The barrier hypothesis and Oncostatin M: Restoration of epithelial barrier function as a novel therapeutic strategy for the treatment of type 2 inflammatory disease

Airway epithelial cells as drivers of severe asthma pathogenesis

Our understanding of the airway epithelium's role in driving asthma pathogenesis has evolved over time. From being regarded primarily as a physical barrier that could be damaged via inflammation, the epithelium is now known to actively contribute to asthma development through interactions with the immune system. The airway epithelium contains multiple cell types with specialized functions spanning barrier action, mucociliary clearance, immune cell recruitment, and maintenance of tissue homeostasis. Environmental insults may cause direct or indirect injury to the epithelium leading to impaired barrier function, epithelial remodelling, and increased release of inflammatory mediators. In severe asthma, the epithelial barrier repair process is inhibited and the response to insults is exaggerated, driving downstream inflammation. Genetic and epigenetic mechanisms also maintain dysregulation of the epithelial barrier, adding to disease chronicity. Here, we review the role of the airway epithelium in severe asthma and how targeting the epithelium can contribute to asthma treatment.

Systemic barrier dysfunction in type 2 inflammation diseases: perspective in the skin, airways, and gastrointestinal tract

The epithelial barrier in different organs is the first line of defense against environmental insults and allergens, with type 2 immunity serving as a protective function. Genetic factors, and biological and chemical insults from the surrounding environment altered regulate epithelial homeostasis through disruption of epithelial tight junction proteins or dilated intercellular spaces. Recent studies suggest that epithelial barrier dysfunction contributes to pathologic alteration in diseases with type 2 immune dysregulation including (but not limited to) atopic dermatitis, prurigo nodularis, asthma, chronic rhinosinusitis with nasal polyps, and eosinophilic esophagitis. In this review, we summarized current understanding of dysfunction of barrier and its interaction with type 2 inflammation across different organs, and discussed the role of epithelial barrier disruption in the pathogenesis of type 2 inflammation. In addition, recent progresses of emerging barrier restorative therapies are reviewed.

Advances in research on gut microbiota and allergic diseases in children

Epidemiological studies indicate a rising prevalence of allergic diseases, now recognized as a major global public health concern. In children, the progression of these diseases often follows the "atopic march," beginning with eczema, followed by food allergies, allergic rhinitis, and asthma. Recent research has linked gut microbiota dysbiosis to the development of allergic diseases in children. The gut microbiota, a crucial component of human health, plays a vital role in maintaining overall well-being, highlighting its potential in preventing and modifying the course of allergic diseases. This review examines the relationship between childhood allergic diseases and gut microbiota, drawing on the latest evidence. We first elaborated the concepts of allergic diseases and gut microbiota, followed by a discussion of the developmental trajectory of the gut microbiota in healthy children. This review further explored the richness, diversity, and composition of the gut microbiota, as well as specific microbial taxa associated with allergic disease. Lastly, we discussed the current status and future potential of probiotic interventions in managing pediatric allergic diseases.

Allergens in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with a complex relationship to allergens. While AD itself is not an allergic reaction and does not necessarily involve allergen sensitization, AD patients show higher rates of sensitization to food and inhalant allergens compared to the general population. Recent evidence refining the "dual allergen exposure hypothesis" demonstrates that early oral exposure to allergens through an intact gastrointestinal barrier typically promotes tolerance, while exposure through compromised skin or respiratory barriers often leads to sensitization. Therefore, the impaired skin barrier function in AD patients increases the risk of transcutaneous sensitization and may interfere with oral tolerance development. Interestingly, AD patients' sensitivity to contact allergens (such as metals and fragrances) is not necessarily higher than that of the general population, which may be related to the inherent properties of these allergens. Personalized allergen testing can help guide appropriate allergen avoidance and reintroduction strategies in AD management. The insights into optimal allergen exposure conditions have also expanded the potential applications of allergen-specific immunotherapy in preventing AD onset in high-risk populations and halting the atopic march.

Beyond classical immunity: Mast cells as signal converters between tissues and neurons

Mast cells are regarded as effectors in immune defense against parasites and venoms and play an essential role in the pathology of allergic diseases. More recently, mast cells have been shown to receive stimuli derived from type 2 immunity, tissue damage, stress, and inflammation. Mast cells then rapidly convert these diverse signals into appropriate, organ-specific protective reflexes that can limit inflammation or reduce tissue damage. In this review, we consider functions of mast cells in sensations-such as pain, itch, and nausea-arising from tissue insults and inflammation and the ensuing protective responses. In light of emerging data highlighting the involvement of mast cells in neuroimmune communication, we also propose that mast cells are "signal converters" linking immunological and tissue states with nervous system responses.

Probiotics as adjuvants to mitigate adverse reactions and enhance effectiveness in Food Allergy Immunotherapy

In the past decades, food allergies became increasingly dominant since early childhood, leading to a lower quality of life and to increasing costs addressed by the health care system. Beside standard avoidance of specific allergens and drug treatments following allergen exposure, a great deal of research has lately focused on Food Allergy Allergen Immunotherapy (FA-AIT). SCIT and EPIT (Subcutaneous and Epicutaneous Immunotherapy), OIT (Oral Immunotherapy), and SLIT (Sublingual Immunotherapy) consist in gradual exposure to allergens to desensitize and achieve tolerance once therapy has ended. Although promising, FA-AIT may bring acute local and systemic adverse reactions. To enhance efficacy, safety and convenience of AIT, the quest of potential adjuvants to mitigate the adverse reactions becomes crucial. Immunomodulatory activities, such as that of increasing the regulatory T cells and decreasing the IgE, have been observed in specific probiotics' strains and multiple studies elucidated the role of gut microbiota as a major interplayer among the host and its immune system. In this review, the microbiome modulation is shown as potential AIT adjuvant, nevertheless the need of more clinical studies in the near future is pivotal to assess the efficacy of targeted bacterial therapies and faecal microbiota transplantation.

Interleukin 1β Mediates the Pathogenesis of Nasal Mucosal Epithelial Barrier Dysfunction in Allergic Rhinitis

Background

The nasal mucosal epithelial barrier is the primary site of allergic rhinitis (AR). Interleukin-1β (IL-1β), as a crucial factor in immune inflammation, not only plays a crucial role in hypersensitivity reactions but also affects the digestive mucosa and skin epithelial barrier. However, the role of IL-1β in the nasal mucosal epithelial barrier in AR has not been reported, and this study aimed to investigate the effect and possible mechanisms involved.

Methods

Dermatophagoides pteronyssinus 1 was used as an allergen to construct an AR mouse model and stimulate human nasal mucosal epithelial cells (HNEpCs) and observe the expression changes of IL-1β and epithelial barrier indicators CLDN1 and OCLN in mouse nasal mucosa and HNEpCs. Then, the possible mechanisms of action were explored via exogenous IL-1β stimulation and pharmacological inhibition of IL-1β or its receptor interleukin-1 receptor type 1 (IL-1R1).

Results

The results showed that Dermatophagoides pteronyssinus 1-primed mouse nasal mucosa or human HENpCs had increased expression of IL-1β and decreased CLDN1 and OCLN, and IL-1β could directly lead to reduced expression of epithelial barrier indexes in HNEpCs. In addition, inhibition of IL-1β or IL-1R1 can effectively alleviate the damage to the epithelial barrier.

Conclusion

IL-1β has a destructive effect on the nasal mucosal epithelial barrier in AR, and inhibition of IL-1β or its receptor IL-1R1 can effectively protect the nasal mucosal barrier. IL-1β is a potential target for the treatment of AR.

Coexistence of Celiac Disease and Allergic Wheat Sensitivity: An Observational Study of Daily Clinical Practice

INTRODUCTION

Although separate immunogenic mechanisms are involved, IgE-type sensitization to wheat and celiac disease (CD) may coexist. We observationally assessed the importance of this relationship in daily practice using CD and wheat sensitization screenings.

METHODS

Celiac antibody (CA) screening and food prick tests (FPTs) were requested simultaneously from patients who presented to the Allergy Clinic between January 2022 and December 2023 and had any complaint accompanied by CD symptoms/findings (non-celiac group). Patients with positive CA (CA+) underwent endoscopy. As another group, FPT results were recorded for patients previously diagnosed with CD following a gluten-free diet (celiac group).

RESULTS

In total, 169 patients (124 non-celiac and 45 celiac) were included in the study. Wheat prick positivity (WP+) was observed in 1 patient with CD. Among 65 WP+ patients without a CD diagnosis, 14 (20.3%) tested positive for CA+, and histopathology detected CD in 4 of these cases. Among the 59 WP- patients, 4 (8.8%) had CA+. The CA+ status of those with WP+ was significantly higher than those with WP- (p = 0.023).

CONCLUSION

The 4 patients unaware of their CD exhibited WP+, with a higher rate of CA+ observed in the WP+ group. The association between WP+ and CA+ suggests that an impaired intestinal barrier may lead to simultaneous T helper 1 and 2 type inflammatory responses. Although different types of sensitization to the same food would not typically be expected, growing evidence indicates that this phenomenon does occur. Further studies are necessary to confirm these findings and to explore the underlying causes.

Hydrogen inhalation: A novel approach to alleviating allergic rhinitis symptoms by modulating nasal flora

Background

Allergic rhinitis (AR) is an allergic reaction dominated by the Th2 immune response in the nasal mucosa. The bacterial infection process affects the balance between Th1 and Th2 immune responses, and the level of exposure to environmental flora is closely related to the development of AR. Hydrogen (H2) is a medical molecule with anti-inflammatory and antioxidant properties. This study aimed to explore the possible mechanism of action of H2 on AR through its ability to regulate the balance of nasal flora.

Methods

Serum eosinophil count (EOS), immunoglobulin E (IgE) concentration, visual analog scale (VAS), total nasal symptom score (TNSS), and rhinoconjunctivitis quality of life questionnaire (RQLQ) were observed before and after hydrogen inhalation in AR patients. Skin prick test (SPT) was used to determine allergen sensitisation. Community composition and relative abundance of nasal flora were examined before and after hydrogen inhalation and in normal subjects using 16S rRNA gene sequencing.

Results

There were no adverse reactions during and after hydrogen inhalation in AR patients, with a favorable safety profile and significant improvements in VAS, TNSS, EOS, and IgE (P < 0.05). Cavity flora 16S rRNA gene sequencing showed higher abundance of Ruminococcus and Erysipelotrichaceae flora in the nasal cavity of AR patients than in normal subjects, and their abundance could be down-regulated after H2 inhalation. H2 significantly increased the abundance of Blautia_faecis and negatively correlated with VAS, TNSS, EOS, and IgE.

Conclusions

H2 may improve symptoms in AR patients by modulating the distribution of nasal flora. Trials with larger sample sizes are required to further test this hypothesis.

Trial registration

This trial was registered in the China Clinical Trial Registry (Registration No. ChiCTR2200062253).

IL-37 protects against house dust mite-induced airway inflammation and airway epithelial barrier dysfunction via inhibiting store-operated calcium entry

BACKGROUND

Airway epithelial barrier dysfunction has been proved to contribute to the development of type 2 inflammation of asthma. Interleukin (IL)-37 is a negative regulator of immune responses and allergic airway inflammation. However, whether IL-37 has any effect on airway epithelial barrier has been unknown.

METHODS

We evaluated the role of IL-37 in both mouse model and cultured 16HBE cells. Histology and ELISA assays were used to evaluate airway inflammation. FITC-dextran permeability assay was used to evaluate the airway epithelial barrier function. Immunofluorescence, western blot and quantitative Real-Time PCR (RT-PCR) were used to evaluate the distribution and expression of tight junction proteins. RT-PCR and Ca2+ fluorescence measurement were used to evaluate the mRNA expression and activity of store-operated calcium entry (SOCE).

RESULTS

IL-37 inhibited house dust mite (HDM)-induced airway inflammation and decreased the levels of IgE in serum and type 2 cytokines in bronchoalveolar lavage fluid (BALF) compared to asthmatic mice. IL-37 protected against HDM-induced airway epithelial barrier dysfunction, including reduced leakage of FITC-dextran, enhanced expression of TJ proteins, and restored the membrane distribution of TJ proteins. Moreover, IL-37 decreased the level of IL-33 in the BALF of asthmatic mice and the supernatants of HDM-treated 16HBE cells. IL-37 decreased the peak level of Ca2+ fluorescence induced by thapsigargin and HDM, and inhibited the mRNA expression of Orai1, suggesting an inhibiting effect of IL-37 on SOCE in airway epithelial cells.

CONCLUSION

IL-37 plays a protective role in airway inflammation and HDM-induced airway epithelial barrier dysfunction by inhibiting SOCE.

The potential of orally exposed risk factors and constituents aggravating food allergy: Possible mechanism and target cells

Food allergy is a significant concern for the health of humans worldwide. In addition to dietary exposure of food allergens, genetic and environmental factors also play an important role in the development of food allergy. However, only the tip of the iceberg of risk factors in food allergy has been identified. The importance of food allergy caused by orally exposed risk factors and constituents, including veterinary drugs, pesticides, processed foods/derivatives, nanoparticles, microplastics, pathogens, toxins, food additives, dietary intake of salt/sugar/total fat, vitamin D, and therapeutic drugs, are highlighted and discussed in this review. Moreover, the epithelial barrier hypothesis, which is closely associated with the occurrence of food allergy, is also introduced. Additionally, several orally exposed risk factors and constituents that have been reported to disrupt the epithelial barrier are elucidated. Finally, the possible mechanisms and key immune cells of orally exposed risk factors and constituents in aggravating food allergy are overviewed. Further work should be conducted to define the specific mechanism by which these risk factors and constituents are driving food allergy, which will be of central importance to the targeted therapy of food allergy.

The Acari Hypothesis, IV: revisiting the role of hygiene in allergy

Allergy and its manifestations were first appreciated in the 1870 s. Today, the mechanism by which specific substances elicit allergic reactions remains poorly understood. This is problematic from a healthcare perspective because the prevalence of allergic disease and its societal costs are substantial. Regarding mechanistic understanding of allergy, a new proposal, The Acari Hypothesis, has been forwarded. The Hypothesis, borne from consideration of alpha-gal syndrome, postulates that acarians, i.e., mites and ticks, are operative agents of allergy. By way of their pathogenic payloads and salivary pattern recognition receptor(s), acarians potentiate in human hosts the generation of IgE against acarian dietary elements. Those elements account for most, if not all, known human allergens. Inasmuch as acarian-human interactions occur on human epithelial surfaces, it is to be expected factors that influence the presence and/or operation of acarians on those surfaces influence the expression of allergic diseases. In this report, it is proposed that two adaptations of catarrhine primates, i.e., Old World monkeys, apes and humans, evolved to deter acarian species: firstly, the expansion of eccrine glands across the entirety of body surface area, and, secondly, the secretion of sweat by those glands. Contemporary hygienic practices that reduce and/or disrupt the operation of eccrine glands are likely responsible for the increase in allergic disease seen today.

The mucosal concept in chronic rhinosinusitis: Focus on the epithelial barrier

Chronic rhinosinusitis (CRS) is a common chronic nasal cavity and sinus disease affecting a growing number of individuals worldwide. Recent advances have shifted our understanding of CRS pathophysiology from a physical obstruction model of ventilation and drainage to a mucosal concept that recognizes the complexities of mucosal immunologic variations and cellular aberrations. A growing number of studies have demonstrated the alteration of the epithelial barrier during inflammatory states. Therefore, the current review has focused on the crucial role of epithelial cells within this mucosal framework in CRS, detailing the perturbed epithelial homeostasis, impaired epithelial cell barrier, dysregulated epithelial cell repair processes, and enhanced interactions between epithelial cells and immune cells. Notably, the utilization of novel technologies, such as single-cell transcriptomics, has revealed the novel functions of epithelial barriers, such as inflammatory memory and neuroendocrine functions. Therefore, this review also emphasizes the importance of epithelial inflammatory memory and the necessity of further investigations into neuroendocrine epithelial cells and neurogenic inflammation in CRS. We conclude by contemplating the prospective benefits of epithelial cell-oriented biological treatments, which are currently under investigation in rigorous randomized, double-blind clinical trials in patients with CRS with nasal polyps.

The last step to achieve barrier damage control

Heterogeneity characterises inflammatory diseases and different phenotypes and endotypes have been identified. Both innate and adaptive immunity contribute to the immunopathological mechanism of these diseases and barrier damage plays a prominent role triggering type 2 inflammation through the alarmins system, such as anti-Thymic Stromal Lymphopoietin (TSLP). Treatment with anti-TSLP monoclonal antibodies showed efficacy in severe asthma and clinical trials for other eosinophilic diseases are ongoing. The aim of this perspective review is to analyse current advances and future applications of TSLP inhibition to control barrier damage.

[Global environmental changes and the epithelial barrier hypothesis]

BACKGROUND

The global burden of noncommunicable diseases (NCD) has seen a strong increase in recent decades and attributable to the influence of environmental factors. For a multitude of diseases an association with epithelial barrier damage has been reported.

OBJECTIVE

This article provides an overview of the health effects of environmental pollution in the context of the epithelial barrier hypothesis of Cezmi Akdis. Additionally, exemplary mechanisms of a barrier damage are described. Finally, possible preventive and therapeutic consequences are discussed.

MATERIAL AND METHODS

The PubMed database was searched for the relevant topics and selected literature was reviewed.

RESULTS

A wide variety of substances can damage the epithelial barriers of the skin, lungs and gastrointestinal tract. The rise in the prevalences of atopic diseases could (partly) be due to an increased exposure to barrier-damaging substances, such as particulate matter and laundry detergents. A possible pathogenetic mechanism is the initiation and maintenance of an immune response by subepithelial penetration of microorganisms through damaged epithelia.

CONCLUSION

Based on the epithelial barrier hypothesis new therapeutic and prevention strategies can be developed. The regulation of hazardous chemicals and the fight against environmental pollution and climate change are necessary to reduce the burden of disease.

The Role of Gut Microbiota and Leaky Gut in the Pathogenesis of Food Allergy

Food allergy (FA) is a growing public health concern, with an increasing prevalence in Western countries. Increasing evidence suggests that the balance of human gut microbiota and the integrity of our intestinal barrier may play roles in the development of FA. Environmental factors, including industrialization and consumption of highly processed food, can contribute to altering the gut microbiota and the intestinal barrier, increasing the susceptibility to allergic sensitization. Compositional and functional alterations to the gut microbiome have also been associated with FA. In addition, increased permeability of the gut barrier allows the translocation of allergenic molecules, triggering Th2 immune responses. Preclinical and clinical studies have highlighted the potential of probiotics, prebiotics, and postbiotics in the prevention and treatment of FA through enhancing gut barrier function and promoting the restoration of healthy gut microbiota. Finally, fecal microbiota transplantation (FMT) is now being explored as a promising therapeutic strategy to prevent FA in both experimental and clinical studies. In this review article, we aim to explore the complex interplay between intestinal permeability and gut microbiota in the development of FA, as well as depict potential therapeutic strategies.

Oncostatin M's Involvement in the Pathogenesis of Chronic Rhinosinusitis: Focus on Type 1 and 2 Inflammation

OBJECTIVES

The cytokine oncostatin M (OSM) elicits pathogenic effects involving disruption of the epithelial barrier function as a part of immunological response networks. It is unclear how these integrated cytokine signals influence inflammation and other physiological processes in the pathology of chronic rhinosinusitis (CRS). We investigated the expression and distribution of OSM and OSM receptor (OSMR) in CRS patients' sinonasal specimens, and we compared the results with a panel of inflammatory cytokine levels and clinical features.

PATIENTS AND METHODS

We classified CRS patients as eosinophilic (ECRS, n = 36) or non-eosinophilic (non-ECRS, n = 35) based on the Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis phenotypic criteria and compared their cases with those of 20 control subjects. We also examined OSM's stimulatory effects on cytokine receptor expression levels using the human bronchial epithelium cell line BEAS-2B.

RESULTS

RT-PCR showed that the OSM mRNA levels were significantly increased in the CRS patients' ethmoid sinus mucosa. The OSM mRNA levels were positively correlated with those of TNF-α, IL-1β, IL-13, and OSMR-β. In BEAS-2B cells, OSM treatment induced significant increases in the OSMRβ, IL-1R1, and IL-13Ra mRNA levels.

CONCLUSIONS

OSM is involved in the pathogenesis of CRS in both type 1 and type 2 inflammation, suggesting the OSM signaling pathway as a potential therapeutic target for modulating epithelial stromal interactions.

Mast cells disrupt the function of the esophageal epithelial barrier

Mast cells (MCs) accumulate in the epithelium of patients with eosinophilic esophagitis (EoE), an inflammatory disorder characterized by extensive esophageal eosinophilic infiltration. Esophageal barrier dysfunction plays an important role in the pathophysiology of EoE. We hypothesized that MCs contribute to the observed impaired esophageal epithelial barrier. Herein, we demonstrate that coculture of differentiated esophageal epithelial cells with immunoglobulin E-activated MCs significanly decreased epithelial resistance by 30% and increased permeability by 22% compared with non-activated MCs. These changes were associated with decreased messenger RNA expression of barrier proteins filaggrin, desmoglein-1 and involucrin, and antiprotease serine peptidase inhibitor kazal type 7. Using targeted proteomics, we detected various cytokines in coculture supernatants, most notably granulocyte-macrophage colony-stimulating factor and oncostatin M (OSM). OSM expression was increased by 12-fold in active EoE and associated with MC marker genes. Furthermore, OSM receptor-expressing esophageal epithelial cells were found in the esophageal tissue of patients with EoE, suggesting that the epithelial cells may respond to OSM. Stimulation of esophageal epithelial cells with OSM resulted in a dose-dependent decrease in barrier function and expression of filaggrin and desmoglein-1 and an increase in protease calpain-14. Taken together, these data suggest a role for MCs in decreasing esophageal epithelial barrier function in EoE, which may in part be mediated by OSM.

Allergies Come Clean: The Role of Detergents in Epithelial Barrier Dysfunction

PURPOSE OF REVIEW

The prevalence and incidence of allergic disease have been rising in Westernized countries since the twentieth century. Increasingly, evidence suggests that damage to the epithelium initiates and shapes innate and adaptive immune responses to external antigens. The objective of this review is to examine the role of detergents as a potential risk factor for developing allergic disease.

RECENT FINDINGS

Herein, we identify key sources of human detergent exposure. We summarize the evidence suggesting a possible role for detergents and related chemicals in initiating epithelial barrier dysfunction and allergic inflammation. We primarily focus on experimental models of atopic dermatitis, asthma, and eosinophilic esophagitis, which show compelling associations between allergic disease and detergent exposure. Mechanistic studies suggest that detergents disrupt epithelial barrier integrity through their effects on tight junction or adhesion molecules and promote inflammation through epithelial alarmin release. Environmental exposures that disrupt or damage the epithelium may account for the increasing rates of allergic disease in genetically susceptible individuals. Detergents and related chemical compounds represent possible modifiable risk factors for the development or exacerbation of atopy.

Primary Prevention of Allergy - Is It Feasible?

The allergy epidemic has been attributed to environmental influences related to urbanization and the modern lifestyle. In this regard, various theories exploring the role of microbes (hygiene, old friends, microbiota, and biodiversity hypotheses), and the epithelial barrier (epithelial, dual allergen exposure and vitamin D hypotheses) have been proposed. These hypotheses have guided clinical studies that led to the formulation of intervention strategies during the proposed window of opportunity dubbed as the "first thousand days." The most significant intervention is a paradigm shift from allergen avoidance to early introduction of allergenic foods, particularly egg and peanut, around 6 months of age for the prevention of food allergy. This recommendation has been adopted globally and included in allergy prevention guidelines. Other strategies with less robust clinical evidence include: encouraging a healthy balanced diet, rich in fish, during pregnancy; continuing allergenic food intake during pregnancy and lactation; vitamin D supplementation in pregnant women with asthma; discouraging social indications for caesarean section delivery; judicious use of antibiotics in early childhood; daily emollient use from birth in high risk babies; and avoiding cow's milk formula use in the first week of life. However, if early supplementation with cow's milk formula is required, continuing at least 10 mL of formula daily until age 2 months may be considered. Translating these strategies to public health and clinical practice is still a work in progress. Long-term population studies are crucial to assess the feasibility of these measures on allergy prevention.

Trained innate immunity, epigenetics, and food allergy

In recent years the increased incidence of food allergy in Western culture has been associated with environmental factors and an inappropriate immune phenotype. While the adaptive immune changes in food allergy development and progression have been well-characterized, an increase in innate cell frequency and activation status has also recently received greater attention. Early in prenatal and neonatal development of human immunity there is a reliance on epigenetic and metabolic changes that stem from environmental factors, which are critical in training the immune outcomes. In the present review, we discuss how trained immunity is regulated by epigenetic, microbial and metabolic factors, and how these factors and their impact on innate immunity have been linked to the development of food allergy. We further summarize current efforts to use probiotics as a potential therapeutic approach to reverse the epigenetic and metabolic signatures and prevent the development of severe anaphylactic food allergy, as well as the potential use of trained immunity as a diagnostic and management strategy. Finally, trained immunity is presented as one of the mechanisms of action of allergen-specific immunotherapy to promote tolerogenic responses in allergic individuals.

Breaking the Gingival Barrier in Periodontitis

The break of the epithelial barrier of gingiva has been a subject of minor interest, albeit playing a key role in periodontal pathology, transitory bacteraemia, and subsequent systemic low-grade inflammation (LGI). The significance of mechanically induced bacterial translocation in gingiva (e.g., via mastication and teeth brushing) has been disregarded despite the accumulated knowledge of mechanical force effects on tight junctions (TJs) and subsequent pathology in other epithelial tissues. Transitory bacteraemia is observed as a rule in gingival inflammation, but is rarely observed in clinically healthy gingiva. This implies that TJs of inflamed gingiva deteriorate, e.g., via a surplus of lipopolysaccharide (LPS), bacterial proteases, toxins, Oncostatin M (OSM), and neutrophil proteases. The inflammation-deteriorated gingival TJs rupture when exposed to physiological mechanical forces. This rupture is characterised by bacteraemia during and briefly after mastication and teeth brushing, i.e., it appears to be a dynamic process of short duration, endowed with quick repair mechanisms. In this review, we consider the bacterial, immune, and mechanical factors responsible for the increased permeability and break of the epithelial barrier of inflamed gingiva and the subsequent translocation of both viable bacteria and bacterial LPS during physiological mechanical forces, such as mastication and teeth brushing.

Intestinal protein uptake and IgE-mediated food allergy

Food allergy is affecting 5-8% of young children and 2-4% of adults and seems to be increasing in prevalence. The cause of the increase in food allergy is largely unknown but proposed to be influenced by both environmental and lifestyle factors. Changes in intestinal barrier functions and increased uptake of dietary proteins have been suggested to have a great impact on food allergy. In this review, we aim to give an overview of the gastrointestinal digestion and intestinal barrier function and provide a more detailed description of intestinal protein uptake, including the various routes of epithelial transport, how it may be affected by both intrinsic and extrinsic factors, and the relation to food allergy. Further, we give an overview of in vitro, ex vivo and in vivo techniques available for evaluation of intestinal protein uptake and gut permeability in general. Proteins are digested by gastric, pancreatic and integral brush border enzymes in order to allow for sufficient nutritional uptake. Absorption and transport of dietary proteins across the epithelial layer is known to be dependent on the physicochemical properties of the proteins and their digestion fragments themselves, such as size, solubility and aggregation status. It is believed, that the greater an amount of intact protein or larger peptide fragments that is transported through the epithelial layer, and thus encountered by the mucosal immune system in the gut, the greater is the risk of inducing an adverse allergic response. Proteins may be absorbed across the epithelial barrier by means of various mechanisms, and studies have shown that a transcellular facilitated transport route unique for food allergic individuals are at play for transport of allergens, and that upon mediator release from mast cells an enhanced allergen transport via the paracellular route occurs. This is in contrast to healthy individuals where transcytosis through the enterocytes is the main route of protein uptake. Thus, knowledge on factors affecting intestinal barrier functions and methods for the determination of their impact on protein uptake may be useful in future allergenicity assessments and for development of future preventive and treatment strategies.

Detergent exposure induces epithelial barrier dysfunction and eosinophilic inflammation in the esophagus

BACKGROUND

Eosinophilic esophagitis (EoE) is a chronic allergic disease associated with type 2 inflammation and epithelial barrier dysfunction. The etiology is unknown, however, genetic heritability studies suggest environmental factors play a key role in pathogenesis. Detergents, such as sodium dodecyl sulfate (SDS), are common ingredients in household products such as dish soap and toothpaste. We hypothesized detergent exposure decreases epithelial barrier function and induces esophageal inflammation.

METHODS

Immortalized esophageal epithelial cells (EPC2) were cultured in air-liquid interface (ALI) and exposed to SDS. Barrier function/activity was assessed by transepithelial electrical resistance (TEER), FITC-dextran flux, and RT-PCR. Additionally, SDS-treated mouse esophageal organoids were evaluated for morphology. To investigate the effects of SDS in vivo, mice were treated with 0.5% SDS in drinking water for 14 days. Esophagi were assessed by gross morphology, histopathology, protein expression, and bulk RNA sequencing.

RESULTS

When EPC2 cells were exposed to SDS (5 μg/ml) for 96 h, TEER decreased (p = 0.03), and FITC-dextran flux increased (p = 0.0002). mRNA expression of IL-33 increased 4.5-fold (p = 0.02) at 6 h and DSG1 decreased (p < 0.0001) by 72 h. Disrupted epithelial integrity was noted in SDS-treated esophageal organoids. When mice were exposed to SDS, they showed increased esophageal width, chemokine, and metalloprotease levels. Mice treated with SDS also showed increased IL-33 protein expression, basal zone hyperplasia, CD4+ cell infiltration, and esophageal eosinophilia. RNA sequencing revealed upregulation of immune response pathway genes.

CONCLUSION

Exposure to SDS decreases esophageal barrier integrity, stimulates IL-33 production, and promotes epithelial hyperplasia and tissue eosinophilia. Detergents may be a key environmental trigger in EoE pathogenesis.

Role of Oncostatin M in the Pathogenesis of Vernal Keratoconjunctivitis: Focus on the Barrier Function of the Epithelium and Interleukin-33 Production by Fibroblasts

Purpose

Vernal keratoconjunctivitis (VKC) is a severe, recurrent allergic conjunctivitis. Previously, we found high concentrations of oncostatin M (OSM) in the tears of patients with VKC. Here, we investigated the role of OSM in VKC by focusing on epithelial barrier function and IL-33 production.

Methods

To assess the effect of OSM on the barrier function of human conjunctival epithelial cells (HConEpiCs), we measured transepithelial electrical resistance and dextran permeability. We also assessed expression of tight junction-related proteins such as E-cadherin and ZO-1 in HConEpiCs by Western blotting and immunofluorescence. Then we used immunohistochemistry to evaluate expression of Ki-67, E-cadherin, epithelial-mesenchymal transition-related proteins, and IL-33 in giant papillae (GPs) from patients with VKC. In addition, we used Western blotting, microarray, quantitative real-time polymerase chain reaction, and enzyme-linked immunosorbent assay to examine whether OSM activates signal transducer and activator of transcription 1 (STAT1) or STAT3 and induces the expression of various genes in human conjunctival fibroblasts (HConFs).

Results

OSM reduced expression of E-cadherin and ZO-1 in HConEpiCs, indicating barrier dysfunction. In immunohistochemistry, Ki-67 expression was present in the lower epithelial layer of the GPs, and E-cadherin expression was reduced in the superficial and lower layers; double staining revealed that GPs had a high number of fibroblasts expressing IL-33. In addition, in HConFs, OSM phosphorylated both STAT1 and STAT3 and induced IL-33.

Conclusions

OSM has important roles in severe, prolonged allergic inflammation by inducing epithelial barrier dysfunction and IL-33 production by conjunctival fibroblasts.

Generation of high affinity ICAM-1-specific nanobodies and evaluation of their suitability for allergy treatment

The nasal cavity is an important site of allergen entry. Hence, it represents an organ where trans-epithelial allergen penetration and subsequent IgE-mediated allergic inflammation can potentially be inhibited. Intercellular adhesion molecule 1 (ICAM-1) is highly expressed on the surface of respiratory epithelial cells in allergic patients. It was identified as a promising target to immobilize antibody conjugates bispecific for ICAM-1 and allergens and thereby block allergen entry. We have previously characterized a nanobody specific for the major birch pollen allergen Bet v 1 and here we report the generation and characterization of ICAM-1-specific nanobodies. Nanobodies were obtained from a camel immunized with ICAM-1 and a high affinity binder was selected after phage display (Nb44). Nb44 was expressed as recombinant protein containing HA- and His-tags in Escherichia coli (E.coli) and purified via affinity chromatography. SDS-PAGE and Western blot revealed a single band at approximately 20 kDa. Nb44 bound to recombinant ICAM-1 in ELISA, and to ICAM-1 expressed on the human bronchial epithelial cell line 16HBE14o- as determined by flow cytometry. Experiments conducted at 4°C and at 37°C, to mimic physiological conditions, yielded similar percentages (97.2 ± 1.2% and 96.7 ± 1.5% out of total live cells). To confirm and visualize binding, we performed immunofluorescence microscopy. While Texas Red Dextran was rapidly internalized Nb44 remained localized on the cell surface. Additionally, we determined the strength of Nb44 and ICAM-1 interaction using surface plasmon resonance (SPR). Nb44 bound ICAM-1 with high affinity (10-10 M) and had slow off-rates (10-4 s-1). In conclusion, our results showed that the selected ICAM-1-specific nanobody bound ICAM-1 with high affinity and was not internalized. Thus, it could be further used to engineer heterodimers with allergen-specific nanobodies in order to develop topical treatments of pollen allergy.

Treating allergies via skin - Recent advances in cutaneous allergen immunotherapy

Subcutaneous allergen immunotherapy has been practiced clinically for decades to treat airborne allergies. Recently, the cutaneous route, which exploits the immunocompetence of the skin has received attention, which is evident from attempts to use it to treat peanut allergy. Delivery of allergens into the skin is inherently impeded by the barrier imposed by stratum corneum, the top layer of the skin. While the stratum corneum barrier must be overcome for efficient allergen delivery, excessive disruption of this layer can predispose to development of allergic inflammation. Thus, the most desirable allergen delivery approach must provide a balance between the level of skin disruption and the amount of allergen delivered. Such an approach should aim to achieve high allergen delivery efficiency across various skin types independent of age and ethnicity, and optimize variables such as safety profile, allergen dosage, treatment frequency, application time and patient compliance. The ability to precisely quantify the amount of allergen being delivered into the skin is crucial since it can allow for allergen dose optimization and can promote consistency and reproducibility in treatment response. In this work we review prominent cutaneous delivery approaches, and offer a perspective on further improvisation in cutaneous allergen-specific immunotherapy.

Elevation of IgE in patients with psoriasis: Is it a paradoxical phenomenon?

Immunoglobulin E (IgE) elevation is a hallmark of allergic conditions such as atopic dermatitis (AD). The pathogenesis of AD is typically associated with high levels of IL-4 and IL-13 produced by activated T helper 2 (Th2) cells. Psoriasis, on the other hand, is an inflammatory skin disease mainly driven by Th17 cells and their related cytokines. Although the immunopathologic reactions and clinical manifestations are often easily distinguished in the two skin conditions, patients with psoriasis may sometimes exhibit AD-like manifestations, such as elevated IgE and persistent pruritic lesions. Given the fact that the effective T cells have great plasticity to re-differentiate in response to innate and environmental factors, this unusual skin condition could be a consequence of a cross-reaction between distinct arms of T-cell and humoral immunity. Here we review the literature concerning the roles of IgE in the development of AD and psoriasis, showing that elevated IgE seems to be an important indicator for this non-typical psoriasis.

Oncostatin M: Risks and Benefits of a Novel Therapeutic Target for Atherosclerosis

BACKGROUND

Cardiovascular disease (CVD) is a leading cause of death worldwide. It is predicted that approximately 23.6 million people will die from CVDs annually by 2030. Therefore, there is a great need for an effective therapeutic approach to combat this disease. The European Cardiovascular Target Discovery (CarTarDis) consortium identified Oncostatin M (OSM) as a potential therapeutic target for atherosclerosis. The benefits of modulating OSM - an interleukin (IL)-6 family cytokine - have since been studied for multiple indications. However, as decades of high attrition rates have stressed, the success of a drug target is determined by the fine balance between benefits and the risk of adverse events. Safety issues should therefore not be overlooked.

OBJECTIVE

In this review, a risk/benefit analysis is performed on OSM inhibition in the context of atherosclerosis treatment. First, OSM signaling characteristics and its role in atherosclerosis are described. Next, an overview of in vitro, in vivo, and clinical findings relating to both the benefits and risks of modulating OSM in major organ systems is provided. Based on OSM's biological function and expression profile as well as drug intervention studies, safety concerns of inhibiting this target have been identified, assessed, and ranked for the target population.

CONCLUSION

While OSM may be of therapeutic value in atherosclerosis, drug development should also focus on de-risking the herein identified major safety concerns: tissue remodeling, angiogenesis, bleeding, anemia, and NMDA- and glutamate-induced neurotoxicity. Close monitoring and/or exclusion of patients with various comorbidities may be required for optimal therapeutic benefit.

The Microbiome as a Gateway to Prevention of Allergic Disease Development

Allergic diseases exclusively affect tissues that face environmental challenges and harbor endogenous bacterial microbiota. The microbes inhabiting the affected tissues may not be mere bystanders in this process but actively affect the risk of allergic sensitization, disease development, and exacerbation or abatement of symptoms. Experimental evidence provides several plausible means by which the human microbiota could influence the development of allergic diseases including, but not limited to, effects on antigen presentation and induction of tolerance and allergen permeation by endorsing or disrupting epithelial barrier integrity. Epidemiological evidence attests to the significance of age-appropriate, nonpathogenic microbiota development in skin, gastrointestinal tract, and airways for protection against allergic disease development. Thus, there exist potential targets for preventive actions either in the prenatal or postnatal period. These could include maternal dietary interventions, antibiotic stewardship for both the mother and infant, reducing elective cesarean deliveries, and understanding barriers to breastfeeding and timing of food diversification. In here, we will review the current understanding and evidence of allergy-associated human microbiota patterns, their role in the development of allergic diseases, and how we could harness these associations to our benefit against allergies.

The Role of Tissue-Resident Macrophages in the Development and Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), comprising Crohn’s disease and ulcerative colitis, is a refractory disease with many immune abnormalities and pathologies in the gastrointestinal tract. Because macrophages can distinguish innocuous antigens from potential pathogens to maintain mucosa barrier functions, they are essential cells in the intestinal immune system. With numerous numbers in the intestinal tract, tissue-resident macrophages have a significant effect on the constant regeneration of intestinal epithelial cells and maintaining the immune homeostasis of the intestinal mucosa. They also have a significant influence on IBD through regulating pro-(M1) or anti-inflammatory (M2) phenotype polarization according to different environmental cues. The disequilibrium of the phenotypes and functions of macrophages, disturbed by intracellular or extracellular stimuli, influences the progression of disease. Further investigation of macrophages’ role in the progression of IBD will facilitate deciphering the pathogenesis of disease and exploring novel targets to develop novel medications. In this review, we shed light on the origin and maintenance of intestinal macrophages, as well as the role of macrophages in the occurrence and development of IBD. In addition, we summarize the interaction between gut microbiota and intestinal macrophages, and the role of the macrophage-derived exosome. Furthermore, we discuss the molecular and cellular mechanisms participating in the polarization and functions of gut macrophages, the potential targeted strategies, and current clinical trials for IBD.

Amoxicillin does not affect the development of cow’s milk allergy in a Brown Norway rat model

The use of antibiotics as well as changes in the gut microbiota have been linked to development of food allergy in childhood. It remains unknown whether administration of a single clinically relevant antibiotic directly promotes food allergy development when administrated during the sensitisation phase in an experimental animal model. We investigated whether the antibiotic amoxicillin affected gut microbiota composition, development of cow's milk allergy (CMA) and frequencies of allergic effector cells and regulatory T cells in the intestine. Brown Norway rats were given daily oral gavages of amoxicillin for six weeks and whey protein concentrate (WPC) with or without cholera toxin three times per week for the last five weeks. Microbiota composition in faeces and small intestine was analysed by 16S rRNA sequencing. The development of CMA was assessed by WPC‐specific IgE in serum, ear swelling response to WPC and body hypothermia following oral gavage of WPC. Allergic effector cells were analysed by histology, and frequencies of regulatory and activated T cells were analysed by flow cytometry. Amoxicillin administration reduced faecal microbiota diversity, reduced the relative abundance of Firmicutes and increased the abundance of Bacteroidetes and Proteobacteria. Despite these effects, amoxicillin did not affect the development of CMA, nor the frequencies of allergic effector cells or regulatory T cells. Thus, amoxicillin does not carry a direct risk for food allergy development when administrated in an experimental model of allergic sensitisation to WPC via the gut. This finding suggests that confounding factors may better explain the epidemiological link between antibiotic use and food allergy.

Gut-derived short-chain fatty acids modulate skin barrier integrity by promoting keratinocyte metabolism and differentiation

Barrier integrity is central to the maintenance of healthy immunological homeostasis. Impaired skin barrier function is linked with enhanced allergen sensitization and the development of diseases such as atopic dermatitis (AD), which can precede the development of other allergic disorders, for example, food allergies and asthma. Epidemiological evidence indicates that children suffering from allergies have lower levels of dietary fibre-derived short-chain fatty acids (SCFA). Using an experimental model of AD-like skin inflammation, we report that a fermentable fibre-rich diet alleviates systemic allergen sensitization and disease severity. The gut-skin axis underpins this phenomenon through SCFA production, particularly butyrate, which strengthens skin barrier function by altering mitochondrial metabolism of epidermal keratinocytes and the production of key structural components. Our results demonstrate that dietary fibre and SCFA improve epidermal barrier integrity, ultimately limiting early allergen sensitization and disease development.The Graphical Abstract was designed using Servier Medical Art images ( https://smart.servier.com ).

Serum oncostatin M is a potential biomarker of disease activity and infliximab response in inflammatory bowel disease measured by chemiluminescence immunoassay

BACKGROUND

Although endoscopy is the gold standard to assess disease activity and infliximab efficacy in inflammatory bowel disease (IBD), the invasive, costly, and time-consuming procedure limits its routine applications. We aimed to investigate the clinical value of serum oncostatin M (OSM) as a surrogate biomarker.

METHODS

Fifty healthy controls, 34 non-IBD patients, and 189 IBD patients who were pre-infliximab treatment (n = 122) or in infliximab maintenance (n = 67) were enrolled. A chemiluminescence immunoassay (CLIA) was constructed to quantify serum OSM concentrations. Receiver operator characteristic (ROC) curve analysis was used to evaluate the performance of blood biomarkers for IBD management.

RESULTS

The methodology of CLIA exhibited great analytical performance with a wide linear range of 31.25-25000 pg/mL, a low detection limit of 23.2 pg/mL, acceptable precision, and applicable accuracy. Patients with IBD (121.5 [43.3-249.4] pg/mL, p < 0.001) and non-IBD (72.4 [51.4-129.6] pg/mL, p = 0.005) had higher serum OSM levels than healthy controls (35.8 [23.2-56.4] pg/mL). In the analysis of clinical and endoscopic activity, serum OSM levels were elevated in moderate and severe patients compared to those in remission. IBD patients without mucosal healing had higher serum OSM levels than those with mucosal healing (AUC = 0.843). Besides, serum OSM levels were increased in clinical non-responders (287.3 [127.9-438] pg/mL) compared to responders (24.1 [23.2-53.4] pg/mL, p < 0.001), and showed great recognition ability with an AUC of 0.898.

CONCLUSIONS

The newly developed methodology of CLIA had great potential for use in the clinic. Elevated serum OSM expression was a promising biomarker of severe disease and infliximab non-response in IBD patients.

Does the epithelial barrier hypothesis explain the increase in allergy, autoimmunity and other chronic conditions?

There has been a steep increase in allergic and autoimmune diseases, reaching epidemic proportions and now affecting more than one billion people worldwide. These diseases are more common in industrialized countries, and their prevalence continues to rise in developing countries in parallel to urbanization and industrialization. Intact skin and mucosal barriers are crucial for the maintenance of tissue homeostasis as they protect host tissues from infections, environmental toxins, pollutants and allergens. A defective epithelial barrier has been demonstrated in allergic and autoimmune conditions such as asthma, atopic dermatitis, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, coeliac disease and inflammatory bowel disease. In addition, leakiness of the gut epithelium is also implicated in systemic autoimmune and metabolic conditions such as diabetes, obesity, multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis and autoimmune hepatitis. Finally, distant inflammatory responses due to a 'leaky gut' and microbiome changes are suspected in Alzheimer disease, Parkinson disease, chronic depression and autism spectrum disorders. This article introduces an extended 'epithelial barrier hypothesis', which proposes that the increase in epithelial barrier-damaging agents linked to industrialization, urbanization and modern life underlies the rise in allergic, autoimmune and other chronic conditions. Furthermore, it discusses how the immune responses to dysbiotic microbiota that cross the damaged barrier may be involved in the development of these diseases.

Risk, Mechanisms and Implications of Asthma-Associated Infectious and Inflammatory Multimorbidities (AIMs) among Individuals With Asthma: a Systematic Review and a Case Study

Our prior work and the work of others have demonstrated that asthma increases the risk of a broad range of both respiratory (e.g., pneumonia and pertussis) and non-respiratory (e.g., zoster and appendicitis) infectious diseases as well as inflammatory diseases (e.g., celiac disease and myocardial infarction [MI]), suggesting the systemic disease nature of asthma and its impact beyond the airways. We call these conditions asthma-associated infectious and inflammatory multimorbidities (AIMs). At present, little is known about why some people with asthma are at high-risk of AIMs, and others are not, to the extent to which controlling asthma reduces the risk of AIMs and which specific therapies mitigate the risk of AIMs. These questions represent a significant knowledge gap in asthma research and unmet needs in asthma care, because there are no guidelines addressing the identification and management of AIMs. This is a systematic review on the association of asthma with the risk of AIMs and a case study to highlight that 1) AIMs are relatively under-recognized conditions, but pose major health threats to people with asthma; 2) AIMs provide insights into immunological and clinical features of asthma as a systemic inflammatory disease beyond a solely chronic airway disease; and 3) it is time to recognize AIMs as a distinctive asthma phenotype in order to advance asthma research and improve asthma care. An improved understanding of AIMs and their underlying mechanisms will bring valuable and new perspectives improving the practice, research, and public health related to asthma.

Oncostatin-M Does Not Predict Treatment Response in Inflammatory Bowel Disease in a Pediatric Cohort

OBJECTIVES

This study aimed to determine whether mRNA expression of oncostatin-M (OSM) and its receptor (OSMR) in initial, pre-treatment intestinal biopsies is predictive of response to tumor necrosis factor antagonists (anti-TNF) in a pediatric inflammatory bowel disease (IBD) cohort. Secondary outcomes correlated OSM and OSMR expression with demographic variables; IBD type, extent, phenotype, and severity; laboratory values; and endoscopic findings.

METHODS

A retrospective chart review was conducted on 98 pediatric patients. Patients' clinical courses were stratified as follows: failed anti-TNF (n = 14), quiescent on anti-TNF (n = 36), anti-TNF naïve (n = 19), and age-matched non-IBD controls (n = 29). The mRNA from each patient's pre-treatment ileal or colonic biopsy was isolated, and expression of OSM and OSMR was analyzed.

RESULTS

There was no difference in OSM or OSMR expression among the three IBD groups; however, expression was significantly higher in patients with IBD than non-IBD controls (P < 0.001). OSM and OSMR were more highly expressed in patients with ulcerative colitis (UC) with a Mayo score of 3 (P = 0.0092 and P = 0.0313, respectively). High OSM expression correlated with severe disease activity indices at diagnosis (P = 0.002), anemia at diagnosis (P = 0.0236), and need for immunomodulators (P = 0.0193) and steroids (P = 0.0273) during patients' clinical courses.

CONCLUSIONS

OSM and OSMR expression were not predictive of response to anti-TNF in our pediatric cohort. OSM expression did correlate with IBD compared with healthy controls as well as with several clinical indicators of severe IBD.

Soluble ligands as drug targets for treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, is characterized by persistent inflammation in a hereditarily susceptible host. In addition to gastrointestinal symptoms, patients with IBD frequently suffer from extra-intestinal complications such as fibrosis, stenosis or cancer. Mounting evidence supports the targeting of cytokines for effective treatment of IBD. Cytokines can be included in a newly proposed classification "soluble ligands" that has become the third major target of human protein therapeutic drugs after enzymes and receptors. Soluble ligands have potential significance for research and development of anti-IBD drugs. Compared with traditional drug targets for IBD treatment, such as receptors, at least three factors contribute to the increasing importance of soluble ligands as drug targets. Firstly, cytokines are the main soluble ligands and targeting of them has demonstrated efficacy in patients with IBD. Secondly, soluble ligands are more accessible than receptors, which are embedded in the cell membrane and have complex tertiary membrane structures. Lastly, certain potential target proteins that are present in membrane-bound forms can become soluble following cleavage, providing further opportunities for intervention in the treatment of IBD. In this review, 49 drugs targeting 25 distinct ligands have been evaluated, including consideration of the characteristics of the ligands and drugs in respect of IBD treatment. In addition to approved drugs targeting soluble ligands, we have also assessed drugs that are in preclinical research and drugs inhibiting ligand-receptor binding. Some new types of targetable soluble ligands/proteins, such as epoxide hydrolase and p-selectin glycoprotein ligand-1, are also introduced. Targeting soluble ligands not only opens a new field of anti-IBD drug development, but the circulating soluble ligands also provide diagnostic insights for early prediction of treatment response. In conclusion, soluble ligands serve as the third-largest protein target class in medicine, with much potential for the drugs targeting them.

The OSMR Gene Is Involved in Hirschsprung Associated Enterocolitis Susceptibility through an Altered Downstream Signaling

Hirschsprung (HSCR) Associated Enterocolitis (HAEC) is a common life-threatening complication in HSCR. HAEC is suggested to be due to a loss of gut homeostasis caused by impairment of immune system, barrier defense, and microbiome, likely related to genetic causes. No gene has been claimed to contribute to HAEC occurrence, yet. Genetic investigation of HAEC by Whole-Exome Sequencing (WES) on 24 HSCR patients affected (HAEC) or not affected (HSCR-only) by enterocolitis and replication of results on a larger panel of patients allowed the identification of the HAEC susceptibility variant p.H187Q in the Oncostatin-M receptor (OSMR) gene (14.6% in HAEC and 5.1% in HSCR-only, p = 0.0024). Proteomic analysis on the lymphoblastoid cell lines from one HAEC patient homozygote for this variant and one HAEC patient not carrying the variant revealed two well distinct clusters of proteins significantly up or downregulated upon OSM stimulation. A marked enrichment in immune response pathways (q < 0.0001) was shown in the HAEC H187 cell line, while proteins upregulated in the HAEC Q187 lymphoblasts sustained pathways likely involved in pathogen infection and inflammation. In conclusion, OSMR p.H187Q is an HAEC susceptibility variant and perturbates the downstream signaling cascade necessary for the gut immune response and homeostasis maintenance.

Environmental factors in epithelial barrier dysfunction

The main interfaces controlling and attempting to homeostatically balance communications between the host and the environment are the epithelial barriers of the skin, gastrointestinal system, and airways. The epithelial barrier constitutes the first line of physical, chemical, and immunologic defenses and provides a protective wall against environmental factors. Following the industrial revolution in the 19th century, urbanization and socioeconomic development have led to an increase in energy consumption, and waste discharge, leading to increased exposure to air pollution and chemical hazards. Particularly after the 1960s, biological and chemical insults from the surrounding environment-the exposome-have been disrupting the physical integrity of the barrier by degrading the intercellular barrier proteins at tight and adherens junctions, triggering epithelial alarmin cytokine responses such as IL-25, IL-33, and thymic stromal lymphopoietin, and increasing the epithelial barrier permeability. A typical type 2 immune response develops in affected organs in asthma, rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, food allergy, and atopic dermatitis. The aim of this article was to discuss the effects of environmental factors such as protease enzymes of allergens, detergents, tobacco, ozone, particulate matter, diesel exhaust, nanoparticles, and microplastic on the integrity of the epithelial barriers in the context of epithelial barrier hypothesis.

Role of oncostatin M in the pathogenesis of vernal keratoconjunctivitis: focus on tissue remodeling

PURPOSE

Vernal keratoconjunctivitis (VKC) is a severe and recurrent allergic conjunctivitis, the mechanism of which is not well understood. In this study, we investigated the role of oncostatin M (OSM) in the pathogenesis of VKC, with a focus on tissue remodeling.

STUDY DESIGN

Clinical and experimental.

PATIENTS AND METHODS

The OSM concentrations in tear fluid samples obtained from VKC patients and healthy controls were measured using ELISA, and the expression of OSM mRNA and protein in giant papillae resected from VKC patients was investigated using RT-PCR and immunohistochemistry, respectively. In cultured human conjunctival epithelial cells (HconEpiCs), expression of OSM receptor β (OSMRβ) was detected using immunocytochemical and FACS analyses. Finally, we investigated whether recombinant OSM activated STAT1 and STAT3 to induce the expression of various genes related to tissue remodeling in HconEpiCs, by using Western blot analysis, microarray analysis, and RT-PCR.

RESULTS

The OSM concentration was higher in the tear fluid of VKC patients than in that of the healthy controls, and strong expression of OSM mRNA was found in the giant papillae. We also detected T cells expressing OSM in the giant papillae. In addition, HconEpiCs showed surface expression of OSMRβ. Recombinant human OSM strongly activated both STAT1 and STAT3 in HconEpiCs and induced various tissue remodeling-related genes, including MMP-1, MMP-3, IL-24, IL-20, serpinB3, S100A7, tenascin C, and SOCS3.

CONCLUSION

Our results suggest that OSM is one of the key molecules involved in remodeling of giant papillae in VKC.

Neutrophil-derived granule cargoes: paving the way for tumor growth and progression

Neutrophils are the key cells of our innate immune system mediating host defense via a range of effector functions including phagocytosis, degranulation, and NETosis. For this, they employ an arsenal of anti-microbial cargoes packed in their readily mobilizable granule subsets. Notably, the release of granule content is tightly regulated; however, under certain circumstances, their unregulated release can aggravate tissue damage and could be detrimental to the host. Several constituents of neutrophil granules have also been associated with various inflammatory diseases including cancer. In cancer setting, their excessive release may modulate tissue microenvironment which ultimately leads the way for tumor initiation, growth and metastasis. Neutrophils actively infiltrate within tumor tissues, wherein they show diverse phenotypic and functional heterogeneity. While most studies are focused at understanding the phenotypic heterogeneity of neutrophils, their functional heterogeneity, much of which is likely orchestrated by their granule cargoes, is beginning to emerge. Therefore, a better understanding of neutrophil granules and their cargoes will not only shed light on their diverse role in cancer but will also reveal them as novel therapeutic targets. This review provides an overview on existing knowledge of neutrophil granules and detailed insight into the pathological relevance of their cargoes in cancer. In addition, we also discuss the therapeutic approach for targeting neutrophils or their microenvironment in disease setting that will pave the way forward for future research.

Airway Epithelial Dynamics in Allergy and Related Chronic Inflammatory Airway Diseases

Allergic rhinitis, chronic rhinosinusitis, and asthma are highly prevalent, multifactorial chronic airway diseases. Several environmental and genetic factors affect airway epithelial dynamics leading to activation of inflammatory mechanisms in the airways. This review links environmental factors to host epithelial immunity in airway diseases. Understanding altered homeostasis of the airway epithelium might provide important targets for diagnostics and therapy of chronic airway diseases.

Oncostatin M in the Regulation of Connective Tissue Cells and Macrophages in Pulmonary Disease

Oncostatin M (OSM), as one of the gp130/IL-6 family of cytokines, interacts with receptor complexes that include the gp130 signaling molecule and OSM receptor β OSMRβ chain subunits. OSMRβ chains are expressed relatively highly across a broad array of connective tissue (CT) cells of the lung, such as fibroblasts, smooth muscle cells, and epithelial cells, thus enabling robust responses to OSM, compared to other gp130 cytokines, in the regulation of extracellular matrix (ECM) remodeling and inflammation. OSMRβ chain expression in lung monocyte/macrophage populations is low, whereas other receptor subunits, such as that for IL-6, are present, enabling responses to IL-6. OSM is produced by macrophages and neutrophils, but not CT cells, indicating a dichotomy of OSM roles in macrophage verses CT cells in lung inflammatory disease. ECM remodeling and inflammation are components of a number of chronic lung diseases that show elevated levels of OSM. OSM-induced products of CT cells, such as MCP-1, IL-6, and PGE2 can modulate macrophage function, including the expression of OSM itself, indicating feedback loops that characterize Macrophage and CT cell interaction.

Oncostatin M as a new diagnostic, prognostic and therapeutic target in inflammatory bowel disease (IBD)

Introduction: Given the high rate of primary and acquired resistance to current inflammatory bowel disease (IBD) treatments, novel drug targets and biomarkers that aid in therapeutic prediction are eagerly awaited. Furthermore, postponing treatment initiation because of a diagnostic delay profoundly affects patient well-being and overall disease evolution. Among the emerging targets and biomarkers, oncostatin M (OSM) has gained much interest in the past few years.Areas covered: A literature search to June 2019 was performed to identify the most relevant reports on Oncostatin M. The authors summarize the biology of OSM, its role in health and disease, its potential as a diagnostic, prognostic and therapeutic biomarker in the field of IBD and how it might be a drug target of the future.Expert opinion: OSM has diagnostic, prognostic and therapeutic capabilities. High mucosal OSM predicts primary non-response to anti-TNF antibodies. However, one could question whether a single cytokine can capture the complexity and heterogeneity of IBD. Neutralizing OSM in patients with elevated mucosal OSM appears to be attractive and should be considered as a valid option for the first biomarker-stratified, proof-of-concept trial that studies a novel therapeutic compound in IBD.

Neutrophil extracellular traps (NETs) contribute to pathological changes of ocular graft-vs.-host disease (oGVHD) dry eye: Implications for novel biomarkers and therapeutic strategies

PURPOSE

To investigate the role of neutrophil extracellular traps (NETs) and NET-associated proteins in the pathogenesis of oGVHD and whether dismantling of NETs with heparin reduces those changes.

METHODS

Ocular surface washings from oGVHD patients and healthy subjects were analyzed. Isolated peripheral blood human neutrophils were stimulated to generate NETs and heparinized NETs. We performed in vitro experiments using cell lines (corneal epithelial, conjunctival fibroblast, meibomian gland (MG) epithelial and T cells), and in vivo experiments using murine models, and compared the effects of NETs, heparinized NETs, NET-associated proteins and neutralizing antibodies to NET-associated proteins.

RESULTS

Neutrophils, exfoliated epithelial cells, NETs and NET-associated proteins (extracellular DNA, Neutrophil Elastase, Myeloperoxidase, Oncostatin M (OSM), Neutrophil gelatinase-associated lipocalin (NGAL) and LIGHT/TNFSF14) are present in ocular surface washings (OSW) and mucocellular aggregates (MCA). Eyes with high number of neutrophils in OSW have more severe signs and symptoms of oGVHD. NETs (and OSM) cause epitheliopathy in murine corneas. NETs (and LIGHT/TNFSF14) increase proliferation of T cells. NETs (and NGAL) inhibit proliferation and differentiation of MG epithelial cells. NETs enhance proliferation and myofibroblast transformation of conjunctival fibroblasts. Sub-anticoagulant dose Heparin (100 IU/mL) dismantles NETs and reduces epithelial, fibroblast, T cell and MG cell changes induced by NETs.

CONCLUSION

NETs and NET-associated proteins contribute to the pathological changes of oGVHD (corneal epitheliopathy, conjunctival cicatrization, ocular surface inflammation and meibomian gland disease). Our data points to the potential of NET-associated proteins (OSM or LIGHT/TNFSF14) to serve as biomarkers and NET-dismantling biologics (heparin eye drops) as treatment for oGVHD.