Protective effects of EphB2 on Aβ1-42 oligomer-induced neurotoxicity and synaptic NMDA receptor signaling in hippocampal neurons

Alzheimer's disease (AD) is a neurodegenerative disorder characterized pathologically by the abnormal deposition of extracellular amyloid-beta (A beta) oligomers. However, the nature and precise mechanism of the toxicity of A beta oligomers are not clearly understood. A beta oligomers have been previously shown to cause a major loss of EphB2, a member of the EphB family of receptor tyrosine kinases. To determine the effect of EphB2 on A beta oligomer-induced neurotoxicity and the underlying molecular mechanisms, we examined the EphB2 gene in cultured hippocampal neurons. Using a cellular model of AD, A beta(1-42) oligomers were confirmed to induce neurotoxicity in a time-dependent manner and result in a major decrease of EphB2. EphB2 overexpression could prevent the neurotoxicity of hippocampal neurons from exposure to A beta(1-42) oligomers for 1 h. Further analysis revealed that EphB2 overexpression increased synaptic NR1 and NR2B expression in A beta(1-42) oligomer-treated neurons. Moreover, EphB2 overexpression prevented A beta(1-42) oligomer-induced downregulation of dephosphorylated p38 MAPK and phosphorylated CREB. Together, these results suggest that EphB2 is a factor which protects hippocampal neurons against the toxicity of A beta(1-42) oligomers, and we infer that the protection of EphB2 is achieved by increasing the synaptic NMDA receptor level and downstream p38 MAPK and CREB signaling in hippocampal neurons. This study provides new molecular insights into the neuroprotective effect of EphB2 and highlights its potential therapeutic role in the management of AD. (C) 2013 Elsevier Ltd. All rights reserved.