Regulation of Weibel–Palade Body Exocytosis

Spatially targeted chemokine exocytosis guides transmigration at lymphatic endothelial multicellular junctions

Migrating cells preferentially breach and integrate epithelial and endothelial monolayers at multicellular vertices. These sites are amenable to forces produced by the migrating cell and subsequent opening of the junctions. However, the cues that guide migrating cells to these entry portals, and eventually drive the transmigration process, are poorly understood. Here, we show that lymphatic endothelium multicellular junctions are the preferred sites of dendritic cell transmigration in both primary cell co-cultures and in mouse dermal explants. Dendritic cell guidance to multicellular junctions was dependent on the dendritic cell receptor CCR7, whose ligand, lymphatic endothelial chemokine CCL21, was exocytosed at multicellular junctions. Characterization of lymphatic endothelial secretory routes indicated Golgi-derived RAB6+ vesicles and RAB3+/27+ dense core secretory granules as intracellular CCL21 storage vesicles. Of these, RAB6+ vesicles trafficked CCL21 to the multicellular junctions, which were enriched with RAB6 docking factor ELKS (ERC1). Importantly, inhibition of RAB6 vesicle exocytosis attenuated dendritic cell transmigration. These data exemplify how spatially-restricted exocytosis of guidance cues helps to determine where dendritic cells transmigrate.

Association of hyperfibrinolysis with poor prognosis in refractory circulatory arrest: implications for extracorporeal cardiopulmonary resuscitation

BACKGROUND

Identifying candidates for extracorporeal cardiopulmonary resuscitation (eCPR) is challenging, and novel predictive markers are urgently needed. Hyperfibrinolysis is linked to tissue hypoxia and is associated with poor outcomes in out-of-hospital cardiac arrest (OHCA). Rotational thromboelastometry (ROTEM) can detect or rule out hyperfibrinolysis, and could, therefore, provide decision support for initiation of eCPR. We explored early detection of hyperfibrinolysis in patients with refractory OHCA referred for eCPR.

METHODS

We analysed ROTEM results and resuscitation parameters of 57 adult patients with ongoing OHCA who presented to our ICU for eCPR evaluation.

RESULTS

Hyperfibrinolysis, defined as maximum lysis ≥15%, was present in 36 patients (63%) and was associated with higher serum lactate, lower arterial blood pH, and increased low-flow intervals. Of 42 patients who achieved return of circulation, 28 had a poor 30-day outcome. The incidence of hyperfibrinolysis was higher in the poor outcome group compared with patients with good outcomes (75% [21 of 28] vs 7.1% [1 of 14]; P<0.001). The ratio of EXTEM A5 to lactate concentration showed good predictive value in detecting hyperfibrinolysis (AUC of 0.89 [95% confidence interval 0.8-1]).

CONCLUSIONS

Hyperfibrinolysis was common in patients with refractory cardiac arrest, and was associated with poor prognosis. The combination of high lactate with early clot firmness values, such as EXTEM A5, appears promising for early detection of hyperfibrinolysis. This finding could facilitate decisions to perform eCPR, particularly for patients with prolonged low-flow duration but lacking hyperfibrinolysis.

Weibel-Palade bodies: function and role in thrombotic thrombocytopenic purpura and in diarrhea phase of STEC-hemolytic uremic syndrome

Vascular endothelial cells are equipped with numerous specialized granules called Weibel-Palade bodies (WPBs). They contain a cocktail of proteins that can be rapidly secreted (3-5 min) into the vascular lumen after an appropriate stimulus such as thrombin. These proteins are ready without synthesis. Von Willebrand factor (VWF) and P-selectin are the main constituents of WPBs. Upon stimulation, release of ultralarge VWF multimers occurs and assembles into VWF strings on the apical side of endothelium. The VWF A1 domain becomes exposed in a shear-dependent manner recruiting and activating platelets. VWF is able to recruit leukocytes via direct leukocyte binding or via the activated platelets promoting NETosis. Ultralarge VWF strings are ultimately cleaved into smaller pieces by the protease ADAMTS-13 preventing excessive platelet adhesion. Under carefully performed flowing conditions and adequate dose of Shiga toxins, the toxin induces the release of ultralarge VWF multimers from cultured endothelial cells. This basic information allows insight into the pathogenesis of thrombotic thrombocytopenic purpura (TTP) and of STEC-HUS in the diarrhea phase. In TTP, ADAMTS-13 activity is deficient and systemic aggregation of platelets will occur after a second trigger. In STEC-HUS, stimulated release of WPB components in the diarrhea phase of the disease can be presumed to be the first hit in the damage of Gb3 positive endothelial cells.

Processing of angiocrine alarmin IL-1α in endothelial cells promotes lung and liver fibrosis

BACKGROUND

Fibrosis results from excessive scar formation after tissue injury. Injured cells release alarmins such as interleukin 1 (IL-1) α and β as primary mediators initiating tissue repair. However, how alarmins from different cell types differentially regulate fibrosis remains to be explored.

METHODS

Here, we used tissue specific knockout strategy to illustrate a unique contribution of endothelial cell-derived IL-1α to lung and liver fibrosis. The two fibrotic animal model triggered by bleomycin and CCl4 were used to study the effects of endothelial paracrine/angiocrine IL-1α in fibrotic progression. Human umbilical vein endothelial cells (HUVEC) were performed to explore the production of angiocrine IL-1α at both transcriptional and post-transcriptional levels in vitro.

RESULTS

We found that endothelial paracrine/angiocrine IL-1α primarily promotes lung and liver fibrosis during the early phase of organ repair. By contrast, myeloid cell-specific ablation of IL-1α in mice resulted in little influence on fibrosis, suggesting the specific pro-fibrotic role of IL-1α from endothelial cell but not macrophage. In vitro study revealed a coordinated regulation of IL-1α production in human primary endothelial cells at both transcriptional and post-transcriptional levels. Specifically, the transcription of IL-1α is regulated by RIPK1, and after caspase-8 (CASP8) cleaves the precursor form of IL-1α, its secretion is triggered by ion channel Pannexin 1 upon CASP8 cleavage.

CONCLUSIONS

Endothelial cell-produced IL-1α plays a unique role in promoting organ fibrosis. Furthermore, the release of this angiocrine alarmin relies on a unique molecular mechanism involving RIPK1, CASP8, and ion channel Pannexin 1.

Evaluation of GSK2789917-induced TRPV4 inhibition in animal models of fluid induced lung injury

Administration of bolus intravenous fluids, common in pre-hospital and hospitalised patients, is associated with increased lung vascular permeability and mortality outside underlying disease states. In our laboratory, the induction of lung injury and oedema through rapid administration of intravenous fluid in rats was reduced by a non-specific antagonist of transient receptor potential vanilloid 4 (TRPV4) channels. The aims of this study were to determine the effect of selective TRPV4 inhibition on fluid-induced lung injury (FILI) and compare the potency of FILI inhibition to that of an established model of TRPV4 agonist-induced lung oedema. In a series of experiments, rats received specific TRPV4 inhibitor (GSK2789917) at high (15 μg/kg), medium (5 μg/kg) or low (2 μg/kg) dose or vehicle prior to induction of lung injury by intravenous infusion of TRPV4 agonist (GSK1016790) or saline. GSK1016790 significantly increased lung wet weight/body weight ratio by 96% and lung wet-to-dry weight ratio by 43% in vehicle pre-treated rats, which was inhibited by GSK2789917 in a dose-dependent manner (IC50 = 3 ng/mL). Similarly, in a single-dose study, bolus saline infusion significantly increased lung wet weight/body weight by 17% and lung wet-to-dry weight ratio by 15%, which was attenuated by high dose GSK2789917. However, in a final GSK2789917 dose-response study, inhibition did not reach significance and an inhibitory potency was not determined due to the lack of a clear dose-response. In the FILI model, TRPV4 may have a role in lung injury induced by rapid-fluid infusion, indicated by inconsistent amelioration with high dose TRPV4 antagonist.

Phenotypes of Disseminated Intravascular Coagulation

Two phenotypes of disseminated intravascular coagulation (DIC) are systematically reviewed. DIC is classified into thrombotic and fibrinolytic phenotypes characterized by thrombosis and hemorrhage, respectively. Major pathology of DIC with thrombotic phenotype is the activation of coagulation, insufficient anticoagulation with endothelial injury, and plasminogen activator inhibitor-1-mediated inhibition of fibrinolysis, leading to microvascular fibrin thrombosis and organ dysfunction. DIC with fibrinolytic phenotype is defined as massive thrombin generation commonly observed in any type of DIC, combined with systemic pathologic hyperfibrinogenolysis caused by underlying disorder that results in severe bleeding due to excessive plasmin formation. Three major pathomechanisms of systemic hyperfibrinogenolysis have been considered: (1) acceleration of tissue-type plasminogen activator (t-PA) release from hypoxic endothelial cells and t-PA-rich storage pools, (2) enhancement of the conversion of plasminogen to plasmin due to specific proteins and receptors that are expressed on cancer cells and endothelial cells, and (3) alternative pathways of fibrinolysis. DIC with fibrinolytic phenotype can be diagnosed by DIC diagnosis followed by the recognition of systemic pathologic hyperfibrin(ogen)olysis. Low fibrinogen levels, high fibrinogen and fibrin degradation products (FDPs), and the FDP/D-dimer ratio are important for the diagnosis of systemic pathologic hyperfibrin(ogen)olysis. Currently, evidence-based treatment strategies for DIC with fibrinolytic phenotypes are lacking. Tranexamic acid appears to be one of the few methods to be effective in the treatment of systemic pathologic hyperfibrin(ogen)olysis. International cooperation for the elucidation of pathomechanisms, establishment of diagnostic criteria, and treatment strategies for DIC with fibrinolytic phenotype are urgent issues in the field of thrombosis and hemostasis.

A defined clathrin-mediated trafficking pathway regulates sFLT1/VEGFR1 secretion from endothelial cells

FLT1/VEGFR1 negatively regulates VEGF-A signaling and is required for proper vessel morphogenesis during vascular development and vessel homeostasis. Although a soluble isoform, sFLT1, is often mis-regulated in disease and aging, how sFLT1 is trafficked and secreted from endothelial cells is not well understood. Here we define requirements for constitutive sFLT1 trafficking and secretion in endothelial cells from the Golgi to the plasma membrane, and we show that sFLT1 secretion requires clathrin at or near the Golgi. Perturbations that affect sFLT1 trafficking blunted endothelial cell secretion and promoted intracellular mis-localization in cells and zebrafish embryos. siRNA-mediated depletion of specific trafficking components revealed requirements for RAB27A, VAMP3, and STX3 for post-Golgi vesicle trafficking and sFLT1 secretion, while STX6, ARF1, and AP1 were required at the Golgi. Live-imaging of temporally controlled sFLT1 release from the endoplasmic reticulum showed clathrin-dependent sFLT1 trafficking at the Golgi into secretory vesicles that then trafficked to the plasma membrane. Depletion of STX6 altered vessel sprouting in 3D, suggesting that endothelial cell sFLT1 secretion influences proper vessel sprouting. Thus, specific trafficking components provide a secretory path from the Golgi to the plasma membrane for sFLT1 in endothelial cells that utilizes a specialized clathrin-dependent intermediate, suggesting novel therapeutic targets.

From Stress to Sick(le) and Back Again-Oxidative/Antioxidant Mechanisms, Genetic Modulation, and Cerebrovascular Disease in Children with Sickle Cell Anemia

Sickle cell anemia (SCA) is a genetic disease caused by the homozygosity of the HBB:c.20A>T mutation, which results in the production of hemoglobin S (HbS). In hypoxic conditions, HbS suffers autoxidation and polymerizes inside red blood cells, altering their morphology into a sickle shape, with increased rigidity and fragility. This triggers complex pathophysiological mechanisms, including inflammation, cell adhesion, oxidative stress, and vaso-occlusion, along with metabolic alterations and endocrine complications. SCA is phenotypically heterogeneous due to the modulation of both environmental and genetic factors. Pediatric cerebrovascular disease (CVD), namely ischemic stroke and silent cerebral infarctions, is one of the most impactful manifestations. In this review, we highlight the role of oxidative stress in the pathophysiology of pediatric CVD. Since oxidative stress is an interdependent mechanism in vasculopathy, occurring alongside (or as result of) endothelial dysfunction, cell adhesion, inflammation, chronic hemolysis, ischemia-reperfusion injury, and vaso-occlusion, a brief overview of the main mechanisms involved is included. Moreover, the genetic modulation of CVD in SCA is discussed. The knowledge of the intricate network of altered mechanisms in SCA, and how it is affected by different genetic factors, is fundamental for the identification of potential therapeutic targets, drug development, and patient-specific treatment alternatives.

Inhalation of an RNA aptamer that selectively binds extracellular histones protects from acute lung injury

Acute lung injury (ALI) is a syndrome of acute inflammation, barrier disruption, and hypoxemic respiratory failure associated with high morbidity and mortality. Diverse conditions lead to ALI, including inhalation of toxic substances, aspiration of gastric contents, infection, and trauma. A shared mechanism of acute lung injury is cellular toxicity from damage-associated molecular patterns (DAMPs), including extracellular histones. We recently described the selection and efficacy of a histone-binding RNA aptamer (HBA7). The current study aimed to identify the effects of extracellular histones in the lung and determine if HBA7 protected mice from ALI. Histone proteins decreased metabolic activity, induced apoptosis, promoted proinflammatory cytokine production, and caused endothelial dysfunction and platelet activation in vitro. HBA7 prevented these effects. The oropharyngeal aspiration of histone proteins increased neutrophil and albumin levels in bronchoalveolar lavage fluid (BALF) and precipitated neutrophil infiltration, interstitial edema, and barrier disruption in alveoli in mice. Similarly, inhaling wood smoke particulate matter, as a clinically relevant model, increased lung inflammation and alveolar permeability. Treatment by HBA7 alleviated lung injury in both models of ALI. These findings demonstrate the pulmonary delivery of HBA7 as a nucleic acid-based therapeutic for ALI.

A defined clathrin-mediated trafficking pathway regulates sFLT1/VEGFR1 secretion from endothelial cells

FLT1/VEGFR1 negatively regulates VEGF-A signaling and is required for proper vessel morphogenesis during vascular development and vessel homeostasis. Although a soluble isoform, sFLT1, is often mis-regulated in disease and aging, how sFLT1 is trafficked and secreted from endothelial cells is not well understood. Here we define requirements for constitutive sFLT1 trafficking and secretion in endothelial cells from the Golgi to the plasma membrane, and we show that sFLT1 secretion requires clathrin at or near the Golgi. Perturbations that affect sFLT1 trafficking blunted endothelial cell secretion and promoted intracellular mis-localization in cells and zebrafish embryos. siRNA-mediated depletion of specific trafficking components revealed requirements for RAB27A, VAMP3, and STX3 for post-Golgi vesicle trafficking and sFLT1 secretion, while STX6, ARF1, and AP1 were required at the Golgi. Depletion of STX6 altered vessel sprouting in a 3D angiogenesis model, indicating that endothelial cell sFLT1 secretion is important for proper vessel sprouting. Thus, specific trafficking components provide a secretory path from the Golgi to the plasma membrane for sFLT1 in endothelial cells that utilizes a specialized clathrin-dependent intermediate, suggesting novel therapeutic targets.

Is Endothelial Activation a Critical Event in Thrombotic Thrombocytopenic Purpura?

Thrombotic thrombocytopenic purpura (TTP) is a severe thrombotic microangiopathy. The current pathophysiologic paradigm suggests that the ADAMTS13 deficiency leads to Ultra Large-Von Willebrand Factor multimers accumulation with generation of disseminated microthrombi. Nevertheless, the role of endothelial cells in this pathology remains an issue. In this review, we discuss the various clinical, in vitro and in vivo experimental data that support the important role of the endothelium in this pathology, suggesting that ADAMTS13 deficiency may be a necessary but not sufficient condition to induce TTP. The "second hit" model suggests that in TTP, in addition to ADAMTS13 deficiency, endogenous or exogenous factors induce endothelial activation affecting mainly microvascular cells. This leads to Weibel-Palade bodies degranulation, resulting in UL-VWF accumulation in microcirculation. This endothelial activation seems to be worsened by various amplification loops, such as the complement system, nucleosomes and free heme.

The complement alternative pathway and hemostasis

The complement and hemostatic systems are complex systems, and both involve enzymatic cascades, regulators, and cell components-platelets, endothelial cells, and immune cells. The two systems are ancestrally related and are defense mechanisms that limit infection by pathogens and halt bleeding at the site of vascular injury. Recent research has uncovered multiple functional interactions between complement and hemostasis. On one side, there are proteins considered as complement factors that activate hemostasis, and on the other side, there are coagulation proteins that modulate complement. In addition, complement and coagulation and their regulatory proteins strongly interact each other to modulate endothelial, platelet and leukocyte function and phenotype, creating a potentially devastating amplifying system that must be closely regulated to avoid unwanted damage and\or disseminated thrombosis. In view of its ability to amplify all complement activity through the C3b-dependent amplification loop, the alternative pathway of complement may play a crucial role in this context. In this review, we will focus on available and emerging evidence on the role of the alternative pathway of complement in regulating hemostasis and vice-versa, and on how dysregulation of either system can lead to severe thromboinflammatory events.

Novel pathophysiological roles of α-synuclein in age-related vascular endothelial dysfunction

Although α-synuclein (SNCA) is a well-known pathological molecule involved in synucleinopathy in neurons, its physiological roles remain largely unknown. We reported that serum SNCA levels have a close inverse correlation with blood pressure and age, which indicates the involvement of SNCA in age-related endothelial dysfunction. Therefore, this study aimed to elucidate the molecular functions of SNCA in the endothelium. We confirmed that SNCA was expressed in and secreted from endothelial cells (ECs). Exogenous treatment with recombinant SNCA (rSNCA) activated the Akt-eNOS axis and increased nitric oxide production in ECs. Treatment with rSNCA also suppressed TNF-α- and palmitic acid-induced NF-κB activation, leading to the suppression of VCAM-1 upregulation and restoration of eNOS downregulation in ECs. As for endogenous SNCA expression, replicative senescence resulted in the attenuation of SNCA expression in cultured ECs, similar to the effects of physiological aging on mice aortas. The siRNA-mediated silencing of SNCA consistently resulted in senescent phenotypes, such as eNOS downregulation, increased β-gal activity, decreased Sirt1 expression, and increased p53 expression, in ECs. Ex vivo assessment of endothelial functions using aortic rings revealed impaired endothelium-dependent acetylcholine-induced relaxation in SNCA knockout (KO) mice. Furthermore, SNCA KO mice, especially those on a high-fat diet, displayed elevated blood pressure compared with wild-type mice; this could be eNOS dysfunction-dependent because of the lower difference caused by L-NAME administration. These results indicate that exogenous and endogenous SNCA in ECs might physiologically maintain vascular integrity, and age-related endothelial dysfunction might be partially ascribed to loss-of-function of SNCA in ECs.

Importance of catecholamine signaling in the development of platelet exhaustion after traumatic injury

BACKGROUND

Impaired ex vivo platelet aggregation is common in trauma patients. The mechanisms driving these impairments remain incompletely understood, but functional platelet exhaustion due to excessive in vivo activation is implicated. Given platelet adrenoreceptors and known catecholamine surges after injury, impaired ex vivo platelet aggregation in trauma patients may be linked to catecholamine-induced functional platelet exhaustion.

OBJECTIVE

To determine the relationship of catecholamines with platelet-dependent hemostasis after injury and to model catecholamine-induced functional platelet exhaustion in healthy donor platelets.

PATIENTS/METHODS

Whole blood was collected from 67 trauma patients as part of a prospective cohort study. Platelet aggregometry and rotational thromboelastometry were performed, and plasma epinephrine (EPI) and norepinephrine (NE) concentrations were measured. The effect of catecholamines on healthy donor platelets was examined in a microfluidic model, with platelet aggregometry, and by flow cytometry examining surface markers of platelet activation.

RESULTS

In trauma patients, EPI and NE were associated with impaired platelet aggregation (both p < 0.05), and EPI was additionally associated with decreased viscoelastic clot strength, increased fibrinolysis, and mortality (all p < 0.05). In healthy donors, short duration incubation with EPI enhanced platelet aggregation, platelet adhesion under flow, and increased glycoprotein IIb/IIIa activation, while weaker effects were observed with NE. Compared with short incubation, longer incubation with EPI resulted in decreased platelet adhesion, platelet aggregation, and surface expression of glycoprotein IIb/IIIa.

CONCLUSIONS

These findings suggest sympathoadrenal activation in trauma patients contributes to impaired ex vivo platelet aggregation, which mechanistically may be explained by a functionally exhausted platelet phenotype under prolonged exposure to high plasma catecholamine levels.

Minimal Change Disease Is Associated With Endothelial Glycocalyx Degradation and Endothelial Activation

Introduction

Minimal change disease (MCD) is considered a podocyte disorder triggered by unknown circulating factors. Here, we hypothesized that the endothelial cell (EC) is also involved in MCD.

Methods

We studied 45 children with idiopathic nephrotic syndrome (44 had steroid sensitive nephrotic syndrome [SSNS], and 12 had biopsy-proven MCD), 21 adults with MCD, and 38 healthy controls (30 children, 8 adults). In circulation, we measured products of endothelial glycocalyx (EG) degradation (syndecan-1, heparan sulfate [HS] fragments), HS proteoglycan cleaving enzymes (matrix metalloprotease-2 [MMP-2], heparanase activity), and markers of endothelial activation (von Willebrand factor [vWF], thrombomodulin) by enzyme-linked immunosorbent assay (ELISA) and mass spectrometry. In human kidney tissue, we assessed glomerular EC (GEnC) activation by immunofluorescence of caveolin-1 (n = 11 MCD, n = 5 controls). In vitro, we cultured immortalized human GEnC with sera from control subjects and patients with MCD/SSNS sera in relapse (n = 5 per group) and performed Western blotting of thrombomodulin of cell lysates as surrogate marker of endothelial activation.

Results

In circulation, median concentrations of all endothelial markers were higher in patients with active disease compared with controls and remained high in some patients during remission. In the MCD glomerulus, caveolin-1 expression was higher, in an endothelial-specific pattern, compared with controls. In cultured human GEnC, sera from children with MCD/SSNS in relapse increased thrombomodulin expression compared with control sera.

Conclusion

Our data show that alterations involving the systemic and glomerular endothelium are nearly universal in patients with MCD and SSNS, and that GEnC can be directly activated by circulating factors present in the MCD/SSNS sera during relapse.

Multimerin-1 and cancer: a review

Multimerin-1 (MMRN1) is a platelet protein with a role in haemostasis and coagulation. It is also present in endothelial cells (ECs) and the extracellular matrix (ECM), where it may be involved in cell adhesion, but its molecular functions and protein–protein interactions in these cellular locations have not been studied in detail yet. In recent years, MMRN1 has been identified as a differentially expressed gene (DEG) in various cancers and it has been proposed as a possible cancer biomarker. Some evidence suggest that MMRN1 expression is regulated by methylation, protein interactions, and non-coding RNAs (ncRNAs) in different cancers. This raises the questions if a functional role of MMRN1 is being targeted during cancer development, and if MMRN1’s differential expression pattern correlates with cancer progression. As a result, it is timely to review the current state of what is known about MMRN1 to help inform future research into MMRN1’s molecular mechanisms in cancer.

Weibel Palade Bodies: Unique Secretory Organelles of Endothelial Cells that Control Blood Vessel Homeostasis

Vascular endothelial cells produce and release compounds regulating vascular tone, blood vessel growth and differentiation, plasma composition, coagulation and fibrinolysis, and also engage in interactions with blood cells thereby controlling hemostasis and acute inflammatory reactions. These interactions have to be tightly regulated to guarantee smooth blood flow in normal physiology, but also allow specific and often local responses to blood vessel injury and infectious or inflammatory insults. To cope with these challenges, endothelial cells have the remarkable capability of rapidly changing their surface properties from non-adhesive (supporting unrestricted blood flow) to adhesive (capturing circulating blood cells). This is brought about by the evoked secretion of major adhesion receptors for platelets (von-Willebrand factor, VWF) and leukocytes (P-selectin) which are stored in a ready-to-be-used form in specialized secretory granules, the Weibel-Palade bodies (WPB). WPB are unique, lysosome related organelles that form at the trans-Golgi network and further mature by receiving material from the endolysosomal system. Failure to produce correctly matured VWF and release it through regulated WPB exocytosis results in pathologies, most importantly von-Willebrand disease, the most common inherited blood clotting disorder. The biogenesis of WPB, their intracellular motility and their fusion with the plasma membrane are regulated by a complex interplay of proteins and lipids, involving Rab proteins and their effectors, cytoskeletal components as well as membrane tethering and fusion machineries. This review will discuss aspects of WPB biogenesis, trafficking and exocytosis focussing on recent findings describing factors contributing to WPB maturation, WPB-actin interactions and WPB-plasma membrane tethering and fusion.

Endothelial cell biomarkers in critically ill COVID-19 patients with encephalitis

COVID-19 is associated with encephalitis in critically ill patients and endothelial dysfunction seems to contribute to this life-threatening complication. Our objective was to determine the hallmark of endothelial activation in COVID-19-related encephalitis. In an observational study in intensive care unit (ICU), we compared vascular biomarkers of critically ill COVID-19 patients with or without encephalitis. To be classified in the encephalitis group, patients had to have new onset of central neurologic symptom, and pathological findings on either brain magnetic resonance imaging (MRI) and/or electroencephalogram (EEG). Among the 32 critically ill COVID-19 consecutive patients, 21 were categorized in the control group and 11 in the encephalitis group. Encephalitis patients had a longer ICU stay than control patients (median length [25th-75th percentile] of 52 [16-79] vs. 20.5 [11-44] days, respectively, p = 0.04). Nine-month overall follow-up mortality reached 21% (7/32 patients), with mortality rates in the encephalitis group and the control group of 27% and 19%, respectively. Encephalitis was associated with significant higher release of soluble endothelial activation markers (sE-selectin, tumor necrosis factor-α (TNF-α), interleukin 6, placental growth factor, and thrombomodulin), but these increases were correlated with TNF-α plasmatic levels. The hypoxia-inducible protein angiopoietin-like 4 (ANGPTL4) was at significantly higher levels in encephalitis patients compared to control patients (p = 0.0099), and in contrary to the other increased factors, was not correlated with TNF-α levels (r = 0.2832, p = 0.1163). Our findings suggest that COVID-19-related encephalitis is a cytokine-associated acute brain dysfunction. ANGPTL4 was the only elevated marker found in encephalitis patients, which was not correlated with systemic inflammation, suggesting that ANGPTL4 might be a relevant factor to predict encephalitis in critically ill COVID-19 patients.

The multifaceted PDCD10/CCM3 gene

The programmed cell death 10 (PDCD10) gene was originally identified as an apoptosis-related gene, although it is now usually known as CCM3, as the third causative gene of cerebral cavernous malformation (CCM). CCM is a neurovascular disease that is characterized by vascular malformations and is associated with headaches, seizures, focal neurological deficits, and cerebral hemorrhage. The PDCD10/CCM3 protein has multiple subcellular localizations and interacts with several multi-protein complexes and signaling pathways. Thus PDCD10/CCM3 governs many cellular functions, which include cell-to-cell junctions and cytoskeleton organization, cell proliferation and apoptosis, and exocytosis and angiogenesis. Given its central role in the maintenance of homeostasis of the cell, dysregulation of PDCD10/CCM3 can result in a wide range of altered cell functions. This can lead to severe diseases, including CCM, cognitive disability, and several types of cancers. Here, we review the multifaceted roles of PDCD10/CCM3 in physiology and pathology, with a focus on its functions beyond CCM.

Proteomic Signature of Dysfunctional Circulating Endothelial Colony-Forming Cells of Young Adults

Background A subpopulation of endothelial progenitor cells called endothelial colony-forming cells (ECFCs) may offer a platform for cellular assessment in clinical studies because of their remarkable angiogenic and expansion potentials in vitro. Despite endothelial cell function being influenced by cardiovascular risk factors, no studies have yet provided a comprehensive proteomic profile to distinguish functional (ie, more angiogenic and expansive cells) versus dysfunctional circulating ECFCs of young adults. The aim of this study was to provide a detailed proteomic comparison between functional and dysfunctional ECFCs. Methods and Results Peripheral blood ECFCs were isolated from 11 subjects (45% men, aged 27±5 years) using Ficoll density gradient centrifugation. ECFCs expressed endothelial and progenitor surface markers and displayed cobblestone-patterned morphology with clonal and angiogenic capacities in vitro. ECFCs were deemed dysfunctional if <1 closed tube formed during the in vitro tube formation assay and proliferation rate was <20%. Hierarchical functional clustering revealed distinct ECFC proteomic signatures between functional and dysfunctional ECFCs with changes in cellular mechanisms involved in exocytosis, vesicle transport, extracellular matrix organization, cell metabolism, and apoptosis. Targeted antiangiogenic proteins in dysfunctional ECFCs included SPARC (secreted protein acidic and rich in cysteine), CD36 (cluster of differentiation 36), LUM (lumican), and PTX3 (pentraxin-related protein PYX3). Conclusions Circulating ECFCs with impaired angiogenesis and expansion capacities have a distinct proteomic profile and significant phenotype changes compared with highly angiogenic endothelial cells. Impaired angiogenesis in dysfunctional ECFCs may underlie the link between endothelial dysfunction and cardiovascular disease risks in young adults.

Metabolomic Profile in Venous Thromboembolism (VTE)

Venous thromboembolism (VTE) is a condition comprising deep venous thrombosis (DVT) and pulmonary embolism (PE). The prevalence of this disease is constantly increasing and it is also a chief reason for morbidity. Therefore, the primary prevention of VTE remains a highly important public health issue. At present, its diagnosis generally relies on subjective clinical examination and ultrasound imaging. D-dimer is also used as a biomarker, but it is considered to be poorly specific and only moderately sensitive. There are also no reliable methods that could accurately guide the type of treatment and potentially identify patients who may benefit from more aggressive therapies without the risk of bleeding. The application of metabolomics profiling in the area of vascular diseases may become a turning point in early diagnosis and patient management. Among the most described metabolites possibly related to VTE are carnitine species, glucose, phenylalanine, 3-hydroxybutarate, lactic acid, tryptophan and some monounsaturated and polyunsaturated fatty acids. The cell response to acute PE was suggested to involve the uncoupling between glycolysis and oxidative phosphorylation. Despite technological advancement in the identification of metabolites and their alteration in thrombosis, we still do not understand the mechanisms and pathways responsible for the occurrence of observed alterations.

Zinc Homeostasis Alters Zinc Transporter Protein Expression in Vascular Endothelial and Smooth Muscle Cells

INTRODUCTION

Zinc is an important essential micronutrient with anti-oxidative and anti-inflammatory properties in humans. The role of zinc in signalling has been characterized in the nervous, endocrine, gastrointestinal, renal and reproductive systems. Relatively little is known regarding its role in the vascular system, but the role of zinc homeostasis in augmenting vascular health and vasorelaxation is emerging. Zinc transport proteins are integral to the protective function of zinc, but knowledge of their expression in vascular endothelial and smooth muscle cells is lacking.

METHODOLOGY

Human coronary artery endothelial cells and pulmonary artery smooth muscle cells were assessed for gene expression (RT-PCR) of SLC39A (ZIP), SLC30A (ZnT) and metallothionein (MT) families of Zn transporters and storage proteins. Protein expression (fluorescence confocal microscopy) was then analysed for the proteins of interest that changed mRNA expression: ZIP2, ZIP12, ZnT1, ZnT2 and MT1/2.

RESULTS

Endothelial and smooth muscle cell mRNA expression of ZnT1, ZnT2 and MT1 was significantly downregulated by low and high Zn conditions, while ZIP2 and ZIP12 expression was induced by Zn depletion with the Zn chelator, TPEN. Changes in gene expression were consistent with protein expression levels for ZIP2, ZIP12 and MT1, where ZIP2 was localized to intracellular bodies and ZIP12 to lamellipodia.

CONCLUSION

Vascular endothelial and smooth muscle cells actively regulate specific Zn transport and metallothionein gene and protein expressions to achieve Zn homeostasis.

Lysophosphatidylcholine in phospholipase A2-modified LDL triggers secretion of angiopoietin 2

BACKGROUND AND AIMS

Secretory phospholipase A₂ (PLA₂) hydrolyzes LDL phospholipids generating modified LDL particles (PLA₂-LDL) with increased atherogenic properties. Exocytosis of Weibel-Palade bodies (WPB) releases angiopoietin 2 (Ang2) and externalizes P-selectin, which both play important roles in vascular inflammation. Here, we investigated the effects of PLA₂-LDL on exocytosis of WPBs.

METHODS

Human coronary artery endothelial cells (HCAECs) were stimulated with PLA₂- LDL, and its uptake and effect on Ang2 release, leukocyte adhesion, and intracellular calcium levels were measured. The effects of PLA₂-LDL on Ang2 release and WPB exocytosis were measured in and ex vivo in mice.

RESULTS

Exposure of HCAECs to PLA₂-LDL triggered Ang2 secretion and promoted leukocyte-HCAEC interaction. Lysophosphatidylcholine was identified as a critical component of PLA₂-LDL regulating the WPB exocytosis, which was mediated by cell-surface proteoglycans, phospholipase C, intracellular calcium, and cytoskeletal remodeling. PLA₂-LDL also induced murine endothelial WPB exocytosis in blood vessels in and ex vivo, as evidenced by secretion of Ang2 in vivo, P-selectin translocation to plasma membrane in intact endothelial cells in thoracic artery and tracheal vessels, and reduced Ang2 staining in tracheal endothelial cells. Finally, in contrast to normal human coronary arteries, in which Ang2 was present only in the endothelial layer, at sites of advanced atherosclerotic lesions, Ang2 was detected also in the intima, media, and adventitia.

CONCLUSIONS

Our studies reveal PLA₂-LDL as a potent agonist of endothelial WPB exocytosis, resulting in increased secretion of Ang2 and translocation of P-selectin. The results provide mechanistic insight into PLA₂-LDL-dependent promotion of vascular inflammation and atherosclerosis.

Estrogen activates endothelial exocytosis

Estrogen therapy is used to treat patients with post-menopausal symptoms, such as hot flashes and dyspareunia. Estrogen therapy also decreases the risk of fractures from osteoporosis in post-menopausal women. However, estrogen increases the risk of venous thromboembolic events, such as pulmonary embolism, but the pathways through which estrogen increase the risk of thromboembolism is unknown. Here, we show that estrogen elicits endothelial exocytosis, the key step in vascular thrombosis and inflammation. Exogenous 17β-estradiol (E2) stimulated endothelial exocytosis of Weibel-Palade bodies (WPBs), releasing von Willebrand factor (vWF) and interleukin-8 (IL-8). Conversely, the estrogen antagonist ICI-182,780 interfered with E2-induced endothelial exocytosis. The ERα agonist propyl pyrazole triol (PPT) but not the ERβ agonist diarylpropionitrile (DPN) induced vWF release, while ERα silencing counteracted vWF release by E2, suggesting that ERα mediates this effect. Exocytosis triggered by E2 occurred rapidly within 15 min and was not inhibited by either actinomycin D or cycloheximide. On the contrary, it was inhibited by the pre-treatment of U0126 or SB203580, an ERK or a p38 inhibitor, respectively, suggesting that E2-induced endothelial exocytosis is non-genomically mediated by the MAP kinase pathway. Finally, E2 treatment enhanced platelet adhesion to endothelial cells ex vivo, which was interfered with the pre-treatment of ICI-182,780 or U0126. Taken together, our data show that estrogen activates endothelial exocytosis non-genomically through the ERα-MAP kinase pathway. Our data suggest that adverse cardiovascular effects such as vascular inflammation and thrombosis should be considered in patients before menopausal hormone treatment.

Evaluation of VEGF-A in platelet and microRNA-126 in serum after coronary artery bypass grafting

Platelet functions are thought to contribute to clinical outcomes after heart surgery. This study was conducted to assess the pivotal roles of vascular endothelial growth factor-A (VEGF-A) and microRNA-126 (miR-126) during coronary artery bypass grafting (CABG). Whole blood was collected for platelet isolation from 67 patients who underwent CABG surgery between July 2013 and March 2014. VEGF-A and miR-126 levels in serum, plasma, and platelets were measured at various time points and compared with clinical characteristics. The platelet count was decreased at 3 days after CABG. This dynamic change in platelet count was larger after conventional coronary artery bypass (CCAB) than off-pump coronary artery bypass (OPCAB). VEGF-A in the same number of platelets (IP-VEGF-A) was increased at 3 days after CABG, followed by an increase of VEGF-A in serum (S-VEGF-A) at 7 days after surgery. The miR-126-3p level in serum (S-miR-126-3p) increased rapidly after CABG and then decreased below preoperative levels. The IP-VEGF-A level on day 7 after CABG in patients with peripheral artery disease (PAD), who suffered from endothelial dysfunction, was higher compared with patients without PAD. Conversely, S-miR-126-3p on day 7 after surgery was lower in patients with PAD than in patients without PAD. Low levels of S-miR-126-3p due to endothelial dysfunction may lead to high IP-VEGF-A, which is closely related to complications after CABG.

Alpha-Synuclein in the Regulation of Brain Endothelial and Perivascular Cells: Gaps and Future Perspectives

Misfolded proteins, inflammation, and vascular alterations are common pathological hallmarks of neurodegenerative diseases. Alpha-synuclein is a small synaptic protein that was identified as a major component of Lewy bodies and Lewy neurites in the brain of patients affected by Parkinson's disease (PD), Lewy body dementia (LBD), and other synucleinopathies. It is mainly involved in the regulation of synaptic vesicle trafficking but can also control mitochondrial/endoplasmic reticulum (ER) homeostasis, lysosome/phagosome function, and cytoskeleton organization. Recent evidence supports that the pathological forms of α-synuclein can also reduce the release of vasoactive and inflammatory mediators from endothelial cells (ECs) and modulates the expression of tight junction (TJ) proteins important for maintaining the blood-brain barrier (BBB). This hints that α-synuclein deposition can affect BBB integrity. Border associated macrophages (BAMs) are brain resident macrophages found in association with the vasculature (PVMs), meninges (MAMs), and choroid plexus (CPMs). Recent findings indicate that these cells play distinct roles in stroke and neurodegenerative disorders. Although many studies have addressed how α-synuclein may modulate microglia, its effect on BAMs has been scarcely investigated. This review aims at summarizing the main findings supporting how α-synuclein can affect ECs and/or BAMs function as well as their interplay and effect on other cells in the brain perivascular environment in physiological and pathological conditions. Gaps of knowledge and new perspectives on how this protein can contribute to neurodegeneration by inducing BBB homeostatic changes in different neurological conditions are highlighted.

Angiopoietin-2 is released during anaphylactic hypotension in anesthetized and unanesthetized rats

Angiopoietin (Angpt)-2, a permeability-increasing growth factor, is involved in vascular leakage of sepsis and acute lung injury, and could be released from endothelium in response to anaphylaxis-related secretagogues such as histamine and leukotrienes, or cytokines. However, roles of Angpt-2 in the hyperpermeability during systemic anaphylaxis are not known. Thus, we determined plasma levels of Angpt-2 and cytokines and vascular permeability during anaphylactic hypotension in unanesthetized rats. Anaphylaxis was induced by an intravenous injection of ovalbumin antigen. Mean arterial blood pressure (MBP) was measured, and hematocrit (Hct) and plasma levels of Angpt-2 and cytokines were assessed for 24 h after antigen injection. Separately, vascular permeability was measured in various organs using the Evans blue dye method, and Angpt-2 mRNA expression in liver was measured. After antigen injection, MBP decreased to the nadir at 6 min, and returned to baseline at 45 min, and Hct peaked at 20 min and thereafter progressively declined, suggesting that vascular leak and hypotension occurred within 20 min. Plasma Angpt-2 levels began to increase significantly at 1 h after antigen, reaching the peak 2.7-fold baseline at 6 h with a return to baseline at 24 h. Detected cytokines of IL-1α, IL-1β, IL-6, IL-10, and TNF-α peaked 1 or 2 h after antigen. Angpt-2 mRNA increased at 2 h and showed an increasing tendency at 6 h. Vascular permeability in bronchus, trachea, intestines, mesentery and skeletal muscle was increased at 10 min but not at 6 h after antigen. In addition, we confirmed using anesthetized rat anaphylaxis models that plasma Angpt-2 levels increased at 1 h after antigen. In conclusion, plasma Angpt-2 is elevated presumably due to increased cytokines and enhanced gene transcription during anaphylaxis in anesthetized and unanesthetized rats.

Vascular toxicity associated with anti-angiogenic drugs

Over the past two decades, the treatment of cancer has been revolutionised by the highly successful introduction of novel molecular targeted therapies and immunotherapies, including small-molecule kinase inhibitors and monoclonal antibodies that target angiogenesis by inhibiting vascular endothelial growth factor (VEGF) signaling pathways. Despite their anti-angiogenic and anti-cancer benefits, the use of VEGF inhibitors (VEGFi) and other tyrosine kinase inhibitors (TKIs) has been hampered by potent vascular toxicities especially hypertension and thromboembolism. Molecular processes underlying VEGFi-induced vascular toxicities still remain unclear but inhibition of endothelial NO synthase (eNOS), reduced nitric oxide (NO) production, oxidative stress, activation of the endothelin system, and rarefaction have been implicated. However, the pathophysiological mechanisms still remain elusive and there is an urgent need to better understand exactly how anti-angiogenic drugs cause hypertension and other cardiovascular diseases (CVDs). This is especially important because VEGFi are increasingly being used in combination with other anti-cancer dugs, such as immunotherapies (immune checkpoint inhibitors (ICIs)), other TKIs, drugs that inhibit epigenetic processes (histone deacetylase (HDAC) inhibitor) and poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitors, which may themselves induce cardiovascular injury. Here, we discuss vascular toxicities associated with TKIs, especially VEGFi, and provide an up-to-date overview on molecular mechanisms underlying VEGFi-induced vascular toxicity and cardiovascular sequelae. We also review the vascular effects of VEGFi when used in combination with other modern anti-cancer drugs.

A multicenter prospective validation study on disseminated intravascular coagulation in trauma-induced coagulopathy

BACKGROUND

Trauma-induced coagulopathy (TIC) may progress to disseminated intravascular coagulation (DIC) due to dysregulated inflammatory and coagulofibrinolytic responses to trauma.

OBJECTIVES

We explored how DIC and TIC elicit the same coagulofibrinolytic changes which lead to massive transfusion.

METHODS

Severely injured trauma patients with an injury severity score ≥ 16 were prospectively included. Platelet counts, global markers of coagulation and fibrinolysis and specific markers of thrombin and plasmin generation, anticoagulation, endothelial injury, and inhibition of fibrinolysis were measured at presentation to the emergency department (0 hour) and 3 hour after arrival. The patients were subdivided into those with and without DIC and those with and without TIC using the 0-hour data. Time courses of specific markers and the frequency of massive transfusion were evaluated. The association of various variables with DIC development was also confirmed.

RESULTS

Two hundred and seventy-six patients were eligible for the analyses. The severity of injury (odds ratio; 1.038, P = .022) and thrombin generation (odds ratio; 1.014, P = .024) were associated with the development of DIC. Both DIC and TIC patients showed increased thrombin generation, insufficient anticoagulation controls, endothelial injury and increased fibrinolysis followed by elevated plasminogen activator inhibitor-1 levels at 0 and 3 hours. The frequency of massive transfusion was higher in both DIC (33.6% vs 7.9%, P < .001) and TIC (50.0% vs 13.3%, P < .001) patients than in those without DIC or TIC, respectively.

CONCLUSIONS

Disseminated intravascular coagulation and TIC evoked the same coagulofibrinolytic responses in severely injured trauma patients immediately after trauma and needed massive transfusion.

Pathophysiological Response to Trauma-Induced Coagulopathy: A Comprehensive Review

Hypercoagulability can occur after severe tissue injury, that is likely related to tissue factor exposure and impaired endothelial release of tissue plasminogen activator (tPA). In contrast, when shock and hypoperfusion occur, activation of the protein C pathway and endothelial tPA release induce a shift from a procoagulant to a hypocoagulable and hyperfibrinolytic state with a high risk of bleeding. Both thrombotic and bleeding phenotypes are associated with increased mortality and are influenced by the extent and severity of tissue injury and degree of hemorrhagic shock. Response to trauma is a complex, dynamic process in which risk can shift from bleeding to thrombosis depending on the injury pattern, hemostatic treatment, individual responses, genetic predisposition, and comorbidities. Based on this body of knowledge, we will review and consider future directions for the management of severely injured trauma patients.

Role of Autophagy in Von Willebrand Factor Secretion by Endothelial Cells and in the In Vivo Thrombin-Antithrombin Complex Formation Promoted by the HIV-1 Matrix Protein p17

Although the advent of combined antiretroviral therapy has substantially improved the survival of HIV-1-infected individuals, non-AIDS-related diseases are becoming increasingly prevalent in HIV-1-infected patients. Persistent abnormalities in coagulation appear to contribute to excess risk for a broad spectrum of non-AIDS defining complications. Alterations in coagulation biology in the context of HIV infection seem to be largely a consequence of a chronically inflammatory microenvironment leading to endothelial cell (EC) dysfunction. A possible direct role of HIV-1 proteins in sustaining EC dysfunction has been postulated but not yet investigated. The HIV-1 matrix protein p17 (p17) is secreted from HIV-1-infected cells and is known to sustain inflammatory processes by activating ECs. The aim of this study was to investigate the possibility that p17-driven stimulation of human ECs is associated with increased production of critical coagulation factors. Here we show the involvement of autophagy in the p17-induced accumulation and secretion of von Willebrand factor (vWF) by ECs. In vivo experiments confirmed the capability of p17 to exert a potent pro-coagulant activity soon after its intravenous administration.

Relationship Between Severity of Fibrinolysis Based on Rotational Thromboelastometry and Conventional Fibrinolysis Markers

The association between severity of fibrinolysis, ascertained by rotational thromboelastometry to diagnose hyperfibrinolysis in patients with out-of-hospital cardiac arrest (OHCA), and conventional fibrinolysis markers (ie, tissue-plasminogen activator [t-PA], plasminogen, α₂-plasmin inhibitor [α₂-PI], and plasminogen activator inhibitor [PAI]) with key roles in the fibrinolytic system was investigated. This prospective observational study included 5 healthy volunteers and 35 patients with OHCA from the Hokkaido University Hospital. Blood samples were drawn immediately upon admission to the emergency department. Assessments of the extrinsic pathway using tissue factor activation (EXTEM) and of fibrinolysis by comparison with EXTEM after aprotinin addition (APTEM) were undertaken. Conventional coagulation and fibrinolysis markers were measured in the stored plasma samples. Significant hyperfibrinolysis observed in EXTEM disappeared in APTEM. Patients exhibited significantly higher levels of fibrinogen/fibrin degradation products, plasmin–α₂-PI complex, and t-PA but lower levels of fibrinogen, plasminogen, and α₂-PI than healthy controls. The PAI level was unchanged. Fibrinolytic parameters of EXTEM correlated with levels of lactate and conventional fibrinolysis markers, especially t-PA. Increased t-PA activity and decreased plasminogen and α₂-PI significantly correlated with increased severity of fibrinolysis (hyperfibrinolysis).

Human endothelial cells size-select their secretory granules for exocytosis to modulate their functional output

BACKGROUND

The secretory granules of endothelial cells, Weibel-Palade bodies, are released in response to numerous extracellular signals. Their cargo is critical to many vascular functions including hemostasis and inflammation. This presents a fundamental problem: how can these cells initiate tailor-made responses from the release of a single type of organelle, each with similar cargo? Each cell contains Weibel-Palade bodies in a wide range of sizes, and we have shown that experimentally shortening these organelles disproportionately reduces their ability to initiate hemostasis in vitro, leaving leukocyte recruitment unaffected. Could the production of this range of sizes underpin differential responses?

OBJECTIVES

To determine whether different agonists drive the exocytosis of different sizes of Weibel-Palade bodies.

METHODS

We used a high-throughput automated unbiased imaging workflow to analyze the sizes of Weibel-Palade bodies within human umbilical vein endothelial cells (HUVECs) before and after agonist activation to determine changes in organelle size distributions.

RESULTS

We found that a subset of agonists differentially evoke the release of the longest, most pro-hemostatic organelles. Inhibiting the release of these longest organelles by just 15% gives a fall of 60% in an assay of secreted von Willebrand factor (vWF) function.

CONCLUSIONS

The size-selection of granules for exocytosis represents a novel layer of control, allowing endothelial cells to provide diverse responses to different signals via the release of a single type of organelle.

Tranexamic Acid for Acute Hemorrhage: A Narrative Review of Landmark Studies and a Critical Reappraisal of Its Use Over the Last Decade

The publication of the Clinical Randomization of an Antifibrinolytic in Significant Hemorrhage-2 (CRASH-2) study and its intense dissemination prompted a renaissance for the use of the antifibrinolytic agent tranexamic acid (TXA) in acute trauma hemorrhage. Subsequent studies led to its widespread use as a therapeutic as well as prophylactic agent across different clinical scenarios involving bleeding, such as trauma, postpartum, and orthopedic surgery. However, results from the existing studies are confounded by methodological and statistical ambiguities and are open to varied interpretations. Substantial knowledge gaps remain on dosing, pharmacokinetics, mechanism of action, and clinical applications for TXA. The risk for potential thromboembolic complications with the use of TXA must be balanced against its clinical benefits. The present article aims to provide a critical reappraisal of TXA use over the last decade and a "thought exercise" in the potential downsides of TXA. A more selective and individualized use of TXA, guided by extended and functional coagulation assays, is advocated in the context of the evolving concept of precision medicine.

Genome-Wide Association Transethnic Meta-Analyses Identifies Novel Associations Regulating Coagulation Factor VIII and von Willebrand Factor Plasma Levels

BACKGROUND

Factor VIII (FVIII) and its carrier protein von Willebrand factor (VWF) are associated with risk of arterial and venous thrombosis and with hemorrhagic disorders. We aimed to identify and functionally test novel genetic associations regulating plasma FVIII and VWF.

METHODS

We meta-analyzed genome-wide association results from 46 354 individuals of European, African, East Asian, and Hispanic ancestry. All studies performed linear regression analysis using an additive genetic model and associated ≈35 million imputed variants with natural log-transformed phenotype levels. In vitro gene silencing in cultured endothelial cells was performed for candidate genes to provide additional evidence on association and function. Two-sample Mendelian randomization analyses were applied to test the causal role of FVIII and VWF plasma levels on the risk of arterial and venous thrombotic events.

RESULTS

We identified 13 novel genome-wide significant ( P≤2.5×10^-8) associations, 7 with FVIII levels ( FCHO2/TMEM171/TNPO1, HLA, SOX17/RP1, LINC00583/NFIB, RAB5C-KAT2A, RPL3/TAB1/SYNGR1, and ARSA) and 11 with VWF levels ( PDHB/PXK/KCTD6, SLC39A8, FCHO2/TMEM171/TNPO1, HLA, GIMAP7/GIMAP4, OR13C5/NIPSNAP, DAB2IP, C2CD4B, RAB5C-KAT2A, TAB1/SYNGR1, and ARSA), beyond 10 previously reported associations with these phenotypes. Functional validation provided further evidence of association for all loci on VWF except ARSA and DAB2IP. Mendelian randomization suggested causal effects of plasma FVIII activity levels on venous thrombosis and coronary artery disease risk and plasma VWF levels on ischemic stroke risk.

CONCLUSIONS

The meta-analysis identified 13 novel genetic loci regulating FVIII and VWF plasma levels, 10 of which we validated functionally. We provide some evidence for a causal role of these proteins in thrombotic events.

Effects of acrolein in comparison to its prodrug cyclophosphamide on human primary endothelial cells in vitro

Cyclophosphamide (CPA) is one of the most successful anticancer prodrugs that becomes effective after biotransformation in the liver resulting in the toxic metabolite acrolein. Cancer is often accompanied by thromboembolic events, which might be a result of dysfunctional endothelial cells due to CPA treatment. Here, the effect of 1 mM CPA or acrolein (10/50/100/500 μM) on human umbilical vein endothelial cells (HUVECs) was analyzed after two days of treatment. The addition of CPA or 10 μM acrolein did not affect HUVECs. However, concentrations of 100 μM and 500 μM acrolein significantly reduced the number of adherent cells by 86 ± 13% and 99 ± 1% and cell viability by 51 ± 29% and 93 ± 8% compared to the control. Moreover, pronounced stress fibers as well as multiple nuclei were observed and von Willebrand factor (vWF) was completely released. Lactate dehydrogenase was 8.5 ± 7.0-fold and 252.9 ± 42.9-fold increased showing a loss of cell membrane integrity. The prostacyclin and thromboxane secretion was significantly increased by the addition of 500 μM acrolein (43.1 ± 17.6-fold and 246.4 ± 106.3-fold) indicating cell activation/pertubation. High doses of acrolein led to HUVEC death and loss of vWF production. This effect might be associated with the increased incidence of thromboembolic events in cancer patients treated with high doses of CPA.

Endothelial glycocalyx-the battleground for complications of sepsis and kidney injury

After briefly discussing endothelial glycocalyx and its role in vascular physiology and renal disease, this overview focuses on its degradation very early in the course of microbial sepsis. We describe our recently proposed mechanism for glycocalyx degradation induced by exocytosis of lysosome-related organelles and release of their cargo. Notably, an intermediate in nitric oxide synthesis, NG-hydroxy-l-arginine, shows efficacy in curtailing exocytosis of these organelles and improvement in animal survival. These data not only depict a novel mechanism responsible for very early glycocalyx degradation, but may also outline a potential preventive therapy. The second issue discussed in this article is related to the therapeutic acceleration of restoration of already degraded endothelial glycocalyx. Here, using as an example our recent findings obtained with sulodexide, we illustrate the importance of the expedited repair of degraded endothelial glycocalyx for the survival of animals with severe sepsis. These two focal points of the review on glycocalyx may not only have broader disease applicability, but they may also provide additional evidence to buttress the idea of the importance of endothelial glycocalyx and its maintenance and repair in the prevention and treatment of an array of renal and nonrenal diseases.

Disseminated intravascular coagulation in cardiac arrest and resuscitation

The aims of this review are to demonstrate that the changes in coagulation and fibrinolysis observed in cardiac arrest and resuscitation can be recognized as disseminated intravascular coagulation (DIC), and to discuss the probability of DIC being a therapeutic target. The appearance of triggers of DIC, such as damage-associated molecular patterns, inflammatory cytokines, and adrenaline, is associated with platelet activation, marked thrombin generation and fibrin formation, insufficient anticoagulation pathways, and increased fibrinolysis by tissue-type plasminogen activator, followed by the suppression of fibrinolysis by plasminogen activator inhibitor-1, in patients with cardiac arrest and resuscitation. Simultaneous neutrophil activation and endothelial injury associated with glycocalyx perturbation have been observed in these patients. The degree of these changes is more severe in patients with prolonged precardiac arrest hypoxia and long no-flow and low-flow times, patients without return of spontaneous circulation, and non-survivors. Animal and clinical studies have confirmed decreased cerebral blood flow and microvascular fibrin thrombosis in vital organs, including the brain. The clinical diagnosis of DIC in patients with cardiac arrest and resuscitation is associated with multiple organ dysfunction, as assessed with the sequential organ failure assessment score, and increased mortality. This review confirms that the coagulofibrinolytic changes in cardiac arrest and resuscitation meet the definition of DIC proposed by the ISTH, and that DIC is associated with organ dysfunction and poor patient outcomes. This evidence implies that established DIC should be considered to be one of the main therapeutic targets in post-cardiac arrest syndrome.

Weibel-Palade Bodies Orchestrate Pericytes During Angiogenesis

Objective Weibel-Palade bodies (WPBs) are endothelial cell (EC)-specific organelles formed by vWF (von Willebrand factor) polymerization and that contain the proangiogenic factor Ang-2 (angiopoietin-2). WPB exocytosis has been shown to be implicated for vascular repair and inflammatory responses. Here, we investigate the role of WPBs during angiogenesis and vessel stabilization. Approach and Results WPB density in ECs decreased at the angiogenic front of retinal vascular network during development and neovascularization compared with stable vessels. In vitro, VEGF (vascular endothelial growth factor) induced a VEGFR-2 (vascular endothelial growth factor receptor-2)-dependent exocytosis of WPBs that contain Ang-2 and consequently the secretion of vWF and Ang-2. Blocking VEGF-dependant WPB exocytosis and Ang-2 secretion promoted pericyte migration toward ECs. Pericyte migration was inhibited by adding recombinant Ang-2 or by silencing Ang-1 (angiopoietin-1) or Tie2 (angiopoietin-1 receptor) in pericytes. Consistently, in vivo anti-VEGF treatment induced accumulation of WPBs in retinal vessels because of the inhibition of WPB exocytosis and promoted the increase of pericyte coverage of retinal vessels during angiogenesis. In tumor angiogenesis, depletion of WPBs in vWF knockout tumor-bearing mice promoted an increase of tumor angiogenesis and a decrease of pericyte coverage of tumor vessels. By another approach, normalized tumor vessels had higher WPB density. Conclusions We demonstrate that WPB exocytosis and Ang-2 secretion are regulated during angiogenesis to limit pericyte coverage of remodeling vessels by disrupting Ang-1/Tie2 autocrine signaling in pericytes.

Effects of crotoxin, a neurotoxin from Crotalus durissus terrificus snake venom, on human endothelial cells

Vascular endothelium plays an important modulatory role due to the production of molecules that mediate vasomotricity, inflammation, and leukocyte adhesion and rolling. Here we addressed whether crotoxin (25-200 μg/mL) - the main component of Crotalus durissus terrificus snake venom - interferes with cell viability, apotosis/necrosis, and cell response to oxidative stress in human umbilical vein endothelial cells (HUVEC) in vitro. We also examined whether crotoxin alters the levels of interleukins, adhesion molecules, and endothelial vasoactive factors in HUVEC cells treated or not with lipopolysaccharide (LPS; 1 μg/mL; 24 h). Crotoxin was not cytotoxic towards HUVEC cells, and downregulated the LPS-induced production of adhesion molecules (VCAM-1, ICAM-1, and E-selectin), vasoactive factors (endothelin-1 and prostaglandin I2), and interleukins (IL-6, IL-8, and IL1β), as well as protected cells against H₂O₂-induced oxidative stress. Hence, crotoxin played anti-inflammatory, antioxidant, immunomodulating, and vasoactive actions on HUVEC cells, in vitro. Considering that the initial stages of atherosclerosis is characterized by vasoconstriction, increased levels of adhesion molecules, inflammatory cytokines, and oxidative stress in the vascular endothelium; and crotoxin downmodulated all these events, our findings indicate that the actions of crotoxin here demonstrated suggest that it may have an anti-atherogenic action in vivo, which deserves to be tested in future studies.

Impact of initial coagulation and fibrinolytic markers on mortality in patients with severe blunt trauma: a multicentre retrospective observational study

Background

Acute coagulopathy is a well-known predictor of poor outcomes in patients with severe trauma. However, using coagulation and fibrinolytic markers, how one can best predict mortality to find out potential candidates for treatment of coagulopathy remains unclear. This study aimed to determine preferential markers and their optimal cut-off values for mortality prediction.

Methods

We conducted a retrospective observational study of patients with severe blunt trauma (injury severity score ≥ 16) transferred directly from the scene to emergency departments at two trauma centres in Japan from January 2013 to December 2015. We investigated the impact and optimal cut-off values of initial coagulation (platelet counts, fibrinogen and prothrombin time-international normalised ratio) and a fibrinolytic marker (D-dimer) on 28-day mortality via classification and regression tree (CART) analysis. Multivariate logistic regression analysis confirmed the importance of these markers. Receiver operating characteristic curve analyses were used to examine the prediction accuracy for mortality.

Results

Totally 666 patients with severe blunt trauma were analysed. CART analysis revealed that the initial discriminator was fibrinogen (cut-off, 130 mg/dL) and the second discriminator was D-dimer (cut-off, 110 μg/mL in the lower fibrinogen subgroup; 118 μg/mL in the higher fibrinogen subgroup). The 28-day mortality was 90.0% (lower fibrinogen, higher D-dimer), 27.8% (lower fibrinogen, lower D-dimer), 27.7% (higher fibrinogen, higher D-dimer) and 3.4% (higher fibrinogen, lower D-dimer). Multivariate logistic regression demonstrated that fibrinogen levels < 130 mg/dL (adjusted odds ratio [aOR], 9.55; 95% confidence interval [CI], 4.50–22.60) and D-dimer ≥110 μg/mL (aOR, 5.89; 95% CI, 2.78–12.70) were independently associated with 28-day mortality after adjusting for probability of survival by the trauma and injury severity score (TRISS Ps). Compared with the TRISS Ps alone (0.900; 95% CI, 0.870–0.931), TRISS Ps with fibrinogen and D-dimer yielded a significantly higher area under the curve (0.942; 95% CI, 0.920–0.964; p < 0.001).

Conclusions

Fibrinogen and D-dimer were the principal markers for stratification of mortality in patients with severe blunt trauma. These markers could function as therapeutic targets because they were significant predictors of mortality, independent from severity of injury.

Synaptotagmin 5 regulates Ca2+-dependent Weibel-Palade body exocytosis in human endothelial cells

Elevations of intracellular free Ca²⁺ concentration ([Ca²⁺]_i) are a potent trigger for Weibel-Palade body (WPB) exocytosis and secretion of von Willebrand factor (VWF) from endothelial cells; however, the identity of WPB-associated Ca²⁺-sensors involved in transducing acute increases in [Ca²⁺]_i into granule exocytosis remains unknown. Here, we show that synaptotagmin 5 (SYT5) is expressed in human umbilical vein endothelial cells (HUVECs) and is recruited to WPBs to regulate Ca²⁺-driven WPB exocytosis. Western blot analysis of HUVECs identified SYT5 protein, and exogenously expressed SYT5-mEGFP localised almost exclusively to WPBs. shRNA-mediated knockdown of endogenous SYT5 (shSYT5) reduced the rate and extent of histamine-evoked WPB exocytosis and reduced secretion of the WPB cargo VWF-propeptide (VWFpp). The shSYT5-mediated reduction in histamine-evoked WPB exocytosis was prevented by expression of shRNA-resistant SYT5-mCherry. Overexpression of SYT5-EGFP increased the rate and extent of histamine-evoked WPB exocytosis, and increased secretion of VWFpp. Expression of a Ca²⁺-binding defective SYT5 mutant (SYT5-Asp197Ser-EGFP) mimicked depletion of endogenous SYT5. We identify SYT5 as a WPB-associated Ca²⁺ sensor regulating Ca²⁺-dependent secretion of stored mediators from vascular endothelial cells.

Serum angiopoietin-2 concentrations of post-PCI are correlated with the parameters of renal function in patients with coronary artery disease

Patients with coronary artery disease (CAD) frequently have comorbidity of chronic kidney disease (CKD). Their renal function may deteriorate because of the use of contrast agent after percutaneous coronary intervention (PCI). Angiopoietin-2 (Ang-2), which is highly expressed in the site of angiogenesis, plays an important role in both CAD and CKD. This study aimed to investigate the relation of serum Ang-2 concentrations with the renal function after PCI.This study enrolled 57 patients with CAD undergoing PCI. Blood samples for Ang-2 were collected in the first morning after admission and within 24 to 48 h after PCI. The parameters of renal function (serum creatinine, cystatin C and eGFR) were tested on the first day after admission and within 72 h after PCI.Overall, serum Ang-2 levels of post-PCI were significantly lower than those of pre-PCI [median, 1733 (IQR, 1100-2568) vs median, 2523 (IQR, 1702-3640) pg/mL; P < .001]. However, in patients with CKD (eGFR < 60 mL/min/1.73 m), there was no significant difference between serum Ang-2 levels of post-PCI and those of pre-PCI [median, 2851 (IQR, 1720-4286) vs. median, 2492 (IQR, 1434-4994) pg/mL; P = .925]. In addition, serum Ang-2 levels of post-PCI, but not pre-PCI, were significantly correlated with the post-PCI parameters of renal function.Serum Ang-2 concentrations of post-PCI are closely related to renal function in patients with CAD. It may have potential to be the early biomarker of contrast-induced nephropathy in the future.

Deficiency of complement factor H-related proteins and autoantibody-positive hemolytic uremic syndrome in an infant with combined partial deficiencies and autoantibodies to complement factor H and ADAMTS13

A 3-month-old male infant developed an extremely severe episode of atypical hemolytic uremic syndrome (aHUS) associated with partial deficiencies of full-length complement factor H (FH; ∼15% of infant normal) and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) (39% of normal) and autoantibodies reactive with both proteins. His FH and ADAMTS13 genes were normal, indicating that the partial deficiencies were acquired, probably as the result of autoantibodies against full-length FH and ADAMTS13. The child also had a homozygous deletion of the complement factor H–related (CFHR)3–CFHR1 portion in the complement factor H (CFH) gene cluster. He therefore had deficiency of CFHR proteins and autoantibody-positive hemolytic uremic syndrome (DEAP-HUS) with an unusual early onset associated with a partial deficiency of ADAMTS13 and an anti-ADAMTS13 autoantibody. His clinical episode of aHUS responded to plasma infusion and subsequent treatment with mycophenolate and rituximab. We believe that this is the first report of DEAP-HUS in an infant with partial deficiencies in both ADAMTS13 and full-length FH acquired in association with autoantibodies to both proteins.

Phenotypic and functional characterization of tumor-derived endothelial cells isolated from primary human hepatocellular carcinoma

AIMS

Tumor endothelial cells (TECs) have been investigated using human tumor xenografts in mice models. In order to provide pure human TECs for the updating of clinical anti-angiogenic cancer therapy, in the present study we established a protocol of purification of TECs derived from clinical hepatocellular carcinoma (HCC) and revealed the TEC features by in vitro and in vivo assays.

METHODS

We isolated TECs from fresh surgical resections of HCC by magnetic-activated cell sorting and purified by flow cytometry sorting upon CD31 expression, referred to as ECDHCCs. Next, we identified cultured ECDHCCs by morphology, phenotype, genotype, and functional assays.

RESULTS

The ECDHCCs appeared as Weibel-Palade bodies under electron microscopy. They expressed endothelial markers, such as CD31, CD105, and vascular endothelial growth factor receptor 2, and expressed the genes that are associated with pro-angiogenesis, especially vascular endothelial growth factor, epiregulin, and programmed cell death 10. Functionally, ECDHCCs were capable of tube formation, wound healing, and Transwell migration in vitro. These in vitro behaviors were validated by in vivo Matrigel plug assay in mice. Finally, comparison of ECDHCC with the Hep-G2 liver cancer cell line showed there was no similarity of phenotype or function between these two types of cells.

CONCLUSIONS

Tumor endothelial cells derived from human HCC can be isolated and purified from clinical samples by flow cytometer. They have the endothelial phenotype and morphologic features and are capable of tube formation and migration. This study provides a useful model for researchers to study tumor angiogenesis and screening of candidate targets.

Phosphodiesterase type 5 inhibitors improve microvascular dysfunction markers in pulmonary arterial hypertension associated with congenital heart disease

BACKGROUND

Ideally, vasodilator therapies for pulmonary arterial hypertension (PAH) should have a favorable impact on markers of vascular dysfunction, in addition to their known effects on hemodynamics, cardiac function, and patient's physical capacity.

METHODS

We analyzed circulating (plasma) markers of endothelial and platelet activation/dysfunction (enzyme-linked immunoassays) in the specific setting of advanced PAH associated with congenital heart disease, during the course of sildenafil and tadalafil therapies. Thirty-one patients were enrolled (age 10-54 years), most of them with chronic hypoxemia and elevated hematocrit. Drugs were administered orally for 6 months (sildenafil [n = 16], 20 mg t.i.d.; tadalafil [n = 15], single daily dose of 40 mg). Measurements were performed at baseline, and 90 and 180 days.

RESULTS

Compared to controls, patients had elevated baseline β-thromboglobulin (β-TG, P = .002), P-selectin (P = .027), tissue-type plasminogen activator (t-PA, P = .009), and von Willebrand factor antigen (VWF:Ag, P = .010). Thrombomodulin was importantly reduced (TM, P < .001), while soluble CD40 Ligand was not changed (P = .320). Tadalafil administration was associated with improvement of β-TG (P = .004), t-PA (P = .003) and TM (P = .046) levels, while P-selectin was improved by sildenafil treatment only (P = .034). VWF:Ag improved transiently in the sildenafil group (P = .019). Both therapies were associated with improvement of the physical capacity (functional class and distance walked during the 6-minute test, P < .05), hematocrit and hemoglobin level (P < .05), and health-related quality of life (physical and mental components, P < .05).

CONCLUSION

In PAH associated with congenital heart disease, phosphodiesterase 5 inhibitors seem to have beneficial actions at microcirculatory level, beyond the proposed effects as vasodilators.

Recent advances in cerebral cavernous malformation research

Cerebral cavernous malformations (CCM) are manifested by microvascular lesions characterized by leaky endothelial cells with minimal intervening parenchyma predominantly in the central nervous system predisposed to hemorrhagic stroke, resulting in focal neurological defects. Till date, three proteins are implicated in this condition: CCM1 (KRIT1), CCM2 (MGC4607), and CCM3 (PDCD10). These multi-domain proteins form a protein complex via CCM2 that function as a docking site for the CCM signaling complex, which modulates many signaling pathways. Defects in the formation of this signaling complex have been shown to affect a wide range of cellular processes including cell-cell contact stability, vascular angiogenesis, oxidative damage protection and multiple biogenic events. In this review we provide an update on recent advances in structure and function of these CCM proteins, especially focusing on the signaling cascades involved in CCM pathogenesis and the resultant CCM cellular phenotypes in the past decade.

Single-Cell Transcriptomics of a Human Kidney Allograft Biopsy Specimen Defines a Diverse Inflammatory Response

Background Single-cell genomics techniques are revolutionizing our ability to characterize complex tissues. By contrast, the techniques used to analyze renal biopsy specimens have changed little over several decades. We tested the hypothesis that single-cell RNA-sequencing can comprehensively describe cell types and states in a human kidney biopsy specimen.Methods We generated 8746 single-cell transcriptomes from a healthy adult kidney and a single kidney transplant biopsy core by single-cell RNA-sequencing. Unsupervised clustering analysis of the biopsy specimen was performed to identify 16 distinct cell types, including all of the major immune cell types and most native kidney cell types, in this biopsy specimen, for which the histologic read was mixed rejection.Results Monocytes formed two subclusters representing a nonclassical CD16+ group and a classic CD16- group expressing dendritic cell maturation markers. The presence of both monocyte cell subtypes was validated by staining of independent transplant biopsy specimens. Comparison of healthy kidney epithelial transcriptomes with biopsy specimen counterparts identified novel segment-specific proinflammatory responses in rejection. Endothelial cells formed three distinct subclusters: resting cells and two activated endothelial cell groups. One activated endothelial cell group expressed Fc receptor pathway activation and Ig internalization genes, consistent with the pathologic diagnosis of antibody-mediated rejection. We mapped previously defined genes that associate with rejection outcomes to single cell types and generated a searchable online gene expression database.Conclusions We present the first step toward incorporation of single-cell transcriptomics into kidney biopsy specimen interpretation, describe a heterogeneous immune response in mixed rejection, and provide a searchable resource for the scientific community.

Perioperative implication of the endothelial glycocalyx

The endothelial glycocalyx (EG) is a gel-like layer lining the luminal surface of healthy vascular endothelium. Recently, the EG has gained extensive interest as a crucial regulator of endothelial funtction, including vascular permeability, mechanotransduction, and the interaction between endothelial and circulating blood cells. The EG is degraded by various enzymes and reactive oxygen species upon pro-inflammatory stimulus. Ischemia-reperfusion injury, oxidative stress, hypervolemia, and systemic inflammatory response are responsible for perioperative EG degradation. Perioperative damage of the EG has also been demonstrated, especially in cardiac surgery. However, the protection of the EG and its association with perioperative morbidity needs to be elucidated in future studies. In this review, the present knowledge about EG and its perioperative implication is discussed from an anesthesiologist's perspective.