CD40 ligand on activated platelets triggers an inflammatory reaction of endothelial cells

The Inhibition of CD40/CD154 Costimulatory Signaling in the Prevention of Renal Transplant Rejection in Nonhuman Primates: A Systematic Review and Meta Analysis

The prevention of allograft transplant rejection by inhibition of the CD40/CD40L costimulatory pathway has been described in several species. We searched pubmed for studies reporting the prevention of kidney transplant rejection in nonhuman primates utilizing either anti CD40 or anti CD40L (CD154) treatment. Inclusion of data required treatment with anti CD40 or anti CD154 as monotherapy treatment arms, full text available, studies conducted in nonhuman primate species, the transplant was renal transplantation, sufficient duration of treatment to assess long term rejection, and the reporting of individual graft survival or survival duration. Eleven publications were included in the study. Rejection free survival was calculated using the Kaplan-Meier (KM) life test methods to estimate the survival functions. The 95% CI for the medians was also calculated. A log-rank test was used to test the equality of the survival curves between control and treatment arms (CD40 and CD154). The hazard ratio for CD154 compared to CD40 and 95% CI was calculated using a Cox proportional-hazards model including treatment as the covariate to assess the magnitude of the treatment effect. Both anti CD40 and anti CD154 treatments prevented acute and long term graft rejection. The median (95% CI) rejection free survival was 131 days (84,169 days) in the anti CD40 treated animals and 352 days (173,710 days) in the anti CD154 treated animals. Median survival in the untreated animals was 6 days. The inhibition of transplant rejection was more durable in the anti CD154 group compared to the anti CD40 group after cessation of treatment. The median (95% CI) rejection free survival after cessation of treatment was 60 days (21,80 days) in the anti CD40 treated animals and 230 days (84,552 days) in the anti CD154 treated animals.

Platelets as Key Factors in Inflammation: Focus on CD40L/CD40

Platelets are anucleate cytoplasmic fragments derived from the fragmentation of medullary megakaryocytes. Activated platelets adhere to the damaged endothelium by means of glycoproteins on their surface, forming the platelet plug. Activated platelets can also secrete the contents of their granules, notably the growth factors contained in the α-granules, which are involved in platelet aggregation and maintain endothelial activation, but also contribute to vascular repair and angiogenesis. Platelets also have a major inflammatory and immune function in antibacterial defence, essentially through their Toll-like Receptors (TLRs) and Sialic acid-binding immunoglobulin-type lectin (SIGLEC). Platelet activation also contributes to the extensive release of anti- or pro-inflammatory mediators such as IL-1β, RANTES (Regulated on Activation, Normal T Expressed and Secreted) or CD154, also known as the CD40-ligand. Platelets are involved in the direct activation of immune cells, polynuclear neutrophils (PNNs) and dendritic cells via the CD40L/CD40 complex. As a general rule, all of the studies presented in this review show that platelets are capable of covering most of the stages of inflammation, primarily through the CD40L/CD40 interaction, thus confirming their own role in this pathophysiological condition.

Recent advance in treatment of atherosclerosis: Key targets and plaque-positioned delivery strategies

Atherosclerosis, a chronic inflammatory disease of vascular wall, is a progressive pathophysiological process with lipids oxidation/depositing initiation and innate/adaptive immune responses. The coordination of multi systems covering oxidative stress, dysfunctional endothelium, diseased lipid uptake, cell apoptosis, thrombotic and pro-inflammatory responding as well as switched SMCs contributes to plaque growth. In this circumstance, inevitably, targeting these processes is considered to be effective for treating atherosclerosis. Arriving, retention and working of payload candidates mediated by targets in lesion direct ultimate therapeutic outcomes. Accumulating a series of scientific studies and clinical practice in the past decades, lesion homing delivery strategies including stent/balloon/nanoparticle-based transportation worked as the potent promotor to ensure a therapeutic effect. The objective of this review is to achieve a very brief summary about the effective therapeutic methods cooperating specifical targets and positioning-delivery strategies in atherosclerosis for better outcomes.

Innovative immunosuppression in kidney transplantation: A challenge for unmet needs

Due to the optimal results obtained in kidney transplantation and to the lack of interest of the industries, new innovative drugs in kidney transplantation are difficult to be encountered. The best strategy to find the new drugs recently developed or under development is to search in the sections of kidney transplantation still not completely covered by the drugs on the market. These unmet needs are the prevention of delayed graft function (DGF), the protection of the graft over the long time and the desensitization of preformed anti human leukocyte antigen antibodies and the treatment of the acute antibody-mediated rejection. These needs are particularly relevant due to the expansion of some kind of kidney transplantation as transplantation from non-heart beating donor and in the case of antibody-incompatible grafts. The first are particularly exposed to DGF, the latter need a safe desensitization and a safe treatments of the antibody mediated rejections that often occur. Particular caution is needed in treating these drugs. First, they are described in very recent studies and the follow-up of their effect is of course rather short. Second, some of these drugs are still in an early phase of study, even if in well-conducted randomized controlled trials. Particular caution and a careful check need to be used in trials launched 2 or 3 years ago. Indeed, is always necessary to verify whether the study is still going on or whether and why the study itself was abandoned.

SARS-CoV-2 infection induces soluble platelet activation markers and PAI-1 in the early moderate stage of COVID-19

Introduction

Coagulation dysfunction and thromboembolism emerge as strong comorbidity factors in severe COVID‐19. However, it is unclear when particularly platelet activation markers and coagulation factors dysregulated during the pathogenesis of COVID‐19. Here, we sought to assess the levels of coagulation and platelet activation markers at moderate and severe stages of COVID‐19 to understand the pathogenesis.

Methods

To understand this, hospitalized COVID‐19 patients with (severe cases that required intensive care) or without pneumonia (moderate cases) were recruited. Phenotypic and molecular characterizations were performed employing basic coagulation tests including prothrombin time (PT), activated partial thromboplastin time (APTT), D‐Dimer, and tissue factor pathway inhibitor (TFPI). The flow cytometry‐based multiplex assays were performed to assess FXI, anti‐thrombin, prothrombin, fibrinogen, FXIII, P‐selectin, sCD40L, plasminogen, tissue plasminogen activator (tPA), plasminogen activator inhibitor‐1 (PAI‐1), and D‐Dimer.

Results

The investigations revealed induction of plasma P‐selectin and CD40 ligand (sCD40L) in moderate COVID‐19 cases, which were significantly abolished with the progression of COVID‐19 severity. Moreover, a profound reduction in plasma tissue factor pathway inhibitor (TFPI) and FXIII were identified particularly in the severe COVID‐19. Further analysis revealed fibrinogen induction in both moderate and severe patients. Interestingly, an elevated PAI‐1 more prominently in moderate, and tPA particularly in severe COVID‐19 cases were observed. Particularly, the levels of fibrinogen and tPA directly correlated with the severity of the disease.

Conclusions

In summary, induction of soluble P‐selectin, sCD40L, fibrinogen, and PAI‐1 suggests the activation of platelets and coagulation system at the moderate stage before COVID‐19 patients require intensive care. These findings would help in designing better thromboprophylaxis to limit the COVID‐19 severity.

Correlation between Platelet Count and Lung Dysfunction in Multiple Trauma Patients-A Retrospective Cohort Analysis

(1) Background: Current findings emphasize the potential contribution of platelets to the immunological response after severe trauma. As clinical relevance remains unclear, this study aims to analyze the correlation between platelets and lung dysfunction in severely injured patients. (2) Methods: We retrospectively enrolled all multiple trauma patients presenting to our level 1 trauma center from 2015 to 2016 with an Injury-Severity Score (ISS) ≥ 16. Apart from demographic data, platelet counts and PaO₂/FiO₂ as an approximate indicator for lung physiology were analyzed and correlated on subsequent days after admission. (3) Results: 83 patients with a median ISS of 22 (IQR 18–36) were included. Compared to day 1, platelet counts were decreased on day 3 (p ≤ 0.001). Platelet counts were significantly lower on day 3 in patients with an ISS ≥ 35 (p = 0.011). There were no differences regarding PaO₂/FiO₂ index. Correlation analysis revealed a positive link between increased platelet counts and PaO₂/FiO₂ index on day 1 only in severely injured patients (p = 0.007). (4) Conclusions: This work supports the concept of platelets modulating the posttraumatic immune response by affecting lung dysfunction in the early phase after multiple trauma in dependence of injury severity. Our findings contribute to the understanding of the impact of platelets on systemic processes in multiple trauma patients.

Diagnosis of Platelet Function Disorders: A Challenge for Laboratories

In patients with normal plasmatic coagulation and bleeding tendency, platelet function defect can be assumed. Congenital platelet function defects are rare. Much more commonly they are acquired. The clinical bleeding tendency of platelet function defects is heterogeneous, which makes diagnostic approaches difficult. During the years, a large variety of tests for morphological phenotyping and functional analysis have been developed. The diagnosis of platelet function defects is based on standardized bleeding assessment tools followed by a profound morphological evaluation of the platelets. Platelet function assays like light transmission aggregation, luminoaggregometry, and impedance aggregometry followed by flow cytometry are commonly used to establish the diagnosis in these patients. Nevertheless, despite great efforts, standardization of these tests is poor and in most cases, quality control is lacking. In addition, these tests are still limited to specialized laboratories. This review summarizes the approaches to morphologic phenotyping and platelet testing in patients with suspected platelet dysfunction, beginning with a standardized bleeding score and ending with flow cytometry testing. The diagnosis of a functional defect requires a good collaboration between the laboratory and the clinician.

Soluble Immune Checkpoints Are Dysregulated in COVID-19 and Heavy Alcohol Users With HIV Infection

Immune checkpoints (ICPs) consist of paired receptor-ligand molecules that exert inhibitory or stimulatory effects on immune defense, surveillance, regulation, and self-tolerance. ICPs exist in both membrane and soluble forms in vivo and in vitro. Imbalances between inhibitory and stimulatory membrane-bound ICPs (mICPs) in malignant cells and immune cells in the tumor immune microenvironment (TIME) have been well documented. Blockades of inhibitory mICPs have emerged as an immense breakthrough in cancer therapeutics. However, the origin, structure, production regulation, and biological significance of soluble ICPs (sICPs) in health and disease largely remains elusive. Soluble ICPs can be generated through either alternative mRNA splicing and secretion or protease-mediated shedding from mICPs. Since sICPs are found in the bloodstream, they likely form a circulating immune regulatory system. In fact, there is increasing evidence that sICPs exhibit biological functions including (1) regulation of antibacterial immunity, (2) interaction with their mICP compartments to positively or negatively regulate immune responses, and (3) competition with their mICP compartments for binding to the ICP blocking antibodies, thereby reducing the efficacy of ICP blockade therapies. Here, we summarize current data of sICPs in cancer and infectious diseases. We particularly focus on sICPs in COVID-19 and HIV infection as they are the two ongoing global pandemics and have created the world's most serious public health challenges. A "storm" of sICPs occurs in the peripheral circulation of COVID-19 patients and is associated with the severity of COVID-19. Similarly, sICPs are highly dysregulated in people living with HIV (PLHIV) and some sICPs remain dysregulated in PLHIV on antiretroviral therapy (ART), indicating these sICPs may serve as biomarkers of incomplete immune reconstitution in PLHIV on ART. We reveal that HIV infection in the setting of alcohol misuse exacerbates sICP dysregulation as PLHIV with heavy alcohol consumption have significantly elevated plasma levels of many sICPs. Thus, both stimulatory and inhibitory sICPs are present in the bloodstream of healthy people and their balance can be disrupted under pathophysiological conditions such as cancer, COVID-19, HIV infection, and alcohol misuse. There is an urgent need to study the role of sICPs in immune regulation in health and disease.

Platelet-Released Factors: Their Role in Viral Disease and Applications for Extracellular Vesicle (EV) Therapy

Platelets, which are small anuclear cell fragments, play important roles in thrombosis and hemostasis, but also actively release factors that can both suppress and induce viral infections. Platelet-released factors include sCD40L, microvesicles (MVs), and alpha granules that have the capacity to exert either pro-inflammatory or anti-inflammatory effects depending on the virus. These factors are prime targets for use in extracellular vesicle (EV)-based therapy due to their ability to reduce viral infections and exert anti-inflammatory effects. While there are some studies regarding platelet microvesicle-based (PMV-based) therapy, there is still much to learn about PMVs before such therapy can be used. This review provides the background necessary to understand the roles of platelet-released factors, how these factors might be useful in PMV-based therapy, and a critical discussion of current knowledge of platelets and their role in viral diseases.

Advances in research on the effects of platelet activation in acute lung injury (Review)

Acute lung injury (ALI) is an acute hypoxic respiratory insufficiency or failure caused by various factors inside and outside the lungs. ALI is associated with high morbidity and a poor prognosis in hospitalized patients. The lungs serve as a reservoir for platelet precursor megakaryocytes and are closely associated with platelets. Platelets not only play a central role in hemostasis, coagulation and wound healing, but can also act as inflammatory cells capable of stimulating non-hemostatic immune functions under inflammatory conditions, participating in the progression of various inflammatory diseases, and can result in tissue damage. Therefore, it was speculated that platelets may play an important role in the pathogenesis of ALI. In this review, the latest research progress on secretion of bioactive mediators from platelets, platelet activation-related signaling pathways, and the direct contact reactions between platelets and neutrophils with endothelial cells that result in ALI are described, providing evidence to support the importance of the consideration of platelets in the search for ALI interventional targets.

Activated platelets and platelet-leukocyte aggregates in the equine systemic inflammatory response syndrome

In humans, activated platelets contribute to sepsis complications and to multiple organ failure. In our prospective analytical study of cases of the equine systemic inflammatory response syndrome (SIRS), we adapted a standard human protocol for the measurement of activated platelets and platelet-leukocyte aggregates (PLAs) in equine platelet-leukocyte-rich plasma (PLRP) by flow cytometry, and we investigated the hypothesis that activated platelets and PLAs are increased in clinical cases of SIRS. We included 17 adult horses and ponies fulfilling at least 2 SIRS criteria, and 10 healthy equids as controls. Activation of platelets was determined by increased expression of CD62P on platelets. Activated platelets and PLAs were measured before and after in vitro activation of platelets with collagen. Median expression of CD62P on platelets was significantly increased after activation in the control group: 1.45% (interquartile range [IQR]: 1.08-1.99%) initially versus 8.78% (IQR: 6.79-14.78%, p = 0.002) after activation. The equids with SIRS had significantly more activated platelets and PLAs in native PLRP than controls: CD62P 4.92% (median, IQR: 2.21-12.41%) versus 1.45% in controls (median, IQR: 1.08-1.99%, p = 0.0007), and PLAs 4.16% (median, IQR: 2.50-8.58%) versus 2.95% in controls (median, IQR: 1.57-3.22%, p = 0.048). To our knowledge, increased platelet activation and PLAs have not been demonstrated previously with flow cytometry in clinical cases of equine SIRS.

Neonatal Sepsis and Hemostasis

Neonatal sepsis is considered critical for a significant increase in neonatal morbidity and mortality among hospitalized neonates. Neonatal sepsis, in most cases, coexists with coagulopathy, which can prove to be life-threatening. Complex molecular and cellular systems are involved in the cross-talk between inflammation and hemostasis during sepsis. Disturbances in the regulating systems of the vascular endothelium, and platelet–endothelial and platelet–neutrophil interactions play a pivotal role in both inflammation and coagulation. This complex process is poorly understood in neonates. In addition to the developmental maturation of hemostasis and the immune response in neonatal sepsis, a cellular model of hemostasis during sepsis should be taken into account. This review focused on the molecular and cellular mechanisms underlying inflammation and hemostasis during neonatal sepsis, taking the developmental immune response and developmental hemostasis into account in order to provide future diagnostic approaches to be applied in everyday clinical settings. Regarding the diagnostic modalities, we briefly provide the limitations of the currently used conventional coagulation assays, focusing on viscoelastic tests and platelet flow cytometry.

Inflammation-Induced Coagulopathy Substantially Differs Between COVID-19 and Septic Shock: A Prospective Observational Study

Critical COVID-19, like septic shock, is related to a dysregulated systemic inflammatory reaction and is associated with a high incidence of thrombosis and microthrombosis. Improving the understanding of the underlying pathophysiology of critical COVID-19 could help in finding new therapeutic targets already explored in the treatment of septic shock. The current study prospectively compared 48 patients with septic shock and 22 patients with critical COVID-19 regarding their clinical characteristics and outcomes, as well as key plasmatic soluble biomarkers of inflammation, coagulation, endothelial activation, platelet activation, and NETosis. Forty-eight patients with matched age, gender, and co-morbidities were used as controls. Critical COVID-19 patients exhibited less organ failure but a prolonged ICU length-of-stay due to a prolonged respiratory failure. Inflammatory reaction of critical COVID-19 was distinguished by very high levels of interleukin (IL)-1β and T lymphocyte activation (including IL-7 and CD40L), whereas septic shock displays higher levels of IL-6, IL-8, and a more significant elevation of myeloid response biomarkers, including Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) and IL-1ra. Subsequent inflammation-induced coagulopathy of COVID-19 also differed from sepsis-induced coagulopathy (SIC) and was characterized by a marked increase in soluble tissue factor (TF) but less platelets, antithrombin, and fibrinogen consumption, and less fibrinolysis alteration. In conclusion, COVID-19 inflammation-induced coagulopathy substantially differs from SIC. Modulating TF release and activity should be evaluated in critical COVID-19 patients.

Comparative Transcriptome Analyses of Gayal (Bos frontalis), Yak (Bos grunniens), and Cattle (Bos taurus) Reveal the High-Altitude Adaptation

Gayal and yak are well adapted to their local high-altitude environments, yet the transcriptional regulation difference of the plateau environment among them remains obscure. Herein, cross-tissue and cross-species comparative transcriptome analyses were performed for the six hypoxia-sensitive tissues from gayal, yak, and cattle. Gene expression profiles for all single-copy orthologous genes showed tissue-specific expression patterns. By differential expression analysis, we identified 3,020 and 1,995 differentially expressed genes (DEGs) in at least one tissue of gayal vs. cattle and yak vs. cattle, respectively. Notably, we found that the adaptability of the gayal to the alpine canyon environment is highly similar to the yak living in the Qinghai-Tibet Plateau, such as promoting red blood cell development, angiogenesis, reducing blood coagulation, immune system activation, and energy metabolism shifts from fatty acid β-oxidation to glycolysis. By further analyzing the common and unique DEGs in the six tissues, we also found that numerous expressed regulatory genes related to these functions are unique in the gayal and yak, which may play important roles in adapting to the corresponding high-altitude environment. Combined with WGCNA analysis, we found that UQCRC1 and COX5A are the shared differentially expressed hub genes related to the energy supply of myocardial contraction in the heart-related modules of gayal and yak, and CAPS is a shared differential hub gene among the hub genes of the lung-related module, which is related to pulmonary artery smooth muscle contraction. Additionally, EDN3 is the unique differentially expressed hub gene related to the tracheal epithelium and pulmonary vasoconstriction in the lung of gayal. CHRM2 is a unique differentially expressed hub gene that was identified in the heart of yak, which has an important role in the autonomous regulation of the heart. These results provide a basis for further understanding the complex transcriptome expression pattern and the regulatory mechanism of high-altitude domestication of gayal and yak.

Platelets after burn injury - hemostasis and beyond

Burn injuries are common and often life-threatening trauma. With this trauma comes an interruption of normal hemostasis, with distinct impacts on platelets. Our interest in the relationships between burn injury and platelet function stems from two key perspectives: platelet function is a vital component of acute responses to injury, and furthermore the incidence of cardiovascular disease (CVD) is higher in burn survivors compared to the general population. This review explores the impact of burn injury on coagulation, platelet function, and the participation of platelets in immunopathology. Potential avenues of further research are explored, and consideration is given to what therapies may be appropriate for mediating post-burn thrombopathology.

Antiplatelet therapy and outcome in COVID-19: the Health Outcome Predictive Evaluation Registry

BACKGROUND

Standard therapy for COVID-19 is continuously evolving. Autopsy studies showed high prevalence of platelet-fibrin-rich microthrombi in several organs. The aim of the study was therefore to evaluate the safety and efficacy of antiplatelet therapy (APT) in hospitalised patients with COVID-19 and its impact on survival.

METHODS

7824 consecutive patients with COVID-19 were enrolled in a multicentre international prospective registry (Health Outcome Predictive Evaluation-COVID-19 Registry). Clinical data and in-hospital complications were recorded. Data on APT, including aspirin and other antiplatelet drugs, were obtained for each patient.

RESULTS

During hospitalisation, 730 (9%) patients received single APT (93%, n=680) or dual APT (7%, n=50). Patients treated with APT were older (74±12 years vs 63±17 years, p<0.01), more frequently male (68% vs 57%, p<0.01) and had higher prevalence of diabetes (39% vs 16%, p<0.01). Patients treated with APT showed no differences in terms of in-hospital mortality (18% vs 19%, p=0.64), need for invasive ventilation (8.7% vs 8.5%, p=0.88), embolic events (2.9% vs 2.5% p=0.34) and bleeding (2.1% vs 2.4%, p=0.43), but had shorter duration of mechanical ventilation (8±5 days vs 11±7 days, p=0.01); however, when comparing patients with APT versus no APT and no anticoagulation therapy, APT was associated with lower mortality rates (log-rank p<0.01, relative risk 0.79, 95% CI 0.70 to 0.94). On multivariable analysis, in-hospital APT was associated with lower mortality risk (relative risk 0.39, 95% CI 0.32 to 0.48, p<0.01).

CONCLUSIONS

APT during hospitalisation for COVID-19 could be associated with lower mortality risk and shorter duration of mechanical ventilation, without increased risk of bleeding.

TRIAL REGISTRATION NUMBER

NCT04334291.

Evolution of Platelet Activation Parameters During Septic Shock in Intensive Care Unit

During severe sepsis, platelet activation may induce disseminate microvascular thrombosis, which play a key role in critical organ failure. Crucially, most of the studies in this field have explored platelet-leukocyte interactions in animal models, or explored platelets under the spectrum of thrombocytopenia or disseminated intravascular coagulation and have not taken into account the complex interplay that might exist between platelets and leukocytes during human septic shock nor the kinetics of platelet activation. Here, we assessed platelet activation parameters at the admission of patients with sepsis to the intensive care unit (ICU) and 48 hours later. Twenty-two patients were enrolled in the study, thirteen (59.1%) of whom were thrombocytopenic. The control group was composed of twelve infection-free patients admitted during the study period. The activation parameters studied included platelet-leukocyte interactions, assessed by flow cytometry in whole blood, as well as membrane surface and soluble platelet activation markers measured by flow cytometry and dedicated ELISA kits. We also investigated platelet aggregation and secretion responses of patients with sepsis following stimulation, compared to controls. At admission, the level of circulating monocyte-platelet and neutrophil-platelet heterotypic aggregates was significantly higher in sepsis patients compared to controls and returned to a level comparable to controls or even below 48 hours later. Basal levels of CD62P and CD63 platelet membrane exposure at admission and 48 hours later were low and similar to controls. In contrast, plasma level of soluble GPVI and soluble CD40 ligand was significantly increased in septic patients, at the two times of analysis, reflecting previous platelet activation. Platelet aggregation and secretion responses induced by specific agonists were significantly decreased in septic conditions, particularly 48 hours after admission. Hence, we have observed for the first time that critically ill septic patients compared to controls have both an early and durable platelet activation while their circulating platelets are less responsive to different agonists.

P2Y12 Inhibition in Murine Myocarditis Results in Reduced Platelet Infiltration and Preserved Ejection Fraction

Previous mouse studies have shown the increased presence of platelets in the myocardium during early stages of myocarditis and their selective detection by MRI. Here, we aimed to depict early myocarditis using molecular contrast-enhanced ultrasound of activated platelets, and to evaluate the impact of a P2Y12 receptor platelet inhibition. Experimental autoimmune myocarditis was induced in BALB/c mice by subcutaneous injection of porcine cardiac myosin and complete Freund adjuvant (CFA). Activated platelets were targeted with microbubbles (MB) coupled to a single-chain antibody that binds to the "ligand-induced binding sites" of the GPIIb/IIIa-receptor (=LIBS-MB). Alongside myocarditis induction, a group of mice received a daily dose of 100 g prasugrel for 1 month. Mice injected with myosin and CFA had a significantly deteriorated ejection fraction and histological inflammation on day 28 compared to mice only injected with myosin. Platelets infiltrated the myocardium before reduction in ejection fraction could be detected by echocardiography. No selective binding of the LIBS-MB contrast agent could be detected by either ultrasound or histology. Prasugrel therapy preserved ejection fraction and significantly reduced platelet aggregates in the myocardium compared to mice without prasugrel therapy. Therefore, P2Y12 inhibition could be a promising early therapeutic target in myocarditis, requiring further investigation.

Preoperative soluble cluster of differentiation 40 ligand level is associated with outcome of pulmonary endarterectomy

Objective

Soluble CD40 ligand (sCD40L) is associated with some pathobiological states. However, whether sCD40L in patients with chronic thromboembolic pulmonary hypertension (CTEPH) who underwent pulmonary endarterectomy (PEA) is associated with perioperative pulmonary hemodynamics and surgical outcomes has not been elucidated. Here we aimed to investigate whether sCD40L is a useful serologic biomarker of poor surgical outcome of PEA in patients with CTEPH.

Methods

Ninety patients with CTEPH who underwent PEA were enrolled. Independent preoperative parameters were examined, including sCD40L related to lower cardiac index (CI), higher pulmonary vascular resistance (PVR), and poor surgical outcomes after PEA, according to the multivariate logistic regression analysis. In addition, the area under the curve (AUC) value of sCD40L to predict poor surgical outcomes was compared with the AUCs of D-dimer and C-reactive protein (CRP). The generalizability of this study model was tested by a 5-fold cross-validation analysis.

Results

Multivariate logistic regression analysis showed that high sCD40L level was related to postoperative lower CI, higher PVR, and poor surgical outcomes independent of other preoperative parameters. The AUC value of sCD40L to predict poor surgical outcomes was higher than those of D-dimer and CRP. A sCD40L cutoff value of 1.45 ng/mL predicted poor surgical outcomes with 79.3% sensitivity and 67.3% specificity. The 5-fold cross-validation analysis showed the effectiveness of our model's performance.

Conclusions

Preoperative sCD40L level could be a promising serologic biomarker associated with poor surgical outcomes in CTEPH. In addition to known preoperative parameters, the biomarker might have the potential to identify patients at high risk of PEA, thereby reducing the mortality rates.

Common Pathophysiology in Cancer, Atrial Fibrillation, Atherosclerosis, and Thrombosis: JACC: CardioOncology State-of-the-Art Review

Cardiovascular disease and cancer are the 2 leading causes of death worldwide. Emerging evidence suggests common mechanisms between cancer and cardiovascular disease, including atrial fibrillation and atherosclerosis. With advances in cancer therapies, screening, and diagnostics, cancer-specific survival and outcomes have improved. This increase in survival has led to the coincidence of cardiovascular disease, including atrial fibrillation and atherosclerosis, as patients with cancer live longer. Additionally, cancer and cardiovascular disease share several risk factors and underlying pathophysiologic mechanisms, including inflammation, cancer-related factors including treatment effects, and alterations in platelet function. Patients with cancer are at increased risk for bleeding and thrombosis compared with the general population. Although optimal antithrombotic therapy, including agent choice and duration, has been extensively studied in the general population, this area remains understudied in patients with cancer despite their altered thrombotic and bleeding risk. Future investigation, including incorporation of cancer-specific characteristics to traditional thrombotic and bleeding risk scores, clinical trials in the cancer population, and the development of novel antithrombotic and anti-inflammatory strategies on the basis of shared pathophysiologic mechanisms, is warranted to improve outcomes in this patient population.

Inflammatory mediators in diabetic retinopathy: Deriving clinicopathological correlations for potential targeted therapy

The role of inflammation in diabetic retinopathy (DR) is well-established and dysregulation of a large number of inflammatory mediators is known. These include cytokines, chemokines, growth factors, mediators of proteogenesis, and pro-apoptotic molecules. This para-inflammation as a response is not directed to a particular pathogen or antigen but is rather directed toward the by-products of the diabetic milieu. The inflammatory mediators take part in cascades that result in cellular level responses like neurodegeneration, pericyte loss, leakage, capillary drop out, neovascularization, etc. There are multiple overlaps between the inflammatory pathways occurring within the diabetic retina due to a large number of mediators, their varied sources, and cross-interactions. This makes understanding the role of inflammation in clinical manifestations of DR difficult. Currently, mediator-based therapy for DR is being evaluated for interventions that target a specific step of the inflammatory cascade. We reviewed the role of inflammation in DR and derived a simplified clinicopathological correlation between the sources and stimuli of inflammation, the inflammatory mediators and pathways, and the clinical manifestations of DR. By doing so, we deliberate mediator-specific therapy for DR. The cross-interactions between inflammatory mediators and the molecular cycles influencing the inflammatory cascades are crucial challenges to such an approach. Future research should be directed to assess the feasibility of the pathology-based therapy for DR.

Cellular and molecular mechanisms in COVID-19 coagulopathy: role of inflammation and endotheliopathy

INTRODUCTION

Coronavirus 2 (CoV-2) infection or coronavirus disease 2019 (COVID-19) is frequently associated with microvascular thrombosis.The microthrombosis in COVID-19 is the result of the interplay between inflammation and endotheliopathy. Elevated interleukin-6 (IL-6) characterizes COVID-19 inflammation resulting in endotheliopathy and coagulopathy marked by elevated D-dimer (DD). Aim of this study is to identify and to describe the coagulation changes in 100 moderate COVID-19 patients having lung involvement and to determine the association of coagulopathy with the severity and prognosis.

METHODS

Inflammation, endothelial and coagulation molecules were measured in moderate and mild disease.

RESULTS

IL-6 and tumor necrosis factor-α (TNF-α) and tissue factor (TF), von Willebrand factor (VWF), and tissue factor pathway inhibitor (TFPI) significantly increased in moderate disease as well as D-dimer, thrombin antithrombin complex (TAT), Fibrinogen (Fib), platelet factor-4 (PF4), β-thromboglobulin (β-TG), P-selectin, and platelet adhesion. Shortened clotting time (CT) and clot formation time (CFT), high maximum clot firmness (MCF) and low LY at 30 min were present in 100% of moderate COVID-19 patients compared with mild COVID-19 patients.

CONCLUSIONS

These findings demonstrate that moderate COVID-19 has a profound inflammation associated with severee ndotheliopathy and intense coagulation activation uncontrolled by TFPI. Attention should be paid to coagulopathy in COVID-19. Closely monitoring of coagulation and application of appropriate anticoagulation may improve the prognosis of moderate COVID-19 and to prevent the progression to severe COVID-19 disease.

Risk factors for mortality in hemodialysis patients with COVID-19: a systematic review and meta-analysis

Background

New evidence from studies on risk factors for mortality in hemodialysis (HD) patients with COVID-19 became available. We aimed to review the clinical risk factors for fatal outcomes in these patients.

Methods

We performed meta-analysis using the PubMed, EMBASE, and Cochrane databases. A fixed- or random-effects model was used for calculating heterogeneity. We used contour-enhanced funnel plot and Egger’s tests to assess potential publication bias.

Results

Twenty-one studies were included. The proportion of males was lower in the survivor group than in the non-survivor group (OR = 0.75, 95% CI [0.61, 0.94]). The proportion of respiratory diseases was significantly lower in the survivor group than in the non-survivor group (OR = 0.42, 95% CI [0.29, 0.60]). The proportion of patients with fever, cough, and dyspnea was significantly lower in the survivor group (fever: OR = 0.53, 95% CI [0.31, 0.92]; cough: OR = 0.50, 95% CI [0.38, 0.65]; dyspnea: OR = 0.25, 95% CI [0.14, 0.47]) than in the non-survivor group. Compared with the non-survivor group, the survivor group had higher albumin and platelet levels and lower leucocyte counts.

Conclusions

Male patients might have a higher risk of developing severe COVID-19. Comorbidities, such as respiratory diseases could also greatly influence the clinical prognosis of COVID-19. Clinical features, such as fever, dyspnea, cough, and abnormal platelet, leucocyte, and albumin levels, could imply eventual death. Our findings will help clinicians identify markers for the detection of high mortality risk in HD patients at an early stage of COVID-19.

A case of resistant multiple plantar warts cured with combined autologous platelet-rich plasma injection and topical salicylic acid 30

BACKGROUND

Plantar warts are common benign cutaneous lesions affecting the plantar aspects of the feet; they are caused by infection of the keratinocytes by the human papillomavirus (HPV). The effective treatment of plantar warts is still a therapeutic challenge.

AIM

This study aimed to assess the possible clinical efficacy and safety of the combined intralesional autologous platelet-rich plasma (PRP) injection with local application of salicylic acid 30% solution in the treatment of multiple resistant plantar warts.

METHOD

In the present case, a 54-year-old immunocompetent male patient presented with multiple, bilateral resistant plantar warts.

RESULTS

A complete clearance of the plantar warts was observed after three sessions of intralesional autologous PRP injections with one-month interval, combined with twice-daily local application of salicylic acid 30% solution between sessions. No recurrence was recorded after a nine-month follow-up from the last session. There were no reported side effects during or after the sessions.

CONCLUSION

The combined intralesional autologous PRP injection with topical salicylic acid is an effective, economic, and safe modality of treatment for multiple resistant plantar warts.

Matrix metalloproteinase-2 on activated platelets triggers endothelial PAR-1 initiating atherosclerosis

AIMS 

Platelets participate in atherogenesis with mechanisms not yet fully clarified. Vascular wall MMP-2 is involved in the arterial remodelling accompanying atherosclerosis. Platelets contain and release MMP-2 but no informations are available on its role in atherosclerotic lesion formation.

METHODS AND RESULTS 

We generated double knockout mice lacking the LDL receptor and MMP-2 only in circulating blood cells showing that they develop significantly lesser femoral intima thickening after photochemical-induced arterial damage and atherosclerotic lesions in the aorta, measured by the en face method, after 4 months of atherogenic diet. Moreover, repeated transfusions of autologous-activated platelets in LDLR-/- mice on atherogenic diet significantly enhanced the extension of aortic atherosclerotic lesions while transfusion of activated platelets from MMP-2-/- mice did not. In vitro coincubation studies showed that platelet-derived MMP-2 plays a pivotal role in the development and progression of atherosclerosis through a complex cross-talk between activated platelets, monocyte/macrophages, and endothelial cells. Translational studies in patients with CAD and chronic HIV infection showed that platelet surface expression of MMP-2 highly significantly correlated with the degree of carotid artery stenosis.

CONCLUSION 

We show a previously unknown mechanism of the pathway through which platelets expressing MMP-2 trigger the initial phases of atherosclerosis and provide a mechanism showing that they activate endothelial PAR-1 triggering endothelial p38MAPK signalling and the expression of adhesion molecules. The development of drugs blocking selectively platelet MMP-2 or its expression may represent a new approach to the prevention of atherosclerosis.

Antithrombogenic properties of Tulbaghia violacea aqueous leaf extracts: assessment of platelet activation and whole blood clotting kinetics

Tulbaghia violacea plant extracts have been investigated for their potential therapeutic effects in the management of various ailments, among which are cardiovascular diseases, due to the wide range of phytocompounds that the plant possesses. One of the major challenges in clinical practice is the inability to control platelet activation and clotting caused by cardiovascular disease interventions. Current treatment methods to inhibit platelet aggregation and thromboxane formation have been associated with major undesirable side effects. This has led to increased research studies on the development of newer and more effective antiplatelet agents. In particular, there has been a growing interest on the potential antiplatelet activity of plant-derived extracts. Hence this study methodically evaluates the anticlotting and antiplatelet properties of T. violacea aqueous leaf extracts. The platelet activity of the plant extracts was assessed using total platelet adhesion, platelet morphology and whole blood clotting kinetics. The 0.1 mg ml-1 T. violacea extract mixed with blood plasma demonstrated the lowest platelet adhesion and activation and also reduced whole blood clotting kinetics. There was a reduction of about 70% in platelet adhesion for the 0.1 mg ml-1 treatment compared to the control in the first 15 min which was supported by morphological characterization under SEM. These observations suggest that T. violacea may be a potential antiplatelet therapeutic agent to inhibit the initial step of platelet adhesion and ultimately reduce the incidence of cardiovascular events.

Inhibition of post-surgery tumour recurrence via a hydrogel releasing CAR-T cells and anti-PDL1-conjugated platelets

The immunosuppressive microenvironment of solid tumours reduces the antitumour activity of chimeric antigen receptor T cells (CAR-T cells). Here, we show that the release-through the implantation of a hyaluronic acid hydrogel-of CAR-T cells targeting the human chondroitin sulfate proteoglycan 4, polymer nanoparticles encapsulating the cytokine interleukin-15 and platelets conjugated with the checkpoint inhibitor programmed death-ligand 1 into the tumour cavity of mice with a resected subcutaneous melanoma tumour inhibits the local recurrence of the tumour as well as the growth of distant tumours, through the abscopal effect. The hydrogel, which functions as a reservoir, facilitates the enhanced distribution of the CAR-T cells within the surgical bed, and the inflammatory microenvironment triggers platelet activation and the subsequent release of platelet-derived microparticles. The post-surgery local delivery of combination immunotherapy through a biocompatible hydrogel reservoir could represent a translational route for preventing the recurrence of cancers with resectable tumours.

Association between serum SCUBE1 levels and thrombus burden in patients with ST-segment elevation myocardial infarction

INTRODUCTION

The signal peptide-CUB-EGF domain-containing protein-1 (SCUBE1) is a recently available biomarker which is expressed by activated and adhered platelets. In present study, we aimed to investigate the association between SCUBE1 levels and thrombus burden in patients with ST elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (PPCI).

METHODS

A total of 88 patients who were diagnosed with STEMI and underwent PPCI were prospectively included between July 2019 and August 2019. Blood samples were collected for routine biochemistry and serum SCUBE1 levels before PPCI and antiplatelet therapy. Angiographic coronary thrombus burden was classified based on thrombolysis in myocardial infarction (TIMI) thrombus grades. We formed two groups based on the thrombus grade: 37 (42%) patients had high thrombus burden whereas 51 (58%) patients had low thrombus burden.

RESULTS

The mean age of study population was 58.2 ± 11.8 years (34% female). The mean peak troponin I level, SCUBE1 level, SYNTAX score, and pain-to-balloon time were significantly higher in the high thrombus burden group compared to the low thrombus burden group (p < .05, for all). In ROC analysis, SCUBE1 level >65.63 ng/dL had a sensitivity of 91.9% and a specificity of 76.6% to predict high thrombus burden (AUC: 0.9256; p < .001). In multivariate analysis, SCUBE1 level (HR: 1.133, p = .004) and troponin (HR: 1.002; 95% CI 1.001-1.004, p = .003) were independent predictors of high thrombus burden.

CONCLUSION

In the present study, we showed that SCUBE1, a novel platelet-endothelial adhesion molecule and a marker of platelet activation, is an independent predictor of high thrombus burden in patients with STEMI.

Thrombo-Inflammation: A Focus on NTPDase1/CD39

There is increasing evidence for a link between inflammation and thrombosis. Following tissue injury, vascular endothelium becomes activated, losing its antithrombotic properties whereas inflammatory mediators build up a prothrombotic environment. Platelets are the first elements to be activated following endothelial damage; they participate in physiological haemostasis, but also in inflammatory and thrombotic events occurring in an injured tissue. While physiological haemostasis develops rapidly to prevent excessive blood loss in the endothelium activated by inflammation, hypoxia or by altered blood flow, thrombosis develops slowly. Activated platelets release the content of their granules, including ATP and ADP released from their dense granules. Ectonucleoside triphosphate diphosphohydrolase-1 (NTPDase1)/CD39 dephosphorylates ATP to ADP and to AMP, which in turn, is hydrolysed to adenosine by ecto-5'-nucleotidase (CD73). NTPDase1/CD39 has emerged has an important molecule in the vasculature and on platelet surfaces; it limits thrombotic events and contributes to maintain the antithrombotic properties of endothelium. The aim of the present review is to provide an overview of platelets as cellular elements interfacing haemostasis and inflammation, with a particular focus on the emerging role of NTPDase1/CD39 in controlling both processes.

CD40L modulates transcriptional signatures of neutrophils in the bone marrow associated with development and trafficking

Neutrophils are produced in the BM in a process called granulopoiesis, in which progenitor cells sequentially develop into mature neutrophils. During the developmental process, which is finely regulated by distinct transcription factors, neutrophils acquire the ability to exit the BM, properly distribute throughout the body, and migrate to infection sites. Previous studies have demonstrated that CD40 ligand (CD40L) influences hematopoiesis and granulopoiesis. Here, we investigate the effect of CD40L on neutrophil development and trafficking by performing functional and transcriptome analyses. We found that CD40L signaling plays an essential role in the early stages of neutrophil generation and development in the BM. Moreover, CD40L modulates transcriptional signatures, indicating that this molecule enables neutrophils to traffic throughout the body and to migrate in response to inflammatory signals. Thus, our study provides insights into the complex relationships between CD40L signaling and granulopoiesis, and it suggests a potentially novel and nonredundant role of CD40L signaling in neutrophil development and function.

The Relationship between Inflammation Markers (CRP, IL-6, sCD40L) and Colorectal Cancer Stage, Grade, Size and Location

The aim of the study was the evaluation whether in primary colorectal cancer (CRC) patients (n = 55): age, sex, TNM classification results, WHO grade, tumor location (proximal colon, distal colon, rectum), tumor size, platelet count (PLT), mean platelet volume (MPV), mean platelet component (MCP), levels of carcinoembryonic antigen (CEA), cancer antigen (CA 19-9), as well as soluble lectin adhesion molecules (L-, E-, and P-selectins) may influence circulating inflammatory biomarkers: IL-6, CRP, and sCD40L. We found that CRP concentration evaluation in routine clinical practice may have an advantage as a prognostic biomarker in CRC patients, as this protein the most comprehensively reflects clinicopathological features of the tumor. Univariate linear regression analysis revealed that in CRC patients: (1) with an increase in PLT by 10 × 10³/μL, the mean concentration of CRP increases by 3.4%; (2) with an increase in CA 19-9 of 1 U/mL, the mean concentration of CRP increases by 0.7%; (3) with the WHO 2 grade, the mean CRP concentration increases 3.631 times relative to the WHO 1 grade group; (4) with the WHO 3 grade, the mean CRP concentration increases by 4.916 times relative to the WHO 1 grade group; (5) with metastases (T1-4N+M+) the mean CRP concentration increases 4.183 times compared to non-metastatic patients (T1-4N0M0); (6) with a tumor located in the proximal colon, the mean concentration of CRP increases 2.175 times compared to a tumor located in the distal colon; (7) in patients with tumor size > 3 cm, the CRP concentration is about 2 times higher than in patients with tumor size ≤ 3 cm. In the multivariate linear regression model, the variables that influence the mean CRP value in CRC patients included: WHO grade and tumor localization. R² for the created model equals 0.50, which indicates that this model explains 50% of the variance in the dependent variable. In CRC subjects: (1) with the WHO 2 grade, the mean CRP concentration rises 3.924 times relative to the WHO 1 grade; (2) with the WHO 3 grade, the mean CRP concentration increases 4.721 times in relation to the WHO 1 grade; (3) with a tumor located in the rectum, the mean CRP concentration rises 2.139 times compared to a tumor located in the distal colon; (4) with a tumor located in the proximal colon, the mean concentration of CRP increases 1.998 times compared to the tumor located in the distal colon; if other model parameters are fixed.

Platelet Innate Immune Receptors and TLRs: A Double-Edged Sword

Platelets are hematopoietic cells whose main function has for a long time been considered to be the maintenance of vascular integrity. They have an essential role in the hemostatic response, but they also have functional capabilities that go far beyond it. This review will provide an overview of platelet functions. Indeed, stress signals may induce platelet apoptosis through proapoptotis or hemostasis receptors, necrosis, and even autophagy. Platelets also interact with immune cells and modulate immune responses in terms of activation, maturation, recruitment and cytokine secretion. This review will also show that platelets, thanks to their wide range of innate immune receptors, and in particular toll-like receptors, and can be considered sentinels actively participating in the immuno-surveillance of the body. We will discuss the diversity of platelet responses following the engagement of these receptors as well as the signaling pathways involved. Finally, we will show that while platelets contribute significantly, via their TLRs, to immune response and inflammation, these receptors also participate in the pathophysiological processes associated with various pathogens and diseases, including cancer and atherosclerosis.

Platelet and Red Blood Cell Transfusions and Risk of Acute Graft-versus-Host Disease after Myeloablative Allogeneic Hematopoietic Cell Transplantation

Transfusion therapy is a critical part of supportive care early after allogeneic hematopoietic cell transplantation (allo-HCT). Platelet and RBC transfusions elicit immunomodulatory effects in the recipient, but if this impacts the risk of acute graft-versus-host disease (aGVHD) has only been scarcely investigated. We investigated if platelet and RBC transfusions were associated with the development of aGVHD following myeloablative allo-HCT in a cohort of 664 patients who underwent transplantation between 2000 and 2019. Data were further analyzed for the impact of blood donor age and sex and blood product storage time. Exploratory analyses were conducted to assess correlations between transfusion burden and plasma biomarkers of inflammation and endothelial activation and damage. Between day 0 and day +13, each patient received a median of 7 (IQR, 5 to 10) platelet transfusions and 3 (IQR, 2 to 6) RBC transfusions (Spearman's ρ = 0.49). The cumulative sums of platelet and RBC transfusions, respectively, received from day 0 to day +13 were associated with subsequent grade II-IV aGVHD in multivariable landmark Cox models (platelets: adjusted hazard ratio [HR], 1.27; 95% confidence interval [CI], 1.06 to 1.51; RBCs: adjusted HR, 1.41; 95% CI, 1.09 to 1.82; both per 5 units; 184 events). For both platelet and RBC transfusions, we did not find support for a difference in the risk of aGVHD according to age or sex of the blood donor. Transfusion of RBCs with a storage time longer than the median of 8 days was inversely associated with aGVHD (HR per 5 units, 0.54; 95% CI, 0.30 to 0.96); however, when using an RBC storage time of ≥14 days as a cutoff, there was no longer evidence for an association with aGVHD (HR, 1.03 per 5 units; 95% CI, 0.53 to 2.00). For platelets, there was no clear association between storage time and the risk of aGVHD. The transfusion burdens of platelets and RBCs were positively correlated with plasma levels of TNF-α, IL-6, and soluble thrombomodulin at day +14. In conclusion, platelet and RBC transfusions in the first 2 weeks after myeloablative allo-HCT were associated with subsequent development of grade II-IV aGVHD. We did not find evidence of an impact of blood donor age or sex or blood product storage time on the risk of aGVHD. Our findings support restrictive transfusion strategies in allo-HCT recipients.

Biomarkers of complement and platelet activation are not correlated with the one or twenty-four hours corrected count increments in prophylactically platelet transfused hematological patients: a prospective cohort study

Platelet transfusion refractoriness is a serious clinical concern that complicates the management of thrombocytopenic patients. Previous studies have suggested a potential role for both complement and platelet activation based on in vitro analyses of platelet concentrates. In this study, the post-transfusion platelet response, as indicated by the corrected count increment at 1 and 24 h after prophylactic platelet transfusions, respectively, was correlated with the 1 h post-transfusion Δconcentration (1 h post-transfusion - pretransfusion) of complement and platelet activation biomarkers. The study was registered as a clinical trial at ClinicalTrials.gov (identifier: NCT02601131) and patients were recruited during inpatient care in the hematological department. Soluble terminal complement complexes, soluble P-selectin and soluble CD40 ligand were analyzed. Confirmed alloimmunized patients were excluded. Included subjects were either given platelet transfusions (n = 43) and categorized into four clinical study groups or included in a non-transfused control group (n = 10). In total, 54 transfusions were included. No transfusion-mediated complement activation was observed. The transfusions were associated with a significant increase in the concentration of soluble P-selectin (p < .001), primarily corresponding to the passive infusion of soluble P-selectin-containing plasma residuals. The Δconcentration of soluble P-selectin was, however, not significantly correlated with the corrected count increments. Thus, significant correlations between biomarkers of complement and platelet activation and the post-transfusion platelet response could not be demonstrated in this study.

Platelets: the point of interconnection among cancer, inflammation and cardiovascular diseases

INTRODUCTION

The association between thrombosis, cancer and inflammation is well-established. Platelets play a major role in atherosclerosis, inflammation and immune response. Furthermore, growing evidence suggests that they are also significantly involved in tumor development and progression so that anti-platelet agents may prevent cancer and improve outcomes in oncological patients. In this review, we aimed at analyzing the relationship between platelets, cardiovascular diseases and cancer. A comprehensive study in the main educational platforms was performed and high-quality original articles and reviews were included.

AREAS COVERED

This review will focus on the role of platelets in cardiovascular disease and in cancer genesis and progression, analyzing their function as immune cells that link inflammation to thrombosis. Finally, it will examine the recent controversies on the use of anti-platelet agents as cancer medications, in particular the already known anti-tumor properties of aspirin, as well as the new perspectives regarding P2Y12 inhibitors.

EXPERT OPINION

Platelet-cancer crosstalk generates a vicious feed-back loop involving tumor cells and secreting molecules that activate platelets, which in turn promote cancer-associated inflammation, proliferation, spreading and immune system evasion. Therefore, platelets inhibition may represent an innovative therapeutical strategy offered to cancer patients, in the perspective of personalized medicine.

Regulation of Platelet-Derived ADAM17: A Biomarker Approach for Breast Cancer?

Tumor progression and metastasis are critically dependent on the tumor microenvironment. A disintegrin and metalloproteinase 17 (ADAM17) is associated with shedding of several substrates involved in tumor progression and known to be expressed by platelets of healthy donors and patients with solid tumors. Here, we report that platelet-derived ADAM17 (pADAM17) is regulated upon platelet activation of breast cancer patients, but not of healthy individuals. The observed downregulation of pADAM17 on platelets of cancer patients correlated with clinical parameters related to tumor progression including tumor stage and the occurrence of metastasis. Our data identify an association between platelet activation, modulation of platelet-derived ADAM17, and metastasis. In conclusion, we demonstrate that further development of pADAM17 as a liquid biomarker is warranted for monitoring disease progression in breast cancer.

Immunophenotypic Analysis of Platelets by Flow Cytometry

Platelets are small but very abundant blood cells that play a key role in hemostasis, contributing to thrombus formation at sites of injury. The ability of platelets to perform this function, as well as functions in immunity and inflammation, is dependent on the presence of cell surface glycoproteins and changes in their quantity and conformation after platelet stimulation. In this article, we describe the characterization of platelet surface markers and platelet function using platelet-specific fluorescent probes and flow cytometry. Unlike traditional platelet tests, immunophenotypic analysis of platelets by flow cytometry allows the analysis of platelet function in samples with very low platelet counts as often encountered in clinical situations. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Immunophenotyping of platelet surface receptors Alternate Protocol: Fix-first method for immunophenotyping of platelet surface receptors Basic Protocol 2: Determination of platelet activation using P-selectin expression and/or PAC1 binding Basic Protocol 3: Determination of procoagulant platelets using annexin V binding or antibodies specific for coagulation factor V/Va or X/Xa Support Protocol: Preparation of isolated platelets.

Soluble Platelet Release Factors as Biomarkers for Cardiovascular Disease

Platelets are the main players in thrombotic diseases, where activated platelets not only mediate thrombus formation but also are involved in multiple interactions with vascular cells, inflammatory components, and the coagulation system. Although in vitro reactivity of platelets provides information on the function of circulating platelets, it is not a full reflection of the in vivo activation state, which may be relevant for thrombotic risk assessment in various disease conditions. Therefore, studying release markers of activated platelets in plasma is of interest. While this type of study has been done for decades, there are several new discoveries that highlight the need for a critical assessment of the available tests and indications for platelet release products. First, new insights have shown that platelets are not only prominent players in arterial vascular disease, but also in venous thromboembolism and atrial fibrillation. Second, knowledge of the platelet proteome has dramatically expanded over the past years, which contributed to an increasing array of tests for proteins released and shed from platelets upon activation. Identification of changes in the level of plasma biomarkers associated with upcoming thromboembolic events allows timely and individualized adjustment of the treatment strategy to prevent disease aggravation. Therefore, biomarkers of platelet activation may become a valuable instrument for acute event prognosis. In this narrative review based on a systematic search of the literature, we summarize the process of platelet activation and release products, discuss the clinical context in which platelet release products have been measured as well as the potential clinical relevance.

Shedding Light on Hemostasis in Patients With Inflammatory Bowel Diseases

Patients with inflammatory bowel diseases (IBD) have an increased risk of thrombosis, possibly due to changes in blood cells and molecules involved in hemostasis. They have increased platelet counts and reactivity as well as increased platelet-derived large extracellular vesicles. Coagulation is continuously activated in patients with IBD, based on measured markers of thrombin generation, and the anticoagulant functions of endothelial cells are damaged. Furthermore, fibrinogen is increased and fibrin clots are denser. However, pathogenesis of thrombosis in patients with IBD appears to differ from that of patients without IBD. Patients with IBD also take drugs that might contribute to risk of thrombosis, complicating the picture. We review the features of homeostasis that are altered in patients with IBD and possible mechanisms of this relationship.

Multimodal analysis for human ex vivo studies shows extensive molecular changes from delays in blood processing

Multi-omic profiling of human peripheral blood is increasingly utilized to identify biomarkers and pathophysiologic mechanisms of disease. The importance of these platforms in clinical and translational studies led us to investigate the impact of delayed blood processing on the numbers and state of peripheral blood mononuclear cells (PBMC) and on the plasma proteome. Similar to previous studies, we show minimal effects of delayed processing on the numbers and general phenotype of PBMC up to 18 hours. In contrast, profound changes in the single-cell transcriptome and composition of the plasma proteome become evident as early as 6 hours after blood draw. These reflect patterns of cellular activation across diverse cell types that lead to progressive distancing of the gene expression state and plasma proteome from native in vivo biology. Differences accumulating during an overnight rest (18 hours) could confound relevant biologic variance related to many underlying disease states.

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Studies of human blood cells and plasma are highly sensitive to process variability

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Time variability distorts biology in cutting-edge single-cell and multiplex assays

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Longitudinal, multi-modal, and aligned data enable data qualification and exploration

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Dataset holds potential novel, multi-modal biological correlations and hypotheses

Monocytes complexed to platelets differentiate into functionally deficient dendritic cells

In addition to their role in hemostasis, platelets store numerous immunoregulatory molecules such as CD40L, TGFβ, β2-microglobulin, and IL-1β and release them upon activation. Previous studies indicate that activated platelets form transient complexes with monocytes, especially in HIV infected individuals and induce a proinflammatory monocyte phenotype. Because monocytes can act as precursors of dendritic cells (DCs) during infection/inflammation as well as for generation of DC-based vaccine therapies, we evaluated the impact of activated platelets on monocyte differentiation into DCs. We observed that in vitro cultured DCs derived from platelet-monocyte complexes (PMCs) exhibit reduced levels of molecules critical to DC function (CD206, dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin, CD80, CD86, CCR7) and reduced antigen uptake capacity. DCs derived from PMCs also showed reduced ability to activate naïve CD4+ and CD8+ T cells, and secrete IL-12p70 in response to CD40L stimulation, resulting in decreased ability to promote type-1 immune responses to HIV antigens. Our results indicate that formation of complexes with activated platelets can suppress the development of functional DCs from such monocytes. Disruption of PMCs in vivo via antiplatelet drugs such as Clopidogrel/Prasugrel or the application of platelet-free monocytes for DCs generation in vitro, may be used to enhance immunization and augment the immune control of HIV.

The Dual Role of Platelets in the Cardiovascular Risk of Chronic Inflammation

Patients with chronic inflammatory diseases often exhibit cardiovascular risk. This risk is associated with the systemic inflammation that persists in these patients, causing a sustained endothelial activation. Different mechanisms have been considered responsible for this systemic inflammation, among which activated platelets have been regarded as a major player. However, in recent years, the role of platelets has become controversial. Not only can this subcellular component release pro- and anti-inflammatory mediators, but it can also bind to different subsets of circulating lymphocytes, monocytes and neutrophils modulating their function in either direction. How platelets exert this dual role is not yet fully understood.

Platelet transfusion for cancer secondary thrombocytopenia: Platelet and cancer cell interaction

Chemoradiotherapy and autoimmune disorder often lead to secondary thrombocytopenia in cancer patients, and thus, platelet transfusion is needed to stop or prevent bleeding. However, the effect of platelet transfusion remains controversial for the lack of agreement on transfusion strategies. Before being transfused, platelets are stored in blood banks, and their activation is usually stimulated. Increasing evidence shows activated platelets may promote metastasis and the proliferation of cancer cells, while cancer cells also induce platelet activation. Such a vicious cycle of interaction between activated platelets and cancer cells is harmful for the prognosis of cancer patients, which results in an increased tumor recurrence rate and decreased five-year survival rate. Therefore, it is important to explore platelet transfusion strategies, summarize mechanisms of interaction between platelets and tumor cells, and carefully evaluate the pros and cons of platelet transfusion for better treatment and prognosis for patients with cancer with secondary thrombocytopenia.

Platelet-Expressed TNFRSF13B (TACI) Predicts Breast Cancer Progression

Although treatment options in breast cancer have been improved significantly, predictive biomarkers for disease progression and metastasis are still lacking. Recent studies indicate that several TNF Receptor Superfamily members are involved in breast cancer cell proliferation and survival. Interestingly, TNFRSF13B (TACI) mRNA level were of prognostic relevance in breast cancer patients. In this study we provide evidence for TACI expression on platelets of breast cancer patients. The level of platelet-expressed TACI (pTACI) was significantly increased on platelets derived from breast cancer patients compared to healthy controls. Upon platelet activation, pTACI was downregulated on the platelet surface of healthy donors and breast cancer patients. Of note, inhibition of matrix metalloprotease (MMP) prevented downregulation of pTACI ex vivo, indicating that proteolytic cleavage of pTACI is responsible for reduction of pTACI level. Stimulation of pTACI via BAFF, BAFF 60-mer or APRIL did not influence platelet activation and function. Remarkably, pTACI was particularly regulated during tumor progression in our breast cancer cohort. TACI expression levels on platelets were correlated with clinical parameters including tumor stage, occurrence of metastasis and tumor cell proliferation (Ki67). In conclusion, our data emphasize the potential use of platelets as a liquid biomarker in breast cancer.

[The CD40-CD40L axis: Current and future implications in clinical immunology]

The CD40-CD40 ligand (CD40L) pathway is a backbone of communication between cells of the immune system. It makes it possible to generate a proinflammatory signal and thus participates in the pathogenesis of dysimmune diseases, transplant rejection and atherosclerosis. Because of this therapeutic target of choice, several generations of anti-CD40L monoclonal antibodies have emerged since the 1990s. The first generation of antibodies was responsible for thromboembolic toxicity for which the mechanisms are starting to be defined. New generations of antibodies were designed to overcome this toxicity and are still being developed in lupus, rheumatoid arthritis, Sjogren's syndrome or immunologic thrombocytopenia. In addition to these targeted therapies, there are data suggesting the impact of several drugs among molecules used in cardiology and clinical immunology on the level of CD40L. The objective of this review is to recall the clinical issues related to the CD40-CD40L axis and to present current or future treatments that block CD40L which would allow clinicians to diversify their options for managing dysimmune diseases.