Biomarkers of Exposure and Potential Harm in Two Weeks of Smoking Abstinence: Changes in Biomarkers of Platelet Function, Oxidative Stress, and Inflammation

: Chronic cigarette smoking is a major risk factor for many serious diseases. While complete cessation of smoking is the best option to reduce harm from smoking, adverse impacts of smoking on health could persist for several years after cessation. Therefore, Biomarkers of Potential Harm (BoPH) are useful in interim evaluations of the beneficial effects of smoking cessation or switching to potentially lower-risk tobacco products. A 14-day smoking abstinence study was conducted under clinical confinement conditions and enrolled 70 subjects into younger (24–34 years, n = 33) and older (35–60 years, n = 37) age cohorts. Biomarkers of Exposure (BoE), which indicate exposure to nicotine and other toxicants, were measured at baseline, 7 and 14 days. Several BoPH including previously identified eicosanoids (leukotriene 4 (LTE4) and 2,3-dinor thromboxane 2 (2,3-d-TXB2) and others were evaluated. Significant declines in BoE, LTE4, 2,3-d-TXB2, neutrophils, WBC and select RBC, and arterial blood gas parameters were observed in both age cohorts at Days 7 and 14 compared to baseline, while other BoPH (e.g., FeNO) showed age-related effects. Rapid and reproducible reductions in LTE4, 2,3-d-TXB2 WBC, and neutrophil counts were consistently detected following smoking abstinence, indicating the value of these markers as useful BoPH.

Antiaggregant effects of (1,2,5-oxadiazolyl)azasydnone ring assemblies as novel antiplatelet agents

A series of biheterocyclic assemblies comprising of 1,2,5-oxadiazole and azasydnone scaffolds were synthesized and biologically evaluated as novel nitric oxide (NO)-donor and antiplatelet agents. Depending on functional substituents at the biheterocyclic core, all studied compounds demonstrated good NO-donor profiles releasing NO in a wide range of concentrations (19.2%-195.1%) according to a Griess assay. (1,2,5-Oxadiazolyl)azasydnones showed excellent antiplatelet activity in the case of ADP and adrenaline used as inducers completely suppressing the aggregate formation even at the lowest test concentration of 0.0375 μmol/ml, which is a rather unique feature. Moreover, studied biheterocycles possess a selective mechanism of inhibition of platelet aggregation mediated only by ADP and adrenaline, which are considered to be the main inducers causing thrombus formation. In addition, (1,2,5-oxadiazolyl)azasydnones were found to be completely non-toxic to hybrid endothelial cells EaHy 926. Studies of hydrolytic degradation of the synthesized compounds afforded benzoic acid as a sole detectable decomposition product, which is considered advantageous in drug design. Therefore, (1,2,5-oxadiazolyl)azasydnones represent a novel class of promising drug candidates with improved antiplatelet profile and reduced toxicity enabling their huge potential in medicinal chemistry and drug design.

Duration of Dual Antiplatelet Therapy After Implantation of Drug-Coated Balloon

The drug-coated balloon (DCB) is an emerging percutaneous coronary intervention (PCI) device with theoretical advantages and promising results. Recent clinical observations have demonstrated that DCB tends to have both good efficacy and a good safety profile in the treatment of in-stent restenosis (ISR) for both bare-metal and drug-eluting stents (DES), de novo coronary artery disease (CAD), and other situation, such as high bleeding risk, chronic total occlusion, and acute coronary syndrome (ACS). Dual antiplatelet therapy (DAPT) has become an essential medication in daily clinical practice, but the optimal duration of DAPT after the implantation of a DCB remains unknown. At the time of the first in vivo implantation of paclitaxel-DCB for the treatment of ISR in 2006, the protocol-defined DAPT duration was only 1 month. Subsequently, DAPT duration ranging from 1 to 12 months has been recommended by various trials. However, there have been no randomized controlled trials (RCTs) on the optimal duration of DAPT after DCB angioplasty. Current clinical guidelines normally recommend the duration of DAPT after DCB-only angioplasty based on data from RCTs on the optimal duration of DAPT after stenting. In this review, we summarized current clinical trials on DCB-only angioplasty for different types of CADs and their stipulated durations of DAPT, and compared their clinical results such as restenosis, target lesion revascularization (TLR) and stent thrombosis event. We hope this review can assist clinicians in making reasonable decisions about the duration of DAPT after DCB implantation.

Dual-pathway inhibition for secondary and tertiary antithrombotic prevention in cardiovascular disease

Advances in antiplatelet therapies for patients with cardiovascular disease have improved patient outcomes over time, but the challenge of balancing the risks of ischaemia and bleeding remains substantial. Moreover, many patients with cardiovascular disease have a residual risk of ischaemic events despite receiving antiplatelet therapy. Therefore, novel strategies are needed to prevent clinical events through mechanisms beyond platelet inhibition and with an acceptable associated risk of bleeding. The advent of non-vitamin K antagonist oral anticoagulants, which attenuate fibrin formation by selective inhibition of factor Xa or thrombin, has renewed the interest in dual-pathway inhibition strategies that combine an antiplatelet agent with an anticoagulant drug. In this Review, we highlight the emerging pharmacological rationale and clinical development of dual-pathway inhibition strategies for the prevention of atherothrombotic events in patients with different manifestations of cardiovascular disease, such as coronary artery disease, cerebrovascular disease and peripheral artery disease.

Relationship of atherogenic index of plasma and mean platelet volume with ejection fraction in ischemic and nonischemic heart failure

AIM

Our aim was to evaluate the relationship and diagnostic value of atherogenic index of plasma (AIP) and mean platelet volume (MPV) for heart failure (HF) and ejection fraction (EF).

MATERIALS AND METHODS

In the present study, AIP and MPV were studied in 114 stable HF patients (48 ischemic [42.1%], 66 nonischemic [57.9%]) and 69 controls.

RESULTS

Mean AIP and MPV were significantly higher in HF compared with controls (p = 0.002; p = 0.03). In multivariate analysis, AIP and MPV were independently associated with EF. In receiver-operating characteristics (ROC) curve analysis both of them had optimal diagnostic value for HF.

CONCLUSION

AIP and MPV regardless of ischemic etiology, were significantly higher in HF compared with controls. Both AIP and MPV are independent predictors of EF and have cut-off values for diagnosis of HF.

Clopidogrel Partially Counteracts Adenosine-5'-Diphosphate Effects on Blood Pressure and Renal Hemodynamics and Excretion in Rats

BACKGROUND

Adenosine-5'-diphosphate (ADP) can influence intrarenal vascular tone and tubular transport, partly through activation of purine P2Y12 receptors (P2Y12-R), but their actual in vivo role in regulation of renal circulation and excretion remains unclear.

METHODS

The effects of intravenous ADP infusions of 2-8mg/kg/hour were examined in anesthetized Wistar rats that were untreated or chronically pretreated with clopidogrel, 20mg/kg/24hours, a selective P2Y12-R antagonist. Renal blood flow (transonic probe) and perfusion of the superficial cortex and medulla (laser-Doppler fluxes) were measured, together with urine osmolality (U_osm), diuresis (V), total solute (U_osmV), sodium (U_NaV) and potassium (U_KV) excretion.

RESULTS

ADP induced a gradual, dose-dependent 15% decrease of mean arterial pressure, a sustained increase of renal blood flow and a 25% decrease in renal vascular resistance. Clopidogrel pretreatment attenuated the mean arterial pressure decrease, and did not significantly alter renal blood flow or renal vascular resistance. Renal medullary perfusion was not affected by ADP whereas U_osm decreased from 1,080 ± 125 to 685 ± 75 mosmol/kg H₂0. There were also substantial significant decreases in U_osmV, U_NaV and U_KV; all these changes were attenuated or abolished by clopidogrel pretreatment. Two-weeks' clopidogrel treatment decreased V while U_osmU_osmV and U_NaV increased, most distinctly after 7 days. Acute clopidogrel infusion modestly decreased mean arterial pressure and significantly increased outer- and decreased inner-medullary perfusion.

CONCLUSIONS

Our functional studies show that ADP can cause systemic and renal vasodilation and a decrease in mean arterial pressure, an action at least partly mediated by P2Y12 receptors. We confirmed that these receptors exert tonic action to reduce tubular water reabsorption and urine concentration.

Inhibitory Effect of Propolis on Platelet Aggregation In Vitro

Platelet hyperactivity plays an important role in arterial thrombosis and atherosclerosis. The present study was aimed to investigate the effects of different extracts of propolis and components of flavonoids on platelet aggregation. Platelet-rich plasma was prepared and incubated in vitro with different concentrations of the tested extracts and components of flavonoids. Platelets aggregation was induced by different agonists including adenosine diphosphate (ADP, 10 μM), thrombin receptor activator peptide (TRAP, 50 μM), and collagen (5 μg/mL). At 25 mg/L to 300 mg/mL, the water extract propolis (WEP) inhibited three agonists-induced platelet aggregations in a dose-dependent manner. The flavonoids isolated from the propolis also showed markedly inhibited platelet aggregation induced by collagen, ADP, and TRAP, respectively. The components including caffeic acid phenethyl ester (CAPE), galangin, apigenin, quercetin, kaempferol, ferulic acid, rutin, chrysin, pinostrobin, and pinocembrin and their abilities of inhibiting platelet aggregation were studied. It was concluded that propolis had an antiplatelet action in which flavonoids were mainly implicated.

Fabrication of an Anti-Biofouling Plasma-Filtration Membrane by an Electrospinning Process Using Photo-Cross-linkable Zwitterionic Phospholipid Polymers

The goal of this study is to fabricate a stable plasma filtration membrane with antibiofouling properties via an electrospinning process. To this end, a random-type copolymer consisting of zwitterionic phosphorylcholine (PC) groups and ultraviolet (UV)-cross-linkable phenyl azide groups was synthesized. The zwitterionic PC group provides antibiofouling properties, and the phenyl azide group enables the stable maintenance of the fibrous nanostructure of hydrophilic zwitterion polymers in aqueous medium via a simple UV curing process. To demonstrate the antibiofouling nature of the PC group, a polymer without antibiofouling PC groups was also prepared for comparison. The successful synthesis of the random-type copolymers containing phenyl azide groups was proven by ¹H nuclear magnetic resonance and Fourier transform infrared spectroscopy, and the fibrous structure of the prepared membranes was observed by field emission scanning electron microscopy. The antibiofouling properties were analyzed by fluorescein isothiocyanate-labeled bovine serum albumin adsorption and platelet adhesion tests. The experimental results show that membranes containing zwitterionic PC groups exhibited obvious decreases in platelet adhesion and protein adsorption. Platelet-rich plasma solution was filtered using the prepared membranes to test their filtration properties. The sequential filtration process removed 80% and almost 98% of the platelets. This finding confirmed that the membrane retained its blood-inert biomaterial surface in a complex medium that included blood plasma and platelets.

Platelet volume indices are associated with systolic and diastolic cardiac dysfunction, and left ventricular hypertrophy

Background

Mean platelet volume (MPV) and platelet distribution width (PDW) are indices that reflect platelet activity. We investigated the association between these platelet indices and left ventricular hypertrophy and cardiac function.

Methods

We analyzed the data of 1241 patients who were admitted to the Cardiology Department.

Results

Both MPV and PDW were selected as independent factors associated with left ventricular systolic and diastolic dysfunction, and left ventricular hypertrophy. The highest tertile of MPV and PDW was associated with left ventricular systolic dysfunction (left ventricular ejection fraction of <50 %) with an odds ratio of 1.53 and 2.03, respectively, when the respective lowest tertile was used as reference. The highest PDW tertile was associated with left ventricular hypertrophy with an odds ratio of 1.56 (95 % CI, 1.13–2.15) and with dysfunction with an odds ratio of 3.34 (95 % CI, 1.54–7.25).

Conclusions

Indices of platelet activation (MPV and/or PDW) were independently associated positively with left ventricular hypertrophy and left ventricular systolic and diastolic dysfunction. Whether these platelet indices represent useful markers for identifying individuals at higher risk for thromboembolic disease and organ damage among cardiac patients awaits further investigation.

Potassium 2-(1-hydroxypentyl)-benzoate inhibits ADP-induced rat platelet aggregation through P2Y1-PLC signaling pathways

Potassium 2-(1-hydroxypenty1)-benzoate (dl-PHPB) is a new drug candidate for treatment of ischemic stroke with antiplatelet effect. In this study, we investigated the mechanisms of dl-PHPB in inhibiting platelet aggregation. The ADP-activated P2Y1-Gq-PLC and P2Y12-Gi-AC pathways were observed, respectively. Intravenous injection of dl-PHPB (1.3, 3.9, 12.9 mg/kg) significantly inhibited ADP-, collagen-, and arachidonic acid-induced rat platelet aggregation in a dose-dependent manner, and dl-PHPB had a relatively more potent inhibitory effect on ADP-induced rat platelet aggregation than other agonists. Dl-PHPB also showed a decreased expression of CD62P (a marker for platelet activation) mediated by ADP. Both dl-PHPB and ticlopidine (P2Y12 receptor antagonist) decreased cytoplasmic Ca(2+) concentration. But, dl-PHPB did not reverse the inhibition of PGE1-induced platelet cAMP formation by ADP, which was different from ticlopidine. Further, dl-PHPB instead of ticlopidine showed increasing phospholipase C-β phosphorylation (ser(1105)). The m-3M3FBS, a phospholipase C activator, attenuated the inhibitory effect of dl-PHPB on ADP-induced platelet aggregation and enhanced IP1 accumulation in rat platelets. Dl-PHPB decreased IP1 accumulation induced by ADP but had no effect on IP1 level enhanced by m-3M3FBS. Our results suggest that dl-PHPB has a potent antiplatelet effect, which is mainly through blockade of P2Y1 receptor-PLC-IP3 pathway and decreasing cytoplasmic calcium.

Platelet P2Y₁₂ receptors are involved in the haemostatic effect of notoginsenoside Ft1, a saponin isolated from Panax notoginseng

BACKGROUND AND PURPOSE

Saponins isolated from Panax notoginseng (Burk.) F.H. Chen have been shown to relieve thrombogenesis and facilitate haemostasis. However, it is not known which saponin accounts for this haemostatic effect. Hence, in the present study we aimed to identify which saponins contribute to its haemostatic activity and to elucidate the possible underlying mechanisms.

EXPERIMENTAL APPROACH

Platelet aggregation was analysed using a platelet aggregometer. Prothrombin time, activated partial thromboplastin time and thrombin time were measured using a blood coagulation analyser, which was further corroborated with bleeding time and thrombotic assays. The interaction of notoginsenoside Ft1 with the platelet P2Y₁₂ receptor was determined by molecular docking analysis, cytosolic Ca(2+) and cAMP measurements, and phosphorylation of PI3K and Akt assays.

KEY RESULTS

Among the saponins examined, Ft1 was the most potent procoagulant and induced dose-dependent platelet aggregation. Ft1 reduced plasma coagulation indexes, decreased tail bleeding time and increased thrombogenesis. Moreover, it potentiated ADP-induced platelet aggregation and increased cytosolic Ca(2+) accumulation, effects that were attenuated by clopidogrel. Molecular docking analysis suggested that Ft1 binds to platelet P2Y₁₂ receptors. The increase in intracellular Ca(2+) evoked by Ft1 in HEK293 cells overexpressing P2Y₁₂ receptors could be blocked by ticagrelor. Ft1 also affected the production of cAMP and increased phosphorylation of PI3K and Akt downstream of P2Y₁₂ signalling pathways.

CONCLUSION AND IMPLICATIONS

Ft1 enhanced platelet aggregation by activating a signalling network mediated through P2Y₁₂ receptors. These novel findings may contribute to the effective utilization of this compound in the therapy of haematological disorders.

Pharmacometabolomics reveals that serotonin is implicated in aspirin response variability

While aspirin is generally effective for prevention of cardiovascular disease, considerable variation in drug response exists, resulting in some individuals displaying high on-treatment platelet reactivity. We used pharmacometabolomics to define pathways implicated in variation of response to treatment. We profiled serum samples from healthy subjects pre- and postaspirin (14 days, 81 mg/day) using mass spectrometry. We established a strong signature of aspirin exposure independent of response (15/34 metabolites changed). In our discovery (N = 80) and replication (N = 125) cohorts, higher serotonin levels pre- and postaspirin correlated with high, postaspirin, collagen-induced platelet aggregation. In a third cohort, platelets from subjects with the highest levels of serotonin preaspirin retained higher reactivity after incubation with aspirin than platelets from subjects with the lowest serotonin levels preaspirin (72 ± 8 vs. 61 ± 11%, P = 0.02, N = 20). Finally, ex vivo, serotonin strongly increased platelet reactivity after platelet incubation with aspirin (+20%, P = 4.9 × 10⁻⁴, N = 12). These results suggest that serotonin is implicated in aspirin response variability.

Integrated microRNA-mRNA analysis of coronary artery disease

Although patients with coronary artery disease (CAD) have a high mortality rate, the pathogenesis of CAD is still poorly understood. The purpose of this study was to explore the underlying molecular mechanisms and potential target molecules for CAD. The platelet miRNA (GSE28858) and blood mRNA (GSE42148) expression profiles of patients with CAD and healthy controls were downloaded from Gene Expression Omnibus. Differentially expressed miRNAs and genes (DEGs) were identified by significant analysis of microarray algorithm after data preprocessing. Furthermore, the miRNA-target gene regulatory network was constructed based on miRecords database. The spearman correlation coefficients (ρ) between miRNAs and their target genes were calculated. Six up- (miR-340, miR-545, miR-451, miR454-5p, miR-624 and miR-585) and four down-regulated (miR-199a, miR-17-3p, miR-154 and miR-339) miRNAs were screened. Total 295 target genes of miR-545, miR-451, miR-585 and miR-154 were predicted. Among these 295 target genes, 7 genes were DEGs. Further analysis showed miR-545-TFEC and miR-585-SPOCK1 were highly positively correlated (ρ = 0.808091264; ρ = 0.874680776) in CAD samples. Therefore, differentially expressed miRNAs might participate in the pathogenesis of CAD by regulating their target genes.

Dietary manipulation of platelet function

Activated platelets contribute to plaque formation within blood vessels in the early and late stages of atherogenesis, and therefore they have been proposed as risk factor for cardiovascular disease. Anti-platelet drugs, such as aspirin, are now the most prescribed pharmacological treatment in Europe. Certain dietary bioactives also beneficially affect platelet function, and with less side effects, albeit that effects are generally more subtle. Therefore, consumption of dietary bioactives could play a role in the prevention of atherothrombotic vascular disease. Here we review the efficacy of dietary treatment strategies, especially those involving certain dietary fatty acids and polyphenols, to modulate platelet function in healthy subjects or in patients with cardiovascular disease. Variation in study populations, small study sizes and lack of comparability between methods to assess platelet function currently limit robust evidence on the efficacy of dietary bioactives in healthy subjects or specific patient groups. Also, limited knowledge of the metabolism of dietary bioactives, and therefore of the bioavailability of bioactive ingredients, restricts our ability to identify the most effective dietary regimes to improve platelet function. Implementation of uniform point-of-care tests to assess platelet function, and enhanced knowledge of the efficacy by which specific dietary compounds and their metabolites affect platelet function, may enable the identification of functional anti-platelet ingredients that are eligible for a health claim, or combined treatment strategies, including both pharmacological anti-platelet treatment as well as dietary intervention, to tackle atherothrombotic vascular disease.

Unmet needs in the management of acute myocardial infarction: role of novel protease-activated receptor-1 antagonist vorapaxar

Platelet activation with subsequent aggregation is a complex process leading to thrombus formation, which remains a key component for atherothrombotic manifestations, in particular myocardial infarction. Therefore, antiplatelet therapies are pivotal for the treatment of these patients. Current oral antiplatelet therapies used for secondary prevention of ischemic recurrences include aspirin and adenosine diphosphate P2Y12 platelet-receptor antagonists. However, despite these therapies, patients who have experienced a myocardial infarction remain at risk for ischemic recurrences. Therefore, more aggressive secondary prevention measures have been an area of research, including identifying additional targets modulating platelet-activation and -aggregation processes. Among these, thrombin-mediated platelet activation via protease-activated receptors (PARs) has been subject to extensive clinical investigation. Several PAR-1 receptor antagonists have been developed. However, vorapaxar is the only one that has completed large-scale clinical investigation. The present manuscript will provide an overview on the role of thrombin-mediated signaling, the impact of PAR-1 blockade with vorapaxar on ischemic and bleeding outcomes, and the potential role for vorapaxar in clinical practice.

Clopidogrel preserves whole kidney autoregulatory behavior in ANG II-induced hypertension

This study tested the hypothesis that P2Y12 receptor blockade with clopidogrel preserves renal autoregulatory ability during ANG II-induced hypertension. Clopidogrel was administered orally to male Sprague-Dawley rats chronically infused with ANG II. After 14 days of treatment, whole kidney autoregulation of renal blood flow was assessed in vivo in pentobarbital-anesthetized rats using an ultrasonic flow probe placed around the left renal artery. In ANG II-vehicle-treated rats, decreasing arterial pressure over a range from 160 to 100 mmHg resulted in a 25 ± 5% decrease in renal blood flow, demonstrating a significant loss of autoregulation with an autoregulatory index of 0.66 ± 0.15. However, clopidogrel treatment preserved autoregulatory behavior in ANG II-treated rats to levels indistinguishable from normotensive sham-operated (sham) rats (autoregulatory index: 0.04 ± 0.14). Compared with normotensive sham-vehicle-treated rats, ANG II infusion increased renal CD3-positive T cell infiltration by 66 ± 6%, induced significant thickening of the preglomerular vessels and glomerular basement membrane and increased glomerular collagen I deposition, tubulointerstitial fibrosis, damage to the proximal tubular brush border, and protein excretion. Clopidogrel significantly reduced renal infiltration of T cells by 39 ± 9% and prevented interstitial artery thickening, ANG II-induced damage to the glomerular basement membrane, deposition of collagen type I, and tubulointerstitial fibrosis, despite the maintenance of hypertension. These data demonstrate that systemic P2Y12 receptor blockade with clopidogrel protects against impairment of autoregulatory behavior and renal vascular injury in ANG II-induced hypertension, possibly by reducing renal T cell infiltration.

Serotonin metabolism in the placenta in exacerbation of herpesvirus infection during pregnancy

Serotonin metabolism in the blood and placental homogenate was studied in pregnancy aggravated by exacerbation of herpesvirus infection. Blood serotonin content in pregnant patients increased with increasing herpesvirus antibody titers and reduction of monoamine oxidase activity. Urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA) decreased. The decrease of monoamine oxidase activity in placental homogenate led to an increase of serotonin level, which was paralleled by destruction of mitochondria in the syncytiotrophoblast, suppression of BCL-2 protein activity, and increase of caspase-3 level.

Crocin, a dietary additive protects platelets from oxidative stress-induced apoptosis and inhibits platelet aggregation

Platelets are the key players in the development of cardiovascular diseases as the microparticles generated by apoptotic platelets and platelet aggregation contribute actively towards the disease propagation. Thus, the aim of this study was to demonstrate the effect of a phytochemical which can prevent these two processes and thereby project it as a cardio-protective compound. Crocin, a natural carotenoid exhibits a wide spectrum of therapeutic potentials through its antioxidant property. The study demonstrated its effects on cytoplasmic apoptotic events of mitochondrial pathway in platelets. Collagen/calcium ionophore-A23187 stimulated platelets were treated with crocin and endogenous generation of reactive oxygen species (ROS) and hydrogen peroxide (H(2)O(2)) were measured. H(2)O(2)-induced changes in crocin-pretreated platelets such as intracellular calcium, mitochondrial membrane potential (ΔΨm), caspase activity, phosphatidylserine exposure and cytochrome c translocation were determined. Crocin dose-dependently ameliorated collagen- and A23187-induced endogenous generation of ROS and H(2)O(2). It also abolished the H(2)O(2)-induced events of intrinsic pathway of apoptosis. Further, it hindered collagen-induced platelet aggregation and adhesion. The current piece of work clearly suggests its anti-apoptotic effect as well as inhibitory effects on platelet aggregation. Thus, crocin can be deemed as a prospective candidate in the treatment regime of platelet-associated diseases.

Endothelial cell and platelet bioenergetics: effect of glucose and nutrient composition

It has been suggested that cells that are independent of insulin for glucose uptake, when exposed to high glucose or other nutrient concentrations, manifest enhanced mitochondrial substrate oxidation with consequent enhanced potential and generation of reactive oxygen species (ROS); a paradigm that could predispose to vascular complications of diabetes. Here we exposed bovine aortic endothelial (BAE) cells and human platelets to variable glucose and fatty acid concentrations. We then examined oxygen consumption and acidification rates using recently available technology in the form of an extracellular oxygen and proton flux analyzer. Acute or overnight exposure of confluent BAE cells to glucose concentrations from 5.5 to 25 mM did not enhance or change the rate of oxygen consumption (OCR) under basal conditions, during ATP synthesis, or under uncoupled conditions. Glucose also did not alter OCR in sub-confluent cells, in cells exposed to low serum, or in cells treated with added pyruvate. Likewise, overnight exposure to fatty acids of varying saturation had no such effects. Overnight exposure of BAE cells to low glucose concentration decreased maximal uncoupled respiration, but not basal or ATP related oxygen consumption. Labeled glucose oxidation to CO₂ increased, but only marginally after high glucose exposure while oleate oxidation to CO₂ decreased. Overnight exposure to linolenic acid, but not oleic or linoleic acid increased extracellular acidification consistent with enhanced glycolytic metabolism. We were unable to detect an increase in production of reactive oxygen species (ROS) from BAE cells exposed to high medium glucose. Like BAE cells, exposure of human platelets to glucose did not increase oxygen consumption. As opposed to BAE cells, platelet mitochondria demonstrate less respiratory reserve capacity (beyond that needed for basal metabolism). Our data do not support the concept that exposure to high glucose or fatty acids accelerates mitochondrial oxidative metabolism in endothelial cells or platelets.

Effects of PPIs and an H2 blocker on the antiplatelet function of clopidogrel in Japanese patients under dual antiplatelet therapy

AIM

Dual antiplatelet therapy (DAPT) with aspirin and clopidogrel is essential after percutaneous coronary intervention (PCI). Clopidogrel is a prodrug and changed into active metabolite by cytochrome p450 enzymes (CYPs), especially CYP2C19. Proton pump inhibitors (PPIs) are used for the prevention of aspirin-induced gastrointestinal bleeding. PPIs are also metabolized by CYP2C19, although the degree of its contribution is dependent on the kind of PPI. Omeprazole, a PPI, has been reported to weaken the antiplatelet effects of clopidogrel. Famotidine, a histamine receptor type 2 (H2) blocker, could also be an alternative to PPIs. The aim of this study was to evaluate the effects of PPIs and an H2 blocker on the antiplatelet function of clopidogrel.

METHODS

Patients receiving DAPT due to prior PCI, who took either omeprazole or rabeprazole, were enrolled (n=25). The initial PPI was changed to the other PPI as a crossover study. In another study, patients undergoing DAPT without taking PPIs or H2 blockers were enrolled (n=30) and famotidine was added.

RESULTS

Platelet aggregability when taking omeprazole was higher than when taking rabeprazole, evaluated by an optical aggregometer using collagen as a stimulus (p=0.0051) and by the VerifyNow P2Y12 assay (p=0.0060). Platelet aggregability when taking rabeprazole was comparable to that in control patients (n=15). Concomitant use of famotidine had no effect.

CONCLUSION

Omeprazole significantly reduced the antiplatelet effect of clopidogrel and this effect on clopidogrel was stronger than that of rabeprazole. Concomitant use of famotidine had no effect on the antiplatelet effect of clopidogrel.

Characterization of the in vivo antiplatelet activity of the antihypertensive agent losartan

OBJECTIVE

The purpose of this study is to investigate the potential in vivo antiplatelet and thromboprotective properties of the antihypertensive drug losartan in mice.

METHODS

Aggregometry studies were performed on platelets obtained from mice administered losartan for 5 days, via tail vein to examine the ex vivo effects (dose dependence) of this agent and to select an appropriate dose for the in vivo studies. Next, the tail bleeding time test and the time for occlusion in a carotid artery injury thrombosis model (ferric chloride) were also performed to assess the in vivo effects of losartan treatment.

RESULTS

These data indicate that the antihypertensive agent losartan exerts dose-dependent inhibition of the thromboxane receptor-mediated (U46619/agonist)-induced platelet aggregation (ex vivo), whereas it produced no detectable effects on aggregation triggered by adenosine diphosphate or the thrombin receptor activating peptide 4. Findings from the in vivo analysis revealed that tail bleeding time of losartan-treated mice was not different from vehicle-treated mice. On the other hand, in the carotid artery injury thrombosis model, it was found that the losartan-treated mice had significantly longer time for occlusion in comparison with those treated with vehicle control.

CONCLUSIONS

These findings provide evidence that administration of the antihypertensive drug losartan into live mice produces thromboxane A(2) receptor-specific antiplatelet effects. Furthermore, interestingly, this antiplatelet activity appears to translate into thromboprotective properties, without resulting in a bleeding phenotype. Consequently, aside from its potential use as an antithrombotic agent, losartan's chemistry may provide a "blueprint" for designing or repurposing novel derivatives which may have the potential to serve as an antiplatelet and thromboprotective agents but are deprived of the usually concomitant bleeding adverse effects.

Aspirin: pharmacology and clinical applications

Antiplatelet therapy has been documented to reduce risks of cardiovascular disease after acute myocardial infarction, coronary artery bypass graft, and in chronic atrial fibrillation patients, amongst other risk factors. Conventional management of thrombosis-based disorders includes the use of heparin, oral anticoagulants, and the preferred antiplatelet agent aspirin. Interestingly, aspirin was not intended to be used as an antiplatelet agent; rather, after being repurposed, it has become one of the most widely prescribed antithrombotic drugs. To this end, there have been several milestones in the development of antiplatelet agents in the last few decades, such as adenosine diphosphate receptor inhibitors, phosphodiesterase inhibitors, and GPIIb/IIIa inhibitors. However, given some of the limitations of these therapies, aspirin continues to play a major role in the management of thrombotic and cardiovascular disorders and is expected to do so for years to come.

Antiplatelet agents for intermittent claudication

BACKGROUND

Peripheral arterial disease (PAD) is common and is a marker of systemic atherosclerosis. Patients with symptoms of intermittent claudication (IC) are at increased risk of cardiovascular events (myocardial infarction (MI) and stroke) and of both cardiovascular and all cause mortality.

OBJECTIVES

To determine the effectiveness of antiplatelet agents in reducing mortality (all cause and cardiovascular) and cardiovascular events in patients with intermittent claudication.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases group searched their Specialised Register (last searched April 2011) and CENTRAL (2011, Issue 2) for publications on antiplatelet agents and IC. In addition reference lists of relevant articles were also searched.

SELECTION CRITERIA

Double-blind randomised controlled trials comparing oral antiplatelet agents versus placebo, or versus other antiplatelet agents in patients with stable intermittent claudication were included. Patients with asymptomatic PAD (stage I Fontaine), stage III and IV Fontaine PAD, and those undergoing or awaiting endovascular or surgical intervention were excluded.

DATA COLLECTION AND ANALYSIS

Data on methodological quality, participants, interventions and outcomes including all cause mortality, cardiovascular mortality, cardiovascular events, adverse events, pain free walking distance, need for revascularisation, limb amputation and ankle brachial pressure indices were collected. For each outcome, the pooled risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI) was calculated.

MAIN RESULTS

A total of 12 studies with a combined total of 12,168 patients were included in this review. Antiplatelet agents reduced all cause (RR 0.76, 95% CI 0.60 to 0.98) and cardiovascular mortality (RR 0.54, 95% CI 0.32 to 0.93) in patients with IC compared with placebo. A reduction in total cardiovascular events was not statistically significant (RR 0.80, 95% CI 0.63 to 1.01). Data from two trials (which tested clopidogrel and picotamide respectively against aspirin) showed a significantly lower risk of all cause mortality (RR 0.73, 95% CI 0.58 to 0.93) and cardiovascular events (RR 0.81, 95% CI 0.67 to 0.98) with antiplatelets other than aspirin compared with aspirin. Antiplatelet therapy was associated with a higher risk of adverse events, including gastrointestinal symptoms (dyspepsia) (RR 2.11, 95% CI 1.23 to 3.61) and adverse events leading to cessation of therapy (RR 2.05, 95% CI 1.53 to 2.75) compared with placebo; data on major bleeding (RR 1.73, 95% CI 0.51, 5.83) and on adverse events in trials of aspirin versus alternative antiplatelet were limited. Risk of limb deterioration leading to revascularisation was significantly reduced by antiplatelet treatment compared with placebo (RR 0.65, 95% CI 0.43 to 0.97).

AUTHORS' CONCLUSIONS

Antiplatelet agents have a beneficial effect in reducing all cause mortality and fatal cardiovascular events in patients with IC. Treatment with antiplatelet agents in this patient group however is associated with an increase in adverse effects, including GI symptoms, and healthcare professionals and patients need to be aware of the potential harm as well as the benefit of therapy; more data are required on the effect of antiplatelets on major bleeding. Evidence on the effectiveness of aspirin versus either placebo or an alternative antiplatelet agent is lacking. Evidence for thienopyridine antiplatelet agents was particularly compelling and there is an urgent need for multicentre trials to compare the effects of aspirin against thienopyridines.