Potential role of reduced environmental UV exposure as a driver of the current epidemic of atopic dermatitis

Exploring the role of breastfeeding, antibiotics, and indoor environments in preschool children atopic dermatitis through machine learning and hygiene hypothesis

The increasing global incidence of atopic dermatitis (AD) in children, especially in Western industrialized nations, has attracted considerable attention. The hygiene hypothesis, which posits that early pathogen exposure is crucial for immune system development, is central to understanding this trend. Furthermore, advanced machine learning algorithms have provided fresh insights into the interactions among various risk factors. This study investigates the relationship between early childhood antibiotic use, the duration of exclusive breastfeeding, indoor environmental factors, and child AD. By integrating machine learning techniques with the hygiene hypothesis, we aim to assess and interpret the significance of these risk factors. In this community-based case-control study with a 1:4 matching design, we evaluated the prevalence of AD in preschool-aged children. Data were collected via questionnaires completed by the parents of 771 children diagnosed with AD, matched with controls based on gender, age, and ethnicity. Univariate analyses identified relevant characteristics, which were further examined using multivariable logistic regression to calculate odds ratios (ORs). Stratified analyses assessed confounders and interactions, while the significance of variables was determined using a machine learning model. Renovating the dwelling during the mother's pregnancy (OR = 1.50; 95% CI 1.15-1.96) was identified as a risk factor for childhood AD. Additionally, antibiotic use three or more times during the child's first year (OR = 1.92; 95% CI 1.29-2.85) increased the risk of AD, independent of the parents' history of atopic disease and the child's mode of birth. Moreover, exclusive breastfeeding for four months or more (OR = 1.59; 95% CI 1.17-2.17) was identified as a risk factor for AD, particularly in the group without a maternal history of atopic disease. In contrast, having older siblings in the family (OR = 0.76; 95% CI 0.63-0.92) and low birth weight (OR = 0.62; 95% CI 0.47-0.81) were identified as protective factors against AD. Machine learning modeling indicated that the duration of exclusive breastfeeding, having older siblings, low birth weight, and parental history of AD or allergic rhinitis are key predictors of childhood AD. Our findings support the broader interpretation of the hygiene hypothesis. Machine learning analysis highlights the key role of the hygiene hypothesis and underscores the need for future AD prevention and healthcare initiatives focusing on children with a parental history of AD or allergic rhinitis. Moreover, minimizing antibiotic overuse may be essential for preventing AD in children. Further research is necessary to elucidate the impact and mechanisms of exclusive breastfeeding on AD to instruct maternal and child healthcare practices.

Association between sun-protective behaviours and psoriasis in US adults in the National Health and Nutrition Examination Survey, 2009-2014: a cross-sectional study

OBJECTIVE

To evaluate the association between sun-protective behaviours and psoriasis in a nationally representative sample of US adults.

DESIGN

Analysis of cross-sectional data.

SETTING

National Health and Nutrition Examination Survey (NHANES), 2009-2014.

PARTICIPANTS

A total of 9735 participants aged 20-59 years with available data on psoriasis, sun-protective behaviours and covariates were included in the analysis.

OUTCOME MEASURES

Information on sun-protective behaviours (staying in the shade, wearing long sleeves and using sunscreen) and psoriasis was obtained from questionnaires in the NHANES database. Logistic regression models and subgroup analyses were employed to investigate the association between sun-protective behaviours and psoriasis.

RESULTS

After adjusting for sociodemographic variables, body mass index (BMI), alcohol drinking status, smoking status, sun sensitivity and time spent outdoors in the multivariable logistic regression model, moderate wearing of long sleeves was negatively associated with psoriasis (OR, 0.55; 95% CI 0.33 to 0.90, p=0.02), while frequent wearing showed no significant relationship. There was no significant association between staying in the shade and psoriasis, regardless of frequency. Subgroup analyses stratified by age, gender, race/ethnicity and smoking status revealed no significant associations in most groups, but moderate wearing of long sleeves was found to be negatively associated with psoriasis among those aged 20-39 years (OR, 0.42; 95% CI 0.18 to 0.98, p=0.04), among non-Hispanic white individuals (OR, 0.52; 95% CI 0.28 to 0.97, p=0.04) and among non-smokers (OR, 0.49; 95% CI 0.25 to 0.95, p=0.04), as it was among women in terms of overall sun protection (OR, 0.58; 95% CI 0.35 to 0.97, p=0.04). However, among non-Hispanic white individuals (staying in the shade: OR, 1.69; 95% CI 1.00 to 2.84, p=0.049) and former/current smokers (overall: OR, 3.28; 95% CI 1.41 to 7.63, p=0.009), frequent sun protection was positively associated with psoriasis.

CONCLUSIONS

Moderate sun-protective behaviours among US adults were found to be negatively associated with psoriasis. However, among non-Hispanic white individuals and former/current smokers, frequent sun protection was positively associated with psoriasis. Future studies with rigorous study design could further explore and validate the potential reasons for these associations to better inform evidence-based behavioural recommendations that protect human health.

Associations of ambient air pollution and daily outpatient visits for pediatric atopic dermatitis in Shanghai, China

Limited evidence was available on ambient air pollution and pediatric atopic dermatitis (AD). The study aimed to evaluate the associations between short-term exposure to air pollutants and outpatient visits for pediatric AD. From 2016-2018, we collected data on six criteria air pollutants (PM2.5, PM10, NO2, SO2, CO and O3) and daily outpatient visits for pediatric AD in 66 hospitals, covering all districts in Shanghai, China. The over-dispersed Poisson generalized additive model (GAM) was applied to fit the associations of criteria air pollutants with hospital visits. Two-pollutant models were fitted and stratified analyses by sex, age and season were conducted. We identified 477,833 outpatient visits for pediatric AD. Each interquartile range (IQR) increase in PM2.5 (IQR: 30.9 μg/m3), PM10 (8.9 μg/m3), NO2 (25.5 μg/m3), SO2 (5.8 μg/m3) and CO (0.283 mg/m3) on the concurrent day was significantly associated with increments of 2.08 % (95 % CI: 0.53 %, 3.65 %), 2.53 % (95 % CI: 0.87 %, 4.22 %), 8.14 % (95 % CI: 6.24 %, 10.08 %), 5.67 % (95 % CI: 3.58 %, 7.80 %), and 2.27 % (95 % CI: 0.70 %, 3.87 %) in pediatric AD outpatient visits, respectively. The effects of NO2 remained robust after adjustment for other air pollutants. The exposure-response curves for PM2.5 and PM10 were steeper for moderate-lower concentrations, with a flatten curves at high concentration; nearly linear relationships were found for NO2. Higher associations of NO2 exposure on AD were detected in children under 6 years old (p=0.01); and we observed larger effect of air pollutants in cool seasons (p<0.001 for PM2.5, PM10, NO2 and CO; p=0.043 for SO2). This study indicated that short-term exposure to air pollution could increase risk of outpatient visits for pediatric AD.

Impact of climate change on atopic dermatitis: A review by the International Eczema Council

Atopic dermatitis (AD), the most burdensome skin condition worldwide, is influenced by climatic factors and air pollution; however, the impact of increasing climatic hazards on AD remains poorly characterized. Leveraging an existing framework for 10 climatic hazards related to greenhouse gas emissions, we identified 18 studies with evidence for an impact on AD through a systematic search. Most climatic hazards had evidence for aggravation of AD the impact ranged from direct effects like particulate matter-induced AD exacerbations from wildfires to the potential for indirect effects like drought-induced food insecurity and migration. We then created maps comparing the past, present, and future projected burden of climatic hazards to global AD prevalence data. Data are lacking, especially from those regions most likely to experience more climatic hazards. We highlight gaps important for future research: understanding the synergistic impacts of climatic hazards on AD, long-term disease activity, the differential impact on vulnerable populations, and how basic mechanisms explain population-level trends.

Skin Barrier in Atopic Dermatitis

A compromised permeability barrier is a hallmark of atopic dermatitis (AD). Localized to the outermost skin layer, the stratum corneum (SC) is critically dependent on terminal differentiation of epidermal keratinocytes, which transform into protein-rich corneocytes surrounded by extracellular lamellae of unique epidermal lipids, conferring permeability barrier function. These structures are disrupted in AD. A leaky barrier is prone to environmental insult, which in AD elicits type 2-dominant inflammation, in turn resulting in a vicious cycle further impairing the SC structure. Therapies directed at enforcing SC structure and anti-inflammatory strategies administered by topical and systemic route as well as UV therapy have differential effects on the permeability barrier. The expanding armamentarium of therapeutic modalities for AD treatment warrants optimization of their effects on permeability barrier function.

Efficacy and safety of narrowband ultraviolet B versus combined ultraviolet A/narrowband ultraviolet B phototherapy in the treatment of chronic atopic dermatitis: A randomised double-blind study

Phototherapy is a useful treatment modality for atopic dermatitis (AD). This is a prospective randomised double-blind study comparing the clinical efficacy of combined ultraviolet-A (UVA)/narrowband ultraviolet-B (NBUVB) versus NBUVB phototherapy in the treatment of chronic AD. Patients with moderate-to-severe AD were randomised to receive either UVA/NBUVB or NBUVB phototherapy twice weekly over 12 weeks. At baseline, weeks 6 and 12, Eczema Area And Severity Index (EASI), itch score and adverse effects were assessed. At baseline and week 12, disease-related quality of life was evaluated using the Dermatology Life Quality Index (DLQI). Nine patients were randomised to receive UVA/NBUVB and 10 received NBUVB. At week 12, both groups showed significant improvement in EASI and itch scores (p < 0.05). Significant improvement in DLQI was seen in the UVA/NBUVB arm (p = 0.009) with a trend towards improvement in the NBUVB arm (p = 0.11). The efficacy of both modalities were comparable, as were reported adverse effects aside from skin dryness which was higher in the NBUVB arm (40% vs. 0%, p = 0.033). Combined UVA/NBUVB and NBUVB phototherapy have comparable clinical efficacy and safety in the treatment of chronic AD. NBUVB may induce greater skin dryness.

The Imprint of Exposome on the Development of Atopic Dermatitis across the Lifespan: A Narrative Review

Atopic dermatitis (AD) is a chronic inflammatory skin condition that affects more than 200 million people worldwide, including up to 20% of children and 10% of the adult population. Although AD appears frequently in childhood and often continues into adulthood, about 1 in 4 adults develop the adult-onset disease. The prenatal period, early childhood, and adolescence are considered critical timepoints for the development of AD when the exposome results in long-lasting effects on the immune system. The exposome can be defined as the measure of all the exposures of an individual during their lifetime and how these exposures relate to well-being. While genetic factors could partially explain AD onset, multiple external environmental exposures (external exposome) in early life are implicated and are equally important for understanding AD manifestation. In this review, we describe the conceptual framework of the exposome and its relevance to AD from conception and across the lifespan. Through a spatiotemporal lens that focuses on the multi-level phenotyping of the environment, we highlight a framework that embraces the dynamic complex nature of exposome and recognizes the influence of additive and interactive environmental exposures. Moreover, we highlight the need to understand the developmental origins of AD from an age-related perspective when studying the effects of the exposome on AD, shifting the research paradigm away from the per se categorized exposome factors and beyond clinical contexts to explore the trajectory of age-related exposome risks and hence future preventive interventions.

Skin Microbiota Profiles from Tape Stripping and Skin Biopsy Samples of Patients with Psoriasis Treated with Narrowband Ultraviolet B

Purpose

Although the pathogenesis of psoriasis involves the dermis, most previous studies collected samples using the swab technique. A recent study examining the microbiomes obtained via both skin biopsies and swabs revealed a significant difference in normal skin. We hypothesized that the microbiome profile of patients with psoriasis from tape stripping and skin biopsy might be different. This study sought to contribute to microbiome research on psoriasis by investigating the changes in the microbiome during narrowband ultraviolet B (NBUVB) therapy by comparing the results from the different sampling techniques of tape stripping and skin biopsy.

Patients and Methods

Twenty-three participants, including 14 patients with chronic plaque psoriasis and nine healthy controls, were recruited, and nine patients with psoriasis completed 20-sessions of NBUVB treatment. Skin microbiota from both techniques was analyzed using the 16S rRNA gene at baseline and after treatment.

Results

A clear difference was observed between the results from the two sampling techniques. Alpha diversity of the microbiota obtained from tape stripping was higher than that of the microbiota from skin biopsy, whereas beta diversity was clustered into two groups by sampling technique. The microbiome was altered during NBUVB treatment using both sampling techniques.

Conclusion

Different sampling techniques resulted in different microbiome profiles in patients with psoriasis. Tape stripping and swabs are feasible procedures and are mostly used in psoriasis and other skin microbiome studies; however, skin biopsy may also expand our understanding of psoriasis and other skin diseases that pathophysiology involves deeper to the dermis or subcutaneous tissue.

Optimizing emollient therapy for skin barrier repair in atopic dermatitis

OBJECTIVE

We compared the principal characteristics of over-the-counter moisturizers with physiological lipid-based barrier repair therapy (BRT).

DATA SOURCES

An extended literature reported that moisturizers are considered standard ancillary therapy for anti-inflammatory skin disorders such as atopic dermatitis (AD). Additional studies have found that physiological lipid-based BRT can comprise effective, stand-alone therapy for pediatric AD.

RESULTS

Not all moisturizers are beneficial-some negatively impact skin function, and in doing so, they risk inducing or exacerbating inflammation in patients with AD. The frequent self-reported occurrences of sensitive skin in patients with AD could reflect the potential toxicity of such formulations. A still unanswered question is whether improper formulations could also prove to be counterproductive in other types of sensitive skin, such as rosacea. In contrast, we found how physiological lipid-based BRT (when comprised of the 3 key stratum corneum lipids in sufficient quantities and at an appropriate molar ratio) can correct the barrier abnormality, thereby reducing inflammation in AD and possibly in other inflammatory dermatoses, such as adult eczemas and possibly even psoriasis.

CONCLUSION

We provide guidelines for the appropriate dispensation of moisturizers and physiological lipid-based, BRT for the treatment of AD. Both over-the-counter (Atopalm) and prescription (EpiCeram) products are available in the United States with these characteristics.

Pre- and Postnatal Vitamin D Status and Allergy Outcomes in Early Childhood

The dramatic increase in the prevalence of allergic disease in recent decades reflects environmental and behavioural changes that have altered patterns of early immune development. The very early onset of allergic diseases points to the specific vulnerability of the developing immune system to environmental changes and the development of primary intervention strategies is crucial to address this unparalleled burden. Vitamin D is known to have immunomodulatory functions. While allergic disease is multifactorial, associations with reduced sunlight exposure have led to the hypothesis that suboptimal vitamin D levels during critical early periods may be one possible explanation. Interventions to improve vitamin D status, especially in early life, may be the key to allergic disease prevention.

Vitamin D, skin filaggrin, allergic sensitization, and race

BACKGROUND

In addition to its involvement in both the innate and adaptive immune systems, vitamin D has been found to affect keratinocyte function and proliferation, suggesting a possible role for vitamin D in cutaneous allergic sensitization.

OBJECTIVE

To explore the role of circulating vitamin D levels in allergic sensitization.

METHODS

Serum 25-hydroxyvitamin D (25(OH)D) levels were measured in a subset of children (N = 323) enrolled in the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children cohort, a prospective early life cohort of children with atopic dermatitis. Allergic sensitization was determined using skin prick testing, and FLG expression in the keratinocytes was measured by quantitative polymerase chain reaction. Multiple Poisson regression was used to evaluate interaction effects between serum 25(OH)D levels and FLG expression with sensitization load as the outcome.

RESULTS

Black participants had significantly lower mean levels of serum 25(OH)D compared with non-Black participants (29.3 vs 32.9 ng/mL; P < .001). FLG expression and sensitization load were negatively correlated in non-Black participants with 25(OH)D levels less than 27.2 ng/mL (Rho = -0.45; P = .02). No association between FLG expression and sensitization load was found in Black participants or participants with 25(OH)D levels greater than or equal to 27.2 ng/mL. Multiple Poisson regression models confirmed that 25(OH)D levels interact with FLG expression to affect sensitization load in non-Black participants.

CONCLUSION

Despite lower vitamin D levels in Black participants, sensitization load was associated with nonlesional skin FLG expression in non-Black, but not Black, children with low vitamin D levels. Thus, a complex interplay of factors determines the impact of vitamin D on allergic sensitization.

Solar UVR and Variations in Systemic Immune and Inflammation Markers

The characterization of the effects of solar UVR on a broad set of circulating markers in systemic immunity and inflammation may provide insight into the mechanisms responsible for the UVR associations observed for several benign and malignant diseases. We examined the associations between exposure to solar UVR and circulating levels of 78 markers among 1,819 individuals aged 55–74 years who participated in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial using multiplex assays. Solar UVR was derived by linking the geocoded locations of 10 screening centers across the continental United States and the date of blood draw to the National Solar Radiation Database from 1993 to 2005. We assessed associations between ambient solar UVR and dichotomized marker levels using adjusted weighted logistic regression models and applied a 5% false discovery rate criterion to P-values. UVR exposure was associated (P < 0.05) with 9 of the 78 markers. CCL27, CCL4, FGF2, GM-CSF, IFN-γ, soluble IL4R, IL-7, and IL-11 levels were lower with increasing UVR tertile, with adjusted ORs ranging from 0.66 to 0.80, and the significant association for CCL27 withstood multiple comparison correction. In contrast, CRP levels were elevated with increasing UVR. Solar UVR was associated with alterations in systemic immune and inflammation marker levels.

Association of the incidence of atopic dermatitis until 3 years old with birth month and with sunshine duration and humidity in the first 6 months of life: Japan Environment and Children's Study

OBJECTIVE

To compare the incidence of atopic dermatitis in children aged from 6 months to 3 years across birth seasons and climate conditions.

DESIGN

Cohort study.

SETTING

Fifteen regional centres across Japan.

PARTICIPANTS

A total of 100 304 children born from 2011 to 2014.

EXPOSURE

Birth month, and mean sunshine duration (short/long) and humidity (high/low) in the first 6 months of life.

PRIMARY OUTCOME MEASURE

Incidence of atopic dermatitis.

RESULTS

The highest incidence of atopic dermatitis was in children born in the months of October to December. The lowest incidence of atopic dermatitis was in the months of April to June and in periods with a long duration of sunshine and high humidity. Low humidity was significantly associated with a higher incidence of atopic dermatitis. However, this significant difference disappeared when the birth season and parental history of allergic disease were considered in multivariate analysis.

CONCLUSIONS

In Japan, being born in the late autumn to early winter months is associated with a risk of developing atopic dermatitis until the age of 3 years. Sunshine duration and humidity from birth to 6 months of age are not associated with the incidence of atopic dermatitis.

Repurposing Belinostat for Alleviation of Atopic Dermatitis

Atopic dermatitis (AD) is a highly prevalent chronic inflammatory skin disease that is characterized by intense pruritus, seriously affecting patients' quality of life. Its pathophysiology, which involves both the adaptive and innate immune responses as well as skin barrier defects, is still poorly understood. We recently identified a microRNA, miR-335, as a key driver of keratinocyte differentiation and cornification, which is essential for the establishment of a healthy skin barrier. However, expression of miR-335 is lost in AD, leading to barrier defect. We further demonstrated how belinostat, a histone deacetylase inhibitor, can effectively restore miR-335 and resolve the barrier defect in a dry skin model. Here, in this commentary, we highlight the role of belinostat in the treatment of AD and discuss the need for more research into crosstalk between epigenetic and non-coding RNA-based regulation, as well as possible therapeutic strategies targeting the epigenome.

Atopic dermatitis among children and adolescents in the Arctic region - a systematic review and meta-analysis

The prevalence of atopic dermatitis (AD) varies across the globe, and the clinical phenotype with racial background and ethnicity. AD in the Arctic region has only been scarcely studied. We performed a systematic review and meta-analysis to examine the prevalence, clinical manifestations and risk factors for AD among children and adolescents in the Arctic. Three medical databases PubMed, Embase and Web of Science were screened. All studies published between 1990 to 2020 with epidemiologic data on AD in children and adolescents in the Arctic region, were included. Data were extracted and a meta-analysis was performed to obtain pooled proportions and incidences with 95% confidence intervals (CI). We identified 21 studies from 8 different Arctic regions with 31 403 participants. The cumulative incidence of AD was 23% (95% CI 20-26) and 1-year prevalence was 19% (95% CI 15-25). The incidence of AD was higher in the Arctic parts of Scandinavia and lower in Greenland and Russia. Children of indigenous descent had a slightly lower incidence of AD (19%, 95% CI 13-26) compared to the overall population. The dominant phenotype of AD was mild to moderate flexural dermatitis with facial involvement. Asthma and allergic rhinitis were common and observed in 20-30% of children with AD. In conclusion, AD is highly prevalent in the Arctic, but varies between regions and races. Indigenous children living in less urbanized countries appear to have a slightly lower risk of AD. Future studies should confirm this and examine whether this correlation relates to behavioural differences or genetic signature.

A deep dive into UV-based phototherapy: Mechanisms of action and emerging molecular targets in inflammation and cancer

UV-based phototherapy (including psoralen plus UVA (PUVA), UVB and UVA1) has a long, successful history in the management of numerous cutaneous disorders. Photoresponsive diseases are etiologically diverse, but most involve disturbances in local (and occasionally systemic) inflammatory cells and/or abnormalities in keratinocytes that trigger inflammation. UV-based phototherapy works by regulating the inflammatory component and inducing apoptosis of pathogenic cells. This results in a fascinating and complex network of simultaneous events-immediate transcriptional changes in keratinocytes, immune cells, and pigment cells; the emergence of apoptotic bodies; and the trafficking of antigen-presenting cells in skin-that quickly transform the microenvironment of UV-exposed skin. Molecular elements in this system of UV recognition and response include chromophores, metabolic byproducts, innate immune receptors, neurotransmitters and mediators such as chemokines and cytokines, antimicrobial peptides, and platelet activating factor (PAF) and PAF-like molecules that simultaneously shape the immunomodulatory effects of UV and their interplay with the microbiota of the skin and beyond. Phototherapy's key effects-proapoptotic, immunomodulatory, antipruritic, antifibrotic, propigmentary, and pro-prebiotic-promote clinical improvement in various skin diseases such as psoriasis, atopic dermatitis (AD), graft-versus-host disease (GvHD), vitiligo, scleroderma, and cutaneous T-cell lymphoma (CTCL) as well as prevention of polymorphic light eruption (PLE). As understanding of phototherapy improves, new therapies (UV- and non-UV-based) are being developed that will modify regulatory T-cells (Treg), interact with (resident) memory T-cells and /or utilize agonists and antagonists as well as antibodies targeting soluble molecules such as cytokines and chemokines, transcription factors, and a variety of membrane-associated receptors.

Glycerol 85% efficacy on atopic skin and its microbiome: a randomized controlled trial with clinical and bacteriological evaluation

Background: Treating atopic dermatitis (AD) is still a challenge. The staphylococcal skin load is known to aggravate AD. Narrow band ultraviolet B (NB-UVB) and glycerol in low concentration (20-40%) are established therapies for AD. NB-UVB has proven antimicrobial actions, while high concentration glycerol (85-100%) showed similar effects in vitro but has not been clinically tested.Objective: To evaluate the efficacy and tolerability of concentrated glycerol 85% compared to NB-UVB in patients with AD, as assessed by clinical improvement and reduction of staphylococcal colonization of the skin.Methods: 30 patients with mild to moderate AD were randomized into either NB-UVB or glycerol 85% group. Patients were treated for one month and followed for an additional month. Swabs were taken from the skin and nose to be cultured on mannitol-salt agar for Staphylococci and quantified to determine Colony Forming Units.Results: Both groups showed statistically insignificant microbial changes and statistically significant clinical improvement after treatment. The results were comparable between both groups.Conclusions: Concentrated glycerol 85% is a cheap effective readily accessible alternative for phototherapy in patients with mild-moderate AD who cannot access the facility. Reduction of staphylococcal skin load seems to be involved, but its role is minimal.

Noncanonical autophagy in dermal dendritic cells mediates immunosuppressive effects of UV exposure

BACKGROUND

Control of the inflammatory response is critical to maintaining homeostasis, and failure to do so contributes to the burden of chronic inflammation associated with several disease states. The mechanisms that underlie immunosuppression, however, remain largely unknown. Although defects in autophagy machinery have been associated with inflammatory pathologic conditions, we now appreciate that autophagic components participate in noncanonical pathways distinct from classical autophagy. We have previously demonstrated that LC3-associated phagocytosis (LAP), a noncanonical autophagic process dependent on Rubicon (rubicon autophagy regulator [RUBCN]), contributes to immunosuppression.

OBJECTIVE

We used Rubcn^-/- mice to examine the role of the LAP pathway in mediating the UV-induced immunotolerant program in a model of contact hypersensitivity (CHS).

METHODS

Flow cytometry and transcriptional analysis were used to measure immune cell infiltration and activation in the skin of Rubcn^+/+ and Rubcn^-/- mice during the CHS response.

RESULTS

Here, we demonstrate that LAP is required for UV-induced immunosuppression and that UV exposure induces a broadly anti-inflammatory transcriptional program dependent on Rubicon. Rubcn^-/- mice are resistant to UV-induced immunosuppression and instead display exaggerated inflammation in a model of CHS. Specifically, RUBCN deficiency in CD301b⁺ dermal dendritic cells results in their increased antigen presentation capacity and subsequent hyperactivation of the CD8⁺ T-cell response.

CONCLUSIONS

LAP functions to limit the immune response and is critical in maintaining the balance between homeostasis and inflammation.

By protecting against cutaneous inflammation, epidermal pigmentation provided an additional advantage for ancestral humans

Pigmentation evolved in ancestral humans to protect against toxic, ultraviolet B irradiation, but the question remains: "what is being protected?" Because humans with dark pigmentation display a suite of superior epidermal functions in comparison with their more lightly pigmented counterparts, we hypothesized and provided evidence that dark pigmentation evolved in Africa to support cutaneous function. Because our prior clinical studies also showed that a restoration of a competent barrier dampens cutaneous inflammation, we hypothesized that resistance to inflammation could have provided pigmented hominins with yet another, important evolutionary benefit. We addressed this issue here in two closely related strains of hairless mice, endowed with either moderate (Skh2/J) or absent (Skh1) pigmentation. In these models, we showed that (a) pigmented mice display a markedly reduced propensity to develop inflammation after challenges with either a topical irritant or allergen in comparison with their nonpigmented counterparts; (b) visible and histologic evidence of inflammation was paralleled by reduced levels of pro-inflammatory cytokines (i.e., IL-1α and INFα); (c) because depigmentation of Skh2/J mouse skin enhanced both visible inflammation and pro-inflammatory cytokine levels after comparable pro-inflammatory challenges, the reduced propensity to develop inflammation was directly linked to the presence of pigmentation; and (d) furthermore, in accordance with our prior work showing that pigment production endows benefits by reducing the surface pH of skin, acidification of albino (Skh1) mouse skin also protected against inflammation, and equalized cytokine levels to those found in pigmented skin. In summary, pigmentation yields a reduced propensity to develop inflammation, consistent with our hypothesis that dark pigmentation evolved in ancestral humans to provide a suite of barrier-linked benefits that now include resistance to inflammation.

The Association Between Season of Birth and Atopic Dermatitis in the Northern Hemisphere: A Systematic Review and Meta-Analysis

BACKGROUND

Cold and dry climate negatively affects skin barrier functions. This could explain the higher incidence of atopic dermatitis (AD) in Northern countries distant from the equator, as well as the general worsening of AD in Northern European winter months. Although it has been suggested that fall and winter birth is associated with AD, this remains unknown.

OBJECTIVES

To examine whether the prevalence of AD is associated with season of birth.

METHODS

We conducted a systematic review and meta-analysis. Two reviewers independently searched 3 databases. Study quality was assessed using a Newcastle-Ottawa scale. Study heterogeneity was assessed with Cochrane Q and I² statistics. Odds ratios with 95% CIs were calculated. Publication bias was assessed using funnel plots.

RESULTS

The systematic review identified 23 relevant articles of which 9 articles were included in the meta-analysis. Among a total of 726,378 children aged 0 to 12 years, the overall pooled prevalence of AD was 12.9%. The pooled prevalence of AD was 15.4% (95% CI, 12.1%-19.1%), 14.9% (95% CI, 12.0%-18.1%), 12.7% (95% CI, 10.2%-15.4%), and 13.7% (95% CI, 10.8%-17.0%), among children born in the fall, winter, spring, and summer, respectively. AD was significantly associated with fall (odds ratio, 1.16; 95% CI, 1.06-1.28; P = .0018) and winter (odds ratio, 1.15; 95% CI, 1.04-1.27; P = .0076) birth compared with spring birth.

CONCLUSIONS

Although a positive and significant association was observed between being born in fall and winter and developing AD on the Northern hemisphere, there is a need for additional and better-designed studies to understand the effect of seasonal changes on the risk of AD.

The influence of treatment in alpine and moderate maritime climate on the composition of the skin microbiome in patients with difficult to treat atopic dermatitis

BACKGROUND

The skin microbiome, characterized by an overgrowth of Staphylococcus aureus, plays an important role in the pathogenesis of atopic dermatitis (AD). Multidisciplinary treatment in alpine climate is known for its positive effect on disease severity in children with AD and can result in a different immune response compared with moderate maritime climate. However, the effect on the composition of the skin microbiome in AD is unknown.

OBJECTIVE

To determine the effect of treatment in alpine climate and moderate maritime climate on the microbiome for lesional and non-lesional skin in children with difficult to treat AD.

RESULTS

Alpine climate treatment led to a significant change in the microbiota on lesional skin, whereas no significant change was found after moderate maritime climate. On both lesional and non-lesional skin, we observed a significant increase in Shannon diversity and a significant decrease in both Staphylococcus abundance and S aureus load after alpine climate treatment. The decrease in S aureus was significantly larger on lesional skin following alpine climate treatment compared with moderate maritime climate treatment. Staphylococcus epidermidis load was stable over time.

CONCLUSIONS AND CLINICAL RELEVANCE

Alpine climate treatment leads to significant changes in the composition of the skin microbiome in children with AD, mainly caused by a reduction in the Staphylococcus genus. This study shows new perspectives in the potential mode of action for therapies in AD.

Predicting Skin Barrier Dysfunction and Atopic Dermatitis in Early Infancy

BACKGROUND

Dry skin is associated with increased transepidermal water loss (TEWL), which has been found to precede atopic dermatitis (AD) in childhood.

OBJECTIVE

We aimed to identify parental, prenatal, and perinatal predictive factors of dry skin, high TEWL, and AD at 3 months of age, and to determine if dry skin or high TEWL at 3 months can predict AD at 6 months.

METHODS

From the Preventing Atopic Dermatitis and Allergies in children prospective birth cohort study, we included 1150 mother-child pairs. Dry skin, TEWL, and eczema were assessed at 3- and 6-month investigations. Eczema, used as a proxy for AD, was defined as the presence of eczematous lesions, excluding differential diagnoses to AD. High TEWL was defined as TEWL >90th percentile, equaling 11.3 g/m²/h. Potential predictive factors were recorded from electronic questionnaires at 18- and 34-week pregnancy and obstetric charts.

RESULTS

Significant predictive factors (P < .05) for dry skin at 3 months were delivery >38 gestational weeks and paternal age >37 years; for high TEWL, male sex, birth during winter season, and maternal allergic disease; and for eczema, elective caesarean section, multiparity, and maternal allergic diseases. Dry skin without eczema at 3 months was predictive for eczema at 6 months (adjusted odds ratio: 1.92, 95% confidence interval: 1.21-3.05; P = .005), whereas high TEWL at 3 months was not.

CONCLUSION

In early infancy, distinct parental- and pregnancy-related factors were predictive for dry skin, high TEWL, and AD. Dry skin at 3 months of age was predictive for AD 3 months later.

Direct infant ultraviolet light exposure is associated with eczema and immune development: a critical appraisal

AIM

Rueter et al. aimed to 'determine the effects of early postnatal vitamin D supplementation on infant eczema and immune development'.

SETTING AND DESIGN

This was a double-blind randomized placebo-controlled trial with an additional nonrandomized exploratory analysis on the effects of ultraviolet (UV) exposure led from a hospital setting.

STUDY EXPOSURE

Vitamin D (400 iU daily) drops or placebo drops (coconut and palm kernel oil) were allocated randomly to 195 infants born to families with a first-degree relative with atopic disease. Eighty-six of these infants were allocated personal UV dosimeters in a nonrandomized fashion to measure UV light (290-380 nm) exposure until 3 months of age.

OUTCOMES

Eczema and wheeze were assessed at 3 and 6 months, and 25 immune function markers were assessed at 6 months of age. Infant vitamin D levels and immune functions were measured at 6 months of age.

RESULTS

Although vitamin D levels were significantly greater in infants in the intervention group than in those in the placebo group at 3 and 6 months of age, there was no difference in eczema between groups at either time point (10·0% vs. 6·7% at 3 months and 21·8 vs. 19·3% at 6 months for the vitamin D and placebo groups, respectively). In the subset of infants given a dosimeter, those with eczema had less UV light exposure (median 555 J m^-2 ) than infants who did not develop eczema (median 998 J m^-2 ). Across the 25 immune functions, UV light exposure was inversely correlated with interleukin-2, granulocyte macrophage colony-stimulating factor and eotaxin production by Toll-like receptor ligands.

CONCLUSIONS

Vitamin D supplementation in high-risk infants increased vitamin D levels but did not reduce eczema. Exploratory post-hoc analyses in a nonrandomized subset showed an association between greater direct UV light exposure and reduction of eczema. The authors claim that their 'findings indicate that UV light exposure appears more beneficial than vitamin D supplementation as an allergy prevention strategy in early life'.

The Role of the Environmental Risk Factors in the Pathogenesis and Clinical Outcome of Atopic Dermatitis

Atopic dermatitis (AD) prevalence is rising worldwide. Literature data suggest the incidence of AD in developing countries is gradually getting close to that of developed ones, in which AD affects 20% of the paediatric population. Such an increment, associated with significant variations in prevalence among the various countries, underlines the importance of environmental factors in the disease onset. Among these, great importance is given to hygiene, intestinal microbiota, exposure to bacterial endotoxins, outdoor living with contact to animals, atmospheric pollution, weather, and diet. Genetic (alteration of the skin barrier function) as well as immunologic factors concur with the environmental ones. Only the systematical study of all these elements can best elucidate AD epidemiology.

Optimization of placebo use in clinical trials with systemic treatments for atopic dermatitis: an International Eczema Council survey-based position statement

BACKGROUND

As novel systemic therapeutics for patients with atopic dermatitis (AD) are developed, ethical and methodological concerns regarding placebo-controlled-trials (PCT) have surfaced.

OBJECTIVE

To guide the design and implementation of PCT in AD, focusing on trials with systemic medications.

METHODS

A subgroup of the International Eczema Council (IEC) developed a consensus e-survey, which was disseminated to IEC members.

RESULTS

The response rate was 43/82 (52%). Consensus was reached on 24/27 statements and on 3/11 options from multiple-selection statements, including: performing monotherapy studies in proof-of-concept phases; avoiding concomitant topical corticosteroids or calcineurin inhibitors until a predefined timepoint as rescue (borderline consensus); selection of sites and assessors with recognized expertise in AD clinical trials; clear definition and identification of baseline disease severity; minimizing time and proportion of patients on placebo; using daily emollients with several options provided; instigating open-label extension studies for enrolment after a predefined timepoint; and including outcomes which set a higher bar for disease clearance.

CONCLUSION

Conducting PCT in AD requires balancing several, sometimes opposing principles, including ethics, methodology, regulatory requirements and real-world needs. This paper can provide a framework for conducting PCT with systemic medications for patients with AD.

Direct infant UV light exposure is associated with eczema and immune development

BACKGROUND

Suboptimal vitamin D levels during critical periods of immune development have emerged as an explanation for higher rates of allergic diseases associated with industrialization and residing at higher latitudes.

OBJECTIVE

We sought to determine the effects of early postnatal vitamin D supplementation on infant eczema and immune development.

METHODS

By using a double-blind randomized controlled trial, newborn infants were randomized to receive vitamin D supplementation (400 IU/d) or a placebo until 6 months of age. Some infants also wore personal UV dosimeters to measure direct UV light (290-380 nm) exposure. Infant vitamin D levels were measured at 3 and 6 months of age. Eczema, wheeze, and immune function outcomes were assessed at 6 months of age.

RESULTS

At 3 (P < .01) and 6 (P = .02) months of age, vitamin D levels were greater for the vitamin D-supplemented group than the placebo group, but there was no difference in eczema incidence between groups. Infants with eczema were found to have had less UV light exposure (median, 555 Joules per square meter [J/m²; interquartile range, 322-1210 J/m²]) compared with those without eczema (median, 998 J/m² [interquartile range, 676-1577 J/m²]; P = .02). UV light exposure was also inversely correlated with IL-2, GM-CSF, and eotaxin production to Toll-like receptor ligands.

CONCLUSION

This study is the first to demonstrate an association between greater direct UV light exposures in early infancy with lower incidence of eczema and proinflammatory immune markers by 6 months of age. Our findings indicate that UV light exposure appears more beneficial than vitamin D supplementation as an allergy prevention strategy in early life.

Moisturizers versus Current and Next-Generation Barrier Repair Therapy for the Management of Atopic Dermatitis

We compare here the principal characteristics of over-the-counter moisturizers with physiologic lipid-based barrier repair therapy. Moisturizers are standard ancillary therapy for anti-inflammatory skin disorders, like atopic dermatitis (AD), and can attenuate the emergence of AD, the initial step in the "atopic march." But not all moisturizers are beneficial; some can make skin function worse, and can even induce inflammation, possibly accounting for the frequent occurrence of "sensitive skin" in women. In contrast, physiologic lipid-based barrier repair therapy, if comprised of the 3 key stratum corneum lipids, in sufficient quantities and at an appropriate molar ratio, can correct the barrier abnormality and reduce inflammation in AD, and perhaps in other inflammatory dermatoses.

Human Microbiome: Composition and Role in Inflammatory Skin Diseases

This review focuses on recent evidences about human microbiome composition and functions, exploring the potential implication of its impairment in some diffuse and invalidating inflammatory skin diseases, such as atopic dermatitis, psoriasis, hidradenitis suppurativa and acne. We analysed current scientific literature, focusing on the current evidences about gut and skin microbiome composition and the complex dialogue between microbes and the host. Finally, we examined the consequences of this dialogue for health and skin diseases. This review highlights how human microbes interact with different anatomic niches modifying the state of immune activation, skin barrier status, microbe-host and microbe-microbe interactions. It also shows as most of the factors affecting gut and skin microorganisms' activity have demonstrated to be effective also in modulating chronic inflammatory skin diseases. More and more evidences demonstrate that human microbiome plays a key role in human health and diseases. It is to be expected that these new insights will translate into diagnostic, therapeutic and preventive measures in the context of personalized/precision medicine.

The interplay between risk and preventive factors explains why some children develop allergies to certain foods and others show tolerance

AIM

A number of studies have clarified the tolerance mechanisms and risk factors for food allergies. Our aim was to explore food allergy symptoms by target organs, together with the risk factors and how to prevent food allergies and induce tolerance.

METHODS

We carried out a thorough review of studies on paediatric food allergies published in the last decade.

RESULTS

Food allergy symptoms may affect the skin, nasal and oral mucosa, conjunctivae, gastrointestinal tract or, in severe cases, the respiratory tract and cardiovascular organs. Immunoglobulin E (IgE)-mediated symptoms appear rapidly after exposure to the offending allergen, whereas non-IgE-mediated symptoms are typically delayed. The immunological processes involved in non-IgE-mediated allergic reactions are poorly understood, but T-cell activation is probably involved. There are several factors that influence the food sensitisation process: genetic predisposition, disruption of oral tolerance development, impaired skin barriers in atopic eczema and the influence of microbiomes.

CONCLUSION

The symptoms and intensity of reactions vary considerably with regard to food allergies, and these depend on the individual's concomitant immunological and regulatory mechanisms. There is strong evidence that dietary diversity is important for children, even when they come from families with high allergy risks.

Mussel adhesive Protein-conjugated Vitronectin (fp-151-VT) Induces Anti-inflammatory Activity on LPS-stimulated Macrophages and UVB-irradiated Keratinocytes

BACKGROUND

Skin inflammation and dermal injuries are a major clinical problem because current therapies are limited to treating established scars, and there is a poor understanding of healing mechanisms. Mussel adhesive proteins (MAPs) have great potential in many tissue engineering and biomedical applications. It has been successfully demonstrated that the redesigned hybrid type MAP (fp-151) can be utilized as a promising adhesive biomaterial. The aim of this study was to develop a novel recombinant protein using fp-151 and vitronectin (VT) and to elucidate the anti-inflammatory effects of this recombinant protein on macrophages and keratinocytes.

METHODS

Lipopolysaccharide (LPS) was used to stimulate macrophages and UVB was used to stimulate keratinocytes. Inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 were analyzed by Western Blot. Inflammatory cytokines and NO and ROS production were analyzed.

RESULT

In macrophages stimulated by LPS, expression of the inflammatory factors iNOS, COX-2, and NO production increased, while the r-fp-151-VT-treated groups had suppressed expression of iNOS, COX-2, and NO production in a dose-dependent manner. In addition, keratinocytes stimulated by UVB and treated with r-fp-151-VT had reduced expression of iNOS and COX-2. Interestingly, in UVB-irradiated keratinocytes, inflammatory cytokines, such as interleukin (IL)-1b, IL-6, and tumor necrosis factor (TNF)-a, were significantly reduced by r-fp-151-VT treatment.

CONCLUSIONS

These results suggest that the anti-inflammatory activity of r-fp-151-VT was more effective in keratinocytes, suggesting that it can be used as a therapeutic agent to treat skin inflammation.

A Systematic Review of the Prevalence of Atopic Diseases in Children on the Arabian Peninsula

OBJECTIVES

To study the available data on the prevalence of atopic diseases and food allergy in children living on the Arabian Peninsula.

METHODS

A PubMed search for relevant published articles was conducted using the following search terms singly or in combination: "atopy," "atopic disease," "atopic disorder," "International Study of Asthma and Allergies in Childhood," "ISAAC," "asthma," "allergic rhinitis," "eczema," and "food allergy" in combination with the names of countries of the Arabian Peninsula (Kuwait, United Arab Emirates, Bahrain, Qatar, Oman, Kingdom of Saudi Arabia, and Yemen). The search captured studies published up to December 2017.

RESULTS

A total of 8 publications reporting prevalence rates of any type of atopic disease in children in 7 countries of the Arabian Peninsula were retrieved. The prevalence of all atopic disorders was comparable between countries of the Arabian Peninsula. The overall prevalence of asthma ranged from 8 to 23%, while the reported prevalence of eczema ranged from 7.5 to 22.5%. There was great variation in the prevalence rates of rhinoconjunctivitis, which ranged from 6.3 to 30.5%. The prevalence of food allergy (8.1%) was reported for 1 country only, the United Arab Emirates.

CONCLUSIONS

The reported overall rates of atopic disease in countries of the Arabian Peninsula are comparable to those reported in other industrialized countries. This is probably related to the good economic status in the region, which is reflected in the living standards and lifestyle. Further, genetic factors, such as factors related to gene polymorphism, and the high rate of consanguinity in the region may contribute to the higher prevalence of atopic diseases.

Food allergy and atopic dermatitis: Prediction, progression, and prevention

The rising burden of allergic diseases in childhood requires a compelling need to identify individuals at risk for atopy very early in life or even predict the onset of food allergy and atopic dermatitis since pregnancy. The development and clinical phenotypes of atopic diseases in childhood depend on a complex interaction between genetic and environmental factors, such as allergen exposure, air pollution, and infections. Preventive strategies may include avoidance measures, diet supplements, and early complementary food introduction. Overall, the management of allergic diseases has been improving to date toward a patient's tailored approach. This review will cover the current understanding of risk factors, prediction, and management of food allergy and atopic dermatitis in childhood and discuss how these may contribute to the modification of the natural history of food allergy and atopic dermatitis.

The Skin as a Route of Allergen Exposure: Part II. Allergens and Role of the Microbiome and Environmental Exposures

PURPOSE OF REVIEW

This second part of the article aims to highlight recent contributions in the literature that enhance our understanding of the cutaneous immune response to allergen.

RECENT FINDINGS

Several properties of allergens facilitate barrier disruption and cutaneous sensitization. There is a strong epidemiologic relationship between the microbiome, both the gut and skin, and atopic dermatitis (AD). The mechanisms connecting these two entities remain enigmatic; however, recent murine models show that commensal skin bacteria play an active role in supporting skin barrier homeostasis and defense against microbial penetration. Likewise, the association between the lack of colonization with Staph species and AD development suggests a potentially functional role for these organisms in regulating the skin barrier and response to environmental allergens. In undisrupted skin, evidence suggests that the cutaneous route may promote allergen tolerance. Properties of environmental allergens and commensal bacteria add to the complex landscape of skin immunity. Further investigation is needed to elucidate how these properties regulate the cutaneous immune response to allergen.

Advances in atopic dermatitis in 2015

This review aims to highlight recently published articles on atopic dermatitis (AD). Updated are the insights into epidemiology, pathology, diagnostics, and therapy. Epidemiologic studies have revealed a positive correlation between AD and systemic conditions, such as rheumatoid arthritis, inflammatory bowel disease, and neonatal adiposity. Pathologic findings highlight the involvement of novel barrier factors (desmoplakin and claudin), novel immune cell subsets (pathogenic effector T_H2 cells and group 2 innate lymphoid cells), and differential skewing of helper T cells (eg, T_H17 dominance in Asians with AD). As diagnostics, noninvasive examinations of the transepidermal water loss of neonates, the density of epidermal Staphylococcus species, and the gut flora might prognosticate the onset of AD. As for therapy, various methods are proposed, including conventional (petrolatum and UV) and molecule-oriented regimens targeting Janus kinase, signal transducer and activator of transcription 3, extracellular signal-regulated kinase, sirtuin 1, or aryl hydrocarbon receptor.

Cellular and molecular immunologic mechanisms in patients with atopic dermatitis

Atopic dermatitis (AD) is a complex skin disease frequently associated with other diseases of the atopic diathesis. Recent evidence supports the concept that AD can also recognize other comorbidities, such as chronic inflammatory bowel or cardiovascular diseases. These comorbidities might result from chronic cutaneous inflammation or from a common, yet-to-be-defined immunologic background leading to immune deviations. The activation of immune cells and their migration to the skin play an essential role in the pathogenesis of AD. In patients with AD, an underlying immune deviation might result in higher susceptibility of the skin to environmental factors. There is a high unmet medical need to define immunologic endotypes of AD because it has significant implications on upcoming stratification of the phenotype of AD and the resulting targeted therapies in the development of precision medicine. This review article emphasizes studies on environmental factors affecting AD development and novel biological agents used in the treatment of AD. Best evidence of the clinical efficacy of novel immunologic approaches using biological agents in patients with AD is available for the anti-IL-4 receptor α-chain antibody dupilumab, but a number of studies are currently ongoing with other specific antagonists to immune system players. These targeted molecules can be expressed on or drive the cellular players infiltrating the skin (eg, T lymphocytes, dendritic cells, or eosinophils). Such approaches can have immunomodulatory and thereby beneficial clinical effects on the overall skin condition, as well as on the underlying immune deviation that might play a role in comorbidities. An effect of these immunologic treatments on pruritus and the disturbed microbiome in patients with AD has other potential consequences for treatment.

Filaggrin loss-of-function mutations, atopic dermatitis and risk of actinic keratosis: results from two cross-sectional studies

BACKGROUND

Common loss-of-function mutations in filaggrin gene (FLG) represent a strong genetic risk factor for atopic dermatitis (AD). Homozygous mutation carriers typically display ichthyosis vulgaris (IV) and many have concomitant AD. Previously, homozygous, but not heterozygous, filaggrin gene mutations have been associated with squamous cell carcinomas.

OBJECTIVE

The first objective was to examine the association between FLG mutations and actinic keratosis (AK). The second objective was to investigate the occurrence of AK in patients with IV and AD, respectively.

METHODS

FLG mutation status in patients with AK was compared with controls from the general population. Furthermore, based on nationwide data from Danish registers, we compared the risk of AK in patients with IV, AD and psoriasis, respectively.

RESULTS

The prevalence of homozygous FLG mutations was significantly higher in the AK group (n = 4, 0.8%) in comparison with the control group (n = 18, 0.2%), whereas the prevalence of heterozygous FLG mutations was lower. In hospital registry data, patients with AD exhibited an increased risk of AK than did psoriasis controls (adjusted OR 1.46; [95% CI 1.12-1.90]), whereas no difference in risk was observed between patients with IV and AD.

CONCLUSIONS

This study indicates an increased susceptibility to AK in individuals with homozygous, but not heterozygous, FLG mutations and in patients with AD compared to psoriasis. Whether a reduction or absence of epidermal filaggrin could contribute to the susceptibility to AK in patients with IV and AD is unknown and additional research is needed to further explore this relationship.

Prevalence of atopic dermatitis in infants by domestic water hardness and season of birth: Cohort study

BACKGROUND

Atopic dermatitis (AD) appears to be more common in regions with hard domestic water and in children with a fall/winter birth. However, it is unknown whether a synergistic effect exists.

OBJECTIVE

We sought to evaluate the association between domestic water hardness and season of birth, respectively, with onset of AD within the first 18 months of life in a large Danish birth cohort.

METHODS

Of children from the Danish National Birth Cohort, 52,950 were included. History of physician-diagnosed AD and population characteristics were obtained from interviews. Birth data were obtained from the Civil Registration System, and domestic water hardness data were obtained from the Geological Survey of Denmark and Greenland. The relative prevalence (RP) of AD was calculated by using log-linear binomial regression.

RESULTS

The prevalence of AD was 15.0% (7,942/52,950). The RP of AD was 5% (RP_trend, 1.05; 95% CI, 1.03-1.07) higher for each 5° increase in domestic water hardness (range, 6.60-35.90 German degrees of hardness [118-641 mg/L]). Although the RP of AD was higher in children with a fall (RP, 1.24; 95% CI, 1.17-1.31) or winter (RP, 1.18; 95% CI, 1.11-1.25) birth, no significant interaction was observed with domestic water hardness. The population attributable risk of hard domestic water on AD was 2%.

CONCLUSION

We observed that early exposure to hard domestic water and a fall/winter birth was associated with an increase in the relative prevalence of AD within the first 18 months of life. Although the 2 exposures did not interact synergistically, a dose-response relationship was observed between domestic water hardness and AD.

The Skin Microbiome: Is It Affected by UV-induced Immune Suppression?

Human skin apart from functioning as a physical barricade to stop the entry of pathogens, also hosts innumerable commensal organisms. The skin cells and the immune system constantly interact with microbes, to maintain cutaneous homeostasis, despite the challenges offered by various environmental factors. A major environmental factor affecting the skin is ultraviolet radiation (UV-R) from sunlight. UV-R is well known to modulate the immune system, which can be both beneficial and deleterious. By targeting the cells and molecules within skin, UV-R can trigger the production and release of antimicrobial peptides, affect the innate immune system and ultimately suppress the adaptive cellular immune response. This can contribute to skin carcinogenesis and the promotion of infectious agents such as herpes simplex virus and possibly others. On the other hand, a UV-established immunosuppressive environment may protect against the induction of immunologically mediated skin diseases including some of photodermatoses such as polymorphic light eruption. In this article, we share our perspective about the possibility that UV-induced immune suppression may alter the landscape of the skin’s microbiome and its components. Alternatively, or in concert with this, direct UV-induced DNA and membrane damage to the microbiome may result in pathogen associated molecular patterns (PAMPs) that interfere with UV-induced immune suppression.

Clinical implications of new mechanistic insights into atopic dermatitis

PURPOSE OF REVIEW

The review will examine recent advances in our understanding of atopic dermatitis and how these mechanisms provide a framework for new approaches to the management of this common skin disease.

RECENT FINDINGS

The mechanisms by which epithelial skin barrier and immune responses contribute to the complex clinical phenotypes found in atopic dermatitis are being elucidated. Atopic dermatitis often precedes food allergy because reduced skin barrier function allows environmental food allergens to penetrate the skin leading to systemic allergen sensitization. There is increasing evidence that atopic dermatitis is a systemic disease. New treatments are focused on intervention in polarized immune responses leading to allergic diseases. This includes antagonism of IL-4 and IL-13 effects. Prevention strategies involve maintaining normal skin barrier function with emollients to prevent allergens and microbes from penetrating the skin.

SUMMARY

Recent work on the pathogenesis of atopic dermatitis has important implications for its clinical management, including the development of effective barrier creams and biologicals targeting specific polarized immune pathways resulting in skin inflammation.

Basis for the gain and subsequent dilution of epidermal pigmentation during human evolution: The barrier and metabolic conservation hypotheses revisited

The evolution of human skin pigmentation must address both the initial evolution of intense epidermal pigmentation in hominins, and its subsequent dilution in modern humans. While many authorities believe that epidermal pigmentation evolved to protect against either ultraviolet B (UV-B) irradiation-induced mutagenesis or folic acid photolysis, we hypothesize that pigmentation augmented the epidermal barriers by shifting the UV-B dose-response curve from toxic to beneficial. Whereas erythemogenic UV-B doses produce apoptosis and cell death, suberythemogenic doses benefit permeability and antimicrobial function. Heavily melanized melanocytes acidify the outer epidermis and emit paracrine signals that augment barrier competence. Modern humans, residing in the cooler, wetter climes of south-central Europe and Asia, initially retained substantial pigmentation. While their outdoor lifestyles still permitted sufficient cutaneous vitamin D3 (VD3) synthesis, their marginal nutritional status, coupled with cold-induced caloric needs, selected for moderate pigment reductions that diverted limited nutritional resources towards more urgent priorities (=metabolic conservation). The further pigment-dilution that evolved as humans reached north-central Europe (i.e., northern France, Germany), likely facilitated cutaneous VD3 synthesis, while also supporting ongoing, nutritional requirements. But at still higher European latitudes where little UV-B breaches the atmosphere (i.e., present-day UK, Scandinavia, Baltic States), pigment dilution alone could not suffice. There, other nonpigment-related mutations evolved to facilitate VD3 production; for example, in the epidermal protein, filaggrin, resulting in reduced levels of its distal metabolite, trans-urocanic acid, a potent UV-B chromophore. Thus, changes in human pigmentation reflect a complex interplay between latitude, climate, diet, lifestyle, and shifting metabolic priorities.