Activation of astrocytic NMDA receptors counteracted Aß-induced reduction of BDNF and elevation of GFAP and complement 3 in the hippocampal astrocytes.

ABSTRACT

N-methyl-D-aspartate receptors (NMDARs) play a crucial role in mediating Amyloid-ß (Aß) synaptotoxicity. Our previous studies have demonstrated an opposite (neuroprotection and neurotoxicity) effect of activating astrocytic and neuronal NMDARs with higher dose (10 µM) of NMDA, an agonist of NMDARs. By contrast, activating neuronal or astrocyitc NMDARs with lower dose (1 µM) of NMDA both exerts neuroprotective effect in Aß-induced neurotoxicity. However, the underlying mechanism of activating astrocytic NMDARs with lower dose of NMDA to protect against Aß neurotoxicity remains unclear. Based on our previous related work, in this study, using a co-cultured cell model of primary hippocampal neurons and astrocytes, we further investigated the possible factors involved in 1 µM of NMDA activating astrocytic NMDARs to oppose Aß-induced synaptotoxicity. Our results showed that activation of astrocytic NMDARs by 1 µM NMDA rescued Aß-induced reduction of brain-derived neurotrophic factor (BDNF), and inhibited Aß-induced increase of GFAP, complement 3 (C3) and activation of NF-κB. Furthermore, blockade of astrocytic GluN2A with TCN201 abrogated the ability of 1 µM NMDA to counteract the effects of Aß decreasing BDNF, and increasing GFAP, C3 and activation of NF-κB. These findings suggest that activation of astrocytic NMDARs protect against Aß-induced synaptotoxicity probably through elevating BDNF and suppressing GFAP and C3. Our present research provides valuable insights for elucidating the underlying mechanism of astrocytic NMDARs activation resisting the toxic effects of Aß.