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Role of ADP-ribosylation in activated monocytes/macrophages
S Hauschildt1, P Scheipers, W Bessler
1Institut für Zoologie Immunobiologie, Universität Leipzig.
Abstract:
Stimulating monocytes/macrophages with bacterial lipopolysaccharide (LPS) results in TNF-alpha, IL-1, IL-6 and nitrite (NO2-) formation. Inhibitors of poly(ADP-ribose)polymerase inhibit release of these mediators by preventing mRNA expression indicating that ADP-ribosylation plays a crucial role in the synthesis of these mediators. Furthermore we present evidence that ADP-ribosylation is involved in modifying cellular proteins. In murine macrophages a 33 kDa cytosolic protein could be identified that in response to LPS changed its state of ADP-ribosylation, and in human monocytes we showed that the inhibitor nicotinamide prevents LPS induced phosphorylation of two cytosolic proteins of 36 kDa and 38 kDa (p36/38) LPS. Taken together these data indicate that protein modification by ADP-ribosylation may control cellular processes involved in distinct steps of monocyte/macrophage activation.
Insights
Bacterial lipopolysaccharide (LPS) stimulates monocytes and macrophages to release inflammatory mediators. ADP-ribosylation, a protein modification process, is crucial for this activation and mediator synthesis.
Area of Science:
- Immunology
- Cellular Biology
- Biochemistry
Background:
- Monocytes and macrophages are key immune cells involved in inflammatory responses.
- Bacterial lipopolysaccharide (LPS) is a potent stimulator of these cells, leading to the release of pro-inflammatory cytokines like TNF-alpha, IL-1, and IL-6, as well as nitrite (NO2-).
- The precise molecular mechanisms controlling this inflammatory response are complex and involve post-translational modifications.
Purpose of the Study:
- To investigate the role of ADP-ribosylation in monocyte and macrophage activation.
- To identify specific cellular proteins and processes regulated by ADP-ribosylation during LPS stimulation.
- To explore the potential of targeting ADP-ribosylation pathways for modulating inflammatory responses.
Main Methods:
- Stimulation of murine macrophages and human monocytes with bacterial lipopolysaccharide (LPS).
- Treatment with inhibitors of poly(ADP-ribose)polymerase (PARP) and nicotinamide.
- Analysis of mRNA expression for inflammatory mediators.
- Identification and characterization of modified cytosolic proteins using biochemical techniques.
Main Results:
- Inhibitors of poly(ADP-ribose)polymerase (PARP) suppressed the release of inflammatory mediators by preventing mRNA expression.
- ADP-ribosylation was shown to modify cellular proteins in response to LPS.
- A 33 kDa cytosolic protein in murine macrophages exhibited altered ADP-ribosylation states upon LPS stimulation.
- Nicotinamide prevented LPS-induced phosphorylation of 36 kDa and 38 kDa cytosolic proteins (p36/38) in human monocytes.
Conclusions:
- ADP-ribosylation plays a critical role in the synthesis and release of inflammatory mediators from monocytes/macrophages stimulated by LPS.
- Protein modification via ADP-ribosylation is involved in regulating distinct steps of monocyte and macrophage activation.
- These findings suggest that ADP-ribosylation pathways represent potential targets for therapeutic intervention in inflammatory conditions.