Expression of Inducible Nitric Oxide Synthase in the Experimental Otitis Media with Effusion

Kang, Jun Myung; Yeo, Sang Won; Chang, Ki Hong; Suh, Byung Do

Abstract

BACKGROUND AND OBJECTIVES: Ntric oxide (NO) is a short-lived biological mediator produced by diverse cell types, including inflammatory cells and epithelial cells. It may be cytotoxic to cells in high concentrations. Inducible nitric oxide synthase (iNOS) expressed in macrophages produce large quantities of NO in response to inflammatory stimuli such as cytokines and lipopolysaccharide. NO is now considered to be a mediator of endotoxin induced middle ear effusion (MEE). The author attempted to identify the expression of iNOS in immune mediated otitis media with effusion (OME). MATERIALS AND METHOD: Immune mediated OME was induced in rats, which were sensitized twice subcutaneously with KLH (keyhole lympet hemocyanine) and challenged with KLH into the middle ear 1 week later. We observed the development of MEE after 1, 3, 7 and 14 days following the challenge and measured nitrite (NO-2) and nitrate (NO - 3) in MEE which are oxidative product of NO. We utilized the RTPCR (reverse transcription polymerase chain reaction) technique to evaluate the presence of iNOS mRNA in MEE. The immunohistochemical method was used to identify the expression of iNOS and infiltration of macrophage in middle ear mucosa.
RESULTS
Serous MEE was developed at 3 days, and with time passed, it was changed to the mucoid type. Nitrite and nitrate were detected in MEE and iNOS mRNA was expressed in MEE. iNOS was expressed extensively with time and macrophages were diffusely infiltrated in middle ear mucosa.
CONCLUSION
NO produced by the expressed iNOS may contribute to the development of OME, and we will be able to apply the role of iNOS and macrophage to research on pathogenesis and treatment of OME.