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Reactive nitrogen intermediates and antimicrobial activity: role of nitrite
1Department of Medicine, University of Washington, Seattle 98195.
Free Radical Biology & Medicine
|April 1, 1993
Summary
Nitrite (NO2-) exhibits dual roles in antimicrobial activity. It can act as a toxic agent or inhibit essential peroxidase-mediated systems, influencing bacterial response to reactive nitrogen intermediates.
Area of Science:
- Microbiology
- Biochemistry
Background:
- Reactive nitrogen intermediates (RNI) like nitric oxide (NO) are formed from L-arginine.
- Secondary reactions produce nitrite (NO2-) and nitrate, which also possess toxic properties.
Purpose of the Study:
- To investigate the complex role of nitrite (NO2-) in antimicrobial activity.
- To explore how nitrite interacts with hydrogen peroxide (H2O2) and peroxidases.
Main Methods:
- Studied the bactericidal effects of nitrous acid (HNO2)/nitrite (NO2-) on Escherichia coli at acid pH.
- Assessed the impact of H2O2, peroxidase (myeloperoxidase [MPO], eosinophil peroxidase, lactoperoxidase), and catalase on these reactions.
- Examined the interaction of nitrite with MPO and hypochlorous acid (HOCl).
Main Results:
- Nitrous acid (HNO2) showed bactericidal activity against E. coli, enhanced by H2O2.
- Peroxidases and catalase conferred bactericidal activity when HNO2/NO2- and H2O2 alone were ineffective.
- Nitrite paradoxically inhibited MPO and HOCl activity through complex formation and reaction.
Conclusions:
- Nitrite (NO2-) is not merely an end product of RNI formation.
- Nitrite can act as a source of toxic agents or inhibit crucial antimicrobial systems.
- Understanding nitrite's dual role is vital for comprehending host defense mechanisms.