Antiplatelet, anticoagulant, and thrombolytic drug interactions.
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Anticoagulants↗
Biomedical subjects
Shaker A Mousa
Publications and source records attributed to Shaker A Mousa.
Angiogenesis inhibitors: current & future directions.
The field of angiogenesis modulation is at a major crossroad. A tremendous advancement in basic science in this field is providing an excellent support for the concept, which is in contrast to a lack of strong clinical support to date. With regard to the large gap between experimental data and clinical data, the best model of human malignancy is in human cancer patients and the best model of human ocular angiogenesis-mediated disorders such as diabetic retinopathy (DR) and age related macular degeneration (AMD) is in human RD and AMD patients. Additionally, clinical outcomes should include benefit/risk ratios, hard end points (mortality and quality of life as opposed to increased microvascular density with pro-angiogenic agents or tumor size reduction with anti-angiogenesis agents) as well as cost effectiveness. Experimental models should be used to provide guidance, placebo effect, comparative data, and mechanistic understanding as opposed to being used for expected clinical efficacy. We also have to understand existing strategies and how angiogenesis modulation can add further value (i.e. not to replace existing strategy but rather improve efficacy/safety). Recent investigation defined numerous strategies in the modulation of angiogenesis. Those strategies are driven from haemostatic, fibrinolytic, cell adhesion molecules, extracellular matrix, growth factors, and other endogenous systems involved in the modulation of angiogenesis.
Angiogenesis Inhibitors↗
Arixtra (fondaparinux sodium).
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Anticoagulants↗
Anti-angiogenic mechanisms and efficacy of the low molecular weight heparin, tinzaparin: anti-cancer efficacy.
Inhibitors of angiogenesis are potential anti-cancer agents in that they deprive tumors of the blood necessary for growth and metastasis. The anti-angiogenic efficacy of tinzaparin, a known anticoagulant low molecular weight heparin (LMWH), was examined in vitro in endothelial cell tube formation assay and in vivo in the chick chorioallantoic membrane model. The observed anti-angiogenic effects of tinzaparin were shown to be dose-related and dependent on the relatively higher molecular weight tinzaparin fragments. These experiments demonstrated that tinzaparin is a potent inhibitor of angiogenesis (ED90-100 range, 0.05-0.1 mg) regardless of the angiogenic factor and suggest that its effect is mediated via cellular release of tissue factor pathway inhibitor (TFPI). This was evident by the reversal of either tinzaparin or r-TFPI anti-angiogenesis efficacy by a specific monoclonal TFPI antibody. The ED90-100 for the inhibition of angiogenesis for r-TFPI ranged from 0.01 to 0.03 mg in the chorioallantoic membrane model regardless of the proangiogenic factor. In addition, either tinzaparin or r-TFPI inhibited the growth of colon carcinoma tumors, human fibrosarcoma tumors, and human lung carcinoma in the chorioallantoic membrane tumor implant model. Thus, the LMWH tinzaparin, in addition to its anticoagulant effects, may offer important benefits in treatment of cancer and other disorders supported by pathologic angiogenesis.
Angiogenesis Inhibitors↗
Signaling through JAM-1 and alphavbeta3 is required for the angiogenic action of bFGF: dissociation of the JAM-1 and alphavbeta3 complex.
Growth factor-induced neovascularization has received a great deal of attention because it is fundamental to the growth and metastasis of solid tumors. This multistep process requires extensive signaling through growth factor receptors and integrins. Among the integrins involved in this process, integrin alphavbeta3 is specific to basic fibroblast growth factor (bFGF)-induced angiogenesis. Here we show that junctional adhesion molecule 1/A (JAM-1/A) and alphavbeta3 form a complex in the absence of bFGF. JAM-1, which is normally localized at the cell-cell junctions of quiescent endothelial cells, redistributes to the cell surface on bFGF treatment. Blockage of the extracellular domain of JAM-1 inhibits bFGF-induced endothelial cell morphology, proliferation, and angiogenesis. Additionally, mutation in the JAM-1 cytoplasmic domain blocks bFGF-induced mitogen-activated protein (MAP) kinase activation and ablates its ability to induce endothelial cell tube formation, suggesting that signaling through JAM-1 is key to bFGF-induced signaling. Immunoprecipitation analysis suggests that bFGF signaling dissociates the JAM-1/ alphavbeta3 complex, allowing for signaling through JAM-1 and alphavbeta3. In addition, blockage of either JAM-1 or alphavbeta3 inhibits bFGF-induced MAP kinase activation. Thus, our results suggest that signaling through JAM-1 and alphavbeta3 is necessary for bFGF-induced angiogenesis.
Allantois↗
Obtustatin: a potent selective inhibitor of alpha1beta1 integrin in vitro and angiogenesis in vivo.
A novel disintegrin, obtustatin, was purified from the venom of the Vipera lebetina obtusa viper. Obtustatin is the shortest disintegrin yet described, containing only 41 amino acids. It contains a similar pattern of cysteines to the short disintegrins echistatin and eristostatin but contains the sequence KTS rather than RGD in its active site loop. Obtustatin is a potent and selective inhibitor of alpha1beta1 integrin. It does not inhibit the closely related integrin alpha2beta1, nor a panel of other integrins tested. It does not inhibit ligand binding to the recombinant alpha1 I-domain. Importantly, obtustatin potently inhibited angiogenesis in vivo in the chicken chorioallantoic membrane assay, and in the Lewis lung syngeneic mouse model, it reduced tumor development by half, confirming and extending previous results on the relevance of alpha1beta1 integrin to angiogenesis and suggesting novel approaches to the generation of angiogenesis inhibitors.
Allantois↗
alphav Vitronectin receptors in vascular-mediated disorders.
Various integrin antagonist candidates including antibodies, cyclic peptides, peptidomimetics, and non-peptides have been clinically evaluated and shown to successfully modulate certain disease processes. This review will focus on the key role of the alphav integrin (alphavbeta3 and alphavbeta5) in vascular disorders such as restenosis and angiogenesis-mediated disorders.
Angioplasty, Balloon, Coronary↗
Inhibition of tumor cell-induced platelet aggregation and lung metastasis by the oral GpIIb/IIIa antagonist XV454.
Platelets are known to play a role in blood borne metastasis. Previous experimental studies have suggested that platelet GpIIb/IIIa may be a therapeutic target. However, the need for intravenous administration limits the potential application of current GpIIb/IIIa inhibitors to cancer therapy. The aim of the present study was to assess the efficacy of a novel, non-peptide oral GpIIb/IIIa antagonist (XV454) on tumor cell-induced platelet aggregation in vivo and on experimental metastasis. A Lewis lung carcinoma (LL2) mouse model of experimental metastasis was used in this study. XV454 (100 micro g) was administered intravenously (via tail vein) or orally (gavages) to 20 g mice. To determine the effect of XV454 on platelet aggregation, blood samples were collected by cardiac puncture 10 minutes after intravenous and 1-24 hrs after oral XV454, and platelet function was assessed by aggregometry, thrombelastography and the Platelet Function Analyzer (PFA100). The effect of XV454 on tumor cell-induced thrombocytopenia was determined 10 minutes after intravenous and 3 hrs after oral XV454 administration. Tumor cells (2 x 10(6)) were injected intravenously and 15 minutes after cell injection, platelet count was measured and compared to baseline (pre-injection) counts. To assess the effect on metastasis, XV454 was administered intravenous or orally 10 minutes and 3 hrs before tumor cell injection, respectively. Eighteen days later, surface lung tumor nodules were counted and the total lung tumor burden assessed. In a fourth group, in addition to the initial oral dose (before tumor cell injection), oral XV454 was given daily for the first week and three times in the second week. Administration of XV454 (5 mg/kg) completely inhibited platelet aggregation and this effect persisted for at least 24 hrs after oral delivery. Both intravenous and oral XV454 significantly inhibited tumor cell-induced thrombocytopenia (P < 0.01), the number of surface lung tumor nodules (80-85%; P < 0.001) and total tumor burden (83% for intravenous group; 50% oral [single treatment] group; 91% oral [multiple treatment] group, P < 0.001). Overall, these data provide further evidence for the effect of oral and intravenous GpIIb/IIIa antagonism on tumor cell-platelet interaction and metastasis.
Administration, Oral↗
Antithrombotics in thrombosis and cancer.
Many cancer patients reportedly are in a hypercoaguable state, with recurrent thrombosis due to the impact of cancer cells and chemotherapy or radiotherapy on the coagulation cascade. Studies have demonstrated that unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) interfere with various processes involved in tumor growth and metastasis. These include fibrin formation, binding of heparin to angiogenic growth factors such as basic fibroblast growth factor and vascular endothelial growth factor, modulation of tissue factor and, perhaps, other more important modulatory mechanisms such as enhanced tissue factor pathway inhibitor (TFPI) release and inhibition of various matrix-degrading enzymes. Clinical trials have suggested a clinically relevant effect of LMWH, compared with UFH on the survival of cancer patients with deep vein thrombosis. Similarly, the impact of warfarin on the survival of cancer patients with thromboembolic disorders was demonstrated. Studies from our laboratory demonstrated a significant role for LMWH, warfarin, anti-VIIa and LMWH-releasable TFPI on the regulation of angiogenesis, tumor growth, and tumor metastasis. Thus, modulation of tissue factor/VIIa noncoagulant activities by LMWH, warfarin, anti-VIIa or TFPI might be a useful therapeutic option for the inhibition of angiogenesis associated with human tumor growth and metastasis.
Anticoagulants↗
Antiplatelet therapies: platelet GPIIb/IIIa antagonists and beyond.
Cardiovascular and cerebrovascular diseases continue to be leading causes of death throughout the world. Blood platelets play a pivotal role not only in haemostasis but also in the pathogenesis of thrombosis and atherosclerosis, platelet aggregation being an essential step in the formation of either an effective haemostatic plug or an intravascular thrombus. The benefits of various antiplatelet therapies ranging from aspirin, ticlopidine, Clopidogrel, and intravenous platelet GPIIb/IIIa antagonists in various thromboembolic disorders are well documented. Despite of the success of intravenous acute GPIIb/IIIa blockade when given in conjunction with heparin, chronic oral GPIIb/IIIa antagonists with or without aspirin failed in various cardiovascular settings. This review highlights the role of the various antiplatelet therapies in thrombotic disorders as well as future directions.
Animals↗
Pharmacodynamic properties of the low molecular weight heparin, tinzaparin: effect of molecular weight distribution on plasma tissue factor pathway inhibitor in healthy human subjects.
Low molecular weight heparins (LMWHs) stimulate the release of endothelial tissue factor pathway inhibitor (TFPI). An inhibitor of tissue factor-induced coagulation, TFPI may contribute to the efficacy of LMWHs. The release of TFPI may be affected by characteristics of LMWHs, such as molecular weight (MW) distribution. The authors measured plasma levels of TFPI after single, subcutaneous injections of tinzaparin (mean MW = 6500 Daltons [Da]; 3.5% of fractions < 2000 Da) or a tinzaparin-like LMWH (mean MW = 5650 Da; 18.3% of fractions < 2000 Da) in 30 healthy subjects. Maximum mean plasma levels of TFPI approached 200 to 230 ng/mL 0.8 hours after administration of either drug. Plasma levels of TFPI remained elevated compared with baseline values for 12 to 16 hours after drug administration. These results suggest that LMWH fractions < 2000 Da do not affect the release of TFPI.
Adult↗
Chronic pulsatile shear stress impacts synthesis of proteoglycans by endothelial cells: effect on platelet aggregation and coagulation.
Endothelial-derived proteoglycans are important regulators of the coagulation-pathway in vivo and our primary objective of this study was to determine whether chronic shear stress affected the synthesis, release, and activity of proteoglycans from bovine aortic endothelial cells (BAEC). BAEC were cultured under shear and proteoglycans were purified from BAEC conditioned media and analyzed using both anionic exchange and size exclusion chromatography. The overall amount of proteoglycans produced per cell was significantly greater for the high shear-treated samples compared to the low shear-treated samples indicating that the shear magnitude did impact cell responsiveness. While overall size and composition of the proteoglycans and glycosaminoglycan (GAG) side chains were not altered by shear, the relative proportion of the high and low molecular weight species was inversely related to shear and differed significantly from that found under static tissue culture conditions. Moreover, a unique proteoglycan peak was identified from low shear stress (5 +/- 2 dynes/cm(2)) conditioned media when compared to high shear conditions (23 +/- 8 dynes/cm(2)) via anionic exchange chromatography, suggesting that subtle changes in the GAG structures may impact activity of these molecules. In order to characterize whether these changes impacted proteoglycan function, we studied the effects of shear specific proteoglycans on the inhibition of thrombin-induced human platelet aggregation as well as on platelet-fibrin clot dynamics. Proteoglycans from high shear-treated samples were less effective inhibitors of both platelet aggregation and blood coagulation inhibition than proteoglycans from low shear-treated samples and both were less effective than proteoglycans isolated from static tissue culture samples. However, due to changes in the overall proteoglycan synthesis and release rate, the high and low shear-treated sample had essentially identical effects on these activities, suggesting that the cells were able to compensate for stress-induced proteoglycan changes. Our data suggests that shear stress, by altering proteoglycan synthesis and fine structure, may play a role in maintaining vascular hemodynamics and hemostasis.
Animals↗
Anti-integrin as novel drug-discovery targets: potential therapeutic and diagnostic implications.
The role of integrin and extracellular matrix proteins in various pathological processes (including angiogenesis, thrombosis, apoptosis and cell migration and proliferation), leading to both acute and chronic disease states (e.g. ocular diseases, metastasis, unstable angina, myocardial infarction, stroke, osteoporosis, a wide range of inflammatory diseases, vascular remodeling and neurodegenerative disorders) has been recently documented. A key success in this field is evident from the potential role of the platelet GPIIb/IIIa (alphaIIbbeta3) integrin in the prevention, treatment and perhaps diagnosis of various thromboembolic disorders. Additionally, progress has been shown in the development of leukocyte alpha4beta1 antagonists for various inflammatory indications and alphav integrin antagonists for angiogenesis and vascular-related disorders. However, the exact modes of action of certain integrin antagonists are still not fully clear. Integrin antagonists in clinical or pre-clinical development are expected to be used as a stand-alone therapy or, better, as an adjunct to other pharmacotherapy, radiotherapy or interventional procedures.
Animals↗
Antiangiogenic and antimetastatic properties of Neovastat (AE-941), an orally active extract derived from cartilage tissue.
A novel naturally occurring antiangiogenic agent isolated from cartilage, referred to as Neovastat (AE-941), was examined for its efficacy against tumor neovascularization and progression. Exposure to Neovastat results in ex ovo antiangiogenic properties in the chorioallantoid membrane of chicken embryo (71% decrease in the angiogenic index as compared to the basic fibroblast growth factor (bFGF) treated control embryos, P < 0.0001). Oral administration of Neovastat inhibits bFGF-induced angiogenesis in the Matrigel mouse model (87.5% decrease in hemoglobin as compared to the bFGF-treated control implants, P < 0.0001). Neovastat also induces a dose response decrease of lung metastases in the Lewis lung carcinoma model (oral administration; 69.1% of inhibition obtained at the maximal dose of 0.5 ml/day, P < 0.0001). Combined with a sub-optimal dose of cisplatinum (2 mg/kg, i.p.), Neovastat (0.5 ml/day) improved the therapeutic index by increasing the antimetastatic efficacy and by exerting a protective activity against cisplatinum-induced body weight loss and myelosuppression. In summary, our experimental data provide evidence of antiangiogenic and antimetastatic properties of Neovastat, following oral administration.
Administration, Oral↗
Anticoagulants in thrombosis and cancer: the missing link.
Many cancer patients reportedly have a hypercoagulable state, with recurrent thrombosis due to the impact of cancer cells and chemotherapy on the coagulation cascade. Studies have demonstrated that unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) interferes with various processes involved in tumor growth and metastasis. These processes might include fibrin formation, binding of heparin to angiogenic growth factors such as basic fibroblast growth factor and vascular endothelial growth factor, modulation of tissue factor, and other mechanisms. Clinical trials have indicated a clinically relevant effect of LMWH as compared with UFH on the survival of cancer patients with deep vein thrombosis. Similarly, the impact of warfarin on the survival of cancer patients with thromboembolic disorders was demonstrated. Recent studies from our laboratory defined the role of an LMWH (tinzaparin), warfarin, anti-factor VIIa, and recombinant tissue factor pathway inhibitor in the modulation of angiogenesis, tumor growth, and tumor metastasis.
Animals↗
Comparative efficacy between the glycoprotein IIb/IIIa antagonists roxifiban and orbofiban in inhibiting platelet responses in flow models of thrombosis.
This study was undertaken to compare the platelet binding characteristics and anti-platelet efficacy of a nonpeptide glycoprotein IIb/IIIa antagonist roxifiban with orbofiban in static and dynamic adhesion and aggregation assays. The results indicate that roxifiban binds with higher affinity to glycoprotein IIb/IIIa receptors and exhibits slower dissociation rates than orbofiban. Furthermore, the platelet inhibitory effects of roxifiban, but not orbofiban, were unaffected by changes in plasma calcium concentrations. Both agents reduced, in a concentration-dependent manner, the size of platelet thrombi deposited onto collagen I upon perfusion of heparinized blood at a shear rate of 1,500/s. At a clinically achievable concentration of 60 nM, roxifiban abrogated the formation of thrombi containing > 20 platelets per thrombus, thereby displaying comparable in vitro efficacy to that achieved by the theoretical maximal abciximab blood concentration (3.5 microg/ml) produced after standard treatment. In contrast, orbofiban, even at 500 nM, was only effective in inhibiting the formation of larger platelet thrombi (> or =150 platelets per thrombus). Pretreatment of surface-anchored platelets with roxifiban (100 nM), but not orbofiban (500 nM), inhibited monocytic THP-1 cell attachment under flow. However, this heterotypic adhesion process was also suppressed when orbofiban (500 nM) was maintained in the perfusion buffer during the entire course of flow experiment. These findings demonstrate roxifiban (unlike orbofiban) is a potent glycoprotein IIb/IIIa antagonist with a long receptor-bound lifetime and prolonged anti-platelet efficacy and may thus be beneficial for the treatment and prevention of acute ischemic syndromes.
Alanine↗
Anti-platelet effects of GPIIb/IIIa and P-selectin antagonism, platelet activation, and binding to neutrophils.
Platelet activation with GPIIb/IIIa binding to fibrinogen, aggregation and interaction with leukocytes constitute the principal mediator of thrombosis. Although the clinical benefits of GPIIb/IIIa antagonists have been documented, the relationship between their anti-platelet properties, platelet activation and binding to leukocytes is still debated. We investigated the effects of abciximab, tirofiban, roxifiban, and an anti-P-selectin blocking monoclonal antibody (Mab) on isolated human platelet aggregation using optical aggregometer, and on platelet P-selectin and GPIIb/IIIa expression, and platelet-neutrophil binding using flow cytometry. Thrombin at 0.025 U/ml induced maximal platelet aggregation (76.3 +/- 2.6%), P-selectin expression (88.5 +/- 4%), GPIIb/IIIa activation (PAC-1 binding, 86.2 +/- 8.9%) and platelet-neutrophil binding (58.0 +/- 6.4%). The GPIIb/IIIa antagonists inhibited in a concentration-dependent manner platelet aggregation (IC50 of 100 nM for abciximab and tirofiban and 50 nM for roxifiban) and PAC-1 binding, without any effect on P-selectin. None of these agents affected significantly platelet-neutrophil binding, whereas an anti-P-selectin Mab abolished this binding and amplified the effect of abciximab on platelet aggregation. These results indicate that the effects of these GPIIb/IIIa antagonists on platelet aggregation are not related to inhibition of platelet activation, as P-selectin levels and platelet-neutrophil binding remained unaffected, and highlight the participation of P-selectin with GPIIb/IIIa in platelet aggregation.
Abciximab↗
Differential efficacy of different platelet glycoprotein IIb/IIIa antagonists on platelet/fibrin-mediated clot dynamics under different conditions using thrombelastography: the critical need for anticoagulant.
BACKGROUND: Intravenous GpIIb/IIIa antagonists demonstrate various significant clinical benefits depending on the agent used. In contrast, oral delivery of GpIIb/IIIa antagonists failed in achieving clinical benefits. This raises the question about the differences among different GpII/IIIa antagonists. METHODS: The effect of various platelet glycoprotein (GP) IIb/IIIa antagonists on the dynamics of platelet/fibrin clot formation and strength was determined using thrombelastography under different conditions. RESULTS: GPIIb/IIIa antagonists with high affinity for resting and activated platelets and with slow rates of dissociation from GPIIb/IIIa (Class I antagonists) demonstrated potent and comparable inhibition of platelet aggregation and platelet-mediated clot strength under different conditions. In contrast to antagonists that dissociate rapidly from GPIIb/IIIa (class II antagonists). Class I antagonists such as the free acid form of roxifiban inhibited platelet-mediated clot strength, with the inhibiting concentration required for 50% effect (IC50) = 70 n mol/l, whereas the IC50 of the class II antagonists such as the free acid forms of orbofiban, sibrafiban, lotrafiban, integrilin or aggrastat ranged from 1 to 15 micromol/l. The IC50s for class II antagonists in inhibiting platelet/fibrin clot formation and strength were substantially greater (10-15 fold) than their clinically achievable concentrations. The limited efficacy for class II antagonists in inhibiting platelet-mediated clot dynamics was enhanced by the combination with heparin. CONCLUSIONS: Thus, these data indicated that there are differences in the efficacy of various GPIIb/IIIa antagonists in inhibiting platelet/fibrin clot formation and strength, which might be corrected by heparin. Data also suggest that inhibition of platelet aggregation may not be the sole determinant for the in-vivo efficacy of various GPIIb/IIIa antagonists.
Anticoagulants↗