Aldosterone and prednisolone control of cochlear function in MRL/MpJ-Fas(lpr) autoimmune mice

Connexins 30 and 43 expression changes in relation to age-related hearing loss

Age-related hearing loss (ARHL), also known as presbycusis, is the number one communication disorder for aging adults. Connexin proteins are essential for intercellular communication throughout the human body, including the cochlea. Mutations in connexin genes have been linked to human syndromic and nonsyndromic deafness; thus, we hypothesize that changes in connexin gene and protein expression with age are involved in the etiology of ARHL. Here, connexin gene and protein expression changes for CBA/CaJ mice at different ages were examined, and correlations were analyzed between the changes in expression levels and functional hearing measures, such as ABRs and DPOAEs. Moreover, we investigated potential treatment options for ARHL. Results showed significant downregulation of Cx30 and Cx43 gene expression and significant correlations between the degree of hearing loss and the changes in gene expression for both genes. Moreover, dose-dependent treatments utilizing cochlear cell lines showed that aldosterone hormone therapy significantly increased Cx expression. In vivo mouse treatments with aldosterone also showed protective effects on connexin expression in aging mice. Based on these functionally relevant findings, next steps can include more investigations of the mechanisms related to connexin family gap junction protein expression changes during ARHL; and expand knowledge of clinically-relevant treatment options by knowing what specific members of the Cx family and related inter-cellular proteins should be targeted therapeutically.

A critical evaluation of "leakage" at the cochlear blood-stria-barrier and its functional significance

The blood-labyrinth-barrier (BLB) is a semipermeable boundary between the vasculature and three separate fluid spaces of the inner ear, the perilymph, the endolymph and the intrastrial space. An important component of the BLB is the blood-stria-barrier, which shepherds the passage of ions and metabolites from strial capillaries into the intrastrial space. Some investigators have reported increased "leakage" from these capillaries following certain experimental interventions, or in the presence of inflammation or genetic variants. This leakage is generally thought to be harmful to cochlear function, principally by lowering the endocochlear potential (EP). Here, we examine evidence for this dogma. We find that strial capillaries are not exclusive, and that the asserted detrimental influence of strial capillary leakage is often confounded by hair cell damage or intrinsic dysfunction of the stria. The vast majority of previous reports speculate about the influence of strial vascular barrier function on the EP without directly measuring the EP. We argue that strial capillary leakage is common across conditions and species, and does not significantly impact the EP or hearing thresholds, either on evidentiary or theoretical grounds. Instead, strial capillary endothelial cells and pericytes are dynamic and allow permeability of varying degrees in response to specific conditions. We present observations from mice and demonstrate that the mechanisms of strial capillary transport are heterogeneous and inconsistent among inbred strains.

Oral Corticosteroids Impair Mucin Production and Alter the Posttransplantation Microbiota in the Gut

INTRODUCTION

Gut microbiota alterations cause inflammation in patients with ulcerative colitis (UC). Fecal microbiota transplantation (FMT) enables manipulating the microbiota's composition, but the mechanisms underlying colonization of the posttransplantation microbiota are poorly understood.

METHODS

In this open-label, nonrandomized study, the FMT efficacy and changes in the gut microbiota were evaluated in 8 UC patients with mild-to-moderately active endoscopic colonic lesions. Compositional changes in the fecal and mucosal microbiotas between donors and recipients were examined via 16S rRNA-based sequencing. To investigate the effects of oral corticosteroids on microbiota colonization, FMT was performed in germ-free prednisolone (PSL)-administered mice to examine the factors determining colonization.

RESULTS

Four UC patients achieved clinical remission (CR) after FMT, and 3 also achieved endoscopic remission. The fecal microbiotas of the CR patients changed similar to those of the donors after FMT. The mucin-coding gene, MUC2, was less expressed in the colons of the PSL-dependent patients than in the PSL-free patients. In the mice, PSL treatment decreased the fecal mucin production and altered the posttransplantation fecal microbiota composition. Adding either exogenous mucin or the mucin secretagogue, rebamipide, partially alleviated the PSL-induced dysbiosis of the gut microbiota. Administering rebamipide with FMT from healthy donors relieved inflammation in mice with Enterococcus faecium-induced colitis.

CONCLUSION

Colonic mucin controlled the gut microbiota composition, and oral corticosteroid treatment modified the gut microbiota partly by reducing the colonic mucin.

Design, Synthesis, and Biological Evaluation of Dexamethasone-Salvianolic Acid B Conjugates and Nanodrug Delivery against Cisplatin-Induced Hearing Loss

Cisplatin (CDDP) is an extensively used chemotherapeutic agent but has a high incidence of severe ototoxicity. Although a few molecules have entered clinical trials, none have been approved to prevent or treat CDDP-induced hearing loss by the Food and Drug Administration. In this study, an amphiphilic drug-drug conjugate was synthesized by covalently linking dexamethasone (DEX) and salvianolic acid B (SAL) through an ester or amide bond. The conjugates could self-assemble into nanoparticles (NPs) with ultrahigh drug loading capacity and favorable stability. Compared with DEX, SAL, or their physical mixture at the same concentrations, both conjugates and NPs showed enhanced otoprotection in vitro and in vivo. More importantly, the conjugates and NPs almost completely restored hearing in a guinea pig model with good biocompatibility. Immunohistochemical analyses suggested that conjugates and NPs activated the glucocorticoid receptor, which may work as one of the major mechanisms for their protective effects.

Translational implications of the interactions between hormones and age-related hearing loss

Provocative research has revealed both positive and negative effects of hormones on hearing as we age; with in some cases, mis-regulation of hormonal levels in instances of medical comorbidities linked to aging, lying at the heart of the problem. Animal model studies have discovered that hormonal fluctuations can sharpen hearing for improved communication and processing of mating calls during reproductive seasons. Sex hormones sometimes have positive effects on auditory processing, as is often the case with estrogen, whereas combinations of estrogen and progesterone, and testosterone, can have negative effects on hearing abilities, particularly in aging subjects. Too much or too little of some hormones can be detrimental, as is the case for aldosterone and thyroid hormones, which generally decline in older individuals. Too little insulin, as in Type 1 diabetics, or poor regulation of insulin, as in Type 2 diabetics, is also harmful to hearing in our aged population. In terms of clinical translational possibilities, hormone therapies can be problematic due to systemic side effects, as has happened for estrogen/progestin combination hormone replacement therapy (HRT) in older women, where the HRT induces a hearing loss. As hormone therapy approaches are further developed, it may be possible to lower needed doses of hormones by combining them with supplements, such as antioxidants. Another option will be to take advantage of emerging technologies for local drug delivery to the inner ear, including biodegradeable, sustained-release hydrogels and micro-pumps which can be implanted in the middle ear near the round window. In closing, exciting research completed to date, summarized in the present report bodes well for emerging biomedical therapies to prevent or treat age-related hearing loss utilizing hormonal strategies.

A Novel Therapy for Presbycusis

Hearing amplification is the mainstay of treatment for presbycusis, but adherence with this therapy remains abysmally low, necessitating the exploration of other treatment modalities. Mineralocorticoids represent one such novel treatment modality. Although research on mineralocorticoids to prevent and retard presbycusis in humans shows promise and the potential to radically change the way clinicians approach age-related hearing loss, it remains in its infancy. Future studies that further evaluate the safety and efficacy of mineralocorticoids for presbycusis are still required for this potentially paradigm shifting therapy to gain widespread acceptance.

Understanding hormone and hormone therapies' impact on the auditory system

Hormones such as estrogen, progesterone, and aldosterone all demonstrate vital roles in sustaining auditory function through either the maintenance of cochlear neurons, up/down regulation of critical molecules (i.e., IGF-1, BDNF, etc.), or generation of the endocochlear potential. With disease and/or age, hormone expression begins to decline drastically, which ultimately affects cochlear structures and the integrity of cochlear cells. The following review explores the latest findings as well as realistic outcomes for hormone therapy treatment in the auditory system. This information could serve as a potential guide for patients considering hormone therapy as a medicinal choice to alleviate the signs of onset of presbycusis-age-related hearing loss. Additional scientific investigations could also be carried out to further enhance recent findings.

A Polymer-Based Extended Release System for Stable, Long-term Intracochlear Drug Delivery

OBJECTIVE

Investigate a new polymer-based drug coating suitability for safe intracochlear delivery and ability to maintain long-term physiologically active levels of the corticosteroid fluticasone propionate.

STUDY DESIGN

In vitro dissolution study to evaluate release profiles of polymer-coated drug particles and in vivo studies using a guinea pig model to measure perilymph drug concentrations at specific time points after implantation with polymer-coated drug particles and evaluate their effect on hearing function.

METHODS

Polymer-coated fluticasone propionate (FP) particles were surgically implanted in guinea pigs through the round window membrane into the cochlear scala tympani. In the pilot study, pre- and post-op hearing thresholds were conducted on days 7, 14, and 42. In a second study, post-op hearing thresholds were conducted on days 90, 120, and 180. Perilymph drug concentrations were measured on the same time points.

RESULTS

In 15 of 16 animals from day 7 through day 90, drug levels were within the targeted range, with no initial burst release detected. Drug was present in all animals on day 90 and was detected in some animals at 120 and 180 days. Hearing was tested and compared with non-implanted ears. Very good hearing preservation was observed in ears implanted with intracochlear particles when compared with contralateral ears.

CONCLUSIONS

The polymer-based extended release system is effective in providing long-term, stable drug delivery for at least 90 days with good hearing outcomes. The results of this study support the potential for achieving long-term drug delivery with a single intracochlear administration.

Recovery From Sudden Sensorineural Hearing Loss May Be Linked to Chronic Stress Levels and Steroid Treatment Resistance

Purpose This article investigates the possible connections between the level of chronic stress and success of steroid therapy in patients with sudden sensorineural hearing loss (SSNHL). Method A single-center, retrospective, longitudinal cohort study on 55 patients in a tertiary referral otology center was examined. Patients diagnosed with SSNHL between 2014 and 2017 were asked to complete a Measure of Perceived Stress (Brajac, Tkalcic, Dragojević, & Gruber, 2003 ) questionnaire. Inclusion criteria were patients > 18 years of age, SSNHL diagnosed within 4 previous weeks, completed steroid treatment, and complete documentation. Results There were 30 patients (55%) that showed significant improvement in their pure-tone audiogram (PTA) hearing threshold average (≥ 15 dB) after steroid treatment. Two-step cluster analysis identified 3 clusters based on average PTA hearing threshold recovery and average Measure of Perceived Stress scores. The difference between pretreatment and posttreatment hearing levels was significantly higher in the cluster with moderate stress compared to clusters with mild and high stress levels (Kruskal-Wallis test, Friedman test, p < .001). There were no significant differences in average PTA hearing threshold recovery after steroid therapy between groups of patients with mild and severe stress. Conclusion Patients with moderate stress levels show significantly better results after steroid treatment for SSNHL than patients with low or high stress levels.

Limited preventive effect of prednisone on neuropsychiatric symptoms in murine systemic lupus erythematosus

OBJECTIVE

To investigate whether glucocorticoids, the hallmark medication for systemic lupus erythematosus (SLE), could prevent the development of neuropsychiatric SLE (NPSLE).

METHODS

The protective effects of prednisone on NPSLE were tested using the open field, object recognition/placement, forced swim, tail suspension, and sucrose preference tests in MRL/lpr mice. Auto-antibody titres and the weight of lymph nodes were also measured.

RESULTS

MRL/lpr mice exhibited mild depression at the age of 8 weeks before progressing with spatial cognitive impairment and severe depression-like behaviour at the age of 16 weeks. Treating MRL/lpr mice with prednisone (5 mg/kg) from the age of 8 weeks decreased anti-cardiolipin and anti-N-methyl-D-aspartate (NMDA) receptor antibody titres in the brain, reduced the weight of lymph nodes, and prolonged the floating latency in the forced swim test. However, prednisone (3 or 5 mg/kg) had no preventive effect on the development of spatial cognitive impairment and other depression-like behaviours in MRL/lpr mice. The dose of prednisone had a positive correlation with the floating latency in the forced swim test, while it offered no effects on all other behavioural tests.

CONCLUSION

Our results provide evidence that early treatment with prednisone had a limited effect on the development of neuropsychiatric symptoms in MRL/lpr mice. Further work is needed in other models beyond NPSLE in MRL/lpr mice before any definitive conclusions are made on the efficacy of prednisone in human NPSLE.

Toxicology study for magnetic injection of prednisolone into the rat cochlea

This paper investigates the safety of a novel 'magnetic injection' method of delivering therapy to the cochlea, in a rodent model. In this method of administration, a magnetic field is employed to actively transport drug-eluting superparamagnetic iron-oxide core nanoparticles into the cochlea, where they then release their drug payload (we delivered the steroid prednisolone). Our study design and selection of control groups was based on published regulatory guidance for safety studies that involve local drug delivery. We tested for both single and multiple delivery doses to the cochlea, and found that magnetic delivery did not harm hearing. There was no statistical difference in hearing between magnetically treated ears versus ears that received intra-tympanic steroid (a mimic of a standard-of-care for sudden sensorineural hearing loss), both 2 and 30 days after treatment. Since our treatment is local to the ear, the levels of steroid and iron circulating systemically after our treatment were low, below mass-spectrometry detection limits for the steroid and no different from normal for iron. No adverse findings were observed in ear tissue histopathology or in animal gross behavior. At 2 and 30 days after treatment, inflammatory changes examined in the ear were limited to the middle ear, were very mild in severity, and by day 90 there was ongoing and almost complete reversibility of these changes. There were no ear tissue scarring or hemorrhage trends associated with magnetic delivery. In summary, after conducting a pre-clinical safety study, no adverse safety issues were observed.

Age-related hearing loss: prevention of threshold declines, cell loss and apoptosis in spiral ganglion neurons

Age-related hearing loss (ARHL) -presbycusis - is the most prevalent neurodegenerative disease and number one communication disorder of our aged population; and affects hundreds of millions of people worldwide. Its prevalence is close to that of cardiovascular disease and arthritis, and can be a precursor to dementia. The auditory perceptual dysfunction is well understood, but knowledge of the biological bases of ARHL is still somewhat lacking. Surprisingly, there are no FDA-approved drugs for treatment. Based on our previous studies of human subjects, where we discovered relations between serum aldosterone levels and the severity of ARHL, we treated middle age mice with aldosterone, which normally declines with age in all mammals. We found that hearing thresholds and suprathreshold responses significantly improved in the aldosterone-treated mice compared to the non-treatment group. In terms of cellular and molecular mechanisms underlying this therapeutic effect, additional experiments revealed that spiral ganglion cell survival was significantly improved, mineralocorticoid receptors were upregulated via post-translational protein modifications, and age-related intrinsic and extrinsic apoptotic pathways were blocked by the aldosterone therapy. Taken together, these novel findings pave the way for translational drug development towards the first medication to prevent the progression of ARHL.

Intratympanic methylprednisolone perfusion as a salvage treatment for profound idiopathic sudden sensorineural hearing loss

Objective:

This study aimed to examine the effectiveness of intratympanic methylprednisolone perfusion as salvage treatment for profound idiopathic sudden sensorineural hearing loss.

Methods:

A retrospective clinical study of 97 patients with unilateral profound idiopathic sudden sensorineural hearing loss was performed. In all, 83 patients who received salvage intratympanic methylprednisolone perfusion plus conventional treatment (except for steroids) as the second-line therapy were assigned to the study group, while 14 patients who received conventional treatment alone were assigned to the comparison group.

Results:

In the study group, treatments in patients with a shorter interval from disease onset to intratympanic methylprednisolone perfusion (up to 15 days) had significantly greater improvements in the overall effective rate and pure tone average compared with patients with a longer interval (over 15 days). For patients with a short interval from disease onset to intratympanic methylprednisolone perfusion, those in the study group had significantly greater improvements in the overall effective rate and pure tone average compared with those in the comparison group. In both the study and comparison groups, hearing improvements were greater at low frequencies than at medium and high frequencies.

Conclusion:

The interval from disease onset to intratympanic methylprednisolone perfusion was the major factor affecting hearing recovery. Early second-line salvage intratympanic methylprednisolone perfusion significantly improved the degree of hearing recovery in profound idiopathic sudden sensorineural hearing loss patients after failure of systemic steroid treatment.

Long-term treatment with aldosterone slows the progression of age-related hearing loss

Age-related hearing loss (ARHL), clinically referred to as presbycusis, is one of the three most prevalent chronic medical conditions of our elderly, with the majority of persons over the age of 60 suffering from some degree of ARHL. The progressive loss of auditory sensitivity and perceptual capability results in significant declines in workplace productivity, quality of life, cognition and abilities to communicate effectively. Aldosterone is a mineralocorticoid hormone produced in the adrenal glands and plays a role in the maintenance of key ion pumps, including the Na-K(+)-Cl co-transporter 1 or NKCC1, which is involved in homeostatic maintenance of the endocochlear potential. Previously we reported that aldosterone (1 μM) increases NKCC1 protein expression in vitro and that this up-regulation of NKCC1 was not dose-dependent (dosing range from 1 nM to 100 μM). In the current study we measured behavioral and electrophysiological hearing function in middle-aged mice following long-term systemic treatment with aldosterone. We also confirmed that blood pressure remained stable during treatment and that NKCC1 protein expression was upregulated. Pre-pulse inhibition of the acoustic startle response was used as a functional measure of hearing, and the auditory brainstem response was used as an objective measure of peripheral sensitivity. Long-term treatment with aldosterone improved both behavioral and physiological measures of hearing (ABR thresholds). These results are the first to demonstrate a protective effect of aldosterone on age-related hearing loss and pave the way for translational drug development, using aldosterone as a key component to prevent or slow down the progression of ARHL.

Human amniotic epithelial cells suppress relapse of corticosteroid-remitted experimental autoimmune disease

BACKGROUND AIMS

Multiple sclerosis (MS) is considered to be a T-cell-mediated disease. Although MS remits with corticosteroid treatment, the disease relapses on discontinuation of therapy. Human amniotic epithelial cells (hAEC) from the placenta are readily accessible in large quantities and have anti-inflammatory properties. Previously we reported that hAEC given near disease onset ameliorated clinical signs and decreased myelin oligodendrocyte glycoprotein (MOG)-specific immune responses in MOG-induced experimental autoimmune encephalomyelitis (EAE), an experimental MS model.

METHODS

To examine the therapeutic effect of hAEC in a clinically relevant setting, we first treated MOG peptide-induced EAE mice with a corticosteroid, prednisolone, in drinking water to induce remission. hAEC were then infused intravenously into the remitted mice. Anti-MOG antibodies in serum were detected by enzyme-linked immunoassay. Splenocyte proliferation was assessed by (3)H-thymidine incorporation. Immune cell subpopulations in spleens and lymph nodes and secreted cytokines in splenocyte culture were quantified by flow cytometry. Central nervous system histology was examined with the use of hematoxylin and eosin, Luxol fast blue and immunostaining.

RESULTS

With cessation of prednisolone treatment, hAEC delayed EAE relapse for 7 days, and, after another 7 days, largely remitted disease in six of eight responder mice. Splenocyte proliferation was suppressed, anti-MOG35-55 antibodies in serum were decreased and interleukin-2 and interleukin-5 production by splenocytes were elevated after hAEC treatment. In the central nervous system, hAEC-treated mice had decreased demyelination and fewer macrophages in the inflammatory infiltrates. hAEC treatment also increased CD4(+)CD25(+)FoxP3(+) regulatory T cells in inguinal lymph nodes.

CONCLUSIONS

These data demonstrate that the therapeutic effects of hAEC after corticosteroid treatment in an MS model probably are the consequence of peripheral immunoregulation. We suggest that hAEC may have potential as a cell therapy for remitted MS.

Expression and dexamethasone-induced nuclear translocation of glucocorticoid and mineralocorticoid receptors in guinea pig cochlear cells

Glucocorticoids (GC) are powerful anti-inflammatory agents frequently used to protect the auditory organ against damage associated with a variety of conditions, including noise exposure and ototoxic drugs as well as bacterial and viral infections. In addition to glucocorticoid receptors (GC-R), natural and synthetic GC are known to bind mineralocorticoid receptors (MC-R) with great affinity. We used light and laser scanning confocal microscopy to investigate the expression of GC-R and MC-R in different cell populations of the guinea pig cochlea, and their translocation to different cell compartments after treatment with the synthetic GC dexamethasone. We found expression of both types of receptors in the cytoplasm and nucleus of sensory inner and outer hair cells as well as pillar, Hensen and Deiters cells in the organ of Corti, inner and outer sulcus cells, spiral ganglion neurons and several types of spiral ligament and spiral limbus cells; stria vascularis cells expressed mostly MC-R whereas fibrocytes type IV were positive for GC-R only. GC-R and MC-R were also localized at or near the plasma membrane of pillar cells and outer hair cells, whereas GC-R were found at or near the plasma membrane of Hensen cells only. We investigated the relative levels of receptor expression in the cytoplasm and the nucleus of Hensen cells treated with dexamethasone, and found they varied in a way suggestive of dose-induced translocation. These results suggest that the oto-protective effects of GC could be associated with the concerted activation of genomic and non-genomic, GC-R and MC-R mediated signaling pathways in different regions of the cochlea.

Corticosteroid therapy for hearing and balance disorders

This review addresses the current status of steroid therapies for hearing and vestibular disorders and how certain misconceptions may be undermining the efficacy in restoring normal ear function, both experimentally and clinically. Specific misconceptions addressed are that steroid therapy is not effective, steroid-responsive hearing loss proves an underlying inflammatory problem in the ear, and steroids only have application to the hearing disorders listed below. Glucocorticoid therapy for hearing and balance disorders has been employed for over 60 years. It is recommended in cases of sudden hearing loss, Meniére's disease, immune-mediated hearing loss, and any vestibular dysfunction suspected of having an inflammatory etiology. The predominant steroids employed today are dexamethasone, prednisone, prednisolone, and methylprednisolone. Despite years of use, little is known of the steroid responsive mechanisms in the ear that are influenced by glucocorticoid therapy. Furthermore, meta-analyses and clinical study reviews occasionally question whether steroids offer any benefit at all. Foremost in the minds of clinicians is the immune suppression and anti-inflammatory functions of steroids because of their efficacy for autoimmune hearing loss. However, glucocorticoids have a strong binding affinity for the mineralocorticoid (aldosterone) and glucocorticoid receptors, both of which are prominent in the ear. Because the auditory and vestibular end organs require tightly regulated endolymph and perilymph fluids, this ion homeostasis role of the mineralocorticoid receptor cannot be overlooked in both normal and pathologic functions of the ear. The function of the glucocorticoid receptor is to provide anti-inflammatory and antiapoptotic signals by mediating survival factors.

Effect of intratympanic dexamethasone, memantine and piracetam on cellular apoptosis due to cisplatin ototoxicity

OBJECTIVE

This study aimed to contribute to the literature on the prevention and treatment of ototoxicity due to various drugs and chemicals.

MATERIAL AND METHODS

This study compared the histological effects of intratympanic dexamethasone, memantine and piracetam on cellular apoptosis due to cisplatin ototoxicity, in 36 rats.

RESULTS

Dexamethasone and memantine had significant effects on the stria vascularis, organ of Corti and spiral ganglion (p < 0.05). Although piracetam decreased the apoptosis rate, this effect was not statistically significant (p > 0.05).

CONCLUSION

Dexamethasone and memantine were found superior to piracetam in reducing apoptosis due to cisplatin ototoxicity. Further studies of this subject are needed, incorporating electron microscopy and auditory brainstem response testing.

Vascular Pathophysiology in Hearing Disorders

The inner ear vasculature is responsible for maintenance of the blood-labyrinth barrier, transport of systemic hormones for ion homeostasis, and supplying nutrients for metabolic functions. Unfortunately, these blood vessels also expose the ear to circulating inflammatory factors resulting from systemic diseases. Thus, while the inner ear blood vessels are critical for normal function, they also are facilitating pathologic mechanisms that result in hearing and vestibular dysfunction. In spite of these numerous critical roles of inner ear vasculature, little is known of its normal homeostatic functions and how these are compromised in disease. The objective of this review is to discuss the current concepts of vascular biology, how blood vessels naturally respond to circulating inflammatory factors, and how such mechanisms of vascular pathophysiology may cause hearing loss.

Immunosuppressive therapy for autoimmune inner ear disease

Autoimmune inner ear disease (AIED) is a rare disease that is diagnosed after clinical suspicion and response to corticosteroids. AIED manifests as progressive, bilateral, although often asynchronous, sensorineural hearing loss and can be associated with vestibular symptoms. Since its description as a defined disease entity in 1979, the initial mainstay of treatment remains high-dose corticosteroids. Several animal models have been developed to assist in determining efficacy of immunosuppression in AIED, and several clinical studies have also investigated the role of both steroid and steroid-sparing treatments. Here we discuss the basic science and clinical research surrounding the history of immunosuppressive therapy in AIED.

Low dose combination steroids control autoimmune mouse hearing loss

The severe side effects of glucocorticoids prevent long term management of hearing loss. Alternative steroid treatments that minimize or eliminate these effects would significantly benefit therapeutic control of hearing disorders. A steroid treatment study of autoimmune mouse hearing loss was conducted to determine the efficacy of combining aldosterone and prednisolone at low doses. An assessment also was made of low dose fludrocortisone, a synthetic mineralocorticoid that also has a slight glucocorticoid effect. MRL/MpJ-Fas(lpr) mice were tested for baseline ABR thresholds at 3 months of age and then treated with aldosterone (3.0 μg/kg) or prednisolone (1.0 mg/kg) to determine the lowest effective dose of each. Other mice were given the two steroids in combination at doses of Pred 0.5 mg+Aldo 1.5 μg; Pred 1.0 mg+Aldo 3.0 μg; or Pred 1.5 mg+Aldo 5.0 μg. Mice were retested with ABR at 1 and 2 months to determine the efficacy of the different steroid treatments in controlling hearing loss. Another series of mice were given the synthetic mineralocorticoid fludrocortisone at low (2.8 μg/kg) or high (10 μg/kg) doses and retested at monthly intervals for 3 months. Autoimmune mouse hearing loss developed in untreated controls. This threshold elevation was not prevented by prednisolone at 1 mg/kg or by aldosterone at 3 μg/kg when each was given alone. However, the two steroids combined at these doses effectively controlled hearing loss. The fludrocortisone treatments also were effective at low doses in preventing or reversing the autoimmune mouse hearing loss. This efficacy of combined steroids at low doses suggests the potential for reducing the side effects of glucocorticoids in the therapeutic control of hearing disorders.

Blocking the glucocorticoid receptor with RU-486 does not prevent glucocorticoid control of autoimmune mouse hearing loss

BACKGROUND/AIMS

Glucocorticoids effectively manage autoimmune hearing loss, although the cochlear mechanisms involved are unknown. Previous studies of steroid-responsive hearing loss in autoimmune (lupus) mice showed glucocorticoids and mineralocorticoids were equally effective, suggesting the ion homeostasis functions of glucocorticoids may be as relevant as immunosuppression for control of autoimmune-induced inner ear disease. Therefore, to better characterize the role of the glucocorticoid receptor in autoimmune hearing loss therapy, its function was blocked with the antagonist RU-486 (mifepristone) during glucocorticoid (prednisolone) treatments.

METHODS

Following baseline auditory brainstem response (ABR) thresholds, MRL/MpJ-Fas(lpr) autoimmune mice were implanted with pellets providing combinations of 1.25 mg/kg of RU-486, 4 mg/kg of prednisolone, or their respective placebos. After 1 month, animals were retested with ABR and blood was collected for immune complex analyses.

RESULTS

Mice receiving no prednisolone (placebo + placebo and placebo + RU-486) showed continued declines in hearing. On the other hand, mice receiving prednisolone (prednisolone + placebo and prednisolone + RU-486) had significantly better hearing (p < 0.05) than the non-prednisolone groups. Immune complexes were significantly elevated in the placebo + RU-486 group, suggesting RU-486 effectively blocked glucocorticoid receptor-mediated immune suppression. These results showed that blockage of the glucocorticoid receptor with RU-486 did not prevent prednisolone's effects in the ear, suggesting its ion homeostasis actions via the mineralocorticoid receptor were more relevant in hearing control.

CONCLUSION

The mineralocorticoid receptor-mediated actions of glucocorticoids are potentially relevant in steroid-responsive hearing disorders, implying disrupted cochlear ion transport functions may underlie the vascular problems proposed in some forms of immune-mediated hearing loss.

Strial microvascular pathology and age-associated endocochlear potential decline in NOD congenic mice

NOD/ShiLtJ (previously NOD/LtJ) inbred mice show polygenic autoimmune disease and are commonly used to model autoimmune-related type I diabetes, as well as Sjogren's syndrome. They also show rapidly progressing hearing loss, partly due to the combined effects of Cdh23ahl and Ahl2. Congenic NOD.NON-H2nb1/LtJ mice, which carry corrective alleles within the H2 histocompatibility gene complex, are free from diabetes and other overt signs of autoimmune disease, but still exhibit rapidly progressive hearing loss. Here we show that cochlear pathology in these congenics broadly includes hair cell and neuronal loss, plus endocochlear potential (EP) decline from initially normal values after two months of age. The EP reduction follows often dramatic degeneration of capillaries in stria vascularis, with resulting strial degeneration. The cochlear modiolus also features perivascular inclusions that resemble those in some mouse autoimmune models. We posit that cochlear hair cell/neural and strial pathology arise independently. While sensory cell loss may be closely tied to Cdh23ahl and Ahl2, the strial microvascular pathology and modiolar anomalies we observe may arise from alleles on the NOD background related to immune function. Age-associated EP decline in NOD.NON-H2nb1 mice may model forms of strial age-related hearing loss caused principally by microvascular disease. The remarkable strial capillary loss in these mice may also be useful for studying the relation between strial vascular insufficiency and strial function.

Methylprednisolone induces reversible clinical and pathological remission and loss of lymphocyte reactivity to myelin oligodendrocyte glycoprotein in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of human multiple sclerosis (MS). EAE, induced by immunisation with myelin-associated autoantigens, is characterised by an inflammatory infiltrate in the central nervous system (CNS) associated with axonal degeneration, demyelination and damage. We have recently shown in an experimental mouse model of autoimmune gastritis that methylprednisolone treatment induces a reversible remission of gastritis with regeneration of the gastric mucosa. Here, we examined the effect of oral methylprednisolone on the mouse EAE model of human MS induced by immunisation with myelin oligodendrocyte glycoprotein peptide (MOG(35-55)). We examined the clinical scores, CNS pathology and lymphocyte reactivity to MOG(35-55) following treatment and withdrawal of the steroid. Methylprednisolone remitted the clinical signs of EAE and the inflammatory infiltrate in the CNS, accompanied by loss of lymphocyte reactivity to MOG(35-55) peptide. Methylprednisolone withdrawal initiated relapse of the clinical features, a return of the CNS inflammatory infiltrate and lymphocyte reactivity to MOG(35-55) peptide. This is the first study to show that methylprednisolone induced a reversible remission in the clinical and pathological features of EAE in mice accompanied by loss of lymphocyte reactivity to the encephalitogen. This model will be useful for studies directed at a better understanding of mechanisms associated with steroid-induced disease remission, relapse and remyelination and also as an essential adjunct to an overall curative strategy.

Intratympanic injection of dexamethasone: time course of inner ear distribution and conversion to its active form

HYPOTHESIS

Intratympanically injected dexamethasone 21-phosphate is converted to its active form dexamethasone in the inner ear and follows the distribution of the glucocorticoid receptor.

BACKGROUND

Although dexamethasone is routinely delivered intratympanically for hearing loss, we know little of its inner ear pharmacokinetics. Dexamethasone 21-phosphate is the pharmaceutical compound available for injection, but it must be converted to its biologically active form (dexamethasone) to bind to the glucocorticoid receptor. Therefore, the current study was conducted to determine the time course of dexamethasone 21-phosphate movement from the middle ear into the inner ear, its conversion to dexamethasone, and the distribution of both forms relative to the glucocorticoid receptor.

METHODS

BALB/c mice were injected intratympanically with the prodrug dexamethasone 21-phosphate and inner ears collected at postinjection times ranging from 5 minutes to 7 days. Ears were immunohistochemically stained for dexamethasone 21-phosphate, dexamethasone, and the glucocorticoid receptor.

RESULTS

Both forms of dexamethasone were seen in the inner ear within 15 minutes, reaching their highest staining intensity at 1 hour. Neither drug was seen after 24 hours. The strongest staining occurred in the spiral ligament, organ of Corti, spiral ganglion, and vestibular sensory epithelia. Distribution of the drug paralleled locations of the glucocorticoid receptor except in the stria vascularis marginal cells, which stained heavily for the receptor but not the drug.

CONCLUSION

Dexamethasone rapidly travels from the middle ear into the inner ear and converts to its active form. The drug distribution follows that of the glucocorticoid receptor. However, it probably has little impact on ear tissues after 24 hours.

Glucocorticoid impact on cochlear function and systemic side effects in autoimmune C3.MRL-Faslpr and normal C3H/HeJ mice

Glucocorticoids are effective in reversing hearing loss, but their severe side effects limit long term management of many ear disorders. A clearer understanding of these side effects is critical for prolonged therapeutic control of hearing and vestibular dysfunction. Therefore, this study characterized the impact of the glucocorticoid prednisolone on cochlear dysfunction and systemic organ systems in C3.MRL-Fas(lpr) autoimmune mice and their normal C3H/HeJ parent strain. Following 3 months of treatment, autoimmune mice had better auditory thresholds and improved hematocrits, anti-nuclear antibodies, and immune complexes. Steroid treatment also lowered body and spleen weights, both of which rise with systemic autoimmune disease. Steroid treatment of the normal C3H/HeJ mice significantly elevated their blood hematocrits and lowered their body and spleen weights to abnormal levels. Thus, systemic autoimmune disease and its related hearing loss in C3.MRL-Fas(lpr) mice are steroid-responsive, but normal hemopoiesis and organ functions can be significantly compromised. This mouse model may be useful for studies of the detrimental side effects of steroid treatments for hearing loss.

Prednisolone promotes remission and gastric mucosal regeneration in experimental autoimmune gastritis

A cardinal feature of organ-specific autoimmunity is destructive pathology in the target organ. In human and experimental models of autoimmune gastritis, mononuclear cell infiltration and cellular destruction in the gastric mucosa are disease hallmarks. Strategies to cure autoimmune disease must not only establish immunological tolerance to autoantigen, but also rid the organ of pathogenic autoreactive cells. The present study has assessed the effect of prednisolone treatment in clearing the inflammatory infiltrate in experimental autoimmune gastritis and in preventing disease relapse in athymic compared with euthymic mice. Experimental autoimmune gastritis was induced by neonatal thymectomy or by transgenic expression of GM-CSF (PC-GMCSF mice). Groups of mice were treated with prednisolone (10 mg/kg per day) for 10 weeks or with prednisolone for 10 weeks followed by 10 weeks without prednisolone. Stomachs were examined for gross morphological changes, and by histology and immunohistochemistry for composition of inflammatory infiltrate and gastric mucosal integrity. Autoantibody to gastric H+/K+ ATPase was determined by ELISA. Prednisolone promoted remission of gastritis in both mouse models of experimental autoimmune gastritis, evident by reduction in stomach size, clearing of gastric inflammatory infiltrate, and regeneration of the gastric mucosa. Prednisolone withdrawal resulted in disease relapse in all PC-GMCSF mice, whereas approximately 40% of neonatal thymectomy mice retained normal stomach morphology and remained free of gastric pathology. It is concluded that prednisolone promotes remission and gastric mucosal regeneration in experimental autoimmune gastritis. Prolonged remission of autoimmune gastritis in some athymic mice suggests a role for the thymus in disease relapse.

Mineralocorticoid receptor mediates glucocorticoid treatment effects in the autoimmune mouse ear

The standard treatment for many hearing disorders is glucocorticoid therapy, although the cochlear mechanisms involved in steroid-responsive hearing loss are poorly understood. Cochlear dysfunction in autoimmune mice has recently been shown to be controlled with the mineralocorticoid aldosterone as effectively as with the glucocorticoid prednisolone. Because aldosterone regulates sodium, potassium, and other electrolyte homeostasis, this implied the restoration of hearing with the mineralocorticoid was due to its impact on cochlear ion transport, particularly in the stria vascularis. This also suggested glucocorticoids may be controlling hearing recovery in part through their binding to the mineralocorticoid receptor in addition to their glucocorticoid receptor-mediated anti-inflammatory and immunosuppressive functions. Therefore, the aim of the present study was to better delineate the role of the mineralocorticoid receptor in steroid control of hearing in the autoimmune mouse. Spironolactone, a mineralocorticoid receptor antagonist, was administered to MRL/MpJ-Fas(lpr) autoimmune mice in combination with either aldosterone or prednisolone to compare their hearing and systemic disease with mice that received either steroid alone. ABR thresholds showed either aldosterone or prednisolone alone preserved hearing in the mice, but spironolactone prevented both steroids from maintaining normal cochlear function. This suggested both steroids are preserving hearing through the mineralocorticoid receptor within the ear to regulate endolymph homeostasis. The spironolactone treatment did not block normal glucocorticoid receptor-mediated immune-suppression functions because mice receiving prednisolone, either with or without spironolactone, maintained normal body weights, hematocrits, and serum immune complexes. Thus, reducing systemic autoimmune disease was not sufficient to control hearing if mineralocorticoid receptor-mediated functions were blocked. It was concluded the inner ear mineralocorticoid receptor is a significant target of glucocorticoids and a factor that should be considered in therapeutic treatments for steroid-responsive hearing loss.

Transtympanic corticoid therapy for acute profound hearing loss

The prognosis of idiopathic sudden hearing loss depends on its severity; acute complete deafness, for example, has a particularly bad prognosis. The treatment of acute deafness is based on a systemic application of corticosteroids. Corticoid concentrations in the cochlea are higher after transtympanic application in comparison to systemic application. We therefore investigated whether an additional transtympanic corticoid therapy gives an advantage over systemic standard therapy. We report on 27 patients with sudden idiopathic profound hearing loss or deafness who were treated in the Department of Otorhinolaryngology, University of Essen, Germany. Fourteen patients were treated with a rheologic infusion therapy with systemic prednisolone. Thirteen patients were treated additionally with methylprednisolone (Urbason) transtympanically through a ventilation tube. In the first group of patients who were treated with infusion therapy and corticoids systemically, three patients had good recovery of hearing. Another five patients had a partial recovery of hearing. The average hearing gain from 0.5-4 kHz was 15 dB. In the group of patients who were treated additionally with local corticoids, two patients reported a good recovery of hearing and another two patients only had a partial recovery of hearing. The average hearing gain in the above-mentioned frequency range was 11 dB. In our patients the additional transtympanic application of corticoids did not result in a significantly improved recovery of hearing in comparison to the patients treated with the standard therapy alone.

Intratympanic treatment of hearing loss with novel and traditional agents

As knowledge of the cellular and molecular pathophysiology behind otopathologies expands, the possibility exists of preventing sensorineural hearing loss and perhaps reversing the loss. Cellular and molecular mechanisms seem to be similar in hearing loss secondary to aging, drug ototoxicity, noise, or other mechanisms. A final common pathway may hinge upon apoptosis. It is likely that anti-apoptotic factors will increasingly be realized as an important intervention strategy for sensorineural hearing loss. Furthermore, it is also possible that mounting a staged attack at the various regions in the pathway leading to cellular damage using a combination of several protective substances such as steroids, antioxidants, neurotrophic factors, anti-apoptotic compounds, and mitochondrial enhancers may prevent hearing loss and even reverse it in some situations. This article has presented some of the molecular and cellular mechanisms for hearing loss and potential ways of treating them. In theory, the delivery of these medications to the inner ear transtympanically would decrease systemic side effects and be more target specific. Because most of the studies conducted to date have been animal studies, randomized, double-blind, placebo-controlled clinical trials would be necessary before the use of these therapies becomes common practice.

Intratympanic corticosteroids for Meniere's disease and vertigo

Hearing loss can be caused by acoustic trauma, aging, ototoxic medications, and various other causes. At the cellular level hearing loss seems to be mediated by reactive oxygen species and ultimately through the activation of apoptotic mechanisms. This article explains the cellular and molecular mechanisms of hearing loss and presents medications that could be used in the intratympanic treatment of hearing loss.

Spironolactone blocks glucocorticoid-mediated hearing preservation in autoimmune mice

HYPOTHESIS

Although autoimmune sensorineural hearing loss can be effectively treated with corticosteroids, little is known about how these drugs affect cochlear function. MRL/MpJ-Faslpr autoimmune mice treated with a mineralocorticoid (aldosterone) have previously been shown to have hearing improvement equal to those treated with a glucocorticoid (prednisolone). This suggested that the restoration of hearing with steroids was the result of an effect on sodium transport rather than an antiinflammatory or immunosuppressive role. We hypothesized that corticosteroids reverse autoimmune hearing loss through the mineralocorticoid receptor and that blocking the mineralocorticoid receptor will prevent glucocorticoid effects.

METHODS

Spironolactone, a mineralocorticoid receptor antagonist, was administered to MRL/MpJ-Faslpr autoimmune mice alone or in combination with corticosteroids. The four treatment groups were: spironolactone, spironolactone + aldosterone, spironolactone + prednisolone, and untreated water controls. Auditory brainstem response (ABR) thresholds were recorded before and during treatment (2, 3, and 4 mo) to measure the effect of steroids on hearing decline.

RESULTS

Hearing in spironolactone and spironolactone + prednisolone mice showed progressive decline in hearing similar to water controls. The hearing was preserved in spironolactone + aldosterone mice, presumably as a result of the fact that aldosterone has a higher affinity for the mineralocorticoid receptor than spironolactone. Thus, aldosterone was able to maintain cochlear function with autoimmune disease progression, similar to previous reports of aldosterone treatment effects.

CONCLUSIONS

Spironolactone effectively blocked prednisolone from improving hearing in MRL/MpJ-Faslpr autoimmune mice. This offers evidence that the inner ear mineralocorticoid receptor is the therapeutic target for corticosteroids used to treat autoimmune and sudden sensorineural hearing loss. Pharmacologic treatments that selectively target the mineralocorticoid receptor may provide greater clinical benefit with fewer systemic side effects than prednisone in patients with autoimmune sensorineural hearing loss.