Noise-Induced Alteration in Apoptosis Inducing Factor (AIF) Expression along Cochlear Basilar Membrane in Rats
WU Jin
CUI Yong
SHI Ze-tao
QIU Jian-hua
Abstract： Objective To Investigate differences in expression of apoptosis-inducing factor (AIF) in outer hair cells along the basilar membrane before and after noise exposure, and its potential relationship with vulnerability of high-frequen-cy hearing in noise-induced hearing loss. Methods Forty adult Sprague-Dawley (SD) rats were randomly divided into a con-trol and a noise-exposure group:animals in the noise-exposure group were exposed to white noise at 115 dB SPL, 2 hours a day, for 3 consecutive days, while animals in the control group were not exposed. Auditory thresholds were assessed by audito-ry brainstem response (ABR), prior to and 1, 3, 7 and 14 days after noise exposure. Upon completing ABR testing, animals were randomly selected to be sacrificed for cochlear sensory epithelia surface preparation which were stained by FITC-phal-loidin and examined under a microscope. Western blot and immunofluorescence methods were used to detect changes of AIF expression on the basilar membrane at different cochlear turns. Results Compared with the control group, the ABR thresholds for all frequencies increased most significantly on Day 1 after noise exposure in the exposure group. ABR thresholds recov-ered gradually and stabilized on Day14 post-exposure with a permanent threshold shift of about 10 dB at low-frequencies and about 30 dB at high-frequencies (P<0.05). Basilar membrane staining showed obvious hair cell loss in the basal turn in the noise-exposure group, with cilia disarrangement and fusion, in contrast to the well-arranged V or W shaped cilias in the same areas in animals from the control group.The difference of outer hair count between these two groups was statistically significant (P<0.05). Western blot analysis revealed stronger AIF expression in the apical turn than in the basal turn in the control group. AIF expression in both apical and basal turns was obviously stronger in the noise-exposure group than in the control group (P<0.05). Conclusions AIF is a proapoptotic factor, but may act as a free radical scavenger in response to noise-induced oxidant stress. Its increased expression may be one of the mechanisms for vulnerability of high-frequency hearing in noise-induced hearing loss, as indicated by the different expression levels in the apical and basal cochlear turns
Keywords：Apoptosis inducing factorNoise-induced hearing lossBasilar membraneOuter hair cell
Publication Date：2013-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：6( 296-301 )