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

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.

Apigenin alleviates neomycin-induced oxidative damage via the Nrf2 signaling pathway in cochlear hair cells

Oxidative stress plays an important role in the pathogenesis of aminoglycoside-induced hearing loss and represents a promising target for treatment. We tested the potential effect of apigenin, a natural flavonoid with anticancer, anti-inflammatory, and antioxidant activities, on neomycin-induced ototoxicity in cochlear hair cells in vitro. Results showed that apigenin significantly ameliorated the loss of hair cells and the accumulation of reactive oxygen species upon neomycin injury. Further evidence suggested that the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway was activated by apigenin treatment. Disruption of the Nrf2 axis abolished the effects of apigenin on the alleviation of oxidative stress and subsequent apoptosis of hair cells. This study provided evidence of the protective effect of apigenin on cochlear hair cells and its underlying mechanism.

Hair Cell Protection from Ototoxic Drugs

Hearing loss is often caused by death of sensory hair cells (HCs) in the inner ear. HCs are vulnerable to some ototoxic drugs, such as aminoglycosides(AGs) and the cisplatin.The most predominant form of drug-induced cell death is apoptosis. Many efforts have been made to protect HCs from cell death after ototoxic drug exposure. These mechanisms and potential targets of HCs protection will be discussed in this review.And we also propose further investigation in the field of HCs necrosis and regeneration, as well as future clinical utilization.

The Effect of Antioxidant Supplementation in Patients with Tinnitus and Normal Hearing or Hearing Loss: A Randomized, Double-Blind, Placebo Controlled Trial

Tinnitus is the perception of sound in the absence of any external stimulus. Oxidative stress is possibly involved in its pathogenesis and a variety of antioxidant compounds have been studied as potential treatment approaches. The objective of the present study was to assess the effects of antioxidant supplementation in tinnitus patients. This is a randomized, double-blind, placebo-controlled clinical trial. Patients (N = 70) were randomly allocated to antioxidant supplementation (N = 35) or to placebo (N = 35) for a total of 3 months. Demographic, anthropometric, clinical, and nutritional data were collected. Serum total antioxidant capacity (TAC), oxidized LDL (oxLDL), and superoxide dismutase (SOD), tinnitus loudness, frequency, and minimum masking level (MML), and scores in Tinnitus Handicap Inventory questionnaire (THI), Tinnitus Functional Index (TFI), and Visual Analogue Scale (VAS) were evaluated at baseline and follow-up. Tinnitus loudness and MML significantly decreased from baseline to post measure (p < 0.001) only in the antioxidant group, the overall change being significantly different between the two groups post-intervention (p < 0.001). THI and VAS decreased only in the antioxidant group. Differences in changes in serum TAC, SOD, and oxLDL post-intervention were insignificant. In conclusion, antioxidant therapy seems to reduce the subjective discomfort and tinnitus intensity in tinnitus patients.

Increased oxidative stress, inflammation, and glutamate: Potential preventive and therapeutic targets for hearing disorders

Hearing disorders constitute one of the major health concerns in the USA. Decades of basic and clinical studies have identified numerous ototoxic agents and investigated their modes of action on the inner ear, utilizing tissue culture as well as animal and human models. Current preventive and therapeutic approaches are considered unsatisfactory. Therefore, additional modalities should be developed. Many studies suggest that increased levels of oxidative stress, chronic inflammation, and glutamate play an important role in the initiation and progression of damage to the inner ear leading to hearing impairments. To prevent these cellular deficits, antioxidants, anti-inflammatory agents, and antagonists of glutamate receptor have been used individually or in combination with limited success. It is essential, therefore, to simultaneously enhance the levels of antioxidant enzymes by activating the Nrf2 (a nuclear transcriptional factor) pathway, dietary and endogenous antioxidant compounds, and B12-vitamins in order to reduce the levels of oxidative stress, chronic inflammation, and glutamate at the same time. This review presents evidence to show that increased levels of these cellular metabolites, biochemical or factors are involved in the pathogenesis of cochlea leading to hearing impairments. It presents scientific rationale for the use of a mixture of micronutrients that may decrease the levels of oxidative damage, chronic inflammation, and glutamate at the same time. The benefits for using oral administration of proposed micronutrient mixture in humans are presented. Animal and limited human studies indirectly suggest that orally administered micronutrients can accumulate in the inner ear. Therefore, this route of administration may be useful in prevention, and in combination with standard care, in improved management of hearing problems following exposure to well-recognized and studied ototoxic agents, such as noise, cisplatin, aminoglycoside antibiotics, and advanced age.

Protection of Hair Cells from Ototoxic Drug-Induced Hearing Loss

Hair cells are specialized sensory epithelia cells that receive mechanical sound waves and convert them into neural signals for hearing, and these cells can be killed or damaged by ototoxic drugs, including many aminoglycoside antibiotics, platinum-based anticancer agents, and loop diuretics, leading to drug-induced hearing loss. Studies of therapeutic approaches to drug-induced hearing loss have been hampered by the limited understanding of the biological mechanisms that protect and regenerate hair cells. This review briefly discusses some of the most common ototoxic drugs and describes recent research concerning the mechanisms of ototoxic drug-induced hearing loss. It also highlights current developments in potential therapies and explores current clinical treatments for patients with hearing impairments.

Interplay between Nutrition and Hearing Loss: State of Art

Hearing loss has been recently ranked as the fifth leading cause of years lived with disability, ahead of many other chronic diseases such as diabetes, dementia, or chronic obstructive pulmonary disease. Moreover, according to the World Health Organization, moderate-to-profound hearing loss affects about 466 million people worldwide. Its incidence varies in each population segment, affecting approximately 10% of children and increasing to 30% of the population over 65 years. However, hearing loss receives still very limited research funding and public awareness. This sensory impairment is caused by genetic and environmental factors, and among the latter, the nutritional status has acquired relevance due its association to hearing loss detected in recent epidemiological studies. Several experimental models have proved that the onset and progression of hearing loss are closely linked to the availability of nutrients and their metabolism. Here, we have reviewed studies focused on nutrient effects on auditory function. These studies support the potential of nutritional therapy for the protection against hearing loss progression, which is especially relevant to the aging process and related quality of life.

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

Objectives

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

Methods

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

Results

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

Conclusion

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

Investigation of the effects of curcumin, vitamin E and their combination in cisplatin-induced testicular apoptosis using immunohistochemical technique

OBJECTIVE

Cisplatin is an effective antineoplastic agent used in cancer therapy. However, the use of cisplatin is restricted due to its toxic side effects. Alleviation of its side effects which restricts cisplatin use is highly important. We aimed to investigate the effects of curcumin, vitamin E and their combination in cisplatin induced testicular apoptosis.

MATERIAL AND METHODS

Thirty-five Wistar albino male adult rats, weighing 300-350 g were divided randomly into five groups including seven rats in each as control, cisplatin, curcumin, vitamin E, and curcumin + vitamin E. On the posttest 5th day, rats were sacrificed, and their testes were removed. 4-5 μm sections from formalin fixed paraffin embedded testis tissues were stained both hematoxylin-eosin to analyze histologically and immunohistochemically to determine the expression of the apoptotic pathway proteins (Bax, Cas-3, Bcl-2).

RESULTS

Increased histological damage with cisplatin administration was reduced in treatment, especially in combination therapy. Cas-3 and Bax protein immunostaining intensities H-scores were significantly increased but Bcl-2 was slightly decreased in the cisplatin group compared to the control. In all treatment groups Bax, Cas-3 decreased compared to cisplatin group however Bcl-2 decreased in the curcumin and vitamin E groups. Bax/Bcl-2 was the highest in the cisplatin, and decreased in all treatment groups in favor of control.

CONCLUSION

Cas-3 expression increased by cisplatin administration suggests that cisplatin causes apoptosis of germ cells. According to the present findings, cisplatin mainly caused testicular apoptosis through the Cas-3 and Bax apoptotic protein pathways. Cisplatin-induced testicular apoptosis can be prevented by administration of curcumin, vitamin E, and combination therapy.

Effects of Spirulina on the functions and redox status of auditory system in senescence-accelerated prone-8 mice

To our knowledge, the effects of Spirulina platensis water extract (SP) on hearing function have not yet been reported. This study investigated the effects of SP on the function and redox status of the auditory system. Auditory brainstem responses and redox status were compared between two groups of 3-month-old senescence-accelerated prone-8 (SAMP8) mice: the control group was fed a normal diet, and the experimental group was fed a normal diet with oral supplementation of SP for 6 weeks. Compared with the control group, the experimental group had significantly lower hearing thresholds according to auditory brainstem responses measured using click sounds and 8-kHz tone burst sound stimulation at the end of this study. The experimental group had a shorter I-III interval of auditory brainstem responses with 16-kHz tone burst stimulation than the control group that was of borderline significance. Additionally, the experimental group had significantly higher mRNA expression of the superoxide dismutase and catalase genes in the cochlea and brainstem and significantly higher mRNA expression of the glutathione peroxidase gene in the cochlea. Further, the experimental group had significantly lower malondialdehyde levels in the cochlea and brainstem than the control group. However, tumor necrosis factor-α mRNA expression was not significantly different between the control and experimental groups. SP could decrease hearing degeneration in senescence-accelerated prone-8 mice possibly by increasing superoxide dismutase, catalase, and glutathione peroxidase gene expression and decreasing damage from oxidative stress in the cochlea and brainstem.

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.

Intraperitoneal curcumin and vitamin E combination for the treatment of cisplatin-induced ototoxicity in rats

INTRODUCTION

Cisplatin ototoxicity is characterized by irreversible, progressive, bilateral sensorineural hearing loss at high frequencies, accompanied by tinnitus. The aim of this study is to demonstrate the protective action of curcumin alone or in combination with vitamin E against cisplatin-induced ototoxicity in animal models.

MATERIAL AND METHODS

The study included 42 rats. Experimental animals were randomized into 6 groups. In the first group, intra-peritoneal cisplatin was administered alone. In the second group, intra-peritoneal cisplatin and curcumin were administered together. In the third group, intra-peritoneal cisplatin and vitamin E were administered together. In the fourth group, intra-peritoneal cisplatin was administered together with curcumin in combination with vitamin E. In the fifth group, intra-peritoneal curcumin was administered alone. The sixth group was sacrificed directly without administration of any drugs. A distortion product otoacoustic emission (DPOAE) test was applied to both ears of all experimental animals. Curcumin was administered 1 h before cisplatin treatment continued for three successive days. Vitamin E was administered only as a single dose 30 min prior to cisplatin. All animals were sacrificed following DPOAE testing on the 5th day of cisplatin administration. Histopathological findings included a TUNEL (TdT-mediated deoxyuridine triphosphate nick end-labeling) assay, and the percentage of apoptotic cells was calculated. DPOAE values and the percentage of apoptotic cells were compared before and after treatment and between experimental groups.

RESULTS

In Group 1, DPOAE values were significantly decreased at all frequencies (3000 Hz, 4000 Hz and 6000 Hz; P < 0.05). In Groups 2, 3, 4 and 5 there was no significant difference between the pre- and post-treatment DPOAE results (p > 0.05). Apoptotic index values were lower in all treatment groups compared to the cisplatin group, however the difference was only statistically significant in group 3 (p = 0.009).

CONCLUSION

In rats, cisplatin ototoxicity can be prevented with curcumin or curcumin-vitamin E combination.

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.

Novel Pactamycin Analogs Induce p53 Dependent Cell-Cycle Arrest at S-Phase in Human Head and Neck Squamous Cell Carcinoma (HNSCC) Cells

Pactamycin, although putatively touted as a potent antitumor agent, has never been used as an anticancer drug due to its high cytotoxicity. In this study, we characterized the effects of two novel biosynthetically engineered analogs of pactamycin, de-6MSA-7-demethyl-7-deoxypactamycin (TM-025) and 7-demethyl-7-deoxypactamycin (TM-026), in head and neck squamous cell carcinoma (HNSCC) cell lines SCC25 and SCC104. Both TM-025 and TM-026 exert growth inhibitory effects on HNSCC cells by inhibiting cell proliferation. Interestingly, unlike their parent compound pactamycin, the analogs do not inhibit synthesis of nascent protein in a cell-based assay. Furthermore, they do not induce apoptosis or autophagy in a dose- or a time-dependent manner, but induce mild senescence in the tested cell lines. Cell cycle analysis demonstrated that both analogs significantly induce cell cycle arrest of the HNSCC cells at S-phase resulting in reduced accumulation of G₂/M-phase cells. The pactamycin analogs induce expression of cell cycle regulatory proteins including master regulator p53, its downstream target p21^Cip1/WAF1, p27^kip21, p19, cyclin E, total and phospho Cdc2 (Tyr15) and Cdc25C. Besides, the analogs mildly reduce cyclin D1 expression without affecting expression of cyclin B, Cdk2 and Cdk4. Specific inhibition of p53 by pifithrin-α reduces the percentage of cells accumulated in S-phase, suggesting contribution of p53 to S-phase increase. Altogether, our results demonstrate that Pactamycin analogs TM-025 and TM-026 induce senescence and inhibit proliferation of HNSCC cells via accumulation in S-phase through possible contribution of p53. The two PCT analogs can be widely used as research tools for cell cycle inhibition studies in proliferating cancer cells with specific mechanisms of action.

Hydrogen protects auditory hair cells from cisplatin-induced free radicals

Cisplatin is a widely used chemotherapeutic agent for the treatment of various malignancies. However, its maximum dose is often limited by severe ototoxicity. Cisplatin ototoxicity may require the production of reactive oxygen species (ROS) in the inner ear by activating enzymes specific to the cochlea. Molecular hydrogen was recently established as an antioxidant that selectively reduces ROS, and has been reported to protect the central nervous system, liver, kidney and cochlea from oxidative stress. The purpose of this study was to evaluate the potential of molecular hydrogen to protect cochleae against cisplatin. We cultured mouse cochlear explants in medium containing various concentrations of cisplatin and examined the effects of hydrogen gas dissolved directly into the media. Following 48-h incubation, the presence of intact auditory hair cells was assayed by phalloidin staining. Cisplatin caused hair cell loss in a dose-dependent manner, whereas the addition of hydrogen gas significantly increased the numbers of remaining auditory hair cells. Additionally, hydroxyphenyl fluorescein (HPF) staining of the spiral ganglion showed that formation of hydroxyl radicals was successfully reduced in hydrogen-treated cochleae. These data suggest that molecular hydrogen can protect auditory tissues against cisplatin toxicity, thus providing an additional strategy to protect against drug-induced inner ear damage.

Dietary vitamin intake correlates with hearing thresholds in the older population: the Korean National Health and Nutrition Examination Survey

BACKGROUND

Previous animal studies have shown that vitamins may prevent age-related hearing loss. However, no concrete conclusions have been reached about the association between vitamin intake and presbycusis in humans.

OBJECTIVE

We investigated the association between dietary vitamin intake and hearing thresholds in adults between 50 and 80 y of age by using data from a large population-based survey.

DESIGN

We used data from the 2011 Korea National Health and Nutrition Examination Survey. A pure-tone audiogram and physical examination of the ear were performed, and vitamin intake was calculated by using the 24-h recall method. Data from 1910 participants were analyzed through univariate and multivariate linear regression analyses.

RESULTS

After adjustment for age, sex, smoking, and exposure to occupational and explosive noise, intake of vitamin C correlated with better hearing at midfrequency (2000 and 3000 Hz) (coefficient: -0.012; 95% CI: -0.022, -0.002). Dietary supplement use was positively associated with better hearing at all frequencies. The univariate analysis indicated that dietary intakes of retinol, riboflavin, niacin, and vitamin C were positively correlated with better hearing at most frequencies. In contrast, serum concentrations of vitamin D were associated with worse hearing at mid and high (4000 and 6000 Hz) frequencies.

CONCLUSIONS

Dietary intake of vitamin C was associated with better hearing in the older population. Because less than one-half of elderly participants in this study consumed a sufficient amount of vitamins, and vitamin intake decreased with age, we should consider proper diet counseling to prevent hearing decline.