Refine
Has Fulltext
- yes (34)
Is part of the Bibliography
- yes (34)
Year of publication
Document Type
- Journal article (34)
Language
- English (34)
Keywords
- ischemic stroke (11)
- neuroinflammation (5)
- stroke (5)
- middle cerebral artery occlusion (4)
- deep brain stimulation (3)
- immunohistochemistry (3)
- inflammasome (3)
- mesencephalic locomotor region (3)
- neutrophils (3)
- photothrombotic stroke (3)
- platelets (3)
- thrombo-inflammation (3)
- GFAP (2)
- NLRP3 (2)
- acute ischemic stroke (2)
- blood brain barrier (2)
- blood–brain barrier (2)
- cognitive impairment (2)
- endoglin (2)
- glial fibrillary acidic protein (2)
- glycoprotein receptor Ib (2)
- hypoxia (2)
- ischemic penumbra (2)
- mechanical thrombectomy (2)
- neurofilament light chain (2)
- ASC (1)
- Alzheimer’s dementia (1)
- Arterial water (1)
- Biomarker (1)
- Brain (1)
- Brain atrophy (1)
- CD105 (1)
- CXCL4 (1)
- CXCL5 (1)
- CXCL7 (1)
- CXCL8 (1)
- CXCR2 (1)
- Cell Index (1)
- Chronic heart failure (1)
- Coefficient (1)
- Cognitive decline (1)
- Experimental stroke (1)
- FXIIa inhibitor rHA-Infestin (1)
- Gehirn (1)
- Glial fibrillary acidic protein (1)
- HBMEC (1)
- HMGB1 (1)
- IgG (1)
- Inflammation (1)
- MCC950 (1)
- MRI (1)
- Magnetic-resonance (1)
- Memory dysfunction (1)
- Mice (1)
- NAP-2 (1)
- NETs (1)
- NfL (1)
- Orai2 (1)
- PF4 (1)
- Perfusion (1)
- SB332235 (1)
- STEMI (1)
- Schlaganfall (1)
- T-cells (1)
- Thrombus (1)
- Vasodilatator-stimuliertes Phosphoprotein (1)
- Vasodilator-Stimulated Phosphoprotein (1)
- Von-Willebrand-factor (1)
- Western blot (1)
- age (1)
- albumin (1)
- alpha-7 nicotinic acetylcholine receptor (1)
- biomarker (1)
- biomarkers (1)
- blood (1)
- blood flow (1)
- blood-brain barrier (1)
- brain endothelium (1)
- cardiac magnetic resonance imaging (1)
- cerebral ischemia (1)
- cerebrovascular diseases (1)
- cerebrovascular disorders (1)
- chemokines (1)
- choline acetyltransferase (1)
- chronic heart failure (1)
- cluster analysis (1)
- coagulation factor XIIa (1)
- collagens (1)
- collateral circulation (1)
- contact activation system (1)
- contrast-enhanced MRI (1)
- demography (1)
- developmental signaling (1)
- emulsions (1)
- fluorine (1)
- gadofluorine (1)
- gadolinium-DTPA (1)
- glial damage (1)
- glycoprotein VI (1)
- glycoprotein receptor Ibα (1)
- heart failure (1)
- human brain endothelium (1)
- human cerebral endothelial cells (1)
- i.v. thrombolysis (1)
- in vivo imaging (1)
- infarction (1)
- infarction size (1)
- integrin α2 (1)
- integrins (1)
- intensity of attention (1)
- interleukin-8 (1)
- intracranial bleeding (1)
- iron oxide nanoparticles (1)
- ischemia/reperfusion injury (1)
- large vessel occlusion (1)
- leukocytes (1)
- macrophages (1)
- magnetic resonance imaging (1)
- mechanisms (1)
- multiple sclerosis (1)
- myocardial infarction (1)
- neurology (1)
- neuronal apoptosis (1)
- neuroprotection (1)
- occlusion (1)
- phosphorylated tau protein (1)
- platelet activation (1)
- platelet aggregation (1)
- preclinical research (1)
- prefrontal cortex (1)
- recombinant tissue-type plasminogen activator (1)
- renal function (1)
- reoxygenation (1)
- reperfusion injury (1)
- rt-PA (1)
- secondary infarct growth (1)
- serotonin (1)
- sex addiction (1)
- shedding (1)
- soluble endoglin (1)
- tMCAO (1)
- thrombemboli (1)
- thromboemboli (1)
- thrombosis (1)
- tight junctions (1)
- transient middle cerebral artery (1)
- transient middle cerebral artery occlusion (1)
- vascular homeostasis (1)
Institute
- Neurologische Klinik und Poliklinik (34)
- Institut für diagnostische und interventionelle Neuroradiologie (ehem. Abteilung für Neuroradiologie) (12)
- Rudolf-Virchow-Zentrum (9)
- Institut für Experimentelle Biomedizin (7)
- Medizinische Klinik und Poliklinik I (4)
- Deutsches Zentrum für Herzinsuffizienz (DZHI) (3)
- Klinik und Poliklinik für Psychiatrie, Psychosomatik und Psychotherapie (3)
- Institut für Klinische Epidemiologie und Biometrie (2)
- Kinderklinik und Poliklinik (2)
- Medizinische Klinik und Poliklinik II (2)
Sonstige beteiligte Institutionen
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.
The clinical and preclinical research of ischemic strokes (IS) is becoming increasingly comprehensive, especially with the emerging evidence of complex thrombotic and inflammatory interactions. Within these, the blood brain barrier (BBB) plays an important role in regulating the cellular interactions at the vascular interface and is therefore the object of many IS-related questions. Consequently, valid, economic and responsible methods to define BBB integrity are necessary. Therefore, we compared the three ex-vivo setups albumin Western blot (WB), IgG WB and albumin intensity measurement (AIM) with regard to validity as well as temporal and economic efficacy. While the informative value of the three methods correlated significantly, the efficacy of the IgG WB dominated.
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.
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.
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.
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.
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
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.
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.
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.