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J. Cell Biol.,
Volume 141, Number 6, June 15, 1998 1423-1432

* Cellular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037; and Reactive oxygen species (ROS) are thought
to be involved in many forms of programmed cell
death. The role of ROS in cell death caused by oxidative glutamate toxicity was studied in an immortalized mouse hippocampal cell line (HT22). The causal relationship between ROS production and glutathione
(GSH) levels, gene expression, caspase activity, and cytosolic Ca2+ concentration was examined. An initial
5-10-fold increase in ROS after glutamate addition is
temporally correlated with GSH depletion. This early
increase is followed by an explosive burst of ROS production to 200-400-fold above control values. The
source of this burst is the mitochondrial electron transport chain, while only 5-10% of the maximum ROS
production is caused by GSH depletion. Macromolecular synthesis inhibitors as well as Ac-YVAD-cmk, an interleukin 1
Department of
Cell Biology, The Scripps Research Institute, La Jolla, California 92037
-converting enzyme protease inhibitor,
block the late burst of ROS production and protect
HT22 cells from glutamate toxicity when added early in
the death program. Inhibition of intracellular Ca2+ cycling and the influx of extracellular Ca2+ also blocks
maximum ROS production and protects the cells. The conclusion is that GSH depletion is not sufficient to
cause the maximal mitochondrial ROS production, and
that there is an early requirement for protease activation, changes in gene expression, and a late requirement for Ca2+ mobilization.
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