Dataset Information

Effects of co-exposure to CS2 and noise on hearing and balance in rats: continuous versus intermittent CS2 exposures.

ABSTRACT: Background:Carbon disulfide (CS2) exacerbates the effect of noise on hearing, and disrupts the vestibular system. The goal of this study was to determine whether these effects are also observed with intermittent CS2 exposure. Methods:Rats were exposed for 4?weeks (5?days/week, 6?h/day) to a band noise at 106?dB SPL either alone or combined with continuous (63?ppm or 250?ppm) or intermittent (15?min/h or 2?×?15 min/h at 250?ppm) CS2. Hearing function was assessed by measuring distortion product otoacoustic emissions (DPOAEs); balance was monitored based on the vestibulo-ocular reflex (VOR). Functional measurements were performed before, at the end of exposure and 4?weeks later. Histological analyses of the inner ear were also performed following exposure and after the 4-week recovery period. Results:The results obtained here confirmed that CS2 exposure exerts two differential temporary effects on hearing: (1) it attenuates the noise-induced DPOAE decrease below 6?kHz probably through action on the middle ear reflex when exposure lasts 15?min per hour, and (2) continuous exposure to 250?ppm for 6?h extends the frequency range affected by noise up to 9.6?kHz (instead of 6?kHz with noise alone). With regard to balance, the VOR was reversibly disrupted at the two highest doses of CS2 (2?×?15?min/h and continuous 250?ppm). No morphological alterations to the inner ear were observed. Conclusion:These results reveal that short periods of CS2 exposure can alter the sensitivity of the cochlea to noise at a dose equivalent to only 10 times the short-term occupational limit value, and intermittent exposure to CS2 (2?×?15?min/h) can alter the function of the vestibular system.

SUBMITTER: Chalansonnet M

PROVIDER: S-EPMC7216478 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Effects of co-exposure to CS<sub>2</sub> and noise on hearing and balance in rats: continuous versus intermittent CS<sub>2</sub> exposures.

Chalansonnet Monique M Carreres-Pons Maria M Venet Thomas T Thomas Aurélie A Merlen Lise L Boucard Stéphane S Cosnier Frédéric F Nunge Hervé H Bonfanti Elodie E Llorens Jordi J Campo Pierre P Pouyatos Benoît B

Journal of occupational medicine and toxicology (London, England) 20200511

<h4>Background</h4>Carbon disulfide (CS<sub>2</sub>) exacerbates the effect of noise on hearing, and disrupts the vestibular system. The goal of this study was to determine whether these effects are also observed with intermittent CS<sub>2</sub> exposure.<h4>Methods</h4>Rats were exposed for 4 weeks (5 days/week, 6 h/day) to a band noise at 106 dB SPL either alone or combined with continuous (63 ppm or 250 ppm) or intermittent (15 min/h or 2 × 15 min/h at 250 ppm) CS<sub>2</sub>. Hearing functio ...[more]

PMID: 32426022

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Project description:BackgroundSouth Korea and surrounding countries in East Asia are believed to have the highest proportion in the world of high frequency hearing loss due to occupational noise exposure, yet there has been limited information published in international journals, and limited information for control of noise in local workplaces beyond strategies from western countries. We exploit medical surveillance information from two worker groups to enhance local knowledge about noise-induced hearing loss and explore the possible importance of shift work to risk.MethodsFour-years of hearing data were evaluated for 81 male farm machine factory workers and 371 male firefighters who had successfully completed a health examination and questionnaires for the duration of the study period. The averages of hearing thresholds at 2, 3, and 4 kHz were used as the primary end-point for comparison. Repeat measure analysis adjusted for age, exposure duration and smoking status was used to measure the difference in hearing threshold between the two groups.ResultsNoise levels were measured in the factory at a mean of 82 dBA, with a range of 66-97. No concurrent measurements were taken for the firefighters, but historic comparison values showed a wider range but a similar mean of 76-79 dBA. Although losses during follow-up were negligible, the factory workers had significantly (P < 0.0001) more hearing loss at the baseline of the study than the firefighters in both ears at 2, 3, and 4 kHz, adjusted for age, duration of employment and smoking status. Among those with 10 years of employment, mean losses at these frequencies among the factory workers fell into the impairment range (> 25 dB loss). Firefighters also showed increased losses associated with longer exposure duration, but these were significantly less marked. Losses at lower frequencies (< or = 1 kHz) were negligible in both groups.ConclusionsKorean work environments with continuous noise exposure in the measured range should consider implementation of a hearing conservation program. Further evaluation of hearing loss in workers exposed to irregular or intermittent high noise levels, such as firefighters, is also warranted.

Project description: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.

Dataset Information

Effects of co-exposure to CS2 and noise on hearing and balance in rats: continuous versus intermittent CS2 exposures.

Publications

Effects of co-exposure to CS<sub>2</sub> and noise on hearing and balance in rats: continuous versus intermittent CS<sub>2</sub> exposures.

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