Up-regulation of MUC5AC mRNA expression in endotoxin-induced otitis media

Characterization of mucoid and serous middle ear effusions from patients with chronic otitis media: implication of different biological mechanisms?

BACKGROUND

Chronic otitis media with effusion (COME) is characterized by persistent middle ear effusions that are in most cases highly viscous, but some patients present with serous fluid. This study aimed at comprehensively characterizing the macromolecular composition of mucoid vs. serous middle ear effusions (MEEs).

METHODS

MEEs from patients with COME were analyzed for proteins by mass spectrometry (MS) and western blot techniques, total DNA quantity, bacterial DNA (16S sequencing), and cytokine content. Proteomics datasets were studied in Ingenuity Pathway Analysis (IPA).

RESULTS

Mucoid samples showed a global tendency of increased pro-inflammatory mediators. Interleukin-1β (IL-1β) and IL-10 were significantly more abundant in serous samples (p < 0.01). Mucoid samples had higher DNA quantity (p = 0.04), more likely to be positive in MUC5B protein (p = 0.008) and higher peptide counts (12,786 vs. 2225), as well as an overall larger number of identified proteins (331 vs. 177), compared to serous. IPA found the mucoid sample dataset to be related to immune cell function and epithelial remodeling, whereas the serous sample dataset showed acute responses and blood-related proteins. Interestingly, serous samples showed more bacterial DNA than mucoid ones, with less bacterial genera variability.

CONCLUSION

This study demonstrates divergent immune responses in children with COME by effusion quality.

Relationship of the Middle Ear Effusion Microbiome to Secretory Mucin Production in Pediatric Patients With Chronic Otitis Media

BACKGROUND

Acute otitis media, an infection of the middle ear, can become chronic after multiple episodes. Microbial influence on chronic otitis media remains unclear. It has been reported that mucin glycoproteins are required for middle ear immune defense against pathogens. We aim to characterize the middle ear effusion (MEE) microbiome using high-throughput sequencing and assess potential associations in microbiome diversity with the presence of the secretory mucins MUC5B and MUC5AC. We hypothesize that MEEs containing MUC5B will exhibit a microbiome largely devoid of typical acute otitis media bacteria.

METHODS

Fifty-five MEEs from children undergoing myringotomy at Children's National Health System were recovered. Mucin was semiquantitatively determined through Western blot analysis. DNA was subjected to 16S rRNA amplicon sequencing using the Illumina MiSeq platform. Raw data were processed in mothur (SILVA reference database). Alpha- and beta-diversity metrics were determined. Abundance differences between sample groups were estimated.

RESULTS

MUC5B was present in 94.5% and MUC5AC in 65.5% of MEEs. Sequencing revealed 39 genera with a relative abundance ≥0.1%. Haemophilus (22.54%), Moraxella (11.11%) and Turicella (7.84%) were the most abundant. Turicella and Pseudomonas proportions were greater in patients older than 24 months of age. In patients with hearing loss, Haemophilus was more abundant, while Turicella and Actinobacteria were less abundant. Haemophilus was also more abundant in samples containing both secretory mucins.

CONCLUSIONS

The microbiome of MEEs from children with chronic otitis media differs according to specific clinical features, such as mucin content, age and presence of hearing loss. These associations provide novel pathophysiologic insights across the spectrum of otitis media progression.

Evaluation of 15 functional candidate genes for association with chronic otitis media with effusion and/or recurrent otitis media (COME/ROM)

DNA sequence variants in genes involved in the innate immune response and secondary response to infection may confer susceptibility to chronic otitis media with effusion and/or recurrent otitis media (COME/ROM). We evaluated single nucleotide polymorphisms (SNPs) in 15 functional candidate genes. A total of 99 SNPs were successfully genotyped on the Sequenom platform in 142 families (618 subjects) from the Minnesota COME/ROM Family Study. Data were analyzed for association with COME/ROM using the Generalized Disequilibrium Test (GDT). Sex and age at exam were adjusted as covariates, relatedness was accounted for, and genotype differences from all phenotypically discordant relative pairs were utilized to measure the evidence of association between COME/ROM and each SNP. SNP rs2735733 in the region of the mucin 5, subtypes A/C gene (MUC5AC) exhibited nominal evidence for association with COME/ROM (P = 0.002). Two additional SNPs from this region had P values<0.05. Other variants exhibiting associations with COME/ROM at P<0.05 included the SCN1B SNP rs8100085 (P = 0.013), SFTPD SNP rs1051246 (P = 0.039) and TLR4 SNP rs2770146 (P = 0.038). However, none of these associations replicated in an independent sample of COME/ROM families. The candidate gene variants examined do not appear to make a major contribution to COME/ROM susceptibility, despite a priori evidence from functional or animal model studies for a role in COME/ROM pathology.

The role of vascular endothelial growth factor in pediatric otitis media with effusion

OBJECTIVES

Vascular endothelial growth factor (VEGF) is a potent and critical inducer of angiogenesis and vascular permeability, and has been shown to play an important role in inflammatory events, together with hypoxia and inflammatory cytokines. VEGF messenger ribonucleic acid (mRNA) is expressed in the middle ear in an experimental animal model of otitis media with effusion (OME) and in patients with OME. However, the protein levels of VEGF in middle ear effusions (MEEs) are unknown and the role of VEGF in the pathogenesis of OME is unclear. The goals of this study were to determine the VEGF levels in MEEs and to investigate the role of VEGF in production of MEEs by comparing these levels with those of interleukin-8 (IL-8), endotoxin, and albumin.

METHODS

Forty-six MEEs obtained from 33 children (24 boys, 9 girls) were used in the study. The mean age of the subjects was 6.3 years old (range, 1-12 years old). The patients underwent myringotomy and/or insertion of a ventilation tube for treatment of OME. After myringotomy, MEEs were collected with a Juhn Tym-Tap. The samples were divided into serous and mucoid types based on observation by the naked eye. After measuring the weight of the MEE, the sample was diluted with phosphate-buffered saline and frozen until use. The concentrations of VEGF and IL-8 in the MEEs were determined by enzyme-linked immunosorbent assays, endotoxin concentrations were measured by the Limulus Amebocyte Lysate test, and albumin levels were determined using an immunoturbidimetric assay.

RESULTS

VEGF, endotoxin, IL-8, and albumin were detected in 100%, 89%, 98%, and 100% of the 46 MEEs, respectively. The concentrations of VEGF, endotoxin, and IL-8 were significantly higher in mucoid MEEs than in serous MEEs (p<0.01), whereas there was no significant difference in the albumin concentration between mucoid and serous MEEs. The VEGF levels were positively correlated with those of endotoxin (R(2)=0.17, p<0.05) and albumin (R(2)=0.65, p<0.01) in mucoid MEEs, but not in serous MEEs.

CONCLUSIONS

Our results suggest that VEGF is produced in response to bacterial components such as endotoxin in the middle ear cavity and is associated with production of mucoid MEEs by increasing serum exudation and mucosal secretion.

Effects of cigarette smoking on mucin production in human middle ear epithelial cells

OBJECTIVE

Otitis media (OM) is the most common disease in preschool age children related to passive cigarette smoking as risk factor. In this study, we investigate whether the cigarette smoking can induce the inflammation in human middle ear epithelial cell, and cigarette smoke-induced inflammation can increase the expression of MUC5AC gene and protein that was known to play an important role in OM with effusion.

METHODS

After treatment of cigarette smoke solution (CSS) on immortalized human middle ear epithelial cells (HMEECs) with or without pretreatment by epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (AG1478), we observed expression of tumor necrosis factor-alpha (TNF-α), EGFR, MUC5AC mRNA by quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and EGFR, MUC5AC protein by western blotting.

RESULTS

Treatment of CSS increased expression of TNF-α mRNA dose dependently. Treatment of CSS upregulated the EGFR and MUC5AC mRNA in a time-dependent manner. CSS-induced upregulation of EGFR and MUC5AC mRNA was suppressed by the pretreatment of AG1478. EGFR and MUC5AC proteins were upregulated by the treatment of CSS and suppressed by the pretreatment of AG1478.

CONCLUSIONS

Treatment of CSS on HMEECs increased the expression of MUC5AC mRNAs and proteins which play a major role in OM with effusion.

The toll-Like receptor adaptor TRIF contributes to otitis media pathogenesis and recovery

Background

Toll-like receptor (TLR) signalling is crucial for innate immune responses to infection. The involvement of TLRs in otitis media (OM), the most prevalent childhood disease in developed countries, has been implicated by studies in middle ear cell lines, by association studies of TLR-related gene polymorphisms, and by altered OM in mice bearing mutations in TLR genes. Activated TLRs signal via two alternative intracellular signaling molecules with differing effects; MyD88 (Myeloid differentiation primary response gene 88) inducing primarily interleukin expression and TRIF (Tir-domain-containing adaptor inducing interferon β) mediating type I interferon (IFN) expression. We tested the hypothesis that TRIF and type I IFN signaling play a role in OM, using a murine model of OM induced by non-typeable Haemophilus influenzae (NTHi). The ME inflammatory response to NTHi was examined in wild-type (WT) and TRIF-/- mice by qPCR, gene microarray, histopathology and bacterial culture.

Results

Expression of TRIF mRNA was only modesty enhanced during OM, but both type I IFN signalling genes and type I IFN-inducible genes were significantly up-regulated in WT mice. TRIF-deficient mice showed reduced but more persistent mucosal hyperplasia and less leukocyte infiltration into the ME in response to NTHi infection than did WT animals. Viable bacteria could be cultured from MEs of TRIF-/- mice for much longer in the course of disease than was the case for middle ears of WT mice.

Conclusion

Our results demonstrate that activation of TRIF/type I IFN responses is important in both the pathogenesis and resolution of NTHi-induced OM.

Prognostic impact of phosphorylcholine expression in nontypeable Haemophilus influenzae in otitis media with effusion

CONCLUSIONS

The expression of phosphorylcholine (ChoP) in the surface of nontypeable Haemophilus influenzae (NTHi) is an important factor in the pathogenesis of persistent otitis media with effusion (OME) in humans.

OBJECTIVES

Lipooligosaccharide (LOS) in NTHi undergoes phase variation in expression of the ChoP epitope. In this study, we examined the phase variation of NTHi isolated from the nasopharynx of children who suffer from OME, and investigated the relationship between the phase variation and the pathogenesis of OME.

SUBJECTS AND METHODS

Forty NTHi strains were isolated from the nasopharynx of children with OME, and the ChoP expression of NTHi was examined by colony immunoblot analysis. The NTHi strains were classified into three groups according to the level of ChoP expression, i.e. strong, moderate, and weak expression groups. An adherence assay was also performed.

RESULTS

The NTHi strains expressing ChoP(+) LOS glycoforms accounted for 63% of all NTHi tested. Clinically, the strong expression group of ChoP were related to prolongation of the duration of OME. The adherence assay with the CCL 20.2 cell line revealed that the strong expression group attached more easily to the cell surface than the weak expression group.

LPS up-regulates mucin and cytokine mRNA expression and stimulates mucin and cytokine secretion in goblet cells

Bacterial inflammation in mucosa is accompanied by morphological and proliferative changes in goblet cells and mucin hypersecretion. Main stimulators of bacterial inflammation are bacterial lipopolysaccharides (LPS). In vitro investigation of the LPS effect on the molecular processes in goblet cells, using the human mucin-secreting goblet cell line HT29-MTX, showed the following results. LPS up-regulated mucin and cytokine mRNA expression and secretion in goblet cells in a concentration and time-dependent manner, with a maximum output at an LPS concentration of 100 ng/ml. LPS (100 ng/ml) increased mRNA expression of MUC5AC (2.4x), MUC5B (2.1x), and IL-8 (2.3x) and stimulated secretion of mucins (MUC5AC up to 39%, MUC5B up to 31%) and the inflammatory cytokine IL-8 (up to 10x). A significant correlation was found between the LPS-induced IL-8 secretion and secretion of mucins. These results suggest: (1) goblet cells, responding to the direct stimulation of bacterial LPS by two inflammatory-related processes such as production and secretion of the gel-forming mucins and the inflammatory cytokine IL-8, can be considered as an important part of mucosal immunity and (2) LPS- induced goblet cell mucin secretion can occur partly via IL-8-dependent pathway.