Type 2/Th2-driven inflammation impairs olfactory sensory neurogenesis in mouse chronic rhinosinusitis model

Secreted Glycoproteins That Regulate Synaptic Function: the Dispatchers in the Central Nervous System

Glycoproteins are proteins that contain oligosaccharide chains. As widely distributed functional proteins in the body, glycoproteins are essential for cellular development, cellular function maintenance, and intercellular communication. Glycoproteins not only play a role in the cell and the membrane, but they are also secreted in the intercell. These secreted glycoproteins are critical to the central nervous system for neurodevelopment and synaptic transmission. More specifically, secreted glycoproteins play indispensable roles in neurite growth mediation, axon guiding, synaptogenesis, neuronal differentiation, the release of synaptic vesicles, subunit composition of neurotransmitter receptors, and neurotransmitter receptor trafficking among other things. Abnormal expressions of secreted glycoproteins in the central nervous system are associated with abnormal neuron development, impaired synaptic organization/transmission, and neuropsychiatric disorders. This article reviews the secreted glycoproteins that regulate neuronal development and synaptic function in the central nervous system, and the molecular mechanism of these regulations, providing reference for research about synaptic function regulation and related central nervous system diseases.

Olfactory Loss in Rhinosinusitis: Mechanisms of Loss and Recovery

Chronic rhinosinusitis (CRS) is a highly prevalent disease and up to 83% of CRS patients suffer from olfactory dysfunction (OD). Because OD is specifically seen in those CRS patients that present with a type 2 eosinophilic inflammation, it is believed that type 2 inflammatory mediators at the level of the olfactory epithelium are involved in the development of this olfactory loss. However, due to the difficulties in obtaining tissue from the olfactory epithelium, little is known about the true mechanisms of inflammatory OD. Thanks to the COVID-19 pandemic, interest in olfaction has been growing rapidly and several studies have been focusing on disease mechanisms of OD in inflammatory conditions. In this paper, we summarize the most recent data exploring the pathophysiological mechanisms underlying OD in CRS. We also review what is known about the potential capacity of olfactory recovery of the currently available treatments in those patients.

The interleukin-4/interleukin-13 pathway in type 2 inflammation in chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is predominantly a type 2 inflammatory disease associated with type 2 (T2) cell responses and epithelial barrier, mucociliary, and olfactory dysfunction. The inflammatory cytokines interleukin (IL)-4, IL-13, and IL-5 are key mediators driving and perpetuating type 2 inflammation. The inflammatory responses driven by these cytokines include the recruitment and activation of eosinophils, basophils, mast cells, goblet cells, M2 macrophages, and B cells. The activation of these immune cells results in a range of pathologic effects including immunoglobulin E production, an increase in the number of smooth muscle cells within the nasal mucosa and a reduction in their contractility, increased deposition of fibrinogen, mucus hyperproduction, and local edema. The cytokine-driven structural changes include nasal polyp formation and nasal epithelial tissue remodeling, which perpetuate barrier dysfunction. Type 2 inflammation may also alter the availability or function of olfactory sensory neurons contributing to loss of sense of smell. Targeting these key cytokine pathways has emerged as an effective approach for the treatment of type 2 inflammatory airway diseases, and a number of biologic agents are now available or in development for CRSwNP. In this review, we provide an overview of the inflammatory pathways involved in CRSwNP and describe how targeting key drivers of type 2 inflammation is an effective therapeutic option for patients.

Neuroimmune interplay during type 2 inflammation: Symptoms, mechanisms, and therapeutic targets in atopic diseases

Type 2 inflammation is characterized by overexpression and heightened activity of type 2 cytokines, mediators, and cells that drive neuroimmune activation and sensitization to previously subthreshold stimuli. The consequences of altered neuroimmune activity differ by tissue type and disease; they include skin inflammation, sensitization to pruritogens, and itch amplification in atopic dermatitis and prurigo nodularis; airway inflammation and/or hyperresponsiveness, loss of expiratory volume, airflow obstruction and increased mucus production in asthma; loss of sense of smell in chronic rhinosinusitis with nasal polyps; and dysphagia in eosinophilic esophagitis. We describe the neuroimmune interactions that underlie the various sensory and autonomic pathologies in type 2 inflammatory diseases and present recent advances in targeted treatment approaches to reduce type 2 inflammation and its associated symptoms in these diseases. Further research is needed to better understand the neuroimmune mechanisms that underlie chronic, sustained inflammation and its related sensory pathologies in diseases associated with type 2 inflammation.

Type 2 and Non-type 2 Inflammation in the Upper Airways: Cellular and Molecular Alterations in Olfactory Neuroepithelium Cell Populations

PURPOSE OF REVIEW

Neurogenesis occurring in the olfactory epithelium is critical to continuously replace olfactory neurons to maintain olfactory function, but is impaired during chronic type 2 and non-type 2 inflammation of the upper airways. In this review, we describe the neurobiology of olfaction and the olfactory alterations in chronic rhinosinusitis with nasal polyps (type 2 inflammation) and post-viral acute rhinosinusitis (non-type 2 inflammation), highlighting the role of immune response attenuating olfactory neurogenesis as a possibly mechanism for the loss of smell in these diseases.

RECENT FINDINGS

Several studies have provided relevant insights into the role of basal stem cells as direct participants in the progression of chronic inflammation identifying a functional switch away from a neuro-regenerative phenotype to one contributing to immune defense, a process that induces a deficient replacement of olfactory neurons. The interaction between olfactory stem cells and immune system might critically underlie ongoing loss of smell in type 2 and non-type 2 inflammatory upper airway diseases. In this review, we describe the neurobiology of olfaction and the olfactory alterations in type 2 and non-type 2 inflammatory upper airway diseases, highlighting the role of immune response attenuating olfactory neurogenesis, as a possibly mechanism for the lack of loss of smell recovery.

Murine model of eosinophilic chronic rhinosinusitis with nasal polyposis inducing neuroinflammation and olfactory dysfunction

BACKGROUND

Chronic rhinosinusitis (CRS) is a common inflammatory condition affecting the nasal and paranasal sinus mucosa, often accompanied by olfactory dysfunction. Eosinophilic CRS with nasal polyps (ECRSwNP) is a subtype of CRS characterized by eosinophilic infiltration. Animal models for ECRSwNP with olfactory dysfunction are necessary for exploring potential therapeutic strategies.

OBJECTIVE

The aim of this study was to establish a mouse model of ECRSwNP combined with olfactory dysfunction in a shorter time frame using intranasal ovalbumin and Aspergillus protease (AP) administration. The efficacy of the model was validated by evaluating sinonasal inflammation, cytokine levels, olfactory function, and neuroinflammation in the olfactory bulb.

METHODS

Male BALB/c mice were intranasally administered ovalbumin and AP for 6 and 12 weeks to induce ECRSwNP. The resultant ECRSwNP mouse model underwent histologic assessment, cytokine analysis of nasal lavage fluid, olfactory behavioral tests, and gene expression profiling to identify neuroinflammatory markers within the olfactory bulb.

RESULTS

The developed mouse model exhibited substantial eosinophil infiltration, increased levels of inflammatory cytokines in nasal lavage fluid, and confirmed olfactory dysfunction through behavioral assays. Furthermore, olfactory bulb inflammation and reduced mature olfactory sensory neurons were observed in the model.

CONCLUSION

This study successfully established a validated mouse model of ECRSwNP with olfactory dysfunction within a remarkably short span of 6 weeks, providing a valuable tool for investigating the pathogenesis and potential therapies for this condition. The model offers an efficient approach for future research in CRS with nasal polyps and olfactory dysfunction.

Mesenchymal stem cell exosomes differentially regulate gene expression of mast cells

Emerging evidence indicates that the immunomodulatory effect of mesenchymal stem cells (MSCs) is primarily attributed to the paracrine pathway. As a key paracrine effector, MSC-derived exosomes are small vesicles that play an important role in cell-to-cell communication by carrying bioactive substances. We previously found that exosomes derived from tonsil-derived mesenchymal stem cells (T-MSCs) were able to effectively attenuate inflammatory responses in mast cells. Here we investigated how T-MSC exosomes impact mast cells in steady state, and how exposure of T-MSCs to Toll-like receptors (TLRs) ligands changes this impact. Transcriptomic analysis of HMC-1 cells, a human mast cell line, using DNA microarrays showed that T-MSC exosomes broadly regulate genes involved in the normal physiology of mast cells. TLR3 or TLR4 primed T-MSC exosomes impacted fewer genes involved in specific functions in mast cells. This distinguishable regulation also was apparent in the analysis of related gene interactions. Our results suggest that MSC exosomes maintain immune homeostasis in normal physiology and impact the inflammatory state by modulating mast cell transcription.

Which are the best murine models to study Eosinophilic Chronic Rhinosinusitis? A contemporary review

OBJECTIVE

Mechanisms that lead to Eosinophilic Chronic Rhinosinusitis (ECRS) are not fully established in the literature. It is desirable to assess ECRS in a model that embraces most of the related events. This article reviewed the murine models for ECRS and compared them regarding eosinophilic polypoid formation.

METHODS

The authors reviewed the articles that included the terms "chronic rhinosinusitis" OR "chronic sinusitis" AND "animal model". We analyzed articles in English that evaluated both the number of polyps and the number of eosinophils in the sinus mucosa of mouse models.

RESULTS

We identified a total of 15 articles describing different models of ECRS that used BALB/c or C57BL/6 mice, and different triggers/stimulants such as Staphylococcus aureus Enterotoxin B (SEB) + Ovalbumin (OVA); House Dust Mite (HDM) ± Ovalbumin (OVA); and Aspergillus oryzae Protease (AP) + Ovalbumin (OVA). OVA associated with SEB was the commonest protocol to induce ECRS in both BALB/c and C57BL/6 mice, and it produced a robust response of eosinophilic nasal polyps in both. AP + OVA protocol also led to a good ECRS response. The other models were not considered adequate to produce eosinophilic polyps in mice.

CONCLUSION

In conclusion, OVA associated with SEB seems to produce the most robust eosinophilic sinonasal inflammation.

A Decade of Pathogenesis Advances in Non-Type 2 Inflammatory Endotypes in Chronic Rhinosinusitis: 2012-2022

Chronic rhinosinusitis (CRS) is a heterogeneous disease characterized by localized inflammation of the upper airways. CRS includes two main phenotypes, namely, CRS with nasal polyps and CRS without nasal polyps. The phenotype-based classification method cannot reflect the pathological mechanism. The endotype-based classification method has been paid more and more attention by researchers. It is mainly divided into type 2 and non-type 2 endotypes. The mechanism driving the pathogenesis of non-type 2 inflammation is currently unknown. In this review, the PubMed and Web of Science databases were searched to conduct a critical analysis of representative literature works on the pathogenesis of non-type 2 inflammation in CRS published in the past decade. This review summarizes the latest evidence that may lead to the pathogenesis of non-type 2 inflammation. It is the main method that analyzing the pathogenesis from the perspective of immunology. Genomics and proteomics technique provide new approaches to the study of the pathogenesis. Due to differences in race, environment, geography, and living habits, there are differences in the occurrence of non-type 2 inflammation, which increase the difficulty of understanding the pathogenesis of non-type 2 inflammation in CRS. Studies have confirmed that non-type 2 endotype is more common in Asian patients. The emergence of overlap and unclassified endotypes has promoted the study of heterogeneity in CRS. In addition, as the source of inflammatory cells and the initiation site of the inflammatory response, microvessels and microlymphatic vessels in the nasal mucosal subepithelial tissue participate in the inflammatory response and tissue remodeling. It is uncertain whether CRS patients affect the risk of infection with SARS-CoV-2. In addition, the pathophysiological mechanism of non-type 2 CRS combined with COVID-19 remains to be further studied, and it is worth considering how to select the befitting biologics for CRS patients with non-type 2 inflammation.

Pathophysiology and management of Staphylococcus aureus in nasal polyp disease

INTRODUCTION

Staphylococcus aureus (S. aureus) is a common pathogen that frequently colonizes the sinonasal cavity. Recent studies demonstrated the essential role of Staphylococcus aureus in the pathophysiology of uncontrolled severe chronic rhinosinusitis with nasal polyps (NP) by initiating an immune response to the germ and its products, resulting in type 2 inflammation.

AREAS COVERED

This review aims to summarize the evidence for the role of S. aureus in the development of NP disease including S. aureus-related virulence factors, the pathophysiologic mechanisms used by S. aureus, and the synergistic effects of S. aureus and other pathogens. It also describes the current management of S. aureus associated with NPs as well as potential therapeutic strategies that are used in clinical practice.

EXPERT OPINION

S. aureus is able to damage the nasal mucosal epithelial barrier, impair the clearance of the host immune system, and trigger adaptive and innate immune reactions which lead to the formation of inflammation and nasal polyp growth. Further studies should focus on the development of novel therapeutic strategies, such as biologics, bacteriophages, probiotics, and nanomedicine, which could be used to treat S. aureus and its immunological consequences in the future.

Antibiotic-induced socio-sexual behavioral deficits are reversed via cecal microbiota transplantation but not androgen treatment

Recent evidence has demonstrated a sex-specific role of the gut microbiome on social behavior such as anxiety, possibly driven by a reciprocal relationship between the gut microbiome and gonadal hormones. For instance, gonadal hormones drive sex differences in gut microbiota composition, and certain gut bacteria can produce androgens from glucocorticoids. We thus asked whether the gut microbiome can influence androgen-dependent socio-sexual behaviors. We first treated C57BL/6 mice with broad-spectrum antibiotics (ABX) in drinking water to deplete the gut microbiota either transiently during early development (embryonic day 16-postnatal day [PND] 21) or in adulthood (PND 60-85). We hypothesized that if ABX interferes with androgens, then early ABX would interfere with critical periods for sexual differentiation of brain and thus lead to long-term decreases in males' socio-sexual behavior, while adult ABX would interfere with androgens' activational effects on behavior. We found that in males but not females, early and adult ABX treatment decreased territorial aggression, and adult ABX also decreased sexual odor preference. We then assessed whether testosterone and/or cecal microbiota transplantation (CMT) via oral gavage could prevent ABX-induced socio-sexual behavioral deficits in adult ABX-treated males. Mice were treated with same- or other-sex control cecum contents or with testosterone for two weeks. While testosterone was not effective in rescuing any behavior, we found that male CMT restored both olfactory preference and aggression in adult ABX male mice, while female CMT restored olfactory preference but not aggression. These results suggest sex-specific effects of the gut microbiome on socio-sexual behaviors, independent of androgens.

Olfactory dysfunction in chronic rhinosinusitis: insights into the underlying mechanisms and treatments

INTRODUCTION

Olfactory dysfunction (OD) is a typical symptom of chronic rhinosinusitis (CRS), which adversely affects the patient's quality of life and results in mood depression. Studies investigating the impairment of olfactory epithelium (OE) have indicated that inflammation-induced cell damage and dysfunction in OE plays a vital role in the development of OD. Consequently, glucocorticoids and biologics are beneficial in the management of OD in CRS patients. However, the mechanisms underlying OE impairment in CRS patients have not been fully elucidated.

AREAS COVERED

This review focuses on mechanisms underlying inflammation-induced cell impairment in OE of CRS patients. Additionally, the methods used for detection of olfaction and both currently available and potentially new clinical treatments for OD are reviewed.

EXPERT OPINION

Chronic inflammation in OE impairs not only olfactory sensory neurons but also non-neuronal cells that are responsible for regeneration and support for neurons. The current treatment for OD in CRS is mainly aimed at attenuating and preventing inflammation. Strategies for use of combinations of these therapies may achieve greater efficacy in restoration of the damaged OE and consequently better management of OD.

Analysis of risk factors affecting olfactory dysfunction in patients with chronic rhinosinusitis: Highlighting the role of metabolic syndrome

Objective

This study aims to evaluate the relationship between chronic sinusitis (CRS) and metabolic syndrome (MS) in a Chinese population and to explore the risk factors for olfactory dysfunction in patients with CRS.

Methods

A total of 387 CRS patients were enrolled. Olfactory function was assessed by the Sniffin' Sticks 12-item test and MS was diagnosed according to the guidelines. Logistic regression analysis was performed on CRS patients to screen independent risk factors of olfactory dysfunction, adjusted for confounding factors.

Results

Among 387 patients, average age of visit and duration of onset were 48.7 years and 1.8 years, respectively. The prevalence of MS was 15.0%. CRS patients with MS were more likely to be older (51.2 vs. 46.8, p = .004), predominantly male (p < .001) and have a higher proportion of olfactory dysfunction (62.1% vs. 44.1%, p = .018) than those without MS. In multivariate logistic regression analysis, MS was associated with olfactory dysfunction in CRS patients (OR: 2.06, 95% CI: 1.14-3.72, p = .016). This association remained significant after controlling for confounding factors. In addition, nasal polyps (OR: 13.41, 95% CI: 8.11-22.17, p < .001) and allergic rhinitis (OR: 3.16, 95% CI: 1.67-5.99, p < .001) were also risk factors for olfactory dysfunction after adjusting for confounding factors.

Conclusions

MS is associated with olfactory dysfunction in patients with CRS. MS, nasal polyps, and allergic rhinitis are risk factors for olfactory dysfunction in CRS patients.

Level of evidence

IV.

Disturbed microbiota-metabolites-immune interaction network is associated with olfactory dysfunction in patients with chronic rhinosinusitis

Purpose

Olfactory dysfunction (OD) is a debilitating symptom frequently reported by patients with chronic rhinosinusitis (CRS) and it is associated with a dysregulated sinonasal inflammation. However, little information is available about the effect of the inflammation-related nasal microbiota and related metabolites on the olfactory function in these patients. Therefore, the current study aimed to investigate the nasal microbiota-metabolites-immune interactions and their role in the pathogenesis of OD in CRS patients.

Methods

23 and 19 CRS patients with and without OD, respectively, were enrolled in the present study. The "Sniffin' Sticks" was used to measure the olfactory function, while the metagenomic shotgun sequencing and the untargeted metabolite profiling were performed to assess the differences in terms of the nasal microbiome and metabolome between the two groups. The levels of nasal mucus inflammatory mediators were investigated by a multiplex flow Cytometric Bead Array (CBA).

Results

A decreased diversity in the nasal microbiome from the OD group compared to the NOD group was evidenced. The metagenomic analysis revealed a significant enrichment of Acinetobacter johnsonii in the OD group, while Mycoplasma arginini, Aeromonas dhakensis, and Salmonella enterica were significantly less represented (LDA value > 3, p < 0.05). The nasal metabolome profiles were significantly different between the OD and NOD groups (P < 0.05). The purine metabolism was the most significantly enriched metabolic subpathway in OD patients compared with NOD patients (P < 0.001). The expressions of IL-5, IL-8, MIP-1α, MCP-1, and TNF were statistically and significantly increased in the OD group (P < 0.05). All these data, including the dysregulation of the nasal microbiota, differential metabolites, and elevated inflammatory mediators in OD patients demonstrated a clear interaction relationship.

Conclusion

The disturbed nasal microbiota-metabolite-immune interaction networks may be implicated in the pathogenesis of OD in CRS patients and the underlying pathophysiological mechanisms need to be further investigated in future studies.

Dupilumab increases aspirin tolerance in NSAID-exacerbated respiratory disease

BACKGROUND

Nonsteroidal anti-inflammatory drug (NSAID)-exacerbated respiratory disease (N-ERD) comprises the triad of chronic rhinosinusitis with nasal polyps, asthma and intolerance to NSAIDs. Dupilumab treatment, targeting the interleukin-4 (IL-4) receptor α, significantly reduces polyp burden as well as asthma symptoms. Here we aimed to investigate the effect of dupilumab on aspirin intolerance, burden of disease and nasal cytokine profiles in patients with N-ERD.

METHODS

In this open-label trial, adult patients with confirmed N-ERD were treated with dupilumab for 6 months. Clinical parameters (e.g. total polyp scores, quality of life questionnaires, smell test, spirometry), oral aspirin provocation testing and blood, nasal and urine sampling were monitored at regular intervals for up to 6 months after starting dupilumab therapy.

RESULTS

Of the 31 patients included in the study, 30 completed both aspirin provocation tests. After 6 months of treatment with dupilumab, 23% of patients (n=7 of 30) developed complete aspirin tolerance and an additional 33% of patients (n=10 of 30) tolerated higher doses. Polyp burden was significantly reduced (total polyp score: -2.68±1.84, p<0.001), while pulmonary symptoms (asthma control test: +2.34±3.67, p<0.001) and olfactory performance improved (University of Pennsylvania Smell Identification Test: +11.16±9.54, p<0.001) in all patients after therapy. Patients with increased aspirin tolerance showed a significant decrease in urinary leukotriene E4 levels and their improvement in clinical parameters was associated with a reduction of eotaxin-1, C-C motif chemokine ligand 17, IL-5, IL-17A and IL-6.

CONCLUSION

In this study, 57% of N-ERD patients tolerated higher doses of aspirin under dupilumab therapy.

Olfactory cleft mucus galectin-10 predicts olfactory loss in chronic rhinosinusitis

BACKGROUND

Eosinophils have been reported to be involved in the pathogenesis of olfactory fluctuation in chronic rhinosinusitis (CRS). Galectin-10 is more frequently associated with type 2 inflammation and potentially a sign of intense eosinophil activation.

OBJECTIVE

To explore olfactory cleft mucus and olfactory mucosa galectin-10 level and its association with olfactory dysfunction (OD) in CRS.

METHODS

We prospectively enrolled 50 patients with CRS and 15 healthy controls. Olfactory cleft mucus and superior turbinate biopsy specimens were collected to analyze galectin-10 levels and quantify tissue eosinophils. Psychophysical olfactory testing, olfactory cleft endoscopy scale, and olfactory cleft computed tomography scores were obtained. The predictability of galectin-10 levels for OD in patients with CRS was analyzed by multivariable logistic regression analysis.

RESULTS

Both olfactory cleft mucus and olfactory mucosa galectin-10 levels in patients with CRS with OD were significantly higher than those in patients with CRS without OD (all P < .001). Mucus galectin-10 levels were positively correlated with tissue eosinophils (r = 0.541, P = 0.002), olfactory cleft endoscopy scale (r = 0.498, P = 0.006), and olfactory cleft computed tomography scores (r = 0.432, P = 0.019) in patients with CRS. Mucus galectin-10 levels were negatively correlated threshold, discrimination, and identification (r = -0.589,  P = 0.001), olfactory threshold (r = -0.522, P = 0.003), olfactory discrimination (r = -0.488, P = 0.007), and olfactory identification (r = -0.466, P = 0.011) scores. After adjusting for patient demographics and comorbidities, mucus galectin-10 levels were significantly associated with OD in patients with CRS (odds ratio, 1.299; P = .008). Mucus galectin-10 levels greater than 8.975 ng/mL were the best predictor of OD in CRS.

CONCLUSION

Olfactory cleft mucus galectin-10 is highly associated with OD in CRS.

Scientific Advancements That Empower Us to Understand CRS Pathophysiology

BACKGROUND

Chronic rhinosinusitis with nasal polyposis (CRSwNP) is a multifactorial inflammatory condition that remains poorly understood. Over the past decade, we have witnessed impressive scientific advancements that have allowed us to better understand the molecular and cellular mechanisms that underlie the inflammatory processes in mucosal diseases including asthma, allergic rhinitis, and CRSwNP.

OBJECTIVE

The present review aims to summarize and highlight the most recent scientific advancements that have enriched our understanding of CRSwNP.

METHODS

A comprehensive review of the available literature on the use of new scientific techniques in CRSwNP was performed. We evaluated the most recent evidence from studies using animal models, cell cultures, and genome sequencing techniques and their impact on our understanding of CRSwNP pathophysiology.

RESULTS

Our understanding of CRSwNP has rapidly progressed with the development of newer scientific techniques to interrogate various pathways involved in its pathogenesis. Animal models remain powerful tools and have elucidated the mechanisms behind esinophilic inflammation in CRSwNP; however, animal models reproducing polyp formation are relatively sparse. 3D cell cultures have significant potential to better dissect the cellular interactions with the sinonasal epithelium and other cell types in CRS. Additionally, some groups are starting to utilize single-cell RNA sequencing to investigate RNA expression in individual cells with high resolution and on a genomic scale.

CONCLUSION

These emerging scientific technologies represent outstanding opportunities to identify and develop more targeted therapeutics for different pathways that lead to CRSwNP. An additional understanding of these mechanisms will be critical for developing future therapies for CRSwNP.

Chronic interleukin-13 expression in mouse olfactory mucosa results in regional aneuronal epithelium

BACKGROUND

Olfactory dysfunction is highly associated with chronic rhinosinusitis with nasal polyps (CRSwNP), and the severity of loss has been linked with biomarkers of type 2 inflammation. The ability of dupilumab to rapidly improve the sense of smell prior to improvement in polyp size suggests a direct role of IL-4/IL-13 receptor signaling in the olfactory epithelium (OE).

METHODS

We created a transgenic mouse model in which IL-13 is inducibly expressed specifically within the OE. Gene expression analysis and immunohistology were utilized to characterize the effect of IL-13 on the structure of the OE.

RESULTS

After induction of olfactory IL-13 expression, there is a time-dependent loss of neurons from OE regions, accompanied by a modest inflammatory infiltrate. Horizontal basal cells undergo morphologic changes consistent with activation and demonstrate proliferation. Mucus production and increased expression of eotaxins is observed, with marked expression of Ym2 by sustentacular cells.

DISCUSSION

Chronic IL-13 exposure has several effects on the OE that are likely to affect function. The neuronal loss is in keeping with other models of allergic type 2 nasal inflammation. Future studies are needed to correlate cellular and molecular alterations in olfactory cell populations with findings in human CRSwNP, as well as to assess olfactory function in behavioral model systems.

Olfaction Now and in the Future in CRSwNP

BACKGROUND

Chronic rhinosinusitis (CRS) is the leading cause of olfactory dysfunction in the general population. Olfactory dysfunction is more common in patients with CRS with nasal polyposis (CRSwNP) compared to those without polyps.

PURPOSE

The present review aims to summarize the current literature on the mechanism behind olfactory dysfunction in CRSwNP and the impact of therapy on olfactory outcomes in this patient population.

METHODS

A comprehensive review of the available literature on olfaction in CRSwNP was performed. We evaluated the most recent evidence from studies on the mechanisms behind smell loss in CRSwNP and the impact of medical and surgical therapy for CRS on olfactory outcomes.

RESULTS

The mechanism behind olfactory dysfunction in CRSwNP is not completely understood, but evidence from clinical research and animal models suggests both an obstructive component causing conductive olfactory loss and an inflammatory response in the olfactory cleft leading to sensorineural olfactory loss. Oral steroids and endoscopic sinus surgery have both shown efficacy in improving olfactory outcomes in CRSwNP in the short term; however, the long-term response of these treatments remains uncertain. Newer targeted biologic therapies, such as dupilumab, have also shown remarkable and durable improvement in smell loss for CRSwNP patients.

CONCLUSION

Olfactory dysfunction is highly prevalent in the CRSwNP population. Although significant advances have been made in our understanding of olfactory dysfunction in the setting of CRS, additional studies are needed to elucidate cellular and molecular changes mediated by type 2-mediated inflammation in the olfactory epithelium with potential downstream effects on the central olfactory system. Further identification of these underlying basic mechanisms will be vital for developing future therapies targeted to improve olfactory dysfunction in patients with CRSwNP.

Effects of zinc deficiency on the regeneration of olfactory epithelium in mice

The olfactory epithelium can regenerate after damage; however, the regeneration process is affected by various factors, such as viral infections, head trauma, and medications. Zinc is an essential trace element that has important roles in organ development, growth, and maturation. Zinc also helps regulate neurotransmission in the brain; nevertheless, its relationship with olfactory epithelium regeneration remains unclear. Therefore, we used a severe zinc deficiency mouse model to investigate the effects of zinc deficiency on olfactory epithelium regeneration. Male wild-type C57BL/6 mice were divided into zinc-deficient and control diet groups at the age of 4 weeks, and methimazole was administered at the age of 8 weeks to induce severe olfactory epithelium damage. We evaluated the olfactory epithelium before and 7, 14, and 28 days after methimazole administration by histologically analyzing paraffin sections. RNA sequencing was also performed at the age of 8 weeks before methimazole administration to examine changes in gene expression caused by zinc deficiency. In the zinc-deficient group, the regenerated olfactory epithelium thickness was decreased at all time points, and the numbers of Ki-67-positive, GAP43-positive, and olfactory marker protein-positive cells (i.e. proliferating cells, immature olfactory neurons, and mature olfactory neurons, respectively) failed to increase at some time points. Additionally, RNA sequencing revealed several changes in gene expression, such as a decrease in the expression of extracellular matrix-related genes and an increase in that of inflammatory response-related genes, in the zinc-deficient group. Therefore, zinc deficiency delays olfactory epithelium regeneration after damage in mice.

Lipopolysaccharide-Initiated Rhinosinusitis Causes Neuroinflammation and Olfactory Dysfunction in Mice

Background

Olfactory dysfunction is a common disease and it may be caused by sinonasal inflammation, toxin inhalation, or neurological disorders. After sinonasal inflammation, if both olfactory neuroinflammation and olfactory dysfunction occur still under investigation.

Objective

This study aimed to investigate whether neuroinflammation and olfactory dysfunction occur after lipopolysaccharide (LPS)-initiated rhinosinusitis.

Methods

Adult C57BL/6 mice were intranasally administered with LPS for 3 weeks. The olfactory function was evaluated with a buried food test. The inflammatory status of sinonasal cavity and olfactory bulb was evaluated with histology and biochemistry.

Results

After 3-week LPS treatment, mice developed olfactory dysfunction, sinonasal cavity, and olfactory bulb inflammation. LPS-treated mice had greater sinonasal mucosal thickness. Besides, pro-inflammatory interleukin-6, the number of goblet cells and neutrophils in the sinonasal cavity was increased after LPS administration. The olfactory sensory neurons in the olfactory epithelium and the olfactory bulb were decreased, and the olfactory function was impaired by LPS administration. Inflammatory cytokines such as interferon-γ and tumor necrosis factor-α were increased in the olfactory bulb.

Conclusion

This study showed that LPS-initiated rhinosinusitis caused olfactory neuroinflammation and olfactory dysfunction in mice.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

The role of Staphylococcus aureus enterotoxin B in chronic rhinosinusitis with nasal polyposis

CRS with nasal polyps (CRSwNP) is a multifactorial disease, and various etiological factors like bacterial superantigens are known to develop this disease. Recent studies reported that Staphylococcus aureus nasal colonization was detected in 67% of the patients with CRSwNP. Moreover, it was reported that specific IgE against S. aureus enterotoxins are discovered in almost half of the nasal tissue homogenates from nasal polyps. Thus, investigations have highlighted the role of staphylococcal enterotoxins, especially enterotoxin B (SEB), in pathogenesis of CRSwNP. The destruction of mucosal integrity was reported as a main SEB-related pathogenic mechanisms in CRSwNP. SEB activates Toll Like Receptor 2 and triggers the production of pro-inflammatory cytokines; furthermore, it induces reactive oxygen species and endoplasmic reticulum stress-induced inflammation that may cause epithelial cell integrity disruption and enhance their permeability. SEB-induced Type 2/Th2 pathway results in degranulation of eosinophils, cationic proteins production, and localized eosinophilic inflammation. Furthermore, SEB may be involved in the expression of RORC and HIF-1α in Tregs and by maintaining the inflammation in sinonasal mucosa that could have a main role in the pathogenesis of nasal polyposis. Different in vitro findings were confirmed in animal studies; however, in vivo analysis of SEB-induced nasal polyps and CRS remains unfulfilled due to the lack of appropriate animal models. Finally, after elucidating different aspects of SEB pathogenesis in CRSwNP, therapeutic agents have been tested in recent studies with some encouraging results. The purpose of this article is to summarize the most important findings regarding SEB-induced CRS and nasal polyposis.

Studies on Clinical Features, Mechanisms, and Management of Olfactory Dysfunction Secondary to Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is one of the most common causes of inflammation of the olfactory system, warranting investigation of the link between chronic inflammation and the loss of olfactory function. Type 2 inflammation is closely related to the clinical features and disease mechanisms of olfactory dysfunction secondary to CRS. Patients with eosinophilic CRS, aspirin-exacerbated respiratory disease, and central compartment atopic disease report increased olfactory dysfunction. Increased levels of interleukin-(IL-)2, IL-5, IL-6, IL-10, and IL-13 in the mucus from the olfactory slit have been reported to be associated with reduced olfactory test scores. The influence of several cytokines and signaling transduction pathways, including tumor necrosis factor-α, nuclear factor-κB, and c-Jun N-terminal kinases, on olfactory signal processing and neurogenesis has been demonstrated. Corticosteroids are the mainstay treatment for olfactory dysfunction secondary to CRS. Successful olfaction recovery was recently demonstrated in clinical trials of biotherapeutics, including omalizumab and dupilumab, although the treatment effect may diminish gradually after stopping the use of the medications. Future studies are required to relate the complex mechanisms underlying chronic inflammation in CRS to dysfunction of the olfactory system.

Interpretation of Clinical Efficacy of Biologics in Chronic Rhinosinusitis With Nasal Polyps via Understanding the Local and Systemic Pathomechanisms

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a heterogeneous disease treated with medication or surgery. For recalcitrant type 2 CRSwNP, biological agents have been effectively used to improve nasal polyp score, nasal congestion score, daily symptoms related to CRSwNP, and time to systemic corticosteroid use or revision surgery. Although general guidelines for using biologics to treat CRSwNP were proposed by the European Position Paper on Rhinosinusitis and Nasal Polyps in 2020 and various studies have tested their efficacy, there is much more to learn about biologics—specific indication and choice of biologics based on the endotypes, for instance. Understanding the vascular distribution of monoclonal antibodies and the differences in the vascularity of the non-polyp mucosa and nasal polyp tissue will not only aid understanding of each biologic’s clinical effect but also provide insights to establishing a more personalized approach to treating recalcitrant CRSwNP with biologics.

Highlights in the advances of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a complex upper airway inflammatory disease with a broad spectrum of clinical variants. As our understanding of the disease pathophysiology evolves, so too does our philosophy towards the approach and management of CRS. Endotyping is gaining favour over phenotype-based classifications, owing to its potential in prognosticating disease severity and delivering precision treatment. Endotyping is especially useful in challenging CRS with nasal polyposis cases, for whom novel treatment options such as biologicals are now available. The latest European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS2020) reflects these changes with updated rhinosinusitis classifications and new integrated care pathways. With the coronavirus disease 2019 (COVID-19) pandemic, physicians and rhinologists have to balance the responsibility of managing their patients' upper airway while adequately protecting themselves from droplet and aerosol transmission. This review summarises the key updates from EPOS2020, endotype-based classification and biomarkers. The role of biologicals in CRS and the lessons we can draw from their use in severe asthma will be examined. Finally, the principles of CRS management during COVID-19 will also be discussed.

Olfactory Outcomes with Dupilumab in Chronic Rhinosinusitis with Nasal Polyps

BACKGROUND

Loss of smell (LoS) is one of the most troublesome and difficult-to-treat symptoms of severe chronic rhinosinusitis with nasal polyps (CRSwNP).

OBJECTIVE

To assess the impact of dupilumab on sense of smell in severe CRSwNP.

METHODS

In the randomized SINUS-24 and SINUS-52 studies, adults with severe CRSwNP received dupilumab 300 mg subcutaneously or matching placebo every 2 weeks for 24 or 52 weeks, respectively. Smell was assessed using daily patient-reported LoS score (0-3) and University of Pennsylvania Smell Identification Test (UPSIT; 0-40). Data from the 2 studies were pooled through week 24. Relationships between patient phenotypes and smell outcomes were also assessed.

RESULTS

We randomized 724 patients (286 placebo, 438 dupilumab); mean CRSwNP duration was 11 years; 63% had prior sinonasal surgery. Mean baseline LoS was 2.74. Dupilumab produced rapid improvement in LoS, evident by day 3, which improved progressively throughout the study periods (least squares mean difference vs placebo -0.07 [95% CI -0.12 to -0.02]; nominal P < .05 at day 3, and -1.04 [-1.17 to -0.91]; P < .0001 at week 24). Dupilumab improved mean UPSIT by 10.54 (least squares mean difference vs placebo 10.57 [9.40-11.74]; P < .0001) at week 24 from baseline (score 13.90). Improvements were unaffected by CRSwNP duration, prior sinonasal surgery, or comorbid asthma and/or nonsteroidal anti-inflammatory drug-exacerbated respiratory disease. Baseline olfaction scores correlated with all measured local and systemic type 2 inflammatory markers except serum total immunoglobulin E.

CONCLUSIONS

Dupilumab produced rapid and sustained improvement in sense of smell, alleviating a cardinal symptom of severe CRSwNP.

Dysregulation of the epithelial barrier by environmental and other exogenous factors

The “epithelial barrier hypothesis” proposes that the exposure to various epithelial barrier–damaging agents linked to industrialization and urbanization underlies the increase in allergic diseases. The epithelial barrier constitutes the first line of physical, chemical, and immunological defense against environmental factors. Recent reports have shown that industrial products disrupt the epithelial barriers. Innate and adaptive immune responses play an important role in epithelial barrier damage. In addition, recent studies suggest that epithelial barrier dysfunction plays an essential role in the pathogenesis of the atopic march by allergen sensitization through the transcutaneous route. It is evident that external factors interact with the immune system, triggering a cascade of complex reactions that damage the epithelial barrier. Epigenetic and microbiome changes modulate the integrity of the epithelial barrier. Robust and simple measurements of the skin barrier dysfunction at the point‐of‐care are of significant value as a biomarker, as recently reported using electrical impedance spectroscopy to directly measure barrier defects. Understanding epithelial barrier dysfunction and its mechanism is key to developing novel strategies for the prevention and treatment of allergic diseases. The aim of this review is to summarize recent studies on the pathophysiological mechanisms triggered by environmental factors that contribute to the dysregulation of epithelial barrier function.

Olfactory dysfunction in LATY136F knock-in mice

OBJECTIVE

This study examined olfactory dysfunction in LATY136F knock-in mice and its pathogenic mechanism.

METHODS

The olfactory function of LATY136F knock-in mice was assessed by a behavioral test using cycloheximide solution, which has been used as a mice repellant because of its peculiar smell and unpleasant taste. The tests were administered to each group of LATY136F knock-in mice and WT mice at 8, 12, 16, 20, and 24 weeks of age. After the behavioral tests to evaluate olfactory function, the mice were sacrificed for evaluations by immunohistochemistry.

RESULTS

Behavioral tests to evaluate olfactory function showed that the LATY136F knock-in mice had a statistically significant level of olfactory dysfunction (P < 0.05). Histological analysis showed that the thickness of the olfactory epithelium in these mice was thinner than that in the age-matched wild type mice. There was no IgG4-RD like lesion in the olfactory epithelium of LATY136F knock-in mice. Olfactory marker protein and growth-associated protein 43 expressions in the olfactory epithelium of the LATY136F knock-in mice were markedly lesser than those in the wild type mice (P < 0.05).

CONCLUSION

The present study demonstrated that olfactory disturbances occurred in LATY136F knock-in mice. Furthermore, the mechanism was suggested to be reduced regeneration of the olfactory epithelium.

Chitinase-Like Protein Ym2 (Chil4) Regulates Regeneration of the Olfactory Epithelium via Interaction with Inflammation

The adult olfactory epithelium (OE) regenerates sensory neurons and nonsensory supporting cells from resident stem cells after injury. How supporting cells contribute to OE regeneration remains largely unknown. In this study, we elucidated a novel role of Ym2 (also known as Chil4 or Chi3l4), a chitinase-like protein expressed in supporting cells, in regulating regeneration of the injured OE in vivo in both male and female mice and cell proliferation/differentiation in OE colonies in vitro We found that Ym2 expression was enhanced in supporting cells after OE injury. Genetic knockdown of Ym2 in supporting cells attenuated recovery of the injured OE, while Ym2 overexpression by lentiviral infection accelerated OE regeneration. Similarly, Ym2 bidirectionally regulated cell proliferation and differentiation in OE colonies. Furthermore, anti-inflammatory treatment reduced Ym2 expression and delayed OE regeneration in vivo and cell proliferation/differentiation in vitro, which were counteracted by Ym2 overexpression. Collectively, this study revealed a novel role of Ym2 in OE regeneration and cell proliferation/differentiation of OE colonies via interaction with inflammatory responses, providing new clues to the function of supporting cells in these processes.SIGNIFICANCE STATEMENT The mammalian olfactory epithelium (OE) is a unique neural tissue that regenerates sensory neurons and nonsensory supporting cells throughout life and postinjury. How supporting cells contribute to this process is not entirely understood. Here we report that OE injury causes upregulation of a chitinase-like protein, Ym2, in supporting cells, which facilitates OE regeneration. Moreover, anti-inflammatory treatment reduces Ym2 expression and delays OE regeneration, which are counteracted by Ym2 overexpression. This study reveals an important role of supporting cells in OE regeneration and provides a critical link between Ym2 and inflammation in this process.

A murine model of eosinophilic chronic rhinosinusitis using the topical application of a vitamin D3 analog

BACKGROUND

Eosinophilic chronic rhinosinusitis (ECRS) is a chronic inflammatory disease, characterized by eosinophilic infiltration, T-helper type 2 (Th2-type) response, and olfactory dysfunction. A master regulator of Th2-type inflammation, thymic stromal lymphopoietin (TSLP), is important for basophil activation. TSLP-elicited basophils are a key factor in the pathogenesis of ECRS.

METHODS

In order to elucidate the mechanisms of ECRS in humans, we aimed to establish a murine model of ECRS based on TSLP production in response to the topical application of MC903 (a vitamin D3 analog) and the subsequent TSLP-induced basophil activation. Histological analyses were performed to assess immune cell infiltration into the nasal mucosa and to explore the impact of eosinophilic inflammation on the olfactory epithelium. The status of Th2-type inflammation was evaluated by quantitative real-time PCR and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Eosinophils, basophils, and M2 macrophages increased significantly in the nasal mucosa of the mice treated with MC903 and ovalbumin (OVA), compared to those treated with OVA alone or the controls. Quantitative real-time PCR and ELISA revealed elevated expression of interleukin (IL)-4, IL-5, IL-13, TSLP, the chemokine CCL11, and CCL24 in the nasal mucosa of the ECRS mice. In parallel, thinned olfactory epithelium and decreased mature olfactory sensory neurons were observed in the ECRS mice.

CONCLUSIONS

Our model of ECRS displayed Th2-type inflammation in the sinonasal region, including both eosinophil infiltration and basophil infiltration. Additionally, olfactory epithelium turned out to be affected by eosinophilic inflammation. These features are consistent with the characteristics of the human ECRS.

Olfactory Dysfunction is not a Determinant Of Patient-Reported Chronic Rhinosinusitis Disease Control

OBJECTIVES/HYPOTHESIS

As a cardinal symptom of chronic rhinosinusitis (CRS), hyposmia has been recommended to be assessed as a component of CRS disease control. Herein we determine the significance of hyposmia in CRS in the context of nasal obstruction and drainage symptoms.

STUDY DESIGN

Prospective, cross-sectional METHODS: Cross-sectional study of 308 CRS patients (102 CRSwNP, 206 CRSsNP) without prior endoscopic sinus surgery. The burden of nasal obstruction and hyposmia were assessed using the corresponding item scores on the 22-item Sinonasal Outcome Test (SNOT-22). Burden of nasal discharge was assessed using the mean of "thick nasal discharge" and "thick post-nasal discharge" SNOT-22 item scores. Patients were all asked to rate their CRS symptom control as "not at all," "a little," "somewhat," "very," or "completely."

RESULTS

In CRSwNP, only 4.9% had a hyposmia score > 1 with nasal obstruction and drainage scores less than or equal to 1. In CRSsNP, only 1.9% had a hyposmia score > 1 with nasal obstruction and drainage scores less than or equal to 1. On univariate association, CRS symptom control was significantly associated with nasal obstruction, hyposmia, and drainage in both CRSwNP and CRSsNP (P < .05 in all cases). Using multivariable regression to account for all nasal symptoms, only nasal obstruction and nasal discharge scores (but not hyposmia) were significantly associated with CRS symptom control.

CONCLUSIONS

Hyposmia rarely occurs without nasal obstruction or nasal drainage, and may therefore be redundant to assess for CRS disease control. Moreover, hyposmia was not associated with patient-reported CRS symptom control when accounting for the burden of nasal obstruction and drainage.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:E2116-E2120, 2021.

Olfaction: Sensitive indicator of inflammatory burden in chronic rhinosinusitis

BACKGROUND AND OBJECTIVE

Olfactory dysfunction has a high prevalence in chronic rhinosinusitis (CRS) patients and significantly affects quality of life. CRS is recognized as a complex disorder encompassing heterogeneous inflammatory processes in the nose and paranasal sinuses. Olfactory dysfunction in CRS patients is associated with the level of inflammatory mediators and the efficiency of inflammatory control. Learning about the association between CRS-related inflammation and olfactory function will provide clues to the pathogenesis of CRS.

STRUCTURE

The first section of this review describes the assessment of olfactory function using various measures, from ratings to MR based imaging. Then, we discuss the conductive and inflammatory mechanisms related to olfactory dysfunction in CRS: olfaction is associated with certain inflammatory patterns and is potentially a marker of CRS subtype. Finally, we review anti-inflammatory therapies including conservative and surgical approaches, and their effectiveness in olfactory dysfunction in CRS.

CONCLUSION

Assessment of olfactory function should be considered in the clinical evaluation of CRS patients, not only for detecting and quantifying patients' symptom, but also because it appears to be useful to objectively assess the efficacy of CRS treatment over time. In addition, olfaction can be expected to expand the library of CRS phenotypes and endotypes and, hence, pave the way for more precise, tailored treatment options.

Biomarkers for diagnosis and prediction of therapy responses in allergic diseases and asthma

Modern health care requires a proactive and individualized response to diseases, combining precision diagnosis and personalized treatment. Accordingly, the approach to patients with allergic diseases encompasses novel developments in the area of personalized medicine, disease phenotyping and endotyping, and the development and application of reliable biomarkers. A detailed clinical history and physical examination followed by the detection of IgE immunoreactivity against specific allergens still represents the state of the art. However, nowadays, further emphasis focuses on the optimization of diagnostic and therapeutic standards and a large number of studies have been investigating the biomarkers of allergic diseases, including asthma, atopic dermatitis, allergic rhinitis, food allergy, urticaria and anaphylaxis. Various biomarkers have been developed by omics technologies, some of which lead to a better classification of distinct phenotypes or endotypes. The introduction of biologicals to clinical practice increases the need for biomarkers for patient selection, prediction of outcomes and monitoring, to allow for an adequate choice of the duration of these costly and long‐lasting therapies. Escalating healthcare costs together with questions about the efficacy of the current management of allergic diseases require further development of a biomarker‐driven approach. Here, we review biomarkers in diagnosis and treatment of asthma, atopic dermatitis, allergic rhinitis, viral infections, chronic rhinosinusitis, food allergy, drug hypersensitivity and allergen immunotherapy with a special emphasis on specific IgE, the microbiome and the epithelial barrier. In addition, EAACI guidelines on biologicals are discussed within the perspective of biomarkers.

Role of IL-25, IL-33, and TSLP in triggering united airway diseases toward type 2 inflammation

Under the concept of "united airway diseases," the airway is a single organ wherein upper and lower airway diseases are commonly comorbid. The upper and lower airways are lined with respiratory epithelium that plays a vital role in immune surveillance and modulation as the first line of defense to various infective pathogens, allergens, and physical insults. Recently, there is a common hypothesis emphasizing epithelium-derived cytokines, namely IL-25, IL-33, and TSLP, as key regulatory factors that link in immune-pathogenic mechanisms of allergic rhinitis (AR), chronic rhinosinusitis (CRS), and asthma, mainly involving in type 2 inflammatory responses and linking innate and adaptive immunities. Herein, we review studies that elucidated the role of epithelium-derived triple cytokines in both upper and lower airways with the purpose of expediting better clinical treatments and managements of AR, CRS, asthma, and other associated allergic diseases via applications of the modulators of these cytokines.

Type 1/type 2 inflammatory cytokines correlate with olfactory function in patients with chronic rhinosinusitis

BACKGROUND

Olfactory dysfunction secondary to chronic rhinosinusitis (CRS) has been highly associated with impaired quality of life. Asian CRS patients showed a distinct inflammatory profile, with less type 2 endotype compared with European and North American. This study aimed to explore the pattern of the inflammatory cytokines in CRS patients from China and their association with olfactory function.

METHODS

Institutional review board-approved prospective study in which the olfactory function of 71 CRS patients was assessed with Sniffin' Sticks before the nasal endoscopic surgery. A set of cytokines and inflammatory mediators including type 1 and type 2 inflammatory cytokines were measured in nasal mucus by using a multiplex flow cytometric bead assay (CBA). Baseline characteristics in CRS patients were collected and the Spearman r statistic was performed to assess the association of olfactory function with cytokines and inflammatory mediators.

RESULTS

A total of 71 nasal mucus samples of CRS patients, including 25 chronic rhinosinusitis without nasal polyposis (CRSsNP) patients and 46 chronic rhinosinusitis with nasal polyposis (CRSwNP) patients, were evaluated in this study. The nasal mucus levels of type 1 inflammatory cytokine IFN-γ (interferon-γ), type 2 inflammatory cytokines including IL-4, IL-5 and GM-CSF (granulocyte-macrophage colony-stimulating factor) and anti-inflammatory cytokine IL-10 were significantly and inversely correlated with olfactory function in total patients with CRS (r = -0.308, p = 0.009; r = -0.250, p = 0.036; r = -0.399, p = 0.001; r = -0.269, p = 0.023; r = -0.273, p = 0.021, respectively). In CRSsNP, the olfactory function was inversely correlated with levels of type 1 inflammatory cytokine TNF-α (tumor necrosis factor-α) (r = -0.637, p = 0.001) and IL-10 (r = -0.468, p = 0.018). Nevertheless, the olfactory function in CRSwNP was inversely correlated with type 2 inflammatory cytokines including IL-4 (r = -0.303, p = 0.041) and IL-5 (r = -0.383, p = 0.009).

CONCLUSION

Both type 1 and type 2 inflammatory cytokines may contribute to the pathogenesis of CRS-associated olfactory dysfunction in the Chinese population.

Novel findings in immunopathophysiology of chronic rhinosinusitis and their role in a model of precision medicine

Our understanding of the pathophysiology of chronic rhinosinusitis (CRS) is continuously evolving. The traditional description of CRS in terms of two phenotypes based on the presence or absence of nasal polyps belies the underlying intricate immunopathophysiological processes responsible for this condition. CRS is being increasingly recognized as a disease spectrum encompassing a range of inflammatory states in the sinonasal cavity, with non-type 2 inflammatory disease on one end, type 2 inflammatory, eosinophil-heavy disease on the other and an overlap of both in different proportions in between. Abundance in research on the immune mechanisms of CRS has revealed various new endotypes that hold promise as biomarkers for the development of targeted therapies in severe, uncontrolled CRS. The introduction of precision medicine to manage this chronic, complex condition is a step forward in providing individualized care for all patients with CRS. In this review, the latest research on the pathophysiology of CRS with a focus on potential novel biomarkers and treatment options over the last 2 years are summarized and integrated into a suggested model of precision medicine in CRS.

Type 2/Th2-driven inflammation impairs olfactory sensory neurogenesis in mouse chronic rhinosinusitis model

BACKGROUND

Chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP) is a chronic inflammatory disease often accompanied by impairment of sense of smell. This symptom has been somewhat overlooked, and its relationship to inflammatory cytokines, tissue compression, neuronal loss, and neurogenesis is still unclear.

METHODS

In order to elucidate potential mechanisms leading to CRS in humans, we have established a type 2/T helper type 2 cell (Th2)-mediated allergic CRS mouse model, based on house dust mite (HDM) and Staphylococcus aureus enterotoxin B (SEB) sensitization. The inflammatory status of the olfactory epithelium (OE) was assessed using histology, biochemistry, and transcriptomics. The sense of smell was evaluated by studying olfactory behavior and recording electro-olfactograms (EOGs).

RESULTS

After 22 weeks, a typical type 2/Th2-mediated inflammatory profile was obtained, as demonstrated by increased interleukin (IL)-4, IL-5, and IL-13 in the OE. The number of mast cells and eosinophils was increased, and infiltration of these cells into the olfactory mucosa was also observed. In parallel, transcriptomic and histology analyses indicated a decreased number of immature olfactory neurons, possibly due to decreased renewal. However, the number of mature sensory neurons was not affected and neither the EOG nor olfactory behavior was impaired.

CONCLUSION

Our mouse model of CRS displayed an allergic response to HDM + SEB administration, including the type 2/Th2 inflammatory profile characteristic of human eosinophilic CRSwNP. Although the sense of smell did not appear to be altered in these conditions, the data reveal the influence of chronic inflammation on olfactory neurogenesis, suggesting that factors unique to humans may be involved in CRSwNP-associated anosmia.

Patterns of olfactory dysfunction in chronic rhinosinusitis identified by hierarchical cluster analysis and machine learning algorithms

BACKGROUND

Olfactory dysfunction is a common symptom of chronic rhinosinusitis (CRS). We previously identified several cytokines potentially linked to smell loss, potentially supporting an inflammatory etiology for CRS-associated olfactory dysfunction. In the current study we sought to validate patterns of olfactory dysfunction in CRS using hierarchical cluster analysis, machine learning algorithms, and multivariate regression.

METHODS

CRS patients undergoing functional endoscopic sinus surgery were administered the Smell Identification Test (SIT) preoperatively. Mucus was collected from the middle meatus using an absorbent polyurethane sponge and 17 inflammatory mediators were assessed using a multiplexed flow-cytometric bead assay. Hierarchical cluster analysis was performed to characterize inflammatory patterns and their association with SIT scores. The random forest approach was used to identify cytokines predictive of olfactory function.

RESULTS

One hundred ten patients were enrolled in the study. Hierarchical cluster analysis identified 5 distinct CRS clusters with statistically significant differences in SIT scores observed between individual clusters (p < 0.001). A majority of anosmic patients were found in a single cluster, which was additionally characterized by nasal polyposis (100%) and a high incidence of allergic fungal rhinosinusitis (50%) and aspirin-exacerbated respiratory disease (AERD) (33%). A random forest approach identified a strong association between olfaction and the cytokines interleukin (IL)-5 and IL-13. Multivariate modeling identified AERD, computed tomography (CT) score, and IL-2 as the variables most predictive of olfactory function.

CONCLUSION

Olfactory dysfunction is associated with specific CRS endotypes characterized by severe nasal polyposis, tissue eosinophilia, and AERD. Mucus IL-2 levels, CT score, and AERD were independently associated with smell loss.