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Nitroxides increase the detectable amount of nitric oxide released from endothelial cells
S Zöllner1, R F Haseloff, I A Kirilyuk
1Berlex Biosciences, Richmond, California 94804, USA.
The Journal of Biological Chemistry
|September 12, 1997
Summary
Nitroxides, known for superoxide dismutase-mimetic activity, were found to increase nitric oxide (.NO) bioavailability in vitro. This study shows nitroxides enhance .NO levels by accelerating superoxide dismutation.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Nitroxides possess superoxide dismutase-mimetic properties, reducing cytotoxicity from superoxide (O-2) and hydrogen peroxide (H2O2).
- The impact of nitroxides on nitric oxide (.NO) homeostasis remains largely uninvestigated.
Purpose of the Study:
- To investigate the effect of nitroxides on the detectable levels of .NO released from 3-morpholinosydnonimine (SIN-1) and cultured endothelial cells.
Main Methods:
- Cultured bovine aortic and atrial endothelial cells were stimulated, and .NO release was detected via chemiluminescence.
- Electron Paramagnetic Resonance (EPR) spin trapping was used to analyze reactions in SIN-1 solutions.
- The effects of superoxide dismutase (SOD) and various nitroxides (TEMPOL, 3-carboxy-proxyl, 3-ethoxycarbonyl-proxyl) were assessed.
Main Results:
- Nitroxides and SOD increased the .NO chemiluminescence signal in endothelial cells.
- The enhancement of .NO levels by nitroxides was dose-dependent, with optimal efficacy at 30-100 microM.
- EPR studies indicated that SOD and TEMPOL accelerated O-2 dismutation, increasing hydroxyl radical (.OH) adduct formation.
Conclusions:
- The superoxide dismutase-mimetic activity of nitroxides contributes to increased bioavailable .NO in vitro.
- Nitroxides can modulate .NO homeostasis, suggesting potential therapeutic applications in conditions involving oxidative stress and .NO dysregulation.