Polyphenols in the Central Nervous System: Cellular Effects and Liposomal Delivery Approaches
Mateusz Kaluza, Dominika Książek-Winiarek, Piotr Szpakowski, Joanna Czpakowska, Julia Fijalkowska, Andrzej Głąbiński
Abstract
Neurodegenerative and neuroinflammatory diseases of the central nervous system are closely linked to aging and sustained oxidative and inflammatory stress. Polyphenols, plant-derived secondary metabolites, exhibit broad biological activities, including antioxidant and anti-inflammatory effects, the modulation of pathways such as PI3K/Akt, MAPK, Nrf2, and CREB, and the regulation of neurogenesis and microglial activation. This review focuses on the cell-specific actions of selected polyphenols in neurons, astrocytes, microglia, and oligodendrocytes within the context of Alzheimer's disease, Parkinson's disease, and multiple sclerosis. A major limitation to the therapeutic use of polyphenols is their poor bioavailability, due to instability, low solubility, and limited blood-brain barrier penetration. Liposomal nanocarriers are explored as promising delivery systems to overcome these barriers. Both conventional and functionalized liposomes (e.g., PEGylated, receptor-targeted) are discussed, alongside in vitro and in vivo studies demonstrating enhanced efficacy compared to free compounds. Intranasal delivery is also presented as a viable alternative to oral administration. Overall, polyphenols offer great potential as neuroprotective agents, and liposome-based delivery platforms have the potential to significantly enhance their clinical potential, provided that key formulation and targeting issues are addressed.