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 Y(1) (Y(1)R) and Y(2) (Y(2)R) 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 Y(1)R or Y(2)R 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 Y(1)R or Y(2)R, 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.