Inhibition of Integrin-Mediated Platelet Aggregation, Fibrinogen-Binding, and Interactions with Extracellular Matrix by Nonpeptidic Mimetics of Arg-Gly-Asp

1993 ◽  
Vol 70 (06) ◽  
pp. 1030-1036 ◽  
Author(s):  
David Varon ◽  
Ofer Lider ◽  
Rima Dardik ◽  
Boris Shenkman ◽  
Ronen Alon ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Platelet Aggregation ◽  
Specific Interaction ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Rgd Sequence ◽  
Fibrinogen Binding ◽  
Inhibitory Potential ◽  
Dose Dependent

SummaryThe interaction of the activated platelet integrin, glycoprotein IIb-IIIa (GPIIb-IIIa) with fibrinogen and von-Wille-brand factor (vWF) is essential for platelet aggregation. The minimal structure required for this integrin’s binding to fibrinogen is the Arg-Gly-Asp (RGD) sequence. Inasmuch as normal level of GPIIb-IIIa-RGD interactions are required for maintaining hemostasis, elevated platelet aggregation can cause adverse pathological effects. We have previously reported that nonpeptidic mimetics of RGD, consisting of carboxylate and guanidinium groups of Asp and Arg divided by a linear 11-atom spacer, acquired a significant affinity for the GPIIb-IIIa integrin and inhibited platelet aggregation. The structural requirements for the interactions of the RGD sequence with GPIIb-IIIa and the inhibitory potential of a newly designed series of mimetics on platelet aggregation and interactions with extracellular matrix (ECM) were assayed herein. Adenosine-diphosphate (ADP)-induced platelet aggregation was inhibited in a dose-dependent manner by various RGD mimetics, with a maximal inhibition of 80-100% with an IC50 of 3 μM for the most potent inhibitor, NS-11 which a six-membered ring was introduced into the spacer chain, which exceeded the IC50 attained with the original RGDS peptide. The inhibitory effect of the RGD mimetics was attributed to their specific interaction with the GPIIb-IIIa integrin, since these mimetics inhibited the binding of the PAC-1 mAb to GPIIb-IIIA. Furthermore, the binding of 125I-labeled fibrinogen to platelets was inhibited by the RGD surrogates in a dose-dependent and saturable manner. The RGD-mimetics also inhibited up to 70% the adhesion, aggregation, and deposition of platelets onto ECM. Thus, we suggest that the novel nonpeptidic mimetics of RGD described herein, which were shown to be resistant to proteolytic digestion, would be valuable in novel therapeutic approaches to treat in RGD-dependent pathological disorders involving platelet-ECM interactions.

scholarly journals Inhibitory Effect of Propolis on Platelet Aggregation In Vitro

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Yun-Xiang Zhang ◽  
Ting-Ting Yang ◽  
Liu Xia ◽  
Wei-Fen Zhang ◽  
Jia-Fu Wang ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Water Extract ◽  
Adenosine Diphosphate ◽  
Caffeic Acid Phenethyl Ester ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Receptor Activator ◽  
Dose Dependent

Platelet hyperactivity plays an important role in arterial thrombosis and atherosclerosis. The present study was aimed to investigate the effects of different extracts of propolis and components of flavonoids on platelet aggregation. Platelet-rich plasma was prepared and incubated in vitro with different concentrations of the tested extracts and components of flavonoids. Platelets aggregation was induced by different agonists including adenosine diphosphate (ADP, 10 μM), thrombin receptor activator peptide (TRAP, 50 μM), and collagen (5 μg/mL). At 25 mg/L to 300 mg/mL, the water extract propolis (WEP) inhibited three agonists-induced platelet aggregations in a dose-dependent manner. The flavonoids isolated from the propolis also showed markedly inhibited platelet aggregation induced by collagen, ADP, and TRAP, respectively. The components including caffeic acid phenethyl ester (CAPE), galangin, apigenin, quercetin, kaempferol, ferulic acid, rutin, chrysin, pinostrobin, and pinocembrin and their abilities of inhibiting platelet aggregation were studied. It was concluded that propolis had an antiplatelet action in which flavonoids were mainly implicated.

Fibrinogen binding to the integrin αIIbβ3 modulates store-mediated calcium entry in human platelets

Blood ◽  
2001 ◽  
Vol 97 (9) ◽  
pp. 2648-2656 ◽  
Author(s):  
Juan A. Rosado ◽  
Else M. Y. Meijer ◽  
Karly Hamulyak ◽  
Irena Novakova ◽  
Johan W. M. Heemskerk ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Integrin Αiibβ3 ◽  
Fibrinogen Binding

Abstract Effects of the occupation of integrin αIIbβ3 by fibrinogen on Ca++signaling in fura-2–loaded human platelets were investigated. Adding fibrinogen to washed platelet suspensions inhibited increases in cytosolic [Ca++] concentrations ([Ca++]i) evoked by adenosine diphosphate (ADP) and thrombin in a concentration-dependent manner in the presence of external Ca++ but not in the absence of external Ca++ or in the presence of the nonselective cation channel blocker SKF96365, indicating selective inhibition of Ca++entry. Fibrinogen also inhibited store-mediated Ca++ entry (SMCE) activated after Ca++ store depletion using thapsigargin. The inhibitory effect of fibrinogen was reversed if fibrinogen binding to αIIbβ3 was blocked using RDGS or abciximab and was absent in platelets from patients homozygous for Glanzmann thrombasthenia. Fibrinogen was without effect on SMCE once activated. Activation of SMCE in platelets occurs through conformational coupling between the intracellular stores and the plasma membrane and requires remodeling of the actin cytoskeleton. Fibrinogen inhibited actin polymerization evoked by ADP or thapsigargin in control cells and in cells loaded with the Ca++ chelator dimethyl BAPTA. It also inhibited the translocation of the tyrosine kinase p60src to the cytoskeleton. These results indicate that the binding of fibrinogen to integrin αIIbβ3 inhibits the activation of SMCE in platelets by a mechanism that may involve modulation of the reorganization of the actin cytoskeleton and the cytoskeletal association of p60src. This action may be important in intrinsic negative feedback to prevent the further activation of platelets subjected to low-level stimuli in vivo.

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.

ROLE OF PLATELET GLYCOPROTEINS lb AND llb/llla IN TUMOR CELL INDUCED PLATELET AGGREGATION AND TUMOR CELL ADHESION TO EXTRACELLULAR MATRIX. I. Grossi

1987 ◽  
Author(s):  
L Grossi ◽  
K V Honn ◽  
B F Sloane ◽  
J Thomopson ◽  
D Ohannesian ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Cell Adhesion ◽  
Platelet Aggregation ◽  
Tumor Cell ◽  
Platelet Adhesion ◽  
Eicosatetraenoic Acid ◽  
Platelet Glycoprotein ◽  
Dependent Manner ◽  
Tumor Cell Adhesion ◽  
Dose Dependent

Platelet glycoproteins are known to play a role in platelet platelet interactions, platelet activation, and platelet adhesion to extracellular matrix (ECM). Monoclonal antibody to human platelet glycoprotein lb (mAblb) and polyclonal antibodies to the llb/llla complex (pAbllb/llla) were used to evaluate the involvement of these glycoproteins in tumor cellinduced platelet aggregation (TCIPA and tumor cell adhesion to the ECM. We have demonstrated that human cervical carcinoma (MS5I7), human colon carcinoma (Clone A), and rat Walker 256 carcinosarcoma (W256) cells induce aggregation of homologous platelets via thrombin generation. MAblb and pAbllb/llla were shown to inhibit TCIPA by MS517, Clone A, and W256 in a dose dependent manner. MAblb was also shown to inhibit platelet thromboxane B2 production in response to tumor cells in a dose dependent manner. Neither mAblb nor pAbllb/llla had any effect on ADP stimulated platelet aggregation. Concentrations of mAblb and pAbllb/llla which produced half maximal inhibition alone were combined resulting in complete inhibition of TCIPA. Preincubation of MS5I7 and W256 with mAblb also resulted in inhibition of TCIPA, while preincubation of Clone A with mAblb did not, suggesting the presence of this glycoprotein on the cell membranes of MS5I7 and W256, but not on Clone A. Immunofluorescence studies confirmed the presence of this glycoprotein on the cell plasma membrane of the MS5I7 and W256, but not on Clone A. Preincubation of MS5I7 and W256 with both mAblb and pAbllb/llla alone or in combination, also resulted in decreased (12S)-12 -hydroxy -5, 8,10, 14 -eicosatetraenoic acid (12-HETE) production, while platelets preincubated with these antibodies had no effect on the concentration of 12-HETE produced. Isolation of platelet membranes and released platelet contentswere tested separately and in combination on platelet adhesion to ECM. Platelet release factors were ineffective, while isolated platelet membrane ghosts enhanced adhesion. Disruption of the platelet cytoskeleton andinhibition of the formation of the llb/llla complex decreased platelet enhanced tumor cell adhesion. These findings suggest a role for these platelet glycoproteins in TCIPA, platelet enhanced tumor cell adhesion to ECM and subsequent tumor metastasis.

Ticlopidine Selectively Inhibits Human Platelet Responses to Adenosine Diphosphate

1991 ◽  
Vol 66 (06) ◽  
pp. 694-699 ◽  
Author(s):  
Marco Cattaneo ◽  
Benjaporn Akkawat ◽  
Anna Lecchi ◽  
Claudio Cimminiello ◽  
Anna M Capitanio ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Clot Retraction ◽  
Fibrinogen Binding ◽  
Low Concentrations ◽  
Binding Inhibition ◽  
High Concentrations ◽  
Formalin Fixed

SummaryPlatelet aggregation and fibrinogen binding were studied in 15 individuals before and 7 days after the oral administration of ticlopidine (250 mg b.i.d.). Ticlopidine significantly inhibited platelet aggregation induced by adenosine diphosphate (ADP), the endoperoxide analogue U46619, collagen or low concentrations of thrombin, but did not inhibit platelet aggregation induced by epinephrine or high concentrations of thrombin. Ticlopidine inhibited 125I-fibrinogen binding induced by ADP, U46619 or thrombin (1 U/ml). The ADP scavengers apyrase or CP/CPK, added in vitro to platelet suspensions obtained before ticlopidine, caused the same pattern of aggregation and 125I-fibrihogen binding inhibition as did ticlopidine. Ticlopidine did not inhibit further platelet aggregation and 125I-fibrinogen binding induced in the presence of ADP scavengers. After ticlopidine administration, thrombin or U46619, but not ADP, increased the binding rate of the anti-GPIIb/IIIa monoclonal antibody 7E3 to platelets. Ticlopidine inhibited clot retraction induced by reptilase plus ADP, but not that induced by thrombin or by reptilase plus epinephrine, and prevented the inhibitory effect of ADP, but not that of epinephrine, on the PGE1-induced increase in platelet cyclic AMP. The number of high- and low-affinity binding sites for 3H-ADP on formalin-fixed platelets and their K d were not modified by ticlopidine. These findings indicate that ticlopidine selectively inhibits platelet responses to ADP.

Thiosulfinates Inhibit Platelet Aggregation and Microparticle Shedding at a Calpain-dependent Step

2001 ◽  
Vol 86 (11) ◽  
pp. 1284-1291 ◽  
Author(s):  
Brigitte Brohard-Bohn ◽  
Sabine Pain ◽  
Christilla Bachelot-Loza ◽  
Jacques Auger ◽  
Francine Rendu
Keyword(s):  
Platelet Aggregation ◽  
Annexin V ◽  
Inhibitory Effect ◽  
Inhibit Platelet Aggregation ◽  
Clot Retraction ◽  
Allium Species ◽  
Calpain Activation ◽  
Fibrinogen Binding ◽  
Ic50 Values ◽  
Dose Dependent

SummaryThiosulfinates (TSs) are sulfur compounds generated through the processing of different Allium species with antiplatelet property. To further define this platelet inhibitory effect we studied diallyl-TS (Al2TS), dipropyl-TS (Pr2TS), and dimethyl-TS (Me2TS) on platelet responses. The three TSs inhibited dose-dependent platelet aggregation, with IC50 values of 15 ± 2, 19 ± 2, and 9 ± 1 μM for Al2TS, Pr2TS and Me2TS, respectively. TSs had no effect on the expression of a platelet procoagulant surface, measured by flow cytometry as the binding of annexin V-FITC. They inhibited the microparticle shedding and clot retraction. Since the microparticle shedding is a calpain-activation dependent step, we assessed calpain activation by analysis of autoproteolysis in shorter active forms and by talin proteolysis in the presence of TSs. Calpain activation was inhibited by TSs independently of fibrinogen binding. Thus, TSs represent a new category of platelet inhibitors, acting on cal-pain-induced events.

Recognition of platelet-associated fibrinogen by polyclonal antibodies: correlation with platelet aggregation

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2028-2033
Author(s):  
EI Peerschke
Keyword(s):  
Platelet Aggregation ◽  
Time Course ◽  
Polyclonal Antibodies ◽  
Surface Membrane ◽  
Adenosine Diphosphate ◽  
Dependent Manner ◽  
Membrane Structures ◽  
Platelet Surface ◽  
Fibrinogen Binding ◽  
Qualitative Changes

Progressive decreases in platelet-bound fibrinogen accessibility to antibody and enzymes were recently reported to occur after adenosine diphosphate (ADP)-induced fibrinogen binding. Because previous studies also indicated that platelets that are activated but not aggregated by ADP in the presence of fibrinogen lose their ability to aggregate in a time-dependent manner despite negligible changes in fibrinogen binding, the present study examined the relationship between platelet aggregation and accessibility of platelet-bound fibrinogen to specific polyclonal antibody F(ab')2 fragments over a 60-minute time course. Although 125I-fibrinogen binding remained virtually unchanged, comparison of antifibrinogen antibody F(ab')2 binding and platelet aggregation 5 minutes and 60 minutes after platelet stimulation with ADP or thrombin showed decreases in F(ab')2 binding of 62% +/- 13% and 73% +/- 7% (mean +/- SD, n = 5), respectively, and decreases of 65% +/- 16% and 60% +/- 10% in platelet aggregation. In contrast, platelets stimulated with A23187 or chymotrypsin retained 87% +/- 16% and 76% +/- 12% of their ability to aggregate over the same time course, and lost only 39% +/- 14% and 36% +/- 12% of their ability to bind antifibrinogen antibody F(ab')2 fragments, respectively. Pretreatment of ADP-stimulated platelets with chymotrypsin largely prevented the progressive loss of platelet aggregability and the accompanying decreased recognition of bound fibrinogen by antifibrinogen F(ab')2 fragments. Preincubation of platelets with cytochalasin D (30 micrograms/mL) also inhibited the decrease in platelet aggregation after exposure of ADP-treated platelets to fibrinogen over a 60-minute time course. This was accompanied by only a 25% +/- 18% decrease in antifibrinogen antibody F(ab')2 binding. Present data support the hypothesis that qualitative changes in platelet-bound fibrinogen correlate with loss of the ability of platelets to aggregate, and implicate both the platelet cytoskeleton and chymotrypsin-sensitive surface membrane structures in modulating qualitative changes in bound fibrinogen on the platelet surface.

scholarly journals Hemolytic activity and platelet aggregation inhibitory effect of vipoxin’s basic sPLA2 subunit

2013 ◽  
Vol 6 (3) ◽  
pp. 136-140 ◽  
Author(s):  
Silviya Stoykova ◽  
Yana Goranova ◽  
Ivayla Pantcheva ◽  
Vasil Atanasov ◽  
Dobri Danchev ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Platelet Aggregation ◽  
Hemolytic Activity ◽  
Blood Cells ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Erythrocyte Morphology ◽  
Dose Dependent ◽  
Vipera Ammodytes

ABSTRACT In the present study we evaluated the effect of secreted phospholipase A2 (sPLA2) (the toxic subunit of the heterodimeric neurotoxin vipoxin, isolated from the Bulgarian long-nosed viper Vipera ammodytes meridionalis) on hemolysis, erythrocyte morphology and platelet aggregation. Hemolytic activity of sPLA2 was examined in the presence of saturated (palmitic) and unsaturated (oleic) fatty acids and it was found that oleic acid increased the hemolytic activity of sPLA2 in a concentration-dependent manner, compared to the effect of palmitic acid and controls. The addition of heparin to red blood cells (RBC) suspension containing sPLA2 or mixture of sPLA2 and the corresponding fatty acid led to an inhibition of hemolytic activity. The effect of sPLA2 on RBC morphology resulted in formation of echinocytes (spherocyte subtype), suggesting that RBC could be the possible targets attacked by sPLA2. Vipoxin sPLA2 inhibited (in a dose-dependent manner) platelet aggregation when arachidonic acid and collagen were used as inducers, while in the case of ADP its inhibitory effect was inappreciable.

scholarly journals Effects of OKM5, a monoclonal antibody to glycoprotein IV, on platelet aggregation and thrombospondin surface expression [see comments]

Blood ◽  
1990 ◽  
Vol 76 (12) ◽  
pp. 2501-2509 ◽  
Author(s):  
ML Aiken ◽  
MH Ginsberg ◽  
V Byers-Ward ◽  
EF Plow
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Aggregation ◽  
Membrane Protein ◽  
Adenosine Diphosphate ◽  
Surface Expression ◽  
Inhibitory Effect ◽  
Target Antigen ◽  
Functional Responses ◽  
Fibrinogen Binding ◽  
Intact Antibody

The monoclonal antibody, OKM5, recognizes an 88-Kd monocyte membrane protein and also binds to the platelet membrane protein, GPIV (GPIIIb, CD36). In this study, we have found that the OKM5 target epitope is present at approximately 12,000 copies per platelet and that interaction with the antibody has both stimulatory and inhibitory effects on platelet function. In the absence of other stimuli, OKM5 induced platelet aggregation, secretion, and expression of fibrinogen receptors. These stimulatory responses required intact antibody as F(ab')2 fragments were not active but blocked the stimulatory activity of the intact antibody. In contrast, exposure of platelets to OKM5 followed by another strong stimulus such as thrombin resulted in a marked suppression of fibrinogen, fibronectin, and von Willebrand factor binding to the cells. This effect was not noted when a weak stimulus, adenosine diphosphate, was the second agonist. At OKM5 concentrations that interfered with fibrinogen binding to thrombin- stimulated platelets by 80% to 90%, platelet binding of exogenous thrombospondin, or surface expression of endogenous thrombospondin was not affected. The inhibitory effect of OKM5 on fibrinogen binding to thrombin-stimulated platelets was related to the formation of massive platelet aggregates in the samples. These results show that interaction of OKM5 with its target antigen on platelets can elicit diverse functional responses from the cells.

Induction of Apatite by the Cooperative Effect of Amelogenin and the 32-kDa Enamelin

2004 ◽  
Vol 83 (4) ◽  
pp. 278-282 ◽  
Author(s):  
N. Bouropoulos ◽  
J. Moradian-Oldak
Keyword(s):  
Extracellular Matrix ◽  
Inhibitory Effect ◽  
Cooperative Effect ◽  
Matrix Proteins ◽  
Dependent Manner ◽  
Nucleation Process ◽  
Gelatin Gels ◽  
Dose Dependent ◽  
Gel Diffusion ◽  
Hydroxyapatite Crystals

Extracellular matrix proteins are considered to play essential roles in controlling the nucleation, growth, and organization of hydroxyapatite crystals during enamel formation. The effects of amelogenin and the 32-kDa enamelin proteins on apatite nucleation were investigated by a steady-state gel diffusion device containing 10% gelatin gels loaded with 0, 0.75%, and 1.5% (w/w) native porcine amelogenins. It was found that the induction time for hydroxyapatite precipitation was strongly increased by the presence of amelogenins, suggesting an inhibitory effect of apatite nucleation. Addition of 18 μg/mL of 32-kDa enamelin to 10% gelatin also caused inhibition of nucleation. Remarkably, addition of 18 and 80 μg/mL of 32-kDa enamelin in gels containing 1.5% amelogenin accelerated the nucleation process in a dose-dependent manner. Our observations strongly suggest that the 32-kDa enamelin and amelogenins cooperate to promote nucleation of apatite crystals and propose a possible novel mechanism of mineral nucleation during enamel biomineralization.

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