Cisplatin-Induced Hearing Loss, Oxidative Stress, and Antioxidants as a Therapeutic Strategy-A State-of-the-Art Review

Cisplatin is an established component of treatment protocols for various solid malignancies but carries a significant potential for serious adverse effects. Ototoxicity from cisplatin treatment is an important dose-limiting toxicity that manifests as bilateral, progressive, irreversible, dose-dependent sensorineural hearing loss, ear pain, tinnitus, and vestibular dysfunction. Despite the recent approval of sodium thiosulphate for the prevention of cisplatin-induced hearing loss (CIHL) in pediatric patients, structured prevention programs are not routinely implemented in most hospitals, and reducing platinum-induced ototoxicity in adults remains an important clinical problem without established treatment options. Cochlear oxidative stress plays a fundamental role in CIHL. Here, we review the molecular mechanisms leading to oxidative stress in CIHL and the clinical and preclinical studies testing antioxidants in CIHL to guide future clinical trials in assessing the efficacy and safety of candidate antioxidant compounds in this clinical setting.

Hearing loss during chemotherapy: prevalence, mechanisms, and protection

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

Unveiling the Role of Oxidative Stress in Cochlear Hair Cell Death: Prospective Phytochemical Therapeutics against Sensorineural Hearing Loss

Hearing loss represents a multifaceted and pervasive challenge that deeply impacts various aspects of an individual's life, spanning psychological, emotional, social, and economic realms. Understanding the molecular underpinnings that orchestrate hearing loss remains paramount in the quest for effective therapeutic strategies. This review aims to expound upon the physiological, biochemical, and molecular aspects of hearing loss, with a specific focus on its correlation with diabetes. Within this context, phytochemicals have surfaced as prospective contenders in the pursuit of potential adjuvant therapies. These compounds exhibit noteworthy antioxidant and anti-inflammatory properties, which hold the potential to counteract the detrimental effects induced by oxidative stress and inflammation-prominent contributors to hearing impairment. Furthermore, this review offers an up-to-date exploration of the diverse molecular pathways modulated by these compounds. However, the dynamic landscape of their efficacy warrants recognition as an ongoing investigative topic, inherently contingent upon specific experimental models. Ultimately, to ascertain the genuine potential of phytochemicals as agents in hearing loss treatment, a comprehensive grasp of the molecular mechanisms at play, coupled with rigorous clinical investigations, stands as an imperative quest.

The Chemoprotective Potentials of Alpha-lipoic Acid against Cisplatin-induced Ototoxicity: A Systematic Review

PURPOSE

Ototoxicity is one of the major adverse effects of cisplatin therapy which restrict its clinical application. Alpha-lipoic acid administration may mitigate cisplatin-induced ototoxicity. In the present study, we reviewed the protective potentials of alpha-lipoic acid against the cisplatin-mediated ototoxic adverse effects.

METHODS

Based on the PRISMA guideline, we performed a systematic search for the identification of all relevant studies in various electronic databases up to June 2022. According to the inclusion and exclusion criteria, the obtained articles (n=59) were screened and 13 eligible articles were finally included in the present study.

RESULTS

The findings of in-vitro experiments showed that cisplatin treatment significantly reduced the auditory cell viability in comparison with the control group; nevertheless, the alpha-lipoic acid co-administration protected the cells against the reduction of cell viability induced by cisplatin treatment. Moreover, the in-vivo results of the auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) tests revealed a decrease in DPOAE and an increase in ABR threshold of cisplatin-injected animals; however, it was shown that alpha-lipoic acid co-treatment had an opposite pattern on the evaluated parameters. Other findings demonstrated that cisplatin treatment could significantly induce the biochemical and histopathological alterations in inner ear cells/tissue; in contrast, alpha-lipoic acid co-treatment ameliorated the cisplatin-mediated biochemical and histological changes.

CONCLUSION

The findings of audiometry, biochemical parameters, and histological evaluation showed that alpha-lipoic acid co-administration alleviates the cisplatin-induced ototoxicity. The protective role of alpha-lipoic acid against the cisplatin-induced ototoxicity can be due to different mechanisms of anti-oxidant, anti-apoptotic, anti-inflammatory activities, and regulation of cell cycle progression.

Pro-Inflammatory Signalling PRRopels Cisplatin-Induced Toxicity

Cisplatin is a platinum-based chemotherapeutic that has long since been effective against a variety of solid-cancers, substantially improving the five-year survival rates for cancer patients. Its use has also historically been limited by its adverse drug reactions, or cisplatin-induced toxicities (CITs). Of these reactions, cisplatin-induced nephrotoxicity (CIN), cisplatin-induced peripheral neuropathy (CIPN), and cisplatin-induced ototoxicity (CIO) are the three most common of several CITs recognised thus far. While the anti-cancer activity of cisplatin is well understood, the mechanisms driving its toxicities have only begun to be defined. Most of the literature pertains to damage caused by oxidative stress that occurs downstream of cisplatin treatment, but recent evidence suggests that the instigator of CIT development is inflammation. Cisplatin has been shown to induce pro-inflammatory signalling in CIN, CIPN, and CIO, all of which are associated with persisting markers of inflammation, particularly from the innate immune system. This review covered the hallmarks of inflammation common and distinct between different CITs, the role of innate immune components in development of CITs, as well as current treatments targeting pro-inflammatory signalling pathways to conserve the use of cisplatin in chemotherapy and improve long-term health outcomes of cancer patients.

Low-Dose Resveratrol Inhibits RIPK3-Mediated Necroptosis and Delays the Onset of Age-Related Hearing Loss

Background: To investigate the pathophysiology of age-related hearing loss (ARHL) and the mechanism of resveratrol (RSV) in prevention and treatment of ARHL.

Methods: C57BL/6 mice of different ages were used in this study. Auditory brainstem response (ABR) was performed to assess hearing and identify abnormalities. Surface preparation and hair cell-specific marker Myo VIIa were employed to evaluated cochlear hair cell losses. Scanning electron microscopy (SEM) was to observe the microstructure of the organ of Corti (OC). The expression of related proteins in the RIPK1/RIPK3/MLKL pathway in cochlear tissue was detected by immunofluorescence.

Results: In old mice (15 months), the ABR threshold increased significantly compared with the young mice. After 50 mg/kg RSV intervention, the hearing threshold of the old mice was significantly reduced at 8 kHz and 12 kHz as well as click. 100 mg/kg RSV led to a statistically significant reduction in hearing threshold only at clicks, whereas 300 mg/kg RSV showed no difference at all frequencies tested. In terms of cochlear hair cell loss, the damage of OHC and IHC was severe in old mice, but the damage was evidently reduced in RSV 50 mg/kg group. Notably, in the RSV 300 mg/kg group, the loss and disorientation of both the OHCs and IHCs were aggravated. Under SEM, a large number of OHCs were lost in the old group, but increased significantly in the RSV 50 mg/kg group, and even the OHCs were more seriously damaged in the RSV 300 mg/kg group. Furthermore, immunofluorescence showed that 50 mg/kg RSV significantly reduced the expression of RIPK3, RIPK1, and MLKL in the cochlea during aging, especially in necroptosis-sensitive regions OCs and SGN.

Conclusion: Low-dose RSV inhibited RIPK3-mediated necroptosis in aging cochlea and delayed the onset of ARHL, which was a promising therapeutic strategy for ARHL.

Long-term auditory follow-up in the management of pediatric platinum-induced ototoxicity

PURPOSE

Irreversible bilateral sensorineural hearing loss is a common side effect of platinum compounds. Because of the extended overall survival, a prolonged hearing surveillance and management of hearing impairments are emerging concerns for pediatric oncology.

METHODS

In this retrospective observational study, we enrolled 38 children out of 116 treated at our institution by chemotherapy (cisplatin and/or carboplatin) with or without irradiation between 2007 and 2014, submitted to hearing monitoring before every cycle of chemotherapy, and who completed a 5-year long-term audiological follow-up. Chemotherapy regimens, demographic findings, cumulative doses, and cranial irradiation were compared.

RESULTS

At the end of 5-year follow-up, ototoxicity was significantly increased compared to that observed at the end of chemotherapy (52.5% vs 39.5%, p < 0.001). A late onset of hearing loss was experienced in 13.1% of children, while in 26.3% progressive hearing loss was measured. Deafness at the end of chemotherapy and irradiation were significant prognostic factors for late ototoxicity outcomes (Odds Ratio 7.2-CI 1.67-31.1-p < 0.01 and 5.25-CI 1.26-21.86-p < 0.01 respectively). No significant differences were found between cisplatin and combined treatment (i.e., cisplatin shifted to carboplatin during monitoring for the onset of ototoxicity) and ototoxicity was not associated with platinum compounds cumulative dose (p > 0.05). 13.1% of children needed hearing aids at the end of follow-up.

CONCLUSION

Long-term monitoring of at least 5 years prevents the harmful effects of hearing deprivation identifying late onset/progressive hearing loss after platinum compound chemotherapy in children thanks to early hearing rehabilitation, especially in those who underwent multimodal therapy or subjected to irradiation.

Dose-Dependent Effects of Resveratrol on Cisplatin-Induced Hearing Loss

Previous preclinical studies have demonstrated the otoprotective effects of resveratrol (RV) at low doses. This study aimed to investigate the dose-dependent effects of RV in rats with cisplatin (CXP)-induced hearing loss. Sprague-Dawley rats (8-weeks old) were divided into six treatment groups (n = 12/group) and treated as follows: control, 0.5 mg/kg RV, 50 mg/kg RV, CXP, 0.5 mg/kg RV + CXP), and 50 mg/kg RV + CXP groups. CXP (3 mg/kg) was intraperitoneally injected for 5 days. RV (0.5 or 50 mg/kg) was intraperitoneally injected for 10 days from the first day of CXP administration. Auditory brainstem response (ABR) thresholds were measured before and within 3 days at the end of the drug administration. Cochlear tissues were harvested, and the outer hair cells were examined using cochlear whole mounts. The mRNA expression of NFκB, IL6, IL1β, and CYP1A1, and protein levels of aryl hydrocarbon receptor (AhR) and cytosolic and nuclear receptor for advanced glycation endproducts (RAGE) were evaluated. The ABR threshold increased in the 50 mg/kg RV and CXP groups at 4, 8, 16, and 32 kHz. The 0.5 mg/kg RV + CXP group demonstrated decreased hearing thresholds at 4 and 32 kHz compared to the CXP group. Cochlear whole-mount analysis revealed loss of outer hair cells in the 50 mg/kg RV and CXP groups and partial prevention of these cells in the 0.5 mg/kg RV + CXP group. The mRNA expressions of NFκB, IL6, and IL1β were increased in the 50 mg/kg RV and CXP groups compared to the control group. In contrast, these levels were decreased in the 0.5 mg/kg RV + CXP group compared to the CXP group. The mRNA expression of CYP1A1 was increased in the CXP group, while it was decreased in the 0.5 mg/kg RV + CXP group compared to the control group. The protein levels of AhR and cytosolic RAGE decreased in the 0.5 mg/kg RV group. Low-dose RV had partial otoprotective effects on CXP ototoxicity. The otoprotective effects of RV may be mediated through anti-oxidative (CYP1A1 and RAGE) and anti-inflammatory (NFκB, IL6, and IL1β) responses. High-dose RV exerted an inflammatory response and did not ameliorate CXP-induced ototoxicity.

Resveratrol stereoselectively affected (±)warfarin pharmacokinetics and enhanced the anticoagulation effect

Resveratrol (RVT) has various beneficial bioactivities and popularly used as a dietary supplement. RVT showed inhibitions on CYP1A2/2C9/3A4, breast cancer resistance protein (BCRP), and some conjugated metabolites of RVT also inhibited BCRP. (±)Warfarin, an anticoagulant for cardiovascular disease but with narrow therapeutic window, were substrates of CYP1A2/3A4(R-form), 2C9(S-form) and BCRP. We hypothesized that the concurrent use of RVT might affect the metabolism and excretion of warfarin. This study investigated the effect of RVT on the pharmacokinetics and anticoagulation effect of (±)warfarin. Rats were orally given (±)warfarin (0.2 mg/kg) without and with RVT (100 mg/kg) in a parallel design. The results showed that RVT significantly increased the AUC_0-t of S-warfarin and international normalized ratio. Mechanism studies showed that both RVT and its serum metabolites (RSM) inhibited BCRP-mediated efflux of R- and S-warfarin. Moreover, RSM activated CYP1A2/3A4, but inhibited CYP2C9. In conclusion, concomitant intake of RVT increased the systemic exposure of warfarin and enhanced the anticoagulation effect mainly via inhibitions on BCRP and CYP2C9.

Investigation of Astaxanthin Effect on Cisplatin Ototoxicity in Rats by Using Otoacoustic Emission, Total Antioxidant Capacity, and Histopathological Methods

BACKGROUND

Cisplatin-induced ototoxicity is related to oxidative stress. Astaxanthin is one of the most powerful antioxidants in nature.

AIMS/OBJECTIVES

To investigate the protective effect of astaxanthin on cisplatin-induced ototoxicity.

MATERIALS AND METHODS

Thirty-five Sprague Dawley female rats were divided into 5 groups: control, cisplatin, and cisplatin with 10, 20, and 40 mg/kg astaxanthin groups. Cisplatin group received a single intraperitoneal injection of 14 mg/kg cisplatin. While saline was administered in the control group, in the other 3 groups, 10, 20, and 40 mg/kg daily doses of astaxanthin were administered through orogastric cannula before administration of cisplatin. Baseline and 10th day otoacoustic emission tests were administered. An intracardiac blood sample was taken to measure total antioxidant capacity (TAC), and the cochleas of the animals were investigated histopathologically.

RESULTS

Hearing level of astaxanthin 40 mg/kg + cisplatin group was higher at 24 kHz and 32 kHz frequencies compared to the cisplatin group. The TAC value of the cisplatin group was lower than both the control and astaxanthin + cisplatin groups (P < .05). On histopathological examination, the other groups were deformed compared to the control group, but no statistically significant difference was observed between the astaxanthin + cisplatin and cisplatin groups.

CONCLUSIONS AND SIGNIFICANCE

Astaxanthin showed protective effect at high frequencies when it was administered at high dose. Thus, astaxanthin may have protective effect against cisplatin-induced ototoxicity.

Dexamethasone-loaded chitosan-based genipin-cross-linked hydrogel for prevention of cisplatin induced ototoxicity in Guinea pig model

OBJECTIVES

The aim of this study was to investigate the protective effects of a sustained release form of dexamethasone (dex) loaded chitosan-based genipin-cross-linked hydrogel (CBGCH) in a guinea pig model of cisplatin (CP) induced hearing loss.

METHODS

Implantation of CBGCH was made by intratympanic (IT) injection. Ototoxicity was produced by intraperitoneal (IP) single dose of 14 mg/kg CP. Animals were randomly divided into four groups with 6 guinea pigs in each. Group 1 received only IP CP; group 2 received only IT dex-loaded CBGCH injections. Group 3 and group 4 received IP CP, plus IT nondrug CBGCH and IT dex-loaded CBGCH respectively 24 h prior to IP CP injections. Distortion product otoacoustic emissions (DPOAEs) and auditory brainstem response (ABR) measurements were obtained before the treatments and solely ABR measurements were done after 3 and 10 days. The ultrastructural effects were investigated by scanning electron microscopy (SEM) analysis.

RESULTS

The postCP ABR thresholds at 4, 8, 12, 16, 32 kHz frequencies were significantly better in group 4 than groups 1 and 3 (p < 0.05). The comparison of time effective ABR thresholds between groups 1 and 4 and between groups 3 and 4 showed significantly lower ABR thresholds in group 4 (p < 0.05). The SEM analysis showed that stereocilia of inner and outer hair cells were preserved in group 4, almost like group 2, whereas cytotoxic degenerations were noted in groups 1 and 3.

CONCLUSIONS

Intratympanic administration of dex-loaded CBGCH has been shown to provide functional and structural protection against CP-induced ototoxicity.

A Review of Cisplatin-Associated Ototoxicity

Cisplatin, an effective antineoplastic drug used in the treatment of many cancers, has ototoxic potential, thus placing cancer patients, receiving this treatment, at risk of hearing loss. It is therefore important for health care professionals managing these patients to be aware of cisplatin's ototoxic properties and its clinical signs to identify patients at risk of developing a hearing impairment. Eighty-five English peer-reviewed articles and two books, from January 1975 to July 2015, were identified from PubMed, ScienceDirect, and EBSCOhost. An overview of cisplatin-associated ototoxicity, namely its clinical features, incidence rates, molecular and cellular mechanisms, and risk factors, is presented in this article. This review further highlights the importance of a team-based approach to complement an audiological monitoring program in reducing any further loss in the quality of life of affected patients, as there is currently no otoprotective agent routinely recommended for the prevention of cisplatin-associated ototoxicity.

Traditional oriental medicine for sensorineural hearing loss: Can ethnopharmacology contribute to potential drug discovery?

ETHNOPHARMACOLOGICAL RELEVANCE

In Traditional Oriental Medicine (TOM), the development of hearing pathologies is related to an inadequate nourishment of the ears by the kidney and other organs involved in regulation of bodily fluids and nutrients. Several herbal species have historically been prescribed for promoting the production of bodily fluids or as antiaging agents to treat deficiencies in hearing.

AIM OF REVIEW

The prevalence of hearing loss has been increasing in the last decade and is projected to grow considerably in the coming years. Recently, several herbal-derived products prescribed in TOM have demonstrated a therapeutic potential for acquired sensorineural hearing loss and tinnitus. Therefore, the aims of this review are to provide a comprehensive overview of the current known efficacy of the herbs used in TOM for preventing different forms of acquired sensorineural hearing loss and tinnitus, and associate the traditional principle with the demonstrated pharmacological mechanisms to establish a solid foundation for directing future research.

METHODS

The present review collected the literature related to herbs used in TOM or related compounds on hearing from Chinese, Korean, and Japanese herbal classics; library catalogs; and scientific databases (PubMed, Scopus, Google Scholar; and Science Direct).

RESULTS

This review shows that approximately 25 herbal species and 40 active compounds prescribed in TOM for hearing loss and tinnitus have shown in vitro or in vivo beneficial effects for acquired sensorineural hearing loss produced by noise, aging, ototoxic drugs or diabetes. The inner ear is highly vulnerable to ischemia and oxidative damage, where several TOM agents have revealed a direct effect on the auditory system by normalizing the blood supply to the cochlea and increasing the antioxidant defense in sensory hair cells. These strategies have shown a positive impact on maintaining the inner ear potential, sustaining the production of endolymph, reducing the accumulation of toxic and inflammatory substances, preventing sensory cell death and preserving sensory transmission. There are still several herbal species with demonstrated therapeutic efficacy whose mechanisms have not been deeply studied and others that have been traditionally used in hearing loss but have not been tested experimentally. In clinical studies, Ginkgo biloba, Panax ginseng, and Astragalus propinquus have demonstrated to improve hearing thresholds in patients with sensorineural hearing loss and alleviated the symptoms of tinnitus. However, some of these clinical studies have been limited by small sample sizes, lack of an adequate control group or contradictory results.

CONCLUSIONS

Current therapeutic strategies have proven that the goal of the traditional oriental medicine principle of increasing bodily fluids is a relevant approach for reducing the development of hearing loss by improving microcirculation in the blood-labyrinth barrier and increasing cochlear blood flow. The potential benefits of TOM agents expand to a multi-target approach on different auditory structures of the inner ear related to increased cochlear blood flow, antioxidant, anti-inflammatory, anti-apoptotic and neuroprotective activities. However, more research is required, given the evidence is very limited in terms of the mechanism of action at the preclinical in vivo level and the scarce number of clinical studies published.

Is Pool Water Disinfectant (Hydrogen Peroxide-Silver Composition) Ototoxic in Rats?

OBJECTIVES

The purpose of our study was to evaluate whether hydrogen peroxide and silver composition (H202-Ag) used in pool water disinfectant is ototoxic to individuals with tympanic membrane perforation.

MATERIALS AND METHODS

The tympanic membranes of both ears of 14 Wistar-type albino female rats were perforated. Since topical application was performed, the right and left ears were categorized as two subgroups (a: right ear, b: left ear). Baseline auditory brainstem response (ABR) was measured. The groups were classified according to topical applications performed as Ia (30 mg/L H202-Ag), Ib (saline), IIa (70 mg/L H202-Ag), and IIb (saline). The topical applications were performed for 30 min/day for 10 days. The ABR was measured 24 hours after the last application, and the animals were sacrificed. Bilateral temporal bones were examined using light microscopy.

RESULTS

An apparent rise in the hearing thresholds of the groups Ia and Ib was not observed. However, there was an apparent rise in the hearing thresholds of the group IIa, which supports ototoxicity. According to histopathology results, there weren't any pathological findings in groups Ia and Ib and did not display special features, but a neurotoxic effect was observed in group II.

CONCLUSION

Our study shows that the H202-Ag used in pool water disinfection can have ototoxic and neurotoxic effects, particularly at high concentrations.

The effect of resveratrol on the histologic characteristics of the cochlea in diabetic rats

OBJECTIVES/HYPOTHESIS

The aim of this study was to investigate changes in the cochlea and the potential dose-dependent effects of resveratrol (RSV) against diabetes mellitus (DM) ototoxicity.

STUDY DESIGN

Animal model.

METHODS

Twenty-four male Wistar albino rats were divided into four groups. Baseline distortion product otoacoustic emission (DPOAE) measurements were evaluated. Group I was the control group, group II was made diabetic with single-dose streptozotocin, and groups III and IV were rendered diabetic as group II and administered 10 and 20 mg RSV, respectively, intraperitoneally for 4 weeks. All animals were sacrificed after repeated DPOAE measurement. Apoptosis was investigated using caspase-3, Bax (Bcl-associated X protein), and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining.

RESULTS

The DPOAE values in the diabetic group were found to be significantly lower compared with the other groups at 5,714 Hz and 8,000 Hz (P < .05). No significant difference in otoacoustic emission was detected in the comparison of the RSV doses (P > .05). The histopathologic investigation using caspase-3, Bax, and TUNEL staining showed that the mean rank of the diabetic group was significantly higher compared with the RSV10, RSV20, and control groups (DM > RSV10 > RSV20 > control) (P < .05).

CONCLUSIONS

These results imply that RSV administration offered statistically significant protection for the cochleas of rats against diabetes. This protective effect improved histologically with higher doses.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E1-E6, 2019.

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.

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.

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.

Survival of auditory hair cells

The inability of mammals to regenerate auditory hair cells creates a pressing need to understand the means of enhancing hair cell survival following insult or injury. Hair cells are easily damaged by noise exposure, by ototoxic medications and as a consequence of aging processes, all of which lead to progressive and permanent hearing impairment as hair cells are lost. Significant efforts have been invested in designing strategies to prevent this damage from occurring since permanent hearing loss has a profound impact on communication and quality of life for patients. In this mini-review, we discuss recent progress in the use of antioxidants, anti-inflammatories and apoptosis inhibitors to enhance hair cell survival. We conclude by clarifying the distinction between protection and rescue strategies and by highlighting important areas of future research.

Prevention and restoration of hearing loss associated with the use of cisplatin

Background. Cisplatin is a well known platinum-based chemotherapeutic agent used for the treatment of various malignant tumours. A frequent side effect of cisplatin therapy is ototoxicity. Unfortunately, currently there are no available treatments. Material and Methods. Experimental, clinical studies and reviews published between 2004 and 2014 in the English medical literature concerning ototoxicity were selected using Medline, PubMed, and Google Scholar databases. Inclusion criteria were cisplatin-induced ototoxicity and therapy aimed at preventing or curing this disorder. Molecular mechanisms and clinical, audiological, and histological markers of cisplatin-induced ototoxicity are described. Moreover, experimental and clinical strategies for prevention or treatment of hearing loss were also reviewed. Results and Discussion. Experimental studies demonstrate a wide range of otoprotective molecules and strategies efficient against cisplatin-induced hearing loss. However, only dexamethasone proved a slight otoprotective effect in a clinical study. Conclusion. Further research must be completed to bring future therapeutic options into clinical setting.