Activation of mGluR5 attenuates NMDA-induced neurotoxicity through disruption of the NMDAR-PSD-95 complex and preservation of mitochondrial function in differentiated PC12 cells.

Shu-Hui Dai,Lei Zhang,Wei Rao,Na Qin,Peng Luo,Tao Chen,Yue-Fan Yang,Xiao-Fan Jiang,Zhou Fei

doi:10.3390/ijms150610892

Shu-Hui Dai, Lei Zhang + Show 7 more

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https://doi.org/10.3390/ijms150610892

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Abstract

Glutamate-mediated toxicity is implicated in various neuropathologic conditions, and activation of ionotropic and metabotropic glutamate receptors is considered to be the most important mechanism. It has been reported that pharmacological saturation of metabotropic glutamate receptors (mGluRs) can facilitate N-methyl-d-aspartate receptor (NMDAR) related signaling cascades, but the mechanism leading to mGluR-NMDAR interactions in excitotoxic neuronal injury has remained unidentified. In the present study, we investigated the role of mGluR5 in the regulation of N-methyl-d-aspartate (NMDA)-induced excitotoxicity in differentiated PC12 cells. We found that activation of mGluR5 with the specific agonist R,S-2-chloro-5-hydroxyphenylglycine (CHPG) increased cell viability and inhibited lactate dehydrogenase (LDH) release in a dose-dependent manner. CHPG also inhibited an increase in the Bax/Bcl-2 ratio, attenuated cleavage of caspase-9 and caspase-3, and reduced apoptotic cell death after NMDA treatment. The NMDA-induced mitochondrial dysfunction, as indicated by mitochondrial reactive oxygen species (ROS) generation, collapse of mitochondrial membrane potential (MMP), and cytochrome c release, was also partly prevented by CHPG treatment. Furthermore, CHPG blocked the NMDA-induced interaction of NMDAR with postsynaptic density protein-95 (PSD-95), but had no effects on intracellular calcium concentrations. All these results indicated that activation of mGluR5 protects differentiated PC12 cells from NMDA-induced neuronal excitotoxicity by disrupting NMDAR-PSD-95 interaction, which might be an ideal target for investigating therapeutic strategies in various neurological diseases where excitotoxicity may contribute to their pathology.

Highlights

Glutamate is the principal excitatory neurotransmitter in the central nervous system (CNS), modulating a series of physiological and pathophysiological processes [1]
To investigate the effects of NMDA on excitotoxicity-associated apoptosis, differentiated PC12 cells were incubated with various concentrations of NMDA from 1 to 200 μM for 24 h
To determine the biological functions of mGluR5 in NMDA-induced excitotoxicity, differentiated PC12 cells were pretreated with CHPG, an mGluR5 agonist, at different doses (1, 10, 50, 100 μM), 1 h before exposure to 100 μM NMDA for 24 h

Summary

Introduction

Glutamate is the principal excitatory neurotransmitter in the central nervous system (CNS), modulating a series of physiological and pathophysiological processes [1]. Glutamate and its receptors-mediated excitotoxicity is thought to play a role in many neurological diseases, such as brain trauma [2], stroke [3], Alzheimer’s disease [4], and Parkinson’s disease [5]. Multiple previous studies demonstrated an association between glutamate receptor function and scaffold proteins at the postsynaptic level. Postsynaptic density-95 (PSD-95), as a major protein constituent of these postsynaptic scaffold proteins, may play an important role by coupling glutamate receptors such as NMDAR and intracellular modulators [6,7,8,9]. The protein-protein interactions probably provide an important approach to facilitate glutamate receptor transmission and participate in the etiology of neurological diseases. It is reported that disturbing the NMDAR-PSD-95 interaction can reduce excitotoxic damage in experimental stroke models [10]

Results

Discussion

Conclusion