Expression of toll-like receptors 2, 4 and nuclear factor kappa B in mucosal lesions of human otitis: pattern and relationship in a clinical immunohistochemical study

Review of potential medical treatments for middle ear cholesteatoma

Middle ear cholesteatoma (MEC), is a destructive, and locally invasive lesion in the middle ear driven by inflammation with an annual incidence of 10 per 100,000. Surgical extraction/excision remains the only treatment strategy available and recurrence is high (up to 40%), therefore developing the first pharmaceutical treatments for MEC is desperately required. This review was targeted at connecting the dysregulated inflammatory network of MEC to pathogenesis and identification of pharmaceutical targets. We summarized the numerous basic research endeavors undertaken over the last 30+ years to identify the key targets in the dysregulated inflammatory pathways and judged the level of evidence for a given target if it was generated by in vitro, in vivo or clinical experiments. MEC pathogenesis was found to be connected to cytokines characteristic for Th1, Th17 and M1 cells. In addition, we found that the inflammation created damage associated molecular patterns (DAMPs), which further promoted inflammation. Similar positive feedback loops have already been described for other Th1/Th17 driven inflammatory diseases (arthritis, Crohn’s disease or multiple sclerosis). A wide-ranging search for molecular targeted therapies (MTT) led to the discovery of over a hundred clinically approved drugs already applied in precision medicine. Based on exclusion criteria designed to enable fast translation as well as efficacy, we condensed the numerous MTTs down to 13 top drugs. The review should serve as groundwork for the primary goal, which is to provide potential pharmaceutical therapies to MEC patients for the first time in history.

Immunomodulation as a Protective Strategy in Chronic Otitis Media

Introduction

Major features of the pathogenesis in otitis media, the most common disease in childhood, include hyperplasia of the middle ear mucosa and infiltration by leukocytes, both of which typically resolve upon bacterial clearance via apoptosis. Activation of innate immune receptors during the inflammatory process leads to the activation of intracellular transcription factors (such as NF-κB, AP-1), which regulate both the inflammatory response and tissue growth. We investigated these leading signaling pathways in otitis media using mouse models, human samples, and human middle ear epithelial cell (HMEEC) lines for therapeutic immunomodulation.

Methods

A stable otitis media model in wild-type mice and immunodeficient KO-mice, as well as human tissue samples from chronic otitis media, skin from the external auditory canal and middle ear mucosa removed from patients undergoing ear surgery, were studied. Gene and protein expression of innate immune signaling molecules were evaluated using microarray, qPCR and IHC. In situ apoptosis detection determined the apoptotic rate. The influence of bacterial infection on immunomodulating molecules (TNFα, MDP, Tri-DAP, SB203580, Cycloheximide) in HMEEC was evaluated. HMEEC cells were examined after bacterial stimulation/inhibition for gene expression and cellular growth.

Results

Persistent mucosal hyperplasia of the middle ear mucosa in chronic otitis media resulted from gene and protein expression of inflammatory and apoptotic genes, including NODs, TNFα, Casp3 and cleaved Casp3. In clinical chronic middle ear samples, these molecules were modulated after a specific stimulation. They also induced a hyposensitive response after bacterial/NOD-/TLR-pathway double stimulation of HMEEC cells in vitro. Hence, they might be suitable targets for immunological therapeutic approaches.

Conclusion

Uncontrolled middle ear mucosal hyperplasia is triggered by TLRs/NLRs immunoreceptor activation of downstream inflammatory and apoptotic molecules.

Toll-Like Receptors: Expression and Roles in Otitis Media

Otitis media is mainly caused by upper respiratory tract infection and eustachian tube dysfunction. If external upper respiratory tract infection is not detected early in the middle ear, or an appropriate immune response does not occur, otitis media can become a chronic state or complications may occur. Therefore, given the important role of Toll-like receptors (TLRs) in the early response to external antigens, we surveyed the role of TLRs in otitis media. To summarize the role of TLR in otitis media, we reviewed articles on the expression of TLRs in acute otitis media (AOM), otitis media with effusion (OME), chronic otitis media (COM) with cholesteatoma, and COM without cholesteatoma. Many studies showed that TLRs 1–10 are expressed in AOM, OME, COM with cholesteatoma, and COM without cholesteatoma. TLR expression in the normal middle ear mucosa is absent or weak, but is increased in inflammatory fluid of AOM, effusion of OME, and granulation tissue and cholesteatoma of COM. In addition, TLRs show increased or decreased expression depending on the presence or absence of bacteria, recurrence of disease, tissue type, and repeated surgery. In conclusion, expression of TLRs is associated with otitis media. Inappropriate TLR expression, or delayed or absent induction, are associated with the occurrence, recurrence, chronicization, and complications of otitis media. Therefore, TLRs are very important in otitis media and closely related to its etiology.

Extensive qPCR analysis reveals altered gene expression in middle ear mucosa from cholesteatoma patients

The middle ear is a small and hard to reach compartment, limiting the amount of tissue that can be extracted and the possibilities for studying the molecular mechanisms behind diseases like cholesteatoma. In this paper 14 reference gene candidates were evaluated in the middle ear mucosa of cholesteatoma patients and two different control tissues. ACTB and GAPDH were shown to be the optimal genes for the normalisation of target gene expression when investigating middle ear mucosa in multiplex qPCR analysis. Validation of reference genes using c-MYC expression confirmed the suitability of ACTB and GAPDH as reference genes and showed an upregulation of c-MYC in middle ear mucosa during cholesteatoma. The occurrence of participants of the innate immunity, TLR2 and TLR4, were analysed in order to compare healthy middle ear mucosa to cholesteatoma. Analysis of TLR2 and TLR4 showed variable results depending on control tissue used, highlighting the importance of selecting relevant control tissue when investigating causes for disease. It is our belief that a consensus regarding reference genes and control tissue will contribute to the comparability and reproducibility of studies within the field.

Current Understanding of Host Genetics of Otitis Media

The pathogenesis of otitis media (OM), an inflammatory disease of the middle ear (ME), involves interplay between many different factors, including the pathogenicity of infectious pathogens, host immunological status, environmental factors, and genetic predisposition, which is known to be a key determinant of OM susceptibility. Animal models and human genetics studies have identified many genes and gene variants associated with OM susceptibility: genes that encode components of multiple signaling pathways involved in host immunity and inflammatory responses of the ME mucosa; genes involved in cellular function, such as mucociliary transport, mucin production, and mucous cell metaplasia; and genes that are essential for Eustachian tube (ET) development, ME cavitation, and homeostasis. Since our last review, several new mouse models with mutations in genes such as CCL3, IL-17A, and Nisch have been reported. Moreover, genetic variants and polymorphisms in several genes, including FNDC1, FUT2, A2ML1, TGIF1, CD44, and IL1-RA variable number tandem repeat (VNTR) allele 2, have been identified as being significantly associated with OM. In this review, we focus on the current understanding of the role of host genetics in OM, including recent discoveries and future research prospects. Further studies on the genes identified thus far and the discovery of new genes using advanced technologies such as gene editing, next generation sequencing, and genome-wide association studies, will advance our understanding of the molecular mechanism underlying the pathogenesis of OM and provide new avenues for early screening and developing effective preventative and therapeutic strategies to treat OM.

Perimatrix of middle ear cholesteatoma: A granulation tissue with a specific transcriptomic signature

OBJECTIVES/HYPOTHESIS

To establish comprehensive transcriptomic profiles of cholesteatoma perimatrix tissue and granulation tissue from chronic otitis media (COM) that did not develop cholesteatoma, which can indicate molecular pathways involved in the cholesteatoma perimatrix pathology and invasiveness.

STUDY DESIGN

Retrospective Case Series.

METHODS

Transcriptome data were obtained from cholesteatoma perimatrix tissue and COM granulation tissue by an Illumina iScan microarray. Differentially expressed genes (DEGs) were subsequently analyzed using both bioinformatical functional annotation and network analysis. Expression of candidate genes (MMP9 and LCN2) was validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) on a larger group of samples.

RESULTS

Analysis of the transcriptome led to the identification of 169 differentially expressed genes between investigated tissues. Bioinformatic analysis suggested that most significant biological processes involving DEGs were previously described in cholesteatoma pathology. Network analysis identified ERBB2, TFAP2A, and TP63 as major hubs of the DEGs molecular network. Furthermore, it was observed that the cellular component most significantly enriched in DEGs was extracellular space containing 47 DEGs. Using qRT-PCR, it was confirmed that mRNA levels of the major extracellular hub (MMP9) are increased, whereas its interacting molecule (LCN2) mRNA levels were decreased in cholesteatoma perimatrix tissue compared to COM granulation tissue.

CONCLUSIONS

The current study approach offers an overall look at molecular mechanisms that describe the cholesteatoma entity by focusing exclusively on the perimatrix processes in comparison to COM granulation tissue. The observed differences in gene expression between cholesteatoma perimatrix and COM granulation tissue could suggest novel markers potentially influenced by the perimatrix-matrix molecular interplay, which is not present in COM without cholesteatoma.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:E220-E227, 2020.

NLRP3 inflammasome expression in lipopolysaccharide-induced otitis media

BACKGROUND

The nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome is a critical molecule mediating interleukin-1β (IL-1β) responses. However, the role of the NLRP3 inflammasome in otitis media has not been fully examined.

AIMS/OBJECTIVES

The purpose of this study is to assess the expression of NLRP3, ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain and a pyrin domain), and caspase-1 in lipopolysaccharide-induced otitis media.

MATERIALS AND METHODS

BALB/c mice received a transtympanic injection of either lipopolysaccharide or phosphate-buffered saline. The mice were sacrificed 24 h after injection. Concentrations of IL-1β, NLRP3, ASC, and caspase-1 in the middle ear effusions were measured by enzyme-linked immunosorbent assay. Temporal bones were processed for histologic examination and immunohistochemistry.

RESULTS

The transtympanic injection of lipopolysaccharide significantly upregulated levels of IL-1β, NLRP3, ASC, and caspase-1 in the middle ear as compared with the control mice. The proteins of NLRP3, ASC, and caspase-1 were observed in infiltrating inflammatory cells induced by lipopolysaccharide in the middle ear cavity.

CONCLUSIONS AND SIGNIFICANCE

Lipopolysaccharide induces NLRP3 inflammasome components in the middle ear. The NLRP3 inflammasome may play an important role in the pathogenesis of otitis media. Modulation of inflammasome-mediated inflammation may be a novel therapeutic strategy for otitis media.

Understanding the aetiology and resolution of chronic otitis media from animal and human studies

Inflammation of the middle ear, known clinically as chronic otitis media, presents in different forms, such as chronic otitis media with effusion (COME; glue ear) and chronic suppurative otitis media (CSOM). These are highly prevalent diseases, especially in childhood, and lead to significant morbidity worldwide. However, much remains unclear about this disease, including its aetiology, initiation and perpetuation, and the relative roles of mucosal and leukocyte biology, pathogens, and Eustachian tube function. Chronic otitis media is commonly modelled in mice but most existing models only partially mimic human disease and many are syndromic. Nevertheless, these models have provided insights into potential disease mechanisms, and have implicated altered immune signalling, mucociliary function and Eustachian tube function as potential predisposing mechanisms. Clinical studies of chronic otitis media have yet to implicate a particular molecular pathway or mechanism, and current human genetic studies are underpowered. We also do not fully understand how existing interventions, such as tympanic membrane repair, work, nor how chronic otitis media spontaneously resolves. This Clinical Puzzle article describes our current knowledge of chronic otitis media and the existing research models for this condition. It also identifies unanswered questions about its pathogenesis and treatment, with the goal of advancing our understanding of this disease to aid the development of novel therapeutic interventions.

Summary: Chronic middle ear inflammation is a common disease. Animal models, and in particular mouse models, have been used to elucidate some potential mechanisms, including dysfunction in immune signalling, mucociliary function or Eustachian tube function.

Panel 8: Report on Recent Advances in Molecular and Cellular Biochemistry

Objectives To update the medical literature on recent cellular and molecular advances in otitis media disease models with a principal focus on developments in the past 5 years. We also aim to explain recent translational advances in cellular and molecular biology that have influenced our understanding and management of otitis media. Data Sources PubMed-indexed peer-reviewed articles. Review Methods A comprehensive review of the literature was conducted with the term otitis media and the following search terms: molecular biology, cell biology, innate immunity, oxidative stress, mucins, molecular diagnostics. Included articles were published in the English language from January 1, 2010, to July 31, 2015. Implications for Practice The molecular understanding of otitis media disease progression has rapidly advanced over the last 5 years. The roles of inflammation, mucins, and cell signaling mechanisms have been elucidated and defined. Advances in the field provide a plethora of opportunities for innovative molecular targeting in the development of novel therapeutic strategies for otitis media.

Bone Marrow Mesenchymal Stem Cells Inhibit Lipopolysaccharide-Induced Inflammatory Reactions in Macrophages and Endothelial Cells

Background. Systemic inflammatory response syndrome (SIRS) accompanied by trauma can lead to multiple organ dysfunction syndrome (MODS) and even death. Early inhibition of the inflammation is necessary for damage control. Bone marrow mesenchymal stem cells (BMSCs), as a novel therapy modality, have been shown to reduce inflammatory responses in human and animal models. Methods. In this study, we used Western blot, quantitative PCR, and enzyme-linked immunosorbent assay (ELISA) to assess the activity of BMSCs to suppress the inflammation induced by lipopolysaccharide (LPS) in human umbilical cord endothelial cells (HUVECs) and alveolar macrophages. Results. Our results demonstrated that LPS caused an inflammatory response in alveolar macrophages and HUVECs, increased permeability of HUVEC, upregulated expression of toll-like receptor (TLR) 2, TLR4, phosphorylated p65, downregulated release of IL10, and promoted release of TNF-α in both cells. Coculture with BMSCs attenuated all of these activities induced by LPS in the two tested cell types. Conclusions. Together, our results demonstrate that BMSCs dosage dependently attenuates the inflammation damage of alveolar macrophages and HUVECs induced by LPS.

CUEDC2 Protects Against Experimental Colitis and Suppresses Excessive Proliferation of Intestinal Mucosa

BACKGROUND

CUEDC2, a CUE domain-containing protein, is highly expressed in many tumors, which also may be associated with inflammation.

AIMS

In this study, we studied whether CUEDC2 plays a role in the progress of inflammatory bowel disease using CUEDC2 knockout (KO) mice and discussed the effects of CUEDC2 on cell proliferation in colonic mucosa.

METHODS

CUEDC2 KO mice were administered with drinking dextran sodium sulfate (DSS) to establish colitis mice model. At different time points after DSS administration, body weight and stool consistency of mice were graded. Cytokines in colon tissue such as IL-6 were measured by RT-PCR. NF-κB and STAT3 signaling pathways in colon tissue were assessed by western blotting. Besides, cell proliferation of intestinal mucosa was analyzed by immunohistochemical staining.

RESULTS

CUEDC2 alleviated the colonic inflammation, showing elevated body weight loss, worse diarrhea, and more severe colonic mucosal injury in CUEDC2 KO mice than WT mice. Moreover, pro-inflammatory cytokines such as IL-6, TNFα, COX2, and MIP2 were significantly elevated. In CUEDC2 KO mice, the NF-κB and STAT3 signaling pathways were increasingly activated in different stages of progression of the colonic inflammation, and the percentage of proliferating cells as indicated by Ki67, CyclinD1, and BrdU in the inflammatory tissues was significantly increased.

CONCLUSIONS

Our findings demonstrate that CUEDC2 plays an important role in protection from colonic inflammation, primarily by inhibiting the NF-κB and STAT3 signaling pathways and preventing excessive proliferation of the inflammatory epithelial cell.

Activation of NLRP3 inflammasome in human middle ear cholesteatoma and chronic otitis media

CONCLUSIONS

The nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome plays an important role in the pathogenesis of middle ear diseases. Modulation of inflammasome-mediated inflammation may be a novel therapeutic strategy for cholesteatoma and chronic otitis media.

OBJECTIVE

NLRP3 inflammasome is a critical molecule mediating interleukin (IL)-1β responses. However, the expression of NLRP3 in the pathogenesis of cholesteatoma and chronic otitis media has not been fully examined. This study sought to assess the expression of NLRP3, ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain and a pyrin domain), and caspase-1 in middle ear tissues in patients with cholesteatoma or chronic otitis media.

METHODS

Middle ear tissue samples were obtained from patients with cholesteatoma or chronic otitis media. Control middle ear samples were collected during cochlear implant surgery of patients without middle ear inflammation. The expression of NLRP3, ASC, and caspase-1 were examined by reverse transcription polymerase chain reaction (RT-PCR) assay and immunohistochemical study.

RESULTS

The levels of mRNA of NLRP3, ASC, and caspase-1 were significantly elevated in cholesteatoma and chronic otitis media as compared with that of normal controls. The proteins of NLRP3, ASC, and caspase-1 were observed in infiltrating inflammatory cells in cholesteatoma and chronic otitis media.

Polymorphisms in Toll-like receptors 2 and 4 genes and their expression in chronic suppurative otitis media

OBJECTIVE

Toll-like receptors (TLRs) have a prominent role in inducing innate immune response. It has been suggested that regulation of TLRs is involved in the pathogenesis of chronic otitis media. TLR 2 and TLR 4 polymorphisms were connected with susceptibility to acute otitis and chronic otitis with effusion. The objective of this study was to establish expression of TLR 2 and 4 on middle ear mucosa in different types of chronic suppurative otitis media (CSOM), and the influence of gene polymorphisms TLR 2 Arg753Gln and TLR 4 Thr399Ile and Asp299Gly to susceptibility to CSOM.

MATERIAL AND METHODS

Middle ear mucosa and full blood samples were obtained from 85 patients with chronic suppurative otitis media with and without cholesteatoma. Control group for mucosal TLR expression consisted of 71 samples of middle ear mucosa taken from patients with otosclerosis, and control group for DNA polymorphism consisted of 100 full blood samples in healthy subjects. DNA polymorphism detection was done with restriction fragment length polymorphism in RT PCR. Expression of TLR 2 and 4 was determined with immunohistochemical staining.

RESULTS

TLR 2 and TLR 4 expression on the middle ear mucosa was not influenced by age of the patients with chronic otitis media. Incidence of TLR 2 Arg753Gln polymorphism was significantly higher in patients with chronic otitis media, compared to control group. Significant association between TLR 2 Arg753Gln polymorphism and different types of mucosal changes in patients with chronic otitis media was established. TLR 2 and 4 expression on experimental group mucosa was significantly different compared to control group, where there was no expression (p=0.000). Strong dependence of TLR 2 and TLR 4 expression on middle ear mucosa with different mucosal changes and immunohistochemical activity after staining was detected.

CONCLUSION

Certain polymorphisms in TLR genes could be indicative for susceptibility to chronic otitis media. Expression of TLR 2 and 4 on middle ear mucosa was more dependable on different types of mucosal changes and type of CSOM than on bacteria found in the specimens. This can indicate that the type of mucosal changes are closely correlated with TLRs activity in middle ear.