EPO is capable of increasing the population of GLAST+ astrocytes. Moreover, this effect of EPO was again more pronounced in aged astrocytes exposed to Glu. The mechanism of glutamate transporter suppression by hypoxia has been ascribed to NF-��B activation. However, the dual role of NF-��B under hypoxia raises the question Sipeimine whether its activation is protective or cytotoxic for neural cells as well as to which extent its activation versus inhibition is involved in EPO effects on astroglia. NF-��B activation was reported to decrease mammalian cell apoptosis and to be an essential pathway for EPO effect on neuronal survival and generation of neural stem cells. The opposite scenario of a GLAST expression-enhancing effect of EPO relies on the study showing its inhibiting effect on NF-��B in a model of peripheral axonal degeneration. Yet, the effect of EPO on GLAST-expression upon simultaneous inhibition of NF-��B remains to be further investigated. Interestingly, EPO protection of cultured neurons against glutamate Atractylenolide-III neurotoxicity can be blocked by EGTA suggesting a critical role for trace metals, in particular zinc, in resistance of cells to glutamate toxicity. Furthermore, it was shown that hippocampal perfusion with Ca-EDTA, a membrane-impermeable zinc chelator, increased the concentration of extracellular Glu. The hippocampal synaptic neurotransmission and synaptic plasticity is thought to be modulated by crosstalk between zinc which is co-released with Glu and calcium through calcium channels. These studies increase the physiological value of EPO-induced up-regulation 
of MT which acts not only as free radical scavenger but also plays a pivotal role in cellular distribution of zinc. Aging of the cell is featured by damage to the cell membranes and mitochondria resulting in LDH leakage and increased concentrations of intracellular lactate. Among many other factors accelerating the development of these hallmarks of neural cell aging not the least place is given to accumulation of free radicals and glutamate. Thus, exposure of rat neurons, C6 glioma cells and cerebral endothelial cells to 1.0 mM glutamate increased the formation of reactive oxygen species, including superoxide radicals, and induced caspase-3 activation, DNA fragmentation, cell detachment and mitochondrial dysfunction illustrated by impairment of oxygen consumption, glutathione depletion three-fold increase of oxygen radicals. Both glutathion and MT are known to be induced by EPO. Our study shows that until 14 day in culture astroglial cells show high resistance to glutamate- and hypoxiainduced toxicity evidenced by relatively low leakage of LDH into the culture medium. Aging of astrocytes in culture by itself, without any additional factors led to 5 fold increase of LDH leakage. The decreased resistance of aged astrocytes against environmental stresses such as glutamate or hypoxia is illustrated by further dramatic increase of LDH release up to 7-8 fold compared to similarly treated young astrocytes. Our results are consistent with other reports demonstrating glutamate-induced mitochondrial depolarisation, a significantly higher release of LDH and formation of ROS in cortical slices of aged rats compared to that of young rats. Treatment with EPO decreased the LDH leakage in all cell age groups in concentration dependent manner. In aged astrocytes administration of EPO minimized the LDH release from astrocytes more than twice, most likely via activation of ROS scavenging systems such as glutathion and MT known to be decreased in aged cells. As demonstrated here silencing of EPOR led to increased apoptosis astroglial cells, with or without exposure to Glu. No difference was observed between 1 and 5 mM Glu on cell apoptosis.