients with hereditary angioedema type III (HAEIII) is protected from CpaA inactivation. This raises the possibility that individuals with HAEIII who harbor this mutation may be partially protected fromA. baumanniiinfection if CpaA contributes to human disease. By inactivating fXII, CpaA may attenuate important antimicrobial defense mechanisms such as intravascular thrombus formation, thus allowingA. baumanniito disseminate.IMPORTANCEVentilator-associated pneumonia and catheter-related bacteremia are the most common and severe infections caused byAcinetobacter baumannii. Besides the capsule, lipopolysaccharides, and the outer membrane porin OmpA, little is known about the contribution of secreted proteins toA. baumanniisurvivalin vivo. Here we focus on CpaA, a potentially recently acquired virulence factor that inhibits blood coagulationin vitro. We identify coagulation factor XII as a target of CpaA, map the cleavage sites, and show that glycosylation is a prerequisite for CpaA-mediated inactivation of factor XII. We propose adding CpaA to a small, but growing list of bacterial proteases that are specific for highly glycosylated components of the host defense system.

New agents for thromboprotection

2015 ◽  
Vol 35 (04) ◽  
pp. 338-350 ◽  
Author(s):  
L. Labberton ◽  
E. Kenne ◽  
T. Renné
Keyword(s):  
Current Knowledge ◽  
Thrombus Formation ◽  
Coagulation Cascade ◽  
Factor Xii ◽  
Bleeding Tendency ◽  
New Agents ◽  
Mechanistic Basis ◽  
Normal Hemostasis ◽  
Coagulation Pathway

SummaryBlood coagulation is essential for hemostasis, however excessive coagulation can lead to thrombosis. Factor XII starts the intrinsic coagulation pathway and contact-induced factor XII activation provides the mechanistic basis for the diagnostic aPTT clotting assay. Despite its function for fibrin formation in test tubes, patients and animals lacking factor XII have a completely normal hemostasis. The lack of a bleeding tendency observed in factor XII deficiency states is in sharp contrast to deficiencies of other components of the coagulation cascade and factor XII has been considered to have no function for coagulation in vivo. Recently, experimental animal models showed that factor XII is activated by an inorganic polymer, polyphosphate, which is released from procoagulant platelets and that polyphosphate-driven factor XII activation has an essential role in pathologic thrombus formation. Cumulatively, the data suggest to target polyphosphate, factor XII, or its activated form factor XIIa for anticoagulation. As the factor XII pathway specifically contributes to thrombosis but not to hemostasis, interference with this pathway provides a unique opportunity for safe anticoagulation that is not associated with excess bleeding.The review summarizes current knowledge on factor XII functions, activators and inhibitors.

scholarly journals Heparin is more effective than apixaban in inhibiting in vitro contact activated coagulation

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
M.M Engelen ◽  
C Van Laer ◽  
M Jacquemin ◽  
C Vandenbriele ◽  
K Peerlinck ◽  
...  
Keyword(s):  
Thrombin Generation ◽  
Heart Valves ◽  
Thrombus Formation ◽  
Oral Anticoagulants ◽  
Direct Oral Anticoagulants ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Mechanical Heart Valves ◽  
Contact Activation

Abstract Introduction Contact of blood with artificial surfaces such as mechanical support devices, catheters, and mechanical heart valves activates the contact activation (CA) pathway of coagulation. Furthermore, recent animal data and clinical studies suggest a more important contribution of CA in pathological thrombus formation in other cardiovascular diseases. Direct oral anticoagulants (DOACs) are recommended as first-line treatment in most patients who require long-term anticoagulation. However, because DOACs directly inhibit a single downstream coagulation factor (thrombin (fXIIa) or factor Xa (fXa)), it has been suggested that their efficacy could be reduced in the presence of strong activation of the CA pathway as compared to anticoagulants that target multiple, more upstream located coagulation factors. Purpose To compare the efficacy of a DOAC (apixaban) and heparin to suppress thrombin generation in the presence of strong CA pathway activation. Methods Pooled platelet-poor plasma was spiked with either apixaban (dissolved in DMSO and PBS) or unfractionated heparin to achieve therapeutic plasma levels. SynthASil, a commercially available mixture of phospholipids and silica, was used to stimulate the CA pathway in two different dilutions (1–80 and 5–80). Downstream coagulation was accessed by Thrombin Generation Test using Thrombinoscope by Stago and associated Thrombin Calibrator (activity 640 nM). The endogenous thrombin potential (area under the thrombin generation curve; ETP), peak thrombin generation (PTG), time to peak (ttPeak) and time to start (ttStart) were accessed. Results With decreasing concentrations of apixaban, stimulation with the lower dose SynthASil reveals an increasing ETP and PTG. As expected, ttPeak and ttStart decreased. Even supratherapeutic levels of apixaban (i.e. 1120 ng/mL) could not inhibit thrombin from being generated, in striking contrast with UFH where no thrombin was formed. Using a five times higher dose of SynthASil showed comparable ETP for all concentrations of apixaban, allocated around the control value. PTG, however, slightly increased with decreasing concentrations of apixaban. ttPeak and ttStart slightly decreased. Except for the subtherapeutic UFH concentration of 0,114 IU/mL, no thrombin was generated with UFH. Conclusion UFH is more effective in inhibiting downstream thrombin generation compared to apixaban as a response to activation of the CA pathway in vitro. These findings could help explain why direct inhibitors were not able to show non-inferiority in patients with mechanical heart valves and support the development of specific CA pathway inhibitors for patients with conditions that activate the CA pathway. Thrombin generation curves Funding Acknowledgement Type of funding source: None

scholarly journals Vascular Gas6 contributes to thrombogenesis and promotes tissue factor up-regulation after vessel injury in mice

Blood ◽  
2013 ◽  
Vol 121 (4) ◽  
pp. 692-699 ◽  
Author(s):  
Richard S. Robins ◽  
Catherine A. Lemarié ◽  
Sandrine Laurance ◽  
Meghedi N. Aghourian ◽  
Jianqiu Wu ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Thrombus Formation ◽  
Vascular Wall ◽  
Specific Gene ◽  
Tissue Factor Expression ◽  
Vessel Injury ◽  
Factor Expression ◽  
Platelet Signaling

Abstract Gas6 (growth-arrest specific gene 6) plays a role in thrombus stabilization. Gas6 null (−/−) mice are protected from lethal venous and arterial thromboembolism through platelet signaling defects induced only by 5μM ADP and 10μM of the thromboxane analog, U46619. This subtle platelet defect, despite a dramatic clinical phenotype, raises the possibility that Gas6 from a source other than platelets contributes to thrombus formation. Thus, we hypothesize that Gas6 derived from the vascular wall plays a role in venous thrombus formation. Bone marrow transplantation and platelet depletion/reconstitution experiments generating mice with selective ablations of Gas6 from either the hematopoietic or nonhematopoietic compartments demonstrate an approximately equal contribution by Gas6 from both compartments to thrombus formation. Tissue factor expression was significantly reduced in the vascular wall of Gas6−/− mice compared with WT. In vitro, thrombin-induced tissue factor expression was reduced in Gas6−/− endothelial cells compared with wild-type endothelium. Taken together, these results demonstrate that vascular Gas6 contributes to thrombus formation in vivo and can be explained by the ability of Gas6 to promote tissue factor expression and activity. These findings support the notion that vascular wall-derived Gas6 may play a pathophysiologic role in venous thromboembolism.

scholarly journals Tissue factor–positive neutrophils bind to injured endothelial wall and initiate thrombus formation

Blood ◽  
2012 ◽  
Vol 120 (10) ◽  
pp. 2133-2143 ◽  
Author(s):  
Roxane Darbousset ◽  
Grace M. Thomas ◽  
Soraya Mezouar ◽  
Corinne Frère ◽  
Rénaté Bonier ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Tissue Factor ◽  
Blood Coagulation ◽  
Thrombus Formation ◽  
Coagulation Cascade ◽  
Factor Xii ◽  
Long Time ◽  
Platelet Accumulation

AbstractFor a long time, blood coagulation and innate immunity have been viewed as interrelated responses. Recently, the presence of leukocytes at the sites of vessel injury has been described. Here we analyzed interaction of neutrophils, monocytes, and platelets in thrombus formation after a laser-induced injury in vivo. Neutrophils immediately adhered to injured vessels, preceding platelets, by binding to the activated endothelium via leukocyte function antigen-1–ICAM-1 interactions. Monocytes rolled on a thrombus 3 to 5 minutes postinjury. The kinetics of thrombus formation and fibrin generation were drastically reduced in low tissue factor (TF) mice whereas the absence of factor XII had no effect. In vitro, TF was detected in neutrophils. In vivo, the inhibition of neutrophil binding to the vessel wall reduced the presence of TF and diminished the generation of fibrin and platelet accumulation. Injection of wild-type neutrophils into low TF mice partially restored the activation of the blood coagulation cascade and accumulation of platelets. Our results show that the interaction of neutrophils with endothelial cells is a critical step preceding platelet accumulation for initiating arterial thrombosis in injured vessels. Targeting neutrophils interacting with endothelial cells may constitute an efficient strategy to reduce thrombosis.

scholarly journals Next-Generation Antithrombotics in Ischemic Stroke: Preclinical Perspective on ‘Bleeding-Free Antithrombosis’

2012 ◽  
Vol 32 (10) ◽  
pp. 1831-1840 ◽  
Author(s):  
Peter Kraft ◽  
Simon F De Meyer ◽  
Christoph Kleinschnitz
Keyword(s):  
Ischemic Stroke ◽  
Thrombus Formation ◽  
Coagulation Factor ◽  
Coagulation Cascade ◽  
Bleeding Complications ◽  
Factor Xii ◽  
Platelet Inhibitors ◽  
Platelet Surface ◽  
Surface Receptors ◽  
Glycoprotein Vi

The present antithrombotic drugs used to treat or prevent ischemic stroke have significant limitations: either they show only moderate efficacy (platelet inhibitors), or they significantly increase the risk for hemorrhages (thrombolytics, anticoagulants). Although most strokes are caused by thrombotic or embolic vessel occlusions, the pathophysiological role of platelets and coagulation is largely unclear. The introduction of novel transgenic mouse models and specific coagulation inhibitors facilitated a detailed analysis of molecular pathways mediating thrombus formation in models of acute ischemic stroke. Prevention of early platelet adhesion to the damaged vessel wall by blocking platelet surface receptors glycoprotein Ib alpha (GPIb α) or glycoprotein VI (GPVI) protects from stroke without provoking bleeding complications. In addition, downstream signaling of GPIb α and GPVI has a key role in platelet calcium homeostasis and activation. Finally, the intrinsic coagulation cascade, activated by coagulation factor XII (FXII), has only recently been identified as another important mediator of thrombosis in cerebrovascular disease, thereby disproving established concepts. This review summarizes the latest insights into the pathophysiology of thrombus formation in the ischemic brain. Potential clinical merits of novel platelet inhibitors and anticoagulants as powerful and safe tools to combat ischemic stroke are discussed.

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