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Tryptophan availability selectively limits NO-synthase induction in macrophages
Alberto Chiarugi1, Elisabetta Rovida, Persio Dello Sbarba
1Department of Preclinical and Clinical Pharmacology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy.
Journal of Leukocyte Biology
|January 15, 2003
Summary
Reduced tryptophan availability impacts immune responses. Low tryptophan levels in macrophages significantly decrease nitric oxide synthesis but do not affect tumor necrosis factor alpha release when activated by interferon-gamma.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Interferon-gamma (IFN-gamma) activates macrophages, increasing nitric oxide (NO) and tumor necrosis factor alpha (TNF-alpha) production.
- IFN-gamma also induces indoleamine-2,3-dioxygenase, initiating tryptophan (TRP) breakdown via the kynurenine pathway, thus lowering local TRP levels.
Purpose of the Study:
- To investigate how varying tryptophan availability affects NO and TNF-alpha synthesis and release in IFN-gamma-activated murine macrophages.
- To understand the role of TRP catabolism in modulating immune cell function.
Main Methods:
- Utilized the BAC1.2F5 murine macrophage cell line.
- Stimulated macrophages with IFN-gamma (100 U/ml).
- Measured NO and TNF-alpha production and assessed TRP levels in culture media under varying TRP concentrations.
Main Results:
- IFN-gamma activation increased NO and TNF-alpha synthesis and release, alongside induced indoleamine-2,3-dioxygenase and reduced TRP.
- In TRP-depleted conditions, IFN-gamma-induced NO synthase induction was significantly diminished.
- TNF-alpha synthesis and release remained unaffected by TRP starvation.
Conclusions:
- Local tryptophan availability is a critical factor influencing macrophage function.
- Reduced TRP levels can selectively impair NO production while preserving TNF-alpha responses in activated macrophages.
- These findings suggest TRP availability may modulate the overall outcome of immune responses.