Platelet ADP Research Articles

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.

Manipulating Metabolic Plasticity By Targeting Pyruvate Kinase M2 in Platelets Inhibits Arterial Thrombosis

Background: Most of the cellular responses initiated upon platelet activation are energy consuming. Like normal cells, resting platelets rely primarily on oxidative phosphorylation (OXPHOS) to generate ATP, whereas activated platelets exhibit a high level of aerobic glycolysis (conversion of glucose to lactate in the presence of oxygen, a phenomenon referred to as the Warburg effect in tumor cells) suggesting that metabolic plasticity exists in activated platelets. Although aerobic glycolysis yields less total ATP when compared to OXPHOS, the rate of ATP generation is faster in aerobic glycolysis compared to OXPHOS, which is well suited for high-energy demands during platelet activation. Pyruvate kinases (PKs) catalyzes the final step of glycolysis, the formation of pyruvate and ATP from phosphoenolpyruvate and ADP. Four PK isoforms exist in mammals: L and R isoforms are expressed in the liver and red blood cells; the M1 isoform is expressed in most adult tissues that have high catabolic demands including muscle and brain; M2 is expressed in cells including activated platelets and leukocytes. While PKM1 and tetrameric PKM2 favor ATP production from OXPHOS through the TCA cycle, dimeric PKM2 drives aerobic glycolysis.Objective: We tested an innovative concept that by manipulating the energy demand of activated platelets (metabolic plasticity), by targeting PKM2, will inhibit platelet function and thrombosis.Methods: Using a specific inhibitor of PKM2 (inhibits PKM2 dimerization and stabilizes tetramers) and standardized platelet in vitro assays, we determined the mechanistic role of PKM2 in modulating platelet function in human and mice. To provide definitive evidence, we generated a megakaryocyte or platelet-specific PKM2-/- mouse (PKM2fl/flPF4Cre). Lactate assay was performed in WT and PKM2 null platelets. Susceptibility to thrombosis was evaluated in vitro (microfluidics flow chamber) and in vivo (FeCl3-induced carotid artery thrombosis and laser injury models) by utilizing intravital microscopy.Results: We found that PKM2 is relatively highly expressed compared to PKM1 in human and murine platelets. Transmission electron microscopy (immunogold staining) revealed that PKM2 is found in the cytoplasm and a- granule in resting platelets, whereas most of PKM2 translocated to cytoplasm upon activation. Human and mouse platelets pretreated with PKM2 inhibitor exhibited decreased platelet aggregation to sub-optimal doses of collagen and convulxin but not to thrombin. In microfluidics flow chamber assay, human and whole mouse blood pretreated with PKM2 inhibitor formed small thrombi when perfused over collagen for 5 min at an arterial shear rate of 1500s-1 (P<0.05 vs. vehicle control). Platelets from PKM2fl/flPF4Cre mice exhibited decreased platelet aggregation to sub-optimal doses of collagen and convulxin, but not to thrombin, compared to PKM2fl/fl mice concomitant with decrease lactate production. In microfluidics flow chamber assay, whole blood from PKM2fl/flPF4Cre mice formed smaller thrombi when perfused over collagen for 5 min at an arterial shear rate of 1500s-1, compared to PKM2fl/fl mice. PKM2fl/flPF4Cre mice were less susceptible to thrombosis in the FeCl3-induced carotid and laser injury-induced mesenteric artery thrombosis models (P<0.05 vs. vehicle control, N=10 mice/group), without altering hemostasis. PKM2 regulates the phosphorylation signal transducer and activator of transcription 3 (STAT3) and p-STAT3 act as a protein scaffold that facilitates the catalytic process of activating PLCg by kinase Syk in response to low-doses of collagen and CRP, but not TRAP or ADP in human and murine platelets. Interestingly, we found that PKM2 and STAT3 colocalized in the convulixn- stimulated control platelets and less phosphorylation of STAT-3 was observed in activated PKM2 null platelets (P<0.05 vs. WT), suggesting a non-glycolytic role of the PKM2 in regulating collagen signaling.Conclusions: Our results suggest that dimeric PKM2 regulates platelet function and arterial thrombosis most likely via GPVI signaling pathway. We suggest that manipulating metabolic plasticity by targeting dimeric PKM2 may be explored as a novel strategy to inhibit platelet function and arterial thrombosis. DisclosuresNo relevant conflicts of interest to declare.

TNF-Induced Vaso-Occlusive and Inflammatory Processes in Mice with Sickle Cell Anemia Are Abrogated By the Platelet Activation Inhibitor, Prasugrel

Background: Vaso-occlusive processes in sickle cell anemia (SCA) are triggered by inflammatory molecules, along with pancellular activation and the recruitment and adhesion of leukocytes to the endothelium. Interactions between platelets, neutrophils, and erythrocytes are observed in the SCA circulation, but the exact role of platelets in the initiation and propagation of vaso-occlusion is not well understood. Aim: We, herein, evaluated the effects of the inhibition of platelet activation on TNF-α (TNF)-triggered vaso-occlusive processes in the microcirculation of mice with SCA, using prasugrel, a platelet ADP P2Y12 receptor inhibitor. Methods: Chimeric male control (CON) and SCA (SCA) mice received prasugrel (1 mg/kg, by gavage) or vehicle (saline) in a single administration, 1h prior to TNF (0.5 μg/g, i.p). In some experiments, 1 mg/kg prasugrel was administered chronically for 5x per week for 4 weeks. Following i.v. injection of anti-CD41 PE, anti-CD45 PeCy-5 and anti-Ly6G Alexa 488 antibodies for labeling platelets, leukocytes (in general) and neutrophils respectively, the cremaster muscle was exposed and the microcirculation was observed by conventional and confocal intravital microscopy. Results: While the acute administration of prasugrel to CON and SCA mice did not alter the quantity of platelets in the microcirculation (data not shown), it significantly reduced the adhesion of platelets to the vascular wall in both CON animals (12±1.6 vs 5.7±1.4 % adhered of total platelets, n=3; p<0.05) and SCA mice after TNF (36.2±7.1 vs 4.8±2.5 % platelets adhered for w/out and with prasugrel, respectively; n=3; p<0.0001) (see Figure). Furthermore, prasugrel significantly reduced the number of platelet/neutrophil aggregates in TNF-treated CON (2.7±0.4 vs 0.53±0.3 aggregates adhered 100 µm−1, p<0.001 n=3) and SCA mice (3.1±0.7 vs 0.76±0.3 aggregates adhered 100 µm−1, p<0.01 n=3), and also platelet/non-neutrophil leukocytes in CON (1.3±0.7 vs 0.2±0.1 aggregates adhered 100 µm−1, p<0.01 n=3) and SCA mice (2.0±0.3 vs 0.2±0.1 aggregates adhered 100 µm−1, p<0.001 n=3). Alterations in platelet adhesion to the vascular wall and platelet-leukocyte aggregate formation were accompanied by reductions in the recruitment of leukocytes to the venule walls, after prasugrel administration. Prasugrel significantly decreased the rolling, adhesion and extravasation of leukocytes in both CON (4.9±2.7 vs 1.14±0.5 min−1; 9.2±0.8 vs 2.7±0.5 100 µm−1; 1.9±0.3 vs 0.4±0.1 100x50 µm-2; for w/out and with prasugrel, respectively; n=3; p<0.001) and SCA mice (36.0±3.0 vs 3.0±0.6 min−1; 16.6±1.5 vs 6.4±1.2 100 µm−1; 6.9±0.8 vs 1.7±0.4 100x50 µm-2; for w/out and with prasugrel, respectively; n=3; p<0.0001). Acute prasugrel treatment also increased blood flow velocity after TNF stimulation in CON mice (37±10 vs 110±35 mm3/s, p<0.01, n=3) and substantially augmented flow in SCA mice (13±2 vs 94±12 mm3/s, p<0.0001, n=3), approaching flow velocities similar to those observed in control animals that had not received TNF (Data not shown). The survival of SCA animals treated with a single dose of prasugrel increased by 1.3 hours compared to the SCA animals that received the vehicle (n=3, p<0.05). Complimentary experiments demonstrated a similar effect of the chronic administration of prasugrel, which significantly reduced leukocyte recruitment to the vascular wall after TNF in both CON and SCA mice (data not shown, P<0.05). Conclusions: Our findings show that the inhibition of platelet activation by prasugrel, while significantly decreasing the adhesion of platelets to venules walls and the formation of heterocellular aggregates, was able to almost abolish the recruitment of leukocytes to the microcirculation of SCA mice after an inflammatory stimulus. This reduction in platelet and leukocyte vascular recruitment was associated with major improvements in blood flow and in the survival of animals with SCA. Thus, our data suggest that platelet activation and the consequent adhesion of platelets to the vascular wall is a fundamental step in the initiation of the vaso-occlusive process in response to inflammatory stimuli. Our findings support further investigations into the use of drugs that inhibit platelet activation (including prasugrel itself) as a therapeutic approach for SCA. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Perioperative point of care platelet function testing and postoperative blood loss in high-risk cardiac surgery patients

Postoperative coagulopathic bleeding is common in cardiac surgery and associated with increased morbidity and mortality. Platelet function is affected by multiple factors, including patient and procedural characteristics. Point-of-care (POC) multiple electrode aggregometry (MEA) can rapidly detect and quantify platelet dysfunction and could contribute to optimal patient blood management.In patients undergoing CABG and heart valve surgery platelet function was assessed using POC MEA at four different perioperative timepoints in response to stimulation with four specific receptor agonists (ADP, AA, COL, TRAP). Postoperative bleeding was recorded during 24 h after surgery. Regression analyses were performed to establish associations between perioperative platelet function and postoperative blood loss.Ninety-nine patients were included in the study. Fifty-nine patients (60%) were on antiplatelet therapy (APT) at time of surgery. ADP- and AA-induced platelet aggregation declined during CPB and after decannulation from CPB, with a maximum decrease of 55% for ADP (35 vs. 77 AU at baseline; P < 0.001) and 78% for ASPI (14 vs. 64 AU at baseline; P < 0.001). A linear relationship was present between ADP-induced platelet aggregometry at baseline and postoperative blood loss (r = −0.249; P = 0.015). In aspirin users, the maximum decline in platelet function between baseline and CPB decannulation was related to postoperative blood loss (r = 0.308; P = 0.037). In multivariate analysis, a reduced ADP platelet function prior to surgery remained associated with postoperative blood loss (r = −0.239; P = 0.012).Reduced ADP-induced platelet aggregation at baseline is associated with increased postoperative blood loss in high-risk cardiac surgery patients.

Reduced nicotinamide adenine dinucleotide phosphate inhibits rat platelet aggregation and p38 phosphorylation

Previous studies found that reduced nicotinamide adenine dinucleotide phosphate (NADPH) protected neurons against ischemia/reperfusion-induced injury. In addition to ROS reduction and ATP increment, preliminary data suggested that NADPH inhibited ADP and thrombin-induced platelet aggregation. As the effect of NADPH on platelet function was not reported by other investigators, the actions of NADPH on platelet function and mechanisms of actions were investigated in the present study. In vitro studies, the effects of different concentrations of NADPH on platelet aggregation induced by ADP (10 μM), thrombin (0.05 U/mL) or AA (50 μM) were determined. The results showed that NADPH could inhibit platelet aggregation induced by ADP, thrombin or AA in a concentration dependent manner. When the inhibitory effects of NAD+, NADH, NADP+ and NADPH on platelet aggregation were compared, NADPH demonstrated the relatively best effect on platelet aggregation. In vivo studies, the effects of NADPH on platelet aggregation, tail bleeding time, coagulation response and ferric chloride-induced thrombosis were determined in mice or rats. The maximum aggregation rate of platelets of rats injected with NADPH (5 mg/kg) was lower than platelets from control rats. NADPH transiently prolonged tail bleeding time in mice at 30 min after the injection of NADPH (7.5 mg/kg), while aspirin (15 mg/kg) significantly prolonged the tail bleeding time in mice at all time points examined. NADPH (5 mg/kg), as well as aspirin (10 mg/kg), had no effect on coagulation response in rats. Using a FeCl3-induced abdominal aorta injury thrombosis model, administration of NADPH (5 mg/kg) significantly delayed the onset of vessel occlusion, while aspirin (10 mg/kg) almost completely prevented the vessel occlusion. With microscopic examination the thrombi in injured vessel sections of rats received NADPH were much smaller and less dense than that of rats received vehicle treatment. ADP induced an increase in phosphorylation of p38 and the effect was markedly inhibited by the p38 inhibitor SB203580. Similarly, NADPH also inhibited ADP-induced phosphorylation of p38. Similar to NADPH, SB203580 robustly inhibited ADP- and thrombin-induced platelet aggregation. In addition, NADPH also reduced ADP-induced increases in ROS in platelets. The current results demonstrated that NADPH inhibited platelet aggregation, oxidative stress and p38 phosphorylation, suggesting that NADPH might be a novel compound for management of high risk of cardiovascular disease.

THE INHIBITION OF HUMAN PLATELET AGGREGATION BY A LOW-MOLECULAR WEIGHT CHITOSAN

Chitosan derivatives were obtained by chemical (MW of 6 kDa, DD 99% - Ch6/99; MW13 kDa, DD 98% - Ch13/98) and enzymatic (MW of 5 kDa, DD 85% - Ch5/85; MW of 10 kDa, DD 85% - Ch10/85) depolymeri-sation of chitosan with a MW of 334 and 1000 kDa. Chitosan derivatives (almost identical MW pairs and different DD) possessed insignificant an-ticoagulant activity, did not promote human platelet aggregation and re-duced ADP or collagen-induced platelet aggregation. The studied sam-ples at a concentration of 2 mg/ml reduced the aggregation of platelets more than twice induced in 2x10-6M and 1x10-5M concentrations; at weak activation in 2x10-6M, the Ch10/85 sample was the most effective. The Ch6/99 and Ch13/98 samples were 20 times more effective at the inhibi-tion of collagen-induced platelet aggregation than the Ch10/85 sample. The latter can be explained by the greater value of positive charge (DD) and polydispersity (Mw/Mn) of chitosan samples obtained by chemical de-polymerisation.

Ginsenoside-Rp3 inhibits platelet activation and thrombus formation by regulating MAPK and cyclic nucleotide signaling

Background & purposeGinseng (Panax ginseng C.A. Mayer) contains saponin fractions called ginsenosides, which are thought to be the main components responsible for its various pharmacological activities. Ginsenosides have cardioprotective and antiplatelet effects. In the present study, we evaluated the effects of ginsenoside Rp3 (G-Rp3) on platelet function. MethodsThe in vitro effects of G-Rp3 were evaluated on agonist-induced human and rat platelet aggregation, while [Ca2+]i mobilization, granule secretion, integrin αIIbβ3 activation, and clot retraction were assessed in rat platelets. Its effects on vasodilator-stimulated phosphoprotein (VASP) expression, phosphorylation of MAPK signaling molecules, and PI3K/Akt activation were also studied. Moreover, the tyrosine phosphorylation of components of the P2Y12 receptor downstream signaling pathway was also examined. The in vivo effects of G-Rp3 were studied using an acute pulmonary thromboembolism model and lung histopathology. Key resultsG-Rp3 significantly inhibited collagen, ADP, and thrombin-induced platelet aggregation. G-Rp3 elevated cAMP levels and VASP phosphorylation and suppressed agonist-induced [Ca2+]i mobilization, ATP release, and P-selectin expression along with fibrinogen binding to integrin αIIbβ3, fibronectin adhesion, and clot retraction. G-Rp3 also attenuated the phosphorylation of MAPK, Src, and PLCγ2 as well as PI3K/Akt activation. Furthermore, it inhibited tyrosine phosphorylation of the Src family kinases (Src, Fyn, and Lyn) and PLCγ2 and protected mice from thrombosis. Conclusion and implicationG-Rp3 modulates agonist-induced platelet activation and thrombus formation by inhibiting granule secretion, integrin αIIbβ3 activation, MAPK signaling, and Src, PLCγ2, and PI3K/Akt activation, and VASP stimulation. Our data suggest that G-Rp3 has therapeutic potential as a treatment for platelet-related cardiovascular disorders.

Hemotoxic and wound healing potential of coelomic fluid of sea-star Astropecten indicus

BackgroundThe coelomic fluid of echinoderms bathes all the internal organs and is a natural reservoir of various bio-active compounds. However, coelomic fluid from Indian sea-star Astropecten indicus is not well characterized for its biochemical and pharmacological profiles. Sea-star (or starfish) Astropecten indicus was collected from the coast of Goa, India during low tides. Sea-star coelomic fluid (SCF) extracted from the sea-stars was concentrated, filtered, and assayed for various hemotoxic activities such as fibrinogenolysis, fibrinolysis, hemolysis, and effects on platelet aggregation.ResultsStudies on effects of SCF on A-549 human lung cancer cell line showed its non-cytotoxic and wound healing abilities in vitro. SCF was found to possess fibrinogen and fibrin digesting ability at a dose of 4 μg/ml within 30 min of incubation with the substrate. Additionally, SCF could hemolyze goat RBC by 50% and human RBC by only 5%. SDS-PAGE analysis showed that SCF contains various proteins and peptides. Two protein components of SCF yielded strong fibrinolytic, fibrinogenolytic, caseinolytic, and gelatinase activities as revealed by zymography. SCF enhanced the aggregation of ADP and collagen-activated platelets in a dose-dependent manner and had a specific proteolytic activity of 2.5 μg/ml in 30 min at 37 °C as assayed using azocasein as substrate.ConclusionThis study focuses on the anticoagulant, pro-platelet aggregation and cell proliferative potential of SCF in vitro and is the first report on hemotoxic and wound healing potential of coelomic fluid of Astropecten indicus.

Powerful P2Y12 inhibition after percutaneous coronary intervention for an acute coronary syndrome: “the times they are a changing”

DAPT using aspirin and a P2Y12 platelet ADP receptor blocker has been established since more than 20 years as the pharmacological background of percutaneous coronary intervention (PCI) and post-acute coronary syndrome (ACS) ( Table 1 ). First, the combination of aspirin and ticlopidine given for 30 days has shown superiority over aspirin and anticoagulant therapy in patients undergoing coronary artery stenting (1).

Comparing coagulation activity of Selaginella tamariscina before and after stir-frying process and determining the possible active constituents based on compositional variation

Context: Selaginella tamariscina (P. Beauv.) Spring (Selaginellaceae) (ST) has been widely used in China as a medicine for improving blood circulation. However, its processed product, S. tamariscina carbonisatus (STC), possesses opposite haemostatic activity.Objective: To comprehensively evaluate the activity of ST and STC on physiological coagulation system of rats, and seek potential active substances accounting for the activity transformation of ST during processing.Materials and methods: The 75% methanol extracts of the whole grass (fine powder) of ST and STC were prepared, respectively. Male Sprague–Dawley rats were randomly divided into five groups: control group, model group, model + ST group, model + STC group and positive control group (model + Yunnanbaiyao). The duration of intragastric administration was 72 h at 12 h intervals. Haemorheology parameters were measured using an LB-2 A cone-plate viscometer and the existed classic methods, respectively. SC40 semi-automatic coagulation analyzer was employed to determine coagulation indices. Meanwhile, HPLC and LC-MS were applied for chemical analyses of ST and STC extracts.Results: STC shortened tail-bleeding time, increased whole blood viscosity (WBV) and plasma viscosity (PV), decreased erythrocyte sedimentation rate blood (ESR), reduced activated partial thromboplastin time (APTT) and increased the fibrinogen (FIB) content in the plasma of bleeding model rats. Although ST could shorten APTT and TT, the FIB content was significantly decreased by ST. Dihydrocaffeic acid with increased content in STC vs. ST showed haemostatic activity for promoting the platelet aggregation induced by collagen and trap-6, and reducing APTT and PT significantly with a concentration of 171.7 μM in vitro. Amentoflavone with reduced content in STC vs. ST inhibited ADP and AA-induced platelet aggregation significantly with a concentration of 40.7 μM.Discussion and conclusions: As the processed product of ST, STC showed strong haemostatic activity on bleeding rat through regulating the parameters involved in haemorheology and plasma coagulation system. Two active compounds, dihydrocaffeic acid and amentoflavone, might be partially responsible for the haemostatic and anticoagulant activity of STC and ST, respectively.

Возможные генетические предикторы развития сердечно-сосудистых осложнений после коронарного шунтирования

to investigate associations of single nucleotide polymorphisms (SNPs) rs2046934, rs1126643, rs5918, rs6065, rs4244285; rs4986893 with cardiovascular complications (CVC) in patients after CABG. We enrolled in this study 130 patients with stable functional class II-IV angina. After CABG 69 patients received ASA (100 mg of enteric form), 61 patients received dual antiplatelet therapy (ASA 100 mg + clopidogrel 75 mg). Mean follow up period was 10.9±5.2 months. The primary composite endpoint included all-cause mortality, myocardial infarction (MI), and ischemic stroke. The control group comprised 185 healthy volunteers. Platelet function was assessed using light transmission aggregometry with ADP (5μM) and arachidonic acid (1 mM). The following single nucleotide polymorphisms (SNPs) were identified by real-time PCR: rs2046934 (H1/H2) on P2RY12 [encoding platelet ADP receptor] (n=100); rs1126643 (C807T, Phe224Phe) on ITGA2 [encoding collagen receptor] (n=87); rs5918 (176T>C, Leu33Pro) on ITGB3 [encoding fibrinogen receptor) (n=91); rs6065 (Thr145Met) on GP1BA [encoding platelet receptor for Von Willebrand factor] (n=114); rs4244285 (*2) (n=84), and rs4986893 (*3) (n=83) on СYP2C19 [encoding cytochrome P450 activity]. The prevalence of rs5918, rs6065, rs4244285, rs4986893, rs2046934 did not differ significantly between patients and healthy volunteers. The mutant allele (T) of ITGA2 was detected more often in healthy volunteers: 67.2 % vs 51.7 % (р=0.021). Before and after CABG there was no significant difference in platelet aggregation between carries and non-carries of the mutant ITGA2 allele. Number of CVCs registered during follow-up was 12: 3 strokes, 6 MIs, 3 deaths. Patients with composite mutant alleles of ITGB3+СYP2C19*2 or СYP2C19*2+ITGA2, and with the mutant allele (*2) of СYP2C19 met end points more often than patients with other gene combinations (wild type homozygotes, presence of one mutant allele of ITGB3 or ITGA2, the composite of mutant alleles of ITGB3+ITGA2 or ITGB3+ITGA2+ СYP2C19*2) (hazard ratio 4.0, 95 % confidence interval 2,19-7.29, р=0.008). Carriers of ITGB3 mutant allele showed higher AA-induced platelet reactivity on the 1st-3rd day after CABG. Amplitude of platelet aggregation in carriers of mutant allele was 27.5 % vs 12.7 % in wild type (p=0.016). No differences in platelet reactivity among carriers of other mentioned mutant alleles and wild types were observed. Carriage of the combination of mutant alleles ITGB3+СYP2C19*2 or СYP2C19*2+ITGA2 or СYP2C19*2 is possible predictor of CVC in patients after CABG.

Antiagregación plaquetaria dual en enfermedad coronaria

Dual antiplatelet therapy (DAPT) with acetylsalicylic acid plus a platelet ADP P2Y12 receptor inhibitor is key in avoiding thrombosis following balloon angioplasty, or angioplasty with stent implantation. The main risk of DAPT is bleeding. The length of DAPT treatment depends on the comprehensive assessment of the patient's risk of thrombotic-ischemic complications and risk of bleeding. Depending on the clinical condition, treatment guidelines from the various societies recommend at least six months of dual treatment (and ideally one year), in patients with acute coronary syndrome.

Clinical pathways and management of antithrombotic therapy in patients with acute coronary syndrome (ACS): a Consensus Document from the Italian Association of Hospital Cardiologists (ANMCO), Italian Society of Cardiology (SIC), Italian Society of Emergency Medicine (SIMEU) and Italian Society of Interventional Cardiology (SICI-GISE).

Antiplatelet therapy is the cornerstone of the pharmacologic management of patients with acute coronary syndrome (ACS). Over the last years, several studies have evaluated old and new oral or intravenous antiplatelet agents in ACS patients. In particular, research was focused on assessing superiority of two novel platelet ADP P2Y12 receptor antagonists (i.e., prasugrel and ticagrelor) over clopidogrel. Several large randomized controlled trials have been undertaken in this setting and a wide variety of prespecified and post-hoc analyses are available that evaluated the potential benefits of novel antiplatelet therapies in different subsets of patients with ACS. The aim of this document is to review recent data on the use of current antiplatelet agents for in-hospital treatment of ACS patients. In addition, in order to overcome increasing clinical challenges and implement effective therapeutic interventions, this document identifies all potential specific care pathway for ACS patients and accordingly proposes individualized therapeutic options.

Hierarchical organization of the hemostatic response to penetrating injuries in the mouse macrovasculature

Background Intravital studies performed in the mouse microcirculation show that hemostatic thrombi formed after penetrating injuries develop a characteristic architecture in which a core of fully activated, densely packed platelets is overlaid with a shell of less activated platelets. Objective Large differences in hemodynamics and vessel wall biology distinguish arteries from arterioles. Here we asked whether these differences affect the hemostatic response and alter the impact of anticoagulants and antiplatelet agents. Methods Approaches previously developed for intravital imaging in the mouse microcirculation were adapted to the femoral artery, enabling real-time fluorescence imaging despite the markedly thicker vessel wall. Results Arterial thrombi initiated by penetrating injuries developed the core-and-shell architecture previously observed in the microcirculation. However, although platelet accumulation was greater in arterial thrombi, the kinetics of platelet activation were slower. Inhibiting platelet ADP P2Y12 receptors destabilized the shell and reduced thrombus size without affecting the core. Inhibiting thrombin with hirudin suppressed fibrin accumulation, but had little impact on thrombus size. Removing the platelet collagen receptor, glycoprotein VI, had no effect. Conclusions These results (i) demonstrate the feasibility of performing high-speed fluorescence imaging in larger vessels and (ii) highlight differences as well as similarities in the hemostatic response in the macro- and microcirculation. Similarities include the overall core-and-shell architecture. Differences include the slower kinetics of platelet activation and a smaller contribution from thrombin, which may be due in part to the greater thickness of the arterial wall and the correspondingly greater separation of tissue factor from the vessel lumen.

Triggering Receptor Expressed on Myeloid cells-1: a new player in platelet aggregation.

Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) is an immunoreceptor initially known to be expressed on neutrophils and monocytes/macrophages. TREM-1 acts as an amplifier of the inflammatory response during both infectious and aseptic inflammatory diseases. Another member of the TREM family, The Triggering receptor expressed on myeloid cells Like Transcript-1 (TLT-1) is exclusively expressed in platelets and promotes platelet aggregation. As the gene that encodes for TLT-1 is located in the TREM-1 gene cluster, this prompted us to investigate the expression of TREM-1 on platelets. Here we show that TREM-1 is constitutively expressed in α-granules and mobilised at the membrane upon platelet activation. Pharmacologic inhibition of TREM-1 reduces platelet activation as well as platelet aggregation induced by collagen, ADP, and thrombin in human platelets. Aggregation is similarly impaired in platelets from Trem-1-/- mice. In vivo, TREM-1 inhibition decreases thrombus formation in a carotid artery model of thrombosis and protects mice during pulmonary embolism without excessive bleeding. These findings suggest that TREM-1 inhibition could be useful adducts in antiplatelet therapies.

Histamine-2 Receptor Antagonist Cannot Prevent Recurrent Peptic Ulcers in Patients With Atherosclerotic Diseases Who Receive Platelet ADP Receptor Antagonist Monotherapy: A Randomized-Controlled, Double-Blind, and Double-Dummy Trial.

Proton pump inhibitor can effectively prevent recurrent peptic ulcers among atherosclerotic patients receiving clopidogrel monotherapy. However, the interaction between proton pump inhibitors and clopidogrel has raised concerns over the safety of combined use of the two medicines in clinical practice. The aims of this randomized-controlled, double-blind and double-dummy trial were to investigate the efficacy of histamine-2 receptor antagonist (H2RA) in the prevention of recurrent peptic ulcer in patients undergoing thienopyridine monotherapy. From January 2012 to 2016, long-termed thienopyridine users with a peptic ulcer history who did not have peptic ulcers at initial endoscopy were randomly assigned to receive either famotidine (40 mg, before bedtime) or placebo (before bedtime) for 6 months. Follow-up endoscopy was performed at the end of the 6th month and whenever dyspepsia, hematemesis, or melena occurred. The cumulative incidence of recurrent peptic ulcer during the 6-month period was 7.0% in famotidine group (n=114) and 11.4% in the placebo group (n=114). The two patient groups had comparable cumulative incidence of peptic ulcer (difference, 4.4%; 95% confidence interval (CI), -11.7 to 2.9%; P=0.239). Additionally, there was no difference in the cumulative incidence of ulcer bleeding (2.6% vs. 1.8%; difference, 0.8%; 95% CI, -0.6 to 2.4%, P=1.000) between famotidine and placebo groups. However, the former had a lower incidence of gastroduodenal erosion than the latter (21.1% vs. 36.8%; difference, 15.7%; 95% CI, -27.3 to -4.1%; P=0.013). Famotidine cannot decrease the incidence of peptic ulcer or ulcer bleeding in thienopyridine users with atherosclerotic disease and a history of peptic ulcer.

A Potential Protective Role of Platelets during Septic Shock Does Not Depend on Their Purinergic Receptors

Thrombocytopenia frequently occurs in septic shock patients and is associated with a worsened outcome. Experimental data indicate that platelets may have a protective role during sepsis. Our aims were to i) assess the potential protective role of platelets during septic shock and ii) evaluate the involvement of platelet P2Y1 and P2Y12 purinergic receptors.We used a model of polymicrobial-induced septic shock in mice by cecal ligation below the ileocecal valve and double puncture (CLP). The impact of moderate to severe thrombocytopenia was evaluated using mice deficient for the thrombopoietin receptor (Mpl-R-/-, 80% reduction in platelet count) and intravenous administration of a platelet specific rat anti-GPIbα monoclonal antibody (RAM.6, 2 mg/kg, 93% reduction in platelet count), respectively. To investigate the role of the P2Y12 receptor, WT mice were treated with clopidogrel, an irreversible inhibitor of the P2Y12 receptor, administered per os at 10 mg/kg, the day before and 2 h prior to surgery. Contribution of the P2Y1 receptor was evaluated using mice deficient for the P2Y1 receptor (P2Y1-/-). Mice underwent sham or CLP surgery (6 animals/group). Twenty hours post-surgery, blood and tissue samples were collected to evaluate critical parameters of septic shock. Mortality was recorded in a second group of animals.Twenty hours after CLP, mice with either normal or reduced platelet counts displayed signs of septic shock such as apathy, fur ruffling, conjunctivitis and diarrhea. Their mean arterial blood pressure (MAP) fell by 30% indicating systemic hypotension and organ failure characteristic of shock. Mpl-R-/- mice, displaying moderate thrombocytopenia, showed enhanced plasma concentrations of the pro-inflammatory cytokines TNF-α and IL-6, and of myeloperoxidase (MPO), indicating increased systemic inflammation relative to WT mice. These effects were more pronounced in RAM.6-treated mice displaying severe thrombocytopenia. Thrombin-antithrombin (TAT) complexes, reflecting in vivo thrombin generation, were enhanced in RAM.6-treated mice as compared to Mpl-R-/-mice or WT mice. Thrombocytopenia was also associated with increased plasma levels of aspartate aminotransferase (ASAT) relative to mice with normal platelet count, an effect also more pronounced in severely thrombocytopenic mice. These results indicate that depletion of platelets worsened organ injury during septic shock. Finally, severely thrombocytopenic mice succumbed more rapidly than control mice after CLP.Twenty hours after CLP, clopidogrel-treated mice and P2Y1-/- mice displayed signs of shock attested by a 30% decrease in MAP, similar to that observed in WT mice. Plasma concentrations of TNF-α, IL-6 and MPO were similarly increased in WT, clopidogrel-treated and P2Y1-/- mice. In addition, no differences in TAT levels were observed between the three groups of mice. Finally, the extent of liver damage, as evaluated by measurement of plasma ASAT levels, was similar between clopidogrel-treated mice, P2Y1-/-mice and WT mice.Overall, these results provide evidence for a beneficial role of platelets during experimental septic shock in mice. However, the platelet ADP receptors do not contribute to this effect, suggesting that anti-platelet therapy with P2Y12 receptor antagonists may not be beneficial in patients with septic shock. The mechanisms by which platelets modulate the host response to septic shock remain to be elucidated. DisclosuresNo relevant conflicts of interest to declare.

Coagulopathy in patients with acute pulmonary embolism: a pilot study of whole blood coagulation and markers of endothelial damage

Whole blood coagulation and markers of endothelial damage were studied in patients with acute pulmonary embolism (PE), and evaluated in relation to PE severity. Twenty-five patients were enrolled prospectively each having viscoelastical analysis of whole blood done using thrombelastography (TEG) and Multiplate aggregometry. Fourteen of these patients were investigated for endothelial damage by ELISA measurements of Syndecan-1 (endothelial glycocalyx degradation), soluble endothelial Selectin (endothelial cell activation), soluble Thrombomodulin (endothelial cell injury) and Histone Complexed DNA fragments (endothelial cytotoxic histones). The mean values of TEG and Multiplate parameters were all within the reference levels, but a significant difference between patients with high and intermediate risk PE was observed for Ly30 (lytic activity) 1.5% [0–10] vs. 0.2% [0–2.2] p = .04, and ADP (platelet reactivity) 92 U [20–145] vs. 59 U [20–111] p = .03. A similar difference was indicated for functional fibrinogen 21 mm [17–29] vs. 18 mm [3–23] p = .05. Analysis of endothelial markers identified a significant difference in circulating levels between high and intermediate risk PE patients for Syndecan-1 118.6 ng/mL [76–133] vs. 36.3 ng/mL [11.8–102.9] p = .008. In conclusion, patients with acute PE had normal whole blood coagulation, but high risk PE patients had signs of increased activity of the haemostatic system and significantly increased level of endothelial glycocalyx degradation.

P21 Characterisation of the acute effects of hyperglycaemia on platelet function

Background Type 2 Diabetic Mellitus (T2DM) is the most challenging public health problem this century. The most common cause of death and disability in these patients are cardiovascular diseases including myocardial infarction and stroke, in which activated platelets play a pivotal role. Patients with T2DM exhibit platelet hyperreactivity and endothelial dysfunction, which indirectly enhances platelet reactivity through loss of inhibitory molecules. Responses to antiplatelet treatment are also perturbed in these patients increasing their risk of thrombosis. In order to enable a more targeted and stratified antithrombotic approach, a better understanding of the complex mechanisms that underpin platelet hyperreactivity is required. The aim of this study was to establish the effects of acute hyperglycaemia on ADP and collagen-mediated platelet activation. Methods Platelet aggregation and dense granule secretion was measured in response to ADP (2.5 µmol/L) or collagen (1 µg/mL) in whole blood and platelet rich plasma (PRP) from healthy donors using lumi-aggregometry, following 1h incubation with D-glucose (5-30 mmol/L) at 20°C and 37°C. Results Paradoxically, in PRP, increased levels of glucose caused a dose-dependent reduction in ADP-mediated aggregation and dense granule secretion at 37°C, but not at 20°C. In contrast, high levels of glucose had no effect on collagen-induced aggregation or secretion at either temperature. Furthermore, glucose had no effect on platelet aggregation with either stimulant, when using whole blood. Conclusion Acute hyperglycaemia is not responsible for platelet hyperreactivity and the increased risk of thrombosis associated with T2DM. Future studies will focus on the chronic effects of hyperglycaemia and insulin resistance on platelet function.

Erythrocytes do not activate purified and platelet soluble guanylate cyclases even in conditions favourable for NO synthesis.

BackgroundDirect interaction between Red blood cells (RBCs) and platelets is known for a long time. The bleeding time is prolonged in anemic patients independent of their platelet count and could be corrected by transfusion of RBCs, which indicates that RBCs play an important role in hemostasis and platelet activation. However, in the last few years, opposing mechanisms of platelet inhibition by RBCs derived nitric oxide (NO) were proposed. The aim of our study was to identify whether RBCs could produce NO and activate soluble guanylate cyclase (sGC) in platelets.MethodsTo test whether RBCs could activate sGC under different conditions (whole blood, under hypoxia, or even loaded with NO), we used our well-established and highly sensitive models of NO-dependent sGC activation in platelets and activation of purified sGC. The activation of sGC was monitored by detecting the phosphorylation of Vasodilator Stimulated Phosphoprotein (VASPS239) by flow cytometry and Western blot. ANOVA followed by Bonferroni’s test and Student’s t-test were used as appropriate.ResultsWe show that in the whole blood, RBCs prevent NO-mediated inhibition of ADP and TRAP6-induced platelet activation. Likewise, coincubation of RBCs with platelets results in strong inhibition of NO-induced sGC activation. Under hypoxic conditions, incubation of RBCs with NO donor leads to Hb-NO formation which inhibits sGC activation in platelets. Similarly, RBCs inhibit activation of purified sGC, even under conditions optimal for RBC-mediated generation of NO from nitrite.ConclusionsAll our experiments demonstrate that RBCs act as strong NO scavengers and prevent NO-mediated inhibition of activated platelets. In all tested conditions, RBCs were not able to activate platelet or purified sGC.