scholarly journals Lecithin Analog as a New Platelet Aggregating Agent

1977 ◽  
Author(s):  
J. Hawiqer ◽  
H. W. Hooper
Keyword(s):  
Platelet Aggregation ◽  
Blood Platelets ◽  
Human Platelets ◽  
Phospholipase A ◽  
Synthetic Analog ◽  
Autologous Plasma ◽  
Vitro Effect ◽  
Dose Dependent ◽  
Phospholipase A Inhibitor

Lecithin comprises 32% of the human platelet phospholipids which are the source of arachidonic acid required for biosynthesis of prostaglandin endoperoxides, potent inducers of platelet aggregation. A synthetic analog of lecithin, dimethly-DL-2,3-distearoyloxypropyl-2’-hydroxy-ethylammonium acetate known as a phospholipase A inhibitor, showed a profound in vitro effect upon human platelets. Blood platelets obtained from normal, healthy, fasting volunteers and suspended in autologous plasma aggregated in response to lecithin analog. Platelet aggregation was dose-dependent within the range of 10-5 to 10-4M of lecithin analog and accompanied by release of [3H] serotonin. In contrast, addition of equimolar or higher amounts of lecithin to human platelets in vitro remained without a measurable effect on their function. Sensitivity of human platelets to the lecithin analog used was increased at least 10-fold by separation of platelets from the bulk of plasma proteins by gel filtration on Sepharose 2B. Release of [3H] serotonin from gel-filtered platelets induced by the lecithin analog studied was dose-dependent and partly reversible due to reuptake of serotonin. Thus, the lecithin analog used in our experiments is a new platelet activating agent which is a “false phospholipid” and phospholipase A inhibitor acting through a previously unrecognized mechanism triggering membrane-mediated functions of human platelets.

Interactions Between Blood Platelets and Vascular Endothelium in vitro Studies

1979 ◽  
Author(s):  
M.A. Gimbrone ◽  
K.D. Curwen ◽  
R. I. Handin
Keyword(s):  
Platelet Aggregation ◽  
Vascular Endothelium ◽  
Potent Inhibitor ◽  
Platelet Reactivity ◽  
Blood Platelets ◽  
Primary Cultures ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Platelet Adherence

Endothelial cells (EC) can actively influence the hemostatic response at sites of vascular injury through multiple mechanisms. For example, EC can degrade adenosine diphosphate, release plasminogen activator, and synthesize prostacyclin (PGI2), a potent inhibitor of platelet aggregation. We have examined whether PGI2 also might account for the normal lack of platelet adherence to the uninjured EC surface. In a monolayer adherence assay, radiolabeled human platelets in citrated plasma showed minimal interaction with primary cultures of human EC (<1 platelet adhering per cell). Platelets from aspirin-treated and untreated donors behaved similarly. However, aspirin pretreatment of EC consistently resulted in ~2-fold increases in platelet adherence which could be completely abolished by exogenous PGI2 (0.5–1.0 μg/ml). SV40-transformed human EC (SVHEC), which are deficient in PGI2 production compared to primary EC, showed 10-30 times more platelet adherence. Exogenous PGI2 produced a dose - related (.001-1.0 μg/ml) decrease in platelet adherence to SVHEC but did not result in the basal levels observed with normal EC monolayers. These data suggest that : 1) In addition to its effects on platelet aggregation, PGI2 can influence platelet endothelial cell interactions; 2) The increased platelet reactivity of transformed EC is associated with, but not completely attributable, to decreased PGI2 production; and 3) Factors other than PGI2 may play a role in the thromboresistance of normal vascular endothelium.

Endotoxin-Induced Platelet Activation in Human Whole Blood In Vitro

1988 ◽  
Vol 59 (03) ◽  
pp. 378-382 ◽  
Author(s):  
Gyorgy Csako ◽  
Eva A Suba ◽  
Ronald J Elin
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Atp Release ◽  
Human Platelets ◽  
Lag Phase ◽  
Human Whole Blood ◽  
Dose Dependent

SummaryThe effect of purified bacterial endotoxin was studied on human platelets in vitro. In adding up to 1 μg/mL of a highly purified endotoxin, we found neither aggregation nor ATP release in heparinized or citrated human platelet-rich plasma. On the other hand, endotoxin at concentrations as low as a few ng/mL (as may be found in septic patients) caused platelet aggregation in both heparinized and citrated human whole blood, as monitored by change in impedance, free platelet count, and size. Unlike collagen, the platelet aggregation with endotoxin occurred after a long lag phase, developed slowly, and was rarely coupled with measurable release of ATP. The platelet aggregating effect of endotoxin was dose-dependent and modified by exposure of the endotoxin to ionizing radiation. Thus, the activation of human platelets by “solubilized” endotoxin in plasma requires the presence of other blood cells. We propose that the platelet effect is mediated by monocytes and/or neutrophils stimulated by endotoxin.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Abstract Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

Monosubstituted Coumarins Inhibit Epinephrine-Induced Platelet Aggregation Antiplatelet Effect of Monosubstituted Coumarins

2021 ◽  
Vol 19 ◽  
Author(s):  
Fausto Alejandro Jiménez-Orozco ◽  
Sergio Galicia-Zapatero ◽  
Edgar López-López ◽  
José L. Medina-Franco ◽  
Fernando León Cedeño ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
In Silico ◽  
Drug Targets ◽  
Platelet Reactivity ◽  
Antiplatelet Agents ◽  
Human Platelets ◽  
In Silico Studies ◽  
Vitro Effect ◽  
Induced Aggregation

Aim: Evaluate the in vitro effect of coumarin and 15 monosubstituted derivatives on the inhibition of human platelet aggregation induced by various pro-aggregatory agonists, particularly by epinephrine. Background: The emergence of residual platelet reactivity during the use of conventional antiplatelet agents (acetylsalicylic acid and clopidogrel) is one of the main causes of double therapy´s therapeutic failure. Platelet adrenoceptors participate in residual platelet reactivity. Therefore, it is necessary to develop new antiplatelet agents that inhibit epinephrine-induced platelet aggregation as a new therapeutic strategy. Information on the antiplatelet activity of coumarins in inhibiting epinephrine-induced aggregation is limited. Objective: Establish the structure-activity relationship (SAR) of coumarin derivatives with hydroxy, methoxy, and acetoxy groups in different positions of the coumarin nucleus to identify the most active molecules. Using in silico studies, suggest potential drug targets to which the molecules bind to produce antiplatelet effects. Methods: The platelet aggregation was performed using a Lumi-aggregometer; the inhibitory activity of 16 compounds were evaluated by inducing the aggregation of human platelets (250 × 103/μl) with epinephrine (10 µM), collagen (2 µg / ml) or ADP (10 µM). The aggregation of controls platelets was considered 100% of the response for each pro-aggregatory agonists. Results: Eleven molecules inhibited epinephrine-induced aggregation, with 3-acetoxycoumarin and 7-methoxycoumarin being the most active. Only coumarin inhibited collagen-induced platelet aggregation, but no molecule showed activity when using ADP as an inducer. Conclusions : In silico studies suggest that most active molecules might have antagonistic interactions in the adrenoceptors α2 and β2. The antiplatelet actions of these coumarins have the potential to reduce residual platelet reactivity and thus contribute to the development of future treatments for patients who do not respond adequately to conventional agents.

In Vitro Evaluation of the Effect of rFVIIa on Anti Coagulated Human Whole Blood Treated with Abciximab Using Thromboelastography (TEG).

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1114-1114
Author(s):  
Dorthe Viuff ◽  
Soeren Andersen ◽  
Brian Lauritzen ◽  
Mirella Ezban
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Ex Vivo ◽  
Maximum Amplitude ◽  
Bleeding Complications ◽  
Clot Lysis ◽  
Anova Model ◽  
Vitro Effect ◽  
Dose Dependent

Abstract Abciximab inhibits platelet aggregation by binding to GPIIb/IIIa. Thus, Abciximab is effective in prevention and treatment of thromboembolic events. Although major bleeding complications are rare, Abciximab has the potential to increase bleeding which often is managed by temporary discontinuation of administration of drug. However, an effective and instant haemostatic intervention may be needed in some cases of acute serious bleeding. The aim of this study was to investigate 1) the effect of in vitro addition of Abciximab to whole blood (WB) from 8 healthy donors, 2) to determine the haemostatic potential of ex vivo addition of 10, 25 (25nM≈90ug/kg), and 100nM rFVIIa (NovoSeven®, Novo Nordisk) to WB treated with 4μg/ml of Abciximab (ReoPro®, Lilly) and 3) to compare the response of rFVIIa in TEG assays containing tissue factor (TF, Innovin 1:42500) or Kaolin (standard initiator provided by Haemsoscope) with or without tPA (0.75nM). TEG Platelet Mapping was performed on all Abciximab-treated blood samples before conducting TEG demonstrating 70–100% inhibition of ADP-induced platelet aggregation. The following TEG parameters were used: Reaction time (R-time), Maximum Thrombin generation (MTG), Maximum Amplitude (MA) and Area under the TEG fibrinolysis curve calculated from MA (AUC lysis). The statistical analysis was performed by a two-way ANOVA model. A significant effect of adding rFVIIa (10 nM) to Abciximab-treated blood was observed for all clot formation parameters and with both TF and Kaolin as initiator. rFVIIa demonstrated a significant dose-dependent improvement of the TEG parameters in the assay containing kaolin, in kaolin+tPA (except MA) and in TF (except for MTG). rFVIIa showed significant dose-dependent protection against clot lysis (AUC lysis) in the assay containing kaolin+tPA, whereas no significant effect on clot lysis was observed in the assay containing TF. In conclusion, addition of rFVIIa to WB treated with Abciximab significantly improves most of the TEG parameters. Comparison of Abciximab+rFVIIa TEG parameters with TEG parameters obtained in normal WB (n=59) showed normalization of the R-value, however, none of the other TEG parameters reached normal values although a significant effect was observed after addition of rFVIIa. The TEG assay using kaolin as initiator showed significant dose-dependent effect of rFVIIa on all TEG parameters. In contrast, in the TEG assay initiated with TF the dose-dependent response of rFVIIa was only significant for some of the parameters. This may be due to a strong initiating effect of TF in the assay thus lowering the sensibility to rFVIIa. In contrast, in the assay initiated with Kaolin only TF-independent effects of rFVIIa are measured. The design of a TEG assay therefore seems to be important for evaluating the in vitro effect of rFVIIa. The clinical relevance of these findings is currently unknown and needs to be evaluated further. TEG values (±SD) using the kaolin assay R (sec) MTG (mm×100/sec) MA (mm) Lysis AUC (+tPA) (mm2) *: Significant effect compared to the Abciximab treated blood sample. P<0.05 Normal value 359±63 14.4±2.2 60±6 31707 Abciximab treated 527±56 7.6±2.3 33±10 14725±5110 rFVIIa 10nM 458±76* 8.3±2.1* 35±10* 15837±4634* rFVIIa 25nM 413±42* 9.2±2.7* 37±11* 16120±4969* rFVIIa 100nM 383±41* 9.0±2.2* 37±10* 18658±5693*

Kinetics of Inhibition of ADP-Induced Platelet Aggregation by Dihomo-β-Linolenic Acid (DHLA).

1979 ◽  
Author(s):  
M. Zuzel ◽  
A. Spencer
Keyword(s):  
Fatty Acids ◽  
Platelet Aggregation ◽  
Competitive Inhibition ◽  
Human Platelets ◽  
Inhibition Of Platelet Aggregation ◽  
Kinetics Of ◽  
Dose Dependent ◽  
Kinetics Of Inhibition ◽  
Primary Platelet

In the study of the effects on platelets of thromboxanes and prostaglandins (PG) large amounts of precursor fatty acids have frequently been added to platelet suspensions. In the case of DHLA, this results in a general inhibition of platelet reactions. We have employed kinetic analysis of the inhibition of ADP-induced primary platelet aggregation to estimate the potency, specificity and mode of action of DHLA on human platelets in citrated PRP. Platelet PG production was estimated from formation of malondialdehyde (MDA) and aspirin (ASA) was used to inhibit production-Inhibition of aggregation and MEA formation were dose-dependent and both were observed at DHLA concentrations of 0.1 mM and above. Inhibition of aggregation was of mixed type, consisting of an ASA-sensitive competitive component (K1 ≈ 0.2mM) and an ASA-insensitve component which was non-competitive and dominated inhibition at higher concentrations of DHLA. The KI (DHLA) of the non-competitive component varied from 0.4 to 1.5 mM with different batches of PRP. Other polyunsaturated fatty acids which are not PG precursors, did not cause competitive inhibition but were as potent as DHLA in the non-competitive inhibition of aggregation. The results show that a large part of the inhibition of platelet aggregation by DHLA in vitro is not due to its transformation into an inhibitor of platelet function in the PG production pathway.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

Interaction of Bacterial Endotoxin and Liquoid with Blood Platelets: Aggregation and Decrease in the Electrokinetic Charge

1969 ◽  
Vol 22 (01) ◽  
pp. 192-202 ◽  
Author(s):  
K. A Gröttum ◽  
P. F Hjort ◽  
M Jeremic
Keyword(s):  
Platelet Aggregation ◽  
Electrophoretic Mobility ◽  
Blood Platelets ◽  
Human Platelets ◽  
Dextran Sulphate ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
Very High

SummaryThe effects of Endotoxin and Liquoid on the electrophoretic mobility of human platelets and erythrocytes in vitro and on rabbit platelets and erythrocytes in vivo and in vitro have been investigated.Liquoid reduced the electrophoretic mobility of human platelets to 74% of normal and rabbit platelets to 59% in vitro and to 68% of normal in vivo, while the erythrocytes were unchanged. Liquoid induced massive aggregation of both human and rabbit platelets. In very high concentrations, Liquoid increased the electrophoretic mobility of human platelets and did not induce aggregation.Endotoxin reduced the electrophoretic mobility of rabbit platelets to 83% of normal and aggregated the platelets, but had none of these effects on human platelets.The effects of Endotoxin and Liquoid were inhibited by EDTA, but not by ADPase, suggesting that aggregation was not mediated through ADP.We conclude that Liquoid has the same pattern of effects on the electrokinetic charge of platelets and platelet aggregation as the acid polymeric agents dextran sulphate and heparin. There was good correlation between reduction in the electrokinetic charge of the platelets and platelet aggregation. There were striking similarities between the effects of these agents and Endotoxin.

Failure of Preactivated Human Blood Platelets to Restore Defective Thromboxane Synthesis despite Prolonged Incubation in Plasma

1989 ◽  
Vol 62 (03) ◽  
pp. 1016-1022 ◽  
Author(s):  
Marcus Stockschläder ◽  
Rüdiger E Scharf
Keyword(s):  
Blood Platelets ◽  
Human Platelets ◽  
Autologous Plasma ◽  
Prolonged Incubation ◽  
Platelet Storage ◽  
Thromboxane Synthetase ◽  
Responsible Mechanism ◽  
Short Time ◽  
Storage Pool Disease

SummaryAcquired platelet storage pool disease has been shown to be associated with reduced platelet thromboxane synthesis. However, the mechanisms for this dysfunction are incompletely understood. The present experiments were designed to evaluate some of the possible defects which may account for impaired thromboxane formation in human platelets previously exposed to thrombin in vitro. Washed platelets pretreated with 0.5 U/ml thrombin for 20 sec and subsequently recovered as single degranulated platelets were incapable of forming normal amounts of thromboxane upon a second stimulation with thrombin (as compared to Tyrode-pretreated control platelets). In contrast, thrombin-degranulated platelets released additional amounts of thromboxane in response to arachidonate, or collagen, indicating that short-time exposure to thrombin does not irreversibly inactivate platelet cyclooxygenase or thromboxane synthetase. Upon incubation of the thrombin-pretreated platelets in autologous plasma in the presence of 14C-arachidonate, the label became associated with the platelets to the same extent as with control platelets. However, the platelets did not recover their ability to synthesize normal amounts of thromboxane upon restimulation with thrombin, and only about half of the label was lost from the thrombin-pretreated platelets as compared to control platelets in response to thrombin. The ability of collagen to cause loss of 14C-arachidonate and formation of thromboxane was the same regardless of whether or not the platelets had been pretreated with thrombin. Incubation of platelets in plasma in the presence of added arachidonate for 90 min resulted in complete refractoriness to a second stimulation with thrombin but not with collagen. However, the control platelets also lost most of their ability to synthesize thromboxane when incubated with arachidonate for 90 min and thereafter stimulated with thrombin. Thus, the presence of added arachidonate affects the thrombin-inducible thromboxane synthesis after prolonged incubation of human platelets in plasma. Our observations suggest that depletion of endogenous arachidonate is not a major cause for the defective thrombin-induced thromboxane synthesis in thrombin-pretreated platelets. It is more likely that impaired mobilization of endogenous arachidonic acid explains this dysfunction. Defective mobilization of arachidonate in thrombin-degranulated platelets may be due to agonists-specific receptor desensitization, but the responsible mechanism has not been identified.

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