Since loss of AQP4 and microglial activation in the optic nerve precedes the loss of ganglion cells, and accumulation of Aβ in the retina, the cause of the neuronal loss appears to be optic nerve degeneration.
The results showed that long-term consumption of alcohol aggravated cognitive decline, increased the permeability of the BBB, led to pathomorphological changes and downregulated some related structural proteins (zonula occludens-1, VE-cadherin, and occludin) and functional proteins (major facilitator superfamily domain-containing protein-2a (Mfsd2a), low-density lipoprotein receptor-related protein-1 (LRP1), receptor for advanced glycation end products (RAGE), and aquaporin-4 (AQP4)) in the BBB but did not increase the concentration of Aβ<sub>1-42</sub>.
This study suggests that AQP4 genetic variation moderates the relationship between sleep and brain Aβ-amyloid burden, which adds weight to the proposed glymphatic system being a potential Aβ-amyloid clearance mechanism and suggests that AQP4 genetic variation may impair this function.
Loss of perivascular AQP4 localization may be a factor that renders the aging brain vulnerable to the misaggregation of proteins, such as amyloid-β, in neurodegenerative conditions such as AD.