Reversible p53 inhibition prevents cisplatin ototoxicity without blocking chemotherapeutic efficacy

Enhancing biocompatibility of the brain-machine interface: A review

In vivo implantation of microelectrodes opens the door to studying neural circuits and restoring damaged neural pathways through direct electrical stimulation and recording. Although some neuroprostheses have achieved clinical success, electrode material properties, inflammatory response, and glial scar formation at the electrode-tissue interfaces affect performance and sustainability. Those challenges can be addressed by improving some of the materials' mechanical, physical, chemical, and electrical properties. This paper reviews materials and designs of current microelectrodes and discusses perspectives to advance neuroprosthetics performance.

An In Vitro Oxidative Stress Model of the Human Inner Ear Using Human-Induced Pluripotent Stem Cell-Derived Otic Progenitor Cells

The inner ear organs responsible for hearing (cochlea) and balance (vestibular system) are susceptible to oxidative stress due to the high metabolic demands of their sensorineural cells. Oxidative stress-induced damage to these cells can cause hearing loss or vestibular dysfunction, yet the precise mechanisms remain unclear due to the limitations of animal models and challenges of obtaining living human inner ear tissue. Therefore, we developed an in vitro oxidative stress model of the pre-natal human inner ear using otic progenitor cells (OPCs) derived from human-induced pluripotent stem cells (hiPSCs). OPCs, hiPSCs, and HeLa cells were exposed to hydrogen peroxide or ototoxic drugs (gentamicin and cisplatin) that induce oxidative stress to evaluate subsequent cell viability, cell death, reactive oxygen species (ROS) production, mitochondrial activity, and apoptosis (caspase 3/7 activity). Dose-dependent reductions in OPC cell viability were observed post-exposure, demonstrating their vulnerability to oxidative stress. Notably, gentamicin exposure induced ROS production and cell death in OPCs, but not hiPSCs or HeLa cells. This OPC-based human model effectively simulates oxidative stress conditions in the human inner ear and may be useful for modeling the impact of ototoxicity during early pregnancy or evaluating therapies to prevent cytotoxicity.

Apigenin attenuates cisplatin-induced hair cell damage in the zebrafish lateral line

Cisplatin, a widely used chemotherapy drug, is notorious for causing ototoxicity, which leads to irreversible sensorineural hearing loss by damaging cochlear sensory hair cells (HCs), spiral ganglion neurons (SGNs), and the stria vascularis (SV). Mechanisms include DNA adduct formation, mitochondrial dysfunction, oxidative stress, and inflammation, ultimately triggering cell death pathways like apoptosis, necroptosis, pyroptosis, or ferroptosis. Apigenin, a natural flavonoid found in various foods and beverages, possesses antioxidant, anti-inflammatory, and anti-tumor properties. Despite these benefits, its potential to mitigate cisplatin-induced ototoxicity remains unexplored. To investigate, we administered varying concentrations of apigenin (1 μM, 20 μM, 100 μM, and 250 μM) alongside cisplatin (200 μM) to zebrafish larvae at 5 days post fertilization. Cisplatin significantly reduced lateral line HCs, impacting auditory function as shown in startle response tests. However, co-administration with apigenin preserved lateral line HCs and mitigated cisplatin-induced hearing loss. In larvae exposed to cisplatin, TUNEL assay confirmed significant HCs apoptosis, which apigenin effectively countered by suppressing reactive oxygen species accumulation in lateral line HCs. RNA-seq analysis highlighted apigenin's role in modulating apoptosis-related pathways, supporting its protective effects against cisplatin-induced ototoxicity. These findings underscore apigenin's potential as a crucial protective agent against cisplatin-induced ototoxicity, meriting further investigation for clinical applications.

Pharmacological Approaches to Hearing Loss

Hearing disorders pose significant challenges to individuals experiencing them and their overall quality of life, emphasizing the critical need for advanced pharmacological approaches to address these conditions. Current treatment options often focus on amplification devices, cochlear implants, or other rehabilitative therapies, leaving a substantial gap regarding effective pharmacological interventions. Advancements in our understanding of the molecular and cellular mechanisms involved in hearing disorders induced by noise, aging, and ototoxicity have opened new avenues for drug development, some of which have led to numerous clinical trials, with promising results. The development of optimal drug delivery solutions in animals and humans can also enhance the targeted delivery of medications to the ear. Moreover, large genome studies contributing to a genetic understanding of hearing loss in humans combined with advanced molecular technologies in animal studies have shown a great potential to increase our understanding of the etiologies of hearing loss. The auditory system exhibits circadian rhythms and temporal variations in its physiology, its vulnerability to auditory insults, and its responsiveness to drug treatments. The cochlear clock rhythms are under the control of the glucocorticoid system, and preclinical evidence suggests that the risk/benefit profile of hearing disorder treatments using chronopharmacological approaches would be beneficial. If translatable to the bedside, such approaches may improve the outcome of clinical trials. Ongoing research into the molecular and genetic basis of auditory disorders, coupled with advancements in drug formulation and delivery as well as optimized timing of drug administration, holds great promise of more effective treatments. SIGNIFICANCE STATEMENT: Hearing disorders pose significant challenges to individuals and their overall quality of life, emphasizing the critical need for advanced pharmacological approaches to address these conditions. Ongoing research into the molecular and genetic basis of auditory disorders, coupled with advancements in drug delivery procedures and optimized timing of drug administration, holds the promise of more effective treatments.

BRCA1 Promotes Repair of DNA Damage in Cochlear Hair Cells and Prevents Hearing Loss

Cochlear hair cells (HCs) sense sound waves and allow us to hear. Loss of HCs will cause irreversible sensorineural hearing loss. It is well known that DNA damage repair plays a critical role in protecting cells in many organs. However, how HCs respond to DNA damage and how defective DNA damage repair contributes to hearing loss remain elusive. In this study, we showed that cisplatin induced DNA damage in outer hair cells (OHCs) and promoted OHC loss, leading to hearing loss in mice of either sex. Cisplatin induced the expression of Brca1, a DNA damage repair factor, in OHCs. Deficiency of Brca1 induced OHC and hearing loss, and further promoted cisplatin-induced DNA damage in OHCs, accelerating OHC loss. This study provides the first in vivo evidence demonstrating that cisplatin mainly induces DNA damage in OHCs and that BRCA1 promotes repair of DNA damage in OHCs and prevents hearing loss. Our findings not only demonstrate that DNA damage-inducing agent generates DNA damage in postmitotic HCs but also suggest that DNA repair factors, like BRCA1, protect postmitotic HCs from DNA damage-induced cell death and hearing loss.

Calcitriol alleviates noise-induced hearing loss by regulating the ATF3/DUSP1 signalling pathway

BACKGROUND

Calcitriol (Cal) is the most active metabolite of vitamin D and has antioxidant and anti-inflammatory properties. The aim of this study was to investigate the role of Cal in noise-induced hearing loss (NIHL) to further elucidate the mechanism of noise-induced oxidative stress in the mouse cochlea.

METHODS

C57BL/6 J mice were given six intraperitoneal injections of Cal (500 ng/kg/d). After 14 days of noise exposure, auditory brainstem response (ABR) thresholds, and the cochlear outer hair cell loss rate were analysed to evaluate auditory function. Real-time fluorescence quantitative PCR, immunofluorescence and western blotting were performed in vitro after the treatment of cochlear explants with 100 µM tert-butyl hydroperoxide (TBHP) for 2.5 h and HEI-OC1 cells with 250 µM TBHP for 1.5 h.

RESULTS

In vivo experiments confirmed that Cal pretreatment mitigated NIHL and outer hair cell death. The in vitro results demonstrated that Cal significantly reduced TBHP-induced cochlear auditory nerve fibre degradation and spiral ganglion neuron damage. Moreover, treatment with Cal inhibited the expression of oxidative stress-related factors (3-NT and 4-HNE) and DNA damage-related factors (γ-H2A.X) and attenuated TBHP-induced apoptosis in cochlear explants and HEI-OC1 cells. A total of 1479 upregulated genes and 1443 downregulated genes were screened in cochlear tissue 1 h after noise exposure. The level of transcription factor 3 (ATF3) was significantly elevated in HEI-OC1 cells after TBHP stimulation. Gene Transcription Regulation Database （GTRD）and Cistrome database analyses revealed that the downstream target gene of ATF3 is dual specificity phosphatase 1 (DUSP1). Cistrome DB Toolkit database results showed that the transcription factor of DUSP1 was ATF3. In addition, the ChIP-PCR results indicated that ATF3 might be a direct transcription factor of DUSP1.

CONCLUSION

The results of our study suggest that Cal attenuates NIHL and inhibits noise-induced apoptosis by regulating the ATF3/DUSP1 signalling pathway.

Hearing loss during chemotherapy: prevalence, mechanisms, and protection

Ototoxicity is an often-underestimated sequela for cancer patients undergoing chemotherapy, with an incidence rate exceeding 50%, affecting approximately 4 million individuals worldwide each year. Despite the nearly 2,000 publications on chemotherapy-related ototoxicity in the past decade, the understanding of its prevalence, mechanisms, and preventative or therapeutic measures remains ambiguous and subject to debate. To date, only one drug, sodium thiosulfate, has gained FDA approval for treating ototoxicity in chemotherapy. However, its utilization is restricted. This review aims to offer clinicians and researchers a comprehensive perspective by thoroughly and carefully reviewing available data and current evidence. Chemotherapy-induced ototoxicity is characterized by four primary symptoms: hearing loss, tinnitus, vertigo, and dizziness, originating from both auditory and vestibular systems. Hearing loss is the predominant symptom. Amongst over 700 chemotherapeutic agents documented in various databases, only seven are reported to induce hearing loss. While the molecular mechanisms of the hearing loss caused by the two platinum-based drugs are extensively explored, the pathways behind the action of the other five drugs are primarily speculative, rooted in their therapeutic properties and side effects. Cisplatin attracts the majority of attention among these drugs, encompassing around two-thirds of the literature regarding ototoxicity in chemotherapy. Cisplatin ototoxicity chiefly manifests through the loss of outer hair cells, possibly resulting from damages directly by cisplatin uptake or secondary effects on the stria vascularis. Both direct and indirect influences contribute to cisplatin ototoxicity, while it is still debated which path is dominant or where the primary target of cisplatin is located. Candidates for hearing protection against cisplatin ototoxicity are also discussed, with novel strategies and methods showing promise on the horizon.

Customized Proteinaceous Nanoformulation for In Vivo Chemical Reprogramming

Sweat gland (SwG) regeneration is crucial for the functional rehabilitation of burn patients. In vivo chemical reprogramming that harnessing the patient's own cells in damaged tissue is of substantial interest to regenerate organs endogenously by pharmacological manipulation, which could compensate for tissue loss in devastating diseases and injuries, for example, burns. However, achieving in vivo chemical reprogramming is challenging due to the low reprogramming efficiency and an unfavorable tissue environment. Herein, this work has developed a functionalized proteinaceous nanoformulation delivery system containing prefabricated epidermal growth factor structure for on-demand delivery of a cocktail of seven SwG reprogramming components to the dermal site. Such a chemical reprogramming system can efficiently induce the conversion of epidermal keratinocytes into SwG myoepithelial cells, resulting in successful in situ regeneration of functional SwGs. Notably, in vivo chemical reprogramming of SwGs is achieved for the first time with an impressive efficiency of 30.6%, surpassing previously reported efficiencies. Overall, this proteinaceous nanoformulation provides a platform for coordinating the target delivery of multiple pharmacological agents and facilitating in vivo SwG reprogramming by chemicals. This advancement greatly improves the clinical accessibility of in vivo reprogramming and offers a non-surgical, non-viral, and cell-free strategy for in situ SwG regeneration.

Nuciferine Protects Cochlear Hair Cells from Ferroptosis through Inhibiting NCOA4-Mediated Ferritinophagy

Cisplatin is a widely used antineoplastic drug for treating various types of cancers. However, it can cause severe side effects, such as bilateral and irreversible hearing loss, which significantly impacts quality of life. Ferroptosis, an iron-dependent form of programmed cell death, has been implicated in the pathogenesis of cisplatin-induced ototoxicity. Here, we investigated the effects of nuciferine, a natural active ingredient isolated from lotus species, on the ferroptosis of cochlear hair cells. Firstly, our results demonstrated that nuciferine can protect hair cells against RSL3-induced and cisplatin-induced damage. Secondly, nuciferine treatment reduced ferrous iron (Fe2+) overload in cochlear hair cells via inhibiting NCOA4-mediated ferritinophagy. Inhibition of ferritinophagy by knocking down Ncoa4 alleviated cisplatin-induced ototoxicity. Importantly, nuciferine treatment mitigated cochlear hair cell loss and damage to ribbon synapse, and improved mouse hearing function in an acute cisplatin-induced hearing loss model. Our findings highlight the role of NCOA4-mediated ferritinophagy in the pathogenesis of cisplatin-induced ototoxicity and provide evidence for nuciferine as a promising protective agent for treating cisplatin-induced hearing loss.

The human OPA1delTTAG mutation induces adult onset and progressive auditory neuropathy in mice

Dominant optic atrophy (DOA) is one of the most prevalent forms of hereditary optic neuropathies and is mainly caused by heterozygous variants in OPA1, encoding a mitochondrial dynamin-related large GTPase. The clinical spectrum of DOA has been extended to a wide variety of syndromic presentations, called DOAplus, including deafness as the main secondary symptom associated to vision impairment. To date, the pathophysiological mechanisms underlying the deafness in DOA remain unknown. To gain insights into the process leading to hearing impairment, we have analyzed the Opa1delTTAG mouse model that recapitulates the DOAplus syndrome through complementary approaches combining morpho-physiology, biochemistry, and cellular and molecular biology. We found that Opa1delTTAG mutation leads an adult-onset progressive auditory neuropathy in mice, as attested by the auditory brainstem response threshold shift over time. However, the mutant mice harbored larger otoacoustic emissions in comparison to wild-type littermates, whereas the endocochlear potential, which is a proxy for the functional state of the stria vascularis, was comparable between both genotypes. Ultrastructural examination of the mutant mice revealed a selective loss of sensory inner hair cells, together with a progressive degeneration of the axons and myelin sheaths of the afferent terminals of the spiral ganglion neurons, supporting an auditory neuropathy spectrum disorder (ANSD). Molecular assessment of cochlea demonstrated a reduction of Opa1 mRNA level by greater than 40%, supporting haploinsufficiency as the disease mechanism. In addition, we evidenced an early increase in Sirtuin 3 level and in Beclin1 activity, and subsequently an age-related mtDNA depletion, increased oxidative stress, mitophagy as well as an impaired autophagic flux. Together, these results support a novel role for OPA1 in the maintenance of inner hair cells and auditory neural structures, addressing new challenges for the exploration and treatment of OPA1-linked ANSD in patients.

NADPH Oxidase 3: Beyond the Inner Ear

Reactive oxygen species (ROS) were formerly known as mere byproducts of metabolism with damaging effects on cellular structures. The discovery and description of NADPH oxidases (Nox) as a whole enzyme family that only produce this harmful group of molecules was surprising. After intensive research, seven Nox isoforms were discovered, described and extensively studied. Among them, the NADPH oxidase 3 is the perhaps most underrated Nox isoform, since it was firstly discovered in the inner ear. This stigma of Nox3 as "being only expressed in the inner ear" was also used by me several times. Therefore, the question arose whether this sentence is still valid or even usable. To this end, this review solely focuses on Nox3 and summarizes its discovery, the structural components, the activating and regulating factors, the expression in cells, tissues and organs, as well as the beneficial and detrimental effects of Nox3-mediated ROS production on body functions. Furthermore, the involvement of Nox3-derived ROS in diseases progression and, accordingly, as a potential target for disease treatment, will be discussed.

Cinchonine and cinchonidine alleviate cisplatin-induced ototoxicity by regulating PI3K-AKT signaling

AIM

Cinchonine (CN) and its isomer cinchonidine (CD), two of the common cinchona alkaloids, are wildly used as antimalarial drugs. However, the effects of CN and CD on the auditory system are unknown.

METHODS

Molecular docking and molecular dynamics (MD) simulation were used for predicting effective drugs. The CCK-8 assay was conducted for assessing cell viability in House Ear Institute-Organ of Corti 1 (HEI-OC1) cells. MitoSox Red staining revealed reactive oxygen species (ROS) amounts. TMRM staining was used to assess the mitochondrial membrane potential (ΔΨm). Immunofluorescence staining of myosin 7a was used to examine hair cells (HCs) in cisplatin-treated neonatal mouse cochlear explants, while TUJ-1 immunostaining was used for the detection of spiral ganglion neurons (SGNs). Cleaved caspase-3 and TUNEL immunostaining were utilized for apoptosis assessment. Immunoblot was carried out to detect PI3K-AKT signaling effectors.

RESULTS

Pretreatment with CN or CD significantly increased cell viability and reduced mitochondrial dysfunction and ROS accumulation in cisplatin-treated HEI-OC1 cells. Immunofluorescent staining of cochlear explants showed that CN and CD attenuated cisplatin-induced damage to SGNs and HCs. Immunoblot revealed that CN and CD downregulated the expression of cleaved caspase-3 and activated PI3K-AKT signaling in cisplatin-injured HEI-OC1 cells.

CONCLUSION

CD and CN can reduce ototoxicity caused by cisplatin and might help treat cisplatin-associated hearing loss.

Oxidative Stress Plays an Important Role in Glutamatergic Excitotoxicity-Induced Cochlear Synaptopathy: Implication for Therapeutic Molecules Screening

The disruption of the synaptic connection between the sensory inner hair cells (IHCs) and the auditory nerve fiber terminals of the type I spiral ganglion neurons (SGN) has been observed early in several auditory pathologies (e.g., noise-induced or ototoxic drug-induced or age-related hearing loss). It has been suggested that glutamate excitotoxicity may be an inciting element in the degenerative cascade observed in these pathological cochlear conditions. Moreover, oxidative damage induced by free hydroxyl radicals and nitric oxide may dramatically enhance cochlear damage induced by glutamate excitotoxicity. To investigate the underlying molecular mechanisms involved in cochlear excitotoxicity, we examined the molecular basis responsible for kainic acid (KA, a full agonist of AMPA/KA-preferring glutamate receptors)-induced IHC synapse loss and degeneration of the terminals of the type I spiral ganglion afferent neurons using a cochlear explant culture from P3 mouse pups. Our results demonstrated that disruption of the synaptic connection between IHCs and SGNs induced increased levels of oxidative stress, as well as altered both mitochondrial function and neurotrophin signaling pathways. Additionally, the application of exogenous antioxidants and neurotrophins (NT3, BDNF, and small molecule TrkB agonists) clearly increases synaptogenesis. These results suggest that understanding the molecular pathways involved in cochlear excitotoxicity is of crucial importance for the future clinical trials of drug interventions for auditory synaptopathies.

Oxidative stress and inflammation cause auditory system damage via glial cell activation and dysregulated expression of gap junction proteins in an experimental model of styrene-induced oto/neurotoxicity

BACKGROUND

Redox imbalance and inflammation have been proposed as the principal mechanisms of damage in the auditory system, resulting in functional alterations and hearing loss. Microglia and astrocytes play a crucial role in mediating oxidative/inflammatory injury in the central nervous system; however, the role of glial cells in the auditory damage is still elusive.

OBJECTIVES

Here we investigated glial-mediated responses to toxic injury in peripheral and central structures of the auditory pathway, i.e., the cochlea and the auditory cortex (ACx), in rats exposed to styrene, a volatile compound with well-known oto/neurotoxic properties.

METHODS

Male adult Wistar rats were treated with styrene (400 mg/kg daily for 3 weeks, 5/days a week). Electrophysiological, morphological, immunofluorescence and molecular analyses were performed in both the cochlea and the ACx to evaluate the mechanisms underlying styrene-induced oto/neurotoxicity in the auditory system.

RESULTS

We showed that the oto/neurotoxic insult induced by styrene increases oxidative stress in both cochlea and ACx. This was associated with macrophages and glial cell activation, increased expression of inflammatory markers (i.e., pro-inflammatory cytokines and chemokine receptors) and alterations in connexin (Cxs) and pannexin (Panx) expression, likely responsible for dysregulation of the microglia/astrocyte network. Specifically, we found downregulation of Cx26 and Cx30 in the cochlea, and high level of Cx43 and Panx1 in the ACx.

CONCLUSIONS

Collectively, our results provide novel evidence on the role of immune and glial cell activation in the oxidative/inflammatory damage induced by styrene in the auditory system at both peripheral and central levels, also involving alterations of gap junction networks. Our data suggest that targeting glial cells and connexin/pannexin expression might be useful to attenuate oxidative/inflammatory damage in the auditory system.

Bile Acid Application in Cell-Targeting for Molecular Receptors in Relation to Hearing: A Comprehensive Review

Bile acids play important roles in the human body, and changes in their pool can be used as markers for various liver pathologies. In addition to their functional effects in modulating inflammatory responses and cellular survivability, the unconjugated or conjugated, secondary, or primary nature of bile acids accounts for their various ligand effects. The common hydrophilic bile acids have been used successfully as local treatment to resolve drug-induced cell damage or to ameliorate hearing loss. From various literature references, bile acids show concentration and tissue-dependent effects. Some hydrophobic bile acids act as ligands modulating vitamin D receptors, muscarinic receptors, and calcium-activated potassium channels, important proteins in the inner ear system. Currently, there are limited resources investigating the therapeutic effects of bile acid on hearing loss and little to no information on detecting bile acids in the remote ear system, let alone baseline bile acid levels and their prevalence in healthy and disease conditions. This review presents both hydrophilic and hydrophobic human bile acids and their tissue-specific effects in modulating cellular integrity, thus considering the possible effects and extended therapeutic applicability of bile acids to the inner ear tissue.

Undifferentially Expressed CXXC5 as a Transcriptionally Regulatory Biomarker of Breast Cancer

This work hypothesizes that some genes undergo radically changed transcription regulations (TRs) in breast cancer (BC), but don't show differential expressions for unknown reasons. The TR of a gene is quantitatively formulated by a regression model between the expression of this gene and multiple transcription factors (TFs). The difference between the predicted and real expression levels of a gene in a query sample is defined as the mqTrans value of this gene, which quantitatively reflects its regulatory changes. This work systematically screens the undifferentially expressed genes with differentially expressed mqTrans values in 1036 samples across five datasets and three ethnic groups. This study calls the 25 genes satisfying the above hypothesis in at least four datasets as dark biomarkers, and the strong dark biomarker gene CXXC5 (CXXC Finger Protein 5) is even supported by all the five independent BC datasets. Although CXXC5 does not show differential expressions in BC, its transcription regulations show quantitative associations with BCs in diversified cohorts. The overlapping long noncoding RNAs (lncRNAs) may have contributed their transcripts to the expression miscalculations of dark biomarkers. The mqTrans analysis serves as a complementary view of the transcriptome-based detections of biomarkers that are ignored by many existing studies.

Loss of synaptic ribbons is an early cause in ROS-induced acquired sensorineural hearing loss

Considerable evidence of reactive oxygen species (ROS) involvement in cochlear hair cell (HC) loss, leading to acquired sensorineural hearing loss (SNHL), were reported. Cochlear synaptopathy between HCs and spiral ganglion neurons has been gathering attention as a cochlear HC loss precursor not detectable by normal auditory evaluation. However, the molecular mechanisms linking ROS with HC loss, as well as the relationship between ROS and cochlear synaptopathy have not been elucidated. Here, we examined these linkages using NOX4-TG mice, which constitutively produce ROS without stimulation. mRNA levels of Piccolo 1, a major component of the synaptic ribbon (a specialized structure surrounded by synaptic vesicles in HCs), were decreased in postnatal day 6 NOX4-TG mice cochleae compared to those in WT mice; they were also decreased by noise exposure in 2-week-old WT cochleae. As noise exposure induces ROS production, this suggests that the synaptic ribbon is a target of ROS. The level of CtBP2, another synaptic ribbon component, was significantly lower in NOX4-TG cochleae of 1-month-old and 4-month-old mice compared to that in WT mice, although no significant differences were noted at 1.5- and 2-months. The decrease in CtBP2 plateaued in 4-month-old NOX4-TG, while it gradually decreased from 1 to 6 months in WT mice. Furthermore, CtBP2 level in 2-month-old NOX4-TG mice decreased significantly after exposure to cisplatin and noise compared to that in WT mice. These findings suggest that ROS lead to developmental delays and early degeneration of synaptic ribbons, which could be potential targets for novel therapeutics for ROS-induced SNHL.

Estimating disease-free survival of thyroid cancer based on novel cuprotosis-related gene model

Background

Cuprotosis is a newly discovered form of cell death that differs from other types of cell death. The aim of this study was to investigate the functional role and a possible prognostic model for thyroid cancer.

Methods

TCGA and GEO were used to investigate the differential expression of CRGs in THCA. KEGG and GO enrichment analyses were applied to investigate the possible molecular functions. The features of CRGs were selected by LASSO regression. 20 pairs of samples were randomly collected from the hospital to compare expression between tumor and normal.

Results

Among the 19 CRGs related to thyroid cancer recurrence, 16 genes were differentially expressed in thyroid cancer. KEGG analysis showed that the 19 CRGs were mainly enriched in cell death, cell cycle and ribosomal pathways. K-M survival analysis and subsequent multiple logistic regression revealed that the expression of BUB1 and GINS2 were potential risk factors for disease-free survival (DFS) of thyroid cancer. In addition, further LASSO-regression selected the following three DFS-related CRGs: FDX1, BUB1 and RPL3. A novel prognostic prediction model was constructed by nomogram, and the prediction probability for 1-, 3- and 5-year survival approached the actual time. As for the possible mechanisms, FDX1, BUB1 and RPL3 were associated with immune infiltration. The cell model experiment illustrated that the ATM signaling pathway might be involved in thyroid cancer cell death.

Conclusion

Three CRG models (FDX1, BUB1, RPL3) could better predict the prognosis of thyroid cancer. Immune cell infiltration and the ATM pathway were the possible mechanisms.

Sensitivity of CNN image analysis to multifaceted measurements of neurite growth

Quantitative analysis of neurite growth and morphology is essential for understanding the determinants of neural development and regeneration, however, it is complicated by the labor-intensive process of measuring diverse parameters of neurite outgrowth. Consequently, automated approaches have been developed to study neurite morphology in a high-throughput and comprehensive manner. These approaches include computer-automated algorithms known as 'convolutional neural networks' (CNNs)-powerful models capable of learning complex tasks without the biases of hand-crafted models. Nevertheless, their complexity often relegates them to functioning as 'black boxes.' Therefore, research in the field of explainable AI is imperative to comprehend the relationship between CNN image analysis output and predefined morphological parameters of neurite growth in order to assess the applicability of these machine learning approaches. In this study, drawing inspiration from the field of automated feature selection, we investigate the correlation between quantified metrics of neurite morphology and the image analysis results from NeuriteNet-a CNN developed to analyze neurite growth. NeuriteNet accurately distinguishes images of neurite growth based on different treatment groups within two separate experimental systems. These systems differentiate between neurons cultured on different substrate conditions and neurons subjected to drug treatment inhibiting neurite outgrowth. By examining the model's function and patterns of activation underlying its classification decisions, we discover that NeuriteNet focuses on aspects of neuron morphology that represent quantifiable metrics distinguishing these groups. Additionally, it incorporates factors that are not encompassed by neuron morphology tracing analyses. NeuriteNet presents a novel tool ideally suited for screening morphological differences in heterogeneous neuron groups while also providing impetus for targeted follow-up studies.

Role of p53 in Cisplatin-Induced Myotube Atrophy

Chemotherapy-induced sarcopenia is an unfavorable prognostic factor implicated in the development of postoperative complications and reduces the quality of life of patients with cancer. Skeletal muscle loss due to cisplatin use is caused by mitochondrial dysfunction and activation of muscle-specific ubiquitin ligases Atrogin-1 and muscle RING finger 1 (MuRF1). Although animal studies suggest the involvement of p53 in age-, immobility-, and denervation-related muscle atrophy, the association between cisplatin-induced atrophy and p53 remains unknown. Herein, we investigated the effect of a p53-specific inhibitor, pifithrin-alpha (PFT-α), on cisplatin-induced atrophy in C2C12 myotubes. Cisplatin increased the protein levels of p53, phosphorylated p53, and upregulated the mRNA expression of p53 target genes PUMA and p21 in C2C12 myotubes. PFT-α ameliorated the increase in intracellular reactive oxygen species production and mitochondrial dysfunction, and also reduced the cisplatin-induced increase in the Bax/Bcl-2 ratio. Although PFT-α also reduced the cisplatin-induced increase in MuRF1 and Atrogin-1 gene expression, it did not ameliorate the decrease in myosin heavy chain mRNA and protein levels and muscle-specific actin and myoglobin protein levels. We conclude that cisplatin increases muscle degradation in C2C12 myotubes in a p53-dependent manner, but p53 has minimal involvement in the reduction of muscle protein synthesis.

Metal-Based Anticancer Complexes and p53: How Much Do We Know?

P53 plays a key role in protecting the human genome from DNA-related mutations; however, it is one of the most frequently mutated genes in cancer. The P53 family members p63 and p73 were also shown to play important roles in cancer development and progression. Currently, there are various organic molecules from different structural classes of compounds that could reactivate the function of wild-type p53, degrade or inhibit mutant p53, etc. It was shown that: (1) the function of the wild-type p53 protein was dependent on the presence of Zn atoms, and (2) Zn supplementation restored the altered conformation of the mutant p53 protein. This prompted us to question whether the dependence of p53 on Zn and other metals might be used as a cancer vulnerability. This review article focuses on the role of different metals in the structure and function of p53, as well as discusses the effects of metal complexes based on Zn, Cu, Fe, Ru, Au, Ag, Pd, Pt, Ir, V, Mo, Bi and Sn on the p53 protein and p53-associated signaling.

Drug-induced oxidative stress in cancer treatments: Angel or devil?

Oxidative stress (OS), defined as redox imbalance in favor of oxidant burden, is one of the most significant biological events in cancer progression. Cancer cells generally represent a higher oxidant level, which suggests a dual therapeutic strategy by regulating redox status (i.e., pro-oxidant therapy and/or antioxidant therapy). Indeed, pro-oxidant therapy exhibits a great anti-cancer capability, attributing to a higher oxidant accumulation within cancer cells, whereas antioxidant therapy to restore redox homeostasis has been claimed to fail in several clinical practices. Targeting the redox vulnerability of cancer cells by pro-oxidants capable of generating excessive reactive oxygen species (ROS) has surfaced as an important anti-cancer strategy. However, multiple adverse effects caused by the indiscriminate attacks of uncontrolled drug-induced OS on normal tissues and the drug-tolerant capacity of some certain cancer cells greatly limit their further applications. Herein, we review several representative oxidative anti-cancer drugs and summarize their side effects on normal tissues and organs, emphasizing that seeking a balance between pro-oxidant therapy and oxidative damage is of great value in exploiting next-generation OS-based anti-cancer chemotherapeutics.

Degranulation of Murine Resident Cochlear Mast Cells: A Possible Factor Contributing to Cisplatin-Induced Ototoxicity and Neurotoxicity

Permanent hearing loss is one of cisplatin's adverse effects, affecting 30-60% of cancer patients treated with that drug. Our research group recently identified resident mast cells in rodents' cochleae and observed that the number of mast cells changed upon adding cisplatin to cochlear explants. Here, we followed that observation and found that the murine cochlear mast cells degranulate in response to cisplatin and that the mast cell stabilizer cromoglicic acid (cromolyn) inhibits this process. Additionally, cromolyn significantly prevented cisplatin-induced loss of auditory hair cells and spiral ganglion neurons. Our study provides the first evidence for the possible mast cell participation in cisplatin-induced damage to the inner ear.

Considering the protective effect of exendin-4 against oxidative stress in spiral ganglion neurons

Objectives

The protection of spiral ganglion neurons (SGNs) is crucial for hearing loss. Exendin-4 has been shown to have neuroprotective effects in several neurological disorders. Therefore, this study aimed to investigate the effect of the glucagon-like protein-1 receptor (GLP-1R) agonist exendin-4 on kanamycin-induced injury in mouse SGNs in vitro.

Materials and Methods

In this study, GLP-1R expression in SGNs was verified by immunofluorescence and immunohistochemical staining. In vitro-cultured SGNs and the organ of Corti were exposed to kanamycin with or without exendin-4 treatment. The cell survival rate was measured using the cell counting kit-8 assay, and the damage to auditory nerve fibers (ANF) projecting radially from the SGNs was evaluated using immunofluorescence staining. Reactive oxygen species (ROS) content was determined by flow cytometry, and glutathione peroxidase (GSH-Px) content, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content were determined by spectrophotometry. Protein expression of nuclear factor erythroid-2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) was detected using western blotting.

Results

GLP-1R was expressed in SGNs. Treatment with 1 mM kanamycin for 24 hr induced SGN damage. Exendin-4 (100 nM) had a protective effect against kanamycin-induced SGN cell injury, improved cell survival rate, reduced nerve fiber injury, increased SOD activity and GSH-Px level, and reduced MDA and ROS contents. The Nrf2/HO-1 pathway was activated.

Conclusion

Exendin-4 alleviates oxidative damage and exerts neuroprotective effects in kanamycin-induced SGN injury through the Nrf2/HO-1 signaling pathway. Exendin-4 has the potential to prevent or treat hearing loss due to SGN damage.

Ellagic acid modulates cisplatin toxicity in DMH induced colorectal cancer: Studies on membrane alterations

Systemic toxicity due to chemotherapy contributes to poor prognosis in patients receiving chemotherapy. The present study, therefore, explores the role of Ellagic acid, a phytochemical, in modulating cisplatin (CP) toxicity in dimethylhydrazine-induced colorectal cancer. Colons excised from DMH administered animals showed abnormal crypts and bulges over the mucosal surface. SEM revealed significant alterations and dysplastic lesions in DMH administered mice. Animals receiving combined treatment showed improvement in colonic epithelium with lesser irregularities. DMH and CP administration disturbed the membrane dynamics and integrity as observed with the fluorescent probes DPH and pyrene. However, EA co-supplementation with CP proved to be beneficial in normalizing the altered membrane. Ellagic acid co-supplementation along with CP; therefore, showed great promise and helped restore the membrane alterations in the colon caused due to CP-induced toxicity and DMH insult. These observations could pave way towards developing a combination therapy targeting colon carcinogenesis in future.

A disease-associated mutation in thyroid hormone receptor α1 causes hearing loss and sensory hair cell patterning defects in mice

Resistance to thyroid hormone due to mutations in THRA, which encodes the thyroid hormone receptor α (TRα1), shows variable clinical presentation. Mutations affecting TRβ1 and TRβ2 cause deafness in mice and have been associated with deafness in humans. To test whether TRα1 also affects hearing function, we used mice heterozygous for a frameshift mutation in Thra that is similar to human THRA mutations (Thra^S1/+ mice) and reduces tissue sensitivity to thyroid hormone. Compared to wild-type littermates, Thra^S1/+ mice showed moderate high-frequency sensorineural hearing loss as juveniles and increased age-related hearing loss. Ultrastructural examination revealed aberrant orientation of ~20% of sensory outer hair cells (OHCs), as well as increased numbers of mitochondria with fragmented morphology and autophagic vacuoles in both OHCs and auditory nerve fibers. Molecular dissection of the OHC lateral wall components revealed that the potassium ion channel Kcnq4 was aberrantly targeted to the cytoplasm of mutant OHCs. In addition, mutant cochleae showed increased oxidative stress, autophagy, and mitophagy associated with greater age-related cochlear cell damage, demonstrating that TRα1 is required for proper development of OHCs and for maintenance of OHC function. These findings suggest that patients with THRA mutations may present underdiagnosed, mild hearing loss and may be more susceptible to age-related hearing loss.

Cisplatin Chemotherapy and Cochlear Damage: Otoprotective and Chemosensitization Properties of Polyphenols

Significance: Cisplatin is an important component of treatment regimens for different cancers. Notwithstanding that therapeutic success often results from partial efficacy or stabilizing the disease, chemotherapy failure is driven by resistance to drug treatment and occurrence of side effects, such as progressive irreversible ototoxicity. Cisplatin's side effects, including ototoxicity, are often dose limiting. Recent Advances: Cisplatin ototoxicity results from several mechanisms, including redox imbalance caused by reactive oxygen species production and lipid peroxidation, activation of inflammation, and p53 and its downstream pathways that culminate in apoptosis. Considerable efforts in research have targeted development of molecular interventions that can be concurrently administered with cisplatin or other chemotherapies to reduce side effect toxicities while preserving or enhancing the antineoplastic effects. Evidence from studies has indicated some polyphenols, such as curcumin, can help to regulate redox signaling and inflammatory effects. Furthermore, polyphenols can exert opposing effects in different types of tissues, that is, normal cells undergoing stressful conditions versus cancer cells. Critical Issues: This review article summarizes evidence of curcumin antioxidant effect against cisplatin-induced ototoxicity that is converted to a pro-oxidant activity in cisplatin-treated cancer cells, thus providing an ideal chemosensitivity combined with otoprotection. Polyphenols can modulate the adaptive responses to stress in the cisplatin-exposed cochlea. These adaptive effects can result from the interaction/cross talk between the cell's defenses, inflammatory molecules, and the key signaling molecules of signal transducers and activators of transcription 3 (STAT-3), nuclear factor κ-B (NF-κB), p53, and nuclear factor erythroid 2-related factor 2 (Nrf-2). Future Directions: We provide molecular evidence for alternative strategies for chemotherapy with cisplatin addressing the otoprotection and chemosensitization properties of polyphenols. Antioxid. Redox Signal. 36, 1229-1245.

N-acetylcysteine protect inner hair cells from cisplatin by alleviated celluar oxidative stress and apoptosis

Cisplatin is a well-known platinum-based chemotherapy drug widely used to treat a variety of malignant tumors. However, cisplatin has serious side-effects include nephrotoxicity and ototoxicity, Cisplatin chemotherapy causes permanent hearing loss at least 40% of treated patients. Our results showed that 20 mM N-acetylcysteine (NAC) can completely protect 50 μM cisplatin-induced hair cell loss in rat cochlear culture and protects against cisplatin-induced hair cell loss in zebrafish in vivo. The fluorescence intensity of mitochondrial ROS significantly increased after the cultures were treated with 15 μM cisplatin for 48 h and was decreased in the group treated with 15 μM cisplatin add 20 mM NAC. In addition, the number of TUNEL positive hair cells was increased after the cultures were treated with 15 μM cisplatin for 48 h and there are null in cisplatin and NAC co-treated group.

Activation of Rictor/mTORC2 signaling acts as a pivotal strategy to protect against sensorineural hearing loss

Significance The mechanistic target of rapamycin (mTOR) plays a central role in growth, metabolism, and aging. It is assembled into two multiprotein complexes, namely, mTORC1 and mTORC2. We previously demonstrated the efficacy of sirolimus in ARHL in mice by decreasing mTORC1. However, the aspect of mTORC2 regulation in the cochlea is poorly characterized. Herein, based on pharmacological and genetic interventions, we found that a high dose of sirolimus resulted in severe hearing loss by reducing the mTORC2/AKT signaling pathway in the cochlea. Furthermore, selective activation of mTORC2 could protect against hearing loss induced by acoustic trauma and cisplatin-induced ototoxicity. Hence, the therapeutic activation of mTORC2 in conjunction with decreasing mTORC1 might represent a promising and effective strategy in preventing hearing loss.

WSG, a Glucose-Rich Polysaccharide from Ganoderma lucidum, Combined with Cisplatin Potentiates Inhibition of Lung Cancer In Vitro and In Vivo

Lung cancer has the highest global mortality rate of any cancer. Although targeted therapeutic drugs are commercially available, the common drug resistance and insensitivity to cisplatin-based chemotherapy, a common clinical treatment for lung cancer, have prompted active research on alternative lung cancer therapies and methods for mitigating cisplatin-related complications. In this study, we investigated the effect of WSG, a glucose-rich, water soluble polysaccharide derived from Ganoderma lucidum, on cisplatin-based treatment for lung cancer. Murine Lewis lung carcinoma (LLC1) cells were injected into C57BL/6 mice subcutaneously and through the tail vein. The combined administration of WSG and cisplatin effectively inhibited tumor growth and the formation of metastatic nodules in the lung tissue of the mice. Moreover, WSG increased the survival rate of mice receiving cisplatin. Co-treatment with WSG and cisplatin induced a synergistic inhibitory effect on the growth of lung cancer cells, enhancing the apoptotic responses mediated by cisplatin. WSG also reduced the cytotoxic effect of cisplatin in both macrophages and normal lung fibroblasts. Our findings suggest that WSG can increase the therapeutic effectiveness of cisplatin. In clinical settings, WSG may be used as an adjuvant or supplementary agent.

Oxidative Stress and Inflammation Caused by Cisplatin Ototoxicity

Hearing loss is a significant health problem that can result from a variety of exogenous insults that generate oxidative stress and inflammation. This can produce cellular damage and impairment of hearing. Radiation damage, ageing, damage produced by cochlear implantation, acoustic trauma and ototoxic drug exposure can all generate reactive oxygen species in the inner ear with loss of sensory cells and hearing loss. Cisplatin ototoxicity is one of the major causes of hearing loss in children and adults. This review will address cisplatin ototoxicity. It includes discussion of the mechanisms associated with cisplatin-induced hearing loss including uptake pathways for cisplatin entry, oxidative stress due to overpowering antioxidant defense mechanisms, and the recently described toxic pathways that are activated by cisplatin, including necroptosis and ferroptosis. The cochlea contains G-protein coupled receptors that can be activated to provide protection. These include adenosine A1 receptors, cannabinoid 2 receptors (CB2) and the Sphingosine 1-Phosphate Receptor 2 (S1PR2). A variety of heat shock proteins (HSPs) can be up-regulated in the cochlea. The use of exosomes offers a novel method of delivery of HSPs to provide protection. A reversible MET channel blocker that can be administered orally may block cisplatin uptake into the cochlear cells. Several protective agents in preclinical studies have been shown to not interfere with cisplatin efficacy. Statins have shown efficacy in reducing cisplatin ototoxicity without compromising patient response to treatment. Additional clinical trials could provide exciting findings in the prevention of cisplatin ototoxicity.

Impulse Noise Induced Hidden Hearing Loss, Hair Cell Ciliary Changes and Oxidative Stress in Mice

Recent studies demonstrated that reversible continuous noise exposure may induce a temporary threshold shift (TTS) with a permanent degeneration of auditory nerve fibers, although hair cells remain intact. To probe the impact of TTS-inducing impulse noise exposure on hearing, CBA/J Mice were exposed to noise impulses with peak pressures of 145 dB SPL. We found that 30 min after exposure, the noise caused a mean elevation of ABR thresholds of ~30 dB and a reduction in DPOAE amplitude. Four weeks later, ABR thresholds and DPOAE amplitude were back to normal in the higher frequency region (8–32 kHz). At lower frequencies, a small degree of PTS remained. Morphological evaluations revealed a disturbance of the stereociliary bundle of outer hair cells, mainly located in the apical regions. On the other hand, the reduced suprathreshold ABR amplitudes remained until 4 weeks later. A loss of synapse numbers was observed 24 h after exposure, with full recovery two weeks later. Transmission electron microscopy revealed morphological changes at the ribbon synapses by two weeks post exposure. In addition, increased levels of oxidative stress were observed immediately after exposure, and maintained for a further 2 weeks. These results clarify the pathology underlying impulse noise-induced sensory dysfunction, and suggest possible links between impulse-noise injury, cochlear cell morphology, metabolic changes, and hidden hearing loss.

PLK1 (polo like kinase 1)-dependent autophagy facilitates gefitinib-induced hepatotoxicity by degrading COX6A1 (cytochrome c oxidase subunit 6A1)

Liver dysfunction is an outstanding dose-limiting toxicity of gefitinib, an EGFR (epidermal growth factor receptor)-tyrosine kinase inhibitor (TKI), in the treatment of EGFR mutation-positive non-small cell lung cancer (NSCLC). We aimed to elucidate the mechanisms underlying gefitinib-induced hepatotoxicity, and provide potentially effective intervention strategy. We discovered that gefitinib could sequentially activate macroautophagy/autophagy and apoptosis in hepatocytes. The inhibition of autophagy alleviated gefitinib-induced apoptosis, whereas the suppression of apoptosis failed to lessen gefitinib-induced autophagy. Moreover, liver-specific Atg7+/- heterozygous mice showed less severe liver injury than vehicle, suggesting that autophagy is involved in the gefitinib-promoted hepatotoxicity. Mechanistically, gefitinib selectively degrades the important anti-apoptosis factor COX6A1 (cytochrome c oxidase subunit 6A1) in the autophagy-lysosome pathway. The gefitinib-induced COX6A1 reduction impairs mitochondrial respiratory chain complex IV (RCC IV) function, which in turn activates apoptosis, hence causing liver injury. Notably, this autophagy-promoted apoptosis is dependent on PLK1 (polo like kinase 1). Both AAV8-mediated Plk1 knockdown and PLK1 inhibitor BI-2536 could mitigate the gefitinib-induced hepatotoxicity in vivo by abrogating the autophagic degradation of the COX6A1 protein. In addition, PLK1 inhibition could not compromise the anti-cancer activity of gefitinib. In conclusion, our findings reveal the gefitinib-hepatotoxicity pathway, wherein autophagy promotes apoptosis through COX6A1 degradation, and highlight pharmacological inhibition of PLK1 as an attractive therapeutic approach toward improving the safety of gefitinib-based cancer therapy.Abbreviations: 3-MA: 3-methyladenine; AAV8: adeno-associated virus serotype 8; ATG5: autophagy related 5; ATG7: autophagy related 7; B2M: beta-2-microglobulin; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CHX: cycloheximide; COX6A1: cytochrome c oxidase subunit 6A1; c-PARP: cleaved poly(ADP-ribose) polymerase; CQ: chloroquine; GOT1/AST: glutamic-oxaloacetic transaminase 1, soluble; GPT/ALT: glutamic pyruvic transaminase, soluble; HBSS: Hanks´ balanced salt solution; H&E: hematoxylin and eosin; MAP1LC3/LC3: microtubule associated proteins 1 light chain 3; PLK1: polo like kinase 1; RCC IV: respiratory chain complex IV; ROS: reactive oxygen species; TUBB8: tubulin beta 8 class VIII.

Hair Cell Protection from Ototoxic Drugs

Hearing loss is often caused by death of sensory hair cells (HCs) in the inner ear. HCs are vulnerable to some ototoxic drugs, such as aminoglycosides(AGs) and the cisplatin.The most predominant form of drug-induced cell death is apoptosis. Many efforts have been made to protect HCs from cell death after ototoxic drug exposure. These mechanisms and potential targets of HCs protection will be discussed in this review.And we also propose further investigation in the field of HCs necrosis and regeneration, as well as future clinical utilization.

Nox3-Derived Superoxide in Cochleae Induces Sensorineural Hearing Loss

Reactive oxygen species (ROS) produced by NADPH oxidases (Nox) contribute to the development of different types of sensorineural hearing loss (SNHL), a common impairment in humans with no established treatment. Although the essential role of Nox3 in otoconia biosynthesis and its possible involvement in hearing have been reported in rodents, immunohistological methods targeted at detecting Nox3 expression in inner ear cells reveal ambiguous results. Therefore, the mechanism underlying Nox3-dependent SNHL remains unclear and warrants further investigation. We generated Nox3-Cre knock-in mice, in which Nox3 was replaced with Cre recombinase (Cre). Using Nox3-Cre;tdTomato mice of either sex, in which tdTomato is expressed under the control of the Nox3 promoter, we determined Nox3-expressing regions and cell types in the inner ear. Nox3-expressing cells in the cochlea included various types of supporting cells, outer hair cells, inner hair cells, and spiral ganglion neurons. Nox3 expression increased with cisplatin, age, and noise insults. Moreover, increased Nox3 expression in supporting cells and outer hair cells, especially at the basal turn of the cochlea, played essential roles in ROS-related SNHL. The extent of Nox3 involvement in SNHL follows the following order: cisplatin-induced hearing loss > age-related hearing loss > noise-induced hearing loss. Here, on the basis of Nox3-Cre;tdTomato, which can be used as a reporter system (Nox3-Cre+/-;tdTomato+/+ and Nox3-Cre+/+;tdTomato+/+), and Nox3-KO (Nox3-Cre+/+;tdTomato+/+) mice, we demonstrate that Nox3 inhibition in the cochlea is a promising strategy for ROS-related SNHL, such as cisplatin-induced HL, age-related HL, and noise-induced HL.SIGNIFICANCE STATEMENT We found Nox3-expressing regions and cell types in the inner ear, especially in the cochlea, using Nox3-Cre;tdTomato mice, a reporter system generated in this study. Nox3 expression increased with cisplatin, age, and noise insults in specific cell types in the cochlea and resulted in the loss (apoptosis) of outer hair cells. Thus, Nox3 might serve as a molecular target for the development of therapeutics for sensorineural hearing loss, particularly cisplatin-induced, age-related, and noise-induced hearing loss.

Cisplatin-induced ototoxicity: Updates on molecular mechanisms and otoprotective strategies

Cisplatin is a highly effective antitumor drug generally used in the treatment of solid malignant tumors. However, cisplatin causes severe side effects such as bone marrow depression, nephrotoxicity, and ototoxicity, thus limiting its clinical application. The incidence of ototoxicity induced by cisplatin ranges from 20% to 70%, and it usually manifests as a progressive, bilateral and irreversible hearing loss. Although the etiology of cisplatin-induced ototoxicity remains unclear, an increasing body of evidence suggests that the ototoxicity of cisplatin is mainly related to the production of reactive oxygen species and activation of apoptotic pathway in cochlear tissues. Many drugs have been well proved to protect cisplatin-induced hearing loss in vitro and in vivo. However, the anti-tumor effect of cisplatin is also weakened by systemic administration of those drugs for hearing protection, especially antioxidants. Therefore, establishing a local administration strategy contributes to the otoprotection without affecting the effect of cisplatin. This review introduces the pathology of ototoxicity caused by cisplatin, and focuses on recent developments in the mechanisms and protective strategies of cisplatin-induced ototoxicity.

Identifying the mechanisms underlying the protective effect of tetramethylpyrazine against cisplatin‑induced in vitro ototoxicity in HEI‑OC1 auditory cells using gene expression profiling

Sensorineural hearing loss is prevalent in patients receiving cisplatin therapy. Tetramethylpyrazine (Tet) and tanshinone IIA (Tan IIA) have protective roles against hearing impairment or ototoxicity. The present study aimed to investigate the molecular mechanisms underlying cisplatin-induced ototoxicity and the protective effect of Tet and Tan IIA against it. House Ear Institute-Organ of Corti 1 auditory cells were treated with titrating doses of Tan IIA, Tet, and cisplatin. In a cell viability assay, cisplatin, Tan IIA and Tet had IC₅₀ values of 42.89 µM, 151.80 and 1.04×10³ mg/l, respectively. Tan IIA augmented cisplatin-induced cytotoxicity. However, Tet concentrations <75 mg/l attenuated cisplatin-induced cytotoxicity and apoptosis. Moreover, RNA sequencing analysis was carried out on auditory cells treated for 30 h with 30 µM cisplatin alone for 48 h or combined with 37.5 mg/l Tet for 30 h. Differentially expressed genes (DEGs) induced in these conditions were identified and examined using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis. Cisplatin increased the expression of genes related to the p53 and FoxO pathways, such as Fas, p21/CDKN1A, and Bcl-2 binding component 3, but decreased the expression of insulin-like growth factor 1 (IGF1), as well as genes in the histone (Hist)1 and Hist2 clusters. Treatment with Tet downregulated FOXO3 and Bcl-2 binding component 3, and increased the expression of IGF1. Moreover, Tet upregulated genes associated with Wnt signaling, but not p53-related genes. Thus, the otoprotective properties of Tet might be mediated by activation of Wnt and IGF1 signaling, and inhibition of FoxO signaling.

Strategies to reduce the risk of platinum containing antineoplastic drug-induced ototoxicity

INTRODUCTION

Cisplatin is a highly effective chemotherapeutic agent against a variety of solid tumors in adults and in children. Unfortunately, a large percentage of patients suffer permanent sensorineural hearing loss. Up to 60% of children and at least 50% of adults suffer this complication that seriously compromises their quality of life. Hearing loss is due to damage to the sensory cells in the inner ear. The mechanisms of cochlear damage are still being investigated. However, it appears that inner ear damage is triggered by reactive oxygen species (ROS) formation and inflammation 34.

AREAS COVERED

We discuss a number of potential therapeutic targets that can be addressed to provide hearing protection. These strategies include enhancing the endogenous antioxidant pathways, heat shock proteins, G protein coupled receptors and counteracting ROS and reactive nitrogen species, and blocking pathways that produce inflammation, including TRPV1 and STAT1 36.

EXPERT OPINION

Numerous potential protective agents show promise in animal models by systemic or local administration. However, clinical trials have not shown much efficacy to date with the exception of sodium thiosulfate. There is an urgent need to discover safe and effective protective agents that do not interfere with the efficacy of cisplatin against tumors yet preserve hearing 151.

Current Strategies to Combat Cisplatin-Induced Ototoxicity

Cisplatin is widely used for the treatment of a number of solid malignant tumors. However, ototoxicity induced by cisplatin is an obstacle to effective treatment of tumors. The basis for this toxicity has not been fully elucidated. It is generally accepted that hearing loss is due to excessive production of reactive oxygen species by cells of the cochlea. In addition, recent data suggest that inflammation may trigger inner ear cell death through endoplasmic reticulum stress, autophagy, and necroptosis, which induce apoptosis. Strategies have been extensively explored by which to prevent, alleviate, and treat cisplatin-induced ototoxicity, which minimize interference with antitumor activity. Of these strategies, none have been approved by the Federal Drug Administration, although several preclinical studies have been promising. This review highlights recent strategies that reduce cisplatin-induced ototoxicity. The focus of this review is to identify candidate agents as novel molecular targets, drug administration routes, delivery systems, and dosage schedules. Animal models of cisplatin ototoxicity are described that have been used to evaluate drug efficacy and side effect prevention. Finally, clinical reports of otoprotection in patients treated with cisplatin are highlighted. For the future, high-quality studies are required to provide reliable data regarding the safety and effectiveness of pharmacological interventions that reduce cisplatin-induced ototoxicity.

2-Hydroxypropyl-β-cyclodextrin Ototoxicity in Adult Rats: Rapid Onset and Massive Destruction of Both Inner and Outer Hair Cells Above a Critical Dose

2-Hydroxypropyl-β-cyclodextrin (HPβCD), a cholesterol chelator, is being used to treat diseases associated with abnormal cholesterol metabolism such as Niemann-Pick C1 (NPC1). However, the high doses of HPβCD needed to slow disease progression may cause hearing loss. Previous studies in mice have suggested that HPβCD ototoxicity results from selective outer hair cell (OHC) damage. However, it is unclear if HPβCD causes the same type of damage or is more or less toxic to other species such as rats, which are widely used in toxicity research. To address these issues, rats were given a subcutaneous injection of HPβCD between 500 and 4000 mg/kg. Distortion product otoacoustic emissions (DPOAE), the cochlear summating potential (SP), and compound action potential (CAP) were used to assess cochlear function followed by quantitative analysis of OHC and inner hair cell (IHC) loss. The 3000- and 4000-mg/kg doses abolished DPOAE and greatly reduced SP and CAP amplitudes. These functional deficits were associated with nearly complete loss of OHC as well as ~ 80% IHC loss over the basal two thirds of the cochlea. The 2000-mg/kg dose abolished DPOAE and significantly reduced SP and CAP amplitudes at the high frequencies. These deficits were linked to OHC and IHC losses in the high-frequency region of the cochlea. Little or no damage occurred with 500 or 1000 mg/kg of HPβCD. The HPβCD-induced functional and structural deficits in rats occurred suddenly, involved damage to both IHC and OHC, and were more severe than those reported in mice.

The monofunctional platinum(II) compounds, phenanthriplatin and pyriplatin, modulate apoptosis signaling pathways in HEI-OC1 auditory hybridoma cells

Cisplatin is a platinum(II) chemotherapy drug that can cause the side-effect of ototoxicity and hearing loss. The monofunctional platinum(II) complexes, phenanthriplatin and pyriplatin, have recently been investigated as anti-cancer agents but their side-effects are largely unknown. Here, we used the auditory hybridoma cell line, HEI-OC1, to investigate the ototoxicity of cisplatin, phenanthriplatin and pyriplatin. The effect of these compounds against cellular viability, on reactive oxygen species (ROS) production, mitochondrial membrane polarization, caspase-3/7 activity, DNA integrity and caspase-12 expression were measured using spectrophotometric, flow cytometric and blot analyses. We found that the monofunctional complexes and cisplatin decreased cellular viability. All three compounds increased ROS yield at 24 h, but at 48 h, ROS levels returned to normal. Also, the compounds did not depolarize the mitochondrial membrane. All three compounds reduced caspase-3/7 activity at 24 h; cisplatin increased caspase-3/7 activity and caused apoptosis at 48 h. Caspase-12 expression was associated with all three compounds. In summary, the monofunctional complexes may cause ototoxicity like cisplatin. Phenanthriplatin and pyriplatin may cause ototoxicity initially by inducing ROS production, but they may also signal through distinct apoptotic pathways that do not integrate caspases-3/7, or may act at different time-points in the same pathways.

Astaxanthin-loaded polymer-lipid hybrid nanoparticles (ATX-LPN): assessment of potential otoprotective effects

Background

Ototoxicity is one of the major side effects of platinum-based chemotherapy, especially cisplatin therapy. To date, no FDA approved agents to alleviate or prevent this ototoxicity are available. However, ototoxicity is generally believed to be produced by excessive generation of reactive oxygen species (ROS) in the inner ear, thus leading to the development of various antioxidants, which act as otoprotective agents. Astaxanthin (ATX) is an interesting candidate in the development of new therapies for preventing and treating oxidative stress-related pathologies, owing to its unique antioxidant capacity.

Methods and results

In this study, we aimed to evaluate the potential antioxidant properties of ATX in the inner ear by using the HEI-OC1 cell line, zebrafish, and guinea pigs. Because ATX has poor solubility and cannot pass through round window membranes (RWM), we established lipid-polymer hybrid nanoparticles (LPN) for loading ATX. The LPN enabled ATX to penetrate RWM and maintain concentrations in the perilymph in the inner ear for 24 h after a single injection. ATX-LPN were found to have favorable biocompatibility and to strongly affect cisplatin-induced generation of ROS, on the basis of DCFHDA staining in HEI-OC1 cells. JC-1 and MitoTracker Green staining suggested that ATX-LPN successfully reversed the decrease in mitochondrial membrane potential induced by cisplatin in vitro and rescued cells from early stages of apoptosis, as demonstrated by FACS stained with Annexin V-FITC/PI. Moreover, ATX-LPN successfully attenuated OHC losses in cultured organ of Corti and animal models (zebrafish and guinea pigs) in vivo. In investigating the protective mechanism of ATX-LPN, we found that ATX-LPN decreased the expression of pro-apoptotic proteins (caspase 3/9 and cytochrome-c) and increased expression of the anti-apoptotic protein Bcl-2. In addition, the activation of JNK induced by CDDP was up-regulated and then decreased after the administration of ATX-LPN, while P38 stayed unchanged.

Conclusions

To best of our knowledge, this is first study concluded that ATX-LPN as a new therapeutic agent for the prevention of cisplatin-induced ototoxicity.

The dual role of curcumin and ferulic acid in counteracting chemoresistance and cisplatin-induced ototoxicity

Platinum-based agents, such as cisplatin, form the mainstay of currently used chemotherapeutic regimens for several malignancies; however, the main limitations are chemoresistance and ototoxic side effects. In this study we used two different polyphenols, curcumin and ferulic acid as adjuvant chemotherapeutics evaluating (1) in vivo their antioxidant effects in protecting against cisplatin ototoxicity and (2) in vitro the transcription factors involved in tumor progression and cisplatin resistance. We reported that both polyphenols show antioxidant and oto-protective activity in the cochlea by up-regulating Nrf-2/HO-1 pathway and downregulating p53 phosphorylation. However, only curcumin is able to influence inflammatory pathways counteracting NF-κB activation. In human cancer cells, curcumin converts the anti-oxidant effect into a pro-oxidant and anti-inflammatory one. Curcumin exerts permissive and chemosensitive properties by targeting the cisplatin chemoresistant factors Nrf-2, NF-κB and STAT-3 phosphorylation. Ferulic acid shows a biphasic response: it is pro-oxidant at lower concentrations and anti-oxidant at higher concentrations promoting chemoresistance. Thus, polyphenols, mainly curcumin, targeting ROS-modulated pathways may be a promising tool for cancer therapy. Thanks to their biphasic activity of antioxidant in normal cells undergoing stressful conditions and pro-oxidant in cancer cells, these polyphenols probably engage an interplay among the key factors Nrf-2, NF-κB, STAT-3 and p53.

Presbycusis: An Update on Cochlear Mechanisms and Therapies

Age-related hearing impairment (ARHI), also referred to as presbycusis, is the most common sensory impairment seen in the elderly. As our cochlea, the peripheral organ of hearing, ages, we tend to experience a decline in hearing and are at greater risk of cochlear sensory-neural cell degeneration and exacerbated age-related hearing impairments, e.g., gradual hearing loss, deterioration in speech comprehension (especially in noisy environments), difficulty in the localization sound sources, and ringing sensations in the ears. However, the aging process does not affect people uniformly; nor, in fact, does the aging process appear to be uniform even within an individual. Here, we outline recent research into chronological cochlear age in healthy people, and exacerbated hearing impairments during aging due to both extrinsic factors including noise and ototoxic medication, and intrinsic factors such as genetic predisposition, epigenetic factors, and aging. We review our current understanding of molecular pathways mediating ARHL and discuss recent discoveries in experimental hearing restoration and future prospects.

Cisplatin induces calcium ion accumulation and hearing loss by causing functional alterations in calcium channels and exocytosis

In recent years, molecular biology and biochemistry have been a focus of studies on the ototoxic side effects of cisplatin. In this paper, the application of cisplatin for 4 h and 72 h was studied from the perspective of electrophysiological function. Patch clamp experiments and immunofluorescence staining were performed on inner hair cells of the cochlea. The patch-clamp results showed that the calcium current amplitude decreased significantly at 4 h and 72 h after cisplatin treatment, the reversal potential was negatively polarized, and the activation time decreased. We suspected that intracellular calcium accumulation was responsible for this result and confirmed this hypothesis by using calpain to measure intracellular calcium concentrations. We tested membrane capacitive function, whose levels after cisplatin application were significantly lower than those in the control group, thus indicating dysfunctional cytoplasmic effervescent function. CtBP2 staining was used to verify this result and indicated a decrease in ribbon synapses. Simultaneously, we observed dysfunction of vesicle circulation after cisplatin application. We found that cisplatin induces the accumulation of calcium ions in inner hair cells by calpain staining and fluoresce intensity calculation, thus decreasing calcium current and synaptic vesicle release, and impairing vesicles cycling, all of which are important mechanisms of cisplatin-induced hearing loss.

Aminoglycoside- and Cisplatin-Induced Ototoxicity: Mechanisms and Otoprotective Strategies

Ototoxicity refers to damage of inner ear structures (i.e., the cochlea and vestibule) and their function (hearing and balance) following exposure to specific in-hospital medications (i.e., aminoglycoside antibiotics, platinum-based drugs), as well as a variety of environmental or occupational exposures (e.g., metals and solvents). This review provides a narrative derived from relevant papers describing factors contributing to (or increasing the risk of) aminoglycoside and cisplatin-induced ototoxicity. We also review current strategies to protect against ototoxicity induced by these indispensable pharmacotherapeutic treatments for life-threatening infections and solid tumors. We end by highlighting several interventional strategies that are currently in development, as well as the diverse challenges that still need to be overcome to prevent drug-induced hearing loss.