Stimulating ERK/PI3K/NFκB signaling pathways upon activation of mGluR2/3 restores OGD-induced impairment in glutamate clearance in astrocytes

• Published in: The European journal of neuroscience Vol. 39; no. 1; pp. 83 - 96
• Main Authors: Lin, Chia-Ho, You, Jie-Ru, Wei, Kai-Che, Gean, Po-Wu
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.01.2014; Blackwell
• Subjects: 1-Phosphatidylinositol 3-kinase; Animals; astrocyte GLAST; Astrocytes - drug effects; Astrocytes - metabolism; Biological and medical sciences; Cell Hypoxia; Cells, Cultured; Excitatory Amino Acid Agonists - pharmacology; Excitatory Amino Acid Antagonists - pharmacology; Excitatory Amino Acid Transporter 1 - metabolism; extracellular signal-regulated kinase; Fundamental and applied biological sciences. Psychology; Glucose - deficiency; Glutamic Acid - metabolism; MAP Kinase Signaling System; mGluR2/3 agonists; NF-kappa B - metabolism; nuclear transcription factor-κΒ; oxygen and glucose deprivation; phosphatidylinositol 3-kinase; Phosphatidylinositol 3-Kinases - metabolism; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate - agonists; Receptors, Metabotropic Glutamate - antagonists & inhibitors; Receptors, Metabotropic Glutamate - metabolism; Vertebrates: nervous system and sense organs; Agonist; extracellular signal-regulated kinase; Extracellular signal-regulated protein kinase; Enzyme; Neuroglia; Transferases; GLAST glutamate/aspartate transporter; nuclear transcription factor-κB; Astrocyte; Clearance; Glucose; Glutamate; mGluR2/3 agonists; astrocyte GLAST; Phosphatidylinositol; Signal transduction; Kinase; Excitatory aminoacid; Neurotransmitter; Transcription factor NFκB; oxygen and glucose deprivation; phosphatidylinositol 3-kinase; nuclear transcription factor-κΒ
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/ejn.12383

We used the oxygen and glucose deprivation (OGD) method in cultured astrocytes as an in vitro ischemic model. We investigated whether activation of group‐II metabotropic glutamate receptors (mGluR2/3) can reverse OGD‐induced impairment in astrocytic glutamate/aspartate transporter (GLAST) expression and elucidated the signaling pathways involving the GLAST expression. Cultured astrocytes exposed to OGD for 6 h resulted in significant reductions in the GLAST expression and extracellular glutamate clearance. These reductions were effectively restored by mGluR2/3 activation with mGluR2/3 agonists, LY379268 or DCG‐IV, after the 6 h OGD insult. These mGluR2/3‐mediated restorative effects were inhibited by selective mGluR2/3 antagonists LY341459 or EGLU. The mGluR2/3 activation also induced activations of signaling pathways including extracellular signal‐regulated kinase (ERK), phosphatidylinositol 3‐kinase (PI3K) and nuclear transcription factor‐κB (NFκB). These activations were prevented by blocking mGluR2/3 with LY341459, an mGluR2/3 antagonist. Furthermore, blocking ERK, PI3K and NFκB signaling pathways with U0126, LY294002 and pyrrolidine dithiocarbamate, respectively, significantly inhibited the mGluR2/3‐mediated restorative effects. These results suggest that application of mGluR2/3 agonists after OGD insult can effectively reverse the OGD‐reduced expression of GLAST proteins and restore clearance of extracellular glutamate by serially activating ERK/PI3K/NFκB signaling pathways in cultured astrocytes. OGD reduces expression of GLAST proteins and glutamate clearance in cultured astrocytes. Activation of mGluR2/3 after OGD insult effectively reverses impaired glutamate clearance and expression of GLAST proteins. ERK/PI3K/NFκB signaling pathways are critical required for mGluR2/3‐mediated restoration of glutamate clearance in cultured astrocytes.