Inhibition of calpain prevents NMDA-induced cell death and β-amyloid-induced synaptic dysfunction in hippocampal slice cultures

Background and purpose: Alzheimer's disease (AD) is a multifactorial, neurodegenerative disease, which is in part caused by an impairment of synaptic function, probably mediated by oligomeric forms of amyloid-beta (A beta). While the A beta pathology mainly affects the physiology of neurotransmission, neuronal decline is caused by excitotoxic cell death, which is mediated by the NMDA receptor. A comprehensive therapeutic approach should address both A beta-induced synaptic deficits, as well as NMDA receptor-mediated neurodegeneration, via one molecular target. This study was designed to test whether calpain could be involved in both pathological pathways, which would offer a promising avenue for new treatments. Experimental approach: Application of the specific, water-soluble calpain inhibitor A-705253 was used to inhibit calpain in hippocampal slice cultures. We examined whether inhibition of calpain would prevent A beta-induced deficits in neurotransmission in CA1, as well as NMDA-induced neuronal cell death. Key results: A-705253 dose-dependently prevented excitotoxicity-induced neurodegeneration at low nanomolar concentrations, determined by propidium iodide histochemistry. Inhibition of the NMDA receptor similarly protected from neuronal damage. Caspase staining indicated that calpain inhibition was protective by reducing apoptosis. Electrophysiological analysis revealed that inhibition of calpain by A-705253 also fully prevented A beta oligomer-induced deficits in neurotransmission. The protective effect of calpain was compared to the clinically available NMDA receptor antagonist memantine, which was also effective in this model. Conclusions and implications: We suggest that inhibition of calpain exhibits a promising strategy to address several aspects of the pathology of AD that may go beyond the available therapeutic intervention by memantine.