Aquaporin-4 mediates astrocyte response to β-amyloid.

It has been demonstrated that the water channel protein aquaporin-4 (AQP4) plays an important role in astrocyte plasticity in response to a variety of injuries or stimuli. However, the potential role of AQP4 in astrocyte response to β-amyloid (Aβ) has not been studied. The purpose of this study was to investigate this issue. Compared to media control, the lower concentrations of Aβ(1-42) (0.1-1 μM) increased AQP4 expression in cultured mouse cortical astrocytes, while the higher concentrations of Aβ(1-42) (10 μM) decreased AQP4 expression. AQP4 gene knockout reduced Aβ(1-42)-induced astrocyte activation and apoptosis, which was associated with a reduction in the uptake of Aβ via decreased upregulation of low-density lipoprotein receptor related protein-1. Moreover, time-course and levels of Aβ(1-42)-induced mitogen-activated protein kinase phosphorylation were altered in AQP4 null astrocytes compared with wild-type controls. Our data reveal a novel role of AQP4 in the uptake of Aβ by astrocytes, indicating that AQP4 is a molecular target for Alzheimer's disease.