ID: 114: AN ANTAGONIST OF LYSOPHOSPHATIDIC ACID RECEPTOR1, AM966, INCREASES PULMONARY ENDOTHELIAL PERMEABILITY THROUGH ACTIVATION OF VE-CADHERIN

2016 ◽  
Vol 64 (4) ◽  
pp. 965.3-966
Author(s):  
J Cai ◽  
J Wei ◽  
AM Jacko ◽  
J Zhao

BackgroundMaintenance of pulmonary endothelial barrier integrity is important for reducing severity of lung injury. VE-cadherin is a major component of cell–cell adherens junctions in endothelium. In response to inflammatory stimuli, VE-cadherin is tyrosine phosphorylated, resulting in dissociation with catenins, which links to f-actin. Lysophosphatidic acid (LPA) is a bioactive lysophospholipid, which regulates cell motility. LPA has been shown to increase lung epithelial barrier integrity, while it reduces endothelial barrier function. AM966 is an antagonist exhibiting an anti-fibrotic property. However, the effect of AM966 on pulmonary endothelial barrier integrity has not been well studied.Methods and ResultsTo investigate endothelial barrier integrity, electric cell-substrate sensing (ECIS) system was used to measure permeability in human lung microvascular endothelial cells (HLMVECs). Similar to the effect of LPA, AM966 increases permeability immediately in a dose dependent manner. To investigate the molecular mechanism by which regulates AM966-mediated reduction of endothelial barrier function, HLMVECs were treated with AM966, and then phosphorylation of myosin light chain (MLC) and VE-cadherin were determined by immunoblotting. AM966 increased phosphorylation of MLC and VE-cadherin. VE-cadherin and f-actin double immunostaining revealed that AM966 induces gap formation and f-actin stress fibers as well as dissociation between VE-cadherin and f-actin.ConclusionThis study reveals that AM966 induces lung endothelial barrier dysfunction, which is regulated by phosphorylation of VE-cadherin.This work was supported by the National Institutes of Health (R01GM115389 to J.Z.), American Heart Association 12SDG9050005 (J.Z.), American Lung Association Biomedical Research Grant RG350146 (J.Z.).

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Junting Cai ◽  
Jianxin Wei ◽  
Shuang Li ◽  
Tomeka Suber ◽  
Jing Zhao

Maintenance of pulmonary endothelial barrier integrity is important for reducing severity of lung injury. Lysophosphatidic acid (LPA) regulates cell motility, cytoskeletal rearrangement, and cell growth. Knockdown of LPA receptor 1 (LPA1) has been shown to mitigate lung injury and pulmonary fibrosis. AM966, an LPA1 antagonist exhibiting an antifibrotic property, has been considered to be a future antifibrotic medicine. Here, we report an unexpected effect of AM966, which increases lung endothelial barrier permeability. An electric cell-substrate sensing (ECIS) system was used to measure permeability in human lung microvascular endothelial cells (HLMVECs). AM966 decreased the transendothelial electrical resistance (TEER) value immediately in a dose-dependent manner. VE-cadherin and f-actin double immunostaining reveals that AM966 increases stress fibers and gap formation between endothelial cells. AM966 induced phosphorylation of myosin light chain (MLC) through activation of RhoA/Rho kinase pathway. Unlike LPA treatment, AM966 had no effect on phosphorylation of extracellular signal-regulated kinases (Erk). Further, in LPA1 silencing cells, we observed that AM966-increased lung endothelial permeability as well as phosphorylation of VE-cadherin and focal adhesion kinase (FAK) were attenuated. This study reveals that AM966 induces lung endothelial barrier dysfunction, which is regulated by LPA1-mediated activation of RhoA/MLC and phosphorylation of VE-cadherin.


2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Maura Knapp ◽  
Mei Zheng ◽  
Nikola Sladojevic ◽  
Qiong Zhao ◽  
Konstaintin G Birukov ◽  
...  

Background: Diabetes leads to endothelial barrier dysfunction and altered endothelial permeability, which results in increased cardiovascular risk. ARNT, also known as HIF-1β, a transcription factor that functions as a master regulator of glucose homeostasis, has been implicated in diabetes. Endothelial-specific ARNT deletion (ArntΔEC) in mice is embryonically lethal, with hemorrhage occurring in the heart during the embryonic stage. However, the particular role of endothelial ARNT(ecARNT) in diabetes is largely unknown. We have found a significant decrease in ARNT expression in both diabetic rodent endothelial cells and diabetic human hearts. We hypothesize that a loss of ecARNT mediates endothelial barrier dysfunction during diabetes. Methods and Results: We generated inducible endothelial specific ARNT knockout mice (ecARNT-/-) by crossing mice with loxP sequences flanking exon 6 of ARNT with Cre ERT2 mice under the VE-cadherin promoter. A 90% deletion of ecARNT was achieved following two weeks of oral tamoxifen administration. ecARNT-/- mice exhibit severe blood vessel leakage, which is restricted to the heart, suggesting a distinct function for ecARNT in different tissues. Cardiomyopathy is evident 6 months after ARNT deletion. In vitro , trans-endothelial electrical resistance (TER) and transwell assays have confirmed endothelial barrier disruption in cardiac microvascular endothelial cells (CMEC) isolated from both ecARNT-/- hearts and diabetic (DB/DB) mouse hearts. To determine the underlying mechanisms by which ARNT may regulate endothelial barrier function, we performed DNA sequencing on CMEC isolated from control, ecARNT-/-, and DB/DB mice. Data suggest a significant increase in TNFa signaling, including ELAM-1 and ICAM-1 in CMEC isolated from ecARNT-/- CMEC and diabetic CMEC. Moreover, use of anti-TNFa antibody rescues endothelial barrier dysfunction in CMEC isolated from ecARNT-/- mice. Taken together, these results suggest that a reduction in ecARNT during diabetes may mediate endothelial barrier dysfunction through a TNFa signaling pathway. Conclusion: ecARNT is a critical mediator of endothelial barrier function and could potentially serve as a therapeutic target for diabetic cardiovascular diseases.


1997 ◽  
Vol 272 (1) ◽  
pp. L38-L43 ◽  
Author(s):  
S. Hippenstiel ◽  
S. Tannert-Otto ◽  
N. Vollrath ◽  
M. Krull ◽  
I. Just ◽  
...  

The endothelial cytoskeleton is important for the regulation of endothelial barrier function. Small GTP-binding Rho proteins play a central role in the organization of the microfilament system. Clostridium difficile toxin B (TcdB) inactivates Rho proteins by glucosylation at Thr-37. We used TcdB as a probe to study the role of Rho proteins in the regulation of endothelial barrier function. TcdB time (50-170 min) and dose (10-100 ng/ml) dependently increased the hydraulic conductivity of cultured porcine pulmonary artery endothelial cell monolayers approximately 10-fold. Simultaneously, the albumin reflection coefficient decreased substantially from 0.8 to 0.15. Before endothelial hyperpermeability, TcdB reduced F-actin content in a dose-dependent manner, whereas G-actin content remained unchanged. Finally, we proved that TcdB caused dose (5-100 ng/ml)- and time-dependent glucosylation of Rho proteins in endothelial cells. Phalloidin, which stabilizes filamentous actin, prevented the effect of TcdB on endothelial permeability. In contrast to thrombin-, hydrogen peroxide-, or Escherichia coli hemolysin-induced hyperpermeability, the elevation of cyclic nucleotides did not block TcdB-related permeability. The data demonstrate a central role of small GTP-binding Rho proteins for the control of endothelial barrier function.


2019 ◽  
Vol 316 (6) ◽  
pp. L1118-L1126 ◽  
Author(s):  
Karthik Suresh ◽  
Kathleen Carino ◽  
Laura Johnston ◽  
Laura Servinsky ◽  
Carolyn E. Machamer ◽  
...  

Noncanonical roles for caspase-3 are emerging in the fields of cancer and developmental biology. However, little is known of nonapoptotic functions of caspase-3 in most cell types. We have recently demonstrated a disassociation between caspase-3 activation and execution of apoptosis with accompanying cytoplasmic caspase-3 sequestration and preserved endothelial barrier function. Therefore, we tested the hypothesis that nonapoptotic caspase-3 activation promotes endothelial barrier integrity. Human lung microvascular endothelial cells were exposed to thrombin, a nonapoptotic stimulus, and endothelial barrier function was assessed using electric cell-substrate impedance sensing. Actin cytoskeletal rearrangement and paracellular gap formation were assessed using phalloidin staining. Cell stiffness was evaluated using magnetic twisting cytometry. In addition, cell lysates were harvested for protein analyses. Caspase-3 was inhibited pharmacologically with pan-caspase and a caspase-3-specific inhibitor. Molecular inhibition of caspase-3 was achieved using RNA interference. Cells exposed to thrombin exhibited a cytoplasmic activation of caspase-3 with transient and nonapoptotic decrease in endothelial barrier function as measured by a drop in electrical resistance followed by a rapid recovery. Inhibition of caspases led to a more pronounced and rapid drop in thrombin-induced endothelial barrier function, accompanied by increased endothelial cell stiffness and paracellular gaps. Caspase-3-specific inhibition and caspase-3 knockdown both resulted in more pronounced thrombin-induced endothelial barrier disruption. Taken together, our results suggest cytoplasmic caspase-3 has nonapoptotic functions in human endothelium and can promote endothelial barrier integrity.


1993 ◽  
Vol 264 (4) ◽  
pp. C894-C905 ◽  
Author(s):  
S. E. Goldblum ◽  
X. Ding ◽  
J. Campbell-Washington

Tumor necrosis factor-alpha (TNF-alpha) influences pulmonary vascular endothelial barrier function in vitro. We studied whether recombinant TNF-alpha (rTNF-alpha) regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to human rTNF-alpha (1,000 U/ml) and evaluated for 1) transendothelial [14C]albumin flux, 2) F-actin organization with fluorescence microscopy, 3) F-actin quantitation by spectrofluorometry, and 4) monomeric G-actin levels by the deoxyribonuclease I inhibition assay. rTNF-alpha induced increments in [14C]albumin flux (P < 0.04) and intercellular gap formation at > or = 2-6 h. During this same time, the endothelial F-actin pool decreased (P = 0.0064), with reciprocal increases in the G-actin pool (P < 0.0001). Prior F-actin stabilization with phallicidin protected against the rTNF-alpha-induced increments in G-actin (P < 0.002) as well as changes in barrier function (P < 0.01). Prior protein synthesis inhibition enhanced the rTNF-alpha-induced decrement in F-actin (P < 0.0001), blunted the G-actin increment (P < 0.002), and increased rTNF-alpha-induced changes in endothelial barrier function (P < 0.003). Therefore, rTNF-alpha induces pulmonary vascular endothelial F-actin depolymerization, intercellular gap formation, and barrier dysfunction. rTNF-alpha also increased total actin (P < 0.02) and new actin synthesis (P < 0.002), which may be a compensatory endothelial cell response to rTNF-alpha-induced F-actin depolymerization.


Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Hiroshi Ohkawra ◽  
Yidan D. Zhao ◽  
Asrar B. Malik

We investigated the use of bone-marrow derived endothelial progenitor cells (EPCs) for the treatment of microvascular endothelial injury caused by inflammatory diseases. As activation of the monomeric RhoGTPase Cdc42 signals annealing of adherens junctions (AJs) in the endothelial barrier, we examined the possibility that EPCs could restore endothelial barrier dysfunction by promoting Cdc42 activation in endothelial cells (ECs). We observed that co-culture of EPCs with ECs prevented the decrease in transendothelial electrical resistance (TER), a measure of AJ assembly, and the decrease in VE-cadherin expression induced by thrombin (4 U/mL). EPCs also significantly reduced the formation of inter-endothelial gaps mediated by RhoA activation as well as myosin light chain phosphorylation in response to thrombin. We showed that EPCs induced activation of Cdc42 in ECs and increased TER within 15 min after the addition EPCs to ECs, indicating the enhancement of endothelial barrier function. Addition of EPCs after thrombin-induced disruption of AJs also promoted rapid recovery of TER compared to controls. Based on siRNA knockdown data, the endothelial barrier protective effect of EPCs was mediated by Cdc42 activation in ECs. Thus, EPC-mediated activation of Cdc42 in ECs decreases basal endothelial permeability and prevents endothelial hyper-permeability induced by the mediator thrombin. EPC/EC cross-talk is a critical mechanism regulating endothelial barrier function suggesting the value of EPCs in the treatment of microvascular injury associated with vascular inflammation.


2020 ◽  
Vol 127 (8) ◽  
pp. 1056-1073 ◽  
Author(s):  
Nikolaos Kakogiannos ◽  
Laura Ferrari ◽  
Costanza Giampietro ◽  
Anna Agata Scalise ◽  
Claudio Maderna ◽  
...  

Rationale: Intercellular tight junctions are crucial for correct regulation of the endothelial barrier. Their composition and integrity are affected in pathological contexts, such as inflammation and tumor growth. JAM-A (junctional adhesion molecule A) is a transmembrane component of tight junctions with a role in maintenance of endothelial barrier function, although how this is accomplished remains elusive. Objective: We aimed to understand the molecular mechanisms through which JAM-A expression regulates tight junction organization to control endothelial permeability, with potential implications under pathological conditions. Methods and Results: Genetic deletion of JAM-A in mice significantly increased vascular permeability. This was associated with significantly decreased expression of claudin-5 in the vasculature of various tissues, including brain and lung. We observed that C/EBP-α (CCAAT/enhancer-binding protein-α) can act as a transcription factor to trigger the expression of claudin-5 downstream of JAM-A, to thus enhance vascular barrier function. Accordingly, gain-of-function for C/EBP-α increased claudin-5 expression and decreased endothelial permeability, as measured by the passage of fluorescein isothiocyanate (FITC)-dextran through endothelial monolayers. Conversely, C/EBP-α loss-of-function showed the opposite effects of decreased claudin-5 levels and increased endothelial permeability. Mechanistically, JAM-A promoted C/EBP-α expression through suppression of β-catenin transcriptional activity, and also through activation of EPAC (exchange protein directly activated by cAMP). C/EBP-α then directly binds the promoter of claudin-5 to thereby promote its transcription. Finally, JAM-A–C/EBP-α–mediated regulation of claudin-5 was lost in blood vessels from tissue biopsies from patients with glioblastoma and ovarian cancer. Conclusions: We describe here a novel role for the transcription factor C/EBP-α that is positively modulated by JAM-A, a component of tight junctions that acts through EPAC to up-regulate the expression of claudin-5, to thus decrease endothelial permeability. Overall, these data unravel a regulatory molecular pathway through which tight junctions limit vascular permeability. This will help in the identification of further therapeutic targets for diseases associated with endothelial barrier dysfunction. Graphic Abstract: An graphic abstract is available for this article.


2014 ◽  
Vol 307 (12) ◽  
pp. L924-L935 ◽  
Author(s):  
Dolly Mehta ◽  
Krishnan Ravindran ◽  
Wolfgang M. Kuebler

Endothelial barrier function is an essential and tightly regulated process that ensures proper compartmentalization of the vascular and interstitial space, while allowing for the diffusive exchange of small molecules and the controlled trafficking of macromolecules and immune cells. Failure to control endothelial barrier integrity results in excessive leakage of fluid and proteins from the vasculature that can rapidly become fatal in scenarios such as sepsis or the acute respiratory distress syndrome. Here, we highlight recent advances in our understanding on the regulation of endothelial permeability, with a specific focus on the endothelial glycocalyx and endothelial scaffolds, regulatory intracellular signaling cascades, as well as triggers and mediators that either disrupt or enhance endothelial barrier integrity, and provide our perspective as to areas of seeming controversy and knowledge gaps, respectively.


2012 ◽  
Vol 32 (suppl_1) ◽  
Author(s):  
Thomas Helbing ◽  
Elena Ketterer ◽  
Bianca Engert ◽  
Jennifer Heinke ◽  
Sebastian Grundmann ◽  
...  

Introduction: Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome, are associated with high morbidity and mortality in patients. During the progression of ALI, the endothelial cell barrier of the pulmonary vasculature becomes compromised, leading to pulmonary edema, a characteristic feature of ALI. It is well-established that EC barrier dysfunction is initiated by cytoskeletal remodeling, which leads to disruption of cell-cell contacts and formation of paracellular gaps, allowing penetration of protein-rich fluid and inflammatory cells. Bone morphogenetic proteins (BMPs) are important players in endothelial dysfunction and inflammation but their effects on endothelial permeability in ALI have not been investigated until now. Methods and Results: As a first approach to assess the role of BMPs in acute lung injury we analysed BMP4 and BMPER expression in an infectious (LPS) and a non-infectious (bleomycin) mouse models of acute lung injury. In both models BMP4 and BMPER protein expression levels were reduced demonstrated by western blots, suggesting that BMPs are involved in progression ALI. To assess the role of BMPs on vascular leakage, a key feature of ALI, BMP activity in mice was inhibited by i.p. administration of LDN193189, a small molecule that blocks BMP signalling. After 3 days Evans blue dye (EVB) was administered i.v. and dye extravasation into the lungs was quantified as a marker for vascular leakage. Interestingly, LDN193189 significantly increased endothelial permeability compared to control lungs, indicating that BMP signaling is involved in maintenance of endothelial barrier function. To quantify effects of BMP inhibition on endothelial barrier function in vitro, HUVECs were seeded onto transwell filters and were exposed to LDN193189. After 3 days FITC-dextrane was added and passage into the lower chamber was quantified as a marker for endothelial barrier function. Thrombin served as a positive control. As expected from our in vivo experiments inhibition of BMP signaling by LDN193189 enhanced FITC-dextrane passage. To study specific effects of BMPs on endothelial barrier function, two protagonist of the BMP family, BMP2 and BMP4, or BMP modulator BMPER were tested in the transwell assay in vitro. Interestingly BMP4 and BMPER, but not BMP2, reduced FITC-dextrane passage demonstrating that BMP4 and BMPER improved endothelial barrier function. Vice versa, specific knock down of BMP4 or BMPER increased leakage in transwell assays. Im immuncytochemistry silencing of BMPER or BMP4 induced hyperpermeability as a consequence of a pro-inflammatory endothelial phenotype characterised by reduced cell-cell contacts and increased actin stress fiber formation. Additionally, the pro-inflammatory endothelial phenotype was confirmed by real-time revealing increased expression of adhesion molecules ICAM-1 or proinflammatory cytokines such as IL-6 and IL-8 in endothelial cells after BMPER or BMP4 knock down. Confirming these in vitro results BMPER +/- mice exhibit increased extravasation of EVB into the lungs, indicating that partial loss of BMPER impairs endothelial barrier function in vitro and in vivo. Conclusion: We identify BMPER and BMP4 as local regulators of vascular permeability. Both are protective for endothelial barrier function and may open new therapeutic avenues in the treatment of acute lung injury.


Author(s):  
Bo-Wen Xu ◽  
Zhi-Qiang Cheng ◽  
Xu-Ting Zhi ◽  
Xiao-Mei Yang ◽  
Zhi-Bo Yan

Abstract Endothelial barrier integrity requires recycling of VE-cadherin to adherens junctions. Both p18 and Rab11a play significant roles in VE-cadherin recycling. However, the underlying mechanism and the role of p18 in activating Rab11a have yet to be elucidated. Performing in vitro and in vivo experiments, we showed that p18 protein bound to VE-cadherin before Rab11a through its VE-cadherin-binding domain (aa 1–39). Transendothelial resistance showed that overexpression of p18 promoted the circulation of VE-cadherin to adherens junctions and the recovery of the endothelial barrier. Silencing of p18 caused endothelial barrier dysfunction and prevented Rab11a-positive recycling endosome accumulation in the perinuclear recycling compartments. Furthermore, p18 knockdown in pulmonary microvessels markedly increased vascular leakage in mice challenged with lipopolysaccharide and cecal ligation puncture. This study showed that p18 regulated the pulmonary endothelial barrier function in vitro and in vivo by regulating the binding of Rab11a to VE-cadherin and the activation of Rab11a.


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