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Abstract Background To mitigate the risk of stent thrombosis, patients treated by percutaneous coronary intervention (PCI) are administered dual anti-platelet therapy comprising aspirin and a platelet P2Y12 receptor inhibitor. Clopidogrel is a prodrug requiring activation by the cytochrome P450 enzyme, CYP2C19. In Saudi Arabia, it has been reported that approximately 26% of the population carries CYP2C19*2 and/or *3 loss-of-function polymorphisms in addition to a high prevalence of CVD. Methods This prospective (April 2013–December 2020) parallel assignment clinical trial focuses on ST-Elevation Myocardial Infarction (STEMI) patient outcomes. The clinical trial includes 1500 STEMI patients from two hospitals in the Eastern Province of Saudi Arabia. Patients are assigned to one of two groups; the control arm receives conventional therapy with clopidogrel, while in the active arm the Spartan RX CYP2C19 assay is used to determine the *2 genotype. Carriers of a CYP2C19*2 loss-of-function allele receive prasugrel or ticagrelor, while non-carriers are treated with clopidogrel. Follow-up is one year after primary PCI. The primary end point is the number of patients who develop an adverse major cardiovascular event, including recurrent MI, non-fatal stroke, cardiovascular death, or major bleeding one year after PCI. Discussion The risk of stent thrombosis in PCI patients is usually reduced by dual anti-platelet therapy, comprising aspirin and a P2Y12 inhibitor, such as clopidogrel. However, clopidogrel requires activation by the cytochrome P450 enzyme, CYP2C19. Approximately 20% of the population are unable to activate clopidogrel as they possess the CYP2C19*2 loss-of function (LoF) allele. The primary goal of this trial is to study the benefits of treating only those patients that cannot activate clopidogrel with an alternative that has shown to be a more effective platelet inhibitor and does not require bioactivation by the cytochrome P450 enzyme. We expect an improvement in net clinical benefit outcome in the active arm patients, thus supporting pharmacogenetic testing in PCI patients post STEMI. Trial registration Trial registration name is “Bedside Testing of CYP2C19 Gene for Treatment of Patients with PCI with Antiplatelet Therapy” (number NCT01823185 ) retrospectively registered with clinicaltrials.gov on April 4, 2013. This trial is currently at the patient recruitment stage.

In Mexico, Cnidoscolus aconitifolius (chaya) has been used to treat cardiovascular diseases (CVD). Because CVD are the number one cause of mortality, chaya use has become a health strategy. The aim of this study was to evaluate the antithrombotic activity and identify the metabolites in the most active extract. Aqueous (Aq), ethanolic (EtOH), acetonic (An), ethyl acetate (AcOEt), diethyl ether (Et2O), and hexanic (Hx) extracts were obtained. Platelet aggregation, phospholipase A2, prothrombin time (PT), activated partial thromboplastin time (aPTT), and clot lysis were evaluated. Metabolites were identified by gas chromatography–mass spectrometry (GC-MS). EtOH showed the greatest inhibition of platelet aggregation and phospholipase A2. Ac had the greatest effect on PT and aPTT. AcOEt had the greatest effect on clot lysis. EtOH, with the highest potential, was analyzed by GC-MS; fatty acids and triterpenes were identified. Thus, EtOH showed greater antiplatelet activity and other extracts showed moderate activity. This is a preliminary antithrombotic study. Future research will allow the development of nutraceuticals or functional ingredients for the prevention and treatment of thrombosis. [ABSTRACT FROM AUTHOR]

What is known and objective: The benefits and risks of restarting antiplatelet therapy (APT) for patients with spontaneous intracranial haemorrhage (ICH) remain controversial. This meta‐analysis was performed to explore the efficacy and safety of restarting APT for these patients. Methods: We followed the recommended PRISMA guidelines for systematic reviews. Studies from PubMed, Embase, Web of Science, CNKI and the Cochrane Library were systematically retrieved from the inception of each database to 31 July 2020. We also manually retrieved studies of reference. Results and discussion: In this study, seven cohort studies and one randomized controlled trial (RCT) with subjects were included. APT resumption after spontaneous ICH did not significantly increase the risk of major haemorrhagic events (HR 1.15; 95% CI: 0.70–1.89; p =.59). However, it did not significantly reduce the risk of a composite endpoint concerning occlusive/thromboembolic events (HR 0.98; 95% CI: 0.81–1.19; p =.83) and all‐cause mortality (HR 0.93; 95% CI: 0.80–1.08; p =.35). What is new and conclusion: Restarting APT for patients with spontaneous ICH is generally safe. However, the benefits of reducing the risk of ischaemic vascular events and all‐cause mortality were not apparent. More RCTs are required. [ABSTRACT FROM AUTHOR]

Background: Dual antiplatelet therapy with aspirin and a P2Y12 inhibitor has been shown to reduce the risk of major adverse cardiovascular events (MACE) compared with aspirin alone after percutaneous coronary intervention (PCI) or acute coronary syndrome but with increased risk of bleeding. The safety of discontinuing aspirin in favor of P2Y12 inhibitor monotherapy remains disputed.Methods: A meta-analysis was conducted from randomized trials (2001-2020) that studied discontinuation of aspirin 1 to 3 months after PCI with continued P2Y12 inhibitor monotherapy compared with traditional dual antiplatelet therapy. Five trials were included; follow-up duration ranged from 12 to 15 months after PCI. Primary bleeding and MACE outcomes were the prespecified definitions in each trial.Results: The study population included 32 145 patients: 14 095 (43.8%) with stable coronary artery disease and 18 046 (56.1%) with acute coronary syndrome. In the experimental arm, background use of a P2Y12 inhibitor included clopidogrel in 2649 (16.5%) and prasugrel or ticagrelor in 13 408 (83.5%) patients. In total, 820 patients experienced a primary bleeding outcome and 937 experienced MACE. Discontinuation of aspirin therapy 1 to 3 months after PCI significantly reduced the risk of major bleeding by 40% compared with dual antiplatelet therapy (1.97% versus 3.13%; hazard ratio [HR], 0.60 [95% CI, 0.45-0.79]), with no increase observed in the risk of MACE (2.73% versus 3.11%; HR, 0.88 [95% CI, 0.77-1.02]), myocardial infarction (1.08% versus 1.27%; HR, 0.85 [95% CI, 0.69-1.06]), or death (1.25% versus 1.47%; HR, 0.85 [95% CI, 0.70-1.03]). Findings were consistent among patients who underwent PCI for an acute coronary syndrome, in whom discontinuation of aspirin after 1 to 3 months reduced bleeding by 50% (1.78% versus 3.58%; HR, 0.50 [95% CI, 0.41-0.61]) and did not appear to increase the risk of MACE (2.51% versus 2.98%; HR, 0.85 [95% CI, 0.70-1.03]).Conclusions: Discontinuation of aspirin with continued P2Y12 inhibitor monotherapy reduces risk of bleeding when stopped 1 to 3 months after PCI. An increased risk of MACE was not observed after discontinuation of aspirin, including in patients with acute coronary syndrome. [ABSTRACT FROM AUTHOR]

Background: To mitigate the risk of stent thrombosis, patients treated by percutaneous coronary intervention (PCI) are administered dual anti-platelet therapy comprising aspirin and a platelet P2Y12 receptor inhibitor. Clopidogrel is a prodrug requiring activation by the cytochrome P450 enzyme, CYP2C19. In Saudi Arabia, it has been reported that approximately 26% of the population carries CYP2C19*2 and/or *3 loss-of-function polymorphisms in addition to a high prevalence of CVD.Methods: This prospective (April 2013-December 2020) parallel assignment clinical trial focuses on ST-Elevation Myocardial Infarction (STEMI) patient outcomes. The clinical trial includes 1500 STEMI patients from two hospitals in the Eastern Province of Saudi Arabia. Patients are assigned to one of two groups; the control arm receives conventional therapy with clopidogrel, while in the active arm the Spartan RX CYP2C19 assay is used to determine the *2 genotype. Carriers of a CYP2C19*2 loss-of-function allele receive prasugrel or ticagrelor, while non-carriers are treated with clopidogrel. Follow-up is one year after primary PCI. The primary end point is the number of patients who develop an adverse major cardiovascular event, including recurrent MI, non-fatal stroke, cardiovascular death, or major bleeding one year after PCI.Discussion: The risk of stent thrombosis in PCI patients is usually reduced by dual anti-platelet therapy, comprising aspirin and a P2Y12 inhibitor, such as clopidogrel. However, clopidogrel requires activation by the cytochrome P450 enzyme, CYP2C19. Approximately 20% of the population are unable to activate clopidogrel as they possess the CYP2C19*2 loss-of function (LoF) allele. The primary goal of this trial is to study the benefits of treating only those patients that cannot activate clopidogrel with an alternative that has shown to be a more effective platelet inhibitor and does not require bioactivation by the cytochrome P450 enzyme. We expect an improvement in net clinical benefit outcome in the active arm patients, thus supporting pharmacogenetic testing in PCI patients post STEMI.Trial Registration: Trial registration name is "Bedside Testing of CYP2C19 Gene for Treatment of Patients with PCI with Antiplatelet Therapy" (number NCT01823185) retrospectively registered with clinicaltrials.gov on April 4, 2013. This trial is currently at the patient recruitment stage. [ABSTRACT FROM AUTHOR]

Patients on P2Y12 inhibitors may still develop thrombosis or bleeding complications. Tailored antiplatelet therapy, based on platelet reactivity testing, might reduce these complications. Several tests have been used, but failed to show a benefit of tailored antiplatelet therapy. This could be due to the narrowness of current platelet reactivity tests, which are limited to analysis of platelet aggregation after stimulation of the adenosine diphosphate (ADP)-pathway. However, the response to ADP does not necessarily reflect the effect of P2Y12 inhibition on platelet function in vivo. Therefore, we investigated whether measuring platelet reactivity toward other physiologically relevant agonists could provide more insight in the efficacy of P2Y12 inhibitors. The effect of in vitro and in vivo P2Y12 inhibition on αIIbβ3-activation, P-selectin and CD63-expression, aggregate formation, release of alpha, and dense granules content was assessed after stimulation of different platelet activation pathways. Platelet reactivity measured with flow cytometry in 72 patients on P2Y12 inhibitors was compared to VerifyNow results. P2Y12 inhibitors caused strongly attenuated platelet fibrinogen binding after stimulation with peptide agonists for protease activated receptor (PAR)-1 and -4, or glycoprotein VI ligand crosslinked collagen-related peptide (CRP-xl), while aggregation was normal at high agonist concentration. P2Y12 inhibitors decreased PAR-agonist and CRP-induced dense granule secretion, but not alpha granule secretion. A proportion of P2Y12-inhibitor responsive patients according to VerifyNow, displayed normal fibrinogen binding assessed with flow cytometry after stimulation with PAR-agonists or CRP despite full inhibition of the response to ADP, indicating suboptimal platelet inhibition. Concluding, measurement of platelet fibrinogen binding with flow cytometry after stimulation of thrombin- or collagen receptors in addition to ADP response identifies different patients as nonresponders to P2Y12 inhibitors, compared to only ADP-induced aggregation-based assays. Future studies should investigate the value of both assays for monitoring on-treatment platelet reactivity.

Background: Identifying patients with the optimal risk:benefit for ticagrelor is challenging. The aim was to identify ticagrelor-responsive platelet transcripts as biomarkers of platelet function and cardiovascular risk., Methods: Healthy volunteers (n=58, discovery; n=49, validation) were exposed to 4 weeks of ticagrelor with platelet RNA data, platelet function, and self-reported bleeding measured pre-/post-ticagrelor. RNA sequencing was used to discover platelet genes affected by ticagrelor, and a subset of the most informative was summarized into a composite score and tested for validation. This score was further analyzed (1) in CD34+ megakaryocytes exposed to an P2Y12 inhibitor in vitro, (2) with baseline platelet function in healthy controls, (3) in peripheral artery disease patients (n=139) versus patient controls (n=30) without atherosclerosis, and (4) in patients with peripheral artery disease for correlation with atherosclerosis severity and risk of incident major adverse cardiovascular and limb events., Results: Ticagrelor exposure differentially expressed 3409 platelet transcripts. Of these, 111 were prioritized to calculate a Ticagrelor Exposure Signature score, which ticagrelor reproducibly increased in discovery and validation cohorts. Ticagrelor's effects on platelets transcripts positively correlated with effects of P2Y12 inhibition in primary megakaryocytes. In healthy controls, higher baseline scores correlated with lower baseline platelet function and with minor bleeding while receiving ticagrelor. In patients, lower scores independently associated with both the presence and extent of atherosclerosis and incident ischemic events., Conclusions: Ticagrelor-responsive platelet transcripts are a biomarker for platelet function and cardiovascular risk and may have clinical utility for selecting patients with optimal risk:benefit for ticagrelor use., Competing Interests: Disclosures Coauthors (R.A. Myers, G.S. Ginsburg, and D. Voora) are listed as coinventors on an invention disclosure related to use of platelet RNA biomarkers to predict bleeding due to platelet P2Y12 inhibitors. This article was prepared while G.S. Ginsburg was employed at Duke University. The opinions expressed in this article are the author’s own and do not reflect the view of the National Institutes of Health, the Department of Health and Human Services, or the United States government.

Platelet antiaggregation is a key element in the treatment of patients undergoing percutaneous coronary intervention with coronary stent implantation. However, a portion of these patients are not adequately antiaggregated. The objective was to identify through the literature review, articles that show the mechanisms of platelet resistance to clopidrogel in diabetic patients submitted to coronary intervention. This is a review of the literature in which the articles were available in the SCIELO, LILACS and PubMed databases, published between the years 2006 and 2015, with the following descriptors: platelet aggregation inhibitors, coronary intervention percutaneous coronary artery disease. Six scientific publications were found between the years 2006 and 2015, addressing the research theme. It was possible to observe a high index of platelet resistance to clopidrogel in diabetic patients in relation to non-diabetic patients. [ABSTRACT FROM AUTHOR]

Background: Clopidogrel low response (CLR) is an independent risk factor of adverse outcomes in patients undergoing percutaneous coronary intervention (PCI), and intensified antiplatelet treatments (IAT) guided by platelet function assays might overcome laboratory CLR. However, whether IAT improves clinical outcomes is controversial. Methods: Relevant trials were identified in PubMed, the Cochrane Library, and the Chinese Medical Journal Network databases from their establishment to September 9, 2014. Trials were screened using predefined inclusion criteria. Conventional meta-analysis and cumulative meta-analysis were performed using the Review Manager 5.0 and STATA 12.0 software programs. Results: Thirteen randomized controlled trials involving 5111 patients with CLR were recruited. During a follow-up period of 1–12 months, the incidences of cardiovascular (CV) death, nonfatal myocardial infarction (MI), and stent thrombosis were significantly lower in the IAT arm than in the conventional antiplatelet treatment arm (relative risk [RR] = 0.45, 95% confidence interval [CI]: 0.36–0.57, P < 0.000,01), whereas bleeding was similar between the two arms (RR = 1.05, 95% CI: 0.86–1.27, P = 0.65). Conclusions: IAT guided by platelet function assays reduces the risk of CV death, nonfatal MI, and stent thrombosis (ST) without an increased risk of bleeding in patients undergoing PCI and with CLR.

Introduction: Spherical agglomeration is one of the novel techniques for improvement of flow and dissolution properties of drugs. Cilostazol is a biopharmaceutics classification system Class II drug with poor solubility resulting in limited bioavailability. The present study aims at improving the solubility and dissolution of cilostazol by crystallo-co-agglomeration technique. Materials and Methods: Cilostazol agglomerates were prepared using various polymers with varying concentration of hydroxypropyl methylcellulose E 50 (HPMC E50), polyvinyl pyrrolidone K30 (PVP K30), and polyethylene glycol 6000. The influence of polymer concentration on spherical agglomerate formation was studied by 32 factorial design. Cilostazol agglomerates were evaluated for percent yield, mean particle size, drug content, aqueous solubility, and in vitro dissolution and further characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Results: The agglomeration process resulted in optimized formulation, F3 with mean agglomerate size of 210.0 ± 0.56 µm, excellent flow properties, approximately 15-fold increase in solubility than pure cilostazol and complete drug release in 60 min. Process yield, agglomerate size, and drug release were affected by amount of PVP K 30 and HPMC E50. The presence of drug microcrystal was confirmed by SEM, whereas FTIR study indicated no chemical change. Increase in drug solubility was attributed to change of crystalline drug to amorphous form that is evident in DSC and XRD. Conclusion: Crystallo.co.agglomeration can be adopted as an important approach for increasing the solubility and dissolution of poorly soluble drug. [ABSTRACT FROM AUTHOR]

Purpose: Network meta-analysis (NMA) has advantages including being able to simultaneously compare and rank multiple treatments over traditional meta-analysis. We evaluated by a NMA the optimal antithrombotic strategy during the perioperative period of implantation of cardiovascular implantable electronic devices (CIEDs).Methods: We performed a network meta-analysis of observational studies (cohort and case-control studies). The eligible studies tested the following antithrombotic therapy during the CIED placement: aspirin, clopidogrel, warfarin, novel oral anticoagulants (NOACs), and heparin bridging.Results: Thirty-one observational studies with 119 study arms were included (41,174 patients receiving long-term antithrombotic therapy; median age, 72.6 years; 70.1% males; median follow-up, 3.6 years). Aspirin (4.26 [2.88-7.22]), warfarin (3.37 [2.17-5.23]), and clopidogrel (3.30 [1.49-5.88]) reduced the risk of bleeding as compared with heparin bridging, and there was no significance difference between continued NOACs and heparin bridging (0.67 [0.21-2.18]). The comparison of commonly used protocols in the management of anticoagulant therapy revealed that continued warfarin (0.38 [0.20-0.74]), continued NOACs (0.19 [0.04-0.89]), and heparin bridging therapy (0.01 [0.05-0.21]) increased the risk of bleeding as compared that of control, and continued warfarin (3.74 [1.96-7.16]), interrupted warfarin (4.89 [2.20-10.88]), and interrupted NOACs (12.5 [1.25-100]) reduced the risk of bleeding compared with that of heparin bridging.Conclusions: Among various antithrombotic drugs, aspirin had the lowest bleeding risk, followed by warfarin, clopidogrel and NOACs, and heparin, with the greatest bleeding risk. NOACs therapy appears safe and effective, and interrupted NOACs may be the optimal anticoagulation protocol for use during the perioperative period of CIED implantation. [ABSTRACT FROM AUTHOR]

Patients on P2Y12 inhibitors may still develop thrombosis or bleeding complications. Tailored antiplatelet therapy, based on platelet reactivity testing, might reduce these complications. Several tests have been used, but failed to show a benefit of tailored antiplatelet therapy. This could be due to the narrowness of current platelet reactivity tests, which are limited to analysis of platelet aggregation after stimulation of the adenosine diphosphate (ADP)-pathway. However, the response to ADP does not necessarily reflect the effect of P2Y12 inhibition on platelet function in vivo. Therefore, we investigated whether measuring platelet reactivity toward other physiologically relevant agonists could provide more insight in the efficacy of P2Y12 inhibitors. The effect of in vitro and in vivo P2Y12 inhibition on αIIbβ3-activation, P-selectin and CD63-expression, aggregate formation, release of alpha, and dense granules content was assessed after stimulation of different platelet activation pathways. Platelet reactivity measured with flow cytometry in 72 patients on P2Y12 inhibitors was compared to VerifyNow results. P2Y12 inhibitors caused strongly attenuated platelet fibrinogen binding after stimulation with peptide agonists for protease activated receptor (PAR)-1 and -4, or glycoprotein VI ligand crosslinked collagen-related peptide (CRP-xl), while aggregation was normal at high agonist concentration. P2Y12 inhibitors decreased PAR-agonist and CRP-induced dense granule secretion, but not alpha granule secretion. A proportion of P2Y12-inhibitor responsive patients according to VerifyNow, displayed normal fibrinogen binding assessed with flow cytometry after stimulation with PAR-agonists or CRP despite full inhibition of the response to ADP, indicating suboptimal platelet inhibition. Concluding, measurement of platelet fibrinogen binding with flow cytometry after stimulation of thrombin- or collagen receptors in addition to ADP response identifies different patients as nonresponders to P2Y12 inhibitors, compared to only ADP-induced aggregation-based assays. Future studies should investigate the value of both assays for monitoring on-treatment platelet reactivity. [ABSTRACT FROM AUTHOR]

Gloydius venom is a rich natural source of proteins possessing platelet aggregation inhibition activity. These proteins or their recombinant analogs are universal instruments for the investigation of proteins and receptors interaction in hemostatic system. At the same time previously studied and potentially new pharmacological properties of platelet aggregation inhibitors from snake venoms create a background for the development of the manufacturing technologies. This study presents a part of technological development of several target proteins parallel obtaining from G. blomhoffii brevicaudus snake venom, in particular deve­lop­ment of manufacturing steps for platelet aggregation inhibitor.The target protein was purified using three different chromatographic approaches. It was shown that it is a single chain protein with molecular weight 12001.55 Da, isoelectrical point 8.03, which inhibited platelet aggregation in the rabbit platelet rich plasma with ID50 = 3.26×10-6 g or 542×10-9 М and revealing no enzyme activity.

A chemically synthesized peptide derived from platelet non-integrin collagen receptor has been shown to be an effective agent for inhibiting collagen-induced platelet aggregation and adhesion of washed radiolabeled platelets onto natural matrices and collagen coated microtiter plates. In order to be a therapeutic agent, we have used a cell culturing system and an animal model to test its cytotoxicities. In cell culture experiments, the peptide is not toxic to MEG-01, a megakaryoblastic cell line. Prior to performing experiments in rats, the existence of both platelet type I and type III collagen receptors and its functional roles in rat platelets had to be established. In this investigation, we report that rat platelets contain both receptors and the cHyB peptide inhibits both type I and type III collagen-induced rat platelet aggregation. In addition, analysis of the rat sera collected at various time intervals following an injection of cHyB into the rat-tail vein, did not show an increase in the activity of key enzymes which indicate tissue and/or organ damage. These results suggest that the cHyB peptide is safe and its development into a potential therapeutic agent for inhibiting thrombi formation is possible.

The authors reflect on the search for the uncertain effects of ticagrelor, a cyclopentyl-triazolo-pyrimidine, which is considered a more effective P2Y12 inhibitor for patients with acute coronary syndrome in the Platelet Inhibition and Patient Outcomes (PLATO) trial than clopidogrel. They discuss a study by Vilahur and colleagues within the issue, which supports the hypothesis on non-P2Y12 and the cardioprotective effects of adenosine.

Aim The aim of the present study was to analyse concomitant drug use and its association with outcome in patients ( N = 17 701) receiving rivaroxaban or standard of care (SOC) for the prevention of venous thromboembolism after major orthopaedic surgery in the non-interventional, phase IV XAMOS (Xarelto® in the prophylaxis of post-surgical venous thromboembolism after elective major orthopaedic surgery of hip or knee) study. Methods Concomitant drug use was at the discretion of the treating physician. Prespecified co-medications of interest were cytochrome P450 (CYP) 3A4/P-glycoprotein inhibitors/inducers, platelet aggregation inhibitors (PAIs) and nonsteroidal anti-inflammatory drugs (NSAIDs). Crude event incidences were compared between rivaroxaban and SOC groups. Results CYP3A4/P-glycoprotein inhibitor/inducer use was infrequent, in contrast to PAI (~7%) and NSAID (~52%) use. Rivaroxaban was associated with a lower incidence of overall symptomatic thromboembolic events compared with SOC, regardless of co-medication use. In both treatment groups, PAI users, with higher age and prevalence of cardiovascular co-morbidities, had similar higher (>7-fold) incidences of symptomatic arterial but not venous thromboembolic events compared with non-users. NSAID use had no influence on thromboembolic events. However, odds ratios (ORs) for major bleeding events ( European Medicines Agency definition) were higher in NSAID users compared with non-users in rivaroxaban [OR = 1.50; 95% confidence interval (CI) 1.06, 2.13] and SOC (OR = 1.70; CI 1.16, 2.49) groups. In PAI users, ORs for major bleeding events were no different from those of non-users in both the rivaroxaban (OR = 1.49; CI 0.84, 2.65) and SOC (OR = 1.46; CI 0.82, 2.62) groups. Conclusions Use of NSAIDs in XAMOS was frequent and associated with a higher frequency of bleeding events in patients receiving rivaroxaban or SOC, although the benefit-risk profile of rivaroxaban compared with SOC was maintained. [ABSTRACT FROM AUTHOR]

Inflammation and hemostasis are part of the host's first line of defense to tick feeding. These systems are in part serine protease mediated and are tightly controlled by their endogenous inhibitors, in the serpin superfamily (serine protease inhibitors). From this perspective ticks are thought to use serpins to evade host defenses during feeding. The cattle tick Rhipicephalus microplus encodes at least 24 serpins, of which RmS-3, RmS-6, and RmS-17 were previously identified in saliva of this tick. In this study, we screened inhibitor functions of these three saliva serpins against a panel of 16 proteases across the mammalian defense pathway. Our data confirm that Pichia pastoris -expressed rRmS-3, rRmS-6, and rRmS-17 are likely inhibitors of pro-inflammatory and pro-coagulant proteases. We show that rRmS-3 inhibited chymotrypsin and cathepsin G with stoichiometry of inhibition (SI) indices of 1.8 and 2.0, and pancreatic elastase with SI higher than 10. Likewise, rRmS-6 inhibited trypsin with SI of 2.6, chymotrypsin, factor Xa, factor XIa, and plasmin with SI higher than 10, while rRmS-17 inhibited trypsin, cathepsin G, chymotrypsin, plasmin, and factor XIa with SI of 1.6, 2.6, 2.7, 3.4, and 9.0, respectively. Additionally, we observed the formation of irreversible complexes between rRmS-3 and chymotrypsin, rRmS-6/rRmS-17 and trypsin, and rRmS-3/rRmS-17 and cathepsin G, which is consistent with typical mechanism of inhibitory serpins. In blood clotting assays, rRmS-17 delayed plasma clotting by 60 s in recalcification time assay, while rRmS-3 and rRmS-6 did not have any effect. Consistent with inhibitor function profiling data, 2.0 μM rRmS-3 and rRmS-17 inhibited cathepsin G-activated platelet aggregation in a dose-responsive manner by up to 96% and 95% respectively. Of significant interest, polyclonal antibodies blocked inhibitory functions of the three serpins. Also notable, antibodies to Amblyomma americanum , Ixodes scapularis , and Rhipicephalus sanguineus tick saliva proteins cross-reacted with the three R. microplus saliva serpins, suggesting the potential of these proteins as candidates for universal anti-tick vaccines. [ABSTRACT FROM AUTHOR]

To reduce pharmacy-related medical expenses, it is necessary to reduce drug costs. One way to achieve this is by increasing the usage rate of generic drugs. The purpose of this study was to identify platelet aggregation inhibitors (PAIs) that contribute to high drug costs and are sold as brand-name drugs in order to increase the usage rate of generic drugs, and to analyze the factors that affect the usage rate of generic drug. We conducted a cross-sectional study based on the National Database of Health Insurance Claims and Specific Health Checkups of Japan Open Data Japan (NODJ) of the Ministry of Health, Labor and Welfare and datasets containing related medical information from official statistical surveys such as the Basic Survey on Wage Structure. Monthly personal income in each prefecture were negatively correlated with outpatient out-of-hospital and outpatient in-hospital prescriptions of the PAIs clopidogrel (75 mg), cilostazol (50 mg), cilostazol (100 mg), and ticlopidine (100 mg), but not between monthly personal income and outpatient out-of-hospital prescription of ticlopidine (100 mg). For outpatient out-of-hospital prescriptions and outpatient in-hospital prescriptions, negative correlation was generally observed between the usage rate of generic drug and monthly personal income, except for ticlopidine (100 mg), which has the lowest price among the brand-name drugs. The usage rate of generic PAIs is negatively correlated with monthly personal income. Promoting the use of generic drugs among high-income earners might be necessary to further increase the usage rate of generic drug., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: MI is an employee of Kifune Pharmacy. The other authors have no conflict of interest.

Snake venoms contain a large variety of proteins and peptides that affect the hemostasis and thrombosis. Numerous antithrombotic peptides have been found in snake venom. However, few studies have been performed on the proteolysis of snake venom for obtaining bioactive peptides. In this study, the Agkistrodon acutus venom was hydrolyzed using four commercial proteases (pepsin, papain, neutrase, and alcalase) and the hydrolysate was tested for antiplatelet aggregation activity. The pepsin hydrolysate, exhibiting the highest activity, was further purified by gel filtration and reversed-phase high performance liquid chromatography. A novel antithrombotic peptide SP-14 was obtained, and its sequence was identified as SHIHGDYSSPSGAP using tandem electrospray mass spectrometry. SP-14 inhibited U46619-induced rabbit platelet aggregation in a dose-dependent manner. It reduced the mortality of mice in acute pulmonary thrombosis model and decreased thrombus weight in rat arteriovenous shunt model, while with lower bleeding risk than aspirin. Therefore, SP-14 may be beneficial for new antithrombotic drug design and development. [ABSTRACT FROM AUTHOR]

Background and Aim The effect of platelet aggregation inhibitors ( PAI) on post-endoscopic sphincterotomy ( ES) bleeding in patients who cannot discontinue PAI for sufficient time in urgent conditions has not been identified. The present study analyzed the effect of sustained use of PAI on post-procedural bleeding in patients undergoing ES. Methods A total of 762 patients were grouped into one of the following groups: no- PAI group ( n = 601), continuation group ( n = 132), and withdrawal group ( n = 29). The continuation group included sustained PAI therapy (sustained user, n = 49) or those in whom therapy was interrupted <7 days prior to ES (non-sustained user, n = 83). The primary outcome was defined as the incidence, type, and severity of post- ES bleeding among groups. Results There were no significant differences between incidence, type, or severity of post- ES bleeding in the three groups. Among 132 patients with continued use of PAI, there was no significant difference regarding incidence and severity of bleeding according to sustained or non-sustained use ( P = 0.071 and P = 0.086, respectively). However, post- ES delayed bleeding was more frequent in sustained PAI users than in non-sustained users (7/49, 14.3% vs 2/83, 2.4%) and was significantly associated with sustained PAI therapy in the continuation group ( P = 0.013). Conclusion Sustained use of PAI without interruption until ES might increase the risk of delayed bleeding. [ABSTRACT FROM AUTHOR]

The centipedes are a type of traditional Chinese herb and can treat cardiovascular diseases. In this study, we aimed to isolate bioactive peptides from the enzymatic hydrolysates of centipedes. Three novel antithrombotic peptides were isolated from centipedes hydrolysates using a combination of ultrafiltration, Sephadex G-50 column, and RP-HPLC C8 column. The molecular mass of the purified peptides are 753, 515 and 985 Da measured by Electrospray Ionization Mass Spectrometry. The primary structures of these peptides were determined to be Phe-Ser-Ala-Pro-Ala-Val-Tyr (FSAPAVY), Ile-Arg-Asp-Leu (IRDL) and Asp-Leu-Asp-His-Tyr-Ser-Phe (DLDHYSF) using Edman degradation method. All isolated peptides potently prolonged the activated partial thromboplastin time. Moreover, IRDL and DLDHYSF can inhibit platelet aggregation, prolong bleeding time and clotting time. These results indicate that the enzymatic hydrolysate of Scolopendra subspinipes mutilans may contribute to the antithrombotic activity of the centipede for treatment of cardiovascular and cerebrovascular diseases. [ABSTRACT FROM AUTHOR]

Objective We aimed to determine the effect of antithrombotics on in-hospital mortality and morbidity in patients with peptic ulcer disease-related upper gastrointestinal bleeding (PUD-related UGIB). Methods The study cohort was retrospectively selected from a tertiary center database of patients with PUD-related UGIB, defined as bleeding due to gastric or duodenal ulcers, or erosive duodenitis, gastritis or esophagitis. Outcomes were compared among patient groups based on their antithrombotic medications before admission. Patients on no antithrombotics served as controls. The composite adverse outcomes, in-hospital mortality, rebleeding and/or need for surgery were measured. Severe bleeding and in-hospital complications were also recorded. Results Of 398 patients with PUD-related UGIB, 44.5% were on aspirin or anticoagulants only. The composite adverse outcome was most common in patients taking anticoagulants only (40.5%), intermediate in controls (23.1%) and least in those taking aspirin only (12.1%). On multivariate analysis, patients taking aspirin alone had a significantly lower risk of adverse outcome events (odds ratio [OR] 0.4, 95% CI 0.2-0.8) and a shorter length of hospital stay (regression coefficient = −3.4, 95% CI [−6.6, −0.6]). In contrast, taking anticoagulants was associated with a greater risk of adverse outcome events ( OR 2.3, 95% CI 1.0-5.3), severe bleeding ( OR 2.6, 95% CI 1.2-5.8) and in-hospital complications ( OR 2.9, 95% CI 1.3-6.6). Conclusions Patients with PUB-related UGIB while taking aspirin had fewer adverse outcomes compared with those taking anticoagulants. Aspirin may have beneficial effects in this population. [ABSTRACT FROM AUTHOR]

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Background: After addressing fundamental questions in preclinical models in vitro or in small animals in vivo, the translation into large animal models has become a prerequisite before transferring new findings to human medicine. Especially in cardiovascular, orthopaedic and reconstructive surgery, the sheep is an important in vivo model for testing innovative therapies or medical devices prior to clinical application. For a wide variety of sheep model based research projects, an optimal anticoagulation and antiplatelet therapy is mandatory. However, no standardised scheme for this model has been developed so far. Thus the efficacy of antiplatelet (acetylsalicylic acid, clopidogrel, ticagrelor) and anticoagulant (sodium enoxaparin, dabigatran etexilate) strategies was evaluated through aggregometry, anti-factor Xa activity and plasma thrombin inhibitor levels in sheep of different ages. Results: Responses to antiplatelet and anticoagulant drugs in different concentrations were studied in the sheep. First, a baseline for the measurement of platelet aggregation was assessed in 20 sheep. The effectiveness of 225 mg clopidogrel twice daily (bid) in 2/5 sheep and 150 mg bid in 3/5 lambs could be demonstrated, while clopidogrel and its metabolite carboxylic acid were detected in every plasma sample. High dose ticagrelor (375 mg bid) resulted in sufficient inhibition of platelet aggregation in 1/5 sheep, while acetylsalicylic acid did not show any antiplatelet effect. Therapeutic anti-factor Xa levels were achieved with age-dependent dosages of sodium enoxaparin (sheep 3 mg/kg bid, lambs 5 mg/kg bid). Administration of dabigatran etexilate resulted in plasma concentrations similar to human ranges in 2/5 sheep, despite receiving quadruple dosages (600 mg bid). Conclusion: High dosages of clopidogrel inhibited platelet aggregation merely in a low number of sheep despite sufficient absorption. Ticagrelor and acetylsalicylic acid cannot be recommended for platelet inhibition in sheep. Efficient anticoagulation can be ensured using sodium enoxaparin rather than dabigatran etexilate in age-dependent dosages. The findings of this study significantly contribute to the improvement of a safe and reliable prophylaxis for thromboembolic events in sheep. Applying these results in future translational experimental studies may help to avoid early dropouts due to thromboembolic events and associated unnecessary high animal numbers. [ABSTRACT FROM AUTHOR]

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Decorsin, an antagonist of integrin glycoprotein IIb/IIIa, contains Arg-Gly-Asp (RGD) sequence and three disulfide bridges. The function of RGD sequence has already been well defined, but the roles of conserved disulfide bonds in antihemostatic proteins still remain unclear. Herein we use the fusion expression and characterization of mutant decorsin to study the functions of disulfide bonds in protein structure, stability and biological activity. The purified protein shows an apparent inhibition of activity to platelet aggregation induced by ADP with IC50 of 500 nM. The removal of cys7-cys15 (from cysteine to serine) at the N-terminal causes a thirty-fold decrease of the inhibition activity with IC50 of 15 μM, whereas the mutation of cys22-cys38 at the C-terminal completely impairs the biological activity of decorsin. The overall secondary and tertiary structures of decorsin are disrupted inevitably without disulfide bonds. Using a domain insertion mutation, the retaining of RGD loop and the adjacent disulfide bond produces a week antihemostatic activity of decorsin. This reveals that the overall structure of decorsin stabilized by the three conserved disulfide bridges is cooperative for antihemostatic function. Our study on the effect of disulfide bonds together with RGD-sequence on the protein function is helpful for structure-based drug design of antithrombotic research. [ABSTRACT FROM AUTHOR]

Abstract: Ethnopharmacological relevance: The centipede has been prescribed for the treatment of cardiovascular diseases in Korea, China and other Far Eastern Asian countries for several hundred years. Materials and methods: A novel antithrombotic peptide was isolated from Scolopendra subspinipes mutilans using a combination of ultrafiltration, Sephadex G-50 column, Source 15Q anion exchange column and RP-HPLC C18 column. Results: The molecular mass of the purified peptide is 346Da measured by Electrospray Ionization Mass Spectrometry (ESI-MS). The primary structure of the peptide is Ser-Gln-Leu (SQL) determined by Edman degradation. SQL potently prolonged the activated partial thromboplastin time (aPTT), and inhibited platelet aggregation. Conclusions: These results help to clarify the mechanism of the antithrombotic activity of the centipede for effective treatment of cardiovascular and cerebrovascular diseases. [Copyright &y& Elsevier]

Salmosin, a snake venom-derived disintegrin, was successfully expressed in the methylotrophic yeast Pichia pastoris and secreted into the culture supernatant, as a 6 kDa protein. High-cell density fermentation of recombinant P. pastoris was optimized for the mass production of salmosin. In a 5 L jar fermentor, recombinant P. pastoris was fermented in growth medium containing 5% (w/v) glycerol at the controlled pH of 5.0. After culturing for 21 h, glycerol feeding medium was fed at one time into the culture broth. After 7 h (a total of 28 h), induction medium that contained methanol was increasingly added until the culture time totaled 75 h. Finally, these optimized culture conditions produced a high cell density of recombinant P. pastoris (dry cell weight of 113.38 g/L) and led to the mass production of salmosin (a total protein concentration of 369.2 mg/L). The culture supernatant containing salmosin inhibited platelet aggregation, resulting in a platelet aggregation of 9% compared to that of 94% in the control experiment, without culture supernatant. These results demonstrate that recombinant salmosin in culture supernatant from high cell density fed-batch fermentation can serve as a platelet aggregation inhibitor. [ABSTRACT FROM AUTHOR]

Abstract: A novel convergent method for the synthesis of α-acyl-γ-hydroxylactams utilizing the aldol reaction of N-Boc-protected γ-methoxylactams was developed. As the first application of this method for the synthesis of biologically active natural products, the total synthesis of platelet aggregation inhibitors PI-090 and PI-091 were also investigated and successfully achieved. [Copyright &y& Elsevier]

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Abstract: This study focuses on the structural and functional characterizations of novel venom phospholipases A2 (PLA2s) from Trimeresurus gracilis, an endemic Taiwanese pitviper. The PLA2 cDNAs were cloned from venom glands and sequenced. The majority of the clones encoded a Glu6-containing PLA2 (designated as Tgc-E6) whose deduced amino acid sequence resembled those of other Crotalinae acidic PLA2s. Tgc-E6 was also purified and constituted about 6% (w/w) of the total venom proteins. For human platelet rich plasma, Tgc-E6 inhibited the ADP- and collagen-induced aggregation with an IC50 of 272 nM and 518 nM, respectively. Like Ovophis okinavensis venom, T. gracilis venom did not contain any Lys49-PLA2s, although a cDNA encoding Lys49-PLA2 has been cloned from each of the species. Their predicted protein sequences are 94% identical, and their pI values 8.3 are lower than those of other Lys49-PLA2s, mainly due to the acidic substitutions within positions 78–111, which are apparently more similar to those in Tgc-E6 than to those in other Lys49-PLA2s. This unique structural feature of the venom PLA2s thus render evidence for close phylogenetic relationship between both species. The structural variations in the venom acidic PLA2s of the two species possibly have resulted from adaptation to different prey ecology. [Copyright &y& Elsevier]

The article presents an executive summary of a guideline which details the procedure for coronary artery bypass graft surgery. It provides information on the methodology and evidence of the said cardiac surgical procedure. It highlights the recommendations for proper anesthetic, echocardiography, and preconditioning of myocardial ischemia procedures. The proper reporting of the disease's morbidity and mortality is also noted.

The article presents an executive summary for a guideline set for percutaneous coronary intervention. It provides information on the safe and systematic procedures for the said medical intervention. It mentions the recommendations addressed for the proper revascularization. Furthermore, the beneficial and adverse effects of drugs for the said intervention are also mentioned.

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Blood coagulation is the process that results in the formation of a blood clot to stop bleeding from a damaged blood vessel. Various pharmacologic agents can affect the coagulation process. The American College of Chest Physicians' evidence-based practice guidelines for perioperative management of antithrombotic therapy provide guidance for anticoagulant or antiplatelet therapy and bridge therapy. Perioperative nurses must understand the pharmacologic principles of the most common blood coagulation modifiers related to perioperative use. The perioperative nurse's responsibilities regarding administration of blood coagulation modifiers include reviewing the patient's pertinent laboratory results (eg, prothrombin time, partial thromboplastin time, international normalized ratio), recognizing the underlying conditions that require blood coagulation therapy, and documenting all pertinent information. Perioperative nurses also should participate in development of detailed storage and retrieval policies related to heparin. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study has been to investigate the antiplatelet activity of a new series of thienylacylhydrazone derivatives analogous to the lead compound LASSBio-294 ((2-thienylidene) 3,4-methylenedioxybenzoylhydrazine). The antiplatelet effect was investigated in rabbit and human platelet rich plasma stimulated by arachidonic acid, collagen, ADP and in washed platelet stimulated by thrombin. The effects on the production of cyclic nucleotides and thromboxane A2 (TXA2) in human platelets were also investigated. Compounds LASSBio-785 (N-Methyl (2-thienylidene) 3,4-methylenedioxybenzoylhydrazine), LASSBio-786 (N-Benzyl (2-thienylidene) 3,4-methylenedioxybenzoylhydrazine), LASSBio-787 ((5-Methyl-2-thienylidene) 3,4-methylenedioxybenzoylhydrazine), LASSBio-788 (N-Allyl (2-thienylidene) 3,4-methylenedioxybenzoylhydrazine) and LASSBio-789 ((5-Bromo-2-thienylidene) 3,4-methylenedioxybezoylhydrazine) inhibited platelet aggregation induced by arachidonic acid, collagen and ADP. LASSBio-785, LASSBio-788 and LASSBio-789 presented the higher potency in platelet aggregation induced by arachidonic acid (IC50 values of 0.3, 0.2 and 3.1μM, respectively) and collagen (IC50 values of 0.9, 1.5 and 3.4uM, respectively), with a 20 to 70-fold increase in potency compared to LASSBio-294. They inhibited the ATP release reaction by 95%, the whole blood aggregation by 35–45% and the TXB2 production was totally abolished. In addition, they presented a significant effect on bleeding time. Qualitative studies in thrombin-induced washed platelet aggregation in the presence of sodium nitroprusside (SNP) suggested a phosphodiesterase-2 (PDE2) like effect for LASSBio-785, LASSBio-788 and LASSBio-789. They were able to increase the cGMP levels in non-stimulated platelets, in SNP-stimulated platelets and in the presence of 1-H- [1, 2, 4] oxadiazolo [4, 3- a] quinoxalin- 1- one (ODQ). The antiplatelet aggregation activity exerted by thienylacylhydrazone derivatives seems to be related to cyclic nucleotides regulation and TXA2 synthesis inhibition. The structural modification of compound LASSBio-294 led to the optimization of its pharmacological properties and to the discovery of new potent antiplatelet prototypes with an antithrombotic potential. [Copyright &y& Elsevier]

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Background: Cilostazol is an antiplatelet agent that inhibits phosphodiesterase III in platelets and vascular endothelium. Previous randomized controlled trials of cilostazol for prevention of cerebrovascular events have garnered mixed results. We performed a systematic review and meta-analysis of the randomized clinical trials in patients with atherothrombotic diseases to determine the effects of cilostazol on cerebrovascular, cardiac, and all vascular events, and on all major hemorrhagic events. Methods: Relevant trials were identified by searching MEDLINE, EMBASE, and the Cochrane Controlled Trial Registry for titles and abstracts. Data from 12 randomized controlled trials, involving 5674 patients, were analyzed for end points of cerebrovascular, cardiac, and major bleeding events. Searching, determination of eligibility, data extraction, and meta-analyses were conducted by multiple independent investigators. Results: Data were available in 3782, 1187, and 705 patients with peripheral arterial disease, cerebrovascular disease, and coronary stenting, respectively. Incidence of total vascular events was significantly lower in the cilostazol group compared with the placebo group (relative risk [RR], 0.86; 95% confidence interval [CI], 0.74-0.99; P=.038). This was particularly influenced by a significant decrease of incidence of cerebrovascular events in the cilostazol group (RR, 0.58; 95% CI, 0.43-0.78; P < .001). There was no significant intergroup difference in incidence of cardiac events (RR, 0.99; 95% CI, 0.83-1.17; P=.908) and serious bleeding complications (RR, 1.00; 95% CI, 0.66-1.51; P=.996). Conclusions: This first meta-analysis of cilostazol in patients with atherothrombosis demonstrated a significant risk reduction for cerebrovascular events, with no associated increase of bleeding risk. [Copyright &y& Elsevier]

The platelet P2Y12 receptor is the target of clopidogrel therapy, which has been shown to reduce thromboembolic complications of atherosclerotic disease but has limitations in terms of variability of response and irreversibility of effect. This receptor is also a target for ticagrelor (AZD6140), the first reversibly binding oral P2Y12 receptor antagonist that does not require metabolic activation and yields more consistent inhibition of platelet aggregation than clopidogrel therapy. Single nucleotide polymorphisms (SNPs) have been described in the gene for this receptor (P2RY12), some of which have been associated with variability in platelet reactivity. SNPs in P2RY1 and ITGB3 have also been reported by some groups to affect platelet reactivity to adenosine diphosphate (ADP). We assessed whether SNPs in these genes influenced the pharmacodynamic response to ticagrelor in patients enrolled in both the DISPERSE study (stable atherosclerotic disease) and the DISPERSE2 study (non-ST-segment elevation acute coronary syndromes). Platelet aggregation data (at baseline and 4 weeks) and DNA samples from clopidogrel-naive Caucasian patients treated with ticagrelor were available for 151 patients. Seventy four SNPs within three genes were genotyped. After adjustment for multiple comparisons, none of these SNPs were found to significantly influence inhibition of ADP-induced platelet aggregation by ticagrelor. [ABSTRACT FROM AUTHOR]

This integrated analysis compared speed of onset, level of platelet inhibition, and response variability to prasugrel and clopidogrel in healthy subjects and in patients with stable coronary artery disease with data pooled from 24 clinical pharmacology studies. Data from subjects (N = 846) were categorized into the following treatment groups: prasugrel 60 mg loading dose (LD)/10 mg maintenance dose (MD), clopidogrel 300 mg LD/75 mg MD, or clopidogrel 600 mg LD/75 mg MDs. Maximum platelet aggregation (MPA) and inhibition of platelet aggregation (IPA) to 5 and 20 μM ADP were assessed by turbidimetric aggregometry. A linear mixed-effect model compared the MPA and IPA between treatments over time points evaluated in the integrated database, and covariates affecting platelet inhibition were identified. Prasugrel 60 mg LD resulted in faster onset, greater magnitude, and more consistent levels of inhibition of platelet function compared to either clopidogrel 300 mg or 600 mg LDs. Greater and more consistent levels of platelet inhibition were observed with the prasugrel 10 mg MD compared to the clopidogrel 75 mg MD. This integrated analysis confirms the findings of earlier individual studies, that prasugrel achieves faster onset of greater extent and more consistent platelet inhibition compared to the approved and higher loading doses of clopidogrel. Gender, race, body weight, and age were identified as statistically significant covariates impacting platelet inhibition. [ABSTRACT FROM AUTHOR]

Abstract: A platelet aggregation inhibitor, named snake venom platelet aggregation dissociator (SV-PAD)-1, with a dissociative reaction of ADP-induced platelet aggregation, was purified from the venom of Protobothrops elegans (Sakishima-habu) by gel-filtration employing Sephadex G-100, and ion-exchange chromatographies using DEAE-Sepharose Fast Flow, CM-Sepharose Fast Flow, and Mono S. By this procedure, about 1.5mg of purified protein was obtained from 1.0g of P. elegans venom. The purified protein showed a single protein band and the molecular weight was about 110kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions. The pI of purified protein showed four-bands of 7.7, 7.8, 7.95, and 8.15. This protein strongly inhibited ADP-induced platelet aggregation in rabbit platelet-rich plasma (PRP), and its IC50 was about 58nM. It inhibited ristocetin-induced platelet aggregation in rabbit PRP (IC50: 100nM), but hardly blocked collagen-induced platelet aggregation. This protein promptly dissociated platelet aggregation in rabbit PRP stimulated by high-concentration ADP. [Copyright &y& Elsevier]

Abstract: Phospholipase A2 (PLA2, EC 3.1.1.4), a major component of snake venoms, specifically catalyzes the hydrolysis of fatty acid ester bonds at position 2 of 1,2-diacyl-sn-3-phosphoglycerides in the presence of calcium. This article reports the purification and biochemical/functional characterization of BmooTX-I, a new myotoxic acidic phospholipase A2 from Bothrops moojeni snake venom. The purification of the enzyme was carried out through three chromatographic steps (ion-exchange on DEAE–Sepharose, molecular exclusion on Sephadex G-75 and hydrophobic chromatography on Phenyl–Sepharose). BmooTX-I was found to be a single-chain protein of 15,000Da and pI 4.2. The N-terminal sequence revealed a high homology with other acidic Asp49 PLA2s from Bothrops snake venoms. It displayed a high phospholipase activity and platelet aggregation inhibition induced by collagen or ADP. Edema and myotoxicity in vivo were also induced by BmooTX-I. Analysis of myotoxic activity was carried out by optical and ultrastructural microscopy, demonstrating high levels of leukocytary infiltrate. Previous treatment of BmooTX-I with BPB reduced its enzymatic and myotoxic activities, as well as the effect on platelet aggregation. Acidic myotoxic PLA2s from Bothrops snake venoms have been little explored and the knowledge of its structural and functional features will be able to contribute for a better understanding of their action mechanism regarding enzymatic and toxic activities. [Copyright &y& Elsevier]

A chemically synthesized peptide derived from platelet non-integrin collagen receptor has been shown to be an effective agent for inhibiting collagen-induced platelet aggregation and adhesion of washed radiolabeled platelets onto natural matrices and collagen coated microtiter plates. In order to be a therapeutic agent, we have used a cell culturing system and an animal model to test its cytotoxicities. In cell culture experiments, the peptide is not toxic to MEG-01, a megakaryoblastic cell line. Prior to performing experiments in rats, the existence of both platelet type I and type III collagen receptors and its functional roles in rat platelets had to be established. In this investigation, we report that rat platelets contain both receptors and the cHyB peptide inhibits both type I and type III collagen-induced rat platelet aggregation. In addition, analysis of the rat sera collected at various time intervals following an injection of cHyB into the rat-tail vein, did not show an increase in the activity of key enzymes which indicate tissue and/or organ damage. These results suggest that the cHyB peptide is safe and its development into a potential therapeutic agent for inhibiting thrombi formation is possible. [ABSTRACT FROM AUTHOR]

Abstract: We have previously reported that a recombinant protein (Mr 47 kDa), which contains both active peptide of platelet receptors for types I and III collagen inhibits both types I and III collagen-induced platelet aggregation. In order to eliminate non-reactive portion of the protein, we have constructed a recombinant of rHyB (Mr 6 kDa). In addition, we chemically synthesized a hybrid peptide with 30 amino acid residues (cHyB, Mr 3 kDa) that contains each of the active peptide derived from platelet receptors for types I and III collagen and a linker of 12 amino acid residues. In the present investigation, we report that both rHyB and cHyB inhibit type I and type III collagen-induced platelet aggregation, and the adhesion of radiolabeled platelets onto rabbit aortic segments in a dose-dependent manner. We have used an animal model, which employs FeCl3 to induce thrombi formation to study the effectiveness of both rHyb and cHyB on preventing thrombi formation. We obtained results that show that both rHyB and cHyB can inhibit thrombi formation in a dose-dependent manner. These results suggest that either rHyB or cHyB may be a possible therapeutic agent in preventing thrombi formation. [Copyright &y& Elsevier]

Introduction: The reported range in rates of aspirin resistance (5.5–60%) may reflect difficulties in studying platelet function and the variety of tests used. This study used a platelet function analyzer (PFA-100) to prospectively document aspirin resistance in a cohort of patients with arterial disease. Methods: Patients with internal carotid artery (ICA) stenosis or intermittent claudication (IC) were recruited. Exclusion criteria were contraindications to aspirin, prescription of other medication with known antiplatelet effects or known platelet abnormalities. After prescription of 100 mg aspirin/day for 2 weeks an uncuffed venous blood sample was taken and analysed with the PFA-100. Aspirin resistance was defined as closure time (CT) less than the upper limit of normal (158 s collagen/epinephrine agonist; 118 s collagen/adenosine diphosphate (ADP) agonist). Results: Thirty-three patients with IC and 12 patients with ICA stenosis were recruited ( n = 45). Median (range) age was 74 years (49–85) and the male to female ratio was 1.5:1. The median (range) CT was >300 (85 to >300) s with collagen/epinephrine and 100 (52 to >300) s with collagen/ADP agonist. Twelve patients (27%) in the collagen/epinephrine group had normal CT despite treatment with 100 mg aspirin, indicating resistance. Of the 33 patients with collagen/epinephrine CT prolonged by aspirin, 10 patients also had prolonged collagen/ADP CT, suggesting excessive platelet inhibition. Conclusion: A significant proportion of patients taking aspirin do not show laboratory evidence of platelet inhibition and may not be protected from atherothrombotic events. The PFA-100 appears to be a useful tool to screen for both aspirin resistance and excessive aspirin mediated platelet inhibition. [ABSTRACT FROM AUTHOR]

Abstract: This study describes the extraction and characterization of a platelet aggregation inhibitory peptide from Inonotus obliquus. Ethanol extract from I. obliquus ASI 74006 mycelia showed the highest platelet aggregation inhibitory activity (81.2%). The maximum platelet aggregation inhibitory activity was found when the mycelia of I. obliquus ASI 74006 was extracted with ethanol at 80°C for 12h. The platelet aggregation inhibitor was purified by systematic solvent fractionation, ultrafiltration, Sephadex G-10 column chromatography, and reverse-phase HPLC. The purified platelet aggregation inhibitor is a novel tripeptide with a molecular mass of 365Da, having a sequence of Trp-Gly-Cys. The purified platelet aggregation inhibitor also showed high platelet aggregation inhibitory activity in Institute of Cancer Research (ICR) mice. [Copyright &y& Elsevier]

Excessive platelet activation and accumulation can lead to vessel occlusion and thus present major therapeutic challenges in cardiovascular medicine. Apyrase, an ecto-enzyme with ADPase and ATPase activities, rapidly metabolizes ADP and ATP released from platelets and endothelial cells, thereby reducing platelet activation and recruitment. In the present study, we expressed a 68-kDa recombinant mosquito (Aedes aegypti) salivary apyrase using a baculovirus/insect cell expression system and purified it to homogeneity using anion-exchange chromatography on a large scale. A yield of 18&ThickSpace;mg of purified recombinant apyrase was obtained from 1 litre of the medium. Kinetic analysis indicated that the recombinant apyrase had a K m of 12.5&ThickSpace;µM for ADP and a K m of 15.0&ThickSpace;µM for ATP. The recombinant apyrase inhibited ADP-, collagen- and thrombin-induced human platelet aggregation in a dose-dependent manner, indicating that the recombinant protein retained nucleotidase activity in a whole cell system, which suggests that it may serve as a therapeutic agent for inhibition of platelet-mediated thrombosis. [ABSTRACT FROM AUTHOR]

Abstract: Bitistatin is a single-chain disintegrin which contains 83 amino acids and is internally crosslinked with seven disulfide bonds. This platelet aggregation inhibitor, which binds with high affinity to the αIIbβ3 integrin, has potential use as the basis for a radiotracer to locate thrombi and emboli by scintigraphic imaging. A method amenable to large-scale, consistent production of bitistatin was sought. A synthetic gene coding for bitistatin was inserted into two different Escherichia coli expression vectors. One vector expressed recombinant bitistatin (rBitistatin) as a cleavable fusion protein and the other expressed rBitistatin as an isolated protein. In both cases, rBitistatin contained an additional amino acid (Gly) at the N-terminus compared with the native protein. The fusion protein was purified by affinity chromatography, then cleaved enzymatically to release rBitistatin, which was purified by reversed-phase high performance liquid chromatography (HPLC) to a single active form. The rBitistatin produced as an isolated protein was purified from cell lysate by HPLC in a reduced form, then refolded, and purified again by HPLC. Yields of active rBitistatin averaged 12mg/L for expression as an isolated protein, 10 times as high as when the fusion protein was employed. Structural assays confirmed the expected mass and sequence of the product. Functional assays (inhibition of platelet aggregation in vitro, equilibrium binding to platelets in vitro, and binding of labeled protein to experimental thrombi and emboli in vivo) confirmed that rBitistatin retained the functional characteristics of native bitistatin. [Copyright &y& Elsevier]

Rhodocetin is a unique heterodimer consisting of α- and β-subunits of 133 and 129 residues, respectively. The molecule, purified from the crude venom of the Malayan pit viper, Calloselasma rhodostoma, functions as an inhibitor of collagen-induced aggregation. Rhodocetin has been shown to have activity only when present as a dimer. The dimer is formed without an intersubunit disulfide bridge, unlike all the other Ca2+-dependent lectin-like proteins. We report here the 1.9 Å resolution structure of rhodocetin, which reveals the compensatory interactions that occur in the absence of the disulfide bridge to preserve activity. [ABSTRACT FROM AUTHOR]