TY - JOUR A1 - Haarmann, Axel A1 - Zimmermann, Lena A1 - Bieber, Michael A1 - Silwedel, Christine A1 - Stoll, Guido A1 - Schuhmann, Michael K. T1 - Regulation and release of vasoactive endoglin by brain endothelium in response to hypoxia/reoxygenation in stroke JF - International Journal of Molecular Sciences N2 - 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. KW - endoglin KW - soluble endoglin KW - CD105 KW - human brain endothelium KW - HBMEC KW - hypoxia KW - reoxygenation KW - ischemia/reperfusion injury KW - vascular homeostasis KW - middle cerebral artery occlusion KW - stroke Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284361 SN - 1422-0067 VL - 23 IS - 13 ER - TY - JOUR A1 - Franke, Maximilian A1 - Bieber, Michael A1 - Stoll, Guido A1 - Schuhmann, Michael Klaus T1 - Validity and Efficacy of Methods to Define Blood Brain Barrier Integrity in Experimental Ischemic Strokes: A Comparison of Albumin Western Blot, IgG Western Blot and Albumin Immunofluorescence JF - Methods and Protocols N2 - 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. KW - IgG KW - albumin KW - immunohistochemistry KW - Western blot KW - stroke KW - tMCAO KW - blood brain barrier KW - neuroinflammation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234214 SN - 2409-9279 VL - 4 IS - 1 ER - TY - JOUR A1 - Bellut, Maximilian A1 - Papp, Lena A1 - Bieber, Michael A1 - Kraft, Peter A1 - Stoll, Guido A1 - Schuhmann, Michael K. T1 - NLPR3 inflammasome inhibition alleviates hypoxic endothelial cell death in-vitro and protects blood-brain barrier integrity in murine stroke JF - Cell Death & Disease N2 - 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. KW - inflammasome KW - preclinical research KW - stroke Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265693 VL - 13 ER -