Microglia at the Crossroads of Neuroinflammation: Irisin and Chrysin-loaded extracellular vesicles as emerging CNS therapeutic strategies

Neuroinflammation contributes to the progression of neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Microglia, the resident immune cells of the central nervous system, serve as critical mediators of neuroinflammation and tissue homeostasis. These cells can polarize into distinct phenotypes: the pro-inflammatory M1 phenotype, characterized by amoeboid morphology and release of inflammatory mediators, and the anti-inflammatory M2 phenotype, which promotes tissue repair and neuroprotection. the pro-inflammatory M1 phenotype, characterized by amoeboid morphology and release of cytokines such as IL-1β, IL-6, and TNF-α, and the anti-inflammatory M2 phenotype, which promotes tissue repair and neuroprotection through markers including CD206 and Arginase-1. Extracellular vesicles (EVs) are nanoscale, membrane-bound particles released by all cell types that facilitate intercellular communication by transporting bioactive cargo including proteins, nucleic acids, and lipids. EVs emerging as key mediators capable of modulating inflammatory responses in both physiological and pathological CNS conditions. EVs are classified based on size into small EVs (30-100 nm), medium EVs (100-1000 nm), and large EVs (500 nm-5 μm), playing crucial roles in both physiological and pathological CNS conditions. The characterization and therapeutic application of EVs represent an innovative biotechnologies and regenerative medicine, offering precise drug delivery systems and novel medical devices for targeted interventions in neurodegenerative disorders. During my PhD the research activity has been focalized in the discover of two novel neuroprotective strategies targeting microglial neuroinflammation using BV2 microglial cell models. In the first period, I have investigated the irisin, an exercise-induced myokine, demonstrated anti-inflammatory effects by modulating the NLRP3 inflammasome pathway. At physiological concentrations (5 nM), irisin reversed LPS-induced amoeboid morphology, reduced cell migration, and decreased CD14 expression. Importantly, irisin downregulated NLRP3 inflammasome components while upregulating Arginase-1, a marker of M2 polarization. Then I evaluated the anti-inflammatory potential of chrysin-loaded extracellular vesicles (EVs-Chry). EVs-Chry significantly attenuated lipopolysaccharide (LPS)-induced microglial activation by reducing cell proliferation, restoring resting morphology, and decreasing migratory capacity. Co-treatment with EVs-Chry and LPS reduced pro-inflammatory cytokines (IL-1β, IL-6) and caspase-1 expression while enhancing anti-apoptotic Bcl-xL levels, indicating a shift toward neuroprotective phenotypes. These findings support the therapeutic potential of chrysin-loaded EVs and irisin as innovative neuroprotective strategies for preventing and treating neuroinflammatory and neurodegenerative disorders through targeted modulation of microglial activation states and inflammasome pathways. These results demonstrate that irisin and chrysin-loaded EVs effectively modulate microglial responses, contributing to the development of innovative biotechnological approaches for treating age-related diseases. This research highlights the potential for targeting the biological processes underlying aging and chronic degenerative disorders, while advancing strategies for healthy aging. The findings support the therapeutic promise of chrysin-loaded EVs and irisin as novel neuroprotective interventions that prevent and treat neuroinflammatory and neurodegenerative conditions through targeted modulation of microglial activation states and inflammasome pathways, directly addressing key priorities in aging research.