Effects of a single high dose of cisplatin on the melanocytes of the stria vascularis in the guinea pig

The effect of cisplatin-based chemotherapy on hearing loss (the frequency of >8 kHz) in children with cancer

INTRODUCTION

In this study we investigated the effect of cisplatin-based chemotherapy on hearing loss in children with cancer.

MATERIAL AND METHOD

In this retrospective study, 20 children aged 6 to 17 years with cancer who were treated with cisplatin and had normal results on initial audiometry test were included. The demographic, clinical, and medical information of all children was extracted and recorded. The hearing thresholds were determined for the frequency of >8 kHz by an audiometrist two weeks after receiving the last course of cisplatin. Finally, all data was analyzed.

RESULTS

In this study, 20 children with cancer were included of who 9 were girls (45 %) and 11 were boys (55 %). The patients' mean age at the time of diagnosis was 6.65 years. Results showed that children who received cisplatin ≥70 mg/m2 (P.value = 0.09) and ≥ 7 courses of cisplatin (P.value = 0.01), and a cumulative dose higher than 400 mg/m2 (P.value = 0.02) had higher chance of hearing loss.

CONCLUSION

According to the results it can be concluded that since higher doses caused higher risk of hearing loss and also since lower doses were effective for treatment of the cancer in children therefore to preventing the hearing loss, lower doses of cisplatin are recommended for cancer treatment in children.

Transgenic Tg(Kcnj10-ZsGreen) fluorescent reporter mice allow visualization of intermediate cells in the stria vascularis

The stria vascularis (SV) is a stratified epithelium in the lateral wall of the mammalian cochlea, responsible for both endolymphatic ion homeostasis and generation of the endocochlear potential (EP) critical for normal hearing. The SV has three layers consisting predominantly of basal, intermediate, and marginal cells. Intermediate and marginal cells form an intricate interdigitated network of cell projections making discrimination of the cells challenging. To enable intermediate cell visualization, we engineered by BAC transgenesis, reporter mouse lines expressing ZsGreen fluorescent protein under the control of Kcnj10 promoter and regulatory sequences. Kcnj10 encodes KCNJ10 protein (also known as Kir4.1 or Kir1.2), an ATP-sensitive inwardly-rectifying potassium channel critical to EP generation, highly expressed in SV intermediate cells. In these transgenic mice, ZsGreen fluorescence mimics Kcnj10 endogenous expression in the cochlea and was detected in the intermediate cells of the SV, in the inner phalangeal cells, Hensen's, Deiters' and pillar cells, in a subset of spiral ganglion neurons, and in glial cells. We show that expression of the transgene in hemizygous mice does not alter auditory function, nor EP. These transgenic Tg(Kcnj10-ZsGreen) mice allow live and fixed tissue visualization of ZsGreen-expressing intermediate cells and will facilitate future studies of stria vascularis cell function.

Transgenic Tg(Kcnj10-ZsGreen) Fluorescent Reporter Mice Allow Visualization of Intermediate Cells in the Stria Vascularis

The stria vascularis (SV) is a stratified epithelium in the lateral wall of the mammalian cochlea, responsible for both endolymphatic ion homeostasis and generation of the endocochlear potential (EP) critical for normal hearing. The SV has three layers consisting predominantly of basal, intermediate, and marginal cells. Intermediate and marginal cells form an intricate interdigitated network of cell projections making discrimination of the cells challenging. To enable intermediate cell visualization, we engineered by BAC transgenesis, reporter mouse lines expressing ZsGreen fluorescent protein under the control of Kcnj10 promoter and regulatory sequences. Kcnj10 encodes KCNJ10 protein (also known as Kir4.1 or Kir1.2), an ATP-sensitive inwardly-rectifying potassium channel critical to EP generation, highly expressed in SV intermediate cells. In these transgenic mice, ZsGreen fluorescence mimics Kcnj10 endogenous expression in the cochlea and was detected in the intermediate cells of the SV, in the inner phalangeal cells, Hensen's, Deiters' and pillar cells, in a subset of spiral ganglion neurons, and in glial cells. We show that expression of the transgene in hemizygous mice does not alter auditory function, nor EP These transgenic Tg(Kcnj10-ZsGreen) mice allow live and fixed tissue visualization of ZsGreen-expressing intermediate cells and will facilitate future studies of stria vascularis cell function.

Special considerations in the design and implementation of pediatric otoprotection trials

PURPOSE

Cisplatin-induced hearing loss (CIHL) is a common late effect after childhood cancer treatment having profound, lifelong consequences that lower quality of life. The recent identification of intravenous sodium thiosulfate (STS) as an effective agent for preventing pediatric CIHL represents a paradigm shift that has created new opportunities for expanding STS usage and developing additional otoprotectants. The purpose of this paper is to discuss key considerations and recommendations for the design and implementation of future pediatric otoprotection trials.

METHODS

An approach synthesizing published data and collective experience was used.

RESULTS

Key issues were identified in the categories of translational research, trial designs for systemic and intratympanic agents, measurement of ototoxicity, and biostatistical challenges.

CONCLUSIONS

Future pediatric otoprotection trials should emphasize (1) deep integration of preclinical and early-phase studies; (2) an embedded or free-standing design for systemic agents based on mechanistic considerations; (3) use of suitable audiologic testing batteries for children, SIOP grading criteria, and submission of raw audiologic data for central review; and (4) novel endpoints and innovative study designs that maximize trial efficiency for limited sample sizes. Additional recommendations include routine collection of DNA specimens for assessing modifying effects of genetic susceptibility and meaningful inclusion of patient/family advocates for informing trial development.

IMPLICATIONS FOR CANCER SURVIVORS

Changing the historical paradigm from acceptance to prevention of pediatric CIHL through expanded research with existing and emerging otoprotectants will dramatically improve quality of life for future childhood cancer survivors exposed to cisplatin.

Cisplatin-induced ototoxicity: From signaling network to therapeutic targets

Administration of cisplatin, a common chemotherapeutic drug, has an inevitable side effect of sensorineural hearing loss. The main etiologies are stria vascularis injury, spiral ganglion degeneration, and hair cell death. Over several decades, the research scope of cisplatin-induced ototoxicity has expanded with the discovery of the molecular mechanism mediating inner ear cell death, highlighting the roles of reactive oxygen species and transport channels for cisplatin uptake into inner ear cells. Upon entering hair cells, cisplatin disrupts organelle metabolism, induces oxidative stress, and targets DNA to cause intracellular damage. Recent studies have also reported the role of inflammation in cisplatin-induced ototoxicity. In this article, we preform a narrative review of the latest reported molecular mechanisms of cisplatin-induced ototoxicity, from extracellular to intracellular. We build up a signaling network starting with cisplatin entering into the inner ear through the blood labyrinth barrier, disrupting cochlear endolymph homeostasis, and activating inflammatory responses of the outer hair cells. After entering the hair cells, cisplatin causes hair cell death via DNA damage, redox system imbalance, and mitochondrial and endoplasmic reticulum dysfunction, culminating in programmed cell death including apoptosis, necroptosis, autophagic death, pyroptosis, and ferroptosis. Based on the mentioned mechanisms, prominent therapeutic targets, such as channel-blocking drugs of cisplatin transporter, construction of cisplatin structural analogues, anti-inflammatory drugs, antioxidants, cell death inhibitors, and others, were collated. Considering the recent research efforts, we have analyzed the feasibility of the aforementioned therapeutic strategies and proposed our otoprotective approaches to overcome cisplatin-induced ototoxicity.

Melatonin Attenuates Cisplatin-Induced Ototoxicity via Regulating the Cell Apoptosis of the Inner Ear

Objective

The mechanism of ototoxicity caused by cisplatin is currently unclear, and the induced apoptosis may play an important role in inner ear injury. Melatonin has high antioxidant and antiapoptotic effects. This study is aimed at clarifying the protective effect on the inner ear and the underlying mechanism of melatonin.

Design

The mice and HEI-OC1 cells were randomly separated into four groups: control group, cisplatin group, melatonin group, and cisplatin exposure after melatonin pretreatment group. Place and Duration of the Study. From September 2018 to September 2021, all experiments were completed at the Second Hospital of Shandong University. And the study was approved by the Ethics Committee of the Second Hospital of Shandong University (KYLL-2020 (KJ) A-0191). Methodology. Mice were pretreated with peritoneal injection of melatonin prior to the application of cisplatin. Auditory Brainstem Response (ABR) test was performed before and after treatment, then the temporal bones were collected for histology investigation. HEI-OC1 cells were pretreated with melatonin before adding cisplatin. The apoptosis of HEI-OC1 cells was observed by MTS, TUNEL, and flow cytometry, respectively. Moreover, the mRNA expression of apoptosis-related factors was detected by qRT-PCR.

Results

ABR and morphological analysis showed that cisplatin caused damage to the function and structure of the inner ear. MTS, TUNEL, and flow cytometry showed that the application of cisplatin caused a significant increase in the apoptosis level of HEI-OC1 cells, and melatonin pretreatment reduced this damage. Moreover, melatonin pretreatment reversed the mRNA expression changes of apoptosis-related factors induced by cisplatin.

Conclusions

Apoptosis is involved in the inner ear dysfunction caused by cisplatin. Melatonin reduces the ototoxicity of cisplatin by regulating the induced apoptosis response.

Local drug delivery using poly(lactic-co-glycolic acid) nanoparticles in thermosensitive gels for inner ear disease treatment

Intratympanic (IT) therapies have been explored to address several side effects that could be caused by systemic administration of steroids to treat inner ear diseases. For effective drug delivery to the inner ear, an IT delivery system was developed using poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and thermosensitive gels to maintain sustained release. Dexamethasone (DEX) was used as a model drug. The size and zeta potential of PLGA NPs and the gelation time of the thermosensitive gel were measured. In vitro drug release was studied using a Franz diffusion cell. Cytotoxicity of the formulations was investigated using SK-MEL-31 cells. Inflammatory responses were evaluated by histological observation of spiral ganglion cells and stria vascularis in the mouse cochlea 24 h after IT administration. In addition, the biodistribution of the formulations in mouse ears was observed by fluorescence imaging using coumarin-6. DEX-NPs showed a particle size of 150.0 ± 3.2 nm in diameter and a zeta potential of −18.7 ± 0.6. The DEX-NP-gel showed a gelation time of approximately 64 s at 37 °C and presented a similar release profile and cytotoxicity as that for DEX-NP. Furthermore, no significant inflammatory response was observed after IT administration. Fluorescence imaging results suggested that DEX-NP-gel sustained release compared to the other formulations. In conclusion, the PLGA NP-loaded thermosensitive gel may be a potential drug delivery system for the inner ear.

Mechanisms of Aminoglycoside- and Cisplatin-Induced Ototoxicity

Purpose This review article summarizes our current understanding of the mechanisms underlying acquired hearing loss from hospital-prescribed medications that affects as many as 1 million people each year in Western Europe and North America. Yet, there are currently no federally approved drugs to prevent or treat the debilitating and permanent hearing loss caused by the life-saving platinum-based anticancer drugs or the bactericidal aminoglycoside antibiotics. Hearing loss has long-term impacts on quality-of-life measures, especially in young children and older adults. This review article also highlights some of the current knowledge gaps regarding iatrogenic causes of hearing loss. Conclusion Further research is urgently needed to further refine clinical practice and better ameliorate iatrogenic drug-induced hearing loss.

Preferential Cochleotoxicity of Cisplatin

Cisplatin-induced ototoxicity in humans is more predominant in the cochlea than in the vestibule. Neither definite nor substantial vestibular dysfunction after cisplatin treatment has been consistently reported in the current literature. Inner ear hair cells seem to have intrinsic characteristics that make them susceptible to direct exposure to cisplatin. The existing literature suggests, however, that cisplatin might have different patterns of drug trafficking across the blood-labyrinth-barrier, or different degrees of cisplatin uptake to the hair cells in the cochlear and vestibular compartments. This review proposes an explanation for the preferential cochleotoxicity of cisplatin based on current evidence as well as the anatomy and physiology of the inner ear. The endocochlear potential, generated by the stria vascularis, acting as the driving force for hair cell mechanoelectrical transduction might also augment cisplatin entry into cochlear hair cells. Better understanding of the stria vascularis might shed new light on cochleotoxic mechanisms and inform the development of otoprotective interventions to moderate cisplatin associated ototoxicity.

Comparison of Age-Related Pigmentary Changes in the Auditory and Vestibular Systems Within Mouse and Human Temporal Bones

Background

Melanin pigmentation is present within the auditory and vestibular systems of the mammalian inner ear and may play a role in maintaining auditory and vestibular function. Melanocytes within the stria vascularis (SV) are necessary for the generation of the endocochlear potential (EP) and decreased EP has been linked to age-related hearing loss. Melanocytes and pigment-containing "dark cells" are present within the vestibular system, but have a less well-defined role. African-American individuals have increased pigmentation within the SV and vestibular system, which is hypothesized to be related to lower rates of age-related hearing loss and vestibular dysfunction. It remains unclear if increased pigmentation confers lifelong protection against hearing loss and vestibular dysfunction.

Methods

Mouse temporal bones were collected from juvenile (3-4 week) and aged (20-32 months) CBA/CaJ mice. Pediatric and adult human temporal bones from Caucasian or African-American individuals were examined from the Johns Hopkins Temporal Bone Collection. Information regarding Fitzpatrick skin type were unavailable, and self-identified race/ethnicity was used as a proxy. Images were taken using light microscopy at 20× magnification. ImageJ software (v1.53) was used to measure pigment within the SV and vestibular system.

Results

In mouse temporal bones pigmentation within the SV increased with age, but pigmentation within the vestibular system did not increase with age. In human temporal bones pigmentation within the SV increased with age and pigmentation within the vestibular system increased within the wall of the utricle, but not other regions of the vestibular system. African-American individuals had higher amounts of pigment within the SV and vestibular system, among both pediatric and adult populations.

Conclusion

Stria vascularis pigmentation increases with age in mouse and human temporal bones. Pigmentation within the vestibular system did not increase with age in mouse specimens and only increased within the utricular wall with age in human specimens. Individuals who identified as African-American had higher pigment content within the SV and vestibular system, both as children and as adults. These results highlight how similar age-related pigmentary changes occur in the auditory and vestibular systems across species and underscore the importance of racial/ethnic diversity in human temporal bone studies.

Potential use of n-3 PUFAs to prevent oxidative stress-derived ototoxicity caused by platinum-based chemotherapy

Platinum-based compounds are widely used for the treatment of different malignancies due to their high effectiveness. Unfortunately, platinum-based treatment may lead to ototoxicity, an often-irreversible side effect without a known effective treatment and prevention plan. Platinum-based compound-related ototoxicity results mainly from the production of toxic levels of reactive oxygen species (ROS) rather than DNA-adduct formation, which has led to test strategies based on direct ROS scavengers to ameliorate hearing loss. However, favorable clinical results have been associated with several complications, including potential interactions with chemotherapy efficacy. To understand the contribution of the different cytotoxic mechanisms of platinum analogues on malignant cells and auditory cells, the particular susceptibility and response of both kinds of cells to molecules that potentially interfere with these mechanisms, is fundamental to develop innovative strategies to prevent ototoxicity without affecting antineoplastic effects. The n-3 long-chain polyunsaturated fatty acids (n-3 PUFAs) have been tried in different clinical settings, including with cancer patients. Nevertheless, their use to decrease cisplatin-induced ototoxicity has not been explored to date. In this hypothesis paper, we address the mechanisms of platinum compounds-derived ototoxicity, focusing on the differences between the effects of these compounds in neoplastic versus auditory cells. We discuss the basis for a strategic use of n-3 PUFAs to potentially protect auditory cells from platinum-derived injury without affecting neoplastic cells and chemotherapy efficacy.

Ototoxicity and Platinum Uptake Following Cyclic Administration of Platinum-Based Chemotherapeutic Agents

Cisplatin is a widely used anti-cancer drug used to treat a variety of cancer types. One of the side effects of this life-saving drug is irreversible ototoxicity, resulting in permanent hearing loss in many patients. In order to understand why cisplatin is particularly toxic to the inner ear, we compared the hearing loss and cochlear uptake of cisplatin to that of two related drugs, carboplatin and oxaliplatin. These three drugs are similar in that each contains a core platinum atom; however, carboplatin and oxaliplatin are considered less ototoxic than cisplatin. We delivered these three drugs to mice using a 6-week cyclic drug administration protocol. We performed the experiment twice, once using equimolar concentrations of the drugs and once using concentrations of the drugs more proportional to those used in the clinic. For both concentrations, we detected a significant hearing loss caused by cisplatin and no hearing loss caused by carboplatin or oxaliplatin. Cochlear uptake of each drug was measured using inductively coupled plasma mass spectrometry (ICP-MS) to detect platinum. Cochlear platinum levels were highest in mice treated with cisplatin followed by oxaliplatin, while carboplatin was largely excluded from the cochlea. Even when the drug doses were increased, cochlear platinum remained low in mice treated with oxaliplatin or carboplatin. We also examined drug clearance from the inner ear by measuring platinum levels at 1 h and 24 h after drug administration. Our findings suggest that the reduced cochlear platinum we observed with oxaliplatin and carboplatin were not due to increased clearance of these drugs relative to cisplatin. Taken together, our data indicate that the differential ototoxicity among cisplatin, carboplatin, and oxaliplatin is attributable to differences in cochlear uptake of these three drugs.

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.

Cisplatin-induced Ototoxicity in Children With Solid Tumor

Cisplatin is the principal chemotherapeutic agent and also tremendously increases the survival for pediatric patients with neuroblastoma or hepatoblastoma. With the extended overall survival period, clinical medical workers and parents gradually attach more attention to the late effect of chemotherapy of these children. The purpose of this study is to analyze the incidence and risk factors of cisplatin-based hearing loss. We retrospectively collected the archives of cisplatin-based chemotherapy and audiometric evaluation from 2005 through 2017 at Xinhua Hospital. From 384 patients treated with cisplatin, full data of 59 patients were available, and 14 cases (23.7%) were identified as significant hearing loss. The median time from usage of platinum compounds to the most recent audio test was 406 days. Cumulative and single maximum cisplatin dose was 622.6±283.2 and 137.6±51.6 mg/m/cycle, respectively. Accumulated cisplatin dose (95% confidence interval, 1.001-1.006; P=0.012) and single maximum cisplatin dose (95% confidence interval, 1.000-1.029; P=0.049) were independently important predictors for moderate to severe hearing loss in children treated with cisplatin. Cisplatin can cause ototoxicity which profoundly handicap language development and social communication for children. Regular audiological management and long-term follow-up are strongly recommended for this vulnerable group.

Inhibition of Mitochondrial Division Attenuates Cisplatin-Induced Toxicity in the Neuromast Hair Cells

Cisplatin and other related platinum antineoplastic drugs are commonly used in the treatment of a variety of cancers in both adults and children but are often associated with severe side effects, including hearing loss. Cisplatin’s ototoxic effects are multifaceted, culminating in irreversible damage to the mechanosensory hair cells in the inner ear. Platinum drugs act on cancerous cells by forming nuclear DNA adducts, which may initiate signaling leading to cell cycle arrest or apoptosis. Moreover, it was reported that cisplatin may induce mitochondrial DNA damage in non-cancerous cells. Therefore, protecting mitochondria may alleviate cisplatin-induced insult to non-proliferating cells. Thus, it is important to identify agents that shield the mitochondria from cisplatin-induced insult without compromising the anti-tumor actions of the platinum-based drugs. In this study we tested the protective properties of mitochondrial division inhibitor, mdivi-1, a derivative of quinazolinone and a regulator of mitochondrial fission. Interestingly, it has been reported that mdivi-1 increases the apoptosis of cells that are resistant to cisplatin. The ability of mdivi-1 to protect hair cells against cisplatin-induced toxicity was evaluated in a fish model. Wild-type (Tübingen strain), cdh23 mutant, and transgenic pvalb3b::GFP zebrafish stably expressing GFP in the hair cells were used in this study. Larvae at 5–6 days post fertilization were placed in varying concentrations of cisplatin (50–200 μM) and/or mdivi-1 (1–10 μM) for 16 h. To evaluate hair cell’s viability the number of hair bundles per neuromast were counted. To assess hair cell function, we used the FM1-43 uptake assay and recordings of neuromast microphonic potentials. The results showed that mdivi-1 protected hair cells of lateral line neuromasts when they were challenged by 50 μM of cisplatin: viability of hair cells increased almost twice from 19% ± 1.8% to 36% ± 2.0% (p < 0.001). No protection was observed when higher concentrations of cisplatin were used. In addition, our data were in accord with previously reported results that functional mechanotransduction strongly potentiates cisplatin-induced hair cell toxicity. Together, our results suggest that mitochondrial protection may prevent cisplatin-induced damage to hair cells.

Prestin as an Otologic Biomarker of Cisplatin Ototoxicity in a Guinea Pig Model

Objective

To evaluate (1) whether changes in serum prestin aid in early detection of cisplatin ototoxicity, (2) the role of diltiazem as an otoprotectant, and (3) whether prestin levels are sensitive to effects of diltiazem.

Study Design

Experimental animal study.

Setting

Translational research laboratory.

Subjects

Twenty female guinea pigs.

Methods

Two groups of 10 guinea pigs were used. The relationship between serum prestin levels and auditory brainstem response (ABR) thresholds was compared between the groups. All animals had baseline blood draws and ABR thresholds recorded prior to cisplatin administration. Intraperitoneal cisplatin bolus (8 mg/kg) was administered followed by 5 consecutive days of intratympanic (IT) diltiazem (2 mg/kg) or sham IT-saline injection. Serum prestin levels and ABR thresholds were measured at days 1, 2, 3, 7, and 14 postcisplatin.

Results

In sham, IT-saline–treated animals, mean prestin levels were elevated above baseline on days 1 to 7. The prestin levels were significantly elevated from baseline on day 1 ( P < .001), while significant ABR threshold elevations did not occur until day 2 ( P = .028) for click-evoked ABRs and day 3 ( P = .041) for tones. In diltiazem-treated animals, prestin levels were not elevated above baseline but ABR thresholds were elevated on days 1 to 3. However, the thresholds returned toward baseline on days 7 and 14.

Conclusion

Changes in serum prestin levels were detectable prior to shifts in ABR thresholds in a guinea pig cisplatin ototoxicity model. These changes did not occur in diltiazem-treated animals. Prestin may serve as a biomarker of cochlear injury that is sensitive to therapeutic interventions in cisplatin ototoxicity.

Cisplatin-induced metabolome changes in serum: an experimental approach to identify markers for ototoxicity

BACKGROUND

Ototoxicity from treatment with the anticancer drug cisplatin remains a clinical problem. A wide range of intracellular targets of cisplatin has been found in vivo.

AIM

To investigate cisplatin-induced change of the serum metabolite profile and its association with ototoxicity.

MATERIAL AND METHODS

Guinea pigs (n = 14) were treated with cisplatin (8 mg/kg b.w., i.v.) 30 min after administration of the otoprotector candidate sodium thiosulfate (group STS; n = 7) or sodium chloride (group NaCl; n = 7). Ototoxicity was evaluated by ABR (3-30 kHz) before and 4 d after drug treatment, and by assessment of hair cell loss. A blood sample was drawn before and 4 d after drug treatment and the polar metabolome in serum was analyzed using LC-MS.

RESULTS

Cisplatin-treatment caused significant threshold elevations and outer hair cell (OHC) loss in both groups. The ototoxicity was generally lower in group STS, but a significant difference was reached only at 30 kHz (p = .007). Cisplatin treatment altered the metabolite profile significantly and similarly in both groups. A significant inverse correlation was found between L-acetylcarnitine, N-acetylneuraminic acid, ceramide, and cysteinylserine and high frequency hearing loss in group NaCl. The implication of these correlations should be explored in targeted studies.

Systemic Delivery and Biodistribution of Cisplatin in Vivo

Cisplatin is widely used to treat a variety of cancers. However, ototoxicity and nephrotoxicity remain serious side effects of cisplatin-based chemotherapy. In order to inform the study of cisplatin's off-target effects, a new drug-fluorophore conjugate was synthesized that exhibited utility as a tracer to determine the cellular uptake and in vivo distribution of cisplatin. This probe will serve as a useful tool to facilitate investigations into the kinetics and biodistribution of cisplatin and its associated side effects in preclinical models after systemic administration.

Age-related hearing impairment and the triad of acquired hearing loss

Understanding underlying pathological mechanisms is prerequisite for a sensible design of protective therapies against hearing loss. The triad of age-related, noise-generated, and drug-induced hearing loss displays intriguing similarities in some cellular responses of cochlear sensory cells such as a potential involvement of reactive oxygen species (ROS) and apoptotic and necrotic cell death. On the other hand, detailed studies have revealed that molecular pathways are considerably complex and, importantly, it has become clear that pharmacological protection successful against one form of hearing loss will not necessarily protect against another. This review will summarize pathological and pathophysiological features of age-related hearing impairment (ARHI) in human and animal models and address selected aspects of the commonality (or lack thereof) of cellular responses in ARHI to drugs and noise.

An integrated view of cisplatin-induced nephrotoxicity and ototoxicity

Cisplatin is one of the most widely-used drugs to treat cancers. However, its nephrotoxic and ototoxic side-effects remain major clinical limitations. Recent studies have improved our understanding of the molecular mechanisms of cisplatin-induced nephrotoxicity and ototoxicity. While cisplatin binding to DNA is the major cytotoxic mechanism in proliferating (cancer) cells, nephrotoxicity and ototoxicity appear to result from toxic levels of reactive oxygen species and protein dysregulation within various cellular compartments. In this review, we discuss molecular mechanisms of cisplatin-induced nephrotoxicity and ototoxicity. We also discuss potential clinical strategies to prevent nephrotoxicity and ototoxicity and their current limitations.

Cochlear pharmacokinetics of cisplatin: an in vivo study in the guinea pig

OBJECTIVES/HYPOTHESIS

Cisplatin produces toxic lesions to outer hair cells (OHCs) in the cochlear base but not in the apex. The objective of this study was to compare the pharmacokinetic profile of cisplatin in scala tympani (ST) perilymph in the cochlear base and apex, respectively.

STUDY DESIGN

In vivo animal study.

METHODS

Forty-seven guinea pigs were given an intravenous bolus injection of an ototoxic dose of cisplatin. Ten to 240 minutes after cisplatin was given, blood, cerebrospinal fluid (CSF), and ST perilymph were aspirated within the same target time. ST perilymph was aspirated from the basal turn and from the apex of the cochlea by two different sampling techniques. Liquid chromatography with postcolumn derivatization was used for quantitative determination of the parent drug.

RESULTS

Ten minutes after administration, the concentration of cisplatin in ST perilymph was 4-fold higher in the basal turn of the cochlea than in the apex. At 30 minutes, the drug concentrations did not differ. At 60 minutes, the level of cisplatin in ST perilymph and blood UF was equivalent. The perilymph-blood ratio increased thereafter with time.

CONCLUSION

The pharmacokinetic findings of an early high concentration of cisplatin in the base of the cochlea and delayed elimination of cisplatin from ST perilymph compared to blood might correlate to the cisplatin-induced loss of OHCs in the base of the cochlea.

Prospective evaluation of cisplatin- and carboplatin-mediated ototoxicity in paediatric and adult soft tissue and osteosarcoma patients

Platinum-compound chemotherapy is known to have ototoxic side-effects. However, there is a paucity of literature examining hearing function prospectively and longitudinally in cohorts containing paediatric and adult patients treated within the same cisplatin- or carboplatin-containing treatment trial protocols. In Germany, Austria and Switzerland, late effects of treatment for osteosarcoma and soft tissue sarcoma have been prospectively and longitudinally registered by the Late Effects Surveillance System since 1998. The aim of this study was to analyse cisplatin- and carboplatin-induced ototoxity in a group of 129 osteosarcoma and soft tissue sarcoma patients treated within the COSS-96, CWS-96 and CWS-2002P treatment trials. The cohort consisted of 112 children and 17 adults. The median age at diagnosis was 13.56 (IQR, 10.26-16.27) years. Follow-up was 6.97 (IQR, 0.87-15.63) months. Hearing function was examined by audiometry before and after platinum treatment. A total of 108 patients were treated with cisplatin with a median cumulative dose of 360 mg/m(2). Thirteen patients received carboplatin with a median cumulative dose of 1500 mg/m(2) and 8 patients were treated with both platinum compounds (median cisplatin dose, 240 mg/m(2); IQR, 240-360 mg/m(2) and median carboplatin dose: 1200 mg/m(2); IQR, 600-3000 mg/m(2)). Following cessation of therapy, 47.3% of the patients demonstrated a hearing impairment, namely 55 children (49.1%) and 6 adults (42.1%). Out of thirteen children treated with carboplatin with a cumulative dose of 1500 mg/m(2), six revealed a significant hearing impairment. Although ototoxicity caused by platinum compounds is considered irreversible, we identified hearing improvements over time in 11 children (9.8%) and 3 adults (17.6%). None of these patients received irradiation to the head. We conclude that hearing loss is frequent in children treated with protocols containing platinum compounds and recommend prospective testing via audiometry.

Platinum-induced ototoxicity in children: a consensus review on mechanisms, predisposition, and protection, including a new International Society of Pediatric Oncology Boston ototoxicity scale

PURPOSE

The platinum chemotherapy agents cisplatin and carboplatin are widely used in the treatment of adult and pediatric cancers. Cisplatin causes hearing loss in at least 60% of pediatric patients. Reducing cisplatin and high-dose carboplatin ototoxicity without reducing efficacy is important.

PATIENTS AND METHODS

This review summarizes recommendations made at the 42nd Congress of the International Society of Pediatric Oncology (SIOP) in Boston, October 21-24, 2010, reflecting input from international basic scientists, pediatric oncologists, otolaryngologists, oncology nurses, audiologists, and neurosurgeons to develop and advance research and clinical trials for otoprotection.

RESULTS

Platinum initially impairs hearing in the high frequencies and progresses to lower frequencies with increasing cumulative dose. Genes involved in drug transport, metabolism, and DNA repair regulate platinum toxicities. Otoprotection can be achieved by acting on several these pathways and generally involves antioxidant thiol agents. Otoprotection is a strategy being explored to decrease hearing loss while maintaining dose intensity or allowing dose escalation, but it has the potential to interfere with tumoricidal effects. Route of administration and optimal timing relative to platinum therapy are critical issues. In addition, international standards for grading and comparing ototoxicity are essential to the success of prospective pediatric trials aimed at reducing platinum-induced hearing loss.

CONCLUSION

Collaborative prospective basic and clinical trial research is needed to reduce the incidence of irreversible platinum-induced hearing loss, and optimize cancer control. Wide use of the new internationally agreed-on SIOP Boston ototoxicity scale in current and future otoprotection trials should help facilitate this goal.

Mechanisms Involved in Ototoxicity

The modern era of evidence-based ototoxicity emerged in the 1940s following the discovery of aminoglycosides and their ototoxic side effects. New classes of ototoxins have been identified in subsequent decades, notably loop diuretics, antineoplastic drugs, and metal chelators. Ototoxic drugs are frequently nephrotoxic, as both organs regulate fluid and ion composition. The mechanisms of ototoxicity are as diverse as the pharmacological properties of each ototoxin, though the generation of toxic levels of reactive oxygen species appears to be a common denominator. As mechanisms of cytotoxicity for each ototoxin continue to be elucidated, a new frontier in ototoxicity is emerging: How do ototoxins cross the blood-labyrinth barrier that tightly regulates the composition of the inner ear fluids? Increased knowledge of the mechanisms by which systemic ototoxins are trafficked across the blood-labyrinth barrier into the inner ear is critical to developing new pharmacotherapeutic agents that target the blood-labyrinth barrier to prevent trafficking of ototoxic drugs and their cytotoxic sequelae.

Effectiveness of different approaches for establishing cisplatin-induced cochlear lesions in mice

CONCLUSIONS

Mouse cochleae are highly resistant to systemically administered cisplatin. However, cochlear lesions can be produced effectively in mice when cisplatin is applied locally through the round window niche or tympanum.

OBJECTIVE

To explore the optimal approach for creating cisplatin-induced cochlear lesions in mice.

MATERIALS AND METHODS

Cisplatin was administered to adult C57BL/6J mice via four approaches: (1) transtympanic injection, (2) round window niche injection, (3) intraperitoneal injection (i.p.) at 4 mg/kg/day for 4 consecutive days, and (4) one 15 mg/kg dose i.p. The hearing was monitored using frequency-specific auditory brainstem responses (ABRs) and distortion-product otoacoustic emissions (DPOAEs). Cochlear pathology was observed in cochleograms with Harris' hematoxylin staining.

RESULTS

Cisplatin applied systemically did not cause any significant ABR threshold elevation across the frequencies tested (2-32 kHz), whereas local application of cisplatin through the round window niche or tympanum resulted in significant ABR threshold elevations from high to medium frequencies. The functional changes were consistent with the cochlear pathology across groups.

Melanin precursors prevent premature age-related and noise-induced hearing loss in albino mice

Strial melanocytes are required for normal development and correct functioning of the cochlea. Hearing deficits have been reported in albino individuals from different species, although melanin appears to be not essential for normal auditory function. We have analyzed the auditory brainstem responses (ABR) of two transgenic mice: YRT2, carrying the entire mouse tyrosinase (Tyr) gene expression-domain and undistinguishable from wild-type pigmented animals; and TyrTH, non-pigmented but ectopically expressing tyrosine hydroxylase (Th) in melanocytes, which generate the precursor metabolite, L-DOPA, but not melanin. We show that young albino mice present a higher prevalence of profound sensorineural deafness and a poorer recovery of auditory thresholds after noise-exposure than transgenic mice. Hearing loss was associated with absence of cochlear melanin or its precursor metabolites and latencies of the central auditory pathway were unaltered. In summary, albino mice show impaired hearing responses during ageing and after noise damage when compared to YRT2 and TyrTH transgenic mice, which do not show the albino-associated ABR alterations. These results demonstrate that melanin precursors, such as L-DOPA, have a protective role in the mammalian cochlea in age-related and noise-induced hearing loss.

Cisplatin and oxaliplatin toxicity: importance of cochlear kinetics as a determinant for ototoxicity

BACKGROUND

Cisplatin is a cornerstone anticancer drug with pronounced ototoxicity, whereas oxaliplatin, a platinum derivative with a different clinical profile, is rarely ototoxic. This difference has not been explained.

METHODS

In HCT-116 cells, cisplatin (20 microM)-induced apoptosis was reduced by a calcium chelator from 9.9-fold induction (95% confidence interval [CI] = 8.1- to 11.7-fold), to 3.1-fold induction (95% CI = 2.0- to 4.2-fold) and by superoxide scavenging from 9.3-fold (95% CI = 8.8- to 9.8-fold), to 5.1-fold (95% CI = 4.4- to 5.8-fold). A guinea pig model (n = 23) was used to examine pharmacokinetics. Drug concentrations were determined by liquid chromatography with post-column derivatization. The total platinum concentration in cochlear tissue was determined by inductively coupled plasma mass spectrometry. Drug pharmacokinetics was assessed by determining the area under the concentration-time curve (AUC). Statistical tests were two-sided.

RESULTS

In HCT-116 cells, cisplatin (20 microM)-induced apoptosis was reduced by a calcium chelator from 9.9-fold induction (95% confidence interval [CI] = 8.1- to 11.7-fold to 3.1-fold induction) (95% CI = 2.0- to 4.2-fold) and by superoxide scavenging (from 9.3-fold, 95% CI = 8.8- to 9.8-fold, to 5.1-fold, 95% CI = 4.4- to 5.8-fold). Oxaliplatin (20 microM)-induced apoptosis was unaffected by calcium chelation (from 7.1- to 6.2-fold induction) and by superoxide scavenging (from 5.9- to 5.6-fold induction). In guinea pig cochlea, total platinum concentration (0.12 vs 0.63 microg/kg, respectively, P = .008) and perilymphatic drug concentrations (238 vs 515 microM x minute, respectively, P < .001) were lower after intravenous oxaliplatin treatment (16.6 mg/kg) than after equimolar cisplatin treatment (12.5 mg/kg). However, after a non-ototoxic cisplatin dose (5 mg/kg) or the same oxaliplatin dose (16.6 mg/kg), the AUC for perilymphatic concentrations was similar, indicating that the two drugs have different cochlear pharmacokinetics.

CONCLUSION

Cisplatin- but not oxaliplatin-induced apoptosis involved superoxide-related pathways. Lower cochlear uptake of oxaliplatin than cisplatin appears to be a major explanation for its lower ototoxicity.

Augmented ototoxic effect of cisplatin in heterozygotes of the German waltzing guinea pig

It has previously been demonstrated that the carriers of the German waltzing guinea pig are less susceptible to noise trauma. To explore whether this represents a general resistance to inner ear trauma, carriers of the German waltzing guinea pig were exposed to the ototoxic agent cisplatin. Two doses of cisplatin were injected intravenously into anesthetized carriers and weight-matched control animals. Prior to and 96 h after the injections hearing thresholds were established by recording the auditory brainstem responses at 3.5, 7, 14, and 28 kHz. The cochleae were harvested to estimate hair cell loss and to analyze total platinum content. The carriers of the German waltzing guinea pig strain suffered from a more pronounced cisplatin-induced hearing loss compared to the control animals. The results suggest that mechanisms responsible for the protection against acoustic stress do not provide any protection against cisplatin in carriers of the German waltzing guinea pig.