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Middle ear epithelium has inflammatory capacity
L P Schousboe1, T Ovesen, C B Pedersen
1Department of Otorhinolaryngology, Aarhus University Hospital, Denmark.
Abstract:
Endotoxin, tumour necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and intercellular adhesion molecule-1 (ICAM-1) were detected in 88%, 51%, 58% and 66% of 152 middle ears from patients suffering from otitis media with effusion. In this study the hypothesis that bacterial endotoxin, TNF-alpha, IL-1 beta and ICAM-1 induce the inflammatory process characteristic of otitis media with effusion was tested. Cultures of rabbit middle ear epithelium were exposed to endotoxin, TNF-alpha or IL-1 beta. The expression of ICAM-1 on the cell surfaces was measured with a direct enzyme-linked immunosorbent assay on the cell layer. For TNF-alpha, 5 ng/ml significantly increased ICAM-1 expression, whereas 100 ng/ml had a toxic effect. For IL-1 beta, as little as 1 ng/ml produced a significant increase in ICAM-1 expression. Endotoxin stimulated ICAM-1 expression less strongly in concentrations from 100 ng/ml to 100 micrograms/ml. The findings indicate that stimulation of ICAM-1 by endotoxin is mediated, at least in part, by TNF-alpha and IL-1 beta. It is concluded that endotoxin induces sustained inflammation in OME, and that this inflammation is mediated, at least in part, by the primary cytokines TNF-alpha and IL-1 beta.
Insights
Bacterial endotoxin triggers inflammation in otitis media with effusion (OME) by increasing intercellular adhesion molecule-1 (ICAM-1) expression, primarily through tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta).
Area of Science:
- Otolaryngology
- Immunology
- Molecular Biology
Background:
- Otitis media with effusion (OME) is characterized by inflammation involving endotoxin, tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and intercellular adhesion molecule-1 (ICAM-1).
- These molecules were detected in a significant percentage of middle ear samples from OME patients.
Purpose of the Study:
- To test the hypothesis that bacterial endotoxin, TNF-alpha, IL-1 beta, and ICAM-1 induce the inflammatory process in OME.
- To investigate the role of TNF-alpha and IL-1 beta in mediating endotoxin-induced ICAM-1 expression.
Main Methods:
- Rabbit middle ear epithelial cell cultures were exposed to endotoxin, TNF-alpha, or IL-1 beta.
- Intercellular adhesion molecule-1 (ICAM-1) expression was quantified using a direct enzyme-linked immunosorbent assay (ELISA).
Main Results:
- Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) significantly increased ICAM-1 expression in a dose-dependent manner.
- Endotoxin also stimulated ICAM-1 expression, though less potently than the cytokines.
- The findings suggest that endotoxin-induced ICAM-1 stimulation is mediated, at least partially, by TNF-alpha and IL-1 beta.
Conclusions:
- Bacterial endotoxin induces sustained inflammation in otitis media with effusion (OME).
- This inflammation is significantly mediated by the primary cytokines TNF-alpha and IL-1 beta.
- Targeting these inflammatory mediators may offer therapeutic strategies for OME.