Attenuated TLRs in middle ear mucosa contributes to susceptibility of chronic suppurative otitis media

Abstract

The variability in the recovery of otitis media (OM) is not well understood. Recent data have shown a critical role for toll-like receptors (TLRs) in inflammatory responses to bacteria. It remains unclear whether TLRs-mediated mucosal immunity plays a role in the OM recovery. The etiology, pathological profile, expression levels of TLR2, TLR4, TLR5, TLR9 and proinflammatory cytokines were measured in human middle-ear mucosae sampled from three subject groups: non-OM group, chronic otitis-media (COM) group, and chronic suppurative otitis-media (CSOM) group. Of the 72 ears, 86.11% CSOM patients were positive for bacteria. The cellular makeup of the middle ear mucosa differs among the three groups. Mucosae from the CSOM group presented chronic inflammation or suppurative inflammation in the rudimentary stroma, mainly with infiltration of monocytes and macrophages. The mRNA and protein levels of TLR2, TLR4, and TLR5 exhibited no difference between the non-OM and COM groups but were significantly lower in the CSOM group. Conversely, there was no significant difference in the TLR9 level among the three groups. Furthermore, proinflammatory cytokines TNF-α, IL-1β, IFN-γ, IL-6 were up-regulated in the CSOM group. This study provides evidence that the variability in clinical otitis media recovery might be associated with the variability in the expression of mucosal TLRs. Reduced TLR levels in the middle-ear mucosa might cause weak host response to bacteria, persistent inflammation and susceptibility to CSOM.

Keywords: Otitis media; Recovery; TLR.