Regulation Of Vascular Permeability Research Articles

Relationship of Cx43 regulation of vascular permeability to osteopontin-tight junction protein pathway after sepsis in rats.

Our previous study demonstrated that connexin (Cx)43 participated in the regulation of vascular permeability in severe sepsis. Osteopontin (OPN) has been demonstrated to participate in the occurrence of atherosclerosis, inflammation, as well as the adhesion and migration of cells. It is not clear whether OPN is involved in Cx43 regulating vascular permeability after sepsis and if it is related to tight-junction proteins. with the use of cecal ligation and puncture (CLP)-induced septic rats and lipopolysaccharide (LPS)-treated pulmonary vein vascular endothelial cells (VECs), the role of zona occuldens 1 (ZO-1) and claudin-5 in Cx43 regulation of vascular permeability and its relationship to OPN were investigated in the present study. The results showed that the expression of ZO-1 and claudin-5 in pulmonary vein were decreased in CLP rats and LPS-treated pulmonary vein VECs. Cx43-overexpressed lentivirus induced the degradation of ZO-1 and claudin-5, while Cx43 RNAi lentivirus abrogated the degradation of ZO-1 and claudin-5 induced by LPS. The vascular permeability and expression of OPN in pulmonary veins were significantly increased in CLP rats and LPS-treated pulmonary vein VECs. Silencing OPN by OPN RNAi lentivirus inhibited the vascular hyperpermeability induced by LPS. Overexpressed Cx43 lentivirus increased the expression of OPN and vascular permeability and downregulated the expression of ZO-1 and claudin-5 in pulmonary vein VECs. Silencing OPN by OPN RNAi lentivirus inhibited the effects of Cx43-overexpressed lentivirus on downregulation of ZO-1 and claudin-5 and vascular hyperpermeability in pulmonary vein VECs. Transfection of specific double-stranded RNA targeting to β-catenin and T-cell factor-4 (Tcf-4) abolished the upregulation of OPN induced by Cx43 overexpression. These results suggest that OPN participates in the regulation of vascular permeability by Cx43 after sepsis. Cx43 upregulation of OPN is via the Tcf-4/β-catenin transcription pathway; OPN increases vascular permeability by downregulating the expression of the tight junction proteins ZO-1 and claudin-5.

Zinc finger gene 217 (ZNF217) Promoted Ovarian Hyperstimulation Syndrome (OHSS) through Regulating E2 Synthesis and Inhibiting Thrombospondin-1 (TSP-1)

Zinc finger gene 217 (ZNF217) is a candidate gene of polycystic ovary syndrome (PCOS) which is vulnerable to ovarian hyperstimulation syndrome (OHSS). However, the relationship between ZNF217 and OHSS is largely unknown. Our study demonstrated that ZNF217 was mainly distributed in the granulosa cells of rat ovary. Significantly higher expression of ovarian ZNF217 was detected in OHSS rats, being consistent with serum 17β-estradiol concentration and ovarian aromatase. Moreover, OHSS rats also showed decreased ovarian TSP-1 mRNA, an acknowledged VEGF signaling suppressor. The same changes were detected in human granulosa cells and follicular fluid. Thus, the increased ZNF217 and decreased TSP-1 may participate in OHSS onset. In vitro experiment revealed that ZNF217 positively regulated E2 synthesis through promoting cAMP response element binding protein (CREB) and thereby CYP19A1 in KGN cells. Furthermore, ZNF217 negatively regulated TSP-1 in KGN cells while TSP-1 promoted claudin1 and inhibited nitric oxide (NO) in HUVECs and HAECs. Both of claudin1 and NO are responsible for the regulation of vascular permeability (VP). Therefore, we demonstrated that ZNF217 contributed to OHSS onset through promoting E2 synthesis and the increase of VP. Moreover, the increased ZNF217 and decreased TSP-1 provided new targets for the prevention or treatment of OHSS in the future.

Protective effects of angiopoietin-like 4 on the blood-brain barrier in acute ischemic stroke treated with thrombolysis in mice

AimsGiven the risk of blood-brain barrier damage (BBB) caused by ischemic and tissue plasminogen activator thrombolysis, the preservation of vascular integrity is important. Angiopoietin-like 4 (ANGPTL4), a protein secreted in hypoxia, is involved in the regulation of vascular permeability. We hypothesized that Angptl4 might exert a protective effect in thrombolysis through stabilizing blood-brain barrier and inhibit hyper-permeability. MethodsWe investigated the role of Angptl4 in stroke using a transient focal cerebral ischemia mouse model. The treated mice were administered Angptl4 1h after the ischemic event upon reperfusion. ResultsOur results showed that Angptl4 combined with thrombolysis greatly reduced the infarct volume and consequent neurological deficit. Western blot analyses and gelatin zymography revealed that Angptl4 protected the integrity of the endothelium damaged by thrombolysis. Angptl4 inhibited the up-regulation of vascular endothelial growth factor (VEGF) in the vascular endothelium after stroke, which was suppressed by counteracting VEGFR signaling and diminishing downstream Src signaling, and led to the increased stability of junctions and improved endothelial cell barrier integrity. ConclusionThese findings demonstrated that Angptl4 protects the permeability of the BBB damaged by ischemic and thrombolysis. Suggested that Angptl4 might be a promising target molecule in therapies for vasoprotection after thrombolysis treatment.

Dynamic Regulation of Vascular Permeability by Vascular Endothelial Cadherin-Mediated Endothelial Cell-Cell Junctions.

Endothelial cells lining blood vessels regulate vascular barrier function, which controls the passage of plasma proteins and circulating cells across the endothelium. In most normal adult tissues, endothelial cells preserve basal vascular permeability at a low level, while they increase permeability in response to inflammation. Therefore, vascular permeability is tightly controlled by a number of extracellular stimuli and mediators to maintain tissue homeostasis. Accordingly, impaired regulation of endothelial permeability causes various diseases, including chronic inflammation, asthma, edema, sepsis, acute respiratory distress syndrome, anaphylaxis, tumor angiogenesis, and diabetic retinopathy. Vascular endothelial (VE)-cadherin, a member of the classical cadherin superfamily, is a component of cell-to-cell adherens junctions in endothelial cells and plays an important role in regulating vascular permeability. VE-cadherin mediates intercellular adhesion through trans-interactions formed by its extracellular domain, while its cytoplasmic domain is anchored to the actin cytoskeleton via α- and β-catenins, leading to stabilization of VE-cadherin at cell-cell junctions. VE-cadherin-mediated cell adhesions are dynamically, but tightly, controlled by mechanisms that involve protein phosphorylation and reorganization of the actomyosin cytoskeleton. Phosphorylation of VE-cadherin, and its associated-catenins, results in dissociation of the VE-cadherin/catenin complex and internalization of VE-cadherin, leading to increased vascular permeability. Furthermore, reorganization of the actomyosin cytoskeleton by Rap1, a small GTPase that belongs to the Ras subfamily, and Rho family small GTPases, regulates VE-cadherin-mediated cell adhesions to control vascular permeability. In this review, we describe recent progress in understanding the signaling mechanisms that enable dynamic regulation of VE-cadherin adhesions and vascular permeability. In addition, we discuss the possibility of novel therapeutic approaches targeting the signaling pathways controlling VE-cadherin-mediated cell adhesion in diseases associated with vascular hyper-permeability.

Hyaluronic Acid in Vascular and Immune Homeostasis during Normal Pregnancy and Preeclampsia

Preeclampsia (PE) is a multisystem pathologic state that clinically manifests itself after the 20th week of pregnancy. It is characterized by high maternal and perinatal morbidity and mortality. According to modern concepts, the impairment of trophoblast invasion into maternal spiral arteries, leading to the development of ischemia in placenta, is considered to be the major pathogenetic factor of PE development. Ischemic lesions initiate the development of a systemic inflammatory response (SIR) and endothelial dysfunction, which is the main cause of the multiple organ failure in PE. Some data has appear indicating the importance of a glycans-forming endothelial glycocalyx and extracellular matrix (ECM) for placenta morphogenesis, as well as their role in the regulation of vascular permeability and vascular tone in hypertension disorders and, in particular, PE. Since intact glycocalyx and ECM are considered to be the major factors that maintain the physiological vascular tone and adequate intercellular interactions, their value in PE pathogenesis is underestimated. This review is focused on hyaluronic acid (HA) as the key glycan providing the organization and stabilization of the ECM and glycocalyx, its distribution in tissues in the case of presence or absence of placental pathology, as well as on the regulatory function of hyaluronic acids of various molecular weights in different physiological and pathophysiological processes. The summarized data will provide a better understanding of the PE pathogenesis, with the main focus on glycopathology.

Perivascular Macrophages Limit Permeability.

Perivascular cells, including pericytes, macrophages, smooth muscle cells, and other specialized cell types, like podocytes, participate in various aspects of vascular function. However, aside from the well-established roles of smooth muscle cells and pericytes, the contributions of other vascular-associated cells are poorly understood. Our goal was to ascertain the function of perivascular macrophages in adult tissues under nonpathological conditions. We combined confocal microscopy, in vivo cell depletion, and in vitro assays to investigate the contribution of perivascular macrophages to vascular function. We found that resident perivascular macrophages are associated with capillaries at a frequency similar to that of pericytes. Macrophage depletion using either clodronate liposomes or antibodies unexpectedly resulted in hyperpermeability. This effect could be rescued when M2-like macrophages, but not M1-like macrophages or dendritic cells, were reconstituted in vivo, suggesting subtype-specific roles for macrophages in the regulation of vascular permeability. Furthermore, we found that permeability-promoting agents elicit motility and eventual dissociation of macrophages from the vasculature. Finally, in vitro assays showed that M2-like macrophages attenuate the phosphorylation of VE-cadherin upon exposure to permeability-promoting agents. This study points to a direct contribution of macrophages to vessel barrier integrity and provides evidence that heterotypic cell interactions with the endothelium, in addition to those of pericytes, control vascular permeability.

Glycocalyx and its involvement in clinical pathophysiologies.

Vascular hyperpermeability is a frequent intractable feature involved in a wide range of diseases in the intensive care unit. The glycocalyx (GCX) seemingly plays a key role to control vascular permeability. The GCX has attracted the attention of clinicians working on vascular permeability involving angiopathies, and several clinical approaches to examine the involvement of the GCX have been attempted. The GCX is a major constituent of the endothelial surface layer (ESL), which covers most of the surface of the endothelial cells and reduces the access of cellular and macromolecular components of the blood to the surface of the endothelium. It has become evident that this structure is not just a barrier for vascular permeability but contributes to various functions including signal sensing and transmission to the endothelium. Because GCX is a highly fragile and unstable layer, the image had been only obtained by conventional transmission electron microscopy. Recently, advanced microscopy techniques have enabled direct visualization of the GCX in vivo, most of which use fluorescent-labeled lectins that bind to specific disaccharide moieties of glycosaminoglycan (GAG) chains. Fluorescent-labeled solutes also enabled to demonstrate vascular leakage under the in vivo microscope. Thus, functional analysis of GCX is advancing. A biomarker of GCX degradation has been clinically applied as a marker of vascular damage caused by surgery. Fragments of the GCX, such as syndecan-1 and/or hyaluronan (HA), have been examined, and their validity is now being examined. It is expected that GCX fragments can be a reliable diagnostic or prognostic indicator in various pathological conditions. Since GCX degradation is strongly correlated with disease progression, pharmacological intervention to prevent GCX degradation has been widely considered. HA and other GAGs are candidates to repair GCX; further studies are needed to establish pharmacological intervention. Recent advancement of GCX research has demonstrated that vascular permeability is not regulated by simple Starling’s law. Biological regulation of vascular permeability by GCX opens the way to develop medical intervention to control vascular permeability in critical care patients.

Select Rab GTPases Regulate the Pulmonary Endothelium via Endosomal Trafficking of Vascular Endothelial-Cadherin.

Pulmonary edema occurs in settings of acute lung injury, in diseases, such as pneumonia, and in acute respiratory distress syndrome. The lung interendothelial junctions are maintained in part by vascular endothelial (VE)-cadherin, an adherens junction protein, and its surface expression is regulated by endocytic trafficking. The Rab family of small GTPases are regulators of endocytic trafficking. The key trafficking pathways are regulated by Rab4, -7, and -9. Rab4 regulates the recycling of endosomes to the cell surface through a rapid-shuttle process, whereas Rab7 and -9 regulate trafficking to the late endosome/lysosome for degradation or from the trans-Golgi network to the late endosome, respectively. We recently demonstrated a role for the endosomal adaptor protein, p18, in regulation of the pulmonary endothelium through enhanced recycling of VE-cadherin to adherens junction. Thus, we hypothesized that Rab4, -7, and -9 regulate pulmonary endothelial barrier function through modulating trafficking of VE-cadherin-positive endosomes. We used Rab mutants with varying activities and associations to the endosome to study endothelial barrier function in vitro and in vivo. Our study demonstrates a key role for Rab4 activation and Rab9 inhibition in regulation of vascular permeability through enhanced VE-cadherin expression at the interendothelial junction. We further showed that endothelial barrier function mediated through Rab4 is dependent on extracellular signal-regulated kinase phosphorylation and activity. Thus, we demonstrate that Rab4 and -9 regulate VE-cadherin levels at the cell surface to modulate the pulmonary endothelium through extracellular signal-regulated kinase-dependent and -independent pathways, respectively. We propose that regulating select Rab GTPases represents novel therapeutic strategies for patients suffering with acute respiratory distress syndrome.

Unraveling Interactions Between Anesthetics and the Endothelium: Update and Novel Insights.

The vascular endothelium is one of the largest organs in the body and consists of a single layer of highly specialized cells with site-specific morphology and functions. Endothelial cells play a vital role in the regulation of vascular tone in arterial, venous, microvascular, and lymphatic vascular beds. The endothelium also coordinates angiogenesis and controls cell adhesion, fluid homeostasis, and both innate and adaptive immunity. Fundamental research has shown that general and local anesthetics markedly modulate the biological activities of endothelial cells under aerobic and ischemia-reperfusion conditions, making the endothelium an important target of anesthetics in the cardiovascular system. Halogenated volatile anesthetics provide significant anti-inflammatory actions and protect the endothelium against ischemia-reperfusion injury, despite their inhibiting effects on endothelium-dependent vasorelaxation. They provide not only acute but also potential long-term, beneficial effects. Although many effects of IV anesthetics on endothelial function are controversial, or completely unexplored, propofol and opioids appear to have the most favorable profile with respect to the preservation of endothelial function. Some opioids and ketamine have stereoselective effects on the endothelium. Finally, there is experimental evidence to suggest important effects of anesthetics on the regulation of vascular permeability, proliferation of stem cells, including endothelial progenitor cells, and promotion or inhibition of tumor growth, potentially related to alterations in angiogenesis. However, most of these findings are from in vitro experiments and await confirmation in an in vivo setting. Thus, the clinical implications of these interactions remain uncertain.

Morphological features of structure of aorta, coronal arteries and myocardium at chronic kidneys disease

The most important functions of endothelium are: hemostasis regulation, inflammation modulation, vascular tone correction, vascular permeability regulation. Chronic pulmonary disease (CPD) breaks this balance and predisposes vessels to vasoconstriction, leukocyte adhesion, platelet activation, mitogenesis, inflammation. The aim of the work was to study morphological changes of the cardiovascular walls and aorta in patients with CPD and to assess the possibilities of its endothelium to reparation. Materials and methods. There was studied an autopsy material of 18 died persons 45-55 years old. All died persons had the signs of chronic pulmonary disease (CPD). For detection of the immune cellular reaction features in zone of inflammation process there were used the primary homogenous antibodies (HGAB) of DAKO (Denmark), Rady-to-Use. The studies were carried out on microscope Primo Star (Carl Zeiss) using AxioCam (ERc 5s). Results and discussion: The changes of endothelium of coronary vessels of heart and aorta were demonstrated with the different degree of disorganization. These pathologic processes were familiar to the immune inflammation. The weak expression of the growth factor of VEGF and bcl-2 vessels endothelium can be the indirect sign of the low ability of the vascular wool structure and endothelium lining to reconstruction because an activation of apoptosis takes place at its deficiency. Conclusions. The changes of coronary arteries and aorta construction at CPD are characterized with unidirectional nature with the different intensity of pathologic process in all layers of the vascular wall and vascular transformation that is typical for immune inflammation. The detected disorders of vascular morphology and immunoinflammatory reaction activity can be the one of the main causes of cardiovascular complications development

Serial change of C1 inhibitor in patients with sepsis—a preliminary report

ObjectiveC1 inhibitor (C1INH) regulates not only the complement system but also the plasma kallikrein-kinin, fibrinolytic, and coagulation systems. The biologic activities of C1INH can be divided into the regulation of vascular permeability and anti-inflammatory functions. The objective was to clarify the serial change of C1INH in patients with sepsis. MethodsWe serially examined C1INH activity values (reference range, 70%-130%) and quantitative values (reference range, 160-330μg/mL) in patients with sepsis admitted into the intensive care unit of the Trauma and Acute Critical Care Center at Osaka University Hospital (Osaka, Japan) during the period between December 2012 and February 2013. We also analyzed their clinical course. We defined “refractory shock” as septic shock requiring steroid administration to maintain hemodynamics. ResultsThe serial change of C1INH was evaluated in 5 patients (4 survivors and 1 nonsurvivor). Two patients were diagnosed as having refractory shock. In the nonsurvivor after refractory shock, C1INH activity on admission was 97.2%, and the quantitative value was 133.1μg/mL. In the other patient with refractory shock, C1INH activity on admission was 94.4%, and the quantitative value was 126.7μg/mL. This patient's general condition had improved by day 6, with increases in C1INH activity (139.9%) and quantitative value (250.1μg/mL). In the 3 nonrefractory shock patients, C1INH activity on admission was 130.6%±8.7%, and the quantitative value was 215±26.5μg/mL. ConclusionsEnhancement of C1INH activity was not observed in the refractory shock patients, and the C1INH quantitative values were low. Further evaluation of the serial change of C1INH and the validity of C1INH replacement therapy in patients with septic shock may lead to a new strategy for sepsis management.

Targeting vascular and leukocyte communication in angiogenesis, inflammation and fibrosis

Regulation of vascular permeability, recruitment of leukocytes from blood to tissue and angiogenesis are all processes that occur at the level of the microvasculature during both physiological and pathological conditions. The interplay between microvascular cells and leukocytes during inflammation, together with the emerging roles of leukocytes in the modulation of the angiogenic process, make leukocyte-vascular interactions prime targets for therapeutics to potentially treat a wide range of diseases, including pathological and dysfunctional vessel growth, chronic inflammation and fibrosis. In this Review, we discuss how the different cell types that are present in and around microvessels interact, cooperate and instruct each other, and in this context we highlight drug targets as well as emerging druggable processes that can be exploited to restore tissue homeostasis.

Role of connexin 43 in vascular hyperpermeability and relationship to Rock1-MLC20pathway in septic rats

Connexin (Cx)43 has been shown to participate in several cardiovascular diseases. Increased vascular permeability is a common and severe complication in sepsis or septic shock. Whether or not Cx43 takes part in the regulation of vascular permeability in severe sepsis is not known, and the underlying mechanism has not been described. With cecal ligation and puncture-induced sepsis in rats and lipopolysaccharide (LPS)-treated vascular endothelial cells (VECs) from pulmonary veins, the role of Cx43 in increased vascular permeability and its relationship to the RhoA/Rock1 pathway were studied. It was shown that vascular permeability in the lungs, kidneys, and mesentery in sepsis rats and LPS-stimulated monolayer pulmonary vein VECs was significantly increased and positively correlated with the increased expression of Cx43 and Rock1 in these organs and cultured pulmonary vein VECs. The connexin inhibitor carbenoxolone (10 mg/kg iv) and the Rock1 inhibitor Y-27632 (2 mg/kg iv) alleviated the vascular leakage of lung, mesentery, and kidney in sepsis rats. Overexpressed Cx43 increased the phosphorylation of 20-kDa myosin light chain (MLC20) and the expression of Rock1 and increased the vascular permeability and decreased the transendothelial electrical resistance of pulmonary vein VECs. Cx43 RNA interference decreased the phosphorylation of MLC20 and the expression of Rock1 and decreased LPS-stimulated hyperpermeability of cultured pulmonary vein VECs. The Rock1 inhibitor Y-27632 alleviated LPS- and overexpressed Cx43-induced hyperpermeability of monolayer pulmonary vein VECs. This report shows that Cx43 participates in the regulation of vascular permeability in sepsis and that the mechanism is related to the Rock1-MLC20 phosphorylation pathway.

Endothelial Gαq/11is required for VEGF-induced vascular permeability and angiogenesis

VEGF A (VEGF-A) is a central regulator of pre- and postnatal vascular development. In vitro studies suggested that heterotrimeric G-proteins of the Gq/11 family contribute to VEGF receptor 2 (VEGFR2) signalling, but the mechanism and physiological relevance of this finding is unknown. The aim of this study is to understand the role of endothelial Gαq/11 in VEGF-dependent regulation of vascular permeability and angiogenesis. We show here that VEGF-A-induced signalling events, such as VEGFR2 autophosphorylation, calcium mobilization, or phosphorylation of Src and Cdh5, were reduced in Gαq/11-deficient endothelial cells (ECs), resulting in impaired VEGF-dependent barrier opening, tube formation, and proliferation. Agonists at Gq/11-coupled receptors facilitated VEGF-A-induced VEGFR2 autophosphorylation in a Gαq/11-dependent manner, thereby enhancing downstream VEGFR2 signalling. In vivo, EC-specific Gαq/11- and Gαq-deficient mice showed reduced VEGF-induced fluid extravasation, and retinal angiogenesis was significantly impaired. Gαq-deficient ECs showed reduced proliferation, Cdh5 phosphorylation, and fluid extravasation, whereas apoptosis was increased. Gαq/11 critically contributes to VEGF-A-dependent permeability control and angiogenic behaviour in vitro and in vivo.

Histamine Induces Vascular Hyperpermeability by Increasing Blood Flow and Endothelial Barrier Disruption In Vivo.

Histamine is a mediator of allergic inflammation released mainly from mast cells. Although histamine strongly increases vascular permeability, its precise mechanism under in vivo situation remains unknown. We here attempted to reveal how histamine induces vascular hyperpermeability focusing on the key regulators of vascular permeability, blood flow and endothelial barrier. Degranulation of mast cells by antigen-stimulation or histamine treatment induced vascular hyperpermeability and tissue swelling in mouse ears. These were abolished by histamine H1 receptor antagonism. Intravital imaging showed that histamine dilated vasculature, increased blood flow, while it induced hyperpermeability in venula. Whole-mount staining showed that histamine disrupted endothelial barrier formation of venula indicated by changes in vascular endothelial cadherin (VE-cadherin) localization at endothelial cell junction. Inhibition of nitric oxide synthesis (NOS) by L-NAME or vasoconstriction by phenylephrine strongly inhibited the histamine-induced blood flow increase and hyperpermeability without changing the VE-cadherin localization. In vitro, measurements of trans-endothelial electrical resistance of human dermal microvascular endothelial cells (HDMECs) showed that histamine disrupted endothelial barrier. Inhibition of protein kinase C (PKC) or Rho-associated protein kinase (ROCK), NOS attenuated the histamine-induced barrier disruption. These observations suggested that histamine increases vascular permeability mainly by nitric oxide (NO)-dependent vascular dilation and subsequent blood flow increase and maybe partially by PKC/ROCK/NO-dependent endothelial barrier disruption.

VEGF-induced blood flow increase causes vascular hyper-permeability in vivo

VEGF is known to cause vascular leak, its detailed mechanisms in vivo remain unclear. Here, we investigated the mechanisms underlying VEGF-induced vascular hyper-permeability focusing on two major regulators of vascular permeability: blood flow and endothelial barrier function. Administration of VEGF caused vascular hyper-permeability and tissue swelling in mouse ears, which were abolished by VEGF receptor-2 blockade. Intravital imaging showed that VEGF dilated ear arteries but not veins, and laser Doppler velocimetry showed that VEGF quickly increased tissue blood flow along with arterial dilation. Whole-mount immunostaining showed that VEGF phosphorylated endothelial nitric oxide synthase (eNOS) at residue Ser1177 and disrupted the alignment of vascular endothelial-cadherin (VE-cadherin) around the endothelial cell borders in mouse ear skin, indicating endothelial nitric oxide (NO) production and barrier disruption. Administration of the nitric oxide synthesis inhibitor, L-NAME, as well as the vasoconstrictor phenylephrine, abolished all VEGF-induced responses, including blood flow increase, dye leakage, and tissue swelling. However, these two treatments did not alter the intracellular localization of VE-cadherin-induced by VEGF. These observations underscore the importance of vascular dilation and, subsequent increase in blood flow, as well as, endothelial barrier disruption in the mechanisms of VEGF-induced vascular hyper-permeability.

Reorganization of actin and microtubule systems in human vein endothelial cells during intercellular contact formation

Endothelial cells tightly joined to each other line the interior surface of all vessels in living organisms and ensure the regulation of vascular permeability and exchange between the blood circulating in vessels and tissue fluids of those organs in which these vessels are located. In vitro, the endothelial cell monolayer retains the basic barrier function of the native endothelium. We use endothelial cells growing in vitro as a model system to study the interaction between cytoskeleton and adhesion structures in endotheliocytes. In the present paper, cultured human vein endothelial cells were used to quantify cytoskeleton alterations from cell spreading and formation of the first cell–cell contacts to confluent monolayer formation. The actin filament system in vein endothelial cells consists of a cortical network and stress fibers arranged parallel to the substrate. This cells express two isoforms of nonmuscle actin: β- and γ-cytoplasmic actins. Antibodies to β-actin stain actin filament bundles, whereas antibodies to γ-actin visualize cortical and lamellar networks. To evaluate the state of actin structures we analyzed their fluorescence intensity near the free edge and zone of cell–cell contacts. Fluorescence intensity of β-actin structures was higher in the areas of cell–cell contacts. Fluorescence of γ-actin was the highest at the leading edges of lamellae and the weakest in the stable edges of the cells with formed cell–cell contacts. The endothelial monolayer formation was accompanied by microtubule system alteration: the number of microtubules increased at the cell edge, and what was more, the quantity of microtubules in the area of the already-formed cell–cell contact always being higher than in the leading edge region.

Tubedown regulation of retinal endothelial permeability signaling pathways.

ABSTRACTTubedown (Tbdn; Naa15), a subunit of the N-terminal acetyltransferase NatA, complexes with the c-Src substrate Cortactin and supports adult retinal homeostasis through regulation of vascular permeability. Here we investigate the role of Tbdn expression on signaling components of retinal endothelial permeability to understand how Tbdn regulates the vasculature and supports retinal homeostasis. Tbdn knockdown-induced hyperpermeability to Albumin in retinal endothelial cells was associated with an increase in the levels of activation of the Src family kinases (SFK) c-Src, Fyn and Lyn and phospho-Cortactin (Tyr421). The knockdown of Cortactin expression reduced Tbdn knockdown-induced permeability to Albumin and the levels of activated SFK. Inhibition of SFK in retinal endothelial cells decreased Tbdn knockdown-induced permeability to Albumin and phospho-Cortactin (Tyr421) levels. Retinal lesions of endothelial-specific Tbdn knockdown mice, with tissue thickening, fibrovascular growth, and hyperpermeable vessels displayed an increase in the levels of activated c-Src. Moreover, the retinal lesions of patients with proliferative diabetic retinopathy (PDR) associated with a loss of Tbdn expression and hyperpermeability to Albumin displayed increased levels of activated SFK in retinal blood vessels. Taken together, these results implicate Tbdn as an important regulator of retinal endothelial permeability and homeostasis by modulating a signaling pathway involving c-Src and Cortactin.

Structure-Function Analysis of the Non-Muscle Myosin Light Chain Kinase (nmMLCK) Isoform by NMR Spectroscopy and Molecular Modeling: Influence of MYLK Variants.

The MYLK gene encodes the multifunctional enzyme, myosin light chain kinase (MLCK), involved in isoform-specific non-muscle and smooth muscle contraction and regulation of vascular permeability during inflammation. Three MYLK SNPs (P21H, S147P, V261A) alter the N-terminal amino acid sequence of the non-muscle isoform of MLCK (nmMLCK) and are highly associated with susceptibility to acute lung injury (ALI) and asthma, especially in individuals of African descent. To understand the functional effects of SNP associations, we examined the N-terminal segments of nmMLCK by 1H-15N heteronuclear single quantum correlation (HSQC) spectroscopy, a 2-D NMR technique, and by in silico molecular modeling. Both NMR analysis and molecular modeling indicated SNP localization to loops that connect the immunoglobulin-like domains of nmMLCK, consistent with minimal structural changes evoked by these SNPs. Molecular modeling analysis identified protein-protein interaction motifs adversely affected by these MYLK SNPs including binding by the scaffold protein 14-3-3, results confirmed by immunoprecipitation and western blot studies. These structure-function studies suggest novel mechanisms for nmMLCK regulation, which may confirm MYLK as a candidate gene in inflammatory lung disease and advance knowledge of the genetic underpinning of lung-related health disparities.

The hydrocortisone protection of glycocalyx on the intestinal capillary endothelium during severe acute pancreatitis.

Malfunctioning of the intestinal microcirculation secondary to severe acute pancreatitis (SAP) can cause injuries to the intestinal mucosal barrier, translocation of gut flora, and sepsis. The glycocalyx on the vascular endothelium helps maintain its normal function through multiple mechanisms, including regulation of vascular permeability and inhibition of intercellular adhesion. It is unknown that whether pancreatitis inflicts injuries to the intestinal mucosal barrier through damaging glycocalyx or stabilizing glycocalyx can be a potential therapeutic target in maintaining the integrity of the intestinal mucosal barrier during SAP. Injecting sodium taurocholate into the pancreatic duct of Sprague-Dawley rats induced SAP. Intestinal perfusion, changes in endothelial glycocalyx, and the associated molecular mechanisms were assessed by laser Doppler velocimetry, electron microscopy, and the levels of heparan sulfate, syndacan-1, and tumor necrosis factor-α (TNF-α) in the superior mesenteric vein. Protective effects of hydrocortisone treatment in the intestinal microcirculation during SAP were evaluated. Degradation of the glycocalyx in intestinal vascular endothelium developed 3 h after the onset of SAP in rats. By 12 h, significant reduction of intestinal perfusion was observed. The concomitant elevated levels of TNF-α in the superior mesenteric vein suggest that TNF-α is involved in the degradation of the glycocalyx. With the use of hydrocortisone, intestinal perfusion was improved and the degradation of glycocalyx was reduced. The degradation of glycocalyx is involved in the malfunction of the intestinal microcirculation. The massive release of TNF-α participates in this process and leads to glycocalyx degradation. Hydrocortisone may be a good therapy to prevent this process.