Toll-Like Receptors 2 and 4 Modulate Pulmonary Inflammation and Host Factors Mediated by Outer Membrane Vesicles
Chad R Marion1, Jaewook Lee2, Lokesh Sharma1
1Section of Pulmonary, Critical Care and Sleep Medicine, Yale University School of Medicine, New Haven, Connecticut, USA.
Abstract:
Pneumonia due to Gram-negative bacteria is associated with high mortality. Acinetobacter baumannii is a Gram-negative bacterium that is associated with hospital-acquired and ventilator-associated pneumonia. Bacteria have been described to release outer membrane vesicles (OMVs) that are capable of mediating systemic inflammation. The mechanism by which A. baumannii OMVs mediate inflammation is not fully defined. We sought to investigate the roles that Toll-like receptors (TLRs) play in A. baumannii OMV-mediated pulmonary inflammation. We isolated OMVs from A. baumannii cultures and intranasally introduced the OMVs into mice. Intranasal introduction of A. baumannii OMVs mediated pulmonary inflammation, which is associated with neutrophil recruitment and weight loss. In addition, A. baumannii OMVs increased the release of several chemokines and cytokines in the mouse lungs. The proinflammatory responses were partially inhibited in TLR2- and TLR4-deficient mice compared to those of wild-type mice. This study highlights the important roles of TLRs in A. baumannii OMV-induced pulmonary inflammation in vivo.
Insights
Acinetobacter baumannii outer membrane vesicles cause lung inflammation in mice. Toll-like receptors 2 and 4 play a role in this inflammatory response, highlighting their importance in pneumonia.
Area of Science:
- Immunology
- Microbiology
- Pulmonary Medicine
Background:
- Gram-negative bacterial pneumonia, particularly from Acinetobacter baumannii, leads to high mortality.
- Acinetobacter baumannii is a common cause of hospital-acquired and ventilator-associated pneumonia.
- Bacterial outer membrane vesicles (OMVs) can trigger systemic inflammation, but their role in A. baumannii-induced pulmonary inflammation is not fully understood.
Purpose of the Study:
- To investigate the role of Toll-like receptors (TLRs) in Acinetobacter baumannii OMV-mediated pulmonary inflammation.
- To elucidate the mechanisms by which A. baumannii OMVs induce inflammation in the lungs.
Main Methods:
- Isolation of OMVs from Acinetobacter baumannii cultures.
- Intranasal administration of A. baumannii OMVs into a mouse model.
- Assessment of pulmonary inflammation, including neutrophil recruitment and weight loss.
- Measurement of chemokine and cytokine release in mouse lungs.
- Comparison of inflammatory responses in wild-type versus TLR2- and TLR4-deficient mice.
Main Results:
- Intranasal administration of A. baumannii OMVs induced pulmonary inflammation, characterized by neutrophil influx and weight loss in mice.
- A. baumannii OMVs significantly increased the release of pro-inflammatory cytokines and chemokines in the lungs.
- The inflammatory responses triggered by A. baumannii OMVs were partially attenuated in mice lacking Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4).
Conclusions:
- Toll-like receptors, specifically TLR2 and TLR4, are crucial mediators of pulmonary inflammation induced by Acinetobacter baumannii OMVs in vivo.
- Understanding the role of TLRs in OMV-mediated inflammation provides insights into the pathogenesis of A. baumannii pneumonia.
- Targeting TLR signaling pathways could represent a potential therapeutic strategy for managing Gram-negative bacterial pneumonia.
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