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Inhibition of Mg2+ Extrusion Attenuates Glutamate Excitotoxicity in Cultured Rat Hippocampal Neurons.

ABSTRACT: Magnesium plays important roles in the nervous system. An increase in the Mg2+ concentration in cerebrospinal fluid enhances neural functions, while Mg2+ deficiency is implicated in neuronal diseases in the central nervous system. We have previously demonstrated that high concentrations of glutamate induce excitotoxicity and elicit a transient increase in the intracellular concentration of Mg2+ due to the release of Mg2+ from mitochondria, followed by a decrease to below steady-state levels. Since Mg2+ deficiency is involved in neuronal diseases, this decrease presumably affects neuronal survival under excitotoxic conditions. However, the mechanism of the Mg2+ decrease and its effect on the excitotoxicity process have not been elucidated. In this study, we demonstrated that inhibitors of Mg2+ extrusion, quinidine and amiloride, attenuated glutamate excitotoxicity in cultured rat hippocampal neurons. A toxic concentration of glutamate induced both Mg2+ release from mitochondria and Mg2+ extrusion from cytosol, and both quinidine and amiloride suppressed only the extrusion. This resulted in the maintenance of a higher Mg2+ concentration in the cytosol than under steady-state conditions during the ten-minute exposure to glutamate. These inhibitors also attenuated the glutamate-induced depression of cellular energy metabolism. Our data indicate the importance of Mg2+ regulation in neuronal survival under excitotoxicity.

SUBMITTER: Shindo Y

PROVIDER: S-EPMC7551965 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Inhibition of Mg2+ Extrusion Attenuates Glutamate Excitotoxicity in Cultured Rat Hippocampal Neurons.

Shindo Yutaka Y Yamanaka Ryu R Hotta Kohji K Oka Kotaro K

Nutrients 20200910 9

Magnesium plays important roles in the nervous system. An increase in the Mg2+ concentration in cerebrospinal fluid enhances neural functions, while Mg2+ deficiency is implicated in neuronal diseases in the central nervous system. We have previously demonstrated that high concentrations of glutamate induce excitotoxicity and elicit a transient increase in the intracellular concentration of Mg2+ due to the release of Mg2+ from mitochondria, followed by ...[more]

PMID: 32927908

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Project description:Glutamate-induced excitotoxicity plays a critical role in the neurological impairment caused by middle cerebral artery occlusion. Achyranthes bidentata polypeptides have been shown to protect against neurological functional damage caused by middle cerebral artery occlusion, but the underlying neuroprotective mechanisms and the relationship to glutamate-induced excitotoxicity remain unclear. Therefore, in the current study, we investigated the protective effects of Achyranthes bidentata polypeptides against glutamate-induced excitotoxicity in cultured hippocampal neurons. Hippocampal neurons were treated with Mg2+-free extracellular solution containing glutamate (300 µM) for 3 hours as a model of glutamate-mediated excitotoxicity (glutamate group). In the normal group, hippocampal neurons were incubated in Mg2+-free extracellular solution. In the Achyranthes bidentata polypeptide group, hippocampal neurons were incubated in Mg2+-free extracellular solution containing glutamate (300 µM) and Achyranthes bidentata polypeptide at different concentrations. At 24 hours after exposure to the agents, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Hoechst 33258 staining were used to assess neuronal viability and nuclear morphology, respectively. Caspase-3 expression and activity were evaluated using western blot assay and colorimetric enzymatic assay, respectively. At various time points after glutamate treatment, reactive oxygen species in cells were detected by H2DCF-DA, and mitochondrial membrane potential was detected by rhodamine 123 staining. To examine the effect of Achyranthes bidentata polypeptides on glutamate receptors, electrophysiological recording was used to measure the glutamate-induced inward current in cultured hippocampal neurons. Achyranthes bidentata polypeptide decreased the percentage of apoptotic cells and reduced the changes in caspase-3 expression and activity induced by glutamate. In addition, Achyranthes bidentata polypeptide attenuated the amplitude of the glutamate-induced current. Furthermore, the glutamate-induced increase in intracellular reactive oxygen species and reduction in mitochondrial membrane potential were attenuated by Achyranthes bidentata polypeptide treatment. These findings collectively suggest that Achyranthes bidentata polypeptides exert a neuroprotective effect in cultured hippocampal neurons by suppressing the overactivation of glutamate receptors and inhibiting the caspase-3-dependent mitochondrial apoptotic pathway. All animal studies were approved by the Animal Care and Use Committee, Nantong University, China (approval No. 20120216-001) on February 16, 2012.

Dataset Information

Inhibition of Mg2+ Extrusion Attenuates Glutamate Excitotoxicity in Cultured Rat Hippocampal Neurons.

Publications

Inhibition of Mg<sup>2+</sup> Extrusion Attenuates Glutamate Excitotoxicity in Cultured Rat Hippocampal Neurons.

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