Platelet reactivity among Asian Indians and Caucasians

Asian Indians are reported to have higher mortality and morbidity from coronary artery disease (CAD) than other ethnic groups. This variation in events cannot be explained only by differences in conventional risk factors. Platelet activation is an important factor in the pathogenesis of CAD, however, there are limited data concerning platelet reactivity in Asian Indians. Therefore, we aimed to examine platelet reactivity in healthy Asian Indians vs. Caucasians. Thirty-five healthy, nonsmoking Asian Indians (mean age 30.1 +/- 3.6 years, 31.4% women) were matched for age and sex with 35 healthy, nonsmoking Caucasians (mean age 30.8 +/- 5 years, 31.4% women). Platelet reactivity was evaluated by measuring platelet aggregation, platelet leukocyte aggregates (PLA) formation in response to a 6-mer thrombin receptor agonist peptide (TRAP) at a final concentration of 40 microM and flow cytometry determined P-selectin expression induced by ADP, TRAP and arachidonic acid (AA). In addition, P-Selectin glycoprotein ligand-1 (PSGL-1) density on leukocytes was measured. There were no differences in platelet aggregation, basal PLA or PSGL-1 density on leukocytes between the two groups. AA-stimulated P-selectin expression was significantly higher in Asian Indians than in Caucasians (6.1 +/- 0.51 vs. 4.2 +/- 0.41 MFI, P < 0.02). After stimulation with TRAP, platelets from Asian Indians had increased PLA formation compared with Caucasians (41.6 +/- 2.9% vs. 31.4 +/- 2.7%, P < 0.02). AA induced P-selectin expression and TRAP stimulated PLA formation is increased in Asian Indians compared with Caucasians. These differences indicate an increase in measures of platelet reactivity among Asian Indians and may help elucidate the reported disparity in cardiovascular disease rates between the two ethnic groups.     

Neonatal platelets from cord blood and peripheral blood

The haemostatic system in neonates is different from that of adults, possibly contributing to an increased incidence of bleeding disorders, such as intracranial hemorrhage. In this study, we analyzed platelets from cord blood and peripheral blood, collected at three time points after delivery from 20 term and 37 preterm neonates as well as blood from 20 healthy adults. Platelet membrane glycoproteins (GP) were quantified and P-selectin expression and PAC-1 binding ability before and after stimulation with TRAP were analyzed by whole blood flow cytometry. We found no significant differences in neonatal platelets from cord blood and peripheral blood within the first 24?h of life. Platelets from infants less than 30 weeks of gestation expressed lower levels of GP (33271?±?9381 vs. 44085?±?17287 for GPIIIa, P?<?0.05) and were less reactive than platelets from term newborns (4.3?±?3.3 vs. 20.1?±?11.8% PAC-1 positive platelets after stimulation with TRAP, P?<?0.05). A significantly lower level of GPIIb/IIIa expression on platelets from peripheral blood was seen in term newborns as well as preterm infants, compared to adults. There was only a partial enhancement in the degranulation ability (α-granules) (13.4?±?12.3 vs. 50.3?±?16.1% P-selectin positive platelets, P?<?0.05) and no significant increase for PAC-1 binding (13.6?±?10.9 vs. 15.3?±?5.9% PAC-1 positive platelets, P?=?0.8) during the first 12 days of life. In conclusion, we could demonstrate that neonatal platelet reactivity increases with gestational age.     

Functional interplay between platelet activation and endothelial dysfunction in patients with coronary heart disease

Platelet–monocyte binding and surface P-selectin expression are sensitive markers of platelet activation. Endothelium-derived factors are known to inhibit platelet activation and may confer important anti-atherothrombotic effects. We assessed the relationship between platelet activation and endothelium-dependent vasomotion in patients with coronary heart disease (CHD). Twenty male patients with stable CHD were compared with 20 healthy men. Platelet–monocyte binding and platelet surface expression of P-selectin were assessed using two-colour flow cytometry on whole blood. Forearm blood flow was assessed in patients using venous occlusion plethysmography during intra-arterial infusions of substance P, acetylcholine and sodium nitroprusside. Platelet activation was higher in patients than healthy men (platelet–monocyte binding, 27?±?3 vs. 20?±?1%; P?<?0.05). In patients with CHD, there was an inverse correlation between maximal substance P induced vasodilatation and both platelet–monocyte binding (P?=?0.003) and P-selectin expression (P?=?0.02). A similar correlation was observed between platelet–monocyte binding and the vasomotor response to acetylcholine (P?=?0.08) but not with sodium nitroprusside. In patients with stable coronary heart disease, there is a strong inverse relationship between markers of platelet activation and endothelium-dependent vasomotor function. This may explain the pathophysiological mechanism linking endothelial vasomotor dysfunction and the risk of acute atherothrombotic events.     

Brachial artery endothelial function predicts platelet function in control subjects and in patients with acute myocardial infarction

Platelet activation occurs in an endothelium-dependent flow-mediated dilation (FMD) impairment environment. The aim of this study was to explore the association between platelet reactivity and brachial artery FMD in individuals without established cardiovascular disease (controls) and acute myocardial infarction (AMI) patients. We prospectively assessed brachial artery FMD in 151 consecutive subjects, 104 (69%) controls, and 47 (31%) AMI patients; 115 (76%) men, mean age 53?±?11 years. Following overnight fasting and discontinuation of all medications for?≥?12?h, percent change in brachial artery FMD (%FMD) and endothelium-independent, nitroglycerin-mediated vasodilation (%NTG) were assessed. Platelet aggregation was assessed by conventional aggregometry, and platelet adhesion and aggregation under flow conditions by cone-and-plate(let) technology (Impact-R). Smoking, diabetes, and hypertension were more common in AMI compared to control subjects (p?<?0.01 for all). Furthermore, aspirin, clopidogrel, beta-blockers, angiotensin-converting enzyme inhibitors, and statin administration were more common in AMI compared to controls (p?<?0.01 for all). %FMD but not %NTG was significantly lower in AMI patients compared to controls (10.2?±?4.2% vs. 15.4?±?4.4%; p?<?0.001 and 17.2?±?3.9% vs. 18.0?±?3.7%, p?=?0.803, respectively). %FMD was significantly and inversely associated with all platelet functions tests (p?<?0.001) in all study participants. In a multivariate logistic regression (unadjusted and adjusted for age, gender, smoking status, diabetes mellitus, hypertension, hypercholesterolemia, overweight, family history, and concomitant medications), %FMD remained the best predictor of platelet function, irrespective of group allocation (AMI patients or controls). In conclusion, FMD is inversely correlated to platelet reactivity in both controls and AMI patients.     

Impaired responsiveness of platelets to epinephrine due to α2A adrenoreceptor deficiency in Male Chinese

Epinephrine is known as a weak, but important, agonist for platelet activation. It has been reported that the responsiveness of platelets to epinephrine was markedly impaired in 6% of Caucasians and in 16% of Japanese. The purpose of this study was to screen and characterize this abnormality in healthy Taiwanese Chinese volunteers. We used aggregometry, flow cytometry and platelet function analyzer (PFA)-100 system to assess in 50 healthy male volunteers the responsiveness of platelets to epinephrine stimulation. Using α2A adrenoceptor antagonist BRL44408 maleate competition and a [³H]yohimbin binding assay, we evaluated α2A adrenoceptors on platelets. The aggregation of platelets after stimulation with 10?μM of epinephrine indicated two distinct groups of study participants: 24 (48.0%) good- and 26 (52.0%) impaired-responders to epinephrine. Flow cytometric analysis of platelets after stimulated with 1?μM epinephrine showed that glycoprotein (GP) IIb/IIIa and P-selectin expression of epinephrine good- and impaired-responders were 27.1?±?11.0% vs. 9.9?±?5.4% (p?=?0.003) and 12.2?±?6.2% vs. 3.6?±?3.5% (p?3H]yohimbine binding studies showed fewer α2A adrenoreceptors on the platelets of epinephrine-impaired-responders than on those of good-responders. The prevalence of impaired responsiveness to epinephrine was high and probably due to α2A adrenoreceptor deficiency in male Taiwanese Chinese.     

Effect of pioglitazone on insulin sensitivity,vascular function and cardiovascular inflammatory markers in insulin‐resistant non‐diabetic Asian Indians

Aims To determine the effects of pioglitazone (30 mg once daily for 16 weeks) on insulin sensitivity, insulin‐mediated vasodilation, vascular inflammatory markers, fat distribution and lipids in Asian Indians and Caucasians of European ancestry. Methods Cross‐sectional study. Eighteen non‐diabetic Asian Indians and 17 Caucasians of comparable age (34 ± 3 vs. 36 ± 3 years) and body mass index (26.0 ± 1.2 vs. 24.7 ± 1.0 kg/m²) had measurements of insulin sensitivity (M, insulin clamp at 6 pmol/kg per min), abdominal fat (computed tomographic scan at L4‐L5), endothelial‐dependent (reactive hyperaemia, RH) and ‐independent (0.4 mg sublingual nitroglycerin, TNG) vasodilation using brachial artery ultrasound before and after the 2‐h clamp at baseline and after pioglitazone therapy. Results Asian Indians were insulin resistant compared with Causasians during the baseline clamp (M = 25.6 ± 1.7 vs. 41.1 ± 2.2 µmol/kg per min, P < 0.0001) and improved significantly after pioglitazone (to 33.9 ± 1.7 µmol/kg per min, P < 0.001). Vasodilatory responses to RH and TNG were similar in Asian Indians and Caucasians at baseline and did not change. Insulin‐mediated vasodilation improved after pioglitazone in Asian Indians, but not in Caucasians, and correlated with the change in insulin sensitivity (r = 0.52, P = 0.03). C‐reactive protein (CRP) was higher in Asian Indians vs. Caucasians (1.6 ± 0.4 vs. 0.9 ± 0.2 mg/l) and was negatively correlated with insulin sensitivity (r = ?0.53, P = 0.02). In the Asian Indian group, CRP and plasminogen activator inhibitor‐1 decreased and adiponectin increased after pioglitazone, but there were no significant changes in total or visceral fat. Conclusions These results demonstrate that insulin‐resistant Asian Indians respond favourably to an insulin sensitizer with improvements in insulin sensitivity, cardiovascular and inflammatory risk markers, and vascular responses to insulin. These agents may have a role in decreasing the risk of diabetes and cardiovascular disease in this high‐risk population.     

Platelets and acute cerebral infarction

Stroke is worldwide a leading cause of death and disability. Its etiology is regarded as heterogeneous. Platelets are implicated in its pathophysiology, but our understanding of their specific role is incomplete. Only sparse and conflicting information exists about platelet reactivity and activity in acute stroke. Some scientists take the view that platelets activate in conjunction with acute cerebral infarctions. Others put forward evidence corroborating the contrary notion. Increased soluble P-selectin as a sign of platelet and/or endothelial activity seems to be a feature of the disease. The latter point of view is opposed by other researchers. Due to these conflicting opinions, this study is devoted to platelet characteristics in acute cerebral infarctions. We studied subjects (n?=?72; age 74?±?10(SD) years; 31 females) having acute stroke. As controls served atrial fibrillation (AF) patients (n?=?58; age 69?±?7(SD) years; 12 females) subject to electrical cardioversion, a flow cytometer was put to use for measuring platelet reactivity and activity. After agonist provocation, both platelet bound P-selectin and fibrinogen were employed as estimates of platelet reactivity. Dilutions of a thrombin-receptor-activating peptide (TRAP-6) (74 and 57?µmol/l) (P-selectin and fibrinogen) and ADP (8.5 and 1.7?µmol/l) (fibrinogen only) were put to use as platelet agonists. Membrane-bound P-selectin without agonist stimulation served as a measure of in vivo platelet activation. Soluble P-selectin, as determined from a commercial ELISA, was used to assess platelet and/or endothelial activity. In acute stroke neither platelet-bound P-selectin nor fibrinogen after stimulation, i.e. reactivity, differed from AF controls. In contrast, lower platelet activity as judged from surface attached and circulating P-selectin without agonist stimulation proved to be a feature of cerebral infarctions. The p-values were p?<?0.001 and p?<?0.01, respectively. It is concluded that acute stroke is not associated with platelet reactivity platelets circulate less activated during the disease. It is evident that the mechanisms reflecting platelet reactivity and activity being investigated in this study play minor roles in stroke pathophysiology. New powerful platelet inhibitory drugs are currently introduced. To avoid major bleeding studies on platelet, behavior in acute stroke are necessary before including these medications in stroke treatment protocols.     

P-selectin in arterial thrombosis

P-selectin is a transmembrane protein present in the alpha granules of platelets and the Weibel-Palade bodies of endothelial cells. Following activation, it is rapidly translocated to the cell surface. P-selectin expression in platelets has been shown to be elevated in disorders associated with arterial thrombosis such as coronary artery disease, acute myocardial infarction, stroke, and peripheral artery disease. P-selectin mediates rolling of platelets and leukocytes on activated endothelial cells as well as interactions of platelets with leukocytes. Platelet P-selectin interacts with P-selectin glycoprotein ligand-1 (PSGL-1) on leukocytes to form platelet-leukocyte aggregates. Furthermore, this interaction of P-selectin with PSGL-1 induces the upregulation of tissue factor, several cytokines in leukocytes and the production of procoagulant microparticles, thereby contributing to a prothrombotic state. P-selectin is also involved in platelet-platelet interactions, i. e. platelet aggregation which is a major factor in arterial thrombosis. P-selectin interacts with platelet sulfatides, thereby stabilizing initial platelet aggregates formed by GPIIb/IIIa-fibrinogen bridges. Inhibtion of the P-selectin-sulfatide interaction leads to a reversal of platelet aggregation. Thus, P-selectin plays a significant role in platelet aggregation and platelet- leukocyte interactions, both important mechanisms in the development of arterial thrombosis.     

St. John’s Wort in Patients Non-responders to Clopidogrel Undergoing Percutaneous Coronary Intervention: a Single-Center Randomized Open-Label Trial (St. John’s Trial)

We assessed if St. John’s Wort (SJW) improves platelet response in patients (pts) resistant to clopidogrel after percutaneous coronary intervention (PCI). Stable angina pts non-responders to 600 mg clopidogrel (P2Y12 reaction units (PRU) >240) were randomized (2:1) to SJW (n?=?15) or placebo (n?=?8). SJW (300 mg × 3/day) was administrated for 2 weeks after PCI. Platelet reactivity was assessed by VerifyNowTM before (BL), 2 (T1), and 4 weeks (T2) after PCI. PRU significantly changed during protocol in SJW (BL (316?±?60) vs. T1 (170?±?87) vs. T2 (220?±?96), p?<?0.0001) and placebo group (BL (288?±?36) vs. T1 (236?±?31) vs. T2 (236?±?62), p?=?0.046). Yet, PRU changes from BL were higher at T1 in SJW than in placebo group (Δ%, ?47?±?24 vs. ?16?±?15, p?=?0.0033), with no differences at T2 between the groups (Δ%, ?30?±?29 vs. ?17?±?24, p?=?0.30). Residual platelet reactivity improved with SJW during the first month post-PCI.     

Downregulation of platelet activation markers during long-term immobilization

Immobilization and sedentary lifestyle are risk factors for venous thromboembolism and cardiovascular disease, yet little is known about platelet function during long-term physical inactivity. Our aim was to investigate platelet activation markers and their coupling to standardized immobilization: platelet-derived growth factor (PDGF-BB) and P-selectin. We studied 15 healthy females participating in the Women International Space simulation for Exploration study. Following a 20-day ambulatory control period, the subjects underwent 60 days of bed rest in head-down tilt position (?6°) 24 hours a day, finalized by 20 days of recovery. The subjects were randomized into two groups during bed rest: a control group (n?=?8) that remained physically inactive and an exercise group (n?=?7) that participated in both supine resistance and aerobic exercise training. Blood samples for the analysis of platelet activation markers were collected at baseline (5 days before bed rest), after 44 days of bed rest and 8 days into the recovery period. Compared to baseline, the levels of P-selectin and PDGF-BB decreased after bed rest (by 55%, p?=?0.01 and 73%, p?<?0.03, respectively) and remained decreased in the recovery period (by 76%, p?<?0.001 and 78%, p?<?0.02, respectively, compared to baseline). Platelet count (baseline value for the exercise group 260?000/µl?±?34?000 and baseline value for the control group 210?000/µl?±?30?000) did not change during the bed rest study (two-way repeated measurements ANOVA, p?=?ns). There were no statistical differences between the physically inactive and the exercise group. During long-term immobilization, a known risk factor for thrombosis, the levels of P-selectin and PDGF-BB decreased. Our findings indicate downregulation of platelet activation during immobilization.     

Nephropathy in Type 1 diabetes is associated with increased circulating activated platelets and platelet hyperreactivity

Patients with diabetes mellitus (DM) have increased platelet activation compared to non-diabetic controls. Platelet hyperreactivity has been associated with adverse cardiovascular outcomes in Type 2 DM, and with diabetic nephropathy. We investigated the relationship between platelet activation and nephropathy in Type 1 DM. Patients with Type 1 DM and diabetic nephropathy (n = 35), age- and sex-matched Type 1 DM patients with persistent normoalbuminuria (n = 51), and healthy age- and sex-matched controls (n = 30) were studied. Platelet surface P-selectin, platelet surface activated GPIIb/IIIa, monocyte-platelet aggregates (MPAs) and neutrophil-platelet aggregates (NPAs) were measured by whole blood flow cytometry as markers of platelet activation. Platelet reactivity was assessed in response to exogenously added ADP and thrombin receptor activating peptide (TRAP). Platelet surface P-selectin (basal and in response to 0.5 or 20 µM ADP) was higher in nephropathy patients compared with normoalbuminuric patients (P = 0.027), and non-diabetic controls (P = 0.0057). NPAs were higher in nephropathy patients compared to normoalbuminuric patients (P = 0.0088). MPAs were higher in nephropathy patients compared to non-diabetic controls (P = 0.0075). There were no differences between groups in activated GPIIb/IIIa or in response to TRAP at any end-point. More patients with nephropathy received aspirin (71.4%) compared to normoalbuminuric patients (27.4%) (P < 0.0001). Type 1 diabetic nephropathy, as compared with normoalbuminuria, is associated with circulating activated platelets and platelet hyperreactivity to ADP, despite the confounding variable of more nephropathy patients receiving aspirin. This platelet activation is likely to contribute to the known increased risk of cardiovascular events in patients with diabetic nephropathy.     

Long-term renal outcome in patients with malignant hypertension: a retrospective cohort study

Background

In patients with chronic kidney disease studies focusing on platelet function and properties often are non-conclusive whereas only few studies use functional platelet tests. In this study we evaluated a recently developed functional flow cytometry based assay for the analysis of platelet function in chronic kidney disease.

Methods

Platelet reactivity was measured using flow cytometric analysis. Platelets in whole blood were triggered with different concentrations of agonists (TRAP, ADP, CRP). Platelet activation was quantified with staining for P-selectin, measuring the mean fluorescence intensity. Area under the curve and the concentration of half-maximal response were determined.

Results

We studied 23 patients with chronic kidney disease (9 patients with cardiorenal failure and 14 patients with end stage renal disease) and 19 healthy controls. Expression of P-selectin on the platelet surface measured as mean fluorescence intensity was significantly less in chronic kidney disease patients compared to controls after maximal stimulation with TRAP (9.7 (7.9-10.8) vs. 11.4 (9.2-12.2), P?=?0.032), ADP (1.6 (1.2-2.1) vs. 2.6 (1.9-3.5), P?=?0.002) and CRP (9.2 (8.5-10.8) vs. 11.5 (9.5-12.9), P?=?0.004). Also the area under the curve was significantly different. There was no significant difference in half-maximal response between both groups.

Conclusion

In this study we found that patients with chronic kidney disease show reduced platelet reactivity in response of ADP, TRAP and CRP compared to controls. These results contribute to our understanding of the aberrant platelet function observed in patients with chronic kidney disease and emphasize the significance of using functional whole blood platelet activation assays.     

Increased Platelet Binding to Circulating Monocytes in Idiopathic Pulmonary Fibrosis

Purpose

Idiopathic pulmonary fibrosis (IPF) is the most common idiopathic interstitial pneumonia and its prognosis is poor. Epidemiological evidence suggests an association of IPF with vascular disease and thrombotic tendency, which may be related to platelet activation.

Methods

Platelet–monocyte adhesion in peripheral blood was examined by flow cytometry in patients with IPF (n = 19), interstitial lung disease (ILD) other than IPF (n = 9), and control subjects without pulmonary fibrosis (n = 14). Expression of platelet activation markers P-selectin (CD62P), PSGL-1 (CD162), and CD40 ligand (CD40L) on leukocytes and platelets were studied. Plasma concentrations of soluble P-selectin and CD40L were measured by ELISA.

Results

Significantly elevated levels of platelet–monocyte binding were found in patients with IPF (35.6 ± 4.34 % [mean ± SEM]) compared with patients with non-IPF ILD (23.5 ± 3.68 %) and non-ILD control subjects (16.5 ± 2.26 %; P < 0.01). There was a trend towards increased divalent cation-independent platelet–monocyte binding in IPF (6.0 ± 0.77 % [mean ± SEM]) compared with non-IPF ILD (4.3 ± 1.38 %) and control subjects without ILD (3.1 ± 1.75 %; P = 0.058). There was no differential surface expression of platelet activation markers on subsets of leukocytes or platelets. Plasma concentrations of CD40L and soluble P-selectin did not differ between IPF and control subjects. Platelet–monocyte binding had no significant correlation with percent predicted TLco or FVC.

Conclusions

Platelet–monocyte binding is increased in IPF, suggesting increased platelet activation. This conjugation is predominantly calcium-dependent, but there may be more calcium-independent adhesion in IPF. These findings support further research into the role of platelet activation in IPF.     

Comparison between a new platelet count drop method PL-11, light transmission aggregometry,VerifyNow aspirin system and thromboelastography for monitoring short-term aspirin effects in healthy individuals

Platelet function has been described by many laboratory assays, and PL-11 is a new point-of-care platelet function analyzer based on platelet count drop method, which counts platelet before and after the addition of agonists in the citrated whole blood samples. The present study sought to compare PL-11 with other three major more established assays, light transmission aggregometry (LTA), VerifyNow? aspirin system and thromboelastography (TEG), for monitoring the short-term aspirin responses in healthy individuals. Ten healthy young men took 100?mg/d aspirin for 3-day treatment. Platelet function was measured via PL-11, LTA, VerifyNow and TEG, respectively. The blood samples were collected at baseline, 2 hour, 1 day during the aspirin treatment and 1 day, 5?±?1 days, 8?±?1 days after the aspirin withdrawal. Moreover, 90 additional healthy subjects were recruited to establish a reference range for PL-11. Platelet function of healthy subjects decreased significantly 2 hours after 100?mg/d aspirin intake and began to recover during 4–6 days after the aspirin withdrawal. Correlations between methods were PL-11 vs. LTA (r?=?0.614, p?<?0.01); PL-11 vs. VerifyNow (r?=?0.829, p?<?0.01); PL-11 vs. TEG (r?=?0.697, p?<?0.001). There was no significant bias between PL-11 and LTA at baseline (bias?=?1.94%, p?=?0.804) using Bland-Altman analysis, while the data of PL-11 were significantly higher than LTA (bias?=?24.02%, p?<?0.001) during the aspirin therapy. The reference range for PL-11 in healthy young individuals was from 66.8 to 90.5% (95%CI). When aspirin low-responsiveness was defined as LTA?>?20%, the cut-off values for each method were, respectively: PL-11?>?50%, VerifyNow?>?533 ARU, TEG?>?60.2%. The results of different platelet function assays were uninterchangeable for monitoring aspirin response and correlations among them were also varied. Correlations among PL-11 and other three major assays suggested the ability of PL-11 to assess the treatment effects of aspirin. But a large cohort study is needed to confirm the cut-off value of aspirin response detected by PL-11.     

The effect of menstrual cycle on platelet aggregation in reproductive-age women

Our aim was to assess the change in platelet activity along the menstrual cycle. We conducted a prospective observational study. The study group included 16 healthy women with regular menstrual cycles, which were compared to a control group of 14 healthy males. Exclusion criteria were age <18 years or >45 years, use of oral contraceptives or any other forms of hormonal therapy and medical disorders or medications that might affect platelet aggregation. Blood samples were taken from each of the women at four different phases of the menstrual cycle: day 1 ± 1, day 7 ± 1, day 14 ± 1, and day 21 ± 1. A single blood sample was taken from the males. Platelet aggregation was assessed in whole blood samples using the Multiplate? analyzer with three different agonists (ADP, arachidonic acid (AA), and thrombin-receptor activating peptide (TRAP)). Platelet aggregation for each of the women at each of the phases of the menstrual cycle was expressed as the percentage change from the day 1 ± 1 value. A total of 390 aggregation assays were performed. The mean aggregation activity was significantly higher in females compared with males, irrespective of the agonist used. For the TRAP and the ADP agonists, the relative platelet activity decreased along the menstrual cycle from day 1 towards day 21 and from day 7 towards day 21, respectively, although differences reached statistical significance only for day 21 (?12.4% ± 3.2%, P < 0.05 for TRAP, and ?9.5% ± 3.9%, P < 0.05 for ADP). When using AA to induce platelet aggregation, the relative platelet activity was highest around the time of ovulation (11.0% ± 4.7%) and was significantly lower on day 21 (?8.5% ± 6.7%, P < 0.05). In conclusion, platelet aggregation activity is higher in females compared with males. The association between the phase of the menstrual cycle and platelet activity appears to vary with the type of agonist, but platelet aggregation is consistently lowest in the mid-luteal phase irrespective of the agonist used.     

The predictive value of mean platelet volume,plateletcrit and red cell distribution width in the differentiation of autoimmune gastritis patients with and without type I gastric carcinoid tumors

Abstract

Autoimmune gastritis is an autoimmune and inflammatory condition that may predispose to gastric carcinoid tumors or adenocarcinomas. The early diagnosis of these tumors is important in order to decrease morbidity and mortality. Platelet indices such as mean platelet volume and plateletcrit levels increase in inflammatory, infectious and malign conditions. The primary aim of this study was to explore wheter platelet indices and red cell distribution width have any predictive role in the discrimination of autoimmune gastritis patients with and without gastric carcinoid tumors. Also secondary aim of this study was to investigate whether any changes exist betwenn autoimmune gastritis and functional dyspepsia patients by means of platelet indices. Plateletcrit (0.22?±?0.06 vs. 0.20?±?0.03%, p?<?0.001) and red cell distribution width (16.11?±?3.04 vs. 13.41?±?0.95%, p?<?0.001) were significantly higher in autoimmune gastritis patients compared to control group. Receiver operating curve analysis suggested that optimum plateletcrit cut-off point was 0.20% (AUC: 0.646), and 13.95% as the cut off value for red cell distribution width (AUC: 0.860). Although plateletcrit (0.22?±?0.06 vs. 0.21?±?0.04%, p?=?0.220) and mean platelet volume (8.94?±?1.44 vs. 8.68?±?0.89?fl, p?=?0.265) were higher in autoimmune gastritis patients without carcinoid tumor compared to patients with carcinoid tumors, these parameters were not statistically significant. Changes in plateletcrit and red cell distribution width values may be used as a marker in the discrimination of autoimmune gastritis and fucntional dyspepsia patients but not useful in patients with gastric carcinoid tumor type I.     

Association of plasma miR-223 and platelet reactivity in patients with coronary artery disease on dual antiplatelet therapy: A preliminary report

Decreased plasma levels of microRNA-223 (miR-223), predominantly of platelet origin, were proposed as a surrogate marker of efficacy of antiplatelet therapy. However, higher on-treatment platelet reactivity was associated with lower plasma miR-223 in patients with coronary artery disease (CAD) on dual antiplatelet therapy (DAPT) including clopidogrel and aspirin. Our aim was to compare plasma miR-223 and platelet reactivity in CAD patients on DAPT with newer P2Y₁₂ antagonists vs. clopidogrel. We studied 21 men with CAD admitted to our centre owing to a non-ST-elevation acute coronary syndrome, and with an uncomplicated hospital course. From the day of admission, the patients were receiving either clopidogrel (n?=?11) or prasugrel/ticagrelor (n?=?10) in addition to aspirin. Before discharge, miR-223 expression in plasma was estimated by quantitative polymerase chain reaction using the comparative Ct method relative to miR-16 as an endogenous control. Multiple electrode aggregometry was used to assess platelet aggregation in response to adenosine diphosphate (ADP). ADP-induced platelet reactivity was decreased in the patients treated with prasugrel or ticagrelor compared with those on clopidogrel (mean?±?SD: 139?±?71 vs. 313?±?162 arbitrary units [AU]*min, p?=?0.006), due to a more potent antiplatelet activity of the novel P2Y₁₂ antagonists. Consequently, six out of seven patients in the lower tertile of the ADP-induced platelet aggregation were treated with the newer P2Y₁₂ blockers, whereas six out of seven patients in the upper tertile were on clopidogrel. Plasma miR-223 was elevated with decreasing platelet reactivity (Spearman’s rho?=?–0.52; p?=?0.015 for trend), being significantly higher in the lower tertile of the ADP-induced platelet aggregation (median [range]: 1.06 [0.25–2.31]) vs. the upper tertile (0.20 [0.13–2.30]) (p?=?0.04). In conclusion, our preliminary results argue against the notion of low plasma miR-223 as a marker of platelet responsiveness to DAPT. On the contrary, more potent platelet inhibition associated mainly with newer P2Y₁₂ antagonists appears to coincide with higher miR-223 relative to the subjects with attenuated responsiveness to DAPT.     

The effect of weight loss on the mean platelet volume in obese patients

Obesity is a chronic metabolic disorder associated with cardiovascular disease and atherosclerosis. Platelet activation and aggregation are central processes in the pathophysiology of cardiovascular disease. Mean platelet volume (MPV), a determinant of platelet activation, is a newly emerging risk marker for atherothrombosis. Our objective was to evaluate the effect of weight loss on the MPV in obese patients. We selected 30 obese women patients and 30 non-obese healthy women subjects. All obese patients took the same content and caloric diet treatment for 3 months. Body mass index (BMI), metabolic parameters and MPV were measured at baseline and after 3 months diet treatment. Before diet treatment, obese group had significantly higher MPV levels than in the non-obese control group (8.18?±?1.09 fl vs. 8.01?±?0.95 fl, p?=?0.004). MPV showed positive correlations with BMI level in the obese group (r?=?0.43, p?=?0.017). BMI significantly decreased after diet treatment (36.2?±?3.2?kg/m² vs. 34.7?±?3.6?kg/m², p?<?0.001), in the obese group. MPV significantly decreased after diet treatment in the obese group (8.18?±?1.09 fl vs. 8.08?±?1.02 fl, p?=?0.013). There was a positive correlation between weight loss and reduction in MPV (r?=?0.41, p?=?0.024). In addition to its well-known positive effects on cardiovascular disease risk, weight loss may also possess significant anti-platelet activation properties that can contribute its antiatherogenic effects in obese patients.     

Comparison of aspirin and indobufen in healthy volunteers

The aim of this study is to quantify the extent and recovery of platelet inhibition after administration of indobufen and aspirin in healthy volunteers. Indobufen inhibits platelet aggregation by reversibly inhibiting the platelet cyclooxygenase enzyme, thereby suppressing thromboxane synthesis. Twenty healthy volunteers completed the study and received aspirin (200?mg/day for 2 weeks) followed by a 4-week washout period and then indobufen (200?mg twice a day for 2 weeks). The percent (%) inhibition of platelet aggregation (IPA) was assessed using arachidonic acid (0.5?mg/ml) and adenosine diphosphate (5?µM) at 4, 12, 24 and 48 hours after last dose of each drug. IPA assessed using arachidonic acid as the agonist was similar at 4 hours after the last dose of indobufen (81.07?±?9.36%) and aspirin (96.99?±?0.29%, p?=?0.10), but significantly lower at 12 hours (74.04?±?9.55% vs. 97.94?±?0.28%, p?=?0.02), 24 hours (33.39?±?11.13% vs. 97.48?±?0.32%, p?p?p?=?0.002). Indobufen (200?mg twice a day) caused equivalent initial inhibition of platelet aggregation to aspirin (200?mg daily), and the anti-aggregation effect diminished faster than after aspirin.     

Impaired responsiveness to clopidogrel and aspirin in patients with recurrent stent thrombosis following percutaneous intervention for peripheral artery disease

Patients with peripheral artery disease (PAD) following peripheral percutaneous transluminal angioplasty (PTA) with stent implantation are prone to stent thrombosis despite treatment with aspirin and clopidogrel. Impaired clopidogrel responsiveness is associated with increased risk of ischemic events in patients following coronary stent implantation. We sought to assess platelet responsiveness to clopidogrel and aspirin in patients with PAD and recurrent stent thrombosis. Platelet aggregation induced by 5 and 20?µmol/l adenosine diphosphate (ADP) and 0.5?mmol/l arachidonic acid (AA), together with platelet reactivity index (PRI) and serum thromboxane B₂ (TXB₂), were determined in 11 patients with PAD and a history of stent thrombosis (mean, 3.1?±?1.14) after PTA and in 15 patients with PAD with no such history, also in 11 controls with coronary artery disease (CAD) and previous stent thrombosis. Platelet aggregation to 5?µmol/l ADP was higher in subjects with PAD and stent thrombosis than in those without stent thrombosis (p?=?0.0003) and CAD subjects (p?=?0.002). Aggregation induced by 20?µmol/l ADP was higher in PAD group with stent thrombosis than in PAD subjects without thrombosis (p?=?0.004). The PAD group with stent thrombosis had higher AA-induced platelet aggregation than CAD controls (p?=?0.007) and serum TXB₂ concentrations higher than PAD group without thrombosis (p?=?0.002) and CAD group (p?=?0.02). Concluding, platelet responsiveness to clopidogrel and aspirin is impaired in patients with PAD and recurrent stent thrombosis following PTA, as compared with similar individuals with CAD, and PAD with no history of stent thrombosis. This indicates that atherosclerosis burden affects platelet function and might contribute to stent thrombosis following percutaneous intervention in peripheral arteries.