Delayed calcium dysregulation in neurons requires both the NMDA receptor and the reverse Na+/Ca2+ exchanger

NEUROBIOLOGY OF DISEASE

卷:46

Article

Brittain, Matthew K.¹  Brustovetsky, Tatiana¹  Sheets, Patrick L.²  Brittain, Joel M.²  Khanna, Rajesh^1,2  Cummins, Theodore R.^1,2  Brustovetsky, Nickolay^1,2 

[1] Indiana Univ Sch Med, Dept Pharmacol & Toxicol, Indianapolis, IN 46202 USA

[2] Indiana Univ Sch Med, Stark Neurosci Res Inst, Indianapolis, IN 46202 USA

关键词: Calcium dysregulation;    NMDA receptor;    Na+/Ca2+ exchanger;    Glutamate;    Neuron;    Excitotoxicity;   

DOI  :  10.1016/j.nbd.2011.12.051

来源: Elsevier

【 摘 要 】

Glutamate-induced delayed calcium dysregulation (DCD) is a causal factor leading to neuronal death. The mechanism of DCD is not clear but Ca2+ influx via N-methyl-D-aspartate receptors (NMDAR) and/or the reverse plasmalemmal Na+/Ca2+ exchanger (NCXrev) could be involved in DCD. However, the extent to which NMDAR and NCXrev contribute to glutamate-induced DCD is uncertain. Here, we show that both NMDAR and NCXrev are critical for DCD in neurons exposed to excitotoxic glutamate. In rat cultured hippocampal neurons, 25 mu M glutamate produced DCD accompanied by sustained increase in cytosolic Na+ ([Na+](c)) and plasma membrane depolarization. MK801 and memantine, noncompetitive NMDAR inhibitors, added shortly after glutamate, completely prevented DCD whereas AP-5, a competitive NMDAR inhibitor, failed to protect against DCD. None of the tested inhibitors lowered elevated [Na+](c), or restored plasma membrane potential. In the experiments with NCX reversal by gramicidin, MK801 and memantine robustly inhibited NCXrev while AP-5 was much less efficacious. In electrophysiological patch-clamp experiments MK801 and memantine inhibited NCXrev-mediated ion currents whereas AP-5 failed. Thus. MK801 and memantine, in addition to NMDAR, inhibited NCXrev. Inhibition of NCXrev either with KB-R7943, or by collapsing Na+ gradient across the plasma membrane, or by inhibiting Na+/H+ exchanger with 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and thus preventing the increase in [Na+](c) failed to preclude DCD. However, NCXrev inhibition combined with NMDAR blockade by AP-5 completely prevented DCD. Overall, our data suggest that both NMDAR and NCXrev are essential for DCD in glutamate-exposed neurons and inhibition of individual mechanism is not sufficient to prevent calcium dysregulation. (C) 2012 Elsevier Inc. All rights reserved.

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