Aspirin increases the bleeding side effects in essential thrombocythemia independent of the cyclooxygenase pathway: role of the lipoxygenase pathway

Platelet proteo-transcriptomic profiling validates mediators of thrombosis and proteostasis in patients with myeloproliferative neoplasms

Patients with chronic Myeloproliferative Neoplasms (MPN) including polycythemia vera (PV) and essential thrombocythemia (ET) exhibit unique clinical features, such as a tendency toward thrombosis and hemorrhage, and risk of disease progression to secondary bone marrow fibrosis and/or acute leukemia. Although an increase in blood cell lineage counts (quantitative features) contribute to these morbid sequelae, the significant qualitative abnormalities of myeloid cells that contribute to vascular risk are not well understood. Here, we address this critical knowledge gap via a comprehensive and untargeted profiling of the platelet proteome in a large (n= 140) cohort of patients (from two independent sites) with an established diagnosis of PV and ET (and complement prior work on the MPN platelet transcriptome from a third site). We discover distinct MPN platelet protein expression and confirm key molecular impairments associated with proteostasis and thrombosis mechanisms of potential relevance to MPN pathology. Specifically, we validate expression of high-priority candidate markers from the platelet transcriptome at the platelet proteome (e.g., calreticulin (CALR), Fc gamma receptor (FcγRIIA) and galectin-1 (LGALS1) pointing to their likely significance in the proinflammatory, prothrombotic and profibrotic phenotypes in patients with MPN. Together, our proteo-transcriptomic study identifies the peripherally-derived platelet molecular profile as a potential window into MPN pathophysiology and demonstrates the value of integrative multi-omic approaches in gaining a better understanding of the complex molecular dynamics of disease.

12(S)-Hydroxyeicosatetraenoic acid downregulates monocyte-derived macrophage efferocytosis: New insights in atherosclerosis

The involvement of 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), a 12-lipooxygenase product of arachidonic acid, has been suggested in atherosclerosis. However, its effect on macrophage functions is not completely understood, so far. The uptake of apoptotic cells (efferocytosis) by macrophages is an anti-inflammatory process, impaired in advanced atherosclerotic lesions. This process induces the release of the anti-inflammatory cytokine interleukin-10 (IL-10), and it is regulated by Rho-GTPases, whose activation involves the isoprenylation, a modification inhibited by statins. We assessed 12-HETE levels in serum of coronary artery disease (CAD) patients, and explored 12(S)-HETE in vitro effect on monocyte-derived macrophage (MDM) efferocytosis. Sixty-four CAD patients and 24 healthy subjects (HS) were enrolled. Serum 12-HETE levels were measured using a tandem mass spectrometry method. MDMs, obtained from a spontaneous differentiation of adherent monocytes, were treated with 12(S)-HETE (10-50 ng/mL). Efferocytosis and RhoA activation were evaluated by flow cytometry. IL-10 was measured by ELISA. CAD patients showed increased 12-HETE serum levels compared to HS (665.2 [438.1-896.2] ng/mL and 525.1 [380.1-750.1] ng/mL, respectively, p < 0.05) and reduced levels of IL-10. MDMs expressed the 12(S)-HETE cognate receptor GPR31. CAD-derived MDMs displayed defective efferocytosis vs HS-MDMs (9.4 [7.7-11.3]% and 11.1 [9.6-14.1]% of MDMs that have engulfed apoptotic cells, respectively, p < 0.01). This reduction is marked in MDMs obtained from patients not treated with statin (9.3 [7.4-10.6]% statin-free CAD vs HS, p = 0.01; and 9.9 [8.6-11.6]% statin-treated CAD vs HS, p = 0.07). The in vitro treatment of MDMs with 12(S)-HETE (20 ng/mL) induced 20% decrease of efferocytosis (p < 0.01) and 71% increase of RhoA activated form (p < 0.05). Atorvastatin (0.1 μM) counteracted these 12(S)-HETE-mediated effects.These results show a 12(S)-HETE pro-inflammatory effect and suggest a new potential contribution of this mediator in the development of atherosclerosis.

Anagrelide reduces thrombotic risk in essential thrombocythaemia vs. hydroxyurea plus aspirin

OBJECTIVE

To evaluate the reduction in thrombotic events (TE) in patients with essential thrombocythaemia (ET) treated with anagrelide versus hydroxyurea + aspirin (HU + ASA).

METHODS

A questionnaire was developed using 2008 WHO diagnostic criteria, and thrombotic risk factors were stratified according to Landolfi criteria. Through questionnaire completion, clinicians at Hungarian haematological centres entered data into the Hungarian MPN Registry on patients with myeloproliferative neoplasms. Based on ET registry data, TEs in anagrelide-treated patients (n = 139) were compared with HU + ASA-treated patients (n = 141).

RESULTS

Patients were followed up for (median) 6 yr. TEs were reported in significantly fewer anagrelide-treated patients versus HU + ASA (15.1% versus 49.6%; P < 0.001). Numbers of major arterial and major venous events were similar between the groups, although there were over fivefold more minor arterial and minor venous events in the HU + ASA group (P < 0.001). While median age at diagnosis was older and length of follow-up shorter in the HU + ASA group (P < 0.05), this did not influence TE incidence; medication and TE before diagnosis only influenced TE incidence.

CONCLUSIONS

Anagrelide significantly decreased the number of patients experiencing minor arterial and minor venous TEs versus HU + ASA over 6 yr. Risk of TE after diagnosis was significantly increased if the patient had TE before diagnosis.

Approach to the Assessment of Platelet Function: Comparison between Optical-based Platelet-rich Plasma and Impedance-based Whole Blood Platelet Aggregation Methods

Platelet aggregation studies play an important role in the assessment of hereditary and acquired platelet function defects. The first aggregation test introduced into laboratory practice used platelet-rich plasma (PRP) where aggregation was detected by an optical method. The assessment of platelet function using whole blood (WB) aggregation by an impedance method followed up nearly 20 years later. The WB impedance aggregation assay appears to be superior to the optical method because it 1) evaluates platelets in a physiologic milieu in the presence of red and white blood cells, which are known to modulate platelet function; 2) is faster; 3) has higher sensitivity; and 4) does not require centrifugation, thus avoiding injury to platelets and loss of giant thrombocytes. These two assays were compared. Clearly, the WB impedance aggregation methodology has many advantages over the optical PRP assay for the assessment of the hyperactive platelet syndrome and the effects of anti-platelet drugs.

The 2016 revision of WHO classification of myeloproliferative neoplasms: Clinical and molecular advances

Clinical evidence supports the need of changing the diagnostic criteria of the 2008 updated WHO classification for polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). In JAK2-mutated patients who show characteristic bone marrow (BM) morphology, clinical studies demonstrated that a hemoglobin level of 16.5g/dL in men and 16.0g/dl for women or a hematocrit value of 49% in men and 48% in women are the optimal cut off levels for distinguishing JAK2-mutated ET from "masked/prodromal" PV. Therefore BM morphology was upgraded to a major diagnostic criterion. Regarding ET the key issue was to improve standardization of prominent BM features enhancing differentiation between "true" ET and prefibrotic/early primary myelofibrosis (prePMF). These two entities have shown a different epidemiology and clinical outcomes. Concerning prePMF a more explicit clinical characterization of minor criteria is mandated for an improved distinction from ET and overt PMF and accurate diagnosis and outcome prediction.

Oxylipid Profile of Low-Dose Aspirin Exposure: A Pharmacometabolomics Study

Background

While aspirin is a well‐established and generally effective anti‐platelet agent, considerable inter‐individual variation in drug response exists, for which mechanisms are not completely understood. Metabolomics allows for extensive measurement of small molecules in biological samples, enabling detailed mapping of pathways involved in drug response.

Methods and Results

We used a mass‐spectrometry‐based metabolomics platform to investigate the changes in the serum oxylipid metabolome induced by an aspirin intervention (14 days, 81 mg/day) in healthy subjects (n=156). We observed a global decrease in serum oxylipids in response to aspirin (25 metabolites decreased out of 30 measured) regardless of sex. This decrease was concomitant with a significant decrease in serum linoleic acid levels (−19%, P=1.3×10⁻⁵), one of the main precursors for oxylipid synthesis. Interestingly, several linoleic acid‐derived oxylipids were not significantly associated with arachidonic‐induced ex vivo platelet aggregation, a widely accepted marker of aspirin response, but were significantly correlated with platelet reactivity in response to collagen.

Conclusions

Together, these results suggest that linoleic acid‐derived oxylipids may contribute to the non‐COX1 mediated variability in response to aspirin. Pharmacometabolomics allowed for more comprehensive interrogation of mechanisms of action of low dose aspirin and of variation in aspirin response.

Changes in response to antiaggregatory treatment in patients with myeloproliferative neoplasms: a sequential study using multiple electrode aggregometry

In the present study, we used multiple electrode aggregometry (MEA) to investigate the response to aspirin and clopidogrel treatment, and its potential changes over a long-time disease course in patients with myeloproliferative neoplasms (MPNs). arachidonic acid (ASPI), ADP, and thrombin receptor activating peptide (TRAP) tests were performed at two timepoints between 32-50 months in 21 patients with MPN and 1-46 months in 29 controls. We further checked the medical records of the participants to identify a potential correlation of changes in the treatment response with clinical events. In MPN, four out of 13 patients treated with 100 mg of aspirin, no patients receiving 50 mg of aspirin, and one out of five clopidogrel-treated patients showed a therapeutic antiplatelet effect. In the subsequent examinations, five patients changed from response to nonresponse or vice versa. Initial nonresponse and changes from an initial response to nonresponse were observed in six patients with thrombotic events. In the controls, 25 out of 26 aspirin-treated patients and two out of three clopidogrel-treated patients showed an initially adequate in-vitro response. Except from one patient changing from initial aspirin nonresponse to response, all controls showed a stable response state. One control with two ischemic strokes showed a nonresponse to clopidogrel. In conclusion, MEA detects the response to antiaggregatory treatment, as well as its changes during the disease course in patients with MPN. An initial or subsequent nonresponse was observed in patients with thrombotic events.

Liquid chromatography-tandem mass spectrometry for simultaneous measurement of thromboxane B2 and 12(S)-hydroxyeicosatetraenoic acid in serum

Arachidonic acid (AA) is metabolized in human platelets by two main pathways: via cyclooxygenase (COX-1) to prostaglandins and thromboxane (TX)A2 and via 12-lipoxygenase (12-LOX) to 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE). While COX products are known to regulate platelet reactivity, the role of 12-LOX metabolites is still controversial. To better understand the platelet enzymatic pathways, we developed a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the simultaneous measurement of both platelet metabolites in human serum. After the addition of deuterated d4-TXB2 and d8-12(S)-HETE as internal standards and the solid-phase extraction of serum samples, analytes were resolved using reversed-phase C18 column and quantified using negative ion electrospray ionization-tandem mass spectrometry. Intra and interassay imprecisions were less than 10% for both analytes. The lower limits of quantification were 0.244ng/ml and 0.976ng/ml for TXB2 and 12(S)-HETE, respectively. This method was applied to measure platelet metabolites in healthy subjects (n=35). LC-MS/MS allows rapid, simultaneous, sensitive and accurate quantification of both platelet AA products in human serum with a small sample volume required and a minimal sample preparation.

Analysis, physiological and clinical significance of 12-HETE: a neglected platelet-derived 12-lipoxygenase product

While the importance of cyclooxygenase (COX) in platelet function has been amply elucidated, the identification of the role of 12-lipoxygenase (12-LOX) and of its stable metabolite, 12-hydroxyeicosatretraenoic acid (12-HETE), has not been clarified as yet. Many studies have analysed the implications of 12-LOX products in different pathological disorders but the information obtained from these works is controversial. Several analytical methods have been developed over the years to simultaneously detect eicosanoids, and specifically 12-HETE, in different biological matrices, essentially enzyme-linked immunosorbent assays (ELISA), radioimmunoassays (RIA), high performance liquid chromatography (HPLC) and mass spectrometry coupled with both gas and liquid chromatography methods (GC- and LC-MS). This review is aimed at summarizing the up to now known physiological and clinical features of 12-HETE together with the analytical methods used for its determination, focusing on the critical issues regarding its measurement.

Anagrelide compared with hydroxyurea in WHO-classified essential thrombocythemia: the ANAHYDRET Study, a randomized controlled trial

High platelet counts in essential thrombocythemia (ET) can be effectively lowered by treatment with either anagrelide or hydroxyurea. In 259 previously untreated, high-risk patients with ET, diagnosed according to the World Health Organization classification system, the efficacy and tolerability of anagrelide compared with hydroxyurea were investigated in a prospective randomized noninferiority phase 3 study in an a priori-ordered hypothesis. Confirmatory proof of the noninferiority of anagrelide was achieved after 6 months using the primary end point criteria and was further confirmed after an observation time of 12 and 36 months for platelet counts, hemoglobin levels, leukocyte counts (P < .001), and ET-related events (HR, 1.19 [95% CI, 0.61-2.30], 1.03 [95% CI, 0.57-1.81], and 0.92 [95% CI, 0.57-1.46], respectively). During the total observation time of 730 patient-years, there was no significant difference between the anagrelide and hydroxyurea group regarding incidences of major arterial (7 vs 8) and venous (2 vs 6) thrombosis, severe bleeding events (5 vs 2), minor arterial (24 vs 20) and venous (3 vs 3) thrombosis and minor bleeding events (18 vs 15), or rates of discontinuation (adverse events 12 vs 15 or lack of response 5 vs 2). Disease transformation into myelofibrosis or secondary leukemia was not reported. Anagrelide as a selective platelet-lowering agent is not inferior compared with hydroxyurea in the prevention of thrombotic complications in patients with ET diagnosed according to the World Health Organization system. This trial was registered at http://www.clinicaltrials.gov as #NCT01065038.

Platelet-induced thrombin generation by the calibrated automated thrombogram assay is increased in patients with essential thrombocythemia and polycythemia vera

The platelet contribution to the thrombophilic state of patients with myeloproliferative neoplasms (MPNs), i.e., essential thrombocythemia (ET) and polycythemia vera (PV), remains uncertain. In this study we aimed to characterize the thrombin generation (TG) potential expressed by platelets from these subjects, compare it to normal platelets, and identify what factors might be responsible for platelet TG. In a group of 140 MPN patients (80 ET and 60 PV) and 72 healthy subjects, we measured the global procoagulant potential of platelet-rich plasma (PRP) utilizing the TG assay by the calibrated automated thrombogram (CAT). To characterize the procoagulant contribution of platelets in PRP, the TG of both isolated platelets and platelet-poor plasma was measured, and the platelet surface expression of TF was determined. Finally, the activation status of platelets was assessed by the levels of P-selectin expressed on platelet surface. MPN patients had significantly increased PRP and isolated platelet TG potential compared to controls. This was associated to the occurrence of platelet activation. Patients carriers of the JAK2V617F mutation showed the highest values of TG and platelet surface TF and P-selectin. Platelet TG potential was significantly lower in hydroxyurea(HU) compared to non-HU-treated patients and was lowest in HU-treated JAK2V617F carriers. In subjects not receiving HU, platelet TG significantly increased by JAK2V617F allele burden increment (P < 0.05).This study demonstrates a platelet-dependent form of hypercoagulability in MPN patients, particularly in those carriers of the JAK2V617F mutation. The cytoreductive therapy with HU significantly affects this prothrombotic phenotype.

Evaluation of platelet function and pharmacological platelet inhibition in patients with myeloproliferative disorders using multiple electrode aggregometry

BACKGROUND

The aim of this study was to describe platelet aggregation characteristics by multiple electrode aggregometry (MEA) and to evaluate MEA for its potential to detect platelet dysfunction and response to anti-aggregatory drugs in patients with myeloproliferative disorders (MPD).

METHODS

We compared the platelet response to arachidonic acid (ASPI test), adenosine diphosphate (ADP test) and thrombin receptor activating peptide (TRAP test) in hirudin-anticoagulated blood of 55 patients with polycythaemia vera and essential thrombocythaemia and 75 controls.

RESULTS

Comparing MPD patients and controls no statistically significant difference indicative of platelet dysfunction was found in MPD patients. Analysis of covariance revealed platelet- and leukocyte count as a significant influencing factor on MEA function. Furthermore we could demonstrate that ASA and clopidogrel treatment results in a statistically significant lower ASPI (Controls: p<0.0001, MPD: p<0.0001) and ADPtest value (MPD: p=0.00125) compared to untreated patients thereby validating the method for monitoring of anti-aggregatory therapy.

CONCLUSION

In this study MEA was confirmed as a valid method for monitoring of ASA and clopidogrel treatment in patients with MPD and normal control subjects. The platelet and leukocyte count were identified as major influencing factors on MEA aggregation tests both in MPD patients and controls. No functional platelet abnormalities were detected in MPD patients.

Acute coronary syndrome associated with essential thrombocythemia

Although essential thrombocythemia (ET) has been rarely reported to cause coronary thrombosis, its appropriate management is still undefined. We describe a case of acute coronary syndrome in a patient with ET. A 47-year-old woman with ET complained of severe acute chest pain. Primary coronary angiography showed severe stenosis with thrombus in the proximal left anterior descending coronary artery. The patient was treated with anti-platelet drugs and hydroxyurea to prevent in-stent thrombosis, and subsequently underwent successful coronary angioplasty using aspiration and a distal protection device without thrombotic coronary complications.

Thrombotic complications in essential thrombocythemia (ET): clinical facts and biochemical riddles

Hemostatic complications which can occur in the arterial or venous vasculature or in the microcirculation are the major causes of morbidity and mortality in patients with ET. In order to prevent these complications, often platelet reductive drugs are used. These agents are by themselves potentially toxic, i.e. may cause leukemia or cardiac side effects. In order to avoid these adverse effects, a better understanding of the mechanism of thrombus formation which is causative in ET is mandatory. Unfortunately, until now, no biomarkers have been identified which allow the estimation of the risk of thrombotic complications. Platelet number is not a good predictor per se since thrombotic complications can occur in some patients at low platelet numbers whereas others do not encounter a thrombosis even at very high platelet levels. On the other hand, lowering of the platelet count usually results in symptomatic improvement. In ET, morphological alterations of the megakaryocyte in the bone marrow and the circulating platelets are observed: megakaryocyte nuclei show a staghorn appearance, circulating platelets are characterized by anisocytosis and giant size. Functional studies indicate that these anatomically altered platelets function abnormally. When platelets are analyzed with a platelet function analyzer (PFA-100, which uses cartridges that measure how well a patient's platelets adhere and aggregate to form a platelet plug in the first phase of thrombus formation), in many patients with ET, closure time using collagen/ADP and collagen/epinephrine cartridges is prolonged. This seems paradoxical since these patients do not show an increased bleeding time. These results indicate that either receptors and/or consecutive signaling events are abnormal in ET platelets. Proteomic analysis of platelets of ET patients has revealed individual differences but not yet led to the identification of disease-specific proteins. Moreover, the search for alternative risk factors (factor V Leiden, prothrombin gene polymorphism, etc.) has not provided evidence for the contribution of these factors to the generation of the thrombotic risk in ET patients. In summary, despite intensive research over several decades, relatively little is known about the pathogenesis and risk factors for thrombosis in ET. I expect that this conference will contribute to the development of new strategies to identify patients at risk for hemostatic complications.

Pathogenesis of Thrombosis in Essential Thrombocythemia and Polycythemia Vera: The Role of Neutrophils

Thrombotic complications are frequently observed in patients with polycythemia vera (PV) and essential thrombocythemia (ET). Abnormalities of red blood cells and platelets arising from the clonal rearrangement of hematopoietic cells have been considered, although causal relationships between any of these specific abnormalities and thrombosis have not been clearly established. The involvement of neutrophils and macrophages, which participate in thrombosis and hemostasis, has been insufficiently explored in PV and ET. Persistent activation of circulating neutrophils was recently demonstrated in ET and PV patients, in parallel with an increase in plasma concentrations of endothelial damage-derived and prothrombotic substances. Other studies have explored whether the augmentation of adhesion of neutrophils may affect neutrophil/platelet interaction since a significant increase in circulating neutrophil/platelet aggregates is found in ET and PV. This review summarizes the current knowledge of the pathogenesis of thrombosis in PV and ET, with emphasis on the role of neutrophils in hemostasis and their possible involvement in the mechanisms of the acquired thrombophilia of these patients. Available data suggest that these hemostatic markers deserve to be included in prospective clinical studies aimed at identifying their predictive role in the vascular complications of patients with ET and PV.

A Thrombelastograph whole blood assay for clinical monitoring of NSAID-insensitive transcellular platelet activation by arachidonic acid

Optical platelet aggregation (OPA) with platelet-rich plasma (PRP) was compared with a Thrombelastograph (TEG) whole blood assay for monitoring arachidonic acid (AA)-induced platelet activation. Assays were performed on 47 interventional cardiology and 24 general surgery patients receiving aspirin therapy for cardiovascular disease, as well as 48 volunteers asked to take nonsteroidal anti-inflammatory drugs (NSAIDs) or 12 volunteers on chronic NSAID therapy unrelated to diagnosed cardiovascular disease. Whole blood TEG monitoring of NSAID inhibition detected NSAID-insensitive AA activation of platelets in a significantly higher number of cardiology (23%) and surgery (25%) patients and normal volunteers on chronic NSAID (25%) therapy relative to normal subjects not on chronic NSAID therapy (0%). Whole blood NSAID insensitivity was observed with cyclooxygenase-I inhibitors, such as aspirin and ibuprofen; was not affected by Celebrex, a cyclooxygenase-II inhibitor; but was completely inhibited by thromboxane-receptor antagonists. This was not due to platelet NSAID insensitivity, because complete inhibition of AA-activation responses in PRP was observed with either TEG or OPA assays. We confirmed that thromboxane B(2) formation in PRP from NSAID-insensitive subjects was completely inhibited by NSAIDs. However, significant amounts were formed in whole blood from NSAID-insensitive subjects, but not in whole blood from NSAID-sensitive subjects. Thromboxane formation after AA addition was not found in washed blood cells with 90% reduced platelet counts or in leukocyte-rich buffy coat fractions, but could be restored by addition of PRP. NSAID-insensitive activation was inhibited by nordihydroguaiaretic acid, with an IC(50) of 30 micromol, implicating 12- and/or 15-lipoxygenases in this transcellular pathway.

Anagrelide: a decade of clinical experience with its use for the treatment of primary thrombocythaemia

Primary thrombocythaemia (PT) is the most frequent among the rare chronic myeloproliferative disorders. Life expectancy is determined by thromboembolic and haemorrhagic complications, which can be prevented by cytoreductive therapy. For a long time, hydroxyurea has been considered as the therapeutic gold standard. However, hydroxyurea treatment is not lineage-specific, may not be tolerated because of adverse effects (skin, gastrointestinal tract) and is leukaemogenic when sequentially used with other DNA-targeting drugs. Hence, anagrelide was welcomed in 1988 when it was first described as being efficient at normalising elevated platelet counts, specific for megakaryocytes and non-mutagenic. Since then, anagrelide has been approved in the US and Canada (Agrylin), Shire Pharmaceuticals) as well as in Austria and other countries of the EU (Thromboreductin), AOP Orphan Pharmaceuticals). Clinical Phase III trials (PT1 and ANAHYDRET) are underway to directly compare the efficacy and safety of anagrelide and hydroxyurea.

Lack of influence of the COX inhibitors metamizol and diclofenac on platelet GPIIb/IIIa and P-selectin expression in vitro

Background

The effect of non-steroidal anti-inflammatory drugs (NSAIDs) for reduced platelet aggregation and thromboxane A₂ synthesis has been well documented. However, the influence on platelet function is not fully explained. Aim of this study was to examine the influence of the COX-1 inhibiting NSAIDs, diclofenac and metamizol on platelet activation and leukocyte-platelet complexes, in vitro. Surface expression of GPIIb/IIIa and P-selectin on platelets, and the percentage of platelet-leukocyte complexes were investigated.

Methods

Whole blood was incubated with three different concentrations of diclofenac and metamizol for 5 and 30 minutes, followed by activation with TRAP-6 and ADP. Rates of GPIIb/IIIa and P-selectin expression, and the percentage of platelet-leukocyte complexes were analyzed by a flow-cytometric assay.

Results

There were no significant differences in the expression of GPIIb/IIIa and P-selectin, and in the formation of platelet-leukocyte complexes after activation with ADP and TRAP-6, regarding both the time of incubation and the concentrations of diclofenac and metamizol.

Conclusions

Accordingly, the inhibitory effect of diclofenac and metamizol on platelet aggregation is not related to a reduced surface expression of P-selectin and GPIIb/IIIa on platelets.

Neuroprotective effects of low-doses of aspirin

Aspirin appears to have a neuroprotective role against glutamate excitotoxicity. In fact, recent animal studies have demonstrated the neuroprotective role of acetylsalicylic acid (ASA) against glutamatergic excitants. It has been pointed out that ASA is neuroprotective against hypoxic hypoxia, chemical hypoxia and also delays the decline of intracellular ATP. Prostaglandins may cause convulsions and high-doses of aspirin appear to protect neurons from excitotoxicity. A case is reported of a woman whose electroencephalogram (EEG) abnormalities reversed and whose psychological symptomatology regressed after treatment with low-doses of aspirin. This appears to be the first description of a disappearance of EEG abnormalities with low-doses of aspirin. The neuroprotective effect of ASA could be of extreme importance in metabolic neuronal disfunction, reversing both clinical symptoms and EEG genetic anomalies: it is probably due to transient neurotransmitter concentration disequilibrium caused by subclinical hypoxic cortical suffering. Copyright 2001 John Wiley & Sons, Ltd.

Polymorphonuclear leukocyte activation and hemostasis in patients with essential thrombocythemia and polycythemia vera

Thrombohemorrhagic complications are a major cause of morbidity and mortality in patients with essential thrombocythemia (ET) and polycythemia vera (PV). The pathogenesis of these complications is not completely clarified. Several studies have described abnormalities of red blood cells and platelets in these patients. However, no studies are available on changes in the polymorphonuclear leukocytes (PMNs), which can play an important role in the activation of the hemostatic system. In patients with ET (n = 37) and PV (n = 34), a series of PMN activation parameters (PMN membrane CD11b and leukocyte alkaline phosphatase [LAP] antigen expression, cellular elastase content, plasma elastase, and myeloperoxidase levels) was evaluated simultaneously with the levels of plasma markers of endothelial damage (thrombomodulin and von Willebrand factor antigen) and hypercoagulation (thrombin-antithrombin complex, prothrombin fragment 1 + 2, and D-dimer). The results show the occurrence of PMN activation in both groups of patients compared with a control group of healthy subjects. An increase in CD11b and LAP expression by PMN membrane was observed, together with a significant increase in cellular elastase content, plasma elastase, and myeloperoxidase levels. In addition, patients had high plasma levels of endothelial and hypercoagulation markers compared with controls. For the first time, these data show that in ET and PV, 2 hematologic conditions that place patients at increased risk for thrombosis, an in vivo leukocyte activation occurs and is associated with laboratory signs of endothelium and coagulation system activation.

Polymorphonuclear leukocyte activation and hemostasis in patients with essential thrombocythemia and polycythemia vera

Thrombohemorrhagic complications are a major cause of morbidity and mortality in patients with essential thrombocythemia (ET) and polycythemia vera (PV). The pathogenesis of these complications is not completely clarified. Several studies have described abnormalities of red blood cells and platelets in these patients. However, no studies are available on changes in the polymorphonuclear leukocytes (PMNs), which can play an important role in the activation of the hemostatic system. In patients with ET (n = 37) and PV (n = 34), a series of PMN activation parameters (PMN membrane CD11b and leukocyte alkaline phosphatase [LAP] antigen expression, cellular elastase content, plasma elastase, and myeloperoxidase levels) was evaluated simultaneously with the levels of plasma markers of endothelial damage (thrombomodulin and von Willebrand factor antigen) and hypercoagulation (thrombin-antithrombin complex, prothrombin fragment 1 + 2, and D-dimer). The results show the occurrence of PMN activation in both groups of patients compared with a control group of healthy subjects. An increase in CD11b and LAP expression by PMN membrane was observed, together with a significant increase in cellular elastase content, plasma elastase, and myeloperoxidase levels. In addition, patients had high plasma levels of endothelial and hypercoagulation markers compared with controls. For the first time, these data show that in ET and PV, 2 hematologic conditions that place patients at increased risk for thrombosis, an in vivo leukocyte activation occurs and is associated with laboratory signs of endothelium and coagulation system activation.

Essential thrombocythaemia

Essential thrombocythaemia (ET) is a clonal stem cell disorder that frequently presents as an incidental finding of elevated platelet counts. Diagnosis depends on exclusion of other myeloproliferative disorders and reactive thrombocytosis. Patients with platelet counts above 1000 x 10(9)/L should receive platelet-lowering therapy, even if asymptomatic. Definitive recommendations cannot yet be made for asymptomatic patients with lower platelet counts. ET can be treated with alkylating agents, radioactive phosphorus or hydroxyurea, but there is evidence that these agents increase transformation to acute leukaemia. Interferon alfa-2a and anagrelide are useful treatment agents, particularly in younger patients.