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Damage to mitochondrial respiration chain is related to phospholipase A2 activation caused by tumor necrosis factor
M Higuchi1, K Shirotani, N Higashi
1Division of Chemical Toxicology and Immunochemistry, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
Abstract:
Tumor necrosis factor (TNF) has been shown to be cytotoxic to tumor cell lines in vitro, but the mechanism by which TNF exerts its cell growth-regulatory effects is not known. In this report, we used various inhibitors to investigate the sequence of events that lead to cytotoxic effects of TNF on L.P3 cells, a highly sensitive, murine fibroblast cell line. Our results indicate that mitochondrial respiration chains are damaged by a hydroxyl radical at an early stage of the cell lysis after TNF treatment. This event is followed by the activation of phospholipase A2, and finally leads to cell lysis.
Insights
Tumor necrosis factor (TNF) causes cell death by damaging mitochondria with hydroxyl radicals early in the process. This leads to phospholipase A2 activation and subsequent cell lysis in sensitive fibroblast cells.
Area of Science:
- Cell Biology
- Biochemistry
- Toxicology
Background:
- Tumor necrosis factor (TNF) exhibits in vitro cytotoxicity against tumor cells.
- The precise mechanism underlying TNF's cell growth-regulatory and cytotoxic effects remains largely unknown.
- Understanding TNF's action is crucial for developing targeted cancer therapies.
Purpose of the Study:
- To elucidate the sequential molecular events mediating TNF-induced cytotoxicity in L.P3 cells.
- To identify the specific cellular components and pathways affected by TNF treatment.
- To investigate the role of reactive oxygen species in TNF-mediated cell death.
Main Methods:
- Utilized a murine fibroblast cell line (L.P3) known for its sensitivity to TNF.
- Employed various chemical inhibitors to dissect the signaling cascade triggered by TNF.
- Analyzed cellular damage at the mitochondrial level and assessed enzyme activity.
Main Results:
- TNF treatment initiates cell lysis through damage to mitochondrial respiration chains.
- Hydroxyl radicals are implicated as early mediators of mitochondrial damage following TNF exposure.
- The observed mitochondrial damage is followed by the activation of phospholipase A2, preceding cell lysis.
Conclusions:
- The cytotoxic mechanism of TNF involves early mitochondrial damage mediated by hydroxyl radicals.
- Phospholipase A2 activation is a key downstream event in the TNF-induced cell death pathway.
- This study clarifies the sequence of events leading to TNF-mediated cell lysis in sensitive cells.