Mechanism of action of antiplatelet drugs on decompression sickness in rats: a protective effect of anti-GPIIbIIIa therapy

2015 ◽  
Vol 118 (10) ◽  
pp. 1234-1239 ◽  
Author(s):  
Kate Lambrechts ◽  
Jean-Michel Pontier ◽  
Aleksandra Mazur ◽  
Michaël Theron ◽  
Peter Buzzacott ◽  
...  
Keyword(s):  
Protective Effect ◽  
Vascular Function ◽  
Decompression Sickness ◽  
Statistical Significance ◽  
Thiobarbituric Acid ◽  
Platelet Factor ◽  
Hyperbaric Exposure ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Acetyl Salicylate

Literature highlights the involvement of disseminated thrombosis in the pathophysiology of decompression sickness (DCS). We examined the effect of several antithrombotic treatments targeting various pathways on DCS outcome: acetyl salicylate, prasugrel, abciximab, and enoxaparin. Rats were randomly assigned to six groups. Groups 1 and 2 were a control nondiving group (C; n = 10) and a control diving group (CD; n = 30). Animals in Groups 3 to 6 were treated before hyperbaric exposure (HBE) with either prasugrel ( n = 10), acetyl salicylate ( n = 10), enoxaparin ( n = 10), or abciximab ( n = 10). Blood samples were taken for platelet factor 4 (PF4), thiobarbituric acid reactive substances (TBARS), and von Willebrand factor analysis. Onset of DCS symptoms and death were recorded during a 60-min observation period after HBE. Although we observed fewer outcomes of DCS in all treated groups compared with the CD, statistical significance was reached in abciximab only (20% vs. 73%, respectively, P = 0.007). We also observed significantly higher levels of plasmatic PF4 in abciximab (8.14 ± 1.40 ng/ml; P = 0.004) and enoxaparin groups (8.01 ± 0.80 ng/ml; P = 0.021) compared with the C group (6.45 ± 1.90 ng/ml) but not CD group (8.14 ± 1.40 ng/ml). Plasmatic levels of TBARS were significantly higher in the CD group than the C group (49.04 ± 11.20 μM vs. 34.44 ± 5.70 μM, P = 0.002). This effect was prevented by all treatments. Our results suggest that abciximab pretreatment, a powerful glycoprotein IIb/IIIa receptor antagonist, has a strong protective effect on decompression risk by significantly improving DCS outcome. Besides its powerful inhibitory action on platelet aggregation, we suggest that abciximab could also act through its effects on vascular function, oxidative stress, and/or inflammation.

scholarly journals Factor VIII Inhibitors: Von Willebrand Factor Makes A Difference In Vitro and In Vivo

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 709-709
Author(s):  
Qizhen Shi ◽  
Erin L. Kuether ◽  
Jocelyn A. Schroeder ◽  
Crystal L. Perry ◽  
Scot A. Fahs ◽  
...  
Keyword(s):  
Protective Effect ◽  
Hemophilia A ◽  
Inhibitory Antibody ◽  
Chromogenic Assay ◽  
Fviii Activity ◽  
Inhibitory Antibodies ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Abstract 709 The important association between von Willebrand factor (VWF) and factor VIII (FVIII) has been investigated for decades, but the effect of VWF on FVIII inhibitors is still controversial. Studies have demonstrated that some anti-FVIII inhibitory antibodies inhibit VWF-FVIII interaction, while others rely on the presence of VWF to inhibit FVIII activities. The influence of VWF on the Bethesda assay, which is routinely used in the clinic to determine the titer of FVIII-neutralizing inhibitors, is still uncertain because the plasma from hemophilia A patients with inhibitors contains normal levels of VWF. To explore the effect of VWF on the reactivity of FVIII inhibitors, we immunized VWF and FVIII double knockout (VWFnullFVIIInull) mice with recombinant human B-domain deleted FVIII (rhFVIII) to induce anti-FVIII inhibitory antibody development. Inhibitory plasma was collected and the titer of inhibitors was determined by Bethesda assay. Murine plasma-derived VWF (from FVIIInull mice) or recombinant human VWF (rhVWF) was used to study the influence of VWF on inhibitor inactivation of FVIII activity (FVIII:C). The remaining FVIII:C after inactivation was determined by chromogenic assay. When inhibitory plasma was incubated with rhFVIII in the presence of 1 U/ml VWF, the residual FVIII activity recovered was higher than in the absence of VWF, resulting in 6.82 ± 1.12 (n = 27) fold lower apparent inhibitor titers. This protective effect is VWF dose dependent. The source of VWF (plasma-derived murine VWF vs. rhVWF) did not affect its protection of FVIII from inhibitor inactivation and VWF does not affect FVIII:C measured in the chromogenic assay in the absence of inhibitors. Interestingly, we found that inhibitor inactivation of FVIII:C in the absence of VWF occurred much faster than in its presence. When the usual 2 hr. incubation at 37°C was omitted from the Bethesda assay, adding rhVWF to rFVIII before mixing with inhibitory plasma resulted in 67.29 ± 20.18 (n = 5) fold lower apparent inhibitor titers than without added VWF. In contrast, if VWF was added to inhibitory plasma first and then mixed with rhFVIII, the inhibitor titers were only 11.04 ± 3.56 (n = 5) fold lower than without added VWF. These results indicate that rhFVIII present in a preformed VWF-FVIII complex is protected from inhibitory antibody inactivation. Conversely, when VWF and inhibitory plasma are added to rhFVIII at the same time, the VWF and inhibitors appear to compete to bind to rhFVIII. Inhibitor titers were lower than in the absence of VWF, but the protective effect is not as efficient as when VWF and rhFVIII were already associated with one another before encountering inhibitors. To confirm the protective effect of VWF on FVIII from inhibitor inactivation, we infused FVIIInull or VWFnullFVIIInull mice with inhibitory plasma and rhFVIII followed by a tail clip survival test. When rhFVIII was infused into FVIIInull mice to 2% followed by inhibitory plasma infusion, all mice with inhibitor titer of 2.5 BU/ml (n = 4) survived tail clipping, and 2 of 4 survived with either 25 BU/ml or 250 BU/ml. If inhibitory plasma was infused first followed by rhFVIII infusion, then only 2 of 6 mice with inhibitor titers of 2.5 BU/ml survived tail clip challenge and none survived with 25 BU/ml and 250 BU/ml. In the first set of mice the infused FVIII was able to form a protective complex with endogenous VWF before encountering inhibitors, while in the second set FVIII is exposed to VWF and pre-infused inhibitory antibodies at the same time, a competitive binding that appears to reduce VWF's protective effect. In contrast, when rhFVIII was infused into VWFnullFVIIInull mice followed by inhibitory plasma infusion, no animals (n = 4 for each group) survived tail clipping with inhibitor titers of 2.5 BU/ml or higher. In summary, our studies demonstrate that VWF exerts a protective effect, reducing inhibitor inactivation of FVIII, both in vitro and in vivo. While the role of VWF in stabilizing plasma FVIII in a milieu rich in proteases has been appreciated for decades, our results indicate that treatment utilizing products containing a complex of FVIII with VWF may be especially beneficial in hemophilia A patients with inhibitors. Disclosures: No relevant conflicts of interest to declare.

scholarly journals PROGNOSTIC SIGNIFICANCE OF ENDOTHELIAL DYSFUNCTION MARKERS IN ARTERIAL HYPERTENSION

2018 ◽  
pp. 7-13 ◽  
Author(s):  
V. I. Podzolkov ◽  
A. E. Bragina ◽  
N. A. Bragina
Keyword(s):  
Endothelial Dysfunction ◽  
Enzyme Assay ◽  
Statistical Significance ◽  
Prognostic Significance ◽  
Risk Level ◽  
Risk Increase ◽  
Tissue Plasminogen ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Development Risk

Aim. Assessment of prognostic significance of endothelial dysfunction markers: stable metabolites of nitric oxide (NOx), von Willebrand factor (vWF), endothelin-1 (E1), homocysteine and tissue plasminogen activator (tPA) in essential hypertension (EAH) patients not taking antihypertension therapy systematically.Material  and  methods. Totally, 12 EAH patients investigated (45 males, 79 females) (mean age 51,4±6,5 y. o., mean duration of AH 7,9±7,3 y.). Concentration of NOx in plasma was measured by spectrophotometry, and of vWF, homocysteine, E1 and tPA — by immune enzyme assay.Results. By the increase of SCORE risk level, there was significant increase of concentrations of NOx, E1, homocysteine and vWF in EAH patients (p<0,05), there were no changes in tPA levels (p>0,05). In 8 (8±1,1) years after baseline assessment, 115 patients were assessed second time. Of those 13 (11,3%) had cardiovascular events (CVE) and 5 (4,3%) died. By single factorial regression, the rate of CVE in EAH patients relate to homocystein level (р=0,01), NOx (р=0,001) and vWF (р=0,001). By multifactorial analysis, prognostic statistical significance is found for NOx (relative risk (RR) =3,8, р=0,006) and vWF (RR =3,5, р=0,005). In ROC-analysis there were found threshold levels of NOx (>46,6 mcM/L, AUC =0,863) and vWF (>1,68 mg/dL, AUC =0,738), the increase of which is followed by CVE development risk for the levels of NOx >46,6 mcM/L 3,8 times (sensitivity 81,9% and specificity 65,8%), vWF >1,68 mg/dL — 3,5 times (sensitivity 74,3% and specificity 62,7%). Combination of the parameters point on the risk increase up to 6,5 times (р=0,00007).Conclusion. NOx with the threshold of >46,6 mcM/L (RR =3,8) and vWF >1,68 mg/dL (RR =3,5) do show independent prognostic value for 5-year CVE risk assessment in EAH patients that can be applied as an additional method for risk stratification to estimate a group for more aggressive therapy and CVE prevention.

Studies of α-granule proteins in cultured human megakaryocytes

2003 ◽  
Vol 90 (11) ◽  
pp. 844-852 ◽  
Author(s):  
Dragoslava Veljkovic ◽  
Elisabeth Cramer ◽  
Gulie Alimardani ◽  
Serge Fichelson ◽  
Jean-Marc Massé ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Protein Processing ◽  
Platelet Factor ◽  
Protein Storage ◽  
Granule Protein ◽  
Granule Proteins ◽  
Processing And Storage ◽  
Von Willebrand ◽  
And Storage ◽  
Willebrand Factor

Summaryα-Granule protein storage is important for producing platelets with normal haemostatic function. The low to undetectable levels of several megakaryocyte-synthesized α-granule proteins in normal plasma suggest megakaryocytes are important to sequester these proteins in vivo. α-Granule protein storage in vitrohas been studied using other cell types, with differences observed in how some proteins are processed compared to platelets. Human megakaryocytes, cultured from cord blood CD34+cells and grown in serum-free media containing thrombopoietin, were investigated to determine if they could be used as a model for studying normal α-granule protein processing and storage. ELISA indicated that cultured megakaryocytes contained the α-granule proteins multimerin, von Willebrand factor, thrombospondin-1, β-thromboglobulin and platelet factor 4, but no detectable fibrinogen and factor V. A significant proportion of the α-granule protein in megakaryocyte cultures was contained within the cells (averages: 41 – 71 %), consistent with storage. Detailed analyses of multimerin and von Willebrand factor confirmed that α-granule proteins were processed to mature forms and were predominantly located in the α-granules of cultured megakaryocytes. Thrombopoietin-stimulated cultured megakaryocytes provide a useful model for studying α-granule protein processing and storage.

scholarly journals Recognition of PF4-VWF complexes by heparin-induced thrombocytopenia antibodies contributes to thrombus propagation

Blood ◽  
2020 ◽  
Vol 135 (15) ◽  
pp. 1270-1280 ◽  
Author(s):  
Ian Johnston ◽  
Amrita Sarkar ◽  
Vincent Hayes ◽  
Gavin T. Koma ◽  
Gowthami M. Arepally ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Complex Formation ◽  
Platelet Adhesion ◽  
Thrombus Formation ◽  
Microfluidic System ◽  
Microfluidic Channels ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder mediated by complexes between platelet factor 4 (PF4) and heparin or other polyanions, but the risk of thrombosis extends beyond exposure to heparin implicating other PF4 partners. We recently reported that peri-thrombus endothelium is targeted by HIT antibodies, but the binding site(s) has not been identified. We now show that PF4 binds at multiple discrete sites along the surface of extended strings of von Willebrand factor (VWF) released from the endothelium following photochemical injury in an endothelialized microfluidic system under flow. The HIT-like monoclonal antibody KKO and HIT patient antibodies recognize PF4-VWF complexes, promoting platelet adhesion and enlargement of thrombi within the microfluidic channels. Platelet adhesion to the PF4-VWF-HIT antibody complexes is inhibited by antibodies that block FcγRIIA or the glycoprotein Ib-IX complex on platelets. Disruption of PF4-VWF-HIT antibody complexes by drugs that prevent or block VWF oligomerization attenuate thrombus formation in a murine model of HIT. Together, these studies demonstrate assembly of HIT immune complexes along VWF strings released by injured endothelium that might propagate the risk of thrombosis in HIT. Disruption of PF4-VWF complex formation may provide a new therapeutic approach to HIT.

Platelet Release Reaction in vivo in Patients with Ischemic Heart Disease (IHD) After Exercise and its Prevention with Dipyridamole

1979 ◽  
Author(s):  
H. Yamazaki ◽  
T. Motomiya ◽  
T. Sano
Keyword(s):  
Platelet Aggregation ◽  
Thrombus Formation ◽  
Statistical Significance ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Anti Platelet Drug ◽  
Healthy Control ◽  
Von Willebrand ◽  
Willebrand Factor

Although an interaction between platelets and arteriosclerotic vessel wall is thought to be important in thrombus formation, a little information was obtained in clinical subjects. We have reported that platelet aggregation Increased in patients with IHD after exercise. To analyse the mechanism of this phenomenon, changes in platelet sensitivity to ADP aggregation, plasma von Willebrand factor and beta-thromboglobulin level were measured in 30 IHD and 30 healthy controls before and Immediately after an isometric exercise (handgrip of 50% voluntary contraction for 2 min). Platelet sensitivity and vWF were determined by original methods detecting microscopically the highest dilution of serially two-fold diluted ADP or test plasma mixed with ristocetin to give platelet aggregation. Beta-TG was measured by RIA Kit. An effect of anti-platelet drug was also observed in IHD. The patients with IHD were administered with placebo or dipyridamole (400 mg/day for 4 weeks) in a crossover single blind fashion. Under placebo, platelet sensitivity to aggregation, vWF and beta-TG increased immediately after the exercise with a statistical significance in IHD. In the healthy control and IHD under dipyridamole, these increases were not observed. The phenomenon may suggest that platelets circulating in sclerotic vessels tend to release and are enhanced in reactivity with smaller stimuli than those in healthy. Such changes might be prevented with dipyridamole.

Tissue Factor Firmly Immobilized on Surfaces Promotes Platelet Adhesion and Fibrin Formation in Studies with Circulating Human Blood: Importance of Shear Rate Conditions and FVIIa.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3925-3925
Author(s):  
Raul Tonda ◽  
Irene Lopez-Vilchez ◽  
Ana M. Galan ◽  
Fulgencio Navalon ◽  
Marcos Pino ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Von Willebrand Factor ◽  
Platelet Adhesion ◽  
Statistical Significance ◽  
Low Molecular Weight ◽  
Shear Rates ◽  
Fibrin Formation ◽  
Closure Time ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract While procoagulant activity of tissue factor (TF) has been widely investigated, its possible proadhesive properties towards platelets have not been studied in detail. We explored the interaction of platelets with human TF (hTF) firmly attached to a surface using anticoagulated blood with low molecular weight heparin (20 U/ml) at different shear rates. For studies at 250 s−1 and 600 s−1, TF adsorbed on a synthetic surface was exposed to circulating blood in flat perfusion devices. Deposition of platelets and fibrin formation were evaluated by morphometric, immunocytochemical and ultrastructural methods. For experiments at 5000 s−1, we used the PFA-100™ with experimental cartridges with collagen or collagen-hTF. Effect of rFVIIa was assessed in all experimental settings. Prothrombin fragment F1+2 levels were also measured. At 250 and 600 s−1 platelet interaction was 19.84±1.33% and 26.12±3.42% of the total surface respectively. Our inmunocytochemical results suggest that von Willebrand factor could mediate these interactions. Fibrin formation was significantly higher at 250 s−1 than at 600 s−1 (p&lt;0.05). FVIIa tended to increase platelet deposition without reaching statistical significance, and raised fibrin formation and thrombin generation (p&lt;0.05). Our At 5000 s−1, closure times in the PFA-100 were significantly shortened in the presence of hTF (154.09 ±14.69 s vs 191.45± 16.09 s with collagen alone; p&lt;0.05). Addition of rFVIIa did not result in a further reduction of closure time. Our studies demonstrate that hTF is reactive for platelets. von Willebrand factor could mediate these interactions. Recombinant FVIIa enhances the procoagulant action of hTF at low and intermediate shear rates, but has no impact on the hemostatic performance at very elevated shear rates.

scholarly journals Binding of fibronectin to alpha-granule-deficient platelets.

1983 ◽  
Vol 97 (2) ◽  
pp. 571-573 ◽  
Author(s):  
M H Ginsberg ◽  
J D Wencel ◽  
J G White ◽  
E F Plow
Keyword(s):  
Surface Expression ◽  
Plasma Fibronectin ◽  
Platelet Factor ◽  
Fibronectin Receptor ◽  
Platelet Binding ◽  
Protein Functions ◽  
Fibronectin Binding ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Molecular Nature

Most of the proposed functions for fibronectin involve its interaction with cells, yet the molecular nature of cellular fibronectin binding site(s) has remained obscure. Thrombin induces saturable platelet binding sites for plasma fibronectin and concurrently stimulates surface expression of a number of platelet alpha-granule constituents including thrombospondin and fibrin which are known to interact with fibronectin. To test the hypothesis that these (or other alpha-granule proteins) mediate plasma fibronectin binding, we used platelets of patients with the Gray Platelet Syndrome. These cells were deficient in thrombospondin, beta-thromboglobulin, platelet factor 4, fibronectin, and fibrinogen as measured in radioimmunoassay. They also had reduced von Willebrand factor content as judged by immunofluorescence. At plasma fibronectin inputs from 0.03 to 3 times the apparent kilodalton, these Gray platelets bound virtually identical quantities of fibronectin as normal cells. Thus, platelets containing 1,500 molecules of thrombospondin per platelet could bind more than 100,000 molecules of plasma fibronectin per cell following thrombin stimulation. These data preclude any simple model in which newly surface expressed thrombospondin (or other alpha-granule protein) functions as the major thrombin-stimulated plasma fibronectin receptor in this cell type.

Repeated Exercise Induces Release of Soluble P-Selectin in Patients with Intermittent Claudication

1997 ◽  
Vol 78 (05) ◽  
pp. 1338-1342 ◽  
Author(s):  
U J Kirkpatrick ◽  
M Mossa ◽  
A D Blann ◽  
C N McCollum
Keyword(s):  
Intermittent Claudication ◽  
Von Willebrand Factor ◽  
Statistical Significance ◽  
Ischaemia Reperfusion Injury ◽  
Biochemical Effect ◽  
Control Subjects ◽  
Repeated Exercise ◽  
Soluble P ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryControversy exists as to whether exercise in patients with intermittent claudication causes a harmful biochemical effect associated with an ischaemia-reperfusion injury of skeletal muscle. We report on exercise-induced changes in neutrophil activation, soluble P-selectin and von Willebrand factor in 34 patients with intermittent claudication and 12 matched controls.Von Willebrand factor (vWF) showed a cyclical pattern of response to exercise in control subjects (rising from 103 ± 8 to 119 ± 7 U/dl); claudicants did not show this pattern but had higher levels of vWF throughout (p <0.03). There was no consistent pattern of response in neutrophil hydrogen peroxide production to exercise in either claudicants or control subjects. Soluble P-selectin levels increased after exercise, but this only reached statistical significance after repeated exercise in claudicants (rising from 320 ± 28 to 357 ± 28 ng/ml). This rise in soluble P-selectin after exercise may indicate progressive platelet activation which may contribute to the excess cardiovascular mortality that claudicants are prone to.

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