The brain's waste system removes harmful tau protein and may protect against its buildup and nerve cell damage

Deletion of aquaporin-4 (AQP4) elevated tau levels in cerebrospinal fluid (CSF) and worsened neurodegeneration in transgenic mice.

• Tau, a protein linked to neurodegenerative diseases, is actively released into brain interstitial fluid and CSF.
• AQP4 plays a critical role in the glymphatic system, which clears extracellular tau from the brain.
• The absence of AQP4 increased tau levels in CSF and led to greater deposition of phosphorylated tau in the brain.
• Exacerbated neurodegeneration was observed in the brains of mice lacking AQP4 and expressing a mutant form of tau.
• Findings suggest that impaired glymphatic clearance of extracellular tau may contribute to tau aggregation and neurodegeneration.

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