Leukocytes use endothelial membrane tunnels to extravasate the vasculature.

Upon inflammation, leukocytes extravasate through endothelial cells. When they extravasate, it is generally accepted that neighboring endothelial cells disconnect. Careful examination of endothelial junctions showed a partial membrane overlap beyond VE-cadherin distribution.

Leukocyte transendothelial migration hotspots at a glance.

Leukocytes traverse the vasculature to reach sites of infection by sequentially crossing two distinct barriers - the endothelial barrier, during transendothelial migration (TEM), and the pericyte barrier, during trans-pericyte migration (TPM). Emerging evidence has underscored that TEM and TPM do not occur randomly but are confined to specialized 'hotspot' regions. This Cell Science at a Glance article and the accompanying poster overview the mechanisms underlying the heterogeneity within the inflamed endothelial monolayer, as well as within the perivascular cells, that defines these hotspots, highlighting how leukocytes themselves can actively induce new hotspots during the extravasation process.

Dynamic cytoskeletal regulation of cell shape supports resilience of lymphatic endothelium.

Lymphatic capillaries continuously take up interstitial fluid and adapt to resulting changes in vessel calibre. The mechanisms by which the permeable monolayer of loosely connected lymphatic endothelial cells (LECs) maintains mechanical stability remain elusive. Here we identify dynamic cytoskeletal regulation of LEC shape, induced by isotropic stretch, as crucial for the integrity and function of dermal lymphatic capillaries.

VE-cadherin RGD motifs are dispensable for cell-cell junctions, endothelial barrier function and monocyte extravasation.

VE-cadherin is a key transmembrane protein involved in endothelial cell-cell junctions, playing a crucial role in maintaining vascular integrity and regulating selective leukocyte extravasation into inflamed tissue. The extracellular domain of human VE-cadherin contains two arginine-glycine-aspartate (RGD) motifs, which are known integrin-binding sites within extracellular matrix proteins, particularly for integrins of the β1, β3, and β5 families. In this study, we examined the functional relevance of these RGD motifs by generating VE-cadherin variants in which the RGD sequences were mutated to nonfunctional RGE.

Presentation of CXCL12γ by heparan sulfate proteoglycans activates CXCR4 without desensitization in normal and malignant B cells.

CXCL12-CXCR4 signaling is involved in a wide variety of homeostatic and pathologic processes, but the role of specific CXCL12 isoforms has remained largely unexplored. We have recently shown that the CXCL12γ isoform, which holds an exceptionally high affinity for heparan sulfate (HS), is produced by human bone marrow stromal cells (BMSCs) and remains cell surface immobilized by HS proteoglycans (HSPGs). This HS-bound CXCL12γ is critical for the adhesion of multiple myeloma cells to BMSCs and for BMSC-mediated drug resistance.

Protection of liver sinusoidal endothelial cells using different preservation solutions.

Donor liver preservation methods and solutions have evolved over the last years. Liver sinusoidal endothelial cell (LSEC) barrier function and integrity during preservation are crucial for outcomes of liver transplantation. Therefore, the present study aimed to determine optimal preservation of LSEC barrier function and integrity using different preservation solutions.

Encompassing view of spatial and single-cell RNA sequencing renews the role of the microvasculature in human atherosclerosis.

Atherosclerosis is a pervasive contributor to ischemic heart disease and stroke. Despite the advance of lipid-lowering therapies and anti-hypertensive agents, the residual risk of an atherosclerotic event remains high, and developing therapeutic strategies has proven challenging. This is due to the complexity of atherosclerosis with a spatial interplay of multiple cell types within the vascular wall.

Apelin modulates inflammation and leukocyte recruitment in experimental autoimmune encephalomyelitis.

Demyelination due to autoreactive T cells and inflammation in the central nervous system are principal features of multiple sclerosis (MS), a chronic and highly disabling human disease affecting brain and spinal cord. Here, we show that treatment with apelin, a secreted peptide ligand for the G protein-coupled receptor APJ/Aplnr, is protective in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Apelin reduces immune cell entry into the brain, delays the onset and reduces the severity of EAE.

The Effects of Heparan Sulfate Infusion on Endothelial and Organ Injury in a Rat Pneumosepsis Model.

Septic shock is characterized by endothelial dysfunction, leading to tissue edema and organ failure. Heparan sulfate (HS) is essential for vascular barrier integrity, possibly via albumin as a carrier. We hypothesized that supplementing fluid resuscitation with HS would improve endothelial barrier function, thereby reducing organ edema and injury in a rat pneumosepsis model.

The effects of resuscitation with different plasma products on endothelial permeability and organ injury in a rat pneumosepsis model.

Background: Endothelial injury and permeability are a hallmark of sepsis. Initial resuscitation of septic patients with crystalloids is associated with aggravation of endothelial permeability, which may be related either to low protein content or to volume. We investigated whether initial resuscitation with different types of plasma or albumin decreases endothelial dysfunction and organ injury in a pneumosepsis rat model compared to the same volume of crystalloids.

VISTA Expression on Cancer-Associated Endothelium Selectively Prevents T-cell Extravasation.

Cancers evade T-cell immunity by several mechanisms such as secretion of anti-inflammatory cytokines, down regulation of antigen presentation machinery, upregulation of immune checkpoint molecules, and exclusion of T cells from tumor tissues. The distribution and function of immune checkpoint molecules on tumor cells and tumor-infiltrating leukocytes is well established, but less is known about their impact on intratumoral endothelial cells. Here, we demonstrated that V-domain Ig suppressor of T-cell activation (VISTA), a PD-L1 homolog, was highly expressed on endothelial cells in synovial sarcoma, subsets of different carcinomas, and immune-privileged tissues.

Intercellular adhesion molecule 2 regulates diapedesis hotspots by allowing neutrophil crawling against the direction of flow.

Intercellular adhesion molecules (ICAMs) are cell surface proteins that play a crucial role in the body's immune response and inflammatory processes. ICAM1 and ICAM2 are two ICAM family members expressed on the surface of various cell types, including endothelial cells. They mediate the interaction between immune cells and endothelial cells, which are critical for the trafficking of leukocytes across the blood vessel wall during inflammation.

Primary adhered neutrophils increase JNK1-MARCKSL1-mediated filopodia to promote secondary neutrophil transmigration.

During inflammation, leukocytes extravasate the vasculature to areas of inflammation in a process termed transendothelial migration. Previous research has shown that transendothelial migration hotspots exist, areas in the vasculature that are preferred by leukocytes to cross. Several factors that contribute to hotspot-mediated transmigration have been proposed already, but whether one leukocyte transmigration hotspot can be used subsequently by a second wave of leukocytes and thereby can increase the efficiency of leukocyte transmigration is not well understood.

Spatiotemporal regulation of Rho GTPase signaling during endothelial barrier remodeling.

The vasculature is characterized by a thin cell layer that comprises the inner wall of all blood vessels, the continuous endothelium. Endothelial cells can also be found in the eye's cornea. And even though cornea and vascular endothelial (VE) cells differ from each other in structure, they both function as barriers and express similar junctional proteins such as the adherens junction VE-cadherin and tight-junction member claudin-5.

Serine phosphorylation of the RhoGEF Trio stabilizes endothelial cell-cell junctions.

The RhoGEF Trio is a large multi-domain protein and an activator of the small GTPases Rac1, RhoG, and RhoA. Although Trio has been implicated in many cellular mechanisms like leukocyte transendothelial migration, cell-cell junction stability, lamellipodia formation, axon outgrowth, and muscle fusion, it remains unclear how Trio is activated. Using stable isotope labelling by amino acids in cell culture (SILAC)-based mass spectrometry analysis of endothelial cells, we identified two serine residues (S1785/S1786) located in between the two exchange domains of Trio that were highly phosphorylated upon short thrombin treatment.

Opto-RhoGEFs, an optimized optogenetic toolbox to reversibly control Rho GTPase activity on a global to subcellular scale, enabling precise control over vascular endothelial barrier strength.

The inner layer of blood vessels consists of endothelial cells, which form the physical barrier between blood and tissue. This vascular barrier is tightly regulated and is defined by cell-cell contacts through adherens and tight junctions. To investigate the signaling that regulates vascular barrier strength, we focused on Rho GTPases, regulators of the actin cytoskeleton and known to control junction integrity.

Systemic Inflammation and Normocytic Anemia in DOCK11 Deficiency.

Background: Increasing evidence links genetic defects affecting actin-regulatory proteins to diseases with severe autoimmunity and autoinflammation, yet the underlying molecular mechanisms are poorly understood. Dedicator of cytokinesis 11 (DOCK11) activates the small Rho guanosine triphosphatase (GTPase) cell division cycle 42 (CDC42), a central regulator of actin cytoskeleton dynamics. The role of DOCK11 in human immune-cell function and disease remains unknown.

Endothelial ICAM-1 Adhesome Recruits CD44 for Optimal Transcellular Migration of Human CTLs.

The endothelial lining of blood vessels is covered with a thin polysaccharide coat called the glycocalyx. This layer of polysaccharides contains hyaluronan that forms a protective coat on the endothelial surface. Upon inflammation, leukocytes leave the circulation and enter inflamed tissue by crossing inflamed endothelial cells, mediated by adhesion molecules such as ICAM-1/CD54.

Endothelial transmigration hotspots limit vascular leakage through heterogeneous expression of ICAM-1.

Upon inflammation, leukocytes leave the circulation by crossing the endothelial monolayer at specific transmigration "hotspot" regions. Although these regions support leukocyte transmigration, their functionality is not clear. We found that endothelial hotspots function to limit vascular leakage during transmigration events.

A pulmonary endothelial amplification loop aggravates ex-vivo transfusion-related acute lung injury via increased toll-like receptor 4 and intra-cellular adhesion molecule-1 expression.

Background: Transfusion-Related Acute Lung Injury (TRALI) is a life-threatening complication of blood transfusions characterized by pulmonary endothelial cell damage and edema, with a high incidence in critically ill patients. The pathophysiology of TRALI is unresolved, but can generally be hypothesized to follow a 2-hit model in which the first hit is elicited by the underlying clinical condition of the patient (e.g.

Prophylactic furosemide to prevent transfusion-associated circulatory overload: a randomized controlled study in rats.

Transfusion-associated circulatory overload (TACO) is the leading cause of transfusion related morbidity and mortality. The only treatment is empirical use of furosemide. Our aim was to investigate if furosemide can prevent TACO.

Protocol to analyze transmigration of human cytotoxic T cells under physiological flow conditions in vitro.

This protocol presents an assay for transmigration analysis of human cytotoxic T cells (CTL) under physiological flow in vitro. We describe detailed analysis steps of human CTL behavior, from adhesion to diapedesis, using live cell imaging which cannot be achieved by in vivo imaging. The flow system is made of 2D plastic surfaces covered by an endothelial monolayer limiting the system but allows for quantitative analysis of CTL behavior with high modifiability.

Differential Contribution of NF-κB Signaling Pathways to CD4 Memory T Cell Induced Activation of Endothelial Cells.

Endothelial cells (ECs) are important contributors to inflammation in immune-mediated inflammatory diseases (IMIDs). In this study, we examined whether CD4 memory T (T) cells can drive EC inflammatory responses. Human T cells produced ligands that induced inflammatory responses in human umbilical vein EC as exemplified by increased expression of inflammatory mediators including chemokines and adhesion molecules.