Neprilysin-sensitive synapse-associated amyloid-beta peptide oligomers impair neuronal plasticity and cognitive...

Area of Science:

• Neuroscience
• Biochemistry
• Pathology

Background:

• Alzheimer disease pathogenesis involves amyloid-beta peptide (Abeta) accumulation.
• The role of reduced Abeta catabolism, specifically neprilysin activity, in neuronal dysfunction remains unclear.
• Investigating the link between neprilysin deficiency and cognitive impairment is crucial for understanding Alzheimer disease.

Purpose of the Study:

• To investigate the causal relationship between reduced neprilysin activity and impaired synaptic and cognitive functions in vivo.
• To determine if decreased neprilysin function leads to the accumulation of specific amyloid-beta peptide (Abeta) forms.
• To examine the impact of neprilysin deficiency on hippocampal synaptic plasticity and learning/memory deficits.

Main Methods:

• Cross-breeding of amyloid precursor protein (APP) transgenic mice (APP23) with neprilysin-deficient mice.
• Biochemical and immunoelectron-microscopic analysis of Abeta accumulation in the brain.
• In vivo hippocampal synaptic plasticity recordings and a battery of behavioral tests for cognitive function.

Main Results:

• Reduced neprilysin activity significantly elevated oligomeric forms of amyloid-beta peptide (Abeta) at synapses.
• Impaired hippocampal synaptic plasticity was observed in mice with reduced neprilysin activity.
• Cognitive deficits in learning and memory tests were evident before the formation of amyloid plaques.

Conclusions:

• Reduced neprilysin activity, the primary Abeta-degrading enzyme, directly causes synaptic and cognitive impairments.
• These impairments are linked to elevated oligomeric Abeta at synapses, preceding amyloid plaque deposition.
• Strategies enhancing neprilysin activity may alleviate Alzheimer disease-associated memory symptoms by reducing Abeta oligomers.