Delayed calcium dysregulation in neurons requires both the NMDA receptor and the reverse Na⁺/Ca^2 + exchanger

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• 作者：Matthew K. Brittain^a ; Tatiana Brustovetsky^a ; Patrick L. Sheets^b ; ¹ ; Joel M. Brittain^b ; Rajesh Khanna^a ; ^b ; Theodore R. Cummins^a ; ^b ; Nickolay Brustovetsky^a ; ^b ; ^{nbrous@iupui.edu}
• 关键词：BAPTA ; 1 ; 2-bis(o-aminophenoxy) ethane-N ; N ; N&prime ; N&prime ; -tetraacetic acid ; DCD ; delayed calcium dysregulation ; NMDA ; N-methyl-d-aspartate ; NMDAR ; NMDA receptor ; NCX ; Na+/Ca2&#xA0 ; + exchanger ; NCXrev ; reverse NCX ; EIPA ; 5-(N-ethyl-N-isopropyl) amiloride
• 刊名：Neurobiology of Disease
• 出版年：2012
• 期刊代码：80_09699961
• 类别：neu
• 出版时间：April, 2012
• 卷：46
• 期：1
• 页码：109-117
• 文件大小：1233 K

摘要

Glutamate-induced delayed calcium dysregulation (DCD) is a causal factor leading to neuronal death. The mechanism of DCD is not clear but Ca^2 + influx via N-methyl-d-aspartate receptors (NMDAR) and/or the reverse plasmalemmal Na⁺/Ca^2 + exchanger (NCX_rev) could be involved in DCD. However, the extent to which NMDAR and NCX_rev contribute to glutamate-induced DCD is uncertain. Here, we show that both NMDAR and NCX_rev are critical for DCD in neurons exposed to excitotoxic glutamate. In rat cultured hippocampal neurons, 25 渭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 NCX_rev while AP-5 was much less efficacious. In electrophysiological patch-clamp experiments MK801 and memantine inhibited NCX_rev-mediated ion currents whereas AP-5 failed. Thus, MK801 and memantine, in addition to NMDAR, inhibited NCX_rev. Inhibition of NCX_rev 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, NCX_rev inhibition combined with NMDAR blockade by AP-5 completely prevented DCD. Overall, our data suggest that both NMDAR and NCX_rev are essential for DCD in glutamate-exposed neurons and inhibition of individual mechanism is not sufficient to prevent calcium dysregulation.