Extrasynaptic glutamate release through cystine/glutamate antiporter contributes to ischemic damage
Federico N. Soria, … , Carlos Matute, María Domercq
Federico N. Soria, … , Carlos Matute, María Domercq
Published July 18, 2014
Citation Information: J Clin Invest. 2014;124(8):3645-3655. https://doi.org/10.1172/JCI71886.
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Research Article

Extrasynaptic glutamate release through cystine/glutamate antiporter contributes to ischemic damage

Abstract

During brain ischemia, an excessive release of glutamate triggers neuronal death through the overactivation of NMDA receptors (NMDARs); however, the underlying pathways that alter glutamate homeostasis and whether synaptic or extrasynaptic sites are responsible for excess glutamate remain controversial. Here, we monitored ischemia-gated currents in pyramidal cortical neurons in brain slices from rodents in response to oxygen and glucose deprivation (OGD) as a real-time glutamate sensor to identify the source of glutamate release and determined the extent of neuronal damage. Blockade of excitatory amino acid transporters or vesicular glutamate release did not inhibit ischemia-gated currents or neuronal damage after OGD. In contrast, pharmacological inhibition of the cystine/glutamate antiporter dramatically attenuated ischemia-gated currents and cell death after OGD. Compared with control animals, mice lacking a functional cystine/glutamate antiporter exhibited reduced anoxic depolarization and neuronal death in response to OGD. Furthermore, glutamate released by the cystine/glutamate antiporter activated extrasynaptic, but not synaptic, NMDARs, and blockade of extrasynaptic NMDARs reduced ischemia-gated currents and cell damage after OGD. Finally, PET imaging showed increased cystine/glutamate antiporter function in ischemic rats. Altogether, these data suggest that cystine/glutamate antiporter function is increased in ischemia, contributing to elevated extracellular glutamate concentration, overactivation of extrasynaptic NMDARs, and ischemic neuronal death.

Authors

Federico N. Soria, Alberto Pérez-Samartín, Abraham Martin, Kiran Babu Gona, Jordi Llop, Boguslaw Szczupak, Juan Carlos Chara, Carlos Matute, María Domercq

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Figure 2

Inhibition of vesicular glutamate release does not change anoxic current or cell death in OGD.

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Inhibition of vesicular glutamate release does not change anoxic current...
(A) OGD-activated currents (recorded at 30 mV) in the absence or presence of vesicular fusion inhibitor Baf A1 (μM). (B) Histograms show the average amplitude (pA ± SEM) and latency (minutes ± SEM) of the OGD-induced current for each condition. Baf did not change the amplitude or latency of the OGD-activated current (n = 7). (C) Cell death measured by LDH release in cultures subjected to 45 minutes of OGD and 24 hours of reperfusion in the presence or absence of the exocytosis inhibitors Baf (1 μM) and TeNT (1 μg/ml). Data are expressed as the mean ± SEM (n = 3–5). *P < 0.001 versus OGD. (D) Representative fields showing propidium iodide labeling of organotypic slices treated as in C. Scale bar: 1 mm.