Platelet Activation Status Research Articles

Zolmitriptan niosomal transdermal patches: combating migraine via epigenetic and endocannabinoid pathways and reversal of migraine hypercoagulability.

Conventional zolmitriptan (ZOL) has limited oral bioavailability, many adverse effects, and poor membrane penetrability that negatively influences its accessibility to its 5-HT1B/1D receptor binding pocket, located transmemberanous. This work aimed at preparing transdermal ZOL-nanoformulation (niosomes) to surpass these limitations and to explore novel antimigraine mechanisms for ZOL via modulation of the epigenetically-altered chronification genes (RAMP-1, NPTX-2) or microRNAs and affecting the endocannabinoid CB-1/MAPK pathway. The prepared ZOL niosomes (Fsp60/6-1:1) exhibited %EE of 57.28%, PS of 472.3nm, PDI of 0.366, and ZP of -26 mV were cast into patch with content uniformity of 93.12%, maintained endurance after 200-times folding, no interaction between its components (FT-IR), a biphasic release pattern and good stability after storage at 4°C for 6 months. In-vivo ZOL-patch application in rats with nitroglycerin-induced migraine showed significant management of migraine pain symptoms and photophobia assessed behaviorally, decreased brain levels of the trigeminal neuronal activation marker (c-fos), the migraine pain neurotransmitter (CGRP) and the serum levels of different migraine pain markers (substance P, nitric-oxide, and TNF-α). It also significantly decreased RAMP-1, NPTX-2, miR-382-5p, and CB-1/MAPK gene expression reflecting improved efficacy and brain receptors delivery to a much greater extent than conventional ZOL has done. Additionally, this nanoformulation significantly opposed migraine-induced platelet activation and hypercoagulable status in both central and peripheral circulations as evidenced by the significant decrease in adenosine diphosphate, thrombin, factor X, CD41, and Von-Willebrand factor levels assessed peripherally and centrally. TPFsp60/6-1:1 significantly improved ZOL efficacy and accessibility to brain-receptors to a much greater extent than conventional ZOL-solution.KeywordsEndocannabinoid receptors; Epigenetically-altered genes; Hemostatic pathways; Niosomal patch; Transdermal; Zolmitriptan.

The impact of depression on platelet activation, cardiocerebral vascular events and arteriovenous fistula dysfunction in patients undergoing haemodialysis

Depression is a common psychiatric disorder among patients undergoing maintenance haemodialysis (MHD). Depression may reportedly contribute to poor prognosis in several ways, including its effects on platelet function. We hypothesised that depression contributes to the occurrence of cardiocerebral vascular events (CCVE) and dysfunction of arteriovenous fistula (DAVF) in patients undergoing MHD through its effects on platelets. In this prospective cohort study, patients undergoing MHD were recruited and divided into depression and non-depression groups according to their Hamilton Depression Scale (HAMD) scores. The 286 enrolled patients had 103 occurrences of depressive symptoms (prevalence = 36.01%). Compared with the non-depression group, depression group had a significantly higher cumulative prevalence of CCVE and DAVF during follow-up. Cox regression analysis indicated that higher HAMD scores and lower plasma platelet distribution width (PDW) were common risk factors for CCVE and DAVF. Furthermore, HAMD scores were significantly negatively correlated with plasma PDW and was the main variable affecting changes in PDW, as indicated by multiple linear regression analysis. Depression may increase the risk of CCVE and DAVF in patients undergoing MHD by activating platelets. Plasma PDW may be a convenient indicator of platelet activation status and may predict the risk of CCVE and DAVF.

Multi-parametric thrombus profiling microfluidics detects intensified biomechanical thrombogenesis associated with hypertension and aging.

Arterial thrombosis, which represents a critical complication of cardiovascular diseases, is a leading cause of death and disability worldwide with no effective bioassay for clinical prediction. As a symbolic feature of arterial thrombosis, severe stenosis in the blood vessel creates a high-shear, high-gradient flow environment that effectively facilitates platelet aggregation towards vessel occlusion even with platelet amplification loops inhibited. However, no approach is currently available to comprehensively characterize the size, composition and platelet activation status of thrombi forming under this biorheological condition. Here, we present a thrombus profiling assay that monitors the multi-dimensional attributes of thrombi forming in conditions mimicking the physiological scenario of arterial thrombosis. Using this platform, we demonstrate that different receptor-ligand interactions contribute distinctively to the composition and activation status of the thrombus. Our investigation into hypertensive and older individuals reveals intensified biomechanical thrombogenesis and multi-dimensional thrombus profile abnormalities, demonstrating a direct contribution of mechanobiology to arterial thrombosis and endorsing the diagnostic potential of the assay. Furthermore, we identify the hyperactivity of GPIbα-integrin αIIbβ3 mechanosensing axis as a molecular mechanism that contributes to hypertension-associated arterial thrombosis. By studying the interactions between anti-thrombotic inhibitors and hypertension, and the inter-individual variability in personal thrombus profiles, our work reveals a critical need for personalized anti-thrombotic drug selection that accommodates each patient's pathological profile.

Coagulation, fibrinolysis and platelet drop in patients undergoing transfemoral transcatheter aortic valve implantation.

Transcatheter aortic valve implantation (TAVI) leads to transient platelet activation and hypercoagulation status, resulting in thrombocytopenia. This study investigated the associations of coagulation/fibrinolysis status after transfemoral TAVI with valve type, post-TAVI thrombocytopenia, and complication of TAVI. Thrombin-antithrombin complex (TAT) and fibrin/fibrinogen degradation product (FDP) levels were measured before and 1 h, 1 day, and 2 days after TAVI. A percentage drop in platelet count (DPC) was determined from the pre- and lowest post-procedural values. SAPIEN 3 (S3) was implanted in 158 patients and Evolut PRO/PRO+ (Evolut) in 117. Both TAT and FDP increased after TAVI. Pre-TAVI balloon dilatation was generally performed on patients undergoing implantation with Evolut. Peak TAT was then stratified into 4 quartiles (Q1 to Q4). Of all 275 study patients, 69 patients reached ultra-hypercoagulation status (Q4). S3, TAVI without pre-balloon dilatation, DPC and bleeding complications were significantly associated with the ultra-hypercoagulation status after TAVI. TAT was significantly greater 1 h after S3 implantation than Evolut (median [IQR], 43.1 [34.1-59.6] vs. 31.0 [25.0-40.4] ng/mL; p < 0.001). In contrast, FDP levels did not differ between the two at any measurement point. The difference in DPC among the peak TAT quartiles was statistically significant (p < 0.001). The occurrence of bleeding complications was significantly higher in the group with ultra-hypercoagulation status (5.8% vs. 1.0%, p = 0.036). The increase in coagulation status and post-TAVI thrombocytopenia were significantly greater after S3 implantation. Ultra-hypercoagulation after TAVI was related to bleeding complications.

Evaluation of coagulation and platelet activation state and function in heartworm-infected dogs.

Enhanced platelet responses have been demonstrated in heartworm-infected (HWI) dogs; however, the cause and clinical implications of altered platelet function have not been fully elucidated. This study evaluated platelet function in HWI dogs. Anticoagulated whole blood collected from eight HWI and eight uninfected dogs was evaluated using turbidometric platelet aggregometry, a platelet function analyzer (PFA-100), a total thrombus analysis system (T-TAS), tissue factor-activated and tissue plasminogen activator modified thromboelastography (TF- and tPA-TEG), CBC, von Willebrand Factor activity, and fibrinogen concentrations. Platelet activation state and the presence of reticulated platelets were assessed via flow cytometric expression of P-selection (CD-62P) and thiazole orange staining. Platelet aggregation responses to adenosine diphosphate (ADP, 10 μM) or collagen (20 μg/mL), PFA-100 closure times, and T-TAS occlusion times did not differ between groups. TEG values TF-R, tPA-R, TF-K, and TF-LY60 were decreased (P = .025, P = .047, P = .038, P = .025) and TF-MA, tPA-MA, TF-G, tPA-G and TF-alpha angle were increased (P < .04) in HWI dogs. HWI dogs had higher fibrinogen concentrations (465.6 ± 161 mg/dL vs 284.5 ± 38 mg/dL, P = .008) and eosinophil counts (0.686 ± 0.27 × 103/μL vs 0.267 ± 0.20 × 103/μL, P = .003). There was no difference in hematocrit, activation state, or percent of reticulated platelets. Non-activated reticulated platelets exhibited higher CD62P expression compared with mature platelets. Chronic canine heartworm disease was accompanied by hypercoagulability, hyperfibrinogenemia, and decreased fibrinolysis. Enhanced platelet activation was not identified in this group of HWI dogs.

Platelet Activation Pathways Controlling Reversible Integrin αIIbβ3 Activation.

Background Agonist-induced platelet activation, with the integrin αIIbβ3 conformational change, is required for fibrinogen binding. This is considered reversible under specific conditions, allowing a second phase of platelet aggregation. The signaling pathways that differentiate between a permanent or transient activation state of platelets are poorly elucidated. Objective To explore platelet signaling mechanisms induced by the collagen receptor glycoprotein VI (GPVI) or by protease-activated receptors (PAR) for thrombin that regulate time-dependent αIIbβ3 activation. Methods Platelets were activated with collagen-related peptide (CRP, stimulating GPVI), thrombin receptor-activating peptides, or thrombin (stimulating PAR1 and/or 4). Integrin αIIbβ3 activation and P-selectin expression was assessed by two-color flow cytometry. Signaling pathway inhibitors were applied before or after agonist addition. Reversibility of platelet spreading was studied by microscopy. Results Platelet pretreatment with pharmacological inhibitors decreased GPVI- and PAR-induced integrin αIIbβ3 activation and P-selectin expression in the target order of protein kinase C (PKC) > glycogen synthase kinase 3 > β-arrestin > phosphatidylinositol-3-kinase. Posttreatment revealed secondary αIIbβ3 inactivation (not P-selectin expression), in the same order, but this reversibility was confined to CRP and PAR1 agonist. Combined inhibition of conventional and novel PKC isoforms was most effective for integrin closure. Pre- and posttreatment with ticagrelor, blocking the P2Y 12 adenosine diphosphate (ADP) receptor, enhanced αIIbβ3 inactivation. Spreading assays showed that PKC or P2Y 12 inhibition provoked a partial conversion from filopodia to a more discoid platelet shape. Conclusion PKC and autocrine ADP signaling contribute to persistent integrin αIIbβ3 activation in the order of PAR1/GPVI > PAR4 stimulation and hence to stabilized platelet aggregation. These findings are relevant for optimization of effective antiplatelet treatment.

Comprehensive investigation of platelet function in patients with cirrhosis

Cirrhosis presents with thrombocytopenia and possibly thrombocytopathy. Previous studies exploring platelet function gave conflicting results and most controversies are explained by the variety of methods employed for investigation. We sought to assess in-vitro the overall platelet function in cirrhosis.We investigated 34 patients by using the following tests. (i)Aggregometry. (ii)Measurement of the content of platelet granules. (iii)Cytometric platelet activation. (iv)Plasmatic markers of in-vivo platelet activation. (v)Platelet procoagulant activity by thrombin generation (TG) in platelet-rich plasma (PRP).TG measured in PRP for patients and controls was similar. Platelets from patients with cirrhosis showed reduction of aggregation and secretion of ATP. Similar results were observed for platelet activation parameters such as P-selectin expression and PAC-1 platelet binding. Plasma levels of βeta-thromboglobulin and soluble P-selectin, were increased in patients-vs-controls. In contrast, there were no patients-vs-controls differences for plasmatic platelet-factor-4. Results are consistent with a state of in-vivo platelet activation and decreased in-vitro aggregation. Since bleeding events following invasive procedures are uncommon in cirrhosis, we speculate that in-vitro aggregometry testing does not reflect the situation occurring in-vivo. Results of the study and pathophysiological considerations support the conclusion that platelet function in cirrhosis as determined by aggregometry, although somewhat impaired, may support the overall hemostatic potential, which is needed for most invasive interventions. These conclusions are in line with the recommendations of international guidelines, warning against indiscriminate use of prophylactic preprocedural administration of platelets before invasive procedures. Decision on platelet support should not be made based on in-vitro laboratory testing for platelet function.

The Effect of Cytokine Adsorption on Leukocyte and Platelet Activation after Extracorporeal Cardiopulmonary Resuscitation.

Post-cardiac arrest syndrome (PCAS) is a frequent complication following successful cardiopulmonary resuscitation and correlates with poor outcome. PCAS is characterized by an excessive inflammatory response to whole-body ischemia and reperfusion. Cytokine adsorption was suggested as an adjunctive treatment option for the removal of cytokines from the patients' blood to restore the physiological equilibrium of pro- and anti-inflammatory activity and thus mitigate hemodynamic instability and end-organ complications. To better understand the cellular effects of cytokine adsorption in patients receiving extracorporeal cardiopulmonary resuscitation (ECPR) after in- and out-of-hospital cardiac arrest, we compared the activation status of neutrophils, monocytes, and platelets as well as the formation of platelet-leukocyte complexes in intravenous whole blood samples from an exploratory subgroup (n = 24) from the randomized CYTER study. At 48 hours after initiation of ECPR, flow cytometry analyses did neither reveal significant differences in neutrophil (CD11b, CD66b, L-selectin, and PSGL-1) and monocyte (CD11b, L-selectin, and PSGL-1) surface molecule expression nor in circulating platelet-monocyte complexes between patients receiving cytokine adsorption and those without. Data did not show a relevant effect of cytokine adsorption on neutrophil and monocyte activation during the first 48 hours after initiation of ECPR.

Platelet derived exosomes disrupt endothelial cell monolayer integrity and enhance vascular inflammation in dengue patients.

Thrombocytopenia is the most notable phenomenon in dengue. Activation status of platelets and interaction of platelets with endothelium contribute towards dengue disease pathogenesis. Platelets are the major cell types known to release extracellular vesicles, especially exosomes in circulation. However, the role of platelet derived exosomes (PLT-EXOs) in endothelial dysfunction during dengue infection remains unknown. In this study, we recruited 28 healthy subjects and 69 dengue patients categorized as WS- (n=31), WS+ (n=29) and SD (n=9). Platelets were isolated from platelet rich plasma of dengue patients and their activation was assessed by flow cytometry. PLT-EXOs were isolated by ultracentrifugation method. Western blot analyses were performed to characterize the exosomes. Exosome uptake experiment was carried out to see the internalization of exosomes inside endothelial cells (HUVECs). To observe the effect of exosomes on endothelial cells, exosomes were added on HUVECs and expression of adherens and tight junctional proteins were examined by immunofluorescence assay and western blot. Expression levels of vascular injury markers were measured in the culture supernatants of Exosome-HUVEC coculture and sera of dengue patients by MSD-multiplex assay. As compared to healthy subjects, CD41/CD61 expression was significantly reduced (p<0.0001) and CD62p expression was significantly increased (p<0.0001) on platelets in dengue patients. PLT-EXOs isolated from the dengue patients showed higher expression of CD63 and CD9 proteins than the healthy subjects. With in-vitro immunofluorescence assays, we illustrated the internalization of PLT-EXOs by the HUVECs and observed disruption of endothelial cell monolayer integrity in the presence of PLT-EXOs from WS+ and SD patients. Furthermore, the significant reduction in the expressions of ZO-2, VE-Cadherin and CD31 in endothelial cells following exposure to PLT-EXOs from the dengue patients provide direct evidence of PLT-EXOs mediated vascular permeability. PLT-EXOs stimulated the release of inflammatory markers CRP, SAA, sVCAM-1 and sICAM-1 in the supernatants of HUVEC cells. Importantly, significantly higher levels of CRP, sVCAM-1 and sICAM-1 in the sera of severe than mild dengue patients (p<0.0001) suggest their role in disease severity. In summary, our data suggest that PLT-EXOs promote vascular leakage via release of proinflammatory mediators and compromise vascular barrier integrity in dengue patients.

Platelet metabolic remodeling in thrombosis

Many human diseases are associated with hyperactivity of platelet metabolism. Understanding in detail the connection between metabolic changes and platelet activation state is an indispensable part of thrombosis treatment. This review describes changes in the energy metabolism of platelets during thrombosis and their potential molecular mechanisms. The metabolic flexibility of energy substrate selection in activated platelets is discussed briefly, along with strategies by which platelet activation and thrombosis formation can be blocked by targeting activated platelet metabolism.

Rapid and Nondestructive Evaluation of Platelet Function in Whole Blood by Microfluidic Deterministic Cytometry.

Platelet size is a determinant of platelet function. Here, a new microfluidic deterministic cytometry packed with S-shaped micropillars (S-MDC) was developed to rapidly and sensitively determine the apparent size (Dapp) of platelets, which was used to evaluate platelet function. The platelet Dapp in the diluted whole blood was rapidly and label-freely measured by S-MDC within 2 min under shear rates (0.4 mm/s) that mimicked physiological conditions. The level of CD62p on platelets scarcely changed before and after platelets went through the whole S-MDC, indicating that the platelet function was nondestructive. Notably, the human platelet Dapp determined before and after thrombin addition by S-MDC was highly coincident with the levels of CD62p on the platelet surface by flow cytometry (r = 0.819), revealing that the human platelet Dapp was available to assess the platelet activation state. In addition, the results of the rat platelet Dapp were consistent with myocardial injury of rats with myocardial ischemia before and after treatment with antiplatelet agents, suggesting that rat platelet Dapp can be used to reflect myocardial injury in vivo outcomes. These findings reveal that S-MDC is a promising technique for screening tests for a bleeding disorder, in addition to monitoring antiplatelet drugs.

Vibro-Acoustic Platelet Activation: An Additive Mechanism of Prothrombosis with Applicability to Snoring and Obstructive Sleep Apnea.

Introduction: Obstructive sleep apnea (OSA) and loud snoring are conditions with increased cardiovascular risk and notably an association with stroke. Central in stroke are thrombosis and thromboembolism, all related to and initiaing with platelet activation. Platelet activation in OSA has been felt to be driven by biochemical and inflammatory means, including intermittent catecholamine exposure and transient hypoxia. We hypothesized that snore-associated acoustic vibration (SAAV) is an activator of platelets that synergizes with catecholamines and hypoxia to further amplify platelet activation. Methods: Gel-filtered human platelets were exposed to snoring utilizing a designed vibro-acoustic exposure device, varying the time and intensity of exposure and frequency content. Platelet activation was assessed via thrombin generation using the Platelet Activity State assay and scanning electron microscopy. Comparative activation induced by epinephrine and hypoxia were assessed individually as well as additively with SAAV, as well as the inhibitory effect of aspirin. Results: We demonstrate that snore-associated acoustic vibration is an independent activator of platelets, which is dependent upon the dose of exposure, i.e., intensity x time. In snoring, acoustic vibrations associated with low-frequency sound content (200 Hz) are more activating than those associated with high frequencies (900 Hz) (53.05% vs. 22.08%, p = 0.001). Furthermore, SAAV is additive to both catecholamines and hypoxia-mediated activation, inducing synergistic activation. Finally, aspirin, a known inhibitor of platelet activation, has no significant effect in limiting SAAV platelet activation. Conclusion: Snore-associated acoustic vibration is a mechanical means of platelet activation, which may drive prothrombosis and thrombotic risk clinically observed in loud snoring and OSA.

Screening for Key Structural Differences in Thrombosis Versus Hemostasis through Single Platelet Analysis

INTRODUCTION: Taking a single platelet analysis (SPA) approach to score platelet activation states distribution within a thrombus provides a unique opportunity to examine cellular difference in the process of thrombotic versus hemostatic clot formation. Potentially, it may reveal platelet activation states are dispensable for hemostasis but critical for thrombosis, e.g., platelet infill within the interior cavities of thrombus. Hence, our goal of determining the distribution of platelet activation states and of a-granule content release in an occlusive clot compared to a hemostatic thrombus. METHODS: We used a femoral artery model in mice in which occlusive clots were induced by ferric chloride and hemostatic processes occurred within a puncture wound. Images were produced by wide area transmission electron microscopy of full thrombi cross sections, 3.185 nm XY pixel size, at various depths. We mapped and analyzed 2D images of ferric chloride induced clotting using automated SPA with locally run Zeiss Arivis Pro software. Through automated SPA, we segmented and mapped the distribution of tens of thousands of platelets and trapped red blood cells versus the vessel wall and associated vascular damage. The incidence of condensed and decondensed a-granules, an indicator of platelet secretion activity, was scored through Cloud implemented APEER models. Occlusive clot cross sections were analyzed at multiple scales to reveal the distribution of platelet activation states based on platelet shape or to reveal a-granule release state (condensed versus decondensed granules). For the simpler problem of SPA of puncture wound hemostasis, we manually scored platelet activation states across tens of thousands of platelets. RESULTS AND CONCLUSIONS: With respect to occlusive clotting, several significant results and conclusions emerged from the platelet shape analysis. In the occlusive clot, we observed that activated platelets adhering directly to the damaged area of the vessel wall, exposed intima, lost their shape, becoming oval with extended pseudopods to more compressed, compacted tightly adherent shape compared to circulating, discoid platelets. Tightly adherent platelets formed column-like projections that structured the interior of the clot. Alpha-granule secretion was apparent. Most interestingly, the interior space between columns was filled with loosely adherent elongated, discoid-shaped platelets that frequently contained decondensed a-granules indicative of granule release (Figure 1). To the best of our knowledge, these data are the first indications that discoid platelets can secrete at least partially, their a-granule contents. In addition to platelets in various activation states, ~7% of the clot cross-sectional area was occupied by shape distorted red blood cells trapped in clusters. Any morphological effect of the red blood cells on platelet activation was restricted to a short distance of ~5 microns. Our SPA analysis of the femoral artery, puncture wound thrombi, support at least two conclusions: 1) Decondensed a-granules were abundant in discoid platelets coating the intravascular “crown” of the 20 min post puncture thrombus, i.e., a-granule secretion by discoid platelet is found in both hemostasis and thrombosis. 2) Circular folding of the hemostatic thrombus to give complete infill of the artery would place discoid platelets within central interior portions of an occlusive clot. We suggest that there may well be shared principles of assembly between the two situations. Importantly, the intravascular accumulation of discoid platelets in hemostasis occurs post-bleeding cessation. Therefore, drugs selectively affecting this state would target preferentially thrombotic clots in which clot infill results in the accumulation of discoid platelets. Figure 1: Distribution of platelets within a cross section through the middle of a ferric chloride induced, occlusive femoral clot. A)Platelet rich clot showing extensive platelet adhesion to the intima, white line encircling the platelet rich clot, inset blowup of the centrally located discoid platelets B) Distribution of red blood cells (red) and elongated, discoid shaped platelets (yellow). C) Cloud based SPA of red blood cells, platelets (yellow), condensed a-granules (light blue) and decondensed a-granules (magenta). D) Global distributions of granules (light blue and magenta) relative to platelets.

Platelets of COVID-19 patients display mitochondrial dysfunction, oxidative stress, and energy metabolism failure compatible with cell death

BackgroundAlterations in platelet function have been implicated in the pathophysiology of COVID-19 since the beginning of the pandemic. While early reports linked hyperactivated platelets to thromboembolic events in COVID-19, subsequent investigations demonstrated hyporeactive platelets with a procoagulant phenotype. Mitochondria are important for energy metabolism and the function of platelets. ObjectivesHere, we sought to map the energy metabolism of platelets in a cohort of noncritically ill COVID-19 patients and assess platelet mitochondrial function, activation status, and responsiveness to external stimuli. MethodsWe enrolled hospitalized COVID-19 patients and controls between October 2020 and December 2021. Platelets function and metabolism was analyzed by flow cytometry, metabolomics, glucose fluxomics, electron and fluorescence microscopy and western blot. ResultsPlatelets from COVID-19 patients showed increased phosphatidylserine externalization indicating a procoagulant phenotype and hyporeactivity to ex vivo stimuli, associated with profound mitochondrial dysfunction characterized by mitochondrial depolarization, lower mitochondrial DNA–encoded transcript levels, an altered mitochondrial morphology consistent with increased mitochondrial fission, and increased pyruvate/lactate ratios in platelet supernatants. Metabolic profiling by untargeted metabolomics revealed NADH, NAD+, and ATP among the top decreased metabolites in patients’ platelets, suggestive of energy metabolism failure. Consistently, platelet fluxomics analyses showed a strongly reduced utilization of 13C-glucose in all major energy pathways together with a rerouting of glucose to de novo generation of purine metabolites. Patients’ platelets further showed evidence of oxidative stress, together with increased glutathione oxidation and synthesis. Addition of plasma from COVID-19 patients to normal platelets partially reproduced the phenotype of patients’ platelets and disclosed a temporal relationship between mitochondrial decay and (subsequent) phosphatidylserine exposure and hyporeactivity. ConclusionThese data link energy metabolism failure in platelets from COVID-19 patients with a prothrombotic platelet phenotype with features matching cell death.

Venous Thromboembolism Risk Assessment among Beta-thalassemia Patients

BACKGROUND: Thromboembolic (TE) disorders are among the most common complications of beta-thalassemia. We designed this cross-sectional study to investigate the state of hypercoagulability and platelet activation in patients with beta-thalassemia. PATIENTS AND METHODS: Seventy-five patients diagnosed with beta-thalassemia by hemoglobin electrophoresis were divided into three groups of 25 patients each: Group I (thalassemia trait), Group II (thalassemia intermedia [TI]), and Group III (thalassemia major). In addition, 50 healthy individuals were included as controls. Both patients and control groups were subjected to clinical and laboratory assessment, which included measurement of protein C, anti-thrombin III, D-dimer, CD41, CD42, CD61, and CD62P, and detection of beta-chain mutations. RESULTS: Levels of the platelet activation marker CD62P were significantly higher in beta-thalassemia patients (26.28 ± 18.01%) than in controls (4.78 ± 2.27%) (P &lt; 0.001). The D-dimer level was significantly higher in beta-thalassemia patients (348.41 ± 571.01 ng/mL) than in controls (71.6 ± 39.61 ng/mL) (P &lt; 0.001). Protein-C and AT-III levels were significantly lower in beta-thalassemia patients (71.45 ± 13.26%, 78.38 ± 15.32%) in comparison with controls (94.9 ± 13.03%, 96.52 ± 11.01%) (P &lt; 0.001 and P &lt; 0.001, respectively). TE disorders were found in 7/25 (9%) beta-thalassemia patients, especially in older and postsplenectomy patients. TE was most commonly found in beta-TI. Beta-chain mutations were found in all patients with TE disorders, especially compound heterozygous intervening sequence (IVS) (IVS1.6 [T &gt; C]/IVS1.110 [G &gt; A]). CONCLUSION: Postsplenectomy teenagers and adults with beta-thalassemia with lower levels of natural anticoagulant in the blood, an increased level of D-dimer, and platelet activator factor had a significantly higher risk for TE than those with childhood beta-thalassemia and the control group. In comparison with other beta-thalassemia patients, TI with beta-chain mutations is more likely to develop TE.

Monitoring circulating platelet activity to predict cancer-associated thrombosis

A characteristic clinical complication in cancer patients is the frequent incidence of thrombotic events. Numerous studies have shown hyperactive/activated platelets to be a critical earlier trigger for cancer-associated thrombus formation. However, there currently is no viable approach to monitor specific changes in tumor-associated platelet activity. Here, we describe a chromatograph-like microfluidic device that is highly sensitive to the activity status of peripheral circulating platelets in both tumor-bearing mice and clinical cancer patients. Our results show a strongly positive correlation between platelet activation status and tumor progression. Six-month follow-up data from advanced cancer patients reveal positive links between platelet activity level and thrombus occurrence rate, with a high predictive capacity of thrombotic events (AUC= 0.842). Our findings suggest that circulating platelet activity status determined by this microfluidic device exhibits sensitive, predictive potential for thrombotic events in cancer patients for directing well-timed antithrombosis treatment.

Thrombotic Mechanism Involving Platelet Activation, Hypercoagulability and Hypofibrinolysis in Coronavirus Disease 2019.

Coronavirus disease 2019 (COVID-19) has spread, with thrombotic complications being increasingly frequently reported. Although thrombosis is frequently complicated in septic patients, there are some differences in the thrombosis noted with COVID-19 and that noted with bacterial infections. The incidence (6-26%) of thrombosis varied among reports in patients with COVID-19; the incidences of venous thromboembolism and acute arterial thrombosis were 4.8-21.0% and 0.7-3.7%, respectively. Although disseminated intravascular coagulation (DIC) is frequently associated with bacterial infections, a few cases of DIC have been reported in association with COVID-19. Fibrin-related markers, such as D-dimer levels, are extremely high in bacterial infections, whereas soluble C-type lectin-like receptor 2 (sCLEC-2) levels are high in COVID-19, suggesting that hypercoagulable and hyperfibrinolytic states are predominant in bacterial infections, whereas hypercoagulable and hypofibrinolytic states with platelet activation are predominant in COVID-19. Marked platelet activation, hypercoagulability and hypofibrinolytic states may cause thrombosis in patients with COVID-19.

Acquired blood platelet disorder in patients with end-stage heart failure after implantation of a continuous centrifugal-flow left ventricular assist device: A prospective cohort study

BackgroundContinuous-flow left ventricular assist devices (CF-LVADs) are an established therapy for advanced heart failure. Thrombosis and hemorrhage are common complications after CF-LVAD implantation, which may be explained by device-induced platelet activation. Few data on the effect of CF-LVAD implantation on platelets are available to date. ObjectivesThe aim of this study was to characterize the change in the platelet activation status after CF-LVAD. MethodsPlatelet phenotype and reactivity were determined with flow cytometry in 32 adults with end-stage heart failure before and 4 to 6 weeks after CF-LVAD implantation. Sixteen adults with a biological aortic valve prosthesis (AVP) using the same antiplatelet regimen were included to discriminate between the effects of CF-LVAD and the antiplatelet regimen. Plasma markers for platelet activation were determined with enzyme-linked immunosorbent assay. ResultsMedian (IQR) plasma levels of soluble P-selectin increased from 115.6 (79.1-142.7) ng/mL to 144.5 (100.4-197.5) ng/mL after CF-LVAD implantation (P < .001). Median (IQR) β-thromboglobulin levels were 60.5 (37.8-81.5) ng/mL before implantation and remained high after LVAD implantation [60.0 (42.0-69.5) ng/mL]. The platelet P-selectin expression after stimulation with ADP (30 and 60 μM) or PAR1-activating peptide (12.5 and 25 μM) was reduced by 17% to 21%, and fibrinogen binding was reduced by 37% to 86%. Platelet responses to agonists were similar in patients with a CF-LVAD and patients with an AVP, except for fibrinogen binding in response to 12.5 μM PAR1-AP, which was lower in patients with a CF-LVAD (P < .001). ConclusionsCombined, these data provide evidence for systemic platelet activation and an acquired platelet disorder after CF-LVAD implantation. This might contribute to the risk of both hemorrhage and thrombosis associated with CF-LVADs.

Characterization of Shear Stress Mediated Platelet Dysfunction: Data from an Ex Vivo Model for Extracorporeal Circulation and a Prospective Clinical Study.

Extracorporeal circulation (ECC) is frequently used in intensive care patients with impaired lung or cardiac function. Despite being a life-saving therapeutic option, ECC is associated with increased risk for both bleeding and thrombosis. The management of bleeding and thromboembolic events in ECC patients is still challenging partly due to the lack of information on the pathophysiological changes in hemostasis and platelet function during the procedure. Using a combination of an ex vivo model for shear stress and a sensitive and easy-to-use laboratory method, we analyzed platelet responsiveness during ECC. After shear stress simulation in an ex vivo closed-loop ECC model, we found a significantly decreased response of α-granules after activation with adenosine diphosphate and thrombin receptor activating peptide (TRAP-6) and CD63 expression after activation with TRAP-6. Mepacrine uptake was also significantly reduced in the ex vivo shear stress model.In the same line, platelets from patients under ECC with venovenous systems and venoarterial systems showed impaired CD62P degranulation after stimulation with ADP and TRAP-6 compared with healthy control on day 1, 6, and 10 after implantation of ECC. However, no correlation between platelet degranulation and the occurrence of bleeding or thromboembolic events was observed.The used whole blood flow cytometry with immediate fixation after drawing introduces a sensitive and easy-to-use method to determine platelet activation status and our data confirm that increased shear stress conditions under ECC can cause impaired degranulation of platelet.

823 MIGRAINE IN PFO PATIENTS: CHARACTERIZATION OF A PLATELET-ASSOCIATED PATHOPHYSIOLOGICAL MECHANISM BEFORE AND AFTER PFO CLOSURE: THE LEARNER STUDY

Abstract Background A strong relationship links migraine with aura (MHA) and patent foramen ovale (PFO). Increased platelet aggregation and oxidative stress were documented in migraineurs. To date, no mechanisms connecting MHA to PFO have been demonstrated. Objectives To perform a comprehensive analysis of platelet activation, inflammation, and oxidative stress status in 78 aspirin-treated MHA-patients before (T0) and 6-months after (T1) PFO closure (LEARNER Study-NCT03521193-clinicaltrials.gov). The primary endpoint was migraine regression rate in relation to these parameters. Methods P-selectinpos-, activated-glycoprotein IIbIIIa (aGPIIbIIIa)pos-, Tissue Factor (TF)pos-, reactive oxygen species (ROS)pos-platelets, platelet-leukocyte aggregates (PLA) and microvesicles (MVs) were evaluated by flow cytometry; thrombin generation (TG) by Calibrated Automated Thrombogram (CAT) assay; oxidative stress status by mass spectrometry; serotonin and cytokines by ELISA. 12 aspirin-treated-healthy subjects (HS) were enrolled for comparison. Results Migraine resolution occurred in 69.7%, a significant reduction in 27%, while no effect was observed in 2 patients (3.2%). Only ROSpos-platelets, and TFpos-platelets and -MVs were significantly higher at T0, sustaining a TG capacity that was associated with an altered blood GSSG/GSH (Oxidized/Reduced Glutathione). This phenotype reverted to HS levels at T1. MHA-PFO plasma, added to HS blood, mirrored the in vivo platelet activation and N-acetylcysteine blunted it. GSSG in vitro reproduced the in vivo condition. Aspirin had little effect on the platelet prothrombotic phenotype which was effectively inhibited by a P2Y12-antagonist. Conclusion This study suggests a pathophysiological mechanism linking PFO, or its right-to-left shunt, with MHA. MHA-PFO patients show a platelet-associated prothrombotic phenotype, sustained by altered oxidative stress status. This phenotype, not fully controlled by aspirin but by P2Y12-antagonism, could play a primary role in producing the prodromal symptoms of migraine, and it is reverted after PFO closure together with a complete migraine remission