Culture medium components modulate retina cell damage induced by glutamate, kainate or "chemical ischemia"

The aim of this study was to determine whether culture-conditioned medium (CCM) can prevent neuronal damage caused by excitotoxicity or by "chemical ischemia" in cultured chick retina cells. Excitotoxic conditions were obtained by incubating retina cells with glutamate or kainate and "chemical ischemia" was induced by metabolic inhibition. In this case, cultures were briefly exposed to sodium cyanide, to block oxidative phosphorylation and iodoacetic acid, to block glycolysis. The assessment of neuronal injury was made spectrophotometrically by quantification of cellularly reduced MTT. Stimulation of retina cells with glutamate or kainate in serum deprived culture medium (BME-FCS), lead to a decrease in the MTT metabolism that was dependent on the time of exposure to the toxic agents. CCM prevented cell damage, either when present during the stimulation period or during the recovery period. This protection was more prominent in the case of kainate-induced neuronal death. "Chemical ischemia" also lead to a decrease of the MTT metabolism in a time-dependent manner and CCM protected retina cells from "ischemia"-induced lesions when present during the stimulation period and during the recovery period. The protective effect of CCM was partially decreased by the tyrosine kinase inhibitor, genistein, when the cells were stimulated with kainate, but not with glutamate, or when the cells were subjected to "chemical ischemia". CCM protected retina cells against both the acute and the delayed toxicity induced by either glutamate or kainate, or by "chemical ischemia", when present during both the insult and the recovery period. The presence of survival factors in the media may effectively inhibit the cell death signals generated by glutamate receptor activation or by "chemical ischemia".