Spiral ganglion neuron (SGN) damage and apoptosis can lead to noise-induced hearing loss, ageassociated hearing loss and, in certain cases, auditory neuropathy. The apoptosisinducing factor (AIF)associated pathway may be important in this process. The present study aimed to investigate
the expression levels of AIF and calpain in damaged SGNs. Glutamate (Glu) perfusion and cell culture in different concentrations of Glu were performed to damage the SGNs of SpragueDawley (SD) rats, with saline water used as a control Different concentrations (5, 10, 20 and 40 mM)
of Glu were injected into the cochlear tympanic canal of 18 SD rats, and 10, 20 and 40 mM Glu were added to SGN cultures. Auditory brainstem responses (ABR) were measured prior to and 2 days following the injection of Glu. Immunofluorescent staining was used to detect the SGN
damage and the expression levels of AIF and calpain in vivo and in in vitro. Transmission electron microscopy (TEM) was used to measure cell apoptosis and reverse transcriptionquantitative polymerase chain reaction was used to analyse the gene expression levels of AIF and calpain
in the damaged SGNs. The TEM identified mitochondrial vacuolisation, swelling of the SGN and heterochromatin formation. Injection of Glu reduced the number of SGNs and induced apoptosis. AIF was observed to translocate into the nuclei of the SGNs in the 20 and 40 mM Glu groups, and the
expression levels of AIF and calpain were markedly upregulated in the modiolus of the Gludamaged SGNs. The upregulation of AIF and calpain may be important in the process of SGN damage and apoptosis.
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Document Type: Research Article
Department of OtolaryngologyHead and Neck Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
Outpatient Department, Logistics Academy, Beijing 100858, P.R. China
Publication date: August 1, 2015
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Molecular Medicine Reports is a monthly, peer-reviewed journal available in print and online, that includes studies devoted to molecular medicine, underscoring aspects including pharmacology, pathology, genetics, neurosciences, infectious diseases, molecular cardiology and molecular surgery. In vitro and in vivo studies of experimental model systems pertaining to the mechanisms of a variety of diseases offer researchers the necessary tools and knowledge with which to aid the diagnosis and treatment of human diseases.
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