Antithrombotic effect of PMC, a potent alpha-tocopherol analogue on platelet plug formation in vivo

A novel fibrinolytic enzyme from marine Pseudomonas aeruginosa KU1 and its rapid in vivo thrombolysis with little haemolysis

A direct acting, extracellular, fibrinolytic enzyme, ~50 KDa from marine Pseudomonas aeruginosa KU1 (PEKU1), was purified. It was found to be a metalloprotease. 60% of the total activity of the purified PEKU1 was retained at 70 °C and the enzyme was practically denatured at 80 °C, 2 h. Metal ions, such as Na⁺, K⁺ and Co²⁺, were found to enhance slightly the fibrinolytic activity, while Fe²⁺, Mn²⁺ and Zn²⁺ were found to be inhibiting. The enzyme showed only less than 5% haemolysis, suggesting its thrombolytic administration safe. Tryptic digestion revealed its similarity to serralysin like alkaline protease of P. aeruginosa. In silico studies showed its binding of protease substrates and fibrin D-dimer in its active site. High affinity binding of bradykinin to the active site of PEKU1, confirmed by in vitro cleaving, suggested its future use as an analgesic. The purified enzyme with Na⁺, K⁺ and Co²⁺, and without Fe²⁺, Mn²⁺ and Zn²⁺ showed thrombolysis in vivo in carrageenan induced murine tail thrombolytic model. The enzyme PEKU1, a novel protease from marine isolate Pseudomonas aeruginosa KU1 has great potential to be developed as a therapeutic agent to combat cardiovascular diseases, as well as analgesic and anti-inflammatory drug in appropriate sites.

Preventive Effect of Aspirin Eugenol Ester on Thrombosis in κ-Carrageenan-Induced Rat Tail Thrombosis Model

Based on the prodrug principle, aspirin eugenol ester (AEE) was synthesized, which can reduce the side effects of aspirin and eugenol. As a good candidate for new antithrombotic and anti-inflammatory medicine, it is essential to evaluate its preventive effect on thrombosis. Preventive effect of AEE was investigated in κ-carrageenan-induced rat tail thrombosis model. AEE suspension liquids were prepared in 0.5% sodium carboxymethyl cellulose (CMC-Na). AEE was administrated at the dosage of 18, 36 and 72 mg/kg. Aspirin (20 mg/kg), eugenol (18 mg/kg) and 0.5% CMC-Na (30 mg/kg) were used as control drug. In order to compare the effects between AEE and its precursor, integration of aspirin and eugenol group (molar ratio 1:1) was also designed in the experiment. After drugs were administrated intragastrically for seven days, each rat was injected intraperitoneally with 20 mg/kg BW κ-carrageen dissolved in physiological saline to induce thrombosis. The length of tail-thrombosis was measured at 24 and 48 hours. The blank group just was given physiological saline for seven days without κ-carrageenan administrated. The results indicated that AEE significantly not only reduced the average length of thrombus, PT values and FIB concentration, but also reduced the red blood cell (RBC), hemoglobin (HGB), hematocrit (HCT) and platelet (PLT). The effects of AEE on platelet aggregation and anticoagulant in vitro showed that AEE could inhibit adenosine diphosphate (ADP)-induced platelet aggregation as dose-dependence but no notable effect on blood clotting. From these results, it was concluded that AEE possessed positive effect on thrombosis prevention in vivo through the reduction of FIB, PLT, inhibition of platelet aggregation and the change of TT and PT values.

Inhibition of ADP-induced platelet aggregation and involvement of non-cellular blood chemical mediators are responsible for the antithrombotic potential of the fruits of Lagenaria siceraria

AIM

The fruits of Lagenaria siceraria (Molina) Standl. (Cucurbitaceae), a commonly used vegetable, are reported to possess various medicinal properties. In previous studies, the fibrinolytic potential of an ethanolic extract of fruits of Lagenaria siceraria was investigated in comparison with kaempferol isolated from it. The aim of the present study was to explore its mechanistic antithrombotic potential and antiplatelet activity using a wide dose range in different in vitro and in vivo models, and to quantify the total phenolic, flavonoid, and kaempferol contents using a colorimetric method.

METHOD

The antithrombotic potential was investigated using tail bleeding time in mice, a plasma recalcification assay, and pulmonary thromboembolism in mice. The antiplatelet activity was studied using an in vitro model to investigate IC50 value.

RESULTS

A significant amount of total phenols, flavonoids, and kaempferol was quantified in L. siceraria ethanolic extract. An ethanolic extract of the fruits of L. siceraria showed a significant increase in tail bleeding time and plasma recalcification time, significant protection against ADP induced pulmonary thromboembolism in mice, and also inhibited the platelet aggregation induced by ADP in vitro. The study suggested that the fruits of L. siceraria exhibit significant antithrombotic potential due to inhibition of ADP-mediated platelet aggregation and the involvement of various non-cellular chemical mediators of blood.

CONCLUSION

This finding may be helpful in treating the serious consequences of the thrombus formed in blood vessels which include atherothrombotic diseases, such as myocardial or cerebral infarction. So, further investigation should be done for revealing exact mechanism of action behind these types of activities.

PMC, a potent hydrophilic α-tocopherol derivative, inhibits NF-κB activation via PP2A but not IκBα-dependent signals in vascular smooth muscle cells

The hydrophilic α-tocopherol derivative, 2,2,5,7,8-pentamethyl-6-hydroxychromane (PMC), is a promising alternative to vitamin E in clinical applications. Critical vascular inflammation leads to vascular dysfunction and vascular diseases, including atherosclerosis, hypertension and abdominal aortic aneurysms. In this study, we investigated the mechanisms of the inhibitory effects of PMC in vascular smooth muscle cells (VSMCs) exposed to pro-inflammatory stimuli, lipopolysaccharide (LPS) combined with interferon (IFN)-γ. Treatment of LPS/IFN-γ-stimulated VSMCs with PMC suppressed the expression of inducible nitric oxide synthase (iNOS) and matrix metalloproteinase-9 in a concentration-dependent manner. A reduction in LPS/IFN-γ-induced nuclear factor (NF)-κB activation was also observed in PMC-treated VSMCs. The translocation and phosphorylation of p65, protein phosphatase 2A (PP2A) inactivation and the formation of reactive oxygen species (ROS) were significantly inhibited by PMC in LPS/IFN-γ-activated VSMCs. However, neither IκBα degradation nor IκB kinase (IKK) or ribosomal s6 kinase-1 phosphorylation was affected by PMC under these conditions. Both treatments with okadaic acid, a PP2A-selective inhibitor, and transfection with PP2A siRNA markedly reversed the PMC-mediated inhibition of iNOS expression, NF-κB-promoter activity and p65 phosphorylation. Immunoprecipitation analysis of the cellular extracts of LPS/IFN-γ-stimulated VSMCs revealed that p65 colocalizes with PP2A. In addition, p65 phosphorylation and PP2A inactivation were induced in VSMCs by treatment with H₂O₂, but neither IκBα degradation nor IKK phosphorylation was observed. These results collectively indicate that the PMC-mediated inhibition of NF-κB activity in LPS/IFN-γ-stimulated VSMCs occurs through the ROS-PP2A-p65 signalling cascade, an IKK-IκBα-independent mechanism. Therapeutic interventions using PMC may therefore be beneficial for the treatment of vascular inflammatory diseases.

Comparison of free radical formation induced by baicalein and pentamethyl-hydroxychromane in human promyelocytic leukemia cells using electron spin resonance

Baicalein and pentamethyl-hydroxychromane (PMC) have been investigated for use as antioxidants. However, antioxidants may stimulate free radical formation under certain conditions. The aim of our study was to determine whether PMC and baicalein exhibit both pro-oxidant and antioxidant activities in human promyelocytic leukemia (HL-60) cells. In this study, electron spin resonance spectrometry was used to investigate the effects of baicalein and PMC on free radical formation. In HL-60 cells, baicalein and PMC produced hydroxyl and phenoxyl radicals, respectively, but each inhibited radical formation by the other. The PMC pro-oxidant activity required H₂O₂, whereas baicalein produced hydroxyl radicals during the cell resting state only. The antioxidant effect of baicalein on PMC-induced oxidative stress in HL-60 cells may involve myeloperoxidase inhibition, which produces the myeloperoxidase-protein radical. Our investigation of the antioxidant effects of baicalein on arachidonic acid (AA)-induced oxidative stress in HL-60 cells showed that the baicalein-phenoxyl radical was the primary product, and that either carbon-centered or acyl radicals were the secondary products. However, the antioxidant effects of PMC on AA-induced oxidative stress produced only nonradical products. In conclusion, we showed that baicalein displayed both pro-oxidant and antioxidant activities in HL-60 cells. PMC exhibited no pro-oxidant activity during the cells’ resting state but produced the PMC-phenoxyl radical in the presence of H₂O₂. The reaction of baicalein with AA in HL-60 cells produced baicalein-derived phenoxyl radicals that may initiate various pro-oxidative reactions. However, PMC does not produce radicals when it acts as an antioxidant. Thus, PMC is more beneficial as an antioxidant than baicalein.

C560Rβ3 caused platelet integrin αII b β3 to bind fibrinogen continuously, but resulted in a severe bleeding syndrome and increased murine mortality

BACKGROUND AND OBJECTIVES

β(3)-Deficient megakaryocytes were modified by human β(3)-lentivirus transduction and transplantation to express sufficient levels of a C560Rβ(3) amino acid substitution, for investigation of how an activated αII b β(3) conformation affects platelets in vivo in mice.

PATIENT/METHODS

As in our previous report of an R560β(3) mutation in a patient with Glanzmann thrombasthenia, R560β(3) murine platelets spontaneously bound antibody that only recognizes activated αII b β3 bound to its ligand, fibrinogen.

RESULTS

With this murine model, we showed that αII b -R560β3 mutation-mediated continuous binding of fibrinogen occurred in the absence of P-selectin surface expression, indicating that the integrin was in an active conformation, although the platelets circulated in a quiescent manner. Remarkably, only 35% of R560β(3) 'mutant' mice survived for 6 months after transplantation, whereas 87% of C560β(3) 'wild-type' mice remained alive. Pathologic examination revealed that R560β(3) mice had enlarged spleens with extramedullary hematopoiesis and increased hemosiderin, indicating hemorrhage. R560β(3) megakaryocytes and platelets showed abnormal morphology and irregular granule distribution. Interestingly, R560β(3) washed platelets could aggregate upon simultaneous addition of fibrinogen and physiologic agonists, but aggregation failed when platelets were exposed to fibrinogen before activation in vitro and in vivo.

CONCLUSIONS

The results demonstrate that continuous occupancy of αIIb β3 with fibrinogen disrupts platelet structure and function, leading to hemorrhagic death consistent with Glanzmann thrombasthenia rather than a thrombotic state.

Cloning of a fibrinolytic enzyme (subtilisin) gene from Bacillus subtilis in Escherichia coli

Several investigations are being pursued to enhance the efficacy and specificity of fibrinolytic therapy. In this regard, microbial fibrinolytic enzymes attracted much more medical interests during these decades. Subtilisin, a member of subtilases (the superfamily of subtilisin-like serine proteases) and also a fibrinolytic enzyme is quite common in Gram-positive bacteria, and Bacillus species stand out in particular, as many extracellular and even intracellular variants have been identified. In the present work, the subtilisin gene from Bacillus subtilis PTCC 1023 was cloned into the vector pET-15b and expressed in Escherichia coli strain BL21 (DE3). Total genomic DNA were isolated and used for PCR amplification of the subtilisin gene by means of the specific primers. SDS-PAGE and enzyme assay were done for characterizing the expressed protein. A ~1,100 bp of the structural subtilisin gene was amplified. The DNA and amino acid sequence alignments resulting from the BLAST search of subtilisin showed high sequence identity with the other strains of B. subtilis, whereas significantly lower identity was observed with other bacterial subtilisins. The recombinant enzyme had the same molecular weight as other reported subtilisins and the E. coli transformants showed high subtilisin activity. This study provides evidence that subtilisin can be actively expressed in E. coli. The commercial availability of subtilisin is of great importance for industrial applications and also pharmaceutical purposes as thrombolytic agent. Thus, the characterization of new recombinant subtilisin and the development of rapid, simple, and effective production methods are not only of academic interest, but also of practical importance.

Antithrombotic effects of ethanol extract of Crataegus orientalis in the carrageenan-induced mice tail thrombosis model

INTRODUCTION

Crataegus species (common name is Hawthorn) are medicinal plants, which have flavonoids, triterpene acids, proanthocyanidins, and organic acids as main constituents, used in the treatment of cardiovascular diseases. One of the main causes of multiple cardiovascular diseases is intravascular thrombosis and current agents, which are used for the treatment and prevention of thrombosis, have some side effects. Therefore, new antithrombotic and thrombolytic agents are still needed.

MATERIALS AND METHODS

Antithrombotic function of ethanol extract of Crataegus orientalis (COE) leaves was investigated in carrageenan-induced mice tail thrombosis model. Mice were injected with 40 μl (1%) carrageenan (Type I) dissolved in physiological saline by intraplantar administration in the right hind paw. After carrageenan injection, the extract was administered at the doses of 100, 200, and 300 mg/kg. Heparin was used as a positive control (10 and 100 IU). The length of tail-thrombosis was measured at 24th, 48th, and 72nd hours.

RESULTS AND CONCLUSION

100mg/kg COE and 10IU heparin were not significant when compared to control groups at the time interval (24-72 h) that results was obtained. At 24th hour, both 200 and 300 mg/kg of COE showed a significant antithrombotic activity (p<0.05 and p<0.01, respectively). However, 200 mg/kg COE lost its significance and there was a decrease in the significance values of 300 mg/kg COE (p<0.05) at 48 and 72 h. From these results, it was concluded that COE significantly inhibited carrageenan-induced mice tail thrombosis in vivo.

Antioxidant enzyme gene transfer for ischemic diseases

The balance of redox is pivotal for normal function and integrity of tissues. Ischemic insults occur as results of a variety of conditions, leading to an accumulation of reactive oxygen species (ROS) and an imbalanced redox status in the tissues. The oxidant stress may activate signaling mechanisms provoking more toxic events, and eventually cause tissue damage. Therefore, treatments with antioxidants, free radical scavengers and their mimetics, as well as gene transfer approaches to overexpress antioxidant genes represent potential therapeutic options to correct the redox imbalance. Among them, antioxidant gene transfer may enhance the production of antioxidant scavengers, and has been employed to experimentally prevent or treat ischemic injury in cardiovascular, pulmonary, hepatic, intestinal, central nervous or other systems in animal models. With improvements in vector systems and delivery approaches, innovative antioxidant gene therapy has conferred better outcomes for myocardial infarction, reduced restenosis after coronary angioplasty, improved the quality and function of liver grafts, as well as outcome of intestinal and cerebral ischemic attacks. However, it is crucial to be mindful that like other therapeutic armentarium, the efficacy of antioxidant gene transfer requires extensive preclinical investigation before it can be used in patients, and that it may have unanticipated short- or long-term adverse effects. Thus, it is critical to balance between the therapeutic benefits and potential risks, to develop disease-specific antioxidant gene transfer strategies, to deliver the therapy with an optimal time window and in a safe manner. This review attempts to provide the rationale, the most effective approaches and the potential hurdles of available antioxidant gene transfer approaches for ischemic injury in various organs, as well as the possible directions of future preclinical and clinical investigations of this highly promising therapeutic modality.

Thrombolytic effect of subtilisin QK on carrageenan induced thrombosis model in mice

Subtilisin QK, a new fibrinolytic enzyme, could cleave directly cross-linked fibrin in vitro. To verify the thrombolytic function of Subtilisin QK in vivo, the thrombolytic effect of purified Subtilisin QK on tail-thrombus of mouse was investigated. After injected with carrageenan, the tail-thrombus of Subtilisin QK treated group were shorter than the physiological saline treated group. Moreover, the tail-thrombus decreased correlate with Subtilisin QK in a dose-dependent manner. Thrombus nearly disappeared while the mice were treated with 12000 IU Subtilisin QK. The result indicated that Subtilisin QK significantly inhibited thrombus formation in mouse tail. This study made more foundation for further development of Subtilisin QK as a novel bifunctional thrombolytic agent.

Therapeutic expression of the platelet-specific integrin, alphaIIbbeta3, in a murine model for Glanzmann thrombasthenia

Integrins mediate the adhesion of cells to each other and to the extracellular matrix during development, immunity, metastasis, thrombosis, and wound healing. Molecular defects in either the alpha- or beta-subunit can disrupt integrin synthesis, assembly, and/or binding to adhesive ligands. This is exemplified by the bleeding disorder, Glanzmann thrombasthenia (GT), where abnormalities of the platelet-specific integrin, alphaIIbbeta3, prevent platelet aggregation following vascular injury. We previously used a retrovirus vector containing a cDNA cassette encoding human integrin beta3 to restore integrin alphaIIbbeta3 on the surface of megakaryocytes derived from peripheral blood stem cells of GT patients. In the present study, bone marrow from beta3-deficient (beta3-/-) mice was transduced with the ITGbeta3-cassette to investigate whether the platelet progeny could establish hemostasis in vivo. A lentivirus transfer vector equipped with the human ITGA2B gene promoter confined transgene expression to the platelet lineage. Human beta3 formed a stable complex with murine alphaIIb, effectively restoring platelet function. Mice expressing significant levels of alphaIIbbeta3 on circulating platelets exhibited improved bleeding times. Intravenous immunoglobulin effectively diminished platelet clearance in animals that developed an antibody response to alphaIIbbeta3. These results indicate the feasibility of targeting platelets with genetic therapies for better management of patients with inherited bleeding disorders.