Peptide correction of prothrombotic erythrocytes effects on platelet aggregation

Author(s):  
М.Г. Голубева

Введение. В патогенезе многих заболеваний важную роль играют изменения функции гемостаза и нарушение реологических свойств крови. Поиск новых лекарственных препаратов, влияющих на взаимодействие форменных элементов крови в процессе тромбообразования, является одной из актуальных задач современной гематологии. Цель исследования: сравнение влияния малых регуляторных пептидов, являющихся фрагментами нейрогормонов, на взаимодействие эритроцитов с тромбоцитами при их агрегации под действием адреналина в экспериментах in vitro. Материалы и методы. Исследовали пептиды, представляющие собой С-концевые фрагменты нейрогормонов: Pro-Arg-Gly-NH2 — фрагмент вазопрессина, Pro-Leu-Gly-NH2 — фрагмент окситоцина. В опытах in vitro пептиды в концентрации 10–4–10–6 М добавляли к пулу богатой тромбоцитами плазмы (БТП) крыс или к смеси БТП с эритроцитарной массой, разведенной 1:1000 физиологическим раствором, или к отмытым эритроцитам и тромбоцитам и их смеси, и определяли изменение агрегации под действием адреналина в конечной концентрации 0,02 ммоль/л. Агрегацию эритроцитов и тромбоцитов регистрировали на агрегометре. Результаты. Установлено, что С-концевой фрагмент вазопрессина обладает более ярко выраженным антиагрегантным действием, чем фрагмент окситоцина, причем это было установлено как в БТП, так и при использовании отмытых клеток крови. Ингибирующее действие фрагмента Pro-Arg-Gly-NH2 сохранялось и на фоне предварительного усиления агрегации тромбоцитов эритроцитами. С-концевой фрагмент окситоцина практически не влиял на агрегацию тромбоцитов. Заключение. Использование малых регуляторных пептидов позволяет снижать агрегационный эффект эритроцитов, улучшая тем самым терапию при тромботических осложнениях. Introduction. Hemostasis changes and disturbances of blood rheological properties play the important role in pathogenesis of many diseases. One of the actual problems of modern hematology is new drugs investigation for aff ecting on blood cells interaction during thrombus formation. Aim: to compare the eff ect of small regulatory peptides (fragments of neurohormones) on the interaction of erythrocytes with platelets under their aggregation by adrenaline in in vitro experiments. Materials and methods. We studied 2 peptides (C-terminal fragments of neurohormones): Pro-Arg-Gly-NH2 — fragment of vasopressin, Pro-Leu-Gly-NH2 — fragment of oxytocin. In in vitro experiments we added peptides (in concentration of 10–4–10–6 М) to a pool of platelet-rich rat plasma (PRP) or to a mixture of PRP with erythrocyte mass diluted 1:1000 by saline solution, or to washed erythrocytes and platelets and their mixture, and determined the aggregation changes under adrenalin in a final concentration of 0.02 mmol/L. Erythrocytes and platelets aggregation was recorded by aggregometer. Results. We found that C-terminal fragment of vasopressin has a more pronounced antiplatelet eff ect than the oxytocin fragment, and it was found both in PRP and with the use of washed blood cells. The inhibitory eff ect of Pro-Arg-Gly-NH2 fragment also remained under preliminary increasing of platelet aggregation by erythrocytes. C-terminal fragment of oxytocin practically had no effect on platelet aggregation. Conclusion. Use of small regulatory peptides helps to reduce the aggregation eff ect of erythrocytes, thereby improving therapy of thrombotic complications.

Author(s):  
М. Голубева

Введение. Изменение реологических свойств крови характерно для различных заболеваний, многие из которых связаны с нарушением реологии и, прежде всего, с изменением агрегации эритроцитов. Целью исследования было сравнение влияния малых регуляторных пептидов, являющихся фрагментами нейрогормонов, на агрегацию эритроцитов и тромбоцитов под действием адреналина в экспериментах in vitro. Материалы и методы. Эксперименты проводили на белых беспородных крысах-самцах, массой тела 180-200 г. Использовали пептиды, представляющие собой С-концевые фрагменты вазопрессина (Pro-Arg-Gly-NH2) и окситоцина (Pro-Leu-Gly-NH2). Результаты. Показано, что малые регуляторные пептиды, являющиеся продуктами протеолиза нейропептидов, оказывают существенное влияние на агрегатное состояние клеток крови. При сравнении влияния пептидов на агрегацию клеток крови, стимулированную адреналином, установлено, что фрагмент вазопрессина Pro-Arg-Gly-NH2 вызывал достоверное усиление агрегации как эритроцитов, так и тромбоцитов; тогда как фрагмент окситоцина Pro-Leu-Gly-NH2 ингибировал только агрегацию эритроцитов, не изменяя агрегации тромбоцитов. Заключение. Изучение путей поэтапного протеолиза пептидов может привести к разработке новых препаратов для направленной коррекции различных нарушений в организме, поэтому изучение эффектов С-концевых фрагментов гипофизарных гормонов на гемостаз является актуальным. Introduction. The changing of blood rheological properties is typical for various diseases; many of them are associated with rheology disorder and primarily with change of erythrocytes aggregation. The aim was to compare the effect of small regulatory peptides (fragments of neurohormones) on the aggregation of erythrocytes and platelets under adrenaline action in experiments in vitro. Materials and methods. Experiments were conducted on white outbred male rats, body weight 180-200 g. We used 2 peptides – C-terminal fragments of vasopressin (Pro-Arg-Gly-NH2) and oxytocin (Pro-Leu-Gly-NH2). Results. It was shown that small regulatory peptides (they are products of neuropeptides proteolysis) had a significant effect on blood cells aggregation. We compared the peptides effect on blood cells aggregation stimulated by adrenaline. It was found that vasopressin fragment Pro-Arg-Gly-NH2 significantly increased both erythrocytes and platelets aggregation, while oxytocin fragment Pro-Leu-Gly-NH2 inhibited only erythrocytes aggregation without changing of platelet aggregation. Conclusion. Investigation of phased peptides proteolysis may result in the development of new drugs for targeted correction of various disturbances. So it is of current interest to study the effects of C-terminal fragments of pituitary hormones on hemostasis.


1961 ◽  
Vol 06 (01) ◽  
pp. 086-097 ◽  
Author(s):  
E Øllgaard

SummaryIn in-vitro experiments, it has been shown that red blood cells and platelets contain a factor which, on addition to a sample of platelet-containing plasma and subsequent rocking of the test tube, causes an aggregation of the platelets which is visible to the naked eye. In equal volumes, the concentration of this factor has been found to be about 5 times as high in platelets as in red cells. The factor is thermostabile, non-protein in nature, and exerts its action independently of the process of coagulation. It is assumed to be carbohydrate in nature. White cells and, to a less degree, plasma and serum seem to be able to destroy the aggregating factor by an enzymatic process.The aggregation is reversible, since white cells as well as certain enzyme poisons and Na+ can reverse the process without any apparent change in the appearance of the platelets. The process observed thus actually seems to be a form of aggregation.


1986 ◽  
Vol 55 (01) ◽  
pp. 012-018 ◽  
Author(s):  
Paolo Gresele ◽  
Jef Arnout ◽  
Hans Deckmyn ◽  
Jos Vermylen

SummaryDipyridamole inhibits platelet aggregation in whole blood at lower concentrations than in plasma. The blood cells responsible for increased effectiveness in blood are the erythrocytes. Using the impedance aggregometer we have carried out a series of pharmacological studies in vitro to elucidate the mechanism of action of dipyridamole in whole blood. Adenosine deaminase, an enzyme breaking down adenosine, reverses the inhibitory action of dipyridamole. Two different adenosine receptor antagonists, 5’-deoxy-5’-methylthioadenosine and theophylline, also partially neutralize the activity of dipyridamole in blood. Enprofylline, a phosphodiesterase inhibitor with almost no adenosine receptor antagonistic properties, potentiates the inhibition of platelet aggregation by dipyridamole. An inhibitory effect similar to that of dipyridamole can be obtained combining a pure adenosine uptake inhibitor (RE 102 BS) with a pure phosphodiesterase inhibitor (MX-MB 82 or enprofylline). Mixing the blood during preincubation with dipyridamole increases the degree of inhibition. Lowering the haematocrit slightly reduces the effectiveness.Although we did not carry out direct measurements of adenosine levels, the results of our pharmacological studies clearly show that dipyridamole inhibits platelet aggregation in whole blood by blocking the reuptake of adenosine formed from precursors released by red blood cells following microtrauma. Its slight phosphodiesterase inhibitory action potentiates the effects of adenosine on platelets.


1987 ◽  
Author(s):  
L Mannucci ◽  
R Redaelli ◽  
E Tremoll

To evaluate the effects of blood cells on the response of platelets to aggregating agents using whole blood impedance aggregometer, studies were carried out on whole blood (WB) of normal subjects and of patients with: polycythemia vera (PV), iatrogenic anemia (IA), primary thrombocytosis (PT), idiopathic thrombotic purpura (ITP), myeloid chronic leukemia (MCL), iatrogenic leukopenia (IL). The in vitro effects of red blood cells (RBC) and of white blood cells (WBC) on platelet rich plasma (PRP) aggregation were also evaluated. WB, PRP, WBC and RBC were prepared by conventional methods. Aggregation was performed using the impedance aggregometer (mod. 540, Chrono Log Corp). In normal subjects the concentration of collagen giving 50 % aggregation (AC50 ) found in PRP did not differ from that of WB, indicating that hematocrit values within the normal range did not appreciably affect platelet aggregation. The results obtained in WB of patients are summarized in the table: In vitro data showed that aggregation in prp in wb of normal subjects was related to the number of platelets present in the sample. RBC added to PRP significant reduced aggregation only when the RBC number was greater than 4.101 cells. No effect of WBC on collagen induced aggregation of PRP was observed, whereas significant inhibition was detected after ADP. It is concluded that the aggregation evaluated in WB with impedance method is dependent on the platelet number. Also, in vitro data and studies in WB of patients indicate that aggregation is significantly affected by the presence of cells other than platelets only in conditions of changes of the ratio between platelets and leukocytes and/or red cells.


2021 ◽  
Vol 23 (1) ◽  
pp. 11
Author(s):  
Jeremy A. Nestele ◽  
Anne-Katrin Rohlfing ◽  
Valerie Dicenta ◽  
Alexander Bild ◽  
Daniela Eißler ◽  
...  

Traditional antithrombotic agents commonly share a therapy-limiting side effect, as they increase the overall systemic bleeding risk. A novel approach for targeted antithrombotic therapy is nanoparticles. In other therapeutic fields, nanoparticles have enabled site-specific delivery with low levels of toxicity and side effects. Here, we paired nanotechnology with an established dimeric glycoprotein VI-Fc (GPVI-Fc) and a GPVI-CD39 fusion protein, thereby combining site-specific delivery and new antithrombotic drugs. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles, NP-BSA, NP-GPVI and NP-GPVI-CD39 were characterized through electron microscopy, atomic force measurements and flow cytometry. Light transmission aggregometry enabled analysis of platelet aggregation. Thrombus formation was observed through flow chamber experiments. NP-GPVI and NP-GPVI-CD39 displayed a characteristic surface coating pattern. Fluorescence properties were identical amongst all samples. NP-GPVI and NP-GPVI-CD39 significantly impaired platelet aggregation. Thrombus formation was significantly impaired by NP-GPVI and was particularly impaired by NP-GPVI-CD39. The receptor-coated nanoparticles NP-GPVI and the bifunctional molecule NP-GPVI-CD39 demonstrated significant inhibition of in vitro thrombus formation. Consequently, the nanoparticle-mediated antithrombotic effect of GPVI-Fc, as well as GPVI-CD39, and an additive impact of CD39 was confirmed. In conclusion, NP-GPVI and NP-GPVI-CD39 may serve as a promising foundation for a novel therapeutic approach regarding targeted antithrombotic therapy.


2018 ◽  
Vol 1 (1) ◽  
pp. 01-03
Author(s):  
Mark I. M. Noble

Over many years, laboratory testing of platelet aggregability have been carried out in attempts to develop drugs that would prevent thrombosis in arteries. The problems encountered included the question of methodology. Blood samples have to be anticoagulated in order to study the platelets. Anti-coagulation with citrate and tests on derived platelet rich plasma did not correlate at all well with thrombus growth in the stenosed coronary arteries of experimental animals and citrate removes the calcium ions which are vital for platelet function. Anticoagulation with heparin also interfered with platelet function, so that now, hirudins are the preferred anticoagulant. However it was observed that if, instead of stimulating platelet aggregation with adrenaline or ADP, serotonin was applied to the preparation, very little aggregation took place in spite of serotonin 5HT2A antagonists being the most potent inhibitors of thrombus growth in experimental animals. Another indicator that primary platelet agggregation is not a predictor of in vivo efficacy was the finding that 5HT2A antagonism inhibited aggregate growth. In a stenosed artery the platelets are activated by increased shear stress and blood turbulence with release of platelet serotonin causing positive feedback activation of more platelets. At present, there does not seem to be a bench in vitro test that accurately predicts in vivo efficacy in stenosed artery occlusive thrombosis.


1981 ◽  
Author(s):  
S C Wong ◽  
G A Rock

number of in-vitro studies have shown that various pair-combinations of aggregating agents such as ADP, epinephrine, collagen, thrombin, arachidonate and ionophore A 23187 can produce synergistic responses to induce platelet aggregation and release reactions. We have also produced synergistic effects by combining much lower doses of 3 or more aggregating agents and found markedly enhanced responses. It appears that the potential for synergistic effects is based both on the combination of the various agents and on the amount of each agent used for stimulation. Epinephrine is the most potent agent among them, although fibrinogen and Ca++ play a very important role. Indomethacin, ASA, PGE 1, and synthetic serine protease inhibitors (carboxylate and sulphonate analog) completely inhibit the platelet aggregation and release response. Of particular interest is the fact that addition of as little as 0.04% of the usual aggregating dose of epinephrine in the presence of 4% of collagen, 2% of thrombin and 10% of the normal plasma level of fibrinogen will initiate a marked response both of platelet aggregation and ATP release. This suggests a possible mechanism whereby acute insults such as stress or exercise, with release of epinephrine, can precipitate a thrombotic event in a patient who has normal or near-normal circulating levels of fibrinogen but who also has exposure of a very limited amount of the vascular endothelium (thereby exposing collagen). Since the effects of the acute insults of epinephrine secretion can be blocked by the presence of indomethacin, ASA, PGE 1 and specific serine protease inhibitors, prostaglandin synthesis must play a major role in this reaction.


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