A novel approach of platelet function test for prediction of attenuated response to clopidogrel

Gravity sedimentation reveals functionally and morphologically different platelets in human blood

In contrast to red blood cells, platelets float rather than sediment when a column of blood is placed in the gravitational field. By the analogy of erythrocyte sedimentation (ESR), it can be expressed with the platelet antisedimentation rate (PAR), which quantitates the difference in platelet count between the upper and lower halves of the blood column after 1 h of 1 g sedimentation. Venous blood samples from 21 healthy subjects were analyzed for PAR. After a 1-h sedimentation, the upper and lower fractions of blood samples were analyzed for platelet count, mean platelet volume (MPV), immature platelet fraction (IPF), and high-fluorescence IPF (H-IPF). The mechanisms behind platelet flotation were explored by further partitioning of the blood column, time-dependent measurements of platelet count and comparison with ESR. The structure and function of the platelets were assessed by electron microscopy (EM) and atomic force microscopy (AFM), and platelet aggregometry, respectively. Platelet antisedimentation is driven by density differences and facilitated by a size-exclusion mechanism caused by progressive erythrocyte sedimentation. The area under the curve (AUC) of the whole blood adenosine diphosphate (ADP) aggregation curves showed significant differences between the upper and lower samples (p < .005). AUC in the upper samples of 38% of healthy subjects exceeded the top of the normal range (53-122) suggesting that ascending platelets show an intensified ADP-induced aggregability ex vivo. H-IPF was significantly higher in the upper samples (p < .05). EM and AFM revealed that platelets in the upper samples were larger in volume and contained 1.6 times more alpha granules compared to platelets in the lower samples. Our results indicate that antisedimentation is able to differentiate platelet populations based on their structural and functional properties. Therefore, PAR may be a suitable laboratory parameter in various thromboinflammatory disorders.

Can we predict critical care mortality with non-conventional inflammatory markers in SARS-CoV-2 infected patients?

BACKGROUND

Severe COVID-19 disease is associated with multiple organ involvement,then failure and often fatal outcomes.In addition,inflammatory mechanisms and cytokine storms,documented in many COVID-19 patients,are responsible for the progression of the disease and high mortality rates.Inflammatory parameters,such as procalcitonin(PCT) and C-reactive protein(CRP), are widely used in clinical practice.

OBJECTIVE

To evaluate the predictive power of non-conventional inflammatory markers regarding mortality risk.

METHODS

In our prospective study 52 patients were followed for 5 days after admission to an intensive care unit immediately with severe SARS-CoV-2 infection.We compared leukocyte-,platelet antisedimentation rate (LAR, PAR),neutrophil lymphocyte ratio(NLR), CRP, PCT levels.

RESULTS

In non-surviving(NSU) patients LAR remained largely constant from D1 to D4 with a statistically significant drop(p <  0.05) only seen on D5.The NSU group showed statistically significant(p <  0.05) elevated LAR medians on D4 and D5, compared to the SU group.NLR values were continually higher in the non-survivor group.The difference between the SU and NSU groups were statistically significant on every examined day.PAR, CRP and PCT levels didn't show any significant differences between the SU and NSU groups.

CONCLUSIONS

In conclusion, this study suggests that LAR and NLR are especially worthy of further investigation as prognostic markers.LAR might be of particular relevance as it is not routinely obtained in current clinical practice.It would seem beneficial to include LAR in data sets to train prognostic artificial intelligence.

Plasma Fibrinogen Independently Predicts Hypofibrinolysis in Severe COVID-19

High rates of thrombosis are present in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Deeper insight into the prothrombotic state is essential to provide the best thromboprophylaxis care. Here, we aimed to explore associations among platelet indices, conventional hemostasis parameters, and viscoelastometry data. This pilot study included patients with severe COVID-19 (n = 21) and age-matched controls (n = 21). Each patient received 100 mg aspirin therapy at the time of blood sampling. Total platelet count, high immature platelet fraction (H-IPF), fibrinogen, D-dimer, Activated Partial Thromboplastin Time, von Willebrand factor antigen and von Willebrand factor ristocetin cofactor activity, plasminogen, and alpha2-antiplasmin were measured. To monitor the aspirin therapy, a platelet function test from hirudin anticoagulated whole blood was performed using the ASPI test by Multiplate analyser. High on-aspirin platelet reactivity (n = 8) was defined with an AUC > 40 cut-off value by ASPI tests. In addition, in vitro viscoelastometric tests were carried out using a ClotPro analyser in COVID-associated thromboembolic events (n = 8) (p = 0.071) nor the survival rate (p = 0.854) showed associations with high on-aspirin platelet reactivity status. The platelet count (p = 0.03), all subjects. COVID-19 patients presented with higher levels of inflammatory markers, compared with the controls, along with evidence of hypercoagulability by ClotPro. H-IPF (%) was significantly higher among non-survivors (n = 18) compared to survivors (p = 0.011), and a negative correlation (p = 0.002) was found between H-IPF and plasminogen level in the total population. The platelet count was significantly higher among patients with high on-aspirin platelet reactivity (p = 0.03). Neither the ECA-A10 (p = 0.008), and ECA-MCF (p = 0.016) were significantly higher, while the tPA-CFT (p < 0.001) was significantly lower among patients with high on-aspirin platelet reactivity. However, only fibrinogen proved to be an independent predictor of hypofibrinolysis in severe COVID-19 patients. In conclusion, a faster developing, more solid clot formation was observed in aspirin ‘non-responder’ COVID-19 patients. Therefore, an individually tailored thromboprophylaxis is needed to prevent thrombotic complications, particularly in the hypofibrinolytic cluster.

Silibinin augments the effect of clopidogrel on atherosclerosis in diabetic ApoE deficiency mice

BACKGROUND

Diabetes mellitus (DM) abolishes the antithrombotic effect of Clopidogrel. Here, we investigated the synergistic effect of Silibinin on Clopidogrel-mediated atherosclerosis treatment in diabetic mice.

METHODS

ApoE-/- mice were fed with high-fat diet (HFD) to establish the atherosclerotic model with diabetes. Animals were treated with Clopidogrel, Silibinin, or the combined to evaluate the protective effects on atherosclerosis and diabetes through Oil-red-O staining, qRT-PCR, Western blot, and metabolic measurements. Platelet activation and aggregation ex vivo assays were performed to detect the anti-thrombotic effect of different administrations.

RESULTS

Silibinin significantly enhanced the inhibitory effect of Clopidogrel on atherosclerosis in DM mice. Co-administration of Silibinin with Clopidogrel remarkedly reduced the aortic lesion, inflammation, and endothelial dysfunction in aorta roots, and diabetic symptoms were significantly improved by the Silibinin-Clopidogrel treatment in HFD-fed ApoE-/- mice. Interestingly, the anti-thrombotic effect of Clopidogrel was further augmented by the Silibinin treatment in atherosclerotic mice.

CONCLUSION

In atherosclerotic mouse model, Silibinin significantly improves the effect of Clopidogrel on atherosclerosis.

Novel Predictors of Future Vascular Events in Post-stroke Patients-A Pilot Study

Introduction: A modified platelet function test (mPFT) was recently found to be superior compared to impedance aggregometry for selection of post-stroke patients with high on-treatment platelet reactivity (HTPR). We aimed to explore some peripheral blood cell characteristics as predictors of recurrent ischemic episodes. The predictive value of mPFT was also assessed in a cohort followed up to 36 months regarding recurrent ischemic vascular events.

Methods: As a novelty, not only whole blood (WB), but after 1-h gravity sedimentation the separated upper (UB) and lower half blood (LB) samples were analyzed including neutrophil antisedimentation rate (NAR) in 52 post-stroke patients taking clopidogrel. Area under the curve (AUC, AUC_upper and AUC_lower, respectively) was separately measured by Multiplate in the WB, UB and LB samples to characterize ex vivo platelet aggregation in the presence of ADP. Next, the occurrence of vascular events (stroke, acute coronary syndrome, ACS) were evaluated during 36-month follow-up.

Results: A total of 11 vascular events (stroke n = 5, ACS n = 6) occurred during the follow-up period. The AUC_upper was significantly higher in patients with recurrent stroke compared to those with uneventful follow-up (p = 0.03). The AUC_upper with a cut-off value ≥70 based on the mPFT, was able to predict all stroke events (p = 0.01), while the total vascular events were independently predicted by NAR with a sensitivity of 82% and specificity of 88%.

Conclusions: A combination of NAR reflecting the inflammatory state and AUC_upper indicating HTPR may provide a better prediction of recurrent ischemic events suggesting a better selection of patients at risk, thus providing an individually tailored vascular therapy.

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.

Assessment of therapeutic platelet inhibition in cardiac patients: Comparative study between VerifyNow-P2Y12 and Anysis-P2Y12 assay

BACKGROUND

Analyzing responsiveness to P2Y12 therapy is vital to preventing thrombotic and hemorrhagic complications in patients with cardiovascular diseases.

OBJECTIVE

This study evaluates a new Anysis-P2Y12 assay system against VerifyNow-P2Y12 in cardiac patients and analyzes the P2Y12 low-response rates of the two devices with various cutoff values.

METHODS

In total, 125 citrated blood samples were collected from cardiac patients referred for a P2Y12 antiplatelet response test. In the Anysis assay, the test result was the migration distance (MD) until the blood flow stops, which is comparable to both P2Y12 reaction units and percent inhibition obtained using VerifyNow.

RESULTS

The MDs without and with P2Y12 were 182±30 and 264±12 mm, respectively (p <  0.0001). Compared to VerifyNow-P2Y12, the sensitivity and specificity of Anysis-200 were 96.8%and 88.7%, respectively. Cohen's kappa coefficient between the two devices was 0.761, indicating a high agreement. However, there was an apparent difference in the low-response rate to P2Y12, which was 36.5%for VerifyNow and 5.9%for Anysis.

CONCLUSIONS

The performance of the newly developed platelet function assay, Anysis-P2Y12 was equivalent to that of VerifyNow-P2Y12 in terms of sensitivity and specificity. The Anysis-P2Y12 assay may help screen patients with abnormal P2Y12 non-responsiveness.

Lack of early platelet and leukocyte activation can indicate complications after major burn injury

BACKGROUND

Major burn injury causes massive tissue destruction consequently enhanced platelet function and leukocyte-mediated inflammatory response.

METHODS

In a prospective, observational study 23 consecutive patients with more than 20% body surface burn injury were followed for five days (T1-T5) after admission to a university intensive care (ICU). Platelet and leukocyte antisedimentation rate (PAR and LAR) was measured by one-hour gravity sedimentation. It detects the percentage of total platelet and leukocyte number crossed the half line of blood sample column, therefore, they can be regarded as cells of decreased specific gravity. We aimed to investigate the time course of PAR and LAR after burn injury, as the trend of platelet and the leukocyte activation in the early post-burn period.

RESULTS

Daily mean PAR and LAR values continuously increased in the observation period (T1 to T5). Daily mean PAR and LAR were lower in ICU non-survivors (n = 7) compared to survivors (n = 16) between T2 and T4 (p < 0.05 and p < 0.01). PAR values of septic patients (n = 10) were lower than that of non-septic ones (n = 13, p < 0.01 at T5).

CONCLUSIONS

Both PAR and LAR, as novel bedside test can predict septic complications and unfavorable outcome after major burn injury. Further studies with higher sample size are warranted.

Effect of Prostanoids on Human Platelet Function: An Overview

Prostanoids are bioactive lipid mediators and take part in many physiological and pathophysiological processes in practically every organ, tissue and cell, including the vascular, renal, gastrointestinal and reproductive systems. In this review, we focus on their influence on platelets, which are key elements in thrombosis and hemostasis. The function of platelets is influenced by mediators in the blood and the vascular wall. Activated platelets aggregate and release bioactive substances, thereby activating further neighbored platelets, which finally can lead to the formation of thrombi. Prostanoids regulate the function of blood platelets by both activating or inhibiting and so are involved in hemostasis. Each prostanoid has a unique activity profile and, thus, a specific profile of action. This article reviews the effects of the following prostanoids: prostaglandin-D₂ (PGD₂), prostaglandin-E₁, -E₂ and E₃ (PGE₁, PGE₂, PGE₃), prostaglandin F_2α (PGF_2α), prostacyclin (PGI₂) and thromboxane-A₂ (TXA₂) on platelet activation and aggregation via their respective receptors.