Lipopolysaccharide induces proinflammatory cytokines and chemokines in experimental otitis media through the prostaglandin D2 receptor (DP)-dependent pathway

Role of cytokines and Th17/Tregs imbalance in the pathogenesis of otitis media with effusion. Modulation of Notch1/Hes1/mTORC1/S6k1 signalling pathway underlies the protective effect of astaxanthin

Otitis media with effusion (OME) is a recurrent middle ear inflammatory condition. It may be complicated by acquired hearing loss and speech impairment especially in children. Accordingly, the current study aimed to assess the role of cytokines and the imbalance of Th17/Tregs in the pathogenesis of OME. Additionally, the protective effect of astaxanthin and its mechanisms related to Notch1/ Hes1/mTORC1/S6K1 signalling were investigated.

METHODS

Forty-eight children were grouped as follow: G1: control healthy group G2: acute otitis media (AOM) group, G3: OME group. In the lipopolysaccharide (LPS) induced OME rat model, 15 rats were randomised into: G1: normal control group, G2: LPS group, and G3: astaxanthin treated group.

RESULTS

Biochemical analysis of the children's peripheral blood samples showed that IL1β, IL-2, IL-4, IL-6, IL-17, and IL-23 were significantly elevated, while TGF-β was significantly decreased in AOM and OME patients (group 2 and 3). In the LPS- induced OME rat model, astaxanthin treatment resulted in suppression of IL-17, IL-6, TNF-α, Muc5A, TFF3, NICD, Hes1, mTORC1, and S6K1 in rat middle ear mucosa. Furthermore, astaxanthin significantly downregulated RORγ while upregulating FoxP3 and restored the balance between Th17/Tregs. Moreover, astaxanthin improved the histopathological picture of the inflamed middle ear mucosa.

CONCLUSIONS

Proinflammatory cytokines as well as Th17/Tregs imbalance play a crucial role in the pathogenesis of AOM and OME. Additionally, astaxanthin alleviated LPS- induced OME in rats through suppression of Notch1/ Hes1/mTORC1/S6K1 pathway, and regulation of Th17/Tregs.

The CRTh2 polymorphism rs533116 G > A associates with asthma severity in older females

Background

CRTh2 is G protein coupled receptor for prostaglandin D2 (PGD)₂ expressed by immune cells that drive type 2 inflammation such as CD4⁺ T cells (Th2), eosinophils and group 2 innate lymphoid cells (ILC2) as well as structural cells including smooth muscle and epithelium. CRTh2-expressing cells are increased in the blood and airways of asthmatics and severe asthma is characterized by increased activity of the PGD₂-CRTh2 pathway. The CRTh2 single nucleotide polymorphism (SNP) rs533116 G > A is associated with development of asthma and increased Th2 cell differentiation.

Objective

To examine whether CRTh2 rs533116G > A associates with asthma severity. Since severe asthma is more common in females than males, we performed a sex-stratified analysis.

Methods

Clinical data from asthmatics (n = 170) were obtained from clinic visits and chart review. Asthma severity was assessed according to ERS/ATS guidelines. Peripheral blood cells were characterized by flow cytometry and qRT-PCR. Genotyping was performed by TaqMan assay.

Results

Older females (≥45 years) homozygous for minor A allele of rs533116 were more likely to have severe asthma, lower FEV₁, a higher prescribed dose of inhaled corticosteroid and more type 2 inflammation than females carrying GA or GG genotypes. Comparing females and males with the AA genotype also revealed that women had more type 2 inflammation.

Conclusions and significance

The polymorphism CRTh2 rs533116 G > A associates with severe asthma and type 2 inflammation in older females. This study reveals a gene-sex-aging interaction influencing the effect of CRTh2 on asthma severity.

In-Silico Study of Immune System Associated Genes in Case of Type-2 Diabetes With Insulin Action and Resistance, and/or Obesity

Type-2 diabetes and obesity are among the leading human diseases and highly complex in terms of diagnostic and therapeutic approaches and are among the most frequent and highly complex and heterogeneous in nature. Based on epidemiological evidence, it is known that the patients suffering from obesity are considered to be at a significantly higher risk of type-2 diabetes. There are several pieces of evidence that support the hypothesis that these diseases interlinked and obesity may aggravate the risk(s) of type-2 diabetes. Multi-level unwanted alterations such as (epi-) genetic alterations, changes at the transcriptional level, and altered signaling pathways (receptor, cytoplasmic, and nuclear level) are the major sources that promote several complex diseases, and such a heterogeneous level of complexity is considered as a major barrier in the development of therapeutics. With so many known challenges, it is critical to understand the relationships and the shared causes between type-2 diabetes and obesity, and these are difficult to unravel and understand. For this purpose, we have selected publicly available datasets of gene expression for obesity and type-2 diabetes, have unraveled the genes and the pathways associated with the immune system, and have also focused on the T-cell signaling pathway and its components. We have applied a simplified computational approach to understanding differential gene expression and patterns and the enriched pathways for obesity and type-2 diabetes. Furthermore, we have also analyzed genes by using network-level understanding. In the analysis, we observe that there are fewer genes that are commonly differentially expressed while a comparatively higher number of pathways are shared between them. There are only 4 pathways that are associated with the immune system in case of obesity and 10 immune-associated pathways in case of type-2 diabetes, and, among them, only 2 pathways are commonly altered. Furthermore, we have presented SPNS1, PTPN6, CD247, FOS, and PIK3R5 as the overexpressed genes, which are the direct components of TCR signaling.

Neutrophils infiltrate into the spiral ligament but not the stria vascularis in the cochlea during lipopolysaccharide-induced inflammation

It has been challenging to apply intravital imaging for monitoring the inner ear, as the anatomical location and intricate structure hamper the access of imaging instruments to the inner ear of live mice. By employing intravital imaging of the cochlea in live mice with two-photon microscopy, we investigated neutrophil infiltration into the cochlea tissue and its characteristics under a lipopolysaccharide (LPS)-induced inflammatory state. Methods: Cochlea inflammation was induced by LPS injection to the middle ear. Using two-photon intravital microscopy with specifically designed surgical exteriorization of the cochlea in live mice, we investigated the dynamic features of neutrophils in the lateral wall of the cochlea. The molecular expression pattern of the cochlea lateral wall was also investigated during the LPS-induce inflammation. Results: Despite the contention of whether neutrophils are recruited to the spiral ligament (SL) during inflammation, we observed that LPS-induced inflammation of the middle ear, which mimics acute otitis media, triggered neutrophil migration to the SL in the lateral wall. Notably, massive neutrophil infiltration to the SL occurred 2 days after LPS inoculation, but there was no neutrophil infiltration into the stria vascularis (SV) region. At 1 day after LPS-induced cochlear inflammation, increased mRNA expression of interleukin-1β, interleukin-6 were identified in both the SL and SV, while the ICAM-1 mRNA expression increased only in the SL. The differential reactivity of ICAM-1 is likely responsible for the different neutrophil recruitment pattern in the cochlea. Conclusion: Intravital imaging of the cochlea revealed that neutrophil recruitment and infiltration during inflammation are spatially controlled and exclusively observed in the SL but not in the SV and organ of Corti.

Biological insights from multi-omic analysis of 31 genomic risk loci for adult hearing difficulty

Age-related hearing impairment (ARHI), one of the most common medical conditions, is strongly heritable, yet its genetic causes remain largely unknown. We conducted a meta-analysis of GWAS summary statistics from multiple hearing-related traits in the UK Biobank (n = up to 330,759) and identified 31 genome-wide significant risk loci for self-reported hearing difficulty (p < 5x10-8), of which eight have not been reported previously in the peer-reviewed literature. We investigated the regulatory and cell specific expression for these loci by generating mRNA-seq, ATAC-seq, and single-cell RNA-seq from cells in the mouse cochlea. Risk-associated genes were most strongly enriched for expression in cochlear epithelial cells, as well as for genes related to sensory perception and known Mendelian deafness genes, supporting their relevance to auditory function. Regions of the human genome homologous to open chromatin in epithelial cells from the mouse were strongly enriched for heritable risk for hearing difficulty, even after adjusting for baseline effects of evolutionary conservation and cell-type non-specific regulatory regions. Epigenomic and statistical fine-mapping most strongly supported 50 putative risk genes. Of these, 39 were expressed robustly in mouse cochlea and 16 were enriched specifically in sensory hair cells. These results reveal new risk loci and risk genes for hearing difficulty and suggest an important role for altered gene regulation in the cochlear sensory epithelium.

The nuclear transcription factor FoxG1 affects the sensitivity of mimetic aging hair cells to inflammation by regulating autophagy pathways

Inflammation is a self-defense response to protect individuals from infection and tissue damage, but excessive or persistent inflammation can have adverse effects on cell survival. Many individuals become especially susceptible to chronic-inflammation-induced sensorineural hearing loss as they age, but the intrinsic molecular mechanism behind aging individuals' increased risk of hearing loss remains unclear. FoxG1 (forkhead box transcription factor G1) is a key transcription factor that plays important roles in hair cell survival through the regulation of mitochondrial function, but how the function of FoxG1 changes during aging and under inflammatory conditions is unknown. In this study, we first found that FoxG1 expression and autophagy both increased gradually in the low concentration lipopolysaccharide (LPS)-induced inflammation model, while after high concentration of LPS treatment both FoxG1 expression and autophagy levels decreased as the concentration of LPS increased. We then used siRNA to downregulate Foxg1 expression in hair cell-like OC-1 cells and found that cell death and apoptosis were significantly increased after LPS injury. Furthermore, we used d-galactose (D-gal) to create an aging model with hair cell-like OC-1 cells and cochlear explant cultures in vitro and found that the expression of Foxg1 and the level of autophagy were both decreased after D-gal and LPS co-treatment. Lastly, we knocked down the expression of Foxg1 under aged inflammation conditions and found increased numbers of dead and apoptotic cells. Together these results suggest that FoxG1 affects the sensitivity of mimetic aging hair cells to inflammation by regulating autophagy pathways.

Epigallocatechin-3-gallate (EGCG) exert therapeutic effect on acute inflammatory otitis media in rats

INTRODUCTION

That EGCG has strong antioxidant and anti-inflammatory activities as well as antibacterial activity against many streptococcus species suggests that it may be beneficial in the treatment of AOM.

OBJECTIVE

Aim of the study is to reveal the molecular and biochemical effects of EGCG on LPS induced otitis media in rats.

METHODS

Forty-two male albino Wistar rats were randomly divided into 7 groups. Inflammation was induced by administrating 50 μL of 1 mg/ml lipopolysaccharide (LPS). EGCG used 50 and 100 mg/kg/day and combined penicillin G (PENG) 48 h after LPS injection.

RESULTS

The combined EGCG 50 and PENG group and the group with EGCG 50 alone showed the best anti-inflammatory effect on LPS-induced AOM. TNF-α and IL-1β gene expression significantly down regulated EGCG 50 and combined with PENG compared to the otitis media group. The combination of PenG and EGCG 50 led to the best histopathological improvement. Both the inflammation and the membrane thickness of this group were at almost the same level as the healthy group and tympanum was seen normal.

CONCLUSION

The results of this study make it clear that EGCG plays an important role in antioxidant and anti-inflammatory activity during AOM.

Current small animal models for LASV hearing loss

Lassa virus (LASV) is endemic in West Africa, causing an estimated 100000-300000 new infections and up to 5000-10000 deaths yearly. There are no vaccines and therapeutics are extremely limited. Typical case fatality rates are ∼1%, although a recent 2018 Nigerian outbreak featured an unprecedented 25.4% case fatality rate. Survivors of infection suffer a lifetime of sequelae with sudden onset sensorineural hearing loss (SNHL) being the most prevalent. The cause of this hearing loss remains unknown, and there is a critical need for further research on its mechanisms and potential therapeutics. The objective of this review is to outline the only currently available small animal model for LASV-induced hearing loss and to identify potential surrogate models.

A CRTH2 antagonist, CT-133, suppresses NF-κB signalling to relieve lipopolysaccharide-induced acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome are life-threatening conditions that still have no definite pharmacotherapy. Hence, we investigate the potential effectiveness and underlying mechanism of CT-133, a newly developed selective antagonist of prostaglandin D2 receptor 2 (DP2) or of chemoattractant receptor homologous molecule expressed on Th2 cells (CRTH2), against lipopolysaccharide (LPS)-induced ALI. CT-133 (10 or 30 mg/kg) or dexamethasone (1 mg/kg, positive control) were intragastrically administered 1 h before and 12 h after intratracheal LPS instillation, and primary neutrophils and macrophages and RAW264.7 macrophages were used to investigate the role of CT-133 in regulation of their functions. LPS induced a significant secretion of PGD₂ from primary macrophages, however, CT-133 dose-dependently and markedly decreased the infiltration of neutrophils and macrophages into lungs, reduced the IL-1β, TNF-α, IL-6, and KC levels in broncho-alveolar lavage (BAL) fluids, decreased the wet weight and myeloperoxidase activity of lungs, reduced Evans blue and albumin exudation into lungs, and improved the lung histopathological changes and hypoxemia. Moreover, CT-133 significantly suppressed the primary neutrophil migration toward the PGD₂ and robustly inhibited the mRNA and protein expression of IL-1β, TNF-α, IL-6, and KC in primary and RAW264.7 macrophages in response to either LPS- or PGD₂ stimulation. Finally, CT-133 significantly blocked the LPS-induced P65 activation in both RAW264.7 macrophages and mouse lungs. Thus, This is the first report that a CRTH2 antagonist, CT-133, is capable of significantly alleviating LPS-induced lung injury by probably down-regulating the NF-κB signalling.

Individuals with obesity and type 2 diabetes have additional immune dysfunction compared with obese individuals who are metabolically healthy

OBJECTIVE

The objective of the current study was to compare the responses to different ex vivo immunogenic challenges between immune cells derived from metabolically healthy subjects with obesity and subjects with obesity and type 2 diabetes.

RESEARCH DESIGN AND METHODS

We recruited 10 metabolically healthy subjects with obesity (Edmonton Obesity Staging System (EOSS) stage 0) and 9 subjects with obesity and type 2 diabetes (EOSS stage 2) aged between 21 years and 70 years and matched for body mass index. Peripheral blood mononuclear cells (PBMCs) were isolated and immune cell phenotypes and ex vivo cytokine production after phytohaemagglutinin (PHA, a T cell mitogen) stimulation were determined. Neutrophil oxidative burst activity was assessed in whole blood.

RESULTS

PBMCs from subjects with stage 2 obesity produced significantly less interleukin (IL)-2, IL-6 and tumour necrosis factor α after PHA stimulation than PBMCs from subjects with stage 0 obesity (all, p<0.05). Subjects with stage 2 obesity also had higher proportions of cytotoxic T cells, activated helper T cells (CD4+CD278+) and inflammatory monocytes (CD14+CRTh2+, all p<0.05). Poststimulation, neutrophils from subjects with stage 2 obesity produced significantly more free radicals, were larger and more granular and had a lower stimulation index (all p<0.05).

CONCLUSIONS

Our results suggest that compared with obese individuals metabolically healthy individuals with obesity and type 2 diabetes have an impaired neutrophil function and T cell response on challenge despite having a T cell population expressing more activation markers which may be partly responsible for the increased prevalence of infection reported in this population.

Otitis media with effusion in an allergic animal model: A functional and morphological study

OBJECTIVES

Allergy is considered as one of important etiologic factor of otitis media with effusion (OME). In present study, we evaluated the causal effect of allergy on OME in an animal model, and investigated the secondary effect of bacterial infection.

METHODS

Allergy and control animals were subdivided into groups with and without intratympanic injection of lipopolysaccharide (IT-LPS). Allergic otitis media was induced via intraperitoneal ovo-albumin injection with intranasal challenge. We assessed the occurrence of OME in allergic animals and the effect of IT-LPS on allergic otitis media. We also investigated the Th1 and Th2 responses in the middle-ear mucosa. Hearing of the animals was measured by ABR and DPOAE.

RESULTS

OME was observed in 75% of the allergic animals. After IT-LPS, 100% of the control and allergy groups showed otitis media. Light microscopy revealed that the middle-ear mucosa of animals of both groups also was significantly increased after IT-LPS, and the Th1 response (IL-2 and IFN-γ) and Th2 response (IL-5 and IL-13) cytokines were expressed at higher levels in the allergy group with IT-LPS than in control group with IT-LPS. Hearing tests between the allergy and control group with IT-LPS did not reveal any differences.

CONCLUSION

Our findings may be direct evidence of an allergic causal effect on OME. Th2 response cytokines were strongly expressed in allergic OME, and the inflammatory reaction to LPS was more intense in the allergic group, which indicates that otitis media related to allergy can be severely aggravated by an inflammatory reaction to bacterial infection.

Sensitivity of spiral ganglion neurons to damage caused by mobile phone electromagnetic radiation will increase in lipopolysaccharide-induced inflammation in vitro model

Background

With the increasing popularity of mobile phones, the potential hazards of radiofrequency electromagnetic radiation (RF-EMR) on the auditory system remain unclear. Apart from RF-EMR, humans are also exposed to various physical and chemical factors. We established a lipopolysaccharide (LPS)-induced inflammation in vitro model to investigate whether the possible sensitivity of spiral ganglion neurons to damage caused by mobile phone electromagnetic radiation (at specific absorption rates: 2, 4 W/kg) will increase.

Methods

Spiral ganglion neurons (SGN) were obtained from neonatal (1- to 3-day-old) Sprague Dawley® (SD) rats. After the SGN were treated with different concentrations (0, 20, 40, 50, 100, 200, and 400 μg/ml) of LPS, the Cell Counting Kit-8 (CCK-8) and alkaline comet assay were used to quantify cellular activity and DNA damage, respectively. The SGN were treated with the moderate LPS concentrations before RF-EMR exposure. After 24 h intermittent exposure at an absorption rate of 2 and 4 W/kg, DNA damage was examined by alkaline comet assay, ultrastructure changes were detected by transmission electron microscopy, and expression of the autophagy markers LC3-II and Beclin1 were examined by immunofluorescence and confocal laser scanning microscopy. Reactive oxygen species (ROS) production was quantified by the dichlorofluorescin-diacetate assay.

Results

LPS (100 μg/ml) induced DNA damage and suppressed cellular activity (P < 0.05). LPS (40 μg/ml) did not exhibit cellular activity changes or DNA damage (P > 0.05); therefore, 40 μg/ml was used to pretreat the concentration before exposure to RF-EMR. RF-EMR could not directly induce DNA damage. However, the 4 W/kg combined with LPS (40 μg/ml) group showed mitochondria vacuoles, karyopyknosis, presence of lysosomes and autophagosome, and increasing expression of LC3-II and Beclin1. The ROS values significantly increased in the 4 W/kg exposure, 4 W/kg combined with LPS (40 μg/ml) exposure, and H₂O₂ groups (P < 0.05, 0.01).

Conclusions

Short-term exposure to radiofrequency electromagnetic radiation could not directly induce DNA damage in normal spiral ganglion neurons, but it could cause the changes of cellular ultrastructure at special SAR 4.0 W/kg when cells are in fragile or micro-damaged condition. It seems that the sensitivity of SGN to damage caused by mobile phone electromagnetic radiation will increase in a lipopolysaccharide-induced inflammation in vitro model.

Prostaglandin D2 regulates human colonic ion transport via the DP1 receptor

AIMS

Prostaglandin D2 is released by mast cells and is important in allergies. Its role in gastrointestinal function is not clearly defined. This study aimed to determine the effect of exogenous PGD2 on ion transport in ex vivo normal human colonic mucosa.

MATERIALS AND METHODS

Mucosal sheets were mounted in Ussing chambers and voltage clamped to zero electric potential. Ion transport was quantified as changes in short-circuit current. In separate experiments epithelial monolayers or colonic crypts, isolated by calcium chelation, were treated with PGD2 and cAMP levels determined by ELISA or calcium levels were determined by fluorimetry.

KEY FINDINGS

PGD2 caused a sustained, concentration-dependent rise in short-circuit current by increasing chloride secretion (EC50=376nM). This effect of PGD2 is mediated by the DP1 receptor, as the selective DP1 receptor antagonist BW A686C inhibited PGD2-induced but not PGE2-induced rise in short-circuit current. PGD2 also increased intracellular cAMP in isolated colonic crypts with no measurable influence on cytosolic calcium. PGD2 induces chloride secretion in isolated human colonic mucosa in a concentration-dependent manner with concomitant elevation of cytoplasmic cAMP in epithelial cells.

SIGNIFICANCE

The involvement of DP2 receptor subtypes has not previously been considered in regulation of ion transport in human intestine. Since inflammatory stimuli may induce production of eicosanoids, selective regulation of these pathways may be pivotal in determining therapeutic strategies and in understanding disease.

Lung inflammation and thymic atrophy after bleomycin are controlled by the prostaglandin D2 receptor DP1

Acute lung injury (ALI) can be accompanied by secondary systemic manifestations. In a model of ALI induced by bleomycin (bleo), we examined the response of D prostanoid receptor 1 (DP1)-deficient mice (DP1(-/-)) to better understand these processes. DP1 deficiency aggravated the toxicity of bleo as indicated by enhanced body weight loss, mortality, and lung inflammation including bronchoalveolar permeability and neutrophilia. Thymic atrophy was also observed after bleo and was strongly exacerbated in DP1(-/-) mice. This resulted from the enhanced depletion of immature T lymphocytes in the thymus of DP1(-/-) mice, a phenomenon usually related to increased glucocorticoid release in blood. Serum corticosterone was more elevated in DP1(-/-) mice after bleo than in wild-type (wt) mice. Thymocytes of DP1(-/-) mice were not more sensitive to dexamethasone in vitro, and systemic delivery of dexamethasone or peritoneal inflammation after LPS induced a similar thymic atrophy in wt and DP1(-/-) mice, indicating that pulmonary DP1 was critical to the control of thymic atrophy after bleo. DP1(-/-) mice showed increased lung and/or blood mediators involved in neutrophil recruitment and/or glucocorticoid production/thymic atrophy (osteopontin, leukemia inhibitory factor, and keratinocyte-derived chemokine) after bleo. Finally, local pulmonary DP1 activation or inhibition in wt mice abrogated or amplified thymic atrophy after bleo, respectively. Altogether, our data reveal that ALI can perturb the systemic T-cell pool by inducing thymic atrophy and that both pathological processes are controlled by the pulmonary DP1 receptor. This new pathway represents a potential therapeutic target in ALI.

Cytokine responses in the common cold and otitis media

Cytokines are a group of diverse molecules that influence the function of every organ system. They are most well studied in their effects on the immune system and their integral role in mediating inflammation. The common cold and otitis media are two such disease states, and much has been learned about the various effects of cytokines in each disease. Most often the viruses isolated include rhinovirus (RV), respiratory syncytial virus (RSV), adenovirus, coronavirus, and picornavirus. Otitis media, sinusitis, bronchiolitis, pneumonia, and asthma exacerbation are commonly accepted as complications of viral upper respiratory tract infections. Furthermore, otitis media and upper respiratory infections are inextricably linked in that the majority (>70 %) of cases of acute otitis media occur as complications of the common cold. Cytokine polymorphisms have been associated with the severity of colds as well as the frequency of otitis media. This article attempts to update the reader on various studies that have recently been published regarding the role of cytokines in these two disease entities.

Neutralizing antibody against granulocyte/macrophage colony-stimulating factor inhibits inflammatory response in experimental otitis media

OBJECTIVES/HYPOTHESIS

Granulocyte/macrophage colony-stimulating factor is important in the pathogenesis of acute and chronic inflammatory disease. We hypothesized that granulocyte/macrophage colony-stimulating factor plays a pivotal role in middle ear inflammation and that neutralization of granulocyte/macrophage colony-stimulating factor would inhibit neutrophil migration into the middle ear and production of inflammatory mediators.

STUDY DESIGN

Animal experiment.

METHODS

We used transtympanic administration of lipopolysaccharide, a major component of gram-negative bacteria, into mice to induce an experimental otitis media. Control mice received injection of phosphate-buffered saline into the middle ear cavity. Mice were systemically treated with granulocyte/macrophage colony-stimulating factor neutralizing antibody or control immunoglobulin G via intraperitoneal injection 2 hours before transtympanic injection of lipopolysaccharide or phosphate-buffered saline. Middle ear effusions were collected. Concentrations of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, keratinocyte chemoattractant, and macrophage inflammatory protein-2 in middle ear effusions were measured by enzyme-linked immunosorbent assay. Histologic examination of the middle ear was also performed.

RESULTS

Transtympanic injection of lipopolysaccharide upregulated levels of granulocyte/macrophage colony-stimulating factor, IL-1β, TNF-α, keratinocyte chemoattractant, and macrophage inflammatory protein-2 in the middle ear. Concentrations of cytokines and chemokines were significantly decreased in mice injected with granulocyte/macrophage colony-stimulating factor neutralizing antibody. Infiltration of inflammatory cells into the middle ear cavity induced by lipopolysaccharide was also significantly reduced by neutralization of granulocyte/macrophage colony-stimulating factor.

CONCLUSIONS

Systemic injection of granulocyte/macrophage colony-stimulating factor neutralizing antibody inhibits the middle ear inflammation induced by lipopolysaccharide in mice. Our findings suggest that granulocyte/macrophage colony-stimulating factor may offer a novel therapeutic target for the management of intractable otitis media.