Childhood atopic dermatitis-Brain-derived neurotrophic factor correlates with serum eosinophil cationic protein and disease severity

Proteomic, miRNA and bacterial biomarker patterns in atopic dermatitis patients and their course upon anti-IL-4Rα therapy

BACKGROUND

Identification of biomarkers is required for a systems medicine approach and personalized treatment in atopic dermatitis (AD). These biomarkers may not only aid in diagnosing but also might be suitable to predict the effectiveness of targeted treatment.

OBJECTIVE

We aimed to identify proteomic, microbial and miRNA biomarkers in AD patients and investigated their course in relation to the clinical response upon anti-IL-4Rα therapy.

METHODS

Proteomic and miRNA screening was performed in AD patients in comparison to healthy controls. Differentially regulated serum proteins, miRNA and selected skin microbiota were measured consecutively in 50 AD patients before and upon systemic dupilumab treatment. A random forest classifier was used to predict the outcome of dupilumab therapy based on the initial biomarker patterns.

RESULTS

We identified 27 proteomic candidates, miRNA and three microbial strains to be dysregulated in AD. CCL17, CCL13, CCL22, E-selectin and BDNF were differently regulated and significantly associated with treatment response. In contrast, neither the microbial composition nor the miRNA pattern was associated with treatment response upon dupilumab treatment.

CONCLUSION

AD patients display defined dysregulations regarding their systemic proteomic serum profile, miRNA patterns and their skin microbiome. The proteomic profile and selected skin bacteria changed profoundly upon anti-IL-4Rα therapy which was associated with an overall clinical response. This was not seen in miRNA-related biomarkers. Our findings support the hypothesis that biomarker profiles reflect treatment responses and may in the future be used to develop a personalized medicine approach for the treatment of AD patients.

Neurotrophin-4 and Brain-Derived Neurotrophic Factor Serum Levels in Renal Transplant Recipients with Chronic Pruritus

INTRODUCTION

Chronic pruritus (CP) is a common symptom defined as a sensation that provokes the desire to scratch and which lasts for at least 6 weeks. CP remains a problem for up to 21.3% of renal transplant recipients (RTRs). Our research aimed to establish the possible association between serum levels of neurotrophin-4 (NT-4) and brain-derived neurotrophic factor (BDNF) and the presence and intensity of CP in RTR.

METHODS

The study was performed on a group of 129 RTRs, who were divided according to the presence or absence of pruritus in the previous 3 days. The assessment of pruritus was performed with the use of a numeric rating scale (NRS), 4-Item Itch Questionnaire (4IIQ), and Itchy Quality of Life (Itchy QoL). A total of 129 blood samples with a volume of 9 ml were drawn from RTRs during the monthly routine control. Serum levels (pg/mL) of NT-4 and BDNF were measured by the ELISA.

RESULTS

Pruritic RTRs have statistically significantly higher serum concentrations of NT-4 serum level compared to non-pruritic RTRs (229.17 ± 143.86 pg/mL and 153.08 ± 78.19 pg/mL [p = 0.024], respectively). Moreover, a statistically significant difference between pruritic and non-pruritic RTRs with healthy controls was shown (p < 0.001 and p < 0.001, respectively). Although there was a numerically higher serum concentration of BDNF in pruritic RTRs (32.18 ± 7.31 pg/mL vs. 31.58 ± 10.84 pg/mL), the difference did not reach statistical significance. No statistically significant difference was also seen in BDNF serum levels between RTRs and healthy controls. Furthermore, there was a statistically significant, positive correlation between serum concentration of NT-4 and NRS score (p = 0.008, r = 0.357).

CONCLUSIONS

The results indicate higher NT-4 serum concentration in RTRs with pruritus compared to RTRs without pruritus. Furthermore, the study revealed a statistically significant, positive correlation between the serum concentration of NT-4 and NRS score.

The Mind Body Connection in Dermatologic Conditions: A Literature Review

Psychodermatology pertains to the relationship between the skin and brain. This review aims to summarize the evidence of the mind body connection in four psychophysiological conditions: rosacea, atopic dermatitis (AD), acne vulgaris (AV), and psoriasis. A literature search was conducted using several English language databases. All four conditions share similar psychiatric co-morbidities, including but not limited to anxiety, depression, and suicidality. In rosacea, the upregulation of transient receptor potential vanilloid type 1, Toll like receptor 2, and Th17 cells releases downstream products that are simultaneously implicated in mood disorders. Stress exacerbates AV through the hypothalamic-pituitary-adrenal (HPA) system, which alters functioning of sebocytes and Cutibacterium acnes. In AD and psoriasis, the HPA axis influences Th1, Th2, Th22, and Th1, Th17 immune mediated responses, respectively. This leads to the secretion of pro-inflammatory cytokines which are also involved in the pathogenesis of anxiety and depression. Neurotransmitters implicated in mental illness, such as gamma-aminobutyric acid and serotonin, may also play a role in the development of AD and psoriasis. The management of cutaneous disease may mitigate psychological distress, and future research may show the corollary to also be true.

Neurotrophins: Neuroimmune Interactions in Human Atopic Diseases

Allergic diseases are accompanied by a variety of symptoms such as pruritus, coughing, sneezing, and watery eyes, which can result in severe physiological and even psychological impairments. The exact mechanisms of these conditions are not yet completely understood. However, recent studies demonstrated a high relevance of neurotrophins in allergic inflammation, as they induce cytokine release, mediate interaction between immune cells and neurons, and exhibit different expression levels in health and disease. In this review, we aim to give an overview of the current state of knowledge concerning the role of neurotrophins in atopic disorders such as atopic dermatitis, allergic asthma, and allergic rhinitis.

Ectodermal origins of the skin-brain axis: a novel model for the developing brain, inflammation, and neurodevelopmental conditions

Early life development and its divergence is influenced by multiple genetic, neurological, and environmental factors. Atypical neurodevelopment, such as that observed in autism spectrum disorder, likely begins in early gestation during a period of entwined growth between the brain and epithelial barriers of the skin, gastrointestinal tract, and airway. This review coalesces epidemiological and neuroinflammatory evidence linking cutaneous atopic disease with both reduced skin barrier integrity and determinants of neurodivergence. We consider the shared developmental origin of epidermal and neural tissue with related genetic and environmental risk factors to evaluate potential pre- and postnatal modifiers of the skin-brain connection. Initial postnatal skin barrier integrity may provide a useful marker for both cortical integrity and meaningful subgroups of children showing early neurodevelopmental delays. It may also modify known risk factors to neurodevelopment, such as pathogen caused immune system activation. These novel insights of a skin-brain-neurodevelopment connection may advance detection and intervention opportunities.

Elevated Level of Serum Neurotrophin-4, but Not of Brain-Derived Neurotrophic Factor, in Patients with Chronic Kidney Disease-Associated Pruritus

Chronic kidney disease-associated pruritus (CKD-aP) is a bothersome condition that occurs in patients with advanced chronic kidney disease (CKD) and severely reduces their quality of life. Recently, much research has focused on the search for markers that are involved in the pathogenesis of CKD-aP and may become a therapeutic target. One of the suggested hypotheses is the increased activation of sensory neurons by molecules such as neurotrophins (NTs). An increased serum concentration of NTs has been demonstrated in pruritic patients, which may suggest their involvement in the pathogenesis of itch. The purpose of this study is to assess the serum concentration of neurotrophin-4 (NT-4) and brain-derived neurotrophic factor (BDNF) in hemodialysis patients. The study enrolled 126 patients undergoing dialysis. Participants were divided into 2 groups: with and without CKD-aP. NRS scale was used to evaluate itch severity. Serum levels of NT-4 and BDNF have been assessed using ELISA. The results showed a significantly higher level of NT-4 in the group with pruritus. No significant difference was reported in the serum level of BDNF between the two groups of patients. There was also no correlation between serum NT-4 nor BDNF levels and the severity of pruritus. In summary, NT-4 may play an important role in the pathophysiology of pruritus in dialysis patients. More research is needed to understand the exact mechanism by which NTs influence the pathogenesis of CKD-aP.

Diversities of allergic pathologies and their modifiers: Report from the second DGAKI-JSA meeting

In October 2021, researchers from the German Society of Allergy and Clinical Immunology (DGAKI) and from the Japanese Society of Allergology (JSA) focused their attention on the pathological conditions and modifiers of various allergic diseases. Topics included 1) the pathophysiology of IgE/mast cell-mediated allergic diseases; 2) the diagnosis and prevention of IgE/mast cell-mediated diseases; 3) the pathophysiology, diagnosis, and treatment of eosinophilic airway diseases; and 4) host-pathogen interaction and allergic diseases. This report summarizes the panel discussions, which highlighted the importance of recognizing the diversity of genetics, immunological mechanisms, and modifying factors underlying allergic diseases.

The Implications of Pruritogens in the Pathogenesis of Atopic Dermatitis

Atopic dermatitis (AD) is a prototypic inflammatory disease that presents with intense itching. The pathophysiology of AD is multifactorial, involving environmental factors, genetic susceptibility, skin barrier function, and immune responses. A recent understanding of pruritus transmission provides more information about the role of pruritogens in the pathogenesis of AD. There is evidence that pruritogens are not only responsible for eliciting pruritus, but also interact with immune cells and act as inflammatory mediators, which exacerbate the severity of AD. In this review, we discuss the interaction between pruritogens and inflammatory molecules and summarize the targeted therapies for AD.

Involvement of Neuro-Immune Interactions in Pruritus With Special Focus on Receptor Expressions

Pruritus is a common, but very challenging symptom with a wide diversity of underlying causes like dermatological, systemic, neurological and psychiatric diseases. In dermatology, pruritus is the most frequent symptom both in its acute and chronic form (over 6 weeks in duration). Treatment of chronic pruritus often remains challenging. Affected patients who suffer from moderate to severe pruritus have a significantly reduced quality of life. The underlying physiology of pruritus is very complex, involving a diverse network of components in the skin including resident cells such as keratinocytes and sensory neurons as well as transiently infiltrating cells such as certain immune cells. Previous research has established that there is a significant crosstalk among the stratum corneum, nerve fibers and various immune cells, such as keratinocytes, T cells, basophils, eosinophils and mast cells. In this regard, interactions between receptors on cutaneous and spinal neurons or on different immune cells play an important role in the processing of signals which are important for the transmission of pruritus. In this review, we discuss the role of various receptors involved in pruritus and inflammation, such as TRPV1 and TRPA1, IL-31RA and OSMR, TSLPR, PAR-2, NK1R, H1R and H4R, MRGPRs as well as TrkA, with a focus on interaction between nerve fibers and different immune cells. Emerging evidence shows that neuro-immune interactions play a pivotal role in mediating pruritus-associated inflammatory skin diseases such as atopic dermatitis, psoriasis or chronic spontaneous urticaria. Targeting these bidirectional neuro-immune interactions and the involved pruritus-specific receptors is likely to contribute to novel insights into the underlying pathogenesis and targeted treatment options of pruritus.

Childhood atopic dermatitis is associated with cognitive dysfunction: A National Health Interview Survey study from 2008 to 2018

BACKGROUND

Atopic dermatitis (AD) is a common inflammatory skin disease in children and adults. Little is known regarding the association of childhood AD with cognitive dysfunction.

OBJECTIVE

To evaluate the association of AD and cognitive dysfunction, including memory impairment, developmental delays and attention deficit (hyperactivity) disorder in US children (age <18 years).

METHODS

Data was analyzed from the National Health Interview Survey 2008 to 2018, which used a multistage, clustered, cross-sectional design.

RESULTS

The prevalences of cognitive dysfunction, such as memory impairment (0.87% vs 0.42%), developmental delays (6.96% vs 3.87%), and attention deficit (hyperactivity) disorder (10.78% vs 8.10%), were higher in children with vs without AD. In multivariable logistic regression models adjusting for age, sex, race, region, socioeconomic factors, allergic conditions, and mental health, childhood AD was associated with higher odds of memory impairment (adjusted odds ratio [95% confidence interval]: 1.84 [1.34-2.51]), developmental delays (1.54 [1.40-1.70]), and attention deficit (hyperactivity) disorder (1.31 [1.20-1.42]) compared with children without AD. Childhood atopic disease (defined as comorbid AD, asthma, allergic rhinitis, and food allergies) further increased the prevalence of developmental delays to 13.44% (2.10 [1.20-3.70]) in boys but not in girls.

CONCLUSION

In a nationally representative sample of the US population, a statistically significant and positive association between childhood AD and atopic disease with cognitive dysfunction was identified (P < .001). Furthermore, a dimorphic relationship with developmental delays was identified between sexes.

Exploration of biomarkers to predict clinical improvement of atopic dermatitis in patients treated with dupilumab: A study protocol

BACKGROUND

Atopic dermatitis (AD) is a common eczematous skin disorder that profoundly reduces the quality of life due to intractable pruritus. Excellent therapeutic success of the anti-interleukin 4 receptor-α antibody dupilumab in clinical trials and a real-world clinical context indicates the crucial roles of interleukin (IL)-4 and IL-13 in the pathogenesis of AD. Along with the clinical improvement in skin scores and pruritus, dupilumab significantly and progressively reduces and normalizes the upregulated expression of T helper type 2 signatures such as Chemokine (C-C motif) ligand (CCL)17, CCL18, CCL22, and CCL26 in the lesional skin of AD. However, no blood/serum biomarkers are known to predict good or poor outcome in patients with AD treated with dupilumab.

METHODS

Patients are at least 18 years of age and have moderate-to-severe AD with Eczema Area and Severity Index (EASI) ≥16, Investigator's Global Assessment ≥3, and body surface area ≥10%. We are going to enroll more than 130 subjects from 18 medical facilities. Clinical objective findings will be evaluated by EASI. Subjective symptoms will be assessed by Patient-Oriented Eczema Measure, Numerical Rating Scale for Pruritus (Pruritus-NRS), Skin Comfort-NRS, and Treatment Satisfaction-NRS. We will measure 18 blood/serum biomarkers including % eosinophils in blood cell count, lactate dehydrogenase, total IgE, soluble interleukin 2 receptor, CCL17, CCL18, CCL22, CCL26, CCL27, IL-13, IL-22, IL-24, IL-25, IL-31, IL-33, thymic stromal lymphopoietin, periostin, and squamous cell carcinoma antigen-2. The clinical evaluation and biomarker sampling will be performed at 0, 2, 4, 8, and 16 weeks of dupilumab treatment. We will also perform proteomic analysis (of roughly 300 proteins) of the patients' sera obtained at 0 and 2 weeks of treatment. The primary endpoint is the association between "baseline levels of 18 biomarkers" and "% change from baseline of EASI at 16 weeks of dupilumab treatment."

DISCUSSION

This is the first clinical trial to explore the biomarkers, including potential proteomic markers, most strongly associated with improvement in EASI in patients with moderate-to-severe AD treated with dupilumab for 16 weeks (B-PAD study). A limitation is that we will only enroll Japanese patients.

Atopic dermatitis in Taiwanese children: The laboratory values that correlate best to the SCORAD index are total IgE and positive Cheddar cheese IgE

Atopic dermatitis (AD) is a common chronic relapsing inflammatory skin disease associated with a personal or family history of atopic diseases. Determining the objective severity scoring of AD index (SCORAD) and total immunoglobulin E (IgE) to help to stage the severity (lesions extent and intensity of the lesions and then the itch and sleep disturbance they may cause) of AD in children.In this study, we adopted the SCORAD index, which consists of severity, area, and sleep disturbance, to evaluate the AD status of children up to 18 years old. We examined the blood levels of total serum IgE, white blood cell count/differential count (WBC/DC), eosinophil counts (EC), eosinophil cationic protein (ECP) and specific IgE.A total of 208 children with AD were enrolled in this study. Serum IgE values and a number of specific IgE that are positive significantly different SCORAD index through simple linear regression; however, after multiple linear regression, only IgE values (95% CI: 0.001-0.004, P < .001), total WBC count (95% CI: 0.112-1.736, P = .026), EC (95% CI: 0.045-6.706, P = .047), and specific IgE to Cheddar cheese (95% CI: 1.814-16.731, P = .015) remain different. After applying the Phi coefficient, we found that specific IgE to tuna (r = 0.632), codfish (r = 0.613), and clam (r = 0.613) each had a moderate correlation with specific IgE to Cheddar cheese. The 6 most common allergens were found to be mite (D. Farinae: 65.9%), mite (D. Pterony: 64.9%), house dust (47.6%), cockroach mix (37.0%), shrimp (30.8%), and crab (22.6%). Covariates of SCORAD index, severity, area, and sleep disturbance differed.In this study, we found that total IgE values, specific IgE values, WBC, EC, and specific IgE to Cheddar cheese have significant correlations with SCORAD index in AD of Taiwanese children.

Neuronal branching of sensory neurons is associated with BDNF-positive eosinophils in atopic dermatitis

BACKGROUND

Pruritus is a major symptom of atopic dermatitis (AD) and is transmitted by a subpopulation of non-myelinated C-type free nerve endings in the epidermis and upper dermis. Stimulation of these nerve terminals is affected by histamine, neurotrophins and physical factors. Eosinophils of patients with AD are a source of neurotrophins, including brain-derived neurotrophic factor (BDNF), levels of which correlate with disease severity.

OBJECTIVE

The purpose of this study was to determine the anatomical localization of eosinophils in the skin of patients with AD with regard to peripheral nerves and to investigate whether eosinophils induce sprouting and neurite outgrowth in murine sensory neurons.

METHODS

Cryosections of skin derived from AD and control (NA) patients were subjected to immunofluorescence analysis with markers for eosinophils, BDNF and neuronal cells. Stimulated eosinophil supernatants were used for the treatment of cultured peripheral mouse dorsal root ganglia (DRG) neurons followed by morphometric analysis.

RESULTS

Dermal axon density and the proximity of eosinophils to nerve fibres were significantly higher in AD patients vs NA. Both neuronal projections and eosinophils expressed BDNF. Furthermore, activated eosinophil supernatants induced BDNF-dependent mouse DRG neuron branching.

CONCLUSIONS AND CLINICAL RELEVANCE

Our results indicate that BDNF-positive eosinophils are also localized in close proximity with nerve fibres in AD, suggesting a functional relationship between BDNF-expressing eosinophils and neuronal projections. These observations suggest that eosinophils may have considerable impact on pruritus by supporting sensory nerve branching.

Immunoregulatory Effects of Neuropeptides on Endothelial Cells: Relevance to Dermatological Disorders

Many skin diseases, including psoriasis and atopic dermatitis, have a neurogenic component. In this regard, bidirectional interactions between components of the nervous system and multiple target cells in the skin and elsewhere have been receiving increasing attention. Neuropeptides released by sensory nerves that innervate the skin can directly modulate functions of keratinocytes, Langerhans cells, dermal dendritic cells, mast cells, dermal microvascular endothelial cells and infiltrating immune cells. As a result, neuropeptides and neuropeptide receptors participate in a complex, interdependent network of mediators that modulate the skin immune system, skin inflammation, and wound healing. In this review, we will focus on recent studies demonstrating the roles of α-melanocyte-stimulating hormone, calcitonin gene-related peptide, substance P, somatostatin, vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, and nerve growth factor in modulating inflammation and immunity in the skin through their effects on dermal microvascular endothelial cells.

Modulation of blood inflammatory markers by benralizumab in patients with eosinophilic airway diseases

Background

Benralizumab, a humanized, afucosylated, monoclonal antibody that targets interleukin-5 receptor α, depletes eosinophils and basophils by enhanced antibody-dependent cell-mediated cytotoxicity. It demonstrated efficacy for patients with moderate to severe asthma and, in a Phase IIa trial, for chronic obstructive pulmonary disease (COPD) with eosinophilic inflammation. We investigated effects of benralizumab 100 mg every 8 weeks (first three doses every 4 weeks) subcutaneous on blood inflammatory markers through proteomic and gene-expression analyses collected during two Phase II studies of patients with eosinophilic asthma and eosinophilic COPD.

Methods

Serum samples for proteomic analysis and whole blood for gene expression analysis were collected at baseline and 52 weeks (asthma study) or 32 weeks (COPD study) post-treatment. Proteomic analyses were conducted on a custom set of 90 and 147 Rules-Based Medicine analytes for asthma and COPD, respectively. Gene expression was profiled by Affymetrix Human Genome U133 plus 2 arrays (~ 54 K probes). Gene set variation analysis (GSVA) was used to determine transcriptomic activity of immune signatures. Treatment-related differences between analytes, genes, and gene signatures were analyzed for the overall population and for patient subgroups stratified by baseline blood eosinophil count (eosinophil-high [≥300 cells/μL] and eosinophil-low [< 300 cells/μL]) via t-test and repeated measures analysis of variance.

Results

Eosinophil chemokines eotaxin-1 and eotaxin-2 were significantly upregulated (false discovery rate [FDR] < 0.05) by approximately 2.1- and 1.4-fold in the asthma study and by 2.3- and 1.7-fold in the COPD study following benralizumab treatment. Magnitude of upregulation of these two chemokines was greater for eosinophil-high patients than eosinophil-low patients in both studies. Benralizumab was associated with significant reductions (FDR < 0.05) in expression of genes associated with eosinophils and basophils, such as CLC, IL-5Rα, and PRSS33; immune-signaling complex genes (FCER1A); G-protein–coupled receptor genes (HRH4, ADORA3, P2RY14); and further immune-related genes (ALOX15 and OLIG2). The magnitude of downregulation of gene expression was greater for eosinophil-high than eosinophil-low patients. GSVA on immune signatures indicated significant treatment reductions (FDR < 0.05) in eosinophil-associated signatures.

Conclusions

Benralizumab is highly selective, modulating blood proteins or genes associated with eosinophils or basophils. Modulated protein and gene expression patterns are most prominently altered in eosinophil-high vs. eosinophil-low patients.

Trial registration

NCT01227278 and NCT01238861.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0968-8) contains supplementary material, which is available to authorized users.

[Neurophysiology of atopic pruritus]

Pruritus is one of the major symptoms of inflammatory skin diseases and strongly affects the quality of life in patients. Although the perception of pruritus and pain are closely intertwined, pruritus represents a distinct sensation, which is also significantly different to pain at a neurophysiological level. The pathophysiological basis of chronic and acute pruritus is not fully understood. Besides histamine, a plethora of different neuromediators of itch, including neurotrophins, neuropeptides and their corresponding receptors, have been identified. In atopic dermatitis the release of these mediators leads to an activation of immune cells, such as mast cells and eosinophilic granulocytes, which in turn release neuromediators and cytokines that activate peripheral neurons. This review focuses on the neurophysiological interactions which regulate pruritus and summarizes the function of neurological and inflammatory mediators in atopic pruritus.

Clinical phenotypes and endophenotypes of atopic dermatitis: Where are we, and where should we go?

Atopic dermatitis (AD) is a paradigmatic chronic inflammatory skin disease characterized by a complex pathophysiology and a wide spectrum of the clinical phenotype. Despite this high degree of heterogeneity, AD is still considered a single disease and usually treated according to the "one-size-fits-all" approach. Thus more tailored prevention and therapeutic strategies are still lacking. As for other disciplines, such as oncology or rheumatology, we have to approach AD in a more differentiated way (ie, to dissect and stratify the complex clinical phenotype into more homogeneous subgroups based on the endophenotype [panel of biomarkers]) with the aim to refine the management of this condition. Because we are now entering the era of personalized medicine, a systems biology approach merging the numerous clinical phenotypes with robust (ie, relevant and validated) biomarkers will be needed to best exploit their potential significance for the future molecular taxonomy of AD. This approach will not only allow an optimized prevention and treatment with the available drugs but also hopefully help assign newly developed medicinal products to those patients who will have the best benefit/risk ratio.