Evaluation of two experimental venous thrombosis models in the rat

Extracellular DNA-A Danger Signal Triggering Immunothrombosis

Clotting and inflammation are effective danger response patterns positively selected by evolution to limit fatal bleeding and pathogen invasion upon traumatic injuries. As a trade-off, thrombotic, and thromboembolic events complicate severe forms of infectious and non-infectious states of acute and chronic inflammation, i.e., immunothrombosis. Factors linked to thrombosis and inflammation include mediators released by platelet granules, complement, and lipid mediators and certain integrins. Extracellular deoxyribonucleic acid (DNA) was a previously unrecognized cellular component in the blood, which elicits profound proinflammatory and prothrombotic effects. Pathogens trigger the release of extracellular DNA together with other pathogen-associated molecular patterns. Dying cells in the inflamed or infected tissue release extracellular DNA together with other danger associated molecular pattern (DAMPs). Neutrophils release DNA by forming neutrophil extracellular traps (NETs) during infection, trauma or other forms of vascular injury. Fluorescence tissue imaging localized extracellular DNA to sites of injury and to intravascular thrombi. Functional studies using deoxyribonuclease (DNase)-deficient mouse strains or recombinant DNase show that extracellular DNA contributes to the process of immunothrombosis. Here, we review rodent models of immunothrombosis and the evolving evidence for extracellular DNA as a driver of immunothrombosis and discuss challenges and prospects for extracellular DNA as a potential therapeutic target.

Animal models of venous thrombosis

Venous thrombosis (VT) is a prevalent clinical condition with significant adverse sequela or mortality. Anticoagulation and pharmacologic or pharmacomechanical thrombolytic therapies are the mainstays of VT treatment. An understanding of thrombosis biology will allow for more effective VT-tailored diagnosis and therapy. In vivo models of thrombosis provide indispensable tools to study the pathogenesis of thrombus formation and to evaluate novel therapeutic or preventive adjuncts for VT management or prevention. In this article, we review the most prominent in vivo models of VT created in rodents and swine species and outline how each model can serve as a useful tool to promote our understanding of VT pathogenesis and to examine novel therapies.

Antithrombotic activity of Batroxase, a metalloprotease from Bothrops atrox venom, in a model of venous thrombosis

BACKGROUND

Snake venoms are great sources of bioactive molecules, which may be used as models for new drugs. Toxins that interfere in hemostasis have received considerable attention over the years.

OBJECTIVES

This study aimed at the evaluation of the antithrombotic activity of Batroxase, a P-I metalloprotease from Bothrops atrox venom, in an animal model of venous thrombosis.

METHODS

The antithrombotic activity of Batroxase was tested in vivo in a model based on two factors of the Virchow's Triad: blood flow alterations (partial stenosis of the inferior vena cava), and vessel wall injury (10% ferric chloride for 5min), in comparison with sodium heparin (positive control) and saline (negative control). Bleeding/clotting time was assessed by a tail bleeding assay. The immunogenicity of Batroxase was also analyzed.

RESULTS

Batroxase (12mg/kg) reduced thrombus formation in 81%, similarly to heparin (100U/kg), which reduced it in 85% in comparison with the saline group. Both Batroxase and heparin increased bleeding/clotting time in approximately 3 fold. Immunizations of rabbits with Batroxase do not result in detectable levels of antibodies against this metalloprotease.

CONCLUSION

Batroxase presents antithrombotic activity in vivo. Moreover, its lack of immunogenicity increases the interest on its possible therapeutic potential over thrombogenic disorders.

Evaluation of the in vivo thrombolytic activity of a metalloprotease from Bothrops atrox venom using a model of venous thrombosis

BACKGROUND

Due to the importance of blood coagulation and platelet aggregation in brain- and cardiovascular diseases, snake venom proteins that interfere in these processes have received significant attention in recent years considering their potential to be used as models for new drugs.

OBJECTIVES

This study aimed at the evaluation of the in vivo thrombolytic activity of Batroxase, a P-I metalloprotease from Bothrops atrox venom.

METHODS

In vivo thrombolytic activity of Batroxase was tested on a model of venous thrombosis in rats, with partial stenosis of the inferior vena cava, and vessel wall injury with ferric chloride at 10% for 5 min. After formation of the thrombus, increasing amounts of Batroxase were administered intravenously. The prescription medication Alteplase (tissue-type plasminogen activator) was used as positive control for thrombolytic activity, while saline was used as negative control. Bleeding time was assessed with a tail bleeding assay.

RESULTS

Batroxase presented thrombolytic activity in vivo in a concentration-dependent manner, with 12 mg/kg of the metalloprotease causing a thrombus reduction of 80%, a thrombolytic activity very similar to the one observed for the positive control Alteplase (85%). The tail bleeding time was not altered by the administration of Batroxase, while it increased 3.5 times with Alteplase. Batroxase presented fibrinolytic and fibrinogenolytic activities in vitro, which were inhibited by alpha 2-macroglobulin.

CONCLUSION

Batroxase presents thrombolytic activity in vivo, thus demonstrating a possible therapeutic potential. The inactivation of the metalloprotease by alpha 2-macroglobulin may reduce its activity, but also its potential side effects, as seen for bleeding time.

Alginate coated chitosan core shell nanoparticles for oral delivery of enoxaparin: in vitro and in vivo assessment

The objective of present research work was to develop alginate coated chitosan core shell nanoparticles (Alg-CS-NPs) for oral delivery of low molecular weight heparin, enoxaparin. Chitosan nanoparticles (CS-NPs) were synthesized by ionic gelation of chitosan using sodium tripolyphosphate. Core shell nanoparticles were prepared by coating CS-NPs with alginate solution under mild agitation. The Alg-CS-NPs were characterized for surface morphology, surface coating, particle size, polydispersity index, zeta potential, drug loading and entrapment efficiency using SEM, Zeta-sizer, FTIR and DSC techniques. Alginate coating increased the size of optimized chitosan nanoparticles from around 213 nm to about 335 nm as measured by dynamic light scattering in zeta sizer and further confirmed by SEM analysis. The performance of optimized enoxaparin loaded Alg-CS-NPs was evaluated by in vitro drug release studies, in vitro permeation study across intestinal epithelium, in vivo venous thrombosis model, particulate uptake by intestinal epithelium using fluorescence microscopy and pharmacokinetic studies in rats. Coating of alginate over the CS-NPs improved the release profile of enoxaparin from the nanoparticles for successful oral delivery. In vitro permeation studies elucidated that more than 75% enoxaparin permeated across the intestinal epithelium with Alg-CS-NPs. The Alg-CS-NPs significantly increased (p<0.05) the oral bioavailability of enoxaparin in comparison to plain enoxaparin solution as revealed by threefold increase in AUC of plasma drug concentration time curve and around 60% reduction in thrombus formation in rat venous thrombosis model. The core shell Alg-CS-NPs showed promising potential for oral delivery and significantly enhanced the in vivo oral absorption of enoxaparin.

Total steroidal alkaloids from Veratrum patulum L. Inhibit platelet aggregation, thrombi formation and decrease bleeding time in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Veratrum patulum L. (Liliaceae) is used as one source of the Chinese traditional drug "Lilu" which has been used in the treatment of aphasia arising from apoplexy, wind type dysentery, headache, etc. for thousands of years.

AIM OF THE STUDY

To evaluate the antithrombotic effect of Veratrum patulum L. (Liliaceae) total steroidal alkaloids (VpA) and explore the potential mechanisms.

MATERIALS AND METHODS

The antithrombotic effect of VpA was evaluated in two experimental thrombosis models in rat. The potential antithrombotic mechanisms of VpA were explored by determining the coagulation parameters and platelet aggregation induced by various agonists. Cutting-tail rat model was used to evaluate the influence of VpA on bleeding time.

RESULTS

VpA significantly inhibit the formation of arterial and venous thrombosis and showed different inhibitory effect on the platelet aggregation induced by various agonists with the following potency order: collagen>ADP>thrombin. VpA showed no influence on the coagulation parameters in rat. But VpA decreased the cutting-tail bleeding time in rat.

CONCLUSION

VpA possess antithrombotic effect on venous and arterial thrombosis. The antithrombotic effect of VpA is due to its inhibition to platelet aggregation, especially induced by collagen.

Investigation into the mechanism(s) of antithrombotic effects of carbon monoxide releasing molecule-3 (CORM-3)

Carbon monoxide (CO) like nitric oxide (NO) has been recognized as activator of soluble guanylate cyclase (sGC) in many physiological functions. Studies, which demonstrate the mechanisms by which CO inhibits platelet aggregation in in vivo models, are few. Here we investigated the possible involvement of sGC, NO, plasminogen activator inhibitor (PAI-1) and p38 MAP Kinase in antithrombotic effects of CO released by a novel, water-soluble, CO releasing molecule-3 (CORM-3) using rat. The effects of CORM-3 on in vitro and ex vivo platelet aggregation induced by thrombin as well as in in vivo thrombosis models were studied. When added to rat washed platelets in in vitro study, CORM-3 (100 and 200 μM) inhibited thrombin-induced platelet aggregation. Similarly, antiplatelet effect was also observed when 3mg/kg i.v. infusion of CORM-3 administered for 10 minutes in ex vivo study using rat. Interestingly, in presence of inhibitor of sGC (ODQ, 10mg/kg,i.p.) and inhibitor of nitric oxide synthase (L-NAME, 30 mg/kg,i.p.), inhibition of thrombin-induced aggregation by CORM-3 was significantly blocked. Notably, in presence of inhibitor of K(ATP) channel (glibenclamide, 10mg/kg,i.p.) and p38 MAP Kinase (SCIO-469, 1mg/kg, i.p.), inhibition of aggregation by CORM-3 was not blocked. In in vivo studies using animal models of thrombosis, we found that CORM-3-mediated antithrombotic effect was dependent on activation of sGC, NO and suppression of PAI-1 in arterial thrombosis and Arterio-Venous (A-V) shunt models. Therefore, we concluded that antithrombotic activity of CORM-3 may be mediated by activation of sGC, NO and inhibition of PAI-1.

Anti-thrombosis effect of diosgenin extract from Dioscorea zingiberensis C.H. Wright in vitro and in vivo

Thrombus formation in blood vessel plays an important role in the pathogenesis and progression of atherosclerosis and cardiovascular diseases. Extract of Dioscorea zingiberensis C.H. Wright (D. zingiberensis) is demonstrated to posses activities for curing cardiovascular diseases such as coronary heart disease and angina pectoris. However, there were few studies on anti-thrombosis activity of it. We investigated the anti-thrombosis effect of diosgenin from D. zingiberensis (Dio) in vitro and in vivo on inferior vena cava ligation thrombosis rat model and pulmonary thrombosis mice model. We evaluated the protective effect of Dio by measuring the platelet aggregation, activated partial thromboplastin time (APTT), thrombin time (TT), prothrombin time (PT) and the venous thrombosis in rats and the bleeding time, clotting time and protection rate in mice. Results showed that Dio inhibited platelet aggregation, thrombosis and prolonged APTT, PT and TT in rats in a dose-dependent manner. They also prolonged the bleeding time, clotting time and increased protection rate in mice in a dose-dependent manner. Taken together, these findings suggested that Dio which contained 95% diosgenin had anti-thrombosis activity. Dio executives the anti-thrombosis activity through improving the anticoagulation function, inhibiting platelet aggregation and thrombosis.

Anti-thrombotic activity and chemical characterization of steroidal saponins from Dioscorea zingiberensis C.H. Wright

Steroidal saponins have long attracted scientific attention, due to their structural diversity and significant biological activities. Total steroidal saponins (TSS) extracted from the rhizomes of Dioscorea zingiberensis C.H. Wright (DZW) constitute an effective treatment for cardiovascular disease. However, the active constituents contained in DZW rhizomes and their pharmacological properties are not fully understood. The aim of this work is to determine and quantify the active constituents in DZW rhizomes using fingerprint technique, and evaluate its anti-thrombotic activity using inferior vena cava ligation thrombosis rat model and pulmonary thrombosis mice model after being gavaged with TSS for 1 or 2weeks. In the study, a chemical fingerprint method was firstly established and validated to quantify and standardize TSS from DZW rhizomes including parvifloside, protodeltonin, protodioscin, protogracillin, zingiberensis saponin, deltonin, dioscin and trillin. TSS extracted from DZW rhizomes were showed to have the inhibitions on platelet aggregation (PAG) and thrombosis, and prolong activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) in a dose-dependent manner in rats. TSS also prolonged the bleeding time and clotting time in a dose-dependent manner in mice. The results indicate that TSS could inhibit thrombosis by both improving the anticoagulation activity and inhibiting PAG action, suggesting that TSS from DZW rhizomes have the potential to reduce the risk of cardiovascular diseases by anti-thrombotic action.

Ir-CPI, a coagulation contact phase inhibitor from the tick Ixodes ricinus, inhibits thrombus formation without impairing hemostasis

Blood coagulation starts immediately after damage to the vascular endothelium. This system is essential for minimizing blood loss from an injured blood vessel but also contributes to vascular thrombosis. Although it has long been thought that the intrinsic coagulation pathway is not important for clotting in vivo, recent data obtained with genetically altered mice indicate that contact phase proteins seem to be essential for thrombus formation. We show that recombinant Ixodes ricinus contact phase inhibitor (Ir-CPI), a Kunitz-type protein expressed by the salivary glands of the tick Ixodes ricinus, specifically interacts with activated human contact phase factors (FXIIa, FXIa, and kallikrein) and prolongs the activated partial thromboplastin time (aPTT) in vitro. The effects of Ir-CPI were also examined in vivo using both venous and arterial thrombosis models. Intravenous administration of Ir-CPI in rats and mice caused a dose-dependent reduction in venous thrombus formation and revealed a defect in the formation of arterial occlusive thrombi. Moreover, mice injected with Ir-CPI are protected against collagen- and epinephrine-induced thromboembolism. Remarkably, the effective antithrombotic dose of Ir-CPI did not promote bleeding or impair blood coagulation parameters. To conclude, our results show that a contact phase inhibitor is an effective and safe antithrombotic agent in vivo.

Characterization of the novel P-selectin inhibitor PSI-697 [2-(4-chlorobenzyl)-3-hydroxy-7,8,9,10-tetrahydrobenzo[h] quinoline-4-carboxylic acid] in vitro and in rodent models of vascular inflammation and thrombosis

P-selectin plays a significant and well documented role in vascular disease by mediating leukocyte and platelet rolling and adhesion. This study characterizes the in vitro activity, pharmacokinetic properties, and the anti-inflammatory and antithrombotic efficacy of the orally active P-selectin small-molecule antagonist PSI-697 [2-(4-chlorobenzyl)-3-hydroxy-7,8,9,10-tetrahydrobenzo[h] quinoline-4-carboxylic acid; molecular mass, 367.83]. Biacore and cell-based assays were used to demonstrate the ability of PSI-697 to dose dependently inhibit the binding of human P-selectin to human P-selectin glycoprotein ligand-1, inhibiting 50% of binding at 50 to 125 microM. The pharmacokinetics of PSI-697 in rats were characterized by low clearance, short half-life, low volume of distribution, and moderate apparent oral bioavailability. A surgical inflammation model, using exteriorized rat cremaster venules, demonstrated that PSI-697 (50 mg/kg p.o.) significantly reduced the number of rolling leukocytes by 39% (P < 0.05) versus vehicle control. In a rat venous thrombosis model, PSI-697 (100 mg/kg p.o.) reduced thrombus weight by 18% (P < 0.05) relative to vehicle, without prolonging bleeding time. Finally, in a rat carotid injury model, PSI-697 (30 or 15 mg/kg p.o.) administered 1 h before arterial injury and once daily thereafter for 13 days resulted in dose-dependent decreases in intima/media ratios of 40.2% (P = 0.025) and 25.7% (P = 0.002) compared with vehicle controls. These data demonstrate the activity of PSI-697 in vitro and after oral administration in animal models of both arterial and venous injury and support the clinical evaluation of this novel antagonist of P-selectin in atherothrombotic and venous thrombotic indications.