RESUMEN
TNF is unusual among the death receptor ligands in being able to induce either apoptotic or necrotic cell death. We have observed that in WEHI 164 fibrosarcoma, cells the mode of TNF-induced cell death is dependent on the stage of the cell cycle. Cells arrested in G(0)/G(1) undergo necrosis, while those progressing through the cell cycle undergo apoptosis. TNF induces caspase activity in both settings, and the broad spectrum caspase inhibitor zVAD-fmk inhibits this activity and blocks both TNF-induced apoptosis and necrosis. Inhibition of oxygen radical accumulation does not block cytotoxicity. The presence and activation of specific caspases were examined by Western blotting. The procaspase-8a isoform was down-regulated in proliferating cells. Procaspases-8b and -7 were cleaved during TNF-induced apoptosis but not necrosis. Thus, a different pattern of caspase expression and activation occurs dependent on the cell cycle and which may determine the mode of cell death.
Asunto(s)
Apoptosis/efectos de los fármacos , Caspasas/metabolismo , Muerte Celular/efectos de los fármacos , Factor de Necrosis Tumoral alfa/farmacología , Secuencia de Aminoácidos , Animales , Apoptosis/fisiología , Hidroxianisol Butilado/farmacología , Caspasa 7 , Caspasa 8 , Caspasa 9 , Ciclo Celular/fisiología , Muerte Celular/fisiología , Línea Celular , Activación Enzimática/efectos de los fármacos , Depuradores de Radicales Libres/farmacología , Ratones , Microscopía Electrónica , Oligopéptidos/química , Proteínas Recombinantes/farmacología , Especificidad por Sustrato , Factor de Necrosis Tumoral alfa/fisiologíaAsunto(s)
Antígenos CD/fisiología , Apoptosis/efectos de los fármacos , Autofagia/efectos de los fármacos , Mitocondrias/efectos de los fármacos , Receptores del Factor de Necrosis Tumoral/fisiología , Factor de Necrosis Tumoral alfa/farmacología , Células 3T3 , Adipocitos/efectos de los fármacos , Adipocitos/ultraestructura , Animales , Células Cultivadas , Humanos , Ratones , Receptores Tipo I de Factores de Necrosis Tumoral , Receptores Tipo II del Factor de Necrosis Tumoral , Transducción de SeñalRESUMEN
Tumor necrosis factor (TNF) may cause apoptosis or necrosis and induces mitochondrial changes that have been proposed to be central to cytotoxicity. We report similar patterns of TNF-induced mitochondrial morphological alterations and autophagy in cell types with differing sensitivity to TNF-induced cytotoxicity. Specific ligation of TNFR-I or TNFR-II induces different rates of apoptosis and mitochondrial morphological change, but similar rates of autophagy. These changes do not invariably lead to cell death, and survival or progression to apoptosis or necrosis following TNF exposure may depend in part on the extent of mitochondrial damage and/or the autophagic capacity of the cell.