Noise-Induced Hearing Loss

Biomaterials as a new option for treating sensorineural hearing loss

Sensorineural hearing loss (SNHL) usually involves damage to complex auditory pathways such as inner ear cells and auditory nerves. The highly intricate and nuanced characteristics of these cells render their repair and regeneration extremely challenging, making it difficult to restore hearing to normal levels once it has been compromised. The effectiveness of traditional drugs is so minimal that they provide little help with the treatment. Fortunately, extensive experiments have demonstrated that combining biomaterials with conventional techniques significantly enhances drug effectiveness. This article reviews the research progress of biomaterials in protecting hair cells and the auditory nerve, repairing genes related to hearing, and developing artificial cochlear materials. By organizing the knowledge presented in this article, perhaps new insights can be provided for the clinical management of SNHL.

Advancing noise management in aviation: Strategic approaches for preventing noise-induced hearing loss

As urbanization and population growth escalate, the challenge of noise pollution intensifies, particularly within the aviation industry. This review examines current insights into noise-induced hearing loss (NIHL) in aviation, highlighting the risks to pilots, cabin crew, aircraft maintenance engineers, and ground staff from continuous exposure to high-level noise. It evaluates existing noise management and hearing conservation strategies, identifying key obstacles and exploring new technological solutions. While progress in developing protective devices and noise control technologies is evident, gaps in their widespread implementation persist. The study underscores the need for an integrated strategy combining regulatory compliance, technological advances, and targeted educational efforts. It advocates for global collaboration and policy development to safeguard the auditory health of aviation workers and proposes a strategic framework to enhance hearing conservation practices within the unique challenges of the aviation sector.

L-Shaped Associations Between Composite Dietary Antioxidant Index and Hearing Loss: A Cross-Sectional Study From the National Health and Nutrition Examination Survey

BACKGROUND

Oxidative stress has been implicated in the pathogenesis of hearing loss (HL). Dietary intake is a modifiable factor that could influence the oxidant and antioxidant capacity. We hypothesized that a higher composite dietary antioxidant index (CDAI) is associated with a reduced odds for HL.

METHODS

Adult participants from the 2001-2012 & 2015-2018 National Health and Nutrition Examination Study were included in this cross-sectional study. The CDAI was calculated from vitamins A, C, E, selenium, zinc, and caretenoid through 24-h dietary recall. Outcomes were HL, speech frequency HL (SFHL), and high frequency HL (HFHL). The associations between CDAI and HL, SFHL, and HFHL were evaluated by weighted multivariable logistic regression.

RESULTS

CDAI was associated with lower odds of HL (OR = 0.98, 95%CI 0.95-1.00, p = .043) and SFHL (OR = 0.97, 95%CI 0.95-1.00, p = .041), but not HFHL (OR = 0.98, 95%CI 0.96-1.00, p = .118) after adjustment for confounders. The multivariable-adjusted model showed a significant trend toward decreased risk of HL, SFHL, and HFHL with increasing CDAI quartile (all p for trend < 0.05). Restricted cubic spline analysis suggested that the associations between CDAI and HL, SFHL, and HFHL were L-shaped, with inflection points of CDAI at -0.61, 2.33, and 4.32, respectively. Subgroup analysis showed that participants with exposure to loud noise benefited from a higher CDAI for SFHL (p for interaction = 0.039).

CONCLUSION

Higher CDAI is associated with reduced odds of HL and SFHL in the U.S. adult population and serves as a promising intervention target to be further explored in prospective longitudinal studies in the future.

Higher exposure to 1,3-butadiene is associated with more severe hearing loss

While volatile organic compounds (VOCs) impair various organs, their influence on hearing loss (HL) has not been extensively researched. We aimed to identify the association between VOCs and HL or high-frequency hearing loss (HFHL). We extracted data on age, sex, pure tone audiometry, hypertension, occupational noise exposure, and creatinine-corrected urine VOC metabolite concentrations from the eighth Korea National Health and Nutrition Survey. Among the VOC metabolites, N-acetyl-S-(benzyl)-L-cysteine (BMA, P = 0.004), N-acetyl-S-(phenyl)-L-cysteine (SPMA, P = 0.027), and N-acetyl-S-(3,4-dihydroxybutyl)-L-cysteine (DHBMA, P < 0.001) showed associations with HL. Additionally, HFHL exhibited significant associations with BMA (P = 0.005), 3- and 4-methylhippuric acid (3, 4 MHA, P = 0.049), mandelic acid (MA, P = 0.015), SPMA (P < 0.001), N-acetyl-S-(3-hydroxypropyl)-L-cysteine (3-HPMA, P < 0.001), and DHBMA (P < 0.001). After controlling other factors, DHBMA were associated with HL (P = 0.021) and HFHL (P = 0.014) and exhibited a linear association with the mean hearing level (β = 0.054, P = 0.024) and high-frequency hearing level (β = 0.045, P = 0.037). Since 1,3-butadiene may act as an ototoxic material, early screening for workers exposed to 1,3-butadiene and reducing exposure to 1,3-butadiene in everyday life may be helpful to prevent further HL.

Polymer-Based Nanoparticles for Inner Ear Targeted Trans Differentiation Gene Therapy

Hearing loss is a significant disability that often goes under recognised, largely due to poor identification, prevention, and treatment. Steps are being made to amend these pitfalls in the investigation of hearing loss, however, the development of a cure to reverse advanced forms remains distant. This review details some current advances in the treatment of hearing loss, with a particular focus on genetic-based nanotechnology and how it may provide a useful avenue for further research. This review presents a broad background on the pathophysiology of hearing loss and some current interventions. We also highlight some potential genes that may be useful in the amelioration of hearing loss. Pathways of cellular differentiation from stem or supporting cell to functional hair cell are covered in detail, as this mechanism represents a key means of regenerating these cell types. Overall, we believe that polymer-based nanotechnology coupled with novel excipients represents a useful area of further research in the treatment of hearing loss, although further studies in this area are required.

Prevalence and associated factors of noise-induced hearing loss among workers in Bishoftu Central Air Base of Ethiopia

Excessive occupational exposure to noise results in a well-recognized occupational hearing loss which is prevalent in many workplaces and now it is taken as a global problem. Therefore, this study aims to assess the prevalence of noise-induced hearing loss and associated factors among workers in the Bishoftu Central Air Base in Ethiopia. An institutional-based cross-sectional study was conducted among 260 central air base workers through face-to-face interviews, an environment noise survey, and an audiometric test for data collection. Data were entered by Epi-data version 3.1 and SPSS was used to analyze the data. Finally, a statistical analysis such as descriptive and binary logistic regression analysis was applied. A P-value < 0.05 at 95% CI was considered statistically significant. The overall prevalence of noise-induced hearing loss and hearing impairments was 24.6 and 30.9%, respectively. The highest prevalence of noise-induced hearing loss was recorded for workers who were exposed to noise levels greater than 90 dBA. Out of 132 workers exposed to the average noise level of 75 dB A, only 5% of workers were affected with noise-induced hearing loss, while 128 workers exposed to an average noise level equal to or greater than 90 dB A, 19.6% of workers were identified with noise-induced hearing loss. Regarding sex, around 21.9% of male workers were identified with noise-induced hearing loss. Workers who were exposed to a high noise level workplace previously or before the Central Air Base workplace were five times (AOR = 5.0, 95% CI 1.74-14.36) more likely affected by noise-induced hearing loss than those workers not previously exposed. Those workers who were exposed to greater or equal to 90dBA noise level were 4.98 times (AOR = 4.98, 95% CI 2.59-9.58) more likely to be exposed to noise-induced levels than those who were exposed to less than 90dBA noise level. Moreover, male air base workers were 3.5 times more likely exposed to hearing impairment than female workers (AOR = 3.5, 95% CI 1.01-12.0). This study identified that the prevalence of noise-induced hearing loss and hearing impairments was significantly high. So implementation of a hearing conservation program, giving noise education, and supplying adequate hearing protective devices (HPDs) are essentials.

C-Phycocyanin Attenuates Noise-Induced Cochlear Synaptopathy via the Inhibition of Oxidative Stress and Intercellular Adhesion Molecule-1 in the Cochlea

The synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) are the most vulnerable structures in the noise-exposed cochlea. Cochlear synaptopathy results from the disruption of these synapses following noise exposure and is considered the main cause of poor speech understanding in noisy environments, even when audiogram results are normal. Cochlear synaptopathy leads to the degeneration of SGNs if damaged IHC-SGN synapses are not promptly recovered. Oxidative stress plays a central role in the pathogenesis of cochlear synaptopathy. C-Phycocyanin (C-PC) has antioxidant and anti-inflammatory activities and is widely utilized in the food and drug industry. However, the effect of the C-PC on noise-induced cochlear damage is unknown. We first investigated the therapeutic effect of C-PC on noise-induced cochlear synaptopathy. In vitro experiments revealed that C-PC reduced the H2O2-induced generation of reactive oxygen species in HEI-OC1 auditory cells. H2O2-induced cytotoxicity in HEI-OC1 cells was reduced with C-PC treatment. After white noise exposure for 3 h at a sound pressure of 118 dB, the guinea pigs intratympanically administered 5 μg/mL C-PC exhibited greater wave I amplitudes in the auditory brainstem response, more IHC synaptic ribbons and more IHC-SGN synapses according to microscopic analysis than the saline-treated guinea pigs. Furthermore, the group treated with C-PC had less intense 4-hydroxynonenal and intercellular adhesion molecule-1 staining in the cochlea compared with the saline group. Our results suggest that C-PC improves cochlear synaptopathy by inhibiting noise-induced oxidative stress and the inflammatory response in the cochlea.

Oseltamivir (Tamiflu), a Commonly Prescribed Antiviral Drug, Mitigates Hearing Loss in Mice

Hearing loss affects up to 10% of all people worldwide, but currently there is only one FDA-approved drug for its prevention in a subgroup of cisplatin-treated pediatric patients. Here, we performed an unbiased screen of 1,300 FDA-approved drugs for protection against cisplatin-induced cell death in an inner ear cell line, and identified oseltamivir phosphate (brand name Tamiflu), a common influenza antiviral drug, as a top candidate. Oseltamivir phosphate was found to be otoprotective by oral delivery in multiple established cisplatin and noise exposure mouse models. The drug conferred permanent hearing protection of 15-25 dB SPL for both female and male mice. Oseltamivir treatment reduced in mice outer hair cells death after cisplatin treatment and mitigated cochlear synaptopathy after noise exposure. A potential binding protein, ERK1/2, associated with inflammation, was shown to be activated with cisplatin treatment and reduced by oseltamivir cotreatment in cochlear explants. Importantly, the number of infiltrating immune cells to the cochleae in mice post noise exposure, were significantly reduced with oseltamivir treatment, suggesting an anti-inflammatory mechanism of action. Our results support oseltamivir, a widespread drug for influenza with low side effects, as a promising otoprotective therapeutic candidate in both cisplatin chemotherapy and traumatic noise exposure.

Role of Oxidative Stress in Sensorineural Hearing Loss

Hearing is essential for communication, and its loss can cause a serious disruption to one's social life. Hearing loss is also recognized as a major risk factor for dementia; therefore, addressing hearing loss is a pressing global issue. Sensorineural hearing loss, the predominant type of hearing loss, is mainly due to damage to the inner ear along with a variety of pathologies including ischemia, noise, trauma, aging, and ototoxic drugs. In addition to genetic factors, oxidative stress has been identified as a common mechanism underlying several cochlear pathologies. The cochlea, which plays a major role in auditory function, requires high-energy metabolism and is, therefore, highly susceptible to oxidative stress, particularly in the mitochondria. Based on these pathological findings, the potential of antioxidants for the treatment of hearing loss has been demonstrated in several animal studies. However, results from human studies are insufficient, and future clinical trials are required. This review discusses the relationship between sensorineural hearing loss and reactive oxidative species (ROS), with particular emphasis on age-related hearing loss, noise-induced hearing loss, and ischemia-reperfusion injury. Based on these mechanisms, the current status and future perspectives of ROS-targeted therapy for sensorineural hearing loss are described.

Differences in Oral Health According to the Presence of Hearing Loss: Data from the 2021 Korea National Health and Nutrition Examination Survey

BACKGROUND

The prevalence of hearing loss is increasing annually and has a strong relationship with oral health. However, existing research on hearing loss is limited to children, making it necessary to expand the analysis to adults. Therefore, this study aims to identify differences in oral health-related factors according to hearing loss in adults over 40 years of age using the Korea National Health and Nutrition Examination Survey.

METHODS

This study analyzed survey data from 2021. The study participants were divided into 1738 individuals in the nonhearing loss group and 1384 in the hearing loss group. Complex sample chi-square and complex sample independent t-tests were performed to determine differences in the sociodemographic characteristics, systemic diseases, hearing loss-related factors, and oral health status between the two groups.

RESULTS

Compared to the nonhearing loss group, the hearing loss group was older and had lower income and education levels. In terms of oral health, the hearing loss group had fewer existing natural teeth, poorer prosthesis conditions, and a higher number of implants than the nonhearing loss group. The hearing loss group also experienced comparatively more problems with chewing and speaking (P < 0.05).

CONCLUSIONS

Individuals with hearing loss exhibited poorer oral health status than those without hearing loss. Therefore, dental professionals in clinical practice should develop their communication skills to interact effectively with patients with hearing loss and strive to improve their oral health.

A Comprehensive Review of Auditory and Non-Auditory Effects of Noise on Human Health

OBJECTIVE

Excessive noise is unpleasant and induces several physiological and psychological effects. Noise pollution is a potential threat to humans, particularly those continuously exposed for extended periods throughout the day over many years. This review aims to examine the various auditory and non-auditory outcomes associated with prolonged exposure to noise pollution.

MATERIALS AND METHODS

The review utilized a combination of relevant keywords to search the electronic databases. After screening based on the applied selection criteria for title, abstract, and full text, 44 articles were finally selected for critical review.

RESULTS

We identified and analyzed research findings related to noise-induced hearing loss, tinnitus, and sleep disturbances along with non-auditory issues such as annoyance, cognitive impairments, and mental stress associated with cardiovascular disorders. Furthermore, the existing studies were compared and collated to highlight the unique challenges and significance of noise pollution as a distinctive environmental concern and to explore the ongoing efforts in its research and prevention, including the early detection and potential reversal of noise-induced hearing loss.

CONCLUSION

The fundamental health consequences of noise pollution underscore the need for extensive research encompassing emerging noise sources and technologies to establish a health management system tailored to address noise-related health concerns and reduce noise exposure risk among populations. Finally, further research is warranted to ensure improved measurement of noise exposure and related health outcomes, especially in the context of occupational noise.

Serum Prestin and Otolin-1 Levels in Pilots of Helicopter-Based Emergency Medical Services: Potential Markers for Ear Injury

INTRODUCTION

Occupational noise exposure is a major public health concern, impacting a large workforce worldwide. In this study, we sought to evaluate the serum concentrations of prestin, a cochlear protein that diminishes following noise exposure, and otolin-1, a protein secreted into the bloodstream subsequent to inner ear damage, among three diverse professional categories, each exposed to varying degrees of noise. Helicopter emergency medical service (HEMS) pilots and construction workers were considered high-risk groups due to their elevated exposure to occupational noise, whereas office workers were regarded as a low-risk group, reflecting their comparatively minimal noise exposure.

METHODS

The study sample included 60 males, encompassing helicopter pilots, construction laborers, and office workers (n=20, each). Recruitment occurred during standard occupational health visits, with all participants presenting normal clinical audiograms. Serum levels of prestin and otolin-1 were measured in duplicate using commercially available immunoassays and compared across the three professional categories.

RESULTS

HEMS pilots had the lowest mean serum prestin level at 211±27 pg/mL, followed by construction workers at 234±29 pg/mL, and office workers at 269±42 pg/mL (p<0.001, one-way analysis of variance), with all inter-group differences statistically significant (p<0.05, Tukey's post hoc tests). For otolin-1, HEMS pilots showed the highest mean at 216±20 pg/mL, with construction workers at 196±22 pg/mL, and office workers at 181±20 pg/mL (p<0.001, one-way analysis of variance). Statistically significant differences were found between HEMS pilots and both other groups for otolin-1 levels (p<0.05, Tukey's post hoc tests), but not between construction workers and office workers.

CONCLUSIONS

 Serum concentrations of prestin and otolin-1 may differ among healthy individuals according to their occupational noise exposure and have the potential to act as indicators of subclinical inner ear injury. To substantiate these preliminary observations, incorporating exposure assessment, especially via direct measurements of noise and vibration exposure, would markedly improve the reliability of our findings.

Perceived occupational health risks, noise and dust exposure levels among street sweepers in Mwanza City in Northern Tanzania

Solid waste has been a major problem particularly in Sub-Saharan Africa countries as it has been increasing in several years. One of the methods employed in solid waste management is street sweeping which is done by street sweepers. Street sweepers are being predisposed to respiratory and non-respiratory infection like eye infection, skin infection and musculoskeletal disorders. This analytical cross-sectional study enrolled a total of 233 street sweepers to assess perceived occupational health risks, particulate matters (i.e., PM2.5, PM5 and PM10 measured in (mg/m3)) dust and noise exposure levels in decibel units-dB(A), and utilization of protective personnel equipment among street sweepers in Mwanza city, Northern Tanzania. Modified poison regression was used to determine the association between exposures variables (i.e., sociodemographic, and socioeconomic factors) and outcomes ((i.e., noise dose level and particulate matters))). More than half (50.2%) of the participants were aged between 46-80 years. Their Median age was 46(IQR: 28-59) years. Large percent (63.1%) of the participants reported that their working environment have high health risks. The Median concentrations of the noise dose and particulates matters were 85.4 (IQR = 76.4-92.3) for noise dose, 13426 (IQR = 9637-17632) for PM2.5, 5522 (IQR = 2453-7679) for PM5, and 2310(IQR = 1263-3201). The Median concentrations of the noise dose and particulates matters were 85.4 (IQR = 76.4-92.3) for noise dose in decibel units dB(A); 13426 (IQR = 9637-17632) for PM2.5; 5522 (IQR = 2453-7679) for PM5; and 2310(IQR = 1263-3201) for PM10. Individual Street sweepers in Mwanza city are highly exposed to noise dose and fine particulate matters at levels above the reference values for human of 85dB(A) and 5mg/m3 respectively, making it a public health issue that requires holistic public health measures.

Effects of Astragaloside IV on Hearing, Inflammatory Factors, and Intestinal Flora in Mice Exposed to Noise

Long-term exposure to noise can cause irreversible hearing loss. Considering that there is no effective drug treatment, it is important to seek preventive treatment for noise-induced hearing loss (NIHL). Although astragaloside IV (AS-IV) protects against NIHL by reducing serum inflammatory factors, there is scarce information on the regulation of inflammatory factors by AS-IV to prevent NIHL. We investigated the hearing thresholds and relationship between the serum levels of inflammatory cytokines and intestinal microbiota of c57bl/6j mice exposed to noise (103 dB SPL 4 h·d-1) for 7 days, treated with or without AS-IV. Our results revealed a lower hearing threshold and lower serum levels of TNF-α, TNF-γ, IL-6, IL-1β, and IFN-γ in the mice treated with AS-IV. Additionally, AS-IV increased the abundance levels of the phylum Firmicutes, class Bacillus, order Lactobacillus, and family Lactobacillus (p < 0.05), and decreased those of the phylum Bacteroidetes and order Bacteroidales (p < 0.05). Lactobacillus and Bacilli negatively correlated with TNF-α, TNF-γ, and IL-1β; Erysipelotrichaceae negatively correlated with INF-γ; and Clostridiales positively correlated with IL-1β. In conclusion, AS-IV reduces the elevation of hearing thresholds in mice, preventing hearing loss in mice exposed to noise, and under the intervention of AS-IV, changes in the levels of inflammatory factors correlate with intestinal flora. We suggest that AS-IV improves intestinal flora and reduces inflammation levels in c57bl/6j mice exposed to noise.

Correction: Natarajan et al. Noise-Induced Hearing Loss. J. Clin. Med. 2023, 12, 2347

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The sensitivity of mechanoelectrical transduction response phase to acoustic overstimulation is calcium-dependent

The Mechanoelectrical transduction (MET) channels of the mammalian hair cells are essential for converting sound stimuli into electrical signals that enable hearing. However, the impact of acoustic overstimulation, a leading cause of hearing loss, on the MET channel function remains poorly understood. In this study, I investigated the effect of loud sound-induced temporary threshold shift (TTS) on the transduction response phase across a wide range of sound frequencies and amplitudes. The results demonstrated an increase in the transduction response phase following TTS, indicating altered transduction apparatus function. Further investigations involving the reduction of extracellular calcium, a known consequence of TTS, replicated the observed phase changes. Additionally, reduction of potassium entry confirmed the specific role of calcium in regulating the transduction response phase. These findings provide novel insights into the impact of loud sound exposure on hearing impairment at the transduction apparatus level and highlight the critical role of calcium in modulating sound transduction. Considering that over 1 billion teenagers and young adults globally are at risk of hearing loss due to unsafe music listening habits, these results could significantly enhance awareness about the damaging effects of loud sound exposure.

Hear and Now: Ongoing Clinical Trials to Prevent Drug-Induced Hearing Loss

Each year over half a million people experience permanent hearing loss caused by treatment with therapeutic drugs with ototoxic side effects. There is a major unmet clinical need for therapies that protect against this hearing loss without reducing the therapeutic efficacy of these lifesaving drugs. At least 17 clinical trials evaluating 10 therapeutics are currently underway for therapies aimed at preventing aminoglycoside- and/or cisplatin-induced ototoxicity. This review describes the preclinical and clinical development of each of these approaches, provides updates on the status of ongoing trials, and highlights the importance of appropriate outcome measures in trial design and the value of reporting criteria in the dissemination of results.

Implication of noise exposure on hearing with emphasis to hOGG1 and GPx-1 polymorphisms and HO-1 protein among textile workers

Noise exposure is a health hazard in the textile industry. In cochlear hair cells, DNA damage caused by 8-oxoguanine (8-oxo G) can result in noise-induced hearing loss. Human 8-hydroxyguanine glycosylase (hOGG1) is a DNA repair enzyme that excises (8-oxo G) in the DNA and repairs DNA damage. Glutathione peroxidase-1 (GPx) is a crucial antioxidant enzyme that aids in limiting cochlear damages. Heme oxygenase-1 (HO-1) is a stress-inducible protein with a high fold change in the hair cells of the cochlea. The study aimed to investigate the association of either hOGG1 and GPx-1 polymorphisms with audiometric notches and HO-1 protein among textile workers. hOGG1 and GPx genotypes were analyzed by PCR-RFLP, and HO-1 levels were measured by ELISA in 115 male textile workers. Blood pressure and audiogram were performed. Results recorded the relation between audiometric notches and ear complaints among workers. Older age workers showed audiometric notches at > 25 dB with a significant decrease in HO-1 levels and higher levels in workers with normal audiogram. Ser/Cys genotype of hOGG1 gene was associated with age and work duration while CC genotype of GPx is associated with HO-1 levels and diastolic pressure. Ser/Cys genotype of hOGG1 gene was associated with age while Cys/Cys genotype was associated with work duration among workers. CC genotype of GPx gene was associated with higher HO-1 levels and TT genotype was associated with high diastolic pressure. Finally, hearing impairment was dependent on the duration of exposure to noise, older age, and the presence of heterozygote TC genotype of GPx gene among textile workers.

Noise-induced hearing loss in the pre-industrial era: early contributions in De Morbis Artificum by Bernardino Ramazzini (1633-1714)

OBJECTIVE

Noise-induced hearing loss is the most prevalent occupational disease worldwide and is historically associated with the Industrial Revolution. This study analyses early descriptions of this disorder during the pre-industrial period in the work of the Italian physician Bernardino Ramazzini (1633-1714).

METHOD

Primary and secondary historical literature were reviewed.

RESULTS

Ramazzini described hearing loss in corn millers and in coppersmiths and recognised that this disorder is irreversible and progressive when exposure to noise continues. He also seemed to describe tinnitus. He further suggested the use of earplugs as a preventive measure for these classes of workers. Ramazzini's anatomical and pathological knowledge appears to be based on ancient authors; he did not discuss contemporaneous medical authors' work on hearing function.

CONCLUSION

Despite some limitations, Ramazzini's work appears pioneering for his time and represents an important milestone in the history of otolaryngology.

Natural Multifunctional Silk Microcarriers for Noise-Induced Hearing Loss Therapy

Noise-induced hearing loss (NIHL) is a common outcome of excessive reactive oxygen species in the cochlea, and the targeted delivery of antioxidants to the inner ear is a potential therapeutic strategy. In this paper, a novel natural biomaterials-derived multifunctional delivery system using silk fibroin-polydopamine (PDA)-composited inverse opal microcarriers (PDA@SFMCs) is presented for inner ear drug delivery and NIHL therapy. Due to their large specific surface area and interpenetrating nanochannels, PDA@SFMCs can rapidly load active biomolecules making them a convenient medium for the storage and delivery of such molecules. In addition, surface modification of PDA enables the microcarriers to remain in the round window niche, thus facilitating the precise local and directed delivery of loaded drugs. Based on these features, it is demonstrated here that n-acetylcysteine-loaded silk microcarriers have satisfactory antioxidant properties on cells and can successfully prevent NIHL in guinea pigs. These results indicate that the natural multifunctional silk microcarriers are promising agents for local inner ear drug delivery in the clinic.

Tinnitus prevalence, associated characteristics, and related healthcare use in the United States: a population-level analysis

Background

Tinnitus is a potentially disabling condition with few treatments. We examined the prevalence and characteristics of tinnitus among demographic groups in the United States (US) and assessed associated factors and tinnitus-related healthcare.

Methods

We included adults with and without bothersome tinnitus from the nationally representative 2014 National Health Interview Survey (NHIS; raw n = 36,697), the latest year with tinnitus data. We evaluated tinnitus prevalence and characteristics (frequency, severity, duration) overall and among groups defined by sex and race/ethnicity. Logistic regression with adjusted Wald tests were used for comparisons in NHIS-weighted populations by sex and race/ethnicity, and to evaluate associations between demographic/medical characteristics and noise exposure on tinnitus risk.

Findings

The US prevalence of tinnitus was 11.2% (95% CI: 10.8%, 11.7%; ∼27 million people) in 2014. Of those with tinnitus, 41.2% always had symptoms and 28.3% had ≥15 years symptom duration; the rates were significantly higher among men vs. women and non-Hispanic (nHW) vs. Hispanic Whites (HW), Blacks, or other ethnicity. Significantly more women vs. men and HW vs. nHW reported severe tinnitus. Sex and race/ethnicity, except Asian, were not significantly associated with tinnitus when age, otologic/medical disorders, and noise exposure were included in the model. Significantly lower rates of all minority groups discussed tinnitus with a doctor compared to nHW, and among those who did, Blacks were significantly less likely to receive tinnitus evaluation than nHWs.

Interpretation

Tinnitus prevalence varies across US demographic groups and racial differences were identified in the delivery of tinnitus-related healthcare.

Funding

Rich Robbins, Bertarelli Foundation Endowed Professorship.

Characteristics of brain glucose metabolism and metabolic connectivity in noise-induced hearing loss

The purpose of this study was to evaluate the differences in cerebral glucose metabolism and metabolic connectivity between noise-induced hearing loss (NIHL) subjects and normal subjects. Eighty-nine subjects who needed close observation for NIHL or were diagnosed with NIHL and 89 normal subjects were enrolled. After pre-processing of positron emission tomography images including co-registration, spatial normalization, and smoothing, a two-sample t-test was conducted to compare cerebral glucose metabolism between the two groups. To evaluate metabolic connectivity between two groups, BRAPH-BRain Analysis using graPH theory, a software package to perform graph theory analysis of the brain connectome was used. NIHL subjects showed hypometabolism compared to normal subjects in both insulae (x - 38, y - 18, z 4; × 42, y - 12, z 4) and right superior temporal gyrus (× 44, y 16, z - 20). No brain regions showed hypermetabolism in the NIHL subjects. In metabolic connectivity analysis, NIHL subjects showed decreased average strength, global efficiency, local efficiency, and mean clustering coefficient when compared with normal subjects. Decreased glucose metabolism and metabolic connectivity in NIHL subject might reflect decreased auditory function. It might be characteristic of sensorineural hearing loss.

Fatty acid binding protein type 7 deficiency preserves auditory function in noise-exposed mice

Fatty acid-binding protein 7 (FABP7) is vital for uptake and trafficking of fatty acids in the nervous system. To investigate the involvement of FABP7 in noise-induced hearing loss (NIHL) pathogenesis, we used Fabp7 knockout (KO) mice generated via CRISPR/Cas9 in the C57BL/6 background. Initial auditory brainstem response (ABR) measurements were conducted at 9 weeks, followed by noise exposure at 10 weeks. Subsequent ABRs were performed 24 h later, with final measurements at 12 weeks. Inner ears were harvested 24 h after noise exposure for RNA sequencing and metabolic analyses. We found no significant differences in initial ABR measurements, but Fabp7 KO mice showed significantly lower thresholds in the final ABR measurements. Hair cell survival was also enhanced in Fabp7 KO mice. RNA sequencing revealed that genes associated with the electron transport chain were upregulated or less impaired in Fabp7 KO mice. Metabolomic analysis revealed various alterations, including decreased glutamate and aspartate in Fabp7 KO mice. In conclusion, FABP7 deficiency mitigates cochlear damage following noise exposure. This protective effect was supported by the changes in gene expression of the electron transport chain, and in several metabolites, including excitotoxic neurotransmitters. Our study highlights the potential therapeutic significance of targeting FABP7 in NIHL.

Comparative transcriptome profiling reveals RNA splicing alterations and biological function in patients exposed to occupational noise

Genetic factors play an important role in susceptibility to noise-induced hearing loss (NIHL). Alternative splicing (AS) is an essential mechanism affecting gene expression associated with disease pathogenesis at the post-transcriptional level, but has rarely been studied in NIHL. To explore the role of AS in the development of NIHL, we performed a comprehensive analysis of RNA splicing alterations by comparing the RNA-seq data from blood samples from NIHL patients and subjects with normal hearing who were exposed to the same noise environment. A total of 356 differentially expressed genes, including 23 transcription factors, were identified between the two groups. Of particular note was the identification of 56 aberrant alternative splicing events generated by 41 differentially expressed genes between the two groups, with exon skipping events accounting for 54% of all the differentially alternative splicing (DAS) events. The results of functional enrichment analysis showed that these intersecting DAS genes and differentially expressed genes were significantly enriched in autophagy and mitochondria-related pathways. Together, our findings provide insights into the role of AS events in susceptibility and pathogenesis of NIHL.

Progress on mechanisms of age-related hearing loss

Age-related hearing loss, or presbycusis, is a common cause of hearing loss in elderly people worldwide. It typically presents as progressive, irreversible, and usually affects the high frequencies of hearing, with a tremendous impact on the quality of life. Presbycusis is a complex multidimensional disorder, in addition to aging, multiple factors including exposure to noise, or ototoxic agents, genetic susceptibility, metabolic diseases and lifestyle can influence the onset and severity of presbycusis. With the aging of the body, its ability to clean up deleterious substances produced in the metabolic process is weakened, and the self-protection and repair function of the body is reduced, which in turn leads to irreversible damage to the cochlear tissue, resulting in the occurrence of presbycusis. Presently, oxidative stress (OS), mitochondrial DNA damage, low-grade inflammation, decreased immune function and stem cell depletion have been demonstrated to play a critical role in developing presbycusis. The purpose of this review is to illuminate the various mechanisms underlying this age-related hearing loss, with the goal of advancing our understanding, prevention, and treatment of presbycusis.