Effect of Peroxynitrite on the Mitochondrial Respiratory Chain: Differential Susceptibility of Neurones and Astrocytes in Primary Culture

Abstract

Abstract: The effect of the neurotoxic nitric oxide derivative, the peroxynitrite anion (ONOO−), on the activity of the mitochondrial respiratory chain complexes in cultured neurones and astrocytes was studied. A single exposure of the neurones to ONOO− (initial concentrations of 0.01–2.0 m M) caused, after a subsequent 24‐h incubation, a dose‐dependent decrease in succinate‐cytochrome c reductase (60% at 0.5 m M) and in cytochrome c oxidase (52% at 0.5 m M) activities. NADH‐ubiquinone‐1 reductase was unaffected. In astrocytes, the activity of the mitochondrial complexes was not affected up to 2 m M ONOO−. Citrate synthase was unaffected in both cell types under all conditions studied. However, lactate dehydrogenase activity released to the culture medium was increased by ONOO− in a dose‐dependent manner (40% at 0.5 m M ONOO−) from the neurones but not from the astrocytes. Neuronal glutathione concentration decreased by 39% at 0.1 m M ONOO−, but astrocytic glutathione was not affected up to 2 m M ONOO−. In isolated brain mitochondria, only succinate‐cytochrome c reductase activity was affected (22% decrease at 1 m M ONOO−). We conclude that the acute exposure of ONOO− selectively damages neurones, whereas astrocytes remain unaffected. Intracellular glutathione appears to be an important factor for ameliorating ONOO−‐mediated mitochondrial damage. This study supports the hypothesis that the neurotoxicity of nitric oxide is mediated through mitochondrial dysfunction.