Platelet - leukocyte interactions: multiple links between inflammation, blood coagulation and vascular risk

Correlation between Peripheric Blood Markers and Surgical Invasiveness during Humeral Shaft Fracture Osteosynthesis in Young and Middle-Aged Patients

The treatment for humeral shaft fractures (HSFs) is still controversial, consisting of a wide variety of orthopedic osteosynthesis materials that imply different grades of invasiveness. The aim of this study is to investigate the correlation between inflammatory blood-derived markers and the magnitude of the surgical procedure in young and middle-aged patients who sustained these fractures. Observational, retrospective research was conducted between January 2018 and December 2023. It followed patients diagnosed with recent HFSs (AO/OTA 12-A and B) and followed operative treatment. They were split in two groups, depending on the surgical protocol: group A, operated by closed reduction and internal fixation (CRIF) with intramedullary nails (IMNs), and group B, operated by open reduction and internal fixation (ORIF) with dynamic compression plates (DCPs). Statistically significant differences (p < 0.05) between the two groups could be observed in injury on the basis of surgery durations, surgical times, pre- and postoperative neutrophil-per-lymphocyte ratio (NLR), postoperative platelet-per-lymphocyte ratio (PLR), monocyte-per-lymphocyte ratio (MLR), systemic inflammatory index (SII), systemic inflammatory response index (SIRI) and aggregate inflammatory systemic index (AISI). The multivariate regression model proposed revealed that NLR > 7.99 (p = 0.007), AISI > 1668.58 (p = 0.008), and the surgical times (p < 0.0001) are strongly correlated to the magnitude of the surgical protocol followed. Using receiver operating characteristic (ROC) curve analysis, a balanced reliability was determined for both postoperative NLR > 7.99 (sensitivity 75.0% and specificity 75.6) and AISI > 1668.58 (sensitivity 70.6% and specificity 82.2%). Postoperative NLR and AISI as inflammatory markers are highly associated with the magnitude of surgical trauma sustained during humeral shaft fracture osteosynthesis in a younger population.

Systemic immune-inflammation index predicts the clinical outcomes in patients with acute uncomplicated type-B aortic dissection undergoing optimal medical therapy

BACKGROUND

Optimal medical therapy (OMT) for uncomplicated type B aortic dissection (uTBAD) provides excellent short-term outcomes during follow up; however, its long-term therapeutic effectiveness is unsatisfactory. This study evaluated the predictive value of systemic immune-inflammation index (SII) for adverse events among patients with acute uTBAD undergoing OMT.

METHODS

We performed a retrospective analysis of a prospectively maintained database between 2013 and 2020. The primary end point in this study was composite outcomes including aortic intervention, all-cause mortality, retrograde type A aortic dissection (rTAAD) and aortic diameter growth > 5 mm. The patients were divided into high and low SII groups according to the optimal cut-off value of SII as determined using the receiver operating characteristic curve. Cox proportional hazards models were constructed to estimate the hazards ratios and identify the predictors of composite outcomes.

RESULTS

A total of 124 patients with acute uTBAD who underwent OMT were enrolled. One patient died during hospitalisation. At the end of a mean follow-up duration of 51 ± 23 months, 53 (43.1%) patients experienced composite outcomes, 15 patients (12.2%) died, 31 (25.2%) underwent aortic intervention, 21 (17.1%) exhibited diameter growth of > 5 mm, and 2 developed rTAAD. The patients were divided into low SII group (n = 78, 62.9%) and high SII group (n = 46, 37.1%) as per the optimal cut-off SII value of 1449. The incidence of composite outcomes in high SII group was significantly higher than that in low SII (28 [60.9%] vs. 26[33.3%], p < 0.01). Patients with high SII demonstrated significantly higher mortality rate than those with a low SII (11 [23.9%] vs. 5 [6.4%], respectively; p < 0.01). In addition, the high SII group had significantly higher rate of aortic-related reinterventions than the low SII group (16 [34.8%] vs. 15 [19.2%], p = 0.03). Multivariable Cox analyses showed that a high SII score was independently associated with composite outcomes rate (hazard ratio, 2.15; 95% confidence interval, 1.22-3.78; p < 0.01).

CONCLUSIONS

The long-term therapeutic effectiveness of OMT alone in patients with acute uTBAD is unsatisfactory. An SII > 1449 at the time of diagnosis is an independent predictor of OMT failure.

The role of monocytes in thrombotic diseases: a review

Cardiovascular and cerebrovascular diseases are the number one killer threatening people's life and health, among which cardiovascular thrombotic events are the most common. As the cause of particularly serious cardiovascular events, thrombosis can trigger fatal crises such as acute coronary syndrome (myocardial infarction and unstable angina), cerebral infarction and so on. Circulating monocytes are an important part of innate immunity. Their main physiological functions are phagocytosis, removal of injured and senescent cells and their debris, and development into macrophages and dendritic cells. At the same time, they also participate in the pathophysiological processes of pro-coagulation and anticoagulation. According to recent studies, monocytes have been found to play a significant role in thrombosis and thrombotic diseases of the immune system. In this manuscript, we review the relationship between monocyte subsets and cardiovascular thrombotic events and analyze the role of monocytes in arterial thrombosis and their involvement in intravenous thrombolysis. Finally, we summarize the mechanism and therapeutic regimen of monocyte and thrombosis in hypertension, antiphospholipid syndrome, atherosclerosis, rheumatic heart disease, lower extremity deep venous thrombosis, and diabetic nephropathy.

Research progress on the interaction between oxidative stress and platelets: Another avenue for cancer?

Oxidative stress (OS) is a chemical imbalance between an oxidant and an antioxidant, causing damage to redox signaling and control or causing molecular damage. Unbalanced oxidative metabolism can produce excessive reactive oxygen species (ROS). These excess ROS can cause drastic changes in platelet metabolism and further affect platelet function. It will also lead to an increase in platelet procoagulant phenotype and cell apoptosis, which will increase the risk of thrombosis. The creation of ROS and subsequent platelet activation, adhesion, and recruitment are then further encouraged in an auto-amplifying loop by ROS produced from platelets. Meanwhile, cancer cells produce a higher concentration of ROS due to their fast metabolism and high proliferation rate. However, excessive ROS can result in damage to and modification of cellular macromolecules. The formation of cancer and its progression is strongly associated with oxidative stress and the resulting oxidative damage. In addition, platelets are an important part of the tumor microenvironment, and there is a significant cross-communication between platelets and cancer cells. Cancer cells alter the activation status of platelets, their RNA spectrum, proteome, and other properties. The "cloaking" of cancer cells by platelets providing physical protection，avoiding destruction from shear stress and the attack of immune cells, promoting tumor cell invasion.We explored the vicious circle interaction between ROS, platelets, and cancer in this review, and we believe that ROS can play a stimulative role in tumor growth and metastasis through platelets.

Unique crosstalk between platelet and leukocyte counts during treatment for acute coronary syndrome: A retrospective observational study

In the pathophysiology of acute coronary syndrome (ACS), platelet (PLT) and neutrophil (Neu) crosstalk may be important for activating coagulation and inflammation. It has been speculated that PLTs and Neu may affect each other's cell counts; however, few studies have investigated this hypothesis. In this study, we measured changes in blood cell counts in 245 patients with ACS during treatment and investigated the mutual effects of each blood cell type. Path diagrams were drawn using structural equation modeling, and temporal changes in the count of each blood cell type and the relevance of these changes were analyzed. Throughout the treatment period, the numbers of all blood cell types (red blood cells [RBCs], leukocytes, and PLTs) were associated with each other before and after treatment. A detailed examination of the different cell types revealed that the PLT count at admission had a significant positive effect on the leukocyte (especially Neu) count after treatment. Conversely, the leukocyte (especially Neu) count at admission had a significant positive effect on the PLT count after treatment. During ACS, PLTs and leukocytes, especially Neu, stimulate each other to increase their numbers. The formation of a PLT-leukocyte complex may increase coagulation activity and inflammation, which can lead to a further increase in the counts of both blood cell types.

Platelet-Derived Exosomes in Atherosclerosis

Atherosclerosis (AS), the main cause of many cardiovascular diseases (CVDs), is a progressive inflammatory disease characterized by the accumulation of lipids, fibrous elements, and calcification in the innermost layers of arteries. The result is the thickening and clogging of these vessel walls. Several cell types are directly involved in the pathological progression of AS. Among them, platelets represent the link between AS, inflammation, and thrombosis. Indeed, besides their pivotal role in hemostasis and thrombosis, platelets are key mediators of inflammation at injury sites, where they act by regulating the function of other blood and vascular cell types, including endothelial cells (ECs), leukocytes, and vascular smooth muscle cells (VSMCs). In recent years, increasing evidence has pointed to a central role of platelet-derived extracellular vesicles (P-EVs) in the modulation of AS pathogenesis. However, while the role of platelet-derived microparticles (P-MPs) has been significantly investigated in recent years, the same cannot be said for platelet-derived exosomes (P-EXOs). For this reason, this reviews aims at summarizing the isolation methods and biological characteristics of P-EXOs, and at discussing their involvement in intercellular communication in the pathogenesis of AS. Evidence showing how P-EXOs and their cargo can be used as biomarkers for AS is also presented in this review.

Platelet Derivatives and the Immunomodulation of Wound Healing

Besides their primary role in hemostasis, platelets contain a plethora of immunomodulatory molecules that profoundly affect the entire process of wound repair. Therefore, platelet derivatives, such as platelet-rich plasma or platelet lysate, have been widely employed with promising results in the treatment of chronic wounds. Platelet derivatives provide growth factors, cytokines, and chemokines targeting resident and immigrated cells belonging to the innate and adaptive immune system. The recruitment and activation of neutrophils and macrophages is critical for pathogen clearance in the early phase of wound repair. The inflammatory response begins with the release of cytokines, such as TGF-β, aimed at damping excessive inflammation and promoting the regenerative phase of wound healing. Dysregulation of the immune system during the wound healing process leads to persistent inflammation and delayed healing, which ultimately result in chronic wound. In this review, we summarize the role of the different immune cells involved in wound healing, particularly emphasizing the function of platelet and platelet derivatives in orchestrating the immunological response.

Mechanism and Potential Target of Blood-Activating Chinese Botanical Drugs Combined With Anti-Platelet Drugs: Prevention and Treatment of Atherosclerotic Cardiovascular Diseases

Atherosclerotic cardiovascular diseases (ASCVDs) are the most important diseases that endanger people’s health, leading to high morbidity and mortality worldwide. In addition, various thrombotic events secondary to cardiovascular and cerebrovascular diseases need must be considered seriously. Therefore, the development of novel anti-platelet drugs with high efficiency, and fewer adverse effects has become a research focus for preventing of cardiovascular diseases (CVDs). Blood-activation and stasis-removal from circulation have been widely considered as principles for treating syndromes related to CVDs. Blood-activating Chinese (BAC botanical drugs, as members of traditional Chinese medicine (TCM), have shown to improve hemodynamics and hemorheology, and inhibit thrombosis and atherosclerosis. Modern medical research has identified that a combination of BAC botanical drugs and anti-platelet drugs, such as aspirin or clopidogrel, not only enhances the anti-platelet effects, but also reduces the risk of bleeding and protects the vascular endothelium. The anti-platelet mechanism of Blood-activating Chinese (BAC) botanical drugs and their compounds is not clear; therefore, their potential targets need to be explored. With the continuous development of bioinformatics and “omics” technology, some unconventional applications of BAC botanical drugs have been discovered. In this review, we will focus on the related targets and signaling pathways of anti-atherosclerotic treatments involving a combination of BAC botanical drugs and anti-platelet drugs reported in recent years.

Systemic immune-inflammation index predicted the clinical outcome in patients with type-B aortic dissection undergoing thoracic endovascular repair

BACKGROUND

The systemic immune-inflammation index (SII) has been reported to have prognostic ability in various cardiovascular diseases; however, it has not been studied in type-B aortic dissection (TBAD). We aimed to explore the relation of SII with short-term and long-term outcomes in TBAD patients undergoing thoracic endovascular repair (TEVAR).

METHODS

We performed a retrospective analysis of a prospectively maintained database from 2010 to 2017. The patients were divided into two groups (high SII and low SII) as per the optimal cut-off value determined using the receiver operating characteristic curve. Multivariate logistic and Cox regression analyses were performed to analyse the relationship between the SII and the short-term and long-term outcomes.

RESULTS

A total of 805 TBAD patients who underwent TEVAR were enrolled. Twenty-six (3.2%) patients died during hospitalisation. At the end of a median follow-up duration of 48.80 mon, 70 (9.8%) patients had died. The patients were divided into the high-SII group [n = 333 (41.4%%)] and the low-SII group [n = 472 (58.6%)] as per the optimal cut-off value of 1,062. Multivariable logistic analyses showed that a high-SII score was independently associated with major adverse cardiovascular events (MACEs) in-hospital (odd ratio [OR], 1.67; 95% confidence interval [CI], 1.13-2.47; p = .01). In addition, multivariable Cox analyses showed that a high-SII score could be an independent indicator for follow-up adverse events (hazard ratio [HR], 1.70; 95% CI, 1.14-2.56, p = .01).

CONCLUSIONS

Systemic immune-inflammation index is associated with both in-hospital and long-term outcomes in patients with TBAD undergoing TEVAR. Therefore, SII may serve as valuable tool for risk stratification before intervention.

The Relationship Between Thrombo-Inflammatory Biomarkers and Cellular Indices of Inflammation in Lymphoma Patients

Introduction

Thrombo-inflammatory biomarkers play an important role in the pathogenesis of lymphoma. We aimed to characterize the interrelationship of thrombo-inflammatory biomarkers and blood cellular indices in lymphoma patients.

Materials and Methods

Ninety-eight lymphoma patient samples were collected from Lymphoma Center of Clinic of Hematology, University of Belgrade, Serbia. Normal controls (n = 50) represented plasma from healthy individuals. Plasminogen activator inhibitor (PAI-1), D-Dimer, factor XIII, C-reactive protein (CRP), microparticles (Mp), Von Willebrand factor (vWF), total protein S, urokinase-type plasminogen activator (uPA), tumor necrosis factor (TNFα), β2-glycoprotein I (β2GPI), and fibronectin levels were measured utilizing commercially-available ELISA methods. Thrombin generation profile (TGA) was measured using a fluorometric kinetic assay. Platelets, leukocytes, lymphocytes, and neutrophils were measured in conjunction with the complete blood profile.

Results

Statistically significant differences were noted in levels of PAI-1, D-Dimer, factor XIII, CRP, microparticles, vWF, uPA, TNFα, β2GPI, fibronectin, and TGA when compared to normal (all P values < .001). Platelet to leukocyte ratio (PLA) correlated to TNFα and fibronectin (R = −0.31 and −0.53, respectively) and the platelet to neutrophil ratio (PNR) correlated to factor XIII and β2GPI (R = 0.40 and 0.40, respectively).

Conclusion

Plasma samples from lymphoma patients demonstrated a significantly altered thrombo-inflammatory biomarker profile that has notable correlations to blood cellular indices.

Enhancement of the anticoagulant capacity of polyvinyl chloride tubing for cardiopulmonary bypass circuit using aluminum oxide nanoscale coating applied through atomic layer deposition

For cardiopulmonary bypass, the polyvinyl chloride (PVC) circuit which can initiate the activation of platelets and the coagulation cascade after blood cell contacting is the possible detrimental effect. Surface coating of the PVC tubing system can be an effective approach to enhance circuit's hemocompatibility. In this study, aluminum oxide (Al₂ O₃ ) thin films were deposited through thermal atomic layer deposition (T-ALD) or plasma-enhanced ALD (PE-ALD) on PVC samples, and the anticoagulation of the Al₂ O₃ -coated PVC samples was demonstrated. The results revealed that Al₂ O₃ deposition through ALD increased surface roughness, whereas T-ALD had a relative hydrophilicity compared with blank PVC and PE-ALD. Whole blood immersion tests showed that blood clots formed on blank PVC and that a large amount of red blood cells was found on PE-ALD substrates, whereas less blood cells were noted in T-ALD samples. Both T-ALD and PE-ALD Al₂ O₃ films did not cause activation of blood cells, as evidenced in CD3⁺ /CD4⁺ /CD8⁺ , CD61⁺ /CD62P⁺ , and CD45⁺ /CD42b⁺ populations. Analysis of serum coagulation factors showed that a lower amount of prothrombin was absorbed on T-ALD Al₂ O₃ samples than that on blank PVC. For albumin and fibrinogen immersion tests, immunostaining and scanning electron microscopy further revealed that a thin albumin layer was absorbed on T-ALD Al₂ O₃ substrates but not on PVC samples. This study revealed that deposition of Al₂ O₃ films by T-ALD can improve anticoagulation of the PVC tubing system.

Biomarkers involved in evaluation of platelets function in South-Eastern Romanian patients with hematological malignancies subtypes

ABSTRACT

At present, various researches presented how subtypes of hematological malignancies are related to stages of the immune response, because the activated immune system represents a promising form in cancer treatment. This study explores the relationship between the adaptive immune system (T cells), and the coagulation system (platelets, platelet membrane glycoproteins, platelets derivate microparticles) which seems to play an important role in host immune defense of patients with acute myeloblastic leukemia (AML) or B cell lymphoma (BCL), 2 of the most common hematological malignancies subtypes.Blood samples (n = 114) obtained from patients with AML or BCL were analyzed for platelet membrane glycoproteins (CD42b, CD61), glycoprotein found on the surface of the T helper cells (CD4+), protein complex-specific antigen for T cells (CD3+), platelet-derived microparticles (CD61 PMP) biomarkers by flow cytometry, and hematological parameters were quantified by usual methods.In patients with AML, the means of the percentage of the expressions of the molecules on platelet surfaces (CD61 and CD42b, P < .01; paired T test) were lower as compared to both control subgroups. The expression of cytoplasmic granules content (CD61 PMP) had a significantly higher value in patients with AML reported to controlling subgroups (P < .01; paired T test), which is suggesting an intravascular activation of platelets.The platelet activation status was presented in patients with low stage BCL because CD61 and CD42b expressions were significantly higher than control subgroups, but the expression of CD 61 PMP had a significantly decreased value reported to control subgroups (all P < .01; paired T test). T helper/inducer lineage CD4+ and T lymphoid lineage CD3+ expressions presented significant differences between patients with AML or low stage BCL reported to control subgroups (all P < .01; paired T test).Platelet-lymphocyte interactions are involved in malignant disorders, and CD61, CD42b present on platelet membranes, as functionally active surface receptors mediate the adhesion of active platelets to lymphocytes, endothelial cells, and cancer cells.

Assessment of thrombotic risk during long-term treatment of immune thrombocytopenia with fostamatinib

Background:

Patients with immune thrombocytopenia (ITP) are at risk of bleeding and, paradoxically, thromboembolic events (TEEs), irrespective of thrombocytopenia. The risk of thrombosis is increased by advanced age, obesity, and prothrombotic comorbidities: cancer, hyperlipidemia, diabetes, hypertension, coronary artery disease, and chronic kidney disease, among others. Certain ITP treatments further increase the risk of TEE, especially splenectomy and thrombopoietin receptor agonists. Spleen tyrosine kinase (SYK) is a key signaling molecule common to thromboembolic and hemostatic (in addition to inflammatory) pathways. Fostamatinib is an orally administered SYK inhibitor approved in the USA and Europe for treatment of chronic ITP in adults.

Methods:

The phase III and extension studies included heavily pretreated patients with long-standing ITP, many of whom had risk factors for thrombosis prior to initiating fostamatinib. This report describes long-term safety and efficacy of fostamatinib in 146 patients with up to 5 years of treatment, a total of 229 patient-years, and assesses the incidence of thromboembolic events (by standardized MedDRA query).

Results:

Platelet counts ⩾50,000/µL were achieved in 54% of patients and the safety profile was as described in the phase III clinical studies with no new toxicities observed over the 5 years of follow-up. The only TEE occurred in one patient (0.7%, or 0.44/100 patient-years), who experienced a mild transient ischemic attack. This is a much lower rate than might be expected in ITP patients.

Conclusion:

This report demonstrates durable efficacy and a very low incidence of TEE in patients receiving long-term treatment of ITP with the SYK inhibitor fostamatinib.

ClinicalTrials.gov identifiers:

NCT02076399, NCT02076412, and NCT02077192.

Hemostatic changes by thrombopoietin-receptor agonists in immune thrombocytopenia patients

Thrombopoietin receptor agonist (TPO-RA) treatment increases the thrombosis rate in immune thrombocytopenia (ITP). We hypothesize that TPO-RAs influence platelet function, global and secondary hemostasis and/or fibrinolysis. A systematic review was performed. If possible, data were compared between responders (relevant increase in platelet count), and non-responders. Twelve observational studies with 305 patients were included (responders (127/150 (85%))). There were indications that TPO-RA treatment enhanced platelet function, with respect to platelet-monocyte aggregates, soluble P-selectin, GPVI expression, and adhesion under flow. Studies addressing global and secondary hemostasis and fibrinolysis were scarce. Overall, no changes were found during TPO-RA treatment, apart from an accelerated clot formation and conflicting data on levels of plasminogen activator inhibitor (PAI)-1. The parameters that increased have previously been associated with thrombosis in other patient groups, and might contribute to the increased rate of thrombosis observed in TPO-RA-treated ITP patients.

Relationship of Platelet Counts and Inflammatory Markers to 30-Day Mortality Risk in Patients with Acute Type A Aortic Dissection

Markers of prothrombotic state and inflammation are associated with the prognosis of patients with acute type A aortic dissection (AAAD). However, it is unclear that the relationship between these biomarkers and their combined impact on risk stratification. The present study evaluated the prognostic value of platelet counts, lymphocyte to neutrophil ratio (LNR), and lymphocyte to monocyte ratio (LMR), alone and in combination. A retrospective analysis of clinical data of 744 AAAD patients was conducted to identify whether these biomarkers were related to the 30-day mortality risk. A Kaplan-Meier analysis and log-rank test were used to compare survival between groups. A Cox hazard regression multivariable analysis was performed for 30-day mortality. Individual biomarker (platelet count, LNR, or LMR) was unable to predict 30-day mortality. However, combinations of all three biomarkers provided additive predictive value over either marker alone, the receiver operating characteristic (ROC) model had a prediction probability of 0.739 when platelet counts, LNR, and LMR were included. Cox hazard regression multivariable analysis showed that combinations of all three biomarkers were the strongest predictor of 30-day mortality (p < 0.021). Combined with these three easily measurable biomarkers at admission, they could help identify AAAD patients with a high risk of 30-day mortality.

Coronin 1 Is Required for Integrin β2 Translocation in Platelets

Remodeling of the actin cytoskeleton is one of the critical events that allows platelets to undergo morphological and functional changes in response to receptor-mediated signaling cascades. Coronins are a family of evolutionarily conserved proteins implicated in the regulation of the actin cytoskeleton, represented by the abundant coronins 1, 2, and 3 and the less abundant coronin 7 in platelets, but their functions in these cells are poorly understood. A recent report revealed impaired agonist-induced actin polymerization and cofilin phosphoregulation and altered thrombus formation in vivo as salient phenotypes in the absence of an overt hemostasis defect in vivo in a knockout mouse model of coronin 1. Here we show that the absence of coronin 1 is associated with impaired translocation of integrin β2 to the platelet surface upon stimulation with thrombin while morphological and functional alterations, including defects in Arp2/3 complex localization and cAMP-dependent signaling, are absent. Our results suggest a large extent of functional overlap among coronins 1, 2, and 3 in platelets, while aspects like integrin β2 translocation are specifically or predominantly dependent on coronin 1.

Engineered human platelet-derived microparticles as natural vectors for targeted drug delivery

Drug targeting has opened a new paradigm in therapeutics with development of delivery vectors like liposomes and polymeric nanoparticles. Although their clinical application is crippled by limited biological adaptability. Off-target toxicity and biocompatibility still remains one of the critical problems in anticancer therapeutics that can be life-threatening. Here we report a quick, simple and facile method of engineering human platelets to generate drug loaded platelet-derived microparticles (PMPs) by top-down approach, which are biocompatible and naturally target leukemia cells. Drug loaded PMPs and cancer cell uptake were characterized by flow cytometry, confocal microscopy, Nanoparticle Tracking Analysis and fluorimetry. Effective drug delivery was tested in cancer cell lines as well as in clinical samples from leukemia patients. We explored that PMPs are capable of carrying multiple drug payloads, have long shelf life and can be harvested in large quantity in short period. Importantly, PMPs exhibited remarkably higher toxicity towards cancer cells than free drug and had lower escape into extravascular spaces. Transfer of drug to cancer cells of leukemia patients was significantly higher than free drug, when delivered through PMPs. Our experiments validated therapeutic application of PMPs as biocompatible drug delivery vector against cancer cells with minimal off-target delivery.

Platelet-leukocyte aggregate is associated with adverse events after surgical intervention for rheumatic heart disease

Platelet-leukocyte aggregate (PLA) is implicated in the etiology of both vascular lesions and cardiovascular events. This prospective cohort study aimed to examine the prognostic value of PLA for major adverse cardiac and cerebrovascular events (MACCE) and perioperative adverse events (AEs) in patients with rheumatic heart disease undergoing surgical intervention by Cox proportional hazard regression and logistic regression. A total of 244 patients were included, of whom 7 were lost to follow-up. Among the analyzed 237 subjects who completed 3-year follow-up, 30 experienced MACCE and 38 experienced perioperative AEs. Preoperative PLA was higher in subjects who developed MACCE (13.32%) than in those who did not (8.69%, p = 0.040). In multivariate regression, elevated PLA was associated with increased MACCE (hazard ratio 1.51 for each quartile, 95% CI 1.07-2.13; p = 0.020), and perioperative AEs (odds ratio 1.61, 95% CI 1.14-2.26; p = 0.007). The optimal PLA cut-off for predicting MACCE was 6.8%. Subjects with PLA > 6.8% had a higher prevalence of MACCE (17.1% vs. 5.5%, p = 0.009) and perioperative AEs (19.9% vs. 8.6%, p = 0.018). Kaplan-Meier analysis showed shorter MACCE-free survival in patients with PLA > 6.8% (p = 0.007, log rank). Elevated preoperative PLA is associated with increased MACCE and perioperative AEs in patients with rheumatic valve disease undergoing surgical intervention.

Comparative Analysis of Blood Clot, Plasma Rich in Growth Factors and Platelet-Rich Fibrin Resistance to Bacteria-Induced Fibrinolysis

Alveolar osteitis (AO) is a common, painful postoperative complication after tooth extraction. Fibrinolytic activity in the extraction socket is one etiological factor. Platelet concentrates are used to prevent and treat AO. The aim of this study was to find out whether the positive effect of platelet concentrates can be related to resistance to bacteria-induced fibrinolysis. Blood from 45 human volunteers was used to prepare four media: blood clot medium as control group; PRF and PRGF first fraction (PRGF I) and PRGF second fraction (PRGF II) as study groups. Additionally, collected blood was used for blood plasma preparation on which evaluation of initial value of d-dimer concentration was performed. A solution of five different microbes (Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumonia, Bacillus cereus, and Candida albicans) was adjusted to 0.5 McFarland (1 × 10⁸ CFU/mL) and then diluted to 0.25 McFarland (0.5 × 10⁸ CFU/mL). The d-dimer concentration was evaluated after one and three hours of bacteria exposure. The resistance to fibrinolysis was not statistically distinguished among any media groups at any time. S. pneumoniae was statistically active in PRF after three hours. C. albicans was statistically active in PRGF II after one hour and in PRF between the first and third hour and after three hours. S. aureus and B. cereus were statistically active in PRGF II after three hours. S. pyogenes was statistically active after one hour, between the first and third hour, and after the third hour in all groups. S. pyogenes was the most active bacterium. Different blood formulations were not distinguishable based on resistance to bacteria-induced fibrinolysis. Low fibrinolytic properties of the found major microbes suggests that bacteria-induced fibrinolysis is one of the leading causes of absence of a clot in a post-extraction socket to be clinically insignificant. The initial absence of a clot or its mechanical elimination during formation or the healing period are major causes of dry socket.

Effects of dietary nitrate on inflammation and immune function, and implications for cardiovascular health

Inorganic dietary nitrate, found abundantly in green leafy and some root vegetables, elicits several beneficial physiological effects, including a reduction in blood pressure and improvements in blood flow through nitrate-nitrite-nitric oxide signaling. Recent animal and human studies have shown that dietary nitrate and nitrite also modulate inflammatory processes and immune cell function and phenotypes. Chronic low-grade inflammation and immune dysfunction play a critical role in cardiovascular disease. This review outlines the current evidence on the efficacy of nitrate-rich plant foods and other sources of dietary nitrate and nitrite to counteract inflammation and promote homeostasis of the immune and vascular systems. The data from these studies suggest that immune cells and immune-vasculature interactions are important targets for dietary interventions aimed at improving, preserving, or restoring cardiovascular health.

Monocytes of Different Subsets in Complexes with Platelets in Patients with Myocardial Infarction

Acute myocardial infarction (AMI) is associated with activation of various cells, including platelets that form monocyte-platelet complexes (MPCs). Here, we analysed MPC in vivo and in vitro and investigated the abilities of different monocyte subclasses to form MPC, the characteristics of the cells involved in MPC formation and MPC changes in AMI. We identified MPC by co-staining for platelet antigen CD41a and monocyte antigens CD14 and CD16. Platelet activation was evaluated from expression of phosphatidylserine as revealed by annexin V. Our results confirm published data and provide new information regarding the patterns of MPC in AMI patients. We found that the patterns of platelet aggregation with monocytes were different in AMI patients and controls: (1) in AMI patients, MPC formed by intermediate monocytes carry more platelets whereas in healthy controls more platelets aggregated with classical monocytes; (2) the numbers of MPC in AMI patients, being already higher than in controls, were further increased if these patients suffered various in-hospital complications; (3) on the basis of the CD41a fluorescence of the antibody-stained MPC, some of the aggregates seem to consist of monocytes and platelet-derived extracellular vesicles (EVs); (4) aggregation of monocytes with platelet EV occurred in in vitro experiments; and (5) these experiments demonstrated that monocytes from AMI patients aggregate with both platelets and platelet EVs more efficiently than do monocytes from controls. MPC in AMI patients may play an important role in this pathology.

Platelet-leucocyte aggregation is augmented in cirrhosis and further increased by platelet transfusion

BACKGROUND

Thrombocytopenia and circulating dysfunctional immune cells are commonly observed in patients with cirrhosis. Platelets may form complexes with neutrophils, monocytes and T cells modulating their function. We recently reported increased frequencies of platelet-complexed neutrophils in cirrhosis with evidence of neutrophil activation upon contact with healthy platelets in vitro. Whether this occurs in vivo following platelet transfusion and contributes to systemic inflammation and endothelial activation is unknown.

AIMS

To characterise platelet-leucocyte aggregation in cirrhosis and to determine whether elective platelet transfusion results in perturbations associated with changes in markers of haemostasis, inflammation or endothelial activation.

METHODS

We collected blood from cirrhotics (n = 19) before and following elective platelet transfusion. We measured platelet-leucocyte aggregation, activation and function, and markers of platelet activation, systemic inflammation and endothelial activation by flow cytometry. Haemostasis was assessed by thromboelastometry and plasma haemostatic proteins.

RESULTS

We observed a 2.5-fold increase in platelet-complexed neutrophils in patients with cirrhosis compared with healthy subjects and twofold more platelets attached per monocyte and T cell. All platelet-complexed leucocytes expressed higher levels of activation markers and platelet-complexed neutrophils had higher resting oxidative burst and phagocytic capacity than their nonplatelet-complexed counterparts (P < 0.001); most pronounced in patients with cirrhosis. Paradoxically, platelet-complexed leucocyte frequency decreased with increasing MELD score. Platelet transfusion increased soluble CD40 ligand (platelet activation marker), the frequency of platelet-complexed monocytes (P < 0.05) and improved haemostatic status.

CONCLUSION

Cirrhotic patients have activated circulating platelet-complexed leucocytes with increased platelet-monocyte aggregation following elective platelet transfusion. Elective platelet transfusion might therefore exacerbate immune dysfunction in cirrhosis.

Platelet Storage Lesions: What More Do We Know Now?

Platelet concentrate (PC) transfusions are a lifesaving adjunct to control and prevent bleeding in cancer, hematologic, surgical, and trauma patients. Platelet concentrate availability and safety are limited by the development of platelet storage lesions (PSLs) and risk of bacterial contamination. Platelet storage lesions are a series of biochemical, structural, and functional changes that occur from blood collection to transfusion. Understanding of PSLs is key for devising interventions that prolong PC shelf life to improve PC access and wastage. This article will review advancements in clinical and mechanistic PSL research. In brief, exposure to artificial surfaces and high centrifugation forces during PC preparation initiate PSLs by causing platelet activation, fragmentation, and biochemical release. During room temperature storage, enhanced glycolysis and reduced mitochondrial function lead to glucose depletion, lactate accumulation, and product acidification. Impaired adenosine triphosphate generation reduces platelet capacity to perform energetically demanding processes such as hypotonic stress responses and activation/aggregation. Storage-induced alterations in platelet surface proteins such as thrombin receptors and glycoproteins decrease platelet aggregation. During storage, there is an accumulation of immunoactive proteins such as leukocyte-derive cytokines (tumor necrosis factor α, interleukin (IL) 1α, IL-6, IL-8) and soluble CD40 ligand which can participate in transfusion-related acute lung injury and nonhemolytic transfusion reactions. Storage-induced microparticles have been linked to enhanced platelet aggregation and immune system modulation. Clinically, stored PCs have been correlated with reduced corrected count increment, posttransfusion platelet recovery, and survival across multiple meta-analyses. Fresh PC transfusions have been associated with superior platelet function in vivo; however, these differences were abrogated after a period of circulation. There is currently insufficient evidence to discern the effect of PSLs on transfusion safety. Various bag and storage media changes have been proposed to reduce glycolysis and platelet activation during room temperature storage. Moreover, cryopreservation and cold storage have been proposed as potential methods to prolong PC shelf life by reducing platelet metabolism and bacterial proliferation. However, further work is required to elucidate and manage the PSLs specific to these storage protocols before its implementation in blood banks.

Emerging Concepts in the Resolution of Periodontal Inflammation: A Role for Resolvin E1

Inflammatory response is a protective biological process intended to eliminate the harmful effect of the insulting influx. Resolution of inflammation constitutes an active sequence of overlapping events mediated by specialized proresolving mediators, such as lipoxins, resolvins, protectins, and maresins, which originate from the enzymatic conversion of polyunsaturated fatty acids (PUFAs). An unresolved acute inflammatory response results in chronic inflammation, which is a leading cause of several common pathological conditions. Periodontitis is a biofilm-induced chronic inflammatory disease, which results in loss of periodontal connective tissue and alveolar bone support around the teeth, leading to tooth exfoliation. An inadequate proresolving host response may constitute a mechanism explaining the pathogenesis of periodontal disease. An emerging body of clinical and experimental evidence has focused on the underlying molecular mechanisms of resolvins and particularly Resolvin E1 (RvE1) in periodontitis. Recently, RvE1 has been directly correlated with the resolution of inflammation in periodontal disease. Herein, we provide a comprehensive overview of the literature regarding the role and possible mechanisms of action of RvE1 on different cell populations recruited in periodontal inflammation as well as its potential therapeutic implications. Along with recent data on the benefits of PUFAs supplementation in periodontal clinical parameters, we touch upon suggested future directions for research.

Effect of thrombopoietin receptor agonists on markers of coagulation and P-selectin in patients with immune thrombocytopenia

Thrombopoietin-receptor-agonists (TPO-RA) are effective treatments of immune thrombocytopenia (ITP). Previous long-term TPO-RA clinical trials have shown that thrombotic events occurred in 6% of TPO-RA-treated ITP patients. To explore the increased risk of thrombosis, the effects of TPO-RA on markers of coagulation and P-selectin were studied. The study comprised two ITP cohorts and controls. Cohort 1 included 26 patients with sequential samples acquired before and during treatment with TPO-RA. Cohort 2 included a single sample in 18 patients on TPO-RA for more than one year. Thrombin generation (endogenous thrombin potential (ETP)) prothrombin fragments 1 + 2 (F₁₊₂), D-dimer, and plasminogen-activator-inhibitor-1 (PAI-1) were measured as well as soluble P-selectin (sP-selectin). Sequential expression of encoding genes for P-selectin (SELP) and PAI-1 (SERPINE1) was determined in four patients in cohort 1. Significantly higher levels of F₁₊₂, D-dimer, and PAI-1 were found in ITP patients before TPO-RA treatment and in patients on long-term TPO-RA treatment than in controls. Pre-treatment levels of sP-selectin did not differ from controls. Analysis of longitudinal trends showed an increase in platelet count, sP-selectin, and PAI-1 after initiation of TPO-RA, followed by gradual decline. Platelet count and sP-selectin remained at higher levels throughout the study, whereas PAI-1 did not. Levels of other studied parameters did not show significant changes after initiation of treatment. Expression of SELP was up-regulated after initiation of TPO-RA, while the expression of SERPINE1 showed no significant changes. In conclusion, elevated pre-treatment levels of F₁₊₂, D-dimer and PAI-1 are compatible with ITP being an intrinsically pro-thrombotic condition. After TPO-RA treatment, there were no significant changes in markers of coagulation activation or fibrinolysis, except for an initial increase in PAI-1 and a significant increase in sP-selectin both of which may contribute to increased thrombotic risk associated with TPO-RA treatment in ITP.

Postprandial cell inflammatory response to a standardised fatty meal in subjects at different degree of cardiovascular risk

A fatty meal may represent a challenge of in vivo acute inflammatory reaction. We evaluated the acute effects of a standardised fatty meal administration on leukocytes and platelets and on their interactions on 61 subjects at different degree of cardiovascular risk, without any clinical event. Before and 2 hours after a fatty meal, blood cells were counted and markers of leukocyte (intracellular myeloperoxidase [MPO] and Mac-1) and platelet (P-selectin and microparticles) activation and mixed platelet-leukocyte conjugates measured by flow-cytometry. After the fatty meal, both white blood cell and platelet count significantly increased, more markedly in subjects with lower cardiovascular risk score. Mac-1 expression too increased (from 32.2 ± 27.2% to 45.6 ± 29.0%, p=0.0016), while MPO decreased (from 83.1 ± 16.3% to 64.5 ± 23.1%, p<0.0001). A trend for increased platelet activation and interaction with leukocytes was also observed. Women were more markedly susceptible to fatty meal challenge, as compared to men, while age did not seem to affect any cell response to fatty meal. Waist-to-hip ratio and body mass index influenced polymorphonuclear cells (PMN) degranulation and platelet count increase, respectively. Cellular responses to the fatty meal, in particular PMN degranulation, were attenuated in subjects at higher degree of cardiovascular risk, who showed a basal mild inflammatory activation status. In conclusion, a fatty meal consumption may represent a model of acute inflammatory response and appears to be modulated by different demographic and cardiovascular risk degree. This model could be applied to study the effect of food-derived antioxidants or nutritional supplements, but its relevance remains to be demonstrated.

A novel lead of P-selectin inhibitor: Discovery, synthesis, bioassays and action mechanism

By docking 126 derivatives of β-carboline-3-carboxylic acid, tetrahydro-β-carboline-3-carboxylic acid and indoloquinolizine into the active pocket of P-selectin (2-(3-(hydroxymethyl)-9H-pyrido[3,4-b]indol-1-yl)ethyl)-l-phenylalanine (HMCEF) was assigned a novel inhibitor. ELISA and flow cytometry experiments showed that HMCEF effectively down-regulated P-selectin expression and supported the rationality of the computer assistant screening, while UV spectrum experiments demonstrated that HMCEF directly bound to P-selectin. In vivo HMCEF dose dependently inhibited the rats and mice to form thrombus and had a minimal effective dose of 20nmol/kg, dose dependently inhibited inflammatory response of mice and had a minimal effective dose of 20nmol/kg. The decrease of serum TNFα and IL-8 of the treated mice was proposed to be the action mechanism of HMCEF inhibiting thrombosis and inflammation. All data imply that HMCEF is a novel lead of P-selectin inhibitor.

Platelet leukocyte aggregates and markers of platelet aggregation, immune activation and disease progression in HIV infected treatment naive asymptomatic individuals

Platelet aggregates play a crucial role in the immune defence mechanism against viruses. Increased levels of lipopolysaccharide have been reported in human immunodeficiency virus (HIV) infected individuals. Platelets are capable of interacting with bacterial LPS and subsequently forming platelet leukocyte aggregates (PLAs). This study aimed at determining the levels of circulating PLAs in treatment naïve HIV infected individuals and correlating them, with markers of immune activation, disease progression and platelet aggregation. Thirty-two HIV negative and 35 HIV positive individuals were recruited from a clinic in the Western Cape. Platelet monocyte and platelet neutrophil aggregates were measured using flow cytometry at baseline and were correlated with markers of platelet activation (CD62P); aggregation (CD36); monocyte and neutrophil activation (CD69); monocyte tissue factor expression (CD142); immune activation (CD38 on T+ cells); D-dimers (a marker of active coagulation); CD4 count and viral load. Platelet monocyte aggregates were also measured post stimulation with lipopolysaccharide. PMA levels were higher in HIV 25.26 (16.16-32.28) versus control 14.12 (8.36-18.83), p = 0.0001. PMAs correlated with %CD38/8 expression (r = 0.54624, p = 0.0155); CD4 count (r = -0.6964, p = 0.0039) viral load (r = 0.633, p < 0.009) and monocyte %CD69 expression (r = 0.757, p = 0.030). In addition the %PMAs correlated with platelet %CD36 (r = 0.606, p = 0.017). The HIV group showed increased levels of %CD62P 5.44 (2.72-11.87) versus control 1.15 (0.19-3.59), p < 0.0001; %CD36 22.53 (10.59-55.15) versus 11.01 (3.69-26.98), p = 0.0312 and tissue factor (CD142) MFI 4.84 (4.01-8.17) versus 1.74 (1.07-9.3), p = 0.0240. We describe increased levels of circulating PMAs which directly correlates with markers of immune activation, disease progression and platelet aggregation in HIV treatment naïve individuals.

Normal platelet function in platelet concentrates requires non-platelet cells: a comparative in vitro evaluation of leucocyte-rich (type 1a) and leucocyte-poor (type 3b) platelet concentrates

Background

Therapeutic success of platelet-rich plasma (PRP) may vary based on the composition and preparation method. The objective of this study was to evaluate the cellular components of platelet concentrates produced by a leucocyte-rich (LR-PRP) and a leucocyte-poor PRP systems (LP-PRP).

Methods

Parameters evaluated included platelet recovery, platelet concentration, red blood cell (RBC) and white blood cell (WBC) composition, platelet growth factor release and stimulation of human tendon cell proliferation in vitro.

Results

Platelet recoveries were 52% for LP-PRP and 89% for LR-PRP. LR-PRP demonstrated greater reproducibility with a 4.2% coefficient of variation (CV) compared with 19.4% for LP-PRP (p<0.001). LR-PRP demonstrated a greater increase in platelet concentration (7.9-fold) than LP-PRP (2.2-fold; p<0.001). LP-PRP showed 5.0-fold reductions in WBCs, while LR-PRP showed a 4.0-fold increase (p<0.001). LP-PRP reduced RBCs to a haematocrit of 0.25, while LR-PRP reduced haematocrit to 11.8. LP-PRP did not coagulate robustly on reactivation with CaCl₂, and released significantly lower levels of epidermal growth factor (EGF) and transforming growth factor β1 (TGF-β1) than whole blood (p<0.03). LP-PRP also did not stimulate tendon cell proliferation greater than whole blood. In contrast, LR-PRP showed increases in each growth factor on activation with CaCl₂ (p<0.01) and stimulated greater proliferation (p<0.05) compared with whole blood. Forced activation of LP-PRP with exogenous thrombin rescued the coagulation deficiency and induced greater growth factor release than comparable whole blood (p<0.03).

Conclusions

These data suggest that non-platelet cellular components in platelet concentrates are important for proper platelet function, including thrombin generation, growth factor release and clot retraction.

Leukocyte Activation in Obese Patients: Effect of Bariatric Surgery

The rising prevalence of obesity is a major global health problem. In severe obesity, bariatric surgery (BS) allows to obtain a significant weight loss and comorbidities improvement, among them one of the factors is the thrombotic risk. In this observational study, we measured indices of leukocyte activation in severely obese patients as markers of increased thrombotic risk in relation with serum markers of inflammation before and after BS. Frequency of polymorphonuclear neutrophil-platelet (PLT) and monocyte (MONO)-PLT aggregates as well as of tissue factor (TF) expressing MONOs was measured in the peripheral blood of 58 consecutive obese patients and 30 healthy controls. In 31 of the 58 obese patients, data obtained at the enrollment were compared with those obtained at 3, 6, and 12 months after BS. Compared with healthy controls, obese patients showed a higher frequency of polymorphonuclear leukocyte (PMNL)-PLT aggregates (7.47 ± 2.45 [6.82-8.11]% vs 5.85 ± 1.89 [5.14-6.55]%, P = 0.001), MONO-PLT aggregates (12.31 ± 7.33 [10.38-14.24]% vs 8.14 ± 2.22 [7.31-8.97]%, P < 0.001), and TF expressing MONOs (4.01 ± 2.11 [3.45-4.56]% vs 2.64 ± 1.65 [2.02-3.25]%, P = 0.002). PMNL-PLT and MONO-PLT aggregate frequency was positively correlated with TF expressing MONOs (R2 = 0.260, P = 0.049 and R2 = 0.318, P = 0.015, respectively). BS was performed in 31 patients and induced a significant reduction of the body mass index, and waist and hip circumferences. These effects were associated with a significant decrease of PMNL-PLT aggregates at 12 months (7.58 ± 2.27 [6.75-8.42]% vs 4.47 ± 1.11 [3.93-5.01]%, P < 0.001), and a reduction of TF expressing MONOs at 6 (3.82 ± 2.04 [3.07-4.57]% vs 1.60 ± 1.69 [0.30-2.90]%, P = 0.008) and 12 months (3.82 ± 2.04 [3.07-4.57]% vs 1.71 ± 0.54 [1.45-1.97]%, P = 0.001) after BS.These data suggest that leukocyte-PLT aggregate formation and MONO activation represent an important mechanism underlying the increased thrombotic risk of obese patients. We also show that BS is effective in normalizing these inflammatory indices.

The fight-or-flight response is associated with PBMC expression profiles related to immune defence and recovery in swine

Defining phenotypes according to molecular features would promote the knowledge of functional traits like behaviour in both human and animal research. Beside physiological states or environmental factors, an innate predisposition of individual coping strategies was discussed, including the proactive and reactive pattern. According to backtest reactivity, animals assigned as high-resisting (proactive) and low-resisting (reactive) were immune challenged with tetanus toxoid in a time course experiment. Using the Affymetrix platform and qPCR, individual coping characteristics were reflected as gene expression signatures in porcine peripheral blood mononuclear cells (PBMC) at naïve state (day 0) and in response to the model antigen (day 14, day 28, and day 140). Further, the blood cell count was analysed at all stages. On the transcriptional level, processes acting on cell communication, vasculogenesis, and blood coagulation were highlighted in high-resisting animals at naïve state (day 0), temporarily blurred due to immune challenge (day 14) but subsequently restored and intensified (day 28). Notably, similar amounts of white and red blood cells, platelets and haematocrit between high-resisting and low-resisting samples suggest coping-specific expression patterns rather than alterations in blood cell distribution. Taken together, the gene expression patterns indicate that proactive pigs might favour molecular pathways enabling an effective strategy for defence and recovery. This corroborates the previously suggested belief, that proactive animals are prone to an increased number of injuries as an evolutionary inherited mechanism. In contrast to previous assumptions, coping-specific immunity in pigs lacks inherited shifts between cellular and humoral immune responses.

Spleen-preserving distal pancreatectomy or distal pancreatectomy with splenectomy?: Perioperative and patient-reported outcome analysis

GOALS

We designed this study to evaluate the efficacy of spleen salvage during distal pancreatectomy for patients with benign and borderline malignant tumors.

BACKGROUND

Despite the emphasis on its role, the spleen has commonly been removed in distal pancreatectomy.

STUDY

From January 2005 to July 2009, 82 patients underwent distal pancreatectomy with splenectomy (DPS) and 78 patients underwent spleen-preserving distal pancreatectomy (SPDP). Medical records were retrospectively reviewed.

RESULTS

There were no significant differences in demographics, final diagnoses, estimated blood loss, intraoperative transfusion, and operative time between the 2 groups. More perioperative complications occurred in the DPS group than in the SPDP group (P=0.0344). Consequently, postoperative hospital stay was significantly shorter in the SPDP group than in the DPS group (P=0.0273). In the follow-up survey, episodes of common cold or flu were apparently more frequent in the DPS group (P=0.047). More patients in the DPS group felt fatigue (P=0.0481) and poor health condition (P=0.0371). Less newly developed (P=0.0193) and aggravated diabetes mellitus (P=0.0361) were also observed in the SPDP group. Platelet counts on postoperative day (POD) 5, hemoglobin on POD 3, WBC counts, and CRP level on POD 2 were significantly higher in the DPS group than in the SPDP group and these differences continued to be significant for months after surgery.

CONCLUSIONS

In addition to frequent higher grade complications, prolonged hospital stays, and severe hematological abnormalities, DPS seemed to result in poor health condition based on the follow-up survey. Even an effort to preserve an adult spleen in distal pancreatectomy is worthwhile.

Abnormal P-selectin localization during megakaryocyte development determines thrombosis in the gata1low model of myelofibrosis

Patients with primary myelofibrosis have increased risk for bleeding and thrombosis. It is debated whether propensity to thrombosis is due to increased numbers of platelet microparticles and/or to pathological platelet-neutrophil interactions. Platelet neutrophil interactions are mediated by P-selectin and even though the megakaryocytes of myelofibrosis patients express normal levels of P-selectin, it remains abnormally localized to the demarcation membrane system rather than being assembled into the α-granules in platelets. Mice carrying the hypomorphic Gata1(low) mutation express the same megakaryocyte abnormalities presented by primary myelofibrosis patients, including abnormal P-selectin localization to the DMS and develop with age myelofibrosis, a disease that closely resembles human primary myelofibrosis. Whether these mice would also develop thrombosis has not been investigated as yet. The aim of this study was to determine whether Gata1(low) mice would develop thrombosis with age and, in this case, the role played by P-selectin in the development of the trait. To this aim, Gata1(low) mice were crossed with P-sel(null) mice according to standard genetic protocols and Gata1(low)P-sel(wt), Gata1(low)P-sel(null) and Gata1(WT)P-sel(null) or Gata1(wt)P-sel(wt) (as controls) littermates obtained. It was shown that platelet counts, but not hematocrit, are reduced in Gata1(low) mice. Moreover, platelet microparticles are reduced in Gata1(low) mice and P-selectin positive platelet microparticles were not found. To determine the phenotypic implications of the different mutations, bleeding time was estimated by a tail cut procedure. Mutant mice were sacrificed and presence of thrombosis was determined by immunohistological staining of organs. Gata1(low) mice with or without the P-selectin null trait had a prolonged bleeding time compared to wild type mice. However, in Gata1(low) mice significantly higher frequency of thrombotic events was seen in adult and old Gata1(low) mice compared to Gata1(low)P-sel(null) mice. Thus, presence of the P-selectin null trait rescued Gata1(low) mice from the thrombotic phenotype, but did not change the level of platelet microparticles. Taken together these data indicate that abnormal localization of P-selectin, induced by the Gata1(low) mutation, and thus, increased pathological interactions with leucocytes, is responsible for the increased presence of thrombosis seen in these mice.

Myeloperoxidase induces the priming of platelets

The release of myeloperoxidase (MPO) from polymorphonuclear neutrophils is a hallmark of vascular inflammation and contributes to the pathogenesis of vascular inflammatory processes. However, the effects of MPO on platelets as a contributory mechanism in vascular inflammatory diseases remain unknown. Thus, MPO interaction with platelets and its effects on platelet function were examined. First, dose-dependent binding of MPO (between 1.7 and 13.8nM) to both human and mouse platelets was observed. This was in direct contrast to the absence of MPO in megakaryocytes. MPO was localized both on the surface of and inside platelets. Cytoskeleton inhibition did not prevent MPO localization inside the three-dimensional platelet structure. MPO peroxidase activity was preserved upon the MPO binding to platelets. MPO sequestered in platelets catabolized NO, documented by the decreased production of NO (on average, an approximately 2-fold decrease). MPO treatment did not affect the viability of platelets during short incubations; however, it decreased platelet viability after long-term storage for 7 days (an approximately 2-fold decrease). The activation of platelets by MPO was documented by an MPO-mediated increase in the expression of surface platelet receptors P-selectin and PECAM-1 (of about 5 to 20%) and the increased formation of reactive oxygen species (of about 15 to 200%). However, the activation was only partial, as MPO did not induce the aggregation of platelets nor potentiate platelet response to classical activators. Nor did MPO induce a significant release of the content of granules. The activation of platelets by MPO was connected with increased MPO-treated platelet interaction with polymorphonuclear leukocytes (an approximately 1.2-fold increase) in vitro. In conclusion, it can be suggested that MPO can interact with and activate platelets, which can induce priming of platelets, rather than the classical robust activation of platelets. This can contribute to the development of chronic inflammatory processes in vessels.

Heritability, genetic correlation and linkage to the 9p21.3 region of mixed platelet-leukocyte conjugates in families with and without early myocardial infarction

BACKGROUND AND AIMS

Variations in mixed platelet-leukocyte conjugate formation in human whole blood could be genetically determined. We quantified platelet and leukocyte activation and interaction in families with or without early myocardial infarction and evaluated their heritability, genetic correlation and linkage to the 9p21.3 region.

METHODS AND RESULTS

The study population included 739 subjects (≥ 15 years old) from 54 large pedigrees, 23 with and 31 without familial myocardial infarction. Mixed platelet-leukocyte conjugates and markers of platelet or leukocyte activation (P-selectin, CD11b and L-selectin surface expression) were measured both before and after in vitro blood stimulation with collagen-ADP. All traits had significant genetic components (17.5-65.3% of the phenotypic variability), while shared household effects (0-39.6%) and environmental covariates (0-10.2%) tended to be smaller. Stimulated platelet-polymorphonuclear leukocyte (PMN) and platelet-monocyte conjugates showed the highest linkage to the 9p21.3 region (LOD = 0.94 and 1.33, respectively; empirical p value = 0.017 and 0.009). PMN markers resulted strongly genetically correlated between them in bivariate analysis among pairs of quantitative traits.

CONCLUSION

This study supports a genetic regulation of human mixed platelet-leukocyte conjugates.

Pharmacological control of platelet-leukocyte interactions by the human anti-P-selectin antibody inclacumab--preclinical and clinical studies

BACKGROUND AND OBJECTIVE

Elevated levels of platelet-leukocyte aggregates (PLAs) have been reported in several cardiovascular diseases and suggested to contribute to disease pathology. Our aim was to characterize the effects of inclacumab, a novel human anti-P-selectin antibody, on the interactions between leukocytes and platelets in preclinical and clinical studies.

EXPERIMENTAL APPROACHES

Dual-label flow cytometry was used to detect the effect of inclacumab on agonist-induced platelet-leukocyte/platelet-monocyte aggregates in cynomolgus monkeys and humans, following ex vivo and in vivo administration. Platelet-dependent leukocyte activation and leukocyte adhesion to a platelet monolayer were also investigated after ex vivo administration of inclacumab to human blood.

RESULTS

Treatment of cynomolgus monkeys with inclacumab profoundly inhibited thrombin receptor-activating peptide (TRAP) or adenosine diphosphate (ADP)-induced PLAs with an IC50 (<2 μg/mL) similar to the in vitro spiking experiments. Maximal inhibition of PLAs persisted for ≥28 days following single dose of inclacumab. In human blood, inclacumab was about 2-fold more potent in inhibiting TRAP-induced PLAs (IC50: 0.7 μg/mL) compared to monkeys. PLA formation was suppressed independently of the inducing platelet agonist. Inclacumab also inhibited the activation of the leukocyte integrin Mac-1 and leukocyte adhesion to a platelet monolayer under flow conditions. In clinical studies, inclacumab inhibited TRAP-induced PLA formation in a dose-dependent manner following single and multiple dose administration to healthy volunteers. It also reduced elevated circulating PLA levels in patients with peripheral arterial disease.

CONCLUSION

By inhibiting platelet-leukocyte interactions, demonstrated in multiple preclinical and clinical studies, inclacumab may provide an effective treatment for cardiovascular diseases.

Platelet-leukocyte interactions in thrombosis

Activated platelets may adhere to leukocytes and form circulating mixed aggregates. The latter are considered a reliable marker of a prothrombotic state and are associated with several cardiovascular conditions. The molecular mechanisms responsible of this cellular interaction include a central role of platelet P-selectin and of P-selectin glycoprotein ligand-1 (PSGL-1), its counter receptor on leukocytes in a signaling cascade, resulting in the activation of the beta-2 integrin Mac-1 and in the firm adhesion between the two cell types. The interaction of P-selectin with PSGL-1 also induces upregulation of leukocyte tissue factor, biosynthesis of several cytokines and other inflammatory reactions, thereby contributing to the thrombotic progression. In this review the main determinants of mixed aggregate formation, the heritability component, the major pathological conditions associated with higher levels of mixed aggregates in the circulation will be discussed. Besides current anti-platelet or antithrombotic drugs, natural compounds, such as the polyphenols present in vegetable foods and red wine, have been tested for their inhibitory effect on mixed aggregate formation. The promising results shown by studies in vitro and in experimental animal models, remain to be carefully investigated in humans. Platelet-leukocyte aggregates provide a novel link between inflammation and thrombosis, two central processes in atherogenesis. A better understanding of the role of platelet-leukocyte interactions in athero-thrombosis will be instrumental for the progress of prevention and treatment of ischaemic cardiovascular disease.

Leukocyte- and platelet-derived microvesicle interactions following in vitro and in vivo activation of toll-like receptor 4 by lipopolysaccharide

Background

Pro-coagulant membrane microvesicles (MV) derived from platelets and leukocytes are shed into the circulation following receptor-mediated activation, cell-cell interaction, and apoptosis. Platelets are sentinel markers of toll-like receptor 4 (TLR4) activation. Experiments were designed to evaluate the time course and mechanism of direct interactions between platelets and leukocytes following acute activation of TLR4 by bacterial lipopolysaccharide (LPS).

Methodology/Principal Findings

Blood from age-matched male and female wild type (WT) and TLR4 gene deleted (dTLR4) mice was incubated with ultra-pure E. coli LPS (500 ng/ml) for up to one hour. At designated periods, leukocyte antigen positive platelets, platelet antigen positive leukocytes and cell-derived MV were quantified by flow cytometry. Numbers of platelet- or leukocyte-derived MV did not increase within one hour following in vitro exposure of blood to LPS. However, with LPS stimulation numbers of platelets staining positive for both platelet- and leukocyte-specific antigens increased in blood derived from WT but not dTLR4 mice. This effect was blocked by inhibition of TLR4 signaling mediated by My88 and TRIF. Seven days after a single intravenous injection of LPS (500 ng/mouse or 20 ng/gm body wt) to WT mice, none of the platelets stained for leukocyte antigen. However, granulocytes, monocytes and apoptotic bodies stained positive for platelet antigens.

Conclusions/Significance

Within one hour of exposure to LPS, leukocytes exchange surface antigens with platelets through TLR4 activation. In vivo, leukocyte expression of platelet antigen is retained after a single exposure to LPS following turn over of the platelet pool. Acute expression of leukocyte antigen on platelets within one hour of exposure to LPS and the sustained expression of platelet antigen on leukocytes following a single acute exposure to LPS in vivo explains, in part, associations of platelets and leukocytes in response to bacterial infection and changes in thrombotic propensity of the blood.

Four-week ingestion of blood orange juice results in measurable anthocyanin urinary levels but does not affect cellular markers related to cardiovascular risk: a randomized cross-over study in healthy volunteers

PURPOSE

Blood orange juice (OJ) is an important source of anthocyanins (ACN). The latter molecules are endowed with antioxidant activity and might thus modulate different cell function. Our aim was to investigate ACN absorption following a 1-month daily supplementation of blood OJ and their potential effects on cell markers of platelet and leukocyte activation and interaction.

METHODS

Eighteen healthy subjects (10 men and 8 women) were supplemented for 4 weeks with 1 L/day of either blood OJ or blond OJ (that contains no ACN), following a cross-over design. Blood samples were obtained from fasting participants both at baseline and after each week of treatment to measure plasma ACN concentration. At the same time-intervals, 24-h urinary excretion of these molecules was also measured. At the beginning and the end of each 4-week intervention period, platelet and leukocyte markers and mixed cell conjugates were assessed both in basal condition and upon in vitro collagen/ADP activation.

RESULTS

After 1 week supplementation with blood OJ, 24-h urinary excretion of ACN reached average levels of 11.47 ± 5.63 nmol that significantly differed from baseline and remained substantially unchanged until the end of treatment. No plasma accumulation of ACN following blood OJ supplementation was observed. Cellular markers were not significantly affected by either OJ after 4-week supplementation.

CONCLUSIONS

Following supplementation of healthy volunteers with 1 L/day of blood OJ for 4 weeks, the ACN plasma levels reached were insufficient to significantly modify cell markers of platelet and leukocyte activation and interaction.