Intranasal Application of Peptides Modulating the Neuropeptide Y System

The neuropeptide Y multireceptor–multiligand system plays an important role in multiple physiological processes. Targeting the neuropeptide Y₁ (Y₁R) and Y₂ (Y₂R) receptors has gained interest in treating weight and mental disorders. Nose-to-brain delivery is an effective tool to overcome the challenges of peptide delivery to cerebral structures. In this study, fluorescently labeled peptides that selectively activate either Y₁R or Y₂R were studied. The permeability of these compounds was evaluated on Calu-3 cells, a model system of the nasal mucosa. Particular attention was paid to the stability of peptides, and translocation of the intact compounds was demonstrated by combining a permeability assay with a receptor activation assay. Two compounds, selectively targeting either Y₁R or Y₂R, were selected, and their uptake after intranasal application was analyzed in vivo. Two different imaging systems were compared: whole slide scanning and confocal microscopy. Both methods allow detecting specific signals from the fluorescently labeled peptides. While whole slide scanning provides a comprehensive anatomical overview, confocal microscopy offers an improved signal-to-noise ratio. Finally, peptide-specific signals were quantified over time, displaying rapid peptide uptake within the first 15 min and sustained signals for up to 24 h. Overall, cell-based and in vivo assays were combined to select peptides with high pharmacological potential for nasal applications.