Abstract
Although hippocampal changes due to noise-induced hearing loss have been suggested, little is known about the miRNA levels due to these hippocampal changes. Three-week-old Sprague-Dawley rats were divided into noise and control groups (n = 20 per group). The noise group rats were exposed to white Gaussian noise (115 dB SPL, 4 hours per day) for three days. One day after noise exposure, the hippocampi of rats were harvested and miRNA expressions were analyzed using the Affymetrix miRNA 4.0 microarray (n = 6 per group). The predicted target genes of each miRNA were retrieved, and the pathways related to the predicted target genes were analyzed. miR-758-5p, miR-210-5p, miR-370-5p, miR-652-5p, miR-3544, miR-128-1-5p, miR-665, miR-188-5p, and miR-874-5p expression increased in the hippocampal tissue of the noise group compared to that in the control group. The overlapping predicted target genes included Bend4, Creb1, Adcy6, Creb5, Kcnj9, and Pten. The pathways related to these genes were the estrogen signaling pathway, vasopressin-regulated water reabsorption, thyroid hormone synthesis, aldosterone synthesis and secretion, insulin secretion, circadian entrainment, insulin resistance, cholinergic synapse, dopaminergic synapse, cGMP-PKG signaling pathway, cAMP signaling pathway, PI3K-Akt signaling pathway, TNF signaling pathway, and AMPK signaling pathway. miR-448-3p, miR204-5p, and miR-204-3p expression decreased in the hippocampal tissue of the noise group compared to that in the control group. The overlapping predicted target genes of these three miRNAs were Rps6kas, Nfactc3, Rictor, Spred1, Cdh4, Cdh6, Dvl3, and Rcyt1b. Pathway analysis suggested that the Wnt signaling pathway is related to Dvl3 and Nfactc3. Noise-induced hearing loss dysregulates miR-758-5p, miR210-5p, miR370-5p, miR-652-5p, miR-3544, miR-128-1-5p, miR-665, miR-188-5p, miR-874-5p, miR-448-3p, miR-204-5p, miR-204-3p, and miR-140-5p expression in the hippocampus. These miRNAs have been predicted to be associated with hormonal, inflammatory, and synaptic pathways.
Highlights
Hearing loss affects daily life in many aspects; in particular, it hampers communication and causes psychosocial problems such as social isolation and depression [1]
The hippocampal region of the brain is involved in learning and memory, and several studies have supported the hypothesis that hearing loss induces cognitive deficit [3]
The auditory thresholds were higher in the noise group 3 days after noise exposure than those before noise exposure
Summary
Hearing loss affects daily life in many aspects; in particular, it hampers communication and causes psychosocial problems such as social isolation and depression [1]. One of the main causes of this handicapped condition is exposure to extreme noises [2]. Such noise exposure negatively affects hair cells in the cochlea and neurons in the auditory pathway. Our previous microarray study showed that acute noise exposure alters hippocampal gene expression [4]. Another study on an Alzheimer’s disease (AD) model has reported that hearing loss induces cognitive deficits and reduced synapse in the hippocampus [5]. The expression of Wnt signaling pathway molecules reduced, and amyloid-β and tau accumulated in the hippocampi of mice after chronic noise exposure [6]
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