Abstract 10210: Effects of Chronic Treatment With the Phosphodiesterase-5 Inhibitors Sildenafil and Tadalafil on Platelet Aggregation in Patients With Eisenmenger Syndrome

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Nair Y Maeda ◽  
Mariana M Clavé ◽  
Sonia M Mesquita ◽  
Sergio P Bydlowski ◽  
Antonio A Lopes
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Oral Treatment ◽  
Impedance Method ◽  
Treatment Groups ◽  
Phosphodiesterase 5 Inhibitors ◽  
Hemodynamic Improvement ◽  
Phosphodiesterase 5

Background: Patients with pulmonary arterial hypertension (PAH) associated with the Eisenmeger syndrome (ES) frequently have decreased platelet counts and aggregation. This is probably due to chronic endogenous platelet activation and consumption associated with hypoxemia and blood hyperviscosity, with "exhausted" platelets present in circulation. When platelets are analyzed in vitro, decreased response to aggregation inducing agents is generally observed. Purpose: Since phosphodiesterase-5 inhibitors (PDE-5Is) are frequently used in the management of PAH, we investigated, the effects of sildenafil and tadalafil on in vitro platelet aggregation (PA) in adults with ES. Methods: Twenty-three naïve patients aged 28 (22-47) years (median and interquartile range) were randomly assigned to oral treatment with sildenafil (20mg t.i.d., N=11) or tadalafil (single daily dose of 40mg, N=12). Baseline spO 2 , Ht, Hb level and platelet count were 87% (80-92%), 52% (49-60%), 17 (16-20)g/dL and 205 (158-248) x 10 3 pl/μL, respectively. Data were collected at baseline, 90 and 180 days of treatment. Whole blood PA was analyzed by the impedance method. Results are expressed as percent normal. Results: Treatment with PDE-5Is resulted in decrease Ht and Hb level (p<0.001), but no change in platelet count. When patients analyzed as a whole (N=23), ADP-induced PA was 44% (23-91%), 54% (23-87%) and 71% (42-124%) respectively at baseline, 90 and 180 days (p=0.029). Collagen-induced PA was 55% (23-138%), 96% (67-162%) and 146% (62-187%), respectively (p=0.041). When treatment groups were investigated separately at 180 days, collagen-induced PA was 2.7 (1.1-11.1) times baseline in sildenafil-treated patients, and 1.8 (0.6-4.2) times baseline in the tadalafil group. ADP-induced PA was 2.2 (1.3-4.8) times baseline in the sildenafil , but 1.0 (0.7-3.6) time baseline for tadalafil. Conclusion: In ES patients, PDE-5Is therapy is associated with improvement of PA. This may be due to decelerated endogenous platelet activation associated with hemodynamic improvement. However, particularly for sildenafil, some patients may become transiently at a higher risk of thrombotic events, as PA increases far above normal levels.

An Anti-Phosphatidylserine (PS) Antibody, Tarvacin™ That Targets Tumor Blood Vessels Does Not Affect Platelet Function In Vitro.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3950-3950
Author(s):  
Anna M. Dyszkiewicz-Korpanty ◽  
Ravindra Sarode ◽  
Philip E. Thorpe ◽  
Eugene P. Frenkel
Keyword(s):  
Endothelial Cells ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Platelet Function ◽  
Whole Blood ◽  
Impedance Method ◽  
Type I ◽  
Tumor Vessels ◽  
Glycoprotein I

Abstract Tarvacin™ is a chimeric anti-PS antibody that is currently in Phase I clinical trials in cancer patients. It acts by targeting PS that becomes exposed on vascular endothelium in tumors in response to oxidative stress in the tumor microenvironment. Tarvacin™ recognizes a complex of PS and the PS-binding protein, β2 glycoprotein I. Host leukocytes are induced to bind to the complex in tumor vessels and destroy tumor vessels by antibody-dependent cellular cytotoxity. However, antibodies directed against PS-associated proteins are also known to elicit anti-phospholipid syndromes (APS). Anti-PS antibodies possibly cause APS by displacing anticoagulant proteins from PS on activated cell or by enhancing the binding of prothrombin; another explanation might be a direct activation of endothelial cells and platelets. The aim of the study was to determine whether Tarvacin ™ induces or interferes with platelet activation caused by ADP, collagen type I or calcimycin in vitro. Blood was drawn from 3 healthy volunteers, aged 31–54, who have not taken any antiplatelet medication for 14 days prior to the study. Dual channel whole blood aggregometer (Chronolog, Havertown, PA, USA) was employed for platelet aggregation studies in whole blood (WB/impedance method) and platelet rich plasma (PRP/optical method). Platelet count in PRP was adjusted to 200 K/μL. Platelet agonists (PS exposure triggers) used in the experiments were as follows: collagen (0.5, 1, 2 μg/mL), ADP (1.25, 2.5, 5, 10 μM), Calcimycin (10, 20, 30 μM) and Calcium ions (1, 2 mmol/L). Tarvacin™ was provided by Peregrine Pharmaceuticals Inc, Tustin, CA. The Anti-CD 20 antibody, Rituxan ™ and physiologic saline were used as controls. Specimens (WB diluted with saline in 1:1 ratio or PRP) with the addition of Tarvacin™ (100 μg/mL) or Rituxan ™ (100 μg/mL) or saline were first incubated on a gentle mixer for 10 minutes; incubation was then continued at 37 ° in the aggregometer well for another 5 minutes. Agonist-induced platelet aggregation was subsequently examined. Platelet aggregation studies in both WB and PRP showed that Tarvacin™ neither induced platelet activation, nor inhibited platelet activation in response to ADP, collagen or calcimycin in vitro. In conclusion, Tarvacin™ does not affect platelet function in the present in vitro assays. Possibly, the epitope on the PS -β2 glycoprotein I complex does not orientate the antibody in a manner that interferes with platelet activation. Alternatively, activated endothelial cells or other factors may be critical to support platelet activation.

Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

1973 ◽  
Vol 29 (02) ◽  
pp. 490-498 ◽  
Author(s):  
Hiroh Yamazaki ◽  
Itsuro Kobayashi ◽  
Tadahiro Sano ◽  
Takio Shimamoto
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
The Other ◽  
Endothelial Surface ◽  
Important Interaction ◽  
Blood Coagulability ◽  
The Difference

SummaryThe authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼5 molar, 121.8 ± 7.8% by 3 × 10-6 molar and 129.4 ± 12.8% of the value before the injection by 10”6 molar ADP. The difference was statistically significant (P<0.01-0.05). The above change was not observed in each group of rabbits injected with saline, 1 µg per Kg of 1-noradrenaline or 0.1 and 10 µg per Kg of adrenaline. Also, it was prevented by oral administration of 10 mg per Kg of phenoxybenzamine or propranolol or aspirin or pyridinolcarbamate 3 hours before the challenge. On the other hand, the enhancement of ADP-induced platelet aggregation was not observed in vitro, when 10-5 or 3 × 10-6 molar and 129.4 ± 12.8% of the value before 10∼6 molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.

The Mechanism of Platelet Aggregation Induced by HLA-Related Antibodies

1996 ◽  
Vol 76 (05) ◽  
pp. 774-779 ◽  
Author(s):  
John T Brandt ◽  
Carmen J Julius ◽  
Jeanne M Osborne ◽  
Clark L Anderson
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Complement Activation ◽  
Thromboembolic Disease ◽  
Clinical Samples ◽  
Hla Antigen ◽  
Aggregation Response ◽  
Immune Mediated ◽  
Dependent Pathway

SummaryImmune-mediated platelet activation is emerging as an important pathogenic mechanism of thrombosis. In vitro studies have suggested two distinct pathways for immune-mediated platelet activation; one involving clustering of platelet FcyRIIa, the other involving platelet-associated complement activation. HLA-related antibodies have been shown to cause platelet aggregation, but the mechanism has not been clarified. We evaluated the mechanism of platelet aggregation induced by HLA-related antibodies from nine patients. Antibody to platelet FcyRIIa failed to block platelet aggregation with 8/9 samples, indicating that engagement of platelet FcyRIIa is not necessary for the platelet aggregation induced by HLA-related antibodies. In contrast, platelet aggregation was blocked by antibodies to human C8 (5/7) or C9 (7/7). F(ab’)2 fragments of patient IgG failed to induce platelet activation although they bound to HLA antigen on platelets. Intact patient IgG failed to aggregate washed platelets unless aged serum was added. The activating IgG could be adsorbed by incubation with lymphocytes and eluted from the lymphocytes. These results indicate that complement activation is involved in the aggregation response to HLA-related antibodies. This is the first demonstration of complement-mediated platelet aggregation by clinical samples. Five of the patients developed thrombocytopenia in relationship to blood transfusion and two patients developed acute thromboembolic disease, suggesting that these antibodies and the complement-dependent pathway of platelet aggregation may be of clinical significance.

The Effect of Dimethyl Sulfoxide on In Vitro Platelet Function

1976 ◽  
Vol 36 (01) ◽  
pp. 221-229 ◽  
Author(s):  
Charles A. Schiffer ◽  
Caroline L. Whitaker ◽  
Morton Schmukler ◽  
Joseph Aisner ◽  
Steven L. Hilbert
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Dimethyl Sulfoxide ◽  
Platelet Function ◽  
Platelet Volume ◽  
Short Term ◽  
Platelet Factor ◽  
Short Term Exposure ◽  
Structural Abnormalities

SummaryAlthough dimethyl sulfoxide (DMSO) has been used extensively as a cryopreservative for platelets there are few studies dealing with the effect of DMSO on platelet function. Using techniques similar to those employed in platelet cryopreservation platelets were incubated with final concentrations of 2-10% DMSO at 25° C. After exposure to 5 and 10% DMSO platelets remained discoid and electron micrographs revealed no structural abnormalities. There was no significant change in platelet count. In terms of injury to platelet membranes, there was no increased availability of platelet factor-3 or leakage of nucleotides, 5 hydroxytryptamine (5HT) or glycosidases with final DMSO concentrations of 2.5, 5 and 10% DMSO. Thrombin stimulated nucleotide and 5HT release was reduced by 10% DMSO. Impairment of thrombin induced glycosidase release was noted at lower DMSO concentrations and was dose related. Similarly, aggregation to ADP was progressively impaired at DMSO concentrations from 1-5% and was dose related. After the platelets exposed to DMSO were washed, however, aggregation and release returned to control values. Platelet aggregation by epinephrine was also inhibited by DMSO and this could not be corrected by washing the platelets. DMSO-plasma solutions are hypertonic but only minimal increases in platelet volume (at 10% DMSO) could be detected. Shrinkage of platelets was seen with hypertonic solutions of sodium chloride or sucrose suggesting that the rapid transmembrane passage of DMSO prevented significant shifts of water. These studies demonstrate that there are minimal irreversible alterations in in vitro platelet function after short-term exposure to DMSO.

The Effect of Warfarin Sodium on the Duration of Platelet Aggregation

1967 ◽  
Vol 18 (03/04) ◽  
pp. 766-778 ◽  
Author(s):  
H. J Knieriem ◽  
A. B Chandler
Keyword(s):  
Platelet Count ◽  
Placebo Group ◽  
Platelet Aggregation ◽  
Prothrombin Time ◽  
Platelet Rich Plasma ◽  
Healthy Adults ◽  
Double Blind Study ◽  
Double Blind ◽  
Warfarin Sodium

SummaryThe effect of the administration of warfarin sodium (Coumadin®) on the duration of platelet aggregation in vitro was studied. Coumadin was given for 4 consecutive days to 10 healthy adults who were followed over a period of 9 days. The duration of adenosine diphosphate-induced platelet aggregation in platelet-rich plasma, the prothrombin time, and the platelet count of platelet-rich plasma were measured. Four other healthy adults received placebos and participated in a double-blind study with those receiving Coumadin.Although administration of Coumadin caused a prolongation of the prothrombin time to 2 or 21/2 times the normal value, a decrease in the duration of platelet aggregation was not observed. In most individuals who received Coumadin an increase in the duration of platelet aggregation occurred. The effect of Coumadin on platelet aggregation was not consistently related to the prothrombin time or to the platelet count. In the placebo group there was a distinct relation between the duration of platelet aggregation and the platelet count in platelet-rich plasma.The mean increase in the duration of platelet aggregation when compared to the control value before medication with Coumadin was 37.7%. In the placebo group there was a mean increase of 8.4%. The difference between the two groups is significant (p <0.001). Increased duration of platelet aggregation also occurred in two individuals who received Coumadin over a period of 10 and 16 days respectively.

A Simple and Rapid Method to Determine GPIIb/IIIa-Receptor Inhibitor Activity in Whole Blood

1999 ◽  
Vol 19 (03) ◽  
pp. 134-138
Author(s):  
Gitta Kühnel ◽  
A. C. Matzdorff
Keyword(s):  
Flow Cytometry ◽  
Platelet Count ◽  
Blood Sample ◽  
Platelet Activation ◽  
Whole Blood ◽  
Receptor Occupancy ◽  
Aggregate Formation ◽  
Inhibitor Activity ◽  
Receptor Inhibitor

SummaryWe studied the effect of GPIIb/IIIa-inhibitors on platelet activation with flow cytometry in vitro. Citrated whole blood was incubated with increasing concentrations of three different GPIIb/IIIa-inhibitors (c7E3, DMP728, XJ757), then thrombin or ADP were added and after 1 min the sample was fixed. Samples without c7E3 but with 0.1 U/ml thrombin had a decrease in platelet count. Samples with increasing concentrations of c7E3 had a lesser or no decrease in platelet count. The two other inhibitors (DMP 725, XJ757) gave similar results. GPIIb/IIIa-inhibitors prevent aggregate formation and more single platelets remain in the blood sample. The agonist-induced decrease in platelet count correlates closely with the concentration of the GPIIb/IIIa inhibitor and receptor occupancy. This correlation may be used as a simple measure for inhibitor activity in whole blood.

The Effect of Heparin vs. Citrate on the Interaction of Platelets with Vascular Graft Materials

1985 ◽  
Vol 54 (04) ◽  
pp. 842-848 ◽  
Author(s):  
Kandice Kottke-Marchant ◽  
James M Anderson ◽  
Albert Rabinovitch ◽  
Richard A Huskey ◽  
Roger Herzig
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Vascular Graft ◽  
Time Course ◽  
Platelet Reactivity ◽  
Polymer Surfaces ◽  
In Vitro Perfusion ◽  
Citrate Anticoagulation ◽  
Platelet Release

SummaryHeparin is known to affect platelet function in vitro, but little is known about the effect of heparin on the interaction of platelets with polymer surfaces in general, and vascular graft materials in particular. For this reason, the effect of heparin vs. citrate anticoagulation on the interaction of platelets with the vascular graft materials expanded polytetrafluoroethylene (ePTFE), Dacron Bionit (DB) and preclotted Dacron Bionit (DB/PC) was studied in a recirculating, in vitro perfusion system. Platelet activation, as shown by a decrease in platelet count, an increase in platelet release and a decrease in platelet aggregation, was observed for all vascular graft materials tested using heparin and was greater for Dacron and preclotted Dacron than for ePTFE. Significant differences between heparin and citrate anticoagulation were seen for platelet release, platelet aggregation and the relative ranking of material platelet-reactivity. However, the trends and time course of platelet activation were similar with both heparin and citrate for the materials tested.

PLATELET ACTIVATION BY HUMAN CANCER CELLS GROWN “IN VITRO” OR DISSOCIATED FROM TUMOUR TISSUES

1987 ◽  
Author(s):  
G Grignani ◽  
L Pacchiarini ◽  
M Zucchella ◽  
L Dezza ◽  
S C Rizzo
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Human Cancer ◽  
Iodoacetic Acid ◽  
Tumour Cells ◽  
Human Cancer Cells ◽  
Human Tumour Cells ◽  
Dissociated Cells ◽  
Lymphoblastic Cells

The mechanisms of platelet activation by human tumour cells grown “in vitro” or freshly dissociated from tumour tissues have been investigated.MoCCL human T-lymphoblastic cells cultured “in vitro” induced platelet aggregation through the production of ADP, as evidenced by inhibition of the effect by apyrase. The maximum of ADP production by tumour cells was reached after 1 hour and was 225 p moles/106 cells.On the contrary, platelet aggregation induced by 5637 human bladder carcinoma cells was not inhibited by apyrase, but was abolished by hirudin, indicating the important role of thrombin in this effect.Tumour cells dissociated from 3 breast carcinomas showed a very high platelet aggregating activity, which was not inhibited by hirudin or apyrase, but was abolished by iodoacetic acid, suggesting a role for a cystein-protease in platelet activation.These results confirm that platelets can be activated by tumour cells through different mechanisms; they also suggest that the methods employed to obtain the tumour cells can influence the results, probably because of the different cell populations which are present in the dissociated tumour tissues.Informations obtained with freshly dissociated cells are interesting, because this method has been used seldom so far and because it provides a more physiological approach to the study of the interactions of tumours and platelets.

scholarly journals ROS Promote Ox-LDL-Induced Platelet Activation by Up-Regulating Autophagy Through the Inhibition of the PI3K/AKT/mTOR Pathway

2018 ◽  
Vol 50 (5) ◽  
pp. 1779-1793 ◽  
Author(s):  
Xiang Wang ◽  
Yun-Feng Fu ◽  
Xiao Liu ◽  
Guo Feng ◽  
Dan Xiong ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Mtor Pathway ◽  
Enhanced Chemiluminescence ◽  
Transmission Electron ◽  
Related Proteins

Background/Aims: Oxidized low-density lipoprotein (oxLDL) promotes unregulated platelet activation in patients with dyslipidemic disorders. Although oxLDL stimulates activating signaling, researchers have not clearly determined how these events drive accelerated thrombosis. Here, we describe the mechanism by which ROS regulate autophagy during ox-LDL-induced platelet activation by modulating the PI3K/AKT/mTOR signaling pathway. Methods: For in vitro experiments, ox-LDL, the ROS scavenger N-acetylcysteine (NAC), the mTOR inhibitor rapamycin and the autophagy inhibitor 3-MA were used alone or in combination with other compounds to treat platelets. Then, platelet aggregation was evaluated on an aggregometer and platelet adhesion was measured under shear stress. The levels of a platelet activation marker (CD62p) were measured by flow cytometry, reactive oxygen species (ROS) levels were then quantified by measuring DCFH-DA fluorescence intensity via flow cytometry. Nitric oxide (NO) and superoxide (O2·-) levels were determined by the nitric acid deoxidize enzyme method and lucigenin-enhanced chemiluminescence (CL), respectively. Transmission electron microscopy was used to observe the autophagosome formation, immunofluorescence staining was employed to detect LC3 expression and western blotting was used to measure the levels of PI3K/AKT/mTOR pathway- and autophagy-related proteins. Results: Ox-LDL-induced platelets showed a significant increase in platelet aggregation and adhesion, CD62p expression, ROS level and O2·- content, with an elevated LC3II/LC3I ratio and Beclin1 expression, but a dramatic reduction in the levels of p62 and pathway-related proteins (all P < 0.05). However, platelet activation and autophagy were aggravated by the Rapamycin treatment, and decreased following treatment with NAC, 3-MA, or NAC and 3-MA, together with increased activity of the PI3K/AKT/mTOR pathway. Additionally, decreased platelet activation and autophagy were observed in platelets treated with NAC and Rapamycin or Rapamycin and 3-MA compared with platelets treated with Rapamycin alone, suggesting that both NAC and 3-MA reversed the effects of Rapamycin. Conclusion: Inhibition of ROS production may reduce autophagy to suppress ox-LDL-induced platelet activation by activating PI3K/AKT/mTOR pathway.

EFFECTS OF BLOOD CELLS ON PLATELET AGGREGATION BY IMPEDANCE METHOD

1987 ◽  
Author(s):  
L Mannucci ◽  
R Redaelli ◽  
E Tremoll
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Blood Cells ◽  
White Blood Cells ◽  
Normal Subjects ◽  
Impedance Method ◽  
Induced Aggregation ◽  
Vitro Data ◽  
In Vitro Data

To evaluate the effects of blood cells on the response of platelets to aggregating agents using whole blood impedance aggregometer, studies were carried out on whole blood (WB) of normal subjects and of patients with: polycythemia vera (PV), iatrogenic anemia (IA), primary thrombocytosis (PT), idiopathic thrombotic purpura (ITP), myeloid chronic leukemia (MCL), iatrogenic leukopenia (IL). The in vitro effects of red blood cells (RBC) and of white blood cells (WBC) on platelet rich plasma (PRP) aggregation were also evaluated. WB, PRP, WBC and RBC were prepared by conventional methods. Aggregation was performed using the impedance aggregometer (mod. 540, Chrono Log Corp). In normal subjects the concentration of collagen giving 50 % aggregation (AC50 ) found in PRP did not differ from that of WB, indicating that hematocrit values within the normal range did not appreciably affect platelet aggregation. The results obtained in WB of patients are summarized in the table: In vitro data showed that aggregation in prp in wb of normal subjects was related to the number of platelets present in the sample. RBC added to PRP significant reduced aggregation only when the RBC number was greater than 4.101 cells. No effect of WBC on collagen induced aggregation of PRP was observed, whereas significant inhibition was detected after ADP. It is concluded that the aggregation evaluated in WB with impedance method is dependent on the platelet number. Also, in vitro data and studies in WB of patients indicate that aggregation is significantly affected by the presence of cells other than platelets only in conditions of changes of the ratio between platelets and leukocytes and/or red cells.

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