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Expression of inducible nitric oxide synthase (iNOS) in middle ear epithelial cells by IL-1beta and TNF-alpha

W Li1, J Lin, G L Adams

  • 1Department of Otolaryngology, School of Medicine, University of Minnesota, Minneapolis, MN 55455, USA.

International Journal of Pediatric Otorhinolaryngology
|September 28, 2000
PubMed
Abstract

Insights

Middle ear epithelial cells (MEEC) express inducible nitric oxide synthase (iNOS) when stimulated by cytokines IL-1beta and TNF-alpha. This finding clarifies a mechanism for nitric oxide (NO) release in the middle ear.

Area of Science:

  • Otorhinolaryngology
  • Immunology
  • Molecular Biology

Background:

  • Nitric oxide (NO) plays a role in mucoid middle ear effusion (MMEE).
  • The precise mechanism of NO regulation in the middle ear remains unclear.
  • Middle ear epithelial cells (MEEC) are a potential source of NO.

Purpose of the Study:

  • To identify and localize inducible nitric oxide synthase (iNOS) in middle ear epithelium.
  • To investigate the effect of cytokines IL-1beta and TNF-alpha on iNOS expression in rat MEEC.
  • To elucidate the regulatory mechanisms of iNOS in the middle ear.

Main Methods:

  • In vitro study: Cultured rat MEEC were stimulated with IL-1beta, TNF-alpha, or PBS.
  • In vivo study: Rats were inoculated with IL-1beta, TNF-alpha, or PBS.
  • iNOS mRNA and protein expression were analyzed using RT-PCR, immunocytochemistry, and Western blot.

Main Results:

  • Cultured MEEC treated with IL-1beta or TNF-alpha expressed iNOS mRNA and protein.
  • iNOS protein was detected in middle ear mucosa of rats treated with IL-1beta and TNF-alpha.
  • Untreated MEEC and control groups showed no detectable iNOS expression.

Conclusions:

  • Rat MEEC can express iNOS.
  • Cytokines IL-1beta and TNF-alpha induce iNOS expression in MEEC.
  • This study demonstrates a mechanism for NO production in the middle ear epithelium.

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