bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lack of In Vivo Function of CD31 in Vascular Thrombosis
Authors: Schmits R. , Kunz D. , Menger M. D. , Vollmar B. 
Published: March 2018

SummaryA murine model of endothelial cell injury-based vascular thrombosis was used to test the role of platelet-endothelial cell adhesion molecule-1 (PECAM-1, CD31) in blood cell aggregate formation and vessel occlusion in vivo. Photochemically-induced thrombus formation was analyzed in detail using intravital fluorescence microscopy of individual microvessels in cremaster muscle preparations of CD31-deficient and wildtype mice. In venules, epi-illumination induced rapid thrombus formation with first platelet deposition after 0.56 ± 0.11min and complete vessel occlusion within 5.05 ± 0.45 min. In arterioles, thrombus formation was markedly delayed with first platelet deposition after 3.03 ± 0.47 min and complete vessel occlusion within 10.04 ± 1.26 min. Kinetics of thrombus formation in both venules (first platelet deposition: 0.52 ± 0.1 min; vessel occlusion: 5.03 ± 0.52 min) and arterioles (first platelet deposition: 3.06 ± 0.68 min; vessel occlusion: 10.02 ± 1.38 min) of CD31-deficient mice was found almost identical compared with that in wildtype animals. Tail bleeding time was 233 ± 24 s in wildtype and 243 ± 32 s in CD31-deficient mice. Moreover, CD31-deficient and wildtype mice revealed comparable interaction of leukocytes to endothelium. This study shows for the first time in vivo that CD31 is not critically involved in blood cell thrombus formation upon endothelial cell injury.
New and Effective Treatment of Experimentally Induced Venous Thrombosis with Anti-inflammatory rPSGL-Ig
Authors: Myers Daniel , Wrobleski Shirley , Londy Frank , Fex Beverly , Hawley Angela , Schaub Robert , Greenfield Lazar , Wakefield Thomas 
Published: March 2018

SummaryP-selectin antagonism decreases thrombosis and inflammation in animal models of venous thrombosis (VT) prophylaxis. This study defines results using a P-selectin receptor antagonist for VT treatment.Eight juvenile baboons underwent 6 h of iliofemoral venous stasis to produce an occlusive VT. Two days later, animals were treated for 14 days with rPSGL-Ig, 4 mg/kg (n3), LMWH (n2) or saline (n3) and treatment continued weekly (rPSGL-Ig) or daily (LMWH, saline). The animals were examined and sacrificed 14 days after treatment initiation (n4) or on day 90 (n4).Percent spontaneous vein reopening revealed a significant increase (p <0.05) in the proximal iliac vein in rPSGL-Ig and LMWH animals compared to controls (62%, 70% vs 8%), without differences in inflammation. No anticoagulation, thrombocytopenia, or wound complications were found in rPSGL-Ig animals. At 90 days, recanalization with iliac vein valve competence was found in treated animals.rPSGLIg successfully treated established VT without anticoagulation.
Human Factor VIII Inhibitor Alloantibodies with a C2 Epitope Inhibit Factor Xa-catalyzed Factor VIII Activation: A new Anti-factor VIII Inhibitory Mechanism
Authors: Nogami Keiji , Nishiya Katsumi , Sakurai Yoshihiko , Tanaka Ichiro , Giddings John , Saenko Evgueni , Yoshioka Akira , Shima Midori 
Published: March 2018

SummaryFactor VIII (FVIII) inhibitor alloantibodies react with the A2, C2, or A3-C1 domains of FVIII and inactivate FVIII activity. We recently demonstrated that an anti-C2 monoclonal antibody with a Val2248Gly2285 epitope, inhibited factor Xa (FXa)-catalyzed FVIII activation, and that a FXa binding site for FVIII was located within residues Thr2253-Gln2270. In this study, we investigated whether anti-C2 alloantibodies inhibit FXa-catalyzed FVIII activation. Anti-C2 alloantibodies from four patients inhibited FVIII activation by FXa in onestage clotting assay. Furthermore, analysis by SDS-PAGE showed that all alloantibodies inhibited FVIII proteolytic cleavage by FXa independently of phospholipid. To confirm direct inhibition of FVIII and FXa interaction, we examined the effect of alloantibodies on FVIII binding to anhydro-FXa, a catalytically inactive FXa, in ELISA. All alloantibodies and C2-affinity purified F(ab)’2 preparations inhibited FVIII binding to anhydro-FXa dose-dependently. Our results revealed a new inhibitory mechanism of FVIII, mediated by inhibition of FXa in the presence of anti-C2 alloantibodies.
Hydroxychloroquine Reverses Platelet Activation Induced by Human IgG Antiphospholipid Antibodies
Authors: Espinola Ricardo , Ghara Azzudin , Harris E. , Pierangeli Silvia 
Published: March 2018

SummaryProthrombotic properties of antiphospholipid (aPL) antibodies may be explained in part by their ability to enhance the activation of platelets pre-treated with low doses of ADP or thrombin. The antimalarial drug hydroxychloroquine (HQ) has been used successfully in prevention of postoperative thrombosis and in treatment of patients with SLE or APS. In one study, administration of HQ reversed the thrombogenic properties of aPL in mice. However, the mechanism of action of HQ in preventing thrombosis is not clearly understood. In order to explore this further, the effects of HQ on activation of platelets by aPL in the presence of a thrombin agonist was studied. The changes in the expression of GPIIb/IIIa (CD41a) and GPIIIa (CD61) on platelet membrane by flow cytometry were used as indicators of platelet activation. Citrated whole blood from a healthy donor was treated at room temperature with suboptimal doses of a thrombin agonist receptor peptide (TRAP) and affinity-purified aPL antibodies, in the presence and in the absence of hydroxychloroquine (1 mM). TRAP increased the expression of GPIIb/IIIa and GPIIIa on platelet surface. The treatment of the platelets with the six aPL antibodies in the presence of 12 nMol/ml TRAP further increased the expression of GPIIb/IIIa by 42.3 ± 12.3% and the expression of GPIIIa was further incremented by 46.8 ± 13.5%. The effects of aPL and TRAP on expression of platelet surface markers of activation was completely abrogated by HQ in a dose-dependent fashion and was effective at concentrations of HQ as low as 25 µg/ml (0.0125 mM). This suggests at least one possible mechanism by which HQ may prevent thrombosis. This may have important implications in treatment of thrombosis in APS patients.
New Aspects in Thrombosis Research: Possible Role of Mast Cells as Profibrinolytic and Antithrombotic Cells
Authors: Baghestanian M. , Bankl H. C. , Sillaber C. , Sperr W. R. , Wojta J. , Binder B. R. , Lechner K. , Valent P. 
Published: March 2018

SummaryVenous thromboembolism represents a significant cause of morbidity worldwide. The factors that underly thrombophilia are manifold. The concept of Virchow defines the well known triad of stasis, humoral factors, and pathologies of the vascular wall. In the current article, an additional factor, the “accumulation of repair cells” is discussed. This novel concept highlights the mast cell that accumulates around thrombosed vessels and provides a number of important repair molecules including heparin, profibrinolytic tPA, and fibrinogenolytic β-tryptase. Thus, mast cell recruitment and activation may result in local thrombolysis and prevention of coagulation. In line with this concept, mast cell-deficient mice are more susceptible to lethal thrombogenic stimuli compared to normal mice. The factors (cytokines) that trigger mast cell accumulation and release of repair molecules have also been identified – the most important one appears to be stem cell factor (SCF). All in all, our novel concept suggests that the patho-physiology of thrombosis may involve a “physiologic” cell that provides the same repair molecules that are used for treatment of thrombotic disorders by the physician. Whether an altered availability of components of this cellular repair system can predispose for thrombophilia remains to be determined.
Complete Defect in vWF-cleaving Protease Activity Associated with Increased Shear-induced Platelet Aggregation in Thrombotic Microangiopathy
Authors: Ajzenberg Nadine , Denis Cécile , Veyradier Agnès , Girma Jean-Pierre , Meyer Dominique , Baruch Dominique 
Published: March 2018

SummaryVon Willebrand factor (vWF) cleaving metalloprotease activity represents an important factor in understanding the pathophysiology of thrombotic microangiopathies (TMA). Thrombotic events, leading to dramatic complications, occur preferentially in the microvasculature. Our aim was to determine the ability of TMA plasma with a complete deficiency of protease activity to promote shear-induced platelet aggregation (SIPA) at high shear rates using a coaxial cylinder shearing device. We have demonstrated the ability of four out of seven TMA plasma to aggregate normal washed platelets at 4,000 s−1. In these four TMA plasma, significant SIPA was obtained, whereas control plasma did not induce more SIPA than buffer. The % of unusually large (UL) multimers in TMA plasma varied from 1 to 18%. Surprisingly, the extent of SIPA in TMA plasma appeared independent of the percentage of UL multimers. Interestingly, anti-GPIb antibody 6D1 could block completely this pathological aggregation, opening new therapeutic possibilities. In contrast, none of eight other TMA patients’ plasma with a normal protease activity, exhibited any increase of SIPA compared with control plasma. These results strongly suggest that the deficiency of vWF-cleaving protease appears to be necessary, but not sufficient for elevated SIPA. In contrast, the % of UL is not associated with increased SIPA.
Functional Role of p38 Mitogen Activated Protein Kinase in Platelet Activation induced by a Thromboxane A2 Analogue and by 8-iso-prostaglandin F2
α
Authors: Gaino Stefania , Zuliani Valeria , Tommasoli Rosa , Benati Donatella , Ortolani Riccardo , Zancanaro Carlo , Berton Giorgio , Santonastaso Clara , Minuz Pietro 
Published: March 2018

SummaryWe investigated similarities in the signaling pathways elicited by the F2 isoprostane 8-iso-PGF2α and by low doses of U46619 to induce platelet activation. Both 0.01-0.1 µmol/L U46619 and 0.01-1 µmol/L 8-isoPGF2α triggered shape change and filopodia extension, as well as adhesion to immobilized fibrinogen of washed platelets. At these doses the two platelet agonists failed to trigger secretion and aggregation, which were however induced by higher doses of U46619 (0.1-1 µmol/L). SB203580 (1-10 µmol/L), a specific inhibitor of the p38 mitogen activated protein (MAP) kinase blunted platelet shape change and adhesion induced by 0.05-1 µmol/L 8-iso-PGF2α and by 0.01 µmol/L U46619. These platelet responses were also inhibited by 20 µmol/L cytochalasin D, an inhibitor of actin polymerization, and 50 µmol/L piceatannol, an inhibitor of the Syk tyrosine kinases. Both 8-iso-PGF2α and U46619-induced p38 MAP kinase phosphorylation in suspended platelets and this was inhibited by piceatannol, indicating that Syk activation occurs upstream p38 MAP kinase phosphorylation. These findings suggest that the signaling pathway triggered by both 8-iso-PGF2α and low concentrations of U46619 to induce platelet adhesion and shape change implicates Syk, the p38 MAP kinase, and actin polymerization.
Increased Angiostatin Levels in Bronchoalveolar Lavage Fluids from ARDS Patients and from Human Volunteers after Lung Instillation of Endotoxin
Authors: Lijnen H. , Suffredini Anthony , Pepper Michael , Steinberg Kenneth , Martin Thomas , Pugin Jérôme , Lucas Rudolf 
Published: March 2018

SummaryAcute respiratory distress syndrome (ARDS) is characterized by a disruption of the alveolar-capillary barrier, due to both an epithelial and an endothelial dysfunction. Whereas epithelial apoptosis seems to be mainly mediated by Fas ligand, the mediators of endothelial damage remain to be identified. Angiostatin, a powerful inhibitor of angiogenesis in vivo, also specifically induces apoptosis in endothelial cells. The concentration of various enzymes that cleave angiostatin from plasminogen was reported to be significantly increased in bronchalveolar lavage (BAL) fluids from patients with ARDS. Therefore, in this study, we investigated whether angiostatin was generated during the pulmonary inflammatory response of both healthy subjects challenged with endobronchial endotoxin and in patients with ARDS. We found significantly elevated angiostatin levels in BAL fluids from patients at risk for and with early ARDS (up to 0.022% and 0.018% of total protein, respectively), as well as in BAL fluids from volunteers treated with endotoxin (up to 1.17% of total protein), as compared to BAL fluids from control patients (<0.005% of total protein). These data suggest that angiostatin may contribute to the endothelial damage observed in ARDS, probably via an increased permeability of the alveolar capillary barrier, allowing for an intra-alveolar processing of its precursor plasminogen.
Anticoagulant and Membrane-degrading Effects of Secretory (Non-pancreatic) Phospholipase A2 Are Inhibited in Plasma
Authors: Billy Didier , Speijer Han , Zwaal Robert , Hack Erik , Hermens Wim 
Published: March 2018

SummaryPlasma concentrations of secretory (non-pancreatic) phospholipase A2 (sPLA2) may rise 1000-fold during inflammation, and this acute phase response has been related to anticoagulant effects. In the present study this hypothesis was further investigated.Prothrombinase activity was measured for model membranes mimicking the phospholipid composition of the outer membrane of resting and activated blood platelets. Using ellipsometry, membrane degradation by sPLA2 could be measured simultaneously with inhibition of thrombin production. The same technique was used to study clotting, by the sudden appearance of fibrin strands on the membrane. Results were compared with the effects of sPLA2 on the activation of washed platelets and platelets in plasma.In buffer solution, model membranes were degraded by (patho)physiological concentrations of sPLA2. Even when only partially degraded, membranes rapidly lost their prothrombinase activity, indicating preferential degradation of phosphatidylserine. Addition of diluted plasma interfered with membrane degradation, and also with inhibition of prothrombinase activity. In agreement with these observations, sPLA2 inhibited thrombin production and annexin V-binding of activated washed platelets, but had no effects on platelet activation or clotting in plasma. These findings indicate that the elevated plasma sPLA2 concentrations observed in inflammatory disease will not reduce hypercoagulability in such patients.
Polymorphonuclear Leucocytes Have Two Opposing Roles in Fibrinolysis
Authors: Moir E. , Robbie L. A. , Bennett B. , Booth N. A. 
Published: March 2018

SummaryPolymorphonuclear leucocytes (PMN) are important in the resolution of human thrombi, with u-PA as a key player. We have shown that the u-PA activity of PMN depends on the presence of plasma; the study presented here provides an explanation for that requirement. Here we show that PMN degraded scu-PA and also tcu-PA, t-PA and plasmin, resulting in loss of fibrinolytic activity. Plasma protected against this degradation; α1-antitrypsin was identified as a protective factor. Purified human neutrophil elastase mirrored the effects of PMN, again neutralized by plasma inhibitors. These findings illustrate the dual role of PMN in the breakdown of thrombi, in that they contribute both u-PA, which lyses fibrin, and other proteases, including elastase, which can cleave fibrin and plasminogen activators/plasmin. Similarly, plasma can potentiate fibrinolysis by neutralization of PMN elastase, in addition to direct inhibition of fibrinolytic proteases. Our previous studies show that PMN in thrombi are mostly pro-fibrinolytic; the antifibrinolytic role defined here may be important in other pathologies where fibrin persists.
The R2-haplotype associated Asp2194Gly mutation in the light chain of human factor V results in lower expression levels of FV, but has no influence on the glycosylation of Asn2181
Authors: Dirven Richard , Vos Hans , Bertina Rogier , Kolfschoten Marijn 
Published: March 2018

SummaryThe R2 haplotype of the FV gene spans from exon 8 through 25 and comprises several strongly linked polymorphisms in the FV gene, including some missense mutations. Carriership of the R2-FV allele has been associated with reduced plasma FV levels, increased FV1/FV2 ratios and mild APC resistance. Some studies have reported that carriership of the R2-FV allele is associated with an increased risk of venous thombosis. At this moment, the individual contribution to the R2-associated phenotypes of the different mutations linked to the R2 haplotype of FV is unclear. The main objective of our study was to obtain insight in the influence of the R2-related Asp2194Gly mutation on FV expression, FV structure and FV function using B-domainless rFV mutants. Replacing Asp at position 2194 by Gly resulted in a more than threefold reduction of rFV expression compared to rFV wild-type. Therefore, we propose that the R2-linked Asp2194Gly mutation is an important determinant of the association of the R2-FV allele with lower FV levels. Furthermore, the light chains from Asp2194Gly containing rFV mutants showed similar molecular weights as the light chains of the non-glycosylated rFVwt or the plasma FV2 isoform, indicating that glycosylation at Asn2181 is not stimulated by the presence of a glycine in position 2194. Finally, the apparent K
d for dissociation of the FXaVa complex (K
1/2Xa) was not higher in rFV mutants with the Asp2194Gly mutation than for rFVwt, suggesting that also the affinity for negatively charged phospho-lipids is not affected by substitution of Asp into Gly at position at 2194.
Compliance and stability of INR of two oral anticoagulants with different half-lives: a randomised trial
Authors: Quenet Sara , Buchmüller-Cordier Andréa , Reynaud Jacqueline , Tardy-Poncet Brigitte , Thirion Christine , Decousus Hervé , Mismetti Patrick , Laporte Silvy 
Published: March 2018

SummaryThe aim of the study was to assess the respective roles of the half-life of elimination of oral anticoagulants and patient education as causes of instability of anticoagulation level in patients on oral anticoagulant therapy. Patients were randomised to receive either warfarin (long half-life) or acenocoumarol (short half-life) and either intensive or standard education, according to a factorial design. Instability of oral anticoagulant therapy was evaluated by the percentage of INRs and the time within the target range, and the variability between successive measurements. Compliance was assessed by means of electronic pill bottles. Eighty-six patients were included. Apart from the variability index, instability was similar between groups. Correlations between compliance and instability were observed only in the acenocoumarol group. No difference was found between the education groups. In patients starting oral anticoagulant therapy, dose determination may be the most important factor contributing to instability.
Age at first treatment and immune tolerance to factor VIII in severe hemophilia
Authors: Mauser-Bunschoten Eveline , Fischer Kathelijn , van den Berg Marijke , van der Bom Johanna 
Published: March 2018

SummaryFindings from a recent study suggest that earlier start of treatment with factor VIII in patients with severe hemophilia is associated with a higher risk to develop inhibitors.We set out to assess the association between age of first administration of clotting factor VIII and the risk to develop inhibitors in infants with severe hemophilia A.This work was a cohort study, carried out in the national hemophilia treatment center. The study included eighty-one consecutive patients with severe hemophilia A who received their first dose of factor VIII between 1975 and 1998. Patients were followed until their last visit in 2001 or 2002.The average follow-up was 16 years (range 3-26). Persistent inhibitory antibodies developed in 12 of 81 patients (15%).Cumulative incidence at 100 exposure days was 34% (95% confidence interval 7-61%) in patients starting therapy before the age of 6 months, 20% (4-36%) in patients starting therapy between 6 months and 1 year, 13% (0-27%) in those starting therapy between 1 and 1.5 years, and 0% in those who started therapy beyond 1.5 years of age (p for trend 0.03).Our findings confirm that age of first factor VIII administration in children with severe hemophilia A is inversely associated with the risk to develop antibodies against factor VIII. The role of confounding factors such as the type of factor VIII mutation and environmental factors needs to be evaluated.
Obesity: risk of venous thrombosis and the interaction with coagulation factor levels and oral contraceptive use
Authors: Abdollahi Morteza , Cushman Mary , Rosendaal Frits 
Published: March 2018

SummaryDeep vein thrombosis (DVT) is a common disease with an annual incidence of about 1 in 1000. Many risk factors have already been studied, both genetic and acquired. It is unclear whether obesity affects thrombotic risk in unselected patients. Obesity is common, with a prevalence of 20-25% and may therefore have a considerable impact on the overall incidence of thrombosis. We evaluated the risk of thrombosis due to overweight and obesity using data from a large population based case-control study.Four hundred and fifty-four consecutive patients with a first episode of objectively diagnosed thrombosis from three Anticoagulation Clinics in the Netherlands were enrolled in a case-control study. Controls were matched on age and sex to patients and were introduced by the patients. All patients completed a standard questionnaire and interview, with weight and height measured under standard conditions. The associations of obesity with clotting factor levels were studied to investigate possible mechanisms.Obesity (BMI ≥30 kg/m2) increased the risk of thrombosis twofold (CI95: 1.5 to 3.4), adjusted for age and sex. Obese individuals had higher levels of factor VIII and factor IX, but not of fibrinogen. The effect on risk of obesity was not changed after adjustment for coagulation factors levels (fibrinogen, F VIII, F IX, D-dimer). The relative risk estimates were similar in different age groups and in both sexes, indicating a larger absolute effect in older age groups. Evaluation of the combined effect of obesity and oral contraceptive pills among women aged 15-45 revealed that oral contraceptives further increased the effect of obesity on the risk of thrombosis, leading to 10-fold increased risk amongst women with a BMI greater than 25 kg/m2 who used oral contraceptives.Obesity is a risk factor for deep vein thrombosis. Among women with a BMI greater than 25 kg/m2 the synergistic effect with oral contraceptives should be considered when prescribing these.