Assessment of Oxidative Stress in Patients with Sudden Hearing Loss: A Non-randomized Prospective Clinical Study

Reassessment of oxidative stress in idiopathic sudden hearing loss and preliminary exploration of the effect of physiological concentration of melatonin on prognosis

Background and purpose

The pathogenesis of idiopathic sudden sensorineural hearing loss (ISSNHL) is still unclear, and there is no targeted treatment. This research aimed to verify the role of oxidative stress in ISSNHL and explore whether melatonin has a protective effect on hearing.

Materials and methods

A total of 43 patients with ISSNHL and 15 healthy controls were recruited to detect the level of melatonin, reactive oxygen species (ROS), and total antioxidant capacity (TAC) in the blood and compared before and after treatment. Multivariate logistic regression models were performed to assess the factors relevant to the occurrence and improvement of ISSNHL.

Results

The patients with ISSNHL showed significantly higher ROS levels than controls (4.42 ± 4.40 vs. 2.30 ± 0.59; p = 0.031). The levels of basal melatonin were higher (1400.83 ± 784.89 vs. 1095.97 ± 689.08; p = 0.046) and ROS levels were lower (3.05 ± 1.81 vs. 5.62 ± 5.56; p = 0.042) in the effective group as compared with the ineffective group. Logistic regression analysis showed that melatonin (OR = 0.999, 95% CI 0.997-1.000, p = 0.049), ROS (OR = 1.154, 95% CI 1.025-2.236, p = 0.037), and vertigo (OR = 3.011, 95% CI 1.339-26.983, p = 0.019) were independent factors associated with hearing improvement. Besides, the level of melatonin (OR = 0.999, 95% CI 0.998-1.000, p = 0.023) and ROS (OR = 3.248, 95% CI 1.109-9.516, p = 0.032) were associated with the occurrence of ISSNHL.

Conclusion

Our findings may suggest oxidative stress involvement in ISSNHL etiopathogenesis. The level of melatonin and ROS, and vertigo appear to be predictive of the effectiveness of hearing improvement following ISSNHL treatment.

Efficacy of Mesotympanum Injection and Posterior Auricular Injection in Sudden Hearing Loss of Diabetes Patients

The efficacy of tympanum injection and posterior auricular injection in diabetes with sudden hearing loss (SHL) was analyzed. A mobile terminal-based portable pure tone audiometry system and its processing method were established. Based on mobile terminals, a portable pure tone audiometry system including an Android system, pure sound signal generation, pure tone hearing threshold, and client module was established. A masking model and self-adaptive algorithm were used to detect and reduce noise. Besides, the performance of the portable pure tone audiometry system was detected. A total of 46 diabetes patients with SHL diagnosed at the otolaryngology department in BeiChen Hospital between August 2019 and November 2021 were selected as the research objects and randomly divided into the retroauricular group (posterior auricular injection) and the tympanic group (tympanum injection). Each group included 23 cases. All patients received pure tone audiometry (PTA) before and after the treatment. The changes in fasting blood glucose (FPG), 2h postprandial blood glucose (2hPG), and glycosylated hemoglobin (HbA1c) of the patients were monitored before and after the treatment. Besides, tinnitus loudness visual analog scale (VAS), pain VAS, efficacy, and the incidence of adverse reactions of the patients in two groups were compared. The results indicated that the hear threshold error detected by the medical audiometer and a portable pure tone audiometry system was within 2dB. Before the optimization, there was an error of about 10dB between the hear thresholds detected by the self-adaptive algorithm and a medical audiometer. After the treatment, the hear threshold and average PTA of the patients in the retroauricular and the tympanic groups under different frequencies were both reduced compared with those before the treatment (P < 0.05). The tinnitus VAS score in the retroauricular group was decreased more notably than that in tympanic group (P < 0.01), and the pain VAS score was much lower than that in the tympanic group (P < 0.001). The comparison of FPG, 2hPG, HbA1c, the proportions of cured, significantly effective, effective, ineffective patients, and the total effective rate in the patients in the retroauricular and the tympanic groups before and after the treatment all showed no statistical differences (P > 0.05). The incidence of adverse reactions in tympanic group after the treatment was dramatically higher than that in retroauricular group (P < 0.001). The above results demonstrated that posterior auricular injection showed potential application values in the treatment of SHL with diabetes and established a portable pure tone audiometry system as well as its noise processing method.

Evaluation of Oxidative-Stress Pathway and Recovery of Sudden Sensorineural Hearing Loss

Introduction  Although the pathogenesis of sudden sensorineural hearing loss (SSNHL) has been discussed in the literature, many unclear points remain. Several authors have hypothesized that oxidative stress plays a role in the pathogenesis of noise-related hearing loss, as well as in drug- and aging-related hearing loss. Reactive oxygen species (ROS) may contribute to the pathogenesis of SSNHL in a similar way as in cases of ototoxicity, noise-induced hearing loss and presbyacusis. Objective  The aim of the present study was to find potential peripheral biomarkers to show the levels of oxidative stress in samples of peripheral blood collected from SSNHL patients with and withouth metabolic disease. Methods  In total, 80 consecutive patients with SSNHL were evaluated in the otolaryngology emergency room and outpatient clinic of a tertiary hospital between May 2017 and May 2019. All patients underwent detailed anamnesis, physical examination, audiometry, magnetic resonance imaging (MRI) of the inner ears, and blood tests for serum lipids and plasma activity of thiobarbituric acid reactive species (TBARS). Results  No significant effect of malondialdehyde (MDA) activity was observed regarding the hearing recovery of patients who developed SSNHL. Conclusion  We did not observe a significant correlation between the concentration of TBARs in the peripheral blood or the presence of arterial hypertension and the severity of the initial hearing loss or the prognosis of hearing recovery in patients with SSNHL. The concentration of TBARs in the peripheral blood may not adequately represent the abnormalities that occur in the intracoclear environment.

N-Acetylcysteine Combined With Dexamethasone Treatment Improves Sudden Sensorineural Hearing Loss and Attenuates Hair Cell Death Caused by ROS Stress

Sudden sensorineural hearing loss (SSNHL) is a common emergency in the world. Increasing evidence of imbalance of oxidant–antioxidant were found in SSNHL patients. Steroids combined with antioxidants may be a potential strategy for the treatment of SSNHL. In cochlear explant experiment, we found that N-acetylcysteine (NAC) combined with dexamethasone can effectively protect hair cells from oxidative stress when they were both at ineffective concentrations alone. A clinic trial was designed to explore whether oral NAC combined with intratympanic dexamethasone (ITD) as a salvage treatment has a better therapeutic effect. 41 patients with SSNHL were randomized to two groups. 23 patients in control group received ITD therapy alone, while 18 patient s in NAC group were treated with oral NAC and ITD. The patients were followed-up on day 1st (initiation of treatment) and day 14th. Overall, there was no statistical difference in final pure-tone threshold average (PTA) improvement between those two groups. However, a significant hearing gain at 8,000 Hz was observed in NAC group. Moreover, the hearing recovery rates of NAC group is much higher than that in control group. These results demonstrated that oral NAC in combination with ITD therapy is a more effective therapy for SSNHL than ITD alone.

Elucidation of the Hdac2/Sp1/miR-204-5p/Bcl-2 axis as a modulator of cochlear apoptosis via in vivo/in vitro models of acute hearing loss

We previously reported that dysregulation of histone deacetylase 2 (Hdac2) was associated with the prognosis of sudden sensorineural hearing loss. However, the underlying molecular mechanisms are poorly understood. In the present study, we developed an acute hearing loss animal model in guinea pigs by infusing lipopolysaccharides (LPS) into the cochlea and measured the expression of Hdac2 in the sensory epithelium. We observed that the level of Hdac2 was significantly decreased in the LPS-infused cochleae. The levels of apoptosis-inhibition genes Bcl-2 and Bcl-xl were also decreased in the cochlea and correlated positively with the levels of Hdac2. Caspase3 or TUNEL-positive spiral ganglion neurons, hair cells, and supporting cells were observed in the LPS-infused cochleae. These in vivo observations were recapitulated in cell culture experiments. Based on bioinformatics analysis, we found miR-204-5p was engaged in the regulation of Hdac2 on Bcl-2. Molecular mechanism experiments displayed that miR-204-5p could be regulated by Hdac2 through interacting with transcription factor Sp1. Taken together, these results indicated that the Hdac2/Sp1/miR-204-5p/Bcl-2 regulatory axis mediated apoptosis in the cochlea, providing potential insights into the progression of acute hearing loss. To our knowledge, the study describes a miRNA-related mechanism for Hdac2-mediated regulation in the cochlea for the first time.