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

The sensory neuroimmune frontier

Sensing and recognition are key properties of both the immune and nervous systems. In the immune system, pattern recognition or antigen-specific receptors represent classic motifs in innate and adaptive immunity, respectively. In the nervous system, there is a major anatomic division between how we sense stimuli from within the body (vagal sensory nervous system) and the outside world (somatosensory nervous system). However, in the last 5 years, there has been an explosion of discoveries revealing interactions between the immune and the sensory nervous systems that govern an array of physiologic and pathologic processes including allergy, infection, autoimmunity, regeneration, cancer, and beyond. Herein, we highlight recent advances that demonstrate how peripheral sensory neuroimmunology has emerged as a powerful field that provides new insights into classic immunologic processes including immune hypersensitivity, inflammation, and tissue homeostasis.

Cardiodermatology: the heart of the connection between the skin and cardiovascular disease

The skin and cardiovascular systems are connected in unique and meaningful ways, and many diseases conventionally considered as being limited to one organ system are more closely related than previously believed. Major cardiovascular diseases and phenomena such as infective endocarditis, congestive heart failure, Kawasaki disease and thromboembolism are associated with specific skin findings, and advances in genetics, immunology and clinical epidemiology show that inflammatory dermatological diseases, such as psoriasis, have serious cardiovascular and cardiometabolic consequences. Additionally, commonly used cardiovascular therapies, such as antihypertensive medications, are associated with important cutaneous adverse effects, including photosensitivity, photocarcinogenesis and eczematous skin reactions. Moreover, systemic dermatological therapies, including retinoids, Janus kinase inhibitors and biologics, can alter the risk of cardiovascular and cardiometabolic diseases. In this Review on cardiodermatology, we provide interdisciplinary insights from dermatology and cardiology that will be of practical use to both cardiologists and generalists who manage cardiovascular and cardiometabolic diseases in patients with dermatological findings or histories. We discuss specific skin findings associated with cardiovascular diseases to aid in diagnosis; important cutaneous adverse effects of common cardiovascular therapies, for the purpose of treatment monitoring; and the effect of dermatological diseases and dermatological treatment on cardiovascular risk.

Interaction between obesity and asthma in children and adolescents with hypertension based on NHANES 2007-2020

Objectives

This study aims to elucidate the relationship between obesity and asthma in children and adolescents with hypertension based on the 2007-2020 National Health and Nutrition Examination Survey (NHANES).

Methods

Weighted logistic regression models assessed obesity and asthma's effects on hypertension risk, reported as odds ratio (OR) and 95% confidence interval (CI).

Results

A cross-sectional analysis of 10,838 NHANES individuals aged 8-17 found 630 (5.8%) had hypertension, with significant differences in age, sex, poverty-to-income ratio, low birth weight, presence or absence of obesity and asthma, triglyceride concentration, fasting glucose concentration, and tobacco exposure compared to those without hypertension (p < .05). After adjusting for all covariates, children and adolescents with obesity or asthma had a higher risk of hypertension (obesity: adjusted OR 2.14, 95% CI 1.7-2.7; asthma: adjusted OR 1.43, 95% CI 1.1-1.9). Individuals with both obesity and asthma showed a significantly higher risk of hypertension compared to those without these conditions (adjusted OR 2.87, 95% CI 1.9-4.4) (p < .001). The synergistic effect of childhood obesity and asthma on hypertension risk remained robust after the stratified subgroup analysis based on age, sex, birth weight, and tobacco exposure.

Conclusion

This study demonstrates that obesity and asthma exert a synergistic effect on childhood hypertension, emphasizing the need for comprehensive interventions targeting weight management and asthma control. There is a pressing need for future research to delve deeper into the mechanisms underlying the interactions between childhood asthma, obesity, and hypertension.

TNF-α counters skin inflammation by restraining mast cell-dependent thymic stromal lymphopoietin production

BACKGROUND

TNF-α is an important proinflammatory cytokine, but its neutralization in the management of inflammatory skin disorders like psoriasis may trigger eczematous skin lesions as an adverse reaction.

OBJECTIVES

This study aimed to elucidate whether TNF-α may protect from skin inflammation and to identify in detail the underlying mechanisms.

METHODS

Wild-type, TNF-α-deficient, thymic stromal lymphopoietin (TSLP) receptor-deficient, mast cell (MC)-deficient, TNF-α-TSLP receptor double-deficient, and TNF-α-MC double-deficient mice were subjected to a skin inflammation model and inspected by physical, clinical, histologic, immunohistochemical, and bioanalytic techniques.

RESULTS

TNF-α deficiency promoted skin inflammation. This was accompanied by MC hyperplasia and potent TSLP production in lesional skin and serum of TNF-α-deficient mice. Specifically, MCs were found to be responsible for inducing high levels of TSLP in the epidermis, compromising barrier function and initiating inflammation. In contrast, the production of immunoglobulins, including IgE, was reduced in mice lacking TNF-α.

CONCLUSIONS

TNF-α restrains MC-dependent TSLP production and the onset of eczema.

Neuroimmune mechanisms of type 2 inflammation in the skin and lung

Type 2 inflammation has a major role in barrier tissues such as the skin and airways and underlies common conditions including atopic dermatitis (AD) and asthma. Cytokines including interleukin 4 (IL-4), IL-5, and IL-13 are key immune signatures of type 2 inflammation and are the targets of multiple specific therapeutics for allergic diseases. Despite shared core immune mechanisms, the distinct structures and functions of the skin and airways lead to unique therapeutic responses. It is increasingly recognized that the nervous system has a major role in sensing and directing inflammatory processes. Indeed, crosstalk between type 2 immune activation and somatosensory functions mediates tissue-specific signatures such as itching in the skin. However, neuroimmune interactions are shaped by distinct neuronal and immune landscapes, and differ between the skin and airways. In the skin, dorsal root ganglia-derived neurons mediate pruritus via type 2 cytokines and neurogenic inflammation by mast cell or basophil activation. Conversely, vagal ganglia-derived neurons regulate airway immune responses by releasing neuropeptides/neurotransmitters such as calcitonin gene-related peptides, neuromedin U, acetylcholine, and noradrenaline. Sensory neuron-derived vasoactive intestinal peptide forms a feedback loop with IL-5, amplifying eosinophilic inflammation in the airways, a mechanism that is absent in the skin. These differences influence the efficacy of cytokine-targeted therapies. For instance, IL-4/IL-13-targeted therapies like dupilumab demonstrate efficacy in AD and allergic airway diseases, whereas IL-5-targeted therapies are effective in eosinophilic asthma but not AD. Understanding these neuroimmune interactions underscores the need for tailored therapeutic approaches to address allergic diseases where barrier tissues are involved.

The big four in the pathogenesis and pathophysiology of prurigo nodularis: Interplay among type 2 inflammation, epidermal hyperplasia, dermal fibrosis, and itch from neuroimmune dysregulation

Prurigo nodularis (PN) is a distinct inflammatory dermatosis. It is characterized by intensely pruritic, firm nodules, typically 1 to 2 cm in diameter, which usually develop on the extensor surfaces of the extremities. Histopathologically, the following characteristics are observed in PN lesions: (1) dermal cellular infiltrates composed of type 2 inflammation-associated immune cells with lesional overexpression of type 2 cytokines (including interleukin [IL]-4, IL-13, and IL-31), (2) dermal fibrosis, and (3) epidermal hyperplasia with hyperkeratosis. Additionally, functional and structural alterations of cutaneous sensory nerve fibers profoundly contribute to itch in cooperation with type 2 inflammation. This abnormal interaction is referred to as neuroimmune dysregulation. The scratching behavior induced by itching from neuroimmune dysregulation initiates the development of prurigo nodules. This distinctive pathogenic feature of "itch-first" in PN is distinct from "inflammation-first" in atopic dermatitis, where the skin initially exhibits type 2 inflammation, which is subsequently followed by itching. The interplay between the four elements, namely type 2 inflammation, epidermal hyperplasia, dermal fibrosis, and itch resulting from neuroimmune dysregulation, appears to be pivotal in the pathogenesis and pathophysiology of PN.

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.

The Effect of the Nasal Structure on the Olfactory Cleft Airflow: A Systematic Review

OBJECTIVE

Conductive olfactory losses mainly involve obstruction of the olfactory cleft (OC) and diminished OC airflow. This study investigated the association between abnormal nasal structure and OC airflow.

METHODS

A systematic search was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis to identify studies on the effect of the nasal structure on the OC airflow and olfaction.

RESULTS

A total of 11 studies were included. Nasal vestibule morphological variabilities directly impact the transport of molecules in odorant-laden air to the OC. A greater airflow vortex and a narrower vestibule region intensified the airflow vortex toward the olfactory region. Middle turbinectomy significantly increased the average flux to the OC. The location of the major airflow and airflow velocity maxima shifted towards the OC in patients with septal deviation. The airflow has been redirected into the upper part of the nasal airway in patients with inferior turbinate hypertrophy. For patients with unilateral cleft lip, unilateral nasal airflow on the cleft side has a lower rate and flow. The mean velocity in the posterior OC correlated well with olfaction compared to that in the anterior OC. The nasal polyps (NP) within the middle meatus increased the olfactory airflow but did not enhance the olfaction. NP in the olfactory region or anterior to the olfactory region significantly decreased the olfactory airflow and olfaction. Furthermore, obstruction of the OC did not change the nasal patency. When the OC shape presented with a stenotic slit or lumen structure among patients with conductive olfactory dysfunction without NP, the inspiratory velocity and flow rate within OC were significantly lower than in the healthy control group.

CONCLUSION

Various nasal structural factors affect patterns of OC airflow and olfaction. Identifying the related airflow-limiting structures may promote the comprehensive evaluation of conductive olfactory losses in patients with olfactory dysfunction.

Type 2 immunity in allergic diseases

Significant advancements have been made in understanding the cellular and molecular mechanisms of type 2 immunity in allergic diseases such as asthma, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis (EoE), food and drug allergies, and atopic dermatitis (AD). Type 2 immunity has evolved to protect against parasitic diseases and toxins, plays a role in the expulsion of parasites and larvae from inner tissues to the lumen and outside the body, maintains microbe-rich skin and mucosal epithelial barriers and counterbalances the type 1 immune response and its destructive effects. During the development of a type 2 immune response, an innate immune response initiates starting from epithelial cells and innate lymphoid cells (ILCs), including dendritic cells and macrophages, and translates to adaptive T and B-cell immunity, particularly IgE antibody production. Eosinophils, mast cells and basophils have effects on effector functions. Cytokines from ILC2s and CD4+ helper type 2 (Th2) cells, CD8 + T cells, and NK-T cells, along with myeloid cells, including IL-4, IL-5, IL-9, and IL-13, initiate and sustain allergic inflammation via T cell cells, eosinophils, and ILC2s; promote IgE class switching; and open the epithelial barrier. Epithelial cell activation, alarmin release and barrier dysfunction are key in the development of not only allergic diseases but also many other systemic diseases. Recent biologics targeting the pathways and effector functions of IL4/IL13, IL-5, and IgE have shown promising results for almost all ages, although some patients with severe allergic diseases do not respond to these therapies, highlighting the unmet need for a more detailed and personalized approach.

In vitro and in vivo efficacy of the Active Oligo Skin complex™, a new active ingredient processed from seawater, on multiple parameters of atopic skin

Background

Different symptoms are associated with atopic skin, including dryness, pruritus and pain, and affect patients' quality of life. The environment, microbiota, epidermis, immune and nerve cells are all implicated in the pathogenesis of atopic skin. Staphylococcus aureus is the focus of particular attention. Epidermis is implicated at multiple levels: inflammatory process, barrier, control of moisture and water loss. Sensory neurons that participate in cutaneous neurogenic inflammation and pruritus are seen as a potential new target. Specific management strategies and new treatments for adults and children are needed to help in more refractory cases. As a baseline of management, guidelines recommend a treatment to moisturize the skin and maintain the skin barrier function, such as an emollient.

Objectives

To evaluate a new product in vitro and in vivo in order to validate the potential of its use in people with atopic skin or dry skin.

Methods

A specific mineral composition, Active Oligo Skin complex™, from seawater was developed and included in a balm. The effects of a solution and balm containing the complex were evaluated in vitro on the growth and biofilm formation of Staphylococcus aureus and Staphylococcus epidermidis in different skin models, and in vivo in adult and young volunteers.

Results

In vitro, the complex modulated bacterial biofilm formation and growth, decreased cytokine [interleukin (IL)-1, IL-6, IL-4] and neuropeptide (substance P) release, and increased the expression of CL1 and CL4. On volunteers with dry skin, the complex had a moisturizing effect after 1 h of application. Dryness and roughness were also reduced in young participants with atopic skin. The balm decreased erythema and pruritus after 21 days of topical application on 60 young participants. On 22 adult participants, stinging score was decreased after -application.

Conclusions

The Active Oligo Skin complex™ appears to display potent antipruritic and anti-inflammatory activities, both in vitro and in vivo.

Thymus and activation-regulated chemokine (CCL17) as a clinical biomarker in atopic dermatitis: significance and limitations in the new treatment era

Thymus and activation-regulated chemokine (TARC; CCL17) is a T-helper-2 chemokine that reflects atopic dermatitis (AD) disease activity. Since 2008, serum TARC levels have been commercially measured in Japan, and clinical experience has shown the usefulness of TARC. The fallacy that eczema is always visible often hinders successful treatment, when there is subclinical inflammation which is inferable from the TARC level. AD treatment has entered a new era with higher therapeutic efficacy. TARC has a different meaning than it did previously, and its significance and limitations are discussed. First, a more appropriate topical therapy monitoring TARC would be useful in selecting truly necessitated patients for expensive new therapies. Dupilumab quickly lowers serum TARC before clinical improvement, and its normalization is not a criterion for dose reduction. However, in some severe cases, TARC may help determine whether to continue treatment. During treatment with JAK inhibitors, serum TARC levels are often elevated and may be abnormally high, leading to the exacerbation of dermatitis. Prurigo nodularis is divided into two types associated with elevated and normal TARC levels, which may aid in the selection of therapeutic agents. In this new era, TARC remains a useful biomarker for more accurate drug selection and the determination of therapeutic efficacy; Currently, in clinical trials of AD, all outcome measurements depend on the clinical score; however the use of a biomarker, such as TARC, as a secondary outcome measure will clarify the characteristics of each drug and the pathophysiological conditions for which it is expected to be effective.

Anti-Inflammatory Effects of Cannabigerol In Vitro and In Vivo Are Mediated Through the JAK/STAT/NFκB Signaling Pathway

Cannabinoid compounds have potential as treatments for a variety of conditions, with cannabigerol (CBG) being known for its anti-inflammatory properties. In this study, we investigated the effects of CBG in a cellular model of 1-chloro-2,4-dinitrobenzene (DNCB)-induced atopic dermatitis (AD). In the cellular model, we confirmed the cytotoxicity of CBG and downregulated the expression of inflammatory markers CCL26, IL1B, IL6, and TNF (p < 0.001). In the mouse model, clinical, histological, and immunological changes were analyzed. The results showed that CBG improved dermatitis severity score, epidermal thickness, and mast cell count and reduced inflammatory cytokines (Tslp, Il1b, Il4, Il6, Il13, Il17, Il18, Il22, and Il33) by qRT-PCR (p < 0.001). Western blot results showed modulated changes in JAK1, JAK2, TYK2, STAT1, STAT2, STAT3, p-STAT3, STAT6, and p-STAT6 (p < 0.05). Subsequently, p-IκBα, NF-κB, and p-NF-κB signaling factors were also reduced (p < 0.05), with corresponding changes in skin barrier factors. The results of this study indicate that CBG effectively alleviates AD-like symptoms and suggest the potential of CBG as a therapeutic agent.

Crosstalk between ROS-inflammatory gene expression axis in the progression of lung disorders

A significant number of deaths and disabilities worldwide are brought on by inflammatory lung diseases. Many inflammatory lung disorders, including chronic respiratory emphysema, resistant asthma, resistance to steroids, and coronavirus-infected lung infections, have severe variants for which there are no viable treatments; as a result, new treatment alternatives are needed. Here, we emphasize how oxidative imbalance contributes to the emergence of provocative lung problems that are challenging to treat. Endogenic antioxidant systems are not enough to avert free radical-mediated damage due to the induced overproduction of ROS. Pro-inflammatory mediators are then produced due to intracellular signaling events, which can harm the tissue and worsen the inflammatory response. Overproduction of ROS causes oxidative stress, which causes lung damage and various disease conditions. Invasive microorganisms or hazardous substances that are inhaled repeatedly can cause an excessive amount of ROS to be produced. By starting signal transduction pathways, increased ROS generation during inflammation may cause recurrent DNA damage and apoptosis and activate proto-oncogenes. This review provides information about new targets for conducting research in related domains or target factors to prevent, control, or treat such inflammatory oxidative stress-induced inflammatory lung disorders.

The Significant Role of Atopic Skin Diathesis in Prurigo Nodularis

Objectives

Atopic skin plays a significant etiological role in the development of prurigo nodularis (PN). In addition to atopic dermatitis (AD), atopic skin diathesis without eczema can also contribute to the development of PN due to its association with itching. This study aims to evaluate PN in terms of AD/atopic skin diathesis, associated comorbidities, and clinical findings.

Methods

Patients diagnosed with PN based on clinical and histopathological findings between 2014 and 2024 were included in the study. Associated diseases that could contribute to the etiology of pruritus were recorded as comorbidities. The diagnosis of AD was evaluated using the Hanifin-Rajka's diagnostic criteria and atopic skin diathesis using the Erlangen Atopy Score. Patients were classified as atopic and non-atopic groups, and these groups were compared in terms of demographic and clinical findings.

Results

The study included a total of 47 patients, of whom 15 (31.9%) were male and 32 (68.1%) were female. At least one comorbidity was identified in 89.4% (n=42) of the patients, and multiple comorbidities were found in 34% (n=16). Atopic dermatitis and/or atopic skin diathesis were present in 55.3% (n=26) of the patients. Among these, 53.8% (n=14) were diagnosed with AD, while 46.2% (n=12) had only an atopic skin diathesis. Compared to the non-atopic group, the atopic group had a lower median age (p=0.001) and higher serum total IgE levels (p=0.031).

Conclusion

In addition to AD, atopic skin diathesis without eczema also appears to play an important role in the etiology of PN. The lower age and higher IgE levels in patients are factors associated with atopic predisposition.

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.

Decoding the neuroimmune axis in the atopic march: mechanisms and implications

The immune and nervous systems have co-evolved complex mechanisms to sense environmental dangers and orchestrate a concerted response to safeguard tissue and mobilize host defenses. This sophisticated interplay, marked by a shared repertoire of receptors and ligands, influences disease pathogenesis. Neuro-immune interactions in allergic diseases are pivotal for symptom development, from anaphylaxis to chronic conditions like asthma and atopic dermatitis. This review explores the neuro-immune interplay within the atopic march, emphasizing its role in host defense, inflammation resolution, and tissue repair. We delve into the multifaceted functions of nociceptors in orchestrating type 2 immune responses and the progression of allergic disorders, focusing on key regulators such as CGRP-RAMP1 and SP-MRGPRB2/A2. Additionally, we discuss the potential of nociceptor neuron-blocking drugs to target neuro-immunity, offering the possibility of reversing the progression of the atopic march. Altogether, we underscore the need for targeted interventions to disrupt the pathological processes and enhance therapeutic outcomes at various stages of the atopic march.

Physiological Effects of Psychological Interventions Among Persons with Financial Stress: A Systematic Review, Meta-analysis, and Introduction to Psychophysiological Economics

It is known that economic problems can cause psychological stress, and that psychological stress causes physiological changes often linked to disease. Here we report a systematic review and meta-analysis of studies on physiological effects of psychological treatment for individuals with economic problems. Of 5071 papers in our initial PsycInfo search, we identified 16 papers on physiological effects for psychological treatment of the economically stressed. We found 11 controlled studies, among which we found a small to moderate significant effect size, Hedges' g = 0.319, p < 0.001. The largest effect sizes were found for heart rate variability and measures of inflammation, and the smallest for measures involving cortisol. The studies were all on chronically poor populations, thus restricting generalization to other financially stressed populations such as students, athletes in training, and those stressed by relative deprivation compared with neighbors or other reference groups. None of the studies examined effects of these psychophysiological changes on disease susceptibility, and none included elements of financial planning. The nascent field of financial psychophysiology calls for more research in these areas. Even so, results suggest that financially stressed people can benefit physiologically from psychological stress management methods.

Evaluation of dupilumab on the disease burden in children and adolescents with atopic dermatitis: A population-based cohort study

BACKGROUND

Dupilumab is the first and only biologic agent approved for the treatment of atopic dermatitis (AD) in pediatric patients aged from 6 months to 17 years. The study aimed to evaluate the impact of dupilumab on the occurrence of comorbidities in pediatric patients with AD.

METHODS

In this population-based cohort study, we utilized electronic health records from multiple healthcare organizations across the United States. Pediatric patients (<18 years of age) with a diagnosis of AD initiating dupilumab were propensity-score matched 1:1 to those initiating other systemic agents (azathioprine, cyclosporine, methotrexate, mycophenolate mofetil, or systemic corticosteroids). The primary outcomes were new-onset comorbidities emerging during the study period measured by the risk ratio (RR) and its confidence interval (CI). Subgroup analyses were stratified by age (0-5 years, 6-11 years, and 12-17 years), sex, and race.

RESULTS

A total of 3575 pediatric patients with AD treated with dupilumab were matched to 3575 patients treated with other systemic agents. The dupilumab cohort was associated with a lowered risk of new-onset atopic comorbidities (including asthma [RR, 0.72; 95% CI, 0.59-0.89] and allergic rhinitis [RR, 0.62; 95% CI, 0.52-0.74]), infections (e.g., skin and soft tissue infection [RR, 0.70; 95% CI, 0.63-0.76] and respiratory tract infection [RR = 0.56; 95% CI, 0.51-0.61]), psychiatric disorders (e.g., mood disorder [RR, 0.52; 95% CI, 0.39-0.70] and anxiety [RR, 0.57; 95% CI, 0.46-0.70], sleep disturbance [RR, 0.60; 95% CI, 0.47-0.77]), neurologic and developmental disorders (e.g., attention deficit hyperactivity disorder [RR, 0.54; 95% CI, 0.38-0.75]). Furthermore, the positive effects are found to be more pronounced in younger children (aged 0-5 years) with AD.

CONCLUSIONS

Treatment with dupilumab compared to systemic agents resulted in reductions in AD-related comorbidities in pediatric patients.

Atopic dermatitis and IgE-mediated food allergy: Common biologic targets for therapy and prevention

OBJECTIVE

To highlight common mechanistic targets for the treatment of atopic dermatitis (AD) and IgE-mediated food allergy (IgE-FA) with potential to be effective for both diseases and prevent atopic progression.

DATA SOURCES

Data sources were PubMed searches or National Clinical Trials (NCT)-registered clinical trials related to AD, IgE-FA, and other atopic conditions, especially focused on the pediatric population.

STUDY SELECTIONS

Human seminal studies and/or articles published in the past decade were emphasized with reference to preclinical models when relevant. NCT-registered clinical trials were filtered by inclusion of pediatric subjects younger than 18 years with special focus on children younger than 12 years as a critical period when AD and IgE-FA diseases may often be concurrent.

RESULTS

AD and IgE-FA share several pathophysiologic features, including epithelial barrier dysfunction, innate and adaptive immune abnormalities, and microbial dysbiosis, which may be critical for the clinical progression between these diseases. Revolutionary advances in targeted biologic therapies have shown the benefit of inhibiting type 2 immune responses, using dupilumab (anti-interleukin-4Rα) or omalizumab (anti-IgE), to potentially reduce symptom burden for both diseases in pediatric populations. Although the potential for biologics to promote disease remission (AD) or sustained unresponsiveness (IgE-FA) remains unclear, the refinement of biomarkers to predict infants at risk for atopic disorders provides promise for prevention through timely intervention.

CONCLUSION

AD and IgE-FA exhibit common features that may be leveraged to develop biologic therapeutic strategies to treat both conditions and even prevent atopic progression. Future studies should be designed with consistent age stratification in the pediatric population and standardized regimens of adjuvant oral immunotherapy or dose escalation (IgE-FA) to improve cross-study interpretation.

Effects of nasal allergens and environmental particulate matter on brainstem metabolites and the consequence of brain-spleen axis in allergic rhinitis

BACKGROUND

The growing consensus links exposure to fine particulate matter (PM2.5) with an increased risk of respiratory diseases. However, little is known about the additional effects of particulate matter on brainstem function in allergic rhinitis (AR). Furthermore, it is unknown to what extent the PM2.5-induced effects in the brainstem affect the inflammatory response in AR. This study aimed to determine the effects, mechanisms and consequences of brainstem neural activity altered by allergenic stimulation and PM2.5 exposure.

METHODS

Using an AR model of ovalbumin (OVA) elicitation and whole-body PM2.5 exposure, the metabolic profile of the brainstem post-allergen stimulation was characterized through in vivo proton magnetic resonance imaging (1H-MRS). Then, the transient receptor potential vanilloid-1 (TRPV1) neuronal expression and sensitivity in the trigeminal nerve in AR were investigated. The link between TRPV1 expression and brainstem differential metabolites was also determined. Finally, we evaluated the mediating effects of brainstem metabolites and the consequences in the brain-spleen axis in the inflammatory response of AR.

RESULTS

Exposure to allergens and PM2.5 led to changes in the metabolic profiles of the brainstem, particularly affecting levels of glutamine (Gln) and glutamate (Glu). This exposure also increased the expression and sensitivity of TRPV1+ neurons in the trigeminal nerve, with the levels of TRPV1 expression closely linked to the brainstem metabolism of Glu and Gln. Moreover, allergens increased the activity of p38, while PM2.5 led to the phosphorylation of p38 and ERK, resulting in the upregulation of TRPV1 expression. The brainstem metabolites Glu and Gln were found to partially mediate the impact of TRPV1 on AR inflammation, which was supported by the presence of pro-inflammatory changes in the brain-spleen axis.

CONCLUSION

Brainstem metabolites are altered under allergen stimulation and additional PM2.5 exposure in AR via sensitization of the trigeminal nerve, which exacerbates the inflammatory response via the brain-splenic axis.

Sequential immunotherapy: towards cures for autoimmunity

Despite major progress in the treatment of autoimmune diseases in the past two decades, most therapies do not cure disease and can be associated with increased risk of infection through broad suppression of the immune system. However, advances in understanding the causes of autoimmune disease and clinical data from novel therapeutic modalities such as chimeric antigen receptor T cell therapies provide evidence that it may be possible to re-establish immune homeostasis and, potentially, prolong remission or even cure autoimmune diseases. Here, we propose a 'sequential immunotherapy' framework for immune system modulation to help achieve this ambitious goal. This framework encompasses three steps: controlling inflammation; resetting the immune system through elimination of pathogenic immune memory cells; and promoting and maintaining immune homeostasis via immune regulatory agents and tissue repair. We discuss existing drugs and those in development for each of the three steps. We also highlight the importance of causal human biology in identifying and prioritizing novel immunotherapeutic strategies as well as informing their application in specific patient subsets, enabling precision medicine approaches that have the potential to transform clinical care.

Induction of Semaphorin 3A by Resveratrol and Pinostilbene via Activation of the AHR-NRF2 Axis in Human Keratinocytes

Semaphorin 3A (SEMA3A), a nerve-repellent factor produced by keratinocytes, has an inhibitory effect on nerve extension to the epidermis. Epidermal innervation is involved in pruritus in inflammatory skin diseases such as atopic dermatitis (AD) and dry skin. We previously reported that tapinarof, a stilbene molecule, upregulates SEMA3A in human keratinocytes. We also showed that this mechanism is mediated via the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, and the nuclear factor erythroid 2-related factor 2 (NRF2) axis. Since some stilbenes activate AHR and NRF2, we attempted to identify other stilbenes that upregulate SEMA3A. We analyzed normal human epidermal keratinocytes (NHEKs) treated with 11 types of stilbenes and examined SEMA3A expression. We found that resveratrol and pinostilbene, antioxidant polyphenols, upregulated SEMA3A and increased nuclear AHR and NRF2 expression. In addition, AHR knockdown by small interfering RNA (siRNA) transfection abolished the NRF2 nuclear expression. Furthermore, AHR and NRF2 knockdown by siRNA transfection abrogated resveratrol- and pinostilbene-induced SEMA3A upregulation. Finally, we confirmed that resveratrol and pinostilbene increased SEMA3A promoter activity through NRF2 binding using ChIP-qPCR analysis. These results suggest that resveratrol and pinostilbene upregulate SEMA3A via the AHR-NRF2 axis in human keratinocytes.

Diagnosis and management of food allergy-induced constipation in young children-An EAACI position paper

The recognition of constipation as a possible non-Immunoglobulin E (IgE)-mediated allergic condition is challenging because functional constipation (unrelated to food allergies) is a common health problem with a reported worldwide prevalence rate of up to 32.2% in children. However, many studies in children report challenge proven cow's milk allergy and constipation as a primary symptom and have found that between 28% and 78% of children improve on a cow's milk elimination diet. Due to the paucity of data and a focus on IgE-mediated allergy, not all food allergy guidelines list constipation as a symptom of food allergy. Yet, it is included in all cow's milk allergy guidelines available in English language. The Exploring Non-IgE-Mediated Allergy (ENIGMA) Task Force (TF) of the European Academy for Allergy and Clinical Immunology (EAACI) considers in this paper constipation in the context of failure of standard treatment and discuss the role of food allergens as culprit in constipation in children. This position paper used the Delphi approach in reaching consensus on both diagnosis and management, as currently published data are insufficient to support a systematic review.

Atopic Dermatitis Itch: Scratching for an Explanation

Chronic pruritus is a cardinal symptom of atopic dermatitis (AD). The mechanisms underlying atopic itch involve intricate crosstalk among skin, immune components, and neural components. In this review, we explore these mechanisms, focusing on key players and interactions that induce and exacerbate itch. We discuss the similarities and differences between pruritus and pain in patients with AD as well as the relationship between pruritus and factors such as sweat and the skin microbiome. Furthermore, we explore novel targets that could provide significant itch relief in these patients as well as exciting future research directions to better understand atopic pruritus in darker skin types.

Animal models of eosinophilic esophagitis, review and perspectives

Eosinophilic oesophagitis (EoE) is an allergen/immune-mediated chronic esophageal disease characterized by esophageal mucosal eosinophilic infiltration and esophageal dysfunction. Although the disease was originally attributed to a delayed allergic reaction to allergens and a Th2-type immune response, the exact pathogenesis is complex, and the efficacy of existing treatments is unsatisfactory. Therefore, the study of the pathophysiological process of EOE has received increasing attention. Animal models have been used extensively to study the molecular mechanism of EOE pathogenesis and also provide a preclinical platform for human clinical intervention studies of novel therapeutic agents. To maximize the use of existing animal models of EOE, it is important to understand the advantages or limitations of each modeling approach. This paper systematically describes the selection of experimental animals, types of allergens, and methods of sensitization and excitation during the preparation of animal models of EoE. It also discusses the utility and shortcomings of each model with the aim of providing the latest perspectives on EoE models and leading to better choices of animal models.

Apoptosis and turnover disruption of olfactory sensory neurons in eosinophilic chronic rhinosinusitis

Olfactory dysfunction (OD) is one of the important and difficult-to-treat symptoms of eosinophilic chronic rhinosinusitis (CRS), which is typically associated with type 2 inflammation where eosinophils (EOSs) function as both effectors and initiators. Eosinophilic infiltration in the olfactory mucosa (OM) is associated with severe OD, mucosal erosion, and more loss of olfactory sensory neurons (OSNs). Active EOS-derived cytokines, chemokines, and eosinophil granule proteins may lead to aggravation of inflammation, tissue damage, and impairment of the survival and regeneration of OSNs. Recent studies show that EOSs can lead to apoptosis of OSNs through axonal and neural body damage, turnover disorder of OSNs through the loss of immature OSNs and globose basal cells (GBCs), changed proliferative activity of horizontal basal cells (HBCs), and dysfunction of OSNs through the breakdown of neuroepithelial integrity and alteration of ion concentration in OSNs and mucin. In this review, we outline the current progress on the role of EOSs on OD in patients with eosinophilic CRS and the mechanism of EOS-associated injury of the OM and OSNs in experimental animal models with sinonasal inflammation. Further investigations on the molecular mechanisms of tissue eosinophilia-induced injury of OSNs are warranted to obtain new therapeutic targets and achieve better restoration of olfactory function.

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.

Spatial characterization of interface dermatitis in cutaneous lupus reveals novel chemokine ligand-receptor pairs that drive disease

Chemokines play critical roles in the recruitment and activation of immune cells in both homeostatic and pathologic conditions. Here, we examined chemokine ligand-receptor pairs to better understand the immunopathogenesis of cutaneous lupus erythematosus (CLE), a complex autoimmune connective tissue disorder. We used suction blister biopsies to measure cellular infiltrates with spectral flow cytometry in the interface dermatitis reaction, as well as 184 protein analytes in interstitial skin fluid using Olink targeted proteomics. Flow and Olink data concordantly demonstrated significant increases in T cells and antigen presenting cells (APCs). We also performed spatial transcriptomics and spatial proteomics of punch biopsies using digital spatial profiling (DSP) technology on CLE skin and healthy margin controls to examine discreet locations within the tissue. Spatial and Olink data confirmed elevation of interferon (IFN) and IFN-inducible CXCR3 chemokine ligands. Comparing involved versus uninvolved keratinocytes in CLE samples revealed upregulation of essential inflammatory response genes in areas near interface dermatitis, including AIM2. Our Olink data confirmed upregulation of Caspase 8, IL-18 which is the final product of AIM2 activation, and induced chemokines including CCL8 and CXCL6 in CLE lesional samples. Chemotaxis assays using PBMCs from healthy and CLE donors revealed that T cells are equally poised to respond to CXCR3 ligands, whereas CD14+CD16+ APC populations are more sensitive to CXCL6 via CXCR1 and CD14+ are more sensitive to CCL8 via CCR2. Taken together, our data map a pathway from keratinocyte injury to lymphocyte recruitment in CLE via AIM2-Casp8-IL-18-CXCL6/CXCR1 and CCL8/CCR2, and IFNG/IFNL1-CXCL9/CXCL11-CXCR3.

Neuroimmune communication in allergic rhinitis

The prevalence rate of allergic rhinitis (AR) is high worldwide. The inhalation of allergens induces AR, which is an immunoglobulin E-mediated and type 2 inflammation-driven disease. Recently, the role of neuroimmune communication in AR pathogenesis has piqued the interest of the scientific community. Various neuropeptides, such as substance P (SP), vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), nerve growth factor (NGF), and neuromedin U (NMU), released via "axon reflexes" or "central sensitization" exert regulatory effects on immune cells to elicit "neurogenic inflammation," which contributes to nasal hyperresponsiveness (NHR) in AR. Additionally, neuropeptides can be produced in immune cells. The frequent colocalization of immune and neuronal cells at certain anatomical regions promotes the establishment of neuroimmune cell units, such as nerve-mast cells, nerve-type 2 innate lymphoid cells (ILC2s), nerve-eosinophils and nerve-basophils units. Receptors expressed both on immune cells and neurons, such as TRPV1, TRPA1, and Mas-related G protein-coupled receptor X2 (MRGPRX2) mediate AR pathogenesis. This review focused on elucidating the mechanisms underlying neuroimmune communication in AR.

Molecular mechanisms of pruritus in prurigo nodularis

Pruritus is the most common symptom of dermatological disorders, and prurigo nodularis (PN) is notorious for intractable and severe itching. Conventional treatments often yield disappointing outcomes, significantly affecting patients' quality of life and psychological well-being. The pathogenesis of PN is associated with a self-sustained "itch-scratch" vicious cycle. Recent investigations of PN-related itch have partially revealed the intricate interactions within the cutaneous neuroimmune network; however, the underlying mechanism remains undetermined. Itch mediators play a key role in pruritus amplification in PN and understanding their action mechanism will undoubtedly lead to the development of novel targeted antipruritic agents. In this review, we describe a series of pruritogens and receptors involved in mediating itching in PN, including cytokines, neuropeptides, extracellular matrix proteins, vasculogenic substances, ion channels, and intracellular signaling pathways. Moreover, we provide a prospective outlook on potential therapies based on existing findings.

Inflammatory loops in the epithelial-immune microenvironment of the skin and skin appendages in chronic inflammatory diseases

The epithelial-immune microenvironment (EIME) of epithelial tissues has five common elements: (1) microbial flora, (2) barrier, (3) epithelial cells, (4) immune cells, and (5) peripheral nerve endings. EIME provides both constant defense and situation-specific protective responses through three-layered mechanisms comprising barriers, innate immunity, and acquired immunity. The skin is one of the largest organs in the host defense system. The interactions between the five EIME elements of the skin protect against external dangers from the environment. This dysregulation can result in the generation of inflammatory loops in chronic inflammatory skin diseases. Here, we propose an understanding of EIME in chronic skin diseases, such as atopic dermatitis, psoriasis, systemic lupus erythematosus, alopecia areata, and acne vulgaris. We discuss the current treatment strategies targeting their inflammatory loops and propose possible therapeutic targets in the future.