BDNF regulates GLAST and glutamine synthetase in mouse retinal Muller cells

This study investigated whether brain-derived neurotrophic factor (BDNF) regulates the L-glutamate/L-aspartate transporter (GLAST) and glutamine synthetase (GS) in mouse retinal Muller cells (RMCs) under normal and hypoxic conditions. Mouse RMCs were treated with recombinant human BDNF (50, 75, 100, 125, or 150 ng/ml) for 24 h or underwent hypoxia induced by CoCl2 (125 mu M; 6, 12, 24, 48, or 72h). An additional group underwent combined treatment with BDNF (100ng/ml; 24, 48, 72, or 96h) and CoCl2 (125M/ml; 72h). GLAST and GS mRNA and protein expression, L-[3,4-3H]-glutamic acid uptake, and apoptosis were assessed. BDNF dose-dependently up-regulated GLAST and GS mRNA and protein and increased glutamate uptake. Similarly, in early-stage CoCl2-induced hypoxia, GLAST and GS were up-regulated and glutamate uptake increased, but these decreased over time. BDNF also up-regulated GLAST and GS and increased glutamate uptake when RMCs under CoCl2 induced hypoxic condition. However, BDNF treatment 24h before CoCl2 had no effect on GLAST or GS expression. CoCl2 alone or combined with BDNF did not induce apoptosis. Hypoxia rapidly increased GLAST and GS expressions. This effect was transient, perhaps due to compensatory mechanisms that reduce GLAST and GS by 72h. BDNF can up-regulate GLAST and GS and increase glutamate uptake during hypoxia, and these functions may underlie its neuroprotective effects. J. Cell. Physiol. 227: 596603, 2012. (C) 2011 Wiley Periodicals, Inc.