Platelets Express Activated P2Y12 Receptor in Patients With Diabetes Mellitus

Regulation of transcription factor function by purinergic signalling in cardiovascular diseases

Cardiovascular diseases (CVDs), including hypertension, atherosclerosis, myocardial ischemia, and myocardial infarction, constitute the primary cause of mortality worldwide. Transcription factors play critical roles in the development of CVDs and contribute to the pathophysiology of these diseases by coordinating the transcription of many genes involved in inflammation, oxidative stress, angiogenesis, and glycolytic metabolism. One important regulator of hemostasis in both healthy and pathological settings has been identified as a purinergic signalling pathway. Research has demonstrated that several signalling networks implicated in the pathophysiology of CVDs are formed by transcription factors that are regulated by purinergic substances. Here, we briefly summarize the roles and mechanisms of the transcription factors regulated by purinergic pathways in various types of CVD. This information will be essential for discovering novel approaches for CVD treatment and prevention.

Clopidogrel-Mediated P2Y12 Inhibition According to Renal Function in Patients With Diabetes Mellitus and CAD

This prospective ex vivo and in vitro pharmacodynamic (PD)/pharmacokinetic investigation was conducted in patients with diabetes mellitus with (n = 31) and without chronic kidney disease (n = 30). PD assessments included platelet reactivity index, maximum platelet aggregation, and P2Y12 reaction units. Ex vivo pharmacokinetic assessments included plasma levels of clopidogrel and its active metabolite. In vitro PD assessments were conducted on baseline samples incubated with escalating concentrations of clopidogrel and its active metabolite. Among patients with diabetes mellitus treated with clopidogrel, impaired renal function was associated with increased maximum platelet aggregation. This finding could be attributed partially to upregulation of the P2Y12 activity without differences in drug absorption or metabolism. (Impact of Chronic Kidney Disease on Clopidogrel Effects in Diabetes Mellitus; NCT03774394).

WY-14643, a novel antiplatelet and antithrombotic agent targeting the GPIbα receptor

BACKGROUND AND PURPOSE

Hypolipidemia and platelet activation play key roles in atherosclerotic diseases. Pirinixic acid (WY-14643) was originally developed as a lipid-lowering drug. Here we focused on its antiplatelet and antithrombotic abilities and the underlying mechanism.

EXPERIMENTAL APPROACH

The effects of WY-14643 on platelet aggregation was measured using a lumi-aggregometer. Clot retraction and spreading on fibrinogen were also assayed. PPARα-/- platelets were used to identify the target of WY-14643. The interaction between WY-14643 and glycoprotein Ibα (GPIbα) was detected using cellular thermal shift assay (CETSA), surface plasmon resonance (SPR) spectroscopy and molecular docking. GPIbα downstream signaling was examined by Western blot. The antithrombotic effect was investigated using mouse mesenteric arteriole thrombosis model. Mouse tail bleeding model was used to study its effect on bleeding side effects.

KEY RESULTS

WY-14643 concentration-dependently inhibits human washed platelet aggregation, clot retraction, and spreading. Significantly, WY-14643 inhibits thrombin-induced activation of human washed platelets with an IC50 of 7.026 μM. The antiplatelet effect of WY-14643 is mainly dependent of GPIbα. CESTA, SPR and molecular docking results indicate that WY-14643 directly interacts with GPIbα and acts as a GPIbα antagonist. WY-14643 also inhibits phosphorylation of PLCγ2, Akt, p38, and Erk1/2 induced by thrombin. Noteworthily, 20 mg/kg oral administration of WY-14643 inhibits FeCl3-induced thrombosis of mesenteric arteries in mice similarly to clopidogrel without increasing bleeding.

CONCLUSION AND IMPLICATIONS

WY-14643 is not only a PPARα agonist with lipid-lowering effect, but also an antiplatelet agent as a GPIbα antagonist. It may have more significant therapeutic advantages than current antiplatelet agents for the treatment of atherosclerotic thrombosis, which have lipid-lowering effects without bleeding side effects.

The mechanisms and therapeutic potential of clopidogrel in mitigating diabetic cardiomyopathy in db/db mice

Clopidogrel has been shown to play a protective role against diabetic nephropathy. However, whether clopidogrel exerts a protective effect against diabetic cardiomyopathy (DCM) is unknown. Three-month-old male db/db mice were administered clopidogrel daily at doses of 5, 10, and 20 mg/kg by gavage for 5 months. Here, we showed that clopidogrel effectively attenuated diabetes-induced cardiac hypertrophy and cardiac dysfunction by inhibiting cardiac fibrosis, inflammatory responses, and oxidative stress damage in db/db mice. Diabetes-induced cardiac fibrosis was inhibited by clopidogrel treatment via blockade of the TGF-β1/Smad3/P2RY12 pathway and inhibition of macrophage infiltration in db/db mice. The protective effects of clopidogrel against oxidative damage were mediated by the induction of the Nrf2 signaling pathway. Taken together, our findings provide strong evidence that clopidogrel is a promising effective agent for the treatment of DCM by alleviating diabetes-induced cardiac hypertrophy and dysfunction. P2RY12 might be an effective target for the treatment of DCM.

Low ambient temperature exposure increases the risk of ischemic stroke by promoting platelet activation

BACKGROUND

Accumulating epidemiological evidence suggests the association between low ambient temperature exposure and the risk of ischemic stroke, but the underlying mechanisms remain unclear.

OBJECTIVE

Given the crucial role of platelet activation and thrombosis in ischemic stroke, this study aims to investigate the effect of ambient temperature on platelet activation through multi-center clinical data in Tianjin as well as animal experiments.

METHODS

From 2018 to 2020, nearly 3000 ischemic stroke patients from three stroke centers in Tianjin were included in the analysis, among them the ADP induced platelet aggregation rate was available. Meteorological data from the same period had also been collected. After controlling for confounding factors, the generalized additive mixed model (GAMM) was used to evaluate the correlation between environmental temperature and platelet aggregation rate. In further animal experiments, platelet function assessments were conducted on mice from the cold exposure group and the normal temperature group, including platelet aggregation, spreading, and clot retraction. Additionally, tail bleeding and mesentery thrombosis were also tested to monitor hemostasis and thrombosis in vivo.

RESULT

A nonlinear "S" shaped relationship between outdoor temperature and platelet aggregation was found. Each 1 °C decrease of mean temperature was associated with an increase of 7.77 % (95 % CI: 2.06 % - 13.48 %) in platelet aggregation. The ambient temperature is not related to other platelet parameters. Subgroup analysis found that males, people aged ≥65 years, and hypertensive individuals are more susceptible to temperature changes. Furthermore, animal experiments demonstrated that the increased CIRBP levels and subsequent activation of p-AKT/p-ERK may be one of the reasons for cold exposure induced platelets activation.

CONCLUSION

Both clinical data and basic research support that low ambient temperature exposure has the potential to increase platelet activation. These results provide a basis for understanding the potential mechanism of temperature variations on the pathogenesis of cerebrovascular diseases.

Platelet P2Y12 signalling pathway in the dysregulated immune response during sepsis

Sepsis is a complicated pathological condition in response to severe infection. It is characterized by a strong systemic inflammatory response, where multiple components of the immune system are involved. Currently, there is no treatment for sepsis. Blood platelets are known for their role in haemostasis, but they also participate in inflammation through cell-cell interaction and the secretion of inflammatory mediators. Interestingly, an increase in platelet activation, secretion, and aggregation with other immune cells (such as monocytes, T-lymphocytes and neutrophils) has been detected in septic patients. Therefore, antiplatelet therapy in terms of P2Y12 antagonists has been evaluated as a possible treatment for sepis. It was found that blocking P2Y12 receptors decreased platelet marker expression and limited attachment to immune cells in some studies, but not in others. This review addresses the role of platelets in sepsis and discusses whether antagonizing P2Y12 signalling pathways can alter the disease outcome. Challenges in studying P2Y12 antagonists in sepsis also are discussed. LINKED ARTICLES: This article is part of a themed issue on Platelet purinergic receptor and non-thrombotic disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.4/issuetoc.

Complete blood count inflammation derived indexes as predictors of metabolic syndrome in type 2 diabetes mellitus

BACKGROUND

Metabolic syndrome (MetS) is a group of comorbidities related to regulating hyperglycemia and acute cardiovascular incidents and complications. With the increasing prevalence in individuals with type 2 diabetes mellitus (T2DM), MetS represents an increasing public health problem and clinical challenge, and early diagnosis is necessary to avoid the accelerated development of diabetic complications.

OBJECTIVE

To investigate the role of Complete Blood Count-derived Inflammation Indexes (CBCIIs) in predicting MetS in T2DM individuals.

METHODS

The study was designed as a two-year prospective study and included 80 T2DM individuals divided into MetS and non-MetS groups based on MetS development over two years. The sera samples were analyzed for complete blood count parameters and C-reactive protein (CRP). Based on the laboratory test results, 13 CBCIIs were calculated and analyzed. The receiver operating characteristic (ROC) curve and their corresponding areas under the curve (AUC) were used to determine prognostic accuracy.

RESULTS

There were significant differences between T2DM participants with Mets and those without MetS concerning Neutrophil to Platelet Ratio (NPR) values (p< 0.001), Neutrophil to Lymphocyte and Platelet Ratio (NLPR) (p< 0.001), Platelet to Lymphocyte Ratio (PLR) (p< 0.001), Lymphocyte to C-reactive protein Ratio (LCR) (p< 0.001), C-reactive protein to Lymphocyte Ratio (CRP/Ly) (p< 0.001), Systemic immune inflammation index (SII) (< 0.001), and Aggregate Index of Systemic Inflammation (AISI) (p= 0.005). The results of ROC curve analysis have shown that the LCR (AUC of 0.907), CRP/Ly (AUC of 0.907) can serve as excellent predictors, but NPR (AUC of 0.734), NLRP (AUC of 0.755), PLR (AUC of 0.823), SII (AUC of 0.745), and AISI (AUC of 0.688) as good predictors of MetS in T2 DM individuals.

CONCLUSION

This study confirms the reliability of the CBCIIs as novel, simple, low cost and valuable predictors of MetS developing in T2DM.

Endothelial YAP Mediates Hyperglycemia-Induced Platelet Hyperactivity and Arterial Thrombosis

BACKGROUND

Hyperglycemia-a symptom that characterizes diabetes-is highly associated with atherothrombotic complications. However, the underlying mechanism by which hyperglycemia fuels platelet activation and arterial thrombus formation is still not fully understood.

METHODS

The profiles of polyunsaturated fatty acid metabolites in the plasma of patients with diabetes and healthy controls were determined with targeted metabolomics. FeCl3-induced carotid injury model was used to assess arterial thrombus formation in mice with endothelial cell (EC)-specific YAP (yes-associated protein) deletion or overexpression. Flow cytometry and clot retraction assay were used to evaluate platelet activation. RNA sequencing and multiple biochemical analyses were conducted to unravel the underlying mechanism.

RESULTS

The plasma PGE2 (prostaglandin E2) concentration was elevated in patients with diabetes with thrombotic complications and positively correlated with platelet activation. The PGE2 synthetases COX-2 (cyclooxygenase-2) and mPGES-1 (microsomal prostaglandin E synthase-1) were found to be highly expressed in ECs but not in other type of vessel cells in arteries from both patients with diabetes and hyperglycemic mice, compared with nondiabetic individuals and control mice, respectively. A combination of RNA sequencing and ingenuity pathway analyses indicated the involvement of YAP signaling. EC-specific deletion of YAP limited platelet activation and arterial thrombosis in hyperglycemic mice, whereas EC-specific overexpression of YAP in mice mimicked the prothrombotic state of diabetes, without affecting hemostasis. Mechanistically, we found that hyperglycemia/high glucose-induced endothelial YAP nuclear translocation and subsequently transcriptional expression of COX-2 and mPGES-1 contributed to the elevation of PGE2 and platelet activation. Blockade of EP3 (prostaglandin E receptor 3) activation by oral administration of DG-041 reversed the hyperactivity of platelets and delayed thrombus formation in both EC-specific YAP-overexpressing and hyperglycemic mice.

CONCLUSIONS

Collectively, our data suggest that hyperglycemia-induced endothelial YAP activation aggravates platelet activation and arterial thrombus formation via PGE2/EP3 signaling. Targeting EP3 with DG-041 might be therapeutic for diabetes-related thrombosis.

New Insights into the Role of HMGB2 in ST-Segment Elevation Myocardial Infarction

Background

Ischemic heart disease is one of the leading causes of death in the world, of which ST-segment elevation myocardial infarction (STEMI) is an important type. Inappropriate activation and accumulation of platelets typically induced thrombosis, which may result in acute vessel occlusion and STEMI. Multiple cytokines have been shown to regulate platelet activation, but the relationship between HMGB2 and platelet activation has not been elucidated.

Methods

We collected peripheral blood of STEMI patients and healthy adults, and mass spectrometry analysis of platelet proteins was conducted. The "edgeR" package was used to identify the differentially expressed proteins (DEPs). The Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene ontology (GO) and Gene Set Enrichment Analysis (GSEA) were used to identify the significantly changed pathways. Western blot and ELISA were used to detect the expression of a high mobility group box 2 (HMGB2). Flow cytometric analysis and platelet aggregation rate were performed to evaluate the activation of platelets.

Results

We identified ALOX5, HIST1H1B, S100A11, HMGB2, and RPS15A were the top five up-regulated proteins by differential expression analysis. Western blot verified that the relative protein expression of HMGB2 in platelet was significantly higher in STEMI patients compared with control adults, and the results of ELISA indicated that the serum HMGB2 level increased and significantly correlated with neutrophil count in STEMI patients. Further investigation showed that the platelet aggregation induced by ADP, the activation of integrin αIIbβ3 and CD62P expression on platelet surface were all enhanced by the recombinant HMGB2 (rHMGB2).

Conclusion

In conclusion, HMGB2 may be the key molecule to regulate platelet activation in patients with STEMI, which may serve as a potential therapeutic target for STEMI.

The potential role of CpG oligodeoxynucleotides on diabetic cardiac autonomic neuropathy mediated by P2Y12 receptor in rat stellate ganglia

Cardiac autonomic neuropathy has a high prevalence in type 2 diabetes, which increases the risk of cardiovascular system disorders. CpG oligodeoxynucleotide (CpG-ODN), a Toll-like receptor 9 (TLR9) ligand, has been shown to have cardioprotection and cellular protection. Our previous work showed that P2Y12 in stellate ganglia (SG) is involved in the process of diabetic cardiac autonomic neuropathy (DCAN). Here, we aim to investigate whether CpG-ODN 1826 plays a protective role in DCAN and whether this beneficial protection involves regulation of the P2Y12-mediated cardiac sympathetic injury. Our results revealed that CpG-ODN 1826 activated TLR9 receptor, improved the abnormal blood pressure (BP), heart rate (HR), heart rate variability (HRV) and sympathetic nerve discharge (SND) activity in diabetic rats and reduced the up-regulated NF-κB, P2Y12 receptor, TNF-α and IL-1β in SG. Meanwhile, CpG-ODN 1826 significantly decreased the elevated ATP, nuclear receptor coactivator 4 (NCOA4), iron, ROS and MDA levels and increased GPX4 and GSH levels. In addition, CpG-ODN 1826 contributes to maintain normalization of mitochondrial structure in SG. Overall, CpG-ODN 1826 alleviates the sympathetic excitation and abnormal neuron-glial signal communication via activating TLR9 receptors to achieve a balance of autonomic activity and relieve the DCAN in rats. The mechanism may involve the regulation of P2Y12 receptor in SG by reducing ATP release and NF-κB expression, which counteract neuroinflammation and ferroptosis mediated by activated P2Y12 in SG.

P2Y12 receptor involved in the development of chronic nociceptive pain as a sensory information mediator

Direct or indirect damage to the nervous system (such as inflammation or tumor invasion) can lead to dysfunction and pain. The generation of pain is mainly reflected in the activation of glial cells and the abnormal discharge of sensory neurons, which transmit stronger sensory information to the center. P2Y12 receptor plays important roles in physiological and pathophysiological processes including inflammation and pain. P2Y12 receptor involved in the occurrence of pain as a sensory information mediator, which enhances the activation of microglia and the synaptic plasticity of primary sensory neurons, and reaches the higher center through the ascending conduction pathway (mainly spinothalamic tract) to produce pain. While the application of P2Y12 receptor antagonists (PBS-0739, AR-C69931MX and MRS2359) have better antagonistic activity and produce analgesic pharmacological properties. Therefore, in this article, we discussed the role of the P2Y12 receptor in different chronic pains and its use as a pharmacological target for pain relief.

G protein-coupled P2Y12 receptor is involved in the progression of neuropathic pain

The pathological mechanism of neuropathic pain is complex, which seriously affects the physical and mental health of patients, and its treatment is also difficult. The role of G protein-coupled P2Y12 receptor in pain has been widely recognized and affirmed. After nerve injury, stimulated cells can release large amounts of nucleotides into the extracellular matrix, act on P2Y12 receptor. Activated P2Y12 receptor activates intracellular signal transduction and is involved in the development of pain. P2Y12 receptor activation can sensitize primary sensory neurons and receive sensory information. By transmitting the integrated information through the dorsal root of the spinal cord to the secondary neurons of the posterior horn of the spinal cord. The integrated information is then transmitted to the higher center through the ascending conduction tract to produce pain. Moreover, activation of P2Y12 receptor can mediate immune cells to release pro-inflammatory factors, increase damage to nerve cells, and aggravate pain. While inhibits the activation of P2Y12 receptor can effectively relieve pain. Therefore, in this article, we described P2Y12 receptor antagonists and their pharmacological properties. In addition, we explored the potential link between P2Y12 receptor and the nervous system, discussed the intrinsic link of P2Y12 receptor and neuropathic pain and as a potential pharmacological target for pain suppression.

The Signaling Pathway of the ADP Receptor P2Y12 in the Immune System: Recent Discoveries and New Challenges

P2Y12 is a G-protein-coupled receptor that is activated upon ADP binding. Considering its well-established role in platelet activation, blocking P2Y12 has been used as a therapeutic strategy for antiplatelet aggregation in cardiovascular disease patients. However, receptor studies have shown that P2Y12 is functionally expressed not only in platelets and the microglia but also in other cells of the immune system, such as in monocytes, dendritic cells, and T lymphocytes. As a result, studies were carried out investigating whether therapies targeting P2Y12 could also ameliorate inflammatory conditions, such as sepsis, rheumatoid arthritis, neuroinflammation, cancer, COVID-19, atherosclerosis, and diabetes-associated inflammation in animal models and human subjects. This review reports what is known about the expression of P2Y12 in the cells of the immune system and the effect of P2Y12 activation and/or inhibition in inflammatory conditions. Lastly, we will discuss the major problems and challenges in studying this receptor and provide insights on how they can be overcome.

Platelet Reactivity and Cardiovascular Mortality Risk in the LURIC Study

BACKGROUND

The clinical and prognostic implications of platelet reactivity (PR) testing in a P2Y₁₂-inhibitor naïve population are poorly understood.

OBJECTIVES

This explorative study aims to assess the role of PR and explore factors that may modify elevated mortality risk in patients with altered PR.

METHODS

Platelet ADP-induced CD62P and CD63 expression were measured by flow-cytometry in 1520 patients who were referred for coronary angiography in the Ludwigshafen Risk and Cardiovascular Health Study (LURIC).

RESULTS

High- and Low-platelet reactivity to ADP were strong predictors of cardiovascular and all-cause mortality and risk equivalent to the presence of coronary artery disease. (High platelet reactivity 1.4 [95% CI 1.1-1.9]; Low platelet reactivity: 1.4 [95% CI 1.0-2.0]). Relative weight analysis indicated glucose control (HbA1c), renal function ([eGFR]), inflammation (high-sensitive C-reactive protein [hsCRP]) and antiplatelet therapy by Aspirin as consistent mortality risk modifiers in patients with Low- and High-platelet reactivity. Pre-specified stratification of patients by risk modifiers HbA1c (<7.0%), eGFR (>60 mL/min/1.73 m²) and CRP (<3 mg/L) was associated with a lower mortality risk, however irrespective of platelet reactivity. Aspirin treatment was associated with reduced mortality in patients with high platelet reactivity only (p for interaction: 0.02 for CV-death [<0.01 for all-cause mortality].

CONCLUSIONS

Cardiovascular mortality risk in patients with High- and Low platelet reactivity is equivalent to the presence of coronary artery disease. Targeted glucose control, improved kidney function and lower inflammation are associated with reduced mortality risk, however independent of platelet reactivity. In contrast, only in patients with High-platelet reactivity was Aspirin treatment associated with lower mortality.

In Vitro Exposure to Glucose Alters the Expression of Phosphorylated Proteins in Platelets

Diabetes mellitus (DM) is a pro-thrombotic state that can potentially cause serious cardiovascular complications. Platelet hyperactivation plays an important role in these pathological processes, however there is little or no information on the effect of hyperglycemia on platelet proteins. The aim of this study was to identify the molecular targets associated with platelet reactivity under hyperglycemia. Towards this goal, we examined the effects of the exposure of platelets to 1 and 2 h glucose (300 mg/dL) and control (vehicle and osmolality control using mannitol) on platelet proteins (n = 4 samples per group) using two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) combined with MALDI-TOF/TOF tandem mass spectrometry. Two-hour exposure to glucose significantly up-regulated the expression of ATP synthase subunit beta, filamin-A, and L-lactate dehydrogenase A chain in platelets. Pro-Q Diamond staining confirmed the effect of 2 h glucose on vinculin, heat shock protein HSP 90-alpha, filamin-A, and fructose-bisphosphate aldolase A (platelet phosphorylated proteins). The identified proteins are involved in various cellular processes and functions and possibly in platelet reactivity under hyperglycemic conditions.

Shear-Mediated Platelet Microparticles Demonstrate Phenotypic Heterogeneity as to Morphology, Receptor Distribution, and Hemostatic Function

Objective

Implantable cardiovascular therapeutic devices (CTD) including stents, percutaneous heart valves and ventricular assist devices, while lifesaving, impart supraphysiologic shear stress to platelets resulting in thrombotic and bleeding device-related coagulopathy. We previously demonstrated that shear-mediated platelet dysfunction is associated with downregulation of platelet GPIb-IX-V and αIIbβ3 receptors via generation of platelet-derived microparticles (PDMPs). Here, we test the hypothesis that shear-generated PDMPs manifest phenotypical heterogeneity of their morphology and surface expression of platelet receptors, and modulate platelet hemostatic function.

Approach and Results

Human gel-filtered platelets were exposed to continuous shear stress and sonication. Alterations of platelet morphology were visualized using transmission electron microscopy. Surface expression of platelet receptors and PDMP generation were quantified by flow cytometry. Thrombin generation was quantified spectrophotometrically, and platelet aggregation in plasma was measured by optical aggregometry. We demonstrate that platelet exposure to shear stress promotes notable alterations in platelet morphology and ejection of several distinctive types of PDMPs. Shear-mediated microvesiculation is associated with the differential remodeling of platelet receptors with PDMPs expressing significantly higher levels of both adhesion (α _IIb β ₃ , GPIX, PECAM-1, P-selectin, and PSGL-1) and agonist-evoked receptors (P ₂ Y ₁₂ & PAR1). Shear-mediated PDMPs have a bidirectional effect on platelet hemostatic function, promoting thrombin generation and inhibiting platelet aggregation induced by collagen and ADP.

Conclusions

Shear-generated PDMPs demonstrate phenotypic heterogeneity as to morphologic features and defined patterns of surface receptor alteration, and impose a bidirectional effect on platelet hemostatic function. PDMP heterogeneity suggests that a range of mechanisms are operative in the microvesiculation process, contributing to CTD coagulopathy and posing opportunities for therapeutic manipulation.

Enhanced metabolic activation of and platelet response to clopidogrel in T cell-deficient mice through induction of Cyp2c and Cyp3a and inhibition of Ces1

BACKGROUND

T cells and platelets reciprocally coordinate mutual functions through crosstalk or interaction. However, it is not known whether metabolic activation of and platelet response to clopidogrel could be changed if T cells were deficient or impaired in some cases and, if any, how it would work.

OBJECTIVES

The objective of this study was to dissect the potential changes in platelet responses to and metabolic activation of clopidogrel in the case of T cell deficiency and to elucidate their mechanisms involved.

METHODS

BALB/c athymic nude mice or euthymic mice (controls) pretreated with cyclosporine A (CsA), thymosin α1 (Tα1), or their combination were used to investigate the changes in ADP-induced platelet activation and aggregation, systemic exposure of clopidogrel and its metabolites, and mRNA/protein expression and activity levels of clopidogrel-metabolizing enzymes in the liver, respectively.

RESULTS

Nude mice exhibited significantly enhanced antiplatelet effects of clopidogrel due to increased formation of clopidogrel active metabolite in the liver, where the enzyme activity levels of Cyp2c and Cyp3a were significantly elevated compared with control mice. Furthermore, the effects of CsA pretreatment on the metabolism of clopidogrel in euthymic mice were identical to those seen in athymic mice. As expected, concomitant use of Tα1 reversed all the observed effects of CsA on clopidogrel metabolism and relevant metabolic enzymes.

CONCLUSIONS

T cell deficiency or suppression enhances the antiplatelet effects of clopidogrel due to the boosted metabolic activation of clopidogrel in the liver through a dramatic induction of Cyp2c and Cyp3a in mice, suggesting that the metabolism of substrate drugs of Cyp2c and Cyp3a may be enhanced by T cell impairment.

Platelet P2Y1 receptor exhibits constitutive G protein signaling and β-arrestin 2 recruitment

BACKGROUND

Purinergic P2Y₁ and P2Y₁₂ receptors (P2Y₁-R and P2Y₁₂-R) are G protein-coupled receptors (GPCR) activated by adenosine diphosphate (ADP) to mediate platelet activation, thereby playing a pivotal role in hemostasis and thrombosis. While P2Y₁₂-R is the major target of antiplatelet drugs, no P2Y₁-R antagonist has yet been developed for clinical use. However, accumulating data suggest that P2Y₁-R inhibition would ensure efficient platelet inhibition with minimal effects on bleeding. In this context, an accurate characterization of P2Y₁-R antagonists constitutes an important preliminary step.

RESULTS

Here, we investigated the pharmacology of P2Y₁-R signaling through Gq and β-arrestin pathways in HEK293T cells and in mouse and human platelets using highly sensitive resonance energy transfer-based technologies (BRET/HTRF). We demonstrated that at basal state, in the absence of agonist ligand, P2Y₁-R activates Gq protein signaling in HEK293T cells and in mouse and human platelets, indicating that P2Y₁-R is constitutively active in physiological conditions. We showed that P2Y₁-R also promotes constitutive recruitment of β-arrestin 2 in HEK293T cells. Moreover, the P2Y₁-R antagonists MRS2179, MRS2279 and MRS2500 abolished the receptor dependent-constitutive activation, thus behaving as inverse agonists.

CONCLUSIONS

This study sheds new light on P2Y₁-R pharmacology, highlighting for the first time the existence of a constitutively active P2Y₁-R population in human platelets. Given the recent interest of P2Y₁₂-R constitutive activity in patients with diabetes, this study suggests that modification of constitutive P2Y₁-R signaling might be involved in pathological conditions, including bleeding syndrome or high susceptibility to thrombotic risk. Thus, targeting platelet P2Y₁-R constitutive activation might be a promising and powerful strategy for future antiplatelet therapy.

The Function and Regulation of Platelet P2Y12 Receptor

In addition to the key role in hemostasis and thrombosis, platelets have also been wildly acknowledged as immune regulatory cells and involving in the pathogenesis of inflammation-related diseases. Since purine receptor P2Y12 plays a crucial role in platelet activation, P2Y12 antagonists such as clopidogrel, prasugrel, and ticagrelor have been widely used in cardiovascular diseases worldwide in recent decades due to their potent antiplatelet and antithrombotic effects. Meanwhile, the role of P2Y12 in inflammatory diseases has also been extensively studied. Relatively, there are few studies on the regulation of P2Y12. This review first summarizes the various roles of P2Y12 in the process of platelet activation, as well as downstream effects and signaling pathways; then introduces the effects of P2Y12 in inflammatory diseases such as sepsis, atherosclerosis, cancer, autoimmune diseases, and asthma; and finally reviews the current researches on P2Y12 regulation.

Platelet CFTR inhibition enhances arterial thrombosis via increasing intracellular Cl- concentration and activation of SGK1 signaling pathway

Platelet hyperactivity is essential for thrombus formation in coronary artery diseases (CAD). Dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) in patients with cystic fibrosis elevates intracellular Cl- levels ([Cl-]i) and enhanced platelet hyperactivity. In this study, we explored whether alteration of [Cl-]i has a pathological role in regulating platelet hyperactivity and arterial thrombosis formation. CFTR expression was significantly decreased, while [Cl-]i was increased in platelets from CAD patients. In a FeCl3-induced mouse mesenteric arteriole thrombosis model, platelet-specific Cftr-knockout and/or pre-administration of ion channel inhibitor CFTRinh-172 increased platelet [Cl-]i, which accelerated thrombus formation, enhanced platelet aggregation and ATP release, and increased P2Y12 and PAR4 expression in platelets. Conversely, Cftr-overexpressing platelets resulted in subnormal [Cl-]i, thereby decreasing thrombosis formation. Our results showed that clamping [Cl-]i at high levels or Cftr deficiency-induced [Cl-]i increasement dramatically augmented phosphorylation (Ser422) of serum and glucocorticoid-regulated kinase (SGK1), subsequently upregulated P2Y12 and PAR4 expression via NF-κB signaling. Constitutively active mutant S422D SGK1 markedly increased P2Y12 and PAR4 expression. The specific SGK1 inhibitor GSK-650394 decreased platelet aggregation in wildtype and platelet-specific Cftr knockout mice, and platelet SGK1 phosphorylation was observed in line with increased [Cl-]i and decreased CFTR expression in CAD patients. Co-transfection of S422D SGK1 and adenovirus-induced CFTR overexpression in MEG-01 cells restored platelet activation signaling cascade. Our results suggest that [Cl-]i is a novel positive regulator of platelet activation and arterial thrombus formation via the activation of a [Cl-]i-sensitive SGK1 signaling pathway. Therefore, [Cl-]i in platelets is a novel potential biomarker for platelet hyperactivity, and CFTR may be a potential therapeutic target for platelet activation in CAD.

Adenosine diphosphate-induced aggregation is enhanced in platelets obtained from patients with thrombotic primary antiphospholipid syndrome (t-PAPS): Role of P2Y12 -cAMP signaling pathway

BACKGROUND

Thrombotic antiphospholipid syndrome (t-PAPS) is characterized by arterial, venous, or microvascular occlusions, which are explained, in part, by the presence of antiphospholipid (aPL) antibodies. Although there is much evidence indicating that isolated aPL antibodies increase the activity of platelets obtained from healthy volunteers, platelet function in t-PAPS has not been as widely studied.

OBJECTIVE

To evaluate platelet reactivity in t-PAPS patients.

METHODS

Platelet aggregation, protein expression, and cyclic nucleotide levels were carried out in platelet rich plasma (PRP) or washed platelets (WPs) obtained from t-PAPS or healthy volunteers.

RESULTS

ADP-induced aggregation was significantly higher in PRP obtained from t-PAPS than obtained from the control. The protein expression of P2Y12 receptor and Gs alpha was significantly higher and lower, respectively in WPs from t-PAPS patients. In PRP incubated with iloprost or sodium nitroprusside, the residual platelet reactivity induced by ADP was still higher in PRP from t-PAPS than from the control. Lower intracellular levels of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) were observed in unstimulated PRP from t-PAPS patients. The protein expression of soluble guanylate cyclase subunits and phosphodiesterases types 3 and 5 did not differ. The antiplatelet activity of ticagrelor was similar between the groups and cilostazol significantly potentiated this response. Isolated aPL antibodies obtained from t-PAPS patients potentiated ADP-induced aggregation in healthy platelets but did not affect the inhibitory responses induced by iloprost or sodium nitroprusside.

CONCLUSIONS

The overexpression of P2Y12 receptor, accompanied by lower levels of cAMP and cGMP levels produced greater amplitude of ADP aggregation in platelets from t-PAPS patients.

Redox Mechanisms of Platelet Activation in Aging

Aging is intrinsically linked with physiologic decline and is a major risk factor for a broad range of diseases. The deleterious effects of advancing age on the vascular system are evidenced by the high incidence and prevalence of cardiovascular disease in the elderly. Reactive oxygen species are critical mediators of normal vascular physiology and have been shown to gradually increase in the vasculature with age. There is a growing appreciation for the complexity of oxidant and antioxidant systems at the cellular and molecular levels, and accumulating evidence indicates a causal association between oxidative stress and age-related vascular disease. Herein, we review the current understanding of mechanistic links between oxidative stress and thrombotic vascular disease and the changes that occur with aging. While several vascular cells are key contributors, we focus on oxidative changes that occur in platelets and their mediation in disease progression. Additionally, we discuss the impact of comorbid conditions (i.e., diabetes, atherosclerosis, obesity, cancer, etc.) that have been associated with platelet redox dysregulation and vascular disease pathogenesis. As we continue to unravel the fundamental redox mechanisms of the vascular system, we will be able to develop more targeted therapeutic strategies for the prevention and management of age-associated vascular disease.

Dysregulation in the Expression of Platelet Surface Receptors in Acute Coronary Syndrome Patients-Emphasis on P2Y12

The pathological conditions caused by blood platelet activation constitute a fundamental core in the pathogenesis of Acute Coronary Syndrome (ACS). The hyperactivity of platelets in ACS is well-documented, but there is still little research into the molecular basis of phenotypic changes in platelet functionality. To expand the knowledge of this phenomenon, we analyzed the disturbances in the expression of several key platelet receptors and the aspect of regulating potential abnormalities. Platelet surface receptors are responsible for maintaining the hemostatic balance, platelet interaction with immune cells, and support of the coagulation cascade leading to occlusion of the vessel lumen. Due to their prominent role, platelet receptors constitute a major target in pharmacological treatment. Our work aimed to identify the molecular alteration of platelet surface receptors, which showed augmented mRNA expression of P2Y12, GP1BB, ITGA2B, and ITGB3 and increased protein concentrations of P2Y12 and GP IIb/IIIa in ACS. The upregulation of the P2Y12 level was also confirmed by confocal and cytometric visualization. Furthermore, we evaluated the expression of two microRNAs: miR-223-3p and miR-126-3p, which were suggested to regulate platelet P2Y12 expression. Results of our study present new insight into the molecular background of ACS.

Aspirin for Primary Cardiovascular Prevention in Patients with Diabetes: Uncertainties and Opportunities

The use of the antiplatelet agent aspirin (acetylsalicylic acid) was previously routinely recommended for the primary prevention of cardiovascular (CV) events in patients with diabetes, but recent large-scale randomized trials have failed to demonstrate a sizeable net clinical benefit with a once-daily, low-dose (81–100 mg) regimen in this population. Previous pharmacokinetic and pharmacodynamic studies have suggested that the aspirin formulation (enteric-coated) and dosing schedule (once daily) studied in randomized trials for primary prevention of CV events defining contemporary clinical practice may not leverage the full potential of the drug, particularly in patients with diabetes. Indeed, the diabetic platelets bear characteristics that increase their thrombotic potential and alter their pharmacologic response to the drug. Consequently, the appropriateness of studying a uniform aspirin regimen in landmark primary prevention trials needs to be revisited. In this review, we present the evidence showing that diabetes not only increases baseline platelet reactivity, but also alters platelet response to aspirin through different mechanisms including a faster platelet turnover rate. Obesity, which is frequently associated with diabetes, also impacts its pharmacokinetics via an increase in distribution volume. Small-scale pharmacokinetic and pharmacodynamic studies have suggested that the relative aspirin resistance phenotype observed in patients with diabetes may be reversed with a twice-daily dosing schedule, and with nonenteric-coated aspirin formulations. Properly powered randomized controlled trials investigating the efficacy and safety of aspirin dosing schedules and formulations tailored to the population of patients with diabetes are urgently required to optimize patient care.

Effect of aspirin on short-term outcomes in hospitalized patients with COVID-19

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 is an ongoing viral pandemic marked by increased risk of thrombotic events. However, the role of platelets in the elevated observed thrombotic risk in COVID-19 and utility of antiplatelet agents in attenuating thrombosis is unknown. We aimed to determine if the antiplatelet effect of aspirin may mitigate risk of myocardial infarction, cerebrovascular accident, and venous thromboembolism in COVID-19. We evaluated 22,072 symptomatic patients tested for COVID-19. Propensity-matched analyses were performed to determine if treatment with aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) affected thrombotic outcomes in COVID-19. Neither aspirin nor NSAIDs affected mortality in COVID-19. Thus, aspirin does not appear to prevent thrombosis and death in COVID-19. The mechanisms of thrombosis in COVID-19, therefore, appear distinct and the role of platelets as direct mediators of SARS-CoV-2-mediated thrombosis warrants further investigation.

NOD2-mediated P2Y12 upregulation increases platelet activation and thrombosis in sepsis

BACKGROUND

Platelets from septic patients exhibit increased reactivity. However, the underlying mechanism of sepsis-induced platelet hyperactivity is still not completely understood.

OBJECTIVE

P2Y₁₂ is a central receptor for platelet activation. In this study, we investigated the role of platelet P2Y₁₂ in platelet hyperactivity during sepsis.

METHODS

We measured platelet P2Y₁₂ expression and aggregation in response to ADP in septic patients and cecal ligation and puncture (CLP)-treated mice. We also detected the downstream signaling of P2Y₁₂ in resting platelets from patients and mice with sepsis. The role of nucleotide-binding oligomerization domain 2 (NOD2)/RIP2/NF-κB/P65 pathway in sepsis-induced platelet P2Y₁₂ high expression was also investigated. Finally, we compared the antiplatelet and antithrombotic effects of clopidogrel, prasugrel, and ticagrelor in experimental sepsis in mice and rats.

RESULTS

Compared to healthy subjects, platelets from septic patients exhibit P2Y₁₂ hyperactivity and higher P2Y₁₂ expression. pAkt is enhanced and pVASP is impaired in resting platelets from the patients, indicating the constitutive activation of platelet P2Y₁₂ receptor. Mouse sepsis model recapitulates the findings in septic patients. NOD2 deficiency attenuates sepsis-induced platelet P2Y₁₂ high expression, hyperactivity, and thrombosis. Prasugrel and ticagrelor are potent P2Y₁₂ inverse agonists, and exhibit superior antiplatelet and antithrombotic efficacy over clopidogrel in mice and rats with sepsis.

CONCLUSIONS

NOD2 activation upregulates platelet P2Y₁₂ expression, which is constitutively activated and contributes to platelet hyperactivity in septic status. Compared to clopidogrel, prasugrel and ticagrelor are potent P2Y₁₂ inverse agonists with superior antiplatelet and antithrombotic efficacy in experimental sepsis.

Pharmacokinetics and Pharmacodynamics of Approved and Investigational P2Y12 Receptor Antagonists

Coronary artery disease remains the major cause of mortality worldwide. Antiplatelet drugs such as acetylsalicylic acid and P2Y12 receptor antagonists are cornerstone treatments for the prevention of thrombotic events in patients with coronary artery disease. Clopidogrel has long been the gold standard but has major pharmacological limitations such as a slow onset and long duration of effect, as well as weak platelet inhibition with high inter-individual pharmacokinetic and pharmacodynamic variability. There has been a strong need to develop potent P2Y12 receptor antagonists with more favorable pharmacological properties. Prasugrel and ticagrelor are more potent and have a faster onset of action; however, they have shown an increased bleeding risk compared with clopidogrel. Cangrelor is highly potent and has a very rapid onset and offset of effect; however, its indication is limited to P2Y12 antagonist-naïve patients undergoing percutaneous coronary intervention. Two novel P2Y12 receptor antagonists are currently in clinical development, namely vicagrel and selatogrel. Vicagrel is an analog of clopidogrel with enhanced and more efficient formation of its active metabolite. Selatogrel is characterized by a rapid onset of action following subcutaneous administration and developed for early treatment of a suspected acute myocardial infarction. This review article describes the clinical pharmacology profile of marketed P2Y12 receptor antagonists and those under development focusing on pharmacokinetic, pharmacodynamic, and drug-drug interaction liability.

Molecular mapping of platelet hyperreactivity in diabetes: the stress proteins complex HSPA8/Hsp90/CSK2α and platelet aggregation in diabetic and normal platelets

The molecular understanding of the pathophysiological changes elicited by diabetes in platelets may help in further elucidating the involvement of this pseudo-cell in the increased risk of developing cardiovascular disease and thrombosis in diabetic subjects. We aimed to investigate the differential characteristics of platelets from diabetic patients and nondiabetic controls to unveil the molecular mechanisms behind the increased platelet reactivity in diabetes. We compared platelets from diabetic and control subjects by 2 dimensional-electrophoresis followed by mass spectrometry. Changes in selected differential proteins were validated by immunoprecipitation assays and western blot. Platelet aggregation was measured by light transmittance aggregometry induced by collagen and ADP, and dynamic coagulation analysis of whole blood was measured by thromboelastometry. We observed significant differences in proteins related to platelet aggregation, cell migration, and cell homeostasis. Subjects with diabetes showed higher platelet aggregation and thrombogenicity and higher contents of the stress-related protein complex HSPA8/Hsp90/CSK2α than nondiabetic subjects. Changes in the chaperones HSPA8 and Hsp90, and in CSK2α protein contents correlated with changes in platelet aggregation and blood coagulation activity. In conclusion, the complex HSPA8/Hsp90/CSK2α is involved in diabetes-related platelet hyperreactivity. The role of the HSPA8/Hsp90/CSK2α complex may become a molecular target for the development of future preventive and therapeutic strategies for platelet dysfunction associated with diabetes and its complications.

Enhanced Diamagnetic Repulsion of Blood Cells Enables Versatile Plasma Separation for Biomarker Analysis in Blood

A hemolysis-free and highly efficient plasma separation platform enabled by enhanced diamagnetic repulsion of blood cells in undiluted whole blood is reported. Complete removal of blood cells from blood plasma is achieved by supplementing blood with superparamagnetic iron oxide nanoparticles (SPIONs), which turns the blood plasma into a paramagnetic condition, and thus, all blood cells are repelled by magnets. The blood plasma is successfully collected from 4 mL of blood at flow rates up to 100 µL min^-1 without losing plasma proteins, platelets, or exosomes with 83.3±1.64% of plasma volume recovery, which is superior over the conventional microfluidic methods. The theoretical model elucidates the diamagnetic repulsion of blood cells considering hematocrit-dependent viscosity, which allows to determine a range of optimal flow rates to harvest platelet-rich plasma and platelet-free plasma. For clinical validations, it is demonstrated that the method enables the greater recovery of bacterial DNA from the infected blood than centrifugation and the immunoassay in whole blood without prior plasma separation.

Diabetes and hypertension: Pivotal involvement of purinergic signaling

Diabetes mellitus (DM) and hypertension are highly prevalent worldwide health problems and frequently associated with severe clinical complications, such as diabetic cardiomyopathy, nephropathy, retinopathy, neuropathy, stroke, and cardiac arrhythmia, among others. Despite all existing research results and reasonable speculations, knowledge about the role of purinergic system in individuals with DM and hypertension remains restricted. Purinergic signaling accounts for a complex network of receptors and extracellular enzymes responsible for the recognition and degradation of extracellular nucleotides and adenosine. The main components of this system that will be presented in this review are: P1 and P2 receptors and the enzymatic cascade composed by CD39 (NTPDase; with ATP and ADP as a substrate), CD73 (5'-nucleotidase; with AMP as a substrate), and adenosine deaminase (ADA; with adenosine as a substrate). The purinergic system has recently emerged as a central player in several physiopathological conditions, particularly those linked to inflammatory responses such as diabetes and hypertension. Therefore, the present review focuses on changes in both purinergic P1 and P2 receptor expression as well as the activities of CD39, CD73, and ADA in diabetes and hypertension conditions. It can be postulated that the manipulation of the purinergic axis at different levels can prevent or exacerbate the insurgency and evolution of diabetes and hypertension working as a compensatory mechanism.

Diabetes and Thrombosis: A Central Role for Vascular Oxidative Stress

Diabetes mellitus is the fifth most common cause of death worldwide. Due to its chronic nature, diabetes is a debilitating disease for the patient and a relevant cost for the national health system. Type 2 diabetes mellitus is the most common form of diabetes mellitus (90% of cases) and is characteristically multifactorial, with both genetic and environmental causes. Diabetes patients display a significant increase in the risk of developing cardiovascular disease compared to the rest of the population. This is associated with increased blood clotting, which results in circulatory complications and vascular damage. Platelets are circulating cells within the vascular system that contribute to hemostasis. Their increased tendency to activate and form thrombi has been observed in diabetes mellitus patients (i.e., platelet hyperactivity). The oxidative damage of platelets and the function of pro-oxidant enzymes such as the NADPH oxidases appear central to diabetes-dependent platelet hyperactivity. In addition to platelet hyperactivity, endothelial cell damage and alterations of the coagulation response also participate in the vascular damage associated with diabetes. Here, we present an updated interpretation of the molecular mechanisms underlying vascular damage in diabetes, including current therapeutic options for its control.

Physiologically-Based Pharmacokinetic-Pharmacodynamics Model Characterizing CYP2C19 Polymorphisms to Predict Clopidogrel Pharmacokinetics and Its Anti-Platelet Aggregation Effect Following Oral Administration to Coronary Artery Disease Patients With or Without Diabetes

Background and Objective: Clopidogrel (CLOP) is commonly used in coronary artery disease (CAD) patients with or without diabetes (DM), but these patients often suffer CLOP resistance, especially those with diabetes. This study was aimed to develop a physiologically-based pharmacokinetic-pharmacodynamic (PBPK-PD) model to describe the pharmacokinetics and pharmacodynamics of clopidogrel active metabolite (CLOP-AM) in CAD patients with or without DM.

Methods: The PBPK-PD model was first established and validated in healthy subjects and then in CAD patients with or without DM. The influences of CYP2C19, CYP2C9, CYP3A4, carboxylesterase 1 (CES1), gastrointestinal transit rates (K_t,i) and platelets response to CLOP-AM (k_irre) on predicted pharmacokinetics and pharmacodynamics were investigated, followed with their individual and integrated effects on CLOP-AM pharmacokinetics due to changes in DM status.

Results: Most predictions fell within 0.5–2.0 folds of observations, indicating successful predictions. Sensitivity analysis showed that contributions of interested factors to pharmacodynamics were CES1> k_irre> K_t,i> CYP2C19 > CYP3A4> CYP2C9. Mimicked analysis showed that the decreased exposure of CLOP-AM by DM was mainly attributed to increased CES1 activity, followed by decreased CYP2C19 activity.

Conclusion: The pharmacokinetics and pharmacodynamics of CLOP-AM were successfully predicted using the developed PBPK-PD model. Clopidogrel resistance by DM was the integrated effects of altered K_t,i, CYP2C19, CYP3A4, CES1 and k_irre.

Sex-Specific Platelet Activation Through Protease-Activated Receptors Reverses in Myocardial Infarction

OBJECTIVE

The platelet phenotype in certain patients and clinical contexts may differ from healthy conditions. We evaluated platelet activation through specific receptors in healthy men and women, comparing this to patients presenting with ST-segment-elevation myocardial infarction and non-ST-segment-elevation myocardial infarction. Approach and Results: We identified independent predictors of platelet activation through certain receptors and a murine MI model further explored these findings. Platelets from healthy women and female mice are more reactive through PARs (protease-activated receptors) compared with platelets from men and male mice. Multivariate regression analyses revealed male sex and non-ST-segment-elevation myocardial infarction as independent predictors of enhanced PAR1 activation in human platelets. Platelet PAR1 signaling decreased in women and increased in men during MI which was the opposite of what was observed during healthy conditions. Similarly, in mice, thrombin-mediated platelet activation was greater in healthy females compared with males, and lesser in females compared with males at the time of MI.

CONCLUSIONS

Sex-specific signaling in platelets seems to be a cross-species phenomenon. The divergent platelet phenotype in males and females at the time of MI suggests a sex-specific antiplatelet drug regimen should be prospectively evaluated.

SARS-CoV-2 Receptors are Expressed on Human Platelets and the Effect of Aspirin on Clinical Outcomes in COVID-19 Patients

Coronavirus disease-2019 (COVID-19) caused by SARS-CoV-2 is an ongoing viral pandemic marked by increased risk of thrombotic events. However, the role of platelets in the elevated observed thrombotic risk in COVID-19 and utility of anti-platelet agents in attenuating thrombosis is unknown. We aimed to determine if human platelets express the known SARS-CoV-2 receptor-protease axis on their cell surface and assess whether the anti-platelet effect of aspirin may mitigate risk of myocardial infarction (MI), cerebrovascular accident (CVA), and venous thromboembolism (VTE) in COVID-19. Expression of ACE2 and TMPRSS2 on human platelets were detected by immunoblotting and confirmed by confocal microscopy. We evaluated 22,072 symptomatic patients tested for COVID-19. Propensity-matched analyses were performed to determine if treatment with aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) affected thrombotic outcomes in COVID-19. Neither aspirin nor NSAIDs affected mortality in COVID-19. However, both aspirin and NSAID therapies were associated with increased risk of the combined thrombotic endpoint of (MI), (CVA), and (VTE). Thus, while platelets clearly express ACE2-TMPRSS2 receptor-protease axis for SARS-CoV-2 infection, aspirin does not prevent thrombosis and death in COVID-19. The mechanisms of thrombosis in COVID-19, therefore, appears distinct and the role of platelets as direct mediators of SARS-CoV-2-mediated thrombosis warrants further investigation.

Antithrombotic Therapy for Atherosclerotic Cardiovascular Disease Risk Mitigation in Patients With Coronary Artery Disease and Diabetes Mellitus

Patients with diabetes mellitus (DM) are characterized by enhanced thrombotic risk attributed to multiple mechanisms including hyperreactive platelets, hypercoagulable status, and endothelial dysfunction. As such, they are more prone to atherosclerotic cardiovascular events than patients without DM, both before and after coronary artery disease (CAD) is established. In patients with DM without established CAD, primary prevention with aspirin is not routinely advocated because of its increased risk of major bleeding that largely offsets its ischemic benefit. In patients with DM with established CAD, secondary prevention with antiplatelet drugs is an asset of pharmacological strategies aimed at reducing the risk of atherosclerotic cardiovascular events and their adverse prognostic consequences. Such antithrombotic strategies include single antiplatelet therapy (eg, with aspirin or a P2Y₁₂ inhibitor), dual antiplatelet therapy (eg, aspirin combined with a P2Y₁₂ inhibitor), and dual-pathway inhibition (eg, aspirin combined with the vascular dose of the direct oral anticoagulant rivaroxaban) for patients with chronic ischemic heart disease, acute coronary syndromes, and those undergoing percutaneous coronary intervention. Because of their increased risk of thrombotic complications, patients with DM commonly achieve enhanced absolute benefit from more potent antithrombotic approaches compared with those without DM, which most often occurs at the expense of increased bleeding. Nevertheless, studies have shown that when excluding individuals at high risk for bleeding, the net clinical benefit favors the use of intensified long-term antithrombotic therapy in patients with DM and CAD. Several studies are ongoing to establish the role of novel antithrombotic strategies and drug formulations in maximizing the net benefit of antithrombotic therapy for patients with DM. The scope of this review article is to provide an overview of current and evolving antithrombotic strategies for primary and secondary prevention of atherosclerotic cardiovascular events in patients with CAD and DM.

GSK669, a NOD2 receptor antagonist, inhibits thrombosis and oxidative stress via targeting platelet GPVI

BACKGROUND AND PURPOSE

Previously, we discovered that the activation of nucleotide-binding oligomerization domain 2 (NOD2) enhances platelet activation. We here investigated the antiplatelet and antithrombotic potential of GSK669, a NOD2 antagonist.

EXPERIMENTAL APPROACH

Effects of GSK669 on platelet functions, reactive oxygen species (ROS) and proinflammatory cytokine generation were detected. NOD2-/- platelets were used to confirm GSK669 target. The interaction between GSK669 and glycoprotein VI (GPVI) was detected using surface plasmon resonance (SPR) spectroscopy. GPVI downstream signaling was examined by Western blot. The antithrombotic and antioxidative effects were investigated using mouse mesenteric arteriole thrombosis model and pulmonary embolism model.

KEY RESULTS

GSK669 significantly inhibits platelet proinflammatory cytokine release induced by muramyl dipeptide, platelet aggregation, ATP release, and ROS generation induced by collagen and collagen related peptide (CRP). Platelet spreading and clot retraction are also inhibited. GSK669 also decreases collagen-induced phosphorylation of Src, Syk, PLCγ2, and Akt. The antiplatelet effect of GSK669 is NOD2-independent and mediated by GPVI antagonism. Consistent with its antiplatelet activity as a GPVI antagonist, GSK669 inhibits platelet adhesion on collagen in flow condition. Notably, GSK669 inhibits mouse mesenteric arteriole thrombosis similarly to aspirin without bleeding. The antithrombotic effect of GSK669 is further confirmed in the pulmonary embolism model; decreased malonaldehyde (MDA) and increased superoxide dismutase (SOD) levels in mouse plasma reveal a significant antioxidant effect of GSK669.

CONCLUSION AND IMPLICATIONS

Beyond its anti-inflammatory effect as a NOD2 antagonist, GSK669 is also an efficient and safe antiplatelet agent combined with antioxidant effect by targeting GPVI. An antiplatelet agent bearing antioxidative and anti-inflammatory activities without bleeding risk may have therapeutic advantage over current antiplatelet drugs for atherothrombosis.

The sodium-glucose cotransporter-2 (SGLT2) inhibitors synergize with nitric oxide and prostacyclin to reduce human platelet activation

Gliflozins (canagliflozin, dapagliflozin and empagliflozin) are the newest anti-hyperglycemic class and have offered cardiovascular and renal benefits. Because platelets are involved in the atherothrombosis process, this study is aimed to evaluate the direct effect of gliflozins on platelet reactivity. Platelet-rich plasma (PRP) or washed platelets (WP) were obtained from healthy volunteers. Aggregation, flow cytometry for glycoprotein IIb/IIIa, cyclic nucleotides and intracellular calcium levels, Western blot, thromboxane B₂ (TXB₂) measurement and COX-1 activity were performed in the presence of gliflozins (1-30 μM) alone or in combination with sodium nitroprusside (SNP, 10 or 100 nM) + iloprost (ILO, 0.1 or 1 nM). SGLT2 protein is not expressed on human platelets. Gliflozins produced little inhibitory effect in agonists-induced aggregation and this effect was greatly potentiated by ~10-fold in the presence of SNP + ILO, accompanied by lower levels of TXB₂ (58.1 ± 5.1%, 47.1 ± 7.2% and 43.4 ± 9.2% inhibition for canagliflozin, dapagliflozin and empagliflozin, respectively). The activity of COX-1 was not affected by gliflozins. Collagen increased Ca²⁺ levels and α(IIb)β(3) activation, both of which were significantly reduced by gliflozins + SNP + ILO. The intracellular levels of cAMP and cGMP and the protein expression of p-VASPSer157 and p-VASPSer239 were not increased by gliflozins while the expression of the serine-threonine kinase, AktSer473 was markedly reduced. Our results showed that the antiplatelet activity of gliflozins were greatly enhanced by nitric oxide and prostacyclin, thus suggesting that the cardiovascular protection seen by this class of drugs could be in part due to platelet inhibition.

PCSK9 (Proprotein Convertase Subtilisin/Kexin 9) Enhances Platelet Activation, Thrombosis, and Myocardial Infarct Expansion by Binding to Platelet CD36

BACKGROUND

PCSK9 (proprotein convertase subtilisin/kexin 9), mainly secreted by the liver and released into the blood, elevates plasma low-density lipoprotein cholesterol by degrading low-density lipoprotein receptor. Pleiotropic effects of PCSK9 beyond lipid metabolism have been shown. However, the direct effects of PCSK9 on platelet activation and thrombosis, and the underlying mechanisms, as well, still remain unclear.

METHODS

We detected the direct effects of PCSK9 on agonist-induced platelet aggregation, dense granule ATP release, integrin αIIbβ3 activation, α-granule release, spreading, and clot retraction. These studies were complemented by in vivo analysis of FeCl₃-injured mouse mesenteric arteriole thrombosis. We also investigated the underlying mechanisms. Using the myocardial infarction (MI) model, we explored the effects of PCSK9 on microvascular obstruction and infarct expansion post-MI.

RESULTS

PCSK9 directly enhances agonist-induced platelet aggregation, dense granule ATP release, integrin αIIbβ3 activation, P-selectin release from α-granules, spreading, and clot retraction. In line, PCSK9 enhances in vivo thrombosis in a FeCl₃-injured mesenteric arteriole thrombosis mouse model, whereas PCSK9 inhibitor evolocumab ameliorates its enhancing effects. Mechanism studies revealed that PCSK9 binds to platelet CD36 and thus activates Src kinase and MAPK (mitogen-activated protein kinase)-extracellular signal-regulated kinase 5 and c-Jun N-terminal kinase, increases the generation of reactive oxygen species, and activates the p38MAPK/cytosolic phospholipase A2/cyclooxygenase-1/thromboxane A₂ signaling pathways downstream of CD36 to enhance platelet activation, as well. Using CD36 knockout mice, we showed that the enhancing effects of PCSK9 on platelet activation are CD36 dependent. It is important to note that aspirin consistently abolishes the enhancing effects of PCSK9 on platelet activation and in vivo thrombosis. Last, we showed that PCSK9 activating platelet CD36 aggravates microvascular obstruction and promotes MI expansion post-MI.

CONCLUSIONS

PCSK9 in plasma directly enhances platelet activation and in vivo thrombosis, and MI expansion post-MI, as well, by binding to platelet CD36 and thus activating the downstream signaling pathways. PCSK9 inhibitors or aspirin abolish the enhancing effects of PCSK9, supporting the use of aspirin in patients with high plasma PCSK9 levels in addition to PCSK9 inhibitors to prevent thrombotic complications.

SARS-CoV-2 binds platelet ACE2 to enhance thrombosis in COVID-19

BACKGROUND

Critically ill patients diagnosed with COVID-19 may develop a pro-thrombotic state that places them at a dramatically increased lethal risk. Although platelet activation is critical for thrombosis and is responsible for the thrombotic events and cardiovascular complications, the role of platelets in the pathogenesis of COVID-19 remains unclear.

METHODS

Using platelets from healthy volunteers, non-COVID-19 and COVID-19 patients, as well as wild-type and hACE2 transgenic mice, we evaluated the changes in platelet and coagulation parameters in COVID-19 patients. We investigated ACE2 expression and direct effect of SARS-CoV-2 virus on platelets by RT-PCR, flow cytometry, Western blot, immunofluorescence, and platelet functional studies in vitro, FeCl3-induced thrombus formation in vivo, and thrombus formation under flow conditions ex vivo.

RESULTS

We demonstrated that COVID-19 patients present with increased mean platelet volume (MPV) and platelet hyperactivity, which correlated with a decrease in overall platelet count. Detectable SARS-CoV-2 RNA in the blood stream was associated with platelet hyperactivity in critically ill patients. Platelets expressed ACE2, a host cell receptor for SARS-CoV-2, and TMPRSS2, a serine protease for Spike protein priming. SARS-CoV-2 and its Spike protein directly enhanced platelet activation such as platelet aggregation, PAC-1 binding, CD62P expression, α granule secretion, dense granule release, platelet spreading, and clot retraction in vitro, and thereby Spike protein enhanced thrombosis formation in wild-type mice transfused with hACE2 transgenic platelets, but this was not observed in animals transfused with wild-type platelets in vivo. Further, we provided evidence suggesting that the MAPK pathway, downstream of ACE2, mediates the potentiating role of SARS-CoV-2 on platelet activation, and that platelet ACE2 expression decreases following SARS-COV-2 stimulation. SARS-CoV-2 and its Spike protein directly stimulated platelets to facilitate the release of coagulation factors, the secretion of inflammatory factors, and the formation of leukocyte-platelet aggregates. Recombinant human ACE2 protein and anti-Spike monoclonal antibody could inhibit SARS-CoV-2 Spike protein-induced platelet activation.

CONCLUSIONS

Our findings uncovered a novel function of SARS-CoV-2 on platelet activation via binding of Spike to ACE2. SARS-CoV-2-induced platelet activation may participate in thrombus formation and inflammatory responses in COVID-19 patients.

PAK Membrane Translocation and Phosphorylation Regulate Platelet Aggregation Downstream of Gi and G12/13 Pathways

Platelet activation plays a pivotal role in physiological hemostasis and pathological thrombosis causing heart attack and stroke. Previous studies conclude that simultaneous activation of Gi and G_12/13 signaling pathways is sufficient to cause platelet aggregation. However, using Gq knockout mice and Gq-specific inhibitors, we here demonstrated that platelet aggregation downstream of coactivation of Gi and G_12/13 depends on agonist concentrations; coactivation of Gi and G_12/13 pathways only induces platelet aggregation under higher agonist concentrations. We confirmed Gi and G_12/13 pathway activation by showing cAMP (cyclic adenosine monophosphate) decrease and RhoA activation in platelets stimulated at both low and high agonist concentrations. Interestingly, we found that though Akt and PAK (p21-activated kinase) translocate to the platelet membrane upon both low and high agonist stimulation, membrane-translocated Akt and PAK only phosphorylate at high agonist concentrations, correlating well with platelet aggregation downstream of concomitant Gi and G_12/13 pathway activation. PAK inhibitor abolishes Akt phosphorylation, inhibits platelet aggregation in vitro and arterial thrombus formation in vivo. We propose that the PAK-PI3K/Akt pathway mediates platelet aggregation downstream of Gi and G_12/13, and PAK may represent a potential antiplatelet and antithrombotic target.

Cangrelor, Tirofiban, and Chewed or Standard Prasugrel Regimens in Patients With ST-Segment-Elevation Myocardial Infarction: Primary Results of the FABOLUS-FASTER Trial

Supplemental Digital Content is available in the text.

Background:

Standard administration of newer oral P2Y₁₂ inhibitors, including prasugrel or ticagrelor, provides suboptimal early inhibition of platelet aggregation (IPA) in patients with ST-segment–elevation myocardial infarction undergoing primary percutaneous coronary intervention. We aimed to investigate the effects of cangrelor, tirofiban, and prasugrel, administered as chewed or integral loading dose, on IPA in patients undergoing primary percutaneous coronary intervention.

Methods:

The FABOLUS-FASTER trial (Facilitation Through Aggrastat or Cangrelor Bolus and Infusion Over Prasugrel: A Multicenter Randomized Open-Label Trial in Patients with ST-Elevation Myocardial Infarction Referred for Primary Percutaneous Intervention) is an investigator-initiated, multicenter, open-label, randomized study. A total of 122 P2Y₁₂-naive patients with ST-segment–elevation myocardial infarction were randomly allocated (1:1:1) to cangrelor (n=40), tirofiban (n=40) (both administered as bolus and 2-hour infusion followed by 60 mg of prasugrel), or 60-mg loading dose of prasugrel (n=42). The latter group underwent an immediate 1:1 subrandomization to chewed (n=21) or integral (n=21) tablets administration. The trial was powered to test 3 hypotheses (noninferiority of cangrelor compared with tirofiban using a noninferiority margin of 9%, superiority of both tirofiban and cangrelor compared with chewed prasugrel, and superiority of chewed prasugrel as compared with integral prasugrel, each with α=0.016 for the primary end point, which was 30-minute IPA at light transmittance aggregometry in response to 20 μmol/L adenosine diphosphate.

Results:

At 30 minutes, cangrelor did not satisfy noninferiority compared with tirofiban, which yielded superior IPA over cangrelor (95.0±8.9 versus 34.1±22.5; P<0.001). Cangrelor or tirofiban were both superior to chewed prasugrel (IPA, 10.5±11.0; P<0.001 for both comparisons), which did not provide higher IPA over integral prasugrel (6.3±11.4; P=0.47), despite yielding higher prasugrel active metabolite concentration (ng/mL; 62.3±82.6 versus 17.1±43.5; P=0.016).

Conclusions:

Cangrelor provided inferior IPA compared with tirofiban; both treatments yielded greater IPA compared with chewed prasugrel, which led to higher active metabolite concentration but not greater IPA compared with integral prasugrel.

Registration:

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02978040; URL: https://www.clinicaltrialsregister.eu; EudraCT 2017-001065-24.

Recent advances in unraveling the molecular mechanisms and functions of HOXA11‑AS in human cancers and other diseases (Review)

A large number of previously published research articles have demonstrated that the expression levels of long noncoding RNAs (lncRNAs) are generally dysregulated, either through overexpression or underexpression, in cancer and other types of disease. As a recently discovered lncRNA, HOXA11 antisense RNA (HOXA11‑AS) is able to serve as an oncogenic or tumor‑suppressor gene and serves a vital role in the processes of proliferation, invasion, and migration of cancer cells. HOXA11‑AS appears to be a major factor contributing to epigenetic modification, and exerts transcriptional, post‑transcriptional, translational and post‑translational regulatory effects on genes through a variety of mechanisms; for example, by competing endogenous RNA (ceRNA) and a molecular scaffold mechanism. A number of reports have demonstrated that HOXA11‑AS functions as a protein scaffold for polycomb repressive complex 2 (PRC2), lysine‑specific histone demethylase 1 (LSD1) and DNA methyltransferase 1 (DNMT1) to perform epigenetic modifications on chromosomes in the nucleus. Furthermore, HOXA11‑AS is also located in the cytoplasm and can act as a ceRNA, which sponges miRNAs. In addition, HOXA11‑AS may be useful as a biomarker for the diagnosis and prognosis of cancer. In the present review article, the clinical value, phenotype and mechanism of HOXA11‑AS in a variety of tumors types are briefly summarized, as well as its clinical value in certain additional diseases. The perspective of the authors is that HOXA11‑AS may represent an effective tumor marker and therapeutic target for cancer diagnosis and therapy.

Opposite Modulatory Effects of Crataegus aronia Aqueous Extract on Platelet Aggregation in Rats

OBJECTIVES

To reveal the mechanisms behind the dual effects of Crataegus aronia (C. aronia) aqueous extract on platelet aggregation by focusing on function, regulation, expression, and signaling of platelets P₂Y₁₂ receptors.

METHODS

Adult male Wistar rats (120 ± 10 g) were classified as control received the vehicle, C. aronia (200 mg/kg), and C. aronia (2,000 mg/kg)-treated rats. After treatments for consecutive 7 days, hematological and molecular experiments were conducted to detect alterations in platelet aggregation, thromboxane B2 (THXB2) and intracellular reactive oxygen species (ROS) content; protein levels of P₂Y₁₂, p-Akt, cyclic adenosine monophosphate (cAMP), phosphorylated vasodilator-stimulated-phosphoprotein (p-VASP), nuclear factor κB (NF-κB), P-selectin, and etc. in platelets were determined by Western blot; mRNA expressions of P₂Y₁₂ and some inflammatory markers were determined by real-time polymerase chain reaction.

RESULTS

At a concentration of 200 mg/kg, C. aronia inhibited platelet aggregation through multiple interconnected mechanisms including downregulation P₂Y₁₂ synthesis and expression, stimulating intracellular cAMP levels and protein levels of p-VASP, inhibiting platelets THXB2 release and protein levels of P-selectin. Also, it inhibited platelets level of ROS and of NF-κB, a major signaling pathway that stimulates the expression of P₂Y₁₂ and THXA2 synthesis. Opposite findings were seen in platelets of rats received C. aronia at a concentration of 2,000 mg/kg. Interestingly, co-administration of N-acetylcysteine prevented all hematological and molecular alterations exerted by the high dose of the extract and inhibited platelet aggregation.

CONCLUSION

Oral administration of C. aronia at low dose inhibits platelet aggregation by reducing THXB2 release, expression of P-selectin and activating cAMP and Akt signaling through two major mechanisms including downregulation of P₂Y₁₂ and inhibition of ROS-induced activation of NF-κB, an effect that is observed to be in the opposite direction with its high dose.

Modulators of platelet function in aging

Platelets are small, anucleated effector cells that play an important role in linking the hemostatic and inflammatory processes in the body. Platelet function is known to be altered under various inflammatory conditions including aging. A gain in platelet function during aging can increase the risk of thrombotic events, such as stroke and acute myocardial infarction. Anti-platelet therapy is designed to reduce risk of serious cerebrovascular and cardiovascular events, but the adverse consequences of therapy, such as risk for bleeding increases with aging as well. Age-associated comorbidities such as obesity, diabetes, and hyperlipidemia also contribute to increased platelet activity and thus can enhance the risk of thrombosis. Therefore, identification of unique mechanisms of platelet dysfunction in aging and in age-associated comorbidities is warranted to design novel antiplatelet drugs. This review outlines some of the current areas of research on aging-related mechanisms of platelet hyperactivity and addresses the clinical urgency for designing anti-platelet therapies toward novel molecular targets in the aging population.

Antiplatelet activity of astaxanthin in control- and high cholesterol-fed rats mediated by down-regulation of P2Y12, inhibition of NF-κB, and increasing intracellular levels of cAMP

This study evaluated the antiplatelet effect of the plant carotenoid, astaxanthin (ASTX) in rats fed either control or high cholesterol plus cholic acid diet (HCCD) and possible underlying mechanisms. Adult male Wistar rats were divided into four groups (n = 8/each), namely, control (fed normal diet), control + ASTX (10 mg/kg/day), HCCD-fed rats, and HCCD + ASTX-treated rats. Diets and treatments were orally administered daily for 30 days. In both control and HCCD-fed rats, ASTX significantly increased fecal levels of triglycerides and cholesterol, reduced platelet count, prolonged bleeding time, and inhibited platelet aggregation. It also reduced platelet levels of reactive oxygen species (ROS) and Bcl-2; thromboxane B2 (TXB2) release; and the expression of P2Y₁₂, P-selectin, and CD36 receptors. Moreover, the activity NF-κB p65 and Akt was inhibited. Concomitantly, it increased the protein levels of cleaved caspase-3 and vasodilator-stimulated phosphoprotein (p-VASP) as well as intracellular levels of cAMP. However, in HCCD-fed rats, the effects of ASTX were associated with reduced serum levels of ox-LDL-c and fasting plasma glucose levels. In conclusion, antiplatelet effects of ASTX involve ROS scavenging, inhibiting NF-κB activity, down-regulating P2Y₁₂ expression, and increasing intracellular levels of cAMP that are attributed to its antioxidant, hypolipidemic, and anti-inflammatory effects.

Long-term effect of clopidogrel in patients with and without diabetes: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Previous studies have shown that patients with diabetes mellitus (DM) respond poorly to clopidogrel treatment.

AIM

To systematically evaluate the efficacy of clopidogrel for the treatment of acute coronary syndromes or ischemic stroke in patients with or without DM.

METHODS

PubMed, the Cochrane Central Register of Controlled Trials, and EMBASE were searched from 1980 on 27 June 2019 to identify relevant randomized controlled trials that compared the effect of a combination of clopidogrel and aspirin with aspirin alone. A random-effects meta-analysis was used to estimate the hazard ratio (HR) and its 95% confidence interval (CI). Sensitivity analysis was performed using a fixed-effect model. The I² statistic was used to evaluate the heterogeneity of the study data.

RESULTS

Six randomized controlled trials, comprising 43352 participants (13491 with and 29861 without DM) who had received antiplatelet therapy for ≥ 3 mo, were included in the meta-analysis. Compared with aspirin alone, a combination of clopidogrel and aspirin significantly reduced the risk of any cardiovascular event in patients without DM (HR = 0.78, 95%CI: 0.71–0.86, P < 0.001; I² = 23%, P = 0.26). Clopidogrel plus aspirin also significantly reduced cardiovascular risk in patients with DM, although the effect was smaller (HR = 0.89, 95%CI: 0.81–0.99, P = 0.030; I² = 0%, P = 0.74). Nevertheless, there was no significant difference in the efficacy of clopidogrel at reducing the risk of cardiovascular events in patients with DM vs those without (P for interaction = 0.062).

CONCLUSION

Thus, the present study shows that the addition of clopidogrel to aspirin significantly lowers cardiovascular risk in patients with or without DM who have experienced ischemic cardiovascular disease. The beneficial effect of the addition of clopidogrel to aspirin for patients with DM was lower than that in patients without DM, although the modifying effect of DM did not reach significance.