The selective BDNF overexpression in neurons protects neuroglial networks against OGD and glutamate-induced excitotoxicity

Objective: Cerebral ischemia is accompanied by damage and death of a significant number of neurons due to glutamate excitotoxicity with subsequent a global increase of cytosolic Ca2+ concentration ([Ca2+](i)). This study aimed to investigate the neuroprotective action of BDNF overexpression in hippocampal neurons against injury under ischemia-like conditions (oxygen and glucose deprivation) and glutamate-induced excitotoxicity (GluTox). Methods: The overexpression of BDNF was reached by the transduction of cell cultures with the adeno-associated (AAV)-Syn-BDNF-EGFP virus construct. Neuroprotective effects were mediated by Ca2+-dependent BDNF release followed by activation of the neuroprotective signaling cascades and changes of the gene expression. Thus, BDNF overexpression modulates Ca2+ homeostasis in cells, preventing Ca2+ overload and initiation of apoptotic and necrotic processes. Results:Antiapoptotic effect of BDNF overexpression is mediated via activation of phosphoinositide-3-kinase (PI3K) pathway and changing the expression of PI3K, HIF-1, Src and an anti-inflammatory cytokine IL-10. On the contrary, the decrease of expression of proapoptotic proteins such as Jun, Mapk8, caspase-3 and an inflammatory cytokine IL-1 beta was observed. These changes of expression were accompanied by the decrease of quantity of IL-1 beta receptors and the level of TNF alpha in cells in control, as well as 24 h after OGD. Besides, BDNF overexpression changes the expression of GABA(B) receptors. Also, the expression of NMDA and AMPA receptor subunits was altered towards a change in the conductivity of the receptors for Ca2+. Conclusion: Thus, our results demonstrate that neuronal BDNF overexpression reveals complex neuroprotective effects on the neurons and astrocytes under OGD and GluTox via inhibition of Ca2+ responses and regulation of gene expression.