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Deletion of astroglial connexins weakens the blood-brain barrier.

ABSTRACT: Astrocytes, the most prominent glial cell type in the brain, send specialized processes named endfeet, which enwrap blood vessels and express a large molecular repertoire dedicated to the physiology of the vascular system. One of the most striking properties of astrocyte endfeet is their enrichment in gap junction protein connexins 43 and 30 (Cx43 and Cx30) allowing for direct intercellular trafficking of ions and small signaling molecules through perivascular astroglial networks. The contribution of astroglial connexins to the physiology of the brain vascular system has never been addressed. Here, we show that Cx43 and Cx30 expression at the level of perivascular endfeet starts from postnatal days 2 and 12 and is fully mature at postnatal days 15 and 20, respectively, indicating that astroglial perivascular connectivity occurs and develops during postnatal blood-brain barrier (BBB) maturation. We demonstrate that mice lacking Cx30 and Cx43 in GFAP (glial fibrillary acidic protein)-positive cells display astrocyte endfeet edema and a partial loss of the astroglial water channel aquaporin-4 and β-dystroglycan, a transmembrane receptor anchoring astrocyte endfeet to the perivascular basal lamina. Furthermore, the absence of astroglial connexins weakens the BBB, which opens upon increased hydrostatic vascular pressure and shear stress. These results demonstrate that astroglial connexins are necessary to maintain BBB integrity.

SUBMITTER: Ezan P

PROVIDER: S-EPMC3421093 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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Deletion of astroglial connexins weakens the blood-brain barrier.

Ezan Pascal P André Pascal P Cisternino Salvatore S Saubaméa Bruno B Boulay Anne-Cécile AC Doutremer Suzette S Thomas Marie-Annick MA Quenech'du Nicole N Giaume Christian C Cohen-Salmon Martine M

Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism 20120404 8

Astrocytes, the most prominent glial cell type in the brain, send specialized processes named endfeet, which enwrap blood vessels and express a large molecular repertoire dedicated to the physiology of the vascular system. One of the most striking properties of astrocyte endfeet is their enrichment in gap junction protein connexins 43 and 30 (Cx43 and Cx30) allowing for direct intercellular trafficking of ions and small signaling molecules through perivascular astroglial networks. The contributi ...[more]

PMID: 22472609

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Project description:AimsIschemic stroke is a life-threatening disease with limited therapeutic strategies. Blood-brain barrier (BBB) disruption is a critical pathological process that contributes to poor outcomes in ischemic stroke. We previously showed that the microglial inhibition of the inflammasome sensor absent in melanoma 2 (AIM2) suppressed the inflammatory response and protected against ischemic stroke. However, whether AIM2 is involved in BBB disruption during cerebral ischemia is unknown.MethodsMiddle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation/reoxygenation (OGD/R) were used to mimic cerebral ischemia in mice and brain microvascular endothelial cells (HBMECs), respectively. The infarct volume, neurological deficits, and BBB permeability were measured in mice after MCAO. Transendothelial electrical resistance (TEER) and neutrophil adhesion to the HBMEC monolayer were assessed after OGD/R treatment. Western blot and immunofluorescence analyses were conducted to evaluate the expression of related proteins.ResultsAIM2 was shown to be expressed in brain endothelial cells and upregulated after ischemic stroke in the mouse brain. AIM2 deletion reduced the infarct volume, improved neurological and motor functions, and decreased BBB disruption. In vitro, OGD/R significantly increased the protein levels of AIM2 and ICAM-1 and decreased those of the tight junction (TJ) proteins ZO-1 and occludin. AIM2 knockdown effectively protected BBB integrity by promoting the expression of TJ proteins and decreasing ICAM-1 expression and neutrophil adhesion. Mechanistically, AIM2 knockdown reversed the OGD/R-induced increases in ICAM-1 expression and STAT3 phosphorylation in brain endothelial cells. Furthermore, treatment with the p-STAT3 inhibitor AG490 mitigated the effect of AIM2 on BBB breakdown.ConclusionOur findings indicated that inhibiting AIM2 preserved the BBB integrity after ischemic stroke, at least partially by modulating STAT3 activation and that AIM2 may be a promising therapeutic target for cerebral ischemic stroke.

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Deletion of astroglial connexins weakens the blood-brain barrier.

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Deletion of astroglial connexins weakens the blood-brain barrier.

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