Glutamate uptake is stimulated by extracellular S100B in hippocampal astrocytes

1. S100B is a calcium- binding protein expressed and secreted by astrocytes, which has been implicated in glial- neuronal communication. Extracellular S100B appears to protect hippocampal neurons against toxic concentrations of glutamate. Here we investigated a possible autocrine role of S100B in glutamate uptake activity. 2. Astrocyte cultures were prepared of hippocampi from neonate Wistar rats. [ H-3] Glutamate uptake was measured after addition of S100B protein, antibody anti- S100B or TRTK- 12, a peptide that blocks S100B activity mediated by the C- terminal region. 3. Antibody anti- S100B addition decreased glutamate uptake measured 30 min after medium replacement, without affecting cell integrity or viability. Moreover, low levels of S100B ( less than 0.1 ng/ mL) stimulated glutamate uptake measured immediately after medium replacement. 4. This finding reinforces the importance of astrocytes in the glutamatergic transmission, particularly the role of S100B neuroprotection against excitotoxic damage.