Advances in antiplatelet therapy

Panax Notoginseng Saponins Combined with Dual Antiplatelet Drugs Potentiates Anti-Thrombotic Effect with Alleviated Gastric Injury in A Carotid Artery Thrombosis Rat Model

OBJECTIVE

To observe the combination effects of Panax notoginseng saponins (PNS)and dual antiplatelet drugs (DAPT), and to explore the mechanism via cyclooxygenase /prostaglandin pathway.

METHODS

Right carotid artery thrombosis was induced in Wistar rats by infiltration with 70% FeCl₃, and the animals were randomly divided into sham group, model group, DAPT group and PNS + DAPT group, intragastrically treated for 4 weeks. The cerebral pia mater microcirculation was observed in vivo after anesthetizing by anatomical microscope. The wet weight of carotid artery thrombosis was measured. Gastric mucosal injury was observed by hematoxylin and eosin staining. Platelet aggregation rate was detected with adenosine diphosphate -induced turbidimetry. Platelet CD62p expression was detected by flow cytometry. Concentrations of 6-Ketoprostaglandin F1 alpha, prostaglandin E₂ in gastric mucosa and thromboxane B₂, 6-Ketoprostaglandin F1 alpha, tissue plasminogen activator, plasminogen activator inhibitor, and fibrin fragment D in the plasma were measured by radioimmunoassay.

RESULTS

PNS and DAPT increased the blood flow volume of cerebral pia mater and decreased erythrocyte aggregation and leukocyte adhesion of model rats. Compared to DAPT, PNS and DAPT further reduced the weight of carotid artery thrombosis with enhanced inhibition of platelet aggregation, increased tissue plasminogen activator levels and decreased fibrin fragment D levels. PNS and DAPT alleviated gastric injury induced by dual antiplatelet drugs and upregulated the expression of 6-Ketoprostaglandin F1 alpha in the gastric mucosa compared with DAPT.

CONCLUSIONS

PNS combined with DAPT increased anti-thrombosis effects of DAPT and mitigated DAPT-related gastric injury. The underlying mechanisms may be associated with enhanced antiplatelet aggregation and activation of the fibrinolytic system and up-regulation of 6-Ketoprostaglandin F1 alpha expression in gastric mucosa.

Acute Coronary Syndromes: Unstable Angina and Non-ST Elevation Myocardial Infarction

Non-ST elevation acute coronary syndromes (NSTE-ACS) encompass the clinical entities of unstable angina and non-ST elevation myocardial infarction. Several advances have occurred over the past decade, including the emergence of new antiplatelet and antithrombotic therapies and novel treatment strategies, leading to marked improvements in mortality. However, there has also been an increased incidence in NSTE-ACS as a result of the use of high-sensitivity troponins and the increase in cardiovascular risk factors. This article provides a focused update on contemporary management strategies pertaining to antiplatelet, antithrombotic, and anti-ischemic therapies and to revascularization strategies in patients with ACS.

A new ibuprofen derivative inhibits platelet aggregation and ROS mediated platelet apoptosis

Thrombocytopenia is a serious issue connected with the pathogenesis of several human diseases including chronic inflammation, arthritis, Alzheimer's disease, cardiovascular diseases (CVDs) and other oxidative stress-associated pathologies. The indiscriminate use of antibiotics and other biological drugs are reported to result in thrombocytopenia, which is often neglected during the treatment regime. In addition, augmented oxidative stress induced by drugs and pathological conditions has also been shown to induce thrombocytopenia, which seems to be the most obvious consequence of elevated rate of platelet apoptosis. Thus, blocking oxidative stress-induced platelet apoptosis would be of prime importance in order to negotiate thrombocytopenia and associated human pathologies. The current study presents the synthesis and platelet protective nature of novel ibuprofen derivatives. The potent anti-oxidant ibuprofen derivative 4f was selected for the study and the platelet protective efficacy and platelet aggregation inhibitory property has been demonstrated. The compound 4f dose dependently mitigates the oxidative stress-induced platelet apoptosis in both platelet rich plasma and washed platelets. The platelet protective nature of compound 4f was determined by assessing various apoptotic markers such as ROS generation, cytosolic Ca2+ levels, PS externalization, cytochrome C translocation, Caspase activation, mitochondrial membrane depolarization, cytotoxicity, LDH leakage and tyrosine phosphorylation of cytosolic proteins. Furthermore, compound 4f dose dependently ameliorated agonist induced platelet aggregation. Therefore, compound 4f can be estimated as a potential candidate in the treatment regime of pathological disorders associated with platelet activation and apoptosis. In addition, compound 4f can be used as an auxiliary therapeutic agent in pathologies associated with thrombocytopenia.

The 2012 ACCF/AHA Focused Update of the Unstable Angina/Non-ST-Elevation Myocardial Infarction (UA/NSTEMI) Guideline: a critical appraisal

The American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA) recently published the 2012 ACCF/AHA Focused Update of the Guidelines for the Management of Patients with Unstable Angina and Non-ST-Elevation Myocardial Infarction (Updating the 2007 Guideline and Replacing the 2011 Update).(1) These guidelines were developed in collaboration with multiple societies and represent an important landmark in the management of patients with unstable angina (UA) and non-ST-elevation myocardial infarction (NSTEMI). This paper provides a critical overview of some of the clinically relevant novel and modified recommendations proposed by the updated guideline.

[Massive subretinal hemorrhage and anticoagulants. An unfortunate combination?]

Exudative age-related macular degeneration (ARMD) is one of the conditions which has been shown to be associated with a risk of massive subretinal hemorrhage. Patients with thick submacular hemorrhage complicating ARMD typically have a poor visual prognosis. Antiplatelet therapy with aspirin, clopidogrel or ticlopidine has significant benefits in the secondary prevention of fatal and non-fatal coronary and cerebrovascular events. Anticoagulation is frequently used in this elderly age group for a variety of other comorbidities including prosthetic heart valves, atrial fibrillation, ischemic heart disease, cerebrovascular disease and venous thromboembolism. However, it is a well established observation that the longer patients remain on anticoagulant therapy, the higher the cumulative risk of bleeding. Over the past years, there has been a rapidly growing body of literature concerning the risk of hemorrhagic ocular complications with ophthalmic surgery in patients receiving anticoagulant therapy. By contrast, there are still little data on the relationship between anticoagulation or antiplatelet therapy and spontaneous ocular hemorrhages and only few reports have focused on patients with ARMD. Just recently, several authors reported a strong association of anticoagulants and antiplatelet agents with the development of large subretinal hemorrhages in ARMD patients. Moreover, arterial hypertension is a high risk factor for large subretinal hemorrhages in ARMD patients receiving anticoagulants or antiplatelet agents. Physicians should be aware of an increased risk of extensive subretinal hemorrhage in ARMD patients when deciding on the initiation and duration of anticoagulant and antiplatelet therapy.

Epidemiology of the association between anticoagulants and intraocular hemorrhage in patients with neovascular age-related macular degeneration

PURPOSE

To determine the cumulative incidence and annual incidence of intraocular hemorrhage (subretinal hemorrhage or vitreous hemorrhage) in patients with neovascular age-related macular degeneration (AMD) and association with daily antiplatelet or anticoagulant (AP/AC) medication usage (aspirin, clopidogrel, and warfarin), age, gender, hypertension, diabetes mellitus, or bilateral neovascular AMD.

METHODS

Retrospective cross-sectional study in a tertiary university setting. Data on 195 eyes of 195 patients without previous intraocular hemorrhage examined over 73 months were reviewed.

RESULTS

Ninety-six of 195 patients (49.2%) were taking daily AP/ACs. Of patients taking daily AP/AC agents, 63.5% had hemorrhage compared with 29.2% of patients not taking (odds ratio = 4.21; 95% confidence interval = 1.42-8.46; P < 0.001). The overall annual incidence of intraocular hemorrhage was 0.14% per year. Among patients taking daily AP/AC, the cumulative incidence (61 of 96, 63.5%) and annual incidence (0.10%) of concurrent intraocular hemorrhage were significantly greater compared with patients not taking them (29 of 99, 29.2% and 0.04%, respectively; P < 0.0001). Fourteen of 18 patients (77%) taking more than 1 daily AP/AC had occurrence of intraocular hemorrhage. Antiplatelet or anticoagulant usage was an independent risk factor for the development of intraocular hemorrhage. The use of any agent resulted in a significantly increased risk of developing intraocular hemorrhage. Additionally, presence of bilateral neovascular AMD was a significant association in those taking daily AP/ACs, whereas age was a significant association in those not taking daily AP/AC agents.

CONCLUSION

All three daily AP/AC types were significantly associated with an increased risk of the development intraocular hemorrhage in patients with neovascular AMD, whereas gender, hypertension, and diabetes were not. Age was not significantly associated with hemorrhage in patients taking daily AP/AC agents, whereas the presence of bilateral neovascular AMD was significantly associated with hemorrhage. These findings indicate that the AP/AC use may predispose patients with neovascular AMD to intraocular hemorrhage more so than age and duration of disease alone. While the risk that discontinuing these medicines would pose to the patients' health may be too great to justify, ensuring that an appropriate medication dosage is maintained should be a priority within this patient population.

Thrombin receptor (PAR-1) antagonists as novel antithrombotic agents

In addition to its central role in haemostasis and wound healing, thrombin activates platelets and smooth muscle cells by proteolytic activation of cell surface protease-activated receptor-1 (PAR-1), which is also known as the thrombin receptor. Thrombin is the most potent activator of human platelets and, as such, a thrombin receptor antagonist is likely to exert potent antithrombotic effect in platelet-rich arterial thrombosis. As thrombin receptor antagonism does not inhibit the ability of thrombin to generate fibrin, such an agent is likely to have less bleeding liability than conventional anticoagulants. The proof-of-concept of the antithrombotic effect of PAR-1 antagonists has been established in several non-human primate models. The current success of PAR-1 research is underscored by the advancement of two candidates into clinical trails for acute coronary syndrome by Schering-Plough and Eisai Company.

Subretinal hemorrhages associated with age-related macular degeneration in patients receiving anticoagulation or antiplatelet therapy

PURPOSE

To evaluate the incidence of and risk factors for subretinal hemorrhages in age-related macular degeneration (AMD) patients on anticoagulation or antiplatelet therapy.

DESIGN

Retrospective, observational case series.

METHODS

We retrospectively reviewed the medical and photographic records of 71 consecutive patients who sought treatment at our institution with acute subretinal hemorrhages complicating age-related macular degeneration. The size of the subretinal hemorrhage was measured in standardized Macular Photocoagulation Study disc areas. Data on the use of medications and medical indications for anticoagulation and antiplatelet therapy were obtained.

RESULTS

Overall, patients receiving antithrombotic therapy had a significantly larger subretinal hemorrhage size (mean, 9.71 disc areas) than patients not receiving anticoagulant or antiplatelet therapy (mean, 2.99 disc areas). Subgroup analysis revealed that both antiplatelet (P < .0001) and anticoagulant therapy (P = .003) were associated with a significantly larger bleeding size. Moreover, subgroup analysis among patients with arterial hypertension revealed that individuals receiving antithrombotic therapy had a statistically significantly larger hemorrhage size than hypertensive patients who did not receive anticoagulants or antiplatelet agents (P < .0001).

CONCLUSIONS

Our results indicate that anticoagulants and antiplatelet agents are strongly associated with the development of large subretinal hemorrhages in AMD patients. Moreover, arterial hypertension is a strong risk factor for large subretinal hemorrhages in AMD patients receiving anticoagulants or antiplatelet agents. Physicians should be aware of an increased risk of extensive subretinal hemorrhage in AMD patients when deciding on the initiation and duration of anticoagulant and antiplatelet therapy.

Discovery of novel protease activated receptors 1 antagonists with potent antithrombotic activity in vivo

Protease activated receptors (PARs) or thrombin receptors constitute a class of G-protein-coupled receptors (GPCRs) implicated in the activation of many physiological mechanisms. Thus, thrombin activates many cell types such as vascular smooth muscle cells, leukocytes, endothelial cells, and platelets via activation of these receptors. In humans, thrombin-induced platelet aggregation is mediated by one subtype of these receptors, termed PAR1. This article describes the discovery of new antagonists of these receptors and more specifically two compounds: 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)penta-1,3-dienyl]benzonitrile 36 (F 16618) and 3-(2-chlorophenyl)-1-[4-(4-fluorobenzyl)piperazin-1-yl]propenone 39 (F 16357), obtained after optimization. Both compounds are able to inhibit SFLLR-induced human platelet aggregation and display antithrombotic activity in an arteriovenous shunt model in the rat after iv or oral administration. Furthermore, these compounds are devoid of bleeding side effects often observed with other types of antiplatelet drugs, which constitutes a promising advantage for this new class of antithrombotic agents.

Therapeutic approaches in arterial thrombosis

The current standard of care for the treatment of arterial thrombosis includes anticoagulants and three classes of antiplatelet agents--aspirin, thienopyridines and glycoprotein IIb-IIIa antagonists. Although these drugs have had a significant impact on morbidity and mortality in several patient populations, up to 15% of the high risk patients with acute coronary syndrome continue to suffer from ischemic events. This problem may occur, in part, because the platelets in many patients are non-responsive to aspirin and clopidogrel. Murine models now indicate that platelets are not only responsible for arterial occlusion, they are also involved in the progression of atherosclerotic disease. New opportunities have emerged identifying potential targets and strategies for drug discovery suited to address these deficiencies by more effectively modulating platelet adhesion, thrombus growth, thrombus stability and the pro-inflammatory activity of platelets. In addition, a growing need has emerged for the development of bedside devices capable of bringing personalized medicine to patients being treated with antithrombotic drugs in order to measure the pharmacodynamic activities of new therapies, to assess the activities achieved by combined antithrombotic therapy, and to identify patients that fail to respond.

Biological evidence for inheritance of exceptional longevity

Subjects with exceptional longevity have a lower incidence and/or significant delay in the onset of age-related disease, and their family members may inherit biological factors that modulate aging processes and disease susceptibility. In a case control study, we aim to determine phenotype and genotype of exceptional longevity in a genetically homogenous population (Ashkenazi Jews), and their offspring, while an age-matched control group of Ashkenazi Jews was used as control groups. We demonstrated that exceptional longevity and healthy aging in humans is an inherited phenotype across three generations. Moreover, we demonstrated that subjects with exceptional longevity and their offspring have significantly larger high-density lipoprotein (HDL) levels and particle sizes and low-density lipoprotein (LDL) levels that reflect on their health and cognitive function performance. This phenotype have led us to study candidate genes involved in lipoprotein metabolism, and to the implication of homozygosity for the 405 valine (V) allele of cholesteryl ester transfer protein (CETP). A markedly higher frequency of a functional CETP variant that led to increased particle sizes of HDL and LDL and thus a better health performance is the first example of a phenotype and an associated genotype in humans with exceptional longevity. Hopefully, this line of research will lead us to establish which genotype is necessary (although not necessary sufficient) for a prolonged disease-free aging.

Cardiac Preconditioning during Percutaneous Coronary Interventions

Ischemic preconditioning (PC) is a polygenic defensive cellular adaptive phenomenon of the heart to ischemic stress, whereby the heart changes its phenotype to become more resistant to subsequent ischemia. Early and late of PC represent two chronologically and pathophysiologically distinct phases of this phenomenon, which can be recruited pharmacologically. We represent a post hoc analysis examining the late PC-mimetic effects of nitroglycerin (NTG) on peri-procedural myocardial necrosis during percutaneous coronary intervention (PCI). A group of 66 patients presenting with angina were randomized, 24 h prior to a scheduled PCI for single obstructive CAD, to a 4 h pretreatment with intravenous NTG or saline. Measurements of electrocardiographic ST-segment shifts, echocardiographic regional wall motion and angina scores demonstrated that NTG pre-treatment preconditioned the heart by rendering it resistant to ischemia during balloon inflations. NTG-pretreated patients exhibited trends towards lower average peak CK (131.1 vs. 188.6 U/L, P = 0.38) and CK-MB levels (7.1 vs. 12.6 ng/ml, P = 0.40). NTG, however, had no significant impact on the incidence of post-procedural MI or any cardiac enzyme elevation. The exploitation of ischemic and pharmacological PC may prove a useful strategy to confer cardioprotection during high-risk PCI and is worth exploring.