Aquaporin 4 is differentially increased and depolarized in association with tau and amyloid-beta

Abstract

AbstractNeurovascular-glymphatic dysfunction plays an important role in Alzheimer’s disease and has been analyzed mainly in association with amyloid-beta (Aβ) pathology. The neurovascular-glymphatic link with tauopathies has not been well elucidated. Here, we aimed to investigate the alterations in the neurovasculature and map the aquaporin 4 (AQP4) distribution and depolarization associated with tau and Aβ. Perfusion, susceptibility weighted imaging and structural magnetic resonance imaging (MRI) were performed in the pR5 P301L mouse model of 4-repeat tau and the arcAβ mouse model of amyloidosis. Immunofluorescence staining was performed using antibodies against AQP4, CD31, astroglia (GFAP, s100β), phospho-tau (AT-8) and Aβ (6E10) in brain tissue slices from P301L, arcAβ and nontransgenic mice. P301L mice showed regional atrophy, preserved cerebral blood flow and reduced cerebral vessel density compared to nontransgenic mice, while arcAβ mice showed cerebral microbleeds and reduced cerebral vessel density. AQP4 depolarization and peri-tau enrichment in the hippocampus and increased AQP4 levels in the forebrain and hippocampus were detected in P301L mice compared to nontransgenic mice. In comparison, cortical AQP4 depolarization and cortical/hippocampal peri-plaque increases were observed in arcAβ mice. Increased s100β-GFAP fluorescence intensities indicative of reactive astrocytes were detected surrounding tau inclusions in P301L mice and Aβ plaques in arcAβ mice. In conclusion, we observed a divergent region-specific AQP4 increase and association with phospho-tau and Aβ pathologies.