Platelet activation patterns in platelet size sub-populations: differential responses to aspirin in vitro

Drug delivery and therapeutic impact of extended-release acetylsalicylic acid

Current treatment guidelines recommend once-daily, low-dose acetylsalicylic acid (ASA; aspirin) for secondary prevention of cardiovascular events. However, the anti-thrombotic benefits of traditional ASA formulations may not extend over a 24-h period, especially in patients at high risk for a recurrent cardiovascular event. A next-generation, extended-release ASA formulation (ER-ASA) has been developed to provide 24-h anti-thrombotic coverage with once-daily dosing. The pharmacokinetics of ER-ASA indicates slower absorption and prolonged ASA release versus immediate-release ASA, with a favorable safety profile. ER-ASA minimizes systemic ASA absorption and provides sustained antiplatelet effects over a 24-h period.

The correlation between the metabolic tumor volume and hematological parameters in patients with esophageal cancer

INTRODUCTION

The aim of this study is to evaluate the correlation of the serum neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and mean platelet volume (MPV), with the standardized uptake value (SUVmax), and metabolic tumor volume (MTV) in F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patient with esophageal squamous cell cancer at baseline.

METHODS

PET/CTs were performed in 52 patients with esophageal squamous cell cancer, making up the patient group. An additional 52 patients who underwent endoscopy due to dyspepsia with normal esophagus (as a control group) were included in the study to compare the hematological parameters between the patient groups.

RESULTS

The median age was 60.0 ± 12.8 years (range 39-84 years) for the patients with esophageal cancer, and 56.9 ± 12.3 years for the control group. Statistical differences were found in terms of the neutrophils, lymphocytes, NLR, PLT, PLR, and MPV between the patients with esophageal cancer and the control group. In the correlation analysis, only the NLR was correlated with the MTV for all of the patients (p = 0.013, r = 0.344). The SUVmax was not correlated with these hematological parameters.

CONCLUSION

At baseline neutrophil-to-lymphocyte ratio is associated with the metabolic tumor volume, which was assessed using the PET/CT in patients with esophageal squamous cell cancer. The SUVmax values were not related to these parameters.

Platelet geometry sensing spatially regulates α-granule secretion to enable matrix self-deposition

Although the biology of platelet adhesion on subendothelial matrix after vascular injury is well characterized, how the matrix biophysical properties affect platelet physiology is unknown. Here we demonstrate that geometric orientation of the matrix itself regulates platelet α-granule secretion, a key component of platelet activation. Using protein microcontact printing, we show that platelets spread beyond the geometric constraints of fibrinogen or collagen micropatterns with <5-µm features. Interestingly, α-granule exocytosis and deposition of the α-granule contents such as fibrinogen and fibronectin were primarily observed in those areas of platelet extension beyond the matrix protein micropatterns. This enables platelets to "self-deposit" additional matrix, provide more cellular membrane to extend spreading, and reinforce platelet-platelet connections. Mechanistically, this phenomenon is mediated by actin polymerization, Rac1 activation, and αIIbβ3 integrin redistribution and activation, and is attenuated in gray platelet syndrome platelets, which lack α-granules, and Wiskott-Aldrich syndrome platelets, which have cytoskeletal defects. Overall, these studies demonstrate how platelets transduce geometric cues of the underlying matrix geometry into intracellular signals to extend spreading, which endows platelets spatial flexibility when spreading onto small sites of exposed subendothelium.

Activating stimuli induce platelet microRNA modulation and proteome reorganisation

Platelets carry megakaryocyte-derived mRNAs whose translation efficiency before and during activation is not known, although this can greatly affect platelet functions, both under basal conditions and in response to physiological and pathological stimuli, such as those involved in acute coronary syndromes. Aim of the present study was to determine whether changes in microRNA (miRNA) expression occur in response to activating stimuli and whether this affects activity and composition of platelet transcriptome and proteome. Purified platelet-rich plasmas from healthy volunteers were collected and activated with ADP, collagen, or thrombin receptor activating peptide. Transcriptome analysis by RNA-Seq revealed that platelet transcriptome remained largely unaffected within the first 2 hours of stimulation. In contrast, quantitative proteomics showed that almost half of > 700 proteins quantified were modulated under the same conditions. Global miRNA analysis indicated that reorganisation of platelet proteome occurring during activation reflected changes in mature miRNA expression, which therefore, appears to be the main driver of the observed discrepancy between transcriptome and proteome changes. Platelet functions significantly affected by modulated miRNAs include, among others, the integrin/cytoskeletal, coagulation and inflammatory-immune response pathways. These results demonstrate a significant reprogramming of the platelet miRNome during activation, with consequent significant changes in platelet proteome and provide for the first time substantial evidence that fine-tuning of resident mRNA translation by miRNAs is a key event in platelet pathophysiology.

Elevated serum neutrophil to lymphocyte and platelet to lymphocyte ratios could be useful in lung cancer diagnosis

BACKGROUND

Lung cancer (LC) is still the primary cause of cancer deaths worldwide, and late diagnosis is a major obstacle to improving lung cancer outcomes. Recently, elevated preoperative or pretreatment neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR) and mean platelet volume (MPV) detected in peripheral blood were identified as independent prognostic factors associated with poor survival with various cancers, including colon cancer, esophageal cancer, gastric cancer and breast cancer.

OBJECTIVE

The aim of this study was to examine whether MPV, NLR and PLR could be useful inflammatory markers to differentiate lung cancer patients from healthy controls. An investigation was also made of the relationship between these markers and other prognostic factors and histopathological subgroups.

MATERIALS AND METHODS

Retrospectively eighty-one lung cancer patients and 81 age-sexes matched healthy subjects included into the study. Patients with hypertension, hematological and renal disease, heart failure, chronic infection, hepatic disorder and other cancer were excluded from the study. The preoperative or pretreatment blood count data was obtained from the recorded computerized database.

RESULTS

NLR and PLR values were significantly higher in the LC patients compared to the healthy subjects.( NLR: 4.42 vs 2.45 p=0.001, PLR: 245.1 vs 148.2 p=0.002) MPV values were similar in both groups (7.7 vs 7.8). No statistically significant relationship was determined between these markers (MPV, NLR and PLR) and histopathological subgroups and TNM stages.

CONCLUSIONS

NLR and PLR can be useful biomarkers in LC patients before treatment. Larger prospective studies are required to confirm these findings.

Mean platelet volume (MPV) predicts middle distance running performance

BACKGROUND

Running economy and performance in middle distance running depend on several physiological factors, which include anthropometric variables, functional characteristics, training volume and intensity. Since little information is available about hematological predictors of middle distance running time, we investigated whether some hematological parameters may be associated with middle distance running performance in a large sample of recreational runners.

METHODS

The study population consisted in 43 amateur runners (15 females, 28 males; median age 47 years), who successfully concluded a 21.1 km half-marathon at 75-85% of their maximal aerobic power (VO2max). Whole blood was collected 10 min before the run started and immediately thereafter, and hematological testing was completed within 2 hours after sample collection.

RESULTS

The values of lymphocytes and eosinophils exhibited a significant decrease compared to pre-run values, whereas those of mean corpuscular volume (MCV), platelets, mean platelet volume (MPV), white blood cells (WBCs), neutrophils and monocytes were significantly increased after the run. In univariate analysis, significant associations with running time were found for pre-run values of hematocrit, hemoglobin, mean corpuscular hemoglobin (MCH), red blood cell distribution width (RDW), MPV, reticulocyte hemoglobin concentration (RetCHR), and post-run values of MCH, RDW, MPV, monocytes and RetCHR. In multivariate analysis, in which running time was entered as dependent variable whereas age, sex, blood lactate, body mass index, VO2max, mean training regimen and the hematological parameters significantly associated with running performance in univariate analysis were entered as independent variables, only MPV values before and after the trial remained significantly associated with running time. After adjustment for platelet count, the MPV value before the run (p = 0.042), but not thereafter (p = 0.247), remained significantly associated with running performance.

CONCLUSION

The significant association between baseline MPV and running time suggest that hyperactive platelets may exert some pleiotropic effects on endurance performance.

Clinical applicability of reticulated platelets

BACKGROUND

Reticulated platelets (RPs), immature platelets newly released from the bone marrow into the circulation, have a high content of ribonucleic acid and are larger and more active in thrombus formation.

OBJECTIVE

This review compiles articles that evaluated RP in order to establish their clinical significance.

DISCUSSION

RPs increase when platelet production rises and decrease when production falls. As such, the measurement of circulating RPs allows the assessment of thrombocytopenia, i.e., bone marrow production or peripheral destruction.

CONCLUSION

RPs are a promising laboratory tool for evaluation of idiopathic thrombocytopenia (differentiating hypoproduction from accelerated platelet destruction), chemotherapy and after stem cell transplantation (predicting platelet recovery) and thrombocytosis (estimating platelet turnover). Additional randomized and well controlled clinical studies are required to clearly establish the significance of circulating RPs in other clinical conditions.

Evaluation of hemostaseological status of pigs experimentally infected with African swine fever virus

African swine fever is a highly contagious hemorrhagic disease of pigs caused by African swine fever virus (ASFV). Hemorrhages are the most frequently reported lesions in acute and subacute forms of ASF. Hemorrhagic lesions are accompanied by impaired hemostasis, which includes thrombocytopenia and changes in the coagulation system. In the present study, experimental infection was conducted to elucidate whether a highly virulent ASFV genotype II circulating in the Trans-Caucasus and Eastern Europe affects the hemostasis of infected pigs. Platelet count changes and platelet size, as well as coagulation parameters were evaluated upon experimental infection. In contrast to other ASFV strains, ASFV genotype II showed a significant decrease in the number of platelets from 3rd dpi onwards. Furthermore, a decrease in platelet size was observed throughout the entire period of experiment. A significant increase in the number of platelet aggregates was observed from the beginning of infection. Unlike other ASFV strains, ASFV genotype II induced a slight shortening of an activated partial thromboplastin time (aPTT) throughout the experiment. Thrombin time (TT) was prolonged from day 5 onwards, whereas no changes in prothrombin time (PT) were found upon infection. The level of d-dimers was permanently higher than in control with a peak on day 3 post-infection. ASFV induced a significant decrease in the level of fibrinogen from day 5 till the end of experiment. Thus, it can be concluded that ASFV genotype II isolated in Armenia affects the hemostasis of infected pigs and causes changes that differ from that of other ASFV strains described previously.

Mean platelet volume could be a useful biomarker for monitoring epithelial ovarian cancer

New studies show that inflammatory markers and blood cells may be related to epithelial ovarian cancer (EOC). We aimed to examine whether mean platelet volume would be a useful marker for EOC patients to predict tumour burden and prognosis, and investigate the difference in MPV values between EOC patients and healthy controls. We retrospectively investigated 113 ovarian cancer patients who underwent surgery between January 2008 and July 2012 and 90 healthy subjects. MPV levels were significantly higher in preoperative EOC patients compared with healthy subjects (8.26 fl vs 7.71 fl; p = 0.004). Also NLR and PLR values were significantly higher in EOC patients (NLR, 3.48 vs 2.37; p = 0.000; PLR, 241 vs 148; p = 0.000). Surgical tumour resection resulted in a significant decrease in MPV levels (8.26 fl vs 7.61 fl; p = 0.001). NLR values also decreased after tumour resection significantly similar to CA125 (NLR, 3.48 vs 2.49; p = 0.000). Our data suggests that MPV could be a promising and easily available biomarker for monitoring EOC patients.

An overview of platelet indices and methods for evaluating platelet function in thrombocytopenic patients

Thrombocytopenia is associated with bleeding risk. However, in thrombocytopenic patients, platelet count does not correlate with bleeding risk and other factors are thus likely to contribute to this risk. This review presents currently available platelet-related markers available on automated haematology analysers and commonly used methods for testing platelet function. The test principles, advantages and disadvantages of each test are described. We also evaluate the current literature regarding the clinical utility of the test for prediction of bleeding in thrombocytopenia in haematological and oncological diseases. We find that several platelet-related markers are available, but information about the clinical utility in thrombocytopenia is limited. Studies support that mean platelet volume (MPV) can aid diagnosing the cause of thrombocytopenia and low MPV may be associated with bleeding in thrombocytopenia. Flow cytometry, platelet aggregometry and platelet secretion tests are used to diagnose specific platelet function defects. The flow cytometric activation marker P-selectin and surface coverage by the Cone-and-Plate[let] analyser predict bleeding in selected thrombocytopenic populations. To fully uncover the clinical utility of platelet-related tests, information about the prevalence of platelet function defects in thrombocytopenic conditions is required. Finally, knowledge of the performance in thrombocytopenic samples from patients is essential.

Platelet volume as a parameter for platelet activation in patients with endometrial cancer

The objective of this study was to use mean platelet volume (MPV) as a measure of platelet activation in patients with endometrial adenocarcinoma and healthy controls. There was a total of 310 patients with endometrial adenocarcinoma retrospectively evaluated and 250 healthy controls. Preoperative haemoglobin, platelet counts and mean platelet volume were evaluated and statistical tests were conducted to determine the differences among early and advanced disease groups and controls. Median haemoglobin (13.0 vs 13.3 g/dl) and platelet count (282,000 vs 280,000/μl) values were similar in patients with endometrial adenocarcinoma and healthy controls (p > 0.05). Subjects with endometrial cancer exhibited slightly higher MPV than the control group (8.4 fl vs 8.2 fl) (p = 0.048). In patients with advanced-stage endometrial cancer, haemoglobin was significantly lower (p < 0.05) and MPV was significantly higher (p < 0.05) than in either patients with early-stage endometrial cancer or the control group. It was concluded that MPV was found to be a marker for predicting advanced-stage endometrial cancers.

ASPIRIN RESISTANCE CANDIDATE GENES AND THEIR ASSOCIATION WITH THE RISK OF CARDIOVASCULAR EVENTS

The review presents the current literature evidence on the most likely genetic polymorphisms of aspirin resistance, such as polymorphisms of cyclooxygenase, glycoproteins GP Ib/IIIa, GP Ibα, GP VI, and adenosine diphosphate receptors P2Y1 and P2Y12. The authors discuss the prevalence of these polymorphisms in laboratory and clinical aspirin resistance, as well as their association with the risk of cardiovascular events during aspirin treatment. 

Whole blood impedance aggregometry as a biomarker for the diagnosis and prognosis of severe sepsis

INTRODUCTION

Sepsis leads to an activation of the immune system and hemostatis. However, studies on platelet aggregation in severe sepsis using impedance aggregometry have not been performed and the diagnostic and prognostic capabilities are unknown. In the present study we hypothesized that impedance aggregometry findings might serve as a biomarker for the diagnosis and prognosis of severe sepsis.

METHODS

Eighty patients with severe sepsis and 50 postoperative patients were included in the prospective observational study. Platelet function was determined at the first day of severe sepsis and surgery, respectively, using impedance aggregometry (Multiplate®). Moreover, platelet count, procalcitonin, interleukin 6, C-reactive protein and 30-day mortality were determined.

RESULTS

Compared to postoperative patients, platelet aggregation was significantly reduced in patients with severe sepsis (collagen-test: 70.8 (44.4, 83.2) arbitrary units (A.U.) vs. 26.8 (12.7, 45.8) A.U.; P <0.001; median and quartiles). Furthermore, marked differences in platelet function were observed in survivors and non-survivors of severe sepsis (collagen-test: 33.4 (10.9, 48.8) A.U. vs. 12.4 (6.5, 25.0) A.U.; P = 0.001). Kaplan-Meier analysis demonstrated that higher platelet function was associated with a mortality of 10%, while mortality was 40% when platelet function was low (collagen-test; P = 0.002). The odds ratio was 6.0. In both univariate and multivariate analyses (including procalcitonin, IL6, C-reactive protein and platelet count) impedance aggregometry using collagen as the activator proved to be the best and an independent predictor for the diagnosis and prognosis of severe sepsis in critical illness.

CONCLUSIONS

In severe sepsis, impedance aggregometry allows better prediction of diagnosis and survival than conventional biomarkers and platelet count.

The role of mean platelet volume in predicting thrombotic events

Studies on platelet function have accelerated and gained popularity since the advent of novel treatment modalities and techniques on atherosclerotic vascular disease, such as antiplatelet drugs and stents. Today it is widely known that platelets exert a fundamental role in inflammation in addition to their long known role in homeostasis and thrombotic events. Interaction with endothelial cells and leukocytes mediates inflammation, contributes to atherogenesis and modulates immune activity. Platelet activation which is a central factor in many arterial disorders may be triggered by multiple pathways. Platelet activation is shown as forming a larger shape, aggregation and releasing various active contents. Mean platelet volume is a marker of platelet size, function and activation. Increased mean platelet volume is shown by active and large platelets that release more thromboxane A2 than smaller ones. The aim of this review is to determine whether early detection of platelet activation via increased mean platelet volume would help to recognize the pro-inflammatory state and administer appropriate and effective treatment properly. An easily detectable marker by using a prompt and functional technique would help our approach to inflammation caused by platelets.

The relationship between diabetes, metabolic syndrome, and platelet activity as measured by mean platelet volume: the National Health And Nutrition Examination Survey, 1999-2004

OBJECTIVE

The association between platelet activity, diabetes, and glucometabolic control is uncertain. We aim to investigate mean platelet volume (MPV), a marker of platelet size and platelet activity, with the prevalence of diabetes, metabolic syndrome, and degree of glycemic control.

RESEARCH DESIGN AND METHODS

This is a retrospective analysis of 13,021 participants in the National Health and Nutrition Examination Survey from 1999 to 2004. Prevalence of diabetes was defined as nonfasting glucose >200 mg/dL, fasting glucose ≥ 126 mg/dL, or treatment with hypoglycemic agents. Presence of metabolic syndrome was determined by the National Cholesterol Education Program Adult Treatment Panel III definition. Odds ratios and 95% CIs were estimated by logistic regression.

RESULTS

MPV was significantly higher in subjects with diabetes (8.20 vs. 8.06 femtoliter [fL], P < 0.01) but not in subjects with metabolic syndrome (8.09 vs. 8.07 fL, P = 0.24). For the metabolic syndrome components, MPV was significantly higher in abdominal obesity (P = 0.03) and low HDL (P = 0.04), and not different in high blood pressure (P = 0.07), abnormal glucose metabolism (P = 0.71), or hypertriglyceridemia (P = 0.46). There was a significant correlation between MPV and glucose (P < 0.0001) and between MPV and hemoglobin A(1c) (P < 0.0001) in subjects with diabetes. These correlations were no longer significant in those without diabetes. The adjusted odds of diabetes rose with increasing MPV levels and were most pronounced in subjects with MPV levels exceeding the 90th percentile (≥ 9.31 fL). The association between MPV and diabetes was most apparent in those with the poorest glucose control.

CONCLUSIONS

Mean platelet volume is strongly and independently associated with the presence and severity of diabetes.

Platelet-rich plasma: a milieu of bioactive factors

Platelet concentrates such as platelet-rich plasma (PRP) have gained popularity in sports medicine and orthopaedics to promote accelerated physiologic healing and return to function. Each PRP product varies depending on patient factors and the system used to generate it. Blood from some patients may fail to make PRP, and most clinicians use PRP without performing cell counts on either the blood or the preparation to confirm that the solution is truly PRP. Components in this milieu have bioactive functions that affect musculoskeletal tissue regeneration and healing. Platelets are activated by collagen or other molecules and release growth factors from alpha granules. Additional substances are released from dense bodies and lysosomes. Soluble proteins also present in PRP function in hemostasis, whereas others serve as biomarkers of musculoskeletal injury. Electrolytes and soluble plasma hormones are required for cellular signaling and regulation. Leukocytes and erythrocytes are present in PRP and function in inflammation, immunity, and additional cellular signaling pathways. This article supports the emerging paradigm that more than just platelets are playing a role in clinical responses to PRP. Depending on the specific constituents of a PRP preparation, the clinical use can theoretically be matched to the pathology being treated in an effort to improve clinical efficacy.

Effect of platelet turnover on whole blood platelet aggregation in patients with coronary artery disease

BACKGROUND

Previous studies have demonstrated considerable variation in the antiplatelet effect of aspirin.

OBJECTIVES

To investigate the impact of platelet turnover on the antiplatelet effect of aspirin in patients with stable coronary artery disease (CAD) and to identify determinants of platelet turnover.

METHODS

Platelet turnover was evaluated by measurements of immature platelets and thrombopoietin in 177 stable CAD patients on aspirin monotherapy, including 85 type 2 diabetics and 92 non-diabetics. Whole blood platelet aggregation was determined using the VerifyNow(®) Aspirin test and multiple electrode aggregometry (MEA, Multiplate(®) ) induced by arachidonic acid (AA) (1.0 mm), adenosine diphosphate (ADP) (10 μm) and collagen (1.0 μg mL(-1) ).

RESULTS

Immature platelet levels significantly correlated with MEA (r = 0.31-0.36, P-values < 0.0001) and the platelet activation marker sP-selectin (r = 0.19, P = 0.014). Contrary to the VerifyNow(®) test, MEA significantly correlated with variations in platelet count (r = 0.45-0.68, P-values < 0.0001). Among patients with residual platelet reactivity according to AA, there were significantly more diabetics (61% vs. 41%, P = 0.027) and higher levels of sP-selectin (77.7 ± 29 vs. 70.2 ± 25 ng mL(-1) , P = 0.070) and serum thromboxane B(2) (0.81 [0.46; 1.70] vs. 0.56 [0.31; 1.12] ng mL(-1) , P = 0.034). In a multivariate regression analysis, immature platelet levels were determined by thrombopoietin levels (P < 0.001), smoking (P = 0.020) and type 2 diabetes (P = 0.042).

CONCLUSIONS

The antiplatelet effect of aspirin was reduced in CAD patients with an increased platelet turnover. Once-daily dosing of aspirin might not suffice to adequately inhibit platelet aggregation in patients with an increased platelet turnover.