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Nitric oxide mediates the microbicidal activity of eosinophils
S H Oliveira1, S G Fonseca, P R Romão
1Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brazil.
Memorias Do Instituto Oswaldo Cruz
|January 1, 1997
Summary
Nitric oxide (NO) plays a crucial role in the microbicidal activity of eosinophils (EO) against Leishmania major. Activated eosinophils release NO, which is essential for killing these parasites, as demonstrated by blocking experiments.
Area of Science:
- Immunology
- Parasitology
- Biochemistry
Background:
- Nitric oxide (NO) is recognized for its role in macrophage microbicidal activity against intracellular pathogens.
- Eosinophils (EO) possess known microbicidal capabilities against various parasites, including Leishmania species.
Purpose of the Study:
- To investigate the involvement of nitric oxide (NO) in the microbicidal activity of eosinophils (EO) against Leishmania major.
Main Methods:
- Eosinophils were harvested from rats and cultured.
- Nitrite release was measured spontaneously and after IFN-gamma activation.
- The effect of the NO synthase inhibitor L-NIO on nitrite release and parasite killing was assessed.
- Leishmanicidal activity was determined by evaluating parasite [(3)H] thymidine incorporation after incubation with activated eosinophils.
Main Results:
- Eosinophils spontaneously released small amounts of nitrite, enhanced by IFN-gamma.
- IFN-gamma-activated eosinophils demonstrated significant killing of Leishmania major.
- Both parasite killing and nitrite release by activated eosinophils were completely inhibited by L-NIO.
- Activated eosinophils released substantial levels of nitrite during parasite killing.
Conclusions:
- Activated eosinophils release nitric oxide (NO).
- This NO release is involved in the microbicidal activity of eosinophils against Leishmania major.
- These findings highlight a novel mechanism of parasite defense involving eosinophils and NO.