Heterogeneity in the protein cores of mucins isolated from human middle ear effusions: evidence for expression of different mucin gene products

DNA Methylation Patterns of Chronic Explosive Breaching in U.S. Military Warfighters

Background: Injuries from exposure to explosions rose dramatically during the Iraq and Afghanistan wars, which motivated investigation of blast-related neurotrauma. We have undertaken human studies involving military "breachers" -exposed to controlled, low-level blast during a 3-days explosive breaching course. Methods: We screened epigenetic profiles in peripheral blood samples from 59 subjects (in two separate U.S. Military training sessions) using Infinium MethylationEPIC BeadChips. Participants had varying numbers of exposures to blast over their military careers (empirically defined as high ≥ 40, and conversely, low < 39 breaching exposures). Daily self-reported physiological symptoms were recorded. Tinnitus, memory problems, headaches, and sleep disturbances are most frequently reported. Results: We identified 14 significantly differentially methylated regions (DMRs) within genes associated with cumulative blast exposure in participants with high relative to low cumulative blast exposure. Notably, NTSR1 and SPON1 were significantly differentially methylated in high relative to low blast exposed groups, suggesting that sleep dysregulation may be altered in response to chronic cumulative blast exposure. In comparing lifetime blast exposure at baseline (prior to exposure in current training), and top associated symptoms, we identified significant DMRs associated with tinnitus, sleep difficulties, and headache. Notably, we identified KCNN3, SOD3, MUC4, GALR1, and WDR45B, which are implicated in auditory function, as differentially methylated associated with self-reported tinnitus. These findings suggest neurobiological mechanisms behind auditory injuries in our military warfighters and are particularly relevant given tinnitus is not only a primary disability among veterans, but has also been demonstrated in active duty medical records for populations exposed to blast in training. Additionally, we found that differentially methylated regions associated with the genes CCDC68 and COMT track with sleep difficulties, and those within FMOD and TNXB track with pain and headache. Conclusion: Sleep disturbances, as well as tinnitus and chronic pain, are widely reported in U.S. military service members and veterans. As we have previously demonstrated, DNA methylation encapsulates lifetime exposure to blast. The current data support previous findings and recapitulate transcriptional regulatory alterations in genes involved in sleep, auditory function, and pain. These data uncovered novel epigenetic and transcriptional regulatory mechanism underlying the etiological basis of these symptoms.

In vivo imaging of the Muc5b gel-forming mucin

Gel-forming mucins are macromolecules produced by goblet cells and responsible for the mucus gel formation. Changes in goblet cell density and in gel-forming mucin production have emerged as sensitive indicators for mucosal diseases. A Muc5b-GFP tagged reporter mouse was used to assess Muc5b production in mouse tissues by immunofluorescence microscopy and fluorescent activity using stereromicroscopy and probe-based confocal laser endomicroscopy. Muc5b production was followed longitudinally by recording the fluorescent activity in vagina and in embryonic lung explants under stimulation by interleukin 13. We show that the GFP is easily visualized in the mouse adult ear, nose, trachea, gallbladder, and cervix. Live Muc5b is also easily monitored in the nasal cavity, trachea and vagina where its production varies during the estrus cycle with a peak at the proestrus phase and in pregnant mice. Explant culture of reporter mouse embryonic whole lung shows that interleukin 13 stimulates Muc5b production. The transgenic Muc5b-GFP mouse is unique and suitable to study the mechanisms that regulate Muc5b production/secretion and mucous cell differentiation by live imaging and can be applied to test drug efficacy in mucosal disease models.

More than one disease process in chronic sinusitis based on mucin fragmentation patterns and amino Acid analysis

Objective. To characterise fragmentation patterns and amino acid composition of MUC2 and MUC5AC in chronic sinusitis. Methods. Antigenic identity of purified sinus mucins was determined by ELISA. Fragmentation patterns of a MUC5AC rich sample mucin were analysed by Sepharose CL-2B gel chromatography. Samples, divided into one MUC2 rich and one MUC5AC rich group, were subjected to sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and their amino acid contents were analysed. Results. Reduction, trypsin digestion, and papain digestion produced progressively smaller mucin species. On SDS-PAGE, digested MUC5AC rich mucin produced four distinct products. Amino acid analysis was characteristic of mucins with high serine, threonine, and proline contents and reduction and proteolysis increased relative proportions of these amino acids. MUC5AC rich mucins contained more protein than MUC2 rich mucins. Conclusion. Sinus mucin fragmentation produced mucin subunits and glycopeptide units of smaller molecular sizes which are likely to have lower viscoelastic properties. Applying this in vivo could alter mucus physical properties and biologic functions. Amino acid contents of MUC2 and MUC5AC mucins are different. This could be contributing to biological properties and functions of sinus mucins. These data suggest that there may be different pathological processes occurring at the cellular level on chronic sinusitis.

MUC5B secretion is up-regulated in sinusitis compared with controls

BACKGROUND

The mucus that lines the airway epithelium provides a barrier against pathogenic and noxious agents and participates in the innate mucosal response to inflammation and infection. Mucins are the major components of mucus and the macromolecules that impart rheologic properties to airway mucus. Airway mucus is overproduced in chronic rhinosinusitis (CRS). Biochemical and biophysical characterization of mucus in CRS and in normal airways will elucidate important aspects of CRS pathophysiology and allow the design of targeted medical treatments. The aim of this study was to estimate secretion of sinus mucus mucins in healthy individuals and CRS and correlate them with mucus biophysical properties.

METHODS

Twenty-seven sinus mucus samples from 21 patients were collected (14 subjects with CRS undergoing sinus surgery as part of their treatment and 7 control subjects undergoing hypophysectomy without sinonasal disease). Biophysical properties of the mucus were measured by rheometry. ELISA was done to estimate MUC5AC and MUC5B mucin content in comparison with standards, i.e., porcine gastric mucin (MUC5AC) and human salivary mucin (MUC5B).

RESULTS

MUC5B secretion +/- SEM was 0.49 +/- 0.16 microg/mL (n = 14) and 0.17 +/- 0.05 microg/mL (n = 7) and MUC5AC secretion +/- SEM was 1.26 +/- 0.26 microg/mL (n = 14) and 1.46 +/- 0.61 microg/mL (n = 7) in chronic sinusitis and control subjects, respectively. There was linear correlation between viscosity and mucin content in the control group but not in the CRS group.

CONCLUSION

MUC5B secretion is significantly up-regulated in CRS compared with control subjects (p = 0.04). Correlation between viscosity and mucin content was lost in CRS. This is likely to have important implications for future therapies in CRS.

beta-Casomorphin-7 regulates the secretion and expression of gastrointestinal mucins through a mu-opioid pathway

We have recently shown that beta-casomorphin-7, a milk opioid peptide, strongly stimulates mucin secretion in the rat jejunum through a nervous pathway and opioid receptor activation. In this study, the hypothesis that beta-casomorphin-7 may also act directly on intestinal goblet cells was investigated in vitro in rat and human intestinal mucin-producing cells (DHE and HT29-MTX) using quantitative and semiquantitative RT-PCR and ELISA. The presence of mu-opioid receptors was demonstrated in rat goblet cells in the upper half of the colonic crypt and in the two cell lines by immunohistochemistry and RT-PCR. In rat DHE cells, beta-casomorphin-7 increased the expression of rat mucin (rMuc)2 and rMuc3 but not rMuc1, rMuc4, and rMuc5AC. This effect was time and dose dependent, with the maximum of increase in transcripts being noticed for a concentration of 10(-4) M after 2 h of stimulation for rMuc2 (225% of controls) and 4 h of stimulation for rMuc3 (208% of controls). Mucin secretion was maximally increased after 8 h of stimulation. Interestingly, these effects were prevented by pretreatment of the cells with the mu-opioid antagonist cyprodime. In human HT29-MTX cells, beta-casomorphin-7 (10(-4) M) also increased MUC5AC mRNA levels (219% after 24 h of stimulation) and the secretion of this mucin (169% of controls). In conclusion, beta-casomorphin-7 may contribute significantly to mucin production via a direct effect on intestinal goblet cells and the activation of mu-opioid receptors. Because intestinal mucins have a crucial mucosal protective function, dairy products containing beta-casomorphin-7 may improve intestinal protection and could have dietary and health applications.

Luminal leptin activates mucin-secreting goblet cells in the large bowel

Leptin has been suggested to be involved in tissue injury and/or mucosal defence mechanisms. Here, we studied the effects of leptin on colonic mucus secretion and rat mucin 2 (rMuc2) expression. Wistar rats and ob/ob mice were used. Secretion of mucus was followed in vivo in the rat perfused colon model. Mucus secretion was quantified by ELISA, and rMuc2 mRNA levels were quantified by real-time RT PCR. The effects of leptin alone or in association with protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) inhibitors on mucin secreted by human mucus-secreting HT29-MTX cells were determined. Leptin was detected in the rat colonic lumen at substantial levels. Luminal perfusion of leptin stimulates mucus-secreting goblet cells in a dose-dependent manner in vivo in the rat. Leptin (10 nmol/l) increased mucus secretion by a factor of 3.5 and doubled rMuc2 mRNA levels in the colonic mucosa. There was no damage to mucosa 24 h after leptin, but the number of stained mucus cells significantly increased. Leptin-deficient ob/ob mice have abnormally dense mucus-filled goblet cells. In human colonic goblet-like HT29-MTX cells expressing leptin receptors, leptin increased mucin secretion by activating PKC- and PI3K-dependent pathways. This is the first demonstration that leptin, acting from the luminal side, controls the function of mucus-secreting goblet cells. Because the gel layer formed by mucus at the surface of the intestinal epithelium has a barrier function, our data may be relevant physiologically in defence mechanisms of the gastrointestinal tract.

Up-Regulation of MUC5AC and MUC5B Mucin Genes in Nasopharyngeal Respiratory Mucosa and Selective Up-Regulation of MUC5B in Middle Ear in Pediatric Otitis Media with Effusion

OBJECTIVES

Mucins are the major component responsible for the gel-like properties of mucus secretion. Currently, little is known about the regulation of mucins in otitis media with effusion (OME). We investigated the expression of MUC5AC and MUC5B mucin gene messenger (m)RNAs in middle ear effusions as well as in tissue biopsies of the respiratory mucosa of the nasopharynx by means of reverse-transcription polymerase chain reaction (RT-PCR).

STUDY DESIGN

A prospective, controlled, clinical trial.

METHODS

The study group consisted of 25 children with a diagnosis of OME who were to undergo bilateral ventilation tube insertion with adenoidectomy. A sample of middle ear effusion (n = 50) as well as tissue biopsy from nasopharyngeal respiratory mucosa (n = 25) were obtained from each patient. For the nasopharyngeal mucosal biopsies, two control groups were made up from 30 children with healthy ears who underwent tonsillectomy +/- adenoidectomy operation; control A, 15 children with adenoid hypertrophy, and control B, 15 children with healthy nasopharynx. RNAs were extracted from effusion and tissue samples, and semiquantitative RT-PCR was performed for MUC5AC and MUC5B to investigate their expression.

RESULTS

In the middle ear effusions, MUC5B mRNA expression was detected in 48 (96%), whereas MUC5AC mRNA was detected in 8 (16%). On semiquantitative analysis, MUC5AC/glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and MUC5B/GAPDH mRNA ratios in the study group were significantly increased compared with those in both control groups (P < .05).

CONCLUSIONS

The results suggest that the middle ear has a unique mucin gene expression pattern when compared with that of the nasopharynx. Up-regulation of MUC5B in the ear may play an important role in the pathogenesis of middle ear effusions.

The immunoregulatory and allergy-associated cytokines in the aetiology of the otitis media with effusion

Inflammation in the middle ear mucosa, which can be provoked by different primary factors such as bacterial and viral infection, local allergic reactions and reflux, is the crucial event in the pathogenesis of otitis media with effusion (OME). Unresolved acute inflammatory responses or defective immunoregulation of middle inflammation can promote chronic inflammatory processes and stimulate the chronic condition of OME. Cytokines are the central molecular regulators of middle ear inflammation and can switch the acute phase of inflammation in the chronic stage and induce molecular-pathological processes leading to the histopathological changes accompanying OME. In this review we present cytokines identified in otitis media, immunoregulatory [interleukin (IL)-2, IL-10, transforming growth factor-beta]) and allergy associated (IL-4, IL-5, granulocyte-macrophage colony-stimulating factor), as crucial molecular regulators, responsible for chronic inflammation in the middle ear and the chronic condition of OME.

The DHE cell line as a model for studying rat gastro-intestinal mucin expression: effects of dexamethasone

The expression of mucin genes was evaluated in rat intestinal cell lines in order to establish an in vitro model for investigating the regulation of intestinal mucin expression in this species. Two rat intestinal cancer cell lines (DHE, LGA) and three nontumoral rat intestinal cell lines (IEC6, IEC17, IEC18) were screened. The mRNA expression of rMuc1, rMuc2, rMuc3, rMuc4, and rMuc5AC mucin genes was studied by semiquantitative RT-PCR, real-time RT-PCR and Northern-blot analysis. Results were correlated with immunohistochemical expression of rat gastric and intestinal mucin proteins, and secretion of glycoconjugates was examined by enzyme-linked lectin assay. We showed that mRNA of rMucl and rMuc2 were constitutively expressed in all IEC cell populations but periodic acid Schiff staining of these cells did not reveal the presence of glycoproteins. DHE cells expressed rMuc1-5AC mRNA and LGA expressed the same mucins but the level of rMuc4 was much lower. Mucin mRNA expression also differed in relation with the length of cultivation. Immunocytochemical studies revealed the presence of gastric and intestinal mucins in the two tumoral cell lines. Functional experiments showed that bethanechol, A23187 and PMA stimulated release of glycoconjugates in DHE but not in LGA cells. Treatment of DHE cells with dexamethasone (10(-7) mol/l) enhanced rMuc2 mRNA but decreased rMuc1 and rMuc5AC mRNA. Real-time RT-PCR showed that the expression of rMuc1 and rMuc5AC genes was reduced by more than tenfold after 24 h. The increased expression of rMuc2 gene was confirmed by Northern blot analysis. In conclusion, DHE cells provide a valuable cellular model for research on rat mucin secretion and expression.

Expression of mucins in mucoid otitis media

A hallmark of mucoid otitis media (MOM, i.e., chronic otitis media with mucoid effusion) is mucus accumulation in the middle ear cavity, a condition that impairs transduction of sounds in the ear and causes hearing loss. The mucin identities of mucus and the underlying mechanism for the production of mucins in MOM are poorly understood. In this study, we demonstrated that the MUC5B and MUC4 were major mucins in MOM that formed distinct treelike polymers (mucus strands). The MUC5B and MUC4 mRNAs in the middle ear mucosa with MOM were up regulated 5-fold and 6-fold, compared with the controls. This upregulation was accompanied by the extensive proliferation of the MUC5B- and MUC4-producing cells in the middle ear epithelium. Further study indicated that the mucin hyperproduction was significantly linked to CD4+ and CD8+ T cells and/or CD68+ monocyte macrophages. It suggests that MUC5B and MUC4 expression may be regulated by the products of these cells.

Influence of prednisolone on the secretion of mucin from the HT29-MTX cell line

Glucocorticoids have been used in the treatment of otitis media with effusion with promising but inconsistent results. The HT29-MTX cell line is a completely differentiated and almost exclusively mucus-secreting goblet cell line. To assess the potential of steroids in suppressing mucin secretion, we have studied the response of this cell culture to prednisolone. Confluent cell cultures were trypsinized, subcultured in six-well plates and incubated with five doses of prednisolone from 10-3 M to 10-11 M and over a varying time course from 6 to 36 h. Analysis was performed using a monoclonal mouse antibody to human gastric mucin by dot-blot ELISA. Prednisolone caused a consistent reduction in mucin production from this cell line. Increasing concentrations of prednisolone resulted in increasing suppression of MUC5AC secretion. There is a dose-dependent suppression of mucin secretion by prednisolone, with a maximum effect of 21% over control seen at the highest steroid concentration used.

Effect of nitric oxide donation on mucin production in vitro

Otitis media with effusion (OME) is characterized by the accumulation of a viscous fluid rich in mucins in the middle ear cleft. There is increasing evidence that this fluid is the result of an inflammatory reaction and that nitric oxide (NO) is an important mediator in this reaction. The goblet cell line HT29-MTX produces principally MUC5AC, an important mucin in middle ear effusions, and thus is a good model for the study of mucus-secreting epithelia. Confluent cell cultures were trypsinized, subcultured and incubated with isosorbide dinitrate (ISDN), a NO donor, for 0.5, 1 and 2 h at a concentration of 1 mm and in concentrations of 0.01, 0.1, 0.5, 1 and 2 mm for 1 h. Experiments were performed four times. Mucin production was detected by a slot blot ELISA assay, using a monoclonal mouse antibody to human MUC5AC mucin. Statistical significance was tested using a one-way analysis of variance. NO donation by ISDN caused a consistent rise in mucin production above control. Maximal mucin production of 35% above control occurred at 1 h with 1 mm ISDN. Mucin production increased from 12% above control with 0.1 mm ISDN dinitrate to 45% above baseline with 2 mm ISDN. NO donation by ISDN results in an increase in mucus production, which is both dose and time related. This adds further evidence to an inflammatory model for mucus secretion in OME.

Mucin gene expression in the effusions of otitis media with effusion

OBJECTIVES

The purpose of the study is to know if mucin gene expression can be detected in the middle ear effusion and if so, which mucin genes are expressed in the effusions.

METHODS

Mucin gene expression in the middle ear effusions obtained from five patients with otitis media with effusion were analyzed by reverse transcription-polymerase chain reaction. Ribonucleic acids (RNAs) were extracted from the effusion and the expression of 12 mucin genes was analyzed by reverse transcription-polymerase chain reaction.

RESULTS

Mucin gene expression examined by reverse transcription-polymerase chain reaction indicated the expression of MUC1, MUC4, MUC5AC, MUC6, MUC7, MUC8, MUC9, MUC11 and MUC12 mRNA in the effusion. This mucin gene expression was similar to that in BEAS-2B cell, a bronchial epithelial cell line.

CONCLUSION

Middle ear effusion can give us valuable information on mucin gene expression in the middle ear. There is similarity between mucin gene expression in the middle ear effusion and that in the bronchial epithelia.

Surfactant in the middle ear and eustachian tube: a review

There has been a recent surge in research on surfactant and surfactant proteins. Fields ranging from immunology to surface chemistry are making contributions to our understanding of this multifunctional compound. This paper reviews the literature on the structure and function of Eustachian tube surfactant. It covers the proposed functions of endogenous surfactant in normal physiology, as well as the experimental applications of exogenous surfactant in the treatment of otitis media. The analysis is based on four platforms of research: the role of surfactant in the innate immune system, the effect of surfactant on surface tension and Eustachian tube opening pressure, the capacity of surfactant to alter the rheological properties of mucus and the efficiency of the mucociliary system, and the ability of surfactant to mitigate oxygen free radical damage.

Induction of mucous cell metaplasia by tumor necrosis factor alpha in rat middle ear: the pathological basis for mucin hyperproduction in mucoid otitis media

Mucoid otitis media (MOM), one of the leading causes of acquired hearing loss in children, is characterized by mucous cell hyperplasia in the middle ear cleft associated with mucin accumulation in the middle ear cavity. The factors that stimulate mucous cell metaplasia-hyperplasia and mucin hyperproduction are poorly understood. Recent studies demonstrated that tumor necrosis factor alpha (TNF-alpha), present in human middle ear effusion, stimulated mucin production in vitro and up-regulated mucin gene expression in vivo. These findings suggest that TNF-alpha is important in the development of mucous cell metaplasia-hyperplasia. This study demonstrated that inoculation of TNF-alpha into the middle ear cavity followed by eustachian tube obstruction stimulated mucous cell metaplasia-hyperplasia in the middle ear cleft, accompanied by abundant mucin or mucin-like glycoproteins in the middle ear effusion--a phenotype of MOM in humans. This finding suggests that TNF-alpha plays a key role in the pathogenesis of MOM through induction of mucous cell metaplasia-hyperplasia and mucin production.

Ciliary and secretory differentiation of normal human middle ear epithelial cells

Recent technical advances now permit the serial culture of normal human middle ear epithelial (NHMEE) cells. However, the ciliary differentiation of these cells has not been achieved. The purpose of this study was to establish a culture system in order to differentiate serially cultured NHMEE cells into ciliated cells. If ciliated cells developed, the percentages of ciliated cells and secretory cells were measured throughout the duration of culture. We also examined the levels of mucin and lysozyme secretion and their mRNAs in a time-dependent manner. Human middle ear mucosa with a normal appearance was harvested and serially cultured after enzymatic disaggregation. These cells were cultured in an air-liquid interface (ALI) culture system for 2, 7, 14, 21 and 28 days after confluence. Ciliogenesis usually began 16-18 days after confluence. The percentage of ciliated cells detected by means of immunohistochemical staining increased over time up to a maximum of 10.6% but the percentage of secretory cells remained stable at approximately 40% throughout the duration of culture. By Day 14 after confluence, the amounts of mucin and lysozyme secretion, as measured by dot-blotting analysis, had increased significantly and then remained stable. The expression levels of mucin gene 5B (MUC5B), MUC8 and lysozyme increased with the duration of culture. MUC8 in particular showed a dramatic increase on Day 28 after confluence. In contrast, the level of MUC5AC mRNA peaked on Day 14 after confluence, and then decreased. In conclusion, ciliary differentiation of NHMEE cells can be induced using an ALI culture system. Our study also suggests that secretory function develops earlier than ciliogenesis, and that the expressions of MUC5B and MUC8 mRNAs increase as a function of differentiation.

In vitro study of IL-8 and goblet cells: possible role of IL-8 in the aetiology of otitis media with effusion

One of the main characteristics of otitis media with effusion (OME) is the differentiation of basal cells into goblet cells with subsequent proliferation in a modified respiratory epithelium leading to the formation of mucin-rich effusion in the middle ear cleft. In order to determine the effect of pro-inflammatory cytokines identified in OME, e.g. IL-1beta, tumour necrosis factor (TNF)-alpha, IL-6 and IL-8, on goblet cells, and to clarify the role of IL-8 in particular, we used the human goblet cell line HT29-MTX, which secretes two OME-related mucins: MUC5AC and MUC5B. IL-1beta and TNF-alpha stimulated the secretion of IL-8 in HT29-MTX goblet cells. Dose- (2-200 ng/ml) and time- (0-5 days) response studies of IL-8-induced mucin secretion were carried out. IL-8 upregulated the secretion of MUC5AC and MUC5B mucins in a concentration-dependent manner, with a maximum response at an IL-8 concentration of 20 ng/ml. IL-8 (20 ng/ml)-mediated mucin secretion persisted for up to 5 days, with a peak response 72 h after the addition of cytokine. These results suggest that: (i) goblet cells are target cells for the pro-inflammatory cytokines IL-1beta, TNF-alpha and IL-8 and can contribute to the pathogenesis of OME by increasing both the concentration of IL-8 and the secretion of mucin; and (ii) IL-8 stimulates prolonged mucin secretion from goblet cells and may be involved in the maintenance of the disease in the chronic stage.

Novel cytoplasmic proteins of nontypeable Haemophilus influenzae up-regulate human MUC5AC mucin transcription via a positive p38 mitogen-activated protein kinase pathway and a negative phosphoinositide 3-kinase-Akt pathway

Nontypeable Haemophilus influenzae (NTHi) is an important human pathogen that causes chronic otitis media with effusion (COME) in children and exacerbation of chronic obstructive pulmonary disease (COPD) in adults. Mucin overproduction, a hallmark of both diseases, has been shown to directly cause conductive hearing loss in COME and airway obstruction in COPD. The molecular mechanisms underlying mucin overproduction in NTHi infections still remain unclear. Here, we show that NTHi strongly up-regulates MUC5AC mucin transcription only after bacterial cell disruption. Maximal up-regulation is induced by heat-stable bacterial cytoplasmic proteins, whereas NTHi surface membrane proteins induce only moderate MUC5AC transcription. These results demonstrate an important role for cytoplasmic molecules from lysed bacteria in the pathogenesis of NTHi infections, and may well explain why many patients still have persistent symptoms such as middle ear effusion in COME after intensive antibiotic treatment. Furthermore, our results indicate that activation of p38 mitogen-activated protein kinase is required for NTHi-induced MUC5AC transcription, whereas activation of phosphoinositide 3-kinase-Akt pathway leads to down-regulation of NTHi-induced MUC5AC transcription via a negative cross-talk with p38 mitogen-activated protein kinase pathway. These studies may bring new insights into molecular pathogenesis of NTHi infections and lead to novel therapeutic intervention for COME and COPD.

Compositional difference in middle ear effusion: mucous versus serous

OBJECTIVES

Serous otitis media is usually responsive to medical treatment, whereas mucoid otitis media is not. The present study was undertaken to elucidate the compositional difference between serous and mucoid effusion and to investigate whether MUC5AC acts as a major mucin in the middle ear mucosa with mucoid otitis media.

STUDY DESIGN

This study involved a chemical analysis of middle ear effusion and immunostaining of the middle ear mucosa.

METHODS

Middle ear effusion samples were collected from 27 patients with mucoid otitis media and 18 patients with serous otitis media. The levels of mucin, lysozyme, secretory immunoglobulin A, and interleukin-8 were measured by dot blotting or enzyme-linked immunosorbent assay. Periodic acid-Schiff and immunohistochemical staining with monoclonal anti-MUC5AC antibody were performed on the serial sections of middle ear mucosa with mucoid otitis media.

RESULTS

Mucoid effusions contained higher levels of mucin, lysozyme, secretory immunoglobulin A, and interleukin-8 than did serous effusions. Immunohistological study revealed that MUC5AC mucin was expressed in only a small portion of the goblet cells of middle ear mucosa with mucoid otitis media.

CONCLUSIONS

The study suggests that both serous secretions and mucin might make the middle ear effusion more viscous and that mucins other than MUC5AC might have a major role in the viscosity of middle ear effusion. Further study is necessary to identify the major mucins in the middle ear effusion of otitis media with effusion.

Pattern changes of mucin gene expression with pneumococcal otitis media

OBJECTIVE

mucins, known to be important components of the mucociliary transport system in the middle ear and Eustachian tube, are subject to changes under inflammatory conditions. Which mucin genes are up-regulated or activated during an inflammatory reaction of the middle ear and Eustachian tube, however, is poorly understood. The purpose of this study was to characterize mucin gene expression in middle ears and Eustachian tubes with pneumococcal ear infection.

METHODS

sixteen rats received intrabullar inoculation of Streptococcus pneumoniae type 6A at 2.5x10(6) colony forming units (CFU). Four animals were sacrificed on days 1, 3, 7, and 14, respectively. The profile of mucin gene expression in the middle ear and Eustachian tube was examined by reverse transcription polymerase chain reaction (RT-PCR) at the above time points. Sixteen rats that received intrabullar inoculation of phosphate-buffered saline (PBS) served as controls.

RESULTS

the Muc2 mucin gene was expressed in middle ear mucosa of the control rats. Following pneumococcal inoculation, Muc1-Muc5 mucin genes were expressed in the middle ear mucosa in a time-dependent manner. In the Eustachian tube, the Muc2, Muc4 and Muc5 mucin genes were expressed in both control and pneumococcal inoculation groups.

CONCLUSION

Muc1, Muc3, Muc4, and Muc5 mucin genes were activated in the middle ear mucosa by pneumococci, which may contribute to hyper-production of mucin in acute pneumococcal otitis media.

Characterization of mucins in human middle ear and Eustachian tube

Mucins are important glycoproteins in the mucociliary transport system of the middle ear and Eustachian tube. Little is known about mucin expression within this system under physiological and pathological conditions. This study demonstrated the expression of MUC5B, MUC5AC, MUC4, and MUC1 in the human Eustachian tube, whereas only MUC5B mucin expression was demonstrated in noninflamed middle ears. MUC5B and MUC4 mucin genes were upregulated 4.2- and 6-fold, respectively, in middle ears with chronic otitis media (COM) or mucoid otitis media (MOM). This upregulation of mucin genes was accompanied by an increase of MUC5B- and MUC4-producing cells in the middle ear mucosa. Electron microscopy of the secretions from COM and MOM showed the presence of chainlike polymeric mucin. These data indicate that the epithelium of the middle ear and Eustachian tube expresses distinct mucin profiles and that MUC5B and MUC4 mucins are highly produced and secreted in the diseased middle ear. These mucins may form thick mucous effusion in the middle ear cavity and compromise the function of the middle ear.

Cell biology of tubotympanum in relation to pathogenesis of otitis media - a review

The sterility of the eustachian tube and tympanic cavity of normal individuals is maintained not only by the adaptive immune system, but also by the mucociliary system and the antimicrobial molecules of innate immunity. Mucin production and periciliary fluid homeostasis are essential for normal mucociliary function and dysfunction of this system is an important risk factor for otitis media. The secreted antimicrobial molecules of the tubotympanum include lysozyme, lactoferrin, beta defensins, and the surfactant proteins A and D (SP-A, SP-D). Defects in the expression or regulation of these molecules may also be the major risk factor for otitis media.

TNF-alpha in the regulation of MUC5AC secretion: some aspects of cytokine-induced mucin hypersecretion on the in vitro model

TNF-alpha has been implicated in the aetiology of otitis media with effusion (OME), where goblet cells proliferate in a modified respiratory epithelium, leading to the accumulation of a mucin-rich effusion in the middle-ear cleft. The MUC5AC mucin gene product has been identified as a component of these effusions. Here we have used the HT29-MTX goblet cell line, which secretes MUC5AC mucin, as a model to study the effect of TNF-alpha on goblet cells. MUC5AC mucin was identified and quantitated with a monoclonal antibody NCL-HGM-45M1. TNF-alpha stimulates MUC5AC mucin secretion in a dose-dependent manner, with 20 ng/ml producing maximal stimulation. Both pre-confluent and confluent cells showed peak stimulation after 7 h, however the pre-confluent cells showed twice the level of mucin hypersecretion. These results suggest that TNF-alpha stimulation of mucin secretion could play an important role in the early acute phase of the development of OME. This hypersecretion of mucin could then lead to the failure of the mucociliary clearance system, resulting in the accumulation of a mucin-rich effusion in the middle ear and the movement to a more chronic phase of the disease.

The aetiology of otitis media with effusion: a review

Otitis media with effusion (OME) is the most common cause of deafness in children in the developed world. In this article we aim to present an overview of current research developments on the aetiology of OME and the resulting implications for treatment. In the model we describe, the primary event is inflammation of the middle ear mucosa, usually due to the presence of bacteria. This leads to the release of inflammatory mediators, which cause secretion of a mucin-rich effusion by up-regulating mucin genes. Prolonged stimulation of the inflammatory response and poor mucociliary clearance lead to persistence of the middle ear fluid, giving rise to the clinical presentation of OME. We describe OME in the following sequence: the initial production of the effusion, the composition of the effusion produced, and factors impairing clearance of the effusion.

Identification of MUC5B mucin gene in human middle ear with chronic otitis media

OBJECTIVES

To identify the mucin gene and its expressing cells in the middle ear mucosa with chronic otitis media (COM), and to study the correlation between infiltration of inflammatory cells in the submucosa and expression of the mucin gene in the mucosal epithelium with COM.

STUDY DESIGN

Middle ear mucosal specimens removed from the inferior promontory area of 19 patients undergoing middle ear surgery for COM were studied.

METHODS

Sections were stained with H&E, Alcian blue-periodic acid Schiff (AB-PAS), polyclonal MUC5B antibody, and specific MUC5B riboprobe for histological, histochemical, immunohistochemical, and mucin mRNA analyses.

RESULTS

H&E staining revealed pseudostratified epithelia in 18 of the middle ear specimens with COM and cuboidal secretory epithelia in one. AB-PAS staining of epithelia revealed abundant secretory cells and their products (glycoconjugates). In situ hybridization and immunohistochemistry studies demonstrated that the secretory cells of the middle ear mucosa with COM expressed MUC5B mucin mRNA and its product MUC5B mucin.

CONCLUSIONS

The MUC5B mucin gene and its product were identified in the middle ear secretory cells of patients with COM. Its expression was extensive in pseudostratified mucosal epithelia and related to infiltration of inflammatory cells in the submucosa of the middle ear cleft with COM, suggestive that inflammatory cell products are involved in the production of MUC5B.