Bacterial Outer Membrane Vesicles Promote Lung Inflammatory Responses and Macrophage Activation via Multi-Signaling...

Area of Science:

• Immunology
• Microbiology
• Cell Biology

Background:

• Gram-negative bacteria release outer membrane vesicles (OMVs) implicated in inflammatory responses and organ damage.
• Previous studies suggested OMVs activate TLR2/4 pathways or induce pyroptosis, but their full role remains unclear.

Purpose of the Study:

• To investigate the complex role of bacterial OMVs in inflammatory lung responses and macrophage activation.
• To compare the effects of OMVs with lipopolysaccharide (LPS) on macrophage activation and inflammatory signaling.

Main Methods:

• Confirmed OMV release from various Gram-negative bacteria.
• Administered OMVs to mice via intratracheal instillation.
• Analyzed cytokine/chemokine profiles using mouse inflammation and autoimmune arrays.
• Utilized Toll-like receptor 4 (TLR4) knockout cells to assess OMV-mediated macrophage activation.
• Examined both cell surface and intracellular signaling pathways, including the S100-A8 pathway.

Main Results:

• OMVs from different Gram-negative bacteria induced pro-inflammatory activation in bone marrow-derived and lung alveolar macrophages.
• Intratracheal OMV instillation in mice led to significant inflammatory lung responses.
• OMVs altered multiple cytokine/chemokines, indicating broader functions than LPS.
• OMVs showed more potent macrophage activation effects than LPS, even in TLR4-deficient cells.
• Bacterial OMVs activated macrophages via both surface protein-mediated and intracellular pathways, including the S100-A8 pathway.

Conclusions:

• Bacterial OMVs strongly induce macrophage pro-inflammatory activation and inflammatory lung responses through multi-signaling pathways.
• OMVs act as a diverse set of pathogen-associated molecular patterns (PAMPs).
• OMVs exhibit more potent inflammatory effects compared to Gram-negative bacteria-derived LPS.