Related Experiment Videos
Different roles for nitrogen monoxide and peroxynitrite in lipid peroxidation induced by activated neutrophils
J Ródenas1, T Carbonell, M T Mitjavila
1Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain.
Abstract:
We studied the roles of nitrogen monoxide (NO&z.rad;) and peroxynitrite produced by the polymorphonuclear leukocytes (PMNs) isolated from an inflammatory exudate. PMNs were incubated either in a medium with a submicromolar concentration of iron or in a diethylenetriaminepenta-acetic acid (DTPA)-containing medium, and stimulated with phorbol 12-myristate 13-acetate (PMA) to generate free radicals. In both conditions superoxide anion (O(2)(*)(-)), NO&z.rad; and peroxynitrite were produced. In the presence of arachidonic acid, malondialdehyde (MDA) was generated. This MDA was generated in one of two way; the peroxynitrite iron-independent mechanism (40%) and the Fenton reaction, caused by free iron (60%). We also observed that the addition of L-arginine was followed by a 42% reduction in MDA, which can be explained by the antioxidant effect of NO&z.rad;. These results indicate that lipid peroxidation can occur in the absence of iron, through a peroxynitrite-mediated mechanism, and that NO&z.rad; may act as an antioxidant when it is produced in large amounts.
Insights
Polymorphonuclear leukocytes (PMNs) generate nitrogen monoxide (NO) and peroxynitrite, contributing to lipid peroxidation. NO acts as an antioxidant, reducing malondialdehyde (MDA) formation, indicating its protective role in inflammation.
Area of Science:
- Biochemistry
- Immunology
- Cell Biology
Background:
- Polymorphonuclear leukocytes (PMNs) are key immune cells involved in inflammatory responses.
- The generation of reactive oxygen and nitrogen species by PMNs plays a critical role in host defense and tissue damage.
- Understanding the interplay between nitrogen monoxide (NO) and peroxynitrite in PMN function is crucial for inflammatory disease research.
Purpose of the Study:
- To investigate the roles of nitrogen monoxide (NO) and peroxynitrite produced by PMNs in lipid peroxidation.
- To elucidate the mechanisms of malondialdehyde (MDA) generation, differentiating iron-dependent and independent pathways.
- To assess the antioxidant potential of NO in the context of PMN-mediated inflammation.
Main Methods:
- Isolation of PMNs from inflammatory exudates.
- Incubation of PMNs in iron-containing or DTPA-treated media.
- Stimulation of PMNs with phorbol 12-myristate 13-acetate (PMA) to induce free radical generation.
- Measurement of superoxide anion, NO, peroxynitrite, and malondialdehyde (MDA).
- Assessment of MDA generation in the presence and absence of L-arginine.
Main Results:
- PMNs produced superoxide anion, NO, and peroxynitrite under both iron-replete and iron-depleted conditions.
- Malondialdehyde (MDA) generation occurred via an iron-independent peroxynitrite mechanism (40%) and iron-dependent Fenton reaction (60%).
- Addition of L-arginine led to a significant reduction (42%) in MDA, suggesting an antioxidant effect of NO.
Conclusions:
- Lipid peroxidation can occur independently of free iron, mediated by peroxynitrite.
- Nitrogen monoxide (NO) exhibits antioxidant properties, mitigating MDA formation when produced in substantial amounts.
- These findings highlight the complex role of NO and peroxynitrite in inflammatory processes and oxidative stress.