A major susceptibility locus for atopic dermatitis maps to chromosome 3q21

Multi-Omics Approach to Improved Diagnosis and Treatment of Atopic Dermatitis and Psoriasis

Psoriasis and atopic dermatitis fall within the category of cutaneous immune-mediated inflammatory diseases (IMIDs). The prevalence of IMIDs is increasing in industrialized societies, influenced by both environmental changes and a genetic predisposition. However, the exact immune factors driving these chronic, progressive diseases are not fully understood. By using multi-omics techniques in cutaneous IMIDs, it is expected to advance the understanding of skin biology, uncover the underlying mechanisms of skin conditions, and potentially devise precise and personalized approaches to diagnosis and treatment. We provide a narrative review of the current knowledge in genomics, epigenomics, and proteomics of atopic dermatitis and psoriasis. A literature search was performed for articles published until 30 November 2023. Although there is still much to uncover, recent evidence has already provided valuable insights, such as proteomic profiles that permit differentiating psoriasis from mycosis fungoides and β-defensin 2 correlation to PASI and its drop due to secukinumab first injection, among others.

Toward Precision Medicine in Atopic Dermatitis Using Molecular-Based Approaches

Atopic dermatitis is the most common chronic inflammatory skin disorder, affecting up to 20% of children and 10% of adults in developed countries. The pathophysiology of atopic dermatitis is complex and involves a strong genetic predisposition and T-cell driven inflammation. Although our understanding of the pathology and drivers of this disease has improved in recent years, there are still knowledge gaps in the immune pathways involved. Therefore, advances in new omics technologies in atopic dermatitis will play a key role in understanding the pathogenesis of this burden disease and could develop preventive strategies and personalized treatment strategies. In this review, we discuss the latest developments in genetics, transcriptomics, epigenomics, proteomics, and metagenomics and understand how integrating multiple omics datasets will identify potential biomarkers and uncover nets of associations between several molecular levels.

Toward Precision Medicine in Atopic Dermatitis Using Molecular-Based Approaches

Atopic dermatitis is the most common chronic inflammatory skin disorder, affecting up to 20% of children and 10% of adults in developed countries. The pathophysiology of atopic dermatitis is complex and involves a strong genetic predisposition and T-cell driven inflammation. Although our understanding of the pathology and drivers of this disease has improved in recent years, there are still knowledge gaps in the immune pathways involved. Therefore, advances in new omics technologies in atopic dermatitis will play a key role in understanding the pathogenesis of this burden disease and could develop preventive strategies and personalized treatment strategies. In this review, we discuss the latest developments in genetics, transcriptomics, epigenomics, proteomics, and metagenomics and understand how integrating multiple omics datasets will identify potential biomarkers and uncover nets of associations between several molecular levels.

The Associations of Single Nucleotide Polymorphisms of the COL3A1, COL6A5, and COL8A1 Genes with Atopic Dermatitis

The pathophysiology of atopic dermatitis (AD) is complex, multifactorial, and not fully understood. Genes encoding collagens, the most abundant proteins in the extracellular matrix (ECM), may play a potential role in the pathogenesis of AD. Our study aimed to estimate the associations between Col3A1/rs1800255, Col6A5 /29rs12488457, and Col8A1/rs13081855 polymorphisms and the occurrence, course, and features of AD in the Polish population. Blood samples were collected from 157 patients with AD and 111 healthy volunteers. The genotype distribution of the investigated collagens genes did not differ significantly between the AD and control subjects (p > 0.05). The AA genotype of Col3A1/rs1800255 was significantly associated with the occurrence of mild SCORAD (OR = 0.16; 95% Cl: 0.03-0.78; p = 0.02) and mild pruritus (OR = 18.5; 95% Cl: 3.48-98.40; p = 0.0006), while the GG genotype was significantly associated with severe SCORAD (OR = 6.6; 95% Cl: 1.23-32.35; p = 0.03). Regarding Col6A5/29rs12488457 polymorphism, the average SCORAD score was significantly lower in the group of patients with genotype AA than in patients with the AC genotype (39.8 vs. 53.4; p = 0.04). Nevertheless, both average SCORAD scores were high, and represent the moderate and severe grades of the diseases, respectively. The single nucleotide polymorphisms (SNPs) of COL3A1/ rs1800255 and Col6A5/29rs12488457 seem to be associated with AD courses and symptoms, suggesting new disease biomarkers. The modulation of collagens, the major component of the ECM, may serve as a therapeutic target of AD in the future.

[Immune system and allergies-An unholy alliance]

Various factors affect the maturation of the infantile immune system both prenatally and postnatally, including risk and protective factors from the environment, nutrition, genetics and epigenetics. The microbiome seems to play a substantial role. The complex interaction and regulation of all these factors is ultimately decisive for whether a child develops an allergy during the course of development of the immune system. The genetic components play a decisive role in the development of allergic diseases. The epigenetic regulation could represent a mechanism where environmental influences act upon the immune regulation in the emergence of allergic diseases. The main factors in the pathophysiology of allergic reactions are a dysregulation of various cells of the innate and acquired immune systems as well as their interaction. This review describes the role of various T helper cell types in allergic diseases. The incidence and duration of airway infections are clearly increased in allergic patients compared to nonallergic controls. In addition to functional aspects, the reason for the more frequent infections is an impairment of the immune defence by the allergy-related persisting inflammation of the mucous membranes. These mechanisms must be differentiated from a true immunodeficiency. Allergic rhinitis (AR) and bronchial asthma are nowadays no longer defined as separate diseases but as two forms of expression of an atopic entity with a similar pathology. Both diseases can be mediated by immunoglobulin E and be elicited by identical triggers. A bronchial hyperreactivity is detectable in the majority of patients with AR but without clinical asthma.

The Role of Collagen VI α6 Chain Gene in Atopic Dermatitis

Background

Objective

Methods

Results

Conclusion

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.

Rhinitis prevalence and association with atopic dermatitis: A systematic review and meta-analysis

BACKGROUND

Atopic dermatitis (AD) and rhinitis are common atopic diseases that may co-occur owing to an overlap in pathophysiology. Although most cases of both diseases are mild and managed with topical anti-inflammatory medicaments, the advent of new systemic and biologic treatments targeting type 2 inflammation in both diseases warrants further insight in the exact overlap of AD and rhinitis.

OBJECTIVE

To determine the association between AD and rhinitis.

METHODS

A systematic review and meta-analysis of the databases PubMed, Embase, and CNKI were performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Pooled prevalence and pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated.

RESULTS

The search resulted in 10,422 citations, and 341 and 302 articles were included in the qualitative and quantitative analyses, respectively. The pooled prevalence of rhinitis was 40.5% (95% CI 39.0-42.0) in patients with AD and 18.0% (95% CI 16.7-19.2) in the reference individuals without AD. The pooled prevalence of having both rhinitis and asthma was 14.2% (95% CI 13.0-15.5) in patients with AD. There was an association between AD and rhinitis (OR 3.00, 95% CI 2.83-3.18), allergic rhinitis (OR 3.25, 95% CI 2.26-4.66), and nonallergic rhinitis (OR 1.99, 95% CI 1.39-2.86), respectively.

CONCLUSION

Rhinitis, both allergic and nonallergic forms, is very common in patients with AD. Future investigations should clarify how medications targeting both diseases should be indicated in these patients.

Pathophysiology and Management of Atopic Dermatitis: A Laconic Review

Conclusion:

Atopic Dermatitis (AD) is long-lasting degenerating skin disease with a characteristic phenotype and stereotypically spread skin lesions. The AD results due to a complex interface among genetic factors, host’s surroundings, pharmacological anomalies and immunological factors. In previous decades, researchers had shown marked interest due to increased prevalence in developed countries. In this review, basics along with the advances in pathogenesis and management of AD have been discussed. The immunological factors i.e. Innate Lymphoid Cells, IL-22 and Toll-like receptors have an important role in the pathogenesis. The proactive topical therapy by skincare, topical glucocorticosteroids and calcineurin inhibitors have improved effect in the management of AD. The human monoclonal antibody-based systemic drug (Duplimab) is a considerable advancement in the management of AD. Other monoclonal antibody-based drugs (Lebrikizumab, Tralokinumab, Apremilast and Nemolizumab) are in different phases of clinical trials. A better understanding of genetics and immunoregulatory cascade will lead to the development of efficacious drugs and better management therapy preventing the relapse of flares and improved life quality of AD patients.

Genetic and Epigenetic Aspects of Atopic Dermatitis

Atopic dermatitis is a heterogeneous disease, in which the pathogenesis is associated with mutations in genes encoding epidermal structural proteins, barrier enzymes, and their inhibitors; the role of genes regulating innate and adaptive immune responses and environmental factors inducing the disease is also noted. Recent studies point to the key role of epigenetic changes in the development of the disease. Epigenetic modifications are mainly mediated by DNA methylation, histone acetylation, and the action of specific non-coding RNAs. It has been documented that the profile of epigenetic changes in patients with atopic dermatitis (AD) differs from that observed in healthy people. This applies to the genes affecting the regulation of immune response and inflammatory processes, e.g., both affecting Th1 bias and promoting Th2 responses and the genes of innate immunity, as well as those encoding the structural proteins of the epidermis. Understanding of the epigenetic alterations is therefore pivotal to both create new molecular classifications of atopic dermatitis and to enable the development of personalized treatment strategies.

How does parental history of atopic disease predict the risk of atopic dermatitis in a child? A systematic review and meta-analysis

BACKGROUND

Parental history of atopic disease is a well-established risk factor for the development of atopic dermatitis (AD), but several aspects of this association remain unclear.

OBJECTIVE

We sought to determine the association of parental history of atopic disease with AD in offspring.

METHODS

We searched PubMed and EMBASE through June 2018 for relevant records and adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Pooled odds ratios (ORs) with 95% CI were calculated using random-effects models.

RESULTS

A total of 163 records covering 149 unique studies were included. Of these, 119 studies were included in the meta-analysis. Individuals with parental history of atopic disease had increased odds of AD (OR, 1.81; 95% CI, 1.65-1.99). Parental asthma (OR, 1.56; 95% CI, 1.18-2.05) and allergic rhinitis (OR, 1.68; 95% CI, 1.34-2.11) had a smaller effect than AD (OR, 3.30; 95% CI, 2.46-4.42). The effect of maternal and paternal history was comparable for all atopic diseases. An increase in odds was observed when comparing the effect of having 1 (OR, 1.30; 95% CI, 1.15-1.47) or 2 atopic parents (OR, 2.08; 95% CI, 1.83-2.36), as well as having a parent with 1 (OR, 1.49; 95% CI, 1.28-1.74) or more atopic diseases (OR, 2.32; 95% CI, 1.92-2.81).

CONCLUSIONS

This study provides evidence-based risk estimates that may guide physicians who counsel parents with a history of atopic disease about their children's risk of AD. This information is of particular importance for future efforts toward establishing prophylactic interventions for AD on a general population level.

[Reasons for the development of allergies in children]

Allergies are one of the most common chronic diseases in childhood, contributing to a tremendous medical and economical burden in health care systems of most industrialized countries. The development of allergies is dependent on a complex interaction of-among others-environmental factors, nutrition, genetic and epigenetic mechanisms as well as the microbiome. These diverse factors can influence early life immune regulation including innate and adaptive immune mechanisms in a complex fashion. In case of any Childhood allergies have increased significantly in past decades. In addition to environmental factors and nutrition, genetic and epigenetic mechanisms as well as the microbiome of children play an important role. Of relevance is the way in which these diverse factors influence early immune development of the innate and adaptive immune systems of children. Their complex regulation is decisive for whether or not a child develops an allergy that manifests in most cases as atopic dermatitis, bronchial asthma, or allergic rhino conjunctivitis, or whether a child develops an immune tolerance. These influences can begin prenatally, already setting the course for later immune system development and occurrence of disease.

Mother Nature in Eczema: Maternal Factors Influencing Atopic Dermatitis

Atopic dermatitis (AD) is a highly prevalent chronic inflammatory skin disease. Current knowledge about the etiology of AD suggests that it is multifactorial and involves the interaction of several factors, including environmental triggers, genetics, immunologic factors, and skin barrier dysfunction. The prenatal environment has a significant influence on fetal development, including the maturation of skin barrier function. This review summarizes maternal factors that have been reported to influence the development of AD in offspring, including maternal genetics, nutrition, breastfeeding, environment, and behaviors.

Identification of novel candidate variants including COL6A6 polymorphisms in early-onset atopic dermatitis using whole-exome sequencing

Background

The prevalence of atopic dermatitis has increased over the last 10 years. Atopic dermatitis tends to run in families and commonly begins to manifest in childhood. The prevalence of atopic dermatitis is as high as 20% in children. Thus, early diagnosis and treatment of atopic dermatitis are important. Understanding its genetic basis is also needed to facilitate early detection.

Methods

To identify family-specific candidate genetic variants associated with early-onset atopic dermatitis in Koreans, we carried out whole-exome sequencing of three separate families with this condition. Additional validation was performed in 112 AD patients and 61 controls using Sanger sequencing.

Results

We focused on both common functional variants with a minor allele frequency higher than 1% and rare variants with a minor allele frequency less than 1%. The relevance of the respective variants was supported by a program that could predict whether the mutations resulted in damaged protein function. Fourteen overlapping genes were identified during exome sequencing. Three variants of the COL6A6 gene appeared in all three families and were in close proximity to atopic dermatitis-related loci on chromosome 3q21. The homozygous frequency for the rs16830494 minor allele (AA) and the rs59021909 (TT) allele and the rs200963433 heterozygous (CT) frequency were all higher in AD cases compared to controls in a population-based case-control study.

Conclusion

Identifying family-specific COL6A6 polymorphisms and genetic variants of other candidate genes associated with AD using WES is a novel approach. Our study suggests that COL6A6 variants may be risk factors for atopic dermatitis. This study provides a genetic basis for early-onset AD diagnosis in Korean patients and the development of new therapies.

Trial registration

Trial registration number: IRB NO. C2008030 (133); Name of registry: The collection research of clinical data and patient blood to identify genetic and protein biomarker of atopic dermatitis; Date of registration: 09-July-2008.

Trial registration number: IRB NO. C2015258 (1716); Name of registry: The collection study of patient blood and clinical data for the development of the prognosis prediction and early diagnosis of atopic dermatitis; Date of registration: 15-jan-2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0368-9) contains supplementary material, which is available to authorized users.

Probiotics and Atopic Dermatitis: An Overview

Atopic dermatitis (AD) is a common, recurrent, chronic inflammatory skin disease that is a cause of considerable economic and social burden. Its prevalence varies substantially among different countries with an incidence rate proclaimed to reach up to 20% of children in developed countries and continues to escalate in developing nations. This increased rate of incidence has changed the focus of research on AD toward epidemiology, prevention, and treatment. The effects of probiotics in the prevention and treatment of AD remain elusive. However, evidence from different research groups show that probiotics could have positive effect on AD treatment, if any, that depend on multiple factors, such as specific probiotic strains, time of administration (onset time), duration of exposure, and dosage. However, till date we still lack strong evidence to advocate the use of probiotics in the treatment of AD, and questions remain to be answered considering its clinical use in future. Based on updated information, the processes that facilitate the development of AD and the topic of the administration of probiotics are addressed in this review.

Genomic imprinting in psoriasis and atopic dermatitis: A review

Genomic imprinting is a genetic process where only one allele of a particular gene is expressed in a parent-of-origin dependent manner. Epigenetic changes in the DNA, such as methylation or acetylation of histones, are primarily thought to be responsible for silencing of the imprinted allele. Recently, global CpG methylation changes have been identified in psoriatic skin in comparison to normal skin, particularly near genes known to be upregulated in psoriasis such as KYNU, OAS2, and SERPINB3. Furthermore, imprinting has been associated with multi-chromosomal human disease, including diabetes and multiple sclerosis. This paper is the first to review the clinical and genetic evidence that exists in the literature for the association between imprinting and general skin disorders, including atopic dermatitis and psoriatic disease. Atopy was found to have evidence of imprinting on chromosomes 6, 11, 14, and 13. The β subunit of the IgE receptor on chromosome 11q12-13 may be imprinted. Psoriatic disease may be related to imprinting effects on chromosome 6 for psoriasis and 16 for psoriatic arthritis.

Atopic Dermatitis; Etio-Pathogenesis, An Overview

Atopic dermatitis is a well-recognized clinical entity, several facets of which continue to be mystified. Accordingly, its etio-pathogenesis is largely elusive. It appears to be an outcome of interplay of several undertones, namely: genetics, maternal factor and inheritance, pregnancy/intrauterine, environmental factors, immune dysregulation, immuno-globulins, role of diet, and infection. Besides, recent innovative breakthroughs consisting of nutritional supplementation, the highlights of which were considered worthwhile to take stock of to define its current status. An endeavor to enlighten the audience has been made for their benefit.

Past, present, and future for biologic intervention in atopic dermatitis

Atopic dermatitis (AD) is a debilitating disease that significantly alters the quality of life for one in four children and one in 10 adults. Current management of AD utilizes combinations of treatments to symptomatically alleviate disease by suppressing the inflammatory response and restoring barrier function in the skin, reducing disease exacerbation and flare, and preventing secondary skin infections. Resolution is temporary and long-term usage of these treatments can be associated with significant side-effects. Antibody therapies previously approved for inflammatory diseases have been opportunistically evaluated in patients with atopic dermatitis; however, they often failed to demonstrate a significant clinical benefit. Monoclonal antibodies currently in development offer hope to those individuals suffering from the disease by specifically targeting immune and molecular pathways important for the pathogenesis of atopic dermatitis. Here, we review the underlying biological pathways and the state of the art in therapeutics in AD.

Factors associated with different results of allergy tests in children with dust mite-induced atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a public health problem, with an increasing prevalence worldwide. AD is a chronic inflammatory disease characterised by skin lesions and severe itching. Immunologically, AD has two forms, IgE-mediated and cell-mediated, but it may also be idiopathic. In the pathogenesis of AD, the gene mutations for filaggrin, a filament-aggregating protein present in the epidermis, are of pivotal importance, but other genetic factors are also operating, including those linked to family atopy.

METHODS

We evaluated the role of family atopy, and of the results of the atopy patch test (APT) in parents, in children with mite-induced AD. 64 children, 38 males and 26 females, mean age 4.97 years, were included for the diagnosis of AD and underwent APT and skin prick test (SPT) with dust mite extracts, with evaluation of atopy and result of APT also in parents.

RESULTS

A positive family history of atopy was shown for children with positivity to both APT and SPT compared to those with negative or only one positive result to APT or SPT (p=0.08). Significant associations were found concerning APT results in children and parents. In particular, children of a positive-APT parent had an 18-fold higher risk of APT-positivity in comparison with children of negative-APT parents, while the risk was 6.6-fold higher if APT was positive in father.

CONCLUSION

Family atopy and a positive APT in fathers are risk factors to develop cell-mediated AD, as assessed by the APT, in children.

Maternal filaggrin mutations increase the risk of atopic dermatitis in children: an effect independent of mutation inheritance

Epidemiological studies suggest that allergy risk is preferentially transmitted through mothers. This can be due to genomic imprinting, where the phenotype effect of an allele depends on its parental origin, or due to maternal effects reflecting the maternal genome's influence on the child during prenatal development. Loss-of-function mutations in the filaggrin gene (FLG) cause skin barrier deficiency and strongly predispose to atopic dermatitis (AD). We investigated the 4 most prevalent European FLG mutations (c.2282del4, p.R501X, p.R2447X, and p.S3247X) in two samples including 759 and 450 AD families. We used the multinomial and maximum-likelihood approach implemented in the PREMIM/EMIM tool to model parent-of-origin effects. Beyond the known role of FLG inheritance in AD (R1_{meta-analysis} = 2.4, P = 1.0 x 10⁻³⁶), we observed a strong maternal FLG genotype effect that was consistent in both independent family sets and for all 4 mutations analysed. Overall, children of FLG-carrier mothers had a 1.5-fold increased AD risk (S1 = 1.50, P_{meta-analysis} = 8.4 x 10⁻⁸). Our data point to two independent and additive effects of FLG mutations: i) carrying a mutation and ii) having a mutation carrier mother. The maternal genotype effect was independent of mutation inheritance and can be seen as a non-genetic transmission of a genetic effect. The FLG maternal effect was observed only when mothers had allergic sensitization (elevated allergen-specific IgE antibody plasma levels), suggesting that FLG mutation-induced systemic immune responses in the mother may influence AD risk in the child. Notably, the maternal effect reported here was stronger than most common genetic risk factors for AD recently identified through genome-wide association studies (GWAS). Our study highlights the power of family-based studies in the identification of new etiological mechanisms and reveals, for the first time, a direct influence of the maternal genotype on the offspring’s susceptibility to a common human disease.

Most human diseases are caused by a combination of multiple environmental and genetic influences. The widely used case/control approach aims to identify disease risk genes by comparing the genetic constitution of affected and healthy individuals. Although successful, this approach ignores additional mechanisms influencing disease risk. Here, we studied mutations in the filaggrin gene (FLG), which are strong risk factors for atopic dermatitis (AD) and allergies, in a large number of families with AD. We found that FLG mutations in the mother, not the father, increased the AD risk of the children, even if the child did not inherit the mutation. Thus, our study revealed, for the first time, a direct influence of a maternal mutation on the child’s risk for a common disease. The maternal FLG effect was only found when the mothers were allergic, and was absent in families of non-allergic mothers. This finding suggests that FLG-induced changes in the maternal immune response shape the child’s immune system during pregnancy and increase the child’s risk for AD. Our study indicates that maternal FLG mutations act as strong environmental risk factors for the child and highlights the potential of family-based studies in uncovering novel disease mechanisms in medical genetics.

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.

Nonmuscle myosin light chain kinase regulates murine asthmatic inflammation

Myosin light chain kinase (MLCK; gene code, MYLK) is a multifunctional enzyme involved in isoform-specific nonmuscle (nm) and smooth muscle contraction, inflammation, and vascular permeability, processes directly relevant to asthma pathobiology. In this report, we highlight the contribution of the nm isoform (nmMLCK) to asthma susceptibility and severity, supported by studies in two lines of transgenic mice with knocking out nmMLCK or selectively overexpressing nmMLCK in endothelium. These mice were sensitized to exhibit ovalbumin-mediated allergic inflammation. Genetically engineered mice with targeted nmMLCK deletion (nmMLCK(-/-)) exhibited significant reductions in lung inflammation and airway hyperresponsiveness. Conversely, mice with overexpressed nmMLCK in endothelium (nmMLCK(ec/ec)) exhibited elevated susceptibility and severity in asthmatic inflammation. In addition, reduction of nmMLCK expression in pulmonary endothelium by small interfering RNA results in reduced asthmatic inflammation in wild-type mice. These pathophysiological assessments demonstrate the positive contribution of nmMLCK to asthmatic inflammation, and a clear correlation of the level of nmMLCK with the degree of experimental allergic inflammation. This study confirms MYLK as an asthma candidate gene, and verifies nmMLCK as a novel molecular target in asthmatic pathobiology.

Dissecting the causes of atopic dermatitis in children: less foods, more mites

Atopic dermatitis (AD) is a common, chronic or chronically relapsing, multifactorial skin disease that mainly occurs in children but affects also adults. AD usually begins early in life and often concerns people with a personal or family history of asthma and allergic rhinitis. AD is characterized by eczematous changes in the epidermis and originates from a late, T-cell mediated reaction associated to the formation and production of memory T-cell of TH2 type, occurrence of homing receptor at skin level and cutaneous lymphocyte-associated (CLA) antigens. Extrinsic or allergic AD, but not intrinsic AD, shows high total serum IgE levels and the presence of specific IgE for environmental and food allergens. A pivotal role in the pathogenesis of AD is played by filaggrin, a protein contained in the granular layer of the epidermis regulating the aggregation of keratin filaments. Mutation in the filaggrin gene causes decreased barrier function of the corny layers of the epidermis. This favours the enter through the skin of environmental allergens, especially the house dust mite, that further facilitates such entering by the proteolytic activity of its major allergen Der p 1. In fact, recent advances suggest that the dust mite, more than foods, is the major cause of allergic AD. As far as the causal diagnosis of AD is concerned, there is notable evidence supporting the capacity of the atopy patch test (APT) to reproduce the pathophysiologic events of AD. This makes APT a valuable diagnostic tool for AD.

Targeting tacrolimus to deeper layers of skin with improved safety for treatment of atopic dermatitis-Part II: in vivo assessment of dermatopharmacokinetics, biodistribution and efficacy

The objective of present investigation was to study in vivo behavior of tacrolimus-loaded lipid-nanoparticles (T-LN) to understand its targeting potential for treatment of atopic-dermatitis-(AD). T-LN have shown significantly improved drug penetration to deeper epidermal and dermal skin-layers than commercial ointment-Protopic(®) and effectively reached target dendritic-immune-cells, responsible for immunopathogenesis of AD. Due to enhanced penetrability of T-LN, it became necessary to evaluate the toxicity of the nanocarrier and the drug at non-target tissues. This paper evaluates dermatopharmacokinetics (DPK), biodistribution, efficacy and safety of T-LN in comparison to Protopic(®) as reference. In vivo DPK in guinea pigs showed 3.02-fold higher bioavailability while γ-scintigraphy in albino-rats demonstrated 1.5-fold rapid penetration of radioactivity in skin for T-LN. Biodistribution in albino-rats revealed restricted localization at the target-skin-area with no general spreading to other body organs suggesting targeting potential of T-LN. In vivo efficacy studies in BALB/c mice showed highly efficient suppression of inflammatory AD-like skin-lesions with T-LN than reference and placebo. Dermal toxicity-studies revealed keratosis and collagenous mass-infiltration with repeated application of reference however interestingly, T-LN treated group showed no evident toxicity demonstrating significantly improved safety. Thus T-LN offered improved penetration to the target site without any toxic-effects and would represent an efficient and commercially viable alternative for AD treatment.

Recent advances in the epigenetics and genomics of asthma

PURPOSE OF REVIEW

Epigenetics is the study of heritable changes in gene expression that occur without direct changes in the DNA sequence. Epigenetic mechanisms may explain important observations in asthma, such as the effect of the environment during certain periods in life, transgenerational, and maternal effects and account for some of the missing heritability in asthma. Here, we review recent evidence for the role of epigenetics and genomics in asthma.

RECENT FINDINGS

Environmental factors known to increase asthma risk affect methylation patterns in the genome, yet the link to subsequent asthma development is not yet established. Posttranslational histone modifications and chromatin remodeling are important in establishing T-helper-2 cell differentiation. MicroRNAs have been shown to regulate experimental asthma in mice. Integration of genomic methods leads to increased understanding on how variation at the DNA levels affects mRNA transcription or chromatin remodeling.

SUMMARY

Epigenetic mechanisms regulate gene expression at the DNA, mRNA, and the chromatin level and more studies are needed to establish its role in human asthma. Integration of genomic methods will provide more insight into the complex pathophysiology of asthma.

Eczema in early life: genetics, the skin barrier, and lessons learned from birth cohort studies

Eczema is a chronic inflammatory disorder of the skin that affects up to 30% of children. It often afflicts infants in the first few months of life and can be the first indicator of the atopic march. Recent results from birth cohort studies have uncovered novel information regarding genetic and environmental factors that promote the development of eczema. Birth cohort studies provide an optimal study design to elucidate these associations and prospectively track longitudinal data including exposure assessment and health outcomes from birth into early life and childhood. This is especially relevant for eczema given the age specific emergence of this disease. In this review, we will provide a general overview of pediatric eczema and discuss the important findings in the literature with respect to genetics and environmental exposures, highlighting those derived from birth cohort studies. Additionally, we will review how these relate to the atopic march, the hygiene hypothesis and the integrity of the skin barrier.

Epidemiology of asthma: risk factors for development

This comprehensive review of the recent literature was undertaken to determine the current state of knowledge of the risk factors involved in the development of asthma in order to focus investigations in a proposed new longitudinal birth cohort study. The origins of asthma appear to lie in the prenatal and early postnatal period, and renewed investigations in this period with long-term close follow-up and objective phenotypic characterization will help to unravel the role of the multiple putative environmental factors in the development of asthma. It is only after understanding these effects that one can hope to design rational prevention studies for asthma.

Eosinophilic bronchitis, eosinophilia associated genetic variants, and notch signaling in asthma

While much has indeed been learned about the biology and role of eosinophils, the paradigm of eosinophils has the pros and cons in development of asthma. To answer the questions in the black box, this review firstly discusses the biological and morphological differences between asthma and eosinophilic bronchitis (EB). EB is an interesting clinical manifestation of eosinophilic airway disease that does not involve airway hyperresponsiveness (AHR), demonstrating that airway eosinophilia alone is insufficient to merit a diagnosis of asthma. Secondly, I will describe and discuss the effect(s) of single-nucleotide polymorphisms (SNPs) in the genes CCR3, IL-5 RECEPTOR ALPHA (IL5RA), and IL1RL1, and finally the in vitro and in vivo effects of Notch inhibition on both eosinophil differentiation and experimental asthma. Eosinophilic airway inflammation is not as important in the pathogenesis and maintenance of asthma as had previously been thought. However, the role of eosinophils in other asthma subphenotypes, including refractory or severely remodeled asthma, needs to be evaluated further. High-throughput methodologies such as genomics will facilitate the discovery of new markers of inflammation; these, in turn, will aid in the evaluation of the role of eosinophils in asthma and its various subphenotypes.

What is really in control of skin immunity: lymphocytes, dendritic cells, or keratinocytes? facts and controversies

The pathophysiology of atopic dermatitis is still under discussion. Although it is widely accepted that environmental factors and a genetic predisposition are essential, the role of the innate and adaptive immune system and the functional cascade of the cells involved is still unclear. A concept that integrates all immune cells as equally essential has allure. In addition, barrier abnormalities due to mutations of the gene coding for filaggrin and down-regulation of antimicrobial peptides, such as LL-37 and beta-defensins 2 and 3, were very recently found to be relevant for the pathogenesis of atopic dermatitis.

An update on the genetics of atopic dermatitis: scratching the surface in 2009

A genetic basis for atopic dermatitis (AD) has long been recognized. Historic documents allude to family history of disease as a risk factor. Before characterization of the human genome, heritability studies combined with family-based linkage studies supported the definition of AD as a complex trait in that interactions between genes and environmental factors and the interplay between multiple genes contribute to disease manifestation. A summary of more than 100 published reports on genetic association studies through mid-2009 implicates 81 genes, in 46 of which at least 1 positive association with AD has been demonstrated. Of these, the gene encoding filaggrin (FLG) has been most consistently replicated. Most candidate gene studies to date have focused on adaptive and innate immune response genes, but there is increasing interest in skin barrier dysfunction genes. This review examines the methods that have been used to identify susceptibility genes for AD and how the underlying pathology of this disease has been used to select candidate genes. Current challenges and the potential effect of new technologies are discussed.

Allergic skin diseases

The skin is one of the largest immunologic organs and is affected by both external and internal factors, as well as innate and adaptive immune responses. Many skin disorders, such as atopic dermatitis, contact dermatitis, urticaria, angioedema, psoriasis, and autoimmune blistering disorders, are immune mediated. Most of these diseases are chronic, inflammatory, and proliferative, in which both genetic and environmental factors play important roles. These immunologic mechanisms might have implications for potential targets of future therapeutic interventions.

Does eczema lead to asthma?

The nature of the relationship between eczema, asthma, and allergic rhinitis has been controversial. It has been commonly held that these disorders, while sharing genetic and environmental risk factors, are unrelated disorders that may develop sequentially along an atopic pathway. Conversely, the link between eczema and these later-onset respiratory disorders may be causal. This review examines the relationship between eczema, asthma, and allergic rhinitis in the context of the atopic march, the skin barrier, and recent developments in eczema genetics; and we propose that the relationship is causal. We describe a plausible biological pathway with eczema as the first step in a progressive atopic march that over time leads to asthma and/or allergic rhinitis. Such a pathway has implications for our understanding of these disorders and steps that might be made to prevent the development of asthma in particular. We propose that intervention studies in eczema should be conducted to confirm or refute this causal relationship. Such studies may materially improve the quality of life of eczema patients and will have important public health benefits if the interventions lead to a reduction in the burden of asthma.

Linkage of atopic dermatitis to chromosomes 4q22, 3p24 and 3q21

Atopic dermatitis (AD) is a common, itchy skin disease of complex inheritance characterized by dermal and epidermal inflammation. The heritability is considerable and well documented. To date, four genome scans have examined the AD phenotype, showing replicated linkage at 3p26-22, 3q13-21 and 18q11-21. Our previous AD scan showed evidence of linkage to loci at 3p and 18q, and furthermore at 4p15-14. In order to further investigate the genetic basis of AD, we collected and analysed a new Danish family sample consisting of 130 AD sib pair families (555 individuals including 295 children with AD). AD was diagnosed after clinical examination, AD severity was scored and specific IgE was determined. A linkage scan of chromosome 3, 4 and 18 was performed using 91 microsatellite markers. Linkage analyses were performed of dichotomous phenotypes and semi-quantitative traits including the AD severity score. We analysed the novel AD sample alone and together with the previously examined sample. AD severity showed a maximum Z-score of 3.7 at 4q22.1 suggesting the localization of a novel gene for AD severity. A maximum MOD score of 4.6 was obtained at 3p24 for the AD phenotype, providing the first significant linkage of AD at this locus. A maximum MLS score of 3.3 was obtained at 3q21 for IgE-associated AD, and evidence of linkage was also obtained at 3p22.2-21.31, 3q13, 4q35, and 18q12. The results presented should provide a firm basis for gene-targeting studies of AD and related disorders.

Epidermal barrier dysfunction in atopic dermatitis

Atopic dermatitis (AD) is a multifactorial, heterogenous disease that arises as a result of the interaction between both environmental and genetic factors. Changes in at least three groups of genes encoding structural proteins, epidermal proteases, and protease inhibitors predispose to a defective epidermal barrier and increase the risk of developing AD. Loss-of-function mutations found within the FLG gene encoding the structural protein, filaggrin, represent the most significant genetic factor predisposing to AD identified to date. Enhanced protease activity and decreased synthesis of the lipid lamellae lead to exacerbated breakdown of the epidermal barrier. Environmental factors, including the use of soap and detergents, exacerbate epidermal barrier breakdown, attributed to the elevation of stratum corneum pH. A sustained increase in pH enhances the activity of degradatory proteases and decreases the activity of the lipid synthesis enzymes. The strong association between both genetic barrier defects and environmental insults to the barrier with AD suggests that epidermal barrier dysfunction is a primary event in the development of this disease. Our understanding of gene-environment interactions should lead to a better use of some topical products, avoidance of others, and the increased use and development of products that can repair the skin barrier.

The cystatin M/E-controlled pathway of skin barrier formation: expression of its key components in psoriasis and atopic dermatitis

BACKGROUND

The antiprotease activity of cystatin M/E regulates skin barrier formation, as it inhibits the activity of cathepsin V, cathepsin L and legumain, thereby controlling the processing of transglutaminase 3. Misregulation of this pathway by unrestrained protease activity, as seen in cystatin M/E-deficient mice, leads to abnormal stratum corneum and hair follicle formation, and severe disturbance of skin barrier function.

OBJECTIVES

Our major aim was to make a quantitative analysis of the expression of all players of this pathway in the epidermis of patients with inflammatory skin diseases. A second aim was to determine if reconstructed human skin could be used as an in vitro model system to investigate this pathway.

METHODS

Autopsy material from normal human tissues, biopsies from normal skin of healthy volunteers, and lesional skin from patients with atopic dermatitis and psoriasis were used to study the expression of the above-mentioned molecules at the mRNA level by quantitative real-time polymerase chain reaction. Localization of the protein was performed by immunofluorescence microscopy, and expression was quantitated by image analysis.

RESULTS

In skin, cystatin M/E is expressed at relatively higher levels than its target proteases, when compared with other tissues, which emphasizes its prominent role in cutaneous biology. We found decreased expression of cystatin M/E and cathepsin V in lesional atopic dermatitis and psoriasis epidermis at the mRNA level as well as the protein level. Cathepsin L and transglutaminase 3 were increased at the transcriptional level; however, this was not reflected by higher protein levels. Interestingly, the expression of all these molecules in reconstructed skin was qualitatively and quantitatively similar to the in vivo situation.

CONCLUSIONS

Disturbance of the cystatin M/E-cathepsin pathway could contribute to the dysregulated skin barrier function observed in inflammatory dermatoses. Human reconstructed skin appears to be a valuable model to study this novel biochemical pathway in vitro.

Variants in the gene encoding C3 are associated with asthma and related phenotypes among African Caribbean families

Proinflammatory and immunoregulatory products from C3 play a major role in phagocytosis, respiratory burst, and airways inflammation. C3 is critical in adaptive immunity; studies in mice deficient in C3 demonstrate that features of asthma are significantly attenuated in the absence of C3. To test the hypothesis that the C3 gene on chromosome 19p13.3-p13.2 contains variants associated with asthma and related phenotypes, we genotyped 25 single nucleotide polymorphism (SNP) markers distributed at intervals of approximately 1.9 kb within the C3 gene in 852 African Caribbean subjects from 125 nuclear and extended pedigrees. We used the multiallelic test in the family-based association test program to examine sliding windows comprised of 2-6 SNPs. A five-SNP window between markers rs10402876 and rs366510 provided strongest evidence for linkage in the presence of linkage disequilibrium for asthma, high log[total IgE], and high log[IL-13]/[log[IFN-gamma] in terms of global P-values (P = 0.00027, 0.00013, and 0.003, respectively). A three-SNP haplotype GGC for the first three of these markers showed best overall significance for the three phenotypes (P = 0.003, 0.007, 0.018, respectively) considering haplotype-specific tests. Taken together, these results implicate the C3 gene as a priority candidate controlling risk for asthma and allergic disease in this population of African descent.

New insights into the mechanism and management of allergic diseases: atopic dermatitis

Rapidly increasing knowledge on the complex background of atopic dermatitis (AD) on the genetic, immunological and environmental level in combination with the continuous improvement in our diagnostic options has initiated an ongoing discussion on factors, which primarily promote the disease on one hand and mechanisms which emerge rather secondarily as a consequence of disease-specific modifications, on the other hand. Beside a sustained search for reliable and meaningful diagnostic tools for elicitors of the disease, novel therapeutic approaches are required, as most of the treatments of AD are limited to symptomatic therapies. In contrast, therapeutic approaches selectively regulating aberrant pathophysiological mechanisms in AD itself would be much more effective and promising.

Cellular and molecular mechanisms in atopic dermatitis

Atopic dermatitis (AD) is a pruritic inflammatory skin disease associated with a personal or family history of allergy. The prevalence of AD is on the rise and estimated at approximately 17% in the USA. The fundamental lesion in AD is a defective skin barrier that results in dry itchy skin, and is aggravated by mechanical injury inflicted by scratching. This allows entry of antigens via the skin and creates a milieu that shapes the immune response to these antigens. This review discusses recent advances in our understanding of the abnormal skin barrier in AD, namely abnormalities in epidermal structural proteins, such as filaggrin, mutated in approximately 15% of patients with AD, epidermal lipids, and epidermal proteases and protease inhibitors. The review also dissects, based on information from mouse models of AD, the contributions of the innate and adaptive immune system to the pathogenesis of AD, including the effect of mechanical skin injury on the polarization of skin dendritic cells, mediated by keratinocyte-derived cytokines such as thymic stromal lymphopoietin (TSLP), IL-6, and IL-1, that results in a Th2-dominated immune response with a Th17 component in acute AD skin lesions and the progressive conversion to a Th1-dominated response in chronic AD skin lesions. Finally, we discuss the mechanisms of susceptibility of AD skin lesions to microbial infections and the role of microbial products in exacerbating skin inflammation in AD. Based on this information, we discuss current and future therapy of this common disease.

Global expression profiling in atopic eczema reveals reciprocal expression of inflammatory and lipid genes

BACKGROUND

Atopic eczema (AE) is a common chronic inflammatory skin disorder. In order to dissect the genetic background several linkage and genetic association studies have been performed. Yet very little is known about specific genes involved in this complex skin disease, and the underlying molecular mechanisms are not fully understood.

METHODOLOGY/FINDINGS

We used human DNA microarrays to identify a molecular picture of the programmed responses of the human genome to AE. The transcriptional program was analyzed in skin biopsy samples from lesional and patch-tested skin from AE patients sensitized to Malassezia sympodialis (M. sympodialis), and corresponding biopsies from healthy individuals. The most notable feature of the global gene-expression pattern observed in AE skin was a reciprocal expression of induced inflammatory genes and repressed lipid metabolism genes. The overall transcriptional response in M. sympodialis patch-tested AE skin was similar to the gene-expression signature identified in lesional AE skin. In the constellation of genes differentially expressed in AE skin compared to healthy control skin, we have identified several potential susceptibility genes that may play a critical role in the pathological condition of AE. Many of these genes, including genes with a role in immune responses, lipid homeostasis, and epidermal differentiation, are localized on chromosomal regions previously linked to AE.

CONCLUSIONS/SIGNIFICANCE

Through genome-wide expression profiling, we were able to discover a distinct reciprocal expression pattern of induced inflammatory genes and repressed lipid metabolism genes in skin from AE patients. We found a significant enrichment of differentially expressed genes in AE with cytobands associated to the disease, and furthermore new chromosomal regions were found that could potentially guide future region-specific linkage mapping in AE. The full data set is available at http://microarray-pubs.stanford.edu/eczema.

Atopic dermatitis: a review of recent advances in the field

Atopic dermatitis is increasing in prevalence and currently affects 15–30% of children in urban areas. Immune dysregulation and an impaired epidermal barrier are important factors in the pathogenesis of this disease. Pruritus and a chronic relapsing remitting course are hallmarks of the disorder, and sleep disturbance can occur in both the patient and family. Preventive interventions include exclusive breastfeeding in the first 4 months of life and withholding solid foods for 6 months. The avoidance of irritants and the use of emollients decrease flares. Topical corticosteroids remain the mainstay of therapy, and should be judiciously utilized. Excessive and inappropriate use must be avoided, as well as ‘steroid phobia’. The topical calcineurin inhibitors can be useful adjuncts. Systemic therapies are available for severe disease, but carry risks of adverse effects.