Combined genetic polymorphisms of the GSTT1 and NRF2 genes increase susceptibility to cisplatin-induced ototoxicity: A preliminary study.

OBJECTIVE: The genotype-phenotype relationship in cisplatin-induced ototoxicity remains unclear. By assessing early shifts in distortion product otoacoustic emission (DPOAE) levels after initial cisplatin administration, we aimed to discriminate patients' susceptibility to cisplatin-induced ototoxicity and elucidate their genetic background. STUDY DESIGN: A prospective cross-sectional study. SETTING: Tertiary referral hospital in Japan. PATIENTS: Twenty-six patients with head and neck cancer were undergoing chemoradiotherapy with three cycles of 100 mg/m2 cisplatin. INTERVENTIONS: Repetitive pure-tone audiometry and DPOAE measurements, and blood sampling for DNA extraction were performed. Patients were grouped into early ototoxicity presence or absence based on whether DPOAE level shifts exceeded the corresponding reference limits of the 21-day test interval. MAIN OUTCOME MEASURES: Hearing thresholds after each cisplatin cycle, severity of other adverse events, and polymorphisms in cisplatin-induced ototoxicity-associated genes were compared. RESULTS: Early ototoxicity was present in 14 and absent in 12 patients. Ototoxicity presence on DPOAEs was associated with greater progression of hearing loss in frequencies ≥2 kHz throughout therapy and with higher ototoxicity grades compared with ototoxicity absence. Ototoxicity was further associated with grade ≥2 nausea. Ototoxicity presence was genetically associated with the GSTT1 null genotype and G-allele of NFE2L2 rs6721961, whereas ototoxicity absence was associated with the GSTM1 null genotype. Dose-dependent progression of hearing loss was the greatest in the combined genotype pattern of GSTT1 null and the T/G or G/G variants of rs6721961. CONCLUSION: Early DPOAE changes reflected genetic vulnerability to cisplatin-induced ototoxicity. Hereditary insufficiency of the antioxidant defense system causes severe cisplatin-induced hearing loss and nausea.

Exogenous neuritin restores auditory following cochlear spiral ganglion neuron denervation of gerbils.

Spiral ganglion neurons (SGNs) transmit sound signals received by hair cells to the auditory center to produce hearing. The quantity and function are important for maintaining normal hearing function. Limited by the regenerative capacity, SGNs are unable to regenerate spontaneously after injury. Various neurotrophic factors play an important role in the regeneration process. Neuritin is a neurite growth factor that plays an important role in neural plasticity and nerve injury repair. In this study, we used bioinformatics analysis to show that neuritin was negatively correlated with cochlear damage. Then, we aimed to establish a cochlear spiral ganglion-specific sensorineural deafness model in gerbils using ouabain and determine the effects of exogenous neuritin protein in protecting damaged cochlear SGNs and repairing damaged auditory nerve function. The provides a new research strategy and scientific basis for the prevention and treatment of sensorineural deafness caused by the loss of SGNs. We were discovered that neuritin is expressed throughout the development of the gerbil cochlea, primarily in the SGNs and Corti regions. The expression of neuritin was negatively correlated with the sensorineural deafness induced by ouabain. In vitro and in vivo revealed that neuritin significantly maintained the number and arrangement of SGNs and nerve fibers in the damaged cochlea and effectively protected the high-frequency listening function of gerbils.

Imeglimin-mediated glycemic control in maternally inherited deafness and diabetes.

Mitochondrial dysfunction causes maternally inherited deafness and diabetes (MIDD). Herein, we report improved glycemic control in a 47-year-old Japanese woman with MIDD using imeglimin without major adverse effects. Biochemical tests and metabolome analysis were performed before and after imeglimin administration. Blood glucose level fluctuations were determined. Sulfonylureas, dipeptidyl peptidase-4 inhibitors (DPP4is), and sodium glucose transporter-2 inhibitors (SGLT2i) were administered to evaluate the efficacy of their combination with imeglimin. Imeglimin decreased the HbA1c and ammonia levels and increased the time-in-range, C-peptide reactivity, and glucagon level. Elevated citrulline and histamine levels were decreased by imeglimin. The hypoglycemic effect was not enhanced by imeglimin when combined with sulfonylurea or DPP4i, but the blood glucose level was improved when combined with SGLT2i. Imeglimin improved glucose concentration-dependent insulin secretion and maximized the insulin secretory capacity by improving mitochondrial function and glutamine metabolism and urea circuit abnormalities by promoting glucagon secretion. Imeglimin could improve glycemic control in MIDD.

Neomycin-induced deafness in neonatal mice.

BACKGROUND: Hearing impairment is a rising public health issue, and current therapeutics fail to restore normal auditory sensation. Animal models are essential to a better understanding of the pathophysiology of deafness and developing therapeutics to restore hearing. NEW METHODS: Wild-type CBA/CaJ neonatal mice P2-5 were used in this study. Neomycin suspension (500 nl of 50 or 100 mg/ml) was micro-injected into the endolymphatic space. Cochlear morphology was examined 3 and 7 days after injection; hair cell (HC) loss, supporting cell morphology, and neurite denervation pattern were assessed with whole-mounts. At 2 and 4 weeks post-injection, the spiral ganglion neuron (SGN) density was analyzed with cryostat sections. Audiometric responses were measured with auditory brain response (ABR) at 4 weeks. RESULTS: Rapid and complete degeneration of the inner and outer HCs occurred as early as 3 days post-injection. Subsequently, time- and dose-dependent degeneration patterns were observed along the axis of the cochlear membranous labyrinth forming a flat epithelium. Likewise, the SGN histology demonstrated significant cell density reduction at 2 and 4 weeks. The ABR threshold measurements confirmed profound deafness at 4 weeks. COMPARISON WITH EXISTING METHODS: Compared to previously described local and systemic aminoglycoside injections, this method provides a reliable, robust, and rapid deafening model with a single infusion of neomycin in neonatal mice. This model also allows for investigating the effects of inner ear damage during auditory maturation. CONCLUSIONS: A single injection of neomycin into the endolymphatic space induces robust HC loss and denervation in neonatal mice.

Platinum-induced ototoxicity in pediatric cancer survivors: GSTP1 c.313A>G variant association.

Hearing damage is one of the main toxic effects of platinum compounds, it derives from the irreversible degeneration of hair cells of the ear. Genetic association studies have suggested an association between GSTP1 c.313A>G variant and platinum-induced ototoxicity in childhood cancer survivors. We aimed to detect the frequency of ototoxicity and associated risk factors in survivors of childhood cancer receiving platinum-based chemotherapy and to detect the relation between GSTP1 c.313A>G (rs1695) polymorphisms and ototoxicity. We conducted a cross-sectional study on 64 cancer survivors who received platinum agents (cisplatin and/or carboplatin) at least 2 years after the end of chemotherapy. The patients underwent comprehensive audiological evaluations and genotyping to detect the presence of the GSTP1 c.313A>G polymorphisms. Hearing loss (HL) was identified in 16/64 patients (25%), including 62.5% treated with cisplatin and 37.5% treated with carboplatin. The greater incidence of ototoxicity was found in children treated for osteosarcoma (28.1%) followed by patients with germ cell tumors (25%) and neuroblastoma (21.9%). The AA, AG, and GG types of GSTP1 c.313A>G variant were detected in 84.4%, 9.4%, and 6.3%, respectively, of patients with HL with a significant association between mutant genotype of GSTP1 rs1695 and platinum-induced ototoxicity (P = .035). HL was not significantly associated with the total cumulative dose of cisplatin and carboplatin. GSTP1 c.313A>G variant may increase the risk of HL in pediatric oncology patients treated with cisplatin or carboplatin chemotherapy.

Mitochondrial tRNAGln 4394C>T Mutation May Contribute to the Clinical Expression of 1555A>G-Induced Deafness

The mitochondrial 1555A>G mutation plays a critical role in aminoglycoside-induced and non-syndromic hearing loss (AINSHL). Previous studies have suggested that mitochondrial secondary variants may modulate the clinical expression of m.1555A>G-induced deafness, but the molecular mechanism has remained largely undetermined. In this study, we investigated the contribution of a deafness-associated tRNAGln 4394C>T mutation to the clinical expression of the m.1555A>G mutation. Interestingly, a three-generation family with both the m.1555A>G and m.4394C>T mutations exhibited a higher penetrance of hearing loss than another family harboring only the m.1555A>G mutation. At the molecular level, the m.4394C>T mutation resides within a very conserved nucleotide of tRNAGln, which forms a new base-pairing (7T-66A) and may affect tRNA structure and function. Using trans-mitochondrial cybrid cells derived from three subjects with both the m.1555A>G and m.4394C>T mutations, three patients with only the m.1555A>G mutation and three control subjects without these primary mutations, we observed that cells with both the m.1555A>G and m.4394C>T mutations exhibited more severely impaired mitochondrial functions than those with only the m.1555A>G mutation. Furthermore, a marked decrease in mitochondrial RNA transcripts and respiratory chain enzymes was observed in cells harboring both the m.1555A>G and m.4394C>T mutations. Thus, our data suggest that the m.4394C>T mutation may play a synergistic role in the m.1555A>G mutation, enhancing mitochondrial dysfunctions and contributing to a high penetrance of hearing loss in families with both mtDNA pathogenic mutations.

The ototoxic effect of locally applied kanamycin and furosemide in guinea pigs.

BACKGROUND: Hearing impairment is a growing social and economic issue. New technical or biological approaches aiming hearing rehabilitation or regeneration require animal testing. Therefore, a reproducible and safe model for hearing-impaired animals is essential. NEW METHOD: Intratympanic injection of kanamycin and furosemide was administered for BFA bunt pigmented guinea pigs for either 1 or 2 h. Hearing loss was regularly measured with compound action potential response to click and tone burst stimuli for up to 26 weeks. Hair cell loss and the density of spiral ganglion neurons were histologically analyzed. RESULTS: One week after the exposure, complete hearing loss was observed in 34 ears from the 36 ears treated for 2 h and remained stable during the follow-up. Histology revealed near complete hair cell loss and secondary degeneration of spiral ganglion neurons. COMPARISON WITH EXISTING METHODS: Animal deafening is usually achieved by systemic application of aminoglycoside antibiotics or chemotherapy drugs, although side effects such as nephrotoxicity may occur which can be avoided by local application. With our procedure, unilateral hearing loss model can also be established. CONCLUSIONS: The single intratympanic application of a solution of 200 mg/ml kanamycin and 50 mg/ml furosemide is a stable and reliable deafening method.

Adverse event of Sinovac Coronavirus vaccine: Deafness.

COVID-19 has spread worldwide and is one of the most threatening infectious diseases in the world. Vaccination is known as an effective method to protect susceptible populations against such diseases. The Coronavirus vaccine developed by Sinovac has been shown to have a high protective effect, but it also has potential adverse events. For example, our department saw two patients with reported cases of deafness that occurred after inoculation with the Sinovac Coronavirus vaccine. While deafness is only a rare adverse event from the Coronavirus vaccine, whether other vaccination centers, hospitals, and centers for disease control (CDCs) have encountered similar cases still needs to be investigated, reported, and analyzed.

[Progress in genetic susceptibility to aminoglycoside-induced deafness].

Aminoglycoside antibiotics can cause irreversible hearing loss, but they are still widely used because of their low production cost and broad-spectrum effect on most infections. Although it has been studied for decades, the mechanism of aminoglycoside-induced deafness has not been fully elucidated. Since patients'individual susceptibility to aminoglycoside-ototoxicity varies considerably, it is necessary to identify high-risk patients. This review summarizes the genetic mutations linked to aminoglycoside-induced deafness, in order to provide reference for further prevention and treatment of aminoglycoside-induced deafness.

Early Physiological and Cellular Indicators of Cisplatin-Induced Ototoxicity.

Cisplatin chemotherapy often causes permanent hearing loss, which leads to a multifaceted decrease in quality of life. Identification of early cisplatin-induced cochlear damage would greatly improve clinical diagnosis and provide potential drug targets to prevent cisplatin's ototoxicity. With improved functional and immunocytochemical assays, a recent seminal discovery revealed that synaptic loss between inner hair cells and spiral ganglion neurons is a major form of early cochlear damage induced by noise exposure or aging. This breakthrough discovery prompted the current study to determine early functional, cellular, and molecular changes for cisplatin-induced hearing loss, in part to determine if synapse injury is caused by cisplatin exposure. Cisplatin was delivered in one to three treatment cycles to both male and female mice. After the cisplatin treatment of three cycles, threshold shift was observed across frequencies tested like previous studies. After the treatment of two cycles, beside loss of outer hair cells and an increase in high-frequency hearing thresholds, a significant latency delay of auditory brainstem response wave 1 was observed, including at a frequency region where there were no changes in hearing thresholds. The wave 1 latency delay was detected as early cisplatin-induced ototoxicity after only one cycle of treatment, in which no significant threshold shift was found. In the same mice, mitochondrial loss in the base of the cochlea and declining mitochondrial morphometric health were observed. Thus, we have identified early spiral ganglion-associated functional and cellular changes after cisplatin treatment that precede significant threshold shift.

Investigational Medicinal Products for the Inner Ear: Review of Clinical Trial Characteristics in ClinicalTrials.gov.

BACKGROUND: The previous 30 years have provided information on the mechanisms of cell death in the inner ear after noise exposure, ototoxic drug injury, and during aging, and clinical trials have emerged for all of these acquired forms of hearing loss. Sudden hearing loss is less well understood, but restoration of hearing after sudden hearing loss is also a long-standing drug target, typically using steroids as an intervention but with other agents of interest as well. PURPOSE: The purpose of this review was to describe the state of the science regarding clinical testing of investigational medicinal products for the inner ear with respect to treatment or prevention of acquired hearing loss. DATA COLLECTION AND ANALYSIS: Comprehensive search and summary of clinical trials listed in the National Library of Medicine (www. CLINICALTRIALS: gov) database identified 61 clinical trials. RESULTS: Study phase, status, intervention, and primary, secondary, and other outcomes are summarized for studies assessing prevention of noise-induced hearing loss, prevention of drug-induced hearing loss, treatment of stable sensorineural hearing loss, and treatment of sudden sensorineural hearing loss. CONCLUSION: This review provides a comprehensive summary of the state of the science with respect to investigational medicinal products for the inner ear evaluated in human clinical trials, and the current challenges for the field.

Simultaneous rather than retrograde spiral ganglion cell degeneration following ototoxically induced hair cell loss in the guinea pig cochlea.

Severe damage to the organ of Corti leads to degeneration of the spiral ganglion cells (SGCs) which form the auditory nerve. This degeneration starts at the level of synaptic connection of the peripheral processes (PPs) of SGCs with the cochlear hair cells. It is generally thought that from this point SGC degeneration progresses in a retrograde fashion: PPs degenerate first, followed by the SGC soma with a delay of several weeks to many months. Evidence for this course of events, both in animals and in humans, is not unambiguous, while this knowledge is important since the presence or absence of the different neural elements may greatly influence the response to electrical stimulation with a cochlear implant (CI). We therefore aimed to provide a comprehensive account of the course of SGC degeneration in the guinea pig cochlea after ototoxic treatment. Histological analysis of eighteen healthy and thirty-three deafened cochleas showed that the degeneration of SGCs and their peripheral processes was simultaneous rather than sequential. As the site of excitation for electrical stimulation with a CI may depend on the course of degeneration of the various neural elements, this finding is relevant both for understanding the electrophysiological mechanisms behind cochlear implantation and for recent efforts to induce PP resprouting for improved electrode-neural interface. Since excitation of the PPs is often thought to result in (secondary) longer-latency activity, we tested the hypothesis that having relatively many PPs produces a larger N2 peak in the electrically evoked compound action potential (eCAP); the present findings however do not support this theory. The course of the degeneration process may vary among species, and may depend on the cause of deafness, but the present findings at least indicate that gradual retrograde degeneration of the auditory nerve is not an elemental process following severe damage to the organ of Corti.

miR-182 prevented ototoxic deafness induced by co-administration of kanamycin and furosemide in rats.

Ototoxic drugs may induce auditory sensory hair cell loss and permanent deafness; however, there is still no effective treatments or prevention strategies for this side effect. A recent study found that microRNA182 (miR-182) protected cochlear hair cells from ototoxic drug-induced apoptosis in vitro. However, it remains unclear whether miR-182 can protect drug-induced deafness in vivo. In this study, we overexpressed cochlear miR-182 in Sprague-Dawley rats by trans-round window niche delivery of miR-182 mimics. The rats subsequently received intraperitoneal injections of kanamycin and furosemide to induce acute cochlear outer hair cell death and permanent deafness. Auditory brainstem response tests showed that miR-182 attenuated permanent threshold shifts. Consistent with this result, miR-182 reduced the loss of outer hair cells and missing stereocilia. miR-182 treatment also increased the level of phosphoinositide-3 kinase regulatory subunit p85α in the outer hair cells after co-administration of kanamycin and furosemide. Our findings suggest that miR-182 has powerful protective potential against ototoxic drug-induced acute auditory sensory hair cell loss and permanent deafness.

Pou4f3 gene mutation promotes autophagy and apoptosis of cochlear hair cells in cisplatin-induced deafness mice.

Pou4f3 plays an important role in the development of hair cells in the inner ear sensory epithelia. Autophagy is related to the auditory damage. However, the role and mechanism of Pou4f3 on drug-induced ototoxicity are incompletely understood. Hence, this study aimed to explore the effects of Pou4f3 on the apoptosis of cochlear hair cells (CHCs) and to explore whether autophagy was involved in this process. The cisplatin was used to produce a loss of CHCs to create a murine model of deafness. The AAV vectors were delivered into the scala media through the lateral wall. Compared with the control mice, the cisplatin-treated mice exhibited significantly enhanced apoptosis and autophagy in the cochleae, accompanied by a notably decreased Pou4f3 levels. Both mutation and knockdown of Pou4f3 promoted the apoptosis- and autophagy-related protein levels, and enhanced the cisplatin-induced levels of apoptosis- and autophagy-related proteins. Furthermore, the autophagy activator rapamycin promoted the apoptosis and autophagy in the cochlea. In addition, the autophagy inhibitor 3-MA overturned the promoting effect of Pou4f3 knockdown on the apoptosis and autophagy. Collectively, in cisplatin-induced deafness mice, the Pou4f3 gene mutation facilitated apoptosis of cochlear hair cells, at least partially, through inducing autophagy.

[Drug-induced hearing loss as a manifestation of drug-induced ototoxicity]. / Lekarstvenno-indutsirovannaia tugoukhost' kak proiavlenie lekarstvenno-indutsirovannoi ototoksichnosti.

The ability of drugs to have an ototoxic effect has been studied for a long time, however, the true prevalence of this undesirable phenomenon is unknown, which is due to the use of various audiological protocols, a wide range of reactions to drugs in different ethnic groups, and most importantly, the lack of caution with regard to otological symptoms due to their reversibility or lack of immediate threat to life. Drug-induced ototoxicity is a functional disorder of the inner ear (cochlea and/or vestibular apparatus) or eighth pair of cranial nerves. Pharmacotherapy, associated with the development of ototoxic drug reactions, may remain undervalued for a long time, often until irreversible hearing impairment is formed. The most frequently prescribed drugs that cause ototoxic phenomena include anticancer drugs, antibacterial drugs of the aminoglycoside group, loop diuretics, calcium channel blockers, non-steroidal anti-inflammatory drugs, antimalarial drugs, salicylates, etc. Monitoring the degree of hearing impairment before and during therapy is important in preventing the development of drug-induced ototoxicity and makes it possible to consider alternative treatment regimens in a timely manner. It is in this connection that the role of participation in the appointment of rational pharmacotherapy to patients with a potential risk of developing otological phenomena of a clinical pharmacologist and audiologist undoubtedly increases.

Endoplasmic reticulum stress is involved in spiral ganglion neuron apoptosis following chronic kanamycin-induced deafness.

Aminoglycoside antibiotics-induced hearing loss is a common sensorineural impairment. Spiral ganglion neurons (SGNs) are first-order neurons of the auditory pathway and are critical for the maintenance of normal hearing. In the present study, we investigated the time-course of morphological changes and the degeneration process of spiral ganglion cells (SGCs) following chronic kanamycin-induced deafness and determined whether the endoplasmic reticulum (ER) stress was involved in the degeneration of SGNs. We detected density changes in SGCs and the expressions of Bip, inositol requirement 1 (IRE1)α, activating transcription factor-6α, p-PERK, p-eIF2α, CHOP, and caspase-12 at each time point after kanamycin treatment. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining was also performed. The number of SGC deletions reached ∼50% at the 70th day after kanamycin administration and the ER of most SGCs were dilated. The expression of p-PERK, p-eIF2α, p-IRE1α, Bip, caspase-12, and Chop was significantly unregulated after kanamycin treatment. The number of SGCs that were positive for both TUNEL and caspase-12 increased from day 7 to 28. Taken together, these data demonstrate that ER stress was involved in kanamycin-induced apoptosis of SGNs. Kanamycin-induced SGN apoptosis is mediated, at least in part, by ER stress-induced upregulation of CHOP and caspase-12.

Aminoglycoside-associated nonsyndromic deafness and speech disorder in mitochondrial A1555G mutation in a family: A case report.

RATIONALE: Mitochondrial DNA mutations have been associated with many maternal inherited diseases. A1555G mutation in mtDNA effects the gene code for rRNA, resulting in the structural change of human ribosome rending it susceptible to binding of the common antibiotic, aminoglycosides. Such mutation has linked with non-syndromic hearing loss and is one of the most common mtDNA mutations in Asian populations. PATIENT CONCERNS: A 50-year-old Taiwanese female visited our neurology department with concern for multiple members with hearing loss in her family, including herself. DIAGNOSES: Physical examination findings were not significant besides hearing loss and brain MRI did not reveal any lesions. BAEP confirmed bilateral peripheral sensory deficit. Given the multiple cases of hearing loss in the family, a genetic cause was suspected. Using PCR and sequences chromatogram technique we have identified A1555G mutation on her mtDNA affecting region codes for 12S rRNA. Additionally, we observed severe speech disorder in two young family members with the onset of hearing loss began in their early childhood. INTERVENTIONS: The patient declined any form of intervention at the time for personal reasons. OUTCOMES: The patient was satisfied with the diagnosis, her and her families are continuously followed by our neurology department. LESSONS: We report on a family with mtDNA mutation hearing loss that is related to exposure to aminoglycosides. Children with such mutation are at high risk for impaired linguistic function. Early identification and intervention with cochlear implant should be considered.