Structure Of Endothelial Glycocalyx Research Articles

Albumin protects the ultrastructure of the endothelial glycocalyx of coronary arteries in myocardial ischemia-reperfusion injury in vivo

Myocardial ischemia-reperfusion (I/R) injury induces endothelial glycocalyx (GCX) degradation. Several candidate GCX-protective factors including albumin have been identified, few have been demonstrated in in vivo studies and most albumins used to date have been heterologous. Albumin is a carrier protein for sphingosine 1-phosphate (S1P), which has protective effects on the cardiovascular system. However, changes inhibited by albumin in the endothelial GCX structure in I/R in vivo via the S1P receptor has not been reported. In this study, we aimed to determine whether albumin prevents the shedding of endothelial GCX in response to I/R in vivo. Rats were divided into four groups: control (CON), I/R, I/R with albumin preload (I/R + ALB), and I/R + ALB with S1P receptor agonist fingolimod (I/R + ALB + FIN). FIN acts as an initial agonist of S1P receptor 1 and downregulates the receptor in an inhibitory manner. The CON and I/R groups received saline and I/R + ALB and I/R + ALB + FIN groups received albumin solution before left anterior descending coronary artery ligation. Our study used rat albumin. Shedding of endothelial GCX was evaluated in the myocardium by electron microscopy, and the concentration of serum syndecan-1 was measured. Thus, albumin administration maintained the structure of endothelial GCX and prevented shedding of endothelial GCX via the S1P receptor in myocardial I/R, and FIN annihilated the protective effect of albumin against I/R injury.

Constructing hierarchical surface structure of hemodialysis membranes to intervene in oxidative stress through Michael addition reaction between tannic acid and PEtOx brushes

Chronic kidney disease (CKD) patients undergoing hemodialysis is often accompanied by high levels of oxidative stress, profoundly affecting the survival rate and long-term outcome of patients. Functionalized hemodialysis membranes with relieving oxidative stress and outstanding biocompatibility have aroused more attention among researchers. In this work, we incorporated a tannic acid (TA) coating onto the poly (ether sulfone) (PES) hemodialysis membrane in order to alleviate the increased oxidative stress status during hemodialysis. Further modification of poly(2-ethyl-2-oxazoline) (PEtOx) brushes devoted to improving the biocompatibility of hemodialysis membrane. The TA/PEtOx brushes functionalized membranes effectively eliminated reactive oxygen species (ROS), increased serum antioxidant level, and inhibited lipid peroxides and glycation products generation. The functionalized membranes attenuated the H2O2-induced oxidative damage to cardiomyocytes (H9C2) and vascular endothelial cells (HUVEC) by modulating the antioxidant enzymes expression (SOD, CAT and GSH). The immobilization of PEtOx brushes significantly improved the biocompatibility, and the TA/PEtOx brushes functionalized membranes have been constructed through the Michael addition reaction between TA and PEtOx brushes. Simultaneously, the cyclic PEtOx (C-PEtOx) brushes simulating the structure of endothelial glycocalyx formed a stronger steric hindrance and a denser hydration layer that significantly suppressed the platelets and erythrocytes adhesion on membrane surface. The optimal functionalized membrane exhibited a 76.5% of urea clearance, 53.4% of lysozyme clearance and 95.9% of bovine serum albumin (BSA) retention. This present work fabricated a biomimetic surface structure for the development and preparation of novel hemodialysis membrane, which would greatly improve the therapeutic effect in patients.

Endothelial Dysfunction in Fabry Disease Is Related to Glycocalyx Degradation.

Fabry disease (FD) is an X-linked multisystemic lysosomal storage disease due to a deficiency of α-galactosidase A (GLA/AGAL). Progressive cellular accumulation of the AGAL substrate globotriaosylceramide (Gb3) leads to endothelial dysfunction. Here, we analyzed endothelial function in vivo and in vitro in an AGAL-deficient genetic background to identify the processes underlying this small vessel disease. Arterial stiffness and endothelial function was prospectively measured in five males carrying GLA variants (control) and 22 FD patients under therapy. AGAL-deficient endothelial cells (EA.hy926) and monocytes (THP1) were used to analyze endothelial glycocalyx structure, function, and underlying inflammatory signals. Glycocalyx thickness and small vessel function improved significantly over time (p<0.05) in patients treated with enzyme replacement therapy (ERT, n=16) and chaperones (n=6). AGAL-deficient endothelial cells showed reduced glycocalyx and increased monocyte adhesion (p<0.05). In addition, increased expression of angiopoietin-2, heparanase and NF-κB was detected (all p<0.05). Incubation of wild-type endothelial cells with pathological globotriaosylsphingosine concentrations resulted in comparable findings. Treatment of AGAL-deficient cells with recombinant AGAL (p<0.01), heparin (p<0.01), anti-inflammatory (p<0.001) and antioxidant drugs (p<0.05), and a specific inhibitor (razuprotafib) of angiopoietin-1 receptor (Tie2) (p<0.05) improved glycocalyx structure and endothelial function in vitro. We conclude that chronic inflammation, including the release of heparanases, appears to be responsible for the degradation of the endothelial glycocalyx and may explain the endothelial dysfunction in FD. This process is partially reversible by FD-specific and anti-inflammatory treatment, such as targeted protective Tie2 treatment.

The endothelial glycocalyx: research methods and prospects for their use in endothelial dysfunction assessment

A modern concept of the endothelial dysfunction in the pathogenesis of many diseases includes the glycocalyx damage along with impaired of the morphology and function of endothelial cells. The glycocalyx is a gel-like submembrane complex of protein-carbohydrate, carbohydrate-lipid components and plasma molecules forming a three-dimensional network on the luminal surface of the endothelium. The features of the borderline location of endothelial glycocalyx in the vascular system determine various important functions: barrier, regulatory, anti-inflammatory, antithrombotic, mechanotransduction ones, etc. In recent years, due to the improvement of visualization methods endothelial glycocalyx structure has been detailed. Its physiological functions and the role in the development of some pathological conditions have been clarified. Modern methods of glycocalyx assessment include invasive and non-invasive research techniques. The most promising ones are dark-field microscopy and the determination of glycocalyx-associated biochemical markers. Endothelial glycocalyx damage is a universal pathogenetic component and the earliest marker of the development of most diseases. Therefore, the endothelial glycocalyx assessment refers to promising areas of research. The ability to correlate with other prognostic indicators allows us to consider the endothelial glycocalyx damage as a marker of the poor health prognosis. That is why, assessment of the endothelial glycocalyx condition will allow to personalize treatment and to prevent the diseases progression.

Shear Stress Regulation of Endothelial Glycocalyx Structure Is Determined by Glucobiosynthesis.

Endothelial cells exposed to laminar shear stress express a thick glycocalyx on their surface that plays an important role in reducing vascular permeability and endothelial anti-inflammatory, antithrombotic, and antiangiogenic properties. Production and maintenance of this glycocalyx layer is dependent on cellular carbohydrate synthesis, but its regulation is still unknown. Approach and Results: Here, we show that biosynthesis of the major structural component of the endothelial glycocalyx, hyaluronan, is regulated by shear. Both in vitro as well as in in vivo, hyaluronan expression on the endothelial surface is increased on laminar shear and reduced when exposed to oscillatory flow, which is regulated by KLF2 (Krüppel-like Factor 2). Using a CRISPR-CAS9 edited small tetracysteine tag to endogenous HAS2 (hyaluronan synthase 2), we demonstrated increased translocation of HAS2 to the endothelial cell membrane during laminar shear. Hyaluronan production by HAS2 was shown to be further driven by availability of the hyaluronan substrates UDP-glucosamine and UDP-glucuronic acid. KLF2 inhibits endothelial glycolysis and allows for glucose intermediates to shuttle into the hexosamine- and glucuronic acid biosynthesis pathways, as measured using nuclear magnetic resonance analysis in combination with 13C-labeled glucose. These data demonstrate how endothelial glycocalyx function and functional adaptation to shear is coupled to KLF2-mediated regulation of endothelial glycolysis.

Large-scale molecular dynamics simulation of flow under complex structure of endothelial glycocalyx

In this research, large-scale molecular dynamics (MD) simulations were conducted to study the fluid dynamics inside the endothelial glycocalyx layer. A work flowchart regarding constructing the flow/glycocalyx system, undertaking production simulation using the MD method and post-processing was proposed. Following the flowchart, physiological and accelerating flow cases were simulated to reveal velocity and shear stress distributions over the dendritic (tree-like) structure of the glycocalyx, thereby contributing to understanding of the influence of biomolecular complex structures on flow profiles. Besides, the selection of thermostat algorithm was discussed. Results have shown that when the forcing is below a critical value, the velocity fluctuates around a zero mean along the height in the presence of the dendritic glycocalyx. When the forcing is larger than a critical value, the bulk flow was accelerated excessively, departing from the typical physiological flow. Furthermore, distributions of shear stress magnitude among three sub-regions in the ectodomain indicate that shear stress is enhanced near the membrane surface but is impaired in the sugar-chain-rich region due to the flow regulation by sugar chains. Finally, comparisons of velocity evolutions under two widely used thermostats (Lowe-Andersen and Berendsen thermostats) imply that the Lowe-Andersen algorithm is a suitable thermostat for flow problems.

Sialic acids regulate microvessel permeability, revealed by novel in vivo studies of endothelial glycocalyx structure and function.

Key points We have developed novel techniques for paired, direct, real‐time in vivo quantification of endothelial glycocalyx structure and associated microvessel permeability.Commonly used imaging and analysis techniques yield measurements of endothelial glycocalyx depth that vary by over an order of magnitude within the same vessel.The anatomical distance between maximal glycocalyx label and maximal endothelial cell plasma membrane label provides the most sensitive and reliable measure of endothelial glycocalyx depth.Sialic acid residues of the endothelial glycocalyx regulate glycocalyx structure and microvessel permeability to both water and albumin. The endothelial glycocalyx forms a continuous coat over the luminal surface of all vessels, and regulates multiple vascular functions. The contribution of individual components of the endothelial glycocalyx to one critical vascular function, microvascular permeability, remains unclear. We developed novel, real‐time, paired methodologies to study the contribution of sialic acids within the endothelial glycocalyx to the structural and functional permeability properties of the same microvessel in vivo. Single perfused rat mesenteric microvessels were perfused with fluorescent endothelial cell membrane and glycocalyx labels, and imaged with confocal microscopy. A broad range of glycocalyx depth measurements (0.17–3.02 μm) were obtained with different labels, imaging techniques and analysis methods. The distance between peak cell membrane and peak glycocalyx label provided the most reliable measure of endothelial glycocalyx anatomy, correlating with paired, numerically smaller values of endothelial glycocalyx depth (0.078 ± 0.016 μm) from electron micrographs of the same portion of the same vessel. Disruption of sialic acid residues within the endothelial glycocalyx using neuraminidase perfusion decreased endothelial glycocalyx depth and increased apparent solute permeability to albumin in the same vessels in a time‐dependent manner, with changes in all three true vessel wall permeability coefficients (hydraulic conductivity, reflection coefficient and diffusive solute permeability). These novel technologies expand the range of techniques that permit direct studies of the structure of the endothelial glycocalyx and dependent microvascular functions in vivo, and demonstrate that sialic acid residues within the endothelial glycocalyx are critical regulators of microvascular permeability to both water and albumin.

Endothelial glycocalyx of blood circulation. I. Finding, components, structure organization

In normal state, a complex multicomponent system called glycocalyx is present on the surface of endothelial vascular system. The structure of the glycocalyx is determined by a group ofproteoglycans, glycoproteins and glycosaminoglycans, originating from endothelial cells and blood flow. Due to its complexity and location on the border of the system of blood circulation, glycocalyx participates in a number of functions supporting the metabolism of the vascular wall. Complete or partial loss of this structure in pathologicalconditions leads to inconsistencies in the vascular wall and changes in its functions. The first part of this review considers the history of detection and determination of endothelial glycocalyx structure, utilized methods and approaches. The molecular composition of the glycocalyx, properties of its components and glycocalyx structure organization are described. The English version of the paper: Russian Journal of Bioorganic Chemistry, see also http://www.maik.ru.

Modulation of endothelial glycocalyx structure under inflammatory conditions.

The glycocalyx of the endothelium is an intravascular compartment that creates a barrier between circulating blood and the vessel wall. The glycocalyx is suggested to play an important role in numerous physiological processes including the regulation of vascular permeability, the prevention of the margination of blood cells to the vessel wall, and the transmission of shear stress. Various theoretical models and experimental approaches provide data about changes to the structure and functions of the glycocalyx under various types of inflammatory conditions. These alterations are suggested to promote inflammatory processes in vessels and contribute to the pathogenesis of number of diseases. In this review we summarize current knowledge about the modulation of the glycocalyx under inflammatory conditions and the consequences for the course of inflammation in vessels. The structure and functions of endothelial glycocalyx are briefly discussed in the context of methodological approaches regarding the determination of endothelial glycocalyx and the uncertainty and challenges involved in glycocalyx structure determination. In addition, the modulation of glycocalyx structure under inflammatory conditions and the possible consequences for pathogenesis of selected diseases and medical conditions (in particular, diabetes, atherosclerosis, ischemia/reperfusion, and sepsis) are summarized. Finally, therapeutic strategies to ameliorate glycocalyx dysfunction suggested by various authors are discussed.

Managing Intraoperative Blood Pressure with Norepinephrine

Managing Intraoperative Blood Pressure with Norepinephrine

Glycocalyx volume: a critical review of tracer dilution methods for its measurement

A clinical measure of endothelial glycocalyx structure would have great potential importance, because lesions of the glycocalyx may be the first changes to occur in diabetes and in a wide range of vascular diseases. A method recently described by Nieuwdorp et al. for estimating the volume of the luminal glycocalyx of the entire human vascular system would seem to be the first attempt to develop a measure of this kind. It is based on the tracer dilution principle, and this review considers the principles and conditions that underlie this method and the extent to which the conditions appear to have been fulfilled in this case. Our analysis raises two questions about 1) the estimation of the concentration of the tracer (dextran 40) at zero time and 2) the estimation of plasma volume, both of which can be answered by changes in experimental protocol. A third question, concerning the partition coefficient of the tracer between plasma and the fluid within the glycocalyx, cannot be answered at the present time, and until it has been resolved, glycocalyx volume cannot be estimated from the dilution of a macromolecular tracer.