Platelet proteome changes associated with diabetes and during platelet storage for transfusion

Current Strategies to Guide the Antiplatelet Therapy in Acute Coronary Syndromes

The role of antiplatelet therapy in patients with acute coronary syndromes is a moving target with considerable novelty in the last few years. The pathophysiological basis of the treatment depends on platelet biology and physiology, and the interplay between these aspects and clinical practice must guide the physician in determining the best therapeutic options for patients with acute coronary syndromes. In the present narrative review, we discuss the latest novelties in the antiplatelet therapy of patients with acute coronary syndromes. We start with a description of platelet biology and the role of the main platelet signal pathways involved in platelet aggregation during an acute coronary syndrome. Then, we present the latest evidence on the evaluation of platelet function, focusing on the strengths and weaknesses of each platelet's function test. We continue our review by describing the role of aspirin and P2Y12 inhibitors in the treatment of acute coronary syndromes, critically appraising the available evidence from clinical trials, and providing current international guidelines and recommendations. Finally, we describe alternative therapeutic regimens to standard dual antiplatelet therapy, in particular for patients at high bleeding risk. The aim of our review is to give a comprehensive representation of current data on antiplatelet therapy in patients with acute coronary syndromes that could be useful both for clinicians and basic science researchers to be up-to-date on this complex topic.

Association of blood donor characteristics with in vitro platelet storage properties

BACKGROUND AND OBJECTIVE

The study was planned to determine the association of blood donor characteristics with in vitro quality of platelets.

MATERIAL AND METHODS

In the prospective observational study, a total of 85 male whole blood donors in the age group of 18-30 and 45-65 years were enrolled using purposive sampling method. Serum total cholesterol, glycosylated hemoglobin (HbA1c), and LDH levels were performed on donor pre-donation sample. Buffy coat platelet concentrates were prepared from 450 mL quadruple blood bags. Samples from platelets were taken on day one and five of storage and biochemical properties were observed.

RESULTS

Median MPV was higher in platelets from older blood donors on day five (9.8 vs 9.4, p = 0.037). Median LDH levels were also higher in platelets on day one and five from older donors (Day one: 204.5 vs 147, p = <0.000; day five: 278 vs 224, p = 0.001 respectively). Platelets from donors with high HbA1c levels had lower median pH (Day one: 7.31 vs 7.37, p = 0.024) and higher median glucose levels on day one of storage (Day one: 358 vs 311, p = 0.001). Higher median lactate levels throughout the storage period were also seen in platelets from donors with higher HbA1c levels (Day one: 7 vs 5.7, p = 0.037; Day five: 16 vs 12.2, p = 0.032). Glucose consumption (108 vs 66, p = 0.025) and lactate production (9 vs 6.4, p = 0.019) was higher in platelets from donors with higher HbA1c levels.

CONCLUSION

In vitro platelet storage properties are affected by blood donor characteristics.

Extracellular vesicles: effectors of transfusion-related acute lung injury

Respiratory transfusion reactions represent some of the most severe adverse reactions related to receiving blood products. Of those, transfusion-related acute lung injury (TRALI) is associated with elevated morbidity and mortality. TRALI is characterized by severe lung injury associated with inflammation, pulmonary neutrophil infiltration, lung barrier leak, and increased interstitial and airspace edema that cause respiratory failure. Presently, there are few means of detecting TRALI beyond clinical definitions based on physical examination and vital signs or preventing/treating TRALI beyond supportive care with oxygen and positive pressure ventilation. Mechanistically, TRALI is thought to be mediated by the culmination of two successive proinflammatory hits, which typically comprise a recipient factor (1st hit-e.g., systemic inflammatory conditions) and a donor factor (2nd hit-e.g., blood products containing pathogenic antibodies or bioactive lipids). An emerging concept in TRALI research is the contribution of extracellular vesicles (EVs) in mediating the first and/or second hit in TRALI. EVs are small, subcellular, membrane-bound vesicles that circulate in donor and recipient blood. Injurious EVs may be released by immune or vascular cells during inflammation, by infectious bacteria, or in blood products during storage, and can target the lung upon systemic dissemination. This review assesses emerging concepts such as how EVs: 1) mediate TRALI, 2) represent targets for therapeutic intervention to prevent or treat TRALI, and 3) serve as biochemical biomarkers facilitating TRALI diagnosis and detection in at-risk patients.

In Vitro Exposure to Glucose Alters the Expression of Phosphorylated Proteins in Platelets

Diabetes mellitus (DM) is a pro-thrombotic state that can potentially cause serious cardiovascular complications. Platelet hyperactivation plays an important role in these pathological processes, however there is little or no information on the effect of hyperglycemia on platelet proteins. The aim of this study was to identify the molecular targets associated with platelet reactivity under hyperglycemia. Towards this goal, we examined the effects of the exposure of platelets to 1 and 2 h glucose (300 mg/dL) and control (vehicle and osmolality control using mannitol) on platelet proteins (n = 4 samples per group) using two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) combined with MALDI-TOF/TOF tandem mass spectrometry. Two-hour exposure to glucose significantly up-regulated the expression of ATP synthase subunit beta, filamin-A, and L-lactate dehydrogenase A chain in platelets. Pro-Q Diamond staining confirmed the effect of 2 h glucose on vinculin, heat shock protein HSP 90-alpha, filamin-A, and fructose-bisphosphate aldolase A (platelet phosphorylated proteins). The identified proteins are involved in various cellular processes and functions and possibly in platelet reactivity under hyperglycemic conditions.

Resveratrol; a Double-Edged Sword Antioxidant Agent for Preserving Platelet Cell Functions During Storage; Molecular Insights

Background

In the current study we have aimed to find the effects of Resveratrol treatment on platelet concentrates (PCs) at the dose dependent manner. We have also attempted to find the molecular mechanism of the effects.

Methods

The PCs, have received from Iranian blood transfusion organization (IBTO). Totally 10 PCs were studied. The PCs divided into 4 groups including untreated (control) and treated by different dose of Resveratrol; 10, 30 and 50 µM. Platelet aggregation and total reactive oxygen species (ROS) levels were evaluated at day 3 of PCs storage. In silico analysis was carried out to find out the potential involved mechanisms.

Results

The aggregation against collagen has fallen dramatically in all studied groups but at the same time, aggregation was significantly higher in the control versus treated groups (p<0.05). The inhibitory effect was dose dependent. The aggregation against Ristocetin did not significantly affect by Resveratrol treatment. The mean of total ROS significantly increased in all studied groups except those PCs treated with 10 µM of Resveratrol (P=0.9). The ROS level significantly increased with increasing Resveratrol concentration even more than control group (slope=11.6, P=0.0034). Resveratrol could potently interact with more than 15 different genes which, 10 of them enrolled in cellular regulation of the oxidative stress.

Conclusions

Our findings indicated that the Resveratrol affect the platelet aggregation at the dose dependent manner. Moreover, we have also found that the Resveratrol play as double-edged sword in the controlling oxidative state of the cells. Therefore, Using the optimal dose of Resveratrol is the great of importance.

DAMPS and complement activation in platelet concentrates that induce adverse reactions in patients

BACKGROUND

Patients with severe thrombocytopenia due to bone marrow failure and after chemotherapy are still treated with platelet transfusions. Platelet concentrates (PC) are associated with a high incidence of adverse reactions (AR). Platelet-derived damage-associated molecular patterns (DAMPS) and complement were proposed to play a role in the pathology of AR.

STUDY DESIGN AND METHODS

Single donor apheresis platelet concentrates (SDA PCs) were produced in a regional setting of the French Blood Establishment. After transfusion samples were collected from PC and possible AR in patients were recorded. Platelet activation markers, High mobility group box 1 (HMGB1) and complement activation products (CAP) were measured. The correlation between platelet activation, and HMGB1 and complement activation was analyzed.

RESULTS

A total of 56 PC were included in the study. 30 PC induced no AR, and 26 induced AR (Febrile non-hemolytic transfusion reaction n = 16; Atypical Allergic Transfusion Reactions n = 11; hemodynamic instability n = 5) in the patients. The levels of P-selectin, sCD40L, HMGB1, C3b/c, and C4b/c were all significantly increased in PC that induced AR following transfusion in patients. Additionally, HMGB1, C3b/c, and C4b/c were positively correlated with P-selectin and sCD40L.

CONCLUSION

In this study, we observed an association between HMGB1 and CAP and the incidence of AR. Furthermore, we demonstrated that both HMGB1 and complement activation were correlated to platelet activation.

Functional annotation and enrichment analysis of differentially expressed serum proteins in patients with type 2 diabetes after dapagliflozin

BACKGROUND

Only 50% of patients with type 2 diabetes mellitus (T2DM) can control their blood glucose levels. Dapagliflozin is a selective inhibitor of sodium-glucose co-transporter 2 (SGLT-2) that improves the insulin sensitivity of the liver and peripheral tissues. Many studies confirmed that SGLT2 inhibitors reduce blood glucose and have multiple beneficial effects such as weight loss, lipid regulation, and kidney protection. Nevertheless, the mechanisms of the renal and cardiovascular protective effects of dapagliflozin from the perspective of differentially expressed proteins in the serum of T2DM patients have not been intensively explored so far.

AIM

To identify differentially expressed proteins associated with dapagliflozin treatment in patients with T2DM.

METHODS

Twenty T2DM patients [hemoglobin A1c (HbA1c) 7.0%-10.0%] were enrolled at The Affiliated Hospital of Inner Mongolia Medical University between January 1, 2017 and December 1, 2018. They received dapagliflozin (10 mg/d) for 3 mo, and the HbA1c < 7.0% target was achieved. The changes in clinical indexes were compared before and after treatments. Label-free quantitative proteomics was used to identify differentially expressed proteins using the serum samples of five patients. The identified differentially expressed proteins were analyzed using various bioinformatics tools.

RESULTS

Dapagliflozin significantly improved the clinical manifestation of the patients. There were 18 downregulated proteins and one upregulated protein in the serum samples of patients after dapagliflozin administration. Bioinformatics analyses, including subcellular localization, EuKaryotic Orthologous Groups, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes annotations, were used to profile the biological characteristics of the 19 differentially expressed proteins. Based on the literature and function enrichment analysis, two downregulated proteins, myeloperoxidase (MPO) and alpha II B integrin (ITGA2B), and one upregulated protein, podocalyxin (PCX), were selected for enzyme linked immunosorbent assay validation. These validated differentially expressed proteins had multiple correlations with clinical indexes, including HbAc1 and fasting C-peptide.

CONCLUSION

Dapagliflozin has hypoglycemic effects and regulates the serum expressions of MPO, ITGA2B, and PCX, possibly contributing to the effects of dapagliflozin on oxidative stress, insulin resistance, and lipid metabolism.

The canine activated platelet secretome (CAPS): A translational model of thrombin-evoked platelet activation response

BACKGROUND

Domestic dogs represent a translational animal model to study naturally occurring human disease. Proteomics has emerged as a promising tool for characterizing human platelet pathophysiology; thus a detailed characterization of the core canine activated platelet secretome (CAPS) will enhance utilization of the canine model. The objectives of this study were development of a robust, high throughput, label-free approach for proteomic identification and quantification of the canine platelet (i) thrombin releasate proteins, and (ii) the protein subgroup that constitutes CAPS.

METHODS

Platelets were isolated from 10 healthy dogs and stimulated with 50 nmol/L of γ-thrombin or saline. Proteins were in-solution trypsin-digested and analyzed by nano-liquid chromatography-tandem spectrometry. Core releasate proteins were defined as those present in 10 of 10 dogs, and CAPS defined as releasate proteins with a significantly higher abundance in stimulated versus saline controls (corrected P < .05).

RESULTS

A total of 2865 proteins were identified; 1126 releasate proteins were present in all dogs, 650 were defined as CAPS. Among the differences from human platelets were a canine lack of platelet factor 4 and vascular endothelial growth factor C, and a 10- to 20-fold lower concentration of proteins such as haptoglobin, alpha-2 macroglobulin, von Willebrand factor, and amyloid-beta A4. Twenty-eight CAPS proteins, including cytokines, adhesion molecules, granule proteins, and calcium regulatory proteins have not previously been attributed to human platelets.

CONCLUSIONS

CAPS proteins represent a robust characterization of a large animal platelet secretome and a novel tool to model platelet physiology, pathophysiology, and to identify translational biomarkers of platelet-mediated disease.

Evaluation of platelet activation in leukocyte-depleted platelet concentrates during storage

Structural and functional changes in platelets during storage can lead to the loss of platelet reactivity and response. Our aim was to evaluate leukocyte-depleted platelet concentrates on storage days 0, 3 and 5, obtained by in-line filtration. In non-filtered platelet concentrates (NF-PC) group, 180 whole blood units were collected with quadruple blood bags and then compared to another group of 180 whole blood units (leukocyte-depleted platelet concentrates [LD-PC]), collected in Imuflex Whole Blood Filter Saving Platelets (WB-SP) bags with an integrated leukoreduction filter, with regard to the platelet quality and characteristics. The efficacy of the two techniques for platelet concentrate preparation was evaluated by white blood cell (WBC) and platelet count on day 0. The partial pressure of oxygen (pO2), pH, platelets positive for P-selectin (CD62P), CD63, cluster of differentiation 42b (CD42b), phosphatidylserine (PS), and mitochondrial membrane potential (MMP) were analyzed during the storage in both groups. A significantly lower WBC count and higher platelet count was observed in LD-PC compared to NF-PC group, indicating the overall efficacy of the first technique. During the 5-day storage, pH and pO2 decreased in both groups. In LD-PC group, higher pH, increased pO2 and decreased platelet surface expression of CD62P, CD63 and PS were observed compared to NF-PC group. In both groups, the percentage of CD42b positive platelets and MMP did not change significantly during the 5-day period. The assessment of different markers of platelet activation may be an effective tool in evaluating the quality of platelets during storage. A better understanding of platelet activation may provide new insights for developing a novel therapeutic approach in the manipulation of platelet aggregation.

Temperature effects on the activity, shape, and storage of platelets from 13-lined ground squirrels

The objective of this study is to determine how a hibernating mammal avoids the formation of blood clots under periods of low blood flow. A microfluidic vascular injury model was performed to differentiate the effects of temperature and shear rate on platelet adhesion to collagen. Human and ground squirrel whole blood was incubated at 15 or 37 °C and then passed through a microfluidic chamber over a 250-µm strip of type I fibrillar collagen at that temperature and the shear rates of 50 or 300 s^-1 to simulate torpid and aroused conditions, respectively. At 15 °C, both human and ground squirrel platelets showed a 90-95% decrease in accumulation on collagen independent of shear rate. At 37 °C, human platelet accumulation reduced by 50% at 50 s^-1 compared to 300 s^-1, while ground squirrel platelet accumulation dropped by 80%. When compared to platelets from non-hibernating animals, platelets from animals collected after arousal from torpor showed a 60% decrease in binding at 37 °C and 300 s^-1, but a 2.5-fold increase in binding at 15 °C and 50 s^-1. vWF binding in platelets from hibernating ground squirrels was decreased by 50% relative to non-hibernating platelets. The source of the plasma that platelets were stored in did not affect the results indicating that the decreased vWF binding was a property of the platelets. Upon chilling, ground squirrel platelets increase microtubule assembly leading to the formation of long rods. This shape change is concurrent with sequestration of platelets in the liver and not the spleen. In conclusion, it appears that ground squirrel platelets are sequestered in the liver during torpor and have reduced binding capacity for plasma vWF and lower accumulation on collagen at low shear rates and after storage at cold temperatures, while still being activated by external agonists. These adaptations would protect the animals from spontaneous thrombus formation during torpor but allow them to restore normal platelet function upon arousal.

Erythrocyte and platelet proteomics in hematological disorders

Erythrocytes undergo ineffective erythropoesis, hemolysis, and premature eryptosis in sickle cell disease and thalassemia. Abnormal hemoglobin variants associated with hemoglobinopathy lead to vesiculation, membrane instability, and loss of membrane asymmetry with exposal of phosphatidylserine. This potentiates thrombin generation resulting in activation of the coagulation cascade responsible for subclinical phenotypes. Platelet activation also results in the release of microparticles, which express and transfer functional receptors from platelet membrane, playing key roles in vascular reactivity and activation of intracellular signaling pathways. Over the last decade, proteomics had proven to be an important field of research in studies of blood and blood diseases. Blood cells and its fluidic components have been proven to be easy systems for studying differential expressions of proteins in hematological diseases encompassing hemoglobinopathies, different types of anemias, myeloproliferative disorders, and coagulopathies. Proteomic studies of erythrocytes and platelets reported from several groups have highlighted various factors that intersect the signaling networks in these anucleate systems. In this review, we have elaborated on the current scenario of anucleate blood cell proteomes in normal and diseased individuals and the cross-talk between the two major constituent cell types of circulating blood.

Combining patient proteomics and in vitro cardiomyocyte phenotype testing to identify potential mediators of heart failure with preserved ejection fraction

BACKGROUND

Heart failure with ejection fraction (HFpEF) is a syndrome resulting from several co-morbidities in which specific mediators are unknown. The platelet proteome responds to disease processes. We hypothesize that the platelet proteome will change composition in patients with HFpEF and may uncover mediators of the syndrome.

METHODS AND RESULTS

Proteomic changes were assessed in platelets from hospitalized subjects with symptoms of HFpEF (n = 9), the same subjects several weeks later without symptoms (n = 7) and control subjects (n = 8). Mass spectrometry identified 6102 proteins with five scans with peptide probabilities of ≥0.85. Of the 6102 proteins, 165 were present only in symptomatic subjects, 78 were only found in outpatient subjects and 157 proteins were unique to the control group. The S100A8 protein was identified consistently in HFpEF samples when compared with controls. We validated the fining that plasma S100A8 levels are increased in subjects with HFpEF (654 ± 391) compared to controls (352 ± 204) in an external cohort (p = 0.002). Recombinant S100A8 had direct effects on the electrophysiological and calcium handling profile in human induced pluripotent stem cell-derived cardiomyocytes.

CONCLUSIONS

Platelets may harbor proteins associated with HFpEF. S100A8 is present in the platelets of subjects with HFpEF and increased in the plasma of the same subjects. We further established a bedside-to-bench translational system that can be utilized as a secondary screen to ascertain whether the biomarkers may be an associated finding or causal to the disease process. S100A8 has been linked with other cardiovascular disease such as atherosclerosis and risk for myocardial infarction, stroke, or death. This is the first report on association of S100A8 with HFpEF.

Resveratrol preserves the function of human platelets stored for transfusion

Stored platelets undergo biochemical, structural and functional changes that lead to decreased efficacy and safety of platelet transfusions. Not only do platelets acquire markers of activation during storage, but they also fail to respond normally to agonists post-storage. We hypothesized that resveratrol, a cardioprotective antioxidant, could act as a novel platelet storage additive to safely prevent unwanted platelet activation during storage, while simultaneously preserving normal haemostatic function. Human platelets treated with resveratrol and stored for 5 d released less thromboxane B2 and prostaglandin E2 compared to control platelets. Resveratrol preserved the ability of platelets to aggregate, spread and respond to thrombin, suggesting an improved ability to activate post-storage. Utilizing an in vitro model of transfusion and thromboelastography, clot strength was improved with resveratrol treatment compared to conventionally stored platelets. The mechanism of resveratrol's beneficial actions on stored platelets was partly mediated through decreased platelet apoptosis in storage, resulting in a longer half-life following transfusion. Lastly, an in vivo mouse model of transfusion demonstrated that stored platelets are prothrombotic and that resveratrol delayed vessel occlusion time to a level similar to transfusion with fresh platelets. We show resveratrol has a dual ability to reduce unwanted platelet activation during storage, while preserving critical haemostatic function.

Platelet transfusion - the new immunology of an old therapy

Platelet transfusion has been a vital therapeutic approach in patients with hematologic malignancies for close to half a century. Randomized trials show that prophylactic platelet transfusions mitigate bleeding in patients with acute myeloid leukemia. However, even with prophylactic transfusions, as many as 75% of patients, experience hemorrhage. While platelet transfusion efficacy is modest, questions and concerns have arisen about the risks of platelet transfusion therapy. The acknowledged serious risks of platelet transfusion include viral transmission, bacterial sepsis, and acute lung injury. Less serious adverse effects include allergic and non-hemolytic febrile reactions. Rare hemolytic reactions have occurred due to a common policy of transfusing without regard to ABO type. In the last decade or so, new concerns have arisen; platelet-derived lipids are implicated in transfusion-related acute lung injury after transfusion. With the recognition that platelets are immune cells came the discoveries that supernatant IL-6, IL-27 sCD40L, and OX40L are closely linked to febrile reactions and sCD40L with acute lung injury. Platelet transfusions are pro-inflammatory, and may be pro-thrombotic. Anti-A and anti-B can bind to incompatible recipient or donor platelets and soluble antigens, impair hemostasis and thus increase bleeding. Finally, stored platelet supernatants contain biological mediators such as VEGF and TGF-β1 that may compromise the host versus tumor response. This is particularly of concern in patients receiving many platelet transfusions, as for acute leukemia. New evidence suggests that removing stored supernatant will improve clinical outcomes. This new view of platelets as pro-inflammatory and immunomodulatory agents suggests that innovative approaches to improving platelet storage and pre-transfusion manipulations to reduce toxicity could substantially improve the efficacy and safety of this long-employed therapy.

Proteomic analysis of venous thromboembolism: an update

Venous thromboembolism is a complex, multifactorial disorder, the pathogenesis of which typically involves a variety of inherited or acquired factors. The multifactorial etiology of this disease and the partial correlation between genotype and prothrombotic phenotype limit greatly the value of genetic analysis in assessing thrombotic risk. The integration of several new 'omics' techniques enables a multifaceted and holistic approach to the study of venous thrombotic processes and pave the way to the search and identification of novel blood biomarkers and/or effectors of thrombus formation that can also be the possible future target of new anticoagulant and thrombolytic therapies for more personalized medicine. This review provides a comprehensive overview of the latest candidate proteomic biomarkers of venous thrombosis and of the proteomics studies relevant to its pathophysiology, some of which seem to confirm the existence of a common physiopathological basis for venous thromboembolism and atherothrombosis.

Optimization of platelet concentrate quality: application of proteomic technologies to donor management

Quality management of blood products is essential for blood banking. It is influenced by both processing and donor characteristics and assured by monitoring routine in vitro parameters to defined product specifications. However, these measures correlate poorly with the in vivo behavior of transfused platelets and cannot be used to select optimal donors. Since radiolabeled platelet recovery and survival studies are expensive and time consuming, there is an ongoing search for simpler measures that predict platelet transfusion outcomes. We performed a pilot study using semi-qualitative proteomics to assess changes in the platelet protein profile of donors with either acceptable or unacceptable in vivo radiolabeled autologous platelet recovery and survival measurements. Proteins changing during a 9-day storage period included cytoskeletal elements talin, vinculin and moesin as well as signal transduction proteins 14-3-3, RhoGDI and Rap1. Two of nine donations exhibited a decrease in these proteins and poor in vivo platelet recovery and survival whereas the remaining donors showed acceptable platelet recovery and survival and expected protein profiles. Analyses revealed a significant correlation between protein levels of Rap1 and RhoGDI during storage and platelet recovery and survival. This study provides for the first time preliminary data showing evidence of the utility of protein profiling to predict platelet transfusion quality. This article is part of a Special Issue entitled: Integrated omics.

The hibernating 13-lined ground squirrel as a model organism for potential cold storage of platelets

Hibernating mammals have developed many physiological adaptations to extreme environments. During hibernation, 13-lined ground squirrels (Ictidomys tridecemlineatus) must suppress hemostasis to survive prolonged body temperatures of 4-8°C and 3-5 heartbeats per minute without forming lethal clots. Upon arousal in the spring, these ground squirrels must be able to quickly restore normal clotting activity to avoid bleeding. Here we show that ground squirrel platelets stored in vivo at 4-8°C were released back into the blood within 2 h of arousal in the spring with a body temperature of 37°C but were not rapidly cleared from circulation. These released platelets were capable of forming stable clots and remained in circulation for at least 2 days before newly synthesized platelets were detected. Transfusion of autologous platelets stored at 4°C or 37°C showed the same clearance rates in ground squirrels, whereas rat platelets stored in the cold had a 140-fold increase in clearance rate. Our results demonstrate that ground squirrel platelets appear to be resistant to the platelet cold storage lesions observed in other mammals, allowing prolonged storage in cold stasis and preventing rapid clearance upon spring arousal. Elucidating these adaptations could lead to the development of methods to store human platelets in the cold, extending their shelf life.

Novel targets for platelet inhibition

Atherothrombosis often underlies coronary artery disease, stroke, and peripheral arterial disease. Antiplatelet drugs have come to the forefront of prophylactic treatment of atherothrombotic disease. Dual antiplatelet therapy of aspirin plus clopidogrel-the current standard-has benefits, but it also has limitations with regard to pharmacologic properties and adverse effects with often severe bleeding complications. For these reasons, within the last decade or so, the investigation of novel antiplatelet targets has prospered. Target identification can be the result of large-scale genomic or proteomic studies, functional genomics in animal models, the genetic analysis of patients with inherited bleeding disorders, or a combination of these techniques.

Platelet storage and transfusions: new concerns associated with an old therapy

Platelet transfusion has long been practiced with rudimentary knowledge about optimal storage conditions and their implications for efficacy and, particularly, safety. Recent concerns about complications such as inflammation, thrombosis and altered recipient immunity have been raised about platelet transfusion. This review will discuss recent important findings that have raised these issues about platelet transfusion associated morbidity, mortality and the possible role of platelet storage in these associations.

An integrated proteomics and genomics analysis to unravel a heterogeneous platelet secretion defect

Eight patients with clinical bleeding problems have evidence for platelet storage pool disease as they present with impaired platelet aggregation and secretion with low concentrations of ADP and collagen and an absence of second phase aggregation with epinephrine. Electron microscopy analysis further showed a reduced but not absent amount of platelet dense granules, and CD63 staining was decreased compared to healthy controls. The presence of alpha granules and CD62P expression after platelet activation was normal. This work aimed at identifying differentially expressed proteins in the platelet releasate and its remaining pellet after activation with A23187 and TRAP in patients and controls using DIGE-based proteomic technology. We identified 44 differentially expressed proteins in patients and the altered expression for some of them was confirmed by immunoblot analysis. Most of these proteins belong to the class of cytoskeleton-related proteins. In addition, 29 cytoskeleton-related genes showed an altered expression in platelet mRNA from patients using a real-time PCR array. In conclusion, our study shows that the dense granule secretion defect in patients with platelet storage pool disease is highly heterogeneous with evidence of an underlying cytoskeleton defect.

Immunomodulatory mediators in platelet transfusion reactions

Our appreciation of the roles that platelets play in vascular biology is constantly expanding. One of the major roles of platelets is in initiating and accelerating immune responses. Platelet transfusion may be associated with adverse inflammatory outcomes manifested as fever, discomfort, tachycardia, and respiratory issues. This may in part be due to immune mediators either expressed by activated platelets or released into the platelet media during platelet storage. This review will highlight some more recent knowledge gained regarding the platelet storage lesion and potential mediators of platelet transfusion reactions.

Preparation of platelet concentrates

Platelets are specialized blood cells that play central roles in physiologic and pathologic processes of hemostasis, wound healing, host defense, thrombosis, inflammation, and tumor metastasis. Activation of platelets is crucial for platelet function that includes a complex interplay of adhesion, signaling molecules, and release of bioactive factors. Transfusion of platelet concentrates is an important treatment component for thrombocytopenia and bleeding. Recent progress in high-throughput mRNA and protein profiling techniques has advanced the understanding of platelet biological functions toward identifying novel platelet-expressed and secreted proteins, analyzing functional changes between normal and pathologic states, and determining the effects of processing and storage on platelet concentrates for transfusion. It is important to understand the different standard methods of platelet preparation and how they differ from the perspective for use as research samples in clinical chemistry. Two simple methods are described here for the preparation of research-scale platelet samples from whole blood, and detailed notes are provided about the methods used for the preparation of platelet concentrates for transfusion.

Nuclear emancipation: a platelet tour de force

Mammalian platelets are anucleate cells produced by the polyploid megakaryocyte. Platelets are more than just key players in hemostasis (blood clotting in response to injury); they also have important roles in inflammation, immunity, tumor progression, and thrombosis. Complex systems of homeostasis have been described for platelets, including posttranscriptional and translational mechanisms to regulate platelet function. Platelets contain transcription factors, and these proteins have essential roles in regulating nongenomic processes. A study provides evidence for a previously unknown negative feedback pathway for limiting platelet activation that occurs through the nuclear factor κB transcription factor family. This pathway is mediated by an adenosine 3',5'-monophosphate-independent protein kinase A activity in response to platelet stimulation. Our appreciation of the role of transcription factors in mammalian platelet biology is nascent but holds great promise for both understanding platelet function and translation into clinical uses.

Real-Time Live Confocal Fluorescence Microscopy as a New Tool for Assessing Platelet Vitality

BACKGROUND: Assessment of platelet vitality is important for patients presenting with inherited or acquired disorders of platelet function and for quality assessment of platelet concentrates. METHODS: Herein we combined live stains with intra-vital confocal fluorescence microscopy in order to obtain an imaging method that allows fast and accurate assessment of platelet vitality. Three fluorescent dyes, FITC-coupled wheat germ agglutinin (WGA), tetramethylrhodamine methyl ester perchlorate (TMRM) and acetoxymethylester (Rhod-2), were used to assess platelet morphology, mitochondrial activity and intra-platelet calcium levels. Microscopy was performed with a microlens-enhanced Nipkow spinning disk-based system allowing live confocal imaging. RESULTS: Comparison of ten samples of donor platelets collected before apheresis and platelets collected on days 5 and 7 of storage showed an increase in the percentage of Rhod-2-positive platelets from 3.6 to 47 and finally to 71%. Mitochondrial potential was demonstrated in 95.4% of donor platelets and in 92.5% of platelets stored for 7 days. CONCLUSION: Such fast and accurate visualization of known key parameters of platelet function could be of relevance for studies addressing the quality of platelets after storage and additional manipulation, such as pathogen inactivation, as well as for the analysis of inherited platelet function disorders.

Proteome of platelets in patients with coronary artery disease

OBJECTIVE

This study aimed at investigating the protein patterns of platelets from patients with stable or acute coronary atherosclerosis (CAD), in which platelets play a key role.

MATERIALS AND METHODS

A proteomic approach was adopted to investigate specific protein patterns in platelets of patients with non-ST elevation acute coronary syndrome, stable angina, or of subjects with no history of CAD.

RESULTS

Six differentially expressed proteins were identified: two involved in energy metabolism (2-oxoglutarate dehydrogenase [OGDH], and lactate dehydrogenase [LDH]); three were associated with cytoskeleton-based processes (gamma-actin, coronin 1B, and pleckstrin); and one involved in protein degradation (proteasome subunit type 8). Expression levels of OGDH and a cleaved form of gamma-actin were significantly higher in the platelets of patients than in controls, whereas that of LDH was higher only in the platelets of patients with acute coronary disease. The increases in protein expression of OGDH and LDH are paralleled by changes in their functional activities. Coronin and proteasome subunit type 8 were less expressed in the platelets of patients, as were the basic isoforms of pleckstrin.

CONCLUSION

The platelet proteome is altered in CAD patients with stable or acute coronary syndrome possibly because of the ongoing atherosclerotic process. The identified protein changes not previously connected with CAD were an increase in the energy metabolism enzymes and alterations in the proteins associated with cytoskeleton-based processes, both of which indicate platelet activation.

Proteomics meets blood banking: identification of protein targets for the improvement of platelet quality

Proteomics has brought new perspectives to the fields of hematology and transfusion medicine in the last decade. The steady improvement of proteomic technology is propelling novel discoveries of molecular mechanisms by studying protein expression, post-translational modifications and protein interactions. This review article focuses on the application of proteomics to the identification of molecular mechanisms leading to the deterioration of blood platelets during storage - a critical aspect in the provision of platelet transfusion products. Several proteomic approaches have been employed to analyse changes in the platelet protein profile during storage and the obtained data now need to be translated into platelet biochemistry in order to connect the results to platelet function. Targeted biochemical applications then allow the identification of points for intervention in signal transduction pathways. Once validated and placed in a transfusion context, these data will provide further understanding of the underlying molecular mechanisms leading to platelet storage lesion. Future aspects of proteomics in blood banking will aim to make use of protein markers identified for platelet storage lesion development to monitor proteome changes when alterations such as the use of additive solutions or pathogen reduction strategies are put in place in order to improve platelet quality for patients.

Blood-related proteomics

Blood-related proteomics is an emerging field, recently gaining momentum. Indeed, a wealth of data is now available and a plethora of groups has contributed to add pieces to the jigsaw puzzle of protein complexity within plasma and blood cells. In this review article we purported to sail across the mare magnum of the actual knowledge in this research endeavour. The main strides in proteomic investigations on red blood cells, platelets, plasma and white blood cells are hereby presented in a chronological order. Moreover, a glance is given at prospective studies which promise to shift the focus of attention from the end product to its provider, the donor, in a sort of Kantian "Copernican revolution". A well-rounded portrait of the usefulness of proteomics in blood-related research is accurately given. In particular, proteomic tools could be adopted to follow the main steps of the blood-banking production processes (a comparison of collection methods, pathogen inactivation techniques, storage protocols). Thus proteomics has been recently transformed from a mere basic-research extremely-expensive toy into a dramatically-sensitive and efficient eye-lens to either delve into the depths of the molecular mechanisms of blood and blood components or to establish quality parameters in the blood-banking production chain totally anew.