Search

The aim of this study is to examine the effect of hyperthermia on tumour necrosis factor-alpha (TNF-alpha) resistance in L929-11E cells. L929-11E is a TNF-alpha resistant variant derived from L929 cells, a commonly used model for TNF-alpha study. Based on the results from flow cytometry and Western blotting, hyperthermia (43 degrees C, 3 h) was found to induce apoptosis, mitochondrial potential (delta psi(m)) depolarization and release of cytochrome c in L929-11E cells. Similar responses were found in L929 cells when treated with TNF-alpha. Heating at 43 degrees C for 1 h did not significantly damage the mitochondria of L929-11E cells but partially reversed their resistance to TNF-alpha. When L929-11E cells were sequentially treated with heating (43 degrees C, 1 h) and TNF-alpha, a more severe damage in mitochondria was observed. Taken together, our results indicate (1) hyperthermia induced apoptosis in L929-11E cells via mitochondrial damages in a way very similar to the action of TNF-alpha in L929 cells, (2) hyperthermia could be used to overcome TNF-alpha resistance by altering mitochondrial activities and (3) L929-11E and its parental cells provide a useful model in elucidating the signalling linkage between TNF-alpha receptor and mitochondria.

Hyperthermia is a potential anti-cancer regimen but the mode of action is far from clear. Based on the flow cytometric analysis with FITC-annexin V and propidium iodide, apoptosis was found to be the major form of cell death after the treatment with hyperthermia (43 degrees C, 3 h) and/or recombinant murine tumour necrosis factor-alpha (TNF-alpha, 50 ng/ml) in L929 cells. Since mitochondria are thought to play a key role in apoptosis, experiments were done to assess their role in the hyperthermia-mediated apoptosis. Our results indicate that hyperthermia was able to depolarize the mitochondrial membrane potential (delta psi m) and release cytochrome c to the cytoplasm, in a way very similar to the action of TNF-alpha. With the use of cyclosporin A to inhibit the delta psi m dissipation, the cytotoxicity mediated by hyperthermia or TNF-alpha was suppressed. Taken together, our results indicate that hyperthermia and TNF-alpha can induce apoptosis in L929 cells and the mitochondrial dysfunction plays a key role in the cell death process.