Mechanisms of cisplatin ototoxicity and progress in otoprotection

Is Hyperbaric Oxygen Therapy Effective in Cisplatin-Induced Ototoxicity in Rats?

Objectives

Cisplatin is an antineoplastic agent, used in the treatment of different types of malignant neoplasms. Side effects such as ototoxicity, nephrotoxicity, and bone marrow toxicity are the main limitations of its clinical use. The aim of the present study was to evaluate the possible effects of hyperbaric oxygen (HBO) therapy as a protective agent in cisplatin-induced ototoxicity in rats.

Methods

A total of 30 adult Wistar rats (60 ears) were divided into five equal groups. Group 1 is a control group; group 2 is HBO therapy group; group 3 received 15 mg/kg cisplatin intraperitoneally; group 4 received 15 mg/kg cisplatin intraperitoneally and HBO treatment on the same day; group 5 received 15 mg/kg cisplatin intraperitoneally and HBO treatment 72 hours later. The effect of ototoxicity was measured with distortion product otoacoustic emission testing performed on the days 1, 3, and 7.

Results

Groups 4 and 5 that received HBO treatment after cisplatin had better signal-to-noise ratio (SNR) values compared with group 3 that received only cisplatin (P<0.05). Compared with group 5, group 4 (same day HBO treatment) had better SNR values (P<0.05).

Conclusion

HBO was found effective for prevention of cisplatin-induced ototoxicity in rats. Our study differs from other studies regarding using a promising treatment, which does not expose subjects to extra stress.

Incidence and associated risk factors for platinum-induced ototoxicity in pediatric patients

OBJECTIVES

Platinum-based chemotherapy is effective against a variety of pediatric malignancies. Unfortunately, the use of cisplatin and carboplatin can lead to permanent and progressive sensorineural hearing loss which can affect the quality of life of cancer survivors. The objectives of this study were to evaluate the incidence of platinum-induced ototoxicity in children and analyze potential risk factors.

METHODS

Prospective cohort study. All pediatric patients receiving chemotherapy with cisplatin and/or carboplatin from 01/2012 until 10/2017 were included. Hearing evaluations were performed before every chemotherapy cycle, and following the end of chemotherapy, with auditory brainstem response, otoacoustic emissions and/or audiometry. Demographics, cumulative doses, cranial irradiation and exposure to other ototoxic agents were analyzed.

RESULTS

Twenty-eight patients were included, with a mean age of 7.2 years at the beginning of chemotherapy (range 5 months-15 years 2 months); twenty-one patients received cisplatin, four received carboplatin, and three received both agents. Twelve patients had cranial irradiation and seven received another ototoxic medication. The most frequent malignancies were germ cell tumors, medulloblastoma and gliomas. Sensorineural hearing loss occurred in 28.6% of the patients with a mean follow-up period of 21.5 months (range: 1-53 months). All patients evaluated with audiometry had ≥ Chang 2b ototoxicity. Risk factors include age less than 5 years, cranial irradiation, and cisplatin cumulative dose greater than 400 mg/m².

CONCLUSION

Sensorineural hearing loss is a potential side effect of platinum-based chemotherapy. Pediatric patients receiving cisplatin chemotherapy with a cumulative dose exceeding 400 mg/m², cranial irradiation as well as patients younger than 5 years are at greater risk of developing hearing loss.

Meclofenamic Acid Reduces Reactive Oxygen Species Accumulation and Apoptosis, Inhibits Excessive Autophagy, and Protects Hair Cell-Like HEI-OC1 Cells From Cisplatin-Induced Damage

Hearing loss is the most common sensory disorder in humans, and a significant number of cases is due to the ototoxicity of drugs such as cisplatin that cause hair cell (HC) damage. Thus, there is great interest in finding agents and mechanisms that protect HCs from ototoxic drug damage. It has been proposed that epigenetic modifications are related to inner ear development and play a significant role in HC protection and HC regeneration; however, whether the m⁶A modification and the ethyl ester form of meclofenamic acid (MA2), which is a highly selective inhibitor of FTO (fatmass and obesity-associated enzyme, one of the primary human demethylases), can affect the process of HC apoptosis induced by ototoxic drugs remains largely unexplored. In this study, we took advantage of the HEI-OC1 cell line, which is a cochlear HC-like cell line, to investigate the role of epigenetic modifications in cisplatin-induced cell death. We found that cisplatin injury caused reactive oxygen species accumulation and increased apoptosis in HEI-OC1 cells, and the cisplatin injury was reduced by co-treatment with MA2 compared to the cisplatin-only group. Further investigation showed that MA2 attenuated cisplatin-induced oxidative stress and apoptosis in HEI-OC1 cells. We next found that the cisplatin-induced upregulation of autophagy was significantly inhibited after MA2 treatment, indicating that MA2 inhibited the cisplatin-induced excessive autophagy. Our findings show that MA2 has a protective effect and improves the viability of HEI-OC1 cells after cisplatin treatment, and they provide new insights into potential therapeutic targets for the amelioration of cisplatin-induced ototoxicity.

Long term platinum-induced ototoxicity in pediatric patients

OBJECTIVES

Platinum-based chemotherapy treatments are effective against a variety of pediatric malignancies. However, its use can lead to permanent hearing loss. The aim of this study was to evaluate the long-term effect of platinum chemotherapy on hearing and evaluate its progression.

METHODS

Prospective cohort study. All records of pediatric patients receiving platinum-based chemotherapy between 2001 and 2006 were reviewed. Demographics and audiograms performed before, during, and following chemotherapy were analyzed. An updated audiogram and a video head impulse test were performed. A hearing ability questionnaire was also completed.

RESULTS

Thirty-nine patients met the inclusion criteria. Of these, 12 patients were included in the study; 14 were deceased, 8 had incomplete data and 5 were excluded for other reasons. Median age at chemotherapy was 4.3 years (range 10 months-14.2 years). Seven patients had received cisplatin, two received carboplatin and three received both agents. Five had also received cranial irradiation. With a median follow-up time of 11.9 years, 58.3% had developed hearing loss and two patients wore bilateral hearing aids; 67% of the patients with hearing loss had worsening of their hearing in the long-term. All patients referred difficulties in various subscales measured by the questionnaire. Three patients had decreased vestibulo-ocular reflex gains.

CONCLUSION

Platinum-induced hearing loss in pediatric patients can be progressive and debilitating. A long term audiometric follow-up of at least 10 years is suggested for these patients.

Chemotherapeutic-Induced Cardiovascular Dysfunction: Physiological Effects, Early Detection-The Role of Telomerase to Counteract Mitochondrial Defects and Oxidative Stress

Although chemotherapeutics can be highly effective at targeting malignancies, their ability to trigger cardiovascular morbidity is clinically significant. Chemotherapy can adversely affect cardiovascular physiology, resulting in the development of cardiomyopathy, heart failure and microvascular defects. Specifically, anthracyclines are known to cause an excessive buildup of free radical species and mitochondrial DNA damage (_mtDNA) that can lead to oxidative stress-induced cardiovascular apoptosis. Therefore, oncologists and cardiologists maintain a network of communication when dealing with patients during treatment in order to treat and prevent chemotherapy-induced cardiovascular damage; however, there is a need to discover more accurate biomarkers and therapeutics to combat and predict the onset of cardiovascular side effects. Telomerase, originally discovered to promote cellular proliferation, has recently emerged as a potential mechanism to counteract mitochondrial defects and restore healthy mitochondrial vascular phenotypes. This review details mechanisms currently used to assess cardiovascular damage, such as C-reactive protein (CRP) and troponin levels, while also unearthing recently researched biomarkers, including circulating _mtDNA, telomere length and telomerase activity. Further, we explore a potential role of telomerase in the mitigation of mitochondrial reactive oxygen species and maintenance of _mtDNA integrity. Telomerase activity presents a promising indicator for the early detection and treatment of chemotherapy-derived cardiac damage.

Toxicities Associated with Cisplatin-Based Chemotherapy and Radiotherapy in Long-Term Testicular Cancer Survivors

Testicular cancer has become the paradigm of adult-onset cancer survivorship, due to the young age at diagnosis and 10-year relative survival of 95%. This clinical review presents the current status of various treatment-related complications experienced by long-term testicular cancer survivors (TCS) free of disease for 5 or more years after primary treatment. Cardiovascular disease and second malignant neoplasms represent the most common potentially life-threatening late effects. Other long-term adverse outcomes include neuro- and ototoxicity, pulmonary complications, nephrotoxicity, hypogonadism, infertility, and avascular necrosis. Future research efforts should focus on delineation of the genetic underpinning of these long-term toxicities to understand their biologic basis and etiopathogenetic pathways, with the goal of developing targeted prevention and intervention strategies to optimize risk-based care and minimize chronic morbidities. In the interim, health care providers should advise TCS to adhere to national guidelines for the management of cardiovascular disease risk factors, as well as to adopt behaviors consistent with a healthy lifestyle, including smoking cessation, a balanced diet, and a moderate to vigorous intensity exercise program. TCS should also follow national guidelines for cancer screening as currently applied to the general population.

Pharmacokinetics of sodium thiosulfate in Guinea pig perilymph following middle ear application

Hypothesis

To determine the pharmacokinetics of sodium thiosulfate in the inner ear perilymph following middle ear application in Guinea pigs.

Background

Cisplatin chemotherapy is often associated with a dose-dependent high frequency sensorineural hearing loss. Sodium thiosulfate has been shown to reduce cisplatin-induced ototoxicity when given intravenously, but this may limit the tumoricidal effects of the chemotherapy. Recent animal studies looking at middle ear application of sodium thiosulfate have shown prevention of outer hair cell and hearing loss, but the perilymph pharmacokinetics have not yet been established.

Methods

Twenty Guinea pig ears were split into two groups and administered sodium thiosulfate to the middle ear at either a concentration of 250 mg/mL or 50 mg/mL for 30 min. Perilymph samples were then obtained serially through the round window over 6 h. Sodium thiosulfate concentrations were obtained using high-pressure liquid chromatography.

Results

The 250 mg/mL group had a maximum perilymph concentration of 7.27 mg/mL (±0.83) that decreased to 0.94 mg/mL (±0.03) over 6 h. The 50 mg/mL group had an initial concentration of 1.63 mg/mL (±0.17) and was undetectable after 1 h. The half-life of sodium thiosulfate within perilymph was 0.74 h.

Conclusions

and Relevance: The results of this study show that sodium thiosulfate is capable of diffusing through round window and into the inner ear perilymph. Peak levels decline over several hours after exposure. This has a potential application as a localized therapy in the prevention of cisplatin induced ototoxicity.

A Store-and-Forward Tele-Audiology Solution to Promote Efficient Screenings for Ototoxicity during Cisplatin Cancer Treatment

BACKGROUND

Tele-audiology improves access, controls cost, and improves efficiency of many aspects within health care. We have developed and validated a device, the ototoxicity identification device (OtoID), which enables remote hearing monitoring by a patient during chemotherapy treatment. Aspects of the design such as patient self-testing and texting of results to the audiology clinic are important features of this device.

PURPOSE

The purpose of this article is to present the efficacy and effectiveness of the OtoID hearing screener.

RESEARCH DESIGN

A repeated measures design was used in this study.

STUDY SAMPLE

Twenty-one veterans undergoing cisplatin chemotherapy were recruited in this study.

DATA COLLECTION AND ANALYSIS

Participants were tested using the OtoID at each cisplatin treatment by an audiologist using the manual mode of test and the participant using the automated mode of test. Test sensitivity and specificity were developed from the detection (yes/no) of an American Speech-Language-Hearing Association (ASHA) change in hearing.

RESULTS

The OtoID had a test sensitivity of 80.6% and specificity of 85.3%. A logistic regression model analysis of the probability of an ASHA shift identified by the automated OtoID was conducted. Separate models were fit to establish effects of age, average baseline thresholds in the sensitive range for ototoxicity (SRO), and dose of cisplatin on the probability of a positive hearing change result. Interactions were also included to evaluate these effects on the sensitivity and false-positive rates of the automated test. Results indicated no statistically significant effects of age, of baseline hearing in the SRO frequencies, or of cisplatin dose.

CONCLUSIONS

The OtoID automated test can be recommended for use. The automated test provides significant personnel efficiencies. The modem with simple text messaging function recently added to the device improves on these efficiencies.

[Development of a Fluorescence Probe for Live Cell Imaging]

 Probes that detect specific biological materials are indispensable tools for deepening our understanding of various cellular phenomena. In live cell imaging, the probe must emit fluorescence only when a specific substance is detected. In this paper, we introduce a new probe we developed for live cell imaging. Glutathione S-transferase (GST) activity is higher in tumor cells than in normal cells and is involved in the development of resistance to various anticancer drugs. We previously reported the development of a general strategy for the synthesis of probes for detection of GST enzymes, including fluorogenic, bioluminogenic, and ¹⁹F-NMR probes. Arylsulfonyl groups were used as caging groups during probe design. The fluorogenic probes were successfully used to quantitate very low levels of GST activity in cell extracts and were also successfully applied to the imaging of microsomal MGST1 activity in living cells. The bioluminogenic and ¹⁹F-NMR probes were able to detect GST activity in Escherichia coli cells. Oligonucleotide-templated reactions are powerful tools for nucleic acid sensing. This strategy exploits the target strand as a template for two functionalized probes and provides a simple molecular mechanism for multiple turnover reactions. We developed a nucleophilic aromatic substitution reaction-triggered fluorescent probe. The probe completed its reaction within 30 s of initiation and amplified the fluorescence signal from 0.5 pM target oligonucleotide by 1500 fold under isothermal conditions. Additionally, we applied the oligonucleotide-templated reaction for molecular releasing and peptide detection.

Impact of high-dose oleuropein on cisplatin-induced oxidative stress, genotoxicity and pathological changes in rat stomach and lung

The current systemic treatments of the various solid tumors involve Cisplatin (CIS)-based chemotherapy. Due to its cytotoxicity, this approach is limited. Moreover, the safety of CIS is only discussed especially in breast and stomach cancers. Therefore, we, for the first time, explored the restorative efficacy of oleuropein (OLE), in stomach and lung injuries induced by CIS. Sprague-Dawley rats were divided into eight groups: control CIS, OLE and CIS + OLE. Single dose of (7 mg/kg) CIS was administered intraperitoneally to CIS and CIS + OLE groups. After 24 h, 50, 100 and 200 mg/kg OLE was given for three consecutive days to OLE and CIS + OLE groups. The 8-OH-dG, total oxidative/antioxidant status (TOS/TAS) and malondialdehyde (MDA) levels were evaluated and histopathological analyses were performed on the studied tissues. The results indicated that CIS significantly increased 8-OH-dG, MDA and TOS levels and caused severe tissue damages. However, high dose of OLE induced a significant decrease in the 8-OH-dG, MDA levels, an increase in TAS levels and it restores CIS-induced tissue damages. We hope that the results of this study will provide an impetus for future studies on novel therapeutic strategies including the protective use of oleuropein in gastric and lung cancers due to chemotherapy.

Pharmacogenetics of drug-induced ototoxicity caused by aminoglycosides and cisplatin

Aminoglycosides and the anticancer drug cisplatin can cause permanent hearing loss, which impacts patients' quality of life and results in considerable subsequent costs. Since patients' individual susceptibility to aminoglycoside- and cisplatin-induced ototoxicity varies considerably, strategies are needed to identify patients at risk, who may require alternative treatments or specific protection strategies. For both drugs, various genetic variants were linked to an increased or decreased risk for ototoxicity. Except for the association between the A1555G mitochondrial DNA mutation and aminoglycoside ototoxicity, their evidence is considered low because study cohorts were often small and replication studies either missing or contradictory. This review summarizes the pharmacogenetic markers linked to aminoglycoside- or cisplatin-induced ototoxicity and discusses reasons for replication failure and future perspective.

The protective effects of whortleberry extract against cisplatin-induced ototoxicity in rats

INTRODUCTION

Cisplatin is one of the main chemotherapeutic agents used for the treatment of many types of cancer. However, ototoxicity, one of the most serious side effects of cisplatin, restricts its usage.

OBJECTIVE

We aimed to investigate the protective effects of whortleberry extract against cisplatin-induced ototoxicity by evaluating hearing and histopathological cochlear damage and by measuring the biochemical parameters affected byoxidative stress.

METHODS

Forty-eight male rats were included in the study after performing Distortion Product Otoacoustic Emission test to confirm that their hearing levels were normal. The rats were randomly divided into six groups: the control group, the sham group, and, which received only whortleberry extract, only cisplatin, cisplatin+100mg whortleberry extract, cisplatin+200mg whortleberry extract, respectively. Audiologic investigation was performed by performing the Distortion Product Otoacoustic Emission test at the beginning and at the eighth day of the study. Cardiac blood samples were collected for biochemical analysis, and the rats were sacrificed to obtain cochlear histopathological specimens on the eighth day.

RESULTS

The results revealed that whortleberry protects hearing against cisplatin-induced ototoxicity independent of the dose. However, high doses of whortleberry extract are needed to prevent histopathological degeneration and oxidative stress.

CONCLUSION

The results obtained in this study show that whortleberry extract has a protective effect against cisplatin-induced ototoxicity.

Phosphorylation of eIF2α suppresses cisplatin-induced p53 activation and apoptosis by attenuating oxidative stress via ATF4-mediated HO-1 expression in human renal proximal tubular cells

Cisplatin is one of the most widely used chemotherapeutic agents for the treatment of human cancers. However, the nephrotoxicity of cisplatin limits its use as a therapeutic agent. It has been suggested that oxidative stress and p53 activation play important roles in cisplatin-induced nephrotoxicity. It has been demonstrated that the eukaryotic translation initiation factor 2α (eIF2α) may protect HK-2 human renal proximal tubular cells against cisplatin-induced apoptosis through inhibition of reactive oxygen species (ROS)‑mediated p53 activation. The aim of the present study was to investigate the effects of siRNA‑mediated knockdown of the PKR-like endoplasmic reticulum kinase (PERK) gene, which induces the phosphorylation of eIF2α, or Sal003, a selective inhibitor of eIF2α dephosphorylation, on cisplatin‑induced apoptosis in HK-2 cells. Cisplatin induced eIF2α phosphorylation as well as p53 activation. In particular, inhibition of p53 by pifithrin‑α, and upregulation of eIF2α phosphorylation by Sal003, reduced cisplatin-induced apoptosis. Of note, Sal003‑mediated upregulation of eIF2α phosphorylation suppressed cisplatin‑induced p53 activation. Furthermore, reduction of eIF2α phosphorylation by PERK knockdown enhanced cisplatin-induced p53 activation and apoptosis. In addition, the ROS scavenger N-acetyl-L-cysteine inhibited eIF2α phosphorylation as well as p53 activation in HK-2 cells treated with cisplatin, suggesting that oxidative stress induced by cisplatin may lead to apoptosis through p53 activation; furthermore, this stress may confer resistance to apoptosis via eIF2α phosphorylation, which was further supported by the finding that cisplatin‑induced ROS generation was attenuated by Sal003, whereas it was enhanced by PERK knockdown. Furthermore, cisplatin induced the expression of activating transcription factor 4 (ATF4) and heme oxygenase-1 (HO-1) that were enhanced by Sal003 and reduced by PERK knockdown. Taken together, these results suggest that phosphorylation of eIF2α suppresses cisplatin‑induced p53 activation and apoptosis by attenuating oxidative stress via ATF4-mediated HO-1 expression in HK-2 cells, as ATF4 expression is usually dependent on the phosphorylation of eIF2α and may also transcriptionally induce the expression of HO-1 in response to oxidative stress. Therefore, regulation of eIF2α phosphorylation may play an important role in alleviating cisplatin-induced nephrotoxicity.

Protein Synthesis Inhibition and Activation of the c-Jun N-Terminal Kinase Are Potential Contributors to Cisplatin Ototoxicity

Cisplatin has been regarded as an effective and versatile chemotherapeutic agent for nearly 40 years. Though the associated dose-dependent ototoxicity is known, the cellular mechanisms by which cochleovestibular hair cell death occur are not well understood. We have previously shown that aminoglycoside ototoxicity is mediated in part by cytosolic protein synthesis inhibition. Despite a lack of molecular similarity, aminoglycosides were shown to elicit similar stress pathways to cisplatin. We therefore reasoned that there may be some role of protein synthesis inhibition in cisplatin ototoxicity. Employing a modification of the bioorthogonal noncanonical amino acid tagging (BONCAT) method, we evaluated the effects of cisplatin on cellular protein synthesis. We show that cisplatin inhibits cellular protein synthesis in organ of Corti explant cultures. Similar to what was found after gentamicin exposure, cisplatin activates both the c-Jun N-terminal kinase (JNK) and mammalian target of rapamycin (mTOR) pathways. In contrast to aminoglycosides, cisplatin also inhibits protein synthesis in all cochlear cell types. We further demonstrate that the multikinase inhibitor sorafenib completely prevents JNK activation, while providing only moderate hair cell protection. Simultaneous stimulation of cellular protein synthesis by insulin, however, significantly improved hair cell survival in culture. The presented data provides evidence for a potential role of protein synthesis inhibition in cisplatin-mediated ototoxicity.

Hydrogen Inhalation Protects against Ototoxicity Induced by Intravenous Cisplatin in the Guinea Pig

Introduction: Permanent hearing loss and tinnitus as side-effects from treatment with the anticancer drug cisplatin is a clinical problem. Ototoxicity may be reduced by co-administration of an otoprotective agent, but the results in humans have so far been modest. Aim: The present preclinical in vivo study aimed to explore the protective efficacy of hydrogen (H₂) inhalation on ototoxicity induced by intravenous cisplatin. Materials and Methods: Albino guinea pigs were divided into four groups. The Cispt (n = 11) and Cispt+H₂ (n = 11) groups were given intravenous cisplatin (8 mg/kg b.w., injection rate 0.2 ml/min). Immediately after, the Cispt+H₂ group also received gaseous H₂ (2% in air, 60 min). The H₂ group (n = 5) received only H₂ and the Control group (n = 7) received neither cisplatin nor H₂. Ototoxicity was assessed by measuring frequency specific ABR thresholds before and 96 h after treatment, loss of inner (IHCs) and outer (OHCs) hair cells, and by performing densitometry-based immunohistochemistry analysis of cochlear synaptophysin, organic transporter 2 (OCT2), and copper transporter 1 (CTR1) at 12 and 7 mm from the round window. By utilizing metabolomics analysis of perilymph the change of metabolites in the perilymph was assessed. Results: Cisplatin induced electrophysiological threshold shifts, hair cell loss, and reduced synaptophysin immunoreactivity in the synapse area around the IHCs and OHCs. H₂ inhalation mitigated all these effects. Cisplatin also reduced the OCT2 intensity in the inner and outer pillar cells and in the stria vascularis as well as the CTR1 intensity in the synapse area around the IHCs, the Deiters' cells, and the stria vascularis. H₂ prevented the majority of these effects. Conclusion: H₂ inhalation can reduce cisplatin-induced ototoxicity on functional, cellular, and subcellular levels. It is proposed that synaptopathy may serve as a marker for cisplatin ototoxicity. The effect of H₂ on the antineoplastic activity of cisplatin needs to be further explored.

Dose-dependent cochlear and vestibular toxicity of trans-tympanic cisplatin in the rat

In vivo studies are needed to study cisplatin ototoxicity and to evaluate candidate protective treatments. Rats and mice are the preferred species for toxicological and pharmacological pre-clinical research, but systemic administration of cisplatin causes high morbidity in these species. We hypothesized that trans-tympanic administration of cisplatin would provide a good model for studying its auditory and vestibular toxicity in the rat. Cisplatin was administered by the trans-tympanic route in one ear (50μl, 0.5-2mg/ml) of rats of both sexes and two different strains. Cochlear toxicity was corroborated by histological means. Vestibular toxicity was demonstrated by behavioral and histological analysis. Cisplatin concentrations were assessed in inner ear after trans-tympanic and i.v. administration. In all experiments, no lethality and only scant body weight loss were recorded. Cisplatin caused dose-dependent cochlear toxicity, as demonstrated by hair cell counts in the apical and middle turns of the cochlea, and vestibular toxicity, as demonstrated by behavioral analysis and hair cell counts in utricles. High concentrations of cisplatin were found in the inner ear after trans-tympanic administration. In comparison, i.v. administration resulted in lower inner ear concentrations. We conclude that trans-tympanic administration provides an easy, reproducible and safe model to study the cochlear and vestibular toxicity of cisplatin in the rat. This route of exposure may be useful to address particular questions on cisplatin induced ototoxicity and to test candidate protective treatments.

Cisplatin-Associated Ototoxicity: A Review for the Health Professional

Cisplatin is an effective drug used in the treatment of many cancers, yet its ototoxic potential places cancer patients, exposed to this drug, at risk of hearing loss, thus negatively impacting further on a patient's quality of life. It is paramount for health care practitioners managing such patients to be aware of cisplatin's ototoxic properties and the clinical signs to identify patients at risk of developing hearing loss. English peer-reviewed articles from January 1975 to July 2015 were assessed from PubMed, Science Direct, and Ebscohost. Seventy-nine articles and two books were identified for this review, using MeSH terms and keywords such as "ototoxicity", "cisplatin", "hearing loss", and "ototoxicity monitoring". This review provides an up-to-date overview of cisplatin-associated ototoxicity, namely, its clinical features, incidence rates, and molecular and cellular mechanisms and risk factors, to health care practitioners managing the patient with cancer, and highlights the need for a team-based approach to complement an audiological monitoring programme to mitigate any further loss in the quality of life of affected patients, as there is currently no otoprotective agent recommended routinely for the prevention of cisplatin-associated ototoxicity. It also sets the platform for effective dialogue towards policy formulation and strengthening of health systems in developing countries.

Comparison of the effects of lipoic acid and glutathione against cisplatin-induced ototoxicity in auditory cells

OBJECTIVES

The aims of this study were to examine lipoic acid (LA)- or glutathione (GSH)-mediated protection against cytotoxicity following cisplatin exposure in HEI-OC1 auditory cells and measure the potential of LA and GSH to scavenge reactive oxygen species (ROS). This study also compares their protective effects and discusses the determination of a preventive or therapeutic dose.

METHODS

HEI-OC1 cells were pretreated with LA or GSH for 24 h and then exposed to 15 μM cisplatin for 48 h. The resulting cytotoxicity was measured using a cell counting kit-8, and intracellular ROS level was measured using flow cytometry. The protective or anti-ROS effects of LA and GSH were compared. Measurement of caspase 3, 8, 9 activity and Western blot analysis of PARP were performed.

RESULTS

Pretreatment with LA at 300 μM and GSH at 3 mM protected HEI-OC1 cells against cisplatin-induced cytotoxicity and significantly reduced the cisplatin-induced increase in ROS. LA showed a significantly more effective protection against cisplatin-induced ototoxicity compared to that shown by GSH (85.4% vs. 73.1% cell viability). Both LA and GSH showed the maximal protective effect at different concentrations in normal or cisplatin-induced cytotoxic conditions. The preventive or therapeutic dose for harmful conditions is quite different for the two drugs and needs careful adjustments.

CONCLUSION

This comparative study on the protective effects of LA and GSH against cisplatin-induced ototoxicity in an auditory cell line posed many challenges. Although LA and GSH showed a significant protective effect against cisplatin, the LA's effect was superior. The concentration at which the maximal protective effect of LA or GSH was noted was 3 times higher in cytotoxic conditions than in normal conditions, which suggests the need for drug dose adjustments based on the purpose (preventive or therapeutic).

Effect of Ecklonia Cava Polyphenol Extract in House Ear Institute-Organ of Corti 1 Cells Against Cisplatin Ototoxicity: A Preliminary Study

Objective

Cisplatin is a widely used agent for the treatment of adult and childhood malignancies. Side effects such as nephrotoxicity, neurotoxicity, and ototoxicity lead to dose limitations. Ecklonia cava polyphenol extract (ECP) is a molecule obtained from algae that live in seawater in the Far East. ECP has recently been shown to have protective effects against oxidative stress. The aim of this study was to evaluate the possible protective effects of ECP on cisplatin ototoxicity.

Methods

In this study, we investigated the protective effects of ECP against cisplatin-induced cell death in mouse-derived House Ear Institute Organ of Corti (HEI-OC1) cochlear cells. Cisplatin (100 μM) and 1, 10, and 25 μM doses of ECP were administered to the cells, and the protective effects of ECP at 24 and 72 hours were investigated. Cell viability was evaluated by the WST-1 (water soluble tetrazolium salt).

Results

Cisplatin (100 μM) reduced cell viability in both the 24^th and 72^nd hour evaluation. Although the 25 μM dose of ECP showed otoprotective effects in the 24^th hour, in the 72^nd hour this effect disappeared. Other doses of ECP showed no otoprotective effects in the 24^th and 72^nd hours.

Conclusion

Although ECP showed some protective effects in the 24^th hour against cisplatin ototoxicity, these effects disappeared by the 72^nd hour. Further studies using recurrent and higher doses of ECP are required.

Analysis of genetic and non genetic risk factors for cisplatin ototoxicity in pediatric patients

OBJECTIVE

The aim of this study was to analyse the genetic and non genetic risk factors for cisplatin ototoxicity.

METHODS

This study was conducted on 72 children who received cisplatin based chemotherapy. Brock and Muenster classifications were used to evaluate ototoxicity seen in these children. 6 single nucleotide polymorphisms (SNP); ERCC1 rs 11615, GSTP1 rs1138272, GSTP1 rs1695, LRP2 rs 2075252, TPMT rs 12201199, COMT rs 9332377, were evaluated as genetic factors by real time PCR. Non genetic factors such as cranial irradiation, cumulative doses of cisplatin, age, gender, administration of other ototoxic drugs were analysed as well. By using Chi-square test, risk factors were matched with the ototoxicity classifications. Significant risk factors were reevaluated using logistic regression modelling.

RESULTS

According to univariate analyses, male gender, co-treatment with aminoglycosides and mutant genotype of GSTP1 rs1695 were significantly related with cisplatin ototoxicity. Logistic regression modelling analyses also showed that male gender, co-treatment with aminoglycosides were found to be significantly related with cisplatin ototoxicity. Mutant genotype of GSTP1 rs1695 was not found to be significant, but close to the level of statistical significance.

CONCLUSION

Male gender, co-treatment with aminoglycosides are significant risk factors for cisplatin ototoxicity in pediatric patients. Mutant genotype of GSTP1 rs1695 seems to be a genetic risk factor in univariate analyses, although not confirmed by multivariate analyses. Therefore, GSTP1 rs1695 SNP needs to be studied in larger series.

Protective effect of Pycnogenol on cisplatin-induced ototoxicity in rats

CONTEXT

Pycnogenol^®, which is French maritime pine bark extract, is a potent antioxidant. It is used in medical conditions caused by oxidative stress. Cisplatin (cis-diamminedichloroplatinum II) is an antineoplastic agent. However, its serious side effects such as ototoxicity limit its usage.

OBJECTIVE

Antioxidants can be used to prevent ototoxicity. We investigated the effect of Pycnogenol^® on cisplatin-induced ototoxicity.

MATERIALS AND METHODS

Rats were randomly assigned to four groups of five. Distortion product-evoked otoacoustic emissions (DPOAE) test was performed for each rat. The experimental groups were as follows: Control Group, Pycnogenol^® Group: 10 mg/kg Pycnogenol^® intraperitoneally for 7 days, Cisplatin Group: intraperitoneally 15 mg/kg single injection of cisplatin on the fifth day, Cisplatin + Pycnogenol^® Group: intraperitoneally 10 mg/kg Pycnogenol^® treatment for 7 days, additionally on the fifth day, 15 mg/kg single injection of cisplatin was given. On the eighth day, DPOAE was re-performed and rats were sacrificed. Apoptosis was evaluated histopathologically.

RESULTS

Mean percentage of apoptotic cells was 1.5, 3, 30 and 11% in organ of Corti and 2, 2, 40, 15% in spiral ganglion neurons in Control Group, Pycnogenol^® Group, Cisplatin Group and Cisplatin + Pycnogenol^® Group, respectively. Cisplatin Group and Cisplatin + Pycnogenol^® Group were significantly different when compared to Control Group histopathologically both in organ of Corti and spiral ganglion neuron (p <0.001, p = 0.019, p = 0.001, p = 0.015). DPOAE results showed that Cisplatin + Pycnogenol^® Group was significantly different when compared to Cisplatin Group at 3, 6 and 8 kHz (p < 0.05).

CONCLUSION

Pycnogenol protected against cisplatin ototoxicity. Also, pycnogenol is not ototoxic.

The effects of the antioxidant α-tocopherol succinate on cisplatin-induced ototoxicity in HEI-OC1 auditory cells

CONCLUSION

D-α-tocopherol succinate significantly reduced a cisplatin-induced hair cell loss in HEI-OC1 cell lines. These effects were mediated by its scavenging activity against reactive oxygen species (ROS) and inhibition of apoptosis.

OBJECTIVES

Alpha-tocopherol is a class of methylated phenols, known as fat-soluble antioxidants, and is a different form of vitamin E, which reduces free radicals and acts as an antioxidant. We hypothesized that the antioxidative effect of α-tocopherol could protect against cisplastin-induced cytotoxicity, and thus evaluated its effects on cisplatin-induced ototoxicity in HEI-OC1 auditory cells.

METHODS

HEI-OC1 cells were pretreated with D-α-tocopherol succinate at a concentration of 10 µM for 24 h, and then exposed to 15 µM cisplatin for 48 h. The cellular viability was measured by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The intracellular ROS level was measured by using a fluorescent dye, 2',7'-dichlorofluorescein diacetate (DCFH-DA). Both Annexin V-FITC and propidium iodide (PI) staining were performed to analyze the pattern of apoptosis. The enzymatic activity of caspase-3 was assayed with caspase3/CPP32 fluorometric assay kit. Also, it was assessed by immunoblotting technique of poly-ADP-ribose polymerase (PARP).

RESULTS

Pretreatment with 10 µM D-α-tocopherol succinate protected HEI-OC1 auditory cells against cisplatin-induced cytotoxicity. D-α-tocopherol succinate significantly reduced the cisplatin-induced increase in ROS. D-α-tocopherol succinate treatment induced a 15% reduction of ROS and 50% decrease in necrosis and late apoptosis as compared to cisplatin treatment. D-α-tocopherol succinate also decreased the activation of caspase-3 and reduced levels of cleaved poly-ADP-ribose polymerase (PARP).

Audiological Monitoring in Children Treated with Platinum Chemotherapy

Platinum compounds constitute the standard treatment for solid tumors in pediatric oncology. The purpose of this study is to assess the impact of platinum compounds in the development of ototoxicity in children following chemotherapy. This study included 160 patients treated with cisplatin and carboplatin for malignant solid diseases from 2007 to 2014. Their audiograms were classified according to the Boston SIOP ototoxicity scale. Twenty-five percent of the children treated with platinum compounds developed ototoxicity. The incidence of ototoxicity was correlated with the type of platinum derivative (i.e. cisplatin vs. carboplatin), coadministration of both drugs and concomitant cranial radiotherapy, but not with sex and age. Cumulative dose was correlated only with the cisplatin administration. Nine patients (8.6%) showed further progression of hearing impairment after the end of chemotherapy. The low rate of ototoxicity suggests the pivotal role of auditory monitoring in children treated with platinum compounds in order to be able to identify hearing loss at an early stage and to provide, jointly with pediatric oncologists, strategies to reduce further progression of cochlear toxicity.

Dexamethasone loaded nanoparticles exert protective effects against Cisplatin-induced hearing loss by systemic administration

Ototoxicity is one of the most important adverse effects of cisplatin chemotherapy. As a common treatment of acute sensorineural hearing loss, systemic administration of steroids was demonstrated ineffective against cisplatin-induced hearing loss (CIHL) in published studies. The current study aimed to evaluate the potential protective effect of dexamethasone (DEX) encapsulated in polyethyleneglycol-coated polylactic acid (PEG-PLA) nanoparticles (DEX-NPs) against cisplatin-induced hearing loss following systemic administration. DEX was fabricated into PEG-PLA nanoparticles using emulsion and evaporation technique as previously reported. DEX or DEX-NPs was administered intraperitoneally to guinea pigs 1h before cisplatin administration. Auditory brainstem response (ABR) threshold shifts were measured at four frequencies (4, 8, 16, and 24kHz) 1 day before and three days after cisplatin injection. Cochlear morphology was examined to evaluate inner ear injury induced by cisplatin exposure. A single dose of DEX-NPs 1h before cisplatin treatment resulted in a significant preservation of the functional and structural properties of the cochlea, which was equivalent to the effect of multidose (3 days) DEX injection. In contrast, no significant protective effect was observed by single dose injection of DEX. The results of histological examination of the cochleae were consistent with the functional measurements. In conclusion, a single dose DEX-NPs significantly attenuated cisplatin ototoxicity in guinea pigs after systemic administration at both histological and functional levels indicating the potential therapeutic benefits of these nanoparticles for enhancing the delivery of DEX in acute sensorineural hearing loss.

The Sustained-Exposure Dexamethasone Formulation OTO-104 Offers Effective Protection against Cisplatin-Induced Hearing Loss

The otoprotective effects of OTO-104 were investigated following both acute and chronic administration of cisplatin. The acute administration of cisplatin to guinea pigs resulted in profound hearing loss (70-80 dB SPL) across all frequencies tested. A single intratympanic injection of 6% OTO-104, but not of lower doses, almost completely protected against cisplatin ototoxicity. In contrast, a dexamethasone solution administered under the same experimental conditions offered no otoprotection. OTO-104 was also very effective in protecting against the progressive hearing loss observed with the chronic administration of cisplatin (3 injections at a weekly interval). The otoprotection was found to be dependent upon the activation of dexamethasone-dependent classical nuclear receptor pathways.

Cisplatin-Induced Ototoxicity: Effects, Mechanisms and Protection Strategies

Cisplatin is a highly effective chemotherapeutic agent that is widely used to treat solid organ malignancies. However, serious side effects have been associated with its use, such as bilateral, progressive, irreversible, dose-dependent neurosensory hearing loss. Current evidence indicates that cisplatin triggers the production of reactive oxygen species in target tissues in the inner ear. A variety of agents that protect against cisplatin-induced ototoxicity have been successfully tested in cell culture and animal models. However, many of them interfere with the therapeutic effect of cisplatin, and therefore are not suitable for systemic administration in clinical practice. Consequently, local administration strategies, namely intratympanic administration, have been developed to achieve otoprotection, without reducing the antitumoral effect of cisplatin. While a considerable amount of pre-clinical information is available, clinical data on treatments to prevent cisplatin ototoxicity are only just beginning to appear. This review summarizes clinical and experimental studies of cisplatin ototoxicity, and focuses on understanding its toxicity mechanisms, clinical repercussions and prevention strategies.

Trichostatin A reduces cisplatin-induced ototoxicity through the STAT6 signaling pathway

Cisplatin-induced ototoxicity limits its wide application in the treatment of cancer. A number of pro-inflammatory factors have been shown to be involved in cisplatin-induced ototoxicity. Trichostatin A (TSA) is an anti-inflammatory agent that has been shown to exert protective effects against cisplatin-induced ototoxicity. In the present study, we hypothesized that TSA may protect cochlear hair cells from cisplatin-induced damage by regulating the interleukin (IL)-4/signal transducer and activator of transcription (STAT)6 signaling pathway. Wistar rat cochlear explants were cultured in DMEM. The differentially expressed genes of the basilar membrane were identified by microarray analysis of global expression profiles. Hair cells were stained with rhodamine phalloidin and observed under a scanning electron microscope to evaluate the protective effects of TSA against cisplatin-induced cochlear hair cell damage. The levels of cytokines in the supernatant of the cultured basilar membranes was measured using ELISA. STAT6 and phosphorylated (p-)STAT6 expression was measured by western blot analysis. Morphological observation revealed that cisplatin induced the disarrangement of the cochlear hair cells, as well as the fusion and detachment of the cilia, while these aberrant alterations were inhibited by TSA, suggesting that TSA exerts a protective effect against cisplatin-induced damage to hair cells. Furthermore, the increase in the expression of STAT6 and p-STAT6 induced by cisplatin was reversed by treatment with TSA, accompanied by the decreased expression of IL-1β, IL-4 and IL-6. Therefore, our data demonstrate that TSA reduces cisplatin-induced ototoxicity by inhibiting pro-inflammatory factor-mediated STAT6 signaling. Thus, TSA may be used to prevent the side-effects associated with the use of cisplatin in cancer treatment.

Short-term cohort study on sensorineural hearing changes in head and neck radiotherapy

The aim of this study was to investigate the risk of sensorineural hearing loss (SNHL) and the relationship between SNHL and radiation dose to the cochlea and frequency range of hearing loss in patients with head and neck cancer. Pure tone audiometry at 250-12,000 Hz was performed on 29 patients diagnosed with head and neck tumours who were treated with 3-dimensional conformal radiation therapy and followed up for 6 months. Paired t test indicated that the mean air conduction threshold before and after radiotherapy was significantly different (paired t test, p < 0.001). SNHL was observed in 15 patients (51 %) according to CTCAE. SNHL increased to 77 % in patients who had received at least five concurrent cisplatin cycles. There was an increased risk of SNHL for ears receiving a mean dose of 5000 cGy compared to those receiving <5000 cGy. SNHL was more severe at higher frequencies of pure tone audiometry in patients with cisplatin-based chemoradiation. The ototoxicity effect of radiation and cisplatin must be considered in the treatment of head and neck tumours. Increasing the dose of cisplatin, radiation dose of cochlea and follow-up interval time may result in increasing severity and frequency of hearing loss incidences. However, characteristic of radiation-induced SNHL seems to be different from chemoradiation-induced SNHL.

The Flavonoid Apigenin Ameliorates Cisplatin-Induced Nephrotoxicity through Reduction of p53 Activation and Promotion of PI3K/Akt Pathway in Human Renal Proximal Tubular Epithelial Cells

Apigenin is a member of the flavone subclass of flavonoids present in fruits and vegetables. Apigenin has long been considered to have various biological activities, such as antioxidant, anti-inflammatory, and antitumorigenic properties, in various cell types. Cisplatin was known to exhibit cytotoxic effect to renal cells by inducing apoptosis through activation of p53. The present study investigated the antiapoptotic effects of apigenin on the cisplatin-treated human renal proximal tubular epithelial (HK-2) cells. HK-2 cells were pretreated with apigenin (5, 10, 20 μM) for 1 h and then treated with 40 μM cisplatin for various times. Apigenin inhibited the cisplatin-induced apoptosis of HK-2 cells. Interestingly, apigenin itself exerted cytostatic activity because of its ability to induce cell cycle arrest. Apigenin inhibited caspase-3 activity and PARP cleavage in cisplatin-treated cells. Apigenin reduced cisplatin-induced phosphorylation and expression of p53, with no significant influence on production of ROS that is known to induce p53 activation. Furthermore, apigenin promoted cisplatin-induced Akt phosphorylation, suggesting that enhanced Akt activation may be involved in cytoprotection. Taken together, these results suggest that apigenin ameliorates cisplatin-induced apoptosis through reduction of p53 activation and promotion of PI3K/Akt pathway in HK-2 cells.

Immunohistochemical localization of OCT2 in the cochlea of various species

Objective

To locate the organic cation transporter 2 (OCT2) in the cochlea of three different species and to modulate the ototoxicity of cisplatin in the guinea pig by pretreatment with phenformin, having a known affinity for OCT2.

Study Design

Immunohistochemical and in vivo study.

Methods

Sections from the auditory end organs were subjected to immunohistochemical staining in order to identify OCT2 in cochlea from untreated rats, guinea pigs, and a pig. In the in vivo study, guinea pigs were given phenformin intravenously 30 minutes before cisplatin administration. Electrophysiological hearing thresholds were determined, and hair cells loss was assessed 96 hours later. The total amount of platinum in cochlear tissue was determined using mass spectrometry.

Results

Organic cation transporter 2 was found in the supporting cells and in type I spiral ganglion cells in the cochlea of all species studied. Pretreatment with phenformin did not reduce the ototoxic side effect of cisplatin. Furthermore, the concentration of platinum in the cochlea was not affected by phenformin.

Conclusions

The localization of OCT2 in the supporting cells and type I spiral ganglion cells suggests that this transport protein is not primarily involved in cisplatin uptake from the systemic circulation. We hypothesize that OCT2 transport intensifies cisplatin ototoxicity via transport mechanisms in alternate compartments of the cochlea.

Level of Evidence

N/A. Laryngoscope, 125:E320–E325, 2015

Hepatocyte growth factor mimetic protects lateral line hair cells from aminoglycoside exposure

Loss of sensory hair cells from exposure to certain licit drugs (e.g., aminoglycoside antibiotics, platinum-based chemotherapy agents) can result in permanent hearing loss. Here we ask if allosteric activation of the hepatocyte growth factor (HGF) cascade via Dihexa, a small molecule drug candidate, can protect hair cells from aminoglycoside toxicity. Unlike native HGF, Dihexa is chemically stable and blood-brain barrier permeable. As a synthetic HGF mimetic, it forms a functional ligand by dimerizing with endogenous HGF to activate the HGF receptor and downstream signaling cascades. To evaluate Dihexa as a potential hair cell protectant, we used the larval zebrafish lateral line, which possesses hair cells that are homologous to mammalian inner ear hair cells and show similar responses to toxins. A dose-response relationship for Dihexa protection was established using two ototoxins, neomycin and gentamicin. We found that a Dihexa concentration of 1 μM confers optimal protection from acute treatment with either ototoxin. Pretreatment with Dihexa does not affect the amount of fluorescently tagged gentamicin that enters hair cells, indicating that Dihexa’s protection is likely mediated by intracellular events and not by inhibiting aminoglycoside entry. Dihexa-mediated protection is attenuated by co-treatment with the HGF antagonist 6-AH, further evidence that HGF activation is a component of the observed protection. Additionally, Dihexa’s robust protection is partially attenuated by co-treatment with inhibitors of the downstream HGF targets Akt, TOR and MEK. Addition of an amino group to the N-terminal of Dihexa also attenuates the protective response, suggesting that even small substitutions greatly alter the specificity of Dihexa for its target. Our data suggest that Dihexa confers protection of hair cells through an HGF-mediated mechanism and that Dihexa holds clinical potential for mitigating chemical ototoxicity.

Protective role of quercetin against cisplatin-induced hair cell damage in zebrafish embryos

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate the protective effects of quercetin on cisplatin-induced hair cell damage in transgenic zebrafish embryos.

MATERIALS AND METHODS

Five days postfertilization zebrafish embryos were exposed to 1 mM cisplatin and quercetin at 10, 50, 100, or 200 μM for 4 h. Hair cells within neuromasts of the supraorbital, otic, and occipital lateral lines were analyzed by fluorescent microscopy (n = 10). Survival of hair cells was calculated as the average number of hair cells in the control group that were not exposed to cisplatin. Ultrastructural changes were evaluated using scanning electron microscopy.

RESULTS

Hair cell damage in neuromasts was decreased by co-treatment of quercetin and cisplatin (quercetin 100 μM: 8.6 ± 1.1 cells; 1 mM cisplatin only: 5.0 ± 0.5 cells; n = 10, p < 0.05); apoptosis of hair cells examined by special stain was also decreased by quercetin. The ultrastructure of hair cells within neuromasts was preserved in zebrafish by the combination of quercetin (100 μM) and cisplatin (1 mM).

CONCLUSION

In conclusion, quercetin showed protective effects against cisplatin-induced toxicity in a zebrafish model. The results of this study suggest the possibility of a protective role of quercetin against cisplatin-induced apoptotic cell death in zebrafish.

Proposed comprehensive ototoxicity monitoring program for VA healthcare (COMP-VA)

Prevention and rehabilitation of hearing loss and tinnitus, the two most commonly awarded service-connected disabilities, are high priority initiatives in the Department of Veterans Affairs (VA). At least 4,000 Veterans, most with significant hearing loss, will receive cisplatin this year, with more than half sustaining permanent hearing shift and nearly 40% developing new tinnitus. With improved survivability following cancer treatment, Veterans treated with cisplatin are approached with the dual goals of effective treatment and preserved quality of life. This article describes COMP-VA, a comprehensive ototoxicity monitoring program developed for VA patients receiving cisplatin. The program includes an individualized pretreatment prediction model that identifies the likelihood of hearing shift given cisplatin dose and patient factors. It supports both manual and automated hearing testing with a newly developed portable audiometer capable of performing the recommended procedures on the chemotherapy unit during treatment. It also includes objective methods for identifying outer hair cell changes and predicting audiogram changes using distortion-product otoacoustic emissions. We describe this program of evidence-based ototoxicity monitoring protocols using a case example to give the reader an understanding of how this program would be applied, along with a plan for future work to accomplish the final stages of program development.

Protective effect of resveratrol against cisplatin-induced ototoxicity in HEI-OC1 auditory cells

OBJECTIVES

Cisplatin is an effective chemotherapeutic drug, but it generates reactive oxygen species (ROS) that induce severe adverse effects such as ototoxicity. Resveratrol reportedly prevents oxidative stress-induced cell death. Thus, we hypothesized that the anti-oxidative effect of resveratrol could protect against cisplatin-induced ototoxicity. The present study examined the protective effect of resveratrol against cisplatin-induced ototoxicity in HEI-OC1 auditory cells.

METHODS

HEI-OC1 cells were pretreated with resveratrol at 1μM for 24h and then exposed to 15μM cisplatin for 48h. Resulting cytotoxicity was measured by the MTT method, and intracellular ROS was measured using flow cytometry. Protective effect of resveratrol was compared with other anti-oxidants.

RESULTS

Pretreatment with resveratrol 1μM protected HEI-OC1 auditory cells against cisplatin-induced cytotoxicity and significantly reduced a cisplatin-induced increase in ROS. Resveratrol provided significant protection against 15μM cisplatin applied for 48h (50.8% cell viability in the cisplatin group vs. 57.6% in the cisplatin-plus-resveratrol group), and there was a 9% decrease in cisplatin-induced ROS associated with resveratrol.

CONCLUSIONS

This is the study investigating the protective effects of resveratrol against cisplatin-induced ototoxicity in an auditory cell line. Resveratrol significantly reduced a cisplatin-induced increase in ROS and thereby inhibited cisplatin-induced cytotoxicity.

Effects of caffeic acid on cisplatin-induced hair cell damage in HEI-OC1 auditory cells

INTRODUCTION

Cisplatin is a widely used anticancer chemotherapeutic agent. However, it is notorious for its ototoxicity and nephrotoxicity due to induction of reactive oxygen species (ROS). Caffeic acid is a naturally occurring polyphenol present in honey that is known to reduce the generation of oxygen-derived free radicals. The objective of the present study was to evaluate the protective effects and mechanism underlying the effect of caffeic acid on cisplatin-induced ototoxicity in HEI-OC1 auditory cell lines.

METHODS

Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was determined by Hoechst 33258 staining and Annexin V-fluorescein isothiocyanate/propidium iodide double staining. Cell cycle stages were analyzed by flow cytometry. The radical-scavenging activity of caffeic acid was assessed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The expression levels of caspase-3, -8, and -9, as well as the activity of caspase-3, were evaluated.

RESULTS

Caffeic acid showed a protective effect against cisplatin-induced HEI-OC1 cell damage as demonstrated by the MTT assay. Caffeic acid decreased cell death by apoptosis and necrosis. Caffeic acid showed strong scavenging activity against the radical DPPH and decreased intracellular ROS production. Caffeic acid decreased the expression of caspase-3 and -8 and increased the activity of caspase-3.

CONCLUSIONS

Caffeic acid attenuated cisplatin-induced hair cell loss in HEI-OC1 cell lines; these effects were mediated by its radical scavenging activity and inhibition of apoptosis.

Hearing loss in a pediatric patient following cisplatin chemotherapy and subsequent exposure to excessive noise

Cisplatin is a commonly-used chemotherapeutic agent that is highly-effective against a variety of pediatric cancers. Unfortunately, it may lead to ototoxicity, with serious consequences on the quality of life of survivors. Patients remain at risk of progression of ototoxicity even after completion of treatment. We report the case of a medulloblastoma survivor with previously documented normal hearing, who developed significant hearing loss and tinnitus following exposure to excessive noise at a nightclub three years after completion of treatment. We highlight the importance of long-term audiological follow up and education about the increased risk of hearing loss in this population.

Dexmedetomidine preconditioning attenuates Cisplatin-induced ototoxicity in zebrafish

Objectives

Utilisation of high-frequency drills is known to increase noise induced hearing loss due to increasing the damages of inner ear cells. This study aimed to investigate whether preconditioning by using dexmedetomidine (DEX) decreased the occurrence of ischemia in inner cells of the ear.

Methods

We utilised a transgenic zebrafish line Brn3C, and the embryos were collected from breeding adult zebrafish. Five-day-old larvae were cultured at the density of 50 embryos, and the larvae were classified into 4 groups: control, cisplatin group, DEX group, and DEX+yohimbine; adrenoreceptor blocker group. The DEX group was categorised into 3 subgroups by dosage; 0.1, 1, and 10 µM. Preconditioning was performed for 150 minutes and then exposed to cisplatin for 6 hours. The experiment was performed in 7 replicates for each group and the number of hair cells in 3 parts of the neuromasts of each fish was determined.

Results

Hair cell apoptosis by cisplatin was attenuated more significantly in the DEX preconditioning group than in the control group. However, the preconditioning effects were not blocked by yohimbine.

Conclusion

The results of this study suggest that hearing loss caused by vibration-induced noise could be reduced by using DEX and may occur through other mechanisms rather than adreno-receptors.

The double-edged sword: Neurotoxicity of chemotherapy

The number of available therapies for hematologic malignancies continues to grow at a rapid pace. Unfortunately, many of these treatments carry both central and peripheral nervous system toxicities, potentially limiting a patient's ability to tolerate a full course of treatment. Neurotoxicity with chemotherapy is common and second only to myelosuppression as a reason to limit dosing. This review addresses the neurotoxicity of newly available therapeutic agents including brentuximab vedotin and blinatumomab as well as classic ones such as methotrexate, vinca alkaloids and platinums. Although peripheral neuropathy is common with many drugs, other complications such as seizures and encephalopathy may require more immediate attention. Rapid recognition of adverse neurologic effects may lead to earlier treatment and appropriate adjustment of dosing regimens. In addition, knowledge of common toxicities may help differentiate chemotherapy-related symptoms from actual progression of cancer into the CNS.

ABR obtained from time-efficient train stimuli for cisplatin ototoxicity monitoring

BACKGROUND

Nonbehavioral methods for identifying cisplatin ototoxicity are important for testing patients with cancer who become too tired or sick to provide a reliable response. The auditory brainstem response (ABR) is a nonbehavioral test that is sensitive to ototoxicity but can be time consuming to implement over a range of frequencies and/or levels. To address this issue, trains of stimuli were developed that offer reliable ABR testing over a range of tone-burst frequencies and levels at a time savings of 77% relative to tone-burst stimuli presented individually. The clinical accuracy of this new method has yet to be determined on a clinical population.

PURPOSE

This project was designed to determine the test performance of a time-effective ABR methodology aimed at identifying hearing shifts from cisplatin among veterans. A secondary goal was to determine whether improved test performance could be achieved by including our previously developed ototoxicity risk assessment model in the ABR prediction algorithm.

RESEARCH DESIGN

A set of discriminant functions were derived using logistic regression to model the risk for cisplatin-induced hearing change. Independent variables were one of several ABR metrics alone and combined with an ototoxicity risk assessment model that includes pre-exposure hearing and cisplatin dose. Receiver operating characteristic curve analysis was used to evaluate the test performance of these discriminant functions.

STUDY SAMPLE

Twenty-two male veterans treated with cisplatin for various cancers provided data from a total of 71 monitoring appointments.

DATA COLLECTION AND ANALYSIS

Data were collected prospectively from one ear of each participant as designated below. Hearing shift was determined for frequencies within an octave of each patient's high-frequency hearing limit, tested in 1/6th-octave steps. ABRs were monitored using a set of two intensity trains from the highest two multiple frequency tone-burst center frequencies (up to 11.3 kHz) that yielded a robust response at baseline. Each intensity train was presented at 65-105 dB peSPL in 10 dB steps. Scorable ABRs were generally limited to the highest two intensities; therefore, analyses concern those levels.

RESULTS

The ABR measurement failure was high, up to 52% for some frequencies and levels. Furthermore, the ABR was not frequently obtained at levels below 85 dB peSPL, consistent with previous studies that suggest a stimulus level of greater than 80 dB peSPL is required to obtain a reliable response to trained stimuli. Using multivariate metrics that included the dose-ototoxicity model, the most accurate scoring function was change in amplitude at lowest half-octave frequency obtained at 105 dB (change in wave V amplitude at frequency 2/105). However, absence of wave V at a monitor patient visit of the ABR response at levels 105 or 95 dB peSPL was deemed the preferred scoring function, because it had lower measurement failure and was within one standard error of the most accurate function.

CONCLUSIONS

Because of the large number of responses that could not be measured at baseline, this technique as implemented holds limited value as an ototoxicity-monitoring method.

Assessing cisplatin-induced ototoxicity and otoprotection in whole organ culture of the mouse inner ear in simulated microgravity

Cisplatin is a widely used anti-cancer drug. Ototoxicity is a major dose-limiting side-effect. A reproducible mammalian in-vitro model of cisplatin ototoxicity is required to screen and validate otoprotective drug candidates. We utilized a whole organ culture system of the postnatal mouse inner ear in a rotating wall vessel bioreactor under "simulated microgravity" culture conditions. As previously described this system allows whole organ culture of the inner ear and quantitative assessment of ototoxic effects of aminoglycoside induced hair cell loss. Here we demonstrate that this model is also applicable to the assessment of cisplatin induced ototoxicity. In this model cisplatin induced hair cell loss was dose and time dependent. Increasing exposure time of cisplatin led to decreasing EC50 concentrations. Outer hair cells were more susceptible than inner hair cells, and hair cells in the cochlear base were more susceptible than hair cells in the cochlear apex. Initial cisplatin dose determined the final extent of hair cell loss irrespective if the drug was withdrawn or continued. Dose dependant otoprotection was demonstrated by co-administration of the antioxidant agent N-acetyl l-cysteine. The results support the use of this inner ear organ culture system as an in vitro assay and validation platform for inner ear toxicology and the search for otoprotective compounds.

Chemotherapy-induced peripheral neurotoxicity and ototoxicity: new paradigms for translational genomics

In view of advances in early detection and treatment, the 5-year relative survival rate for all cancer patients combined is now approximately 66%. As a result, there are more than 13.7 million cancer survivors in the United States, with this number increasing by 2% annually. For many patients, improvements in survival have been countered by therapy-associated adverse effects that may seriously impair long-term functional status, workplace productivity, and quality of life. Approximately 20% to 40% of cancer patients given neurotoxic chemotherapy develop chemotherapy-induced peripheral neurotoxicity (CIPN), which represents one of the most common and potentially permanent nonhematologic side effects of chemotherapy. Permanent bilateral hearing loss and/or tinnitus can result from several ototoxic therapies, including cisplatin- or carboplatin-based chemotherapy. CIPN and ototoxicity represent important challenges because of the lack of means for effective prevention, mitigation, or a priori identification of high-risk patients, and few studies have applied modern genomic approaches to understand underlying mechanisms/pathways. Translational genomics, including cell-based models, now offer opportunities to make inroads for the first time to develop preventive and interventional strategies for CIPN, ototoxicity, and other treatment-related complications. This commentary provides current perspective on a successful research strategy, with a focus on cisplatin, developed by an experienced, transdisciplinary group of researchers and clinicians, representing pharmacogenomics, statistical genetics, neurology, hearing science, medical oncology, epidemiology, and cancer survivorship. Principles outlined herein are applicable to the construction of research programs in translational genomics with strong clinical relevance and highlight unprecedented opportunities to understand, prevent, and treat long-term treatment-related morbidities.