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

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.

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

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1133-1133
Author(s):  
Qi Yingxue ◽  
Wenchun Chen ◽  
Ke Xu ◽  
Fengying Wu ◽  
Xuemei Fan ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Binding Sites ◽  
Tumor Metastasis ◽  
Cancer Metastasis ◽  
Platelet Glycoprotein ◽  
Induce Platelet Aggregation ◽  
Metastasis Model

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.

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

1978 ◽  
Vol 40 (02) ◽  
pp. 428-438 ◽  
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.

Prostaglandins and Platelet Aggregation in Vivo

1970 ◽  
Vol 23 (02) ◽  
pp. 286-292 ◽  
Author(s):  
J Kloeze
Keyword(s):  
Platelet Aggregation ◽  
Intravenous Injection ◽  
Adenosine Diphosphate ◽  
Causative Factor ◽  
Respiratory Arrest ◽  
Platelet Thrombi ◽  
Eventual Death ◽  
The Brain

SummaryProstaglandins E1 and ω-homo-E1 which were shown previously to inhibit adenosine diphosphate (ADP)-induced platelet aggregation in vitro have now been found to inhibit this process also in vivo. Both prostaglandins inhibit transient thrombocytopenia induced by intravenous injection of ADP; PGE1 increases also the LD 50 of ADP when injected in high amounts into young rats. In both cases platelet aggregation in vivo is the primary cause of the phenomena observed.The symptoms observed on overdosing ADP by intravenous injection are unconsciousness within 10-20 sec after completion of the injection immediately followed by respiratory arrest and eventual death of the animal, generally within 10 min. It seems that blocking of the supply of blood to the brain by platelet thrombi, which on histological examination were found to occlude blood vessels in different organs, is the most important causative factor of the symptoms observed.

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

1997 ◽  
Vol 77 (02) ◽  
pp. 303-307 ◽  
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.

scholarly journals Brain Targeting of anti-HIV Nucleosides: in vitro and in vivo Evaluation of 6-chloro-2′,3′-dideoxypurine, a Lipophilic Prodrug of 2′,3′-dideoxyinosine

1994 ◽  
Vol 5 (5) ◽  
pp. 304-311 ◽  
Author(s):  
K. J. Doshi ◽  
F. D. Boudinot ◽  
J. M. Gallo ◽  
R. F. Schinazi ◽  
C. K. Chu
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Oral Administration ◽  
Intravenous Administration ◽  
Brain Targeting ◽  
The Central Nervous System ◽  
Intravenous And Oral Administration ◽  
The Brain

Lipophilic 6-halo-2′,3′-dideoxypurine nucleosides may be useful prodrugs for the targeting of 2′,3′-dideoxyinosine (ddl) to the central nervous system. The purpose of this study was to evaluate the potential effectiveness of 6-chloro-2′,3′-dideoxypurine (6-CI-ddP) for the targeting of ddl to the brain. In vitro studies indicated that the adenosine deaminase-mediated biotransformation of 6-CI-ddP to ddl was more rapid in mouse brain homogenate than in mouse serum. The brain distribution of 6-CI-ddP and ddl was assessed in vivo in mice following intravenous and oral administration of the prodrug or parent drug. Brain concentrations of ddl were similar after intravenous administration of 6-CI-ddP or ddl. However, after oral administration of the 6-CI-ddP prodrug, significantly greater concentrations of ddl were seen in the brain compared to those found after oral administration of ddl. The brain:serum AUG ratio (expressed as a percentage) of ddl after intravenous administration of 50 mg kg−1 of the active nucleoside was 3%. Following oral administration of 250 mg kg−1 ddl, low concentrations of ddl were detected in the brain. Brain:serum AUC ratios following intravenous and oral administration of the prodrug 6-CI-ddP were 19–25%. Thus, brain:serum AUC ratios were 6- to 8-fold higher after prodrug administration than those obtained after administration of the parent nucleoside. Oral administration of 6-CI-ddP yielded concentrations of ddl in the brain similar to those obtained following intravenous administration. The results of this study provide further evidence that 6-CI-ddP may be a useful prodrug for delivering ddl to the central nervous system, particularly after oral administration.

Polyphenols: Anti-Platelet Nutraceutical?

2018 ◽  
Vol 24 (2) ◽  
pp. 146-157 ◽  
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.

Platelet Activation Markers in Patients with Peripheral Arterial Disease

1997 ◽  
Vol 78 (06) ◽  
pp. 1434-1437 ◽  
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.

scholarly journals An Antithrombotic Strategy by Targeting Phospholipase D in Human Platelets

2018 ◽  
Vol 7 (11) ◽  
pp. 440 ◽  
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.

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

2008 ◽  
Vol 99 (03) ◽  
pp. 609-615 ◽  
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.

Discovery of a New Signaling Complex Based on Spinophilin That Regulates Platelet Activation In Vitro and In Vivo

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 161-161 ◽  
Author(s):  
Peisong Ma ◽  
Aleksandra Cierniewska ◽  
Rachel Signarvic ◽  
Andrew Sinnamon ◽  
Marcin Cieslak ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Phosphatase Activity ◽  
Platelet Activation ◽  
Conflicts Of Interest ◽  
Tyrosine Phosphatase ◽  
Artery Occlusion ◽  
Rgs Proteins ◽  
Regulatory Complex

Abstract Abstract 161 Platelets play an essential role in hemostasis, but excessive platelet responses to vascular injury or disease can be catastrophic. We have recently reported that members of the RGS protein family can modulate platelet responses to injury by limiting the duration of G protein-dependent signaling initiated by platelet agonists. Here we show that platelets contain a previously-unrecognized regulatory complex comprised of the 130 kDa scaffold protein, spinophilin (SPL) with at least two RGS proteins (RGS10 and RGS18) and the protein tyrosine phosphatase, SHP-1. In resting platelets, this complex is phosphorylated on spinophilin residues Y398 and Y483. Mutating both tyrosines to phenylalanine inhibits the binding of SHP-1 to spinophilin. Platelet activation by thrombin or thromboxane A2, but not ADP or collagen, stimulates a transient increase in spinophilin-associated SHP-1 tyrosine phosphatase activity and causes dephosphorylation and decay of the SPL/RGS/SHP-1 complex. Conversely, blocking SHP-1 phosphatase activity in platelets or omitting SHP-1 in transfected CHO cells inhibits dephosphorylation of spinophilin and prevents dissociation of the SPL/RGS/SHP-1 complex. While we have shown previously that inhibiting interactions between G proteins and RGS proteins produces a gain of function in platelets, knocking out spinophilin in mice inhibits platelet aggregation. This aggregation defect does not occur with all agonists, but is selective for those that are able to trigger decay and dephosphorylation of the SPL/RGS/SHP-1 complex. In addition to inhibiting platelet aggregation in vitro, the spinophilin knockout delays carotid artery occlusion in vivo following application of FeCl3 and reduces platelet accumulation following laser injury in cremaster muscle arterioles. Underlying these effects of the knockout is a decrease in Rap1 activation, an event that supports integrin activation, and attenuation of the cAMP increase otherwise caused by endothelial PGI2. Collectively, these observations show for the first time that a regulatory complex based on spinophilin helps to regulate platelet responses to injury and suggest that it does this by sequestering RGS proteins in resting platelets and releasing them after activation begins. Dissociation of the SPL/RGS complex is regulated by an agonist-induced increase in the activity of SHP-1 associated with spinophilin. Disclosures: No relevant conflicts of interest to declare.

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