Rat cerebellar granule cells are protected from glutamate-induced excitotoxicity by S-nitrosoglutathione but not glutathione

Open Access
Publisher Website
Google Scholar
Abstract
In cultured rat cerebellar granule cells, glutamate or N -methyl-d-aspartate (NMDA) activation of the NMDA receptor caused a sustained increase in cytosolic Ca2+ levels ([Ca2+]i), reactive oxygen species (ROS) generation, and cell death (respective EC50 values for glutamate were 12, 30, and 38 μM) but no increase in caspase-3 activity. Removal of extracellular Ca2+ blocked all three glutamate-induced effects, whereas pretreatment with an ROS scavenger inhibited glutamate-induced cell death but had no effect on the [Ca2+]i increase. This indicates that glutamate-induced cell death is attributable to [Ca2+]i increase and ROS generation, and the [Ca2+]i increase precedes ROS generation. Apoptotic cell death was not seen until 24 h after exposure of cells to glutamate. S -nitrosoglutathione abolished glutamate-induced ROS generation and cell death, and only a transient [Ca2+]i increase was seen; similar results were observed with another nitric oxide (NO) donor, S -nitroso- N -acetylpenicillamine, but not with glutathione, which suggests that the effects were caused by NO. The transient [Ca2+]i increase and the abolishment of ROS generation induced by glutamate and S -nitrosoglutathione were still seen in the presence of an ROS scavenger. Glial cells, which were present in the cultures used, showed no [Ca2+]i increase in the presence of glutamate, and glutamate-induced granule cell death was independent of the percentage of glial cells. In conclusion, NO donors protect cultured cerebellar granule cells from glutamate-induced cell death, which is mediated by ROS generated by a sustained [Ca2+]i increase, and glial cells provide negligible protection against glutamate-induced excitotoxicity.