Monitoring Compound-Related Effects on Coagulability in Rats and Cynomolgus and Rhesus Monkeys by Thrombin Generation Kinetic Measurement

Thrombin generation assay (TGA) is a sensitive method for the assessment of the global clotting potential of plasma. This kinetic assay can detect both hypocoagulable and hypercoagulable conditions: delayed or reduced thrombin generation leading to a prolonged clotting time, or induced thrombin activity, shifting the coagulation cascade toward thrombosis. The purpose of this study is to qualify the TGA in nonhuman primates (NHP) and rats for its use during nonclinical in vivo and in vitro studies. Blood was drawn from nonanesthetized animals, and platelet-poor plasma was obtained after double centrifugation; coefficients of variation were <10% for all derived parameters of thrombin generation assessed with 5 pM of tissue factor. Thrombin generation was evaluated in vitro in rat and NHP plasmas with ascending doses of unfractionated heparin (UFH), recombinant tissue factor, and anticoagulant compounds. Thrombin generation was decreased with UFH and anticoagulant compounds, but was increased in the presence of tissue factor, in a dose-dependent manner. In a rat model of inflammation, animals were administered a low dose of lipopolysaccharides. Thrombin generation measurements were decreased 3 hours post-LPS administration with a nadir at 24 hours, while thrombin–antithrombin complexes reached a peak at 8 hours, supporting an earlier production of thrombin. In conclusion, these data demonstrated that TGA can be performed in vitro for screening of compounds expected to have effects on coagulation cascade, and thrombin generation can be measured at interim time points during nonclinical in vivo studies in rats and NHP.

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Heme Induces Systemic Activation of Coagulation in Vivo in a Tissue Factor-Dependent Manner

Blood ◽

10.1182/blood.v120.21.820.820 ◽

2012 ◽

Vol 120 (21) ◽

pp. 820-820

Author(s):

Erica M Sparkenbaugh ◽

Pichika Chantrathammachart ◽

Nigel Mackman ◽

Nigel S Key ◽

Rafal Pawlinski

Keyword(s):

Endothelial Cells ◽

Tissue Factor ◽

Bacterial Infections ◽

Time Course ◽

Conflicts Of Interest ◽

Ischemia Reperfusion ◽

Coagulation Cascade ◽

Dependent Manner

Abstract Abstract 820 Heme is released from red blood cells and hemoproteins during several pathological states, including bacterial infections, ischemia-reperfusion and hemolytic anemias. An excess of free heme is toxic, causing oxidative stress that activates endothelial cells and the inflammatory response. Heme has been reported to increase the expression of tissue factor (TF) on endothelial cells in vitro. TF is the primary initiator of the coagulation cascade. We tested the hypothesis that heme induces TF-dependent activation of coagulation in vivo. Eight week old C57 Bl/6 mice were given a bolus injection (0.035ml/g i.v.) of hemin ranging from 0 – 35 μmols/kg, and plasma was collected 6 hours after treatment. Coagulation activation was assessed by measuring plasma thrombin-antithrombin (TAT) levels. Administration of 17.5 and 35 μmols/kg of hemin significantly increased TAT from 5.3 ± 0.7 ng/L to 9.7 ± 1.3 ng/L (p<0.001) and 13.8 ± 1.9 ng/L (p<0.0001), respectively. Mice were treated with 35 μmols/kg of hemin in all further experiments. In a time course study, plasma was collected after 1, 3 and 6 hrs. Plasma TAT levels were significantly increased as early as 1 hour after treatment (14.1 ± 2.4 ng/L compared to 6.46 ± 0.6 ng/L, p<0.0001), and remained elevated at 3 (12.5 ± 0.6 ng/L, p<0.0001) and 6 hours (14.5 ± 1.0 ng/L, p<0.0001). To determine the role of TF in hemin-induced activation of coagulation, mice were pretreated with the rat anti-mouse TF antibody (1H1) or IgG control (single i.p. injection; 20mg/kg). Hemin significantly increased plasma TAT levels in IgG treated mice (4.6 ± 1.3 ng/Lto 9.6 ± 1.3 ng/L, p<0.0001). Importantly, inhibition of TF with 1H1 significantly attenuated this increase (6.8 ± 0.4 ng/L, p<0.01 compared to IgG/ hemin group). Moreover, plasma TAT levels were also significantly reduced in hemin injected low TF mice (expressing 1–2% of normal TF levels) compared to control mice injected with hemin (p<0.01). These data indicate that heme-induced activation of coagulation is TF-dependent. Next, we used TF flox/flox, Tie-2 Cre mice to determine the effect of TF gene deletion in all hematopoietic and endothelial cells on hemin-induced activation of coagulation. Interestingly, plasma TAT levels in TF flox/flox, Tie-2 Cre mice (11.9 ± 2.7 ng/L) were not different from that observed in control TF flox/flox mice 6 hours after hemin injection (11.6 ± 3.2 ng/L), indicating that TF expressed by other cell types contributes to the activation of coagulation. It has been previously shown that heme induces vascular damage and increases vascular permeability which could expose perivascular TF. Therefore perivascular cells are the likely source of TF that may contribute to the activation of coagulation in hemin treated mice. In addition to the activation of coagulation, hemin (35 μmols/kg) increased total number of white cells (2.3 fold, p = 0.000032), monocytes (1.75, p=0.07) and neutrophils (3.5 fold, p=0.0002) as well as reduced platelet counts (0.86 fold, p=0.003) 6 hours after injection. Furthermore, plasma levels of the proinflamatory cytokine interleukin-6 were also increased (8.5-fold, p=0.002). However, inhibition of TF with 1H1 antibody did not affect any of these parameters. Our data indicate that heme-induced activation of coagulation is TF-dependent whereas heme-induced inflammation is independent of TF. Disclosures: No relevant conflicts of interest to declare.

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The Effect of Active Site-inhibited Factor VIIa on Tissue Factor-initiated Coagulation Using Platelets before and after Aspirin Administration

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657715 ◽

1997 ◽

Vol 78 (04) ◽

pp. 1202-1208 ◽

Cited By ~ 18

Author(s):

Marianne Kjalke ◽

Julie A Oliver ◽

Dougald M Monroe ◽

Maureane Hoffman ◽

Mirella Ezban ◽

...

Keyword(s):

Tissue Factor ◽

Active Site ◽

Large Scale ◽

Thrombin Generation ◽

Factor Viia ◽

Dependent Manner ◽

Antithrombotic Agent ◽

Before And After ◽

Ic50 Values

SummaryActive site-inactivated factor VIIa has potential as an antithrombotic agent. The effects of D-Phe-L-Phe-L-Arg-chloromethyl ketone-treated factor VIla (FFR-FVIIa) were evaluated in a cell-based system mimicking in vivo initiation of coagulation. FFR-FVIIa inhibited platelet activation (as measured by expression of P-selectin) and subsequent large-scale thrombin generation in a dose-dependent manner with IC50 values of 1.4 ± 0.8 nM (n = 8) and 0.9 ± 0.7 nM (n = 7), respectively. Kd for factor VIIa binding to monocytes ki for FFR-FVIIa competing with factor VIIa were similar (11.4 ± 0.8 pM and 10.6 ± 1.1 pM, respectively), showing that FFR-FVIIa binds to tissue factor in the tenase complex with the same affinity as factor VIIa. Using platelets from volunteers before and after ingestion of aspirin (1.3 g), there were no significant differences in the IC50 values of FFR-FVIIa [after aspirin ingestion, the IC50 values were 1.7 ± 0.9 nM (n = 8) for P-selectin expression, p = 0.37, and 1.4 ± 1.3 nM (n = 7) for thrombin generation, p = 0.38]. This shows that aspirin treatment of platelets does not influence the inhibition of tissue factor-initiated coagulation by FFR-FVIIa, probably because thrombin activation of platelets is not entirely dependent upon expression of thromboxane A2.

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Modulatory Effects of Osthole on Lipopolysaccharides-Induced Inflammation in Caco-2 Cell Monolayer and Co-Cultures with THP-1 and THP-1-Derived Macrophages

Nutrients ◽

10.3390/nu13010123 ◽

2020 ◽

Vol 13 (1) ◽

pp. 123

Author(s):

Natalia K. Kordulewska ◽

Justyna Topa ◽

Małgorzata Tańska ◽

Anna Cieślińska ◽

Ewa Fiedorowicz ◽

...

Keyword(s):

Gene Expression ◽

Inflammatory Reaction ◽

Wide Spectrum ◽

Cell Monolayer ◽

In Vivo Studies ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Tnf Α

Lipopolysaccharydes (LPS) are responsible for the intestinal inflammatory reaction, as they may disrupt tight junctions and induce cytokines (CKs) secretion. Osthole has a wide spectrum of pharmacological effects, thus its anti-inflammatory potential in the LPS-treated Caco-2 cell line as well as in Caco-2/THP-1 and Caco-2/macrophages co-cultures was investigated. In brief, Caco-2 cells and co-cultures were incubated with LPS to induce an inflammatory reaction, after which osthole (150–450 ng/mL) was applied to reduce this effect. After 24 h, the level of secreted CKs and changes in gene expression were examined. LPS significantly increased the levels of IL-1β, -6, -8, and TNF-α, while osthole reduced this effect in a concentration-dependent manner, with the most significant decrease when a 450 ng/mL dose was applied (p < 0.0001). A similar trend was observed in changes in gene expression, with the significant osthole efficiency at a concentration of 450 ng/μL for IL1R1 and COX-2 (p < 0.01) and 300 ng/μL for NF-κB (p < 0.001). Osthole increased Caco-2 monolayer permeability, thus if it would ever be considered as a potential drug for minimizing intestinal inflammatory symptoms, its safety should be confirmed in extended in vitro and in vivo studies.

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Effect of Synchronous Versus Sequential Regimens on the Pharmacokinetics and Biodistribution of Regorafenib with Irradiation

Pharmaceutics ◽

10.3390/pharmaceutics13030386 ◽

2021 ◽

Vol 13 (3) ◽

pp. 386

Author(s):

Tung-Hu Tsai ◽

Yu-Jen Chen ◽

Li-Ying Wang ◽

Chen-Hsi Hsieh

Keyword(s):

Stereotactic Body Radiation Therapy ◽

In Vivo Studies ◽

Control Group ◽

High Dose ◽

Dependent Manner ◽

Hep G2 ◽

Time Curve ◽

Dose Dependent

This study was performed to evaluate the interaction between conventional or high-dose radiotherapy (RT) and the pharmacokinetics (PK) of regorafenib in concurrent or sequential regimens for the treatment of hepatocellular carcinoma. Concurrent and sequential in vitro and in vivo studies of irradiation and regorafenib were designed. The interactions of RT and regorafenib in vitro were examined in the human hepatoma Huh-7, HA22T and Hep G2 cell lines. The RT–PK phenomenon and biodistribution of regorafenib under RT were confirmed in a free-moving rat model. Regorafenib inhibited the viability of Huh-7 cells in a dose-dependent manner. Apoptosis in Huh-7 cells was enhanced by RT followed by regorafenib treatment. In the concurrent regimen, RT decreased the area under the concentration versus time curve (AUC)regorafenib by 74% (p = 0.001) in the RT2 Gy × 3 fraction (f’x) group and by 69% (p = 0.001) in the RT9 Gy × 3 f’x group. The AUCregorafenib was increased by 182.8% (p = 0.011) in the sequential RT2Gy × 1 f’x group and by 213.2% (p = 0.016) in the sequential RT9Gy × 1 f’x group. Both concurrent regimens, RT2Gy × 3 f’x and RT9Gy × 3 f’x, clearly decreased the biodistribution of regorafenib in the heart, liver, lung, spleen and kidneys, compared to the control (regorafenib × 3 d) group. The concurrent regimens, both RT2Gy × 3 f’x and RT9Gy × 3 f’x, significantly decreased the biodistribution of regorafenib, compared with the control group. The PK of regorafenib can be modulated both by off-target irradiation and stereotactic body radiation therapy (SBRT).

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In vitro effects of human neutrophil cathepsin G on thrombin generation: Both acceleration and decreased potential

Thrombosis and Haemostasis ◽

10.1160/th09-10-0690 ◽

2010 ◽

Vol 104 (09) ◽

pp. 514-522 ◽

Cited By ~ 3

Author(s):

Thomas Lecompte ◽

Agnès Tournier ◽

Lise Morlon ◽

Monique Marchand-Arvier ◽

Claude Vigneron ◽

...

Keyword(s):

Tissue Factor ◽

Thrombin Generation ◽

Time Course ◽

Anticoagulant Activity ◽

Cathepsin G ◽

Coagulation Cascade ◽

Clotting Factor ◽

Factor V ◽

Clotting Factors

SummaryCathepsin G (Cath G), a serine-protease found in neutrophils, has been reported to have effects that could either facilitate or impede coagulation. Thrombin generation (CAT method) was chosen to study its overall effect on the process, at a plasma concentration (240 nM) observed after neutrophil activation. Coagulation was triggered by tissue factor in the presence of platelets or phospholipid vesicles. To help identify potential targets of Cath G, plasma depleted of clotting factors or of inhibitors was used. Cath G induced a puzzling combination of two diverging effects of varying intensities depending on the phospholipid surface provided: accelerating the process under the three conditions (shortened clotting time by up to 30%), and impeding the process during the same thrombin generation time-course since thrombin peak and ETP (total thrombin potential) were decreased, up to 45% and 12%, respectively, suggestive of deficient prothrombinase. This is consistent with Cath G working on at least two targets in the coagulation cascade. Our data indicate that coagulation acceleration can be attributed neither to platelet activation and nor to activation of a clotting factor. When TFPI (tissue factor pathway inhibitor) was absent, no effect on lag time was observed and the anticoagulant activity of TFPI was decreased in the presence of Cath G. Consistent with the literature and the hypothesis of deficient prothrombinase, experiments using Russel’s Viper Venom indicate that the anticoagulant effect can be attributed to a deleterious effect on factor V. The clinical relevance of these findings deserves to be studied.

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Isopsoralen Enhanced Osteogenesis by Targeting AhR/ERα

Molecules ◽

10.3390/molecules23102600 ◽

2018 ◽

Vol 23 (10) ◽

pp. 2600 ◽

Cited By ~ 8

Author(s):

Luna Ge ◽

Yazhou Cui ◽

Kai Cheng ◽

Jinxiang Han

Keyword(s):

Osteoblast Differentiation ◽

Estrogen Receptor Alpha ◽

Biological Effects ◽

Hormone Deficiency ◽

In Vivo Studies ◽

Osteogenic Potential ◽

Type I ◽

Dependent Manner

Isopsoralen (IPRN), one of the main effective ingredients in Psoralea corylifolia Linn, has a variety of biological effects, including antiosteoporotic effects. In vivo studies show that IPRN can increase bone strength and trabecular bone microstructure in a sex hormone deficiency-induced osteoporosis model. However, the mechanism underlying this osteogenic potential has not been investigated in detail. In the present study, we investigated the molecular mechanism of IPRN-induced osteogenesis in MC3T3-E1 cells. Isopsoralen promoted osteoblast differentiation and mineralization, increased calcium nodule levels and alkaline phosphatase (ALP) activity and upregulated osteoblast markers, including ALP, runt-related transcription factor 2 (RUNX2), and collagen type I alpha 1 chain (COL1A1). Furthermore, IPRN limited the nucleocytoplasmic shuttling of aryl hydrocarbon receptor (AhR) by directly binding to AhR. The AhR target gene cytochrome P450 family 1 subfamily A member 1 (CYP1A1) was also inhibited in vitro and in vivo. This effect was inhibited by the AhR agonists indole-3-carbinol (I3C) and 3-methylcholanthrene (3MC). Moreover, IPRN also increased estrogen receptor alpha (ERα) expression in an AhR-dependent manner. Taken together, these results suggest that IPRN acts as an AhR antagonist and promotes osteoblast differentiation via the AhR/ERα axis.

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IWR-1 Inhibits Collagen-Induced Platelet Activation and Protects against Thrombogenesis

Hämostaseologie ◽

10.1055/s-0038-1676822 ◽

2019 ◽

Vol 39 (04) ◽

pp. 392-397

Author(s):

Wei Wang ◽

Songqing Lai ◽

ZiJin Xiao ◽

Haiyue Yan ◽

Yongxi Li ◽

...

Keyword(s):

Platelet Activation ◽

Antiplatelet Agent ◽

Wnt Signalling ◽

In Vivo Studies ◽

Dependent Manner ◽

Platelet Activity ◽

Occlusion Time ◽

Negative Effect

AbstractPlatelets play a crucial role in haemostasis and several pathophysiological processes. Collagen is a main initiator for platelet activation and aggregation. Given that Wnt signalling negatively regulates platelet function, and IWR-1 (a small molecule inhibitor for Wnt signalling) has the potential of inhibiting collagen synthesis, it is essential to investigate whether IWR-1 regulates collagen-induced platelet activation and protects against thrombogenesis. In the present study we found that IWR-1 pretreatment effectively suppressed collagen-induced platelet aggregation in a dose-dependent manner. In addition, IWR-1 also resulted in a decrease of P-selectin and phosphatidylserine surface exposure using fluorescence-activated cell sorting analysis. In vitro studies further revealed that IWR-1 had a negative effect on integrin a2β1 activation and platelet spreading. More importantly, the results from in vivo studies showed that IWR-1 exhibited a robust bleeding diathesis in the tail-bleeding assay and a prolonged occlusion time in the FeCl3-induced carotid injury model. Taken together, current results demonstrate that IWR-1 could effectively block collagen-induced platelet activity in vitro and in vivo, and suggest its candidacy as a new antiplatelet agent.

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Measurement of axial forces during emptying from the human stomach

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1992.263.2.g230 ◽

1992 ◽

Vol 263 (2) ◽

pp. G230-G239 ◽

Cited By ~ 10

Author(s):

M. J. Vassallo ◽

M. Camilleri ◽

C. M. Prather ◽

R. B. Hanson ◽

G. M. Thomforde

Keyword(s):

Axial Force ◽

Longitudinal Axis ◽

Force Transducer ◽

Human Stomach ◽

In Vitro Studies ◽

In Vivo Studies ◽

Dependent Manner ◽

Axial Forces

Our aim was to measure axial forces in the stomach and to evaluate their relation to circumferential contractions of the gastric walls and the emptying of gastric content. We used a combination of simultaneous radioscintigraphy, gastroduodenal manometry, and an axial force transducer with an inflatable 2-ml balloon fluoroscopically placed in the antrum. In vitro studies demonstrated that the axial force transducer records only antegrade forces along the longitudinal axis of this probe in an intensity-dependent manner. In vivo studies were performed in five healthy subjects for at least 3 h after ingestion of radiolabeled meals. When administered separately, the emptying of liquids or solids from the stomach is associated with generation of antral axial forces and coincident phasic pressure activity; however, almost 20% (average) of gastric axial forces during emptying of liquids or solids are unassociated with proximal or distal antral pressure activity ("isolated" forces). High amplitude antral axial forces and pressures occur during both lag and postlag emptying phases. During emptying of liquids, there is a trend for axial forces to be coincident more often with proximal than with distal antral pressure activity and vice versa for the emptying of solids (P = 0.015). These data suggest that when placed in the antrum, the transducer can semiquantitatively record axial forces during gastric emptying. By combining these observations with the data from in vitro studies, it appears that axial forces predominantly result from traction on the balloon by the longitudinal vector resulting from circumferential gastric contractions. The combination of radioscintigraphy and measurement of antral axial forces is a promising method to evaluate mechanical forces involved in the emptying of the human stomach.

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In Vitro Effect of Danaparoid Sodium (Orgaran®) on Thrombin Generation after Minimal Tissue Factor Pathway Activation.

Blood ◽

10.1182/blood.v106.11.4151.4151 ◽

2005 ◽

Vol 106 (11) ◽

pp. 4151-4151

Author(s):

Ismail Elalamy ◽

Anna D. Petropoulou ◽

Mohamed Hatmi ◽

Meyer M. Samama ◽

Grigoris T. Gerotziafas

Keyword(s):

Molecular Weight ◽

Tissue Factor ◽

Thrombin Generation ◽

Lag Time ◽

Dependent Manner ◽

Pathway Activation ◽

Coagulation Tests ◽

Vitro Effect ◽

Routine Coagulation

Abstract Introduction: Orgaran® (Org 10172) is a low molecular weight heparinoid which consists of natural sulphated glycosaminoglycans (heparan, dermatan, chondroitin sulphate). It has a mean molecular weight of approximately 6 kDa (4–10 kDa), an excellent bioavailability following subcutaneous administration and an anti-Xa/anti-IIa activity ratio superior to 22. It is the anticoagulant of choice in patients developping Heparin-Induced Thrombocytopenia (HIT), whereas its’ use is also proposed for surgical thromboprophylaxis. Orgaran® has no effect on routine coagulation tests (aPTT, PT, TT). Thrombin generation test(TG) is a global clotting assay proven to be sensitive to the anticoagulant effect of LMWHs and specific FXa inhibitors (i.e. fondaparinux and BAY-597939). In this in vitro study, we determined the tissue factor (TF)-induced TG inhibition potency of Orgaran® using the Thrombogram-Thrombinoscope® assay. Materials and Methods: TG was assessed after TF pathway activation in Platelet Rich Plasma (PRP) (1.5x105 platelets/μl) using diluted thromboplastin (Dade Innovin®, 1:1000 final dilution). The clotting process is provoked by a physiologically relevant TF concentration. Orgaran® was added to control plasma from 8 healthy volunteers at five different final concentrations (0.2, 0.4, 0.6, 0.8 and 1IU anti-Xa/ml). TG was initiated by adding the triggering solution containing CaCl2 and the fluorogenic substrate. The analyzed TG parameters are the lag time, the maximal concentration of thrombin (Cmax), the time to reach Cmax (Tmax), the TG velocity and the endogenous thrombin potential (ETP). Results: Orgaran® prolonged significantly the lag time and the Tmax at a concentration over 0.40 IU anti-Xa/ml (p<0.05). At the lowest studied concentration (0.20 IU anti-Xa/ml), lag time and Tmax were only prolonged by 12%, whereas their maximal prolongation (around 50%) was observed at 1IU anti-Xa/ml. Furthermore, Orgaran® inhibited ETP, Cmax and TG velocity in an almost linear dose dependent manner. A significant inhibition of ETP, Cmax and TG velocity was obtained at concentrations superior to 0.20 IU anti-Xa/ml. (p<0.05). At the highest studied concentration (1IU anti-Xa/ml) Orgaran® suppressed all TG parameters by about 80% (Table 1). Conclusion: Orgaran® exhibited a significant inhibitory activity of in vitro TG. At concentrations achieved in clinical practice (prophylactic or therapeutic dose), Orgaran® modified in vitro TG profile while it has no effect on routine coagulation tests. Thus, TG assay is a sensitive method for monitoring Orgaran® and this test requires a clinical prospective evaluation. Table 1. Determination of IC20 and IC50 anti-Xa inhibitory concentrations of Orgaran® on TG parameters Lag Time Tmax ETP Cmax Velocity IC: Inhibitory Concentration * or Concentration increasing 20% and 50% the lag time and the Tmax respectively IC 20 (IU/ml) 0.30 0.30 0.18 0.18 0.15 IC 50 (IU/ml) 0.83 >1 0.30 0.50 0.35 1IU anti-Xa/ml 53% 47% 68% 76% 84%

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Endothelial Cell-Derived Microparticles in the Pathogenesis of Chemotherapy-Associated Hypercoagulability.

Blood ◽

10.1182/blood.v108.11.1457.1457 ◽

2006 ◽

Vol 108 (11) ◽

pp. 1457-1457

Author(s):

Daniel Lechner ◽

Marietta Kollars ◽

Sabine Eichinger ◽

Paul Alexander Kyrle ◽

Ansgar Weltermann

Keyword(s):

Thrombin Generation ◽

Culture Media ◽

Annexin V ◽

Membrane Vesicles ◽

Procoagulant Activity ◽

Dependent Manner ◽

Thrombin Generation Assay ◽

Apoptotic Effect ◽

Mitochondrial Dehydrogenase Activity

Abstract Background: Cisplatin-based chemotherapy is a risk factor of venous thromboembolism in cancer patients. The underlying pathogenesis remains unclear. We hypothesized an apoptotic effect of cisplatin on endothelial cells (EC) inducing a release of small membrane vesicles, so-called microparticles (MP) which are known to cause hemostasis activation. Objectives: To quantify the release of MP from EC following administration of cisplatin and to investigate MP-associated procoagulant mechanisms. Methods: Two EC lines (HUVEC, HMVEC-L) were exposed to cisplatin (1, 2.5, 5, 10, and 20 μM) for up to 120 h. Cell viability was assessed by quantification of mitochondrial dehydrogenase activity, counts and procoagulant activity of MP were measured by flow cytometry and a thrombin generation assay, respectively. Tissue factor (TF) antigen levels were determined by ELISA. Results: EC viability decreased in a dose- and time-dependent manner and was accompanied by an increasing release of MP into culture media (maximum: HUVEC + 544%; HMVEC-L + 1738%). In parallel, procoagulant activity of media increased by up to 150% (HUVEC) and 493% (HMVEC-L), respectively. The procoagulant activity was almost abolished by annexin V but was not suppressed by a monoclonal TF-antibody. TF antigen levels on MP were persistently low even at high cisplatin concentrations. Conclusion: At pharmacologically relevant concentrations, cisplatin induced a marked release of procoagulant MP from EC. Negatively charged phospholipids but not TF on MP were decisive for total thrombin generation. Further studies are warranted to investigate the cisplatin-induced release of EC-derived MP in vivo.

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