Neutrophil oxygen metabolite inhibition of cultured chinchilla middle ear epithelial cell growth
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M Kawana1, C Kawana, R Amesara
1Otitis Media Research Center, University of Minnesota School of Medicine, Minneapolis.
Abstract:
Middle ear inflammation in acute bacterial otitis media is characterized by accumulation of neutrophils in middle ear effusion. Since neutrophils release products that may injure surrounding tissues, we studied the effect of neutrophil metabolic products on middle ear epithelial cells (MEECs) in vitro. Chinchilla MEECs were incubated with phorbol myristate acetate (PMA)-activated human neutrophils or with hydrogen peroxide (H2O2). Cell growth, which was measured by 3H-thymidine incorporation, was inhibited by activated neutrophils and by H2O2. Unstimulated neutrophils, PMA alone, and catalase alone did not affect the viability of MEECs. Catalase, an enzyme that reduces H2O2, partially blocked the inhibitory effect of activated neutrophils and completely blocked the inhibitory effect of H2O2. Inhibition of MEEC metabolism by neutrophil-reactive oxygen species may contribute to epithelial injury, which may prolong the middle ear inflammatory response and lead to chronic tissue damage.
Insights
Neutrophil metabolic products, like hydrogen peroxide, inhibit middle ear epithelial cell growth. This finding suggests reactive oxygen species contribute to inflammation and potential chronic damage in otitis media.
Area of Science:
- Otolaryngology
- Cell Biology
- Immunology
Background:
- Acute bacterial otitis media involves neutrophil accumulation in middle ear effusions.
- Neutrophils release substances that can harm surrounding tissues.
Purpose of the Study:
- To investigate the impact of neutrophil metabolic products on middle ear epithelial cells (MEECs) in vitro.
- To determine the role of reactive oxygen species in MEEC injury during otitis media.
Main Methods:
- Chinchilla MEECs were exposed to phorbol myristate acetate (PMA)-activated human neutrophils or hydrogen peroxide (H2O2).
- Cell growth was quantified using 3H-thymidine incorporation.
- The effect of catalase on H2O2-mediated inhibition was assessed.
Main Results:
- Activated neutrophils and H2O2 significantly inhibited MEEC growth.
- Unstimulated neutrophils, PMA, and catalase alone did not affect MEEC viability.
- Catalase partially blocked the inhibitory effect of activated neutrophils and fully blocked H2O2's effect.
Conclusions:
- Neutrophil-derived reactive oxygen species can inhibit MEEC metabolism and cause epithelial injury.
- This injury may prolong middle ear inflammation and lead to chronic tissue damage in otitis media.