Aβ_25-35 induces presynaptic changes in organotypic hippocampal slice cultures

Memory loss in Alzheimer's disease (AD) may be related to synaptic defects in damaged hippocampal neurons. We investigated the relationship between amyloid peptide Aβ_25-35-induced neuronal death pattern and presynaptic changes in organotypic hippocampal slice cultures. In propidium iodide (PI) uptake and annexin V labeling, Aβ_25-35-induced neuronal damage dramatically increased in a concentration dependent manner, indicating both types of cell death. In ultrastructural analysis, apoptotic features in CA1 and CA3 area and synaptic disruption in stratum lucidum were detected in Aβ_25-35-treated slices. Immunofluorescence and Western blot analysis for caspase-3 showed Aβ_25-35 concentration dependently induced caspase-3 activation. Immunofluorescence and Western blot analysis to determine changes in presynaptic marker proteins demonstrated that expression of synaptosomal-associated protein-25 (SNAP-25) and synaptophysin were reduced by Aβ_25-35 in CA1, CA3 and DG area at concentrations >2.5 μM. In conclusion, Aβ_25-35-induced apoptotic cell death and caspase-3 activation at relatively low concentration, and induced synaptic disruption and loss of synaptic marker protein at concentrations >2.5 μM in organotypic hippocampal slice cultures. These suggest that Aβ_25-35-induced apoptosis via triggering caspase-3 activation and lead to synaptic dysfunction in organotypic hippocampal slice cultures.