Protective effect of N-acetylcysteine against cisplatin ototoxicity in rats: a study with hearing tests and scanning electron microscopy

Nanodelivery of antioxidant Agents: A promising strategy for preventing sensorineural hearing loss

Sensorineural hearing loss (SNHL), often stemming from reactive oxygen species (ROS) generation due to various factors such as ototoxic drugs, acoustic trauma, and aging, remains a significant health concern. Oxidative stress-induced damage to the sensory cells of the inner ear, particularly the non-regenerating hair cells, is a critical pathologic mechanism leading to SNHL. Despite the proven efficacy of antioxidants in mitigating oxidative stress, their clinical application for otoprotection is hindered by the limitations of conventional drug delivery methods. This review highlights the challenges associated with systemic and intratympanic administration of antioxidants, including the blood-labyrinthine barrier, restricted permeability of the round window membrane, and inadequate blood flow to the inner ear. To overcome these hurdles, the application of nanoparticles as a delivery platform for antioxidants emerges as a promising solution. Nanocarriers facilitate indirect drug delivery to the cochlea through the round and oval window membrane, optimising drug absorption while reducing dosage, Eustachian tube clearance, and associated side effects. Furthermore, the development of nanoparticles carrying antioxidants tailored to the intracochlear environment holds immense potential. This literature research aimed to critically examine the root causes of SNHL and ROS overproduction in the inner ear, offering insights into the application of nanoparticle-based drug delivery systems for safeguarding sensorineural hair cells. By focusing on the intricate interplay between oxidative stress and hearing loss, this research aims to contribute to the advancement of innovative therapeutic strategies for the prevention of SNHL.

Efficacy and Mechanisms of Antioxidant Compounds and Combinations Thereof against Cisplatin-Induced Hearing Loss in a Rat Model

Cisplatin is an election chemotherapeutic agent used for many cancer treatments. Its cytotoxicity against neoplastic cells is mirrored by that taking place in healthy cells and tissues, resulting in serious adverse events. A very frequent one is ototoxicity, causing hearing loss which may permanently affect quality of life after successful oncologic treatments. Exacerbated oxidative stress is a main cytotoxic mechanism of cisplatin, including ototoxicity. Previous reports have shown antioxidant protection against cisplatin ototoxicity, but there is a lack of comparative studies on the otoprotectant activity and mechanism of antioxidant formulations. Here, we show evidence that a cocktail of vitamins A, C, and E along with Mg++ (ACEMg), previously shown to protect against noise-induced hearing loss, reverses auditory threshold shifts, promotes outer hair cell survival, and attenuates oxidative stress in the cochlea after cisplatin treatment, thus protecting against extreme cisplatin ototoxicity in rats. The addition of 500 mg N-acetylcysteine (NAC), which, administered individually, also shows significant attenuation of cisplatin ototoxicity, to the ACEMg formulation results in functional degradation of ACEMg otoprotection. Mg++ administered alone, as MgSO4, also prevents cisplatin ototoxicity, but in combination with 500 mg NAC, otoprotection is also greatly degraded. Increasing the dose of NAC to 1000 mg also results in dramatic loss of otoprotection activity compared with 500 mg NAC. These findings support that single antioxidants or antioxidant combinations, particularly ACEMg in this experimental series, have significant otoprotection efficacy against cisplatin ototoxicity. However, an excess of combined antioxidants and/or elevated doses, above a yet-to-be-defined "antioxidation threshold", results in unrecoverable redox imbalance with loss of otoprotectant activity.

Hear and Now: Ongoing Clinical Trials to Prevent Drug-Induced Hearing Loss

Each year over half a million people experience permanent hearing loss caused by treatment with therapeutic drugs with ototoxic side effects. There is a major unmet clinical need for therapies that protect against this hearing loss without reducing the therapeutic efficacy of these lifesaving drugs. At least 17 clinical trials evaluating 10 therapeutics are currently underway for therapies aimed at preventing aminoglycoside- and/or cisplatin-induced ototoxicity. This review describes the preclinical and clinical development of each of these approaches, provides updates on the status of ongoing trials, and highlights the importance of appropriate outcome measures in trial design and the value of reporting criteria in the dissemination of results.

Effect of N-Acetylcysteine on Cisplatin Toxicity: A Review of the Literature

N-acetylcysteine (NAC) is a membrane-permeable cysteine precursor capable of enhancing the intracellular cysteine pool, enhancing cellular glutathione (GSH) synthesis, and thus potentiating the endogenous antioxidant mechanism. Late administration of NAC after cisplatin has been shown in different in vivo studies to reduce the side effects caused by various toxicities at different levels without affecting the antitumor efficacy of platinum, improving total and enzymatic antioxidant capacity and decreasing oxidative stress markers. These characteristics provide NAC with a rationale as a potentially effective chemo protectant in cisplatin-based therapeutic cycles. NAC represents a potential candidate as a chemoprotective agent to decrease toxicities secondary to cisplatin treatment. It suggests that it could be used in clinical trials, whereby the effective dose, timing, and route should be adjusted to optimize chemoprotection. This review provides an overview of the effect of NAC on cisplatin toxicity, a drug widely used in the clinic in adults and children.

Effects of natural products on cisplatin ototoxicity and chemotherapeutic efficacy

INTRODUCTION

Cisplatin is a very effective chemotherapeutic agent against a variety of solid tumors. Unfortunately, cisplatin causes permanent sensorineural hearing loss in at least two-thirds of patients treated. There are no FDA approved drugs to prevent this serious side effect.

AREAS COVERED

This paper reviews various natural products that ameliorate cisplatin ototoxicity. These compounds are strong antioxidants and anti-inflammatory agents. This review includes mostly preclinical studies but also discusses a few small clinical trials with natural products to minimize hearing loss from cisplatin chemotherapy in patients. The interactions of natural products with cisplatin in tumor-bearing animal models are highlighted. A number of natural products did not interfere with cisplatin anti-tumor efficacy and some agents actually potentiated cisplatin anti-tumor activity.

EXPERT OPINION

There are a number of natural products or their derivatives that show excellent protection against cisplatin ototoxicity in preclinical studies. There is a need to insure uniform standards for purity of drugs derived from natural sources and to ensure adequate pharmacokinetics and safety of these products. Natural products that protect against cisplatin ototoxicity and augment cisplatin's anti-tumor effects in multiple studies of tumor-bearing animals are most promising for advancement to clinical trials. The most promising natural products include honokiol, sulforaphane, and thymoquinone.

Curcumin Prevents Ototoxicity Induced by Cisplatin as Evaluated with OAE

Introduction

This study, assess the efficacy of curcumin therapy in preventing/improving cochlear damage in Rattus norvegicus ototoxic model as evaluated with OAE examination.

Materials and Methods

This study utilized 27 rats which had been injected with single dose 8mg/KgBB of cisplatin, and then divided into 3 groups. The first group was not given curcumin. The second group received curcumin at a dose of 150 mg/KgBB. The third group received curcumin at a dose of 300 mg/KgBB. Curcumin was given from the time of single dose cisplatin injection (day 0) to day 7. OAE examination was performed on the day before the single dose of cisplatin (day 0), day 3, 4 and 7 after curcumin administration.

Results

There was a decline in the average value of SNR in all groups starting from high frequency. However, in the rat groups receiving curcumin there was a slow decrease in the SNR value, which also obtained statistically significant differences in the SNR values of all groups.

Conclusion

Administration of certain doses of curcumin may reduce the modest and statistically insignificant decrease in mean SNR values indicating a reduction in ototoxicity from cisplatin.

N-Acetyl-L-cysteine Affects Ototoxicity Evoked by Amikacin and Furosemide Either Alone or in Combination in a Mouse Model of Hearing Threshold Decrease

Drug-induced ototoxicity resulting from therapy with aminoglycoside antibiotics and loop diuretics is one of the main well-known causes of hearing loss in patients. Unfortunately, no specific protection and prevention from hearing loss are recommended for these patients. This study aimed at evaluating the ototoxic effects produced by mixtures of amikacin (AMI, an aminoglycoside antibiotic) and furosemide (FUR, a loop diuretic) in the mouse model as the hearing threshold decreased by 20% and 50% using auditory brainstem responses (ABRs). Ototoxicity was produced by the combinations of a constant dose of AMI (500 mg/kg; i.p.) on FUR-induced hearing threshold decreases, and a fixed dose of FUR (30 mg/kg; i.p.) on AMI-induced hearing threshold decreases, which were determined in two sets of experiments. Additionally, the effects of N-acetyl-L-cysteine (NAC; 500 mg/kg; i.p.) on the hearing threshold decrease of 20% and 50% were determined by means of an isobolographic transformation of interactions to detect the otoprotective action of NAC in mice. The results indicate that the influence of a constant dose of AMI on FUR-induced hearing threshold decreases was more ototoxic in experimental mice than a fixed dose of FUR on AMI-induced ototoxicity. Moreover, NAC reversed the AMI-induced, but not FUR-induced, hearing threshold decreases in this mouse model of hearing loss. NAC could be considered an otoprotectant in the prevention of hearing loss in patients receiving AMI alone and in combination with FUR.

Therapeutic role of N-acetyl cysteine (NAC) for the treatment and/or management of SARS-CoV-2-induced lung damage in hamster model

Oxidative stress by reactive oxygen species (ROS) has been hypothesized to be the major mediator of SARS-CoV-2-induced pathogenesis. During infection, the redox homeostasis of cells is altered as a consequence of virus-induced cellular stress and inflammation. In such scenario, high levels of ROS bring about the production of pro-inflammatory molecules like IL-6, IL-1β, etc. that are believed to be the mediators of severe COVID-19 pathology. Based on the known antioxidant, anti-inflammatory, mucolytic and antiviral properties of NAC, it has been hypothesized that NAC will have beneficial effects in COVID-19 patients. In the current study efforts have been made to evaluate the protective effect of NAC in combination with remdesivir against SARS-CoV-2 induced lung damage in the hamster model. The SARS-CoV-2 infected animals were administered with high (500 mg/kg/day) and low (150 mg/kg/day) doses of NAC intraperitoneally with and without remdesivir. Lung viral load, pathology score and expression of inflammatory molecules were checked by using standard techniques. The findings of this study show that high doses of NAC alone can significantly suppress the SARS-CoV-2 mediated severe lung damage (2 fold), but on the contrary, it fails to restrict viral load. Moreover, high doses of NAC with and without remdesivir significantly suppressed the expression of pro-inflammatory genes including IL-6 (4.16 fold), IL-1β (1.96 fold), and TNF-α (5.55 fold) in lung tissues. Together, results of this study may guide future preclinical and clinical attempts to evaluate the efficacy of different doses and routes of NAC administration with or without other drugs against SARS-CoV-2 infection.

Nimodipine Treatment Protects Auditory Hair Cells from Cisplatin-Induced Cell Death Accompanied by Upregulation of LMO4

Ototoxicity is one of the main dose-limiting side effects of cisplatin chemotherapy and impairs the quality of life of tumor patients dramatically. Since there is currently no established standard therapy targeting hearing loss in cisplatin treatment, the aim of this study was to investigate the effect of nimodipine and its role in cell survival in cisplatin-associated hearing cell damage. To determine the cytotoxic effect, the cell death rate was measured using undifferentiated and differentiated UB/OC−1 and UB/OC−2 cells, after nimodipine pre-treatment and stress induction by cisplatin. Furthermore, immunoblot analysis and intracellular calcium measurement were performed to investigate anti-apoptotic signaling, which was associated with a reduced cytotoxic effect after nimodipine pre-treatment. Cisplatin’s cytotoxic effect was significantly attenuated by nimodipine up to 61%. In addition, nimodipine pre-treatment counteracted the reduction in LIM Domain Only 4 (LMO4) by cisplatin, which was associated with increased activation of Ak strain transforming/protein kinase B (Akt), cAMP response element-binding protein (CREB), and signal transducers and activators of transcription 3 (Stat3). Thus, nimodipine presents a potentially well-tolerated substance against the ototoxicity of cisplatin, which could result in a significant improvement in patients’ quality of life.

Does N-acetylcysteine Improve Established Hearing Loss in Guinea Pigs?

Objective

To assess whether multiple injections of a powerful antioxidant can improve established sensorineural hearing loss in guinea pigs.

Study Design

Animal study.

Setting

Animal science laboratory, University of Manitoba.

Methods

A total of 16 guinea pigs were used in our study: 8 underwent unilateral intracochlear neomycin injection, and 8 underwent unilateral saline to serve as controls. After a period of 3 weeks for hearing loss to stabilize, 4 guinea pigs from each group received weekly intraperitoneal injections of N-acetylcysteine (NAC) for 4 weeks. Click auditory brainstem response (ABR) testing was conducted at baseline, weekly after the start of NAC injections, and after the last injection. Pure tone ABR tests were conducted prior to intracochlear injections and at completion of the study.

Results

Click ABR thresholds were significantly worse in ears treated with neomycin (P < .001), as expected, but not significantly different when treated with NAC (P = .664). Thresholds for pure tone ABR were also not statistically different in neomycin-treated ears with or without NAC (P > .99).

Conclusions

The aggressive antioxidant therapy performed in this study was not successful in improving established hearing loss via an antioxidant regimen that is known to change the oxidation-reduction potential in the cochlea.

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

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

Oxidative Stress and Inflammation Caused by Cisplatin Ototoxicity

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

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.

Current Strategies to Combat Cisplatin-Induced Ototoxicity

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

Clinical trials evaluating transtympanic otoprotectants for cisplatin-induced ototoxicity: what do we know so far?

BACKGROUND

Cisplatin (CDDP) chemotherapy can cause serious side effects including irreversible and progressive hearing loss. Studies have aimed to assess potential protective strategies; however, systemic treatments have presented variable results, and potential interactions with CDDP have limited clinical trials.

METHODS

A review of the literature was performed in order to evaluate clinical trials that have studied a transtympanic approach as an otoprotectant strategy.

RESULTS

Six clinical trials were included. While a transtympanic approach can limit side effects and avoid interactions with CDDP, recurrent issues have been expressed including which otoprotectant to test, time delays between CDDP treatment and transtympanic injections, side effects such as pain and dizziness, concentrations, and number of injections. Clinical trials have used sodium thiosulfate, N-acetylcysteine and dexamethasone.

CONCLUSIONS

While a transtympanic approach seems like an attractive strategy, further research is needed to clarify which is the optimal otoprotectant, its dosage, and the number of injections.