Amyloid-β-induced Alteration of Fast and Localized Calcium Elevations in Cultured Astrocytes
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that causes cognitive decline. Uncovering the mechanisms of neurodegeneration in the early stages is essential to establish a treatment for AD. Recent research has proposed the hypothesis that amyloid-{beta} (A{beta}) oligomers elicit an excessive glutamate release from astrocytes toward synapses through intracellular free Ca2+ ([Ca2+]i) elevations in astrocytes, finally resulting in neuronal dendritic spine loss. Under physiological conditions, astrocytic [Ca2+]i elevations range spatially from microdomains to network-wide propagation and temporally from milliseconds to tens of seconds. Astrocytic localized and fast [Ca2+]i elevations might correlate with glutamate release; however, the A{beta}-induced alteration of localized, fast astrocytic [Ca2+]i elevations remains unexplored. In this study, we quantitatively investigated the A{beta} dimers-induced changes in the spatial and temporal patterns of [Ca2+]i in a primary culture of astrocytes by two-photon excitation spinning-disk confocal microscopy. The frequency of fast [Ca2+]i elevations occurring locally in astrocytes ([≤]0.5 s, [≤]35 m2) and [Ca2+]i event occupancy relative to cell area significantly increased after exposure to A{beta} dimers. The effect of A{beta} dimers appeared dose-dependently above 500 nM, and these A{beta} dimers-induced [Ca2+]i elevations were primarily mediated by a metabotropic purinergic receptor (P2Y1 receptor) and Ca2+ release from the endoplasmic reticulum. Our findings suggest that the A{beta} dimers-induced alterations and hyperactivation of astrocytic [Ca2+]i is a candidate cellular mechanism in the early stages of AD.