A beta 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 A beta 25-35-induced neuronal death pattern and presynaptic changes in organotypic hippocampal slice cultures. In propidium iodide (PI) uptake and annexin V labeling, A beta 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 A beta 25-35-treated slices. Immunofluorescence and Western blot analysis for caspase-3 showed A beta 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 A beta 25-35 in CA1, CA3 and DG area at concentrations >2.5 microM. In conclusion, A beta 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 microM in organotypic hippocampal slice cultures. These suggest that A beta 25-35-induced apoptosis via triggering caspase-3 activation and lead to synaptic dysfunction in organotypic hippocampal slice cultures.