Antiplatelet drug resistance: Molecular insights and clinical implications

A novel antibody against GPIbα inhibits platelet function and thrombosis without increasing bleeding

Glycoprotein Ibα (GPIbα), the initiation protein of arterial thrombosis, was selected as a target for developing new antiplatelet drugs to prevent and treat arterial thrombosis. However, no anti-GPIbα drug is used successfully in clinical. We used human platelets as an antigen to immunize mice and obtained mouse anti-human GPIbα antibody 9C9. The chimeric antibody 1A09 was constructed, and the antibody binding sites were validated, before employing 3D modeling. Following design of a humanized anti-GPIbα, a mouse-derived antibody was mutated into a human sequence to construct the humanized anti-GPIbα antibody SZ003. ELISA, western blot, platelet aggregation, and thrombus model experiments were used to test the specificity, affinity, safety, and thrombus inhibition effects. The experimental results showed that SZ003 bound to GPIbα, inhibited GPIbα-mediated platelet aggregation, and induced in vivo platelet clearance. Furthermore, SZ003-Fab inhibited GPIbα-mediated platelet aggregation and thrombosis but did not induce in vivo platelet clearance, prolong bleeding time in mouse tails, nor have cytotoxic effects on human platelets. The Fab fragment of anti-human GPIbα humanized antibody SZ003 effectively inhibited GPIbα receptor-mediated platelet activation and thrombosis in vivo without leading to thrombocytopenia and bleeding. Therefore, SZ003-Fab has clinical value as a novel antithrombotic drug to treat arterial thrombus-related diseases.

Prevalence of Aspirin or Clopidogrel Pharmacological Resistance in Ischemic Stroke: A Step Toward Precision Medicine

BACKGROUND AND OBJECTIVES

Currently, there is not sufficient data regarding the prevalence of resistance or inadequate platelet function inhibition with the use of antiplatelet therapy in patients with noncardioembolic stroke. This study was designed to evaluate the prevalence of antiplatelet inactivity to aspirin and clopidogrel in the setting of chronic use and presentation with primary or recurrent stroke.

METHODS

Patients who were taking aspirin, clopidogrel, or both at the time of presentation for stroke were selected in this study. Those with confirmed stroke on MRI or clinically determined TIA and age > 18 years were included. A standard laboratory test, VerifyNow aspirin or P2Y12 assay, was utilized to assess the responsiveness to the platelet inhibitors. A total of 158 patients were identified, 52 presenting with primary stroke and 106 with recurrent stroke. Data were analyzed using chi-squared or Fisher's exact as well as t-test analysis.

RESULTS

Of the primary stroke population, 4% of patients demonstrated resistance to aspirin and 30% to clopidogrel. Of the patients presenting with recurrent stroke, 13% demonstrated resistance to aspirin and 38% to clopidogrel. The data also suggest increased resistance to aspirin and clopidogrel in Caucasians compared to minorities, with 11% versus 8% in regard to aspirin and 33% versus 17% to clopidogrel. Additionally, this study demonstrated 17% resistance to aspirin in males compared to 4% in females and 13% in males compared to 36% in females, respectively, regarding resistance to clopidogrel. No difference in inactivity to either aspirin or clopidogrel was detected between patients with stroke mechanisms of small or large vessel disease.

CONCLUSIONS

The present result demonstrated that a sizeable portion of the population has inefficacious activity in the setting of specific antiplatelet agents. Additionally, sex and ethnicity differences in responsiveness to aspirin or clopidogrel have been noted. Determining a patient's response to medications could provide opportunities to individualize treatment and better prevent future strokes. Further studies of a larger scale are indeed needed to apply this information to pursue individualized treatment.

Aspirin 15cH has Different Effects on Morphology and Function of Lipopolysaccharide-Challenged RAW 264.7 Macrophages In Vitro Compared to a Pharmacological Dose of Aspirin

INTRODUCTION

Aspirin is one of the most commonly used drugs worldwide. It is known to present antipyretic, anti-inflammatory and anti-thrombotic actions, making it extremely useful in a wide range of clinical contexts. Interestingly, homeopathically prepared Aspirin 15cH has been found to have a pro-thrombotic effect in rats, raising the hypothesis that Aspirin 15cH could also modulate the activity of inflammatory cells in different pathological processes.

OBJECTIVE

Our objective was to assess what effect Aspirin 15cH has on RAW 264.7 macrophages in vitro.

METHODS

The effects of Aspirin 15cH on biochemical and morphological activities of lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages were evaluated. These effects were compared with unchallenged macrophages (negative control), untreated LPS-stimulated macrophages, macrophages treated with succussed water (vehicle control), or aspirin 200 µg/mL (pharmacological inhibitor of LPS activity). Cell morphology (adhered cell area and cytoskeleton arrangements), cell viability, toll-like receptor-4 (TLR-4) expression, and the production of nitric oxide, cytokines and intracellular reactive oxygen species were assessed.

RESULTS

Aspirin 15cH reduced the number of cells expressing TLR-4 on the surface (p = 0.03) and induced a "columnar" morphology of macrophage pseudopods, indicating changes in cytoskeleton arrangement. When cells were treated with both Aspirin 15cH and LPS, cell morphology became heterogeneous, suggesting that sub-populations of cells had differing sensitivities to LPS or Aspirin 15cH. Exposure of the cells to LPS alone, succussed water or aspirin 200 µg/mL produced effects consistent with the literature.

CONCLUSION

Aspirin 15cH, aspirin 200 µg/mL, LPS and succussed water appear to act as independent stimuli able to induce different patterns of macrophage response. Aspirin 15cH induced changes suggestive of M2 polarization of the macrophages (i.e., toward a wound healing or tissue repair, rather than inflammatory, phenotype). These preliminary findings need to be confirmed in further specific studies.

Establishment of a forward primers-superposed amplification analysis for accurate aspirin pharmacogenomic measurement

Genotyping of gDNA rs12041331 (PEAR1), rs6065 (GP1BA), and rs730012 (LTC4S) can provide systematic guidance on the use of aspirin. However, an accurate, reliable and economical approach to simultaneous detection of the above single nucleotide polymorphisms (SNPs) is not reported. Herein, we designed and substantiated an allele-specific (AS) forward primer-superposed amplification analysis for measurement of the SNPs in PEAR1, GP1BA and LTC4S genes, in which the values of ∆Cq (differences in threshold cycles between the wild-type forward primer-based assay and the mutated-type forward primer-based assay) were employed to decide genotype. Mismatch AS forward primers were screened with the singleplex amplification analysis. Moreover, Cq extension optimized by AS forward primer superposition was observed in the selected forward primer-based triplex analysis. Further, robustness assessment of the triplex analysis showed the amplification efficiency ranging from 0.9 to 1.1. Precision test demonstrated the coefficient of variation of less than 2%. And the detective results of 189 DNA samples was completely concordant with that of commercial Sanger sequencing. In summary, we developed a simple, accurate and economical approach to genotyping of rs12041331 (PEAR1), rs6065 (GP1BA) and rs730012 (LTC4S) to provide a valuable pharmacogenomics tool for guidance of aspirin delivery.

Anti-thrombotics and major adverse cardiovascular events in anti-phospholipid syndrome: a cross-sectional study using the 2016-2018 National Inpatient Sample database

OBJECTIVE

This study assessed the relationship between anti-thrombotics and major adverse cardiovascular events (MACE) in patients with anti-phospholipid syndrome (APS).

METHOD

We included 13 947 subjects with APS from the National (Nationwide) Inpatient Sample (NIS) database for 2016-2018, and collected relevant covariates and demographic data using ICD-10 codes. Our two primary outcomes were MACE and death. We performed multivariate logistic regression analysis to assess the impact of various anti-thrombotic regimens on MACE/death in our primary cohort and high-risk subgroups.

RESULTS

Patients on anti-coagulants had significantly reduced odds of MACE [odds ratio (OR) 0.68, 95% confidence interval (CI) 0.62-0.76, p < 0.001] as well as each of its subcomponents. Those not on any anti-coagulants had significantly increased odds of MACE (OR 1.47, 95% CI 1.24-1.72, p < 0.001). No significant association was found between anti-platelet use and the odds of MACE (p > 0.05). Patients on anti-coagulants were the only class that appeared to have a mortality benefit with reduced odds for death (OR 0.64, 95% CI 0.49-0.84, p = 0.001). In the subgroups at higher risk for MACE (those with atrial fibrillation and thrombocytopenia), full anti-coagulation therapy was also the only anti-thrombotic class that significantly affected the odds of MACE, with a protective effect on MACE, but had no mortality benefit.

CONCLUSION

Patients with APS are most likely to benefit from anti-coagulant therapy in reducing MACE. Furthermore, anti-platelets alone or in combination with anti-coagulants are probably not beneficial in MACE reduction and may even increase risk.

Artificial Intelligence and Neurosurgery: Tracking Antiplatelet Response Patterns for Endovascular Intervention

Platelets play a critical role in blood clotting and the development of arterial blockages. Antiplatelet therapy is vital for preventing recurring events in conditions like coronary artery disease and strokes. However, there is a lack of comprehensive guidelines for using antiplatelet agents in elective neurosurgery. Continuing therapy during surgery poses a bleeding risk, while discontinuing it before surgery increases the risk of thrombosis. Discontinuation is recommended in neurosurgical settings but carries an elevated risk of ischemic events. Conversely, maintaining antithrombotic therapy may increase bleeding and the need for transfusions, leading to a poor prognosis. Artificial intelligence (AI) holds promise in making difficult decisions regarding antiplatelet therapy. This paper discusses current clinical guidelines and supported regimens for antiplatelet therapy in neurosurgery. It also explores methodologies like P2Y12 reaction units (PRU) monitoring and thromboelastography (TEG) mapping for monitoring the use of antiplatelet regimens as well as their limitations. The paper explores the potential of AI to overcome such limitations associated with PRU monitoring and TEG mapping. It highlights various studies in the field of cardiovascular and neuroendovascular surgery which use AI prediction models to forecast adverse outcomes such as ischemia and bleeding, offering assistance in decision-making for antiplatelet therapy. In addition, the use of AI to improve patient adherence to antiplatelet regimens is also considered. Overall, this research aims to provide insights into the use of antiplatelet therapy and the role of AI in optimizing treatment plans in neurosurgical settings.

Coagulation status and determinants of possible aspirin resistance in patients with essential thrombocythemia

Objectives

The currently recommended aspirin regimen appears inadequate for thromboprophylaxis in essential thrombocythemia (ET). This study aimed not only to evaluate the curative effect of aspirin but also to explore the coagulation status and determinants of aspirin resistance (AR) of ET patients.

Methods

A total of 80 ET patients who underwent coagulation tests, thromboelastography (TEG), and next-generation sequencing (NGS) were involved in the study. Patients were divided into the aspirin sensitivity (AS) group and AR group according to the arachidonic acid inhibition rate. Their clinical features and coagulation function were analyzed.

Results

The incidence of AR was 53.75% (43/80) in 80 ET patients. Fbg was significantly higher in coagulation tests in AR patients compared with AS patients (P < 0.05), while the differences in other variables (D-D, PT, PTA, INR, APTT, TT, FDP, and AT-III) were not statistically significant (P > 0.05). Compared with AS patients, the K values, α angles, MA values, and CI values of TEG in AR patients were statistically smaller (P < 0.05), but there was no significant difference in R value between them (P > 0.05). Univariate and multivariate logistic regression analysis showed that age, irregular use of aspirin, smoking, dyslipidemia, and hypertension increased the risk of AR (P < 0.05). In the routine NGS, the driver gene and non-driver gene had no effect on AR in ET patients.

Conclusion

Compared with AS patients, AR patients have enhanced platelet aggregation function, are in a relatively hypercoagulable state, and haveelevated fibrinogen function/levels, all of which cause a worse coagulation status. ET patients with increasing age, irregular use of aspirin, smoking, dyslipidemia, and hypertension are possibly at higher risk of AR. The routine NGS may not be helpful for the prediction of AR, therefore we recommend adding relevant drug-resistance genes to NGS.

Naoxintong capsule limits myocardial infarct expansion by inhibiting platelet activation through the ERK5 pathway

BACKGROUND

In the clinic, Naoxintong capsule (NXT) has been applied in two level prevention of ischemic disease. However, its mechanism of action requires further study.

PURPOSE

This study investigated whether NXT could affect platelet function and activation under ischemic pathological conditions.

MATERIALS AND METHODS

Wistar rats were divided into six groups, sham, saline, NXT (250, 500, 1000 mg/kg), and aspirin group (10 mg/kg). For the pre-treatment assays, MI model was established after pre-administration of saline, NXT-L, NXT-M, NXT-H, and aspirin respectively for 14 days, and after surgery, there were no continuous treatments. For the post-treatment assay, rats were orally administered for 3 days after MI. FeCl3-induced thrombosis model was applied to determine the thrombus wet weight. Bleeding time was used to assess the ability of the platelets to develop a hemostatic plug.

RESULTS

NXT decreased infarct size, decreased LDH, CK, and CK-MB values, and improved cardiac function. NXT inhibited platelets activation through reducing CD62P-positive platelets and inhibited infarct expansion by decreasing the number of CD45-positive cells and the amount of MMP9 secreted into the heart tissue. Mechanistically, NXT inhibited platelets activation through decreasing ROS levels, decreasing ERK5 phosphorylation, and increasing RAC1 phosphorylation in MI rats. Pre-treatment with NXT decreased thrombus formation and had normal bleeding times.

CONCLUSION

NXT showed obviously preventive effects, which was associated with negative control of platelet activation. The above results provide a basis for clinically expanding application of NXT.

Novel serotonin 5-HT2A receptor antagonists derived from 4-phenylcyclohexane-5-spiro-and 5-methyl-5-phenyl-hydantoin, for use as potential antiplatelet agents

BACKGROUND

Antiplatelet drugs have been used in the treatment of acute coronary syndromes and for the prevention of recurrent events. Unfortunately, many patients remain resistant to the available antiplatelet treatment. Therefore, there is a clinical need to synthesize novel antiplatelet agents, which would be associated with different pathways of platelet aggregation, to develop an alternative or additional treatment for resistant patients. Recent studies have revealed that 5-HT_2A receptor antagonists could constitute alternative antiplatelet therapy.

METHODS

Based on the structures of the conventional 5-HT_2A receptor ligands, two series of compounds with 4-phenylcyclohexane-5-spiro- or 5-methyl-5-phenyl-hydantoin core linked to various arylpiperazine moieties were synthesized and their affinity for 5-HT_2A receptor was assessed. Further, we evaluated their antagonistic potency at 5-HT_2A receptors using isolated rat aorta and cells expressing human 5-HT_2A receptors. Finally, we studied their anti-aggregation effect and compared it with ketanserin and sarpogrelate, the reference 5-HT_2A receptor antagonists. Moreover, the structure-activity relationships were studied following molecular docking to the 5-HT_2A receptor model.

RESULTS

Functional bioassays revealed some of the synthesized compounds to be moderate antagonists of 5-HT_2A receptors. Among them, 13, 8-phenyl-3-(3-(4-phenylpiperazin-1-yl)propyl)-1,3-diazaspiro[4.5]decane-2,4-dione, inhibited collagen stimulated aggregation (IC₅₀ = 27.3 μM) being more active than sarpogrelate (IC₅₀ = 66.8 μM) and comparable with ketanserin (IC₅₀ = 32.1 μM). Moreover, compounds 2-5, 9-11, 13, 14 inhibited 5-HT amplified, ADP- or collagen-induced aggregation.

CONCLUSIONS

Our study confirmed that the 5-HT_2A antagonists effectively suppress platelet aggregation and remain an interesting option for the development of novel antiplatelet agents with an alternative mechanism of action.

Biomarkers for Antiplatelet Therapies in Acute Ischemic Stroke: A Clinical Review

Stroke is one of the world's leading causes of disability and death. Antiplatelet agents are administered to acute ischemic stroke patients as secondary prevention. Clopidogrel involves biotransformation by cytochrome P450 (CYP) enzymes into an active metabolite, and single nucleotide polymorphisms (SNPs) can influence the efficacy of this biotransformation. Despite the therapeutic advantages of aspirin, there is significant inter-individual heterogeneity in response to this antiplatelet drug. In this clinical review, the recent advances in the biomarkers of antiplatelet agents in acute ischemic stroke are discussed. The studies reviewed herein highlight the clinical relevance of antiplatelet resistance, pharmacotherapy of antiplatelet agents predicting drug response, strategies for identifying aspirin resistance, pharmacogenetic variants of antiplatelet agents, miRNAs, and extracellular vesicles (EVs) as biomarkers toward the personalized approach in the management of acute ischemic stroke. The precise pathways contributing to antiplatelet resistance are not very well known but are presumably multi-factorial. It is essential to understand the clinical relevance of clopidogrel and aspirin-related single nucleotide polymorphism (SNPs) as potential predictive and prognostic biomarkers. Prasugrel is a next-generation antiplatelet agent that prevents ADP-platelet activation by binding irreversibly to P2Y12 receptor. There are sporadic reports of prasugrel resistance and polymorphisms in the Platelet endothelial aggregation receptor-1 (PEAR1) that may contribute to a change in the pharmacodynamics response. Ticagrelor, a direct-acting P2Y12-receptor antagonist, is easily absorbed and partly metabolized to major AR-C124910XX metabolite (ARC). Ticagrelor's primary active metabolite, ARC124910XX (ARC), is formed via the most abundant hepatic cytochrome P450 (CYP) enzyme, CYP3A4, and CYP3A5. The integration of specific biomarkers, genotype as well as phenotype-related data in antiplatelet therapy stratification in patients with acute ischemic stroke will be of great clinical significance and could be used as a guiding tool for more effective, personalized therapy.

Efficacy of Monitoring Platelet Function by an Automated PL-12 Analyzer During the Treatment of Acute Cerebral Infarction With Antiplatelet Medicine

Numerous methods can be used to investigate the function of platelets; however, technical issues limit tends to limit the applicability of such methods in the clinic.

Effect of prediabetes on asprin or clopidogrel resistance in patients with recent ischemic stroke/TIA

OBJECTIVE

Diabetes mellitus (DM) had been discovered as an independent risk factor for high on-treatment platelet reactivity (HPR) in patients with ischemic stroke. However, studies on the relationship between prediabetes and the occurrence of HPR remain scarce. This study is aimed at clarifying the association between prediabetes and HPR among patients with recent ischemic stroke or transient ischemic stroke (TIA).

METHODS

Patients with ischemic stroke or TIA within 90 days after onset were recruited consecutively. All patients were divided into three groups: DM, prediabetes, and normal glucose tolerance according to fasting glucose, HbA1c, or OGTT. Three months later, all patients were performed platelet aggregation inhibition test and screened for high on-treatment platelet reactivity. The effect of prediabetes on HPR was analyzed in a multivariable logistic regression model.

RESULTS

This study recruited 237 patients with ischemic stroke or TIA, including 57 cases with prediabetes, 108 with DM, and 72 with normal glucose tolerance. Aspirin and/or clopidogrel resistance was discovered in 28 cases among prediabetes group, which was significantly more frequent than normal glucose tolerance group(49.1% versus 33.3%, P = 0.046). After adjusting for confounding factors, prediabetes was found as an independent risk factor for high on-treatment platelet reactivity (HPR) among patients with recent ischemic stroke or TIA (odds ratio 2.92; 95% CI, 1.29 to 6.63, P = 0.01).

CONCLUSIONS

Prediabetes was an independent risk factor for high on-treatment platelet reactivity in patients with recent ischemic cerebrovascular disease. Patients with prediabetes should be highlighted for the efficacy test of antiplatelet drugs.

Lipoxins, RevD1 and 9, 13 HODE as the most important derivatives after an early incident of ischemic stroke

There is limited information available regarding the association of plasma free fatty acids (FFA) and inflammation mediators with ischemic stroke. At the same time, new treatment strategies are being pursued. The aim of this study was to carry out a thorough analysis of inflammation with multiple FFA-derivative mediators after and ischemic stroke and standard treatment. HPLC separations of 17 eicosanoids were performed using an Agilent Technologies 1,260 liquid chromatograph. The profiles of the esters of fatty acids were labelled by means of gas chromatography. FFA, and eicosanoid profiles in the group of patients after ischemic stroke significantly differed from the profile of the control group. Studies confirmed the involvement of derivative synthesis pathways responsible for the inflammation, especially palmitic acid (9 and 13 HODE), arachidonic acid, EPA and DHA. Arachidonic acid derivatives were synthesised on 5LOX, 15 LOX and COX pathways with the participation of prostaglandins while omega 3 derivatives strengthened the synthesis of resolvins, RevD1 in particular. The ability to accelerate the quenching of inflammation after ischemic stroke seems to be a promising strategy of stroke treatment in its early stage. In this context, our study points to lipoxins, RevD1, and 9, 13 HODE as the most important derivatives.

Dual Antiplatelet Therapy in Coronary Artery Disease: Comparison Between ACC/AHA 2016 and ESC 2017 Guidelines

Dual antiplatelet therapy (DAPT) is integral to the management of coronary artery disease (CAD) but there remains uncertainty as to the optimal approach for balancing an individual's risk of atherothrombotic events versus their risk of bleeding complications. A myriad of clinical trials have investigated how factors such as antiplatelet selection or duration of treatment can affect outcomes in both stable CAD and acute coronary syndromes. To aid clinicians in the challenge of applying trial findings to the circumstances of individual patients, the American College of Cardiology/American Heart Association and European Society of Cardiology have released focused updates on prescribing DAPT in CAD. While the two guidelines agree on many issues, there are some differences in the recommendations. This article highlights those differences and provides comment on their aetiology.

o-Hydroxycinnamic derivatives as prospective anti-platelet candidates: in silico pharmacokinetic screening and evaluation of their binding sites on COX-1 and P2Y12 receptors

Background The high prevalence of thrombotic abnormalities has become a major concern in the health sector. This is triggered by uncontrolled platelet aggregation, which causes complications and death. The problem becomes more complicated because of the undesirable side effects of the drugs currently in use, some of which have reportedly become resistant. This study aims to evaluate the potency of o-hydroxycinnamic acid derivatives (OCA1a-22a) and their pharmacokinetic properties and toxicity for them to be developed as new antiplatelet candidates. Methods In silico analysis of pharmacokinetics was carried out using pKCSM. Molecular docking of the compounds OCA 1a-22a was performed using the Molegro Virtual Docker. In silico evaluation of the potency of biological activity was done by measuring the bonding energy of each tested compound to the target receptor i.e. COX-1 and P2Y12, as the Moldock score (MDS). Results pKCSM analyses showed that more than 90% of OCA 1a-22a are absorbed through the intestine and distributed in plasma. Most tested compounds are not hepatotoxic, and none is mutagenic. An evaluation of the COX-1 receptor showed that OCA 2a-22a have lower binding energy compared to aspirin, which is the COX-1 inhibitor used today. So, it can be predicted that OCA 2-22a have stronger activity. Interactions with P2Y12 show lower MDS than aspirin, but slightly higher than ibuprofen, which is the standard ligand. Conclusions ADMET (absorption, distribution, metabolism, excretion, and toxicity) profile prediction shows that OCA 1a-22a have the potential to be developed as oral preparations. OCA 1a-22a have strong potential to interact with COX-1 and P2Y12 receptors, so they are prospective anti-platelet candidates.

Design, synthesis, and biological evaluation of 4-methoxy-3-arylamido-N-(substitutedphenyl)benzamide derivatives as potential antiplatelet agents

A series of 4-methoxy-3-arylamido-N-(substitutedphenyl)benzamides 6a-u were designed according to the splicing principle of structural design in the medicinal chemistry theory and were synthesized in five steps: nitration, acylation, ammoniation, reduction, and secondary ammoniation. The structures of the target compounds were characterized and verified by infrared, ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, and electron spray ionization spectroscopy. Their in vitro antiplatelet aggregation activities induced by adenosine diphosphate (ADP) or arachidonic acid (AA) were assessed by Born's method. The biological evaluation revealed that all compounds exhibited certain levels of activities in both of the antiplatelet aggregation assays; compounds 6c (IC₅₀  = 3.84 μM) and 6f (IC₅₀  = 3.12 μM) displayed the strongest antiplatelet aggregation activities in the ADP-induced and AA-induced assay, separately. Moreover, compounds that had stronger activities were chosen for cell toxicity testing via the cell counting kit-8 assay. The results indicated that none of the compounds had obvious cell toxicity against L929 cells at the doses of 10 and 20 μM. It is worth pointing out that compound 6c showed the highest antiplatelet activity and the lowest cell toxicity. In general, 4-methoxy-3-arylamido-N-(substitutedphenyl)benzamides have the potential to become a kind of safer and more effective antiplatelet agents.

Aspirin & clopidogrel non-responsiveness & its association with genetic polymorphisms in patients with myocardial infarction

Background & objectives:

Cytochrome P450, P2Y12, cyclooxygenase-1 (COX1) and glycoprotein V1 (GPVI) gene polymorphisms are known to affect patient responsiveness towards aspirin and clopidogrel dual antiplatelet therapy (DAPT). The present study was undertaken to identify aspirin and clopidogrel non-responsiveness and its association with genetic polymorphism in patients with myocardial infarction (MI).

Methods:

A total of 207 MI patients who were on DAPT, were included. The DAPT non-responsiveness was determined by light transmittance aggregometry using arachidonic acid and adenosine diphosphate and high platelet reactivity by collagen. Platelet activation biomarkers, thromboxane B₂ (TxB₂) and soluble CD40 ligand (sCD40L) were measured in plasma. Patient compliance was checked by estimating drug and its metabolite levels (aspirin and clopidogrel) in plasma using liquid chromatography-mass spectrometry/mass spectrometry. Genomic DNA was extracted, amplified by polymerase chain reaction and subsequently sequenced to identify CYP450, P2Y12, COX1 and GPVI gene polymorphisms.

Results:

Of the 207 patients, 32 were non-responders. The DAPT non-responsiveness was found in 15.5 per cent patients. The non-responsiveness showed a significant and an independent association with gender [odds ratio (OR)=0.18, 95% confidence interval (CI)=0.01-0.78, P=0.023], TxB₂ (OR=1.00, 95% CI=1.00-1.01, P=0.013), CYP2C19*2 G>A (OR=3.33, 95% CI=1.04-10.69, P=0.044) and GPVI T>C (OR=0.23, 95% CI=0.08-0.67, P=0.007) after adjusting the demographic, clinical and genetic confounding factors when assessed between non-responder and responder compliant patients.

Interpretation & conclusions:

The study showed a significant association of genetic polymorphisms (CYP2C19*2 G>A and GPVI T>C) with DAPT non-responsiveness in MI patients. The findings of this study need further validation in a large cohort of patients with clinical follow up.

Bioactive peptides and proteins as alternative antiplatelet drugs

Antiplatelet drugs reduce the risks associated with atherothrombotic events and show various applications in diverse cardiovascular diseases including myocardial infarctions. Efficacy of the current antiplatelet medicines including aspirin, clopidogrel, prasugrel and ticagrelor, and the glycoprotein IIb/IIIa antagonists, are limited due to their increased risks of bleeding, and antiplatelet drug resistance. Hence, it is important to develop new effective antiplatelet drugs, with fewer side-effects. The vast repertoire of natural peptides can be explored towards this goal. Proteins and peptides derived from snake venoms and plants represent exciting candidates for the development of novel and potent antiplatelet agents. Consequently, this review discusses multiple peptides that have displayed antiplatelet aggregation activity in preclinical drug development stages. This review also describes the antiplatelet mechanisms of the peptides, emphasizing the signaling pathways intervened by them. Also, the hurdles encountered during the development of peptides into antiplatelet drugs have been listed. Finally, hitherto unexplored peptides with the potential to prevent platelet aggregation are explored.

Synthesis and in vitro anti-platelet aggregation activities of 2-methoxy-5-arylamido-N-(pyridin-3-yl-methyl)benzamides

In order to discover novel compounds with anti-platelet aggregation activities, a series of novel 2-methoxy-5-arylamido-N-(pyridin-3-ylmethyl)benzamides (1a-n) were synthesized and their anti-platelet aggregation activities were evaluated by the turbidimetric method in response to the following agonists: adenosine diphosphate (ADP) (5 mM/L), arachidonic acid (AA) (20 µM/L), and collagen (1 mg/mL). Those synthesized compounds that have better in vitro activities were subjected to cell toxicity tests via cell counting kit-8 (CCK-8) assay. The biological evaluation revealed that compound 1a (IC₅₀ : 0.21 µM/L) exhibited the highest anti-platelet aggregation activities when ADP was selected as an inducer, and compound 1b (IC₅₀ : 0.23 µM/L) showed the best activities when AA was selected as inducer, and compound 1m (inhibition rate: 55.06%) had significant anti-platelet aggregation activities when collagen was selected as inducer among all target compounds. Moreover, the effect of cell toxicity exhibited that none of the compounds had obvious cell toxicity against L929 cells. Therefore, 2-methoxy-5-arylamido-N-(pyridin-3-ylmethyl)benzamides have the potential to become a novel kind of anti-platelet drugs and deserve further study.

The impact of CYP2C19*2, CYP4F2*3, and clinical factors on platelet aggregation, CYP4F2 enzyme activity, and 20-hydroxyeicosatetraenoic acid concentration in patients treated with dual antiplatelet therapy

: The aim of the current study was to evaluate the impact of CYP2C192 (rs4244285), CYP4F23 (rs2108622), and nongenetic factors on platelet aggregation and to investigate the mechanism of CYP4F2's effect on platelet aggregation in the patients treated with dual antiplatelet therapy. A total of 146 patients were included in this study. Ticagrelor or clopidogrel were administered in a loading dose of 180 mg and 600 mg, respectively, in combination with aspirin (300 mg). Blood samples for analysis were taken the next morning after antiplatelet therapy induction. Clopidogrel users with the CYP2C1912 variant had higher platelet aggregation values (median 43, range 30-54%) compared with 11 wild-type carriers (median 33, range 15-77%; P = 0.009). Carriers of the CYP4F213 variant had higher platelet aggregation values than carriers of the 33 variant (median 34, range 8-70% vs. median 24.5, range 10-47%, P = 0.016, respectively). Higher CYP4F2 concentrations were detected in clopidogrel users than in ticagrelor users (median 3.6, range 1.6-22.0 ng/ml vs. median 2.3, range 1.6-27.2 ng/ml, P = 0.056, respectively) and in carriers of the CYP4F213 variant compared with carriers of the 11 variant (median 4.3, range 1.6-27.2 ng/ml vs. median 2.4, range 1.6-22.0 ng/ml, P = 0.009, respectively). No correlation between plasma 20-hydroxyeicosatetraenoic acid and CYP4F2 enzyme concentrations were detected (r = -0.045, P = 0.587). Our results proved that CYP2C192 might significantly affect antiplatelet function of clopidogrel. Plasma CYP4F2 concentrations were significantly lower in ticagrelor users than in clopidogrel users.

Anti-platelet effects of epigallocatechin-3-gallate in addition to the concomitant aspirin, clopidogrel or ticagrelor treatment

BACKGROUND/AIMS

Although epigallocatechin-3-gallate (EGCG), which is found in high contents in the dried leaves of green tea, has been reported to have an anti-platelet effect, synergistic effects of EGCG in addition to current anti-platelet medications remains to be elucidated.

METHODS

Blood samples were obtained from 40 participants who took aspirin (ASA, n = 10), clopidogrel (CPD, n = 10), ticagrelor (TCG, n = 10) and no anti-platelet medication (Control, n = 10). Ex vivo platelet aggregation and adhesion under various stimulators were analyzed by multiple electrode aggregometry (MEA) and Impact-R systems. PAC-1 and P-selectin expressions in human platelets were analyzed by flow cytometry.

RESULTS

In MEA analysis, adenosine diphosphate (ADP) and thrombin receptor activating peptide (TRAP)-induced platelet aggregations were lower in the CPD and the TCG groups; arachidonic acid (AA)-induced platelet aggregation was lower in the ASA group, whereas collagen (COL)-induced platelet aggregations were comparable among four groups. EGCG significantly reduced ADP- and COL-induced platelet aggregation in dose-dependent manner (ADP, p = 0.04; COL, p < 0.01). There were no additional suppressions of platelet aggregation stimulated by AA in the ASA group, and by ADP in the CPD and TCG groups. Moreover, EGCG suppressed shear stress-induced platelet adhesion on Impact-R, and had no effect on P-selectin and PAC-1 expressions.

CONCLUSIONS

Ex vivo treatment of EGCG inhibited platelet adhesion and aggregation without changes in P-selectin and PAC-1 expression. There was no additional suppressions in platelet aggregation stimulated by AA in the ASA group and ADP in the CPD and TCG groups.

Splicing of platelet resident pre-mRNAs upon activation by physiological stimuli results in functionally relevant proteome modifications

Platelet activation triggers thrombus formation in physiological and pathological conditions, such as acute coronary syndromes. Current therapies still fail to prevent thrombotic events in numerous patients, indicating that the mechanisms modulating platelet response during activation need to be clarified. The evidence that platelets are capable of de novo protein synthesis in response to stimuli raised the issue of how megakaryocyte-derived mRNAs are regulated in these anucleate cell fragments. Proteogenomics was applied here to investigate this phenomeon in platelets activated in vitro with Collagen or Thrombin Receptor Activating Peptide. Combining proteomics and transcriptomics allowed in depth platelet proteome characterization, revealing a significant effect of either stimulus on proteome composition. In silico analysis revealed the presence of resident immature RNAs in resting platelets, characterized by retained introns, while unbiased proteogenomics correlated intron removal by RNA splicing with changes on proteome composition upon activation. This allowed identification of a set of transcripts undergoing maturation by intron removal during activation and resulting in accumulation of the corresponding peptides at exon-exon junctions. These results indicate that RNA splicing events occur in platelets during activation and that maturation of specific pre-mRNAs is part of the activation cascade, contributing to a dynamic fine-tuning of the transcriptome.

Adequate Platelet Function Inhibition Confirmed by Two Inductive Agents Predicts Lower Recurrence of Ischemic Stroke/Transient Ischemic Attack

Background

The correlation between platelet function and recurrent ischemic stroke or TIA remains uncertain.

Objective

To investigate two inductive agents to detect platelet functions and assess associations with recurrent ischemic stroke/TIA.

Method

The study included 738 ischemic stroke/TIA patients. On days 0, 3, and 9 after antiplatelet therapy, platelet function tests were determined by maximum aggregation rate (MAR) using a PL-11 platelet function analyzer and phase matching reagents. Two induction agents were used: arachidonic acid (AA) and adenosine diphosphate (ADP). At 3-month follow-up, recurrence of stroke/TIA was recorded.

Result

Cut-off values of adequate platelet function inhibition were MAR_ADP < 35% and MAR_AA < 35%. Data showed that antiplatelet therapy could reduce the maximum aggregation rate. More importantly, adequate platelet function inhibition of either MAR_ADP or MAR_AA was not associated with the recurrence of stroke/TIA, but adequate platelet function inhibition of not only MAR_ADP but also MAR_AA predicts lower recurrence (0/121 (0.00%) versus 18/459 (3.92%), P = 0.0188).

Conclusion

The platelet function tested by PL-11 demonstrated that adequate inhibition of both MAR_ADP and MAR_AA could predict lower risk of ischemic stroke/TIA recurrence.

Interactions among COX-2, GPIIIa and P2Y1 variants are associated with aspirin responsiveness and adverse events in patients with ischemic stroke

Background:

The effect of gene variants and their interactions on response to aspirin and clinical adverse outcomes after an acute ischemic stroke (IS) is not fully understood. The aim of this study was to investigate the association of aspirin-relevant gene variants and their interactions with clinical adverse outcomes in IS patients taking aspirin.

Methods:

A total of 14 variants from six genes encoding COX enzymes (COX-1, COX-2), platelet membrane receptors (TXAS1, P2Y1, P2Y12) and glycoprotein receptor (GPIIIa) were examined in 850 acute IS patients. Gene–gene interactions were analyzed using generalized multifactor dimensionality reduction (GMDR) analysis. All patients were followed up for 1 year after admission. Primary outcome was a composite of recurrent ischemic stroke (RIS), myocardial infarction (MI) and death.

Results:

The primary outcome occurred in 112 (13.5%) patients (81 RIS, 16 MI and 15 deaths). There were no significant differences in the frequencies of the genotypes of the 14 variants between the patients with and without primary outcome using single-locus analytical approach. However, there was significant gene–gene interaction among rs20417, rs1371097 and rs2317676. The high-risk interactive genotypes of rs20417, rs1371097 and rs2317676 were independently associated with primary adverse outcome of RIS, MI, and death after acute IS.

Conclusion:

The three-loci interactions are associated with sensitivity of IS patients to aspirin and aspirin-induced adverse clinical events. The combinatorial analysis used in this study may be helpful to elucidate complex genetic risk of aspirin resistance (AR).

Clinical trial registration:

The study described here is registered at http://www.chictr.org/ (unique identifier: ChiCTR-OCH-14004724).

Anti-platelet Therapy Resistance - Concept, Mechanisms and Platelet Function Tests in Intensive Care Facilities

It is well known that critically ill patients require special attention and additional consideration during their treatment and management. The multiple systems and organ dysfunctions, typical of the critical patient, often results in different patterns of enteral absorption in these patients. Anti-platelet drugs are the cornerstone in treating patients with coronary and cerebrovascular disease. Dual anti-platelet therapy with aspirin and clopidogrel is the treatment of choice in patients undergoing elective percutaneous coronary interventions and is still widely used in patients with acute coronary syndromes. However, despite the use of dual anti-platelet therapy, some patients continue to experience cardiovascular ischemic events. Recurrence of ischemic events is partly attributed to the fact that some patients have poor inhibition of platelet reactivity despite treatment. These patients are considered low- or non-responders to therapy. The underlying mechanisms leading to resistance are not yet fully elucidated and are probably multifactorial, cellular, genetic and clinical factors being implicated. Several methods have been developed to asses platelet function and can be used to identify patients with persistent platelet reactivity, which have an increased risk of thrombosis. In this paper, the concept of anti-platelet therapy resistance, the underlying mechanisms and the methods used to identify patients with low responsiveness to anti-platelet therapy will be highlighted with a focus on aspirin and clopidogrel therapy and addressing especially critically ill patients.