A low dose of the γ-secretase inhibitor DAPT improves learning and memory by regulating the NaV1.6/Notch axis in C57BL/6 male mice.
BACKGROUND AND PURPOSE: Cognitive impairment poses a major challenge in neurodegenerative diseases and inflammatory brain disorders due to limited treatment options. The voltage-gated sodium channel NaV1.6 is associated with synaptic plasticity and cognitive decline in APP/PS1 mice. DAPT, a γ-secretase inhibitor that blocks Notch signalling, has variable cognitive effects depending on dosage. This study investigates the dose-dependent effects of DAPT on cognition in C57BL/6 male mice, elucidating its mechanisms through NaV1.6 channels, Notch signalling, synaptic plasticity, and neurogenesis. EXPERIMENTAL APPROACH: Mice received unilateral stereotactic injections in the right hemisphere of low-dose DAPT (1 μg·μl-1), high-dose DAPT (2 μg·μl-1), or DMSO (control). Cognitive abilities were evaluated using the Morris Water Maze and Y-maze, western blots, immunofluorescence, and RT-qPCR analysed NaV1.6, synaptic proteins, NMDA/AMPA receptors, and neuroinflammatory markers. Neurogenesis was assessed via Nissl and doublecortin (DCX) staining. Primary neuron experiments examined DAPT effects on NaV1.6 interactions. KEY RESULTS: Low-dose DAPT significantly improved cognition, suppressed Notch pathway genes, reduced NaV1.6, and up-regulated synaptic proteins, NMDA/AMPA receptors, and neuronal markers in vivo/in vitro. In primary culture neurons, DAPT reduced Notch-1/NICD with TTX but not ATX-II. Inflammatory markers/cytokines were unchanged. In vitro, 5-μM DAPT decreased NaV 1.6, increased Notch receptors and reduced Notch-1/HES-1 mRNA. Low-dose DAPT enhanced neurogenesis (increased dentate gyrus DCX+ cells). Molecular docking confirmed favourable DAPT- NaV 1.6 interactions. CONCLUSION AND IMPLICATIONS: Low-dose DAPT improved cognitive function in C57BL/6 male mice, by modulating the NaV 1.6/Notch axis and enhancing neurogenesis, indicating its potential as a therapeutic strategy for Alzheimer's-related cognitive decline.