Increased Platelet Activation Research Articles

Hyperexpression of PTAFR and PF4 as Possible Platelet Risk Biomarkers in Patients With COVID-19.

SARS-CoV-2 infection presents different severity levels that suggest the influence of genetic factors on the clinical outcome of the disease. In cases of severe COVID-19, the presence of elevated coagulation markers, increased platelet activation and aggregation and the risk of thrombotic complications are described. Given the participation of these cells in several serious viral infections and their negative role when associated with a prothrombotic response, it is important to understand the mechanistic role of SARS-CoV-2 in platelet physiology. This study evaluated the hyperexpression of platelet-activating factor receptor (PTAFR) and platelet factor 4 (PF4) in unvaccinated and hospitalized patients with COVID-19. The study included 43 COVID-19 patients stratified according to WHO guidelines. Subsequently, the expression of the PTAFR and PF4 genes were evaluated using the real-time quantitative PCR and their possible correlation with the severity of the disease and clinical variables including hospitalization, outcome, sex, age and laboratory parameters (platelet count, INR and D-dimer). The analysis demonstrated a significant (p<0.05) hyperexpression of these genes COVID-19 patients (n=43) compared to healthy controls. Expression of these genes in patients was not statistically significant (p>0.05) different between patients stratified according to clinical variables. The expression of PTAFR and PF4 suggests an important molecular pathway in the pathophysiology of the disease and may be valuable platelet biomarkers to indicate increased risk in patients with COVID-19 who require hospital care, contributing to personalized intervention strategies and improving their clinical management.

Platelet Function, Platelet Size and Content of Reticulated Platelets: Interactions in Patients Receiving Dual Antiplatelet Therapy.

Increased platelet activity is a risk factor of thrombotic events in cardiovascular patients. We studied the relationship between platelet function, platelet size, and the content of reticulated platelets (RP) in patients with coronary heart disease (CHD, n = 55) and acute coronary syndrome (ACS, n = 95) receiving acetylsalicylic acid + clopidogrel or ticagrelor, respectively. The control group consisted of patients with risk factors for CHD, but with no CHD/ACS and free of antiplatelet drugs (n = 66). Platelet function was evaluated by the exposure of activated glycoprotein (GP) IIb-IIIa and P-selectin. In the control group, platelets were activated by TRAP (Thrombin Receptor Activating Peptide) 10 µM, and ADP 20, 5, 2.5 µM, and in the CHD/ACS groups, by TRAP 10 µM, and ADP 20 5 µM (±epinephrine 20 µM). Platelet size was assessed by the mean volume, % large forms, and forward scattering. RP were stained by thiazole orange. In the control group, activated GP IIb-IIIa and P-selectin correlated with platelet size and RP content after platelet activation by all agonists. Despite the decrease in platelet activity by antiplatelet drugs, most correlations (primarily for activated GP IIb-IIIa) were preserved in the CHD/ACS patients. In conclusion, increased platelet size and RP content are associated with increased platelet activity and the reduced efficacy of antiplatelet therapy.

Thrombosis in Hypertension: Pathophysiology, Biomarkers, and the Effect of Antihypertensive Treatment.

Hypertension, characterized by elevated blood pressure levels, remains a global health concern due to its association with cardiovascular complications, notably thrombosis. Thrombosis, the formation of blood clots within blood vessels, poses a significant risk for myocardial infarction, stroke, and limb ischemia, leading to adverse patient outcomes. Understanding the pathophysiological mechanisms underlying thrombosis in hypertension is crucial for developing effective preventive and therapeutic strategies. Hypertension induces structural and functional alterations in the vasculature, endothelium, and platelets, creating a prothrombotic milieu. Endothelial dysfunction, increased platelet activation, and alterations in coagulation factors contribute to the heightened thrombotic risk observed in hypertensive individuals. Biomarkers associated with thrombotic events, such as mean platelet volume, D-Dimer, and fibrinogen offer valuable insights into the pathogenesis of thrombosis and may serve as prognostic indicators for cardiovascular events in hypertensive populations. Investigating the impact of antihypertensive treatment on thrombotic risk is essential, as these medications exert pleiotropic effects on the vasculature and hemostatic system. By elucidating the intricate interplay between hypertension and thrombosis, this review aims to enhance our understanding of cardiovascular risk in hypertensive individuals and identify novel therapeutic targets for preventing thrombotic complications.

Impact of Hypertension and Physical Exercise on Hemolysis Risk in the Left Coronary Artery: A Computational Fluid Dynamics Analysis.

Background and Objectives: Hypertension increases the risk of developing atherosclerosis and arterial stiffness, with secondarily enhanced wall stress pressure that damages the artery wall. The coexistence of atherosclerosis and hypertension leads to artery stenosis and microvascular angiopathies, during which the intravascular mechanical hemolysis of red blood cells (RBCs) occurs, leading to increased platelet activation, dysfunction of the endothelium and smooth muscle cells due to a decrease in nitric oxide, and the direct harmful effects of hemoglobin and iron released from the red blood cells. This study analyzed the impact of hypertension and physical exercise on the risk of hemolysis in the left coronary artery. Methods: To analyze many different cases and consider the decrease in flow through narrowed arteries, a flow model was adopted that considered hydraulic resistance in the distal section, which depended on the conditions of hypertension and exercise. The commercial ANSYS Fluent 2023R2 software supplemented with user-defined functions was used for the simulation. CFD simulations were performed and compared with the FSI simulation results. Results: The differences obtained between the FSI and CFD simulations were negligible, which allowed the continuation of analyses based only on CFD simulations. The drops in pressure and the risk of hemolysis increased dramatically with increased flow associated with increased exercise. A relationship was observed between the increase in blood pressure and hypertension, but in this case, the increase in blood pressure dropped, and the risk of hemolysis was not so substantial. However, by far, the case of increased physical activity with hypertension had the highest risk of hemolysis, which is associated with an increased risk of clot formation that can block distal arteries and lead to myocardial hypoxia. Conclusions: The influence of hypertension and increased physical exercise on the increased risk of hemolysis has been demonstrated.

Platelet indices as predictors of poor glucoregulation in type 2 diabetes mellitus adults at Bishoftu General Hospital, Ethiopia.

Diabetes is a chronic metabolic syndrome that has become a global public health problem with significant morbidity and mortality. It is a pro-inflammatory and pro-thrombotic condition characterized by increased platelet activation and alterations in platelet indices. However, the use of platelet indices as predictors of poor glucoregulation has not been fully evaluated in this context, and evidence for their role as predictors of poor glycemic status in diabetic patients is limited. To evaluate platelet indices and determine their prognostic significance in relation to inadequate glucoregulation among individuals diagnosed with type 2 diabetes at Bishoftu General Hospital in Ethiopia, from June 15 to August 12, 2022. A comparative cross-sectional study was conducted in 261 participants including 174 individuals with type 2 diabetes mellitus (T2DM) and 87 non-diabetic controls. The systematic random sampling technique was used to select par-ticipants. Data were collected using structured questionnaires, physical measurements, checklists, and laboratory tests. Platelet parameters and fasting blood glucose levels were determined from blood samples using Sysmex-XN550 and CobasC311 analyzers, respectively. The hematology analyzer output was checked and participants were also screened for malaria parasites using a prepared blood smear. Collected data were entered into Epi-data version 3.1 and exported to SPSS version 25 for analysis. The χ 2 test, Mann-Whitney U test, Kruskal-Wallis test, post hoc test, Spearman correlation, and receiver operating characteristic curve were used for analysis. A P value < 0.05 was considered statistically significant. The results of our study indicate that diabetic patients have significantly higher levels of platelet distribution width (PDW), mean platelet volume (MPV), platelet large cell ratio (PLCR), and plateletcrit (PCT) compared to healthy individuals (P < 0.001). Furthermore, these indices were found to be significantly elevated in individuals with poor glycemic control in T2DM compared to those with good glycemic control and healthy controls. We also observed significant correlations between these indices and various anthropometric and clinical variables. Our findings suggest that PDW, with a cut-off value of 15.75 fL and an area under the curve (AUC) of 0.803, MPV, with a cut-off value of 12.25 fL and an AUC of 0.774, PLCR, with a cut-off value of 36.3% and an AUC of 0.775, and PCT, with a cut-off value of 0.24% and an AUC of 0.761, can serve as predictors of poor glycemic control in patients with diabetes mellitus. The observed correlation between diabetic patients and a significant increase in platelet indices has highlighted their potential as predictors of poor glycemic control in diabetes. Therefore, regular screening and profiling of platelet indices is recommended as part of the follow-up process for individuals with diabetes mellitus.

Adequate serum 25-hydroxy-vitamin D levels are correlated with low anti-PF4 levels in mild COVID-19 Patients: An observational study.

The worldwide spread of coronavirus disease 2019 (COVID-19) has resulted in an unparalleled health emergency of global proportions. Around 31% of individuals with COVID-19 experience thrombosis associated with hypercoagulation. COVID-19 patients have shown an increase in platelet activation, but the mechanism has not been fully understood yet. One theory suggests that this could be related to the heparin-induced thrombocytopenia phenomenon, where platelet activation involves anti-PF4 antibodies that are associated with thrombosis. Vitamin D has been established to exert an influence on immunological responses and inflammation. The aim of this study is to analyze the correlation between serum 25-hydroxy-cholecalciferol [25(OH)D] levels and anti-PF4 antibodies among COVID-19 patients. A cross-sectional study was conducted among 160 COVID-19 patients at Cipto Mangunkusumo General Hospital and Wisma Atlit Hospital Jakarta from October 2021 to January 2022. The mean serum 25(OH)D level was 15.1 ng/mL. A significant negative correlation was found between serum 25(OH)D and anti-PF4 levels in mild COVID-19 patients (P = .035; R = -0.236). Remarkably, P-selectin levels were significantly higher in the moderate COVID-19 group compared to the severe group (P = .031). Serum 25(OH)D level had a significant negative correlation with anti-PF4 level in mild COVID-19 patients. Thus, it is highly recommended to ensure that serum 25(OH)D levels are maintained above 30 ng/mL. Remarkably, the P-selectin level was significantly higher in the moderate COVID-19 group compared to the severe group.

Understanding the Role of Oxidative Stress in Platelet Alterations and Thrombosis Risk among Frail Older Adults.

Frailty and cardiovascular diseases are increasingly prevalent in aging populations, sharing common pathological mechanisms, such as oxidative stress. The evidence shows that these factors predispose frail individuals to cardiovascular diseases but also increase the risk of thrombosis. Considering this background, this review aims to explore advances regarding the relationship between oxidative stress, platelet alterations, and cardiovascular diseases in frailty, examining the role of reactive oxygen species overproduction in platelet activation and thrombosis. The current evidence shows a bidirectional relationship between frailty and cardiovascular diseases, emphasizing how frailty not only predisposes individuals to cardiovascular diseases but also accelerates disease progression through oxidative damage and increased platelet function. Thus, oxidative stress is the central axis in the increase in platelet activation and secretion and the inadequate response to acetylsalicylic acid observed in frail people by mitochondrial mechanisms. Also, key biomarkers of oxidative stress, such as isoprostanes and derivate reactive oxygen metabolites, can be optimal predictors of cardiovascular risk and potential targets for therapeutic intervention. The potential of antioxidant therapies in mitigating oxidative stress and improving cardiovascular clinical outcomes such as platelet function is promising in frailty, although further research is necessary to establish the efficacy of these therapies. Understanding these mechanisms could prove essential in improving the health and quality of life of an aging population faced with the dual burden of frailty and cardiovascular diseases.

Macrophage Migration Inhibitory Factor Promotes Thromboinflammation and Predicts Fast Progression of Aortic Stenosis.

Aortic stenosis (AS) is driven by progressive inflammatory and fibrocalcific processes regulated by circulating inflammatory and valve resident endothelial and interstitial cells. The impact of platelets, platelet-derived mediators, and platelet-monocyte interactions on the acceleration of local valvular inflammation and mineralization is presently unknown. We prospectively enrolled 475 consecutive patients with severe symptomatic AS undergoing aortic valve replacement. Clinical workup included repetitive echocardiography, analysis of platelets, monocytes, chemokine profiling, aortic valve tissue samples for immunohistochemistry, and gene expression analysis. The patients were classified as fast-progressive AS by the median ∆Vmax of 0.45 m/s per year determined by echocardiography. Immunohistological aortic valve analysis revealed enhanced cellularity in fast-progressive AS (slow- versus fast-progressive AS; median [interquartile range], 247 [142.3-504] versus 717.5 [360.5-1234]; P<0.001) with less calcification (calcification area, mm2: 33.74 [27.82-41.86] versus 20.54 [13.52-33.41]; P<0.001). MIF (macrophage migration inhibitory factor)-associated gene expression was significantly enhanced in fast-progressive AS accompanied by significantly elevated MIF plasma levels (mean±SEM; 6877±379.1 versus 9959±749.1; P<0.001), increased platelet activation, and decreased intracellular MIF expression indicating enhanced MIF release upon platelet activation (CD62P, %: median [interquartile range], 16.8 [11.58-23.8] versus 20.55 [12.48-32.28], P=0.005; MIF, %: 4.85 [1.48-9.75] versus 2.3 [0.78-5.9], P<0.001). Regression analysis confirmed that MIF-associated biomarkers are strongly associated with an accelerated course of AS. Our findings suggest a key role for platelet-derived MIF and its interplay with circulating and valve resident monocytes/macrophages in local and systemic thromboinflammation during accelerated AS. MIF-based biomarkers predict an accelerated course of AS and represent a novel pharmacological target to attenuate progression of AS.

Plant-derived compounds normalize platelet bioenergetics and function in hyperglycemia

BackgroundPolyphenols have been shown to decrease oxidative stress and modulate glycemic response. Nevertheless, their effect on platelet bioenergetics and clot structure in diabetes and hyperglycemia is unknown. ObjectivesTo investigate the effect of polyphenols on human platelet bioenergetics and its subsequent effect on clot structure in normoglycemia vs acute hyperglycemia in vitro. MethodsFour polyphenols (resveratrol, hesperetin, epigallocatechin gallate [EGCG], and quercetin) were selected for initial analysis. Healthy volunteers’ isolated platelets/platelet-rich plasma were treated with 5 or 25 mM glucose to represent normoglycemia and acute hyperglycemia, respectively. Platelet-derived reactive oxygen species (ROS), citrate synthase activity (mitochondrial density), mitochondrial calcium flux, and mitochondrial respiration were performed following exposure to polyphenols (20 µM, 1 hour) to determine their effects on platelet bioenergetics. Procoagulant platelets (annexin V) and fibrin fiber density (Alexa Fluor-488 fibrinogen; Invitrogen) were analyzed by laser scanning confocal microscopy, while clot porosity was determined using platelet-rich plasma following exposure to polyphenols (20 µM, 20 minutes). ResultsAcute hyperglycemia increased ROS, mitochondrial calcium flux, maximal respiration, and procoagulant platelet number. Resveratrol, quercetin, and EGCG reduced platelet ROS in normoglycemic and acute hyperglycemic conditions. Mitochondrial density was decreased by quercetin and EGCG in normoglycemia. Resveratrol and EGCG reduced mitochondrial calcium flux in acute hyperglycemia. Resveratrol also decreased procoagulant platelet number and attenuated oxygen consumption rate in normoglycemia and acute hyperglycemia. No effect of hyperglycemia or polyphenols was observed on fibrin fiber density or clot pore size. ConclusionOur results suggest polyphenols attenuate increased platelet activity stemming from hyperglycemia and may benefit thrombosis-preventative strategies in patients with diabetes.

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.

Peculiarities of morpho-functional characteristics of platelets in women with early and late preeclampsia

Introduction. In preeclampsia (PE), the hemostasis system, including the platelet component, changes significantly. The purpose of the work was to identify the peculiarities of the morpho-functional characteristics of platelets in women with early and late PE. Material and methods. The main group consisted of 26 women with early PE and 46 women with late PE. The control group consisted of women with normal pregnancies without hypertensive disorders, of whom 17 were at a gestational age of 260–336 weeks and 42 were at a gestational age of 340–394 weeks. The ADVIA 2120i hematology analyzer was used to evaluate platelet concentration (PLT), platelet distribution width (PDW), mean platelet volume (MPV), concentration of large platelets (Large PLT), percentage of large platelets from the total number of platelets (%LP), mean platelet component concentration (MPC), mean dry platelet mass (MPM). Results. Women with early PE have increased PDW, MPV, LargePlt, %LP and MPM indices compared to women with normal pregnancies up to 34 weeks. Female patients with late PE had lower PLT and higher PDW, %LP, MPC, MPM compared to women with normal pregnancies after 34 weeks. In late PE, PLT is reduced and PDW, %LP and MPM are increased compared to early PE. Conclusion. The detected changes in platelet indices in women with PE, regardless of the period of its onset, indirectly indicate increased thrombopoiesis and high functional activity of young platelets. However, the mechanisms that increase platelet activation in early and late preeclampsia differ.

Association of elevated circulating monocyte-platelet aggregates with hypercoagulability in patients with nephrotic syndrome

BackgroundHypercoagulability emerges as a central pathological feature and clinical complication in nephrotic syndrome. Increased platelet activation and aggregability are closely related to hypercoagulability in nephrotic syndrome. Monocyte-platelet aggregates (MPAs) have been proposed to represent a robust biomarker of platelet activation. The aim of this study was to investigate levels of the circulating MPAs and MPAs with the different monocyte subsets to evaluate the association of MPAs with hypercoagulability in nephrotic syndrome.MethodsThirty-two patients with nephrotic syndrome were enrolled. In addition, thirty-two healthy age and sex matched adult volunteers served as healthy controls. MPAs were identified by CD14 monocytes positive for CD41a platelets. The classical (CD14 + + CD16-, CM), the intermediate (CD14 + + CD16+, IM) and the non-classical (CD14 + CD16++, NCM) monocytes, as well as subset specific MPAs, were measured by flow cytometry.ResultsPatients with nephrotic syndrome showed a higher percentage of circulating MPAs as compared with healthy controls (p < 0.001). The percentages of MPAs with CM, IM, and NCM were higher than those of healthy controls (p = 0.012, p < 0.001 and p < 0.001, respectively). Circulating MPAs showed correlations with hypoalbuminemia (r=-0.85; p < 0.001), hypercholesterolemia (r = 0.54; p < 0.001), fibrinogen (r = 0.70; p < 0.001) and D-dimer (r = 0.37; p = 0.003), but not with hypertriglyceridemia in nephrotic syndrome. The AUC for the prediction of hypercoagulability in nephrotic syndrome using MPAs was 0.79 (95% CI 0.68–0.90, p < 0.001). The sensitivity of MPAs in predicting hypercoagulability was 0.71, and the specificity was 0.78.ConclusionIncreased MPAs were correlated with hypercoagulability in nephrotic syndrome. MPAs may serve as a potential biomarker for thrombophilic or hypercoagulable state and provide novel insight into the mechanisms of anticoagulation in nephrotic syndrome.

Circulating levels of erythrocytes-derived vesicles related to poor glycaemia control in type 2 diabetes mellitus patients with atrial fibrillation

Abstract Background Previous studies demonstrated that insulin resistance, hyperglycemia contribute to the development of a pro-thrombotic state characterized by increased platelet activation, activation of coagulation cascade and elevated number of extracellular vesicles (EVs) in type 2 diabetes mellitus (T2DM) patients. There is a less known impact of glycaemia control in T2DM patients with concomitant heart failure (HF) and atrial fibrillation (AF) on a number of erythrocytes-derived EVs. The aim of the study was to elucidate whether glucose control in T2DM patients with HF and AF affect a circulating number of erythrocytes-derived EVs. Methods The entire patient population composes of 417 patients (231 male, 55.4% and 186 female, 44.6%) with average age of 53 years as well as 25 healthy volunteers and 30 T2DM non-HF individuals. As inclusion, age ≥ 18 years, T2DM, established HF, and written consent to participate in the study was used. Patients after successful ablation procedure (mainly radiofrequency ablation) were included in the group non-AF in 6 weeks after procedure if cardiac rhythm is sinus. All patients were divided into two groups depending on criteria of poor glycemic control (HbA1c &amp;lt; 6.9% and ≥7.0%, respectively). Hemodynamics features, conventional biochemistry parameters and EVs measure were performed at the baseline. Flow cytometry was performed according to conventional protocol with FMO standards to detect and measure EVs. Results Circulating levels of CD235a+ PS+ erythrocytes-derived vesicles differed amongst T2DM patients depending on HF presentation when compared with healthy volunteers (Figure 1). Figure 2 illustrated the differences in circulating amount of CD235a+ PS+ RBC-derived vesicles in AF and non-AF patients with T2DM and HF depending on glycaemia control. There were significantly lower levels of CD235a+ PS+ RBC-derived vesicles were detected in those with HbA1c &amp;lt; 6.9% than in patients with HbA1c ≥ 7.0%. To note, there were no significant differences in circulating amount of CD235a+ PS+ erythrocytes-derived vesicles between patients in entire cohort (p = 0.24) and in non-AF sub-cohort (p = 0.40) with HbA1c &amp;lt; 6.9% and HbA1c ≥ 7.0%, respectively. The Receive Operation Characteristics curve analysis revealed that the well-balanced cut-off point for circulating amount of CD235a+ PS+ erythrocytes-derived vesicles (HbA1c ≥ 7.0% versus HbA1c &amp;lt; 6.9%) were 545 particles in µL (area under curve = 0.91, sensitivity = 74.2%, specificity = 90.3%; p = 0.0001). Multivariate linear regression yielded that NT-proBNP (OR = 1.07; 95% CI = 1.02–1.10, p = 0.04) and CD235a+ PS+ erythrocytes-derived vesicles ≥ 545 particles in µL (OR = 1.06; 95% CI = 1.01–1.11, p = 0.044) remained independent predictors for HbA1c ≥ 7.0%. Conclusion Poor glycaemia control is associated with elevated levels of CD235a+ PS+ EVs, which were found to be independent predictor for AF presentation in T2DM patients with HF.Circulating levels of EVsEVs in AF and non-AF patients

Platelet hyperresponsiveness and increased platelet-neutrophil aggregates in dogs with myxomatous mitral valve disease and pulmonary hypertension.

Pulmonary hypertension (PH) in dogs with myxomatous mitral valve disease (MMVD) is caused by increased pulmonary venous pressure. Thrombosis, vascular remodeling, and vasoconstriction mediated by platelets could exacerbate PH. Dogs with PH will exhibit a hypercoagulable state, characterized by increased platelet activation, platelet-leukocyte, and platelet-neutrophil aggregate formation. Eleven dogs (≥3.5 kg) diagnosed with MMVD and PH and 10 dogs with MMVD lacking PH. Prospective cohort ex vivo study. All dogs underwent echocardiographic examination, CBC, 3-view thoracic radiographs, and heartworm antigen testing. Severity of PH and MMVD were assessed by echocardiography. Viscoelastic monitoring of coagulation was assessed using thromboelastography (TEG). Platelet activation and platelet-leukocyte/platelet-neutrophil interactions were assessed using flow cytometry. Plasma serotonin concentrations were measured by ELISA. Unstimulated platelets from dogs with MMVD and PH expressed more surface P-selectin than MMVD controls (P = .03). Platelets from dogs with MMVD and PH had persistent activation in response to agonists. The number of platelet-leukocyte aggregates was higher in dogs with MMVD and PH compared with MMVD controls (P = .01). Ex vivo stimulation of whole blood resulted in higher numbers of platelet-neutrophil aggregates in dogs with MMVD and PH (P = .01). Assessment of hypercoagulability based on TEG or plasma serotonin concentrations did not differ between groups. Platelet hyperresponsiveness and increased platelet-neutrophil interaction occur in dogs with MMVD and PH, suggesting that platelets play a role of in the pathogenesis of PH. Clinical benefits of antiplatelet drugs in dogs with MMVD and PH require further investigation.

Effect of Heat Exposure on Inflammation and Platelet Activity in Adults with Heart Disease

INTRODUCTION: Extreme heat events are associated with a greater risk of cardiovascular mortality, especially in adults with pre-existing heart disease. The pathophysiological mechanisms mediating these relationships remain unknown. One proposed mechanism, supported by pre-clinical studies employing heat stroke models of severe body hyperthermia, is that heat exposure causes an inflammatory response leading to platelet activation and clot formation. It remains unknown if milder body hyperthermia, such as the one experienced during exposure to a hot environment, elicits an inflammatory response and/or increases platelet activity in adults living with heart disease.OBJECTIVES &amp; HYPTOHESES: To assess whether exposure to a hot and humid environment (1) increases circulating concentrations of inflammatory cytokines and (2) induces platelet activation in adults with heart disease.METHODOLOGY: Adults living with coronary artery disease (67±8 years; 13M/2F) sat within a climate chamber maintained at 38°C and 50% humidity for 3h. Core (rectal) and skin temperatures were measured continuously. Blood samples were drawn before and 2.5h into heat exposure. The blood samples were analyzed for IL-6, IL-8, IL-18, TNFα and IL-1β (multiplexed bead-based immunoassay). Platelet aggregation was measured by impedance (Multiplate assay) induced with ADP (6.5 μM), TRAP (15 μM) and collagen (1.5 μg/ml). The total-thrombus analysis system (T-TAS, PL-CHIP) was used to measure thrombus onset time and total thrombogenicity.RESULTS: Core and skin temperatures increased by 0.35 ± 0.24°C and 4.85 ± 0.84°C, respectively (p&lt;0.05). There were no changes (Δpost-pre) in IL-6 (0.31 ± 1.91 pg/ml, p=0.60), IL-18 (-10.29 ± 21.01 pg/ml, p=0.16), IL-8 (1.10 ± 2.39 pg/ml, p=0.18), TNFα (-1.12 ± 4.10 pg/ml, p =0.39), or IL-1β (0.53 ± 2.36 pg/ml, p=0.48) during heat exposure. Moreover, heat exposure did not increase platelet activation in response to ADP (-8.31 ± 33.70 U, p=0.34), TRAP (16.19 ± 36.54 U, p=0.10), or collagen (-9.19 ± 30.31 U, p=0.24). Lastly, there was no change in thrombus onset time (2.18 ± 37.31 s, p=0.850) or total thrombogenicity (2.8 ± 168.7 PL-AUC, p=0.90).CONCLUSION: These results suggest that inflammation predisposing to thrombus formation may not contribute to the greater cardiac risk associated with short-term exposure to humid heat. Canadian Institutes for Health Research. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 2097: Jak2 V617f Clonal Hematopoiesis Promotes Arterial Thrombosis Via Platelet Activation And Cross-talk

JAK2 V617F ( JAK2 VF ) clonal hematopoiesis (CH) is associated with a marked increase in atherothrombotic cardiovascular disease (CVD). The role of JAK2 VF CH in arterial thrombosis has not been assessed. Using mice simulating JAK2 VF CH, we showed accelerated carotid artery thrombosis, with increased platelet counts and activation and increased leukocytes and red blood cells. There was increased platelet activation in both Jak2 VF and wild type (WT) platelets in Jak2 VF CH suggesting cross-talk between mutant and WT platelets. To assess platelet-specific effects, we used Gp1ba-Cre (VFGp1ba) to selectively express Jak2 VF in platelets. VFGp1ba increased platelet counts to a similar level as in 20% Jak2 VF CH mice but had no effect on leukocyte counts. Like Jak2 VF CH, VFGp1ba increased platelet activation and accelerated arterial thrombosis. Mechanistically, Jak2 VF platelets showed 2.8-fold up-regulation of COX-1, increased activation of cytosolic phospholipase A2, an enzyme important for arachidonic acid generation, and increased thromboxane A2 production. Conditioned media from activated Jak2 VF platelets induced WT platelet activation that was reversed by a thromboxane receptor antagonist. Low dose aspirin ameliorated carotid thrombosis in VFGp1ba and Jak2 VF CH but not in WT control mice. This study shows increased arterial thrombosis in Jak2 VF CH related to Jak2 VF platelet activation and cross-talk with WT platelets via thromboxane, suggesting a potential beneficial role of aspirin treatment in JAK2 VF CH.

An Evaluation of Platelet Indices in Newly Diagnosed Cases of Acute Myocardial Infarction

Acute myocardial infarction (AMI) is characterized by prothrombotic phenotype associated with endothelial dysfunction, an increase in platelet activation and systemic inflammation. Platelet aggregation and activation are crucial in the formation of thrombi and acceleration of atherosclerosis, associated with unstable angina, sudden cardiac death is brought on by an acute myocardial infarction. Objective: To evaluate the platelet-indices in newly diagnosed cases of acute myocardial infarction. Methods: This cross-sectional study was conducted during November 2022 to December 2023 in Pathology Department of Sheikh Zayed Medical College/Hospital Rahim Yar Khan. Samples were collected from the patients of AMI admitted to Emergency Ward and from healthy controls as well. Complete Blood Count (CBC) with platelet indices, platelet count, Mean Platelet Volume (MPV), Platelet Crit (PCT) and Platelet Distribution Width (PDW) were investigated on five-part automated hematology analyzer BT-PRO 2300. Analysis of the data was done by using SPSS version 20.0. Results: Total 140 patients were divided into a healthy control group (70) and newly diagnosed cases of acute myocardial infarction (70). Among diagnosed cases of AMI 46 (65.7%) had ST-elevation myocardial infarction (STEMI) and 24 cases (34.2%) got non-ST-elevation myocardial infarction (NSTEMI). It was found that AMI patients had lower platelet counts and PCT with higher MPV and PDW. Conclusions: It was concluded that the platelet indices (PDW, and PCT, MPV) are significant predictors of myocardial infarction. They might be applied as an easy, reliable, and economical way to anticipate an impending acute coronary event.

Platelets retain function and can be stored following disruption of human leucocyte antigens.

Antibodies to human leucocyte antigen (HLA) Class-I antigens can lead to refractoriness to platelet transfusion. Although this can be overcome by transfusion of HLA-compatible platelets, they are not always available. Disruption of HLA antigens on platelets by acid treatment may be a suitable alternative when no other components are available. The aim of this study was to assess the effect of HLA disruption and subsequent storage of platelet components. Platelet components were treated with 0.9% saline or citric acid solution (pH 3.0), and then stored until expiry (Day 7). HLA and platelet glycoprotein expression, platelet viability, activation and sialylation were measured by flow cytometry. Release of soluble factors was measured by ELISA and metabolism by biochemistry analyser. Reactivity to patient anti-sera containing anti-HLA antibodies was measured using platelet immunofluorescence tests (PIFTs) and monoclonal antibody immobilization of platelet antigen (MAIPA) assays. Platelet function was measured using aggregometry and thromboelastography (TEG). Acid treatment reduced detection of HLA Class-I on platelets by 75%, with significant reductions in reactivity to patient anti-sera. Acid treatment reduced platelet content and viability, increased platelet activation and accelerated metabolism. Glycan cleavage was increased by acid treatment. Treatment reduced platelet activation following agonist stimulation by ADP and TRAP-6, but platelets remained functional, displaying increased aggregation response and reduced time to clot formation by TEG. Although HLA disruption had some detrimental effects, acid-treated platelets remained functional, retaining their capacity to respond to agonists and form clots, and with further development could be used to support refractory patients.

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.

Off-target effect of high-dose sildenafil on adenosine 5'- diphosphate and collagen-induced platelet activation through mitogen-activated protein kinase pathway in treated BALB/C mice and in vitro experiments: A preliminary study.

Sildenafil, a common over-the-counter pill often self-administered at high doses for erectile dysfunction, has been reported to rarely cause prothrombotic events and sudden cardiac death in a few case reports. Therefore, we investigated the in vitro and in vivo effect of sildenafil treatment and dosage on platelet activation and mitogen-activated protein kinase (MAPK) phosphorylation. BALB/C mice were segregated into four groups, each having four mice each (control, low [3.25 mg/kg], medium [6.5 mg/kg], and high [13 mg/kg] sildenafil), and after the treatment, blood was drawn from each mouse and washed platelets prepared. Washed platelets were incubated with CD41 PE-Cy7 and Phospho-p38 MAPK PE antibodies and analyzed using a flow cytometer for platelet activation and adenosine 5'- diphosphate (ADP)/collagen-induced MAPK phosphorylation. Washed platelets obtained from the venous blood of 18 human volunteers, were incubated with PAC-1 FITC and Phospho-p38 MAPK PE antibodies, and platelet activation (ADP and collagen), followed by flow cytometry analysis. There was a significant increase in both platelet activation as well as MAPK phosphorylation in the presence of collagen in the high-dose (13 mg/kg) sildenafil group (P = 0.000774). Further, increased platelet activation was observed in samples that were treated with high-dose sildenafil as compared to the untreated samples (P < 0.00001). These studies show the risk of prothrombotic episodes in patients on high-dose sildenafil (100 mg), in those with even mild endothelial dysfunction due to ADP, and collagen-induced platelet activation through MAPK phosphorylation, which was not seen in the low-and intermediate-dose cohorts.