Increased Platelet Reactivity Research Articles

G protein–coupled receptor kinase 5 regulates thrombin signaling in platelets

BackgroundOur prior genome-wide association study of thrombin-induced platelet aggregation identified a G protein–coupled receptor kinase 5 (GRK5) noncoding variant (rs10886430-G) that is strongly associated with increased platelet reactivity to thrombin. This variant predisposes to increased risk of stroke, pulmonary embolism, and venous thromboembolism. ObjectivesTo determine role of platelet specific GRK5 in platelet responses to agonists and injury. MethodsPlatelets from GRK5 mutant mice have been shown to have increased thrombin sensitivity, indicating that GRK5 may be a negative regulator of platelet activation. However, this has not been studied in a platelet-specific manner. We therefore used platelet-specific GRK5 mutant mice and models of thrombosis and pulmonary embolism. ResultsWe now demonstrate that mice lacking GRK5 specifically in platelets had a mild increase in thrombin responses in vitro and a shortened time to arterial thrombosis in vivo. In addition, platelet GRK5 mutant mice had increased thrombin but not collagen-induced thrombus burden in a mouse model of pulmonary embolism. ConclusionThese data indicate that platelet GRK5 has a significant role in limiting platelet responses to thrombin.

Marijuana may lead to increased platelet activity in trauma patients

IntroductionDelta-9-tetraydrocannabinol (THC) usage is associated with venous thromboembolic events (VTE) in trauma patients. We hypothesized that THC ​+ ​trauma patients would have less platelet inhibition than THC - patients using thromboelastography with platelet mapping (TEG-PM). MethodsResults from initial TEG- PM assays and patient's UDS were reviewed between 2019 and 2023. Mean levels of arachidonic acid (AA) and adenosine diphosphate (ADP) percent inhibition were compared by THC status. Results793 patients had TEG-PM and UDS data. Mean levels of arachidonic acid (AA) percentage inhibition were 32.6 ​± ​34.2. AA inhibition was lower for THC ​+ ​vs THC- patients (THC+ 23.9 ​± ​27.0 vs THC- 34.3 ​± ​35.3, P ​< ​0.001). There was no association between THC status and ADP inhibition (THC+ 32.5 ​± ​27.1 vs THC- 30.8 ​± ​28.4, P ​= ​0.536). DiscussionTo our knowledge, our data are the first to suggest a clinically measurable increase in platelet reactivity in THC ​+ ​trauma patients. More work is needed to determine if addition of aspirin to the chemoprophylaxis strategy for THC ​+ ​patients would mitigate the known association of THC with VTE.

Inflammation and platelet reactivity during adjunctive colchicine versus aspirin in patients with acute coronary syndrome treated with potent P2Y12 inhibitor.

In patients undergoing percutaneous coronary intervention (PCI), the use of anti-inflammatory therapy with colchicine is associated with a reduction of recurrent ischemic events. The mechanisms of such findings are not fully elucidated. To investigate the effects of colchicine versus aspirin on inflammation and platelet reactivity in patients with acute coronary syndrome (ACS) undergoing PCI. This observational study compared laboratory measurements in ACS patients receiving single antiplatelet therapy with ticagrelor or prasugrel plus colchicine (MACT) (n = 185) versus conventional dual-antiplatelet therapy (DAPT) with aspirin plus ticagrelor or prasugrel (n = 497). The primary outcome was the frequency of high residual inflammation, defined as high-sensitivity C-reactive protein (hs-CRP) ≥2 mg/L at 1 month post-PCI. Multiple sensitivity analyses were performed for the primary outcome, including multivariable adjustment, propensity-score matching, and inverse-probability weighted methods. One month after PCI, patients treated with MACT had significantly lower levels of hs-CRP compared to those treated with DAPT (0.6 [0.4-1.2] vs. 0.9 [0.6-2.3] mg/L, p < 0.001). The frequency of high residual inflammation was also lower in the MACT group (10.8% vs. 27.2%, p < 0.001) (odds ratio [95% confidence interval] = 0.33 [0.20-0.54], p < 0.001). This effect was consistent across sensitivity analyses. There was no difference in platelet reactivity between MACT and DAPT (49.6 ± 49.0 vs. 51.5 ± 66.4 P2Y12 reaction unit [PRU] measured by VerifyNow, p = 0.776). In ACS patients undergoing PCI, MACT was associated with a lower rate of high residual inflammation without increasing platelet reactivity compared to conventional DAPT. NCT04949516 for MACT pilot trial and NCT04650529 for Gyeongsang National University Hospital registry.

Correlation of Platelet Indices in Patients With Type 2 Diabetes Mellitus and Associated Microvascular Complications: A Hospital-Based, Prospective, Case-Control Study.

Background Diabetic patients exhibit increased platelet activity. Insulin inhibits the activation of platelets. Therefore, a relative or absolute deficiency of insulin would increase platelet reactivity. Theyounger (larger) platelets are also more metabolically and enzymatically active.If detected early, microvascular complications could alert us regarding the possible macrovascular complications.Thus, the aims and objectives of the present study were to determine platelet indices in patients with type 2 diabetes mellitus withcontrols (non-diabetics) and to find an association of platelet indices with microvascular complications. Material & methods In this prospective case-control study conducted from 2021 to 2022 (2 years), a total number of 200 subjects were taken and were divided into two groups of 100 each,cases (I) andcontrols (II). The cases included patients of diabetes mellitus (DM) ofa duration of more than 5 years, which were further divided into two groups of 50 each, IA and IB. Group IA consisted of patients with diabetes mellitus of a duration of more than five years with at least one microvascular complication and group IB wasdiabetics of more than five years duration without any microvascular complications, which includes diabetic retinopathy, diabetic nephropathy, and diabetic neuropathy. An automated cell counter (Thermo Fisher Scientific, Waltham, MA, US) provided hemoglobin values along with the platelet count and platelet indices, i.e. mean platelet volume (MPV), platelet large cell ratio (P-LCR), and platelet distribution width (PDW). Results The present study consisted of 200 subjects divided into 2 groups of 100 each, cases (I) andcontrols (II). The average MPV (9.4-12.3 femtolitre) in diabetics was 12.089±1.450 fLas compared to the controls where it was 9.464±1.424 fL with a statistically significant p-value of 0.001. PDWamong the cases was 16.868±2.352 fL while in controls, it was 12.753±10.559 fL (p=0.001). The mean P-LCR was 34.975±8.056% amongthe cases, in comparison to the mean P-LCR amongthe controls, which was 26.031±7.004 (p=0.001). In this study, the MPV, PDW, and P-LCR were significantly raised in individuals having diabetes with microvascular complications when compared with patients without complications. The mean MPV in diabetics with complications was 12.5960±0.95660 fL and in those without complications was 11.5820±1.67609 fL (with a p-value of P = 2×10-3)which is statistically significant. Similar results were obtained in cases of PDW and P-LCR. The mean PDW in diabetics with complications was 17.1140±2.58228 fL and without complications was 15.6220±2.10532 fL ((with a p-value of P = 2×10-3)). The mean P-LCR in diabetics with microvascular complications was 35.408±3.5490% and without complications was 33.542±4.8694% (with a p-value of P = 3.1×10-3). Conclusion Based on the findings of the present study, there is a statistical correlation between type 2 diabetes and variations in platelet indices, resulting in the associated microvascular complications. Higher MPV, PDW, and P-LCR values suggest that these parameters are more reliable predictors of early vascular complications in individuals with type 2 diabetes mellitus and can be utilized as an easy-to-use, low-cost method. They are a readily available, economical, practical, noninvasive, and simple-to-understand approach for assessing platelet dysfunction, which in turn helps anticipate the existence of microvascular complications.

Platelet Reactivity in the Exacerbation of Psoriasis.

Background: Psoriasis is a chronic, inflammatory, immune-mediated disease with a specific cutaneous presentation. Increased platelet aggregation has been observed in patients with extensive psoriatic lesions. The aim of this study was to evaluate the clinical factors affecting platelet reactivity in patients with an exacerbation of psoriasis. Methods: This was a prospective, single-center, observational study, enrolling patients hospitalized for an aggravation of psoriasis. Enrolled patients underwent single platelet function testing with light transmission aggregometry on the first morning of hospitalization. Results: 120 patients were enrolled in the study. Of the compared subgroups, women had higher maximal platelet aggregation (MPA) than men (77% vs. 72%; p = 0.03), and those with BMIs < 25 kg/m2 showed higher platelet reactivity compared to subjects with BMIs ≥ 25 kg/m2 (75% vs. 73%; p = 0.02). There was a positive correlation between MPA and platelet count (r = 0.27; p < 0.01), as well as C-reactive protein concentration (r = 0.20; p = 0.03), while a negative correlation was observed with total cholesterol (r = -0.24; p = 0.01) and triglycerides (r = -0.30; p < 0.01). A two-step analysis based on multidimensional models with random effects revealed that every increase in the platelet count by 103/μL led to an increase in MPA by 0.07% (R2 = 0.07; p < 0.01), and an increase in triglycerides' concentration by 1 mg/dL was related to a reduction in MPA by 0.05% (R2 = 0.07; p < 0.01). Conclusions: The increased platelet reactivity observed in patients with psoriasis appears to be multifactorial and related to several clinical and laboratory features. Further research is warranted to put these findings into a clinical perspective.

Elevated High-Sensitivity C-Reactive Protein Level Enhances the Impact of Lipoprotein(a) on Platelet Reactivity in PCI Patients Treated with Clopidogrel.

Recently, the effect of Lipoprotein(a) [Lp(a)] on thrombogenesis has aroused great interest, while inflammation has been reported to modify the Lp(a)-associated risks through an unidentified mechanism. This study aimed to evaluate the association between platelet reactivity with Lp(a) and high-sensitivity C-reactive protein (hs-CRP) levels in percutaneous intervention (PCI) patients treated with clopidogrel. Data were collected from 10,724 consecutive PCI patients throughout the year 2013 in Fuwai Hospital. High on-treatment platelet reactivity (HTPR) and low on-treatment platelet reactivity (LTPR) were defined as thrombelastography (TEG) maximum amplitude of adenosine diphosphate-induced platelet (MAADP) > 47 mm and < 31 mm, respectively. 6615 patients with TEG results were finally enrolled. The mean age was 58.24 ± 10.28 years and 5131 (77.6%) were male. Multivariable logistic regression showed that taking Lp(a) < 30 mg/dL and hs-CRP < 2 mg/L as the reference, isolated Lp(a) elevation [Lp(a) ≥ 30 mg/dL and hs-CRP < 2 mg/L] was not significantly associated with HTPR (P = 0.153) or LTPR (P = 0.312). However, the joint elevation of Lp(a) and hs-CRP [Lp(a) ≥ 30 mg/dL and hs-CRP ≥ 2 mg/L] exhibited enhanced association with both HTPR (OR:1.976, 95% CI 1.677-2.329) and LTPR (OR:0.533, 95% CI 0.454-0.627). The isolated elevation of Lp(a) level was not an independent indicator for platelet reactivity, yet the concomitant elevation of Lp(a) and hs-CRP levels was significantly associated with increased platelet reactivity. Whether intensified antiplatelet therapy or anti-inflammatory strategies could mitigate the risks in patients presenting combined Lp(a) and hs-CRP elevation requires future investigation.

Pharmacodynamic and pharmacokinetic profiles associated with switching from cangrelor to prasugrel in patients undergoing percutaneous coronary intervention: the SWAP-6 study

Abstract Background Cangrelor is an intravenous P2Y12 inhibitor used in patients undergoing coronary intervention (PCI). Preliminary studies have shown the potential for a drug-drug interaction (DDI) when transitioning from cangrelor to oral P2Y12 inhibition with prasugrel. However, to date this has not been prospectively tested in patients undergoing PCI. Purpose To rule out a DDI when cangrelor and prasugrel are concomitantly administered in patients undergoing PCI. Methods SWAP-6 is a prospective, randomized, 3-arm, open-label, pharmacokinetic (PK) and pharmacodynamic (PD) study conducted in patients undergoing PCI (n=77). Patients were randomized to either a) prasugrel only administered at the start of PCI; b) cangrelor plus prasugrel concomitantly administered at the start of PCI; c) cangrelor administered at the start of PCI plus prasugrel administered at the end of the cangrelor infusion. Cangrelor (30 μg/kg bolus followed by 4 μg/kg/min infusion) was maintained for 2 hours and all patients were on a background of aspirin therapy. Prasugrel was administered as a 60 mg loading dose. PK analysis included plasma levels of prasugrel active metabolite, and PD assessments included VerifyNow PRU, total thrombus-formation analysis system (T-TAS), and vasodilator-stimulated phosphoprotein (VASP), at baseline and 6 time points after prasugrel/cangrelor administration. The primary end point was non-inferiority in PRU measured at 4 hours after prasugrel/cangrelor loading (2 hours after stopping cangrelor infusion) of cangrelor plus prasugrel concomitantly administered versus prasugrel only. The noninferiority margin was defined as 45 PRU. Results Cangrelor achieved lower PRU levels than prasugrel only as early as 30 minutes and up to 2 hours after bolus administration (Figure). At 3 hours after prasugrel/cangrelor loading, PRU levels were higher with cangrelor compared to prasugrel only. At 4 hours after loading (2 hours after stopping cangrelor infusion), PRU levels were significantly lower with prasugrel only compared to cangrelor and prasugrel concomitantly administered (LSM difference 130; 95% CI: 85-176), failing to meet the prespecified noninferiority primary end point (Figure). At this time point, cangrelor followed by prasugrel at the end of the infusion had higher PRU than prasugrel only, but lower than cangrelor and prasugrel concomitantly. Platelet reactivity by T-TAS and VASP showed consistent findings. PK analysis tracked PD results (data not shown). Conclusions In patients undergoing PCI, cangrelor is associated with more potent platelet inhibition than prasugrel alone. However, concomitant administration of prasugrel with cangrelor leads to a marked increase in platelet reactivity after stopping cangrelor infusion, supporting the presence of a DDI. This underscores the importance of administering prasugrel not until the end of cangrelor infusion, a strategy which mitigates the increase in platelet reactivity.

Interplay among proton pump inhibitors, platelet reactivity and CYP2C19 genotyping in clopidogrel-treated patients after drug-eluting stent implantation

Abstract Background Several published data suggested that concomitant use of clopidogrel and proton pump inhibitors (PPIs) is associated with reduced antiplatelet efficacy of clopidogrel and increased adverse clinical outcomes. We sought to evaluate the interplay between PPI and clopidogrel on platelet reactivity and long-term clinical outcomes in patients after percutaneous coronary intervention (PCI) with drug-eluting stent (DES) implantation. Methods The PTRG-DES (Platelet function and genoType-Related long-term proGnosis in DES-treated patients) registry is a multi-center, real-world registry of patients who underwent PCI with DES and received dual antiplatelet therapy of aspirin and clopidogrel in South Korea. Patients prescribed with PPI were compared to those without the use of PPI (the control group). The primary outcome was a composite of all-cause death, myocardial infarction, stent thrombosis, and stroke at 5 years. Secondary outcomes included cardiac death, major bleeding, and gastrointestinal bleeding. Adjusted outcomes were compared after 1:2 propensity score (PS) matching analysis. Results Among 13,160 patients, 2235 (17.0%) were prescribed with concomitant PPI at the time of clopidogrel loading. Average age was 64.4 years, 67.2% were men, and 35.1% had diabetes. The PPI group demonstrated a higher on-treatment P2Y12 reaction unit than the control group (p&amp;lt;0.001). The 5-year cumulative incidence of the composite primary outcome was higher in the PPI group (12.1% vs. 9.8%, log-rank p&amp;lt;0.001). After PS matching, the primary outcome was similar between the two groups (12.9% vs. 12.1%, log-rank p=0.24). However, the PPI group with CYP2C19 poor metabolizers showed an increased adjusted risk of the primary outcome (hazard ratio 2.69, p&amp;lt;0.001). Conclusions PPI use in patients with clopidogrel administration after DES implantation was associated with increased platelet reactivity, but similar cardiovascular outcomes in real-world practice. Physicians should be careful when administering PPI with clopidogrel in patients with CYP2C19 poor metabolizers.Distribution of P2Y12 reaction unitCumulative Incidence of outcomes

Increased Responsiveness of Stored Platelets after Short-Term Refrigeration

Introduction: Refrigeration of platelets is considered to provide advantages in therapy of acute hemorrhage due to increased platelet responsiveness. The alleviation of inhibitory signaling caused by cold temperature (CT) has been identified as an important mechanism contributing to enhanced platelet reactivity, detectable in freshly prepared platelets within 1 h of cold storage. The aim of this study was to confirm the effects of short-term refrigeration in platelets from apheresis-derived platelet concentrates (APC). Methods: APC were stored under standardized conditions for 1 day or for 2 days at room temperature and then refrigerated for 1 h, followed by sampling of platelets for analysis. Platelet reactivity was measured by aggregation studies using threshold concentrations of different agonists and by detection of fibrinogen binding using flow cytometry. The exploration of inhibitory signaling comprised the detection of VASP phosphorylation using flow cytometry or Western blot and the measurement of cyclic nucleotide levels. Results: Aggregation responses induced with ADP, collagen, or thrombin receptor-activating peptide-6 (TRAP-6) were increased in APC after cold storage for 1 h, associated with elevated TRAP-6-induced fibrinogen binding. VASP phosphorylation levels were decreased after cold exposition, detectable in 1-day- and 2-day-stored APC with flow cytometry, and in 2-day-stored APC with Western blot technique. Induced cGMP levels were lower after storage at CT in APC on day 1 and on day 2, whereas cAMP levels were reduced on 2-day-stored APC. Conclusion: Short-term refrigeration for 1 h is sufficient to induce an attenuation of inhibitory signaling, accompanied with increased aggregation responses in APC stored for up to 2 days. The “on demand” refrigeration of PC may be a reasonable approach for the preparation of platelets with enhanced responsiveness to treat patients with hemorrhage more effectively, which should be further addressed in consecutive studies.

Switching From Cangrelor to Prasugrel in Patients Undergoing Percutaneous Coronary Intervention: The Switching Antiplatelet-6 (SWAP-6) Study

BackgroundA drug-drug interaction (DDI) may occur when transitioning from intravenous P2Y12 inhibition with cangrelor to oral P2Y12 inhibition with prasugrel. However, this has never been tested in patients undergoing percutaneous coronary intervention (PCI). ObjectivesThis study sought to rule out a DDI when cangrelor and prasugrel are concomitantly administered in PCI patients. MethodsSWAP-6 (Switching Antiplatelet-6) was a prospective, randomized, 3-arm, open-label pharmacokinetic (PK) and pharmacodynamic (PD) study. Patients (N = 77) were randomized to 1) prasugrel only at the start of PCI, 2) cangrelor plus prasugrel concomitantly at the start of PCI, or 3) cangrelor at the start of PCI plus prasugrel at the end of infusion. Cangrelor infusion was maintained for 2 hours. PK/PD assessments were performed at baseline and 6 time points postrandomization. The primary endpoint was noninferiority in VerifyNow (Werfen) P2Y12 reaction units measured at 4 hours after randomization between cangrelor plus prasugrel concomitantly administered vs prasugrel only. PK assessments included plasma levels of the active metabolite of prasugrel. ResultsCompared with prasugrel, cangrelor further enhances P2Y12 inhibitory effects. At 4 hours postrandomization, P2Y12 reaction unit levels were significantly lower with prasugrel only compared to cangrelor and prasugrel concomitantly administered (least squares means difference = 130; 95% CI: 85-176), failing to meet the prespecified noninferiority margin. Findings were corroborated by multiple PD assays. The active metabolite of prasugrel levels were not affected by concomitant administration of cangrelor and were low at the end of cangrelor infusion. ConclusionsIn patients undergoing PCI, concomitant administration of prasugrel with cangrelor leads to a marked increase in platelet reactivity after stopping cangrelor infusion, supporting the presence of a DDI. (Switching Antiplatelet Therapy-6 [SWAP-6]; NCT04668144)

Impact of renal function on Ticagrelor-induced antiplatelet effects in coronary artery disease patients.

Chronic renal failure (CKD) is associated with the presence of increased platelet reactivity and lower clinical benefit of clopidogrel. Ticagrelor has a more favorable pharmacodynamic and pharmacokinetic profile compared to clopidogrel, which has translated into better clinical outcomes in patients with acute coronary syndrome (ACS). We conducted a prospective mechanistic cohort study in order to investigate the impact of renal failure on the pharmacokinetics and pharmacodynamics of ticagrelor in patients with acute ACS. Patients were divided into two groups based on their estimated renal clearances (eGFR≥60mL/min and eGFR<60mL/min). Platelet function was determined using the VerifyNow system at baseline, after the ticagrelor loading dose and at discharge. In addition, levels of ticagrelor and its active metabolite (AR-C124910XX) were determined in the first hour after loading dose. 48 patients were recruited (eGFR≥60mL/min: 35 and eGFR<60mL/min: 13). There were no significant differences between the groups in terms of platelet inhibition after the loading or after 7days of treatment (p=0.219). However, the levels of ticagrelor and its active metabolite were lower in subjects with normal renal function than in CKD, especially at 4 (p=0.02 and 0.04 respectively) and 6h of loading (p=0.042 and 0.08 respectively). No differences in platelet inhibition were observed after treatment with ticagrelor in patients with different renal function, although patients with renal impairment showed higher levels of ticagrelor and AR-C124910XX after 4h of the loading dose.

Pilot study: The LIPL-PLATELET study postprandial LIPid paneLs and PLATELET activity in coronary heart disease after treatment with PCSK9-inhibitors

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Sanofi AVentis Reports about a pleiotropic potential of pro-protein convertase subtilisin/kexin type 9 inhibitor are scarce. This hypothesis-generating study investigates the platelet reactivity after standardized oral fat tolerance testing (OFTT) under an optimized lipid-lowering therapy (statin plus ezetimibe) alone and during the add-on treatment with the alirocumab. We investigated ten patients with the chronic coronary syndrome (CCS). Lipid variables and markers of platelet function were assessed during the fasting state and 3 and 5 hours after OFTT using a milkshake with 90g of fat. Measurements were performed in the same CCS patients under dual lipid-lowering therapy (DLLT) alone and after three months of add-on therapy with alirocumab. Postprandial inflammatory reaction did not change, irrespective of alirocumab. Neutrophile to lymphocyte ratio increased during the OFTT more significantly when on dual lipid-lowering therapy (p=0.021). The multiplate electrode aggregometry test with ASPI reagents (p=0.037) showed a paradoxically higher platelet reactivity five hours after OFTT with the addition of alirocumab compared to the DLLT only. Platelet reactivity remained unchanged during OFTT in CCS patients before or after alirocumab therapy. Altogether, alirocumab showed a trend of decreased postprandial inflammation and an increase in platelet reactivity.

The LIPL Study Postprandial lipid profile, inflammation and platelet activity in patients with chronic coronary syndrome

Abstract Funding Acknowledgements Type of funding sources: None. Introduction In general, most people spend their day in a non-fasting state. Hence, it is suggested that the changes in atherosclerosis happen mainly under the influence of non-fasting lipids. Up to date, the studies in the postprandial state were primarily performed on healthy subjects. Aim This exploratory, cross-sectional study investigates the change in lipid profile, in biomarkers of inflammation, as well as markers of platelet activation in patients with different cardiovascular risk profiles in the postprandial state. Methods The studied population consists of 66 patients with different cardiovascular risk: patients with a history of chronic coronary syndrome (CCS) and diabetes mellitus type 2 (DM2) (n=20), CCS without DM2 (n=25), and a healthy control group (n=21). Lipid variables and markers of platelet function were assessed during the fasting state (baseline) and three and five hours after a standardized fat meal using a standardized oral fat tolerance test (OFTT), a milkshake with 90g of fat. Platelet activity was measured with the Multiplate Assay using adenosine diphosphate (ADP), arachidonic acid (ASPI) and thrombin-receptor activating peptide (TRAP) as stimulants. Results Patients with CCS and DM2 were significantly older and had the highest BMI. All patients with CCS were on acetylsalicylic acid, and 95% of CCS patients were on high-dose statins. HDL-c decreased significantly during the OFTT, with a peak after five hours (3.46±0.4 mg/dL, p&amp;lt;0.001). Triglycerides (TG) increased significantly during the OFTT, with a peak after five hours (130.2 ± 14.5 mg/dL, p&amp;lt;0.001) irrespective of the group. All other variables of the lipid profile remained stable during the OFTT. The absolute leucocyte and neutrophile count and the neutrophile to lymphocyte ratio (NLR) increased significantly during the OFTT in the whole study population, whereas the absolute lymphocyte count increased significantly only in the control group. A significant increase in platelet activity during OFTT was shown in the control group by the increased absolute platelet count, increased reticulated thrombocytes, and increased platelet reactivity measured by the ASPI and TRAP tests, respectively. There was no significant change in the markers of platelet activity during the OFTT in patients with CCS with/without DM2. Conclusion This study showed that a standardized fatty meal changes HDL-c and TG concentrations and leads to an increased postprandial inflammation response irrespective of the cardiovascular risk and to increased platelet activity in healthy subjects, while there was no increase in platelet activity in higher-risk CCS patients.

Altered platelet reactivity, coagulation, endothelial and inflammatory markers early after smoking cessation verified with cotinine plasma concentration

Background/Introduction: Cigarette smoking is a potent modifiable risk factor for coronary artery disease (CAD). However, little is known about alterations to prothrombotic state and platelet reactivity early after smoking cessation following percutaneous coronary interventions (PCI). Purpose: We investigated alterations to platelet reactivity, coagulation and markers of platelet, endothelial, inflammatory and coagulation activation in clopidogrel-treated patients with CAD after PCI before and after smoking cessation. Methods: Smoking patients aged 18 years or older at least 30 days after PCI were recruited and encouraged to quit the habit. At baseline and at 30 days, we measured platelet reactivity with VerifyNow system, thrombomodulin, P-selectin, platelet factor 4 (CXCL4/PF4), citrullinated histone H3 (H3cit) and cotinine level. Results: Among 117 patients, 84 patients (72%) at a median age of 60.5 years (40 [interquartile range 30–47] pack-years) completed a 30-day follow-up. At day 30, 30 (35.7%) patients stopped smoking with cotinine level < 50 ng/ml. Baseline characteristics were similar in both groups. In smoking quitters a change in platelet reactivity was larger (Δ platelet reactivity units (PRU) 19 [2, 43] vs. -6 [-32, 37], p = 0.018), along with a change in P-selectin concentration (-11.82 [-23.62, 1.34] vs. 7.19 [-14.24, 17.19] ng/ml, p = 0.005). Positive correlations was noticed between cotinine and both P-selectin ( r = 0.23, p = 0.045) and CXCL4 (r = 0.27, p = 0.02). Conclusion: After smoking cessation in CAD patients following PCI an increase in platelet reactivity and a decrease in P-selectin levels were observed. The risk of thrombotic complications post PCI might be paradoxically enhanced among patients who stopped smoking.

Platelet Parameters May be Predictors of Coronary Artery Disease in Prediabetes: Rural Hospital-based Cross-sectional Study

Introduction: Prediabetes is a state of impaired glucose tolerance that often precedes overt diabetes mellitus and is frequently underdiagnosed. Glycation of platelet proteins leads to increased platelet reactivity which can be an essential predisposing event in the pathogenesis of coronary artery disease (CAD). Although research has been conducted to diagnose CAD in prediabetes and to assess platelet indices in prediabetes, there has been no attempt to assess platelet indices in prediabetic patients who have CAD. Methods: This cross-sectional study was carried out in a rural tertiary care center in Central India from September 2019 to August 2021. A total of 180 patients were enrolled in this study, having documented CAD in coronary angiography (CAG) and blood glucose levels in the diagnostic range of prediabetes by the criteria set by the World Health Organization. Platelet indices, glycosylated hemoglobin, blood sugar levels, and CAG findings were documented for all participants. Results: The mean platelet volume (MPV) in our study population was 9.58 ± 1.14 fL, platelet distribution width (PDW) was 15.69% ± 1.36%, plateletcrit was 0.3% ± 0.07%, and platelet count was 319 ± 44 × 103 cells/mm3. PDW was the best tool to predict double-vessel disease (P &lt; 0.0001), while MPV (P = 0.6146) and PDW (P = 0.0266) were best predictors of triple-vessel disease. Conclusion: Platelet indices that are readily available investigations prescribed by clinicians routinely are significantly associated with blood sugar levels and can predict the severity of CAD in prediabetics in terms of the number of vessels involved. Early assessment of platelet indices in prediabetics can aid in the diagnosis and prognosis of CAD, thereby helping in planning early intervention.

Loss of P2Y1 receptor desensitization does not impact hemostasis or thrombosis despite increased platelet reactivity in vitro

BackgroundThe hemostatic plug formation at sites of vascular injury is strongly dependent on rapid platelet activation and integrin-mediated adhesion and aggregation. However, to prevent thrombotic complications, platelet aggregate formation must be a self-limiting process. The second-wave mediator adenosine diphosphate (ADP) activates platelets via Gq-coupled P2Y1 and Gi-coupled P2Y12 receptors. After ADP exposure, the P2Y1 receptor undergoes rapid phosphorylation-induced desensitization, a negative feedback mechanism believed to be critical for limiting thrombus growth. ObjectiveThe objective of this study was to examine the role of rapid P2Y1 receptor desensitization on platelet function and thrombus formation in vivo. MethodsWe analyzed a novel knock-in mouse strain expressing a P2Y1 receptor variant that cannot be phosphorylated beyond residue 340 (P2Y1340-0P), thereby preventing the desensitization of the receptor. ResultsP2Y1340-0P mice followed a Mendelian inheritance pattern, and peripheral platelet counts were comparable between P2Y1340-0P/340-0P and control mice. In vitro, P2Y1340-0P/340-0P platelets were hyperreactive to ADP, showed a robust activation response to the P2Y1 receptor-selective agonist, MRS2365, and did not desensitize in response to repeated ADP challenge. We observed increased calcium mobilization, protein kinase C substrate phosphorylation, alpha granule release, activation of the small GTPase Rap1, and integrin inside-out activation/aggregation. This hyperreactivity, however, did not lead to increased platelet adhesion or excessive plug formation under physiological shear conditions. ConclusionOur studies demonstrate that receptor phosphorylation at the C-terminus is critical for P2Y1 receptor desensitization in platelets and that impaired desensitization leads to increased P2Y1 receptor signaling in vitro. Surprisingly, desensitization of the P2Y1 receptor is not required for limiting platelet adhesion/aggregation at sites of vascular injury, likely because ADP is degraded quickly or washed away in the bloodstream.

The LIPL-PLATELET Study Postprandial LIPid Panels and PLATELET Activity in Coronary Heart Disease after Treatment with PCSK9-Inhibitors

Reports about a pleiotropic potential of pro-protein convertase subtilisin/kexin type 9 inhibitor are scarce. This hypothesis-generating study investigates the platelet reactivity after standardized Oral Fat Tolerance Testing (OFTT) under an optimized lipid-lowering therapy (statin plus ezetimibe) alone and during the add-on treatment with the alirocumab. We investigated ten patients with Chronic Coronary Syndrome (CCS). Lipid variables and markers of platelet function were assessed during the fasting state and 3 and 5 hours after OFTT using a milkshake with 90 g of fat. Measurements were performed in the same CCS patients under Dual Lipid-Lowering Therapy (DLLT) alone and after three months of add-on therapy with alirocumab. Postprandial inflammatory reaction did not change, irrespective of alirocumab. Neutrophile to lymphocyte ratio increased during the OFTT more significantly when on dual lipid-lowering therapy (p=0.021). The multiplate electrode aggregometry test with ASPI reagents (p=0.037) showed a paradoxically higher platelet reactivity five hours after OFTT with addition of alirocumab compared to the DLLT only. Platelet reactivity remained unchanged during OFTT in CCS patients before or after alirocumab therapy. Altogether, alirocumab showed a trend of decreased postprandial inflammation and increase in platelet reactivity.

Advanced Flow Cytometry Using the SYTO-13 Dye for the Assessment of Platelet Reactivity and Maturity in Whole Blood

Newly produced immature platelets are larger, contain higher amounts of residual RNA, and are more reactive than mature platelets. Flow cytometry using the SYTO-13 dye is a method for the subdivision of immature platelets from mature platelets based on the labelling of intracellular platelet RNA, enabling the simultaneous investigation of the reactivity of each platelet population. This method provides detailed information on several aspects of platelet physiology using a combination of platelet surface markers and agonists. Currently, no standardized protocol exists across laboratories. Here, we describe a flow cytometry protocol in detail to investigate platelet reactivity and its relation to platelet maturity. We analyzed 20 healthy individuals with the protocol and compared the platelet subpopulation with the highest SYTO-13 labelling (in the first quintile, "SYTO-high") corresponding to the most immature platelets (highest RNA content) with the platelet subpopulation with the lowest SYTO-13 labelling (in the fifth quintile, "SYTO-low") corresponding to the mature platelets with the lowest RNA content. SYTO-high platelets had overall significantly increased platelet reactivity compared with that of SYTO-low platelets. The presented method may be a valuable research tool for the analysis of platelet reactivity and its relation to platelet maturity.

Association of Erythrocytes Sedimentation Rate and Platelets Indices in Diabetes in the Elderly

Recent research indicates that inflammation can contribute to the etiology of diabetes which is characterized by hyperglycemia and abnormalities in insulin secretion and/or activity. Erythrocyte sedimentation rate (ESR) is the most often utilized laboratory test for detecting systemic inflammation among all plasma inflammatory indicators. Patients with diabetes have reportedly shown altered platelets, due to "prothrombotic condition" with increased platelet reactivity leading to vascular problems. The objective of the study was to relate platelet indices and erythrocyte sedimentation rates with Diabetes. The morphology, metabolism, and function of erythrocytes are invariably subject to a number of alterations when there is persistent hyperglycemia. Few prospective studies have looked at this issue, hence, the investigation of the link between Erythrocytes Sedimentation Rate and Platelets indices in Diabetes in a private hospital in Port Harcourt (Port Harcourt, the capital of Rivers State is the major city, situated by the Bonny River in Southern Nigeria), The study had 100 subjects who gave their consent and were chosen from among others for this cross-sectional study. Fifty patients were confirmed diabetes (21 men and 29 women; mean age: 60.1±5.02 years) and 50 control subjects without diabetes (20 men and 30 women; mean age: 58.08±5.67 years). Aseptic blood collection techniques were used to obtain blood samples from the diabetic and control groups into EDTA vials. The Sysmex XE-2100 Haematology Automated Analyzer was used to estimate platelet indices, and the Western green method was used to calculate ESR. Using the Excel Data Analysis Tool pack, the estimated values of the parameters were statistically evaluated. Both the control and diabetes groups, displayed a statistically significant difference in the mean values of ESR hence the level in the diabetic group showed greater mean values when compared to the control group values 37.42±20.55 mm/hr and 29.78±13.26 mm/hr respectively at (P=0.029). Comparing the means of the platelet indices between the two groups at a significance level of (P=0.674), there was no discernible change. The clinical diagnostic utility of ESR as a helpful indicator for following diabetic patients' progress strongly correlates with the frequency and intensity of inflammation in diabetes. It was concluded that inflammation plays a role in the development of diabetes is constantly supported by this study.

Individual predictors of platelet response to aspirin therapy in pregnancy

Aspirin (81mg daily) reduces the risk of preeclampsia in high-risk individuals, however, up to 30% of treated high-risk individuals still develop preeclampsia. Aspirin response in non-pregnant adults can vary widely. The objective of this study is to identify individual factors predictive of response to aspirin therapy in pregnancy. PFA-100 closure time is a measure of platelet response to epinephrine and is a quantitative measure of aspirin induced platelet inhibition. We conducted a prospective cohort study at Thomas Jefferson University Hospital of 130 patients with a singleton pregnancy at risk for preeclampsia and recommended aspirin therapy, 81mg daily initiated ≤16 weeks. PFA-100 closure time was analyzed at baseline and then 2-4 weeks after aspirin initiation. The primary outcome was PFA-100 closure time at follow-up #1. Predictors were evaluated with multivariable least squares model with stepwise variable selection using R package. 114 participants completed follow-up visit #1 with complete data for all variables. Average gestational age at baseline was 12.6±1.5 and at follow-up#1 was 16.0 ±2.3 weeks’ (p< 0.001). There was a significant increase in mean PFA-100 from baseline to follow-up #1 (131±39 vs 170±61, p< 0.001). In multivariable logistic regression, obesity and pre-gestational diabetes were associated with reduced aspirin response (lower PFA-100). Those with diabetes or obesity had lower mean PFA-100 at follow up in unadjusted and adjusted analyses (Figure). In contrast, Black race was associated with increased platelet response to aspirin therapy (MD 29 (95% CI 7-51), p=0.01) (Table). Baseline PFA-100 was also positively associated with follow-up PFA-100 (Table). Individuals with pre-gestational diabetes or obesity have a reduced platelet response to aspirin therapy. This is consistent with findings in non-pregnant adults. Aspirin dosing in pregnancy may need to be adjusted based on individual characteristics.View Large Image Figure ViewerDownload Hi-res image Download (PPT)