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Journal of Applied Physiology... Sep 2019Acute respiratory distress syndrome is a severe form of respiratory failure, occurring in up to 20% of patients admitted to the intensive care unit with sepsis....
Acute respiratory distress syndrome is a severe form of respiratory failure, occurring in up to 20% of patients admitted to the intensive care unit with sepsis. Dysregulated leukocyte diapedesis is a major contributor to acute respiratory distress syndrome. Endocan is a circulating proteoglycan that binds to the leukocyte integrin leukocyte functional antigen-1 and blocks its interaction with its endothelial ligand, ICAM-1. The objective of this study was to evaluate the role of endocan in the control of acute lung inflammation. In vitro, endocan inhibited human leukocyte transendothelial migration as well as ICAM-1-dependent migration but had a very mild effect on ICAM-1-dependent adhesion. Endocan also acted as an inhibitor of transendothelial migration of mouse leukocytes. The effect of systemic administration of recombinant human endocan was assessed in a model of acute lung inflammation in BALB/c mice. Treatment with endocan 1 h after intratracheal LPS challenge reduced the alveolar inflammatory response, diminished histological features of acute lung injury, and improved respiratory function. These results highlight the anti-inflammatory role of human endocan and its protective effect against acute lung injury. We show here that endocan inhibits ICAM-1-dependent human leukocyte transendothelial migration and ICAM-1-dependent adhesion. We also found that in BALB/c mice with tracheal LPS-induced acute lung injury treatment with recombinant human endocan reduces lung inflammation, notably through reduction of neutrophilic recruitment, and restores normal lung function. These results confirm the hypothesis that human endocan may have a protective effect against acute lung inflammation.
Topics: Acute Lung Injury; Animals; Capillary Permeability; Cell Adhesion; Cell Movement; Drug Evaluation, Preclinical; HEK293 Cells; Humans; Intercellular Adhesion Molecule-1; Leukocytes; Lipopolysaccharides; Male; Mice, Inbred BALB C; Neoplasm Proteins; Proteoglycans; Respiratory Rate; Transendothelial and Transepithelial Migration
PubMed: 31295063
DOI: 10.1152/japplphysiol.00337.2019 -
Journal of Cell Science Apr 2021The migration of activated T cells across the blood-brain barrier (BBB) is a critical step in central nervous system (CNS) immune surveillance and inflammation. Whereas...
The migration of activated T cells across the blood-brain barrier (BBB) is a critical step in central nervous system (CNS) immune surveillance and inflammation. Whereas T cell diapedesis across the intact BBB seems to occur preferentially through the BBB cellular junctions, impaired BBB integrity during neuroinflammation is accompanied by increased transcellular T cell diapedesis. The underlying mechanisms directing T cells to paracellular versus transcellular sites of diapedesis across the BBB remain to be explored. By combining in vitro live-cell imaging of T cell migration across primary mouse brain microvascular endothelial cells (pMBMECs) under physiological flow with serial block-face scanning electron microscopy (SBF-SEM), we have identified BBB tricellular junctions as novel sites for T cell diapedesis across the BBB. Downregulated expression of tricellular junctional proteins or protein-based targeting of their interactions in pMBMEC monolayers correlated with enhanced transcellular T cell diapedesis, and abluminal presence of chemokines increased T cell diapedesis through tricellular junctions. Our observations assign an entirely novel role to BBB tricellular junctions in regulating T cell entry into the CNS. This article has an associated First Person interview with the first author of the paper.
Topics: Animals; Biological Transport; Blood-Brain Barrier; Endothelial Cells; Mice; T-Lymphocytes; Tight Junctions; Transendothelial and Transepithelial Migration
PubMed: 33912914
DOI: 10.1242/jcs.253880 -
Inflammation Dec 2017Leukocyte recruitment is a fundamental event in the response of the innate immune system to injury. This process is promoted in part by the opening of endothelial cell...
Leukocyte recruitment is a fundamental event in the response of the innate immune system to injury. This process is promoted in part by the opening of endothelial cell adherens junctions that allows leukocyte extravasation through gaps between adjacent endothelial cells. VE-cadherin is a key component of endothelial cell adherens junctions and a negative regulator of leukocyte emigration. Accumulating evidence implicates bone morphogenetic protein (BMP) 4 as a critical regulator in vascular biology, but its role in leukocyte extravasation in vitro and in vivo has not been investigated so far. To assess the impact of BMP4 on leukocyte emigration in vivo, we used the thioglycollate-induced peritonitis model. C57BL/6 mice were intraperitoneally (i.p.) injected with recombinant BMP4 in addition to thioglycollate. Compared to solvent-treated controls, we observed higher accumulation of leukocytes in the peritoneal lavage of BMP4-treated mice indicating that BMP4 promotes leukocyte diapedesis into the inflamed peritoneal cavity. Endothelial cell-specific deletion of BMP4 in mice markedly diminished leukocyte diapedesis following thioglycollate administration suggesting that endothelial BMP4 is required for leukocyte recruitment. Consistent with these in vivo results, transwell migration assays with human umbilical vein endothelial cells (HUVECs) in vitro revealed that recombinant BMP4 enhanced leukocyte transmigration through the endothelial monolayer. Conversely, silencing of endothelial BMP4 by siRNA dampened leukocyte diapedesis in vitro. Mechanistic studies showed that loss of BMP4 improved endothelial junction stability by upregulation of VE-cadherin expression in vitro and in vivo. Vice versa, treatment of HUVECs with recombinant BMP4 decreased expression of VE-cadherin and impaired endothelial junction stability shown by Western blotting and immunocytochemistry. Finally, severe endothelial damage in HUVECs in response to serum of patients collected 24 h after survived cardiac arrest was accompanied by increase in leukocyte migration in transwell assays and activation of the BMP pathway most probably by upregulation of endothelial BMP4 RNA and protein expression. Collectively, the present study provides novel evidence that endothelial BMP4 controls leukocyte recruitment through a VE-cadherin-dependent mechanism and that BMP4-induced inflammation might be involved in the pathogenesis of endothelial cell damage following successful resuscitation after cardiac arrest.
Topics: Antigens, CD; Bone Morphogenetic Protein 4; Cadherins; Chemotaxis, Leukocyte; Endothelium, Vascular; Heart Arrest; Human Umbilical Vein Endothelial Cells; Humans; Inflammation; Leukocytes; Transendothelial and Transepithelial Migration
PubMed: 28755278
DOI: 10.1007/s10753-017-0627-0 -
Molecular Therapy : the Journal of the... Mar 2023
Topics: Transendothelial and Transepithelial Migration; Cell Movement; Liver; Endothelium, Vascular; Cells, Cultured
PubMed: 36754053
DOI: 10.1016/j.ymthe.2023.01.024 -
Proceedings of the National Academy of... Jan 2018Leukocyte transmigration across vessel walls is a critical step in the innate immune response. Upon their activation and firm adhesion to vascular endothelial cells...
Leukocyte transmigration across vessel walls is a critical step in the innate immune response. Upon their activation and firm adhesion to vascular endothelial cells (VECs), leukocytes preferentially extravasate across junctional gaps in the endothelial monolayer (paracellular diapedesis). It has been hypothesized that VECs facilitate paracellular diapedesis by opening their cell-cell junctions in response to the presence of an adhering leukocyte. However, it is unclear how leukocytes interact mechanically with VECs to open the VEC junctions and migrate across the endothelium. In this study, we measured the spatial and temporal evolution of the 3D traction stresses generated by the leukocytes and VECs to elucidate the sequence of mechanical events involved in paracellular diapedesis. Our measurements suggest that the contractile stresses exerted by the leukocytes and the VECs can separately perturb the junctional tensions of VECs to result in the opening of gaps before the initiation of leukocyte transmigration. Decoupling the stresses exerted by the transmigrating leukocytes and the VECs reveals that the leukocytes actively contract the VECs to open a junctional gap and then push themselves across the gap by generating strong stresses that push into the matrix. In addition, we found that diapedesis is facilitated when the tension fluctuations in the VEC monolayer were increased by proinflammatory thrombin treatment. Our findings demonstrate that diapedesis can be mechanically regulated by the transmigrating leukocytes and by proinflammatory signals that increase VEC contractility.
Topics: HL-60 Cells; Human Umbilical Vein Endothelial Cells; Humans; Intercellular Junctions; Leukocytes; Models, Biological; Transendothelial and Transepithelial Migration
PubMed: 29255056
DOI: 10.1073/pnas.1717489115 -
Frontiers in Bioscience (Landmark... Jan 2018Pericytes build together with endothelial cells the microvascular vessel wall. They have been mainly implicated in angiogenesis and maintenance of the blood brain... (Review)
Review
Pericytes build together with endothelial cells the microvascular vessel wall. They have been mainly implicated in angiogenesis and maintenance of the blood brain barrier, but there is accumulating evidence for an immunological function of pericytes. Occupying a strategic position between the blood stream and the interstitial space, pericytes are able to sense environmental cues from both sides in an organ-specific manner and serve as gatekeepers for innate immune cells. In addition, pericytes are able to interact with leukocytes mediated by adhesion molecules as well as chemokines and are involved from the development of leukocytes in the bone marrow to their migration to injured or infected areas in target tissues. During disease processes pericytes regulate blood flow, vascular permeability, and leukocyte recruitment, but also contribute to maladaptive tissue responses, such as fibrosis making pericytes an attractive therapeutic target.
Topics: Animals; Cell Communication; Endothelium, Vascular; Humans; Leukocytes; Monitoring, Immunologic; Pericytes; Transendothelial and Transepithelial Migration
PubMed: 28930571
DOI: 10.2741/4615 -
Small GTPases May 2020Active remodeling of the actin cytoskeleton in endothelial cells is necessary for allowing leukocytes to cross the barrier during the process of transendothelial...
Active remodeling of the actin cytoskeleton in endothelial cells is necessary for allowing leukocytes to cross the barrier during the process of transendothelial migration (TEM). Involvement of RhoGTPases to regulate actin organization is inevitable, and we recently reported on the local function of RhoA in limiting vascular leakage during leukocyte TEM. As a follow-up we investigated here the possible involvement of two other closely-related GTPases; RhoB and RhoC, in regulating leukocyte TEM and vascular barrier maintenance. Physiological flow experiments showed no substantial involvement of either endothelial RhoB or RhoC in neutrophil adhesion and transmigration efficiency. Besides neutrophil TEM, we did not observe a role for endothelial RhoB or RhoC in limiting vascular leakage in both inflammatory conditions and during TEM. In conclusion, endothelial RhoB and RhoC are both dispensable for regulating leukocyte diapedesis and for maintaining vascular barrier function under inflammatory conditions and during leukocyte diapedesis.
Topics: Cells, Cultured; Human Umbilical Vein Endothelial Cells; Humans; Leukocytes; Transendothelial and Transepithelial Migration; rhoB GTP-Binding Protein; rhoC GTP-Binding Protein
PubMed: 28960175
DOI: 10.1080/21541248.2017.1377815 -
Small GTPases Jan 2017Inflammation is part of the complex biological response of body tissues to harmful stimuli, such as pathogens. It serves as a protective response that involves... (Review)
Review
Inflammation is part of the complex biological response of body tissues to harmful stimuli, such as pathogens. It serves as a protective response that involves leukocytes, blood vessels and molecular mediators with the purpose to eliminate the initial cause of cell injury and to initiate tissue repair. Inflammation is tightly regulated by the body and is associated with transient crossing of leukocytes through the blood vessel wall, a process called transendothelial migration (TEM) or diapedesis. TEM is a close collaboration between leukocytes on one hand and the endothelium on the other. Limiting vascular leakage during TEM but also when the leukocyte has crossed the endothelium is essential for maintaining vascular homeostasis. Although many details have been uncovered during the recent years, the molecular mechanisms from the vascular part that drive TEM still shows significant gaps in our understanding. This review will focus on the local signals that are induced in the endothelium that regulate leukocyte TEM and simultaneous preservation of endothelial barrier function.
Topics: Endothelium; Humans; Leukocytes; Signal Transduction; Transendothelial and Transepithelial Migration
PubMed: 27715453
DOI: 10.1080/21541248.2016.1197872 -
ELife Aug 2019Arrest of rapidly flowing neutrophils in venules relies on capturing through selectins and chemokine-induced integrin activation. Despite a long-established concept, we...
Arrest of rapidly flowing neutrophils in venules relies on capturing through selectins and chemokine-induced integrin activation. Despite a long-established concept, we show here that gene inactivation of activating paired immunoglobulin-like receptor (PILR)-β1 nearly halved the efficiency of neutrophil arrest in venules of the mouse cremaster muscle. We found that this receptor binds to CD99, an interaction which relies on flow-induced shear forces and boosts chemokine-induced β-integrin-activation, leading to neutrophil attachment to endothelium. Upon arrest, binding of PILR-β1 to CD99 ceases, shifting the signaling balance towards inhibitory PILR-α. This enables integrin deactivation and supports cell migration. Thus, flow-driven shear forces guide sequential signaling of first activating PILR-β1 followed by inhibitory PILR-α to prompt neutrophil arrest and then transmigration. This doubles the efficiency of selectin-chemokine driven neutrophil arrest by PILR-β1 and then supports transition to migration by PILR-α.
Topics: 12E7 Antigen; Animals; Blood Cells; CD18 Antigens; Mice; Neutrophils; Protein Binding; Receptors, Immunologic; Transendothelial and Transepithelial Migration
PubMed: 31385804
DOI: 10.7554/eLife.47642 -
Journal of Immunology (Baltimore, Md. :... Apr 2013Despite expanded definition of the leukocyte adhesion cascade and mechanisms underlying individual steps, very little is known about regulatory mechanisms controlling...
Despite expanded definition of the leukocyte adhesion cascade and mechanisms underlying individual steps, very little is known about regulatory mechanisms controlling sequential shifts between steps. We tested the hypothesis that metalloproteinases provide a mechanism to rapidly transition monocytes between different steps. Our study identifies diapedesis as a step targeted by metalloproteinase activity. Time-lapse video microscopy shows that the presence of a metalloproteinase inhibitor results in a doubling of the time required for human monocytes to complete diapedesis on unactivated or inflamed human endothelium, under both static and physiological-flow conditions. Thus, diapedesis is promoted by metalloproteinase activity. In contrast, neither adhesion of monocytes nor their locomotion over the endothelium is altered by metalloproteinase inhibition. We further demonstrate that metalloproteinase inhibition significantly elevates monocyte cell surface levels of integrins CD11b/CD18 (Mac-1), specifically during transendothelial migration. Interestingly, such alterations are not detected for other endothelial- and monocyte-adhesion molecules that are presumed metalloproteinase substrates. Two major transmembrane metalloproteinases, a disintegrin and metalloproteinase (ADAM)17 and ADAM10, are identified as enzymes that control constitutive cleavage of Mac-1. We further establish that knockdown of monocyte ADAM17, but not endothelial ADAM10 or ADAM17 or monocyte ADAM10, reproduces the diapedesis delay observed with metalloproteinase inhibition. Therefore, we conclude that monocyte ADAM17 facilitates the completion of transendothelial migration by accelerating the rate of diapedesis. We propose that the progression of diapedesis may be regulated by spatial and temporal cleavage of Mac-1, which is triggered upon interaction with endothelium.
Topics: ADAM Proteins; ADAM17 Protein; Cells, Cultured; Human Umbilical Vein Endothelial Cells; Humans; Macrophage-1 Antigen; Metalloproteases; Monocytes; Substrate Specificity; Time-Lapse Imaging; Transendothelial and Transepithelial Migration
PubMed: 23479224
DOI: 10.4049/jimmunol.1300046