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Inhibition of mitochondrial ATP generation by nitric oxide switches apoptosis to necrosis
1Chair of Molecular Toxicology, Faculty of Biology, University of Konstanz, Konstanz, D-78457, Germany.
Abstract:
Under pathological conditions, the mode of cell death, apoptosis or necrosis, is relevant for the subsequent fate of the tissue. Cell demise may be shaped by endogenous mediators such as nitric oxide (NO) which interfere with subroutines of the death program. Here we show that apoptosis of Jurkat cells elicited by either staurosporine (STS) or anti-CD95 antibodies in glucose-free medium is converted to necrosis by NO donors. In the presence of NO, release of mitochondrial cytochrome c was delayed and activation of execution caspases was prevented. Stimulated cells died nonetheless. The switch in the mode of cell death was due to NO-dependent failure of mitochondrial energy production. Restoration of intracellular ATP by glucose supplementation recovered the cells' ability to activate caspases and undergo apoptosis. In this system, the apoptosis/necrosis conversion promoted by NO was not mediated by cyclic guanosine monophosphate-dependent mechanisms, poly-(ADP-ribose)-polymerase (PARP) activation, or inhibition of caspases due to S-nitrosylation and glutathione depletion. In contrast, depleting intracellular ATP with rotenone, an inhibitor of mitochondrial complex I mimicked the effect of NO. The findings presented here suggest that NO can decide the shape of cell death by lowering intracellular ATP below the level required to allow the coordinated execution of apoptosis.
Insights
Nitric oxide (NO) converts programmed cell death (apoptosis) to necrosis in Jurkat cells by disrupting mitochondrial energy production. Restoring ATP levels with glucose re-enables apoptosis, highlighting NO's role in dictating cell death pathways.
Area of Science:
- Cell Biology
- Biochemistry
- Pathology
Background:
- Cell death pathways, including apoptosis and necrosis, are critical in tissue homeostasis and disease.
- Endogenous mediators like nitric oxide (NO) can modulate cell death.
- The specific mode of cell death influences tissue outcomes.
Purpose of the Study:
- To investigate the effect of nitric oxide (NO) on the mode of cell death in Jurkat cells.
- To elucidate the mechanisms by which NO influences apoptosis and necrosis.
- To determine the role of mitochondrial energy production in NO-mediated cell death conversion.
Main Methods:
- Jurkat cells were treated with staurosporine (STS) or anti-CD95 antibodies in glucose-free medium.
- Nitric oxide (NO) donors were used to induce NO production.
- Mitochondrial cytochrome c release, caspase activation, and intracellular ATP levels were measured.
- Rotenone, a mitochondrial complex I inhibitor, was used to mimic NO effects.
- Cyclic guanosine monophosphate (cGMP)-dependent pathways, PARP activation, and S-nitrosylation were assessed.
Main Results:
- NO donors converted STS- or anti-CD95-induced apoptosis to necrosis in Jurkat cells.
- NO delayed mitochondrial cytochrome c release and prevented execution caspase activation.
- The switch to necrosis was attributed to NO-dependent failure of mitochondrial energy production.
- Restoration of intracellular ATP with glucose re-established apoptosis.
- NO's effect was mimicked by rotenone, indicating a role for mitochondrial dysfunction.
- NO-induced apoptosis-to-necrosis conversion was independent of cGMP, PARP activation, S-nitrosylation, and glutathione depletion.
Conclusions:
- Nitric oxide (NO) can dictate the mode of cell death by reducing intracellular ATP levels.
- NO-induced cell death switch occurs when ATP falls below the threshold required for apoptosis execution.
- Mitochondrial energy metabolism is a key target for NO in modulating cell death pathways.