Investigated Platelet Aggregation Research Articles

Role of <i>ITGB3</i>, <i>GP1B1</i>, and <i>ITGA2</i> gene polymorphisms in platelet dysfunction in patients with COVID-19-associated lung damage

The aim of the work. To investigate platelet aggregation, polymorphism in the genes that ensure its implementation, and the association between these indicators in patients with COVID-19-associated lung damage, depending on the severity of the clinical course. Methodology. The study involved 75 patients with COVID-19, which, depending on the severity of lung involvement, were divided into two groups: patients with damage of up to 50 % of the lung parenchyma (n = 48) and with damage of more than 50 % (n = 27) respectively. The control group consisted of healthy people (n = 24), comparable in sex and age. In all individuals, the number of platelets, platelet aggregation induced by ADP, collagen and ristomycin were studied; polymorphisms rs6065 in the GP1BA gene, rs1126643 in the ITGA2 gene, and rs5918 in the ITGB3 gene were determined by polymerase chain reaction. The analysis of the obtained data was executed using the IBM SPSS Statistics v. 23 (IMB Corp., USA). Results and discussion. In patients with moderate and severe COVID-19-associated lung damage, platelet aggregation induced by ADP, collagen, and ristomycin accelerated; in severe cases, the number of platelets decreased. The frequency of variants of the rs6065 polymorphism did not change, the frequency of occurrence of the T/C genotype of the rs5918 polymorphism increased; with moderate severity, the frequency of occurrence of the C/T and T/T genotypes of the rs1126643 polymorphism increased; with severe lung damage, the frequency of occurrence of the mutant C/C genotype polymorphism rs5918 increased. In moderate lung damage, the presence of the mutant T/T polymorphism rs1126643 accelerated collagen-induced platelet aggregation; in severe cases, the presence of mutant C/C and heterozygous variant C/T polymorphism rs5918 accelerated ADP-induced platelet aggregation. There was no effect of the rs6065 polymorphism on platelet aggregation. The data obtained indicate the possible role of genetic predisposition in the activation of platelet aggregation in patients with COVID-19-associated lung damage.

Platelet aggregation in Klinefelter syndrome is not aggravated by testosterone replacement therapy: A longitudinal follow-up study.

Men with Klinefelter syndrome (KS) are routinely offered testosterone replacement therapy (TRT) suggested to potentially promote platelet aggregation and increase cardiovascular risk. We investigated platelet aggregation in men with KS before and during TRT. Forty-one adult men with KS participated, of which 20 had no history of TRT at baseline, with 15 completing follow-up after 18 months TRT. Further, we included 21 adult men with KS on long-term TRT(>10 years) and a male reference population. We assessed platelet impedance aggregometry using adenosine diphosphate (6.5μM), thrombin-receptor-activating-peptide-6 (TRAP 32μM), and arachidonic acid (ASPI 0.5mM) as agonists in KS compared to a male reference population and stratified by route of TRT administration. Platelet aggregation among men with KS at baseline or during TRT was not increased compared with the male reference population. For all three agonist, no change was seen in platelet aggregation in KS at follow-up compared with baseline (p ≥ 0.2). Platelet aggregation was not associated with total testosterone and furthermore, platelet count was not affected by treatment with testosterone. Men with KS treated with testosterone gel showed slightly increased TRAP- and ASPI-induced platelet aggregation compared with those treated with testosterone injection (p=0.02 and p=0.04, respectively). We observed normal platelet aggregation in men with KS before TRT and following both short and long term treatment. Our findings do not support an independent role of platelets in driving the cardiovascular risk in KS.

Aspirin Administration Mitigates Platelet Hyperaggregability After Splenectomy in a Murine Model

IntroductionPatients who undergo splenectomy (SPLN) have an estimated 10%-35% risk of venous thromboembolic events; however, the underlying mechanism and strategy for prevention have yet to be identified. The goals of this study were to 1) investigate platelet aggregation after SPLN, 2) examine if aspirin administration could mitigate this effect, and 3) determine if concomitant hemorrhage would affect post-SPLN platelet function and response to aspirin. MethodsMurine models of operative SPLN and submandibular bleed (SMB) were utilized. Mice were randomized to eight groups as follows: untouched, SPLN, sham (laparotomy only), SMB, SPLN + SMB, SPLN + aspirin (ASA), SMB + ASA, and SPLN + SMB + ASA. Aspirin (50 mg/kg) was administered on postoperative days (PODs) one and two via oral gavage. Mice were euthanized on POD 3, platelet counts were obtained, and blood samples were analyzed via rotational thromboelastometry and impedance aggregometry with adenosine diphosphate (ADP) and arachidonic acid (AA) as agonists. ResultsBy POD 3, SPLN mice displayed a significant thrombocytosis compared to untouched, SMB, and sham SPLN mice. Clotting time and clot formation time were significantly decreased in SPLN and SPLN + SMB cohorts compared to untouched and sham controls with elevated mean clot firmness. SPLN mice also displayed a significant increase in ADP- and AA-mediated platelet aggregability compared to untouched controls, SMB, and SPLN + SMB. ASA significantly decreased platelet aggregation via both ADP and AA signaling in SPLN and SPLN + SMB cohorts without affecting viscoelastic coagulation testing. ConclusionsPlatelet hyperaggregability after SPLN is mediated by both ADP and AA signaling. Early aspirin administration may prevent increased platelet aggregation exacerbated after polytrauma.

АНАЛИЗ АГРЕГАЦИИ ТРОМБОЦИТОВ У ДОНОРОВ КОМПОНЕНТОВ КРОВИ

The functional state of platelets can be determined using the method of platelet aggregation. The aim of our study was to investigate platelet aggregation in donors of blood components and to identify the features of the reactions of these platelets with the most common inducers of aggregation. Material and methods. 31 donors of fresh frozen plasma and platelet concentrate were included in the study. The study of platelet aggregation was carried out by the turbidimetric method with AP2110 analyzer (SOLAR, Minsk, Republic of Belarus). Results. A total of 33 studies of platelet aggregation in donors were carried out before the collection of blood components. Normal platelet aggregation was found in 10 cases (30.3%), hypoaggregation in 15 cases (45.5%), and hyperaggregation in 8 studies. (24.2%). Thus, in 23 (69.7%) cases, platelet aggregation disorders were found in donors. Statistical analysis showed that the incidence of platelet aggregation disorders (hypo- or hyperaggregation) was high in donors who had undergone COVID-19 infection (5 - hypoaggregation, 4 - hyperaggregation). In donors with no history of this infection, the incidence of platelet aggregation disorders was statistically significantly lower - 63.6% (in 10 - hypoaggregation, in 4 - hyperaggregation), p=0.04. A history of previous COVID-19 infection in the donor is an independent predictor of platelet aggregation disorder (Chi-square=7.24, p=0.007). Conclusion. When preparing platelet mass, it is necessary to first monitor platelet aggregation, especially in donors with a previous COVID-19 infection, and take into account the results obtained to predict the therapeutic effect of using platelet concentrate in clinical practice. Keywords: platelet aggregation, platelets, blood component donor, platelet concentrate, novel coronavirus infection, COVID-19.

Evolution of platelet activation parameters during septic shock in intensive care unit

During severe sepsis, platelet activation may induce disseminate microvascular thrombosis, which play a key role in critical organ failure. Crucially, most of the studies in this field have explored platelet–leukocyte interactions in animal models, or explored platelets under the spectrum of thrombocytopenia or disseminated intravascular coagulation and have not taken into account the complex interplay that might exist between platelets and leukocytes during human septic shock nor the kinetics of platelet activation. Here, we assessed platelet activation parameters at the admission of patients with sepsis to the intensive care unit (ICU) and 48 hours later. Twenty-two patients were enrolled in the study, thirteen (59.1%) of whom were thrombocytopenic. The control group was composed of twelve infection-free patients admitted during the study period. The activation parameters studied included platelet-leukocyte interactions, assessed by flow cytometry in whole blood, as well as membrane surface and soluble platelet activation markers measured by flow cytometry and dedicated ELISA kits. We also investigated platelet aggregation and secretion responses of patients with sepsis following stimulation, compared to controls. At admission, the level of circulating monocyte-platelet and neutrophil-platelet heterotypic aggregates was significantly higher in sepsis patients compared to controls and returned to a level comparable to controls or even below 48 hours later. Basal levels of CD62P and CD63 platelet membrane exposure at admission and 48 hours later were low and similar to controls. In contrast, plasma level of soluble GPVI and soluble CD40 ligand was significantly increased in septic patients, at the two times of analysis, reflecting previous platelet activation. Platelet aggregation and secretion responses induced by specific agonists were significantly decreased in septic conditions, particularly 48 hours after admission. Hence, we have observed for the first time that critically ill septic patients compared to controls have both an early and durable platelet activation while their circulating platelets are less responsive to different agonists.

Interference of C6O4 on platelet aggregation pathways: Cues on the new-generation of perfluoro-alkyl substance

BackgroundHealth concerns associated with the exposure to legacy perfluoro-alkyl substances (PFAS) led to the development of new-generation PFAS, such as C6O4. Here we investigated the possible effects of C6O4 on the platelet’s activation profile, by incubating human platelets from healthy donors with C6O4 at different concentrations and evaluating the effects on activation, production and phenotype of platelets micro-particles (MPV) and aggregation under-flow. Based on the eventual platelet pro-aggregation profile detected, the preventive effect of acetylsalicylic acid (ASA) was also explored. MethodsAdhesion-induced platelet aggregation of platelet rich plasma (PRP) under flow was evaluated on collagen-coated microchip at a shear stress of 10 Dyne. The turbidimetric method was used to investigate platelet aggregation. Finally, the in vitro generation of pro-coagulant MPV in PRP was evaluated by flow cytometry, as characterized by CD41 and annexin V positive events, under resting conditions and after stimulation with agonists at low shear stress. ResultsThe generation of platelet aggregates under flow was significantly increased by the pretreatment of PRP with 100–200 ng/mL C6O4, compared to both the control condition and the experiment performed in presence of ASA. Arachidonic acid (AA), ADP and collagen induced an higher maximal aggregation, at turbidimetric evaluation, when PRP was pretreated with 100–500 ng/mL C6O4. In addition, PRP stimulated with AA also showed a steeper slope of the aggregation curve. The aggregation induced by the tested agonists was almost abolished by ASA. Finally, pretreatment with C6O4 increased the number of MPV in resting conditions and in presence of ADP and TRAP. ASA tended to reduce MPV generation. ConclusionsExposure to C6O4 associates with an increased platelet response to agonists, translating into a possible increased risk of cardiovascular events. Pending a further clarification on the toxicokinetics of this compound, our results claim the possible prophylactic use of ASA.

Computational Fluid Dynamics Simulations at Micro-Scale Stenosis for Microfluidic Thrombosis Model Characterization

Platelet aggregation plays a central role in pathological thrombosis, preventing healthy physiological blood flow within the circulatory system. For decades, it was believed that platelet aggregation was primarily driven by soluble agonists such as thrombin, adenosine diphosphate and thromboxane A2. However, recent experimental findings have unveiled an intriguing but complementary biomechanical mechanism—the shear rate gradients generated from flow disturbance occurring at sites of blood vessel narrowing, otherwise known as stenosis, may rapidly trigger platelet recruitment and subsequent aggregation. In our Nature Materials 2019 paper [1], we employed microfluidic devices which incorporated micro-scale stenoses to elucidate the molecular insights underlying the prothrombotic effect of blood flow disturbance. Nevertheless, the rheological mechanisms associated with this stenotic microfluidic device are poorly characterized. To this end, we developed a computational fluid dynamics (CFD) simulation approach to systematically analyze the hemodynamic influence of bulk flow mechanics and flow medium. Grid sensitivity studies were performed to ensure accurate and reliable results. Interestingly, the peak shear rate was significantly reduced with the device thickness, suggesting that fabrication of microfluidic devices should retain thicknesses greater than 50 µm to avoid unexpected hemodynamic aberration, despite thicker devices raising the cost of materials and processing time of photolithography. Overall, as many groups in the field have designed microfluidic devices to recapitulate the effect of shear rate gradients and investigate platelet aggregation, our numerical simulation study serves as a guideline for rigorous design and fabrication of microfluidic thrombosis models.

Clot Permeability, Agonist Transport, and Platelet Binding Kinetics in Arterial Thrombosis

The formation of wall-adherent platelet aggregates is a critical process in arterial thrombosis. A growing aggregate experiences frictional drag forces exerted on it by fluid moving over or through the aggregate. The magnitude of these forces is strongly influenced by the permeability of the developing aggregate; the permeability depends on the aggregate’s porosity. Aggregation is mediated by formation of ensembles of molecular bonds; each bond involves a plasma protein bridging the gap between specific receptors on the surfaces of two different platelets. The ability of the bonds existing at any time to sustain the drag forces on the aggregate determines whether it remains intact or sheds individual platelets or larger fragments (emboli). We investigate platelet aggregation in coronary-sized arteries using both computational simulations and in vitro experiments. The computational model tracks the formation and breaking of bonds between platelets and treats the thrombus as an evolving porous, viscoelastic material, which moves differently from the background fluid. This relative motion generates drag forces which the fluid and thrombus exert on one another. These forces are computed from a permeability-porosity relation parameterized from experimental measurements. Basing this relation on measurements from occlusive thrombi formed in our flow chamber experiments, along with other physiological parameter values, the model produced stable dense thrombi on a similar timescale to the experiments. When we parameterized the permeability-porosity relation using lower permeabilities reported by others, bond formation was insufficient to balance drag forces on an early thrombus and keep it intact. Under high shear flow, soluble agonist released by platelets was limited to the thrombus and a boundary layer downstream, thus restricting thrombus growth into the vessel lumen. Adding to the model binding and activation of unactivated platelets through von Willebrand-factor-mediated processes allowed greater growth and made agonist-induced activation more effective.

Platelet function in lung cancer patients undergoing lobectomy

A growing interest concerns arterial thromboembolic disease in cancer patients. As platelets may be key players in this process, investigation of platelet aggregation in cancer patients is of importance. We aimed to investigate platelet aggregation in patients with lung cancer prior to surgery and during video-assisted thoracoscopic surgery (VATS) lobectomy compared with lobectomy performed through a thoracotomy. We included 93 patients (VATS + low molecular weight heparin (LMWH), n = 32; VATS no LMWH, n = 31; thoracotomy + LMWH, n = 30). Data obtained from 121 healthy individuals were used for comparison prior to surgery. Platelet aggregation was analysed by impedance aggregometry using adenosine diphosphate 6.5 μM (ADPtest) and collagen 3.2 μg/mL (COLtest) as agonists. Prior to surgery, platelet aggregation was significantly increased in both VATS-patients (ADPtest, p < .0001; COLtest, p = .0002) and patients undergoing thoracotomy (ADPtest, p < .0001; COLtest, p < .0001) compared with healthy individuals. Platelet aggregation did not differ between VATS-patients and thoracotomy patients prior to surgery (p-values >.11). At the first postoperative day, VATS-patients demonstrated significantly higher collagen-induced platelet aggregation than preoperatively (p = .001), but the increase in platelet aggregation did not differ significantly between VATS and thoracotomy patients (p-values ≥.24). At the second postoperative day, platelet aggregation was significantly reduced in thoracotomy patients compared with the preoperative level (ADPtest, p = .002; COLtest, p = .05). In conclusion, platelet aggregation was significantly increased in patients with primary lung cancer prior to surgery compared with healthy individuals. At the first postoperative day, platelet aggregation was significantly higher than the preoperative level in VATS-patients; however, this increase did not differ between patient groups.

It's About Time: Transfusion effects on postinjury platelet aggregation over time.

Impaired postinjury platelet aggregation is common, but the effect of transfusion on this remains unclear. Data suggest that following injury platelet transfusion may not correct impaired platelet aggregation, and impaired platelet aggregation may not predict the need for platelet transfusion. We sought to further investigate platelet aggregation responses to transfusions, using regression statistics to isolate the independent effects of transfusions given in discrete time intervals from injury on both immediate and longitudinal platelet aggregation. We hypothesized that platelet aggregation response to platelet transfusion increases over time from injury. Serial (0-96 hours) blood samples were collected from 248 trauma patients. Platelet aggregation was assessed in vitro with impedance aggregometry stimulated by adenosine diphosphate, collagen, and thrombin receptor-activating peptide-6. Using regression, transfusion exposure was modeled against platelet aggregation at each subsequent timepoint and adjusted for confounders (Injury Severity Score, international normalized ratio (INR), base deficit, platelet count, and interval transfusions). The expected change in platelet aggregation at each timepoint under the intervention of transfusion exposure was calculated and compared with the observed platelet aggregation. The 248 patients analyzed were severely injured (Injury Severity Score, 21 ± 19), with normal platelet counts (mean, 268 × 10/L ± 90), and 62% were transfused in 24 hours. The independent effect of transfusions on subsequent platelet aggregation over time was modeled with observed platelet aggregation under hypothetical treatment of one unit transfusion of blood, plasma, or platelets. Platelet transfusions had increasing expected effects on subsequent platelet aggregation over time, with the maximal expected effect occurring late (4-5 days from injury). Controversy exists on whether transfusions improve impaired postinjury platelet aggregation. Using regression modeling, we identified that expected transfusion effects on subsequent platelet aggregation are maximal with platelet transfusion given late after injury. This is critical for tailored resuscitation, identifying a potential early period of resistance to platelet transfusion that resolves by 96 hours. Therapeutic, level V.

Evaluation of platelet function in essential thrombocythemia under different analytical conditions

Background. Studies of platelet aggregation (PA) in essential thrombocythemia (ET) reported contrasting results, likely due to differences in analytical conditions.Objective. We investigated platelet aggregation using different techniques and analytical conditions.Patients and Methods. PA was studied by light-transmission aggregometry (LTA) in platelet-rich plasma (PRP) and impedance aggregometry in PRP and whole blood (WB). ADP, collagen, thrombin receptor activating peptide (TRAP-14) and adrenaline were used as agonists. Since ET patients (n = 41) were on treatment with aspirin (100 mg/d), healthy controls (n = 29) were given aspirin (100 mg/d) for 5 days before testing: therefore, thromboxane A2-independent PA was tested in all subjects. Blood samples were collected in citrate (C) [low Ca2+] or lepirudin (L) [physiological Ca2+]; platelet count was adjusted to 250 x 109/L in a set of C-PRP (adjusted C-PRP) and left unmodified in the other samples.Results. Results of PA in 17 ET patients who were poor responders to aspirin (high serum thromboxane B2 levels) were not included in the analysis. With LTA, PA in ET was lower than in controls in adjusted C-PRP and normal in native C-PRP and L-PRP. With impedance aggregometry, PA in L-PRP and L-WB tended to be higher in ET than in controls. Platelet serotonin and ADP contents were reduced in ET. The percentages of circulating platelets expressing P-selectin and platelet-leukocyte hetero-aggregates were higher in ET.Conclusions. Analytical conditions dramatically affect in vitro PA of ET patients, which appears defective under the least physiological conditions and normal/supranormal under conditions that are closer to the physiological.

Возможность получения реагента для определения ристоцетин-кофакторной активности фактора Виллебранда (ФВ:РКФА) из тромбоцитарных концентратов длительного срока хранения

Введение. Фактор Виллебранда (ФВ) является важным компонентом системы гемостаза, и отклонение от нормы его содержания или состава вызывает развитие различных типов болезни Виллебранда. Определение ристоцетин-кофакторной активности ФВ (ФВ:РКФА) является особенно значимым при выявлении таких типов болезни Виллебранда как 2А, 2В и 2М, при которых содержание антигена ФВ находится в нормальных пределах, а ФВ:РКФА значительно снижена. Цель исследования: получение реагента для измерения ФВ:РКФА из концентратов тромбоцитов с длительным сроком хранения, обеспечивающего правильность диагностики. Материалы и методы. Функционально полноценные тромбоциты получали из донорских тромбоцитарных концентратов со сроком хранения 7–14 суток. Результаты. При создании реагента для измерений ФВ:РФКА нами был подобран метод отбора функционально полноценных донорских тромбоцитов для получения фиксированных формальдегидом клеток. На основе таких тромбоцитов был разработан реагент, позволяющий измерять ФВ:РКФА с использованием как агрегационного, так и агглютинационного метода. Выявлено соответствие результатов определения ФВ обоими методами с коэффициентом корреляции 0,96. Проведена оценка агрегационного метода измерения ФВ:РКФА по результатам участия в международной программе внешнего контроля качества UK NEQAS for Blood Coagulation (Великобритания). Заключение. Показано, что использование полученного из фиксированных тромбоцитов реагента позволяет правильно измерять ФВ:РКФА. Introduction. Von Willebrand factor (vWF) is an important component of hemostatic system and deviations from the norm of its content or composition are the cause of various types of von Willebrand disease development. Determination of ristocetin-cofactor activity of vWF (vWF:RCo) is particularly important for identifying 2A, 2B and 2M types of von Willebrand disease, in which the content of vWF antigen is within the normal range, and vWF:RCo signifi cantly reduced. Aim: to obtain a reagent for the measurement of vWF:RCo from platelet concentrates with a long shelf life, providing correct diagnostics. Materials and methods. Fully functional platelets were obtained from donor platelet concentrates with a shelf life of 7–14 days. Results. We discovered the method for selection of fully functional donor platelets to produce formaldehyde-fi xed cells. On the basis of these platelets we developed a reagent that allows to measure vWF:RCo using both aggregation and agglutination methods. The appropriateness was found between the results of vWF determination by both methods with a correlation coeffi cient 0.96. The aggregation method of measuring vWF:RCo was evaluated by a result of participation in the international program of external quality control UK NEQAS for Blood Coagulation (United Kingdom). Conclusion. It is shown that the use of a reagent obtained from fi xed platelets allows for the correct measurement of vWF:RCo.

Novel Antibodies Against Glycoprotein Ibα Inhibit Pulmonary Metastasis By Affecting Vwf-Gpibα Interaction

Background:Platelet glycoprotein Ibα (GPIbα) extracellular domain, which is part of the receptor complex GPIb-IX-V, plays an important role in tumor metastasis. However, the mechanism through which GPIbα participates in the metastatic process remains unclear. In addition, potential bleeding complication remains an obstacle for the clinical use of anti-platelet agents in cancer therapy.Methods and Results:To generate antibodies that bind to mouse platelet GPIbα, washed mouse platelet lysate was used as the antigen for rat immunization. Obtained hybridoma clones were screened in ELISA for binding affinity to the GPIb-IX complex. Positive clones were further screened for their abilities to inhibit platelet-cancer cell adhesion. Finally, at static condition, two antibodies, 2B4 and 1D12, had virtually no effect on the activation of integrin αIIbβ3, which is used to indicate platelet activation. Then, we characterized the binding sites of 2B4 and 1D12 by 20 purified recombinant GPIbα fragments binding. Results showed that 2B4 and 1D12 shared the same binding sites with vWF.To determine whether 2B4 and 1D12 affect vWF binding, we tested the binding by flow cytometry using recombined mouse vWF, and then, we investigated platelet aggregation induced by several agonists, including vWF binding agonist ristocetin. Our data demonstrated clearly that 2B4 and 1D12 could inhibit vWF binding.To investigate whether the inhibition of vWF-GPIbα interaction was associated with tumor metastasis, we examined the effect of 2B4 and 1D12 in each of the following interactions in vitro: between activated platelets and tumor cells, platelets and endothelial cells. Meanwhile, We further investigated the inhibitory effect of these antibodies in vivo using the experimental metastasis model and the spontaneous metastasis model. Results showed that 2B4 and 1D12 could potently inhibit the adhesion of cancer cells in vitro, and metastasisin vivo.We next investigated whether 2B4 and 1D12 could affect platelet activation and/or induce thrombocytopenia in vivo. Results showed that the addition of 2B4 or 1D12 to PRP did not induce platelet aggregation and injection of 2B4 or 1D12 Fab at appropriate dose did not affect tail-bleeding time and platelet count.Based on the above findings, we obtained anti-human platelet GPIbα monoclonal antibody YQ3 using the same approach to explore the role of human GPIbα in cancer metastasis. As expected, YQ3 inhibited lung cancer adhesion and demonstrated similar value in metastasis. More importantly, for all three mAbs in our study, none of their Fabs induced thrombocytopenia.Conclusion:Our results therefore supported the hypothesis that GPIbα contributes to tumor metastasis, and suggested potential value of using anti-GPIbα mAb to suppress cancer metastasis. DisclosuresLi:Neoletix: Consultancy, Equity Ownership.

Reduced Antiplatelet Effect of Aspirin Does Not Predict Cardiovascular Events in Patients With Stable Coronary Artery Disease.

BackgroundIncreased platelet aggregation during antiplatelet therapy may predict cardiovascular events in patients with coronary artery disease. The majority of these patients receive aspirin monotherapy. We aimed to investigate whether high platelet‐aggregation levels predict cardiovascular events in stable coronary artery disease patients treated with aspirin.Methods and ResultsWe included 900 stable coronary artery disease patients with either previous myocardial infarction, type 2 diabetes mellitus, or both. All patients received single antithrombotic therapy with 75 mg aspirin daily. Platelet aggregation was evaluated 1 hour after aspirin intake using the VerifyNow Aspirin Assay (Accriva Diagnostics) and Multiplate Analyzer (Roche; agonists: arachidonic acid and collagen). Adherence to aspirin was confirmed by serum thromboxane B2. The primary end point was the composite of nonfatal myocardial infarction, ischemic stroke, and cardiovascular death. At 3‐year follow‐up, 78 primary end points were registered. The primary end point did not occur more frequently in patients with high platelet‐aggregation levels (first versus fourth quartile) assessed by VerifyNow (hazard ratio: 0.5 [95% CI, 0.3–1.1], P=0.08) or Multiplate using arachidonic acid (hazard ratio: 1.0 [95% CI, 0.5–2.1], P=0.92) or collagen (hazard ratio: 1.4 [95% CI, 0.7–2.8], P=0.38). Similar results were found for the composite secondary end point (nonfatal myocardial infarction, ischemic stroke, stent thrombosis, and all‐cause death) and the single end points. Thromboxane B2 levels did not predict any end points. Renal insufficiency was the only clinical risk factor predicting the primary and secondary end points.ConclusionsThis study is the largest to investigate platelet aggregation in stable coronary artery disease patients receiving aspirin as single antithrombotic therapy. We found that high platelet‐aggregation levels did not predict cardiovascular events.

Pathogenetic effects of low-intensity laser therapy for chronic obstructive pulmonary disease

To study the impact of low-intensity laser therapy (LILT) on typical pathological processes of impairments in platelet aggregation and microcirculation (MC) in patients with chronic obstructive pulmonary disease (COPD). A photo optical aggregatometric method was used to investigate platelet aggregation function in patients with COPD and MC was estimated by laser Doppler flowmetry over time. There were muitidirectional changes in platelet aggregation function with a predominance of hyperaggregation, as well as a significant improvement in aggregation indicators during LILT; the latter was shown to have a correcting impact on MC disorders in patients with COPD in the presence of the spastic and stagnant-stasic types of MC, which were prevalent in the majority of patients. Laser therapy used in the combination treatment of patients with COPD promotes correction of the typical pathological processes.

Group G streptococci mediate fibrinogen-dependent platelet aggregation leading to transient entrapment in platelet aggregates.

Platelets have been reported to become activated in response to bacteria and this is proposed to contribute to the acute response to bacterial infection. In the present study, we investigated platelet aggregation in response to group G streptococci (GGS) in vitro in healthy human donors and in vivo in a mouse model of streptococcal sepsis. Platelet aggregation by GGS was dependent on the bacterial surface protein FOG and engagement of the platelet fibrinogen receptor; however, it was independent of IgG and the platelet Fc receptor. Platelets exerted no antibacterial effects on the bacteria, and aggregates formed were markedly unstable, allowing bacteria to rapidly return to the plasma and grow post-aggregation. Thrombocytopenia and platelet activation occurred during invasive infection with GGS, and platelets were demonstrated to contribute to bacterial dissemination during infection. These findings reveal an important role for bacteria-platelet interactions during the pathogenesis of streptococcal infection.

Platelet-Derived Microparticles and Platelet Function Profile in Children With Congenital Heart Disease

Platelet microparticles (PMPs) and function profile in children with congenital heart disease (CHD) have not been widely explored. We investigated platelet aggregation, flow cytometric platelet surface receptors (P-selectin and glycoprotein (GP) IIb/IIIa) and PMPs in 23 children with cyanotic CHD (CCHD), 30 children with acyanotic CHD (ACHD) and 30 healthy controls correlating these variables to hematological and coagulation parameters including von Willebrand factor antigen (vWF Ag) as a marker of endothelial dysfunction. Hemoglobin, hematocrit (HCT), D-dimer, and vWF Ag were significantly higher in CCHD than ACHD group. Platelet MPs and P-selectin expression were increased in patients than controls, particularly in CCHD and positively correlated to HCT, D-dimer, and vWF Ag while platelet count, aggregation, and GP IIb/IIIa expression were decreased in CCHD compared with ACHD group and negatively correlated to HCT. The overproduction of PMPs and platelet activation with suppressed aggregation may be implicated in the pathogenesis of coagulation/hemostatic abnormalities in children with CCHD.

Spontaneous platelet aggregation evaluated by laser light scatter in patients with type 2 diabetes: Effects of short-term improved glycemic control and adiponectin

Spontaneous platelet aggregation (SPA) is enhanced in patients with type 2 diabetes. Adiponectin may inhibit platelet aggregation. The aims of the current study were to identify factors associated with in vitro SPA measured by a laser light scattering method and to investigate the effects of short-term glycemic control and adiponectin on SPA. In study 1, we investigated platelet aggregation in 20 healthy control subjects and 82 patients with type 2 diabetes. In study 2, we evaluated the changes of SPA and serum high-molecular-weight (HMW) adiponectin after 2 weeks of improved glycemic control in 20 hospitalized diabetic patients. In study 3, using washed platelets from 10 healthy subjects, in vitro SPA was measured over 15 min in the absence or presence of recombinant adiponectin (20 μg/mL). Platelet aggregation was assessed with a laser light scatter aggregometer that measured the size of platelet aggregates. SPA was defined as formation of small aggregates under constant stirring in the absence of any agonists. The area under the curve was calculated for SPA and also for agonist-induced small, medium, and large aggregates. SPA was increased in diabetic patients compared with control subjects. In diabetic patients, SPA was correlated positively with plasma fibrinogen, fasting plasma glucose, glycated albumin, and high-sensitivity C-reactive protein. A stepwise multivariate analysis showed that plasma fibrinogen was the strongest independent determinant of SPA in diabetic patients. In 20 diabetic patients, SPA decreased significantly after 2 weeks of glycemic control. A significant negative correlation was found between changes of SPA and those of HMW adiponectin during treatment. The in vitro study showed that adiponectin inhibited the spontaneous aggregation of washed platelets. In conclusion, hyperfibrinogenemia and hyperglycemia are associated independently with SPA in patients with type 2 diabetes. SPA is reduced after even short-term improvement of glycemic control and adiponectin also inhibits SPA directly.

Changes of platelets’ function in preeclampsia

AbstractIncreased aggregation of platelets during preeclampsia was shown in several studies, yet several others reported no change. The aim of our study was to investigate platelet aggregation in a group of patients suffering from preeclampsia. In a cross-sectional study blood samples were taken from 89 hospitalized patients in the third trimester of pregnancy: 38 were suffering from mild to moderate preeclampsia and 51 patients were without preeclampsia. From the blood samples platelet aggregation, secretion of adenine nucleotides from platelets, concentration of energy-rich adenine compounds and levels of cyclic adenosine-mono-phosphate and cyclic guanosine mono-phosphate in platelets were measured. In the patients with preeclampsia, the adenosine diphosphate threshold for biphasic aggregation [odds ratio (OR):.75; 95% Confidence Interval (CI): 0.55–1.02; p&lt;0.05], total adenine nucleotides concentration in the metabolic pool of platelets (OR:0.99; CI: 0.62–1.57; p&lt;0.01) and cyclic adenosine-mono-phosphate (OR:0.81; CI: 0.57, 1.14; p&lt;0.05) and cyclic guanosine mono-phosphate (OR:.78; CI: 0.55–1.09; p&lt;0.05) levels in platelets were decreased in comparison with the control group, while adenylate energy charge in the metabolic pool of platelets (OR: &gt;100.00; CI: 0.00-&gt;100.00; p&lt;0.05) and secretion of adenosine triphosphate (OR:.13; CI: 0.00–14.26; p&lt;0.05) and adenosine diphosphate (OR:.77; CI: 0.08–36.79; p&lt;0.05) were increased. The results of our study show increased activation and aggregation of platelets in pregnant females with preeclampsia.

The Number and Function of Late Outgrowth Endothelial Cells Correlate with the Extent of Coronary Collateralisation in Humans

file of T80/A10 single-pill combination was comparable to that of its respective components. doi:10.1016/j.hlc.2011.05.050 48 Sleep Disordered Breathing in Children is Associated with Increased Platelet Aggregation, Systemic Inflammation and Endothelial Dysfunction S. Willoughby1,∗, C. van den Heuvel 1, A. Chin1, G. Hodge2, J. Martin2, A. Nelson1,3, M. Worthley1,3, D. Kennedy1 1 University of Adelaide, Australia 2 Women’s and Children’s Hospital, Australia 3 Royal Adelaide Hospital, Australia Introduction: Sleep disordered breathing (SDB) in adults is an independent risk factor for coronary artery disease and stroke. Altered platelet reactivity, endothelial dysfunction and inflammation in adults with SDB are known to contribute to the pathogenesis of its cardiovascular complications. Sleep disordered breathing also occurs in children; however little is known about these parameters in non-obese children with SDB. Therefore, this study investigated platelet aggregation, inflammation and endothelial function in childrenwith SDBandhealthy matched controls.