Auditory Cells Research Articles

Clinical outcomes of temporal bone squamous cell carcinoma: A single-institution experience.

This study aimed to investigate the survival outcomes and potential prognostic factors of patients with temporal bone squamous cell carcinoma (TBSCC) treated at our institution. We retrospectively included patients who were diagnosed with TBSCC between 2008 and 2019. The Kaplan-Meier (KM) method was used to describe overall survival (OS), and the association between baseline characteristics and prognoses was examined using Cox proportional hazards models. Fifty consecutive patients with TBSCC were included in this study. The results showed that patients with advanced modified Pittsburgh (MPB)- T classifications had a poorer prognosis (T3 vs. T1-2: HR: 2.81, 95% CI: 0.34-23.43; T4 vs. T1-2: HR: 7.25, 95% CI: 0.95-55.41; p=0.041). Meanwhile, middle ear squamous cell carcinoma (MESCC) showed a significantly worse prognosis than external auditory canal squamous cell carcinoma (EACSCC, HR: 2.65, 95% CI: 1.04-6.76, p=0.04). MESCC and advanced MPB-T classifications might be considered predictors of unfavorable outcomes in patients with TBSCC, indicating that special attention should be paid to the original tumor subsite and tumor extension in the management of patients with TBSCC.

The Efficacy of Radiotherapy without Surgery for External Auditory Canal Squamous Cell Carcinoma.

External auditory canal (EAC) cancer is a rare disease for which there are no adequate evidence-based treatment strategies. Radiotherapy is often used as the initial treatment to preserve the organ. This study aimed to elucidate the efficacy of radiotherapy for EAC squamous cell carcinoma (SCC). Patients with T1 disease were treated with radiotherapy alone. Patients with T2–4 disease were treated with chemoradiotherapy. The median follow-up period was 30.4 months. The 3-year local control (LC) rate for all patients was 51%, the disease-free survival (DFS) rate was 44%, and the overall survival (OS) rate was 73%. For T1–3 disease, the 3-year LC rate was 74%, DFS was 62%, and OS was 89%. However, for T4 disease, the 3-year LC rate was 17%, DFS was 17%, and OS was 50%. In a univariate analysis, only the T-category was a significant factor for LC and DFS (p = 0.006 and 0.02, respectively). All local recurrences were within the high-dose irradiated area. The results of this study suggest chemoradiotherapy can be an alternative to a combination of surgery and postoperative radiation for T1–3 SCC of the EAC. However, the efficacy of chemoradiotherapy in T4 cases was inadequate.

Cellular autophagy, the compelling roles in hearing function and dysfunction.

Sensorineural hearing loss (SNHL) is currently a major health issue. As one of the most common neurodegenerative diseases, SNHL is associated with the degradation of hair cells (HCs), spiral ganglion neurons (SGNs), the stria vascularis, supporting cells and central auditory system cells. Autophagy is a highly integrated cellular system that eliminates impaired components and replenishes energy to benefit cellular homeostasis. Etiological links between autophagy alterations and neurodegenerative diseases, such as SNHL, have been established. The hearing pathway is complex and depends on the comprehensive functions of many types of tissues and cells in auditory system. In this review, we discuss the roles of autophagy in promoting and inhibiting hearing, paying particular attention to specific cells in the auditory system, as discerned through research. Hence, our review provides enlightening ideas for the role of autophagy in hearing development and impairment.

Fine-tuned cholesterol solubilizer, mono-6-O-α-D-maltosyl-γ-cyclodextrin, ameliorates experimental Niemann–Pick disease type C without hearing loss

Niemann–Pick disease type C (NPC) is a fatal disorder with abnormal intracellular cholesterol trafficking resulting in neurodegeneration and hepatosplenomegaly. A cyclic heptasaccharide with different degrees of substitution of 2-hydroxypropyl groups, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), acts as a strong cholesterol solubilizer and is under investigation for treating this disease in clinical trials, but its physicochemical properties and ototoxicity remain a concern. Here, we evaluated the potential of mono-6-O-α-maltosyl-γ-CD (G2-γ-CD), a single-maltose-branched cyclic octasaccharide with a larger cavity than HP-β-CD, for treating NPC. We identified that G2-γ-CD ameliorated NPC manifestations in model mice and showed lower ototoxicity in mice than HP-β-CD. To investigate the molecular mechanisms of action behind the differential ototoxicity of these CDs, we performed cholesterol solubility analysis, proton nuclear magnetic resonance spectroscopy, and molecular modeling, and estimated that the cholesterol inclusion mode of G2-γ-CD maintained solely the 1:1 inclusion complex, whereas that of HP-β-CD shifted to the highly-soluble 2:1 complex at higher concentrations. We predicted the associations of these differential complexations of CDs with cholesterol with the profile of disease attenuation and of the auditory cell toxicity using specific cell models. We proposed that G2-γ-CD can serve as a fine-tuned cholesterol solubilizer for treating NPC, being highly biocompatible and physicochemically suitable for clinical application.

Network pharmacology and experimental evidence reveal the protective mechanism of Yi-Qi Cong-Ming decoction on age-related hearing loss

Context Yi-Qi Cong-Ming (YQCM) decoction has been widely used to prevent age-related hearing loss (ARHL), the most prevalent neurodegenerative disease in the elderly. Objective To explore the mechanism of YQCM decoction in the treatment of ARHL. Materials and methods The chemical constituents of YQCM were screened from the Traditional Chinese Medicine Systems Pharmacology Database. Potential targets of YQCM against ARHL were predicted by DrugBank, GeneCards, and OMIM database. Protein-protein network and enrichment analysis were used for exploring possible molecular mechanisms. Molecular docking and an in vitro model of ARHL by exposing auditory cells with 100 μM H2O2 for 3 h were applied. Cell viability and mitochondrial membrane potential (ΔΨM) were detected by CCK-8 and high-content analysis. γH2AX and cleaved caspase-3 were detected by Western blot. Results The main compounds have good affinities with hub targets, especially AKT1, PTGS2, and CASP3. GO and KEGG analysis showed that the main biological process and key targets were related to negative regulation of the apoptotic process. H2O2 treatment could reduce the cell viability by 68% and impaired ΔΨM, while 90 μg/mL YQCM pre-treatment could restore the cell viability by 97.45% and increase ΔΨM (2-fold higher). YQCM pre-treatment also reduced γH2AX and cleaved caspase-3 protein levels. Conclusions Our study suggested that YQCM prevents ARHL by modulating the apoptosis process in auditory hair cells. Moreover, this study proved that bioinformatics analysis combined with molecular docking and cell model is a promising method to explore other possible pharmacological interventions of ARHL.

Pitavastatin protects against neomycin-induced ototoxicity through inhibition of endoplasmic reticulum stress.

Irreversible injury to inner ear hair cells induced by aminoglycoside antibiotics contributes to the formation of sensorineural hearing loss. Pitavastatin (PTV), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, has been reported to exert neuroprotective effects. However, its role in aminoglycoside-induced hearing loss remains unknown. The objectives of this study were to investigate the beneficial effects, as well as the mechanism of action of PTV against neomycin-induced ototoxicity. We found that PTV remarkably reduced hair cell loss in mouse cochlear explants and promoted auditory HEI-OC1 cells survival after neomycin stimulation. We also observed that the auditory brainstem response threshold that was increased by neomycin was significantly reduced by pretreatment with PTV in mice. Furthermore, neomycin-induced endoplasmic reticulum stress in hair cells was attenuated by PTV treatment through inhibition of PERK/eIF2α/ATF4 signaling. Additionally, we found that PTV suppressed the RhoA/ROCK/JNK signal pathway, which was activated by neomycin stimulation in HEI-OC1 cells. Collectively, our results showed that PTV might serve as a promising therapeutic agent against aminoglycoside-induced ototoxicity.

Biopolymer Lipid Hybrid Microcarrier for Transmembrane Inner Ear Delivery of Dexamethasone.

Dexamethasone is one of the most often used corticosteroid drugs for sensorineural hearing loss treatment, and is used either by intratympanic injection or through systemic delivery. In this study, a biopolymer lipid hybrid microcarrier was investigated for enhanced local drug delivery and sustained release at the round window membrane level of the middle ear for the treatment of sensorineural hearing loss (SNHL). Dexamethasone-loaded and dexamethasone-free microparticles were prepared using biopolymers (polysaccharide and protein, pectin and bovine serum albumin, respectively) combined with lipid components (phosphatidylcholine and Dimethyldioctadecylammonium bromide) in order to obtain a biopolymer–liposome hybrid system, with a complex structure combining to enhance performance in terms of physical and chemical stability. The structure of the microparticles was evaluated by FTIR, XRD, thermal analysis, optical microscopy, and scanning electron microscopy (SEM). The encapsulation efficiency determination and the in vitro Dexamethasone release study were performed using UV-Vis spectroscopy. The high value of encapsulation efficiency and the results of the release study indicated six days of sustained release, encouraging us to evaluate the in vitro cytotoxicity of Dexamethasone-loaded microparticles and their influence on the cytotoxicity induced by Cisplatin on auditory HEI-OC1 cells. The results show that the new particles are able to protect the inner ear sensory cells.

Preventive Effect of Cocoa Flavonoids via Suppression of Oxidative Stress-Induced Apoptosis in Auditory Senescent Cells.

Presbycusis or Age-related hearing loss (ARHL) is a sensorineural hearing loss that affects communication, leading to depression and social isolation. Currently, there are no effective treatments against ARHL. It is known that cocoa products have high levels of polyphenol content (mainly flavonoids), that are potent anti-inflammatory and antioxidant agents with proven benefits for health. The objective is to determine the protective effect of cocoa at the cellular and molecular levels in Presbycusis. For in vitro study, we used House Ear Institute-Organ of Corti 1 (HEI-OC1), stria vascularis (SV-k1), and organ of Corti (OC-k3) cells (derived from the auditory organ of a transgenic mouse). Each cell line was divided into a control group (CTR) and an H2O2 group (induction of senescence by an oxygen radical). Additionally, every group of every cell line was treated with the cocoa polyphenolic extract (CPE), measuring different markers of apoptosis, viability, the activity of antioxidant enzymes, and oxidative/nitrosative stress. The data show an increase of reactive oxidative and nitrogen species (ROS and RNS, respectively) in senescent cells compared to control ones. CPE treatment effectively reduced these high levels and correlated with a significant reduction in apoptosis cells by inhibiting the mitochondrial-apoptotic pathway. Furthermore, in senescence cells, the activity of antioxidant enzymes (Superoxide dismutase, SOD; Catalase, CAT; and Glutathione peroxidase, GPx) was recovered after CPE treatment. Administration of CPE also decreased oxidative DNA damage in the auditory senescent cells. In conclusion, CPE inhibits the activation of senescence-related apoptotic signaling by decreasing oxidative stress in auditory senescent cells.

NPC1 Deficiency Contributes to Autophagy-Dependent Ferritinophagy in HEI-OC1 Auditory Cells.

Niemann–Pick type C disease (NPCD) is a rare genetic syndrome characterized by cholesterol accumulation in multiple organelles. NPCD is mainly caused by gene deficiency of NPC intracellular cholesterol transporter 1 (NPC1). It has been reported that some of the NPCD patients exhibit clinical features of progressive hearing loss at high frequency and iron disorder, but the underlying relationship is unknown. A recent study has reported that ferroptosis contributes to the impairment of cochlear hair cells that are related to sensory hearing. In this study, we generated NPC1-deficient HEI-OC1 cells to show the effect of NPC1 deficiency on cochlear outer hair cells. We found that NPC1 deficiency enhances autophagy-dependent ferritinophagy to release Fe (II). Our work provides important insights into the effect of NPC1 deficiency in auditory cells, indicating that it induces ferroptosis and results in hearing loss.

Association of gene mutations with clinicopathologic features in patients with external auditory canal squamous cell carcinoma.

External auditory canal squamous cell carcinoma (EACSCC) is a rare form of malignant tumor. Due to the extremely limited understanding of the genomic landscape in EACSCC, the association between gene mutations and clinicopathologic features remains unclear. This study aimed to explore somatic gene mutations associated with the clinicopathological features in patients with EACSCC, and to identify the candidate gene mutations for predicting survival outcome in EACSCC. Twenty-two tissue samples obtained from patients with EACSCC were analyzed for genetic mutations based on targeted next-generation sequencing and genetic expression based on IHC staining to investigate the driver of tumorigenesis and/or the candidates of genes for predicting clinical outcome in EACSCC. Gene alterations were most frequently observed in TP53 (59.1%), followed by CREBBP (9.1%). TP53 mutations showed significant correlation with T classification (P = 0.027) and p53 expression phenotype (P < 0.001). The 5-year overall survival (OS) rates for EACSCC patients with TP53 mutations and wild-type TP53 were 45.0% and 75.0%, respectively. Multivariable analysis using the Cox proportional hazards model demonstrated that TP53 mutations were independent predictors of OS rates for EACSCC patients (P = 0.007). This study has suggested that TP53 mutations have potential for use as a biomarker for identifying individuals at high risk of developing tumors and for predicting survival outcome in EACSCC. IHC staining for p53 might play a useful role as screening tool for detecting TP53 mutations in patients with EACSCC.

MiR-34a predicts the prognosis of advanced-stage external auditory canal squamous cell carcinoma

Background External auditory canal (EAC) squamous cell carcinoma (SCC) is a rare disease, and the survival rate is low in the advanced stages. It has been reported that miR-34a expression is low in many cancers and acts as a tumor suppressor, but its function in EACSCC has not yet been reported. Aims To analyze the miR-34a expression levels in EACSCC specimens using in situ hybridization (ISH). Material and Methods We performed microRNA ISH for miR-34a detection and immunohistochemical analysis of p53 and Ki67 in the EACSCC and otitis externa (OE) specimens. Results miR-34a was expressed in the basal and suprabasal layers in the OE epidermis. The pronounced expression of miR-34a was observed in the two cases of T2 (Stage II). In the one case of T3 (Stage III), it was almost the same as that of the OE. On the other hand, the expression levels of miR-34a in the one case of T3 (Stage IV) and two cases of T4 (Stage IV) were apparently reduced. Conclusion We demonstrated that the expression level of miR-34a was higher in early-stage EACSCC and lower in advanced-stage EACSCC. Significance The expression level of miR-34a may predict a prognosis in patients with advanced-stage EACSCC.

Salubrinal Protects Against Cisplatin-Induced Cochlear Hair Cell Endoplasmic Reticulum Stress by Regulating Eukaryotic Translation Initiation Factor 2α Signalling.

ObjectiveCisplatin is a broad-spectrum anti-tumour drug commonly used in clinical practice. However, its ototoxicity greatly limits its clinical application, and no effective method is available to prevent this effect. Endoplasmic reticulum stress (ERS) is reportedly involved in cisplatin ototoxicity, but the exact mechanism remains unclear. Therefore, this study aimed to investigate the role of eukaryotic translation initiation factor 2α (eIF2α) signalling and its dephosphorylation inhibitor salubrinal in cisplatin ototoxicity.MethodsWe evaluated whether salubrinal could protect against cisplatin-induced damage in House Ear Institute-Organ of Corti 1 (HEI-OC1) cells and mouse cochlear explants. By knocking down eIF2α, we elucidated the vital role of eIF2α in cisplatin-induced damage in HEI-OC1 cells. Whole-mount immunofluorescent staining and confocal microscopy of mouse cochlear explants and HEI-OC1 cells were performed to analyse cisplatin-induced damage in cochlear hair cells and the auditory cell line.ResultsData suggested salubrinal attenuated cisplatin-induced hair cell injury by inhibiting apoptosis. In addition, salubrinal significantly reduced ERS levels in hair cells via eIF2α signalling, while eIF2α knockdown inhibited the protective effect of salubrinal.SignificanceSalubrinal and eIF2α signalling play a role in protecting against cisplatin-induced ototoxicity, and pharmacological inhibition of eIF2α-mediated ERS is a potential treatment for cisplatin-induced damage in the cochlea and HEI-OC1 cells.

Protective Effect of Agmatine Against Cisplatin- Induced Cellular Apoptosis in an Auditory Cell Line.

The aims of this study were to evaluate the protective effects of agmatine against cisplatin-induced cellular apoptosis in an audi- tory cell line and to prove the protective mechanism of agmatine. The House Ear Institute-Organ of Corti 1 cells were co-treated with agmatine at different concentrations and 15 μM of cisplatin for 48 hours. Cell viability and proliferation were measured. Annexin V-fluorescein isothiocyanate /propidium iodide staining was performed to analyze apoptosis. The levels of intracellular reactive oxygen species were measured using flow cytometry. The expression of BCL2-associated X protein and the enzymatic activity of caspase-3 was measured to examine the pathway of apoptosis induction. In normal conditions, the maximal protective effect occurred with 10 mM of agmatine. However, in the presence of cisplatin, the maximal protective effect was observed from 8 mM of agmatine. Thus, 8 mM was chosen as the ideal agmatine concentration for the analysis of protective effects against cisplatin-induced cytotoxicity. Agmatine exerted a significant protective effect against 15 μM of cisplatin when applied for 48 hours and reduced the proportion of necrotic and late apoptotic cells. Agmatine did not significantly reduce the cisplatin-induced increase in reactive oxygen species but decreased the expression of BCL2-associated X protein and the activity of caspase-3. Agmatine protected against cisplatin-induced cellular apoptosis in an auditory cell line. These effects were mediated by the pro- tection of mitochondrial function and inhibition of apoptosis.

Urolithin A attenuates auditory cell senescence by activating mitophagy

Aging of sensory organs is associated with a decline in mitochondrial function and the accumulation of dysfunctional mitochondria. Impaired mitophagy blocks the turnover of dysfunctional mitochondria and leads to their accumulation. Urolithin A (UA) induces mitophagy in various mammalian cells. This study was aimed at investigating the effect of the mitophagy activator, UA, on premature senescent auditory cells. The levels of cellular senescence-associated p53 and p21 significantly increased in H2O2-induced senescent House Ear Institute‐Organ of Corti 1 (HEI-OC1) cells and cochlear explants. However, the levels of mitophagy-related molecules significantly decreased. UA significantly decreased the expression of senescence-associated p53 and p21, and increased the expression of mitophagy-related proteins, in H2O2-induced senescent cells and cochlear explants. The percentage of β-galactosidase-stained senescent cells also reduced in H2O2-treated cells and cochlear explants upon UA pre-treatment. The formation of mitophagosomes and mitophagolysosomes was restored upon UA pre-treatment of H2O2-induced senescent cells. The knockdown of mitophagy-related genes (Parkin and Bnip3) resulted in annulment of UA-induced anti-senescent activity. UA significantly increased the ATP content, mitochondrial DNA (mtDNA) integrity, and mitochondrial membrane potential in senescent HEI-OC1 cells. These findings indicate that UA counteracted mitophagy decline and prevented premature senescence in auditory cells. Hence, UA administration might be a promising strategy for preventing mitochondrial dysfunction in patients with age-related hearing loss.

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

Ototoxic hearing loss results from hair cell death via reactive oxygen species (ROS) overproduction and consequent apoptosis. We investigated the effects of vitamin C (VC) on neomycin-induced HEI-OC1 cell damage, as well as the mechanism of inhibition. HEI-OC1 cells were treated with neomycin or with vitamin C (VC). The results indicated that VC had a protective effect on neomycin-induced HEI-OC1 cell death. Mechanistically, VC decreased neomycin-induced ROS generation, suppressed cell death, and increased cell viability. VC inhibited neomycin-induced apoptosis, ameliorated neomycin reduced antiapoptotic Bcl-2 expression, and suppressed neomycin increased expression of proapoptotic Bax, caspase-3 cleavage and caspase-8. TUNEL labeling demonstrated that VC blocked neomycin-induced apoptosis. Further study revealed that the effect of VC on neomycin-induced hair cell death was through interference with JNK activation and p38 phosphorylation. These results indicate that VC via suppressed ROS generation, which inhibited cell death by counteracting apoptotic signaling induced by neomycin in cells. Hence, VC is a potential candidate for protection agent against neomycin-induced HEI-OC1 cell ototoxicity.

Medical-Grade Silicone Rubber-Hydrogel-Composites for Modiolar Hugging Cochlear Implants.

The gold standard for the partial restoration of sensorineural hearing loss is cochlear implant surgery, which restores patients’ speech comprehension. The remaining limitations, e.g., music perception, are partly due to a gap between cochlear implant electrodes and the auditory nerve cells in the modiolus of the inner ear. Reducing this gap will most likely lead to improved cochlear implant performance. To achieve this, a bending or curling mechanism in the electrode array is discussed. We propose a silicone rubber–hydrogel actuator where the hydrogel forms a percolating network in the dorsal silicone rubber compartment of the electrode array to exert bending forces at low volume swelling ratios. A material study of suitable polymers (medical-grade PDMS and hydrogels), including parametrized bending curvature measurements, is presented. The curvature radii measured meet the anatomical needs for positioning electrodes very closely to the modiolus. Besides stage-one biocompatibility according to ISO 10993-5, we also developed and validated a simplified mathematical model for designing hydrogel-actuated CI with modiolar hugging functionality.

Pyrroloquinoline quinone (PQQ) protects mitochondrial function of HEI-OC1 cells under premature senescence

The aim of this study was to investigate the effects of pyrroloquinoline quinone (PQQ), an oxidoreductase cofactor, on the H2O2-induced premature senescence model in HEI-OC1 auditory cells and to elucidate its mechanism of action in vitro. Cells were treated with PQQ for 1 day before H2O2 (100 μM) exposure. Mitochondrial respiratory capacity was damaged in this premature senescence model but was restored in cells pretreated with PQQ (0.1 nM or 1.0 nM). A decrease in mitochondrial potential, the promotion of mitochondrial fusion and the accelerated movement of mitochondria were all observed in PQQ-pretreated cells. The protein expression of sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) were significantly decreased under H2O2 exposure while they were increased with PQQ pretreatment, and PGC-1α acetylation was significantly decreased. In conclusion, PQQ has a protective effect on the premature senescence model of HEI-OC1 auditory cells and is associated with the SIRT1/PGC-1α signaling pathway, mitochondrial structure, and mitochondrial respiratory capacity.

A Novel External Auditory Canal Squamous Cell Carcinoma Cell Line Sensitive to CDK4/6 Inhibition.

To characterize cell line CAE606 derived from a squamous cell carcinoma (SCC) of the external auditory canal (EAC) and to show its usefulness as a model for testing candidate therapeutic agents. Preclinical translational research. Biomedical research institute. The cell line was initiated from a moderately differentiated T2N0M0 EAC SCC. We studied its histologic and genetic features as well as growth and invasion parameters. Sensitivity to cell CDK4/6 cell cycle inhibitor palbociclib was analyzed. CAE606 cells expressed heavy molecular weight cytokeratin, p63, and vimentin. The population doubling time was 25.8 hours, and the cells showed fast collective cell migration in a wound-healing assay. Short tandem repeat analysis confirmed it to be derived from the primary tumor of the patient. Next-generation sequencing revealed alterations in cell cycle regulation genes, including inactivating mutations in CDKN2A and TP53 and high-level amplification of CCND1 and EGFR. CAE606 showed a strong decrease of phospo-Rb expression upon exposure to the CDK4/6 inhibitor palbociclib, causing significant growth inhibition with an IC50 of 0.46 µM. This is the first report of a stable EAC SCC cell line. Its genetic features make it a useful tool for preclinical testing of new therapeutic agents for EAC SCC, particularly those targeting cell cycle regulation in combination with radio- and chemotherapy or other specific signaling pathway inhibitors.

Mutations in OSBPL2 cause hearing loss associated with primary cilia defects via sonic hedgehog signaling.

Defective primary cilia cause a range of diseases called ciliopathies, which include hearing loss (HL). Variants in the human oxysterol-binding protein like 2 (OSBPL2/ORP2) are responsible for autosomal dominant nonsyndromic HL (DFNA67). However, the pathogenesis of OSBPL2 deficiency has not been fully elucidated. In this study, we show that the Osbpl2-KO mice exhibited progressive HL and abnormal cochlear development with defective cilia. Further research revealed that OSBPL2 was located at the base of the kinocilia in hair cells (HCs) and primary cilia in supporting cells (SCs) and functioned in the maintenance of ciliogenesis by regulating the homeostasis of PI(4,5)P2 (phosphatidylinositol 4,5-bisphosphate) on the cilia membrane. OSBPL2 deficiency led to a significant increase of PI(4,5)P2 on the cilia membrane, which could be partially rescued by the overexpression of INPP5E. In addition, smoothened and GL13, the key molecules in the Sonic Hedgehog (Shh) signaling pathway, were detected to be downregulated in Osbpl2-KO HEI-OC1 cells. Our findings revealed that OSBPL2 deficiency resulted in ciliary defects and abnormal Shh signaling transduction in auditory cells, which helped to elucidate the underlying mechanism of OSBPL2 deficiency in HL.

Inhibition of macrophage migration inhibitory factor alleviates LPS-induced inflammation response of HEI-OC1 cells via suppressing NF-κB signaling

Sudden sensorineural hearing loss (SSNHL) is acute and unexplained. Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine in several inflammatory diseases. However, its role in SSNHL remains elusive. Lipopolysaccharide (LPS) was used to induce the inflammatory response of murine auditory cells, HEI-OC1. Silencing of MIF in HEI-OC1 cells was achieved by transfection of short hairpin RNA against MIF. 740Y-P and IMD0354 were used to stimulate the PI3K pathway and suppress the NF-κB pathway, respectively. RT-qPCR and western blotting were used to examine MIF and cyclooxygenase 2 (COX2) expression in LPS-treated HEI-OC1 cells. ELISA was employed to assess prostaglandin E2 (PGE2) concentrations. MIF was upregulated in LPS-treated HEI-OC1 cells. MIF knockdown reduced PGE2 synthesis and COX2 expression in LPS-treated HEI-OC1 cells. Moreover, MIF knockdown suppressed activation of the PI3K/AKT and NF-κB pathway in LPS-treated HEI-OC1 cells. Additionally, inhibition of MIF decreased PGE2 production and COX2 expression via inactivation of the NF-κB pathway. Inhibition of MIF alleviated LPS-induced inflammation in HEI-OC1 cells via inactivating the NF-κB signaling, which might provide a better understanding for SSNHL development.