TY  - JOUR
A1  - Nagy, Magdolna
A1  - van Geffen, Johanna P.
A1  - Stegner, David
A1  - Adams, David J.
A1  - Braun, Attila
A1  - de Witt, Susanne M.
A1  - Elvers, Margitta
A1  - Geer, Mitchell J.
A1  - Kuijpers, Marijke J. E.
A1  - Kunzelmann, Karl
A1  - Mori, Jun
A1  - Oury, Cécile
A1  - Pircher, Joachim
A1  - Pleines, Irina
A1  - Poole, Alastair W.
A1  - Senis, Yotis A.
A1  - Verdoold, Remco
A1  - Weber, Christian
A1  - Nieswandt, Bernhard
A1  - Heemskerk, Johan W. M.
A1  - Baaten, Constance C. F. M. J.
T1  - Comparative Analysis of Microfluidics Thrombus Formation in Multiple Genetically Modified Mice: Link to Thrombosis and Hemostasis
JF  - Frontiers in Cardiovascular Medicine
N2  - Genetically modified mice are indispensable for establishing the roles of platelets in arterial thrombosis and hemostasis. Microfluidics assays using anticoagulated whole blood are commonly used as integrative proxy tests for platelet function in mice. In the present study, we quantified the changes in collagen-dependent thrombus formation for 38 different strains of (genetically) modified mice, all measured with the same microfluidics chamber. The mice included were deficient in platelet receptors, protein kinases or phosphatases, small GTPases or other signaling or scaffold proteins. By standardized re-analysis of high-resolution microscopic images, detailed information was obtained on altered platelet adhesion, aggregation and/or activation. For a subset of 11 mouse strains, these platelet functions were further evaluated in rhodocytin- and laminin-dependent thrombus formation, thus allowing a comparison of glycoprotein VI (GPVI), C-type lectin-like receptor 2 (CLEC2) and integrin α6β1 pathways. High homogeneity was found between wild-type mice datasets concerning adhesion and aggregation parameters. Quantitative comparison for the 38 modified mouse strains resulted in a matrix visualizing the impact of the respective (genetic) deficiency on thrombus formation with detailed insight into the type and extent of altered thrombus signatures. Network analysis revealed strong clusters of genes involved in GPVI signaling and Ca2+ homeostasis. The majority of mice demonstrating an antithrombotic phenotype in vivo displayed with a larger or smaller reduction in multi-parameter analysis of collagen-dependent thrombus formation in vitro. Remarkably, in only approximately half of the mouse strains that displayed reduced arterial thrombosis in vivo, this was accompanied by impaired hemostasis. This was also reflected by comparing in vitro thrombus formation (by microfluidics) with alterations in in vivo bleeding time. In conclusion, the presently developed multi-parameter analysis of thrombus formation using microfluidics can be used to: (i) determine the severity of platelet abnormalities; (ii) distinguish between altered platelet adhesion, aggregation and activation; and (iii) elucidate both collagen and non-collagen dependent alterations of thrombus formation. This approach may thereby aid in the better understanding and better assessment of genetic variation that affect in vivo arterial thrombosis and hemostasis.
KW  - arterial thrombus formation
KW  - bleeding
KW  - collagen
KW  - glycoprotein VI
KW  - platelets
KW  - microfluidics
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-232194
VL  - 6
ER  - 
TY  - JOUR
A1  - Gotru, Sanjeev Kiran
A1  - van Geffen, Johanna P.
A1  - Nagy, Magdolna
A1  - Mammadova-Bach, Elmina
A1  - Eilenberger, Julia
A1  - Volz, Julia
A1  - Manukjan, Georgi
A1  - Schulze, Harald
A1  - Wagner, Leonard
A1  - Eber, Stefan
A1  - Schambeck, Christian
A1  - Deppermann, Carsten
A1  - Brouns, Sanne
A1  - Nurden, Paquita
A1  - Greinacher, Andreas
A1  - Sachs, Ulrich
A1  - Nieswandt, Bernhard
A1  - Hermanns, Heike M.
A1  - Heemskerk, Johan W. M.
A1  - Braun, Attila
T1  - Defective Zn2+ homeostasis in mouse and human platelets with α- and δ-storage pool diseases
JF  - Scientific Reports
N2  - Zinc (Zn2+) can modulate platelet and coagulation activation pathways, including fibrin formation. Here, we studied the (patho)physiological consequences of abnormal platelet Zn2+ storage and release. To visualize Zn2+ storage in human and mouse platelets, the Zn2+ specific fluorescent dye FluoZin3 was used. In resting platelets, the dye transiently accumulated into distinct cytosolic puncta, which were lost upon platelet activation. Platelets isolated from Unc13d−/− mice, characterized by combined defects of α/δ granular release, showed a markedly impaired Zn2+ release upon activation. Platelets from Nbeal2−/− mice mimicking Gray platelet syndrome (GPS), characterized by primarily loss of the α-granule content, had strongly reduced Zn2+ levels, which was also confirmed in primary megakaryocytes. In human platelets isolated from patients with GPS, Hermansky-Pudlak Syndrome (HPS) and Storage Pool Disease (SPD) altered Zn2+ homeostasis was detected. In turbidity and flow based assays, platelet-dependent fibrin formation was impaired in both Nbeal2−/− and Unc13d−/− mice, and the impairment could be partially restored by extracellular Zn2+. Altogether, we conclude that the release of ionic Zn2+ store from secretory granules upon platelet activation contributes to the procoagulant role of Zn2+ in platelet-dependent fibrin formation.
KW  - coagulation system
KW  - metals
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-227455
VL  - 9
ER  - 
TY  - JOUR
A1  - Elgheznawy, Amro
A1  - Öftering, Patricia
A1  - Englert, Maximilian
A1  - Mott, Kristina
A1  - Kaiser, Friederike
A1  - Kusch, Charly
A1  - Gbureck, Uwe
A1  - Bösl, Michael R.
A1  - Schulze, Harald
A1  - Nieswandt, Bernhard
A1  - Vögtle, Timo
A1  - Hermanns, Heike M.
T1  - Loss of zinc transporters ZIP1 and ZIP3 augments platelet reactivity in response to thrombin and accelerates thrombus formation in vivo
JF  - Frontiers in Immunology
N2  - Zinc (Zn2+) is considered as important mediator of immune cell function, thrombosis and haemostasis. However, our understanding of the transport mechanisms that regulate Zn2+ homeostasis in platelets is limited. Zn2+ transporters, ZIPs and ZnTs, are widely expressed in eukaryotic cells. Using mice globally lacking ZIP1 and ZIP3 (ZIP1/3 DKO), our aim was to explore the potential role of these Zn2+ transporters in maintaining platelet Zn2+ homeostasis and in the regulation of platelet function. While ICP-MS measurements indicated unaltered overall Zn2+ concentrations in platelets of ZIP1/3 DKO mice, we observed a significantly increased content of FluoZin3-stainable free Zn2+, which, however, appears to be released less efficiently upon thrombin-stimulated platelet activation. On the functional level, ZIP1/3 DKO platelets exhibited a hyperactive response towards threshold concentrations of G protein-coupled receptor (GPCR) agonists, while immunoreceptor tyrosine-based activation motif (ITAM)-coupled receptor agonist signalling was unaffected. This resulted in enhanced platelet aggregation towards thrombin, bigger thrombus volume under flow ex vivo and faster in vivo thrombus formation in ZIP1/3 DKO mice. Molecularly, augmented GPCR responses were accompanied by enhanced Ca2+ and PKC, CamKII and ERK1/2 signalling. The current study thereby identifies ZIP1 and ZIP3 as important regulators for the maintenance of platelet Zn2+ homeostasis and function.
KW  - platelets
KW  - zinc
KW  - ZIP
KW  - thrombin
KW  - signaling
KW  - thrombosis
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-320154
VL  - 14
ER  - 
TY  - JOUR
A1  - Ascheid, David
A1  - Baumann, Magdalena
A1  - Funke, Caroline
A1  - Volz, Julia
A1  - Pinnecker, Jürgen
A1  - Friedrich, Mike
A1  - Höhn, Marie
A1  - Nandigama, Rajender
A1  - Ergün, Süleyman
A1  - Nieswandt, Bernhard
A1  - Heinze, Katrin G.
A1  - Henke, Erik
T1  - Image-based modeling of vascular organization to evaluate anti-angiogenic therapy
JF  - Biology Direct
N2  - In tumor therapy anti-angiogenic approaches have the potential to increase the efficacy of a wide variety of subsequently or co-administered agents, possibly by improving or normalizing the defective tumor vasculature. Successful implementation of the concept of vascular normalization under anti-angiogenic therapy, however, mandates a detailed understanding of key characteristics and a respective scoring metric that defines an improved vasculature and thus a successful attempt. Here, we show that beyond commonly used parameters such as vessel patency and maturation, anti-angiogenic approaches largely benefit if the complex vascular network with its vessel interconnections is both qualitatively and quantitatively assessed. To gain such deeper insight the organization of vascular networks, we introduce a multi-parametric evaluation of high-resolution angiographic images based on light-sheet fluorescence microscopy images of tumors. We first could pinpoint key correlations between vessel length, straightness and diameter to describe the regular, functional and organized structure observed under physiological conditions. We found that vascular networks from experimental tumors diverted from those in healthy organs, demonstrating the dysfunctionality of the tumor vasculature not only on the level of the individual vessel but also in terms of inadequate organization into larger structures. These parameters proofed effective in scoring the degree of disorganization in different tumor entities, and more importantly in grading a potential reversal under treatment with therapeutic agents. The presented vascular network analysis will support vascular normalization assessment and future optimization of anti-angiogenic therapy.
KW  - vascular structure
KW  - cancer
KW  - tumor microenvironment
KW  - optical clearing
KW  - light sheet fluorescence microscopy
KW  - 3D image analysis
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-357242
VL  - 18
ER  - 
TY  - JOUR
A1  - Bieber, Michael
A1  - Schuhmann, Michael K.
A1  - Bellut, Maximilian
A1  - Stegner, David
A1  - Heinze, Katrin G.
A1  - Pham, Mirko
A1  - Nieswandt, Bernhard
A1  - Stoll, Guido
T1  - Blockade of platelet glycoprotein Ibα augments neuroprotection in Orai2-deficient mice during middle cerebral artery occlusion
JF  - International Journal of Molecular Sciences
N2  - During ischemic stroke, infarct growth before recanalization diminishes functional outcome. Hence, adjunct treatment options to protect the ischemic penumbra before recanalization are eagerly awaited. In experimental stroke targeting two different pathways conferred protection from penumbral tissue loss: (1) enhancement of hypoxic tolerance of neurons by deletion of the calcium channel subunit Orai2 and (2) blocking of detrimental lymphocyte–platelet responses. However, until now, no preclinical stroke study has assessed the potential of combining neuroprotective with anti-thrombo-inflammatory interventions to augment therapeutic effects. We induced focal cerebral ischemia in Orai2-deficient (Orai2\(^{-/-}\)) mice by middle cerebral artery occlusion (MCAO). Animals were treated with anti-glycoprotein Ib alpha (GPIbα) Fab fragments (p0p/B Fab) blocking GPIbα–von Willebrand factor (vWF) interactions. Rat immunoglobulin G (IgG) Fab was used as the control treatment. The extent of infarct growth before recanalization was assessed at 4 h after MCAO. Moreover, infarct volumes were determined 6 h after recanalization (occlusion time: 4 h). Orai2 deficiency significantly halted cerebral infarct progression under occlusion. Inhibition of platelet GPIbα further reduced primary infarct growth in Orai2\(^{-/-}\) mice. During ischemia–reperfusion, upon recanalization, mice were likewise protected. All in all, we show that neuroprotection in Orai2\(^{-/-}\) mice can be augmented by targeting thrombo-inflammation. This supports the clinical development of combined neuroprotective/anti-platelet strategies in hyper-acute stroke.
KW  - ischemic penumbra
KW  - Orai2
KW  - glycoprotein receptor Ibα
KW  - ischemic stroke
KW  - thrombo-inflammation
KW  - middle cerebral artery occlusion
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-286038
SN  - 1422-0067
VL  - 23
IS  - 16
ER  - 
TY  - JOUR
A1  - Neagoe, Raluca A. I.
A1  - Gardiner, Elizabeth E.
A1  - Stegner, David
A1  - Nieswandt, Bernhard
A1  - Watson, Steve P.
A1  - Poulter, Natalie S.
T1  - Rac inhibition causes impaired GPVI signalling in human platelets through GPVI shedding and reduction in PLCγ2 phosphorylation
JF  - International Journal of Molecular Sciences
N2  - Rac1 is a small Rho GTPase that is activated in platelets upon stimulation with various ligands, including collagen and thrombin, which are ligands for the glycoprotein VI (GPVI) receptor and the protease-activated receptors, respectively. Rac1-deficient murine platelets have impaired lamellipodia formation, aggregation, and reduced PLCγ2 activation, but not phosphorylation. The objective of our study is to investigate the role of Rac1 in GPVI-dependent human platelet activation and downstream signalling. Therefore, we used human platelets stimulated using GPVI agonists (collagen and collagen-related peptide) in the presence of the Rac1-specific inhibitor EHT1864 and analysed platelet activation, aggregation, spreading, protein phosphorylation, and GPVI clustering and shedding. We observed that in human platelets, the inhibition of Rac1 by EHT1864 had no significant effect on GPVI clustering on collagen fibres but decreased the ability of platelets to spread or aggregate in response to GPVI agonists. Additionally, in contrast to what was observed in murine Rac1-deficient platelets, EHT1864 enhanced GPVI shedding in platelets and reduced the phosphorylation levels of PLCγ2 following GPVI activation. In conclusion, Rac1 activity is required for both human and murine platelet activation in response to GPVI-ligands, but Rac1’s mode of action differs between the two species.
KW  - platelets
KW  - Rac1
KW  - glycoprotein VI
KW  - EHT1864
KW  - GPVI shedding
KW  - phospholipase C gamma 2
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284350
SN  - 1422-0067
VL  - 23
IS  - 7
ER  - 
TY  - JOUR
A1  - Koo, Chek Ziu
A1  - Matthews, Alexandra L.
A1  - Harrison, Neale
A1  - Szyroka, Justyna
A1  - Nieswandt, Bernhard
A1  - Gardiner, Elizabeth E.
A1  - Poulter, Natalie S.
A1  - Tomlinson, Michael G.
T1  - The platelet collagen receptor GPVI is cleaved by Tspan15/ADAM10 and Tspan33/ADAM10 molecular scissors
JF  - International Journal of Molecular Sciences
N2  - The platelet-activating collagen receptor GPVI represents the focus of clinical trials as an antiplatelet target for arterial thrombosis, and soluble GPVI is a plasma biomarker for several human diseases. A disintegrin and metalloproteinase 10 (ADAM10) acts as a ‘molecular scissor’ that cleaves the extracellular region from GPVI and many other substrates. ADAM10 interacts with six regulatory tetraspanin membrane proteins, Tspan5, Tspan10, Tspan14, Tspan15, Tspan17 and Tspan33, which are collectively termed the TspanC8s. These are emerging as regulators of ADAM10 substrate specificity. Human platelets express Tspan14, Tspan15 and Tspan33, but which of these regulates GPVI cleavage remains unknown. To address this, CRISPR/Cas9 knockout human cell lines were generated to show that Tspan15 and Tspan33 enact compensatory roles in GPVI cleavage, with Tspan15 bearing the more important role. To investigate this mechanism, a series of Tspan15 and GPVI mutant expression constructs were designed. The Tspan15 extracellular region was found to be critical in promoting GPVI cleavage, and appeared to achieve this by enabling ADAM10 to access the cleavage site at a particular distance above the membrane. These findings bear implications for the regulation of cleavage of other ADAM10 substrates, and provide new insights into post-translational regulation of the clinically relevant GPVI protein.
KW  - ADAM10
KW  - GPVI
KW  - tetraspanin
KW  - platelet
KW  - shedding
KW  - TspanC8
KW  - metalloproteinase
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284468
SN  - 1422-0067
VL  - 23
IS  - 5
ER  - 
TY  - JOUR
A1  - Schanbacher, Constanze
A1  - Bieber, Michael
A1  - Reinders, Yvonne
A1  - Cherpokova, Deya
A1  - Teichert, Christina
A1  - Nieswandt, Bernhard
A1  - Sickmann, Albert
A1  - Kleinschnitz, Christoph
A1  - Langhauser, Friederike
A1  - Lorenz, Kristina
T1  - ERK1/2 activity is critical for the outcome of ischemic stroke
JF  - International Journal of Molecular Sciences
N2  - Ischemic disorders are the leading cause of death worldwide. The extracellular signal-regulated kinases 1 and 2 (ERK1/2) are thought to affect the outcome of ischemic stroke. However, it is under debate whether activation or inhibition of ERK1/2 is beneficial. In this study, we report that the ubiquitous overexpression of wild-type ERK2 in mice (ERK2\(^{wt}\)) is detrimental after transient occlusion of the middle cerebral artery (tMCAO), as it led to a massive increase in infarct volume and neurological deficits by increasing blood–brain barrier (BBB) leakiness, inflammation, and the number of apoptotic neurons. To compare ERK1/2 activation and inhibition side-by-side, we also used mice with ubiquitous overexpression of the Raf-kinase inhibitor protein (RKIP\(^{wt}\)) and its phosphorylation-deficient mutant RKIP\(^{S153A}\), known inhibitors of the ERK1/2 signaling cascade. RKIP\(^{wt}\) and RKIP\(^{S153A}\) attenuated ischemia-induced damages, in particular via anti-inflammatory signaling. Taken together, our data suggest that stimulation of the Raf/MEK/ERK1/2-cascade is severely detrimental and its inhibition is rather protective. Thus, a tight control of the ERK1/2 signaling is essential for the outcome in response to ischemic stroke.
KW  - ERK1/2
KW  - tMCAO
KW  - ischemic stroke
KW  - RKIP
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-283991
SN  - 1422-0067
VL  - 23
IS  - 2
ER  - 
TY  - JOUR
A1  - Navarro, Stefano
A1  - Stegner, David
A1  - Nieswandt, Bernhard
A1  - Heemskerk, Johan W. M.
A1  - Kuijpers, Marijke J. E.
T1  - Temporal roles of platelet and coagulation pathways in collagen- and tissue factor-induced thrombus formation
JF  - International Journal of Molecular Sciences
N2  - In hemostasis and thrombosis, the complex process of thrombus formation involves different molecular pathways of platelet and coagulation activation. These pathways are considered as operating together at the same time, but this has not been investigated. The objective of our study was to elucidate the time-dependency of key pathways of thrombus and clot formation, initiated by collagen and tissue factor surfaces, where coagulation is triggered via the extrinsic route. Therefore, we adapted a microfluidics whole-blood assay with the Maastricht flow chamber to acutely block molecular pathways by pharmacological intervention at desired time points. Application of the technique revealed crucial roles of glycoprotein VI (GPVI)-induced platelet signaling via Syk kinase as well as factor VIIa-induced thrombin generation, which were confined to the first minutes of thrombus buildup. A novel anti-GPVI Fab EMF-1 was used for this purpose. In addition, platelet activation with the protease-activating receptors 1/4 (PAR1/4) and integrin αIIbβ3 appeared to be prolongedly active and extended to later stages of thrombus and clot formation. This work thereby revealed a more persistent contribution of thrombin receptor-induced platelet activation than of collagen receptor-induced platelet activation to the thrombotic process.
KW  - coagulation
KW  - fibrin
KW  - glycoprotein VI
KW  - platelet receptors
KW  - spatiotemporal thrombus
KW  - thrombin
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284219
SN  - 1422-0067
VL  - 23
IS  - 1
ER  - 
TY  - JOUR
A1  - Vogelsang, Anna
A1  - Eichler, Susann
A1  - Huntemann, Niklas
A1  - Masanneck, Lars
A1  - Böhnlein, Hannes
A1  - Schüngel, Lisa
A1  - Willison, Alice
A1  - Loser, Karin
A1  - Nieswandt, Bernhard
A1  - Kehrel, Beate E.
A1  - Zarbock, Alexander
A1  - Göbel, Kerstin
A1  - Meuth, Sven G.
T1  - Platelet inhibition by low-dose acetylsalicylic acid reduces neuroinflammation in an animal model of multiple sclerosis
JF  - International Journal of Molecular Sciences
N2  - Aside from the established immune-mediated etiology of multiple sclerosis (MS), compelling evidence implicates platelets as important players in disease pathogenesis. Specifically, numerous studies have highlighted that activated platelets promote the central nervous system (CNS)-directed adaptive immune response early in the disease course. Platelets, therefore, present a novel opportunity for modulating the neuroinflammatory process that characterizes MS. We hypothesized that the well-known antiplatelet agent acetylsalicylic acid (ASA) could inhibit neuroinflammation by affecting platelets if applied at low-dose and investigated its effect during experimental autoimmune encephalomyelitis (EAE) as a model to study MS. We found that oral administration of low-dose ASA alleviates symptoms of EAE accompanied by reduced inflammatory infiltrates and less extensive demyelination. Remarkably, the percentage of CNS-infiltrated CD4\(^+\) T cells, the major drivers of neuroinflammation, was decreased to 40.98 ± 3.28% in ASA-treated mice compared to 56.11 ± 1.46% in control animals at the disease maximum as revealed by flow cytometry. More interestingly, plasma levels of thromboxane A\(_2\) were decreased, while concentrations of platelet factor 4 and glycoprotein VI were not affected by low-dose ASA treatment. Overall, we demonstrate that low-dose ASA could ameliorate the platelet-dependent neuroinflammatory response in vivo, thus indicating a potential treatment approach for MS.
KW  - acetylsalicylic acid
KW  - experimental autoimmune encephalomyelitis
KW  - platelets
KW  - multiple sclerosis
KW  - thromboxane
KW  - glycoprotein VI
KW  - platelet factor 4
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284535
SN  - 1422-0067
VL  - 22
IS  - 18
ER  -