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[Possible cytotoxic mechanisms of TNF in vitro]
Abstract:
TNF is a protein originally isolated by its ability to induce hemorrhagic necrosis of some tumors in vivo, and cytotoxic effects against certain tumor cells, but not against normal cells in vitro. Though mechanisms of the cytotoxicity and selectivity of TNF action in vitro are not clear, there is much evidence that free radicals such as superoxide and hydroxyl radicals, mediated by TNF, are correlated with TNF cytotoxicity. Recently, manganous superoxide dismutase (MnSOD) in mitochondria has been demonstrated to be a rescue protein against TNF cytotoxicity and to be induced when the cells are exposed to TNF in the resistant cells. Two steroid hormones, glucocorticoid and 1,25-dihydroxyvitamin D3, block the cytotoxicity of TNF. Glucocorticoid may reduce TNF cytotoxicity by inhibiting phospholipase A2 and 1,25-dihydroxyvitamin D3 by inducing MnSOD in combination with TNF.
Insights
Tumor necrosis factor (TNF) exhibits cytotoxicity against tumor cells, potentially mediated by free radicals. Manganous superoxide dismutase (MnSOD) and certain steroid hormones show protective effects against TNF-induced cell death.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Context:
- Tumor necrosis factor (TNF) is a protein known for its selective cytotoxic effects on tumor cells in vitro and in vivo.
- The precise mechanisms underlying TNF's cytotoxicity and selectivity remain under investigation.
- Free radicals, including superoxide and hydroxyl radicals, are implicated in TNF-mediated cytotoxicity.
Purpose:
- To explore the role of free radicals in TNF cytotoxicity.
- To investigate the protective mechanisms against TNF-induced cell death.
- To examine the influence of specific steroid hormones on TNF cytotoxicity.
Summary:
- TNF induces hemorrhagic necrosis in tumors and exhibits cytotoxicity against specific tumor cells.
- Manganous superoxide dismutase (MnSOD), located in mitochondria, acts as a rescue protein against TNF cytotoxicity and is induced in resistant cells.
- Glucocorticoid and 1,25-dihydroxyvitamin D3 inhibit TNF cytotoxicity; glucocorticoid by inhibiting phospholipase A2, and 1,25-dihydroxyvitamin D3 by inducing MnSOD.
Impact:
- Elucidates the involvement of free radicals in TNF's anti-tumor activity.
- Identifies MnSOD as a key protective factor against TNF-induced cell death.
- Suggests potential therapeutic strategies using steroid hormones to mitigate TNF side effects or enhance its efficacy.