scholarly journals Platelets as Predictors of Vascular Risk: Is There a Practical Index of Platelet Activity?

2003 ◽  
Vol 9 (3) ◽  
pp. 177-190 ◽  
Author(s):  
Stavroula Tsiara ◽  
Moses Elisaf ◽  
I. Anita Jagroop ◽  
Dimitri P. Mikhailidis
Keyword(s):  
Flow Cytometry ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Platelet Rich Plasma ◽  
Vascular Risk ◽  
Platelet Activity ◽  
Vascular Events ◽  
Bioactive Substances ◽  
Platelet Surface ◽  
Soluble P

Activated platelets play a role in the pathogenesis of coronary heart disease (CHD). Following activation, platelets change shape, aggregate, and release several bioactive substances. The aim of this review is to identify if there is a simple and cost-effective method that indicates platelet activation and predicts the risk of CHD and vascular events. The rationale for identifying high-risk patients is to reduce their risk of vascular events by administering appropriate and effective antiplatelet treatment, like aspirin, clopidogrel, or combination regimens. Many laboratory tests estimating platelet activity have been described. Some are relatively simple, such as spontaneous or agonist-induced platelet aggregation. Other tests include measuring the mean platelet volume (MPV) or plasma soluble P-selectin levels. Some more complex tests include flow cytometry to determine platelet GP Ilb/Illa receptors, platelet surface P-selectin, plateletmonocyte aggregates, and microparticles. Only few prospective studies assessed the predictive value of platelet activation in healthy individuals. Although the MPV seems an 'easy method, there are insufficient data supporting its ability to predict the risk of a vascular event in healthy adults. Platelet aggregation, in whole blood or in platelet-rich plasma was not consistently predictive of vascular risk. Soluble P-selectin measurement is a promising method but it needs further evaluation. Flow cytometry methods are costly, time-consuming, and need specialized equipment. Thus, they are unlikely to be useful in estimating the risk in large numbers of patients. There is as yet no ideal test for the detection of platelet activation. Each currently available test has merits and disadvantages. Simple methods such as the MPV and the determination of platelet release products need further evaluation.

Fucosyltransferase VI Induces Platelet Activation: A Novel Property of a Plasma Glycosyltransferase.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4016-4016
Author(s):  
José-Tomás Navarro ◽  
Shwan Tawfiq ◽  
Roland Wohlgemuth ◽  
Karin M. Hoffmeister ◽  
Robert Sackstein
Keyword(s):  
Flow Cytometry ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Light Transmission ◽  
Conflicts Of Interest ◽  
Platelet Rich Plasma ◽  
Surface Protein ◽  
Surface Flow ◽  
Platelet Surface ◽  
Biochemical Studies

Abstract Abstract 4016 Poster Board III-952 A number of glycosyltransferases are present in human plasma with the α(1→3) fucosyltransferase, Fucosyltransferase VI (FTVI), having the highest plasma concentration. Notably, elevated plasma levels of FTVI are associated with a variety of cancers and correlate with tumor load/progression. The well-known association of neoplasia with thromboembolic complications prompted us to examine whether FTVI has direct effect(s) on platelet function. We obtained human platelets from blood of healthy donors and separated from platelet-rich plasma by differential centrifugation. Freshly isolated platelets (x108/ml) were stirred and exposed at 37°C to varying concentrations (20, 40, 60 and 80 mU/mL) of glycosyltransferases FTVI, β-1-4-galactosyltransferase-I (βGalT-I), or α,2-3-N-sialyltransferase (α2,3-N-ST), or to 1 U/mL thrombin. Platelet aggregation and activation was assessed by aggregometry (light transmission) or by flow cytometry of FSC/SSC characteristics and of surface expression of P-Selectin, respectively. FT-VI reproducibly induced platelet aggregation and activation, whereas other glycosyltransferases (β4GalT-I and α2,3-N-ST) had no effect on platelets. FTVI activation of platelets was concentration-dependent, and the aggregation curve for FTVI was one wave, similar to that for thrombin. FTVI-induced platelet activation was independent of catalytic conversion of surface glycans, but was inhibited by FTVI denaturation, indicating that FTVI-induced platelet activation is a lectin-mediated process. To determine the membrane target(s) mediating FTVI-induced platelet activation, biochemical studies were performed after catalytic exofucosylation of the platelet surface. Flow cytometry after platelet exofucosylation showed formation of the carbohydrate structure sLex, detected by the mAb Heca452, but no formation of Lex (CD15). Western blot showed that enforced fucosylation induced sLex on a single platelet surface protein, and further biochemical studies revealed that this protein is GPIbα. These findings unveil a previously unrecognized property of FTVI as an activator of platelets, mediated via a specific lectin/carbohydrate interaction on GP1ba, and offer novel perspectives on the pathobiology of tumor-associated thrombogenesis. Disclosures: No relevant conflicts of interest to declare.

scholarly journals von Willebrand factor bound to glycoprotein Ib is cleared from the platelet surface after platelet activation by thrombin

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2011-2021 ◽  
Author(s):  
P Hourdille ◽  
HR Gralnick ◽  
E Heilmann ◽  
A Derlon ◽  
AM Ferrer ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Surface Expression ◽  
Von Willebrand Disease ◽  
Platelet Surface ◽  
Immunogold Staining ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract We recently reported that after activation of human platelets by thrombin, glycoprotein (GP) Ib-IX complexes are translocated to the surface-connected canalicular system (SCCS) (Blood 76:1503, 1990). As GPIb is a major receptor for von Willebrand factor (vWF) in platelet adhesion, we have now examined the consequences of thrombin activation on the organization of vWF bound to GPIb on the platelet surface. Studies were performed using monoclonal or polyclonal antibodies in either immunogold staining and electron microscopy (Au-EM) or in flow cytometry. When unstirred platelet-rich plasma was incubated with ristocetin, bound vWF was located by Au-EM as discrete masses regularly distributed over the cell surface. Platelets from a patient with Glanzmann's thrombasthenia, lacking GPIIb-IIIa complexes, gave a similar pattern, confirming that this represented binding to GPIb. That ristocetin was not precipitating vWF before their binding to the platelets was shown by the detection of similar masses on the surface of platelets of a patient with type IIB von Willebrand disease. Experiments were continued using washed normal platelets incubated in Tyrode-EDTA, the purpose of the EDTA being to limit the surface expression of endogenous vWF after platelet stimulation. Under these conditions, platelets were treated with ristocetin for 5 minutes at 37 degrees C in the presence of increasing amounts of purified vWF. This was followed by incubation with thrombin (0.5 U/mL) for periods of up to 10 minutes. Flow cytometry showed a time-dependent loss in the surface expression of vWF bound to GPIb and these changes were confirmed by Au-EM. In particular, immunogold staining performed on ultrathin sections showed that the bulk of the vWF was being cleared to internal membrane systems. Surface clearance of vWF during thrombin- induced platelet activation is a potential mechanism for regulating platelet adhesivity.

The active metabolite of prasugrel inhibits ADP-stimulated thrombo-inflammatory markers of platelet activation: Influence of other blood cells, calcium, and aspirin

2007 ◽  
Vol 98 (07) ◽  
pp. 192-200 ◽  
Author(s):  
Joseph Jakubowski ◽  
You FuLi ◽  
Marc Barnard ◽  
Marsha Fox ◽  
Matthew Linden ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Whole Blood ◽  
Blood Cells ◽  
Inflammatory Markers ◽  
Active Metabolite ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Flow Cytometric Analysis ◽  
Platelet Surface

SummaryThe novel thienopyridine prodrug prasugrel, a platelet P2Y12 ADP receptor antagonist, requires in vivo metabolism for activity. Although pharmacological data have been collected on the effects of prasugrel on platelet aggregation,there are few data on the direct effects of the prasugrel’s active metabolite, R-138727, on other aspects of platelet function. Here we examined the effects of R-138727 on thrombo-inflammatory markers of platelet activation, and the possible modulatory effects of other blood cells, calcium, and aspirin. Blood (PPACK or citrate anticoagulated) from healthy donors pre- and post-aspirin was incubated with R-138727 and the response to ADP assessed in whole blood or platelet-rich plasma (PRP) by aggregometry and flow cytometric analysis of leukocyte-platelet aggregates,platelet surface P-selectin, and GPIIb-IIIa activation. Low-micromolar concentrations of R-138727 resulted in a rapid and consistent in-hibition of these ADP-stimulated thrombo-inflammatory markers.These rapid kinetics required physiological calcium levels, but were largely unaffected by aspirin. Lower IC50 values in whole blood relative to PRP suggested that other blood cells affect ADP-induced platelet activation and hence the net inhibition by R-138727. R-138727 did not inhibit P2Y12-mediated ADP-induced shape change, even at concentrations that completely inhibited platelet aggregation, confirming the specificity of R-138727 for P2Y12. In conclusion, R-138727, the active metabolite of prasugrel, results in rapid, potent, consistent, and selective inhibition of P2Y12-mediated up-regulation of thromboinflammatory markers of platelet activation.This inhibition is enhanced in the presence other blood cells and calcium,but not aspirin.

scholarly journals The Effect of Tirofiban on Fibrinogen/Agonist-Induced Platelet Shape Change and Aggregation

2008 ◽  
Vol 14 (3) ◽  
pp. 295-302 ◽  
Author(s):  
I. Anita Jagroop ◽  
Dimitri P. Mikhailidis
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Adenosine Diphosphate ◽  
Vascular Events ◽  
Spontaneous Platelet Aggregation ◽  
Induced Aggregation ◽  
Platelet Shape

There is evidence linking raised plasma fibrinogen (fib) and platelet hyperactivity with vascular events. One way to inhibit platelets is to block the platelet membrane glycoprotein (GP) IIb/IIIa receptor, which binds circulating fib or von Willebrand factor and cross-links platelets at the final common pathway to platelet aggregation. Tirofiban is a potent and specific fib receptor antagonist, used in the treatment of unstable angina. The authors assessed the effect of tirofiban on spontaneous platelet aggregation (SPA), fib-induced, serotonin (5HT)-induced, and adenosine diphosphate (ADP)-induced aggregation in whole blood by calculating the percentage free platelet count. These various agonists were used alone and in combination. The authors also measured the effect of tirofiban on agonists-induced (ADP, 5HT) platelet shape change (PSC). The effect of fib on PSC was also evaluated in platelet-rich plasma using a high-resolution (0.07 fL) channelyzer. Tirofiban significantly inhibited SPA, fib (2, 4, 8 g/L), ADP, ADP + fib combination, and 5HT-induced aggregation. Tirofiban had no effect on agonist-induced PSC. There was no apparent change in platelet volume with fib. In conclusion, tirofiban does not appear to have an effect on PSC, an early phase of platelet activation. Tirofiban seems to be a nonspecific and an effective inhibitor of platelet aggregation (a later phase of platelet activation) in whole blood. The clinical significance of these findings remains to be established.

scholarly journals von Willebrand factor bound to glycoprotein Ib is cleared from the platelet surface after platelet activation by thrombin

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2011-2021
Author(s):  
P Hourdille ◽  
HR Gralnick ◽  
E Heilmann ◽  
A Derlon ◽  
AM Ferrer ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Surface Expression ◽  
Von Willebrand Disease ◽  
Platelet Surface ◽  
Immunogold Staining ◽  
Von Willebrand ◽  
Willebrand Factor

We recently reported that after activation of human platelets by thrombin, glycoprotein (GP) Ib-IX complexes are translocated to the surface-connected canalicular system (SCCS) (Blood 76:1503, 1990). As GPIb is a major receptor for von Willebrand factor (vWF) in platelet adhesion, we have now examined the consequences of thrombin activation on the organization of vWF bound to GPIb on the platelet surface. Studies were performed using monoclonal or polyclonal antibodies in either immunogold staining and electron microscopy (Au-EM) or in flow cytometry. When unstirred platelet-rich plasma was incubated with ristocetin, bound vWF was located by Au-EM as discrete masses regularly distributed over the cell surface. Platelets from a patient with Glanzmann's thrombasthenia, lacking GPIIb-IIIa complexes, gave a similar pattern, confirming that this represented binding to GPIb. That ristocetin was not precipitating vWF before their binding to the platelets was shown by the detection of similar masses on the surface of platelets of a patient with type IIB von Willebrand disease. Experiments were continued using washed normal platelets incubated in Tyrode-EDTA, the purpose of the EDTA being to limit the surface expression of endogenous vWF after platelet stimulation. Under these conditions, platelets were treated with ristocetin for 5 minutes at 37 degrees C in the presence of increasing amounts of purified vWF. This was followed by incubation with thrombin (0.5 U/mL) for periods of up to 10 minutes. Flow cytometry showed a time-dependent loss in the surface expression of vWF bound to GPIb and these changes were confirmed by Au-EM. In particular, immunogold staining performed on ultrathin sections showed that the bulk of the vWF was being cleared to internal membrane systems. Surface clearance of vWF during thrombin- induced platelet activation is a potential mechanism for regulating platelet adhesivity.

Comparison of platelet aggregation parameters and expression of platelet granule markers

2019 ◽  
Author(s):  
В.В. Малышева ◽  
О.А. Шустова ◽  
С.Г. Хаспекова ◽  
Я.А. Наймушин ◽  
А.В. Мазуров
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Light Transmission ◽  
Platelet Rich Plasma ◽  
Thrombin Receptor ◽  
Platelet Surface ◽  
Dense Granules ◽  
Turbidimetric Method ◽  
Healthy Donors ◽  
Aggregation Parameters

Введение. Активация тромбоцитов стимулирует их агрегацию и ассоциированный с секрецией экзоцитоз внутриклеточных гранул. Агрегацию чаще всего изучают турбидиметрическим методом, а экзоцитоз гранул методом проточной цитофлуориметрии, определяя экспрессию их маркеров на поверхности тромбоцитов. Цель исследования: сравнение чувствительности двух методов оценки активации тромбоцитов, исследования их агрегации и экспрессии маркеров внутриклеточных гранул. Материалы и методы. Тромбоциты здоровых доноров активировали АДФ и пептидом, активирующим рецептор тромбина (thrombin receptor activating peptide, TRAP). Агрегацию тромбоцитов изучали турбидиметрическим методом в обогащенной тромбоцитами плазме, регистрируя максимальный уровень светопропускания (Т макс). Экспрессию маркеров гранул изучали в цельной крови с помощью проточной цитофлуориметрии, регистрируя процент тромбоцитов, окрашенных антителами против маркеров альфагранул (CD62P) и плотных гранул (CD63). Результаты. У всех доноров 20 мкМ АДФ и 10 мкМ TRAP стимулировали мощную, необратимую агрегацию тромбоцитов (62,1 10,3 и 65,1 5,1 T макс, соответственно). Средние уровни агрегации были ниже при ее стимуляции 2,5 мкМ АДФ (30,9 23,2 T макс) и 1 мкМ TRAP (24,4 29,1 T макс). Экспрессия маркеров гранул была максимальной при активации тромбоцитов 10 мкМ TRAP (77,6 13,7 CD62P и 73,9 13,3 CD63), ниже при активации 1 мкМ TRAP (46,3 25,1 CD62P и 38,3 23,8 CD63), еще ниже при активации 20 мкМ АДФ (19,8 8,5 CD62P и 13,6 5,2 CD63) и минимальной при активации 2,5 мкМ АДФ (8,0 4,2 CD62P и 8,3 3,3 CD63). Адреналин (20 мкМ) не стимулировал экспрессию маркеров гранул, но при совместном добавлении с 20 мкМ АДФ повышал ее в 1,9 раза для обоих маркеров CD62P и CD63. Заключение. При активации тромбоцитов АДФ исследование агрегации является более чувствительным методом, чем определение экспрессии маркеров гранул. При активации тромбоцитов TRAP чувствительность обоих методов приблизительно одинакова. Экспрессия маркеров гранул увеличивается при совместном добавлении к тромбоцитам АДФ и адреналина, хотя адреналин сам по себе не стимулирует их экспрессию. Introduction. Platelet activation stimulates their aggregation and secretion associated exocytosis of intracellular granules. Aggregation is usually studied by turbidimetric method and granule exocytosis by detecting expression of their markers on platelet surface using flow cytofluorimetry. Aim: сomparison of the sensitivity of two methods for evaluation of platelet activation, studies of their aggregation and expression of intracellular granule markers. Materials and methods. Healthy donors platelets were activated by ADP and thrombin receptor activating peptide (TRAP). Platelet aggregation was investigated in platelet rich plasma by turbidimetric method, assessed by the maximal level of light transmission (T max). Expression of granule markers was detected in whole blood by fl ow cytofl uorimetry registering the percent of platelets stained with antibodies against the markers of alphagranules (CD62P) and dense granules (CD63). Results. In all donors 20 M ADP and 10 M TRAP stimulated strong irreversible platelet aggregation (62.1 10.3 and 65.1 5.1 T max). Mean aggregation levels were lower when it was stimulated by 2.5 M ADP (30.9 23.2 T max) and 1 M TRAP (24.4 29.1 T max). Expression of granule markers was maximal at platelet activation by 10 M TRAP (77.6 13.7 CD62P and 73.9 13.3 CD63), lower at activation by 1 M TRAP (46.3 25.1 CD62P and 38.3 23.8 CD63), more lower at activation by 20 M ADP (19.8 8.5 CD62P and 13.6 5.4 CD63), and minimal at activation by 2.5 M ADP (8.0 4.2 CD62P and 8.3 3.3 CD63). Epinephrine (20 M) did not stimulate expression of granule markers but at combined addition with 20 M ADP increased its level by 1.9 for both markers, CD62P and CD63. Conclusion. Platelet aggregation is more sensitive method than detection of expression of granule markers when platelets are activated by ADP. Both methods demonstrate about the same sensitivity when platelets are activated by TRAP. Expression of granule markers is increased at combined addition of ADP and epinephrine although epinephrine by itself fails to stimulate their expression.

scholarly journals ROS Promote Ox-LDL-Induced Platelet Activation by Up-Regulating Autophagy Through the Inhibition of the PI3K/AKT/mTOR Pathway

2018 ◽  
Vol 50 (5) ◽  
pp. 1779-1793 ◽  
Author(s):  
Xiang Wang ◽  
Yun-Feng Fu ◽  
Xiao Liu ◽  
Guo Feng ◽  
Dan Xiong ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Mtor Pathway ◽  
Enhanced Chemiluminescence ◽  
Transmission Electron ◽  
Related Proteins

Background/Aims: Oxidized low-density lipoprotein (oxLDL) promotes unregulated platelet activation in patients with dyslipidemic disorders. Although oxLDL stimulates activating signaling, researchers have not clearly determined how these events drive accelerated thrombosis. Here, we describe the mechanism by which ROS regulate autophagy during ox-LDL-induced platelet activation by modulating the PI3K/AKT/mTOR signaling pathway. Methods: For in vitro experiments, ox-LDL, the ROS scavenger N-acetylcysteine (NAC), the mTOR inhibitor rapamycin and the autophagy inhibitor 3-MA were used alone or in combination with other compounds to treat platelets. Then, platelet aggregation was evaluated on an aggregometer and platelet adhesion was measured under shear stress. The levels of a platelet activation marker (CD62p) were measured by flow cytometry, reactive oxygen species (ROS) levels were then quantified by measuring DCFH-DA fluorescence intensity via flow cytometry. Nitric oxide (NO) and superoxide (O2·-) levels were determined by the nitric acid deoxidize enzyme method and lucigenin-enhanced chemiluminescence (CL), respectively. Transmission electron microscopy was used to observe the autophagosome formation, immunofluorescence staining was employed to detect LC3 expression and western blotting was used to measure the levels of PI3K/AKT/mTOR pathway- and autophagy-related proteins. Results: Ox-LDL-induced platelets showed a significant increase in platelet aggregation and adhesion, CD62p expression, ROS level and O2·- content, with an elevated LC3II/LC3I ratio and Beclin1 expression, but a dramatic reduction in the levels of p62 and pathway-related proteins (all P < 0.05). However, platelet activation and autophagy were aggravated by the Rapamycin treatment, and decreased following treatment with NAC, 3-MA, or NAC and 3-MA, together with increased activity of the PI3K/AKT/mTOR pathway. Additionally, decreased platelet activation and autophagy were observed in platelets treated with NAC and Rapamycin or Rapamycin and 3-MA compared with platelets treated with Rapamycin alone, suggesting that both NAC and 3-MA reversed the effects of Rapamycin. Conclusion: Inhibition of ROS production may reduce autophagy to suppress ox-LDL-induced platelet activation by activating PI3K/AKT/mTOR pathway.

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 Activation of human platelets by immune complexes prepared with cationized human IgG

Blood ◽  
1993 ◽  
Vol 82 (10) ◽  
pp. 3045-3051
Author(s):  
M Schattner ◽  
M Lazzari ◽  
AS Trevani ◽  
E Malchiodi ◽  
AC Kempfer ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Immune Complexes ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Human Igg ◽  
Experimental Conditions ◽  
Induce Platelet Aggregation ◽  
Soluble Immune Complexes ◽  
High Concentrations

The present study shows that the ability of soluble immune complexes (IC), prepared with human IgG and rabbit IgG antibodies against human IgG, to trigger platelet activation was markedly higher for IC prepared with cationized human IgG (catIC) compared with those prepared with untreated human IgG (cIC). CatIC induced platelet aggregation and adenosine triphosphate release in washed platelets (WP), gel-filtered platelets (GFP), or platelet-rich plasma (PRP) at physiologic concentrations of platelets (3 x 10(8)/mL) and at low concentrations of catIC (1 to 30 micrograms/mL). On the contrary, under similar experimental conditions, cIC did not induce aggregation in PRP, WP, or GFP. Low aggregation responses were only observed using high concentrations of both WP (9 x 10(8)/mL) and cIC (500 micrograms/mL). Interestingly, catIC were also able to induce platelet activation under nonaggregating conditions, as evidenced by P-selectin expression. Cationized human IgG alone did not induce platelet aggregation in PRP but triggered either WP or GFP aggregation. However, the concentration needed to induce these responses, was about eightfold higher than those required for catIC. The responses induced either by catIC or cationized human IgG were completely inhibited by treatment with heparin, dextran sulphate, EDTA, prostaglandin E1, or IV3, a monoclonal antibody against the receptor II for the Fc portion of IgG (Fc gamma RII). The data presented in this study suggest that IgG charge constitutes a critical property that conditions the ability of IC to trigger platelet activation.

Diabetic Retinopathy And Thromboxane Like Substance

1981 ◽  
Author(s):  
M A Lazzari ◽  
M Gimeno ◽  
N M Sutton ◽  
J R Lopez
Keyword(s):  
Diabetes Mellitus ◽  
Arachidonic Acid ◽  
Diabetic Retinopathy ◽  
Risk Factor ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Thromboxane A2 ◽  
Initial Step ◽  
Platelet Activity

Diabetes Mellitus (DM) is a risk factor in the development of vasculopathies and its complications. It produces also its own microangiopathy. Evidence was reported of increased platelet activity in DM in different assays. Platelets aggregation and the arachidonic cycle could play a key role in the increased tendency to thrombosis. A disorder of ratio TXA2/PGI2, two opposing prostaglandin derivatives, could be the initial step. We intended to evaluate a thromboxane like substance (TLS) produced from platelet rich plasma (PRP) and to compare between normals and diabetic retinopathy (DR) patients. TLS was measured in 16 controls and 16 patients. Assay was done with the aggregating activity developed in PRP (considered TLS) after addition of arachidonic acid (f.c. 2 mM). The supernatant of the PRP (100 μl) was taken 40 sec. after the aggregation started and were added to a normal PRP treated with aspirin (f.c. 40 μl/ml) adjusted to 250.000 - 300.000 pl/μl and the degree of platelet aggregation measured in a Chrono Log Aggregometer. TLS was inactivated after its incubation during 2 min. at 37°C. This finding suggests this activity is due to TXA2.The results obtained (expressed in % of platelet aggregation) were: controls x 16.37% ± 6.28 and DR x 36.00% ± 9.72.The increase detected in the DR group supports previous experimental reports suggesting the role of the thromboxane A2 in vaso occlusive complication of diabetes mellitus.

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