Unified Methodology for the Primary Preclinical In Vivo Screening of New Anticoagulant Pharmaceutical Agents from Hematophagous Organisms.

The development of novel anticoagulants requires a comprehensive investigational approach that is capable of characterizing different aspects of antithrombotic activity. The necessary experiments include both in vitro assays and studies on animal models. The required in vivo approaches include the assessment of pharmacokinetic and pharmacodynamic profiles and studies of hemorrhagic and antithrombotic effects. Comparison of anticoagulants with different mechanisms of action and administration types requires unification of the experiment scheme and its adaptation to existing laboratory conditions. The rodent thrombosis models in combination with the assessment of hemostasis parameters and hematological analysis are the classic methods for conducting preclinical studies. We report an approach for the comparative study of the activity of different anticoagulants in vivo, including the investigation of pharmacodynamics and the assessment of hemorrhagic effects (tail-cut bleeding model) and pathological thrombus formation (inferior vena cava stenosis model of venous thrombosis). The reproducibility and uniformity of our set of experiments were illustrated on unfractionated heparin and dabigatran etexilate (the most common pharmaceuticals in antithrombic therapy) as comparator drugs and an experimental drug variegin from the tick Amblyomma variegatum. Variegin is notorious since it is a potential analogue of bivalirudin (Angiomax, Novartis AG, Basel, Switzerland), which is now being actively introduced into antithrombotic therapy.

Efficacy of Ficus tikoua Bur. extract in ethylene glycol-induced urolithiasis model in SD rats.

The development of new herbal preparations for the treatment of urolithiasis is an urgent task of medical science. Ficus have attracted the attention of pharmacologists due to a wide range of biological properties, including antioxidant, anti-inflammatory, antibacterial and antifungal activity. We studied the effectiveness of Ficus tikoua Bur. in SD rats in which urolithiasis was induced by 6 weeks of oral administration of ethylene glycol 0.5% ad libitum instead of drinking water. Administration of the extract of Ficus tikoua Bur., as well as comparative drug Cystone® after modeling of urolithiasis lead to the restoration of diuresis and the concentration of inorganic phosphates starting from the 6th week of the experiment. The use of the Ficus tikoua Bur. extract for 6 weeks, both during the modeling of urolithiasis and during the recovery period, led to the restoration of the percentage of lymphocytes in the blood, content of sodium, chlorine and inorganic phosphates in the blood to the control level. Thus, the extract of Ficus tikoua Bur. seems to be a promising drug for effective treatment of the initial stages of the development of urolithiasis.

Screening of the Promising Direct Thrombin Inhibitors from Haematophagous Organisms. Part I: Recombinant Analogues and Their Antithrombotic Activity In Vitro.

The success in treatment of venous thromboembolism and acute coronary syndromes using direct thrombin inhibitors has stimulated research aimed at finding a new anticoagulant from haematophagous organisms. This study deals with the comparison between hirudin-1 from Hirudomedicinalis(desirudin), being the first-known and most well-studied natural anticoagulant, along with recombinant analogs of haemadin from the leech Haemadipsa sylvestris, variegin from the tick Amblyomma variegatum, and anophelin from Anopheles albimanus. These polypeptides were chosen due to their high specificity and affinity for thrombin, as well as their distinctive inhibitory mechanisms. We have developed a universal scheme for the biotechnological production of these recombinant peptides as pharmaceutical substances. The anticoagulant activities of these peptides were compared using the thrombin amidolytic activity assay and prolongation of coagulation time (thrombin time, prothrombin time, and activated partial thromboplastin time) in mouse and human plasma. The preliminary results obtained suggest haemadin as the closest analog of recombinant hirudin-1, the active substance of the medicinal product Iprivask (Aventis Pharmaceuticals, USA) for the prevention of deep venous thrombosis in patients undergoing elective hip or knee replacement surgery. In contrast, variegin can be regarded as a natural analog of bivalirudin (Angiomax, The Medicines Company), a synthetic hirudin-1 derivative certified for the treatment of patients undergoing percutaneous coronary intervention and of patients with unstable angina pectoris after percutaneous transluminal coronary angioplasty.

Azemiopsin, a Selective Peptide Antagonist of Muscle Nicotinic Acetylcholine Receptor: Preclinical Evaluation as a Local Muscle Relaxant.

Azemiopsin (Az), a linear peptide from the Azemiops feae viper venom, contains no disulfide bonds, is a high-affinity and selective inhibitor of nicotinic acetylcholine receptor (nAChR) of muscle type and may be considered as potentially applicable nondepolarizing muscle relaxant. In this study, we investigated its preclinical profile in regard to in vitro and in vivo efficacy, acute and chronic toxicity, pharmacokinetics, allergenic capacity, immunotoxicity and mutagenic potency. The peptide effectively inhibited (IC50 ~ 19 nM) calcium response of muscle nAChR evoked by 30 µM (EC100) acetylcholine but was less potent (IC50 ~ 3 µM) at α7 nAChR activated by 10 µM (EC50) acetylcholine and had a low affinity to α4ß2 and α3-containing nAChR, as well as to GABAA or 5HT3 receptors. Its muscle relaxant effect was demonstrated at intramuscular injection to mice at doses of 30-300 µg/kg, 30 µg/kg being the initial effective dose and 90 µg/kg-the average effective dose. The maximal muscle relaxant effect of Az was achieved in 10 min after the administration and elimination half-life of Az in mice was calculated as 20-40 min. The longest period of Az action observed at a dose of 300 µg/kg was 55 min. The highest acute toxicity (LD50 510 µg/kg) was observed at intravenous injection of Az, at intramuscular or intraperitoneal administration it was less toxic. The peptide showed practically no immunotoxic, allergenic or mutagenic capacity. Overall, the results demonstrate that Az has good drug-like properties for the application as local muscle relaxant and in its parameters, is not inferior to the relaxants currently used. However, some Az modification might be effective to extend its narrow therapeutic window, a typical characteristic and a weak point of all nondepolarizing myorelaxants.

Using Tiletamine-Zolazepam-Xylazine Anesthesia Compared to CO2-inhalation for Terminal Clinical Chemistry, Hematology, and Coagulation Analysis in Mice.

INTRODUCTION: It is important that the method of anesthesia of mice does not considerably alter the animal's physiological and metabolic status before terminal blood sampling taken in order to analyze clinical pathology parameters. METHODS: Hematology, hemostasis, and clinical chemistry parameters were compared in male and female BALB/c mice exposed to either tiletamine-zolazepam-xylazine (TZX) anesthesia or euthanasia in carbon dioxide (CO2) chamber to reveal an alternative method of anesthesia vs. the recommended CO2 inhalation. Blood samples were taken from the inferior vena cava. RESULTS: Clinical blood parameters in mice exposed to CO2 inhalation or TZX anesthesia proved to be substantially different. The TZX group had lower activated partial thromboplastin time (APTT) and fibrinogen (statistically in males and tending in females) and lower platelets (PLT), red blood cells (RBC), hemoglobin (HGB), and white blood cells (WBC) in both sexes. TZX anesthesia resulted in lower blood serum concentrations of total protein, albumin and globulins, creatinine in males (higher in females); cholesterol, triglycerides, alanine aminotransferase (АLT) and alkaline phosphatase (AP) in both sexes, and bilirubin in males. The calcium level decreased in TZX-anesthetized males and females while the phosphates decreased only in females. The volume of serum obtained from females of TZX group was approximately two times higher than in the CO2-anesthetized group, with the degree of hemolysis tending to decrease. DISCUSSION: The studied method of mouse anesthesia, followed by terminal blood sampling and analysis of clinical pathology parameters, suggests that TZX is a good alternative to CO2 inhalation in toxicological and other nonclinical studies. The differences in hemostasis, hematology, and clinical chemistry parameters between these groups are supposedly associated with alterations in physiological and metabolic status of mice under conditions of increasing hypoxia, respiratory standstill, and circulatory arrest after CO2 inhalation.