scholarly journals No Association Between Platelet Function and Hemophilia B Phenotype

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4994-4994 ◽  
Author(s):  
Roger E.G. Schutgens ◽  
Esther R. van Bladel ◽  
Kathelijn Fischer ◽  
Mark Roest ◽  
Rolf Urbanus
Keyword(s):  
Platelet Activation ◽  
Platelet Reactivity ◽  
Adenosine Diphosphate ◽  
Hemophilia B ◽  
Healthy Controls ◽  
Severe Hemophilia ◽  
Platelet Activity ◽  
Activation Markers ◽  
Receptor Associated Protein ◽  
The Individual

Abstract Introduction In hemophilia, unravelling the mechanisms behind interindividual variability in phenotype remains a big challenge. Objectives To study platelet activation and platelet responsiveness in relation to hemostatic phenotypes in hemophilia B by 1) comparing hemophilia B patients to healthy controls and 2) relating these to the clinical phenotype of the individual patients with severe hemophilia B. Methods Platelet reactivity was determined in whole blood measuring expression of P-selectin and binding of fibrinogen with FACS analysis after stimulating or inhibiting platelets with concentration series of several (ant-)agonists, including adenosine diphosphate (ADP), convulxin (CVX) and thrombin receptor associated protein (TRAP)and iloprost. Concentration of soluble platelet activation markers (soluble P-selectin, β-Thromboglobulin and RANTES) were measured in platelet poor plasma by ELISA. Markers of platelet activation and responsiveness were compared between healthy controls (n=12), patients with mild/moderate (n=12) or severe hemophilia B (n=19). In severe hemophilia patients, annual FIX consumption/kg was calculated over the last 6 years. Data were analysed with linear regression using SPSS 20. Results Levels of basal platelet activation (both P-selectin and fibrinogen) were equal between controls, mild/moderate and severe hemophilia B (Figure 1). For basal P-selectin expression, the mean area under the curves for were 28.5 (95% CI 23.3-33.6), 33.0(95% CI 24.4-41.6) and 28.4(95% CI 23.9-32.9) respectively (p=0.4). After stimulation with ADP, CVX and TRAP (with and without iloprost), platelet responsiveness was similar in all groups. There was no relation between annual FIX consumption and any marker of platelet activity. For basal P-selectin expression, the beta coefficient was -0.212 (p=0.38)(Figure 2). Conclusion In hemophilia B, platelet activity and responsiveness was similar to healthy controls. In severe hemophilia patients, there was no relation between FIX consumption and platelet activity. Figure 1. Basal P-selectin activity between healthy controls and hemophilia patients Figure 1. Basal P-selectin activity between healthy controls and hemophilia patients Figure 2. Basal P-selectin activity according to FIX consumption in severe hemophilia B Figure 2. Basal P-selectin activity according to FIX consumption in severe hemophilia B Disclosures Schutgens: Pfizer: Research Funding.

scholarly journals Association of lipoprotein(a) with intrinsic and on-clopidogrel platelet reactivity

2021 ◽  
Author(s):  
Alexander Kille ◽  
Thomas Nührenberg ◽  
Kilian Franke ◽  
Christian M. Valina ◽  
Gregor Leibundgut ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Activation ◽  
Platelet Reactivity ◽  
Laboratory Data ◽  
Adenosine Diphosphate ◽  
Surface Proteins ◽  
Activation Markers ◽  
Platelet Surface ◽  
Lipoprotein A ◽  
Artery Disease

AbstractLipoprotein(a) [Lp(a)] is an independent, genetically determined, and causal risk factor for cardiovascular disease. Laboratory data have suggested an interaction of Lp(a) with platelet function, potentially caused by its interaction with platelet receptors. So far, the potential association of Lp(a) with platelet activation and reactivity has not been proven in larger clinical cohorts. This study analyzed intrinsic platelet reactivity before loading with clopidogrel 600 mg and on-treatment platelet reactivity tested 24 h following loading in patients undergoing elective coronary angiography. Platelet reactivity was tested by optical aggregometry following stimulation with collagen or adenosine diphosphate as well as by flow cytometry. Lp(a) levels were directly measured in all patients from fresh samples. The present analysis included 1912 patients. Lp(a) levels ranged between 0 and 332 mg/dl. There was a significant association of rising levels of Lp(a) with a higher prevalence of a history of ischemic heart disease (p < 0.001) and more extensive coronary artery disease (p = 0.001). Results for intrinsic (p = 0.80) and on-clopidogrel platelet reactivity (p = 0.81) did not differ between quartiles of Lp(a) levels. Flow cytometry analyses of expression of different platelet surface proteins (CD41, CD62P or PAC-1) confirmed these findings. Correlation analyses of levels of Lp(a) with any of the tested platelet activation markers did not show any correlation. The present data do not support the hypothesis of an interaction of Lp(a) with platelet reactivity.

scholarly journals Increased Pro-Thrombotic Platelet Activity Associated with Thrombin/PAR1-Dependent Pathway Disorder in Patients with Secondary Progressive Multiple Sclerosis

2020 ◽  
Vol 21 (20) ◽  
pp. 7722
Author(s):  
Angela Dziedzic ◽  
Elzbieta Miller ◽  
Michal Bijak ◽  
Lukasz Przyslo ◽  
Joanna Saluk-Bijak
Keyword(s):  
Multiple Sclerosis ◽  
Mrna Expression ◽  
Platelet Activation ◽  
Blood Platelets ◽  
Surface Expression ◽  
Epidemiological Studies ◽  
Progressive Multiple Sclerosis ◽  
Apolipoprotein A1 ◽  
Platelet Activity ◽  
Activation Markers

Epidemiological studies confirm the high risk of ischemic events in multiple sclerosis (MS) that are associated with increased pro-thrombotic activity of blood platelets. The most potent physiological platelet agonist is thrombin, which activates platelets via cleavage of specific protease-activated receptors (PARs). Our current study is aimed to determine the potential genetics and proteomic abnormalities of PAR1 in both platelets and megakaryocytes, which may have thromboembolic consequences in the course of MS. The obtained results were correlated with the expression level of platelet and megakaryocyte transcripts for APOA1 and A2M genes encoding atherosclerosis biomarkers: apolipoprotein A1 (ApoA1) and α-2-macroglobulin (α2M), respectively. Moreover, PAR1 functionality in MS platelets was assessed by flow cytometry, determining the level of platelet–platelet and platelet–leukocyte aggregates, platelet microparticles and surface expression of P-selectin. As a PAR1 agonist, the synthetic TRAP-6 peptide was used, which made it possible to achieve platelet activation in whole blood without triggering clotting. Comparative analyses showed an elevated level of platelet activation markers in the blood of MS patients compared to controls. The mRNA expression of gene coding α2M was upregulated, whilst ApoA1 was down-regulated, both in platelets and megakaryocytes from MS patients. Furthermore, we observed an increase in both mRNA expression and surface density of PAR1 in platelets and megakaryocytes in MS compared to controls. Both the level of platelet activation markers and PAR1 expression showed a high correlation with the expression of transcripts for APOA1 and A2M genes.

scholarly journals Neutrophil and lymphocyte counts are associated with different immunopathological mechanisms in systemic lupus erythematosus

2020 ◽  
Vol 7 (1) ◽  
pp. e000382
Author(s):  
Bobby Kwanghoon Han ◽  
Katherine D Wysham ◽  
Kevin C Cain ◽  
Helena Tyden ◽  
Anders A Bengtsson ◽  
...  
Keyword(s):  
Neutrophil Count ◽  
Lupus Erythematosus ◽  
Lymphocyte Count ◽  
Neutrophil Activation ◽  
Type I ◽  
Healthy Controls ◽  
Type I Ifn ◽  
Healthy Individuals ◽  
Activation Markers ◽  
The Individual

ObjectiveNeutrophils contribute to the SLE pathogenesis. Neutrophil to lymphocyte ratio (NLR) is reported to correlate with disease activity in SLE. The aim of the study was to evaluate whether NLR reflects underlying immunopathogenic activity in SLE, as well as to determine the contribution of each component of NLR, neutrophil and lymphocyte count.MethodsData were obtained from a cohort of patients with SLE (n=141) recruited at Lund University, Sweden. NLR levels were compared between patients with SLE and healthy controls (n=79). The relationship between NLR and clinical and immunological markers was examined using Mann-Whitney U test and logistic regression analysis. High NLR was defined as above the 90th percentile of healthy individuals.ResultsPatients with SLE had elevated neutrophil count (p=0.04) and reduced lymphocyte count (p<0.0001), resulting in elevated NLR as compared with healthy controls (p<0.0001). Patients with high NLR had more active disease, and were more frequently on prednisone use and immunosuppressive medicines. High NLR was associated with immune complex (IC)-driven disease with presence of antidouble-stranded DNA antibodies (p=0.006), circulating ICs (p=0.02) and type I interferon (IFN) activity (p=0.009). Further, high NLR was associated with neutrophil abnormalities, including enrichment for low-density granulocytes (LDGs) (p=0.001), and increased levels of the serum neutrophil activation marker, calprotectin (p=0.02). Assessing the individual components within NLR, that is, neutrophil and lymphocyte count, high neutrophil count was associated with neutrophil activation markers (p<0.0001), whereas low lymphocyte count was associated with type I IFN activity and elevated numbers of LDGs (p=0.006 and p=0.001, respectively).ConclusionsNLR is elevated in patients with SLE as compared with healthy individuals, and is associated with key immunopathological events, including type I IFN activity and neutrophil activation. Neutrophil and lymphocyte count reflected different aspects of the pathogenesis of SLE. Further studies are needed to determine the causality of the associations.

scholarly journals Erythrocytes metabolically enhance collagen-induced platelet responsiveness via increased thromboxane production, adenosine diphosphate release, and recruitment

Blood ◽  
1991 ◽  
Vol 78 (1) ◽  
pp. 154-162 ◽  
Author(s):  
J Valles ◽  
MT Santos ◽  
J Aznar ◽  
AJ Marcus ◽  
V Martinez-Sales ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Therapeutic Potential ◽  
Platelet Reactivity ◽  
Adenosine Diphosphate ◽  
Stimulus Response ◽  
Absolute Requirement ◽  
Thromboxane Production ◽  
And Function ◽  
Aspirin Ingestion

Abstract Erythrocytes promoted platelet reactivity in a plasma medium, as demonstrated in an in vitro system that independently evaluated the biochemistry of platelet activation and recruitment. The prothrombotic erythrocyte effects were metabolically regulated, as evidenced by lack of activity of ATP-depleted or glutaraldehyde-fixed erythrocytes. They occurred in the absence of cell lysis as verified by lactate dehydrogenase assays, and had an absolute requirement for platelet activation. The presence of erythrocytes induced a twofold increase in platelet thromboxane B2 (TXB2) synthesis upon collagen stimulation, indicating that erythrocytes modulated platelet eicosanoid formation. Cell-free releasates from stimulated platelet-erythrocyte suspensions, which exhibited increased recruiting capacity, contained 6.9-fold more ADP and 4.9-fold more ATP than releasates from stimulated platelets alone. Following aspirin ingestion, TXB2 formation was blocked, but erythrocyte promotion of platelet reactivity persisted at those doses of collagen that reinduced platelet activation. Moreover, when platelet mixtures consisted of as little as 10% obtained before aspirin plus 90% obtained post-aspirin ingestion, significant erythrocyte enhancement of platelet reactivity occurred, even at low agonist concentrations. These erythrocyte effects would decrease the therapeutic potential of inhibition of platelet cyclooxygenase by aspirin. The erythrocyte- induced modulation of platelet biochemistry and function emphasizes the importance of cell-cell interactions in stimulus-response coupling.

scholarly journals In vivo effects of eltrombopag on platelet function in immune thrombocytopenia: no evidence of platelet activation

Blood ◽  
2012 ◽  
Vol 119 (17) ◽  
pp. 4066-4072 ◽  
Author(s):  
Bethan Psaila ◽  
James B. Bussel ◽  
Matthew D. Linden ◽  
Bracken Babula ◽  
Youfu Li ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Platelet Function ◽  
Whole Blood ◽  
Immune Thrombocytopenia ◽  
Ex Vivo ◽  
Platelet Reactivity ◽  
Adenosine Diphosphate ◽  
High Dose ◽  
Platelet Surface

Abstract The effects of eltrombopag, a thrombopoietin-receptor agonist, on platelet function in immune thrombocytopenia (ITP) are not fully characterized. This study used whole blood flow cytometry to examine platelet function in 20 patients receiving eltrombopag treatment at days 0, 7, and 28. Platelet surface expression of activated GPIIb/IIIa, P-selectin, and GPIb was measured with and without low and high adenosine diphosphate (ADP) and thrombin receptor activating peptide (TRAP) concentrations. Before eltrombopag treatment with no ex vivo agonist, platelet activation was higher in ITP patients than controls. Platelet GPIb and activated GPIIb/IIIa expression without added agonist was unchanged following eltrombopag treatment, whereas a slight increase in P-selectin was observed. Expression of P-selectin and activated GPIIb/IIIa in response to high-dose ADP was lower during eltrombopag treatment than at baseline. Eltrombopag led to a slight increase in platelet reactivity to TRAP only in responders to eltrombopag but not to levels above those in controls; whole blood experiments demonstrated that this increase was probably because of higher platelet counts rather than higher platelet reactivity. In conclusion, although thrombocytopenic ITP patients have higher baseline platelet activation than controls, eltrombopag did not cause platelet activation or hyper-reactivity, irrespective of whether the platelet count increased.

Mechanisms of platelet activation: Need for new strategies to protect against platelet-mediated atherothrombosis

2009 ◽  
Vol 102 (08) ◽  
pp. 248-257 ◽  
Author(s):  
Lisa Jennings
Keyword(s):  
Antiplatelet Therapy ◽  
Platelet Activation ◽  
Platelet Reactivity ◽  
Thrombus Formation ◽  
Antiplatelet Agents ◽  
Bleeding Risk ◽  
Adenosine Diphosphate ◽  
Adp Receptor ◽  
Activation Pathways ◽  
New Strategies

SummaryPlatelets are central mediators of haemostasis at sites of vascular injury, but they also mediate pathologic thrombosis. Activated platelets stimulate thrombus formation in response to rupture of an atherosclerotic plaque or endothelial cell erosion, promoting atherothrombotic disease. They also interact with endothelial cells and leukocytes to promote inflammation, which contributes to atherosclerosis. Multiple pathways contribute to platelet activation, and current oral antiplatelet therapy with aspirin and a P2Y12 adenosine diphosphate (ADP) receptor antagonist target the thromboxane A2 and ADP pathways, respectively. Both can diminish activation by other factors, but the extent of their effects depends upon the agonist, agonist strength, and platelet reactivity status. Although these agents have demonstrated significant clinical benefit, residual morbidity and mortality remain high. Neither agent is effective in inhibiting thrombin, the most potent platelet activator. This lack of comprehensive inhibition of platelet function allows continued thrombus formation and exposes patients to risk for recurrent thrombotic events. Moreover, bleeding risk is a substantial limitation of antiplatelet therapy, because these agents target platelet activation pathways critical for both protective haemostasis and pathologic thrombosis. Novel antiplatelet therapies that provide more complete inhibition of platelet activation without increasing bleeding risk could considerably decrease residual risk for ischemic events. Inhibition of the protease-activated receptor (PAR)-1 platelet activation pathway stimulated by thrombin is a novel, emerging approach to achieve more comprehensive inhibition of platelet activation when used in combination with current oral antiplatelet agents. PAR-1 inhibition is not expected to increase bleeding risk, as this pathway does not interfere with haemostasis.

scholarly journals Effect of ultrapure lipopolysaccharides derived from diverse bacterial species on the modulation of platelet activation

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Thomas M. Vallance ◽  
Divyashree Ravishankar ◽  
Dina A. I. Albadawi ◽  
Harry Layfield ◽  
Jonathan Sheard ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Platelet Reactivity ◽  
Platelet Rich Plasma ◽  
Bacterial Species ◽  
Human Platelets ◽  
Innate Immune Responses ◽  
Experimental Conditions ◽  
Activation Markers ◽  
The Impact ◽  
Inside Out

AbstractPlatelets are small circulating blood cells that play essential roles in the maintenance of haemostasis via blood clotting. However, they also play critical roles in the regulation of innate immune responses. Inflammatory receptors, specifically Toll-like receptor (TLR)-4, have been reported to modify platelet reactivity. A plethora of studies have reported controversial functions of TLR4 in the modulation of platelet function using various chemotypes and preparations of its ligand, lipopolysaccharide (LPS). The method of preparation of LPS may explain these discrepancies however this is not fully understood. Hence, to determine the impact of LPS on platelet activation, we used ultrapure preparations of LPS from Escherichia coli (LPSEC), Salmonella minnesota (LPSSM), and Rhodobacter sphaeroides (LPSRS) and examined their actions under diverse experimental conditions in human platelets. LPSEC did not affect platelet activation markers such as inside-out signalling to integrin αIIbβ3 or P-selectin exposure upon agonist-induced activation in platelet-rich plasma or whole blood whereas LPSSM and LPSRS inhibited platelet activation under specific conditions at supraphysiological concentrations. Overall, our data demonstrate that platelet activation is not largely influenced by any of the ultrapure LPS chemotypes used in this study on their own except under certain conditions.

The significance of vasodilator-stimulated phosphoprotein for risk stratification of stent thrombosis

2007 ◽  
Vol 98 (12) ◽  
pp. 1329-1334 ◽  
Author(s):  
Katja Stellbrink ◽  
Anita de Taeye ◽  
Robert Müller ◽  
Paul Kiefer ◽  
Eray Yagmur ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Stent Thrombosis ◽  
Platelet Reactivity ◽  
Linear Regression Analysis ◽  
Adenosine Diphosphate ◽  
Individual Risk ◽  
Roc Curve Analysis ◽  
Platelet Aggregometry ◽  
Increased Risk ◽  
The Individual

SummaryLow-response to the P2Y12 adenosine diphosphate (ADP)-receptor antagonist clopidogrel was suggested to correspond to a higher incidence of stent thrombosis (ST). This prospective observational study assessed the capability of two platelet function assays, e.g. direct measurement of the phosphorylation status of vasodilator-stimulated phosphoprotein (VASP) and ADP-induced platelet aggregation for definition of the individual risk to develop ST. Ninety-nine patients with an elevated high risk to develop ST were enrolled. All patients received a dual antiplatelet therapy consisting of 100 mg aspirin and 75 mg clopidogrel during an observation period of six months. Flow cytometry of VASP phosphorylation and densitometrically-determined measurement of ADP-induced platelet aggregation was performed 72–96 hours after stent implantation. These data were related to angiographically confirmed ST. Nine patients suffered from angiographically confirmed ST (9.1%). The meanVASP-platelet reactivity indices (VASP-PRI) and values for ADP-induced platelet aggregation in the ST group were significantly higher (60.8 ± 13.0 and 60.9 ± 13.1, respectively) compared to patients without ST (41.3 ± 14.0 and 50.8 ± 14.4, P<0.001 vs. 0.048, respectively). There was a fair correlation between both methods using non-linear regression analysis (r=0.332). In a multivariate analysis, VASP was the only independent predictor of ST and was superior to previously identified angiographic parameters. Receiver- operator characteristic (ROC) curve analysis revealed a cut-off value for VASP-PRI of <48% to be associated with low risk of ST. In conclusion, determination ofVASP phosphorylation is superior to conventional platelet aggregometry and angiographic parameters for assessing the risk of ST. Patients with a VASP-PRI >48% seem to have a significantly increased risk.

In vivo platelet activation and platelet hyperreactivity in abacavir-treated HIV-infected patients

2013 ◽  
Vol 110 (08) ◽  
pp. 349-357 ◽  
Author(s):  
Barbara Belfiori ◽  
Eleonora Petito ◽  
Giuseppe Guglielmini ◽  
Lisa Malincarne ◽  
AnnaMaria Mezzasoma ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Cardiovascular Events ◽  
Light Transmission ◽  
Ex Vivo ◽  
Platelet Reactivity ◽  
Retrospective Case ◽  
Activation Markers ◽  
Induced Aggregation

SummaryAbacavir (ABC) has been associated with ischaemic cardiovascular events in HIV-infected patients, but the pathogenic mechanisms are unknown. Aim of our study was to assess whether ABC induces in vivo platelet activation and ex vivo platelet hyper-reactivity. In a retrospective, case-control study, in vivo platelet activation markers were measured in 69 HIV-infected patients, before starting therapy and after 6–12 months of either ABC (n=35) or tenofovir (TDF) (n=34), and compared with those from 20 untreated HIV-infected patients. A subgroup of patients was restudied after 28–34 months for ex vivo platelet reactivity. In vivo platelet activation markers were assessed by ELISA or flow cytometry, ex vivo platelet reactivity by light transmission aggregometry (LTA) and PFA-100®. The in vitro effects of the ABC metabolite, carbovir triphosphate, on aggregation and intra-platelet cGMP were also studied. sPLA2, sPsel and sGPV increased significantly 6–12 months after the beginning of ABC, but not of TDF or of no treatment. Ex vivo platelet function studies showed enhanced LTA, shorter PFA-100® C/ADP closure time and enhanced platelet expression of P-sel and CD40L in the ABC group. The intake of ABC blunted the increase of intraplatelet cGMP induced by nitric oxide (NO) and acutely enhanced collagen-induced aggregation. Preincubation of control platelets with carbovir triphosphate in vitro enhanced platelet aggregation and blunted NO-induced cGMP elevation. In conclusion, treatment with ABC enhances in vivo platelet activation and induces platelet hyperreactivity by blunting the inhibitory effects of NO on platelets. These effects may lead to an increase of ischaemic cardiovascular events.

scholarly journals The Molecular Aspects of Disturbed Platelet Activation Through ADP/P2Y12 Pathway in Multiple Sclerosis

2021 ◽  
Vol 22 (12) ◽  
pp. 6572
Author(s):  
Angela Dziedzic ◽  
Elzbieta Miller ◽  
Joanna Saluk-Bijak ◽  
Marta Niwald ◽  
Michal Bijak
Keyword(s):  
Multiple Sclerosis ◽  
Platelet Activation ◽  
Platelet Reactivity ◽  
Adenosine Diphosphate ◽  
Receptor Expression ◽  
P2y12 Receptor ◽  
Platelet Surface ◽  
Molecular Abnormalities ◽  
Increased Risk ◽  
Ischemic Events

Epidemiological studies confirm a high risk of ischemic events in secondary-progressive multiple sclerosis (SP MS) patients, directly associated with an increased level of pro-thrombotic activity of platelets. Our work aimed to verify potential molecular abnormalities of the platelet P2Y12 receptor expression and functionality as a cause of an increased risk of thromboembolism observed in the course of MS. We have demonstrated an enhanced platelet reactivity in response to adenosine diphosphate (ADP) in SP MS relative to controls. We have also shown an increased mRNA expression for the P2RY12 gene in both platelets and megakaryocytes, as well as enhanced density of these receptors on the platelet surface. We postulate that one of the reasons for the elevated risk of ischemic events observed in MS may be a genetically or phenotypically reinforced expression of the platelet P2Y12 receptor. In order to analyze the effect of the PAR1 (protease activated receptor type 1) signaling pathway on the expression level of P2Y12, we also analyzed the correlation parameters between P2Y12 expression and the markers of platelet activation in MS induced by selective PAR1 agonist (thrombin receptor activating peptide-6, TRAP-6). Identifying the molecular base responsible for the enlarged pro-thrombotic activity of platelets in SP MS could contribute to the implementation of prevention and targeted treatment, reducing the development of cardiovascular disorders in the course of the disease.

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