Dose-dependent effect of 8-day cisplatin administration upon the morphology of the albino guinea pig cochlea

Pharmacodynamic, pharmacokinetic, toxicity, and recent advances in Eugenol's potential benefits against natural and chemical noxious agents: A mechanistic review

The active biological phytochemicals, crucial compounds employed in creating hundreds of medications, are derived from valuable and medicinally significant plants. These phytochemicals offer excellent protection from various illnesses, including inflammatory disorders and chronic conditions caused by oxidative stress. A phenolic monoterpenoid known as eugenol (EUG), it is typically found in the essential oils of many plant species from the Myristicaceae, Myrtaceae, Lamiaceae, and Lauraceae families. One of the main ingredients of clove oil (Syzygium aromaticum (L.), Myrtaceae), it has several applications in industry, including flavoring food, pharmaceutics, dentistry, agriculture, and cosmeceuticals. Due to its excellent potential for avoiding many chronic illnesses, it has lately attracted attention. EUG has been classified as a nonmutant, generally acknowledged as a safe (GRAS) chemical by the World Health Organization (WHO). According to the existing research, EUG possesses notable anti-inflammatory, antioxidant, analgesic, antibacterial, antispasmodic, and apoptosis-promoting properties, which have lately gained attention for its ability to control chronic inflammation, oxidative stress, and mitochondrial malfunction and dramatically impact human wellness. The purpose of this review is to evaluate the scientific evidence from the most significant research studies that have been published regarding the protective role and detoxifying effects of EUG against a wide range of toxins, including biological and chemical toxins, as well as different drugs and pesticides that produce a variety of toxicities, throughout view of the possible advantages of EUG.

The protective effect of aspirin-induced temporary threshold shift in an animal model of cisplatin-related ototoxicity

PURPOSE

The purpose of this study was to evaluate whether induction of temporary threshold shift (TTS) with aspirin prior to cisplatin exposure can prevent or minimize cisplatin detrimental effects on hearing.

METHODS

We randomly divided BALB mice into three groups: (1) cisplatin only, (2) aspirin only, and (3) combined aspirin/cisplatin. Cisplatin was administered as a single intraperitoneal injection of 14 mg/kg. Aspirin was administered for three weeks via intraperitoneal injection of 200 mg/kg sodium salicylate, twice daily. Air conduction thresholds were recorded using Auditory Brainstem Responses (ABR). Cochleae were harvested and cochlear hair cells were counted using a scanning electron microscope (SEM).

RESULTS

Aspirin-induced TTS have reached an average of 30.05±16.9 dB after 2 weeks. At 60 days, cisplatin-only treated mice experienced an average threshold shifts of 50.7 dB at 4 kHz, 35.16 dB at 8 kHz, 70 dB at 16 kHz, 53.1 dB at 32 kHz. All threshold shifts were significantly worse than for cisplatin/aspirin treated mice with TTS of 11.85 dB at 4 kHz, 3.58 dB at 8 kHz, 16.58  dB at 16 kHz, 20.41 dB at 32 kHz (p < 0.01). Cochlear cell count with SEM has shown reduction in the number of both inner and outer hair cells in the mid-turn in cisplatin treated mice.

CONCLUSION

Aspirin induced TTS can protect from cisplatin-induced ototoxicity. This beneficial effect was demonstrated by auditory thresholds as well as SEM. Larger pre-clinical and clinical studies are still needed to confirm these findings.

c-Myb protects cochlear hair cells from cisplatin-induced damage via the PI3K/Akt signaling pathway

The transcription factor c-Myb is vital for cell survival, proliferation, differentiation, and apoptosis. We have previously reported that c-Myb knockdown exacerbates neomycin-induced damage to cochlea cells. However, the function and regulation of c-Myb in the mammalian inner ear remains unclear. Here, we first found that the expression of c-Myb in cochlear HCs was downregulated after cisplatin damage in vivo. Next, to investigate the role of c-Myb in HCs treated with cisplatin, the recombinant virus AAV-ie-CAG-Myb-HA (AAV-c-Myb) that overexpresses c-Myb was constructed and transfected into HCs. The protein expression of c-Myb was effectively up-regulated in cultured cochlear HCs after the virus transfection, which increased cochlear HC viability, decreased HC apoptosis and reduced intracellular reactive oxygen species (ROS) levels after cisplatin injury in vitro. The overexpression of c-Myb in HCs after AAV-c-Myb transfection in vivo also promoted HC survival, improved the hearing function of mice and reduced HC apoptosis after cisplatin injury. Furthermore, c-Myb-HC conditional knockout mice (Prestin; c-Myb-cKO) in which c-Myb expression is downregulated only in cochlear OHCs were generated and the cisplatin-induced HCs loss, apoptosis and hearing deficit were all exacerbated in Prestin; c-Myb-cKO mice treated with cisplatin in vivo. Finally, mechanistic studies showed that upregulation of the PI3K/Akt signaling pathway by c-Myb contributed to the increased HC survival after cisplatin exposure in vitro. The findings from this work suggest that c-Myb might serve as a new target for the prevention of cisplatin-induced HC damage and hearing loss.

The effects of ethyl pyruvate against experimentally induced cisplatin ototoxicity in rats

INTRODUCTION

Cisplatin (CDDP) is a widely used antineoplastic drug. However, its use is limited due to the ototoxic side effects. In this study, the effects of ethyl pyruvate (EP), known for its antioxidant and anti-inflammatory effects, against CDDP ototoxicity were investigated.

METHODS

Thirty-two Wistar albino rats (n:8) were used in this study. CDDP was administered i.p. as a single dose of 15 mg/kg/day in order to cause ototoxicity. EP was applied i.p. at a dose of 50 mg/kg/day for 7 days.

RESULTS

When the Auditory Brainstem Responses (ABR) and Distortion Product Otoacoustic Emissions (DPOAE) tests carried out in the pre-treatment and post-treatment periods were examined, it was observed that the hearing functions were significantly impaired with the CDDP application, while a significant improvement was observed in the CDDP + EP group. Compared to the control group, the CDDP group had significantly higher malondialdehyde (MDA) levels and significantly lower glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) levels. In the CDDP + EP group, there was no deterioration in MDA, SOD and CAT levels that was observed in the CDDP group. The increase in pro-inflammatory cytokine (IL-1β, IL-6 and TNF-α) levels caused by CDDP administration was observed to be significantly decreased in the CDDP + EP group.

CONCLUSIONS

Hearing tests and biochemical results show that ethyl pyruvate is protective against cisplatin ototoxicity with its antioxidant and anti-inflammatory effects.

Early Physiological and Cellular Indicators of Cisplatin-Induced Ototoxicity

Cisplatin chemotherapy often causes permanent hearing loss, which leads to a multifaceted decrease in quality of life. Identification of early cisplatin-induced cochlear damage would greatly improve clinical diagnosis and provide potential drug targets to prevent cisplatin's ototoxicity. With improved functional and immunocytochemical assays, a recent seminal discovery revealed that synaptic loss between inner hair cells and spiral ganglion neurons is a major form of early cochlear damage induced by noise exposure or aging. This breakthrough discovery prompted the current study to determine early functional, cellular, and molecular changes for cisplatin-induced hearing loss, in part to determine if synapse injury is caused by cisplatin exposure. Cisplatin was delivered in one to three treatment cycles to both male and female mice. After the cisplatin treatment of three cycles, threshold shift was observed across frequencies tested like previous studies. After the treatment of two cycles, beside loss of outer hair cells and an increase in high-frequency hearing thresholds, a significant latency delay of auditory brainstem response wave 1 was observed, including at a frequency region where there were no changes in hearing thresholds. The wave 1 latency delay was detected as early cisplatin-induced ototoxicity after only one cycle of treatment, in which no significant threshold shift was found. In the same mice, mitochondrial loss in the base of the cochlea and declining mitochondrial morphometric health were observed. Thus, we have identified early spiral ganglion-associated functional and cellular changes after cisplatin treatment that precede significant threshold shift.

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.

Cisplatin-Induced Ototoxicity in Rats Is Driven by RIP3-Dependent Necroptosis

Cisplatin-induced early-onset ototoxicity is linked to hearing loss. The mechanism by which cisplatin causes ototoxicity remains unclear. The purpose of this study was to identify the involvement of receptor-interacting protein kinase (RIP)3-dependent necroptosis in cisplatin-induced ototoxicity in vitro and in vivo. Sprague-Dawley rats (SD, 8 week) were treated via intraperitoneal (i.p.) injection with cisplatin (16 mg/kg for 1 day), and their hearing thresholds were measured by the auditory brainstem response (ABR) method. Hematoxylin and eosin (H & E) staining, immunohistochemistry, and western blots were performed to determine the effect of cisplatin-induced ototoxicity on cochlear morphology. Inhibitor experiments with necrostatin 1 (Nec-1) and Z-VAD were also performed in HEI-OC1 cell line. H&E stains revealed that the necroptotic changes were increased in the organ of Corti (OC) and spiral ganglion neurons (SGNs). Moreover, immunohistochemistry and western blot analysis showed that cisplatin treatment increased the protein levels of RIP3 in both OCs and SGNs. The treatment of Nec-1, a selective RIP1 inhibitor, resulted in markedly suppression of cisplatin-induced cell death in HEI-OC1 cells, whereas Z-VAD treatment did not change the cisplatin-induced cell death. Our results suggest that RIP3-dependent necroptosis was substantial in cisplatin-induced ototoxicity; inner cochlear regions, the OCs, and SGNs were especially sensitive to necroptosis.

The Effects of Riluzole on Cisplatin-induced Ototoxicity

Introduction  Riluzole (2-amino-6-trifluoromethoxy benzothiazole) is known as a neuroprotective, antioxidant, antiapoptotic agent. It may have beneficial effects on neuronal cell death due to cisplatin-induced ototoxicity.

Objective  To evaluate the effect of riluzole on cisplatin-induced ototoxicity in guinea pigs.

Methods  Twenty-four guinea pigs, studied in three groups, underwent auditory brainstem response evaluation using click and 8 kHz tone burst stimuli. Subsequently, 5 mg/kg of cisplatin were administered to all animals for 3 days intraperitoneally (i.p.) to induce ototoxicity. Half an hour prior to cisplatin, groups 1, 2 and 3 received 2 ml of saline i.p., 6 mg/kg of riluzole hydrochloride i.p., and 8 mg/kg of riluzole hydrochloride i.p., respectively, for 3 days. The auditory brainstem responses were repeated 24 hours after the last drug administration. The cochleae were analyzed by transmission electron microscopy (TEM).

Results  After drug administiration, for 8,000 Hz stimulus, group 1 had significantly higher threshold shifts when compared with groups 2 ( p  < 0.05) and 3 ( p  < 0.05), and there was no significant difference in threshold shifts between groups 2 and 3 ( p  > 0.05). Transmission electron microscopy findings demonstrated the protective effect of riluzole on the hair cells and the stria vascularis, especially in the group treated with 8 mg/kg of riluzole hydrochloride.

Conclusion  We can say that riluzole may have a protective effect on cisplatin- induced ototoxicity. However, additional studies are needed to confirm these results and the mechanisms of action of riluzole.

Non-autonomous Cellular Responses to Ototoxic Drug-Induced Stress and Death

The first major recognition of drug-induced hearing loss can be traced back more than seven decades to the development of streptomycin as an antimicrobial agent. Since then at least 130 therapeutic drugs have been recognized as having ototoxic side-effects. Two important classes of ototoxic drugs are the aminoglycoside antibiotics and the platinum-based antineoplastic agents. These drugs save the lives of millions of people worldwide, but they also cause irreparable hearing loss. In the inner ear, sensory hair cells (HCs) and spiral ganglion neurons (SGNs) are important cellular targets of these drugs, and most mechanistic studies have focused on the cell-autonomous responses of these cell types in response to ototoxic stress. Despite several decades of studies on ototoxicity, important unanswered questions remain, including the cellular and molecular mechanisms that determine whether HCs and SGNs will live or die when confronted with ototoxic challenge. Emerging evidence indicates that other cell types in the inner ear can act as mediators of survival or death of sensory cells and SGNs. For example, glia-like supporting cells (SCs) can promote survival of both HCs and SGNs. Alternatively, SCs can act to promote HC death and inhibit neural fiber expansion. Similarly, tissue resident macrophages activate either pro-survival or pro-death signaling that can influence HC survival after exposure to ototoxic agents. Together these data indicate that autonomous responses that occur within a stressed HC or SGN are not the only (and possibly not the primary) determinants of whether the stressed cell ultimately lives or dies. Instead non-cell-autonomous responses are emerging as significant determinants of HC and SGN survival vs. death in the face of ototoxic stress. The goal of this review is to summarize the current evidence on non-cell-autonomous responses to ototoxic stress and to discuss ways in which this knowledge may advance the development of therapies to reduce hearing loss caused by these drugs.

Ginkgo biloba and Lycopene are Effective on Cisplatin Induced Ototoxicity?

OBJECTIVE

The purpose of this study was to examine the anti-ototoxic impact of Ginkgo biloba extract and lycopene on the model of cisplatin-induced ototoxicity in rats.

MATERIALS AND METHODS

Thirty-two Wistar albino rats were examined with the distortion product otoacoustic emission (DPOAE) test (MADSEN Capella2 ; GN Otometrics, ICS Medical, Chicago USA), and they were randomly divided into four groups. Group 1 (n=8) was defined as the healthy control group. Cisplatin was given intraperitoneally as single dose of 12 mg/kg to group 2 (n=8), group 3 (n=8), and group 4 (n=8). Group 2 was determined as ototoxic control group. G. biloba extract (100 mg/kg) was given to group 3, and 20 mg/kg lycopene was given to group 4 with orogastric feeding tube daily for 10 days. DPOAE test was repeated on day 10 on all the groups. Finally, histopathological examination was performed. The study has been lead in agreement with the principles by the Institutional Animal Care and Use Committee Review Board at Kocaeli University Medical Center (KOÜ HADYEK- 1/9-14). The animals were treated in accordance with protocols approved by this committee.

RESULTS

When DPOAE tests were compared, there was no significant difference in the four groups before the application (p > 0.05). At the end of day 10, in groups 2 to 4, statistically significant changes were observed (p < 0.05). According to the cisplatin group, a significant increase in the DP-grams on G. biloba and lycopene groups was observed (p < 00.5). Corti organ and spiral ganglion neurons of groups 1, 3, and 4 were observed to have weak expression. Strong reactions were determined in organum spirale and some spiral ganglions of the cisplatin group. The striae vascularis damage on group 2 was found to be more significant more compared with groups 3 and 4.

CONCLUSION

There is a protective effect of G. biloba and lycopene on cisplatin-dependent ototoxic rat model.

Protective Effect of Selenium Against Cisplatin-Induced Ototoxicity in an Experimental Design

Cisplatin is an effective chemotherapeutic agent in the treatment of several types of malignant solid tumors but its clinical use is associated with ototoxicity. In the present study, we investigated the effect of selenium administration on lipid peroxidation (malondialdehyde [MDA]) and cisplatin-induced ototoxicity in rats. Healthy wistar albino rats (n = 21) were randomly divided into 3 groups: control (C), cisplatin (Cis), cisplatin and selenium (Cis+Se). Cisplatin was administered for 3 days to Cis and Cis+Se groups. Cis+Se group received selenium 5 days before cisplatin injection and continued for 11 consecutive days. Hearing thresholds and lipid peroxidation (MDA) levels of the rats were recorded before injections and at the end of experimental protocol. The cochleas of animals were harvested for histologic and immunuhistochemical examinations. In biochemichal analyses, pretreatment with selenium prevented the elevation of MDA levels in Cis+Se group rats. Moreover, animals in Cis+Se group had better hearing threshold levels than animals in cis group. Samples obtained from the animals in Cis group revealed extensive loss of the normal microarchitecture of the organ of Corti. On the other hand, animals in Cis+Se group exhibited a preservation of the morphology of the organ of Corti and outer hair cells. In the immunohistochemical examinations of cochlear tissues stained with anti-caspase-3, a higher degree of immunopositivity was found in the Cis group. When Cis+Se group and Cis group were compared, significantly less immunopositivity occurred in the Cis+Se group (P < 0.05). Thus, it appears that pretreatment with selenium may reduce cisplatin-induced ototoxicity in rats.

Coenzyme Q10 plus Multivitamin Treatment Prevents Cisplatin Ototoxicity in Rats

Cisplatin (Cpt) is known to induce a high level of oxidative stress, resulting in an increase of reactive oxygen species damaging the inner ear and causing hearing loss at high frequencies. Studies on animal models show that antioxidants may lower Cpt-induced ototoxicity. The aim of this study is to evaluate the ototoxic effects of two different protocols of Cpt administration in a Sprague-Dawley rat model, and to test in the same model the synergic protective effects of a solution of coenzyme Q10 terclatrate and Acuval 400®, a multivitamin supplement containing antioxidant agents and minerals (Acu-Qter). The Cpt was administered intraperitoneally in a single dose (14 mg/kg) or in three daily doses (4.6 mg/kg/day) to rats orally treated or untreated with Acu-Qter for 5 days. The auditory function was assessed by measuring auditory brainstem responses from 2 to 32 kHz at day 0 and 5 days after treatment. Similar hearing threshold and body weight alterations were observed in both Cpt administration protocols, but mortality reduced to zero when Cpt was administered in three daily doses. The Acu-Qter treatment was able to prevent and completely neutralize ototoxicity in rats treated with three daily Cpt doses, supporting the synergic protective effects of coenzyme Q terclatrate and Acuval 400® against Cpt-induced oxidative stress. The administration protocol involving three Cpt doses is more similar to common human chemotherapy protocols, therefore it appears more useful for long-term preclinical studies on ototoxicity prevention.

Pathophysiology of the cochlear intrastrial fluid-blood barrier (review)

The blood-labyrinth barrier (BLB) in the stria vascularis is a highly specialized capillary network that controls exchanges between blood and the intrastitial space in the cochlea. The barrier shields the inner ear from blood-born toxic substances and selectively passes ions, fluids, and nutrients to the cochlea, playing an essential role in the maintenance of cochlear homeostasis. Anatomically, the BLB is comprised of endothelial cells (ECs) in the strial microvasculature, elaborated tight and adherens junctions, pericytes (PCs), basement membrane (BM), and perivascular resident macrophage-like melanocytes (PVM/Ms), which together form a complex "cochlear-vascular unit" in the stria vascularis. Physical interactions between the ECs, PCs, and PVM/Ms, as well as signaling between the cells, is critical for controlling vascular permeability and providing a proper environment for hearing function. Breakdown of normal interactions between components of the BLB is seen in a wide range of pathological conditions, including genetic defects and conditions engendered by inflammation, loud sound trauma, and ageing. In this review, we will discuss prevailing views of the structure and function of the strial cochlear-vascular unit (also referred to as the "intrastrial fluid-blood barrier"). We will also discuss the disrupted homeostasis seen in a variety of hearing disorders. Therapeutic targeting of the strial barrier may offer opportunities for improvement of hearing health and amelioration of auditory disorders. This article is part of a Special Issue entitled <Annual Reviews 2016>.

Hearing and tinnitus in head and neck cancer patients after chemoradiotherapy

Head and neck cancer patients treated with high-dose cisplatin and radiotherapy will suffer from hearing deficits. The current low-dose regimen seldom causes hearing threshold decrease. Tinnitus in this patient population has not been investigated earlier. We aimed to evaluate the possible ototoxicity of low-dose (40 mg/m(2)) weekly administered cisplatin with concomitant radiotherapy. Twenty-two patients with locally advanced head and neck cancer were prospectively recruited to participate the study after treatment recommendation for chemoradiotherapy with low-dose cisplatin and intensity-modulated radiotherapy. They filled in a Tinnitus Handicap Inventory and undertook audiologic evaluations before and after treatment. Ototoxicity was determined by >10 dB threshold shift at frequencies 4 and 8 kHz or in pure tone average. A historical cohort of nine patients treated with high-dose (100 mg/m(2)) cisplatin and radiotherapy was used for comparison. After treatment, study patients demonstrated no significant changes in their hearing over frequencies 0.5-4 kHz, and the threshold shifts were minor at 4 and 8 kHz. More than 50 % of patients reported no tinnitus after treatment and the remainder only had slight to moderate tinnitus causing no interference with their daily activities. In contrast, five of the nine patients having received high-dose cisplatin reported disturbing tinnitus. Further, changes in pure tone averages were exhibited in three of these patients and six had significant threshold shifts at 4 and 8 kHz. Head and neck cancer patients treated with concomitant intensity-modulated radiotherapy and low-dose cisplatin seem to experience only minor audiological sequelae and therefore, these patients appear to require no routine audiological monitoring. Such evaluation could be performed only when needed.

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

Animal models of subjective tinnitus

Tinnitus is one of the major audiological diseases, affecting a significant portion of the ageing society. Despite its huge personal and presumed economic impact there are only limited therapeutic options available. The reason for this deficiency lies in the very nature of the disease as it is deeply connected to elementary plasticity of auditory processing in the central nervous system. Understanding these mechanisms is essential for developing a therapy that reverses the plastic changes underlying the pathogenesis of tinnitus. This requires experiments that address individual neurons and small networks, something usually not feasible in human patients. However, in animals such invasive experiments on the level of single neurons with high spatial and temporal resolution are possible. Therefore, animal models are a very critical element in the combined efforts for engineering new therapies. This review provides an overview over the most important features of animal models of tinnitus: which laboratory species are suitable, how to induce tinnitus, and how to characterize the perceived tinnitus by behavioral means. In particular, these aspects of tinnitus animal models are discussed in the light of transferability to the human patients.

Review: ototoxic characteristics of platinum antitumor drugs

Cisplatin, carboplatin, nedaplatin, and oxaliplatin are widely used in contemporary oncology; however, their ototoxic and neurotoxic side effects are quite different as discussed in this review. Cisplatin is considered the most ototoxic, but despite its reputation, the magnitude of hair cell loss that occurs with a single, large drug bolus is limited and confined to the base of the cochlea. For all of these platinum compounds, a major factor limiting damage is drug uptake from stria vascularis into the cochlear fluids. Disrupting the blood-labyrinth barrier with diuretics or noise exposure enhances drug uptake and significantly increases the amount of damage. Combined treatment with ethacrynic acid (a loop diuretic) and cisplatin results in rapid apoptotic hair cell death characterized by upregulation of initiator caspase-8 and membrane death receptor, TRADD, followed by downstream executioners, caspase-3 and caspase-6. Unlike cisplatin, nedaplatin and oxaliplatin are highly neurotoxic when applied to cochlear cultures preferentially damaging auditory nerve fibers at low concentrations and hair cells at high concentrations. Carboplatin, considered far less ototoxic than cisplatin, is paradoxically highly toxic to chinchilla inner hair cells and type I spiral ganglion neurons; however, at high doses it also damages outer hair cells. Hair cell death from cisplatin and carboplatin is characterized in its early stages by upregulation of p53; blocking p53 expression with pifithrin-α prevents hair cell death. Major differences in the toxicity of these four platinum compounds may arise from several different metal transporters that selectively regulate the influx, efflux, and sequestration of these drugs.

The protective effect of Ginkgo biloba extract against experimental cisplatin ototoxicity: animal research using distortion product otoacoustic emissions

BACKGROUND

Cisplatin, an effective therapeutic agent for various human cancers, has dose-limiting side effects of ototoxicity and nephrotoxicity. Cisplatin ototoxicity is thought to result from increased amounts of toxic free radicals or cell membrane changes leading to increased intracellular calcium content. Ginkgo biloba extract prevents lipid peroxidation, decreases intracellular free oxygen radical levels, regulates the cell membrane calcium transport mechanism and prevents cell death. This study aimed to investigate the protective effect of Ginkgo biloba extract against cisplatin-induced ototoxicity in rats.

METHODS

Twenty Wistar albino rats with normal hearing (confirmed by distortion product otoacoustic emission testing prior to cisplatin application) were randomly allocated to two groups. Both groups received a single intraperitoneal dose of cisplatin (12 mg/kg). Group two also received daily intraperitoneal doses of Ginkgo biloba extract (100 mg/kg) for 10 days. Distortion product otoacoustic emission measurements were repeated on days 10 and 17 and signal-to-noise ratios were compared.

RESULTS

Compared with group one, group two had significantly better distortion product otoacoustic emission results at 3, 4, 6 and 8 kHz on days 10 and 17.

CONCLUSION

These findings suggest that Ginkgo biloba extract protects the inner ear against cisplatin-induced ototoxicity.

Protective effects of vitamins E, B and C and l-carnitine in the prevention of cisplatin-induced ototoxicity in rats

Objective:

This experimental study aimed to investigate the effects of vitamins E, B and C and l-carnitine in preventing cisplatin-induced ototoxicity.

Methods:

Twenty-five adult, male, Wistar albino rats were randomly allocated to receive intraperitoneal cisplatin either alone or preceded by vitamins B, E or C or l-carnitine. Auditory brainstem response (i.e. hearing thresholds and wave I–IV intervals) and distortion product otoacoustic emissions (i.e. signal-to-noise ratios) were recorded before and 72 hours after cisplatin administration.

Results:

The following statistically significant differences were seen: control group pre- vs post-treatment wave I–IV interval values (p < 0.05); control vs vitamin E and B groups' I–IV interval values (p < 0.05); control vs other groups' hearing thresholds; vitamin E vs vitamin B and C and l-carnitine groups' hearing thresholds (p < 0.05); and vitamin B vs vitamin C and l-carnitine groups' hearing thresholds (p < 0.05). Statistically significant decreases were seen when comparing the initial and final signal-to-noise ratios in the control, vitamin B and l-carnitine groups (2000 and 3000 Hz; p < 0.01), and the initial and final signal-to-noise ratios in the control group (at 4000 Hz; p < 0.01).

Conclusion:

Vitamins B, E and C and l-carnitine appear to reduce cisplatin-induced ototoxicity in rats. The use of such additional treatments to decrease cisplatin-induced ototoxicity in humans is still under discussion.

Spontaneous reversibility of damage to outer hair cells after sodium salicylate induced ototoxicity

BACKGROUND

High sodium salicylate doses can cause reversible hearing loss and tinnitus, possibly due to reduced outer hair cell electromotility. Sodium salicylate is known to alter outer hair cell structure and function. This study determined the reversibility and cochlear recovery time after administration of an ototoxic sodium salicylate dose to guinea pigs with normal cochlear function.

STUDY DESIGN

Prospective experimental investigation.

METHODS

All animals received a single 500 mg sodium salicylate dose, but with different durations of action. Function was evaluated before drug administration and immediately before sacrifice. Cochleae were processed and viewed using scanning electron microscopy.

RESULTS

Changes in outer hair cell function were observed to be present 2 hours after drug administration, with recovery of normal anatomy beginning after 24 hours. Subsequently, derangement and distortion of cilia reduced, with effects predominantly in row three. At 168 hours, cilia were near-normal but with mild distortions which interfered with normal cochlear physiology.

CONCLUSIONS

Ciliary changes persisted for up to 168 hours after ototoxic sodium salicylate administration.

Cisplatin ototoxicity in rat cochlear organotypic cultures

Ototoxicity is a dose-limiting side effect of chemotherapeutic treatment with cisplatin. In a series of experiments on neonatal rat cochlear organotypic cultures, the extent of damage induced by a broad range of cisplatin treatment concentrations was examined. Paradoxically, it was found that hair cell loss was greater following 48 h exposure to low (10, 50 and 100 μM) versus high (400 and 1000 μM) concentrations of cisplatin; these findings indicate that hair cells possess intrinsic resistance to high levels of extracellular cisplatin. Using cisplatin conjugated to Alexa Fluor 488, it was found that cisplatin is readily taken up by hair cells at low concentrations, but is largely excluded at high concentrations. Recent studies indicate that the major influx of cisplatin into hair cells occurs via the copper transporter, Ctr1, whereas ATP7A and ATP7B are copper pumps responsible for cisplatin sequestration and efflux. Using immunolabeling procedures for these copper trafficking proteins, it was found that Ctr1 and ATP7B were localized in the hair cells, whereas ATP7A showed extensive labeling in the pillar cells in the organ of Corti. Additional experiments confirmed the protective effect of copper sulfate and cimetidine in attenuating cisplatin-induced hair cell loss. However, because neither copper sulfate nor cimetidine provided complete protection against cisplatin, and high levels of copper sulfate itself were found to be ototoxic, it is suggested that future therapeutic efforts may benefit from a combination of pharmacological treatments which seek to not only limit the uptake of cisplatin into cochlear cells but also increase its efflux.

Hearing impairment after platinum-based chemotherapy in childhood

BACKGROUND

Chemotherapy is used in the treatment of children and adolescents with malignant diseases. Some of the chemotherapeutic agents are highly toxic and may cause a number of side effects. The primary objective of this study was to evaluate the long-term effects on hearing in cancer survivors who had received platinum-based chemotherapy in childhood or adolescence.

PROCEDURE

Medical records of 297 patients, who had received treatment for cancer at the Children's Hospital, Landspitali University Hospital in Iceland between 1981 and 2006, were retrospectively reviewed. Fifteen subjects fulfilled the eligibility criteria for the study and underwent an extended audiometric evaluation.

RESULTS

The results showed that three of the subjects had a high frequency hearing loss. In one subject, we observed a hearing recovery just after the completion of chemotherapy, but the hearing deteriorated again some years later. Nine of the 15 subjects (60%) had tinnitus after the cancer treatment. An evaluation of subjective hearing disability and handicap (The Hearing Measurements Scale) revealed that some subjects had great difficulties with hearing in certain situations. The Hearing Measurement Scale showed that the pure-tone audiogram findings were only partly associated with the apparent hearing difficulties.

CONCLUSION

Regular follow-up hearing examinations, which include both pure-tone audiogram investigations and subjective hearing disability assessments, should be performed during and after chemotherapy to identify subjects who require particular attention. This will ensure that hearing impaired individuals are provided with the most suitable listening devices, to promote good speech and social development.

Role of the copper transporter, CTR1, in platinum-induced ototoxicity

The goal of this study was to determine the role of an influx copper transporter, CTR1, in the ototoxicity induced by cisplatin, a potent anticancer platinum analog used in the treatment of a variety of solid tumors. As determined through reverse transcriptase-PCR (RT-PCR), quantitative RT-PCR, Western blot, and immunohistochemistry, mouse CTR1 (Ctr1) was found to be abundantly expressed and highly localized at the primary sites of cisplatin toxicity in the inner ear, mainly outer hair cells (OHCs), inner hair cells, stria vascularis, spiral ganglia, and surrounding nerves in the mouse cochlea. A CTR1 substrate, copper sulfate, decreased the uptake and cytotoxicity of cisplatin in HEI-OC1, a cell line that expresses many molecular markers reminiscent of OHCs. Small interfering RNA-mediated knockdown of Ctr1 in this cell line caused a corresponding decrease in cisplatin uptake. In mice, intratympanic administration of copper sulfate 30 min before intraperitoneal administration of cisplatin was found to prevent hearing loss at click stimulus and 8, 16, and 32 kHz frequencies. To date, the utility of cisplatin remains severely limited because of its ototoxic effects. The studies described in this report suggest that cisplatin-induced ototoxicity and cochlear uptake can be modulated by administration of a CTR1 inhibitor, copper sulfate. The possibility of local administration of CTR1 inhibitors during cisplatin therapy as a means of otoprotection is thereby raised.

Effects of hyperbaric oxygen treatment on auditory hair cells after acute noise damage

Acute acoustic trauma (AAT) is a sudden sensorineural hearing loss caused by exposure of the hearing organ to acoustic overstimulation, typically an intense sound impulse, hyperbaric oxygen therapy (HOT), which favors repair of the microcirculation, can be potentially used to treat it. Hence, this study aimed to assess the effects of HOT on guinea pigs exposed to acoustic trauma. Fifteen guinea pigs were exposed to noise in the 4-kHz range with intensity of 110 dB sound level pressure for 72 h. They were assessed by brainstem auditory evoked potential (BAEP) and by distortion product otoacoustic emission (DPOAE) before and after exposure and after HOT at 2.0 absolute atmospheres for 1 h. The cochleae were then analyzed using scanning electron microscopy (SEM). There was a statistically significant difference in the signal-to-noise ratio of the DPOAE amplitudes for the 1- to 4-kHz frequencies and the SEM findings revealed damaged outer hair cells (OHC) after exposure to noise, with recovery after HOT (p = 0.0159), which did not occur on thresholds and amplitudes to BAEP (p = 0.1593). The electrophysiological BAEP data did not demonstrate effectiveness of HOT against AAT damage. However, there was improvement of the anatomical pattern of damage detected by SEM, with a significant reduction of the number of injured cochlear OHC and their functionality detected by DPOAE.

Cisplatin ototoxicity blocks sensory regeneration in the avian inner ear

Cisplatin is a chemotherapeutic agent that is widely used in the treatment of solid tumors. Ototoxicity is a common side effect of cisplatin therapy and often leads to permanent hearing loss. The sensory organs of the avian ear are able to regenerate hair cells after aminoglycoside ototoxicity. This regenerative response is mediated by supporting cells, which serve as precursors to replacement hair cells. Given the antimitotic properties of cisplatin, we examined whether the avian ear was also capable of regeneration after cisplatin ototoxicity. Using cell and organ cultures of the chick cochlea and utricle, we found that cisplatin treatment caused apoptosis of both auditory and vestibular hair cells. Hair cell death in the cochlea occurred in a unique pattern, progressing from the low-frequency (distal) region toward the high-frequency (proximal) region. We also found that cisplatin caused a dose-dependent reduction in the proliferation of cultured supporting cells as well as increased apoptosis in those cells. As a result, we observed no recovery of hair cells after ototoxic injury caused by cisplatin. Finally, we explored the potential for nonmitotic hair cell recovery via activation of Notch pathway signaling. Treatment with the gamma-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester failed to promote the direct transdifferentiation of supporting cells into hair cells in cisplatin-treated utricles. Taken together, our data show that cisplatin treatment causes maintained changes to inner ear supporting cells and severely impairs the ability of the avian ear to regenerate either via proliferation or by direct transdifferentiation.

Differential sensitivity of the inner ear sensory cell populations to forced cell cycle re-entry and p53 induction

Previous studies have shown that the maintenance of post-mitotic state is critical for the life-long survival of the inner ear mechanosensory cells, the hair cells. A general concept is that differentiated, post-mitotic cells rapidly die following cell cycle re-entry. Here we have compared the response of postnatal cochlear (auditory) and utricular (balance) hair cells to forced cell cycle reactivation and p53 up-regulation. Forced S-phase entry was triggered through the human papillomavirus-16 E7 oncogene misexpression in explant cultures. It induced DNA damage and p53 induction in cochlear outer hair cells and these cells were rapidly lost, before entry into mitosis. The death was attenuated by p53 inactivation. In contrast, despite DNA damage and p53 induction, utricular hair cells showed longer term survival and a proportion of them progressed into mitosis. Consistently, pharmacological elevation of p53 levels by nutlin-3a led to a death-prone phenotype of cochlear outer hair cells, while other hair cell populations were death-resistant. These data have important clinical implications as they show the importance of p53 in sensory cells that are essential in hearing function.

Distortion-product otoacoustic emissions and auditory brainstem responses sensitivity assessment in cisplatin-induced ototoxicity in rats

Cisplatin (cis-diamminedicloroplatinum) is an antineoplastic drug used in the treatment of a variety of cancers, especially head-and-neck cancer. Its ototoxicity, however, has been noted as a common side-effect which limits its use and causes significant morbidity.

Aim

to assess distortion-product otoacoustic emissions (DPOAE) and brainstem evoked response audiometry (BERA) sensitivity to detect secondary ototoxicity caused by different doses and means of administration of cisplatin in rats.

Study Design

Experimental.

Materials and Methods

Male Wistar rats were intraperitoneally (i.p.) injected with 24 mg/kg cisplatin, divided into three equal doses (8mg/kg) or a single i.p. injection of 16 mg/kg. The animals were evaluated by distortion product otoacoustic emission (DPOAE) or brainstem evoked response audiometry (BERA) on the 3rd and 4th days after the cisplatin injection.

Results

Treatment with cisplatin 24 mg/kg resulted in significant DPOAE decrease and it raised the BERA electrophysiological threshold. The 16mg/kg dose could not significantly reduce the DPOAE amplitude, but it raised the animals' hearing thresholds – detected by the BERA.

Conclusion

In rats, BERA was more sensitivity than DPOAE at detecting cisplatin-induced ototoxicity in rats considering different doses and means of administration.

The role of hyperbaric oxygen therapy (hot) as an otoprotection agent against cisplatin ototoxicity

PURPOSE

Hyperbaric oxygen therapy (HOT) consists of intermittent inhalations of 100% oxygen at a pressure higher than 1 atm. It is an important adjuvant therapy in pathological processes like soft tissue infections, radiation injury, gas gangrene, osteomyelitis and decompressive diseases. Cisplatin, a potent antineoplastic drug, widely used in cancer therapy is highly ototoxic causing bilateral, irreversible damage to the hearing of high frequency sounds (4-8 KHz).

OBJECTIVE

This experimental study conducted at the Faculty of Medicine of Ribeirao Preto, University of Sao Paulo aims to evaluate Hyperbaric Oxygen Therapy as an otoprotection agent against drug toxicity.

METHODS

Albino guinea pigs were divided into two groups: in Group A, 5 animals (10 cochlea) received cisplatin, i. p., 8.0 mg/kg/day during three days and afterwards were submitted to HOT; in Group B, 3 animals (6 cochlea) received cisplatin, i. p. 8.0 mg/kg/day during three days. Guinea pigs were evaluated by acoustic otoemissions (AOE) and scanning electron microscopy (SEM).

RESULTS

Group B animals showed loss of auditory functions as measured by AOE and distorted outer hair cells by SEM. In Group A, outer hair cells shown by SEM images were mostly preserved.

CONCLUSION

It is presumed that Hyperbaric Oxygen Therapy has a protector effect against cisplatin ototoxicity.

DNA repair proteins and telomerase reverse transcriptase in the cochlear lateral wall of cisplatin-treated rats

Cochlear lateral wall damage is a side effect of cisplatin chemotherapy. Recent studies have shown that cisplatin treatment precipitates platinated DNA adducts in the cochlear lateral wall which suggest that DNA damage may contribute to ototoxicity. Platinated adducts are high-affinity substrates for the global genomic nucleotide excision repair (GG-NeR) pathway which is facilitated by xeroderma pigmentosum (Xp) complementing proteins, such as XpC, XpD and XpA. tumor biology has shown that in addition to stimulating GG-NeR, cisplatin may deplete telomerase reverse transcriptase (teRt). in the current study Fischer344 rats were treated with cisplatin (2 mg/kg/4 days, i.p.) and their cochleae harvested for immunohistochemistry. XpC, XpD and XpA expression increased while teRt expression decreased among cisplatin treated animals compared to vehicle control. these findings suggest that in addition to forming platinated adducts, cisplatin chemotherapy may up-regulate DNA repair proteins and modify teRt expression in the cochlear lateral wall.

Light microscopy study of cisplatin-induced ototoxicity in rats

BACKGROUND

Although most studies on animal ototoxicity employ scanning electron microscopy, all cochlear structures may be identified with light microscopy. This paper describes a simple method of histological assessment of cisplatin-induced ototoxicity in rats, and relates morphological changes to functional changes in hearing detected by distortion product evoked otoacoustic emissions.

MATERIALS AND METHODS

Male Wistar rats were injected with 8 mg/kg/day cisplatin, or with an equivalent volume of saline solution, for three consecutive days. They underwent distortion product evoked otoacoustic emission testing at baseline and at 24 or 48 hours after the last administration. At the end of the experiment, the animals were sacrificed and their cochleae were retrieved and prepared for haematoxylin and eosin staining.

RESULTS

A four-point scoring system was used to grade injury to the external ciliated cells, as indicated by the number of cells absent from the basal turn of the cochlear duct. A four-point scoring system was also used to grade stria vascularis injury, as indicated by the degree of shrinkage of the intermediate cells. Scores were significantly higher in groups treated with cisplatin compared with controls. Morphological changes were confirmed by decreased distortion product evoked otoacoustic emission amplitudes in animals treated with cisplatin.

CONCLUSION

This method is simple to perform with routine histology equipment and is appropriate for the study of acute, cisplatin-induced ototoxicity in rats.

Proapoptotic effects of NF-kappaB on cisplatin-induced cell death in auditory cell line

CONCLUSIONS

The findings suggest that nuclear factor (NF)-kappaB is activated by cisplatin and plays a proapoptotic role during cell death in the auditory cell line HEI-OC1.

OBJECTIVES

Cisplatin is a very effective antineoplastic drug but in high doses it shows ototoxicity by inducing apoptosis of hair cells in the cochlea. NF-kappaB is a transcription factor regulating apoptosis in many organs and tissues. This study examined the role of NF-kappaB in the apoptotic pathway induced by cisplatin in the auditory cell line, HEI-OC1.

MATERIALS AND METHODS

Apoptotic cell death was identified by measuring caspase 3 activity and immunostaining with anti-caspase 3 antibody after cisplatin treatment (50 microM) for 24 h. To investigate the role of NF-kappaB in apoptotic cell death, HEI-OC1 cells treated with 50 microM of cisplatin were immunostained with anti-NF-kappaB (p65) antibody. Two different NF-kappaB inhibitors, Bay 11-7085 and SN-50, were co-incubated with cisplatin (50 microM) for 24 h and caspase 3 activity was assayed.

RESULTS

Immunostaining with anti-caspase 3 antibody and caspase 3 assay showed that cisplatin induced apoptosis in HEI-OC1 cells. After cisplatin treatment, NF-kappaB (p65) was activated to translocate from the cytoplasm into the nucleus. Co-treatment with NF-kappaB inhibitors reduced the cisplatin-induced apoptosis of HEI-OC1 cells.

Secondary apoptosis of spiral ganglion cells induced by aminoglycoside: Fas-Fas ligand signaling pathway

OBJECTIVES/HYPOTHESIS

Hair cell loss results in the secondary loss of spiral ganglion neurons (SGNs), over a period of several weeks. The death of the SGNs themselves results from apoptosis. Previous studies have shown that several molecules are involved in the apoptosis of SGNs that occurred secondary to hair cell loss. However, the precise mechanism of apoptosis of the SGNs remains unclear. The aim of this study was to ascertain the secondary apoptosis of spiral ganglion cells induced by aminoglycoside and to investigate the role of the Fas-FasL signaling pathway using guinea pigs as an experimental animal model.

STUDY DESIGN

Laboratory study using experimental animals.

METHODS

Guinea pigs weighing 250 to 300 g (n = 21) from 3 to 4 weeks of age were used. Gentamicin (60 microL) was injected through a cochleostomy site on their left side. At 1 (n = 7), 2 (n = 7), and 3 (n = 7) weeks after gentamicin treatment, their cochleas were obtained from their temporal bone. Hematoxylin and eosin and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling staining were performed to observe apoptosis. To investigate the involvement of the Fas-FasL signaling pathway in the secondary apoptosis of SGNs, we performed reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and immunohistochemistry.

RESULTS

A progressive loss of spiral ganglion cells with increasing time after gentamicin treatment was observed on light microscopic examination. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling staining demonstrated induction of apoptotic cell death in SGNs after gentamicin treatment. Expression of FasL increased over time after gentamicin treatment as determined by RT-PCR and western blotting. On immunohistochemical staining, we observed the localization of FasL in the SGNs. The proapoptotic molecules Bax and Bad were increased, but levels of the antiapoptotic molecule Bcl-2 were decreased at increasing survival times after gentamicin treatment on RT-PCR. The gentamicin-treated group displayed initial activation of caspase-8 and increased the cleavage of caspase-3, caspase-8, and PARP protein in a time-dependent manner.

CONCLUSIONS

The secondary apoptosis of SGNs could be a result of the apoptotic Fas-FasL signaling pathway. Blocking the Fas-FasL signaling pathway could be considered as a method for preventing secondary degeneration of SGNs, and further studies are needed to confirm this.

Cisplatin ototoxicity and otoprotection with sodium salicylate

Cisplatin is a potent antineoplastic drug widely used for the treatment of cancer in both adults and children. One of its most important side effects is ototoxicity, which leads to irreversible bilateral hearing loss for high frequencies (4-8 kHz). Several studies have tried to identify drugs that, when combined with cisplatin, may act as otoprotectors. The mechanism of ototoxicity of cisplatin is known to be related to changes in the antioxidant mechanisms of hair cells, especially the outer hair cells of the cochlea. Our proposal was to assess the action of sodium salicylate, which has a known antioxidant property, as a possible otoprotector of outer hair cells against the action of cisplatin, using distortion product otoacoustic emissions (DPOAEs) and scanning electron microscopy. The study was conducted on albino guinea pigs divided into two groups: group 1 (n = 9, 18 cochleae) receiving a cisplatin dose of 8.0 mg/kg/day by the intraperitoneal (ip) route for 3 days, group 2 (n = 10, 20 cochleae) receiving 100 mg/kg sodium salicylate by the subcutaneous route followed 90 min later by cisplatin, 8.0 mg/kg/day ip for 3 days, and group 3 (n = 3, six cochleae) treated with 100 mg/kg day sodium salicylate for 3 days. In group 1, there was damage with the absence of cilia in all three rows of outer hair cells in the basal turn, followed by turns 2 and 3. In group 2, hair cells were present in all cochlear turns, but exhibited disarrangement of the ciliary structure, especially in row 1, and the DPOAEs were absent after 3 days of treatment. We conclude that drugs such as sodium salicylate, because of their antioxidant properties, may protect, at least partially, the outer hair cells against cisplatin ototoxicity.

The cochlear targets of cisplatin: an electrophysiological and morphological time-sequence study

Cisplatin ototoxicity has at least three major targets in the cochlea: the stria vascularis, the organ of Corti, and the spiral ganglion. This study aims to differentiate between these three targets. In particular, we address the question of whether the effects at the level of the organ of Corti and spiral ganglion are mutually dependent or whether they develop in parallel. This question was approached by studying the ototoxic effects while they develop electrophysiologically and comparing these to earlier presented histological data [Van Ruijven et al., 2004. Hear. Res. 197, 44-54]. Guinea pigs were treated with intraperitoneal injections of cisplatin at a dose of 2 mg/kg/day for either 4, 6, or 8 consecutive days. This time sequence has not revealed any evidence of one ototoxic process triggering another. Therefore, we have to stay with the conclusion of Van Ruijven et al. (2004) that both processes run in parallel.

Immunohistochemical detection of platinated DNA in the cochlea of cisplatin-treated guinea pigs

Cisplatin-induced ototoxicity is correlated with functional and morphological changes in the organ of Corti, the stria vascularis and the spiral ganglion. However, the cochlear sites of cisplatin uptake and accumulation have not been properly identified. Therefore, we have developed an immunohistochemical method to, indirectly, detect cisplatin in semithin cryosections of the guinea pig cochlea (basal turn) using an antiserum containing antibodies against cisplatin-DNA adducts. Platinated DNA was present in the nuclei of most cells in the organ of Corti and the lateral wall after cisplatin administration. Nuclear immunostaining was most pronounced in the outer hair cells, the marginal cells and the spiral ligament fibrocytes. This study is the first to demonstrate the presence of cisplatin in histological sections of the cochlea.

Otoproteção da amifostina aos efeitos ototóxicos da cisplatina: estudo em cobaias albinas por emissões otoacústicas produtos de distorção e microscopia eletrônica de varredura

A Cisplatina é uma potente droga antineoplásica, largamente utilizada para o tratamento do câncer, tanto em adultos quanto em crianças. Dentre seus efeitos colaterais, a ototoxicidade se apresenta como um dos mais importantes e leva à perda auditiva irreversível, bilateral, para as altas freqüências (4KHz -8KHz). Estudos têm tentado identificar drogas que, associadas à cisplatina, possam atuar como otoprotetores. Sabe-se que o mecanismo da ototoxicidade pela cisplatina está relacionado a alterações nos mecanismos antioxidantes das células ciliadas, principalmente as células ciliadas externas da cóclea. A amifostina tem conhecida ação antioxidante, com conhecido efeito otoprotetor aos efeitos lesivos da radioterapia. OBJETIVO: Nossa proposta foi avaliar através de emissões otoacústicas, por produtos de distorção (EOAPD) e por microscopia eletrônica de varredura (MEV), a existência de possível efeito otoprotetor da amifostina no tratamento com cisplatina. FORMA DE ESTUDO: Experimental. MATERIAL E MÉTODO: O estudo foi realizado em cobaias albinas, que foram divididas em três grupos: Grupo 1: 6 animais -12 orelhas - cisplatina 8,0 mg/Kg/dia (via intraperitoneal) por três dias; Grupo 2: 6 animais - 12 orelhas - amifostina 100 mg/Kg/ dia (via intraperitoneal) e 90 minutos após, cisplatina 8,0 mg/Kg/dia (via intraperitoneal) por três dias; Grupo 3: 03 animais - 06 orelhas - amifostina 100 mg/Kg/dia (via intraperitoneal) por três dias. RESULTADO: Encontramos EOAPD presentes e células ciliadas externas presentes, sem lesão anatômica a MEV, nos grupos 2 e 3. Concluímos que a amifostina, por sua ação antioxidante, atua como otoprotetor a ototoxicidade pela cisplatina. No entanto, seu uso não é recomendável nos casos de tumores potencialmente curáveis, por não se saber exatamente a influência da cisplatina na eficácia da quimioterapia.

Amifostine otoprotection to cisplatin ototoxicity: a guinea pig study using otoacoustic emission distortion products (DPOEA) and scanning electron microscopy

Cisplatin is an antineoplastic drug for cancer treatment in children and adults. The side effects of cisplatin ototoxicity are significant: irreversible bilateral hearing damage to high frequencies (4 kHz - 8 kHz). Reports recognize some drugs that are associated with cisplatin to obtain an otoprotector effect. The ototoxicity mechanisms of cisplatin are related to injury of hair cell oxidation mechanism, especially of outer hair cells. Aim: Using otoacoustic emissions distortion products (DPOEA) and scanning electron microscopy we intended to verify the action of amifostine, a radioprotective drug that has well known antioxidant characteristics and otoprotector effects to cisplatin injury. Study design: Experimental. Material and Method: We used an experimental guinea pig model. The study was performed as follows: group 1: 6 animals, 12 ears, cisplatin 8.0 mg/Kg/day (IP), 3 days. Group 2: 6 animals, 12 ears, amifostine 100 mg/Kg/day (IP) and after 90 minutes, cisplatin 8.0 mg/Kg/day (IP), 3 days and group 3: 3 animals, 6 ears, amifostine 100 mg/Kg/day (IP), 3 days. Results: DPOEA were present before and after treatment in groups 2 and 3. The normal cilium architecture of outer hair cells was supported in all cochlear turns in groups 2 and 3. We concluded that amifostine has a potential otoprotector effect against cisplatin ototoxicity and could be used in clinical trials.

Acceleration of cisplatin ototoxicity by perilymphatic application of 4-methylthiobenzoic acid

The antitumor agent cisplatin has dose-limiting side effects such as ototoxicity. Systemical co-treatment with anti-oxidants like 4-methylthiobenzoic acid (MTBA) and sodium thiosulfate (STS) provides protection against cisplatin ototoxicity. However, systemically administered protective agents may reduce the chemotherapeutic effect of cisplatin. Local application of the protective agents could avoid this undesirable effect. In the present study, we aimed at suppressing cisplatin-induced ototoxicity in guinea pigs by administering MTBA or STS perilymphatically through cochlear perfusion. Guinea pig cochleas were perfused for 10 min with artificial perilymph (ArtP) containing cisplatin at 0.3 mg/ml, either alone, or in combination with MTBA (0.1 or 1.0 mg/ml) or STS (0.75 or 3.0 mg/ml). The compound action potential (CAP) and the summating potential (SP), evoked by 8 kHz tone bursts, and the endocochlear potential (EP; MTBA only) were measured just before and 1, 2, 3 and 4 h after perfusion. Cisplatin gradually reduced the CAP amplitude in time. Adding MTBA only accelerated this ototoxic effect. After cisplatin treatment a decline was found in the EP, irrespective of co-treatment, i.e., addition of MTBA did not accelerate the EP decrease. In contrast to MTBA, STS ameliorated the ototoxic effect of cisplatin. In conclusion, local application of anti-oxidants can ameliorate cisplatin ototoxicity but this is not a feature of all anti-oxidants.