High Contrast Detection of Carotid Neothrombus with Strong Near-Infrared Absorption Selenium Nanosphere Enhanced Photoacoustic Imaging.

Background: Carotid artery thrombosis is the leading cause of stroke. Since there are no apparent symptoms in the early stages of carotid atherosclerosis onset, it causes a more significant clinical diagnosis. Photoacoustic (PA) imaging provides high contrast and good depth information, which has been used for the early detection and diagnosis of many diseases. Methods: We investigated thrombus formation by using 20% ferric chloride (FeCl3) in the carotid arteries of KM mice for the thrombosis model. The near-infrared selenium/polypyrrole (Se@PPy) nanomaterials are easy to synthesize and have excellent optical absorption in vivo, which can be used as PA contrast agents to obtain thrombosis information. Results: In vitro experiments showed that Se@PPy nanocomposites have fulfilling PA ability in the 700 nm to 900 nm wavelength range. In the carotid atherosclerosis model, maximum PA signal enhancement up to 3.44, 4.04, and 5.07 times was observed by injection of Se@PPy nanomaterials, which helped to diagnose the severity of carotid atherosclerosis. Conclusion: The superior PA signal of Se@PPy nanomaterials can identify the extent of atherosclerotic carotid lesions, demonstrating the feasibility of PA imaging technology in diagnosing carotid thrombosis lesion formation. This study demonstrates nanocomposites and PA techniques for imaging and diagnosing carotid thrombosis in vivo.

A rabbit model of cerebral microembolic signals for translational research: preclinical validation for aspirin and clopidogrel.

UNLABELLED: Essentials Microembolic signal (MES) is an independent predictor of stroke risk in patients. A rabbit model of cerebral microembolic signals was established. Therapeutic efficacy was demonstrated for aspirin and clopidogrel on microembolic signals. Potential translational value of this preclinical model of MES was demonstrated. SUMMARY: Objectives Cerebral microembolic signals (MESs) detected by transcranial Doppler (TCD) ultrasound constitute an independent predictor of stroke risk and prognosis. The aim of this study was to develop a novel preclinical model of MESs to facilitate translational research. Methods A clinical TCD ultrasound machine was used to detect MESs in the cerebral circulation of New Zealand White rabbits. Technical feasibility was assessed for the measurement of MESs in the middle cerebral artery (MCA) by TCD. FeCl3 -induced carotid arterial thrombosis was optimized for the generation of endogenous microemboli. Ascending doses of two antithrombotic agents (aspirin and clopidogrel) were evaluated individually and in combination for their effects on both arterial thrombosis and MESs in a 30% FeCl3 -induced carotid arterial thrombosis model, along with ex vivo functional assays. Results Dose-dependent FeCl3 -induced arterial thrombosis studies showed that 30% FeCl3 resulted in the most consistent and reproducible MESs in the MCA (3.3 ± 0.7 MESs h(-1) ). Ascending-dose studies showed that the effective doses for 50% inhibition (ED50 ) of thrombus formation, based on integrated blood flow and thrombus weight, respectively, were 3.1 mg kg(-1) and 4.2 mg kg(-1) orally for aspirin, and 0.3 mg kg(-1) and 0.28 mg kg(-1) orally for clopidogrel. The ED50 values for MES incidence were 12.7 mg kg(-1) orally for aspirin, and 0.25 mg kg(-1) orally for clopidogrel. Dual treatment with aspirin (5 mg kg(-1) ) and clopidogel (0.3 mg kg(-1) ) resulted in significant reductions in cerebral MESs (P < 0.05) as compared with monotherapy with either agent. Conclusions Our study demonstrated the successful establishment of the MES model in rabbits, and it may provide translational value for MESs and ischemic stroke research.

Effects of Cydonia oblonga Miller extracts on blood hemostasis, coagulation and fibrinolysis in mice, and experimental thrombosis in rats.

INTRODUCTION: Cydonia oblonga Miller (COM) is traditionally used in Uyghur medicine for the prevention of cardiovascular disease. The present study is designed to explore the effects of COM extracts on models and markers of thrombosis and related biomarkers. MATERIALS AND METHODS: 20, 40, 80 mg/kg/day COM aqueous extracts and 5mg/kg/day aspirin, orally for 14 days were compared to untreated controls in mice on bleeding and clotting times, using the tail cutting and glass slide methods and for death rates in collagen-epinephrine pulmonary thrombosis, thrombolysis in vitro and euglobulin lysis time (ELT). In rats, common carotid artery FeCl3-induced thrombus and inferior vena cava thrombosis occlusion time, plasma concentrations of thromboxane B2 (TXB2) and 6-keto-prostaglandine F1α (6-keto-PGF1α) were measured. RESULTS AND CONCLUSION: Compared to controls, COM extracts dose-dependently prolonged bleeding by 2.17, 2.78 and 3.63 times, vs. aspirin 2.58, and the clotting time by 1.44, 2.47 and 2.48 times, vs. aspirin 1.91. COM reduced pulmonary embolus mortality by 27, 40 and 53%, vs. 47% for aspirin. COM dose-dependently increased thrombolysis by 45, 55 and 63%, vs. 56% for aspirin, and shortened ELT to 71, 61 and 43%, vs. 43% for aspirin. In rats, venous occlusion time was prolonged. Arterial and venous thrombus weights were dose-dependently reduced in COM groups. TXB2 decreased and 6-keto-PGF1α increased with COM and aspirin, with an association between 6-keto-PGF1α/TXB2 and arterial or venous thrombus weight for all products, and for occlusion time with COM but not for aspirin. CONCLUSION: We confirm the experimental effects of COM on hemostasis and thrombosis. Further exploration of putative clinical effects appear justified.

Troubleshooting the rabbit ferric chloride-induced arterial model of thrombosis to assess in vivo efficacy of antithrombotic drugs.

INTRODUCTION: The FeCl3-induced arterial model of thrombosis is one of the most widely used animal models to assess arterial efficacy of new antithrombotic drug candidates. This model is well-established in rodents but in a less extent in the rabbit. In this work, we present a methodology for a rabbit FeCl3-induced arterial model of thrombosis derived from our troubleshooting which allows the generation of reliable efficacy data for new antithrombotic drug candidates. METHODS: Rabbits were administered with heparin 4.5U/kg/min, argatroban 10µg/kg/min or saline by intravenous infusion. The blood flow was monitored using a Doppler flow probe. The time from the application of FeCl3 to the recorded zero blood flow was defined as the time to occlusion, with a maximum recording time of 60min post-FeCl3 application. After 30min of infusion, thrombosis was induced by wrapping a FeCl3-saturated filter paper around the carotid artery caudal to the flow probe. Animals were subject to exclusion criteria based on the visual aspect of the artery FeCl3-induced injury and based on changes in blood flow upon FeCl3 application. RESULTS: Following the application of FeCl3, a mean time to occlusion for saline, heparin and argatroban of 24.3±1.8, 52.5±4.8 and 53.5±4.5min was obtained, respectively. Mean time to occlusion for heparin and argatroban administered groups was significantly different when compared to the saline-treated group (p<0.05). These results for the test compounds represent approximately 80% of the maximum possible prolongation. DISCUSSION: The rabbit FeCl3-induced arterial model of thrombosis presented in this paper derived from our troubleshooting is sensitive and reproducible for the generation of accurate and reliable efficacy data in the assessment of new antithrombotic agents in preclinical drug development.

Endogenous and natural complement inhibitor attenuates myocardial injury and arterial thrombogenesis.

BACKGROUND: Coagulation disorders and reperfusion of ischemic myocardium are major causes of morbidity and mortality. Lectin pathway initiation complexes are composed of multimolecular carbohydrate recognition subcomponents and 3 lectin pathway-specific serine proteases. We have recently shown that the lectin pathway-specific carbohydrate recognition subcomponent mannose-binding lectin plays an essential role in the pathophysiology of thrombosis and ischemia/reperfusion injury. Thus, we hypothesized that the endogenous mannose-binding lectin (MBL)/ficolin-associated protein-1 (MAP-1) that inhibits complement activation in vitro also could be an in vivo regulator by attenuating myocardial schema/reperfusion injury and thrombogenesis when used at pharmacological doses in wild-type mice. METHODS AND RESULTS: In 2 mouse models, MAP-1 preserves cardiac function, decreases infarct size, decreases C3 deposition, inhibits MBL deposition, and prevents thrombogenesis. Furthermore, we demonstrate that MAP-1 displaces MBL/ficolin-associated serine protease (MASP)-1, MASP-2, and MASP-3 from the MBL complex. CONCLUSIONS: Our results suggest that the natural, endogenous inhibitor MAP-1 effectively inhibits lectin pathway activation in vivo. MAP-1 at pharmacological doses represents a novel therapeutic approach for human diseases involving the lectin pathway and its associated MASPs.

Murine model of ferric chloride-induced vena cava thrombosis: evidence for effect of potato carboxypeptidase inhibitor.

BACKGROUND/OBJECTIVE: Thrombin-activatable fibrinolysis inhibitor (TAFI) is a plasma carboxypeptidase that renders a fibrin-containing thrombus less sensitive to lysis. In the present study, we describe the development of a murine model of vena cava thrombosis and its use to characterize the antithrombotic activity of potato carboxypeptidase inhibitor (PCI) of TAFIa (activated TAFI) in mice. METHODS/RESULTS: Vena cava thrombosis was induced by various concentrations of FeCl(3) in C57BL/6 mice. A relatively mild stimulus (3.5% FeCl(3)) induced thrombosis that was consistent and sensitive to reference antithrombotic agents such as clopidogrel and heparin. Dose-response studies identified a PCI dose (5 mg kg(-1) bolus plus 5 mg kg(-1) h(-1), i.v.) that produced a maximum 45% decrease in vena cava thrombus mass as assessed by protein content (n = 8, P < 0.01 compared to vehicle) in the 3.5% FeCl(3)-induced model without exogenous tissue plasminogen activator administration. In contrast, PCI had no effect on 3.5% FeCl(3)-induced carotid artery thrombosis in mice. In a tail transection bleeding model, the 5 mg kg(-1) bolus plus 5 mg kg(-1) h(-1) dose of PCI increased tail-bleeding time up to 3.5 times control (n = 8, P < 0.05). The ex vivo activity of antithrombotic doses of PCI was also demonstrated by the enhanced lysis of whole blood clots formed in a thrombelastograph with the addition of a sub-threshold concentration of tPA. CONCLUSION: These studies provide evidence for a role of TAFIa in venous thrombosis in mice, and describe an optimized vena cava injury model appropriate for the evaluation of antithrombotic drugs and the characterization of novel therapeutic targets.

Effects of scorpion venom bioactive polypolypeptides on platelet aggregation and thrombosis and plasma 6-keto-PG F1alpha and TXB2 in rabbits and rats.

Effects of scorpion venom active polypeptide (SVAP) from scorpion venom of Buthus Martensii Karsch of Chinese on platelet aggregation in ex vivo and vitro in rabbits, thrombosis in carotid artery of rats and plasma 6-keto-PG F1alpha and TXB2 in rats were studied by the turbidimetry, the duplicated thrombosis model by electrostimulation and RIA, respectively. The results showed that SVAP 0.125, 0.25, 0.5 mg/ml inhibited significantly the rabbit platelet aggregation triggered by 0.3 U/ml thrombin, 10 microM ADP in vitro (P<0.05 or 0.01) and SVAP at the dose of 0.32, 0.64 mg/kg iv prolonged distinctively the occlusion time of thrombosis that were induced by electrical stimulation. Increased% of 0.16, 0.32 and 0.64 mg/kg were 30.16, 71.74, 98.27%, respectively, which showed a good dose-effect relationship. SVAP 0.22 mg/ml (in vitro) or 0.2, 0.4 mg/kg (in ex vivo) could obviously increase the plasma concentration of 6-keto-PG F1alpha, but slightly effect rats plasma concentration of TXB2 in vitro and in ex vivo and significantly increase of value of PG I2/TXA2, which suggested that the mechanism of the antithrombotic action of SVAP is related to the resistance against platelet aggregation, increase of the concentration of PG I2 in plasma.

A new animal model of thrombophilia confirms that high plasma factor VIII levels are thrombogenic.

The thrombotic risk associated with elevated plasma levels of clotting factor VIII (FVIII) was investigated in a mouse model of thrombophilia. After the intravenous injection of recombinant human FVIII and/or of purified FVIII-free human von Willebrand factor (vWF), a controlled mild injury was inflicted on the carotid artery of FVB mice by irradiation with filtered green light in combination with intravenous injection of the dye rose bengal. Formation of a platelet-rich thrombus was continuously monitored for 40 min via transillumination and the thrombus size was measured via image analysis. Administration of recombinant human FVIII at 40 microg/kg led to initial FVIII plasma activities equivalent to 250% of normal human plasma FVIII activity and significantly enhanced thrombus size. Immunohistochemical staining illustrated the accumulation of FVIII within the thrombi. Human vWF, even at 10 mg/kg, had no effect on thrombus formation. The thrombotic tendency induced by FVIII was significantly inhibited by the administration of human vWF in a dose-dependent manner. Separate plasma measurements revealed that human FVIII has comparable affinities for human and murine vWF but that human vWF does not effectively bind murine platelets. The inhibition by human vWF of the thrombotic tendency induced by human FVIII could therefore be explained by a lack of accumulation of FVIII within the developing thrombus because of the reduced affinity of human vWF for murine platelets and the reduced occupancy of murine von Willebrand factor by human FVIII after injection of human vWF. These results show that vWF actively participates in FVIII accumulation in the arterial thrombus and provide experimental evidence for epidemiological findings that elevated plasma FVIII levels are associated with an increased thrombotic risk, also in arteries.

Thrombolytic effect of nattokinase on a chemically induced thrombosis model in rat.

Nattokinase is a new fibrinolytic enzyme which cleaves directly cross-linked fibrin in vitro. In this study, we investigated the thrombolytic effect of nattokinase on a thrombus in the common carotid artery of rat in which the endothelial cells of the vessel wall were injured by acetic acid. When a section of occluded vessel was stained for CD61 antigen by immunofluorescence utilizing a monoclonal antibody, the antigen was localized around the surface of the occluded blood vessels. This result suggests that the occlusive thrombosis was caused by platelet aggregation. In addition, thrombolysis with urokinase (UK; 50000 IU/kg, i.v.) or tissue plasminogen activator (tPA; 13300 IU/kg, i.v.) in our model was observed to restore the blood flow over a 60 min monitoring period. The results indicate that our chemically induced model is useful for screening and evaluating a thrombolytic agent. We evaluated the thrombolytic activity of nattokinase using this model and compared it with fibrino(geno)lytic enzyme, plasmin or elastase. On a molar basis, the recovery of the arterial blood flow with nattokinase, plasmin and elastase were 62.0 +/- 5.3%, 15.8 +/- 0.7% and 0%, respectively. The results indicate that the thrombolytic activity of nattokinase is stronger than that of plasmin or elastase in vivo.

Effect of Y-20811, a thromboxane synthetase inhibitor, on photochemically induced cerebral embolism in rabbits.

The effect of Y-20811, a selective thromboxane A2 synthetase inhibitor, was investigated on cerebral embolism using a new model of embolic cerebral infarction in rabbits. Most of cerebral infarctions were observed in the hemisphere, ipsilateral to the irradiated carotid artery. Cerebral infarction, ranging from 0.2 to 1.0 mm in size, appeared only on the surface of the cortex. The platelet emboli were identified in the carotid artery and cortex arteriole by light microscopy. In our study, 83% of the control group had cerebral infarction. Y-20811 significantly suppressed the infarction number and the incidence at doses of 1 mg/kg and 10 mg/kg (p.o.), respectively. Aspirin significantly inhibited the infarction number at a dose of 10 mg/kg, but its inhibitory effect decreased at 30 mg/kg. Ticlopidine showed no effect even at a dose of 300 mg/kg. These results indicate that Y-20811 may be useful in preventing embolic cerebral infarction and transient ischemic attacks.