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Macrophage-mediated N-nitrosation of thioproline and proline
1National Food Research Institute, Ibaraki, Japan.
Abstract:
Thioproline (Thiazolidine-4-carboxylic acid) and proline were nitrosated by stimulated mouse macrophages in vitro. A macrophage cell line (J774.1, 1.0 x 10(6)/well, 1 ml) was incubated with Escherichia coli lipopolysaccharide, interferon-gamma and thioproline (5 mM) or proline (5 mM). After 72 hr incubation at 37 degrees C, 4 microM N-nitrosothioproline was produced. The amount of N-nitrosoproline was much lower than that of N-nitrosothioproline. Thioproline and proline inhibited the formation of carcinogenic N-nitrosomorpholine. N-nitrosothioproline and N-nitrosoproline are found as major N-nitroso compounds in human urine. Macrophage mediated N-nitrosation may contribute to the formation of these N-nitrosamino acids in the human body.
Insights
Macrophages can nitrosate thioproline (Thiazolidine-4-carboxylic acid) and proline, forming N-nitrosothioproline and N-nitrosoproline. These compounds, found in human urine, may be produced by macrophages in vivo.
Area of Science:
- Immunology
- Biochemistry
- Toxicology
Background:
- Macrophages play a role in immune responses and can produce reactive nitrogen species.
- N-nitroso compounds are known carcinogens, and their formation in vivo is a concern.
- Amino acids like proline and its derivative thioproline are present in biological systems.
Purpose of the Study:
- To investigate the nitrosation of thioproline and proline by activated macrophages in vitro.
- To quantify the formation of N-nitrosothioproline and N-nitrosoproline.
- To assess the potential role of macrophages in the in vivo formation of these N-nitroso amino acids.
Main Methods:
- Incubation of a macrophage cell line (J774.1) with lipopolysaccharide and interferon-gamma.
- Addition of thioproline or proline to stimulated macrophage cultures.
- Measurement of N-nitrosothioproline and N-nitrosoproline concentrations after 72 hours.
- Assessment of the effect of thioproline and proline on N-nitrosomorpholine formation.
Main Results:
- Stimulated macrophages produced N-nitrosothioproline (4 microM) and N-nitrosoproline in vitro.
- N-nitrosothioproline formation was significantly higher than N-nitrosoproline.
- Thioproline and proline inhibited the formation of carcinogenic N-nitrosomorpholine.
- N-nitrosothioproline and N-nitrosoproline are major N-nitroso compounds found in human urine.
Conclusions:
- Activated macrophages mediate the nitrosation of thioproline and proline.
- Macrophage-mediated N-nitrosation may contribute to the endogenous formation of N-nitrosothioproline and N-nitrosoproline in humans.
- Thioproline and proline may have a protective role by inhibiting the formation of other carcinogenic N-nitroso compounds.