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Activation of nuclear factor-kappaB in macrophages by mycoplasmal lipopeptides
1Immunobiology Research Group, Gesellschaft für Biotechnologische Forschung mbH, Braunschweig, Germany.
Abstract:
Mycoplasmas are potent macrophage stimulators. The active principle are lipopeptides or lipoproteins with a characteristic N-terminal S-[dihydroxypropyl]-cysteinyl group bearing two ester-bound fatty acids and lacking the amide-bound one common to other bacterial lipoproteins. Using synthetic analogues of mycoplasmal lipopeptides, we investigated activation of the transcription factor NF-kappaB in the C3H/HeJ mouse-derived DMBM-3 cell line. The lipopeptides activated NF-kappaB at below nanomolar concentrations. Activation in the murine system occurred distinctly earlier than TNF-alpha liberation, excluding autocrine stimulation by TNF-alpha. As determined from a supershift experiment, the active NF-kappaB complex consisted of the heterodimer p50/p65(RelA). The relevance of these findings for the inflammatory response to mycoplasmas and for mycoplasma-mediated effects on HIV-infected macrophages is discussed.
Insights
Mycoplasmal lipopeptides potently activate the NF-kappaB transcription factor in macrophages at nanomolar concentrations. This early activation precedes tumor necrosis factor-alpha release, highlighting a direct inflammatory pathway.
Area of Science:
- Immunology
- Microbiology
- Molecular Biology
Background:
- Mycoplasmas are known potent stimulators of macrophages.
- Their active components are lipopeptides/lipoproteins with unique N-terminal structures.
- These structures differ from typical bacterial lipoproteins.
Purpose of the Study:
- To investigate the activation of the transcription factor NF-kappaB by mycoplasmal lipopeptides.
- To understand the early molecular events in macrophage activation by mycoplasmas.
- To elucidate the composition of the activated NF-kappaB complex.
Main Methods:
- Utilized synthetic analogues of mycoplasmal lipopeptides.
- Studied activation of NF-kappaB in the DMBM-3 cell line (C3H/HeJ mouse origin).
- Performed supershift experiments to identify NF-kappaB complex components.
Main Results:
- Mycoplasmal lipopeptides activated NF-kappaB at sub-nanomolar concentrations.
- NF-kappaB activation occurred earlier than TNF-alpha liberation, ruling out autocrine TNF-alpha stimulation.
- The active NF-kappaB complex was identified as the p50/p65(RelA) heterodimer.
Conclusions:
- Mycoplasmal lipopeptides are direct and potent activators of NF-kappaB.
- This early activation is a key event in the inflammatory response to mycoplasmas.
- Findings are relevant to understanding mycoplasma-induced inflammation and effects on HIV-infected macrophages.