title: Effects of oxidants and glutamate receptor activation on mitochondrial membrane potential in rat forebrain neurons.
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 (delta psi). We measured delta psi 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 mM) or 1 mM xanthine/0.06 U/ml xanthine oxidase decreased delta psi 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 microM) had less of an effect on delta psi 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 delta psi. 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.
authors.affiliation: Department of Pharmacology, University of Pittsburgh, School of Medicine, Pennsylvania 15261, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Scanlon
authors.forename: I J
authors.initials: IJ
authors.lastname: Reynolds
mesh_terms: D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009840:Oligomycins / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology*; D016548:Prosencephalon / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D017470:Receptors, Glutamate / Q000502:physiology*; D014475:Uncoupling Agents / Q000494:pharmacology; D019820:Xanthine / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000494:pharmacology; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D009840:Oligomycins; D016877:Oxidants; D017382:Reactive Oxygen Species; D017470:Receptors, Glutamate; D014475:Uncoupling Agents; D019820:Xanthine; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D018698:Glutamic Acid; D020122:tert-Butylhydroperoxide; D014969:Xanthine Oxidase