Explore the vast range of titles available.

AbstractObjectiveTo test the hypothesis that ticagrelor plus aspirin is safe and superior to clopidogrel plus aspirin for reducing high platelet reactivity at 90 days and stroke recurrence in patients with minor stroke or transient ischaemic attack, particularly in carriers of the CYP2C19 loss-of-function allele and patients with large artery atherosclerosis.DesignOpen label, blinded endpoint, randomised controlled phase II trial.SettingProspective studies conducted at 26 centres in China, August 2015 to March 2017.Participants675 patients with acute minor stroke or transient ischaemic attack.InterventionTicagrelor (180 mg loading dose, 90 mg twice daily thereafter) or clopidogrel (300 mg loading dose, 75 mg daily thereafter) on a background of aspirin (100 mg daily for the first 21 days) within 24 hours of symptom onset.Main outcome measuresPrimary outcome was the proportion of patients with high platelet reactivity at 90 days. High platelet reactivity was defined as P2Y12 reaction units of more than 208. Secondary outcomes included high platelet reactivity at 90 days (7 days either way) in patients carrying genetic variants that would affect clopidogrel metabolism, and any stroke (ischaemic or haemorrhagic) recurrence at 90 days (7 days either way), six months, and one year.ResultsAt 90 days, high platelet reactivity occurred in 35 (12.5%) of 280 patients in the ticagrelor/aspirin group and 86 (29.7%) of 290 patients in the clopidogrel/aspirin group (risk ratio 0.40; 95% confidence interval 0.28 to 0.56; P<0.001), and in 10.8% versus 35.4% (0.31; 0.18 to 0.49; P<0.001) of patients carrying CYP2C19 loss-of-function alleles. Stroke occurred in 21 (6.3%) of 336 patients in the ticagrelor/aspirin group and 30 (8.8%) of 339 patients in the clopidogrel/aspirin group (hazard ratio 0.70; 95% confidence interval 0.40 to 1.22; P=0.20). Patients with large artery atherosclerosis in the ticagrelor/aspirin group had a lower stroke recurrence at 90 days than those in the clopidogrel/aspirin group (6.0% v 13.1%; hazard ratio 0.45, 95% confidence interval 0.20 to 0.98; P=0.04). No difference was seen in the rates of major or minor haemorrhagic events between the ticagrelor/aspirin and clopidogrel/aspirin groups (4.8% v 3.5%; P=0.42).ConclusionPatients with minor stroke or transient ischaemic attack who are treated with ticagrelor plus aspirin have a lower proportion of high platelet reactivity than those who are treated with clopidogrel plus aspirin, particularly for those who are carriers of the CYP2C19 loss-of-function allele. The results of this study should be evaluated further in large scale, phase III trials and in different populations.Trial registrationClinicaltrials.gov NCT02506140.

Platelets — blood cells continuously produced from megakaryocytes mainly in the bone marrow — are implicated not only in haemostasis and arterial thrombosis, but also in other physiological and pathophysiological processes. This Review describes current evidence for the heterogeneity in platelet structure, age, and activation properties, with consequences for a diversity of platelet functions. Signalling processes of platelet populations involved in thrombus formation with ongoing coagulation are well understood. Genetic approaches have provided information on multiple genes related to normal haemostasis, such as those encoding receptors and signalling or secretory proteins, that determine platelet count and/or responsiveness. As highly responsive and secretory cells, platelets can alter the environment through the release of growth factors, chemokines, coagulant factors, RNA species, and extracellular vesicles. Conversely, platelets will also adapt to their environment. In disease states, platelets can be positively primed to reach a pre-activated condition. At the inflamed vessel wall, platelets interact with leukocytes and the coagulation system, interactions mediating thromboinflammation. With current antiplatelet therapies invariably causing bleeding as an undesired adverse effect, novel therapies can be more beneficial if directed against specific platelet responses, populations, interactions, or priming conditions. On the basis of these novel concepts and processes, we discuss several initiatives to target platelets therapeutically.

Heparin-induced thrombocytopenia/thrombosis (HIT) is a serious immune reaction to heparins, characterized by thrombocytopenia and often severe thrombosis with high morbidity and mortality. HIT is mediated by IgG antibodies against heparin/platelet factor 4 antigenic complexes. These complexes are thought to activate platelets leading to thrombocytopenia and thrombosis. Here we show that HIT immune complexes induce NETosis via interaction with FcγRIIa on neutrophils and through neutrophil-platelet association. HIT immune complexes induce formation of thrombi containing neutrophils, extracellular DNA, citrullinated histone H3 and platelets in a microfluidics system and in vivo, while neutrophil depletion abolishes thrombus formation. Absence of PAD4 or PAD4 inhibition with GSK484 abrogates thrombus formation but not thrombocytopenia, suggesting they are induced by separate mechanisms. NETs markers and neutrophils undergoing NETosis are present in HIT patients. Our findings demonstrating the involvement of NETosis in thrombosis will modify the current concept of HIT pathogenesis and may lead to new therapeutic strategies. The pathogenesis of heparin-induced thrombocytopenia and thrombosis (HIT) is mediated by heparin-reactive autoantibodies binding to platelets (thrombocytes). Here the authors show neutrophil activation and NETosis are elevated in patients with HIT, and are essential for thrombosis in HIT mouse models.

Diabetes is associated with a high rate of events after acute coronary syndrome and percutaneous coronary intervention despite aspirin treatment. Once daily aspirin might not provide 24-hour stable biological efficacy in patients with diabetes. We compared the biological efficacy of the same daily dose of aspirin given either once (OPD) or divided twice per day in a population of diabetic patients with previous coronary artery disease. Ninety-two consecutive diabetic patients with at least 1 criteria of time-dependent aspirin efficacy, elevated high-sensibility C-reactive protein (hs-CRP), fibrinogen, platelet count, or active smoking were prospectively included. Consecutive patients were randomly treated with 150-mg aspirin daily given either OPD (150 mg in the morning) or twice per day (75 mg in the morning and 75 mg in the evening) in a crossover study. The main outcome was platelet reactivity to arachidonic acid (0.5 mg/mL) measured by light transmission aggregometry at trough level before morning aspirin intake. Mean maximum aggregation intensity triggered by arachidonic acid was 19.7% ± 15.4% on OPD and 11.9% ± 10.4% on twice per day (P < .0001). Biological resistance (maximum aggregation intensity ≥20%) was observed in 42% of patients on OPD and 17% on twice per day (P < .001). Of the 39 patients with biological resistance on OPD, 24 (62%) overcame resistance on twice per day. Of the 16 resistant on twice per day, only 1 patient (6%) overcame resistance on OPD. Results were concordant with global evaluation of platelet reactivity by Platelet Function Analyzer-100. A better twice per day efficacy was independent of clopidogrel cotreatment. In a population of diabetic patients with coronary artery disease and a high risk of time-dependent aspirin resistance, aspirin divided twice per day can significantly decrease the rate of biological loss of efficacy at trough level.

Significance Platelets are cell fragments in the blood that initiate clot formation at the site of bleeding. Although the biological aspects of this process have been well characterized, whether platelets can detect and physiologically respond to the mechanical aspects of its local environment is unclear. Here, we show that platelets sense the stiffness of the underlying clot substrate, and increasing substrate stiffness increases platelet adhesion and spreading. Importantly, adhesion on stiffer substrates leads to higher levels of platelet activation. Mechanistically, we determined that Rac1, actin, and myosin activity mediate this process. This newfound capability of how platelets adjust their degree of activation based on the mechanical properties of their environment provides new insight into how clots are formed. As platelets aggregate and activate at the site of vascular injury to stem bleeding, they are subjected to a myriad of biochemical and biophysical signals and cues. As clot formation ensues, platelets interact with polymerizing fibrin scaffolds, exposing platelets to a large range of mechanical microenvironments. Here, we show for the first time (to our knowledge) that platelets, which are anucleate cellular fragments, sense microenvironmental mechanical properties, such as substrate stiffness, and transduce those cues into differential biological signals. Specifically, as platelets mechanosense the stiffness of the underlying fibrin/fibrinogen substrate, increasing substrate stiffness leads to increased platelet adhesion and spreading. Importantly, adhesion on stiffer substrates also leads to higher levels of platelet activation, as measured by integrin α IIbβ ₃ activation, α-granule secretion, and procoagulant activity. Mechanistically, we determined that Rac1 and actomyosin activity mediate substrate stiffness-dependent platelet adhesion, spreading, and activation to different degrees. This capability of platelets to mechanosense microenvironmental cues in a growing thrombus or hemostatic plug and then mechanotransduce those cues into differential levels of platelet adhesion, spreading, and activation provides biophysical insight into the underlying mechanisms of platelet aggregation and platelet activation heterogeneity during thrombus formation.

To examine the effects of acute insulin-induced hypoglycemia on inflammation, endothelial dysfunction, and platelet activation in adults with and without type 1 diabetes. We studied 16 nondiabetic adults and 16 subjects with type 1 diabetes during euglycemia (blood glucose 4.5 mmol/l) and hypoglycemia (blood glucose 2.5 mmol/l). Markers of inflammation, thrombosis, and endothelial dysfunction (soluble P-selectin, interleukin-6, von Willebrand factor [vWF], tissue plasminogen activator [tPA], high-sensitivity C-reactive protein [hsCRP], and soluble CD40 ligand [sCD40L]) were measured; platelet-monocyte aggregation and CD40 expression on monocytes were determined using flow cytometry. In nondiabetic participants, platelet activation occurred after hypoglycemia, with increments in platelet-monocyte aggregation and P-selectin (P

Journal Article

Share this book

Add to My Shelf