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Myeloperoxidase potentiates nitric oxide-mediated nitrosation
Vijaya M Lakshmi1, William M Nauseef, Terry V Zenser
1Veterans Administration Medical Center, St. Louis, Missouri 63125, USA.
The Journal of Biological Chemistry
|November 9, 2004
Summary
Myeloperoxidase (MPO) enhances nitrosation during nitric oxide (NO) reactions, particularly at sites of inflammation. This study reveals MPO
Area of Science:
- Biochemistry
- Cell Biology
- Inflammation Research
Background:
- Nitrosation reactions, crucial for nitric oxide (NO) signaling, are influenced by inflammatory mediators.
- Myeloperoxidase (MPO), an enzyme prevalent during inflammation, plays a role in oxidative processes.
- Understanding MPO's impact on NO-mediated nitrosation is vital for comprehending biological redox signaling.
Purpose of the Study:
- To investigate the effect of myeloperoxidase (MPO) on nitrosation reactions involving nitric oxide (NO).
- To elucidate the mechanism by which MPO potentiates nitrosation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ).
- To determine the reactive species involved in MPO-dependent nitrosation in biological systems.
Main Methods:
- Nitrosation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) to 2-nitrosoamino-3-methylimidazo[4,5-f]quinoline (N-NO-IQ) was quantified using High-Performance Liquid Chromatography (HPLC).
- Reactions were conducted using NO donors (spermine NONOate) and varying concentrations of MPO, hydrogen peroxide (H2O2), and NO at pH 7.4.
- Experiments utilized inhibitors (azide, NADH) and activators (superoxide dismutase, catalase) to probe reaction mechanisms and employed MPO-deficient neutrophils.
Main Results:
- MPO significantly potentiated N-NO-IQ formation at low nitric oxide (NO) concentrations, with specific minimum effective quantities of MPO, H2O2, and NO.
- MPO-derived nitrosating species exhibited an 8.8-fold increased affinity for IQ compared to autoxidation.
- Inhibition patterns with azide and NADH suggested an oxidative nitrosylation mechanism involving MPO, distinct from NO(+) or peroxynitrite, and confirmed MPO's role in neutrophils.
Conclusions:
- Myeloperoxidase (MPO) potentiates nitrosation reactions initiated by nitric oxide (NO), especially under inflammatory conditions.
- The findings suggest MPO-derived reactive nitrogen species, not peroxynitrite, are responsible for enhanced nitrosation.
- Nitric oxide (NO) can initiate nitrosation at neutrophil infiltration sites, mediated by MPO.