Monocyte-platelet aggregates and platelet micro-particles in patients with post-hepatitic liver cirrhosis

The evolving knowledge on primary hemostasis in patients with cirrhosis: A comprehensive review

Patients with cirrhosis develop complex alterations in primary hemostasis that include both hypocoagulable and hypercoagulable features. This includes thrombocytopenia, multiple alterations of platelet function, and increased plasma levels of von Willebrand factor. Contrary to the historical view that platelet dysfunction in cirrhosis might be responsible for an increased bleeding tendency, the current theory posits a rebalanced hemostasis in patients with cirrhosis. Severe thrombocytopenia is not indicative of the bleeding risk in patients undergoing invasive procedures and does not dictate per se the need for pre-procedural prophylaxis. A more comprehensive and individualized risk assessment should combine hemostatic impairment, the severity of decompensation and systemic inflammation, and the presence of additional factors that may impair platelet function, such as acute kidney injury and bacterial infections. Although there are multiple, complex alterations of platelet function in cirrhosis, their net effect is not yet fully understood. More investigations evaluating the association between alterations of platelet function and bleeding/thrombosis may improve risk stratification in patients with decompensated cirrhosis. Besides hemostasis, the assessment of von Willebrand factor Ag and ADP-induced, whole-blood platelet aggregation normalized by platelet count (VITRO score and PLT ratio) are promising biomarkers to predict the risk of hepatic decompensation and survival in both compensated and decompensated patients. Further investigations into the in vivo interplay between platelets, circulating blood elements, and endothelial cells may help advance our understanding of cirrhotic coagulopathy. Here, we review the complex changes in platelets and primary hemostasis in cirrhosis and their potential clinical implications.

Targeting von Willebrand factor in liver diseases: A novel therapeutic strategy?

Acute and chronic liver disease are associated with substantial alterations in the hemostatic system. Evidence from both experimental and clinical studies suggests that anticoagulants slow the progression of liver disease. Efficacy of those anticoagulant drugs is, in part, attributed to a reduction of microthrombi formation within the liver. Although anticoagulant drugs show promising results, bleeding risk associated with these drugs is an obvious drawback, particularly in patients with a complex coagulopathy driven by decreased liver function. Identifying therapies that reduce intrahepatic thrombosis with minimal bleeding risk would significantly advance the field. Among the hemostatic alterations observed in patients are substantially increased levels of the platelet-adhesive protein von Willebrand factor (VWF). In contrast, levels of A Disintegrin and Metalloproteinase with Thrombospondin motifs, the enzyme that regulates VWF activity, are significantly reduced in patients with liver disease. Highly elevated VWF levels are proposed to accelerate intrahepatic thrombus formation and thus be a driver of disease progression. Strong clinical evidence suggesting a link between liver disease and changes in VWF is now being matched by emerging mechanistic data showing a detrimental role for VWF in the progression of liver disease. This review focuses on clinical and experimental evidence supporting a connection between VWF function and the progression of acute and chronic liver diseases. Furthermore, with the recent anticipated approval of several novel therapies targeting VWF, we discuss potential strategies and benefits of targeting VWF as an innovative therapy for patients with liver disease.

Small Annexin V-Positive Platelet-Derived Microvesicles Affect Prognosis in Cirrhosis: A Longitudinal Study

INTRODUCTION

Microvesicles (MVs) with procoagulant properties may favor liver parenchymal extinction, then cirrhosis-related complications and mortality. In a longitudinal cohort of cirrhotic patients, we measured plasma levels of platelet-derived MVs (PMVs), endothelial-derived MVs, and red blood cell-derived MVs, expressing phosphatidylserine (annexin V-positive [AV+]) or not, and evaluated their impact on Model for End-Stage Liver Disease (MELD) score and transplant-free survival.

METHODS

MVs were quantified using flow cytometry in plasma from 90 noninfected cirrhotic patients and 10 healthy volunteers matched for age and sex. Impact of plasma microvesicle levels on 6-month transplant-free survival was assessed using log-rank tests and logistic regression.

RESULTS

Microvesicle levels, mostly platelet-derived, were 2.5-fold higher in healthy volunteers compared with cirrhotic patients. Circulating small AV+ PMV levels were lower in cirrhotic patients (P = 0.014) and inversely correlated with MELD scores (R = -0.28; P = 0.0065). During 1-year follow-up, 8 patients died and 7 underwent liver transplantation. In the remaining patients, circulating microvesicle levels did not change significantly. Six-month transplant-free survival was lower in patients with low baseline small AV+ PMV levels (72.6% vs 96.2%; P = 0.0007). In multivariate analyses adjusted for age, ascites, esophageal varices, encephalopathy, clinical decompensation, total platelet counts, MELD score, and/or Child-Pugh C stage, patients with lower small AV+ PMV levels had a significant 5- to 8-fold higher risk of 6-month death or liver transplant. Other PMV levels did not impact on survival.

DISCUSSION

Decreased circulating small AV+ PMV levels are associated with significantly lower transplant-free survival in cirrhotic patients independently of MELD score and platelet counts.

Translational insight into prothrombotic state and hypercoagulation in nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is an emerging and threatening pathological condition, ranging from fatty liver (FL) to chronic steatohepatitis (NASH), liver cirrhosis, and eventually to hepatocellular carcinoma (HCC). Recent findings suggest that patients with NAFLD have a higher risk of cardiovascular events and thromboembolism and that this risk is independent of metabolic diseases that are frequently associated with NAFLD, such as diabetes, hyperlipidaemia, and obesity. The vascular involvement of NAFLD might be considered its systemic burden, conditioning higher mortality in patients affected by the disease. These clinical findings suggested the existence of a prothrombotic state in NAFLD, which is partially unexplored and whose underlying mechanisms are to date not completely understood. Here, we review the mechanisms involved in the pathogenesis of the prothrombotic state in NAFLD across the progression from the healthy liver through the different stages of the disease. We focused on the possible role of several metabolic features of NAFLD possibly leading to hypercoagulation other than endothelial and platelet activation, such as insulin-resistance, nitric oxide production regulation, and gut microbiota homeostasis. Also, we analysed the involvement of plasminogen activator inhibitor-1 (PAI-1) and thromboinflammation taking place in NAFLD. Finally, we described factors striking a prothrombotic imbalance in NASH cirrhosis, with a particular focus on the pathogenesis of portal vein thrombosis.

Extracellular vesicles as biomarkers in liver diseases: A clinician's point of view

Extracellular vesicles are membrane-bound vesicles containing proteins, lipids, RNAs and microRNAs. They can originate from both healthy and stressed cells, and provide a snapshot of the cell of origin in physiological and pathological circumstances. Various processes that may give rise to the release of extracellular vesicles occur in liver diseases, including hepatocyte apoptosis, hepatic stellate cell activation, liver innate immune system activation, systemic inflammation, and organelle dysfunction (mitochondrial dysfunction and endoplasmic reticulum stress). Numerous studies have therefore investigated the potential role of extracellular vesicles as biomarkers in liver diseases. This review provides an overview of the methods that can be used to measure extracellular vesicle concentrations in clinical settings, ranging from plasma preparation to extracellular vesicle measurement techniques, as well as looking at the challenges of using extracellular vesicles as biomarkers. We also provide a comprehensive review of studies that test extracellular vesicles as diagnostic, severity and prognostic biomarkers in various liver diseases, including non-alcoholic and alcoholic steatohepatitis, viral hepatitis B and C infections, cirrhosis, primary liver cancers, primary sclerosing cholangitis and acute liver failure. In particular, extracellular vesicles could be useful tools to evaluate activity and fibrosis in non-alcoholic fatty liver disease, predict risk of hepatitis B virus reactivation, predict complications and mortality in cirrhosis, detect early hepatocellular carcinoma, detect malignant transformation in primary sclerosing cholangitis and predict outcomes in acute liver failure. While most studies draw on data derived from pilot studies, which still require clinical validation, some extracellular vesicle subpopulations have already been evaluated in solid prospective studies.

Platelet-derived microparticles enhance megakaryocyte differentiation and platelet generation via miR-1915-3p

Thrombosis leads to platelet activation and subsequent degradation; therefore, replenishment of platelets from hematopoietic stem/progenitor cells (HSPCs) is needed to maintain the physiological level of circulating platelets. Platelet-derived microparticles (PMPs) are protein- and RNA-containing vesicles released from activated platelets. We hypothesized that factors carried by PMPs might influence the production of platelets from HSPCs, in a positive feedback fashion. Here we show that, during mouse acute liver injury, the density of megakaryocyte in the bone marrow increases following an increase in circulating PMPs, but without thrombopoietin (TPO) upregulation. In vitro, PMPs are internalized by HSPCs and drive them toward a megakaryocytic fate. Mechanistically, miR-1915-3p, a miRNA highly enriched in PMPs, is transported to target cells and suppresses the expression levels of Rho GTPase family member B, thereby inducing megakaryopoiesis. In addition, direct injection of PMPs into irradiated mice increases the number of megakaryocytes and platelets without affecting TPO levels. In conclusion, our data reveal that PMPs have a role in promoting megakaryocytic differentiation and platelet production.

Platelets derive from megakaryocytes, which differentiate from hematopoietic stem/progenitor cells (HSPCs). Here, Qu et al show that platelet-derived microparticles carrying miR-1915-3p target HSPCs and promote megakaryopoiesis by suppressing RHOB expression levels.

Assessment of hemostatic profile in patients with mild to advanced liver cirrhosis

BACKGROUND

Hemostasis of patients suffering from liver cirrhosis is challenging due to both, pro- and anticoagulatory disorders leading to hemostatic alterations with distinct abnormalities of coagulation. Pathological changes in conventional coagulation analysis and platelet count are common manifestations of decreased liver synthesis of coagulation factors and reduced platelet count in these patients. However, conventional coagulation analysis and platelet count do not reflect in-vivo coagulation status or platelet function. The purpose of this present observational study was therefore to assess the haemostatic profile including plasmatic coagulation using thrombelastometry and impedance aggregometry for platelet function in patients suffering from liver cirrhosis.

AIM

To assess the hemostatic profile of cirrhotic patients according to model for end-stage liver disease (MELD) score.

METHODS

Our study included both in- and outpatients suffering from liver cirrhosis attending the out- and inpatient care of the department of hepatology. Demographic and biochemical data as well as medical history including cause of liver cirrhosis, end stage kidney failure and medication with anticoagulants were recorded. To assess the hemostatic profile, platelet function was analyzed by multiple electrode aggregometry (MEA) using Multiplate^® (ADP-, ASPI- and TRAP-test) and thrombelastometry using ROTEM^® (EXTEM, INTEM, FIBTEM). Data were compared using Mann-Whitney U- or χ²-test. Spearman correlation was performed to analyze the association between MELD Score and results of thrombelastometry and MEA.

RESULTS

A total of 68 patients attending the out- and inpatient care suffering from liver cirrhosis were screened. Of these, 50 patients were included and assigned to groups according to MELD score 6 to 11 (n = 25) or ≥ 17 (n = 25). Baseline patient characteristics revealed significant differences for MELD score (8 vs 22, P < 0.0001) and underlying laboratory parameters (international normalized ratio, bilirubine, creatinine) as well as fibrinogen level (275 mg/dL vs 209 mg/dL, P = 0.006) and aPTT (30 s vs 35 s, P = 0.047). MEA showed a moderately impaired platelet function (medians: AUC_ADP = 43U, AUC_ASPI = 71U, AUC_TRAP = 92U) but no significant differences between both groups. Thrombelastometry using ROTEM^® (EXTEM, INTEM, FIBTEM) revealed values within normal range in both groups. No significant correlation was observed between MELD score and results of MEA/thrombelastometry.

CONCLUSION

Our data demonstrate a partially impaired hemostatic profile in liver cirrhosis patients unrelated to MELD score. An individual assessment of a potential coagulopathy should therefore be considered.

Primary Hemostasis in Chronic Liver Disease and Cirrhosis: What Did We Learn over the Past Decade?

Changes in primary hemostasis have been described in patients with chronic liver disease (CLD) and cirrhosis and are still subject to ongoing debate. Thrombocytopenia is common and multifactorial. Numerous studies also reported platelet dysfunction. In spite of these changes, primary hemostasis seems to be balanced. Patients with CLD and cirrhosis can suffer from both hemorrhagic and thrombotic complications. Variceal bleeding is the major hemorrhagic complication and is mainly determined by high portal pressure. Non portal hypertension-related bleeding due to hemostatic failure is uncommon. Thrombocytopenia can complicate management of invasive procedures in CLD patients. Recently, oral thrombopoietin agonists have been approved to raise platelets before invasive procedures. In this review we aim to bundle literature, published over the past decade, discussing primary hemostasis in CLD and cirrhosis including (1) platelet count and the role of thrombopoietin (TPO) agonists, (2) platelet function tests and markers of platelet activation, (3) von Willebrand factor and (4) global hemostasis tests.

Acquired platelet function disorders

The possibility of an acquired platelet function disorder should be considered in patients who present with recent onset muco-cutaneous bleeding. Despite the availability of newer and faster platelet function assays, light transmission aggregometry (LTA) remains the preferred diagnostic test. This review examines and discusses the causes of acquired platelet dysfunction; most commonly drugs, dietary factors, medical disorders and procedures. In addition to well-known antiplatelet therapies, clinicians should be alert for newer drugs which can affect platelets, such as ibrutinib. There is little clinical trial evidence to guide the management of acquired platelet function defects, but we summarise commonly employed strategies, which include addressing the underlying cause, antifibrinolytic agents, desmopressin infusions, and in selected patients, platelet transfusions.

Platelets and Platelet-Derived Extracellular Vesicles in Liver Physiology and Disease

Beyond their role in hemostasis, platelets are proposed as key mediators of several physiological and pathophysiological processes of the liver, such as liver regeneration, toxic or viral acute liver injury, liver fibrosis, and carcinogenesis. The effects of platelets on the liver involve interactions with sinusoidal endothelial cells and the release of platelet‐contained molecules following platelet activation. Platelets are the major source of circulating extracellular vesicles, which are suggested to play key roles in platelet interactions with endothelial cells in several clinical disorders. In the present review, we discuss the implications of platelet‐derived extracellular vesicles in physiological and pathophysiological processes of the liver.

Monocyte-platelet aggregates affect local inflammation in patients with acute myocardial infarction

The local inflammatory response following acute myocardial infarction (AMI) is increasingly being recognized as a central factor determining infarct healing. Myocardial inflammation can be visualized in patients using fasting ¹⁸F-FDG PET/MRI. Although this novel biosignal correlates with long-term functional outcome, the corresponding cellular substrate is not well understood. Here we present a retrospective analysis of 29 patients with AMI who underwent revascularization, suggesting a connection between post infarction myocardial fasting ¹⁸F-FDG uptake, monocyte platelet aggregates (MPA), and P2Y₁₂ inhibition. In detail, patients with high MPA percentages of CD14^highCD16⁺ and CD14^lowCD16⁺ monocytes had significantly higher local ¹⁸F-FDG uptake (SUV_mean) in the infarcted myocardium than patients with low MPA (p < 0.05). Furthermore, there was an association of high MPA percentage in all monocyte subpopulations with deteriorating ΔLV-EF after 6 months (p < 0.01), which was confirmed in an extended analysis with additional 29 patients without PET/MRI data available. In this analysis, administration of Ticagrelor was associated with lower MPA percentage of CD14^high monocyte subpopulations than Clopidogrel (p < 0.01) or Prasugrel (p < 0.05). Taken together, the findings from this analysis suggest that platelet aggregability may affect monocyte extravasation into the infarcted myocardium and influence long-term functional outcome. P2Y₁₂ inhibition may intervene in this pathophysiologic process. Prospective studies are needed to further examine this important relationship.

Role of Peripheral Inflammation in Hepatic Encephalopathy

A growing body of evidence now highlights a key role for systemic inflammation in altering behavior and mood in patients with liver disease. How inflammation occurring in the periphery in the context of liver disease, communicates with the brain to mediate changes in neurotransmission and thereby behavior is incompletely understood. Traditional routes of communication between the periphery and the brain involve neural (i.e. vagal afferent nerves) and humoral (blood-borne) pathways, with increased circulating levels of endotoxin and cytokines (especially Tumor Necrosis Factor α, TNFα) that occur during systemic inflammatory responses, as being primarily implicated in mediating signaling via these pathways. However, in recent years communication via peripheral immune-cell-to-brain and the gut-microbiota-to-brain routes have received increasing attention in the context of liver disease for their ability to modulate brain function, and generate a spectrum of symptoms ranging from fatigue and altered mood to overt Hepatic Encephalopathy (HE). In this review, we discuss periphery-to-brain communication pathways and their potential role in mediating systemic inflammation-associated alterations in behavior, that are in turn ultimately part of a spectrum of brain changes linked to the development of clinically apparent HE.

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.

Interactions Between Platelets and Inflammatory Monocytes Affect Sickness Behavior in Mice With Liver Inflammation

BACKGROUND & AIMS

Patients with inflammatory liver disease commonly develop debilitating symptoms, called sickness behaviors, which arise via changes in brain function. Monocytes that produce tumor necrosis factor interact with cerebral endothelial cells to activate microglial cells and promote sickness behavior. Platelets regulate inflammation, and aggregates of monocytes and platelets are increased in the circulation of patients with liver disease. We investigated the role of platelets in inducing inflammatory features of circulating monocytes and promoting sickness behaviors in mice with cholestatic liver injury.

METHODS

We performed bile-duct ligations or sham surgeries on C57BL/6 or toll-like receptor 4 (TLR4)-knockout mice to induce liver inflammation. Liver inflammation was also induced in a separate group of mice by administration of concanavalin A. Circulating platelets, aggregates of monocytes and platelets, and activation of microglial cells were measured by flow cytometry. To deplete platelets, mice were given anti-thrombocyte serum or normal rabbit serum (control) 4 days after surgery. Interactions between monocytes and cerebral endothelial cells were analyzed by intravital microscopy. Sickness behaviors were quantified based on time spent by adult mice engaging in social behaviors toward a juvenile mouse, compared with time spent in nonsocial behavior or remaining immobile.

RESULTS

Aggregates of monocytes and platelets in circulation of mice increased significantly following bile-duct ligation. Platelet-monocyte interactions were required for activation of inflammatory monocytes and production of tumor necrosis factor. Platelet depletion greatly reduced adhesive interactions between inflammatory monocytes and adhesive interactions with cerebral endothelial cells and activation of the microglia, as well as development of sickness behavior. Furthermore, TLR4 signaling was important for aggregation of monocytes and platelets, and development of sickness behavior following bile-duct ligation. These findings were confirmed in mice with concanavalin A-induced liver injury.

CONCLUSIONS

In mice with liver inflammation, we found TLR4 and aggregates of monocytes and platelets to regulate microglial activation and development of sickness behavior. These findings might lead to new therapeutic strategies for liver disease-associated symptoms.

Platelets in liver and renal disease

This review will discuss how 2 common and morbid conditions, renal disease and liver disease, alter platelet number and function. It will review the impact of thrombocytopenia on bleeding complications in patients with these disorders and whether the low platelet count actually correlates with bleeding risk. Emerging data also suggest that platelets are much more than bystanders in both renal and liver disease, but instead play an active role in the pathobiology of these disorders. This review will briefly cover the emerging information on novel roles of platelets in the biology of renal and liver disease.

Phosphatidylserine on blood cells and endothelial cells contributes to the hypercoagulable state in cirrhosis

BACKGROUND & AIMS

The mechanism of thrombogenicity in cirrhosis is largely unknown. Our objective was to study the relationship between phosphatidylserine on blood cells and endothelial cells and the hypercoagulable state in cirrhotic patients.

METHODS

Patients with cirrhosis and healthy controls were studied. Lactadherin was used to quantify phosphatidylserine exposure on blood cells and endothelial cells. Procoagulant activity of cells was evaluated using clotting time and purified coagulation complex assays. Fibrin production was determined by turbidity. Phosphatidylserine exposure, fibrin strands and FVa/Xa binding on cells were observed using confocal microscopy.

RESULTS

Our study showed that phosphatidylserine exposure on erythrocytes, platelets and leucocytes in cirrhotic patients increased progressively with Child-Pugh categories. In addition, we found that endothelial cells treated with cirrhotic serum in vitro exposed more phosphatidylserine than those exposed to healthy serum. The exposed phosphatidylserine supported a shorter coagulation time and increased FXa, thrombin and fibrin formation. Notably, phosphatidylserine⁺ erythrocytes also promoted shorter coagulation times and more fibrin generation in cirrhotic microparticle-depleted plasma, regardless of Child-Pugh categories. Confocal microscopy data showed that the FVa/FXa complex and fibrin fibrils colocalized with phosphatidylserine on endothelial cells. Lactadherin significantly inhibited FXa and thrombin generation and consequently decreased fibrin production in normal or cirrhotic plasma.

CONCLUSIONS

These results lead us to believe that exposed phosphatidylserine on activated or injured erythrocytes, platelets, leucocytes and endothelial cells plays an important role in the hypercoagulable state in cirrhotic patients. Thus, blocking phosphatidylserine binding sites might be a new therapeutic target for preventing thrombosis.

Hemostatic balance in patients with liver cirrhosis: Report of a consensus conference

Patients with cirrhosis present with hemostatic alterations secondary to reduced availability of pro-coagulant and anti-coagulant factors. The net effect of these changes is a rebalanced hemostatic system. The Italian Association of the Study of the Liver (AISF) and the Italian Society of Internal Medicine (SIMI) promoted a consensus conference on the hemostatic balance in patients with cirrhosis. The consensus process started with the review of the literature by a scientific board of experts and ended with a formal consensus meeting in Rome in December 2014. The statements were graded according to quality of evidence and strength of recommendations, and approved by an independent jury. The statements presented here highlight strengths and weaknesses of current laboratory tests to assess bleeding and thrombotic risk in cirrhotic patients, the pathophysiology of hemostatic perturbations in this condition, and outline the optimal management of bleeding and thrombosis in patients with liver cirrhosis.

Non-Classical monocytes display inflammatory features: Validation in Sepsis and Systemic Lupus Erythematous

Given the importance of monocytes in pathogenesis of infectious and other inflammatory disorders, delineating functional and phenotypic characterization of monocyte subsets has emerged as a critical requirement. Although human monocytes have been subdivided into three different populations based on surface expression of CD14 and CD16, published reports suffer from contradictions with respect to subset phenotypes and function. This has been attributed to discrepancies in reliable gating strategies for flow cytometric characterization and purification protocols contributing to significant changes in receptor expression. By using a combination of multicolour flow cytometry and a high-dimensional automated clustering algorithm to confirm robustness of gating strategy and analysis of ex-vivo activation of whole blood with LPS we demonstrate the following: a. ‘Classical’ monocytes are phagocytic with no inflammatory attributes, b. ‘Non-classical’ subtype display ‘inflammatory’ characteristics on activation and display properties for antigen presentation and c. ‘Intermediate’ subtype that constitutes a very small percentage in circulation (under physiological conditions) appear to be transitional monocytes that display both phagocytic and inflammatory function. Analysis of blood from patients with Sepsis, a pathogen driven acute inflammatory disease and Systemic Lupus Erythmatosus (SLE), a chronic inflammatory disorder validated the broad conclusions drawn in the study.

The emerging roles of microvesicles in liver diseases

Microvesicles (MVs) are extracellular vesicles released by virtually all cells, under both physiological and pathological conditions. They contain lipids, proteins, RNAs and microRNAs and act as vectors of information that regulate the function of target cells. This Review provides an overview of the studies assessing circulating MV levels in patients with liver diseases, together with an insight into the mechanisms that could account for these changes. We also present a detailed analysis of the implication of MVs in key processes of liver diseases. MVs have a dual role in fibrosis as certain types of MVs promote fibrolysis by increasing expression of matrix metalloproteinases, whereas others promote fibrosis by stimulating processes such as angiogenesis. MVs probably enhance portal hypertension by contributing to intrahepatic vasoconstriction, splanchnic vasodilation and angiogenesis. As MVs can modulate vascular permeability, vascular tone and angiogenesis, they might contribute to several complications of cirrhosis including hepatic encephalopathy, hepatopulmonary syndrome and hepatorenal syndrome. Several results also suggest that MVs have a role in hepatocellular carcinoma. Although MVs represent promising biomarkers in patients with liver disease, methods of isolation and subsequent analysis must be standardized.

The pro- and anticoagulant role of blood-borne phagocytes in patients with acute coronary syndrome

This study was performed to gain further insight in pro- and anticoagulant characteristics of leukocytes in acute coronary syndrome (ACS). For this purpose, patients presenting on the emergency department (ED) with anginal chest pain were included in this study. In peripheral blood, procoagulant tissue factor (TF) expression was measured in the different blood-borne phagocytes, i.e. neutrophilic granulocytes and the three different monocyte subsets based on expression of CD14 and CD16. Simultaneously, intracellular presence of platelet-(CD41) and/or endothelial cell-remnants (CD62e) was analysed in these different leukocyte subsets. Neutrophils showed a weak intracellular staining of CD62e and CD41 that increased with severity of ACS. Monocytes, and especially the classical (CD14++CD16-) and intermediate monocytes (CD14++CD16+) showed a clear and significant increase in intracellular CD41-staining after coronary damage. The different monocyte subsets showed an increase in expression of TF in severe ACS. Finally, it appeared that also neutrophils showed a significant increase in expression of TF on their membrane. In conclusion, this study showed an increased intracellular staining in blood-borne phagocytes for CD62e and CD41 in patients with ACS compared to non-cardiac related control patients. This indicates that at least in the acute phase of ACS phagocytosis of platelet and endothelial cell-remnants is increased. These data support the recent hypothesis that neutrophils protect against further thrombotic processes by clearing platelet and endothelial cell-remnants. In addition, this study shows that the different monocyte subsets are also involved in this process. Furthermore, both monocytes and neutrophils show increased TF expression in ACS.

CD14, CD16 and HLA-DR reliably identifies human monocytes and their subsets in the context of pathologically reduced HLA-DR expression by CD14(hi) /CD16(neg) monocytes: Expansion of CD14(hi) /CD16(pos) and contraction of CD14(lo) /CD16(pos) monocytes in acute liver failure

Changes in monocytes and their subsets (CD14(hi)/CD16(neg), CD14(hi)/CD16(pos) and CD14(lo)/CD16(pos)) have been described in several diseases. The combination of CD14, CD16 and HLA-DR has been suggested to discriminate monocytes from the CD16(pos) /HLA-DR(neg) NK-cells and neutrophils but no data exist whether this strategy can be used in situations when monocyte HLA-DR expression is pathologically reduced. Monocytes and their subsets were concurrently identified through negative (exclusion of CD66b(pos) neutrophils, CD56(pos) NKcells, CD19(pos) B-cells, and CD3(pos) T-cells) and positive gating (inclusion of monocytes by expression of CD14, CD16, and HLA-DR) strategies on 30 occasions [9 healthy controls (HC) and 21 patients with conditions associated with low monocyte HLA-DR expression]. Bland-Altman and Passing and Bablok regression statistics did not demonstrate any significant measurement bias between the two strategies of monocyte identification. Monocyte subset phenotype was then compared in 18 HC and 41 patients with acute liver failure (ALF). Compared with HC, in ALF, the percentage of CD14(hi)/CD16(pos) monocytes was higher (7% vs 4%) whilst the percentage of CD14(lo)/CD16(pos) was lower (1.9% vs. 7%) (P ≤ 0.001); HLA-DR and CD86 MFIs on all monocyte subsets were lower, whilst CCR5, CD64, and CD11b MFIs were higher (P < 0.05). The relative expression by monocyte subsets of HLA-DR, CCR2, CCR5, CX3CR1, and CD11a was similar in ALF patients and HCs. Repeat analysis of an identical antibody-fluorochrome "backbone" targeting HLA-DR, CD14, and CD16 was assessed in 189 samples across 5 different experiments. There was excellent agreement in the results obtained using the positive gating strategy (interclass correlation coefficients > 0.8). Monocytes and their subsets can be reliably identified using an antibody-fluorochrome "backbone" of HLA-DR, CD14, and CD16. CD16(pos) monocytes continue to constitutively express HLA-DR even in conditions where HLA-DR is pathologically reduced on CD14(hi)/CD16(neg) monocytes. Understanding the changes in monocyte pheontype in ALF and similar clinico-pathological diseases may allow the development of novel biomarkers or therapeutic strategies.

Patients with liver cirrhosis suffer from primary haemostatic defects? Fact or fiction?

Patients with cirrhosis can have abnormalities in laboratory tests reflecting changes in primary haemostasis, including bleeding time, platelet function tests, markers of platelet activation, and platelet count. Such changes have been considered particularly relevant in the bleeding complications that occur in cirrhosis. However, several studies have shown that routine diagnostic tests, such as platelet count, bleeding time, PFA-100, thromboelastography are not clinically useful to stratify bleeding risk in patients with cirrhosis. Moreover, treatments used to increase platelet count or to modulate platelet function could potentially do harm. Consequently the optimal management of bleeding complications is still a matter of discussion. Moreover, in the last two decades there has been an increased recognition that not only bleeding but also thrombosis complicates the clinical course of cirrhosis. Thus, we performed a literature search looking at publications studying both qualitative and quantitative aspects of platelet function to verify which primary haemostasis defects occur in cirrhosis. In addition, we evaluated the contribution of qualitative and quantitative aspects of platelet function to the clinical outcome in cirrhosis and their therapeutic management according to the data available in the literature. From the detailed analysis of the literature, it appears clear that primary haemostasis may not be defective in cirrhosis, and a low platelet count should not necessarily be considered as an automatic index of an increased risk of bleeding. Conversely, caution should be observed in patients with severe thrombocytopenia where its correction is advised if bleeding occurs and before invasive diagnostic and therapeutic procedures.

The functional expression of calcium-sensing receptor in the differentiated THP-1 cells

The expression and function of calcium-sensing receptor (CaSR) in differentiated THP-1 (human acute monocytic leukemia cell line) cells are unknown currently. This study investigated above-mentioned issues using TRAP staining, immunofluorescence staining, Western blotting, ELISA, and Laser Confocal Scanning Microscopy techniques. We found that CaSR protein was expressed, and mainly located in the membrane and cytoplasm in differentiated THP-1 cells. Elevated extracellular calcium or GdCl(3) (an agonist of CaSR) raised intracellular calcium concentration. And this increase was inhibited or abolished by NPS2390 (an inhibitor of CaSR), U73122 (a specific inhibitor of phospholipase C, PLC) or thapsigargin (a Ca(2+)-ATPase inhibitor). The extracellular GdCl(3) elevation stimulated both of IL-1beta and TNFalpha release, and this effect of GdCl(3) was inhibited by NPS2390. In conclusion, CaSR is functionally expressed in differentiated THP-1 cells, and the activated CaSR contributes to intracellular calcium increment through Gq-PLC- inositol triphosphate (IP3) pathway and commits to cytokine secretion. These results suggest that CaSR might be involved in a variety of pathological processes mediated by activated monocyte-macrophages.