Manganese-mediated acceleration of age-related hearing loss in mice

Omata

et al. 2017

Sci Rep

Self Cite

There is no information on the association between oral exposure to arsenic (As) and hearing loss in humans or mice. In this combined epidemiological study and experimental study, the association of oral exposure to As with hearing loss in people aged 12–29 years and young mice was examined. Subjects in the exposure group (n = 48), who were drinking tube well water contaminated with As, showed significantly higher risks of hearing loss at 4 kHz [odds ratio (OR) = 7.60; 95% confidence interval (CI): 1.56, 57.88], 8 kHz (OR = 5.00; 95% CI: 1.48, 18.90) and 12 kHz (OR = 8.72; 95% CI: 2.09, 47.77) than did subjects in the control group (n = 29). We next performed an experiment in which young mice were exposed to As via drinking water at 22.5 mg/L, which is a much greater concentration than that in human studies. The exposure group showed hearing loss and accumulation of As in inner ears. Ex vivo exposure of the organ of Corti from mice exposed to As significantly decreased the number of auditory neurons and fibers. Thus, our combined study showed that oral exposure to As caused hearing loss in young people and young mice.

Section: Discussionsupporting

confidence: 90%

Oral exposure to arsenic causes hearing loss in young people aged 12–29 years and in young mice

Omata

et al. 2017

Sci Rep

Self Cite

“…As levels in biological samples including toenails and urine were measured by inductively coupled plasma mass spectrometry (ICP-MS; Agilent 7500cx) as described previously [ 14 , 22 , 23 ]. In brief, toenails were washed with detergent water.…”

Section: Methodsmentioning

confidence: 99%

“…In experimental studies, oral exposure to As has been shown to cause several health risks including carcinogenesis [ 20 ] and cardiovascular diseases [ 21 ]. Levels of toxic elements in inner ears, which are known to be the sensory organ for hearing, have been determined to demonstrate the correlation with hearing loss [ 22 , 23 ]. Exposure of guniea pigs to As at 200 mg/L via intraperitoneal injection for 2 months resulted in morphological impairments of the inner ear [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

Arsenic level in toenails is associated with hearing loss in humans

Yajima

et al. 2018

PLoS ONE

Self Cite

Arsenic (As) pollution in drinking water is a worldwide health risk for humans. We previously showed hearing loss in young people who live in areas of As-polluted drinking water and in young mice orally treated with As. In this study, we epidemiologically examined associations between As levels in toenails and hearing in 145 Bangladeshi aged 12–55 years in 2014. Levels of As in toenails, but not those in urine, were shown to be significantly correlated with hearing loss at 4 kHz [odds ratio (OR) = 4.27; 95% confidence interval (CI): 1.51, 12.05], 8 kHz (OR = 3.91; 95% CI: 1.47, 10.38) and 12 kHz (OR = 4.15; 95% CI: 1.55, 11.09) by multivariate analysis with adjustments for age, sex, smoking and BMI. Our experimental study further showed a significant association between As levels in inner ears and nails (r = 0.8113, p = 0.0014) in mice orally exposed to As, suggesting that As level in nails is a suitable index to assess As level in inner ears. Taken together, the results of our study suggest that As level in nails could be a convenient and non-invasive biomarker for As-mediated hearing loss in humans.

“…The specimens were observed under a fluorescent microscope (Leica DMI6000B). The software program WinROOF (Mitani Corp., Fukui, Japan) was used for immunohistochemical estimation of positive cells detected by antibodies as previously reported (Ohgami et al, 2016a ). A total of 9 serial sections from 3 mice per group were used for the estimation.…”

Section: Methodsmentioning

confidence: 99%

Risk Assessment of Neonatal Exposure to Low Frequency Noise Based on Balance in Mice

Front. Behav. Neurosci.

Oshino

Ninomiya

et al. 2017

Self Cite

General electric devices and ventilation systems are known to generate low frequency noise (LFN) with frequencies of <100 Hz. Previous studies showed that exposure to LFN caused impairments of balance in humans and mice during adulthood. On the other hand, a previous study showed that noise levels in the neonatal intensive care unit (NICU) were greater than those in general home or office environments. Therefore, it is possible that neonates have a potential risk to be exposed to LFN in the NICU. However, the risk of neonatal exposure to LFN remains unclear in humans and mice. In this study, male ICR mice were exposed to LFN at 100 Hz for 4 weeks after birth and then subjected to rotarod and beam crossing tests in order to assess LFN-mediated risk of imbalance during the neonatal period. Exposure to LFN at 70 dB, but not exposure to LFN up to 60 dB, during the neonatal period significantly decreased performance scores for rotarod and beam crossing tests compared to the scores of the control group. The number of calbindin-positive hair cells in the saccule and utricle was decreased in mice exposed to LFN at 70 dB for 4 weeks in the neonatal phase. Cessation of exposure for 10 weeks did not result in recovery of the decreased performance in rotarod and beam crossing tests. Thus, our results suggest that 70 dB is a possible threshold for exposure to LFN for 4 weeks during the neonatal period causing unrecoverable imbalance in mice.