title: Loss of astrocyte polarization in the tg-ArcSwe mouse model of Alzheimer's disease.
abstract: Aquaporin-4 (AQP4) is the predominant water channel in brain and is selectively expressed in astrocytes. Astrocytic endfoot membranes exhibit tenfold higher densities of AQP4 than non-endfoot membranes, making AQP4 an excellent marker of astrocyte polarization. Loss of astrocyte polarization is known to compromise astrocytic function and to be associated with impaired water and K+ homeostasis. Here we investigate by a combination of light and electron microscopic immunocytochemistry whether amyloid deposition is associated with a loss of astrocyte polarization, using AQP4 as a marker. We used the tg-ArcSwe mouse model of Alzheimer's disease, as this model displays perivascular plaques as well as plaques confined to the neuropil. 3D reconstructions were done to establish the spatial relation between plaques and astrocytic endfeet, the latter known to contain the perivascular pool of AQP4. Changes in AQP4 expression emerge just after the appearance of the first plaques. Typically, there is a loss of AQP4 from endfoot membranes at sites of perivascular amyloid deposits, combined with an upregulation of AQP4 in the neuropil surrounding plaques. By electron microscopy it could be verified that the upregulation reflects an increased concentration of AQP4 in those delicate astrocytic processes that abound in synaptic regions. Thus, astrocytes exhibit a redistribution of AQP4 from endfoot membranes to non-endfoot membrane domains. The present data suggest that the development of amyloid deposits is associated with a loss of astrocyte polarization. The possible perturbation of water and K+ homeostasis could contribute to cognitive decline and seizure propensity in patients with Alzheimer's disease.
authors: Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, PR China.
authors: Jing
authors: J
authors: Yang
authors: Lisa K
authors: LK
authors: Lunde
authors: Paworn
authors: P
authors: Nuntagij
authors: Tomohiro
authors: T
authors: Oguchi
authors: Laura M A
authors: LM
authors: Camassa
authors: Lars N G
authors: LN
authors: Nilsson
authors: Lars
authors: L
authors: Lannfelt
authors: Yuming
authors: Y
authors: Xu
authors: Mahmood
authors: M
authors: Amiry-Moghaddam
authors: Ole Petter
authors: OP
authors: Ottersen
authors: Reidun
authors: R
authors: Torp
mesh_terms: D000544:Alzheimer Disease / Q000235:genetics* / Q000473:pathology*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism; D001253:Astrocytes / Q000502:physiology* / Q000648:ultrastructure; D016764:Cell Polarity / Q000235:genetics*; D003936:Diagnosis, Computer-Assisted; D004195:Disease Models, Animal; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D016253:Microscopy, Immunoelectron; D009154:Mutation / Q000235:genetics; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D051401:Aquaporin 4; D005904:Glial Fibrillary Acidic Protein; D019408:Platelet Endothelial Cell Adhesion Molecule-1