Filaggrin mutations associated with skin and allergic diseases

Association between loss-of-function mutations in the filaggrin gene and self-reported food allergy and alcohol sensitivity

BACKGROUND

Loss-of-function mutations of the filaggrin (FLG) gene cause an impaired skin barrier and increase the risk of atopic dermatitis. Interestingly, FLG mutations have also been found to be associated with a high risk of peanut allergy.

OBJECTIVE

We investigated the association of FLG mutations with self-reported food allergy, symptoms of oral allergy syndrome (OAS), and alcohol sensitivity.

METHODS

A total of 3,471 adults from the general population participated in a health examination. Information on food allergies, OAS and alcohol sensitivity was obtained by questionnaire. FLG mutation carriers were defined as having at least one null mutation allele of R501X or 2282del4. Primary lactose intolerance (PLI) was defined as the C/C genotype of the rs4988235 polymorphism.

RESULTS

FLG mutations were associated with a higher risk of self-reported allergy to eggs (OR 3.22 and 95% CI 1.46-7.11), milk (OR 2.10 and 95% CI 1.12-3.92), fish (OR 4.54 and 95% CI 1.88-10.96) and wheat (OR 3.59 and 95% CI 1.61-8.02), but not with symptoms of OAS (OR 1.05 and 95% CI 0.73-1.51). Serum-specific IgE was measured in a subsample and confirmed the association between FLG and IgE to milk. A significant gene-by-gene interaction between FLG and PLI was observed in relation to self-reported allergy to milk. Furthermore, FLG mutations were associated with a higher risk of alcohol sensitivity.

CONCLUSIONS

We found that loss-of-function mutations in the FLG gene were significantly associated with self-reported food allergy and alcohol sensitivity, but not with OAS. These findings, if confirmed, support the idea that skin barrier functions may be involved in the pathogenesis of food allergy.

Why is eczema herpeticum unexpectedly rare?

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease of humans, affecting approximately 17% of children. AD patients are especially susceptible to cutaneous bacterial and viral infections, and may develop severe or fatal herpes simplex virus (HSV) infection (eczema herpeticum, EH), requiring intensive antiviral therapy. However, even though a majority of adults show serologic evidence of previous HSV exposure, EH occurs in less than 3% of AD patients. The unexpected rarity of AD patients with EH (ADEH+) suggests that multiple host factors play a role in the clinical expression of this complex phenotype. Recent studies comparing ADEH+ versus ADEH- patients reveal that patients prone to ADEH+ have more severe AD skin disease, biomarkers associated with Th2 helper cell responses (reduced interferon levels, circulating eosinophil counts, increased serum IgE and allergen sensitization) and decreased epidermal expression of filaggrin and antimicrobial peptides. ADEH+ subjects are also more likely to have a history of food allergy or asthma, early onset of AD and a history of other cutaneous infections with Staphylococcus aureus or molluscum contagiosum.

The effect of Psoroptes ovis infestation on ovine epidermal barrier function

Sheep scab is an intensively pruritic, exudative and allergic dermatitis of sheep caused by the ectoparasitic mite Psoroptes ovis. The purpose of the present study was to investigate the effect of P. ovis infestation on different components of the ovine epidermal barrier within the first 24 hours post-infestation (hpi). To achieve this, the expression of epidermal differentiation complex (EDC) genes and epidermal barrier proteins, the nature and severity of epidermal pathology and transepidermal water loss (TEWL) were evaluated.

By 1 hpi a significant dermal polymorphonuclear infiltrate and a significant increase in TEWL with maximal mean TEWL (598.67 g/m²h) were observed. Epidermal pathology involving intra-epidermal pustulation, loss of epidermal architecture and damage to the basement membrane was seen by 3 hpi. Filaggrin and loricrin protein levels in the stratum corneum declined significantly in the first 24 hpi and qPCR validation confirmed the decrease in expression of the key EDC genes involucrin, filaggrin and loricrin observed by microarray analysis, with 5.8-fold, 4.5-fold and 80-fold decreases, respectively by 24 hpi.

The present study has demonstrated that early P. ovis infestation disrupts the ovine epidermal barrier causing significant alterations in the expression of critical barrier components, epidermal pathology, and TEWL. Many of these features have also been documented in human and canine atopic dermatitis suggesting that sheep scab may provide a model for the elucidation of events occurring in the early phases of atopic sensitisation.

Impact of atopic dermatitis and loss-of-function mutations in the filaggrin gene on the development of occupational irritant contact dermatitis

BACKGROUND

Atopic dermatitis (AD) and loss-of-function mutations in the filaggrin gene (FLG) are both associated with chronic irritant contact dermatitis (ICD). As FLG mutations also are a major risk factor for AD, it is not clear whether FLG mutations are an independent risk factor for ICD or whether the risk is mediated by AD.

OBJECTIVES

To investigate the relative contribution and interaction of FLG mutations and AD in German patients with occupational ICD and controls (vocational school apprentices).

METHODS

A total of 634 patients and 393 controls were genotyped for R501X, 2282del4, R2447X and S3247X. Current or past flexural eczema was used as an indicator of AD.

RESULTS

FLG mutations were found in 15·9% of the patients with ICD and 8·3% of the controls, with a crude odds ratio (OR) of 2·09 [95% confidence interval (CI) 1·33-3·28] for the combined genotype. The adjusted OR for FLG mutations, corrected for AD, was 1·62 (95% CI 1·01-2·58). Subjects with AD were at approximately three times higher risk of developing ICD than controls (OR 2·89; 95% CI 2·09-3·99). There was no evidence of an interaction between these two risk factors.

CONCLUSIONS

Our results indicate that both FLG mutations and AD increase the risk of ICD. Individuals with concurrent FLG mutations and AD are at the highest risk of developing ICD.

Old King coal - molecular mechanisms underlying an ancient treatment for atopic eczema

Traditional remedies for common disorders have been known for centuries, but insight into their mechanism of action is often limited. In this issue of the JCI, Joost Schalkwijk's research group at the Radboud University Nijmegen Medical Centre in The Netherlands advances our understanding of why topical coal tar is an effective treatment for atopic dermatitis (AD), both rationalizing the use of this traditional medicine, and providing the scientific basis for new therapeutic approaches.

Coal tar induces AHR-dependent skin barrier repair in atopic dermatitis

Topical application of coal tar is one of the oldest therapies for atopic dermatitis (AD), a T helper 2 (Th2) lymphocyte-mediated skin disease associated with loss-of-function mutations in the skin barrier gene, filaggrin (FLG). Despite its longstanding clinical use and efficacy, the molecular mechanism of coal tar therapy is unknown. Using organotypic skin models with primary keratinocytes from AD patients and controls, we found that coal tar activated the aryl hydrocarbon receptor (AHR), resulting in induction of epidermal differentiation. AHR knockdown by siRNA completely abrogated this effect. Coal tar restored filaggrin expression in FLG-haploinsufficient keratinocytes to wild-type levels, and counteracted Th2 cytokine-mediated downregulation of skin barrier proteins. In AD patients, coal tar completely restored expression of major skin barrier proteins, including filaggrin. Using organotypic skin models stimulated with Th2 cytokines IL-4 and IL-13, we found coal tar to diminish spongiosis, apoptosis, and CCL26 expression, all AD hallmarks. Coal tar interfered with Th2 cytokine signaling via dephosphorylation of STAT6, most likely due to AHR-regulated activation of the NRF2 antioxidative stress pathway. The therapeutic effect of AHR activation herein described opens a new avenue to reconsider AHR as a pharmacological target and could lead to the development of mechanism-based drugs for AD.

Molecular dermatology comes of age

Groundbreaking advances on the molecular and cellular physiological and physiopathological skin processes, including the complete sequencing of the genome of several species and the increased availability of gene-modified organisms, paved the way to firmly establishing molecular approaches and methods in experimental, translational, and clinical dermatology. As a result, newly developed experimental ex vivo assays and animal models prove exquisite tools for addressing fundamental physiological cutaneous processes and pathogenic mechanisms of skin diseases. A plethora of new findings that were generated using these experimental tools serve as a strong basis for intense translational research efforts aiming at developing new, specific, and sensitive diagnostic tests and efficient "personalized" therapies with less side-effects. Consequently, a broad array of molecular diagnostic tests and therapies for a wide spectrum of skin diseases ranging from genodermatoses through skin neoplasms, allergy, inflammatory and autoimmune diseases, are already routinely used in the clinical dermatology practice. This article highlights several major developments in molecular experimental and clinical dermatology.

Histamine suppresses epidermal keratinocyte differentiation and impairs skin barrier function in a human skin model

Background

Defects in keratinocyte differentiation and skin barrier are important features of inflammatory skin diseases like atopic dermatitis. Mast cells and their main mediator histamine are abundant in inflamed skin and thus may contribute to disease pathogenesis.

Methods

Human primary keratinocytes were cultured under differentiation-promoting conditions in the presence and absence of histamine, histamine receptor agonists and antagonists. The expression of differentiation-associated genes and epidermal junction proteins was quantified by real-time PCR, Western blot, and immunofluorescence labeling. The barrier function of human skin models was tested by the application of biotin as tracer molecule.

Results

The addition of histamine to human keratinocyte cultures and organotypic skin models reduced the expression of the differentiation-associated proteins keratin 1/10, filaggrin, and loricrin by 80–95%. Moreover, the addition of histamine to skin models resulted in the loss of the granular layer and thinning of the epidermis and stratum corneum by 50%. The histamine receptor H1R agonist, 2-pyridylethylamine, suppressed keratinocyte differentiation to the same extent as did histamine. Correspondingly, cetirizine, an antagonist of H1R, virtually abrogated the effect of histamine. The expression of tight junction proteins zona occludens-1, occludin, claudin-1, and claudin-4, as well as that of desmosomal junction proteins corneodesmosin and desmoglein-1, was down-regulated by histamine. The tracer molecule biotin readily penetrated the tight junction barrier of skin cultures grown in the presence of histamine, while their diffusion was completely blocked in nontreated controls.

Conclusions

Our findings suggest a new mechanism by which mast cell activation and histamine release contribute to skin barrier defects in inflammatory skin diseases.

Management of difficult-to-treat atopic dermatitis

Atopic dermatitis is a complex disorder caused by the interplay between multiple genetic and environmental factors. Particularly in patients with severe disease, the effect is not just an itchy rash but also the secondary effects on the psychological well-being of the patient and their carers, particularly disturbed sleep. The aim of this review is to provide health care professionals with a holistic approach to the management of difficult-to-treat atopic dermatitis, defined as atopic dermatitis seemingly unresponsive to simple moisturizers and mild potency (classes VI and VII) topical corticosteroids. The critical importance of education and advice is emphasized, as is the seminal role of secondary bacterial infection and polyclonal T-cell activation in causing acute flares in patients with severe, generalized disease. In atypical cases or those that do not respond to treatment, alternative diagnoses should be considered.

Filaggrin-dependent secretion of sphingomyelinase protects against staphylococcal α-toxin-induced keratinocyte death

BACKGROUND

The skin of patients with atopic dermatitis (AD) has defects in keratinocyte differentiation, particularly in expression of the epidermal barrier protein filaggrin. AD skin lesions are often exacerbated by Staphylococcus aureus-mediated secretion of the virulence factor α-toxin. It is unknown whether lack of keratinocyte differentiation predisposes to enhanced lethality from staphylococcal toxins.

OBJECTIVE

We investigated whether keratinocyte differentiation and filaggrin expression protect against cell death induced by staphylococcal α-toxin.

METHODS

Filaggrin-deficient primary keratinocytes were generated through small interfering RNA gene knockdown. RNA expression was determined by using real-time PCR. Cell death was determined by using the lactate dehydrogenase assay. Keratinocyte cell survival in filaggrin-deficient (ft/ft) mouse skin biopsies was determined based on Keratin 5 staining. α-Toxin heptamer formation and acid sphingomyelinase expression were determined by means of immunoblotting.

RESULTS

We found that filaggrin expression, occurring as the result of keratinocyte differentiation, significantly inhibits staphylococcal α-toxin-mediated pathogenicity. Furthermore, filaggrin plays a crucial role in protecting cells by mediating the secretion of sphingomyelinase, an enzyme that reduces the number of α-toxin binding sites on the keratinocyte surface. Finally, we determined that sphingomyelinase enzymatic activity directly prevents α-toxin binding and protects keratinocytes against α-toxin-induced cytotoxicity.

CONCLUSIONS

The current study introduces the novel concept that S aureus α-toxin preferentially targets and destroys filaggrin-deficient keratinocytes. It also provides a mechanism to explain the increased propensity for S aureus-mediated exacerbation of AD skin disease.

Atopic dermatitis 2.0: from the clinical phenotype to the molecular taxonomy and stratified medicine

Atopic dermatitis (AD) is a paradigmatic inflammatory chronic skin disease. As for other chronic skin diseases, (i) the spectrum of the clinical phenotype and severity as well as (ii) the genetic background and (iii) the underlying mechanisms strongly suggest a high degree of pathophysiological heterogeneity yet leading to a similar clinical pattern, that is, the eczematous skin lesion, but showing distinct progression patterns. This review suggests to exploit the recent knowledge about AD for a novel approach proposing a tentative first molecular taxonomy of this disease based on the genotype and endophenotype. The consequences in terms of personalized prevention and management are delineated.

Increase in short-chain ceramides correlates with an altered lipid organization and decreased barrier function in atopic eczema patients

A hallmark of atopic eczema (AE) is skin barrier dysfunction. Lipids in the stratum corneum (SC), primarily ceramides, fatty acids, and cholesterol, are crucial for the barrier function, but their role in relation to AE is indistinct. Filaggrin is an epithelial barrier protein with a central role in the pathogenesis of AE. Nevertheless, the precise causes of AE-associated barrier dysfunction are largely unknown. In this study, a comprehensive analysis of ceramide composition and lipid organization in nonlesional SC of AE patients and control subjects was performed by means of mass spectrometry, infrared spectroscopy, and X-ray diffraction. In addition, the skin barrier and clinical state of the disease were examined. The level of ceramides with an extreme short chain length is drastically increased in SC of AE patients, which leads to an aberrant lipid organization and a decreased skin barrier function. Changes in SC lipid properties correlate with disease severity but are independent of filaggrin mutations. We demonstrate for the first time that changes in ceramide chain length and lipid organization are directly correlated with the skin barrier defects in nonlesional skin of AE patients. We envisage that these insights will provide a new therapeutic entry in therapy and prevention of AE.

Topical antihistamines display potent anti-inflammatory activity linked in part to enhanced permeability barrier function

Systemic antagonists of the histamine type 1 and 2 receptors (H1/2r) are widely used as anti-pruritics and central sedatives, but demonstrate only modest anti-inflammatory activity. Because many inflammatory dermatoses result from defects in cutaneous barrier function, and because keratinocytes express both Hr1 and Hr2, we hypothesized that H1/2r antagonists might be more effective, if they were used topically to treat inflammatory dermatoses. Topical H1/2r antagonists additively enhanced permeability barrier homeostasis in normal mouse skin by: i) stimulation of epidermal differentiation, leading to thickened cornified envelopes; and ii) enhanced epidermal lipid synthesis and secretion. Since barrier homeostasis was enhanced to a comparable extent in mast cell-deficient mice, with no further improvement following application of topical H1/2r antagonists, H1/2r antagonists likely oppose mast cell-derived histamine. In four immunologically-diverse, murine disease models, characterized by either inflammation alone (acute irritant contact dermatitis, acute allergic contact dermatitis), or by prominent barrier abnormalities (subacute allergic contact dermatitis, atopic dermatitis), topical H1/2r agonists aggravated, while H1/2r antagonists improved inflammation and/or barrier function. The apparent ability of topical H1r/2r antagonists to target epidermal H1/2r could translate into increased efficacy in the treatment of inflammatory dermatoses, likely due to decreased inflammation and enhanced barrier function. These results could shift current paradigms of antihistamine utilization from a predominantly-systemic to a topical approach.

DNA methylation of the filaggrin gene adds to the risk of eczema associated with loss-of-function variants

BACKGROUND

Loss-of-function variants within the filaggrin gene (FLG) are associated with a dysfunctional skin barrier that contributes to the development of eczema. Epigenetic modifications, such as DNA methylation, are genetic regulatory mechanisms that modulate gene expression without changing the DNA sequence.

OBJECTIVES

To investigate whether genetic variants and adjacent differential DNA methylation within the FLG gene synergistically act on the development of eczema.

METHODS

A subsample (n = 245, only females aged 18 years) of the Isle of Wight birth cohort participants (n = 1456) had available information for FLG variants R501X, 2282del4 and S3247X and DNA methylation levels for 10 CpG sites within the FLG gene. Log-binomial regression was used to estimate the risk ratios (RRs) of eczema associated with FLG variants at different methylation levels.

RESULTS

The period prevalence of eczema was 15.2% at age 18 years and 9.0% of participants were carriers (heterozygous) of FLG variants. Of the 10 CpG sites spanning the genomic region of FLG, methylation levels of CpG site 'cg07548383' showed a significant interaction with FLG sequence variants on the risk for eczema. At 86% methylation level, filaggrin haploinsufficient individuals had a 5.48-fold increased risk of eczema when compared to those with wild type FLG genotype (P-value = 0.0008).

CONCLUSIONS

Our novel results indicated that the association between FLG loss-of-function variants and eczema is modulated by DNA methylation. Simultaneously assessing the joint effect of genetic and epigenetic factors within the FLG gene further highlights the importance of this genomic region for eczema manifestation.

The anti-inflammatory effect of alloferon on UVB-induced skin inflammation through the down-regulation of pro-inflammatory cytokines

UVB irradiation can induce biological changes in the skin, modulate immune responses and activate inflammatory reactions leading to skin damage. Alloferon, which is isolated from the blood of an experimentally infected insect, the blow fly Calliphora vicina, is known for its anti-viral and anti-tumor activities in mice model. However, the effect of alloferon against UVB irradiation and its specific mechanism are still unknown. In this study, we investigated the effect of alloferon on UVB-induced cutaneous inflammation in a human keratinocyte cell line, HaCaT. RPA and ELISA data showed that alloferon decreased the production of UVB-induced pro-inflammatory cytokines, such as IL-1α, IL-1β, IL-6 and IL-18, both on the mRNA and protein level. Western blot analysis was done to determine if alloferon regulates the MAPK signaling pathway since the MAPK signaling pathway is activated by numerous inflammatory mediators and environmental stresses including UVB irradiation. Alloferon inhibited the activation of p38 mitogen-activated protein kinase (MAPK) induced by UVB irradiation. Furthermore, the topical application of alloferon on the UVB exposed skin of hairless mice showed that alloferon treatment significantly inhibited an increase in epithelial thickness in chronic UVB-irradiated mouse skin. These findings suggest that alloferon has significant anti-inflammatory effects not only on UVB-induced inflammation in the human keratinocyte cell line, HaCaT, but also on mouse skin.

Synthesis of porcine pCLCA2 protein during late differentiation of keratinocytes of epidermis and hair follicle inner root sheath

Despite the discovery of the widely expressed CLCA (chloride channel regulators, calcium-activated) proteins more than 15 years ago, their seemingly diverse functions are still poorly understood. With the recent generation of porcine animal models for cystic fibrosis (CF), members of the porcine CLCA family are becoming of interest as possible modulators of the disease in the pig. Here, we characterize pCLCA2, the porcine ortholog of the human hCLCA2 and the murine mCLCA5, which are the only CLCA members expressed in the skin. Immunohistochemical studies with a specific antibody against pCLCA2 have revealed a highly restricted pCLCA2 protein expression in the skin. The protein is strictly co-localized with filaggrin and trichohyalin in the granular layer of the epidermis and the inner root sheath of the hair follicles, respectively. No differences have been observed between the expression patterns of wild-type pigs and CF transmembrane conductance regulator(-/-) pigs. We speculate that pCLCA2 plays an as yet undefined role in the structural integrity of the skin or, possibly, in specialized functions of the epidermis, including barrier or defense mechanisms.

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.

Nicotinic acetylcholine receptor stimulation impairs epidermal permeability barrier function and recovery and modulates cornified envelope proteins

AIM

To characterize how nicotinic acetylcholine receptors (nAChRs) influence epidermal barrier function and recovery following prolonged stress or direct nAChR activation or antagonism.

MAIN METHODS

Mice were subjected to psychological stress or treated topically with nAChR agonist or antagonist for 3 days. We assessed barrier permeability and recovery by measuring transepidermal water loss (TEWL) before and after barrier disruption. In parallel, we analyzed the production and localization of several epidermal cornified envelope proteins in mouse skin and in human EpiDerm™ organotypic constructs stimulated with a nAChR agonist (nicotine) and/or a nAChR selective antagonist (α-bungarotoxin).

KEY FINDINGS

We determined that psychological stress in mice impairs barrier permeability function and recovery, an effect that is reversed by application of the α7 selective nAChR antagonist, α-bungarotoxin (Bung). In the absence of stress, both topical nicotine or Bung treatment alone impaired barrier permeability. We further observed that stress, topical nicotine, or topical Bung treatment in mice influenced the abundance and/or localization of filaggrin, loricrin, and involucrin. Similar alterations in these three major cornified envelope proteins were observed in human EpiDerm™ cultures.

SIGNIFICANCE

Perceived psychological stress and nicotine usage can both initiate or exacerbate several dermatoses by altering the cutaneous permeability barrier. Modulation of nAChRs by topical agonists or antagonists may be used to improve epidermal barrier function in skin diseases associated with defects in epidermal barrier permeability.

Atopic dermatitis: a candidate for disease-modifying strategy

The concept of disease modification has been introduced to define the therapeutic strategies aimed to break, stop, or reverse the natural course of a chronic invalidating disease. This strategy is tightly related to the biomarker-based stratification of affected patients using genetic and other biological markers. With regard to the progress in understanding the genetic background of atopic dermatitis (AD), its natural history and its pivotal role in the emergence of allergic asthma, the time is mature to foster the research field of biomarkers in AD and to consider the elaboration of disease-modifying strategies in the management of AD with the goal to stop or even reverse the atopic march.

Chronically relapsing pruritic dermatitis in the rats treated as neonate with capsaicin; a potential rat model of human atopic dermatitis

BACKGROUND

The pathophysiological mechanisms underlying chronic pruritic skin diseases, e.g. atopic dermatitis (AD), and effective therapies remain elusive due to the paucity of animal models. Recently, we rediscovered that injection of capsaicin into rat pups resulted in vigorous scratching behavior and chronically relapsing AD-like cutaneous lesions well into adulthood.

OBJECTIVES

To characterize the chronic pruritic dermatitis induced by neonatal capsaicin treatment.

METHODS

Capsaicin (50mg/kg) was given to rat pups subcutaneously within 48 h after birth, and then scratching behavior, dermatitis and pathophysiological changes of rat skin were investigated chronologically.

RESULTS

Neonatal capsaicin treatment led to not only severe scratching and cutaneous lesions but also a large number of pathophysiological changes in the skin, such as histopathological changes including the deficiency of epidermal filaggrin expression, increases in the number of mast cells, levels of tissue NGF and Th2 cytokine mRNA, impaired skin barrier function and colonization with S. aureus. In addition, we observed the hyperproduction of serum IgE, which is clinically similar to the pathophysiology seen in the patients with atopic dermatitis. During the follow-up observation, the rats showed the alternative periods of relapsing and remitting skin lesions.

CONCLUSION

Injection of capsaicin into rat pups results in chronically relapsing pruritic dermatitis, similar to human AD. Therefore, we think neonatal capsaicin treatment could be a useful model for studying human AD and for the development of novel therapeutic drugs.

Staphylococcus aureus α-toxin modulates skin host response to viral infection

BACKGROUND

Patients with atopic dermatitis (AD) with a history of eczema herpeticum have increased staphylococcal colonization and infections. However, whether Staphylococcus aureus alters the outcome of skin viral infection has not been determined.

OBJECTIVE

We investigated whether S aureus toxins modulated host response to herpes simplex virus (HSV) 1 and vaccinia virus (VV) infections in normal human keratinocytes (NHKs) and in murine infection models.

METHODS

NHKs were treated with S aureus toxins before incubation of viruses. BALB/c mice were inoculated with S aureus 2 days before VV scarification. Viral loads of HSV-1 and VV were evaluated by using real-time PCR, a viral plaque-forming assay, and immunofluorescence staining. Small interfering RNA duplexes were used to knockdown the gene expression of the cellular receptor of α-toxin, a disintegrin and metalloprotease 10 (ADAM10). ADAM10 protein and α-toxin heptamers were detected by using Western blot assays.

RESULTS

We demonstrate that sublytic staphylococcal α-toxin increases viral loads of HSV-1 and VV in NHKs. Furthermore, we demonstrate in vivo that the VV load is significantly greater (P < .05) in murine skin inoculated with an α-toxin-producing S aureus strain compared with murine skin inoculated with the isogenic α-toxin-deleted strain. The viral enhancing effect of α-toxin is mediated by ADAM10 and is associated with its pore-forming property. Moreover, we demonstrate that α-toxin promotes viral entry in NHKs.

CONCLUSION

The current study introduces the novel concept that staphylococcal α-toxin promotes viral skin infection and provides a mechanism by which S aureus infection might predispose the host toward disseminated viral infections.

[Atopic dermatitis]

Atopic dermatitis (AD), or atopic eczema, is a pruriginous inflammatory dermatosis with a genetic predisposition evolving in recurrent flare-ups on a background of chronicity, affecting essentially infants and small children. The clinical phenotype of AD results from interactions between genes and susceptibility, a defect in the cutaneous barrier function (abnormalities in filaggrin and the proteins of the epidermic differentiation complex) and dysfunction of the innate and/or adaptive immune response. With its multifactorial origin, it is dependent on the TH2 lymphocyte system, with a tendency to produce immunoglobulin E (IgE) and the risk of asthma, rhinitis, or allergic conjunctivitis define an atopic susceptibility. Staphylococcus aureus colonization plays a vital role in the perpetuation of the inflammatory phenomena. The disease often regresses in older children. Its prevalence is on the rise in industrialized countries. Diagnosis is clinical, facilitated by certain criteria initially proposed by Hanifin and Rajka and then simplified by Williams. The allergological investigation is reserved for cases that are stubborn, severe, or associated with respiratory symptoms. AD is a dermatosis that evolves in erratic and often unpredictable flare-ups. AD flare-up treatment is based on local corticosteroid therapy. Maintenance therapy attempts to correct the cutaneous dryness with hydrating products whose efficacy has now been proven. Optimal management includes the family's and/or the child's comprehension of the treatment, explaining to them that the goal to reach is not only to relieve the child, but also to attempt to modify the course of the disease. AD is thus a star disease and a public health problem. The major progress made in the comprehension of the physiopathological mechanisms of AD promise targeted therapies from new biotechnologies.

Probiotics and atopic dermatitis in children

There is increasing interest in the potential beneficial role of probiotic supplementation in the prevention and treatment of atopic diseases in children. Probiotics are defined as ingested live microorganisms that, when administered in an adequate amount, confer a health benefit to the host. They are mainly represented by Lactobacilli and Bifidobacteria. Several epidemiological data demonstrate that intestinal microflora of atopic children is different from the one of healthy children. Many literature data show that probiotics may modulate the intestinal microflora composition and may have immunomodulatory effect. Based on this hypothesis, probiotics are supposed to confer benefits to allergic diseases. Administration of probiotics when a natural population of indigenous intestinal bacteria is still developing could theoretically influence immune development by favoring the balance between Th1 and Th2 inflammatory responses. For this reason, some studies have evaluated the potential impact of probiotics supplementation in the prevention of atopic dermatitis, with contrasting results. Clinical improvement in immunoglobulin (Ig)E-sensitized (atopic) eczema following probiotic supplementation has been reported in some published studies and the therapeutic effects of probiotics on atopic dermatitis seemed to be encouraging. However, as far as the usefulness of probiotics as a prevention strategy is concerned, results are still inconclusive. In fact, the clinical benefits of probiotic therapy depend upon numerous factors, such as the type of bacteria, dosing regimen, delivery method and other underlying host factors, such as age and diet. More studies are still needed to definitively prove the role of probiotics in the treatment of allergic eczema.

A novel multiplex analysis of filaggrin polymorphisms: a universally applicable method for genotyping

BACKGROUND

The filaggrin protein is expressed as profilaggrin mainly in stratum granulosum cells of the epidermis. The profilaggrin gene codes for 10-12 filaggrin repeats. The filaggrin protein is important for skin barrier function. Filaggrin deficiency due to functional null-polymorphisms affects 8-10% of the people in Northern Europe and is a strong risk factor for several diseases. Here, we describe a novel method for efficient, multiplexed genotyping of variations in the profilaggrin gene.

METHODS

Five known techniques were combined: i) allele-specific PCR, ii) PCR with tagged primers, iii) asymmetric PCR, iv) multiplex PCR, and v) hybridization of single-stranded PCR products to spectrally coded microbeads carrying tag sequences as capture probes. Asymmetry of PCR was accomplished by having the tagged and allele-specific forward primers present in limiting concentrations. Asymmetry ensured that the later PCR cycles generated only single-stranded reverse-strand products. This greatly improved the assay sensitivity and allowed for simple optimization.

RESULTS

The specificity of the tags was verified with single PCR in wildtype and homozygous samples. Only the PCR products with the appropriate anti-tag hybridized to the corresponding beads, demonstrating the specificity of the signal. The hybridization signal is strongly dependent on single-stranded PCR products. After 46 PCR cycles, double-stranded products are clearly present, but only the single-stranded products generated in later cycles hybridize to the beads and elicit the strong signals that allow for unambiguous genotyping.

CONCLUSIONS

We have tested 17,000 samples for three filaggrin polymorphisms using this method, with a call rate exceeding 99% and a reagent cost of US $ 0.75 per sample. The method is universally applicable for multiplex genotyping of e.g. hereditary hemochromatosis, lactose intolerance, or cystic fibrosis.

Editorial update on emerging treatments of atopic dermatitis

Various new agents are in the research pipeline for atopic dermatitis. These include IL-4 receptor antagonist, cis-urocanic acid, κ-opiod receptor agonist, neurokinin receptor antagonist and antimicrobial peptide. The current review updates the status of these clinical trials and provides insight into other potential molecular targets including IL-22 and TLR-2.

Filaggrin mutations and atopy: consequences for future therapeutics

Filaggrin is a key component of the epidermal differentiation complex of the stratum corneum in the epidermal layer of human skin. Loss-of-function mutations in filaggrin have been described in patients with atopic eczema and are associated with an increased risk of atopic sensitization in these individuals. Atopic eczema is the first stage of the atopic march that describes the phenomenon of increased rates of allergic rhinitis and allergic asthma observed in individuals with early atopic dermatitis. The skin barrier disruptions of atopic eczema associated with loss-of-function mutations in filaggrin are thought to provide a nidus for allergic sensitization to food and aeroallergens, which can then lead to increased allergic disease. It is on this foundation that therapies aimed at restoration of barrier function are thought to play a role, not only in the effective treatment of atopic eczema, but also in the prevention of further allergic disease development.

[New advances in atopic dermatitis]

Atopic Dermatitis (AD) is one of the most frequent chronic skin diseases. AD is characterized by a complex, heterogeneous pathogenesis. In this review, we highlight some selected aspects of the pathophysiology of AD, which have gained much attention during recent years. These aspects profoundly changed our view of the pathogenesis of AD and will have impact on its management.

Atopic diseases by filaggrin mutations and birth year

BACKGROUND

The prevalence of atopic disorders has increased in recent years. The pathogenesis is complex with genetic and environmental risk factors. Filaggrin loss-of-function mutations are common and associated with atopic disorders. We investigated whether the prevalence of filaggrin mutations increased in different birth cohorts in adults from the general population in Denmark.

METHODS

Cross-sectional questionnaire and filaggrin gene mutation (R501X and 2282del4) data from 3335 18- to 69-year-old adults were available for analyses.

RESULTS

The effect of filaggrin mutations on the prevalence of atopic diseases, albeit not statistically significant, depended mostly on birth year for atopic dermatitis (AD). A nonsignificant increase in the prevalence of filaggrin mutations was noted across birth year groups reporting AD, with 12.9% in adults born in 1936-1949 and 19.0% born in 1976-1988.

CONCLUSIONS

If confirmed in other populations, the observed increase suggests that mutation carriers have been more susceptible to environmental changes accentuating the rise in AD prevalence.

Allergic host defences

Allergies are generally thought to be a detrimental outcome of a mistargeted immune response that evolved to provide immunity to macroparasites. Here we present arguments to suggest that allergic immunity has an important role in host defence against noxious environmental substances, including venoms, haematophagous fluids, environmental xenobiotics and irritants. We argue that appropriately targeted allergic reactions are beneficial, although they can become detrimental when excessive. Furthermore, we suggest that allergic hypersensitivity evolved to elicit anticipatory responses and to promote avoidance of suboptimal environments.

The human epidermal differentiation complex: cornified envelope precursors, S100 proteins and the 'fused genes' family

  The skin is essential for survival and protects our body against biological attacks, physical stress, chemical injury, water loss, ultraviolet radiation and immunological impairment. The epidermal barrier constitutes the primordial frontline of this defense established during terminal differentiation. During this complex process proliferating basal keratinocytes become suprabasally mitotically inactive and move through four epidermal layers (basal, spinous, granular and layer, stratum corneum) constantly adapting to the needs of the respective cell layer. As a result, squamous keratinocytes contain polymerized keratin intermediate filament bundles and a water-retaining matrix surrounded by the cross-linked cornified cell envelope (CE) with ceramide lipids attached on the outer surface. These cells are concomitantly insulated by intercellular lipid lamellae and hold together by corneodesmosmes. Many proteins essential for epidermal differentiation are encoded by genes clustered on chromosomal human region 1q21. These genes constitute the 'epidermal differentiation complex' (EDC), which is divided on the basis of common gene and protein structures, in three gene families: (i) CE precursors, (ii) S100A and (iii) S100 fused genes. EDC protein expression is regulated in a gene and tissue-specific manner by a pool of transcription factors. Among them, Klf4, Grhl3 and Arnt are essential, and their deletion in mice is lethal. The importance of the EDC is further reflected by human diseases: FLG mutations are the strongest risk factor for atopic dermatitis (AD) and for AD-associated asthma, and faulty CE formation caused by TG1 deficiency causes life-threatening lamellar ichthyosis. Here, we review the EDC genes and the progress in this field.

Interplay of filaggrin loss-of-function variants, allergic sensitization, and eczema in a longitudinal study covering infancy to 18 years of age

Background

Immune specific genes as well as genes regulating the formation of skin barrier are major determinants for eczema manifestation. There is a debate as to whether allergic sensitization and filaggrin gene (FLG) variants lead to eczema or FLG variants and eczema increase the risk of allergic sensitization. To investigate the time-order between eczema and allergic sensitization with respect to FLG variants, data from a large prospective study covering infancy to late adolescence were analyzed.

Methodology/Principal Findings

Repeated measurements of eczema and allergic sensitization (documented by skin prick tests) at ages 1, 2, 4, 10, and 18 years were ascertained in the Isle of Wight birth cohort (n = 1,456). Three transition periods were analyzed: age 1-or-2 to 4, 4 to 10, and 10 to 18 years. FLG variants were genotyped in 1,150 participants. Over the three transition periods, in temporal sequence analyses of initially eczema-free participants, the combined effect of FLG variants and allergic sensitization showed a 2.92-fold (95% CI: 1.47–5.77) increased risk ratio (RR) of eczema in subsequent examinations. This overall risk was more pronounced at a younger age (transition period 1-or-2 to 4, RR = 6.47, 95% CI: 1.96–21.33). In contrast, FLG variants in combination with eczema showed a weaker, but significant, risk ratio for subsequent allergic sensitization only up to 10 years of age.

Conclusions/Significance

Taking the time order into account, this prospective study demonstrates for the first time, that a combination of FLG variants and allergic sensitization increased the risk of eczema in subsequent years. Also FLG variants interacted with eczema and increased the risk of subsequent allergic sensitization, which, was limited to the younger age. Hence, early restoration of defective skin barrier could prevent allergic sensitization and subsequently reduce the risk of eczema development.