Filaggrin mutations associated with skin and allergic diseases

Filaggrin mutations in relation to skin barrier and atopic dermatitis in early infancy

BACKGROUND

Loss-of-function mutations in the skin barrier gene filaggrin (FLG) increase the risk of atopic dermatitis (AD), but their role in skin barrier function, dry skin and eczema in infancy is unclear.

OBJECTIVES

To determine the role of FLG mutations for impaired skin barrier function, dry skin, eczema and AD at three months of age and through infancy.

METHODS

FLG mutations were analyzed in 1836 infants in the Scandinavian population-based PreventADALL study. Transepidermal water loss (TEWL), dry skin, eczema and AD were assessed at three, six and 12 months of age.

RESULTS

Filaggrin mutations were observed in 166 (9%) infants. At three months, carrying FLG mutations was not associated with impaired skin barrier function (TEWL > 11.3 g/m² /h) or dry skin, but with eczema (OR(95%CI): 2.76 (1.81, 4.23), p < 0.001). At six months, mutation carriers had significantly higher TEWL than non-mutation carriers (mean (95%CI) 9.68 (8.69, 10.68) vs. 8.24 (7.97, 8.15), p < 0.01) and at three and six months an increased risk of dry skin on truncus (OR: 1.87 (1.25, 2.80), p = 0.002; 2.44 (1.51, 3.95), p < 0.001) or extensor limb surfaces (1.52 (1.04, 2.22), p = 0.028; 1.74 (1.17, 2.57), p = 0.005). FLG mutations were associated with eczema and AD in infancy.

CONCLUSION

Filaggrin mutations were not associated with impaired skin barrier function or dry skin in general at three months of age, but increased the risk for eczema, as well as for dry skin on truncus and extensors at three and six months.

Atopic Dermatitis: From Etiology and History to Treatment

Atopic dermatitis (AD) is a chronic recurrent inflammatory skin disease in patients with atopy. Atopy itself, is defined as a predisposition to develop immune response with overproduction of immunoglobulin E to low doses of allergens. AD is one of the most common skin disorders in the developed world, affecting up to 20% of children and about 3% of adults. The pathogenesis of the disease is complex, with both genetic and environmental factors playing a significant role in it. Clinically, hallmarks of atopic dermatitis include dry, itchy skin and various cutaneous efflorescence, compatible to dermatitis or eczema. Atopic dermatitis subdivides into three morphological variants manifesting during infancy, childhood and adulthood. Various environmental factors and associated diseases may have serious influence on the clinical course or may trigger disease relapses. The aim of this review article is to serve as a comprehensive overview of the etiology, pathogenesis, clinical course and diagnosis, as well as potential challenges facing the successful treatment of atopic dermatitis.

S100A7 Co-localization and Up-regulation of Filaggrin in Human Sinonasal Epithelial Cells

OBJECTIVE

Filaggrin (FLG) is a protein expressed in the epidermis and involved in the maintenance of the epidermal barrier. However, the expression and localization of FLG in the upper airway remain controversial. The present study aimed to determine the significance of FLG and the effect of S100A7 on FLG expression in the upper respiratory mucosa.

METHODS

Human nasal epithelial cells (HNECs) were cultured and examined for FLG expression and S100A7 effects by real-time polymerase chain reaction and Western blotting. The localization and distribution of FLG were assessed using sinonasal mucosa.

RESULTS

A significant expression of FLG was detected at the mRNA and protein levels in HNECs. A moderate FLG immunoreactivity was observed in the epithelial cells, but no staining was seen in epithelial goblet cells. S100A7 increased the FLG mRNA level in HNECs in a dose-dependent manner and also up-regulated the FLG protein in a dose-dependent manner.

CONCLUSION

This study significantly contributes to a better understanding of the role of FLG in the pathogenesis of airway inflammation from the viewpoint of the epithelial barrier function. FLG-related events in response to S100A7 protein may represent novel therapeutic targets for the treatment of upper airway inflammation.

A Common Variant at 11q23.3 Is Associated with Susceptibility to Atopic Dermatitis in the Han Chinese Population

Background: Genome-wide association studies (GWASs) have identified many genetic variants that are risk factors for numerous immune-mediated diseases. In particular, different immune-mediated diseases have been found to share the same susceptibility loci. Therefore, exploring the genetic overlap between atopic dermatitis (AD) and other immune-mediated diseases in more detail may help identify additional shared susceptibility loci among common immune-mediated diseases. Recent evidence suggests that the 11q23.3 locus is a susceptibility locus shared among multiple immune-mediated diseases. Objective: This study was designed to investigated whether SNPs at the chromosome 11q23.3 locus are associated with AD in the Han Chinese population. Methods: In total, 16 SNPs within the 11q23.3 locus were genotyped using TaqMan assays for 1,012 AD cases and 1,362 controls. From these SNPs, we selected rs638893 with an association values of p < 5 × 10^-2 for AD for further analysis in an independent replication study using the Sequenom MassARRAY system to genotype an additional (consisting of 1,288 cases and 1,380 controls). The combined analyses were performed in two stages using a meta-analytical method. Results: We identified a common variant at 11q23.3 (rs638893), that was significantly associated (p = 1.58 × 10^-3, OR = 1.22) with AD. The genotype-based association analysis revealed that the recessive model provided the best fit for rs638893. Conclusion: Our study identified a variant on chromosome 11q23.3 that likely confers susceptibility to AD, thereby advancing our understanding of the genetic basis of this disease.

Targeted Screening of Lactic Acid Bacteria With Antibacterial Activity Toward Staphylococcus aureus Clonal Complex Type 1 Associated With Atopic Dermatitis

Atopic dermatitis (AD) is a common inflammatory skin disease characterized by an epidermal barrier impairment, as well as a Th2/Th22-skewed immune response, both favoring skin colonization with Staphylococcus aureus. Colonization is strongly related to severity of the disease, and a reduction of S. aureus has been found to alleviate symptoms. Lactic acid bacteria (LAB) produce antimicrobial compounds such as organic acids and bacteriocins and are widely used as probiotics. The aim of this study was to isolate LAB and screen for antibacterial effect specifically toward S. aureus clonal complex type 1. A total of 680 LAB were isolated from fermented vegetables and swab samples from healthy volunteers (vaginal, stool and skin). Screening for antibacterial activity toward S. aureus, narrowed the field of isolates down to four LAB strains with high antibacterial activity. The activity varied according to the specific LAB strain and the origin of the strain. The results suggested different modes of action, including co-aggregation, expression of bacteriocins and production of specific organic acids. However, the ability to acidify the surroundings appeared as the main effect behind inhibition of S. aureus. Broth microdilution assays showed a significant reduction of S. aureus growth when using down to 10% cell free supernatant (CFS). Our results underline the use of specific living LAB or their CFS as potential future treatment strategies to reduce S. aureus colonization of AD skin.

Very Elevated IgE, Atopy, and Severe Infection: A Genomics-Based Diagnostic Approach to a Spectrum of Diseases

Elevated IgE has been long recognized as an important clinical marker of atopy but can be seen in a myriad of conditions. The discovery of autosomal dominant STAT3 deficiency marked the first recognition of hyper-IgE syndrome (HIES) and the first primary immunodeficiency linked to elevated IgE. Since then, genomic testing has increased the number of defects with associated mutations causing hyper-IgE syndrome and atopic diseases with FLG, DOCK8, SPINK5, and CARD11, among others. A spectrum of recurrent infections and atopy are hallmarks of elevated IgE with significant phenotypic overlap between each underlying condition. As treatment is predicated on early diagnosis, genomic testing is becoming a more commonly used diagnostic tool. We present a 6-year-old male patient with markedly elevated IgE and severe atopic dermatitis presenting with staphylococcal bacteremia found to have a heterozygous variant in FLG (p.S3247X) and multiple variants of unknown significance in BCL11B, ZAP70, LYST, and PTPRC. We review the genetic defects underpinning elevated IgE and highlight the spectrum of atopy and immunodeficiency seen in patients with underlying mutations. Although no one mutation is completely causative of the constellation of symptoms in this patient, we suggest the synergism of these variants is an impetus of disease.

HDAC6 and CXCL13 Mediate Atopic Dermatitis by Regulating Cellular Interactions and Expression Levels of miR-9 and SIRT1

Histone deacetylase 6 (HDAC6) has been known to regulate inflammatory diseases. The role of HDAC6 in allergic skin inflammation has not been studied. We studied the role of HDAC6 in atopic dermatitis (AD) and the mechanisms associated with it. The decreased expression or chemical inhibition of HDAC6 suppressed AD by decreasing autophagic flux and cellular features of AD. AD increased expression levels of the Th1 and Th2 cytokines, but decreased expression levels of forkhead box P3 (FoxP3) and interleukin-10 (IL-10) in an HDAC6-dependent manner. CXC chemokine ligand 13 (CXCL13), which was increased in an HDAC6-depenednt manner, mediated AD. MiR-9, negatively regulated by HDAC6, suppressed AD by directly regulating the expression of sirtuin 1 (SIRT1). The downregulation or inhibition of SIRT1 suppressed AD. Experiments employing culture medium and transwell suggested that cellular interactions involving mast cells, keratinocytes, and dermal fibroblast cells could promote AD; HDAC6 and CXCL13 were found to be necessary for these cellular interactions. Mouse recombinant CXCL13 protein increased HDAC6 expression in skin mast cells and dermal fibroblast cells. CXCL13 protein was found to be present in the exosomes of DNCB-treated skin mast cells. Exosomes of DNCB-treated skin mast cells enhanced invasion potentials of keratinocytes and dermal fibroblast cells and increased expression levels of HDAC6, SIRT1 and CXCL13 in keratinocytes and dermal fibroblast cells. These results indicate that HDAC6 and CXCL13 may serve as targets for the developing anti-atopic drugs.

Eczema herpeticum in atopic dermatitis

Atopic dermatitis (AD) is one of the most common chronic inflammatory skin diseases leading to pruritic skin lesions. A subset of AD patients exhibits a disseminated severe HSV infection called eczema herpeticum (EH) that can cause life-threatening complications. This review gives an overview of the clinical picture, and characteristics of the patients as well as the diagnosis and therapy of EH. A special focus lies on the pathophysiological hallmarks identified so far that predispose for EH. This aspect covers genetic aberrations, immunological changes, and environmental influences displaying a complex multifactorial situation, which is not completely understood. Type 2 skewing of virus-specific T cells in ADEH⁺ patients has been implicated in immune profile abnormalities, along with impaired functions of dendritic cells and natural killer cells. Furthermore, aberrations in interferon pathway-related genes such as IFNG and IFNGR1 have been identified to increase the risk of EH. IL-4, IL-25, and thymic stromal lymphopoietin (TSLP) are overexpressed in EH, whereas antimicrobial peptides like human β-defensins and LL-37 are reduced. Concerning the epidermal barrier, single nucleotide polymorphisms (SNPs) in skin barrier proteins such as filaggrin were identified in ADEH⁺ patients. A dysbalance of the skin microbiome also contributes to EH due to an increase of Staphylococcus aureus, which provides a supporting role to the viral infection via secreted toxins such as α-toxin. The risk of EH is reduced in AD patients treated with dupilumab. Further research is needed to identify and specifically target risk factors for EH in AD patients.

From Emollients to Biologicals: Targeting Atopic Dermatitis

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease and significantly impacts patients' lives, particularly in its severe forms. AD clinical presentation varies over the course of the disease, throughout different age groups, and across ethnicities. AD is characterized by a spectrum of clinical phenotypes as well as endotypes. Starting from the current description of AD pathogenesis, this review explores the rationale of approved AD therapies from emollients to biologicals and introduces novel promising drugs.

Partially Hydrolysed Whey-Based Infant Formula Improves Skin Barrier Function

Specific partially hydrolysed whey-based infant formulas (pHF-W) have been shown to decrease the risk of atopic dermatitis (AD) in infants. Historically, AD has been associated primarily with milk allergy; however, defective skin barrier function can be a primary cause of AD. We aimed to ascertain whether oral supplementation with pHF-W can improve skin barrier function. The effect of pHF-W was assessed on transepidermal water loss (TEWL) and antibody productions in mice epicutaneously exposed to Aspergillus fumigatus. Human primary keratinocytes were stimulated in vitro, and the expression of genes related to skin barrier function was measured. Supplementation with pHF-W in neonatal mice led to a significant decrease in TEWL and total IgE, but not in allergen-specific antibody levels. The whey hydrolysate was sufficient to decrease both TEWL and total IgE. Aquaporin-3 gene expression, linked with skin hydration, was modulated in the skin of mice and human primary keratinocytes following protein hydrolysate exposure. Skin barrier improvement may be an additional mechanism by which pHF-W may potentially reduce the risk of AD development in infants. Further human studies are warranted to confirm the clinical efficacy of these observations.

Moisturisers from birth in at-risk infants of atopic dermatitis - a pragmatic randomised controlled trial

Background

Atopic dermatitis (AD) is a common, chronic dermatosis, with onset of disease often manifesting in early infancy. Past studies evaluating the early use of moisturisers in the prevention of AD had mixed results.

Objectives

To compare the incidence of moderate or severe AD and total incidence of AD in a cohort of ‘at‐risk’ infants treated with moisturisers from the first 2 weeks of life, to a similar group without moisturisers.

Methods

We performed a single‐centre, prospective, parallel‐group, randomised study in infants with at least 2 first‐degree relatives with atopy. Subjects were randomised into either a treatment group with moisturisers or a control group without moisturisers. Participants were assessed at 2, 6, and 12 months for AD and if present, the severity was assessed using SCORAD index. We also compared the overall incidence of AD, trans‐epidermal water loss (TEWL), stratum corneum (SC) hydration, pH, and incidence of food and environmental sensitisation and allergies between both groups. Genotyping for loss‐of‐functions mutations in the FLG gene was conducted.

Results

A total of 200 subjects were recruited, with 100 subjects in each arm. There was no significant difference in incidence of moderate or severe AD, and total incidence of AD at 12 months between the treatment and control groups. There was a lower mean SCORAD in the treatment group than in the control group, but no significant difference in TEWL, SC hydration, and skin pH. No significant side‐effects were reported.

Conclusions

The early use of moisturisers in ‘at‐risk’ infants does not reduce the incidence of moderate‐to‐severe AD and overall incidence of AD in infancy.

Baricitinib for the treatment of atopic dermatitis

Atopic dermatitis is a common, chronic and recurrent inflammatory skin disease, which often appears in childhood but can last into adulthood. It negatively impacts patients, their families and society in general. There is a therapeutic unmet need, with patients requiring new drugs that are safe and effective. The increasing knowledge of the pathophysiology of AD and the role of the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathway in the development and maintenance of AD, has led to the development of agents blocking this intracellular signaling pathway, the JAK inhibitors. Baricitinib shows high selectivity for JAK1 and JAK2, making it appealing for the treatment of this condition. Phase II and phase III trials evaluated the efficacy and safety of baricitinib in the treatment of AD, and the results have been encouraging, showing a good efficacy and a favorable safety and tolerability profile. At the end of 2020, EMA approved baricitinib for the treatment of adult patients with moderate-to-severe atopic dermatitis who are candidates for systemic therapy, increasing the therapeutic option for this debilitating disease.

Dysregulation of the epithelial barrier by environmental and other exogenous factors

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

Atopic dermatitis: an expanding therapeutic pipeline for a complex disease

Atopic dermatitis (AD) is a common chronic inflammatory skin disease with a complex pathophysiology that underlies a wide spectrum of clinical phenotypes. AD remains challenging to treat owing to the limited response to available therapies. However, recent advances in understanding of disease mechanisms have led to the discovery of novel potential therapeutic targets and drug candidates. In addition to regulatory approval for the IL-4Ra inhibitor dupilumab, the anti-IL-13 inhibitor tralokinumab and the JAK1/2 inhibitor baricitinib in Europe, there are now more than 70 new compounds in development. This Review assesses the various strategies and novel agents currently being investigated for AD and highlights the potential for a precision medicine approach to enable prevention and more effective long-term control of this complex disease.

Recent advances in understanding of the complex phenotype and mechanisms underlying atopic dermatitis (AD) have revealed multiple new potential targets for pharmacological intervention. Here, Bieber reviews therapeutic strategies and assesses the expanding pipeline for the therapy of AD, highlighting the potential for a precision medicine approach to the management of this complex disorder.

The power and potential of BIOMAP to elucidate host-microbiome interplay in skin inflammatory diseases

The two most common chronic inflammatory skin diseases are atopic dermatitis (AD) and psoriasis. The underpinnings of the remarkable degree of clinical heterogeneity of AD and psoriasis are poorly understood and, as a consequence, disease onset and progression are unpredictable and the optimal type and time-point for intervention are as yet unknown. The BIOMAP project is the first IMI (Innovative Medicines Initiative) project dedicated to investigating the causes and mechanisms of AD and psoriasis and to identify potential biomarkers responsible for the variation in disease outcome. The consortium includes 7 large pharmaceutical companies and 25 non-industry partners including academia. Since there is mounting evidence supporting an important role for microbial exposures and our microbiota as factors mediating immune polarization and AD and psoriasis pathogenesis, an entire work package is dedicated to the investigation of skin and gut microbiome linked to AD or psoriasis. The large collaborative BIOMAP project will enable the integration of patient cohorts, data and knowledge in unprecedented proportions. The project has a unique opportunity with a potential to bridge and fill the gaps between current problems and solutions. This review highlights the power and potential of BIOMAP project in the investigation of microbe-host interplay in AD and psoriasis.

Epithelial-immune crosstalk with the skin microbiota in homeostasis and atopic dermatitis - a mini review

The skin is a complex and dynamic ecosystem, wherein epithelial cells, immune cells and the skin microbiota actively interact and maintain barrier integrity and functional immunity. Skin microbes actively tune the functions of the resident immune cells. Dysbiosis - alterations in the resident microbiota - leads to the dysregulation of host immunity. Microbiome analyses in humans and dogs with atopic dermatitis (AD) have shown shifts in microbial diversity, and in particular, an increased proportion of staphylococci. Monogenic diseases that manifest AD-like symptoms provide insights into the pathogenesis of AD and the mechanisms of dysbiosis, from both the epithelial and immunological perspectives. The symbiotic relationships between the host and microbiota must be maintained constitutively. Detailed mechanisms of how host immunity regulates commensal bacteria in the steady state have been reported. The skin harbours multiple tissue-resident immune cells, including both innate and adaptive immune cells. Recent studies have highlighted the fundamental role of innate lymphoid cells (ILCs) in the maintenance of barrier functions and tissue homeostasis. ILCs directly respond to tissue-derived signals and are instrumental in barrier immunity. Epithelial cells produce alarmins such as thymic stromal lymphopoietin (TSLP) and interleukins (IL)-33 and IL-25, all of which activate group 2 ILCs (ILC2s), which produce type 2 cytokines, such as IL-5 and IL-13, boosting type 2 immune reactions. Dysregulation of the epithelial-ILC crosstalk results in allergic inflammation. This review highlights our understanding of the active interactions between the host epithelial and immune cells, and microbiota, providing a foundation for novel therapeutic strategies for inflammatory skin diseases.

A loss of function mutation in the filaggrin gene associated with ichthyosis vulgaris and rheumatoid arthritis

Introduction

Mutations in the filaggrin ( FLG) gene are known to cause ichthyosis vulgaris.

Methods

We used whole-genome sequencing (WGS) technology to investigate the genetic causes of rare and complex inherited diseases including rheumatoid arthritis, ichthyosis, and congenital fibrosis of the extraocular muscles type 1 (CFEOM1) in a Chinese family. WGS was performed in four topics, and the identified candidate mutations were further verified through Sanger sequencing.

Results

We identified a mutation in FLG gene (g.152280098 C>A, p.E2422∗) that may be associated with ichthyosis and arthritis. Moreover, a mutation in KIF21A (g.39726207 G>A, p.R954 W) was also determined in affected members as the cause of CFEOM1. The gene interaction network demonstrated an interesting correlation between FLG and genes associated with arthritis and ichthyosis. Functional enrichment analysis of these interacting genes revealed several possible pathways that might be linked to arthritis and ichthyosis.

Conclusion

In general, we confirmed a loss of function mutation in the FLG gene associated with ichthyosis vulgaris and rheumatoid arthritis in this family.

Update on the Pathogenesis and Therapy of Atopic Dermatitis

Atopic dermatitis (AD) is a common inflammatory skin disorder characterized by recurrent eczematous lesions and intense itch. Although it most often starts in infancy and affects children, it is also highly prevalent in adults. In this article, the main aspects of AD have been updated, with a focus on the pathogenetic and therapeutic aspects. The pathogenesis of AD is complex, and it is evident that a strong genetic predisposition, epidermal dysfunction, skin microbiome abnormalities, immune dysregulation, and the neuroimmune system are critical in AD development. Mutations in the genes associated with disrupted epidermal barrier, exaggerated pathological inflammation and inadequate antimicrobial peptides can promote enhanced Th2 inflammation and mediate pruritus. Current understanding of etiology highlights gut microbial diversity, NK cell deficiency, and different immunological phenotype with age and race. For topical anti-inflammatory treatment for mild-to-severe AD, phosphodiesterase 4 inhibitors (PDE-4), JAK inhibitors, and microbiome transplantation with Roseomonas mucosa provided more management selections. The treatment of moderate-to-severe AD has been limited to merely symptomatic and relatively nonspecific immunosuppressive approaches. In-depth understanding of the pathogenesis of AD has led to the development of innovative and targeted therapies, such as biologic agents targeting interleukin (IL)-4, IL-13 and JAK/STAT inhibitors. Other potential therapeutic agents for AD include agents targeting the T helper (Th) 22 and Th17/IL23 pathway. Antipruritic therapy and complementary probiotics therapy have also been reviewed.

Repetitive aeroallergen challenges elucidate maladaptive epithelial and inflammatory traits that underpin allergic airway diseases

BACKGROUND

Signifying the 2-compartments/1-disease paradigm, allergic rhinoconjunctivitis (ARC) and asthma (AA) are prevalent, comorbid conditions triggered by environmental factors (eg, house dust mites [HDMs]). However, despite the ubiquity of triggers, progression to severe ARC/AA is infrequent, suggesting either resilience or adaptation.

OBJECTIVE

We sought to determine whether ARC/AA severity relates to maladaptive responses to disease triggers.

METHODS

Adults with HDM-associated ARC were challenged repetitively with HDMs in an aeroallergen challenge chamber. Mechanistic traits associated with disease severity were identified.

RESULTS

HDM challenges evoked maladaptive (persistently higher ARC symptoms), adaptive (progressive symptom reduction), and resilient (resistance to symptom induction) phenotypes. Symptom severity in the natural environment was an imprecise correlate of the phenotypes. Nasal airway traits, defined by low inflammation-effectual epithelial integrity, moderate inflammation-effectual epithelial integrity, and higher inflammation-ineffectual epithelial integrity, were hallmarks of the resilient, adaptive, and maladaptive evoked phenotypes, respectively. Highlighting a crosstalk mechanism, peripheral blood inflammatory tone calibrated these traits: ineffectual epithelial integrity associated with CD8⁺ T cells, whereas airway inflammation associated with both CD8⁺ T cells and eosinophils. Hallmark peripheral blood maladaptive traits were increased natural killer and CD8⁺ T cells, lower CD4⁺ mucosal-associated invariant T cells, and deficiencies along the TLR-IRF-IFN antiviral pathway. Maladaptive traits tracking HDM-associated ARC also contributed to AA risk and severity models.

CONCLUSIONS

Repetitive challenges with HDMs revealed that maladaptation to disease triggers may underpin ARC/AA disease severity. A combinatorial therapeutic approach may involve reversal of loss-of-beneficial-function traits (ineffectual epithelial integrity, TLR-IRF-IFN deficiencies), mitigation of gain-of-adverse-function traits (inflammation), and blocking of a detrimental crosstalk between the peripheral blood and airway compartments.

Increased Th22 cell numbers in a general pediatric population with filaggrin haploinsufficiency: The Generation R Study

BACKGROUND

Mutations in the filaggrin gene (FLG) affect epidermal barrier function and increase the risk of atopic dermatitis (AD). We hypothesized that FLG mutations affect immune cell composition in a general pediatric population. Therefore, we investigated whether school-aged children with and without FLG mutations have differences in T- and B-cell subsets.

METHODS

This study was embedded in a population-based prospective cohort study, the Generation R Study, and included 523 children of European genetic ancestry aged 10 years. The most common FLG mutations in the European population (R501X, S1085CfsX36, R2447X, and S3247X) were genotyped. Additionally, 11-color flow cytometry was performed on peripheral blood samples to determine helper T (Th), regulatory T (Treg), and CD27⁺ and CD27^- memory B cells. Subset analysis was performed in 358 non-AD and 102 AD cases, assessed by parental questionnaires.

RESULTS

FLG mutations were observed in 8.4% of the total population and in 15.7% of the AD cases. Children with any FLG mutation had higher Th22 cell numbers compared to FLG wild-type children in the general and non-AD population. Children with and without FLG mutations had no difference in Th1, Th2, Th17, Treg, or memory B-cell numbers. Furthermore, in children with AD, FLG mutation carriership was not associated with differences in T- and B-cell subsets.

CONCLUSIONS

School-aged children of a general population with FLG mutations have higher Th22 cell numbers, which reflects the immunological response to the skin barrier dysfunction. FLG mutations did not otherwise affect the composition of the adaptive immunity in this general pediatric population.

Effect of Neferine on DNCB-Induced Atopic Dermatitis in HaCaT Cells and BALB/c Mice

Atopic dermatitis (AD) is a chronic and persistent inflammatory skin disease characterized by eczematous lesions and itching, and it has become a serious health problem. However, the common clinical treatments provide limited relief and are accompanied by adverse effects. Therefore, there is a need to develop novel and effective therapies to treat AD. Neferine is a small molecule compound isolated from the green embryo of the mature seeds of lotus (Nelumbo nucifera). It has a bisbenzylisoquinoline alkaloid structure. Relevant studies have shown that neferine has many pharmacological and biological activities, including anti-inflammatory, anti-thrombotic, and anti-diabetic activities. However, there are very few studies on neferine in the skin, especially the related effects on inflammatory skin diseases. In this study, we proved that it has the potential to be used in the treatment of atopic dermatitis. Through in vitro studies, we found that neferine inhibited the expression of cytokines and chemokines in TNF-α/IFN-γ-stimulated human keratinocyte (HaCaT) cells, and it reduced the phosphorylation of MAPK and the NF-κB signaling pathway. Through in vivo experiments, we used 2,4-dinitrochlorobenzene (DNCB) to induce atopic dermatitis-like skin inflammation in a mouse model. Our results show that neferine significantly decreased the skin barrier damage, scratching responses, and epidermal hyperplasia induced by DNCB. It significantly decreased transepidermal water loss (TEWL), erythema, blood flow, and ear thickness and increased surface skin hydration. Moreover, it also inhibited the expression of cytokines and the activation of signaling pathways. These results indicate that neferine has good potential as an alternative medicine for the treatment of atopic dermatitis or other skin-related inflammatory diseases.

Filaggrin-gene mutation has minimal effect on the disease severity in the lesions of atopic dermatitis

Loss-of-function mutations of filaggrin (FLG) gene (FLG) are the strongest known genetic risk factor for atopic dermatitis (AD). It is still debatable how FLG gene mutations and the resulting abnormal amount of FLG protein contribute to skin barrier function and symptoms of AD. In this study, we examined the effects of loss-of-function mutations of FLG gene on the severity of skin lesions and skin barrier function in 55 patients with AD by evaluating eight patients with AD with FLG gene mutations and 47 patients with AD without mutations. The results showed that the FLG gene mutation did not affect the duration of AD, severity of AD, degree of local inflammatory symptoms, skin water content and trans-epidermal water loss of the lesions. Next, in these eight mutation carriers and the 47 non-carriers, stratum corneum was collected from the three site of skin lesions using tape-stripping method, and the amounts of FLG protein and total amino acid contained in the stratum corneum was measured to investigate the effect of the FLG gene mutation on the amount of FLG gene product in the local lesion. FLG abnormalities had little effect on FLG protein and total amino acid content in the stratum corneum in the lesional skin. The amount of the FLG products, especially amino acids derived from FLG, in the stratum corneum of AD lesional skin is influenced by development of dermatitis. The results obtained from this study supports that the activation of Th2-dominant inflammatory cells, together with FLG abnormality, plays a role in suppressing the production of FLG in skin lesions.

A Clinical Investigation of the Performance and Safety of Epaderm®, an Emollient Cream

Introduction

Emollients provide an occlusive barrier for dry and atopic skin, retain moisture, protect it from irritants, and form the basis of eczema treatment.

Methods and Analysis

A prospective interventional single arm study to evaluate the performance and safety of Epaderm^® Cream, an emollient and cleanser containing 25% (w/w) paraffin and 5% (w/w) glycerine (thereafter, an emollient cream), in patients with dry skin conditions. The primary outcome measure was participant evaluation of skin moisturisation after treatment with an emollient cream for up to 4 weeks. Secondary outcome measures included: evaluation of skin softness using a questionnaire and of pruritus on a visual analogue scale (VAS); clinician assessment of xerosis using Overall Dry Skin (ODS) score and measurement of skin hydration using a non-invasive device (MoistureMeterEpiD, Delfin Technologies) at each visit. Sign test and Wilcoxon signed rank test were used to analyse changes from baseline.

Results

A total of 114 participants completed the study. 84.2% (80 out of 95) of participants or parents strongly agreed or agreed that the cream improved skin moisturisation at 4 weeks of treatment at the target area (p<0.0001). 86.3% of participants agreed that skin softness improved after 4 weeks (p <0.0001). ODS score improved from 2.1 (standard deviation (SD) 1.0) to 0.7 (SD 0.8) at 4 weeks. Skin hydration at the target area improved from 31.5 (SD 9.3) to 40.5 (SD 8.3) (p<0.001) at 4 weeks. Mean skin itchiness reduced from 38.0 (SD 25.4) to 17.7 (SD 19.8) at 4 weeks (p<0.0001). Ten (8.3%) adverse device events (ADEs) were reported.

Conclusion

The emollient cream was well tolerated and demonstrated significant improvements in patient-reported skin moisturisation and softness as well as in clinical measurement of xerosis and skin hydration across all age groups including infants. The emollient cream can be recommended for dry skin conditions including atopic dermatitis and psoriasis.

Atopic Eczema: Pathophysiological Findings as the Beginning of a New Era of Therapeutic Options

Atopic eczema (AE) is a chronic inflammatory disease hallmarked by intense pruritus and eczematous lesions. It depicts one of the most common skin diseases affecting a major part of children and several percentages of adults.Both pathogenesis and pathophysiology are based on complex orchestrated interactions of skin barrier defects, immunological changes, the environment, and an abundance of other contributing factors. Frequently, AE displays the starting point for other allergic diseases such as allergic asthma and rhinoconjunctivitis. Additionally, the risk of developing food allergy is increased. Furthermore, the disease is accompanied by a susceptibility to bacterial, fungal, and viral infections. The development of new therapies received great impetus by an ample research of the pathophysiological mechanisms, leading to a new era in the treatment of severe atopic eczema due to targeted treatments, e.g. the IL-4R alpha specific monoclonal antibody dupilumab.This article provides an overview of the causative and pathophysiological characteristics, the clinical and diagnostic aspects as well as current and future therapeutical possibilities focusing allergic aspects contributing to the course of the disease.

Climate Effect, Globalization, and Ethics in Allergy

The prevalence of allergic diseases is increasing rapidly and has already reached an epidemic level. Two major drivers of this development are climate change and globalization, which both induce an increase in allergens. Concomitant climate change fosters the spreading of the latter on a global scale. The increase in allergens not only aggravates the symptoms and the degree of suffering for patients who already are allergic, but also gives rise to new cases of allergies. The distribution of allergies in society follows a steep socioeconomic gradient worldwide. According to well-established theories of justice such a distribution of the allergy burden is unfair. This fact adds a major ethical dimension and challenge to the allergy epidemic. This chapter draws on the key points of policies for allergy prevention and treatment. It shows how related programs and measures can be conceptualized and prioritized according to the principles of distributional justice.

So close, and yet so far away: The dichotomy of the specific immune response and inflammation in psoriasis and atopic dermatitis

Characterization of the complex interplay between cytokines, chemokines and microorganisms has led to a better understanding of the pathogenesis of both psoriasis and AD and resulted in new therapeutics targeting distinct immune responses. Psoriasis and AD share many characteristics: they are highly prevalent, chronic, cause primarily skin inflammation, but are associated with comorbidities, and come with a devastating quality of life due to itch and stigmatization. However, the pathogenesis of psoriasis and AD is opposing - psoriasis is dominated by a Th17 immune response that causes neutrophil migration, induction of innate immunity and exaggerated epithelial metabolism. Leading cytokines of this Th17 immune response are IL-17A and F, IL-22 and TNF-a. AD is characterized by Th2 immunity characterized by the signature cytokines IL-4 and IL-13 leading to an impaired epidermal barrier, dampened innate immunity and eosinophil migration. This review compares genetics, microbiome and T-cell infiltrate and resulting epithelial response in psoriasis and AD. Whilst the antagonistic course of psoriasis and AD is confirmed by response to specific biologics targeting the key cytokines of inflammation in psoriasis and AD, respectively, clinically overlapping phenotypes are challenging in our daily clinical practice. We conclude this review by summarizing what is known about these mixed phenotypes and how the identification of clinically relevant endotypes and molecular-driven decision-making is the next step in the field of dermato-immunology.

[Dysbalance between the immune system and skin microbiome in chronic inflammatory dermatoses]

BACKGROUND

The skin is an organ frequently affected by chronic diseases. Inflammatory, immune-mediated dermatoses such as atopic dermatitis and psoriasis show a high prevalence as well as a significant impact on the quality of life of those affected. In a large proportion of cases, atopic dermatitis is associated with a marked change in microbial colonization of both clinically healthy and affected skin. In psoriasis, changes to this effect have been described, but clinical relevance remains elusive.

AIM

In recent years, increasing knowledge has been gained in microbiome research with resulting clinical relevance. The present article deals with the disturbed balance of the immune system and the skin microbiome in chronic inflammatory dermatoses on the basis of atopic dermatitis and psoriasis vulgaris.

MATERIALS AND METHODS

A literature search was performed in PubMed and Medline databases (entries until 09 April 2021).

RESULTS

Staphylococcus aureus is known to play a central pathophysiological role in atopic dermatitis. This is revisited in light of new insights regarding biodiversity and immunoregulatory processes. In psoriasis, a more heterogeneous body of data emerges regarding the microbiome and its contribution to disease development.

DISCUSSION

While topical applications to directly influence the microbiome are already being tested in atopic dermatitis, further knowledge regarding the pathophysiological significance of the microbiota is still needed in psoriasis.

Large contribution of copy number alterations in early stage of Papillary Thyroid Carcinoma

Papillary Thyroid Carcinoma (PTC) accounts for approximately 85% of patients with thyroid cancer. Despite its indolent nature, progression to higher stages is expected in a subgroup of patients. Hence, genomic characterization of the early stages of PTC may help to identify this subgroup, leading to better clinical management. Here, we conducted a comprehensive mutational and somatic copy number alteration (SCNA) investigation on 277 stage one PTC from TCGA. SCNA analysis revealed amplification and deletion of several cancer related genes. We found amplification of 60 oncogenes (Oncs), from which 15 were recurrently observed. Deletion of 58 tumor suppressors (TSs) was also detected. MAPK, PI3K-Akt, Rap1 and Ras were the signaling pathways with large numbers of amplified Oncs. On the other hand, deleted TSs belonged mostly to cell cycle, PI3K-Akt, mTOR and cellular senescence pathways. This suggests that despite heterogeneity in SCNA events, the final results would be the activation/deactivation of a few cancer signaling pathways. Of note, despite large amounts of heterogeneity in stage one PTC, recurrent broad deletion on Chr22 was detected in 21 individuals, leading to deletion of several tumor suppressors. In parallel, the oncogenic/pathogenic mutations in the RTK-RAS and PI3k-Akt pathways were detected. However, no pathogenic mutation was identified in known tumor suppressor genes. In order to identify a potential subgroup of BRAF (V600E) positive patients, who might progress to higher stages, low frequency mutations accompanying BRAF (V600E) were also identified. In conclusion, our findings imply that SCNA have a substantial contribution to early stages of PTC. Experimental validation of the observed genomic alterations could help to stratify patients at the time of diagnosis, and to move toward precision medicine in PTC.

New Treatments for Atopic Dermatitis Targeting Skin Barrier Repair via the Regulation of FLG Expression

Atopic dermatitis (AD) is one of the most common chronic, inflammatory skin disorders with a complex etiology and a broad spectrum of clinical phenotypes. Despite its high prevalence and effect on the quality of life, safe and effective systemic therapies approved for long-term management of AD are limited. A better understanding of the pathogenesis of atopic dermatitis in recent years has contributed to the development of new therapeutic approaches that target specific pathophysiological pathways. Skin barrier dysfunction and immunological abnormalities are critical in the pathogenesis of AD. Recently, the importance of the downregulation of epidermal differentiation complex (EDC) molecules caused by external and internal stimuli has been extensively emphasized. The purpose of this review is to discuss the innovations in the therapy of atopic dermatitis, including biologics, small molecule therapies, and other drugs by highlighting regulatory mechanisms of skin barrier-related molecules, such as filaggrin (FLG) as a crucial pathway implicated in AD pathogenesis.

Immunological Aspects of Skin Aging in Atopic Dermatitis

The cutaneous immune response is important for the regulation of skin aging well as for the development of immune-mediated skin diseases. Aging of the human skin undergoes immunosenescence with immunological alterations and can be affected by environmental stressors and internal factors, thus leading to various epidermal barrier abnormalities. The dysfunctional epidermal barrier, immune dysregulation, and skin dysbiosis in the advanced age, together with the genetic factors, facilitate the late onset of atopic dermatitis (AD) in the elderly, whose cases have recently been on the rise. Controversial to the healthy aged skin, where overproduction of many cytokines is found, the levels of Th2/Th22 related cytokines inversely correlated with age in the skin of older AD patients. As opposed to an endogenously aged skin, the expression of the terminal differentiation markers significantly increases with age in AD. Despite the atenuated barrier disturbances in older AD patients, the aged skin carries an impairment associated with the aging process, which reflects the persistence of AD. The chronicity of AD in older patients might not directly affect skin aging but does not allow spontaneous remission. Thus, adult- and elderly subtypes of AD are considered as a lifelong disease.

Staphylococcus aureus binds to the N-terminal region of corneodesmosin to adhere to the stratum corneum in atopic dermatitis

Staphylococcus aureus colonizes the skin of the majority of patients with atopic dermatitis (AD), and its presence increases disease severity. Adhesion of S. aureus to corneocytes in the stratum corneum is a key initial event in colonization, but the bacterial and host factors contributing to this process have not been defined. Here, we show that S. aureus interacts with the host protein corneodesmosin. Corneodesmosin is aberrantly displayed on the tips of villus-like projections that occur on the surface of AD corneocytes as a result of low levels of skin humectants known as natural moisturizing factor (NMF). An S. aureus mutant deficient in fibronectin binding protein B (FnBPB) and clumping factor B (ClfB) did not bind to corneodesmosin in vitro. Using surface plasmon resonance, we found that FnBPB and ClfB proteins bound with similar affinities. The S. aureus binding site was localized to the N-terminal glycine-serine-rich region of corneodesmosin. Atomic force microscopy showed that the N-terminal region was present on corneocytes containing low levels of NMF and that blocking it with an antibody inhibited binding of individual S. aureus cells to corneocytes. Finally, we found that S. aureus mutants deficient in FnBPB or ClfB have a reduced ability to adhere to low-NMF corneocytes from patients. In summary, we show that FnBPB and ClfB interact with the accessible N-terminal region of corneodesmosin on AD corneocytes, allowing S. aureus to take advantage of the aberrant display of corneodesmosin that accompanies low NMF in AD. This interaction facilitates the characteristic strong binding of S. aureus to AD corneocytes.

Beneficial effects of coagulase-negative Staphylococci on Staphylococcus aureus skin colonization

Our skin is constantly exposed to a large number of pathogens while at the same time undergoing selective colonization by commensal microorganisms such as coagulase-negative Staphylococci. Staphylococcus aureus, however, is a facultative pathogen that is usually absent from healthy skin but frequently colonizes the inflamed skin of atopic dermatitis patients, where it further promotes inflammation. Enhanced S. aureus skin colonization was shown to correlate with a loss of microbiome diversity indicating a role for skin commensals to shape pathogen colonization. Together, keratinocytes and immune cells in the skin need to discriminate commensals from pathogens and orchestrate subsequent immune reactions in response to colonizing microbes. However, the mechanisms how individual commensals cooperate with keratinocytes and the immune system of the skin to prevent pathogen colonization are barely understood. In this review, we discuss the current knowledge on the functional effects of coagulase-negative staphylococci, the most frequently isolated skin commensals, on S. aureus skin colonization.

Topical therapy of atopic dermatitis with a focus on pimecrolimus

Atopic dermatitis (AD) is a chronic and relapsing, inflammatory skin disease characterized by impaired skin barrier function and immune system dysregulation that results in dryness, skin microbiome dysbiosis and intense pruritus. It is highly heterogeneous, and its management is demanding. Patients with AD are at greater risk of comorbidities such as attention-deficit hyperactivity disorder as well as other atopic diseases. Early-onset AD cases typically improve or resolve in late childhood; however, it is proposed that the prevalence of persistent or adult-onset AD is higher than previously thought. Basic therapy consists of emollient application and trigger avoidance, and when insufficient, topical corticosteroids (TCS) are the first-line treatment. However, corticophobia/steroid aversion and TCS side-effects, particularly on sensitive skin areas, lead to low compliance and insufficient disease control. Several long- and short-term randomized controlled and daily practice studies have demonstrated that topical calcineurin inhibitors, such as pimecrolimus, have similar anti-inflammatory effects to low-to-medium strength TCS, reduce pruritus and improve the quality of life of patients. In addition, pimecrolimus does not cause skin atrophy, is steroid-sparing and has a good safety profile, with no evidence for an increased risk of malignancies or skin infections. In general, pimecrolimus cream is well-accepted and well-tolerated, encouraging patient adherence and leading to its use by many physicians as a preferred therapy for children and sensitive skin areas.

Atopic dermatitis: Role of the skin barrier, environment, microbiome, and therapeutic agents

Atopic dermatitis (AD) is a chronic, inflammatory skin disorder characterized by eczematous and pruritic skin lesions. In recent decades, the prevalence of AD has increased worldwide, most notably in developing countries. The enormous progress in our understanding of the complex composition and functions of the epidermal barrier allows for a deeper appreciation of the active role that the skin barrier plays in the initiation and maintenance of skin inflammation. The epidermis forms a physical, chemical, immunological, neuro-sensory, and microbial barrier between the internal and external environment. Not only lesional, but also non-lesional areas of AD skin display many morphological, biochemical and functional differences compared with healthy skin. Supporting this notion, genetic defects affecting structural proteins of the skin barrier, including filaggrin, contribute to an increased risk of AD. There is evidence to suggest that natural environmental allergens and man-made pollutants are associated with an increased likelihood of developing AD. A compromised epidermal barrier predisposes the skin to increased permeability of these compounds. Numerous topical and systemic therapies for AD are currently available or in development; while anti-inflammatory therapy is central to the treatment of AD, some existing and novel therapies also appear to exert beneficial effects on skin barrier function. Further research on the skin barrier, particularly addressing epidermal differentiation and inflammation, lipid metabolism, and the role of bacterial communities for skin barrier function, will likely expand our understanding of the complex etiology of AD and lead to identification of novel targets and the development of new therapies.

It is no skin off my nose: The relationship between the skin and allergic rhinitis

OBJECTIVE

Evidence supports the relationship between the skin barrier and allergic conditions. This narrative review evaluates what role the cutaneous barrier may play in the pathogenesis, disease course, and management of allergic rhinitis (AR).

DATA SOURCES

A literature review of the MEDLINE (PubMed), Embase, Cochrane, and SCOPUS Sciverse databases was conducted to identify available evidence. Reference lists of pertinent papers were searched using a snowball technique.

STUDY SELECTIONS

Papers published in English from all years until December 2020 were included. Papers that did not address the relationship between AR and the skin and hypothesis papers were excluded.

RESULTS

The cutaneous barrier shares histologic characteristics with the sinonasal epithelial barrier, which may explain commonalities between AR and atopic dermatitis. A disruption in the epithelial barrier could be a common pathway in the development of multiple allergic conditions. The skin is a common target for the treatment of AR. Available data that look at the relationship between the skin and AR often include other topics such as other atopic disorders and the role of the epithelial barrier. Increased understanding of how the cutaneous barrier affects AR may lead to new innovations in its management.

CONCLUSION

The connection between the cutaneous barrier and AR holds possibilities for further investigation, and these may lead to a better understanding and future innovations for all atopic diseases.

Low Threshold for Cutaneous Allergen Sensitization but No Spontaneous Dermatitis or Atopy in FLG-Deficient Mice

Loss of FLG causes ichthyosis vulgaris. Reduced FLG expression compromises epidermal barrier function and is associated with atopic dermatitis, allergy, and asthma. The flaky tail mouse harbors two mutations that affect the skin barrier, Flg^ft, resulting in hypomorphic FLG expression, and Tmem79^ma, inactivating TMEM79. Mice defective only for TMEM79 featured dermatitis and systemic atopy, but also Flg^ft/ft BALB/c congenic mice developed eczema, high IgE, and spontaneous asthma, suggesting that FLG protects from atopy. In contrast, a targeted Flg-knockout mutation backcrossed to BALB/c did not result in dermatitis or atopy. To resolve this discrepancy, we generated FLG-deficient mice on pure BALB/c background by inactivating Flg in BALB/c embryos. These mice feature an ichthyosis phenotype, barrier defect, and facilitated percutaneous sensitization. However, they do not develop dermatitis or atopy. Whole-genome sequencing of the atopic Flg^ft BALB/c congenics revealed that they were homozygous for the atopy-causing Tmem79^matted mutation. In summary, we show that FLG deficiency does not cause atopy in mice, in line with lack of atopic disease in a fraction of patients with ichthyosis vulgaris carrying two Flg null alleles. However, the absence of FLG likely promotes and modulates dermatitis caused by other genetic barrier defects.

The Association Between Intestinal Bacteria and Allergic Diseases-Cause or Consequence?

The incidence of allergic disorders has been increasing over the past few decades, especially in industrialized countries. Allergies can affect people of any age. The pathogenesis of allergic diseases is complex and involves genetic, epigenetic, and environmental factors, and the response to medication is very variable. For some patients, avoidance is the sole effective therapy, and only when the triggers are identifiable. In recent years, the intestinal microbiota has emerged as a significant contributor to the development of allergic diseases. However, the precise mechanisms related to the effects of the microbiome on the pathogenesis of allergic diseases are unknown. This review summarizes the recent association between allergic disorders and intestinal bacterial dysbiosis, describes the function of gut microbes in allergic disease development from both preclinical and clinical studies, discusses the factors that influence gut microbial diversity and advanced techniques used in microbial analysis. Ultimately, more studies are required to define the host-microbial relationship relevant to allergic disorders and amenable to new therapeutic interventions.

Changes in Gut Microbiota Correlates with Response to Treatment with Probiotics in Patients with Atopic Dermatitis. A Post Hoc Analysis of a Clinical Trial

Atopic dermatitis (AD) is a chronic recurrent inflammatory skin disease with a high impact on the comfort of those who are affected and long-term treated with corticosteroids with limited efficacy and a high prevalence of relapses. Because of the limited effectiveness of these treatments, new strategies for recovery from AD lesions are continually being explored. In this article, we describe the gut microbiome changes achieved in a recently published clinical trial with the probiotic formulation Bifidobacterium animalis subsp. lactis CECT 8145, Bifidobacterium longum CECT 7347, and Lacticaseibacillus casei CECT 9104 (formerly Lactobacillus casei CECT 9104), showing a significant improvement in SCORAD (scoring atopic dermatitis) index in children (4-17 years) with AD (Clinicaltrials.gov identifier: NCT02585986). The present gut microbiome post hoc study showed no significant changes in diversity (Shannon and Simpson indexes) after probiotic consumption. In the probiotic group, genera Bacteroides, Ruminococcus, and Bifidobacterium significantly increased their levels while Faecalibacterium decreased, compared to the placebo group. Faecalibacterium showed the highest presence and significant positive correlation with AD severity (SCORAD index), whereas Abyssivirga, Bifidobacterium, and Lactococcus were inversely correlated. The results suggest that the consumption of the probiotic formulation here assayed modulates the gut microbiome with significant changes in genera Bacteroides and Faecalibacterium. In turn, the improvement in SCORAD correlates with a decrease in Faecalibacterium and an increase in Bifidobacterium, among others.

Impact of solar ultraviolet radiation on daily outpatient visits of atopic dermatitis in Shanghai, China

The potential roles of solar ultraviolet radiation (UVR) as an environmental risk factor in inducing atopic dermatitis (AD) have not been well quantified. To determine the short-term associations between UVR and AD outpatient visits, we obtained daily outpatient visits of AD in Shanghai Skin Disease Hospital from 2013 to 2018. Data of hourly ground UVR were collected. We applied overdispersed generalized additive model to explore its associations. We found that daily exposure to UVR-A rather than UVR-B was positively associated with AD outpatient visits. The visits increased on the present day (lag 0 days) and decreased appreciably with longer lags and became insignificant at lag 4 days. For 10 w/m² increase in daytime mean and noontime mean exposure to overall UVR and UVR-A from lag 0 to 6 days, the cumulative relative risk of AD was 1.12/1.13 and 1.08/1.08, respectively. Stronger effects of UVR exposure on AD occurred in patients aged 0-7 and > 45 years and in the cold seasons. This study contributed to the few epidemiological evidences that acute exposure to solar UVR may elevate the risks of AD.

Early intervention of atopic dermatitis as a preventive strategy for progression of food allergy

Background

Atopic diseases, such as atopic dermatitis (AD) and food allergy (FA), have increased in prevalence in industrialized countries during the past few decades and pose a significant health burden. They appear to have a common underlying mechanism and a natural disease progression. AD is generally the first atopic disease to manifest followed by other atopic diseases, such as FA, allergic rhinitis, or allergic asthma suggesting that they are likely different manifestations of the same disease.

Body

Evidence suggests that allergic sensitization occurs through an impaired skin barrier, while consumption of these foods at an early age may actually result in tolerance. This has been termed the Dual-Allergen-Exposure hypothesis. Loss of barrier integrity has been hypothesized to enable penetration of allergens, pollutants, and microbes and initiation of an inflammatory immune cascade of events leading to sensitization. The immune dysfunction is thought to further exacerbate the impaired skin barrier to form a vicious cycle. There is much interest in preventing or protecting the skin barrier from developing a proinflammatory atopic state, which may potentially lead to the development of AD and subsequently, FA.

Conclusion

Research on preventing or treating skin barrier dysfunction is ongoing. A number of studies have evaluated the efficacy of emollients in preventing AD and FA with mixed results. Studies have differed in the study design, population characteristics, emollients type, and frequency, duration, and area of application. Emollient type has varied widely from oils, creams, petrolatum-based lotions, and trilipid creams. Current research is directed towards the use of trilipid emollients that are similar to the skin’s natural lipid composition with a 3:1:1 ratio of ceramides, cholesterol and free fatty acids and a pH that is similar to that of skin to determine their effectiveness for skin barrier repair and prevention of AD and FA.

Particulate matter causes skin barrier dysfunction

The molecular mechanisms that underlie the detrimental effects of particulate matter (PM) on skin barrier function are poorly understood. In this study, the effects of PM_2.5 on filaggrin (FLG) and skin barrier function were investigated in vitro and in vivo. The levels of FLG degradation products, including pyrrolidone carboxylic acid, urocanic acid (UCA), and cis/trans-UCA, were significantly decreased in skin tape stripping samples of study subjects when they moved from Denver, an area with low PM_2.5, to Seoul, an area with high PM_2.5 count. Experimentally, PM_2.5 collected in Seoul inhibited FLG, loricrin, keratin-1, desmocollin-1, and corneodesmosin but did not modulate involucrin or claudin-1 in keratinocyte cultures. Moreover, FLG protein expression was inhibited in human skin equivalents and murine skin treated with PM_2.5. We demonstrate that this process was mediated by PM_2.5-induced TNF-α and was aryl hydrocarbon receptor dependent. PM_2.5 exposure compromised skin barrier function, resulting in increased transepidermal water loss, and enhanced the penetration of FITC-dextran in organotypic and mouse skin. PM_2.5-induced TNF-α caused FLG deficiency in the skin and subsequently induced skin barrier dysfunction. Compromised skin barrier due to PM_2.5 exposure may contribute to the development and the exacerbation of allergic diseases such as atopic dermatitis.

Sequestosome 1/p62 enhances chronic skin inflammation

BACKGROUND

The molecular control of inflammation and epidermal thickening in skin lesions of patients with atopic dermatitis (AD) is not known. Sequestosome 1/p62 is a multifunctional adapter protein implicated in the control of key regulators of cellular homeostasis, such as proinflammatory and mechanistic target of rapamycin signaling.

OBJECTIVE

We sought to determine whether p62 plays a role in the cutaneous and systemic manifestations of an AD-like mouse model.

METHODS

AD-like skin lesions were induced by deletion of JunB/AP-1, specifically in epidermal keratinocytes (JunB^Δep). The contribution of p62 to pathological changes was determined by inactivation of p62 in JunB^Δepp62^-/- double knockout mice.

RESULTS

Expression of p62 was elevated in skin lesions of JunB^Δep mice, resembling upregulation of p62 in AD and psoriasis. When p62 was inactivated, JunB^Δep-associated defects in the differentiation of keratinocytes, epidermal thickening, skin infiltration by mast cells and neutrophils, and the development of macroscopic skin lesions were significantly reduced. p62 inactivation had little effect on circulating cytokines, but decreased serum IgE. Signaling through mechanistic target of rapamycin and natural factor kappa B was increased in JunB^Δep but not in JunB^Δepp62^-/- double knockout skin, indicating an important role of p62 in enhancing these signaling pathways in the skin during AD-like inflammation.

CONCLUSIONS

Our results provide the first in vivo evidence for a proinflammatory role of p62 in skin and suggest that p62-dependent signaling pathways may be promising therapeutic targets to ameliorate the skin manifestations of AD and possibly psoriasis.

Atopic dermatitis: new insight into the etiology, pathogenesis, diagnosis and novel treatment strategies

Atopic dermatitis (AD) is the long-lasting chronic inflammatory skin condition associated with cutaneous hyper-reactivity and triggered by environmental factors. The attributes of AD include dry skin, pruritus, lichenification and frequent eczematous abrasions. This has a strong heritable aspect and typically occurs with asthma and allergic rhinitis. The complex pathological mechanism behind AD etiology is epidermal barrier destruction resulting in the lack of filaggrin protein that can induce inflammation and T-cell infiltration. T-helper 2 cell-mediated pathways also bear the responsibility of damage to the epidermal barrier. Certain causative factors for AD include microbial imbalance of skin microbiota, immunoglobulin-E-induced sensitization and neuro-inflammation. Numerous beneficial topical and oral treatments have been available to patients and there are even more drugs in the pipeline for the treatment of AD. Topical moisturizers, corticosteroids, anti-inflammatory agents such as calcineurin inhibitors, phototherapy, cAMP-specific 3, 5 half-cyclic phosphodiesterase 4 inhibitors and systemic immunosuppressants are widely available for AD treatments. Different positions and pathways inside the immune system including JAK-STAT, phosphodiesterase 4, aryl hydrocarbon receptor and T-helper 2 cytokines are targeted by above-mentioned drug treatments. Instead of the severe side effects of topical steroids and oral antihistamines, herbal plants and their derived phytoconstituents are commonly used for the treatment of AD. A clear understanding of AD's cellular and molecular pathogenesis through substantial advancement in genetics, skin immunology and psychological factors resulted in advancement of AD management. Therefore, the review highlights the recent advancements in the understanding of clinical features, etiology, pathogenesis, treatment and management and non-adherence to AD treatment.

Diet and Skin Barrier: The Role of Dietary Interventions on Skin Barrier Function

Multiple research studies have examined the role of specific dietary interventions and their effects on skin barrier function. The skin barrier is one of the body's first lines of protection against environmental insults, and disruption of this natural line of defense can result in xerosis, irritation, chronic dermatitis, and other cutaneous effects. Multiple laboratory, animal, and human studies have demonstrated that certain dietary interventions have the potential to impact skin barrier function. Measurements of skin barrier function include stratum corneum hydration and transepidermal water loss. In this review, we examine this research and provide an overview of the effects of prebiotics, probiotics, fatty acids, and emerging research on other substances.

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.

Cutaneous barrier dysfunction in allergic diseases

The fundamental defect(s) that drives atopic dermatitis (AD) remains controversial. "Outside in" proponents point to the important association of filaggrin gene mutations and other skin barrier defects with AD. The "inside out" proponents derive support from evidence that AD occurs in genetic animal models with overexpression of type 2 immune pathways in their skin, and humans with gain-of-function mutations in their type 2 response develop severe AD. The observation that therapeutic biologics, targeting type 2 immune responses, can reverse AD provides compelling support for the importance of "inside out" mechanisms of AD. In this review, we propose a central role for epithelial cell dysfunction that accounts for the dual role of skin barrier defects and immune pathway activation in AD. The complexity of AD has its roots in the dysfunction of the epithelial barrier that allows the penetration of allergens, irritants, and microbes into a cutaneous milieu that facilitates the induction of type 2 immune responses. The AD phenotypes and endotypes that result in chronic skin inflammation and barrier dysfunction are modified by genes, innate/adaptive immune responses, and different environmental factors that cause skin barrier dysfunction. There is also compelling evidence that skin barrier dysfunction can alter the course of childhood asthma, food allergy, and allergic rhinosinusitis. Effective management of AD requires a multipronged approach, not only restoring cutaneous barrier function, microbial flora, and immune homeostasis but also enhancing skin epithelial differentiation.