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Gene expression profile of the age-related hearing loss cochlea in DBA/2J mice

ABSTRACT: Age-related hearing loss (AHL) is the progressive loss of auditory function with aging. The DBA/2J (DBA) mice have been used as a model of AHL and undergoes progressive, age-related hearing loss by 12 weeks of age. Here we analyzed cochlear gene expression of 7-week-old and 36-week-old DBA mice using microarrays. Auditory brainstem response (ABR) analysis confrimed that severe age-related hearing loss occured in 36-week-old mice, whereas moderate hearing loss occured in 7-week-old mice. Comprehensive gene expression analysis identified genes correlated with AHL and revealeed that 15 mitochondrial process categories, including “mitochondrial electron transport chain”, “oxidative phosphorylation”, “respiratory chain complex I”, “respiratory chain complex IV”, and “respiratory chain complex V”, were statistically associated with AHL-correlated genes in the cochlea of 36-week-old DBA mice, and that 25 genes encoding components of the mitochondrial respiratory chain (respiratory chain complex I, IV, and V) were significantly down-regulated in the cochlea. These observations provide evidence that AHL is associated with down-regulation of genes involved in the mitochondrial respiratory chain in the cochlea of DBA mice, and suggest that mitochondrial respiratory chain dysfunction may be a key feature of AHL in mammalian cochlea. Keywords: Disease state analysis, Time course analysis

ORGANISM(S): Mus musculus

PROVIDER: GSE6045 | GEO | 2007/10/16

SECONDARY ACCESSION(S): PRJNA97781

REPOSITORIES: GEO

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Project description:Alzheimer's disease (AD) is the most common type of dementia and is characterized by cognitive and behavioral impairment that significantly interferes with social functioning. Over the last decade, there has been an increased interest in whether sensory deficiency may be associated with the development of AD. Notably, the relationship between hearing impairment and AD is of great relevance, but still poorly understood. In this study, we found an early-onset hearing loss in 3xTgAD and 3xTgAD/Polβ+/− mouse models. The hearing assessment was measured by auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) recordings. Herein, we report that both 3xTgAD and 3xTgAD/Polβ+/− mice showed increased ABR thresholds between at 16 and 32 kHz at 4 weeks of age, much earlier than any AD behavioral changes. The ABR thresholds were significantly higher in 3xTgAD/Polβ+/− mice than in 3xTgAD mice at 16 kHz, and DPOAE signals were also reduced, indicating that DNA damage may affect hearing impairment in AD. Poly ADP-ribosylation levels and protein expression of DNA damage markers increased significantly and NAD+ levels were reduced in the cochlea of 3xTgAD and 3xTgAD/Polβ+/− mice. Remarkably, we observed the downregulation of phosphoglycerate mutase 2 (PGAM2) in cochlea and a decrease in the number of synaptic ribbons in the presynaptic zones of inner hair cells in 3xTgAD/Polβ+/− mice. We also find that the activity of sirtuin 3 (SIRT3) is downregulated in cochlea, indicative of impaired mitochondrial function. Taken together, hearing impairment may be a potential early marker of AD. In addition, these findings provide new insights into the mechanism of the relationship between hearing dysfunction and AD and suggest that DNA damage in the cochlea can contributes to the development of early hearing loss of AD. The hearing assessment was measured by auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) at 4 weeks of age, thereafter whole cochlea and auditory cortex tissue were collected from each mouse (WT, Polβ+/−, 3xTgAD, and 3xTgAD/Polβ+/−) and subjected to total RNA isolation to understand what metabolism-related gene expression changes in cochlea and auditory cortex.

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Gene expression profile of the age-related hearing loss cochlea in DBA/2J mice

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