Publications by authors named "Peter L Hordijk"

114 Publications

The interplay of Rac1 activity, ubiquitination and GDI binding and its consequences for endothelial cell spreading.

PLoS One 2021 12;16(7):e0254386. Epub 2021 Jul 12.

Department of Physiology, Amsterdam University Medical Centers, Amsterdam, The Netherlands.

Signaling by the Rho GTPase Rac1 is key to the regulation of cytoskeletal dynamics, cell spreading and adhesion. It is widely accepted that the inactive form of Rac1 is bound by Rho GDI, which prevents Rac1 activation and Rac1-effector interactions. In addition, GDI-bound Rac1 is protected from proteasomal degradation, in line with data showing that Rac1 ubiquitination occurs exclusively when Rac1 is activated. We set out to investigate how Rac1 activity, GDI binding and ubiquitination are linked. We introduced single amino acid mutations in Rac1 which differentially altered Rac1 activity, and compared whether the level of Rac1 activity relates to Rac1 ubiquitination and GDI binding. Results show that Rac1 ubiquitination and the active Rac1 morphology is proportionally increased with Rac1 activity. Similarly, we introduced lysine-to-arginine mutations in constitutively active Rac1 to inhibit site-specific ubiquitination and analyze this effect on Rac1 signaling output and ubiquitination. These data show that the K16R mutation inhibits GTP binding, and consequently Rac1 activation, signaling and-ubiquitination, while the K147R mutation does not block Rac1 signaling, but does inhibits its ubiquitination. In both sets of mutants, no direct correlation was observed between GDI binding and Rac1 activity or -ubiquitination. Taken together, our data show that a strong, positive correlation exists between Rac1 activity and its level of ubiquitination, but also that GDI dissociation does not predispose Rac1 to ubiquitination.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0254386PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8274835PMC
July 2021

Preservation of renal endothelial integrity and reduction of renal edema by aprotinin does not preserve renal perfusion and function following experimental cardiopulmonary bypass.

Intensive Care Med Exp 2021 Jun 25;9(1):30. Epub 2021 Jun 25.

Department of Anesthesiology, Experimental Laboratory for Vital Signs, Amsterdam Cardiovascular Sciences, Amsterdam UMC, Vrije Universiteit, Amsterdam, The Netherlands.

Background: Acute kidney injury is a severe complication following cardiopulmonary bypass (CPB) and is associated with capillary leakage and microcirculatory perfusion disturbances. CPB-induced thrombin release results in capillary hyperpermeability via activation of protease-activated receptor 1 (PAR1). We investigated whether aprotinin, which is thought to prevent thrombin from activating PAR1, preserves renal endothelial structure, reduces renal edema and preserves renal perfusion and reduces renal injury following CPB.

Methods: Rats were subjected to CPB after treatment with 33.000 KIU/kg aprotinin (n = 15) or PBS (n = 15) as control. A secondary dose of 33.000 KIU/kg aprotinin was given 60 min after initiation of CPB. Cremaster and renal microcirculatory perfusion were assessed using intravital microscopy and contrast echography before CPB and 10 and 60 min after weaning from CPB. Renal edema was determined by wet/dry weight ratio and renal endothelial structure by electron microscopy. Renal PAR1 gene and protein expression and markers of renal injury were determined.

Results: CPB reduced cremaster microcirculatory perfusion by 2.5-fold (15 (10-16) to 6 (2-10) perfused microvessels, p < 0.0001) and renal perfusion by 1.6-fold (202 (67-599) to 129 (31-292) au/sec, p = 0.03) in control animals. Both did not restore 60 min post-CPB. This was paralleled by increased plasma creatinine (p < 0.01), neutrophil gelatinase-associated lipocalin (NGAL; p = 0.003) and kidney injury molecule-1 (KIM-1; p < 0.01). Aprotinin treatment preserved cremaster microcirculatory perfusion following CPB (12 (7-15) vs. 6 (2-10) perfused microvessels, p = 0.002), but not renal perfusion (96 (35-313) vs. 129 (31-292) au/s, p > 0.9) compared to untreated rats. Aprotinin treatment reduced endothelial gap formation (0.5 ± 0.5 vs. 3.1 ± 1.4 gaps, p < 0.0001), kidney wet/dry weight ratio (4.6 ± 0.2 vs. 4.4 ± 0.2, p = 0.046), and fluid requirements (3.9 ± 3.3 vs. 7.5 ± 3.0 ml, p = 0.006) compared to untreated rats. In addition, aprotinin treatment reduced tubulointerstitial neutrophil influx by 1.7-fold compared to untreated rats (30.7 ± 22.1 vs. 53.2 ± 17.2 neutrophil influx/section, p = 0.009). No differences were observed in renal PAR1 expression and plasma creatinine, NGAL or KIM-1 between groups.

Conclusions: Aprotinin did not improve renal perfusion nor reduce renal injury during the first hour following experimental CPB despite preservation of renal endothelial integrity and reduction of renal edema.
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http://dx.doi.org/10.1186/s40635-021-00393-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8225734PMC
June 2021

Regulation of Rho GTPases in the Vasculature by Cullin3-Based E3 Ligase Complexes.

Front Cell Dev Biol 2021 31;9:680901. Epub 2021 May 31.

Department of Physiology, Amsterdam UMC, Amsterdam, Netherlands.

Cullin3-based ubiquitin E3 ligases induce ubiquitination of substrates leading to their proteasomal or lysosomal degradation. BTB proteins serve as adaptors by binding to Cullin3 and recruiting substrate proteins, which enables specific recognition of a broad spectrum of targets. Hence, Cullin3 and its adaptors are involved in myriad cellular processes and organ functions. Cullin3-based ubiquitin E3 ligase complexes target small GTPases of the Rho subfamily, which are key regulators of cytoskeletal dynamics and cell adhesion. In this mini review, we discuss recent insights in Cullin3-mediated regulation of Rho GTPases and their impact on cellular function and disease. Intriguingly, upstream regulators of Rho GTPases are targeted by Cullin3 complexes as well. Thus, Rho GTPase signaling is regulated by Cullin3 on multiple levels. In addition, we address current knowledge of Cullin3 in regulating vascular function, focusing on its prominent role in endothelial barrier function, angiogenesis and the regulation of blood pressure.
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http://dx.doi.org/10.3389/fcell.2021.680901DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8201781PMC
May 2021

Patient-Specific 3-Dimensional Model of Smooth Muscle Cell and Extracellular Matrix Dysfunction for the Study of Aortic Aneurysms.

J Endovasc Ther 2021 08 26;28(4):604-613. Epub 2021 Apr 26.

Amsterdam Cardiovascular Sciences, Department of Vascular Surgery, Amsterdam University Medical Centers, Location VUmc, Amsterdam, The Netherlands.

Introduction: Abdominal aortic aneurysms (AAAs) are associated with overall high mortality in case of rupture. Since the pathophysiology is unclear, no adequate pharmacological therapy exists. Smooth muscle cells (SMCs) dysfunction and extracellular matrix (ECM) degradation have been proposed as underlying causes. We investigated SMC spatial organization and SMC-ECM interactions in our novel 3-dimensional (3D) vascular model. We validated our model for future use by comparing it to existing 2-dimensional (2D) cell culture. Our model can be used for translational studies of SMC and their role in AAA pathophysiology.

Materials And Methods: SMC isolated from the medial layer of were the aortic wall of controls and AAA patients seeded on electrospun poly-lactide--glycolide scaffolds and cultured for 5 weeks, after which endothelial cells (EC) are added. Cell morphology, orientation, mechanical properties and ECM production were quantified for validation and comparison between controls and patients.

Results: We show that cultured SMC proliferate into multiple layers after 5 weeks in culture and produce ECM proteins, mimicking their behavior in the medial aortic layer. EC attach to multilayered SMC, mimicking layer interactions. The novel SMC model exhibits viscoelastic properties comparable to biological vessels; cytoskeletal organization increases during the 5 weeks in culture; increased cytoskeletal alignment and decreased ECM production indicate different organization of AAA patients' cells compared with control.

Conclusion: We present a valuable preclinical model of AAA constructed with patient specific cells with applications in both translational research and therapeutic developments. We observed SMC spatial reorganization in a time course of 5 weeks in our robust, patient-specific model of SMC-EC organization and ECM production.
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http://dx.doi.org/10.1177/15266028211009272DOI Listing
August 2021

Depletion of Arg/Abl2 improves endothelial cell adhesion and prevents vascular leak during inflammation.

Angiogenesis 2021 Aug 26;24(3):677-693. Epub 2021 Mar 26.

Angiogenesis Laboratory, Department of Medical Oncology, Cancer Center Amsterdam, Amsterdam University Medical Center, Amsterdam, The Netherlands.

Endothelial barrier disruption and vascular leak importantly contribute to organ dysfunction and mortality during inflammatory conditions like sepsis and acute respiratory distress syndrome. We identified the kinase Arg/Abl2 as a mediator of endothelial barrier disruption, but the role of Arg in endothelial monolayer regulation and its relevance in vivo remain poorly understood. Here we show that depletion of Arg in endothelial cells results in the activation of both RhoA and Rac1, increased cell spreading and elongation, redistribution of integrin-dependent cell-matrix adhesions to the cell periphery, and improved adhesion to the extracellular matrix. We further show that Arg is activated in the endothelium during inflammation, both in murine lungs exposed to barrier-disruptive agents, and in pulmonary microvessels of septic patients. Importantly, Arg-depleted endothelial cells were less sensitive to barrier-disruptive agents. Despite the formation of F-actin stress fibers and myosin light chain phosphorylation, Arg depletion diminished adherens junction disruption and intercellular gap formation, by reducing the disassembly of cell-matrix adhesions and cell retraction. In vivo, genetic deletion of Arg diminished vascular leak in the skin and lungs, in the presence of a normal immune response. Together, our data indicate that Arg is a central and non-redundant regulator of endothelial barrier integrity, which contributes to cell retraction and gap formation by increasing the dynamics of adherens junctions and cell-matrix adhesions in a Rho GTPase-dependent fashion. Therapeutic inhibition of Arg may provide a suitable strategy for the treatment of a variety of clinical conditions characterized by vascular leak.
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http://dx.doi.org/10.1007/s10456-021-09781-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7996118PMC
August 2021

Microembolus clearance through angiophagy is an auxiliary mechanism preserving tissue perfusion in the rat brain.

Acta Neuropathol Commun 2020 11 17;8(1):195. Epub 2020 Nov 17.

Amsterdam UMC, Biomedical Engineering and Physics, Amsterdam Cardiovascular Sciences, University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands.

Considering its intolerance to ischemia, it is of critical importance for the brain to efficiently process microvascular occlusions and maintain tissue perfusion. In addition to collateral microvascular flow and enzymatic degradation of emboli, the endothelium has the potential to engulf microparticles and thereby recanalize the vessel, through a process called angiophagy. Here, we set out to study the dynamics of angiophagy in relation to cytoskeletal remodeling in vitro and reperfusion in vivo. We show that polystyrene microspheres and fibrin clots are actively taken up by (brain) endothelial cells in vitro, and chart the dynamics of the actin cytoskeleton during this process using live cell imaging. Whereas microspheres were taken up through the formation of a cup structure by the apical endothelial membrane, fibrin clots were completely engulfed by the cells, marked by dense F-actin accumulation surrounding the clot. Both microspheres and fibrin clots were retained in the endothelial cells. Notably, fibrin clots were not degraded intracellularly. Using an in vivo microembolization rat model, in which microparticles are injected into the common carotid artery, we found that microspheres are transported by the endothelium from the microvasculature into the brain parenchyma. Microembolization with microspheres caused temporal opening of the blood-brain barrier and vascular nonperfusion, followed by microsphere extravasation and restoration of vessel perfusion over time. Taken together, angiophagy is accompanied by active cytoskeletal remodeling of the endothelium, and is an effective mechanism to restore perfusion of the occluded microvasculature in vivo.
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http://dx.doi.org/10.1186/s40478-020-01071-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7671188PMC
November 2020

Bosutinib prevents vascular leakage by reducing focal adhesion turnover and reinforcing junctional integrity.

J Cell Sci 2020 05 14;133(9). Epub 2020 May 14.

Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Pulmonology, Amsterdam Cardiovascular Sciences, 1081 BT Amsterdam, The Netherlands

Endothelial barrier dysfunction leads to edema and vascular leak, causing high morbidity and mortality. Previously, Abl kinase inhibition has been shown to protect against vascular leak. Using the distinct inhibitory profiles of clinically available Abl kinase inhibitors, we aimed to provide a mechanistic basis for novel treatment strategies against vascular leakage syndromes. We found that the inhibitor bosutinib most potently protected against inflammation-induced endothelial barrier disruption. , bosutinib prevented lipopolysaccharide (LPS)-induced alveolar protein extravasation in an acute lung injury mice model. Mechanistically, mitogen-activated protein 4 kinase 4 (MAP4K4) was identified as important novel mediator of endothelial permeability, which signaled via ezrin, radixin and moesin proteins to increase turnover of integrin-based focal adhesions. The combined inhibition of MAP4K4 and Abl-related gene (Arg, also known as ABL2) by bosutinib preserved adherens junction integrity and reduced turnover of focal adhesions, which synergistically act to stabilize the endothelial barrier during inflammation. We conclude that MAP4K4 is an important regulator of endothelial barrier integrity, increasing focal adhesion turnover and disruption of cell-cell junctions during inflammation. Because it inhibits both Arg and MAP4K4, use of the clinically available drug bosutinib might form a viable strategy against vascular leakage syndromes.
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http://dx.doi.org/10.1242/jcs.240077DOI Listing
May 2020

In vitro endothelial hyperpermeability occurs early following traumatic hemorrhagic shock.

Clin Hemorheol Microcirc 2020 ;75(2):121-133

Department of Anesthesiology, Experimental Laboratory for VItal Signs, Amsterdam Cardiovascular Sciences, Amsterdam UMC, VU University, Amsterdam, The Netherlands.

Background: Endothelial hyperpermeability is suggested to play a role in the development of microcirculatory perfusion disturbances and organ failure following hemorrhagic shock, but evidence is limited.

Objective: To study the effect of plasma from traumatic hemorrhagic shock patients on in vitro endothelial barrier function.

Methods: Plasma from traumatic hemorrhagic shock patients was obtained at the emergency department (ED), the intensive care unit (ICU), 24 h after ICU admission and from controls (n = 8). Sublingual microcirculatory perfusion was measured using incident dark field videomicroscopy at matching time points. Using electric cell-substrate impedance sensing, the effects of plasma exposure on in vitro endothelial barrier function of human endothelial cells were assessed.

Results: Plasma from traumatic hemorrhagic shock patients collected at ED admission induced a 19% loss of in vitro endothelial resistance compared to plasma from controls (p < 0.001). This loss was due to reduced cell-cell contacts (p < 0.01). Plasma withdrawn at later time points did not affect endothelial barrier function (p > 0.99). Interestingly, in vitro endothelial resistance showed a positive association with in vivo microcirculatory perfusion (r = 0.56, p < 0.01).

Conclusions: Plasma from traumatic hemorrhagic shock patients obtained following ED admission, but not at later stages, induced in vitro endothelial hyperpermeability. This coincided with in vivo microcirculatory perfusion disturbances.
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http://dx.doi.org/10.3233/CH-190642DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7504990PMC
September 2020

Pharmacological interventions to reduce edema following cardiopulmonary bypass: A systematic review and meta-analysis.

J Crit Care 2020 04 10;56:63-72. Epub 2019 Dec 10.

Department of Anesthesiology, Experimental Laboratory for VItal Signs, Amsterdam UMC, Vrije Universiteit, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands; Department of Physiology, Amsterdam UMC, Vrije Universiteit, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands.

Purpose: To compare the effectiveness of different types of pharmacological agents to reduce organ specific edema following cardiopulmonary bypass (CPB).

Methods: Pubmed, Embase.com and Cochrane were searched for studies administrating a pharmacological agent before CPB. Primary outcome was postoperative edema.

Results: Forty-four studies (clinical n = 6, preclinical n = 38) fulfilled eligibility criteria. Steroids were used in most clinical studies (n = 5, 83%) and reduced postoperative edema in 4 studies, however heterogeneity precluded meta-analysis. In preclinical studies, a total of 31 different drugs were tested of which 20 (65%) reduced edema in at least one organ. Particularly neutrophil inhibitors, and modulators of coagulation or endothelial barrier reduced pulmonary edema (SMD -2.77 [-3.93, -1.61]; -1.29 [-2.12, -0.46], -2.33 [-4.69, 0.03], respectively) compared to no treatment. Reducing renal (SMD -0.91 [CI -1.65 to -0.18]), intestinal (SMD -1.98 [CI -3.92 to -0.04]) or myocardial (SMD -1.95 [CI -3.91 to -0.01]) edema following CPB required specific modulators of endothelial barrier.

Conclusion: Overall, neutrophil inhibitors and direct modulators of endothelial barrier (PAR1, Tie2 signaling) most effectively reduced edema following CPB, in particular pulmonary edema. Future research should focus on a combination of these strategies to reduce edema and assess the effect on organ function and outcome following CPB.
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http://dx.doi.org/10.1016/j.jcrc.2019.12.006DOI Listing
April 2020

Ubiquitin-based modifications in endothelial cell-cell contact and inflammation.

J Cell Sci 2019 09 5;132(17). Epub 2019 Sep 5.

Department of Physiology, Amsterdam University Medical Centers, location VUmc, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands

Endothelial cell-cell contacts are essential for vascular integrity and physiology, protecting tissues and organs from edema and uncontrolled invasion of inflammatory cells. The vascular endothelial barrier is dynamic, but its integrity is preserved through a tight control at different levels. Inflammatory cytokines and G-protein-coupled receptor agonists, such as histamine, reduce endothelial integrity and increase vascular leakage. This is due to elevated myosin-based contractility, in conjunction with phosphorylation of proteins at cell-cell contacts. Conversely, reducing contractility stabilizes or even increases endothelial junctional integrity. Rho GTPases are key regulators of such cytoskeletal dynamics and endothelial cell-cell contacts. In addition to signaling-induced regulation, the expression of junctional proteins, such as occludin, claudins and vascular endothelial cadherin, also controls endothelial barrier function. There is increasing evidence that, in addition to protein phosphorylation, ubiquitylation (also known as ubiquitination) is an important and dynamic post-translational modification that regulates Rho GTPases, junctional proteins and, consequently, endothelial barrier function. In this Review, we discuss the emerging role of ubiquitylation and deubiquitylation events in endothelial integrity and inflammation. The picture that emerges is one of increasing complexity, which is both fascinating and promising given the clinical relevance of vascular integrity in the control of inflammation, and of tissue and organ damage.
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http://dx.doi.org/10.1242/jcs.227728DOI Listing
September 2019

Identification of guanine nucleotide exchange factors that increase Cdc42 activity in primary human endothelial cells.

Small GTPases 2021 May 30;12(3):226-240. Epub 2019 Aug 30.

Molecular Cytology, Swammerdam Institute for Life Sciences, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, Amsterdam, The Netherlands.

The Rho GTPase family is involved in actin dynamics and regulates the barrier function of the endothelium. One of the main barrier-promoting Rho GTPases is Cdc42, also known as cell division control protein 42 homolog. Currently, regulation of Cdc42-based signalling networks in endothelial cells (ECs) lack molecular details. To examine these, we focused on a subset of 15 Rho guanine nucleotide exchange factors (GEFs), which are expressed in the endothelium. By performing single cell FRET measurements with Rho GTPase biosensors in primary human ECs, we monitored GEF efficiency towards Cdc42 and Rac1. A new, single cell-based analysis was developed and used to enable the quantitative comparison of cellular activities of the overexpressed full-length GEFs. Our data reveal GEF dependent activation of Cdc42, with the most efficient Cdc42 activation induced by PLEKHG2, FGD1, PLEKHG1 and PREX1 and the highest selectivity for FGD1. Additionally, we generated truncated GEF constructs that comprise only the catalytic dbl homology (DH) domain or together with the adjacent pleckstrin homology domain (DHPH). The DH domain by itself did not activate Cdc42, whereas the DHPH domain of ITSN1, ITSN2 and PLEKHG1 showed activity towards Cdc42. Together, our study characterized endothelial GEFs that may directly or indirectly activate Cdc42, which will be of great value for the field of vascular biology.
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http://dx.doi.org/10.1080/21541248.2019.1658509DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7939571PMC
May 2021

CSN5 inhibition triggers inflammatory signaling and Rho/ROCK-dependent loss of endothelial integrity.

Sci Rep 2019 05 31;9(1):8131. Epub 2019 May 31.

Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Physiology, Amsterdam Cardiovascular Sciences, De Boelelaan 1117, 1081HZ, Amsterdam, The Netherlands.

RhoGTPases regulate cytoskeletal dynamics, migration and cell-cell adhesion in endothelial cells. Besides regulation at the level of guanine nucleotide binding, they also undergo post-translational modifications, for example ubiquitination. RhoGTPases are ubiquitinated by Cullin RING ligases which are in turn regulated by neddylation. Previously we showed that inhibition of Cullin RING ligase activity by the neddylation inhibitor MLN4924 is detrimental for endothelial barrier function, due to accumulation of RhoB and the consequent induction of contractility. Here we analyzed the effect of pharmacological activation of Cullin RING ligases on endothelial barrier integrity in vitro and in vivo. CSN5i-3 induced endothelial barrier disruption and increased macromolecule leakage in vitro and in vivo. Mechanistically, CSN5i-3 strongly induced the expression and activation of RhoB and to lesser extent of RhoA in endothelial cells, which enhanced cell contraction. Elevated expression of RhoGTPases was a consequence of activation of the NF-κB pathway. In line with this notion, CSN5i-3 treatment decreased IκBα expression and increased NF-κB-mediated ICAM-1 expression and consequent adhesion of neutrophils to endothelial cells. This study shows that sustained neddylation of Cullin RING-ligases leads to activation the NF-κB pathway in endothelial cells, elevated expression of RhoGTPases, Rho/ROCK-dependent activation of MLC and disruption of the endothelial barrier.
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http://dx.doi.org/10.1038/s41598-019-44595-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6544660PMC
May 2019

Extravasation of Microspheres in a Rat Model of Silent Brain Infarcts.

Stroke 2019 06 18;50(6):1590-1594. Epub 2019 Apr 18.

From the Department of Biomedical Engineering and Physics, Amsterdam Cardiovascular Sciences (A.-E.v.d.W., N.L., J.D.V., E.N.T.P.B., E.v.B.), Amsterdam University Medical Center, University of Amsterdam, the Netherlands.

Background and Purpose- We developed a rat model of silent brain infarcts based on microsphere infusion and investigated their impact on perfusion and tissue damage. Second, we studied the extent and mechanisms of perfusion recovery. Methods- At day 0, 15 µm fluorescent microspheres were injected into the right common carotid artery of F344 rats. At days 1, 7, or 28, the brain was removed, cut in 100-µm cryosections, and processed for immunofluorescent staining and analysis. Results- Injection of microspheres caused mild and transient damage to the treated hemisphere, with a decrease in perfused capillary volume at day 1, as compared with the untreated hemisphere. At day 1 but not at days 7 and 28, we observed IgG staining outside of the vessels, indicating vessel leakage. All microspheres were located inside the lumen of the vessels at day 1, whereas the vast majority (≈80%) of the microspheres were extravascular at day 7, and 100% at day 28. This was accompanied by restoration of perfused capillary volume. Conclusions- Microspheres cause mild and transient damage, and effective extravasation mechanisms exist in the brain to clear microsized emboli from the vessels.
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http://dx.doi.org/10.1161/STROKEAHA.119.024975DOI Listing
June 2019

DLC3 suppresses MT1-MMP-dependent matrix degradation by controlling RhoB and actin remodeling at endosomal membranes.

J Cell Sci 2019 06 5;132(11). Epub 2019 Jun 5.

Institute of Cell Biology and Immunology, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany

Cancer cells degrade the extracellular matrix through actin-rich protrusions termed invadopodia. The formation of functional invadopodia requires polarized membrane trafficking driven by Rho GTPase-mediated cytoskeletal remodeling. We identify the Rho GTPase-activating protein deleted in liver cancer 3 (DLC3; also known as STARD8) as an integral component of the endosomal transport and sorting machinery. We provide evidence for the direct regulation of RhoB by DLC3 at endosomal membranes to which DLC3 is recruited by interacting with the sorting nexin SNX27. In TGF-β-treated MCF10A breast epithelial cells, DLC3 knockdown enhanced metalloproteinase-dependent matrix degradation, which was partially rescued by RhoB co-depletion. This was recapitulated in MDA-MB-231 breast cancer cells in which early endosomes demonstrated aberrantly enriched F-actin and accumulated the metalloproteinase MT1-MMP (also known as MMP14) upon DLC3 knockdown. Remarkably, Rab4 (herein referring to Rab4A) downregulation fully rescued the enhanced matrix degradation of TGF-β-treated MCF10A and MDA-MB-231 cells. In summary, our findings establish a novel role for DLC3 in the suppression of MT1-MMP-dependent matrix degradation by inactivating RhoB signaling at endosomal membranes. We propose that DLC3 function is required to limit endosomal actin polymerization, Rab4-dependent recycling of MT1-MMP and, consequently, matrix degradation mediated by invadopodial activity.
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http://dx.doi.org/10.1242/jcs.223172DOI Listing
June 2019

Most exposed: the endothelium in chronic kidney disease.

Nephrol Dial Transplant 2020 09;35(9):1478-1487

Department of Nephrology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands.

Accumulating evidence indicates that the pathological changes of the endothelium may contribute to the development of cardiovascular complications in chronic kidney disease (CKD). Non-traditional risk factors related to CKD are associated with the incidence of cardiovascular disease, but their role in uraemic endothelial dysfunction has often been disregarded. In this context, soluble α-Klotho and vitamin D are of importance to maintain endothelial integrity, but their concentrations decline in CKD, thereby contributing to the dysfunction of the endothelial lining. These hormonal disturbances are accompanied by an increment of circulating fibroblast growth factor-23 and phosphate, both exacerbating endothelial toxicities. Furthermore, impaired renal function leads to an increment of inflammatory mediators, reactive oxygen species and uraemic toxins that further aggravate the endothelial abnormalities and in turn also inhibit the regeneration of disrupted endothelial lining. Here, we highlight the distinct endothelial alterations mediated by the abovementioned non-traditional risk factors as demonstrated in experimental studies and connect these to pathological changes in CKD patients, which are driven by endothelial disturbances, other than atherosclerosis. In addition, we describe therapeutic strategies that may promote restoration of endothelial abnormalities by modulating imbalanced mineral homoeostasis and attenuate the impact of uraemic retention molecules, inflammatory mediators and reactive oxygen species. A clinical perspective on endothelial dysfunction in CKD may translate into reduced structural and functional abnormalities of the vessel wall in CKD, and ultimately improved cardiovascular disease.
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http://dx.doi.org/10.1093/ndt/gfz055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7473805PMC
September 2020

Impaired smooth muscle cell contractility as a novel concept of abdominal aortic aneurysm pathophysiology.

Sci Rep 2019 05 2;9(1):6837. Epub 2019 May 2.

Departments of Vascular Surgery, Amsterdam University Medical Centers, location VU University Medical center, Amsterdam, The Netherlands.

Ruptured abdominal aortic aneurysms (AAA) are associated with overall mortality rates up to 90%. Despite extensive research, mechanisms leading to AAA formation and advancement are still poorly understood. Smooth muscle cells (SMC) are predominant in the aortic medial layer and maintain the wall structure. Apoptosis of SMC is a well-known phenomenon in the pathophysiology of AAA. However, remaining SMC function is less extensively studied. The aim of this study is to assess the in vitro contractility of human AAA and non-pathologic aortic SMC. Biopsies were perioperatively harvested from AAA patients (n = 21) and controls (n = 6) and clinical data were collected. Contractility was measured using Electric Cell-substrate Impedance Sensing (ECIS) upon ionomycin stimulation. Additionally, SMC of 23% (5 out of 21) of AAA patients showed impaired maximum contraction compared to controls. Also, SMC from patients who underwent open repair after earlier endovascular repair and SMC from current smokers showed decreased maximum contraction vs. controls (p = 0.050 and p = 0.030, respectively). Our application of ECIS can be used to study contractility in other vascular diseases. Finally, our study provides with first proof that impaired SMC contractility might play a role in AAA pathophysiology.
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http://dx.doi.org/10.1038/s41598-019-43322-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6497672PMC
May 2019

Microcirculatory perfusion disturbances following cardiac surgery with cardiopulmonary bypass are associated with in vitro endothelial hyperpermeability and increased angiopoietin-2 levels.

Crit Care 2019 Apr 11;23(1):117. Epub 2019 Apr 11.

Amsterdam UMC, Vrije Universiteit Amsterdam, Anesthesiology, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands.

Background: Endothelial hyperpermeability following cardiopulmonary bypass (CPB) contributes to microcirculatory perfusion disturbances and postoperative complications after cardiac surgery. We investigated the postoperative course of renal and pulmonary endothelial barrier function and the association with microcirculatory perfusion and angiopoietin-2 levels in patients after CPB.

Methods: Clinical data, sublingual microcirculatory data, and plasma samples were collected from patients undergoing coronary artery bypass graft surgery with CPB (n = 17) before and at several time points up to 72 h after CPB. Renal and pulmonary microvascular endothelial cells were incubated with patient plasma, and in vitro endothelial barrier function was assessed using electric cell-substrate impedance sensing. Plasma levels of angiopoietin-1,-2, and soluble Tie2 were measured, and the association with in vitro endothelial barrier function and in vivo microcirculatory perfusion was determined.

Results: A plasma-induced reduction of renal and pulmonary endothelial barrier function was observed in all samples taken within the first three postoperative days (P < 0.001 for all time points vs. pre-CPB). Angiopoietin-2 and soluble Tie2 levels increased within 72 h after CPB (5.7 ± 4.4 vs. 1.7 ± 0.4 ng/ml, P < 0.0001; 16.3 ± 4.7 vs. 11.9 ± 1.9 ng/ml, P = 0.018, vs. pre-CPB), whereas angiopoietin-1 remained stable. Interestingly, reduced in vitro renal and pulmonary endothelial barrier moderately correlated with reduced in vivo microcirculatory perfusion after CPB (r = 0.47, P = 0.005; r = 0.79, P < 0.001). In addition, increased angiopoietin-2 levels moderately correlated with reduced in vitro renal and pulmonary endothelial barrier (r = - 0.46, P < 0.001; r = - 0.40, P = 0.005) and reduced in vivo microcirculatory perfusion (r = - 0.43, P = 0.01; r = - 0.41, P = 0.03).

Conclusions: CPB is associated with an impairment of in vitro endothelial barrier function that continues in the first postoperative days and correlates with reduced postoperative microcirculatory perfusion and increased circulating angiopoietin-2 levels. These results suggest that angiopoietin-2 is a biomarker for postoperative endothelial hyperpermeability, which may contribute to delayed recovery of microcirculatory perfusion after CPB.

Trial Registration: NTR4212 .
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http://dx.doi.org/10.1186/s13054-019-2418-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6460737PMC
April 2019

FBXW7 regulates endothelial barrier function by suppression of the cholesterol synthesis pathway and prenylation of RhoB.

Mol Biol Cell 2019 03 2;30(5):607-621. Epub 2019 Jan 2.

Department of Physiology, Amsterdam Cardiovascular Sciences, and.

Rho GTPases control both the actin cytoskeleton and adherens junction stability and are recognized as essential regulators of endothelial barrier function. They act as molecular switches and are primarily regulated by the exchange of GDP and GTP. However, posttranslational modifications such as phosphorylation, prenylation, and ubiquitination can additionally alter their localization, stability, and activity. F-box proteins are involved in the recognition of substrate proteins predestined for ubiquitination and subsequent degradation. Given the importance of ubiquitination, we studied the effect of the loss of 62 members of the F-box protein family on endothelial barrier function in human umbilical vein endothelial cells. Endothelial barrier function was quantified by electrical cell impedance sensing and macromolecule passage assay. Our RNA interference-based screen identified FBXW7 as a key regulator of endothelial barrier function. Mechanistically, loss of FBXW7 induced the accumulation of the RhoB GTPase in endothelial cells, resulting in their increased contractility and permeability. FBXW7 knockdown induced activation of the cholesterol biosynthesis pathway and changed the prenylation of RhoB. This effect was reversed by farnesyl transferase inhibitors and by the addition of geranylgeranyl pyrophosphate. In summary, this study identifies FBXW7 as a novel regulator of endothelial barrier function in vitro. Loss of FBXW7 indirectly modulates RhoB activity via alteration of the cholesterol biosynthesis pathway and, consequently, of the prenylation status and activity of RhoB, resulting in increased contractility and disruption of the endothelial barrier.
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http://dx.doi.org/10.1091/mbc.E18-04-0259DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6589702PMC
March 2019

Vitamin D Attenuates Endothelial Dysfunction in Uremic Rats and Maintains Human Endothelial Stability.

J Am Heart Assoc 2018 09;7(17):e008776

1 Department of Nephrology VU University Medical Center Amsterdam The Netherlands.

Background Dysfunctional endothelium may contribute to the development of cardiovascular complications in chronic kidney disease ( CKD ). Supplementation with active vitamin D has been proposed to have vasoprotective potential in CKD , not only by direct effects on the endothelium but also by an increment of α-Klotho. Here, we explored the capacity of the active vitamin D analogue paricalcitol to protect against uremia-induced endothelial damage and the extent to which this was dependent on increased α-Klotho concentrations. Methods and Results In a combined rat model of CKD with vitamin D deficiency, renal failure induced vascular permeability and endothelial-gap formation in thoracic aorta irrespective of baseline vitamin D, and this was attenuated by paricalcitol. Downregulation of renal and serum α-Klotho was found in the CKD model, which was not restored by paricalcitol. By measuring the real-time changes of the human endothelial barrier function, we found that paricalcitol effectively improved the recovery of endothelial integrity following the addition of the pro-permeability factor thrombin and the induction of a wound. Furthermore, immunofluorescence staining revealed that paricalcitol promoted vascular endothelial-cadherin-based cell-cell junctions and diminished F-actin stress fiber organization, preventing the formation of endothelial intracellular gaps. Conclusions Our results demonstrate that paricalcitol attenuates the CKD -induced endothelial damage in the thoracic aorta and directly mediates endothelial stability in vitro by enforcing cell-cell interactions.
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http://dx.doi.org/10.1161/JAHA.118.008776DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6201442PMC
September 2018

A functional siRNA screen identifies RhoGTPase-associated genes involved in thrombin-induced endothelial permeability.

PLoS One 2018 26;13(7):e0201231. Epub 2018 Jul 26.

Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands.

Thrombin and other inflammatory mediators may induce vascular permeability through the disruption of adherens junctions between adjacent endothelial cells. If uncontrolled, hyperpermeability leads to an impaired barrier, fluid leakage and edema, which can contribute to multi-organ failure and death. RhoGTPases control cytoskeletal dynamics, adhesion and migration and are known regulators of endothelial integrity. Knowledge of the precise role of each RhoGTPase, and their associated regulatory and effector genes, in endothelial integrity is incomplete. Using a combination of a RNAi screen with electrical impedance measurements, we quantified the effect of individually silencing 270 Rho-associated genes on the barrier function of thrombin-activated, primary endothelial cells. Known and novel RhoGTPase-associated regulators that modulate the response to thrombin were identified (RTKN, TIAM2, MLC1, ARPC1B, SEPT2, SLC9A3R1, RACGAP1, RAPGEF2, RHOD, PREX1, ARHGEF7, PLXNB2, ARHGAP45, SRGAP2, ARHGEF5). In conclusion, with this siRNA screen, we confirmed the roles of known regulators of endothelial integrity but also identified new, potential key players in thrombin-induced endothelial signaling.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0201231PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6062096PMC
January 2019

Early-onset preeclampsia predisposes to preclinical diastolic left ventricular dysfunction in the fifth decade of life: An observational study.

PLoS One 2018 12;13(6):e0198908. Epub 2018 Jun 12.

Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands.

Background: Systemic inflammation, endothelial dysfunction and deficient vascularization of either uterus or myocardium are mechanistic hallmarks of early-onset preeclampsia and heart failure with preserved ejection fraction (HFpEF). HFpEF is especially prevalent in elderly women and preceded in middle age by preclinical left ventricular (LV) diastolic dysfunction. To detect if preeclampsia predisposes to HFpEF at later age, echocardiographic indices of LV function and of LV structure and biomarkers of systemic inflammation and of endothelial dysfunction were compared in middle-aged women with a history of early-onset preeclampsia or uncomplicated pregnancy.

Methods And Findings: Middle-aged women with a history of early-onset preeclampsia (n = 131) or uncomplicated pregnancy (n = 56) were prospectively recruited 9 to 16 years after pregnancy. Women with a history of preeclampsia had higher body mass index (p = 0.006), blood pressure (p<0.001) and plasma levels of interleukin-6 (p = 0.005) and soluble intercellular adhesion molecule-1 (sICAM-1) (p = 0.014). They had thicker septal (p = 0.001) and posterior (p = 0.003) LV walls and worse diastolic LV function evident from reduced mean mitral annular lengthening velocity (E'mean; p = 0.007) and higher ratio of early diastolic mitral flow velocity (E) over E'mean (E/E'mean; p<0.001). Differences of sICAM-1, E'mean and E/E'mean remained significant after accounting for BMI and blood pressure.

Conclusions: History of preeclampsia predisposes in middle age to worse LV diastolic function, which could increase the likelihood of later HFpEF development. This predisposition derives not only from persistent cardiovascular risk but may also be caused by persistent endothelial dysfunction hindering adequate vascularization in the uterus during pregnancy and in the myocardium in middle age.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0198908PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5997308PMC
January 2019

Stabilization of cell-cell junctions by active vitamin D ameliorates uraemia-induced loss of human endothelial barrier function.

Nephrol Dial Transplant 2019 02;34(2):252-264

Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands.

Background: Uraemia induces endothelial cell (EC) injury and impaired repair capacity, for which the underlying mechanism remains unclear. Active vitamin D (VD) may promote endothelial repair, however, the mechanism that mediates the effects of VD in chronic kidney disease are poorly understood. Thus, we investigated uraemia-induced endothelial damage and the protection against such damage by active VD.

Methods: We applied electric cell-substrate impedance sensing (ECIS) to study real-time responses of human ECs exposed to pooled uraemic and non-uraemic plasma with or without the addition of active VD. The effects of indoxyl sulphate and p-cresol were tested in non-uraemic plasma. Structural changes for vascular endothelial (VE)-cadherin and F-actin were assessed by immunostaining and quantified.

Results: The exposure of ECs to uraemic media significantly decreased endothelial barrier function after 24 h. Cell migration after electrical wounding and recovery of the barrier after thrombin-induced loss of integrity were significantly impaired in uraemic-medium stimulated cells and cells exposed to indoxyl sulphate and p-cresol. This effect on ECIS was dependent on loss of cell-cell interaction. Mechanistically, we found that EC, exposed to uraemic media, displayed disrupted VE-cadherin interactions and F-actin reorganization. VD supplementation rescued both endothelial barrier function and cell-cell interactions in ECs exposed to uraemic media. These events were associated with an increment of VE-cadherin at intercellular junctions.

Conclusions: Our data demonstrate a potentially clinically relevant mechanism for uraemia-induced endothelial damage. Furthermore, active VD rescued the uraemic medium-induced loss of cell-cell adhesion, revealing a novel role of active VD in preservation of endothelial integrity during uraemia.
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http://dx.doi.org/10.1093/ndt/gfy111DOI Listing
February 2019

The Cullin-3-Rbx1-KCTD10 complex controls endothelial barrier function via K63 ubiquitination of RhoB.

J Cell Biol 2018 03 22;217(3):1015-1032. Epub 2018 Jan 22.

Department of Physiology, Vrije Universiteit University Medical Center, Amsterdam, Netherlands

RhoGTPases control endothelial cell (EC) migration, adhesion, and barrier formation. Whereas the relevance of RhoA for endothelial barrier function is widely accepted, the role of the RhoA homologue RhoB is poorly defined. RhoB and RhoA are 85% identical, but RhoB's subcellular localization and half-life are uniquely different. Here, we studied the role of ubiquitination for the function and stability of RhoB in primary human ECs. We show that the K63 polyubiquitination at lysine 162 and 181 of RhoB targets the protein to lysosomes. Moreover, we identified the RING E3 ligase complex Cullin-3-Rbx1-KCTD10 as key modulator of endothelial barrier integrity via its regulation of the ubiquitination, localization, and activity of RhoB. In conclusion, our data show that ubiquitination controls the subcellular localization and lysosomal degradation of RhoB and thereby regulates the stability of the endothelial barrier through control of RhoB-mediated EC contraction.
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http://dx.doi.org/10.1083/jcb.201606055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5839774PMC
March 2018

The balance between Gα-Cdc42/Rac and Gα/-RhoA pathways determines endothelial barrier regulation by sphingosine-1-phosphate.

Mol Biol Cell 2017 Nov 27;28(23):3371-3382. Epub 2017 Sep 27.

van Leeuwenhoek Centre for Advanced Microscopy, Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, Netherlands

The bioactive sphingosine-1-phosphatephosphate (S1P) is present in plasma, bound to carrier proteins, and involved in many physiological processes, including angiogenesis, inflammatory responses, and vascular stabilization. S1P can bind to several G-protein-coupled receptors (GPCRs) activating a number of different signaling networks. At present, the dynamics and relative importance of signaling events activated immediately downstream of GPCR activation are unclear. To examine these, we used a set of fluorescence resonance energy transfer-based biosensors for different RhoGTPases (Rac1, RhoA/B/C, and Cdc42) as well as for heterotrimeric G-proteins in a series of live-cell imaging experiments in primary human endothelial cells. These experiments were accompanied by biochemical GTPase activity assays and transendothelial resistance measurements. We show that S1P promotes cell spreading and endothelial barrier function through S1PR-Gα-Rac1 and S1PR-Gα-Cdc42 pathways. In parallel, a S1PR-Gα-RhoA pathway is activated that can induce cell contraction and loss of barrier function, but only if Gα-mediated signaling is suppressed. Our results suggest that Gα activity is not involved in S1P-mediated regulation of barrier integrity. Moreover, we show that early activation of RhoA by S1P inactivates Rac1 but not Cdc42, and vice versa. Together, our data show that the rapid S1P-induced increase in endothelial integrity is mediated by a S1PR-Gα-Cdc42 pathway.
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http://dx.doi.org/10.1091/mbc.E17-03-0136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5687037PMC
November 2017

RhoA, RhoB and RhoC differentially regulate endothelial barrier function.

Small GTPases 2019 11 26;10(6):466-484. Epub 2017 Sep 26.

Department of Physiology, VU University Medical Center Amsterdam , Amsterdam , The Netherlands.

RhoGTPases are known regulators of intracellular actin dynamics that are important for maintaining endothelial barrier function. RhoA is most extensively studied as a key regulator of endothelial barrier function, however the function of the 2 highly homologous family-members (> 88%) RhoB and RhoC in endothelial barrier function is still poorly understood. This study aimed to determine whether RhoA, RhoB and RhoC have overlapping or distinct roles in barrier function and permeability in resting and activated endothelium. By using primary endothelial cells in combination with siRNA transfection to establish individual, double or triple knockdown of the RhoA/B/C RhoGTPases, we found that RhoB, but not RhoA or RhoC, is in resting endothelium a negative regulator of permeability. Loss of RhoB accounted for an accumulation of VE-cadherin at cell-cell contacts. Thrombin-induced loss of endothelial integrity is mediated primarily by RhoA and RhoB. Combined loss of RhoA/B showed decreased phosphorylation of Myosin Light Chain and increased expression of VE-cadherin at cell-cell contacts after thrombin stimulation. RhoC contributes to the Rac1-dependent restoration of endothelial barrier function. In summary, this study shows that these highly homologous RhoGTPases differentially control the dynamics of endothelial barrier function.
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http://dx.doi.org/10.1080/21541248.2017.1339767DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6748378PMC
November 2019

Stasis Promotes Erythrocyte Adhesion to von Willebrand Factor.

Arterioscler Thromb Vasc Biol 2017 09 3;37(9):1618-1627. Epub 2017 Aug 3.

From the Departments of Molecular Cell Biology (M.W.J.S., P.L.H.) and Plasma Proteins (M.J.M.), Sanquin-Academic Medical Center Landsteiner Laboratory, Amsterdam, The Netherlands; and Department of Pathology and Cardiac Surgery, ICaR-VU (H.W.M.N.) and Department of Physiology (P.L.H.), VU University Medical Center, Amsterdam, The Netherlands.

Objective: Venous thromboembolism is a major contributor to global disease burden. Leukocytes and platelets initiate thrombogenesis on blood stasis and initiate the formation of a fibrin, VWF (von Willebrand factor), and neutrophil extracellular trap scaffold for erythrocytes. However, there is little knowledge on how erythrocytes become stably incorporated into this scaffold. Recently, we described the adhesion of calcium-loaded erythrocytes to endothelial-derived VWF strings. Because VWF is part of the scaffold of venous thrombi, we questioned whether reduced flow or stasis promotes the adhesion of normal erythrocytes to VWF and whether venous thrombi show evidence of erythrocyte-VWF interactions.

Approach And Results: In the present work, we perfused, under controlled shear conditions, washed, normal erythrocytes over surface-immobilized plasma and extracellular matrix proteins and showed that normal erythrocytes specifically bind to VWF. The interaction between erythrocytes and VWF significantly increased when the wall shear stress was reduced. Next, we investigated whether erythrocyte-VWF interactions support the structure of venous thrombi. High-resolution immunofluorescence imaging of human venous thrombi showed a striking pattern between erythrocytes, VWF, and fibrin, which suggests that VWF plays a supporting role, linking erythrocytes to fibrin in the thrombus.

Conclusions: Our data suggest that erythrocyte retention in venous thrombi is mediated by erythrocyte-VWF or erythrocyte-VWF-fibrin interactions. Targeting erythrocyte retention could be a new strategy in the treatment or prevention of venous thrombosis.
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http://dx.doi.org/10.1161/ATVBAHA.117.309885DOI Listing
September 2017

Endothelial CD2AP Binds the Receptor ICAM-1 To Control Mechanosignaling, Leukocyte Adhesion, and the Route of Leukocyte Diapedesis In Vitro.

J Immunol 2017 06 8;198(12):4823-4836. Epub 2017 May 8.

Department of Molecular Cell Biology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam 1066CX, the Netherlands.

Inflammation is driven by excessive transmigration (diapedesis) of leukocytes from the blood to the tissue across the endothelial cell monolayer that lines blood vessels. Leukocyte adhesion, crawling, and transmigration are regulated by clustering of the endothelial mechanosensitive receptor intercellular adhesion molecule-1 (ICAM-1). Whereas several proteins are known to promote ICAM-1 function, the molecular mechanisms that limit ICAM-1-mediated adhesion to prevent excessive leukocyte transmigration remain unknown. We identify the endothelial actin-binding protein CD2-associated protein (CD2AP) as a novel interaction partner of ICAM-1. Loss of CD2AP stimulates the dynamics of ICAM-1 clustering, which facilitates the formation of ICAM-1 complexes on the endothelial cell surface. Consequently, neutrophil adhesion is increased, but crawling is decreased. In turn, this promotes the neutrophil preference for the transcellular over the paracellular transmigration route. Mechanistically, CD2AP is required for mechanosensitive ICAM-1 downstream signaling toward activation of the PI3K, and recruitment of F-actin and of the actin-branching protein cortactin. Moreover, CD2AP is necessary for ICAM-1-induced Rac1 recruitment and activation. Mechanical force applied on ICAM-1 impairs CD2AP binding to ICAM-1, suggesting that a tension-induced negative feedback loop promotes ICAM-1-mediated neutrophil crawling and paracellular transmigration. To our knowledge, these data show for the first time that the mechanoreceptor ICAM-1 is negatively regulated by an actin-binding adaptor protein, i.e., CD2AP, to allow a balanced and spatiotemporal control of its adhesive function. CD2AP is important in kidney dysfunction that is accompanied by inflammation. Our findings provide a mechanistic basis for the role of CD2AP in inflamed vessels, identifying this adaptor protein as a potential therapeutic target.
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http://dx.doi.org/10.4049/jimmunol.1601987DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5510545PMC
June 2017

Platelet-independent adhesion of calcium-loaded erythrocytes to von Willebrand factor.

PLoS One 2017 1;12(3):e0173077. Epub 2017 Mar 1.

Department of Molecular Cell Biology, Sanquin-Academic Medical Center Landsteiner Laboratory, Amsterdam, The Netherlands.

Adhesion of erythrocytes to endothelial cells lining the vascular wall can cause vaso-occlusive events that impair blood flow which in turn may result in ischemia and tissue damage. Adhesion of erythrocytes to vascular endothelial cells has been described in multiple hemolytic disorders, especially in sickle cell disease, but the adhesion of normal erythrocytes to endothelial cells has hardly been described. It was shown that calcium-loaded erythrocytes can adhere to endothelial cells. Because sickle erythrocyte adhesion to ECs can be enhanced by ultra-large von Willebrand factor multimers, we investigated whether calcium loading of erythrocytes could promote binding to endothelial cells via ultra-large von Willebrand factor multimers. We used (immunofluorescent) live-cell imaging of washed erythrocytes perfused over primary endothelial cells at venular flow rate. Using this approach, we show that calcium-loaded erythrocytes strongly adhere to histamine-stimulated primary human endothelial cells. This adhesion is mediated by ultra-large von Willebrand factor multimers. Von Willebrand factor knockdown or ADAMTS13 cleavage abolished the binding of erythrocytes to activated endothelial cells under flow. Platelet depletion did not interfere with erythrocyte binding to von Willebrand factor. Our results reveal platelet-independent adhesion of calcium-loaded erythrocytes to endothelium-derived von Willebrand factor. Erythrocyte adhesion to von Willebrand factor may be particularly relevant for venous thrombosis, which is characterized by the formation of erythrocyte-rich thrombi.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0173077PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5332109PMC
August 2017
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