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Yang M, Boye-Doe A, Abosabie SAS, Barr AM, Mendez LM, Sharda AV. RalB uncoupled exocyst mediates endothelial Weibel-Palade body exocytosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.16.613344. [PMID: 39345530 PMCID: PMC11429928 DOI: 10.1101/2024.09.16.613344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 10/01/2024]
Abstract
Ras-like (Ral) GTPases play essential regulatory roles in many cellular processes, including exocytosis. Cycling between GDP- and GTP-bound states, Ral GTPases function as molecular switches and regulate effectors, specifically the multi-subunit tethering complex exocyst. Here, we show that Ral isoform RalB controls regulated exocytosis of Weibel-Palade bodies (WPBs), the specialized endothelial secretory granules that store hemostatic protein von Willebrand factor. Remarkably, unlike typical small GTPase-effector interactions, RalB binds exocyst in its GDP-bound state in resting endothelium. Upon endothelial cell stimulation, exocyst is uncoupled from RalB-GTP resulting in WPB tethering and exocytosis. Furthermore, we report that PKC-dependent phosphorylation of the C-terminal hypervariable region (HVR) of RalB modulates its dynamic interaction with exocyst in endothelium. Exocyst preferentially interacts with phosphorylated RalB in resting endothelium. Dephosphorylation of RalB either by endothelial cell stimulation, or PKC inhibition, or expression of nonphosphorylatable mutant at a specific serine residue of RalB HVR, disengages exocyst and augments WPB exocytosis, resembling RalB exocyst-binding site mutant. In summary, it is the uncoupling of exocyst from RalB that mediates endothelial Weibel-Palade body exocytosis. Our data shows that Ral function may be more dynamically regulated by phosphorylation and may confer distinct functionality given high degree of homology and the shared set of effector protein between the two Ral isoforms.
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Affiliation(s)
- Moua Yang
- Bloodworks Northwest Research Institute, Seattle, WA 98102, USA
- Division of Hematology and Oncology, Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA
| | - Alexandra Boye-Doe
- Section of Hematology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT, USA
| | - Salma A S Abosabie
- Section of Hematology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT, USA
| | - Alexandra M Barr
- Section of Hematology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT, USA
| | - Lourdes M Mendez
- Section of Hematology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT, USA
| | - Anish V Sharda
- Section of Hematology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT, USA
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Raghavan S, Brishti MA, Collier DM, Leo MD. Hypoxia induces purinergic receptor signaling to disrupt endothelial barrier function. Front Physiol 2022; 13:1049698. [PMID: 36479340 PMCID: PMC9720161 DOI: 10.3389/fphys.2022.1049698] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 11/10/2022] [Indexed: 09/15/2023] Open
Abstract
Blood-brain-barrier permeability is regulated by endothelial junctional proteins and is vital in limiting access to and from the blood to the CNS. When stressed, several cells, including endothelial cells, can release nucleotides like ATP and ADP that signal through purinergic receptors on these cells to disrupt BBB permeability. While this process is primarily protective, unrestricted, uncontrolled barrier disruption during injury or inflammation can lead to serious neurological consequences. Purinergic receptors are broadly classified into two families: the P1 adenosine and P2 nucleotide receptors. The P2 receptors are further sub-classified into the P2XR ion channels and the P2YR GPCRs. While ATP mainly activates P2XRs, P2YRs have a broader range of ligand selectivity. The P2Y1R, essential for platelet function, is reportedly ubiquitous in its expression. Prior studies using gene knockout and specific antagonists have shown that these approaches have neuroprotective effects following occlusive stroke. Here we investigated the expression of P2Y1R in primary cultured brain endothelial cells and its relation to the maintenance of BBB function. Results show that following in vitro hypoxia and reoxygenation, P2Y1R expression is upregulated in both control and diabetic cells. At the same time, endothelial junctional markers, ZO-1 and VE-cadherin, were downregulated, and endothelial permeability increased. siRNA knockdown of P2Y1R and MRS 2500 effectively blocked this response. Thus, we show that P2Y1R signaling in endothelial cells leads to the downregulation of endothelial barrier function.
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Affiliation(s)
| | | | | | - M. Dennis Leo
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, TN, United States
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3
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Giri H, Srivastava AK, Naik UP. Apoptosis signal-regulating kinase-1 regulates thrombin-induced endothelial permeability. Vascul Pharmacol 2022; 145:107088. [DOI: 10.1016/j.vph.2022.107088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 06/17/2022] [Accepted: 06/29/2022] [Indexed: 11/16/2022]
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4
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Wettschureck N, Strilic B, Offermanns S. Passing the Vascular Barrier: Endothelial Signaling Processes Controlling Extravasation. Physiol Rev 2019; 99:1467-1525. [PMID: 31140373 DOI: 10.1152/physrev.00037.2018] [Citation(s) in RCA: 150] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
A central function of the vascular endothelium is to serve as a barrier between the blood and the surrounding tissue of the body. At the same time, solutes and cells have to pass the endothelium to leave or to enter the bloodstream to maintain homeostasis. Under pathological conditions, for example, inflammation, permeability for fluid and cells is largely increased in the affected area, thereby facilitating host defense. To appropriately function as a regulated permeability filter, the endothelium uses various mechanisms to allow solutes and cells to pass the endothelial layer. These include transcellular and paracellular pathways of which the latter requires remodeling of intercellular junctions for its regulation. This review provides an overview on endothelial barrier regulation and focuses on the endothelial signaling mechanisms controlling the opening and closing of paracellular pathways for solutes and cells such as leukocytes and metastasizing tumor cells.
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Affiliation(s)
- Nina Wettschureck
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research , Bad Nauheim , Germany ; and Centre for Molecular Medicine, Medical Faculty, J.W. Goethe University Frankfurt , Frankfurt , Germany
| | - Boris Strilic
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research , Bad Nauheim , Germany ; and Centre for Molecular Medicine, Medical Faculty, J.W. Goethe University Frankfurt , Frankfurt , Germany
| | - Stefan Offermanns
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research , Bad Nauheim , Germany ; and Centre for Molecular Medicine, Medical Faculty, J.W. Goethe University Frankfurt , Frankfurt , Germany
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5
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A positive circuit of VEGF increases Glut-1 expression by increasing HIF-1α gene expression in human retinal endothelial cells. Arch Pharm Res 2017; 40:1433-1442. [DOI: 10.1007/s12272-017-0971-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 10/07/2017] [Indexed: 01/07/2023]
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6
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Beckers CML, Knezevic N, Valent ET, Tauseef M, Krishnan R, Rajendran K, Hardin CC, Aman J, van Bezu J, Sweetnam P, van Hinsbergh VWM, Mehta D, van Nieuw Amerongen GP. ROCK2 primes the endothelium for vascular hyperpermeability responses by raising baseline junctional tension. Vascul Pharmacol 2015; 70:45-54. [PMID: 25869521 PMCID: PMC4606924 DOI: 10.1016/j.vph.2015.03.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 03/04/2015] [Accepted: 03/08/2015] [Indexed: 12/25/2022]
Abstract
Rho kinase mediates the effects of inflammatory permeability factors by increasing actomyosin-generated traction forces on endothelial adherens junctions, resulting in disassembly of intercellular junctions and increased vascular leakage. In vitro, this is accompanied by the Rho kinase-driven formation of prominent radial F-actin fibers, but the in vivo relevance of those F-actin fibers has been debated, suggesting other Rho kinase-mediated events to occur in vascular leak. Here, we delineated the contributions of the highly homologous isoforms of Rho kinase (ROCK1 and ROCK2) to vascular hyperpermeability responses. We show that ROCK2, rather than ROCK1 is the critical Rho kinase for regulation of thrombin receptor-mediated vascular permeability. Novel traction force mapping in endothelial monolayers, however, shows that ROCK2 is not required for the thrombin-induced force enhancements. Rather, ROCK2 is pivotal to baseline junctional tension as a novel mechanism by which Rho kinase primes the endothelium for hyperpermeability responses, independent from subsequent ROCK1-mediated contractile stress-fiber formation during the late phase of the permeability response.
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Affiliation(s)
- Cora M L Beckers
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands
| | - Nebojsa Knezevic
- Department of Pharmacology, Center for Lung and Vascular Biology, University of Illinois, College of Medicine, Chicago, IL 60612, USA
| | - Erik T Valent
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands
| | - Mohammad Tauseef
- Department of Pharmacology, Center for Lung and Vascular Biology, University of Illinois, College of Medicine, Chicago, IL 60612, USA
| | - Ramaswamy Krishnan
- Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Kavitha Rajendran
- Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - C Corey Hardin
- Division of Pulmonary and Critical Care Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Jurjan Aman
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands
| | - Jan van Bezu
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands
| | - Paul Sweetnam
- Surface Logix-737, Concord Ave., Cambridge, MA 02138, USA
| | - Victor W M van Hinsbergh
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands
| | - Dolly Mehta
- Department of Pharmacology, Center for Lung and Vascular Biology, University of Illinois, College of Medicine, Chicago, IL 60612, USA
| | - Geerten P van Nieuw Amerongen
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands; Department of Pharmacology, Center for Lung and Vascular Biology, University of Illinois, College of Medicine, Chicago, IL 60612, USA.
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The angiopoietin/TIE receptor system: Focusing its role for ischemia-reperfusion injury. Cytokine Growth Factor Rev 2014; 26:281-91. [PMID: 25466648 DOI: 10.1016/j.cytogfr.2014.10.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Revised: 10/23/2014] [Accepted: 10/30/2014] [Indexed: 02/07/2023]
Abstract
Ischemia and reperfusion (I/R) are of fatal consequence for the affected organs, as they provoke a profound inflammatory reaction. This thoroughly destroys cells and tissues, inducing functional failure or even complete loss of organ function. Since I/R is primarily a vascular problem, the interaction between the endothelium and the surrounding environment is of great significance. The angiopoietins (ANG) and the TIE receptors are key players for the vascular homeostasis. This review summarizes biochemical and cellular mechanisms leading to I/R injury. After a brief introduction to the ANG/TIE system, a comprehensive overview of its role for the development of I/R syndrome is given. Finally, current therapeutic approaches to mitigate the consequences of I/R by modulating ANG/TIE signaling are reviewed in detail.
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Noncanonical PAR3 activation by factor Xa identifies a novel pathway for Tie2 activation and stabilization of vascular integrity. Blood 2014; 124:3480-9. [PMID: 25320242 DOI: 10.1182/blood-2014-06-582775] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Endothelial barrier protective effects of activated protein C (APC) require the endothelial protein C receptor (EPCR), protease-activated receptor (PAR) 1, and PAR3. In contrast, PAR1 and PAR3 activation by thrombin results in barrier disruption. Noncanonical PAR1 and PAR3 activation by APC vs canonical activation by thrombin provides an explanation for the functional selectivity of these proteases. Here we found that factor Xa (FXa) activated PAR1 at canonical Arg41 similar to thrombin but cleaved PAR3 at noncanonical Arg41 similar to APC. This unique PAR1-PAR3 activation profile permitted the identification of noncanonical PAR3 activation as a novel activation pathway for barrier protective tunica intima endothelial receptor tyrosine kinase 2 (Tie2). APC, FXa, and the noncanonical PAR3 tethered-ligand peptide induced prolonged activation of Tie2, whereas thrombin and the canonical PAR3 tethered-ligand peptide did not. Tie2 activation by FXa required PAR3 and EPCR. FXa and the noncanonical PAR3 tethered-ligand peptide induced Tie2- and PAR3-dependent upregulation of tight-junction-associated protein zona occludens 1 (ZO-1), translocation of ZO-1 to cell-cell borders, and the formation of typical ZO-1 honeycomb patterns that are indicative of tight-junction stabilization. These data provide intriguing novel insights into the diversification of functional selectivity of protease signaling achievable by canonical and noncanonical PAR activation, such as the activation of vascular-protective Tie2 by noncanonical PAR3 activation.
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Liu ZC, Yu EH, Liu W, Liu XC, Tang SB, Zhu BH. Translocation of protein kinase C δ contributes to the moderately high glucose-, but not hypoxia-induced proliferation in primary cultured human retinal endothelial cells. Mol Med Rep 2014; 9:1780-6. [PMID: 24626810 DOI: 10.3892/mmr.2014.2049] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 02/10/2014] [Indexed: 11/05/2022] Open
Abstract
Diabetic retinopathy is one of the most common complications in patients with diabetes and affects ~75% of them within 15 years of the onset of the disease. Activation of protein kinase C (PKC) is a key feature of diabetes mellitus and may be involved in the pathogenesis of diabetic retinopathy. The present study aimed to examine the translocation of protein kinase C (PKC) isoforms, which are triggered by high an moderately high glucose levels as well as hypoxic conditions. The underlying cell mechanisms of PKC translocation in primary cultured human retinal endothelial cells (HRECs) were also investigated. The expression levels of PKC isoforms were assessed using western blot analysis. Cell proliferation was determined using the MTT assay and DNA synthesis was assessed by bromodeoxyuridine incorporation. Translocation of PKC isoforms was examined by western blot analysis and immunofluorescence. The expression of PKC α, βI, βII, δ and ε was detected, while PKC ζ was not detected in HRECs. The results of the present study were consistent with the findings of a previous study by our group, reporting that moderately high glucose levels and hypoxia, but not high glucose levels, significantly increased cell proliferation. It was demonstrated that the PKC δ isoform was translocated from the cytosol to the membrane only under moderately high glucose conditions, while PKC α and ε isoforms were translocated from the cytosol to the membrane at high glucose conditions. In addition, PKC βI was translocated under all three conditions. Translocation of PKC βII was comparable among all groups. Furthermore, rottlerin, an inhibitor of PKC δ, blocked cell proliferation, which was induced by moderately high glucose levels, but not by hypoxia. Ro32-0432, an inhibitor of PKC α, βI and ε, did not significantly affect proliferation of HRECs in all treatment groups. In conclusion, the present study suggested that PKC α, βI, βII, δ and ε were expressed in primary cultured HRECs, whereas PKC ζ was not. Cell proliferation induced by moderately high glucose concentrations was associated with translocation of the PKC δ isoform; however, hypoxic conditions did not induce translocation.
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Affiliation(s)
- Zhao-Chun Liu
- Department of Pharmacology, Cardiac and Cerebral Vascular Research Center, Zhongshan School of Medicine, Sun Yat‑Sen University, Guangzhou, Guangdong 510080, P.R. China
| | - En-Hong Yu
- Department of Pharmacology, Cardiac and Cerebral Vascular Research Center, Zhongshan School of Medicine, Sun Yat‑Sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Wei Liu
- Department of Pharmacology, Cardiac and Cerebral Vascular Research Center, Zhongshan School of Medicine, Sun Yat‑Sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Xiao-Chang Liu
- Department of Pharmacology, Cardiac and Cerebral Vascular Research Center, Zhongshan School of Medicine, Sun Yat‑Sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Shi-Bo Tang
- Zhongshan Ophthalmic Center, Sun Yat‑Sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Bang-Hao Zhu
- Department of Pharmacology, Cardiac and Cerebral Vascular Research Center, Zhongshan School of Medicine, Sun Yat‑Sen University, Guangzhou, Guangdong 510080, P.R. China
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Mittal M, Siddiqui MR, Tran K, Reddy SP, Malik AB. Reactive oxygen species in inflammation and tissue injury. Antioxid Redox Signal 2014; 20:1126-67. [PMID: 23991888 PMCID: PMC3929010 DOI: 10.1089/ars.2012.5149] [Citation(s) in RCA: 2843] [Impact Index Per Article: 284.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Abstract Reactive oxygen species (ROS) are key signaling molecules that play an important role in the progression of inflammatory disorders. An enhanced ROS generation by polymorphonuclear neutrophils (PMNs) at the site of inflammation causes endothelial dysfunction and tissue injury. The vascular endothelium plays an important role in passage of macromolecules and inflammatory cells from the blood to tissue. Under the inflammatory conditions, oxidative stress produced by PMNs leads to the opening of inter-endothelial junctions and promotes the migration of inflammatory cells across the endothelial barrier. The migrated inflammatory cells not only help in the clearance of pathogens and foreign particles but also lead to tissue injury. The current review compiles the past and current research in the area of inflammation with particular emphasis on oxidative stress-mediated signaling mechanisms that are involved in inflammation and tissue injury.
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Affiliation(s)
- Manish Mittal
- 1 Department of Pharmacology, Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, Illinois
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Song HB, Jun HO, Kim JH, Yu YS, Kim KW, Kim JH. Suppression of protein kinase C-ζ attenuates vascular leakage via prevention of tight junction protein decrease in diabetic retinopathy. Biochem Biophys Res Commun 2014; 444:63-8. [DOI: 10.1016/j.bbrc.2014.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Accepted: 01/07/2014] [Indexed: 01/17/2023]
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12
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Abstract
The acute respiratory distress syndrome (ARDS) is a major public health problem and a leading source of morbidity in intensive care units. Lung tissue in patients with ARDS is characterized by inflammation, with exuberant neutrophil infiltration, activation, and degranulation that is thought to initiate tissue injury through the release of proteases and oxygen radicals. Treatment of ARDS is supportive primarily because the underlying pathophysiology is poorly understood. This gap in knowledge must be addressed to identify urgently needed therapies. Recent research efforts in anti-inflammatory drug development have focused on identifying common control points in multiple signaling pathways. The protein kinase C (PKC) serine-threonine kinases are master regulators of proinflammatory signaling hubs, making them attractive therapeutic targets. Pharmacological inhibition of broad-spectrum PKC activity and, more importantly, of specific PKC isoforms (as well as deletion of PKCs in mice) exerts protective effects in various experimental models of lung injury. Furthermore, PKC isoforms have been implicated in inflammatory processes that may be involved in the pathophysiologic changes that result in ARDS, including activation of innate immune and endothelial cells, neutrophil trafficking to the lung, regulation of alveolar epithelial barrier functions, and control of neutrophil proinflammatory and prosurvival signaling. This review focuses on the mechanistic involvement of PKC isoforms in the pathogenesis of ARDS and highlights the potential of developing new therapeutic paradigms based on the selective inhibition (or activation) of specific PKC isoforms.
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Regulation of vascular leak and recovery from ischemic injury by general and VE-cadherin-restricted miRNA antagonists of miR-27. Blood 2013; 122:2911-9. [PMID: 24009229 DOI: 10.1182/blood-2012-12-473017] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Cellular junctions are essential to the normal functioning of the endothelium and control angiogenesis, tissue leak, and inflammation. From a screen of micro RNAs (miRNAs) altered in in vitro angiogenesis, we selected a subset predicted to target junctional molecules. MiR-27a was rapidly downregulated upon stimulation of in vitro angiogenesis, and its level of expression is reduced in neovessels in vivo. The downregulation of miR-27a was essential for angiogenesis because ectopic expression of miR-27a blocked capillary tube formation and angiogenesis. MiR-27a targets the junctional, endothelial-specific cadherin, VE-cadherin. Consistent with this, vascular permeability to vascular endothelial growth factor in mice is reduced by administration of a general miR-27 inhibitor. To determine that VE-cadherin was the dominant target of miR-27a function, we used a novel technology with "Blockmirs," inhibitors that bind to the miR-27 binding site in VE-cadherin. The Blockmir CD5-2 demonstrated specificity for VE-cadherin and inhibited vascular leak in vitro and in vivo. Furthermore, CD5-2 reduced edema, increased capillary density, and potently enhanced recovery from ischemic limb injury in mice. The Blockmir technology offers a refinement in the use of miRNAs, especially for therapy. Further, targeting of endothelial junctional molecules by miRNAs has clinical potential, especially in diseases associated with vascular leak.
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15
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Novel atypical PKC inhibitors prevent vascular endothelial growth factor-induced blood-retinal barrier dysfunction. Biochem J 2012; 446:455-67. [PMID: 22721706 DOI: 10.1042/bj20111961] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Pro-inflammatory cytokines and growth factors such as VEGF (vascular endothelial growth factor) contribute to the loss of the BRB (blood-retinal barrier) and subsequent macular oedema in various retinal pathologies. VEGF signalling requires PKCβ [conventional PKC (protein kinase C)] activity; however, PKCβ inhibition only partially prevents VEGF-induced endothelial permeability and does not affect pro-inflammatory cytokine-induced permeability, suggesting the involvement of alternative signalling pathways. In the present study, we provide evidence for the involvement of aPKC (atypical PKC) signalling in VEGF-induced endothelial permeability and identify a novel class of inhibitors of aPKC that prevent BRB breakdown in vivo. Genetic and pharmacological manipulations of aPKC isoforms were used to assess their contribution to endothelial permeability in culture. A chemical library was screened using an in vitro kinase assay to identify novel small-molecule inhibitors, and further medicinal chemistry was performed to delineate a novel pharmacophore. We demonstrate that aPKC isoforms are both sufficient and required for VEGF-induced endothelial permeability. Furthermore, these specific, potent, non-competitive, small-molecule inhibitors prevented VEGF-induced tight junction internalization and retinal endothelial permeability in response to VEGF in both primary culture and in rodent retina. The results of the present study suggest that aPKC inhibition with 2-amino-4-phenyl-thiophene derivatives may be developed to preserve the BRB in retinal diseases such as diabetic retinopathy or uveitis, and the BBB (blood-brain barrier) in the presence of brain tumours.
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Su Y, Liu W, Ma L, Liu X, Liu Z, Zhu B. Scutellarin inhibits translocation of protein kinase C in diabetic thoracic aorta of the rat. Clin Exp Pharmacol Physiol 2012; 39:136-40. [PMID: 22092277 DOI: 10.1111/j.1440-1681.2011.05645.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The aims of the present study were to explore the effects of: (i) scutellarin (Scu) on protein kinase C (PKC) translocation caused by diabetic conditions in diabetic rat thoracic aorta; and (ii) phorbol-12-myristate-13-acetate (PMA) treatment of cultured thoracic aortic smooth muscle cells. Diabetes was induced in rats by streptozotocin and diabetic rats were divided into two groups: (i) an Scu-treated group, administered 0.1 g/kg Scu by gavage; and (ii) an aminoquanidine (AG)-treated group, which received dietary supplementation of 0.1% AG from Week 1 of diabetes induction. After 10 weeks, rats were killed and thoracic aortic smooth muscle cells were isolated and cultured. Cell fractions were obtained by ultracentrifugation and PKC activity was assayed by ELISA, whereas the distribution of PKC was verified by western immunoblotting. The PKC activity in the membrane fraction of thoracic aortic smooth muscle cells was significantly increased in diabetic compared with control rats, whereas the administration of Scu significantly inhibited this increase. Phorbol myristate acetate (100 nmol/L, 10 min) induced the translocation of the PKCα, βI, βII, δ and ε isoforms, whereas 48 h pretreatment of cells with 1 μmol/L Scu significantly inhibited PMA-induced PKCβI, βII and δ translocation. The results of the present study suggest that Scu inhibits the translocation of PKC in vivo and in vitro and may have value as a drug in the treatment of diabetic complications via its inhibition of PKC βI, βII and δ translocation.
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Affiliation(s)
- Yingxue Su
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
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17
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Thurston G, Daly C. The complex role of angiopoietin-2 in the angiopoietin-tie signaling pathway. Cold Spring Harb Perspect Med 2012; 2:a006550. [PMID: 22951441 DOI: 10.1101/cshperspect.a006650] [Citation(s) in RCA: 187] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The angiopoietin-Tie signaling system is a vascular-specific receptor tyrosine kinase pathway that is essential for normal vascular development. Although the basic functioning of the pathway is understood, many uncertainties remain about the role of certain members of the pathway, particularly angiopoietin-2 (Ang2), in pathological vascular remodeling and angiogenesis. We summarize the components of the angiopoietin-Tie pathway and then focus on studies that highlight the role of Ang2 in disease settings, including cancer and inflammation. The expression of Ang2 is elevated in many cancers and types of inflammation, which prompted the development of specific reagents to block its interaction with the Tie2 receptor. The application of these reagents in preclinical models of inflammation and cancer has begun to elucidate the role of Ang2 in vascular remodeling and disease pathogenesis and has led to emerging clinical tests of Ang2 inhibitors.
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18
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Molecular and cellular mechanisms underlying the role of blood vessels in spinal cord injury and repair. Cell Tissue Res 2012; 349:269-88. [PMID: 22592628 DOI: 10.1007/s00441-012-1440-6] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 04/24/2012] [Indexed: 02/07/2023]
Abstract
Spinal cord injury causes immediate damage of nervous tissue accompanied by the loss of motor and sensory function. The limited self-repair ability of damaged nervous tissue underlies the need for reparative interventions to restore function after spinal cord injury. Blood vessels play a crucial role in spinal cord injury and repair. Injury-induced loss of local blood vessels and a compromised blood-brain barrier contribute to inflammation and ischemia and thus to the overall damage to the nervous tissue of the spinal cord. Lack of vasculature and leaking blood vessels impede endogenous tissue repair and limit prospective repair approaches. A reduction of blood vessel loss and the restoration of blood vessels so that they no longer leak might support recovery from spinal cord injury. The promotion of new blood vessel formation (i.e., angio- and vasculogenesis) might aid repair but also incorporates the danger of exacerbating tissue loss and thus functional impairment. The delicate interplay between cells and molecules that govern blood vessel repair and formation determines the extent of damage and the success of reparative interventions. This review deals with the cellular and molecular mechanisms underlying the role of blood vessels in spinal cord injury and repair.
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Li X, Zheng Z, Mao Y, Ma X. Unfractionated heparin promotes LPS-induced endothelial barrier dysfunction: A preliminary study on the roles of angiopoietin/Tie2 axis. Thromb Res 2012; 129:e223-8. [DOI: 10.1016/j.thromres.2012.03.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Revised: 02/22/2012] [Accepted: 03/03/2012] [Indexed: 01/19/2023]
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Korff T, Ernst E, Nobiling R, Feldner A, Reiss Y, Plate KH, Fiedler U, Augustin HG, Hecker M. Angiopoietin-1 mediates inhibition of hypertension-induced release of angiopoietin-2 from endothelial cells. Cardiovasc Res 2012; 94:510-8. [PMID: 22505659 DOI: 10.1093/cvr/cvs124] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
AIMS Adequate endothelial cell stimulation is a prerequisite for the adaptive remodelling of macro- and microvessels. A pivotal autocrine mechanism following endothelial cell activation is the release of angiopoietin-2 (Ang-2), which subsequently antagonizes the binding of Ang-1 to the Tie-2 receptor, thus sensitizing the endothelial cells to pro-angiogenic and/or pro-inflammatory stimuli. Based on the observation that hypertension in mice reduces the abundance of Ang-2 stored in arterial endothelial cells, this study was aimed at testing the hypothesis that an increase in wall stress (WS) or stretch-a hallmark of hypertension-is sufficient to release Ang-2 from endothelial cells. METHODS AND RESULTS In fact, stretching of isolated perfused mouse arteries or human cultured endothelial cells rapidly elicited an increased release of Ang-2. In the cultured endothelial cells, this was preceded by a transient rise in intracellular free calcium, abrogated through calcium chelation and accompanied by a decrease in Tie-2 phosphorylation. Interestingly, Ang-1 abolished the stretch-induced release of Ang-2 from both cultured and native endothelial cells through inhibiting the stretch-dependent mobilization of intracellular calcium. CONCLUSION Collectively, these results indicate that increased WS or stretch facilitates the release of Ang-2 from endothelial cell Weibel-Palade bodies, and that Ang-1 can block this by attenuating the stretch-mediated rise in intracellular calcium.
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Affiliation(s)
- Thomas Korff
- Division of Cardiovascular Physiology, Institute of Physiology and Pathophysiology, University of Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
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Epithelial inducible nitric oxide synthase causes bacterial translocation by impairment of enterocytic tight junctions via intracellular signals of Rho-associated kinase and protein kinase C zeta. Crit Care Med 2011; 39:2087-98. [PMID: 21552122 DOI: 10.1097/ccm.0b013e31821cb40e] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Gut barrier dysfunction and bacterial translocation occur in various disorders, including intestinal obstruction. Overexpression of inducible nitric oxide synthase is implicated in the pathogenesis of bacterial translocation, of which the molecular mechanism remains unclear. Epithelial permeability is regulated by tight junction reorganization and myosin light chain phosphorylation. Our aim was to investigate the roles of Rho-associated kinase and protein kinase C ζ in epithelial nitric oxide synthase-mediated barrier damage. DESIGN Animal study and cell cultures. SETTING Research laboratory. SUBJECTS BALB/c mice. INTERVENTIONS : Mouse distal small intestine was obstructed in vivo by a 10-cm loop ligation in which vehicle, L-Nil (a nitric oxide synthase inhibitor), or Y27632 (a Rho-associated kinase inhibitor) was luminally administered. After obstruction for 24 hrs, intestinal tissues were mounted on Ussing chambers for macromolecular flux. Liver and spleen tissues were assessed for bacterial counts. Caco-2 cells were exposed to 1 mM S-nitroso-N-acetylpenicillamine (a nitric oxide donor) for 24 hrs, and transepithelial resistance and permeability were evaluated. MEASUREMENTS AND MAIN RESULTS Mice with intestinal obstruction displayed epithelial barrier dysfunctions, such as permeability rise and bacterial translocation, associated with tight junction disruption and myosin light chain phosphorylation. Increased inducible nitric oxide synthase and phosphorylated protein kinase C ζ were observed in villus epithelium. Enteric instillation of L-Nil and Y27632 attenuated the functional and structural barrier damage caused by intestinal obstruction. L-Nil decreased intestinal obstruction-induced myosin light chain, myosin phosphatase target subunit 1, and protein kinase C ζ phosphorylation, suggesting that inducible nitric oxide synthase is upstream of Rho-associated kinase and protein kinase C ζ signaling. The intestinal phosphorylated myosin light chain level did not increase in inducible nitric oxide synthase(-/-) mice following intestinal obstruction. In vitro studies showed that S-nitroso-N-acetylpenicillamine-induced transepithelial resistance drop and permeability rise was independent of cell apoptosis. Y27632 inhibited S-nitroso-N-acetylpenicillamine-induced myosin light chain phosphorylation and permeability rise. S-nitroso-N-acetylpenicillamine also triggered phosphorylation and membrane translocation of protein kinase C ζ. Inhibitory protein kinase C ζ pseudosubstrate blocked S-nitroso-N-acetylpenicillamine-induced tight junction reorganization, but not myosin light chain phosphorylation. CONCLUSIONS Epithelial inducible nitric oxide synthase activates two distinct signals, protein kinase C ζ and Rho-associated kinase, to disrupt tight junctions leading to bacterial influx.
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Heo KS, Lee H, Nigro P, Thomas T, Le NT, Chang E, McClain C, Reinhart-King CA, King MR, Berk BC, Fujiwara K, Woo CH, Abe JI. PKCζ mediates disturbed flow-induced endothelial apoptosis via p53 SUMOylation. ACTA ACUST UNITED AC 2011; 193:867-84. [PMID: 21624955 PMCID: PMC3105539 DOI: 10.1083/jcb.201010051] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Disturbed flow-mediated PKCζ–PIASy association is critical for p53 SUMOylation and induces p53 nuclear export and endothelial cell apoptosis. Atherosclerosis is readily observed in regions of blood vessels where disturbed blood flow (d-flow) is known to occur. A positive correlation between protein kinase C ζ (PKCζ) activation and d-flow has been reported, but the exact role of d-flow–mediated PKCζ activation in atherosclerosis remains unclear. We tested the hypothesis that PKCζ activation by d-flow induces endothelial cell (EC) apoptosis by regulating p53. We found that d-flow–mediated peroxynitrite (ONOO−) increased PKCζ activation, which subsequently induced p53 SUMOylation, p53–Bcl-2 binding, and EC apoptosis. Both d-flow and ONOO− increased the association of PKCζ with protein inhibitor of activated STATy (PIASy) via the Siz/PIAS-RING domain (amino acids 301–410) of PIASy, and overexpression of this domain of PIASy disrupted the PKCζ–PIASy interaction and PKCζ-mediated p53 SUMOylation. En face confocal microscopy revealed increases in nonnuclear p53 expression, nitrotyrosine staining, and apoptosis in aortic EC located in d-flow areas in wild-type mice, but these effects were significantly decreased in p53−/− mice. We propose a novel mechanism for p53 SUMOylation mediated by the PKCζ–PIASy interaction during d-flow–mediated EC apoptosis, which has potential relevance to early events of atherosclerosis.
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Affiliation(s)
- Kyung-Sun Heo
- Aab Cardiovascular Research Institute, University of Rochester, Rochester, NY 14642, USA
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van der Heijden M, van Nieuw Amerongen GP, van Bezu J, Paul MA, Groeneveld ABJ, van Hinsbergh VWM. Opposing effects of the angiopoietins on the thrombin-induced permeability of human pulmonary microvascular endothelial cells. PLoS One 2011; 6:e23448. [PMID: 21858121 PMCID: PMC3156229 DOI: 10.1371/journal.pone.0023448] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 07/18/2011] [Indexed: 01/25/2023] Open
Abstract
Background Angiopoietin-2 (Ang-2) is associated with lung injury in ALI/ARDS. As endothelial activation by thrombin plays a role in the permeability of acute lung injury and Ang-2 may modulate the kinetics of thrombin-induced permeability by impairing the organization of vascular endothelial (VE-)cadherin, and affecting small Rho GTPases in human pulmonary microvascular endothelial cells (HPMVECs), we hypothesized that Ang-2 acts as a sensitizer of thrombin-induced hyperpermeability of HPMVECs, opposed by Ang-1. Methodology/Principal Findings Permeability was assessed by measuring macromolecule passage and transendothelial electrical resistance (TEER). Angiopoietins did not affect basal permeability. Nevertheless, they had opposing effects on the thrombin-induced permeability, in particular in the initial phase. Ang-2 enhanced the initial permeability increase (passage, P = 0.010; TEER, P = 0.021) in parallel with impairment of VE-cadherin organization without affecting VE-cadherin Tyr685 phosphorylation or increasing RhoA activity. Ang-2 also increased intercellular gap formation. Ang-1 preincubation increased Rac1 activity, enforced the VE-cadherin organization, reduced the initial thrombin-induced permeability (TEER, P = 0.027), while Rac1 activity simultaneously normalized, and reduced RhoA activity at 15 min thrombin exposure (P = 0.039), but not at earlier time points. The simultaneous presence of Ang-2 largely prevented the effect of Ang-1 on TEER and macromolecule passage. Conclusions/Significance Ang-1 attenuated thrombin-induced permeability, which involved initial Rac1 activation-enforced cell-cell junctions, and later RhoA inhibition. In addition to antagonizing Ang-1, Ang-2 had also a direct effect itself. Ang-2 sensitized the initial thrombin-induced permeability accompanied by destabilization of VE-cadherin junctions and increased gap formation, in the absence of increased RhoA activity.
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Affiliation(s)
- Melanie van der Heijden
- Department of Intensive Care, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands
| | - Geerten P. van Nieuw Amerongen
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands
- * E-mail:
| | - Jan van Bezu
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands
| | - Marinus A. Paul
- Department of Cardiothoracic Surgery, VU University Medical Centre, Amsterdam, The Netherlands
| | - A. B. Johan Groeneveld
- Department of Intensive Care, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands
| | - Victor W. M. van Hinsbergh
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands
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Nag S, Kapadia A, Stewart DJ. Review: molecular pathogenesis of blood-brain barrier breakdown in acute brain injury. Neuropathol Appl Neurobiol 2011; 37:3-23. [PMID: 20946242 DOI: 10.1111/j.1365-2990.2010.01138.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Historically, the blood-brain barrier (BBB) was considered to be at the level of cerebral endothelium. Currently, the interaction of endothelium with other components of the vessel wall and with neurones and glial cells is considered to constitute a functional unit, termed the neurovascular unit that maintains cerebral homeostasis in steady states and brain injury. The emphasis of this review is on cerebral endothelium, the best-studied component of the neurovascular unit, and its permeability mechanisms in health and acute brain injury. Major advances have been made in unravelling the molecular structure of caveolae and tight junctions, both of which are components of the structural barrier to the entry of plasma proteins into brain. Time course studies suggest that caveolar changes precede junctional changes in acute brain injury. Additional factors modulating BBB permeability in acute brain injury are matrix metalloproteinases-2 and 9 and angiogenic factors, the most notable being vascular endothelial growth factor-A and angiopoietins (Ang) 1 and 2. Vascular endothelial growth factor-A and Ang2 have emerged as potent inducers of BBB breakdown while Ang1 is a potent anti-leakage factor. These factors have the potential to modulate permeability in acute brain injury and this is an area of ongoing research. Overall, a combination of haemodynamic, structural and molecular alterations affecting brain endothelium results in BBB breakdown in acute brain injury.
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Affiliation(s)
- S Nag
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
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Grinnell KL, Harrington EO. Interplay between FAK, PKCδ, and p190RhoGAP in the regulation of endothelial barrier function. Microvasc Res 2011; 83:12-21. [PMID: 21549132 DOI: 10.1016/j.mvr.2011.04.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Revised: 04/15/2011] [Accepted: 04/16/2011] [Indexed: 11/16/2022]
Abstract
Disruption of either intercellular or extracellular junctions involved in maintaining endothelial barrier function can result in increased endothelial permeability. Increased endothelial permeability, in turn, allows for the unregulated movement of fluid and solutes out of the vasculature and into the surrounding connective tissue, contributing to a number of disease states, including stroke and pulmonary edema (Ermert et al., 1995; Lee and Slutsky, 2010; van Hinsbergh, 1997; Waller et al., 1996; Warboys et al., 2010). Thus, a better understanding of the molecular mechanisms by which endothelial cell junction integrity is controlled is necessary for development of therapies aimed at treating such conditions. In this review, we will discuss the functions of three signaling molecules known to be involved in regulation of endothelial permeability: focal adhesion kinase (FAK), protein kinase C delta (PKCδ), and p190RhoGAP (p190). We will discuss the independent functions of each protein, as well as the interplay that exists between them and the effects of such interactions on endothelial function.
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Affiliation(s)
- Katie L Grinnell
- Vascular Research Laboratory, Providence VA Medical Center, Department of Medicine, Warren Alpert Medical School of Brown University, Providence, RI 02908, USA
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Ruiz-Loredo AY, López E, López-Colomé AM. Thrombin promotes actin stress fiber formation in RPE through Rho/ROCK-mediated MLC phosphorylation. J Cell Physiol 2011; 226:414-23. [PMID: 20672289 DOI: 10.1002/jcp.22347] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The retinal pigment epithelium (RPE) forms the outer blood-retina barrier (BRB). Most retinal diseases involve BRB breakdown, whereupon thrombin contained in serum directly contacts the RPE. Thrombin is known to promote actin stress fiber formation, an important determinant in eye diseases involving the epithelial-mesenchymal transition (EMT) and migration of RPE cells, such as proliferative vitreoretinopathy. We analyzed thrombin effect on signaling pathways leading to myosin light chain (MLC) phosphorylation and actin stress fiber formation in primary cultures of rat RPE cells, in order to support a role for thrombin in RPE transdifferentiation. MLC phosphorylation was measured by Western blot; actin cytoskeleton was visualized using immunofluorescent phalloidin, and Rho GTPase activation was assessed by ELISA. We showed that thrombin/PAR-1 induces the time- and dose-dependent phosphorylation of MLC through the activation of Rho/ROCK and myosin light chain kinase (MLCK). ROCK increased phospho-MLC by phosphorylating MLC and by inhibiting MLC phosphatase. Thrombin effect was abolished by the ROCK inhibitor Y-27632, whereas MLCK inhibitor ML-7 and PLC-β inhibitor U73122 attenuated MLC phosphorylation by ≈50%, suggesting the activation of MLCK by PLC-β-mediated calcium increase. Additionally, thrombin-induced MLC phosphorylation was blocked by the inhibitory PKCζ pseudosubstrate, wortmannin, and LY294002, indicating IP(3)/PKCζ involvement in the control of MLC phosphorylation. Moreover, we demonstrated that thrombin effect on MLC induces actin stress fiber formation, since this effect was prevented by inhibiting the pathways leading to MLC phosphorylation. We conclude that thrombin stimulation of MLC phosphorylation and actin stress fiber formation may be involved in thrombin-induced RPE cell transformation subsequent to BRB dysfunction.
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Affiliation(s)
- Ariadna Yolanda Ruiz-Loredo
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, D.F., Mexico
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Abstract
The molecular advances in various aspects of brain endothelial cell function in steady states are considerable and difficult to summarize in one chapter. Therefore, this chapter focuses on endothelial permeability mechanisms in steady states and disease namely vasogenic edema. The morphology and properties of caveolae and tight junctions that are involved in endothelial permeability to macromolecules are reviewed. Endothelial transport functions are briefly reviewed. Diseases with alterations of endothelial permeability are mentioned and details are provided of the molecular alterations in caveolae and tight junctions in vasogenic edema. Other factors involved in increased endothelial permeability such as the matrix metalloproteinases are briefly discussed. Of the modulators of endothelial permeability, angioneurins such as the vascular endothelial growth factors and angiopoietins are discussed. The chapter concludes with a brief discussion on delivery of therapeutic substances across endothelium.
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28
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Bae JS, Kim IS, Rezaie AR. Thrombin down-regulates the TGF-beta-mediated synthesis of collagen and fibronectin by human proximal tubule epithelial cells through the EPCR-dependent activation of PAR-1. J Cell Physiol 2010; 225:233-9. [PMID: 20506163 DOI: 10.1002/jcp.22249] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Human proximal tubule (HK-2) cells are commonly used as cellular models to understand the mechanism by which inflammatory mediators cause renal injury. It has been observed that thrombin stimulates the expression of TGF-beta, extracellular matrix (ECM) proteins and proinflammatory cytokines by HK-2 cells. These in vitro responses correlate well with the pathology of glomerular and tubular diseases observed in acute renal injury. HK-2 cells express PAR-1 and the thrombin activation of this receptor has been reported to up-regulate the TGF-beta-mediated expression of ECM proteins, suggesting a possible pathogenic role for PAR-1 signaling by thrombin in acute renal injury. On the other hand, several recent studies have indicated that activated protein C plays a renoprotective role, thus inhibiting the inflammatory responses and attenuating renal injury, presumably by activating the same cell surface receptor. In this study, we show that HK-2 cells express endothelial protein C receptor (EPCR) and that the occupancy of this receptor by protein C switches the signaling specificity of thrombin so that the activation of PAR-1 by thrombin inhibits the TNF-alpha-mediated synthesis of IL-6 and IL-8 and down-regulates the TGF-beta-mediated expression of ECM proteins. These results suggest a possible protective role for EPCR in acute kidney injury.
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Affiliation(s)
- Jong-Sup Bae
- Department of Herbal Pharmaceutical Engineering, College of Herbal Bio-Industry, Daegu Haany University, Gyeongsangbuk-do, Republic of Korea.
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Bae JS, Rezaie AR. Thrombin upregulates the angiopoietin-Tie2 Axis: endothelial protein C receptor occupancy prevents the thrombin mobilization of angiopoietin 2 and P-selectin from Weibel-Palade bodies. J Thromb Haemost 2010; 8:1107-15. [PMID: 20180904 PMCID: PMC2891946 DOI: 10.1111/j.1538-7836.2010.03812.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
SUMMARY BACKGROUND Activated protein C (APC) in complex with endothelial protein C receptor (EPCR) can reverse the barrier-disruptive and cytotoxic effects of proinflammatory cytokines by cleaving protease-activated receptor 1 (PAR-1). Recently, it was reported that the PAR-1-dependent vascular barrier-protective effect of APC is mediated through transactivation of the angiopoietin (Ang)-Tie2 signaling pathway. The antagonist of this pathway, Ang2, is stored in Weibel-Palade bodies within endothelial cells. OBJECTIVES To determine whether the occupancy of EPCR by its ligand can switch the PAR-1-dependent signaling specificity of thrombin through the Ang-Tie2 axis. METHODS We activated endothelial cells with thrombin before and after treating them with the catalytically inactive Ser195-->Ala substitution mutant of protein C. The expression levels of Ang1, Ang2 and Tie2 in response to thrombin were measured by both an enzyme-linked immunosorbent assay and a cell permeability assay in the absence and presence of small interfering RNA and a blocking antibody to Tie2. RESULTS Thrombin upregulated the expression of both Ang1 and Tie2 but downregulated the expression of Ang2 when EPCR was occupied by its ligand. The Ang1-Tie2-dependent protective effect of thrombin was initiated through protein C inhibiting the rapid mobilization of Ang2 from Weibel-Palade bodies. Interestingly, the protein C mutant also inhibited the thrombin mobilization of P-selectin. CONCLUSIONS These results suggest a physiologic role for the low concentration of thrombin in maintaining the integrity of the EPCR-containing vasculature through the PAR-1-dependent inhibition of Ang2 and P-selectin release from Weibel-Palade bodies.
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Affiliation(s)
- Jong-Sup Bae
- Department of Herbal Pharmaceutical Engineering, College of Herbal Bio-Industry, Daegu Haany University, Gyeongsan 712-715 Republic of Korea
| | - Alireza R. Rezaie
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri 63104 USA
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Minshall RD, Vandenbroucke EE, Holinstat M, Place AT, Tiruppathi C, Vogel SM, van Nieuw Amerongen GP, Mehta D, Malik AB. Role of protein kinase Czeta in thrombin-induced RhoA activation and inter-endothelial gap formation of human dermal microvessel endothelial cell monolayers. Microvasc Res 2010; 80:240-9. [PMID: 20417648 DOI: 10.1016/j.mvr.2010.04.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Revised: 03/12/2010] [Accepted: 04/16/2010] [Indexed: 12/30/2022]
Abstract
We studied the potential involvement of the Ca(2+)-independent atypical protein kinase C isoform PKCzeta in mediating the thrombin-induced increase in endothelial permeability. Studies were done using human dermal microvessel endothelial cells (HMEC), which we showed constitutively expressed PKCzeta. We quantified the patency of inter-endothelial junctions (IEJs) and endothelial barrier function by measuring transendothelial electrical resistance (TER) in confluent HMEC monolayers. In control monolayers, thrombin decreased TER by approximately 50%, indicating thrombin-dependent opening of IEJs. Thrombin also elicited increases in cytosolic Ca(2+) concentration [Ca(2+)](i), actin stress fiber formation, and myosin light chain (MLC) phosphorylation. Pan-PKC inhibitors, calphostin C and chelerythrine, abrogated these responses. Thrombin also decreased TER after depletion of conventional and novel Ca(2+)-dependent PKC isoforms using phorbol 12-myristate 13-acetate (PMA). In these PMA-treated cells, thrombin induced inter-endothelial gap formation, MLC phosphorylation, and actin stress fiber formation, but failed to increase [Ca(2+)](i). Inhibition of PKCzeta activation using the PKCzeta pseudosubstrate peptide (PSI), depletion of PKCzeta protein with siRNA, and competitive inhibition of PKCzeta activity using dominant-negative (dn) PKCzeta mutant all prevented the thrombin-induced decrease in TER and MLC phosphorylation. Expression of dn-PKCzeta also inhibited thrombin-induced RhoA activation. These findings reveal a novel Ca(2+)-independent, PKCzeta-dependent mechanism of thrombin-induced increase in endothelial permeability. The results raise the possibility that inhibition of PKCzeta may be a novel drug target for thrombin-induced inflammatory hyperpermeability.
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Affiliation(s)
- Richard D Minshall
- Department of Pharmacology, University of Illinois at Chicago, Chicago, IL, USA.
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Pathology and new players in the pathogenesis of brain edema. Acta Neuropathol 2009; 118:197-217. [PMID: 19404652 DOI: 10.1007/s00401-009-0541-0] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Revised: 04/16/2009] [Accepted: 04/21/2009] [Indexed: 12/20/2022]
Abstract
Brain edema continues to be a major cause of mortality after diverse types of brain pathologies such as major cerebral infarcts, hemorrhages, trauma, infections and tumors. The classification of edema into vasogenic, cytotoxic, hydrocephalic and osmotic has stood the test of time although it is recognized that in most clinical situations there is a combination of different types of edema during the course of the disease. Basic information about the types of edema is provided for better understanding of the expression pattern of some of the newer molecules implicated in the pathogenesis of brain edema. These molecules include the aquaporins, matrix metalloproteinases and growth factors such as vascular endothelial growth factors A and B and the angiopoietins. The potential of these agents in the treatment of edema is discussed. Since many molecules are involved in the pathogenesis of brain edema, effective treatment cannot be achieved by a single agent but will require the administration of a "magic bullet" containing a variety of agents released at different times during the course of edema in order to be successful.
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Phosphorylation of endothelial nitric oxide synthase by atypical PKC zeta contributes to angiopoietin-1-dependent inhibition of VEGF-induced endothelial permeability in vitro. Blood 2009; 114:3343-51. [PMID: 19564638 DOI: 10.1182/blood-2008-12-196584] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Vascular endothelial growth factor (VEGF) is a potent angiogenic cytokine that also increases vascular permeability. Nitric oxide (NO) released from endothelial cells, after activation of endothelial NO synthase (eNOS), contributes to proangiogenic and permeability effects of VEGF. Angiopoietin-1 (Ang-1), via Tie2 receptors, shares many of the proangiogenic properties of VEGF on endothelial cells. However, in contrast to VEGF, Ang-1 protects blood vessels from increased plasma leakage, which contributes to their stabilization. Because eNOS-derived NO is central to increased permeability in response to VEGF, we investigated whether Ang-1 interferes with VEGF signaling to eNOS. We demonstrate that Ang-1 stimulation of endothelial cells inhibits VEGF-induced NO release and transendothelial permeability. In contrast to VEGF stimulation, Ang-1 causes a marked protein kinase C (PKC)-dependent increase in phosphorylation of eNOS on the inhibitory Thr(497). Furthermore, using pharmacologic inhibitors, overexpression studies, and small interfering RNA-mediated gene silencing, we demonstrate that atypical PKC zeta is responsible for phosphorylation of eNOS on Thr(497) in response to Ang-1. In addition, PKC zeta knockdown abrogates the capacity of Ang-1 to inhibit VEGF-induced NO release and endothelial permeability. Thus, inhibition of NO production by Ang-1, via phosphorylation of eNOS on Thr(497) by PKC zeta, is responsible, at least in part, for inhibition of VEGF-stimulated endothelial permeability by Ang-1.
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Li X, Stankovic M, Lee BPL, Aurrand-Lions M, Hahn CN, Lu Y, Imhof BA, Vadas MA, Gamble JR. JAM-C induces endothelial cell permeability through its association and regulation of {beta}3 integrins. Arterioscler Thromb Vasc Biol 2009; 29:1200-6. [PMID: 19461049 DOI: 10.1161/atvbaha.109.189217] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE The molecular mechanisms regulating vascular permeability are only now being elucidated. The junctional adhesion molecule (JAM) JAM-C has been linked to the induction of vascular permeability. We sought to understand the mechanism whereby JAM-C may disrupt junctional integrity in endothelial cells (ECs). METHODS AND RESULTS We show here that JAM-C alters permeability through modulation of integrin activity. JAM-C overexpression results in an increase in JAM-C at junctions and an increase in permeability. Conversely, knockdown of JAM-C by siRNA results in a reduction in permeability. JAM-C associates with alphavbeta3 integrin and regulates its localization and activity. JAM-C also inhibits the activation state of the beta(1) integrin although it does not associate with this integrin. These changes induced on the integrins are mediated through regulation of the small GTPase, Rap1b but not Rap1a. Thrombin, a powerful inductor of vascular leak, causes localization of JAM-C into the junctions, whereas angiopoietin-1, an inhibitor of permeability, prevents JAM-C translocation. CONCLUSIONS The regulation of EC junctional integrity involves the coordinated and dynamic modification of localization and activity of junctional stabilizers such as the integrin beta(3) and the destabilizer, JAM-C.
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Affiliation(s)
- Xiaochun Li
- Centenary Institute of Cancer Medicine and Cell Biology, Locked bag#6, Newtown, NSW, Australia
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Thomas M, Augustin HG. The role of the Angiopoietins in vascular morphogenesis. Angiogenesis 2009; 12:125-37. [PMID: 19449109 DOI: 10.1007/s10456-009-9147-3] [Citation(s) in RCA: 278] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Accepted: 04/24/2009] [Indexed: 01/20/2023]
Abstract
The Angiopoietin/Tie system acts as a vascular specific ligand/receptor system to control endothelial cell survival and vascular maturation. The Angiopoietin family includes four ligands (Angiopoietin-1, Angiopoietin-2 and Angiopoietin-3/4) and two corresponding tyrosine kinase receptors (Tie1 and Tie2). Ang-1 and Ang-2 are specific ligands of Tie2 binding the receptor with similar affinity. Tie2 activation promotes vessel assembly and maturation by mediating survival signals for endothelial cells and regulating the recruitment of mural cells. Ang-1 acts in a paracrine agonistic manner inducing Tie2 phosphorylation and subsequent vessel stabilization. In contrast, Ang-2 is produced by endothelial cells and acts as an autocrine antagonist of Ang-1-mediated Tie2 activation. Ang-2 thereby primes the vascular endothelium to exogenous cytokines and induces vascular destabilization at higher concentrations. Ang-2 is strongly expressed in the vasculature of many tumors and it has been suggested that Ang-2 may act synergistically with other cytokines such as vascular endothelial growth factor to promote tumor-associated angiogenesis and tumor progression. The better mechanistic understanding of the Ang/Tie system is gradually paving the way toward the rationale exploitation of this vascular signaling system as a therapeutic target for neoplastic and non-neoplastic diseases.
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Affiliation(s)
- Markus Thomas
- Joint Research Division Vascular Biology, Medical Faculty Mannheim (CBTM), University of Heidelberg, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
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van der Heijden M, van Nieuw Amerongen GP, Chedamni S, van Hinsbergh VWM, Johan Groeneveld AB. The angiopoietin-Tie2 system as a therapeutic target in sepsis and acute lung injury. Expert Opin Ther Targets 2009; 13:39-53. [PMID: 19063705 DOI: 10.1517/14728220802626256] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND Sepsis and acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are life-threatening syndromes characterised by inflammation and increased vascular permeability. Amongst other factors, the angiopoietin-tyrosine kinase with immunoglobulin-like and EGF-like domains 2 (Tie2) system is involved. OBJECTIVE To explore whether the angiopoietin-Tie2 system provides suitable targets for the treatment of sepsis and ALI/ARDS. METHODS Original experimental and patient studies on angiopoietins and sepsis/endotoxemia, inflammation, lung injury, hyperpermeability, apoptosis, organ functions and vital outcomes were reviewed. RESULTS/CONCLUSION The angiopoietin-Tie2 system controls the responsiveness of the endothelium to inflammatory, hyperpermeability, apoptosis and vasoreactive stimuli. Angiopoietin-2 provokes inflammation and vascular hyperpermeability, while angiopoietin-1 has a protective effect. Targeted angiopoietin-2 inhibition with RNA aptamers or blocking antibodies is a potential anti-inflammatory and anti-vascular hyperpermeability strategy in the treatment of sepsis and ALI/ARDS.
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Affiliation(s)
- Melanie van der Heijden
- VU University Medical Center, Institute for Cardiovascular Research, Department of Intensive Care, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands.
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Milner CS, Hansen TM, Singh H, Brindle NP. Roles of the receptor tyrosine kinases Tie1 and Tie2 in mediating the effects of angiopoietin-1 on endothelial permeability and apoptosis. Microvasc Res 2009; 77:187-91. [DOI: 10.1016/j.mvr.2008.09.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 09/04/2008] [Accepted: 09/08/2008] [Indexed: 10/21/2022]
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Gotsch F, Romero R, Kusanovic JP, Chaiworapongsa T, Dombrowski M, Erez O, Than NG, Mazaki-Tovi S, Mittal P, Espinoza J, Hassan SS. Preeclampsia and small-for-gestational age are associated with decreased concentrations of a factor involved in angiogenesis: soluble Tie-2. J Matern Fetal Neonatal Med 2008; 21:389-402. [PMID: 18570117 DOI: 10.1080/14767050802046069] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE An anti-angiogenic state has been described in patients with preeclampsia, small-for-gestational age (SGA) fetuses and fetal death, and changes in the concentration of circulating angiogenic and anti-angiogenic factors can precede the clinical recognition of preeclampsia and SGA by several weeks. Gene deletion studies demonstrate that a selective group of endothelial growth factors are required for vascular development, including members of the vascular endothelial growth factor (VEGF) family, as well as angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2), both ligands for the tyrosine kinase endothelial cell receptor Tie-2. These angiogenic factors have been proposed to promote angiogenesis in a coordinated and complementary fashion. Soluble Tie-2 (sTie-2) is the soluble form of the Tie-2 receptor, which is detectable in biological fluids. The purpose of this study was to determine whether patients with preeclampsia and mothers who deliver a SGA neonate have changes in the plasma concentrations of sTie-2. STUDY DESIGN This cross-sectional study included patients in the following groups: (1) non-pregnant women (n = 40), (2) women with normal pregnancies (n = 135), (3) patients with preeclampsia (n = 112), and (4) patients who delivered an SGA neonate (n = 53). Maternal plasma concentrations of sTie-2 were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis. RESULTS (1) The median maternal plasma concentration of sTie-2 was lower in normal pregnant women than in non-pregnant women [median 16.0 ng/mL (range 5.0-71.6) vs. median 20.7 ng/mL (range 10.8-52.4), respectively; p = 0.01)). (2) Plasma sTie-2 concentrations in normal pregnancy changed significantly as a function of gestational age. (3) Patients with preeclampsia and those who delivered SGA neonates had a lower median maternal plasma concentration of sTie-2 than those with a normal pregnancy [preeclampsia: median 14.9 ng/mL (range 4.9-67.3); SGA: median 10.9 ng/mL (range 5.1-29.1); normal pregnancy: median 16.0 ng/mL (range 5.0-71.6); p = 0.048 and p < 0.001, respectively]. (4) Patients with SGA neonates had a lower median plasma concentration of sTie-2 than that of those with preeclampsia [median 10.9 ng/mL (range 5.1-29.1) vs. median 14.9 ng/mL (range 4.9-67.3), respectively; p < 0.001]. (5) Patients with early-onset preeclampsia (<or=34 weeks) had lower concentrations of sTie-2 than women with late-onset preeclampsia (>34 weeks) median of delta values: -0.13 ng/mL (range -0.47-0.58) vs. median of delta values: -0.09 ng/mL (range: -0.60-0.58), respectively; p = 0.043]. In contrast, there were no significant differences in the maternal plasma sTie-2 concentration between women with severe and mild preeclampsia (p = 0.6). CONCLUSION Patients with preeclampsia and those with SGA fetuses have lower median plasma concentrations of soluble Tie-2 than women with normal pregnancies.
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Affiliation(s)
- Francesca Gotsch
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, USA.
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Gavard J, Gutkind JS. Protein kinase C-related kinase and ROCK are required for thrombin-induced endothelial cell permeability downstream from Galpha12/13 and Galpha11/q. J Biol Chem 2008; 283:29888-96. [PMID: 18713748 DOI: 10.1074/jbc.m803880200] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Increase in vascular permeability occurs under many physiological conditions such as wound repair, inflammation, and thrombotic reactions and is central in diverse human pathologies, including tumor-induced angiogenesis, ocular diseases, and septic shock. Thrombin is a pro-coagulant serine protease, which causes the local loss of endothelial barrier integrity thereby enabling the rapid extravasation of plasma proteins and the local formation of fibrin-containing clots. Available information suggests that thrombin induces endothelial permeability by promoting actomyosin contractility through the Rho/ROCK signaling pathway. Here we took advantage of pharmacological inhibitors, knockdown approaches, and the emerging knowledge on how permeability factors affect endothelial junctions to investigate in detail the mechanism underlying thrombin-induced endothelial permeability. We show that thrombin signals through PAR-1 and its coupled G proteins Galpha(12/13) and Galpha(11/q) to induce RhoA activation and intracellular calcium elevation, and that these events are interrelated. In turn, this leads to the stimulation of ROCK, which causes actin stress-fiber formation. However, this alone is not sufficient to account for thrombin-induced permeability. Instead, we found that protein kinase C-related kinase, a Rho-dependent serine/threonine kinase, is activated in endothelial cells upon thrombin stimulation and that its expression is required for endothelial permeability and the remodeling of cell-extracellular matrix and cell-cell adhesions. Our results demonstrate that the signal initiated by thrombin bifurcates at the level of RhoA to promote changes in the cytoskeletal architecture through ROCK, and the remodeling of focal adhesion components through protein kinase C-related kinase. Ultimately, both pathways converge to cause cell-cell junction disruption and provoke vascular leakage.
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Affiliation(s)
- Julie Gavard
- Oral and Pharyngeal Cancer Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Voskas D, Babichev Y, Ling LS, Alami J, Shaked Y, Kerbel RS, Ciruna B, Dumont DJ. An eosinophil immune response characterizes the inflammatory skin disease observed in Tie-2 transgenic mice. J Leukoc Biol 2008; 84:59-67. [PMID: 18443190 DOI: 10.1189/jlb.0607347] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Although mouse models of inflammatory skin diseases such as psoriasis and atopic dermatitis fail to completely phenocopy disease in humans, they provide invaluable tools to examine the molecular and cellular mechanisms responsible for the epidermal hyperplasia, inflammation, and excess angiogenesis observed in human disease. We have previously characterized a tyrosine kinase with immunoglobin-like and epidermal growth factor-like domain-2 (Tie-2) transgenic mouse model of an inflammatory skin disease exhibiting these features. More specifically, we demonstrated that the inflammatory component consisted of increased infiltration of CD3-positive T lymphocytes and mast cells in the skin. Here, we further characterize the inflammatory component in the blood and skin of Tie-2 transgenic mice at cellular and molecular levels. We observed increased numbers of CD3-positive T lymphocytes in the blood and increased infiltration of eosinophils in the skin. Furthermore, we characterized cytokine protein and gene expression in the blood and skin, respectively, and observed the deregulated expression of cytokines associated with Th1 and eosinophil immune responses. Interestingly, treatment of Tie-2 transgenic mice with anti-CD4 antibody appeared to resolve aspects of inflammation but did not resolve epidermal hyperplasia, suggesting an important role for eosinophils in mediating the inflammatory skin disease observed in Tie-2 transgenic mice.
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Affiliation(s)
- Daniel Voskas
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
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Choi YK, Kim KW. AKAP12 in astrocytes induces barrier functions in human endothelial cells through protein kinase Czeta. FEBS J 2008; 275:2338-53. [PMID: 18397319 DOI: 10.1111/j.1742-4658.2008.06387.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Interactions between astrocytes and blood vessels are essential for the formation and maintenance of the blood-neural barrier (BNB). Astrocyte-derived A-kinase anchor protein 12 (AKAP12) influences BNB formation, but the mechanism of regulation of BNB functions by AKAP12 is not fully understood. We have defined a new pathway of barriergenesis in human retina microvascular endothelial cells (HRMECs) involving astrocytic AKAP12. Treatment of HRMECs with conditioned media from AKAP12-overexpressing astrocytes reduced phosphorylation of protein kinase Czeta (PKCzeta), decreased the levels of vascular endothelial growth factor (VEGF) mRNA and protein, and increased thrombospondin-1 (TSP-1) levels, which led to antiangiogenesis and barriergenesis. Transfection of a small interference RNA targeting PKCzeta decreased VEGF levels and increased TSP-1 levels in HRMECs. Rho is a putative downstream signal of PKCzeta, and inhibition of Rho kinase with a specific inhibitor, Y27632, decreased VEGF levels and increased TSP-1 levels. We therefore suggest that AKAP12 in astrocytes differentially regulates the expression of VEGF and TSP-1 via the inhibition of PKCzeta phosphorylation and Rho kinase activity in HRMECs.
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Affiliation(s)
- Yoon Kyung Choi
- NeuroVascular Coordination Research Center, College of Pharmacy and Research, Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Korea
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van Nieuw Amerongen GP, Musters RJP, Eringa EC, Sipkema P, van Hinsbergh VWM. Thrombin-induced endothelial barrier disruption in intact microvessels: role of RhoA/Rho kinase-myosin phosphatase axis. Am J Physiol Cell Physiol 2008; 294:C1234-41. [PMID: 18353893 DOI: 10.1152/ajpcell.00551.2007] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Endothelial hyperpermeability is regulated by a myosin light chain-2 (MLC2) phosphorylation-dependent contractile mechanism. Thrombin is a potent inducer of hyperpermeability of cultured monolayers of endothelial cells (ECs) via Rho kinase-mediated MLC2-phosphorylation. The aim of the present study was to investigate the effects of thrombin on in situ endothelial morphology and barrier integrity. Cytoskeletal dynamics, regions of paracellular flux, and MLC2-phosphorylation of ECs were visualized by digital three-dimensional imaging microscopy of pressurized rat kidney arterioles. Myosin phosphatase targeting subunit (MYPT1)-phosphorylation was used as a surrogate marker for Rho kinase activity. Thrombin induced the formation of F-actin filaments in ECs in situ and rounding of the ECs in the absence of obvious formation of gaps between ECs. These changes were accompanied by an increase in MLC2 phosphorylation and a decrease in barrier integrity. In vitro analysis revealed that Rho kinase activity on F-actin filaments was associated with a contractile response that enhanced opening of the barrier. Rho kinase activity was not detectable on F-actin filaments induced by histamine, an inducer of a more transient hyperpermeability response. Inhibition of the myosin phosphatase mimicked the effects of thrombin on barrier function. The thrombin-induced changes in in situ MLC2 phosphorylation and barrier function were Rho kinase dependent. These data demonstrate a direct effect of thrombin on EC morphology and barrier integrity in intact microvessels. Furthermore, they establish an important contribution of enhanced Rho kinase activity to the development of prolonged but not transient types of endothelial barrier dysfunction.
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Affiliation(s)
- G P van Nieuw Amerongen
- Laboratory for Physiology, Institute for Cardiovascular Research, Vrije Universiteit University Medical Center, Amsterdam, The Netherlands.
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Makinde T, Agrawal DK. Intra and extravascular transmembrane signalling of angiopoietin-1-Tie2 receptor in health and disease. J Cell Mol Med 2008; 12:810-28. [PMID: 18266978 PMCID: PMC4401129 DOI: 10.1111/j.1582-4934.2008.00254.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Angiopoietin-1 (Ang-1) is the primary agonist for Tie2 tyrosine kinase receptor (Tie2), and the effect of Ang-1-Tie2 signalling is context-dependent. Deficiency in either Ang-1 or Tie2 protein leads to severe microvascular defects and subsequent embryonic lethality in murine model. Tie2 receptors are expressed in several cell types, including endothelial cells, smooth muscle cells, fibroblasts, epithelial cells, monocytes, neutrophils, eosinophils and glial cells. Ang-1-Tie2 signalling induces a chemotactic effect in smooth muscle cells, neutrophils and eosinophils, and induces differentiation of mesenchymal cells to smooth muscle cells. Additionally, this signalling pathway induces the secretion of serotonin, matrix metalloproteinases (MMPs) and plasmin. Ang-1 inhibits the secretion of tissue inhibitor of matrix metalloproteinase (TIMPs). Aberrant expression and activity of Tie2 in vascular and non-vascular cells may result in the development of rheumatoid arthritis, cancer, hypertension and psoriasis. Ang-1 has an anti-inflammatory effect, when co-localized with vascular endothelial growth factor (VEGF) in the vasculature. Thus, Ang-1 could be potentially important in the therapy of various pathological conditions such as pulmonary hypertension, arteriosclerosis and diabetic retinopathy. In this article, we have summarized and critically reviewed the pathophysiological role of Ang-1-Tie2 signalling pathway.
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Affiliation(s)
- T Makinde
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
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Basal and angiopoietin-1-mediated endothelial permeability is regulated by sphingosine kinase-1. Blood 2008; 111:3489-97. [PMID: 18199826 DOI: 10.1182/blood-2007-05-092148] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Endothelial cells (ECs) regulate the barrier function of blood vessels. Here we show that basal and angiopoietin-1 (Ang-1)-regulated control of EC permeability is mediated by 2 different functional states of sphingosine kinase-1 (SK-1). Mice depleted of SK-1 have increased vascular leakiness, whereas mice transgenic for SK-1 in ECs show attenuation of leakiness. Furthermore, Ang-1 rapidly and transiently stimulates SK-1 activity and phosphorylation, and induces an increase in intracellular sphingosine-1-phosphate (S1P) concentration. Overexpression of SK-1 resulted in inhibition of permeability similar to that seen for Ang-1, whereas knockdown of SK-1 by small interfering RNA blocked Ang-1-mediated inhibition of permeability. Transfection with SKS225A, a nonphosphorylatable mutant of SK-1, inhibited basal leakiness, and both SKS225A and a dominant-negative SK-1 mutant removed the capacity of Ang-1 to inhibit permeability. These effects were independent of extracellular S1P as knockdown or inhibition of S1P1, S1P2, or S1P3, did not affect the Ang-1 response. Thus, SK-1 levels in ECs powerfully regulate basal permeability in vitro and in vivo. In addition, the Ang-1-induced inhibition of leakiness is mediated through activation of SK-1, defining a new signaling pathway in the Ang-1 regulation of permeability.
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Adamson RH, Ly JC, Sarai RK, Lenz JF, Altangerel A, Drenckhahn D, Curry FE. Epac/Rap1 pathway regulates microvascular hyperpermeability induced by PAF in rat mesentery. Am J Physiol Heart Circ Physiol 2008; 294:H1188-96. [PMID: 18178724 DOI: 10.1152/ajpheart.00937.2007] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Experiments in cultured endothelial cell monolayers demonstrate that increased intracellular cAMP strongly inhibits the acute permeability responses by both protein kinase A (PKA)-dependent and -independent pathways. The contribution of the PKA-independent pathways to the anti-inflammatory mechanisms of cAMP in intact mammalian microvessels has not been systematically investigated. We evaluated the role of the cAMP-dependent activation of the exchange protein activated by cAMP (Epac), a guanine nucleotide exchange factor for the small GTPase Rap1, in rat venular microvessels exposed to the platelet-activating factor (PAF). The cAMP analog 8-pCPT-2'-O-methyl-cAMP (O-Me-cAMP), which stimulates the Epac/Rap1 pathway but has no effect on PKA, significantly attenuated the PAF increase in microvessel permeability as measured by hydraulic conductivity (Lp). We also demonstrated that PAF induced a rearrangement of vascular endothelial (VE)-cadherin seen as numerous lateral spikes and frequent short breaks in the otherwise continuous peripheral immunofluorescent label. Pretreatment with O-Me-cAMP completely prevented the PAF-induced rearrangement of VE-cadherin. We conclude that the action of the Epac/Rap1 pathway to stabilize cell-cell adhesion is a significant component of the activity of cAMP to attenuate an acute increase in vascular permeability. Our results indicate that increased permeability in intact microvessels by acute inflammatory agents such as PAF is the result of the decreased effectiveness of the Epac/Rap1 pathway modulation of cell-cell adhesion.
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Affiliation(s)
- R H Adamson
- Physiology and Membrane Biology, School of Medicine, University of California at Davis, Davis, CA 95616, USA.
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Gavard J, Patel V, Gutkind JS. Angiopoietin-1 Prevents VEGF-Induced Endothelial Permeability by Sequestering Src through mDia. Dev Cell 2008; 14:25-36. [DOI: 10.1016/j.devcel.2007.10.019] [Citation(s) in RCA: 275] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 10/05/2007] [Accepted: 10/31/2007] [Indexed: 10/22/2022]
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Ushio-Fukai M, Frey RS, Fukai T, Malik AB. Chapter 8 Reactive Oxygen Species and Endothelial Permeability. CURRENT TOPICS IN MEMBRANES 2008. [DOI: 10.1016/s1063-5823(08)00208-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Klinger JR, Murray JD, Casserly B, Alvarez DF, King JA, An SS, Choudhary G, Owusu-Sarfo AN, Warburton R, Harrington EO. Rottlerin causes pulmonary edema in vivo: a possible role for PKCδ. J Appl Physiol (1985) 2007; 103:2084-94. [PMID: 17901241 DOI: 10.1152/japplphysiol.00695.2007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, we assessed the effects of chemical inhibitors shown to be selective for protein kinase C (PKC) isoforms on lung barrier function both in vitro and in vivo. Rottlerin, a purported inhibitor of PKCδ, but not other chemical inhibitors, dose dependently promoted barrier dysfunction in lung endothelial cells in vitro. This barrier dysfunction correlated with structural changes in focal adhesions and stress fibers, which were consistent with functional changes in cell stiffness. To determine whether the effects noted in vitro correlated with changes in intact lungs, we tested the effects of rottlerin in the formation of pulmonary edema in rats using both ex vivo and in vivo models. Isolated, perfused lungs demonstrated a significant increase in filtration coefficients on exposure to rottlerin, compared with vehicle-treated lungs, an effect that correlated with increased extravasation of Evan's blue dye (EBD)-conjugated albumin. Additionally, compared with vehicle, the ratio of the wet lung weights to dry lung weights was significantly greater on exposure of animals to rottlerin; rottlerin also produced a dose-dependent increase in EBD extravasation into the lungs. These effects on lung edema occurred without any increase in right ventricular pressures. Microscopic assessment of edema in the ex vivo lungs demonstrated perivascular cuffing, with no evidence of septal capillary leak, in rottlerin-exposed lungs. Taken together, rottlerin increases barrier dysfunction in pulmonary endothelial cell monolayers and causes pulmonary edema in rats; results suggestive of an important role for PKCδ in maintaining lung endothelial barrier function.
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Affiliation(s)
- James R Klinger
- Vascular Research Laboratory, Providence Veterans Affairs Medical Center, and Department of Medicine, Brown Medical School, Providence, RI 02908, USA
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van Nieuw Amerongen GP, Beckers CML, Achekar ID, Zeeman S, Musters RJP, van Hinsbergh VWM. Involvement of Rho kinase in endothelial barrier maintenance. Arterioscler Thromb Vasc Biol 2007; 27:2332-9. [PMID: 17761936 DOI: 10.1161/atvbaha.107.152322] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Rho kinase mediates vascular leakage caused by many vasoactive agents including thrombin. Enhanced Rho kinase activity induces endothelial barrier dysfunction by a contractile mechanism via inactivation of Myosin Phosphatase (MP). Here, we investigated the contribution of basal Rho kinase activity to the regulation of endothelial barrier integrity. METHODS AND RESULTS Using a phospho-specific antibody against the myosin phosphatase targeting subunit (Thr696-MYPT1) as a marker for Rho kinase activity, basal endothelial Rho kinase activity was observed at cell-cell contact sites, in vitro and in situ. Thrombin enhanced MYPT phosphorylation at F-actin stress fibers. Inhibition of basal Rho kinase activity for 24 hours or depletion of Rho kinase (ROCK-I and -II) by siRNA disrupted endothelial barrier integrity, opposite to the previously observed protection from the thrombin-enhanced endothelial permeability. This barrier dysfunction could not be explained by changes in RhoA, Rac1, eNOS, or apoptosis. Remarkably, basal Rho kinase activity was essential for proper expression of the adhesion molecule VE-cadherin. CONCLUSIONS Rho kinase has opposing activities in regulation of endothelial barrier function: (1) an intrinsic barrier-protective activity at the cell margins, and (2) an induced barrier-disruptive activity at contractile F-actin stress fibers. These findings may have implications for long-term antivascular leak therapy.
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Affiliation(s)
- G P van Nieuw Amerongen
- VU university Medical Center, Laboratory for Physiology, Institute for Cardiovascular Research, Amsterdam, The Netherlands.
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Mammoto T, Parikh SM, Mammoto A, Gallagher D, Chan B, Mostoslavsky G, Ingber DE, Sukhatme VP. Angiopoietin-1 Requires p190 RhoGAP to Protect against Vascular Leakage in Vivo. J Biol Chem 2007; 282:23910-8. [PMID: 17562701 DOI: 10.1074/jbc.m702169200] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Angiopoietin-1 (Ang-1), a ligand of the endothelium-specific receptor Tie-2, inhibits permeability in the mature vasculature, but the mechanism remains unknown. Here we show that Ang-1 signals Rho family GTPases to organize the cytoskeleton into a junction-fortifying arrangement that enhances the permeability barrier function of the endothelium. Ang-1 phosphorylates Tie-2 and its downstream effector phosphatidylinositol 3-kinase. This induces activation of one endogenous GTPase, Rac1, and inhibition of another, RhoA. Loss of either part of this dual effect abrogates the cytoskeletal and anti-permeability actions of Ang-1, suggesting that coordinated GTPase regulation is necessary for the vessel-sealing effects of Ang-1. p190 RhoGAP, a GTPase regulatory protein, provides this coordinating function as it is phosphorylated by Ang-1 treatment, requires Rac1 activation, and is necessary for RhoA inhibition. Ang-1 prevents the cytoskeletal and pro-permeability effects of endotoxin but requires p190 RhoGAP to do so. Treatment with p190 RhoGAP small interfering RNA completely abolishes the ability of Ang-1 to rescue endotoxemia-induced pulmonary vascular leak and inflammation in mice. We conclude that Ang-1 prevents vascular permeability by regulating the endothelial cytoskeleton through coordinated and opposite effects on the Rho GTPases Rac1 and RhoA. By linking Rac1 activation and RhoA inhibition, p190 RhoGAP is critical to the protective effects of Ang-1 against endotoxin. These results provide mechanistic evidence that targeting the endothelium through Tie-2 may offer specific therapeutic strategies in life-threatening endotoxemic conditions such as sepsis and acute respiratory distress syndrome.
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Affiliation(s)
- Tadanori Mammoto
- Department of Medicine, Division of Interdisciplinary Medicine and Biotechnology and Center for Vascular Biology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
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Abstract
Angiopoietin-1 (Ang1) has powerful vascular protective effects: suppressing plasma leakage, inhibiting vascular inflammation, and preventing endothelial death. Preclinical studies indicate that Ang1 may be therapeutically useful in a number of situations, including treatment of edema, endotoxemia, and transplant arteriosclerosis. However, the ligand has also been implicated in vessel remodeling, induction of angiogenesis and pulmonary hypertension, indicating that strategies to minimize any deleterious effects while optimizing vessel protection are likely to be needed. This review surveys the published data on vascular protective effects of Ang1 and highlights the therapeutic potential of this ligand, as well as possible limitations to its use. We also consider the data on Ang1 receptors and speculate on how to maximize therapeutic benefit by targeting the Tie receptors.
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Affiliation(s)
- Nicholas P J Brindle
- Department of Cardiovascular Sciences, University of Leicester, RKCSB, PO Box 65, Leicester, LE2 7LX, UK.
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