Abstract
Otitis media is mainly caused by upper respiratory tract infection and eustachian tube dysfunction. If external upper respiratory tract infection is not detected early in the middle ear, or an appropriate immune response does not occur, otitis media can become a chronic state or complications may occur. Therefore, given the important role of Toll-like receptors (TLRs) in the early response to external antigens, we surveyed the role of TLRs in otitis media. To summarize the role of TLR in otitis media, we reviewed articles on the expression of TLRs in acute otitis media (AOM), otitis media with effusion (OME), chronic otitis media (COM) with cholesteatoma, and COM without cholesteatoma. Many studies showed that TLRs 1–10 are expressed in AOM, OME, COM with cholesteatoma, and COM without cholesteatoma. TLR expression in the normal middle ear mucosa is absent or weak, but is increased in inflammatory fluid of AOM, effusion of OME, and granulation tissue and cholesteatoma of COM. In addition, TLRs show increased or decreased expression depending on the presence or absence of bacteria, recurrence of disease, tissue type, and repeated surgery. In conclusion, expression of TLRs is associated with otitis media. Inappropriate TLR expression, or delayed or absent induction, are associated with the occurrence, recurrence, chronicization, and complications of otitis media. Therefore, TLRs are very important in otitis media and closely related to its etiology.
Highlights
Given that immune cells in the middle ear cavity are abundantly generated during otitis media and epithelial cells and endothelial cells are present in the middle ear mucosa, TLR10, which is expressed in these cell types, is expected to play a role in otitis media, no studies have yet directly investigated this
Studies have mainly concentrated on the pathophysiology, complications and prognosis of otitis media under conditions of Toll-like receptors (TLRs) overexpression and deficiency
TLR substance related to otitis media, microorganisms, and cytokines which can lead to improved prognosis, fewer complications and early treatment of acute otitis media (AOM), otitis media with effusion (OME), and chronic otitis media (COM)
Summary
The causes of otitis media are diverse and include interactions between various factors that affect the middle ear cavity. Otitis media can be classified according to its associated clinical symptoms, otoscopic findings, duration, frequency, pathology, and complications into AOM, OME (residual or persistent effusion), and COM with or without cholesteatoma. COM without cholesteatoma causes changes in the mucosa, submucosa and surrounding bony tissue as a result of a persistent inflammatory reaction in the middle ear cavity or mastoid cavity. TLRs recognize a set of molecular modalities that are not normally found in vertebrates, allowing them to differentiate between self and pathogens and play important roles in the host’s primary defense. Activated NF-κB moves to the nucleus, where it acts as a transcription factor to induce expression of cytokines and other bioactive molecules, serving as a bridge between innate and adaptive immune responses [15,16]. We selected 26 articles satisfying search criteria for comprehensive review
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