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  - Haarmann, Axel
A1  - Vollmuth, Christoph
A1  - Kollikowski, Alexander M.
A1  - Heuschmann, Peter U.
A1  - Pham, Mirko
A1  - Stoll, Guido
A1  - Neugebauer, Hermann
A1  - Schuhmann, Michael K.
T1  - Vasoactive soluble endoglin: a novel biomarker indicative of reperfusion after cerebral large-vessel occlusion
JF  - Cells
N2  - 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.
KW  - endoglin
KW  - brain endothelium
KW  - stroke
KW  - shedding
KW  - mechanical thrombectomy
KW  - hypoxia
KW  - reperfusion injury
KW  - biomarker
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-304995
SN  - 2073-4409
VL  - 12
IS  - 2
ER  -