Protective Effects of Vitamin C against Neomycin-Induced Apoptosis in HEI-OC1 Auditory Cell

Antioxidant Therapies in the Treatment of Aminoglycoside-Induced Ototoxicity: A Meta-Analysis

OBJECTIVE

A feared complication of aminoglycoside treatment is ototoxicity, which is theorized to be attributed to the production of aminoglycoside-induced reactive oxygen species. Previous studies using animal models have suggested that numerous therapies targeting reducing oxidative stress may prevent ototoxicity from aminoglycosides. However, few clinical studies have been conducted on these antioxidants. This systematic review and meta-analysis examines the effectiveness of antioxidant therapies in the treatment of aminoglycoside-induced ototoxicity.

DATA SOURCES

PubMed, Embase, Web of Science, and ClinicalTrials.gov.

REVIEW METHOD

A literature search was conducted in August 2024. This review sought randomized controlled trials to be conducted on humans to examining otologic outcomes in aminoglycoside-induced ototoxicity following administration of medications intended to reduce oxidative stress.

RESULTS

A systematic review yielded 2037 results, of which seven studies met inclusion criteria. N-acetylcysteine (NAC) was investigated in four studies, aspirin in two studies, and vitamin E in one study. Six studies examined the benefit of antioxidant treatments for up to 8 weeks after administration while one study tested subjects' hearing after 1 year. In pooled analysis, two studies assessing NAC showed the greatest reduction in ototoxicity (RR 0.112, 95% CI, 0.032-0.395; p = 0.0007; I2 = 18%), followed by two studies examining aspirin (RR 0.229, 95% CI, 0.080-0.650; p = 0.0057; I2 = 0%). One study performed with vitamin E did not find a reduction in ototoxicity compared to the placebo (RR 0.841, 95% CI, 0.153-4.617; p = 0.8416).

CONCLUSIONS

Multiple studies have shown that NAC and aspirin are effective in reducing ototoxicity from treatment with aminoglycosides. However, there is a lack of high-quality evidence. Additional studies should examine whether aspirin and N-acetylcysteine provide long-term benefit, and which of the other promising antioxidants translate from animal models.

LEVEL OF EVIDENCE

NA Laryngoscope, 135:1278-1286, 2025.

Vitamin C ameliorates D-galactose-induced senescence in HEI-OC1 cells by inhibiting the ROS/NF-κB pathway

BACKGROUND

Cochlear hair cell senescence is one of the major causes of age-related hearing loss (ARHL) and is significantly related to reactive oxygen species (ROS) accumulation. Research shows that vitamin C (VC) can inhibit ROS accumulation; however, its association with cochlear hair cell senescence remains elusive.

METHODS AND RESULTS

Firstly, a cellular senescence model was established using D-galactose (D-gal) induced HEI-OC1 cells for 24 h. Senescent HEI-OC1 cells were then continued to be treated with the addition of VC or ROS inhibitor (N-acetylcysteine; NAC) for another 24 h, and explored the impact of VC on senescent cochlear hair cell and the potential regulatory mechanisms. The results indicated that D-gal-induced senescent HEI-OC1 cells, manifested as decreased cell viability, increased β-galactosidase activity and p21 protein level, and ROS and pro-inflammatory factors were upregulated, and NF-κB p65 phosphorylation was enhanced. However, the use of VC or NAC can significantly ameliorate these effects and improve HEI-OC1 cell senescence.

CONCLUSIONS

This research indicates that VC can ameliorate D-gal-induced senescence of HEI-OC1 cochlear hair cells, and its protective effect may be related to the inhibition of the ROS/NF-κB pathway, which provides a new research direction for the prevention and treatment of ARHL.

Mechanisms and otoprotective strategies of programmed cell death on aminoglycoside-induced ototoxicity

Aminoglycosides are commonly used for the treatment of life-threatening bacterial infections, however, aminoglycosides may cause irreversible hearing loss with a long-term clinical therapy. The mechanism and prevention of the ototoxicity of aminoglycosides are still limited although amounts of studies explored widely. Specifically, advancements in programmed cell death (PCD) provide more new perspectives. This review summarizes the general signal pathways in programmed cell death, including apoptosis, autophagy, and ferroptosis, as well as the mechanisms of aminoglycoside-induced ototoxicity. Additionally, novel interventions, especially gene therapy strategies, are also investigated for the prevention or treatment of aminoglycoside-induced hearing loss with prospective clinical applications.

A hydrogel system for drug loading toward the synergistic application of reductive/heat-sensitive drugs

The preparation of hydrogels as drug carriers via radical-mediated polymerization has significant prospects, but the strong oxidizing ability of radicals and the high temperatures generated by the vigorous reactions limits the loading for reducing/heat-sensitive drugs. Herein, an applicable hydrogel synthesized by radical-mediated polymerization is reported for the loading and synergistic application of specific drugs. First, the desired sol is obtained by polymerizing functional monomers using a radical initiator, and then tannic-acid-assisted specific drug mediates sol-branched phenylboric acid group to form the required functional hydrogel (New-gel). Compared with the conventional single-step radical-mediated drug-loading hydrogel, the New-gel not only has better chemical/physical properties but also efficiently loads and releases drugs and maintains drug activity. Particularly, the New-gel has excellent loading capacity for oxygen, and exhibits significant practical therapeutic effects for diabetic wound repair. Furthermore, owing to its high light transmittance, the New-gel synergistically promotes the antibacterial effect of photosensitive drugs. This gelation strategy for loading drugs has further promising biomedical applications.

Curcumin protects against the age-related hearing loss by attenuating apoptosis and senescence via activating Nrf2 signaling in cochlear hair cells

Age-related hearing loss (ARHL) is a most widespread neurodegenerative disease affecting the elderly population, but effective pharmacological treatments remain limited. Curcumin is a bioactive compound of Curcuma longa with antioxidant properties. Herein, we looked into the effects of curcumin on the H₂O₂-induced oxidative stress in cochlear hair cells and hearing function in an ARHL animal model (C57BL/6J mice). We found that pretreatment of curcumin could attenuate H₂O₂-induced apoptosis and cell senescence in auditory hair cells and prevent mitochondrial function dysfunction. More specifically, Western blot and luciferase activity assay showed that curcumin activated the nuclear translocation of Nrf2, which in turn triggered the activation of its downstream target gene Heme Oxygenase1 (HO-1). The enhanced Nrf2 and HO-1 activity by curcumin was blocked by the AKT inhibitor LY294002, indicating the protective effect of curcumin was mainly achieved by activating Nrf2/HO-1 through the AKT pathway. Furthermore, the knockdown of Nrf2 with siRNA diminished the protective effects of Nrf2 against apoptosis and senescence, consolidating the pivotal role of Nrf2 in the protective effect of curcumin on auditory hair cells. More importantly, curcumin (10 mg/kg/d) could attenuate progressive hearing loss in C57BL/6J mice, as evident from the reduced threshold of auditory nerve brainstem response. Administration of curcumin also elevated the expression of Nrf2 and reduced the expression of cleaved-caspase-3, p21, and γ-H2AX in cochlear. This study is the first to demonstrate that curcumin can prevent oxidative stress-induced auditory hair cell degeneration through Nrf2 activation, highlighting its potential therapeutic value in preventing ARHL.

Amelioration of Sensorineural Hearing Loss through Regulation of Trpv1, Cacna1h, and Ngf Gene Expression by a Combination of Cuscutae Semen and Rehmanniae Radix Preparata

Sensorineural hearing loss (SNHL) is a common condition that results from the loss of function of hair cells, which are responsible for converting sound into electrical signals within the cochlea and auditory nerve. Despite the prevalence of SNHL, a universally effective treatment has yet to be approved. To address this absence, the present study aimed to investigate the potential therapeutic effects of TS, a combination of Cuscutae Semen and Rehmanniae Radix Preparata. To this end, both in vitro and in vivo experiments were performed to evaluate the efficacy of TS with respect to SNHL. The results showed that TS was able to protect against ototoxic neomycin-induced damage in both HEI-OC1 cells and otic hair cells in zebrafish. Furthermore, in images obtained using scanning electron microscopy (SEM), an increase in the number of kinocilia, which was prompted by the TS treatment, was observed in the zebrafish larvae. In a noise-induced hearing loss (NIHL) mouse model, TS improved hearing thresholds as determined by the auditory brainstem response (ABR) test. Additionally, TS was found to regulate several genes related to hearing loss, including Trpv1, Cacna1h, and Ngf, as determined by quantitative real-time polymerase chain reaction (RT-PCR) analysis. In conclusion, the findings of this study suggest that TS holds promise as a potential treatment for sensorineural hearing loss. Further research is necessary to confirm these results and evaluate the safety and efficacy of TS in a clinical setting.

Comparative neuroprotective effects of Cerebrolysin, dexamethasone, and ascorbic acid on sciatic nerve injury model: Behavioral and histopathological study

Background

The majority of the suggested experimental modalities for peripheral nerve injury (PNI) result in varying degrees of recovery in animal models; however, there are not many reliable clinical pharmacological treatment models available. To alleviate PNI complications, research on approaches to accelerate peripheral nerve regeneration is encouraged. Cerebrolysin, dexamethasone, and ascorbic acid (vitamin C) drug models were selected in our study because of their reported curative effects of different mechanisms of action.

Methodology

A total of 40 adult male albino rats were used in this study. Sciatic nerve crush injury was induced in 32 rats, which were divided equally into four groups (model, Cerebrolysin, dexamethasone, and vitamin C groups) and compared to the sham group (n = 8). The sciatic nerve sensory and motor function regeneration after crushing together with gastrocnemius muscle histopathological changes were evaluated by the sciatic function index, the hot plate test, gastrocnemius muscle mass ratio, and immune expression of S100 and apoptosis cascade (BAX, BCL2, and BAX/BCL2 ratio).

Results

Significant improvement of the behavioral status and histopathological assessment scores occurred after the use of Cerebrolysin (as a neurotrophic factor), dexamethasone (as an anti-inflammatory), and vitamin C (as an antioxidant). Despite these seemingly concomitant, robust behavioral and pathological changes, vitamin C appeared to have the best results among the three main outcome measures. There was a positive correlation between motor and sensory improvement and also between behavioral and histopathological changes, boosting the effectiveness, and implication of the sciatic function index as a mirror for changes occurring on the tissue level.

Conclusion

Vitamin C is a promising therapeutic in the treatment of PNI. The sciatic function index (SFI) test is a reliable accurate method for assessing sciatic nerve integrity after both partial disruption and regrowth.