Aspirin: Promise and Resistance in the New Millennium

Predicting laboratory aspirin resistance in Chinese stroke patients using machine learning models by GP1BA polymorphism

This study aims to use machine learning model to predict laboratory aspirin resistance (AR) in Chinese stroke patients by incorporating patient characteristics and single nucleotide polymorphisms of GP1BA and LTC4S. 2405 patients were analyzed to measure the Mutation frequency of GP1BA rs6065 and LTC4S rs730012. 112 patients with first-stroke arteriostenosis were prospectively enrolled to establish machine learning model. GP1BA rs6065 mutation frequency is 5.26% and LTC4S rs730012 is 14.78%. GP1BA rs6065 CT patients have more sensitivity to aspirin than CC genotype. Simple linear regression identified significant associations with age, smoking, HDL and GP1BA rs6065. Random forest (RF) and extreme gradient boosting (XGBoost) demonstrated predictive capabilities for AR. Findings suggest pre-identifying GP1BA rs6065 could optimize aspirin treatment, enabling personalized care and future research avenues.

Aspirin With or Without Statin in Individuals Without Atherosclerotic Cardiovascular Disease Across Risk Categories

Background

The effects of aspirin in adults without atherosclerotic cardiovascular disease (ASCVD), stratified by statin use across different ASCVD risks, remain uncertain.

Objectives

The purpose of this study was to examine the effects of aspirin in adults without ASCVD, stratified by statin use across different ASCVD risks.

Methods

We searched databases through March 2022 and selected randomized controlled trials of aspirin without ASCVD and follow-up of ≥1 year. We used random-effects models and estimated relative and absolute risks for cardiovascular outcomes, major bleeding, and mortality over 5 years. We calculated absolute risk differences assuming constant relative risks (RRs) across statin use and ASCVD risks. The Cholesterol Treatment Trialists Collaboration, and the ASCEND (A Study of Cardiovascular Events in Diabetes) trial were used to estimate baseline risks.

Results

In 16 trials [171,215 individuals; median age, 64 (Q1-Q3: 60-65) years], aspirin vs control reduced myocardial infarction (MI) [RR: 0.85 (95% CI: 0.77-0.95)] but increased major bleeding [RR: 1.48 (95% CI: 1.32-1.66)]. Aspirin did not reduce mortality. Statin vs no statin was associated with lower bleeding and MI risk; the bleeding and MI risk were proportional to ASCVD risk. For every 10,000 adults, aspirin reduced MI (very low risk: 3 events as monotherapy or 1 event with statin; very high risk: 49 events as monotherapy or 37 events with statin) and increased major bleeding (very low risk: 21 events as monotherapy or 20 events with statin; very high risk: 98 events as monotherapy or 94 events with statin) proportional to baseline ASCVD risk.

Conclusions

In adults without ASCVD, concomitant statin appeared to significantly reduce absolute risk reduction for MI associated with aspirin without influencing bleeding risk. The anticipated absolute risk of major bleeding with aspirin exceeds absolute MI benefits for every level of ASCVD risk.

Factors Associated with Aspirin Resistance in Hong Kong Chinese Patients with Stable Coronary Heart Disease Using the Multiplate® Analyzer and Serum Thromboxane B2

Introduction: Aspirin resistance may be associated with various conditions. We measured serum thromboxane B2 (TXB2) and platelet function using the Multiplate® Analyzer with arachidonic acid (ASPI) in patients on long term aspirin therapy to identify aspirin resistance and associated factors. Materials and Methods: Chinese patients with stable coronary heart disease had samples for serum TXB2 and ASPI measurement taken before and 1 h after taking a morning dose of 80 mg aspirin. Results: In 266 patients with mean age 66.6 ± 10.7 years, 17% were female and 55% were current or previous smokers. TXB2 and ASPI measurements were significantly higher before the dose than at 1 h post dose, with 46% of subjects having high ASPI values (AUC > 300 AU*min) pre dose compared with 27% at 1 h post dose. TXB2 and ASPI measures of platelet aggregation showed weak correlations, which were only significant before the dose (r = 0.219, p = 0.001). Increased ASPI measurements were associated with white blood cell (WBC) count, haematocrit, platelet count and heart rate at 24 h post dose but only with WBC count, smoking history and heart rate at 1 h post dose. Diabetes was not associated with reduced platelet response to aspirin. The WBC count associated with aspirin resistance was over 6.55 × 109/L by receiver operating characteristic analysis. Conclusions: The antiplatelet response to aspirin was reduced in a large proportion of patients. Patients with higher WBC count within the normal range appear to be at increased risk of aspirin resistance. Higher or more frequent doses of aspirin may be needed in many patients.

Prostaglandin E2 and Cancer: Insight into Tumor Progression and Immunity

The involvement of inflammation in cancer progression has been the subject of research for many years. Inflammatory milieu and immune response are associated with cancer progression and recurrence. In different types of tumors, growth and metastatic phenotype characterized by the epithelial mesenchymal transition (EMT) process, stemness, and angiogenesis, are increasingly associated with intrinsic or extrinsic inflammation. Among the inflammatory mediators, prostaglandin E2 (PGE2) supports epithelial tumor aggressiveness by several mechanisms, including growth promotion, escape from apoptosis, transactivation of tyrosine kinase growth factor receptors, and induction of angiogenesis. Moreover, PGE2 is an important player in the tumor microenvironment, where it suppresses antitumor immunity and regulates tumor immune evasion, leading to increased tumoral progression. In this review, we describe the current knowledge on the pro-tumoral activity of PGE2 focusing on its role in cancer progression and in the regulation of the tumor microenvironment.

NSAID therapy for PIK3CA-Altered colorectal, breast, and head and neck cancer

Epidemiologic evidence indicates that regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) provides a protective effect against the development of colorectal, breast, and head and neck cancers. Genomic characterization of these cancers has lent considerable insight into the subpopulations of cancer patients who are most likely to benefit from NSAID therapy. The PIK3CA gene encodes the catalytic subunit of phosphatidylinositol 3-kinase (PI3K) and is among the most frequently mutated genes in solid tumor malignancies. Cancer-associated mutations in PIK3CA promote signaling via the PI3K pathway and stimulate tumor cell growth. In addition, activation of the PI3K pathway leads to induction of cyclooxygenase-2 (COX-2) enzyme and production of immunosuppressive prostaglandin E2 (PGE2). Notably, in both colorectal cancer and head and neck cancer the subpopulation of patients that benefit from NSAID use is restricted to those whose tumors exhibit PIK3CA genomic alterations. Preclinical studies, particularly in models of head and neck cancer, support the hypothesis that the chemopreventive impact of NSAIDs may be due, in part, to inhibition of COX-2 and reduction of PGE2 levels in the tumor microenvironment.

Measurement of Thromboxane Biosynthesis in Health and Disease

Thromboxane (TX) A₂ is a chemically unstable lipid mediator involved in several pathophysiologic processes, including primary hemostasis, atherothrombosis, inflammation, and cancer. In human platelets, TXA₂ is the major arachidonic acid derivative via the cyclooxygenase (COX)-1 pathway. Assessment of platelet TXA₂ biosynthesis can be performed ex vivo through measurement of serum TXB₂, an index of platelet COX-1 activity, as well as in vivo through measurement of urinary enzymatic metabolites, a non-invasive index of platelet activation. This article reviews the main findings of four decades of clinical investigation based on these analytical approaches, focusing on the measurement of TXA₂ metabolites to characterize the pathophysiologic role of transiently or persistently enhanced platelet activation and to describe the clinical pharmacology of COX-1 inhibition in health and disease.

Bioactive peptides and proteins as alternative antiplatelet drugs

Antiplatelet drugs reduce the risks associated with atherothrombotic events and show various applications in diverse cardiovascular diseases including myocardial infarctions. Efficacy of the current antiplatelet medicines including aspirin, clopidogrel, prasugrel and ticagrelor, and the glycoprotein IIb/IIIa antagonists, are limited due to their increased risks of bleeding, and antiplatelet drug resistance. Hence, it is important to develop new effective antiplatelet drugs, with fewer side-effects. The vast repertoire of natural peptides can be explored towards this goal. Proteins and peptides derived from snake venoms and plants represent exciting candidates for the development of novel and potent antiplatelet agents. Consequently, this review discusses multiple peptides that have displayed antiplatelet aggregation activity in preclinical drug development stages. This review also describes the antiplatelet mechanisms of the peptides, emphasizing the signaling pathways intervened by them. Also, the hurdles encountered during the development of peptides into antiplatelet drugs have been listed. Finally, hitherto unexplored peptides with the potential to prevent platelet aggregation are explored.

Platelets and extracellular vesicles in cancer: diagnostic and therapeutic implications

Several pieces of evidence support the role of activated platelets in the development of the chronic inflammation-related diseases, such as atherothrombosis and cancer, mainly via the release of soluble factors and microparticles (MPs). Platelets and MPs contain a repertoire of proteins and genetic material (i.e., mRNAs and microRNAs) which may be influenced by the clinical condition of the individuals. In fact, platelets are capable of up-taking proteins and genetic material during their lifespan. Moreover, the content of platelet-derived MPs can be delivered to other cells, including stromal, immune, epithelial, and cancer cells, to change their phenotype and functions, thus contributing to cancer promotion and its metastasization. Platelets and MPs can play an indirect role in the metastatic process by helping malignant cells to escape from immunological surveillance. Furthermore, platelets and their derived MPs represent a potential source for blood biomarker development in oncology. This review provides an updated overview of the roles played by platelets and MPs in cancer and metastasis formation. The possible analysis of platelet and MP molecular signatures for the detection of cancer and monitoring of anticancer treatments is discussed. Finally, the potential use of MPs as vectors for drug delivery systems to cancer cells is put forward.

Are Prior Aspirin Users With ST-Elevation Myocardial Infarction at Increased Risk of Adverse Events and Worse Angiographic Features?

Despite its clinical benefits, aspirin has been considered one of the predictors of worse outcomes in patients with unstable angina/non-ST-segment-elevation myocardial infarction. Nevertheless, such association has not been demonstrated in patients with ST-elevation myocardial infarction (STEMI). Five hundred eighty-six STEMI patients undergoing primary percutaneous coronary intervention were evaluated including 116 prior aspirin users. Angiographic characteristics and 1-year major adverse cardiac events (MACE) were then compared between the 2 groups. Adjusted analysis showed that the prior aspirin users had a significantly higher rate of totally occluded infarct-related artery before primary percutaneous coronary intervention (odds ratio: 1.859; P = 0.019). Postprocedural Thrombolysis in Myocardial Infarction flow grade 3 was less often demonstrated in the prior aspirin users (odds ratio: 1.512; P = 0.059). Aspirin consumption was associated with increased long-term mortality and MACE. Prior aspirin users had higher rate of MACE and worse pre- and postprocedural angiographic features. We suppose that patients who develop STEMI despite long-term aspirin intake probably reflect more vulnerable pre-existing coronary plaques with more thrombogenicity, which could negatively affect long-term cardiovascular outcomes.

Green Strategies for Molecularly Imprinted Polymer Development

Molecular imprinting is a powerful technology to create artificial receptors within polymeric matrices. Although it was reported for the first time by Polyakov, eighty-four years ago, it remains, nowadays, a very challenging research area. Molecularly imprinted polymers (MIPs) have been successfully used in several applications where selective binding is a requirement, such as immunoassays, affinity separation, sensors, and catalysis. Conventional methods used on MIP production still use large amounts of organic solvents which, allied with stricter legislation on the use and release of chemicals to the environment and the presence of impurities on final materials, will boost, in our opinion, the use of new cleaner synthetic strategies, in particular, with the application of the principles of green chemistry and engineering. Supercritical carbon dioxide, microwave, ionic liquids, and ultrasound technology are some of the green strategies which have already been applied in MIP production. These strategies can improve MIP properties, such as controlled morphology, homogeneity of the binding sites, and the absence of organic solvents. This review intends to give examples reported in literature on green approaches to MIP development, from nano- to micron-scale applications.

TGF-β1 mediates the effects of aspirin on colonic tumor cell proliferation and apoptosis

Previous studies have demonstrated that aspirin serves an important role in chemoprevention and the suppression of colorectal cancer (CRC); however, the underlying mechanisms for this inhibition by aspirin remain unclear. Aspirin is capable of promoting apoptosis through prostaglandin-dependent orprostaglandin-independent signaling pathways. In the prostaglandin-dependent pathways, inhibition of cyclooxygenase (COX), particularly COX-2, is the primary mechanism known to be involved in aspirin-induced CRC suppression. Previous studies have implicated prostaglandin-independent signaling pathways and certain associated proteins, including SOX7, in aspirin-induced CRC suppression. In the present study, a newly-characterized association between aspirin, transforming growth factor (TGF)-β1 and CRC inhibition was identified. Specifically, aspirin triggers CRC cell apoptosis by inducing the secretion of TGF-β1, and the increased TGF-β1 then leads to apoptosis and proliferation inhibition in CRC cells.

Novel pharmacological inhibitors demonstrate the role of the tyrosine kinase Pyk2 in adhesion and aggregation of human platelets

Pyk2 is a Ca2+-regulated kinase predominantly expressed in neuronal and in haematopoietic cells. Previous studies on Pyk2-null mice have demonstrated that Pyk2 plays a crucial role in platelet activation and thrombus formation, thus representing a possible target for antithrombotic therapy. Very limited information is available about the role of Pyk2 in human platelets, mainly because of the lack of specific pharmacological inhibitors. In this work, we have tested two novel Pyk2 inhibitors, PF-4594755 and PF-4520440, to validate their specificity and to investigate their ability to modulate platelet activation. Both molecules were able to efficiently block Pyk2 activity in human and mouse platelets stimulated with thrombin or with the Ca2+-ionophore. In wild-type murine platelets, PF-4594755 and PF-4520440 reduced thrombin-induced aggregation to the level observed in Pyk2 knockout platelets, but did not affect aggregation induced by GPVI stimulation. Importantly, neither compounds affected the residual thrombin-induced aggregation of Pyk2-null platelets, thus excluding possible off-target effects. In human platelets, PF-4594755 and PF-4520440 significantly reduced aggregation stimulated by thrombin, but not by the GPVI agonist convulxin. Both inhibitors reduced platelet adhesion on fibrinogen and prevented Akt phosphorylation in adherent cells, indicating that Pyk2 regulates PI3K and cell spreading downstream of integrins in human platelets. Finally, the Pyk2 inhibitors significantly inhibited thrombus formation upon blood perfusion on immobilized collagen under arterial flow rate. These results demonstrate that PF-4594755 and PF-4520440 are specific inhibitors of Pyk2 in intact platelets and allowed to reliably document that this kinase plays a relevant role in human platelet activation.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Differential Impact of Serial Measurement of Nonplatelet Thromboxane Generation on Long-Term Outcome After Cardiac Surgery

BACKGROUND

Systemic thromboxane generation, not suppressible by standard aspirin therapy and likely arising from nonplatelet sources, increases the risk of atherothrombosis and death in patients with cardiovascular disease. In the RIGOR (Reduction in Graft Occlusion Rates) study, greater nonplatelet thromboxane generation occurred early compared with late after coronary artery bypass graft surgery, although only the latter correlated with graft failure. We hypothesize that a similar differential association exists between nonplatelet thromboxane generation and long-term clinical outcome.

METHODS AND RESULTS

Five-year outcome data were analyzed for 290 RIGOR subjects taking aspirin with suppressed platelet thromboxane generation. Multivariable modeling was performed to define the relative predictive value of the urine thromboxane metabolite, 11-dehydrothromboxane B₂ (11-dhTXB₂), measured 3 days versus 6 months after surgery on the composite end point of death, myocardial infarction, revascularization or stroke, and death alone. 11-dhTXB₂ measured 3 days after surgery did not independently predict outcome, whereas 11-dhTXB₂ >450 pg/mg creatinine measured 6 months after surgery predicted the composite end point (adjusted hazard ratio, 1.79; P=0.02) and death (adjusted hazard ratio, 2.90; P=0.01) at 5 years compared with lower values. Additional modeling revealed 11-dhTXB₂ measured early after surgery associated with several markers of inflammation, in contrast to 11-dhTXB₂ measured 6 months later, which highly associated with oxidative stress.

CONCLUSIONS

Long-term nonplatelet thromboxane generation after coronary artery bypass graft surgery is a novel risk factor for 5-year adverse outcome, including death. In contrast, nonplatelet thromboxane generation in the early postoperative period appears to be driven predominantly by inflammation and did not independently predict long-term clinical outcome.

Aspirin and Cancer

The place of aspirin in primary prevention remains controversial, with North American and European organizations issuing contradictory treatment guidelines. More recently, the U.S. Preventive Services Task Force recommended "initiating low-dose aspirin use for the primary prevention of cardiovascular disease (CVD) and colorectal cancer in adults aged 50 to 59 years who have a 10% or greater 10-year CVD risk, are not at increased risk for bleeding, have a life expectancy of at least 10 years, and are willing to take low-dose aspirin daily for at least 10 years." This recommendation reflects increasing evidence for a chemopreventive effect of low-dose aspirin against colorectal (and other) cancer. The intent of this paper is to review the evidence supporting a chemopreventive effect of aspirin, discuss its potential mechanism(s) of action, and provide a conceptual framework for assessing current guidelines in the light of ongoing studies.

Study of oxidative and inflammatory parameters in LDLr-KO mice treated with a hypercholesterolemic diet: Comparison between the use of Campomanesia xanthocarpa and acetylsalicylic acid

BACKGROUND

Atherosclerosis is an inflammatory disease that affects the arterial wall leading to myocardial, cerebral, and peripheral ischemic syndromes. The use of low doses of aspirin inhibits platelet aggregation and inflammation and prevents cardiovascular mortality. However, ASA may produce hemorrhagic events. Thus, several studies have sought new natural compounds to suppress platelet aggregation without causing serious adverse effects.

PURPOSE

In this sense, this study aims to compare the effects of Campomanesia xanthocarpa plant extract with those of acetylsalicylic acid (ASA) on inflammatory parameters observed in homozygous mice knockout for the low-density lipoprotein receptor (LDLr-KO) treated with a hypercholesterolemic diet.

MATERIAL AND METHODS

In this study, 28 male LDLr-KO mice were divided into three groups and fed a hypercholesterolemic diet for 4 weeks. Thereafter, the animals that received the hypercholesterolemic diet were treated for 5 days with (1) distilled water, (2) C. xanthocarpa extract, or (3) acetylsalicylic acid. The levels of inflammatory markers were assessed in the blood samples. The gastric tolerability of the animals after oral administration of the treatments was assessed through quantification of the lesions in the gastric mucosa.

RESULTS

The levels of proinflammatory cytokines IL-1, IL-6, TNF-α, and INF-γ were reduced to 19.2 ± 3%, 20.4 + 1.3%, 24.7 ± 1.2%, and 20.8 ± 1.7%, respectively, in the group treated with C. xanthocarpa, when compared to control group. Furthermore, treatment with plant extract significantly increased the levels of the anti-inflammatory cytokine IL-10 by 27.3 ± 5.9%, but ASA showed no significant effect on the same cytokines when compared to the control group, with the exception of IL-10, which presented an increase of 8.6 ± 3.5%. Treatments with C. xanthocarpa and ASA also caused significant reductions of 26.4 ± 3% and 38.4± 6% in the serum levels of oxLDL, respectively. However, only treatment with C. xanthocarpa reduced the levels of anti-oxLDL antibodies when compared with the control (25.8 ± 6%). In addition, the analyzed extract did not induce ulcerogenic activity, while ASA induced the formation of lesions.

CONCLUSION

In conclusion, treatment with C. xanthocarpa causes anti-inflammatory activity in hypercholesterolemic animals, with results superior to those obtained with the use of ASA.

Urinary 11-Dehydro-Thromboxane B2 as a Predictor of Acute Myocardial Infarction Outcomes: Results of Leukotrienes and Thromboxane In Myocardial Infarction (LTIMI) Study

BACKGROUND

Urinary 11-dehydro-thromboxane (TX)B2 has been described as a potential predictive biomarker of major adverse cardiovascular events (MACEs) in high cardiac risk patients. This part of LTIMI (Leukotrienes and Thromboxane In Myocardial Infarction) study aimed to evaluate the relationship between 11-dehydro-TXB2 and MACEs in patients with acute myocardial infarction (AMI).

METHODS AND RESULTS

LTIMI was an observational, prospective study in 180 consecutive patients with AMI type 1 referred for primary percutaneous coronary intervention. On admission and at follow-up visits (1 month, 1 year), 11-dehydro-TXB2 was measured in urinary samples by using high-performance liquid chromatography-tandem mass spectrometry. The primary outcome was occurrence of composite MACEs during 1-year after AMI. Left ventricular ejection fraction was assessed in echocardiography on admission and at 1-year follow-up. Analyses of 11-dehydro-TXB2 (pg/mg creatinine) were performed on log-transformed data and expressed as median with IQR (Q1-Q3). 11-Dehydro-TXB2 level on admission was 7.39 (6.85-8.01) and decreased at 1 month (6.73, 6.27-7.12; P<0.001) and 1-year follow-up (6.37, 5.91-6.94; P<0.001). In univariate analysis, baseline 11-dehydro-TXB2 was higher in patients with MACEs (n=60; 7.73, 7.07-8.60) compared with those without MACEs (n=119; 7.28, 6.68-7.79; P=0.002). In multivariate regression model, 11-dehydro-TXB2 and 3 other variables (diabetes, multivessel disease, and left ventricular ejection fraction) were found to be best 1-year cumulative MACE predictors with odds ratio for 11-dehydro-TXB2 of 1.58 (95% CI 1.095-2.33; P=0.017) and area under the curve (in receiver operating characteristic analysis of 0.8). Baseline 11-dehydro-TXB2 negatively correlated with both left ventricular ejection fraction on admission (R=-0.21; P=0.006) and after 1 year (R=-0.346; P<0.001).

CONCLUSIONS

11-Dehydro-TXB2 predicts 1-year cumulative MACEs in AMI patients and provides prognostic information on the left ventricular performance.

Association of Cytochrome P450 Genetic Variants with Clopidogrel Resistance and Outcomes in Acute Ischemic Stroke

Aims: Clopidogrel is an antiplatelet drug primarily used to treat or prevent acute ischemic stroke (IS) or myocardial infarction (MI). This prodrug requires biotransformation to an active metabolite by cytochrome P450 (CYP) enzymes, and CYP single nucleotide polymorphisms (SNPs) could affect the efficiency of such biotransformation.

Methods: A total of 375 consecutive IS patients were genotyped for eight CYP SNPs using mass spectrometry. Platelet aggregation activity was measured before and after the 7 – 10 day treatment. Gene–gene interactions were analyzed using generalized multifactor dimensionality reduction (GMDR) analysis. All patients received clopidogrel therapy and were followed up for six months. Primary outcomes were evaluated as a composite of recurrent ischemic stroke (RIS), MI, and death. The secondary outcome was the modified Rankin Scale (mRS).

Results: Clopidogrel resistance occurred in 153 patients (40.8%). The frequency of CYP3A5 (rs776746) GG/AG and CYP2C19*2 (rs4244285) AA/AG genotypes was significantly higher in clopidogrel-resistant patients than in sensitive patients. There was a significant gene-gene interaction between CYP3A5 (rs776746) and CYP2C19*2 (rs4244285). CYP2C19*2 AA and its interaction with CYP3A5 GG were independent predictors of clopidogrel resistance and affected the activity of platelet aggregation. Diabetes mellitus, CYP2C19*2 (rs4244285), clopidogrel resistance, and the interaction of CYP2C19*2 with CYP3A5 were all independent risk factors for the primary outcomes of clopidogrel treatment. Clopidogrel-resistant patients were more likely to have poor outcomes (mRS > 2 points) compared with clopidogrel-sensitive patients.

Conclusion:CYP SNPs and their interactions are associated with drug resistance and outcomes in acute IS patients.

Aspirin has limited ability to modulate shear-mediated platelet activation associated with elevated shear stress of ventricular assist devices

Continuous flow ventricular assist devices (cfVADs) while effective in advanced heart failure, remain plagued by thrombosis related to abnormal flows and elevated shear stress. To limit cfVAD thrombosis, patients utilize complex anti-thrombotic regimens built upon a foundation of aspirin (ASA). While much data exists on ASA as a modulator of biochemically-mediated platelet activation, limited data exists as to the efficacy of ASA as a means of limiting shear-mediated platelet activation, particularly under elevated shear stress common within cfVADs. We investigated the ability of ASA (20, 25 and 125 μM) to limit shear-mediated platelet activation under conditions of: 1) constant shear stress (30 dynes/cm(2) and 70 dynes/cm(2)); 2) dynamic shear stress, and 3) initial high shear exposure (70 dynes/cm(2)) followed by low shear exposure - i.e. a platelet sensitization protocol, utilizing a hemodynamic shearing device providing uniform shear stress in vitro. The efficacy of ASA to limit platelet activation mediated via passage through a clinical cfVAD system (DeBakey Micromed) in vitro was also studied. ASA reduced platelet activation only under conditions of low shear stress (38% reduction compared to control, n=10, p<0.004), with minimal protection at higher shear stress and under dynamic conditions (n=10, p>0.5) with no limitation of platelet sensitization. ASA had limited ability (25.6% reduction in platelet activation rate) to modulate shear-mediated platelet activation induced via cfVAD passage. These findings, while performed under "deconstructed" non-clinical conditions by utilizing purified platelets alone in vitro, provide a potential contributory mechanistic explanation for the persistent thrombosis rates experienced clinically in cfVAD patients despite ASA therapy. An opportunity exists to develop enhanced pharmacologic strategies to limit shear-mediated platelet activation at elevated shear levels associated with mechanical circulatory support devices.

Oxidative stress-related mechanisms affecting response to aspirin in diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a major cardiovascular risk factor. Persistent platelet activation plays a key role in atherothrombosis in T2DM. However, current antiplatelet treatments appear less effective in T2DM patients vs nondiabetics at similar risk. A large body of evidence supports the contention that oxidative stress, which characterizes DM, may be responsible, at least in part, for less-than-expected response to aspirin, with multiple mechanisms acting at several levels. This review discusses the pathophysiological mechanisms related to oxidative stress and contributing to suboptimal aspirin action or responsiveness. These include: (1) mechanisms counteracting the antiplatelet effect of aspirin, such as reduced platelet sensitivity to the antiaggregating effects of NO, due to high-glucose-mediated oxidative stress; (2) mechanisms interfering with COX acetylation especially at the platelet level, e.g., lipid hydroperoxide-dependent impaired acetylating effects of aspirin; (3) mechanisms favoring platelet priming (lipid hydroperoxides) or activation (F2-isoprostanes, acting as partial agonists of thromboxane receptor), or aldose-reductase pathway-mediated oxidative stress, leading to enhanced platelet thromboxane A2 generation or thromboxane receptor activation; (4) mechanisms favoring platelet recruitment, such as aspirin-induced platelet isoprostane formation; (5) modulation of megakaryocyte generation and thrombopoiesis by oxidative HO-1 inhibition; and (6) aspirin-iron interactions, eventually resulting in impaired pharmacological activity of aspirin, lipoperoxide burden, and enhanced generation of hydroxyl radicals capable of promoting protein kinase C activation and platelet aggregation. Acknowledgment of oxidative stress as a major contributor, not only of vascular complications, but also of suboptimal response to antiplatelet agents in T2DM, may open the way to designing and testing novel antithrombotic strategies, specifically targeting oxidative stress-mediated mechanisms of less-than-expected response to aspirin.

Acetylsalicylic acid does not alter thermo-effector responses during mild whole-body passive heat stress in young men

Acetylsalicylic acid (ASA), aspirin, exerts potent systemic effects that may interfere with normal thermo-effector responses. We investigated the influence of commonly ingested ASA doses on measures of skin blood flow (SkBF) and local sweat rate (SR) during whole-body, passive heat stress. Seven male participants completed counter-balanced trials to compare ASA treatments (single dose 325 mg or 4 consecutive days 81 mg (4-d 81 mg)) to control (no ASA). Laser-Doppler flowmetry provided an index of SkBF. A ventilated capsule measured local sweat rate via capacitance hygrometry. Mean body temperature ([Formula: see text]) was increased by 1 °C above baseline using a water-perfused suit. [Formula: see text] was similar at the onset of cutaneous vasodilation among trials. Cutaneous vascular conductance, expressed as a percentage change from baseline, was not different among trials. Additionally, [Formula: see text] at the onset of local SR and SR sensitivity did not differ among trials. While ASA has previously been shown to influence SkBF during heat stress, it is possible our cohort's relatively young age may have contributed to our dissimilar results.

Effect of common single nucleotide polymorphisms in COX-1 gene on related metabolic activity in diabetic patients treated with acetylsalicylic acid

INTRODUCTION

The objective of this study was to investigate the effect of common single nucleotide genomic polymorphisms in the cyclooxygenase-1 (COX-1) gene on the thromboxane A2 (TxA2) metabolite concentrations in serum and urine, as well as on prostaglandin F2α (PGF2α) urinary excretion in the diabetic population on acetylsalicylic acid (ASA) therapy.

MATERIAL AND METHODS

The study cohort consisted of 284 Caucasians with diabetes type 2 who had been taking ASA tablets at the dose of 75 mg/day for at least 3 months. Genotyping for the 4 selected SNPs within the COX-1 gene (two nonsynonymous-coding variants, rs3842787 [C50T, P17L] and rs5789 [C174A, L237M]; and two other synonymous SNPs, rs3842788 [G128A, Q41Q] and rs5788 [C644A]) was performed using the Sequenom iPLEX platform.

RESULTS

No statistically significant results were observed for the investigated SNPs and measured metabolites in the investigated cohort of patients. Statistically significant differences in S-TxB2 could however be observed for rs5788 in the subgroup of patients with very high S-TxB2 concentrations. In particular, more patients who were carriers of the minor allele for this polymorphism were observed in the group with S-TxB2 levels > 95(th) percentile, when compared with similar carriers in the group with S-TxB2 < 95(th) percentile (20% vs. 1.1%, respectively, p < 0.001, Mann-Whitney test).

CONCLUSIONS

The results of our study suggest that the four investigated common SNPs in the COX1 gene are not associated with obviously altered TxA2 metabolism and PGF2α synthesis in the investigated diabetic cohort treated with ASA.

H2S-releasing drugs: anti-inflammatory, cytoprotective and chemopreventative potential

Hydrogen sulfide exerts a number of cytoprotective and anti-inflammatory effects in many organ systems. In an effort to exploit these potent and beneficial effects, a number of hydrogen sulfide-releasing derivatives of existing drugs have been developed and extensively tested in pre-clinical models. In particular, efforts have been made by several groups to develop hydrogen sulfide-releasing derivatives of a number of nonsteroidal anti-inflammatory drugs. The main goal of this approach is to reduce the gastrointestinal ulceration and bleeding caused by this class of drugs, particularly when used chronically such as in the treatment of arthritis. However, these drugs may also have utility for prevention of various types of cancer. This paper provides an overview of some of the mechanisms underlying the anti-inflammatory and cytoprotective actions of hydrogen sulfide. It also gives some examples of hydrogen sulfide-releasing anti-inflammatory drugs, and their actions in terms of reducing inflammation and attenuating the development of cancer in experimental models.

Myocardial infarction and gastro-intestinal bleeding risks associated with aspirin use among elderly individuals with type 2 diabetes

INTRODUCTION

The benefit of aspirin in primary prevention of myocardial infarction and the associated gastro-intestinal bleeding risks have not been well established in the elderly population with diabetes.

METHODS

Using Quebec administrative databases, we conducted two nested case-control analyses within a cohort of individuals aged ≥ 66 years newly treated with an oral antidiabetes drug between 1998 and 2003. The 28,067 individuals had no cardiovascular disease recorded in the database in the year prior cohort entry. They had not used prescribed aspirin, antiplatelet, or anticoagulant drugs, and were not hospitalized for gastro-intestinal bleeding in the year prior cohort entry. The odds of myocardial infarction and gastro-intestinal bleedings were compared between individuals who were current, past, or non-users of aspirin.

RESULTS

There were 1101 (3.9%) cases of myocardial infarction. Compared to non-users, neither aspirin users (OR 0.89; 95% CI 0.71-1.13) nor aspirin past users (0.81; 0.62-1.06) showed a statistically significant lower risk of myocardial infarction. There were 373 (1.3%) cases of gastro-intestinal bleeding. Current users of aspirin had about a 2-fold greater risk of gastro-intestinal bleeding compared to non-users (2.19; 1.53-3.13).

CONCLUSIONS

Our results suggest that individual assessment of bleeding risk and cardiovascular risk is mandatory among elderly people with diabetes before introducing aspirin therapy.

Aspirin resistant patients with recent ischemic stroke

Some patients with a recent ischemic stroke who are being treated with aspirin as an antiaggregant suffer a new ischemic stroke. These patients (15-25%) have been called unresponsive to aspirin or aspirin resistant. The aspirin-resistant patients have a four-time greater risk of suffering a stroke. Furthermore, these strokes are generally more severe, with increased infarct volume and greater risk of recurrence. There is currently no ideal laboratory test to detect the resistance to the antiaggregant effect of aspirin. The study of resistance to aspirin would only be indicated in selected cases. In these patients, one should first rule out any "pseudo-resistance" to aspirin (lack of compliance, concomitant treatments that interfere with the action of the aspirin).

Thromboxane A(2) generation, in the absence of platelet COX-1 activity, in patients with and without atherothrombotic myocardial infarction

BACKGROUND

Aspirin's therapeutic action is via inhibition of platelet cyclooxygenase 1 (COX-1) thromboxane A2 (TxA2) production. The aim of this study was to evaluate TxA2 production, in the absence of platelet COX-1 activity, in coronary atherosclerotic heart disease patients with and without atherothrombotic myocardial infarction (MI).

METHODS AND RESULTS

TxA2 production, in the absence of platelet COX-1 activity, was evaluated in 44 patients taking aspirin on 3 commercially available assays that detect metabolites of TxA2 in the urine. Two assays measure urine 11-dehydro-thromboxane B2 (TxB2) alone and 1 measures urine 11-dehydro-TxB2 plus 11-dehydro-2,3-dinor-TxB2. Platelet COX-1 inhibition was confirmed on <10% platelet aggregation in response to ≥1 mmol/L arachidonic acid. Median urine 11-dehydro-TxB2 was no different in those with and without a diagnosis of atherothrombotic MI (325 vs. 311 pg/mg creatinine, P=0.59 via polyclonal ELISA) and (312 vs. 244 pg/mg creatinine, P=0.11 via LC-MS/MS). Median urine 11-dehydro-TxB2 plus 11-dehydro-2,3-dinor-TxB2, however, was higher in those with vs. those without a diagnosis of atherothrombotic MI (1,035 vs. 606 pg/mg creatinine, P=0.03 via monoclonal ELISA).

CONCLUSIONS

Differences in TxA2 production, in the absence of platelet COX-1 activity, between those with vs. without atherothrombotic MI were not observed when TxA2 generation was assessed on 11-dehydro-TxB2 production alone (polyclonal ELISA or LC-MS/MS), but differences were observed when TxA2 generation was assessed using 11-dehydro-TxB2 plus 11-dehydro-2,3-dinor-TxB2 (monoclonal ELISA). These findings highlight important differences between different commercially available assays for TxA2 generation and suggest that 11-dehydro-2,3-dinor-TxB2 may be critical to the biology of atherothrombosis.

Associations between aspirin and other non-steroidal anti-inflammatory drugs and aortic valve or coronary artery calcification: the Multi-Ethnic Study of Atherosclerosis and the Heinz Nixdorf Recall Study

BACKGROUND

The association between non-steroidal anti-inflammatory drugs (NSAIDs) and the incidence of valvular and arterial calcification is not well established despite known associations between these drugs and cardiovascular events.

OBJECTIVE

To compare the association between the baseline use of aspirin with other NSAID class medications with the incidence and prevalence of aortic valve calcification (AVC) and coronary artery calcification (CAC).

METHODS

The relationship of NSAID use to AVC and CAC detected by computed tomography was assessed in 6814 participants within the Multi-Ethnic Study of Atherosclerosis (MESA) using regression modeling. Results were adjusted for age, sex, ethnicity, study site, anti-hypertensive medication use, education, income, health insurance status, diabetes, smoking, exercise, body mass index, blood pressure, serum lipids, inflammatory markers, fasting glucose, statin medication use, and a simple diet score. Medication use was assessed by medication inventory at baseline which includes the use of non-prescription NSAIDs. MESA collects information on both incident and prevalent calcification. The 4814 participants of the Heinz Nixdorf Recall (HNR) Study, a German prospective cohort study with similar measures of calcification, were included in this analysis to enable replication.

RESULTS

Mean age of the MESA participants was 62 years (51% female). After adjustment for possible confounding factors, a possible association between aspirin use and incident AVC (Relative Risk(RR): 1.60; 95%Confidence Interval (CI): 1.19-2.15) did not replicate in the HNR cohort (RR: 1.06; 95%CI: 0.87-1.28). There was no significant association between aspirin use and incident CAC in the MESA cohort (RR 1.08; 95%CI: 0.91-1.29) or in the HNR cohort (RR 1.24; 95%CI: 0.87-1.77). Non-aspirin NSAID use was not associated with either AVC or CAC in either cohort. There were no associations between regular cardiac dose aspirin and incident calcification in either cohort.

CONCLUSION

Baseline NSAID use, as assessed by medication inventory, appears to have no protective effect regarding the onset of calcification in either coronary arteries or aortic valves.

Aspirin Resistance in Chinese Stroke Patients Increased the Rate of Recurrent Stroke and other Vascular Events

Introduction

To investigate the prevalent of aspirin resistance (AR) in Chinese stroke patients and its association with recurrent stroke and other vascular events, including cardiovascular disease and death.

Methods

We prospectively enrolled 634 Chinese stroke patients. Aspirin was administrated to every patient from the first day of admission. Whole blood samples were collected for platelet aggregation testing after aspirin was administered for 7–10 days. A follow-up period of 12–24 months was performed to record vascular events and hemorrhagic side effects.

Results

Aspirin resistance (AR) was detected in 129 patients (20·4%), aspirin semi-resistance (ASR) in 28 patients (4·4%) and aspirin sensitivity (AS) in 477 patients (75·2%). Logistic regression analysis found that diabetes and high levels of low density lipoprotein cholesterol (LDL) were independent risk factors for ASR and AR. During a median follow-up period of 19·4 months, the prevalence of recurrent stroke, death from all causes, myocardial infarction and vascular events overall were higher in patients with AR + ASR than in patients with AS. Cox regression analysis found that diabetes and AR were independent risk factors for vascular events.

Conclusion

Aspirin resistance is common in Chinese patient taking antiplatelet medications. Diabetes and high LDL may induce platelet activation and thrombosis and increase the occurrence of aspirin resistance. Patients who are detected to be aspirin resistant are at a greater risk of clinically important vascular events.

High glucose inhibits the aspirin-induced activation of the nitric oxide/cGMP/cGMP-dependent protein kinase pathway and does not affect the aspirin-induced inhibition of thromboxane synthesis in human platelets

Since hyperglycemia is involved in the "aspirin resistance" occurring in diabetes, we aimed at evaluating whether high glucose interferes with the aspirin-induced inhibition of thromboxane synthesis and/or activation of the nitric oxide (NO)/cGMP/cGMP-dependent protein kinase (PKG) pathway in platelets. For this purpose, in platelets from 60 healthy volunteers incubated for 60 min with 5-25 mmol/L d-glucose or iso-osmolar mannitol, we evaluated the influence of a 30-min incubation with lysine acetylsalicylate (L-ASA; 1-300 μmol/L) on 1) platelet function under shear stress; 2) aggregation induced by sodium arachidonate or ADP; 3) agonist-induced thromboxane production; and 4) NO production, cGMP synthesis, and PKG-induced vasodilator-stimulated phosphoprotein phosphorylation. Experiments were repeated in the presence of the antioxidant agent amifostine. We observed that platelet exposure to 25 mmol/L d-glucose, but not to iso-osmolar mannitol, 1) reduced the ability of L-ASA to inhibit platelet responses to agonists; 2) did not modify the L-ASA-induced inhibition of thromboxane synthesis; and 3) prevented the L-ASA-induced activation of the NO/cGMP/PKG pathway. Preincubation with amifostine reversed the high-glucose effects. Thus, high glucose acutely reduces the antiaggregating effect of aspirin, does not modify the aspirin-induced inhibition of thromboxane synthesis, and inhibits the aspirin-induced activation of the NO/cGMP/PKG pathway. These results identify a mechanism by which high glucose interferes with the aspirin action.

Apixaban: a novel oral inhibitor of factor Xa

PURPOSE

The pharmacology, pharmacokinetics, efficacy, and safety of apixaban are reviewed.

SUMMARY

Apixaban is an oral, direct, selective factor Xa inhibitor with a rapid onset of action. It has a plasma elimination half-life of 12 hours and has been administered in a twice-daily dosing regimen in clinical trials without the need for anticoagulation monitoring or dosage adjustment. Apixaban has multiple elimination pathways, and its pharmacokinetics is not substantially altered by patient age, sex, race, or ethnicity. The results of three Phase III trials indicated that apixaban was similar to or more effective than enoxaparin for preventing venous thromboembolism (VTE) in patients undergoing total hip or knee replacement, with similar or lower rates of bleeding. Two Phase III trials found that apixaban was more effective for stroke prevention than either aspirin or warfarin in patients with atrial fibrillation (AF), with a similar (versus aspirin) or improved (versus warfarin) safety profile. A Phase III trial evaluating apixaban plus antiplatelet monotherapy or dual-antiplatelet therapy in patients with acute coronary syndrome ended early due to clear evidence of a clinically important increase in bleeding among patients randomized to apixaban without any meaningful reduction in ischemic events. The adverse-event profiles for apixaban and comparators have been similar in studies conducted to date.

CONCLUSION

Apixaban, a new anticoagulant, appears to offer an efficacy and safety profile comparable with that of enoxaparin for preventing VTE after orthopedic surgery, with the advantage of oral administration. In patients with AF, apixaban is more effective than either warfarin or aspirin for stroke prevention, with an acceptable safety profile.

Platelet response to aspirin in Chinese stroke patients is independent of genetic polymorphisms of COX-1 C50T and COX-2 G765C

AIM

Aspirin resistance (AR) is common in Chinese stroke patients taking antiplatelet medications; however, few studies have documented the role of cyclooxygenase (COX)-1 C50T and COX-2 G765C polymorphisms in AR. The aim of this study was to investigate the prevalence of AR in Chinese stroke patients and the relationships between AR and COX-1 C50T and COX-2 G765C polymorphisms, and to evaluate the effect of these polymorphisms on platelet response to aspirin.

METHODS

We prospectively enrolled 634 Chinese stroke patients. Platelet aggregation testing was performed before and after aspirin administration. The pre- and post-aspirin levels of 11-dehydrothromboxane B(2) (11-dTxB(2)) were determined in urine samples. COX-1 C50T and COX-2 G765C genotypes were determined by a polymerase chain reaction-allelic restriction assay.

RESULTS

AR was detected in 129 patients (20.4%), aspirin semi-resistance (ASR) was detected in 28 patients (4.4%), and aspirin sensitivity (AS) was detected in 477 patients (75.2%). There was no association between COX-1 C50T or COX-2 G765C polymorphisms and ASR+AR. Aspirin could efficiently reduce 11-dTxB(2) production by approximately 75%. In addition, platelet aggregation, both in response to arachidonic acid (AA) and adenosine 5'-diphosphate (ADP), was inhibited by more than 80% and 40%, respectively; however, the percentage reduction in platelet aggregation and 11-dTxB(2) levels was not significantly different between the COX-1 C50T and COX-2 G765C genotypes (p＞0.05).

CONCLUSIONS

There was no association between COX-1 C50T and COX-2 G765C polymorphisms and AR in Chinese stroke patients. In addition, COX-1 C50T and COX-2 G765C polymorphisms had no effect on the platelet response to aspirin.

High On-Aspirin Platelet Reactivity and Clinical Outcome in Patients With Stable Coronary Artery Disease: Results From ASCET (Aspirin Nonresponsiveness and Clopidogrel Endpoint Trial)

Background

Patients with stable coronary artery disease on single-antiplatelet therapy with aspirin are still at risk for atherothrombotic events, and high on-aspirin residual platelet reactivity (RPR) has been suggested as a risk factor.

Methods and Results

In this randomized trial, the association between platelet function determined by the PFA100 platelet function analyzer system (Siemens Healthcare Diagnostics, Germany) and clinical outcome in 1001 patients, all on single-antiplatelet therapy with aspirin (160 mg/d) was studied. Patients were randomized to continue with aspirin 160 mg/d or change to clopidogrel 75 mg/d. A composite end point of death, myocardial infarction, ischemic stroke, and unstable angina was used. At 2-year follow-up, 106 primary end points were registered. The prevalence of high RPR was 25.9%. High on-aspirin RPR did not significantly influence the primary end point in the aspirin group (13.3% versus 9.9%, P=0.31). However, in post hoc analysis, patients with von Willebrand factor levels or platelet count below median values and high on-aspirin RPR had a statistically significant higher end point rate than that of patients with low RPR (20% versus 7.5%, P=0.014, and 18.2% versus 10.8%, P=0.039, respectively). The composite end point rate in patients with high on-aspirin RPR treated with clopidogrel was not different from that of patients treated with aspirin (7.6% versus 13.3%, P=0.16).

Conclusions

In stable, aspirin-treated patients with coronary artery disease, high on-aspirin RPR did not relate to clinical outcome and did not identify a group responsive to clopidogrel. Post hoc subgroup analysis raised the possibility that high on-aspirin RPR might be predictive in patients with low von Willebrand factor or platelet count, but these findings will require confirmation in future studies.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov Unique identifier: NCT00222261. (J Am Heart Assoc. 2012;1:e000703 doi: 10.1161/JAHA.112.000703.)

P2RY1 and P2RY12 polymorphisms and on-aspirin platelet reactivity in patients with coronary artery disease

INTRODUCTION

Association of P2RY1 and P2RY12 polymorphisms with on-aspirin platelet reactivity was investigated.

MATERIALS AND METHODS

Platelet reactivity was assessed by the light transmission aggregometry and TxB(2) assay in 423 patients with coronary artery disease (CAD) on aspirin. High residual platelet reactivity (RPR) was defined by ≥20% and ≥70% maximal aggregation stimulated with 0.5 mg/mL arachidonic acid (AA) and 10 μm ADP, respectively. Moderate RPR was considered aggregation ≥20% with AA, ≥70% with ADP, or ≥1 ng/mL stimulated TxB(2) . Fourteen P2RY1 and 35 P2RY12 single nucleotide polymorphisms (SNPs) were genotyped.

RESULTS

High RPR was detected in 24% of the patients. Moderate RPR was observed in 31% with AA, 57% with 5 μm ADP, and 82% with 10 μm ADP. Stimulated TxB(2) was ≥1 ng/mL in 23% of patients. P2RY12 SNP rs9859538 was associated with high RPR (OR = 2.16, 95% CI = 1.24-3.75, P-value = 0.004). Four P2RY12 SNPs, rs1491974, rs10513398, rs3732765, and rs10935841, showed association with moderate RPR (OR = 1.79-2.94, P-value = 0.04-0.028), while five, rs7615865, rs1388623, rs1388622, rs7634096, and rs7637803, were associated with low RPR (OR = 0.50-0.55, P-value = 0.008-0.026), following ADP stimulation. TxB(2) level <1 ng/mL was linked to five P2RY1 SNPs, rs1439010, rs1371097, rs701265, rs12497578, and rs2312265 (OR = 0.36-0.54, P-value = 0.003-0.039).

CONCLUSIONS

Polymorphisms in P2RY1 and P2RY12 are associated with on-aspirin platelet reactivity in patients with CAD.

Description of response to aspirin and clopidogrel in outpatients with coronary artery disease using multiple electrode impedance aggregometry

Identification of outpatients with high platelet reactivity (HPR) on antiplatelet treatment is an unmet need. The present study was conducted in healthy individuals (n = 50) and in outpatients with coronary artery disease (CAD) at a distance from the acute ischemic episode (aspirin group, n = 71; aspirin/clopidogrel group, n = 106). We studied the feasibility and the precision of whole blood multiple electrode aggregometry (MEA) after triggering platelet aggregation by arachidonic acid or adenosine diphospate (ADP). The MEA can be performed on whole blood within 2 hours after sample venipuncture. The threshold for the diagnosis of HPR is situated at 55 and 50 U for the arachidonic acid and ADP test, respectively. Frequency of HPR was 7% and 20% in aspirin and aspirin/clopidogrel groups, respectively. In 3.8% of patients in aspirin/clopidogrel group, combined HPR on aspirin and clopidogrel was found. In outpatients with CAD, use of MEA is feasible for the diagnosis of HPR.

Good short-term but not long-term reproducibility of the antiplatelet efficacy laboratory assessment

BACKGROUND

The antiplatelet effect of acetylsalicylic acid (ASA) varies among individual patients. We assessed the short-term reproducibility (STR) and long-term reproducibility (LTR) of light transmission aggregometry (LTA).

METHODS

Residual platelet reactivity was measured twice using LTA in a group of 207 consecutive patients (56 females, mean age 67 ± 9 years) on ASA therapy in 10 ± 6 months interval. The STR was assessed in 15 patients (6 females, mean age 61 ± 7 years) with 10 measurements on 2 consecutive days.

RESULTS

There was no correlation between both measurements in the long-term part of the study, and also Bland-Altman plot showed a diverging pattern. However, LTA STR was good with a correlation coefficient of .800 (P < .05) confirmed by Bland-Altman plot.

CONCLUSIONS

Although short-term intraindividual reproducibility of LTA assessment of platelet reactivity is very good, in the long-term perspective the antiplatelet ASA effectivity may be influenced by additional variables and repeated measurements are warranted.

Microglial p38α MAPK is a key regulator of proinflammatory cytokine up-regulation induced by toll-like receptor (TLR) ligands or beta-amyloid (Aβ)

BACKGROUND

Overproduction of proinflammatory cytokines from activated microglia has been implicated as an important contributor to pathophysiology progression in both acute and chronic neurodegenerative diseases. Therefore, it is critical to elucidate intracellular signaling pathways that are significant contributors to cytokine overproduction in microglia exposed to specific stressors, especially pathways amenable to drug interventions. The serine/threonine protein kinase p38α MAPK is a key enzyme in the parallel and convergent intracellular signaling pathways involved in stressor-induced production of IL-1β and TNFα in peripheral tissues, and is a drug development target for peripheral inflammatory diseases. However, much less is known about the quantitative importance of microglial p38α MAPK in stressor-induced cytokine overproduction, or the potential of microglial p38α MAPK to be a druggable target for CNS disorders. Therefore, we examined the contribution of microglial p38αMAPK to cytokine up-regulation, with a focus on the potential to suppress the cytokine increase by inhibition of the kinase with pharmacological or genetic approaches.

METHODS

The microglial cytokine response to TLR ligands 2/3/4/7/8/9 or to Aβ1-42 was tested in the presence of a CNS-penetrant p38α MAPK inhibitor, MW01-2-069A-SRM. Primary microglia from mice genetically deficient in p38α MAPK were used to further establish a linkage between microglia p38α MAPK and cytokine overproduction. The in vivo significance was determined by p38α MAPK inhibitor treatment in a LPS-induced model of acute neuroinflammation.

RESULTS

Increased IL-1β and TNFα production by the BV-2 microglial cell line and by primary microglia cultures was inhibited in a concentration-dependent manner by the p38α MAPK-targeted inhibitor. Cellular target engagement was demonstrated by the accompanying decrease in the phosphorylation state of two p38α MAPK protein substrates, MK2 and MSK1. Consistent with the pharmacological findings, microglia from p38α-deficient mice showed a diminished cytokine response to LPS. Further, oral administration of the inhibitor blocked the increase of IL-1β in the cerebral cortex of mice stressed by intraperitoneal injection of LPS.

CONCLUSION

The p38α MAPK pathway is an important contributor to the increased microglial production of proinflammatory cytokines induced by diverse stressors. The results also indicate the feasibility of targeting p38α MAPK to modulate CNS proinflammatory cytokine overproduction.

Historical perspective and future directions in platelet research

Platelets are a remarkable mammalian adaptation that are required for human survival by virtue of their ability to prevent and arrest bleeding. Ironically, however, in the past century, the platelets' hemostatic activity became maladaptive for the increasingly large percentage of individuals who develop age-dependent progressive atherosclerosis. As a result, platelets also make a major contribution to ischemic thrombotic vascular disease, the leading cause of death worldwide. In this brief review, I provide historical descriptions of a highly selected group of topics to provide a framework for understanding our current knowledge and the trends that are likely to continue into the future of platelet research. For convenience, I separate the eras of platelet research into the "Descriptive Period" extending from ~1880-1960 and the "Mechanistic Period" encompassing the past ~50 years since 1960. We currently are reaching yet another inflection point, as there is a major shift from a focus on traditional biochemistry and cell and molecular biology to an era of single molecule biophysics, single cell biology, single cell molecular biology, structural biology, computational simulations, and the high-throughput, data-dense techniques collectively named with the "omics postfix". Given the progress made in understanding, diagnosing, and treating many rare and common platelet disorders during the past 50 years, I think it appropriate to consider it a Golden Age of Platelet Research and to recognize all of the investigators who have made important contributions to this remarkable achievement..