RECENT ADVANCES IN HAEMOSTASIS AND THROMBOSIS

Bioabsorbable Carboxymethyl Starch-Calcium Ionic Assembly Powder as a Hemostatic Agent

In contrast to hemostatic fabrics, foams, and gels, hemostatic spray powders may be conveniently applied on narrow and complex bleeding sites. However, powdered hemostatic agents are easily desorbed from the bleeding surface because of blood flow, which seriously decreases their hemostatic function. In this study, the hemostatic performance of a bioabsorbable powder with decreased desorption was investigated. The proposed hemostatic powder (OOZFIXTM) is an ionic assembly of carboxymethyl starch and calcium. The microstructure and chemical properties of the hemostatic powder were analyzed. The hemostatic performance (blood absorption, blood absorption rate, and coagulation time), thromboelastography (TEG), rheology, adhesion force, and C3a complement activation of the OOZFIXTM were evaluated and compared with those of the carboxymethyl starch-based commercial hemostatic powder (AristaTM AH). The in vivo rat hepatic hemorrhage model for hemostasis time and bioabsorption of the OOZFIXTM showed quick biodegradation (<3 weeks) and a significantly improved hemostasis rate (78 ± 17 s) compared to that of AristaTM AH (182 ± 11) because of the reduced desorption. The bioabsorbable hemostatic powder OOZFIXTM is expected to be a promising hemostatic agent for precise medical surgical treatments.

Current update on herbal sources of antithrombotic activity—a comprehensive review

Background

Herbs are commonly used to treat cardiovascular diseases in various traditional medicine. On the other hand, herb-drug interactions are most commonly encountered with conventional antiplatelet and anticoagulant drug prescriptions. This review presents a compilation of plants investigated for antiplatelet and anticoagulation recently and enumerates their possible lead compounds responsible for its action for paving further drug discovery and knowledge update.

Main body of the abstract

Information about the herbs was withdrawn from the PubMed database of the previous 5 years. We also hand-searched the bibliography of relevant articles for the acquisition of additional information. About 72 herbal sources were identified with the effect of antiplatelet activity, antithrombotic activity, and anticoagulant activity. Bioactive compounds and various secondary metabolites responsible for it, such as alkaloids, saponins, flavonoids, coumarins, polyphenols, furan derivatives, iridoid glycosides, sesquiterpenes, aporphine compounds, were reported.

Conclusion

Newer pharmacological moieties are needed to prevent or reduce the adverse effects of current anti-thrombotic agents and to improve the safety of patients and cost-effectiveness.

An in vitro and in vivo study on the properties of hollow polycaprolactone cell-delivery particles

The field of dermal fillers is evolving rapidly and numerous products are currently on the market. Biodegradable polymers such as polycaprolactone (PCL) have been found to be compatible with several body tissues, and this makes them an ideal material for dermal filling purposes. Hollow PCL spheres were developed by the Council for Scientific and Industrial Research (CSIR) to serve both as an anchor point and a "tissue harbour" for cells. Particles were tested for cytotoxicity and cell adherence using mouse embryo fibroblasts (MEF). MEFs adhered to the particles and no significant toxic effects were observed based on morphology, cell growth, cell viability and cell cycle analysis, suggesting that the particles are suitable candidates for cell delivery systems in an in vivo setting. The objective of providing a "tissue harbour" was however not realized, as cells did not preferentially migrate into the ported particles. In vivo studies were conducted in BALB/c mice into whom particles were introduced at the level of the hypodermis. Mice injected with PCL particles (ported and non-ported; with or without MEFs) showed evidence of local inflammation and increased adipogenesis at the site of injection, as well as a systemic inflammatory response. These effects were also observed in mice that received apparently inert (polystyrene) particles. Ported PCL particles can therefore act as a cell delivery system and through their ability to induce adipogenesis, may also serve as a dermal bulking agent.

Warfarin monitoring with viscoelastic haemostatic assays, thrombin generation, coagulation factors and correlations to Owren and Quick prothrombin time

The anticoagulant warfarin is commonly monitored with prothrombin time (PT). Viscoelastic haemostatic assays (VHA) are primarily used in situations of acute bleeding to guide haemostatic therapy. Much research has focused on VHA monitoring of new oral anticoagulants. However, many patients are still anticoagulated with warfarin and effect of warfarin anticoagulation on VHA is uncertain. The aim of this study was to assess warfarin anticoagulation on three different VHA and compare these findings with prothrombin time (PT), coagulation factor analyses and a thrombin generation assay (TGA). Citrated whole blood was drawn from 80 patients admitted for routine PT-INR Owren. VHA analysis with ROTEM (EXTEM, INTEM and FIBTEM), ReoRox (Fibscreen 1 and 2) and Sonoclot (gbACT+) was performed. Blood was also drawn for plasma analysis with PT (PT-INR Owren and PT Quick), TGA and analysis of factors I, II, VII, IX and X. Extrinsically activated VHA, including ROTEM EXTEM and FIBTEM Clotting Time (CT) and ReoRox Fibscreen1 and 2 clot onset time 1 correlated moderately with PT-INR Owren , with R 0.66-0.71. These four variables were likely to be prolonged above reference interval in patients with prolonged PT-INR Owren >1.2. Two patients with normal ROTEM CTs had Owren PT-INRs >1.5. Warfarin affects extrinsically activated VHA variables of initial clotting. The role of VHA for clinical decision-making in patients planned for invasive procedures, such as spinal/epidural anaesthesia needs further study. None of the recent guidelines on regional anaesthesia include VHA testing to define adequate haemostasis.

Homotypic endothelial nanotubes induced by wheat germ agglutinin and thrombin

Endothelial barrier formation is maintained by intercellular communication through junctional proteins. The mechanisms involved in maintaining endothelial communication subsequent to barrier disruption remain unclear. It is known that low numbers of endothelial cells can be interconnected by homotypic actin-driven tunneling nanotubes (TNTs) which could be important for intercellular transfer of information in vascular physiology. Here we sought insight into the triggers for TNT formation. Wheat germ agglutinin, a C-type lectin and known label for TNTs, unexpectedly caused striking induction of TNTs. A succinylated derivative was by contrast inactive, suggesting mediation by a sialylated protein. Through siRNA-mediated knockdown we identified that this protein was likely to be CD31, an important sialylated membrane protein normally at endothelial cell junctions. We subsequently considered thrombin as a physiological inducer of endothelial TNTs because it reduces junctional contact. Thrombin reduced junctional contact, redistributed CD31 and induced TNTs, but its effect on TNTs was CD31-independent. Thrombin-induced TNTs nevertheless required PKCα, a known mediator of thrombin-dependent junctional remodelling, suggesting a necessity for junctional proteins in TNT formation. Indeed, TNT-inducing effects of wheat germ agglutinin and thrombin were both correlated with cortical actin rearrangement and similarly Ca²⁺-dependent, suggesting common underlying mechanisms. Once formed, Ca²⁺ signalling along TNTs was observed.

Differential stability of therapeutic peptides with different proteolytic cleavage sites in blood, plasma and serum

Proteolytic degradation of peptide-based drugs is often considered as major weakness limiting systemic therapeutic applications. Therefore, huge efforts are typically devoted to stabilize sequences against proteases present in serum or plasma, obtained as supernatants after complete blood coagulation or centrifugation of blood supplemented with anticoagulants, respectively. Plasma and serum are reproducibly obtained from animals and humans allowing consistent for clinical analyses and research applications. However, the spectrum of active or activated proteases appears to vary depending on the activation of proteases and cofactors during coagulation (serum) or inhibition of such enzymes by anticoagulants (plasma), such as EDTA (metallo- and Ca²⁺-dependent proteases) and heparin (e.g. thrombin, factor Xa). Here, we studied the presumed effects on peptide degradation by taking blood via cardiac puncture of CD-1 mice using a syringe containing a peptide solution. Due to absence of coagulation activators (e.g. glass surfaces and damaged cells), visible blood clotting was prevented allowing to study peptide degradation for one hour. The remaining peptide was quantified and the degradation products were identified using mass spectrometry. When the degradation rates (half-life times) were compared to serum derived freshly from the same animal and commercial serum and plasma samples, peptides of three different families showed indeed considerably different stabilities. Generally, peptides were faster degraded in serum than in plasma, but surprisingly all peptides were more stable in fresh blood and the order of degradation rates among the peptides varied among the six different incubation experiments. This indicates, that proteolytic degradation of peptide-based therapeutics may often be misleading stimulating efforts to stabilize peptides at degradation sites relevant only in vitro, i.e., for serum or plasma stability assays, but of lower importance in vivo.

A quantitative systems pharmacology model of blood coagulation network describes in vivo biomarker changes in non-bleeding subjects

Essentials Baseline coagulation activity can be detected in non-bleeding state by in vivo biomarker levels. A detailed mathematical model of coagulation was developed to describe the non-bleeding state. Optimized model described in vivo biomarkers with recombinant activated factor VII treatment. Sensitivity analysis predicted prothrombin fragment 1 + 2 and D-dimer are regulated differently.

SUMMARY

Background Prothrombin fragment 1 + 2 (F1 + 2 ), thrombin-antithrombin III complex (TAT) and D-dimer can be detected in plasma from non-bleeding hemostatically normal subjects or hemophilic patients. They are often used as safety or pharmacodynamic biomarkers for hemostatis-modulating therapies in the clinic, and provide insights into in vivo coagulation activity. Objectives To develop a quantitative systems pharmacology (QSP) model of the blood coagulation network to describe in vivo biomarkers, including F1 + 2 , TAT, and D-dimer, under non-bleeding conditions. Methods The QSP model included intrinsic and extrinsic coagulation pathways, platelet activation state-dependent kinetics, and a two-compartment pharmacokinetics model for recombinant activated factor VII (rFVIIa). Literature data on F1 + 2 and D-dimer at baseline and changes with rFVIIa treatment were used for parameter optimization. Multiparametric sensitivity analysis (MPSA) was used to understand key proteins that regulate F1 + 2 , TAT and D-dimer levels. Results The model was able to describe tissue factor (TF)-dependent baseline levels of F1 + 2 , TAT and D-dimer in a non-bleeding state, and their increases in hemostatically normal subjects and hemophilic patients treated with different doses of rFVIIa. The amount of TF required is predicted to be very low in a non-bleeding state. The model also predicts that these biomarker levels will be similar in hemostatically normal subjects and hemophilic patients. MPSA revealed that F1 + 2 and TAT levels are highly correlated, and that D-dimer is more sensitive to the perturbation of coagulation protein concentrations. Conclusions A QSP model for non-bleeding baseline coagulation activity was established with data from clinically relevant in vivo biomarkers at baseline and changes in response to rFVIIa treatment. This model will provide future mechanistic insights into this system.

The Role of Platelet and its Interaction with Aspirin

<p>Introduction. Platelets are not strictly “cells”, they are cytoplasmic fragments that are produced by the division of the cytoplasm of the megakaryocytes in the bone marrow; among its properties of adhesion and aggregation, platelets are involved in primary hemostasis, thrombosis, repair and tissue regeneration processes. To modify the pro-thrombotic platelet properties aspirin (ASA) is provided, which allows blocking the synthesis of prostaglandins in order to irreversibly inhibit the COX1 and prevent platelet aggregation. The current guidelines govern the use of aspirin in the prevention of cardiovascular diseases. Objective. In this review paper graphics were created to facilitate the understanding of platelets and its interaction with various physiological and pathological processes. Methodology. A literature review of a total of 74 documents such as articles and books was carried out; it was obtained from bibliographic searches in the following databases: Scielo, NEJM, Elsevier, Pubmed, Redalyc, Wiley, Springer, ScienceDirect, BVS, Nature Riviews, EBSCO, Naxos (databases offered by the University of Cauca). Mendeley free access program was used for the management and organization of information. Conclusion. It is recognized the role of platelet in different physiopathological processes and thus its interaction with aspirin, preventing its aggregation and thrombus formation in the spleen and other organs, this way contributing to the prevention of future cardiovascular events.</p>

Association of Coagulation Factors VIII/XI/XIII Polymorphisms With Coagulation Factor Activities and Deep Vein Thrombosis After Artificial Joints Replacement

The study aims at investigating the effects of coagulation factors VIII/XI/XIII polymorphisms in coagulation factor activities and deep vein thrombosis (DVT). A total of 130 patients with history of artificial joint replacement surgery were recruited, including 65 patients with DVT (cases) and 65 patients without DVT (controls). Cases and controls had comparable age, sex, and body mass index. Activities of VIII/XI and XIII were, respectively, detected by 1 phase anticoagulation method and microtitrimetry. Polymorphisms of VIII rs1800291 (3591C>G), XI rs2289252 (25264C>T), and XIII rs5985 (103G>T) were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Activities of VIII/XI were significantly increased in cases than in controls (P < 0.001 for VIII, P = 0.024 for XI). Activity of XI was significantly increased by 11.11% in CT + TT mutant type (25264C>T) compared with wild-type CC (95% confidence interval (CI), 2.28-19.95). In univariate analysis, incidence of DVT for CT mutant was 2.41-fold compared with wild-type CC (95% CI, 1.16-5.03). T allele had 1.83-fold increased risk of DVT than C allele (95% CI, 1.06-3.14). In multivariate analysis, incidence of DVT for CT + TT mutant type was 2.39-fold compared with wild type (95% CI, 1.07-5.35). Distributions of VIII gene 3951C>G and genotypes were not significant between groups (both P > 0.05). The mutation rate of VIII gene 103G>T was low in study population (0.77%) and was not significant between groups. XI 25264C>T genotype is significantly associated with XI activity. T mutation of this locus significantly increases XI activity and is a risk factor for DVT.

Emergency reversal of anticoagulation: novel agents

Historically, oral anticoagulation involved the administration of vitamin K antagonists, such as warfarin. However, because of the need for frequent monitoring and the desire for safer anticoagulants, several novel oral anticoagulants have been developed. These newer agents include the factor Xa inhibitors (eg, rivaroxaban, apixaban, edoxaban), along with the direct thrombin inhibitors (eg, dabigatran). This manuscript provides a brief overview of their uses and mechanisms of action, along with a review of currently available evidence for reversal strategies when life-threatening bleeding occurs.

Metabolic syndrome, platelet activation and the development of transient ischemic attack or thromboembolic stroke

Stroke is the second most common cause of mortality in the world today, where transient ischemic attack (TIA) is a period of focal ischemia, the symptoms of which resemble a thromboembolic stroke. Contrary to stroke, TIA symptoms typically last less than one hour and necrosis is absent. Stroke is often preceded by TIA, making it an important predictor of future ischemic events. The causal role of atherosclerosis in the development of TIA is well established, however, research indicates that the atherosclerotic process begins years earlier with the development of metabolic syndrome, which affects approximately 45% of the adult population worldwide. Metabolic syndrome is present if three or more of the following is present: increased waist circumference, increased triglycerides, decreased HDL, increased fasting glucose and hypertension. This syndrome causes systemic inflammation that activates the coagulation system and may cause the formation of pathological thrombi. The role of platelets in stroke has been studied and platelet activation pathways identified. ADP and thromboxane A(2) are the most common activators of platelets in normal physiology. Several pharmacological treatments have been employed to prevent the activation of platelets, the most common of which include aspirin and P2Y(12)-inhibitors. Although treatment is administered strokes and subsequent TIAs are very common in individuals that suffered an initial event. This indicates that research needs to be done in order to elucidate new therapeutic targets, but also to better treat ischemic events to not only decrease the amount of recurring events but also decrease stroke mortality worldwide.

Diagnostic morphology: biophysical indicators for iron-driven inflammatory diseases

Most non-communicable diseases involve inflammatory changes in one or more vascular systems, and there is considerable evidence that unliganded iron plays major roles in this. Most studies concentrate on biochemical changes, but there are important biophysical correlates. Here we summarize recent microscopy-based observations to the effect that iron can have major effects on erythrocyte morphology, on erythrocyte deformability and on both fibrinogen polymerization and the consequent structure of the fibrin clots formed, each of which contributes significantly and negatively to such diseases. We highlight in particular type 2 diabetes mellitus, ischemic thrombotic stroke, systemic lupus erythematosus, hereditary hemochromatosis and Alzheimer's disease, while recognizing that many other diseases have co-morbidities (and similar causes). Inflammatory biomarkers such as ferritin and fibrinogen are themselves inflammatory, creating a positive feedback that exacerbates disease progression. The biophysical correlates we describe may provide novel, inexpensive and useful biomarkers of the therapeutic benefits of successful treatments.

An antibody-drug conjugate that targets tissue factor exhibits potent therapeutic activity against a broad range of solid tumors

Tissue factor (TF) is aberrantly expressed in solid cancers and is thought to contribute to disease progression through its procoagulant activity and its capacity to induce intracellular signaling in complex with factor VIIa (FVIIa). To explore the possibility of using tissue factor as a target for an antibody-drug conjugate (ADC), a panel of human tissue factor-specific antibodies (TF HuMab) was generated. Three tissue factor HuMab, that induced efficient inhibition of TF:FVIIa-dependent intracellular signaling, antibody-dependent cell-mediated cytotoxicity, and rapid target internalization, but had minimal impact on tissue factor procoagulant activity in vitro, were conjugated with the cytotoxic agents monomethyl auristatin E (MMAE) or monomethyl auristatin F (MMAF). Tissue factor-specific ADCs showed potent cytotoxicity in vitro and in vivo, which was dependent on tissue factor expression. TF-011-MMAE (HuMax-TF-ADC) was the most potent ADC, and the dominant mechanism of action in vivo was auristatin-mediated tumor cell killing. Importantly, TF-011-MMAE showed excellent antitumor activity in patient-derived xenograft (PDX) models with variable levels of tissue factor expression, derived from seven different solid cancers. Complete tumor regression was observed in all PDX models, including models that showed tissue factor expression in only 25% to 50% of the tumor cells. In conclusion, TF-011-MMAE is a promising novel antitumor agent with potent activity in xenograft models that represent the heterogeneity of human tumors, including heterogeneous target expression.

Aspirin: pharmacology and clinical applications

Antiplatelet therapy has been documented to reduce risks of cardiovascular disease after acute myocardial infarction, coronary artery bypass graft, and in chronic atrial fibrillation patients, amongst other risk factors. Conventional management of thrombosis-based disorders includes the use of heparin, oral anticoagulants, and the preferred antiplatelet agent aspirin. Interestingly, aspirin was not intended to be used as an antiplatelet agent; rather, after being repurposed, it has become one of the most widely prescribed antithrombotic drugs. To this end, there have been several milestones in the development of antiplatelet agents in the last few decades, such as adenosine diphosphate receptor inhibitors, phosphodiesterase inhibitors, and GPIIb/IIIa inhibitors. However, given some of the limitations of these therapies, aspirin continues to play a major role in the management of thrombotic and cardiovascular disorders and is expected to do so for years to come.

Pentadecapeptide BPC 157 reduces bleeding time and thrombocytopenia after amputation in rats treated with heparin, warfarin or aspirin

Recently, in rat abdominal aorta terminoterminal-anastomosis the stable gastric pentadecapeptide BPC 157 prevents obstructive thrombus formation and rapidly destroys already formed obstructive thrombus. Also, BPC 157 wound healing may signify the clot as conductive matrix or "scaffold" to speed up wound healing process, and decrease bleeding. Here, in rats, BPC 157 (10 μg/kg, 10 ng/kg) improved always reduced bleeding time and amount of bleeding after (tail) amputation only, heparin (250 mg/kg, 25mg/kg, 10mg/kg i.v.), warfarin (1.5mg/kg i.g. once daily for 3 consecutive days), aspirin (0.1g/kg i.g. (once daily/3 consecutive days) or 1.0 g/kg i.p. once), and amputation associated with those agents application. BPC 157 counteracting regimens (i.v., i.p., i.g. (immediately after any challenge)) correspondingly follow the route of bleeding-agents application. All heparin-, warfarin-, and aspirin-rats and normal-rats that received BPC 157 exhibited lesser fall in platelets count. BPC 157 attenuated over-increased APTT-, TT-values in 10mg/kg heparin-rats, but did not influence heparin activity (anti-Xa test). Indicatively, unless counteracted in BPC 157 rats, excessive bleeding-acute thrombocytopenia (<20% of initial values in heparin-rats) approaches substantial fall in platelets count known in type II HIT. Also, BPC 157 markedly prolongs the survival time (heparin-rats, 25mg/kg, right foot amputation).

Activation of protease activated receptor 1 increases the excitability of the dentate granule neurons of hippocampus

Protease activated receptor-1 (PAR1) is expressed in multiple cell types in the CNS, with the most prominent expression in glial cells. PAR1 activation enhances excitatory synaptic transmission secondary to the release of glutamate from astrocytes following activation of astrocytically-expressed PAR1. In addition, PAR1 activation exacerbates neuronal damage in multiple in vivo models of brain injury in a manner that is dependent on NMDA receptors. In the hippocampal formation, PAR1 mRNA appears to be expressed by a subset of neurons, including granule cells in the dentate gyrus. In this study we investigate the role of PAR activation in controlling neuronal excitability of dentate granule cells. We confirm that PAR1 protein is expressed in neurons of the dentate cell body layer as well as in astrocytes throughout the dentate. Activation of PAR1 receptors by the selective peptide agonist TFLLR increased the intracellular Ca²⁺ concentration in a subset of acutely dissociated dentate neurons as well as non-neuronal cells. Bath application of TFLLR in acute hippocampal slices depolarized the dentate gyrus, including the hilar region in wild type but not in the PAR1-/- mice. PAR1 activation increased the frequency of action potential generation in a subset of dentate granule neurons; cells in which PAR1 activation triggered action potentials showed a significant depolarization. The activation of PAR1 by thrombin increased the amplitude of NMDA receptor-mediated component of EPSPs. These data suggest that activation of PAR1 during normal function or pathological conditions, such as during ischemia or hemorrhage, can increase the excitability of dentate granule cells.

Deletion of the thrombin cleavage domain of osteopontin mediates breast cancer cell adhesion, proteolytic activity, tumorgenicity, and metastasis

BACKGROUND

Osteopontin (OPN) is a secreted phosphoprotein often overexpressed at high levels in the blood and primary tumors of breast cancer patients. OPN contains two integrin-binding sites and a thrombin cleavage domain located in close proximity to each other.

METHODS

To study the role of the thrombin cleavage site of OPN, MDA-MB-468 human breast cancer cells were stably transfected with either wildtype OPN (468-OPN), mutant OPN lacking the thrombin cleavage domain (468-ΔTC) or an empty vector (468-CON) and assessed for in vitro and in vivo functional differences in malignant/metastatic behavior.

RESULTS

All three cell lines were found to equivalently express thrombin, tissue factor, CD44, αvβ5 integrin and β1 integrin. Relative to 468-OPN and 468-CON cells, 468-ΔTC cells expressing OPN with a deleted thrombin cleavage domain demonstrated decreased cell adhesion (p < 0.001), decreased mRNA expression of MCAM, maspin and TRAIL (p < 0.01), and increased uPA expression and activity (p < 0.01) in vitro. Furthermore, injection of 468-ΔTC cells into the mammary fat pad of nude mice resulted in decreased primary tumor latency time (p < 0.01) and increased primary tumor growth and lymph node metastatic burden (p < 0.001) compared to 468-OPN and 468-CON cells.

CONCLUSIONS

The results presented here suggest that expression of thrombin-uncleavable OPN imparts an early tumor formation advantage as well as a metastatic advantage for breast cancer cells, possibly due to increased proteolytic activity and decreased adhesion and apoptosis. Clarification of the mechanisms responsible for these observations and the translation of this knowledge into the clinic could ultimately provide new therapeutic opportunities for combating breast cancer.

Repeated inspiratory occlusions in anesthetized rats acutely increase blood coagulability as assessed by thromboelastography

Many of the components contributing to coagulability are enhanced by repeated episodes of hypoxia, as occurs in obstructive sleep apnea, but no one has yet measured the global hemostatic properties of blood in an animal model of this disease. Using thromboelastography, a hemostatic assay, we measured hemostasis in six pentobarbital-anesthetized rats before and after 3h of repeated inspiratory occlusions lasting 30s applied every 2 min and compared the results to those in six identically prepared rats before and after 3h of resting breathing. Rats subjected to occlusions displayed faster onset of clotting (p<0.031) and more rapid coagulation (p<0.031). Thus, repeated inspiratory occlusions acutely cause hypercoagulability in rats. Thromboelastography, a simple test of hemostasis, may help evaluate the factors responsible for this increase and, in patients with obstructive sleep apnea, the risk of future cardiovascular disease.

Identification of an anticoagulant peptide that inhibits both fXIa and fVIIa/tissue factor from the blood-feeding nematode Ancylostoma caninum

Factor VIIa-tissue factor complex (fVIIa/TF) and factor XIa (fXIa) play important roles in the initiation and amplification of coagulation, respectively. They may be good targets for the development of novel anticoagulants to treat and prevent thromboembolic disease. In this study, we cloned, expressed and identified a novel anticoagulant peptide, AcaNAP10, from the blood-feeding nematode Ancylostoma caninum. AcaNAP10 showed potent anticoagulant activity and doubled the activated partial thromboplastin and prothrombin times at estimated concentrations of 92.9 nM and 28.8 nM, respectively. AcaNAP10 demonstrated distinct mechanisms of action compared with known anticoagulants. It inhibited fXIa and fVIIa/TF with IC(50) values of 25.76+/-1.06 nM and 123.9+/-1.71 nM, respectively. This is the first report on an anticoagulant that can inhibit both fXIa and fVIIa/TF. This anticoagulant peptide may be an alternative molecule for the development of novel anticoagulants.

Achieving hemostasis in the surgical field

Hemostatic mechanisms are an integral part of the human physiology. Traditionally divided into intrinsic and extrinsic arms, the coagulation cascade converges, through the interactions of many different factors, at a common element-thrombin. As a consequence, a number of different agents have been developed to supplement this common, critical step to aid surgical hemostasis. Intraoperative interventions most commonly include sutures and heat-generating cautery devices; however, these methods are sometimes insufficient or inappropriate for a specific procedure or anatomic location, leading to the development of other adjunctive therapies, including topical hemostats. Topical hemostatic agents generally act as active, passive, and combinations therapies, depending on their individual composition and mode of action. We provide a brief review of the normal coagulation cascade, including critical points, followed by a discussion of surgical strategies and adjuctive therapies used to achieve surgical hemostasis and concluding with a discussion of topical thrombins.

An anticoagulant peptide from the human hookworm, Ancylostoma duodenale that inhibits coagulation factors Xa and XIa

A full-length cDNA encoding an anticoagulant peptide, named AduNAP4, was cloned and identified from the human hookworm Ancylostoma duodenale. AduNAP4 has 104 amino acids including a predicted 23-residue signal peptide and shows <or= 50% similarity with other known nematode anticoagulant protein/peptide (NAP). AduNAP4 is extremely efficient at prolonging the activated partial thromboplastin time, and is an inhibitor of both fXa (K(i)=7.34+/-1.74 nM) and fXIa (K(i)=42.45+/-3.25 nM). No fXIa inhibitor has previously been described from other blood-feeding animals. Our results suggest that hookworms have evolved a potent mechanism that interferes with coagulation by inhibition of fXIa to facilitate its blood-feeding lifestyle.