Breach Delivery: Increased Solute Uptake Points to a Defective Skin Barrier in Atopic Dermatitis

Increased 1-Deoxysphingolipids and Skin Barrier Dysfunction in the Skin of X-ray or Ultraviolet B Irradiation and Atopic Dermatitis Lesion Could Be Prevented by Moisturizer with Physiological Lipid Mixture

Background

Skin diseases characterized by epithelial barrier dysfunction show altered sphingolipid metabolism, which results in changes in the stratum corneum intercellular lipid components and structure. Under pathological conditions, 1-deoxysphingolipids form as atypical sphingolipids from de novo sphingolipid biosynthesis.

Objective

This study investigated the potential role of 1-deoxysphingolipids in skin barrier dysfunction secondary to X-ray and ultraviolet B (UVB) irradiation in vitro and in vivo. It was also evaluated changes in the expression of 1-deoxysphingolipids in lesional human skin of atopic dermatitis.

Methods

In this study, the changes in these 1-deoxysphingolipids levels of skin and serum samples were investigated in skin barrier dysfunction associated with X-ray and UVB irradiation in vitro and in vivo.

Results

Increased 1-deoxysphingolipids were observed in cultured normal human epidermal keratinocytes after X-ray irradiation. X-ray or UVB irradiation increased the production of 1-deoxysphingosine in a reconstituted 3-dimensional (3D) skin model. Interestingly, treatment with a physiological lipid mixture (multi-lamellar emulsion contained pseudoceramide), which can strengthen the epidermal permeability barrier function, resulted in decreased 1-deoxysphingosine formation in a reconstituted 3D skin model. Further investigation using a hairless mouse model showed similar preventive effects of physiological lipid mixture against 1-deoxysphingosine formation after X-ray irradiation. An increased level of 1-dexoysphingosine in the stratum corneum was also observed in lesional skin of atopic dermatitis.

Conclusion

1-deoxysphingosine might be a novel biomarker of skin barrier dysfunction and a physiological lipid mixture treatment could prevent 1-deoxysphingosine production and consequent skin barrier dysfunction.

Glucocerebrosidase: Functions in and Beyond the Lysosome

Glucocerebrosidase (GCase) is a retaining β-glucosidase with acid pH optimum metabolizing the glycosphingolipid glucosylceramide (GlcCer) to ceramide and glucose. Inherited deficiency of GCase causes the lysosomal storage disorder named Gaucher disease (GD). In GCase-deficient GD patients the accumulation of GlcCer in lysosomes of tissue macrophages is prominent. Based on the above, the key function of GCase as lysosomal hydrolase is well recognized, however it has become apparent that GCase fulfills in the human body at least one other key function beyond lysosomes. Crucially, GCase generates ceramides from GlcCer molecules in the outer part of the skin, a process essential for optimal skin barrier property and survival. This review covers the functions of GCase in and beyond lysosomes and also pays attention to the increasing insight in hitherto unexpected catalytic versatility of the enzyme.

Clinico-etiologic profile of hand dermatitis and patch response of patients at a tertiary hospital in Lagos, Nigeria: results of a prospective observational study

BACKGROUND

Hand dermatitis is an acute or chronic inflammation of the skin of the hands from a multifactorial cause which may be endogenous, exogenous, or a combination of both. With a wide range in severity and recurrent periods of flares, it has significant impact on the quality of life of its sufferers. A history of atopy predisposes patients to hand dermatitis, but contact dermatitis, either allergic or irritant, is the more commonly implicated factor in the etiology of hand dermatitis. Patch testing is an important tool in identifying the allergen responsible for allergic hand dermatitis, and this knowledge will contribute to improved management.

AIM AND OBJECTIVES

This study was undertaken to evaluate the clinical and etiologic profile and review the patch responses of patients who presented with hand dermatitis at a foremost tertiary skin clinic in the most populous state of the most populous country in Africa.

METHODS

A prospective, observational study in which consecutive walk-in patients who fulfilled the inclusion criteria were enrolled. Ethical clearance was obtained. Study tools included self-administered questionnaires, physical examination, and patch tests (European Hermal series), amongst others. The patch tests were carried out. Results were documented, and treatment was individualized based on clinical and investigation findings. The results were collated and analyzed with SPSS^® 17.0 edition (SPSS II).

RESULTS

Hand dermatitis was seen in 177 (13.3%) patients who presented during the study period. The mean age was 34.6 + 17.4 years. Almost two-thirds of patients (119; 67.2%) had chronic hand dermatitis, while 53 (32.8%) presented acutely. Patch responses were positive in 65 (36.7%) patients with paraphenylenediamine identified as the most frequent cause. Respondents had at least one (+) response to 20 of the 28 allergens, while there was no response to eight of the allergens in the European series.

CONCLUSION

The study reveals that hand dermatitis is present in a younger age group and a variety of subtypes coexist. Locally sourced allergens are needed to improve the yield of patch responses.

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.

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.

The pro-inflammatory role of TGFβ1: a paradox?

TGFβ1 was initially identified as a potent chemotactic cytokine to initiate inflammation, but the autoimmune phenotype seen in TGFβ1 knockout mice reversed the dogma of TGFβ1 being a pro-inflammatory cytokine to predominantly an immune suppressor. The discovery of the role of TGFβ1 in Th17 cell activation once again revealed the pro-inflammatory effect of TGFβ1. We developed K5.TGFβ1 mice with latent human TGFβ1 overexpression targeted to epidermal keratinocytes by keratin 5. These transgenic mice developed significant skin inflammation. Further studies revealed that inflammation severity correlated with switching TGFβ1 transgene expression on and off, and genome wide expression profiling revealed striking similarities between K5.TGFβ1 skin and human psoriasis, a Th1/Th17-associated inflammatory skin disease. Our recent study reveals that treatments alleviating inflammatory skin phenotypes in this mouse model reduced Th17 cells, and antibodies against IL-17 also lessen the inflammatory phenotype. Examination of inflammatory cytokines/chemokines affected by TGFβ1 revealed predominantly Th1-, Th17-related cytokines in K5.TGFβ1 skin. However, the finding that K5.TGFβ1 mice also express Th2-associated inflammatory cytokines under certain pathological conditions raises the possibility that deregulated TGFβ signaling is involved in more than one inflammatory disease. Furthermore, activation of both Th1/Th17 cells and regulatory T cells (Tregs) by TGFβ1 reversely regulated by IL-6 highlights the dual role of TGFβ1 in regulating inflammation, a dynamic, context and organ specific process. This review focuses on the role of TGFβ1 in inflammatory skin diseases.

Allergic characteristics of urban schoolchildren with atopic eczema in Ghana

BACKGROUND

Atopic eczema is an increasing clinical problem in Africa.

OBJECTIVE

To determine allergic characteristics and to identify possible risk factors for eczema among schoolchildren in an urbanized area in Ghana.

PATIENTS AND METHODS

Schoolchildren aged 3-16 years with eczema were recruited. For each patient, one to three age- and sex-matched controls were selected. All children completed a questionnaire and were skin prick tested with a panel of allergens. Blood was drawn to determine the total and allergen-specific IgE. Conditional logistic regression models with the matching factors included in the model were used to calculate the odds ratios and to adjust for possible confounders.

RESULTS

A total of 52 children with eczema (27 boys and 25 girls) and 99 controls were included. Levels of total IgE were found to be 9.1 (1.1; 78.4) times more often elevated in children with eczema. This association was mainly driven by elevated IgE levels against cockroach antigen. Children with eczema were found to have 2.0 (0.87; 4.7) times more often positive skin prick tests (SPT), but this association diminished to 1.2 (0.40; 3.6) after adjustment for total IgE levels. Frequent washing with soap was identified as a risk factor for the development of eczema among these children.

CONCLUSION

Schoolchildren with eczema in Ghana were characterized by elevated IgE levels especially against cockroach antigen. The association between eczema and positive SPT was much weaker suggesting immune hyporesponsiveness of the skin. After adjustment for IgE level, SPT were less suitable to distinguish children with and without eczema.

TLR2 expression is increased in rosacea and stimulates enhanced serine protease production by keratinocytes

A diverse environment challenges skin to maintain temperature, hydration, and electrolyte balance while also maintaining normal immunological function. Rosacea is a common skin disease that manifests unique inflammatory responses to normal environmental stimuli. We hypothesized that abnormal function of innate immune pattern recognition could explain the enhanced sensitivity of patients with rosacea, and observed that the epidermis of patients with rosacea expressed higher amounts of Toll-like receptor 2 (TLR2) than normal patients. Increased expression of TLR2 was not seen in other inflammatory skin disorders such as atopic dermatitis or psoriasis. Overexpression of TLR2 on keratinocytes, treatment with TLR2 ligands, and analysis of TLR2-deficient mice resulted in a calcium-dependent release of kallikrein 5 from keratinocytes, a critical protease involved in the pathogenesis of rosacea. These observations show that abnormal TLR2 function may explain enhanced inflammatory responses to environmental stimuli and can act as a critical element in the pathogenesis of rosacea.

Periorbital dermatitis: causes, differential diagnoses and therapy

Periorbital dermatitis is common and frequently difficult to treat. Patients with periorbital dermatitis often suffer severely because their disease is in such a visible location. Because of the variety of clinical appearance, the differential diagnostic considerations are often difficult. We examined the causes of periorbital dermatitis and compared the data of 88 patients from the Department of Dermatology, University Hospital Erlangen to those of the German IVDK (Information Network of the Departments of Dermatology). Between 1999 and 2004, predominant causes of periorbital dermatitis were allergic contact dermatitis (Erlangen 44%, IVDK 32%), atopic eczema (Erlangen 25%, IVDK 14%), airborne contact dermatitis (Erlangen 10%, IVDK 2%) and irritant contact dermatitis (Erlangen 9%, IVDK 8%). Less frequent causes for secondary eczematous periocular skin lesions were periorbital rosacea, allergic conjunctivitis or psoriasis vulgaris. Female gender, atopic skin diathesis and age of 40 years and older were identified as risk factors for periocular dermatitis. Common elicitors of periorbital allergic contact dermatitis were leave-on cosmetic products (face cream, eye shadow) and eye drops with the usual allergens being fragrances, preservatives and drugs. Exact identification of relevant contact allergens and allergen elimination are essential for successful treatment. Calcineurin inhibitors are the first-line therapy for facial atopic eczema. They may be also effective in periocular eczematous lesions of other origins although they are not approved for such use.

Atopic eczema and the filaggrin story

The discovery that null mutations in the filaggrin gene (FLG) are associated with atopic eczema represents the single most significant breakthrough in understanding the genetic basis of this complex disorder. The association has been replicated in multiple independent studies during the past 2 years with the use of various methodologies, from populations in Europe, the United States, and Japan. Filaggrin plays a key role in epidermal barrier function, and its association with atopic eczema emphasizes the importance of barrier dysfunction in eczema pathogenesis. This review aims to summarize the current state of knowledge regarding the role of FLG mutations in ichthyosis vulgaris, atopic eczema, and other skin disorders, with an emphasis on potential clinical applications. Further research is needed to clarify the precise role of filaggrin in skin and systemic atopic disease, to pave the way for novel therapeutic interventions.

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

BACKGROUND

Polymorphisms in the serine protease inhibitor gene serine peptidase inhibitor Kazal type 5 (SPINK5) and the serine protease kallikrein-related peptidase 7 gene (KLK7) appear to confer risk to eczema in some cohorts, but these findings have not been widely replicated. These genes encode proteins thought to be involved in the regulation of posttranslation processing of filaggrin (FLG), the strongest identified genetic risk factor for eczema to date.

OBJECTIVES

We sought to clarify the individual risk of eczema conferred by the SPINK5 polymorphism rs2303067 (Glu420Lys) and a previously described insertion in the 3' untranslated region of KLK7 and to examine potential epistatic effects between these variants and FLG mutations.

METHODS

Initially, we examined the effects of these polymorphisms and FLG in 486 unrelated patients from a German family-based study, an additional 287 German patients, and 418 unrelated Irish/English patients with eczema (n for 3 genes studied = 1191 vs 4544 control subjects). We then additionally studied the SPINK5 polymorphism and FLG mutations in 1583 patients with eczema from the Avon Longitudinal Study of Parents and Children cohort (sample size for 2 genes studied = 2774 vs 10,607 control subjects).

RESULTS

No association was seen with the SPINK5 or KLK7 variants in the case-control analysis; however, a weaker effect was observed for the SPINK5 variant with maternal transmission in the family-based study. No interactions were seen between the polymorphisms in KLK7, SPINK5, and FLG.

CONCLUSION

The SPINK5 420LysSer mutation confers a risk of eczema when maternally inherited but is not a major eczema risk factor. The KLK7 insertion appears to confer no risk of eczema. We found no interaction between the SPINK5 risk allele or the putative KLK7 risk allele and FLG mutations.

Filaggrin loss-of-function mutations and association with allergic diseases

Human skin constitutes a highly organized barrier against environmental agents. Its unrestricted function depends on a complex interplay between multiple proteins and lipids expressed in the terminally differentiating epithelium. Recently, attention has been drawn to the protein filaggrin, an integral part of the epidermis that plays a key role in engineering and maintaining the barrier function. Common loss-of-function mutations within the filaggrin gene have been demonstrated to cause ichthyosis vulgaris, one of the most common heritable disorders of cornification, and to represent major risk factors for atopic eczema and secondary allergic diseases. The observations on filaggrin provide striking new insights into the etiology of atopic diseases and might pave the way for the development of new therapeutic approaches.

The filaggrin story: novel insights into skin-barrier function and disease

Recent reports have uncovered the key role of the protein filaggrin in maintaining an effective skin barrier against the external environment. Loss-of-function mutations in the profilaggrin gene (FLG) are common and are present in up to 10% of the population. These mutations are the cause of the semi-dominant skin-scaling disorder ichthyosis vulgaris and are a major risk factor for the development of atopic dermatitis. The discovery of these mutations also provides new data concerning the genetics of atopic asthma as well as intriguing insight into disease mechanisms of systemic allergies involving antigen exposure in skin with defective barrier function. Collectively, these novel findings have significant implications for the classification and future clinical management of patients with atopic and allergic diseases.

How to improve skin notation. Position paper from a workshop

The ICOH Scientific Committee on Occupational and Environmental Dermatoses organized an International Workshop on "Dermal risk assessment at workplace" with the aim of focussing on the different ways of approaching the concept of skin notation (S) for chemicals. The Workshop participants presented their ideas on several aspects of S such as the problems related to the absorption through the compromised skin, the different approaches to S and models that can be used as alternatives to S. Participants agreed to produce a position paper with the goal of exploring the actions needed to improve the S system towards international harmonization. They consider that further discussions are needed to obtain an international consensus, but at the same time they believe that by improving and harmonizing systems for setting S we can make an important contribution to improving health of people with potential dermal exposure to chemicals at work.

Hand Eczema Is Common and Multifactorial

Clinicians agree that hand eczema is multifactorial, although there are many uncertainties regarding causative factors. Atopic dermatitis is assumed to be a major risk factor, whereas the role of allergies is overestimated. Twin studies may shed light on the contribution of other endogenous, possibly genetic factors versus the role of exposure to environmental agents, with the latter being amenable to prevention and intervention.