title: Rapid sodium signaling couples glutamate uptake to breakdown of ATP in perivascular astrocyte endfeet.
abstract: Perivascular endfeet of astrocytes are highly polarized compartments that ensheath blood vessels and contribute to the blood-brain barrier. They experience calcium transients with neuronal activity, a phenomenon involved in neurovascular coupling. Endfeet also mediate the uptake of glucose from the blood, a process stimulated in active brain regions. Here, we demonstrate in mouse hippocampal tissue slices that endfeet undergo sodium signaling upon stimulation of glutamatergic synaptic activity. Glutamate-induced endfeet sodium transients were diminished by TFB-TBOA, suggesting that they were generated by sodium-dependent glutamate uptake. With local agonist application, they could be restricted to endfeet and immunohistochemical analysis revealed prominent expression of glutamate transporters GLAST and GLT-1 localized towards the neuropil vs. the vascular side of endfeet. Endfeet sodium signals spread at an apparent maximum velocity of ∼120 µm/s and directly propagated from stimulated into neighboring endfeet; this spread was omitted in Cx30/Cx43 double-deficient mice. Sodium transients resulted in elevation of intracellular magnesium, indicating a decrease in intracellular ATP. In summary, our results establish that excitatory synaptic activity and stimulation of glutamate uptake in astrocytes trigger transient sodium increases in perivascular endfeet which rapidly spread through gap junctions into neighboring endfeet and cause a reduction of intracellular ATP. The newly discovered endfeet sodium signaling thereby represents a fast, long-lived and inter-cellularly acting indicator of synaptic activity at the blood-brain barrier, which likely constitutes an important component of neuro-metabolic coupling in the brain. GLIA 2017;65:293-308.
authors: Faculty of Mathematics and Natural Sciences, Institute of Neurobiology, Heinrich Heine University Duesseldorf, Universitätsstrasse 1, Duesseldorf, D-40225, Germany.
authors: Julia
authors: J
authors: Langer
authors: Faculty of Mathematics and Natural Sciences, Institute of Neurobiology, Heinrich Heine University Duesseldorf, Universitätsstrasse 1, Duesseldorf, D-40225, Germany.
authors: Niklas J
authors: NJ
authors: Gerkau
authors: Institute of Anatomy II and Dr. Senckenbergisches Chronomedizinisches Institut, Goethe-University of Frankfurt, Theodor-Stern-Kai 7, Frankfurt/M, D-60590, Germany.
authors: Amin
authors: A
authors: Derouiche
authors: Faculty of Mathematics and Natural Sciences, Institute of Neurobiology, Heinrich Heine University Duesseldorf, Universitätsstrasse 1, Duesseldorf, D-40225, Germany.
authors: Christian
authors: C
authors: Kleinhans
authors: Faculty of Mathematics and Natural Sciences, Institute of Neurobiology, Heinrich Heine University Duesseldorf, Universitätsstrasse 1, Duesseldorf, D-40225, Germany.
authors: Behrouz
authors: B
authors: Moshrefi-Ravasdjani
authors: Institute of Anatomy II and Dr. Senckenbergisches Chronomedizinisches Institut, Goethe-University of Frankfurt, Theodor-Stern-Kai 7, Frankfurt/M, D-60590, Germany.
authors: Michaela
authors: M
authors: Fredrich
authors: Faculty of Mathematics and Natural Sciences, Institute of Neurobiology, Heinrich Heine University Duesseldorf, Universitätsstrasse 1, Duesseldorf, D-40225, Germany.
authors: Karl W
authors: KW
authors: Kafitz
authors: Medical Faculty, Institute of Cellular Neurosciences, University of Bonn, Bonn, D-53105, Germany.
authors: Gerald
authors: G
authors: Seifert
authors: Medical Faculty, Institute of Cellular Neurosciences, University of Bonn, Bonn, D-53105, Germany.
authors: Christian
authors: C
authors: Steinhäuser
authors: Faculty of Mathematics and Natural Sciences, Institute of Neurobiology, Heinrich Heine University Duesseldorf, Universitätsstrasse 1, Duesseldorf, D-40225, Germany.
authors: Christine R
authors: CR
authors: Rose
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D027322:Amino Acid Transport System X-AG / Q000037:antagonists & inhibitors; D000818:Animals; D000831:Animals, Newborn; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001253:Astrocytes / Q000166:cytology* / Q000187:drug effects; D000075302:Connexin 30 / Q000172:deficiency / Q000235:genetics; D018031:Connexin 43 / Q000172:deficiency / Q000235:genetics; D026603:D-Aspartic Acid / Q000494:pharmacology; D005260:Female; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: C508240:(2S,3S)-3-(3-(4-(trifluoromethyl)benzoylamino)benzyloxy)aspartate; D027322:Amino Acid Transport System X-AG; D000075302:Connexin 30; D018031:Connexin 43; C100629:Gjb6 protein, mouse; D026941:Sodium Channel Blockers; D001224:Aspartic Acid; D018698:Glutamic Acid; D013779:Tetrodotoxin; D026603:D-Aspartic Acid; D000255:Adenosine Triphosphate; D012964:Sodium
keywords: GLAST; GLT-1; SBFI; hippocampus; neuro-metabolic coupling