iNOS Expression in Inner Ears of Guinea Pigs Injured by PAF / 대한이비인후과학회지

ABSTRACT

BACKGROUND AND OBJECTIVES: Platelet-activating factor (PAF) in middle ear effusion is thought to induce hearing loss. The purpose of this study is to determine the effects of PAF placed on round window membrane (RWM) on hearing and cochlear hair cells in guinea pigs, and we also wanted to investigate the role of nitric oxide (NO) in the mechanism of PAF-induced hearing loss by comparing its immunoreactivity to iNOS between the control group and PAF application group. MATERIALS AND METHOD: Guinea pigs were divided into 2 groups PBS, PAF. The PBS group received phosphate buffered saline (PBS) and the PAF groups received 10, 20, and 40 mug/ml of PAF soaked in gelfoam placed on the RWM. The following three tests were performed on each animal group hearing was tested with an auditory brainstem response (ABR) test through 24 hours. At the end of 24 hours, cochlear hair cells were examined by scanning electron microscopy (SEM) and immunohistochemistry was carried out on the cochlea to test the expression of inducible nitric oxide (iNOS). RESULTS: The PAF group developed significant elevation of ABR threshold and cochlear hair cell damage in SEM compared with the PBS control group. Strong expression of iNOS on cochlea was observed in the PAF group and lighter expression was seen in PBS group. CONCLUSION: This study demonstrated that PAF placed on the RWM induced hearing loss, and cochlear hair cell damage, and strong iNOS expression in the cochlea. These findings suggest that the PAF-induced hearing loss caused by cochlear hair cell damage may have been mediated by NO. PAF-antagonists and NOS inhibitor may have future therapeutic implications in preventing sensorineural hearing loss associated with chronic otitis media.