Tumor necrosis factor-alpha increases the steady-state reduction of cytochrome b of the mitochondrial respiratory chain in metabolically inhibited L929 cells
Ja. Sanchez-alcazar et al., Tumor necrosis factor-alpha increases the steady-state reduction of cytochrome b of the mitochondrial respiratory chain in metabolically inhibited L929 cells, J BIOL CHEM, 275(18), 2000, pp. 13353-13361
The mechanism of tumor necrosis factor alpha (TNF alpha)-induced cytotoxici
ty in metabolically inhibited cells is unclear, although some studies have
suggested that mitochondrial dysfunction and generation of reactive oxygen
species may be involved. Here we studied the effect of TNF alpha on the red
ox state of mitochondrial cytochromes and its involvement in the generation
of reactive oxygen species in metabolically inhibited L929 cells. Treatmen
t with TNF alpha and cycloheximide (TNF alpha/CHX) induced mitochondrial cy
tochrome c release, increased the steady-state reduction of cytochrome b, a
nd decreased the steady-state reduction of cytochromes cc(1) and aa(3). TNF
alpha/CHX treatment also induced lipid peroxidation, intracellular generat
ion of reactive oxygen species, and cell death. Furthermore, as the cells d
ied mitochondrial morphology changed from an orthodox to a hyperdense and c
ondensed and finally to a swollen conformation. Antimycin A, a mitochondria
l respiratory chain complex III inhibitor that binds to cytochrome b, block
ed the formation of reactive oxygen species, suggesting that the free radic
als are generated at the level of cytochrome b. Moreover, antimycin A, when
added after 3 h of TNF alpha/CHX treatment, arrested the further release o
f cytochrome c and the cytotoxic response. We propose that the reduced cyto
chrome b promotes the formation of reactive oxygen species, lipid peroxidat
ion of the cell membrane, and cell death.