IL-1β is overexpressed and aberrantly regulated in corticosteroid nonresponders with autoimmune inner ear disease

Negative regulator IL-1 receptor 2 (IL-1R2) and its roles in immune regulation of autoimmune diseases

The decoy receptor interleukin 1 receptor 2 (IL-1R2), also known as CD121b, has different forms: membrane-bound (mIL-1R2), soluble secreted (ssIL-1R2), shedded (shIL-1R2), intracellular domain (IL-1R2ICD). The different forms of IL-1R2 exert not exactly similar functions. IL-1R2 can not only participate in the regulation of inflammatory response by competing with IL-1R1 to bind IL-1 and IL-1RAP, but also regulate IL-1 maturation and cell activation, promote cell survival, participate in IL-1-dependent internalization, and even have biological activity as a transcriptional cofactor. In this review, we provide a detailed description of the biological characteristics of IL-1R2 and discuss the expression and unique role of IL-1R2 in different immune cells. Importantly, we summarize the role of IL-1R2 in immune regulation from different autoimmune diseases, hoping to provide a new direction for in-depth studies of pathogenesis and therapeutic targets in autoimmune diseases.

Relevant Research of Inflammatory Cytokines Spectrum in Peripheral Blood of Sudden Hearing Loss

OBJECTIVE

To investigate whether there is a correlation between the inflammatory state and the pathogenesis and clinical features of sudden hearing loss (SHL) by studying the expression of inflammation-related cytokines in the peripheral blood of patients with SHL.

METHODS

In this work, we analyzed the cytokine profiles of 48 analytes in 38 patients with SHL compared to 38 healthy donors using a multiplex immunoassay. This study used appropriate statistical methods to screen for inflammatory cytokines associated with the pathogenesis of SHL, to analyze their network correlation, and to analyze the relationship between clinical features of SHL and inflammatory cytokines.

RESULTS

Several cytokines, including CTACK, Eotaxin, HGF, INF-α2, IFN-β, IL-1β, IL-1ra, IL-2Rα, IL-4, IL-7, IL-8, IL-9, IL-10, IL-12(p40), IL-13, MIG, β-NGF, SCF, and TNF-α, exhibited significantly higher levels in the peripheral blood of the SHL group compared to the control group. An inflammatory network composed of multiple cytokines, including IL-1β, is a risk factor for the development of SHL.

CONCLUSION

This study identified several inflammatory cytokines with elevated expression, which may be linked with the onset of SHL. The results of this study also provide a basis for the theoretical hypothesis of inflammation in SHL.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:3293-3301, 2024.

A TH17-intrinsic IL-1β-STAT5 axis drives steroid resistance in autoimmune neuroinflammation

Steroid resistance poses a major challenge for the management of autoimmune neuroinflammation. T helper 17 (TH17) cells are widely implicated in the pathology of steroid resistance; however, the underlying mechanisms are unknown. In this study, we identified that interleukin-1 receptor (IL-1R) blockade rendered experimental autoimmune encephalomyelitis (EAE) mice sensitive to dexamethasone (Dex) treatment. Interleukin-1β (IL-1β) induced a signal transducer and activator of transcription 5 (STAT5)-mediated steroid-resistant transcriptional program in TH17 cells, which promoted inflammatory cytokine production and suppressed Dex-induced anti-inflammatory genes. TH17-specific deletion of STAT5 ablated the IL-1β-induced steroid-resistant transcriptional program and rendered EAE mice sensitive to Dex treatment. IL-1β synergized with Dex to promote the STAT5-dependent expression of CD69 and the development of central nervous system (CNS)-resident CD69+ TH17 cells. Combined IL-1R blockade and Dex treatment ablated CNS-resident TH17 cells, reduced EAE severity, and prevented relapse. CD69+ tissue-resident TH17 cells were also detected in brain lesions of patients with multiple sclerosis. These findings (i) demonstrate that IL-1β-STAT5 signaling in TH17 cells mediates steroid resistance and (ii) identify a therapeutic strategy for reversing steroid resistance in TH17-mediated CNS autoimmunity.

Serum metabolomics of treatment response in myasthenia gravis

OBJECTIVE

High-dose prednisone use, lasting several months or longer, is the primary initial therapy for myasthenia gravis (MG). Upwards of a third of patients do not respond to treatment. Currently no biomarkers can predict clinical responsiveness to corticosteroid treatment. We conducted a discovery-based study to identify treatment responsive biomarkers in MG using sera obtained at study entry to the thymectomy clinical trial (MGTX), an NIH-sponsored randomized, controlled study of thymectomy plus prednisone versus prednisone alone.

METHODS

We applied ultra-performance liquid chromatography coupled with electro-spray quadrupole time of flight mass spectrometry to obtain comparative serum metabolomic and lipidomic profiles at study entry to correlate with treatment response at 6 months. Treatment response was assessed using validated outcome measures of minimal manifestation status (MMS), MG-Activities of Daily Living (MG-ADL), Quantitative MG (QMG) score, or a strictly defined composite measure of response.

RESULTS

Increased serum levels of phospholipids were associated with treatment response as assessed by QMG, MMS, and the Responders classification, but all measures showed limited overlap in metabolomic profiles, in particular the MG-ADL. A panel including histidine, free fatty acid (13:0), γ-cholestenol and guanosine was highly predictive of the strictly defined treatment response measure. The AUC in Responders' prediction for these markers was 0.90 irrespective of gender, age, thymectomy or baseline prednisone use. Pathway analysis suggests that xenobiotic metabolism could play a major role in treatment resistance. There was no association with outcome and gender, age, thymectomy or baseline prednisone use.

INTERPRETATION

We have defined a metabolomic and lipidomic profile that can now undergo validation as a treatment predictive marker for MG patients undergoing corticosteroid therapy. Metabolomic profiles of outcome measures had limited overlap consistent with their assessing distinct aspects of treatment response and supporting unique biological underpinning for each outcome measure. Interindividual variation in prednisone metabolism may be a determinate of how well patients respond to treatment.

The NLRP3 inflammasome as a target for sensorineural hearing loss

Sensorineural hearing loss is the most common type of hearing loss in adults and occurs due to damage of the inner ear caused by a range of factors including ageing, excessive noise, toxins, and cancer. Auto-inflammatory disease is also a cause of hearing loss and there is evidence that inflammation could contribute to hearing loss in other conditions. Within the inner ear there are resident macrophage cells that respond to insults and whose activation correlates with damage. The NLRP3 inflammasome is a multi-molecular pro-inflammatory protein complex that forms in activated macrophages and may contribute to hearing loss. The aim of this article is to discuss the evidence for the NLRP3 inflammasome and associated cytokines as potential therapeutic targets for sensorineural hearing loss in conditions ranging from auto-inflammatory disease to tumour-induced hearing loss in vestibular schwannoma.

Disease-Modifying Antirheumatic Drugs in the Treatment of Autoimmune Inner Ear Disease: A Systematic Review and Meta-Analysis of Auditory and Vestibular Outcomes

OBJECTIVE

To answer the following question: In patients with primary autoimmune inner ear disease (AIED), (population) what impact do disease-modifying antirheumatic agents (DMARDs) (intervention) when compared with no treatment or corticosteroids (comparison) have on auditory and vestibular outcomes (outcome)?

STUDY DESIGN

Systematic review and meta-analysis.

DATA SOURCES

According to PRISMA guidelines, PubMed, Scopus, CINAHL, and Cochrane Library databases were searched from inception to March 10, 2022.

STUDY SELECTION

Studies of patients receiving DMARDs for the treatment of AIED were selected for review. Case reports, phase I/II trials, studies of patients with secondary AIED, and studies of AIED patients receiving solely corticosteroids were excluded.

DATA EXTRACTION

Primary outcomes were pure-tone audiometry and speech discrimination scores at baseline and after DMARD treatment. Secondary outcomes were rates of subjective audiovestibular complaints and rates of adverse reactions. No objective vestibular outcomes underwent meta-analysis.

DATA SYNTHESIS

Mean differences were calculated using RevMan 5.4. Heterogeneity was assessed with the Q test and I2 statistic. Pooled prevalence rates of audiovestibular symptoms were expressed as a percentage with 95% confidence intervals.

RESULTS

Ten studies with a total of 187 patients were included. Treatments included methotrexate, etanercept, azathioprine, anakinra, cyclophosphamide, rituximab, and infliximab. Mean treatment duration was 10.8 ± 22.2 months and mean follow-up was 13.7 ± 8.1 months. The pure-tone audiometry and speech discrimination scores mean differences between baseline and post-DMARD were -2.1 [-4.1, -0.1] dB and 13.9 [8.5, 19.4] %, respectively. Seven studies reported 38 adverse events, four of which were classified as serious.

CONCLUSION

DMARDs showed statistically significant improvement in auditory outcomes, as well as subjective symptoms, with relatively low rates of adverse events. They warrant further exploration to better compare with corticosteroids.

The role of hypoxia-associated miRNAs in acquired sensorineural hearing loss

Introduction: Sensorineural hearing loss (SNHL) is a prevalent sensory deficit presenting commonly as age-related hearing loss. Other forms of SNHL include noise-induced and sudden SNHL. Recent evidence has pointed to oxidative stress as a common pathogenic pathway in most subtypes of acquired SNHL. MicroRNAs (miRNAs) are small non-coding RNA sequences that suppress target mRNA expression and affect downstream processes. Many studies have shown that miRNAs are integral biomolecules in hypoxia-adaptive responses. They also promote apoptosis in response to oxidative stress resulting in SNHL. Our hypothesis is that miRNAs are involved in the pathophysiological responses to hypoxia and oxidative stress that result in SNHL. This study reviews the evidence for hypoxia-adaptive miRNAs (hypoxamiRs) in different types of acquired SNHL and focuses on miRNAs involved in hypoxia driven SNHL.

Methods: Electronic bibliographic databases PubMed, Ovid MEDLINE, Ovid EMBASE, and Web of Science Core Collection were searched independently by two investigators for articles published in English from the inception of individual databases to the end of July 2020. The text word or medical subject heading searches of all fields, titles, abstracts, or subject headings depending on the database were undertaken with combinations of the words “microRNAs”, “hypoxia”, “hypoxamiRs”, “oxidative stress”, “ischemia” and “hearing loss”. The reference lists of studies meeting the inclusion criteria were searched to identify additional relevant studies. The inclusion criteria included relevant clinical studies with human subjects, animals, and in vitro experiments. The risk of bias was assessed using the Cochrane risk of bias assessment tool for human studies and the Systematic Review Center for Laboratory animal Experimentation (SYRCLE) a risk of bias assessment tool for animal model and in vitro studies.

Results: A total of 15 primary articles were selected for full text screening after excluding duplicates, reviews, retracted articles, and articles not published in English. All nine articles meeting the study inclusion criteria were from animal or in vitro model studies and were assessed to be at low risk of bias. miRNAs miR-34a and miR-29b were reported to be involved in SNHL in inner ear cell models exposed to oxidative stress. Signaling pathways Sirtuin 1/peroxisome proliferator-activated receptor gamma coactivator-1-alpha (SIRT1/PGC-1α), SIRT1/p53, and SIRT1/hypoxia-inducible factor 1-alpha (HIF-1α) were identified as underlying pathways involved in acquired SNHL.

Conclusion: There is evidence that miR-34a and -29b are involved in hypoxia-driven and other causes of oxidative stress-related acquired SNHL. Further studies are required to determine if these findings are clinically applicable.

Safety and Efficacy of Intratympanic Alpha-Lipoic Acid Injection in a Mouse Model of Noise-Induced Hearing Loss

Alpha-lipoic acid (ALA) is an antioxidant with oto-protective effects. In the present study, the safety and effectiveness of ALA therapy after noise-induced hearing loss was confirmed based on the administration method. The safety of intratympanic ALA (IT-ALA) was evaluated with oto-endoscopy and middle ear mucosa morphologic study. Perilymph ALA concentrations according to the administration routes were compared, and the efficacy of ALA was investigated through hearing tests and cochlear histological studies. The middle ear mucosa was swollen 1 week after IT-ALA but completely recovered within 3 weeks. ALA concentration in the perilymph was significantly higher in the IT-ALA group. Recovery of organ of Corti morphology and hearing levels were predominant in the IT-ALA group compared with the intraperitoneal injection group (IP-ALA) and showed similar rescue effects in the IT-dexamethasone group (IT-DEX). Interleukin-1 beta and nuclear factor-kappa B expression was significantly downregulated in the IT-ALA group. IT-ALA showed better cochlear recovery from acoustic trauma with higher inner ear penetration rate than IP-ALA. The rescue effect of IT-ALA after noise-induced hearing loss was similar to IT-DEX; however, the ALA and DEX mechanisms are different. IT-ALA appears to be another safe and effective treatment modality after acoustic trauma and comparable to IT-DEX.

The Gut Microbiota: A Novel Player in Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a chronic immune-mediated liver disease distributed globally in all ethnicities with increasing prevalence. If left untreated, the disease will lead to cirrhosis, liver failure, or death. The intestinal microbiota is a complex ecosystem located in the human intestine, which extensively affects the human physiological and pathological processes. With more and more in-depth understandings of intestinal microbiota, a substantial body of studies have verified that the intestinal microbiota plays a crucial role in a variety of digestive system diseases, including alcohol-associated liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). However, only a few studies have paid attention to evaluate the relationship between AIH and the intestinal microbiota. While AIH pathogenesis is not fully elucidated yet, some studies have indicated that intestinal microbiota putatively made significant contributions to the occurrence and the development of AIH by triggering several specific signaling pathways, altering the metabolism of intestinal microbiota, as well as modulating the immune response in the intestine and liver. By collecting the latest related literatures, this review summarized the increasing trend of the aerobic bacteria abundance in both AIH patients and AIH mice models. Moreover, the combination of specific bacteria species was found distinct to AIH patients, which could be a promising tool for diagnosing AIH. In addition, there were alterations of luminal metabolites and immune responses, including decreased short-chain fatty acids (SCFAs), increased pathogen associated molecular patterns (PAMPs), imbalanced regulatory T (Treg)/Th17 cells, follicular regulatory T (TFR)/follicular helper T (TFH) cells, and activated natural killer T (NKT) cells. These alterations participate in the onset and the progression of AIH via multiple mechanisms. Therefore, some therapeutic methods based on restoration of intestinal microbiota composition, including probiotics and fecal microbiota transplantation (FMT), as well as targeted intestinal microbiota-associated signaling pathways, confer novel insights into the treatment for AIH patients.

Serum Fibrinogen Level and Cytokine Production as Prognostic Biomarkers for Idiopathic Sudden Sensorineural Hearing Loss

OBJECTIVES

No clinically useful prognostic factors have been identified for idiopathic sudden sensorineural hearing loss (ISSNHL). The current study therefore sought to identify useful prognostic factors for idiopathic sudden sensorineural hearing loss from blood biomarkers while attempting to classify the pathogenic mechanism and formulate treatment strategies based on these results.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary referral center.

METHODS

A total of 47 patients with acute phase ISSNHL were treated with steroid at an initial dose of 1 mg/kg/day and hyperbaric oxygen therapy and followed up for 6 months. Serum fibrinogen levels, peripheral blood mononu- clear cells (PBMCs), and interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α production levels from PBMCs were measured, after which patient's pre- and post- treatment hearing was compared.

RESULTS

In the overall cohort, the mean improvement level, mean recovery rate, and mean fibrinogen level was 20.3 dB, 46.2%, 292.0 mg/mL, respectively. The mean levels of IL-1β, IL-6, and TNF-α produced by peripheral blood mononu- clear cells cultured under lipopolysaccharide stimulation were 318.4, 498.1, and 857.6 pg/mL, respectively. High fibrinogen levels were associated with poor hearing progno- sis. Lipopolysaccharide-stimulated cytokine production by PBMCs did not correlate with hearing changes; however, the prognosis was significantly better in patients with low fibrinogen levels and high IL-1β levels produced by PBMCs than in other patients.

CONCLUSIONS

Our results suggest that patients with simple inflammatory-type ISSNHL responded well to standard therapy. Therefore, serum fibrinogen levels and PBMCs cytokine production may help determine the management of ISSNHL based on its pathogenic mechanism.

NaCl exposure results in increased expression and processing of IL-1β in Meniere's disease patients

Meniere's disease (MD) is a chronic disease that causes episodic vertigo, fluctuating hearing loss, and aural fullness, initially managed by dietary salt reduction, and use of diuretics. Our prior research in autoimmune inner ear disease (AIED) demonstrated that in peripheral blood mononuclear cell (PBMC) from corticosteroid-resistant AIED patients, increased production, processing and release of interleukin-1β (IL-1β) is observed and hearing could be improved with use of anakinra, an interleukin-1 receptor antagonist. We have further identified that in these AIED patients, IL-1β is uniquely processed to a 28 kDa pro-inflammatory product by caspase-7. In the present study, we characterize the production, processing and release of the pro-inflammatory cytokines IL-1β and IL-6 from PBMC of MD (n = 14) patients in response to sodium chloride (NaCl), and determined the effect of the diuretic triamterene-hydrocholothiazide (T-HCTZ), or anakinra in these patients. We observed that PBMC cultured with NaCl from MD patients show processing of IL-1β to the 28 kDa product, and that this product is abrogated with T-HCTZ. Our observations are consistent with other autoimmune diseases where high concentrations of NaCl caused release of pro-inflammatory cytokines and may provide further insight as to the mechanism of disease progression in MD patients.

Combination Immunosuppressive Therapy in Primary Autoimmune Inner Ear Disease in Pregnancy

Objective. Autoimmune inner ear disease (AIED) is a rare disorder characterized by rapidly progressive, sensorineural hearing loss that demonstrates good responsiveness to corticosteroid and immunosuppressive therapy. The pathophysiology is likely driven by chronic trafficking of immune cells into the inner ear, targeting inner ear proteins to coordinate inflammation. Suppression or modulation of the immune response can minimize cochleitis allowing for potential recovery of hearing. It is an otologic emergency requiring a multidisciplinary approach to management to commence immunosuppressive therapy. This can be achieved using steroids, immunomodulators, plasmapheresis, intravenous immunoglobulin, or biologic agents. Treatment decisions are further complicated in pregnancy and require supervision by an obstetrician and maternal-fetal medicine (MFM) specialist. Concerns include safe dosing of steroids and potential for transplacental migration of immune complexes. We provide the first comprehensive literature review on AIED and its implications in pregnancy. We frame our discussion in the context of the second reported case of primary AIED in pregnancy and the first to show excellent response to immunosuppressive therapy. Methods. We reviewed the presented case and literature on AIED. Results. A 27-year-old, pregnant, HSP-70 positive woman was diagnosed with AIED and had excellent recovery of hearing and balance following a combination of steroid treatment, augmented by oral immunomodulators, plasmapheresis, and IVIG. Conclusion. AIED is a diagnostic challenge, and treatment considerations are complex when encountered in pregnancy. Management requires multidisciplinary involvement between otolaryngologists, immunologists, and obstetricians to balance maternal and fetal health outcomes.

Cytokines and Inflammation in Meniere Disease

Meniere disease (MD) is a rare set of conditions associated with the accumulation of endolymph in the cochlear duct and the vestibular labyrinth with a decrease of endocochlear potential. It is considered a chronic inflammatory disorder of the inner ear with a multifactorial origin. The clinical syndrome includes several groups of patients with a core phenotype: sensorineural hearing loss, episodes of vertigo, and tinnitus with a non-predictable course. Genetic factors and the innate immune response seem to play a central role in the pathophysiology of the condition. Autoimmune MD should be diagnosed if a patient fulfills the diagnostic criteria for MD and one of the following autoimmune disorders: autoimmune thyroid disease, psoriasis, autoimmune arthritis, ankylosing spondylitis, or systemic lupus erythematosus. We summarize the evidence to support autoimmune MD as an endophenotype in bilateral MD associated with the allelic variant rs4947296 and nuclear factor-kappa B (NF-κB)-mediated inflammation, the role of cytokines (particularly interleukin-1β and tumor necrosis factor-α) in defining a subset of patients with autoinflammation, and the potential role of cytokines as biomarkers to distinguish between patients with MD and vestibular migraine. Finally, we also introduce a list of potential drugs that could regulate the immune response in MD with potential for repurposing in clinical trials.

Transcriptome analysis of the early stage ifnlr1-mutant zebrafish indicates the immune response to auditory dysfunction

BACKGROUND

IFNLR1 has been recently identified to be related to autosomal dominant nonsyndromic sensorineural hearing loss (ADNSHL). It is reported to be expressed in the inner ear of mice and the lateral line of zebrafish. However, it remains unclear how defects in this gene lead to hearing loss.

OBJECTIVES

To elucidate the global gene expression changes in zebrafish when the expression of ifnlr1 is downregulated.

METHODS

Transcriptome analysis was performed on ifnlr1 morpholino knockdown zebrafish and the control zebrafish using RNA-seq technology.

RESULTS

The results show that 262 differentially expressed genes (DEGs) were up-regulated while 146 DEGs were down-regulated in the E4I4-Mo zebrafish larvae compared to the control-Mo. Six pathways were significantly enriched, including steroid biosynthesis pathway, adipocytokine signaling pathway, cytokine-cytokine receptor interaction pathway, p53 signaling pathway, AGE-RAGE signaling pathway in diabetic complications, and terpenoid backbone biosynthesis pathway. Among them, three pathways (steroid biosynthesis pathway, cytokine-cytokine receptor interaction pathway and p53 signaling pathway) are immune-associated.

CONCLUSIONS

The transcriptome analysis results contribute to the groundwork for future research on the pathogenesis of IFNLR1-associated hearing loss.

The association of genetic polymorphisms in interleukin-1 receptors type 1 and type 2 with sudden sensorineural hearing loss in a Taiwanese population: a case control study

Background

Sudden sensorineural hearing loss (SSNHL) is a disease with an unknown etiology; damage to the auditory nerve from inflammation due to viral infection or vascular incidents has been implicated. According to several studies, cytokines, including interleukins, are associated with SSNHL in terms of serum expression and genetic polymorphisms. Interleukin-1 (IL-1) plays a key role in inflammation and may be associated with SSNHL. This study analyzed the association of single nucleotide polymorphisms (SNPs) of IL-1 receptor (IL-1R) genes with SSNHL in Taiwan.

Methods

We conducted a case–control study involving 401 patients with SSNHL and 730 healthy controls. Four SNPs (IL-1R type 1 gene [IL1R1] [rs3917225 and rs2234650] and IL-1R type 2 gene [IL1R2] [rs4141134 and rs2071008]) were selected. The genotypes were determined using the TaqMan assay. The Hardy–Weinberg equilibrium (HWE) was tested for each SNP, and genetic effects were evaluated.

Results

The TT genotype of rs2234650 had an adjusted odds ratio (OR) of 2.988 (95% confidence interval [95% CI] 1.27–6.82) (P = 0.012) compared with the CC genotype in patients with SSNHL. The SNP rs2234650 was associated with SSNHL in the recessive model (TT vs. CC + CT, P = 0.0206, OR = 2.681). The CT genotype of rs4141134 had an adjusted OR of 3.860 (95% CI 2.01–7.44; P < 0.0001) compared with the TT genotype, in patients with SSNHL. The SNP rs4141134 was associated with SSNHL under the dominant model (CC + CT vs. TT, P < 0.0001, OR = 4.087).

Conclusion

These findings suggest that IL1R1 and IL1R2 gene polymorphisms may contribute to an increased risk of SSNHL in Taiwan.

Hearing restoration and the stria vascularis: evidence for the role of the immune system in hearing restoration

PURPOSE OF REVIEW

This article reviews the current literature regarding the pathogenesis of immune-mediated sensorineural hearing loss, utilizes previously published single-nucleus transcriptional profiles to characterize cytokine and cytokine receptor expression in the adult stria vascularis cell types to support immune system interaction with the stria vascularis and reviews the current literature on immunomodulatory agents currently being used for hearing-restoration treatment.

RECENT FINDINGS

The literature review highlights recent studies that elucidate many cytokines and immune markers, which have been linked to various immune-mediated disease processes that have been observed with sensorineural hearing loss within the stria vascularis and highlights recent publications studying therapeutic targets for these pathways.

SUMMARY

This review highlights the current literature regarding the pathogenesis of immune-mediated hearing loss. The role of cochlear structures in human temporal bones from patients with immune-mediated sensorineural hearing loss are highlighted, and we review cytokine signalling pathways relevant to immune-mediated sensorineural hearing loss and localize genes encoding both cytokine and cytokine receptors involved in these pathways. Finally, we review immunomodulatory therapeutics in light of these findings and point to opportunities for the application of novel therapeutics by targeting these signalling pathways.

The Correlation of Clinical Corticosteroid Responsiveness With Expression of IL-6 in Peripheral Blood Immune Cells (PBMC) in Patients With Autoimmune Inner Ear Disease (AIED)

HYPOTHESIS

Autoimmune inner ear disease (AIED) patients will differentially express interleukin (IL)-6 based on corticosteroid responsiveness.

BACKGROUND

AIED is characterized by periods of acute sensorineural hearing loss (SNHL). In a majority of patients corticosteroid responsiveness is lost over time. The mechanisms that control corticosteroid responsiveness have not been fully elucidated.

METHODS

Thirty-five AIED patients and 13 age-matched control subjects were enrolled in this study. Steroid responsive (n = 15) and steroid nonresponsive AIED patients (n = 20) were characterized based on audiometry before and after treatment for acute SNHL. Plasma and peripheral blood mononuclear cells (PBMC) were obtained at the time of acute SNHL to quantify plasma IL-6, soluble IL-6 receptor (sIL-6R), and C-C Motif Chemokine Ligand 3 (CCL3). PBMCs were stimulated with dexamethasone and release of soluble IL-6, sIL-6R, and CCL3 protein into conditioned supernatants was measured. Plasma IL-6 was also correlated to serum c-reactive protein (CRP), cardiac CRP, erythrocyte sedimentation rate.

RESULTS

Statistically significant differences were observed in the plasma IL-6 between AIED patients and controls (2.37 versus 2.03 pg/ml, p < 0.01), plasma IL-6, and CCL3 between responders and nonresponders (0.136 versus 3.84 pg/ml, p < 0.005; 30.5 versus 32.4, p < 0.05) and released IL-6 from dexamethasone stimulated PBMC in AIED patients compared with controls (0.54 versus 1.12 pg/ml, p < 0.001). There was a correlation between plasma IL-6 levels of AIED patients to both serum CRP and cardiac CRP (R2 = 0.83, R2 = 0.88).

CONCLUSIONS

We observed AIED patients, specifically nonresponders expressed greater levels of IL-6. Elevated IL-6 levels in AIED patients correlated with CRP levels, providing a commonly available laboratory test that may aid in rapid clinical decision-making in these patients.

Allergy, Immunotherapy, and Alternative Treatments for Dizziness

Allergic reactions may result in central symptoms of dizziness, including nonspecific chronic imbalance, Meniere's disease, and autoimmune inner ear disease. Excepting first-generation antihistamines, and short-term use of steroids, most pharmacotherapies used to treat allergic rhinitis have limited benefit in treating allergically induced or related dizziness. Allergy immunotherapy and/or an elimination diet for diagnosed food allergies have been found to be effective treatments. Individuals diagnosed with autoimmune inner ear disease remain challenging to treat and may require high-dose, long-term steroid treatment, biologics, or immunomodulators for symptom control.

Biologics for Immune-Mediated Sensorineural Hearing Loss

Immune-mediated hearing losses include autoimmune inner ear disease, sudden sensorineural hearing loss, and Meniere's disease. Standard therapy for an acute decline in hearing is timely use of corticosteroids. Although 60% to 70% of patients are initially corticosteroid-responsive, that responsiveness is lost over time. In corticosteroid-resistant patients, increased expression of interleukin (IL)-1 is observed, and these patients may benefit from IL-1 inhibition. Autoinflammatory diseases are characterized by dysregulation of the innate immune response, clinically include sensorineural hearing loss, and benefit from IL-1 inhibition, thereby further establishing the relationship of IL-1 with immune-mediated sensorineural hearing loss.

The Pathogenesis of secondary forms of Autoimmune Inner Ear Disease (AIED): advancing beyond the audiogram data

INTRODUCTION

Autoimmune Inner Ear Disease (AIED) can be of a primary or secondary type. To date, a clear pathogenesis of the disease is still not available. Focusing on the secondary forms of AIED, the aim of this review is to (i) assess and describe the hearing involvement in patients affected by autoimmune diseases, (ii) describe the possible association between clinical features (among serological/laboratory data and disease activity/duration) and hearing impairment, (iii) show evidence connecting the AIED types with various etiopathogenetic mechanisms.

AREAS COVERED

A PRISMA-compliant systematic review was performed. Medline, Cochrane, Embase, and Cinahl were searched from 1 January 2015 through to 5 August 2020. Overall, 16 studies (involving 1043 participants) were included in the review. The data in the literature suggested that bilateral mild-to-moderate sensorineural hearing loss is a commonly reported clinical symptom of AIED.

EXPERT OPINION

Patients with systemic autoimmune disorders present a cochlear injury which might be associated with the humoral and/or cellular immune response against the inner ear. To date, AIED pathogenesis remains an open issue, due to the rarity of these clinical entities and due to the difficulties in investigating the inner ear immunology, considering the inner ear inaccessibility for tissue sampling.

Serum interferon-γ and urinary monocyte chemoattractant peptide-1 are important factors in the pathogenesis of immunoglobulin A nephropathy

Background

Imbalance of T helper (Th) 1/2 cells has been shown to contribute to the development of immunoglobulin A nephropathy (IgAN). To address the inconsistent results on the role of Th1/Th2 polarization, we evaluated the levels of Th1/Th2 cytokines in various samples from patients with IgAN.

Methods

Thirty-one patients with biopsy-proven IgAN (age, 34.48 ± 12.10 years) and 25 healthy controls (age, 44.84 ± 13.72 years) were enrolled. We evaluated the relationship between the levels of Th1/Th2 cytokines and the response to glucocorticoid treatment.

Results

The levels of serum interferon-gamma (IFNγ) and urinary monocyte chemoattractant peptide (MCP)-1 were higher in the IgAN group than in the control group. The levels of MCP-1 in urine and secreted by peripheral blood mononuclear cells (PBMCs) were significantly different among three groups categorized based on daily proteinuria. The level of urinary MCP-1 was significantly correlated with proteinuria. The levels of urinary MCP-1, serum interleukin (IL)-4, IFNγ, and IL-2 secreted by PBMCs and intrarenal IL-1 messenger RNA (mRNA) were significantly correlated with the ratio of proteinuria at 6 months to baseline proteinuria in patients undergoing glucocorticoid treatment. MCP-1 mRNA and protein levels were significantly upregulated in mesangial cells stimulated with IFNγ among representative Th1/Th2 cytokines.

Conclusion

IFNγ was shown to be a key cytokine in the pathogenic processes underlying IgAN, and its upregulation induced an increase in urinary MCP-1 production. These findings suggest that Th1 cytokines may play an important role in the development of IgAN.

Clinical characteristics and correlation between hearing outcomes after different episodes of recurrent idiopathic sudden sensorineural hearing loss

OBJECTIVES

Recurrent idiopathic sudden sensorineural hearing loss (ISSNHL) is a rare disease. In this study, we evaluated the correlations between hearing recovery after the first and recurrent episodes of ISSNHL and characterized the clinical features of different episodes of ISSNHL.

METHODS

This retrospective study was conducted by reviewing medical records pertaining to the period 2008-2018. A total of 30 patients (16 male, 14 female) who had experienced at least two episodes of ISSNHL were included. All patients were had received steroid therapy (including systemic and IT) and/or hyperbaric oxygen therapy within 2 weeks after the onset of disease. The SDRG's criteria was used for the grading of hearing recovery.

RESULTS

The median age at the first and second episode of ISSNHL was 48 and 53.5 years, respectively; a total of 30% of patients presented with vertigo in the first episode and 40% presented with vertigo in the second episode. The hearing outcomes of both episodes showed significant improvement after treatment. The rate of complete recovery after the first and second episodes was 46.67% and 33.33%, respectively. A significant positive correlation was observed between the treatment outcomes of the first and second episodes (r = 0.721, p < 0.001).

CONCLUSION

In ISSNHL, hearing recovery after a recurrent episode is significantly correlated with the hearing outcome after the initial episode (p = 0.042). The treatment outcome of the first episode is a prognostic factor for the outcomes of recurrent episodes.

Carotid imaging changes and serum IL-1β, sICAM-1, and sVAP-1 levels in benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo. This study was performed to evaluate serum levels of inflammatory factors and changes in B-mode carotid ultrasound findings in patients with BPPV. The study population consisted of 90 BPPV patients and 90 age- and sex-matched controls. ELISA was used to compare the levels of inflammatory factors, such as interleukin-1β (IL-1β), tumor necrosis factor-alpha (TNF-α), soluble intercellular adhesion molecule-1 (sICAM-1), prostaglandin-E2 (PG-E2), and soluble vascular adhesion protein-1 (sVAP-1), between BPPV patients and controls. In addition, the results of ultrasonographic imaging to determine carotid intima-media thickness (C-IMT), carotid atheromatous plaque, and vertebral artery stenosis were also compared between the BPPV and control groups. Serum levels of IL-1β, sICAM-1, and sVAP-1 were significantly higher in BPPV patients than controls (P < 0.001, P < 0.05, and P < 0.001, respectively). C-IMT and vertebral artery stenosis were significantly different in BPPV patients compared to controls (both P < 0.05). There were no significant relations between other parameters and BPPV. IL-1β, sICAM-1, and sVAP-1 are potentially associated with the pathogenesis of BPPV, and C-ITM and carotid vertebral stenosis may be useful reference imaging findings for the diagnosis of BPPV.

Autoimmune inner ear disease: A systematic review of management

OBJECTIVES

The study systematically reviewed the existing literature on the management of autoimmune inner ear disease (AIED).

STUDY DESIGN

Systematic review.

METHODS

We performed a literature search of Embase, NCBI, Cochrane, and Web of Science databases from April 1990 to April 2020. Inclusion criteria included studies that were retrospective or prospective in nature evaluating the treatment of AIED with audiometric data measuring hearing outcomes during treatment. Hearing improvement was the primary study outcome and improvement in vestibular symptoms was the secondary study outcome.

RESULTS

Sixteen of 412 candidate articles were included in our study. Systemic steroid treatment is most commonly described. Alternative treatment modalities included intratympanic steroid treatment, methotrexate, cyclophosphamide, azathioprine, infliximab, etanercept, adalimumab, golimumab, methylprednisolone, rituximab, and anakinra.

CONCLUSION

Systemic corticosteroids are the first line treatment of AIED. Intratympanic steroids are a potential adjuvant or alternative treatment for patients who cannot tolerate or become refractory to steroid treatment. Steroid nonresponders may benefit from biologic therapy. Alternative treatment modalities including nonsteroidal immunosuppressants and biologics have been studied in small cohorts of patients with varying results. Prospective studies investigating the efficacy of biologic and nonsteroidal therapy are warranted.

LEVEL OF EVIDENCE

2.

Autoimmune inner ear disease patient-associated 28-kDa proinflammatory IL-1β fragment results from caspase-7-mediated cleavage in vitro

Interleukin-1β (IL-1β) is a key proinflammatory cytokine involved in the progression of many autoinflammatory and autoimmune diseases, including autoimmune inner ear disease (AIED). IL-1β inhibition has been shown to result in clinical hearing improvement in a small cohort of corticosteroid-resistant patients with AIED. Canonical processing of pro-IL-1β by caspase-1 generates an active 17-kDa fragment, capable of instigating a proinflammatory microenvironment. However, in response to LPS, PBMCs from patients with AIED uniquely express a 28-kDa IL-1β fragment, as compared with PBMCs from control subjects. We synthesized and compared the biologic activity of the 28-kDa fragment to the 17-kDa IL-1β product and the pro-IL-1 31-kDa protein. The 28-kDa IL-1β fragment induces IL-6, TNF-α, and CCL3 in PBMCs. Uniquely, only caspase-7 treatment showed a dose- and time-dependent increase in 28-kDa band generation. Mass spectrometry confirmed the putative caspase-7 cleavage site of pro-IL-1β, which was used to generate the 28-kDa fragment used for PBMC stimulation studies. Collectively, these results provide insight into the function of a poorly understood, processed 28-kDa form of IL-1β in patients with AIED that is uniquely generated by caspase-7 and is capable of activating further downstream proinflammatory cytokines. Further investigation may provide novel pharmacologic targets for the treatment of this rare disease.

Differential Proinflammatory Signature in Vestibular Migraine and Meniere Disease

Vestibular Migraine (VM) and Meniere's Disease (MD) are episodic vestibular syndromes defined by a set of associated symptoms such as tinnitus, hearing loss or migraine features during the attacks. Both conditions may show symptom overlap and there is no biological marker to distinguish them. Two subgroups of MD patients have been reported, according to their IL-1β profile. Therefore, considering the clinical similarity between VM and MD, we aimed to investigate the cytokine profile of MD and VM as a means to distinguish these patients. We have also carried out gene expression microarrays and measured the levels of 14 cytokines and 11 chemokines in 129 MD patients, 82 VM patients, and 66 healthy controls. Gene expression profile in peripheral blood mononuclear cells (PBMC) showed significant differences in MD patients with high and low basal levels of IL- 1β and VM patients. MD patients with high basal levels of IL- 1β (MDH) had overall higher levels of cytokines/chemokines when compared to the other subsets. CCL4 levels were significantly different between MDH, MD with low basal levels of IL- 1β (MDL), VM and controls. Logistic regression identified IL- 1β, CCL3, CCL22, and CXCL1 levels as capable of differentiating VM patients from MD patients (area under the curve = 0.995), suggesting a high diagnostic value in patients with symptoms overlap.

Emerging options in immune-mediated hearing loss

Objective

AIED (autoimmune inner ear disease) is an autoimmune process that leads to the dysfunction of the inner ear, resulting in fluctuating, audiovestibular symptoms. Although the pathogenesis is likely heterogeneous, immune processes within the inner ear ultimately lead to histopathologic changes and sensorineural hearing loss. This review will discuss the latest evidence on treatment options.

Methods

A literature search on articles pertaining to the treatment of autoimmune inner ear disease was performed on PubMed.

Results

Corticosteroid treatment continues to remain as first line therapy for AIED but long-term responsiveness is poor. Cytotoxic chemotherapies can be effective alternatives for steroid nonresponsive patients, but significant side effects may limit their use. Intratympanic steroid injections are beneficial and although there is not enough evidence currently to supplant oral steroid trial they may be a useful adjunct if steroid toxicity is an issue. The efficacy of biologic agents has been variable. Compared to placebo, etanercept does not improve the hearing improvement already attained by steroids alone. However, open pilot studies of other biologic agents show hearing improvements, improvements in tinnitus/aural fullness/vertigo, ability to wean steroid dependency, or benefits in steroid-resistant AIED.

Conclusion

There is currently not enough evidence that alternative treatments supersede the use of initial steroid treatment. Biologic agents and intratympanic steroid injections are relatively well tolerated and should be considered as adjunctive therapy. More studies on the efficacy of various biologics and more studies on the treatment of steroid resistant disease especially after initial benefit are still needed. For those who eventually lose their hearing, cochlear implantation remains as a viable option.

Level of Evidence

expert opinion.

Anakinra Therapy for Non-cancer Inflammatory Diseases

Interleukin-1 (IL-1) is the prototypical inflammatory cytokine: two distinct ligands (IL-1α and IL-1β) bind the IL-1 type 1 receptor (IL-1R1) and induce a myriad of secondary inflammatory mediators, including prostaglandins, cytokines, and chemokines. IL-1α is constitutively present in endothelial and epithelial cells, whereas IL-1β is inducible in myeloid cells and released following cleavage by caspase-1. Over the past 30 years, IL-1-mediated inflammation has been established in a broad spectrum of diseases, ranging from rare autoinflammatory diseases to common conditions such as gout and rheumatoid arthritis (RA), type 2 diabetes, atherosclerosis, and acute myocardial infarction. Blocking IL-1 entered the clinical arena with anakinra, the recombinant form of the naturally occurring IL-1 receptor antagonist (IL-1Ra); IL-1Ra prevents the binding of IL-1α as well as IL-1β to IL-1R1. Quenching IL-1-mediated inflammation prevents the detrimental consequences of tissue damage and organ dysfunction. Although anakinra is presently approved for the treatment of RA and cryopyrin-associated periodic syndromes, off-label use of anakinra far exceeds its approved indications. Dosing of 100 mg of anakinra subcutaneously provides clinically evident benefits within days and for some diseases, anakinra has been used daily for over 12 years. Compared to other biologics, anakinra has an unparalleled record of safety: opportunistic infections, particularly Mycobacterium tuberculosis, are rare even in populations at risk for reactivation of latent infections. Because of this excellent safety profile and relative short duration of action, anakinra can also be used as a diagnostic tool for undefined diseases mediated by IL-1. Although anakinra is presently in clinical trials to treat cancer, this review focuses on anakinra treatment of acute as well as chronic inflammatory diseases.

Effects of Azilsartan, Aliskiren or their Combination on High Fat Diet-induced Non-alcoholic Liver Disease Model in Rats

INTRODUCTION

In addition to its role in regulation of blood pressure, fluid and electrolyte homeostasis, the renin-angiotensin system (RAS) components were expressed in many other tissues suggesting potential roles in their functions.

AIM

The present study aims to evaluate the protective effect aliskiren, when used alone or in combination with azilsartan against high fat diet-induced liver disease in rats.

MATERIAL AND METHODS

Thirty-two Wistar male rats, weighing 150-200 gm were allocated evenly into four groups and treated as follow: group I, rats were fed a specially formulated high-fat diet for 8 weeks to induce non-alcoholic liver disease and considered as control group; groups II, III and IV, the rats were administered azilsartan (0.5 mg/kg), aliskiren (25 mg/kg) or their combination orally via gavage tube once daily, and maintained on high fat diet for 8 weeks. The possible treatment outcome was evaluated through measuring serum levels of glucose, insulin, lipid profile, TNF-α, IL-1β and liver enzymes. Additionally, the liver tissue contents of glycogen and lipids and histological changes were also evaluated.

RESULT

The results showed that azilsartan significantly improves the studied markers greater than aliskiren, and their combination o has no additive or synergistic effects on the activity of each one of them.

CONCLUSION

Both azilsartan and aliskiren protects the rats against high-fat diet induced NAFLD with predominant effects for the former, and their combination showed no beneficial synergistic or additive effects.

The Role of Autoimmunity in the Pathogenesis of Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSHL) is a clinically common acute symptom in otolaryngology. Although the incidence of SSHL has increased around the world in recent years, the etiology of the disease is still unclear. It has been reported that infections, ototoxic drugs, membrane labyrinth rupture, carcinomas, circulatory system diseases, autoimmune diseases, brain lesions, mental diseases, congenital or inherited diseases, and so on, are all risk factors for SSHL. Here, we discuss the autoimmune mechanisms behind SSHL, which might be induced by type II–IV allergic reactions. We also introduce the main immunosuppressive medications that have been used to treat SSHL, which will help us to identify potential targets for immune therapy.

Interleukin-1 Blockade: An Update on Emerging Indications

Interleukin (IL)-1 is a pro-inflammatory cytokine that induces local and systemic inflammation aimed to eliminate microorganisms and tissue damage. However, an increasing number of clinical conditions have been identified in which IL-1 production is considered inappropriate and IL-1 is part of the disease etiology. In autoinflammatory diseases, gout, Schnitzler's syndrome, and adult-onset Still's disease, high levels of inappropriate IL-1 production have been shown to be a key process in the etiology of the disease. In these conditions, blocking IL-1 has proven very effective in clinical studies. In other diseases, IL-1 has shown to be present in disease process but is not the central driving force of inflammation. In these conditions, including type 1 and 2 diabetes mellitus, acute coronary syndrome, amyotrophic lateral sclerosis, and several neoplastic diseases, the benefits of IL-1 blockade are minimal or absent.

Regulation of Fn14 Receptor and NF-κB Underlies Inflammation in Meniere's Disease

Meniere’s disease (MD) is a rare disorder characterized by episodic vertigo, sensorineural hearing loss, tinnitus, and aural fullness. It is associated with a fluid imbalance between the secretion of endolymph in the cochlear duct and its reabsorption into the subarachnoid space, leading to an accumulation of endolymph in the inner ear. Epidemiological evidence, including familial aggregation, indicates a genetic contribution and a consistent association with autoimmune diseases (AD). We conducted a case–control study in two phases using an immune genotyping array in a total of 420 patients with bilateral MD and 1,630 controls. We have identified the first locus, at 6p21.33, suggesting an association with bilateral MD [meta-analysis leading signal rs4947296, OR = 2.089 (1.661–2.627); p = 1.39 × 10⁻⁰⁹]. Gene expression profiles of homozygous genotype-selected peripheral blood mononuclear cells (PBMCs) demonstrated that this region is a trans-expression quantitative trait locus (eQTL) in PBMCs. Signaling analysis predicted several tumor necrosis factor-related pathways, the TWEAK/Fn14 pathway being the top candidate (p = 2.42 × 10⁻¹¹). This pathway is involved in the modulation of inflammation in several human AD, including multiple sclerosis, systemic lupus erythematosus, or rheumatoid arthritis. In vitro studies with genotype-selected lymphoblastoid cells from patients with MD suggest that this trans-eQTL may regulate cellular proliferation in lymphoid cells through the TWEAK/Fn14 pathway by increasing the translation of NF-κB. Taken together; these findings suggest that the carriers of the risk genotype may develop an NF-κB-mediated inflammatory response in MD.

Active nuclear transcriptome analysis reveals inflammasome-dependent mechanism for early neutrophil response to Mycobacterium marinum

The mechanisms governing neutrophil response to Mycobacterium tuberculosis remain poorly understood. In this study we utilise biotagging, a novel genome-wide profiling approach based on cell type-specific in vivo biotinylation in zebrafish to analyse the initial response of neutrophils to Mycobacterium marinum, a close genetic relative of M. tuberculosis used to model tuberculosis. Differential expression analysis following nuclear RNA-seq of neutrophil active transcriptomes reveals a significant upregulation in both damage-sensing and effector components of the inflammasome, including caspase b, NLRC3 ortholog (wu: fb15h11) and il1β. Crispr/Cas9-mediated knockout of caspase b, which acts by proteolytic processing of il1β, results in increased bacterial burden and less infiltration of macrophages to sites of mycobacterial infection, thus impairing granuloma development. We also show that a number of immediate early response genes (IEGs) are responsible for orchestrating the initial neutrophil response to mycobacterial infection. Further perturbation of the IEGs exposes egr3 as a key transcriptional regulator controlling il1β transcription.

The Balance of Tissue Inhibitor of Metalloproteinase-1 and Matrix Metalloproteinase-9 in the Autoimmune Inner Ear Disease Patients

Tissue inhibitor of metalloproteinase-1 (TIMP-1) is a protein implicated in the control of inflammation in a number of autoimmune diseases. We hypothesized that the balance of TIMP-1 and matrix metalloproteinase-9 (MMP-9) may influence the control or perpetuation of inflammation in corticosteroid-responsive (RES) and corticosteroid-resistant (NR) autoimmune inner ear disease (AIED) patients. In the present study, we observed that plasma from AIED patients exhibited greater levels of TIMP-1 values compared with normal healthy controls. TIMP-1 abrogates lipopolysaccharide-mediated interleukin (IL)-1β release from peripheral blood mononuclear cells in a dose-dependent manner. RES AIED patients have higher basal TIMP-1 levels and produce more TIMP-1 in response to IL-1β. Conversely, consistent with our previous studies, we found that NR patients have higher basal MMP-9 levels and produce more MMP-9 levels in response to IL-1β.

AAO: Autoimmune and Autoinflammatory (Disease) in Otology: What is New in Immune-Mediated Hearing Loss

OBJECTIVES

Autoinflammatory diseases are a family of immune-mediated, rare diseases, some of which, exhibit sensorineural hearing loss (SNHL), suggesting potentially similar mechanisms of molecular pathogenesis between autoinflammatory-mediated hearing loss and autoimmune inner ear disease (AIED) may exist. The purpose of this review is to compare the clinical features of autoimmune and autoinflammatory diseases that affect hearing, discuss the limitations of our knowledge, and highlight potential new disease mechanisms and therapeutics.

DATA SOURCES

Pubmed Literature Review; Google Scholar Literature review.

REVIEW METHODS

A focused comparison of AIED with a number of autoinflammatory diseases that manifest with sensorineural hearing loss was performed. The pathogenesis of these diseases is reviewed in the context of the innate and adaptive immune system, cytokine expression and genetic polymorphisms.

RESULTS

AIED, since first described by Cogan and Lehnhardt and first clinically characterized by McCabe, has remained an enigmatic disease, with limited advances in both new diagnostics and new therapeutics. Since the discovery of autoinflammatory diseases, a number of systemic autoimmune diseases have either been re-classed as autoinflammatory diseases or identified to have features of autoinflammatory disease.

CONCLUSION

AIED has clinical features of both autoimmune and autoinflammatory disease. It is critical that autoinflammatory diseases be correctly identified, as failure to do so may result in systemic amyloidosis and kidney damage.

N-Acetylcysteine attenuates tumor necrosis factor alpha levels in autoimmune inner ear disease patients

Autoimmune inner ear disease (AIED) is a poorly understood disease marked by bilateral, rapidly progressive hearing loss triggered by unknown stimuli, which is corticosteroid responsive in 60 % of patients. Although the mechanism of the disease is not precisely understood, a complex interaction of cytokines is believed to contribute toward the inflammatory disease process and hearing loss. Previously, we showed the role of TNF-α in steroid-sensitive and IL-1β in steroid-resistant immune-mediated hearing loss. N-Acetylcysteine (NAC), a broad spectrum antioxidant, has been effective in other autoimmune disorders. Other studies have shown NAC to have a protective adjunct role in human idiopathic sudden hearing loss, where the addition of NAC resulted in better hearing recovery than with steroids alone, although the mechanism of this protection was not elucidated. In the present study, we observed PBMCs from AIED patients exhibited higher baseline TNF-α and MPO levels compared with normal healthy controls. NAC effectively abrogates LPS-mediated TNF-α release from PBMC of both AIED patients and controls. We demonstrated that in AIED patients, the TNF-α downstream signaling pathway appears aberrantly regulated, influencing both MPO and IL-8 expression. Given that NAC effectively abrogated LPS-mediated TNF-α release and exerted minimal effects on the downstream targets of this pathway, we feel NAC may be a rational adjunct therapy for this enigmatic disease, worthy of clinical exploration.

Elucidating novel disease mechanisms in severe asthma

Corticosteroids are broadly active and potent anti-inflammatory agents that, despite the introduction of biologics, remain as the mainstay therapy for many chronic inflammatory diseases, including inflammatory bowel diseases, nephrotic syndrome, rheumatoid arthritis, chronic obstructive pulmonary disease and asthma. Significantly, there are cohorts of these patients with poor sensitivity to steroid treatment even with high doses, which can lead to many iatrogenic side effects. The dose-limiting toxicity of corticosteroids, and the lack of effective therapeutic alternatives, leads to substantial excess morbidity and healthcare expenditure. We have developed novel murine models of respiratory infection-induced, severe, steroid-resistant asthma that recapitulate the hallmark features of the human disease. These models can be used to elucidate novel disease mechanisms and identify new therapeutic targets in severe asthma. Hypothesis-driven studies can elucidate the roles of specific factors and pathways. Alternatively, 'Omics approaches can be used to rapidly generate new targets. Similar approaches can be used in other diseases.

Current understanding of the pathogenesis of autoimmune inner ear disease: a review

BACKGROUND

Autoimmune inner ear disease (AIED) is a poorly understood form of sensorineural hearing loss that causes bilateral, asymmetric, progressive hearing loss, sometimes with vestibular symptoms, often associated with a systemic autoimmune disease, which is noteworthy as the only sensorineural loss responsive to medical therapy. Despite much research interest of the past 25 years, its aetiopathogenesis is still unproven.

OBJECTIVE OF REVIEW

To succinctly consolidate research and opinion regarding the pathogenesis of autoimmune inner ear disease, in ongoing efforts to elucidate the molecular and intracellular pathways that lead to inner ear damage, which may identify new targets for pharmacotherapy.

TYPE OF REVIEW

Systematic review

SEARCH STRATEGY

PubMed/MEDLINE search using key terms to identify articles published between January 1980 and Apr 2014. Additionally, any landmark works discussed in this body of literature were obtained and relevant information extracted as necessary.

EVALUATION METHOD

Inclusion criterion was any information from animal or human studies with information relevant to possible aetiopathogenesis of AIED. Studies that focused on diagnosis, ameliorating symptoms or treatment, without specific information relevant to mechanisms of immune-mediated injury were excluded from this work. Articles meeting the inclusion criteria were digested and summarised.

RESULTS

A proposed pathogenic mechanism of AIED involves inflammation and immune-mediated attack of specific inner ear structures, leading to an excessive Th1 immune response with vascular changes and tissue damage in the cochlea. Studies have identified self-reactive T cells and immunoglobulins, and have variously implicated immune-complex deposition, microthrombosis and electrochemical disturbances causing impaired neurosignalling in the pathogenesis of AIED. Research has also demonstrated abnormalities in the cytokine milieu in subjects with AIED, which may prove a target for therapy in the future.

CONCLUSION

Ongoing research is needed to further elucidate the aetiopathogenesis of AIED and discern between various mechanisms of tissue injury. Large-cohort clinical studies employing IL-1 receptor blockade are warranted to determine its potential for future therapy.