Analysis of the individual and aggregate genetic contributions of previously identified serine peptidase inhibitor Kazal type 5 (SPINK5), kallikrein-related peptidase 7 (KLK7), and filaggrin (FLG) polymorphisms to eczema risk

Intrinsic Effects of Exposome in Atopic Dermatitis: Genomics, Epigenomics and Regulatory Layers

Atopic dermatitis (AD) or atopic eczema is an increasingly manifested inflammatory skin disorder of complex etiology which is modulated by both extrinsic and intrinsic factors. The exposome includes a person's lifetime exposures and their effects. We recently reviewed the extrinsic exposome's environmental risk factors that contribute to AD. The periods of pregnancy, infancy, and teenage years are recognized as crucial stages in the formation of AD, where the exposome leads to enduring impacts on the immune system. However, research is now focusing on the interactions between intrinsic pathways that are modulated by the extrinsic exposome, including genetic variation, epigenetic modifications, and signals, such as diet, stress, and microbiome interactions. As a result, immune dysregulation, barrier dysfunction, hormonal fluctuations, and skin microbiome dysbiosis are important factors contributing to AD development, and their in-depth understanding is crucial not only for AD treatment but also for similar inflammatory disorders.

Immunomodulatory Role of Staphylococcus aureus in Atopic Dermatitis

Staphylococcus aureus is a gram-positive bacterium commonly found on humans, and it constitutes the skin microbiota. Presence of S. aureus in healthy individuals usually does not pose any threat, as the human body is equipped with many mechanisms to prevent pathogen invasion and infection. However, colonization of S. aureus has been correlated with many healthcare-associated infections, and has been found in people with atopic diseases. In atopic dermatitis, constant fluctuations due to inflammation of the epidermal and mucosal barriers can cause structural changes and allow foreign antigens and pathogens to bypass the first line of defense of the innate system. As they persist, S. aureus can secrete various virulence factors to enhance their survival by host invasion and evasion mechanisms. In response, epithelial cells can release damage-associated molecular patterns, or alarmins such as TSLP, IL-25, IL-33, and chemokines, to recruit innate and adaptive immune cells to cause inflammation. Until recently, IL-36 had been found to play an important role in modulating atopic dermatitis. Secretion of IL-36 from keratinocytes can activate a Th2 independent pathway to trigger symptoms of allergic reaction resulting in clinical manifestations. This mini review aims to summarize the immunomodulatory roles of S. aureus virulence factors and how they contribute to the pathogenesis of atopic diseases.

The role of genetics in food allergy

INTRODUCTION

As the prevalence of food allergies (FA) increases worldwide, our understanding of its pathophysiology and risk factors is markedly expanding. In the past decades, an increasing number of genes have been linked to FA. Identification of such genes may help in predicting the genetic risk for FA development, age of onset, clinical manifestation, causative allergen(s), and possibly the optimal treatment strategies. Furthermore, identification of these genetic factors can help to understand the complex interactions between genes and the environment in predisposition to FA.

AREAS COVERED

We outline the recent important progress in determining genetic variants and disease-associated genes in IgE-mediated FA. We focused on the monogenic inborn errors of immunity (IEI) where FA is one of the clinical manifestations, emphasizing the genes and gene variants which were linked to FA with some of the most robust evidence.

EXPERT OPINION

Genetics play a significant role, either directly or along with environmental factors, in the development of FA. Since FA is a multifactorial disease, it is expected that multiple genes and genetic loci contribute to the risk for its development. Identification of the involved genes should contribute to the area of FA regarding pathogenesis, prediction, recognition, prognosis, prevention, and possibly therapeutic interventions.

Atopic Dermatitis: The Fate of the Fat

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease in which dry and itchy skin may develop into skin lesions. AD has a strong genetic component, as children from parents with AD have a two-fold increased chance of developing the disease. Genetic risk loci and epigenetic modifications reported in AD mainly locate to genes involved in the immune response and epidermal barrier function. However, AD pathogenesis cannot be fully explained by (epi)genetic factors since environmental triggers such as stress, pollution, microbiota, climate, and allergens also play a crucial role. Alterations of the epidermal barrier in AD, observed at all stages of the disease and which precede the development of overt skin inflammation, manifest as: dry skin; epidermal ultrastructural abnormalities, notably anomalies of the lamellar body cargo system; and abnormal epidermal lipid composition, including shorter fatty acid moieties in several lipid classes, such as ceramides and free fatty acids. Thus, a compelling question is whether AD is primarily a lipid disorder evolving into a chronic inflammatory disease due to genetic susceptibility loci in immunogenic genes. In this review, we focus on lipid abnormalities observed in the epidermis and blood of AD patients and evaluate their primary role in eliciting an inflammatory response.

The role of kallikreins in inflammatory skin disorders and their potential as therapeutic targets

The skin is a vital organ of the human body, serving numerous protective and functional roles that are essential for survival. Residing in the epidermis are various epidermal proteases responsible for the establishment and regulation of barrier function. The human tissue kallikrein-related peptidase family conserves homeostasis of the skin barrier through their roles in desquamation, antimicrobial defense, innate immune response, and barrier maintenance. The activity of kallikreins is tightly regulated and dysregulation of kallikrein activity is seen to contribute to the formation of several inflammatory skin disorders. This review highlights the roles of kallikreins in skin homeostasis and pathologies. Due to their part in these skin disorders, inhibitors of the skin kallikreins have become attractive therapeutics. Over the past few years, both natural and synthetic inhibitors of several kallikreins have been identified and are undergoing further development as treatments to restore compromised barrier function. This review summarizes the kallikrein inhibitors under development for this purpose. These inhibitors remain promising therapeutics in cases of severe skin inflammation not well managed by current therapies.

Medical Systems Biology

The aim of this volume is to encourage the use of systems-level methodologies to contribute to the improvement of human-health . We intend to motivate biomedical researchers to complement their current theoretical and empirical practice with up-to-date systems biology conceptual approaches. Our perspective is based on the deep understanding of the key biomolecular regulatory mechanisms that underlie health, as well as the emergence and progression of human-disease . We strongly believe that the contemporary systems biology perspective opens the door to the effective development of novel methodologies to the improvement of prevention . This requires a deeper and integrative understanding of the involved underlying systems-level mechanisms. In order to explain our proposal in a simple way, in this chapter we privilege the conceptual exposition of our chosen framework over formal considerations. The formal exposition of our proposal will be expanded and discussed later in the next chapters.

The COL5A3 and MMP9 genes interact in eczema susceptibility

BACKGROUND

Genetic studies of eczema have identified many genes, which explain only 14% of the heritability. Missing heritability may be partly due to ignored gene-gene (G-G) interactions.

OBJECTIVE

Our aim was to detect new interacting genes involved in eczema.

METHODS

The search for G-G interaction in eczema was conducted using a two-step approach, which included as a first step, a biological selection of genes, which are involved either in the skin or epidermis development or in the collagen metabolism, and as a second step, an interaction analysis of the selected genes. Analyses were carried out at both SNP and gene levels in three asthma-ascertained family samples: the discovery dataset of 388 EGEA (Epidemiological study on the Genetics and Environment of Asthma) families and the two replication datasets of 253 SLSJ (Saguenay-Lac-Saint-Jean) families and 207 MRCA (Medical Research Council) families.

RESULTS

One pair of SNPs, rs2287807 in COL5A3 and rs17576 in MMP9, that were detected in EGEA at P ≤ 10^-5 showed significant interaction by meta-analysis of EGEA, SLSJ and MRCA samples (P = 1.1 × 10^-8 under the significant threshold of 10^-7 ). Gene-based analysis confirmed strong interaction between COL5A3 and MMP9 (P = 4 × 10^-8 under the significant threshold of 4 × 10^-6 ) by meta-analysis of the three datasets. When stratifying the data on asthma, this interaction remained in both groups of asthmatic and non-asthmatic subjects.

CONCLUSION

This study identified significant interaction between two new genes, COL5A3 and MMP9, which may be accounted for by a degradation of COL5A3 by MMP9 influencing eczema susceptibility. Further confirmation of this interaction as well as functional studies is needed to better understand the role of these genes in eczema.

Staphylococcal Biofilms in Atopic Dermatitis

PURPOSE OF REVIEW

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disorder that is a major public health burden worldwide. AD lesions are often colonized by Staphylococcus aureus and Staphylococcus epidermidis. An important aspect of Staphylococcus spp. is their propensity to form biofilms, adhesive surface-attached colonies that become highly resistant to antibiotics and immune responses, and recent studies have found that clinical isolates colonizing AD skin are often biofilm-positive. Biofilm formation results in complex bacterial communities that have unique effects on keratinocytes and host immunity. This review will summarize recent studies exploring the role of staphyloccocal biofilms in atopic dermatitis and the implications for treatment.

RECENT FINDINGS

Recent studies suggest an important role for biofilms in the pathogenesis of numerous dermatologic diseases including AD. S. aureus biofilms have been found to colonize the eccrine ducts of AD skin, and these biofilms influence secretion of keratinocyte cytokines and trigger differentiation and apoptosis of keratinocytes. These activities may act to disrupt barrier function and promote disease pathogenesis as well as allergen sensitization. Formation of biofilm is a successful strategy that protects the bacteria from environmental danger, antibiotics, and phagocytosis, enabling chronic persistence in the host. An increasing number of S. aureus skin isolates are resistant to conventional antibiotics, and staphylococcal biofilm communities are prevalent on the skin of individuals with AD. Staphylococcal colonization of the skin impacts skin barrier function and plays multiple important roles in AD pathogenesis.

The skin barrier function gene SPINK5 is associated with challenge-proven IgE-mediated food allergy in infants

BACKGROUND

A defective skin barrier is hypothesized to be an important route of sensitization to dietary antigens and may lead to food allergy in some children. Missense mutations in the serine peptidase inhibitor Kazal type 5 (SPINK5) skin barrier gene have previously been associated with allergic conditions.

OBJECTIVE

To determine whether genetic variants in and around SPINK5 are associated with IgE-mediated food allergy.

METHOD

We genotyped 71 "tag" single nucleotide polymorphisms (tag-SNPs) within a region spanning ~263 kb including SPINK5 (~61 kb) in n=722 (n=367 food-allergic, n=199 food-sensitized-tolerant and n=156 non-food-allergic controls) 12-month-old infants (discovery sample) phenotyped for food allergy with the gold standard oral food challenge. Transepidermal water loss (TEWL) measures were collected at 12 months from a subset (n=150) of these individuals. SNPs were tested for association with food allergy using the Cochran-Mantel-Haenszel test adjusting for ancestry strata. Association analyses were replicated in an independent sample group derived from four paediatric cohorts, total n=533 (n=203 food-allergic, n=330 non-food-allergic), mean age 2.5 years, with food allergy defined by either clinical history of reactivity, 95% positive predictive value (PPV) or challenge, corrected for ancestry by principal components.

RESULTS

SPINK5 variant rs9325071 (A⟶G) was associated with challenge-proven food allergy in the discovery sample (P=.001, OR=2.95, CI=1.49-5.83). This association was further supported by replication (P=.007, OR=1.58, CI=1.13-2.20) and by meta-analysis (P=.0004, OR=1.65). Variant rs9325071 is associated with decreased SPINK5 gene expression in the skin in publicly available genotype-tissue expression data, and we generated preliminary evidence for association of this SNP with elevated TEWL also.

CONCLUSIONS

We report, for the first time, association between SPINK5 variant rs9325071 and challenge-proven IgE-mediated food allergy.

The Pathogenetic Effect of Natural and Bacterial Toxins on Atopic Dermatitis

Atopic dermatitis (AD) is a common allergic skin disease that is associated with chronic, recurrent eczematous and pruritic lesions at the flexural folds caused by interacting factors related to environmental and immune system changes. AD results in dry skin, and immunoglobulin E-mediated allergic reactions to foods and environmental allergens. While steroids and anti-histamines temporarily relieve the symptoms of AD, the possibility of side effects from pharmacological interventions remains. Despite intensive research, the underlying mechanisms for AD have not been clarified. A study of Staphylococcus aureus (S. aureus) established the role of its toxins in the pathogenesis of AD. Approximately 90% of patients with AD experience S. aureus colonization and up to 50%–60% of the colonizing S. aureus is toxin-producing. Any damage to the protective skin barrier allows for the entry of invading allergens and pathogens that further drive the pathogenesis of AD. Some natural toxins (or their components) that have therapeutic effects on AD have been studied. In addition, recent studies on inflammasomes as one component of the innate immune system have been carried out. Additionally, studies on the close relationship between the activation of inflammasomes and toxins in AD have been reported. This review highlights the literature that discusses the pathogenesis of AD, the role of toxins in AD, and the positive and negative effects of toxins on AD. Lastly, suggestions are made regarding the role of inflammasomes in AD.

Exacerbation of atopic dermatitis on grass pollen exposure in an environmental challenge chamber

BACKGROUND

It has frequently been speculated that pruritus and skin lesions develop after topical exposure to aeroallergens in sensitized patients with atopic dermatitis (AD).

OBJECTIVE

We sought to study cutaneous reactions to grass pollen in adult patients with AD with accompanying clear IgE sensitization to grass allergen in an environmental challenge chamber using a monocenter, double-blind, placebo-controlled study design.

METHODS

Subjects were challenged on 2 consecutive days with either 4000 pollen grains/m(3) of Dactylis glomerata pollen or clean air. The severity of AD was assessed at each study visit up to 5 days after challenge by (objective) scoring of AD (SCORAD). Additionally, air-exposed and non-air-exposed skin areas were each scored using local SCORAD scoring and investigator global assessments. Levels of a series of serum cytokines and chemokines were determined by using a Luminex-based immunoassay. The primary end point of the study was the change in objective SCORAD scores between prechallenge and postchallenge values.

RESULTS

Exposure to grass pollen induced a significant worsening of AD. A pronounced eczema flare-up of air-exposed rather than covered skin areas occurred. In grass pollen-exposed subjects a significantly higher increase in CCL17, CCL22, and IL-4 serum levels was observed.

CONCLUSIONS

This study demonstrates that controlled exposure to airborne allergens of patients with a so-called extrinsic IgE-mediated form of AD induced a worsening of cutaneous symptoms.

From the outside-in: Epidermal targeting as a paradigm for atopic disease therapy

Atopic dermatitis (AD) is a chronic inflammatory skin disorder which can precede asthma and allergic rhinitis in a disease trajectory known as the atopic march. The pathophysiology of AD includes cutaneous inflammation, disrupted epidermal barrier function, xerosis and propensity to secondary infections. AD had previously been thought to arise from the systemic atopic immune response and therapies are therefore directed towards ameliorating Th2-mediated inflammation. However in recent years the focus has shifted towards primary defects in the skin barrier as an initiating event in AD. Links between loss-of-function variants in the gene encoding filaggrin and disrupted activity of epidermal serine proteases and AD have been reported. Based on these observations, a mechanism has been described by which epidermal barrier dysfunction may lead to inflammation and allergic sensitization. Exogenous and endogenous stressors can further exacerbate inherited barrier abnormalities to promote disease activity. Pathways underlying progression of the atopic march remain unclear, but recent findings implicate thymic stromal lymphopoietin as a factor linking AD to subsequent airway inflammation in asthma. This new appreciation of the epidermis in the development of AD should lead to deployment of more specific strategies to restore barrier function in atopic patients and potentially halt the atopic march.

Gene expression in the skin of dogs sensitized to the house dust mite Dermatophagoides farinae

Atopic dermatitis is a multifactorial allergic skin disease in humans and dogs. Genetic predisposition, immunologic hyperreactivity, a defective skin barrier, and environmental factors play a role in its pathogenesis. The aim of this study was to analyze gene expression in the skin of dogs sensitized to house dust mite antigens. Skin biopsy samples were collected from six sensitized and six nonsensitized Beagle dogs before and 6 hr and 24 hr after challenge using skin patches with allergen or saline as a negative control. Transcriptome analysis was performed by the use of DNA microarrays and expression of selected genes was validated by quantitative real-time RT-PCR. Expression data were compared between groups (unpaired design). After 24 hr, 597 differentially expressed genes were detected, 361 with higher and 226 with lower mRNA concentrations in allergen-treated skin of sensitized dogs compared with their saline-treated skin and compared with the control specimens. Functional annotation clustering and pathway- and co-citation analysis showed that the genes with increased expression were involved in inflammation, wound healing, and immune response. In contrast, genes with decreased expression in sensitized dogs were associated with differentiation and barrier function of the skin. Because the sensitized dogs did not show differences in the untreated skin compared with controls, inflammation after allergen patch test probably led to a decrease in the expression of genes important for barrier formation. Our results further confirm the similar pathophysiology of human and canine atopic dermatitis and revealed genes previously not known to be involved in canine atopic dermatitis.

Skin barrier defects in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin condition with complex etiology that is dependent upon interactions between the host and the environment. Acute skin lesions exhibit the features of a Th2-driven inflammatory disorder, and many patients are highly atopic. The skin barrier plays key roles in immune surveillance and homeostasis, and in preventing penetration of microbial products and allergens. Defects that compromise the structural integrity or else the immune function of the skin barrier play a pivotal role in the pathogenesis of AD. This article provides an overview of the array of molecular building blocks that are essential to maintaining healthy skin. The basis for structural defects in the skin is discussed in relation to AD, with an emphasis on filaggrin and its genetic underpinnings. Aspects of innate immunity, including the role of antimicrobial peptides and proteases, are also discussed.

Epistasis between serine protease inhibitor Kazal-type 5 (SPINK5) and thymic stromal lymphopoietin (TSLP) genes contributes to childhood asthma

BACKGROUND

Epithelial genes have previously been associated with asthma but only explain a small fraction of heritability. In part, this might be due to epistasis, which is often not considered.

OBJECTIVE

We sought to determine independent and epistatic associations between filaggrin (FLG), serine protease inhibitor Kazal-type 5 (SPINK5), and thymic stromal lymphopoietin (TSLP) gene variants and childhood asthma.

METHODS

Using a candidate gene approach, we genotyped 29 variants in FLG, SPINK5, and TSLP in asthmatic, allergic, and nonallergic nonasthmatic white and black children participating in the well-phenotyped Greater Cincinnati Pediatric Clinic Repository. Associations with asthma were also assessed in 6 replication populations.

RESULTS

We observed independent associations of variants in SPINK5 (P = .003) and TSLP (P = .006) with childhood asthma; a SPINK5 single nucleotide polymorphism was replicated. In subjects with 1 or more SPINK5 risk alleles, the absence of the TSLP protective minor alleles was associated with a significant increase in asthma (67% vs 53%, P = .0017). In contrast, the presence or absence of TSLP minor alleles did not affect asthma risk in subjects without the SPINK5 risk alleles. The SPINK5 and TSLP epistasis was replicated in a black population (P = .036) who did not display independent association with variants in these genes.

CONCLUSIONS

Our results support epistasis between SPINK5 and TSLP, which contributes to childhood asthma. These findings emphasize the importance of using biology to inform analyses to identify genetic susceptibility to complex diseases. The results from our study have clinical relevance and support that the therapeutic effects of anti-TSLP therapy in asthmatic patients might be dependent on SPINK5 genotype.

The persistence of atopic dermatitis and filaggrin (FLG) mutations in a US longitudinal cohort

BACKGROUND

Atopic dermatitis (AD) is a common skin disease that is characterized by recurrent episodes of itching. Filaggrin (FLG) loss-of-function (FLG null) mutations have been associated with an increased risk of AD.

OBJECTIVE

We sought to evaluate the effect of individual FLG null mutations on the persistence of AD over time.

METHODS

We evaluated a multiyear prospective cohort study of children with AD with respect to FLG null mutations (R501X, 2282del4, R2447X, and S3247X). We evaluated the association of these mutations with the persistence of AD symptoms over time with respect to reports of no symptoms of AD and whether topical medication was needed for symptom resolution.

RESULTS

Eight hundred fifty-seven subjects were followed for 3684 person-years. One or more FLG null mutations were noted in 16.3% of subjects and specifically in 27.5% of white subjects and 5.8% of African American subjects. Subjects with an FLG null mutation were less likely (odds ratio [OR], 0.54; 95% CI, 0.41-0.71) to report that their skin was symptom free at any time compared with those without an FLG null mutation. The effect of these mutations was similar in white subjects (OR, 0.42; 95% CI, 0.31-0.57) and African-American subjects (OR, 0.53; 95% CI, 0.25-1.12; P = .62). Children with the R501X mutation (OR, 0.44; 95% CI, 0.22-0.88) were the least responsive to therapy.

CONCLUSIONS

In a US cohort with AD, FLG null mutations were common. Children with FLG null mutations were more likely to have persistent AD. Although these mutations were more common in those of European ancestry, their effect on persistence was similar in those of African ancestry. Response to therapy was not uniform among children with FLG null mutations.

Abnormal epidermal barrier in the pathogenesis of atopic dermatitis

Despite the acknowledged contributions of a defective epidermal permeability barrier, dryness of the skin, and the propensity to develop secondary infections to the etiology and pathophysiology of atopic dermatitis (AD), these epidermal changes have, until recently, been assumed to reflect downstream consequences that are secondary phenomena of the primary immunologic abnormality--the historical "inside-outside" view that AD is basically an intrinsic inflammatory disease. In this review, we focused on the role of the epidermal barrier function in the pathophysiology of AD. Specifically, we presented data in support of a barrier-initiated pathogenesis of AD, ie, the "outside-inside" concept. First, we reviewed the evidence on the existence of inherited barrier abnormalities in AD. Reported studies on the possible association of mutations in the filaggrin gene (FLG) and data on human tissue kallikreins (KLKs) and AD have been addressed. We then dealt with the question of the causal link between impaired epidermal barrier and inflammation. Finally, the association between innate immune defense system and the increased avidity of Staphylococcus aureus for atopic skin was examined. Despite very convincing evidence to support the barrier-initiated pathogenesis of AD, the view that AD reflects the downstream consequences of a primary immunologic abnormality cannot be dismissed out of hand. Almost every line of evidence in support of the role of the epidermal barrier as the "driver" of the disease activity can be challenged and at least partially contradicted by opposing evidence. Until more data are available and until all the dust settles around this issue, we should take advantage of what we already know and use our knowledge for practical purposes. Deployment of specific strategies to restore the barrier function in AD means the use of moisturizers as first-line therapy.

Therapeutic implications of a barrier-based pathogenesis of atopic dermatitis

Excessive Th2 cell signaling and IgE production play key roles in the pathogenesis of atopic dermatitis (AD). Yet, recent information suggests that the inflammation in AD instead is initiated by inherited insults to the barrier, including a strong association between mutations in FILAGGRIN and SPINK5 in Netherton syndrome, the latter of which provides an important clue that AD is provoked by excess serine protease activity. But acquired stressors to the barrier may also be required to initiate inflammation in AD, and in addition, microbial colonization by Staphylococcus aureus both amplifies inflammation, but also further stresses the barrier in AD. Therapeutic implications of these insights are as follows: While current therapy has been largely directed toward ameliorating Th2-mediated inflammation and/or pruritus, these therapies are fraught with short-term and potential long-term risks. In contrast, "barrier repair" therapy, with a ceramide-dominant triple-lipid mixture of stratum corneum lipids, is more logical, of proven efficacy, and it provides a far-improved safety profile.

One remarkable molecule: filaggrin

The discovery, in 2006, that loss-of-function mutations in the filaggrin (FLG) gene are the cause of ichthyosis vulgaris-the most common disorder of keratinization-and also a strong genetic risk factor for atopic eczema, marked a significant breakthrough in the understanding of eczema pathogenesis. Subsequent investigations of the role of FLG-null mutations have identified a series of significant associations with atopic disease phenotypes, including atopic asthma, allergic rhinitis, and peanut allergy. However, many questions remain to be answered in relation to the precise mechanisms by which deficiency of an intracellular protein expressed primarily in the differentiating epidermis may contribute to the development of cutaneous and systemic pathology. This review aims to highlight the key milestones in filaggrin research over the past 25 years, to discuss the mechanistic, clinical, and therapeutic implications, and to consider possible future directions for ongoing investigation.

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

The term 'hand dermatitis' describes inflammatory skin condition localized to the hands. Nurses working at hospital settings are prone to develop hand dermatitis. The current study aimed to evaluate whether certain genetic polymorphisms were associated with the development of atopic eczema or non-atopic hand dermatitis in Taiwanese population. Nurses of Kaohsiung Medical University Hospital were recruited. Atopic eczema, non-atopic hand dermatitis and normal control groups were identified. The serine protease inhibitor Kazal type 5 (SPINK5), filaggrin and interleukin-31 (IL-31) gene variants were compared between the diseased and control groups. Our results showed that rs2303070 T allele of SPINK5 (assuming recessive model; OR=3.58, 95% CI 1.63-7.84; P=0.0014) and rs7977932 G allele of IL-31 (assuming recessive model; OR=18.25, 95% CI =3.27-101.94; P=0.0009) were associated with increased risks of developing atopic eczema, while rs6892205 G allele of SPINK5 (assuming dominant model; OR=3.79, 95% CI 1.55-9.28; P=0.0036) was associated with the development of non-atopic hand dermatitis. In summary, our results showed that distinct SPINK5 and IL-31 gene variants were associated with the development of atopic eczema and non-atopic hand dermatitis. The barrier function, particularly those regulated by SPINK5, may play an important role in the development of both atopic eczema and non-atopic hand dermatitis.

Reversal of atopic dermatitis with narrow-band UVB phototherapy and biomarkers for therapeutic response

BACKGROUND

Atopic dermatitis (AD) is a common inflammatory skin disease exhibiting a predominantly T(H)2/"T22" immune activation and a defective epidermal barrier. Narrow-band UVB (NB-UVB) is considered an efficient treatment for moderate-to-severe AD. In patients with psoriasis, NB-UVB has been found to suppress T(H)1/T(H)17 polarization, with subsequent reversal of epidermal hyperplasia. The immunomodulatory effects of this treatment are largely unknown in patients with AD.

OBJECTIVE

We sought to evaluate the effects of NB-UVB on immune and barrier abnormalities in patients with AD, aiming to establish reversibility of disease and biomarkers of therapeutic response.

METHODS

Twelve patients with moderate-to-severe chronic AD received NB-UVB phototherapy 3 times weekly for up to 12 weeks. Lesional and nonlesional skin biopsy specimens were obtained before and after treatment and evaluated by using gene expression and immunohistochemistry studies.

RESULTS

All patients had at least a 50% reduction in SCORAD index scores with NB-UVB phototherapy. The T(H)2, T22, and T(H)1 immune pathways were suppressed, and measures of epidermal hyperplasia and differentiation normalized. The reversal of disease activity was associated with elimination of inflammatory leukocytes and T(H)2/T22- associated cytokines and chemokines and normalized expression of barrier proteins.

CONCLUSIONS

Our study shows that resolution of clinical disease in patients with chronic AD is accompanied by reversal of both the epidermal defects and the underlying immune activation. We have defined a set of biomarkers of disease response that associate resolved T(H)2 and T22 inflammation in patients with chronic AD with reversal of barrier pathology. By showing reversal of the AD epidermal phenotype with a broad immune-targeted therapy, our data argue against a fixed genetic phenotype.

Filaggrin polymorphism P478S, IgE level, and atopic phenotypes

BACKGROUND

Whether environmental exposures may modulate the effect of the skin barrier gene on atopic dermatitis (AD) remains to be elucidated.

OBJECTIVES

To determine whether filaggrin (FLG) variants can serve as a predictor for atopic disorders in Chinese individuals and if allergen exposures may modify the effect of FLG variants on AD by total IgE levels.

METHODS

In total, 116 children aged 2-5years with AD and 212 control subjects were analysed for the FLG variants using DNA sequencing. Multiple logistic regression models were performed to estimate the association among FLG polymorphisms and atopic phenotypes. Serum total IgE level, standing for the degree of allergen exposures, was later stratified to determine the effects of FLG polymorphisms on AD.

RESULTS

A significant difference in genotype frequency was found among AD cases and controls in FLG P478S polymorphism. FLG P478S GG genotype significantly increased the risk of AD [odds ratio (OR) 4·60, 95% confidence interval (CI) 1·88-11·24]. In addition, among subjects with AD, GG genotypes also significantly increased the risk of developing asthma (OR 4·68, 95% CI 1·37-16·03). Further, a similar result was obtained for allergic rhinitis (OR 3·23, 95% CI 1·01-10·30). Interestingly, the P478S GG genotype was significantly related to AD (OR 5·67, 95% CI 1·93-16·60) in children with IgE level ≥100 kU L(-1) . However, the association was not evident when IgE level was < 100 kU L(-1) .

CONCLUSIONS

Our results suggest that the FLG P478S polymorphism may confer susceptibility to the development of AD among Chinese individuals and may be modified by IgE levels.

Genetics of atopic dermatitis

Atopic dermatitis (AD) is a multifactorial disease, with a strong genetic predisposition. Genome-wide studies as well as candidate gene studies revealed several susceptibility loci. Since the observation of a strong association of "loss of function" mutations in the filaggrin gene with AD, the epidermal barrier was rediscovered as important pathophysiological co-factor of this disease.

Hint for association of single nucleotide polymorphisms and haplotype in SPINK5 gene with atopic dermatitis in Koreans

Clinical studies, including twin studies, support the concept that the risk of atopic dermatitis (AD) may be mediated through skin-specific genes, rather than simply through systemic immune or atopy risk genes. The SPINK5 gene is expressed on epithelial surfaces and may provide protection against other allergenic serine proteases. Mutations in the SPINK5 gene result in Netherton syndrome, a disorder characterised by AD, ichthyosis, and elevated serum IgE levels. We genotyped 21 single nucleotide polymorphisms (SNPs) from the SPINK5 gene for 1090 case-control samples (631 patients with AD and 459 normal controls) and analysed the SNPs and haplotypes in this gene and also searched for gene-gene interactions between SPINK5 and the DEFB1 gene that we previously reported. Six SNPs [rs17718511 (P = 0.026), rs17860502 (P = 0.024), KN0001820 (P = 0.045), rs60978485 (P = 0.007), rs17718737 (P = 0.02), and rs1422985 (P = 0.038)] and the haplotype TAA (rs60978485, rs6892205, rs2303064; P = 0.023) in the SPINK5 gene showed significant different allelic or genotypic distributions between the AD group and the control group. We also found that four SNPs [rs17718511 (P = 0.033), rs17860502 (P = 0.031), rs60978485 (P = 0.005), rs17718737 (P = 0.023)] and the haplotype TAA (P = 0.02) in the SPINK5 gene showed associations with the susceptibility of the allergic type of AD (ADe). In addition to this finding, we speculate that the SNPs from DEFB1 and SPINK5 affect the individual susceptibility to development of ADe in an additive manner. This study provides evidence for a significant interaction between allergens and the SPINK5 gene that may contribute to ADe susceptibility.

The role of filaggrin in the atopic diathesis

Atopic dermatitis (AD) is an inflammatory disease characterized by pruritic skin lesions, immunodysregulation, disrupted epidermal barrier function and IgE-mediated sensitization to food and environmental allergens. Identification of the aetiology of AD has become increasingly a priority, as it is clear that the disease burden exceeds AD alone, with many children suffering severe, multi-system and occasionally life-threatening allergic disease. Previous approaches to understanding AD have centred on mechanisms in the adaptive immune system, often with an emphasis on the Th1-Th2 paradigm. Recently, the conceptual focus has increasingly shifted to include a primary defect in the epithelial barrier as a threshold event in moderate-to-severe AD. Familial aggregation of the disease is well established through many family studies of AD, asthma and allergic rhinitis, suggesting a significant heritable component. The identification of loss-of-function mutations in the filaggrin (FLG) gene, whose product is a key structural protein in the outermost layer of the epidermis in up to 50% of patients with AD, provides a significant insight into explaining disease initiation and points to a complex secondary interplay of environmental and immunological sequelae once barrier disruption is established. The elucidation of the environmental, genetic and immunobiological modifiers of this structural molecule may also direct our understanding of the pathomechanisms and endotypes central to the atopic diathesis. The recent identification of a murine model for FLG-AD, with the detection of a homozygous frame-shift mutation in the Flg gene in flaky-tail (ft/ft) mice, stands to rapidly accelerate our understanding of mechanisms and therapeutic intervention points in AD. Refining the molecular understanding of AD and its subtypes will allow for specific diagnostic, treatment and ultimately, preventative algorithms, and has opened an exciting new world of investigative challenges and collaborations.

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.

Therapeutic Implications of a Barrier-based Pathogenesis of Atopic Dermatitis

In this review, I first provide relevant background information about normal epidermal barrier structure and function. I then update recent information about how inherited defects in either filaggrin and/or in the serine protease inhibitor, lymphoepithelial Kazal-type inhibitor 1, converge to stimulate the development of atopic dermatitis (AD). Next I explain the multiple mechanisms whereby a primary barrier abnormality in AD can lead to inflammation. Furthermore, I explore how certain acquired stressors, such as a reduced external humidity, high pH soaps/surfactants, psychological stress, as well as secondary Staphylococcus aureus infections initiate or further aggravate AD. Finally, and most importantly, I compare various therapeutic paradigms for AD, highlighting the risks and benefits of glucocorticoids and immunomodulators vs. corrective, lipid replacement therapy.

Deletion of Late Cornified Envelope 3B and 3C genes is not associated with atopic dermatitis

Atopic dermatitis (AD) and psoriasis are common skin diseases characterized by cutaneous inflammation and disturbed epidermal differentiation. Genome-wide analyses have shown overlapping susceptibility loci, such as the epidermal differentiation complex on chromosome 1q21. Recently, a deletion on 1q21 (LCE3C_LCE3B-del), comprising LCE3B and LCE3C, two members of the late cornified envelope (LCE) gene cluster, was found to be associated with psoriasis. Although the mechanistic role of LCE proteins in psoriasis has not been identified, these proteins are putatively involved in skin barrier formation and repair. Considering the potential genetic overlap between the two diseases and the recent finding that mutations in the skin barrier protein filaggrin are associated with AD, we investigated a possible association between LCE3C_LCE3B-del and AD. Evaluation of four different cohorts of European ancestry, containing a total of 1075 AD patients and 1658 controls, did not provide evidence for such an association. Subgroup analysis did not reveal an association with concomitant asthma. Our data suggest that the potential roles of skin barrier defects in the pathogenesis of AD and psoriasis are based on distinct genetic causes.

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.

Chromosome 11q13.5 variant associated with childhood eczema: an effect supplementary to filaggrin mutations

Background

Atopic eczema is a common inflammatory skin disease with multifactorial etiology. The genetic basis is incompletely understood; however, loss of function mutations in the filaggrin gene (FLG) are the most significant and widely replicated genetic risk factor reported to date. The first genome-wide association study in atopic eczema recently identified 2 novel genetic variants in association with eczema susceptibility: a single nucleotide polymorphism on chromosome 11q13.5 (rs7927894) and a single nucleotide polymorphism (rs877776) within the gene encoding hornerin on chromosome 1q21.

Objective

To test the association of these 2 novel variants with pediatric eczema and to investigate their interaction with FLG null mutations.

Methods

Case-control study to investigate the association of rs7927894, rs877776 and the 4 most prevalent FLG null mutations with moderate-severe eczema in 511 Irish pediatric cases and 1000 Irish controls. Comprehensive testing for interaction between each of the loci was also performed.

Results

The association between rs7927894 and atopic eczema was replicated in this population (P = .0025, χ² test; odds ratio, 1.27; 95% CI, 1.09-1.49). The 4 most common FLG null variants were strongly associated with atopic eczema (P = 1.26 × 10⁻⁵⁰; combined odds ratio, 5.81; 95% CI, 4.51-7.49). Interestingly, the rs7927894 association was independent of the well-established FLG risk alleles and may be multiplicative in its effect. There was no significant association between rs877776 and pediatric eczema in this study.

Conclusion

Single nucleotide polymorphism rs7927894 appears to mark a genuine eczema susceptibility locus that will require further elucidation through fine mapping and functional analysis.

Looking ahead in dermatology: skin and allergy

The prevalence of allergic diseases has increased tremendously over the last decades. Clinically they comprise a spectrum of many different conditions caused by specific immunological hypersensitivity in response to a mostly apathogenic substance. Environmental factors such as lack of immune-stimulating contacts (infection, vaccination) and exposure to allergy-enhancing anthropogenic pollutants from tobacco smoke or traffic exhaust particles are suspected to be involved in the increase of allergies. Recently it has been shown that pollens are not only allergen carriers but also secrete highly active proinflammatory lipid mediators, pollen-associated lipid mediators (PALMs), which have proinflammatory and immuno-modulatory capacity that facilitates allergic sensitization of the skin and mucous membranes. The skin is one of the most important organs where allergic reactions manifest. Many different morphological and physiopathological entities can be observed in the skin that represent all kinds of pathogenetic immune reactions from immediate-type allergy, urticaria, angioedema, anaphylaxis, cytotoxic and immune complex reactions such as thrombocytopenic purpura or allergic leukocytoclastic vasculitis, exanthematous drug eruptions, granulomatous skin reactions to tattoos or fillers as well as a wide spectrum of dermatitis and eczema with allergic contact dermatitis being one of the most common occupational diseases in many countries. Recent progress in pathophysiology has revealed a role of epidermal barrier function as well as immunodeviation in atopic eczema giving rise to new diagnostic and therapeutic strategies. The interdisciplinary character of allergy implies a close cooperation between different disciplines where dermatology plays a major role in the management of allergic diseases, covering diagnostic, therapeutic and preventive aspects.

Abnormal skin barrier in the etiopathogenesis of atopic dermatitis

PURPOSE OF REVIEW

Many recent studies have revealed the key roles played by Th1/Th2 cell dysregulation, IgE production, mast cell hyperactivity, and dendritic cell signaling in the pathogenesis of atopic dermatitis. Accordingly, current therapy has been largely directed towards ameliorating Th2-mediated inflammation and/or pruritus. We will review here emerging evidence that the inflammation in atopic dermatitis results from inherited and acquired insults to the barrier and the therapeutic implications of this new paradigm.

RECENT FINDINGS

Recent molecular genetic studies have shown a strong association between mutations in FILAGGRIN and atopic dermatitis, particularly in Northern Europeans. But additional acquired stressors to the barrier are required to initiate inflammation. Sustained hapten access through a defective barrier stimulates a Th1 --> Th2 shift in immunophenotype, which in turn further aggravates the barrier. Secondary Staphylococcus aureus colonization not only amplifies inflammation but also further stresses the barrier in atopic dermatitis.

SUMMARY

These results suggest a new 'outside-to-inside, back to outside' paradigm for the pathogenesis of atopic dermatitis. This new concept is providing impetus for the development of new categories of 'barrier repair' therapy.

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.

Genetik des atopischen Ekzems

Das atopische Ekzem (AE) – auch atopische Dermatitis – ist eine chronisch-entzündliche Erkrankung der Haut, zu deren Charakteristika starker Juckreiz, eine gestörten Hautbarriere und die Bildung von IgE-Antikörpern (Immunglobulin E) gegen Umweltallergene zählen. Das AE ist eine multifaktoriell-polygene Erkrankung, die genetische Prädisposition und der Einfluss von Umweltfaktoren gelten seit langem als entscheidende Auslöser. Dennoch stellt die Aufdeckung der Krankheitsursachen aufgrund der Vielzahl der beteiligten Gene und Umwelteinflüsse sowie deren möglicher Interaktionen eine enorme Herausforderung für die Wissenschaft dar. Der vorliegende Beitrag gibt einen Überblick über den aktuellen Stand der Genetik des AE, über jüngste Erfolge und mögliche Probleme. Vor allem die Identifizierung einer genetischen Ursache des Hautbarrieredefekts hat unser Verständnis des AE in den letzten Jahren entscheidend vorangebracht und könnte zu neuen Ansätzen in dessen Prävention und Therapie führen.

Abnormal skin barrier in the etiopathogenesis of atopic dermatitis

Prior studies revealed the key roles played by T-helper type 1 and type 2 (Th1/Th2) cell dysregulation, IgE production, mast cell hyperactivity, and dendritic cell signaling in the evolution of the chronic, pruritic, inflammatory dermatosis that characterizes atopic dermatitis (AD). Accordingly, current therapy has been largely directed toward ameliorating Th2-mediated inflammation and pruritus. This article reviews emerging evidence that the inflammation in AD results from inherited and acquired insults to the barrier, as well as the therapeutic implications of this new paradigm.

Role of the epidermal barrier in atopic dermatitis

The skin's permeability barrier protects against extensive water loss and prevents the entry into the skin of harmful substances like irritants, allergens and microorganisms. The permeability barrier is mainly located in the stratum corneum and consists of corneocytes and a lipid-enriched intercellular domain. The barrier is formed during epidermal differentiation. In atopic dermatitis the skin barrier is disturbed already in non-lesional skin. The disturbed skin barrier allows the entry of environmental allergens from house dust mites, animal dander and grass pollen into the skin. In predisposed individuals these allergens may trigger via immunologic pathways the inflammation of atopy. The causes for the disturbed epidermal skin barrier are changes in skin lipids and in epidermal differentiation, in particular filaggrin mutations. Filaggrin mutations lead to a disturbed skin barrier and dry skin which are hallmarks in atopic dermatitis. Therapeutic agents influence the skin barrier differently; topical therapy with potent corticosteroids does not lead to the repair of the barrier in atopic dermatitis, whereas therapy with the calcineurin inhibitors and lipid-containing emulsions support barrier repair.

Alterations in epithelial barrier function and host defense responses in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is characterized by a chronic symptomatic inflammation of the nasal and paranasal sinus mucosae and is one of the most frequently reported chronic diseases in the United States, with an estimated prevalence of greater than 10% of the general population. Although the pathogenesis of CRS remains poorly understood, there is evidence for a role of bacteria and fungi, as well as the presence of a robust adaptive immune response in the upper airways and sinuses. Recent studies of CRS, as well as several other diseases in the skin and respiratory epithelium, have uncovered evidence that deficiencies in epithelial immune barrier function might compromise the interaction between the host and external immune stimuli. Recent studies suggest the hypothesis that reduced expression of antimicrobial S100 proteins, particularly psoriasin and calprotectin, might lead to increased susceptibility to bacterial and fungal colonization in patients with CRS. The main emphasis of this review will be to highlight the current literature that suggests that a defect in the expression of a broad set of epithelially derived genes might lead to barrier compromise and subsequently a dysfunctional host immune response to environmental agents in patients with CRS.