Heparin enhances the specificity of antithrombin for thrombin and factor Xa independent of the reactive center loop sequence. Evidence for an exosite determinant of factor Xa specificity in heparin-activated antithrombin

Anticoagulation activity of sulfated carboxymethyl cellulose/Azadirachta indica leaf powder-based bio-composite

Polymeric bio-composites synthesized via a green approach using natural herbs have fascinating anticoagulant activity due to their eco-friendly and non-toxic behavior towards various physical and chemical actions. Herein, we introduce a simple and eco-friendly approach for the fabrication of a new hybrid type of bio-composite based on sulfated carboxymethyl cellulose (S-CMC) and Azadirachta indica leaf powder (S-CMC/NLP). First, a non-toxic sulfating agent called N(SO3Na)3 was used to modify carboxymethyl cellulose into S-CMC. With an ion exchange capacity of 0.25 meq. g-1, the level of sulfation (%) of S-CMC (modified polysaccharide) was measured to be 12.01%. Three types of S-CMC/NLP bio-composites were developed by varying the concentration of NLP. FE-SEM, EDX, and XRD were used to characterize the structural features of S-CMC/NLP bio-composites. FTIR spectroscopy indicated that the S-CMC/NLP bio-composite possesses COO-, -OH and SO3- groups, suggesting the structural similarity to heparin. In addition, the anticoagulant effect of the S-CMC/NLP bio-composite was investigated using PT and APTT assays. The APTT investigation confirmed that following the intrinsic pathway of the coagulation system, 2-NLP/S-CMC bio-composite dose-dependently (0.045-0.28 mg mL-1) prolonged the time of blood coagulation compared to control (pure plasma). The S-CMC/NLP bio-composite showed its potential as a new, safe, and effective candidate for anticoagulant activity.

Inhibition of catechol-O-methyltransferase (COMT) by heparin oligosaccharides with specific structures

COMT inhibitors are commonly used to improve the effectiveness of levodopa in treating Parkinson's disease by inhibiting its conversion to 3-O-methyldopa. Because of the serious side effect of nitrocatechol COMT inhibitors, it is necessary to develop non-nitrocatechol COMT inhibitors with a higher safety profile. Heparin has been observed to bind to COMT. However, the exact functional significance of this interaction is not fully understood. In this study, the contribution of different substitution of heparin to its binding with COMT was investigated. In vitro and in vivo, heparin oligosaccharides can bind to COMT and inhibit its activity. Furthermore, we enriched the functional heparin oligosaccharides that bind to COMT and identified the sequence UA2S-GlcN(S/Ac)6(S/H)-UA2S-GlcNS6(S/H)-UA2(S/H)-GlcNS6S as the characteristic structural domain of these functional oligosaccharides. This study has elucidated the relationship between the structure of heparin oligosaccharides and their activity against COMT, providing valuable insights for the development of non-nitrocatechol COMT inhibitors with improved safety and efficacy.

Heparan Sulfate-Mimicking Glycopolymers Bind SARS-CoV-2 Spike Protein in a Length- and Sulfation Pattern-Dependent Manner

Heparan sulfate-mimicking glycopolymers, composed of glucosamine (GlcN)-glucuronic acid (GlcA) repeating units, bind to the receptor-binding subunit (S1) and spike glycoprotein (S) domains of the SARS-CoV-2 spike protein in a length- and sulfation pattern-dependent fashion. A glycopolymer composed of 12 repeating GlcNS6S-GlcA units exhibits a much higher affinity to the S1 protein (IC50 = 13 ± 1.1 nM) compared with the receptor-binding domain (RBD). This glycopolymer does not interfere in angiotensin-converting enzyme 2 binding of the RBD. Although this compound binds strongly to the S1/membrane-fusion subunit (S2) junction (KD = 29.7 ± 4.18 nM), it does not shield the S1/S2 site from cleavage by furin-a behavior contrary to natural heparin. This glycopolymer lacks iduronic acid, which accounts for 70% of heparin. Further, this compound, unlike natural heparin, is well defined in both sulfation pattern and length, which results in fewer off-target interactions with heparin-binding proteins. The results highlight the potential of using polymeric heparan sulfate (HS) mimetics for the therapeutic agent development.

Advances in Enhancing Hemocompatibility of Hemodialysis Hollow-Fiber Membranes

Hemodialysis, the most common modality of renal replacement therapy, is critically required to remove uremic toxins from the blood of patients with end-stage kidney disease. However, the chronic inflammation, oxidative stress as well as thrombosis induced by the long-term contact of hemoincompatible hollow-fiber membranes (HFMs) contribute to the increase in cardiovascular diseases and mortality in this patient population. This review first retrospectively analyzes the current clinical and laboratory research progress in improving the hemocompatibility of HFMs. Details on different HFMs currently in clinical use and their design are described. Subsequently, we elaborate on the adverse interactions between blood and HFMs, involving protein adsorption, platelet adhesion and activation, and the activation of immune and coagulation systems, and the focus is on how to improve the hemocompatibility of HFMs in these aspects. Finally, challenges and future perspectives for improving the hemocompatibility of HFMs are also discussed to promote the development and clinical application of new hemocompatible HFMs.

Graphical Abstract

A cysteine enzyme hemostat for efficient heparin-tolerant blood coagulation

It is challenging to stop bleeding effectively in patients treated with heparin which leads to enhanced risk of uncontrolled bleeding during operation. Herein, we report an easy-to-use and heparin-tolerant hemostatic agent based on a thrombin-like cysteine enzyme (papain), which catalyzes the hydrolysis of fibrinogen and cross-linking of fibrin clots. A papain-based hemostat with increased procoagulant activity is developed through immobilizing papain on the cellulose carrier, which displays short clotting time in both normal and heparinized plasmas. The excellent hemostatic performance of the papain-based hemostat is further confirmed with reduced hemostatic time and limited blood loss in a mouse tail amputation model, rabbit auricular artery injury model and rat liver injury model, in which a natural coagulation system fails to function on account of heparin. This bio-hemostat has great potential to reverse the effect of heparin and stop topical hemorrhage rapidly in surgical procedures.

Post-discharge Thromboembolic Events in COVID-19 Patients: A Review on the Necessity for Prophylaxis

Coronavirus disease 2019 (COVID-19) affects the respiratory system of patients and is characterized by pneumonia with hypoxemia. Hospitalized patients and particularly those admitted to intensive care unit (ICU) may encounter a cascade of coagulopathies, which may lead to macrovessel thrombotic events such as pulmonary embolism (PE), deep vein thrombosis (DVT), or arterial thromboembolism (ATE). These events can result in serious life-threatening diseases including cerebrovascular stroke and myocardial infarction. Despite all available information about the incidence, prevention, and treatment of venous thromboembolism (VTE) among hospitalized patients, few data are available on the incidence of both symptomatic and subclinical VTE after discharge. Therefore, there is no precise suggestion or guideline for prophylaxis against VTE in post-discharge period, and some controversies exist over the current guidelines. In the present study, we aimed to review and summarize available literature upon incidence, prevention, diagnosis, and therapeutic approaches for VTE in COVID-19 patients. Also, the pathogenic mechanisms of VTE in infected individuals with COVID-19 were discussed.

Small-animal blood exchange is an emerging approach for systemic aging research

We describe a small-animal blood exchange approach developed for aging research as an alternative to heterochronic parabiosis or plasma injections. In parabiosis, animals are surgically coupled, which has several disadvantages, including difficulty controlling experimental procedure, the effects of shared organs, environmental enrichment from jointly exploring the housing enclosure, involuntary exercise and an imprecise onset of blood sharing. Likewise, in plasma injections, the added volumes need to be small, and there is little flexibility in changing the relative contributions of ectopic to endogenous blood components. These factors complicate the conclusions and interpretations, including the identification of key mechanisms and molecular or cellular determinants. Our approach, where blood is exchanged between animals without them being surgically coupled, is less invasive than parabiosis. The percentage of exchanged blood or other exchanged fluids is known and precise. The age of plasma and cells can be mixed and matched at all desired relative contributions to the endogenous systemic milieu, and the onset of the effects can be accurately delineated. In this protocol, we describe the preparatory and animal surgery steps required for small-animal blood exchange in mice and compare this process with parabiosis and plasma injections. We also provide the design, hardware and software for the blood exchange device and compare automated and manual exchange methods. Lastly, we report mathematical modeling of the dilution of blood factors. The fluid exchange takes ~30 min when performed by a well-trained biomedical scientist; the entire process takes ~2 h.

A potential new pathway for heparin treatment of sepsis-induced lung injury: inhibition of pulmonary endothelial cell pyroptosis by blocking hMGB1-LPS-induced caspase-11 activation

Sepsis is a significant cause of mortality in critically ill patients. Acute lung injury (ALI) is a leading cause of death in these patients. Endothelial cells exposed to the bacterial endotoxin lipopolysaccharide (LPS) can progress into pyroptosis, a programmed lysis of cell death triggered by inflammatory caspases. It is characterized by lytic cell death induced by the binding of intracellular LPS to caspases 4/5 in human cells and caspase-11 in mouse cells. In mice,caspase-11-dependent pyroptosis plays an important role in endotoxemia. HMGB1 released into the plasma binds to LPS and is internalized into lysosomes in endothelial cells via the advanced glycation end product receptor. In the acidic lysosomal environment, HMGB1 permeates the phospholipid bilayer, which is followed by the leakage of LPS into the cytoplasm and the activation of caspase-11. Heparin is an anticoagulant widely applied in the treatment of thrombotic disease. Previous studies have found that heparin could block caspase-11-dependent inflammatory reactions, decrease sepsis-related mortality, and reduce ALI, independent of its anticoagulant activity. Heparin or modified heparin with no anticoagulant property could inhibit the alarmin HMGB1-LPS interactions, minimize LPS entry into the cytoplasm, and thus blocking caspase-11 activation. Heparin has been studied in septic ALI, but the regulatory mechanism of pulmonary endothelial cell pyroptosis is still unclear. In this paper, we discuss the potential novel role of heparin in the treatment of septic ALI from the unique mechanism of pulmonary endothelial cell pyroptosis.

Heparan Sulfate Mimicking Glycopolymer Prevents Pancreatic β Cell Destruction and Suppresses Inflammatory Cytokine Expression in Islets under the Challenge of Upregulated Heparanase

Diabetes is a chronic disease in which the levels of blood glucose are too high because the body does not effectively produce insulin to meet its needs or is resistant to insulin. β Cells in human pancreatic islets produce insulin, which signals glucogen production by the liver and causes muscles and fat to uptake glucose. Progressive loss of insulin-producing β cells is the main cause of both type 1 and type 2 diabetes. Heparan sulfate (HS) is a ubiquitous polysaccharide found at the cell surface and in the extracellular matrix (ECM) of a variety of tissues. HS binds to and assembles proteins in ECM, thus playing important roles in the integrity of ECM (particularly basement membrane), barrier function, and ECM-cell interactions. Islet HS is highly expressed by the pancreatic β cells and critical for the survival of β cells. Heparanase is an endoglycosidase and cleaves islet HS in the pancreas, resulting in β-cell death and oxidative stress. Heparanase could also accelerate β-cell death by promoting cytokine release from ECM and secretion by activated inflammatory and endothelial cells. We demonstrate that HS-mimicking glycopolymer, a potent heparanase inhibitor, improves the survival of cultured mouse pancreatic β cells and protects HS contents under the challenge of heparanase in human pancreatic islets. Moreover, this HS-mimicking glycopolymer reduces the expression levels of cytokines (IL8, IL1β, and TNFα) and the gene encoding Toll-like Receptor 2 (TLR2) in human pancreatic islets.

Anticoagulant SERPINs: Endogenous Regulators of Hemostasis and Thrombosis

Appropriate activation of coagulation requires a balance between procoagulant and anticoagulant proteins in blood. Loss in this balance leads to hemorrhage and thrombosis. A number of endogenous anticoagulant proteins, such as antithrombin and heparin cofactor II, are members of the serine protease inhibitor (SERPIN) family. These SERPIN anticoagulants function by forming irreversible inhibitory complexes with target coagulation proteases. Mutations in SERPIN family members, such as antithrombin, can cause hereditary thrombophilias. In addition, low plasma levels of SERPINs have been associated with an increased risk of thrombosis. Here, we review the biological activities of the different anticoagulant SERPINs. We further consider the clinical consequences of SERPIN deficiencies and insights gained from preclinical disease models. Finally, we discuss the potential utility of engineered SERPINs as novel therapies for the treatment of thrombotic pathologies.

Heparin prevents caspase-11-dependent septic lethality independent of anticoagulant properties

Heparin, a mammalian polysaccharide, is a widely used anticoagulant medicine to treat thrombotic disorders. It is also known to improve outcomes in sepsis, a leading cause of mortality resulted from infection-induced immune dysfunction. Whereas it is relatively clear how heparin exerts its anticoagulant effect, the immunomodulatory mechanisms enabled by heparin remain enigmatic. Here, we show that heparin prevented caspase-11-dependent immune responses and lethality in sepsis independent of its anticoagulant properties. Heparin or a chemically modified form of heparin without anticoagulant function inhibited the alarmin HMGB1-lipopolysaccharide (LPS) interaction and prevented the macrophage glycocalyx degradation by heparanase. These events blocked the cytosolic delivery of LPS in macrophages and the activation of caspase-11, a cytosolic LPS receptor that mediates lethality in sepsis. Survival was higher in septic patients treated with heparin than those without heparin treatment. The identification of this previously unrecognized heparin function establishes a link between innate immune responses and coagulation.

Comparison of Surgical Site Infection Risk Between Warfarin, LMWH, and Aspirin for Venous Thromboprophylaxis in TKA or THA: A Systematic Review and Meta-Analysis

BACKGROUND

Infection following arthroplasty can have devastating effects for the patient and necessitate further surgery. Venous thromboembolism (VTE) prophylaxis is required to minimize the risk of deep venous thrombosis and pulmonary embolism. Anticoagulation has been demonstrated to interfere with wound-healing and increase the risk of infection. We hypothesized that different anticoagulation regimes will have differing effects on rates of periprosthetic joint infection. The aim of this study was to compare the surgical site infection risk between the use of warfarin, low-molecular-weight heparin (LMWH), and aspirin for VTE prophylaxis following total knee or hip arthroplasty.

METHODS

A systematic literature search was conducted in November 2018 using the PubMed, CINAHL, and Cochrane Central Register of Controlled Trials (CENTRAL) databases to identify studies that compared warfarin, LMWH, and/or aspirin with regard to surgical site infection rates following hip or knee arthroplasty. Meta-analyses were performed to compare the infection and VTE risks between groups.

RESULTS

Nine articles involving 184,037 patients met the inclusion criteria. Meta-analysis showed that warfarin prophylaxis was associated with a higher risk of deep infection (or infection requiring reoperation) (odds ratio [OR] = 1.929, 95% confidence interval [CI] = 1.197 to 3.109, p = 0.007) and surgical site infection overall (OR = 1.610, 95% CI = 1.028 to 2.522, p = 0.038) compared with aspirin in primary total joint arthroplasty, with similar findings also seen when primary and revision procedures were combined. There was no significant difference in infection risk between warfarin and LMWH and between LMWH and aspirin. There was a nonsignificant trend for VTE risk to be higher with warfarin compared with aspirin therapy for primary procedures (OR = 1.600, 95% CI = 0.875 to 2.926, p = 0.127), and this was significant when both primary and revision cases were included (OR = 2.674, 95% CI = 1.143 to 6.255, p = 0.023).

CONCLUSIONS

These findings caution against the use of warfarin for VTE prophylaxis for hip and knee arthroplasty. Further randomized head-to-head trials and mechanistic studies are warranted to determine how specific anticoagulants impact infection risk.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Anticoagulant and signaling functions of antithrombin

Antithrombin (AT) is a major plasma glycoprotein of the serpin superfamily that regulates the proteolytic activity of the procoagulant proteases of both intrinsic and extrinsic pathways. Two important structural features that participate in the regulatory function of AT include a mobile reactive center loop that binds to active site of coagulation proteases, trapping them in the form of inactive covalent complexes, and a basic D-helix that binds to therapeutic heparins and heparan sulfate proteoglycans (HSPGs) on vascular endothelial cells. The binding of D-helix of AT by therapeutic heparins promotes the reactivity of the serpin with coagulation proteases by several orders of magnitude by both a conformational activation of the serpin and a template (bridging) mechanism. In addition to its essential anticoagulant function, AT elicits a potent anti-inflammatory signaling response when it binds to distinct vascular endothelial cell HSPGs, thereby inducing prostacyclin synthesis. Syndecans-4 has been found as a specific membrane-bound HSPG receptor on endothelial cells that relays the signaling effect of AT to the relevant second messenger molecules in the signal transduction pathways inside the cell. However, following cleavage by coagulation proteases and/or by spontaneous conversion to a latent form, AT loses both its anti-inflammatory activity and high-affinity interaction with heparin and HSPGs. Interestingly, these low-affinity heparin conformers of AT elicit potent proapoptotic and antiangiogenic activities by also binding to specific HSPGs by unknown mechanisms. This review article will summarize current knowledge about mechanisms through which different conformers of AT exert their serine protease inhibitory and intracellular signaling functions in these biological pathways.

Prophylaxis of thromboembolism during therapy with asparaginase in adults with acute lymphoblastic leukaemia

BACKGROUND

The risk of venous thromboembolism is increased in adults and enhanced by asparaginase-based chemotherapy, and venous thromboembolism introduces a secondary risk of treatment delay and premature discontinuation of key anti-leukaemic agents, potentially compromising survival. Yet, the trade-off between benefits and harms of primary thromboprophylaxis in adults with acute lymphoblastic leukaemia (ALL) treated according to asparaginase-based regimens is uncertain.  OBJECTIVES: The primary objectives were to assess the benefits and harms of primary thromboprophylaxis for first-time symptomatic venous thromboembolism in adults with ALL receiving asparaginase-based therapy compared with placebo or no thromboprophylaxis. The secondary objectives were to compare the benefits and harms of different groups of primary systemic thromboprophylaxis by stratifying the main results per type of drug (heparins, vitamin K antagonists, synthetic pentasaccharides, parenteral direct thrombin inhibitors, direct oral anticoagulants, and blood-derived products for antithrombin substitution).

SEARCH METHODS

We conducted a comprehensive literature search on 02 June 2020, with no language restrictions, including (1) electronic searches of Pubmed/MEDLINE; Embase/Ovid; Scopus/Elsevier; Web of Science Core Collection/Clarivate Analytics; and Cochrane Central Register of Controlled Trials (CENTRAL) and (2) handsearches of (i) reference lists of identified studies and related reviews; (ii) clinical trials registries (ClinicalTrials.gov registry; the International Standard Randomized Controlled Trial Number (ISRCTN) registry; the World Health Organisation's International Clinical Trials Registry Platform (ICTRP); and pharmaceutical manufacturers of asparaginase including Servier, Takeda, Jazz Pharmaceuticals, Ohara Pharmaceuticals, and Kyowa Pharmaceuticals), and (iii) conference proceedings (from the annual meetings of the American Society of Hematology (ASH); the European Haematology Association (EHA); the American Society of Clinical Oncology (ASCO); and the International Society on Thrombosis and Haemostasis (ISTH)). We conducted all searches from 1970 (the time of introduction of asparaginase in ALL treatment). We contacted the authors of relevant studies to identify any unpublished material, missing data, or information regarding ongoing studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs); including quasi-randomised, controlled clinical, cross-over, and cluster-randomised trial designs) comparing any parenteral/oral preemptive anticoagulant or mechanical intervention with placebo or no thromboprophylaxis, or comparing two different pre-emptive anticoagulant interventions in adults aged at least 18 years with ALL treated according to asparaginase-based chemotherapy regimens. For the description of harms, non-randomised observational studies with a control group were eligible for inclusion.  DATA COLLECTION AND ANALYSIS: Using a standardised data collection form, two review authors independently screened and selected studies, extracted data, assessed risk of bias for each outcome using standardised tools (RoB 2.0 tool for RCTs and ROBINS-I tool for non-randomised studies) and the certainty of evidence for each outcome using the GRADE approach. Primary outcomes included first-time symptomatic venous thromboembolism, all-cause mortality, and major bleeding. Secondary outcomes included asymptomatic venous thromboembolism, venous thromboembolism-related mortality, adverse events (i.e. clinically relevant non-major bleeding and heparin-induced thrombocytopenia for trials using heparins), and quality of life. Analyses were performed according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions. For non-randomised studies, we evaluated all studies (including studies judged to be at critical risk of bias in at least one of the ROBINS-I domains) in a sensitivity analysis exploring confounding.  MAIN RESULTS: We identified 23 non-randomised studies that met the inclusion criteria of this review, of which 10 studies provided no outcome data for adults with ALL. We included the remaining 13 studies in the 'Risk of bias' assessment, in which we identified invalid control group definition in two studies and judged outcomes of nine studies to be at critical risk of bias in at least one of the ROBINS-I domains and outcomes of two studies at serious risk of bias. We did not assess the benefits of thromboprophylaxis, as no RCTs were included. In the main descriptive analysis of harms, we included two retrospective non-randomised studies with outcomes judged to be at serious risk of bias. One study evaluated antithrombin concentrates compared to no antithrombin concentrates. We are uncertain whether antithrombin concentrates have an effect on all-cause mortality (risk ratio (RR) 0.55, 95% confidence interval (CI) 0.26 to 1.19 (intention-to-treat analysis); one study, 40 participants; very low certainty of evidence). We are uncertain whether antithrombin concentrates have an effect on venous thromboembolism-related mortality (RR 0.10, 95% CI 0.01 to 1.94 (intention-to-treat analysis); one study, 40 participants; very low certainty of evidence). We do not know whether antithrombin concentrates have an effect on major bleeding, clinically relevant non-major bleeding, and quality of life in adults with ALL treated with asparaginase-based chemotherapy, as data were insufficient. The remaining study (224 participants) evaluated prophylaxis with low-molecular-weight heparin versus no prophylaxis. However, this study reported insufficient data regarding harms including all-cause mortality, major bleeding, venous thromboembolism-related mortality, clinically relevant non-major bleeding, heparin-induced thrombocytopenia, and quality of life. In the sensitivity analysis of harms, exploring the effect of confounding, we also included nine non-randomised studies with outcomes judged to be at critical risk of bias primarily due to uncontrolled confounding. Three studies (179 participants) evaluated the effect of antithrombin concentrates and six studies (1224 participants) evaluated the effect of prophylaxis with different types of heparins. When analysing all-cause mortality; venous thromboembolism-related mortality; and major bleeding (studies of heparin only) including all studies with extractable outcomes for each comparison (antithrombin and low-molecular-weight heparin), we observed small study sizes; few events; wide CIs crossing the line of no effect; and substantial heterogeneity by visual inspection of the forest plots. Although the observed heterogeneity could arise through the inclusion of a small number of studies with differences in participants; interventions; and outcome assessments, the likelihood that bias due to uncontrolled confounding was the cause of heterogeneity is inevitable. Subgroup analyses were not possible due to insufficient data.  AUTHORS' CONCLUSIONS: We do not know from the currently available evidence, if thromboprophylaxis used for adults with ALL treated according to asparaginase-based regimens is associated with clinically appreciable benefits and acceptable harms. The existing research on this question is solely of non-randomised design, seriously to critically confounded, and underpowered with substantial imprecision. Any estimates of effect based on the existing insufficient evidence is very uncertain and is likely to change with future research.

Feline aortic thromboembolism: Presentation, diagnosis, and treatment outcomes of 15 cats

Background

Feline aortic thromboembolism (FATE) is a fatal disease where a blood clot gets lodged into the aortic trifurcation.

Methods

Fifteen cats with a sudden onset of hind limb paresis/paralysis, vocalization, and pain were admitted to the surgery clinic. A full case history was obtained and clinical, orthopedic, neurologic, radiographic, electrocardiographic, and echocardiographic examinations were performed for each cat. The treatment protocol included daily administration of multiple anticoagulant drugs with different mode of actions and meloxicam for 7 successive days. Prophylactic anticoagulant therapy (clopidogrel and acetylsalicylic acid) was continued for 6 months. All data were statistically analyzed and the correlation between time of admission and treatment outcome was tested using Pearson's correlation coefficient.

Results

The case history and clinical, orthopedic, and neurologic examinations revealed a sudden onset of hind limb paralysis (n = 12) or paresis (n = 3) associated with vocalization and pain, absence of trauma, cold and pale paws of hind limbs (n = 13, 86.7%) or cyanosed hind paws (n = 2, 13.3%), absence of femoral pulsation, shallow and rapid open-mouth respiration (61 ± 8 breaths/minutes), hypothermia (37.9°C ± 0.6°C) and tachycardia (155 ± 12 beats/minutes), with a muffled heart sound in four cats (26.7%). Radiography revealed no abnormalities in the hind limbs, pelvis, and spines, cardiomegaly in five cats (33.3%), mild pleural effusion and vascular pattern of the lung in six cats (40%), and Valentine's heart shape in four cats (26.7%). Electrocardiography (ECG) revealed an R-wave< 0.9 mV, prolongation of QRS interval in five cats (33.3%), and conduction disturbance in four cats (26.7%). Echocardiography was consistent with hypertrophic cardiomyopathy (HCM) in five cats (33.3%). A statistically significant (p= 0.023) strong negative correlation (r= -0.6) was reported between time of admission and subsequent early treatment and recovery from clinical signs. The treatment was successful in nine cats (60%), while four cats (26.7) were euthanized and two cats (13.3%) were subjected to hind limb amputation, at the owners' requests.

Conclusion

Clinical signs, radiography, ECG, and echocardiography are valuable for diagnosis of FATE. The outcome of the multiple anticoagulants therapy depends mainly upon early diagnosis and treatment within the first 6 hours from the onset of clinical signs.

Primary prophylaxis for venous thromboembolism in people undergoing major amputation of the lower extremity

BACKGROUND

People undergoing major amputation of the lower limb are at increased risk of venous thromboembolism (VTE). Risk factors for VTE in amputees include advanced age, sedentary lifestyle, longstanding arterial disease and an identifiable hypercoagulable condition. Evidence suggests that pharmacological prophylaxis (e.g. heparin, factor Xa inhibitors, vitamin K antagonists, direct thrombin inhibitors, antiplatelets) is effective in preventing deep vein thrombosis (DVT), but is associated with an increased risk of bleeding. Mechanical prophylaxis (e.g. antiembolism stockings, intermittent pneumatic compression and foot impulse devices), on the other hand, is non-invasive and has minimal side effects. However, mechanical prophylaxis is not always appropriate for people with contraindications such as peripheral arterial disease (PAD), arteriosclerosis or bilateral lower limb amputations. It is important to determine the most effective thromboprophylaxis for people undergoing major amputation and whether this is one treatment alone or in combination with another. This is an update of the review first published in 2013.

OBJECTIVES

To determine the effectiveness of thromboprophylaxis in preventing VTE in people undergoing major amputation of the lower extremity.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, Cochrane Central Register of Controlled Trials, MEDLINE, Embase and Cumulative Index to Nursing and Allied Health Literature databases, the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 5 November 2019. We planned to undertake reference checking of identified trials to identify additional studies. We did not apply any language restrictions.

SELECTION CRITERIA

We included randomised controlled trials and quasi-randomised controlled trials which allocated people undergoing a major unilateral or bilateral amputation (e.g. hip disarticulation, transfemoral, knee disarticulation and transtibial) of the lower extremity to different types or regimens of thromboprophylaxis (including pharmacological or mechanical prophylaxis) or placebo.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, extracted data and assessed risk of bias. We resolved any disagreements by discussion. Outcomes of interest were VTE (DVT and pulmonary embolism (PE)), mortality, adverse events and bleeding. We used GRADE criteria to assess the certainty of the evidence. The two included studies compared different treatments, so we could not pool the data in a meta-analysis.

MAIN RESULTS

We did not identify any eligible new studies for this update. Two studies with a combined total of 288 participants met the inclusion criteria for this review. Unfractionated heparin compared to low molecular weight heparin One study compared unfractionated heparin with low molecular weight heparin and found no evidence of a difference between the treatments in the prevention of DVT (odds ratio (OR) 1.23, 95% confidence interval (CI) 0.28 to 5.35; 75 participants; very low-certainty evidence). No bleeding events occurred in either group. Deaths and adverse events were not reported. This study was open-label and therefore at a high risk of performance bias. Additionally, the study did not report the method of randomisation, so the risk of selection bias was unclear. Heparin compared to placebo In the second study, there was no evidence of a benefit from heparin use in preventing PE when compared to placebo (OR 0.84, 95% CI 0.35 to 2.01; 134 participants; low-certainty evidence). Similarly, no evidence of improvement was detected when the level of amputation was considered, with a similar incidence of PE between the two treatment groups: above knee amputation (OR 0.79, 95% CI 0.31 to 1.97; 94 participants; low-certainty evidence); and below knee amputation (OR 1.53, 95% CI 0.09 to 26.43; 40 participants; low-certainty evidence). Ten participants died during the study; five underwent a post-mortem and three were found to have had a recent PE, all of whom had been on placebo (low-certainty evidence). Bleeding events were reported in less than 10% of participants in both treatment groups, but the study did not present specific data (low-certainty evidence). There were no reports of other adverse events. This study did not report the methods used to conceal allocation of treatment, so it was unclear whether selection bias occurred. However, this study appeared to be free from all other sources of bias. No study looked at mechanical prophylaxis.

AUTHORS' CONCLUSIONS

We did not identify any eligible new studies for this update. As we only included two studies in this review, each comparing different interventions, there is insufficient evidence to make any conclusions regarding the most effective thromboprophylaxis regimen in people undergoing lower limb amputation. Further large-scale studies of good quality are required.

Possible therapeutic agents for COVID-19: a comprehensive review

INTRODUCTION

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has emerged in China. There are no available vaccines or antiviral drugs for COVID-19 patients. Herein, we represented possible therapeutic agents that may stand as a potential therapy against COVID-19.

AREAS COVERED

We searched PubMed, Google Scholar, and clinicaltrials.gov for relevant papers. We showed some agents with potentially favorable efficacy, acceptable safety as well as good pharmacokinetic profiles. Several therapies are under assessment to evaluate their efficacy and safety for COVID-19. However, some drugs were withdrawn due to their side effects after demonstrating some clinical efficacy. Indeed, the most effective therapies could be organ function support, convalescent plasma, anticoagulants, and immune as well as antiviral therapies, especially anti-influenza drugs due to the similarities between respiratory viruses regarding viral entry, uncoating, and replication. We encourage giving more attention to favipiravir, remdesivir, and measles vaccine.

EXPERT OPINION

A combination, at least dual or even triple therapy, of the aforementioned efficacious and safe therapies is greatly recommended for COVID-19. Further, patients should have a routine assessment for their coagulation and bleeding profiles as well as their inflammatory and cytokine concentrations.

Aspirin or heparin or both for improving pregnancy outcomes in women with persistent antiphospholipid antibodies and recurrent pregnancy loss

BACKGROUND

Aspirin and heparin are widely used as preventive strategy to reduce the high risk of recurrent pregnancy loss in women with antiphospholipid antibodies (aPL). This review supersedes a previous, out-of-date review that evaluated all potential therapies for preventing recurrent pregnancy loss in women with aPL. The current review focusses on a narrower scope because current clinical practice is restricted to using aspirin or heparins, or both for women with aPL in an attempt to reduce pregnancy complications.

OBJECTIVES

To assess the effects of aspirin or heparin, or both for improving pregnancy outcomes in women with persistent (on two separate occasions) aPL, either lupus anticoagulant (LAC), anticardiolipin (aCL) or aβ₂-glycoprotein-I antibodies (aβ₂GPI) or a combination, and recurrent pregnancy loss (two or more, which do not have to be consecutive).

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (3 June 2019), and reference lists of retrieved studies. Where necessary, we attempted to contact trial authors.

SELECTION CRITERIA

Randomised, cluster-randomised and quasi-randomised controlled trials that assess the effects of aspirin, heparin (either low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH]), or a combination of aspirin and heparin compared with no treatment, placebo or another, on pregnancy outcomes in women with persistent aPL and recurrent pregnancy loss were eligible. All treatment regimens were considered.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion criteria and risk of bias. Two review authors independently extracted data and checked them for accuracy and the certainty of the evidence was assessed using the GRADE approach.

MAIN RESULTS

Eleven studies (1672 women) met the inclusion criteria; nine randomised controlled trials and two quasi-RCTs. The studies were conducted in the USA, Canada, UK, China, New Zealand, Iraq and Egypt. One included trial involved 1015 women, all other included trials had considerably lower numbers of participants (i.e. 141 women or fewer). Some studies had high risk of selection and attrition bias, and many did not include sufficient information to judge the risk of reporting bias. Overall, the certainty of evidence is low to very low due to the small numbers of women in the studies and to the risk of bias. The dose and type of heparin and aspirin varied among studies. One study compared aspirin alone with placebo; no studies compared heparin alone with placebo and there were no trials that had a no treatment comparator arm during pregnancy; five studies explored the efficacy of heparin (either UFH or LMWH) combined with aspirin compared with aspirin alone; one trial compared LMWH with aspirin; two trials compared the combination of LMWH plus aspirin with the combination of UFH plus aspirin; two studies evaluated the combination of different doses of heparin combined with aspirin. All trials used aspirin at a low dose. Aspirin versus placebo We are very uncertain if aspirin has any effect on live birth compared to placebo (risk ratio (RR) 0.94, 95% confidence interval (CI) 0.71 to 1.25, 1 trial, 40 women, very low-certainty evidence). We are very uncertain if aspirin has any effect on the risk of pre-eclampsia, pregnancy loss, preterm delivery of a live infant, intrauterine growth restriction or adverse events in the child, compared to placebo. We are very uncertain if aspirin has any effect on adverse events (bleeding) in the mother compared with placebo (RR 1.29, 95% CI 0.60 to 2.77, 1 study, 40 women). The certainty of evidence for these outcomes is very low because of imprecision, due to the low numbers of women involved and the wide 95% CIs, and also because of risk of bias. Venous thromboembolism and arterial thromboembolism were not reported in the included studies. Heparin plus aspirin versus aspirin alone Heparin plus aspirin may increase the number of live births (RR 1.27, 95% CI 1.09 to 1.49, 5 studies, 1295 women, low-certainty evidence). We are uncertain if heparin plus aspirin has any effect on the risk of pre-eclampsia, preterm delivery of a live infant, or intrauterine growth restriction, compared with aspirin alone because of risk of bias and imprecision due to the low numbers of women involved and the wide 95% CIs. We are very uncertain if heparin plus aspirin has any effect on adverse events (bleeding) in the mother compared with aspirin alone (RR 1.65, 95% CI 0.19 to 14.03, 1 study, 31 women). No women in either the heparin plus aspirin group or the aspirin alone group had heparin-induced thrombocytopenia, allergic reactions, or venous or arterial thromboembolism. Similarly, no infants had congenital malformations. Heparin plus aspirin may reduce the risk of pregnancy loss (RR 0.48, 95% CI 0.32 to 0.71, 5 studies, 1295 women, low-certainty evidence). When comparing LMWH plus aspirin versus aspirin alone the pooled RR for live birth was 1.20 (95% CI 1.04 to 1.38, 3 trials, 1155 women). In the comparison of UFH plus aspirin versus aspirin alone, the RR for live birth was 1.74 (95% CI 1.28 to 2.35, 2 trials, 140 women).

AUTHORS' CONCLUSIONS

The combination of heparin (UFH or LMWH) plus aspirin during the course of pregnancy may increase live birth rate in women with persistent aPL when compared with aspirin treatment alone. The observed beneficial effect of heparin was driven by one large study in which LMWH plus aspirin was compared with aspirin alone. Adverse events were frequently not, or not uniformly, reported in the included studies. More research is needed in this area in order to further evaluate potential risks and benefits of this treatment strategy, especially among women with aPL and recurrent pregnancy loss, to gain consensus on the ideal prevention for recurrent pregnancy loss, based on a risk profile.

Biological Activities of Rhamnan Sulfate Extract from the Green Algae Monostroma nitidum (Hitoegusa)

Monostroma nitidum is a green single-cell layered algae that grows on the southwest coast of Japan. It is often used for salad ingredients, boiled tsukudani, soups, etc., due to its health benefits. M. nitidum is composed of many cell aggregates, and the various substances that fill the intercellular space are dietary fibers, vitamins, and minerals. Rhamnan sulfate (RS), a sulfated polysaccharide, is main the component of the fiber extracted from M. nitidum. Recently, some biological properties of RS have been demonstrated by in vitro and in vivo studies that probably protect human subjects from viruses and ameliorate vascular dysfunction caused by metabolic disorders, especially lifestyle-related diseases. In this review, we focus on the antithrombotic effects of RS and introduce its antiviral and other biological activities.

Extraction, purification, characterization, anticoagulant activity, and anticoagulant mechanism of polysaccharides from the heads of Hypomesus olidus

The aim of this work was to extract, isolate, and purify polysaccharides from the heads of Hypomesus olidus and to evaluate their anticoagulant activities and anticoagulant mechanisms. Response surface methodology was used to optimize the extraction conditions for ultrasonic-assisted extraction of polysaccharides from the heads of Hypomesus olidus. The optimal extraction conditions consisted of ultrasonic power of 275 W, ultrasonic time of 50 min, and solid-liquid ratio of 5 ml/g, giving the yield of crude polysaccharides (GYT) of 7.73 ± 0.042%. Three polysaccharide fractions, GYT-1, GYT-2, and GYT-3 were purified from GYT by using DEAE-cellulose-52 column and Sephadex G-100 column for anticoagulant activities. The results showed that two doses (2 and 4 mg/ml) of GYT-1 and GYT-3 could significantly prolong (p < .01) in partial thromboplastin time (APTT) (2.19 and 2.37 times, 2.22 and 2.44 times, respectively) and thrombin time (TT) (2.39 and 2.46 times, 2.44 and 2.80 times, respectively) compared with normal control. In particular, GYT-3 had stronger anticoagulant activity than GYT-1, and it was composed of arabinose, fructose, glucose, and lactose with molar ratios of 0.595:1: 2.026:0.273. However, GYT-2 had no anticoagulant activity (p > .05). In addition, anticoagulation mechanism of polysaccharides from the heads of Hypomesus olidus (GYT-3) was evaluated. The results showed that the anticoagulant activity of GYT-3 was based on their binding with antithrombin AT-III. And the inhibitory effects of GYT-3 on factor IIa and Xa were related to the concentration of AT-III in plasma. This study may provide a new and promising anticoagulant drug.

Preoperative Low-Molecular-Weight Heparin Prophylaxis Associated with Increased Heparin Resistance Frequency in On-Pump Coronary Artery Bypass Graft Surgery

Background

Unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) are being used for preoperative management of critical coronary artery disease. However, preoperative UFH therapy may cause a reduction in antithrombin concentrations, leading to various degrees of heparin resistance (HR). The main purpose of this study is to investigate the effects of preoperative LMWH on HR during cardiopulmonary bypass (CPB).

Methods

Data were retrospectively reviewed from adult patients that underwent on-pump coronary artery bypass graft (CABG) surgery. Four hundred fifty-seven patients underwent CABG, and 139 of them, who had isolated on-pump CABG, were included in the study. The heparin sensitivity index was calculated if activated clotting time levels were discovered below 400 seconds. Values less than 1.3 were accepted as HR.

Results

Of 139 patients who underwent on-pump CABG, preoperative LMWH was administered in 59 patients (56.8%). Intraoperative HR occurred in 29 patients (20.9%). Patients who received preoperative LMWH had an increased risk of developing HR compared with patients who did not receive LMWH (odds ratio 4.8 and 95% confidence interval 1.7–13.5). CPB duration and aortic clamp duration were significantly longer in patients who developed intraoperative HR when compared to those in patients who did not develop HR.

Conclusion

Preoperative treatment with LMWH may cause intraoperative HR. Corrective and preventive arrangements with close follow-up should be performed in this group of patients.

Colorimetric sensing strategy for heparin assay based on PDDA-induced aggregation of gold nanoparticles

Herein, we report a highly sensitive colorimetric sensor for the detection of heparin based on its anti-aggregation effect of the PDDA-gold nanoparticle colloidal system. PDDA-induced non-crosslinking aggregation of gold nanoparticles is firstly investigated and the phenomenon of heparin mediated color recovery is then observed, which can be used to indicate the concentration of heparin. This method is proved to be highly sensitive and selective. Moreover, it has been successfully applied to determine human blood serum samples, the results of which demonstrate great potential practical utility with simple operations.

Carbon Nanotube Strain Sensor Based Hemoretractometer for Blood Coagulation Testing

Coagulation monitoring is essential for perioperative care and thrombosis treatment. However, existing assays for coagulation monitoring have limitations such as a large footprint and complex setup. In this work, we developed a miniaturized device for point-of-care blood coagulation testing by measuring dynamic clot retraction force development during blood clotting. In this device, a blood drop was localized between a protrusion and a flexible force-sensing beam to measure clot retraction force. The beam was featured with micropillar arrays to assist the deposition of carbon nanotube films, which served as a strain sensor to achieve label-free electrical readout of clot retraction force in real time. We characterized mechanical and electrical properties of the force-sensing beam and optimized its design. We further demonstrated that this blood coagulation monitoring device could obtain results that were consistent with those using an imaging method and that the device was capable of differentiating blood samples with different coagulation profiles. Owing to its low fabrication cost, small size, and low consumption of blood samples, the blood coagulation testing device using carbon nanotube strain sensors holds great potential as a point-of-care tool for future coagulation monitoring.

Inhibitory serpins. New insights into their folding, polymerization, regulation and clearance

Serpins are a widely distributed family of high molecular mass protein proteinase inhibitors that can inhibit both serine and cysteine proteinases by a remarkable mechanism-based kinetic trapping of an acyl or thioacyl enzyme intermediate that involves massive conformational transformation. The trapping is based on distortion of the proteinase in the complex, with energy derived from the unique metastability of the active serpin. Serpins are the favoured inhibitors for regulation of proteinases in complex proteolytic cascades, such as are involved in blood coagulation, fibrinolysis and complement activation, by virtue of the ability to modulate their specificity and reactivity. Given their prominence as inhibitors, much work has been carried out to understand not only the mechanism of inhibition, but how it is fine-tuned, both spatially and temporally. The metastability of the active state raises the question of how serpins fold, whereas the misfolding of some serpin variants that leads to polymerization and pathologies of liver disease, emphysema and dementia makes it clinically important to understand how such polymerization might occur. Finally, since binding of serpins and their proteinase complexes, particularly plasminogen activator inhibitor-1 (PAI-1), to the clearance and signalling receptor LRP1 (low density lipoprotein receptor-related protein 1), may affect pathways linked to cell migration, angiogenesis, and tumour progression, it is important to understand the nature and specificity of binding. The current state of understanding of these areas is addressed here.

Use of Patterned Collagen Coated Slides to Study Normal and Scleroderma Lung Fibroblast Migration

Systemic sclerosis (SSc) is a spreading fibrotic disease affecting the skin and internal organs. We aimed to model pathogenic fibroblast migration in SSc in order to identify enhancing factors, measure the effect of migrating cells on underlying extracellular matrix (ECM) and test possible therapeutic inhibitors. Novel patterned collagen substrates were used to investigate alignment and migration of skin and lung fibroblasts from SSc patients and healthy controls. Normal lung but not skin fibroblasts consistently elongated and aligned with underlying collagen and migrated dependent on PDGF or serum. SSc lung fibroblasts remained growth factor dependent, did not migrate more rapidly and were less restricted to alignment of the collagen. Multiple collagen proline and lysine-modifying enzymes were identified in SSc but not control fibroblast extracellular matrix preparations, indicating differential levels of ECM modification by the diseased cells. Profiling of migrating cells revealed a possible SCF/c-Kit paracrine mechanism contributing to migration via a subpopulation of cells. Heparin, which binds ligands including PDGF and SCF, and imatininib which blocks downstream tyrosine kinase receptors, both inhibited lung fibroblast migration individually but showed synergy in SSc cells. Pathologic lung fibroblasts from SSc patients modify ECM during migration but remain growth factor dependent and sensitive to inhibitors.

Polyphenolic-polysaccharide conjugates of Sanguisorba officinalis L. with anticoagulant activity mediated mainly by heparin cofactor II

A macromolecular complex has been isolated from the dried flowering parts of medicinal plant Sanguisorba officinalis L. (So) by multi-step extraction procedure, including that with extraction by organic solvents to degrease the plant material, then with hot alkali, followed by neutralization, partitioning with organic solvents and dialysis. The complex was purified by size-exclusion chromatography into five fractions labeled as So1-So5. Individual fractions differed in the chemical composition and molecular weight distribution patterns. In vitro anticoagulant activity tests showed in all fractions more or less important inhibition of plasma clots, however, So3 and So4 were the most active. The anticoagulant activity of So3 was even more significant than that of the unfractionated complex So. These S. officinalis conjugates were able to inhibit mainly the activity of thrombin when they were mediated by heparin cofactor II, but what was unexpected they were the non-direct inhibitors of factor Xa, mediated by antitrombin, where such mechanism of action is typical for a highly sulphated glycosaminoglycans.

Comparative studies on biological activity of generic and branded enoxaparin in vivo and vitro

As per US Food and Drug Administration (FDA) requirement, the study was designed to conduct the fourth and fifth criteria of Abbreviated New Drug Application to demonstrate equivalence of generic and branded Enoxaparin in vivo and vitro.Pharmacodynamic behavior of branded and generic Enoxaparin was compared in a parallel study in rats based upon measurement of anti-FXa and anti-FIIa profiles. Blood samples collected at baseline and at 0.5, 1, 2, 4, 6, 8, 12 and 24 h postsubcutaneous administration of six batches of Lovenox and nine batches of generic Enoxaparin were evaluated for anti-FXa and anti-FIIa using chromogenic substrate method. Anti-FXa, Anti-FIIa, activated partial thromboplastin time (APTT), and Heptest prolongation time were conducted in vitro as per the United States Pharmacopeia method. Pharmacodynamics parameters were obtained including peak effect (anti-FXamax, anti-FIIamax), area under the effect curve (AUEC0-T and AUEC0-∞), Tmax, and T1/2.Pharmacokinetic differences were not observed using anti-FXa or anti-FIIa. No statistically significant differences were observed between branded and generic Enoxaparin either in vitro anti-FXa, anti-FIIa, APTT, or Heptest assay.It can be concluded that they are bioequivalent in anticoagulant activity tested in vivo and vitro.

Intravenous heparin during ruptured abdominal aortic aneurysmal repair

BACKGROUND

There have been enormous advances in the screening, diagnosis, intervention and overall prognosis of abdominal aortic aneurysms (AAAs) in the last decade, but despite these, ruptured AAAs (rAAAs) still cause around 3500 to 6000 deaths in England and Wales each year. Open repair remains standard treatment for rAAA in most centres but increasingly endovascular aneurysm repair (EVAR) is being adopted. This has a 30-day postoperative mortality of 40%. This has remained static despite surgical, anaesthetic and critical care advances.One significant change to current practice for elective repairs of AAAs, as opposed to emergency repairs of rAAAs, has been the introduction of intravenous heparin. This provides a protective effect against cardiac and thrombotic disease in the postoperative period. This practice has not gained widespread acceptance for emergency repairs of rAAA even though a reduction in mortality and morbidity has been demonstrated in elective repairs.

OBJECTIVES

The primary objective was to assess the effect of intravenous heparin on all-cause mortality in ruptured abdominal aortic aneurysm (rAAA) management in people undergoing an emergency repair.The secondary objectives were to assess the effect of intravenous heparin in rAAA management on the incidence of general arterial disease, for example, cardiovascular, cerebral, pulmonary and renal pathologies, in people undergoing emergency repair.

SEARCH METHODS

The Cochrane Vascular Information Specialist (CIS) searched the Specialised Register (December 2015). In addition the CIS searched CENTRAL;2015, Issue 11). The CIS searched clinical trials registries for details of ongoing or unpublished studies.

SELECTION CRITERIA

We sought all published and unpublished randomised controlled trials (RCTs) and controlled clinical trials (CCTs) of intravenous heparin in rAAA repairs (including parallel designs).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies identified for potential inclusion in the review. We used standard methodological procedures in accordance with the Cochrane Handbook for Systematic Review of Interventions.

MAIN RESULTS

We identified no RCTs or CCTs that satisfied the inclusion criteria.

AUTHORS' CONCLUSIONS

We identified no RCTs or CCTs of intravenous heparin in rAAA repairs (including parallel designs). Therefore, we were unable to assess the effect of intravenous heparin on all-cause mortality and incidence of general arterial disease, for example, cardiovascular, cerebral, pulmonary and renal pathologies in rAAA management in people undergoing an emergency repair. It is clear that an RCT is needed to address this question in rAAA management as there is no high quality evidence.

Vioserpin, a serine protease inhibitor from Gloeobacter violaceus possibly regulated by heparin

Serine peptidase inhibitor (serpin) is the name given to the superfamily of proteins with wide range of biological functions, and that the main feature is the inhibition of serine proteases. Here we describe the inhibitory characterization of a serpin from Gloeobacter violaceus that we named vioserpin. The serpin presented a high specificity to inhibit trypsin-like enzymes with a rapid inhibition rate constant (2.1 × 10(6) M(-1) s(-1)). We also demonstrated that the inhibitory activity of the vioserpin is influenced by the concentration of heparin, and this finding may throw a new light on understanding the molecular evolution of serpins.

Heparin for the prevention of intraventricular haemorrhage in preterm infants

BACKGROUND

Preterm birth remains the major risk factor for the development of intraventricular haemorrhage, an injury that occurs in 25% of very low birth weight infants. Intraventricular haemorrhage is thought to be venous in origin and intrinsic thromboses in the germinal matrix are likely to play a triggering role. Heparin activates antithrombin and promotes the inactivation of thrombin and other target proteinases. The administration of anticoagulants such as heparin may offset the increased risk of developing intraventricular haemorrhage and may also reduce the risk of developing parenchymal venous infarct, a condition known to complicate intraventricular haemorrhage.

OBJECTIVES

To assess whether the prophylactic administration of heparin reduces the incidence of germinal matrix-intraventricular haemorrhage in very preterm neonates when compared to placebo, no treatment, or other anticoagulants.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2015), MEDLINE (1996 to 22 November 2015), EMBASE (1980 to 22 November 2015) and CINAHL (1982 to 22 November 2015), applying no language restrictions. We searched the abstracts of the major congresses in the field (Perinatal Society of Australia and New Zealand and Pediatric Academic Societies) from 2000 to 2015.

SELECTION CRITERIA

Randomised controlled trials, quasi-randomised controlled trials and cluster trials comparing the administration of early, i.e. within the first 24 hours of life, heparin in very preterm infants (gestational age < 32 weeks).

DATA COLLECTION AND ANALYSIS

For each of the included trials, two authors independently extracted data (e.g. number of participants, birth weight, gestational age, dose of heparin, mode of administration, and duration of therapy, etc.) and assessed the risk of bias (e.g. adequacy of randomisation, blinding, completeness of follow up). The primary outcomes considered in this review are intraventricular haemorrhage, severe intraventricular haemorrhage and neonatal mortality.

MAIN RESULTS

Two randomised controlled trials enrolling a total of 155 infants met the inclusion criteria of this review. Both trials compared low-dose heparin to the same solution without heparin in very preterm newborns requiring umbilical catheterisation. No trials were identified that specifically studied the use of heparin in infants at risk of germinal matrix-intraventricular haemorrhage.We found no differences in the rates of intraventricular haemorrhage (typical RR 0.93, 95% CI 0.61 to 1.41; typical RD -0.03, 95% CI -0.17 to 0.12; 2 studies, 155 infants; I² = 57% for RR and I² = 65% for RD), severe intraventricular haemorrhage (typical RR 1.01, 95% CI 0.46 to 2.23; typical RD 0.00, 95% CI -0.11 to 0.11; 2 studies, 155 infants; I² = 0% for RR and I² = 0% for RD) and neonatal mortality (typical RR 0.69, 95% CI 0.28 to 1.67; typical RD -0.04, 95% CI -0.14 to 0.06; 2 studies, 155 infants; I² = 28% for RR and I² = 50% for RD). We judged the quality of the evidence supporting these findings as very low (rates of intraventricular haemorrhage) and low (severe intraventricular haemorrhage and neonatal mortality) mainly because of limitations in the study designs and the imprecision of estimates. We found very few data on other relevant outcomes, such as bronchopulmonary dysplasia, pulmonary haemorrhage and patent ductus arteriosus; and no study assessing long-term outcomes (e.g. neurodevelopmental disability).

AUTHORS' CONCLUSIONS

There is very limited data on the effect of prophylactic administration of heparin on the incidence and severity of IVH in very preterm neonates. Both the identified trials used heparin in the context of maintaining umbilical line patency and not specifically as an agent to prevent germinal matrix-intraventricular haemorrhage. Given the imprecision of our estimates, the results of this systematic review are consistent with either a benefit or a detrimental effect of heparin and do not provide a definitive answer to the review question. Limited evidence is available on other clinically relevant outcomes.

A Novel Direct Factor Xa Inhibitory Peptide with Anti-Platelet Aggregation Activity from Agkistrodon acutus Venom Hydrolysates

Snake venom is a natural substance that contains numerous bioactive proteins and peptides, nearly all of which have been identified over the last several decades. In this study, we subjected snake venom to enzymatic hydrolysis to identify previously unreported bioactive peptides. The novel peptide ACH-11 with the sequence LTFPRIVFVLG was identified with both FXa inhibition and anti-platelet aggregation activities. ACH-11 inhibited the catalytic function of FXa towards its substrate S-2222 via a mixed model with a K_i value of 9.02 μM and inhibited platelet aggregation induced by ADP and U46619 in a dose-dependent manner. Furthermore, ACH-11 exhibited potent antithrombotic activity in vivo. It reduced paralysis and death in an acute pulmonary thrombosis model by 90% and attenuated thrombosis weight in an arterio-venous shunt thrombosis model by 57.91%, both at a dose of 3 mg/kg. Additionally, a tail cutting bleeding time assay revealed that ACH-11 did not prolong bleeding time in mice at a dose of 3 mg/kg. Together, our results reveal that ACH-11 is a novel antithrombotic peptide exhibiting both FXa inhibition and anti-platelet aggregation activities, with a low bleeding risk. We believe that it could be a candidate or lead compound for new antithrombotic drug development.

Conformational activation of antithrombin by heparin involves an altered exosite interaction with protease

Heparin allosterically activates antithrombin as an inhibitor of factors Xa and IXa by enhancing the initial Michaelis complex interaction of inhibitor with protease through exosites. Here, we investigate the mechanism of this enhancement by analyzing the effects of alanine mutations of six putative antithrombin exosite residues and three complementary protease exosite residues on antithrombin reactivity with these proteases in unactivated and heparin-activated states. Mutations of antithrombin Tyr(253) and His(319) exosite residues produced massive 10-200-fold losses in reactivity with factors Xa and IXa in both unactivated and heparin-activated states, indicating that these residues made critical attractive interactions with protease independent of heparin activation. By contrast, mutations of Asn(233), Arg(235), Glu(237), and Glu(255) exosite residues showed that these residues made both repulsive and attractive interactions with protease that depended on the activation state and whether the critical Tyr(253)/His(319) residues were mutated. Mutation of factor Xa Arg(143), Lys(148), and Arg(150) residues that interact with the exosite in the x-ray structure of the Michaelis complex confirmed the importance of all residues for heparin-activated antithrombin reactivity and Arg(150) for native serpin reactivity. These results demonstrate that the exosite is a key determinant of antithrombin reactivity with factors Xa and IXa in the native as well as the heparin-activated state and support a new model of allosteric activation we recently proposed in which a balance between attractive and repulsive exosite interactions in the native state is shifted to favor the attractive interactions in the activated state through core conformational changes induced by heparin binding.

A new peptide (Ruviprase) purified from the venom of Daboia russelii russelii shows potent anticoagulant activity via non-enzymatic inhibition of thrombin and factor Xa

Compounds showing dual inhibition of thrombin and factor Xa (FXa) are the subject of great interest owing to their broader specificity for effective anticoagulation therapy against cardiovascular disorders. This is the first report on the functional characterization and assessment of therapeutic potential of a 4423.6 Da inhibitory peptide (Ruviprase) purified from Daboia russelii russelii venom. The secondary structure of Ruviprase is composed of α-helices (61.9%) and random coils (38.1%). The partial N-terminal sequence (E(1)-V(2)-X(3)-W(4)-W(5)-W(6)-A(7)-Q(8)-L(9)-S(10)) of Ruviprase demonstrated significant similarity (80.0%) with an internal sequence of apoptosis-stimulating protein reported from the venom of Ophiophagus hannah and Python bivittatus; albeit Ruviprase did not show sequence similarity with existing thrombin/FXa inhibitors, suggesting its uniqueness. Ruviprase demonstrated a potent in vitro anticoagulant property and inhibited both thrombin and FXa following slow binding kinetics. Ruviprase inhibited thrombin by binding to its active site via an uncompetitive mechanism with a Ki value and dissociation constant (KD) of 0.42 μM and 0.46 μM, respectively. Conversely, Ruviprase demonstrated mixed inhibition (Ki = 0.16 μM) of FXa towards its physiological substrate prothrombin. Furthermore, the biological properties of Ruviprase could not be neutralized by commercial polyvalent or monovalent antivenom. Ruviprase at a dose of 2.0 mg/kg was non-toxic and showed potent in vivo anticoagulant activity after 6 h of intraperitoneal treatment in mice. Because of the potent anticoagulant property as well as non-toxic nature of Ruviprase, the possible application of the peptide as an antithrombotic agent for combating thrombosis-associated ailments appears promising.

Network pharmacology analyses of the antithrombotic pharmacological mechanism of Fufang Xueshuantong Capsule with experimental support using disseminated intravascular coagulation rats

ETHNOPHARMACOLOGICAL RELEVANCE

Fufang Xueshuantong (FXST) Capsule is developed on a traditional Chinese medicine remedy, with a four-herb formula of Panax notoginseng, Radix astragali, Salvia miltiorrhizae and Radix scrophulariaceae. It has been used for treatment of the clinic cardiovascular disease for many years.

MATERIALS AND METHODS

Due to its complexity of compositions and polypharmacological effects, it often complicates understanding of the mechanisms of action. In the present work, we have constructed an integrated model of system pharmacology to investigate the polypharmacological mechanisms of FXST formulation for treatment of thrombosis disease.

RESULTS

The predicted results showed that 22 ingredients in FXST were closely associated with 41 protein targets related to blood coagulation, fibrinolysis and platelet aggregation. Through analysis of the compound-protein target association, significant cross-targets between each herb indicated the multiple active chemical ingredients might interact with the same target simultaneously and thus explained the synergistic mechanisms of the principle of Traditional Chinese medicines (TCMs) as ''Jun (emperor) - Chen (minister) - Zuo (adjuvant) - Shi (courier)''. To validate the polypharmacological effects predicted by our network pharmacology (NetPharm) analysis, we have carried out experimental investigation the effects of FXST on the disorders of the blood coagulation system in a lipopolysaccharide-induced disseminated intravascular coagulation (DIC) rat model. The results showed that FXST could significantly ameliorate the activation of coagulation system, which is congruent with the cross-target prediction by NetPharm approach.

CONCLUSIONS

The combined investigations provide more insight into better understanding of the pharmacological mechanisms of FXST, and may also offer an alternative avenue to further explore the chemical and pharmacological basis of TCMs.

Validation of an enzyme-linked immunoassay (ELISA) for plasma oxytocin in a novel mammal species reveals potential errors induced by sampling procedure

BACKGROUND

The neuropeptide oxytocin is increasingly the focus of many studies investigating human and animal social behaviours and diseases. However, interpretation and comparison of results is made difficult by a lack of consistent methodological approaches towards analysing this hormone.

NEW METHOD

This study determined the sample collection and analysis protocols that cause the least amounts of protocol dependant variation in plasma oxytocin concentrations detected by ELISA. The effect of vacutainer type, sample extraction prior to analysis and capture and restraint protocol were investigated while validating an assay protocol for two novel species, grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina).

RESULTS

Where samples are extracted prior to analysis, vacutainer type (EDTA mean: 8.25±0.56 pg/ml, heparin mean: 8.25±0.62 pg/ml, p=0.82), time taken to obtain a sample and restraint protocol did not affect the concentration of oxytocin detected. However, concentrations of oxytocin detected in raw plasma samples were significantly higher than those in extracted samples, and varied significantly with vacutainer type (EDTA mean: 534.4±43.7 pg/ml, heparin mean: 300.9±19.6 pg/ml, p<0.001) and capture and restraint methodology. There was no relationship between oxytocin concentrations detected in raw and extracted plasma (p=0.25).

COMPARISON WITH EXISTING METHOD(S)

Over half the reviewed published studies analysing plasma oxytocin use raw plasma and different vacutainer types are used without consistency or justification through-out the literature.

CONCLUSIONS

We caution that studies using raw plasma are likely to over estimate oxytocin concentrations, cannot be used to accurately infer true values via correlations and are susceptible to variation according vacutainer type.

Primary prophylaxis for venous thromboembolism in people undergoing major amputation of the lower extremity

BACKGROUND

Patients undergoing major amputation of the lower limb are at increased risk of venous thromboembolism (VTE). Risk factors for VTE in amputees include advanced age, sedentary lifestyle, longstanding arterial disease and an identifiable hypercoagulable condition. Evidence suggests that pharmacological prophylaxis (for example heparin, factor Xa inhibitors, vitamin K antagonists, direct thrombin inhibitors, antiplatelets) is effective in preventing deep vein thrombosis (DVT) but it is associated with an increased risk of bleeding. Mechanical prophylaxis (for example antiembolism stockings, intermittent pneumatic compression and foot impulse devices), on the other hand, is non-invasive and has no side effects. However, it is not always appropriate in patients with contraindications such as peripheral arterial disease (PAD), arteriosclerosis or bilateral lower limb amputations. It is important to determine the most effective thromboprophylaxis and whether this is one treatment alone or in combination with another. To date, no systematic review has been conducted examining the effectiveness of thromboprophylaxis in preventing VTE in people undergoing amputation.

OBJECTIVES

To determine the effectiveness of thromboprophylaxis in preventing VTE in people undergoing major amputation of the lower extremity.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched May 2013) and CENTRAL (2013, Issue 4). Clinical trials databases were searched (May 2013). No date or language restrictions were applied. Non-English trials were translated where required and reference lists of identified studies were handsearched.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials in which people undergoing a major unilateral or bilateral amputation (for example hip disarticulation, transfemoral, knee disarticulation and transtibial) of the lower extremity were allocated to different types or regimens of thromboprophylaxis (including pharmacological or mechanical prophylaxis) or placebo.

DATA COLLECTION AND ANALYSIS

Selection of studies, data extraction and risk of bias were completed independently by two review authors. Any disagreements were resolved by discussion. Meta-analysis could not be completed as the two included studies compared different treatments and therefore the data could not be pooled.

MAIN RESULTS

Two studies with a combined total of 288 participants met the inclusion criteria for this review. One study compared low molecular weight heparin with unfractionated heparin and found no difference between the treatments in the prevention of DVT (odds ratio (OR) 1.23, 95% confidence interval (CI) 0.28 to 5.35). No bleeding events or deaths occurred. This study was open label and therefore at a high risk of performance bias. Additionally, the method of randomisation was not reported and therefore the risk of selection bias was unclear. In the second study heparin did not significantly improve prevention of pulmonary embolism (OR 1.02, 95% CI 0.44 to 2.37) when compared to placebo. Furthermore, when the level of amputation was considered, the incidence of pulmonary embolism was similar between the two treatment groups: above knee amputation (OR 0.79, 95% CI 0.31 to 1.97) and below knee amputation (OR 1.53, 95% CI 0.09 to 26.43). Ten participants died during the study; five underwent a post-mortem and three were found to have had a recent pulmonary embolism, all of whom had been on placebo. Bleeding events were reported in less than 10% of participants in both treatment groups but specific data were not presented. This study did not report the methods used to conceal allocation of treatment and therefore it was unclear if selection bias occurred. However, this study appeared to be free from all other sources of bias. No study looked at mechanical prophylaxis.

AUTHORS' CONCLUSIONS

As only two studies were included in this review, each comparing different interventions, there is insufficient evidence to make any conclusions regarding the most effective thromboprophylaxis regimen in patients undergoing lower limb amputation. Further large-scale studies that are of good quality are required.

Ficolin-2 reveals different analytical and biological properties dependent on different sample handling procedures

Ficolin-2 (L-ficolin) is a germ line encoded pattern recognition molecule circulating in the blood, and functions as a recognition molecule in the lectin complement pathway. However, consistent and reliable measurements of Ficolin-2 concentration and activity have been difficult to achieve. After recurrent observations of deviations in Ficolin-2 properties between different blood sample procedures, we decided to investigate this closer. Blood samples from ten healthy donors were collected in various serum and plasma tubes and Ficolin-2 properties were evaluated by different ELISA setups. We found that serum prepared from tubes containing the clot activator silica used as a standard technique in many routine laboratories held a significantly lower concentration of Ficolin-2 as compared to the other sample types. Furthermore, Ficolin-2 binding and complement activation potential in this type of serum was impaired when using an acetylated compound as matrix. On the other hand, Ficolin-2 in serum made without clot activator and in plasma irrespective of additive used, had the same concentration and was capable of initiating the lectin pathway measured as C4 and C3 deposition on the ligand. No Ficolin-2 mediated formation of the terminal complement complex was observed under the applied assay conditions. In conclusion, our results show that Ficolin-2 is a promiscuous molecule and that care should be taken during sampling, handling and matrix chosen for measurement of Ficolin-2 levels and activity.

Decreased thrombin activity by a Congolese herbal medicine used in sickle cell anemia

ETHNOPHARMACOLOGICAL RELEVANCE

Aqueous extracts from Ceiba pentandra (Malvaceae/Bombacoideae) and Quassia africana (Simaroubaceae) are used as crude medicines for the management of sickle cell anemia (SCA) in the Democratic Republic of Congo (DR Congo). Since it is postulated that the pathogenesis of SCA is associated with an increased blood coagulation activity, the present study is conducted to determine the effect of the two extracts on the coagulation by assessing the thrombin activity and the plasma clotting time.

MATERIALS AND METHODS

Thrombin activity was measured by chromogenic assay in the presence of the aqueous extracts (10, 100 or 200 µg/ml); and plasma clotting times were measured by activated partial thromboplastin time (APTT) and prothrombin time (PT) in the presence of C. pentandra (10, 100 or 200 µg/ml) and Q. africana (5, 20 or 50 µg/ml).

RESULTS

Reduced thrombin activity and prolonged plasma clotting time measured by APTT were observed in the presence of C. pentandra extract only. However, plasma clotting time measured by PT was not modified by the use of the two extracts.

CONCLUSIONS

This study suggests that the aqueous extract of C. pentandra may contain active components that reduce the thrombin activity and prolong the plasma clotting time by affecting the coagulation intrinsic pathway.