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Bronchoalveolar Lavage Microvesicles Protect Burn-Injured Mice from Pulmonary Infection
Teresa C Rice1, Amanda M Pugh, Brent T Xia
1Division of Research, Department of Surgery, University of Cincinnati, Cincinnati, OH Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany.
Background:
Pseudomonas aeruginosa is a major cause of morbidity and mortality among burn patients, despite antibiotic therapy. There is a need to identify innate immune defenses that prevent P aeruginosa infection in injured adults in an effort to find therapeutic alternatives to antibiotics. Here, we tested our hypothesis that microvesicles (MVs) in bronchoalveolar (BAL) fluid have a role in the immunity of the lung in response to pathogens.
Study Design:
Microvesicles were isolated from murine BAL fluid, quantified using Nanoparticle Tracking Analysis, and injected into burn-injured mice before P aeruginosa infection. Survival was assessed and BAL bacterial loads enumerated. Neutrophil number and interleukin 6 activity were determined. Lungs were harvested and sphingosine (SPH) content analyzed via immunohistochemistry. Antimicrobial effects of MVs and SPH-enriched MVs were assessed in an in vitro assay.
Results:
Burn-injured mice have reduced BAL MV number and SPH content compared with sham. When BAL MVs from healthy mice are administered to injured mice, survival and bacterial clearance are improved robustly. We also observed that intranasal administration of MVs restores SPH levels after burn injury, MVs kill bacteria directly, and this bacterial killing is increased when the MVs are supplemented with SPH.
Conclusions:
Using a preclinical model, BAL MVs are reduced after scald injury and BAL MV restoration to injured mice improves survival and bacterial clearance. The antimicrobial mechanisms leading to improved survival include the quantity and SPH content of BAL MVs.
Insights
Microvesicles in bronchoalveolar lavage fluid are reduced in burn-injured mice. Restoring these microvesicles, especially those enriched with sphingosine, improves survival and bacterial clearance, offering a potential alternative to antibiotics.
Area of Science:
- Innate immunity
- Pulmonary defense mechanisms
- Wound healing and infection control
Background:
- Pseudomonas aeruginosa poses a significant threat to burn patients, leading to high morbidity and mortality.
- Current antibiotic therapies are insufficient, necessitating novel approaches to combat P. aeruginosa infections.
- The role of innate immune components in the lung, such as microvesicles, in preventing pathogen invasion requires further investigation.
Purpose of the Study:
- To investigate the role of microvesicles (MVs) in bronchoalveolar lavage (BAL) fluid in lung immunity against P. aeruginosa.
- To test the hypothesis that MVs contribute to host defense in burn-injured individuals.
- To explore MVs as potential therapeutic alternatives to antibiotics for P. aeruginosa infections.
Main Methods:
- Microvesicles were isolated from murine BAL fluid and characterized.
- Burn-injured mice received MVs, and outcomes like survival and bacterial load were assessed.
- Levels of sphingosine (SPH) in MVs and lung tissue were analyzed.
- In vitro assays evaluated the direct antimicrobial effects of MVs and SPH-enriched MVs.
Main Results:
- Burn injury significantly reduced the number and SPH content of BAL MVs.
- Administration of BAL MVs to injured mice markedly improved survival and reduced bacterial burden.
- Intranasal MVs restored SPH levels, exhibited direct antimicrobial activity, and enhanced bacterial killing when supplemented with SPH.
Conclusions:
- Bronchoalveolar lavage microvesicles are diminished following burn injury.
- Restoring BAL MVs in injured mice enhances survival and bacterial clearance.
- The quantity and sphingosine content of BAL MVs are key antimicrobial mechanisms contributing to improved outcomes.
