Platelet aggregation is dependent on platelet count in patients with coronary artery disease

Introduction

Platelet function testing in whole blood is widely used to evaluate the effect of antiplatelet agents, but it is not known whether results are affected by whole blood parameters. This study investigated the importance of platelet count, haematocrit, red blood cells (RBC), and white blood cells in whole blood platelet aggregometry.

Materials and methods

We included 417 patients with coronary artery disease on aspirin mono-therapy and 21 aspirin-naïve healthy individuals. Blood sampling was performed one hour after aspirin ingestion. The antiplatelet effect of aspirin was evaluated using the VerifyNow® Aspirin assay and multiple electrode aggregometry (MEA, Multiplate®) induced by collagen (1.0 μg/mL) and arachidonic acid (1.0 or 0.75 mmol/L). Measurements of whole blood parameters were performed to evaluate the three major cell lines in circulating blood.

Results

In patients, platelet count correlated significantly with platelet aggregation (MEA_collagen, p < 0.0001; MEA_{arachidonic acid}, p < 0.0001; VerifyNow®, p = 0.03). Haematocrit and RBC correlated inversely with MEA induced by collagen (p_haematocrit < 0.001; p_RBC = 0.07) and with VerifyNow® (p_haematocrit < 0.0001; p_RBC < 0.0001), but not with MEA induced by arachidonic acid (p_haematocrit = 1; p_RBC = 0.87). White blood cells correlated significantly with platelet aggregation (MEA_collagen, p < 0.001; MEA_{arachidonic acid}, p < 0.0001; VerifyNow®, p = 0.05). Similar associations were observed in aspirin-naïve healthy individuals.

Conclusions

Whole blood aggregometry is dependent on all major cell lines in whole blood. Importantly, platelet aggregation is significantly associated with platelet count even within the normal range.     

Baseline platelet size is increased in patients with acute coronary syndromes developing early stent thrombosis and predicts future residual platelet reactivity. A case-control study

Introduction

Pre-procedural predictors of early stent thrombosis (ST) and future response to platelet inhibitors are in demand. We sought to evaluate the impact of baseline platelet indices on the occurrence of early ST and future residual platelet reactivity.

Materials and methods

Hundred and eight patients with acute coronary syndromes (ACS) in whom stents were implanted were included: 36 consecutive ST cases and 72 matched controls. Platelet indices assessed with flow cytometry before stent implantation were retrieved from the department's data base. Residual platelet reactivity specific to aspirin (aspirin reaction units-ARU) and clopidogrel (P2Y12 reaction units-PRU) was assessed prospectively with VerifyNow^® under dual antiplatelet treatment.

Results

Platelet size reported as mean platelet volume (MPV) or proportion of large platelets (LPLT) was significantly higher in ST cases compared with controls (10.4, 95% confidence intervals [CI], 10.1-10.8 vs. 9.7, CI, 9.5-9.9, P = 0.0004 and 35.8, CI, 34.2-37.3 vs. 33.3, CI, 32.2-34.3, P = 0.007, respectively). Dual aspirin and clopidogrel poor-responsiveness was diagnosed significantly more often in ST cases than in controls (19.6% vs. 1.4%, P = 0.004), whereas no difference was observed for single aspirin or clopidogrel poor-responsiveness. A strong correlation was found between MPV and both, ARU (r = 0.66, P < 0.0001) and PRU (r = 0.55, P < 0.0001). Similarly, higher LPLT was associated with higher ARU (r = 0.47, P < 0.0001) and PRU (r = 0.38, P = 0.0001).

Conclusions

Baseline platelet size is increased in patients with ACS developing early ST and correlates with future residual platelet reactivity under aspirin and clopidogrel therapy. Dual but not isolated aspirin or clopidogrel poor-responsiveness appears to be associated with early ST.     

The effect of clopidogrel besylate and clopidogrel hydrogensulfate on platelet aggregation in patients with coronary artery disease: a retrospective study

Background

Recently several alternative forms of the original clopidogrel hydrogensulfate (CHS) were spread worldwide. A large amount of such drugs turned out to be clopidogrel besylate (CB). Only three studies, involving healthy volunteers, investigated the antiplatelet effect of CB, whereas its attribute remained unexplored in the case of patients with cardiovascular diseases. This retrospective study aimed to evaluate the difference between the antiplatelet effects of two clopidogrel formulas, CHS and CB, on patients with coronary artery diseases.

Methods

Data of 150 patients with previous CHS treatment were investigated. According to the documentations, the CHS therapy was shifted to CB. 94 patients of the selected population received dual antiplatelet therapy, clopidogrel and aspirin. The antiplatelet effects of CHS and CB were compared by ADP induced platelet aggregation measurements using light transmission aggregometry.

Results

Irrespective of the therapeutic combinations the performed statistical investigations failed to show significant difference (p = 0.30) between the effect of CB (AGGmax_CB: 27.6 ± 13.7%) or CHS (AGGmax_CHS: 29.0 ± 15.3%) on the ADP induced platelet aggregation. Insignificant deviations were found in both forms of clopidogrel salts, either in the lack (AGGmax_CB : 32.5 ± 14,2%; AGGmax_CHS: 34,0 ± 16,1%; p = 0,29) or in the presence of aspirin (AGGmax_CB: 24.7 ± 12,5%; AGGmax_CHS: 26,0 ± 14,1%; p = 0,31).

Conclusion

Our results indicated that both CB and CHS had an identical inhibitory effect on ADP induced platelet aggregation in patients with cardiovascular diseases. Moreover their efficiency showed no overall significant difference in the case of dual antiplatelet therapy with aspirin as well. However there might be an inter- and intraindividual variability between the two clopidogrel formulas.     

Aspirin resistance following pediatric cardiac surgery

Introduction

Aspirin is often used to prevent thrombosis in pediatric cardiac surgery. The primary study aim was to assess aspirin resistance in this context. Secondary aims were to evaluate (1) the relationship between elevated inflammatory markers and thrombosis and (2) aspirin's effect on these levels.

Materials and Methods

This was a prospective observational study of children undergoing cardiac surgery managed with and without aspirin. Aspirin response was assessed using the VerifyNow™ system and urinary 11-dehydrothromboxane B₂ (uTxB₂) measurements. Laboratory studies of inflammation were also obtained.

Results

101 subjects were studied; 50 received aspirin. Six subjects (5.9%), 5 aspirin-treated, experienced symptomatic thrombosis. When measured by VerifyNow™ resistance was 43% after aspirin suppositories and 14% after additional days of oral aspirin. There was no correlation with thrombosis. Upper quartile post-operative day (POD) #5 uTxB₂ was correlated with thrombosis in aspirin treated subjects (p < 0.01). High risk aspirin-treated subjects who experienced thrombosis had higher POD#5 uTxB_2. This finding did not reach statistical significance (p = 0.07). Elevated pre-operative C-reactive protein (CRP) was independently associated with thrombosis (p < 0.02) in all subjects and in high risk subjects (p = 0.01). Inflammatory markers were not affected by aspirin.

Conclusions

Aspirin inhibited ex-vivo platelet function with a low incidence of resistance. Elevated POD#5 uTxB₂ and pre-operative CRP were correlated with thrombosis in aspirin treated subjects. Further studies are needed to determine whether children with high levels of uTxB₂ despite aspirin therapy and/or those with elevated preoperative CRP are at increased risk for thrombosis.     

Reduced platelet response to aspirin in patients with coronary artery disease and type 2 diabetes mellitus

Introduction

Diabetes mellitus is complicated by accelerated atherosclerosis, resulting in an increased risk of coronary artery disease (CAD) and thrombosis. Despite the proven benefits of aspirin, previous studies indicate a reduced cardiovascular protection from aspirin in diabetic patients. We aimed to investigate whether diabetes mellitus influenced the platelet response to aspirin in patients with CAD.

Materials and Methods

Platelet aggregation and activation were evaluated during aspirin treatment in 85 diabetic and 92 non-diabetic patients with CAD. Adherence to aspirin was carefully controlled. All patients had CAD verified by coronary angiography and were taking 75 mg non-enteric coated aspirin daily.

Results

Diabetic patients showed significantly higher levels of platelet aggregation compared to non-diabetic patients evaluated by VerifyNow^® Aspirin (p = 0.03) and Multiplate^® aggregometry using arachidonic acid (AA) 0.5 mM (p = 0.005) and 1.0 mM (p = 0.009). In addition, platelet activation determined by soluble P-selectin was significantly higher in diabetics compared to non-diabetics (p = 0.005). The higher AA-induced aggregation was associated with higher levels of HbA_1c. Compliance was confirmed by low levels of serum thromboxane B₂ (below 7.2 ng/mL). Diabetics had significantly higher levels of serum thromboxane B₂ (p < 0.0001).

Conclusions

Diabetic patients with CAD had significantly higher levels of both platelet aggregation and activation compared to non-diabetic patients with CAD despite treatment with the same dosage of aspirin. These findings may partly explain the reduced cardiovascular protection from aspirin in diabetic patients.     

P2Y12 platelet reactivity after thrombolytic therapy for ST-segment elevation myocardial infarction

Introduction

Thrombolysis, as reperfusion therapy for ST segment elevation myocardial infarction (STEMI), induces a pro-thrombotic status with enhanced platelet activity; this study aims to evaluate P2Y12 platelet reactivity and response to clopidogrel in the post-thrombolysis scenario.

Materials and Methods

Observational, prospective study, including consecutive patients with elective angiography after thrombolytic therapy for STEMI. Every patient received antiplatelet therapy with loading doses of 250 mg aspirin and 300 mg clopidogrel on admission followed by 100 mg aspirin and 75 mg clopidogrel daily. P2Y12-dependent platelet reactivity (expressed in P2Y12-Reaction Units, PRU) was assessed with VerifyNow® device on admission, daily after thrombolysis and pre-angiography.

Results

41 patients fulfilled the inclusion criteria. Median time between thrombolysis and angiography was 2,5 days (IQR 1,8-4,1). Post-treatment platelet reactivity (PPR) showed poor correlation with time on clopidogrel treatment (r2 = 0.04) and reached a maximum value of 274 ± 84 PRU during the first 24 h after thrombolysis (Day + 1 determination). After this, values showed a progressive reduction until the point of angiography (249 ± 82 PRU), without significant differences between consecutive time-points (p = 0,549).Inhibition of platelet aggregation (IPA) assessed as a percentage of P2Y12 receptor blockage was poor, increasing gradually from 0 ± 4% on admission to 11 ± 6% the day of the angiography (p = 0,001). 71,4% of patients showed PPR ≥ 208 PRU during angiography.

Conclusions

Platelet reactivity, as assessed by post-treatment P2Y12 mediated reactivity, is heightened after thrombolytic therapy during STEMI management. In this scenario, standard doses of clopidogrel did not achieve significant inhibition of ADP-mediated platelet reactivity.     

Markers of endothelial and platelet activation are associated with high on-aspirin platelet reactivity in patients with stable coronary artery disease

Introduction

Aspirin inhibits the cyclooxygenase-1 (COX-1) mediated thromboxane A2 synthesis. Despite COX-1 inhibition, in patients with coronary artery disease (CAD), platelets can be activated through other mechanisms, like activation by thrombin.

Materials and Methods

At baseline in this cross-sectional substudy of the ASCET trial, 1001 stable CAD patients, all on single aspirin treatment, were classified by the PFA100® method, as having high on-aspirin residual platelet reactivity (RPR) or not. Markers of hypercoagulability, endothelial and platelet activation as related to RPR, were evaluated to explore the potential mechanisms behind high on-aspirin RPR.

Results

Altogether, 25.9% (n = 259) of the patients were found to have high on-aspirin RPR. S-thromboxane B₂ levels were very low and did not differ between patients having high on-aspirin RPR or not. Patients with high on-aspirin RPR had significantly higher levels of von Willebrand Factor (vWF) (124 vs 100%, p < 0.001, platelet count (236 vs 224 × 10⁹/l, p = 0.008), total TFPI (68.4 vs 65.5 ng/ml, p = 0.005) and ß-thromboglobulin (ß-TG) (33.3 vs 31.3 IU/ml, p = 0.041) compared to patients with low on-aspirin RPR. No significant differences between the groups were observed in levels of endogenous thrombin generation (ETP), pro-thrombin fragment 1+2 (F1+2), D-dimer, soluble TF (sTF) or P-selectin (all p > 0.05).

Conclusions

The high on-aspirin RPR as defined by PFA100® seems not to be due to increased thrombin activity as evaluated with ETP, sTF, F1+2 or D-dimer. The elevated levels of platelet count, ß-TG, TFPI and especially vWF might be explained by increased endothelial and platelet activation in these patients.     

Aspirin response evaluated by the VerifyNow Aspirin System and light transmission aggregometry

Introduction

Patients with inadequate platelet inhibition by aspirin, referred to as aspirin resistance, might have an increased risk of suffering cardiovascular events. Therefore, identification of these patients by measuring platelet function is of great interest. Our objectives were to evaluate performance parameters of VerifyNow™ and to determine the agreement between VerifyNow™ and light transmission aggregometry (LTA) ad modum Born.

Materials and Methods

We included 21 healthy volunteers and 40 patients with stable coronary artery disease. Duplicate measurements of platelet aggregation were performed using VerifyNow™ and LTA (arachidonic acid 1.0 mM) in healthy volunteers before aspirin and in all participants on four consecutive days during treatment with non-enteric-coated aspirin 75 mg daily. VerifyNow™ test results were expressed in Aspirin Reaction Units (ARU) and LTA test results in percent of maximal aggregation. The cut-off for determination of aspirin resistance was ≥ 550 ARU and ≥ 20%, respectively.

Results

All participants were compliant, confirmed by complete suppression of serum-thromboxane B₂. VerifyNow™ was highly repeatable with a coefficient of variance of 0.5% at baseline and 3.0% during aspirin treatment. No individuals were identified as aspirin resistant with VerifyNow™, whereas seven (12%) individuals were identified with LTA. ROC analysis using LTA as the gold standard showed poor sensitivity and good specificity with a cut-off at 550 ARU.

Conclusion

VerifyNow™ was highly repeatable, but further studies are needed to investigate the relevance of the cut-off level at 550 ARU for detecting aspirin resistance.     

Evaluation of platelet function and pharmacological platelet inhibition in patients with myeloproliferative disorders using multiple electrode aggregometry

Background

The aim of this study was to describe platelet aggregation characteristics by multiple electrode aggregometry (MEA) and to evaluate MEA for its potential to detect platelet dysfunction and response to anti-aggregatory drugs in patients with myeloproliferative disorders (MPD).

Methods

We compared the platelet response to arachidonic acid (ASPI test), adenosine diphosphate (ADP test) and thrombin receptor activating peptide (TRAP test) in hirudin-anticoagulated blood of 55 patients with polycythaemia vera and essential thrombocythaemia and 75 controls.

Results

Comparing MPD patients and controls no statistically significant difference indicative of platelet dysfunction was found in MPD patients. Analysis of covariance revealed platelet- and leukocyte count as a significant influencing factor on MEA function. Furthermore we could demonstrate that ASA and clopidogrel treatment results in a statistically significant lower ASPI (Controls: p < 0.0001, MPD: p < 0.0001) and ADPtest value (MPD: p = 0.00125) compared to untreated patients thereby validating the method for monitoring of anti-aggregatory therapy.

Conclusion

In this study MEA was confirmed as a valid method for monitoring of ASA and clopidogrel treatment in patients with MPD and normal control subjects. The platelet and leukocyte count were identified as major influencing factors on MEA aggregation tests both in MPD patients and controls. No functional platelet abnormalities were detected in MPD patients.     

Role of serotonergic-related systems in suicidal behavior: Data from a case-control association study

Objective

To investigate whether functional polymorphisms directly (HTR2A and SLC6A4 genes) or indirectly (IL-1 gene complex, APOE and ACE genes) related with serotonergic neurotransmission were associated with suicidal behavior.

Subjects and methods

227 suicide attempters, 686 non-suicidal psychiatric patients, and 420 healthy controls from a homogeneous Spanish Caucasian population were genotyped using standard methods.

Results

There were no differences in genotype frequencies between the three groups. The −1438A/G [χ² (df) = 9.80 (2), uncorrected p = 0.007] and IL-1α −889C/T [χ² (df) = 8.76 (2), uncorrected p = 0.013] genotype frequencies between impulsive and planned suicide attempts trended toward being different (not significant after Bonferroni correction). Suicide attempts were more often impulsive in the presence of −1438G/G or IL-1α −889C/T or C/C genotypes. There was interaction between the polymorphism 5-HTTLPR and age [LRT (df) = 6.84 (2), p = 0.033] and between the polymorphisms APOE and IL-1RA (86 bp)_n [LRT (df) = 12.21 (4), p = 0.016] in relation to suicide attempt lethality.

Conclusion

These findings further evidence the complexity of the association between genetics and suicidal behavior, the need to study homogenous forms of the behavior and the relevance of impulsive and aggressive traits as endophenotypes for suicidal behavior.     

Multi-parameter assessment of platelet inhibition and its stability during aspirin and clopidogrel therapy

Introduction

Poor response to antiplatelet drugs is associated with adverse outcomes. We assessed platelet inhibition and its stability and tested correlation and agreement between platelet function assays.

Methods

Peripheral blood from 58 patients on both aspirin and clopidogrel who underwent percutaneous coronary intervention (PCI) was collected at hospital discharge (visit-1) and at 30-90 days (visit-2). Platelet function was measured using light transmission aggregometry (LTA-AA and LTA-ADP), VerifyNow® (Aspirin; ARU and P2Y12; PRU), ex vivo TxB₂, urinary 11dhTxB₂, and VASP (PRI) assays. Data were analyzed as continuous, quartiles and binary. Patients were defined as aspirin poor responder (PR) with ARU ≥ 550, LTA-AA maximum ≥ 20%, TxB₂ ≥ 1 ng/mL or 11dhTxB₂ ≥ 1,500 pg/mg of creatinine and as clopidogrel PR with PRU ≥ 240, PRU ≥ 208, LTA-ADP maximum ≥ 40%, PRI ≥ 50%, or PRI ≥ 66%.

Results

Aspirin PR was 3-33% and clopidogrel PR was 10-35% in visit-1. LTA-AA, 11dhTxB_2, and all clopidogrel-response measures showed correlation and agreement between visit-1 and visit-2. The highest agreement between two visits was revealed by PRU ≥ 240 and PRI ≥ 66% (PRU-κ = 0.7, 95% CI = 0.47, 0.93; PRI-κ = 0.69, 95% CI = 0.42, 0.95, p-values < 0.001). Comparison of platelet function assays in a single visit (visit-1) revealed a poor correlation between LTA-AA and 11dhTxB₂ assays and no agreement among aspirin-response assays. The highest correlation and agreement were obtained between VerifyNow® P2Y12 and VASP assays (rho = 0.7, p-value < 0.001 and PRU ≥ 208-PRI-κ = 0.41-0.42, 95% CI = 0.13, 0.69, p-values < 0.001).

Conclusions

Platelet inhibition is stable during aspirin and clopidogrel treatment. Clopidogrel-response assays correlate and agree with each other better than aspirin-response assays.     

Influence of cytochrome 2C19 allelic variants on on-treatment platelet reactivity evaluated by five different platelet function tests

Background

The antiplatelet effect of clopidogrel has been linked to cytochrome P450 2C19 (CYP2C19) carrier status. The presence of loss of function and gain of function variants were found to have a gene-dose effect on clopidogrel metabolism. However, genotyping is only one aspect of predicting response to clopidogrel and several platelet function tests are available to measure platelet response.Patients and methodsWe studied the influence of CYP2C19 allelic variants on on-treatment platelet reactivity as assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the VASP assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after stenting for cardiovascular disease. Allelic variants of CYP2C19 were determined with the Infiniti® CYP450 2C19 + assay and categorized into four metabolizer states (ultrarapid, extensive, intermediate, poor).

Results

Platelet reactivity increased linearly from ultrarapid to poor metabolizers using the VerifyNow P2Y12 assay (P = 0.04), the VASP assay (P = 0.02) and the Impact-R (P = 0.04). The proportion of patients with high on-treatment residual platelet reactivity (HRPR) identified by LTA, the VerifyNow P2Y12 assay and the VASP assay increased when the metabolizer status decreased, while no such relationship could be identified for results of MEA and Impact-R. The presence of loss of function variants (*2/*2, *2-8*/wt, *2/*17) was an independent predictor of HRPR in LTA and the VASP assay while it did not reach statistical significance in the VerifyNow P2Y12 assay, MEA, and the Impact-R.

Conclusion

Depending on the type of platelet function test differences in the association of on-treatment platelet reactivity with CYP2C19 carrier status are observed.     

Endogenous thrombin potential (ETP) in plasma from patients with AMI during antithrombotic treatment

Background

The beneficial impact of warfarin in preventing new events after AMI is well established. Decrease in thrombin generation seems to be the key element in anticoagulant treatment.

Objectives

The aims were to investigate the effect of warfarin and platelet inhibition on thrombin generation, assessed by the endogenous thrombin potential (ETP), and study the relation between coagulation parameters and ETP in patients with AMI.

Patients/Methods

In the present sub-study of the WARIS II trial, patients with AMI were randomly assigned to treatment with aspirin 160 mg/d (n = 57), aspirin 75 mg/d and warfarin (INR 2.0-2.5) (n = 68) or warfarin (INR 2.8-4.2) (n = 61). Fasting blood samples were collected from patients at discharge from hospital and after 6 weeks treatment.

Results

Correlation analyses showed that both ETP and peak thrombin levels were significantly correlated with Factor VII Ag (r = 0.38 and 0.36 respectively, p < 0.01 for both) and with F1+2 (r = 0.26 and 0.23 respectively, p = 0.01 for both) at baseline. Antithrombotic treatment for 6 weeks caused a highly significant inhibition of ETP in patients treated with warfarin (− 28% ± 5%, p < 0.001), and patients treated with aspirin/warfarin (− 24% ± 8%, p = 0.04). Similarly, peak thrombin levels were reduced in patients treated with warfarin (− 18% ± 7%, p = 0.049) and aspirin/warfarin (− 19% ± 5%, p = 0.029), whereas an increase (12% ± 4%, p = 0.029) occurred during aspirin treatment alone. F1+2 levels decreased by 64% and 58% in the warfarin and aspirin/warfarin groups, respectively (p = 0.001 for both).

Conclusions

In patients with AMI, warfarin significantly reduced the endogenous thrombin generation and the potential to generate thrombin in plasma ex vivo, whereas aspirin alone had no effect on thrombin generation in vivo or ex vivo, assessed by ETP.     

Adjunctive treatment of bimodal repetitive transcranial magnetic stimulation (rTMS) in pharmacologically non-responsive patients with schizophrenia: a preliminary study

Objectives

We evaluated the efficacy of bimodal repetitive transcranial magnetic stimulation (rTMS) in treating pharmacologically non-responsive patients with schizophrenia.

Methods

Ten patients with DSM-IV schizophrenia, unresponsive to pharmacological treatment, underwent treatment with 15 rTMS sessions, as an adjunctive therapy, for three weeks. Each session comprised 40 trains, beginning every 30 s: 20 trains of 10 Hz rTMS to the left dorsolateral prefrontal cortex (DLPFC) with a 3-s duration and 20 trains of 1 Hz rTMS to the left temporoparietal cortex (TPC) with a 30-s duration. We assessed patients via the Positive and Negative Syndrome Scale (PANSS) and Korean Version of the Calgary Depression Scale for Schizophrenia (K-CDSS), at five time points: baseline, Days 8, 15, and 22, and 1 week after final treatment (Day 29). Patients who agreed to take neurocognitive tests underwent neurocognitive function evaluations at baseline and 1 week after final treatment.

Results

At Day 29, all PANSS subscale scores in had decreased significantly compared to baseline (Z = − 2.214, p = 0.027, positive; Z = − 2.132, p = 0.033, negative; Z = − 2.023, p = 0.043, general pathology; Z = − 2.371, p = 0.018, total). Effect over time was significant for the PANSS positive and negative subscale scores and total score (χ² = 13.35, p = 0.010; χ² = 10.27, p = 0.036; and χ² = 16.50, p = 0.002, respectively) but not for the general pathology subscale. Among the neurocognitive tests, the fourth and fifth trials and total K-AVLT scores showed significant increases (Z = − 2.041, p = 0.041; Z = − 2.251, p = 0.024; and Z = − 2.201, p = 0.028, respectively), suggesting improvement in short-term auditory verbal memory.

Conclusions

Bimodal rTMS stimulation of left DLPFC and left TPC induced clinical improvement in pharmacologically non-responsive schizophrenia patients and may have improved their short-term verbal memories.     

Exploring soluble urokinase plasminogen activator receptor and its relationship with arterial stiffness in a bi-ethnic population: the SAfrEIC-study

Introduction

Elevated soluble urokinase-type plasminogen activator receptor (suPAR) indicates an inflammatory state caused by conditions such as HIV and cancer. Recently suPAR was identified as an indicator of cardiovascular disease (CVD). CVD is highly prevalent in black South Africans, but the potential role of suPAR is unknown. We investigated suPAR as a possible marker of arterial stiffness in Africans and Caucasians.

Methods

This study involved 207 Africans and 314 Caucasians (aged 20-70 yrs). C-reactive protein (CRP) and suPAR were determined in fasting blood samples. We measured blood pressure, pulse wave velocity (PWV) and Windkessel arterial compliance (Cwk).

Results

Africans displayed higher suPAR, CRP, PWV and lower Cwk (p < 0.001) compared to Caucasians. SuPAR was elevated in Africans irrespective of gender and smoking. We found strong relationships between PWV and suPAR (r = 0.27; p < 0.001) and Cwk and suPAR (r = − 0.39; p < 0.001) in the whole group, but found no independent relationship of any arterial stiffness measure and suPAR in Africans after adjustment for confounders. Caucasian men indicated a weak significant independent association between Cwk and suPAR (β = − 0.09; p = 0.028).

Conclusion

Africans had higher levels of suPAR and arterial stiffness than Caucasians (p < 0.001), but there was no independent relationship between arterial stiffness and suPAR in the Africans. It is speculated that due to the inflammatory role of suPAR, it will have stronger relationships with atherosclerosis, which has not yet manifested in this relatively young population group. SuPAR may therefore not be an ideal early marker of cardiovascular dysfunction, but may rather indicate established CVD.     

Genome-wide association study of blood pressure response to methylphenidate treatment of attention-deficit/hyperactivity disorder

Objective

We conducted a genome-wide association study of blood pressure in an open-label study of the methylphenidate transdermal system (MTS) for the treatment of attention-deficit/hyperactivity disorder (ADHD).

Method

Genotyping was conducted with the Affymetrix Genome-Wide Human SNP Array 6.0. Multivariate association analyses were conducted using the software package PLINK. After data cleaning and quality control we tested 316,934 SNPs in 140 children with ADHD.

Results

We observed no genome-wide statistically significant findings, but a SNP in a K⁺-dependent Na⁺/Ca²⁺ exchanger expressed in vascular smooth muscle (SLC24A3) was included in our top associations at p < 1E-04. Genetic enrichment analyses of genes with ≥ 1 SNP significant at p < 0.01, implicated several functional categories (FERM domain, p = 5.0E-07; immunoglobulin domain, p = 8.1E-06; the transmembrane region, p = 4.4E-05; channel activity, p = 2.0E-04; and type-III fibronectins, p = 2.7E-05) harboring genes previously associated with related cardiovascular phenotypes.

Conclusions

The hypothesis generating results from this study suggests that polymorphisms in several genes consistently associated with cardiovascular diseases may impact changes in blood pressure observed with methylphenidate pharmacotherapy in children with ADHD.     

Platelet protease-activated receptor 1 and membrane expression of P-selectin in pulmonary arterial hypertension

Introduction

Pulmonary arterial hypertension (PAH) is frequently associated with thrombotic events, particularly involving the pulmonary microcirculation at sites of vascular injury. We therefore decided to analyse protease-activated receptor 1 (PAR1), a key element in the activation of human platelets by thrombin, in PAH patients in stable clinical condition.

Methods

Using flow cytometry, we analyzed platelet PAR1 density, PAR1-mediated exposure of P-selectin and the formation of platelet-leukocyte aggregates in 30 PAH patients aged 11 to 78 years (median 50.5 years). The control group consisted of 25 healthy subjects with the same age range as patients.

Results

In patients, total platelet PAR1 density and uncleaved PAR1 density correlated negatively with platelet count (r² = 0.33 and r² = 0.34 respectively, p < 0.0015). In patients with a low platelet count (< 150 × 10⁹ platelets/L), both densities were increased relative to controls (82% and 33% respectively, p < 0.05). Thrombin peptide-induced platelet exposure of P-selectin was directly related to total and uncleaved PAR1 density (respectively, r² = 0.33 and r² = 0.29, p < 0.0025) and increased in subjects with low platelet count (46% versus those with normal platelet count, p < 0.05). Patients with low platelet count had decreased in vitro thrombin-induced formation of platelet-leukocyte aggregates (57% decrease versus controls, p < 0.05).

Conclusions

There seems to be a subpopulation of PAH patients with increased propensity to thrombotic events as suggested by increased platelet PAR1 expression and PAR-mediated surface exposure of P-selectin associated with decreased platelet count.     

A case-control study provides evidence of association for a common SNP rs974819 in PDGFD to coronary heart disease and suggests a sex-dependent effect

Introduction

Peden et al. have revealed a significant association between four new risk loci and coronary heart disease (CHD) in Europeans and South Asians. The goal of this study is to evaluate the contribution of these genetic loci to CHD risk in Han Chinese.

Methods

We recruited 161 CHD patients and 112 controls proved by angiography originated from Ningbo in the Eastern China, and performed a case-control association study of the four significant SNPs.

Results

Among the four tested SNPs, we found a significant association of rs974819 in PDGFD gene with CHD (allele p = 0.04; OR = 1.45, 95% CI = 1.02 - 2.08) and the allele A/G of rs974819 shows significant difference in females (allele p = 0.04; OR = 1.83, 95% CI = 1.01 - 3.31). A further meta-analysis showed that rs974819 of PDGFD gene was significantly associated with an increasing risk of CHD (OR = 1.08, 95% CI = 1.05 - 1.11) in both Europeans and South Asians including Han Chinese.

Conclusions

Our findings suggests that rs974819 of PDGFD is also a CHD risk factor in Han Chinese. In addition, it presents a sex-dependent genetic effect.     

Thrombocyte serotonin and serum cholesterol concentration in suicidal and non-suicidal depressed patients

Introduction

Numerous studies have confirmed the connection of reduced serum cholesterol and thrombocyte serotonin concentration with suicidal behavior in psychiatric patients. The purpose of such studies was to determine the link among cholesterol and serotonin concentration, comparing depressed patients with and without attempted suicide with phenotypically healthy control group.

Materials and methods

The examinees' groups consisted of 55 depressed patients with suicide attempt and 77 depressed patients with no suicide attempt. In accordance to ICD-10, the above patients were separated in two subgroups; F32.2 and F33.2. Phenotypically healthy control group was presented by the group of healthy blood donors. The fasting serum cholesterol concentration was established using standard enzymatic method, while the thrombocyte serotonin concentration was determined by the enzymatic immune-chemical method (ELISA).

Results

The ANOVA test (N = 228, F_ratio = 8.26, p < 0.001) found significant difference of cholesterol concentration between groups, with lowest concentration in depressed patients with attempted suicide (SNK post hoc test, p < 0.05). Upon gender stratification, the significance remained for the female patients (ANOVA, N = 125, F_ratio = 6.06, p = 0.003). The serum cholesterol was shown to be statistically lower in the group of depressed patients with attempted suicide, diagnoses F32.2 (p = 0.031) and F33.2 (p = 0.011), compared to the group of depressed patients without attempted suicides. The thrombocyte serotonin was found to be significantly different in all examined groups, with the lowest thrombocyte serotonin in the group of depressed patients with no suicide attempt (SNK post hoc test, p < 0.05, N = 187, F_ratio = 37.69, p < 0.001). The same significance was found for the group of female (ANOVA, N = 103, F_ratio = 11.81, p < 0.001) and the group of male patients (ANOVA, N = 84, F_ratio = 30.40, p < 0.001). The thrombocyte serotonin was significantly lower in the group of depressed patients with no suicide attempt (F32.2), compared to the same diagnosis in the group of depressed patients with suicide attempt (MW-test, p = 0.018).

Conclusion

In the group of depressed patients with attempted suicide, statistically significant lower serum cholesterol values have been confirmed. In the group of depressed patients with no suicide attempt, statistically significant lower values of thrombocyte serotonin have been confirmed, presumably as the response to the psychopharmacological therapy.     

Genetic determinants of response to aspirin: appraisal of 4 candidate genes

Introduction

Intersubject variability in platelet response to aspirin could be related to genetic factors that regulate platelet enzymes or receptors. This study evaluates the impact of the selected polymorphisms in the COX-1 gene, the CYP5A1 gene, the P2RY1 receptor gene, and the GPIIbIIIa receptor gene on platelet response to aspirin and risk of suffering from major adverse cardiovascular and cerebrovascular events (MACCE).

Materials and methods

192 Caucasian patients with stable coronary artery disease treated with daily aspirin were recruited and followed for 3 years. Platelet aggregation was measured by light transmission aggregometry with arachidonic acid (1.6 mM) and adenosine diphosphate (5, 10 or 20 μM) used as agonists. Genotyping was performed by standard PCR methods.

Results

Arachidonic acid-induced platelet aggregation was unaffected by the COX-1 22C/T and by the Pl^A1/A2 polymorphisms. However, carriers of the 1622 G/G genotype of the P2RY1 gene had significantly higher levels of arachidonic acid-induced platelet aggregation compared with non-carriers (AA 2.0%, AG 2.0% vs. GG 9.0%, p = 0.047). Carrying the 1622 G/G genotype increased the risk of inadequate platelet response to aspirin, defined as arachidonic acid-induced aggregation ≥ 20%, by a factor of 8.5 (1.4 - 53.3, p = 0.022) and the risk of 3-year MACCE by a factor of 7 (1.4 - 34.7, p = 0.017).

Conclusion

The 1622A/G mutation of the P2RY1 gene could contribute to inadequate platelet response to aspirin and is associated with an increased risk of suffering from MACCE.