Distinct SPINK5 and IL-31 polymorphisms are associated with atopic eczema and non-atopic hand dermatitis in Taiwanese nursing population

Overview of Atopic Dermatitis in Different Ethnic Groups

Atopic dermatitis (AD) is a common chronic inflammatory skin disease with a high prevalence worldwide, including countries from Asia, Africa, and Latin America, and in different ethnic groups. In recent years, more attention has been placed on the heterogeneity of AD associated with multiple factors, including a patient's ethnic background, resulting in an increasing body of clinical, genetic, epidemiologic, and immune-phenotypic evidence that delineates differences in AD among racial groups. Filaggrin (FLG) mutations, the strongest genetic risk factor for the development of AD, are detected in up to 50% of European and 27% of Asian AD patients, but very rarely in Africans. Th2 hyperactivation is a common attribute of all ethnic groups, though the Asian endotype of AD is also characterized by an increased Th17-mediated signal, whereas African Americans show a strong Th2/Th22 signature and an absence of Th1/Th17 skewing. In addition, the ethnic heterogeneity of AD may hold important therapeutic implications as a patient's genetic predisposition may affect treatment response and, thereby, a tailored strategy that better targets the dominant immunologic pathways in each ethnic subgroup may be envisaged. Nevertheless, white patients with AD represent the largest ethnicity enrolled and tested in clinical trials and the most treated in a real-world setting, limiting investigations about safety and efficacy across different ethnicities. The purpose of this review is to describe the heterogeneity in the pathophysiology of AD across ethnicities and its potential therapeutic implications.

RELEVANCE OF CODING VARIATION IN FILAGGRIN AND DOCK8 IN FINNISH PEDIATRIC PATIENTS WITH EARLY-ONSET MODERATE-TO-SEVERE ATOPIC DERMATITIS

Early-onset, persistent atopic dermatitis (AD) is proposed as a distinct subgroup that may have specific genotypic features. FLG gene loss-of-function variants are the best known genetic factors contributing to epidermal barrier impairment and eczema severity. In a cohort of 140 Finnish children with early-onset moderate-to-severe AD, we investigated the effect of coding variation in FLG and 13 other genes with epidermal barrier or immune function through the use of targeted amplicon sequencing and genotyping. A FLG loss-of-function variant (Arg501Ter, Ser761fs, Arg2447Ter, or Ser3247Ter) was identified in 20 of 140 patients showing higher transepidermal water loss values than patients without these variants. Total FLG loss-of-function variant frequency (7.14%) was significantly higher than in the general Finnish population (2.34%). When tested separately, only Arg2447Ter showed a significant association with AD (P = 0.003104). In addition, a modest association with moderate-to-severe pediatric AD was seen for rs12730241 and rs6587667 (FLG2:Gly137Glu). Loss-of-function variants, previously reported pathogenic variants, or statistically significant enrichment of nonsynonymous coding region variants were not found in the 13 candidate genes studied by amplicon sequencing. However, higher IgE and eosinophil counts were found in carriers of potentially pathogenic DOCK8 missense variants, suggesting that the role of DOCK8 variation in AD should be further investigated in larger cohorts.

Genetic/Protein Association of Atopic Dermatitis and Tooth Agenesis

Atopic dermatitis and abnormalities in tooth development (including hypomineralization, hypodontia and microdontia) have been observed to co-occur in some patients. A common pathogenesis pathway that involves genes and protein interactions has been hypothesized. This review aims to first provide a description of the key gene mutations and signaling pathways associated with atopic dermatitis and tooth agenesis (i.e., the absence of teeth due to developmental failure) and identify the possible association between the two diseases. Second, utilizing a list of genes most commonly associated with the two diseases, we conducted a protein–protein network interaction analysis using the STRING database and identified a novel association between the Wnt/β-catenin signaling pathway (major pathway responsible for TA) and desmosomal proteins (component of skin barrier that affect the pathogenesis of AD). Further investigation into the mechanisms that may drive their co-occurrence and underlie the development of the two diseases is warranted.

Genetic/Environmental Contributions and Immune Dysregulation in Children with Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin conditions in humans. AD affects up to 20% of children worldwide and results in morbidity for both patients and their caregivers. The basis of AD is an interplay between genetics and the environment characterized by immune dysregulation. A myriad of mutations that compromise the skin barrier and/or immune function have been linked to AD. Of these, filaggrin gene (FLG) mutations are the most evidenced. Many other mutations have been implicated in isolated studies that are often unreplicated, creating an archive of genes with potential but unconfirmed relevance to AD. Harnessing big data, polygenic risk scores (PRSs) and genome-wide association studies (GWAS) may provide a more practical strategy for identifying the genetic signatures of AD. Epigenetics may also play a role. Staphylococcus aureus is the most evidenced microbial contributor to AD. Cutaneous dysbiosis may result in over-colonization by pathogenic strains and aberrant skin immunity and inflammation. Aeroallergens, air pollution, and climate are other key environmental contributors to AD. The right climate and/or commensals may improve AD for some patients.

Atopy as Immune Dysregulation: Offender Genes and Targets

Allergic diseases are a heterogeneous group of disorders resulting from exaggerated type 2 inflammation. Although typically viewed as polygenic multifactorial disorders caused by the interaction of several genes with the environment, we have come to appreciate that allergic diseases can also be caused by monogenic variants affecting the immune system and the skin epithelial barrier. Through a myriad of genetic association studies and high-throughput sequencing tools, many monogenic and polygenic culprits of allergic diseases have been described. Identifying the genetic causes of atopy has shaped our understanding of how these conditions occur and how they may be treated and even prevented. Precision diagnostic tools and therapies that address the specific molecular pathways implicated in allergic inflammation provide exciting opportunities to improve our care for patients across the field of allergy and immunology. Here, we highlight offender genes implicated in polygenic and monogenic allergic diseases and list targeted therapeutic approaches that address these disrupted pathways.

IL-31: State of the Art for an Inflammation-Oriented Interleukin

Interleukin 31 belongs to the IL-6 superfamily, and it is an itch mediator already studied in several diseases, comprising atopic dermatitis, allergic pathologies, and onco-hematological conditions. This research aims to assess the role of this cytokine in the pathogenesis of these conditions and its potential therapeutic role. The research has been conducted on articles, excluding reviews and meta-analysis, both on animals and humans. The results showed that IL-31 plays a crucial role in the pathogenesis of systemic skin manifestations, prognosis, and itch severity. Traditional therapies target this interleukin indirectly, but monoclonal antibodies (Mab) directed against it have shown efficacy and safety profiles comparable with biological drugs that are already available. Future perspectives could include the development of new antibodies against IL-31 both for humans and animals, thus adding a new approach to the therapy, which often has proven to be prolonged and specific for each patient.

Establishing subclasses of childhood eczema, their risk factors and prognosis

Background

The heterogeneity of development and progression of eczema suggests multiple underlying subclasses for which aetiology and prognosis may vary. A better understanding may provide a comprehensive overview of eczema development and progression in childhood. Thus, we aimed to determine longitudinal eczema subclasses based on assessments and identify their associations with risk factors and allergic outcomes.

Methods

A total of 619 participants with a family history of allergic disease were assessed at 24 time‐points from birth to 12 years. At each time, eczema was defined as the report of current rash treated with topical steroid‐based preparations. Longitudinal latent class analysis was used to determine eczema subclasses. Subsequent analyses using regression models assessed the associations between eczema subclasses and potential risk factors and allergic outcomes at 18‐ and 25‐year follow‐ups (eczema, allergic rhinitis, asthma and allergic sensitization).

Results

We identified five eczema subclasses ‘early‐onset persistent’, ‘early‐onset resolving’, ‘mid‐onset persistent’, ‘mid‐onset resolving’ and ‘minimal eczema’. Filaggrin null mutations were associated with the early‐onset persistent (OR = 2.58 [1.09–6.08]) and mid‐onset persistent class (OR = 2.58 [1.32–5.06]). Compared with ‘minimal eczema’, participants from early‐onset persistent class had higher odds of eczema (OR = 11.8 [5.20–26.6]) and allergic rhinitis (OR = 3.13 [1.43–6.85]) at 18 and at 25 years eczema (OR = 9.37 [3.17–27.65]), allergic rhinitis (OR = 3.26 [1.07–9.93]) and asthma (OR = 2.91 [1.14–7.43]). Likewise, mid‐onset persistent class had higher odds of eczema (OR = 2.59 [1.31–5.14]), allergic rhinitis (OR = 1.70 [1.00–2.89]) and asthma (OR = 2.00 [1.10–3.63]) at 18 and at 25 years eczema (OR = 6.75 [3.11–14–65]), allergic rhinitis (OR = 2.74 [1.28–5.88]) and asthma (OR = 2.50 [1.25–5.00]). Allergic and food sensitization in early life was more common in those in the persistent eczema subclasses.

Conclusion

We identified five distinct eczema subclasses. These classes were differentially associated with risk factors, suggesting differences in aetiology, and also with the development of allergic outcomes, highlighting their potential to identify high‐risk groups for close monitoring and intervention.

Genetic variants affecting chemical mediated skin immunotoxicity

The skin is an immune-competent organ and this function may be impaired by exposure to chemicals, which may ultimately result in immune-mediated dermal disorders. Interindividual variability to chemical-induced skin immune reactions is associated with intrinsic individual characteristics and their genomes. In the last 30-40 years, several genes influencing susceptibility to skin immune reactions were identified. The aim of this review is to provide information regarding common genetic variations affecting skin immunotoxicity. The polymorphisms selected for this review are related to xenobiotic-metabolizing enzymes (CYPA1 and CYPB1 genes), antioxidant defense (GSTM1, GSTT1, and GSTP1 genes), aryl hydrocarbon receptor signaling pathway (AHR and ARNT genes), skin barrier function transepidermal water loss (FLG, CASP14, and SPINK5 genes), inflammation (TNF, IL10, IL6, IL18, IL31, and TSLP genes), major histocompatibility complex (MHC) and neuroendocrine system peptides (CALCA, TRPV1, ACE genes). These genes present variants associated with skin immune responses and diseases, as well as variants associated with protecting skin immune homeostasis following chemical exposure. The molecular and association studies focusing on these genetic variants may elucidate their functional consequences and contribution in the susceptibility to skin immunotoxicity. Providing information on how genetic variations affect the skin immune system may reduce uncertainties in estimating chemical hazards/risks for human health in the future.

Significance of interleukin-31 (IL-31) gene polymorphisms and IL-31 serum level in psoriasis in correlation with pruritus

Introduction

Interleukin-31 (IL-31) impact on the development and clinical presentation of psoriasis as well as pruritus has not been widely investigated so far.

Aim

To analyse IL-31 -1066G/A and -2057G/A promoter gene polymorphisms as well as serum IL-31 level and their correlation with severity of psoriasis and pruritus in the population of northern Poland.

Material and methods

The study included 300 psoriasis patients and 186 healthy volunteers. The polymorphisms were analysed using amplified refractory mutation system - polymerase chain reaction (ARMS-PCR) method. Serum levels of IL-31 were measured using the enzyme-linked immunosorbent assay (ELISA) test.

Results

The -1066 AA genotype of the IL-31 gene was statistically more frequent in patients and it increased the risk of psoriasis (OR = 1.80; p = 0.04). The GG genotype as well as G allele of the IL-31 -2057 gene polymorphism were rarely observed in psoriasis and were associated with a decreased risk of the disease (OR = 0.6, p = 0.007 and OR = 0.7, p = 0.01, respectively). Serum levels of IL-31 were significantly elevated in psoriasis patients (p < 0.000001), however, they did not correlate with the studied polymorphic variants of the IL-31 gene, severity of psoriasis, disease onset, presence of psoriatic arthritis and pruritus intensity.

Conclusions

Distinct IL-31 promoter gene polymorphisms may be involved in psoriasis development. It seems that serum concentration of IL-31 may not be a reliable marker of psoriatic pruritus.

Vesicular hand eczema transcriptome analysis provides insights into its pathophysiology

Hand eczema is a common inflammatory skin condition of the hands whose pathogenesis is largely unknown. More insight and knowledge of the disease on a more fundamental level might lead to a better understanding of the biological processes involved, which could provide possible new treatment strategies. We aimed to profile the transcriptome of lesional palmar epidermal skin of patients suffering from vesicular hand eczema using RNA‐sequencing. RNA‐sequencing was performed to identify differentially expressed genes in lesional vs. non‐lesional palmar epidermal skin from a group of patients with vesicular hand eczema compared to healthy controls. Comprehensive real‐time quantitative PCR analyses and immunohistochemistry were used for validation of candidate genes and protein profiles for vesicular hand eczema. Overall, a significant and high expression of genes/proteins involved in keratinocyte host defense and inflammation was found in lesional skin. Furthermore, we detected several molecules, both up or downregulated in lesional skin, which are involved in epidermal differentiation. Immune signalling genes were found to be upregulated in lesional skin, albeit with relatively low expression levels. Non‐lesional patient skin showed no significant differences compared to healthy control skin. Lesional vesicular hand eczema skin shows a distinct expression profile compared to non‐lesional skin and healthy control skin. Notably, the overall results indicate a large overlap between vesicular hand eczema and earlier reported atopic dermatitis lesional transcriptome profiles, which suggests that treatments for atopic dermatitis could also be effective in (vesicular) hand eczema.

Epidemiology and Characterization of Atopic Dermatitis in East Asian Populations: A Systematic Review

Introduction

As atopic dermatitis (AD) grows increasingly prevalent in Asian populations worldwide, understanding how environmental, genetic, and cultural factors uniquely influence AD in Asians is essential for informing disease management. Our objectives were to characterize the epidemiology of AD in East Asian populations with sensitivity to the changing demographics of AD in these populations and the effects of urbanization and immigration.

Methods

A systematic review was performed on epidemiologic studies of AD in East Asian populations over the past 10 years.

Results

There is a rising prevalence of both pediatric and adult AD in Asian populations worldwide, particularly in Asians living in urban areas. Studies suggest that the children of Asian immigrants may be at higher risk for developing AD, potentially resulting from epigenetic phenomena unique to immigrant populations. A number of genetic polymorphisms implicated in AD are shared by Asian populations around the world and appear to be rare among other ethnic populations.

Conclusions

As the prevalence of AD continues to increase in Asian populations, it is important to understand its distinct genetic and pathophysiologic profile in these populations, as well as characterize the cultural beliefs and practices surrounding its treatment. Future research should aim to capitalize on our growing understanding of pathophysiologic differences to inform the most promising treatments for AD in Asians. Additionally, the impact of immigration on AD suggests that further investigation of these trends may lead to a greater understanding of the epigenetics of AD.

The ambiguous pruritogenic role of interleukin-31 in cutaneous T-cell lymphomas in comparison to atopic dermatitis: a review

Cutaneous T-cell lymphomas (CTCLs) comprise a group of chronic heterogeneous diseases of unknown pathogenesis, characterized by non-specific skin lesions such as patches, plaques and tumours. CTCL is accompanied by persistent pruritus poorly responding to antihistamines and therefore significantly reducing quality of life in patients with lymphomas. According to research data, interleukin-31 (IL-31) contributes to initiation and maintenance of the inflammatory process of the skin and pruritus in inflammatory dermatoses such as atopic dermatitis (AD), which is well established. The studies of a similar role of IL-31 in CTCLs are less homogenous. Due to contradictory reports concerning IL-31 and CTCL we have analysed available literature to summarize its role, focusing on CTCL and AD.

Exonic mutations associated with atopic dermatitis disrupt lympho-epithelial Kazal-type related inhibitor action and enhance its degradation

BACKGROUND

Skin desquamation is facilitated by serine proteases KLK5 and KLK7, which are tightly regulated by lympho-epithelial Kazal-type related inhibitor (LEKTI). LEKTI itself is controlled through degraded by mesotrypsin. Here, we sought to determine whether LEKTI exonic mutations associated with atopic dermatitis (AD) affect the protease inhibitory activity of LEKTI or its susceptibility to mesotrypsin degradation.

METHODS

The inhibitory activities of the LEKTI domain 4 (D4) and D6 WT and AD-associated mutants on the enzyme activities of KLK5 and KLK7 were compared using fluorogenic substrates. A keratinocyte cell culture system using HaCat cells was established to assess the role of D6 WT and D386N on triggering inflammation via the induction of thymic stromal lymphopoietin (TSLP). A degradation assay was used to assess the susceptibility of D4 and D6 mutants to mesotrypsin degradation.

RESULTS

Enzymatic assays revealed that the D6 D386N mutation affected the inhibitory activity of LEKTI on KLK5 but not KLK7. Other exonic mutations on D6 (N368S, V395M, and E420K) and D4 (R267Q) did not alter LEKTI inhibition. The D386N mutation disrupted the role of D6 in suppressing TSLP induction by KLK5 in HaCat cells. Although WT D4 is more susceptible to mesotrypsin degradation than WT D6, the D4 R267Q mutant was more resistant to mesotrypsin degradation, whereas the D6 E420K mutant showed enhanced mesotrypsin-mediated degradation.

CONCLUSION

Exonic mutations in D6, which previously have been associated with AD, may cause a disruption of inhibitory activity on KLK5 or enhance the degradation by mesotrypsin.

Childhood atopic dermatitis: current developments, treatment approaches, and future expectations

Atopic dermatitis (AD) is the most common chronic inflammatory skin disorder of childhood. Underlying factors that contribute to AD are impaired epithelial barrier, alterations in the lipid composition of the skin, immunological imbalance including increased Th2/Th1 ratio, proinflammatory cytokines, decreased T regulatory cells, genetic mutations, and epigenetic alterations. Atopic dermatitis is a multifactorial disease with a particularly complicated pathophysiology. Discoveries to date may be considered the tip of the iceberg, and the increasing number of studies in this field indicate that there are many points to be elucidated in AD pathophysiology. In this review, we aimed to illustrate the current understanding of the underlying pathogenic mechanisms in AD, to evaluate available treatment options with a focus on recently discovered therapeutic agents, and to determine the personal, familial, and economic burdens of the disease, which are frequently neglected issues in AD. Currently available therapies only provide transient solutions and cannot fully cure the disease. However, advances in the understanding of the pathogenic mechanisms of the disease have led to the production of new treatment options, while ongoing drug trials also have had promising results.

Racial differences in atopic dermatitis

OBJECTIVE

To summarize studies investigating ethnical and racial differences in atopic dermatitis (AD) epidemiology, clinical features, and skin and blood phenotypes.

DATA SOURCES

PubMed literature review (years 2000-2018).

STUDY SELECTIONS

Articles discussing primarily human disease.

RESULTS

Higher overall rates of AD were found in Africa and Oceania as opposed to India and Northern and Eastern Europe. In the United States, AD prevalence was found to be higher in African American (19.3%) compared with European American (16.1%) children. Although several studies have consistently found FLG loss-of-function mutations in up to 50% of European and 27% of Asian patients with AD, FLG mutations were 6 times less common in African American than in European American patients, even in patients with severe AD. Thus, FLG mutations seem to play less a pathogenic role in patients of African origin than in individuals of European or Asian ancestry. The immune phenotype of all ethnic groups was characterized by strong TH2 activation, but important differences in immune polarization exist among the different ethnicities. Asian patients with AD had stronger TH17/TH22 activation than African American and European American patients with AD, whereas African American patients had the highest serum IgE levels among all groups, while largely lacking TH1 and TH17 activation.

CONCLUSION

AD is a heterogeneous disease that has differences among various ethnic and racial groups, which might be important for the development of future, targeted treatments and for personalized medicine approaches.

Correlation of IL-31 gene polymorphisms with susceptibility and clinical recurrence of bladder cancer

Interleukin-31 is a crucial cytokine triggering inflammation which could be one of the risk factors of tumors. However, data for correlation between IL-31 and tumors are limited. The purpose of our study was to discuss whether genetic polymorphisms of IL-31 were associated with the susceptibility and clinical outcomes of bladder cancer. Our study enrolled 478 controls, 156 non-muscle-invasive bladder cancer (NMIBC) and 138 muscle-invasive bladder cancer (MIBC) patients. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used for genotyping two single nucleotide polymorphisms (SNPs) of IL-31 gene including rs7977932 and rs4758680. Our results showed that A allele and CA/AA genotypes of rs4758680 were associated with susceptibility to bladder cancer (P = 0.04, OR 1.32, 95% CI 1.01-1.72, and P = 0.02, OR 1.43, 95% CI 1.05-1.96, respectively), and G allele of rs7977932 might be a protect factor for tobacco smoking patients compared with non-smoking patients (P = 0.005, OR 0.42, 95% CI 0.23-0.76). Furthermore, CA/AA genotypes of rs4758680 might be the independent risk factors for the decreased recurrence-free survival of the patients with MIBC (P = 0.03, OR 2.02, 95% CI 1.06-3.85. Our data indicated that polymorphisms of IL-31 are associated with bladder cancer, and rs4758680 could be an independent prediction for MIBC patients with a high risk of recurrence.

Effects of a ceramide-containing water-in-oil ointment on skin barrier function and allergen penetration in an IL-31 treated 3D model of the disrupted skin barrier

Atopic dermatitis (AD) is a chronically relapsing, pruritic inflammation of the skin with dryness and disturbed skin barrier function. Recently, we established that IL-31 treatment of human 3D skin models resulted in a disrupted skin barrier phenotype resembling AD. In this model, we found that IL-31 interferes with the differentiation of keratinocytes and inhibits the expression of terminal differentiation markers. In the present study, we investigated the effects of a ceramide-containing water-in-oil skin care ointment on the physical skin barrier structure and function in disrupted skin barrier models, generated either by using primary normal human epidermal keratinocytes (NHEK) or HaCaT cells. We observed that the physical skin barrier of the models recovered after daily topical treatment with the ceramide-containing ointment. Topical application of the ointment prevented downregulation of filaggrin and disorganization of other differentiation markers, such as keratin 10 and β4-integrin, as demonstrated by immunohistological analysis. The expression of Ki67 was also upregulated in response to the ointment. Furthermore, functional studies revealed that local application of the ointment diminished the increased uptake of fluorescently labelled recombinant allergens of timothy grass (phl p1) in our model. In conclusion, our data revealed that topical application of a ceramide-containing skin care ointment reduced IL-31 induced impairments of the physical skin barrier and skin barrier function in an in vitro model of the disrupted skin barrier. This standardized model can be utilized in the future to monitor ex vivo effects of various topical therapies on skin morphology, physiology, and gene expression.

Genetic Association of Interleukin-31 Gene Polymorphisms with Epithelial Ovarian Cancer in Chinese Population

Roles of interleukin-31 (IL-31) in the development and progression of human epithelial ovarian cancer are largely unknown. Studies report that the polymorphisms, rs7977932 C>G and rs4758680 C>A in IL-31, affect the expression level of IL-31. In the present study, we examined 412 patients with epithelial ovarian cancer and 428 healthy individuals to explore whether these polymorphisms are associated with the epithelial ovarian cancer in Chinese women. The genotype of the polymorphisms in each individual was identified. The associations of the polymorphisms with patients' clinical characteristics and outcomes were evaluated. For rs7977932, the frequency of the CG/GG was significantly decreased in patients with epithelial ovarian cancer. However, the frequency of the rs4758680 CA/AA was significantly increased in those patients. Moreover, the frequency of rs7977932 CG/GG genotype was significantly higher in patients with less advanced FIGO stages. Kaplan-Meier curve showed that patients with CG/GG genotypes of rs7977932 had a decreased risk for recurrence compared to those with CC genotype. Our findings suggested that rs7977932 and rs4758680 of IL-31 may be associated with the development and progression of the epithelial ovarian cancer in the Chinese population. IL-31, therefore, may be a potential therapeutic target for the development of drugs to treat the disease.

IL-31: A new key player in dermatology and beyond

IL-31 is a novel cytokine expressed in many human tissues and involved mainly in T_H2-weighted inflammation. IL-31 signals through a receptor complex consisting of IL-31 receptor α and oncostatin M receptor β. The available data show that IL-31 is strongly linked with chronic pruritic skin disorders, such as atopic eczema, and represents a novel target for directed drug therapy. Regulation of immune responses and cellular differentiation and proliferation are recently elucidated effects of IL-31, suggesting a more complex and diverse area of effect for this novel cytokine. This review summarizes the current knowledge on IL-31 and its receptors and the involvement of IL-31 in diseases both in human subjects and mouse models.

Interleukin-31 pathway and its role in atopic dermatitis: a systematic review

BACKGROUND

Atopic dermatitis, a chronic inflammatory disease, has a lifetime prevalence of 10-20%. Atopic dermatitis reduces quality of life, primarily due to pruritus. Interleukin-31 and its target receptor are newly discovered entities that are involved in pruritus.

PURPOSE

To summarize the current understanding of interleukin-31 and its role in atopic dermatitis, potential therapeutic interventions and future prospects.

METHODS

A systematic review was designed to identify articles related to interleukin-31 and its role in pruritus. Predefined queries containing interleukin-31 and related key terms were searched with no past date restriction, through 31 August 2016, using MEDLINE, Cochrane Controlled Trials Register, ClinicalTrials.gov and the International Clinical Trials Registry Platform Search Portal database.

RESULTS

Of 151 identified articles, 61 met eligibility criteria. Interleukin-31 receptors are expressed constitutively on the surface of keratinocytes, eosinophils and small diameter neurons. Overexpression of interleukin-31, independent of mast cells and lymphocytes, induces clinical and histological features consistent with atopic dermatitis. In addition, overexpression of interleukin-31 causes reversible alopecia. Human monoclonal interleukin-31 antagonist, CIM331, decreased pruritus in phase-I and phase-II clinical trials.

CONCLUSIONS

Interleukin-31 plays an important role in atopic dermatitis and alopecia. Inhibiting this pathway may provide an alternative to antihistamines for the pruritus of atopic dermatitis.

The Genetics and Epigenetics of Atopic Dermatitis-Filaggrin and Other Polymorphisms

Atopic dermatitis (AD) is a chronic inflammatory skin disease caused by a combination of genetic and environmental factors. Genetic evidences depict a complex network comprising by epidermal barrier dysfunctions and dysregulation of innate and adaptive immunity in the pathogenesis of AD. Mutations in the human filaggrin gene (FLG) are the most significant and well-replicated genetic mutation associated with AD, and other mutations associated with epidermal barriers such as SPINK5, FLG-2, SPRR3, and CLDN1 have all been linked to AD. Gene variants may also contribute to the abnormal innate and adaptive responses found in AD, including mutations in PRRs and AMPs, TSLP and TSLPR, IL-1 family cytokines and receptors genes, vitamin D pathway genes, FCER1A, and Th2 and other cytokines genes. GWAS and Immunochip analysis have identified a total of 19 susceptibility loci for AD. Candidate genes at these susceptibility loci identified by GWAS and Immunochip analysis also suggest roles for epidermal barrier functions, innate and adaptive immunity, interleukin-1 family signaling, regulatory T cells, the vitamin D pathway, and the nerve growth factor pathway in the pathogenesis of AD. Increasing evidences show the modern lifestyle (i.e., the hygiene hypothesis, Western diet) and other environmental factors such as pollution and environmental tobacco smoke (ETS) lead to the increasing prevalence of AD with the development of industrialization. Epigenetic alterations in response to these environmental factors, including DNA methylation and microRNA related to immune system and skin barriers, have been found to contribute to the pathogenesis of AD. Genetic variants and epigenetic alteration might be the key tools for the molecular taxonomy of AD and provide the background for the personalized management.

Genetic and epigenetic studies of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory disease caused by the complex interaction of genetic, immune and environmental factors. There have many recent discoveries involving the genetic and epigenetic studies of AD.

METHODS

A retrospective PubMed search was carried out from June 2009 to June 2016 using the terms "atopic dermatitis", "association", "eczema", "gene", "polymorphism", "mutation", "variant", "genome wide association study", "microarray" "gene profiling", "RNA sequencing", "epigenetics" and "microRNA". A total of 132 publications in English were identified.

RESULTS

To elucidate the genetic factors for AD pathogenesis, candidate gene association studies, genome-wide association studies (GWAS) and transcriptomic profiling assays have been performed in this period. Epigenetic mechanisms for AD development, including genomic DNA modification and microRNA posttranscriptional regulation, have been explored. To date, candidate gene association studies indicate that filaggrin (FLG) null gene mutations are the most significant known risk factor for AD, and genes in the type 2 T helper lymphocyte (Th2) signaling pathways are the second replicated genetic risk factor for AD. GWAS studies identified 34 risk loci for AD, these loci also suggest that genes in immune responses and epidermal skin barrier functions are associated with AD. Additionally, gene profiling assays demonstrated AD is associated with decreased gene expression of epidermal differentiation complex genes and elevated Th2 and Th17 genes. Hypomethylation of TSLP and FCER1G in AD were reported; and miR-155, which target the immune suppressor CTLA-4, was found to be significantly over-expressed in infiltrating T cells in AD skin lesions.

CONCLUSIONS

The results suggest that two major biologic pathways are responsible for AD etiology: skin epithelial function and innate/adaptive immune responses. The dysfunctional epidermal barrier and immune responses reciprocally affect each other, and thereby drive development of AD.

Molecular Mechanisms of Cutaneous Inflammatory Disorder: Atopic Dermatitis

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease resulting from interactions between genetic susceptibility and environmental factors. The pathogenesis of AD is poorly understood, and the treatment of recalcitrant AD is still challenging. There is accumulating evidence for new gene polymorphisms related to the epidermal barrier function and innate and adaptive immunity in patients with AD. Newly-found T cells and dendritic cell subsets, cytokines, chemokines and signaling pathways have extended our understanding of the molecular pathomechanism underlying AD. Genetic changes caused by environmental factors have been shown to contribute to the pathogenesis of AD. We herein present a review of the genetics, epigenetics, barrier dysfunction and immunological abnormalities in AD with a focus on updated molecular biology.

Control of the Physical and Antimicrobial Skin Barrier by an IL-31-IL-1 Signaling Network

Atopic dermatitis, a chronic inflammatory skin disease with increasing prevalence, is closely associated with skin barrier defects. A cytokine related to disease severity and inhibition of keratinocyte differentiation is IL-31. To identify its molecular targets, IL-31-dependent gene expression was determined in three-dimensional organotypic skin models. IL-31-regulated genes are involved in the formation of an intact physical skin barrier. Many of these genes were poorly induced during differentiation as a consequence of IL-31 treatment, resulting in increased penetrability to allergens and irritants. Furthermore, studies employing cell-sorted skin equivalents in SCID/NOD mice demonstrated enhanced transepidermal water loss following s.c. administration of IL-31. We identified the IL-1 cytokine network as a downstream effector of IL-31 signaling. Anakinra, an IL-1R antagonist, blocked the IL-31 effects on skin differentiation. In addition to the effects on the physical barrier, IL-31 stimulated the expression of antimicrobial peptides, thereby inhibiting bacterial growth on the three-dimensional organotypic skin models. This was evident already at low doses of IL-31, insufficient to interfere with the physical barrier. Together, these findings demonstrate that IL-31 affects keratinocyte differentiation in multiple ways and that the IL-1 cytokine network is a major downstream effector of IL-31 signaling in deregulating the physical skin barrier. Moreover, by interfering with IL-31, a currently evaluated drug target, we will have to consider that low doses of IL-31 promote the antimicrobial barrier, and thus a complete inhibition of IL-31 signaling may be undesirable.

Interleukin-4 Downregulation of Involucrin Expression in Human Epidermal Keratinocytes Involves Stat6 Sequestration of the Coactivator CREB-Binding Protein

Skin barrier defects play an important role in atopic dermatitis (AD). Involucrin, an important barrier protein suppressed in human AD, is downregulated by interleukin-4 (IL-4). However, the molecular mechanism for IL-4 downregulation of involucrin has not been delineated, and especially how Stat6, a transcriptional activator, represses involucrin expression is unknown. Since Stats usually recruit p300/CBP in the general transcription machinery of their target genes and involucrin expression also involves p300/CBP, we hypothesize that Stat6 activated by IL-4 may sequestrate p300/CBP from the involucrin transcription complex, thus suppressing involucrin expression in keratinocytes. Using IL-4 transgenic mice, an AD mouse model, we find that involucrin expression is similarly downregulated as in human AD. In HaCat cells, the Jak inhibitor and dominant negative studies indicate that the Jaks-Stat6 pathway is involved in IL-4 downregulation of involucrin. Next, we transfected HaCat cells with an involucrin promoter-luciferase construct and then treated them with IL-4. IL-4 greatly suppresses the promoter activity, which is totally abolished by cotransfecting the CREB-binding protein (CBP) expression vector, indicating that IL-4 cannot downregulate involucrin in the presence of excess CBP. Finally, chromatin immunoprecipitation assay demonstrates that IL-4 decreases CBP binding to the involucrin transcription complex. For the first time, we defined a molecular mechanism for IL-4 downregulation of involucrin in keratinocytes, which may play an important role in the pathogenesis of AD.

The association of interleukin-31 polymorphisms with interleukin-31 serum levels and risk of systemic lupus erythematosus

Interleukin-31 (IL-31) is the most recently discovered member of the gp130/IL-6 cytokine family which is produced mainly by activated Th2 cells. IL-31 was proved to play a crucial role in autoimmune and inflammatory diseases such as atopic dermatitis, asthma, cutaneous T cell lymphomas, Kawasaki disease and allergic rhinitis. Previous studies have identified that IL-31 could significantly induce the release of proinflammatory cytokines IL-6. Moreover, a large number of studies have shown that IL-6 plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). However, up to date, no study to data was reported on the relationship between IL-31 and SLE. Therefore, in the present study, we investigated the association between IL-31 polymorphisms and its serum levels with the risk of SLE in a Chinese population. We analyzed two single nucleotide polymorphisms of IL-31 gene rs7977932 C/G and rs4758680 G/T in 190 patients with SLE and 250 age- and sex-matched controls, using polymerase chain reaction-single base extension and DNA sequencing methods. Soluble IL-31 (sIL-31) levels were measured by ELISA. From this study, we found that there were significant differences in the genotype and allele frequencies of IL-31 gene rs7977932 C/G polymorphism between the group of patients with SLE and the control group (P < 0.05). sIL-31 levels were increased in patients with SLE compared with controls (P < 0.01). Moreover, genotypes carrying the IL-31 rs7977932 G variant allele were associated with increased IL-31 levels compared to the homozygous wild-type genotype in patients with SLE. The rs7977932 C/G polymorphism of IL-31 gene and its sIL-31 levels were associated with SLE in the Chinese population. Our data suggest that IL-31 gene may play a role in the development of SLE.

The frequencies of haplotypes defined by three polymorphisms of the IL-31 gene: -1066, -2057, and IVS2+12 in Polish patients with atopic dermatitis

BACKGROUND

Severe pruritus is one of the cardinal symptoms of atopic dermatitis (AD). Recently, the interleukin (IL)-31 cytokine has been implicated in the induction and maintenance of severe pruritus and chronic skin inflammation in several pruritic skin diseases, including AD.

OBJECTIVE

We aimed to investigate the association of the IL-31 gene haplotypes with pruritus and severity of AD, as well as their correlation to the serum IL-31 levels.

METHODS

A total of 127 patients with AD and 96 healthy controls were analyzed for polymorphic variants of the IL-31 gene using an amplification refractory mutation system-polymerase chain reaction method. IL-31 haplotype frequencies were estimated with the use of tagging single nucleotide polymorphisms, expectation-maximization, and Excoffier-Laval-Balding algorithms. Serum IL-31 levels were measured using a standard enzyme-linked immunosorbent assay kit.

RESULTS

The frequency of AAG, AGA, AGG, and GAA haplotypes of the IL-31 gene was higher in patients with AD than in controls. The mean IL-31 levels in serum were lower in controls than in the patients (P < 0.00001) and were higher in those with severe vs. mild AD (P = 0.008). No correlation was found between IL-31 and the severity of pruritus. The haplotype AAA was associated with a high IL-31 serum level (P = 0.008) and with severe AD (high SCORing Atopic Dermatitis index) (P = 0.013). The haplotype GAA was associated with a severe form of pruritus (P = 0.016) and the haplotype GGG with the mild one (P = 0.07).

CONCLUSION

The results of this study suggest that the severity of AD in a Polish population is associated with some specific haplotypes of the IL-31 gene, which can indicate their prognostic role also renews the questions concerning the role of IL-31 in pruritus in AD.

The hand eczema proteome: imbalance of epidermal barrier proteins

BACKGROUND

Chronic hand eczema (CHE) is a common skin disease with a high socioeconomic impact. While some light has been shed on the genetic factors that predispose individuals to the disease, little is known about its actual pathogenesis.

OBJECTIVES

We aimed to carry out a systematic and comprehensive analysis of the differential protein expression in CHE using modern mass spectrometry.

METHODS

We performed liquid chromatography with tandem mass spectrometry analyses and label-free quantification to analyse the proteomic profile of palmar skin from 12 individuals (six patients with hand eczema and six healthy volunteers). Immunohistochemistry of the palmar skin from seven different patients with hand eczema and seven different healthy volunteers was performed in a second step.

RESULTS

With this method we were able to identify 185 candidate proteins with a significantly different abundance in the hand eczema samples. Among them we found several barrier proteins: filaggrin (FLG), FLG-2 and hornerin were all downregulated in the hand eczema samples, as were the desquamation-related enzymes kallikrein-related peptidase (KLK)5 and KLK7 and cystatin E/M. The antimicrobial peptides S100A7 and S100A8/A9 and the small proline-rich protein 2B and S100A11 were upregulated in the diseased skin. Immunohistochemistry confirmed these findings.

CONCLUSIONS

Our results corroborate the assumption that skin barrier dysfunction plays an essential role in the pathogenesis of CHE.

Use of traditional Chinese medicine reduces exposure to corticosteroid among atopic dermatitis children: a 1-year follow-up cohort study

ETHNOPHARMACOLOGICAL RELEVANCE

Atopic dermatitis is a prevalent dermatologic disease in children. Corticosteroid is an important treatment but side effects caused by long-term and excessive use heavily concern patients. Traditional Chinese medicine (TCM) is potentially an alternative treatment and might cause less adverse effects. This nationwide retrospective cohort study aimed to examine the hypothesis that TCM use is associated with lower exposure to corticosteroid.

MATERIALS AND METHODS

Children under 12 years of age with ICD-9 codes 691.8 and 692.x were identified as atopic dermatitis patients from 2007/1/1 to 2007/12/31. Corticosteroid use was compared between TCM users and non-users for one-year follow-up by using a general estimation equation model with propensity-score matching.

RESULTS

A total of 9012 TCM users were identified and the use of corticosteroid after treatment was compared with matched TCM non-users. Use of TCM significantly reduced exposure to corticosteroids after 1-year follow-up. Among TCM users, the exposure to any corticosteroids was lower (42.1% reduction in TCM users versus 34.5% increase in TCM non-users, relative risk: 0.36; p-Value<0.001), the duration was shorter (relative risk for using corticosteroid more than 14 days: 0.37; p-Value<0.001), and the rate of frequent visits with steroid prescription was also lower. CHM was the most commonly used TCM modality (98.5% of all visits) and Xiao-Feng-San was the most commonly used CHM (33% of all prescriptions) with extensive coverage for pathogenesis of atopic dermatitis.

CONCLUSIONS

Lower use rate of corticosteroid can be found after TCM treatment, which can be considered as an integrative therapy for atopic dermatitis. Further studies are warranted on the basis of this study.

Molecular biology of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with specific genetic and immunological mechanisms. The rapid development of new techniques in molecular biology had ushered in new discoveries on the role of cytokines, chemokines, and immune cells in the pathogenesis of AD. New polymorphisms of AD are continually being reported in different populations. The physical and immunological barrier of normal intact skin is an important part of the innate immune system that protects the host against microbials and allergens that are associated with AD. Defects in the filaggrin gene FLG may play a role in facilitating exposure to allergens and microbial pathogens, which may induce Th2 polarization. Meanwhile, Th22 cells also play roles in skin barrier impairment through IL-22, and AD is often considered to be a Th2/Th22-dominant allergic disease. Mast cells and eosinophils are also involved in the inflammation via Th2 cytokines. Release of pruritogenic substances by mast cells induces scratching that further disrupts the skin barrier. Th1 and Th17 cells are mainly involved in chronic phase of AD. Keratinocytes also produce proinflammatory cytokines such as thymic stromal lymphopoietin (TSLP), which can further affect Th cells balance. The immunological characteristics of AD may differ for various endotypes and phenotypes. Due to the heterogeneity of the disease, and the redundancies of these mechanisms, our knowledge of the pathophysiology of the disease is still incomplete, which is reflected by the absence of a cure for the disease.

Interleukin-31: a novel diagnostic marker of allergic diseases

Interleukin-31 (IL-31) is a newly discovered cytokine associated with chronic skin inflammation and pruritus. Patients with atopic dermatitis, chronic spontaneous urticaria, allergic contact dermatitis, prurigo nodularis, primary cutaneous lymphoma and mastocytosis exhibit increased serum levels of IL-31 protein and elevated IL-31 mRNA in the skin. Interestingly, in some of these diseases, IL-31 serum levels correlate with disease activity. In the present review, we particularly focus on studies investigating IL-31 as a novel diagnostic biomarker indicating the severity of allergic diseases. We highlight a recent study on IL-31 in mastocytosis, which reports on elevated serum levels of IL-31 in adults correlating with the severity of disease categories, tryptase levels and percentage of bone marrow infiltration. We conclude that growing knowledge about IL-31, its receptors and signaling pathways serves to better understand the pathogenesis of allergic diseases and may lead to the development of novel treatment approaches.

Association between non-atopic hand eczema and interleukin-13 gene polymorphism in Taiwanese nursing population

Chronic hand eczema is an important occupational skin disease with atopic dermatitis (AD) and wet work being the most important risk factors. This study was launched to analyse the potential association between AD-related inflammation genes and development of non-atopic hand eczema among nurses in University Hospital. Atopic eczema, non-atopic hand dermatitis and control groups were identified. The association between occurrence of non-atopic hand eczema and interleukin (IL)-13, IL-4 and IL-5 gene variants was analysed. IL13 rs20541 A allele [assuming recessive model; odds ratio (OR) = 3.38, 95% CI: (1.63-7.00)] showed association with development of non-atopic hand eczema. Additive score analyses showed combination of this gene variant with previously identified risk factors including certain SPINK5 polymorphism and more than 10 years of work experience conferred highest risk for development of non-atopic hand eczema. As non-atopic hand eczema made up significant portion of occupational skin diseases, further studies should be focused on this commonly encountered skin condition.