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Oxidative metabolic products released from polymorphonuclear leukocytes in middle ear fluid during experimental
1Otitis Media Research Center, University of Minnesota, School of Medicine, Minneapolis 55455.
Abstract:
To determine whether oxidative metabolic products of phagocytic cells are present in the middle ear during experimental pneumococcal otitis media, we measured the concentration of myeloperoxidase (MPO) in middle ear fluid (MEF) and the capacity of neutrophils isolated from MEF and peripheral blood to produce MPO and superoxide anion (O2-) after in vitro stimulation. Free MPO in MEF was significantly increased 24 and 48 h after either viable or nonviable pneumococci were inoculated into the middle ear. In vitro-stimulated production of MPO and O2- from middle ear neutrophils was significantly less than that from peripheral blood neutrophils 24 h after nonviable pneumococci were inoculated but similar to it after 48 h. Twenty-four hours after viable pneumococci were inoculated, middle ear neutrophils stimulated in vitro produced less MPO but the same amount of O2- as did blood neutrophils. Oxidative metabolic products, therefore, are released from phagocytic cells into the MEF during pneumococcal otitis media, and future studies will need to define the contribution of these products to acute and chronic middle ear tissue injury.
Insights
Oxidative metabolic products are present in middle ear fluid during pneumococcal otitis media. Phagocytic cells release these products, potentially contributing to middle ear tissue injury.
Area of Science:
- Immunology
- Otolaryngology
- Microbiology
Background:
- Otitis media is a common middle ear infection.
- Phagocytic cells, like neutrophils, play a role in the immune response.
- Oxidative stress is implicated in tissue damage during infections.
Purpose of the Study:
- To investigate the presence of oxidative metabolic products in the middle ear during experimental pneumococcal otitis media.
- To quantify myeloperoxidase (MPO) levels in middle ear fluid (MEF).
- To assess the oxidative capacity of neutrophils from MEF and peripheral blood.
Main Methods:
- Experimental pneumococcal otitis media model in animals.
- Measurement of MPO concentration in MEF.
- Isolation and in vitro stimulation of neutrophils from MEF and peripheral blood.
- Assay for MPO and superoxide anion (O2-) production.
Main Results:
- Free MPO levels in MEF were significantly elevated 24 and 48 hours post-pneumococcal inoculation.
- Neutrophils from MEF showed reduced MPO and O2- production compared to blood neutrophils at 24 hours after nonviable pneumococci.
- At 48 hours, MEF neutrophil oxidative capacity became similar to blood neutrophils.
- MEF neutrophils produced less MPO but similar O2- compared to blood neutrophils after viable pneumococci inoculation.
Conclusions:
- Oxidative metabolic products are released into the MEF by phagocytic cells during pneumococcal otitis media.
- These products may contribute to acute and chronic middle ear tissue injury.
- Further research is needed to define the specific contribution of these products to otitis media pathogenesis.
