Excitotoxic Calcium Overload in a Subpopulation of Mitochondria Triggers Delayed Death in Hippocampal Neurons
Open Access
- 16 June 2004
- journal article
- Published by Society for Neuroscience in Journal of Neuroscience
- Vol. 24 (24) , 5611-5622
- https://doi.org/10.1523/jneurosci.0531-04.2004
Abstract
In neurons, excitotoxic stimulation induces mitochondrial calcium overload and the release of pro-apoptotic proteins, which triggers delayed cell death. The precise mechanisms of apoptogen release, however, remain controversial. To characterize the linkage between mitochondrial calcium load and cell vulnerability, and to test the hypothesis that only a subpopulation of mitochondria damaged by calcium overload releases apoptogens, we have measured directly the concentrations of total Ca (free plus bound) in individual mitochondria and monitored in parallel structural changes and the subcellular localization of pro-apoptotic cytochrome c after NMDA overstimulation in cultured hippocampal neurons. Beyond transient elevation of cytosolic calcium and perturbation of Na+/K+ homeostasis, NMDA stimulation induced dramatic, but mainly reversible, changes in mitochondria, including strong calcium elevation, membrane potential depolarization, and variable swelling. Elevation of matrix Ca in the approximately one-third of mitochondria that were strongly swollen, as well as the absence of swelling when Ca2+ entry was abolished, indicate an essential role for Ca overload. Shortly after NMDA exposure, cytochrome c, normally localized to mitochondria, became diffusely distributed in the cytoplasm, coincident with the appearance of severely swollen mitochondria with ruptured outer membranes; under these conditions, cytochrome c was retained in intact mitochondria, implying that it was released mainly from damaged mitochondria. Consistent with the role of mitochondrial Ca overload, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone decreased Ca accumulation, prevented cytochrome c release, and was neuroprotective. These results support a mechanism in which delayed excitotoxic death involves apoptogen release from a subpopulation of calcium-overloaded mitochondria, whereas other, undamaged mitochondria maintain normal function.Keywords
This publication has 71 references indexed in Scilit:
- Mitochondrial cytochrome c release may occur by volume-dependent mechanisms not involving permeability transitionBiochemical Journal, 2004
- The ADP/ATP translocator is not essential for the mitochondrial permeability transition poreNature, 2004
- Regulation of cell death: the calcium–apoptosis linkNature Reviews Molecular Cell Biology, 2003
- Cyclosporin A-insensitive Permeability Transition in Brain MitochondriaJournal of Biological Chemistry, 2003
- Mitochondrial permeability transition and calcium dynamics in striatal neurons upon intense NMDA receptor activationJournal of Neurochemistry, 2002
- Quantitative evaluation of mitochondrial calcium content in rat cortical neurones following a glutamate stimulusThe Journal of Physiology, 2001
- Glutamate‐induced mitochondrial depolarisation and perturbation of calcium homeostasis in cultured rat hippocampal neuronesThe Journal of Physiology, 1999
- Mitochondrial deenergization underlies neuronal calcium overload following a prolonged glutamate challengeFEBS Letters, 1996
- Glutamate impairs neuronal calcium extrusion while reducing sodium gradientNeuron, 1994
- The localization and assay of chemical elements by microprobe methodsQuarterly Reviews of Biophysics, 1983