The ototoxic drug cisplatin localises to stress granules altering their dynamics and composition.

Cisplatin is an effective platinum-based chemotherapeutic with several side effects, including ototoxicity. Cochlear cells have low rates of proliferation yet are highly susceptible to cisplatin. We hypothesised that cisplatin ototoxicity might be caused by cisplatin-protein interactions rather than cisplatin-DNA interactions. Two known cisplatin-binding proteins are involved in the stress granule (SG) response. SGs are a pro-survival mechanism involving formation of transient ribonucleoprotein complexes during stress. We examined the effects of cisplatin on SG dynamics and composition in cell lines derived from the cochlea and retinal pigment epithelium. Cisplatin-induced SGs are significantly diminished in size and quantity compared to arsenite-induced SGs and are persistent after 24 h recovery. Additionally, cisplatin pre-treated cells were unable to form a typical SG response to subsequent arsenite stress. Cisplatin-induced SGs had significant reductions in the sequestration of eIF4G and the proteins RACK1 and DDX3X. Live-cell imaging of Texas Red-conjugated cisplatin revealed its localisation to SGs and retention for at least 24 h. We show cisplatin-induced SGs have impaired assembly, altered composition and are persistent, providing evidence of an alternate mechanism for cisplatin-induced ototoxicity via an impaired SG response.

Inhibition of Gpx4-mediated ferroptosis alleviates cisplatin-induced hearing loss in C57BL/6 mice.

Cisplatin-induced hearing loss is a common side effect of cancer chemotherapy in clinics; however, the mechanism of cisplatin-induced ototoxicity is still not completely clarified. Cisplatin-induced ototoxicity is mainly associated with the production of reactive oxygen species, activation of apoptosis, and accumulation of intracellular lipid peroxidation, which also is involved in ferroptosis induction. In this study, the expression of TfR1, a ferroptosis biomarker, was upregulated in the outer hair cells of cisplatin-treated mice. Moreover, several key ferroptosis regulator genes were altered in cisplatin-damaged cochlear explants based on RNA sequencing, implying the induction of ferroptosis. Ferroptosis-related Gpx4 and Fsp1 knockout mice were established to investigate the specific mechanisms associated with ferroptosis in cochleae. Severe outer hair cell loss and progressive damage of synapses in inner hair cells were observed in Atoh1-Gpx4-/- mice. However, Fsp1-/- mice showed no significant hearing phenotype, demonstrating that Gpx4, but not Fsp1, may play an important role in the functional maintenance of HCs. Moreover, findings showed that FDA-approved luteolin could specifically inhibit ferroptosis and alleviate cisplatin-induced ototoxicity through decreased expression of transferrin and intracellular concentration of ferrous ions. This study indicated that ferroptosis inhibition through the reduction of intracellular ferrous ions might be a potential strategy to prevent cisplatin-induced hearing loss.

Pharmacogenetics of aminoglycoside-related ototoxicity: a systematic review.

BACKGROUND: Aminoglycosides (AGs) are important antibiotics in the treatment of Gram-negative sepsis. However, they are associated with the risk of irreversible sensorineural hearing loss (SNHL). Several genetic variants have been implicated in the development of ototoxicity. OBJECTIVES: To evaluate the pharmacogenetic determinants of AG-related ototoxicity. METHODS: This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses and was registered on Prospero (CRD42022337769). In Dec 2022, PubMed, Cochrane Library, Embase and MEDLINE were searched. Included studies were those reporting original data on the effect of the AG-exposed patient's genome on the development of ototoxicity. RESULTS: Of 10 202 studies, 31 met the inclusion criteria. Twenty-nine studies focused on the mitochondrial genome, while two studied the nuclear genome. One study of neonates found that 30% of those with the m.1555A > G variant failed hearing screening after AG exposure (level 2 evidence). Seventeen additional studies found the m.1555A > G variant was associated with high penetrance (up to 100%) of SNHL after AG exposure (level 3-4 evidence). Nine studies of m.1494C > T found the penetrance of AG-related SNHL to be up to 40%; however, this variant was also identified in those with SNHL without AG exposure (level 3-4 evidence). The variants m.1005T > C and m.1095T > C may be associated with AG-related SNHL; however, further studies are needed. CONCLUSIONS: This review found that the m.1555A > G and m.1494C > T variants in the MT-RNR1 gene have the strongest evidence in the development of AG-related SNHL, although study quality was limited (level 2-4). These variants were associated with high penetrance of a SNHL phenotype following AG exposure.

Frequency and Patterns of Hearing Dysfunction in Patients Treated with Teprotumumab.

PURPOSE: To better characterize the frequency and patterns of hearing dysfunction in patients who have received teprotumumab to treat thyroid eye disease. DESIGN: Noncomparative case series. PARTICIPANTS: Patients who underwent audiology testing before and after completion of teprotumumab infusions. METHODS: A review of patients who underwent audiology testing before and after completion of teprotumumab infusions was carried out. Additional audiogram testing during treatment was included when available. Hearing function was analyzed using audiogram data measuring threshold hearing levels at specific frequencies. Basic demographic data as well as information regarding otologic symptoms also were obtained and analyzed. MAIN OUTCOME MEASURES: Hearing loss demonstrated by a significant change in decibel hearing thresholds or that meets criteria for ototoxicity. RESULTS: Twenty-two patients (44 ears) were included in the study, with baseline and most recent audiology testing after treatment ranging from 84 days before to 496 days after treatment. Fifteen patients (30 ears) also underwent testing during treatment starting after the second infusion up until the day of, but before, the eighth infusion. Hearing loss after treatment met criteria for ototoxicity in 17 of the 44 ears (38.6%), with 11 of the 22 patients (50.0%) meeting criteria in at least 1 ear. The pure-tone average decibel hearing levels (HLs) across all 44 ears demonstrated hearing loss after treatment (P = 0.0029), specifically at high (P = 0.0008) and middle frequencies (P = 0.0042), but not at low frequencies (P = 0.8344). Patients who were older also were more likely to experience hearing loss after treatment (P = 0.0048). CONCLUSIONS: Audiometric data demonstrate that teprotumumab influences hearing function, most significantly at higher frequencies and in older patients. Audiometric testing is critical for counseling patients regarding teprotumumab treatment. A protocol for monitoring hearing during treatment is needed to detect and manage hearing changes associated with teprotumumab use. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

SERCA2 protects against cisplatin-induced damage of auditory cells: Possible relation with alleviation of ER stress.

AIMS: SERCA2, one of the P-type pumps encoded by gene ATP2A2, is the only calcium reflux channel of the endoplasmic reticulum (ER) and participates in maintaining calcium homeostasis. The present study was designed to explore SERCA2 expression pattern in auditory hair cells and the possible mechanism underlying the effects of SERCA2 on cisplatin-induced ototoxicity. MAIN METHODS: The SERCA2 expression pattern in cochlea hair cells and HEI-OC1 cells was measured by Western blot (WB) and immunofluorescence staining. The apoptosis and its related factors were detected by TUNEL assay and WB. The expression levels of ER stress-related factors, ATF6, PERK, IRE1α, and GRP78, were measured via WB. As for the determination of SERCA2 overexpression and knockdown, plasmids and lentiviral vectors were constructed, respectively. KEY FINDINGS: We found that SERCA2 was highly expressed in cochlea hair cells and HEI-OC1 cells. Of note, the level of SERCA2 expression in neonatal mice was remarkably higher than that in adult mice. Under the exposure of 30 µM cisplatin, SERCA2 was down-regulated significantly compared with the control group. In addition, cisplatin administration triggered the occurrence of ER stress and apoptosis. Those events were reversed by overexpressing SERCA2. On the contrary, SERCA2 knockdown could aggravate the above processes. SIGNIFICANCE: The findings from the present study disclose, for the first time, that SERCA2 is abundantly expressed in cochlea hair cells, and the suppression of SERCA2 caused by cisplatin could trigger ER homeostasis disruption, thereby implying that SERCA2 might be a promising target to prevent cisplatin-induced cytotoxicity of hair cells.

Occupational Lead Exposure Ototoxicity Evaluated With Distortion-Product Otoacoustic Emissions.

OBJECTIVES: To evaluate the extent of hearing loss among pottery workers in Mexico exposed to lead. DESIGN: The authors conducted a cross-sectional study including 315 adult pottery workers. Auditory function was evaluated by air conduction pure-tone audiometry (pure-tone average) and distortion-product otoacoustic emission (DPOAE) levels (amplitude and signal-to-noise ratio). Lead exposure was assessed with a single blood sample test and classified as low, medium, and high according to blood lead tertiles. Logistic regression models were calculated for the association between blood lead levels, pure-tone average, and DPOAE records. RESULTS: Median (25th-75th) blood lead levels were 14 µg/dL (7.5-22.6 µg/dL). The audiometric pattern and DPOAE records were similar across blood lead levels groups in all frequencies, and no statistically significant differences were found. Adjusted logistic regression models showed no increase in the odds for hearing thresholds >25 dB (HL) and DPOAE absence associated with blood lead levels, and no dose-response pattern was observed ( p > 0.05). CONCLUSIONS: Given the results from this cross-sectional study, no association was found between blood lead levels and hearing loss assessed with DPOAE. Future longitudinal work should consider chronic lead exposure estimates among underrepresented populations, which can potentially inform safer work practices to minimize the risk of ototoxicity.

Ototoxic and nephrotoxic drugs in neonatal intensive care units: results of a Spanish and Italian survey.

Neonates face heightened susceptibility to drug toxicity, often exposed to off-label medications with dosages extrapolated from adult or pediatric studies. Premature infants in Neonatal Intensive Care Units (NICUs) are particularly at risk due to underdeveloped pharmacokinetics and exposure to multiple drugs. The study aimed to survey commonly used medications with a higher risk of ototoxicity and nephrotoxicity in Spanish and Italian neonatal units. A prospective cross-sectional study was conducted in Italian and Spanish neonatal units using a web-based survey with 43 questions. A modified Delphi method involved experts refining the survey through online consensus. Ethical approval was obtained, and responses were collected from January to July 2023. The survey covered various aspects, including drug-related ototoxic and nephrotoxic management, hearing screening, and therapeutic drug monitoring. Responses from 131 participants (35.9% from Spain and 64.1% from Italy) revealed awareness of drug toxicity risks. Varied practices were observed in hearing screening protocols, and a high prevalence of ototoxic and nephrotoxic drug use, including aminoglycosides (100%), vancomycin (70.2%), loop diuretics (63.4%), and ibuprofen (62.6%). Discrepancies existed in guideline availability and adherence, with differences between Italy and Spain in therapeutic drug monitoring practices. CONCLUSIONS: The study underscores the need for clinical guidelines and uniform practices in managing ototoxic and nephrotoxic drugs in neonatal units. Awareness is high, but inconsistencies in practices indicate a necessity for standardization, including the implementation of therapeutic drug monitoring and the involvement of clinical pharmacologists. Addressing these issues is crucial for optimizing neonatal care in Southern Europe. WHAT IS KNOWN: • Neonates in intensive care face a high risk of nephrotoxicity and ototoxicity from drugs like aminoglycosides, vancomycin, loop diuretics, and ibuprofen. • Therapeutic drug monitoring is key for managing these risks, optimizing dosing for efficacy and minimizing side effects. WHAT IS NEW: • NICUs in Spain and Italy show high drug toxicity awareness but differ in ototoxic/nephrotoxic drug management. • Urgent need for standard guidelines and practices to address nephrotoxic risks from aminoglycosides, vancomycin, loop diuretics, and ibuprofen.

Calcium channel inhibitor and extracellular calcium improve aminoglycoside-induced hair cell loss in zebrafish.

Aminoglycosides are commonly used antibiotics for treatment of gram-negative bacterial infections, however, they might act on inner ear, leading to hair-cell death and hearing loss. Currently, there is no targeted therapy for aminoglycoside ototoxicity, since the underlying mechanisms of aminoglycoside-induced hearing impairments are not fully defined. This study aimed to investigate whether the calcium channel blocker verapamil and changes in intracellular & extracellular calcium could ameliorate aminoglycoside-induced ototoxicity in zebrafish. The present findings showed that a significant decreased number of neuromasts in the lateral lines of zebrafish larvae at 5 days' post fertilization after neomycin (20 µM) and gentamicin (20 mg/mL) exposure, which was prevented by verapamil. Moreover, verapamil (10-100 µM) attenuated aminoglycoside-induced toxic response in different external calcium concentrations (33-3300 µM). The increasing extracellular calcium reduced hair cell loss from aminoglycoside exposure, while lower calcium facilitated hair cell death. In contrast, calcium channel activator Bay K8644 (20 µM) enhanced aminoglycoside-induced ototoxicity and reversed the protective action of higher external calcium on hair cell loss. However, neomycin-elicited hair cell death was not altered by caffeine, ryanodine receptor (RyR) agonist, and RyR antagonists, including thapsigargin, ryanodine, and ruthenium red. The uptake of neomycin into hair cells was attenuated by verapamil and under high external calcium concentration. Consistently, the production of reactive oxygen species (ROS) in neuromasts exposed to neomycin was also reduced by verapamil and high external calcium. Significantly, zebrafish larvae when exposed to neomycin exhibited decreased swimming distances in reaction to droplet stimulus when compared to the control group. Verapamil and elevated external calcium effectively protected the impaired swimming ability of zebrafish larvae induced by neomycin. These data imply that prevention of hair cell damage correlated with swimming behavior against aminoglycoside ototoxicity by verapamil and higher external calcium might be associated with inhibition of excessive ROS production and aminoglycoside uptake through cation channels. These findings indicate that calcium channel blocker and higher external calcium could be applied to protect aminoglycoside-induced listening impairments.

Protective role of pyrroloquinoline quinone against gentamicin induced cochlear hair cell ototoxicity.

Gentamicin (GM) is one of the commonly used antibiotics in the aminoglycoside class but is ototoxic, which constantly impacts the quality of human life. Pyrroloquinoline quinone (PQQ) as a redox cofactor produced by bacteria was found in soil and foods that exert an antioxidant and redox modulator. It is well documented that the PQQ can alleviate inflammatory responses and cytotoxicity. However, our understanding of PQQ in ototoxicity remains unclear. We reported that PQQ could protect against GM-induced ototoxicity in House Ear Institute-Organ of Corti 1 (HEI-OC1) cells in vitro. To evaluate reactive oxygen species (ROS) production and mitochondrial function, ROS and JC-1 staining, oxygen consumption rate (OCR), and extracellular acidification rate (ECAR) measurements in living cells, mitochondrial dynamics analysis was performed. GM-mediated damage was performed by reducing the production of ROS and inhibiting mitochondria biogenesis and dynamics. PQQ ameliorated the cellular oxidative stress and recovered mitochondrial membrane potential, facilitating the recovery of mitochondrial biogenesis and dynamics. Our in vitro findings improve our understanding of the GM-induced ototoxicity with therapeutic implications for PQQ.

Ototoxicity among cisplatin, carboplatin, and oxaliplatin in zebrafish model.

Platinum-based antineoplastic drugs, including cisplatin, carboplatin, and oxaliplatin, are widely used in the treatment of various cancers. Ototoxicity is a common adverse effect of platinum-based drugs. Ototoxicity leads to irreversible hearing impairment. We hypothesize that different platinum-based drugs exhibit varying ototoxic concentrations, time effects, and ototoxic mechanisms. We tested this hypothesis by using a zebrafish model (pvalb3b: TagGFP) to assess the viability of hair cells collected from zebrafish larvae. Cisplatin, carboplatin, and oxaliplatin were administered at dosages of 100, 200, or 400 µM, and the ototoxic effects of these drugs were assessed 1, 2, or 3 h after administration. Fm4-64 and a TUNEL assay were used to label the membranes of living hair cells and to detect cell apoptosis, respectively. We observed that >50% of hair cells were damaged at 1 h after cisplatin (100 µM) exposure, and this ototoxic effect increased at higher dosages and over time. Owing to the smaller ototoxic effects of carboplatin and oxaliplatin, we conducted higher-strength and longer-duration experiments with these drugs. Neither carboplatin nor oxaliplatin was obviously ototoxic, even at 1600 µM and after 6 h. Moreover, only cisplatin damaged the membranes of the hair cells. Cell apoptosis and significantly increased antioxidant gene expression were observed in only the cisplatin group. In conclusion, cisplatin significantly damages sensory hair cells and has notable dosage and time effects. Carboplatin and oxaliplatin are less ototoxic than cisplatin, likely due to having different ototoxic mechanisms than cisplatin.

Exploring NICU nurses' views of a novel genetic point-of-care test identifying neonates at risk of antibiotic-induced ototoxicity: A qualitative study.

AIM: To explore the views of neonatal intensive care nursing staff on the deliverability of a novel genetic point-of-care test detecting a genetic variant associated with antibiotic-induced ototoxicity. DESIGN: An interpretive, descriptive, qualitative interview study. METHODS: Data were collected using semi-structured interviews undertaken between January and November 2020. Participants were neonatal intensive care nursing staff taking part in the Pharmacogenetics to Avoid Loss of Hearing trial. RESULTS: Thematic analysis resulted in four themes: perceived clinical utility; the golden hour; point-of-care device; training and support. Recommendations were made to streamline the protocol and ongoing training and support were considered key to incorporating the test into routine care. CONCLUSION: Exploring the views of nurses involved in the delivery of the point-of-care test was essential in its implementation. By the study endpoint, all participants could see the value of routine clinical introduction of the point-of care test. IMPLICATIONS FOR THE PROFESSION AND/OR PATIENT CARE: Nurses are in a key position to support the delivery of point-of-care genetic testing into mainstream settings. This study has implications for the successful integration of other genetic point-of-care tests in acute healthcare settings. IMPACT: The study will help to tailor the training and support required for routine deployment of the genetic point-of-care test. The study has relevance for nurses involved in the development and delivery of genetic point-of-care tests in other acute hospital settings. REPORTING METHOD: This qualitative study adheres to the Standards for Reporting Qualitative Research EQUATOR guidelines and utilizes COREQ and SRQR checklists. PATIENT OR PUBLIC CONTRIBUTION: All staff working on the participating neonatal intensive care units were trained to use the genetic point-of-care test. All inpatients on the participating units were eligible to have testing via the point-of-care test. The Pharmacogenetics to Avoid Loss of Hearing Patient and Public Involvement and Engagement group provided valuable feedback. TRIAL AND PROTOCOL REGISTRATION: Registered within the University of Manchester. Ethics approval reference numbers: IRAS: 253102 REC reference: 19/NW/0400. Also registered with the ISRCTN ref: ISRCTN13704894.

A pilot study of antimicrobial effects and ototoxicity of a Norway spruce (Picea abies) resin-based canine otic rinse product.

BACKGROUND: Norway spruce (Picea abies) resin-based products are used in human medicine. A resin-based otic rinse also could be useful in supportive care of canine otitis externa (COE), yet information on its antimicrobial effect against canine pathogens or ototoxicity is lacking. OBJECTIVES: To investigate the antimicrobial properties and ototoxicity of a commercial resin-based otic product. MATERIALS AND METHODS: Antimicrobial effect was evaluated using a standardised challenge test on Staphylococcus pseudintermedius, Corynebacterium auriscanis, Pseudomonas aeruginosa, Escherichia coli, Malassezia pachydermatis, and Streptococcus halichoeri strains to measure reduction in growth after 24 h exposure to the product. Effect on cell morphology was investigated by exposing S. pseudintermedius, C. auriscanis, P. aeruginosa and M. pachydermatis to the product in 20% and 100% (v/v) concentrations for 6, 24 and 48 h, and evaluating cells by transmission (TEM) and scanning (SEM) electron microscopy. An in vitro microbial kill-rate assay also was performed. Auditory brain stem response test, clinical evaluation and postmortem histological evaluation of ear canals were undertaken on experimental guinea pigs treated with the test product or saline controls. RESULTS: The product showed >log 5 growth reduction for all strains in the challenge test. TEM and SEM images showed clear changes in the cells' inner structures and deterioration of cells, and 100% (v/v) test product exposure induced microbial killing in 1-2 h. Ototoxicity was not detected in guinea pigs. CONCLUSIONS AND CLINICAL RELEVANCE: The product may be an option in supportive care of COE because of antimicrobial effects and lack of ototoxic properties in a guinea pig model.

Exploring Embryo-Ototoxic Effects: Insights into Deodorant-Induced Hair Cell Damage in Zebrafish.

Our study investigated the embryo-ototoxic effects of deodorant2 (DA2) on zebrafish embryos, which serve as valuable model organisms due to genetic and physiological similarities to humans. We focused on understanding DA2's impact on zebrafish hair cells, which are vital for sensory perception and balance regulation. DA2, provided by the Ministry of Environment, Republic of Korea, was used at 460 µg/mL in dimethyl sulfoxide (DMSO), with a 0.43% DMSO solvent control group. Three experiments, each using 10 zebrafish specimens from each group, showed an initial 13% hair cell count reduction in the DA2-exposed group. Subsequent experiments demonstrated reductions of 37% and 22%, each with one mortality case. Statistical analysis revealed a significant 24% hair cell count reduction in the DA2-exposed group. We also assessed DA2's impact on zebrafish behavior. Although not statistically significant, differences in distances traveled (0.33-0.39, 95% confidence interval: -0.46-1.1, p = 0.2033) and latencies (-0.016-0.018, 95% confidence interval: -0.052-0.021, p = 0.1917) hinted at negative effects. These results highlight DA2's ototoxic properties affecting zebrafish auditory systems and behavior. Further investigation into DA2's effects on aquatic organisms and potential mitigation strategies are essential. These findings contribute to understanding DA2's safety profile, benefiting aquatic ecosystems and human health assessments.

The miR-182-5p/GPX4 Pathway Contributes to Sevoflurane-Induced Ototoxicity via Ferroptosis.

Our study aimed to investigate the role of ferroptosis in sevoflurane-induced hearing impairment and explore the mechanism of the microRNA-182-5p (miR-182-5p)/Glutathione Peroxidase 4 (GPX4) pathway in sevoflurane-induced ototoxicity. Immunofluorescence staining was performed using myosin 7a and CtBP2. Cell viability was assessed using the CCK-8 kit. Fe2+ concentration was measured using FerroOrange and Mi-to-FerroGreen fluorescent probes. The lipid peroxide level was assessed using BODIPY 581/591 C11 and MitoSOX fluorescent probes. The auditory brainstem response (ABR) test was conducted to evaluate the hearing status. Bioinformatics tools and dual luciferase gene reporter analysis were used to confirm the direct targeting of miR-182-5p on GPX4 mRNA. GPX4 and miR-182-5p expression in cells was assessed by qRT-PCR and Western blot. Ferrostatin-1 (Fer-1) pretreatment significantly improved hearing impairment and damage to ribbon synapses in mice caused by sevoflurane exposure. Immunofluorescence staining revealed that Fer-1 pretreatment reduced intracellular and mitochondrial iron overload, as well as lipid peroxide accumulation. Our findings indicated that miR-182-5p was upregulated in sevoflurane-exposed HEI-OC1 cells, and miR-182-5p regulated GPX4 expression by binding to the 3'UTR of GPX4 mRNA. The inhibition of miR-182-5p attenuated sevoflurane-induced iron overload and lipid peroxide accumulation. Our study elucidated that the miR-182-5p/GPX4 pathway was implicated in sevoflurane-induced ototoxicity by promoting ferroptosis.

Ultrasound-Mediated Lysozyme Microbubbles Targeting NOX4 Knockdown Alleviate Cisplatin-Exposed Cochlear Hair Cell Ototoxicity.

The nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) protein plays an essential role in the cisplatin (CDDP)-induced generation of reactive oxygen species (ROS). In this study, we evaluated the suitability of ultrasound-mediated lysozyme microbubble (USMB) cavitation to enhance NOX4 siRNA transfection in vitro and ex vivo. Lysozyme-shelled microbubbles (LyzMBs) were constructed and designed for siNOX4 loading as siNOX4/LyzMBs. We investigated different siNOX4-based cell transfection approaches, including naked siNOX4, LyzMB-mixed siNOX4, and siNOX4-loaded LyzMBs, and compared their silencing effects in CDDP-treated HEI-OC1 cells and mouse organ of Corti explants. Transfection efficiencies were evaluated by quantifying the cellular uptake of cyanine 3 (Cy3) fluorescein-labeled siRNA. In vitro experiments showed that the high transfection efficacy (48.18%) of siNOX4 to HEI-OC1 cells mediated by US and siNOX4-loaded LyzMBs significantly inhibited CDDP-induced ROS generation to almost the basal level. The ex vivo CDDP-treated organ of Corti explants of mice showed an even more robust silencing effect of the NOX4 gene in the siNOX4/LyzMB groups treated with US sonication than without US sonication, with a marked abolition of CDDP-induced ROS generation and cytotoxicity. Loading of siNOX4 on LyzMBs can stabilize siNOX4 and prevent its degradation, thereby enhancing the transfection and silencing effects when combined with US sonication. This USMB-derived therapy modality for alleviating CDDP-induced ototoxicity may be suitable for future clinical applications.

Modulating the Activity of the Human Organic Cation Transporter 2 Emerges as a Potential Strategy to Mitigate Unwanted Toxicities Associated with Cisplatin Chemotherapy.

Cisplatin (CDDP) stands out as an effective chemotherapeutic agent; however, its application is linked to the development of significant adverse effects, notably nephro- and ototoxicity. The human organic cation transporter 2 (hOCT2), found in abundance in the basolateral membrane domain of renal proximal tubules and the Corti organ, plays a crucial role in the initiation of nephro- and ototoxicity associated with CDDP by facilitating its uptake in kidney and ear cells. Given its limited presence in cancer cells, hOCT2 emerges as a potential druggable target for mitigating unwanted toxicities associated with CDDP. Potential strategies for mitigating CDDP toxicities include competing with the uptake of CDDP by hOCT2 or inhibiting hOCT2 activity through rapid regulation mediated by specific signaling pathways. This study investigated the interaction between the already approved cationic drugs disopyramide, imipramine, and orphenadrine with hOCT2 that is stably expressed in human embryonic kidney cells. Regarding disopyramide, its influence on CDDP cellular transport by hOCT2 was further characterized through inductively coupled plasma isotope dilution mass spectrometry. Additionally, its potential protective effects against cellular toxicity induced by CDDP were assessed using a cytotoxicity test. Given that hOCT2 is typically expressed in the basolateral membrane of polarized cells, with specific regulatory mechanisms, this work studied the regulation of hOCT2 that is stably expressed in Madin-Darby Canine Kidney (MDCK) cells. These cells were cultured in a matrix to induce the formation of cysts, exposing hOCT2 in the basolateral plasma membrane domain, which was freely accessible to experimental solutions. The study specifically tested the regulation of ASP+ uptake by hOCT2 in MDCK cysts through the inhibition of casein kinase II (CKII), calmodulin, or p56lck tyrosine kinase. Furthermore, the impact of this manipulation on the cellular toxicity induced by CDDP was examined using a cytotoxicity test. All three drugs-disopyramide, imipramine, and orphenadrine-demonstrated inhibition of ASP+ uptake, with IC50 values in the micromolar (µM) range. Notably, disopyramide produced a significant reduction in the CDDP cellular toxicity and platinum cellular accumulation when co-incubated with CDDP. The activity of hOCT2 in MDCK cysts experienced a significant down-regulation under inhibition of CKII, calmodulin, or p56lck tyrosine kinase. Interestingly, only the inhibition of p56lck tyrosine kinase demonstrated the capability to protect the cells against CDDP toxicity. In conclusion, certain interventions targeting hOCT2 have demonstrated the ability to reduce CDDP cytotoxicity, at least in vitro. Further investigations in in vivo systems are warranted to ascertain their potential applicability as co-treatments for mitigating undesired toxicities associated with CDDP in patients.

Prevention and treatment of cisplatin-induced ototoxicity in adults: A systematic review.

OBJECTIVES: Ototoxicity is a common disabling side effect of platinum-based chemotherapy. This study aimed to assess the evidence on the management of platinum-induced ototoxicity in adult cancer patients. METHODS: Four databases were searched up to 1 November 2022. Original studies were included if they reported on a pharmacologic or non-pharmacologic intervention to prevent or treat platinum ototoxicity in adults. The articles' quality was assessed via two grading scales. RESULTS: Nineteen randomised controlled trials and five quasi-experimental studies with 1673 patients were analysed. Eleven interventions were identified, nine pharmacological and two non-pharmacological. Six of the interventions (sodium thiosulphate, corticoids, sertraline, statins, multivitamins and D-methionine) showed mild benefits in preventing cisplatin-induced ototoxicity. Only one trial assessed corticoids as a potential treatment. Overall, only six trials were deemed with a low risk of bias. The majority of studies inadequately documented intervention-related adverse effects, thereby limiting safety conclusions. CONCLUSIONS: Current interventions have mild benefits in preventing cisplatin-induced ototoxicity in adult cancer patients. Sodium thiosulphate is the most promising intervention as a preventive strategy. Rigorous, high-quality research is warranted, encompassing an evaluation of all potential symptoms and innovative treatment modalities.

Binocular 3-D otolith-ocular reflexes: responses of chinchillas to natural and prosthetic stimulation after ototoxic injury and vestibular implantation.

The otolith end organs inform the brain about gravitational and linear accelerations, driving the otolith-ocular reflex (OOR) to stabilize the eyes during translational motion (e.g., moving forward without rotating) and head tilt with respect to gravity. We previously characterized OOR responses of normal chinchillas to whole body tilt and translation and to prosthetic electrical stimulation targeting the utricle and saccule via electrodes implanted in otherwise normal ears. Here we extend that work to examine OOR responses to tilt and translation stimuli after unilateral intratympanic gentamicin injection and to natural/mechanical and prosthetic/electrical stimulation delivered separately or in combination to animals with bilateral vestibular hypofunction after right ear intratympanic gentamicin injection followed by surgical disruption of the left labyrinth at the time of electrode implantation. Unilateral intratympanic gentamicin injection decreased natural OOR response magnitude to about half of normal, without markedly changing OOR response direction or symmetry. Subsequent surgical disruption of the contralateral labyrinth at the time of electrode implantation surgery further decreased OOR magnitude during natural stimulation, consistent with bimodal-bilateral otolith end organ hypofunction (ototoxic on the right ear, surgical on the left ear). Delivery of pulse frequency- or pulse amplitude-modulated prosthetic/electrical stimulation targeting the left utricle and saccule in phase with whole body tilt and translation motion stimuli yielded responses closer to normal than the deficient OOR responses of those same animals in response to head tilt and translation alone.NEW & NOTEWORTHY Previous studies to expand the scope of prosthetic stimulation of the otolith end organs showed that selective stimulation of the utricle and saccule is possible. This article further defines those possibilities by characterizing a diseased animal model and subsequently studying its responses to electrical stimulation alone and in combination with mechanical motion. We show that we can partially restore responses to tilt and translation in animals with unilateral gentamicin ototoxic injury and contralateral surgical disruption.

Decreased expression of synaptic genes in the vestibular ganglion of rodents following subchronic ototoxic stress.

The vestibular ganglion contains primary sensory neurons that are postsynaptic to the transducing hair cells (HC) and project to the central nervous system. Understanding the response of these neurons to HC stress or loss is of great interest as their survival and functional competence will determine the functional outcome of any intervention aiming at repair or regeneration of the HCs. We have shown that subchronic exposure to the ototoxicant 3,3'-iminodipropionitrile (IDPN) in rats and mice causes a reversible detachment and synaptic uncoupling between the HCs and the ganglion neurons. Here, we used this paradigm to study the global changes in gene expression in vestibular ganglia using RNA-seq. Comparative gene ontology and pathway analyses of the data from both model species indicated a robust downregulation of terms related to synapses, including presynaptic and postsynaptic functions. Manual analyses of the most significantly downregulated transcripts identified genes with expressions related to neuronal activity, modulators of neuronal excitability, and transcription factors and receptors that promote neurite growth and differentiation. For choice selected genes, the mRNA expression results were replicated by qRT-PCR, validated spatially by RNA-scope, or were demonstrated to be associated with decreased expression of the corresponding protein. We conjectured that decreased synaptic input or trophic support on the ganglion neurons from the HC was triggering these expression changes. To support this hypothesis, we demonstrated decreased expression of BDNF mRNA in the vestibular epithelium after subchronic ototoxicity and also downregulated expression of similarly identified genes (e.g Etv5, Camk1g, Slc17a6, Nptx2, Spp1) after HC ablation with another ototoxic compound, allylnitrile. We conclude that vestibular ganglion neurons respond to decreased input from HCs by decreasing the strength of all their synaptic contacts, both as postsynaptic and presynaptic players.

P2X7 receptor is required for the ototoxicity caused by aminoglycoside in developing cochlear hair cells.

Aminoglycoside antibiotics (AGAs) are widely used in life-threatening infections, but they accumulate in cochlear hair cells (HCs) and result in hearing loss. Increases in adenosine triphosphate (ATP) concentrations and P2X7 receptor expression were observed after neomycin treatment. Here, we demonstrated that P2X7 receptor, which is a non-selective cation channel that is activated by high ATP concentrations, may participate in the process through which AGAs enter hair cells. Using transgenic knockout mice, we found that P2X7 receptor deficiency protects HCs against neomycin-induced injury in vitro and in vivo. Subsequently, we used fluorescent gentamicin-Fluor 594 to study the uptake of AGAs and found fluorescence labeling in wild-type mice but not in P2rx7-/- mice in vitro. In addition, knocking-out P2rx7 did not significantly alter the HC count and auditory signal transduction, but it did inhibit mitochondria-dependent oxidative stress and apoptosis in the cochlea after neomycin exposure. We thus conclude that the P2X7 receptor may be linked to the entry of AGAs into HCs and is likely to be a therapeutic target for auditory HC protection.