Effects of Oxidants and Glutamate Receptor Activation on Mitochondrial Membrane Potential in Rat Forebrain Neurons |
| |
Authors: | Joelle M. Scanlon Ian J. Reynolds |
| |
Affiliation: | Department of Pharmacology, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, U.S.A. |
| |
Abstract: | Abstract: Both glutamate and reactive oxygen species have been implicated in excitotoxic neuronal injury, and mitochondria may play a key role in the mediation of this process. In this study, we examined whether glutamate-receptor stimulation and oxidative stress interact to affect the mitochondrial membrane potential (ΔΨ). We measured ΔΨ in rat forebrain neurons with the ratiometric fluorescent dye JC-1 by using laser scanning confocal imaging. Intracellular oxidant levels were measured by using the oxidation-sensitive dyes 2',7'-dichlorodihydrofluorescein (DCFH2) and dihydroethidium (DHE). Application of hydrogen peroxide (0.3–3 m M ) or 1 m M xanthine/0.06 U/ml xanthine oxidase decreased ΔΨ in a way that was independent of the presence of extracellular Ca2+ and was not affected by the addition of cyclosporin A, suggesting the presence of either a cyclosporin A-insensitive form of permeability transition, or a separate mechanism. tert -Butylhydroperoxide (730 µ M ) had less of an effect on ΔΨ than hydrogen peroxide despite similar effects on intracellular DCFH2 or DHE oxidation. Hydrogen peroxide-, tert -butylhydroperoxide-, and superoxide-enhanced glutamate, but not kainate, induced decreases in ΔΨ. The combined effect of peroxide or superoxide plus glutamate was Ca2+ dependent and was partially inhibited by cyclosporin A. These results suggest that oxidants and glutamate depolarize mitochondria by different mechanisms, and that oxidative stress may enhance glutamate-mediated mitochondrial depolarization. |
| |
Keywords: | JC-1 Depolarization Hydrogen peroxide tert-Butylhydroperoxide Superoxide Excitotoxicity |
|
|