Dexamethasone protects auditory hair cells against TNFα-initiated apoptosis via activation of PI3K/Akt and NFκB signaling

Inhibition of CISD1 attenuates cisplatin-induced hearing loss in mice via the PI3K and MAPK pathways

Cisplatin is an effective chemotherapeutic drug for different cancers, but it also causes severe and permanent hearing loss. Oxidative stress and mitochondrial dysfunction in cochlear hair cells (HCs) have been shown to be important in the pathogenesis of cisplatin-induced hearing loss (CIHL). CDGSH iron sulfur domain 1 (CISD1, also known as mitoNEET) plays a critical role in mitochondrial oxidative capacity and cellular bioenergetics. Targeting CISD1 may improve mitochondrial function in various diseases. However, the role of CISD1 in cisplatin-induced ototoxicity is unclear. Therefore, this study was performed to assess the role of CISD1 in cisplatin-induced ototoxicity. We found that CISD1 expression was significantly increased after cisplatin treatment in both HEI-OC1 cells and cochlear HCs. Moreover, pharmacological inhibition of CISD1 with NL-1 inhibited cell apoptosis and reduced mitochondrial reactive oxygen species accumulation in HEI-OC1 cells and cochlear explants. Inhibition of CISD1 with small interfering RNA in HEI-OC1 cells had similar protective effects. Furthermore, NL-1 protected against CIHL in adult C57 mice, as evaluated by the auditory brainstem response and immunofluorescent staining. Mechanistically, RNA sequencing revealed that NL-1 attenuated CIHL via the PI3K and MAPK pathways. Most importantly, NL-1 did not interfere with the antitumor efficacy of cisplatin. In conclusion, our study revealed that targeting CISD1 with NL-1 reduced reactive oxygen species accumulation, mitochondrial dysfunction, and apoptosis via the PI3K and MAPK pathways in HEI-OC1 cell lines and mouse cochlear explants in vitro, and it protected against CIHL in adult C57 mice. Our study suggests that CISD1 may serve as a novel target for the prevention of CIHL.

Clinical efficacy of intratympanic steroid injection for treating idiopathic sudden sensorineural hearing loss

BACKGROUND

Idiopathic sudden sensorineural hearing loss (ISSNHL) is an emergency that causes permanent hearing loss if timely treatment is not provided. However, the evidence supporting the effect of intratympanic steroid injection (ITSI) starting time on hearing outcome is limited.

METHODS

We retrospectively enrolled 582 patients with ISSNHL who were treated with ITSIs and reviewed their clinical and audiological variables. The relationship between ITSI starting time and hearing recovery was analyzed.

RESULTS

The mean starting time of ITSI was 13.17 ± 16.53 days. The overall hearing recovery rate was 55.15% (recovery = mean hearing level gain of ≥10 dB). The recovery rates were 79.2%, 67.4%, 50%, 36.6%, and 17.8% for the ITSI starting times of 1 to 3, 4 to 7, 8 to 14, 15 to 28, and ≥29 days, respectively. A multivariate analysis revealed that ITST starting time (odds ratio [OR] = 0.94, 95% CI, 0.92-0.96, p < 0.001) and salvage therapy (OR = 0.55, 95% CI, 0.35-0.86, p = 0.009) were independent poor prognostic factors for patients with ISSNHL.

CONCLUSION

Earlier ITSI treatment is associated with a higher hearing recovery rate. Comorbidities and post-ITSI complications were nonsignificant independent risk factors.

Dexamethasone treatment of murine auditory hair cells and cochlear explants attenuates tumor necrosis factor-α-initiated apoptotic damage

The most common cause of sensorineural hearing loss is damage of auditory hair cells. Tumor necrosis factor-alpha (TNF-α) is closely associated with sensorineural hearing loss. The present study examined the preconditioning effect of dexamethasone (DEX) on TNF-α-induced ototoxicity in mouse auditory hair cells (HEI-OC1) and cochlear explants. Treatment of HEI-OC1 with 10 ng/ml TNF-α for 24 h decreased cell viability, increased the accumulation of reactive oxygen species (ROS), and induced caspase-mediated apoptotic signaling pathways. Pretreatment with 10 nM DEX for 6 h before TNF-α exposure restored cell viability, decreased ROS accumulation, and attenuated apoptotic signaling activation induced by TNF-α. Incubation of cochlear explants with 20 ng/ml TNF-α for 24 h resulted in significant loss of both inner hair cells (IHCs) and outer hair cells (OHCs) and an increase in apoptotic activation accessed by annexin V staining. The cochlear explants pre-incubated with 10 nM DEX attenuated TNF-α ototoxicity in both IHCs and OHCs and apoptotic cell death. These results indicated that DEX plays a protective role in ototoxicity induced by TNF-α through attenuation of caspase-dependent apoptosis signaling pathway and ROS accumulation.

Prevention of noise-induced hearing loss by calpain inhibitor MDL-28170 is associated with upregulation of PI3K/Akt survival signaling pathway

Introduction

Noise-induced calcium overload in sensory hair cells has been well documented as an early step in the pathogenesis of noise-induced hearing loss (NIHL). Alterations in cellular calcium homeostasis mediate a series of cellular events, including activation of calcium-dependent protein kinases and phosphatases. Using cell-membrane- and blood-brain-barrier-permeable calpain-1 (μ-calpain) and calpain-2 (m-calpain) inhibitor MDL-28170, we tested the involvement of calpains, a family of calcium-dependent cysteine proteases, and the potential of MDL-28170 in preventing NIHL.

Methods

CBA/J mice at the age of 12 weeks were exposed to broadband noise with a frequency spectrum from 2-20 kHz for 2 h at 101 dB sound pressure level to induce permanent hearing loss as measured by auditory brainstem response and distortion product otoacoustic emissions. Morphological damage was assessed by quantification of remaining sensory hair cells and inner hair cell synapses 2 weeks after the exposure.

Results

MDL-28170 treatment by intraperitoneal injection significantly attenuated noise-induced functional deficits and cochlear pathologies. MDL-28170 treatment also prevented noise-induced cleavage of alpha-fodrin, a substrate for calpain-1. Furthermore, MDL-28170 treatment prevented reduction of PI3K/Akt signaling after exposure to noise and upregulated p85α and p-Akt (S473) in outer hair cells.

Discussion

These results indicate that noise-induced calpain activation negatively regulates PI3K/Akt downstream signaling, and that prevention of NIHL by treatment with MDL-28170 is associated with upregulation of PI3K/Akt survival signaling pathways.

Association of Psoriasis With Hearing Loss: A Systematic Review and Meta-Analysis

BACKGROUND

The relation between psoriasis and hearing loss has been unclear.

OBJECTIVE

To investigate the association of psoriasis with hearing loss.

METHODS

We searched MEDLINE and Embase on 12th November 2022 for studies on the association between psoriasis and hearing loss. We conducted a random-effects model meta-analysis to calculate pooled mean difference (MD) in the pure tone thresholds, pooled odds ratio for sensorineural hearing loss, and pooled hazard ratio for sudden sensorineural hearing loss related to psoriasis.

RESULTS

We included 12 case-control/cross-sectional and 3 cohort studies with 202,683 subjects. Psoriasis was associated with hearing loss at 500 Hz (pooled MD 2.21, 95% CI (CI) 0.13 to 4.29), 1000 Hz (pooled MD 2.97, 95% CI 1.01 to 4.93), 2000 Hz (pooled MD 5.13, 95% CI 2.45 to 7.82), 4000 Hz (pooled MD 9.3, 95% CI 5.1 to 13.51), and 6000 Hz (pooled MD 11.04, 95% CI 5.05 to 17.03). Patients with psoriasis had increased odds for sensorineural hearing loss (pooled odds ratio 3.85, 95% CI 1.07-13.9) and risk for sudden sensorineural hearing loss (pooled hazard ratio 1.45; 95% CI 1.22-1.71).

CONCLUSION

Psoriasis is associated with hearing loss, especially at high frequencies.

The role of calcium, Akt and ERK signaling in cadmium-induced hair cell death

Exposure to heavy metals has been shown to cause damage to a variety of different tissues and cell types including hair cells, the sensory cells of our inner ears responsible for hearing and balance. Elevated levels of one such metal, cadmium, have been associated with hearing loss and shown to cause hair cell death in multiple experimental models. While the mechanisms of cadmium-induced cell death have been extensively studied in other cell types they remain relatively unknown in hair cells. We have found that calcium signaling, which is known to play a role in cadmium-induced cell death in other cell types through calmodulin and CaMKII activation as well as IP3 receptor and mitochondrial calcium uniporter mediated calcium flow, does not appear to play a significant role in cadmium-induced hair cell death. While calmodulin inhibition can partially protect hair cells this may be due to impacts on mechanotransduction activity. Removal of extracellular calcium, and inhibiting CaMKII, the IP3 receptor and the mitochondrial calcium uniporter all failed to protect against cadmium-induced hair cell death. We also found cadmium treatment increased pAkt levels in hair cells and pERK levels in supporting cells. This activation may be protective as inhibiting these pathways enhances cadmium-induced hair cell death rather than protecting cells. Thus cadmium-induced hair cell death appears distinct from cadmium-induced cell death in other cell types where calcium, Akt and ERK signaling all promote cell death.

Aucubin protects mouse cochlear hair cells from cisplatin-induced ototoxicity via activation of the PI3K/AKT/STAT3 pathway

Cisplatin is commonly used to treat cancers and is associated with a significant risk of irreversible sensorineural hearing loss. However, no effective preventive strategies are available for cisplatin-induced HL. Therefore, significant efforts have been made to discover new drugs protecting cochlear hair cells from cisplatin-induced damage. We found that a new phytochemical, aucubin, attenuated cisplatin-induced apoptosis, the production of reactive oxygen species, and mitochondrial dysfunction in House Ear Institute Organ of Corti 1 cells and cochlear hair cells. Moreover, aucubin attenuated cisplatin-induced sensorineural hearing loss and hair cells loss in vivo. Furthermore, RNA sequencing analysis revealed that the otoprotective effects of aucubin were mainly mediated by increased STAT3 phosphorylation via the PI3K/AKT pathway. Inhibition of the STAT3 signaling pathway with the inhibitor S3I-201 or siRNA disrupted the protective effects of aucubin on cisplatin-induced apoptosis. In conclusion, we identified an otoprotective effect of aucubin. Therefore, aucubin could be used to prevent cisplatin-induced ototoxicity.

Mild therapeutic hypothermia protects against inflammatory and proapoptotic processes in the rat model of cochlear implant trauma

OBJECTIVE

Mild therapeutic hypothermia (MTH) has been demonstrated to prevent residual hearing loss from surgical trauma associated with cochlear implant (CI) insertion. Here, we aimed to characterize the mechanisms of MTH-induced hearing preservation in CI in a well-established preclinical rodent model.

APPROACH

Rats were divided into four experimental conditions: MTH-treated and implanted cochleae, cochleae implanted under normothermic conditions, MTH only cochleae and un-operated cochleae (controls). Auditory brainstem responses (ABRs) were recorded at different time points (up to 84 days) to confirm long-term protection and safety of MTH locally applied to the cochlea for 20 min before and after implantation. Transcriptome sequencing profiling was performed on cochleae harvested 24 h post CI and MTH treatment to investigate the potential beneficial effects and underlying active gene expression pathways targeted by the temperature management.

RESULTS

MTH treatment preserved residual hearing up to 3 months following CI when compared to the normothermic CI group. In addition, MTH applied locally to the cochleae using our surgical approach was safe and did not affect hearing in the long-term. Results of RNA sequencing analysis highlight positive modulation of signaling pathways and gene expression associated with an activation of cellular inflammatory and immune responses against the mechanical damage caused by electrode insertion.

SIGNIFICANCE

These data suggest that multiple and possibly independent molecular pathways play a role in the protection of residual hearing provided by MTH against the trauma of cochlear implantation.

Spatial architecture of the cochlear immune microenvironment in noise-induced and age-related sensorineural hearing loss

The cochlea encodes sound stimuli and transmits them to the central nervous system, and damage to sensory cells and synapses in the cochlea leads to hearing loss. The inner ear was previously considered to be an immune privileged organ to protect the auditory organ from reactions with the immune system. However, recent studies have revealed the presence of resident macrophages in the cochlea, especially in the spiral ligament, spiral ganglion, and stria vascularis. The tissue-resident macrophages are responsible for the detection, phagocytosis, and clearance of cellular debris and pathogens from the tissues, and they initiate inflammation and influence tissue repair by producing inflammatory cytokines and chemokines. Insult to the cochlea can activate the cochlear macrophages to initiate immune responses. In this review, we describe the distribution and functions of cochlear macrophages in noise-induced hearing impairment and age-related hearing disabilities. We also focus on potential therapeutic interventions concerning hearing loss by modulating local immune responses.

Network pharmacology and experimental evidence reveal the protective mechanism of Yi-Qi Cong-Ming decoction on age-related hearing loss

CONTEXT

Yi-Qi Cong-Ming (YQCM) decoction has been widely used to prevent age-related hearing loss (ARHL), the most prevalent neurodegenerative disease in the elderly.

OBJECTIVE

To explore the mechanism of YQCM decoction in the treatment of ARHL.

MATERIALS AND METHODS

The chemical constituents of YQCM were screened from the Traditional Chinese Medicine Systems Pharmacology Database. Potential targets of YQCM against ARHL were predicted by DrugBank, GeneCards, and OMIM database. Protein-protein network and enrichment analysis were used for exploring possible molecular mechanisms. Molecular docking and an in vitro model of ARHL by exposing auditory cells with 100 μM H₂O₂ for 3 h were applied. Cell viability and mitochondrial membrane potential (ΔΨM) were detected by CCK-8 and high-content analysis. γH2AX and cleaved caspase-3 were detected by Western blot.

RESULTS

The main compounds have good affinities with hub targets, especially AKT1, PTGS2, and CASP3. GO and KEGG analysis showed that the main biological process and key targets were related to negative regulation of the apoptotic process. H₂O₂ treatment could reduce the cell viability by 68% and impaired ΔΨM, while 90 μg/mL YQCM pre-treatment could restore the cell viability by 97.45% and increase ΔΨM (2-fold higher). YQCM pre-treatment also reduced γH2AX and cleaved caspase-3 protein levels.

CONCLUSIONS

Our study suggested that YQCM prevents ARHL by modulating the apoptosis process in auditory hair cells. Moreover, this study proved that bioinformatics analysis combined with molecular docking and cell model is a promising method to explore other possible pharmacological interventions of ARHL.

Cochlear implants: Causes, effects and mitigation strategies for the foreign body response and inflammation

Cochlear implants provide effective auditory rehabilitation for patients with severe to profound sensorineural hearing loss. Recent advances in cochlear implant technology and surgical approaches have enabled a greater number of patients to benefit from this technology, including those with significant residual low frequency acoustic hearing. Nearly all cochleae implanted with a cochlear implant electrode array develop an inflammatory and fibrotic response. This tissue reaction can have deleterious consequences for implant function, residual acoustic hearing, and the development of the next generation of cochlear prosthetics. This article reviews the current understanding of the inflammatory/foreign body response (FBR) after cochlear implant surgery, its impact on clinical outcome, and therapeutic strategies to mitigate this response. Findings from both in human subjects and animal models across a variety of species are highlighted. Electrode array design, surgical techniques, implant materials, and the degree and type of electrical stimulation are some critical factors that affect the FBR and inflammation. Modification of these factors and various anti-inflammatory pharmacological interventions have been shown to mitigate the inflammatory/FBR response. Ongoing and future approaches that seek to limit surgical trauma and curb the FBR to the implanted biomaterials of the electrode array are discussed. A better understanding of the anatomical, cellular and molecular basis of the inflammatory/FBR response after cochlear implantation has the potential to improve the outcome of current cochlear implants and also facilitate the development of the next generation of neural prostheses.

Intratympanic corticosteroids for sudden sensorineural hearing loss

BACKGROUND

Idiopathic sudden sensorineural hearing loss (ISSNHL) is common, and defined as a sudden decrease in sensorineural hearing sensitivity of unknown aetiology. Systemic corticosteroids are widely used, however their value remains unclear. Intratympanic injections of corticosteroids have become increasingly common in the treatment of ISSNHL.

OBJECTIVES

To assess the effects of intratympanic corticosteroids in people with ISSNHL.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the Cochrane ENT Trials Register; CENTRAL (2021, Issue 9); PubMed; Ovid Embase; CINAHL; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials (search date 23 September 2021).

SELECTION CRITERIA

We included randomised controlled trials (RCTs) involving people with ISSNHL and follow-up of over a week. Intratympanic corticosteroids were given as primary or secondary treatment (after failure of systemic therapy).

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods, including GRADE to assess the certainty of the evidence. Our primary outcome was change in hearing threshold with pure tone audiometry. Secondary outcomes included the proportion of people whose hearing improved, final hearing threshold, speech audiometry, frequency-specific hearing changes and adverse effects.

MAIN RESULTS

We included 30 studies, comprising 2133 analysed participants. Some studies had more than two treatment arms and were therefore relevant to several comparisons. Studies investigated intratympanic corticosteroids as either primary (initial) therapy or secondary (rescue) therapy after failure of initial treatment. 1. Intratympanic corticosteroids versus systemic corticosteroids as primary therapy We identified 16 studies (1108 participants). Intratympanic therapy may result in little to no improvement in the change in hearing threshold (mean difference (MD) -5.93 dB better, 95% confidence interval (CI) -7.61 to -4.26; 10 studies; 701 participants; low-certainty). We found little to no difference in the proportion of participants whose hearing was improved (risk ratio (RR) 1.04, 95% CI 0.97 to 1.12; 14 studies; 972 participants; moderate-certainty). Intratympanic therapy may result in little to no difference in the final hearing threshold (MD -3.31 dB, 95% CI -6.16 to -0.47; 7 studies; 516 participants; low-certainty). Intratympanic therapy may increase the number of people who experience vertigo or dizziness (RR 2.53, 95% CI 1.41 to 4.54; 1 study; 250 participants; low-certainty) and probably increases the number of people with ear pain (RR 15.68, 95% CI 6.22 to 39.49; 2 studies; 289 participants; moderate-certainty). It also resulted in persistent tympanic membrane perforation (range 0% to 3.9%; 3 studies; 359 participants; very low-certainty), vertigo/dizziness at the time of injection (1% to 21%, 3 studies; 197 participants; very low-certainty) and ear pain at the time of injection (10.5% to 27.1%; 2 studies; 289 participants; low-certainty). 2. Intratympanic plus systemic corticosteroids (combined therapy) versus systemic corticosteroids alone as primary therapy We identified 10 studies (788 participants). Combined therapy may have a small effect on the change in hearing threshold (MD -8.55 dB better, 95% CI -12.48 to -4.61; 6 studies; 435 participants; low-certainty). The evidence is very uncertain as to whether combined therapy changes the proportion of participants whose hearing is improved (RR 1.27, 95% CI 1.15 to 1.41; 10 studies; 788 participants; very low-certainty). Combined therapy may result in slightly lower (more favourable) final hearing thresholds but the evidence is very uncertain, and it is not clear whether the change would be important to patients (MD -9.11 dB, 95% CI -16.56 to -1.67; 3 studies; 194 participants; very low-certainty). Some adverse effects only occurred in those who received combined therapy. These included persistent tympanic membrane perforation (range 0% to 5.5%; 5 studies; 474 participants; very low-certainty), vertigo or dizziness at the time of injection (range 0% to 8.1%; 4 studies; 341 participants; very low-certainty) and ear pain at the time of injection (13.5%; 1 study; 73 participants; very low-certainty).  3. Intratympanic corticosteroids versus no treatment or placebo as secondary therapy We identified seven studies (279 participants). Intratympanic therapy may have a small effect on the change in hearing threshold (MD -9.07 dB better, 95% CI -11.47 to -6.66; 7 studies; 280 participants; low-certainty). Intratympanic therapy may result in a much higher proportion of participants whose hearing is improved (RR 5.55, 95% CI 2.89 to 10.68; 6 studies; 232 participants; low-certainty). Intratympanic therapy may result in lower (more favourable) final hearing thresholds (MD -11.09 dB, 95% CI -17.46 to -4.72; 5 studies; 203 participants; low-certainty). Some adverse effects only occurred in those who received intratympanic injection. These included persistent tympanic membrane perforation (range 0% to 4.2%; 5 studies; 185 participants; very low-certainty), vertigo or dizziness at the time of injection (range 6.7% to 33%; 3 studies; 128 participants; very low-certainty) and ear pain at the time of injection (0%; 1 study; 44 participants; very low-certainty).  4. Intratympanic plus systemic corticosteroids (combined therapy) versus systemic corticosteroids alone as secondary therapy We identified one study with 76 participants. Change in hearing threshold was not reported. Combined therapy may result in a higher proportion with hearing improvement, but the evidence is very uncertain (RR 2.24, 95% CI 1.10 to 4.55; very low-certainty). Adverse effects were poorly reported with only data for persistent tympanic membrane perforation (rate 8.1%, very low-certainty).

AUTHORS' CONCLUSIONS

Most of the evidence in this review is low- or very low-certainty, therefore it is likely that further studies may change our conclusions.   For primary therapy, intratympanic corticosteroids may have little or no effect compared with systemic corticosteroids. There may be a slight benefit from combined treatment when compared with systemic treatment alone, but the evidence is uncertain. For secondary therapy, there is low-certainty evidence that intratympanic corticosteroids, when compared to no treatment or placebo, may result in a much higher proportion of participants whose hearing is improved, but may only have a small effect on the change in hearing threshold. It is very uncertain whether there is additional benefit from combined treatment over systemic steroids alone. Although adverse effects were poorly reported, the different risk profiles of intratympanic treatment (including tympanic membrane perforation, pain and dizziness/vertigo) and systemic treatment (for example, blood glucose problems) should be considered when selecting appropriate treatment.

Effects of oral N-acetylcysteine combined with oral prednisolone on idiopathic sudden sensorineural hearing loss

BACKGROUND

Idiopathic sudden sensorineural hearing loss (ISSNHL) is an acute condition that presents with sudden hearing loss, for which steroids remain the main treatment. N-acetylcysteine (NAC), as a precursor of glutathione, can reduce the production of reactive oxygen species to protect hair cells in the inner ear from damage. However, data regarding the therapeutic outcomes of oral steroid combined with oral NAC for ISSNHL are still limited. This study was performed to investigate this issue.

METHODS

Between June 2016 and October 2021, 219 patients (219 ears) diagnosed with ISSNHL and treated with oral prednisolone were enrolled in this retrospective study. Oral NAC was prescribed to 94 of these patients (NAC group) but not to the remaining 125 patients (non-NAC group). The clinical and audiological findings were assessed.

RESULTS

The NAC group showed a mean hearing level gain of 29.5 ± 21.8 dB, speech reception threshold (SRT) gain of 26.2 ± 34.4 dB, and speech discrimination score (SDS) gain of 25.5 ± 30.4%. Although the NAC group had better mean hearing level, SRT, and SDS gains than the non-NAC group, the differences were not statistically significant (all P > .05). The only significant difference between the NAC and non-NAC groups was the posttreatment pure tone audiometry (PTA) thresholds at 8 kHz, which were 54.2 ± 24.4 and 60.9 ± 34.1 dB, respectively (P = .046).

CONCLUSIONS

This study demonstrated the effect of oral steroid combined with oral NAC for ISSNHL. Both the NAC and non-NAC groups showed obvious improvement in all PTA thresholds, as well as mean hearing level, SRT, and SDS gains. The NAC group showed significantly better PTA performance at a high frequency (8 kHz) than the non-NAC group. Therefore, for oral treatment of ISSNHL, we advocate concurrent use of oral prednisolone and oral NAC.

Pro-Inflammatory Signalling PRRopels Cisplatin-Induced Toxicity

Cisplatin is a platinum-based chemotherapeutic that has long since been effective against a variety of solid-cancers, substantially improving the five-year survival rates for cancer patients. Its use has also historically been limited by its adverse drug reactions, or cisplatin-induced toxicities (CITs). Of these reactions, cisplatin-induced nephrotoxicity (CIN), cisplatin-induced peripheral neuropathy (CIPN), and cisplatin-induced ototoxicity (CIO) are the three most common of several CITs recognised thus far. While the anti-cancer activity of cisplatin is well understood, the mechanisms driving its toxicities have only begun to be defined. Most of the literature pertains to damage caused by oxidative stress that occurs downstream of cisplatin treatment, but recent evidence suggests that the instigator of CIT development is inflammation. Cisplatin has been shown to induce pro-inflammatory signalling in CIN, CIPN, and CIO, all of which are associated with persisting markers of inflammation, particularly from the innate immune system. This review covered the hallmarks of inflammation common and distinct between different CITs, the role of innate immune components in development of CITs, as well as current treatments targeting pro-inflammatory signalling pathways to conserve the use of cisplatin in chemotherapy and improve long-term health outcomes of cancer patients.

Prognostic factors in elderly patients after an intra-tympanic steroid injection for idiopathic sudden sensorineural hearing loss

BACKGROUND

Idiopathic sudden sensorineural hearing loss (ISSNHL) presents with emergent hearing impairment and is mainly treated with steroids. However, limited data exist regarding the prognostic factors among elderly patients (>65 years old) who receive an intra-tympanic steroid injection (ITSI). Therefore, we investigated the prognostic factors in these patients.

METHODS

Between July 2016 and March 2022, we retrospectively enrolled 105 elderly patients (>65 years old) with unilateral ISSNHL who were treated with an ITSI, and recorded their clinical and audiological variables.

RESULTS

The patients had a mean age of 72.03 ± 6.33 years and mean hearing level gain of 22.86 ± 21.84 dB, speech reception threshold (SRT) gain of 15.77 ± 35.27 dB, and speech discrimination score (SDS) gain of 19.54 ± 27.81 %. According to Siegel's criteria, 5 (4.76 %), 44 (41.91 %), 46 (43.81 %), and 10 (9.52 %) patients had complete recovery, partial recovery, slight improvement, and no improvement, respectively. In the univariate analysis, vertigo (odds ratio [OR] = 0.290, 95 % confidence interval [CI]: 0.130-0.651, p = 0.002) and profound hearing loss on pure tone audiometry (PTA; OR = 0.233, 95 % CI: 0.101-0.536, p = 0.004) were negative prognostic factors among elderly ISSNHL patients. In the multivariate analysis, vertigo (OR = 0.300, 95 % CI: 0.128-0.705, p = 0.005) and profound pure tone audiometry (OR = 0.240, 95 % CI: 0.101-0.570, p = 0.001) were independent adverse prognostic factors among elderly ISSNHL patients.

CONCLUSIONS

We demonstrated the treatment outcomes of 105 elderly ISSNHL patients after an ITSI. Vertigo and profound PTA are independent adverse risk factors among elderly ISSNHL patients, and patients with these risk factors require active treatment.

Resveratrol Ameliorates Lipopolysaccharide-Induced Sudden Sensorineural Hearing Loss in In Vitro Model through Multitarget Antiapoptotic Mechanism Based on Network Pharmacology and Molecular Docking

Objective

To explore the effects of resveratrol (RSV) on hair cell apoptosis caused by sudden sensorineural hearing loss (SSNHL) and its effect on lipopolysaccharide-induced apoptosis of HEI-OC1 cells.

Methods

We used the network pharmacology method to screen molecules related to RSV for the treatment of SSNHL and analyzed these molecules and their enriched biological processes and signaling pathways through Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis. We selected hub genes related to apoptosis using protein-protein interaction (PPI) analysis for in vitro and molecular docking verification.

Results

Eighty overlapping genes were identified as potential targets for RSV treatment of SSNHL. Further GO analysis showed that the biological processes were mainly related to toxicity, cell proliferation, and lipopolysaccharide reactions. KEGG analysis showed that the AGE-RAGE signaling pathway in diabetic complications, Kaposi's sarcoma-associated herpesvirus infection, FoxO signaling pathway, PI3K-Akt signaling pathway, and other inflammatory signaling pathways were concentrated. AKT1, STAT3, JUN, TNF, TP53, MAPK3, CASP3, and VEGFA were screened as HUB genes using PPI analysis. The apoptosis-related proteins TNF, CASP3, AKT1, and TP53 were selected for in vitro experiments, which showed that mRNA was significantly different before and after RSV intervention, confirming that the corresponding protein receptors could bind well with RSV.

Conclusion

RSV mainly affects the prognosis of SSNHL through anti-inflammatory effects and may improve hair cell apoptosis caused by inflammatory factors through multitargeted interventions involving TNF, CASP3, AKT1, and TP53.

Inhibiting DNA methylation alleviates cisplatin-induced hearing loss by decreasing oxidative stress-induced mitochondria-dependent apoptosis via the LRP1-PI3K/AKT pathway

Cisplatin-related ototoxicity is a critical side effect of chemotherapy and can lead to irreversible hearing loss. This study aimed to assess the potential effect of the DNA methyltransferase (DNMT) inhibitor RG108 on cisplatin-induced ototoxicity. Immunohistochemistry, apoptosis assay, and auditory brainstem response (ABR) were employed to determine the impacts of RG108 on cisplatin-induced injury in murine hair cells (HCs) and spiral ganglion neurons (SGNs). Rhodamine 123 and TMRM were utilized for mitochondrial membrane potential (MMP) assessment. Reactive oxygen species (ROS) amounts were evaluated by Cellrox green and Mitosox-red probes. Mitochondrial respiratory function evaluation was performed by determining oxygen consumption rates (OCRs). The results showed that RG108 can markedly reduce cisplatin induced damage in HCs and SGNs, and alleviate apoptotic rate by protecting mitochondrial function through preventing ROS accumulation. Furthermore, RG108 upregulated BCL-2 and downregulated APAF1, BAX, and BAD in HEI-OC1 cells, and triggered the PI3K/AKT pathway. Decreased expression of low-density lipoprotein receptor-related protein 1 (LRP1) and high methylation of the LRP1 promoter were observed after cisplatin treatment. RG108 treatment can increase LRP1 expression and decrease LRP1 promoter methylation. In conclusion, RG108 might represent a new potential agent for preventing hearing loss induced by cisplatin via activating the LRP1-PI3K/AKT pathway.

c-Myb protects cochlear hair cells from cisplatin-induced damage via the PI3K/Akt signaling pathway

The transcription factor c-Myb is vital for cell survival, proliferation, differentiation, and apoptosis. We have previously reported that c-Myb knockdown exacerbates neomycin-induced damage to cochlea cells. However, the function and regulation of c-Myb in the mammalian inner ear remains unclear. Here, we first found that the expression of c-Myb in cochlear HCs was downregulated after cisplatin damage in vivo. Next, to investigate the role of c-Myb in HCs treated with cisplatin, the recombinant virus AAV-ie-CAG-Myb-HA (AAV-c-Myb) that overexpresses c-Myb was constructed and transfected into HCs. The protein expression of c-Myb was effectively up-regulated in cultured cochlear HCs after the virus transfection, which increased cochlear HC viability, decreased HC apoptosis and reduced intracellular reactive oxygen species (ROS) levels after cisplatin injury in vitro. The overexpression of c-Myb in HCs after AAV-c-Myb transfection in vivo also promoted HC survival, improved the hearing function of mice and reduced HC apoptosis after cisplatin injury. Furthermore, c-Myb-HC conditional knockout mice (Prestin; c-Myb-cKO) in which c-Myb expression is downregulated only in cochlear OHCs were generated and the cisplatin-induced HCs loss, apoptosis and hearing deficit were all exacerbated in Prestin; c-Myb-cKO mice treated with cisplatin in vivo. Finally, mechanistic studies showed that upregulation of the PI3K/Akt signaling pathway by c-Myb contributed to the increased HC survival after cisplatin exposure in vitro. The findings from this work suggest that c-Myb might serve as a new target for the prevention of cisplatin-induced HC damage and hearing loss.

Mild Therapeutic Hypothermia and Putative Mechanisms of Hair Cell Survival in the Cochlea

Significance: Sensorineural hearing loss has significant implications for quality of life and risk for comorbidities such as cognitive decline. Noise and ototoxic drugs represent two common risk factors for acquired hearing loss that are potentially preventable. Recent Advances: Numerous otoprotection strategies have been postulated over the past four decades with primary targets of upstream redox pathways. More recently, the application of mild therapeutic hypothermia (TH) has shown promise for otoprotection for multiple forms of acquired hearing loss. Critical Issues: Systemic antioxidant therapy may have limited application for certain ototoxic drugs with a therapeutic effect on redox pathways and diminished efficacy of the primary drug's therapeutic function (e.g., cisplatin for tumors). Future Directions: Mild TH likely targets multiple mechanisms, contributing to otoprotection, including slowed metabolics, reduced oxidative stress, and involvement of cold shock proteins. Further work is needed to identify the mechanisms of mild TH at play for various forms of acquired hearing loss.

Cochlear Inflammaging in Relation to Ion Channels and Mitochondrial Functions

The slow accumulation of inflammatory biomarker levels in the body-also known as inflammaging-has been linked to a myriad of age-related diseases. Some of these include neurodegenerative conditions such as Parkinson's disease, obesity, type II diabetes, cardiovascular disease, and many others. Though a direct correlation has not been established, research connecting age-related hearing loss (ARHL)-the number one communication disorder and one of the most prevalent neurodegenerative diseases of our aged population-and inflammaging has gained interest. Research, thus far, has found that inflammatory markers, such as IL-6 and white blood cells, are associated with ARHL in humans and animals. Moreover, studies investigating ion channels and mitochondrial involvement have shown promising relationships between their functions and inflammaging in the cochlea. In this review, we summarize key findings in inflammaging within the auditory system, the involvement of ion channels and mitochondrial functions, and lastly discuss potential treatment options focusing on controlling inflammation as we age.

Improving Clinical Outcomes in Cochlear Implantation Using Glucocorticoid Therapy: A Review

Cochlear implant surgery is a successful procedure for auditory rehabilitation of patients with severe to profound hearing loss. However, cochlear implantation may lead to damage to the inner ear, which decreases residual hearing and alters vestibular function. It is now of increasing interest to preserve residual hearing during this surgery because this is related to better speech, music perception, and hearing in complex listening environments. Thus, different efforts have been tried to reduce cochlear implantation-related injury, including periprocedural glucocorticoids because of their anti-inflammatory properties. Different routes of administration have been tried to deliver glucocorticoids. However, several drawbacks still remain, including their systemic side effects, unknown pharmacokinetic profiles, and complex delivery methods. In the present review, we discuss the role of periprocedural glucocorticoid therapy to decrease cochlear implantation-related injury, thus preserving inner ear function after surgery. Moreover, we highlight the pharmacokinetic evidence and clinical outcomes which would sustain further interventions.

Key Signaling Pathways Regulate the Development and Survival of Auditory Hair Cells

The loss of auditory sensory hair cells (HCs) is the most common cause of sensorineural hearing loss (SNHL). As the main sound transmission structure in the cochlea, it is necessary to maintain the normal shape and survival of HCs. In this review, we described and summarized the signaling pathways that regulate the development and survival of auditory HCs in SNHL. The role of the mitogen-activated protein kinase (MAPK), phosphoinositide-3 kinase/protein kinase B (PI3K/Akt), Notch/Wnt/Atoh1, calcium channels, and oxidative stress/reactive oxygen species (ROS) signaling pathways are the most relevant. The molecular interactions of these signaling pathways play an important role in the survival of HCs, which may provide a theoretical basis and possible therapeutic interventions for the treatment of hearing loss.

N-Acetylcysteine Combined With Dexamethasone Treatment Improves Sudden Sensorineural Hearing Loss and Attenuates Hair Cell Death Caused by ROS Stress

Sudden sensorineural hearing loss (SSNHL) is a common emergency in the world. Increasing evidence of imbalance of oxidant–antioxidant were found in SSNHL patients. Steroids combined with antioxidants may be a potential strategy for the treatment of SSNHL. In cochlear explant experiment, we found that N-acetylcysteine (NAC) combined with dexamethasone can effectively protect hair cells from oxidative stress when they were both at ineffective concentrations alone. A clinic trial was designed to explore whether oral NAC combined with intratympanic dexamethasone (ITD) as a salvage treatment has a better therapeutic effect. 41 patients with SSNHL were randomized to two groups. 23 patients in control group received ITD therapy alone, while 18 patient s in NAC group were treated with oral NAC and ITD. The patients were followed-up on day 1st (initiation of treatment) and day 14th. Overall, there was no statistical difference in final pure-tone threshold average (PTA) improvement between those two groups. However, a significant hearing gain at 8,000 Hz was observed in NAC group. Moreover, the hearing recovery rates of NAC group is much higher than that in control group. These results demonstrated that oral NAC in combination with ITD therapy is a more effective therapy for SSNHL than ITD alone.

Dexamethasone Inhibits TRAIL-Induced Apoptosis through c-FLIP(L) Upregulation and DR5 Downregulation by GSK3β Activation in Cancer Cells

Simple Summary

Dexamethasone (DEX) is commonly used as immunosuppressive and chemotherapeutic agent. The effects of DEX on cell death is different, depending on cell types and stimuli. Here, we found that DEX inhibited tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell death in cancer cells. Upregulation of c-FLIP(L) and downregulation of death receptor 5 (DR5) play a critical role in anti-apoptotic effects of DEX in TRAIL-induced apoptosis. DEX upregulated c-FLIP(L) expression at the transcriptional levels through the GSK-3β signaling pathway. Furthermore, DEX also modulated protein stability of DR5 via the GSK-3β/Cbl axis-mediated ubiquitin–proteasome system. Therefore, DEX-induced GSK3β activation plays a critical role in the modulation of c-FLIP(L) and DR5. This finding suggests that DEX reduced effects of anti-cancer drugs in cancer cells.

Abstract

Dexamethasone (DEX), a synthetic glucocorticoid, is commonly used as immunosuppressive and chemotherapeutic agent. This study was undertaken to investigate the effects of DEX on the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in cancer cells. We found that upregulation of c-FLIP(L) and downregulation of death receptor 5 (DR5; receptor for TRAIL ligand) contribute to the anti-apoptotic effect of DEX on TRAIL-induced apoptosis. DEX increased c-FLIP(L) expression at the transcriptional levels through the GSK-3β signaling pathway. The pharmacological inhibitor and catalytic mutant of GSK-3β suppressed DEX-induced upregulation of c-FLIP(L) expression. Furthermore, GSK-3β specific inhibitor markedly abolished DEX-mediated reduction of TRAIL-induced apoptosis in human renal cancer cells (Caki-1 and A498), human lung cancer cells (A549), and human breast cancer cells (MDA-MB361). In addition, DEX decreased protein stability of DR5 via GSK-3β-mediated upregulation of Cbl, an E3 ligase of DR5. Knockdown of Cbl by siRNA markedly inhibited DEX-induced DR5 downregulation. Taken together, these results suggest that DEX inhibits TRAIL-mediated apoptosis via GSK-3β-mediated DR5 downregulation and c-FLIP(L) upregulation in cancer cells.

Evaluating the Efficacy of L-N-acetylcysteine and Dexamethasone in Combination to Provide Otoprotection for Electrode Insertion Trauma

BACKGROUND

Electrode insertion trauma (EIT) during cochlear implantation (CI) can cause loss of residual hearing. L-N-acetylcysteine (L-NAC) and dexamethasone (Dex) have been individually shown to provide otoprotection albeit at higher concentrations that may be associated with adverse effects. Objective/Aims: The aim of this study is to determine whether L-NAC and Dex could be combined to decrease their effective dosage.

MATERIALS AND METHODS

The organ of Corti (OC) explants were divided into various groups: 1) control; 2) EIT; 3) EIT treated with different concentrations of Dex; 4) EIT treated with different concentrations of L-NAC; 5) EIT treated with L-NAC and Dex in combination. Hair cell (HC) density, levels of oxidative stress, proinflammatory cytokines and nitric oxide (NO) was determined.

RESULTS

There was a significant loss of HCs in explants subjected to EIT compared to the control group. L-NAC and Dex in combination was able to provide significant otoprotection at lower concentrations compared to individual drugs.

CONCLUSIONS AND SIGNIFICANCE

A combination containing L-NAC and Dex is effective in protecting sensory cells at lower protective doses than each compound separately. These compounds can be combined allowing a decrease of potential side effects of each compound and providing significant otoprotection for EIT.

Inner ear is a target for insulin signaling and insulin resistance: evidence from mice and auditory HEI-OC1 cells

OBJECTIVE

The mechanisms underlying the association between diabetes and inner ear dysfunction are not known yet. The aim of the present study is to evaluate the impact of obesity/insulin resistance on inner ear fluid homeostasis in vivo, and to investigate whether the organ of Corti could be a target tissue for insulin signaling using auditory House Ear Institute-Organ of Corti 1 (HEI-OC1) cells as an in vitro model.

METHODS

High fat diet (HFD) fed C57BL/6J mice were used as a model to study the impact of insulin resistance on the inner ear. In one study, 12 C57BL/6J mice were fed either control diet or HFD and the size of the inner ear endolymphatic fluid compartment (EFC) was measured after 30 days using MRI and gadolinium contrast as a read-out. In another study, the size of the inner ear EFC was evaluated in eight C57BL/6J mice both before and after HFD feeding, with the same techniques. HEI-OC1 auditory cells were used as a model to investigate insulin signaling in organ of Corti cells.

RESULTS

HFD feeding induced an expansion of the EFC in C57BL/6J mice, a hallmark of inner ear dysfunction. Insulin also induced phosphorylation of protein kinase B (PKB/Akt) at Ser473, in a PI3-kinase-dependent manner. The phosphorylation of PKB was inhibited by isoproterenol and IBMX, a general phosphodiesterase (PDE) inhibitor. PDE1B, PDE4D and the insulin-sensitive PDE3B were found expressed and catalytically active in HEI-OC1 cells. Insulin decreased and AICAR, an activator of AMP-activated protein kinase, increased the phosphorylation at the inhibitory Ser79 of acetyl-CoA carboxylase, the rate-limiting enzyme in de novo lipogenesis. Furthermore, the activity of hormone-sensitive lipase, the rate-limiting enzyme in lipolysis, was detected in HEI-OC1 cells.

CONCLUSIONS

The organ of Corti could be a target tissue for insulin action, and inner ear insulin resistance might contribute to the association between diabetes and inner ear dysfunction.

Intracochlear Perfusion of Tumor Necrosis Factor-Alpha Induces Sensorineural Hearing Loss and Synaptic Degeneration in Guinea Pigs

Tumor necrosis factor-alpha (TNF-α) is a proinflammatory cytokine that plays a prominent role in the nervous system, mediating a range of physiologic and pathologic functions. In the auditory system, elevated levels of TNF-α have been implicated in several types of sensorineural hearing loss, including sensorineural hearing loss induced by vestibular schwannoma, a potentially fatal intracranial tumor that originates from the eighth cranial nerve; however, the mechanisms underlying the tumor's deleterious effects on hearing are not well-understood. Here, we investigated the effect of acute elevations of TNF-α in the inner ear on cochlear function and morphology by perfusing the cochlea with TNF-α in vivo in guinea pigs. TNF-α perfusion did not significantly change thresholds for compound action potential (CAP) responses, which reflect cochlear nerve activity, or distortion product otoacoustic emissions, which reflect outer hair cell integrity. However, intracochlear TNF-α perfusion reduced CAP amplitudes and increased the number of inner hair cell synapses without paired post-synaptic terminals, suggesting a pattern of synaptic degeneration that resembles that observed in primary cochlear neuropathy. Additionally, etanercept, a TNF-α blocker, protected against TNF-α-induced synaptopathy when administered systemically prior to intracochlear TNF-α perfusion. Findings motivate further investigation into the harmful effects of chronically elevated intracochlear levels of TNF-α, and the potential for etanercept to counter these effects.

Nanomechanical mapping reveals localized stiffening of the basilar membrane after cochlear implantation

Cochlear implantation leads to many structural changes within the cochlea which can impair residual hearing. In patients with preserved low-frequency hearing, a delayed hearing loss can occur weeks-to-years post-implantation. We explore whether stiffening of the basilar membrane (BM) may be a contributory factor in an animal model. Our objective is to map changes in morphology and Young's modulus of basal and apical areas of the BM after cochlear implantation, using quantitative nanomechanical atomic force microscopy (QNM-AFM) after cochlear implant surgery. Cochlear implantation was undertaken in the guinea pig, and the BM was harvested at four time-points: 1 day, 14 days, 28 days and 84 days post-implantation for QNM-AFM analysis. Auditory brainstem response thresholds were determined prior to implantation and termination. BM tissue showed altered morphology and a progressive increase in Young's modulus, mainly in the apex, over time after implantation. BM tissue from the cochlear base demonstrated areas of extreme stiffness which are likely due to micro-calcification on the BM. In conclusion, stiffening of the BM after cochlear implantation occurs over time, even at sites far apical to a cochlear implant.

Methylprednisolone Decreases Mitochondria-Mediated Apoptosis and Autophagy Dysfunction in Hepatocytes of Experimental Autoimmune Hepatitis Model via the Akt/mTOR Signaling

Autoimmune hepatitis (AIH) is characterized by massive immune cell-mediated hepatocyte destruction. Glucocorticoids, particularly methylprednisolone (MP), are the most effective treatment for AIH; however, the mechanism underlying the effects of glucocorticoid treatment has not been fully elucidated. The present study explored the effects of MP on damaged hepatocytes in mice with concanavalin A (ConA)−induced experimental autoimmune hepatitis (EAH). C57BL/6 mice were divided into three groups: a normal control group (injected with normal saline), a ConA (20 mg/kg) group, and a ConA + MP (3.12 mg/kg) group. The serum levels of liver enzymes, cytokines, activated T cells, and apoptosis− and autophagy−associated marker proteins were determined 12 h after ConA injection. Human hepatocyte cell line LO2 was used to verify the effects of ConA and MP in vitro. MP treatment significantly decreased inflammatory reactions in the serum and liver tissues and activated the Akt/mTOR signaling pathway to inhibit apoptosis and autophagy in hepatocytes in vivo. Transmission electron microscopy (TEM) revealed fewer autophagosomes in the MP-treated group than in the ConA-treated group. MP treatment obviously suppressed apoptosis and mitochondrial membrane potential (ΔΨm) loss in hepatocytes in vitro. Furthermore, ConA treatment increased the levels of LC3-II, p62/SQSTM1, and Beclin-1, while bafilomycin A1 did not augment the levels of LC3-II. MP treatment decreased the levels of LC3-II, p62/SQSTM1, and Beclin-1 and upregulated the levels of phosphorylated (p)-Akt and p-mTOR. In conclusion, MP ameliorated mitochondria-mediated apoptosis and autophagy dysfunction in ConA-induced hepatocyte injury in vivo and in vitro via the Akt/mTOR signaling pathway.

Mutations in TOP2B cause autosomal-dominant hereditary hearing loss via inhibition of the PI3K-Akt signalling pathway

Hereditary hearing impairment is a clinically and genetically heterogeneous disease. Whole-exome sequencing was performed on seven affected and six unaffected members in a large Chinese family with autosomal-dominant nonsyndromic hearing loss. The pathogenic variant of the gene encoding human topoisomerase IIβ TOP2B (c.G4837C:p.D1613H) was cosegregated with hearing loss in this pedigree and another two variants of TOP2B were detected in 66 sporadic patients with hearing loss. top2b knockdown led to significant defects in zebrafish inner ears and caused downregulation of akt which resulted in inactivation of PI3K-Akt signalling. As a result, supporting cell and hair cell numbers were reduced through inhibition of the PI3K-Akt pathway. Therefore, we hypothesized that mutations in TOP2B can cause autosomal-dominant nonsyndromic hearing impairment through inhibition of the PI3K-Akt signalling pathway. DATABASE: The whole-exome sequence data in the study are available at the Sequence Read Archive database (NCBI) under the accession numbers SRR9050868, SRR9050867, SRR90508676, SRR90508675, SRR90508674, SRR90508673, SRR90508672, SRR90508671, SRR90508679, SRR90508670, SRR9050859. SRR9050858 and SRR9050857, respectively.

Anti-inflammatory and Oto-Protective Effect of the Small Heat Shock Protein Alpha B-Crystallin (HspB5) in Experimental Pneumococcal Meningitis

Sensorineural hearing loss is the most common long-term deficit after pneumococcal meningitis (PM), occurring in up to 30% of surviving patients. The infection and the following overshooting inflammatory host response damage the vulnerable sensory cells of the inner ear, resulting in loss of hair cells and spiral ganglion neurons, ultimately leading to elevated hearing thresholds. Here, we tested the oto-protective properties of the small heat shock protein alpha B-crystallin (HspB5) with previously reported anti-inflammatory, anti-apoptotic and neuroprotective functions, in an experimental model of PM-induced hearing loss. We analyzed the effect of local and systemic delivery of HspB5 in an infant rat model of PM, as well as ex vivo, using whole mount cultures. Cytokine secretion profile, hearing thresholds and inner ear damage were assessed at predefined stages of the disease up to 1 month after infection. PM was accompanied by elevated pro-inflammatory cytokine concentrations in the cerebrospinal fluid (CSF), leukocyte and neutrophil infiltration in the perilymphatic spaces of the cochlea with neutrophils extracellular trap formation during the acute phase of the disease. Elevated hearing thresholds were measured after recovery from meningitis. Intracisternal but not intraperitoneal administration of HspB5 significantly reduced the levels of TNF-α, IL-6 IFN-γ and IL-10 in the acute phase of the disease. This resulted in a greater outer hair cell survival, as well as improved hearing thresholds at later stages. These results suggest that high local concentrations of HspB5 are needed to prevent inner ear damage in acute PM. HspB5 represents a promising therapeutic option to improve the auditory outcome and counteract hearing loss after PM.

Association Between Psoriasis with Arthritis and Hearing Impairment in US Adults: Data from the National Health and Nutrition Examination Survey

Objective.

Emerging data has linked inflammatory arthritis with hearing impairment (HI). The objective of this study was to investigate the relationship between psoriasis with arthritis (PsA) and HI in the US population. Given the known association of HI and depression, a secondary aim is to investigate the effect of PsA on mental well-being.

Methods.

Cross-sectional study using the National Health and Nutrition Examination Survey for adults aged ≥ 20 years (n = 10,747). Association of PsA with above outcomes was examined using multivariable generalized linear and ordinal logistic regression models, adjusted for demographics and medical comorbidities. Structural equation models examined the extent to which HI mediated the effect of PsA on mental health.

Results.

Individuals with PsA were more likely to report hearing difficulties (OR 1.50, p = 0.043), visit a mental health provider (OR 1.62, p = 0.084), have 1.62 more days of poor mental health over the previous month (p = 0.033), and have depression (OR 2.01, p = 0.015) compared to controls. HI mediated 6.5%, 8.3%, and 5.0% of the effect of PsA on the above mental health outcomes, respectively.

Conclusion.

PsA is independently associated with a significantly increased risk of HI, which partially mediates an association with worsened psychiatric outcomes.

A666-conjugated nanoparticles target prestin of outer hair cells preventing cisplatin-induced hearing loss

Background

The delivery of treatment agents to inner ear with drug delivery system (DDS) has been under investigation to overcome the limitations of the conventional therapeutic agents in curing or alleviating the cisplatin ototoxicity.

Methods

In the present study, a novel targeted dexamethasone (DEX)-loaded DDS, A666-DEX-NP, was constructed for prevention from cisplatin-induced hearing loss. A666-(CLEPRWGFGWWLH) peptides specifically bind to prestin, which is limited to the outer hair cells (OHCs). HEI-OC1 and cisplatin-treated guinea pigs (12 mg/kg, intraperitoneal) were used as in vitro and in vivo models for investigating the targeting and protective efficiency against cisplatin.

Results

As expected, compared to A666-unconjugated nanoparticles (NP), A666-conjugated coumarin 6-labeled NP showed active targeting to OHCs. Furthermore, A666-coumarin 6-labeled NP could be significantly internalized by HEI-OC1 cells via the A666-prestin interaction. This facilitated the uptake of cells pretreated with A666-DEX-NP, followed by the cisplatin-treated group, which led to enhanced cell viability, reduced apoptotic properties, and decreased reactive oxygen species levels as compared to cells pretreated with DEX or DEX-NP, 4 hours in advance of cisplatin treatment. In cisplatin-treated guinea pigs, pretreatment with A666-DEX-NP effectively preserved OHCs and showed significant hearing protection at 4, 8, and 16 kHz as compared to pretreatment with saline, DEX, or DEX-NP formulation.

Conclusion

This OHC-targeting DDS provides a novel strategy for DEX application that can be potentially used to combat cisplatin ototoxicity.

Development of Second-Generation CDK2 Inhibitors for the Prevention of Cisplatin-Induced Hearing Loss

There are currently no FDA-approved therapies to prevent the hearing loss associated with the usage of cisplatin in chemotherapeutic regimens. We recently demonstrated that the pharmacologic inhibition with kenpaullone or genetic deletion of CDK2 preserved hearing function in animal models treated with cisplatin, which suggests that CDK2 is a promising therapeutic target to prevent cisplatin-induced ototoxicity. In this study, we identified two lead compounds, AT7519 and AZD5438, from a focused library screen of 187 CDK2 inhibitors, performed in an immortalized cell line derived from neonatal mouse cochleae treated with cisplatin. Moreover, we screened 36 analogues of AT7519 and identified analogue 7, which exhibited an improved therapeutic index. When delivered locally, analogue 7 and AZD5438 both provided significant protection against cisplatin-induced ototoxicity in mice. Thus, we have identified two additional compounds that prevent cisplatin-induced ototoxicity in vivo and provided further evidence that CDK2 is a druggable target for treating cisplatin-induced ototoxicity.

Effects of dexamethasone on intracochlear inflammation and residual hearing after cochleostomy: A comparison of administration routes

Preservation of residual hearing after cochlear implant is an important issue with regards to hearing performance. Various methods of steroid administration have been widely used in clinical practice to reduce inflammation and preserve residual hearing. Here we compare the effect of different routes of dexamethasone administration on intracochlear inflammation and residual hearing in guinea pig ears. Dexamethasone was delivered into the guinea pigs either through intracochlear, intratympanic or systemic route. The intracochlear concentration of dexamethasone, residual hearing, inflammatory cytokines and histopathologic changes were evaluated over time. A higher intracochlear dexamethasone concentration was observed after intracochlear administration than through the other routes. Residual hearing was better preserved with local dexamethasone administration as was supported by the reduced inflammatory cytokines, more hair cell survival and less severe intracochlear fibrosis and ossification concurrently seen in the local delivery group than in the systemic group. The results demonstrate that local dexamethasone delivery can reduce intracochlear inflammation and preserve residual hearing better than in systemically administered dexamethasone.

Progress in the Development of Preventative Drugs for Cisplatin-Induced Hearing Loss

Cisplatin is a highly effective treatment for malignant cancers and has become a cornerstone in chemotherapeutic regimens. Unfortunately, its use in the clinic is often coupled with a high incidence of severe hearing loss. Over the past few decades, enormous effort has been put forth to find protective agents that selectively protect against the ototoxic side effects of cisplatin and do not interfere with its antitumoral activity. Many therapies have been successful in preclinical work, but only a few have shown any protection in the clinic, and none have been approved by the FDA. This review summarizes the clinical and preclinical studies of the most effective small-molecule candidates currently in clinical trials, while also detailing their molecular mechanisms of action, to gain insight for future drug development in the field.

Third-generation bisphosphonates for cochlear otosclerosis stabilizes sensorineural hearing loss in long-term follow-up

Objective

To assess long‐term hearing outcomes in patients treated with third‐generation bisphosphonates for otosclerosis‐related progressive sensorineural hearing loss (SNHL).

Study Design

Retrospective case series review

Methods

We performed a retrospective case series review of patients with otosclerosis and progressive SNHL. Patients were treated with either risedronate or zoledronate after a diagnosis of otosclerosis with a significant SNHL component. Bone conduction pure tone threshold averages (BC‐PTAs) and word recognition scores (WRS) before and after bisphosphonate administration in long‐term follow‐up was analyzed. Significant change in BC‐PTA was defined as greater than 10dB or between 4% and 18% in WRS based on binomial variance.

Results

Seven patients were identified and 14 ears met inclusion criteria. Three patients were female and the mean age was 48.3 ± 10.3 years. The mean duration between treatment with bisphosphonate administration and long‐term post‐treatment follow‐up audiometry was 87.6 ± 18.3 months, with a range of 61.6 to 109.1 months and median of 89.2 months. Analysis using BC‐PTA and WRS demonstrated that 11 ears remained stable while 2 improved and 1 worsened. No patient experienced any major complication as the result of bisphosphonate therapy.

Conclusion

Treatment with third‐generation bisphosphonates is associated with stability in otosclerosis‐related sensorineural hearing over 5‐ to 9‐year period. These results suggest that such medications may prevent the progression of SNHL in patients with otosclerosis.

Level of Evidence

4 (Case series).

The Severity of Infection Determines the Localization of Damage and Extent of Sensorineural Hearing Loss in Experimental Pneumococcal Meningitis

Hearing loss is an important sequela of pneumococcal meningitis (PM), occurring in up to 30% of survivors. The role of the severity of infection on hearing function and pathomorphological consequences in the cochlea secondary to PM have not been investigated to date. Using a well-established model of PM, we systematically investigated the functional hearing outcome and the long-term fate of neurosensory cells in the cochlea, i.e., hair cells and spiral ganglion neurons (SGNs), with a focus on their tonotopic distribution. Intracisternal infection of infant rats with increasing inocula of Streptococcus pneumoniae resulted in a dose-dependent increase in CSF levels of interleukin-1β, interleukin-6, tumor necrosis factor α, interleukin-10, and interferon-γ in acute disease. The severity of long-term hearing loss at 3 weeks after infection, measured by auditory brainstem response recordings, correlated to the initial inoculum dose and to the levels of proinflammatory cytokines determined in the acute phase of PM. Quantitative cochlear histomorphology revealed a significant loss of SGNs and outer hair cells that strongly correlated to the level of infection, with the most severe damage occurring in the basal part of the cochlea. Inner hair cells (IHCs) were not significantly affected throughout the entire cochlea. However, surviving IHCs lost synaptic connectivity to remaining SGNs in all cochlear regions. These findings provide evidence that the inoculum concentration, i.e., severity of infection, is the major determinant of long-term morphological cell pathologies in the cochlea and functional hearing loss.

SIGNIFICANCE STATEMENT

Hearing loss is a neurofunctional deficit occurring in up to 30% of patients surviving pneumococcal meningitis (PM). Here, we analyze the correlation between the severity of infection and the inflammatory response in the CSF, the tonotopic distribution of neurosensory pathologies in the cochlea, and the long-term hearing function in a rat model of pneumococcal meningitis. Our study identifies the severity of infection as the key determinant of long-term hearing loss, underlining the importance of the prompt institution of antibiotic therapy in patients suffering from PM. Furthermore, our findings reveal in detail the spatial loss of cochlear neurosensory cells, providing new insights into the pathogenesis of meningitis-associated hearing loss that reveal new starting points for the development of otoprotective therapies.

Resolution of Cochlear Inflammation: Novel Target for Preventing or Ameliorating Drug-, Noise- and Age-related Hearing Loss

A significant number of studies support the idea that inflammatory responses are intimately associated with drug-, noise- and age-related hearing loss (DRHL, NRHL and ARHL). Consequently, several clinical strategies aimed at reducing auditory dysfunction by preventing inflammation are currently under intense scrutiny. Inflammation, however, is a normal adaptive response aimed at restoring tissue functionality and homeostasis after infection, tissue injury and even stress under sterile conditions, and suppressing it could have unintended negative consequences. Therefore, an appropriate approach to prevent or ameliorate DRHL, NRHL and ARHL should involve improving the resolution of the inflammatory process in the cochlea rather than inhibiting this phenomenon. The resolution of inflammation is not a passive response but rather an active, highly controlled and coordinated process. Inflammation by itself produces specialized pro-resolving mediators with critical functions, including essential fatty acid derivatives (lipoxins, resolvins, protectins and maresins), proteins and peptides such as annexin A1 and galectins, purines (adenosine), gaseous mediators (NO, H₂S and CO), as well as neuromodulators like acetylcholine and netrin-1. In this review article, we describe recent advances in the understanding of the resolution phase of inflammation and highlight therapeutic strategies that might be useful in preventing inflammation-induced cochlear damage. In particular, we emphasize beneficial approaches that have been tested in pre-clinical models of inflammatory responses induced by recognized ototoxic drugs such as cisplatin and aminoglycoside antibiotics. Since these studies suggest that improving the resolution process could be useful for the prevention of inflammation-associated diseases in humans, we discuss the potential application of similar strategies to prevent or mitigate DRHL, NRHL and ARHL.

Hearing Preservation: Does Electrode Choice Matter?

Objective Evaluate if electrode design affects hearing preservation (HP) following cochlear implantation (CI) with full-length electrodes. Study Design Case series with chart review. Setting Tertiary referral academic center. Subjects and Methods Forty-five adults with low-frequency hearing (≤85 dB at 250 and 500 Hz) who underwent unilateral CI with full-length electrode arrays made by 1 manufacturer were included. HP was calculated with (1) mean low-frequency pure-tone average (LFPTA) at 250 and 500 Hz (MEAN method), (2) a percentile method across the audiometric frequency spectrum generating an S-value (HEARRING method), and (3) functional if hearing remained ≤85 dB at 250 and 500 Hz. Audiometric testing was performed approximately 1 month and 1 year postoperatively, yielding short-term and long-term results, respectively. Results Of 45 patients who underwent CI, 46.7% received lateral wall (LW) and 53.3% received perimodiolar (PM) electrodes. At short-term follow-up, LW electrodes were associated with significantly better HP than PM (LFPTA method: 27.7 vs 39.3 dB, P < .05; S-value method: 48.2 vs 21.8%, P < .05). In multivariate regression of short-term outcomes, LW electrode use was a significant predictor of better HP ( P < .05). At long-term follow-up, electrode type was not associated with HP. Younger patient age was the only significant predictor of long-term HP on multivariate analysis ( P < .05). Conclusion The LW electrode is associated with short-term HP, suggesting its design is favorable for limiting trauma to the cochlea during and directly following CI. Other factors, including age, are relevant for maintaining HP over the long term. The data support further investigation into what modifiable factors may promote long-term HP.

The Protective Effect of Intratympanic Dexamethasone on Streptomycin Ototoxicity in Rats

The purpose of this experimental study was to investigate the protective role of intratympanically administered dexamethasone on the inner ears of rats that were exposed to streptomycin ototoxicity. Twenty-four adult Wistar albino rats were separated into 4 groups: Group 1 (only streptomycin), Group 2 (only intratympanic dexamethasone), Group 3 (streptomycin and intratympanic dexamethasone), and Group 4 (streptomycin and intratympanic saline). All rats were evaluated with distortion product otoacoustic emissions (DPOAE) tests before the start of treatment and on the day it ended. On the 45th day, after the final DPOAE tests, animals of all groups were sacrificed under general anesthesia. The differences between the amplitudes of DPOAE results were determined, and hearing results were statistically analyzed. Also, the cochleas of each rat were histopathologically evaluated under a light microscope with hematoxylin and eosin staining. In the intratympanic dexamethasone group it was observed that cochlear hair cells were mostly protected. No significant difference was seen between the DPOAE results before and after treatment (p > 0.05). On the other hand, loss was observed in the hearing functions and hair cells of the rats that received streptomycin and streptomycin plus intratympanic saline (p < 0.05). In the streptomycin plus intratympanic dexamethasone group, the cochlear hair cells were partially protected. A significant difference was observed when the DPOAE results (DP-grams) of the streptomycin plus intratypmanic dexamethasone group were compared to those of the streptomycin plus intratympanic saline group (p < 0.05). After the experimental study, ototoxic effects of the administration of streptomycin and intratympanic dexamethasone were observed on the rats’ cochlear hair cells. We conclude that intratympanic dexamethasone has protective effects against this cochlear damage in rats.

Activation of CHK1 in Supporting Cells Indirectly Promotes Hair Cell Survival

The sensory hair cells of the inner ear are exquisitely sensitive to ototoxic insults. Loss of hair cells after exposure to ototoxic agents causes hearing loss. Chemotherapeutic agents such as cisplatin causes hair cell loss. Cisplatin forms DNA mono-adducts as well as intra- and inter-strand DNA crosslinks. DNA cisplatin adducts are repaired through the DNA damage response. The decision between cell survival and cell death following DNA damage rests on factors that are involved in determining damage tolerance, cell survival and apoptosis. Cisplatin damage on hair cells has been the main focus of many ototoxic studies, yet the effect of cisplatin on supporting cells has been largely ignored. In this study, the effects of DNA damage response in cochlear supporting cells were interrogated. Supporting cells play a major role in the development, maintenance and oto-protection of hair cells. Loss of supporting cells may indirectly affect hair cell survival or maintenance. Activation of the Phosphoinositide 3-Kinase (PI3K) signaling was previously shown to promote hair cell survival. To test whether activating PI3K signaling promotes supporting cell survival after cisplatin damage, cochlear explants from the neural subset (NS) Cre Pten conditional knockout mice were employed. Deletion of Phosphatase and Tensin Homolog (PTEN) activates PI3K signaling in multiple cell types within the cochlea. Supporting cells lacking PTEN showed increased cell survival after cisplatin damage. Supporting cells lacking PTEN also showed increased phosphorylation of Checkpoint Kinase 1 (CHK1) levels after cisplatin damage. Nearest neighbor analysis showed increased numbers of supporting cells with activated PI3K signaling in close proximity to surviving hair cells in cisplatin damaged cochleae. We propose that increased PI3K signaling promotes supporting cell survival through phosphorylation of CHK1 and increased survival of supporting cells indirectly increases hair cell survival after cisplatin damage.

The effect of systemic lipoic acid on hearing preservation after cochlear implantation via the round window approach: A guinea pig model

The present study aimed to evaluate the effects of systemic lipoic acid on hearing preservation after cochlear implantation. Twelve Dunkin-Hartley guinea pigs were randomly divided into two groups: the control group and the lipoic acid group. Animals in the lipoic acid group received lipoic acid intraperitoneally for 4 weeks. A sterilised silicone electrode-dummy was inserted through the round window to a depth of approximately 5 mm. The hearing level was measured using auditory brainstem responses (ABRs) prior to electrode-dummy insertion, and at 4 days and 1, 2, 3 and 4 weeks after electrode-dummy insertion. The threshold shift was defined as the difference between the pre-operative threshold and each of the post-operative thresholds. The cochleae were examined histologically 4 weeks after electrode-dummy insertion. Threshold shifts changed with frequency but not time. At 2kHz, ABR threshold shifts were statistically significantly lower in the lipoic acid group than the control group. At 8, 16 and 32kHz, there was no significant difference in the ABR threshold shift between the two groups. Histologic review revealed less intracochlear fibrosis along the electrode-dummy insertion site in the lipoic acid group than in the control group. The spiral ganglion cell densities of the basal, middle and apical turns were significantly higher in the lipoic acid group compared with the control group. Therefore, systemic lipoic acid administration appears to effectively preserve hearing at low frequencies in patients undergoing cochlear implantation. These effects may be attributed to the protection of spiral ganglion cells and prevention of intracochlear fibrosis.

Dexamethasone Protects Against Radiation-induced Loss of Auditory Hair Cells In Vitro

HYPOTHESIS

Dexamethasone (DXM) protects against radiation-induced loss of auditory hair cells (HCs) in rat organ of Corti (OC) explants by reducing levels of oxidative stress and apoptosis.

BACKGROUND

Radiation-induced sensorineural hearing loss (HL) is progressive, dose-dependent, and irreversible. Currently, there are no preventative therapeutic modalities for radiation-induced HL. DXM is a synthetic steroid that can potentially target many of the pathways involved in radiation-induced ototoxicity.

METHODS

Whole OC explants were dissected from 3-day-old rat cochleae exposed to specific dosages of single-fraction radiation (0, 2, 5, 10, or 20 Gy), were either untreated or treated with DXM (75, 150, 300 μg/mL), and then cultured for 48 or 96 hours. Confocal microscopy for oxidative stress (CellRox, 48 h) and apoptosis (TUNEL assay, 96 h) and fluorescent microscopy for viable HC counts (fluorescein isothiocyanate-phalloidin, 96 h) were performed. Analysis of variance and Tukey post hoc testing were used for statistical analysis.

RESULTS

Radiation exposure initiated dose-dependent losses of inner and outer HCs, predominantly in the basal turns of the OC explants. DXM protected against radiation-induced HC losses in a dose-dependent manner. DXM significantly reduced levels of oxidative stress and apoptosis in radiation-injured OC explants (p < 0.001).

CONCLUSIONS

Radiation-initiated HC losses were dose-dependent in OC explants. DXM treatment protected explant HCs against radiation-initiated losses by decreasing the levels of oxidative stress and apoptosis. DXM may potentially be a therapeutic modality for preventing radiation-induced HL; further in vivo studies are necessary.