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Nitric oxide can function as either a killer molecule or an antiapoptotic effector in cardiomyocytes
C Stefanelli1, C Pignatti, B Tantini
1Department of Biochemistry 'G. Moruzzi', University of Bologna, Via Irnerio, 48, 40126, Bologna, Italy. cstefan@biocfarm.unibo.it
Abstract:
Caspase enzymes are a family of cysteine proteases that play a central role in apoptosis. Recently, it has been demonstrated that caspases can be S-nitrosylated and inhibited by nitric oxide (NO). The present report shows that in chick embryo heart cells (CEHC), NO donor molecules such as S-nitroso-N-acetylpenicillamine (SNAP), S-nitrosoglutathione, spermine-NO or sodium nitroprusside inhibit caspase activity in both basal and staurosporine-treated cells. However, the inhibitory effect of NO donors on caspase activity is accompanied by a parallel cytotoxic effect, that precludes NO to exert its antiapoptotic capability. N-Acetylcysteine (NAC) at a concentration of 10 mM blocks depletion of cellular glutathione and cell death in SNAP-treated CEHC, but it poorly affects the ability of SNAP to inhibit caspase activity. Consequently, in the presence of NAC, SNAP attenuates not only caspase activity but also cell death of staurosporine-treated CEHC. These data show that changes in the redox environment may inhibit NO-mediated toxicity, without affecting the antiapoptotic capability of NO, mediated by inhibition of caspase enzymes. NO may thus be transformed from a killer molecule into an antiapoptotic agent.
Insights
Nitric oxide (NO) inhibits caspase activity, crucial for apoptosis. However, NO is also toxic. N-Acetylcysteine (NAC) reduces NO toxicity, allowing NO to act as an antiapoptotic agent by inhibiting caspases.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Caspase enzymes are key regulators of apoptosis.
- Nitric oxide (NO) can S-nitrosylate and inhibit caspases.
- The dual role of NO in cell death and survival requires further investigation.
Purpose of the Study:
- To investigate the effect of NO donors on caspase activity and cell viability in chick embryo heart cells (CEHC).
- To determine if N-Acetylcysteine (NAC) can mitigate NO-induced cytotoxicity without affecting its caspase inhibitory properties.
- To explore the potential of NO as an antiapoptotic agent under specific redox conditions.
Main Methods:
- Treatment of CEHC with NO donors (SNAP, S-nitrosoglutathione, spermine-NO, sodium nitroprusside).
- Assessment of caspase activity and cellular glutathione levels.
- Evaluation of cell viability and death.
- Co-treatment with NO donors and N-Acetylcysteine (NAC).
Main Results:
- NO donors inhibited caspase activity in both basal and staurosporine-treated CEHC.
- NO donor treatment resulted in parallel cytotoxic effects, masking potential antiapoptotic actions.
- NAC (10 mM) prevented glutathione depletion and cell death in SNAP-treated cells.
- NAC did not significantly inhibit SNAP's effect on caspase activity.
- In the presence of NAC, SNAP inhibited both caspase activity and cell death in staurosporine-treated CEHC.
Conclusions:
- Modulating the cellular redox environment with NAC can decouple NO's toxicity from its caspase-inhibitory effects.
- This suggests NO can be repurposed from a cytotoxic molecule to an antiapoptotic agent.
- Targeting redox balance may enhance the therapeutic potential of NO in conditions involving apoptosis.