Newer antithrombotic drugs

Pharmacological Investigation of Asphodelus tenuifolius Cav. for its Potential Against Thrombosis in Experimental Models

Background

Thrombosis is a major disorder which is an outcome of an imbalance in the hemostatic system that develop undesirable blood clot and hinder blood circulation.

Purpose

The current study was designed to verify the potential of aqueous methanolic crude extract of Asphodelus tenuifolius Cav. (At.Cr), used traditionally as remedy in circulatory problems.

Research Design

Antioxidant activity, FTIR, and HPLC analysis were performed. In-vitro clot lysis assay was performed on human blood samples, and in-vivo acute pulmonary thromboembolism model was developed by administering the mixture of collagen and epinephrine in tail vein of mice. Carrageenan-induced thrombosis and FeCl₃-induced carotid arterial thrombosis models were developed in rats.

Results

At.Cr demonstrated significant increase in lysis of human blood clot. Bleeding and clotting times were increased dose-dependently. Lungs histology showed clear alveolar spaces with decreased red blood cells congestion. Reduction in infarcted tail length, augmentation in prothrombin time, and activated partial thromboplastin time with decrease in platelet count were observed. At.Cr also prolonged the arterial occlusion time and reduced the weight of thrombus and TXB₂ levels dose-dependently.

Conclusions

The results demonstrated the antithrombotic and thrombolytic potential of At.Cr due to activation of coagulation factors through extrinsic and intrinsic pathways.

Phenolic Bioactives as Antiplatelet Aggregation Factors: The Pivotal Ingredients in Maintaining Cardiovascular Health

Cardiovascular diseases (CVD) are one of the main causes of mortality in the world. The development of these diseases has a specific factor-alteration in blood platelet activation. It has been shown that phenolic compounds have antiplatelet aggregation abilities and a positive impact in the management of CVD, exerting prominent antioxidant, anti-inflammatory, antitumor, cardioprotective, antihyperglycemic, and antimicrobial effects. Thus, this review is intended to address the antiplatelet activity of phenolic compounds with special emphasis in preventing CVD, along with the mechanisms of action through which they are able to prevent and treat CVD. In vitro and in vivo studies have shown beneficial effects of phenolic compound-rich plant extracts and isolated compounds against CVD, despite that the scientific literature available on the antiplatelet aggregation ability of phenolic compounds in vivo is scarce. Thus, despite the current advances, further studies are needed to confirm the cardioprotective potential of phenolic compounds towards their use alone or in combination with conventional drugs for effective therapeutic interventions.

Synthesis and Bioactivities of Marine Pyran-Isoindolone Derivatives as Potential Antithrombotic Agents

2,5-Bis-[8-(4,8-dimethyl-nona-3,7-dienyl)-5,7-dihydroxy-8-methyl-3-keto-1,2,7,8-teraahydro-6H-pyran[a]isoindol-2-yl]-pentanoic acid (FGFC1) is a marine pyran-isoindolone derivative isolated from a rare marine microorganism Stachybotrys longispora FG216, which showed moderate antithrombotic(fibrinolytic) activity. To further enhance its antithrombotic effect, a series of new FGFC1 derivatives (F1-F7) were synthesized via chemical modification at C-2 and C-2' phenol groups moieties and C-1″ carboxyl group. Their fibrinolytic activities in vitro were evaluated. Among the derivatives, F1-F4 and F6 showed significant fibrinolytic activities with EC50 of 59.7, 87.1, 66.6, 82.8, and 42.3 μM, respectively, via enhancement of urokinase activity. Notably, derivative F6 presented the most remarkable fibrinolytic activity (2.72-fold than that of FGFC1). Furthermore, the cytotoxicity of derivative F6 was tested as well as expression of Fas/Apo-1 and IL-1 on HeLa cells. The results showed that, compared to FGFC1, derivative F6 possessed moderate cytotoxicity and apoptotic effect on HeLa cells (statistical significance p > 0.1), making F6 a potential antithrombotic agent towards clinical application.

Dual antiplatelet and anticoagulant (APAC) heparin proteoglycan mimetic with shear-dependent effects on platelet-collagen binding and thrombin generation

Heparin proteoglycans (HEP-PGs) carry standard heparin-mediated anticoagulant properties as well as novel antiplatelet functions, a combination that may be significant for targeting multiple pathways in a single therapy. Recent work developing semisynthetic HEP-PG mimetics has shown promising results also in vivo, however flow conditions in vitro that replicate in vivo hemodynamics have not been reported. In this work, we present several assays (platelet calcium mobilization, aggregometry, microfluidic tests at venous and arterial hemodynamics) to characterize specific mechanistic effects of dual antiplatelet and anticoagulant (APAC) constructs as mimetics of HEP-PGs. Three APACs with different conjugation levels of heparin chains (CL10, CL18, HICL) were shown to decrease platelet deposition to collagen surfaces in PPACK-treated whole blood at venous shear rate (200 s^-1). FXIIa-inhibited whole blood (CTI: corn trypsin inhibitor, 40 μg/mL) perfused over collagen/tissue factor showed reduced both platelet and fibrin deposition when treated with APACs. IC50 values for platelet and fibrin inhibition were calculated for each molecule at venous shear rate. Increasing the shear rate to arterial flows (1000 s^-1) and using APAC as the sole anticoagulant, resulted in a more potent antiplatelet effect of APAC, suggesting an added effect on von Willebrand Factor (vWF) function. Additionally, APAC caused an inhibition of calcium mobilization specific to thrombin and collagen stimulation and a dose-dependent reduction in collagen-mediated platelet aggregation. Understanding the sensitivity of APAC activity to shear rate, platelet signaling and procoagulant pathways is important for applications in which APAC administration may have beneficial therapeutic effects.

Isolation, purification, structural analysis and coagulatory activity of water-soluble polysaccharides from Ligustrum lucidum Ait flowers

In this study, Ligustrum lucidum flowers as raw material, the extraction, isolation and coagulatory activity of polysaccharides were carried out for the first time. The crude polysaccharide was obtained by hot water extraction and ethanol precipitation, and preliminarily purified by Sevage method and D101 macroporous resin. Then the polysaccharide was further purified by DEAE-52 cellulose and Sephadex G-100 column chromatography, respectively. The structural characteristics were detected by LC, GC, FT-IR and NMR. Furthermore, the coagulatory activity of the polysaccharides were investigated by APTT, TT, PT and FIB assays in vitro. The results demonstrated that four polysaccharides were isolated from flowers of L. lucidum, named as LLP-1a, LLP-1b, LLP-2 and LLP-3, and the yields were 0.039, 0.0054, 0.0055 and 0.017%, respectively based on the weight of the dried flowers. The four polysaccharides components were free of nucleic acids and proteins, and their average molecular weights were 25,912, 64,919, 3,940,246 and 2,975,091 g/mol, respectively. The monosaccharide compositions of LLp-1a were L-rhamnose, L-arabinose, D-xylose, D-glucose and D-galactose (molar ratio of 3.16: 2.46: 1.00: 7.27: 4.22). Only D-galactose was detected from LLp-1b. LLp-2 was composed of L-arabinose, D-glucose and D-galactose (molar ratio of 1.28:1.32:1.00). LLp-3 was composed of L-rhamnose, L-arabinose, D-xylose, D-glucose and D-galactose (molar ratio of 5.85: 2.21: 2.23: 1.00: 2.25). Coagulation assays indicated that LLp-1a and LLp-3 had good anticoagulant effect in vitro, while LLp-1b showed procoagulant activity.

Dual inhibition of PI3K and mTOR by VS-5584 suppresses thrombus formation

VS-5584 is a highly selective dual kinase inhibitor which suppresses phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) activity. Because these kinases are crucially involved in primary hemostasis, we herein investigated the effect of this compound on thrombus formation in vitro and in vivo. Pretreatment of washed platelets (WP) or platelet-rich plasma (PRP) with VS-5584 inhibited the agonist-induced activation of surface glycoprotein complex (GP)IIb/IIIa and the upregulation of P-selectin. This was associated with a significantly reduced formation of platelet-leukocyte aggregates (PLA). VS-5584 further attenuated platelet aggregation and adhesion after agonist stimulation. In contrast, endothelial expression of intercellular adhesion molecule (ICAM)-1 and vascular cellular adhesion molecule (VCAM)-1 and secretion of von Willebrand Factor (vWF) were not affected by the dual kinase inhibitor. In vivo, VS-5584 inhibited photochemically induced thrombus formation as shown by a significantly prolonged time to complete vessel occlusion when compared to vehicle-treated controls. This was associated with an elevated tail vein bleeding time, indicating a potential hemorrhagic risk in VS-5584-treated mice. Taken together, these novel findings demonstrate that VS-5584 is a potent inhibitor of primary hemostasis targeting multiple platelet functions.

Therapeutic potential of abalone and status of bioactive molecules: A comprehensive review

Marine organisms are increasingly being investigated as sources of bioactive molecules with therapeutic applications as nutraceuticals and pharmaceuticals. In particular, nutraceuticals are gaining popularity worldwide owing to their therapeutic potential and incorporation in functional foods and dietary supplements. Abalone, a marine gastropod, contains a variety of bioactive compounds with anti-oxidant, anti-thrombotic, anti-inflammatory, anti-microbial, and anti-cancer activities. For thousands of years different cultures have used abalone as a traditional functional food believing consumption provides health benefits. Abalone meat is one of the most precious commodities in Asian markets where it is considered a culinary delicacy. Recent research has revealed that abalone is composed of many vital moieties like polysaccharides, proteins, and fatty acids that provide health benefits beyond basic nutrition. A review of past and present research is presented with relevance to the therapeutic potential of bioactive molecules from abalone.

Influence of Prescribed Blood Products on the Incidence of Deep Vein Thrombosis and Pulmonary Embolism in Surgical Patients

Deep vein thrombosis (DVT) and pulmonary embolisms (PEs) are common complications after surgical procedures. The influence of prescribed blood products on the occurrence of DVT and PE was evaluated in postsurgical patients in this retrospective case-control study. The records of 286 surgical patients were analyzed: DVT (n = 52), PE (n = 92), and a control group (n = 142). The amounts of prescribed blood, blood products, and vitamin K were reviewed, together with appropriate prescribing of low-molecular-weight heparins. The influence of prescribed blood products on the occurrence of DVT or PE was analyzed using multinomial logistic regression. We demonstrated a significant difference between the test and control groups ( P < .05) in relation to receiving packed red blood cells. Treatment with red blood cells was associated with an increased risk of PE but not DVT. Patients who developed PE after surgery were hospitalized for longer (median 10 days) than patients with DVT (median 6 days). There was no difference between the test and control groups concerning treatment with fresh frozen plasma. Inadequate thromboprophylaxis significantly increased the likelihood of DVT. There is a connection between receiving packed red blood cells and occurrence of postoperative PE in surgical patients. Thus, patients receiving red blood cells should be monitored more closely after surgery, as they are more likely to develop PE postoperatively.

Evaluation of fibrinolytic and antioxidant effects of Allium elburzense bulb extracts

OBJECTIVE

Allium elburzense is an endemic plant of the family Amaryllidaceae that grows wild in northern Iran with some nutritional and medicinal applications. The present study was aimed to investigate the fibrinolytic and antioxidant effects of A. elburzense bulb extracts.

MATERIALS AND METHODS

Hydroalcoholic, aqueous, chloroformic and butanolic extracts were evaluated in this research. In vitro antioxidant assays were performed using total phenolic, DPPH, and FRAP methods. In the in vivo analysis, animals received i.p. injection of A. elburzense hydroalcoholic extract for 21 days and hydroperoxides level, FRAP value, PT and aPTT were determined in serum samples. The fibrinolytic activity of different extracts was quantitatively evaluated by measurement of clot weight.

RESULTS

In vitro antioxidant assay showed that A. elburzense aqueous extract had the highest DPPH scavenging and the highest total antioxidant capacity. In the in vivo assay, A. elburzense hydroalcoholic extract reduced serum hydroperoxides level and increased serum total antioxidant capacity in rats. In vitro fibrinolytic assay revealed remarkable thrombolytic activity for this plant with the highest effect for the aqueous extract. However, coagulation parameters including PT and aPTT were not affected by administration of A. elburzense hydroalcoholic extract in rats.

CONCLUSION

In conclusion, the results of this study revealed the potential antioxidant and fibrinolytic effects of A. elburzense bulb extracts. For developing novel thrombolytic agents, further investigations for isolation of bioactive constituents and finding the underlying mechanisms are suggested.

In vitro Anti-Thrombotic Activity of Extracts from Blacklip Abalone (Haliotis rubra) Processing Waste

Waste generated from the processing of marine organisms for food represents an underutilized resource that has the potential to provide bioactive molecules with pharmaceutical applications. Some of these molecules have known anti-thrombotic and anti-coagulant activities and are being investigated as alternatives to common anti-thrombotic drugs, like heparin and warfarin that have serious side effects. In the current study, extracts prepared from blacklip abalone (Haliotis rubra) processing waste, using food grade enzymes papain and bromelain, were found to contain sulphated polysaccharide with anti-thrombotic activity. Extracts were found to be enriched with sulphated polysaccharides and assessed for anti-thrombotic activity in vitro through heparin cofactor-II (HCII)-mediated inhibition of thrombin. More than 60% thrombin inhibition was observed in response to 100 μg/mL sulphated polysaccharides. Anti-thrombotic potential was further assessed as anti-coagulant activity in plasma and blood, using prothrombin time (PT), activated partial thromboplastin time (aPTT), and thromboelastography (TEG). All abalone extracts had significant activity compared with saline control. Anion exchange chromatography was used to separate extracts into fractions with enhanced anti-thrombotic activity, improving HCII-mediated thrombin inhibition, PT and aPTT almost 2-fold. Overall this study identifies an alternative source of anti-thrombotic molecules that can be easily processed offering alternatives to current anti-thrombotic agents like heparin.

Triple Antiplatelet Therapy and Combinations with Oral Anticoagulants After Stent Implantation

Triple oral anticoagulation or triple antiplatelet therapies may be administered for various reasons. They reduce cardiac complications following percutaneous coronary intervention and stroke or other thromboembolic phenomenon in conditions such as atrial fibrillation. There is an elevated risk of severe bleeding, so it is necessary to balance risk and benefits. Newer oral anticoagulants and antiplatelet drugs may be considered; the number of options is increasing. This article examines triple therapies and the efficacy and safety of combinations of traditional anticoagulant and antiplatelet drugs, and reviews clinical trial data on novel agents. Guidelines to inform clinical decision-making are presented.

Two new nonacosanetriols from Ginkgo biloba sarcotesta

Two new fatty alcohols named as (7S,8R,11S)-nonacosanetriol (1) and (10R,12R,15S)-nonacosanetriol (2), along with eight known compounds including ginkgolic acid (3), hydroginkgolic acid (4), sciadopitysin (5), ginkgetin (6), isoginkgetin (7), ginkgolide A (8), ginkgolide B (9) and ginkgolide C (10) have been isolated from the petroleum ether extract of Ginkgo biloba sarcotesta. Their structures were elucidated by means of chemical and extensive spectroscopic analysis. The absolute stereochemistry of compounds 1 and 2 was elucidated on the spectroscopic analysis of the R- and S-MTPA esters. Compounds 1 and 2 exhibited slight activity of antithrombin and moderate activity of antiplatelet aggregation in vitro. This was the first report regarding the anticoagulative activities of biflavonoids in G. biloba, and isoginkgetin (7) showed significant antithrombin and antiplatelet aggregation activity.

Pharmacokinetic and pharmacodynamic effects of comedication of clopidogrel and dabigatran etexilate in healthy male volunteers

Purpose

To evaluate the pharmacokinetic and pharmacodynamic effects of concomitant administration of single loading doses of clopidogrel or multiple doses of clopidogrel with multiple doses of dabigatran etexilate.

Methods

This was an open-label trial in healthy male subjects. In part 1 (pilot, n = 8) and part 3 (n = 12), a single dose of clopidogrel (300 or 600 mg, respectively) was given concomitantly with dabigatran etexilate at steady state; part 2 was a randomized, multiple-dose, crossover study with the test treatment being clopidogrel at steady state [300 mg loading dose on day 1, then 75 mg once daily (qd)] with concomitant dabigatran.

Results

Bioavailability was moderately increased when a loading dose of clopidogrel (300 mg in part 1 and 600 mg in part 3) was administered concomitantly with dabigatran etexilate 150 mg twice daily (bid). Test/reference ratios for AUC_τ,ss were 135% (90% CI 107–169%) and 132% (90% CI 112–156%), respectively. Steady-state dosing of clopidogrel 75 mg qd and dabigatran etexilate 150 mg bid (part 2) demonstrated minor effects on dabigatran pharmacokinetics (AUC_τ,ss ratio test/reference: 91.9%, 90% CI 78.7–107%) or its pharmacokinetic/pharmacodynamic relationships (activated partial thromboplastin time, ecarin clotting time, thrombin time). Similarly, clopidogrel bioavailability remained unchanged by chronic administration of dabigatran etexilate (part 3: ratio test/reference for AUC₀₋₂₄ was 103%; 90% CI 80.3–131%), as did its pharmacodynamic effects on the inhibition of platelet aggregation.

Conclusions

When given concomitantly, dabigatran etexilate and clopidogrel at clinically relevant doses did not appear to have significant effects on the pharmacokinetic and pharmacodynamic profiles of either agent.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-012-1304-8) contains supplementary material, which is available to authorized users.