Abstract Details

Title Excessive glutamate transport causes rapid astrocytic mitochondrial loss and dysfunction following focal ischemic stroke

Topic Cerebrovascular Disease and Interventional Neurology

Presentation(s) S22 - Stroke Genetics, Cellular Responses, and Animal Models (4:36 PM-4:47 PM)

Poster/Presentation
Number 007

Background Astrocytes provide bioenergetic support to neurons, mediate neurovascular coupling, buffer extracellular ions, and limit excitotoxicity. They undergo many rapid changes following ischemic brain injury, which may shape the extent of damage. The role of astrocytic mitochondria in astroglial functioning and response to brain injury remain underexplored.

Objective Investigate changes to astrocytic mitochondria following focal ischemic stroke in vivo using a mouse model of middle cerebral artery (MCA) occlusion.

Design/Methods Male and female wildtype C57BL/6J neonatal mice underwent intraventricular injections of AAV2/5 viral vectors containing mitochondrial targeted enhanced green fluorescent protein under the control of the astrocyte-specific glial fibrillary acidic protein promoter. Mice were allowed to age to 10-20 weeks. Proximal right MCA occlusion was provoked via photothrombosis using Rose Bengal dye and a targeted 532 nm laser beam. Mice were perfused at 1, 3 or 24 hours post-stroke onset. Brains were processed and sectioned for mitochondrial analysis (n = 3 animals per time point, 21 cells per group). A subset of mice were treated with local intraparenchymal injection of the glutamate transport inhibitor (2S,3S)-3-[3-[4-(trifluoromethyl)-benzoylamino]benzyloxy]-aspartate (TFB-TBOA) 1 hour prior to stroke ictus. Quantitative analyses were performed using ImageJ and Imaris.

Results Peri-infarct astrocytic mitochondria are markedly reduced in density, demonstrate decreased network complexity and adopt punctate spherical morphology compared to the contralateral non-stroke hemisphere and sham animals. Preliminary data indicate 50% change on each measure. These changes are present within 1 hour of stroke onset. Pre-treatment with TFB-TBOA attenuated these changes.

Conclusions Astrocytic mitochondria within the peri-infarct region undergo rapid loss and morphologic changes suggestive of dysfunction following proximal MCA occlusion. These changes are likely mediated by excessive glutamate transport into astrocytes given attenuation of effects with TFB-TBOA administration. These findings suggest toxic effects of elevated extracellular glutamate to astrocytes, similar to excitotoxicity of neurons, which may exacerbate secondary stroke injury.

Authors/Disclosures
Evelyn K. Shih, MD, PhD (Neurelis, Inc.) PRESENTER	Dr. Shih has received personal compensation for serving as an employee of Neurelis, Inc..
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file

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