L-glutamate suppresses amyloid β-protein-induced stellation of cultured rat cortical astrocytes

Alzheimer's amyloid beta-protein (A beta) has been reported to potentiate glutamate toxicity in neurons, but very little is known about interaction between A beta and glutamate in astrocytes, Therefore, in the present study, we investigated the effects of A beta and glutamate on morphology of astrocytes. Cultured rat cortical astrocytes exhibited polygonal morphology in the absence of stimulation and differentiated into process-bearing stellate cells following exposure to A beta (20 mu M). L-Glutamate (30-1,000 mu M) had no effect on astrocyte morphology in the absence of stimulation but strongly suppressed A beta-induced stellation. The suppressive effect of L-glutamate on A beta-induced stellation was not mimicked by glutamate receptor agonists and not blocked by glutamate receptor antagonists. In contrast, the suppressive effect of L-glutamate was mimicked by D- and L-aspartate and transportable glutamate uptake inhibitors. These results suggest that A beta-induced astrocyte stellation is suppressed by a mechanism related to glutamate transporters.