Effects of middle ear effusion on neutrophil function

Interleukin-8 gene expression in middle ear effusions

Interleukin-8 (IL-8), a monocyte- and macrophage-derived cytokine, displays potent chemotactic-activating properties toward neutrophils, and thus may contribute to the pathogenesis of otitis media with effusion (OME). The objective of this investigation was to demonstrate the expression of the IL-8 gene in middle ear effusion (MEEs) of children and adults with OME. Ribonucleic acids (RNAs) were extracted from MEEs from 16 ears of 13 pediatric patients and 12 ears of 12 adult patients with OME. The RNAs were reverse-transcribed and amplified by the polymerase chain reaction. Interleukin-8 transcripts were detected in 75% of both pediatric (12/16) and adult MEEs (9/12). The levels of expression of IL-8 and beta-actin messenger RNAs were quantitated. No significant difference was observed in IL-8/beta-actin ratios between pediatric MEEs and adult MEEs. These data suggest that IL-8 may contribute to neutrophil involvement in both pediatric and adult OME.

Effects of endotoxin and neutrophil lysate on experimental otitis media with effusion in cats

Middle ear effusion (MEE) from otitis media with effusion (OME) contains large amounts of chemical mediators and substances from bacteria, which may act on the mucosa itself and cause further changes in the inflamed mucosa and MEE. To clarify the effects of such substances in MEE, we instilled endotoxin (LPS) or allogeneic neutrophil lysate (NL) into the middle ear cavity of OME induced by Eustachian tube obstruction (ETO). ETO + LPS and ETO + NL groups showed retention of a large amount of MEE as a characteristic difference between ETO alone group and these groups. The instillation of LPS into the middle ear cavity of the ETO model significantly increased the number of total cells and the ratio of the concentrations of albumin to total protein in MEEs. The instillation of NL significantly increased the number of goblet cells in the middle ear. These facts indicate that the pathology of OME may change in response to various factors added to MEE. Hence, we propose that a vicious circle of self-mediated inflammation is a possible causative factor for chronic OME.

Otitis media induced by inoculation of a chemotactic factor

Phagocytic cells in middle ear effusion obtained from patients with acute or chronic otitis media, have antibacterial activity which is an element of the host defense system. In addition, they modify inflammatory responses as they release degranulated substances, phospholipid-derived substances, and active oxygens. To demonstrate both the direct and indirect biological activities of chemotactic factor through migrating inflammatory phagocytic cells in acute otitis media, a synthetic chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (fmlp), was inoculated into the middle ear of guinea pigs. Fmlp induced severe vascular damage, mucosal edema, and infiltration of phagocytic cells 1 and 3 days after inoculation and interstitial fibrosis and calcification 2 weeks after inoculation. Chemotactic factor in the middle ear cavity caused middle ear tissue damage and may play a role in the development of acute and chronic otitis media.