Comparison of the effects of lipoic acid and glutathione against cisplatin-induced ototoxicity in auditory cells

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Polyphenols in Inner Ear Neurobiology, Health and Disease: From Bench to Clinics

There is substantial experimental and clinical interest in providing effective ways to both prevent and slow the onset of hearing loss. Auditory hair cells, which occur along the basilar membrane of the cochlea, often lose functionality due to age-related biological alterations, as well as from exposure to high decibel sounds affecting a diminished/damaged auditory sensitivity. Hearing loss is also seen to take place due to neuronal degeneration before or following hair cell destruction/loss. A strategy is necessary to protect hair cells and XIII cranial/auditory nerve cells prior to injury and throughout aging. Within this context, it was proposed that cochlea neural stem cells may be protected from such aging and environmental/noise insults via the ingestion of protective dietary supplements. Of particular importance is that these studies typically display a hormetic-like biphasic dose-response pattern that prevents the occurrence of auditory cell damage induced by various model chemical toxins, such as cisplatin. Likewise, the hormetic dose-response also enhances the occurrence of cochlear neural cell viability, proliferation, and differentiation. These findings are particularly important since they confirmed a strong dose dependency of the significant beneficial effects (which is biphasic), whilst having a low-dose beneficial response, whereas extensive exposures may become ineffective and/or potentially harmful. According to hormesis, phytochemicals including polyphenols exhibit biphasic dose-response effects activating low-dose antioxidant signaling pathways, resulting in the upregulation of vitagenes, a group of genes involved in preserving cellular homeostasis during stressful conditions. Modulation of the vitagene network through polyphenols increases cellular resilience mechanisms, thus impacting neurological disorder pathophysiology. Here, we aimed to explore polyphenols targeting the NF-E2-related factor 2 (Nrf2) pathway to neuroprotective and therapeutic strategies that can potentially reduce oxidative stress and inflammation, thus preventing auditory hair cell and XIII cranial/auditory nerve cell degeneration. Furthermore, we explored techniques to enhance their bioavailability and efficacy.

Protective effects of alpha lipoic acid (ALA) are mediated by hormetic mechanisms

The endogenous and dietary agent, alpha lipoic acid (ALA) is evaluated for its capacity to induce a broad spectrum of adaptive responses via hormetic dose responses and their underlying mechanisms. ALA was shown to induce hormetic effects in a wide range of experimental models within in vitro and in vivo experimental settings which included direct exposure and pre- and post-conditioning experimental protocols. The hormetic effects occur in a broad range of organ systems, including the brain, heart, kidney and other tissues, with possible public health and clinical/therapeutic applications linked to reducing the onset and progression of neurogenerative diseases and also in the preservation of sperm health and functionality during cryopreservation. This paper provides the first integrated assessment of ALA-induced hormetic dose responses. Underlying mechanisms that mediated the occurrence of ALA-induced hormetic effects involved the induction of low levels of ROS that activate key cell signaling antioxidant (e.g. Nrf2) pathways.

Protective Potentials of Alpha-Lipoic Acid against Ionizing Radiation-Induced Brain Damage in Rats

Background

This study was aimed at determining the effects of alpha-lipoic acid on ionizing irradiation-induced oxidative damage and apoptosis in the brain of rats.

Methods

The animals were exposed to whole-brain X-radiation with a 15 Gy single dose in the absence or presence of alpha-lipoic acid (200 mg/kg body weight) pretreatment for one week. The rats were divided into four groups (5 rats in each group): vehicle control, alpha-lipoic acid alone (ALA), radiation alone (RAD), and radiation plus alpha-lipoic acid (RAD+ALA). In the next stage, malondialdehyde (MDA), nitric oxide, catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in the brain tissue of the rats were measured. Furthermore, the Western blot analysis technique was performed to assess the NOX2, NOX4, and caspase-3 protein expression levels.

Results

Twenty-four hours after the irradiation, MDA and nitric oxide levels in the irradiated rats were significantly higher than those in the control group (p < 0.001); however, the pretreatment with alpha-lipoic acid resulted in a significant reduction in these stress oxidative markers (p < 0.05). Moreover, a significant decrease in CAT, SOD, and GPx levels was observed in the radiation group alone compared to the control group (p < 0.01); in contrast, the activities of these antioxidant enzymes significantly increased in the radiation plus alpha-lipoic acid group in comparison to the radiation group alone (p < 0.05). The results of Western blot analysis revealed that NOX2, NOX4, and caspase-3 protein expressions significantly elevated in the irradiated rats compared to the control group (p < 0.001). The pretreatment with alpha-lipoic acid could significantly decrease the expression levels of NOX2, NOX4, and caspase-3 in comparison with the radiation group alone (p < 0.05).

Conclusion

According to the obtained findings, it can be mentioned that the alpha-lipoic acid pretreatment could mitigate the ionizing irradiation-induced oxidative damage and apoptosis in the brain of the rats.

Safety and Efficacy of Intratympanic Alpha-Lipoic Acid Injection in a Mouse Model of Noise-Induced Hearing Loss

Alpha-lipoic acid (ALA) is an antioxidant with oto-protective effects. In the present study, the safety and effectiveness of ALA therapy after noise-induced hearing loss was confirmed based on the administration method. The safety of intratympanic ALA (IT-ALA) was evaluated with oto-endoscopy and middle ear mucosa morphologic study. Perilymph ALA concentrations according to the administration routes were compared, and the efficacy of ALA was investigated through hearing tests and cochlear histological studies. The middle ear mucosa was swollen 1 week after IT-ALA but completely recovered within 3 weeks. ALA concentration in the perilymph was significantly higher in the IT-ALA group. Recovery of organ of Corti morphology and hearing levels were predominant in the IT-ALA group compared with the intraperitoneal injection group (IP-ALA) and showed similar rescue effects in the IT-dexamethasone group (IT-DEX). Interleukin-1 beta and nuclear factor-kappa B expression was significantly downregulated in the IT-ALA group. IT-ALA showed better cochlear recovery from acoustic trauma with higher inner ear penetration rate than IP-ALA. The rescue effect of IT-ALA after noise-induced hearing loss was similar to IT-DEX; however, the ALA and DEX mechanisms are different. IT-ALA appears to be another safe and effective treatment modality after acoustic trauma and comparable to IT-DEX.

Encapsulation of Alpha-Lipoic Acid in Functional Hybrid Liposomes: Promising Tool for the Reduction of Cisplatin-Induced Ototoxicity

In this study, in order to address the drawback of cisplatin (CDDP)-induced ototoxicity, we propose a straightforward strategy based on the delivery of a sulfur-based antioxidant, such as lipoic acid (LA), to HEI-OC1 cells. To this aim, hybrid liposomes (LA@PCGC) with a spherical shape and a mean diameter of 25 nm were obtained by direct sonication of LA, phosphatidylcholine and a gelatin-curcumin conjugate in a physiological buffer. LA@PCGC were found to be stable over time, were quickly (i.e., by 1 h) taken up by HEI-OC1 cells, and guaranteed strong retention of the bioactive molecule, since LA release was less than 20%, even after 100 h. Cell viability studies showed the efficiency of LA@PCGC for stabilizing the protective activity of LA. Curcumin residues within the functional liposomes were indeed able to maintain the biological activity of LA, significantly improving (up to 2.19-fold) the viability of HEI-OC1 cells treated with 5 μM CDDP. Finally, LA@PCGC was incorporated within an alginate-based injectable hydrogel carrier to create a formulation with physical chemical features suitable for potential ear applications.

Intratympanic administration of alpha-lipoic acid-loaded pluronic F-127 nanoparticles ameliorates acute hearing loss

We used antioxidant-containing nanoparticles (NPs) to treat acute hearing loss. Alpha-lipoic acid (ALA) served as the antioxidant; we employed Pluronic F127 to fabricate NPs. In vitro, ALA-NPs protected cells of the organ of Corti in HEI-OC1 mice, triggering nuclear translocation of NRF2 and increases in the levels of antioxidant proteins, including Nrf2, HO-1, SOD-1, and SOD-2. In vivo, the hearing of mice that received ALA-NP injections into the middle ear cavity was better preserved after induction of ototoxicity than in control animals. The cochlear Nrf2 level increased in test mice, indicating that the ALA-NPs protected hearing via the antioxidant mechanism observed in vitro. ALA-NPs effectively protected against acute hearing loss by activating the Nrf2/HO-1 pathway.

α-Lipoic acid prevents against cisplatin cytotoxicity via activation of the NRF2/HO-1 antioxidant pathway

The production of reactive oxygen species (ROS) by cisplatin is one of the major mechanisms of cisplatin-induced cytotoxicity. We examined the preventive effect of α-lipoic acid (LA) on cisplatin-induced toxicity via its antioxidant effects on in vitro and ex vivo culture systems. To elucidate the mechanism of the antioxidant activity of LA, NRF2 was inhibited using NRF2 siRNA, and the change in antioxidant activity of LA was characterized. MTT assays showed that LA was safe at concentrations up to 0.5 mM in HEI-OC1 cells and had a protective effect against cisplatin-induced cytotoxicity. Intracellular ROS production in HEI-OC1 cells was rapidly increased by cisplatin for up to 48 h. However, treatment with LA significantly reduced the production of ROS and increased the expression of the antioxidant proteins HO-1 and SOD1. Ex vivo, the organs of Corti of the group pretreated with LA exhibited better preservation than the group that received cisplatin alone. We also confirmed the nuclear translocation of NRF2 after LA administration, and that NRF2 inhibition decreased the antioxidant activity of LA. Together, these results indicate that the antioxidant activity of LA was through the activation of the NRF2/HO-1 antioxidant pathway.

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.

Toward Cochlear Therapies

Sensorineural hearing impairment is the most common sensory disorder and a major health and socio-economic issue in industrialized countries. It is primarily due to the degeneration of mechanosensory hair cells and spiral ganglion neurons in the cochlea via complex pathophysiological mechanisms. These occur following acute and/or chronic exposure to harmful extrinsic (e.g., ototoxic drugs, noise...) and intrinsic (e.g., aging, genetic) causative factors. No clinical therapies currently exist to rescue the dying sensorineural cells or regenerate these cells once lost. Recent studies have, however, provided renewed hope, with insights into the therapeutic targets allowing the prevention and treatment of ototoxic drug- and noise-induced, age-related hearing loss as well as cochlear cell degeneration. Moreover, genetic routes involving the replacement or corrective editing of mutant sequences or defected genes are showing promise, as are cell-replacement therapies to repair damaged cells for the future restoration of hearing in deaf people. This review begins by recapitulating our current understanding of the molecular pathways that underlie cochlear sensorineural damage, as well as the survival signaling pathways that can provide endogenous protection and tissue rescue. It then guides the reader through to the recent discoveries in pharmacological, gene and cell therapy research towards hearing protection and restoration as well as their potential clinical application.

Lipoic acid inhibited desflurane-induced hippocampal neuronal apoptosis through Caspase3 and NF-KappaB dependent pathway

Desfluraneis a widely-used general anesthetics. However, recent reports showed its significant side effect in the nervous system. Desflurane could lead to the neuronal death and affect the working memory. Unfortunately, the mechanism underlying the action of desflurane is still not clear and there is still no potent medicine to prevent the lesion in the central nervous system caused by general anesthetics. In this study, we found α-lipoic acid, an antioxidant exerting protective effect on multiple cells tissues, could resist the neurotoxicity caused by desflurane exposure. Lipoic acid possessed strong anti-apoptotic effect on the desflurane-treated hippocampal neurons, which was mediated by the Caspase-3 dependent pathway and NF-kappaB signaling. Collectively, we found a promising candidate to be clinically applied in intervention against the damage in nervous system by the desflurane.