Strong Inhibition Of Platelet Aggregation Research Articles

RGD and Scutellarin Conjugate (WK001) Targeting Platelet Glycoprotein IIb/IIIa Receptor Protects from Myocardial Ischemia/Reperfusion Injury: Synthesis, Characterization, and Bioactivity Evaluation.

Myocardial ischemia/reperfusion (MI/R) injury is an unresolved clinical challenge. The blockade of binding fibrinogen by glycoprotein IIb/IIIa (GPIIb-IIIa) inhibitors has become a new therapeutic approach against MI/R injury. In this study, we modified the RGD structure to combine with scutellarin and synthesized a novel peptide, scutellarin-HomoArg-Gly-Asp-Trp-NH2 (WK001). Herein, reported experimental and docking evidence indicates that WK001 provides immediate and potent platelet inhibition, with stronger inhibition of platelet aggregation than eptifibatide and scutellarin. In particular, it is administered intravenously to prevent thrombus formation and attenuate myocardial fibrosis progression in vivo. Therefore, WK001 could be developed as an antiplatelet drug to treat thrombosis-associated diseases, such as stroke and myocardial infarction.

복분자주 주박의 항균, 항산화 및 항혈전 활성

복분자는 당도가 낮고 신맛이 강해 과실주로 주로 제조되고 있으며, 복분자주 제조 후 부생되는 주박은 대부분 폐기되고 있다. 본 연구에서는 현재까지 생리활성이 보고된 바 없는 복분자주 주박을 대상으로 열수 추출물, ethanol 추출물 및 이들의 다양한 분획물을 조제하여 항균, 항산화 및 항혈전 활성을 평가하였다. 그 결과, 복분자주 주박의 ethylacetate (EA) 분획은 413~459 mg/g의 높은 polyphenol을 함유하고 있으며, 그람양성세균에 대한 강력한 성장억제 활성과, DPPH 음이온, ABTS 양이온에 대한 우수한 radical 소거능, nitrite 소거능 및 환원력을 나타내었다. 또한 혈액내의 thrombin, prothrombin, coagulation factor 에 대한 저해를 통한 혈액응고저해 활성이 우수하였다. 복분자주 주박의 butanol 분획은 우수한 항산화력과 함께 내인성 혈전 생성에 관련된 aPTT 연장활성을 나타내었으며, aspirin에 필적하는 강력한 혈소판 응집저해 활성을 나타내었다. 한편 복분자주 주박의 열수 추출물의 순차적 유기용매 분획 후의 물 잔류물은 aspirin보다 강력한 혈소판 응집저해를 나타내어 새로운 항혈소판제 개발 소재로 이용 가능함을 확인하였다. 본 연구결과는 폐기되고 있는 복분자주 주박을 이용한 고부가가치 식품 및 향장소재 개발이 가능함을 제시하고 있다. The immature fruit of Rubus coreanus Miquel (bokbunja in Korean) is mainly consumed as a fruit wine due to its sour taste and low sugar content. The lees (LBW) remaining after the production of bokbunja wine are discarded as they have no specific usage. The aim of this study was to develop high-value-added biomaterials for functional foods and beauty/health products by investigating the anti-microbial, anti-oxidant, and anti-thrombosis activities of LBW using ethanol and hot water extracts and their subsequent organic solvent fractions. The ethyl acetate (EA) fraction of LBW extracts has a high polyphenol content (413–459 mg/g), and showed strong anti-microbial activity against gram-positive bacteria. The EA fraction also showed excellent radical-scavenging activity against DPPH anion, ABTS cation, and nitrite, with strong reducing power. The polyphenol-enriched EA fraction strongly inhibited thrombin, prothrombin, and blood coagulation factors. The butanol fraction showed a specific inhibition of coagulation factors, as measured in activated partial thromboplastin time assay, which is linked to intrinsic blood coagulation. The butanol fraction also showed strong inhibition of platelet aggregation, at levels comparable to aspirin. The residue of the hot-water extract, which is produced by sequential solvent fractionation of the LBW extract, showed superior inhibition against platelet aggregation when compared to aspirin. Our results suggest that the LBW, which are currently discarded, are a promising source of novel functional foods and beauty/health products.

Pharmacokinetics and Pharmacodynamics of Ticagrelor and Prasugrel in Healthy Male Korean Volunteers

PurposeA combination of clopidogrel and aspirin is the standard treatment for patients with acute coronary syndrome and those undergoing percutaneous coronary intervention. Two novel antiplatelet agents, ticagrelor and prasugrel, have been shown to rapidly and more effectively inhibit the P2Y12 receptor compared with clopidogrel. The aim of this study was to evaluate and compare the pharmacokinetics (PK) and pharmacodynamics (PD) of ticagrelor and prasugrel in healthy male Korean volunteers. MethodsTwo separate studies were conducted. One study was performed by using a single-sequence, open-label, crossover design in 12 volunteers who received a single oral dose of ticagrelor (180 mg) and then a single oral dose of prasugrel (60 mg for 4 volunteers and 30 mg for 8 volunteers) with a 7-day washout period. The other study was a randomized, open-label, parallel-group investigation in which 8 volunteers received a single oral dose of prasugrel (10 mg for 4 volunteers and 30 mg for 4 volunteers). In each study, blood samples for PK and platelet aggregation inhibition analysis were serially collected after the administration of each dose. Plasma concentrations of ticagrelor, AR-C124910XX (the active metabolite of ticagrelor), R-95913 (the inactive metabolite of prasugrel), and R-138727 (the active metabolite of prasugrel) were measured by using a validated LC-MS/MS method. PK was analyzed by using a noncompartmental method. Maximal platelet aggregations were assessed with light transmission aggregometry after induction with 20 μmol/L of adenosine diphosphate. FindingsTwenty healthy male Korean volunteers participated in the 2 studies. Plasma concentrations of ticagrelor and AR-C124910XX were obtained from 12 subjects, R-95913 from 20 subjects, and R-138727 from 8 subjects. Both ticagrelor and prasugrel were rapidly absorbed, with the shortest median Tmax of 2.0 and 2.25 hours for ticagrelor and AR-C124910XX, respectively, and a Tmax of 0.5 hour for both R-95913 and R-138727. Strong inhibition of platelet aggregation was shown after administration of both ticagrelor and prasugrel, with slightly stronger and more rapid inhibition with prasugrel in the tested doses. Inhibitory activities of prasugrel lasted longer than those of ticagrelor, reflecting the difference in binding kinetics between the 2 drugs. ImplicationsPrasugrel 30 and 60 mg exhibited slightly stronger, more rapid, and sustainable platelet inhibitory effects compared with ticagrelor 180 mg. These differing effects should be considered when determining the efficacy and adverse effects of ticagrelor and prasugrel. ClinicalTrials.gov identifier: NCT01876797 and NCT02075268.

Elucidation of Mild Bleeding Disorders Reported Under Ibrutinib (Imbruvica(R)) Therapy: Implications for Optimal Clinical Management

IntroductionIbrutinib is the first-in-class covalent inhibitor of Bruton’s Tyrosine Kinase (BTK), now approved for the therapy of mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL). Mild bleeding disorders (grade 1-2) have been reported in 44-60% of patients across clinical trials, with <5% grade 3 hemorrhages after trauma. After vascular injury, platelets adhere onto von Willebrand factor (vWF, through GPIb-IX-V complex) and collagen (through a2b1 and GPVI receptor), and activate phospholipase Cg2 (PLCg2) through BTK phosphorylation. In this study, we sought to examine phosphorylation pathways and platelet functions in vitro and ex vivo from ibrutinib-treated patients.Patients and MethodsWithin the compassionate access program of ibrutinib in France (started Feb 2014), we investigated whether ibrutinib could impact on platelet functions in vitro and ex vivo, as measured at day 0 and day 15-30 by: aggregometry using various agonists, measurement of intra-cellular levels of phosphorylation of BTK and PLCg2 phosphorylations, monitoring adhesion onto vWF matrix under high shear rate.We next assess how in vitro tests could help identify bleeding risk in a larger cohort of patients from three institutions.ResultsFirst, we demonstrated that in healthy donors’ platelets, ibrutinib inhibits collagen and collagen related peptide (CRP) -induced platelet aggregation in a dose-dependent manner (mean EC50=250nM, a dose achievable in patients). This effect was paralleled by the inhibition of PLCg2 phosphorylation on the Btk-dependent phosphorylation site Tyr753, and of the auto-phosphorylation Tyr223 site of BTK itself, suggesting a specific targeting by ibrutinib. Of note, adhesion on vWF under high shear rate was dramatically decreased. In parallel, in 7/14 patients had bleeding symptoms (5/7 with grade 1-2 bleedings) and they all presented a strong inhibition of platelet aggregation in response to collagen and a significant decrease in adhesion onto vWF. Thus, the easy-to-use collagen-induced platelet aggregation test in platelet rich plasma could help physicians to decide when to perform surgical procedures without haemostasis concerns. Moreover, we show that addition of 50% untreated platelets is sufficient to efficiently reverse the effects of ibrutinib, and that platelet functions recover following treatment interruption as physiological platelet renewal occurs, supporting the in vitro data. On the other hand, patients who received aspirin (n=6) had no cases of severe bleeding and no significant impact on collagen/CRP-induced platelet aggregation. Because aspirin+P2Y12 inhibitors (such as clopidogrel, Plavix®) is widely used in the elderly population, ibrutinib therapy should be given very cautiously to these patients (who receive then three major pathway platelet activation pathway inhibitor), as recommended for vitamin K antagonists drugs. Aggregometry tests may provide important information to physicians to predict the bleeding risk as observed in our cohort of >30 patients (as of June 2014, recruitment still ongoing). Two last points should be emphasized when considering bleeding risk of ibrutinib: (i) from our study, some patients had no anti-platelet detectable effect ex vivo under ibrutinib therapy, the mechanism of which still remains unclear, and (ii) in patients with mild bleedings, platelet functions recovery and cessation of symptoms occured in virtually all patients (except those on aspirin therapy) after 3-6 months despite ongoing lymphoma responses, suggesting a potential adaptative process in platelets.Summary and ConclusionWe identified that ibrutinib affects collagen and Von Willebrand Factor-mediated platelet activation in vitro and ex vivo. The mild bleeding diathesis observed in a subgroup of ibrutinib-treated patients correlates with defects in collagen-induced platelet aggregation and platelet adhesion on von Willebrand Factor at high shear rate. Based on in vitro analyses and in vivo platelet turnover, 2-3 days ibrutinib cessation appears to be enough for effective aggregation response recovery, and reintroduction of the drug should be rapid to avoid disease recurrence. Our study also suggests that platelet transfusion at a dose sufficient to get 50 % of fresh platelets may correct haemostasis in emergency, provided it was given after elimination of ibrutinib from blood (4-6h). DisclosuresTam:Pharmacyclics and Janssen: Honoraria, Membership on an entity’s Board of Directors or advisory committees.

Antiplatelet aggregation triterpene saponins from the barks of Ilex rotunda

Four new triterpene saponins, rotundinosides A–D (1–4) and seven known triterpene saponins (5–11) were isolated from a methanol extract of the barks of Ilex rotunda Thunb. The new saponins were characterized as 3-O-β-d-glucopyranosy1-(1→2)-β-d-xylopyranosyl siaresinolic acid 28-O-β-d-glucopyranoside (1), 3-O-[β-d-glucopyranosy1-(1→2)-β-d-xylopyranosyl]-3β,19α-dihydroxyurs-12-en-28-oic-O-β-d-glucopranosy1ester (2), 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosy1-(1→2)-α-l-arabinopyranosyl]-3β,19α-dihydroxyurs-12-en-28-oic-O-β-d-glucopyranosy1 ester (3), and 3-O-α-l-rhamanopyranosyl-(1→2)-β-d-glucopyranosy1-(1→2)-α-l-arabinopyranosyl ilexgenin B 28-O-β-d-glucopyranosy1 ester (4), respectively. Their structures were established by extensive spectroscopic analysis, including HSQC, HMBC, 1H–1H COSY, NOESY and acid hydrolysis, and also by the comparison of their spectroscopic data with those of related compounds. The known compounds 5–11 were all obtained from this species for the first time. The biological activity of compounds 1–11 against ADP induced platelet aggregation in rabbit plasma was determined. Among the tested compounds 1, 3, 5 and 10 exhibited strong inhibition of platelet aggregation in vitro, with IC50 values of 11.4±2.2, 10.4±1.3, 13.2±2.4, and 15.1±3.4μM, respectively.

Antithrombotic Properties of Water-Soluble Carbon Monoxide-Releasing Molecules

We compared the antithrombotic effects in vivo of 2 chemically different carbon monoxide-releasing molecules (CORM-A1 and CORM-3) on arterial and venous thrombus formation and on hemostatic parameters such as platelet activation, coagulation, and fibrinolysis. The hypotensive response to CORMs and their effects on whole blood gas analysis and blood cell count were also examined. CORM-A1 (10-30 µmol/kg, i.v.), in a dose-dependent fashion, significantly decreased weight of electrically induced thrombus in rats, whereas CORM-3 inhibited thrombosis only at the highest dose used (30 µmol/kg). CORM-A1 showed a direct and stronger inhibition of platelet aggregation than CORM-3 in healthy rats, both in vitro and in vivo. The antiaggregatory effect of CORM-A1, but not CORM-3, correlated positively with weight of the thrombus. Concentration of active plasminogen activator inhibitor-1 in plasma also decreased in response to CORM-A1, but not to CORM-3. Neither CORM-A1 nor CORM-3 had an effect on plasma concentration of active tissue plasminogen activator. CORM-3, but not CORM-A1, decreased the concentration of fibrinogen, fibrin generation, and prolonged prothrombin time. Similarly, laser-induced venous thrombosis observed intravitally via confocal system in green fluorescent protein mice was significantly decreased by CORMs. Although both CORM-A1 and CORM-3 (30 µmol/kg) decreased platelets accumulation in thrombus, only CORM-A1 (3-30 µmol/kg) inhibited platelet activation to phosphatidylserine on their surface. CORM-3 and CORM-A1 inhibited thrombosis in vivo, however CORM-A1, which slowly releases carbon monoxide, and displayed a relatively weak hypotensive effect had a more pronounced antithrombotic effect associated with a stronger inhibition of platelet aggregation associated with a decrease in active plasminogen activator inhibitor-1 concentration. In contrast, the fast CO releaser CORM-3 that displayed a more pronounced hypotensive effect inhibited thrombosis primarily through a decrease in fibrin generation, but had no direct influence on platelet aggregation and fibrynolysis.

Variability and treatment of high on-prasugrel platelet reactivity in patients with initial high on-clopidogrel platelet reactivity

Highon-treatmentplatelet reactivity (HTPR) following clopidogrel is awell studiedphenomenonassociatedwithprognostic significancepost percutaneous coronary angioplasty (PCI). Platelet reactivity variability over time while on clopidogrel is also well appreciated [1]. Prasugrel, a newer P2Y12 inhibitor, has been shown to result in a faster, more consistent and stronger inhibition of platelet aggregation, compared to clopidogrel mainly attributed to its more efficient metabolic activation. Cases of HTPR while on prasugrel have scarcely been reported, with minimal data on its variabilityover timeandways for its treatment [2-5]. We describe our experience in patients who exhibited HTPR while on 10 mg maintenance dose of prasugrel, its variability over time and strategies to overcome. During a 15 monthperiod and in the contextof 3 randomized studies assessing the pharmacodynamic effects of prasugrel 10 mg vs clopidogrel 150 mg daily in patients with HTPR while on clopidogrel, we have performed platelet function testing using the VerifyNow (Accumetrics Inc., San Diego, CA, USA) point-of-care P2Y12 assay, as previously described [6-8]. Results are reported as P2Y12 reaction units (PRU) with a value≥235 considered as an indication of HTPR [6]. Patients with demonstration of HTPR while on prasugrel in their respective trial were invited – 6 to 12 months after the end of the trial – for a second measurement of platelet reactivity after receiving prasugrel 10 mg for at least 15 days. TheHTPR persistence between the first and the second platelet function measurement while on prasugrel was assessed. Intrasubject variability of platelet reactivity was calculated using coefficient of variation after log transformation of the existing data. Patients, with HTPR in the second measurement, were prescribed 20 mg of prasugrel daily for 15 days, when a final platelet reactivity assessment was performed. Out of 334 patients screened while on clopidogrel, 123 (36.8%) exhibited HTPR and 107 of them received prasugrel for at least 15 days. Among them, 11 (10.3%) were identified with HTPR while on prasugrel. Demographic and clinical details are presented in Table 1. A second assessment of platelet reactivity revealed that the majority (7/11) exhibited an adequate platelet inhibition (Fig. 1). Ιntrasubject variability was 63.2% (coefficient of variation). Persistence of HTPR was observed in only 4 patients, in whom increasing prasugrel to 20 mg was able to overcome HTPR in 3 of them. Only 1 patient remained nonresponsive to the 20 mg of prasugrel dose. HTPR while on prasugrel is a recently appreciated phenomenon [4,5]. When HTPR is observed in acute coronary syndrome patients 6 to 12 h following prasugrel loading, it is predictive of ischemic events at International Journal of Cardiology 154 (2012) 333–385

Critical appraisal of ticagrelor in the management of acute coronary syndrome

Ticagrelor is a novel P2Y12 receptor antagonist which, like clopidogrel and prasugrel, functions by blocking adenosine diphosphate-mediated platelet aggregation. However, unlike the aforementioned agents, the binding of ticagrelor to this receptor is reversible. Ticagrelor is also believed to mediate some of its beneficial effects by augmenting the effects of adenosine, which is another unique pharmacologic property of this drug. In terms of antiplatelet effect, ticagrelor is more potent than clopidogrel and produces a faster and stronger inhibition of platelet aggregation. This may also be an advantage of ticagrelor over prasugrel, but this has not been adequately studied. Due to the reversible nature of the binding of ticagrelor to the platelet receptor, ticagrelor has a relatively fast offset of effect, with platelet aggregation approaching pretreatment levels about 3 days after discontinuation of therapy. This has advantages in patients requiring invasive procedures, but also makes medication adherence very important in order to be able to maintain an effective antiplatelet effect. Ticagrelor has been shown to be clinically superior to clopidogrel when given to patients with an acute coronary syndrome, resulting in significantly lower rates of myocardial infarction and vascular death. However, ticagrelor is indicated to be administered with aspirin, and the clinical benefits of ticagrelor may be less when daily dosages of aspirin exceed 100 mg. As expected, bleeding is the most common adverse effect with ticagrelor, although it occurs at rates comparable with those seen for clopidogrel with the exception of noncoronary artery bypass graft-related major bleeding and fatal intracranial bleeds, the latter of which occurs only rarely. Dyspnea is another common adverse effect with ticagrelor, although this is usually not severe and resolves with drug discontinuation. Unlike clopidogrel, there are no known pharmacogenomic concerns with ticagrelor, and emerging data suggest ticagrelor to be effective in patients resistant to clopidogrel, although more study is needed on this topic. While preliminary data suggest ticagrelor to be cost effective when compared with generic clopidogrel, the acquisition cost of ticagrelor is not insignificant and this will likely be an issue for many health care organizations. Currently, ticagrelor is well positioned to assume an active role in the treatment of coronary artery disease due to an impressive efficacy profile and reasonable safety. Its ultimate role in therapy will continue to evolve as studies on this drug continue eg, (Prevention of Cardiovascular Events in Patients with Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin, PEGASUS) and more information hopefully becomes available on its use in clopidogrel nonresponders and relative safety and efficacy compared with prasugrel.

Ticagrelor: An investigational oral antiplatelet treatment for reduction of major adverse cardiac events in patients with acute coronary syndrome

Acute coronary syndromes (ACS) are the leading cause of mortality and one of the main reasons for hospital admissions in the developed nations. Due to high rates of mortality and reinfarction, ACS represent a major public health concern. Platelets play a central role in atherothrombosis, the main pathologic substrate in ACS. Sufficient inhibition of platelet aggregation is therefore one of the key targets in the treatment of ACS. Blockade of the P2Y12 subtype of adenosine diphosphate (ADP) receptor on platelet cell membranes has been established as a key mechanism of platelet inhibition. Clopidogrel, an ADP receptor antagonist and a second-generation thienopyridine, has been demonstrated to be of clinical benefit in patients with ACS when added to aspirin. A delayed onset of action due to two-step conversion to the active metabolite, irreversible binding to P2Y12 receptors, and broad interindividual variability in levels of platelet response are the main limitations of clopidogrel. Prasugrel, a novel third-generation thienopyridine, provides faster and stronger inhibition of platelet aggregation than clopigodrel. However, like the active metabolite of clopidogrel, prasugrel binds irreversibly to the P2Y12 ADP receptor site, causing inhibition of platelet aggregation for the life of the platelet. Although in a randomized, double-blind trial prasugrel demonstrated superiority for multiple cardiovascular endpoints compared with standard-dose clopidogrel, it was also associated with an increased bleeding risk, including fatal bleeding. This review discusses the optimal antiplatelet regimens for management of patients with ACS, with special focus on ticagrelor, the first oral agent in a new chemical class of nonthienopyridine antiplatelet agents termed cyclopentyltriazolo-pyrimidines. Faster and greater platelet inhibition than clopidogrel, quick recovery of platelet function, and high efficacy regardless of clopidogrel response status, are the obvious advantages of ticagrelor as compared with thienopyridines. The prospective, randomized Platelet Inhibition and Patient Outcomes trial has established the clinical utility, enhanced efficacy, and similar safety of ticagrelor as compared with clopidogrel in a wide range of patients with ACS managed with contemporary antithrombotic therapies and invasive strategies when indicated. Dyspnea, ventricular pauses ≥3 seconds, and elevation of serum creatinine and uric acid are the most common known adverse effects associated with ticagrelor, and require further comprehensive assessment.

Nouveaux antiagrégants plaquettaires

Platelet-aggregation inhibitors are the cornerstone of the treatment and prevention of atherothrombotic events. Long limited to aspirin alone, new drugs have appeared in the past two decades. But only very recently have new targets been developed. The synergy of their mechanisms of action now makes it possible to obtain ever stronger inhibition of platelet aggregation.

Inhibitory mechanisms of resveratrol in platelet activation: pivotal roles of p38 MAPK and NO/cyclic GMP

Resveratrol has been reported to have antiplatelet activity; however, the detailed mechanisms have not yet been resolved. This study aimed to systematically examine the detailed mechanisms of resveratrol in the prevention of platelet activation in vitro and in vivo. Resveratrol (0.05-0.25 micromol/l) showed stronger inhibition of platelet aggregation stimulated by collagen (1 microg/ml) than other agonists. Resveratrol (0.15 and 0.25 micromol/l) inhibited collagen-induced platelet activation accompanied by [Ca(+2)]i mobilization, thromboxane A(2) (TxA(2)) formation, phosphoinositide breakdown, and protein kinase C (PKC) activation. Resveratrol markedly increased levels of NO/cyclic guanosine monophosphate (GMP), and cyclic GMP-induced vasodilator-stimulated phosphoprotein phosphorylation. Resveratrol markedly inhibited p38 mitogen-activated protein kinase (MAPK) but not Jun N-terminal kinase or extracellular signal-regulated kinase-2 phosphorylation in washed platelets. Resveratrol-reduced hydroxyl radical (OH(-)) formation in the electron spin resonance study. In an in vivo study, resveratrol (5 mg/kg) significantly prolonged platelet plug formation of mice. In conclusion, the main findings of this study suggest that the inhibitory effects of resveratrol possibly involve (i) inhibition of the p38 MAPK-cytosolic phospholipase A(2)-arachidonic acid-TxA(2)-[Ca(+2)]i cascade and (ii) activation of NO/cyclic GMP, resulting in inhibition of phospholipase C and/or PKC activation. Resveratrol is likely to exert significant protective effects in thromboembolic-related disorders by inhibiting platelet aggregation.

Naftidrofuryl-driven regulation of endothelial ICAM-1 involves nitric oxide.

Naftidrofuryl is a selective inhibitor of the 5-HT2 receptor expressed on human endothelial cells. This drug has been used over the years to cope with cerebral or peripheral ischemic accidents; however, no clear mechanism of action of this molecule has been highlighted to explain its vascular effects. In the present work, we demonstrate that the involvement of nitric oxide can account for the effects of naftidrofuryl. Indeed, naftidrofuryl potently inhibited the TNF-alpha-triggered increase of intercellular adhesion molecule-1 (ICAM-1) expression as well as stress fiber formation in human umbilical vein endothelial cells (HUVEC). Moreover, naftidrofuryl induced the expression of type II nitric oxide synthase (NOS II) messenger and protein, leading to a noticeable increase in nitric oxide synthesis. Furthermore, using the specific NOS II inhibitor 1400W, we verified that the observed effects of naftidrofuryl were NOS II-dependent. The biology of nitric oxide accounts for the reduction of the vasospasm associated with stroke and the strong inhibition of platelet aggregation. In conclusion, our work provides evidence for the inhibition of leukocyte recruitment by downregulation of CD54/ICAM-1, an additional key factor to be dealt with during thrombotic accidents. Importantly, it also highlights a novel NOS II-dependent mechanism of action for naftidrofuryl.

Influence of acetylsalicylic acid on development of radiation-induced nephropathy

Purpose : Previous studies have demonstrated that long-term treatment with acetylsalicylic acid (ASA) can significantly reduce the renal functional impairment that develops after high doses of irradiation. The effect is hypothesized to be mediated by selective inhibition of thromboxane A 2 synthesis and inhibition of platelet aggregation. The present study was undertaken to investigate this phenomenon further using more clinically relevant fractionated and re-irradiation schedules. Methods and materials : Groups of mice were given bilateral renal irradiation with a series of four or 20 daily fractions of X-rays, or 10 daily fractions with a single dose of re-irradiation (0-10Gy) after 27 weeks. Half the mice received ASA in drinking water (2.4 g.l -1) from 1 week before the start of irradiation and continuously throughout the follow-up period. Renal function was assessed by clearance of [ 51 Cr]EDTA, about every 4 weeks for up to 80 weeks after the start of treatment. Histological damage in representative groups of mice was also assessed. Results : Oral administration of ASA caused inhibition of thromboxane A2 synthesis (to < 36% of controls) and a strong inhibition of platelet aggregation in whole mouse blood (ex vivo) . Prolonged treatment with ASA also resulted in a small, non-significant reduction of radiation-induced renal functional damage. No reduction in histological damage was seen in the ASA treated mice. Conclusion : Long-term oral administration of ASA gave only a modest, non-significant reduction of renal radiation injury after clinically relevant fractionated irradiation schedules.

Structure and Synthesis of Simulansamide, a Platelet Aggregation Inhibitor from Zanthoxylum Simulans

AbstractSimulansamide, isolated from the root bark of Zanthoxylum simulans, shows strong inhibition of platelet aggregation. The structure of this compound was deduced from spectral data and verified by synthesis.

Ridogrel, a Combined Thromboxane Synthase Inhibitor and Receptor Blocker, Decreases Elevated Plasma β-Thromboglobulin Levels in Patients with Documented Peripheral Arterial Disease

The combination of thromboxane synthase inhibition with thromboxane receptor antagonism has been shown to result in a strong inhibition of platelet aggregation and a prolongation of the bleeding time (Gresele et al., J. Clin Invest 1987; 80: 1435-45). Ridogrel is a single molecule that efficiently achieves both inhibitions in human volunteers. The present study was performed in patients with obstructive peripheral arterial disease and elevated plasma beta-thromboglobulin levels. Patients were treated with either 2 x 300 mg ridogrel or 2 x 300 mg placebo per day for 2 1/2 days, according to a double blind randomised parallel design. Plasma beta-thromboglobulin decreased significantly throughout active treatment starting within 2 h after administration; serum and urinary immunoreactive TxB2 levels and urinary 11-dehydro-TxB2 excretion were significantly lower and serum PGE2 and 6-keto-PGF1 alpha levels significantly higher with ridogrel; no changes were observed in the placebo-treated group. In conclusion this study demonstrates a reduction of platelet activation in vivo by ridogrel.

Protective effect of ticlopidine on thrombotic obstruction of an experimental arterio-venous shunt in rats

A polyethylene tubing was installed between the right carotid artery and the jugular vein of the rat to make a loop-shaped arterio-venous shunt. In most of the rats, the vascular shunt was obstructed by white thrombi together with blood clot within 4 hours after installation of the vascular shunt.Oral administration of ticlopidine at doses above 5mg/kg markedly prevented the shunt obstruction through strong inhibition of platelet aggregation by this agent. In the ticlopidine-treated rats, only small numbers of single platelets scattered on the inner surface of the shunt were observed.On the other hand, acetylsalicylic acid did not show any antithrombotic effect in this vascular shunt model, despite of its inhibitory action on collagen-induced platelet aggregation. Such ineffectiveness of acetylsalicylic acid seems to be probably related to almost complete inhibition of PGI2 generation in the carotid artery by this agent.Dipyridamole did not exert any effect on platelet aggregation at doses ranging from 10 to 300mg/kg, but increased the generation of PGI2-like activity in the vascular tissue in a dose-dependent manner. This effect of dipyridamole, however, was too short in duration to give a significant antithrombotic effect in the present shunt model, although a tendency to prevent shunt obstruction was observed only at an extremely high oral dose or frequently repeated intraperitoneal doses of this agent.

Vasodilation and inhibition of platelet aggregation by prostacyclins with modified ω-side chain

Prostacyclin analogs with modified ω-side chain were synthetized in search of therapeutically useful agents. To characterize the vasodilator and platelet-antiaggregating properties, prostacyclin analogs were tested on systemic blood pressure in anesthetized rats, relaxation of bovine coronary artery and inhibition of arachidonic acid induced human platelet aggregation. The sodium salt of prostacyclin induced a dose dependent decrease of blood pressure with an ED 25 of 0.23 μg/kg i.v., a marked relaxation of bovine coronary artery with an IC 5p of 5.9 ng/ml and a strong inhibition of platelet aggregation with an ED 50 of 3x10 −9 M. Similar results were obtained with prostacyclin-methylester. Replacement of the n-pentyl moiety attached to C-15 of prostacyclin by cyclohexyl, 2-(2-furyl)ethyl, 2-(3-thienyl)ethyl and especially by 3-thienyloxymethyl yielded analogs with comparable prostacyclin properties, while substitution by 1,1-dimethyloxaalkyl residues was followed by a marked loss of activity. The order of potency among the analogs of the sodium salt and methylester of prostacyclin with strong vasodepressor and antiaggregatory properties was identical in all three models used. The three test systems used for evaluation have demonstrated that suitable modifications of the ω-side chain of prostacyclin result in potent vasodilator and plateletantiaggregating agents.