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.
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