Ticagrelor induces adenosine triphosphate release from human red blood cells

Progress in the clinical effects and adverse reactions of ticagrelor

BACKGROUND

Ticagrelor is a novel receptor antagonist that selectively binds to the P2Y12 receptor, thereby inhibiting adenosine diphosphate (ADP)-mediated platelet aggregation. Compared to clopidogrel, ticagrelor has the advantages of a fast onset, potent effects, and a reversible platelet inhibition function, which make this drug clinically suitable for treating acute coronary syndrome (ACS), especially acute ST-segment elevation myocardial infarction (STEMI).

OBJECTIVE

This review was performed to determine the basic characteristics, clinical effects, and adverse reactions of ticagrelor.

METHODS

Relevant trials and reports were obtained from the MEDLINE, Embase, and Cochrane Library databases.

RESULTS

Ticagrelor is rapidly absorbed by the body after oral administration, exhibits inherent activity without requiring metabolic activation, and binds reversibly to the P2Y12 receptor. Ticagrelor has been recommended in ACS treatment guidelines worldwide due to its advantageous pharmacological properties and significant clinical benefits. Ticagrelor inhibits platelet aggregation, inhibits inflammatory response, enhances adenosine function, and has cardioprotective effects. However, ticagrelor also causes adverse reactions such as bleeding tendency, dyspnea, ventricular pause, gout, kidney damage, and thrombotic thrombocytopenic purpura in clinical treatment. Therefore, it is necessary to pay attention to risk assessments when using ticagrelor.

CONCLUSION

Ticagrelor is a promising drug for the effective treatment of ACS. When using ticagrelor, individualized treatment should be provided based on the specific conditions of the patients to avoid serious adverse events.

Refractory drug-induced systemic small-vessel vasculitis with two varied extracutaneous manifestations: a case report and review of the literature

BACKGROUND

Clopidogrel and ticagrelor are rarely reported to cause vasculitis via drug hypersensitivity reaction, largely mediated by T cells and immunoglobulin E (IgE). Despite therapeutic advances, the etiology of refractory vasculitides remains incompletely understood. Recently, (non)immunological mechanisms bypassing T cells and IgE have been proposed to explain resistance to standard immunosuppressants. Herein, we report a case of refractory drug-induced systemic small-vessel vasculitis with varied extracutaneous manifestations and incorporate multiple sources of data to provide detailed accounts of complex (non)immunological phenomena involved in this case. Study objectives are to provide an insight about rare presentations of commonly used drugs, upgrade the pathophysiological concepts of drug-induced vasculitis, raise need for further investigation to define causes and risk factors for refractory vasculitis, and discuss most of the current knowledge suggesting novel therapeutic approaches to treat this vasculitis. To our knowledge, this is the first case of the two flares of systemic small-vessel vasculitis in a single patient in response to clopidogrel and ticagrelor exposure, respectively. However, this report is limited by attribution/observer bias.

CASE PRESENTATION

We herein report a 24-year-old Caucasian male student with a medical history of mild seasonal allergic rhinoconjunctivitis, tension-type headaches, posttraumatic arterial stenosis, and previous exposure to ibuprofen, acetylsalicylic acid, and mRNA coronavirus disease 2019 (COVID-19) vaccine who suffered largely from acute urticaria and dyspnea after 20 days of acetylsalicylic acid and clopidogrel introduction. A skin punch biopsy confirmed leukocytoclastic vasculitis. Serologic antibody testing, complement analysis, microbiologic testing, and cancer biomarkers revealed no abnormalities. Regarding the patient's medical history, both acetylsalicylic acid and clopidogrel were exchanged for ticagrelor. Furthermore, the addition of naproxen, cyclosporine, bilastine, prednisolone, and montelukast resulted in complete recovery. After 7 days, diarrhea and hematuria occurred. Urinalysis and computed tomography showed reversible proteinuria with gross hematuria and hypodense changes in kidney medulla, respectively, associated with discontinuation of ticagrelor and naproxen. In addition, the patient recovered completely without any immunosuppression up-titration.

CONCLUSIONS

This case highlights the role of clopidogrel and ticagrelor as possible triggering agents for systemic small-vessel vasculitis and offers an insight into novel therapeutic strategies for refractory vasculitides. Further research is needed to build on the findings of a current report.

Drugs targeting adenosine signaling pathways: A current view

Adenosine is an endogenous nucleoside that regulates many physiological and pathological processes. It is derived from either the intracellular or extracellular dephosphorylation of adenosine triphosphate and interacts with cell-surface G-protein-coupled receptors. Adenosine plays a substantial role in protecting against cell damage in areas of increased tissue metabolism and preventing organ dysfunction in pathological states. Targeting adenosine metabolism and receptor signaling may be an effective therapeutic approach for human diseases, including cardiovascular and central nervous system disorders, rheumatoid arthritis, asthma, renal diseases, and cancer. Several lines of evidence have shown that many drugs exert their beneficial effects by modulating adenosine signaling pathways but this knowledge urgently needs to be summarized, and most importantly, actualized. The present review collects pharmaceuticals and pharmacological or diagnostic tools that target adenosine signaling in their primary or secondary mode of action. We overviewed FDA-approved drugs as well as those currently being studied in clinical trials. Among them are already used in clinic A2A adenosine receptor modulators like istradefylline or regadenoson, but also plenty of anti-platelet, anti-inflammatory, or immunosuppressive, and anti-cancer drugs. On the other hand, we investigated dozens of specific adenosine pathway regulators that are tested in clinical trials to treat human infectious and noninfectious diseases. In conclusion, targeting purinergic signaling represents a great therapeutic challenge. The actual knowledge of the involvement of adenosinergic signaling as part of the mechanism of action of old drugs has open a path not only for drug-repurposing but also for new therapeutic strategies.

Association of ADP-Induced Whole-Blood Platelet Aggregation with Serum Low-Density Lipoprotein Cholesterol in Patients with Coronary Artery Disease When Receiving Maintenance Ticagrelor-Based Dual Antiplatelet Therapy

The degree of platelet inhibition in patients undergoing dual antiplatelet therapy (DAPT) affects cardiovascular outcomes after acute coronary syndromes (ACS) and/or percutaneous coronary intervention. Our aim was to search for correlates of residual ex vivo platelet reactivity and circulating soluble P-selectin (sP-selectin), an index of in vivo platelet activation, in patients being treated by DAPT with ticagrelor. Adenosine diphosphate (ADP)-induced platelet aggregability (by multiple electrode aggregometry) and plasma sP-selectin were estimated in 62 stable post-ACS subjects (46 men and 16 women; mean age: 64 ± 10 years; 30 with type 2 diabetes (T2DM)) undergoing maintenance DAPT with ticagrelor and aspirin. These patients did not exhibit heart failure or other relevant coexistent diseases except for properly controlled T2DM, mild renal insufficiency, and hypertension. We also assessed this in 64 subjects on clopidogrel-based DAPT matched for age, sex, and T2DM status. ADP-induced platelet aggregation was below the optimal levels (190-460 arbitrary units (AU) * min) in most patients receiving ticagrelor-based DAPT, especially in those with below-median (<1.9 mmol/L) serum concentrations of low-density lipoprotein cholesterol (LDL-c) (128 ± 61 vs. 167 ± 73 AU * min for below-median and above-median LDL-c, respectively, p = 0.025). In contrast, platelet reactivity did not differ by LDL-c on clopidogrel-based DAPT (246 ± 101 vs. 268 ± 108 AU * min for below-median and above-median LDL-c, respectively, p > 0.4). Plasma sP-selectin was found to be unrelated to serum LDL-c when receiving DAPT with ticagrelor (p > 0.4) or clopidogrel (p > 0.8). In conclusion, our preliminary observational study suggests the association of lower residual ex vivo platelet aggregability with better LDL-c control in patients undergoing ticagrelor-based maintenance DAPT, which does not appear to be reflected by plasma sP-selectin. Whether the serum LDL-c level should be considered among the factors affecting the degree of platelet inhibition for those treated with ticagrelor-based DAPT needs to be investigated in larger studies.

Ticagrelor Treatment is Associated With Increased Coronary Flow Reserve in Survivors of Myocardial Infarction

BACKGROUND

The pleiotropic action of ticagrelor, with effects in addition to platelet inhibition, has been shown to improve endothelial function in patients with coronary artery disease. These positive effects are possibly adenosine mediated. This study investigated the association of ticagrelor therapy and coronary artery flow reserve in survivors of myocardial infarction (MI).

METHODS

This was an exploratory, cross-sectional, open substudy of PROFLOW. High-risk individuals with a history of MI were identified. Coronary flow reserve (CFR) was measured non-invasively in the left anterior descending artery using transthoracic Doppler echocardiography. Coronary flow velocity was measured at rest and at maximal flow after induction of hyperaemia by intravenous infusion of adenosine at 140 μg/kg/min. Patients receiving ticagrelor (n=75) were compared with those not receiving ticagrelor (n=506), using simple and multiple linear regression models. Most patients in both groups were treated with aspirin (97% in the ticagrelor and 94% in the non-ticagrelor group). Adjustment for traditional risk factors was conducted.

RESULTS

The mean age at study inclusion was 68.5±6.8 years, and most patients were male (81.8%). The simple linear regression analysis showed ticagrelor treatment to be significantly associated with increased CFR: ticagrelor 2.95±0.76 (mean±SD), non-ticagrelor 2.70±0.77, (coefficient 0.25; 95% CI 0.063-0.438; p=0.009). This association was significant in two of the three multiple linear regression models with increasing numbers of variables: Model 1 (0.28; 0.06-0.50; p=0.014), Model 2 (0.26; 0.03-0.48; p=0.025), and borderline significant in Model 3 (0.21; -0.01 to 0.43; p=0.058).

CONCLUSIONS

Ticagrelor treatment was associated with increased CFR in this high-risk population. Increased CFR may be a clinically important therapeutic effect of ticagrelor in addition to platelet inhibition.

The Pleiotropic Role of Extracellular ATP in Myocardial Remodelling

Myocardial remodelling is a molecular, cellular, and interstitial adaptation of the heart in response to altered environmental demands. The heart undergoes reversible physiological remodelling in response to changes in mechanical loading or irreversible pathological remodelling induced by neurohumoral factors and chronic stress, leading to heart failure. Adenosine triphosphate (ATP) is one of the potent mediators in cardiovascular signalling that act on the ligand-gated (P2X) and G-protein-coupled (P2Y) purinoceptors via the autocrine or paracrine manners. These activations mediate numerous intracellular communications by modulating the production of other messengers, including calcium, growth factors, cytokines, and nitric oxide. ATP is known to play a pleiotropic role in cardiovascular pathophysiology, making it a reliable biomarker for cardiac protection. This review outlines the sources of ATP released under physiological and pathological stress and its cell-specific mechanism of action. We further highlight a series of cardiovascular cell-to-cell communications of extracellular ATP signalling cascades in cardiac remodelling, which can be seen in hypertension, ischemia/reperfusion injury, fibrosis, hypertrophy, and atrophy. Finally, we summarize current pharmacological intervention using the ATP network as a target for cardiac protection. A better understanding of ATP communication in myocardial remodelling could be worthwhile for future drug development and repurposing and the management of cardiovascular diseases.

Endothelial biomarkers and platelet reactivity on ticagrelor versus clopidogrel in patients after acute coronary syndrome with and without concomitant type 2 diabetes: a preliminary observational study

BACKGROUND

Pleiotropic effects have been implicated in clinical benefits of ticagrelor compared to thienopyridine P2Y₁₂ antagonists. There are conflicting data regarding effects of ticagrelor vs. thienopyridine P2Y₁₂ blockers on endothelial function. Our aim was to compare endothelial biomarkers and their relations with platelet reactivity in real-world patients after acute coronary syndrome (ACS) on maintenance dual antiplatelet therapy (DAPT) with ticagrelor or clopidogrel stratified by diabetes status.

METHODS

Biochemical indices of endothelial dysfunction/activation and platelet reactivity by multiple electrode aggregometry were compared in 126 stable post-ACS subjects (mean age: 65 ± 10 years, 92 men and 34 women), including patients with (n = 61) or without (n = 65) coexistent type 2 diabetes (T2DM) on uneventful maintenance DAPT with either ticagrelor (90 mg b.d.) or clopidogrel (75 mg o.d.) in addition to low-dose aspirin. Exclusion criteria included a complicated in-hospital course, symptomatic heart failure, left ventricular ejection fraction < 40% and relevant coexistent diseases except for well-controlled diabetes, mild renal insufficiency or hypertension.

RESULTS

Clinical characteristics were similar in patients on ticagrelor (n = 62) and clopidogrel (n = 64). The adenosine diphosphate-induced platelet aggregation and circulating soluble P-selectin (sP-selectin) were decreased in ticagrelor users irrespective of T2DM status (p < 0.001 and p < 0.01 for platelet reactivity and sP-selectin, respectively). Plasma levels of soluble vascular cell adhesion molecule-1 (sVCAM-1) were lower in T2DM subjects on ticagrelor vs. clopidogrel (758 ± 162 vs. 913 ± 217 µg/L, p < 0.01). In contrast, plasma sVCAM-1 was similar in non-diabetic patients on ticagrelor and clopidogrel (872 ± 203 vs. 821 ± 210 µg/L, p > 0.7). The concentrations of sE-selectin, monocyte chemoattractant protein-1 and asymmetric dimethylarginine did not differ according to the type of P2Y₁₂ antagonist regardless of T2DM status. Platelet reactivity was unrelated to any endothelial biomarker in subjects with or without T2DM.

CONCLUSIONS

Our preliminary findings may suggest an association of ticagrelor-based maintenance DAPT with favorable endothelial effects compared to clopidogrel users in stable post-ACS patients with T2DM. If proven, this could contribute to more pronounced clinical benefits of ticagrelor in diabetic subjects.

Effects of the flow diversion technique on nucleotide levels in intra-cranial aneurysms: A feasibility study providing new research perspectives

Introduction

The flow diverter stent (FDS) has become a first-line treatment for numerous intra-cranial aneurysms (IAs) by promoting aneurysm thrombosis. However, the biological phenomena underlying its efficacy remain unknown. We proposed a method to collect in situ blood samples to explore the flow diversion effect within the aneurysm sac. In this feasibility study, we assessed the plasma levels of nucleotides within the aneurysm sac before and after flow diversion treatment.

Materials and methods

In total, 14 patients with unruptured IAs who were selected for FDS implantation were prospectively recruited from February 2015 to November 2015. Two catheters dedicated to (1) FDS deployment and (2) the aneurysm sac were used to collect blood samples within the parent artery (P1) and the aneurysm sac before (P2) and after (P3) flow diversion treatment. The plasma levels of adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP) at each collection point were quantified with liquid chromatography and tandem mass spectrometry.

Results

The aneurysms were extradural in nine (64.3%) patients and intra-dural in five (35.7%) patients. They presented an average diameter of 15.5 ± 7.1 mm, height of 15.8 ± 4.6 mm, and volume of 2,549 ± 2,794 ml. In all patients (100%), 16 FDS implantations and 42 in situ blood collections were performed successfully without any complications associated with the procedure. The ATP, ADP, and AMP concentrations within the aneurysm sac were decreased after flow diversion (p = 0.005, p = 0.03, and p = 0.12, respectively). Only the ATP levels within the aneurysm sac after flow diversion were significantly correlated with aneurysm volume (adjusted R² = 0.43; p = 0.01).

Conclusion

In situ blood collection within unruptured IAs during a flow diversion procedure is feasible and safe. Our results suggest that the flow diversion technique is associated with changes in the nucleotide plasma levels within the aneurysm sac.

Protective or Inhibitory Effect of Pharmacological Therapy on Cardiac Ischemic Preconditioning: A Literature Review

Ischemic preconditioning (IP) is an innate phenomenon, triggered by brief, non-lethal cycles of ischemia/reperfusion applied to a tissue or organ that confers tolerance to a subsequent more prolonged ischemic event. Once started, it can reduce the severity of myocardial ischemia associated with some clinical situations, such as percutaneous coronary intervention (PCI) and intermittent aortic clamping during coronary artery bypass graft surgery (CABG). Although the mechanisms underlying IP have not been completely elucidated, several studies have shown that this phenomenon involves the participation of cell triggers, intracellular signaling pathways, and end-effectors. Understanding this mechanism enables the development of preconditioning mimetic agents. It is known that a range of medications that activate the signaling cascades at different cellular levels can interfere with both the stimulation and the blockade of IP. Investigations of signaling pathways underlying ischemic conditioning have identified a number of therapeutic targets for pharmacological manipulation. This review aims to present and discuss the effects of several medications on myocardial IP.

Assessment of myocardial salvage in patients with STEMI undergoing thrombolysis: ticagrelor versus clopidogrel

Background

In the setting of ST-segment elevation myocardial infarction (STEMI), the faster and stronger antiplatelet action of ticagrelor compared to clopidogrel, as well as its pleiotropic effects, could result in a greater degree of cardioprotection and final infarct size (FIS) limitation. The aim of our study was to comparatively evaluate the effect of ticagrelor and clopidogrel on myocardial salvage index (MSI) in STEMI patients undergoing thrombolysis.

Methods

Forty-two STEMI patients treated with thrombolysis were randomized to receive clopidogrel (n = 21) or ticagrelor (n = 21), along with aspirin. Myocardial area at risk (AAR) was calculated according to the BARI and the APPROACH jeopardy scores. FIS was quantified by cardiac magnetic resonance imaging (CMR) performed 5–6 months post-randomization. MSI was calculated as (AAR-FIS)/AAR × 100%. Primary endpoint of our study was MSI. Secondary endpoints were FIS and CMR-derived left ventricular ejection fraction (LVEF) at 5 –6 months post-randomization.

Results

By using the BARI score for AAR calculation, mean MSI was 52.25 ± 30.5 for the clopidogrel group and 54.29 ± 31.08 for the ticagrelor group (p = 0.83), while mean MSI using the APPROACH score was calculated at 51.94 ± 30 and 53.09 ± 32.39 (p = 0.9), respectively. Median CMR-derived FIS—as a percentage of LV—was 10.7% ± 8.25 in the clopidogrel group and 12.09% ± 8.72 in the ticagrelor group (p = 0.6). Mean LVEF at 5–6 months post-randomization did not differ significantly between randomization groups.

Conclusions

Our results suggest that the administration of ticagrelor in STEMI patients undergoing thrombolysis offer a similar degree of myocardial salvage, compared to clopidogrel.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02735-1.

Role of Erythrocytes in Nitric Oxide Metabolism and Paracrine Regulation of Endothelial Function

Emerging studies provide new data shedding some light on the complex and pivotal role of red blood cells (RBCs) in nitric oxide (NO) metabolism and paracrine regulation of endothelial function. NO is involved in the regulation of vasodilatation, platelet aggregation, inflammation, hypoxic adaptation, and oxidative stress. Even though tremendous knowledge about NO metabolism has been collected, the exact RBCs’ status still requires evaluation. This paper summarizes the actual knowledge regarding the role of erythrocytes as a mobile depot of amino acids necessary for NO biotransformation. Moreover, the complex regulation of RBCs’ translocases is presented with a particular focus on cationic amino acid transporters (CATs) responsible for the NO substrates and derivatives transport. The main part demonstrates the intraerythrocytic metabolism of L-arginine with its regulation by reactive oxygen species and arginase activity. Additionally, the process of nitrite and nitrate turnover was demonstrated to be another stable source of NO, with its reduction by xanthine oxidoreductase or hemoglobin. Additional function of hemoglobin in NO synthesis and its subsequent stabilization in steady intermediates is also discussed. Furthermore, RBCs regulate the vascular tone by releasing ATP, inducing smooth muscle cell relaxation, and decreasing platelet aggregation. Erythrocytes and intraerythrocytic NO metabolism are also responsible for the maintenance of normotension. Hence, RBCs became a promising new therapeutic target in restoring NO homeostasis in cardiovascular disorders.

Purinergic interplay between erythrocytes and platelets in diabetes-associated vascular dysfunction

Cardiovascular complications in diabetes are the leading causes for high morbidity and mortality. It has been shown that alteration of purinergic signaling contributes to diabetes-associated cardiovascular complications. Red blood cells (RBCs) and platelets play a fundamental role in regulation of oxygen transport and hemostasis, respectively. Of note, these cells undergo purinergic dysfunction in diabetes. Recent studies have established a novel function of RBCs as disease mediators for the development of endothelial dysfunction in type 2 diabetes (T2D). RBC-released ATP is defective in T2D, which has implication for induction of vascular dysfunction by dysregulating purinergic signaling. Platelets are hyperactive in diabetes. ADP-mediated P2Y₁ and P2Y₁₂ receptor activation contributes to platelet aggregation and targeting P2Y receptors particularly P2Y₁₂ receptor in platelets is effective for the treatment of cardiovascular events. In contrast to other P2Y₁₂ receptor antagonists, platelet-targeting drug ticagrelor has potential to initiate purinergic signaling in RBCs for the beneficial cardiovascular outcomes. It is increasingly clear that altered vascular purinergic signaling mediated by various nucleotides and nucleoside contributes to diabetes-associated vascular dysfunction. However, the contribution of complex purinergic networks between RBCs and platelets to the vascular dysfunction in diabetes remains unclear. This study discusses the possible interplay of RBCs and platelets via the purinergic network for diabetes-associated vascular dysfunction.

A review of the effects of ticagrelor on adenosine concentration and its clinical significance

BACKGROUND

Ticagrelor is an oral antiplatelet drug that can reversibly bind to the platelet P2Y12 receptor. Ticagrelor is metabolized mainly by CYP3A4 and produces a rapid blood concentration-dependent platelet inhibitory effect. Unlike other P2Y12 receptor antagonists, many clinical features of ticagrelor are not related to P2Y12 receptor antagonism.

PURPOSE

This review aims to gather existing literature on the clinical effects of ticagrelor after inhibiting adenosine uptake.

METHODOLOGY

The current study reviewed literature related to the effects of ticagrelor on adenosine metabolism. The review also examined the drug's biological effects and clinical characteristics to see how it could be used in a clinical setting.

RESULTS

Many studies have shown that ticagrelor can inhibit equilibrative nucleoside transporter 1 (ENT1). This inhibition leads to intracellular adenosine uptake, increased adenosine half-life and plasma concentration levels and an enhanced adenosine-mediated biological effect.

CONCLUSIONS

Based on the studies reviewed, it was found that ticagrelor essentially inhibits adenosine absorption of adenosine into cells through ENT1, which increases the concentration in the blood and subsequently increases the protection of the heart muscle by adenosine. It also prevents platelet aggregation, and extends the biological effects of coronary arteries. Moreover, it leads to a lower mortality rate in acute coronary syndrome (ACS) patients.

Coronary microvascular injury in myocardial infarction: perception and knowledge for mitochondrial quality control

Endothelial cells (ECs) constitute the innermost layer in all blood vessels to maintain the structural integrity and microcirculation function for coronary microvasculature. Impaired endothelial function is demonstrated in various cardiovascular diseases including myocardial infarction (MI), which is featured by reduced myocardial blood flow as a result of epicardial coronary obstruction, thrombogenesis, and inflammation. In this context, understanding the cellular and molecular mechanisms governing the function of coronary ECs is essential for the early diagnosis and optimal treatment of MI. Although ECs contain relatively fewer mitochondria compared with cardiomyocytes, they function as key sensors of environmental and cellular stress, in the regulation of EC viability, structural integrity and function. Mitochondrial quality control (MQC) machineries respond to a broad array of stress stimuli to regulate fission, fusion, mitophagy and biogenesis in mitochondria. Impaired MQC is a cardinal feature of EC injury and dysfunction. Hence, medications modulating MQC mechanisms are considered as promising novel therapeutic options in MI. Here in this review, we provide updated insights into the key role of MQC mechanisms in coronary ECs and microvascular dysfunction in MI. We also discussed the option of MQC as a novel therapeutic target to delay, reverse or repair coronary microvascular damage in MI. Contemporary available MQC-targeted therapies with potential clinical benefits to alleviate coronary microvascular injury during MI are also summarized.

The pleiotropic effects of antithrombotic drugs in the metabolic-cardiovascular-neurodegenerative disease continuum: impact beyond reduced clotting

Antithrombotic drugs are widely used for primary and secondary prevention, as well as treatment of many cardiovascular disorders. Over the past few decades, major advances in the pharmacology of these agents have been made with the introduction of new drug classes as novel therapeutic options. Accumulating evidence indicates that the beneficial outcomes of some of these antithrombotic agents are not solely related to their ability to reduce thrombosis. Here, we review the evidence supporting established and potential pleiotropic effects of four novel classes of antithrombotic drugs, adenosine diphosphate (ADP) P2Y12-receptor antagonists, Glycoprotein IIb/IIIa receptor Inhibitors, and Direct Oral Anticoagulants (DOACs), which include Direct Factor Xa (FXa) and Direct Thrombin Inhibitors. Specifically, we discuss the molecular evidence supporting such pleiotropic effects in the context of cardiovascular disease (CVD) including endothelial dysfunction (ED), atherosclerosis, cardiac injury, stroke, and arrhythmia. Importantly, we highlight the role of DOACs in mitigating metabolic dysfunction-associated cardiovascular derangements. We also postulate that DOACs modulate perivascular adipose tissue inflammation and thus, may reverse cardiovascular dysfunction early in the course of the metabolic syndrome. In this regard, we argue that some antithrombotic agents can reverse the neurovascular damage in Alzheimer's and Parkinson's brain and following traumatic brain injury (TBI). Overall, we attempt to provide an up-to-date comprehensive review of the less-recognized, beneficial molecular aspects of antithrombotic therapy beyond reduced thrombus formation. We also make a solid argument for the need of further mechanistic analysis of the pleiotropic effects of antithrombotic drugs in the future.

Adenosine and adenosine receptor-mediated action in coronary microcirculation

Adenosine is an ubiquitous extracellular signaling molecule and plays a fundamental role in the regulation of coronary microcirculation through activation of adenosine receptors (ARs). Adenosine is regulated by various enzymes and nucleoside transporters for its balance between intra- and extracellular compartments. Adenosine-mediated coronary microvascular tone and reactive hyperemia are through receptors mainly involving A_2AR activation on both endothelial and smooth muscle cells, but also involving interaction among other ARs. Activation of ARs further stimulates downstream targets of H₂O₂, K_ATP, K_V and K_Ca2+ channels leading to coronary vasodilation. An altered adenosine-ARs signaling in coronary microcirculation has been observed in several cardiovascular diseases including hypertension, diabetes, atherosclerosis and ischemic heart disease. Adenosine as a metabolite and its receptors have been studied for its both therapeutic and diagnostic abilities. The present review summarizes important aspects of adenosine metabolism and AR-mediated actions in the coronary microcirculation.

Ticagrelor versus clopidogrel in patients with STEMI treated with thrombolysis: the MIRTOS trial

AIMS

We aimed to demonstrate whether coronary microvascular function is improved after ticagrelor administration compared to clopidogrel administration in STEMI subjects undergoing thrombolysis.

METHODS AND RESULTS

MIRTOS is a multicentre study of ticagrelor versus clopidogrel in STEMI subjects treated with fibrinolysis. We enrolled 335 patients <75 years old with STEMI eligible for thrombolysis, of whom 167 were randomised to receive clopidogrel and 168 to receive ticagrelor together with thrombolysis. Primary outcome was the difference in post-PCI corrected TIMI frame count (CTFC). All clinical events were recorded in a three-month follow-up period. From the 335 patients who were randomised, 259 underwent PCI (129 clopidogrel and 130 ticagrelor) and 154 angiographies were analysable for the study primary endpoint. No significant difference was found between the clopidogrel (n=85) and ticagrelor (n=69) groups for CTFC (24.33±17.35 vs 28.33±17.59, p=0.10). No significant differences were observed in MACE and major bleeding events between randomisation groups (OR 2.0, 95% CI: 0.18-22.2, p=0.99).

CONCLUSIONS

Thrombolysis with ticagrelor in patients <75 years old was not able to demonstrate superiority compared to clopidogrel in terms of microvascular injury, while there was no difference between the two groups in MACE and major bleeding events.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02429271. EudraCT Number 2014-004082-25.

Ticagrelor: a cardiometabolic drug targeting erythrocyte-mediated purinergic signaling?

Cardiometabolic diseases lead to vascular complications, which cause increasing morbidity and mortality worldwide. The underlying mechanisms are multifactorial and complex but may involve altered purinergic signaling that significantly contributes to cardiovascular dysfunction. Ticagrelor is a successful purinergic drug directly targeting ADP-mediated P2Y₁₂R signaling for platelet aggregation and is widely used in patients with acute coronary syndrome. In addition, ticagrelor can target red blood cells (RBCs) to release ATP and inhibit adenosine uptake by RBCs, which subsequently activate purinergic signaling. This involvement in purinergic signaling may allow ticagrelor to mediate pleiotropic effects and contribute to the beneficial cardiovascular outcomes observed in clinical studies. Recent studies have established a novel function of RBCs, which is that RBCs act as disease mediators for the development of cardiovascular complications in type 2 diabetes (T2D). RBC-released ATP is defective in T2D, which has implications for the induction of vascular dysfunction by dysregulating purinergic signaling. Ticagrelor might target RBCs and restore the bioavailability of ATP and adenosine, thereby attenuating cardiovascular complications. The present perspective discusses the pleiotropic effect of ticagrelor, with a focus on the possibility of ticagrelor for the treatment of cardiometabolic complications by targeting RBCs and initiating purinergic activation. A better understanding of the proposed cardiometabolic effects could support novel clinical indications for ticagrelor application.

Ticagrelor Conditioning Effects Are Not Additive to Cardioprotection Induced by Direct NLRP3 Inflammasome Inhibition: Role of RISK, NLRP3, and Redox Cascades

Inhibition of either P2Y12 receptor or the nucleotide-binding oligomerization domain- (NOD-) like receptor pyrin domain containing 3 (NLRP3) inflammasome provides cardioprotective effects. Here, we investigate whether direct NLRP3 inflammasome inhibition exerts additive effects on myocardial protection induced by the P2Y12 receptor antagonist Ticagrelor. Ticagrelor (150 mg/kg) was orally administered to rats for three consecutive days. Then, isolated hearts underwent an ischemia/reperfusion (30 min ischemia/60 min reperfusion; IR) protocol. The selective NLRP3 inflammasome inhibitor INF (50 μM) was infused before the IR protocol to the hearts from untreated animals or pretreated with Ticagrelor. In parallel experiments, the hearts isolated from untreated animals were perfused with Ticagrelor (3.70 μM) before ischemia and subjected to IR. The hearts of animals pretreated with Ticagrelor showed a significantly reduced infarct size (IS, 49 ± 3% of area at risk, AAR) when compared to control IR group (69 ± 2% of AAR). Similarly, ex vivo administration of INF before the IR injury resulted in significant IS reduction (38 ± 3% of AAR). Myocardial IR induced the NLRP3 inflammasome complex formation, which was attenuated by either INF pretreatment ex vivo, or by repeated oral treatment with Ticagrelor. The beneficial effects induced by either treatment were associated with the protective Reperfusion Injury Salvage Kinase (RISK) pathway activation and redox defence upregulation. In contrast, no protective effects nor NLRP3/RISK modulation were recorded when Ticagrelor was administered before ischemia in isolated heart, indicating that Ticagrelor direct target is not in the myocardium. Our results confirm that Ticagrelor conditioning effects are likely mediated through platelets, but are not additives to the ones achieved by directly inhibiting NLRP3.

Red blood cell dysfunction: a new player in cardiovascular disease

The primary role of red blood cells (RBCs) is to transport oxygen to the tissues and carbon dioxide to the lungs. However, emerging evidence suggests an important role of the RBC beyond being just a passive carrier of the respiratory gases. The RBCs are of importance for redox balance and are actively involved in the regulation of vascular tone, especially during hypoxic and ischaemic conditions by the release of nitric oxide (NO) bioactivity and adenosine triphosphate. The role of the RBC has gained further interest after recent discoveries demonstrating a markedly altered function of the cell in several pathological conditions. Such alterations include increased adhesion capability, increased formation of reactive oxygen species as well as altered protein content and enzymatic activities. Beyond signalling increased oxidative stress, the altered function of RBCs is characterized by reduced export of NO bioactivity regulated by increased arginase activity. Of further importance, the altered function of RBCs has important implications for several cardiovascular disease conditions. RBCs have been shown to induce endothelial dysfunction and to increase cardiac injury during ischaemia-reperfusion in diabetes mellitus. Finally, this new knowledge has led to novel therapeutic possibilities to intervene against cardiovascular disease by targeting signalling in the RBC. These novel data open up an entirely new view on the underlying pathophysiological mechanisms behind the cardiovascular disease processes in diabetes mellitus mediated by the RBC. This review highlights the current knowledge regarding the role of RBCs in cardiovascular regulation with focus on their importance for cardiovascular dysfunction in pathological conditions and therapeutic possibilities for targeting RBCs in cardiovascular disease.

Ticagrelor reverses the mitochondrial dysfunction through preventing accumulated autophagosomes-dependent apoptosis and ER stress in insulin-resistant H9c2 myocytes

Ticagrelor, a P₂Y₁₂-receptor inhibitor, and a non-thienopyridine agent are used to treat diabetic patients via its effects on off-target mechanisms. However, the exact sub-cellular mechanisms by which ticagrelor exerts those effects remains to be elucidated. Accordingly, the present study aimed to examine whether ticagrelor influences directly the cardiomyocytes function under insulin resistance through affecting mitochondria-sarco(endo)plasmic reticulum (SER) cross-talk. Therefore, we analyzed the function and ultrastructure of mitochondria and SER in insulin resistance-mimicked (50-μM palmitic acid for 24-h) H9c2 cardiomyocytes in the presence or absence of ticagrelor (1-µM for 24-h). We found that ticagrelor treatment significantly prevented depolarization of mitochondrial membrane potential and increases in reactive oxygen species with a marked increase in the ATP level in insulin-resistant H9c2 cells. Ticagrelor treatment also reversed the increases in the resting level of free Ca²⁺ and mRNA level of P₂Y₁₂ receptors as well as preserved ER stress and apoptosis in insulin-resistant H9c2 cells. Furthermore, we determined marked repression with ticagrelor treatment in the increased number of autophagosomes and degeneration of mitochondrion, including swelling and loss of crista besides recoveries in enlargement and irregularity seen in SER in insulin-resistant H9c2 cells. Moreover, ticagrelor treatment could prevent the altered mRNA levels of Becklin-1 and type 1 equilibrative nucleoside transporter (ENT1), which are parallel to the preservation of ultrastructural ones. Our overall data demonstrated that ticagrelor can directly affect cardiomyocytes and provide marked protection against ER stress and dramatic induction of autophagosomes, and therefore, can alleviate the ER stress-induced oxidative stress increase and cell apoptosis during insulin resistance.

Platelet Inhibition, Endothelial Function, and Clinical Outcome in Patients Presenting With ST-Segment-Elevation Myocardial Infarction Randomized to Ticagrelor Versus Prasugrel Maintenance Therapy: Long-Term Follow-Up of the REDUCE-MVI Trial

Background

Off‐target properties of ticagrelor might reduce microvascular injury and improve clinical outcome in patients with ST‐segment–elevation myocardial infarction. The REDUCE‐MVI (Evaluation of Microvascular Injury in Revascularized Patients with ST‐Segment–Elevation Myocardial Infarction Treated With Ticagrelor Versus Prasugrel) trial reported no benefit of ticagrelor regarding microvascular function at 1 month. We now present the follow‐up data up to 1.5 years.

Methods and Results

We randomized 110 patients with ST‐segment–elevation myocardial infarction to either ticagrelor 90 mg twice daily or prasugrel 10 mg once a day. Platelet inhibition and peripheral endothelial function measurements including calculation of the reactive hyperemia index and clinical follow‐up were obtained up to 1.5 years. Major adverse clinical events and bleedings were scored. An intention to treat and a per‐protocol analysis were performed. There were no between‐group differences in platelet inhibition and endothelial function. At 1 year the reactive hyperemia index in the ticagrelor group was 0.66±0.26 versus 0.61±0.28 in the prasugrel group (P=0.31). Platelet inhibition was lower at 1 month versus 1 year in the total study population (61% [42%–81%] versus 83% [61%–95%]; P<0.001), and per‐protocol platelet inhibition was higher in patients randomized to ticagrelor versus prasugrel at 1 year (91% [83%–97%] versus 82% [65%–92%]; P=0.002). There was an improvement in intention to treat endothelial function in patients randomized to ticagrelor (P=0.03) but not in patients randomized to prasugrel (P=0.88). Major adverse clinical events (10% versus 14%; P=0.54) and bleedings (47% versus 63%; P=0.10) were similar in the intention‐to‐treat analysis in both groups.

Conclusions

Platelet inhibition at 1 year was higher in the ticagrelor group, without an accompanying increase in bleedings. Endothelial function improved over time in ticagrelor patients, while it did not change in the prasugrel group.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov/. Unique Identifier: NCT02422888.

Ticagrelor and preconditioning in patients with stable coronary artery disease (TAPER-S): a randomized pilot clinical trial

Background

Ticagrelor is a reversibly binding, direct-acting, oral, P₂Y₁₂ antagonist used for the prevention of atherothrombotic events in patients with coronary artery disease (CAD). Ticagrelor blocks adenosine reuptake through the inhibition of equilibrative nucleoside transporter 1 (ENT-1) on erythrocytes and platelets, thereby facilitating adenosine-induced physiological responses such as an increase in coronary blood flow velocity. Meanwhile, adenosine plays an important role in triggering ischemic preconditioning through the activation of the A1 receptor. Therefore, an increase in ticagrelor-enhanced adenosine bioavailability may confer beneficial effects through mechanisms related to preconditioning activation and improvement of coronary microvascular dysfunction.

Methods

To determine whether ticagrelor can trigger ischemic preconditioning and influence microvascular function, we designed this prospective, open-label, pilot study that enrolled patients with stable multivessel CAD requiring staged, fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI). Participants will be randomized in 1:1 ratios either to ticagrelor (loading dose (LD) 180 mg, maintenance dose (MD) 90 mg bid) or to clopidogrel (LD 600 mg, MD 75 mg) from 3 to 1 days before the scheduled PCI. The PCI operators will be blinded to the randomization arm. The primary endpoint is the delta (difference) between ST segment elevations (in millimeters, mm) as assessed by intracoronary electrocardiogram (ECG) during the two-step sequential coronary balloon inflation in the culprit vessel. Secondary endpoints are 1) changes in coronary flow reserve (CFR), index of microvascular resistance (IMR), and FFR measured in the culprit vessel and reference vessel at the end of PCI, and 2) angina score during inflations. This study started in 2018 with the aim of enrolling 100 patients. Based on the rate of negative FFR up to 30% and a drop-out rate up to 10%, we expect to detect an absolute difference of 4 mm among the study arms in the mean change of ST elevation following repeated balloon inflations. All study procedures were reviewed and approved by the Ethical Committee of the Catholic University of Sacred Heart.

Discussion

Ticagrelor might improve ischemia tolerance and microvascular function compared to clopidogrel, and these effects might translate to better long-term clinical outcomes.

Trial registration

EudraCT No. 2016–004746-28. No. NCT02701140. 

Trial status

Information provided in this manuscript refers to the definitive version (n. 3.0) of the study protocol, dated 31 October 2017, and includes all protocol amendments. Recruitment started on 18 September 2018 and is currently ongoing. The enrollment is expected to be completed by the end of 2019.

Trial sponsor

Fondazione Policlinico Universitario A. Gemelli – Roma, Polo di Scienze Cardiovascolari e Toraciche, Largo Agostino Gemelli 8, 00168 Rome, Italy.

Ticagrelor Enhances Release of Anti-Hypoxic Cardiac Progenitor Cell-Derived Exosomes Through Increasing Cell Proliferation In Vitro

Despite the widespread clinical use of cardioprotection by long-term direct antagonism of P2Y12 receptor, underlying mechanisms are unclear. Here, we identify how release of pro-survival exosomes from human cardiac-derived mesenchymal progenitor cells (hCPCs) is regulated by clinically relevant dose of ticagrelor (1 μM), an oral selective and reversible non-thienopyridine P2Y₁₂ inhibitor. Ticagrelor-induced enhancement of exosome levels is related to increased mitotic activity of hCPCs. We show a drug-response threshold above which the effects on hCPCs are lost due to higher dose of ticagrelor and larger adenosine levels. While it is known that pan-Aurora kinase inhibitor halts cell proliferation through dephosphorylation of histone H3 residue Ser10, we demonstrate that it also prevents ticagrelor-induced effects on release of cardiac progenitor cell-derived exosomes delivering anti-apoptotic HSP70. Indeed, sustained pre-treatment of cardiomyocytes with exosomes released from explant-derived hCPCs exposed to low-dose ticagrelor attenuated hypoxia-induced apoptosis through acute phosphorylation of ERK42/44. Our data indicate that ticagrelor can be leveraged to modulate release of anti-hypoxic exosomes from resident hCPCs.

Beneficial Effects of Ticagrelor on Oxidized Low-Density Lipoprotein (ox-LDL)-Induced Apoptosis in Human Umbilical Vein Endothelial Cells

Background

Ticagrelor is the first oral anti-platelet agent which has direct anti-platelet aggregation effect by combining with ADP P2Y12 receptors in platelets. It has been approved to reduce the incidence of thrombus cardiovascular events in acute coronary syndrome patients. However, the effects of ticagrelor on endothelial apoptosis have not been investigated.

Material/Methods

Oxidized low-density lipoprotein (ox-LDL) was used to establish a human umbilical vein endothelial cell (HUVEC) apoptosis model. To investigate the effects of ticagrelor on endothelial apoptosis, the HUVECs were treated with different dose of ticagrelor. Apoptosis rates of HUVECs was evaluated by flow cytometry, and the expression levels of Akt, p-Akt, Bcl-2, Bax, caspase-3, endothelial nitric oxide synthase (eNOS), and nitric oxide (NO) concentration were assessed.

Results

After treatment with 50 ug/mL ox-LDL or 100 ug/mL ox-LDL, we found that the late apoptosis and necrosis rate and the expression levels of Bax and caspase-3 were significantly increased in HUVECs, whereas the expression levels of Akt, p-Akt, Bcl-2, eNOS, and NO were significantly decreased. Ticagrelor restored the apoptosis rate of ox-LDL-induced HUVECs in a dose-dependent manner. In addition, compared with ox-LDL group, ticagrelor treatment significantly increased the expression levels of Akt, p-Akt, Bcl-2, eNOS, and NO concentration, and significantly decreased the expression levels of Bax and caspase-3.

Conclusions

We found that ox-LDL induced significant apoptosis and necrosis in our model, which was dose-dependently improved by ticagrelor. These changes might be explained by alterations in apoptosis and antioxidant pathways.

Ticagrelor improves blood viscosity-dependent microcirculatory flow in patients with lower extremity arterial disease: the Hema-kinesis clinical trial

Background

Microvascular blood flow (MBF) impairment in patients with lower extremity arterial disease (LEAD) is associated with more severe major adverse limb events (MALE). The contribution of ticagrelor, a P2Y12 antagonist and an adenosine enhancer, on blood viscosity (BV) and BV-dependent MBF in LEAD is unknown. The aim of the trial is to investigate the effects of ticagrelor on BV, and explore the association of BV-dependent MBF in participants with LEAD and type 2 diabetes (T2DM).

Methods

Randomized, double-blind, double-dummy, crossover trial design that compares treatment with aspirin 81 mg/ticagrelor placebo, aspirin 81 mg/ticagrelor 90 mg twice daily and aspirin placebo/ticagrelor 90 mg twice daily on high-shear (300 s⁻¹) and low-shear (5 s⁻¹) BV, and laser Doppler flowmetry (LDF) in the dorsum of the feet of participants with T2DM.

Results

We randomized 70 (45% female) participants aged (mean ± SD) 72 ± 9 years. The duration of LEAD was 12.3 ± 10.3 years, and 96.9% reported intermittent claudication symptoms. Use of statins was 93% (high-intensity 43%, moderate intensity 49%), renin–angiotensin–aldosterone system inhibitors (75%) and beta-blockers (61%). Treatment with ticagrelor with or without aspirin reduced high-shear BV by 5%, in both cases, while aspirin monotherapy increased high-shear BV by 3.4% (p < 0.0001). Ticagrelor with or without aspirin reduced low-shear BV by 14.2% and 13.9% respectively, while aspirin monotherapy increased low-shear BV by 9.3% (p < 0.0001). The combination of ticagrelor and aspirin increased MBF in the left foot compared to the other two treatments (p = 0.02), but not in the right foot (p = 0.25).

Conclusions

Ticagrelor should be considered in the treatment of microvascular disease in patients with LEAD and T2DM.

Trial registration Registration number: NCT02325466, registration date: December 25, 2014

Electronic supplementary material

The online version of this article (10.1186/s12933-019-0882-5) contains supplementary material, which is available to authorized users.

Ticagrelor Does Not Improve Endothelial Dysfunction in Stable Survivors of Acute Coronary Syndrome

Background:

Ticagrelor is an intriguing antiplatelet agent with a potentially beneficial impact on endothelial dysfunction and confers a mortality benefit beyond 1 month after acute coronary syndrome (ACS). However, little data exist on whether ticagrelor improves endothelial dysfunction in stable patients who survive the acute period and receive guideline-directed medical therapy.

Methods and Results:

This study is a prospective, randomized, parallel, open-labeled study that enrolled 30-day survivors of non-ST-segment elevation ACS (NSTE-ACS). Forty patients with NSTE-ACS were randomly assigned to ticagrelor or clopidogrel groups. The primary end point was the change in the percentage brachial artery flow-mediated dilation (baFMD) from baseline. Baseline characteristics were not different between the 2 groups. The median time from the stent implantation to screening was 269 days. After 30 days of study medication administration, the change in the percentage baFMD value was similar between the ticagrelor and clopidogrel groups (−0.08 [1.42] vs 0.30 [1.69], P = .66). There was no difference in the change in high-sensitive C-reactive protein (−0.61 [1.48] vs −0.01 [0.57], P = .28); however, the change in platelet inhibition significantly differed (P2Y12 reaction units, −140.5 [49.5] vs −3.9 [51.4], P < .001).

Conclusions:

This dual time point baFMD study demonstrated that treatment with ticagrelor was not superior to clopidogrel for improving endothelial dysfunction in stabilized patients with NSTE-ACS.

Ticagrelor Does Not Protect Isolated Rat Hearts, Thus Clouding Its Proposed Cardioprotective Role Through ENT 1 in Heart Tissue

P2Y₁₂ receptor-blocking drugs given at reperfusion offer protection against myocardial infarction in animal models of transient coronary occlusion. Two recent reports concluded that ticagrelor was more cardioprotective than clopidogrel and attributed this to ticagrelor's unique ability to raise tissue adenosine by blocking the equilibrative nucleoside transporter 1. Indeed, an adenosine receptor blocker attenuated ticagrelor's protection. The related P2Y₁₂ inhibitor cangrelor, which does not block the transporter, protects hearts only when platelets are in the perfusate, while adenosine is known to protect equally in situ blood-perfused and crystalloid-perfused isolated hearts. We, therefore, tested whether ticagrelor liberates a sufficient amount of adenosine to protect a Krebs buffer-perfused isolated rat heart subjected to 40 minutes of global ischemia followed by 2 hours of reperfusion. In untreated hearts, 77.6% ± 4.0% of the ventricle was infarcted as measured by triphenyltetrazolium staining. Ischemically preconditioned hearts had only 32.7% ± 3.6% infarction ( P < .001 vs untreated), indicating that our model could be protected by preconditioning which is known to involve adenosine. Strikingly, hearts treated with 10 μmol/L ticagrelor in the buffer throughout the reperfusion period had 77.5% ± 2.4% infarction comparable to unprotected controls ( P = NS vs untreated). These data strongly suggest that ticagrelor was unable to release sufficient adenosine from the crystalloid-perfused rat heart to protect it against infarction. Our previous studies have found no difference in the anti-infarct potency among clopidogrel, cangrelor, and ticagrelor in open-chest rats and rabbits, and surprisingly adenosine receptor antagonists block protection from all 3 drugs. We have no explanation why ticagrelor is more protective in the pig than clopidogrel but suspect a species or perhaps a treatment schedule difference that may or may not involve adenosine.

Adenosine as a Marker and Mediator of Cardiovascular Homeostasis: A Translational Perspective

Adenosine, a purine nucleoside, is produced broadly and implicated in the homeostasis of many cells and tissues. It signals predominantly via 4 purinergic adenosine receptors (ADORs) - ADORA1, ADORA2A, ADORA2B and ADOosine signaling, both through design as specific ADOR agonists and antagonists and as offtarget effects of existing anti-platelet medications. Despite this, adenosine has yet to be firmly established as either a therapeutic or a prognostic tool in clinical medicine to date. Herein, we provide a bench-to-bedside review of adenosine biology, highlighting the key considerations for further translational development of this proRA3 in addition to non-ADOR mediated effects. Through these signaling mechanisms, adenosine exerts effects on numerous cell types crucial to maintaining vascular homeostasis, especially following vascular injury. Both in vitro and in vivo models have provided considerable insights into adenosine signaling and identified targets for therapeutic intervention. Numerous pharmacologic agents have been developed that modulate adenmising molecule.

Interaction between platelets and endothelium: from pathophysiology to new therapeutic options

Platelets were traditionally considered to purely have a role in the maintenance of haemostasis. Recently their role in vasomotor function, inflammation and atherosclerosis has been very well-recognized. Endothelium which was originally considered as a simple passive barrier, it is now viewed as an organ whose normal functioning is crucial for maintaining vascular health. When endothelial balance is disturbed, vascular disease initiates. Platelet interactions with endothelium have an important contribution in this process. Low-grade inflammation, endothelial dysfunction, and platelet hyper-reactivity are all independently associated with an increased risk of cardiovascular events. Older antiplatelet agents like aspirin and clopidogrel and newer more potent agents like prasugrel and ticagrelor have been proven effective in all the clinical spectrum of coronary artery disease patients. Current antiplatelet medications and especially newer generation P2Y12 inhibitor ticagrelor, offer clinical benefits not only due to their well-recognized antithrombotic effect, but also via the attenuation of platelet inflammatory action, impediment of P2Y12 activation effects in other cells and through other complex and sometimes undefined pathways. Future research is expected to better define platelet-endothelium interactions and the multiple impact of current antiplatelet therapy on them.

Does Ticagrelor Improve Endothelial Function?

Ticagrelor is a P2Y12 receptor antagonist with proven clinical benefit in patients with acute coronary syndrome. Apart from its principal antiplatelet action, pleiotropic effects have been implicated in the clinical profile of ticagrelor, including a potentially beneficial impact on endothelial function. In light of the common presence and prognostic value of endothelial dysfunction in patients with coronary artery disease, several clinical studies have investigated the postulated effect of ticagrelor on endothelial function, yielding conflicting results. Limitations of the relevant studies as well as substantial differences in patient population, study design, and methods may account for these controversial findings. Most of these studies, however, support a beneficial impact of ticagrelor on endothelial function, which seems to be significant in the higher risk patients. In order to elucidate this effect, further research efforts should aim to clarify how quickly does endothelial function respond to ticagrelor, how sustained this response is during the dosing intervals and in the long term, which mechanisms are implicated, and whether this pleiotropic action is clinically significant. Future studies should include larger and diverse populations of patients, assess endothelial function at several time points after treatment initiation, and use multiple methods of endothelial function measurement, while implementing strict methodology. Nevertheless, the extent of the clinical benefit of ticagrelor attributable to actions beyond its potent and consistent antiplatelet effect remains uncertain.

Effect of preoperative loading dose ticagrelor and clopidogrel on no-reflow phenomenon during intervention in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention: a systematic review and meta-analysis

BACKGROUND

Previous studies have shown that ticagrelor is more effective than clopidogrel in platelet inhibition. However, this conclusion remains controversial. Therefore, we performed this meta-analysis to assess the effect of preoperative loading dose ticagrelor and clopidogrel on no-reflow (NRF) during intervention in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention (PPCI).

MATERIALS AND METHODS

Randomized controlled trials and observational studies were reviewed. The retrieval time was limited from inception to October 1, 2017. The retrieved databases included PubMed, Embase, the Cochrane Library, Web of Science, CBM, CNKI, the VIP database, and the Wang Fang database. RevMan 5.3 software was used for data analysis.

RESULTS

Fourteen randomized controlled trials and one observational study, including 4,162 patients, were included. In these articles, 1,521 patients were in the ticagrelor group (180 mg) and 2,641 patients were in the clopidogrel group (600 mg). The meta-analysis showed that compared with clopidogrel group, preoperative loading dose ticagrelor: 1) significantly reduced the incidence of NRF during PPCI (95% confidence interval [CI]: 0.15, 0.39, P<0.05) as well as the level of postoperative corrected thrombolysis in myocardial infarction frame count (95% CI: -8.89, -6.91, P<0.05); 2) significantly reduced the incidence of major adverse cardiovascular events during hospitalization, including 30 and 180 days after PPCI (95% CI: 0.41, 0.82, P<0.05; 95% CI: 0.15, 0.46, P<0.05, respectively); and 3) significantly improved thrombolysis in myocardial infarction flow after PPCI (95% CI: 1.40, 2.45, P<0.05). No significant difference was observed in terms of bleeding events within 30 and 180 days after PPCI (95% CI: 0.71, 1.54, P=0.82; 95% CI: 0.81, 3.19, P=0.18, respectively).

CONCLUSION

Compared with clopidogrel, loading dose ticagrelor effectively reduced both the occurrence of NRF during PPCI and the incidence of major adverse cardiovascular event in patients with ST-segment elevation myocardial infarction undergoing PPCI. Furthermore, it did not increase the risk of bleeding after PPCI.

Ticagrelor - toward more efficient platelet inhibition and beyond

Novel antiplatelet drugs, including ticagrelor, are being successively introduced into the therapy of atherothrombotic conditions due to their superiority over a standard combination of clopidogrel with acetylsalicylic acid in patients with acute coronary syndromes (ACS). A P2Y12 receptor antagonist, ticagrelor, is unique among antiplatelet drugs, because ticagrelor inhibits the platelet P2Y12 receptor in a reversible manner, and because it demonstrates a wide palette of advantageous pleiotropic effects associated with the increased concentration of adenosine. The pleiotropic effects of ticagrelor comprise cardioprotection, restoration of the myocardium after an ischemic event, promotion of the release of anticoagulative factors and, eventually, anti-inflammatory effects. Beyond the advantageous effects, the increased concentration of adenosine is responsible for some of ticagrelor's adverse effects, including dyspnea and bradycardia. Large-scale clinical trials demonstrated that both standard 12-month therapy and long-term use of ticagrelor reduce the risk of cardiovascular events in patients with ACS, but at the expense of a higher risk of major bleeding. Further trials focused on the use of ticagrelor in conditions other than ACS, including ischemic stroke, peripheral artery disease and status after coronary artery bypass grafting. The results of these trials suggest comparable efficacy and safety of ticagrelor and clopidogrel in extra-coronary indications, but firm conclusions are anticipated from currently ongoing studies. Here, we summarize current evidence on the superiority of ticagrelor over other P2Y12 antagonists in ACS, discuss the mechanism underlying the drug-drug interactions and pleiotropic effects of ticagrelor, and present future perspectives of non-coronary indications for ticagrelor.

Absence of differential effect of ticagrelor versus prasugrel maintenance dose on endothelial function in patients with stable coronary artery disease

BACKGROUND

Endothelial function may be improved by ticagrelor through adenosine-mediated mechanisms. We aimed to assess the effect of ticagrelor versus prasugrel on endothelial function in patients with stable coronary artery disease (CAD).

METHODS

In a prospective, randomized, crossover study, 22 stable CAD patients under prasugrel 10 mg once daily maintenance dose (MD) for at least 3 months were randomized to either ticagrelor 90 mg twice daily or prasugrel 10 mg once daily for 15 days with a direct treatment-crossover for another 15 days. Endothelial function was assessed by peripheral arterial tonometry (EndoPAT 2000 system, Itamar Medical, Caesarea, Israel) at Day 0 (randomization), Day 15, and Day 30. Reactive Hyperemia Index (RHI) was calculated by using an automated software, and endothelial dysfunction (ED) was defined as RHI <1.67. RHI at the end of the two treatment periods did not differ between ticagrelor and prasugrel MD treatments. Least squares estimates (95% confidence interval) were 1.78 (1.58-1.99) versus 1.88 (1.67-2.08), with a fixed estimate of -0.099 (95% CI: -0.45 to 0.25) for the difference between them (p = 0.5). ED rate did not differ significantly between ticagrelor and prasugrel (45.5% vs 45.5%, p = 0.6).

CONCLUSIONS

In CAD patients, we have failed to find evidence of alteration of endothelial function following ticagrelor compared to prasugrel MD treatment, as assessed by peripheral arterial tonometry. CLINICALTRIALS.

GOV UNIQUE IDENTIFIER

NCT01957540.

Comparison of treatment outcomes of ticagrelor and clopidogrel among patients undergoing percutaneous coronary intervention: A meta-analysis

We performed a meta-analysis of randomized controlled trials (RCTs) to investigate the efficacy and safety of ticagrelor (TIC) vs. clopidogrel (CLO) in patients undergoing percutaneous coronary intervention (PCI). In Jun 2016, a literature search was started and all the studies were conducted from 2010 to 2015. We systematically searched the literature through the MEDLINE database, Cochrane library, and EMBASE database. Quality assessments were evaluated with Jadad quality scale. Data were extracted considering the characteristics of efficacy and safety designs. Six RCTs enrolling 26 244 participants and satisfying the inclusion criteria were finally analyzed. There was a significant decrease of all-cause mortality (MD=0.83, 95%CI=0.74-0.93, P=0.001) and myocardial infarction (MI) (MD=0.78, 95%CI=0.70-0.88, P=0.000). There were no significant differences in stroke (MD=1.34, 95%CI=0.99-1.79, P=0.06), total bleeding (MD=0.97, 95%CI=0.84-1.12, P=0.66), minor or major bleeding (MD=1.06, 95%CI=0.94-1.19, P=0.35) in patients undergoing PCI after treatment with TIC vs. CLO. TIC could be more significant in decreasing all-cause mortality and MI than CLO, but there were no significant differences between TIC and CLO in inhibiting stroke, major bleeding, major or minor bleeding in patients undergoing PCI.

Long-Term Use of Ticagrelor in Patients with Coronary Artery Disease

PURPOSE OF REVIEW

This review aims to summarize and discuss safety and effectiveness of the long-term use of ticagrelor in patients with coronary artery disease (CAD).

RECENT FINDINGS

Ticagrelor is an orally administered, direct, and reversible inhibitor of the P2Y₁₂-platelet receptor. Long-term use of ticagrelor in patients with previous myocardial infarction (MI) has been investigated in the PEGASUS-TIMI-54 trial. Overall, 21,162 patients with a spontaneous MI 1 to 3 years before randomization were randomly assigned to ticagrelor 90 mg bid, ticagrelor 60 mg bid, or placebo. Compared with placebo, both doses of ticagrelor showed that they were capable of significantly reducing the primary efficacy endpoint, although with a significant increase in TIMI major bleeding. Intracranial hemorrhage or fatal bleeding did not differ across groups. These findings establish clear benefit of DAPT extension with ticagrelor beyond 1 year of treatment, which comes with a tradeoff of clinically meaningful bleeding. Altogether, current evidence suggests that the duration of DAPT remains a patient-by-patient decision based on thrombotic and bleeding risk profiles.

Rationale and design of the Hunting for the off-target propertIes of Ticagrelor on Endothelial function and other Circulating biomarkers in Humans (HI-TECH) trial

BACKGROUND

Among the 3 approved oral P2Y₁₂ inhibitors for the treatment for patients with acute coronary syndrome (ACS), ticagrelor, but not prasugrel or clopidogrel, has been associated with off-target properties, such as improved endothelial-dependent vasomotion and increased adenosine plasma levels.

METHODS

The HI-TECH study (NCT02587260) is a multinational, randomized, open-label, crossover study with a Latin squares design, conducted at 5 European sites, in which patients free from recurrent ischemic or bleeding events ≥30 days after a qualifying ACS were allocated to sequentially receive a 30 ± 5-day treatment with prasugrel, clopidogrel, and ticagrelor in random order. The primary objective was to evaluate whether ticagrelor, at treatment steady state (ie, after 30 ± 5 days of drug administration), as compared with both clopidogrel and prasugrel, is associated with an improved endothelial function, assessed with peripheral arterial tonometry. Thirty-six patients undergoing evaluable endothelial function assessment for each of the assigned P2Y₁₂ inhibitor were needed to provide 90% power to detect a 10% relative change of the reactive hyperemia index in the ticagrelor group.

CONCLUSION

The HI-TECH study is the first randomized, crossover study aiming to ascertain whether ticagrelor, when administered at approved regimen in post-ACS patients, improves endothelial function as compared with both clopidogrel and prasugrel.

Effect of ticagrelor on endothelial calcium signalling and barrier function

The P2Y₁₂ receptor is a G_i-coupled receptor whose activation inhibits adenylyl cyclase and thereby reduces the concentration of intracellular cAMP. Here the hypothesis was tested whether AR-C 66096 or ticagrelor, two direct-acting and reversibly binding P2Y₁₂ receptor antagonists, protect endothelial cell (EC) barrier function by raising intracellular cAMP in ECs. The study was carried out on primary human umbilical vein ECs (HUVECs) and human pulmonary microvascular ECs (hPMECs). AR-C66096 (10 µM) induced a 50 % increase in cAMP in ECs whereas ticagrelor (2-10 µM) had no effect. Likewise, AR-C666096 antagonised thrombin-induced hyperpermeability in both HUVECs and hPMECs, but ticagrelor had no effect on basal EC monolayer permeability. Ticagrelor, however, sensitised ECs for thrombin-induced hyperpermeability and potentiated the thrombin effect. Ticagrelor but not AR-C66096 caused an increase in cytosolic calcium ([Ca²⁺]_i). This increase in [Ca²⁺]_i was abrogated by LaCl₃ (Ca²⁺ influx inhibitor) but not by xestospongin C (IP₃ receptor antagonist) or by depletion of intracellular stores with thapsigargin, suggesting a Ca²⁺ influx from the extracellular space. Accordingly, ticagrelor caused an increase in myosin light chain (MLC) phosphorylation, an important regulator of EC contractile machinery and thus permeability, which was abrogated by LaCl₃. The ability of ticagrelor to potentiate EC permeability was abrogated by a MLC kinase inhibitor (ML-7; 10 µM). Our data demonstrate that the P2Y₁₂ receptor antagonist AR-C66096 exerts a protective effect on ECs in vitro, possibly by raising intracellular cAMP, whereas ticagrelor sensitises EC barrier function by inducing Ca²⁺ influx and activating downstream EC contractile machinery.

Effects of P2Y12 receptor antagonists beyond platelet inhibition--comparison of ticagrelor with thienopyridines

The effect and clinical benefit of P2Y12 receptor antagonists may not be limited to platelet inhibition and the prevention of arterial thrombus formation. Potential additional effects include reduction of the pro-inflammatory role of activated platelets and effects related to P2Y12 receptor inhibition on other cells apart from platelets. P2Y12 receptor antagonists, thienopyridines and ticagrelor, differ in their mode of action being prodrugs instead of direct acting and irreversibly instead of reversibly binding to P2Y12 . These key differences may provide different potential when it comes to additional effects. In addition to P2Y12 receptor blockade, ticagrelor is unique in having the only well-documented additional target of inhibition, the equilibrative nucleoside transporter 1. The current review will address the effects of P2Y12 receptor antagonists beyond platelets and the protection against arterial thrombosis. The discussion will include the potential for thienopyridines and ticagrelor to mediate anti-inflammatory effects, to conserve vascular function, to affect atherosclerosis, to provide cardioprotection and to induce dyspnea.

Blood cells: an historical account of the roles of purinergic signalling

The involvement of purinergic signalling in the physiology of erythrocytes, platelets and leukocytes was recognised early. The release of ATP and the expression of purinoceptors and ectonucleotidases on erythrocytes in health and disease are reviewed. The release of ATP and ADP from platelets and the expression and roles of P1, P2Y(1), P2Y(12) and P2X1 receptors on platelets are described. P2Y(1) and P2X(1) receptors mediate changes in platelet shape, while P2Y(12) receptors mediate platelet aggregation. The changes in the role of purinergic signalling in a variety of disease conditions are considered. The successful use of P2Y(12) receptor antagonists, such as clopidogrel and ticagrelor, for the treatment of thrombosis, myocardial infarction and stroke is discussed.

P2X and P2Y receptor signaling in red blood cells

Purinergic signaling involves the activation of cell surface P1 and P2 receptors by extracellular nucleosides and nucleotides such as adenosine and adenosine triphosphate (ATP), respectively. P2 receptors comprise P2X and P2Y receptors, and have well-established roles in leukocyte and platelet biology. Emerging evidence indicates important roles for these receptors in red blood cells. P2 receptor activation stimulates a number of signaling pathways in progenitor red blood cells resulting in microparticle release, reactive oxygen species formation, and apoptosis. Likewise, activation of P2 receptors in mature red blood cells stimulates signaling pathways mediating volume regulation, eicosanoid release, phosphatidylserine exposure, hemolysis, impaired ATP release, and susceptibility or resistance to infection. This review summarizes the distribution of P2 receptors in red blood cells, and outlines the functions of P2 receptor signaling in these cells and its implications in red blood cell biology.

Ticagrelor Does Not Inhibit Adenosine Transport at Relevant Concentrations: A Randomized Cross-Over Study in Healthy Subjects In Vivo

BACKGROUND AND PURPOSE

In patients with myocardial infarction, ticagrelor reduces cardiovascular and sepsis-related mortality, and can cause dyspnea. It is suggested that this is caused by adenosine receptor stimulation, because in preclinical studies, ticagrelor blocks the nucleoside transporter and increases cellular ATP release. We now investigated the effects of ticagrelor on the adenosine system in humans in vivo.

EXPERIMENTAL APPROACH

In a double-blinded, placebo-controlled cross-over trial in 14 healthy subjects, we have tested whether ticagrelor (180 mg) affects adenosine- and dipyridamole-induced forearm vasodilation, as surrogates of nucleoside uptake inhibition and adenosine formation, respectively. Also, ex vivo uptake of adenosine and uridine in isolated red blood cells was measured. Primary endpoint was adenosine-induced vasodilation.

KEY RESULTS

Ticagrelor did not affect adenosine- or dipyridamole-induced forearm vasodilation. Also, ex vivo uptake of adenosine and uridine in isolated red blood cells was not affected by ticagrelor. In vitro, ticagrelor dose-dependently inhibited nucleoside uptake, but only at supra-physiological concentrations.

CONCLUSION AND IMPLICATIONS

In conclusion, at relevant plasma concentration, ticagrelor does not affect adenosine transport, nor adenosine formation in healthy subjects. Therefore, it is unlikely that this mechanism is a relevant pleiotropic effect of ticagrelor.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01996735.

Design and rationale of TROCADERO: A TRial Of Caffeine to Alleviate DyspnEa Related to ticagrelOr

BACKGROUND

Ticagrelor treatment has the side effect of increased incidence of dyspnea. Adenosine-induced dyspnea is augmented by ticagrelor and can be alleviated with the adenosine antagonist theophylline. Caffeine is a closely related xanthine derivative.

OBJECTIVES

The primary objective of the TROCADERO is to evaluate the effect of caffeine versus placebo on ticagrelor-associated dyspnea, measured by the visual analog scale area under the curve in patients with ongoing ticagrelor treatment after an acute coronary syndrome event.

DESIGN

After a run-in period of 1 to 7 days of absence of caffeine intake, acute coronary syndrome patients with ticagrelor-induced dyspnea (planned inclusion 416) are randomized in a blinded fashion to either caffeine 200 mg twice daily or matching placebo with a treatment duration of 1 week. The primary efficacy end point is change in visual analog scale area under the curve for dyspnea, and the primary safety end point is occurrence of high on-treatment platelet reactivity measured by the VerifyNow P2Y12 assay.

CONCLUSIONS

This trial will determine if adenosine antagonism by caffeine can alleviate ticagrelor-related dyspnea, without impairing the antiplatelet effect of ticagrelor.