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Serine-protease inhibitors modulate nitric oxide-synthase activity of alveolar macrophages
P G Jorens1, F J Van Overeld, H Bult
1Department of Respiratory Medicine, University of Antwerp (UIA), Belgium.
Abstract:
Immunostimulated peritoneal macrophages of mice and rat have been demonstrated to produce L-arginine-derived nitrogen oxides. This metabolic pathway has also recently been found in rat alveolar macrophages and is suggested to play a certain role in lung injury. In vitro nitrite production from alveolar macrophages stimulated in vitro with lipopolysaccharide and recombinant interferon-gamma was inhibited by the addition of the irreversible serine-protease inhibitors, N-tosyl-L-phenylalanine chloromethyl-ketone (3 x 10(-7)-3 x 10(-4) M) and N-tosyl-L-lysine chloromethyl-ketone (3 x 10(-7)-3 x 10(-4) M) in a concentration-dependent manner. Two reversible inhibitors, N-alpha-p-tosyl-L-arginine methyl ester hydrochloride and benzoyltyrosine ethyl ester, were also effective but to a lesser extent. These antiproteases provide an opportunity to study the modulating influence on this recently discovered inflammatory pathway in alveolar phagocytic cells.
Insights
Serine protease inhibitors block L-arginine metabolism in rat alveolar macrophages, suggesting a role in lung injury. This finding offers new ways to study inflammatory pathways in lung phagocytic cells.
Area of Science:
- Immunology
- Cell Biology
- Pulmonary Medicine
Background:
- Macrophages, immune cells found in tissues, produce L-arginine-derived nitrogen oxides when stimulated.
- This pathway is implicated in lung injury and has been identified in rat alveolar macrophages.
Purpose of the Study:
- To investigate the role of serine proteases in the L-arginine metabolic pathway in rat alveolar macrophages.
- To explore the potential of protease inhibitors in modulating this inflammatory pathway.
Main Methods:
- Rat alveolar macrophages were stimulated in vitro with lipopolysaccharide and interferon-gamma.
- The effect of irreversible serine protease inhibitors (N-tosyl-L-phenylalanine chloromethyl-ketone and N-tosyl-L-lysine chloromethyl-ketone) and reversible inhibitors on nitrite production was measured.
Main Results:
- Nitrite production was inhibited by both irreversible and reversible serine protease inhibitors in a concentration-dependent manner.
- Irreversible inhibitors showed greater efficacy in blocking nitrite production compared to reversible ones.
Conclusions:
- Serine proteases play a role in the L-arginine metabolic pathway in rat alveolar macrophages.
- Protease inhibitors can modulate this pathway, offering potential therapeutic targets for lung inflammatory conditions.