Expressions of ion co-transporter genes in salicylate-induced tinnitus and treatment effects of spirulina

C-Phycocyanin Attenuates Noise-Induced Cochlear Synaptopathy via the Inhibition of Oxidative Stress and Intercellular Adhesion Molecule-1 in the Cochlea

The synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) are the most vulnerable structures in the noise-exposed cochlea. Cochlear synaptopathy results from the disruption of these synapses following noise exposure and is considered the main cause of poor speech understanding in noisy environments, even when audiogram results are normal. Cochlear synaptopathy leads to the degeneration of SGNs if damaged IHC-SGN synapses are not promptly recovered. Oxidative stress plays a central role in the pathogenesis of cochlear synaptopathy. C-Phycocyanin (C-PC) has antioxidant and anti-inflammatory activities and is widely utilized in the food and drug industry. However, the effect of the C-PC on noise-induced cochlear damage is unknown. We first investigated the therapeutic effect of C-PC on noise-induced cochlear synaptopathy. In vitro experiments revealed that C-PC reduced the H2O2-induced generation of reactive oxygen species in HEI-OC1 auditory cells. H2O2-induced cytotoxicity in HEI-OC1 cells was reduced with C-PC treatment. After white noise exposure for 3 h at a sound pressure of 118 dB, the guinea pigs intratympanically administered 5 μg/mL C-PC exhibited greater wave I amplitudes in the auditory brainstem response, more IHC synaptic ribbons and more IHC-SGN synapses according to microscopic analysis than the saline-treated guinea pigs. Furthermore, the group treated with C-PC had less intense 4-hydroxynonenal and intercellular adhesion molecule-1 staining in the cochlea compared with the saline group. Our results suggest that C-PC improves cochlear synaptopathy by inhibiting noise-induced oxidative stress and the inflammatory response in the cochlea.

Analysis of Studies in Tinnitus-Related Gene Research

Objective

Summarize and analyze the current research results of tinnitus-related genes, explore the potential links between the results of each study, and provide reference for subsequent studies.

Methods

Collect and sort out the research literature related to tinnitus genes included in PubMed, Web of Science, China National Knowledge Infrastructure, and Wanfang Data Knowledge Service Platform before December 31, 2019. Then the relevant contents of the literature were sorted out and summarized.

Results

Fifty-one articles were finally selected for analysis: 31 articles (60.8%) were classified as researches on animal models of tinnitus, and 20 (39.2%) as researches on tinnitus patients. Existing studies have shown that genes related to oxidative stress, inflammatory response, nerve excitation/inhibition, and nerve growth are differentially expressed in tinnitus patients or animal models, and have presented the potential links between genes or proteins in the occurrence and development of tinnitus.

Conclusion

The research on tinnitus-related genes is still in the exploratory stage, and further high-quality research evidence is needed.

Pharmacologic treatments in preclinical tinnitus models with special focus on Ginkgo biloba leaf extract EGb 761®

Tinnitus is defined as the perception of sound in the absence of external acoustic stimuli. Frequent comorbidities or associated factors are depression, anxiety, concentration problems, insomnia, resignation, helplessness, headache, bruxism, or social isolation, just to name a few. Although many therapeutic approaches have already been tested with varying success, there still is no cure available for tinnitus. The search for an effective treatment has been hampered by the fact that the mechanisms of tinnitus development are still not fully understood, although several models are available and discussed in this review. Our review will give a brief overview about preclinical models, presenting the heterogeneity of tinnitus sub-types depending on the different inner ear and brain structures involved in tinnitus etiology and pathogenesis. Based on these models we introduce the different target structures and transmitter systems implicated in tinnitus development and provide an extensive overview on preclinical drug-based therapeutic approaches that have been explored in various animal models. As the special extract from Ginkgo biloba leaves EGb 761® has been the most widely tested drug in both non-clinical tinnitus models as well as in clinical trials, a special focus will be given to EGb 761®. The efficacy of terpene lactones, flavone glycosides and proanthocyanidines with their distinct contribution to the overall efficacy profile of the multi-constituent drug EGb 761® will be discussed.

Association of periodic limb movements during sleep and tinnitus in humans

Both of periodic limb movements during sleep (PLMS) and tinnitus were related with dopaminergic system dysfunction. However, it was still unclear whether PLMS, one kind of sleep disturbances, was associated with chronic tinnitus or not. Thus, we aimed to investigate this issue in humans. Clinical and overnight polysomnographic data of 2849 adults from a community hospital during Nov. 2011 to Jun 2017 in Taiwan was collected retrospectively. The association of PLMS and chronic tinnitus was analyzed by Student’s t-test, Pearson’s Chi-Square test, and multivariate logistic regression. The results showed that the mean age was 50.6 years old (standard deviation, SD = 13.3, range = 18~91) for all subjects. There were 1886 subjects without tinnitus and 963 subjects with tinnitus in this study. The PLMS was not significantly different between subjects without tinnitus (mean = 1.0/h, SD = 3.5/h) and subjects with tinnitus mean = 1.1/h, SD = 3.4/h) by Student’s t-test. The severity of PLMS was not significantly between non-tinnitus and tinnitus subjects by Pearson’s Chi-Square test. Multivariate logistic regression also showed that PLMS was not significantly associated with tinnitus after adjusting age, sex, subjective hearing loss, Parkinson’s disease, and insomnia. In conclusion, PLMS was not associated with chronic tinnitus in humans.

The association between tinnitus and the risk of ischemic cerebrovascular disease in young and middle-aged patients: A secondary case-control analysis of a nationwide, population-based health claims database

Background

Tinnitus and ischemic cerebrovascular disease (ICVD) may share common pathophysiologic mechanisms. Nevertheless, no studies have investigated whether tinnitus is associated with a higher risk of ICVD. The aim of this study was to evaluate the risk of ICVD among young and middle-aged patients with tinnitus.

Methods

Using the Taiwan’s National Health Insurance Research Database, we identified 3,474 patients 20–45 years old with incident ICVD diagnosed between January 1, 2000 and December 31, 2010 and 17,370 controls, frequency matched on age interval, sex, and year of the index date. Risk of ICVD associated with tinnitus was assessed using multiple logistic regression analyses.

Results

Tinnitus was significantly associated with a higher risk of incident ICVD among young and middle-aged patients (adjusted odds ratio [OR] 1.66, 95% confidence interval [CI] 1.34–2.04), adjusting for sex, age, and comorbidities. In addition, sex-stratified analysis showed that the associations were significant in both male (adjusted OR 1.55, 95% CI 1.16–2.07) and female patients (adjusted OR 1.77, 95% CI 1.30–2.41). Furthermore, tinnitus was significantly associated with a higher risk of ICVD in the 20.0–29.9 years (adjusted OR 4.11, 95% CI 1.98–8.52) and 30.0–39.9 years (adjusted OR 2.19, 95% CI 1.57–3.05) age groups, but not in the 40.0–45.0 years age group.

Conclusions

Tinnitus could be a novel risk factor or clinical indicator for young ischemic stroke, and further investigations are warranted.