GLIAL INFLAMMASOME ACTIVATION AND BLOOD-BRAIN BARRIER BREAKDOWN IN AGE-RELATED NEURODEGENERATION

Errede M¹, Girolamo F¹, d’Amati A^1,2, de Giorgis M¹, Lorusso L¹, Pierucci C³, Bernardini N³, Pellegrini C³, Virgintino D¹ and Annese T² | ¹University of Bari, Department of Translational Biomedicine and Neuroscience – Human Anatomy and Histology Unit, Bari, Italy; ²Libera Università del Mediterraneo (LUM) Giuseppe Degennaro University, Department of Medicine and Surgery, Bari, Italy; ³University of Pisa, Department of Clinical and Experimental Medicine - Unit of Histology and Medical Embryology, Pisa, Italy

Blood-brain barrier (BBB) breakdown, characterized by the disruption of endothelial tight junctions (TJs), is an early pathogenic event in aging-related neurodegenerative diseases, where neuroinflammation plays a key role. Activation of the NLRP3 inflammasome in glial cells represents a major inflammatory hub contributing to this process. However, its precise role in BBB dysfunction and its potential as a therapeutic target remain to be fully elucidated. In the present study, senescence-accelerated SAMP8 mice and SAMR1 controls were used as models of BBB impairment. Confocal immunofluorescence analysis of brain sections was performed to assess the tight junction proteins occludin and claudin- 5, as well as the inflammasome components NLRP3 and ASC in GFAP+ astrocytes and IBA1+ microglia. The effects of two immunomodulatory treatments–the selective NLRP3 inhibitor MCC950 and interferon-gamma (IFN-γ) – were subsequently evaluated. SAMP8 mice exhibited downregulation and a discontinuous staining pattern of occludin and claudin-5, paralleled by inflammasome activation, including upregulation of NLRP3 and ASC in both reactive astrocytes and microglia. Both MCC950 and IFN-γ treatments partially restored BBB integrity, improving TJ staining pattern and protein expression in both microvessels and larger vessels. Structural recovery of TJs correlated with a significant reduction in NLRP3 expression and ASC speck formation in glial cells. These findings demonstrate that glial inflammasome activation is a key driver of BBB structural failure in this aging model. The partial restoration of TJ architecture following inflammasome inhibition with MCC950 or immunomodulation with IFN-γ confirms the link between neuroinflammation and vascular pathology. Overall, this study identifies the NLRP3 inflammasome pathway as a critical therapeutic target to preserve BBB integrity in age-related neurodegeneration.