VE-cadherin Cleavage Research Articles

Endothelial cell sphingosine 1-phosphate receptor 1 restrains VE-cadherin cleavage and attenuates experimental inflammatory arthritis.

In rheumatoid arthritis, inflammatory mediators extravasate from blood into joints via gaps between endothelial cells (ECs), but the contribution of ECs is not known. Sphingosine 1-phosphate receptor 1 (S1PR1), widely expressed on ECs, maintains the vascular barrier. Here, we assessed the contribution of vascular integrity and EC S1PR1 signaling to joint damage in mice exposed to serum-induced arthritis (SIA). EC-specific deletion of S1PR1 or pharmacological blockade of S1PR1 promoted vascular leak and amplified SIA, whereas overexpression of EC S1PR1 or treatment with an S1PR1 agonist delayed SIA. Blockade of EC S1PR1 induced membrane metalloproteinase-dependent cleavage of vascular endothelial cadherin (VE-cadherin), a principal adhesion molecule that maintains EC junctional integrity. We identified a disintegrin and a metalloproteinase domain 10 (ADAM10) as the principal VE-cadherin "sheddase." Mice expressing a stabilized VE-cadherin construct had decreased extravascular VE-cadherin and vascular leakage in response to S1PR1 blockade, and they were protected from SIA. Importantly, patients with active rheumatoid arthritis had decreased circulating S1P and microvascular expression of S1PR1, suggesting a dysregulated S1P/S1PR1 axis favoring vascular permeability and vulnerability. We present a model in which EC S1PR1 signaling maintains homeostatic vascular barrier function by limiting VE-cadherin shedding mediated by ADAM10 and suggest this signaling axis as a therapeutic target in inflammatory arthritis.

Molecular Mechanisms of Endothelialitis in SARS-CoV-2 Infection: Evidence for VE-Cadherin Cleavage by ACE2.

Long COVID-19 syndrome appears after Severe Acute Respiratory Syndrome-Corona Virus (SARS-CoV-2) infection with acute damage to microcapillaries, microthrombi, and endothelialitis. However, the mechanisms involved in these processes remain to be elucidated. All blood vessels are lined with a monolayer of endothelial cells called vascular endothelium, which provides a the major function is to prevent coagulation. A component of endothelial cell junctions is VE-cadherin, which is responsible for maintaining the integrity of the vessels through homophilic interactions of its Ca++-dependent adhesive extracellular domain. Here we provide the first evidence that VE-cadherin is a target in vitro for ACE2 cleavage because its extracellular domain (hrVE-ED) contains two amino acid sequences for ACE2 substrate recognition at the positions 256P-F257 and 321PMKP-325L. Indeed, incubation of hrVE-ED with the active ectopeptidase hrACE2 for 16 hrs in the presence of 10 μM ZnCl2 showed a dose-dependent (from 0.2 ng/μL to 2 ng/μL) decrease of the VE-cadherin immunoreactive band. In vivo, in the blood from patients having severe COVID-19 we detected a circulating form of ACE2 with an apparent molecular mass of 70 kDa, which was barely detectable in patients with mild COVID-19. Of importance, in the patients with severe COVID-19 disease, the presence of three soluble fragments of VE-cadherin (70, 62, 54 kDa) were detected using the antiEC1 antibody while only the 54 kDa fragment was present in patients with mild disease. Altogether, these data clearly support a role for ACE2 to cleave VE-cadherin, which leads to potential biomarkers of SARS-CoV-2 infection related with the vascular disease in "Long COVID-19".

Abstract 132: Mechanism By Which Coagulation Factor XI Regulates Endothelial Cell Permeability And Barrier Function In Vitro And In Vivo

Introduction: Proteolysis of vascular endothelial (VE)-cadherin is a biomarker for disruption of endothelial cell (EC) barrier function, with elevated levels of soluble VE (sVE)-cadherin associated with atherosclerosis and sepsis. Factor XI (FXI) plays a regulatory role in inflammation, and while a relationship between FXI activity and VE-cadherin expression levels has been observed, the mechanism by which this process is mediated is unknown. Hypothesis: Activated FXI (FXIa) induces VE-cadherin proteolysis. Methods: Human umbilical vein ECs were stimulated with FXIa (30 and 5 nM) for six hours. Western blot analysis was used to study VE-cadherin proteolysis, disintegrin and metalloproteinase 10 (ADAM10) expression, FXIa-PAI-1 or -very low density lipoprotein receptor (VLDLR) interactions, and cell signaling events. SVE-cadherin in baboons challenged with Staphylococcus aureus was detected by ELISA. Results: FXIa (5 nM) generated a VE-cadherin fragment and increased ECs permeability; the serine protease inhibitor, PPACK, and an inhibitor of ADAM10 reversed these processes. FXIa induced the expression of active ADAM10 on ECs. The receptor-associated protein (RAP) blocked FXIa-induced VE-cadherin proteolysis by preventing FXIa interaction with PAI-1 and VLDLR on ECs. FXIa-VLDLR interaction induced Dab1 and Src kinases phosphorylation. FXIa activated the VEGFR2-PLCgamma1-ERK1/2 signaling pathway. The ERK1/2 inhibitor, LY3214996, and the Src kinases inhibitor, PP2, inhibited VE-cadherin proteolysis by FXIa. PLCgamma1 phosphorylation was also prevented with PP2. The VEGFR2 kinase inhibitor, SU1498, prevented the cleavage of VE-cadherin by FXIa; in contrast, a VEGF blocking antibody had no effect on FXIa-induced VE-cadherin cleavage. Finally, the inhibition of FXI activation in a baboon model of sepsis significantly decreased the levels of sVE-cadherin. Conclusion: The complex formation of FXIa with PAI-1 and VLDLR promoted Src kinase phosphorylation. Src activation triggered the VEGFR2-PLCgamma1-ERK1/2 signaling pathway, which induced the trafficking of active ADAM10 to the EC surfaces inducing the cleavage of VE-cadherin. FXI may be a druggable target to protect EC barrier function in inflammatory diseases.

Inhibition of Vascular Endothelial Cadherin Cleavage Prevents Elastic Fiber Alterations and Atherosclerosis Induced by Intermittent Hypoxia in the Mouse Aorta.

Intermittent hypoxia (IH), the major feature of obstructive sleep apnea syndrome (OSAS), induces atherosclerosis and elastic fiber alterations. VE-cadherin cleavage is increased in OSAS patients and in an IH-cellular model. It is mediated by HIF-1 and Src-tyr-kinases pathways and results in endothelial hyperpermeability. Our aim was to determine whether blocking VE-cadherin cleavage in vivo could be an efficient strategy to inhibit deleterious IH-induced vascular remodeling, elastic fiber defects and atherogenesis. VE-cadherin regulation, aortic remodeling and atherosclerosis were studied in IH-exposed C57Bl/6J or ApoE-/-mice treated or not with Src-tyr-kinases inhibitors (Saracatinib/Pazopanib) or a HIF-1 inhibitor (Acriflavine). Human aortic endothelial cells were exposed to IH and treated with the same inhibitors. LDL and the monocytes transendothelium passage were measured. In vitro, IH increased transendothelium LDL and monocytes passage, and the tested inhibitors prevented these effects. In mice, IH decreased VE-cadherin expression and increased plasmatic sVE level, intima-media thickness, elastic fiber alterations and atherosclerosis, while the inhibitors prevented these in vivo effects. In vivo inhibition of HIF-1 and Src tyr kinase pathways were associated with the prevention of IH-induced elastic fiber/lamella degradation and atherogenesis, which suggests that VE-cadherin could be an important target to limit atherogenesis and progression of arterial stiffness in OSAS.

VE-cadherin cleavage in obstructive sleep apnea syndrome: Signalling pathway and proteases as anti-atherogenic targets

Cardiovascular complications of obstructive sleep apnea syndrome (OSA), such as atherosclerosis, are a real public health concern. They result from endothelial dysfunction induced by intermittent hypoxia (IH). VE-cadherin (VE-cad) undergoes IH-induced cleavage leading to be a biomarker of endothelial dysfunction in several pathologies (sVE). Our hypothesis is that, in OSA, VE-cad cleavage would contribute to the onset of endothelial permeability, resulting in endothelial dysfunction and atherosclerosis. Our aim is to characterize the signalling pathway and proteases that perform VE-cad cleavage in a cellular model of IH and determine if blocking VE-cad cleavage in vitro and in vivo could inhibit IH-induced atherogenesis. Human Aortic Endothelial Cells (HAEC) monolayers were exposed to 6 h IH and treated with tyr-kinase inhibitors (Saracatinib, Pazopanib), HIF-1 inhibitor (Acriflavine) and protease's inhibitors. Candidate proteases (MMP2, PCSK9 and ADAM10) were identified by performing a human protease array in OSA patient's sera. Endothelial permeability was assessed by measuring FITC-Dextran permeability and monocyte passage. VE-cad cleavage was studied by measuring sVE in cells’ supernatants. Vascular remodeling and VE-cad regulation were studied in C57BL/6 mice (2 weeks IH), atherosclerotic plaques and arterial pressure were studied in ApoE-/- mice (8 weeks IH), both treated with tyr-kinase and HIF-1 inhibitors. In our IH cellular model, VE-cad cleavage and endothelial permeability increased. These effects were reversed by the HIF-1 and tyr-kinase inhibitors and the proteases’ inhibitors. In vivo, IH increased aorta intima-media thickness and sVE serum level, and decreased VE-cad expression in the endothelium of mice. In ApoE-/- mice, IH increased atherosclerotic plaques formation. These effects were blocked by inhibitors of VE-cad cleavage signaling pathway ( Fig. 1 ). We suggest that IH increases endothelial permeability by inducing VE-cad cleavage via the HIF-1 and tyr-kinase pathways, and possibly involving MMP2, PCSK9 and/or ADAM10 proteases. Blocking VE-cad cleavage prevents vascular remodeling and atherosclerotic plaques formation which suggests that VE-cad could be a potential target to a new anti-atherogenesis strategy.

VE-cadherin cleavage in sleep apnoea: new insights into intermittent hypoxia-related endothelial permeability.

Obstructive sleep apnoea (OSA) causes intermittent hypoxia that in turn induces endothelial dysfunction and atherosclerosis progression. We hypothesised that VE-cadherin cleavage, detected by its released extracellular fragment solubilised in the blood (sVE), may be an early indicator of emergent abnormal endothelial permeability. Our aim was to assess VE-cadherin cleavage in OSA patients and in in vivo and in vitro intermittent hypoxia models to decipher the cellular mechanisms and consequences. Sera from seven healthy volunteers exposed to 14 nights of intermittent hypoxia, 43 OSA patients and 31 healthy control subjects were analysed for their sVE content. Human aortic endothelial cells (HAECs) were exposed to 6 h of intermittent hypoxia in vitro, with or without an antioxidant or inhibitors of hypoxia-inducible factor (HIF)-1, tyrosine kinases or vascular endothelial growth factor (VEGF) pathways. VE-cadherin cleavage and phosphorylation were evaluated, and endothelial permeability was assessed by measuring transendothelial electrical resistance (TEER) and fluorescein isothiocyanate (FITC)-dextran flux. sVE was significantly elevated in sera from healthy volunteers submitted to intermittent hypoxia and OSA patients before treatment, but conversely decreased in OSA patients after 6 months of continuous positive airway pressure treatment. OSA was the main factor accounting for sVE variations in a multivariate analysis. In in vitro experiments, cleavage and expression of VE-cadherin increased upon HAEC exposure to intermittent hypoxia. TEER decreased and FITC-dextran flux increased. These effects were reversed by all of the pharmacological inhibitors tested. We suggest that in OSA, intermittent hypoxia increases endothelial permeability in OSA by inducing VE-cadherin cleavage through reactive oxygen species production, and activation of HIF-1, VEGF and tyrosine kinase pathways.

Intermittent hypoxia increases VE-Cadherin cleavage in OSAS through ROS and HIF-1 pathways

Obstructive Sleep Apnea syndrome (OSAS), characterized by intermittent hypoxia (IH) cycles during sleep, induces endothelial dysfunction and atherogenesis lesions, which could be mediated by an increase in endothelial permeability. VE-Cadherin (VECad) cleavage, detected by the soluble extracellular fragment released (sVE), may be a key step in this regulation of endothelial permeability. Our aim was to search for sVE in sera from healthy volunteers submitted to IH, and from OSAS patients before and after treatment by continuous positive airway pressure (CPAP) and to characterize mechanisms regulating VECad cleavage in endothelial cells submitted to IH. sVE was searched in sera from 7 healthy volunteers exposed to IH, 44 OSAS patients and 31 control subjects. Human Aortic Endothelial Cells (HAEC) were exposed to 6 hours of IH in vitro, then endothelial permeability was assessed by measuring trans-endothelial electrical resistance (TEER) and VECad cleavage was evaluated by detecting sVE in cells supernatants after treatment by IH and tyrosine kinase inhibitor (30 μM Genistein or 10 μM PP2), HIF-1 inhibitor (1 μM 2-Methoxyestradiol), an anti-oxidant (100 μM Tempol) or anti-hVEGF blocking antibody (0.5 μg/mL). sVE was significantly elevated in healthy volunteers submitted to IH and in OSAS patient sera before treatment, but decreased in OSAS patients after 6 months of CPAP therapy. We found a significant positive correlation between sVE and OSAS severity and between sVE and serum VEGF. In HAEC supernatants, TEER decreased by 37.5% and sVE increased by 39% after cell exposure to IH. These effects were reversed by all the pharmacological inhibitors tested. we suggest that, in OSAS, IH increases endothelial permeability by inducing VECad cleavage via the ROS, HIF1, VEGF and tyrosine kinase pathways. Future studies will determine whether sVE could be a potential biomarker to evaluate early endothelial alterations in OSAS.

Transfusion-related acute lung injury: critical neutrophil activation by anti-HLA-A2 antibodies for endothelial permeability.

Transfusion-related acute lung injury (TRALI) is a major complication of hemotherapy that may occur after the transfusion of any blood type component. Several clinical reports have suggested the presence of anti-HLA antibodies in the blood product. This study sought to examine the role of anti-HLA-A2 antibodies in polymorphonuclear neutrophil (PMN) activation and thus in endothelial permeability. PMN activation was assessed by both nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) activity and reactive oxygen species (ROS) production. A coculture assay of EA.hy926 endothelial cells with PMNs or differentiated-PLB-985 cells, a model of neutrophil-like cells, was performed to estimate the impact of ROS on endothelial permeability. Anti-HLA-A2 antibodies significantly increased PMN activation, with subsequent endothelial dysfunction. Phagocyte NADPH oxidase (NOX2) activity was shown to be involved in this process and ROS themselves were demonstrated to induce VE-cadherin cleavage and endothelial permeability. Our data may support the existence of a critical anti-HLA-A2 antibody threshold for PMN activation, with NOX2 activity and subsequent endothelial permeability in the two-hit model of TRALI.

Low concentration of uncouplers of oxidative phosphorylation decreases the TNF-induced endothelial permeability and lethality in mice

Mitochondrial dysfunctions occur in many diseases linked to the systemic inflammatory response syndrome (SIRS). Mild uncoupling of oxidative phosphorylation is known to rescue model animals from pathologies related to mitochondrial dysfunctions and overproduction of reactive oxygen species (ROS). To study the potential of SIRS therapy by uncoupling, we tested protonophore dinitrophenol (DNP) and a free fatty acid (FFA) anion carrier, lipophilic cation dodecyltriphenylphosphonium (C12TPP) in mice and in vitro models of SIRS. DNP and C12TPP prevented the body temperature drop and lethality in mice injected with high doses of a SIRS inducer, tumor necrosis factor (TNF). The mitochondria-targeted antioxidant plastoquinonyl decyltriphenylphosphonium (SkQ1) which also catalyzes FFA-dependent uncoupling revealed similar protective effects and downregulated expression of the NFκB-regulated genes (VCAM1, ICAM1, MCP1, and IL-6) involved in the inflammatory response of endothelium in aortas of the TNF-treated mice. In vitro mild uncoupling rescued from TNF-induced endothelial permeability, disassembly of cell contacts and VE-cadherin cleavage by the matrix metalloprotease 9 (ММР9). The uncouplers prevented TNF-induced expression of MMP9 via inhibition of NFκB signaling. Water-soluble antioxidant Trolox also prevented TNF-induced activation and permeability of endothelium in vitro via inhibition of NFκB signaling, suggesting that the protective action of the uncouplers is linked to their antioxidant potential.

Mitochondria-Targeted Antioxidant SkQR1 Reduces TNF-Induced Endothelial Permeability in vitro.

Prolonged or excessive increase in the circulatory level of proinflammatory tumor necrosis factor (TNF) leads to abnormal activation and subsequent damage to endothelium. TNF at high concentrations causes apoptosis of endothelial cells. Previously, using mitochondria-targeted antioxidants of SkQ family, we have shown that apoptosis of endothelial cells is dependent on the production of reactive oxygen species (ROS) in mitochondria (mito-ROS). Now we have found that TNF at low concentrations does not cause cell death but activates caspase-3 and caspase-dependent increase in endothelial permeability in vitro. This effect is probably due to the cleavage of β-catenin - an adherent junction protein localized in the cytoplasm. We have also shown that extracellular matrix metalloprotease 9 (MMP9) VE-cadherin shedding plays a major role in the TNF-induced endothelial permeability. The mechanisms of the caspase-3 and MMP9 activation are probably not related to each other since caspase inhibition did not affect VE-cadherin cleavage and MMP9 inhibition had no effect on the caspase-3 activation. Mitochondria-targeted antioxidant SkQR1 inhibited TNF-induced increase in endothelial permeability. SkQR1 also inhibited caspase-3 activation, β-catenin cleavage, and MMP9-dependent VE-cadherin shedding. The data suggest that mito-ROS are involved in the increase in endothelial permeability due to the activation of both caspase-dependent cleavage of intracellular proteins and of MMP9-dependent cleavage of the transmembrane cell-to-cell contact proteins.

VE-cadherin cleavage by ovarian cancer microparticles induces β-catenin phosphorylation in endothelial cells.

Microparticles (MPs) are increasingly recognized as important mediators of cell-cell communication in tumour growth and metastasis by facilitating angiogenesis-related processes. While the effects of the MPs on recipient cells are usually well described in the literature, the leading process remains unclear. Here we isolated MPs from ovarian cancer cells and investigated their effect on endothelial cells. First, we demonstrated that ovarian cancer MPs trigger β-catenin activation in endothelial cells, inducing the upregulation of Wnt/β-catenin target genes and an increase of angiogenic properties. We showed that this MPs mediated activation of β-catenin in ECs was Wnt/Frizzled independent; but dependent on VE-cadherin localization disruption, αVβ3 integrin activation and MMP activity. Finally, we revealed that Rac1 and AKT were responsible for β-catenin phosphorylation and translocation to the nucleus. Overall, our results indicate that MPs released from cancer cells could play a major role in neo-angiogenesis through activation of beta catenin pathway in endothelial cells.

Abstract 11078: Granzyme B Deficiency Protects Against Angiotensin II-induced Cardiac Fibrosis via a Perforin-independent Mechanism

Introduction: Granzyme B (GzmB) is a serine protease involved in immune cell-mediated apoptosis that is enabled through a mechanism involving the pore-forming protein, perforin that facilitates internalization. However, recent evidence suggests that GzmB contributes to matrix remodeling and fibrosis through an extracellular, perforin-independent process. Hypothesis: GzmB contributes to cardiac fibrosis through a perforin-independent pathway involving extracellular proteolysis. Methods: Using a murine model of Angiotensin II (Ang II)-induced cardiac fibrosis, wild-type, GzmB deficient and Perforin deficient mice were treated with Ang II for 4 weeks, and were examined for the presence of cardiac fibrosis. Echocardiography was performed in these mice to examine the cardiac function. The level of Inflammation and inflammatory cells infiltration were examined by immunohistochemistry and RT-PCR analysis. The in vitro endothelial barrier function was measured by electric cell-substrate impedance sensing. Results: GzmB was highly up-regulated in both murine and human cardiac fibrosis. Genetic deficiency of GzmB markedly reduced Ang II-induced cardiac dysfunction, hypertrophy and fibrosis, independently of perforin. GzmB deficiency also decreases microhemorrhage, inflammation, and fibroblast accumulation in vivo. In vitro studies identified VE-cadherin as a GzmB substrate. VE-cadherin is a key endothelial cell-cell junction protein. GzmB-mediated VE-cadherin cleavage resulted in increased endothelial permeability, and increased transcellular conductance. These results were also observed in vivo. Conclusions: GzmB contributes to the onset and progression of cardiac fibrosis through a perforin-independent process involving the cleavage of VE-cadherin.

Endothelial tyrosine kinase receptor B prevents VE-cadherin cleavage and protects against atherosclerotic lesion development in ApoE−/− mice

Tyrosine kinase receptor B (TrkB) is a high-affinity receptor for brain-derived neurotrophic factor (BDNF). In addition to its nervous system functions, TrkB is also expressed in the aortic endothelium. However, the effects of endothelial TrkB signaling on atherosclerosis remained unknown. Immunofluorescence analysis revealed that TrkB expression is downregulated in the endothelium of atherosclerotic lesions from ApoE-/- mice compared with the atheroma-free aorta of WT mice. Endothelial TrkB knockdown led to increased lesion size, lipid deposition and inflammatory responses in the atherosclerotic lesions of the ApoE-/- mice compared with the control mice. Mechanistic studies showed that TrkB activation prevented VE-cadherin shedding by enhancing the interaction between vascular endothelial protein tyrosine phosphatase and VE-cadherin, maintaining VE-cadherin in a dephosphorylated state. Our data demonstrate that TrkB is an endothelial injury-response molecule in atherogenesis. Endothelial BDNF/TrkB signaling reduces VE-cadherin shedding and protects against atherosclerotic lesion development in ApoE-/- mice.

Abstract 5222: Endothelial plasticity generates aberrant angiogenesis and therapy resistance in glioblastoma

Abstract Overgrown, abnormal vasculature characterizes the microenvironment that fuels cancer progression and induces therapeutic resistance. Here we reveal that endothelial plasticity drives excessive and abnormal tumor angiogenesis. Glioblastoma multiforme (GBM) is among the most lethal of human malignancies, distinguished by prominent vascularity and extreme vascular abnormality. We identify endothelial fibro-transformation (Endo-FT) in GBM, contributing significantly to aberrant vascularization, tumor progression, and therapeutic resistance. Utilizing human GBM specimens and allograft and genetic murine GBM models driven by RCAS/Ntv-a-mediated gene transfer of PDGF in Ink4a-Arf-/-PTEN-/- mice, we reveal robust Endo-FT in the tumor vasculature, characterized by endothelial cell (EC) expression of the fibroblast and mesenchymal cell markers including FSP-1, α-smooth muscle actin, N-cadherin. Moreover, genetic lineage tracing shows a prominent population of GBM-associated fibroblast-like cells with EC origin. Furthermore, glioma-conditioned medium induces EC in vitro acquisition of the fibroblast signature with decreased expression of EC-specific proteins including CD31, VE-cadherin, Tie2, VEGFR2, leading to enhanced cell proliferation, motility, and invasiveness, and vessel permeability. Interestingly, the fibroblast-like ECs retain the key EC-specific functions including Ac-LDL absorption and tube formation, suggesting Endo-FT without complete EC transition to fibroblasts. Proteomic analysis identifies c-Met is a regulator of Endo-FT, requisite for the vascular abnormality. Pharmacological inhibition and siRNA-mediated knockdown of c-Met or neutralization with a HGF antibody remarkably abrogate tumor-conditioned medium-induced Endo-FT and EC malfunctions, suggesting a critical role of HGF/c-Met in Endo-FT. Furthermore, c-Met activation induces ETS-1-dependent matrix metalloproteinase (MMP)-14 expression, leading to VE-cadherin cleavage and Endo-FT. Finally, we test the in vivo role of c-Met-mediated Endo-FT in GBM progression by using mice with Tie2-Cre-driven, EC-specific Met knockout. Met deletion in ECs significantly improves mouse survival and inhibits GBM growth after temozolomide (TMZ) treatment. Moreover, Met deletion in ECs abolishes Endo-FT and vascular abnormality, as shown by remarkable decreases in CD31+FSP-1+ cell population and intratumor hypoxia, and increases in vasculature-mediated perfusion and vascular pericyte coverage, suggesting that c-Met-mediated Endo-FT is required for vascular abnormality and GBM progression and therapeutic resistance. In sum, these findings illustrate a novel mechanism controlling aberrant vascularization and GBM progression, and suggest that targeting Endo-FT may offer selective and efficient therapeutic strategies for the treatment-resistant GBM, and possibly other malignant tumors. Citation Format: Menggui Huang, Yi Fan. Endothelial plasticity generates aberrant angiogenesis and therapy resistance in glioblastoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5222. doi:10.1158/1538-7445.AM2015-5222

Soluble VE-cadherin is involved in endothelial barrier breakdown in systemic inflammation and sepsis.

Microvascular endothelial barrier breakdown in sepsis precedes organ failure and death in patients. We tested the hypothesis that the formation of endothelium-derived soluble vascular endothelial (VE)-cadherin fragments (sVE-cadherin) is involved in inflammation-induced endothelial barrier disruption. Incubation of human dermal microvascular endothelial cells (HDMEC) with tumour necrosis factor-α (TNF-α) and bacterial lipopolysaccharide (LPS) led to endothelial barrier disruption which correlated with significantly increased sVE-cadherin at a size of ∼90 kDa in cell culture supernatants. Inhibition of the VE-cadherin-cleaving disintegrin and metalloproteinase ADAM10 using GI254023X attenuated inflammation-induced formation of sVE-cadherin and endothelial barrier disruption, suggesting ADAM10-mediated shedding as a mechanism underlying sVE-cadherin release. Formation of VE-cadherin fragments at 90 and 110 kDa was observed when recombinant VE-cadherin (rVE-cadherin) was digested with recombinant ADAM10. Mass spectrometry of the VE-cadherin fragments showed that they originated from cleavage of the extracelluar domain and thereby several cleavage sites of ADAM10 were identified. Atomic force microscopy measurements demonstrated that cell culture supernatants containing sVE-cadherin and application of rVE-cadherin blocked VE-cadherin binding. Accordingly rVE-cadherin dose-dependently led to loss of endothelial barrier functions in HDMEC monolayers. Finally, in patients suffering from severe sepsis or septic shock with clinical signs of a microvascular leackage, serum levels of sVE-cadherin were significantly increased. Taken together, formation of sVE-cadherin is associated and contributes to inflammation-induced breakdown of endothelial barrier functions by inhibition of VE-cadherin binding. The underlying mechanism of VE-cadherin cleavage involves ADAM10 and appears to be of clinical relevance since sVE-cadherin was augmented in patients with severe sepsis.

VE-cadherin cleavage by LasB protease from Pseudomonas aeruginosa facilitates type III secretion system toxicity in endothelial cells.

Infection of the vascular system by Pseudomonas aeruginosa (Pa) occurs during bacterial dissemination in the body or in blood-borne infections. Type 3 secretion system (T3SS) toxins from Pa induce a massive retraction when injected into endothelial cells. Here, we addressed the role of type 2 secretion system (T2SS) effectors in this process. Mutants with an inactive T2SS were much less effective than wild-type strains at inducing cell retraction. Furthermore, secretomes from wild-typeswere sufficient to trigger cell-cell junction opening when applied to cells, while T2SS-inactivated mutants had minimal activity. Intoxication was associated with decreased levels of vascular endothelial (VE)-cadherin, a homophilic adhesive protein located at endothelial cell-cell junctions. During the process, the protein was cleaved in the middle of its extracellular domain (positions 335 and 349). VE-cadherin attrition was T3SS-independent but T2SS-dependent. Interestingly, the epithelial (E)-cadherin was unaffected by T2SS effectors, indicating that this mechanism is specific to endothelial cells. We showed that one of the T2SS effectors, the protease LasB, directly affected VE-cadherin proteolysis, hence promoting cell-cell junction disruption. Furthermore, mouse infection with Pa to induce acute pneumonia lead to significant decreases in lung VE-cadherin levels, whereas the decrease was minimal with T2SS-inactivated or LasB-deleted mutant strains. We conclude that the T2SS plays a pivotal role during Pa infection of the vascular system by breaching the endothelial barrier, and propose a model in which the T2SS and the T3SS cooperate to intoxicate endothelial cells.

Soluble VE‐cadherin in rheumatoid arthritis patients correlates with disease activity: Evidence for tumor necrosis factor α–induced VE‐cadherin cleavage

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disorder that principally attacks synovial joints. However, accelerated atherosclerosis and increased cardiovascular morbidity and mortality are major clinical consequences of endothelial dysfunction in RA patients. Tumor necrosis factor α (TNFα) is the major mediator of inflammation in RA, related to vascular injury by targeting VE-cadherin, an endothelium-specific adhesion molecule of vital importance for endothelium integrity and angiogenesis. We undertook this study to examine the mechanisms regulating VE-cadherin processing by TNFα and their occurrence in RA. Human umbilical vein endothelial cells were used in primary culture and treated with recombinant TNFα to study VE-cadherin cleavage. Cell lysates and conditioned media were analyzed by Western blotting for VE-cadherin cytoplasmic domain and extracellular domain (VE-90) generation, respectively. VE-90 was analyzed at baseline and at the 1-year followup in sera from 63 RA patients (from the Very Early Rheumatoid Arthritis cohort) with disease duration of <6 months. TNFα induced a time-dependent shedding of VE-90 in cell media. This effect was prevented by tyrosine kinase inhibitors (genistein and PP2) or by knocking down Src kinase. In contrast, tyrosine phosphatase blockade enhanced VE-cadherin cleavage, confirming the requirement of tyrosine phosphorylation processes. In addition, using the matrix metalloproteinase (MMP) activator APMA and the MMP inhibitor GM6001, we demonstrated that MMPs are involved in TNFα-induced VE-cadherin cleavage. Of major importance, VE-90 was detected in sera from the 63 RA patients and was positively correlated with the Disease Activity Score at baseline and after 1-year followup. These findings provide the first evidence of VE-cadherin proteolysis upon TNFα stimulation and suggest potential clinical relevance of soluble VE-cadherin in management of RA.

ADAM10 Regulates Endothelial Permeability and T-Cell Transmigration by Proteolysis of Vascular Endothelial Cadherin

Vascular endothelial (VE)-cadherin is the major adhesion molecule of endothelial adherens junctions. It plays an essential role in controlling endothelial permeability, vascular integrity, leukocyte transmigration, and angiogenesis. Elevated levels of soluble VE-cadherin are associated with diseases like coronary atherosclerosis. Previous data showed that the extracellular domain of VE-cadherin is released by an unknown metalloprotease activity during apoptosis. In this study, we used gain-of-function analyses, inhibitor studies, and RNA interference experiments to analyze the proteolytic release of VE-cadherin in human umbilical vein endothelial cells (HUVECs). We found that VE-cadherin is specifically cleaved by the disintegrin and metalloprotease ADAM10 in its ectodomain, releasing a soluble fragment and generating a carboxyl-terminal membrane-bound stub, which is a substrate for a subsequent gamma-secretase cleavage. This ADAM10-mediated proteolysis could be induced by Ca(2+) influx and staurosporine treatment, indicating that ADAM10-mediated VE-cadherin cleavage contributes to the dissolution of adherens junctions during endothelial cell activation and apoptosis, respectively. In contrast, protein kinase C activation or inhibition did not modulate VE-cadherin processing. Increased ADAM10 expression was functionally associated with an increase in endothelial permeability. Remarkably, our data indicate that ADAM10 activity also contributes to the thrombin-induced decrease of endothelial cell-cell adhesion. Moreover, knockdown of ADAM10 in HUVECs as well as in T cells by small interfering RNA impaired T-cell transmigration. Taken together, our data identify ADAM10 as a novel regulator of vascular permeability and demonstrate a hitherto unknown function of ADAM10 in the regulation of VE-cadherin-dependent endothelial cell functions and leukocyte transendothelial migration.

Identification of Proteases Involved in the Proteolysis of Vascular Endothelium Cadherin during Neutrophil Transmigration

Transmigration of neutrophils across the endothelium occurs at the cell-cell junctions where the vascular endothelium cadherin (VE cadherin) is expressed. This adhesive receptor was previously demonstrated to be involved in the maintenance of endothelium integrity. We propose that neutrophil transmigration across the vascular endothelium goes in parallel with cleavage of VE cadherin by elastase and cathepsin G present on the surface of neutrophils. This hypothesis is supported by the following lines of evidence. 1) Proteolytic fragments of VE cadherin are released into the culture medium upon adhesion of neutrophils to endothelial cell monolayers; 2) conditioned culture medium, obtained after neutrophil adhesion to endothelial monolayers, cleaves the recombinantly expressed VE cadherin extracellular domain; 3) these cleavages are inhibited by inhibitors of elastase; 4) VE cadherin fragments produced by conditioned culture medium or by exogenously added elastase are identical as shown by N-terminal sequencing and mass spectrometry analysis; 5) both elastase- and cathepsin G-specific VE cadherin cleavage patterns are produced upon incubation with tumor necrosis factor alpha-stimulated and fixed neutrophils; 6) transendothelial permeability increases in vitro upon addition of either elastase or cathepsin G; and 7) neutrophil transmigration is reduced in vitro in the presence of elastase and cathepsin G inhibitors. Our results suggest that cleavage of VE cadherin by neutrophil surface-bound proteases induces formation of gaps through which neutrophils transmigrate.