Glycoconjugate expression of sinus mucosa in chronic rhinosinusitis: a lectin histochemical study

Analysis of Bacterial Biofilm Formation and MUC5AC and MUC5B Expression in Chronic Rhinosinusitis Patients

Chronic rhinosinusitis (CRS) is a condition affecting as much as 16% of the adult population in developed countries with many factors attributed to its development, including the more recently proposed role of bacterial biofilm infections. Plenty of research has been conducted on biofilms in CRS and the causes behind the development of such an infection in the nasal cavity and sinuses. One such probable cause is the production of mucin glycoproteins by the mucosa of the nasal cavity. To investigate the possible link between biofilm formation and mucin expression levels and their relationship with CRS etiology, we examined samples from 85 patients by means of spinning disk confocal microscopy (SDCM) to establish their biofilm status and quantitative reverse transcription polymerase chain reaction (qRT-PCR) to determine MUC5AC and MUC5B expression levels. We observed a significantly higher prevalence of bacterial biofilms in the CRS patient group compared to the control group. In addition, we detected higher expression levels of MUC5B but not MUC5AC in the CRS group, which suggested a possible role for MUC5B in CRS development. Finally, we found no direct relationship between biofilm presence and mucin expression levels, thereby showing a multifaceted connection between these two major factors implicated in CRS etiology.

Mucus composition abnormalities in sinonasal mucosa of chronic rhinosinusitis with and without nasal polyps

Mucus secretion and its composition are vital in the maintenance of airway health, among which hypoxia-inducible factors (HIFs) are thought to be involved in the regulation of mucin synthesis and regulation. Nasal mucus composition difference between healthy individuals and chronic rhinosinusitis (CRS) patients may contribute to the pathology of chronic nasal diseases, but so far, their role has yet to be completely understood. Nasal biopsy specimens were obtained from 24 healthy subjects and 99 patients with CRS without (CRSsNP, n=36) or with (CRSwNP, n=63) nasal polyps. Immunohistochemical (IHC) and immunofluorescent (IF) staining, quantitative real-time PCR, and western blot were performed to compare the nasal mucus composition between the subjects. Areas of the serous gland and mucous gland were both significantly increased in CRSsNP patients. In CRSwNP patients, a decrease in submucosal gland density and a marked increase in goblet cells were observed. The major gel-forming mucins in the sinonasal mucosa of CRSsNP and CRSwNP are MUC5B and MUC5AC respectively. Mucous cells are found in a higher proportion in both CRSsNP and CRSwNP. The proportion of MUC5AC-positive goblet cells was increased in CRSwNP. The mRNA level of HIF-2α was significantly increased in CRS, and both HIF-1α and HIF-2α were expressed in serous cell but not mucous cell. Over secretion and altered composition of mucus are observed in sinonasal mucosa of CRS, which was mainly associated with glandular hyperplasia in CRSsNP and goblet cell hyperplasia in CRSwNP. Mucus abnormality compromised both non-specific and specific antimicrobial capabilities in the sinonasal mucosa. HIF expression may contribute to differences in mucin synthesis and serous gland regulation, which needs further investigation to understand the pathology of CRS.

MUC1 contributes to goblet cell metaplasia and MUC5AC expression in response to cigarette smoke in vivo

Goblet cell metaplasia (GCM) and mucin overproduction are a hallmark of chronic rhinosinusitis (CRS) and chronic obstructive pulmonary disease (COPD). In the airways, cigarette smoke (CS) induces activation of the epidermal growth factor receptor (EGFR) leading to GCM and overexpression of the gel-forming mucin MUC5AC. Although previous studies have demonstrated that a membrane-bound mucin, MUC1, modulates the activation of CS-induced EGFR, the role of MUC1 in CS-induced GCM and mucin overproduction has not been explored. In response to CS exposure, wild-type (WT) rats displayed Muc1 translocation from the apical surface of airway epithelium to the intracellular compartment of hyperplastic intermediate cells, EGFR phosphorylation, GCM, and Muc5ac overproduction. Similarly, human CRS sinonasal tissues demonstrated hyperplasia of intermediate cells enriched with MUC1 in the intracellular compartment, which was accompanied by GCM and increased MUC5AC expression. To further evaluate the role of Muc1 in vivo, a Muc1 knockout (KO) rat (MUC in humans and Muc in animals) was developed. In contrast to WT littermates, Muc1-KO rats exhibited no activation of EGFR, and were protected from GCM and Muc5ac overproduction. Genetic knockdown of MUC1 in human lung or Muc1 knockout in primary rat airway epithelial cells led to significantly diminished EGF-induced MUC5AC production. Together, these findings suggest that MUC1-dependent EGFR activation mediates CS-induced GCM and mucin overproduction. Strategies designed to suppress MUC1-dependent EGFR activation may provide a novel therapeutic approach for treating mucin hypersecretion in CRS and COPD.

A Comprehensive Systematic Review of the Association Between Airway Mucins and Chronic Rhinosinusitis

Objective

Airway mucins are the major constituents of mucus and one of the first lines of host defense against inhaled pathogens. However, aberrant expression of mucins is associated with mucus hypersecretion resulting in chronic nasal drainage, a common complaint from patients with chronic rhinosinusitis (CRS). Our goal in this systematic review was to determine (1) expression profiles, (2) regulatory mechanisms, and (3) the pathologic roles of mucins associated with CRS.

Methods

MEDLINE, Cochrane Library, Embase, Scopus, Web of Science, and ClinicalTrials.gov were searched for studies focused on the role of mucins in CRS. Quality was assessed using the Cochrane Risk of Bias tool. The full text articles selected were then categorized into 3 study groups: (1) clinical, (2) animal, and (3) in vitro cultures. Data regarding study design, population/setting, methods, and bias were extracted and synthesized.

Results

Our initial search generated 392 titles/abstracts. After the primary review, 111 articles underwent secondary review. The final review included 53 articles, including 34 articles (64%) in the clinical study group, 3 articles (6%) in the animal study group, and 16 articles (30%) in the in vitro study group. In total, aberrant expression of 8 mucins—6 secreted-mucins (MUC2, -5AC, -5B, -6, -7, and -8) and 2 membrane-bound mucins (MUC1 and -4)—were identified in CRS tissues compared to healthy controls. Mucin expression was associated with bacterial sinusitis, inflammatory markers, and the response to steroid therapy in patients with CRS with nasal polyposis.

Conclusion

There is a strong correlation between alterations in mucin expression profiles and CRS. This systematic review highlights the most recent literature on the role of mucins in CRS. The analysis of these studies is limited by the heterogeneity in study designs, relatively few numbers of clinical samples, and lack of mechanistic studies in animal models and in vitro cultures.

Expression of Neu5Acα2,3Gal and Neu5Acα2,6Gal on the nasal mucosa of patients with chronic rhinosinusitis and its possible effect on bacterial biofilm formation

OBJECTIVE

Adherence of pathogen to nasal mucosa and colonization is the first step of bacterial biofilm(BBF) formation in patients with chronic rhinosinusitis (CRS).Terminal sialic acids presenting on cell surface are potential targets for bacterial binding, thus may partly contribute to the pathogenesis of CRS. However, little has been published in this respect, the purpose of our study aimed to investigate the expression of sialic acids on the nasal mucosa in CRS patients and its possible effect on BBF formation.

METHODS

Sinus mucosa were harvested from CRS patients undergoing endoscopic surgery. The positive of BBF formation were detected by scanning electronic microscopy (SEM) and the expression of Neu5Acα2,3Gal(α2,3-linked sialic acid) and Neu5Acα2,6Gal(α2,6-linked sialic acid) on nasal mucosa were determined by fluorescent-immunohistochemical staining (F-IHC) with MAL-II and SNA respectively. A semi-quantitative scoring system was used to assess their different expression between CRS group and the control, as well as BBF positive and negative group.

RESULTS

Expression of Neu5Acα2,3Gal and Neu5Acα2,6Gal were both detected in the epithelium and submucosal glands of all 40 CRS patients and 23 controls, they were significantly up-regulated in CRS group(p < 0.05). Among 24 CRS patients, typical BBF formation were identified in 13 cases while the other 11 were regarded as negative, Between the subgroup of BBF(+) and BBF(-), both of Neu5Acα2,3Gal and Neu5Acα2,6Gal had a trend of increasing in BBF(+) group, however, the increased expression of Neu5Acα2,3Gal was statistical significance (4.77 ± 0.90 versus 3.45 ± 1.40; p = 0.0282), whereas the difference of Neu5Acα2,6Gal was insignificant(4.15 ± 1.27 versus 3.55 ± 1.59; p = 0.4281).

CONCLUSION

Expression of MAL-II binding (most probable Neu5Acα2,3Gal) and SNA binding (Neu5Acα2,6Gal) were up-regulated in inflamed nasal mucosa, and the increased expression of them may contribute to bacterial biofilm formation which deserved a further investigation.

Comparative histochemical analysis of glycoconjugates in the nasal vestibule of camel and sheep

While Corriedale sheep survive in a wide range of climates, which prevents them to specialize for one climatic condition only, dromedary camels strictly adapted to desert areas. This demands more adaptive mechanisms to hot, dry conditions in camels than in sheep. Being the entrance of the nasal cavity, nasal vestibule is subjected to various environmental stressors. A protective way is the lining epithelium which is cornified in camel, but not in sheep. Mucus nasal secretions also play a key role in the protection of underlyings. Additionally, arterio-venous anastomosis is present in the lamina propria of the nasal vestibule of camel. In the present paper, sugar residues in the nasal vestibule of camel were analyzed and compared with those of sheep using 14 types of lectins to explore the distribution of glycoconjugates that may help the function of camel nasal vestibule in desert environment. In camel, none of the lectins could label the basal cells of the vestibular epithelium, although the basal cells reacted with six lectins in sheep. In camel, LEL and RCA-120 markedly labeled the luminal surface. WGA, DBA, SBA, and VVA produced marked intensities on the luminal surface in sheep. The mucous glands reacted with six lectins: WGA, s-WGA, VVA, PNA, PHA-E, and PHA-L in camel, while all lectins used except s-WGA and PHA-E reacted in the sheep. In summary, great differences are observed in the glycoconjugate expression between camel and sheep. This suggests that these glycoconjugate are related to camel's tolerance for environmental stressors.

Glycoconjugates pattern and chemosensory cells in the camel respiratory mucosa: Lectin and immunohistochemical studies

The glycoconjugates pattern of acidic secretions and distribution of chemosensory cells (SCCs) in the respiratory mucosa of dromedary camels were analyzed so as to identify their functional role. Secretions of the goblet cells and mucous glandular cells were analyzed to evaluate the variety of sugar chains, focusing on the acidic glycoconjugates. Using lectin histochemistry, WGA, STL, DBA, SBA, VVA and RCA-120 intensely bound to the goblet cells. PNA and ECL labeled the goblet cells with moderate intensity. While, s-WGA, UEA-I faintly bound to them. Lectins bound to the glycocalyx: WGA, LEL, STL, DSL, DBA, SBA, VVA, RCA-120, ECL and PHA-L (tetra- and tri-antennary N-glycans). The mucous secretory cells reacted with: WGA, s-WGA, STL, DBA, SBA, ECL and Con A. Glycoconjugates secreted by the camel respiratory mucosa are rich in sialomucins, glucosaminy-lated residuals with some galactosyl/galactosaminylated residues; few L-fucose and mannosylated sugar residues are also included. For identification of SCCs, the camel respiratory mucosa was immunostained with phospholipase C-β2 (PLC-β2), a taste signaling marker. Several PLC-β2 immunoreactive cells were detected in camel respiratory epithelium. Finally, prevalence of sialomucins and SCCs which can respond to noxious chemicals may suggest a vital role in optimizing physiological and pathological reactions in camel respiratory mucosa.

Chronic rhinosinusitis as a multifactorial inflammatory disorder

Chronic rhinosinusitis (CRS) is a prevalent health condition characterized by sinonasal mucosal inflammation lasting at least 12 weeks. Heterogeneous in clinical presentation, histopathology, and therapeutic response, CRS represents a spectrum of disease entities with variable pathophysiology. Increased knowledge of cellular and molecular derangements in CRS suggests potential etiologies and targets for therapy. Microbial elements including fungi, staphylococcal enterotoxin, and biofilms have been implicated as inflammatory stimuli, along with airborne irritants and allergens. Defects in innate immunity have gained increased attention as contributors to the chronic inflammatory state. A combination of host susceptibility and environmental exposure is widely believed to underlie CRS, although direct evidence is lacking. Presently, without precise disease definitions and identifiable universal triggers, CRS pathogenesis is broadly described as multifactorial. Current research is beginning to unravel complex and diverse effects of chronic inflammation on sinonasal mucosal homeostasis, but dysfunctional pathways of inflammatory regulation and resolution require further elucidation.

Rheologic properties of sinonasal mucus in patients with chronic sinusitis

BACKGROUND

Mucociliary clearance is impaired in chronic rhinosinusitis (CRS). Clearance of sinonasal secretions is influenced by its rheological properties. The purpose of this study was to describe the rheological properties of sinonasal mucus in patients with CRS and correlate them with disease severity.

METHODS

Twenty-three adult subjects with CRS underwent collection of sinonasal secretions. Samples were analyzed using the AR2000 cone and plate rheometer (TA Instruments, New Castle, DE) to determine the dynamic viscosity and elasticity. These properties were used to calculate mucus clearance indices. All patients completed the Sinonasal Outcome Test (SNOT-20). Recent sinus computed tomography (CT) scans were electronically reviewed and scored according to the Lund-McKay staging system.

RESULTS

The mean dynamic elasticity and viscosity of sinus mucus at 1 Hz were 78.24 +/- 103.4 Pa and 22.09 +/- 29.62 Pa, respectively. The mean elasticity and viscosity values at 10 Hz were 118.9 +/- 155.5 Pa and 32.36 +/- 45.58 Pa, respectively. Three indices of disease severity (SNOT-20 score, Lund-McKay score, and nasal polyps) correlated with increased mucus viscoelasticity and/or worsened mucociliary clearance indices (MCIs).

CONCLUSION

This study establishes the range of rheological properties of sinonasal mucus in patients with CRS and suggests an association between disease severity and MCIs.

The role of innate immunity in the pathogenesis of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a heterogeneous inflammatory condition with a multifactorial basis. Infectious triggers of CRS have been proposed, but demonstration remains elusive. Evolving research suggests that abnormal host mucosal immune responses, rather than specific pathogens themselves, may underlie the chronic inflammatory state. Despite constant contact with airborne particulates and microorganisms, the sinonasal epithelium maintains mucosal homeostasis through innate and adaptive immune mechanisms that eliminate potential threats. Innate immunity encompasses a broad collection of constitutive and inducible processes that can be nonspecific or pathogen directed. Some innate immune pathways are closely intertwined with tissue growth and repair. The persistent inflammation observed in CRS may result from a pathologic imbalance in innate immune interactions between the host and the environment. Impairment of critical innate immune protection renders the sinonasal mucosal surface susceptible to colonization and potential injury, stimulating the prominent adaptive immune response that characterizes CRS.