title: Tumour necrosis factor induced an early release of superoxide and a late mitochondrial membrane depolarization in L929 cells. Increase in the production of superoxide is not sufficient to mimic the action of TNF.
abstract: Tumour necrosis factor alpha (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 (Delta(Psi)m) 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 Delta(Psi)m. Reduction in the release of O2-* by rotenone (50 microM) or thenoyltrifluoroacetone (250 microM) suppressed both the TNF-mediated Delta(Psi)m depolarization and cyto c release. However, increase in the production of O2-* by antimycin A (25 microM) only slightly enhanced the TNF effect in altering the Delta(Psi)m and the release of cyto c. Treating cells with antimycin A alone could not induce a reduction in Delta(Psi)m 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.
authors.affiliation: Department of Biochemistry, Chinese University of Hong Kong, Shatin, Hong Kong, China.
authors.forename: S
authors.initials: S
authors.lastname: Ko
authors.forename: T T
authors.initials: TT
authors.lastname: Kwok
authors.forename: K P
authors.initials: KP
authors.lastname: Fung
authors.forename: Y M
authors.initials: YM
authors.lastname: Choy
authors.forename: C Y
authors.initials: CY
authors.lastname: Lee
authors.forename: S K
authors.initials: SK
authors.lastname: Kong
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D007739:L Cells / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects*; D011994:Recombinant Proteins / Q000494:pharmacology; D012402:Rotenone / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D012402:Rotenone; D013481:Superoxides; D000968:Antimycin A