Thrombolytic effects of a combined therapy with targeted microbubbles and ultrasound in a 6 h cerebral thrombosis rabbit model.

Our previous study has shown that P1 polypeptide-loaded microbubbles (clot-targeted microbubbles, TMB) are effective for thrombolysis and recanalization in a 0.5 h cerebral thrombosis rabbit model when combined with low-frequency ultrasound (LFUS, 0.8 MHz). However, the thrombolytic effects of TMB combined with LFUS are still unclear in a 6 h cerebral thrombosis rabbit model, which closely resembles human embolic stroke. Aiming to extend the 3 h therapeutic window limitation of thrombolytic drugs, a 6 h cerebral thrombosis model of common carotid artery (CCA) occlusion was induced in rabbits, and thrombolysis using TMB by intra-arterial (IA) and intravenous (IV) application combined with LFUS was then compared to untargeted microbubbles (UTMB) and recombinant tissue plasminogen activator (rt-PA). The patency score and thrombolysis in brain ischemia (TIBI) in IA TMB combined with LFUS (IA TMB/LFUS) were significantly higher compared to the IA normal saline control with LFUS (IA SC/LFUS) (both P < 0.05) and IA UTMB plus LFUS (IA UTMB/LFUS) (both P < 0.05), respectively. The recanalization rate in the IA TMB/LFUS group (66.67%) was significantly higher compared to the IA SC/LFUS group (12.50%, P < 0.05). The patency score, TIBI and recanalization rate of IA TMB/LFUS were higher than in the IV TMB/LFUS group, but there was no significant difference between the two groups, which was similar to the infarction ratio. TMB/LFUS is an effective and safe therapy for thrombolysis in a 6 h cerebral thrombosis rabbit model, and the IA TMB/LFUS group was slightly better than the IV TMB/LFUS group.

Cold exposure does not decrease serum leptin concentration, but increases energy intake and thermogenic capacity in pregnant Brandt's voles (Lasiopodomys brandtii).

In most mammals, maternal body mass and fat mass increase during pregnancy due to hyperphagia. These physiological changes provide the fetus with energy and nutrients and prepare the mother for the high energetic demands of lactation. In the present study, metabolic changes in response to cold and pregnancy were examined in female Brandt's voles (Lasiopodomys brandtii). At 23+/-1 degrees C, the voles increased body mass and deposited body fat during pregnancy. However, at 5+/-1 degrees C pregnant voles did not deposit body fat even though energy intake increased above the level in the warm. Serum leptin concentration increased during pregnancy and was not influenced by cold exposure. Thermogenic capacity, as indicated by uncoupling protein 1 (UCP1) content in brown adipose tissue (BAT), increased in cold-exposed pregnant voles. The number and mass of fetuses were not affected by cold exposure. Our data may indicate the importance of an increased serum leptin concentration for a successful outcome of the pregnancy and also the independence of leptin secretion from body fat in pregnant voles. It also implies the need to develop central leptin resistance with respect to control of energy balance for pregnant voles.

Antithrombotic effect of Z4A5 on coronary thrombosis in a canine model of acute unstable angina.

BACKGROUND AND PURPOSE: The glycoprotein IIb/IIIa receptor is the final common pathway of platelet aggregation, regardless of the agonist, and thus represents an ideal therapeutic target for blocking coronary thrombosis. In this study, the anti-platelet and antithrombotic actions of Z4A5, a new glycoprotein IIb/IIIa receptor inhibitor, were evaluated in a canine model of acute unstable angina. EXPERIMENTAL APPROACH: Z4A5 was given i.v. as a bolus followed by 60 min of continuous infusion at doses of 30 µg·kg⁻¹ + 1 µg·kg⁻¹·min⁻¹, 30 µg·kg⁻¹ + 5 µg·kg⁻¹·min⁻¹ or 300 µg·kg⁻¹ + 5 µg·kg⁻¹·min⁻¹. Its antithrombotic effect was evaluated in a model of coronary thrombosis, the injured, stenosed left circumflex coronary artery, in which platelet-dependent cyclic flow reductions (CFRs) were induced by vascular compression and constriction to simulate clinical acute unstable angina. Platelet aggregation and coagulation parameters were determined in platelet-rich plasma and platelet poor plasma respectively. KEY RESULTS: The Z4A5 infusion induced a dose-dependent reduction in CFR frequency, which returned to baseline levels after the termination of the infusion at low doses. At medium dose that inhibited most part of platelet aggregation, it increased tongue bleeding time marginally with no dramatic changes in haemodynamic and coagulation parameters. Furthermore, the inhibition of ADP-induced platelet aggregation and prolonged bleeding time observed during Z4A5 infusion reverted to baseline levels after the termination of the infusion. CONCLUSIONS AND IMPLICATIONS: Z4A5 is an effective antithrombotic agent for coronary artery thrombosis with a rapid-on and rapid-off pharmacological profile, and could be used as an alternative treatment of coronary artery ischaemic syndromes.

Antithrombotic activity of Z4A5, a new platelet glycoprotein IIb/IIIa receptor antagonist evaluated in a rabbit arteriovenous shunt thrombosis model.

INTRODUCTION: The antithrombotic effect of the glycopreotein IIb/IIIa (GP IIb/IIIa) receptor antagonist Z4A5, exert alone or combination with heparin, and/or aspirin, was examined in a rabbit arteriovenous shunt thrombosis model. MATERIALS AND METHODS: Thrombosis was induced by the insertion of a silk thread (thrombogenic substrate) into an extracorporeal shunt. Before and after drug administration (0, 5, and 15 min), ex vivo adenosine diphosphate (ADP)-induced platelet aggregation and coagulation parameters (prothrombin time (PT) and activated partial thromboplastin time (APTT)) were determined in platelet-rich plasma (PRP) and platelet poor-plasma (PPP), respectively. RESULTS: Our data demonstrated that, compared to the control, Z4A5 decreased the thrombus weight (31-65%) in a dose-dependent manner and inhibited ADP-induced platelet aggregation (47-98%) 5 min after Z4A5 administration (25-100 mg/kg). However, PT and APTT remained stable, even at the highest dose (100 mg/kg). Heparin (100 U/kg) and aspirin (15 mg/kg) also significantly reduced thrombus mass, but this effect was accompanied by an increase of APTT by heparin. Furthermore, the combination of heparin (100 U/kg) and a low dose of Z4A5 (25 mg/kg) failed to produce an additional benefit beyond that provided by heparin or Z4A5 alone, whereas Z4A5 (25 mg/kg) plus aspirin (15 mg/kg) potentiated the antithrombotic effects of both compounds without further increasing the values of coagulation. CONCLUSIONS: Our results indicate that Z4A5 is an effective antithrombotic agent with no significant effects on values of coagulation. Furthermore, Z4A5 can potentiate these antithrombotic effects when prescribed with aspirin.

The preparation of a new self-made microbubble-loading urokinase and its thrombolysis combined with low-frequency ultrasound in vitro.

Urokinase (uPA) is used widely for thrombosis therapy in the clinic. However, ways to minimize its adverse effect of hemorrhage are still being studied. As a new technique for the local delivery of genes and drugs, ultrasound (US) contrast agents, microbubbles (MBs), have been mentioned. The purpose of this study is to explore a more efficacious and safer thrombolytic method by preparing three groups of self-made microbubble-loading uPA (uPA-MBs) (1 uPA-MBs, 5 uPA-MBs and 10 uPA-MBs) using freeze-drying methods and measuring their thrombolysis when combined in vitro with low-frequency US. The results showed the mean concentration, mean diameter, pH value and encapsulation efficiency of uPA of the three groups of uPA-MBs were approximately 2.08-2.82 × 10(8)/mL, ∼3.13 µm, 6.89-6.99 and from (78.08% ± 0.57%) to (57.23% ± 0.94%), respectively. Under US exposure, the loaded uPA demonstrated bioactivity by agarose fibrin plate and in vitro thrombolysis of the three uPA-MBs also showed higher effects than in the group of those who received uPA-MBs alone, the control group or the US group. In conclusion, the physiochemical properties of these self-made uPA-MBs are suitable for intravenous administration but 1 uPA-MB and 5 uPA-MBs are better than 10 uPA-MBs. uPA-MBs combined with US can decrease the in vitro dosage of uPA for thrombolysis.