@article{HaarmannVollmuthKollikowskietal.2023,
  author    = {Haarmann, Axel and Vollmuth, Christoph and Kollikowski, Alexander M. and Heuschmann, Peter U. and Pham, Mirko and Stoll, Guido and Neugebauer, Hermann and Schuhmann, Michael K.},
  title     = {Vasoactive soluble endoglin: a novel biomarker indicative of reperfusion after cerebral large-vessel occlusion},
  series = {Cells},
  volume    = {12},
  journal   = {Cells},
  number    = {2},
  issn      = {2073-4409},
  doi       = {10.3390/cells12020288},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-304995},
  year      = {2023},
  abstract  = {Now that mechanical thrombectomy has substantially improved outcomes after large-vessel occlusion stroke in up to every second patient, futile reperfusion wherein successful recanalization is not followed by a favorable outcome is moving into focus. Unfortunately, blood-based biomarkers, which identify critical stages of hemodynamically compromised yet reperfused tissue, are lacking. We recently reported that hypoxia induces the expression of endoglin, a TGF-β co-receptor, in human brain endothelium in vitro. Subsequent reoxygenation resulted in shedding. Our cell model suggests that soluble endoglin compromises the brain endothelial barrier function. To evaluate soluble endoglin as a potential biomarker of reperfusion (-injury) we analyzed its concentration in 148 blood samples of patients with acute stroke due to large-vessel occlusion. In line with our in vitro data, systemic soluble endoglin concentrations were significantly higher in patients with successful recanalization, whereas hypoxia alone did not induce local endoglin shedding, as analyzed by intra-arterial samples from hypoxic vasculature. In patients with reperfusion, higher concentrations of soluble endoglin additionally indicated larger infarct volumes at admission. In summary, we give translational evidence that the sequence of hypoxia and subsequent reoxygenation triggers the release of vasoactive soluble endoglin in large-vessel occlusion stroke and can serve as a biomarker for severe ischemia with ensuing recanalization/reperfusion.},
  language  = {en}
}
@article{BieberFoersterHaefelietal.2021,
  author    = {Bieber, Michael and Foerster, Kathrin I. and Haefeli, Walter E. and Pham, Mirko and Schuhmann, Michael K. and Kraft, Peter},
  title     = {Treatment with edoxaban attenuates acute stroke severity in mice by reducing blood-brain barrier damage and inflammation},
  series = {International Journal of Molecular Sciences},
  volume    = {22},
  journal   = {International Journal of Molecular Sciences},
  number    = {18},
  issn      = {1422-0067},
  doi       = {10.3390/ijms22189893},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-284481},
  year      = {2021},
  abstract  = {Patients with atrial fibrillation and previous ischemic stroke (IS) are at increased risk of cerebrovascular events despite anticoagulation. In these patients, treatment with non-vitamin K oral anticoagulants (NOAC) such as edoxaban reduced the probability and severity of further IS without increasing the risk of major bleeding. However, the detailed protective mechanism of edoxaban has not yet been investigated in a model of ischemia/reperfusion injury. Therefore, in the current study we aimed to assess in a clinically relevant setting whether treatment with edoxaban attenuates stroke severity, and whether edoxaban has an impact on the local cerebral inflammatory response and blood-brain barrier (BBB) function after experimental IS in mice. Focal cerebral ischemia was induced by transient middle cerebral artery occlusion in male mice receiving edoxaban, phenprocoumon or vehicle. Infarct volumes, functional outcome and the occurrence of intracerebral hemorrhage were assessed. BBB damage and the extent of local inflammatory response were determined. Treatment with edoxaban significantly reduced infarct volumes and improved neurological outcome and BBB function on day 1 and attenuated brain tissue inflammation. In summary, our study provides evidence that edoxaban might exert its protective effect in human IS by modulating different key steps of IS pathophysiology, but further studies are warranted.},
  language  = {en}
}
@article{SchuhmannKraftBieberetal.2019,
  author    = {Schuhmann, Michael K. and Kraft, Peter and Bieber, Michael and Kollikowski, Alexander M. and Schulze, Harald and Nieswandt, Bernhard and Pham, Mirko and Stegner, David and Stoll, Guido},
  title     = {Targeting platelet GPVI plus rt-PA administration but not α2β1-mediated collagen binding protects against ischemic brain damage in mice},
  series = {International Journal of Molecular Science},
  volume    = {20},
  journal   = {International Journal of Molecular Science},
  number    = {8},
  issn      = {1422-0067},
  doi       = {10.3390/ijms20082019},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201700},
  year      = {2019},
  abstract  = {Platelet collagen interactions at sites of vascular injuries predominantly involve glycoprotein VI (GPVI) and the integrin α2β1. Both proteins are primarily expressed on platelets and megakaryocytes whereas GPVI expression is also shown on endothelial and integrin α2β1 expression on epithelial cells. We recently showed that depletion of GPVI improves stroke outcome without increasing the risk of cerebral hemorrhage. Genetic variants associated with higher platelet surface integrin α2 (ITGA2) receptor levels have frequently been found to correlate with an increased risk of ischemic stroke in patients. However until now, no preclinical stroke study has addressed whether platelet integrin α2β1 contributes to the pathophysiology of ischemia/reperfusion (I/R) injury. Focal cerebral ischemia was induced in C57BL/6 and Itga2\(^{-/-}\) mice by a 60 min transient middle cerebral artery occlusion (tMCAO). Additionally, wild-type animals were pretreated with anti-GPVI antibody (JAQ1) or Fab fragments of a function blocking antibody against integrin α2β1 (LEN/B). In anti-GPVI treated animals, intravenous (IV) recombinant tissue plasminogen activator (rt-PA) treatment was applied immediately prior to reperfusion. Stroke outcome, including infarct size and neurological scoring was determined on day 1 after tMCAO. We demonstrate that targeting the integrin α2β1 (pharmacologic; genetic) did neither reduce stroke size nor improve functional outcome on day 1 after tMCAO. In contrast, depletion of platelet GPVI prior to stroke was safe and effective, even when combined with rt-PA treatment. Our results underscore that GPVI, but not ITGA2, is a promising and safe target in the setting of ischemic stroke.},
  language  = {en}
}
@article{HoppAlbertWeissenbergerMencletal.2016,
  author    = {Hopp, Sarah and Albert-Weissenberger, Christiane and Mencl, Stine and Bieber, Michael and Schuhmann, Michael K. and Stetter, Christian and Nieswandt, Bernhard and Schmidt, Peter M. and Monoranu, Camelia-Maria and Alafuzoff, Irina and Marklund, Niklas and Nolte, Marc W. and Sir{\´e}n, Anna-Leena and Kleinschnitz, Christoph},
  title     = {Targeting coagulation factor XII as a novel therapeutic option in brain trauma},
  series = {Annals of Neurology},
  volume    = {79},
  journal   = {Annals of Neurology},
  number    = {6},
  doi       = {10.1002/ana.24655},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188800},
  pages     = {970-982},
  year      = {2016},
  abstract  = {Objective: Traumatic brain injury is a major global public health problem for which specific therapeutic interventions are lacking. There is, therefore, a pressing need to identify innovative pathomechanism-based effective therapies for this condition. Thrombus formation in the cerebral microcirculation has been proposed to contribute to secondary brain damage by causing pericontusional ischemia, but previous studies have failed to harness this finding for therapeutic use. The aim of this study was to obtain preclinical evidence supporting the hypothesis that targeting factor XII prevents thrombus formation and has a beneficial effect on outcome after traumatic brain injury. Methods: We investigated the impact of genetic deficiency of factor XII and acute inhibition of activated factor XII with a single bolus injection of recombinant human albumin-fused infestin-4 (rHA-Infestin-4) on trauma-induced microvascular thrombus formation and the subsequent outcome in 2 mouse models of traumatic brain injury. Results: Our study showed that both genetic deficiency of factor XII and an inhibition of activated factor XII in mice minimize trauma-induced microvascular thrombus formation and improve outcome, as reflected by better motor function, reduced brain lesion volume, and diminished neurodegeneration. Administration of human factor XII in factor XII-deficient mice fully restored injury-induced microvascular thrombus formation and brain damage. Interpretation: The robust protective effect of rHA-Infestin-4 points to a novel treatment option that can decrease ischemic injury after traumatic brain injury without increasing bleeding tendencies.},
  language  = {en}
}
@article{HaarmannZimmermannBieberetal.2022,
  author    = {Haarmann, Axel and Zimmermann, Lena and Bieber, Michael and Silwedel, Christine and Stoll, Guido and Schuhmann, Michael K.},
  title     = {Regulation and release of vasoactive endoglin by brain endothelium in response to hypoxia/reoxygenation in stroke},
  series = {International Journal of Molecular Sciences},
  volume    = {23},
  journal   = {International Journal of Molecular Sciences},
  number    = {13},
  issn      = {1422-0067},
  doi       = {10.3390/ijms23137085},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-284361},
  year      = {2022},
  abstract  = {In large vessel occlusion stroke, recanalization to restore cerebral perfusion is essential but not necessarily sufficient for a favorable outcome. Paradoxically, in some patients, reperfusion carries the risk of increased tissue damage and cerebral hemorrhage. Experimental and clinical data suggest that endothelial cells, representing the interface for detrimental platelet and leukocyte responses, likely play a crucial role in the phenomenon referred to as ischemia/reperfusion (I/R)-injury, but the mechanisms are unknown. We aimed to determine the role of endoglin in cerebral I/R-injury; endoglin is a membrane-bound protein abundantly expressed by endothelial cells that has previously been shown to be involved in the maintenance of vascular homeostasis. We investigated the expression of membranous endoglin (using Western blotting and RT-PCR) and the generation of soluble endoglin (using an enzyme-linked immunosorbent assay of cell culture supernatants) after hypoxia and subsequent reoxygenation in human non-immortalized brain endothelial cells. To validate these in vitro data, we additionally examined endoglin expression in an intraluminal monofilament model of permanent and transient middle cerebral artery occlusion in mice. Subsequently, the effects of recombinant human soluble endoglin were assessed by label-free impedance-based measurement of endothelial monolayer integrity (using the xCELLigence DP system) and immunocytochemistry. Endoglin expression is highly inducible by hypoxia in human brain endothelial monolayers in vitro, and subsequent reoxygenation induced its shedding. These findings were corroborated in mice during MCAO; an upregulation of endoglin was displayed in the infarcted hemispheres under occlusion, whereas endoglin expression was significantly diminished after transient MCAO, which is indicative of shedding. Of note is the finding that soluble endoglin induced an inflammatory phenotype in endothelial monolayers. The treatment of HBMEC with endoglin resulted in a decrease in transendothelial resistance and the downregulation of VE-cadherin. Our data establish a novel mechanism in which hypoxia triggers the initial endothelial upregulation of endoglin and subsequent reoxygenation triggers its release as a vasoactive mediator that, when rinsed into adjacent vascular beds after recanalization, can contribute to cerebral reperfusion injury.},
  language  = {en}
}
@article{KleinschnitzGrundWingleretal.2010,
  author    = {Kleinschnitz, Christoph and Grund, Henrike and Wingler, Kirstin and Armitage, Melanie E. and Jones, Emma and Mittal, Manish and Barit, David and Schwarz, Tobias and Geis, Christian and Kraft, Peter and Barthel, Konstanze and Schuhmann, Michael K. and Herrmann, Alexander M. and Meuth, Sven G. and Stoll, Guido and Meurer, Sabine and Schrewe, Anja and Becker, Lore and Gailus-Durner, Valerie and Fuchs, Helmut and Klopstock, Thomas and de Angelis, Martin Hrabe and Jandeleit-Dahm, Karin and Shah, Ajay M. and Weissmann, Norbert and Schmidt, Harald H. H. W.},
  title     = {Post-Stroke Inhibition of Induced NADPH Oxidase Type 4 Prevents Oxidative Stress and Neurodegeneration},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-68416},
  year      = {2010},
  abstract  = {Ischemic stroke is the second leading cause of death worldwide. Only one moderately effective therapy exists, albeit with contraindications that exclude 90\% of the patients. This medical need contrasts with a high failure rate of more than 1,000 pre-clinical drug candidates for stroke therapies. Thus, there is a need for translatable mechanisms of neuroprotection and more rigid thresholds of relevance in pre-clinical stroke models. One such candidate mechanism is oxidative stress. However, antioxidant approaches have failed in clinical trials, and the significant sources of oxidative stress in stroke are unknown. We here identify NADPH oxidase type 4 (NOX4) as a major source of oxidative stress and an effective therapeutic target in acute stroke. Upon ischemia, NOX4 was induced in human and mouse brain. Mice deficient in NOX4 (Nox42/2) of either sex, but not those deficient for NOX1 or NOX2, were largely protected from oxidative stress, blood-brain-barrier leakage, and neuronal apoptosis, after both transient and permanent cerebral ischemia. This effect was independent of age, as elderly mice were equally protected. Restoration of oxidative stress reversed the stroke-protective phenotype in Nox42/2 mice. Application of the only validated low-molecular-weight pharmacological NADPH oxidase inhibitor, VAS2870, several hours after ischemia was as protective as deleting NOX4. The extent of neuroprotection was exceptional, resulting in significantly improved long-term neurological functions and reduced mortality. NOX4 therefore represents a major source of oxidative stress and novel class of drug target for stroke therapy.},
  subject      = {Schlaganfall},
  language  = {en}
}
@article{SchuhmannBieberFrankeetal.2021,
  author    = {Schuhmann, Michael K. and Bieber, Michael and Franke, Maximilian and Kollikowski, Alexander M. and Stegner, David and Heinze, Katrin G. and Nieswandt, Bernhard and Pham, Mirko and Stoll, Guido},
  title     = {Platelets and lymphocytes drive progressive penumbral tissue loss during middle cerebral artery occlusion in mice},
  series = {Journal of Neuroinflammation},
  volume    = {18},
  journal   = {Journal of Neuroinflammation},
  number    = {1},
  doi       = {10.1186/s12974-021-02095-1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259172},
  pages     = {46},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{KollikowskiPhamMaerzetal.2022,
  author    = {Kollikowski, Alexander M. and Pham, Mirko and M{\"a}rz, Alexander G. and Papp, Lena and Nieswandt, Bernhard and Stoll, Guido and Schuhmann, Michael K.},
  title     = {Platelet Activation and Chemokine Release Are Related to Local Neutrophil-Dominant Inflammation During Hyperacute Human Stroke},
  series = {Translational Stroke Research},
  volume    = {13},
  journal   = {Translational Stroke Research},
  number    = {3},
  issn      = {1868-601X},
  doi       = {10.1007/s12975-021-00938-w},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-270194},
  pages     = {364-369},
  year      = {2022},
  abstract  = {Experimental evidence has emerged that local platelet activation contributes to inflammation and infarct formation in acute ischemic stroke (AIS) which awaits confirmation in human studies. We conducted a prospective observational study on 258 consecutive patients undergoing mechanical thrombectomy (MT) due to large-vessel-occlusion stroke of the anterior circulation (08/2018-05/2020). Intraprocedural microcatheter aspiration of 1 ml of local (occlusion condition) and systemic arterial blood samples (self-control) was performed according to a prespecified protocol. The samples were analyzed for differential leukocyte counts, platelet counts, and plasma levels of the platelet-derived neutrophil-activating chemokine C-X-C-motif ligand (CXCL) 4 (PF-4), the neutrophil attractant CXCL7 (NAP-2), and myeloperoxidase (MPO). The clinical-biological relevance of these variables was corroborated by specific associations with molecular-cellular, structural-radiological, hemodynamic, and clinical-functional parameters. Seventy consecutive patients fulfilling all predefined criteria entered analysis. Mean local CXCL4 (+ 39\%: 571 vs 410 ng/ml, P = .0095) and CXCL7 (+ 9\%: 693 vs 636 ng/ml, P = .013) concentrations were higher compared with self-controls. Local platelet counts were lower (- 10\%: 347,582 vs 383,284/µl, P = .0052), whereas neutrophil counts were elevated (+ 10\%: 6022 vs 5485/µl, P = 0.0027). Correlation analyses revealed associations between local platelet and neutrophil counts (r = 0.27, P = .034), and between CXCL7 and MPO (r = 0.24, P = .048). Local CXCL4 was associated with the angiographic degree of reperfusion following recanalization (r =  - 0.2523, P = .0479). Functional outcome at discharge correlated with local MPO concentrations (r = 0.3832, P = .0014) and platelet counts (r = 0.288, P = .0181). This study provides human evidence of cerebral platelet activation and platelet-neutrophil interactions during AIS and points to the relevance of per-ischemic thrombo-inflammatory mechanisms to impaired reperfusion and worse functional outcome following recanalization.},
  language  = {en}
}
@article{WolfBraunHainingetal.2016,
  author    = {Wolf, Karen and Braun, Attila and Haining, Elizabeth J. and Tseng, Yu-Lun and Kraft, Peter and Schuhmann, Michael K. and Gotru, Sanjeev K. and Chen, Wenchun and Hermanns, Heike M. and Stoll, Guido and Lesch, Klaus-Peter and Nieswandt, Bernhard},
  title     = {Partially Defective Store Operated Calcium Entry and Hem(ITAM) Signaling in Platelets of Serotonin Transporter Deficient Mice},
  series = {PLoS One},
  volume    = {11},
  journal   = {PLoS One},
  number    = {1},
  doi       = {10.1371/journal.pone.0147664},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-146399},
  pages     = {e0147664},
  year      = {2016},
  abstract  = {Background Serotonin (5-hydroxytryptamin, 5-HT) is an indolamine platelet agonist, biochemically derived from tryptophan. 5-HT is secreted from the enterochromaffin cells into the gastrointestinal tract and blood. Blood 5-HT has been proposed to regulate hemostasis by acting as a vasoconstrictor and by triggering platelet signaling through 5-HT receptor 2A (5HTR2A). Although platelets do not synthetize 5-HT, they take 5-HT up from the blood and store it in their dense granules which are secreted upon platelet activation. Objective To identify the molecular composite of the 5-HT uptake system in platelets and elucidate the role of platelet released 5-HT in thrombosis and ischemic stroke. Methods: 5-HT transporter knockout mice (5Htt\(^{-/-}\)) were analyzed in different in vitro and in vivo assays and in a model of ischemic stroke. Results In 5Htt\(^{-/-}\) platelets, 5-HT uptake from the blood was completely abolished and agonist-induced Ca2+ influx through store operated Ca\(^{2+}\) entry (SOCE), integrin activation, degranulation and aggregation responses to glycoprotein VI (GPVI) and C-type lectin-like receptor 2 (CLEC-2) were reduced. These observed in vitro defects in 5Htt\(^{-/-}\) platelets could be normalized by the addition of exogenous 5-HT. Moreover, reduced 5-HT levels in the plasma, an increased bleeding time and the formation of unstable thrombi were observed ex vivo under flow and in vivo in the abdominal aorta and carotid artery of 5Htt\(^{-/-}\) mice. Surprisingly, in the transient middle cerebral artery occlusion (tMCAO) model of ischemic stroke 5Htt\(^{-/-}\) mice showed nearly normal infarct volume and the neurological outcome was comparable to control mice. Conclusion Although secreted platelet 5-HT does not appear to play a crucial role in the development of reperfusion injury after stroke, it is essential to amplify the second phase of platelet activation through SOCE and plays an important role in thrombus stabilization.},
  language  = {en}
}
@article{BellutRaimondiHaarmannetal.2022,
  author    = {Bellut, Maximilian and Raimondi, Anthony T. and Haarmann, Axel and Zimmermann, Lena and Stoll, Guido and Schuhmann, Michael K.},
  title     = {NLRP3 inhibition reduces rt-PA induced endothelial dysfunction under ischemic conditions},
  series = {Biomedicines},
  volume    = {10},
  journal   = {Biomedicines},
  number    = {4},
  issn      = {2227-9059},
  doi       = {10.3390/biomedicines10040762},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-267261},
  year      = {2022},
  abstract  = {Thrombolysis with recombinant tissue plasminogen activator (rt-PA) is a mainstay of acute ischemic stroke treatment but is associated with bleeding complications, especially after prolonged large vessel occlusion. Recently, inhibition of the NLRP3 inflammasome led to preserved blood-brain barrier (BBB) integrity in experimental stroke in vivo. To further address the potential of NLRP3 inflammasome inhibition as adjunct stroke treatment we used immortalized brain derived endothelial cells (bEnd5) as an in vitro model of the BBB. We treated bEnd5 with rt-PA in combination with the NLRP3 specific inhibitor MCC950 or vehicle under normoxic as well as ischemic (OGD) conditions. We found that rt-PA exerted a cytotoxic effect on bEnd5 cells under OGD confirming that rt-PA is harmful to the BBB. This detrimental effect could be significantly reduced by MCC950 treatment. Moreover, under ischemic conditions, the Cell Index — a sensible indicator for a patent BBB — and the protein expression of Zonula occludens 1 stabilized after MCC950 treatment. At the same time, the extent of endothelial cell death and NLRP3 expression decreased. In conclusion, NLRP3 inhibition can protect the BBB from rt-PA-induced damage and thereby potentially increase the narrow time window for safe thrombolysis in stroke.},
  language  = {en}
}
@article{BellutPappBieberetal.2022,
  author    = {Bellut, Maximilian and Papp, Lena and Bieber, Michael and Kraft, Peter and Stoll, Guido and Schuhmann, Michael K.},
  title     = {NLPR3 inflammasome inhibition alleviates hypoxic endothelial cell death in-vitro and protects blood-brain barrier integrity in murine stroke},
  series = {Cell Death \& Disease},
  volume    = {13},
  journal   = {Cell Death \& Disease},
  doi       = {10.1038/s41419-021-04379-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265693},
  year      = {2022},
  abstract  = {In ischemic stroke (IS) impairment of the blood-brain barrier (BBB) has an important role in the secondary deterioration of neurological function. BBB disruption is associated with ischemia-induced inflammation, brain edema formation, and hemorrhagic infarct transformation, but the underlying mechanisms are incompletely understood. Dysfunction of endothelial cells (EC) may play a central role in this process. Although neuronal NLR-family pyrin domain-containing protein 3 (NLRP3) inflammasome upregulation is an established trigger of inflammation in IS, the contribution of its expression in EC is unclear. We here used brain EC, exposed them to oxygen and glucose deprivation (OGD) in vitro, and analyzed their survival depending on inflammasome inhibition with the NLRP3-specific drug MCC950. During OGD, EC death could significantly be reduced when targeting NLRP3, concomitant with diminished endothelial NLRP3 expression. Furthermore, MCC950 led to reduced levels of Caspase 1 (p20) and activated Gasdermin D as markers for pyroptosis. Moreover, inflammasome inhibition reduced the secretion of pro-inflammatory chemokines, cytokines, and matrix metalloproteinase-9 (MMP9) in EC. In a translational approach, IS was induced in C57Bl/6 mice by 60 mins transient middle cerebral artery occlusion and 23 hours of reperfusion. Stroke volume, functional outcome, the BBB integrity, and-in good agreement with the in vitro results-MMP9 secretion as well as EC survival improved significantly in MCC950-treated mice. In conclusion, our results establish the NLRP3 inflammasome as a critical pathogenic effector of stroke-induced BBB disruption by activating inflammatory signaling cascades and pyroptosis in brain EC.},
  language  = {en}
}
@article{BittnerBobakHofmannetal.2015,
  author    = {Bittner, Stefan and Bobak, Nicole and Hofmann, Majella-Sophie and Schuhmann, Michael K. and Ruck, Tobias and G{\"o}bel, Kerstin and Br{\"u}ck, Wolfgang and Wiendl, Heinz and Meuth, Sven G.},
  title     = {Murine K\(_{2P}\)5.1 Deficiency Has No Impact on Autoimmune Neuroinflammation due to Compensatory K\(_{2P}\)3.1-and K\(_{V}\)1.3-Dependent Mechanisms},
  series = {International Journal of Molecular Sciences},
  volume    = {16},
  journal   = {International Journal of Molecular Sciences},
  doi       = {10.3390/ijms160816880},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-151454},
  pages     = {16880 -- 16896},
  year      = {2015},
  abstract  = {Lymphocytes express potassium channels that regulate physiological cell functions, such as activation, proliferation and migration. Expression levels of K\(_{2P}\)5.1(TASK2; KCNK5) channels belonging to the family of two-pore domain potassium channels have previously been correlated to the activity of autoreactive T lymphocytes in patients with multiple sclerosis and rheumatoid arthritis. In humans, K\(_{2P}\)5.1 channels are upregulated upon T cell stimulation and influence T cell effector functions. However, a further clinical translation of targeting K\(_{2P}\)5.1 is currently hampered by a lack of highly selective inhibitors, making it necessary to evaluate the impact of KCNK5 in established preclinical animal disease models. We here demonstrate that K\(_{2P}\)5.1 knockout (K\(_{2P}\)5.1\(^{-/-}\) mice display no significant alterations concerning T cell cytokine production, proliferation rates, surface marker molecules or signaling pathways. In an experimental model of autoimmune neuroinflammation, K\(_{2P}\)5.1\(^{-/-}\) mice show a comparable disease course to wild-type animals and no major changes in the peripheral immune system or CNS compartment. A compensatory upregulation of the potassium channels K\(_{2P}\)3.1 and K\(_{V}\)1.3 seems to counterbalance the deletion of K\(_{2P}\)5.1. As an alternative model mimicking autoimmune neuroinflammation, experimental autoimmune encephalomyelitis in the common marmoset has been proposed, especially for testing the efficacy of new potential drugs. Initial experiments show that K\(_{2P}\)5.1 is functionally expressed on marmoset T lymphocytes, opening up the possibility for assessing future K\(_{2P}\)5.1-targeting drugs.},
  language  = {en}
}
@article{SchuhmannPappStolletal.2021,
  author    = {Schuhmann, Michael K. and Papp, Lena and Stoll, Guido and Blum, Robert and Volkmann, Jens and Fluri, Felix},
  title     = {Mesencephalic electrical stimulation reduces neuroinflammation after photothrombotic stroke in rats by targeting the cholinergic anti-inflammatory pathway},
  series = {International Journal of Molecular Sciences},
  volume    = {22},
  journal   = {International Journal of Molecular Sciences},
  number    = {3},
  issn      = {1422-0067},
  doi       = {10.3390/ijms22031254},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259099},
  year      = {2021},
  abstract  = {Inflammation is crucial in the pathophysiology of stroke and thus a promising therapeutic target. High-frequency stimulation (HFS) of the mesencephalic locomotor region (MLR) reduces perilesional inflammation after photothrombotic stroke (PTS). However, the underlying mechanism is not completely understood. Since distinct neural and immune cells respond to electrical stimulation by releasing acetylcholine, we hypothesize that HFS might trigger the cholinergic anti-inflammatory pathway via activation of the α7 nicotinic acetylcholine receptor (α7nAchR). To test this hypothesis, rats underwent PTS and implantation of a microelectrode into the MLR. Three hours after intervention, either HFS or sham-stimulation of the MLR was applied for 24 h. IFN-γ, TNF-α, and IL-1α were quantified by cytometric bead array. Choline acetyltransferase (ChAT)\(^+\) CD4\(^+\)-cells and α7nAchR\(^+\)-cells were quantified visually using immunohistochemistry. Phosphorylation of NFĸB, ERK1/2, Akt, and Stat3 was determined by Western blot analyses. IFN-γ, TNF-α, and IL-1α were decreased in the perilesional area of stimulated rats compared to controls. The number of ChAT\(^+\) CD4\(^+\)-cells increased after MLR-HFS, whereas the amount of α7nAchR\(^+\)-cells was similar in both groups. Phospho-ERK1/2 was reduced significantly in stimulated rats. The present study suggests that MLR-HFS may trigger anti-inflammatory processes within the perilesional area by modulating the cholinergic system, probably via activation of the α7nAchR.},
  language  = {en}
}
@article{KollikowskiSchuhmannNieswandtetal.2020,
  author    = {Kollikowski, Alexander M. and Schuhmann, Michael K. and Nieswandt, Bernhard and M{\"u}llges, Wolfgang and Stoll, Guido and Pham, Mirko},
  title     = {Local Leukocyte Invasion during Hyperacute Human Ischemic Stroke},
  series = {Annals of Neurology},
  volume    = {87},
  journal   = {Annals of Neurology},
  number    = {3},
  doi       = {10.1002/ana.25665},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212168},
  pages     = {466-479},
  year      = {2020},
  abstract  = {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},
  language  = {en}
}
@article{GoebVollZimmermannetal.2021,
  author    = {G{\"o}b, Vanessa and Voll, Maximilian G. and Zimmermann, Lena and Hemmen, Katharina and Stoll, Guido and Nieswandt, Bernhard and Schuhmann, Michael K. and Heinze, Katrin G. and Stegner, David},
  title     = {Infarct growth precedes cerebral thrombosis following experimental stroke in mice},
  series = {Scientific Reports},
  volume    = {11},
  journal   = {Scientific Reports},
  number    = {1},
  doi       = {10.1038/s41598-021-02360-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265791},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{EssigKollikowskiPhametal.2020,
  author    = {Essig, Fabian and Kollikowski, Alexander M. and Pham, Mirko and Solymosi, L{\´a}szl{\´o} and Stoll, Guido and Haeusler, Karl Georg and Kraft, Peter and Schuhmann, Michael K.},
  title     = {Immunohistological analysis of neutrophils and neutrophil extracellular traps in human thrombemboli causing acute ischemic stroke},
  series = {International Journal of Molecular Sciences},
  volume    = {21},
  journal   = {International Journal of Molecular Sciences},
  number    = {19},
  issn      = {1422-0067},
  doi       = {10.3390/ijms21197387},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236192},
  year      = {2020},
  abstract  = {Ischemic stroke caused by thromboembolic occlusion of large cerebral arteries, such as the internal carotid (ICA) and/or the middle cerebral artery (MCA), is treated by mechanical thrombectomy (MT). MT allows salvage of the vessel-occluding thrombemboli, which most frequently originate from the left atrium or the left ventricle of the heart or from sites of plaque rupture within large arteries above the heart. Clot composition may influence the efficacy of (intravenous) thrombolysis and MT, respectively. We analyzed 37 human thrombemboli obtained from acute ischemic stroke patients during MT with special emphasis on histological staining of neutrophils and neutrophil extracellular traps (NETs). We found neutrophils as the main cellular component of cerebral thrombemboli but encountered considerable morphological heterogeneity. Neutrophils accumulated in the border region of fibrin-rich structures indicating possible interaction of neutrophils with distinct structural thrombembolus components. Web-like NETs were found in 35 of 37 thrombemboli in varying amounts. NETs were almost exclusively found within fibrin-rich areas. Importantly, stroke etiology, age and present oral anticoagulation was associated with morphological patterns and the amount of neutrophils. Correlation of histological data and imaging data revealed that relative Hounsfield units of cerebral thrombemboli positively correlated with the amount of red blood cells. In summary, our results demonstrate that neutrophils and NETs are substantial constituents of cerebral thrombemboli and contribute to their structural complexity.},
  language  = {en}
}
@article{SchuhmannGunrebenKleinschnitzetal.2016,
  author    = {Schuhmann, Michael K. and Gunreben, Ignaz and Kleinschnitz, Christoph and Kraft, Peter},
  title     = {Immunohistochemical Analysis of Cerebral Thrombi Retrieved by Mechanical Thrombectomy from Patients with Acute Ischemic Stroke},
  series = {International Journal of Molecular Sciences},
  volume    = {17},
  journal   = {International Journal of Molecular Sciences},
  number    = {3},
  doi       = {10.3390/ijms17030298},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-166206},
  pages     = {298},
  year      = {2016},
  abstract  = {Mechanical thrombectomy is a novel treatment option for patients with acute ischemic stroke (AIS). Only a few studies have previously suggested strategies to categorize retrieved clots according to their histologic composition. However, these reports did not analyze potential biomarkers that are of importance in stroke-related inflammation. We therefore histopathologically investigated 37 intracerebral thrombi mechanically retrieved from patients with AIS, and focused on the composition of immune cells and platelets. We also conducted correlation analyses of distinctive morphologic patterns (erythrocytic, serpentine, layered, red, white, mixed appearance) with clinical parameters. Most T cells and monocytes were detected in erythrocytic and red clots, in which the distribution of these cells was random. In contrast, von Willebrand factor (vWF)-positive areas co-localized with regions of fibrin and collagen. While clots with huge amounts of vWF seem to be associated with a high National Institute of Health Stroke Scale score at admission, histologic findings could not predict the clinical outcome at discharge. In summary, we provide the first histologic description of mechanically retrieved intracerebral thrombi regarding biomarkers relevant for inflammation in ischemic stroke.},
  language  = {en}
}
@article{StrinitzPhamMaerzetal.2021,
  author    = {Strinitz, Marc and Pham, Mirko and M{\"a}rz, Alexander G. and Feick, J{\"o}rn and Weidner, Franziska and Vogt, Marius L. and Essig, Fabian and Neugebauer, Hermann and Stoll, Guido and Schuhmann, Michael K. and Kollikowski, Alexander M.},
  title     = {Immune cells invade the collateral circulation during human stroke: prospective replication and extension},
  series = {International Journal of Molecular Sciences},
  volume    = {22},
  journal   = {International Journal of Molecular Sciences},
  number    = {17},
  issn      = {1422-0067},
  doi       = {10.3390/ijms22179161},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-284281},
  year      = {2021},
  abstract  = {It remains unclear if principal components of the local cerebral stroke immune response can be reliably and reproducibly observed in patients with acute large-vessel-occlusion (LVO) stroke. We prospectively studied a large independent cohort of n = 318 consecutive LVO stroke patients undergoing mechanical thrombectomy during which cerebral blood samples from within the occluded anterior circulation and systemic control samples from the ipsilateral cervical internal carotid artery were obtained. An extensive protocol was applied to homogenize the patient cohort and to standardize the procedural steps of endovascular sample collection, sample processing, and laboratory analyses. N = 58 patients met all inclusion criteria. (1) Mean total leukocyte counts were significantly higher within the occluded ischemic cerebral vasculature (I) vs. intraindividual systemic controls (S): +9.6\%, I: 8114/µL ± 529 vs. S: 7406/µL ± 468, p = 0.0125. (2) This increase was driven by neutrophils: +12.1\%, I: 7197/µL ± 510 vs. S: 6420/µL ± 438, p = 0.0022. Leukocyte influx was associated with (3) reduced retrograde collateral flow (R\(^2\) = 0.09696, p = 0.0373) and (4) greater infarct extent (R\(^2\) = 0.08382, p = 0.032). Despite LVO, leukocytes invade the occluded territory via retrograde collateral pathways early during ischemia, likely compromising cerebral hemodynamics and tissue integrity. This inflammatory response can be reliably observed in human stroke by harvesting immune cells from the occluded cerebral vascular compartment.},
  language  = {en}
}
@article{KraftSchuhmannGarzetal.2017,
  author    = {Kraft, Peter and Schuhmann, Michael K. and Garz, Cornelia and Jandke, Solveig and Urlaub, Daniela and Mencl, Stine and Zernecke, Alma and Heinze, Hans-Jochen and Carare, Roxana O. and Kleinschnitz, Christoph and Schreiber, Stefanie},
  title     = {Hypercholesterolemia induced cerebral small vessel disease},
  series = {PLoS ONE},
  volume    = {12},
  journal   = {PLoS ONE},
  number    = {8},
  doi       = {10.1371/journal.pone.0182822},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170493},
  pages     = {e0182822},
  year      = {2017},
  abstract  = {Background While hypercholesterolemia plays a causative role for the development of ischemic stroke in large vessels, its significance for cerebral small vessel disease (CSVD) remains unclear. We thus aimed to understand the detailed relationship between hypercholesterolemia and CSVD using the well described Ldlr\(^{-/-}\) mouse model. Methods We used Ldlr\(^{-/-}\) mice (n = 16) and wild-type (WT) mice (n = 15) at the age of 6 and 12 months. Ldlr\(^{-/-}\) mice develop high plasma cholesterol levels following a high fat diet. We analyzed cerebral capillaries and arterioles for intravascular erythrocyte accumulations, thrombotic vessel occlusions, blood-brain barrier (BBB) dysfunction and microbleeds. Results We found a significant increase in the number of erythrocyte stases in 6 months old Ldlr\(^{-/-}\) mice compared to all other groups (P < 0.05). Ldlr\(^{-/-}\) animals aged 12 months showed the highest number of thrombotic occlusions while in WT animals hardly any occlusions could be observed (P < 0.001). Compared to WT mice, Ldlr\(^{-/-}\) mice did not display significant gray matter BBB breakdown. Microhemorrhages were observed in one Ldlr\(^{-/-}\) mouse that was 6 months old. Results did not differ when considering subcortical and cortical regions. Conclusions In Ldlr\(^{-/-}\) mice, hypercholesterolemia is related to a thrombotic CSVD phenotype, which is different from hypertension-related CSVD that associates with a hemorrhagic CSVD phenotype. Our data demonstrate a relationship between hypercholesterolemia and the development of CSVD. Ldlr\(^{-/-}\) mice appear to be an adequate animal model for research into CSVD.},
  language  = {en}
}
@article{HaarmannSchuhmannSilwedeletal.2019,
  author    = {Haarmann, Axel and Schuhmann, Michael K. and Silwedel, Christine and Monoranu, Camelia-Maria and Stoll, Guido and Buttmann, Mathias},
  title     = {Human brain endothelial CXCR2 is inflammation-inducible and mediates CXCL5- and CXCL8-triggered paraendothelial barrier breakdown},
  series = {International Journal of Molecular Science},
  volume    = {20},
  journal   = {International Journal of Molecular Science},
  number    = {3},
  issn      = {1422-0067},
  doi       = {10.3390/ijms20030602},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201297},
  year      = {2019},
  abstract  = {Chemokines (C-X-C) motif ligand (CXCL) 5 and 8 are overexpressed in patients with multiple sclerosis, where CXCL5 serum levels were shown to correlate with blood-brain barrier dysfunction as evidenced by gadolinium-enhanced magnetic resonance imaging. Here, we studied the potential role of CXCL5/CXCL8 receptor 2 (CXCR2) as a regulator of paraendothelial brain barrier function, using the well-characterized human cerebral microvascular endothelial cell line hCMEC/D3. Low basal CXCR2 mRNA and protein expression levels in hCMEC/D3 were found to strongly increase under inflammatory conditions. Correspondingly, immunohistochemistry of brain biopsies from two patients with active multiple sclerosis revealed upregulation of endothelial CXCR2 compared to healthy control tissue. Recombinant CXCL5 or CXCL8 rapidly and transiently activated Akt/protein kinase B in hCMEC/D3. This was followed by a redistribution of tight junction-associated protein zonula occludens-1 (ZO-1) and by the formation of actin stress fibers. Functionally, these morphological changes corresponded to a decrease of paracellular barrier function, as measured by a real-time electrical impedance-sensing system. Importantly, preincubation with the selective CXCR2 antagonist SB332235 partially prevented chemokine-induced disturbance of both tight junction morphology and function. We conclude that human brain endothelial CXCR2 may contribute to blood-brain barrier disturbance under inflammatory conditions with increased CXCL5 and CXCL8 expression, where CXCR2 may also represent a novel pharmacological target for blood-brain barrier stabilization.},
  language  = {en}
}
@article{EssigBabilonVollmuthetal.2021,
  author    = {Essig, Fabian and Babilon, Lilith and Vollmuth, Christoph and Kollikowski, Alexander M. and Pham, Mirko and Solymosi, L{\´a}szl{\´o} and Haeusler, Karl Georg and Kraft, Peter and Stoll, Guido and Schuhmann, Michael K.},
  title     = {High mobility group box 1 protein in cerebral thromboemboli},
  series = {International Journal of Molecular Sciences},
  volume    = {22},
  journal   = {International Journal of Molecular Sciences},
  number    = {20},
  issn      = {1422-0067},
  doi       = {10.3390/ijms222011276},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265568},
  year      = {2021},
  abstract  = {High-mobility group box 1 protein (HMGB1) is a damage-associated molecular pattern (DAMP) involved in neutrophil extracellular trap (NET) formation and thrombosis. NETs are regularly found in cerebral thromboemboli. We here analyzed associated HMGB1 expression in human thromboemboli retrieved via mechanical thrombectomy from 37 stroke patients with large vessel occlusion. HMGB1 was detected in all thromboemboli, accounting for 1.7\% (IQR 0.6-6.2\%) of the total thromboemboli area and was found to be colocalized with neutrophils and NETs and in spatial proximity to platelets. Correlation analysis revealed that the detection of HMGB1 was strongly related to the number of neutrophils (r = 0.58, p = 0.0002) and platelets (r = 0.51, p = 0.001). Our results demonstrate that HMGB1 is a substantial constituent of thromboemboli causing large vessel occlusion stroke.},
  language  = {en}
}
@article{SchuhmannBittnerMeuthetal.2015,
  author    = {Schuhmann, Michael K. and Bittner, Stefan and Meuth, Sven G. and Kleinschnitz, Christoph and Fluri, Felix},
  title     = {Fingolimod (FTY720-P) does not stabilize the blood-brain barrier under inflammatory conditions in an in vitro model},
  series = {International Journal of Molecular Sciences},
  volume    = {16},
  journal   = {International Journal of Molecular Sciences},
  doi       = {10.3390/ijms161226177},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-145047},
  pages     = {29454-29466},
  year      = {2015},
  abstract  = {Breakdown of the blood-brain barrier (BBB) is an early hallmark of multiple sclerosis (MS), a progressive inflammatory disease of the central nervous system. Cell adhesion in the BBB is modulated by sphingosine-1-phosphate (S1P), a signaling protein, via S1P receptors (S1P\(_1\)). Fingolimod phosphate (FTY720-P) a functional S1P\(_1\) antagonist has been shown to improve the relapse rate in relapsing-remitting MS by preventing the egress of lymphocytes from lymph nodes. However, its role in modulating BBB permeabilityin particular, on the tight junction proteins occludin, claudin 5 and ZO-1has not been well elucidated to date. In the present study, FTY720-P did not change the transendothelial electrical resistance in a rat brain microvascular endothelial cell (RBMEC) culture exposed to inflammatory conditions and thus did not decrease endothelial barrier permeability. In contrast, occludin was reduced in RBMEC culture after adding FTY720-P. Additionally, FTY720-P did not alter the amount of endothelial matrix metalloproteinase (MMP)-9 and MMP-2 in RBMEC cultures. Taken together, our observations support the assumption that S1P\(_1\) plays a dual role in vascular permeability, depending on its ligand. Thus, S1P\(_1\) provides a mechanistic basis for FTY720-P-associated disruption of endothelial barrierssuch as the blood-retinal barrierwhich might result in macular edema.},
  language  = {en}
}
@article{SchuhmannStollPappetal.2019,
  author    = {Schuhmann, Michael K. and Stoll, Guido and Papp, Lena and Bohr, Arne and Volkmann, Jens and Fluri, Felix},
  title     = {Electrical stimulation of the mesencephalic locomotor region has no impact on blood-brain barrier alterations after cerebral photothrombosis in rats},
  series = {International Journal of Molecular Science},
  volume    = {20},
  journal   = {International Journal of Molecular Science},
  number    = {16},
  issn      = {1422-0067},
  doi       = {10.3390/ijms20164036},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201284},
  year      = {2019},
  abstract  = {Blood-brain barrier (BBB) disruption is a critical event after ischemic stroke, which results in edema formation and hemorrhagic transformation of infarcted tissue. BBB dysfunction following stroke is partly mediated by proinflammatory agents. We recently have shown that high frequency stimulation of the mesencephalic locomotor region (MLR-HFS) exerts an antiapoptotic and anti-inflammatory effect in the border zone of cerebral photothrombotic stroke in rats. Whether MLR-HFS also has an impact on BBB dysfunction in the early stage of stroke is unknown. In this study, rats were subjected to photothrombotic stroke of the sensorimotor cortex and implantation of a stimulating microelectrode into the ipsilesional MLR. Thereafter, either HFS or sham stimulation of the MLR was applied for 24 h. After scarifying the rats, BBB disruption was assessed by determining albumin extravasation and tight junction integrity (claudin 3, claudin 5, and occludin) using Western blot analyses and immunohistochemistry. In addition, by applying zymography, expression of pro-metalloproteinase-9 (pro-MMP-9) was analyzed. No differences were found regarding infarct size and BBB dysfunction between stimulated and unstimulated animals 24 h after induction of stroke. Our results indicate that MLR-HFS neither improves nor worsens the damaged BBB after stroke. Attenuating cytokines/chemokines in the perilesional area, as mediated by MLR-HFS, tend to play a less significant role in preventing the BBB integrity.},
  language  = {en}
}
@article{SchuhmannStollBohretal.2019,
  author    = {Schuhmann, Michael K. and Stoll, Guido and Bohr, Arne and Volkmann, Jens and Fluri, Felix},
  title     = {Electrical stimulation of the mesencephalic locomotor region attenuates neuronal loss and cytokine expression in the perifocal region of photothrombotic stroke in rats},
  series = {International Journal of Molecular Science},
  volume    = {20},
  journal   = {International Journal of Molecular Science},
  number    = {9},
  issn      = {1422-0067},
  doi       = {10.3390/ijms20092341},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201355},
  year      = {2019},
  abstract  = {Deep brain stimulation of the mesencephalic locomotor region (MLR) improves the motor symptoms in Parkinson's disease and experimental stroke by intervening in the motor cerebral network. Whether high-frequency stimulation (HFS) of the MLR is involved in non-motor processes, such as neuroprotection and inflammation in the area surrounding the photothrombotic lesion, has not been elucidated. This study evaluates whether MLR-HFS exerts an anti-apoptotic and anti-inflammatory effect on the border zone of cerebral photothrombotic stroke. Rats underwent photothrombotic stroke of the right sensorimotor cortex and the implantation of a microelectrode into the ipsilesional MLR. After intervention, either HFS or sham stimulation of the MLR was applied for 24 h. The infarct volumes were calculated from consecutive brain sections. Neuronal apoptosis was analyzed by TUNEL staining. Flow cytometry and immunohistochemistry determined the perilesional inflammatory response. Neuronal apoptosis was significantly reduced in the ischemic penumbra after MLR-HFS, whereas the infarct volumes did not differ between the groups. MLR-HFS significantly reduced the release of cytokines and chemokines within the ischemic penumbra. MLR-HFS is neuroprotective and it reduces pro-inflammatory mediators in the area that surrounds the photothrombotic stroke without changing the number of immune cells, which indicates that MLR-HFS enables the function of inflammatory cells to be altered on a molecular level.},
  language  = {en}
}
@article{SchuhmannFluri2017,
  author    = {Schuhmann, Michael K. and Fluri, Felix},
  title     = {Effects of fullerenols on mouse brain microvascular endothelial cells},
  series = {International Journal of Molecular Sciences},
  volume    = {18},
  journal   = {International Journal of Molecular Sciences},
  number    = {8},
  issn      = {1422-0067},
  doi       = {10.3390/ijms18081783},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-158072},
  year      = {2017},
  abstract  = {Fullerenols, water-soluble C60-fullerene derivatives, have been shown to exert neuroprotective effects in vitro and in vivo, most likely due to their capability to scavenge free radicals. However, little is known about the effects of fullerenols on the blood-brain barrier (BBB), especially on cerebral endothelial cells under inflammatory conditions. Here, we investigated whether the treatment of primary mouse brain microvascular endothelial cells with fullerenols impacts basal and inflammatory blood-brain barrier (BBB) properties in vitro. While fullerenols (1, 10, and 100 µg/mL) did not change transendothelial electrical resistance under basal and inflammatory conditions, 100 µg/mL of fullerenol significantly reduced erk1/2 activation and resulted in an activation of NFκB in an inflammatory milieu. Our findings suggest that fullerenols might counteract oxidative stress via the erk1/2 and NFκB pathways, and thus are able to protect microvascular endothelial cells under inflammatory conditions.},
  language  = {en}
}
@article{BellutBieberKraftetal.2023,
  author    = {Bellut, Maximilian and Bieber, Michael and Kraft, Peter and Weber, Alexander N. R. and Stoll, Guido and Schuhmann, Michael K.},
  title     = {Delayed NLRP3 inflammasome inhibition ameliorates subacute stroke progression in mice},
  series = {Journal of Neuroinflammation},
  volume    = {20},
  journal   = {Journal of Neuroinflammation},
  number    = {1},
  doi       = {10.1186/s12974-022-02674-w},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-300599},
  year      = {2023},
  abstract  = {Background Ischemic stroke immediately evokes a strong neuro-inflammatory response within the vascular compartment, which contributes to primary infarct development under vessel occlusion as well as further infarct growth despite recanalization, referred to as ischemia/reperfusion injury. Later, in the subacute phase of stroke (beyond day 1 after recanalization), further inflammatory processes within the brain parenchyma follow. Whether this second wave of parenchymal inflammation contributes to an additional/secondary increase in infarct volumes and bears the potential to be pharmacologically targeted remains elusive. We addressed the role of the NLR-family pyrin domain-containing protein 3 (NLRP3) inflammasome in the subacute phase of ischemic stroke. Methods Focal cerebral ischemia was induced in C57Bl/6 mice by a 30-min transient middle cerebral artery occlusion (tMCAO). Animals were treated with the NLRP3 inhibitor MCC950 therapeutically 24 h after or prophylactically before tMCAO. Stroke outcome, including infarct size and functional deficits as well as the local inflammatory response, was assessed on day 7 after tMCAO. Results Infarct sizes on day 7 after tMCAO decreased about 35\% after delayed and about 60\% after prophylactic NLRP3 inhibition compared to vehicle. Functionally, pharmacological inhibition of NLRP3 mitigated the local inflammatory response in the ischemic brain as indicated by reduction of infiltrating immune cells and reactive astrogliosis. Conclusions Our results demonstrate that the NLRP3 inflammasome continues to drive neuroinflammation within the subacute stroke phase. NLRP3 inflammasome inhibition leads to a better long-term outcome—even when administered with a delay of 1 day after stroke induction, indicating ongoing inflammation-driven infarct progression. These findings may pave the way for eagerly awaited delayed treatment options in ischemic stroke.},
  language  = {en}
}
@article{KraemerSchuhmannVolkmannetal.2022,
  author    = {Kr{\"a}mer, Stefanie D. and Schuhmann, Michael K. and Volkmann, Jens and Fluri, Felix},
  title     = {Deep brain stimulation in the subthalamic nucleus can improve skilled Forelimb movements and retune dynamics of striatal networks in a rat stroke model},
  series = {International Journal of Molecular Sciences},
  volume    = {23},
  journal   = {International Journal of Molecular Sciences},
  number    = {24},
  doi       = {10.3390/ijms232415862},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312828},
  year      = {2022},
  abstract  = {Recovery of upper limb (UL) impairment after stroke is limited in stroke survivors. Since stroke can be considered as a network disorder, neuromodulation may be an approach to improve UL motor dysfunction. Here, we evaluated the effect of high-frequency stimulation (HFS) of the subthalamic nucleus (STN) in rats on forelimb grasping using the single-pellet reaching (SPR) test after stroke and determined costimulated brain regions during STN-HFS using 2-[\(^{18}\)F]Fluoro-2-deoxyglucose-([\(^{18}\)F]FDG)-positron emission tomography (PET). After a 4-week training of SPR, photothrombotic stroke was induced in the sensorimotor cortex of the dominant hemisphere. Thereafter, an electrode was implanted in the STN ipsilateral to the infarction, followed by a continuous STN-HFS or sham stimulation for 7 days. On postinterventional day 2 and 7, an SPR test was performed during STN-HFS. Success rate of grasping was compared between these two time points. [\(^{18}\)F]FDG-PET was conducted on day 2 and 3 after stroke, without and with STN-HFS, respectively. STN-HFS resulted in a significant improvement of SPR compared to sham stimulation. During STN-HFS, a significantly higher [\(^{18}\)F]FDG-uptake was observed in the corticosubthalamic/pallidosubthalamic circuit, particularly ipsilateral to the stimulated side. Additionally, STN-HFS led to an increased glucose metabolism within the brainstem. These data demonstrate that STN-HFS supports rehabilitation of skilled forelimb movements, probably by retuning dysfunctional motor centers within the cerebral network.},
  language  = {en}
}
@article{KraftDrechslerSchuhmannetal.2015,
  author    = {Kraft, Peter and Drechsler, Christiane and Schuhmann, Michael K. and Gunreben, Ignaz and Kleinschnitz, Christoph},
  title     = {Characterization of Peripheral Immune Cell Subsets in Patients with Acute and Chronic Cerebrovascular Disease: A Case-Control Study},
  series = {International Journal of Molecular Science},
  volume    = {16},
  journal   = {International Journal of Molecular Science},
  number    = {10},
  doi       = {10.3390/ijms161025433},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-126319},
  pages     = {25433-25449},
  year      = {2015},
  abstract  = {Immune cells (IC) play a crucial role in murine stroke pathophysiology. However, data are limited on the role of these cells in ischemic stroke in humans. We therefore aimed to characterize and compare peripheral IC subsets in patients with acute ischemic stroke/transient ischemic attack (AIS/TIA), chronic cerebrovascular disease (CCD) and healthy volunteers (HV). We conducted a case-control study of patients with AIS/TIA (n = 116) or CCD (n = 117), and HV (n = 104) who were enrolled at the University Hospital W{\"u}rzburg from 2010 to 2013. We determined the expression and quantity of IC subsets in the three study groups and performed correlation analyses with demographic and clinical parameters. The quantity of several IC subsets differed between the AIS/TIA, CCD, and HV groups. Several clinical and demographic variables independently predicted the quantity of IC subsets in patients with AIS/TIA. No significant changes in the quantity of IC subsets occurred within the first three days after AIS/TIA. Overall, these findings strengthen the evidence for a pathophysiologic role of IC in human ischemic stroke and the potential use of IC-based biomarkers for the prediction of stroke risk. A comprehensive description of IC kinetics is crucial to enable the design of targeted treatment strategies.},
  language  = {en}
}
@article{KraftSchuhmann2022,
  author    = {Kraft, Peter and Schuhmann, Michael K.},
  title     = {Cellular and molecular targets in acute ischemic stroke},
  series = {International Journal of Molecular Sciences},
  volume    = {23},
  journal   = {International Journal of Molecular Sciences},
  number    = {19},
  issn      = {1422-0067},
  doi       = {10.3390/ijms231911097},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-288294},
  year      = {2022},
  abstract  = {No abstract available},
  language  = {en}
}
@article{AlbertWeissenbergerMenclSchuhmannetal.2014,
  author    = {Albert-Weissenberger, Christiane and Mencl, Stine and Schuhmann, Michael K. and Salur, Irmak and G{\"o}b, Eva and Langhauser, Friederike and Hopp, Sarah and Hennig, Nelli and Meuth, Sven G. and Nolte, Marc W. and Sir{\´e}n, Anna-Leena and Kleinschnitz, Christoph},
  title     = {C1-Inhibitor protects from focal brain trauma in a cortical cryolesion mice model by reducing thrombo-inflammation},
  series = {Frontiers in Cellular Neuroscience},
  volume    = {8},
  journal   = {Frontiers in Cellular Neuroscience},
  issn      = {1662-5102},
  doi       = {10.3389/fncel.2014.00269},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-119263},
  pages     = {269},
  year      = {2014},
  abstract  = {Traumatic brain injury (TBI) induces a strong inflammatory response which includes blood-brain barrier damage, edema formation and infiltration of different immune cell subsets. More recently, microvascular thrombosis has been identified as another pathophysiological feature of TBI. The contact-kinin system represents an interface between inflammatory and thrombotic circuits and is activated in different neurological diseases. C1-Inhibitor counteracts activation of the contact-kinin system at multiple levels. We investigated the therapeutic potential of C1-Inhibitor in a model of TBI. Male and female C57BL/6 mice were subjected to cortical cryolesion and treated with C1-Inhibitor after 1 h. Lesion volumes were assessed between day 1 and day 5 and blood-brain barrier damage, thrombus formation as well as the local inflammatory response were determined post TBI. Treatment of male mice with 15.0 IU C1-Inhibitor, but not 7.5 IU, 1 h after cryolesion reduced lesion volumes by ~75\% on day 1. This protective effect was preserved in female mice and at later stages of trauma. Mechanistically, C1-Inhibitor stabilized the blood-brain barrier and decreased the invasion of immune cells into the brain parenchyma. Moreover, C1-Inhibitor had strong antithrombotic effects. C1-Inhibitor represents a multifaceted anti-inflammatory and antithrombotic compound that prevents traumatic neurodegeneration in clinically meaningful settings.},
  language  = {en}
}
@article{GoebelPankratzAsaridouetal.2016,
  author    = {G{\"o}bel, Kerstin and Pankratz, Susann and Asaridou, Chloi-Magdalini and Herrmann, Alexander M. and Bittner, Stefan and Merker, Monika and Ruck, Tobias and Glumm, Sarah and Langhauser, Friederike and Kraft, Peter and Krug, Thorsten F. and Breuer, Johanna and Herold, Martin and Gross, Catharina C. and Beckmann, Denise and Korb-Pap, Adelheid and Schuhmann, Michael K. and Kuerten, Stefanie and Mitroulis, Ioannis and Ruppert, Clemens and Nolte, Marc W. and Panousis, Con and Klotz, Luisa and Kehrel, Beate and Korn, Thomas and Langer, Harald F. and Pap, Thomas and Nieswandt, Bernhard and Wiendl, Heinz and Chavakis, Triantafyllos and Kleinschnitz, Christoph and Meuth, Sven G.},
  title     = {Blood coagulation factor XII drives adaptive immunity during neuroinflammation via CD87-mediated modulation of dendritic cells},
  series = {Nature Communications},
  volume    = {7},
  journal   = {Nature Communications},
  number    = {11626},
  doi       = {10.1038/ncomms11626},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-165503},
  year      = {2016},
  abstract  = {Aberrant immune responses represent the underlying cause of central nervous system (CNS) autoimmunity, including multiple sclerosis (MS). Recent evidence implicated the crosstalk between coagulation and immunity in CNS autoimmunity. Here we identify coagulation factor XII (FXII), the initiator of the intrinsic coagulation cascade and the kallikrein-kinin system, as a specific immune cell modulator. High levels of FXII activity are present in the plasma of MS patients during relapse. Deficiency or pharmacologic blockade of FXII renders mice less susceptible to experimental autoimmune encephalomyelitis (a model of MS) and is accompanied by reduced numbers of interleukin-17A-producing T cells. Immune activation by FXII is mediated by dendritic cells in a CD87-dependent manner and involves alterations in intracellular cyclic AMP formation. Our study demonstrates that a member of the plasmatic coagulation cascade is a key mediator of autoimmunity. FXII inhibition may provide a strategy to combat MS and other immune-related disorders.},
  language  = {en}
}
@article{SchuhmannGuthmannStolletal.2017,
  author    = {Schuhmann, Michael K. and Guthmann, Josua and Stoll, Guido and Nieswandt, Bernhard and Kraft, Peter and Kleinschnitz, Christoph},
  title     = {Blocking of platelet glycoprotein receptor Ib reduces "thrombo-inflammation" in mice with acute ischemic stroke},
  series = {Journal of Neuroinflammation},
  volume    = {14},
  journal   = {Journal of Neuroinflammation},
  number    = {18},
  doi       = {10.1186/s12974-017-0792-y},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-157582},
  year      = {2017},
  abstract  = {Background: Ischemic stroke causes a strong inflammatory response that includes T cells, monocytes/macrophages, and neutrophils. Interaction of these immune cells with platelets and endothelial cells facilitates microvascular dysfunction and leads to secondary infarct growth. We recently showed that blocking of platelet glycoprotein (GP) receptor Ib improves stroke outcome without increasing the risk of intracerebral hemorrhage. Until now, it has been unclear whether GPIb only mediates thrombus formation or also contributes to the pathophysiology of local inflammation. Methods: Focal cerebral ischemia was induced in C57BL/6 mice by a 60-min transient middle cerebral artery occlusion (tMCAO). Animals were treated with antigen-binding fragments (Fab) against the platelet surface molecules GPIb (p0p/B Fab). Rat immunoglobulin G (IgG) Fab was used as control treatment. Stroke outcome, including infarct size and functional deficits as well as the local inflammatory response, was assessed on day 1 after tMCAO. Results: Blocking of GPIb reduced stroke size and improved functional outcome on day 1 after tMCAO without increasing the risk of intracerebral hemorrhage. As expected, disruption of GPIb-mediated pathways in platelets significantly reduced thrombus burden in the cerebral microvasculature. In addition, inhibition of GPIb limited the local inflammatory response in the ischemic brain as indicated by lower numbers of infiltrating T cells and macrophages and lower expression levels of inflammatory cytokines compared with rat IgG Fab-treated controls. Conclusion: In acute ischemic stroke, thrombus formation and inflammation are closely intertwined ("thrombo-inflammation"). Blocking of platelet GPIb can ameliorate thrombo-inflammation.},
  language  = {en}
}
@article{BieberSchuhmannBellutetal.2022,
  author    = {Bieber, Michael and Schuhmann, Michael K. and Bellut, Maximilian and Stegner, David and Heinze, Katrin G. and Pham, Mirko and Nieswandt, Bernhard and Stoll, Guido},
  title     = {Blockade of platelet glycoprotein Ibα augments neuroprotection in Orai2-deficient mice during middle cerebral artery occlusion},
  series = {International Journal of Molecular Sciences},
  volume    = {23},
  journal   = {International Journal of Molecular Sciences},
  number    = {16},
  issn      = {1422-0067},
  doi       = {10.3390/ijms23169496},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-286038},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{SchuhmannLanghauserKraftetal.2017,
  author    = {Schuhmann, Michael K. and Langhauser, Friederike and Kraft, Peter and Kleinschnitz, Christoph},
  title     = {B cells do not have a major pathophysiologic role in acute ischemic stroke in mice},
  series = {Journal of Neuroinflammation},
  volume    = {14},
  journal   = {Journal of Neuroinflammation},
  number    = {112},
  doi       = {10.1186/s12974-017-0890-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-158155},
  year      = {2017},
  abstract  = {Background Lymphocytes have been shown to play an important role in the pathophysiology of acute ischemic stroke, but the properties of B cells remain controversial. The aim of this study was to unravel the role of B cells during acute cerebral ischemia using pharmacologic B cell depletion, B cell transgenic mice, and adoptive B cell transfer experiments. Methods Transient middle cerebral artery occlusion (60 min) was induced in wild-type mice treated with an anti-CD20 antibody 24 h before stroke onset, JHD\(^{-/-}\) mice and Rag1\(^{-/-}\) mice 24 h after adoptive B cell transfer. Stroke outcome was assessed at days 1 and 3. Infarct volumes were calculated from 2,3,5-triphenyltetrazolium chloride (TTC)-stained brain sections, and neurological scores were evaluated. The local inflammatory response was determined by real-time PCR and immunohistochemistry. Apoptosis was analyzed by TUNEL staining, and astrocyte activation was revealed using immunohistochemistry and Western blot. Results Pharmacologic depletion of B cells did not influence infarct volumes and functional outcome at day 1 after stroke. Additionally, lack of circulating B cells in JHD\(^{-/-}\) mice also failed to influence stroke outcome at days 1 and 3. Furthermore, reconstitution of Rag1\(^{-/-}\) mice with B cells had no influence on infarct volumes. Conclusion Targeting B cells in experimental stroke did not influence lesion volume and functional outcome during the acute phase. Our findings argue against a major pathophysiologic role of B cells during acute ischemic stroke.},
  language  = {en}
}