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Bacterial lipopeptides induce nitric oxide synthase and promote apoptosis through nitric oxide-independent pathways
F Terenzi1, M J Díaz-Guerra, M Casado
1Instituto de Bioquímica (CSIC-UCM), Facultad de Farmacia, Universidad Complutense, Madrid, Spain.
Abstract:
Stimulation of resident peritoneal macrophages with S-[2,3-bis(pamitoyloxy)-(2R,2S)-propyl]-N-palmytoyl-(R)-C ysSerLys4 or S(-)[2,3-bis(pamitoyloxy)-(2R,2S)-propyl]-N-palmytoyl-(R)-++ +CysAlaLys4, two synthetic bacterial lipopeptides, promoted the expression of the inducible form of nitric oxide synthase, exhibiting a temporal pattern of nitric oxide release that was delayed with respect to the induction elicited by bacterial lipopolysaccharide. Treatment of macrophages with genistein blocked the nitric oxide synthesis triggered by the lipopeptides or lipopolysaccharide. Simultaneous incubation with lipopolysaccharide and lipopeptide resulted in an antagonistic effect on nitric oxide synthase mRNA levels and on nitrite plus nitrate release to the medium. Triggering with bacterial lipopeptides induced macrophage programmed cell death. In macrophages activated with lipopeptide, apoptosis was observed even in the absence of nitric oxide synthesis, therefore indicating the existence of alternative pathways in the control of programmed cell death in these cells.
Insights
Synthetic bacterial lipopeptides stimulate macrophages to release nitric oxide and induce programmed cell death. Genistein inhibits this nitric oxide synthesis, while lipopolysaccharide and lipopeptide show antagonistic effects.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Macrophages play a crucial role in the innate immune response.
- Nitric oxide synthase (NOS) is a key enzyme in immune signaling.
- Bacterial lipopeptides are potent immune modulators.
Purpose of the Study:
- To investigate the effects of synthetic bacterial lipopeptides on macrophage activation.
- To elucidate the role of nitric oxide synthesis in lipopeptide-induced macrophage responses.
- To explore the mechanisms of lipopeptide-induced programmed cell death in macrophages.
Main Methods:
- Macrophage stimulation with synthetic lipopeptides and bacterial lipopolysaccharide.
- Measurement of nitric oxide release and nitric oxide synthase expression.
- Inhibition studies using genistein.
- Analysis of apoptosis using specific assays.
Main Results:
- Lipopeptides induced inducible nitric oxide synthase expression and nitric oxide release with a delayed pattern compared to lipopolysaccharide.
- Genistein inhibited lipopeptide- and lipopolysaccharide-induced nitric oxide synthesis.
- Lipopolysaccharide and lipopeptides exhibited antagonistic effects on nitric oxide synthase mRNA levels and nitric oxide release.
- Bacterial lipopeptides induced macrophage programmed cell death, occurring independently of nitric oxide synthesis.
Conclusions:
- Synthetic bacterial lipopeptides are potent activators of macrophages, leading to nitric oxide production and programmed cell death.
- Nitric oxide synthesis is involved in lipopeptide-mediated macrophage responses but is not essential for lipopeptide-induced apoptosis.
- Alternative pathways contribute to the regulation of programmed cell death in lipopeptide-activated macrophages.