A novel bifunctional peptide predicted to target neuropeptide Y4 and GLP-1 receptors alleviates cognitive deficits in 5 × FAD mice by modulating cGAS-STING-mediated neuroinflammation

Effective disease-modifying therapies for Alzheimer's disease (AD) remain limited. Glucagon-like peptide-1 receptor (GLP-1R) activation has shown neuroprotective potential in AD, whereas the neuropeptide Y/pancreatic polypeptide-Y4 receptor (NPY/PP-Y4R) axis has been implicated in central homeostasis and inflammatory regulation, although its role in AD remains insufficiently defined. Here, we evaluated a rationally designed bifunctional peptide predicted to target both NPY4R and GLP-1R in 5 × FAD mice and LPS-stimulated BV2 cells. In vivo, NPY4/GLP-1 improved spatial learning and memory, working memory, and exploratory behavior, and was accompanied by reduced hippocampal Aβ burden (P < 0.05), alleviated neuronal injury (P < 0.01), improved synaptic integrity (P < 0.01), and attenuated mitochondrial abnormalities (P < 0.01). These changes were associated with lower hippocampal levels of cytosolic mitochondrial DNA (mtDNA) (P < 0.05), cGAS (P < 0.05), STING (P < 0.05), and phosphorylated IRF3 (P < 0.01), together with decreased IL-1β (P < 0.05) and increased IL-10 (P < 0.05) expression. In LPS-stimulated BV2 cells, NPY4/GLP-1 similarly reduced STING-related signaling (P < 0.05) and inflammatory responses (P < 0.05). Co-treatment with the STING inhibitor C-176 provided additional support for the involvement of STING-associated inflammatory signaling under in vitro inflammatory conditions. Molecular docking suggested that NPY4/GLP-1 may interact with both NPY4R and GLP-1R, providing a structural rationale for its bifunctional design. Collectively, these findings indicate that NPY4/GLP-1 exerts beneficial effects in AD-related models and that these effects are associated with attenuation of mtDNA-cGAS-STING-related neuroinflammatory signaling. This study provides initial evidence supporting further evaluation of this novel bifunctional peptide as a candidate therapeutic strategy for AD.