Memory deficits in hypertensive ApoE4 mice reversed by P2Y12 inhibition via different mechanisms in males and perimenopausal females

Residual platelet activation through protease-activated receptors (PAR)-1 and ‐4 in patients on P2Y12 inhibitors

BackgroundCilostazol combined with P2Y12 receptor inhibitor has been used as a substitute regimen for aspirin‐intolerant patients undergoing percutaneous coronary stent implantation on a small scale. Its exact impact on platelet functions and clinical benefits of aspirin‐intolerant patients is unknown.HypothesisCilostazol combined with P2Y12 receptor inhibitors could be used as a substitute antiplatelet regimen for aspirin‐intolerant patients undergoing percutaneous coronary stent implantation.MethodsIn this multicenter prospective cohort trial, patients undergoing elective percutaneous coronary stent implantation were assigned to the cilostazol group (cilostazol plus P2Y12 receptor inhibitors), based on aspirin intolerance criteria, or the aspirin group (aspirin plus P2Y12 receptor inhibitors). Platelet PAC‐1, CD62p, and vasodilator‐stimulated phosphoprotein phosphorylation (VASP‐P) were detected by flow cytometry. The primary endpoints were major adverse cardiovascular and cerebrovascular events (MACCE) including all‐cause death, acute myocardial infarction, emerging arrhythmia, nonfatal stroke, and heart failure. The secondary endpoints were the Bleeding Academic Research Consortium (BARC) bleeding events.ResultsOne hundred and fifty‐four aspirin‐intolerant percutaneous coronary stent implantation patients and 154 matched aspirin‐tolerant patients from a total of 2059 percutaneous coronary stent implantation patients were enrolled. The relative activation level of PAC‐1, CD62p, and platelet reaction index reflected by the VASP‐P test were similar in the two groups (p > .05). After 12 months of follow‐up, the incidence of all‐cause death was 1.9% in the cilostazol group and 1.3% in the aspirin group (risk ratio [RR], 1.500; 95% confidence interval [CI], 0.254–8.852; p = 1.000); the incidence of acute myocardial infarction was 0.6% in the cilostazol group and 1.3% in the aspirin group (RR, 0.500; 95% CI, 0.046–5.457; p = 1.000). No significant difference was seen in other MACCE events, or in any types of BARC bleeding events.ConclusionsCilostazol combined with P2Y12 inhibitors was not inferior to aspirin‐based standard therapy and could be used as a reasonable substitute antiplatelet regimen for aspirin‐intolerant patients undergoing percutaneous coronary stent implantation, but again with limitations, which required a larger sample and longer follow‐up to confirm its efficacy.

Introduction: P2Y12 inhibitors are a critical component of dual antiplatelet therapy (DAPT), which is the superior strategy to prevent arterialthrombosis in patients with acute coronary syndromes (ACS) and undergoing stent implantation.. Areas covered: Basic science articles, clinical studies, and reviews from 1992–2017 were searched using Pubmed library to collet impactful literature. After an introduction to the purinergic receptor biology, this review summarizes current knowledge on P2Y12 receptor inhibitors. Furthermore, we describe the subsequent improvements of next-generation P2Y12 receptor inhibitors facing the ambivalent problem of bleeding events versus prevention of arterial thrombosis in a variety of clinical settings. Therefore, we summarize data from relevant preclinical and clinical trials of currently approved P2Y12 receptor inhibitors (clopidogrel, prasugrel, ticagrelor, cangrelor) and provide strategies of drug switching and management of bleeding events. Expert opinion: An enormous amount of pharmacologic and clinical data is available for the application of P2Y12 receptor inhibitors. Today prasugrel, ticagrelor and clopidogrel are the standard of care drugs during dual antiplatelet therapy for ACS patients, but have considerable rates of bleeding. Recent and future clinical trials will provide evidence for subsequent escalation and de-escalation strategies of P2Y12 receptor inhibition. These data may pave the way for an evidence-based, individualized P2Y12 receptor inhibitor therapy.

Recent Advances in the Understanding of Thrombosis.

Comparison of the ApoE allelic variants in the formation of intracerebral Aβ deposits.

BackgroundSeveral genetic and cardiovascular risk factors increase incidence of Alzheimer’s disease and related dementias (ADRD). Hypertension and the ε4 allele of apolipoprotein E (ApoE) are powerful drivers of cognitive impairment in ADRD. These risk factors are also associated with decreased cerebral blood flow (CBF). Experimental data suggest that the CBF reduction may be due to temporary capillary occlusions (capillary stalls) caused by circulating vascular and immune cells. To gain insight into how these risk factors may contribute to cognitive decline, we induced hypertension in mice expressing human ApoE3 or E4 (ApoE3‐ or E4‐TR mice), and focused on the resulting CBF and cognitive alterations, and their potential reversal by preventing capillary stalling.MethodsMale ApoE3 and 4‐TR mice (n = 9‐15/group) were assessed at three timepoints: Baseline, following two weeks of angiotensin II‐induced hypertension (AngII, 500ng/kg/min), and after an additional week of anti‐platelet treatment (prasugrel, 10mg/kg, daily). We tested spatial memory function in a Y‐maze, and imaged cortical microvascular flow using two‐photon microscopy.ResultsAt baseline, ApoE3 and 4‐TR mice showed similar memory performance, but with hypertension (∼25 mmHg increase in blood pressure) ApoE4‐TR mice exhibited a spatial working memory deficit, which coincided with a 26% decrease in capillary flow speed (4.11±0.3 vs. 3.05±0.29 mm/s, p<0.01), and a 1.8X increase in the incidence of non‐flowing capillaries. Most stalled capillaries contained only red blood cells in the stalled segment (57%), with some also containing leukocytes (30%), or platelets (12%) (Fig. 1). Treatment with prasugrel led to a 55% reduction in stalling (65±9 vs. 144±24 stalls/mm3), and a concomitant 23% increase in capillary blood flow (3.75±0.36 vs. 3.05±0.29 mm/s, p = 0.11), and significantly improved blood flow in penetrating arterioles that correlated with restored performance on the Y‐maze task (Fig. 2). Immunohistochemistry further revealed improved BBB integrity and reduced gliosis following prasugrel treatment.ConclusionParalleling human findings, we show that mice with the e4 allele of ApoE experience more deleterious consequences from hypertension, as compared to their e3 counterparts. Prasugrel treatment led to an almost complete recovery of these deficits, suggesting that anti‐platelet agents may be of therapeutic value by improving CBF and cognitive function in the presence of these risk factors.

Platelet P2Y12 receptor inhibitors are routinely prescribed for patients after acute coronary syndromes and percutaneous coronary interventions. Patients may have underresponsiveness (or resistance) to these drugs and in particular to clopidogrel, the most often used type. This review aims to focus on the concept of P2Y12 receptor inhibitor resistance and discuss incidence, mechanisms, novel diagnostic techniques and past and future clinical trials on the topic. Patients treated with P2Y12 receptor inhibitors may develop high on-treatment platelet reactivity (HPR), a phenomenon of impaired response toward the drug, which has been associated with ischemic complications. Although potent P2Y12 inhibitors provide better ischemic protection, this must be balanced with increased bleeding risk. Several clinical factors, including common genetic variants such as Cytochrome P450 2C19 loss-of-function alleles, have been shown to predispose to HPR among patients on clopidogrel. Platelet function tests and genotyping platforms have enabled identification of patients at-risk for HPR. Past studies using platelet testing and tailoring therapy among patients with HPR have failed to provide conclusive data to support its routine use. Ongoing studies using genotyping and novel antiplatelet regimens may identify potential strategies to minimize ischemic and bleeding risks concurrently. Until definitive studies demonstrate clear benefit of a personalized approach to P2Y12 inhibitor prescription, the choice of P2Y12 inhibitors should continue to be based on best evidence from previous large clinical trials.

Importance of More Potent Antiplatelet Therapy in Myocardial Infarction With Cardiac Arrest or Cardiogenic Shock

Excessive platelet reactivity plays a pivotal role in the pathogenesis of acute myocardial infarction. Today, the vast majority of patients presenting with acute coronary syndromes qualify for invasive treatment strategy and thus require fast and efficient platelet inhibition. Since 2008, in cases of ST-elevation myocardial infarction, the European Society of Cardiology guidelines have recommended pretreatment with a P2Y12 inhibitor. This approach has become the standard of care in the majority of centers worldwide. Nevertheless, the latest guidelines for the management of patients presenting with acute coronary syndrome without persisting ST-elevation preclude routine pretreatment with the P2Y12 receptor inhibitor. Those who oppose pretreatment support their stance with trials failing to prove the benefits of this strategy at the cost of an increased risk of major bleeding, especially in individuals inappropriately diagnosed with an acute coronary syndrome, thus having no indication for platelet inhibition. However, adequate platelet inhibition requires even up to several hours after application of a loading dose of P2Y12 receptor inhibitors. Omission of data from pharmacokinetic and pharmacodynamic studies in the absence of data from clinical studies makes generalization of the pretreatment recommendations difficult to accept. We aimed to review the scientific evidence supporting the current recommendations regarding pretreatment with P2Y12 inhibitors.

BackgroundEndothelium‐derived prostacyclin and nitric oxide elevate platelet cyclic nucleotide levels and maintain quiescence. We previously demonstrated that a synergistic relationship exists between cyclic nucleotides and P2Y12 receptor inhibition. A number of clinically approved drug classes can modulate cyclic nucleotide tone in platelets including activators of NO‐sensitive guanylyl cyclase (GC) and phosphodiesterase (PDE) inhibitors. However, the doses required to inhibit platelets produce numerous side effects including headache. ObjectiveWe investigated using GC‐activators in combination with P2Y12 receptor antagonists as a way to selectively amplify the anti‐thrombotic effect of both drugs. MethodsIn vitro light transmission aggregation and platelet adhesion under flow were performed on washed platelets and platelet rich plasma. Aggregation in whole blood and a ferric chloride‐induced arterial thrombosis model were also performed. ResultsThe GC‐activator BAY‐70 potentiated the action of the P2Y12 receptor inhibitor prasugrel active metabolite in aggregation and adhesion studies and was associated with raised intra‐platelet cyclic nucleotide levels. Furthermore, mice administered sub‐maximal doses of the GC activator cinaciguat together with the PDE inhibitor dipyridamole and prasugrel, showed significant inhibition of ex vivo platelet aggregation and significantly reduced in vivo arterial thrombosis in response to injury without alteration in basal carotid artery blood flow. ConclusionsUsing in vitro, ex vivo, and in vivo functional studies, we show that low dose GC activators synergize with P2Y12 inhibition to produce powerful anti‐platelet effects without altering blood flow. Therefore, modulation of intra‐platelet cyclic nucleotide levels alongside P2Y12 inhibition can provide a strong, focused anti‐thrombotic regimen while minimizing vasodilator side effects.

Switching of platelet P2Y12 receptor inhibitors in patients with acute coronary syndromes undergoing percutaneous coronary intervention: Review of the literature and practical considerations

Antiplatelet therapy with P2Y12-receptor inhibitors has become the cornerstone of medical treatment in patients with acute coronary syndrome treated with percutaneous coronary intervention (PCI). With over 100 million prescriptions filled since its approval, clopidogrel is the most widely used P2Y12-receptor inhibitor. Dual antiplatelet therapy with clopidogrel plus aspirin has been associated with a lower rate of major cardiovascular events in patients after PCI than aspirin monotherapy. However, an alarmingly high number of clopidogrel-treated patients experience adverse thrombotic events. Insufficient P2Y12-inhibition or high on-treatment platelet reactivity to adenosine diphosphate has stimulated the increased use of more potent P2Y12 inhibitors: prasugrel (a third generation thienopyridine) and ticagrelor (a cyclopentyl-triazolo-pyrimidine). However, more potent platelet inhibition and low on-treatment platelet reactivity has resulted in increased major bleeding and higher costs. These limitations have suggested the need for an individualized antiplatelet approach in order to decrease thrombotic events and minimize bleeding. This model of personalized medicine integrates a patient's demographic and biological data (pharmacodynamic, genomic, epigenomic, transcriptomic, and metabolic information) to target therapy in order to maximize efficacy while minimizing bleeding and costs. This review discusses the role of diagnostic tools such as platelet function and pharmacogenomic testing to personalize antiplatelet therapy.

Outcomes from randomized controlled trials (RCTs) inform the latest recommendations on percutaneous coronary intervention (PCI) management of a short period of oral anticoagulation (OAC), a P2Y12 receptor inhibitor, and aspirin for 1week or until hospital discharge in patients with atrial fibrillation (AF) undergoing PCI, and up to 4weeks in individuals considered to be at high-risk for ischemic events, followed by discontinuation of aspirin and continuation of OAC and a P2Y12 inhibitor for up to 12months. We examined and summarized the outcomes of bleeding and major adverse cardiac events (MACEs) from RCTs and meta-analyses, published between 2013 and 2022, comparing therapy with OAC and a P2Y12 inhibitor with and without aspirin in AF patients undergoing PCI with stenting. Data comparing dual therapy with OAC and a P2Y12 inhibitor alone to triple therapy with OAC, a P2Y12 inhibitor, and aspirin with respect to the risks of MACEs, including stent thrombosis within the first 30days, are underpowered and inconclusive. The addition of aspirin does not appear to be associated with a decreased risk of ischemic events, even in patients with high-risk CHA2DS2-VASc scores, but does significantly increase bleeding hazards. The increased safety of newer generation drug-eluting stents may have further minimized any theoretical anti-ischemic benefits of aspirin. The possible attenuation of the pleiotropic effects of concomitant cardiovascular medications by aspirin may also have been a contributing factor. The addition of aspirin to OAC and a P2Y12 inhibitor is likely associated with a net clinical harm in patients with AF who undergo PCI with stenting, even within the first 1-4weeks after PCI. Revisiting the guideline recommendations to administer aspirin in this timeframe may be warranted.

Several platelet function tests (PFT) are available to assess the pharmacodynamic (PD) effects of P2Y12 inhibitors. However, there are technical variances between PFT, and P2Y12 inhibitors differ in pharmacological properties. Manufactures of PFT recommend a time-frame within which assessments needs to be executed. However, if the timing from blood sampling to processing affects PD results is unknown. We conducted a prospective study assessing the impact of timing from blood sampling to processing on PD measures using three different PFT. We studied 60 aspirin-treated patients with coronary artery disease (CAD) on maintenance P2Y12 inhibiting therapy [clopidogrel 75 mg/day (n=20), prasugrel 10 mg/day (n=20) and ticagrelor 90 mg bid (n=20)]. PD assessments (trough levels) were performed by VerifyNow P2Y12 (VN), light transmittance aggregometry (LTA) and vasodilator-stimulated phosphoprotein (VASP) at 30 minutes, 2 and 4 hours post-sampling; VASP was also performed at 24 hours. P2Y12 reaction units (PRU) by VN significantly decreased over time with all P2Y12 inhibitors (clopidogrel p<0.001; prasugrel p=0.016; ticagrelor p<0.001). PRU at 30 minutes and 2 hours were similar, but decreased at 4 hours. LTA showed consistent findings with VN. Conversely, PD measures as assessed by VASP were stable over time (p>0.1 for all P2Y12 inhibitors). In conclusion, in CAD patients on maintenance therapy with P2Y12 inhibitors, timing from blood sampling to processing significantly influences PD measures as assessed by VN and LTA, but not by VASP.

Assessment of platelet function utilizing viscoelastic testing.