scholarly journals Both Complement- and Fibrinogen-Dependent Mechanisms Contribute to Platelet Aggregation Mediated by Staphylococcus aureus Clumping Factor B

2007 ◽  
Vol 75 (7) ◽  
pp. 3335-3343 ◽  
Author(s):  
Helen Miajlovic ◽  
Anthony Loughman ◽  
Marian Brennan ◽  
Dermot Cox ◽  
Timothy J. Foster
Keyword(s):  
Staphylococcus Aureus ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Lag Time ◽  
Dependent Manner ◽  
Wild Type ◽  
Factor B ◽  
Fibrinogen Binding ◽  
Aggregation Of Platelets ◽  
Dependent Mechanism

ABSTRACT Staphylococcus aureus can stimulate activation and aggregation of platelets, which are thought to be factors in the development of infective endocarditis. Previous studies have identified clumping factor A (ClfA) and fibronectin binding proteins A and B (FnBPA and FnBPB) as potent platelet aggregators. These proteins are able to stimulate rapid platelet aggregation by either a fibrinogen- or a fibronectin-dependent process which also requires antibodies specific to each protein. Slower aggregation has been seen in other systems where specific fibrinogen binding ligands are absent and platelet aggregation is mediated by complement and specific antibodies. Bacteria expressing ClfB aggregate platelets with a longer lag time than ClfA or FnBPA and FnBPB. In order to investigate whether ClfB causes platelet aggregation in a complement- or fibrinogen-dependent manner, a non-fibrinogen-binding mutant of ClfB (ClfB Q235A) was constructed. Lactococcus lactis expressing ClfB Q235A was able to stimulate platelet aggregation in platelet-rich plasma without a significant increase in lag time. The requirements for platelet aggregation were investigated using gel-filtered platelets. Fibrinogen and specific anti-ClfB antibodies were found to be sufficient to allow platelet aggregation mediated by the wild-type ClfB protein. It seems that ClfB causes platelet aggregation by a fibrinogen-dependent mechanism. The non-fibrinogen-binding ClfB mutant was unable to stimulate platelet aggregation under these conditions. However, bacteria expressing ClfB Q235A caused platelet aggregation in a complement-dependent manner which required specific anti-ClfB antibodies.

Platelet Aggregation By Membrane Glycoprotein I

1981 ◽  
Author(s):  
K Watanabe ◽  
M Yamamoto ◽  
Y Ando ◽  
H Iri ◽  
K Furihata ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Lag Phase ◽  
Affinity Column ◽  
Membrane Glycoprotein ◽  
Dependent Manner ◽  
Membrane Glycoproteins ◽  
Aggregation Mechanism ◽  
Membrane Components ◽  
Aggregation Of Platelets

It has been recently shown that platelet membrane components, particularly glycoproteins, have a lectin activity, thus mediating an aggregation of platelets. To obtain further evidences for a crucial role of glycoproteins in an aggregation mechanism,we have investigated the possibility that membrane glycoprotein can directly induce an aggregation of platelets. The membrane glycoproteins ( GP I, GP II and GP III ) were isolated from 3-4 mg of human platelet membranes using preparative electrophoresis on 5 % polyacrylamide gels with 0.1% SDS. Platelet aggregation by isolated GP I, GP II or GP III was examined under phase_contrast microscopy after the incubation of these peptides with platelet rich plasma at 37°C for 15 min.. Among glycoproteins tested, only GP I( 20 μg/ml < ) exerted an apparent platelet aggregation. No such aggregation was induced by either GP II or GP III even at concentration of 80 μg/ml. GP I isolated separately using the wheat germ agglutinin affinity column also produced a platelet aggregation. Aggregation curve recorded with an aggregometer showed a long lag phase ( 10 min. < ) followed by an irreversible aggregation. The GP I-induced platelet aggregation occured in a dose dependent manner. This aggregation was completely inhibited by the addition of aggregating inhibitors such as indomethacin ( 25 μM ), PGE1 ( 1 μM ), EDTA ( 0.5 mM ) and TMB-8 ( lmg/ml ). A significant amount of serotonin ( 27% ) and β-thromboglobulin ( 14.6% ) was released from platelets by GP I ( 100 μg/ml ). Treatment of GP I with either trypsin ( 50 μg/ml ) or chymotrypsin ( 40 μg/ml ) reduced the aggregating activity of this glycopeptides. The platelet aggregation by GP I was inhibited in the presense of 30 mM N-acetylneuraminic acid, arginin or L-lysine, but N-acetyl- ated amino sugars and neutral sugars were without effect. This GP I-induced platelet aggregation may be an important findings in elucidating platelet aggregation mechanism.

Abstract 351: Plasma Phospholipid Transfer Protein Promotes Platelet Aggregation

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Xiao-Min Zhao ◽  
Yun Wang ◽  
Shu-Cun Qin ◽  
Xian Jiang
Keyword(s):  
Plasma Membrane ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Phospholipid Transfer Protein ◽  
Dependent Manner ◽  
Exterior Surface ◽  
Transfer Protein ◽  
Fibrinogen Binding ◽  
Phospholipid Transfer ◽  
Dose Dependent

Hypothesis: Phospholipid transfer protein (PLTP) has a direct effect on platelet aggregation, since PLTP knockout mice have longer bleeding time. Methods and Results: Platelets from humans or mice were prepared as were mouse platelet-rich plasma and human recombinant PLTP (rPLTP). In mice, we assessed ADP- and collagen-induced platelet aggregation, phosphatidylserine (PS) externalization, and photothrombosis-induced cerebral infarction. We found that human platelets produce PLTP. Platelet aggregation increased upon PLTP overexpression whereas it decreased with PLTP deficiency in a gene dose-dependent manner. Human rPLTP increased mouse or human platelet aggregation in a dose-dependent manner. PS externalization provides a water/lipid surface for the interaction of coagulation factors, which accelerates thrombosis. Compared with wild type controls, platelets from PLTP transgenic mice had significantly greater amounts of PS on the exterior surface of the plasma membrane, whereas platelets from PLTP-deficient mice had significantly less on the surface, thus influencing fibrinogen binding. Moreover, rPLTP together with ADP significantly increased PS exposure on the plasma membrane of PLTP-deficient platelets, thereby increasing fibrinogen binding. Importantly, PLTP overexpression significantly accelerated the incidence of photothrombosis-induced infarction, whereas PLTP deficiency reduced the incidence. Conclusions: PLTP promotes PS externalization at the plasma membrane of platelets and accelerates ADP- or collagen-induced platelet aggregation. Thus, PLTP is involved in hypercoagulation. Therefore, PLTP inhibition could be a novel approach for countering thrombosis.

scholarly journals Anti-Heparin and Platelet Aggregation Activities of Polyamino Acids

1977 ◽  
Author(s):  
Jawed Fareed ◽  
Harry L. Messmore ◽  
John U. Balis ◽  
Rogelio Moncada
Keyword(s):  
Platelet Aggregation ◽  
Contrast Media ◽  
Platelet Rich Plasma ◽  
Anticoagulant Activity ◽  
Lag Time ◽  
Thrombin Time ◽  
Irreversible Aggregation ◽  
Induced Aggregation ◽  
Aggregation Of Platelets ◽  
Biphasic Process

An earlier report from this laboratory has described the antagonism of the anticoagulant effect of heparin by certain basic polyamino acids. Of the numerous polyamino acids tested, only basic polyarnino acids such as poly-L-lysine (MW 85,000) and poly-L-omithine (MW 120,000) effectively neutralized heparinized plasma (1 u/ml) in concentrations less than 10 μg/ml. Addition of these two polyamino acids in quantities up to 50 μg/ml citrated plasma, significantly shortened the thrombin time. Poly-L-proline (MW 19,000), poly-L-histidine (MW 16,000) and poly-L-lysine (MW 85,000) possessed weak anti-heparin action. These polyamino acids also neutralized the anticoagulant activity of hirudin and polyanetholsulfonic acid in varying degrees. The effects of polyamino acids on platelet aggregation was also tested. Of the 15 basic polyamino acids tested, only poly-L-α-omithine was found to induce aggregation of platelets. Polyornithine in the amounts of 50.0, 25.0 and 12.5 μg/ml to platelet rich plasma caused a 65, 45 and 30% change in transmittance, respectively. The polyornithine induced aggregation (PIA) of platelets was only partially blocked by acetylsalicylic acid. Contrast media (6.0 mg/ml) used in diagnostic radiology and meglumine (5 mg/ml) totally blocked the PIA. The PIA of platelets was found to be a biphasic process, an initial lag time of 30 seconds, after which irreversible aggregation was observed. These studies suggest that basic polyamino acids may be used clinically to antagonize overheparinization; in addition, polyornithine may prove useful in the diagnosis of platelet function defects.

scholarly journals 3’5’-Adenosine Diphosphate (3′5′ADP):A Physiological Inhibitor of Platelet Aggregation and Platelet Release Reaction

1977 ◽  
Author(s):  
K. Subbarao ◽  
K. Jaya
Keyword(s):  
Platelet Aggregation ◽  
Coenzyme A ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Serotonin Release ◽  
Dependent Manner ◽  
Release Reaction ◽  
Inhibition Of Platelet Aggregation ◽  
Vitro Effect ◽  
Aggregation Of Platelets

Certain analogues of adenosine have been shown to inhibit ADP-induced platelet aggregation. We therefore studied the in vitro effect of 3′5′ADP and coenzyme A on human platelet aggregation and [14C]-serotonin release reaction induced by the addition of ADP, thrombin, collagen and epinephrine to human platelet rich plasma (PRP). It was found that coenzyme A Li3·2H2O at a concentration of 0.12 mM strongly inhibited ADP-induced platelet aggregation of PRP but did not show similar effect on the aggregation of platelets induced by other aggregating agents. The 3′5′ADP which is a part of coenzyme A structure, on the other hand, inhibited both ADP and thrombin induced platelet aggregation. The extent of inhibition of platelet aggregation by coenzyme A and 3′5′ADP was found to depend upon the concentration of the inhibitor and the incubation time. Whereas 3′5′ADP Li2·3H2O at a concentration of 10 μM produced about 70% inhibition of ADP-induced platelet aggregation of human PRP, total inhibition of thrombin induced platelet aggregation was observed when platelets were incubated with 60 μM of 3′5′ADP. The 3′5′ADP also inhibited the [14C]-adeonsine uptake by platelets in a concentration dependent manner. The inhibitory potency of 3′5′ADP on platelet aggregation was found to be 10-fold higher than that of N6-2′-0-dibutyryl-cyclic 3′5′-adenosine monophosphate. The inhibition of platelet aggregation by coenzyme A and 3′5′ADP was always accompanied by the inhibition of [14C]-serotonin release reaction. If coenzyme A and 3′5′ADP are indeed physiological inhibitors of platelet aggregation, then aggregation of platelets should depend on metabolic events that regulate the concentration of these agents in blood.

scholarly journals Effect of prostaglandin E1 alone and in combination with theophylline or aspirin on collagen-induced platelet aggregation and on platelet nucleotides including adenosine 3′:5′-cyclic monophosphate

1970 ◽  
Vol 120 (4) ◽  
pp. 709-718 ◽  
Author(s):  
G. Ball ◽  
G. G. Brereton ◽  
Mary Fulwood ◽  
D. M. Ireland ◽  
Patricia Yates
Keyword(s):  
Platelet Aggregation ◽  
Cyclic Amp ◽  
Prostaglandin E1 ◽  
Platelet Rich Plasma ◽  
Dependent Manner ◽  
Intracellular Changes ◽  
Induced Aggregation ◽  
Dose Dependent ◽  
Aggregation Of Platelets ◽  
Collagen Treatment

1. Human platelet nucleotides were labelled by incubating platelet-rich plasma with [U-14C]adenine. With such platelets, the effects of prostaglandin E1, theophylline and aspirin were determined on collagen-induced platelet aggregation and release of platelet ATP and ADP. Intracellular changes of platelet radioactive nucleotides, particularly 3′:5′-cyclic AMP, were also determined both with and without collagen treatment. 2. Prostaglandin E1, theophylline and aspirin inhibited collagen-induced aggregation of platelets in a dose-dependent manner. Collagen-induced release of ATP and ADP and breakdown of radioactive ATP were also inhibited in a dose-dependent manner. 3. Prostaglandin E1 stimulated the formation of platelet radioactive 3′:5′-cyclic AMP in a dose-dependent manner. With a given dose of prostaglandin E1, maximum formation of radioactive 3′:5′-cyclic AMP occurred by 10–30s and thereafter the concentrations declined. The degree of inhibition of aggregation produced by prostaglandin E1, however, increased with its time of incubation in platelet-rich plasma before addition of collagen, so that there was an inverse relationship between the radioactive 3′:5′-cyclic AMP concentration measured at the time of collagen addition and the subsequent degree of inhibition of aggregation obtained. 4. Neither theophylline nor aspirin at a concentration in platelet-rich plasma of 1.7mm altered platelet radioactive 3′:5′-cyclic AMP contents. In the presence of prostaglandin E1, theophylline increased the concentration of radioactive 3′:5′-cyclic AMP over that noted with prostaglandin E1 alone, but aspirin did not. 5. Mixtures of prostaglandin E1 and theophylline had a synergistic effect on inhibition of platelet aggregation. The same was true to a lesser extent with mixtures of prostaglandin E1 and aspirin. Such mixtures also inhibited collagen-induced release of platelet ATP and ADP and breakdown of platelet radioactive ATP. 6. Certain concentrations of either theophylline or aspirin and mixtures of small concentrations of prostaglandin E1 with either theophylline or aspirin caused little or no increase of radioactive 3′:5′-cyclic AMP at the time of collagen addition, but inhibited aggregation to a marked degree, whereas higher concentrations of prostaglandin E1 alone caused a much greater increase of radioactive 3′:5′-cyclic AMP at the time of collagen addition but inhibited aggregation to a lesser extent. With these compounds there does not appear to be a correlation between these parameters.

Extracellular fibrinogen binding protein, Efb, from Staphylococcus aureus binds to platelets and inhibits platelet aggregation

2004 ◽  
Vol 91 (04) ◽  
pp. 779-789 ◽  
Author(s):  
Oonagh Shannon ◽  
Jan-Ingmar Flock
Keyword(s):  
Platelet Aggregation ◽  
Potent Inhibitor ◽  
Specific Binding ◽  
Binding Protein ◽  
Dependent Manner ◽  
Platelet Surface ◽  
Putative Receptor ◽  
Activated Platelets ◽  
Fibrinogen Binding ◽  
Dose Dependent

Summary S. aureus produces and secretes a protein, extracellular fibrinogen binding protein (Efb), which contributes to virulence in wound infection. We have shown here that Efb is a potent inhibitor of platelet aggregation. Efb can bind specifically to platelets by two mechanisms; 1) to fibrinogen naturally bound to the surface of activated platelets and 2) also directly to a surface localized component on the platelets. This latter binding of Efb is independent of fibrinogen. The specific binding of Efb to the putative receptor on the platelet surface results in a stimulated, non-functional binding of fibrinogen in a dose dependent manner, distinct from natural binding of fibrinogen to platelets. The natural binding of fibrinogen to GPIIb/IIIa on activated platelets could be blocked by a monoclonal antibody against this integrin, whereas the Efb-mediated fibrinogen binding could not be blocked. The enhanced Efb-dependent fibrinogen binding to platelets is of a nature that does not promote aggregation of the platelets; instead it inhibits aggregation. The anti-thrombotic action of Efb may explain the effect of Efb on wound healing, which is delayed in the presence of Efb.

FUNDC2 regulates platelet activation through AKT/GSK-3β/cGMP axis

2018 ◽  
Vol 115 (11) ◽  
pp. 1672-1679 ◽  
Author(s):  
Qi Ma ◽  
Weilin Zhang ◽  
Chongzhuo Zhu ◽  
Junling Liu ◽  
Quan Chen
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Mitochondrial Protein ◽  
Dependent Manner ◽  
Clot Retraction ◽  
Akt Phosphorylation ◽  
Gsk 3Β

Abstract Aims AKT kinase is vital for regulating signal transduction in platelet aggregation. We previously found that mitochondrial protein FUNDC2 mediates phosphoinositide 3-kinase (PI3K)/phosphatidylinositol-3,4,5-trisphosphate (PIP3)-dependent AKT phosphorylation and regulates platelet apoptosis. The aim of this study was to evaluate the role of FUNDC2 in platelet activation and aggregation. Methods and results We demonstrated that FUNDC2 deficiency diminished platelet aggregation in response to a variety of agonists, including adenosine 5′-diphosphate (ADP), collagen, ristocetin/VWF, and thrombin. Consistently, in vivo assays of tail bleeding and thrombus formation showed that FUNDC2-knockout mice displayed deficiency in haemostasis and thrombosis. Mechanistically, FUNDC2 deficiency impairs the phosphorylation of AKT and downstream GSK-3β in a PI3K-dependent manner. Moreover, cGMP also plays an important role in FUNDC2/AKT-mediated platelet activation. This FUNDC2/AKT/GSK-3β/cGMP axis also regulates clot retraction of platelet-rich plasma. Conclusion FUNDC2 positively regulates platelet functions via AKT/GSK-3β/cGMP signalling pathways, which provides new insight for platelet-related diseases.

scholarly journals A potent antiplatelet peptide, triflavin, from Trimeresurus flavoviridis snake venom

1991 ◽  
Vol 277 (2) ◽  
pp. 351-357 ◽  
Author(s):  
T F Huang ◽  
J R Sheu ◽  
C M Teng
Keyword(s):  
Platelet Aggregation ◽  
Snake Venom ◽  
Ionic Exchange ◽  
Dependent Manner ◽  
Single Chain ◽  
Platelet Suspension ◽  
Trimeresurus Flavoviridis ◽  
Platelet Membranes ◽  
Fibrinogen Binding ◽  
Induced Aggregation

The interaction of fibrinogen with its receptors on platelet surfaces leads to platelet aggregation. A snake-venom peptide, trigramin, has previously been demonstrated to inhibit platelet aggregation by acting as a fibrinogen-receptor antagonist. By means of gel filtration, ionic-exchange chromatography and reverse-phase h.p.l.c., a potent platelet-aggregation inhibitor, triflavin, has now been purified from the venom of Trimeresurus flavoviridis. The purified triflavin is a single-chain polypeptide, consisting of about 71 amino acid residues with a molecular mass of 7600 Da, and its N-terminal sequence is Gly-Glu-Glu-Cys-Asp. Triflavin dose-dependently inhibited human platelet aggregation stimulated by ADP, adrenaline, collagen, thrombin or prostaglandin endoperoxide analogue U46619 in preparations of platelet-rich plasma, platelet suspension and whole blood. Its IC50 ranged from 38 to 84 nM, depending on the aggregation inducer used and the platelet preparation. However, triflavin apparently did not affect the platelet shape change and ATP-release reactions caused by these agonists. Triflavin inhibited fibrinogen-induced aggregation of human elastase-treated platelets in a dose-dependent manner, indicating that it directly interferes with the binding of fibrinogen to its receptors on platelet membranes exposed by elastase treatment. Additionally, triflavin dose-dependently blocked 125I-labelled fibrinogen binding to ADP-activated platelets. In conclusion, triflavin inhibits platelet aggregation through the blockade of fibrinogen binding to fibrinogen receptors on platelet membranes.

scholarly journals Improved Antithrombotic Activity and Diminished Bleeding Side Effect of a PEGylated αIIbβ3 Antagonist, Disintegrin

Toxins ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 426
Author(s):  
Yu-Ju Kuo ◽  
Yao Tsung Chang ◽  
Ching-Hu Chung ◽  
Woei-Jer Chuang ◽  
Tur-Fu Huang
Keyword(s):  
Platelet Aggregation ◽  
Side Effect ◽  
Half Life ◽  
Platelet Rich Plasma ◽  
Drug Stability ◽  
Severe Thrombocytopenia ◽  
Bleeding Tendency ◽  
Dependent Manner

Polymer polyethylene glycol (PEG), or PEGylation of polypeptides improves protein drug stability by decreasing degradation and reducing renal clearance. To produce a pharmaceutical disintegrin derivative, the N-terminal PEGylation technique was used to modify the disintegrin derivative [KGDRR]trimucrin for favorable safety, pharmacokinetic profiles, and antithrombotic efficacy. We compared intact [KGDRR]trimucrin (RR) and PEGylated KGDRR (PEG-RR) by in vitro and in vivo systems for their antithrombotic activities. The activity of platelet aggregation inhibition and the bleeding tendency side effect were also investigated. PEG-RR exhibited optimal potency in inhibiting platelet aggregation of human/mouse platelet-rich plasma activated by collagen or ADP with a lower IC50 than the intact derivative RR. In the illumination-induced mesenteric venous thrombosis model, RR and PEG-RR efficaciously prevented occlusive thrombosis in a dose-dependent manner. In rotational thromboelastometry assay, PEG-RR did not induce hypocoagulation in human whole blood even given at a higher concentration (30 μg/mL), while RR slightly prolonged clotting time. However, RR and PEG-RR were not associated with severe thrombocytopenia or bleeding in FcγRIIa-transgenic mice at equally efficacious antithrombotic dosages. We also found the in vivo half-life of PEGylation was longer than RR (RR: 15.65 h vs. PEG-RR: 20.45 h). In conclusion, injectable PEG-RR with prolonged half-life and decreased bleeding risk is a safer anti-thrombotic agent for long-acting treatment of thrombus diseases.

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