The current status of coagulation

Role of pyroptosis in hemostasis activation in sepsis

Sepsis is frequently associated with hemostasis activation and thrombus formation, and systematic hemostatic changes are associated with a higher risk of mortality. The key events underlying hemostasis activation during sepsis are the strong activation of innate immune pathways and the excessive inflammatory response triggered by invading pathogens. Pyroptosis is a proinflammatory form of programmed cell death, that defends against pathogens during sepsis. However, excessive pyroptosis can lead to a dysregulation of host immune responses and organ dysfunction. Recently, pyroptosis has been demonstrated to play a prominent role in hemostasis activation in sepsis. Several studies have demonstrated that pyroptosis participates in the release and coagulation activity of tissue factors. In addition, pyroptosis activates leukocytes, endothelial cells, platelets, which cooperate with the coagulation cascade, leading to hemostasis activation in sepsis. This review article attempts to interpret the molecular and cellular mechanisms of the hemostatic imbalance induced by pyroptosis during sepsis and discusses potential therapeutic strategies.

Pathophysiology of Coagulation and Emerging Roles for Extracellular Vesicles in Coagulation Cascades and Disorders

The notion of blood coagulation dates back to the ancient Greek civilization. However, the emergence of innovative scientific discoveries that started in the seventeenth century formulated the fundamentals of blood coagulation. Our understanding of key coagulation processes continues to evolve, as novel homeostatic and pathophysiological aspects of hemostasis are revealed. Hemostasis is a dynamic physiological process, which stops bleeding at the site of injury while maintaining normal blood flow within the body. Intrinsic and extrinsic coagulation pathways culminate in the homeostatic cessation of blood loss, through the sequential activation of the coagulation factors. Recently, the cell-based theory, which combines these two pathways, along with newly discovered mechanisms, emerged to holistically describe intricate in vivo coagulation mechanisms. The complexity of these mechanisms becomes evident in coagulation diseases such as hemophilia, Von Willebrand disease, thrombophilia, and vitamin K deficiency, in which excessive bleeding, thrombosis, or unnecessary clotting, drive the development and progression of diseases. Accumulating evidence implicates cell-derived and platelet-derived extracellular vesicles (EVs), which comprise microvesicles (MVs), exosomes, and apoptotic bodies, in the modulation of the coagulation cascade in hemostasis and thrombosis. As these EVs are associated with intercellular communication, molecular recycling, and metastatic niche creation, emerging evidence explores EVs as valuable diagnostic and therapeutic approaches in thrombotic and prothrombotic diseases.

Point-of-Care Device for Assessment of Blood Coagulation Status in COVID-19 Patients

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent driving the current COVID-19 pandemic. The acute respiratory distress that occurs in some severe COVID-19 cases has been linked with hypercoagulation or thrombotic events as well as a worse prognosis and increased risk of death. Thus, point-of-care devices that can be used for early detection of coagulation abnormalities would assist in COVID-19 management. This chapter describes the use of the Roche Diagnostics CoaguChek^® XS test kit for potential use in COVID-19 personalized medicine approaches.

Thrombin: An Approach to Developing a Higher-Order Reference Material and Reference Measurement Procedure for Substance Identity, Amount, and Biological Activities

Thrombin, the proteolytic enzyme that catalyzes the transformation of soluble fibrinogen to the polymerized fibrin clot, participates in multiple reactions in blood coagulation in addition to the clotting reaction. Although reference materials have existed for many years, structural characterization and measurement of biological activity have never been sufficient to permit claims of clear metrological traceability for the thrombin preparations. Our current state-of-the-art methods for protein characterization and determination of the catalytic properties of thrombin now make it practical to develop and characterize a metrologically acceptable reference material and reference measurement procedure for thrombin. Specifically, α-thrombin, the biologically produced protease formed during prothrombin activation, is readily available and has been extensively characterized. Dependences of thrombin proteolytic and peptide hydrolytic activities on a variety of substrates, pH, specific ions, and temperature are established, although variability remains for the kinetic parameters that describe thrombin enzymatic action. The roles of specific areas on the surface of the thrombin molecule (exosites) in substrate recognition and catalytic efficiency are described and characterized. It is opportune to develop reference materials of high metrological order and technical feasibility. In this article, we review the properties of α-thrombin important for its preparation and suggest an approach suitable for producing a reference material and a reference measurement procedure that is sensitive to thrombin’s catalytic competency on a variety of substrates.

A Network Pharmacology Approach Used to Estimate the Active Ingredients of Moutan Cortex Charcoal and the Potential Targets in Hemorrhagic Diseases

Moutan Cortex charcoal has been used to ameliorate blood heat symptoms and treat pathologic hemorrhage down the ages. Although well known as an agent with the effect of astringency and hemostasis, its active ingredients and action mechanism remain unclear. In the present study, molecular docking technology was employed to screen the potential hemostatic compounds in Moutan Cortex charcoal and their target proteins. Protein-protein-interaction (PPI) analysis was performed to explain the functions and enrichment pathways of the target proteins. The results showed that a total of 25 compounds were estimated as active constituents targeting multiple proteins related to hemostatic diseases, including 5 proteins (SERPINC1, FVIII, FX, FII and FXII) that were considered as the key targets. Then the drug-target (D-T) network was constructed to analyze the underlying hemostatic mechanism of Moutan Cortex charcoal, followed by a hierarchical cluster analysis (HCA) for compounds clustering, and a coagulation screening test for compound verification on their coagulation activities, with the results indicating that M15 (5-Tetradecenoic acid) and M31 (1-Monolinolein) might be the key compounds contributing to the hemostasis effect of Moutan Cortex charcoal by involving in the pathways related to complement, coagulation cascades and the platelet activation, particularly by activating FVIII, FX, FII and FXII and inhibiting SERPINC1. This study has demonstrated that Moutan Cortex charcoal may work as a hemostatic through the interaction between multiple-compounds and multiple-proteins, which provides the basis for further researches on the hemostasis mechanism of Moutan Cortex charcoal.

Identification and In Silico Prediction of Anticoagulant Peptides from the Enzymatic Hydrolysates of Mytilus edulis Proteins

Mytilus edulis is a typical marine bivalve mollusk. Many kinds of bioactive components with nutritional and pharmaceutical activities in Mytilus edulis were reported. In this study, eight different parts of Mytilus edulis tissues, i.e., the foot, byssus, pedal retractor muscle, mantle, gill, adductor muscle, viscera, and other parts, were separated and the proteins from these tissues were prepared. A total of 277 unique peptides from the hydrolysates of different proteins were identified by UPLC-Q-TOF-MS/MS, and the molecular weight distribution of the peptides in different tissues was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The bioactivity of the peptides was predicted through the Peptide Ranker database and molecular docking. Moreover, the peptides from the adductor muscle were chosen to do the active validation of anticoagulant activity. The active mechanism of three peptides from the adductor muscle, VQQELEDAEERADSAEGSLQK, RMEADIAAMQSDLDDALNGQR, and AAFLLGVNSNDLLK, were analyzed by Discovery Studio 2017, which also explained the anticoagulant activity of the hydrolysates of proteins from adductor muscle. This study optimized a screening and identification method of bioactive peptides from enzymatic hydrolysates of different tissues in Mytilus edulis.

Development of a User-Friendly App for Assisting Anticoagulation Treatment

Blood coagulation time is an important factor to consider for postoperative and cardiac disorder patients who have been prescribed anticoagulant coagulant medications. This chapter describes a patient self-management system for assessment of blood coagulation times and determining appropriate anticoagulant dosages using a test strip device and the Coagu app. This app can also be used as a patient reminder of treatment times and to monitor treatment and effects over time.

Why factor XI deficiency is a clinical concern

INTRODUCTION

Inherited fXI deficiency has been an enigma since its discovery in 1953. The variable and relatively mild symptoms in patients with even the most severe form of the disorder seem out of step with the marked abnormalities in standard clotting assays. Indeed, the contribution of factor XI to hemostasis in an individual is not adequately assessed by techniques available in modern clinical laboratories.

AREAS COVERED

We discuss clinical studies, genetic/genomic analyses, and advances in laboratory medicine that are reshaping our views on the role of factor XI in pathologic coagulation. We review how the disorder associated with factor XI deficiency has contributed to changes in blood coagulation models, and discuss the complex genetics of the deficiency state and its relationship to bleeding. Finally, we cover new laboratory approaches that may distinguish deficient patients who are prone to bleeding from those without such predisposition. Expert commentary: Advances in understanding the biology of factor XI have led to modifications in treatment of factor XI-deficient patients. Factor replacement is used more judiciously, and alternative approaches are gaining favor. In the future, better laboratory tests may allow us to target therapy to those patients who would benefit most.

Organic carbamates in drug design and medicinal chemistry

The carbamate group is a key structural motif in many approved drugs and prodrugs. There is an increasing use of carbamates in medicinal chemistry and many derivatives are specifically designed to make drug-target interactions through their carbamate moiety. In this Perspective, we present properties and stabilities of carbamates, reagents and chemical methodologies for the synthesis of carbamates, and recent applications of carbamates in drug design and medicinal chemistry.

Anticoagulation in intermittent hemodialysis: pathways, protocols, and pitfalls

Several methods to prevent extracorporeal circuit clotting during hemodialysis have been used in human medicine. Unfractionated (UF) heparin remains the mainstay of anticoagulant therapy in both human and veterinary intermittent hemodialysis. Different UF heparin regimes may be used depending on the bleeding risk of the patient. In patients with active bleeding or with a recent history of surgery or hemorrhagic episodes, hemodialysis may be performed without any anticoagulation or with regional anticoagulation.

Polymorphisms in coagulation factor genes and their impact on arterial and venous thrombosis

Arterial and venous thromboses, with their clinical manifestations such as stroke, myocardial infarction (MI), or pulmonary embolism, are the major causes of death in developed countries. Several studies in twins and siblings have shown that genetic factors contribute significantly to the development of these diseases. Since the advent of molecular genetics in medicine, it has been a focus of interest to elucidate the role of mutations in various candidate genes and their impact on hemostatic disorders such as arterial and venous thromboses. In this article, we review the current knowledge of the contribution of polymorphisms in coagulation factors to the development of thrombotic diseases. We show that in arterial thrombosis, results are controversial. Only for factor XIII 34Leu a protective effect on the development of myocardial infarction has been demonstrated in several studies. No other single polymorphism in a coagulation factor could be confirmed as a relevant risk factor, although there is evidence for a role of factor V Arg506Gln, factor VII Arg353Gln, and vWF Thr789Ala polymorphisms in patient subgroups. Further studies will be necessary to confirm the value of testing for genetic polymorphisms in arterial thrombosis. A large body of data is available on the role of factor V Arg506Gln and the prothrombin G20210A mutation in venous thrombosis. Some papers already recommend diagnosis and treatment strategies. We will discuss these recent publications on venous thrombosis in our review.

The effect of long-term methylprednisolone treatment on the femoral head in growing pigs

The effect of long term steroid treatment on coagulation, intraosseous pressure (IOP), femoral head (FH) blood flow, and histology in the normal organism was investigated in this study in growing pigs. From 24 growing female Danish Landrace pigs from 12 litters, 12 animals daily received 100 mg methylprednisolone orally for three months. Their 12 sister pigs served as controls without steroid treatment. Prothrombin time, activated partial thromboplastin time (aPTT), fibrinogen, and antithrombin III levels were recorded in jugular venous blood. Blood flow of the hip regions was measured by means of the radioactive microsphere technique. Metaphyseal and epiphyseal IOP of the left or right proximal femur were measured. Histomorphometry of the left or right FH epiphysis was performed. Major growth inhibition was found in the corticosteroid (CS) treated group. In CS pigs, aPTT was shortened to 50% compared to control pigs. Plasma fibrinogen was higher in the CS animals. Total FH blood flow was not different while regional blood flow in the cranial subregion of the FH epiphysis was higher in the CS group. Metaphyseal and epiphyseal IOP of the proximal femur were not different in the CS animals. Histomorphometrically, cancellous bone volume (23 +/- 1% vs. 34 +/- 2%; p < 0.001) and bone turnover (10 +/- 2% vs. 55 +/- 8%; p < 0.001) of the FH epiphysis was lowerin the CS than in the control group. The FH epiphysis of the CS animals invariably showed an irregular cartilage-bone interface with cartilaginous projections into the subchondral bone mainly in its cranial part. In normal growing pigs, long term high dose CS treatment has induced a hypercoagulable state of plasma via the intrinsic pathway of coagulation, cartilaginous projections into FH subchondral bone, FH osteopenia, and reduced bone turnover. Long-term steroid treatment did not produce FH necrosis or FH IOP alterations in the immature pig model.

Novel drug development opportunities for heparin

The glycosaminoglycan heparin has been used in the clinic as an anticoagulant for more than 50 years. A fully characterized sequence in native heparin is known to be responsible for this activity. However, heparin is a complex polysaccharide, which has an array of properties that are unrelated to its anticoagulant activity. Recent research has provided us with an increased understanding of the specific structural requirements for the various actions of heparin, indicating that it might be possible to create 'tailor-made' sequences based on the heparin template to isolate specific therapeutic activities. This research should provide the basis for novel drug treatments for a range of diseases, including cancer and various inflammatory diseases.

Characterization of the anticoagulant actions of a semisynthetic curdlan sulfate

Sulfation of curdlan, a natural, linear beta-1,3-glucan results in potent anticoagulant and antithrombotic agents. The different activity characteristics in the classical coagulation assays were shown to depend on various structural parameters. To obtain more detailed information about their structure-dependent mechanisms of action, one representative of these beta-1,3-glucan sulfates (CurS), was further investigated using several coagulation assays and amidolytic tests with chromogenic substrates. The mode of action of CurS differs from that of heparin. CurS reduces the thrombin formation by principally inhibiting the intrinsic FXa generation. As shown by amidolytic assays, it eliminates already generated thrombin mainly by accelerating the HCII-mediated thrombin inactivation, whereas its AT-mediated anti-thrombin activity is considerably lower than that of heparin. Further, it prevents the thrombin-mediated fibrin polymerization by directly interfering with the thrombin action on fibrinogen as well as by binding to fibrinogen. Finally, CurS is capable to activate the contact system with the consequence of a potential fibrinolytic effect. In conclusion, beta-1,3-glucan sulfates do not inhibit the blood coagulation nonspecifically due to their anionic character, but in dependence on their individual structure, they interfere specifically with the coagulation process at several sites.

Coagulation protein function VII: diametric effects of acetaldehyde on factor VII and factor IX function

The first metabolite of ethanol, acetaldehyde, has the ability to form adducts with proteins and alter their function. It has been shown that acetaldehyde reacts with various proteins of the blood coagulation pathway and, subsequently, produces a prolongation of the clotting time. This study evaluated the function of clotting proteins from the extrinsic coagulation pathway (factor VII) and the intrinsic coagulation pathway (factor IX) when preincubated with acetaldehyde as compared to a control and compared to preincubation with ethanol. Prior to use in a clotting assay, incubation times with acetaldehyde, ethanol, and the control were the same for both factors VII and IX. An automatic fibrometer measured the clotting times. Factor VII preincubated with acetaldehyde prolonged the clotting time. However, factor IX preincubated with acetaldehyde actually decreased the clotting time. Of interest, both factors VII and IX preincubated with acetaldehyde produced statistically significant results when compared to the control and ethanol. This experiment indicates that acetaldehyde, in forming an adduct with proteins of the blood coagulation pathway, may induce a conformational change of factors VII and IX so as to either increase or decrease the clotting time. Therefore, it is possible that some of the deranged coagulation in alcohol abusers may be a final net result of the interaction of acetaldehyde and proteins of the coagulation pathway.

Antithrombotic efficacy of a novel murine antihuman factor IX antibody in rats

A murine antihuman factor IX monoclonal antibody (BC2) has been generated and evaluated for its capacity to prolong the activated partial thromboplastin time (aPTT) in vitro and ex vivo and to prevent arterial thrombosis in a rat model in vivo. BC2 extended aPTT to a maximum of 60 to 80 seconds at 100 to 1000 nmol/L in vitro (rat and human plasma, respectively) and ex vivo (rat) after dosing of rats up to 6 mg/kg in vivo. BC2, administered as bolus (1 to 6 mg/kg) followed by infusion (0.3 to 2 mg x kg(-1) x h(-1)), dose-dependently prevented thrombosis of an injured rat carotid artery (FeCl(3)-patch model), increased time to artery occlusion, and reduced incidence of vessel occlusion. BC2 efficacy in preventing arterial thrombosis exceeded that of heparin (bolus 15 to 120 U/kg followed by infusion 0.5 to 4.0 U x kg(-1) x min(-1)), whereas the latter rendered the blood incoagulable (aPTT>1000 seconds). BC2 demonstrated complete antithrombotic efficacy also as a single bolus given either as prevessel or postvessel injury as evidenced by reduction of thrombus mass (from 4.18+/-0.49 to 1.80 +/-0.3 mg, P<0.001), increasing vessel patency time (from 14.9+/-0.9 minutes to 58.3+/-1.7 minutes, P<0.001) and decreasing incidence of vessel occlusion from 100% to 0% in vehicle- versus BC2-treated rats, respectively. BC2 (3 mg/kg, IV) administered in a single bolus resulted in 50% reduction in thrombus mass (P<0.01), extended vessel patency time (P<0.001), extended aPTT only 4-fold, and had no effect on blood loss via a tail surgical wound; heparin, at doses that reduced thrombus mass to a similar extent, extended aPTT beyond 1000 seconds (over 500-fold) and increased blood loss from 1.8+/-0.7 to 3.3 +/-0.6 mL (P<0.001). These data suggest that BC2 may provide enhanced therapeutic efficacy in humans at lesser interference with blood hemostasis than heparin.

The pathogenesis of vascular thrombosis and its impact in microvascular surgery

As the use of free tissue transfer becomes more wide-spread, it is important for both the ablative surgeon and the reconstructive surgeon to understand the factors that contribute to successful revascularized tissue transfer. The purpose of this two part review is to provide a basic science overview of the problem of failed free tissue transfers. The first part will focus on the pathogenesis of thrombosis at the anastomotic site, and part two will discuss the pathogenesis of the no-reflow phenomenon. The pathophysiology and therapeutic interventions to prevent and treat anastomotic thrombosis and the no-reflow phenomenon will be discussed.

Identification and SAR for a selective, nonpeptidyl thrombin inhibitor

A novel, nonpeptidyl thrombin inhibitor, L-636,619 (1), was identified via topological similarity searching over the Merck Corporate Sample Database. X-ray crystallographic studies determined the geometry for ligand binding to the enzyme. Chemical modification of the P1 and P3 segments of the ligand resulted in enhanced potency and improvement in the chemical stability of the lead. Analog 9 proved to be the most interesting lead from this structurally novel series.

Endothelial Cell-Blood Interface Actions and the Procoagulant Response

Anesthesiologists and surgeons have focused on the problems of hypocoagulability and resulting hemorrhage after cardiopulmonary bypass. Recent work in endothelial cell biology has demonstrated that the interaction of inflammatory processes and coagulation dysfunction with the endothelium may contribute to either hypocoagulability (bleeding) or hypercoagulability (thrombosis). New work with endothelial cell function and intracellular signaling of procoagulant responses may allow for unique therapeutic interventions in the future.

Lipoproteins and coagulation

A broad range of molecular and cellular interactions contribute to various pathophysiological alterations in haemostasis. Recent studies have shown strong links between lipoproteins and coagulation factors. Findings suggest that lipoproteins play an important role in the fibrinolytic and thrombogenic mechanisms that influence the risks of patients in acute coronary syndromes. We will examine specific aspects of lipoproteins with reference to the effects of hyperlipidaemia on endothelial dysfunction and haemostasis, and its relevance in the patient presenting for revascularization.

The role of tyrosine phosphorylation in lipopolysaccharide- and zymosan-induced procoagulant activity and tissue factor expression in macrophages

The expression of surface procoagulants by exudative macrophages represents an important mechanism underlying local fibrin deposition at sites of extravascular inflammation. The present studies investigated the contribution of tyrosine phosphorylation to the generation of macrophage procoagulant activity (PCA) and tissue factor expression in response to proinflammatory stimuli. Both lipopolysaccharide (LPS) and zymosan rapidly stimulated tyrosine phosphorylation in elicited murine peritoneal macrophages. This effect was prevented by the tyrosine kinase inhibitors genistein and herbimycin and augmented by the addition of the phosphotyrosine phosphatase inhibitor vanadate. The vanadate-mediated rise in phosphotyrosine accumulation was abrogated by the use of diphenylene iodonium, an inhibitor of the respiratory burst oxidase, suggesting a role for peroxides of vanadate as contributors to the tyrosine phosphorylation. This notion was supported by the finding that vanadyl hydroperoxide markedly increased the accumulation of phosphotyrosine residues. To define the role of tyrosine phosphorylation in the induction of macrophage PCA by LPS, the effects of tyrosine kinase inhibition by genistein and herbimycin were investigated. Both agents inhibited the expression of macrophage PCA. Further, Northern blot analysis with the cDNA probe for murine tissue factor indicated that the inhibition occurred at the mRNA level or earlier. Since vanadate augmented phosphotyrosine accumulation, it was hypothesized that it might enhance generation of macrophage products. However, vanadate reduced induction of PCA in response to LPS. By contrast, vanadate augmented basal prostaglandin E2 (PGE2) release and stimulated PGE2 release by macrophages. Indomethacin prevented the increase in PGE2 but only partially restored normal levels of PCA. The effect of vanadate on tissue factor expression appeared to be posttranscriptional. These studies thus demonstrate, by functional Western blotting and Northern blotting techniques, that tyrosine phosphorylation plays a role in the regulation of macrophage PCA and tissue factor expression in response to proinflammatory stimuli.

Endothelial cell injury in cardiovascular surgery: the procoagulant response

The vascular endothelium plays a critical role in the regulation of coagulation through the constitutive expression and release of anticoagulants and the inducible expression of procoagulant substances. Cardiopulmonary bypass dysregulates this process by activating endothelial cells, initially promoting bleeding and then thrombosis. Endothelial cell activation in response to circulating inflammatory mediators leads to the initiation of coagulation when tissue factor is expressed throughout the intravascular space. This results in the widespread consumption of coagulation factors. Additionally, there is a cardiopulmonary bypass-related qualitative platelet defect that is exacerbated by thrombocytopenia as platelets are consumed from the circulation by clot and adherence to the cardiopulmonary bypass circuit. Finally, cardiopulmonary bypass results in the endothelial release of plasminogen activators, which lead to an increase in systemic fibrinolysis. The diffuse generation of thrombin, driven by the inducible intravascular expression of tissue factor, plays a major role in all of these processes. Efforts to understand the critical role of the endothelium in coagulation may lead to novel therapies to prevent bleeding or thrombosis in cardiovascular surgery patients.

Magnesium(II) is a crucial constituent of the blood coagulation cascade. Potentiation of coagulant activities of factor IX by Mg2+ ions

We recently showed that not only Ca2+ ions but also Mg2+ ions play a crucial role in stabilizing the native conformation of coagulation factor IX. We here report that Mg2+ ions at physiological concentrations greatly augment the biological activities of factor IX. In clotting assays with dialyzed plasma, addition of Mg2+ ions enhanced the apparent coagulant activity of factor IXa, while that of factor Xa was scarcely affected. Activation of factor X by factor IXa in the presence of factor VIIIa, phospholipids, and Ca2+ ions was accelerated by Mg2+ ions. It appeared that the cation increased the affinity between factor IXa and factor VIIIa, thereby increasing the apparent catalytic efficacy of the enzyme. We also evaluated the effect of Mg2+ ions in the coagulation pathway initiated by tissue factor and found that activation of factor IX by factor VIIa*tissue factor was accelerated by the cation. Consequently, clotting of normal plasma induced by factor VIIa*tissue factor was shortened by the cation, while no such effect was observed in plasma deficient in factor IX or VIII. These results indicate that the previously unrecognized plasma component, Mg2+ ions, plays crucial roles in blood coagulation and, moreover, that contributions of factors IX and VIII in the coagulation cascade have been seriously underestimated in previous investigations.