The APPswe/PS1A246E mutations in an astrocytic cell line leads to increased vulnerability to oxygen and glucose deprivation, Ca2+ dysregulation, and mitochondrial abnormalities

Abstract

Growing evidence suggests a close relationship between Alzheimer's Disease (AD) and cerebral hypoxia. Astrocytes play a key role in brain homeostasis and disease states, while some of the earliest changes in AD occur in astrocytes. We have therefore investigated whether mutations associated with AD increase astrocyte vulnerability to ischemia. Two astroglioma cell lines derived from APP_SWE /PS1A246E (APP, amyloid precursor protein; PS1, presenilin 1) transgenic mice and controls from normal mice were subjected to oxygen and glucose deprivation (OGD), an in vitro model of ischemia. Cell death was increased in the APP_SWE /PS1A246E line compared to the control. Increasing extracellular calcium concentration ([Ca²⁺ ]) exacerbated cell death in the mutant but not in the control cells. In order to explore cellular Ca²⁺ homeostasis, the cells were challenged with ATP or thapsigargin and [Ca²⁺ ] was measured by fluorescence microscopy. Changes in cytosolic Ca²⁺ concentration ([Ca²⁺ ]_c ) were potentiated in the APP_SWE /PS1A246E transgenic line. Mitochondrial function was also altered in the APP_SWE /PS1A246E astroglioma cells; mitochondrial membrane potential and production of reactive oxygen species were increased, while mitochondrial basal respiratory rate and ATP production were decreased compared to control astroglioma cells. These results suggest that AD mutations in astrocytes make them more sensitive to ischemia; Ca²⁺ dysregulation and mitochondrial dysfunction may contribute to this increased vulnerability. Our results also highlight the role of astrocyte dyshomeostasis in the pathophysiology of neurodegenerative brain disorders.

Keywords: Alzheimer′s disease; astrocytes; calcium dyshomeostasis; cell death; ischemia; mitochondrial dysfunction.