Regulation of airway inflammation by Siglec-8 and Siglec-9 sialoglycan ligand expression

Supplementing Glucose Intake Reverses the Inflammation Induced by a High-Fat Diet by Increasing the Expression of Siglec-E Ligands on Erythrocytes

Siglec-9/E is a cell surface receptor expressed on immune cells and can be activated by sialoglycan ligands to play an immunosuppressive role. Our previous study showed that increasing the expression of Siglec-9 (the human paralog of mouse Siglec-E) ligands maintains functionally quiescent immune cells in the bloodstream, but the biological effects of Siglec-9 ligand alteration on atherogenesis were not further explored. In the present study, we demonstrated that the atherosclerosis risk factor ox-LDL or a high-fat diet could decrease the expression of Siglec-9/E ligands on erythrocytes. Increased expression of Siglec-E ligands on erythrocytes caused by dietary supplementation with glucose (20% glucose) had anti-inflammatory effects, and the mechanism was associated with glucose intake. In high-fat diet-fed apoE-/- mice, glucose supplementation decreased the area of atherosclerotic lesions and peripheral inflammation. These data suggested that increased systemic inflammation is attenuated by increasing the expression of Siglec-9/E ligands on erythrocytes. Therefore, Siglec-9/E ligands might be valuable targets for atherosclerosis therapy.

Current and emerging biological therapies for Chronic rhinosinusitis with nasal polyps with type 2 inflammation

INTRODUCTION

Chronic rhinosinusitis with nasal polyps (CRSwNP), especially CRSwNP with type 2 inflammation, remains the most difficult-to-treat subtype with high prevalence worldwide. The emergence of biologics has the potential to fulfill the unmet medical needs of patients with CRSwNP driven by type 2 inflammation.

AREAS COVERED

A current review of the literature was performed to overview current and emerging biological therapies in the treatment of CRSwNP.

EXPERT OPINION

In an era of precision medicine, biologics have been given expectations to provide customized therapies to patients with CRSwNP, particularly those with refractory CRSwNP. Large clinical trials and real-world experiences are both essential for the application of biologics. Moreover, to make biological therapy more tailored to patients, an in-depth understanding of the different mechanisms of biologics, further elucidating the relationship between biologics and conventional medical and surgical treatments, and identifying predictive biomarkers warrant thorough investigations.

Profiles of immune infiltration in seasonal allergic rhinitis and related genes and pathways

BACKGROUND

Seasonal allergic rhinitis (SAR) is a chronic inflammatory disease for which the molecular mechanism is unclear.

METHODS

Whole blood, CD4⁺ T cells in peripheral blood mononuclear cells (PBMCs), and CD4⁺ T cells in nasal mucosa from SAR-related datasets (GSE43497, GSE50223, and GSE49782) were downloaded from the Gene Expression Omnibus (GEO) database. Differences in SAR-associated immune cell infiltration in the PBMCs were analyzed using the CIBERSORT algorithm. Differential gene expression analysis was conducted between different groups. Gene set enrichment analysis (GSEA) was performed using the clusterProfiler package to explore functional changes in signaling pathways.

RESULTS

There was a significant increase in the proportion of CD8⁺ T cells and a significant decrease in the proportion of neutrophils in the whole blood of SAR patients after allergen challenge compared to SAR patients after diluent challenge. This pattern was also found in SAR patients compared to healthy controls (HCs) by flow cytometry. The NF-κB and Toll-like receptor signaling pathways were enriched in SAR patients following allergen challenge. The expression of CD4⁺ T cell marker genes and associated cytokines significantly differed between allergen-treated SAR patients, diluent-treated SAR patients and HCs. We also observed heightened CD4⁺ T cell related genes, cytokines and pathways activation in the nasal mucosa region of SAR patients after allergen challenge.

CONCLUSION

Our analysis revealed that T cell receptor signaling pathways, T helper 1 (Th1) /T helper 2 (Th2) cell differentiation may contribute to the development of SAR. The present study is the first bioinformatic analysis to quantify immune cell infiltration and identify underlying SAR mechanisms from combined microarray data and provides insight for further research into the molecular mechanisms of SAR.

Computationally guided conversion of the specificity of E-selectin to mimic that of Siglec-8

Sulfated glycans have been found to be associated with various diseases and therefore have significant potential in molecular pathology as biomarkers. Although lectins are useful reagents for detecting glycans, there is a paucity of sulfate-recognizing lectins, and those that exist, such as from Maackia amurensis, display mixed specificities. Recombinant lectin engineering offers an emerging tool for creating novel glycan recognition by altering and/or enhancing endogenous specificities. The present study demonstrated the use of computational approaches in the engineering of a mutated form of E-selectin that displayed highly specific recognition of 6'-sulfo-sialyl Lewis X (6'-sulfo-sLe^x), with negligible binding to its endogenous nonsulfated ligand, sLe^x. This new specificity mimics that of the unrelated protein Siglec-8, for which 6'-sulfo-sLe^x is its preferred ligand. Molecular dynamics simulations and energy calculations predicted that two point mutations (E92A/E107A) would be required to stabilize binding to the sulfated oligosaccharide with E-selectin. In addition to eliminating putative repulsions between the negatively charged side chains and the sulfate moiety, the mutations also abolished favorable interactions with the endogenous ligand. Glycan microarray screening of the recombinantly expressed proteins confirmed the predicted specificity change but also identified the introduction of unexpected affinity for the unfucosylated form of 6'-sulfo-sLe^x (6'-sulfo-sLacNAc). Three key requirements were demonstrated in this case for engineering specificity for sulfated oligosaccharide: 1) removal of unfavorable interactions with the 6'-sulfate, 2) introduction of favorable interactions for the sulfate, and 3) removal of favorable interactions with the endogenous ligand.

The ingenious mast cell: Contemporary insights into mast cell behavior and function

Mast cells are (in)famous for their role in allergic diseases, but the physiological and pathophysiological roles of this ingenious cell are still not fully understood. Mast cells are important for homeostasis and surveillance of the human system, recognizing both endogenous and exogenous agents, which induce release of a variety of mediators acting on both immune and non-immune cells, including nerve cells, fibroblasts, endothelial cells, smooth muscle cells, and epithelial cells. During recent years, clinical and experimental studies on human mast cells, as well as experiments using animal models, have resulted in many discoveries that help decipher the function of mast cells in health and disease. In this review, we focus particularly on new insights into mast cell biology, with a focus on mast cell development, recruitment, heterogeneity, and reactivity. We also highlight the development in our understanding of mast cell-driven diseases and discuss the development of novel strategies to treat such conditions.

Eosinophils, a Jack of All Trades in Immunity: Therapeutic Approaches for Correcting Their Functional Disorders

BACKGROUND AND OBJECTIVE

Eosinophils are primitive myeloid cells derived from bonemarrow precursors and require the intervention of interleukin (IL)-5 for their survival and persistence in blood and tissues. Under steady-state conditions, they contribute to immune regulation and homeostasis. Under pathological circumstances, eosinophils are involved in host protection against parasites and participate in allergy and inflammation.

DISCUSSION

Mostly, in asthma, eosinophils provoke airway damage via the release of granule contents and IL-13 with mucus hypersecretion and differentiation of goblet cells. Then, tissue remodeling follows with the secretion of transforming growth factor-β. Eosinophils are able to kill helminth larvae acting as antigen-presenting cells with the involvement of T helper (h)-2 cells and subsequent antibody response. However, they also exert pro-worm activity with the production of suppressive cytokine (IL- 10 and IL-4) and inhibition of nitric oxide. Eosinophils may play a pathogenic role in the course of chronic and autoimmune disease, e.g., inflammatory bowel disease and eosinophilic gastroenteritis, regulating Th2 responses and promoting a profibrotic effect. In atopic dermatitis, eosinophils are commonly detected and may be associated with disease severity. In cutaneous spontaneous urticaria, eosinophils participate in the formation of wheals, tissue remodeling and modifications of vascular permeability. With regard to tumor growth, it seems that IgE can exert anti-neoplastic surveillance via mast cell and eosinophil-mediated cytotoxicity, the so-called allergo-oncology. From a therapeutic point of view, monoclonal antibodies directed against IL-5 or the IL-5 receptors have been shown to be very effective in patients with severe asthma. Finally, as an alternative treatment, polyphenols for their anti-inflammatory and anti-allergic activities seem to be effective in reducing serum IgE and eosinophil count in bronchoalveolar lavage in murine asthma.

CONCLUSION

Eosinophils are cells endowed with multiple functions and their modulation with monoclonal antibodies and nutraceuticals may be effective in the treatment of chronic disease.

Carbohydrates in allergy: from disease to novel immunotherapies

Respiratory allergic disorders are a global public health problem that are responsible for substantial morbidity and healthcare expenditure. Despite the availability of allergen immunotherapy (AIT), its efficacy is suboptimal and regimens are lengthy, with a significant risk of potentially severe side effects. Studies on the recognition of allergens by immune cells through carbohydrate-lectin interactions, which play a crucial role in immune modulation and pathogenesis of allergy, have paved the way for improvements in AIT. We highlight innovative approaches for more effective and safer AIT, including the use of allergens conjugated to specific carbohydrates that bind to C-type lectins (CLRs) and sialic acid-binding immunoglobulin-type lectins (Siglecs) on immune cells to induce suppressive responses.

Targetable pathogenic mechanisms in nasal polyposis

Chronic rhinosinusitis with nasal polyps (CRSwNP) represents a challenging disease entity with significant rates of recurrence following appropriate medical and surgical therapy. Recent approval of targeted biologics in CRSwNP compels deeper understanding of underlying disease pathophysiology. Both of the approved biologics for CRSwNP modulate the type 2 inflammatory pathway, and the majority of drugs in the clinical trials pathway are similarly targeted. However, there remain multiple other pathogenic mechanisms relevant to CRSwNP for which targeted therapeutics already exist in other inflammatory diseases that have not been studied directly. In this article we summarize pathogenic mechanisms of interest in CRSwNP and discuss the results of ongoing clinical studies of targeted therapeutics in CRSwNP and other related human inflammatory diseases.

The Role of Heat Shock Protein 70 kDa in Asthma

Asthma is a complex chronic disorder of the airways, affecting immune and structural cells and inducing both protein and tissue remodeling. Heat shock proteins 70 kDa (HSP70s) are highly conserved members of the stress-induced family, possessing precisely described chaperone activity. There is growing evidence of a tight relationship between inflammatory diseases of different origins and the elevation of local HSP70 expression and secretion. Although extracellular HSP70 does not serve as a common marker of asthma, elevated HSP70 levels have been detected in the peripheral blood serum and sputum of patients with asthma, as well as in the bronchoalveolar lavage fluid of mice with induced allergic airway inflammation. Possessing diverse immunomodulating properties, extracellular HSP70 can manifest different activities in airway inflammatory processes and asthma, acting either as a pro-inflammatory trigger, or an anti-inflammatory agent. This review will discuss the effects and possible mechanisms concerning HSP70 implication in airway inflammation regulation in asthma. We examine ATPase and chaperone activities of HSP70 as potential modulators of immune responses in asthma. Given the crucial role of a chronic inflammatory response in asthma, understanding the effects of HSP70 on immune and structural cells may reveal new perspectives for the therapeutic control of inflammation.

Discovery, Function, and Therapeutic Targeting of Siglec-8

Siglecs (sialic acid-binding immunoglobulin-like lectins) are single-pass cell surface receptors that have inhibitory activities on immune cells. Among these, Siglec-8 is a CD33-related family member selectively expressed on human mast cells and eosinophils, and at low levels on basophils. These cells can participate in inflammatory responses by releasing mediators that attract or activate other cells, contributing to the pathogenesis of allergic and non-allergic diseases. Since its discovery in 2000, initial in vitro studies have found that the engagement of Siglec-8 with a monoclonal antibody or with selective polyvalent sialoglycan ligands induced the cell death of eosinophils and inhibited mast cell degranulation. Anti-Siglec-8 antibody administration in vivo to humanized and transgenic mice selectively expressing Siglec-8 on mouse eosinophils and mast cells confirmed the in vitro findings, and identified additional anti-inflammatory effects. AK002 (lirentelimab) is a humanized non-fucosylated IgG1 antibody against Siglec-8 in clinical development for mast cell- and eosinophil-mediated diseases. AK002 administration has safely demonstrated the inhibition of mast cell activity and the depletion of eosinophils in several phase 1 and phase 2 trials. This article reviews the discovery and functions of Siglec-8, and strategies for its therapeutic targeting for the treatment of eosinophil- and mast cell-associated diseases.

The Roles of Siglec7 and Siglec9 on Natural Killer Cells in Virus Infection and Tumour Progression

The function of natural killer (NK) cells, defending against virus infection and tumour progression, is regulated by multiple activating and inhibiting receptors expressed on NK cells, among which sialic acid-bind immunoglobulin-like lectins (Siglecs) act as a vital inhibitory group. Previous studies have shown that Siglec7 and Siglec9 are expressed on NK cells, which negatively regulate the function of NK cells and modulate the immune response through the interaction of sialic acid-containing ligands. Siglec7 and Siglec9 are very similar in distribution, gene encoding, protein sequences, ligand affinity, and functions in regulating the immune system against virus and cancers, but differences still exist between them. In this review, we aim to discuss the similarities and differences between Siglec7 and Siglec9 and analyze their functions in virus infection and tumour progression in order to develop better anti-viral and anti-tumor immunotherapy in the future.

Promoter region single nucleotide polymorphism of siglec-8 gene associates with susceptibility to allergic asthma

Aim: Siglec-8 is exclusively expressed on mast cells, eosinophils and basophils. Possible association of six siglec-8 single nucleotide polymorphisms (SNPs) with susceptibility to allergic asthma in the Azeri population of Iran was investigated in this study. Materials & methods: A total of 194 patients and 190 normal subjects were enrolled. PCR single strand conformation polymorphism (PCR-SSCP) was used to determine the genotypes of the studied SNPs. Results: The rs36498 showed significant association with allergic asthma (odds ratio [OR]: 0.65; p = 0.022) and the T allele was found as a protective allele (OR: 0.61; p = 0.008). Also, eosinophil count in the CC genotype was significantly higher than that in the other genotypes (p = 0.026). Conclusion: The rs36498 is thought to influence the expression level of siglec-8. Siglec-8 could be a potential therapeutic target for allergic asthma.

Sialic acid-binding immunoglobulin-like lectins (Siglecs) detect self-associated molecular patterns to regulate immune responses

The mammalian immune system evolved to tightly regulate the elimination of pathogenic microbes and neoplastic transformed cells while tolerating our own healthy cells. Here, we summarize experimental evidence for the role of Siglecs-in particular CD33-related Siglecs-as self-receptors and their sialoglycan ligands in regulating this balance between recognition of self and non-self. Sialoglycans are found in the glycocalyx and extracellular fluids and matrices of all mammalian cells and can be considered as self-associated molecular patterns (SAMPs). We also provide an overview of the known interactions of Siglec receptors and sialoglycan-SAMPs. Manipulation of the Siglec-SAMP axis offers new therapeutic opportunities for the treatment of inflammatory conditions, autoimmune diseases and also cancer immunotherapy.

Asthma and Chronic Rhinosinusitis: Diagnosis and Medical Management

Asthma is a prevalent inflammatory condition of the lower airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchial hyperresponsiveness (BHR). Symptomatically, these patients may demonstrate wheezing, breathlessness, chest tightness, and coughing. This disease is a substantial burden to a growing population worldwide that currently exceeds 300 million individuals. This is a condition that is frequently encountered, but often overlooked in the field of otolaryngology. In asthma, comorbid conditions are routinely present and contribute to respiratory symptoms, decreased quality of life, and poorer asthma control. It is associated with otolaryngic diseases of the upper airways including allergic rhinitis (AR) and chronic rhinosinusitis (CRS). These conditions have been linked epidemiologically and pathophysiologically. Presently, they are considered in the context of the unified airway theory, which describes the upper and lower airways as a single functional unit. Thus, it is important for otolaryngologists to understand asthma and its complex relationships to comorbid diseases, in order to provide comprehensive care to these patients. In this article, we review key elements necessary for understanding the evaluation and management of asthma and its interrelatedness to CRS.

Sialylated keratan sulfate proteoglycans are Siglec-8 ligands in human airways

Human siglecs are a family of 14 sialic acid-binding proteins, most of which are expressed on subsets of immune cells where they regulate immune responses. Siglec-8 is expressed selectively on human allergic inflammatory cells—primarily eosinophils and mast cells—where engagement causes eosinophil apoptosis and inhibits mast cell mediator release. Evidence supports a model in which human eosinophils and mast cells bind to Siglec-8 sialoglycan ligands on inflammatory target tissues to resolve allergic inflammation and limit tissue damage. To identify Siglec-8-binding sialoglycans from human airways, proteins extracted from postmortem human trachea were resolved by size-exclusion chromatography and composite agarose–acrylamide gel electrophoresis, blotted and probed by Siglec-8-Fc blot overlay. Three size classes of Siglec-8 ligands were identified: 250 kDa, 600 kDa and 1 MDa, each of which was purified by affinity chromatography using a recombinant pentameric form of Siglec-8. Proteomic mass spectrometry identified all size classes as the proteoglycan aggrecan, a finding validated by immunoblotting. Glycan array studies demonstrated Siglec-8 binding to synthetic glycans with a terminal Neu5Acα2-3(6-sulfo)-Gal determinant, a quantitatively minor terminus on keratan sulfate (KS) chains of aggrecan. Treating human tracheal extracts with sialidase or keratanase eliminated Siglec-8 binding, indicating sialylated KS chains as Siglec-8-binding determinants. Treating human tracheal histological sections with keratanase also completely eliminated the binding of Siglec-8-Fc. Finally, Siglec-8 ligand purified from human trachea extracts induced increased apoptosis of freshly isolated human eosinophils in vitro. We conclude that sialylated KS proteoglycans are endogenous human airway ligands that bind Siglec-8 and may regulate allergic inflammation.

Targeting sialic acid-Siglec interactions to reverse immune suppression in cancer

Changes in sialic acids in cancer have been observed for many years. In particular, the increase of sialoglycan density or hypersialylation in tumors has been described. Recent studies have identified mechanisms for immune evasion based on sialoglycan interactions with immunoregulatory Siglec receptors that are exploited by tumor cells and microorganisms alike. Siglecs are mostly inhibitory receptors similar to known immune checkpoints including PD-1 or CTLA-4 that are successfully targeted with blocking antibodies for cancer immunotherapy. Here, we summarize the known changes of sialic acids in cancer and the role Siglec receptors play in cancer immunity. We also focus on potential ways to target these Siglec receptors or sialoglycans in order to improve anti-cancer immunity.

Immunoregulatory Siglec ligands are abundant in human and mouse aorta and are up-regulated by high glucose

AIM

Inflammation is a driving force in development of atherosclerosis, and hyperglycemia is a significant risk factor for angiopathy. Siglec-9, expressed on human neutrophils and macrophages, engages specific glycan ligands on tissues to diminish ongoing inflammation.

MATERIALS AND METHOD

Siglec-9 ligands on human aorta were characterized and the effects of high glucose exposure on the expression of ligands for Siglec-9 on human umbilical vein endothelial cells (HUV-EC-C) in vitro and ligands for the comparable siglec (Siglec-E) on mouse aorta in vivo were studied.

KEY FINDINGS

Siglec-9 ligands were expressed broadly on human aorta, as well as on HUV-EC-C. Siglec-9 ligands on HUV-EC-C were sharply up-regulated under high glucose exposure in vitro, as were Siglec-E ligands on the aortas of hyperglycemic mice. Exposure of HUV-EC-C to high-glucose resulted in consistent inhibitory changes in co-cultured macrophages including increased apoptosis and decreased phagocytosis. Control of Siglec-9 ligand expression on HUV-EC-C was downstream of changes in an enzyme involved in their biosynthesis, UDP-galactose-4-epimerase (GALE) and increased cellular N-acetylgalactosamine. The alteration of GALE was associated with the regulatory microRNA hsa-let-7f.

SIGNIFICANCE

We conclude that exposure to high-glucose results in up-regulation of immune inhibitory Siglec-9 sialoglycan ligands on aorta and HUV-EC-C cells downstream of altered GALE and GalNAc expression, resulting in up-regulation of apoptosis and decrease of phagocytic activity of macrophages. Changes in Siglec-9 sialoglycan ligand expression on vascular endothelial cells may be a natural response to the initial steps of atherosclerosis and might be a potential target to regulate inflammation in diabetic angiopathy.

Immunomodulators in chronic rhinosinusitis

Objective

To provide new insight into how chronic rhinosinusitis (CRS) is conceptualized and treated with a focus on immunomodulator therapy.

Data sources

Pubmed, Medline, and Embase.

Methods

A current review of the evidence is provided for immunomodulators investigated for treatment of CRS with nasal polyps (CRSwNP).

Results

Biologic therapies targeting IgE, IL-4, IL-5, and IL-13 for the treatment of CRSwNP have shown promise and are currently in phase 3 trials. Anti-immunoglobin E (IgE) therapy with omalizumab was assessed in 6 studies, anti-interleukin (IL)-5 therapy in 3 studies (2 mepolizumab, 1 reslizumab) and anti IL-4/IL-13 (dupilumab) therapy in one study. Studied outcomes varied, but the majority of trials identified clinical benefit of therapy over placebo. Other potential targets include thymic stromal lymphopoetin (TSLP), IL-25, IL-33, and sialic acid-binding immunoglobulin-type lectin (Siglec)-8. Small molecule drugs that target the dysregulation of the immune system in CRS are also being investigated for their immunomodulatory effects on inflammation.

Conclusion

Immunomodulator therapies for CRS currently in development will likely provide another therapeutic option for patients who have severe disease unresponsive to corticosteroids and surgery. Targeted monoclonal antibody therapies have shown encouraging results and phase 3 trials are underway. IL-4/IL-13 inhibition has shown the most promise to date. Further larger, well-designed trials are needed to improve understanding of these molecules and to offer endotype-driven therapies in the management of CRS. None of these therapeutics have shown long-term immunomodulation when discontinued and therefore further investigation into the pathomechanism of disease continues to be needed.

Chronic Rhinosinusitis-Could Phenotyping or Endotyping Aid Therapy?

OBJECTIVES

We reviewed the phenotyping and endotyping of chronic rhinosinusitis (CRS) and treatment options.

METHODS

We searched PubMed, Google, Google Scholar, and the Proquest Central Database of the Kırıkkale University Library.

RESULTS

Phenotypes are observable properties of an organism produced by the environment acting upon the genotype, that is, patients with a particular disorder are subgrouped according to common characteristics. Currently, CRS is usually phenotyped as being with (CRSwNP) or without (CRSsNP) nasal polyps. However, this is not immutable as some individuals progress from nonpolyp to polypoid CRS over time. Phenotypes of CRS are also based on inflammatory patterns, generally CRSwNP is eosinophilic, CRSsNP neutrophilic; but there is a spectrum, rather than a clear-cut division into 2 types. An endotype is a subtype of a condition defined by a distinct functional or pathobiological mechanism. Endotypes of CRS can be (1) nontype Th2, (2) moderate type Th2, and (3) severe type Th2 immune reactions, based on cytokines and mediators such as IL4, 5, 13. CRS endotyping can also include a (1) type 2 cytokine-based approach, (2) eosinophil-mediated approach, (3) immunoglobulin E-based approach, and (4) cysteinyl leukotriene-based approach. Subdivisions of CRSwNP can be made into nonsteroidal anti-inflammatory drug-exacerbated respiratory disease, allergic fungal sinusitis, and eosinophil pauci-granulomatous arteritis by testing. General treatment for all CRS is nasal douching. The place of surgery needs careful reconsideration. Endotype-directed therapies include glucocorticosteroids, antibiotics, aspirin, antifungals, anticytokines, and immunoglobulin replacement. The recognition of united airways and the co-occurrence of CRSwNPs and severe asthma should lead to common endotyping of both upper and lower airways in order to better direct therapy.

CONCLUSION

Endotyping can allow for the identification of groups of patients with CRS with a high likelihood of successful treatment, such as patients with a moderate type 2 immune reaction or those with acquired immune deficiency.

Siglec-8 and Siglec-9 binding specificities and endogenous airway ligand distributions and properties

Siglecs are transmembrane sialoglycan binding proteins, most of which are expressed on leukocyte subsets and have inhibitory motifs that translate cell surface ligation into immune suppression. In humans, Siglec-8 on eosinophils, mast cells and basophils and Siglec-9 on neutrophils, monocytes and some T-cells, mediate immune cell death, inhibition of immune mediator release and/or enhancement of anti-inflammatory mediator release. Endogenous sialoglycan ligands in tissues, mostly uncharacterized, engage siglecs on leukocytes to inhibit inflammation. Glycan array analyses demonstrated that Siglec-8, Siglec-9 and their mouse counterparts Siglec-F and Siglec-E (respectively) have distinct glycan binding specificities, with Siglec-8 more structurally restricted. Since siglecs are involved in lung inflammation, we studied Siglec-8 and Siglec-9 ligands in human lungs and airways. Siglec-8 ligands are in tracheal submucosal glands and cartilage but not airway epithelium or connective tissues, whereas Siglec-9 ligands are broadly distributed. Mouse airways do not have Siglec-8 ligands, whereas Siglec-9 ligands are on airways of both species. Extraction of human airways and lung followed by electrophoretic resolution and siglec blotting revealed Siglec-8 ligands in extracts of human trachea and cultured tracheal gland cells, but not parenchyma or cultured airway epithelial cells whereas Siglec-9 ligands were extracted from all airway and lung tissues and cells tested. Siglec-8 and Siglec-9 ligands in airways appear to be high molecular weight O-linked sialoglycoproteins. These data reveal differential glycan specificities of Siglec-8, Siglec-9 and their mouse counterparts Siglec-F and Siglec-E, and the tissue distributions and molecular characteristics of Siglec-8 and Siglec-9 sialoglycan ligands on human airways and lungs.

Precision Medicine in Chronic Rhinosinusitis with Nasal Polyps

Purpose of Review

Chronic rhinosinusitis is a disease with high prevalence, significant impact on health-related quality of life (HRQoL) and it is associated with substantial healthcare and productivity costs. We face an urgent need to improve the level of disease control and achieve higher patient satisfaction and disease prevention. Precision medicine is increasingly recognized as the way forward in optimal patient care. The combination of personalized care, prevention of disease, prediction of success of treatment, and participation of the patient in the elaboration of the treatment plan is expected to guarantee the best possible therapeutic approach for individuals suffering from a chronic disabling condition.

Recent Findings

This is a narrative review on the current state of endotypes, biomarkers, and targeted treatments in chronic inflammatory conditions of the nose and paranasal sinuses. Different phenotypes of rhinitis and chronic rhinosinusitis (CRS) have been described based on symptom severity and duration, atopy status, level of control, comorbidities, and presence or absence of nasal polyps in CRS. The underlying pathophysiological mechanisms are diverse, with different endotypes being recognized. Novel emerging therapies are targeting specific pathophysiological pathways or endotypes. This endotype-driven treatment approach requires careful selection of the patient population who might benefit from a specific treatment.

Summary

This review provides a comprehensive overview of the current state of endotypes, biomarkers and targeted treatments in chronic inflammatory conditions of the nose and paranasal sinuses.

Contemporary Pharmacotherapy for Allergic Rhinitis and Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) and allergic rhinitis (AR) are chronic conditions causing nasal inflammation. CRS is increasingly recognized as a chronic inflammatory process rather than a chronic infection. Although the primary initiating factors in CRS remain unclear, AR is driven by IgE-mediated hypersensitivity to environmental allergens. Understanding the underlying inflammatory pathways and disease endotypes are driving innovation toward novel pharmacotherapies targeting critical mediators implicated in CRS and AR, including IL-4, IL-13, IL-5, IgE, and epithelial initiators IL-33 and TSLP. Extensive investigations are needed to determine the role, timing, predictive prognostic factors and long-term safety and efficacy of these agents.

Recent advances in understanding eosinophil biology

With the advent of novel therapies targeting eosinophils, there has been renewed interest in understanding the basic biology of this unique cell. In this context, murine models and human studies have continued to highlight the role of the eosinophil in homeostatic functions and immunoregulation. This review will focus on recent advances in our understanding of eosinophil biology that are likely to have important consequences on the development and consequences of eosinophil-targeted therapies. Given the breadth of the topic, the discussion will be limited to three areas of interest: the eosinophil life cycle, eosinophil heterogeneity, and mechanisms of cell-cell communication.

A Review of Classification Schemes for Chronic Rhinosinusitis with Nasal Polyposis Endotypes

Objective

The recent development of endotypes to categorize disease variants of chronic rhinosinusitis (CRS) reflects an evolving understanding of the various pathophysiologic and pathogenetic mechanisms that contribute to the clinical heterogeneity of CRS manifestations. This review highlights popular endotype‐based criteria used to define different CRS with nasal polyposis (CRSwNP) subtypes and further discusses the emerging therapeutic advances for each classificatory approach.

Data Sources

PubMed literature review.

Methods

A review of the current literature was conducted to determine present‐day uses of immunologic and molecular profiles in the CRSwNP disease spectrum to identify specific endotypes.

Results

Four distinct but overlapping classification schemes have emerged to define endotypes within the CRSwNP phenotype: 1) type 2 cytokine‐based approach, 2) eosinophil‐based approach, 3) immunoglobulin (Ig)E‐based approach, and 4) cysteinyl based approach. The identification of key inflammatory biomarkers related to these CRSwNP endotypes has broadened the classification of CRS beyond common phenotypic expressions. Furthermore, CRSwNP endotypes may improve the selection of CRSwNP patients who are suitable candidates for biomarker‐specific treatment options, such as anti‐interleukin‐5; anti‐IgE; and platelet‐directed therapies.

Conclusion

Chronic rhinosinusitis endotyping with key biomarker patterns of inflammation allows for improved diagnostic and potentially therapeutic classifications of CRSwNP variants.

Glycobiology simplified: diverse roles of glycan recognition in inflammation

Glycans and complementary glycan-binding proteins are essential components in the language of cell-cell interactions in immunity. The study of glycan function is the purview of glycobiology, which has often been presented as an unusually complex discipline. In fact, the human glycome, composed of all of its glycans, is built primarily from only 9 building blocks that are combined by enzymes (writers) with specific and limited biosynthetic capabilities into a tractable and increasingly accessible number of potential glycan patterns that are functionally read by several dozen human glycan-binding proteins (readers). Nowhere is the importance of glycan recognition better understood than in infection and immunity, and knowledge in this area has already led to glycan mimetic anti-infective and anti-inflammatory drugs. This review includes a brief tutorial on human glycobiology and a limited number of specific examples of glycan-binding protein-glycan interactions that initiate and regulate inflammation. Examples include representatives from different glycan-binding protein families, including the C-type lectins (E-selectin, P-selectin, dectin-1, and dectin-2), sialic acid-binding immunoglobulin-like lectins (sialic acid-binding immunoglobulin-like lectins 8 and 9), galectins (galectin-1, galectin-3, and galectin-9), as well as hyaluronic acid-binding proteins. As glycoscience technologies advance, opportunities for enhanced understanding of glycans and their roles in leukocyte cell biology provide increasing opportunities for discovery and therapeutic intervention.