Increased Platelet Reactivity Research Articles

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)

Dolutegravir potentiates platelet activation by a calcium-dependent, ionophore-like mechanism

Dolutegravir is a highly potent HIV integrase strand transfer inhibitor that is recommended for first-line anti-retroviral treatment in all major treatment guidelines. A recent study has shown that people taking this class of anti-retroviral treatment have a substantially higher risk of early-onset cardiovascular disease, a condition shown previously to be associated with increased platelet reactivity. To date, few studies have explored the effects of dolutegravir on platelet activation. Accordingly, the current study was undertaken with the primary objective of investigating the effects of dolutegravir on the reactivity of human platelets in vitro. Platelet-rich plasma, isolated platelets, or buffy coat cell suspensions prepared from the blood of healthy adults were treated with dolutegravir (2.5–10 µg/ml), followed by activation with adenosine 5’-diphosphate (ADP), thrombin, or a thromboxane A2 receptor agonist U46619. Expression of platelet CD62P (P-selectin), formation of heterotypic neutrophil:platelet aggregates, and calcium (Ca2+) fluxes were measured using flow cytometry and fluorescence spectrometry, respectively. Dolutegravir caused dose-related potentiation of ADP-, thrombin- and U46619-activated expression of CD62P by platelets, as well as a significant increases in formation of neutrophil:platelet aggregates. These effects were paralleled by a spontaneous, receptor-independent elevation in cytosolic Ca2+ that appears to underpin the mechanism by which the antiretroviral agent augments the responsiveness of these cells to ADP, thrombin and U46619. The most likely mechanism of dolutegravir-mediated increases in platelet cytosolic Ca2+ relates to a combination of lipophilicity and divalent/trivalent metal-binding and/or chelating properties of the anti-retroviral agent. These properties are likely to confer ionophore-type activities on dolutegravir that would promote movement of Ca2+ across the plasma membrane, delivering the cation to the cytosol where it would augment Ca2+-dependent intracellular signaling mechanisms. These effects of dolutegravir may lead to hyper-activation of platelets which, if operative in vivo, may contribute to an increased risk for cardiometabolic co-morbidities.

A Common Variant in GRK5 Reveals a PAR1-Specific Mechanism for Its Regulation of Platelet Function

Two separate genome wide association studies (GWAS), recently conducted by our group and another group, have identified the variant rs10886430 in the G protein-coupled receptor kinase 5 (GRK5) gene with a minor allele frequency of ~14% in Caucasians. Both studies show that the variant resides in a megakaryocyte-specific enhancer that alters the binding of the transcription factors GATA1 and MEIS1. In contrast to the major allele (A), the minor allele (G) is associated with decreased GRK5 mRNA expression, increased platelet reactivity, and greater risk of cardiovascular disease. However, the effect of the variant on protein expression has not been investigated by either group. In addition, there is an inconsistency between the findings of each of the studies regarding the specific role of GRK5 in thrombin receptor PAR1- and PAR4-mediated platelet activation. Further studies are needed to clarify whether, and how, GRK5 regulates platelet activity via PAR1, PAR4, or both. Here we introduce the A>G mutation into a megakaryoblastic cell line, Meg-01, by CRISPR-Cas9 genome editing. GRK5 protein expression is decreased by 80% in A>G mutant Meg-01 cells compared to WT control cells. To determine whether GRK5 regulates PAR1, PAR4, or both, we have isolated human platelets and specifically blocked GRK5 activity with compound CCG273261 to compare platelet responses to PAR1- and PAR4-specific agonists. Our data show that pharmacological inhibition of GRK5 increases markers of platelet activation such as integrin activation and P-selectin surface exposure in response to PAR1 receptor agonist peptide. Platelet activation in response to PAR4 receptor agonist peptide is normal. Furthermore, this inhibition increases Ca2+ mobilization in response to PAR1 receptor agonist, but not to PAR4 receptor agonist. Consistent with the results of our functional assays, mass spectrometry analysis revealed an interaction between GRK5 and PAR1 but did not detect an interaction with PAR4. Collectively, our data show that 1) this GRK5 intronic variant regulates GRK5 expression at both transcriptional and translational levels, 2) GRK5 preferentially regulates PAR-1 over PAR4-mediated signaling, and 3) GRK5 has a binding interaction with PAR1 (Fig 1). Our findings will enable us to develop superior therapeutics for cardiovascular risk groups especially those individuals who carry the intronic variant in GRK5 and as a result are more likely to experience thrombotic events. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Predicting Arterial Thrombotic Events Following Peripheral Revascularization Utilizing Objective Viscoelastic Data

Background Peripheral artery disease (PAD) is endemic in our globally aging population with >200 million affected worldwide. Graft/stent thrombosis after revascularization is common and frequently results in amputation, major adverse cardiovascular events, and cardiovascular mortality. Optimizing medications to decrease thrombosis is of paramount importance, however limited guidance exists on how to utilize and monitor therapy in this heterogeneous population. Thromboelastography with Platelet Mapping (TEG-PM) provides comprehensive coagulation metrics and may be integral to the next stage of patient-centered thrombophrophylaxis. This prospective study aimed to determine if TEG-PM could predict subacute graft/stent thrombosis following lower extremity revascularization and if objective cut-point values could be established that were associated with graft thrombosis. Methods We conducted a single-center prospective observational study on patients undoing lower extremity revascularization within the vascular surgery department. Patients were enrolled over a two year period between December 2020-May 2022, underwent preoperative and serial postoperative TEG-PM analysis at 10 timepoints (pre, peri, post operative), and were followed for up to one year. The primary outcome was a composite endpoint of graft/stent thrombosis requiring reintervention or amputation. Cox proportional hazards (PH) regression analysis examined the association of thrombosis and TEG-PM metrics. Cut-point analysis explored the predictive capacity of TEG-PM metrics for thrombosis and were based on the Youden index. Results A total of 144 patients were analyzed, of which 29 (20.1%) experienced graft/stent thrombosis. Patients who developed thrombosis had statistically greater % platelet aggregation [80.6±15.1 vs. 58.9±25.3] and statistically lower % platelet inhibition [19.8±15.0 vs. 40.8±25.4] (all p<0.01) compared to those who did not (Figure1). Cox PH analysis revealed that for every 1% increase in platelet aggregation, the hazard of experiencing an event during the study period increased by 5% [HR= 1.05, 95% CI 1.03-1.08, p<0.01]. An optimal cut-point of >70.8% platelet aggregation or <29.2% platelet inhibition identifies those at high risk of thrombosis with 90.0% sensitivity. Conclusions Among patients undergoing lower extremity revascularization, increased platelet reactivity, found on point-of-care viscoelastic technology, was predictive of subacute postoperative graft/stent thrombosis. Based on the cut-points of >70.8% platelet aggregation and <29.2% platelet inhibition, consideration of an alternative or augmented antithrombotic regimen for high risk patients may decrease the risk of postoperative thrombotic events.Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Gender-differences in antithrombotic therapy across the spectrum of ischemic heart disease: Time to tackle the Yentl syndrome?

The incidence and clinical presentation of ischemic heart disease (IHD), as well as thrombotic and bleeding risks, appear to differ between genders. Compared with men, women feature an increased thrombotic risk, probably related to an increased platelet reactivity, higher level of coagulation factors, and sex-associated unique cardiovascular risk factors, such as pregnancy-related (i.e., pre-eclampsia and gestational diabetes), gynecological disorders (i.e., polycystic ovary syndrome, early menopause) and autoimmune or systemic inflammatory diseases. At the same time, women are also at increased risk of bleeding, due to inappropriate dosing of antithrombotic agents, smaller blood vessels, lower body weight and comorbidities, such as diabetes and chronic kidney disease. Pharmacological strategies focused on the personalization of antithrombotic treatment may, therefore, be particularly appealing in women in light of their higher bleeding and ischemic risks. Paradoxically, although women represent a large proportion of cardiovascular patients in our practice, adequate high-quality clinical trial data on women remain scarce and inadequate to guide decision-making processes. As a result, IHD in women tends to be understudied, underdiagnosed and undertreated, a phenomenon known as a "Yentl syndrome." It is, therefore, compelling for the scientific community to embark on dedicated clinical trials to address underrepresentation of women and to acquire evidence-based knowledge in the personalization of antithrombotic therapy in women.

Independent association of PCSK9 with platelet reactivity in subjects without statin or antiplatelet agents.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) levels could predict cardiovascular event in patients with well-controlled LDL-C levels, suggesting an LDL-independent mechanism of PCSK9 on the cardiovascular system. Accumulating evidence suggests PCSK9 might be associated with increased platelet reactivity. This study aimed to assess the relationship between PCSK9 levels and platelet reactivity in subjects not taking statins or antiplatelet agents. A cross-sectional study was conducted to investigate the independent contribution of PCSK9 to platelet activity by controlling for the potential confounding factors. The study population included 89 subjects from a health examination centre who underwent routine annual health check-ups or had an examination before a selective operation. Subjects taking statins or antiplatelet agents were excluded. Adenosine diphosphate (ADP)-induced platelet aggregation was determined by PL-11 platelet analyzer using impedance aggregometry and plasma PCSK9 levels were determined using an ELISA. Serum Lipid profile was assessed by measuring the concentration of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG), with low-density lipoprotein cholesterol (LDL-C) being directly measured using enzymatic techniques. The association between PCSK9 and platelet reactivity was investigated. The study subjects were composed of 53 males and 36 females with an average age of 55 (±11) years old. The univariate correlation analysis showed significant correlation between ADP-induced maximal aggregation rate (MAR) and PCSK9 (r = 0.55, p < 0.001) as well as TC (r = 0.23, p = 0.028), LDL-C (r = 0.27, p < 0.001), and PLT (r = 0.31, p = 0.005). Being male (41.2% vs. 46.6, p = 0.04) and smoking (37.4 vs. 46.2%, p = 0.016) were associated with lower ADP-induced MAR than being female and non-smoking. However, there is no correlation between PCSK9 and AA-induced platelet maximal aggregation rate (r = 0.17, p = 0.12). Multiple regression analysis suggested that PCSK9 contributed independently to ADP-induced maximal aggregation rate (β = 0.08, p = 0.004) after controlling for the effect of TC, LDL-C, PLT, being male, and smoking. PCSK9 is positively associated with platelet reactivity, which may partly account for the beneficial effect of PCSK9 inhibition in reducing the risk of major adverse cardiovascular events after acute coronary syndrome (ACS).

Hyperresponsive Platelets and a Reduced Platelet Granule Release Capacity Are Associated with Severity and Mortality in COVID-19 Patients.

Coronavirus disease 2019 (COVID-19) is often associated with mild thrombocytopenia and increased platelet reactivity. The aim of the current study was to investigate the adenosine triphosphate (ATP) release kinetics of platelets in hospitalized SARS-CoV-2-infected patients. We studied time-dependent platelet activation in whole blood by monitoring the ATP release kinetics upon stimulation with a PAR1 receptor agonist in 41 hospitalized critically ill COVID-19 patients, 47 hospitalized noncritically ill COVID-19 patients, and 30 healthy controls. Our study demonstrated that platelets of critically ill COVID-19 patients were hyper-responsive with a shorter platelet response time (PRT) and a reduced platelet granule release capacity (GRC), probably due to chronic activation. The median PRT of COVID-19 patients admitted to the critical care unit was 10 and 7 seconds shorter than the median PRT in healthy controls and noncritical COVID-19 patients, respectively. Both PRT and GRC were also associated with D-dimer (Spearman r [r s] = -0.51, p < 0.0001 and r s = -0.23, p < 0.05), C-reactive protein (CRP) (r s = -0.59, p < 0.0001 and r s = -0.41, p < 0.01), and neutrophil-to-lymphocyte ratio (NLR) (r s = -0.42, p < 0.0001 and r s = -0.26, p < 0.05). Moreover, an increased PRT and a reduced GRC were associated with an increased mortality (odds ratio [OR]: 18.8, 95% confidence interval [CI]: 6.5-62.8, p < 0.0001 and OR: 4.0; 95% CI: 1.6-10.4, p < 0.01). These relationships remained significant after adjustment for age, sex, D-dimer, CRP, and NLR. Using an accessible agonist-induced platelet granule ATP release assay, we show that platelet hyper-responsiveness and reduced platelet GRC in COVID-19 patients were associated with critical illness and mortality.

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

Abstract Background/Introduction Cigarette smoking is a potent modifiable risk factor for coronary artery disease (CAD) including patients after percutaneous coronary interventions (PCI). Cigarette smoking is associated with major changes in platelet, endothelial, inflammatory, and coagulation responses. The early period after PCI witnesses the highest risk of thrombotic events. However, data regarding alterations of prothrombotic state and platelet reactivity early after smoking cessation are scarce. Purpose We investigated alterations to platelet reactivity, coagulation and markers of platelet, endothelial and neutrophil activation in clopidogrel-treated patients with CAD after PCI before and after smoking cessation. Methods Patients aged 18 years or older, who smoked at least 10 cigarettes per day, at least 30 days after successful PCI with stent placement, and those treated with 75 mg clopidogrel and 75 mg acetylsalicylic acid (ASA) once daily, were included in the study and were encouraged to quit the habit. Platelet reactivity was measured with VerifyNow system and the concentrations of cotinine, thrombomodulin, P-selectin, platelet factor 4 (CXCL4/PF4), citrullinated histone H3 (H3cit), were assessed in blood samples at baseline and at the 30-day follow-up visit. Smoking cessation was defined as cotinine concentrations of &amp;lt;50 ng/ml. Results Among 117 patients, being current smokers, who attended the baseline visit, 84 patients completed a 30-day follow-up. The median [interquartile range] age of patients was 50 [55–65] years, median body mass index was 27.55 [25.2–30.9] kg/m2, and a median load of smoking was 40 [30–47] pack-years. At the follow-up visit, 30 patients stopped smoking as confirmed by cotinine concentrations (study group) and 54 patients continued smoking (control group). Baseline characteristics were similar in both groups. In the study group as compared to the control group, at day 30 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). The change in the concentrations of thrombomodulin, CXCL4/PF4, and citH3 did not differ significantly between groups. Conclusion In the early period after smoking cessation in coronary artery disease patients following PCI treated with clopidogrel and ASA, an increase in platelet reactivity with a decrease in P-selectin levels was observed. No significant changes in other markers were noticed. It might be speculated that the risk of thrombotic complications might be paradoxically enhanced among such patients after smoking cessation despite dual antiplatelet therapy. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Centre of Postgraduate Medical Education

Impact of diabetes mellitus on the pharmacodynamic effects of prasugrel and ticagrelor after switching from clopidogrel in patients with coronary artery disease

Switching P2Y12 inhibitors is common in clinical practice. However, data on the pharmacodynamic (PD) effects of switching in clinical settings characterized by high platelet reactivity, such as diabetes mellitus (DM), are limited. This is a post-hoc analysis from a prospective, randomized, open-label study conducted in coronary artery disease patients comparing the PD effects of loading dose (LD) and maintenance dose regimens of prasugrel vs ticagrelor according to DM status. A total of 110 patients were enrolled: 42 (38%) with DM and 68 (62%) without DM. All patients were on maintenance dual antiplatelet therapy with aspirin and clopidogrel. PD assessments were performed using whole blood vasodilator-stimulated phosphoprotein (VASP), with results quantified by the platelet reactivity index (PRI), VerifyNow P2Y12 (VN-P2Y12) with results reported as P2Y12 reaction units(PRU), and light transmittance aggregometry(LTA) following 20 and 5µM adenosine diphosphate stimuli with results reported as maximum platelet aggregation (MPA). PD assessments were performed at baseline (while on clopidogrel), 30min after LD, 2h after LD, and 1week after LD. Overall, platelet reactivity was higher in DM than in non-DM patients while on clopidogrel therapy. After switching to either prasugrel or ticagrelor, platelet reactivity dropped but remained significantly higher among patients with DM at 30min with all tests (VN-PRU p < 0.01, MPA 20µM p < 0.01, VASP-PRI p = 0.02) and at 2h with VN-PRU (p < 0.01) and LTA-MPA 20µM (p < 0.01) but not with VASP-PRI (p = 0.19). There were no significant differences between prasugrel and ticagrelor both among patients with or without DM, except for lower LTA-MPA 20 at 30min (p < 0.01) among non-DM patients treated with prasugrel. Patients with DM treated with clopidogrel have higher platelet reactivity compared to patients without DM. Although platelet reactivity markedly reduces to a similar extent after switching to prasugrel or ticagrelor, patients with DM persist with increased platelet reactivity compared to patients without DM.Study registration: ClinicalTrials.gov identifier: NCT01852175.

Joint Effect of Multiple Prothrombotic Genotypes and Mean Platelet Volume on the Risk of Incident Venous Thromboembolism.

A high mean platelet volume (MPV), a marker of increased platelet reactivity, is a risk factor for venous thromboembolism (VTE). Whether established prothrombotic single nucleotide polymorphisms (SNPs) further increase the VTE risk in subjects with high MPV because of biological interaction remains unknown. To investigate the joint effect of high MPV and prothrombotic genotypes, comprising a 5-SNP genetic risk score (GRS), on the risk of VTE in a population-based case-cohort. Incident VTE cases (n = 653) and a subcohort (n = 1,774) were derived from the Tromsø Study (1994-2012). DNA was genotyped for rs8176719 (ABO), rs6025 (F5), rs1799963 (F2), rs2036914 (F11), and rs2066865 (FGG). Hazard ratios (HRs) for VTE with 95% confidence intervals (CIs) were estimated according to predefined MPV-strata (<8.5, 8.5-9.5, ≥9.5 fL) and number of risk alleles for each individual SNP and the GRS (0-1, 2-3, ≥4 risk alleles) in models adjusted for age, sex, body mass index, and platelet count. The combination of high MPV and risk alleles, either as individual SNPs or the GRS, had an additive effect on VTE risk. Compared with subjects with MPV <8.5 fL and 0-1 risk allele, those with high MPV (≥9.5 fL) and ≥4 risk alleles had HRs of 2.80 (95% CI: 1.77-4.43) for overall VTE and 4.60 (95% CI: 2.20-9.60) for unprovoked events, respectively, but there was no supra-additive effect on risk estimates. The combination of high MPV and prothrombotic genotypes had an additive effect on VTE risk, suggesting there is no biological interaction between these risk factors in the pathogenesis of VTE.

Staphylococcus aureus increases platelet reactivity in patients with infective endocarditis

Thromboembolism is frequent in infective endocarditis (IE). However, the optimal antithrombotic regimen in IE is unknown. Staphylococcus aureus (SA) is the leading cause of IE. First studies emphasize increased platelet reactivity by SA. In this pilot study, we hypothesized that platelet reactivity is increased in patients with SA− IE, which could be abrogated by antiplatelet medication. We conducted a prospective, observatory, single-center cohort study in 114 patients with IE, with four cohorts: (1) SA coagulase positive IE without aspirin (ASA) medication, (2) coagulase negative IE without ASA, (3) SA coagulase positive IE with ASA, (4) coagulase negative IE with ASA. Platelet function was measured by Multiplate electrode aggregometry, blood clotting by ROTEM thromboelastometry. Bleeding events were assessed according to TIMI classification. In ASA-naïve patients, aggregation with ADP was increased with coag. pos. IE (coagulase negative: 39.47 ± 4.13 AUC vs. coagulase positive: 59.46 ± 8.19 AUC, p = 0.0219). This was abrogated with ASA medication (coagulase negative: 42.4 ± 4.67 AUC vs. coagulase positive: 45.11 ± 6.063 AUC p = 0.7824). Aspirin did not increase bleeding in SA positive patients. However, in SA negative patients with aspirin, red blood cell transfusions were enhanced. SA coagulase positive IE is associated with increased platelet reactivity. This could be abrogated by aspirin without increased bleeding risk. The results of this pilot study suggest that ASA might be beneficial in SA coagulase positive IE. This needs to be confirmed in clinical trials.

Platelet Priming and Activation in Naturally Occurring Thermal Burn Injuries and Wildfire Smoke Exposure Is Associated With Intracardiac Thrombosis and Spontaneous Echocardiographic Contrast in Feline Survivors.

Wildfires pose a major health risk for humans, wildlife, and domestic animals. We previously discovered pathophysiologic parallels between domestic cats with naturally occurring smoke inhalation and thermal burn injuries and human beings with similar injuries; these were characterized by transient myocardial thickening, cardiac troponin I elevation and formation of intracardiac thrombosis. While the underlying mechanisms remain unclear, results from murine models suggest that platelet priming and activation may contribute to a global hypercoagulable state and thrombosis. Herein, we evaluated and compared the degree of platelet activation, platelet response to physiologic agonists and levels of platelet-derived microvesicles (PDMV) in 29 cats with naturally occurring wildfire thermal injuries (WF), 21 clinically healthy cats with subclinical hypertrophic cardiomyopathy (HCM) and 11 healthy cats without HCM (CC). We also quantified and compared circulating PDMVs in WF cats to CC cats. In addition, we examined the association between thrombotic events, severity of burn injuries, myocardial changes, and the degree of platelet activation in cats exposed to wildfires. Flow cytometric detection of platelet surface P-selectin expression showed that WF cats had increased platelet response to adenosine diphosphate (ADP) and thrombin compared to the two control groups indicating the presence of primed platelets in circulation. In addition, cats in the WF group had increased circulating levels of PDMV, characterized by increased phosphatidylserine on the external leaflet. Cats in the WF group with documented intracardiac thrombosis had elevated platelet activation and platelet priming in the presence of ADP. While high dose arachidonic acid (AA) mostly resulted in platelet inhibition, persistent response to AA was noted among cats in the WF group with intracardiac thrombosis. Univariate and multiple logistic regression analyses demonstrated that increased platelet response to AA was independently associated with thrombotic events. This is the first study reporting the significant association between platelet priming and intracardiac thrombosis in domestic cats with naturally occurring wildfire-related injuries and smoke inhalation. Further studies are required to delineate additional mechanisms between inflammation and thrombosis, especially regarding platelet primers and the cyclooxygenase pathway.One Sentence SummaryPlatelet activation and shedding of platelet-derived microvesicles due to platelet priming is present following naturally occurring wildfire smoke exposure and thermal burn injuries in a population of domestic cats.

Early Change in Platelet Count and MPV Levels of Patients Who Received Hemodialysis for the First Time: Mogadishu Somalia Experience.

Introduction Mean platelet volume (MPV) is a marker used to assess the platelet' size and is also an indicator of platelet reactivity and prothrombotic status. Objective In this study, we aimed to determine the relationship between MPV and biochemical parameters in patients who had received hemodialysis (HD) for the first time and then in respect of those same patients after their fourth HD. Method 151 HD patients were enrolled in this study. Patients were eligible for inclusion if they had received their first HD session during this study protocol. Prehemodialysis blood samples were taken. Most laboratory values, including mean platelet volume (MPV) level and platelets (PLT) count, were measured before the first HD and after the fourth HD session for each patient. Results Among the patients in our study, the mean age profile of the male patients (n = 103; 68.2%) was found to be higher than that of the female patients (n = 48; 31.8%) (53.62 ± 18.19 vs. 46.17 ± 17.9 years) (p = 0.019).In the patients' laboratory results after the fourth HD session, MPV, MPV/Plt, and Na values had increased to those after the first HD session (p < 0.001). When age and gender status were taken into account, the level of weak positive correlation with white blood cell count (WBC), neutrophil, and red cell distribution width (RDW) was found, while the weak negative correlation with platelet to lymphocyte ratio (PLR) was found (p < 0.001). Conclusions In our study, we found that increase in MPV and MPV/PLT levels was significant in the fourth HD session of patients with CKD. It is also debatable that there are findings indicating an increase in platelet reactivity in the first weeks of the onset of HD. This could be an early indicator of the early prevention of cardiovascular diseases.

Increased Platelet Reactivity and Proinflammatory Profile Are Associated with Intima-Media Thickness and Arterial Stiffness in Prediabetes.

Alterations of glucose homeostasis are associated with subclinical vascular damage; however, the role of platelet reactivity in this process has not been fully investigated. In this cross-sectional study, we evaluated the correlation between markers of platelet reactivity and inflammation and markers of vascular disease in subjects with prediabetes. Markers of platelet reactivity such as 11-dehydro-thromboxane B2 urinary levels (11-dh-TXB2) and mean platelet volume (MPV) and inflammatory indexes such as platelet-to-lymphocyte ratio (PLR) were evaluated in subjects with prediabetes (n = 48), new-onset type 2 diabetes (NODM, n = 60) and controls (n = 62). Furthermore, we assessed the cardiovascular risk profile of the study population with arterial stiffness and quality intima–media thickness (qIMT). Subjects with prediabetes and NODM exhibited higher 11-dh-TXB2 urinary levels and MPV and a proinflammatory profile with an increased PLR, high-sensitivity C-reactive protein, ferritin and fibrinogen. Furthermore, after multiple regression analyses, we found that urinary 11-dh-TXB2 was one of the major determinants of IMT and arterial stiffness parameters. In conclusion, subjects with prediabetes exhibit increased platelet reactivity as well as a proinflammatory profile. Furthermore, this condition is associated with early markers of cardiovascular disease.

GPVI expression is linked to platelet size, age, and reactivity

AbstractPlatelets within one individual display heterogeneity in reactivity, size, age, and expression of surface receptors. To investigate the combined intraindividual contribution of platelet size, platelet age, and receptor expression levels on the reactivity of platelets, we studied fractions of large and small platelets from healthy donors separated by using differential centrifugation. Size-separated platelet fractions were perfused over a collagen-coated surface to assess thrombus formation. Multicolor flow cytometry was used to characterize resting and stimulated platelet subpopulations, and platelet age was determined based on RNA and HLA-I labeling. Signal transduction was analyzed by measuring consecutive phosphorylation of serine/threonine-protein kinase Akt. Compared with small platelets, large platelets adhered faster to collagen under flow and formed larger thrombi. Among the large platelets, a highly reactive juvenile platelet subpopulation was identified with high glycoprotein VI (GPVI) expression. Elevated GPVI expression correlated with high HLA-I expression, RNA content, and increased platelet reactivity. There was a stronger difference in Akt phosphorylation and activation upon collagen stimulation between juvenile and older platelets than between large and small platelets. GPVI expression and platelet reactivity decreased throughout platelet storage at 22°C and was better maintained throughout cold storage at 4°C. We further detected higher GPVI expression in platelets of patients with immune thrombocytopenia. Our findings show that high GPVI expression is a feature of highly reactive juvenile platelets, which are predominantly found among the large platelet population, explaining the better performance of large platelets during thrombus formation. These data are important for studies of thrombus formation, platelet storage, and immune thrombocytopenia.

IgG fractions from patients with antiphospholipid syndrome and systemic lupus erythematosus bind to platelets, but do not affect collagen-induced platelet activation

ABSTRACT Anti-beta-2 glycoprotein 1 (anti-β2GP1) is an antiphospholipid antibody found in patients with antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). Its presence commonly is associated with thrombosis; however, the mechanisms of interaction of anti-β2GP1 antibodies and platelets remain unclear. We investigated the effects of APS and SLE patient-derived IgG fractions on collagen-mediated platelet aggregation and examined the binding of patient-derived IgG to platelets before and after activation by collagen. IgG fractions, 150, 200, 300 or 350 µg/ml, isolated from 11 patients with APS and SLE were incubated with two sets of platelet-rich plasma (PRP) in the incubation wells of an aggregometer. The first set was activated by collagen and the other set was incubated for an additional 10 min. All platelets were collected by centrifugation and fixed in cell blocks. We assessed binding of IgG to platelets using immunocytochemistry (ICC). Patient-derived IgG fractions did not affect collagen-induced platelet aggregation. ICC staining using anti-human IgG antibodies demonstrated that patient-derived IgG fractions had greater affinity for non-activated platelets than those activated by 0.75 µg/ml collagen. Patient-derived IgG fractions bound to the surface of platelets and potentially could be internalized by platelets. IgG fractions from APS and SLE patients may sensitize non-activated platelets, which could increase platelet reactivity and thrombotic risk in patients. We did not detect secondary effects of patient-derived IgG fractions.

Platelet FcγRIIa Expression in Ischemic Stroke: A Marker of Increased Platelet Reactivity

Background Platelet FcγRIIa amplifies platelet activation and, thus, increased expression identifies patients with increased platelet reactivity. Previous work has demonstrated that platelet FcγRIIa can identify patients at high and low risk of subsequent cardiovascular events after myocardial infarction (MI). This study was designed to compare platelet expression of FcγRIIa in patients with stroke and transient ischemic attack (TIA) with that in patients with a recent MI. Methods Patients were enrolled based on an admitting diagnosis of stroke/TIA, and the discharge diagnosis was used to categorize patients into stroke/TIA (n=99) and other causes of neurologic dysfunction (hemorrhagic, trauma, toxic, and seizure; n=14). Patients with stroke/TIA were divided into embolic (both cardioembolic and thromboembolic; n=32) and not embolic causes (n=67). Results were compared with platelet FcγRIIa expression in patients with recent MI from a previous study (n=197). Platelet expression of FcγRIIa (molecules of FcγRIIa/platelet) was quantified with the use of flow cytometry. Results are mean±SD. Results Platelet expression of FcγRIIa was similar in patients with ischemic (both embolic and nonembolic) stroke/TIA (11 332±4127), embolic (11 204±3889) and nonembolic (11 393±4263) causes, and MI (11 479±2405). Patients with other causes of neurologic dysfunction had modestly but not significantly lower platelet expression of FcγRIIa (9389±2883; P =0.13). Conclusions Platelet expression of FcγRIIa was similar in patients with stroke/TIA and recent MI. These results support future studies designed to determine whether platelet FcγRIIa expression can discriminate risk of subsequent stroke/TIA and its potential use as a precision tool capable of guiding individualized treatment decisions.

Pleiotropic Effects of PCSK9: Focus on Thrombosis and Haemostasis.

The proprotein convertase subtilisin/keying 9 (PCSK9) is a serine protease that has gained importance in recent years as a drug target, mainly due to its effect on cholesterol metabolism in promoting the degradation of the low-density lipoprotein receptor (LDLR). However, this protease may also play an important role in lipid-independent reactions, including the process of thrombogenesis. Considering this, we reviewed the effects and implications of PCSK9 on platelet function and blood coagulation. PCSK9 knockout mice exhibited reduced platelet activity and developed less agonist-induced arterial thrombi compared to the respective control animals. This is in line with known research that elevated blood levels of PCSK9 are associated with an increased platelet reactivity and total number of circulating platelets in humans. Moreover, PCSK9 also has an effect on crucial factors of the coagulation cascade, such as increasing factor VIII plasma levels, since the degradation of this blood clotting factor is promoted by the LDLR. The aforementioned pleiotropic effects of the PCSK9 are important to take into account when evaluating the clinical benefit of PCSK9 inhibitors.

Cardiovascular involvement in patients with COVID-19 pneumonia

Background: Covid 19 pneumonia presents with various cardiovascular manifestations. The proposed mechanisms of cardiovascular involvement in COVID-19 are direct invasion of myocardial cell by the virus, hyper- inflammatory state secondary to cytokine storm, increased angiotensin II, low ACE2 levels, antiphospholipid antibodies and increased platelet reactivity which contribute significantly to thrombus formation in systemic and pulmonary vasculature. Objectives: To find out various cardiovascular manifestation of patients admitted with covid 19 pneumonia. Methodology: A retrospective observational study had been conducted in a tertiary care infectious disease hospital from July 2020 to December 2020 that included a total of 108 patients. Results: Most common risk factor were combination of hypertension and diabetes(40.7%) followed by hypertension alone (28.7%)and diabetes in 18.5% patients. Most common presentation was asymptomatic myocarditis found in 37 patients followed by sinus tachycardia in 34, sinus bradycardia in 18, Orthostatic hypotensionin in 16, Atrial fibrillation in 14, cerebrovascular accident in 9, Acute limb ischemia in 7, and acute coronary syndrome in 4 patients. Asymptomatic diastolic dysfunction (Grade 2 or more) found in 17 patients without any overt features of heart failure (all have raised NTproBNP and HSTrop I along with clinical features). A positive correlation was found between D- dimer level and severity of pneumonia by CT severity score. Conclusion: A high index of suspicion and necessary investigation may be needed for early detection of myocarditis and to prevent any complication particularly fatal arrhythmia and sudden cardiac death.