Novel Antibodies Against Glycoprotein Ibα Inhibit Pulmonary Metastasis By Affecting Vwf-Gpibα Interaction

Abstract Background: Platelet glycoprotein Ibα (GPIbα) extracellular domain, which is part of the receptor complex GPIb-IX-V, plays an important role in tumor metastasis. However, the mechanism through which GPIbα participates in the metastatic process remains unclear. In addition, potential bleeding complication remains an obstacle for the clinical use of anti-platelet agents in cancer therapy. Methods and Results: To generate antibodies that bind to mouse platelet GPIbα, washed mouse platelet lysate was used as the antigen for rat immunization. Obtained hybridoma clones were screened in ELISA for binding affinity to the GPIb-IX complex. Positive clones were further screened for their abilities to inhibit platelet-cancer cell adhesion. Finally, at static condition, two antibodies, 2B4 and 1D12, had virtually no effect on the activation of integrin αIIbβ3, which is used to indicate platelet activation. Then, we characterized the binding sites of 2B4 and 1D12 by 20 purified recombinant GPIbα fragments binding. Results showed that 2B4 and 1D12 shared the same binding sites with vWF. To determine whether 2B4 and 1D12 affect vWF binding, we tested the binding by flow cytometry using recombined mouse vWF, and then, we investigated platelet aggregation induced by several agonists, including vWF binding agonist ristocetin. Our data demonstrated clearly that 2B4 and 1D12 could inhibit vWF binding. To investigate whether the inhibition of vWF-GPIbα interaction was associated with tumor metastasis, we examined the effect of 2B4 and 1D12 in each of the following interactions in vitro: between activated platelets and tumor cells, platelets and endothelial cells. Meanwhile, We further investigated the inhibitory effect of these antibodies in vivo using the experimental metastasis model and the spontaneous metastasis model. Results showed that 2B4 and 1D12 could potently inhibit the adhesion of cancer cells in vitro, and metastasisin vivo. We next investigated whether 2B4 and 1D12 could affect platelet activation and/or induce thrombocytopenia in vivo. Results showed that the addition of 2B4 or 1D12 to PRP did not induce platelet aggregation and injection of 2B4 or 1D12 Fab at appropriate dose did not affect tail-bleeding time and platelet count. Based on the above findings, we obtained anti-human platelet GPIbα monoclonal antibody YQ3 using the same approach to explore the role of human GPIbα in cancer metastasis. As expected, YQ3 inhibited lung cancer adhesion and demonstrated similar value in metastasis. More importantly, for all three mAbs in our study, none of their Fabs induced thrombocytopenia. Conclusion: Our results therefore supported the hypothesis that GPIbα contributes to tumor metastasis, and suggested potential value of using anti-GPIbα mAb to suppress cancer metastasis. Disclosures Li: Neoletix: Consultancy, Equity Ownership.

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Selective inhibition of the platelet phosphoinositide 3-kinase p110β as promising new strategy for platelet protection during extracorporeal circulation

Thrombosis and Haemostasis ◽

10.1160/th07-07-0452 ◽

2008 ◽

Vol 99 (03) ◽

pp. 609-615 ◽

Cited By ~ 22

Author(s):

Hans Wendel ◽

Klaus Dietz ◽

Daniela Schiebold ◽

Karlheinz Peter ◽

Simone Schoenwaelder ◽

...

Keyword(s):

Platelet Aggregation ◽

Platelet Activation ◽

Platelet Function ◽

Extracorporeal Circulation ◽

Ventricular Assist Devices ◽

Platelet Glycoprotein ◽

Promising Alternative ◽

Phosphoinositide 3 Kinase

SummaryExtracorporeal circulation (ECC) is used in cardiac surgery for cardiopulmonary bypass as well as in ventricular assist devices and for extracorporeal membrane oxygenation. Blood contact with the artificial surface and shear stress of ECC activates platelets and leukocytes resulting in a coagulopathy and proinflammatory events. Blockers of the platelet glycoprotein (GP) IIb/IIIa (CD41/CD61) can protect platelet function during ECC, a phenomenon called “platelet anaesthesia”, but may be involved in post-ECC bleeding. We hypothesized that the new selective phosphoinositide 3-kinase p110β inhibitor TGX-221 that inhibits shear-induced platelet activation without prolonging the bleeding time in vivo may also protect platelet function during ECC. Heparinized blood of healthy volunteers (n=6) was treated in vitro with either the GP IIb/IIIa blocker tirofiban, TGX-221 or as control and circulated in an ECC moand after 30 minutes circulation CD41 expression on the ECCtubing as measure for platelet-ECC binding and generation of the platelet activation marker β-thromboglobulin were determined using ELISA. Platelet aggregation and platelet-granulocyte binding were analysed in flow cytometry. After log-transforming the data statistical evaluation was performed using multifactor ANOVA in combination with Tukey’s HSD test (global alpha = 5%).Tirofiban and TGX-221 inhibited platelet-ECC interaction, platelet aggregation and platelet-granulocyte binding. Tirofiban also inhibited ECC-induced β-thromboglobulin release.The observed inhibition of platelet-ECC interaction and platelet activation by tirofiban contributes to explain the mechanism of“platelet anaesthesia”.TGX-221 represents a promising alternative to GP IIb/IIIa blockade and should be further investigated for use during ECC in vivo.

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Involvement of platelet-derived VWF in metastatic growth of melanoma in the brain

Neuro-Oncology Advances ◽

10.1093/noajnl/vdab175 ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Jose R Robador ◽

Manuel J Feinauer ◽

Stefan W Schneider ◽

Frank T Mayer ◽

Christian Gorzelanny ◽

...

Keyword(s):

Platelet Aggregation ◽

Platelet Activation ◽

Fiber Formation ◽

Brain Targeting ◽

Induce Platelet Aggregation ◽

Promising Therapeutic Approach ◽

Metastatic Growth ◽

The Brain

Abstract Background The prognosis of patients with brain metastases (BM) is poor despite advances in our understanding of the underlying pathophysiology. The high incidence of thrombotic complications defines tumor progression and the high mortality rate. We, therefore, postulated that von Willebrand factor (VWF) promotes BM via its ability to induce platelet aggregation and thrombosis. Methods We measured the abundance of VWF in the blood and intravascular platelet aggregates of patients with BM, and determined the specific contribution of endothelial and platelet-derived VWF using in vitro models and microfluidics. The relevance for the brain metastatic cascade in vivo was demonstrated in ret transgenic mice, which spontaneously develop BM, and by the intracardiac injection of melanoma cells. Results Higher levels of plasma VWF in patients with BM were associated with enhanced intraluminal VWF fiber formation and platelet aggregation in the metastatic tissue and peritumoral regions. Platelet activation triggered the formation of VWF multimers, promoting platelet aggregation and activation, in turn enhancing tumor invasiveness. The absence of VWF in platelets, or the blocking of platelet activation, abolished platelet aggregation, and reduced tumor cell transmigration. Anticoagulation and platelet inhibition consistently reduced the number of BM in preclinical animal models. Conclusions Our data indicate that platelet-derived VWF is involved in cerebral clot formation and in metastatic growth of melanoma in the brain. Targeting platelet activation with low-molecular-weight heparins represents a promising therapeutic approach to prevent melanoma BM.

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Studies investigating platelet aggregation and release initiated by sera from patients with thrombotic thrombocytopenic purpura

Blood ◽

10.1182/blood.v69.3.924.bloodjournal693924 ◽

1987 ◽

Vol 69 (3) ◽

pp. 924-928 ◽

Cited By ~ 1

Author(s):

JG Kelton ◽

JC Moore ◽

WG Murphy

Keyword(s):

Platelet Aggregation ◽

Thrombotic Thrombocytopenic Purpura ◽

Disease Process ◽

The Other ◽

Platelet Glycoprotein ◽

Glycoprotein Ib ◽

Thrombocytopenic Purpura ◽

Induced Aggregation

Many patients with thrombotic thrombocytopenic purpura (TTP) have a platelet aggregating factor in their serum that may be pathologically linked with the disease process. To help characterize the type of platelet aggregation and platelet release induced by the sera from seven TTP patients, we measured the ability of a variety of inhibitors of platelet function as well as the ability of monoclonal antibodies (MoAbs) against platelet glycoproteins to inhibit TTP sera-induced platelet aggregation and release. These results were compared with the ability of the same inhibitors to block platelet aggregation induced by ristocetin, collagen, ADP, thrombin, and IgG-immune complexes. Monoclonal antibody directed against platelet glycoprotein Ib totally inhibited ristocetin-induced aggregation and release but had no effect on aggregation and release induced by the TTP sera or by any of the other platelet agonists. However, the MoAb against glycoproteins IIb/IIIa inhibited aggregation and release caused by TTP sera as well as by collagen, thrombin, and ADP but had no effect on aggregation and release induced by ristocetin. The aggregating activity could be abolished by heparin but not by the serine protease inhibitor PMSF (1 mmol/L). And although monomeric human IgG and purified Fc fragments of IgG inhibited IgG-immune complex-induced aggregation and release, they had no effect on TTP sera-induced aggregation and release nor on aggregation and release induced by any of the other agonists. Consistent with these in vitro studies showing no effect of IgG were the in vivo observations that intravenous (IV) IgG was without effect when administered to three patients with TTP. This study indicates that although a von Willebrand factor (vWF)-rich preparation of cryoprecipitate enhances the in vitro platelet aggregation and release caused by sera from the seven TTP patients we studied, the pathway of aggregation and release is not via platelet glycoprotein Ib. Also the aggregating factor of TTP sera is not neutralized in vitro or in vivo by IgG.

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Studies investigating platelet aggregation and release initiated by sera from patients with thrombotic thrombocytopenic purpura

Blood ◽

10.1182/blood.v69.3.924.924 ◽

1987 ◽

Vol 69 (3) ◽

pp. 924-928 ◽

Cited By ~ 35

Author(s):

JG Kelton ◽

JC Moore ◽

WG Murphy

Keyword(s):

Platelet Aggregation ◽

Thrombotic Thrombocytopenic Purpura ◽

Disease Process ◽

The Other ◽

Platelet Glycoprotein ◽

Glycoprotein Ib ◽

Thrombocytopenic Purpura ◽

Induced Aggregation

Abstract Many patients with thrombotic thrombocytopenic purpura (TTP) have a platelet aggregating factor in their serum that may be pathologically linked with the disease process. To help characterize the type of platelet aggregation and platelet release induced by the sera from seven TTP patients, we measured the ability of a variety of inhibitors of platelet function as well as the ability of monoclonal antibodies (MoAbs) against platelet glycoproteins to inhibit TTP sera-induced platelet aggregation and release. These results were compared with the ability of the same inhibitors to block platelet aggregation induced by ristocetin, collagen, ADP, thrombin, and IgG-immune complexes. Monoclonal antibody directed against platelet glycoprotein Ib totally inhibited ristocetin-induced aggregation and release but had no effect on aggregation and release induced by the TTP sera or by any of the other platelet agonists. However, the MoAb against glycoproteins IIb/IIIa inhibited aggregation and release caused by TTP sera as well as by collagen, thrombin, and ADP but had no effect on aggregation and release induced by ristocetin. The aggregating activity could be abolished by heparin but not by the serine protease inhibitor PMSF (1 mmol/L). And although monomeric human IgG and purified Fc fragments of IgG inhibited IgG-immune complex-induced aggregation and release, they had no effect on TTP sera-induced aggregation and release nor on aggregation and release induced by any of the other agonists. Consistent with these in vitro studies showing no effect of IgG were the in vivo observations that intravenous (IV) IgG was without effect when administered to three patients with TTP. This study indicates that although a von Willebrand factor (vWF)-rich preparation of cryoprecipitate enhances the in vitro platelet aggregation and release caused by sera from the seven TTP patients we studied, the pathway of aggregation and release is not via platelet glycoprotein Ib. Also the aggregating factor of TTP sera is not neutralized in vitro or in vivo by IgG.

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Vigorous exercise acutely changes platelet and B-lymphocyte CD39 expression

Journal of Applied Physiology ◽

10.1152/japplphysiol.00315.2004 ◽

2005 ◽

Vol 98 (4) ◽

pp. 1414-1419 ◽

Cited By ~ 15

Author(s):

Antonino Coppola ◽

Ludovico Coppola ◽

Liliana dalla Mora ◽

Francesco M. Limongelli ◽

Antonio Grassia ◽

...

Keyword(s):

Platelet Aggregation ◽

B Lymphocytes ◽

Platelet Activation ◽

Critical Role ◽

Strenuous Exercise ◽

Platelet Glycoprotein ◽

Vigorous Exercise ◽

Platelet Aggregates

CD39/ATP diphosphohydrolase is expressed on B lymphocytes, cytotoxic T lymphocytes, monocytes, platelets, and endothelial cells, and it has a critical role in the inhibition of platelet responsiveness. To determine whether strenuous exercise could acutely change expression of CD39 in platelets and lymphocytes, eight healthy sedentary men, 34 yr old (SD 7), and eight physically active men, 34 yr old (SD 6), performed graded upright cycle ergometry to volitional exhaustion. Blood samples collected both at baseline and after exercise test were employed to measure CD39 expression in platelets and lymphocytes. The percentage of circulating platelet-platelet aggregates, the “in vitro” ADP and collagen-induced platelet aggregation, and the expression of both platelet glycoprotein IIb-IIIa (PAC-1) and P-selectin (CD62) were also considered markers of platelet activation. After strenuous exercise, all subjects demonstrated significant platelet activation as judged by the increased percentage of platelet-platelet aggregates. The in vitro ADP-induced platelet aggregation and the expression of CD62P on ADP-stimulated platelets significantly increased in sedentary but not in active subjects. After exercise, all of the subjects showed a significant reduction of CD39 expression in platelet [sedentary: from 2.2 (SD 0.8) to 1.1% (SD 0.8), P = 0.008; active: from 0.6 (SD 0.2) to 0.35% (SD 0.1), P = 0.009] and an increase of CD39 expression in B lymphocytes [sedentary: from 47 (SD 13) to 60% (SD 11), P = 0.0039; active: from 46 (SD 11) to 59% (SD 11), P = 0.0038]. Taken together, these findings confirm the critical role of this ADPase in inhibition of platelet responsiveness, also suggesting a possible role of B lymphocytes in thromboregulation mechanism.

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In Vitro and In Vivo Effects of Adrenaline and Phentolamine on Platelet Function

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648677 ◽

1978 ◽

Vol 40 (02) ◽

pp. 428-438 ◽

Cited By ~ 7

Author(s):

Oreste Ponari ◽

Emilio Civardi ◽

Alessandro Megha ◽

Mario Pini ◽

Raffaele Poti’ ◽

...

Keyword(s):

Platelet Aggregation ◽

Platelet Rich Plasma ◽

Threshold Concentration ◽

Two Phase ◽

Platelet Factor ◽

Induce Platelet Aggregation ◽

In Vivo Effects ◽

In Vivo Administration

Summary In vitro and in vivo effects of adrenaline (ADR) on platelet aggregation, on platelet factor 3 (PF3) availability and on platelet factor 4 (PF4) release were studied in man. Inhibitory action of an alpha-blocker, phentolamine (PHEN) was investigated in the same conditions.The threshold concentration (TC) of ADR inducing the typical two-phase response in aggregation tests when added to platelet-rich plasma (PRP) varied in different pools of plasma, but always induced an evident PF4 release and increased PF3 availability. A further increase in both parameters was obtained with higher concentrations but without any significant dose/response correlation.Adding PHEN alone to PRP did not induce platelet aggregation or modify PF4 release induced by stirring, but it reduced PF3 availability. On the other hand, PHEN prevented the effects of ADR in different platelet tests, at appropriate concentrations.Intravenous infusion of ADR lowered the TC, and increased PF3 availability and PF4 release. In vivo administration of PHEN, in contrast, increased TC and reduced PF3 availability, while PF4 remained unchanged.

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Differential Effects of Reconstituted High-density Lipoprotein on Coagulation, Fibrinolysis and Platelet Activation during Human Endotoxemia

Thrombosis and Haemostasis ◽

10.1055/s-0038-1655958 ◽

1997 ◽

Vol 77 (02) ◽

pp. 303-307 ◽

Cited By ~ 64

Author(s):

Dasja Pajkrt ◽

Peter G Lerch ◽

Tom van der Poll ◽

Marcel Levi ◽

Marlies Illi ◽

...

Keyword(s):

Platelet Aggregation ◽

Platelet Activation ◽

Plasma Levels ◽

Density Lipoprotein ◽

High Density ◽

Tissue Type ◽

High Density Lipoproteins ◽

Double Blind

SummaryHigh-density lipoproteins (HDL) can bind and neutralize lipopoly- saccharides (LPS) in vitro and in vivo. HDL can also affect fibrinolytic activity and can directly influence platelet function by reducing platelet aggregation. In this study, the effects of reconstituted HDL (rHDL) on LPS-induced coagulation, fibrinolysis and platelet activation in humans were investigated. In a double-blind, randomized, placebo-controlled, cross-over study, eight healthy male volunteers were injected with LPS (4 ng/kg) on two occasions, once in conjunction with rHDL (40 mg/kg, given as a 4 h infusion starting 3.5 h prior to LPS injection), and once in conjunction with placebo. rHDL significantly reduced LPS-induced activation of coagulation (plasma levels of prothrombin fragment F1+2) and fibrinolysis (plasma levels of tissue type plasminogen activator antigen, t-PA). No effect was observed on LPS-induced inhibition of the fibrinolytic pathway (PAI-1) or on the transient thrombocytopenia elicited by LPS. Furthermore, rHDL treatment significantly enhanced the inhibition of collagen-stimulated inhibition of platelet aggregation during endotoxemia, but had no such effect on arachido- nate-stimulated platelet aggregation. rHDL treatment per se also reduced collagen-induced platelet aggregation. These results indicate that rHDL modifies the procoagulant state associated with endotoxemia.

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Polyphenols: Anti-Platelet Nutraceutical?

Current Pharmaceutical Design ◽

10.2174/1381612823666171109104600 ◽

2018 ◽

Vol 24 (2) ◽

pp. 146-157 ◽

Cited By ~ 3

Author(s):

Valeria Ludovici ◽

Jens Barthelmes ◽

Matthias P. Nagele ◽

Andreas J. Flammer ◽

Isabella Sudano

Keyword(s):

Platelet Aggregation ◽

Platelet Activation ◽

Therapeutic Potential ◽

Critical Role ◽

Organ Damage ◽

Low Grade ◽

Protective Effects ◽

Dietary Polyphenols

Background: Coronary artery disease (CAD) is a disease progressing over many years. Genetic factors, as well as the exposure to risk factors, are continuously leading to endothelial dysfunction, vascular alterations and, eventually, organ damage, major cardiovascular events and deaths. Oxidative stress, platelet hyperactivity and low-grade inflammation are important modulators in this context, contributing to plaque formation. Since platelet activation plays a critical role in the development and progression of atherothrombotic events, the inhibition of platelet hyperactivity may contribute to decreased atherothrombotic risk. The consumption of bioactive foods, and plant-derived polyphenols in particular, might impart anti-thrombotic and cardiovascular protective effects. Methods: Aim of this work is to focus on the potential of dietary derived polyphenols to reduce platelet hyperactivity or hypercoagulability in addition to discussing their possible complementary anti-platelet therapeutic potential. All the relevant publications on this topic were systematically reviewed. Results: Various studies demonstrated that polyphenol supplementation affects platelet aggregation and function in vitro and in vivo, mainly neutralizing free radicals, inhibiting platelet activation and related signal transduction pathways, blocking thromboxane A2 receptors and enhancing nitric oxide production. Experimental data concerning the effect of dietary polyphenols on platelet aggregation in vivo are poor, and results are often conflicting. Only flavanols clearly mirrored in vivo showed the efficacy in vitro in modulating platelet function. Conclusion: Dietary polyphenols, and above all flavanols contained in cocoa and berries, reduce platelet activation and aggregation via multiple pathways. However, more controlled interventional studies are required to establish which doses are required as well as what circulating concentrations are sufficient to induce functional antiplatelet effects.

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Platelet Activation Markers in Patients with Peripheral Arterial Disease

Thrombosis and Haemostasis ◽

10.1055/s-0038-1665429 ◽

1997 ◽

Vol 78 (06) ◽

pp. 1434-1437 ◽

Cited By ~ 33

Author(s):

Paolo Gresele ◽

Mariella Catalano ◽

Carlo Giammarresi ◽

Raul Volpato ◽

Rosanna Termini ◽

...

Keyword(s):

Platelet Aggregation ◽

Platelet Activation ◽

Platelet Function ◽

Arterial Disease ◽

Platelet Function Test ◽

Activation Markers ◽

Significant Difference ◽

Peripheral Arterial

SummaryPeripheral vascular disease (PVD) is an indicator of diffuse atherosclerosis and is associated with a greatly increased incidence of coronary heart and cerebrovascular disease. Although several studies have assessed whether in vivo platelet activation takes place in patients with PVD, no data are available comparing different platelet function tests in this patient population.We have compared prospectively four tests for the measurement of in vivo platelet activation (plasma βTG, plasma PF4, intraplatelet (βTG and urinary excretion of 11-dehydro-TXB2) and one in vitro platelet function test (ADP-induced platelet aggregation) in 63 well-characterized patients with intermittent claudication and in 18 age- and sex- matched healthy volunteers.No statistically significant difference was found between patients and controls for plasma βTG (20.0 ± 11.8 vs. 18.8 ± 9.0 ng/ml, respectively), plasma PF4 (5.2 ± 2.9 vs. 6.3 ± 3.5 ng/ml), βTG/PF4 ratio (4.0 ± 2.9 vs. 3.6 ± 1.8), intraplatelet pTG (4503 ± 1482 vs. 4059 ± 1065 ng/ml), and threshold aggregatory concentration of ADP (1.7 ± 0.72 vs. 1.45 ± 0.56 μM).Urinary 11-dehydro-TXB2 was instead significantly higher in the PVD group (55.4 ± 27.5 vs. 26.7 ± 7.0 ng/h, p <0.001).Our study shows that urinary 11-dehydro-TXB2 is a more sensitive index of in vivo platelet activation than the measurement of either platelet specific proteins or of in vitro platelet aggregation in patients with PVD.

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An Antithrombotic Strategy by Targeting Phospholipase D in Human Platelets

Journal of Clinical Medicine ◽

10.3390/jcm7110440 ◽

2018 ◽

Vol 7 (11) ◽

pp. 440 ◽

Cited By ~ 3

Author(s):

Wan Lu ◽

Chi Chung ◽

Ray Chen ◽

Li Huang ◽

Li Lien ◽

...

Keyword(s):

Platelet Aggregation ◽

Platelet Activation ◽

Phospholipase D ◽

Thrombus Formation ◽

Human Platelets ◽

Platelet Activity ◽

Clot Retraction ◽

First Time

Phospholipase D (PLD) is involved in many biological processes. PLD1 plays a crucial role in regulating the platelet activity of mice; however, the role of PLD in the platelet activation of humans remains unclear. Therefore, we investigated whether PLD is involved in the platelet activation of humans. Our data revealed that inhibition of PLD1 or PLD2 using pharmacological inhibitors effectively inhibits platelet aggregation in humans. However, previous studies have showed that PLD1 or PLD2 deletion did not affect mouse platelet aggregation in vitro, whereas only PLD1 deletion inhibited thrombus formation in vivo. Intriguingly, our data also showed that the pharmacological inhibition of PLD1 or PLD2 does not affect mouse platelet aggregation in vitro, whereas the inhibition of only PLD1 delayed thrombus formation in vivo. These findings indicate that PLD may play differential roles in humans and mice. In humans, PLD inhibition attenuates platelet activation, adhesion, spreading, and clot retraction. For the first time, we demonstrated that PLD1 and PLD2 are essential for platelet activation in humans, and PLD plays different roles in platelet function in humans and mice. Our findings also indicate that targeting PLD may provide a safe and alternative therapeutic approach for preventing thromboembolic disorders.

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