Platelet Activation Markers Research Articles

Combined Effect of Acute Altitude Exposure and Vigorous Exercise on Platelet Activation

Exposure to high altitudes and exercise alters body's physiology and may cause acute cardiovascular events. Platelet activation is one of the key players in these events. Therefore, we investigated the effect of vigorous exercise at higher altitude (2650 m) on platelet aggregation and serum markers of platelet activation. 14 healthy subjects performed a step incremental ergometer test until exhaustion at the Environmental Research Station (UFS, 2650 m) at Zugspitze. Platelet aggregation and serum levels of endothelin-1, soluble p-selectin, platelet factor 4 and Chromogranin A were measured. Platelet activation was significantly enhanced after exercise at high altitude compared to measures immediately prior exercise. We detected significantly enhanced serum levels of endothelin-1 and soluble p-selectin whereas chromogranin A and platelet factor 4 remained unchanged. This effect might be due to increased endothelin-1 levels causing pulmonary vasoconstriction, rheological changes and direct platelet activation. This might be of clinical relevance, especially in patients with pre-existing diseases.

The effect of transdermal gender-affirming hormone therapy on markers of inflammation and hemostasis.

Cardiovascular risk is increased in transgender persons using gender-affirming hormone therapy. To gain insight into the mechanism by which sex hormones affect cardiovascular risk in transgender persons, we investigated the effect of hormone therapy on markers of inflammation and hemostasis. In this exploratory study, 48 trans women using estradiol patches plus cyproterone acetate (CPA) and 47 trans men using testosterone gel were included. They were between 18 and 50 years old and did not have a history of cardiovascular events. Measurements were performed before and after 3 and 12 months of hormone therapy. After 12 months, in trans women, systemic and endothelial inflammatory markers decreased (hs-CRP -66%, (95% CI -76; -53), VCAM-1-12%, (95% CI -16; -8)), while platelet activation markers increased (PF-4 +17%, (95% CI 4; 32), β-thromboglobulin +13%, (95% CI 2; 24)). The coagulation marker fibrinogen increased transiently, after 3 months (+15%, (95% CI 1; 32)). In trans men, hs-CRP increased (+71%, (95% CI 19; 145)); platelet activation and coagulation markers were not altered. In both trans women and trans men, leptin and adiponectin changed towards reference values of the experienced gender. Platelet activation and coagulation marker concentrations increased in trans women using transdermal estradiol plus CPA, but not in trans men using testosterone. Also, concentrations of inflammatory markers decreased in trans women, while hs-CRP increased in trans men. Our results indicate that hormone therapy may affect hemostasis in transgender persons, which could be an underlying mechanism explaining the increased cardiovascular risk in this population.

Circadian nuclear receptor Rev-erbα is expressed by platelets and potentiates platelet activation and thrombus formation.

AimsAdverse cardiovascular events have day/night patterns with peaks in the morning, potentially related to endogenous circadian clock control of platelet activation. Circadian nuclear receptor Rev-erbα is an essential and negative component of the circadian clock. To date, the expression profile and biological function of Rev-erbα in platelets have never been reported.Methods and resultsHere, we report the presence and functions of circadian nuclear receptor Rev-erbα in human and mouse platelets. Both human and mouse platelet Rev-erbα showed a circadian rhythm that positively correlated with platelet aggregation. Global Rev-erbα knockout and platelet-specific Rev-erbα knockout mice exhibited defective in haemostasis as assessed by prolonged tail-bleeding times. Rev-erbα deletion also reduced ferric chloride-induced carotid arterial occlusive thrombosis, prevented collagen/epinephrine-induced pulmonary thromboembolism, and protected against microvascular microthrombi obstruction and infarct expansion in an acute myocardial infarction model. In vitro thrombus formation assessed by CD41-labelled platelet fluorescence intensity was significantly reduced in Rev-erbα knockout mouse blood. Platelets from Rev-erbα knockout mice exhibited impaired agonist-induced aggregation responses, integrin αIIbβ3 activation, and α-granule release. Consistently, pharmacological inhibition of Rev-erbα by specific antagonists decreased platelet activation markers in both mouse and human platelets. Mechanistically, mass spectrometry and co-immunoprecipitation analyses revealed that Rev-erbα potentiated platelet activation via oligophrenin-1-mediated RhoA/ERM (ezrin/radixin/moesin) pathway.ConclusionWe provided the first evidence that circadian protein Rev-erbα is functionally expressed in platelets and potentiates platelet activation and thrombus formation. Rev-erbα may serve as a novel therapeutic target for managing thrombosis-based cardiovascular disease.Key questionAdverse cardiovascular events have day/night patterns with peaks in the morning, potentially related to endogenous circadian clock control of platelet activation. Whether circadian nuclear receptor Rev-erba is present in platelets and regulates platelet function remains unknown.Key findingWe provide the first evidence that Rev-erba is functionally expressed in platelets and acts as a positive regulator of platelet activation/thrombus formation through the oligophrenin-1-mediated RhoA/ERM signalling pathway.Take home messageOur observations highlight the importance of circadian clock machinery in platelet physiology and support the notion that Rev-erba may serve as a novel therapeutic target for managing thrombosis-based cardiovascular diseases.

SARS-CoV-2 infection induces soluble platelet activation markers and PAI-1 in the early moderate stage of COVID-19.

IntroductionCoagulation dysfunction and thromboembolism emerge as strong comorbidity factors in severe COVID‐19. However, it is unclear when particularly platelet activation markers and coagulation factors dysregulated during the pathogenesis of COVID‐19. Here, we sought to assess the levels of coagulation and platelet activation markers at moderate and severe stages of COVID‐19 to understand the pathogenesis.MethodsTo understand this, hospitalized COVID‐19 patients with (severe cases that required intensive care) or without pneumonia (moderate cases) were recruited. Phenotypic and molecular characterizations were performed employing basic coagulation tests including prothrombin time (PT), activated partial thromboplastin time (APTT), D‐Dimer, and tissue factor pathway inhibitor (TFPI). The flow cytometry‐based multiplex assays were performed to assess FXI, anti‐thrombin, prothrombin, fibrinogen, FXIII, P‐selectin, sCD40L, plasminogen, tissue plasminogen activator (tPA), plasminogen activator inhibitor‐1 (PAI‐1), and D‐Dimer.ResultsThe investigations revealed induction of plasma P‐selectin and CD40 ligand (sCD40L) in moderate COVID‐19 cases, which were significantly abolished with the progression of COVID‐19 severity. Moreover, a profound reduction in plasma tissue factor pathway inhibitor (TFPI) and FXIII were identified particularly in the severe COVID‐19. Further analysis revealed fibrinogen induction in both moderate and severe patients. Interestingly, an elevated PAI‐1 more prominently in moderate, and tPA particularly in severe COVID‐19 cases were observed. Particularly, the levels of fibrinogen and tPA directly correlated with the severity of the disease.ConclusionsIn summary, induction of soluble P‐selectin, sCD40L, fibrinogen, and PAI‐1 suggests the activation of platelets and coagulation system at the moderate stage before COVID‐19 patients require intensive care. These findings would help in designing better thromboprophylaxis to limit the COVID‐19 severity.

Responses of platelet CD markers and indices to resistance exercise with and without blood flow restriction in patients with type 2 diabetes

Diabetes mellitus is a common disorder with the risk of vascular injury. The aim of this study was to compare the effects of low-intensity resistance exercise with blood flow restriction versus high-intensity resistance exercise on platelet CD markers and indices in patients with type 2 diabetes. Fifteen female patients with type 2 diabetes (Mean±SD; age, 47.6±7.2 yrs) randomly completed two resistance exercise at an intensity corresponding to 20% and 80% of one-repetition maximum (1-RM), with and without blood flow restriction (REBFR and RE), respectively. We measured markers of platelet activation (P-selectin, GpIIb/IIIa, and CD42) and platelet indices before and immediately after exercise, and after 30 min recovery. Platelet count (PLT) and plateletcrit (PCT) increased in response to REBFR more than the RE (p < 0.05), though, no significant differences in PDW and MPV were observed (p < 0.05). Although P-selectin (CD62P), CD61, CD41, and CD42 were reduced following resistance exercise in both trials, these reductions were non-significant (p < 0.05). Besides, no significant between-group differences were found for platelet CD markers (p < 0.05). It is concluded that REBFR induces thrombocytosis, but responses of platelet CD markers in patients with type 2 diabetes are similar following low-intensity REBFR and high-intensity RE.

Platelet Activation Markers in Children with Pulmonary Arterial Hypertension Associated with Congenital Heart Disease

The study aimed to evaluate mean platelet volume (MPV), platelet distribution width (PDW), and platecrit in children with pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD), to assess the predictive value of these platelet activation markers for adverse outcomes, and to correlate their levels with various data in these patients. This prospective cohort study included 60 children with PAH-CHD as group I and 60 children with CHD and no PAH as group II. Another 60 healthy children of matched age and sex served as the control group. All included children were evaluated by echocardiography. MPV, PDW, and platecrit were also measured using an automated blood counter. All patients were followed up for death or readmission for 6 months. MPV, PDW, and platecrit were significantly higher in group I compared to group II and the control group and they correlated well with increasing severity of PAH. MPV, PDW, and platecrit positively correlated with right ventricular diameter and mean pulmonary artery pressure, however they correlated negatively with right ventricular systolic and diastolic function. The best cut-off of platelet activation markers levels to predict poor prognosis in group I was > 11.2 FL with 75% sensitivity and 96.6% specificity for MPV, > 12.7 FL with 75% sensitivity and 61.5% specificity for PDW, and > 0.505% with 75% sensitivity and 93.2% specificity for platecrit. MPV, PDW, and platecrit were elevated in children with PAH-CHD and found to be good predictive markers for poor prognosis in these children.

Red blood cell-derived phosphatidylserine positive extracellular vesicles are associated with past thrombotic events in patients with systemic erythematous lupus

BackgroundExtracellular vesicles (EVs) released by blood cells have proinflammation and procoagulant action. Patients with systemic lupus erythematosus (SLE) present high vascular inflammation and are prone to develop cardiovascular diseases. Therefore,...

Prognostic significance of mean platelet volume in patients with lung cancer: a meta-analysis.

ObjectiveThe mean platelet volume (MPV) is a measure of platelet size, and it is considered a surrogate marker of platelet activation. Because the correlation between platelet count/size and lung cancer prognosis remains unclear, this meta-analysis comprehensively evaluated the prognostic significance of MPV among patients with lung cancer.MethodsA systematic search of PubMed, Embase, Google Scholar, and additional sources of relevant studies were conducted with no language restrictions from inception to 7 May 2021. Overall survival (OS) and disease-free survival (DFS)/progression-free survival (PFS), as well as their hazard ratios (HR) and 95% confidence intervals (CIs), were pooled to evaluate the relationship between MPV and survival. The study protocol was registered on PROSPERO.ResultsEleven studies involving 2421 patients with lung cancer were included in our analysis. Nine studies including only patients with non-small cell lung cancer were included in the meta-analysis. Our analysis revealed no significant associations of MPV with OS (HR = 1.09, 95% CI = 0.84–1.41) and DFS/PFS (HR = 1.13, 95% CI = 0.58–2.20).ConclusionPretreatment MPV levels did not display prognostic significance in patients with NSCLC. Large-scale prospective studies and a validation study considering ethnicity and lung cancer staging are warranted.

Clinical Significance of PAC-1, CD62P, and Platelet-Leukocyte Aggregates in Acute Ischemic Stroke.

We studied diagnostic and treatment values of the blood levels of platelet activation markers PNA, PMA, PLyA, PAC-1, and CD62P in 30 patients with acute ischemic stroke (median NIHSS score 4 (2; 6)) before and after treatment as well as in comparison with the control group. The levels of these markers were measured by flow cytometry. In patients with acute ischemic stroke, the levels of PLyA, PAC-1, and CD62P were significantly increased in comparison with the controls; therapy significantly reduced the levels of PAC-1, CD62P, and PMA in patients with acute ischemic stroke. The areas under the ROC curve differentiating acute ischemic stroke from healthy controls for PAC-1, CD62P, and PLyA were 0.694, 0.862, and 0.760, respectively. Our findings suggest that the levels of PLyA, PAC-1, and CD62P can be potential noninvasive biomarkers of acute ischemic stroke.

Radiotherapy Is Associated with an Accelerated Risk of Carotid Atherosclerosis in Patients with Nasopharyngeal Carcinoma: A Nine-Year Prospective Follow-Up Study.

Simple SummaryRadiotherapy has become a common treatment modality for nasopharyngeal carcinoma, and concurrent chemoradiation therapy prolongs the survival of patients. Radiotherapy leads to the increased generation of reactive oxygen species and free radicals to destroy abnormal cell growths within normal cell environmental conditions. However, the late effects on “bystander” organs (e.g., extracranial arteries) among survivors after radiotherapy have become increasingly prevalent. This study showed radiation-related extracranial vasculopathy is a progressive process that begins immediately after radiotherapy with significantly increased carotid IMT compared to the control group during the 9-year follow-up. Chronic inflammation and oxidative stress might serve to drive the process and also contribute to increased platelet activation.Radiation-related extracranial vasculopathy is a common late effect after radiation in patients with nasopharyngeal carcinoma (NPC). We proposed the hypothesis that radiation-related extracranial vasculopathy is a progressive process that can begin immediately after radiotherapy and persist for a longer period, and inflammation and oxidative stress may play a pivotal role in this process. Thirty-six newly diagnosed NPC patients were assessed with B-mode ultrasound for the common carotid artery (CCA) intima media thickness (IMT) measurement as well as surrogate markers at three different stages (baseline, immediately after concurrent chemoradiation therapy (CCRT), and 9 years after enrollment). A healthy control group was also recruited for comparison. Surrogate markers including a lipid profile, HbA1c, inflammation, oxidative stress, and platelet activation markers were assessed. The mean CCA IMT in the NPC group were increased immediately after CCRT (p = 0.043). The mean CCA IMT value after a 9-year follow-up also showed a significant increase in NPC and control group, respectively (p < 0.0001 and p < 0.0001, paired t test). The annual increase mean CCA IMT (mm) was 0.053 ± 0.025 and 0.014 ± 0.013 in NPC and control group, respectively (p < 0.0001). The baseline high sensitivity CRP (hs-CRP), thiol, TBARS, and CD63 level were significantly higher in the NPC group (hs-CRP, p = 0.001, thiol, p < 0.0001, TBARS, p = 0.05, and CD63 level, p = 0.04). The thiol and TBARS levels were significantly lower in NPC patients immediately after CCRT (thiol, p < 0.0001, and TBARS, p = 0.043). The CD62P level was significantly higher while the thiol level was significantly lower in the NPC group after a 9-year follow-up (CD62P level, p = 0.007; and thiol level, p = 0.004). Radiation-related extracranial vasculopathy is a progressive process that begins immediately after radiotherapy with significantly increased carotid IMT compared to the control group during the 9-year follow-up. Chronic inflammation and oxidative stress might serve to drive the process and also contribute to increased platelet activation.

Anti-PF4/polyanion antibodies in COVID-19 patients are associated with disease severity and pulmonary pathology

Thromboembolic events are frequent and associated with poor outcome in severe COVID-19 disease. Anti-PF4/polyanion antibodies are related to heparin-induced thrombocytopenia (HIT) and thrombus formation, but data on these antibodies in unselected COVID-19 populations are scarce. We assessed the presence of anti-PF4/polyanion antibodies in prospectively collected serum from an unselected cohort of hospitalized COVID-19 patients and evaluated if elevated levels could give prognostic information on ICU admission and respiratory failure (RF), were associated with markers of inflammation, endothelial activation, platelet activation, coagulation and fibrosis and were associated with long-term pulmonary CT changes. Five out of 65 patients had anti-PF4/polyanion reactivity with OD ≥0.200. These patients had more severe disease as reflected by ICU admission without any evidence of HIT. They also had signs of enhanced inflammation and fibrinogenesis as reflected by elevated ferritin and osteopontin, respectively, during the first 10 days of hospitalization. Increased ferritin and osteopontin persisted in these patients at 3 months follow-up, concomitant with pulmonary CT pathology. Our finding shows that the presence of anti-PF4/polyanion antibodies in unselected hospitalized COVID−19 patients was not related to HIT, but was associated with disease severity, inflammation, and pulmonary pathology after 3 months.

Clinical Correlates Identify ProBDNF and Thrombo-Inflammatory Markers as Key Predictors of Circulating p75NTR Extracellular Domain Levels in Older Adults.

The p75NTR receptor binds all neurotrophins and is mostly known for its role in neuronal survival and apoptosis. Recently, the extracellular domain (ECD) of p75NTR has been reported in plasma, its levels being dysregulated in numerous neurological diseases. However, the factors associated with p75NTR ECD levels remain unknown. We investigated clinical correlates of plasma p75NTR ECD levels in older adults without clinically manifested neurological disorders. Circulating p75NTR levels were measured by enzyme-linked immunosorbent assay in plasma obtained from participants in the BEL-AGE cohort (n = 1,280). Determinants of plasma p75NTR ECD levels were explored using linear and non-linear statistical models. Plasma p75NTR ECD levels were higher in male participants; were positively correlated with circulating concentrations of pro-brain-derived neurotrophic factor, and inflammatory markers interleukin-6 and CD40 Ligand; and were negatively correlated with the platelet activation marker P-selectin. While most individuals had p75NTR levels ranging from 43 to 358 pg/ml, high p75NTR levels reaching up to 9,000 pg/ml were detectable in a subgroup representing 15% of the individuals studied. In this cohort of older adults without clinically manifested neurological disorders, there was no association between plasma p75NTR ECD levels and cognitive performance, as assessed by the Montreal Cognitive Assessment score. The physiological relevance of high p75NTR ECD levels in plasma warrants further investigation. Further research assessing the source of circulating p75NTR is needed for a deeper understanding of the direction of effect, and to investigate whether high p75NTR ECD levels are predictive biomarkers or consequences of neuropathology.

Soluble P-Selectin and von Willebrand Factor Rise in Healthy Volunteers Following Non-exertional Ascent to High Altitude.

Reduced oxygen tensions experienced at high altitudes are thought to predispose to thrombosis, yet there are few studies linking hypoxia, platelet activation, and thrombosis. Reports of platelet phenotypes in hypoxia are inconsistent, perhaps due to differing degrees of hypoxia experienced and the duration of exposure. This study aimed to investigate the relationship between soluble P-selectin, a marker of platelet activation, and von Willebrand factor (vWF) on exposure to hypoxia. We measured plasma concentrations of P-selectin and vWF in sixteen healthy volunteers before, during and after the APEX 2 expedition. APEX 2 consisted of a non-exertional ascent to 5,200 m, followed by 7 consecutive days at high altitude. We showed that high altitude significantly increased mean plasma P-selectin and vWF compared to pre-expedition levels. Both plasma marker levels returned to baseline post-expedition. We found a strong positive correlation between vWF and P-selectin, but no association between P-selectin and platelet count. Our results are consistent with previous work showing evidence of platelet activation at high altitude and demonstrate that the rise in P-selectin is not simply due to an increase in platelet count. As vWF and P-selectin could be derived from either platelets or endothelial cells, further work assessing more specific markers of endothelial activation is proposed to provide insight into the source of these potential pro-thrombotic biomarkers at altitude.

HEPCR.hTBM.hCD47.hHO-1 with donor clodronate and DDAVP treatment improves perfusion and function of GalTKO.hCD46 porcine livers perfused with human blood.

Platelet sequestration, inflammation, and inappropriate coagulation cascade activation are prominent in liver xenotransplant models and are associated with poor outcomes. Here, we evaluate a cassette of six additional genetic modifications to reduce anti-pig antibody binding (α-1,3-galactosyl transferase knockout [GalTKO]) and target coagulation dysregulation (human endothelial protein C receptor [hEPRC] and thrombomodulin [hTBM]), complement pathway regulation (human membrane cofactor protein, hCD46), inflammation heme oxygenase 1 [hHO-1]), and a self-recognition receptor (integrin-associated protein [hCD47]), as well as donor pharmacologic treatments designed to blunt these phenomena. Livers from GaltKO.hCD46 pigs ("2-gene," n=3) and GalTKO.hCD46 pigs also transgenic for hEPRC, hTBM, hCD47, and hHO-1 ("6-gene," n=4) were perfused ex vivo with whole human blood. Six-gene pigs were additionally pretreated with desmopressin (DDAVP) and clodronate liposomes to deplete vWF and kupffer cells, respectively. The average perfusion times increased from 304 (±148) min in the 2-gene group to 856(±61) min in the 6-gene group (p=.010). The average heparin administration was decreased from 8837 U/h in the 2-gene to 1354 U/h in the 6-gene group (p=.047). Platelet sequestration tended to be delayed in the 6-gene group (p=.070), while thromboxane B2 (TXB2, a platelet activation marker) levels were lower over the first hour (p=.044) (401±124vs. 2048±712 at 60min). Thrombin production as measured by F1+2 levels tended to be lower in the 6-gene group (p=.058). The combination of the hEPCR.hTBM.hCD47.hHO-1 cassette along with donor pig DDAVP and clodronate liposome pretreatment was associated with prolonged function of xenoperfused livers, reduced coagulation pathway perturbations, and decreased TXB2 elaboration, and reflects significant progress to modulate liver xenograft injury in a pig to human model.

Changing profile of platelet activity and turnover indices during treatment response of immune thrombocytopenia.

Both platelet count and function change after treatment of immune thrombocytopenia. Platelet function can be measured by plasma markers, including platelet activity [e.g., soluble P-selectin (sP-selectin) and soluble CD40 ligand (sCD40L)] and platelet turnover markers [e.g., glycocalicin (GC)]. Patients were classified into no response (NR, including new diagnosis), partial response (PR) and complete response (CR). One hundred and sixteen samples (29 CR, 32 PR, 55 NR) from 79 patients were collected. Plasma markers (sP-selectin, sCD40L and GC) were measured by ELISA. Platelet counts and mean platelet volume (MPV) were obtained in the clinical laboratory using GenS System-2. The results showed that responsive patients (PR + CR) had higher levels of sP-selectin (P = 0.026) and sCD40L (P = 0.001). Although there was no difference in MPV (P = 0.077) or GC (P = 0.078), there was a marked decrease of GC index (P < 0.001) in responsive patients. Paired sample analysis showed no difference in sP-selectin, sCD40L, MPV or GC but significant difference in GC index (P = 0.017) between NR and PR. Another paired sample analysis showed no difference in sP-selectin, sCD40L, MPV or GC but significant difference in GC index (P = 0.029) between PR and CR. Patients with refractory and newly diagnosed disease had a significant difference in GC (P = 0.020) and sCD40L (P = 0.001), despite similarly low platelet counts. In conclusion, platelet activity markers (sP-selectin and sCD40L) and GC indices change in parallel with treatment response. Plasma levels of GC and sCD40L may be predictors of treatment response.

Abstract WP198: Hematological And Embolic Biomarkers And Clinical Outcomes In Patients With Cancer And Ischemic Stroke

Introduction: We previously showed that patients with cancer and acute ischemic stroke (AIS) have higher markers of coagulation, platelet, and endothelial activation, and more circulating microemboli than patients with AIS and no cancer. Herein, we evaluate whether these markers are associated with clinical outcomes in patients with cancer and AIS. Methods: In the MOST-Cancer prospective study, we enrolled 50 adults with active solid-tumor cancer and AIS at 2 New York hospitals from 2016-2020. We collected blood from participants 72-120 hours after stroke onset. We performed a 30-minute transcranial Doppler (TCD) microemboli detection study a median of 4 days after stroke onset. The exposure variables were hematological markers of coagulation (D-dimer, thrombin-antithrombin), platelet (P-selectin), and endothelial activation (thrombomodulin, soluble intercellular adhesion molecule-1 [sICAM-1], soluble vascular cell adhesion molecule-1 [sVCAM-1]), and the presence of microemboli on TCD. The primary outcome was a composite of recurrent arterial or venous thromboembolism or death. The secondary outcome was recurrent AIS. We used Cox regression to evaluate individual associations between biomarkers and subsequent outcomes. Results: Median age was 69 years (IQR, 60-76) and 24 participants (48%) were women. The most common cancers were lung (28%) and pancreatic (22%); 86% of participants had distant metastases. During a mean follow-up of 278 days (SD, 367), 43 (86%) participants had the primary outcome of recurrent thromboembolism or death, including 28 (56%) who had recurrent thromboembolism, 13 who had recurrent AIS (26%), and 30 (60%) who died. D-dimer, P-selectin, sICAM-1, sVCAM-1, and microemboli were associated with the composite outcome (Table). Similar results were seen for recurrent AIS. Conclusion: Markers of hypercoagulability and embolic disease were associated with adverse clinical outcomes in cancer-related stroke.

Platelet-Leucocyte Aggregates as Novel Biomarkers in Cardiovascular Diseases.

Simple SummaryCardiovascular diseases are the most common cause of death worldwide. Hence, novel biomarkers are urgently needed to improve diagnosis and treatment. Platelet–leucocyte aggregates are conglomerates of platelets and leucocytes and are widely investigated as biomarkers in cardiovascular diseases. Platelet–leucocytes aggregates are present in health, but increase in patients with cardiovascular risk factors and acute or stable coronary syndromes, making them a potential diagnostic marker. Moreover, platelet–leucocyte aggregates predict outcomes after surgery or percutaneous treatment and could be used to monitor antiplatelet therapy. Emerging data about the participation of platelet–leucocyte aggregates in cardiovascular diseases pathogenesis make them an attractive target for novel therapies. Furthermore, simple detection with conventional flow cytometry provides accurate and reproducible results, although requires specific sample handling. The main task for the future is to determine the standardized protocol to measure blood concentrations of platelet–leucocyte aggregates and subsequently establish their normal range in health and disease.Platelet–leucocyte aggregates (PLA) are a formation of leucocytes and platelets bound by specific receptors. They arise in the condition of sheer stress, thrombosis, immune reaction, vessel injury, and the activation of leukocytes or platelets. PLA participate in cardiovascular diseases (CVD). Increased levels of PLA were revealed in acute and chronic coronary syndromes, carotid stenosis cardiovascular risk factors. Due to accessible, available, replicable, quick, and low-cost quantifying using flow cytometry, PLA constitute an ideal biomarker for clinical practice. PLA are promising in early diagnosing and estimating prognosis in patients with acute or chronic coronary syndromes treated by percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). PLA were also a reliable marker of platelet activity for monitoring antiplatelet therapy. PLA consist also targets potential therapies in CVD. All of the above potential clinical applications require further studies to validate methods of assay and proof clinical benefits.

Differential Expression of Platelet Activation Markers, CD62P and CD63, after Exposure to Breast Cancer Cells Treated with Kigelia Africana, Ximenia Caffra and Mimusops Zeyheri Seed Oils In Vitro

Cancer patients, including breast cancer patients, live in a hypercoagulable state. Chemo- and hormone- therapy used in the treatment of breast cancer increases the risk of thrombosis. Due to differences in health care services between developed and developing countries, the survival rate of women with breast cancer in developing countries is low. Consequently, ethnomedicines are used and their efficacy as potential alternatives are being scientifically explored. The seed oils of Kigelia africana, Ximenia caffra and Mimusops zeyheri have anti-proliferative effects on hormone-dependent (MCF-7) and cytotoxic effects on hormone-independent (MDA-MB-231) breast cancer cells. In this study, we determined if these seed oils reduce the thrombogenic ability of breast cancer cells by measuring the platelet surface expression of the activation-specific antigens CD62P and CD63. MDA-MB-231 and MCF-7 cells were pretreated with the seed oils before being exposed to whole blood of human female volunteers. An increase in CD62P and CD63 expression following whole blood exposure to untreated breast cancer cells was observed. Treated MDA-MB-231 cells reduced CD62P and CD63 expression while treated MCF-7 cells increased CD62P and decreased CD63 expression. Kigelia africana, Ximenia caffra and Mimusops zeyheri seed oils are able to reduce the thrombogenic ability of MDA-MB-231 breast cancer cells.

Current and novel biomarkers of thrombotic risk in COVID-19: a Consensus Statement from the International COVID-19 Thrombosis Biomarkers Colloquium.

Coronavirus disease 2019 (COVID-19) predisposes patients to thrombotic and thromboembolic events, owing to excessive inflammation, endothelial cell activation and injury, platelet activation and hypercoagulability. Patients with COVID-19 have a prothrombotic or thrombophilic state, with elevations in the levels of several biomarkers of thrombosis, which are associated with disease severity and prognosis. Although some biomarkers of COVID-19-associated coagulopathy, including high levels of fibrinogen and d-dimer, were recognized early during the pandemic, many new biomarkers of thrombotic risk in COVID-19 have emerged. In this Consensus Statement, we delineate the thrombotic signature of COVID-19 and present the latest biomarkers and platforms to assess the risk of thrombosis in these patients, including markers of platelet activation, platelet aggregation, endothelial cell activation or injury, coagulation and fibrinolysis as well as biomarkers of the newly recognized post-vaccine thrombosis with thrombocytopenia syndrome. We then make consensus recommendations for the clinical use of these biomarkers to inform prognosis, assess disease acuity, and predict thrombotic risk and in-hospital mortality. A thorough understanding of these biomarkers might aid risk stratification and prognostication, guide interventions and provide a platform for future research.

Platelet-to-Lymphocyte Ratio as Marker of Platelet Activation in Patients on Potent P2Y12 Inhibitors.

A high platelet-to-lymphocyte ratio (PLR) has recently been associated with ischemic outcomes in cardiovascular disease. Increased platelet reactivity and leukocyte-platelet aggregate formation are directly involved in the progress of atherosclerosis and have been linked to ischemic events following percutaneous coronary intervention (PCI). In order to understand the relation of PLR with platelet reactivity, we assessed PLR as well as agonist-inducible platelet aggregation and neutrophil-platelet aggregate (NPA) formation in 182 acute coronary syndrome (ACS) patients on dual antiplatelet therapy with aspirin and prasugrel (n = 96) or ticagrelor (n = 86) 3 days after PCI. PLR was calculated from the blood count. Platelet aggregation was measured by multiple electrode aggregometry and NPA formation was determined by flow cytometry, both in response to ADP and SFLLRN. A PLR ≥91 was considered as high PLR based on previous data showing an association of this threshold with adverse ischemic outcomes. In the overall cohort and in prasugrel-treated patients, high PLR was associated with higher SFLLRN-inducible platelet aggregation (67 AU [50-85 AU] vs 59.5 AU [44.3-71.3 AU], P = .01, and 73 AU [50-85 AU] vs 61.5 AU [46-69 AU], P = .02, respectively). Further, prasugrel-treated patients with high PLR exhibited higher ADP- (15% [11%-23%] vs 10.9% [7.6%-15.9%], P = .007) and SFLLRN-inducible NPA formation (64.3% [55.4%-73.8%] vs 53.8% [44.1%-70.1%], P = .01) as compared to patients with low PLR. These differences were not seen in ticagrelor-treated patients. In conclusion, high PLR is associated with increased on-treatment platelet reactivity in prasugrel-treated patients, but not in patients on ticagrelor.