Regulation of functions of vascular wall cells by tissue factor pathway inhibitor: basic and clinical aspects

Experimental and clinical perspectives on glycocalyx integrity and its relation to acute respiratory distress syndrome

The development of microcirculation imaging devices has significantly advanced our comprehension of the capillary environment's dynamics. Early research suggested that erythrocytes did not contact the vessel's inner surface due to the Fåhraeus effect, implying the presence of a covering on the endothelial cell surface. Subsequent electron microscopy studies revealed this layer to be a complex part of the vessel wall, now known as the endothelial glycocalyx (EG). The EG is a network of proteoglycans and glycoproteins bound to the endothelial membrane, incorporating soluble molecules from the endothelium and plasma. Over time, studies have elucidated the structure, function, and therapeutic targets of the glycocalyx, underscoring its pivotal role in vascular biology. The presence of cellular extensions of lung tissue cells in both vascular and nonvascular areas demonstrates the pivotal role of the glycocalyx in pulmonary vascular leak, surfactant dysfunction, impaired lung compliance and gas exchange abnormalities, which are hallmarks of acute respiratory distress syndrome (ARDS). It is of the utmost importance to elucidate the mechanisms underlying alveolocapillary glycocalyx degradation to develop efficacious treatments for ARDS, which has a mortality rate of 35 %. An understanding of the glycocalyx's role in vascular integrity provides a foundation for exploring new therapeutic avenues to mitigate lung injury and improve clinical outcomes in ARDS patients.

The acute effect of exercise on the endothelial glycocalyx in healthy adults: A systematic review and meta-analysis

BACKGROUND

In recent years, it has been demonstrated that when the endothelial glycocalyx, composed of proteoglycans, glycosaminoglycans and glycoproteins, is altered or modified, this property is lost, playing a fundamental role in cardiovascular pathologies. Cardiovascular risk factors can destroy the endothelial glycocalyx layer. Exercise has a positive effect on cardiovascular risk factors, but little is known about its direct effect on the integrity of the endothelial layer.

METHODS

The Cochrane Library, PubMed, Web of Science and Scopus databases were searched from their inception to June 30, 2022. The DerSimonian and Laird method was used to compute pooled effect size estimates and their respective 95% confidence intervals for the acute effect of exercise (within 24 h) on the endothelial glycocalyx and its components in healthy adults.

RESULTS

Ten studies were included in the meta-analysis, with a total of 252 healthy subjects. The types of exercise included were resistance training, interval training, resistance training and maximal incremental exercise, with a duration range of 30-60 min. Glycocalyx assessment times included ranged from 0 to 90 min post-exercise. Our findings showed that endothelial glycocalyx increases after acute effect of exercise in healthy population (.56, 95% CI: .38, .74). The acute effect of exercise on endothelial glycocalyx components were .47 (95% CIs: .27, .67) for glycosaminoglycans, .67 (95% CIs: .08, 1.26) for proteoglycans and .61 (95% CIs: .35, .86) for glycoproteins.

CONCLUSIONS

In a healthy population, various types of exercise showed an acute improvement of the endothelial glycocalyx and its individual components.

The Brain Endothelial Cell Glycocalyx Plays a Crucial Role in the Development of Enlarged Perivascular Spaces in Obesity, Metabolic Syndrome, and Type 2 Diabetes Mellitus

The brain endothelial cell (BEC) glycocalyx (ecGCx) is a BEC surface coating consisting of a complex interwoven polysaccharide (sweet husk) mesh-like network of membrane-bound proteoglycans, glycoproteins, and glycosaminoglycans (GAGs) covering the apical luminal layer of the brain endothelial cells. The ecGCx may be considered as the first barrier of a tripartite blood-brain barrier (BBB) consisting of (1) ecGCx; (2) BECs; and (3) an extravascular compartment of pericytes, the extracellular matrix, and perivascular astrocytes. Perturbations of this barrier allow for increased permeability in the postcapillary venule that will be permissive to both fluids, solutes, and proinflammatory peripherally derived leukocytes into the perivascular spaces (PVS) which result in enlargement as well as increased neuroinflammation. The ecGCx is known to have multiple functions, which include its physical and charge barrier, mechanical transduction, regulation of vascular permeability, modulation of inflammatory response, and anticoagulation functions. This review discusses each of the listed functions in detail and utilizes multiple transmission electron micrographs and illustrations to allow for a better understanding of the ecGCx structural and functional roles as it relates to enlarged perivascular spaces (EPVS). This is the fifth review of a quintet series that discuss the importance of EPVS from the perspective of the cells of brain barriers. Attenuation and/or loss of the ecGCx results in brain barrier disruption with increased permeability to proinflammatory leukocytes, fluids, and solutes, which accumulate in the postcapillary venule perivascular spaces. This accumulation results in obstruction and results in EPVS with impaired waste removal of the recently recognized glymphatic system. Importantly, EPVS are increasingly being regarded as a marker of cerebrovascular and neurodegenerative pathology.

Endothelial Glycocalyx Injury in SARS-CoV-2 Infection: Molecular Mechanisms and Potential Targeted Therapy

This review aims at summarizing state-of-the-art knowledge on glycocalyx and SARS-CoV-2. The endothelial glycocalyx is a dynamic grid overlying the surface of the endothelial cell (EC) lumen and consists of membrane-bound proteoglycans and glycoproteins. The role of glycocalyx has been determined in the regulation of EC permeability, adhesion, and coagulation. SARS-CoV-2 is an enveloped, single-stranded RNA virus belonging to β-coronavirus that causes the outbreak and the pandemic of COVID-19. Through the respiratory tract, SARS-CoV-2 enters blood circulation and interacts with ECs possessing angiotensin-converting enzyme 2 (ACE2). Intact glycolyx prevents SARS-CoV-2 invasion of ECs. When the glycocalyx is incomplete, virus spike protein of SARS-CoV-2 binds with ACE2 and enters ECs for replication. In addition, cytokine storm targets glycocalyx, leading to subsequent coagulation disorder. Therefore, it is intriguing to develop a novel treatment for SARS-CoV-2 infection through the maintenance of the integrity of glycocalyx. This review aims to summarize state-of-the-art knowledge of glycocalyx and its potential function in SARS-CoV-2 infection.

rTFPI Protects Cardiomyocytes from Hypoxia/Reoxygenation Injury through Inhibiting Autophagy and the Class III PI3K/Beclin-1 Pathway

Autophagy plays various roles at different stages of ischemia reperfusion (I/R) injury in cardiomyocytes. It has been reported that tissue factor pathway inhibitor (TFPI) has a protective effect on I/R injury. This study aimed to determine the roles of TFPI in autophagy during the I/R injury process in cardiomyocytes and the possible mechanisms. An isolated hypoxia/reoxygenation (H/R) pattern of cardiomyocytes was established by the MIC101 system. The cell viability and oxidative stress of cardiomyocytes were detected by an MTT assay and ROS assay, respectively. The autophagy level was measured by Ad-mCherry-GFP-LC3B and MDC. We detected the expression levels of autophagy-related proteins by western blotting. After 2 h of hypoxia and 12 h of reoxygenation, the cardiomyocyte viability in the H/R group was significantly lower than that in the control group (p < 0.05) than in the H/R group. According to intracellular ROS production, the fluorescence intensity in the H/R group was enhanced compared with that in the negative control group, and it was weaker in the H/R + rTFPI group compared with the H/R group. The level of autophagy and the expression levels of autophagy-related proteins (LC3-II/LC3-I, Beclin-1 and PI3K) were markedly increased in the H/R group compared to the control group (p < 0.05) whereas the levels were markedly decreased in the H/R + rTFPI group compared to the H/R group (p < 0.05). TFPI could relieve cardiomyocyte injury by inhibiting the Class III PI3K/Beclin-1 pathway and oxidative stress; thus, TFPI decreased autophagy and protected cardiomyocytes induced by H/R injury. In conclusion, TFPI may be a new direction for the prevention of myocardial I/R injury.

Structural and functional properties of the Kunitz-type and C-terminal domains of Amblyomin-X supporting its antitumor activity

Amblyomin-X is a Kunitz-type FXa inhibitor identified through the transcriptome analysis of the salivary gland from Amblyomma sculptum tick. This protein consists of two domains of equivalent size, triggers apoptosis in different tumor cell lines, and promotes regression of tumor growth, and reduction of metastasis. To study the structural properties and functional roles of the N-terminal (N-ter) and C-terminal (C-ter) domains of Amblyomin-X, we synthesized them by solid-phase peptide synthesis, solved the X-Ray crystallographic structure of the N-ter domain, confirming its Kunitz-type signature, and studied their biological properties. We show here that the C-ter domain is responsible for the uptake of Amblyomin-X by tumor cells and highlight the ability of this domain to deliver intracellular cargo by the strong enhancement of the intracellular detection of molecules with low cellular-uptake efficiency (p15) after their coupling with the C-ter domain. In contrast, the N-ter Kunitz domain of Amblyomin-X is not capable of crossing through the cell membrane but is associated with tumor cell cytotoxicity when it is microinjected into the cells or fused to TAT cell-penetrating peptide. Additionally, we identify the minimum length C-terminal domain named F2C able to enter in the SK-MEL-28 cells and induces dynein chains gene expression modulation, a molecular motor that plays a role in the uptake and intracellular trafficking of Amblyomin-X.

The effects of female sexual hormones on the endothelial glycocalyx

The glycocalyx is a layer composed of carbohydrate side chains bound to core proteins that lines the vascular endothelium. The integrity of the glycocalyx is essential for endothelial cells' performance and vascular homeostasis. The neuroendocrine and immune systems influence the composition, maintenance, activity and degradation of the endothelial glycocalyx. The female organism has unique characteristics, and estrogen and progesterone, the main female hormones are essential to the development and physiology of the reproductive system and to the ability to develop a fetus. Female sex hormones also exert a wide variety of effects on other organs, including the vascular endothelium. They upregulate nitric oxide synthase expression and activity, decrease oxidative stress, increase vasodilation, and protect from vascular injury. This review will discuss how female hormones and pregnancy, which prompts to high levels of estrogen and progesterone, modulate the endothelial glycocalyx. Diseases prevalent in women that alter the glycocalyx, and therapeutic forms to prevent glycocalyx degradation and potential treatments that can reconstitute its structure and function will also be discussed.

Endothelial Cells and the Cerebral Circulation

Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.

Endothelial Cell Phenotype, a Major Determinant of Venous Thrombo-Inflammation

Reduced blood flow velocity in the vein triggers inflammation and is associated with the release into the extracellular space of alarmins or damage-associated molecular patterns (DAMPs). These molecules include extracellular nucleic acids, extracellular purinergic nucleotides (ATP, ADP), cytokines and extracellular HMGB1. They are recognized as a danger signal by immune cells, platelets and endothelial cells. Hence, endothelial cells are capable of sensing environmental cues through a wide variety of receptors expressed at the plasma membrane. The endothelium is then responding by expressing pro-coagulant proteins, including tissue factor, and inflammatory molecules such as cytokines and chemokines involved in the recruitment and activation of platelets and leukocytes. This ultimately leads to thrombosis, which is an active pro-inflammatory process, tightly regulated, that needs to be properly resolved to avoid further vascular damages. These mechanisms are often dysregulated, which promote fibrinolysis defects, activation of the immune system and irreversible vascular damages further contributing to thrombotic and inflammatory processes. The concept of thrombo-inflammation is now widely used to describe the complex interactions between the coagulation and inflammation in various cardiovascular diseases. In endothelial cells, activating signals converge to multiple intracellular pathways leading to phenotypical changes turning them into inflammatory-like cells. Accumulating evidence suggest that endothelial to mesenchymal transition (EndMT) may be a major mechanism of endothelial dysfunction induced during inflammation and thrombosis. EndMT is a biological process where endothelial cells lose their endothelial characteristics and acquire mesenchymal markers and functions. Endothelial dysfunction might play a central role in orchestrating and amplifying thrombo-inflammation thought induction of EndMT processes. Mechanisms regulating endothelial dysfunction have been only partially uncovered in the context of thrombotic diseases. In the present review, we focus on the importance of the endothelial phenotype and discuss how endothelial plasticity may regulate the interplay between thrombosis and inflammation. We discuss how the endothelial cells are sensing and responding to environmental cues and contribute to thrombo-inflammation with a particular focus on venous thromboembolism (VTE). A better understanding of the precise mechanisms involved and the specific role of endothelial cells is needed to characterize VTE incidence and address the risk of recurrent VTE and its sequelae.

A Cancer Associated Fibroblasts-Related Six-Gene Panel for Anti-PD-1 Therapy in Melanoma Driven by Weighted Correlation Network Analysis and Supervised Machine Learning

Background

Melanoma is a highly aggressive skin cancer with a poor prognosis and mortality. Immune checkpoint blockade (ICB) therapy (e.g., anti-PD-1 therapy) has opened a new horizon in melanoma treatment, but some patients present a non-responsive state. Cancer-associated fibroblasts (CAFs) make up the majority of stromal cells in the tumor microenvironment (TME) and have an important impact on the response to immunotherapy. There is still a lack of identification of CAFs-related predictors for anti-PD-1 therapy, although the establishment of immunotherapy biomarkers is well underway. This study aims to explore the potential CAFs-related gene panel for predicting the response to anti-PD-1 therapy in melanoma patients and elucidating their potential effect on TME.

Methods

Three gene expression datasets from melanoma patients without anti-PD-1 treatment, in a total of 87 samples, were downloaded from Gene Expression Omnibus (GEO) as the discovery sets (GSE91061) and validation sets (GSE78220 and GSE122220). The CAFs-related module genes were identified from the discovery sets by weighted gene co-expression network analysis (WGCNA). Concurrently, we utilized differential gene analysis on the discovery set to obtain differentially expressed genes (DEGs). Then, CAFs-related key genes were screened with the intersection of CAFs-related module genes and DEGs, succeeded by supervised machine learning-based identification. As a consequence of expression analysis, gene set enrichment analysis, survival analysis, staging analysis, TME analysis, and correlation analysis, the multidimensional systematic characterizations of the key genes were uncovered. The diagnostic performance of the CAFs-related gene panel was assessed by receiver operating characteristic (ROC) curves in the validation sets. Eventually, the CAFs-related gene panel was verified by the expression from the single-cell analysis.

Results

The six-gene panel associated with CAFs were finally identified for predicting the response to anti-PD-1 therapy, including CDK14, SYNPO2, TCF4, GJA1, CPXM1, and TFPI. The multigene panel demonstrated excellent combined diagnostic performance with the area under the curve of ROC reaching 90.5 and 75.4% ~100% in the discovery and validation sets, respectively.

Conclusion

Confirmed by clinical treatment outcomes, the identified CAFs-related genes can be used as a promising biomarker panel for prediction to anti-PD-1 therapy response, which may serve as new immunotherapeutic targets to improve survival outcomes of melanoma patients.

The Impact of Anticoagulant Activity of Tissue Factor Pathway Inhibitor Measured by a Novel Functional Assay for Predicting Deep Venous Thrombosis in Trauma Patients: A Prospective Nested Case-Control Study

Deep venous thrombosis (DVT) is a common complication in patients with traumatic injury. Tissue factor pathway inhibitor (TFPI) is a natural anticoagulant protein in the extrinsic coagulation pathway. However, the relationship between DVT after trauma and the anticoagulant activity of TFPI remains unclear. In this prospective study, we investigated the role of TFPI in trauma patients with DVT to evaluate whether the anticoagulant activity of TFPI measured by a new functional assay can be used to help predict the risk of DVT. Patients and methods: This prospective nested case-control study enrolled trauma patients and healthy volunteers. Forty-eight trauma patients diagnosed with DVT and forty-eight matched trauma patients without DVT were included in the study. 120 healthy volunteers were also included as controls. Blood samples and case information were collected at admission. Patients accepted angiography before surgery to diagnose DVT. The parameters examined included TFPI anticoagulant activity, free-TFPI antigen, blood cell counts, and routine clinical coagulation tests. Results: For the parameters of TFPI anticoagulant activity, three were markedly increased in the DVT group compared to the non-DVT group (TFPI initial anticoagulant time ratio, P  =  .022; TFPI whole anticoagulant time ratio, P  =  .048; and TFPI anticoagulant rate, P  =  .034). The free-TFPI antigen concentration also showed a significant increasing trend in trauma patients with DVT compared with trauma patients without DVT (P  =  .035). Multivariate logistic regression analysis identified four independent factors for the development of DVT (TFPI initial anticoagulant time ratio, free-TFPI antigen, prothrombin time, and red blood cell count). We calculated the TFPI correlation coefficient and found that the area under the receiver operating characteristic curve was .821. Conclusions: A novel functional assay was developed to measure the anticoagulant activity of TFPI. The anticoagulant activity of TFPI can be used as a potential biomarker for diagnosing DVT in trauma patients.

Effect of heparanase inhibitor on tissue factor overexpression in platelets and endothelial cells induced by anti-β2-GPI antibodies

BACKGROUND

Anti-phospholipid syndrome (APS) is characterized by arterial and/or venous thrombosis and pregnancy morbidity associated with the presence of "anti-phospholipid antibodies." Thrombosis may be the result of a hypercoagulable state related to activation of endothelial cells and platelets by anti-β2-glycoprotein I (β2-GPI) antibodies. Anti-β2-GPI antibodies induce a proinflammatory and procoagulant phenotype in these cells that, after activation, express tissue factor (TF), the major initiator of the clotting cascade, playing a role in thrombotic manifestations. Moreover, TF expression may also be induced by heparanase, an endo-β-D-glucuronidase, that generates heparan sulfate fragments, regulating inflammatory responses.

OBJECTIVES

In this study we analyzed, in human platelets and endothelial cells, the effect of a new symmetrical 2-aminophenyl-benzazolyl-5-acetate derivative (RDS3337), able to inhibit heparanase activity, on signal transduction pathways leading to TF expression triggered by anti-β2-GPI.

METHODS

Platelets and endothelial cells were incubated with affinity purified anti-β2-GPI after pretreatment with RDS3337. Cell lysates were analyzed for phospho-interleukin-1 receptor-associated kinase 1 (IRAK1), phospho-p65 nuclear factor kappa B (NF-κB) and TF by western blot. In addition, platelet activation and secretion by ATP release dosage were evaluated.

RESULTS

IRAK phosphorylation and consequent NF-κB activation, as well as TF expression triggered by anti-β2-GPI treatment were significantly prevented by previous pretreatment with RDS3337. In the same vein, pretreatment with RDS3337 prevented platelet aggregation and ATP release triggered by anti-β2-GPI antibodies.

CONCLUSION

These findings support the view of heparanase involvement in a prothrombotic state related to APS syndrome, suggesting a novel target to regulate overexpression of procoagulant protein(s).

New insight into biology, molecular diagnostics and treatment options of unstable carotid atherosclerotic plaque: a narrative review

Indications for intervention in hemodynamically relevant carotid artery stenosis (carotid endarterectomy or stenting) are primarily based on a degree of stenosis and symptomatology. To date the plaque vulnerability is rarely taken into account in clinical decision making although development of molecular imaging allows a better understanding of plaque biology and provides new techniques detecting potentially vulnerable plaque at risk. A significant number of reports describing the mechanisms of unstable plaque formation suggest that it is a multifactorial process. Inflammation, lipid accumulation, apoptosis, proteolysis, the thrombotic process and angiogenesis are among the main factors of carotid plaque destabilization. Although inflammation is a key process in development of plaque vulnerability, the hemostasis and neoangiogenesis should be regarded as equally important. Only a small group of asymptomatic patients may benefit from the invasive treatment and it remains a challenge to determine whether initially asymptomatic carotid plaque become unstable or vulnerable. Currently, the main task of research on atherosclerotic lesion imaging is focused on functional state of the plaque. The presence of one or more features such as stenosis progression, large plaque area, large juxta-luminal black area, plaque echolucency, intra-plaque hemorrhage, impaired cerebral vascular reserve and spontaneous embolization may indicate patients at higher risk for stroke suitable for revascularization. Treatment of carotid stenosis as one of the manifestations of generalized atherosclerosis requires a broad approach. Nowadays pharmacological treatment options for the atherosclerotic process are largely aimed at stimulating the plaque stabilization, but in symptomatic patients and selected asymptomatic patients, carotid plaque should be removed as a potential source of embolism.

Heparin prevents in vitro glycocalyx shedding induced by plasma from COVID-19 patients

The severe forms and worsened outcomes of COVID-19 (coronavirus disease 19) are closely associated with hypertension and cardiovascular disease. Endothelial cells express Angiotensin-Converting Enzyme 2 (ACE2), which is the entrance door for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The hallmarks of severe illness caused by SARS-CoV-2 infection are increased levels of IL-6, C-reactive protein, D-dimer, ferritin, neutrophilia and lymphopenia, pulmonary intravascular coagulopathy and microthrombi of alveolar capillaries. The endothelial glycocalyx, a proteoglycan- and glycoprotein-rich layer covering the luminal side of endothelial cells, contributes to vascular homeostasis. It regulates vascular tonus and permeability, prevents thrombosis, and modulates leukocyte adhesion and inflammatory response. We hypothesized that cytokine production and reactive oxygen species (ROS) generation associated with COVID-19 leads to glycocalyx degradation. A cohort of 20 hospitalized patients with a confirmed COVID-19 diagnosis and healthy subjects were enrolled in this study. Mechanisms associated with glycocalyx degradation in COVID-19 were investigated. Increased plasma concentrations of IL-6 and IL1-β, as well as increased lipid peroxidation and glycocalyx components were detected in plasma from COVID-19 patients compared to plasma from healthy subjects. Plasma from COVID-19 patients induced glycocalyx shedding in cultured human umbilical vein endothelial cells (HUVECs) and disrupted redox balance. Treatment of HUVECs with low molecular weight heparin inhibited the glycocalyx perturbation. In conclusion, plasma from COVID-19 patients promotes glycocalyx shedding and redox imbalance in endothelial cells, and heparin treatment potentially inhibits glycocalyx disruption.

Vascular Endothelial Damage in the Pathogenesis of Organ Injury in Severe COVID-19

[Figure: see text].

Polarized Proteins in Endothelium and Their Contribution to Function

Protein localization in endothelial cells is tightly regulated to create distinct signaling domains within their tight spatial restrictions including luminal membranes, abluminal membranes, and interendothelial junctions, as well as caveolae and calcium signaling domains. Protein localization in endothelial cells is also determined in part by the vascular bed, with differences between arteries and veins and between large and small arteries. Specific protein polarity and localization is essential for endothelial cells in responding to various extracellular stimuli. In this review, we examine protein localization in the endothelium of resistance arteries, with occasional references to other vessels for contrast, and how that polarization contributes to endothelial function and ultimately whole organism physiology. We highlight the protein localization on the luminal surface, discussing important physiological receptors and the glycocalyx. The protein polarization to the abluminal membrane is especially unique in small resistance arteries with the presence of the myoendothelial junction, a signaling microdomain that regulates vasodilation, feedback to smooth muscle cells, and ultimately total peripheral resistance. We also discuss the interendothelial junction, where tight junctions, adherens junctions, and gap junctions all convene and regulate endothelial function. Finally, we address planar cell polarity, or axial polarity, and how this is regulated by mechanosensory signals like blood flow.

The glycocalyx: a central regulator of vascular function

The endothelial glycocalyx is a specialized extracellular matrix that covers the apical side of vascular endothelial cells, projecting into the lumen of blood vessels. The composition of the glycocalyx has been studied in great detail, and it is known to be composed of a mixture of proteoglycans, glycosaminoglycans, and glycoproteins. Although this structure was once believed to be a passive physical barrier, it is now recognized as a multifunctional and dynamic structure that participates in many vascular processes, including but not limited to vascular permeability, inflammation, thrombosis, mechanotransduction, and cytokine signaling. Because of its participation in many physiological and pathophysiological states, comprehensive knowledge of the glycocalyx will aid future vascular biologists in their research. With that in mind, this review discusses the biochemical structure of the glycocalyx and its function in many vascular physiological processes. We also briefly review a more recent discovery in glycocalyx biology, the placental glycocalyx.

The Role of Glycocalyx and Caveolae in Vascular Homeostasis and Diseases

This review highlights recent findings about the role that endothelial glycocalyx and caveolae play in vascular homeostasis. We describe the structure, synthesis, and function of glycocalyx and caveolae in vascular cells under physiological and pathophysiological conditions. Special focus will be given in glycocalyx and caveolae that are associated with impaired production of nitric oxide (NO) and generation of reactive oxygen species (ROS). Such alterations could contribute to the development of cardiovascular diseases, such as atherosclerosis, and hypertension.

Endothelial glycocalyx as an important factor in composition of blood-brain barrier

The blood‐brain barrier is a dynamic and complex neurovascular unit that protects neurons from somatic circulatory factors as well as regulates the internal environmental stability of the central nervous system. Endothelial glycocalyx is a critical component of an extended neurovascular unit that influences the structure of the blood‐brain barrier and plays various physiological functions, including an important role in maintaining normal neuronal homeostasis. Specifically, glycocalyx acts in physical and charge barriers, mechanical transduction, regulation of vascular permeability, modulation of inflammatory response, and anticoagulation. Since intact glycocalyx is necessary to maintain the stability and integrity of the internal environment of the blood‐brain barrier, damage to glycocalyx can lead to the dysfunction of the blood‐brain barrier. This review discusses the role of glycocalyx in the context of the substantial literature regarding the blood‐brain barrier research, in order to provide a theoretical basis for the diagnosis and treatment of neurological diseases as well as point to new breakthroughs and innovations in glycocalyx‐dependent blood‐brain barrier function.

The Endothelial Glycocalyx as a Key Mediator of Albumin Handling and the Development of Diabetic Nephropathy

The endothelial glycocalyx is a complex mesh of proteoglycans, glycoproteins and other soluble components, which cover the vascular endothelium. It plays an important role in many physiological processes including vascular permeability, transduction of shear stress and interaction of blood cells and other molecules with the vascular wall. Its complex structure makes its precise assessment challenging, and many different visualization techniques have been used with varying results. Diabetes, one of the main disease models where disorders of the glycocalyx are present, causes degradation of the glycocalyx through a variety of molecular pathways and especially through oxidative stress due to the action of reactive oxygen species. As the glycocalyx has been primarily studied in the glomerular endothelium, more evidence points towards a vital role in albumin handling and, consequently, in diabetic nephropathy. Therefore, the maintenance or restoration of the integrity of the glycocalyx seems a promising therapeutic target. In this review, we consider the structural and functional capacities of the endothelial glycocalyx, the available methods for its evaluation, the mechanisms through which diabetes leads to glycocalyx degradation and albuminuria, and possible treatment options targeting the glycocalyx.

Vascular endothelial injury exacerbates coronavirus disease 2019: The role of endothelial glycocalyx protection

The potential for a rapid increase in severity is among the most frightening aspects of severe acute respiratory syndrome coronavirus 2 infection. Evidence increasingly suggests that the symptoms of coronavirus disease‐2019 (COVID‐19)‐related acute respiratory distress syndrome (ARDS) differ from those of classic ARDS. Recently, the severity of COVID‐19 has been attributed to a systemic, thrombotic, and inflammatory disease that damages not only the lungs but also multiple organs, including the heart, brain, toes, and liver. This systemic form of COVID‐19 may be due to inflammation and vascular endothelial cell injury. The vascular endothelial glycocalyx comprises glycoproteins and plays an important role in systemic capillary homeostasis maintenance. The glycocalyx covers the entire vascular endothelium, and its thickness varies among organs. The endothelial glycocalyx is very thin in the pulmonary capillaries, where it is affected by gaseous exchange with the alveoli and the low intravascular pressure in the pulmonary circulation. Despite the clearly important roles of the glycocalyx in vascular endothelial injury, thrombosis, vasculitis, and inflammation, the link between this structure and vascular endothelial cell dysfunction in COVID‐19 remains unclear. In this prospective review, we summarize the importance of the glycocalyx and its potential as a therapeutic target in cases of systemic COVID‐19.

Procoagulant activity in children and adolescents on intensive insulin therapy

BACKGROUND

Type 1 diabetes is associated with atherothrombosis, but limited data exist on procoagulant activity in the young. We investigated procoagulant activity in children/adolescents with type 1 diabetes using intensified insulin treatment compared with controls in a 5-year follow-up study, and further any associations with cardiovascular risk factors.

METHODS

The study included 314 diabetes children/adolescents and 120 healthy controls. Prothrombin fragment 1+2 (F1+2), D-dimer, tissue-factor-procoagulant-activity (TF-PCA), and tissue-factor-pathway-inhibitor (TFPI) were analyzed with ELISAs.

RESULTS

F1+2, D-dimer, and TF-PCA did not differ between the groups or correlate to HbA_1c in the diabetes group at either time points. TFPI was significantly higher in the diabetes group compared with controls both at inclusion and follow-up (both P < .001). In the diabetes group, TFPI correlated significantly to HbA_1c at both time points (r = 0.221 and 0.304, both P < .001). At follow-up, females using oral contraceptives had significantly elevated F1+2, D-dimer, and TF-PCA and lower TFPI compared to no-users (all P < .005), and females had lower TFPI (P = .017) and higher F1+2 compared with males (P = .052), also after adjusting for the use of oral contraceptives.

CONCLUSIONS

The current results show similar procoagulant activity in children/adolescents with type 1 diabetes compared with controls over a 5-year period, indicating that these children using modern intensified insulin treatment are not at high thrombotic risk at younger age. The elevated levels of TFPI in the diabetes group, related to hyperglycaemia, are probably reflecting increased endothelial activation. These findings highlight the significance of optimal blood glucose control in children/adolescents with type 1 diabetes, to maintain a healthy endothelium.

Implications of Hemostasis Disorders in Patients with Critical Limb Ischemia-An In-Depth Comparison of Selected Factors

BACKGROUND

Atherosclerosis is a systemic disease. Among patients with atherosclerosis, those suffering from peripheral arterial disease (PAD) represent a group of individuals with particularly high death risk, especially during the course of critical limb ischemia (CLI). In the pathogenesis of PAD/CLI complications, blood coagulation disorders play a significant role. The study aim was to examine the activation of the coagulation system depending on tissue factor (TF) in patients with CLI as compared with those with intermittent claudication (IC).

METHODS

Before initiating proper treatment (invasive or maintenance), blood samples were collected from 65 patients with CLI and 15 with IC to measure the following selected hemostasis parameters: concentrations and activation of tissue factor (TF Ag and TF Act) and tissue factor pathway inhibitor (TFPI Ag and TFPI Act), concentrations of thrombin-antithrombin complex (TAT Ag) and fibrinogen, platelet count (PLT), and concentrations of tissue-plasminogen activator (t-PA Ag), plasminogen activator inhibitor 1 (PAI-1), and D-dimer. The control group included 30 healthy volunteers (10 female/20 male).

RESULTS

The values of all analyzed parameters (except for lower TFPI Act) were significantly higher in the blood of PAD patients (with respect to PLT only in the CLI subgroup) in comparison with healthy subjects. The blood of patients with CLI as compared to the IC subgroup revealed much higher concentrations of TF Ag (p < 0.001), with slightly decreased TF Act, significantly lower concentrations of TFPI Ag (p < 0.001), slightly increased TFPI Act, and significantly higher levels of TAT Ag (p < 0.001), fibrinogen (p = 0.026), and D-dimer (p < 0.05).

CONCLUSIONS

In patients with CLI, we can observe coagulation activation and a shifting balance toward prothrombotic processes. Furthermore, increased concentrations of D-dimer suggest a secondary activation of fibrinolysis and confirm the phenomenon as a prothrombotic condition with heightened fibrinolysis.

Lipoprotein(a) – Link between Atherogenesis and Thrombosis

Lipoprotein(a) – Lp(a) – is an independent risk factor for cardiovascular disease (CVD). Indeed, individuals with plasma concentrations of Lp(a) > 200 mg/l carry an increased risk of developing CVD. Circulating levels of Lp(a) are remarkably resistant to common lipid lowering therapies, currently available treatment for reduction of Lp(a) is plasma apheresis, which is costly and labour intensive. The Lp(a) molecule is composed of two parts: LDL/apoB-100 core and glycoprotein, apolipoprotein(a) – Apo(a), both of them can interact with components of the coagulation cascade, inflammatory pathways and blood vessel cells (smooth muscle cells and endothelial cells). Therefore, it is very important to determine the molecular pathways by which Lp(a) affect the vascular system in order to design therapeutics for targeting the Lp(a) cellular effects. This paper summarises the cellular effects and molecular mechanisms by which Lp(a) participate in atherogenesis, thrombogenesis, inflammation and development of cardiovascular diseases.

Vascular Endothelial Cell Biology: An Update

The vascular endothelium, a monolayer of endothelial cells (EC), constitutes the inner cellular lining of arteries, veins and capillaries and therefore is in direct contact with the components and cells of blood. The endothelium is not only a mere barrier between blood and tissues but also an endocrine organ. It actively controls the degree of vascular relaxation and constriction, and the extravasation of solutes, fluid, macromolecules and hormones, as well as that of platelets and blood cells. Through control of vascular tone, EC regulate the regional blood flow. They also direct inflammatory cells to foreign materials, areas in need of repair or defense against infections. In addition, EC are important in controlling blood fluidity, platelet adhesion and aggregation, leukocyte activation, adhesion, and transmigration. They also tightly keep the balance between coagulation and fibrinolysis and play a major role in the regulation of immune responses, inflammation and angiogenesis. To fulfill these different tasks, EC are heterogeneous and perform distinctly in the various organs and along the vascular tree. Important morphological, physiological and phenotypic differences between EC in the different parts of the arterial tree as well as between arteries and veins optimally support their specified functions in these vascular areas. This review updates the current knowledge about the morphology and function of endothelial cells, particularly their differences in different localizations around the body paying attention specifically to their different responses to physical, biochemical and environmental stimuli considering the different origins of the EC.

Leukocyte-endothelial cell interaction is enhanced in podocalyxin-deficient mice

The highly sialoglycosylated extracellular domain of podocalyxin (Podxl) is a constituent of the endothelial glycocalyx of most blood vessels but it is unknown if Podxl plays a prominent role in the function of the glycocalyx as a regulator of leukocyte-endothelial adhesion. We have recently found that mice lacking Podxl in the vascular endothelium develop histological lesions compatible with severe vasculitis resulting in organ failure and premature death. In this work, we show that these mice have an increased quantity of resident leukocytes within the peritoneal cavity in both basal and inflammatory conditions. Adhesion of macrophagic cells to lung endothelial cells from Podxl-deficient mice was increased under inflammatory stimuli. Both, chemokine binding and chemokine-mediated adhesion of immune cells were significantly higher in Podxl-deficient endothelial cells. Moreover, glycocalyx function assessed by measuring the anticoagulant capacity of endothelial cell monolayers to inactivate thrombin was significantly altered in the absence of Podxl. Overall, the results suggest that Podxl is an essential component of the glycocalyx and has an important so far unknown role in preventing leukocyte-endothelial cell adhesion under resting and inflammatory conditions.

Translational Pharmacokinetic/Pharmacodynamic Characterization and Target-Mediated Drug Disposition Modeling of an Anti-Tissue Factor Pathway Inhibitor Antibody, PF-06741086

Tissue factor pathway inhibitor (TFPI) exhibits multiple isoforms, which are known to present in multiple locations such as plasma, endothelium, and platelets. TFPI is an endogenous negative modulator of the coagulation pathway, and therefore, neutralization of TFPI function can potentially increase coagulation activity. A human monoclonal antibody, PF-06741086, which interacts with all isoforms of TFPI is currently being tested in clinic for treating hemophilia patients with and without inhibitors. To support clinical development of PF-06741086, pharmacokinetics (PK) and pharmacodynamics of PF-06741086 were characterized in monkeys. In addition, a mechanistic model approach was used to estimate PK parameters in monkeys and simulate PK profiles in human. The results show that PF-06741086 exhibited target-mediated drug disposition and had specific effects on various hemostatic markers including diluted prothrombin time, thrombin generation, and thrombin-antithrombin complex in monkeys after administration. The model-predicted and observed human exposures were compared retrospectively, and the result indicates that the exposure prediction was reasonable within less than 2-fold deviation. This study demonstrated in vivo efficacy of PF-06741086 in monkeys and the utility of a rational mechanistic approach to describe PK for a monoclonal antibody with complex target binding.

Venous thromboembolic events in lymphoma patients: Actual relationships between epidemiology, mechanisms, clinical profile and treatment

Venous thromboembolic events (VTE) are an underestimated health problem in patients with lymphoma. Many factors contribute to the pathogenesis of thromboembolism and the interplay between various mechanisms that provoke VTE is still poorly understood. The identification of parameters that are associated with an increased risk of VTE in lymphoma patients led to the creation of several risk-assessment models. The models that evaluate potential VTE risk in lymphoma patients in particular are quite limited, and have to be validated in larger study populations. Furthermore, the VTE prophylaxis in lymphoma patients is largely underused, despite the incidence of VTE. The lack of adequate guidelines for the prophylaxis and treatment of VTE in lymphoma patients, together with a cautious approach due to an increased risk of bleeding, demands great efforts to ensure the implementation of current knowledge in order to reduce the incidence and complications of VTE in lymphoma patients.

Procoagulant activity in patients with combined type 2 diabetes and coronary artery disease: No effects of long-term exercise training

We investigated the effects of 12-month exercise training on hypercoagulability in patients with combined type 2 diabetes mellitus and coronary artery disease. Associations with severity of disease were further explored. Patients ( n = 131) were randomized to exercise training or a control group. Blood was collected at inclusion and after 12 months. Tissue factor, free and total tissue factor pathway inhibitor, prothrombin fragment 1 + 2 (F1 + 2) and D-dimer were determined by enzyme-linked immunosorbent assay and ex vivo thrombin generation by the calibrated automated thrombogram assay. Tissue factor and ex vivo thrombin generation increased from baseline to 12 months ( p < 0.01, all), with no significant differences in changes between groups. At baseline, free and total tissue factor pathway inhibitor significantly correlated to fasting glucose ( p < 0.01, both) and HbA1c ( p < 0.05, both). In patients with albuminuria ( n = 34), these correlations were strengthened, and elevated levels of D-dimer, free and total tissue factor pathway inhibitor ( p < 0.01, all) and decreased ex vivo thrombin generation ( p < 0.05, all) were observed. These results show no effects of exercise training on markers of hypercoagulability in our population with combined type 2 diabetes mellitus and coronary artery disease. The association between poor glycaemic control and tissue factor pathway inhibitor might indicate increased endothelial activation. More pronounced hypercoagulability and increased tissue factor pathway inhibitor were demonstrated in patients with albuminuria.

Heparanase procoagulant activity in cancer progression

Heparanase is an endo-β-D-glucuronidase that is capable of cleaving heparan sulfate side chains of heparan sulfate proteoglycans on cell surfaces and the extracellular matrix. This activity is strongly implicated in tumor metastasis and angiogenesis. We have earlier demonstrated that apart of its well characterized enzymatic activity, heparanase may also affect the hemostatic system in a non-enzymatic manner. We showed that heparanase up-regulated the expression of the blood coagulation initiator-tissue factor (TF) and interacted with the tissue factor pathway inhibitor (TFPI) on the cell surface membrane of endothelial and tumor cells, leading to dissociation of TFPI and resulting in increased cell surface coagulation activity. Moreover, we demonstrated that heparanase directly enhanced TF activity, which led to increased factor Xa production and subsequent activation of the coagulation system. In patients with cancer, increased heparanase procoagulant activity appeared to be a potential predictor of survival. We have also shown that JAK-2 is involved in heparanase up-regulation via the erythropoietin receptor, a finding that may point to a new mechanism of thrombosis in JAK-2 positive patents with essential thrombocytosis. Recently, we found that the solvent accessible surface of TFPI-2 first Kunitz domain had a role in TF/heparanase complex inhibition. Peptides derived from TFPI-2 inhibitory site were shown to reduce coagulation activation induced by heparanase and to attenuate sepsis severity and tumor growth in a mouse model, without predisposing to significant bleeding tendency. These data imply that inhibition of heparanase procoagulant domain is potentially a good target for sepsis and cancer therapy.

New Functional Tools for Antithrombogenic Activity Assessment of Live Surface Glycocalyx

OBJECTIVE

It is widely accepted that the presence of a glycosaminoglycan-rich glycocalyx is essential for endothelialized vasculature health; in fact, a damaged or impaired glycocalyx has been demonstrated in many vascular diseases. Currently, there are no methods that characterize glycocalyx functionality, thus limiting investigators' ability to assess the role of the glycocalyx in vascular health.

APPROACH AND RESULTS

We have developed novel, easy-to-use, in vitro assays that directly quantify live endothelialized surface's functional heparin weights and their anticoagulant capacity to inactivate Factor Xa and thrombin. Using our assays, we characterized 2 commonly used vascular models: native rat aorta and cultured human umbilical vein endothelial cell monolayer. We determined heparin contents to be ≈10 000 ng/cm(2) on the native aorta and ≈10-fold lower on cultured human umbilical vein endothelial cells. Interestingly, human umbilical vein endothelial cells demonstrated a 5-fold lower anticoagulation capacity in inactivating both Factor Xa and thrombin relative to native aortas. We verified the validity and accuracy of the novel assays developed in this work using liquid chromatography-mass spectrometry analysis.

CONCLUSIONS

Our assays are of high relevance in the vascular community because they can be used to establish the antithrombogenic capacity of many different types of surfaces such as vascular grafts and transplants. This work will also advance the capacity for glycocalyx-targeting therapeutics development to treat damaged vasculatures.

The emerging role of coagulation proteases in kidney disease

A role of coagulation proteases in kidney disease beyond their function in normal haemostasis and thrombosis has long been suspected, and studies performed in the past 15 years have provided novel insights into the mechanisms involved. The expression of protease-activated receptors (PARs) in renal cells provides a molecular link between coagulation proteases and renal cell function and revitalizes research evaluating the role of haemostasis regulators in renal disease. Renal cell-specific expression and activity of coagulation proteases, their regulators and their receptors are dynamically altered during disease processes. Furthermore, renal inflammation and tissue remodelling are not only associated, but are causally linked with altered coagulation activation and protease-dependent signalling. Intriguingly, coagulation proteases signal through more than one receptor or induce formation of receptor complexes in a cell-specific manner, emphasizing context specificity. Understanding these cell-specific signalosomes and their regulation in kidney disease is crucial to unravelling the pathophysiological relevance of coagulation regulators in renal disease. In addition, the clinical availability of small molecule targeted anticoagulants as well as the development of PAR antagonists increases the need for in-depth knowledge of the mechanisms through which coagulation proteases might regulate renal physiology.

[Endothelial glycocalyx of blood circulation. II. Biological functions, state at norm and pathology, bioengineering application]

In normal state, a complex multicomponent system called glycocalyx is present on the surface of endothelial vascular system. Due to complexity of its composition and location on the border between vessel wall and blood circulation, glycocalyx participates in a number of functions supporting the metabolism of the vascular wall. In pathological conditions undergo complete or partial loss of this structure, which leads to inconsistencies in the vascular wall and change its functions. The functions of endothelial glycocalyx are its involvement in the regulation of vascular permeability, transduction and transformation by the shear stress of blood flow on endothelium, the molecular regulation of glycocalyx microenvironment and its interaction with circulating blood cells. Also briefly be considered participation of glycocalyx in the implementation of cardiovascular diseases, their correction, bioengineering application of glycocalyx and its components.

Cystic fibrosis transmembrane conductance regulator is involved in polyphenol-induced swelling of the endothelial glycocalyx

Previous studies show that polyphenol-rich compounds can induce a swelling of the endothelial glycocalyx (eGC). Our goal was to reveal the mechanism behind the eGC-swelling. As polyphenols are potent modulators of fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, the hypothesis was tested whether polyphenol-induced increase in CFTR activity is responsible for the eGC-swelling. The impact of the polyphenols resveratrol, (-)-epicatechin, and quercetin on nanomechanics of living endothelial GM7373 cells was monitored by AFM-nanoindentation. The tested polyphenols lead to eGC-swelling with a simultaneous decrease in cortical stiffness. EGC-swelling, but not the change in cortical stiffness, was prevented by the inhibition of CFTR. Polyphenol-induced eGC-swelling could be mimicked by cytochalasin D, an actin-depolymerizing agent. Thus, in the vascular endothelium, polyphenols induce eGC-swelling by softening cortical actin and activating CFTR. Our findings imply that CFTR plays an important role in the maintenance of vascular homeostasis and may explain the vasoprotective properties of polyphenols.

FROM THE CLINICAL EDITOR

Many vascular problems clinically can be attributed to a dysregulation of endothelial glycocalyx (eGC). The underlying mechanism however remains unclear. In this article, the authors used nanoindentation and showed that polyphenols could swell the endothelial glycocalyx and alter its function. This investigative method can lead to further mechanistic studies of other molecular pathways.

Heparanase multiple effects in cancer

Heparanase is an endo-β-D-glucuronidase that is capable of cleaving heparan sulfate side chains of heparan sulfate proteoglycans on cell surfaces and the extracellular matrix, activity that is strongly implicated in tumor metastasis and angiogenesis. Apart of its well characterized enzymatic activity, heparanase was noted to exert also enzymatic-independent functions. Among these are the up-regulation of vascular endothelial growth factor (VEGF)-A, VEGF-C and activation of intra-cellular signaling involved in cell survival and proliferation. We had earlier demonstrated that heparanase may also affect the hemostatic system in a non-enzymatic manner. We had shown that heparanase up-regulated the expression of the blood coagulation initiator- tissue factor (TF) and interacted with the tissue factor pathway inhibitor (TFPI) on the cell surface membrane of endothelial and tumor cells, leading to dissociation of TFPI and resulting in increased cell surface coagulation activity. Moreover, we have demonstrated that heparanase directly enhanced TF activity which led to increased factor Xa production and subsequent activation of the coagulation system. Taking into account the prometastatic, pro-angiogenic and pro-coagulant functions of heparanase, over-expression in human malignancies and abundance in platelets, implies that heparanase is potentially a good target for cancer therapy.

Low levels of tissue factor pathway inhibitor increase the risk of cerebral venous thrombosis

Background:

Decreased concentration of tissue factor pathway inhibitor (TFPI) is a risk factor for development of deep venous thrombosis and coronary heart disease, but there is no evidence for the relationship between TFPI and cerebral venous and sinus thrombosis (CVST). The aim of this study was to determine the level of TFPI in healthy population and in patients with CVST.

Materials and Methods:

We determined the plasma level of TFPI in 20 patients with CVST (cases) and 31 healthy volunteer subjects (as control group) by enzyme linked immunoassay method. We also examined the association between TFPI and the risk of CVST. Continuous variables were compared between groups using Student's t test, and odds ratio was calculated by multiple logistic regression analysis.

Results:

The mean TFPI was significantly lower in the CVST group compared with the control group (8.60 ± 4.05 ng/mL; 14.6 ± 8.6 ng/mL; P = 0. 005), respectively. The odds ratio for CVST associated with low (<25^th percentile) levels of TFPI was 5.429 (95% CI, 1.487-19.82, P = 0.012).

Conclusion:

Our investigation demonstrates that reduced TFPI may be one of the risk factors of CVST and associated with increasing the risk of developing CVST.

Heparanase and coagulation-new insights

Heparanase, a β-D-endoglucuronidase abundant in platelets that was discovered 30 years ago, is an enzyme that cleaves heparan sulfate side chains on the cell surface and in the extracellular matrix. It was later recognized as being a pro-inflammatory and pro-metastatic protein. We had earlier demonstrated that heparanase may also affect the hemostatic system in a non-enzymatic manner. We had shown that heparanase up-regulated the expression of the blood coagulation initiator tissue factor (TF) and interacted with the tissue factor pathway inhibitor (TFPI) on the cell surface membrane of endothelial and tumor cells, leading to dissociation of TFPI and resulting in increased cell surface coagulation activity. Moreover, we have demonstrated that heparanase directly enhanced TF activity which led to increased factor Xa production and subsequent activation of the coagulation system. Recently, heparanase inhibitory peptides derived of TFPI-2 were demonstrated by us to inhibit heparanase procoagulant activity and attenuate sepsis in mouse models.

Nanomechanics of vascular endothelium

The mechanical characteristics of endothelial cells reveal four distinct compartments, namely glycocalyx, cell cortex, cytoplasm and nucleus. There is accumulating evidence that endothelial nanomechanics of these individual compartments control vascular physiology. Depending on protein composition, filament formation and interaction with cross-linker proteins, these four compartments determine endothelial stiffness. Structural organization and mechanical properties directly influence physiological processes such as endothelial barrier function, nitric oxide release and gene expression. This review will focus on endothelial nanomechanics and its impact on vascular function.

High fat diet induces adhesion of platelets to endothelium in two models of dyslipidemia

Cardiovascular diseases (CVD) represent about 30% of all global deaths. It is currently accepted that, in the atherogenic process, platelets play an important role, contributing to endothelial activation and modulation of the inflammatory phenomenon, promoting the beginning and formation of lesions and their subsequent thrombotic complications. The objective of the present work was to study using immunohistochemistry, the presence of platelets, monocytes/macrophages, and cell adhesion molecules (CD61, CD163, and CD54), in two stages of the atheromatous process. CF-1 mice fed a fat diet were used to obtain early stages of atheromatous process, denominated early stage of atherosclerosis, and ApoE(-/-) mice fed a fat diet were used to observe advanced stages of atherosclerosis. The CF-1 mice model presented immunostaining on endothelial surface for all three markers studied; the advanced atherosclerosis model in ApoE(-/-) mice also presented granular immunostaining on lesion thickness, for the same markers. These results suggest that platelets participate in atheromatous process from early stages to advance d stages. High fat diet induces adhesion of platelets to endothelial cells in vivo. These findings support studying the participation of platelets in the formation of atheromatous plate.

Purification and characterization of a stable Kunitz trypsin inhibitor from Trigonella foenum-graecum (fenugreek) seeds

Kunitz trypsin inhibitor was purified from the seeds of Trigonella foenum-graecum (TfgKTI) belonging to fabaceae family by ammonium sulphate precipitation, cation exchange, gel filtration and hydrophobic chromatography. Purity of the protein was analyzed by RP-HPLC and native-PAGE. SDS-PAGE analysis under reducing and non-reducing conditions showed that protein consists of a single polypeptide chain with molecular mass of approximately 20 kDa. Mass spectroscopy analysis revealed that the intact mass of purified inhibitor is 19,842.154 Da. One dimensional SDS gel was tryptically digested, resulting peptides were subjected to MALDI-TOF-MS analysis, and peptide mass fingerprinting (PMF) analysis of TfgKTI shows sequence similarity with Kunitz trypsin inhibitor in database search. Two dimensional electrophoresis identified presence of four isoinhibitors (pI values of 5.1, 5.4, 5.7 and 6.1). Kinetic studies showed that the protein is a competitive inhibitor and has high binding affinity with trypsin (Ki 3.01×10(-9)M) and chymotrypsin (Ki 0.52×10(-9)M). The TfgKTI retained the inhibitory activity over a broad range of pH (pH 3-10), temperature (37-100°C) and salt concentration (up to 3.5%). Far-UV circular dichroism measurements revealed that TfgKTI is predominantly composed of β-sheets (39%) and unordered structures (48%) with slight helical content (13%). TfgKTI retained over 90% trypsin inhibition upon storage at 4°C for over a period of six months.

The effect of tissue factor pathway inhibitor on the expression of monocyte chemotactic protein-3 and IκB-α stimulated by tumour necrosis factor-α in cultured vascular smooth muscle cells

BACKGROUND

In recent years, the importance of inflammation in restenosis has been recognized gradually. When vascular injury occurs, NF-κB, which controls transcription of many inflammatory genes in restenosis (such as monocyte chemotactic protein-3 [MCP-3]), is activated by IκB degradation, leaving the NF-κB dimer-free to translocate to the nucleus to activate specific target genes.

AIMS

To investigate the effect of tissue factor pathway inhibitor (TFPI) on MCP-3 expression and IκB-α degradation stimulated by tumour necrosis factor (TNF)-α in vascular smooth muscle cells (VSMCs), thus further elucidating the mechanism of the inhibitory effect of TFPI on restenosis.

METHODS

Dulbecco's modified Eagle's medium or human recombinant adenoviruses expressing TFPI or bacterial β-galactosidase (LacZ) were used to infect rat aortic VSMCs in vitro. Enzyme-linked immunosorbent assays were used to detect exogenous TFPI expression and reverse transcription-polymerase chain reactions were used to detect MCP-3 expression after TNF-α stimulation in transfected cells. Western blotting and immunofluorescence microscopy were used to examine IκB-α expression.

RESULTS

TFPI protein was detected in the TFPI group after gene transfer. The cells were stimulated with TNF-α for 6 hours on the third day after gene transfer. MCP-3 messenger ribonucleic acid expression was lower in the TFPI group than in the LacZ group (P<0.05) and IκB-α degradation was lower in the TFPI group than in the LacZ group in the cytoplasm (P<0.05).

CONCLUSION

TFPI inhibited MCP-3 expression induced by TNF-α; this effect may be propagated through the NF-κB pathway. TFPI gene transfer may be a new therapeutic strategy for inhibiting restenosis in clinical situations.

Hepatic transcriptome analysis of inter-family variability in flesh n-3 long-chain polyunsaturated fatty acid content in Atlantic salmon

Background

Genetic selection of Atlantic salmon families better adapted to alternative feed formulations containing high levels of vegetable ingredients has been suggested to ensure sustainable growth of aquaculture. The present study aimed to identify molecular pathways that could underlie phenotypic differences in flesh n-3 long-chain polyunsaturated fatty acid (LC-PUFA) levels when fish are fed vegetable oil diets. Liver transcriptome was analyzed and compared in four families presenting higher or lower n-3 LC-PUFA contents at two contrasting flesh total lipid levels.

Results

The main effect of n-3 LC-PUFA contents was in the expression of immune response genes (38% of all significantly affected genes), broadly implicated in the modulation of inflammatory processes and innate immune response. Although genetic evaluations of traits used in the breeding program revealed that the chosen families were not balanced for viral disease resistance, this did not fully explain the preponderance of immune response genes in the transcriptomic analysis. Employing stringent statistical analysis no lipid metabolism genes were detected as being significantly altered in liver when comparing families with high and low n-3 LC-PUFA flesh contents. However, relaxing the statistical analysis enabled identification of potentially relevant effects, further studied by RT-qPCR, in cholesterol biosynthesis, lipoprotein metabolism and lipid transport, as well as eicosanoid metabolism particularly affecting the lipoxygenase pathway. Total lipid level in flesh also showed an important effect on immune response and 8% of significantly affected genes related to lipid metabolism, including a fatty acyl elongase (elovl2), an acyl carrier protein and stearoyl-CoA desaturase.

Conclusions

Inter-family differences in n-3 LC-PUFA content could not be related to effects on lipid metabolism, including transcriptional modulation of the LC-PUFA biosynthesis pathway. An association was found between flesh adiposity and n-3 LC-PUFA in regulation of cholesterol biosynthesis, which was most likely explained by variation in tissue n-3 LC-PUFA levels regulating transcription of cholesterol metabolism genes through srebp2. A preponderance of immune response genes significantly affected by n-3 LC-PUFA contents could be potentially associated with disease resistance, possibly involving anti-inflammatory actions of tissue n-3 LC-PUFA through eicosanoid metabolism. This association may have been fortuitous, but it is important to clarify if this trait is included in future salmon breeding programmes.

Endothelial cell attachment and shear response on biomimetic polymer-coated vascular grafts

Endothelial cell (EC) adhesion, shear retention, morphology, and hemostatic gene expression on fibronectin (FN) and RGD fluorosurfactant polymer (FSP)-coated expanded polytetrafluoroethylene grafts were investigated using an in vitro perfusion system. ECs were sodded on both types of grafts and exposed to 8 dyn/cm(2) of shear stress. After 24 h, the EC retention on RGD-FSP-coated grafts was 59 ± 14%, which is statistically higher than the 36 ± 11% retention measured on FN grafts (p < 0.02). Additionally, ECs on RGD-FSP exhibited a more spread morphology and oriented in the direction of shear stress, as demonstrated by actin fiber staining. This spread morphology has been observed earlier in cells that are adapting to shear stress. Real-time PCR for vascular cell adhesion molecule 1, tissue factor, tissue plasminogen activator, and inducible nitric oxide synthase indicated that the RGD-FSP material did not activate the cells and that shear stress appears to induce a more vasoprotective phenotype, as shown by a significant decrease in VCAM-1 expression, compared with sodded grafts. RGD-FSP-coating allows for a cell layer that is more resistant to physiological shear stress, as shown by the increased cell retention over FN. This shear stable EC layer is necessary for in vivo endothelialization of the graft material, which shows promise to increase the patency of synthetic small diameter vascular grafts.

Heparanase-A Link between Coagulation, Angiogenesis, and Cancer

Heparanase that was cloned from and is abundant in the placenta is implicated in cell invasion, tumor metastasis, and angiogenesis. Recently we have demonstrated that heparanase may also affect the hemostatic system in a non-enzymatic manner. Heparanase was shown to up-regulate tissue factor (TF) expression and interact with tissue factor pathway inhibitor (TFPI) on the cell surface, leading to dissociation of TFPI from the cell membrane of endothelial and tumor cells, resulting in increased cell surface coagulation activity. More recently, we have shown that heparanase directly enhances TF activity, resulting in increased factor Xa production and activation of the coagulation system. Data indicate increased levels and possible involvement of heparanase in vascular complications in pregnancy. Taking into account the prometastatic and proangiogenic functions of heparanase, overexpression in human malignancies, and abundance in platelets and placenta, its involvement in the coagulation machinery is an intriguing novel arena for further research.