Risk Factor For Thrombotic Disease Research Articles

Factors associated with thrombotic disease in dogs with renal proteinuria: A retrospective of 150 cases.

Knowledge of additional risk factors for thrombotic disease (TD) among dogs with renal proteinuria is limited; these might differ for TD affecting the systemic arterial (AT), systemic venous (VT), and pulmonary circulation (PT). To compare signalment and clinicopathological data between dogs with renal proteinuria with or without TD, and between dogs with AT, VT, and PT. One hundred fifty client-owned dogs with renal proteinuria, 50 of which had TD. Retrospective case-controlled study. A database search (2004-2021) identified proteinuric dogs (UPC > 2) with and without TD. Clinicopathological data were obtained from the records. TD and non-TD (NTD) groups were compared by binary logistic regression, and AT, VT, and PT groups by multinomial regression. Normal data presented as mean ± SD, non-normal data presented as median [25th, 75th percentiles]. Cavalier King Charles Spaniels were overrepresented in the TD group (OR = 98.8, 95% CI 2.09-4671, P = .02). Compared to NTD cases, TD cases had higher concentration of neutrophils (11.06 [8.92, 16.58] × 109 /L vs 7.31 [5.63, 11.06] × 109 /L, P = .02), and lower concentration of eosinophils (0 [0, 0.21] × 109 /L vs 0.17 [0.04, 0.41] × 109 /L, P = .002) in blood, and lower serum albumin (2.45 ± 0.73 g/dL vs 2.83 ± 0.73 g/dL, P = .04). AT cases had higher serum albumin concentrations than VT cases (2.73 ± 0.48 g/dL vs 2.17 ± 0.49 g/dL, P = .03) and were older than PT cases (10.6 ± 2.6 years vs 7.0 ± 4.3 years, P = .008). VT cases were older (9.1 ± 4.2 years vs 7.0 ± 4.3 years, P = .008) and had higher serum cholesterol concentration (398 [309-692 mg/dL] vs 255 [155-402 mg/dL], P = .03) than PT cases. Differences between thrombus locations could reflect differences in pathogenesis.

Integrin β Expression as a New Diagnostic Marker for Arteriovenous Thrombosis: A Single-Center Prospective Study.

Integrin β plays an important role in the pathogenesis of thrombosis and inflammation, and it may be a shared pathogenic mechanism between arterial and venous thromboses. With the goal of identifying new treatment targets for thrombotic diseases and specific diagnostic markers for venous thromboembolism (VTE), this prospective clinical study was performed to clarify the relationship between integrin and thrombosis. The levels of integrin β1-3, interleukin-6 (IL-6), and C-reactive protein were significantly higher in patients with acute myocardial infarction (AMI; n = 44) and acute VTE (n = 43) compared to healthy controls (n = 33). The IL-6 and integrin β1-3 levels were also significantly higher in the AMI group compared to the VTE and control groups. Logistic regression analysis identified IL-6 and integrin β1-3 levels as independent risk factors for thrombotic disease. Based on the receiver-operating characteristic curve, Youden index, sensitivity, and specificity, the diagnostic accuracy value for VTE was greater than 0.8 when integrins β1, β2, and β3 were combined. Overall, these results suggest that integrin β levels can contribute to improving the diagnosis and treatment of arteriovenous thrombosis.

Antithrombotic management of patients with deep vein thrombosis and venous stents: an international registry

BackgroundIn patients with acute deep vein thrombosis (DVT) treated with catheter-based thrombolysis and venous stenting, poststenting anticoagulant management is uncertain. ObjectivesTo determine the type and duration of antithrombotic therapy used in patients who have received venous stents for treatment of acute lower extremity DVT. MethodsWe created an international registry of patients with leg DVT from 2005 to 2019 who received venous stents as part of their acute management. We collected data on baseline clinical characteristics and pre-venous and post-venous stent antithrombotic therapy. ResultsWe studied 173 patients with venous stents: 101 (58%) were aged ≤50 years, 105 (61%) were female, and 128 (74%) had risk factors for thrombotic disease. DVT was iliofemoral in 150 (87%) patients, and catheter-based treatment was given within 7 days of diagnosis in 92 (53%) patients. After venous stenting, 109 (63%) patients received anticoagulant-only therapy with a direct oral anticoagulant (29%), warfarin (22%), or low-molecular-weight heparin (10%), and 59 (34%) received anticoagulant-antiplatelet therapy. In patients taking anticoagulant-only therapy, 29% received indefinite treatment; in patients on anticoagulant-antiplatelet therapy, 19% received indefinite treatment. Factors associated with combined anticoagulant-antiplatelet therapy vs anticoagulant-only therapy were use of thrombolytic, thrombectomy, and aspiration interventions (odds ratio [OR], 5.11; 95% CI, 1.45-18.05); use of balloon angioplasty (OR, 2.62; 95% CI, 1.20-5.76); and immediate stent restenosis (OR, 7.2; 95% CI, 1.45-5.89). ConclusionAnticoagulant therapy without concomitant antiplatelet therapy appears to be the most common antithrombotic strategy in patients with DVT and venous stenting. More research is needed to determine outcomes of venous stenting in relation to antithrombotic therapy.

>Clopidogrel Rescues the Adverse Cerebral Vascular Effects Associated with Angiotensin II‐Induced Hypertension

Hypertension is a common risk factor for thrombotic diseases like heart attack and stroke. Chronic high blood pressure causes endothelial dysfunction which accelerates the atherosclerotic process resulting in plaque instability. Since hypertensive patients have an increased risk of thrombotic diseases, many are prescribed the antiplatelet drug, clopidogrel. The present study sought to determine clopidogrel’s effect on blood pressure, cerebral blood flow, and vascular remodeling in angiotensin II (Ang II)‐induced hypertensive mice. Previous results from our laboratory demonstrated that clopidogrel attenuated P2Y2‐induced vasoconstriction in cerebral arteries which could result in an increase in downstream cerebral blood flow. Therefore, we hypothesized that clopidogrel increases cerebral blood flow and decreases vascular remodeling in Ang II‐induced hypertensive mice. Ang II infusion pump implantation or sham surgeries were performed in 48 C57BL/6 mice at 16‐18 weeks of age. Ang II was infused continuously at a rate of 800ng/kg/min for 4 weeks. The mice were also administered vehicle or clopidogrel (10mg/kg/day) starting the day after surgery. Data are presented as means ± SEM, n = 8‐12 mice/group. Ang II significantly reduced blood flow, and clopidogrel‐treated mice had blood flow that was not different from either the sham or Ang II mice (sham vehicle: 305.6 ± 16.17; sham clopidogrel: 313.0 ± 15.27; Ang II vehicle: 244.1 ± 12.76; Ang II clopidogrel: 267.6 ± 14.96). Posterior cerebral arteries were harvested from animals at the end of the experiment. The outer and lumen diameters were reduced in the vessels in Ang II treated mice. However, clopidogrel treatment did not modify this vascular remodeling in the Ang II treated mice. The results suggest that clopidogrel demonstrates protective potential in hypertensive mice. Further studies are required to determine the long‐term effects of clopidogrel on hypertension associated vascular remodeling.

COVID-19-INDUCED AORTIC THROMBOSIS

TOPIC: Chest Infections TYPE: Medical Student/Resident Case Reports INTRODUCTION: As of April 2021, Coronavirus disease (COVID-19) has infected over 147 million people and claimed the lives of over 3 million globally. Despite becoming a significant burden on the healthcare community, complications and sequalae of this lethal virus are still not fully known. While primarily being defined as a respiratory illness, COVID-19 has been known to cause venous thrombotic events and less commonly increased arterial clot burden. CASE PRESENTATION: A 63-year-old female with a history of 30 pack year tobacco use presented to the emergency department (ED) complaining of shortness of breath, chest tightness, and right lower extremity pain starting 2-3 hours prior to presentation. In the ED she was noted to be COVID-19 positive and found to be hypoxic with an oxygen saturation of 84% on room air for which she was placed on 4 liters of oxygen per minute via nasal cannula for a goal oxygen saturation of >92%. The remainder of her vitals were unremarkable and physical exam did not reveal any pathology or acute findings. An emergent CT angiogram of the chest, abdomen, and pelvis was obtained which showed a large focus of thrombus in the ascending thoracic aorta measuring up to 2.2 x 1.3 cm in the axial plane, which appears free-floating abutting the anterior wall of the aorta. There were also some smaller scattered eccentric thrombi in the descending thoracic and infrarenal abdominal aorta. A focus of thrombus extending from the distal abdominal aorta into the right common iliac artery results in severe stenosis of the right common iliac artery. Venous doppler studies revealed diminished velocity in the right popliteal and posterior tibial arteries without identified thrombosis. Vascular surgery was consulted however the patient remained clinically stable and was started on a heparin drip prior to being bridged to warfarin with a goal international normalized ratio of 2.5 to 3.5 for a total of 6 months duration. At her 1 and 3 month outpatient follow-up she remained in stable condition and her presenting symptoms resolved. DISCUSSION: COVID-19 is known to bind to the peptidase domain of the angiotensin-converting enzyme 2 receptor leading to severe respiratory disease and an overwhelming activation of cytokines and complements. Through this process, a hypercoagulable state is induced leading to venous and arterial thrombotic events. Our patient had no risk factors for thrombotic disease and hypercoagulable work-up was largely unremarkable leading to the suspicion of COVID-19 infection as the cause. CONCLUSIONS: COVID-19 infection is a lethal viral disease affecting millions of people globally. As this disease continues to spread, it is imperative clinicians become aware of the devastating complications such as venous and arterial thrombosis risk and appropriately anti-coagulate their patients. REFERENCE #1: Ji YL, Wu Y, Qiu Z, et al. The Pathogenesis and Treatment of COVID-19: A System Review. Biomed Environ Sci. 2021;34(1):50-60. doi:10.3967/bes2021.007 REFERENCE #2: Cevik M, Kuppalli K, Kindrachuk J, Peiris M. Virology, transmission, and pathogenesis of SARS-CoV-2. BMJ. 2020;371:m3862. doi: 10.1136/bmj.m3862. DISCLOSURES: No relevant relationships by Abbas Alshami, source=Web Response No relevant relationships by Steven Douedi, source=Web Response No relevant relationships by Mihir Odak, source=Web Response No relevant relationships by Swapnil Patel, source=Web Response

S2437 Budd-Chiari Syndrome Secondary to SARS-CoV-2 Infection

INTRODUCTION: SARS-CoV-2 is a novel coronavirus with potentially severe multi-organ complications. Currently, a major discussion revolves around the thrombotic risk of this disease, though little is known about this risk within the gastrointestinal tract and portal system. The below case describes a patient with SARS-CoV-2 subsequently diagnosed with Budd-Chiari syndrome. CASE DESCRIPTION/METHODS: A 50-year-old male with a history of alcohol-associated cirrhosis presented to the emergency department with altered mental status. On exam he was somnolent and jaundiced, with ascites but no focal neurologic deficits. Initial blood work revealed a leukocytosis with elevated transaminases, bilirubin and INR (Table 1), resulting in a MELD-Na score of 29 and a discriminant function over 32. Nasal swab detected SARS-CoV-2. His presentation was consistent with decompensated cirrhosis complicated by alcoholic hepatitis and hepatic encephalopathy. Paracentesis showed no evidence of spontaneous bacterial peritonitis. He was started on empiric antibiotics, prophylaxis for deep venous thrombosis, lactulose and rifaximin for hepatic encephalopathy, and prednisolone for alcoholic hepatitis. After initial clinical improvement, he developed right upper quadrant abdominal pain and recurrent elevation in his liver enzymes. An abdominal ultrasound was performed showing poor flow through the portal venous system. Subsequently, an abdominal CT demonstrated extensive veno-occlusive disease involving the inferior vena cava and hepatic veins, consistent with Budd-Chiari syndrome (Figure 1). To minimize bleeding risk, he underwent variceal band ligation prior to initiation of anticoagulation. DISCUSSION: Budd-Chiari syndrome is a rare, veno-occlusive condition characterized by obstruction of the hepatic veins; treatment often involves anticoagulation. In most cases, there is an underlying disorder generating a hypercoagulable state. Recent studies have raised concerns about the thrombotic nature of SARS-CoV-2, especially due to the high incidence of infarcts, emboli, and strokes seen in this population. In the absence of other known risk factors for thrombotic disease in this patient, it is likely SARS-CoV-2 was the predisposing pro-thrombotic factor. In patients with SARS-CoV-2 infection and new or worsening liver findings, early consideration of and testing for hepatic veno-occlusive disease and timely initiation of anticoagulation may help prevent serious complications.Table 1.: Laboratory Results on Initial Presentation.Figure 1.: CT evidence of veno-occlusive disease in hepatic veins and IVC consistent with Budd-Chiari Syndrome.

Exploration in the mechanism of rhubarb for the treatment of hyperviscosity syndrome based on network pharmacology

Ethnopharmacological relevanceHyperviscosity syndrome (HVS) is a major risk factor for thrombotic diseases. Rhubarb, well-known as a traditional Chinese medicine, exhibits multiple pharmacological activities, especially for promoting blood circulation to remove blood stasis (PBRB), which has been become a functional health food for decreasing the risk of cardiovascular diseases. However, due to the complexity of rhubarb components, it is still difficult to clarify the specific targets of effective substances in PBRB, and the pharmacodynamic mechanism needs to be further probed. Materials and methodsThe “compound-target-cell-disease” network analysis was initially used to predict potential targets and bioactive compounds. The effect of rhubarb for the treatment of HVS was examined by histopathology and biochemical assays based on the HVS rat model. ResultsThrough the “compound-target-cell-disease” network analysis, eight potential therapeutic targets were eventually screened out, and platelets were predicted as the main effector cells of rhubarb in PBRB. Among targets coagulation factor II (prothrombin, F2) and fibrinogen gamma chain (FGG) were closely related to platelets, and five compounds associated with F2 and FGG were predicted including emodin-8-O-beta-D-glucopyranoside (Emo), physcion-8-O-beta-D-glucopyranoside (Phy), procyanidin B-5,3′-O-gallate, torachrysone-8-O-beta-D-(6′-oxayl)-glucoside and epicatechin. Furthermore, thoracic aorta histopathology and biochemical examinations showed middle dose of rhubarb (0.42 g/kg/day) significantly ameliorated pathological changes, hemorheology parameters, as well as levels of representative biomarkers such as plasma P-selectin (P-sel) and thromboxane (TXB2) in platelet activation compared to HVS rat model, whose effects were comparable to the positive drug aspirin or even better. Finally, it was further validated F2 and FGG as the major effective targets of rhubarb as well as its two active ingredients Emo and Phy in PBRB. ConclusionsThis study may provide an innovative way and scientific information to further understand the main effective components of rhubarb and its mechanisms about targets of F2 and FGG in PBRB, especially the new therapeutic target FGG, which also provide a basis for establishing a quality control for rhubarb by bioassays that could correlate the clinical efficacy and its mechanism.

Hypothermia‐induced activation of the splenic platelet pool as a risk factor for thrombotic disease in a mouse model

BackgroundHypothermia, either therapeutically induced or accidental (ie, an involuntary decrease in core body temperature to <35°C), results in hemostatic disorders. However, it remains unclear whether hypothermia enhances or inhibits coagulation, especially in severe hypothermia. The present study evaluated the thrombocytic and hemostatic changes in hypothermic mice. MethodsC57Bl/6 mice were placed at an ambient temperature of −20°C under general anesthesia. When the rectal temperature decreased to 15°C, 10 mice were immediately euthanized, while another 10 mice were rewarmed, kept in normal conditions for 24 hours, and then euthanized. These treatments were also performed in 20 splenectomized mice. ResultsThe hypothermic mice had adhesion of CD62P‐positive platelets with high expression of von Willebrand factor (vWF) in their spleens, while the status of the peripheral platelets was unchanged. Furthermore, the plasma levels of platelet factor 4 (PF4) and pro‐platelet basic protein (PPBP), which are biomarkers for platelet degranulation, were significantly higher in hypothermic mice than in control mice, indicating that hypothermia activated the platelets in the splenic pool. Thus, we analyzed these biomarkers in asplenic mice. There was no increase in either PF4 or PPBP in splenectomized hypothermic mice. Additionally, the plasma D‐dimer elevation and microthrombosis were caused in rewarmed mice, but not in asplenic rewarmed mice. ConclusionsOur results indicate that hypothermia leads to platelet activation in the spleen via the upregulation of vWF, and this activation causes hypercoagulability after rewarming.

Positions of Hydroxyl Groups in Chrysin are Critical for Inhibiting Plasminogen Activator Inhibitor-1 Release from Human Umbilical Vein Endothelial Cells

Chrysin suppresses the TNFα-induced increase in the secretion of plasma plasminogen activator inhibitor 1 (PAl-1), a risk factor for thrombotic diseases, from human umbilical vein endothelial cells (HUVECs). The present study aimed to determine the association between the location of the hydroxyl groups in chrysin.to levels of-PAI-1. in the medium of HUVEC stimulated with TNFα. We cultured HUVEC for 3 h in medium containing chrysin or various flavonoids and then stimulated them with TNFα (10 ng/mL) for 12 h. Levels of PAI-1 antigen measured using ELISA showed that chrysin significantly inhibited the PAl- I increase with an IC50 of 15.6 μM. The flavones, galangin, baicalein, 5-hydroxyflavone, 6-hydroxyflavone, 7-hydroxyflavone and quercetin did not significantly inhibit the PAI- increase. Apigenin and luteolin were cytotoxic and thus their ability to inhibit PAI production could not be evaluated. Chrysin also inhibited PAI- mRNA expression whereas the other compounds did not. Hydroxyl groups located in the A-5 and A-7 positions were essential for the inhibitoryactivity, which along with cytotoxicity, was significantly influenced by adding a third hydroxyl group.

The Role of Fibrinogen and Factor XIII in Hemostasis, and the Identification and Treatment of Associated Disorders

The thrombin-mediated conversion of fibrinogen to fibrin and the subsequent stabilization of thefibrin clot by activated FXIII are vital to adequate hemostasis. Once cross-linked, the fibrin clot is relatively resistant to fibrinolysis, ensuring longterm stability of the fibrin clot to permit repair of the damaged vessel. Indeed, qualitative or quantitative defects in either fibrinogen or FXIII may result in bleeding.1,2 Conversely, elevated fibrinogen levels are considered a risk factor for thrombotic disease, whereas FXIII may affect thrombotic risk in selected patient groups.3–5 Thus, thrombosis and hemostasis critically involve both fibrinogen and FXIII, which in turn are fascinating molecules in terms of structure and function, and clinical impact. The biochemical and biophysical properties of the fibrin clot have been partly elucidated and help us understand the mode of action of clot formation; moreover, determinants of (in)stability of the clot have been identified.6–8 FXIII is a complex molecule that exists in a different form in plasma (as a A2B2 heterotetramer) and within cells including platelets (as an A2 homodimer). Both fibrinogen and FXIII have properties beyond their well-recognized role in thrombosis and hemostasis.9–11 We are proud and pleased to present a comprehensive overview of new clinical and basic science developments in the field of fibrin formation and crosslinking. This issue of Seminars in Thrombosis & Haemostasis starts with a provocative paper by Litvinov andWeiselwho review the relevance of fibrin(ogen) for clinicians and biochemists.12 The relatively mild phenotype of thefibrinogen knockoutmicehas led some biochemists and clinicians to conclude that fibrinogen is not very important, but critical arguments against this conclusion are provided by Litvinov and Weisel. Subsequently, Macrae and coworkers present an update of biochemical and clinical studies on the fibrinogen gamma prime splice variant,13 which has biophysical and biochemical features that are markedly distinct from “normal” fibrinogen, and appears associated with thrombotic disease. Besides the fibrinogen gamma prime variant, which is present in all of us, rare mutations in fibrinogen leading to decreased plasma levels, decreased fibrinogen function, or both, can occur and are associated with both a bleeding tendency and thrombotic complications. Neerman-Arbez and coworkers provide a comprehensive description of the screening for, and molecular characterization of, congenital fibrinogen abnormalities, and provide an update on themutations that have so far been identified.14 Casini and colleagues then discuss therapeutic options in patients with congenital fibrinogen abnormalities and highlight difficult situations, including obstetric management and treatment of thrombotic events.15 The use of fibrinogen concentrate to treat acquired fibrinogen deficiencies, such as encountered in massive bleeding due to trauma, surgery, or due to postpartum bleeding, has gained popularity over the past decade. Samama argues against the liberal use of fibrinogen concentrates inmassively bleeding patients and calls for additional studies to clarify the role of fibrinogen concentrates in this setting.16 Subsequently, Undas provides in-depth information on commonly used laboratory tests to assessfibrin clot properties in both routine diagnostics and research settings.17 Fibrinogen is synthesized in the liver, and patients with liver diseases may acquire quantitative and qualitative defects in fibrinogen. The consequences of these changes are discussed by Lisman and Ariens, who provide evidence of qualitative improvements in fibrin structure in these patients despite quantitative defects.18 Alterations in fibrin(ogen) may contribute to thrombotic events that may occur in patients with liver diseases. In addition, fibrin(ogen) may play a role in the pathogenesis of liver diseases. Evidence from experimental animal models linking fibrin(ogen) to disease pathology is

Inhibition of plasminogen activator inhibitor-1 release from human endothelial cells by Angelica keiskei Koidzumi (Ashitaba) chalcones is structure-dependent.

Angelica keiskei Koidzumi (Ashitaba) is a traditional herbal medicine and it is also regarded in Japan as a health food that might have antithrombotic properties. Ashitaba exudate suppresses lipopolysaccharide (LPS)-induced plasma plasminogen activator inhibitor 1 (PAI-1), a risk factor for thrombotic diseases in mice. Xanthoangelol (XA) and 4-hydroxyderricin (4-HD) comprise > 95% of total chalcones from Ashitaba exudates that also contain trace amounts of other chalcone subtypes. The present study aimed to determine the effects of Ashitaba chalcones including xanthoangelols B (XB), D (XD), E (XE), F (XF) and XA as well as 4-HD on PAI-1 levels in the medium of stimulated human EA.hy926 endothelial cells. Xanthoangelol (10 M) inhibited PAI-1 production at a rate of 77.1%, whereas the inhibition rates of XB, XD, XE and 4-HD were not significant. Xanthoangelol F was highly cytotoxic and thus its ability to inhibit PAI-1 production could not be evaluated. The side hydrocarbon chain of XA played an important role in the excretion of inhibitory activity. Small modifications of the hydrocarbon chain or small functional groups on the A ring measurably influenced the inhibitory activity of xanthoangelols. These findings warrant future research towards an understanding of the mechanism of antithrombotic action of Ashitaba as herbal medicine or antithrombotic health food.

Plasma factor VIII in non-puerperal cerebral venous thrombosis: A prospective case–control study

Elevated plasma factor VIII (FVIII) is increasingly recognized as an independent risk factor for thrombotic diseases. Our aim was to evaluate the association of increased plasma FVIII with cerebral venous thrombosis (CVT). Forty eight patients with non-puerperal, aseptic CVT were recruited for the study along with 50 age- and gender-matched, healthy controls. Blood samples were collected 3months after the thrombotic event in patients. Plasma FVIII and fibrinogen levels were measured by a functional clot-based assay. Mean plasma FVIII was significantly higher in patients when compared to controls (235.40±94.5 vs.121.2±28.3IU/dl, p<0.001). Absence of significant elevation of fibrinogen suggested that the increase in FVIII was not due to an acute phase reaction. Elevated FVIII (>170IU/dl) was associated with >18-fold increase in the risk for non-puerperal CVT (adjusted OR: 18.754, 95% CI 10.2–203.0, p<0.001). Non-O blood groups were more prevalent in CVT patients. Mean FVIII levels were higher in subjects with non-O blood group as compared to those with O blood group (155.16±46.05 vs. 129.09±40.06IU/dl, p<0.001). Multivariate analysis with logistic regression showed that only elevated FVIII, and not blood group, was significantly associated with CVT. Our study demonstrates that elevated FVIII is an independent risk factor for non-puerperal CVT in an Indian population.

Thiol pathways in the regulation of tissue factor prothrombotic activity

The transmembrane protein tissue factor (TF), the initiator of the extrinsic coagulation cascade and a risk factor for thrombotic disease, largely resides on the cell surface in an inactive, encrypted conformation. Whereas TF procoagulant activation, or decryption, is closely associated with the exposure of procoagulant phosphatidylserine in the outer leaflet of cell membranes, thiol pathways and protein disulfide isomerase (PDI) play increasingly recognized roles in regulating TF prothrombotic pathways. TF contains a solvent-exposed allosteric disulfide bond that stabilizes the carboxyl-terminal domain involved in ligand interactions with coagulation factors VIIa and X. PDI is a prime candidate to modify the allosteric disulfide by reduction, S-nitrosylation and glutathionation, implicated as regulators of TF procoagulant activity. In-vivo studies localize PDI to sites of thrombus formation and inhibition of PDI attenuates arterial thrombosis. PDI also contributes to the biogenesis of procoagulant microparticles that are released in the context of TF decryption following ATP-mediated activation of the purinergic P2X7 receptor. Genetic deletion of P2X7 signaling attenuates TF and PDI-dependent thrombosis, identifying a new connection between prothrombotic and proinflammatory pathways. Although the precise biochemical events of TF encryption and decryption require further study, PDI and thiol pathways emerge as important regulators of vascular thrombotic diseases.

Extensive Thrombosis and First-Trimester Pregnancy Loss Caused by Sticky Platelet Syndrome

Sticky platelet syndrome is an autosomal-dominant thrombophilia characterized by platelet hyperaggregability in the presence of adenosine diphosphate or epinephrine. The result clinically can be widespread thromboses, often arterial, in patients without apparent risk factors for thrombotic disease. Limited data exist regarding its role in adverse pregnancy outcomes. A gravid woman with two previous first-trimester miscarriages presented at 11 weeks of gestation with a deep venous thrombosis. Despite anticoagulation, she developed extensive and progressive arterial and venous thromboses and suffered a fetal demise. A thrombophilia panel was unremarkable, but platelet aggregometry demonstrated hyperactive platelets in the presence of adenosine diphosphate and epinephrine consistent with sticky platelet syndrome. Sticky platelet syndrome causes arterial thromboses and may be an underappreciated etiology for adverse pregnancy outcomes.

Assessment of thrombin-activatable fibrinolysis inhibitor (TAFI) activation in acquired hemostatic dysfunction: a diagnostic challenge

Human thrombin activatable fibrinolysis inhibitor (TAFI) is a carboxypeptidase zymogen that was first described in 1995 [1]. It had been previously reported under different names such as carboxypeptidase basic (B), unstable (U), and arginine (R) [2]. The mature TAFI protein contains 401 amino acids, and after glycosylation, the molecular weight becomes 60 kDa. TAFI in its plasma zymogen form can be activated by thrombin, the thrombin-thrombomodulin complex, or plasmin. The activated TAFI (TAFIa) decays spontaneously into the inactive form of TAFI (TAFIai) through a temperature-dependent conformational change. TAFIa plays a role in the inhibition of fibrinolysis by cleaving the carboxyl-terminal lysine residues from partially degraded fibrin. In the coagulation cascade, the generated thrombin can activate TAFI, and the resulting TAFIa inhibits fibrinolysis, finally resulting in the formation of more stable clots [3]. Therefore, a deficiency of the coagulation factors might reduce the TAFIa levels via reduced thrombin generation, resulting in the formation of an unstable clot. In an animal study, TAFI was activated during a thrombotic event, and the inhibition of TAFIa activity enhanced the efficacy of thrombolytic therapy, thereby confirming its role as an inhibitor of fibrinolysis [4-6]. TAFIa also plays a role in the modulation of inflammation through down-regulation of pericellular plasminogen activation and inactivation of the inflammatory peptides bradykinin and anaphylatoxins C3a and C5a. In mice with Escherichia coli-induced sepsis, TAFI deficiency prevented liver damage via inactivation of C3a and C5a [7]. The plasma concentration of TAFI appears to be under the control of genetic factors and non-genetic factors such as sex hormones, cytokines, and lipids [2]. Several diseases, including diabetes, kidney transplantation, hypertension, nephritic syndrome, insulin resistance, obesity, and inflammatory bowel disease, have been shown to be positively associated with plasma TAFI levels [2]. Because TAFI is expressed in adipocytes, an increased TAFI level can be expected in metabolic disturbance. The TAFI levels were also elevated in thrombotic diseases. In keeping with the role of TAFI as an antifibrinolytic factor, high plasma level of TAFI is a risk factor for thrombotic diseases. Meanwhile, TAFI levels are reduced in acquired hemostatic dysfunctions, such as post-partum hemorrhage and sepsis accompanying disseminated intravascular coagulation [3], because the enhanced generation of thrombin or plasmin may result in enhanced TAFI activation and consequent consumption of the TAFI zymogen. Many different methods for measuring TAFI by using ELISA, enzymological methods, or functional methods have been described. All the methods have their inherent advantages and disadvantages, and to date, there is no reference standard for TAFI. Most studies have used the total antigen level of TAFI, but this has yielded ambiguous results, because of the existence of different isoforms and various degrees of activation. Ceres et al. [8] have reported the use of an ELISA that specifically detects TAFI activation. Since substantial TAFI activation occurs in acquired hemostatic dysfunction, ELISA that measures the extent of TAFI activation is potentially useful. In this issue of the Korean Journal of Hematology, Park et al. [9] reported high levels of TAFI activation in sepsis patients by measuring TAFIa/ai levels using an ELISA that they developed in-house. In the in-house ELISA, potato tuber carboxypeptidase inhibitor was used as a capture agent that specifically captured the activated and inactivated TAFI isoforms and did not capture the intact TAFI zymogen. Although only a few septic patients (n=25) were enrolled in the study, the activation status of TAFI could clearly differentiate septic patients from healthy controls. This result is in agreement with the results of a recent study [10] that reported a significant elevation of TAFI activation in meningococcal infection. Since decreases in total TAFI level are associated with increases of TAFI activation level, simultaneous determination of total TAFI and TAFI activation marker is required to interpret the role of TAFI in acquired hemostatic dysfunctions including sepsis. Although the principal physiologic role of TAFI is still a matter of debate, TAFI is reported to be an important protein in the fibrinolytic system. The advent of more accurate assays for measuring plasma TAFI levels may help validate the mechanism underlying TAFI activation in acquired hemostatic dysfunction. This information may help elucidate the contribution of the TAFI pathway to acquired hemostatic dysfunction and will form the basis of potential therapeutic strategies to manipulate the TAFI pathway for acquired hemostatic dysfunction.

Diagnosis and Initial Treatment of Venous Thromboembolism in Patients With Cancer

Venous thromboembolism (VTE) is a common complication of cancer and its therapy. The purpose of this article is to review the diagnosis and initial treatment of VTE in the patient with cancer. I conducted a survey of the English-language literature on topics relevant to the diagnosis and initial treatment of VTE in patients with cancer. Patients with cancer are at increased risk for VTE because of the presence of multiple risk factors for thrombotic disease. The most common signs and symptoms of VTE as well as the utility of clinical prediction rules and D-dimer testing in the diagnosis of VTE in the patient with cancer are reviewed. Duplex ultrasound and computer tomography angiography are the primary objective diagnostic modalities for VTE. Low molecular weight heparin is the preferred initial therapy for VTE. Until further data emerge, thrombolysis and vena cava filters should be reserved for patients in whom anticoagulation is insufficient or contraindicated. Outpatient management is feasible for carefully selected patients with cancer with deep vein thrombosis (DVT) and low-risk pulmonary embolism. Anticoagulation is the preferred initial therapy for cancer patients with central venous catheter-associated DVT, calf DVT, and unsuspected VTE. Optimal initial management of VTE in patients with cancer entails maintaining a high index of suspicion for thrombotic disease, confirming diagnostic suspicions with objective testing and evidence-based use of anticoagulation, and adjunctive therapeutic modalities (thrombolysis, vena cava interruption, venous stenting). Further investigation of initial diagnostic and treatment strategies for VTE focusing on patients with cancer are warranted.

Regulation of Human Thrombin-Activable Fibrinolysis Inhibitor Gene Expression in Megakaryocyte-Like (Dami) and Monocyte/Macrphage- Like (THP-1) Cell Lines

Thrombin-activable fibrinolysis inhibitor (TAFI) is a carboxypeptidase zymogen defining a pathway that functions as a molecular link between coagulation and fibrinolysis. Activation by thrombin, the thrombin-thrombomodulin complex, or plasmin, the resultant enzyme (TAFIa) affects the balance between these two cascades by attenuating positive feedback in the fibrinolytic cascade, thereby inhibiting fibrin clot lysis. Plasma TAFI antigen levels vary significantly between individuals, which has implicated TAFI as a risk factor for thrombotic diseases. TAFIa can also inactivate pro-inflammatory peptides such as the anaphylatoxins and bradykinin, suggesting a role for the TAFI pathway as a link between coagulation and inflammation. TAFI expression in cultured hepatic cells is decreased by interleukins −1 and −6, and plasma TAFI levels in human are decreased in experimental endotoxemia. Although the liver is the main source of plasma TAFI, TAFI has also been identified in platelets, and TAFI mRNA has been detected in the Dami (megakaryoblastic) cell line (but not the MEG-01 cell line). TAFI mRNA has also been detected in adipocytes of patients with type 2 diabetes; however, TAFI mRNA expression in human umbilical vein endothelial cells is still a point of controversy. It has been hypothesized that platelet TAFI arises from TAFI gene expression in megakaryocytes (MK). Using RT-PCR and real-time RT-PCR, we not only confirmed the presence of TAFI mRNA in Dami cells, but also found that TAFI mRNA abundance was increased throughout Dami cell differentiation along the megakaryocytes/platelet lineage (up to 8 fold increase after 48 hours) stimulated by phorbol myristate acetate (PMA) treatment. The quantitative real-time RT-PCR experiments revealed that TAFI mRNA is present in differentiated Dami cells at a level that is only one-hundredth of that observed in HepG2 (hepatoma) cells. Using transfection experiments with luciferase reporter plasmids containing progressive deletions of the human TAFI 5′-flanking region, we identified the sequence between −438 and −257 (relative to the initiator methionine codon) to be responsible for the enhanced TAFI gene transcription as Dami cells differentiate into more mature MK-like cells. Moreover, using western blot analysis, we detected TAFI protein expression in the medium of differentiated Dami cells, but not untreated Dami cells. Together, these data provide further evidence supporting the idea that platelet TAFI is generated from TAFI gene expression in megakaryocytes rather than by uptake from the plasma. To study TAFI gene regulation in monocytes and macrophages, RT-PCR and realtime RT-PCR were used to detected and quantify, respectively, TAFI mRNA expression in both THP-1 and THP-1 cells that have been differentiated into macrophage-like cells (THP-1ma) by PMA treatment. TAFI mRNA abundance was similar in THP-1 cells as what was observed in differentiated Dami cells. In addition, we found a progressive decrease in TAFI mRNA abundance throughout the THP-1 differentiation with an 85% decrease after 24 hours of PMA treatment. Transfection experiments using luciferase reporter plasmids representing progressive deletions of the human TAFI 5′-flanking region identified sequences between −151 and −121 as harboring key promoter elements for the differentiation-associated decrease in TAFI gene expression as THP-1 differentiate into macrophage-like cells. However, no TAFI protein was detected in either THP-1 or THP-1ma conditioned medium using western blot analyses. Nonetheless, extra-hepatic expression of TAFI, such as platelet, monocytes and macrophages, suggests novel roles for TAFI pathway beyond regulation of fibrin clot breakdown.

A genome-wide exploration suggests an oligogenic model of inheritance for the TAFI activity and its antigen levels

Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) is a protein that potently attenuates fibrinolysis. A considerable proportion of its variability levels is genetically determined. It has been associated with arterial and venous thrombosis. We conducted a Genome Wide Scan for genes affecting variation in plasma TAFI levels in 398 subjects from 21 extended Spanish families. The data were analyzed by a variance-component linkage method. A strong linkage signal was found on the long arm of Chromosome 13, near the DNA marker D13S156, where the structural gene encoding for TAFI is located. In addition, other new linkage signals were detected on chromosome regions 5p and 7q. More importantly, we performed another multipoint linkage analysis of functional TAFI conditioned on TAFI antigen levels. We detected a strong linkage signal on Chromosome 19 (LOD = 3.0, P = 0.0001) suggesting a novel QTL in this region involved in the specific functional activity of TAFI, regardless of the TAFI antigen levels. One notable aspect of this study is the identification of new QTLs that reveal a clearer picture of the genetic determinants responsible for variation in TAFI levels. Another is the replication of the linkage signal of the CPB2 gene, which confirms an important genetic determinant for TAFI antigen levels. These results strongly suggest an oligogenic mode of inheritance for TAFI, in which CPB2 gene accounts for a proportion of the variation of the phenotype together with other unknown genes that may represent potential risk factors for thrombotic disease.

RECURRENT THROMBO-EMBOLISM IN A CHILD WITH A CONGENITAL DISORDER OF GLYCOSYLATION (CDG) TYPE IB AND TREATMENT WITH MANNOSE

Thrombosis is a multifactorial disorder. Congenital disorders of glycosylation (CDG) are one of the known risk factors for its occurrence. These disorders result in glycosylation defects of glycoproteins, including those of the (anti-)coagulation system. CDG-Ib can specifically be treated with mannose, as illustrated by the case of a 4-year-old girl in whom deep venous thrombosis was the presenting symptom after a common viral infection. The diagnosis was made after recurrent episodes of thrombo-embolism and consumptive coagulopathy. After treatment with mannose no such episodes recurred. The pathophysiology of CDG as a risk factor for thrombotic disease is discussed.

Cerebrovascular disease associated with antiphospholipid antibodies: more questions than answers

Neurological syndromes occur in a significant number of patients with antiphospholipid antibodies. The optimal management for these patients however remains uncertain.Our study is a descriptive analysis looking retrospectively at 45 patients who presented to the principal tertiary referral centre in the Australian Capital Territory, with either cerebral arterial or venous thrombosis for which there was no obvious cause for their presentation when initially reviewed. The diagnosis was based on the clinical findings made by one of three neurologists attached to our centre. Radiological findings and the presence of either IgM or IgG anticardiolipin antibodies, IgG anti-beta-2 glycoprotein 1 antibodies or a lupus anticoagulant were then documented.In this group of patients three subgroups were identified:1. Individuals that fulfilled the Sapporo Classification Criteria2. Individuals with transiently positive antiphospholipid antibodies and3. Individuals with persistently low positive antiphospholipid antibodies.The most interesting of these three groups are those individuals with transiently positive antiphospholipid antibodies. A potential cause for presentation was identified in only one patient of this group with documented infective endocarditis and bacteraemia. Comparison with the other two groups suggested that there was little in terms of clinical presentation, radiological findings or intercurrent risk factors for thrombotic disease to distinguish between them. With disappearance of antiphospholipid antibodies, the individuals within this group have not had further thrombotic events.Our observations emphasise the problems that continue to exist in relation to the occurrence of cerebrovascular disease in the context of antiphospholipid antibodies and the optimal management of these stratified groups. Our findings also raise an as yet unanswered question as to the signficance of these transiently positive antiphospholipid antibodies. In the absence of significant intercurrent risk factors our findings would suggest that in the group we describe that they are likely to be of clinical significance.