Inhibition Of Platelet Reactivity Research Articles

The Effects of Caffeine on Blood Platelets and the Cardiovascular System through Adenosine Receptors.

Caffeine is the most popular and widely consumed behaviourally active substance in the world. This review describes the influence of caffeine on the cardiovascular system, with a special focus on blood platelets. For many years, caffeine was thought to have a negative effect on the cardiovascular system mainly due to increasing blood pressure. However, more recent data suggest that habitual caffeine consumption may reduce the risk of cardiovascular disease and hypertension. This could be a significant finding as cardiovascular disease is the leading cause of death worldwide. Caffeine is known to inhibit A1 adenosine receptors, through which it is believed to modulate inter alia coronary blood flow, total peripheral resistance, diuresis, and heart rate. It has been shown that coffee possesses antiplatelet activity, but depending on the dose and the term of its use, caffeine may stimulate or inhibit platelet reactivity. Also, chronic exposure to caffeine may sensitize or upregulate the adenosine receptors in platelets causing increased cAMP accumulation and anti-aggregatory effects and decrease calcium levels elicited by AR agonists. The search for new, selective, and safe AR agonists is one of the new strategies for improving antiplatelet therapy involving targeting multiple pathways of platelet activation. Therefore, this review examines the AR-dependent impact of caffeine on blood platelets in the presence of adenosine receptor agonists.

The Complement System and C4b-Binding Protein: A Focus onthe Promise of C4BPα as a Biomarker to Predict Clopidogrel Resistance.

The complement system plays a dual role in the body, either as a first-line defense barrier when balanced between activation and inhibition or as a potential driver of complement-associated injury or diseases when unbalanced or over-activated. C4b-binding protein (C4BP) was the first circulating complement regulatory protein identified and itfunctions as an important complement inhibitor. C4BP can suppress the over-activation of complement components and prevent the complement system from attacking the host cells through the binding of complement cleavage products C4b and C3b, working in concert as a cofactor for factor I in the degradation of C4b and C3b, and consequently preventing or reducing the assembly of C3 convertase and C5 convertase, respectively. C4BP, particularly C4BP α-chain (C4BPα), exerts its unique inhibitory effects on complement activation and opsonization, systemic inflammation, and platelet activation and aggregation. It has long been acknowledged that crosstalk or interplay exists between the complement system and platelets. Our unpublished preliminary data suggest that circulating C4BPα exerts its antiplatelet effects through inhibition of both complement activity levels and complement-induced platelet reactivity. Plasma C4BPα levels appear to be significantly higher in patients sensitive to, rather than resistant to, clopidogrel, and we suggest that a plasma C4BPα measurement could be used to predict clopidogrelresistance in the clinical settings.

Genetic and nongenetic drivers of platelet reactivity in healthy Tanzanian individuals

BackgroundPlatelets play a key role in hemostasis, inflammation, and cardiovascular diseases. Platelet reactivity is highly variable between individuals. The drivers of this variability in populations from Sub-Saharan Africa remain largely unknown. ObjectivesWe aimed to investigate the nongenetic and genetic determinants of platelet reactivity in healthy adults living in a rapidly urbanizing area in Northern Tanzania. MethodsPlatelet activation and reactivity were measured by platelet P-selectin expression and the binding of fibrinogen in unstimulated blood and after ex vivo stimulation with adenosine diphosphate and PAR-1 and PAR-4 ligands. We then analyzed the associations of platelet parameters with host genetic and nongenetic factors, environmental factors, plasma inflammatory markers, and plasma metabolites. ResultsOnly a few associations were found between platelet reactivity parameters and plasma inflammatory markers and nongenetic host and environmental factors. In contrast, untargeted plasma metabolomics revealed a large number of associations with food-derived metabolites, including phytochemicals that were previously reported to inhibit platelet reactivity. Genome-wide single-nucleotide polymorphism genotyping identified 2 novel single-nucleotide polymorphisms (rs903650 and rs4789332) that were associated with platelet reactivity at the genome-wide level (P < 5 × 10−8) as well as a number of variants in the PAR4 gene (F2RL3) that were associated with PAR4-induced reactivity. ConclusionOur study uncovered factors that determine variation in platelet reactivity in a population in East Africa that is rapidly transitioning to an urban lifestyle, including the importance of genetic ancestry and the gradual abandoning of the traditional East African diet.

The Anti-Aggregative Potential of Resolvin E1 on Human Platelets.

Resolvin E1 is a metabolite of eicosapentaenoic acid (EPA) which is one of the omega-3 polyunsaturated fatty acids (omega-3 PUFAs). The antiplatelet properties of omega-3 PUFAs are well known, but the effect of resolvin E1 on platelets via the collagen receptors is extremely poorly reported. We investigated the effect of resolvin E1 on collagen-induced platelet aggregation, activation, and reactivity, and also platelet membrane fluidity. The ultimate and statistically significant results showed that resolvin E1 may inhibit platelet reactivity due to the reduction of collagen-induced platelet aggregation in platelet-rich plasma and isolated platelets, but not in whole blood. Also, resolvin E1 significantly reduced P-selectin exposure on collagen-stimulated platelets. Moreover, we demonstrated that resolvin E1 can maintain platelet membrane structure (without increasing membrane fluidity). The association between platelet reactivity and membrane fluidity, including resolvin E1 and collagen receptors requires further research. However, the goal of this study was to shed light on the molecular mechanisms behind the anti-aggregative effects of resolvin E1 on platelets, which are still not fully clarified. We also indicate an innovative research direction focused on further analysis and then use of omega-3 PUFAs metabolites as antiplatelet compounds for future applications in the treatment and prevention of cardiovascular diseases.

S298: CS585 IS A FIRST-IN-CLASS COMPOUND TARGETING THE IP RECEPTOR FOR PREVENTION OF THROMBOSIS WITHOUT INCREASED RISK OF BLEEDING

Background: Uncontrolled platelet activation leads to the formation of occlusive thrombi resulting in myocardial infarction, stroke, VTE and critical limb ischemia. There is an unmet need for more efficacious anti-thrombotics with less bleeding in this area. Our group recently identify a novel oxidized lipid in the blood that potently and selectively inhibits platelet activation through activation of the prostacyclin receptor. Aims: Develop a first-in-class antiplatelet drug, CS585, that potently and selectively inhibits platelet reactivity and thrombosis without altering hemostasis and bleeding risk. Methods: We developed a mimetic of the oxidized lipid shown to selectively bind to and activate the prostacyclin receptor. Using human platelets, we assessed the ability of CS585 to inhibit platelet activation by assessing 1)aggregometry, 2)adhesion under arterial flow, and 3) granule secretion and integrin activation using flow cytometry. We additionally assessed thrombosis in vivo in 2 different mouse models as well as bleeding. Finally, we assessed potential off-target effects using thromboelastography (TEG). Results: CS585 potently inhibited both collagen and thrombin-induced platelet aggregation. This inhibition was confirmed by measuring inhibition of αIIbβ3 activation, α-granule secretion, and dense-granule secretion by flow cytometry. Selectivity was confirmed in human platelets by demonstrating a full reversal of inhibition when the IP receptor was pharmacologically blocked or genetically eliminated in IP receptor knockout mice. In vivo inhibition of injury-induced thrombosis in the small (laser-induced cremaster thrombosis model) and large (FeCl3-induced carotid artery thrombosis model) vessels by CS585 was demonstrated and no increased risk for bleeding was observed using the tail vein bleeding model. Finally, TEG experiments in human blood spiked with CS585 demonstrated no delay or decrease in clot strength confirming the tail vein bleeding assay experiments in the mouse. Summary/Conclusion: We have shown for the first time that CS585, a first-in-class analog of an oxidized lipid in the blood potently and selectively activates the prostacyclin receptor resulting in inhibition of human and mouse platelet activation and thrombosis without an increased risk of bleeding. This discovery represents a new class of inhibitors for prevention of platelet activation and thrombosis and protection from myocardial infarction, stroke, VTE, and critical limb ischemia.

Differential Inhibition of Platelet Reactivity by Dual Therapy With Aspirin and Low-Dose Rivaroxaban in Peripheral Arterial Disease: A Pilot Study.

Patients with peripheral arterial disease (PAD) benefit from combination therapy with acetylsalicylic acid (ASA, 100 mg, one time per day) plus low-dose rivaroxaban (2.5 mg, two times per day) compared to ASA monotherapy. In particular, major adverse cardiac and limb events were significantly reduced after peripheral endovascular revascularization (EVR). In this pilot study, the platelet activation status in vivo and platelet reactivity in vitro were longitudinally analyzed by flow cytometric assays and calibrated automated thrombography in platelet-rich plasma (PRP) from 10 patients with PAD receiving ASA (100 mg, one time per day) before EVR, ASA plus clopidogrel (75 mg, one time per day) after EVR, and ASA plus rivaroxaban (2.5 mg, two times per day) during a long-term follow-up. Platelet responsiveness to clopidogrel was compared to additional 10 patients with stable PAD and clopidogrel (75 mg, one time per day) monotherapy. ASA plus rivaroxaban treatment resulted in a significantly decreased thrombin peak in PRP for two triggers, namely, low concentration of tissue factor (TF) and thrombin, compared to ASA monotherapy. TF-controlled thrombin generation was additionally characterized by a significantly prolonged lag time in PRP and platelet-free plasma during ASA plus rivaroxaban combination therapy. In comparison, ASA plus clopidogrel treatment presented a significant reduction of the thrombin peak in PRP, which was less pronounced than during subsequent ASA plus rivaroxaban therapy. Platelet responsiveness to clopidogrel was observed for 60% of patients receiving ASA plus clopidogrel and clopidogrel monotherapy, respectively. Blocking of CD36 on the platelet surface further reduced the thrombin peak in PRP induced by TF for all three therapy regimes. Platelet activation in vivo and in response to the GPVI-agonist convulxin or thrombin in vitro was similar, whereas integrin αIIbβ3 activation and α-granule release induced by the PAR-1 activating peptide TRAP-6 were significantly diminished during ASA plus rivaroxaban treatment compared to ASA monotherapy. In conclusion, the data of this pilot study indicate an inhibitory effect of rivaroxaban on the thrombin propagation phase of CD36-sensitive platelet thrombin formation in patients with PAD treated with ASA plus rivaroxaban combination therapy, which is associated with decreased PAR-1 but not thrombin-mediated platelet activation.

A pilot clinical study to Evaluate Liraglutide-mediated Anti-platelet activity in patients with type-2 Diabetes (ELAID study)

BackgroundLiraglutide is an effective treatment for the management of type 2 diabetes mellitus (T2DM). In addition to glycemic control and potential cardioprotective effects, recent studies suggest a possible role for liraglutide in the inhibition of platelet reactivity, further attenuating atherothrombotic risk in patients with T2DM. We evaluated the in-vivo antiplatelet effect of liraglutide in T2DM patients without macrovascular disease or concurrent anti-platelet therapy. MethodsA double-blind, placebo-controlled pilot study of 16 T2DM patients, 51–69 y/o, (mean age 60.4 y/o, 63.0% male) randomised to receive liraglutide (1.8 mg/day) or placebo (saline) for 6 months was conducted. Platelet aggregation studies at baseline and after initiation of the study intervention: days 1, 7, and 14 and months 1, 3 and 6 were performed. ResultsLiraglutide (n = 7) and placebo (n = 9) treated patients demonstrated normal platelet aggregation responses although transient and significant attenuation in maximum slope of platelet aggregation in response to collagen (p ≤ 0.05), arachidonic acid (p ≤ 0.05) and ADP (p ≤ 0.02) was observed in liraglutide compared to placebo treated patients in the first week. ConclusionsIn this pilot study of patients with T2DM liraglutide treatment was associated with a significant, early and transient decrease in maximum slope of platelet aggregation. The clinical significance of this effect is currently unknown and may warrant further investigation.Clinical Trial Registration Number: UTN 1111-1181-9567.

Prostacyclin analogues decrease platelet aggregation but have no effect on thrombin generation, fibrin clot structure, and fibrinolysis in pulmonary arterial hypertension: PAPAYA coagulation

Prostacyclin (PGI2) analogues (epoprostenol, treprostonil, iloprost) are the cornerstone of pulmonary arterial hypertension (PAH) treatment. PGI2 analogues inhibit platelet reactivity, but their impact on coagulation and fibrinolysis parameters has not been elucidated. We compared platelet reactivity, thrombin generation, clot permeation, and lysis properties in patients with PAH treated with PGI2 analogues (n = 20) and those not receiving PGI2 analogues (n = 20). Platelet reactivity was lower in patients treated with PGI2 analogues, compared to the control group, as evaluated with arachidonic acid (ASPI), adenosine diphosphate (ADP), and thrombin receptor-activating peptide-6 (TRAP) tests (p = .009, p = .02, p = .007, respectively). In the subgroup analysis, both treprostinil and epoprostenol decreased platelet reactivity to the similar extent. There were no differences regarding thrombin generation, clot permeation, and lysis parameters in patients receiving and not receiving PGI2 analogues (p ≥ .60 for all). In the subgroup analysis, there were no differences regarding coagulation and fibrinolysis parameters between treprostinil, epoprostenol, and no PGI2 analogues. To conclude, patients with PAH treated with PGI2 analogues have reduced platelet reactivity, but similar clot formation and lysis parameters, compared to patients not receiving PGI2 analogues. Further randomized clinical trials are required to confirm these findings.

Near-infrared photobiomodulation of blood reversibly inhibits platelet reactivity and reduces hemolysis

Photobiomodulation (PBM) in the red/near-infrared (R/NIR) spectral range has become widely recognized due to its anti-inflammatory and cytoprotective potential. We aimed to assess the effects of blood PBM on platelets function and hemolysis in an in vitro setting. Porcine blood samples were separated into four aliquots for this study, one of which served as a control, while the other three were subjected to three different NIR PBM dosages. The platelet count and functions and the plasma free haemoglobin and osmotic fragility of red blood cells were measured during the experiment. The control group had a considerable drop in platelet number, but the NIR exposed samples had more minimal and strictly dose-dependent alterations. These modifications were consistent with ADP and collagen-induced platelet aggregation. Furthermore, red blood cells that had received PBM were more resistant to osmotic stress and less prone to hemolysis, as seen by a slightly lower quantity of plasma free hemoglobin. Here we showed under well-controlled in vitro conditions that PBM reversibly inhibits platelet activation in a dose-dependent manner and reduces hemolysis.

Comparative analysis of hemostasis system state indicators in severe COVID-19

Introduction. Clinical experience in managing patients with a new coronavirus infection caused by the SARS-CoV-2 allowed to identify specific hemostasis disorders, and enables to introduce the concept of COVID-associated coagulopathy. The aim of the study was to assess the direction of coagulogram parameter changes, whole blood clotting parameters and characteristics of platelet and plasma hemostasis in patients with severe COVID-19. Materials and methods. The parameters of the hemostasis system were assessed using venous blood of 12 patients with severe COVID-19 and 16 healthy volunteers. The whole blood clotting process was investigated by low-frequency piezothromboelastography. The platelet count and indicators of spontaneous and ADP-induced platelet aggregation were estimated with the help of a laser platelet aggregation analyzer. Fibrinolytic activity of plasma, plasminogen activity, content of fibrinogen, D-dimer, PTT, APTT, PTI and INR were assessed. Results. An increased level of fibrinogen, a 6-fold increased D-dimer level, and increased PTT were found in patients with severe COVID-19. The patient platelets count was reduced by 51 % (p &lt;0.05), spontaneous platelet aggregation remained at nearly normal level. Almost complete inhibition of ADP-induced platelet reactivity and inhibition of XIIa-dependent fibrinolysis was revealed, despite an increased by 19.3 % (p &lt;0.05) plasminogen activity. Parameters of the whole blood coagulation process pointed a pronounced activation of platelet hemostasis, a significant intensification of the polymerization stage of clot formation and an increased intensity of clot lysis and retraction. Conclusion. The significant increase of D-dimer level and paradoxical inhibition of plasma fibrinolytic activity revealed by test of XIIa-dependent fibrinolysis (in contrast to the increased intensity of clot lysis when assessing the coagulation of whole blood) indicate the complex pathogenic mechanisms of coagulopathy caused by SARS-CoV-2 infection, and the involvement of blood cells and the vascular wall in the process of pathological thrombus formation.

Sex-Dependent Effect of Platelet Nitric Oxide: Production and Platelet Reactivity in Healthy Individuals

A nitrate-rich diet has many cardiovascular benefits, but the mechanism behind this is unclear. We hypothesized that the ingestion of nitrate augments nitrate to nitrite reduction, leading to nitric oxide (NO) production, which may suppress platelet reactivity. In a randomized, double-blinded, placebo-controlled study involving healthy individuals, ingestion of nitrate augmented saliva and plasma nitrite/nitrate concentration and enhanced platelet NO production disproportionately in women compared with men. The response of elevated platelet NO in men was increased platelet reactivity and the response of markedly elevated platelet NO in women slightly inhibited platelet reactivity.

Untargeted Plasma Metabolomics and Gut Microbiome Profiling Provide Novel Insights into the Regulation of Platelet Reactivity in Healthy Individuals.

Considerable variation exists in platelet reactivity to stimulation among healthy individuals. Various metabolites and metabolic pathways influence platelet reactivity, but a comprehensive overview of these associations is missing. The gut microbiome has a strong influence on the plasma metabolome. Here, we investigated the association of platelet reactivity with results of untargeted plasma metabolomics and gut microbiome profiling. We used data from a cohort of 534 healthy adult Dutch volunteers (the 500 Functional Genomics study). Platelet activation and reactivity were measured by the expression of the alpha-granule protein P-selectin and the binding of fibrinogen to the activated integrin αIIbβ3, both in unstimulated blood and after ex vivo stimulation with platelet agonists. Plasma metabolome was measured using an untargeted metabolic profiling approach by quadrupole time-of-flight mass spectrometry. Gut microbiome data were measured by shotgun metagenomic sequencing from stool samples. Untargeted metabolomics yielded 1,979 metabolites, of which 422 were identified to play a role in a human metabolic pathway. Overall, 92/422 (21.8%) metabolites were significantly associated with at least one readout of platelet reactivity. The majority of associations involved lipids, especially members of eicosanoids, including prostaglandins and leukotrienes. Dietary-derived polyphenols were also found to inhibit platelet reactivity. Validation of metabolic pathways with functional microbial profiles revealed two overlapping metabolic pathways ("alanine, aspartate, and glutamate metabolism" and "arginine biosynthesis") that were associated with platelet reactivity. This comprehensive overview is an resource for understanding the regulation of platelet reactivity by the plasma metabolome and the possible contribution of the gut microbiota.

Pharmacokinetics, Pharmacodynamics and Safety of Ticagrelor in Children with Sickle Cell Disease: Results of a Two-Part Phase 2 Study

▪ INTRODUCTIONActivated platelets promote the adhesion of sickle cells to endothelial cells and the formation of platelet-leukocyte aggregates, contributing to vaso-occlusion (VOC). It has been suggested that inhibition of platelet reactivity may reduce the rate of VOCs in sickle cell disease (SCD). A study with ticlopidine reported a reduced rate of VOCs versus placebo. A recent, placebo-controlled, pediatric study with prasugrel showed a non-significant reduction in VOCs events, which was likely due to the low level of platelet inhibition. Ticagrelor is a reversible P2Y12 receptor antagonist shown to inhibit ADP-induced platelet aggregation and is approved for use in adults with coronary artery disease (CAD). A phase 2 study was conducted to characterize the pharmacokinetic (PK), pharmacodynamic (PD) and safety profiles of ticagrelor in children aged 2-17 years with SCD (HbSS or HbS/β0; NCT02214121). METHODSThis study was conducted in 2 parts: Part A was an open-label, randomized, dose-ranging study in which patients received two single doses of ticagrelor 1 week apart, followed by twice daily (bid) ticagrelor for 1 week. Initially, single doses of 0.125-0.563 mg/kg were given, followed by repeated dosing with 0.125 mg/kg bid. Individual platelet response was used to inform further dosing. After an interim analysis including the first 14 patients in Part A, single doses were increased to a maximum of 2.25 mg/kg and repeated dosing up to 0.75 mg/kg bid. Part B (optional) immediately followed the repeated dosing in Part A: patients were randomized 2:1 to continue ticagrelor with the same dose used during Part A or matching placebo as a double-blind treatment for 4 weeks. Safety was assessed during both parts, pain and analgesic use were recorded daily in an eDiary, and painful crises were reported at each visit. Exposure to ticagrelor and the active metabolite (AR-C124910XX), as well as the subsequent platelet inhibition, were determined after single and repeated doses in Parts A and B. RESULTSA total of 45 children with SCD, mean age 11.2 years (range: 3-17) received study drug in Part A and 23 (15 ticagrelor, 8 placebo) children, mean age 10.0 years (range: 3-17) in Part B. Most patients were of African descent (35/45 in Part A and 22/23 in Part B). Ticagrelor exposure increased approximately dose-linearly, with maximum plasma concentration values ranging from 15.2 to 566.6 ng/mL (with 0.125 mg/kg to 2.25 mg/kg) for ticagrelor and 3.1-156.0 ng/mL for AR-C124910XX. The parent:metabolite ratio in children with SCD was similar to that previously observed in adults. Mean P2Y12 reaction units (PRU) after single doses of ticagrelor decreased from pre-dose to 2 hours post-dose (change from baseline: -23.4 to -207.8 PRU for 0.125 mg/kg to 2.25 mg/kg), and returned towards baseline up to the last timepoint (6 or 8 hours' post-dose). In Part B, no difference was seen between the placebo and ticagrelor groups in pain ratings and analgesic use, although the study was not statistically powered to detect differences in these outcomes. Ticagrelor was well tolerated, with no bleeding during treatment and no patient discontinued treatment due to an adverse event. CONCLUSIONSThe PK/PD profile of ticagrelor in children with SCD was suitably characterized and the exposure-response relationship appeared similar to that previously observed in adults with CAD. Ticagrelor was well tolerated and no safety concerns were raised. The potential to impact SCD-related pain crises needs further evaluation, as the number of patients, low doses for some patients and short study duration limit the efficacy conclusions from this study. DisclosuresHsu:AstraZeneca: Other: steering committee for HESTIA trial; Emmi: Other: consultant for Emmi. Sarnaik:AstraZeneca: Other: Advisory Board. Amilon:AstraZeneca: Employment. Rensfeldt:AstraZeneca: Employment. Berggren:AstraZeneca: Employment.

Not-high before-treatment platelet reactivity in patients with STEMI: prevalence, clinical characteristics, response to therapy and outcomes

Platelet reactivity (PR) has been indicated as a pathophysiological key element for ST-Elevation Myocardial Infarction (STEMI) development. Patients with not-high before-treatment platelet reactivity (NHPR) have been poorly studied so far. The aim of this study is to investigate the prevalence, clinical characteristics, response to therapy and outcomes of baseline prior to treatment NHPR among patients with STEMI undergoing primary PCI. We analyzed the data from 358 STEMI patients with assessment of PR by VerifyNow before P2Y12 inhibitor loading dose (LD). Blood samples were obtained at baseline, and after 1 hour, 2 hours, 4–6 hours and 8–12 hours after LD. High platelet reactivity (HPR) was defined as Platelet Reactivity Unit values ≥208, while patients with values <208 at baseline were defined as having NHPR. Overall, 20% patients had NHPR. Age and male gender both resulted independent predictors of NHPR, even after propensity score adjustment. The percentage of inhibition of PR after ticagrelor or prasugrel LD was similar between HPR and NHPR patients at each time point. However, patients with HPR showed worse in-hospital clinical outcomes, and the composite adverse outcome endpoint of death, reinfarction, stroke, acute kidney injury or heart failure was significantly higher (10.0% vs 1.4%; p = .017) as compared with the NHPR group. In conclusion, a significant proportion of patients presenting with STEMI has a baseline NHPR that is associated with better in-hospital outcomes as compared with patients with HPR. Further studies are needed to better elucidate the potential therapeutic implications of NHPR in terms of secondary prevention.

Impact of Platelet Reactivity in ACS Patients on Clinical Outcomes with Triple Antithrombotic Therapy.

Optimal antithrombotic therapy after percutaneous coronary intervention (PCI) in patients on oral anticoagulants (OAC) remains a clinical conundrum. In fact, combining an OAC with dual antiplatelet therapy (triple antithrombotic therapy, TAT) increases the risk of bleeding. Clopidogrel is the only thienopyridine recommended in TAT patients. Whether its response plays a relevant role in this setting remains uncertain. We aimed to evaluate the level of platelet reactivity inhibition (PRI) achieved by oral TAT in Acute Coronary Syndrome (ACS) patients undergoing PCI and its relationship with outcomes. We performed a multicenter prospective observational study and assessed PRI by vasodilator-stimulated phosphoprotein (VASP) index following a loading dose of clopidogrel. The primary endpoint was the incidence of major adverse cerebral or cardiovascular events (MACCE) at six months based on High on Treatment Platelet Reactivity (HTPR, VASP > 50%). The secondary endpoint was the incidence of bleeding at six months based on Low on Treatment Platelet Reactivity (LTPR, VASP < 16%). 491 patients were followed up for six months: 7.7% experienced MACCE and 17.3% experienced bleeding. There was no significant relationship between HTPR and MACCE, neither between LTPR and bleeding. Vitamin-K antagonist (VKA) treatment was associated with more MACCE and bleeding events, and the majority of events occurred within the first months. VASP index failed to predict outcomes in post-ACS patients with TAT. We confirm that direct acting OAC should be prioritized over VKA in TAT regimen.

Prostacyclin Analogues Inhibit Platelet Reactivity, Extracellular Vesicle Release and Thrombus Formation in Patients with Pulmonary Arterial Hypertension.

(1) Background: Prostacyclin analogues (epoprostenol, treprostinil, and iloprost) induce vasodilation in pulmonary arterial hypertension (PAH) but also inhibit platelet function. (2) Objectives: We assessed platelet function in PAH patients treated with prostacyclin analogues and not receiving prostacyclin analogues. (3) Methods: Venous blood was collected from 42 patients treated with prostacyclin analogues (49.5 ± 15.9 years, 81% female) and 38 patients not receiving prostacyclin analogues (55.5 ± 15.6 years, 74% female). Platelet reactivity was analyzed by impedance aggregometry using arachidonic acid (AA; 0.5 mM), adenosine diphosphate (ADP; 6.5 µM), and thrombin receptor-activating peptide (TRAP; 32 µM) as agonists. In a subset of patients, concentrations of extracellular vesicles (EVs) from all platelets (CD61+), activated platelets (CD61+/CD62P+), leukocytes (CD45+), and endothelial cells (CD146+) were analyzed by flow cytometry. Platelet-rich thrombus formation was measured using a whole blood perfusion system. (4) Results: Compared to controls, PAH patients treated with prostacyclin analogues had lower platelet reactivity in response to AA and ADP (p = 0.01 for both), lower concentrations of platelet and leukocyte EVs (p ≤ 0.04), delayed thrombus formation (p ≤ 0.003), and decreased thrombus size (p = 0.008). Epoprostenol did not affect platelet reactivity but decreased the concentrations of platelet and leukocyte EVs (p ≤ 0.04). Treprostinil decreased platelet reactivity in response to AA and ADP (p ≤ 0.02) but had no effect on the concentrations of EVs. All prostacyclin analogues delayed thrombus formation and decreased thrombus size (p ≤ 0.04). (5) Conclusions: PAH patients treated with prostacyclin analogues had impaired platelet reactivity, EV release, and thrombus formation, compared to patients not receiving prostacyclin analogues.

Impact of smoking habit on platelet reactivity in a cohort of patients admitted due to an acute coronary syndrome

Abstract Background Several pharmacodynamic studies have shown the impact of smoking habit on platelet reactivity; with a reduction on platelet aggregation. Wether this inhibition in platelet reactivity is due to tobacco effects in platelet signaling pathways or due to a pharmacodynamic interaction with antiplatelet therapies is not well stablished. Purpose Our aim was to study the influence of smoking habit in platelet reactivity and in the response to P2Y12 inhibitors. Methods Patients admitted in four tertiary care hospitals due to an acute coronary syndrome that undergone percutaneous coronary intervention (PCI) were consecutively and prospectively recruited. All the patients received dual antiplatelet therapy with aspirin and a P2Y12 inhibitor following current European Guidelines. Platelet function was assessed at day 1 and day 30 post-PCI by VerifyNow P2Y12, VASP (Vasodilator-stimulated phosphoprotein) y MEA (Multiple electrode aggregometry). Results A total of 1000 patients were enrolled, of whom 12 had to be excluded due to inaccurate processing of blood samples. 372 patients (37,6%) had smoking habit. Non-smoking patients showed higher prevalence of high blood pressure [423 (68.7%) vs 196 (52.7%)] and diabetes mellitus [213 (34.6%) vs 81 (21.8%)]. Smoking patients were younger [57.3 (9,6) years old vs 68.4 (11.1)], with higher incidence of acute coronary syndrome with ST segment elevation [184 patients (49,5%) vs 241 (39.1%), p&amp;lt;0,001]. There were no differences in platelet function at day 1. When analysing platelet function 30 days post-PCI, a lower inhibition of platelet reactivity in non-smoking patients as compared with smoking patients was observed in those treated with clopidogrel, with higher prevalence of clopidogrel-resistance in non-smoking patients (VerifyNow, 51,2% prevalence of high platelet reactivity in non-smoking patients vs 34,9% 30 days after PCI, p=0,023). On the other hand, smoking patients that received ticagrelor did not show any differences. Patients with smoking habit treated with prasugrel showed a lower response of borderline statistical significance. Conclusion Smoking habit was associated with a lower response to prasugrel of borderline significance, and with higher response to clopidogrel, according with previous studies suggesting a pharmacodynamics interaction between tobacco use and P2Y12 inhibitors. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fondo de Investigaciones Sanitarias (FIS)

Omega-6 DPA and its 12-lipoxygenase–oxidized lipids regulate platelet reactivity in a nongenomic PPARα-dependent manner

AbstractArterial thrombosis is the underlying cause for a number of cardiovascular-related events. Although dietary supplementation that includes polyunsaturated fatty acids (PUFAs) has been proposed to elicit cardiovascular protection, a mechanism for antithrombotic protection has not been well established. The current study sought to investigate whether an omega-6 essential fatty acid, docosapentaenoic acid (DPAn-6), and its oxidized lipid metabolites (oxylipins) provide direct cardiovascular protection through inhibition of platelet reactivity. Human and mouse blood and isolated platelets were treated with DPAn-6 and its 12-lipoxygenase (12-LOX)–derived oxylipins, 11-hydroxy-docosapentaenoic acid and 14-hydroxy-docosapentaenoic acid, to assess their ability to inhibit platelet activation. Pharmacological and genetic approaches were used to elucidate a role for DPA and its oxylipins in preventing platelet activation. DPAn-6 was found to be significantly increased in platelets following fatty acid supplementation, and it potently inhibited platelet activation through its 12-LOX–derived oxylipins. The inhibitory effects were selectively reversed through inhibition of the nuclear receptor peroxisome proliferator activator receptor-α (PPARα). PPARα binding was confirmed using a PPARα transcription reporter assay, as well as PPARα−/− mice. These approaches confirmed that selectivity of platelet inhibition was due to effects of DPA oxylipins acting through PPARα. Mice administered DPAn-6 or its oxylipins exhibited reduced thrombus formation following vessel injury, which was prevented in PPARα−/− mice. Hence, the current study demonstrates that DPAn-6 and its oxylipins potently and effectively inhibit platelet activation and thrombosis following a vascular injury. Platelet function is regulated, in part, through an oxylipin-induced PPARα-dependent manner, suggesting that targeting PPARα may represent an alternative strategy to treat thrombotic-related diseases.

Suppression of platelet reactivity during dialysis by addition of a nitric oxide donor to the dialysis fluid

BackgroundDialysis membranes that release nitric oxide (NO) from their surface, mimicking one of the functions of endothelial cells, may suppress platelet reactivity during hemodialysis treatment. The aim of the present study was to examine whether the addition of a NO donor to the dialysis fluid can suppress platelet reactivity during dialysis.MethodsPorcine whole blood was circulated for 4 h through a polysulfone (PS) dialyzer or polymethylmethacrylate (PMMA) dialyzer. After the blood was circulated through the blood circuit and dialyzer, sodium nitroprusside was added to the dialysis fluid as a NO donor. The changes in the platelet reactivity, measured by the platelet aggregation activity by the addition of adenosine diphosphate or collagen in the blood sample, were evaluated during ex vivo dialysis experiments in the presence of a dialysis fluid containing or not containing a NO donor.ResultsThe platelet aggregation activity was significantly decreased at 30 min after the start of the experiment in the case where nitroprusside was added to the dialysis fluid (the NO (+) condition) as compared to the case where no nitroprusside was added to the dialysis fluid (the NO (−) condition), for both the PS and PMMA membranes. The suppression of the platelet reactivity in the NO (+) condition was sustained until the end of the experimental period (240 min). The platelet cyclic guanosine monophosphate level was also significantly increased in the NO (+) condition as compared to the NO (−) condition.ConclusionsNO in the dialysis fluid appears to be capable of suppressing the increase of the platelet reactivity observed during dialysis.

Impact of smoking on platelet function of ticagrelor versus clopidogrel in minor stroke or transient ischaemic attack.

It remains unclear whether smoking status has an impact on platelet reactivity and clinical outcomes of ticagrelor versus clopidogrel in patients with acute minor stroke or transient ischaemic attack (TIA). A subgroup analysis of a randomized controlled trial was conducted. Patients with minor stroke or TIA were randomized for treatment with ticagrelor plus aspirin or clopidogrel plus aspirin. Platelet reactivity was assessed by VerifyNow P2Y12 assay at baseline, 7+2days and 90±7days. High on-treatment platelet reactivity (HOPR) was defined as P2Y12 reaction units >208. Clinical outcomes included any stroke, composite clinical vascular events and bleeding events at 90days. Patients who smoked one or more cigarettes per day for at least 1year in their lives were defined as smokers. Of 675 patients enrolled in the trial, 370 patients (54.8%) were smokers. At 7+2days, the proportion of HOPR in ticagrelor versus clopidogrel was significantly lower in smokers (5.2% vs. 21.8%) and non-smokers (2.3% vs. 34.4%). There were marginal significant interactions between treatment groups and smoking status for the proportion of HOPR (P=0.058). At 90±7days, there were significant interactions between treatment groups and smoking status for the risk of new stroke (smokers: 7.0% vs. 4.9%; hazard ratio, 1.57; 95% confidence interval, 0.65-3.79; P=0.39; non-smokers: 5.3% vs. 13.5%; hazard ratio, 0.39; 95% confidence interval, 0.17-0.91; P=0.01; P for interaction=0.02). Among patients with minor stroke or TIA, ticagrelor was superior to clopidogrel in inhibiting platelet reactivity and reducing the risk of new stroke, particularly for non-smokers.