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

Ototoxicity among cisplatin, carboplatin, and oxaliplatin in zebrafish model

Platinum-based antineoplastic drugs, including cisplatin, carboplatin, and oxaliplatin, are widely used in the treatment of various cancers. Ototoxicity is a common adverse effect of platinum-based drugs. Ototoxicity leads to irreversible hearing impairment. We hypothesize that different platinum-based drugs exhibit varying ototoxic concentrations, time effects, and ototoxic mechanisms. We tested this hypothesis by using a zebrafish model (pvalb3b: TagGFP) to assess the viability of hair cells collected from zebrafish larvae. Cisplatin, carboplatin, and oxaliplatin were administered at dosages of 100, 200, or 400 μM, and the ototoxic effects of these drugs were assessed 1, 2, or 3 h after administration. Fm4-64 and a TUNEL assay were used to label the membranes of living hair cells and to detect cell apoptosis, respectively. We observed that >50% of hair cells were damaged at 1 h after cisplatin (100 μM) exposure, and this ototoxic effect increased at higher dosages and over time. Owing to the smaller ototoxic effects of carboplatin and oxaliplatin, we conducted higher-strength and longer-duration experiments with these drugs. Neither carboplatin nor oxaliplatin was obviously ototoxic, even at 1600 μM and after 6 h. Moreover, only cisplatin damaged the membranes of the hair cells. Cell apoptosis and significantly increased antioxidant gene expression were observed in only the cisplatin group. In conclusion, cisplatin significantly damages sensory hair cells and has notable dosage and time effects. Carboplatin and oxaliplatin are less ototoxic than cisplatin, likely due to having different ototoxic mechanisms than cisplatin.

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.

Aucubin protects mouse cochlear hair cells from cisplatin-induced ototoxicity via activation of the PI3K/AKT/STAT3 pathway

Cisplatin is commonly used to treat cancers and is associated with a significant risk of irreversible sensorineural hearing loss. However, no effective preventive strategies are available for cisplatin-induced HL. Therefore, significant efforts have been made to discover new drugs protecting cochlear hair cells from cisplatin-induced damage. We found that a new phytochemical, aucubin, attenuated cisplatin-induced apoptosis, the production of reactive oxygen species, and mitochondrial dysfunction in House Ear Institute Organ of Corti 1 cells and cochlear hair cells. Moreover, aucubin attenuated cisplatin-induced sensorineural hearing loss and hair cells loss in vivo. Furthermore, RNA sequencing analysis revealed that the otoprotective effects of aucubin were mainly mediated by increased STAT3 phosphorylation via the PI3K/AKT pathway. Inhibition of the STAT3 signaling pathway with the inhibitor S3I-201 or siRNA disrupted the protective effects of aucubin on cisplatin-induced apoptosis. In conclusion, we identified an otoprotective effect of aucubin. Therefore, aucubin could be used to prevent cisplatin-induced ototoxicity.

Establishment of an optimized guinea pig model of cisplatin-induced ototoxicity

Background

Cisplatin is among the most effective antineoplastic agents and has revolutionized the treatment of many cancer diseases. However, one of its serious side effects is a progressive and irreversible hearing loss, occurring in both adults and children. For the development of otoprotective therapies that prevent this side effect, cisplatin-induced hearing loss animal models are indispensable. Due to the high toxicity of cisplatin, the establishment of such animal models is a difficult and time-consuming task. Here we introduce the detailed protocol of a sophisticated guinea pig model with a sufficient and permanent hearing loss induced by cisplatin. This manuscript is intended to provide guidance in the development of future cisplatin guinea pig models which may reduce the mortality rate of the animals and help to gain more reproducible results.

Methods

Pigmented and unpigmented guineapigs were treated with an intravenous single application of 8 mg/kg cisplatin under general anesthesia. An extensive and long-term intensive care protocol consisting of scheduled application of fluids, antiemetics, analgesics, glucose and supportive feeding among others, was used to ensure wellbeing of the animals. Hearing tests were performed prior to and 5 days after cisplatin application. Animals were then euthanized.

Results

The ABR audiometry 5 days after cisplatin application revealed a hearing threshold ranging from 70 dB to 90 dB in the frequencies from 1 kHz to 32 kHz respectively.All animals presented a good health condition despite the treatment with cisplatin.

Discussion

The introduced care protocol in this manuscript is intended to serve as a guidance for the establishment of a stable guinea pig model for short- and long-term investigation regarding the inner ear and its protection in the frame work of cisplatin-induced damage.

Dual role of quercetin in enhancing the efficacy of cisplatin in chemotherapy and protection against its side effects: a review

Chemotherapy has opened a new window in cancer therapy. However, the resistance of cancer cells has dramatically reduced the efficacy of chemotherapy. Cisplatin is a chemotherapeutic agent and its potential in cancer therapy has been restricted by resistance of cancer cells. As a consequence, the scientists have attempted to find new strategies in elevating chemotherapy efficacy. Due to great anti-tumour activity, naturally occurring compounds are of interest in polychemotherapy. Quercetin is a flavonoid with high anti-tumour activity against different cancers that can be used with cisplatin to enhance its efficacy and also are seen to sensitise cancer cells into chemotherapy. Furthermore, cisplatin has side effects such as nephrotoxicity and ototoxicity. Administration of quercetin is advantageous in reducing the adverse effects of cisplatin without compromising its anti-tumour activity. In this review, we investigate the dual role of quercetin in enhancing anti-tumour activity of cisplatin and simultaneous reduction in its adverse effects.

Does Hypochlorous Acid Cause Ototoxicity? An Experimental Study

AIM

Hypochlorous acid (HOCl) is a weak acid that ionizes in water. It is an effective antiseptic exhibiting low toxicity on living tissues. We aimed to investigate the ototoxic effects of HOCl on an animal model by using electrophysiological and histological methods.

MATERIALS AND METHODS

The study comprised 32 Sprague-Dawley rats, which were separated into four groups: control group (A), saline solution group (B), 70% isopropyl alcohol + 2% chlorhexidine group (C), and HOCl group (D). After recording the auditory brainstem response (ABR) for basal hearing thresholds (8, 16, 24, and 32 kHz), 0.03 ml of the aforementioned materials was injected intratympanically three times every 2 days in groups B, C, and D. ABR measurements were repeated on the 7th and 21st days. All animals were sacrificed, and temporal bones were prepared for examinations of cochlear histology and vascular endothelial growth factor immunohistochemistry.

RESULTS

Basal hearing levels were normal across all frequencies and groups, with no statistical differentiation. On the 7th and 21st days after the ABR test, all other groups demonstrated a significant deterioration in hearing levels compared with group A. When the results from 7th and 21st days were compared within group D, a partial recovery was observed. In histopathology, groups C and D demonstrated moderate and severe cochlear degeneration, along with decreased immunoreactivity in the organ of Corti, stria vascularis, and spiral ligament.

CONCLUSION

This is the first study to evaluate the safety of using HOCl in otology. Although HOCI is less ototoxic than the disinfectant used, it may have a toxic effect on cochlea.Level of Evidence: Animal Research.

Astaxanthin protects against hearing impairment in diabetic rats

OBJECTIVE

Diabetes Mellitus (DM) causes an increase in oxidative stress that leads to deterioration in auditory functions. Astaxanthine (AST) is known to have strong antioxidant effects. In this study, the aim is to investigate the effect of AST against hearing loss that is due to DM.

METHODS

This study is an experimental animal study. The study was designed in four groups with 8 animals (n = 8) in each group. The groups were as follows; Control Group (CNT), Diabetic Group (DM), AST applied diabetic group (DM+AST), and AST applied non-diabetic group (AST). Streptozotocin was applied in rats to induce DM. AST was administered by oral gavage. Auditory Brainstem Responses (ABR) and Distortion Product Otoacoustic Emissions (DPOAE) tests were performed on several days of the study. At the end of the study, pro-inflammatory cytokine levels were analyzed in cochlear tissue samples, and Glutathione Peroxidase (GPx), Superoxide Dismutase (SOD), Catalase (CAT) and Malondialdehyde (MDA) levels were measured.

RESULTS

When the findings obtained in the ABR and DPOAE tests in the DM group, it was observed that there was a significant deterioration in the hearing sense. This deterioration was not observed in the DM+AST group. In the DM group, GPx, SOD and CAT levels decreased and MDA levels increased in blood and cochlear tissue. Compared to the DM group, it was noted that antioxidant enzyme levels increased and MDA levels decreased in the DM+AST group. Cochlear tissue pro-inflammatory cytokine levels, which increased with DM, were significantly decreased in the DM+AST group.

CONCLUSION

Even though the effects of AST were investigated in a diabetic experimental animal model, if this molecule is proven to be effective in diabetic humans, it can be considered an adjunct therapeutic option with its antioxidant effects.

LEVEL OF EVIDENCE

The level of evidence of this article is 5. This article is an experimental animal and laboratory study.

Cisplatin for cancer therapy and overcoming chemoresistance

Cisplatin spearheads the anticancer chemotherapeutics in present-day use although acute toxicity is its primary impediment factor. Among a plethora of experimental medications, a drug as effective or surpassing the benefits of cisplatin has not been discovered yet. Although Oxaliplatin is considered more superior to cisplatin, the former has been better for colorectal cancer while cisplatin is widely used for treating gynaecological cancers. Carcinoma imposes a heavy toll on mortality rates worldwide despite the novel treatment strategies and detection methods that have been introduced; nanomedicine combined with precision medicine, immunotherapy, volume-regulated anion channels, and fluorodeoxyglucose-positron emission tomography. Millions of deaths occur annually from metastatic cancers which escape early detection and the concomitant diseases caused by highly toxic chemotherapy that causes organ damage. It continues due to insufficient knowledge of the debilitative mechanisms induced by cancer biology. To overcome chemoresistance and to attenuate the adverse effects of cisplatin therapy, both in vitro and in vivo models of cisplatin-treated cancers and a few multi-centred, multi-phasic, randomized clinical trials in pursuant with recent novel strategies have been tested. They include plant-based phytochemical compounds, de novo drug delivery systems, biochemical/immune pathways, 2D and 3D cell culture models using small molecule inhibitors and genetic/epigenetic mechanisms, that have contributed to further the understanding of cisplatin's role in modulating the tumour microenvironment. Cisplatin was beneficial in cancer therapy for modulating the putative cellular mechanisms; apoptosis, autophagy, cell cycle arrest and gene therapy of micro RNAs. Specific importance of drug influx, efflux, systemic circulatory toxicity, half-maximal inhibition, and the augmentation of host immunometabolism have been identified. This review offers a discourse on the recent anti-neoplastic treatment strategies to enhance cisplatin efficacy and to overcome chemoresistance, given its superiority among other tolerable chemotherapies.

Astaxanthine attenuates cisplatin ototoxicity in vitro and protects against cisplatin-induced hearing loss in vivo

Astaxanthine (AST) has important biological activities including antioxidant and anti-inflammatory effects that could alleviate neurological and heart diseases, but its role in the prevention of cisplatin-induced hearing loss (CIHL) is not yet well understood. In our study, a steady interaction between AST and the E3 ligase adapter Kelch-like ECH-associated protein 1, a predominant repressor of nuclear factor erythroid 2-related factor 2 (NRF2), was performed and tested via computer molecular docking and dynamics. AST protected against cisplatin-induced ototoxicity via NRF2 mediated pathway using quantitative PCR and Western blotting. The levels of reactive oxygen species (ROS) and mitochondrial membrane potential revealed that AST reduced ROS overexpression and mitochondrial dysfunction. Moreover, AST exerted anti-apoptosis effects in mouse cochlear explants using immunofluorescence staining and HEI-OC1 cell lines using quantitative PCR and Western blotting. Finally, AST combined with poloxamer was injected into the middle ear through the tympanum, and the protection against CIHL was evaluated using the acoustic brain stem test and immunofluorescent staining in adult mice. Our results suggest that AST reduced ROS overexpression, mitochondrial dysfunction, and apoptosis via NRF2-mediated pathway in cisplatin-exposed HEI-OC1 cell lines and mouse cochlear explants, finally promoting cell survival. Our study demonstrates that AST is a candidate therapeutic agent for CIHL.

Curcumin and its derivatives in cancer therapy: Potentiating antitumor activity of cisplatin and reducing side effects

Curcumin is a phytochemical isolated from Curcuma longa with potent tumor-suppressor activity, which has shown significant efficacy in pre-clinical and clinical studies. Curcumin stimulates cell death, triggers cycle arrest, and suppresses oncogenic pathways, thereby suppressing cancer progression. Cisplatin (CP) stimulates DNA damage and apoptosis in cancer chemotherapy. However, CP has adverse effects on several organs of the body, and drug resistance is frequently observed. The purpose of the present review is to show the function of curcumin in decreasing CP's adverse impacts and improving its antitumor activity. Curcumin administration reduces ROS levels to prevent apoptosis in normal cells. Furthermore, curcumin can inhibit inflammation via down-regulation of NF-κB to maintain the normal function of organs. Curcumin and its nanoformulations can reduce the hepatoxicity, neurotoxicity, renal toxicity, ototoxicity, and cardiotoxicity caused by CP. Notably, curcumin potentiates CP cytotoxicity via mediating cell death and cycle arrest. Besides, curcumin suppresses the STAT3 and NF-ĸB as tumor-promoting pathways, to enhance CP sensitivity and prevent drug resistance. The targeted delivery of curcumin and CP to tumor cells can be mediated nanostructures. In addition, curcumin derivatives are also able to reduce CP-mediated side effects, and increase CP cytotoxicity against various cancer types.

Cytotoxicity of Seaweed Compounds, Alone or Combined to Reference Drugs, against Breast Cell Lines Cultured in 2D and 3D

Seaweed bioactive compounds have shown anticancer activities in in vitro and in vivo studies. However, tests remain limited, with conflicting results, and effects in combination with anticancer drugs are even scarcer. Here, the cytotoxic effects of five seaweed compounds (astaxanthin, fucoidan, fucosterol, laminarin, and phloroglucinol) were tested alone and in combination with anticancer drugs (cisplatin-Cis; and doxorubicin-Dox), in breast cell lines (three breast cancer (BC) subtypes and one non-tumoral). The combinations revealed situations where seaweed compounds presented potentiation or inhibition of the drugs' cytotoxicity, without a specific pattern, varying according to the cell line, concentration used for the combination, and drug. Fucosterol was the most promising compound, since: (i) it alone had the highest cytotoxicity at low concentrations against the BC lines without affecting the non-tumoral line; and (ii) in combination (at non-cytotoxic concentration), it potentiated Dox cytotoxicity in the triple-negative BC cell line. Using a comparative approach, monolayer versus 3D cultures, further investigation assessed effects on cell viability and proliferation, morphology, and immunocytochemistry targets. The cytotoxic and antiproliferative effects in monolayer were not observed in 3D, corroborating that cells in 3D culture are more resistant to treatments, and reinforcing the use of more complex models for drug screening and a multi-approach that should include histological and ICC analysis.

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.