Search

None.

Background Anti-phospholipid syndrome (APS) is characterized by arterial and/or venous thrombosis and pregnancy morbidity associated with the presence of "anti-phospholipid antibodies." Thrombosis may be the result of a hypercoagulable state related to activation of endothelial cells and platelets by anti-β2-glycoprotein I (β2-GPI) antibodies. Anti-β2-GPI antibodies induce a proinflammatory and procoagulant phenotype in these cells that, after activation, express tissue factor (TF), the major initiator of the clotting cascade, playing a role in thrombotic manifestations. Moreover, TF expression may also be induced by heparanase, an endo-β-D-glucuronidase, that generates heparan sulfate fragments, regulating inflammatory responses. Objectives In this study we analyzed, in human platelets and endothelial cells, the effect of a new symmetrical 2-aminophenyl-benzazolyl-5-acetate derivative (RDS3337), able to inhibit heparanase activity, on signal transduction pathways leading to TF expression triggered by anti-β2-GPI. Methods Platelets and endothelial cells were incubated with affinity purified anti-β2-GPI after pretreatment with RDS3337. Cell lysates were analyzed for phospho-interleukin-1 receptor-associated kinase 1 (IRAK1), phospho-p65 nuclear factor kappa B (NF-κB) and TF by western blot. In addition, platelet activation and secretion by ATP release dosage were evaluated. Results IRAK phosphorylation and consequent NF-κB activation, as well as TF expression triggered by anti-β2-GPI treatment were significantly prevented by previous pretreatment with RDS3337. In the same vein, pretreatment with RDS3337 prevented platelet aggregation and ATP release triggered by anti-β2-GPI antibodies. Conclusion These findings support the view of heparanase involvement in a prothrombotic state related to APS syndrome, suggesting a novel target to regulate overexpression of procoagulant protein(s).

The impact of inhibition of multidrug resistance protein 4 (MRP4) on nitric oxide (NO) resistance and on ADP-induced platelet aggregation is unknown. The aim of this investigation was to verify whether platelet NO resistance correlates with MRP4 expression and evaluate whether this can be reduced by in vitro MRP4 inhibition mediated by cilostazol. Moreover, we assessed if inhibition of MRP4-mediated transport reduces ADP-induced platelet reactivity. The inhibitory effect of sodium nitroprusside (SNP), a NO-donor that enhances cyclic guanosine monophosphate (cGMP) cytosolic concentration, was assessed in platelets obtained from aspirin treated patients and in a control population. The inhibitory effect of SNP was evaluated by ADP-induced aggregation in SNP-treated platelets. The impact of MRP4 on ADP-induced platelet aggregation was performed in high on aspirin residual platelet reactivity (HARPR) patients and compared to healthy volunteers (HV), and a control cohort (CTR). In aspirin-treated patients with high levels of MRP4, reduced SNP inhibition was found compared to those with low levels of MRP4. MRP4 inhibition by cilostazol significantly reduced ADP-induced platelet aggregation in HARPR population, and to a lesser extent in HV and CTR populations. In conclusion, cilostazol can mitigate the hyper-reactive platelet phenotype of HARPR patients by reducing residual ADP-induced platelet aggregation and increasing NO-dependent endothelial antiplatelet effects. Electronic supplementary material The online version of this article (10.1007/s11239-020-02214-4) contains supplementary material, which is available to authorized users.

Background and purposeAcute ischemic stroke (AIS) is a fearful complication of Coronavirus Disease-2019 (COVID-19). Aims of this study were to compare clinical/radiological characteristics, endothelial and coagulation dysfunction between acute ischemic stroke (AIS) patients with and without COVID-19 and to investigate if and how the SARS-CoV-2 spike protein (SP) was implicated in triggering platelet activation.MethodsWe enrolled AIS patients with COVID-19 within 12 h from onset and compared them with an age- and sex-matched cohort of AIS controls without COVID-19. Neuroimaging studies were performed within 24 h. Blood samples were collected in a subset of 10 patients.ResultsOf 39 AIS patients, 22 had COVID-19 and 17 did not. Admission levels of Factor VIII and von Willebrand factor antigen were significantly higher in COVID-19 patients and positively correlated with the infarct volume. In multivariate linear regression analyses, COVID-19 was an independent predictor of infarct volume (B 20.318, Beta 0.576, 95%CI 6.077–34.559; p = 0.011). SP was found in serum of 2 of the 10 examined COVID-19 patients. Platelets from healthy donors showed a similar degree of procoagulant activation induced by COVID-19 and non-COVID-19 patients' sera. The anti-SP and anti-FcγRIIA blocking antibodies had no effect in modulating platelet activity in both groups.ConclusionsSARS-CoV-2 infection seems to play a major role in endothelium activation and infarct volume extension during AIS.

Background. Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare syndrome of unclear aetiology occurring after DNA-based vaccinations against COVID-19. The aim of this study was to investigate the DNA vaccine-encoded Sars-cov-2 soluble spike protein (SP). as a potential trigger of platelet activation in VITT. Methods. We studied three VITT patients and seven healthy controls (HCs) within 3 weeks from the first dose of ChAdOx1 nCoV-19, and one non vaccinated HC. Serum levels of SP and soluble angiotensin-converting enzyme 2 (sACE2), ACE2 expression in platelets and platelet response to VITT serum stimulation were studied. A thrombus retrieved during mechanical thrombectomy from one VITT patients, was analysed by immunohistochemistry for SP and ACE2. Neutrophil extracellular traps (NETs) markers and coagulation parameters were also measured. Results. We detected serum SP (up to 35 days post-vaccination) and sACE2 in all VITT patients, and respectively in two and three out of 7 vaccinated HCs. Only platelets from one non-vaccinated HC expressed ACE2. VITT sera markedly activated platelets and this activation was inhibited by both anti-SP and anti-FcγRIIA blocking antibodies. The thrombus showed positive immunohistochemical labelling of platelets using an anti-SP antibody with reduced ACE2 expression, compared to a thrombus from a pre-pandemic stroke patient. Markers of endothelial dysfunction, NETs and hypercoagulability state were present in all VITT sera. Conclusions. The present data provides first evidence that DNA vaccine-encoded Sars-cov-2 SP is detectable in VITT sera (several weeks post-vaccination) and in a platelet-rich thrombus, and that may contribute to the initial platelet stimulation in VITT patients.

Vaccine induced thrombotic thrombocytopenia is a new syndrome recently described in young adults within two weeks from the first dose of the ChAdOx1 nCoV-19 vaccine and characterized by cerebral venous thrombosis. We report two cases of malignant middle cerebral artery (MCA) infarct and thrombocytopenia within 10 days after vaccination with ChAdOx1 nCoV-19. Patient 1 was a 57-year-old woman who underwent decompressive craniectomy despite two successful mechanical thrombectomies. Patient 2 was a 55-year-old woman who developed a fatal bilateral malignant MCA infarct. Both the patients had pulmonary and portal vein thrombosis and high level of antibodies to platelet factor 4-polyanion complexes.

Vaccine-induced thrombotic thrombocytopenia with cerebral venous thrombosis is a syndrome recently described in young adults within two weeks from the first dose of the ChAdOx1 nCoV-19 vaccine. Here we report two cases of malignant middle cerebral artery (MCA) infarct and thrombocytopenia 9-10 days following ChAdOx1 nCoV-19 vaccination. The two cases arrived in our facility around the same time but from different geographical areas, potentially excluding epidemiological links; meanwhile, no abnormality was found in the respective vaccine batches. Patient 1 was a 57-year-old woman who underwent decompressive craniectomy despite two prior, successful mechanical thrombectomies. Patient 2 was a 55-year-old woman who developed a fatal bilateral malignant MCA infarct. Both patients manifested pulmonary and portal vein thrombosis and high level of antibodies to platelet factor 4-polyanion complexes. None of the patients had ever received heparin in the past before stroke onset. Our observations of rare arterial thrombosis may contribute to assessment of possible adverse effects associated with COVID-19 vaccination., Vaccination is an effective strategy in suppressing COVID-19 pandemic, but rare adverse effects have been reported, including cerebral venous thrombosis. Here the authors report two cases of middle cerebral artery infarct within 9-10 days following ChAdOx1 nCov-19 vaccination that also manifest pulmonary and portal vein thrombosis.

This study shows that pancreatic cancer cells undergoing cell death by valproic acid (VPA) treatment activated dendritic cells (DCs) more efficiently than those treated with trichostatin A (TSA), as demonstrated by CD86 and CD80 surface expression. Surprisingly though, DCs cultured in the presence of supernatant derived from VPA-treated cancer cells showed a reduced allostimulatory capacity and an increased release of IL10 and IL8 cytokines in comparison with those exposed to TSA-treated cell culture supernatant. Searching for molecular mechanisms leading to such differences, we found that VPA treatment dysregulated choline metabolism and triggered a stronger endoplasmic reticulum (ER) stress in pancreatic cancer cells than TSA, upregulating CCAAT/enhancer-binding protein homologous protein, and activated cyclooxygenase-2, thus promoting the release of prostaglandin (PG) E2. Interestingly, dysfunctional DCs cultured in the presence of VPA-treated cells culture supernatant showed a higher level of intracellular reactive oxygen species, 4-hydroxy-trans-2-nonenal protein adducts, and ER stress, as evidenced by the upregulation of spliced X-box binding protein 1 (XBP1s), effects that were reduced when DCs were exposed to supernatant of cancer cells treated with Celecoxib before VPA. Celecoxib prevented PGE2 release, restoring the function of DCs exposed to VPA-treated cells culture supernatant, and a similar effect was obtained by silencing XBP1s in DCs treated with VPA-treated cells culture supernatant. These results suggest that PGE2 could be one of the yet unidentified factors able to transfer the stress from cancer cells to DCs, resulting in an impairment of their function.

Dear Editor,We read the work by Di Napoli et al. [1] with great interest. We congratulate the authors. In our opinion, cilostazol has the potential to be very important in reducing cerebrovascular ...

BACKGROUND Multidrug resistance protein-4 (MRP4) is an ATP binding cassette membrane transporter, actively involved in the efflux of important pharmacological and physiological molecules. Recently, its over-expression has been associated with reduced aspirin (ASA) efficacy after by-pass surgery. MicroRNAs (miRNAs) are small molecules of non-coding RNA involved in the regulation of many physiological and pathophysiological pathways, are abundant in platelets, and can be modulated by several drugs. In the present study, we assessed the role of platelet miRNAs in modulating MRP4 function in response to ASA. METHODS MRP4 mRNA expression has been analyzed by RealTime PCR in platelets from patients on chronic ASA treatment versus a control group. A panel of miRNAs was run on the pool of each cohort. MiRNAs validation was performed by RealTime PCR. To verify whether MRP4 is the target of miR-26b also in platelets, miR-26b was transfected in platelet and DAMI cells with miRNA mimic technology. MRP4 expression was evaluated by flow cytometry and western blotting. RESULTS We observed a higher MRP4 mRNA expression in platelets of patients under ASA treatment compared to the control group (p

Left ventricular assist device (LVAD) management is very challenging since many adverse events can occur in ongoing patients. Inadequate anticoagulation treatment can lead to life-threatening situations like ischemic stroke or pump thrombosis. The main intention of our study was to investigate if early identification of aspirin nonresponders by using aggregometry can improve anticoagulation management, reducing the risk of pump thrombosis. Methods From December 2010 to May 2018, 24 patients were implanted with a HeartMate II (HMII), 6 received a HeartWare HVAD system--full support VAD (HVAD), and 22 received a HeartMate III (HMIII). All patients were maintained with a target INR of 2.0 to 3.0. When the aggregometry test revealed a normal platelet function, 100 mg of aspirin were initiated. Only aspirin nonresponders were early identified by repeating the aggregometry after 7 days of aspirin administration. In acetylsalicylic acid nonresponder patients, 75 mg of clopidogrel was used, and the patients were tested again. Ticlopidine (250 mg) was used when clopidogrel was unsuccessful. Results Four patients required modification in antiplatelet therapy. Three patients (5%), 2 HVAD and 1 HMII, suffered from pump thrombosis. One patient died as a consequence of a large intracranial hemorrhagic event following thrombolytic treatment. One patient required a pump exchange; in 1 patient, thrombolytic infusion was conducted successfully. Conclusion Reported rates of pump thrombosis at 12 months for patients implanted with commonly used LVADs were 6% to 12% for axial-flow pumps and 8% with centrifugal-flow devices. In our series, the reported 5% overall incidence of pump thrombosis encourages the routine use of an aggregometry test for early identification of aspirin nonresponders.

Chronic treatment with aspirin in healthy volunteers (HVs) is associated with recovery of adenosine diphosphate (ADP)-induced platelet activation. The purinergic P2Y1 receptor exerts its effects via a Gq-protein, which is the same biochemical pathway activated by thromboxane-A2 receptor. We hypothesized that recovery of ADP-induced platelet activation could be attributed to increased P2Y1 expression induced by chronic aspirin exposure. We performed a multi-phase investigation which embraced both in vitro and in vivo experiments conducted in (1) human megakaryoblastic DAMI cells, (2) human megakaryocytic progenitor cell cultures, (3) platelets obtained from HVs treated with aspirin and (4) platelets obtained from aspirin-treated patients. DAMI cells treated with aspirin or WY14643 (PPARα agonist) had a significant up-regulation of P2Y1 mRNA, which was shown to be a PPARα-dependent process. In human megakaryocytic progenitors, in the presence of aspirin or WY14643, P2Y1 mRNA expression was higher than in mock culture. P2Y1 expression increased in platelets obtained from HVs treated with aspirin for 8 weeks. Platelets obtained from patients who were on aspirin for more than 2 months had increased P2Y1 expression and ADP-induced aggregation compared with patients on aspirin treatment for less than a month. Overall, our results suggest that aspirin induces genomic changes in megakaryocytes leading to P2Y1 up-regulation and that PPARα is the nuclear receptor involved in this regulation. Since P2Y1 is coupled to the same Gq-protein of thromboxane-A2 receptor, platelet adaptation in response to pharmacological inhibition seems not to be receptor specific, but may involve other receptors with the same biochemical pathway.

Platelet multidrug resistance protein 4 (MRP4) plays a modulating role on platelet activation. Platelet function and thrombus formation are impaired in MRP4 knockout mice models, and, among aspirin-treated patients, high on-aspirin residual platelet reactivity (HARPR) positively correlates with MRP4 levels. To better understand the effects of MRP4 on platelet function, the aim of this investigation was to assess the impact of cilostazol-induced inhibition of MRP4-mediated transport and assess aspirin-induced antiplatelet effects and rates of HARPR in human subjects.Cilostazol-dependent inhibition of MRP4-mediated transport was assessed with the release of the fluorescent adduct bimane-glutathione and aspirin entrapment. Effect of Cilostazol on cAMP inhibition was evaluated by vasodilator-stimulated phosphoprotein (VASP). Platelet function was studied by collagen and TRAP-6-induced platelet aggregation and secretion.Cilostazol reduced the release of bimane-glutathione and enhanced aspirin entrapment demonstrating an inhibitory effect on MRP4 in platelets. VASP phosphorylation was absent until 10 seconds after addition of cilostazol, and becomes evident after 30 seconds. An inhibitory effect on platelet aggregation and secretion was found in activated platelets, with threshold concentration of agonists, 10 seconds after addition of cilostazol, supporting a role of MRP4 on platelet function that is cAMP independent. Cilostazol effects were also shown in aspirin-treated platelets. A reduction of platelet aggregation and secretion were observed in aspirin-treated patients with HARPR.This study supports the role of MRP4 on modulating platelet function which occurs through cAMP-independent mechanisms. Moreover, inhibition of MRP4 induced by cilostazol enhances aspirin-induced antiplatelet effects and reduces HARPR.

High mobility group box 1 (HMGB1) is an ubiquitous protein that plays different roles in the nucleus, cytoplasm, and extracellular space. It is an important DAMP molecule that allows communication between damaged or tumor cells and the immune system. Tumor cells exploit HMGB1’s ability to activate intracellular pathways that lead to cell growth and migration. Papillary thyroid cancer is a well-differentiated tumor and is often used to study relationships between cells and the inflammatory microenvironment as the latter is characterized by high levels of inflammatory cells and cytokines. Anaplastic thyroid cancer is one of the most lethal human cancers in which many microRNAs and tumor suppressor genes are deregulated. Upregulation of microRNAs 221 and 222 has been shown to induce the malignant phenotype in many human cancers via inhibition of PTEN expression. In this study we suggest that extracellular HMGB1 interaction with RAGE enhances expression of oncogenic cluster miR221/222 that in turn inhibits tumor suppressor gene PTEN in two cell lines derived from human thyroid anaplastic and papillary cancers. The newly identified pathway HMGB1/RAGE/miR221/222 may represent an effective way of tumor escape from immune surveillance that could be used to develop new therapeutic strategies against anaplastic tumors.

Overexpression of efflux transporters, in human cells, is a mechanism of resistance to drug and also to chemotherapy. We found that multidrug resistance protein-4 (MRP4) overexpression has a role in reducing aspirin action in patients after bypass surgery and, very recently, we found that aspirin enhances platelet MRP4 levels through peroxisome proliferator activated receptor-α(PPARα). In the present paper, we verified whether exposure of human embryonic kidney-293 cells (Hek-293) to aspirin modifies MRP4 gene expression and its correlation with drug elimination and cell toxicity. We first investigated the effect of high-dose aspirin in Hek-293 and we showed that aspirin is able to increase cell toxicity dose-dependently. Furthermore, aspirin effects, induced at low dose, already enhance MRP4 gene expression. Based on these findings, we compared cell viability in Hek-293, after high-dose aspirin treatment, in MRP4 overexpressing cells, either after aspirin pretreatment or in MRP4 transfected cells; in both cases, a decrease of selective aspirin cell growth inhibition was observed, in comparison with the control cultures. Altogether, these data suggest that exposing cells to low nontoxic aspirin dosages can induce gene expression alterations that may lead to the efflux transporter protein overexpression, thus increasing cellular detoxification of aspirin.

Background A mechanism involved in high on‐aspirin treatment residual platelet reactivity is platelet multidrug resistance protein 4 (MRP4) overexpression. Aspirin enhances platelet MRP4 expression with a PPARα‐dependent mechanism and reduces miR‐21 expression that, in turn, downregulates PPARα expression. Objective The aim of our study was to verify the relationship between miR‐21 and MRP4‐PPARα levels induced by aspirin treatment. Methods We evaluated the changes in MRP4‐PPARα, mRNA, MRP4 protein, and miR‐21 expression induced by aspirin in: (i) in vitro–treated megakaryoblastic cell line (DAMI), (ii) primary megakaryocytes cultures and derived platelets, (iii) healthy volunteers’ platelets treated with aspirin, and (iv) aspirinated patients (aspirin‐treated patients) and in a control population (control). Results We observed an aspirin‐induced reverse relationship between the expression of miR‐21 and PPARα‐MRP4. In DAMI cells the miR‐21 mimic transfection reduces PPARα and MRP4 expression, even if cells were treated with aspirin after transfection. MiR‐21 inhibitor transfection induces PPARα and MRP4 expression that are not enhanced by aspirin treatment. In human megakaryocytes, aspirin treatment lead to a miR‐21 downregulation and a MRP4 upregulation and this trend is confirmed in derived platelets. In aspirin‐treated volunteers, an inverse relationship between miR‐21 and MRP4 platelet expression was found after aspirin treatment. A similar negative relationship was found in aspirin‐treated patients vs the control population. Conclusion The results reported in this study provide information that aspirin induces the modulation of platelet miR‐21 expression levels and this modulation can be responsible for MRP4 enhancement in circulating platelets.

Heparin-induced thrombocytopenia (HIT) is a thrombotic complication of heparin therapy. The most used functional method for HIT diagnosis is serotonin release assay (SRA). A different functional method based on ATP release with luciferin/luciferase long-life and stable luminescent signal is used here, which is shown to be comparable for accuracy with SRA in both negative (patients 4Ts ≤3, and negative for both anti-PF4/heparin immunoassay and SRA) and positive (4Ts >3, and positive for both PF4/heparin antibodies and SRA) patients. Our results show that ATP release is higher in washed platelets activated by sera from positive patients than in platelets activated by sera from negative patients. In conclusion, we demonstrate that ATP release assay is a valid alternative method to SRA for the identification of pathogenic anti-PF4/heparin antibodies.

We read with a great interest the recent article published in Stroke by Gonzalez-Valcarcel et al1 on the association between paracetamol and ibuprofen use with major cardiovascular events or major bleeding in patients. The authors accomplished a huge task analyzing a cohort of 19 120 patients with recent ischemic stroke or transient ischemic attack of mainly atherothrombotic origin. They observed that patients who used paracetamol daily have a higher risk of major cardiovascular events; patients who used ibuprofen seems not to have a significant increase in the risk of major cardiovascular events, but the results become consistent when …

SummaryPlatelet multidrug resistance protein4 (MRP4)-overexpression has a role in reducing aspirin action. Aspirin in vivo treatment enhances platelet MRP4 expression and MRP4 mediated transport inhibition reduces platelet function and delays thrombus formation. The aim of our work was to verify whether MRP4 expression is enhanced in platelets obtained from patients under chronic aspirin treatment and whether it correlates with residual platelet reactivity. We evaluated changes on mRNA and protein-MRP4 expression and platelet aggregation in four populations: healthy volunteers (HV), aspirin-free control population (CTR), patients who started the treatment less than one month ago (ASA2 months patients). In platelets obtained from ASA>2 months patients, it was found a statistically significant MRP4 enhancement of both mRNA and protein expression compared to HV, CTR and ASA2 months patients that present high levels of platelet MRP4, have higher serum TxB2 levels and collagen-induced platelet aggregation compared to patient with low levels of MRP4 in platelets. In addition collagen induced platelet aggregation is higher in in vitro aspirinated platelets obtained from patients with high levels of MRP4 patients compared to those obtained from patients with low MRP4 levels. We can assert that, in patients under chronic aspirin treatment, platelets that present high MRP4 levels have an increase of residual platelet reactivity, which is due in part to incomplete COX-1 inhibition, and in part to COX-1–independent mechanism.

The prescription of aspirin (acetylsalicylic acid (ASA)) to patients with a history of hypersensitivity to this drug could prove harmful. The aim of the study was to assess the antiplatelet activity and safety of a combined antiplatelet treatment with indobufen and clopidogrel in acute coronary syndrome (ACS) patients with hypersensitivity to aspirin, undergoing coronary stenting. Forty-two consecutive ACS patients treated with stent implantation were randomly assigned to receive clopidogrel 75 mg daily (loading dose 300 mg) plus indobufen 100 mg twice a day (group A), or clopidogrel 75 mg daily, after 300 mg of loading dose (group B). Platelet activity and safety were monitored in both groups at 1, 3, 6, 12, and 18 months with laboratory and clinical evaluation. A lower value of max % platelet aggregation to arachidonic acid and collagen was found in group A compared to group B (31.79 ± 27.33 vs. 73.67 ± 19.92; p 0.0001 and 28.53 ± 21.32 vs. 73.58 ± 17.71; p 0.0001, respectively). There was no difference in max % of platelet inhibition to adenosine diphosphate between the two groups (14.23 ± 18.92 vs. 10.30 ± 18.97; p = 0.23). In the population that was under indobufen treatment, the serum thromboxane B2 (TXB2) production at 1 week and 1 month was very low (2.6 ± 1.6 ng/ml and 3.0 ± 2.7 ng/ml, respectively; p = 0.82). The combined treatment was well tolerated in group A patients. This study suggests that the combined antiplatelet treatment with clopidogrel and indobufen could be a good option in ACS patients with hypersensitivity to aspirin undergoing coronary stenting.

SummaryCyclic nucleotide-dependent inhibition of platelets represents the most important physiological way to limit thrombus formation. cAMP and cGMP increase in platelets as a consequence of prostacyclin and nitric oxide production by endothelial cells and act through PKA and PKG, respectively. The cytosolic concentration of cyclic nucleotides in platelets is regulated by AC- and GC-dependent synthesis and PDE-dependent degradation. In some cells cyclic nucleotides are eliminated also through MRP4/5/8-dependent efflux. As only MRP4 is expressed in platelets, at high levels in dense granules, we determined its role in the elimination of cyclic nucleotides from platelet cytosol. We studied the effects of MRP4 inhibition on cAMP/cGMP effects in platelets. Cyclic nucleotide inhibitory effects triggered by cAMP and cGMP-elevating agents on platelet aggregation are strongly enhanced by MRP4 inhibition and so is cyclic nucleotide-dependent phosphorylation of the common substrate VASP. MRP4 inhibition decreases cAMP concentration in platelet granules and both cAMP and cGMP compete with an established substrate of MRP4 (fluo-cAMP) for entrance in granules. Here we provide the first evidence of the transport of cyclic nucleotides mediated by MRP4 as part of their physiological mechanism of elimination in human platelets, which might represent a novel target to increase cyclic nucleotide-dependent inhibition.

SUMMARY Platelet transfusions, main therapy of Glanzmann Thromboasthenia (GT), can induce an allo-immunization against human leucocyte antigen and integrin alphaIIbbeta3. We have investigated in our GT patients the rate of allo-immunization and of refractoriness to platelet transfusions. From 1975 until December 2005, we have followed 17 GT patients: 14 type 1, 3 variant type; nine females, eight males; median age at diagnosis 9.8 years (range 1-44.5); median age at the time of the study 35.5 years (range 23.6-68.5). In our patients, 121 bleeding episodes occurred (24 severe, 37 moderate, and 60 mild). Ten major and 22 minor surgical procedures have been performed. Two spontaneous deliveries and three caesarian sections with five live births were performed; moreover, one late foetal loss occurred, and one voluntary abortion was performed. Sixteen of 17 patients have been transfused at least once in life with platelets and/or red blood cells (RBC). All transfused patients have been investigated for the presence of anti-HLA and anti-integrin alphaIIbbeta3 allo-antibodies. The positiveness of allo-antibodies has been demonstrated in 4/16 transfused patients (25%): isolated for anti-HLA in two; isolated for anti-integrin alphaIIbbeta3 in one; and combined in one. In spite of the presence of allo-antibodies, platelet transfusions have always been effective and the haemostasis was not compromised.

Thromboxane A2 (TXA2) is a key mediator of platelet activation and aggregation, and an important mediator of platelet-induced coronary artery constriction. We sought to investigate whether baseline plasma levels of TXA2 are associated with coronary no-reflow after primary percutaneous coronary intervention (PPCI).A total of 47 consecutive patients (age, 62.5 +/- 12.7; male sex, 76.6%) admitted to our hospital for a first ST-segment elevation myocardial infarction and undergoing PPCI within 12 h of onset of symptoms were enrolled. Admission TXA2 plasma levels were measured by enzyme-linked immunosorbent assay (ELISA). Angiographic no-reflow was defined as a final TIMI flow ofor=2 or final TIMI flow of 3 with a myocardial blush grade of2, whereas ST-segment resolution from baseline value ofor=50% was used as ECG index of no-reflow. At multivariable analysis TXA2 plasma levels, endothelin-1 (ET-1) plasma levels, and left anterior descending coronary artery (LAD) as culprit vessel were significant predictors of angiographic no-reflow (P = 0.04), whereas TXA2 and ET-1 plasma levels were the only independent predictors of lack of ST-segment resolution (P = 0.013 and 0.04, respectively). Of note, TXA2 tertiles were independent predictors of both angiographic no-reflow and lack of ST-segment resolution (OR, 3.5; 95% CI, 1.1-11; P = 0.03 and OR, 3; 95% CI, 1.3-7; P = 0.01, respectively).TXA2 is an independent indicator of no-reflow that occurs after PPCI. This observation may open new therapeutic opportunity in the setting of PPCI.

Platelet Multidrug Resistance Protein 4 (MRP4)-overexpression has a role in reducing aspirin action in patients after by-pass surgery. Aspirin induces platelet MRP4 over-expression, through megakaryocytes genomic modulation. Aim of our work was to verify whether other non-steroidal antiinflammatory drugs (NSAIDs) enhance platelet MRP4 expression and evaluate platelet function in patients who overexpressed MRP4. We evaluated MRP4-mRNA in a human megakacaryoblastic cell line (DAMI), treated with both COX-2 inhibitor (celecoxib) and traditional NSAIDs (diclofenac and naproxen). Osteoarthritis patients, who reported to take NSAIDs twice a week for at least four continuous weeks and a control population, who didn't take any drugs during the previous month, were enrolled. We evaluated platelet MRP4 amount, by both mRNA levels and protein expression (Western-Blot) and ADP induced platelet aggregation. DAMI cells treated with celecoxib, diclofenac, and naproxen showed a significant increase in MRP4-mRNA expression compared to the mock culture. Osteoarthritis patient platelets presented a higher expression of MRP4 (both at mRNA and protein levels) and an increase in ADP-induced platelet aggregation compared to the control population. NSAID treatment induced platelet MRP4 overexpression. Osteoarthritis patients, who overexpress MRP4, showed platelet hyper-reactivity. These evidences could explain in part the increased cardiovascular risk present during NSAID treatment.

Serum thromboxane-B2 (TxB2), together with arachidonic acid (AA)-induced platelet aggregation, are, at the moment, the most used tests to identify patients displaying high on-aspirin treatment platelet reactivity (HAPR). Both tests are specific for aspirin action on cyclooxygenase-1. While the correlation between serum TxB2 assay and clinical outcome is established, data are conflicting with regard to aspirin treatment and a possible association with AA-stimulated platelet markers and clinical outcome. To understand such discrepancy, we performed a retrospective study to compare both assays. We collected data from 132 patients receiving a daily dose of aspirin (100 mg/day) and data from 48 patients receiving aspirin on alternate days. All Patients who received a daily dose of aspirin were studied for AA-induced platelet aggregation together with serum TxB2 levels and AA-induced TxB2 formation was also studied in 71 patients out of entire population. Consistent with recommendations in the literature, we defined HAPR by setting a cut-off point at 3.1 ng/ml for serum levels of thromboxane B2 and 20% for AA-induced platelet aggregation. According to this cut-off point, we divided our overall population into two groups: (1) TxB23.1 ng/ml and (2) TxB23.1 ng/ml. We found low agreement between such tests to identify patients displaying HAPR. Our results show that AA-induced platelet aggregation20% identify a smaller number of HAPR patients in comparison with TxB2. A good correlation between serum TxB2 and arachidonic acid-induced TxB2 production was found (r = 0.76619).

Purpose of investigation The aim of this study was to evaluate the correlation between endometriosis and pathologies on an immune basis for the possible involvement of the immune system in the pathogenesis of endometriosis. Materials and methods In this retrospective study, data of 304 patients with endometriosis and 318 without endometriosis were collected in a uniform manner for both groups and inserted into two databases, respectively, for patients with and without endometriosis. The authors calculated the percentages of patients with allergies, autoimmune diseases, asthma in both groups, and later statistical analysis were performed with two different chi-square tests. Results The results obtained have shown that patients with endometriosis have a higher prevalence of allergies (p = 0.0003) and coexistence of both allergies and autoimmune diseases (p = 0.0274), compared to those without. Conclusions The present study seems to support the possible association between endometriosis and allergic diseases.

Summary. Background: Patients treated with aspirin may have a reduced sensitivity to its antiplatelet effect. The mechanism accounting for such a reduced sensitivity might involve an impaired interaction of aspirin with cyclooxygenase-1 (COX)-1. Objective: We sought to investigate whether platelets from patients under chronic treatment with aspirin still produce TxA2 and whether there is any relationship between the eventual persistent TxA2 formation and platelet aggregation. Finally, whether platelet-derived TxA2 can be inhibited by in vitro addition of aspirin. Methods: Collagen-induced platelet aggregation and thromboxane-A2 (TxA2) were measured in 196 patients treated with aspirin (100–330 mg day−1) because of previous vascular events or presence of risk factors of atherosclerosis. Results: Collagen-induced TxA2 production of the entire cohort was 128.7 ± 21.6 pg 10−8 cells, and was significantly correlated with platelet aggregation (Spearman's correlation coefficient = 0.44; P

Shape change is the earliest response of platelets to stimuli; it is mainly dependent upon Ca(2+)/calmodulin interaction subsequent to Ca(2+) mobilization and is mediated by myosin light chain kinase (MLCK) activation. It has been recently suggested that collagen itself is not able to elicit platelet shape change in the absence of ADP and thromboxane A(2) costimulation but is capable of inducing MLCK activation. Since we hypothesize that the morphological changes of the few platelets that adhere to collagen might not be revealed by turbidimetry, the aim of this study was to assess platelet shape change using transmission electron microscopy, in the absence of the amplificatory feedback pathways of ADP and thromboxane A(2). Our results demonstrated that only the platelets in contact with insoluble collagen fibers underwent a typical shape change, whereas those further away remained quiescent. Moreover, since cAMP enhances Ca(2+) mobilization in response to collagen, in the present study, we also investigated whether cAMP is involved in the inhibition of collagen-induced platelet shape change and MLC phosphorylation. Platelets were thus treated with iloprost (28 nm) prior to stimulation. Electron microscopy studies demonstrated that iloprost did not modify collagen-induced shape change, whereas immunoblotting studies showed a slight inhibition of MLC phosphorylation in the presence of enhanced cAMP levels. We can thus conclude that collagen is able to cause platelet shape change through activation of Ca(2+)/calmodulin-dependent MLCK, without the involvement of amplificatory pathways. Enhanced cytosolic cAMP levels do not inhibit collagen-induced platelet shape change but exert a weak inhibitory action on MLCK.

Aim The aim of the study was to investigate whether human megakaryocytic cells have an adaptive response to aspirin treatment, leading to an enhancement of multidrug resistance protein-4 (MRP4) expression in circulating platelets responsible for a reduced aspirin action. We recently found that platelet MRP4 overexpression has a role in reducing aspirin action in patients after by-pass surgery. Aspirin enhances MRP4-mRNA levels in rat liver and drug administration transcriptionally regulates MRP4 gene expression through peroxisome proliferator-activated receptor-α (PPARα). Methods The effects induced by aspirin or PPARα agonist (WY14643) on MRP4 modulation were evaluated in vitro in a human megakaryoblastic DAMI cell line, in megakaryocytes (MKs) and in platelets obtained from human haematopoietic progenitor cell (HPC) cultures, and in vivo platelets obtained from aspirin treated healthy volunteers (HV). Results In DAMI cells, aspirin and WY14643 treatment induced a significant increase in MRP4 and PPARα expression. In human MKs grown in the presence of either aspirin or WY14643, MRP4 and PPARα-mRNA were higher than in control cultures and derived platelets showed an enhancement in MRP4 protein expression. The ability of aspirin to modulate MRP4 expression in MKs and to transfer it to platelets was also confirmed in vivo. In fact, we found the highest MRP4 mRNA and protein expression in platelets obtained from HV after 15 days' aspirin treatment. Conclusions The present study provides evidence, for the first time, that aspirin treatment affects the platelet protein pattern through MK genomic modulation. This work represents an innovative and attractive approach, useful both to identify patients less sensitive to aspirin and to improve pharmacological treatment in cardiovascular high-risk patients.

We studied the effect of nickel ions on platelet function because hypernickelemia has been found in patients with acute myocardial infarction. We previously demonstrated that nickel can activate an intracellular pathway leading to cytoskeleton reorganization consequent to tyrosine phosphorylation of p60(src) in human platelets independently of integrin alpha-IIb-beta(3). Moreover, in von Willebrand factor-stimulated platelets, the tyrosine phosphorylation of pp60(c-src) is closely associated with the activation of phosphatidylinositol 3-kinase (PIK), and two adhesion receptors, glycoprotein (Gp)Ib and GpIIb/IIIa(alpha-IIb-beta(3)), are involved. In our study, 1 and 5 mM nickel in the presence of fibrinogen induced platelet aggregation (independently of protein kinase C activation) and secretion. The pretreatment with a PIK inhibitor, wortmannin, strongly decreased nickel-induced platelet aggregation. Platelet treatment with mocarhagin, a cobra venom metalloproteinase that cleaves GpIba, significantly reduced aggregation induced by 5 mM without affecting the response to other agonists such as adenosine diphosphate (ADP). Moreover, nickel caused PIK translocation to the cytoskeleton. Taken together, these observations suggest a partial involvement of both integrins alpha-IIb-beta(3) and GpIb-V-IX complex in Ni(2+)-induced platelet activation.

SummaryCyclic nucleotides, such as cAMP, are known to inhibit the multistep cascade that results in platelet aggregation. In the present study we provide evidence that it is possible to bypass cAMP inhibitory effect on fibrinogen binding site exposure induced by the thromboxane A2 synthetic analogue U46619, the snake venom toxin convulxin, or by the direct PKC activator OAG, by concomitantly activating a Gi-coupled receptor by means of epinephrine or by inducing cytosolic calcium influx by means of ionomycin. In fact, in our study we demonstrate that, in iloprost-treated platelets, the inhibition of both platelet aggregation and fibrinogen binding was overcome by adding epinephrine or ionomycin. To further confirm this, we used the cAMP analogue dibutyryl cAMP and we obtained platelet aggregation in response to U46619, convulxin or OAG plus epinephrine. Moreover, a complete inhibition of platelet aggregation in the presence of high concentrations of cAMP was observed only in the case of U46619, while a small percentage of aggregation persisted when convulxin or OAG were used, due to the small amount of ADP that both convulxin and OAG are able to release.Since PKC inhibition didn’t allow platelet aggregation to occur in response to the concomitant activation of U46619 or convulxin, plus epinephrine or ionomycin, we can conclude that cAMP-induced inhibition of aggregation can be counteracted by the simultaneous activation of PKC in the presence of an activated Gi-coupled receptor or of an induced calcium influx.

Abstract —In this study, we investigated whether vitamin E at concentrations achievable in blood after supplementation inhibits platelet function in humans. Gel-filtered platelets were incubated 30 minutes with scalar concentrations (50 to 250 mmol/L) of vitamin E and then stimulated with collagen. Compared with controls, vitamin E inhibited collagen-induced platelet aggregation and thromboxane A2 formation in a dose-dependent manner. Furthermore, vitamin E inhibited, in a dose-dependent manner, Ca 2+ mobilization and formation of inositol 1,4,5-triphosphate. Because it was previously shown that hydrogen peroxide formation mediates arachidonic acid metabolism and phospholipase C activation in collagen-induced platelet activation, we investigated whether vitamin E was able to blunt hydrogen peroxide. In experiments performed in unstimulated platelets supplemented with hydrogen peroxide and in collagen-stimulated platelets, vitamin E was able to blunt hydrogen peroxide. In 6 healthy subjects given vitamin E for 2 weeks (600 mg/d), we found a significant decrease of collagen-induced H 2 O 2 formation, platelet aggregation, and calcium mobilization. This study demonstrated in vitro and ex vivo that vitamin E inhibits collagen-induced platelet activation by blunting hydrogen peroxide formation.

OBJECTIVE Patients with hypertension tend to have a high prevalence of atherothrombotic accidents. Platelet hyperactivity is frequently associated with hypertension. Because the vascular disease associated with hypertension evolves over the years, we investigated platelet activity parameters in a population of older hypertensive patients with no other risk factors for cardiovascular disease. PARTICIPANTS We studied 34 older, nonsmoking patients (mean age 74 ± 5 years) with uncomplicated hypertension before and after the normalization of blood pressure (BP) was achieved with the angiotensin-converting enzyme inhibitor quinapril alone or in combination with the Ca2+ antagonist nifedipine. MEASUREMENTS Platelet aggregation, P-selectin (CD62) expression on the platelet surface, serum levels of Interleukin-1β (IL-1β) and of Interleukin-6 (IL-6), as well as plasma levels of soluble P-selectin and Endothelin-1 (ET-1), were analyzed. RESULTS All platelet hyperactivity parameters were reduced significantly with the normalization of BP at the end of antihypertensive drug treatment (systolic/diastolic: 186.2 ± 2.7/103.4 ± 1.1 mm Hg vs 135.0 ± 1.3/85.9 ± 1.9 mm Hg; P < .001). Those factors more strictly associated with endothelium injury, such as ET-1 and IL-6, did not show variations. A significant correlation (Spearman Rank test) was observed among all platelet function parameters and blood pressure values. CONCLUSIONS This study demonstrated that even in a population of older hypertensive patients with no other risk factor for atherogenic disease, normalization of blood pressure induces a significant reduction of the parameters of enhanced platelet hyperactivity independent of the action exerted, at the platelet level, by the antihypertensive drugs.

We read with great interest the paper by Mayer et al. [(1)][1] demonstrating an association between high on-aspirin treatment platelet reactivity and cardiovascular complications in patients undergoing percutaneous coronary intervention. We would like to congratulate the investigators for this