Intermittent white noise exposure is associated with rat cochleae damage and changes in the gene expression

Background

Noise, a physical factor in most work environments, has many effects on human health. Exposure to excessive noise can modify the expression of associated genes with NIHL. The aim of this study to elucidate changes in expression of GJB2 and SLC26A4 after exposure to intense noise which are the most frequent causing genes to apparent autosomal recessive non-syndromic hearing loss.

Methods

In this experimental and case–control study, 17 male Wistar rats were randomly divided into exposure groups (n = 12) and without exposure (n = 5). First group was exposed to noise (90–120 dB, 70 Hz–16 kHz, 8 h/day) for 3–6 days. Cochlear biopsies performed 1 h and 1 week post-exposure, relative gene expression levels were calculated using $${2}^{-\Delta \Delta Ct}$$ 2 - Δ Δ C t . From each group, one ear was stained by hematoxylin and eosin method for histopathological survey. Real-time PCR technique took place, and gene expression data were normalized by GAPDH gene. One-way ANOVA test was performed with a significance level of 0.05 by GraphPad prism software.

Results

Both GJB2 and SLC26A4 in all groups were down-regulated after exposure compared to their controls. Fold changes in the highest times were related to 1 week after 6 days of exposure, 0.052 and 0.015, respectively. Serious damages occurred in different parts of cochlea, and they were more severe after 6 days and 1-week later.

Conclusion

It is expected that if the hearing threshold tests be performed before/after exposure and considering longer post-exposure times, subsequently, the expression of these genes does not return to basal level, and irrecoverable damage to the cochlea, progressive and irreversible ARNSHL will be expected.

Effects of hypothermia and pentoxifylline on the adnexal torsion/detorsion injuries in a rat testis model

This study was designed to investigate the effects of separate and combined administration of hypothermia and pentoxifylline to preserve the effects on the testicles in an experimental model of testicular torsion/ detorsion injuries in rats. Forty male adult Wistar rats were randomly divided into five groups, control, torsion/detorsion (TD), torsion/detorsion/hypothermia (TD+ICE), torsion/detorsion received of pentoxifylline (40mg/kg, ip) (TD+PTX) and torsion/detorsion/hypothermia/PTX (TD+ICE+PTX). Left testicular torsion (TT) was performed for 4 and half hours, and ice fragments have been used at the beginning of torsion. After the reperfusion period (a week), oxidative maker's serum levels, testosterone hormone, sperm parameters, and histopathological and gene expression evaluations have been performed. Significant adverse changes were observed in the TD group for histological variables, sperm count, oxidative marker, testosterone hormone, Bax, BCL2 and caspase-3 expression. The parameters studied in the group receiving PTX improved in comparison with the TD group, while macroscopical parameters of both the hypothermia and PTX+ICE groups were not different compared with the TD group. The results revealed that PTX, as an antioxidant component, was protective against testicular torsion, while hypothermia and hypothermia plus PTX did not exhibit this property, which may have been due to the duration of hypothermia (4 hr) or reperfusion period.

New Insights on the Effect of TNF Alpha Blockade by Gene Silencing in Noise-Induced Hearing Loss

Noise exposure represents the second most common cause of acquired sensorineural hearing loss and we observed that tumor necrosis factor α (TNFα) was involved in this context. The effect of Tnfα gene silencing on the expression profile related to the TNFα metabolic pathway in an experimental model of noise-induced hearing loss had not previously been studied. Methods: Single ears of Wistar rats were pretreated with Tnfα small interfering RNA (siRNA) by trans-tympanic administration 24 h before they were exposed to white noise (120 dBSPL for three hours). After 24 h of noise exposure, we analyzed the electrophysiological threshold and the amplitude of waves I, II, III, and IV in the auditory brain response click. In addition, qRT-PCR was performed to evaluate the TNFα metabolic pathway in the ears submitted or not to gene silencing. Results: Preservation of the electrophysiological threshold and the amplitude of waves was observed in the ears submitted to gene silencing compared to the ears not treated. Increased anti-apoptotic gene expression and decreased pro-apoptotic gene expression were found in the treated ears. Conclusion: Our results allow us to suggest that the blockade of TNFα by gene silencing was useful to prevent noise-induced hearing loss.