Epithelium, cilia, and mucus: their importance in chronic rhinosinusitis

Host-microbe interactions in chronic rhinosinusitis biofilms and models for investigation

Chronic rhinosinusitis (CRS) is a debilitating condition characterized by long-lasting inflammation of the paranasal sinuses. It affects a significant portion of the population, causing a considerable burden on individuals and healthcare systems. The pathogenesis of CRS is multifactorial, with bacterial infections playing a crucial role in CRS development and persistence. In recent years, the presence of biofilms has emerged as a key contributor to the chronicity of sinusitis, further complicating treatment and exacerbating symptoms. This review aims to explore the role of biofilms in CRS, focusing on the involvement of the bacterial species Staphylococcus aureus and Pseudomonas aeruginosa, their interactions in chronic infections, and model systems for studying biofilms in CRS. These species serve as an example of how microbial interplay can influence disease progression and exemplify the need for continued investigation and innovation in CRS research.

Unraveling the Role of Epithelial Cells in the Development of Chronic Rhinosinusitis

The pathophysiology of CRS is multifactorial and complex yet needs to be completed. Recent evidence emphasizes the crucial part played by epithelial cells in the development of CRS. The epithelial cells act as physical barriers and play crucial roles in host defense, including initiating and shaping innate and adaptive immune responses. This review aims to present a comprehensive understanding of the significance of nasal epithelial cells in CRS. New research suggests that epithelial dysfunction plays a role in developing CRS through multiple mechanisms. This refers to issues with a weakened barrier function, disrupted mucociliary clearance, and irregular immune responses. When the epithelial barrier is compromised, it can lead to the passage of pathogens and allergens, triggering inflammation in the body. Furthermore, impaired mucociliary clearance can accumulate pathogens and secretions of inflammatory mediators, promoting chronic inflammation. Epithelial cells can release cytokines and chemokines, which attract and activate immune cells. This can result in an imbalanced immune response that continues to cause inflammation. The interaction between nasal epithelial cells and various immune cells leads to the production of cytokines and chemokines, which can either increase or decrease inflammation. By comprehending the role of epithelial cells in CRS, we can enhance our understanding of the disease's pathogenesis and explore new therapeutics.

Topical Administration of Verapamil in Poly(ethylene glycol)-Modified Liposomes for Enhanced Sinonasal Tissue Residence in Chronic Rhinosinusitis: Ex Vivo and In Vivo Evaluations

Verapamil is a calcium channel blocker that holds promise for the therapy of chronic rhinosinusitis (CRS) with and without nasal polyps. The verapamil-induced side effects limit its tolerated dose via the oral route, underscoring the usefulness of localized intranasal administration. However, the challenge to intranasal administration is mucociliary clearance, which diminishes localized dose availability. To overcome this challenge, verapamil was loaded into a mucoadhesive cationic poly(ethylene glycol)-modified (PEGylated) liposomal carrier. Organotypic nasal explants were exposed to verapamil liposomes under flow conditions to mimic mucociliary clearance. The liposomes resulted in significantly higher tissue residence compared with the free verapamil control. These findings were further confirmed in vivo in C57BL/6 mice following intranasal administration. Liposomes significantly increased the accumulation of verapamil in nasal tissues compared with the control group. The developed tissue-retentive verapamil liposomal formulation is considered a promising intranasal delivery system for CRS therapy.

Cilia Stimulatory and Antibacterial Activities of T2R Bitter Taste Receptor Agonist Diphenhydramine: Insights into Repurposing Bitter Drugs for Nasal Infections

T2R bitter taste receptors in airway motile cilia increase ciliary beat frequency (CBF) and nitric oxide (NO) production. Polymorphisms in some T2Rs are linked to disease outcomes in chronic rhinosinusitis (CRS) and cystic fibrosis (CF). We examined the expression of cilia T2Rs during the differentiation of human nasal epithelial cells grown at air–liquid interface (ALI). The T2R expression increased with differentiation but did not vary between CF and non-CF cultures. Treatment with Pseudomonas aeruginosa flagellin decreased the expression of diphenhydramine-responsive T2R14 and 40, among others. Diphenhydramine increased both NO production, measured by fluorescent dye DAF-FM, and CBF, measured via high-speed imaging. Increases in CBF were disrupted after flagellin treatment. Diphenhydramine impaired the growth of lab and clinical strains of P. aeruginosa, a major pathogen in CF and CF-related CRS. Diphenhydramine impaired biofilm formation of P. aeruginosa, measured via crystal violet staining, as well as the surface attachment of P. aeruginosa to CF airway epithelial cells, measured using colony-forming unit counting. Because the T2R agonist diphenhydramine increases NO production and CBF while also decreasing bacterial growth and biofilm production, diphenhydramine-derived compounds may have potential clinical usefulness in CF-related CRS as a topical therapy. However, utilizing T2R agonists as therapeutics within the context of P. aeruginosa infection may require co-treatment with anti-inflammatories to enhance T2R expression.

Erythromycin reduces nasal inflammation by inhibiting immunoglobulin production, attenuating mucus secretion, and modulating cytokine expression

Allergic rhinitis (AR) and chronic rhinosinusitis (CRS) share some similar pathological mechanisms. In current study, we intend to investigate the impact of AR on CRS. In addition, we explored the efficacy of erythromycin (EM) treatment on CRS mice with or without AR (CRSwoAR, CRSwAR). Study subjects were divided into control, CRSwoAR, and CRSwAR groups. Experimental mice were divided similarly into control, CRSwoAR, and CRSwAR groups. In addition, CRS mice were treated with EM at 0.75, 7.5, or 75 mg/kg or with dexamethasone (Dex) at 1 mg/kg. In our results, allergy exacerbates inflammation that was evident in nasal histology and cytokine expression both in patients and in mice with CRS. Dex 1 mg/kg, EM 7.5 or 75 mg/kg treatments significantly inhibited serum IgE and IgG2a in CRS mice. EM-treated CRS mice had significantly elevated IL-10 levels and had a reversal of Th-1/Th-2 cytokine expression in nasal-associated lymphoid tissue. MUC5AC expressions were significantly reduced in the 7.5 or 75 mg/kg EM-treated mice compared with untreated mice. EM showed inhibitions on immunoglobulin production and mucus secretion stronger than Dex. We concluded that comorbid AR enhanced inflammation of CRS. EM and Dex treatments showed similar anti-inflammatory effects on CRS but through partly different mechanisms.

In Vitro Ciliotoxicity and Cytotoxicity Testing of Repeated Chronic Exposure to Topical Nasal Formulations for Safety Studies

Certain active drugs and excipients of nasal formulations may impair ciliary function and mucociliary clearance. The ciliary beat frequency (CBF) is a key parameter for determining mucociliary clearance rate, and in vitro assessments of CBF have proven to be accurate and reproducible. Since topical nasal formulations are applied with repeated doses, it is essential to elucidate their chronic, as opposed to acute, effect on mucociliary clearance and nasal mucosa. The aim of this study was to assess for the first time the ciliotoxicity and cytotoxicity of nasal sprays intended for chronic treatment (with repeated doses) using a previously designed set-up for CBF measurements. For 2 weeks, the 3D nasal MucilAir™ in vitro models were treated daily with undiluted or clinically relevant doses of mometasone nasal spray, placebo nasal spray, culture medium, or they were untreated. We demonstrated a dose-dependent and time-dependent (cumulative) effect of the nasal sprays on ciliary activity and cytotoxicity using CBF measurements and ultrastructural analysis, respectively. Our results indicate that repeated administration of clinically relevant doses of mometasone nasal spray is safe for in vivo use, which is in good agreement with a previous clinical study. Overall, our study suggests that such in vitro assays have great potential for topical nasal drug screening.

Sinonasal Tissue Remodelling during Chronic Rhinosinusitis

The purpose of this review is to summarise contemporary knowledge of sinonasal tissue remodelling during chronic rhinosinusitis (CRS), a chronic disease involving long-term inflammation of the paranasal sinuses and nasal passage. The concept of tissue remodelling has significant clinical relevance because of its potential to cause irreversibility in chronic airway tissues. Recent studies have indicated that early surgical treatment of CRS may improve clinical outcome. Tissue remodelling has been described in the literature extensively with no consensus on how remodelling is defined. This review describes various factors implicated in establishing remodelling in sinonasal tissues with a special mention of asthma as a comorbid condition. Some of the main histological features of remodelling include basement membrane thickening and collagen modulation. This may be an avenue of research with regard to targeted therapy against remodelling in CRS.

International consensus statement on allergy and rhinology: rhinosinusitis 2021

I.

EXECUTIVE SUMMARY

BACKGROUND: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR-RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR-RS-2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence-based findings of the document.

METHODS

ICAR-RS presents over 180 topics in the forms of evidence-based reviews with recommendations (EBRRs), evidence-based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary.

RESULTS

ICAR-RS-2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence-based management algorithm is provided.

CONCLUSION

This ICAR-RS-2021 executive summary provides a compilation of the evidence-based recommendations for medical and surgical treatment of the most common forms of RS.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

Inhaled RNA Therapeutics for Obstructive Airway Diseases: Recent Advances and Future Prospects

Obstructive airway diseases, e.g., chronic obstructive pulmonary disease (COPD) and asthma, represent leading causes of morbidity and mortality worldwide. However, the efficacy of currently available inhaled therapeutics is not sufficient for arresting disease progression and decreasing mortality, hence providing an urgent need for development of novel therapeutics. Local delivery to the airways via inhalation is promising for novel drugs, because it allows for delivery directly to the target site of action and minimizes systemic drug exposure. In addition, novel drug modalities like RNA therapeutics provide entirely new opportunities for highly specific treatment of airway diseases. Here, we review state of the art of conventional inhaled drugs used for the treatment of COPD and asthma with focus on quality attributes of inhaled medicines, and we outline the therapeutic potential and safety of novel drugs. Subsequently, we present recent advances in manufacturing of thermostable solid dosage forms for pulmonary administration, important quality attributes of inhalable dry powder formulations, and obstacles for the translation of inhalable solid dosage forms to the clinic. Delivery challenges for inhaled RNA therapeutics and delivery technologies used to overcome them are also discussed. Finally, we present future prospects of novel inhaled RNA-based therapeutics for treatment of obstructive airways diseases, and highlight major knowledge gaps, which require further investigation to advance RNA-based medicine towards the bedside.

Non-Reflex Defense Mechanisms of Upper Airway Mucosa: Possible Clinical Application

The sinonasal mucosa has an essential role in defense mechanisms of the upper respiratory tract. The innate immune system presents the primary defense against noxious microorganisms followed by induction of the adaptive immune mechanisms as a consequence of the presence of pathogens. This well-known activation of adaptive immune system in response to presence of the antigen on mucosal surfaces is now broadly applicated in vaccinology research. Prevention of infectious diseases belongs to substantial challenges in maintaining the population health. Non-invasive, easily applicable mucosal vaccination purposes various research opportunities that could be usable in daily practice. However, the existence of multiple limitations such as rapid clearance of vaccine from nasal mucosa by means of mucociliary transport represents a great challenge in development of safe and efficient vaccines. Here we give an updated view on nasal functions with focus on nasal mucosal immunity and its potential application in vaccination in nearly future.

Taste Receptors in Upper Airway Innate Immunity

Taste receptors, first identified on the tongue, are best known for their role in guiding our dietary preferences. The expression of taste receptors for umami, sweet, and bitter have been demonstrated in tissues outside of the oral cavity, including in the airway, brain, gastrointestinal tract, and reproductive organs. The extra-oral taste receptor chemosensory pathways and the endogenous taste receptor ligands are generally unknown, but there is increasing data suggesting that taste receptors are involved in regulating some aspects of innate immunity, and may potentially control the composition of the nasal microbiome in healthy individuals or patients with upper respiratory diseases like chronic rhinosinusitis (CRS). For this reason, taste receptors may serve as potential therapeutic targets, providing alternatives to conventional antibiotics. This review focuses on the physiology of sweet (T1R) and bitter (T2R) taste receptors in the airway and their activation by secreted bacterial products. There is particular focus on T2R38 in sinonasal ciliated cells, as well as the sweet and bitter receptors found on specialized sinonasal solitary chemosensory cells. Additionally, this review explores the impact of genetic variations in these receptors on the differential susceptibility of patients to upper airway infections, such as CRS.

Responses of Well-differentiated Human Sinonasal Epithelial Cells to Allergen Exposure and Environmental Pollution in Chronic Rhinosinusitis

Background

Evidence suggests that intrinsic cell dysfunction leads to dysregulated immune responses to environmental triggers in chronic rhinosinusitis (CRS). Although epidemiological and in vivo studies support this theory, in vitro studies are lacking.

Methods

Epithelial cells from human sinonasal mucosa were cultured using an air–liquid interface culture model producing a well-differentiated phenotype. Specimens were characterized as chronic rhinosinusitis with (CRSwNP) or without (CRSsNP) nasal polyps and healthy control mucosa. Culture wells were exposed to house dust mite (HDM), diesel exhaust particles (DPM), or a combination (HDM + DPM) over 24 hours and responses in the 3 groups compared. Ciliary beat frequency (CBF) and transepithelial electrical resistance (TEER) were measured to assess mucociliary and barrier function, respectively. Interleukin-6 (IL-6) and 33 (IL-33) were measured after 24 hours. Results following challenge testing are expressed as fold change from baseline.

Results

Baseline CBF was lower in CRSsNP compared with control (5.27 ± 0.51 Hz vs 5.88 ± 1.22 Hz, P = .003). HDM significantly reduced CBF and TEER in the CRSwNP group compared with its vehicle (CBF: 0.55 ± 0.25 vs 1.03 ± 0.22, P < .001; TEER: 0.54 [0.13] Ω cm2 vs 0.93 [0.5] Ω cm2, P = .001). In CRSwNP and CRSsNP, HDM induced an increase in IL-6 compared with its vehicle (CRSwNP: 81.11 [67.19] pg/mL vs 3.15 [44.64] pg/mL, P = .016; CRSsNP: 321.46 [182.04] pg/mL vs 21.54 [53.93] pg/mL, P = .004). Results are expressed as median (interquartile range) and in IL-33 in CRswNP (84.04 [69.96] pg/mL vs 16.62 [20.19] pg/mL, P = .025). Exposure to DPM did not affect CBF, TEER, and cytokine release in all groups.

Conclusion

CRSwNP and CRSsNP cells exhibit altered responses particularly to HDM even after they have been removed from their host and cultured in vitro, suggesting an intrinsic cell dysfunction of the upper airway epithelium.

Aberrant localization of FOXJ1 correlates with the disease severity and comorbidities in patients with nasal polyps

Background

Upper airway inflammatory diseases are associated with abnormal expression of nasal epithelial forkhead-box J1 (FOXJ1) which regulates motile cilia formation. We sought to investigate whether aberrant FOXJ1 localizations correlate with the disease severity and the co-existence of allergic rhinitis (AR) or asthma in patients with nasal polyps (NPs).

Methods

We elucidated localization patterns of FOXJ1 by performing immunofluorescence assays in nasal specimens and cytospin samples from controls and patients with NPs. We also assayed mRNA expression levels of FOXJ1 by using quantitative real-time polymerase chain reaction. Four localization patterns [normal (N), intermediate (I), mislocalization (M), and absence (A)] were defined. A semi-quantitative scoring system was applied for demonstrating FOXJ1 localization in five areas per paraffin section, with individual sections being scored between 0 and 2.

Results

FOXJ1 localization score was significantly higher in samples from NPs than in controls (P < 0.001). Elevated FOXJ1 localization scores and down-regulation of FOXJ1 mRNA levels were observed in NPs with co-existing AR or asthma (all P < 0.05). Moreover, FOXJ1 localization scores positively correlated with Lund–Mackay score (r = 0.362, P = 0.007). Of primary cytospin samples, the mean percentage of patients with FOXJ1 localization patterns N, I, M and A was 15.0%, 3.3%, 53.3% and 28.3% in NPs, and 82.5%, 5.0%, 5.0% and 7.5% in controls, respectively (P < 0.001).

Conclusions

Aberrant localization of FOXJ1 correlates with the severity and co-existence of AR or asthma in patients with NPs, and might be a novel target for assessment and intervention in NPs.

Electronic supplementary material

The online version of this article (10.1186/s13223-018-0296-z) contains supplementary material, which is available to authorized users.

Exosome swarms eliminate airway pathogens and provide passive epithelial immunoprotection through nitric oxide

BACKGROUND

Nasal mucosa-derived exosomes (NMDEs) harbor immunodefensive proteins and are capable of rapid interepithelial protein transfer.

OBJECTIVES

We sought to determine whether mucosal exposure to inhaled pathogens stimulates a defensive swarm of microbiocidal exosomes, which also donate their antimicrobial cargo to adjacent epithelial cells.

METHODS

We performed an institutional review board-approved study of healthy NMDE secretion after Toll-like receptor (TLR) 4 stimulation by LPS (12.5 μg/mL) in the presence of TLR4 inhibitors. Interepithelial transfer of exosomal nitric oxide (NO) synthase and nitric oxide was measured by using ELISAs and NO activity assays. Exosomal antimicrobial assays were performed with Pseudomonas aeruginosa. Proteomic analyses were performed by using SOMAscan.

RESULTS

In vivo and in vitro LPS exposure induced a 2-fold increase in NMDE secretion along with a 2-fold increase in exosomal inducible nitric oxide synthase expression and function through TLR4 and inhibitor of nuclear factor κB kinase activation. LPS stimulation increased exosomal microbiocidal activity against P aeruginosa by almost 2 orders of magnitude. LPS-stimulated exosomes induced a 4-fold increase in NO production within autologous epithelial cells with protein transfer within 5 minutes of contact. Pathway analysis of the NMDE proteome revealed 44 additional proteins associated with NO signaling and innate immune function.

CONCLUSIONS

We provide direct in vivo evidence for a novel exosome-mediated innate immunosurveillance and defense mechanism of the human upper airway. These findings have implications for lower airway innate immunity, delivery of airway therapeutics, and host microbiome regulation.

Exosomes and chronic rhinosinusitis

The objective of this manuscripts to review current knowledge regarding exosomes as they relate to the physiology and pathology of the human nose as well as their role as biomarkers of chronic rhinosinusitis with nasal polyps (CRSwNP).

Exosomes are 30–150 nm membrane-bound vesicles secreted by virtually all cell types. Exosomes contribute to the rapid inter-epithelial transfer of proteins and mediate innate immunosurveillance and defense mechanisms in the human nasal cavity. Exosomes also protect their cell specific cargo from degradation by nucleases and proteases and mirrorCRS related tissue protein perturbations more effectively than whole mucus. Thus, exosomal isolation and analysis may be used to non-invasively monitor disease severity, prognosis, and potentially even treatment response.

Recent studies of exosomes in CRS suggest they can be used to study the immunopathology of chronic sinonasal inflammation. Furthermore, their relative accessibility suggests that exosomal proteomescan be used as non-invasive, serial, and quantitative biosignatures for rhinosinusitis that can be sampled in clinic in order to predict disease severity, prognosis, and treatment response. Exosomal research has also led to important revelations regarding their physiologic function as they seem to play an important role in innate immunosurveillance and defense. However, exosomal research is still nascent and cost-effectiveness as well as feasibility of implementation in the routine workup for CRS have to be further explored.

A synthetic glycosaminoglycan reduces sinonasal inflammation in a murine model of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is characterized by sustained mucosal inflammation, impaired mucociliary clearance, loss of cilia and epithelial barrier breakdown, and tissue remodeling. Certain glycosaminoglycans inhibit various inflammatory mediators, suppress bacterial growth, and provide important functions in mucosal tissue repair and mucociliary clearance. Herein, we evaluated the effects of a synthetic glycosaminoglycan, GM-1111, on the clinical signs and inflammatory tissue changes associated with CRS in mice. CRS was generated by repeated intranasal applications of Aspergillus fumigatus (A. fumigatus) extracts over 4 weeks. Mice were then intranasally administered GM-1111 (600 μg per dose, 5 times a week) or vehicle (phosphate buffered saline, PBS) for an additional 4 weeks while still being given A. fumigatus extracts to maintain a chronic inflammatory environment with acute exacerbations. Clinical signs indicative of sinonasal inflammation were recorded throughout the study. After 9 weeks, whole blood and sinonasal tissues were harvested for hematological, histological, and biochemical examination. The clinical signs, white blood cell counts, tissue markers of sinonasal inflammation, and histological changes caused by A. fumigatus extract administration were compared to the healthy (PBS vehicle) and GM-1111-treated groups (n = 12 per treatment group). Compared to vehicle-treated animals, animals treated with GM-1111 demonstrated significant reductions in clinical signs (p<0.05), degenerative tissue changes, goblet cell hyperplasia, inflammatory cell infiltration (p<0.01), innate immunity- (tlr2, tlr4, myd88, il1b, tnfa, il6, and il12) and adaptive immunity-associated (ccl11, ccl24, ccl5, il4, il5, and il13) cytokine gene expression (p<0.05 to p<0.0001) in sinonasal tissues, and serum IgE levels (p<0.01). Our data suggest that GM-1111 significantly reduces local and systemic effects of CRS-associated sinonasal inflammation.

Influence of MP 29-02 on ciliary beat frequency in human epithelial cells in vitro

PURPOSE

MP 29-02, which contains fluticasone propionate and azelastine hydrochloride, is used as a topical nasal application for the treatment of seasonal and perennial allergic rhinitis. Although a multitude of data is available on the clinical symptom reduction and treatment safety of MP 29-02, the effect of MP 29-02 on ciliary beat frequency (CBF) has not been evaluated thus far.

METHODS

MP 29-02-containing solution was applied at concentrations of 2.5, 5, 10, and 20% to 14 healthy subjects, and nasal ciliated epithelial cells were then visualized using a phase-contrast microscope. CBF was measured after the application of MP 29-02. For a comparison, fluticasone propionate was used. CBF measurements were then performed for 15 min at 22 °C. Ringer's solution was applied as a negative control.

RESULTS

MP 29-02 significantly reduced CBF at all the tested concentrations compared with that of the control group within the observation time. At a 2.5% concentration, MP 29-02 significantly reduced CBF from 6.81 Hz (SD ± 1.35 Hz) at baseline to 4.88 Hz (SD ± 1.52 Hz, p < 0.001) after 15 min. In contrast, for fluticasone propionate, a significant reduction was observed only with the 20% concentration after 5, 10, and 15 min.

CONCLUSIONS

MP 29-09 significantly reduced CB, with an almost linear relationship between the MP 29-09 concentration and reduction in CBF. For fluticasone propionate, a significant reduction of CBF was observed only at the highest analyzed concentration. The findings have implications for the long-term use of the MP 29-02. Yet, further clinical studies are needed to confirm these results in vivo, especially in patients with seasonal or perennial allergic rhinits.

Taste receptors in the upper airway

Taste receptors were named for their originally-identified expression on the tongue and role in the sensation of taste (gustation). They are now known to be involved in many chemosensory processes outside the tongue. Expression of the receptors for bitter, sweet, and umami was recently identified in many organs, including the brain, airway, gastrointestinal tract, and reproductive systems. We do not yet know the full roles of these receptors in all of these tissues, nor do we know all of the endogenous ligands that activate them. However, taste receptors are emerging as potentially important therapeutic targets. Moreover, they may mediate some off target effects of drugs, as many medications in common clinical use are known to be bitter. The focus of this review is on recent basic and clinical data describing the expression of bitter (T2R) and sweet (T1R) receptors in the airway and their activation by secreted bacterial compounds. These receptors play important roles in innate immune nitric oxide production and antimicrobial peptide secretion, and may be useful targets for stimulating immune responses in the upper respiratory tract via topical therapies. Moreover, genetic variation in these receptors may play a role in the differential susceptibility of patients to certain types of respiratory infections as well as to differential outcomes in patients with chronic rhinosinusitis (CRS). CRS is a syndrome of chronic upper respiratory infection and inflammation and has a significant detrimental impact on patient quality of life. CRS treatment accounts for approximately 20% of adult antibiotic prescriptions and is thus a large driver of the public health crisis of antibiotic resistance. Taste receptors represent a novel class of therapeutic target to potentially stimulate endogenous immune responses and treat CRS patients without conventional antibiotics.

Taste Receptor Polymorphisms and Immune Response: A Review of Receptor Genotypic-Phenotypic Variations and Their Relevance to Chronic Rhinosinusitis

Bitter (T2R) and sweet taste (T1R) receptors have emerged as regulators of upper airway immune responses. Genetic variation of these taste receptors additionally confers susceptibility to infection and has been implicated in severity of disease in chronic rhinosinusitis (CRS). Ongoing taste receptor research has identified a variety of biologically active compounds that activate T1R and T2R receptors, increasing our understanding of not only additional receptor isoforms and their function but also how receptor function may contribute to the pathophysiology of CRS. This review will discuss the function of taste receptors in mediating airway immunity with a focus on recently described modulators of receptor function and directions for future research into the potential role of genotypic and phenotypic receptor variation as a predictor of airway disease and response to therapy.

Absence or mislocalization of DNAH5 is a characteristic marker for motile ciliary abnormality in nasal polyps

OBJECTIVE

Motile cilia impairment is a common condition in patients with chronically inflamed airways, such as is seen in nasal polyps (NPs). The mechanism underlying this pathogenic condition is complex and not fully understood.

METHODS

We investigated the presence and localization of dynein axonemal heavy chain 5 (DNAH5) in motile cilia using immunofluorescence staining in paraffin-embedded nasal biopsies from NPs (n = 120) and inferior turbinate mucosa (n = 35) of healthy controls. We also performed single-cell staining on cytospin samples (NP = 5, control = 5). Three patterns of DNAH5 localization are defined, including pattern A (presence throughout the axoneme), pattern B (undetectable in the distal part of the axoneme), and pattern C (completely missing throughout the entire axoneme). We developed a semiquantitative scoring system for which 0 = (pattern A > 70%); 1 = (patterns A + B > 70%); and 2 = (pattern C ≥ 30%) in each high-power field (5 fields per sample).

RESULTS

Based on our DNAH5 scoring system, the median (1st and 3rd quartile) score was 0.3 (0.2 and 0.4) for samples from controls, and 1.1 (0.6 and 1.6) for samples from NPs in paraffin specimens (P < 0.001). The DNAH5 score had a significant positive relationship with the Lund-Mackay computed tomography score (r = 0.329, P = 0.005) and was higher in patients with eosinophilic NPs (P = 0.006). For cytospin samples, the mean percentage of patterns A, B, and C were 74%, 14%, and 12% in controls, and 48%, 20%, and 32% in NPs, respectively.

CONCLUSION

Our results suggest that the absence or mislocalization of DNAH5 from motile cilia is a common and potentially important pathological phenomenon in chronically inflamed airway epithelium.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:E97-E104, 2018.

Models for the study of nasal and sinus physiology in health and disease: A review of the literature

Objective

Chronic sinusitis is a very common yet poorly understood medical condition with significant morbidity. Hence, it remains an entity that is difficult to treat with unsatisfactory outcomes of current management options. This necessitates research into the etiology and pathophysiology of the condition to enhance our knowledge and the therapeutic options. Unfortunately, this kind of research is not always feasible on human subjects due to practical and ethical limitations. Therefore, an alternative model that simulates the disease had to be found in order to overcome these limitations. These models could either be in vivo or in vitro. The aim of our review is to summarize the research findings and key discoveries of both in vivo and in vitro models of chronic sinusitis that have enhanced our understanding of the condition today and have paved the way for the future research of tomorrow.

Data Sources: PubMed literature review.

Methods

A review of the literature was conducted to identify the main successful in vivo and in vitro models for chronic sinusitis.

Results

Creating a successful model for chronic sinusitis is no easy task. Over the years, both in vivo animal models and in vitro tissue culture models were proposed, with each model having its accolades and pitfalls, with the ideal model remaining elusive to this day. However, advancing three‐dimensional cell culturing techniques seems to be a promising new way to find a more accurate model.

Conclusion

None of the current models is perfect for a thorough study of chronic sinusitis. However, three‐dimensional cell cultures have the potential to bridge the gap between in vivo and in vitro studies.

Level of Evidence

NA

Chronic Rhinosinusitis without Nasal Polyps

Chronic rhinosinusitis without nasal polyps (CRSsNP) is more prevalent than chronic rhinosinusitis with nasal polyps (CRSwNP). Certain diseases predispose to whereas others are associated with CRSsNP. Predisposing diseases include allergic and nonallergic upper and lower airway diseases, epithelial cell disorders, immunodeficiencies, autoimmune diseases, and some infectious diseases. In addition, environmental and host factors, examples of which include smoking, a higher incidence of abnormal biofilms, and innate immune defects, play a role in the pathogenesis of this disease. CRSsNP is characterized by histologic abnormalities, including basement membrane thickening (fibrosis) and goblet cell hyperplasia. Neutrophils and several chemokines, TGF-β and C-X-C motif chemokine ligand (CXCL)-8, play a role in CRSsNP remodeling. However, there are conflicting data about CRSsNP endotypes, for example, whether it is characterized by neutrophilia or eosinophilia or both. In spite of advancements and the understanding of the pathogenesis of this disease, additional study is necessary to better comprehend its underlying mechanisms, endotypes, and evidence-based treatment strategies.

Neuroendocrine cells derived chemokine vasoactive intestinal polypeptide (VIP) in allergic diseases

Worldwide increase incidences of allergic diseases have heightened the interest of clinicians and researchers to understand the role of neuroendocrine cells in the recruitment and activation of inflammatory cells. Several pieces of evidence revealed the association of neuropeptides in the pathogenesis of allergic diseases. Importantly, one such peptide that is secreted by neuronal cells and immune cells exerts a wide spectrum of immunological functions as cytokine/chemokine is termed as Vasoactive Intestinal Peptide (VIP). VIP mediates immunological function through interaction with specific receptors namely VPAC-1, VPAC-2, CRTH2 and PAC1 that are expressed on several immune cells such as eosinophils, mast cells, neutrophils, and lymphocytes; therefore, provide the basis for the action of VIP on the immune system. Additionally, VIP mediated action varies according to target organ depending upon the presence of specific VIP associated receptor, involved immune cells and the microenvironment of the organ. Herein, we present an integrative review of the current understanding on the role of VIP and associated receptors in allergic diseases, the presence of VIP receptors on various immune cells with particular emphasis on the role of VIP in the pathogenesis of allergic diseases such as asthma, allergic rhinitis, and atopic dermatitis. Being crucial signal molecule of the neuroendocrine-immune network, the development of stable VIP analogue and/or antagonist may provide the future therapeutic drug alternative for the better treatment of these allergic diseases. Taken together, our current review summarizes the current understandings of VIP biology and further explore the significance of neuroendocrine cells derived VIP in the recruitment of inflammatory cells in allergic diseases that may be helpful to the investigators for planning the experiments and accordingly predicting new therapeutic strategies for combating allergic diseases. Summarized graphical abstract will help the readers to understand the significance of VIP in allergic diseases.

Chemosensory function before and after multimodal treatment in chronic rhinosinusitis patients

OBJECTIVES/HYPOTHESIS

Olfactory dysfunction is common among the general population, with chronic rhinosinusitis (CRS) as one of the leading causes. Patients affected by CRS often report changes in taste sensations; however, quantitative measurements have not been performed to date. Therefore, the present study aimed to investigate gustatory and olfactory function in CRS patients prior to and after multimodal treatment.

STUDY DESIGN

Prospective cohort study.

METHODS

Twenty-one patients suffering from CRS with nasal polyps (14 male, seven female) with a mean age of 48 ± 15 years were included in the study. Chemosensory function was assessed prior to and approximately 190 days after multimodal treatment, which included endoscopic sinus surgery, oral antibiotics for 5 days, oral steroids for 12 days, and at least 6 weeks of topical nasal steroids. Olfactory function was tested with the Sniffin' Sticks test battery, whereas gustatory function was measured with taste strips. A clinically relevant change in olfactory function was defined as a change of ≥5 points in the threshold, discrimination, and identification scores.

RESULTS

Compared to normative data, patients baseline gustatory and olfactory function was impaired. After multimodal treatment, improvements were seen in olfactory function for eight patients (42%), remained stable in 10 patients (53%), and deteriorated in one patient (5%). Taste function remained unchanged following sinus surgery.

CONCLUSIONS

Patients suffering from CRS with polyps exhibit olfactory and taste dysfunctions. Multimodal treatment leads to an improvement in olfactory, but not gustatory functionality.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:E86-E90, 2018.

Radiofrequency volumetric inferior turbinate reduction: long-term clinical results

The aim of our study was to assess long-term results of radiofrequency volumetric tissue reduction of inferior turbinates (RVTR). We performed a prospective long-term longitudinal evaluation of 305 patients affected by rhinitis (114 allergic and 191 non-allergic) who were unresponsive to medical treatment and underwent RVTR (January 2004 - December 2010). Subjects were followed for a mean period of 39.70 ± 19.41 months (range 24-60). Patients completed the NOSE-scale questionnaire pre- and post-operatively after 1 month and yearly for 5-years. Recurrence was assumed if the post-operative total NOSE score increased by at least 75% during follow-up and the patient restarted medical treatments. Estimation of relapse over time was performed by Kaplan-Meyer analyses. We documented overall good satisfaction of patients regarding the procedure, with a good rate of pain control and a low rate of complications. Post-operatively there was a significant improvement in nasal stuffiness, nasal obstruction and mouth breathing (p < 0.05). We observed a worsening trend for symptoms after 36 months with progressive increasing rate of recurrences that were significantly higher in allergic than non-allergic patients (p < 0.05). We also observed a slight worsening trend of global satisfaction of patients. Our study confirms the minor discomfort and low risk of side effects of RVTR. Our data showed good efficacy of the procedure in the majority of patients for at least 36 months after surgery, and in fact in this time period the cumulative probability to remain relapse-free was up to 0.8. In the following 2 years, we observed a worse temporal trend in term of recurrence rate, and in particular in allergic patients with a significant difference vs non-allergic individuals (p < 0.05).

The in vitro mucolytic effect of xylitol and dornase alfa on chronic rhinosinusitis mucus

BACKGROUND

The overproduction and stagnation of purulent mucus impair mucociliary clearance and exacerbate the symptoms of chronic rhinosinusitis (CRS). There is a clinical need for effective topical mucolytic agents to facilitate removal of mucus and improve postoperative outcomes.

METHODS

The effects of xylitol (5%) and dornase alfa (1 mg/mL) on mucus and mucus crusts were investigated. Viscoelasticity and viscosity of wet mucus derived from 30 CRS patients was measured with a plate rheometer. Postoperative dried mucus crust dissolution was measured by examining peripheral transparency, central transparency, and border definition of treated crust samples from 17 CRS patients.

RESULTS

Xylitol and dornase alfa reduced wet mucus viscoelasticity at a frequency of 0.1 Hz significantly more than the saline control. Treatments also produced significantly lower viscosities than saline at a shear rate of 10 and 100 seconds^-1 . Xylitol and dornase alfa significantly decreased mucus crust border definition relative to saline.

CONCLUSION

Xylitol and dornase alfa may be efficacious mucolytics, encouraging the breakdown of postoperative mucus crusts and the reduction of viscoelasticity and viscosity of wet mucus. In vivo study is required to evaluate the potential of these agents in treating recalcitrant CRS.

Healing of the nasal septal mucosa in an experimental rabbit model of mucosal injury

Objective

The aim of this study was to investigate the regeneration process of the nasal mucosa after a surgically created mucosal defect in the rabbit nasal septum, and to evaluate the effects of different interventions.

Methods

A 7 mm-diameter circular mucosal defect was made in the septum of forty New Zealand white rabbits. The rabbits were divided into four groups (ten rabbits in each group) according to the type of intervention; no treatment (control), silastic sheet (SS), hyaluronic acid (HA), and silastic sheet and hyaluronic acid (SS + HA) group. The diameter of the defect, mucosal thickness, epithelial thickness, and ciliated cell count were evaluated every week for five weeks.

Results

The average diameter of the defect in the control group were 5.1, 3.65, 1.2, 0.75, and 0.05 mm at postoperative 1, 2, 3, 4, and 5 weeks. In the SS group, the diameter decreased to 4.35, 2.1, 0.35, 0.15, and 0 mm at postoperative 1, 2, 3, 4, and 5 weeks, respectively, in which the mean diameter of the postoperative week 2 was significantly smaller compared to control (3.65 mm vs. 2.1 mm, P = 0.039). For the HA group and SS + HA group, the diameter of the defect did not show a significant difference from the control group during the five weeks. The mucosal thickness, epithelial thickness, and ciliated cell count of the regenerated mucosa were not significantly different among the groups.

Conclusion

The regeneration process of the nasal septal mucosa was identified using a novel rabbit model. Mucosal regeneration can be accelerated by applying silastic sheets.

Taste Receptors Mediate Sinonasal Immunity and Respiratory Disease

The bitter taste receptor T2R38 has been shown to play a role in the pathogenesis of chronic rhinosinusitis (CRS), where the receptor functions to enhance upper respiratory innate immunity through a triad of beneficial immune responses. Individuals with a functional version of T2R38 are tasters for the bitter compound phenylthiocarbamide (PTC) and exhibit an anti-microbial response in the upper airway to certain invading pathogens, while those individuals with a non-functional version of the receptor are PTC non-tasters and lack this beneficial response. The clinical ramifications are significant, with the non-taster genotype being an independent risk factor for CRS requiring surgery, poor quality-of-life (QOL) improvements post-operatively, and decreased rhinologic QOL in patients with cystic fibrosis. Furthermore, indirect evidence suggests that non-tasters also have a larger burden of biofilm formation. This new data may influence the clinical management of patients with infectious conditions affecting the upper respiratory tract and possibly at other mucosal sites throughout the body.

IL-13 regulates human nasal epithelial cell differentiation via H3K4me3 modification

Introduction

Epigenetic regulation has been shown to play an important role in the development of inflammatory diseases, including chronic rhinosinusitis and nasal polyps. The latter are characterized by epithelial mis-differentiation and infiltration of inflammatory cytokines. H3K4me3 has been shown to be involved in regulating lineage commitment. However, the underlying mechanisms, especially in human nasal epithelial cells (HNEpC), remain underexplored. The objective of this study was to investigate the role of H3K4me3 in HNEpC differentiation treated with the Th2 cytokine IL-13.

Patients and methods

The expression levels of mRNA and proteins were investigated using reverse transcription-polymerase chain reaction (RT-PCR) assays and Western blot in nasal polyp tissues and human nasal epithelial cells respectively. We measured these levels of H3K4me3, MLL1 and targeted genes compared with control subjects.

Results

We demonstrate that expression of H3K4me3 and its methyltransferase MLL1 was significantly upregulated in IL-13-treated HNEpC. This elevation was also observed in nasal polyps. Expression of cilia-related transcription factors FOXJ1 and DNAI2 decreased, while goblet cell-derived genes CLCA1 and MUC5a increased upon IL-13 treatment. Mechanistically, knockdown of MLL1 restored expression of these four genes induced by IL-13.

Conclusion

These findings suggest that H3K4me3 is a critical regulator in control of nasal epithelial cell differentiation. MLL1 may be a potential therapeutic target for nasal inflammatory diseases.

The genetics of the bitter taste receptor T2R38 in upper airway innate immunity and implications for chronic rhinosinusitis

OBJECTIVE

Chronic rhinosinusitis (CRS) refractory to therapeutic intervention may involve a particularly resistant infection known as a bacterial biofilm. Critical to biofilm formation is the microbial process of quorum sensing whereby microbes secrete factors that regulate the expression of microbial genes involved in biofilm formation, persistence, and virulence. Here, we review recent work demonstrating that the bitter taste receptor T2R38, expressed on the apical surface of the sinonasal epithelium, serves a sentinel role in eavesdropping on microbial quorum-sensing communications and regulates localized innate biocidal defenses. Furthermore, studies investigating whether cilia are necessary for T2R38 expression and function in the upper airway are presented.

METHODS

Primary human sinonasal air-liquid interface cultures were used to elucidate cellular pathways responsive to quorum-sensing molecules, whereas clinical studies investigated the contribution of T2R38 polymorphisms to recalcitrant chronic rhinosinusitis.

RESULTS

T2R38 is stimulated by acyl-homoserine lactones, gram-negative quorum-sensing molecules, and subsequently activates nitric oxide-dependent innate immune responses. The formation of mature cilia is necessary for T2R38 expression and function, and polymorphisms that underlie T2R38 functionality appear to be involved in susceptibility to upper respiratory infection and recalcitrant CRS.

CONCLUSION

Taste receptors are emerging as critical components of early-phase respiratory innate immunity, detecting molecules used by microbes to communicate and stimulating localized host defenses. Genetic polymorphisms are very common within the taste receptors, and recent linkage studies have demonstrated associations of taste receptor genetics with CRS. Lastly, ciliogenesis, which is often impacted in CRS, is critical for the functional expression of T2R38.

LEVEL OF EVIDENCE

N/A. Laryngoscope, 127:44-51, 2017.

Role of IFN-γ, IL-13, and IL-17 on mucociliary differentiation of nasal epithelial cells in chronic rhinosinusitis with nasal polyps

BACKGROUND

Mucociliary dysfunction is a prominent pathophysiological feature of chronic rhinosinusitis with nasal polyps (CRSwNP); however, the precise mechanisms underlying mucociliary dysfunction are still unclear.

OBJECTIVE

The aim of this study was therefore to evaluate the effects of IFN-γ, IL-13, and IL-17 on human nasal mucociliary differentiation and ciliary beat frequency (CBF) in patients with CRSwNP.

METHODS

Human nasal epithelial cells from tissue of patients with CRSwNP and control subjects were established as air-liquid interface (ALI) primary cultures. Confluent cultures were incubated with10 ng/mL each of IFN-γ, IL-13, or IL-17 for 14 days and assessed for expression of specific morphological markers and factors associated with mucociliary differentiation, the percentage of ciliated and goblet cells, and CBF.

RESULTS

In comparison with control subjects, percentage of ciliated cells and CBF were decreased; while percentage of goblet cells, FOXJ1, and MUC5AC mRNA expression were increased in nasal polyp-derived epithelial cultures. Treatment with IFN-γ and IL-13 significantly decreased the expression of β-tubulin IV (specific cilia marker), ciliated cell number, and expression of FOXJ1 and DNAI2, in epithelial cultures derived from both CRSwNP patients and control subjects. Furthermore, while both IFN-γ and IL-13 treatment significantly decreased the CBF of cells from both CRSwNP patients and control subjects, IL-13 additionally significantly increased goblet cell number and the expression of MUC5AC and CLCA1, in these cultures. IL-17 treatment did not significantly affect ciliated or goblet cell differentiation, CBF, nor MUC5AC and CLCA1 expression, but increased both MUC5B mRNA and protein expression in these cultures.

CONCLUSION AND CLINICAL RELEVANCE

The demonstration that IFN-γ and IL-13 both significantly reduce ciliated cell differentiation and CBF in CRSwNP patients, and IL-13 additionally induces significant goblet cell hyperplasia and MUC5AC mucin expression, as well as IL-17 significantly increases MUC5B mucin expression, suggests that these inflammatory cytokines may be potential therapeutic targets in the management of CRSwNP.

Fungal Aflatoxins Reduce Respiratory Mucosal Ciliary Function

Aflatoxins are mycotoxins secreted by Aspergillus flavus, which can colonize the respiratory tract and cause fungal rhinosinusitis or bronchopulmonary aspergillosis. A. flavus is the second leading cause of invasive aspergillosis worldwide. Because many respiratory pathogens secrete toxins to impair mucociliary immunity, we examined the effects of acute exposure to aflatoxins on airway cell physiology. Using air-liquid interface cultures of primary human sinonasal and bronchial cells, we imaged ciliary beat frequency (CBF), intracellular calcium, and nitric oxide (NO). Exposure to aflatoxins (0.1 to 10 μM; 5 to 10 minutes) reduced baseline (~6-12%) and agonist-stimulated CBF. Conditioned media (CM) from A. fumigatus, A. niger, and A. flavus cultures also reduced CBF by ~10% after 60 min exposure, but effects were blocked by an anti-aflatoxin antibody only with A. flavus CM. CBF reduction required protein kinase C but was not associated with changes in calcium or NO. However, AFB2 reduced NO production by ~50% during stimulation of the ciliary-localized T2R38 receptor. Using a fluorescent reporter construct expressed in A549 cells, we directly observed activation of PKC activity by AFB2. Aflatoxins secreted by respiratory A. flavus may impair motile and chemosensory functions of airway cilia, contributing to pathogenesis of fungal airway diseases.

Chronic rhinosinusitis: the rationale for current treatments

INTRODUCTION

Chronic rhinosinusitis (CRS) is a broad clinical syndrome linked by mucosal inflammation. Primary treatment modalities are corticosteroids and antibiotics with surgery an option for failures, but the level of supporting evidence is generally low. The primary reason is that CRS is a symptom complex and not a specific disease. Areas covered: The primary treatment modalities for CRS are corticosteroids, antibiotics and surgery. Corticosteroids, which have very broad anti-inflammatory properties, also have the strongest evidence for efficacy. Antibiotics are likely effective in a subpopulation of patients but the various phenotypes and endotypes that make up CRS have thus far been poorly defined. Early surgery as well as biologics may also be more efficacious and cost effective in some phenotypes as well. Expert commentary: A better understanding of the inflammatory pathways that drive CRS will permit investigators to separate patient groups. This will allow for clinical trials that target specific subpopulations and more personalized therapy for CRS patients in the future.

Human upper airway epithelium produces nitric oxide in response to Staphylococcus epidermidis

BACKGROUND

Nitric oxide (NO) is produced by sinonasal epithelial cells as part of the innate immune response against bacteria. We previously described bitter-taste-receptor-dependent and -independent NO responses to product(s) secreted by Pseudomonas aeruginosa and Staphylococcus aureus, respectively. We hypothesized that sinonasal epithelium would be able to detect the gram-positive, coagulase-negative bacteria Staphylococcus epidermidis and mount a similar NO response.

METHODS

Sinonasal air-liquid interface cultures were treated with conditioned medium (CM) from lab strains and clinical isolates of coagulase-negative staphylococci and S aureus. NO production was quantified by fluorescence imaging. Bitter taste receptor signaling inhibitors were utilized to characterize the pathway responsible for NO production in response to S epidermidis CM.

RESULTS

S epidermidis CM contains a low-molecular-weight, heat, and protease-stabile product that induces an NO synthase (NOS)-mediated NO production that is less robust than the response triggered by S aureus CM. The S epidermidis CM-stimulated NO response is not inhibited by antagonists of phospholipase C isoform β-2 nor the transient receptor potential melastatin isoform 5 ion channel, both critical to bitter taste signaling.

CONCLUSION

This study identifies an NO-mediated innate defense response in sinonasal epithelium elicited by S epidermidis product(s). The active bacterial product is likely a small, nonpeptide molecule that stimulates a pathway independent of bitter taste receptors. Although the NO response to S epidermidis is less vigorous compared with S aureus, the product(s) share similar characteristics. Together, the responses to staphylococci species may help explain the pathophysiology of upper respiratory infections.

Correlation of T2R38 taste phenotype and in vitro biofilm formation from nonpolypoid chronic rhinosinusitis patients

BACKGROUND

Sinonasal biofilms have been demonstrated in specimens collected from chronic rhinosinusitis (CRS) patients. Mounting evidence suggests that biofilms contribute to therapeutically recalcitrant CRS. Recently, the bitter taste receptor T2R38 has been implicated in the regulation of the sinonasal mucosal innate immune response. TAS2R38 gene polymorphisms affect receptor functionality and contribute to variations seen in sinonasal innate defense as well as taste perception reflected in gustatory sensitivity to the bitter compound phenylthiocarbamide (PTC). In a population of CRS patients with active infection or inflammation, we sought to determine if a correlation between T2R38 phenotype and in vitro biofilm formation existed.

METHODS

Endoscopically guided sinonasal swabs were obtained prospectively from CRS (±polyp) patients with evidence of persistent inflammation or mucopurulence. In vitro biofilm formation was assessed with a modified Calgary Biofilm Detection Assay. Patients' phenotypic (functional) expression of the bitter taste receptor T2R38 was evaluated with a taste test including the compound PTC. Linear regression was used to determine the level of significance between mean in vitro biofilm formation levels and mean PTC taste test intensity ratings across CRS patients.

RESULTS

Sinonasal swabs were obtained from 59 patients, with 42 of the 59 samples demonstrating in vitro biofilm formation. Analysis revealed an inverse linear association between in vitro biofilm formation and PTC taste intensity ratings (p = 0.019) for all patients. This association was exclusively driven by nonpolypoid CRS patients (p = 0.0026).

CONCLUSION

In vitro biofilm formation from sinonasal clinical isolates is inversely correlated with PTC taste sensitivity in nonpolypoid CRS patients.

In vitro effects of anthocyanidins on sinonasal epithelial nitric oxide production and bacterial physiology

BACKGROUND

T2R bitter taste receptors play a crucial role in sinonasal innate immunity by upregulating mucociliary clearance and nitric oxide (NO) production in response to bitter gram-negative quorum-sensing molecules in the airway surface liquid. Previous studies showed that phytochemical flavonoid metabolites, known as anthocyanidins, taste bitter and have antibacterial effects. Our objectives were to examine the effects of anthocyanidins on NO production by human sinonasal epithelial cells and ciliary beat frequency, and their impact on common sinonasal pathogens Pseudomonas aeruginosa and Staphylococcus aureus.

METHODS

Ciliary beat frequency and NO production were measured by using digital imaging of differentiated air-liquid interface cultures prepared from primary human cells isolated from residual surgical material. Plate-based assays were used to determine the effects of anthocyanidins on bacterial swimming and swarming motility. Biofilm formation and planktonic growth were also assessed.

RESULTS

Anthocyanidin compounds triggered epithelial cells to produce NO but not through T2R receptors. However, anthocyanidins did not impact ciliary beat frequency. Furthermore, they did not reduce biofilm formation or planktonic growth of P. aeruginosa. In S. aureus, they did not reduce planktonic growth, and only one compound had minimal antibiofilm effects. The anthocyanidin delphinidin and anthocyanin keracyanin were found to promote bacterial swimming, whereas anthocyanidin cyanidin and flavonoid myricetin did not. No compounds that were tested inhibited bacterial swarming.

CONCLUSION

Results of this study indicated that, although anthocyanidins may elicited an innate immune NO response from human cells, they do not cause an increase in ciliary beating and they may also cause a pathogenicity-enhancing effect in P. aeruginosa. Additional studies are necessary to understand how this would affect the use of anthocyanidins as therapeutics. This study emphasized the usefulness of in vitro screening of candidate compounds against multiple parameters of both epithelial and bacterial physiologies to prioritize candidates for in vivo therapeutic testing.

Taste Receptors: Regulators of Sinonasal Innate Immunity

Taste receptors in the oral cavity guide our preferences for foods, preventing toxic ingestions and encouraging proper nutrient consumption. More recently, expression of taste receptors has been demonstrated in other locations throughout the body, including the airway, gastrointestinal tract, pancreas, and brain. The extent and specific roles of extraoral taste receptors are largely unknown, but a growing body of evidence suggests that taste receptors in the airway serve a critical role in sensing bacteria and regulating innate immunity. This review will focus on the function of bitter and sweet taste receptors in the human airway, with particular emphasis on T2R38, a bitter taste receptor found in sinonasal ciliated cells, and the bitter and sweet receptors found on specialized sinonasal solitary chemosensory cells. The importance of these novel taste receptor‐immune circuits in the human airway and their clinical relevance in airway disease will also be reviewed.

The Role of Bitter and Sweet Taste Receptors in Upper Airway Immunity

Over the past several years, taste receptors have emerged as key players in the regulation of innate immune defenses in the mammalian respiratory tract. Several cell types in the airway, including ciliated epithelial cells, solitary chemosensory cells, and bronchial smooth muscle cells, all display chemoresponsive properties that utilize taste receptors. A variety of bitter products secreted by microbes are detected with resultant downstream inflammation, increased mucous clearance, antimicrobial peptide secretion, and direct bacterial killing. Genetic variation of bitter taste receptors also appears to play a role in the susceptibility to infection in respiratory disease states, including that of chronic rhinosinusitis. Ongoing taste receptor research may yield new therapeutics that harness innate immune defenses in the respiratory tract and may offer alternatives to antibiotic treatment. The present review discusses taste receptor-protective responses and analyzes the role these receptors play in mediating airway immune function.

Nasal Mucociliary Clearance in Adenoid Hypertrophy and Otitis Media with Effusion

Mucociliary clearance (MCC), which exists in many systems, is the first defensive mechanism of the human body. Nasal MCC has an important role in transporting the secretions of the nasal cavity and paranasal sinuses along with the trapped inhaled pathogens to the nasopharynx. Physiologic or pathologic situations that effect nasal MCC, such as temperature, humidity, nasal obstruction, allergic rhinitis, chronic infections, etc., lead to impaired MCC and related local or circumjacent system disorders. With this perspective, when a unified airway with a multiple disease principle is considered, investigating the relationship between adenoid hypertrophy (AH), otitis media with effusion (OME) and nasal MCC is logical. In this review, histological and physiologic properties of nasal MCC and its possible role involving pathologic situations such as AH and OME is discussed together with recent literature findings.

The effect of drugs and other compounds on the ciliary beat frequency of human respiratory epithelium

BACKGROUND

Cilia in the human respiratory tract play a critical role in clearing mucus and debris from the airways. Their function can be affected by a number of drugs or other substances, many of which alter ciliary beat frequency (CBF). This has implications for diseases of the respiratory tract and nasal drug delivery. This article is a systematic review of the literature that examines 229 substances and their effect on CBF.

METHODS

MEDLINE was the primary database used for data collection. Eligibility criteria based on experimental design were established, and 152 studies were ultimately selected. Each individual trial for the substances tested was noted whenever possible, including concentration, time course, specific effect on CBF, and source of tissue.

RESULTS

There was a high degree of heterogeneity between the various experiments examined in this article. Substances and their general effects (increase, no effect, decrease) were grouped into six categories: antimicrobials and antivirals, pharmacologics, human biological products, organisms and toxins, drug excipients, and natural compounds/other manipulations.

CONCLUSION

Organisms, toxins, and drug excipients tend to show a cilioinhibitory effect, whereas substances in all other categories had mixed effects. All studies examined were in vitro experiments, and application of the results in vivo is confounded by several factors. The data presented in this article should be useful in future respiratory research and examination of compounds for therapeutic and drug delivery purposes.

Role of the bitter taste receptor T2R38 in upper respiratory infection and chronic rhinosinusitis

PURPOSE OF REVIEW

Taste receptor family 2 (T2R) bitter taste receptors were originally identified and named on the basis of their role in type 2 taste cells of the tongue, in which they serve to detect the presence of potentially harmful ingested chemicals. In 2009, researchers demonstrated that airway epithelial cells also express T2R receptors, but their role in airway physiology and human disease has only recently begun to be identified.

RECENT FINDINGS

Recent research has demonstrated that at least one airway T2R receptor, taste receptor family 2 isoform 38 protein (T2R38) is activated by secreted bacterial products. Activation of T2R38 in sinonasal epithelial cells stimulates nitric oxide production, increasing ciliary beating and directly killing bacteria. Clinical studies have also found correlations of TAS2R38 genotype with susceptibility to gram-negative upper respiratory infection and established T2R38 as an independent risk factor for chronic rhinosinusitis requiring sinus surgery.

SUMMARY

These recent studies identify a role for T2R38 in sinonasal innate immunity and chronic rhinosinusitis. Clinical implications include the potential development of T2R38-directed topical therapies, as well as using taste testing and/or genotyping to predict susceptibility to infection. Further studies are needed to more clearly determine how TAS2R38 genotype affects patient outcomes in chronic rhinosinusitis and other upper airway diseases.

Increased expression of the epithelial anion transporter pendrin/SLC26A4 in nasal polyps of patients with chronic rhinosinusitis

BACKGROUND

Chronic rhinosinusitis (CRS) is a multifactorial disease of unknown cause characterized by sinonasal inflammation, increased mucus production, and defective mucociliary clearance. Expression of Pendrin, an epithelial anion transporter, is increased in asthma and chronic obstructive pulmonary disease. Pendrin increases mucus production and regulates mucociliary clearance.

OBJECTIVES

We sought to investigate the expression of pendrin and the mucus-related protein Muc5AC in sinonasal tissues of control subjects and patients with CRS and to evaluate the regulation of pendrin expression in nasal epithelial cells (NECs) in vitro.

METHODS

The expression and distribution of pendrin in sinonasal tissues was analyzed by using real-time PCR, immunoblot analysis, and immunohistochemistry. Differentiated NECs were used to study the regulation of pendrin expression.

RESULTS

Increased pendrin expression was observed in nasal polyp (NP) tissue of patients with CRS. Immunohistochemistry analysis revealed that pendrin was largely restricted to the epithelial layer. Pendrin expression significantly correlated with inflammatory cell markers, suggesting that the factors made by these cells might induce pendrin expression. Furthermore, both pendrin and periostin levels (a biomarker in asthma) correlated with IL-13 levels, suggesting that pendrin can be induced by this cytokine in sinonasal tissues. Expression of the mucus component protein Muc5AC correlated weakly with pendrin expression, indicating that pendrin might modulate mucus production in NPs. In cultured NECs pendrin expression was induced by TH2 cytokines and induced synergistically when TH2 cytokines were combined with IL-17A. Interestingly, human rhinovirus had a potentiating effect on IL-13-induced pendrin expression. Dexamethasone suppressed pendrin expression, suggesting that the therapeutic benefit of dexamethasone in asthmatic patients and those with CRS might involve regulation of pendrin expression.

CONCLUSIONS

TH2-mediated pendrin expression is increased in NPs of patients with CRS and might lead to increased inflammation, mucus production, and decreased mucociliary clearance.

The Etiology and Pathogenesis of Chronic Rhinosinusitis: a Review of Current Hypotheses

Chronic rhinosinusitis (CRS) is a broad clinical syndrome that is characterized by prolonged mucosal inflammation of the nose and paranasal sinuses, and is typically divided into two subtypes based on the presence or absence of nasal polyps. The etiology and pathogenesis of both forms remain areas of active research. Over the last 15 years, a number of hypotheses have been proposed to explain all or part of the clinical CRS spectrum. These hypotheses reflect the concept that CRS results from a dysfunctional interplay between individual host characteristics and factors exogenous to the host. Six broad theories on CRS etiology and pathogenesis are discussed as follows: (1) the "fungal hypothesis," (2) the "superantigen hypothesis," (3) the "biofilm hypothesis," and (4) the "microbiome hypothesis," all of which emphasize key environmental factors, and (5) the "eicosanoid hypothesis" and (6) the "immune barrier hypothesis," which describe specific host factors. These theories are reviewed, and the evidence supporting them is critically appraised.

Staphylococcus aureus triggers nitric oxide production in human upper airway epithelium

BACKGROUND

Nitric oxide (NO) is an important antibacterial defense molecule produced by upper airway (sinonasal) epithelial cells. We previously showed that a bitter taste receptor expressed in airway epithelium detects quorum-sensing molecules secreted by Gram-negative bacteria and subsequently triggers bactericidal NO production. We hypothesized that the upper airway epithelium may also be able to detect the Gram-positive aerobe Staphylococcus aureus and mount an NO response.

METHODS

Human sinonasal air-liquid interface (ALI) cultures were treated with methicillin-resistant S. aureus (MRSA)-conditioned medium (CM), and NO production was measured using fluorescence imaging. Inhibitors of bitter taste receptor signaling were used to pharmacologically determine if this pathway was involved in the production of NO.

RESULTS

A low-molecular-weight, heat, and protease-stabile product found in MRSA CM induced differential, NO synthase (NOS)-mediated NO production. This response varied markedly between individual patients. The MRSA-stimulated NO production was not dependent on 2 important components of bitter taste signaling: phospholipase C isoform β-2 or the transient receptor potential melastatin isoform 5 (TRPM5) ion channel.

CONCLUSION

This study shows that a S. aureus product elicits an NO-mediated innate defense response in human upper airway epithelium. The active bacterial product is likely a small, nonpeptide molecule that triggers a pathway independent of bitter taste receptors. Patient variation in the NO response to MRSA product(s), potentially due to genetic differences, might play a role in pathophysiology of Gram-positive upper respiratory infections and/or pathogenesis of chronic rhinosinusitis.