Amyloid-β-driven glymphatic dysfunction in Alzheimer's disease model mice is driven by Ca2+-mediated increases in astrocytic cholesterol

Disruptions in the glymphatic system and its downstream meningeal lymphatic drainage pathway, crucial for brain waste clearance, are linked to the pathogenesis of Alzheimer's disease (AD), yet the underlying mechanisms remain unclear. Abnormal calcium dynamics in astrocytes represents an early event in the mouse models of AD. Here we show functional association between amyloid-β-induced elevation of CA²⁺ dynamics in medial prefrontal cortex astrocytes and glymphatic dysfunction in cognitively impaired 5xFAD mice, which can be alleviated by the attenuation of G_q GPCR-evoked CA²⁺ activity. Mechanistically, CA²⁺ hyperactivity increases Cholesterol synthesis in astrocytes, leading to increased aquaporin-4 (AQP4) endocytosis and relocalization to lysosomes, thereby disrupting AQP4 polarity and glymphatic function. Suppressing Cholesterol synthesis by either specifically knocking down squalene epoxidase in astrocytes or atorvastatin administration improves glymphatic perfusion, meningeal lymphatic drainage and cognition performance in 5xFAD mice. Our data reveal potential therapeutic benefits of lowering astrocyte calcium activity and Cholesterol synthesis for enhancing glymphatic-lymphatic coupling integrity in the early stages of AD pathogenesis.