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Lipid peroxides in middle ear fluid after acute otitis media in guinea pigs
1Division of Pediatric Otolaryngology-Head and Neck Surgery, Columbia-Presbyterian Medical Center, Babies and Children's Hospital, New York, New York 10032, USA.
Abstract:
Oxygen free radical damage has been demonstrated in the middle ear mucosa of a guinea pig model of acute otitis media (AOM). Potential sources of free radicals include both neutrophils responding to infection and Streptococcus pneumoniae, a common AOM pathogen. This project was conducted to examine the middle ear fluid in a guinea pig model of AOM for evidence of elevated lipid peroxide (LPO) as a marker of free radical damage. Twenty-one guinea pigs were injected transtympanically with bacteria into the left (infected) middle ear cavity and sterile saline into the right (control) middle ear. Middle ear fluid was recovered on postoperative day 5. The fluid was weighed and analyzed for quantity of LPO. Results indicated an increased absolute level of LPO, as well as an increased level of LPO divided by the weight of the fluid recovered. Histologic examination confirmed leukocyte infiltration and mucosal edema that were consistent with mucosal damage. While free radical damage to the middle ear mucosa in a guinea pig model of AOM is well documented, this is the first study to demonstrate evidence of free radical damage in middle ear fluid. These results are relevant because they correlate mucosal damage with lipoperoxidation in fluid. Additionally, this serves as an important precursor to human studies, since middle ear fluid is readily available in patients with otitis media.
Insights
This study found elevated lipid peroxide (LPO) in middle ear fluid of guinea pigs with acute otitis media (AOM), indicating free radical damage. This finding correlates mucosal damage with lipoperoxidation in middle ear fluid.
Area of Science:
- Otolaryngology
- Pathology
- Biochemistry
Background:
- Oxygen free radical damage is documented in the middle ear mucosa during acute otitis media (AOM).
- Neutrophils and Streptococcus pneumoniae are potential sources of free radicals in AOM.
- Previous studies focused on mucosal damage, not middle ear fluid.
Purpose of the Study:
- To investigate middle ear fluid for evidence of lipid peroxide (LPO) as a marker of free radical damage in an AOM guinea pig model.
- To correlate LPO levels in middle ear fluid with observed mucosal damage.
- To establish a precursor for human studies on otitis media.
Main Methods:
- Transtympanic bacterial injection into the left middle ear and sterile saline into the right (control) of 21 guinea pigs.
- Recovery and weighing of middle ear fluid on postoperative day 5.
- Analysis of middle ear fluid for LPO quantity and LPO/weight ratio; histologic examination for leukocyte infiltration and mucosal edema.
Main Results:
- Significantly increased absolute LPO levels were found in the infected middle ear fluid.
- Elevated LPO levels normalized by fluid weight were also observed.
- Histology confirmed leukocyte infiltration and mucosal edema consistent with mucosal damage.
Conclusions:
- This study provides the first evidence of free radical damage, indicated by LPO, within middle ear fluid in an AOM model.
- The findings correlate mucosal damage with lipoperoxidation in middle ear fluid.
- This research is a crucial step towards understanding and potentially treating human otitis media by analyzing readily available middle ear fluid.