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Redox regulation of TNF signaling
V Goossens1, K De Vos, D Vercammen
1Department of Molecular Biology, Flanders Interuniversity Institute for Biotechnology and University of Gent, Belgium.
Abstract:
TNF is produced during inflammation and induces, among other activities, cell death in sensitive tumour cells. We previously reported an increased generation of ROS in TNF-treated L929 fibrosarcoma cells prior to cell death. These ROS are of mitochondrial origin and participate in the cell death process. Presently, we focus on the identification of parameters that control ROS production and subsequent cytotoxicity. From the cytotoxic properties and susceptibility to scavenging of TNF-induced ROS as compared to pro-oxidant-induced ROS we conclude that TNF-mediated ROS generation and their lethal action are confined to the inner mitochondrial membrane. Oxidative substrates, electron-transport inhibitors, glutathione and thiol-reactive agents but also caspase inhibitors modulate TNF-induced ROS production and imply the existence of a negative regulator of ROS production. Inactivation of this regulator by a TNF-induced reduction of NAD(P)H levels and/or formation of intraprotein disulfides would be responsible for ROS generation.
Insights
Tumor necrosis factor (TNF) triggers cell death by inducing reactive oxygen species (ROS) from mitochondria. This study identifies factors controlling ROS production and cell death in fibrosarcoma cells.
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Tumor necrosis factor (TNF) is a key inflammatory cytokine.
- TNF induces cell death in sensitive tumor cells.
- Previous work showed TNF increases mitochondrial reactive oxygen species (ROS) before cell death.
Purpose of the Study:
- Identify parameters controlling TNF-induced ROS production.
- Determine the role of ROS in TNF-mediated cytotoxicity.
- Pinpoint the mitochondrial location of TNF-induced ROS generation.
Main Methods:
- Comparing TNF-induced ROS with pro-oxidant-induced ROS.
- Assessing the effects of various agents (oxidative substrates, inhibitors, glutathione, thiol-reactive agents, caspase inhibitors) on ROS production.
- Analyzing the localization of ROS generation within mitochondria.
Main Results:
- TNF-mediated ROS generation and cytotoxicity are localized to the inner mitochondrial membrane.
- Specific agents modulate TNF-induced ROS production, suggesting a negative regulator.
- TNF-induced reduction in NAD(P)H levels and/or disulfide bond formation may inactivate this regulator, leading to ROS generation.
Conclusions:
- TNF-induced cell death involves mitochondrial ROS originating from the inner mitochondrial membrane.
- A negative regulatory mechanism for ROS production exists and is influenced by TNF.
- Changes in cellular redox state, like NAD(P)H depletion, are implicated in initiating ROS production and subsequent cell death.