Hypoxia suppresses astrocyte glutamate transport independently of amyloid formation

Sustained hypoxia alters the expression of numerous proteins and predisposes individuals to Alzheimer's disease (AD). We have previously shown chat hypoxia in vitro alters Ca2+ homeostasis in astrocytes and promotes increased production of amyloid beta peptides (A beta) of AD. Indeed, alteration of Ca2+ homeostasis requires amyloid formation. Here, we show that electrogenic glutamate uptake by astrocytes is suppressed by hypoxia (1% O-2, 24 h) in a manner that is independent of amyloid beta peptide formation. Thus, hypoxic suppression of glutamate uptake and expression levels of glutamate transporter proteins EAAT1 and EAAT2 were not mimicked by exogenous application of amyloid beta peptide, or by prevention of endogenous amyloid peptide formation (using inhibitors of either beta or gamma secretase). Thus. dysfunction in glutamate homeostasis in hypoxic conditions is independent of A beta production, but will likely contribute to neuronal damage and death associated with AD following hypoxic events. (C) 2007 Elsevier Inc. All rights reserved.