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The effects of hyperoxia on pulmonary clearance of Pseudomonas aeruginosa
Abstract:
Among the toxic effects of hyperoxia may be impaired pulmonary clearance of gram-negative bacteria. To better define this effect, we exposed BALB/c mice to 100% O2 for 24, 48, or 72 hr and intrabronchially inoculated them with 10(6) Pseudomonas aeruginosa. Clearance was assessed 4 hr later by quantitative lung cultures of air- and O2-exposed mice. Clearance was first reduced at 48 and 72 hr in mice exposed to O2. To determine the mechanism responsible, we measured bronchoalveolar lavage neutrophil (PMN) counts and neutrophil chemotactic activity at 0, 2, and 4 hr after instillation of P. aeruginosa into mice first exposed to air or O2 for 48 hr. Air-exposed mice had more PMNs than did O2-exposed mice after challenge (13.3 +/- 2.1 X 10(5) vs. 4.4 +/- 0.6 X 10(5)). There was no difference in neutrophil chemotactic activity between air- and O2-exposed mice at any time, although chemotactic activity increased in both groups after challenge. Our data suggest that hyperoxia impairs pulmonary clearance of P. aeruginosa by decreasing the influx of PMNs and that this effect is not due to diminished chemotactic activity in bronchoalveolar lavage fluid.
Insights
High oxygen levels impair the lungs' ability to clear Pseudomonas aeruginosa infections. This is due to reduced neutrophil influx, not changes in chemotactic activity.
Area of Science:
- Pulmonary immunology
- Microbiology
- Toxicology
Background:
- Hyperoxia (exposure to high oxygen concentrations) can have toxic effects on the lungs.
- Impaired pulmonary clearance of gram-negative bacteria is a potential toxic effect of hyperoxia.
Purpose of the Study:
- To investigate the effect of hyperoxia on the pulmonary clearance of Pseudomonas aeruginosa.
- To determine the underlying mechanism responsible for any observed changes in bacterial clearance.
Main Methods:
- BALB/c mice were exposed to 100% oxygen for 24, 48, or 72 hours.
- Mice were inoculated with Pseudomonas aeruginosa, and bacterial clearance was assessed via quantitative lung cultures.
- Bronchoalveolar lavage neutrophil counts and chemotactic activity were measured in air- vs. oxygen-exposed mice.
Main Results:
- Bacterial clearance was significantly reduced in mice exposed to oxygen for 48 and 72 hours.
- Oxygen-exposed mice showed significantly lower neutrophil counts in bronchoalveolar lavage fluid after bacterial challenge.
- No significant difference in neutrophil chemotactic activity was observed between air- and oxygen-exposed mice.
Conclusions:
- Hyperoxia impairs pulmonary clearance of Pseudomonas aeruginosa.
- This impairment is associated with a decreased influx of neutrophils into the lungs.
- The mechanism does not involve diminished chemotactic activity in bronchoalveolar lavage fluid.