Inhibition of mitochondrial respiration by endogenous nitric oxide: a critical step in Fas signaling.
We have found that activation of human adult T cell leukemia (Jurkat) cells with anti-Fas Ab leads, in a concentration-dependent manner, to an early burst of production of nitric oxide (NO), which inhibits cell respiration. This results in mitochondrial hyperpolarization, dependent on the hydrolysis of glycolytic ATP by the F1F(o)-ATPase acting in reverse mode. During this early phase of activation, there is a transient release of superoxide anion. All these processes can be prevented by an inhibitor of NO synthase. Approximately 2 h after stimulation with anti-Fas Ab, a distinct second phase can be detected. This comprises a concentration-dependent collapse in mitochondrial membrane potential, a second wave of free radical production, and activation of caspase-8 leading to apoptosis. This second phase is abolished by an inhibitor of caspase activation. In contrast, inhibition of NO synthesis leads to an enhancement and acceleration of these latter processes, suggesting that the early NO-dependent phase represents a protective mechanism. The significance of the two phases in relation to cell survival and death remains to be studied.
Beltrán
Belén
B
Centro Nacional de Investigaciones Cardiovasculares, C/Sinesio Delgado, 6 - Pab.5 28029 Madrid, Spain.
Quintero
Marisol
M
García-Zaragozá
Eugenia
E
O'Connor
Enrique
E
Esplugues
Juan V
JV
Moncada
Salvador
S
D017209:Apoptosis; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival; D006801:Humans; D019169:Jurkat Cells; D008564:Membrane Potentials; D008928:Mitochondria / Q000201:enzymology / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D010101:Oxygen Consumption; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism*
D017382:Reactive Oxygen Species; D019014:fas Receptor; D009569:Nitric Oxide; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases