Estradiol preserves synapse-related proteins against oligomeric amyloid beta in the hippocampal cultured cells: possible involvement of proteinkinase M zeta

Introduction: Estradiol has been shown to facilitate synaptic long-term potentiation (LTP) mainly through translocation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor from intracellular pool to the post synaptic membrane. On the other hand, oligomeric amyloid beta (oAβ) decreases number of AMPA receptors in the synapses. It is well known that trafficking of AMPA receptors is governed by an atypical and autonomously active isoform of PKC called protein kinase M zeta (PKMζ). In spite of these evidence, the effect of estradiol on PKMζ expression is not yet studied. We aim to examine the possible protective effect of estradiol on PKMζ and AMPA receptor subunits against oAβ in hippocampal primary cell culture. Methods: Primary cell culture was prepared from postnatal (P0 to P3) rat pups. They were decapitated and the brains were removed. Hippocampi were isolated and collected in cold phosphate buffer saline. Then, they were trypsinized at 37°C for 15min. The cells were treated with 1μM OAβ or vehicle for 24h and then with 100nM estradiol for another 24h. Using the western blot analysis, the expression level of AMPAR subunit glutamate receptor 1 (GluA1), GluA2 and PKMζ were determined. Results: OAβ decreased the level of GluA1, GluA2 and PKMζ. Estradiol did not change the molecule levels in healthy cells; however, it preserved their expression levels in OAβ treated cells. Conclusion: These findings suggest that estradiol may restore expression level of synapse related molecules in an Alzheimer’ disease cell model, in part, through acting on PKMζ signaling pathway.