Tumour necrosis factor α (TNF) cytotoxicity is mediated, at least in part, by oxidative stress. One of the post-receptor events shortly after the addition of TNF is the generation of the superoxide anion (O2–·). In the present study, we attempted to examine the role of O2–· in the regulation of mitochondrial membrane potential (ΔΨm) and the release of cytochrome c (cyto c) in L929 cells after stimulation with TNF. Challenge of cells with TNF (50 ng/ml) resulted in an early (30 min after the addition of TNF) increase in the production of O2–·. The use of mitochondrial electron transport chain inhibitors such as antimycin A and rotenone could, respectively, potentiate or suppress the TNF-mediated release of O2–· and cytotoxicity. TNF also induced a late (>3 h after the addition of TNF) depolarization in the ΔΨm. Reduction in the release of O2–· by rotenone (50 µM) or thenoyltrifluoroacetone (250 µM) suppressed both the TNF-mediated ΔΨm depolarization and cyto c release. However, increase in the production of O2–· by antimycin A (25 µM) only slightly enhanced the TNF effect in altering the ΔΨm and the release of cyto c. Treating cells with antimycin A alone could not induce a reduction in ΔΨm nor a release of cyto c. Taken together, our results indicate that TNF induced damage in mitochondria in L929 cells. Our data also show that an increase in the production of O2–· was important in the TNF cytotoxicity, but was not sufficient to mimic the action of TNF.

Keywords:
Tumour necrosis factor, Mitochondria, Mitochondrial membrane potential, Depolarization, Superoxide, Apoptosis
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© 2001 S. Karger AG, Basel
2001
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