The auditory function in migraine model rats induced by postauricular nitroglycerin injection

Heavy metal biomarkers and their impact on hearing loss risk: a machine learning framework analysis

Background

Exposure to heavy metals has been implicated in adverse auditory health outcomes, yet the precise relationships between heavy metal biomarkers and hearing status remain underexplored. This study leverages a machine learning framework to investigate these associations, offering a novel approach to understanding the interplay between environmental exposures and hearing loss.

Methods

We conducted a retrospective cross-sectional analysis using data from the 2012-2018 National Health and Nutrition Examination Survey (NHANES), encompassing 2,772 participants after applying exclusion criteria. Demographic, clinical, and heavy metal biomarker data (e.g., blood lead and cadmium levels) were analyzed as features, with hearing loss status-defined as a pure-tone average threshold exceeding 25 dB HL across 500, 1,000, 2000, and 4,000 Hz in the better ear-serving as the binary outcome. Multiple machine learning algorithms, including Random Forest, XGBoost, Gradient Boosting, Logistic Regression, CatBoost, and MLP, were optimized and evaluated. Model performance was assessed using accuracy, area under the curve (AUC), sensitivity, and specificity, while SHAP (SHapley Additive exPlanations) elucidated feature contributions.

Results

The CatBoost model demonstrated the strongest performance, achieving an accuracy of 74.9% and an AUC of 0.792 on test data. Age, education level, gender, and blood levels of lead and cadmium emerged as the most significant features associated with hearing loss, as determined by SHAP analysis. These findings highlight key correlates of hearing impairment within the study population.

Conclusion

This study underscores the utility of a machine learning framework in identifying associations between heavy metal biomarkers and hearing loss in a nationally representative sample. While not designed to forecast hearing loss over time, our findings suggest potential clinical relevance for identifying individuals with elevated heavy metal exposure who may warrant further audiometric evaluation. This work lays a foundation for future longitudinal studies to explore these relationships more comprehensively.

Ototoxic effects of unilateral postauricular neomycin administration on the inner ears of Guinea pigs

BACKGROUNDS

Due to the therapeutic needs of inner ear diseases, a simple method of inner ear drug delivery has been under exploration. Postauricular administration, which involves injecting the drug through the middle of the retroauricular groove, is a potential novel approach, but its mechanisms remain unclear.

OBJECTIVES

To investigate threshold shifts in the auditory brainstem response (ABR), as well as the morphology and quantity of hair cells on the bilateral inner ear of guinea pigs after postauricular neomycin administration.

MATERIAL AND METHODS

Thirty healthy guinea pigs were divided randomly into two groups and administered either neomycin 200 mg/kg or saline 1 ml via daily postauricular injection for 10 days. Auditory threshold-shifts were examined by tests of the ABR. The quantity and morphology of hair cells in the organ of Corti were assessed by confocal laser scanning microscopy.

RESULTS

The ABR results showed that at a frequency of 16 kHz, the threshold shift was 21.00 ± 14.49 dB in the neomycin injection side, 10.00 ± 16.67 dB in the contralateral side, and 0.50 ± 3.69 dB in the saline group. At a frequency of 24 kHz, the threshold shift was 37.00 ± 16.36 dB in the neomycin injection side, 14.50 ± 9.26 dB in the contralateral side, and 1.00 ± 2.11 dB in the saline group. Histopathological analysis revealed that the outer hair cells (OHCs) in the neomycin injection side suffered significant morphological and numerical loss, while the OHC loss in the contralateral ear was less severe than in the injection side but greater than in the saline group.

CONCLUSIONS AND SIGNIFICANCE

This study confirms that postauricular administration is a novel method of local drug delivery to the inner ear, which has practical value in future experimental modeling and the treatment of inner ear diseases.

A role of NLRP3 and MMP9 in migraine progression: a systematic review of translational study

Background

Migraines affect one billion individuals globally, with a higher occurrence among young adults and women. A significant survey in the United States indicated that 17.1% of women and 5.6% of men suffer from migraines. This study seeks to investigate the potential connection between NLRP3 and MMP9 in migraine pathology.

Methods

The research involved searching databases such as PubMed, Scopus, Science Direct, Google Scholar, and Proquest, with the search concluding on March 31, 2024. Following PRISMA guidelines, PICO data were collected, focusing exclusively on animal models induced by Nitroglycerine (10 mg/kg), while excluding clinical studies.

Results

The study, originally registered in Prospero Reg. No. CRD42022355893, conducted bias analysis using SYRCLE's RoB tool and evaluated author consensus using GraphPad v9.5.1. Out of 7,359 search results, 22 papers met the inclusion criteria. Inter-rater reliability among reviewers was assessed using Cohen's kappa statistics.

Conclusion

This review summarizes 22 preclinical studies on Nitroglycerin (NTG), NLRP3, MMP9, and related biomarkers in migraine. They reveal that NTG, especially at 10 mg/kg, consistently induces migraine-like symptoms in rodents by activating NLRP3 inflammasome and stimulating proinflammatory molecule production.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, CRD42022355893.

Association between blood volatile organic aromatic compound concentrations and hearing loss in US adults

OBJECTIVE

Benzene, ethylbenzene, meta/para-xylene, and ortho-xylene, collectively referred to as benzene, ethylbenzene, and xylene (BEX), constitute the main components of volatile organic aromatic compounds (VOACs) and can have adverse effects on human health. The relationship between exposure to BEX and hearing loss (HL) in the adult U.S. population was aimed to be assessed.

METHODS

Cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) for the years 2003-2004, 2011-2012, and 2015-2016 were analyzed. This dataset included complete demographic characteristics, pure-tone audiometry measurements, and volatile organic compound detection data from the NHANES database. A weighted multivariate logistic regression model was employed to investigate the associations between blood BEX concentrations HL, low-frequency hearing loss (SFHL), and high-frequency hearing loss (HFHL).

RESULTS

2174 participants were included, with weighted prevalence rates of HL, SFHL, and HFHL being 46.81%, 25.23%, and 45.86%, respectively. Exposure to benzene, ethylbenzene, meta/para-xylene, and ortho-xylene, and cumulative BEX concentrations increased the risk of hearing loss (odds ratios [ORs] were 1.36, 1.22, 1.42, 1.23, and 1.31, respectively; all P < 0.05). In the analysis with SFHL as the outcome, ethylbenzene, m-/p-xylene, o-xylene, benzene, and overall BEX increased the risk (OR 1.26, 1.21, 1.28, 1.20, and 1.25, respectively; all P < 0.05). For HFHL, exposure to ethylbenzene, m-/p-xylene, o-xylene, benzene, and overall BEX increased the risk (OR 1.36, 1.22, 1.42, 1.22, and 1.31, respectively; all P < 0.05).

CONCLUSION

Our study indicated that a positive correlation between individual or cumulative exposure to benzene, ethylbenzene, meta/para-xylene, and ortho-xylene and the risk of HL, SFHL, and HFHL. Further research is imperative to acquire a more comprehensive understanding of the mechanisms by which organic compounds, notably BEX, in causing hearing loss and to validate these findings in longitudinal environmental studies.