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Streptomyces spores from mouldy houses induce nitric oxide, TNFα and IL-6 secretion from RAW264.7 macrophage cell
M R Hirvonen1, A Nevalainen, N Makkonen
1Division of Environmental Health, National Public Health Institute, P.O. Box 95, FIN-70701 Kuopio, Finland.
Abstract:
The current view is that only bacterial lipopolysaccharide (LPS) and gamma interferon (IFNγ) are able to alone activate macrophages to secrete nitric oxide (NO), probably a causative agent of cell death. Moreover, some cytokines and gram positive pathogens together with IFNγ induce NO-production. Surprisingly, spores of Streptomyces sp., which are mesophilic gram-positive bacteria found in mouldy houses, stimulated RAW264.7 macrophages to produce pro-inflammatory cytokines, tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6), and induced the expression of inducible NO-synthase (iNOS) with a subsequent NO-production. However, the Streptomyces spores did not kill NO-producing macrophages, as did both LPS and gram negative bacteria Pseudomonas fluorescens, strong inducers of cytokine- and NO-production. These results imply that Streptomyces sp., induced cytokine and NO-secretion, may play a role in the responses evoked by exposure to these microbes. Moreover, factors other than, or in addition to NO, are necessary for cytotoxicity in murine macrophages.
Insights
Spores from Streptomyces bacteria, unlike typical immune activators, stimulate macrophages to produce nitric oxide (NO) and cytokines without causing cell death. This suggests NO alone is not responsible for macrophage cytotoxicity.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Macrophages are typically activated to produce nitric oxide (NO) by lipopolysaccharide (LPS) and gamma interferon (IFNγ).
- NO is considered a causative agent of macrophage cell death.
- Gram-positive pathogens and cytokines, along with IFNγ, can also induce NO production.
Purpose of the Study:
- To investigate the effect of Streptomyces spores on macrophage activation and nitric oxide production.
- To determine if Streptomyces spores induce cytotoxicity in macrophages.
- To explore the role of NO in microbial-induced macrophage responses.
Main Methods:
- Exposure of RAW264.7 macrophages to Streptomyces spores.
- Measurement of pro-inflammatory cytokine production (TNFα, IL-6).
- Assessment of inducible NO-synthase (iNOS) expression and subsequent NO production.
- Comparison of cytotoxicity with LPS and Pseudomonas fluorescens.
Main Results:
- Streptomyces spores stimulated RAW264.7 macrophages to produce TNFα and IL-6.
- These spores induced iNOS expression and NO production.
- Unlike LPS and Gram-negative bacteria, Streptomyces spores did not cause cell death in NO-producing macrophages.
Conclusions:
- Streptomyces spores can induce cytokine and NO secretion in macrophages.
- Factors beyond NO are necessary for macrophage cytotoxicity.
- These findings suggest a role for Streptomyces-induced responses in microbial exposure reactions.
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