Glycine enhances microglial calcium fluxes: A possible role for neutral amino acid transporters

Abstract

Based on recent electrophysiological data, we hypothesized a possible role for neutral amino acid transporters in glycine modulation of microglial activity. Since it has been demonstrated that calcium (Ca2+) signals correlate to microglial activity, Ca2+ signal modulation was investigated. Results showed that glycine enhanced microglial Ca2+ signals induced by ATP, LPS and thapsigargin. These effects were GlyR-independent and could be blocked by the competitive amino acid transporter substrate AIB ('-amino-isobutyric acid). Glycine immunostaining also showed an AIB-sensitive uptake of glycine in microglial cells. Together, these results provide strong arguments for neutral amino acid transporter involvement in glycine enhancement of microglial Ca2+ signals. Additional results obtained using ELISA assays, showed enhanced TNF-' production in glycine conditions. This further confirms that the immune function of microglial cells is enhanced by glycine and that the glycine effects on microg