Potent Inhibitor Of Platelet Aggregation Research Articles

Antioxidant and antiplatelet potential of different methanol fractions and flavonols extracted from onion (Allium cepa L.).

In this study, we reported the potential of various methanol fractions of onion (MFO) and its components quercetin and quercetin glucosides on platelet aggregation and antioxidant activity. The onion extracts were separated into several fractions using methanol and water. Further, these extracts were analyzed using simple high-performance liquid chromatography-diode array detector method to separate quercetin (Q), quercetin-4'-O-monoglucoside and quercetin-3, 4'-O-diglucoside from onion sample. It was observed that the bioactive compounds were accumulated in the non-polar portions rather than in the polar one. MFO and flavonol glucosides inhibited collagen-induced platelet aggregation, and the anti-aggregatory effects were comparatively studied using rat PRP (platelet-rich plasma). Among the extracted compounds, quercetin was found as a potent inhibitor of platelet aggregation compared to quercetin glucosides, whereas quercetin glucosides showed high antioxidant activities. These results suggest that MFO, quercetin and quercetin glucosides have powerful antiplatelet and antioxidant activities. These studies provide possible information leading to the intake of onions rich in these flavonols as a dietary supplement and functional food ingredient to prevent thrombosis and cardiovascular and oxidative stress-related diseases and might be utilized as a real source of valuable phytochemicals for the pharmaceutical and food industries for the development of antioxidant, anticoagulant and antiplatelet agents.

Rational Design, Synthesis, and Biological Activity of N‐(1,4‐Benzoxazinone)Acetamide Derivatives as Potent Platelet Aggregation Inhibitors

Inappropriate thrombus formation within blood vessels is the leading cause of mortality in the industrialized world. Platelet aggregation activated by thrombin may have close relationship with thrombosis. Based on our studies on the pharmacophoric role of 1,4‐benzoxazine‐3(4H)‐one for desirable platelet aggregation inhibitory activity, we identified N‐(4‐ethyl‐3‐oxo‐3,4‐dihydro‐2H‐benzo[b][1,4]oxazin‐7‐yl)‐2‐(4‐methylpiperazin‐1‐yl)acetamide (BOAP‐AM6) and N‐(4‐butyl‐3‐oxo‐3,4‐dihydro‐2H‐benzo[b][1,4]oxazin‐7‐yl)‐2‐(4‐(4‐fluorophenyl)piperazin‐1‐yl)acetamide (BOAP‐AM21) as platelet aggregation inhibitors with an IC50 of 8.93 and 8.67 μM, respectively, as potent as the positive control aspirin. A combination of structure–activity relationships studies and molecular modeling revealed that the molecule BOAP‐AM6 interacted with the amino acid residue TYR166 and ARG214 in the binding site of GPIIb/IIIa receptor through hydrogen bond and compound BOAP‐AM21 acted on the amino acid residue ASN215 and ALA218, both through the same approach as the reported potent molecules 7a and 7b.

Synergistic effect of peptide inhibitors derived from the extracellular and intracellular domain of αIIb subunit of integrin αIIbβ3 on platelet activation and aggregation

αIIbβ3, the major platelet integrin, plays a central role in hemostasis and thrombosis. Upon platelet activation, conformation of αIIbβ3 changes and allows fibrinogen binding and, subsequently, platelet aggregation. It was previously shown that a lipid-modified platelet permeable peptide, which corresponds to the intracellular acidic membrane distal sequence 1000LEEDDEEGE1008 of αIIb (pal-K-LEEDDEEGE or pal-K-1000-1008), inhibits thrombin-induced human platelet aggregation, by inhibiting talin association with the integrin. YMESRADR, a peptide corresponding to the extracellular sequence 313–320 of αIIb, is also a potent platelet aggregation inhibitor by mimicking the effect of a clasp between the head domains of αIIb and β3. The aim of the present study was to investigate the synergistic effect of the intra- and extracellular- peptide inhibitors on platelet aggregation, as well as on the phosphorylation of two signaling proteins, focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK). Platelet preincubation with Pal-K-LEEDDEGE followed by YMESRADR showed a synergistic inhibitory activity on platelet aggregation. Platelet incubation with threshold inhibitory concentrations of both peptides provoked almost the total inhibition of aggregation, PAC-1 binding, and fibrinogen binding, but not P-selectin exposure on activated platelets’ surface. Like RGDS peptide, this mixture inhibits FAK phosphorylation whose phosphorylation is well known to be consecutive to the aggregation (postoccupancy events). However, in contrast to RGDS peptide that enhances ERK phosphorylation and activation, the mixture of threshold inhibitory concentrations of Pal-K-LEEDDEEGE and YMESRADR inhibits ERK phosphorylation. We suggest that the use of the intracellular in combination with the extracellular peptide inhibitor, acting with a non-RGD-like mechanism, may provide an alternative way to antagonize integrin αIIbβ3 activation.

Buddleja globosa (matico) prevents collagen-induced platelet activation by decreasing phospholipase C-gamma 2 and protein kinase C phosphorylation signaling

Platelets play a key role in thrombosis and cardiovascular diseases. Medicinal plants could be one of the most important factors that influence risks for platelet activation. Buddleja globosa (known as “matico”) is a medicinal plant with many biological activities. The high content of polyphenols suggest that matico could have antiplatelet activity. The present study was aimed at evaluating mechanisms of antiplatelet action of an extract of matico. We demonstrated that matico extract at low concentrations and in a concentration dependent manner (0.05–1 mg/mL) was a potent inhibitor of platelet aggregation in response to collagen, convulsion and ADP (IC50 values was 61 μg/mL, 72 μg/mL and 290 μg/mL, respectively). In this sense matico extract exerted the greatest antiaggregant activity induced by collagen. Similarly, matico showed a decrease in % of positive platelet for P-selectina (vehicle, 0.01, 0.05, 0.1, 0.5 and 1 mg/mL were 32 ± 2%, 29 ± 2 (p < 0.05), 19 ± 1 (p < 0.01), 15 ± 2 (p < 0.01), 10 ± 1% (p < 0.01) and 7 ± 2% (p < 0.01), respectively) and PAC-1 binding (vehicle, 0.01, 0.05, 0.1, 0.5 and 1 mg/mL were 59 ± 1, 58 ± 3 (n.s), 55 ± 2 (p < 0.05), 50 ± 2 (p < 0.01), 38 ± 1 (p < 0.01), 36 ± 2 (p < 0.01). The cellular mechanism for the antiplatelet activity of matico might be mediated by the inhibition of phospholipase C-gamma 2 and protein kinase C phosphorylation. This beneficial property of matico may be of importance in thrombosis, in which platelet activation and aggregation are important determinants of thrombus initiation and development, and may contribute to the beneficial effects of matico intake in the prevention of cardiovascular diseases.

In vitro inhibition of platelets aggregation with generic form of clopidogrel versus branded in patients with stable angina pectoris.

Introduction: Clopidogrel is a potent platelet activation and aggregation inhibitor that prevents thrombosis in coronary artery diseases (CADs). In comparison to locally produced generic one (Osvix®), original brand of clopidogrel (Plavix®) is expensive. This study was designed to evaluate the effectiveness and uniformity of Osvix® versus Plavix® in patients with percutaneous coronary intervention (PCI) by means of platelet aggregation indexes. Methods: This randomized, double blind clinical study was conducted at Shahid Madani heart hospital, Tabriz, Iran, and 129 patients with previous PCI were enrolled in two independent treatment groups. All patients participated in this study were on dual antiplatelet therapy at least for 30 days. ASA 80 mg/d and clopidogrel 75 mg/d and a stat dose of 300 mg of clopidogrel before PCI were administered for all patients. To evaluate the anti-platelet activity, blood samples were taken from the patients and platelet aggregation test was performed. Results: The total study population represents a group of 129 patients (99 men and 30 women) with mean age of 57.7 ± 9.7 years with stable angina pectoris. The baseline characteristics and laboratory findings of two groups (except mean platelet volume [MPV]) were not different statistically. The mean platelets aggregation at 30th day was 13.7±7.0 in Plavix® group and 14.8±5.8 in Osvix® group (P value = 0.35). Conclusion: This study showed that Osvix® as a generic form of clopidogrel was not significantly different from the original brand (Plavix) in terms of in vitro platelet inhibition.

Timosaponin AIII induces antiplatelet and antithrombotic activity via Gq-mediated signaling by the thromboxane A2 receptor.

The thromboxane (Tx) A2 pathway is a major contributor to the amplification of initial platelet activation and is therefore a key drug target. To identify potent small-molecule inhibitors of the thromboxane prostaglandin (TP) receptor, we screened a small steroidal saponin library using U46619-induced rat platelet aggregation assays. Timosaponin AIII (TAIII) was identified as a potent inhibitor of U46619-induced rat platelet aggregation and exhibited superior selectivity for the TP receptor versus other G protein-coupled receptors and a PKC activator. TAIII inhibited U46619-induced rat platelet aggregation independent of increases in cAMP and cGMP and the inhibition of TxA2 production. Both PKC and PLC activators restored TAIII-inhibited platelet aggregation, whereas TAIII did not inhibit platelet aggregation induced by co-activation of the G12/13 and Gz pathways. Furthermore, TAIII did not affect the platelet shape change or ROCK2 phosphorylation evoked by low-dose U46619. In vivo, TAIII prolonged tail bleeding time, reduced the mortality of animals with acute pulmonary thromboembolism and significantly reduced venous thrombus weight. Our study suggests that TAIII, by preferentially targeting Gq-mediated PLC/PKC signaling from the TP receptor, induces stronger in vitro antiplatelet activity and in vivo antithrombotic effects and may be an excellent candidate for the treatment of thrombotic disorders.

Design, synthesis and evaluation of novel 2-amino-3-(naphth-2-yl)propanoic acid derivatives as potent inhibitors of platelet aggregation

Based upon LX2421, a previously identified antiplatelet aggregation agent, a series of novel 2-amino-3-(naphth-2-yl)propanoic acid derivatives were designed, synthesized and evaluated. Among them, compounds LX14 and LX25 were identified as promising antiplatelet aggregation agents. The in vitro biologic study demonstrated that LX14 can block platelet aggregation induced by four different inducers and displays comparable potency in inhibiting GPIIb/IIIa receptor in comparison with Tirofiban. In addition, LX14 has much lower risk of bleeding than Tirofiban and shows significant antithrombotic activity in vivo. Taking together, the results indicated that LX14 is a promising GPIIb/IIIa receptor antagonist against platelet aggregation worthy of further evaluation.

Preparation and Characterization of Clopidogrel Bisulfate Solid Dispersion using Vigna radiata Extract as a Natural Drug Carrier

Context: Clopidogrel is a potent inhibitor of platelet aggregation, active in vivo against a large spectrum of inducers. The drug has low solubility in biological fluid, lead to the poor bioavailability after oral administration. Aim: This study aims at enhancement of dissolution profile of clopidogrel bisulfate using green gram (Vigna radiata) as a natural carrier by solid dispersion (SD) technique. Materials and Methods: Natural carrier was prepared by hot water extraction method. The natural carrier was characterized for swelling index, viscosity, hydration capacity, and angle of repose. The natural carrier green gram (V. radiata) was also characterized by differential scanning calorimetry and X-ray diffraction technique for physical interaction and crystallinity, respectively. SD was prepared by solvent evaporation method using the natural carrier in the ratio 1:1, 1:2, and 1:3. Results: The extracted water-soluble carrier from V. radiata shown requires properties for the preparation of SD. SD 1:3 formulation shows the higher in vitro drug release within 120 min. Conclusions: From this study, it concludes that green gram could be a novel approach as a carrier with an enhancing effect on solubility of poorly water-soluble drug in SD.

Edoxaban, a direct factor Xa inhibitor, suppresses tissue-factor induced human platelet aggregation and clot-bound factor Xa in vitro: Comparison with an antithrombin-dependent factor Xa inhibitor, fondaparinux

IntroductionTissue factor-induced platelet aggregation and factor Xa (FXa) activity bound to clot contribute to the formation and growth of thrombus. The effects of edoxaban, a direct FXa inhibitor, on these responses were determined and compared with that of fondaparinux, an antithrombin-dependent (indirect) FXa inhibitor. Material and methodsHuman platelet aggregation was induced by human tissue factor (Dade Innovin or RecombiPlasTin) in platelet-rich plasma spiked with edoxaban or fondaparinux. Clot formed from human whole blood was incubated with 0.9μM prothrombin in the absence or presence of FXa inhibitors. As the index of FXa activity, the amount of prothrombin fragment F1+2 was measured with an ELISA. Free FXa activity was measured using human FXa and its chromogenic substrate S-2222. ResultsEdoxaban inhibited tissue factor-induced platelet aggregation in a concentration-dependent manner with the IC50 values of 150 and 110nM for Dade Innovin and RecombiPlasTin-induced platelet aggregation, respectively. At 1μM, edoxaban completely inhibited the aggregation. Fondaparinux inhibited RecombiPlasTin-induced aggregation with the IC50 of 9.3μM, but did not show complete inhibition up to 30μM and had no effect on Dade Innovin-induced aggregation. Edoxaban inhibited both free and clot-bound FXa with the IC50 of 2.3 and 8.2nM, respectively. Fondaparinux inhibited free FXa (IC50 5.4nM), but 40-times higher concentration were required to inhibit clot-bound FXa (IC50 217nM). ConclusionsEdoxaban, a direct FXa inhibitor, was a more potent inhibitor of tissue factor-induced platelet aggregation and clot-bound FXa than fondaparinux, an indirect FXa inhibitor.

Inhibition of αIIbβ3 Ligand Binding by an αIIb Peptide that Clasps the Hybrid Domain to the βI Domain of β3.

Agonist-stimulated platelet activation triggers conformational changes of integrin αIIbβ3, allowing fibrinogen binding and platelet aggregation. We have previously shown that an octapeptide, p1YMESRADR8, corresponding to amino acids 313–320 of the β-ribbon extending from the β-propeller domain of αIIb, acts as a potent inhibitor of platelet aggregation. Here we have performed in silico modelling analysis of the interaction of this peptide with αIIbβ3 in its bent and closed (not swing-out) conformation and show that the peptide is able to act as a substitute for the β-ribbon by forming a clasp restraining the β3 hybrid and βI domains in a closed conformation. The involvement of species-specific residues of the β3 hybrid domain (E356 and K384) and the β1 domain (E297) as well as an intrapeptide bond (pE315-pR317) were confirmed as important for this interaction by mutagenesis studies of αIIbβ3 expressed in CHO cells and native or substituted peptide inhibitory studies on platelet functions. Furthermore, NMR data corroborate the above results. Our findings provide insight into the important functional role of the αIIb β-ribbon in preventing integrin αIIbβ3 head piece opening, and highlight a potential new therapeutic approach to prevent integrin ligand binding.

Studies on the antiplatelet and antithrombotic profile of anti-inflammatory coumarin derivatives

The interest towards coumarin-based structures stems from their polypharmacological profile. Herein, we present a series of Mannich bases and 7-azomethine-linked coumarin derivatives exhibiting antiplatelet and antithrombotic activities, in addition to the already known anti-inflammatory and antioxidant activities. Among others, compounds 15 and 16 were found to be the most potent and selective inhibitors of platelet aggregation whereas compound 3 also proved to be the most potent in the clot retraction assay. Structure–activity relationship studies were conducted to elucidate the molecular determinants responsible for the herein observed activities. The chance of inhibiting cyclooxygenase-1 was also investigated for evaluating the platelet aggregation induced by arachidonic acid. Taken together, these results suggest that the investigation of other targets connected to the antiplatelet activity, such as phosphodiesterase-3 (PDE3), could be a viable strategy to shed light on the polypharmacological profile of coumarin-based compounds. Docking simulations towards PDE3 were also carried out.

Hypertonic saline: a brief overview of hemodynamic response and anti-inflammatory properties in head injury.

Hypertonic saline: a brief overview of hemodynamic response and anti-inflammatory properties in head injury.

Cobalt(II) catalyzed C(sp)-H bond functionalization of alkynes with phenyl hydrazines: facile access to diaryl 1,2-diketones.

A cobalt acetylacetonate catalyzed oxidative diketonation of alkynes via C(sp)-H bond functionalization has been described. The reaction involves a free-radical mechanism, wherein the phenyl radical formed from phenyl hydrazine couples with Co(II) activated alkyne to produce 1,2-diketones. The reaction proceeds at room temperature in DMF with the use of Ag2O/air as the oxidizing system. The utility of the protocol for the synthesis of a series of imidazoles including a potent platelet aggregation inhibitor trifenagrel has been demonstrated.

Clopidogrel use in end-stage kidney disease.

Clopidogrel irreversibly binds to the P2Y12 platelet receptor and acts as a potent inhibitor of platelet activation and aggregation. It is currently recommended for the prevention of cardiovascular events in patients with acute coronary syndromes, recent ischemic stroke, and peripheral arterial disease. Clopidogrel is a prodrug requiring hepatic conversion into its active metabolite. In the general population, genetic polymorphisms in the CYP2C19 gene interfering with hepatic conversion and the ABCB1 gene interfering with gut absorption of clopidogrel, account for the large interindividual response to clopidogrel and clopidogrel resistance. Chronic kidney disease (CKD) and ESKD are independent risk factors for clopidogrel resistance; 50-80% of patients with ESKD have high on-treatment residual platelet reactivity when treated with clopidogrel. This may partially explain the abysmal outcomes for patients with kidney disease post coronary intervention. Several assays are used to determine residual on-treatment platelet reactivity; however, their use in tailoring the suitability of clopidogrel treatment in patients with ESKD is unclear. Although clopidogrel decreased cardiovascular events in the general population after acute coronary syndromes and percutaneous intervention in the CURE and CREDO trials, a reanalysis of these studies in patients with CKD (eGFR <60ml/minute) showed either a reduced or no benefit from clopidogrel treatment. ESKD patients were not represented in these two large trials; this is true for most of the trials that established clopidogrel as an integral part of the therapeutic armamentarium for cardiovascular disease. Furthermore, clopidogrel has been associated with an increased risk of death, death from bleeding, and hospitalization for bleeding in patients with ESKD. In conclusion, current evidence suggests that ESKD patients may not derive the same benefits from clopidogrel therapy as the general population and this therapy may be associated with harm. Properly designed observational studies and randomized controlled trials are needed to establish the role of clopidogrel in patients with ESKD, the use of platelet assays to tailor therapy, and the role of other antiplatelet agents such as prasugrel or ticagrelor in patients who exhibit high on-treatment residual platelet reactivity.

Ticagrelor: pharmacokinetics, pharmacodynamics, clinical efficacy, and safety.

Dual antiplatelet therapy, composed of aspirin plus a P2Y12-receptor antagonist, is the cornerstone of treatment for patients with acute coronary syndrome (ACS). A number of U.S. Food and Drug Administration–approved P2Y12-receptor antagonists are available for treating patients with ACS, including the thienopyridine compounds clopidogrel and prasugrel. Ticagrelor, the first of a new class of antiplatelet agents, is a noncompetitive, direct-acting P2Y12-receptor antagonist. Unlike the thienopyridine compounds, ticagrelor does not require metabolism for activity. Also, whereas clopidogrel and prasugrel are irreversible inhibitors of the P2Y12 receptor, ticagrelor binds reversibly to inhibit receptor signaling and subsequent platelet activation. In pharmacodynamic studies, ticagrelor demonstrated faster onset and more potent inhibition of platelet aggregation than clopidogrel. These properties of ticagrelor may contribute to reduced rates of thrombotic outcomes compared with clopidogrel, as demonstrated in a phase III clinical trial. However, in addition to bleeding, distinctive adverse effects of this new chemical entity have not been reported with the thienopyridine P2Y12-receptor inhibitors. Although ticagrelor represents an advancement in P2Y12-receptor inhibition therapy, a thorough understanding of this compound as an antiplatelet therapy remains to be elucidated.

N-[6-(4-butanoyl-5-methyl-1H-pyrazol-1-yl)pyridazin-3-yl]-5-chloro-1-[2-(4-methylpiperazin-1-yl)-2-oxoethyl]-1H-indole-3-carboxamide (SAR216471), a novel intravenous and oral, reversible, and directly acting P2Y12 antagonist.

In the search of a potential backup for clopidogrel, we have initiated a HTS campaign designed to identify novel reversible P2Y12 antagonists. Starting from a hit with low micromolar binding activity, we report here the main steps of the optimization process leading to the identification of the preclinical candidate SAR216471. It is a potent, highly selective, and reversible P2Y12 receptor antagonist and by far the most potent inhibitor of ADP-induced platelet aggregation among the P2Y12 antagonists described in the literature. SAR216471 displays potent in vivo antiplatelet and antithrombotic activities and has the potential to differentiate from other antiplatelet agents.

The effect of prasugrel on ADP-stimulated markers of platelet activation in patients with sickle cell disease

Platelets of patients with sickle cell disease (SCD) show evidence of mild activation in the non-crisis steady state and greater activation during vaso-occlusive crises (VOC). Prasugrel, a potent inhibitor of ADP-mediated platelet activation and aggregation, may be useful in attenuating VOC. We compared platelet responses to ADP stimulation in patients with SCD and healthy subjects before and after treatment with prasugrel. In a phase 1 study, platelet biomarker levels were assessed in 12 adult patients with SCD and 13 healthy subjects before and after 12 ± 2 days of 5.0 or 7.5 mg/day prasugrel. The following were determined in whole blood samples stimulated with 20 µM ADP: (i) percentages of monocytes and neutrophils with adherent platelets (cell–platelet aggregates); (ii) the relative number (mass) of platelets associated with each monocyte and neutrophil as reported by CD61 mean fluorescence intensity (MFI) of the monocyte–platelet and neutrophil–platelet aggregates; (iii) the percentages of platelets positive for surface expression of CD40 ligand (CD40L), P-selectin (CD62p) and activated glycoprotein IIb-IIIa (GPIIb-IIIa); and (iv) the percentages of platelets and monocyte–platelet aggregates positive for surface tissue factor (TF) expression. At baseline, there were no significant differences between cohorts in the percentages of platelets expressing activation biomarkers. Following 12 days of prasugrel administration, the percentages of platelets expressing activation biomarkers following ADP stimulation were reduced in both cohorts, and there were no significant differences between groups. Both patients with SCD and healthy subjects had significant reductions in the monocyte–platelet and neutrophil–platelet aggregate MFI and the percentage of platelets expressing P-selectin and activated GPIIb-IIIa (all p < 0.05). Healthy subjects also had significant reductions in monocyte–platelet aggregate percentages (p = 0.004), neutrophil–platelet aggregate percentages (p = 0.011) and the percentage of CD40L-positive platelets (p = 0.044) that were not observed in patients with SCD. Prasugrel administration to SCD patients attenuates ex vivo ADP-stimulated platelet activation as measured by the percentage of platelets positive for P-selectin and GPIIb–IIIa, thus reducing the proportion of platelets that may participate in aggregates. Furthermore, prasugrel decreases ex vivo ADP-stimulated platelet aggregation with monocytes and neutrophils as measured by the monocyte–platelet and neutrophil–platelet aggregate MFI. This implies that in the presence of prasugrel, fewer platelets adhere to monocytes and neutrophils, which may result in reducing cell–platelet aggregate size. Therefore, reduced platelet reactivity and decreased size of leukocyte–platelet aggregates suggest additional mechanisms by which prasugrel may provide benefit to patients with SCD and support further investigation of possible therapeutic benefits of prasugrel in this population.

Effects of continuous prostacyclin infusion on regional blood flow and cerebral vasospasm following subarachnoid haemorrhage: statistical analysis plan for a randomized controlled trial.

BackgroundOne of the main causes of mortality and morbidity following subarachnoid hemorrhage (SAH) is the development of cerebral vasospasm, a frequent complication arising in the weeks after the initial bleeding. Despite extensive research, no effective treatment of vasospasm exists to date. Prostacyclin is a potent vasodilator and inhibitor of platelet aggregation. In vitro models have shown a relaxing effect of prostacyclin after induced contraction in cerebral arteries, and a recent pilot trial showed a positive effect on cerebral vasospasm in a clinical setting. No randomized clinical trials have investigated the possible pharmacodynamic effects of prostacyclin on the human brain following SAH.Methods/DesignThis trial is a single centre, randomized, placebo-controlled, parallel group, double blinded, clinical pilot trial. A total of 90 patients with SAH will be randomized to one of three intervention arms: epoprostenol at 1 ng/kg/min, epoprostenol at 2 ng/kg/min, or placebo in addition to the standard treatment. Trial medication will start on Day 5 after SAH and continue to Day 10. The primary outcome measure is changes in cerebral blood flow measured by a computed tomography (CT) perfusion scan. The secondary outcomes are vasospasm measured by a CT angiography, regional blood flow, clinical symptoms of cerebral ischemia, and outcome at three months (Glasgow Outcome Scale).DiscussionThe primary outcome has been altered slightly since the publication of our study protocol. Global cerebral blood flow is now primary outcome, whereas regional blood flow is a secondary outcome.Trial registrationClinicaltrials.gov NCT01447095. Registration date: 11 October 2011.

Anti-platelet effect of ginkgolide a from Ginkgo biloba

Effects of ginkgolide A (GA) from Ginkgo biloba leaves in collagen (10 μg/mL)-stimulated platelet aggregation were investigated. Zymographic analysis confirmed that pro-matrix metalloproteinase-9 (MMP-9) (92 kDa) was activated by GA to form an activated MMP-9 (86-kDa) on gelatinolytic activities. GA concentration-dependently inhibited platelet aggregation, intracellular Ca2+ mobilization, and thromboxane A2 (TXA2) formation by inhibiting the cyclooxygenase-1 (COX-1) activity in collagen-stimulated platelets. In addition, GA increased the formation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which have an anti-platelet function in both resting and collagen-stimulated platelets. On the other hand, GA did not prolong prothrombin time (PT) and activated partial thromboplastin time (aPTT) associated with the extrinsic and intrinsic coagulation pathways on human plasma, respectively. Therefore, we suggest that the inhibitory effect of GA on platelet aggregation might involve the following pathway. GA may increase the MMP-9 activity and intracellular cAMP and cGMP production, inhibit intracellular Ca2+ mobilization, and decrease TXA2 production by down-regulating the COX-1, thereby leading to inhibition of platelet aggregation without cytotoxicity. These results strongly indicate that GA is a potent inhibitor of collagen-stimulated platelet aggregation. It may play an important role as a negative regulator during platelet activation.

Nonsteroidal Anti-Inflammatory Drugs and the Heart

Aspirin has been on the market for 115 years. Beginning with the marketing of indomethacin for the treatment of rheumatoid arthritis in 1963, at least 20 other nonsteroidal anti-inflammatory drugs (NSAIDs) with aspirin-like actions have been developed over the past 50 years,1 culminating with the introduction of a new class of selective inhibitors of cyclooxygenase (COX)-2, the coxibs, approximately 15 years ago.2 The NSAIDs represent the single most crowded family of drugs sharing the same therapeutic activities and mechanism of action, perhaps reflecting the unmet therapeutic need in the area of pain management and the large interindividual variability in response to these agents. NSAIDs provide symptomatic relief of pain and inflammation associated with a variety of human disorders, including the rheumatic diseases. Their shared therapeutic actions (ie, analgesic, anti-inflammatory, and antipyretic) are usually accompanied by mechanism-based adverse effects that can, at least in part, be attenuated as a function of individual pharmacokinetic or pharmacodynamic properties.1 Nuances in the tolerability of different NSAIDs had been described in the precoxib era on the basis of clinical trials of a few hundred patients treated for up to a few months with soft end points. More recently, however, important differences in safety have been demonstrated in head-to-head randomized comparisons of individual coxibs and 1 or more traditional NSAIDs that involved tens of thousands of patients treated for up to a few years with hard end points. Even more significantly, the interpretation of the effects of NSAIDs has been greatly enhanced by the availability, for the first time, of large, placebo-controlled trials that aimed to assess the potential for chemoprevention of colorectal cancer by rofecoxib or celecoxib. As a result of these developments, the whole field of NSAIDs has been illuminated during the past 15 years. Although epidemiological studies had previously associated …