Interleukin-1beta upregulates Na+-K+-2Cl- cotransporter in human middle ear epithelia

Evaluation of Caspase-1, Interleukin-1β, and Interleukin-18, in the Middle Ear Effusion in Children With Otitis Media With Effusion

Objectives: The present study aimed to assess the expression of caspase-1 and caspase-1-dependent processing of cytokines, such as interleukin (IL)-1β and IL-18, in the middle ear effusion of children with otitis media with effusion (OME) in order to identify the potential role of inflammasomes in OME. Methods: This study included 29 children scheduled for myringotomy with the insertion of tympanostomy tubes due to OME. Middle ear effusion (MEE) was collected during the surgery. Caspase-1, IL-1β, and IL-18 were assayed using enzyme-linked immunosorbent assay kits. The levels were compared between those with mucoid and serous MEE and those with and without a history of ventilation tube insertion. Results: Caspase-1, IL-1β, and IL-18 were detected in all samples. The caspase-1, IL-1β, and IL-18 levels did not significantly differ between mucoid samples and serous samples. No statistical significances were discovered in caspase-1, IL-1β, and IL-18 levels between with and without a history of ventilation tube groups. There was a significant negative correlation between IL-1β and IL-18 and the duration of OME (p < 0.05). However, no significant correlation was found between caspase-1 and disease duration. Conclusions: Inflammasomes may participate in the inflammatory process of OME. IL-1β and IL-18 levels in the MEE decreased over time.

Off-Label Use of Bumetanide for Brain Disorders: An Overview

Bumetanide (BTN or BUM) is a FDA-approved potent loop diuretic (LD) that acts by antagonizing sodium-potassium-chloride (Na-K-Cl) cotransporters, NKCC1 (SLc12a2) and NKCC2. While NKCC1 is expressed both in the CNS and in systemic organs, NKCC2 is kidney-specific. The off-label use of BTN to modulate neuronal transmembrane Cl⁻ gradients by blocking NKCC1 in the CNS has now been tested as an anti-seizure agent and as an intervention for neurological disorders in pre-clinical studies with varying results. BTN safety and efficacy for its off-label use has also been tested in several clinical trials for neonates, children, adolescents, and adults. It failed to meet efficacy criteria for hypoxic-ischemic encephalopathy (HIE) neonatal seizures. In contrast, positive outcomes in temporal lobe epilepsy (TLE), autism, and schizophrenia trials have been attributed to BTN in studies evaluating its off-label use. NKCC1 is an electroneutral neuronal Cl⁻ importer and the dominance of NKCC1 function has been proposed as the common pathology for HIE seizures, TLE, autism, and schizophrenia. Therefore, the use of BTN to antagonize neuronal NKCC1 with the goal to lower internal Cl⁻ levels and promote GABAergic mediated hyperpolarization has been proposed. In this review, we summarize the data and results for pre-clinical and clinical studies that have tested off-label BTN interventions and report variable outcomes. We also compare the data underlying the developmental expression profile of NKCC1 and KCC2, highlight the limitations of BTN’s brain-availability and consider its actions on non-neuronal cells.

Characterization and Activation of NLRP3 Inflammasomes in the Renal Medulla in Mice

BACKGROUND/AIMS

Recent studies have indicated that local inflammatory mediators are importantly involved in the regulation of renal function. However, it remains unknown how such local inflammation is triggered intracellularly in the kidney. The present study was designed to characterize the inflammasome centered by Nlrp3 in the kidney and also test the effect of its activation in the renal medulla.

METHODS AND RESULTS

By immunohistochemistry analysis, we found that inflammasome components, Nlrp3, Asc and caspase-1, were ubiquitously distributed in different kidney areas. The caspase-1 activity and IL-1β production were particularly high in the renal outer medulla compared to other kidney regions. Further confocal microscopy and RT-PCR analysis showed that Nlrp3, Asc and caspase-1 were particularly enriched in the thick ascending limb of Henle's loop. In anesthetized mice, medullary infusion of Nlrp3 inflammasome activator, monosodium urate (MSU), induced significant decreases in sodium excretion and medullary blood flow without changes in mean arterial blood pressure and renal cortical blood flow. Caspase-1 inhibitor, Ac-YVAD-CMK and deletion of Nlrp3 or Asc gene abolished MSU-induced decreases in renal sodium excretion and MBF.

CONCLUSION

Our results indicate that renal medullary Nlrp3 inflammasomes represent a new regulatory mechanism of renal MBF and sodium excretion which may not depend on classical inflammatory response.

Interleukin-1 Receptor Activation Potentiates Salt Reabsorption in Angiotensin II-Induced Hypertension via the NKCC2 Co-transporter in the Nephron

Hypertension is among the most prevalent and catastrophic chronic diseases worldwide. While the efficacy of renin angiotensin system (RAS) blockade in lowering blood pressure illustrates that the RAS is broadly activated in human hypertension, the frequent failure of RAS inhibition to prevent or reverse hypertensive organ damage highlights the need for novel therapies to combat RAS-dependent hypertension. We previously discovered elevated levels of the macrophage cytokine IL-1 in the kidney in a murine model of RAS-mediated hypertension. Here we report that IL-1 receptor (IL-1R1) deficiency or blockade limits blood pressure elevation in this model by mitigating sodium reabsorption via the NKCC2 co-transporter in the nephron. In this setting, IL-1R1 activation prevents intra-renal myeloid cells from maturing into Ly6C(+)Ly6G(-) macrophages that elaborate nitric oxide, a natriuretic hormone that suppresses NKCC2 activity. By revealing how the innate immune system regulates tubular sodium transport, these experiments should lead to new immunomodulatory anti-hypertensive therapies.

Control of middle ear inflammatory and ion homeostasis genes by transtympanic glucocorticoid and mineralocorticoid treatments

HYPOTHESIS

Transtympanic steroid treatment will induce changes in ion homeostasis and inflammatory gene expression to decrease middle ear inflammation due to bacterial inoculation.

BACKGROUND

Otitis media is common, but treatment options are limited to systemic antibiotic therapy or surgical intervention. Systemic glucocorticoid treatment of mice decreases inflammation and improves fluid clearance. However, transtympanic delivery of glucocorticoids or mineralocorticoid has not been explored to determine if direct steroid application is beneficial.

METHODS

Balb/c mice received transtympanic inoculation of heat-killed Haemophilus influenzae (H flu), followed by transtympanic treatment with either prednisolone or aldosterone. Mice given PBS instead of steroid and untreated mice were used as controls. Four hours after steroid treatment, middle ears were harvested for mRNA extraction and 24 hours after inoculation middle ears were harvested and examined for measures of inflammation.

RESULTS

H flu inoculation caused the increased expression of nearly all inflammatory cytokine genes and induced changes in expression of several genes related to cellular junctions and transport channels. Both steroids generally reversed the expression of inflammatory genes and caused ion and water regulatory genes to return to normal or near normal levels. Histologic evaluation of middle ears showed improved fluid and inflammatory cell clearance.

CONCLUSION

Improvement in middle ear inflammation was noted with both the glucocorticoid prednisolone and the mineralocorticoid aldosterone. This was due to reversal of inflammation-induced changes in middle ear cytokine genes, as well as those involved in ion and water homeostasis. Because glucocorticoids bind to the mineralocorticoid receptor, but not the reverse, it is concluded that much of the reduction of fluid and other inflammation measures was due to these steroids impact on ion and water transport channels. Further research is necessary to determine if this alternative mineralocorticoid treatment for otitis media will be clinically effective with fewer side effects than glucocorticoids.

Panel 4: Recent advances in otitis media in molecular biology, biochemistry, genetics, and animal models

BACKGROUND

Otitis media (OM) is the most common childhood bacterial infection and also the leading cause of conductive hearing loss in children. Currently, there is an urgent need for developing novel therapeutic agents for treating OM based on full understanding of molecular pathogenesis in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM.

OBJECTIVE

To provide a state-of-the-art review concerning recent advances in OM in the areas of molecular biology, biochemistry, genetics, and animal model studies and to discuss the future directions of OM studies in these areas.

DATA SOURCES AND REVIEW METHODS

A structured search of the current literature (since June 2007). The authors searched PubMed for published literature in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM.

RESULTS

Over the past 4 years, significant progress has been made in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM. These studies brought new insights into our understanding of the molecular and biochemical mechanisms underlying the molecular pathogenesis of OM and helped identify novel therapeutic targets for OM.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Our understanding of the molecular pathogenesis of OM has been significantly advanced, particularly in the areas of inflammation, innate immunity, mucus overproduction, mucosal hyperplasia, middle ear and inner ear interaction, genetics, genome sequencing, and animal model studies. Although these studies are still in their experimental stages, they help identify new potential therapeutic targets. Future preclinical and clinical studies will help to translate these exciting experimental research findings into clinical applications.

Panel 3: Recent advances in anatomy, pathology, and cell biology in relation to otitis media pathogenesis

BACKGROUND AND OBJECTIVES

The pathogenesis of otitis media (OM) involves a number of factors related to the anatomy, pathology, and cell biology of the middle ear, the mastoid, the Eustachian tube, and the nasopharynx. Although some issues of pathogenesis are fairly well established, others are only marginally indicated by current knowledge, and yet others remain undisclosed. The objective of this article is to provide a state-of-the-art review on recent scientific achievements in the pathogenesis of OM, as related to anatomy, pathology, and cell biology.

DATA SOURCES

PubMed, Ovid Medline, and Cochrane Library.

REVIEW METHODS

Articles published on the pathogenesis of OM and the anatomy, pathology, and cell biology of the middle ear, the mastoid, the Eustachian tube, and the nasopharynx between January 2007 and June 2011 were identified. Among almost 1900 abstracts, the authors selected 130 articles for full article review and inclusion in this report.

RESULTS

New knowledge on a number of issues emerged, including cell-specific expression and function of fluid transportation and innate immune system molecules, mucous cell metaplasia, mucin expression, bacterial adherence, and epithelial internalization, as well as the occurrence, composition, dynamics, and potential role of bacterial biofilm. In addition, the potential role of gastroesophageal reflux disease and cigarette smoke exposure has been explored further.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Over the past 4 years, considerable scientific progress has been made on the pathogenesis of OM, as related to issues of anatomy, pathology, and cell biology. Based on these new achievements and a sustained lack of essential knowledge, suggestions for future research are outlined.

Progressive familial hearing loss in Muckle-Wells syndrome

CONCLUSION

The age-dependent disease progression requires accelerating diagnosis of Muckle-Wells syndrome (MWS) in order to start treatment as early as possible. The most frequent, but not obligate symptoms are familial fatigue, hearing loss, and arthralgia. The design of further clinical trials should focus on hearing in order to document the long-term effect of anti-interleukin (IL)-1 drugs on hearing preservation.

OBJECTIVES

This paper describes the otologic features of a genetically defined syndrome causing progressive hearing loss by cochlear degeneration. This is the first study reporting the pretreatment otologic presentation of a selected population with familial MWS.

METHODS

A single-center cohort was examined by audiologic and neurotologic methods including pure tone audiograms, vestibular testing, and tinnitus questionnaire. The audiograms of members of the same family were compared to describe the family-specific risk of hearing loss progression.

RESULTS

Nineteen patients (aged 3-72 years) belonging to four families with three different mutations of the NLRP3 gene were examined. Almost all patients (89%, 17/19) demonstrated bilateral sensorineural hearing loss. Hearing loss started in the high frequencies and led to profound deafness in the most severe cases. Even in cases of profound hearing loss the vestibular caloric reactivity was normal. Nearly half of the adults reported intermittent or permanent tinnitus.

Murine middle ear inflammation and ion homeostasis gene expression

HYPOTHESIS

Ion homeostasis genes are responsible for the movement of ions and water in the epithelium of the middle ear.

BACKGROUND

It is not well known to what extent disruption of ion homeostasis is a factor in the accumulation of middle ear fluid during otitis media.

METHODS

Balb/c mice were transtympanically injected with heat-killed Hemophilus influenza bacteria. Untreated and saline-injected mice were used as controls. Mice were euthanized at 6, 24, and 72 hours and 1 week after injection, the bullae harvested, and total ribonucleic acid isolated from the middle ear tissues. Ion homeostasis genes were analyzed with real-time quantitative reverse transcription-polymerase chain reaction from the following gene families: Na,K-ATPase, claudins, K transport channels, epithelial Na channels, gap junctions, and aquaporins. Inflammatory genes also were analyzed to document inflammation.

RESULTS

All inflammatory genes analyzed were significantly upregulated, more at 6 hours than at 24 hours, with the exception of vascular endothelial growth factor and Mapk8. Most middle ear ion homeostasis genes experienced downregulation because of inflammation. This was most prominent in the aquaporin and Na,K-ATPase genes. Significant upregulation was seen in several genes in response to inflammation and saline independently.

CONCLUSION

The innate immune response to bacteria in the middle ear induces expression of several inflammatory genes. Coinciding with this inflammation is the downregulation of numerous ion homeostasis genes that are involved in ion and water transport and maintenance of tight junctions. This may explain the fluid accumulation within the middle ear seen with both acute and chronic otitis media.

Altered electrolyte handling of the choroid plexus in rats with glycerol-induced acute renal failure

The altered electrolyte handling of the choroid plexus was investigated in rats with acute renal failure (ARF) using lithium and rubidium as surrogate markers for sodium and potassium, respectively. Firstly, the transport of these two markers from the plasma to cerebrospinal fluid (CSF) was evaluated after they were concurrently injected into the femoral vein. As a result, their disposition from the plasma to CSF was shown to decrease in ARF rats, but the relationship profile between those two markers was not different from that observed in normal rats, indicating that the decreased disposition of lithium and rubidium occurs without affecting the stoichiometric balance. To clarify the mechanisms accounting for the decreased disposition, an inhibition study was then performed. When bumetanide, an inhibitor of the Na(+) /K(+) /2Cl(-) co-transporter, was directly introduced into the cerebroventricle prior to lithium and rubidium being intravenously administered, a marked increase in the markers' disposition was observed. However, such an increased disposition did not occur when bumetanide was injected into the femoral vein. Other inhibitors, such as amiloride for the Na(+) /H(+) exchanger and ouabain for Na(+) /K(+) -ATPase, did not show any effects on marker disposition regardless of the inhibitor being administered into either the cerebroventricle or femoral vein. These findings suggest that the decreased marker disposition in ARF rats is due to an increased efflux process of the choroid plexus mediated by the Na(+) /K(+) /2Cl(-) co-transporter. That is, electrolyte efflux from the CSF to plasma increases, and thereby the electrolyte influx from the plasma to CSF is counteracted.

Nkcc1 (Slc12a2) is required for the regulation of endolymph volume in the otic vesicle and swim bladder volume in the zebrafish larva

Endolymph is the specialised extracellular fluid present inside the inner ear. In mammals, disruptions to endolymph homeostasis can result in either collapse or distension of the endolymphatic compartment in the cochlea, with concomitant hearing loss. The zebrafish little ears (lte) mutant shows a collapse of the otic vesicle in the larva, apparently owing to a loss of endolymphatic fluid in the ear, together with an over-inflation of the swim bladder. Mutant larvae display signs of abnormal vestibular function by circling and swimming upside down. The two available alleles of lte are homozygous lethal: mutant larvae fail to thrive beyond 6 days post-fertilisation. Patterning of the otic vesicle is apparently normal. However, the expression of several genes thought to play a role in endolymph production is downregulated, including the sodium-potassium-chloride cotransporter gene nkcc1 (slc12a2) and several Na(+)/K(+)-ATPase channel subunit genes. We show here that lte mutations correspond to lesions in nkcc1. Each allele has a point mutation that disrupts splicing, leading to frame shifts in the coding region that predict the generation of truncated products. Endolymph collapse in the lte/nkcc1 mutant shows distinct parallels to that seen in mouse Nkcc1 mutants, validating zebrafish as a model for the study of endolymph disorders. The collapse in ear volume can be ameliorated in the to27d allele of lte by injection of a morpholino that blocks splicing at an ectopic site introduced by the mutation. This exemplifies the use of morpholinos as potential therapeutic agents for genetic disease.

The role of inflammatory mediators in the pathogenesis of otitis media and sequelae

This review deals with the characteristics of various inflammatory mediators identified in the middle ear during otitis media and in cholesteatoma. The role of each inflammatory mediator in the pathogenesis of otitis media and cholesteatoma has been discussed. Further, the relation of each inflammatory mediator to the pathophysiology of the middle and inner ear along with its mechanisms of pathological change has been described. The mechanisms of hearing loss including sensorineural hearing loss (SNHL) as a sequela of otitis media are also discussed. The passage of inflammatory mediators through the round window membrane into the scala tympani is indicated. In an experimental animal model, an application of cytokines and lipopolysaccharide (LPS), a bacterial toxin, on the round window membrane induced sensorineural hearing loss as identified through auditory brainstem response threshold shifts. An increase in permeability of the blood-labyrinth barrier (BLB) was observed following application of these inflammatory mediators and LPS. The leakage of the blood components into the lateral wall of the cochlea through an increase in BLB permeability appears to be related to the sensorineural hearing loss by hindering K⁺ recycling through the lateral wall disrupting the ion homeostasis of the endolymph. Further studies on the roles of various inflammatory mediators and bacterial toxins in inducing the sensorineumral hearing loss in otitis media should be pursued.

Moraxella catarrhalis lipooligosaccharide selectively upregulates ICAM-1 expression on human monocytes and stimulates adjacent naïve monocytes to produce TNF-alpha through cellular cross-talk

To elucidate the role of Moraxella catarrhalis lipooligosaccharide (LOS) in otitis media with effusion (OME), the effects of LOS on adhesion antigens of human monocytes were investigated. M. catarrhalis LOS selectively enhanced intercellular adhesion molecule 1 (ICAM-1 or CD54) expression on human monocytes by significantly increasing both the surface expression intensity and the percentage of ICAM-1(+) cells. ICAM-1 upregulation on human monocytes by the LOS required surface CD14, TLR4, NF-kappaB p65 and c-Jun N-terminal kinase (JNK) activity. Our study also revealed that the LOS-induced surface ICAM-1 expression was partially mediated through a TNF-alpha dependent autocrine mechanism and could be further augmented by lipopolysaccharide-binding protein in serum. In addition, M. catarrhalis LOS also stimulated human monocytes to produce pro-inflammatory cytokines in both TLR4- and CD14-dependent pathways. Our results also indicated that enhanced surface ICAM-1 expression on monocytes may hinder their adherence to the lung epithelial monolayer. Furthermore, the LOS-activated human monocytes secreted a significantly high level of IL-8, and could stimulate adjacent naïve monocytes to produce TNF-alpha which was partially mediated via membrane ICAM-1 and IL-8/IL-8RA. These results suggest that M. catarrhalis LOS could induce excessive middle ear inflammation through a cellular cross-talk mechanism during OME.