Effect of inflammatory mediators of otitis media and otic drops on morphology of isolated cochlear outer hair cells: Review and update

Abstract

Biochemical or chemical substances in the middle ear cavity can affect inner ear function. Among them, inflammatory mediators (IMs) in the middle ear effusion may induce sensorineural hearing loss (SNHL). Otic drops used for otorrhea m the presence of tympanostomy tubes or tympanic membrane perforation may also cause SNHL. The purpose of this study was to determine ototoxicity of IMs of otitis media and common otic drops using isolated cochlear outer hair cells (OHCs) in vitro. OHCs from cochleae of adult chinchilla were isolated and exposed to standard bathing solution (SBS) (control group), albumin-phosphate buffer saline solution (albumin control), various IMs, and otic drops. All experiments were performed at an osmolality of 305 ± 5 mOsm, room temperature, and for 60 minutes. The cells were observed with inverted microscope; images were stored and analyzed on the IMAGE PRO-plus program. The change in cell length of OHCs exposed to cyclooxygenase metabolites and the albumin control were not significantly different from the SBS control group (p > 0.05). The OHCs in the lipoxygenase metabolites, platelet activating factor, tumor necrosis factor-α, histamine, nitric oxide donor compound, 3-morpholinosynonimine (SIN-1) and S-nitroso-N-acetyl-L-penicillamine (SNAP) groups demonstrated significant shortening (p < 0.05). Among the otic drops, Vosol was the most toxic and CiproHC was the least toxic to OHCs. The GM with liver extract group was significantly more cytotoxic than the GM alone group. This study demonstrated that IMs of otitis media and otic drops can change the morphology of OHCs in vitro and suggests the involvement of these IMs and otic drops in the pathogenesis of SNHL observed in patients with chronic otitis media.