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 - 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 - 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 - Navarro, Stefano A1 - Starke, Andreas A1 - Heemskerk, Johan W. M. A1 - Kuijpers, Marijke J. E. A1 - Stegner, David A1 - Nieswandt, Bernhard T1 - Targeting of a conserved epitope in mouse and human GPVI differently affects receptor function JF - International Journal of Molecular Sciences N2 - Glycoprotein (GP) VI is the major platelet collagen receptor and a promising anti-thrombotic target. This was first demonstrated in mice using the rat monoclonal antibody JAQ1, which completely blocks the Collagen-Related Peptide (CRP)-binding site on mouse GPVI and efficiently inhibits mouse platelet adhesion, activation and aggregation on collagen. Here, we show for the first time that JAQ1 cross-reacts with human GPVI (huGPVI), but not with GPVI in other tested species, including rat, rabbit, guinea pig, swine, and dog. We further demonstrate that JAQ1 differently modulates mouse and human GPVI function. Similar to its effects on mouse GPVI (mGPVI), JAQ1 inhibits CRP-induced activation in human platelets, whereas, in stark contrast to mouse GPVI, it does not inhibit the adhesion, activation or aggregate formation of human platelets on collagen, but causes instead an increased response. This effect was also seen with platelets from newly generated human GPVI knockin mice (hGP6\(^{tg/tg\)). These results indicate that the binding of JAQ1 to a structurally conserved epitope in GPVI differently affects its function in human and mouse platelets. KW - glycoprotein VI KW - JAQ1 KW - platelet receptors KW - platelet activation KW - platelet inhibition Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-286227 SN - 1422-0067 VL - 23 IS - 15 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 - Göb, Vanessa A1 - Voll, Maximilian G. A1 - Zimmermann, Lena A1 - Hemmen, Katharina A1 - Stoll, Guido A1 - Nieswandt, Bernhard A1 - Schuhmann, Michael K. A1 - Heinze, Katrin G. A1 - Stegner, David T1 - Infarct growth precedes cerebral thrombosis following experimental stroke in mice JF - Scientific Reports N2 - Ischemic stroke is among the leading causes of disability and death worldwide. In acute ischemic stroke, successful recanalization of occluded vessels is the primary therapeutic aim, but even if it is achieved, not all patients benefit. Although blockade of platelet aggregation did not prevent infarct progression, cerebral thrombosis as cause of secondary infarct growth has remained a matter of debate. As cerebral thrombi are frequently observed after experimental stroke, a thrombus-induced impairment of the brain microcirculation is considered to contribute to tissue damage. Here, we combine the model of transient middle cerebral artery occlusion (tMCAO) with light sheet fluorescence microscopy and immunohistochemistry of brain slices to investigate the kinetics of thrombus formation and infarct progression. Our data reveal that tissue damage already peaks after 8 h of reperfusion following 60 min MCAO, while cerebral thrombi are only observed at later time points. Thus, cerebral thrombosis is not causative for secondary infarct growth during ischemic stroke. KW - cerebrovascular disorders KW - thrombosis Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265791 VL - 11 IS - 1 ER - TY - JOUR A1 - Beck, Sarah A1 - Stegner, David A1 - Loroch, Stefan A1 - Baig, Ayesha A. A1 - Göb, Vanessa A1 - Schumbutzki, Cornelia A1 - Eilers, Eva A1 - Sickmann, Albert A1 - May, Frauke A1 - Nolte, Marc W. A1 - Panousis, Con A1 - Nieswandt, Bernhard T1 - Generation of a humanized FXII knock-in mouse-A powerful model system to test novel anti-thrombotic agents JF - Journal of Thrombosis and Haemostasis N2 - Background Effective inhibition of thrombosis without generating bleeding risks is a major challenge in medicine. Accumulating evidence suggests that this can be achieved by inhibition of coagulation factor XII (FXII), as either its knock-out or inhibition in animal models efficiently reduced thrombosis without affecting normal hemostasis. Based on these findings, highly specific inhibitors for human FXII(a) are under development. However, currently, in vivo studies on their efficacy and safety are impeded by the lack of an optimized animal model expressing the specific target, that is, human FXII. Objective The primary objective of this study is to develop and functionally characterize a humanized FXII mouse model. Methods A humanized FXII mouse model was generated by replacing the murine with the human F12 gene (genetic knock-in) and tested it in in vitro coagulation assays and in in vivo thrombosis models. Results These hF12\(^{KI}\) mice were indistinguishable from wild-type mice in all tested assays of coagulation and platelet function in vitro and in vivo, except for reduced expression levels of hFXII compared to human plasma. Targeting FXII by the anti-human FXIIa antibody 3F7 increased activated partial thromboplastin time dose-dependently and protected hF12\(^{KI}\) mice in an arterial thrombosis model without affecting bleeding times. Conclusion These data establish the newly generated hF12\(^{KI}\) mouse as a powerful and unique model system for in vivo studies on anti-FXII(a) biologics, supporting the development of efficient and safe human FXII(a) inhibitors. KW - hemostasis, KW - blood coagulation KW - factor XII KW - animal models KW - thrombosis Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259567 VL - 19 IS - 11 ER - TY - JOUR A1 - Schuhmann, Michael K. A1 - Bieber, Michael A1 - Franke, Maximilian A1 - Kollikowski, Alexander M. A1 - Stegner, David A1 - Heinze, Katrin G. A1 - Nieswandt, Bernhard A1 - Pham, Mirko A1 - Stoll, Guido T1 - Platelets and lymphocytes drive progressive penumbral tissue loss during middle cerebral artery occlusion in mice JF - Journal of Neuroinflammation N2 - Background In acute ischemic stroke, cessation of blood flow causes immediate tissue necrosis within the center of the ischemic brain region accompanied by functional failure in the surrounding brain tissue designated the penumbra. The penumbra can be salvaged by timely thrombolysis/thrombectomy, the only available acute stroke treatment to date, but is progressively destroyed by the expansion of infarction. The underlying mechanisms of progressive infarction are not fully understood. Methods To address mechanisms, mice underwent filament occlusion of the middle cerebral artery (MCAO) for up to 4 h. Infarct development was compared between mice treated with antigen-binding fragments (Fab) against the platelet surface molecules GPIb (p0p/B Fab) or rat immunoglobulin G (IgG) Fab as control treatment. Moreover, Rag1\(^{−/−}\) mice lacking T-cells underwent the same procedures. Infarct volumes as well as the local inflammatory response were determined during vessel occlusion. Results We show that blocking of the platelet adhesion receptor, glycoprotein (GP) Ibα in mice, delays cerebral infarct progression already during occlusion and thus before recanalization/reperfusion. This therapeutic effect was accompanied by decreased T-cell infiltration, particularly at the infarct border zone, which during occlusion is supplied by collateral blood flow. Accordingly, mice lacking T-cells were likewise protected from infarct progression under occlusion. Conclusions Progressive brain infarction can be delayed by blocking detrimental lymphocyte/platelet responses already during occlusion paving the way for ultra-early treatment strategies in hyper-acute stroke before recanalization. KW - ischemic penumbra KW - glycoprotein receptor Ib KW - T-cells KW - ischemic stroke KW - thrombo-inflammation KW - middle cerebral artery occlusion Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259172 VL - 18 IS - 1 ER - TY - JOUR A1 - Balkenhol, Johannes A1 - Kaltdorf, Kristin V. A1 - Mammadova-Bach, Elmina A1 - Braun, Attila A1 - Nieswandt, Bernhard A1 - Dittrich, Marcus A1 - Dandekar, Thomas T1 - Comparison of the central human and mouse platelet signaling cascade by systems biological analysis JF - BMC Genomics N2 - Background Understanding the molecular mechanisms of platelet activation and aggregation is of high interest for basic and clinical hemostasis and thrombosis research. The central platelet protein interaction network is involved in major responses to exogenous factors. This is defined by systemsbiological pathway analysis as the central regulating signaling cascade of platelets (CC). Results The CC is systematically compared here between mouse and human and major differences were found. Genetic differences were analysed comparing orthologous human and mouse genes. We next analyzed different expression levels of mRNAs. Considering 4 mouse and 7 human high-quality proteome data sets, we identified then those major mRNA expression differences (81%) which were supported by proteome data. CC is conserved regarding genetic completeness, but we observed major differences in mRNA and protein levels between both species. Looking at central interactors, human PLCB2, MMP9, BDNF, ITPR3 and SLC25A6 (always Entrez notation) show absence in all murine datasets. CC interactors GNG12, PRKCE and ADCY9 occur only in mice. Looking at the common proteins, TLN1, CALM3, PRKCB, APP, SOD2 and TIMP1 are higher abundant in human, whereas RASGRP2, ITGB2, MYL9, EIF4EBP1, ADAM17, ARRB2, CD9 and ZYX are higher abundant in mouse. Pivotal kinase SRC shows different regulation on mRNA and protein level as well as ADP receptor P2RY12. Conclusions Our results highlight species-specific differences in platelet signaling and points of specific fine-tuning in human platelets as well as murine-specific signaling differences. KW - interspecies comparison KW - transcriptome KW - proteome KW - platelet KW - network KW - signaling KW - mouse KW - human KW - interactome KW - cascade Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230377 VL - 21 ER - TY - JOUR A1 - Kollikowski, Alexander M. A1 - Schuhmann, Michael K. A1 - Nieswandt, Bernhard A1 - Müllges, Wolfgang A1 - Stoll, Guido A1 - Pham, Mirko T1 - Local Leukocyte Invasion during Hyperacute Human Ischemic Stroke JF - Annals of Neurology N2 - Objective Bridging the gap between experimental stroke and patients by ischemic blood probing during the hyperacute stage of vascular occlusion is crucial to assess the role of inflammation in human stroke and for the development of adjunct treatments beyond recanalization. Methods We prospectively observed 151 consecutive ischemic stroke patients with embolic large vessel occlusion of the anterior circulation who underwent mechanical thrombectomy. In all these patients, we attempted microcatheter aspiration of 3 different arterial blood samples: (1) within the core of the occluded vascular compartment and controlled by (2) carotid and (3) femoral samples obtained under physiological flow conditions. Subsequent laboratory analyses comprised leukocyte counting and differentiation, platelet counting, and the quantification of 13 proinflammatory human chemokines/cytokines. Results Forty patients meeting all clinical, imaging, interventional, and laboratory inclusion criteria could be analyzed, showing that the total number of leukocytes significantly increased under the occlusion condition. This increase was predominantly driven by neutrophils. Significant increases were also apparent for lymphocytes and monocytes, accompanied by locally elevated plasma levels of the T‐cell chemoattractant CXCL‐11. Finally, we found evidence that short‐term clinical outcome (National Institute of Health Stroke Scale at 72 hours) was negatively associated with neutrophil accumulation. Interpretation We provide the first direct human evidence that neutrophils, lymphocytes, and monocytes, accompanied by specific chemokine upregulation, accumulate in the ischemic vasculature during hyperacute stroke and may affect outcome. These findings strongly support experimental evidence that immune cells contribute to acute ischemic brain damage and indicate that ischemic inflammation initiates already during vascular occlusion. Ann Neurol 2020;87:466–479 KW - neurology Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-212168 VL - 87 IS - 3 ER -