@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{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{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{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{SchuhmannLanghauserZimmermannetal.2023,
  author    = {Schuhmann, Michael K. and Langhauser, Friederike and Zimmermann, Lena and Bellut, Maximilian and Kleinschnitz, Christoph and Fluri, Felix},
  title     = {Dimethyl fumarate attenuates lymphocyte infiltration and reduces infarct size in experimental stroke},
  series = {International journal of molecular sciences},
  volume    = {24},
  journal   = {International journal of molecular sciences},
  number    = {21},
  doi       = {10.3390/ijms242115540},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-357731},
  year      = {2023},
  abstract  = {Ischemic stroke is associated with exacerbated tissue damage caused by the activation of immune cells and the initiation of other inflammatory processes. Dimethyl fumarate (DMF) is known to modulate the immune response, activate antioxidative pathways, and improve the blood-brain barrier (BBB) after stroke. However, the specific impact of DMF on immune cells after cerebral ischemia remains unclear. In our study, male mice underwent transient middle cerebral artery occlusion (tMCAO) for 30 min and received oral DMF (15 mg/kg) or a vehicle immediately after tMCAO, followed by twice-daily administrations for 7 days. Infarct volume was assessed on T2-weighted magnetic resonance images on days 1 and 7 after tMCAO. Brain-infiltrating immune cells (lymphocytes, monocytes) and microglia were quantified using fluorescence-activated cell sorting. DMF treatment significantly reduced infarct volumes and brain edema. On day 1 after tMCAO, DMF-treated mice showed reduced lymphocyte infiltration compared to controls, which was not observed on day 7. Monocyte and microglial cell counts did not differ between groups on either day. In the acute phase of stroke, DMF administration attenuated lymphocyte infiltration, probably due to its stabilizing effect on the BBB. This highlights the potential of DMF as a therapeutic candidate for mitigating immune cell-driven damage in 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}
}
@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{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{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}
}