Assessment of platelet functional activity in healthy individuals and patients receiving antiplatelet therapy. Possible inconsistencies between aggregation and flow cytometry tests.

Platelet functional activity was assessed in healthy volunteers (HV, n=92), patients with stable angina pectoris (SA, n=42) and acute coronary syndrome (ACS, n=73), treated with acetylsalicylic acid (ASA) + clopidogrel and ASA + ticagrelor, respectively. In all HV and patients we have compared parameters of platelet aggregation (maximum light transmission and velocity, Tmax and Vmax) and parameters, characterizing exposure of platelet activation markers, evaluated by flow cytometry. HV platelets were activated by 10 µM, 1 µM TRAP, and 20 µM, 5 µM, 2.5 µM ADP; patient platelets were activated by 10 µM TRAP and by 20 µM and 5 µM ADP. Strong and significant correlations between the aggregation and flow cytometry parameters (the r correlation coefficient from 0.4 up to >0.6) most frequently were registered in HV platelet during activation by 1 µM TRAP and in SA patients during platelet activation by 20 µM and 5 µM ADP. However, in many other cases these correlations were rather weak (r < 0.3) and sometimes statistically insignificant. In HV the differences in PAC-1 binding parameters between platelets activated by 10 µM TRAP (the strongest agonist) and all ADP concentrations were negligible (≤ 10%), while CD62P binding (at all ADP concentrations) and LTA parameters for (5 µM and 2.5 µM ADP) were significantly lower (by 40-60%). Antiplatelet therapy in patients decreased all parameters as compared to HV, but to varying extents. For 10 µM TRAP the MFI index for PAC-1 binding (40-50% decrease) and for both ADP concentrations the Tmax values (60-85% decrease) appeared to be the most sensitive in comparison with the other parameters that decreased to a lesser extent. The data obtained indicate a possibility of inconsistency between different LTA and flow cytometry parameters in assessing platelet activity and efficacy of antiplatelet drugs.

Antiplatelet Effects of Flavonoid Aglycones Are Mediated by Activation of Cyclic Nucleotide-Dependent Protein Kinases.

Flavonoid aglycones are secondary plant metabolites that exhibit a broad spectrum of pharmacological activities, including anti-inflammatory, antioxidant, anticancer, and antiplatelet effects. However, the precise molecular mechanisms underlying their inhibitory effect on platelet activation remain poorly understood. In this study, we applied flow cytometry to analyze the effects of six flavonoid aglycones (luteolin, myricetin, quercetin, eriodictyol, kaempferol, and apigenin) on platelet activation, phosphatidylserine externalization, formation of reactive oxygen species, and intracellular esterase activity. We found that these compounds significantly inhibit thrombin-induced platelet activation and decrease formation of reactive oxygen species in activated platelets. The tested aglycones did not affect platelet viability, apoptosis induction, or procoagulant platelet formation. Notably, luteolin, myricetin, quercetin, and apigenin increased thrombin-induced thromboxane synthase activity, which was analyzed by a spectrofluorimetric method. Our results obtained from Western blot analysis and liquid chromatography-tandem mass spectrometry demonstrated that the antiplatelet properties of the studied phytochemicals are mediated by activation of cyclic nucleotide-dependent signaling pathways. Specifically, we established by using Förster resonance energy transfer that the molecular mechanisms are, at least partly, associated with the inhibition of phosphodiesterases 2 and/or 5. These findings underscore the therapeutic potential of flavonoid aglycones for clinical application as antiplatelet agents.

Ticagrelor downregulates the expression of proatherogenic and proinflammatory miR125-b compared to clopidogrel: A randomized, controlled trial.

BACKGROUND: Platelet P2Y12 antagonist ticagrelor reduces cardiovascular mortality after acute myocardial infarction (AMI) compared to clopidogrel, but the underlying mechanism is unknown. Because activated platelets release proatherogenic and proinflammatory microRNAs, including miR-125a, miR-125b and miR-223, we hypothesized that the expression of these miRNAs is lower on ticagrelor, compared to clopidogrel. OBJECTIVES: We compared miR-125a, miR-125b and miR-223 expression in plasma of patients after AMI treated with ticagrelor or clopidogrel. METHODS: After percutaneous coronary intervention on acetylsalicylic acid and clopidogrel, 60 patients with first AMI were randomized to switch to ticagrelor or to continue with clopidogrel. Plasma expression of miR-223, miR-125a-5p, miR-125b was measured using quantitative polymerase chain reaction at baseline and after 72 h and 6 months of treatment with ticagrelor or clopidogrel in patients and one in 30 healthy volunteers. Multiple electrode aggregometry using ADP test was used to determine platelet reactivity in response to P2Y12 inhibitors. RESULTS: Expression of miR-125b was higher in patients with AMI 72 h and 6 months, compared to healthy volunteers (p = 0.001), whereas expression of miR-125a-5p and miR-223 were comparable. In patients randomized to ticagrelor, expression of miR-125b decreased at 72 h (p = 0.007) and increased back to baseline at 6 months (p = 0.005). Expression of miR-125a-5p and miR-223 was not affected by the switch from clopidogrel to ticagrelor. CONCLUSIONS: Ticagrelor treatment leads to lower plasma expression of miR-125b after AMI, compared to clopidogrel. Higher expression of miR-125b might explain recurrent thrombotic events and worse clinical outcomes in patients treated with clopidogrel, compared to ticagrelor.

Investigation of smoking on the antiplatelet response to clopidogrel: Unravelling the smoker's paradox.

The intricate relationship between smoking and the effects of the antiplatelet drug clopidogrel has been termed the "smoker's paradox". This paradox details the enhanced efficacy of clopidogrel in smokers compared to non-smokers. This review begins with an exploration of the proposed mechanisms of the smoker's paradox, particularly drawing attention to the induction of cytochrome P450 (CYP) isoenzymes via tobacco smoke, specifically the enzymes CYP1A2 and CYP2C19. Moreover, an investigation of the effects of genetic variability on the smoker's paradox was undertaken from both clinical and molecular perspectives, delving into the effects of ethnicity and genetic polymorphisms. The intriguing role of CYP1A2 genotypes and the response to clopidogrel in smoking and non-smoking populations was examined conferring insight into the individuality rather than universality of the smoker's paradox. CYP1A2 induction is hypothesised to elucidate the potency of smoking in exerting a counteracting effect in those taking clopidogrel who possess CYP2C19 loss of function polymorphisms. Furthermore, we assess the comparative efficacies of clopidogrel and other antiplatelet agents, namely prasugrel and ticagrelor. Studies indicated that prasugrel and ticagrelor provided a more consistent effect and further reduced platelet reactivity compared to clopidogrel within both smoking and non-smoking populations. Personalised dosing was another focus of the review considering patient comorbidities, genetic makeup, and smoking status with the objective of improving the antiplatelet response of those taking clopidogrel. In summation, this review provides insight into multiple areas of research concerning clopidogrel and the smoker's paradox taking into account proposed mechanisms, genetics, other antiplatelet agents, and personalised dosing.

Determination of clopidogrel effect in cats using point-of-care Plateletworks ADP and shipped samples for PFA-200 analysis in a clinical practice setting.

OBJECTIVES: Clopidogrel is the recommended first-line antithrombotic in cats for a variety of conditions; however, it is ineffective in 15-20% of cats. The determination of clopidogrel effectiveness with platelet function assays has historically been limited to specialty centers; however, recent work has suggested that in-hospital or shipped analyses of samples may be feasible. The aim of the present study was to investigate the utility of an in-house analysis and shipping of blood samples collected in primary practices for the determination of clopidogrel effectiveness. METHODS: Citrated blood samples were collected from cats receiving clopidogrel therapy by veterinarians in clinical practices across Canada, a median of 304.4 km from the reference laboratory (range 8-4425). Samples were analyzed in-house using Plateletworks ADP and shipped for remote analysis using PFA-200 P2Y and COL/ADP cartridges. RESULTS: A total of 30 samples were collected from 25 cats. Of these, the percentage of samples analyzable for the presence or absence of the clopidogrel effect was 86% for Plateletworks ADP, 90% for PFA-200 P2Y and 87% for PFA-200 COL/ADP. There was no significant difference in the number of samples unable to be analyzed by each modality (P = 0.689) due to flow obstruction or other sample characteristics. The prevalence of absence of clopidogrel effectiveness on platelet function assays was 8% with the PFA-200 COL/ADP assay, 25% with the PFA-200 P2Y assay and 30% with the Plateletworks ADP assay. CONCLUSIONS AND RELEVANCE: The results of this study confirm that samples of feline blood can be collected in clinical practices and shipped to a reference laboratory for PFA-200 analysis with a high rate of success, comparable to point-of-care analysis.

Study on the Mechanism of the Adrenaline-Evoked Procoagulant Response in Human Platelets.

Adrenaline has recently been found to trigger phosphatidylserine (PS) exposure on blood platelets, resulting in amplification of the coagulation process, but the mechanism is only fragmentarily established. Using a panel of platelet receptors' antagonists and modulators of signaling pathways, we evaluated the importance of these in adrenaline-evoked PS exposure by flow cytometry. Calcium and sodium ion influx into platelet cytosol, after adrenaline treatment, was examined by fluorimetric measurements. We found a strong reduction in PS exposure after blocking of sodium and calcium ion influx via Na+/H+ exchanger (NHE) and Na+/Ca2+ exchanger (NCX), respectively. ADP receptor antagonists produced a moderate inhibitory effect. Substantial limitation of PS exposure was observed in the presence of GPIIb/IIIa antagonist, phosphoinositide-3 kinase (PI3-K) inhibitors, or prostaglandin E1, a cyclic adenosine monophosphate (cAMP)-elevating agent. We demonstrated that adrenaline may develop a procoagulant response in human platelets with the substantial role of ion exchangers (NHE and NCX), secreted ADP, GPIIb/IIIa-dependent outside-in signaling, and PI3-K. Inhibition of the above mechanisms and increasing cytosolic cAMP seem to be the most efficient procedures to control adrenaline-evoked PS exposure in human platelets.

Discovery of Novel Hybrids of Edaravone and 6-Phenyl-4,5-dihydropyridazin-3(2H)-one with Antiplatelet Aggregation and Neuroprotection for Ischemic Stroke Treatment.

Drugs with anti-platelet aggregation and neuroprotection are of great significance for the treatment of ischemic stroke. A series of edaravone and 6-phenyl-4,5-dihydropyridazin-3(2H)-one hybrids were designed and synthesized. Among them, 6g showed the most effective cytoprotective effect against oxygen-glucose deprivation/reoxygenation-induced damage in BV2 cells and an excellent inhibitory effect on platelet aggregation induced by adenosine diphosphate and arachidonic acid. Additionally, 6g could prevent thrombosis caused by ferric chloride in rats and pose a lower risk of causing bleeding compared with aspirin. It provides better protection against ischemia/reperfusion injury in rats compared with edaravone and alleviates the oxidative stress related to cerebral ischemia/reperfusion by increasing the GSH and SOD levels and decreasing the MDA concentration. Finally, molecular docking results showed that 6g probably acts on PDE3 A and plays an anti-platelet aggregation effect. Overall, 6g could be a potential candidate compound for the treatment of ischemic stroke.

Desmopressin, Misoprostol, nor Carboprost Affect Platelet Aggregability Following Traumatic Brain Injury and Aspirin.

INTRODUCTION: Desmopressin (DDAVP) has been utilized clinically in patients taking aspirin (ASA) to improve drug-induced platelet dysfunction. Misoprostol and carboprost, prostaglandin analogs commonly used for postpartum hemorrhage, may also induce platelet aggregation. The aim of this study was to determine the effects of DDAVP, misoprostol, and carboprost administration on platelet aggregability following traumatic brain injury (TBI) in mice treated with ASA. METHODS: Male C57BL/6 mice were randomized into seven groups (n = 5 each): untouched, ASA only, Saline/TBI, ASA/TBI, ASA/TBI/DDAVP 0.4 µg/kg, ASA/TBI/misoprostol 1 mg/kg, and ASA/TBI/carboprost 100 µg/kg. TBI was induced via a weight drop model 4-h after ASA (50 mg/kg) gavage. Mice were given an intraperitoneal injection of DDAVP, misoprostol, or carboprost 10 minutes after TBI. In vivo testing was completed utilizing tail vein bleed. Mice were sacrificed 30-min posttreatment and blood was collected via cardiac puncture. Whole blood was analyzed via Multiplate impedance aggregometry, rotational thromboelastometry, and TEG6s. RESULTS: Mice receiving misoprostol after ASA/TBI demonstrated decreased tail vein bleeding times compared to ASA only treated mice. However, mice treated with misoprostol following ASA and TBI demonstrated decreased platelet aggregability compared to untouched mice and TBI only mice within the arachidonic acid agonist pathway. By contrast, DDAVP and carboprost did not significantly change platelet aggregability via adenosine diphosphate or arachidonic acid following ASA and TBI. However, DDAVP did decrease the platelet contribution to clot via rotational thromboelastometry. CONCLUSIONS: Reversal of medication-induced platelet inhibition has become increasingly controversial after TBI. Based on these results, DDAVP, misoprostol, nor carboprost consistently improve platelet aggregability following TBI in those also treated with ASA.

Ginkgetin effectively mitigates collagen and AA-induced platelet activation via PLCγ2 but not cyclic nucleotide-dependent pathway in human.

Platelets assume a pivotal role in the cardiovascular diseases (CVDs). Thus, targeting platelet activation is imperative for mitigating CVDs. Ginkgetin (GK), from Ginkgo biloba L, renowned for its anticancer and neuroprotective properties, remains unexplored concerning its impact on platelet activation, particularly in humans. In this investigation, we delved into the intricate mechanisms through which GK influences human platelets. At low concentrations (0.5-1 µM), GK exhibited robust inhibition of collagen and arachidonic acid (AA)-induced platelet aggregation. Intriguingly, thrombin and U46619 remained impervious to GK's influence. GK's modulatory effect extended to ATP release, P-selectin expression, intracellular calcium ([Ca2+ ]i) levels and thromboxane A2 formation. It significantly curtailed the activation of various signaling cascades, encompassing phospholipase Cγ2 (PLCγ2)/protein kinase C (PKC), phosphoinositide 3-kinase/Akt/glycogen synthase kinase-3ß and mitogen-activated protein kinases. GK's antiplatelet effect was not reversed by SQ22536 (an adenylate cyclase inhibitor) or ODQ (a guanylate cyclase inhibitor), and GK had no effect on the phosphorylation of vasodilator-stimulated phosphoproteinSer157 or Ser239 . Moreover, neither cyclic AMP nor cyclic GMP levels were significantly increased after GK treatment. In mouse studies, GK notably extended occlusion time in mesenteric vessels, while sparing bleeding time. In conclusion, GK's profound impact on platelet activation, achieved through inhibiting PLCγ2-PKC cascade, culminates in the suppression of downstream signaling and, ultimately, the inhibition of platelet aggregation. These findings underscore the promising therapeutic potential of GK in the CVDs.

Antiplatelet effects of the CEACAM1-derived peptide QDTT.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) restricts platelet activation via platelet collagen receptor GPVI/FcRγ-chain. In this study, screening against collagen-induced platelet aggregation was performed to identify functional CEACAM1 extracellular domain fragments. CEACAM1 fragments, including Ala-substituted peptides, were synthesized. Platelet assays were conducted on healthy donor samples for aggregation, cytotoxicity, adhesion, spreading, and secretion. Mice were used for tail bleeding and FeCl3-induced thrombosis experiments. Clot retraction was assessed using platelet-rich plasma. Extracellular segments of CEACAM1 and A1 domain-derived peptide QDTT were identified, while N, A2, and B domains showed no involvement. QDTT inhibited platelet aggregation. Ala substitution for essential amino acids (Asp139, Thr141, Tyr142, Trp144, and Trp145) in the QDTT sequence abrogated collagen-induced aggregation inhibition. QDTT also suppressed platelet secretion and "inside-out" GP IIb/IIIa activation by convulxin, along with inhibiting PI3K/Akt pathways. QDTT curtailed FeCl3-induced mesenteric thrombosis without significantly prolonging bleeding time, implying the potential of CEACAM1 A1 domain against platelet activation without raising bleeding risk, thus paving the way for novel antiplatelet drugs.

What is the context? The study focuses on Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) and its role in platelet activation, particularly through the GPVI/FcRγ-chain pathway.The research aims to identify specific fragments of CEACAM1's extracellular domain that could restrict platelet activation, without increasing bleeding risk.What is new? The researchers identified a peptide called QDTT derived from the A1 domain of CEACAM1's extracellular segment. This peptide demonstrated the ability to inhibit platelet aggregation, secretion, and GP IIb/IIIa activation.The study also revealed that specific amino acids within the QDTT sequence were essential for its inhibitory effects on collagen-induced aggregation.What is the impact? The findings suggest that the A1 domain-derived peptide QDTT from CEACAM1 could serve as a potential basis for developing novel antiplatelet drugs. This peptide effectively limits platelet activation and aggregation without significantly prolonging bleeding time, indicating a promising approach to managing thrombosis and related disorders while minimizing bleeding risks.

Population Pharmacokinetic/Pharmacodynamic Models for P2Y12 Inhibitors: A Systematic Review and Clinical Appraisal Using Exposure Simulation.

BACKGROUND AND OBJECTIVE: Recent research indicates a correlation between plasma concentration of P2Y12 inhibitors and clinical events, particularly bleeding, which significantly impeded their clinical therapeutic performance. It is therefore vital to delve into the factors that might affect the plasma concentration. The study aims to summarize population pharmacokinetics/pharmacodynamics (PopPKPD) models for commonly prescribed P2Y12 inhibitors (clopidogrel, prasugrel, and ticagrelor) and assess bleeding risk in specific individual groups. METHODS: The PopPKPD models of P2Y12 inhibitors were collected and summarized based on predetermined inclusion and exclusion criteria. The collected models were replicated in simulations, which were used to assess factors affecting plasma concentrations of P2Y12 inhibitors. Simulation results for special populations were compared to therapeutic window based on reported exposure-effect relationships (PK/PD-related bleeding and thrombotic clinical outcomes) to predict bleeding risk in special populations with different dosing regimens and cumulative covariates. RESULT: Finally, 12 studies were included for PK simulation, 7 of which that also included PD data were subjected to further analysis, with the majority being based on Phase I or II trials. Simulations showed that several covariates such as female gender, weight, elderly can significantly impact on exposure, with special populations reaching up to 179% of the general population. However, after dose adjustment, blood concentrations for special populations can reach approximately ±20% of general population exposure. Therefore, lowering the maintenance dose of ticagrelor from 90 to 60 mg bid was first recommended to reduce bleeding risk without significantly increasing ischemic risk, particularly in elderly, small-weight Asian females. CONCLUSION: Lowering the maintenance dose of ticagrelor from 90 to 60 mg bid effectively reduces bleeding risk without increasing thrombotic infarction risk in elderly, small-weight Asian females.

The Effect of Platelet Activity, ABCB1 Genetic Polymorphism, and Renal Function on the Development of Ticagrelor-Related Dyspnea in Patients with Acute Coronary Syndrome.

Purpose: The aim of this study was to determine the effect of ABCB1 genetic polymorphism and renal function on the occurrence of ticagrelor-related dyspnea. Patients and Methods: A total of 299 patients with acute with type 1, 2, or 3 myocardial infarction (with and without ST-segment elevation), who underwent coronary angiography and PTCA with stent implantation and were treated with antiplatelet drugs (ticagrelor and aspirin), were enrolled in this prospective study. For all enrolled patient's platelet aggregation (induction with high-sensitivity adenosine diphosphate, ADP HS) testing was performed using a MULTIPLATE® analyzer. Venous blood was also collected for genotyping. Results: Patients experiencing ticagrelor-related dyspnea had lower ADP HS value (ADP HS ≤ 19.5 U; OR = 2.254; P = 0.009), higher creatinine concentration (>90 µmol/l; OR = 3.414; P = 0.019), and lower GFR value (<60 mL/min/1.73 m2; OR = 2.211; P = 0.035). ABCB1 T allele was associated with ticagrelor-related dyspnea (OR = 2.550; P = 0.04). Conclusion: Ticagrelor-related dyspnea was found to be related to low platelet aggregation, increased plasma creatinine concentration, decreased GFR, and ABCB1 T allele. Carriers of the ABCB1 T allele had a higher plasma creatinine concentration that could be associated with an inhibitory effect of ticagrelor on P-glycoprotein function.

Discovering peptide inhibitors of thrombin as a strategy for anticoagulation.

Unusual blood clots can cause serious health problems, such as lung embolism, stroke, and heart attack. Inhibiting thrombin activity was adopted as an effective strategy for preventing blood clots. In this study, we explored computational-based method for designing peptide inhibitors of human thrombin therapeutic peptides to prevent platelet aggregation. The random peptides and their 3-dimentional structures were generated to build a virtual peptide library. The generated peptides were docked into the binding pocket of human thrombin. The designed strong binding peptides were aligned with the native binder by comparative study, and we showed the top 5 peptide binders display strong binding affinity against human thrombin. The 5 peptides were synthesized and validated their inhibitory activity. Our result showed the 5-mer peptide AEGYA, EVVNQ, and FASRW with inhibitory activity against thrombin, range from 0.53 to 4.35 µM. In vitro anti-platelet aggregation assay was carried out, suggesting the 3 peptides can inhibit the platelet aggregation induced by thrombin. This study showed computer-aided peptide inhibitor design can be a robust method for finding potential binders for thrombin, which provided solutions for anticoagulation.

Flow cytometry for comprehensive assessment of platelet functional activity in response to ADP stimulation.

OBJECTIVES: Flow cytometry with adenosine diphosphate (ADP) allows to characterize molecular changes of platelet function caused by this physiologically important activation, but the methodology has not been thoroughly investigated, standardized and characterized yet. We analyzed the influence of several major variables and chose optimal conditions for platelet function assessment. METHODS: For activation, 2.5 µM CaCl2 , 5 µM ADP and antibodies were added to diluted blood and incubated for 15 min. We analyzed kinetics of antibody binding and effects of their addition sequence, agonist concentration, blood dilution, exogenous calcium addition and platelet fixation. RESULTS: We tested our protocol on 11 healthy children, 22 healthy adult volunteers, 9 patients after a month on dual antiplatelet therapy after percutaneous coronary intervention (PCI), 7 adult patients and 14 children with immune thrombocytopenia (ITP). We found that our protocol is highly sensitive to ADP stimulation with low percentage of aggregates formation. The assay is also sensitive to platelet function inhibition in post-PCI patients. Finally, platelet preactivation with ITP plasma was stronger and caused increase in activation response to ADP stimulation compared to preactivation with low dose of ADP. CONCLUSIONS: Our assay is sensitive to antiplatelet therapy and platelet preactivation in ITP patients under physiological conditions with minimal percentage of aggregates formation.

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.

Potential antithrombotic effect of two new phenylpropanoid sucrose esters and other secondary metabolites of Canna indica L. rhizome.

Canna indica L. has been traditionally used to treat various diseases. Based on previously reported antithrombotic effect for this plant, two new phenylpropanoid sucrose esters (canindicoside A (1) and canindicoside B (2)) and seven known compounds: nepetoidin B (3), caffeic acid (4), ferulic acid (5), (R)-(+)-rosmarinic acid (6), isorinic acid (7), (S)-(-)-rosmarinic acid (8) and (S)-(-)-rosmarinic acid methyl ester (9) were isolated from the ethyl acetate extract. Compounds were elucidated by NMR and MS spectroscopic methods. The antiplatelet effect was evaluated using turbidimetric method. Anticoagulant activity was examined by measuring activated partial thromboplastine time (APTT), prothrombin time, and thrombine time (TT). It was shown for the first time that both new phenylpropanoid sucrose esters 1 and 2, 7 and 9 displayed dose-dependent antiplatelet effects. 2 and 9 had the highest inhibitory activity on both adenosine diphosphate (ADP)- and collagen-induced platelet aggregation. Moreover, 1, 7 and 9 also exhibited anticoagulant activity. At 0.4 mg/mL, both 1 and 7 prolonged APTT compared to the negative control (p < 0.05), suggesting the possible inhibitory impact on the intrinsic coagulation pathway. Moreover, 9 at 0.4 mg/mL exerted higher TT values than the negative control (p < 0.05). C. indica and its bioactive phytochemicals are potential candidates for development of anti-thrombosis therapy.

The role of platelet P2Y12 receptors in inflammation.

Inflammation is a complex pathophysiological process underlying many clinical conditions. Platelets contribute to the thrombo-inflammatory response. Platelet P2Y12 receptors amplify platelet activation, potentiating platelet aggregation, degranulation and shape change. The contents of platelet alpha granules, in particular, act directly on leucocytes, including mediating platelet-leucocyte aggregation and activation via platelet P-selectin. Much evidence for the role of platelet P2Y12 receptors in inflammation comes from studies using antagonists of these receptors, such as the thienopyridines clopidogrel and prasugrel, and the cyclopentyltriazolopyrimidine ticagrelor, in animal and human experimental models. These suggest that antagonism of P2Y12 receptors decreases markers of inflammation with some evidence that this reduces incidence of adverse clinical sequelae during inflammatory conditions. Interpretation is complicated by pleiotropic effects such as those of the thienopyridines on circulating leucocyte numbers and of ticagrelor on adenosine reuptake. The available evidence suggests that P2Y12 receptors are prominent mediators of inflammation and P2Y12 receptor antagonism as a potentially powerful strategy in a broad range of inflammatory conditions. 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.

Anti-thrombotic Effects Mediated by a Novel Dual-Target Peptide Inhibiting Both Platelet Aggregation and Thrombin Activity without Causing Bleeding.

BACKGROUND: Classical anticoagulants and antiplatelets are associated with high frequencies of bleeding complications or treatment failure when used as single agents. Thrombin plays an important role in the blood coagulation system. GP IIb/IIIa is the central receptor of platelets, which can recognize the Arg-Gly-Asp (RGD) sequence and activate platelets. MATERIAL AND METHODS: Molecular simulation and homology modeling were performed to design a novel dual-target anticoagulant short peptide (PTIP ). The activities of PTIP on coagulation and platelet in vitro were analyzed. The antithrombotic activity of PTIP was determined by pulmonary thromboembolism model, ferric chloride injury model and arteriovenous bypass thrombosis model. Bleeding effect and toxicity of PTIP were evaluated. RESULTS: We have constructed a novel dual-target peptide (PTIP) based on the direct thrombin inhibitor peptide (DTIP). PTIP was expressed at high levels in Pichia pastoris. PTIP interfered with thrombin-mediated coagulation and ADP-induced platelet aggregation in vitro. When injected intravenously or subcutaneously, PTIP showed potent and dose-dependent extension of aPTT and PT which were similar to DTIP; but only PTIP was capable of inhibiting platelet aggregation. PTIP (1.0 mg/kg) decelerated thrombosis formation in venous and arterial vessels induced by FeCl3 injury. PTIP (1.0 mg/kg) also prevented deep venous thrombosis and increased the survival rate associated with pulmonary thromboembolism. And PTIP effectively reduced thrombus length in arteriovenous bypass thrombosis model. Moreover, the antithrombotic dose of PTIP could not induce bleeding. CONCLUSION: These data establish that PTIP represents a novel antithrombotic agent whose effects involve both inhibition of platelet activation and reduction of fibrin generation. And PTIP not only can be used in venous thrombosis and arterial thrombosis, it can also replace the combined treatment of antiplatelet and anticoagulant drugs in thrombotic diseases.