Exposure to gene-environment interactions before 1 year of age may favor the development of atopic dermatitis

The Interaction between the Host Genome, Epigenome, and the Gut-Skin Axis Microbiome in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease that occurs in genetically predisposed individuals. It involves complex interactions among the host immune system, environmental factors (such as skin barrier dysfunction), and microbial dysbiosis. Genome-wide association studies (GWAS) have identified AD risk alleles; however, the associated environmental factors remain largely unknown. Recent evidence suggests that altered microbiota composition (dysbiosis) in the skin and gut may contribute to the pathogenesis of AD. Examples of environmental factors that contribute to skin barrier dysfunction and microbial dysbiosis in AD include allergens, irritants, pollution, and microbial exposure. Studies have reported alterations in the gut microbiome structure in patients with AD compared to control subjects, characterized by increased abundance of Clostridium difficile and decreased abundance of short-chain fatty acid (SCFA)-producing bacteria such as Bifidobacterium. SCFAs play a critical role in maintaining host health, and reduced SCFA production may lead to intestinal inflammation in AD patients. The specific mechanisms through which dysbiotic bacteria and their metabolites interact with the host genome and epigenome to cause autoimmunity in AD are still unknown. By understanding the combination of environmental factors, such as gut microbiota, the genetic and epigenetic determinants that are associated with the development of autoantibodies may help unravel the pathophysiology of the disease. This review aims to elucidate the interactions between the immune system, susceptibility genes, epigenetic factors, and the gut microbiome in the development of AD.

Relationship between air pollution and childhood atopic dermatitis in Chongqing, China: A time-series analysis

Background

The prevalence of atopic dermatitis (AD) in children has increased substantially in China over past decades. The ongoing rise in the prevalence stresses the important role of the environmental factors in the pathogenesis of AD. However, studies evaluating the effects of air pollution on AD in children are scarce.

Objective

To quantitatively assess the association between air pollution and outpatient visits for AD in children.

Methods

In this time-series study, we collected 214,747 children of AD from January 1, 2015 to December 31, 2019 through the electronic data base in the Children's Hospital of Chongqing Medical University. The number of daily visits was treated as the dependent variable, and generalized additive models with a Poisson like distribution were constructed, controlling for relevant potential confounders and performing subgroup analyses.

Results

Each 10 μg/m³ increase in PM_2.5, PM₁₀, SO₂, NO₂ and each 1 mg/m³ increase in CO concentrations was significantly associated with a 0.7% (95% CI: 0.2, 1.3%), 0.9% (95% CI: 0.5, 1.4%), 11% (95% CI: 7.5, 14.7%), 5.5% (95% CI: 4.3, 6.7%) and 10.1% (95% CI: 2.7, 18.2%) increase of AD outpatient visits on the current day, respectively. The lag effect was found in SO₂, PM₁₀, and NO_2. The effects were stronger in cool season and age 0-3 group.

Conclusions

Our study suggests that short-term exposure to ambient air pollution contributes to more childhood AD outpatient visits in Chongqing, China.

12-month prevalence of atopic dermatitis in resource-rich countries: a systematic review and meta-analysis

There is a lack of robust prevalence estimates of atopic dermatitis (AD) globally and trends over time due to wide variation of populations and age groups studied, different study methodologies and case definitions used. We sought to characterize 12-month AD prevalence across the life span and change over time in resource-rich countries focusing on population-based studies and using a standardized AD case definition. This systematic review was conducted according to PRISMA guidelines. Medline (Ovid), Embase, WOS core collection, Cinahl, and Popline were searched for studies published since inception through August 15, 2016. Studies were synthesized using random effects meta-analysis. Sources of heterogeneity were investigated using subgroup analyses and meta-regression. From 12,530 records identified, 45 studies met the inclusion criteria. Meta-analysis with random effects revealed the 12-month period prevalence of 9.2% (95% confidence interval 8.4–10.1%). The prevalence was significantly higher among 0–5-year-old children (16.2%; 95% confidence interval 14.2–18.7%) than in older age groups. Studies using a random sampling strategy yielded lower prevalence estimates than studies relying on other sampling methods. There was no clear time trend in AD prevalence over the period of 1992–2013.

Differences in Occurrence, Risk Factors and Severity of Early-onset Atopic Dermatitis among Preterm and Term Children

This prospective birth cohort followed 150 preterm and 300 term newborns during the first year of life to assess possible differences in risk factors, age at onset, anatomical location, and severity of atopic dermatitis. Atopic dermatitis was diagnosed clinically, and severity was assessed using Eczema Area Severity Index (EASI). DNA was analysed for filaggrin gene mutations. Parents were asked about environmental exposures and emollient use. Atopic dermatitis during the first year of life was observed in 21.2% of children and was more common in term children compared with preterm children (26.7% vs 11.7%, p < 0.001), with lower age of onset (4 vs 6 months, p < 0.05) and more severe disease at onset (EASI: 4.8 vs 0.4, p < 0.0005). Environmental risk factors for atopic dermatitis were essentially similar for preterm and term born children, apart from winter and autumn births. Filaggrin gene mutations were less common in preterm than term children (4.1% vs 9.2%, p = 0.06).

The Relationship between Aeroallergen Sensitization and Chronic Cough in School-Aged Children from General Population

Objective

Determining sensitivity to allergens is an essential step in diagnosing children with allergic diseases. Chronic cough has remained poorly understood with causative triggers. The purpose of our study was to shed light on the relationship between sensitization to aeroallergens and chronic cough.

Methods

This population-based study examined children (aged 7 years to 13 years) between June and July 2016. The 1,259 children, 72 of whom (5.7%) had a chronic cough, and 1,187 of whom (94.3%) did not (controls), completed the questionnaire, but 1,051 children completed skin prick tests (SPTs) with eight aeroallergens.

Results

There were positive SPT results to at least 1 allergen in 549 children (52.2%). Sensitization to house dust mite (HDM) was most common (chronic cough = 46.9%; controls = 47.2%), followed by pollen (chronic cough = 21.9%; controls = 16.5%) in both groups, but there was no difference in allergic profile and sensitization to aeroallergen (P > 0.05 for all comparisons). Multivariable analysis with adjustment for confounding indicated that children who were in sensitization to pollen had an increased risk of chronic cough (aOR = 2.387; 95% CI: 1.115 to 5.111; P = 0.025). Multivariable analysis with adjustment for confounding indicated that children who were exposed to current smoking (aOR = 4.442; 95% CI: 1.831 to 10.776; P = 0.001) and mold (aOR = 1.988; 95% CI: 1.168 to 3.383; P = 0.011) were associated with chronic cough.

Conclusion

Sensitization to pollen should be considered as a potential contributing factor to the development of chronic cough in school-aged children.

Innate Type 2 Response to Aspergillus fumigatus in a Murine Model of Atopic Dermatitis-like Skin Inflammation

BACKGROUND

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease mediated by T helper type 2 (Th2) cells in acute phase. Group 2 innate lymphoid cells (ILCs) play a role in the initiation of the Th2 response. Although mold exposure is associated with the development of AD, studies on the underlying mechanisms are lacking. This study investigated whether group 2 ILCs are involved in inflammation in AD-like skin induced by Aspergillus fumigatus (Af).

METHODS

We investigated changes of group 2 ILCs population in Af-induced AD-like skin lesions. To induce AD-like skin lesions, Af extracts were applied to the dorsal skin of BALB/c and Rag1^-/- mice five times per week, with repeat exposures at 2-week intervals.

RESULTS

The clinical parameters were higher in the Af-treated group than in the control group. Histologic findings revealed epiderrmal and dermal thickening as well as eosinophil and mast cell infiltration into the skin of Af-treated mice. Populations of group 2 ILCs in the skin were also significantly higher in the Af-treated group. In addition, interleukin-33 mRNA expression was significantly higher in the skin lesions of the Af-treated mice. In the Rag1^-/- mice lacking mature lymphocytes, AD-like skin lesions were still induced by Af and ILCs depletion using an anti-CD90.2 mAb lowered the Af-induced inflammatory response.

CONCLUSIONS

Group 2 ILCs may play a role in a murine model of Af-induced AD-like skin lesions.

Prenatal PM2.5 affects atopic dermatitis depending on maternal anxiety and gender: COCOA study

BACKGROUND

The prevalence of atopic dermatitis (AD) is increasing worldwide. Prenatal particulate matter with an aerodynamic diameter <2.5 μm (PM2.5) and maternal anxiety during pregnancy has been suggested as a potential causes of AD. This study investigated the effects of prenatal PM2.5 and maternal anxiety on AD and identified the critical period of PM2.5 exposure for AD in infants.

METHODS

This study included 802 children from the COCOA birth cohort study with follow-up data at 1 year of age. PM2.5 was estimated by land-use regression models and prenatal anxiety was measured with a questionnaire. AD was diagnosed by doctor at 1 year of age. Logistic regression analysis and Bayesian distributed lag interaction models were applied.

RESULTS

Higher PM2.5 during the first trimester of pregnancy, higher prenatal maternal anxiety, and male gender were associated with AD at 1 year of age (adjusted odds ratio [aOR] and 95% confidence interval [CI]: 1.86 [1.08-3.19], 1.58 [1.01-2.47], and 1.54 [1.01-2.36], respectively). Higher PM2.5 during the first trimester and higher maternal anxiety during pregnancy showed an additive effect on the risk of AD (aOR: 3.13; 95% CI: 1.56-6.28). Among boys exposed to higher maternal anxiety during pregnancy, gestational weeks 5-8 were the critical period of PM2.5 exposure for the development of AD.

CONCLUSIONS

Higher PM2.5 exposure during gestational weeks 5-8 increased the probability of AD in infancy, especially in boys with higher maternal anxiety. Avoiding PM2.5 exposure and maternal anxiety from the first trimester may prevent infant AD.

How to prevent skin damage from air pollution part 2: Current treatment options

In the first part of this review, we have summarized the methods used to examine skin exposure to air pollution and the fundamental concept of skin-exposome interactions. Part 2 of this review focuses on dermatoses, whose aggravation or initiation by air pollution has been confirmed in evidence based medicine manner. Based on the model of photodermatology and photodermatoses, we propose a new concept of "polludermatoses." A key feature of this concept is identifying patients at risk, which will reveal the noxious effects of air pollutants on skin health. Identifying clinical signs of pollution-damaged skin could be beneficial in categorizing conditions caused or exacerbated by exposure to air pollution. Finally, we discuss the current treatment options and the pathogenetic processes targeted by these therapeutics or the development of novel treatment modalities.

Comprehensive Analysis of the Effect of Probiotic Intake by the Mother on Human Breast Milk and Infant Fecal Microbiota

BACKGROUND

Human breast milk (HBM) contains optimal nutrients for infant growth. Probiotics are used to prevent disease and, when taken by the mother, they may affect infant microbiome as well as HBM. However, few studies have specifically investigated the effect of probiotic intake by the mother on HBM and infant microbiota at genus/species level. Therefore, we present a comprehensive analysis of paired HBM and infant feces (IF) microbiome samples before and after probiotic intake by HBM-producing mothers.

METHODS

Lactating mothers were administered with Lactobacillus rhamnosus (n = 9) or Saccharomyces boulardii capsules (n = 9), for 2 months; or no probiotic (n = 7). Paired HBM and IF samples were collected before and after treatment and analyzed by next-generation sequencing.

RESULTS

Forty-three HBM and 49 IF samples were collected and sequenced. Overall, in 43 HBM samples, 1,190 microbial species belonging to 684 genera, 245 families, 117 orders, and 56 classes were detected. In 49 IF samples, 372 microbial species belonging to 195 genera, 79 families, 42 orders, and 18 classes were identified. Eight of 20 most abundant genera in both HBM and IF samples overlapped: Streptococcus (14.42%), Lactobacillus, Staphylococcus, and Veillonella, which were highly abundant in the HBM samples; and Bifidobacterium (27.397%), Bacteroides, and Faecalibacterium, which were highly abundant in the IF samples. Several major bacterial genera and species were detected in the HBM and IF samples after probiotic treatment, illustrating complex changes in the microbiomes upon treatment.

CONCLUSION

This is the first Korean microbiome study in which the effect of different probiotic intake by the mother on the microbiota in HBM and IF samples was investigated. This study provides a cornerstone to further the understanding of the effect of probiotics on the mother and infant microbiomes.

Interactions Between IL-17 Variants and Streptococcus in the Gut Contribute to the Development of Atopic Dermatitis in Infancy

Purpose

Interleukin (IL)-17 variants and perturbations in the gut microbiota may influence the development of atopic dermatitis (AD). However, unifying principles for variants of host and microbe interaction remains unclear. We sought to investigate whether IL-17 variants and gut microbiota affect the development of AD in infancy.

Methods

Composition of the gut microbiota was analyzed in fecal samples from 99 normal healthy and 61 AD infants at 6 months of age. The associations between total immunoglobulin E (IgE), the scoring atopic dermatitis (SCORAD), short-chain fatty acids, transcriptome and functional profile of the gut measured in these subjects and Streptococcus were analyzed. IL-6 and IL-8 in the human intestinal epithelial cell line (HIEC-6) were measured after stimulation of IL-17 and Streptococcus mitis.

Results

In this study, Streptococcus was enriched in infants with AD and was higher in those with the GA + AA of IL-17 (rs2275913) variant. Streptococcus was positively correlated with IgE and SCORAD in infants with AD and GA + AA of IL-17. Butyrate and valerate were negatively correlated with Streptococcus and were decreased in infants with AD and GA + AA. Bacterial genes for oxidative phosphorylation induced by reduced colonization of Clostridium were decreased compared with normal and GG. In transcriptome analysis, lactate dehydrogenase A-like 6B was higher in infants with AD compared with healthy infants. IL-6 and IL-8 were increased in IL-17 and/or S. mitis-stimulated HIEC-6 cells.

Conclusions

These findings suggest that increased Streptococcus and A allele of IL-17 (rs2275913) may contribute to the pathogenesis of AD via modulation of the immune system in infancy.

Prenatal PM2.5 exposure and vitamin D-associated early persistent atopic dermatitis via placental methylation

BACKGROUND

The effects of prenatal particulate matter with an aerodynamic diameter ranging from 0.1 μm to 2.5 μm (PM_2.5) and vitamin D on atopic dermatitis (AD) phenotypes have not been evaluated. DNA methylation and cord blood (CB) vitamin D could represent a plausible link between prenatal PM_2.5 exposure and AD in an offspring.

OBJECTIVE

To determine the critical windows of prenatal PM_2.5 exposure on the AD phenotypes, if vitamin D modulated these effects, and if placental DNA methylation mediated these effects on AD in offspring.

METHODS

Mother-child pairs were enrolled from the birth cohort of the Cohort for Childhood Origin of Asthma and allergic diseases (COCOA) study. PM_2.5 was estimated by land-use regression models, and CB vitamin D was measured by chemiluminescence immunoassay. AD was identified by the parental report of a physician's diagnosis. We defined the following 4 AD phenotypes according to onset age (by the age of 2 years) and persistence (by the age of 3 years): early-onset transient and persistent, late onset, and never. Logistic regression analysis and Bayesian distributed lag interaction model were used. DNA methylation microarray was analyzed using an Infinium Human Methylation EPIC BeadChip (Illumina, San Diego, California) in placenta.

RESULTS

PM_2.5 exposure during the first trimester of pregnancy, especially during 6 to 7 weeks of gestation, was associated with early-onset persistent AD. This effect increased in children with low CB vitamin D, especially in those with PM_2.5 exposure during 3 to 7 weeks of gestation. AHRR (cg16371648), DPP10 (cg19211931), and HLADRB1 (cg10632894) were hypomethylated in children with AD with high PM_2.5 and low CB vitamin D.

CONCLUSION

Higher PM_2.5 during the first trimester of pregnancy and low CB vitamin D affected early-onset persistent AD, and the most sensitive window was 6 to 7 weeks of gestation. Placental DNA methylation mediated this effect.

Effects of chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) on Th2/Th17-related immune modulation in an atopic dermatitis mouse model

Exposure to chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) has been associated with allergic contact dermatitis and occupational asthma. Despite this association however, no study has investigated the effects of CMIT/MIT exposure on the development of atopic dermatitis (AD). This study was conducted to investigate the influence of epicutaneous exposure to CMIT/MIT on AD in a mouse model and the underlying biological mechanisms. BALB/C mice were exposed to CMIT/MIT for 3 weeks and AD was developed using ovalbumin (OVA) epidermal sensitization. CMIT/MIT epicutaneous exposure in normal mice significantly enhanced AD-like phenotypes (e.g., transepidermal water loss, clinical score, total serum immunoglobulin E level and infiltration of inflammatory cells). In addition, CMIT/MIT exposure significantly augmented the mRNA expression level of T helper (Th) 2-related cytokines (thymic stromal lymphopoietin, interleukin (IL)-6 and IL-13), Th2 chemokine (chemokine (C-C motif) ligand 17) and the population of CD4⁺IL-4⁺ cells in the skin. Moreover, mice exposed to CMIT/MIT in the OVA challenge had greater AD-like phenotypes, higher IL-4 and IL-17A skin mRNA expression levels, and a larger population of CD4⁺IL-4⁺- and IL-17A⁺-producing cells in the skin-draining lymph nodes. Our current findings in a mouse model thus suggest that CMIT/MIT exposure may cause AD symptoms through the dysregulation of Th2/Th17-related immune responses.

Antibiotics-Induced Dysbiosis of Intestinal Microbiota Aggravates Atopic Dermatitis in Mice by Altered Short-Chain Fatty Acids

PURPOSE

Alterations in the intestinal microbiota in early life affects the development of atopic dermatitis (AD) in humans. This study aimed to further investigate the effects of gut dysbiosis in early life in an ovalbumin (OVA)-induced mouse model of AD.

METHODS

The AD mouse model was developed by serial OVA sensitization and mice were treated with an antibiotic cocktail in their drinking water for 2 weeks before primary sensitization. Probiotics (Lactobacillus rhamnosus, 1 × 10⁹ CFU) or 100 μL of fresh fecal supernatant were orally administered daily from 1 week before the first sensitization until the end of the study.

RESULTS

The AD mice which received antibiotics had significantly aggravated phenotypes, including clinical score, transepidermal water loss, and histopathology, compared to those treated with healthy feces or probiotics. Total systemic immunoglobulin E production and skin interleukin (IL) 4 levels were significantly increased in the antibiotic-treated mice compared to the other groups. Antibiotic treatment also increased the levels of IL17 and group 3 innate lymphoid cells (ILC3) in the gut and significantly suppressed the production of short-chain fatty acids (SCFAs) and decreased the number FOXP3⁺ cells.

CONCLUSIONS

Our results suggest that the status of the gut microbiota in early life in the mouse may play a crucial role in AD development through intestinal SCFA production through regulate the numbers of CD4⁺IL17⁺/CD4⁺FOXP3⁺ regulatory T cells and ILC3s.

Prenatal mold exposure is associated with development of atopic dermatitis in infants through allergic inflammation

OBJECTIVE

Mold exposure in early life may be associated with development of atopic dermatitis; however, studies of this link are inconclusive and evidence for the underlying mechanism(s) is lacking. This study identified the association between the time of mold exposure and development of atopic dermatitis and investigated the underlying mechanisms.

METHOD

The association between atopic dermatitis and mold exposure was examined in the Cohort for Childhood Origin of Asthma and Allergic Diseases birth cohort study (n=1446). Atopic dermatitis was diagnosed at 1 year of age by pediatric allergists. Exposure to mold was assessed by questionnaire. The Illumina MiSeq platform was used to examine the environmental mycobiome in 20 randomly selected healthy infants and 20 infants with atopic dermatitis at 36 weeks of gestation.

RESULTS

Prenatal, but not postnatal, mold exposure was significantly associated with atopic dermatitis (adjusted odds ratio, 1.36; 95% confidence interval, 1.01-1.83). Levels of total serum IgE at 1 year of age were higher in infants with atopic dermatitis exposed to mold during pregnancy than in healthy infants not exposed to mold during pregnancy (p=0.021). The relative abundance of uncultured Ascomycota was higher in infants with atopic dermatitis than in healthy infants. The relative abundance of uncultured Ascomycota correlated with total serum IgE levels at 1 year of age (r=0.613, p<0.001).

CONCLUSION

Indoor mold exposure during the fetal period is associated with development of atopic dermatitis via IgE-mediated allergic inflammation. Avoidance of mold exposure during this critical period might prevent the development of atopic dermatitis.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

High prevalence of eczema among preschool children related to home renovation in China: A multi-city-based cross-sectional study

We surveyed 40 010 three- to six-year-old children in seven Chinese cities (Beijing, Taiyuan, Urumqi, Shanghai, Nanjing, Changsha, and Chongqing) during 2010-2012 so as to investigate possible links between home renovation and childhood eczema. Their parents responded to questions on home renovation and childhood eczema. Multivariate and two-level (city-child) logistic regression analyses yielding odds ratios with 95% confidence intervals were performed. Sensitivity analyses stratifying data for region, climate, and income level were also performed. The prevalences of childhood eczema in children with different floor and wall covering materials were significantly different and were significantly higher with home renovation during early lifetime. Exposure to synthetic materials significantly increased the risk of childhood eczema by 20%-25%. The risks (AOR, 95% CI) of current eczema among children in families with solid wood flooring and oil paint wall covering were 1.25 (1.04-1.49) and 1.35 (1.14-1.60), respectively. Home renovation during pregnancy was related to children's lifetime and current eczema.

The impact of airborne pollution on skin

Indoor and outdoor airborne pollutants modify our environment and represent a growing threat to human health worldwide. Airborne pollution effects on respiratory and cardiac health and diseases have been well established, but its impact on skin remains poorly described. Nonetheless, the skin is one of the main targets of pollutants, which reach the superficial and deeper skin layers by transcutaneous and systemic routes. In this review, we report the outcomes of basic and clinical research studies monitoring pollutant levels in human tissues including the skin and hair. We present a current understanding of the biochemical and biophysical effects of pollutants on skin metabolism, inflammatory processes and oxidative stress, with a focus on polyaromatic hydrocarbons and ground-level ozone that are widespread outdoor pollutants whose effects are mostly studied. We reviewed the literature to report the clinical effects of pollutants on skin health and skin ageing and their impact on some chronic inflammatory skin diseases. We also discuss the potential interactions of airborne pollutants with either ultraviolet radiation or human skin microbiota and their specific impact on skin health.

Climate change and atopic dermatitis: is there a link?

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease with a growing health concern, because of its high prevalence and associated low quality of life. The etiology of AD is multifactorial with interaction between various factors such as genetic predisposition, immune, and importantly, environmental factors. Since climate change is associated with a profound shift in environmental factors, we suggest that AD is being influenced by climate change. This review highlights the effects of ultraviolet light, temperature, humidity, pollens, air pollutants, and their interaction between them contributing to the epidemiology and pathophysiology of AD.

Perturbations of gut microbiome genes in infants with atopic dermatitis according to feeding type

BACKGROUND

Perturbations of the infant gut microbiota can shape development of the immune system and link to the risk of allergic diseases.

OBJECTIVE

We sought to understand the role of the gut microbiome in patients with atopic dermatitis (AD). The metagenome of the infant gut microbiome was analyzed according to feeding types.

METHODS

Composition of the gut microbiota was analyzed in fecal samples from 129 infants (6 months old) by using pyrosequencing, including 66 healthy infants and 63 infants with AD. The functional profile of the gut microbiome was analyzed by means of whole-metagenome sequencing (20 control subjects and 20 patients with AD). In addition, the total number of bacteria in the feces was determined by using real-time PCR.

RESULTS

The gut microbiome of 6-month-old infants was different based on feeding types, and 2 microbiota groups (Bifidobacterium species-dominated and Escherichia/Veillonella species-dominated groups) were found in breast-fed and mixed-fed infants. Bacterial cell amounts in the feces were lower in infants with AD than in control infants. Although no specific taxa directly correlated with AD in 16S rRNA gene results, whole-metagenome analysis revealed differences in functional genes related to immune development. The reduction in genes for oxidative phosphorylation, phosphatidylinositol 3-kinase-Akt signaling, estrogen signaling, nucleotide-binding domain-like receptor signaling, and antigen processing and presentation induced by reduced colonization of mucin-degrading bacteria (Akkermansia muciniphila, Ruminococcus gnavus, and Lachnospiraceae bacterium 2_1_58FAA) was significantly associated with stunted immune development in the AD group compared with the control group (P < .05).

CONCLUSIONS

Alterations in the gut microbiome can be associated with AD because of different bacterial genes that can modulate host immune cell function.

Microbiome in the Gut-Skin Axis in Atopic Dermatitis

The microbiome is vital for immune system development and homeostasis. Changes in microbial composition and function, termed dysbiosis, in the skin and the gut have recently been linked to alterations in immune responses and to the development of skin diseases, such as atopic dermatitis (AD). In this review, we summarize the recent findings on the gut and skin microbiome, highlighting the roles of major commensals in modulating skin and systemic immunity in AD. Although our understanding of the gut-skin axis is only beginning, emerging evidence indicates that the gut and skin microbiome could be manipulated to treat AD.

Association of atopy phenotypes with new development of asthma and bronchial hyperresponsiveness in school-aged children

BACKGROUND

Although previous studies have investigated the association between atopy phenotypes and allergic diseases, atopy characterizations in association with the development of allergic diseases remain poorly understood.

OBJECTIVE

To identify atopy phenotypes in school-age children and to evaluate the association between atopy phenotypes and allergic diseases.

METHODS

We enrolled 616 children with atopy defined as 1 or more positive allergen responses on skin prick tests and 665 children without atopy from the Children's Health and Environmental Research (CHEER) study. All children were followed up for 4 years at 2-year intervals. Atopy phenotypes were classified using latent class analysis.

RESULTS

Four atopy phenotypes were characterized: later sensitization to indoor allergens (cluster 1); multiple early sensitization (cluster 2); early sensitization to outdoor allergens, especially Alternaria, and later sensitization to indoor allergens, including Aspergillus (cluster 3); and early sensitization to indoor allergens and later sensitization to outdoor allergens (cluster 4). New cases of asthma during follow-up were increased in clusters 2 and 3 (adjusted odds ratio [aOR], 2.76 and 4.25, respectively). The risk of new-onset bronchial hyperresponsiveness was highest in cluster 3 (aOR, 5.03). Clusters 2 and 4 had an increased risk of allergic rhinitis (aOR, 7.21 and 2.37, respectively).

CONCLUSION

Identification of atopy phenotypes facilitates prediction of the development of asthma and bronchial hyperresponsiveness in school-age children. Our study suggests prevention of additional sensitization is required to modify the progression of allergic diseases.

Preconceptional and perinatal exposure to traffic-related air pollution and eczema in preschool children

BACKGROUND

Evidence linking prenatal exposure to outdoor air pollution with eczema in early childhood is scare, and the role of components of air pollution and exposure timing remains unclear.

OBJECTIVES

We investigated the association between exposure to air pollution during preconceptional and perinatal period and the risk of eczema in preschool children.

METHODS

We conducted a prospective cohort study of 2598 children aged 3-6 years in Changsha, China. The prevalence of eczema was assessed by a standardized health questionnaire administered by the parents. Individual exposures to nitrogen dioxide (NO₂), sulfur dioxide (SO₂) and particulate matter with an aerodynamic diameter≤10μm (PM₁₀) during the 4th-6th and 1st-3rd month before pregnancy, entire pregnancy, and three trimesters were estimated by an inverse distance weighted (IDW) method based on concentrations measured at monitoring stations. Association between childhood eczema and exposure to air pollution was examined by logistic regression models in terms of odds ratio (OR) and 95% confidence interval (CI) for an interquartile range (IQR) increase in exposure.

RESULTS

Life-time prevalence of eczema in preschool children in Changsha was 28.6%. Childhood eczema was associated with traffic-related air pollutant NO₂ during 3 months before pregnancy and entire pregnancy with adjusted ORs=1.19 (95% CI: 1.04-1.37) and 1.21 (95% CI: 1.03-1.42) respectively. The highest risk of eczema was observed for the 1st trimester exposure to NO₂ [OR=1.26 (95% CI: 1.09-1.46)]. However, no association was detected for SO₂ and PM₁₀ exposure during any window. High-level exposure to NO₂ during the whole time period significantly increased the effect of NO₂ in all windows on eczema risk as compared with low-level exposure. Sensitivity analysis indicated that the association between both preconceptional and perinatal exposure to NO₂ and childhood eczema was consistent and robust, and this association was modified by some personal, parental hereditary and indoor environmental factors.

CONCLUSION

Our findings support the hypothesis that early childhood eczema is associated with exposure to traffic-related air pollutant during both preconceptional and perinatal period, especially at a high level of exposure.

Environmental risk factors and their role in the management of atopic dermatitis

INTRODUCTION

The etiology of atopic dermatitis (AD) is multifactorial with interaction between genetics, immune and environmental factors. Areas covered: We review the role of prenatal exposures, irritants and pruritogens, pathogens, climate factors, including temperature, humidity, ultraviolet radiation, outdoor and indoor air pollutants, tobacco smoke exposure, water hardness, urban vs. rural living, diet, breastfeeding, probiotics and prebiotics on AD. Expert commentary: The increased global prevalence of AD cannot be attributed to genetics alone, suggesting that evolving environmental exposures may trigger and/or flare disease in predisposed individuals. There is a complex interplay between different environmental factors, including individual use of personal care products and exposure to climate, pollution, food and other exogenous factors. Understanding these complex risk factors is crucial to developing targeted interventions to prevent the disease in millions. Moreover, patients require counseling on optimal regimens for minimization of exposure to irritants and pruritogens and other harmful exposures.

Association between Dietary Patterns and Atopic Dermatitis in Relation to GSTM1 and GSTT1 Polymorphisms in Young Children

Previous research suggests the association of glutathione S-transferase (GST) gene polymorphisms or diet, but no interactions between these factors in atopic dermatitis (AD). We conducted a community-based case-control study including 194 AD and 244 matched non-AD preschoolers. Glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) present/null genotypes were evaluated uisng a multiplex PCR method. We measured dietary intakes by a validated food frequency questionnaire and constructed three dietary patterns such as “traditional healthy”, “animal foods”, and “sweets” diets. In stratified analyses by GST genotypes, the “traditional healthy” diet and reduced AD showed association only in the GSTM1-present group (odd ratio (OR) 0.31, 95% confidence interval (CI) 0.13–0.75). A similar pattern of the association existed in the combined GSTM1/T1 genotype that indicated the inverse association between the “traditional healthy” diet and AD in the double GSTM1/T1-present genotype group (OR 0.24, 95% CI 0.06–0.93). Results from the multiplicative test analyses showed that the “traditional healthy” diet on reduced AD was significant or borderline significant in the GSTM1-present group (OR 0.71, 95% CI 0.54–0.92 vs. GSTM1-null group) or the GSTM1/T1 double present group (OR 0.63, 95% CI 0.39–1.03 vs. GSTM1/T1 double null group). These findings demonstrate that the present type of GSTM1 may increase susceptibility to the potential effect of the “traditional healthy” diet on AD.

Mold elicits atopic dermatitis by reactive oxygen species: Epidemiology and mechanism studies

Mold has been implicated in the development of atopic dermatitis (AD); however, the underlying mechanisms remain unknown. The aim of the study was to investigate the effects of mold exposure in early life through epidemiologic and mechanistic studies in vivo and in vitro. Exposure to visible mold inside the home during the first year of life was associated with an increased risk for current AD by two population-based cross-sectional human studies. Children with the AG+GG genotype of GSTP1 showed increased risk for current AD when exposed to mold. In the mouse model, treatment with patulin induced and aggravated clinically significant AD and Th2-related inflammation of the affected mouse skin. Additionally, reactive oxygen species (ROS) were released in the mouse skin as well by human keratinocytes. In conclusions, mold exposure increases the risk for AD related to ROS generation mediated by Th2-promoting inflammatory cytokines.

Influences of Environmental Chemicals on Atopic Dermatitis

Atopic dermatitis is a chronic inflammatory skin condition including severe pruritus, xerosis, visible eczematous skin lesions that mainly begin early in life. Atopic dermatitis exerts a profound impact on the quality of life of patients and their families. The estimated lifetime prevalence of atopic dermatitis has increased 2~3 fold during over the past 30 years, especially in urban areas in industrialized countries, emphasizing the importance of life-style and environment in the pathogenesis of atopic diseases. While the interplay of individual genetic predisposition and environmental factors contribute to the development of atopic dermatitis, the recent increase in the prevalence of atopic dermatitis might be attributed to increased exposure to various environmental factors rather than alterations in human genome. In recent decades, there has been an increasing exposure to chemicals from a variety of sources. In this study, the effects of various environmental chemicals we face in everyday life - air pollutants, contact allergens and skin irritants, ingredients in cosmetics and personal care products, and food additives - on the prevalence and severity of atopic dermatitis are reviewed.

The role of air pollutants in atopic dermatitis

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease and a growing health concern, especially in children, because of its high prevalence and associated low quality of life. Genetic predisposition, environmental triggers, or interactions between them contribute to the pathophysiology of AD. Therefore, it is very important to identify and control risk factors from the environment in susceptible subjects for successful treatment and prevention. Both indoor and outdoor air pollution, which are of increasing concern with urbanization, are well-known environmental risk factors for asthma, whereas there is relatively little evidence in AD. This review highlights epidemiologic and experimental data on the role of air pollution in patients with AD. Recent evidence suggests that a variety of air pollutants, such as environmental tobacco smoke, volatile organic compounds, formaldehyde, toluene, nitrogen dioxide, and particulate matter, act as risk factors for the development or aggravation of AD. These air pollutants probably induce oxidative stress in the skin, leading to skin barrier dysfunction or immune dysregulation. However, these results are still controversial because of the low number of studies, limitations in study design, inaccurate assessment of exposure and absorption, and many other issues. Further research about the adverse effects of air pollution on AD will help to expand our understanding and to establish a better strategy for the prevention and management of AD.

The Cohort for Childhood Origin of Asthma and allergic diseases (COCOA) study: design, rationale and methods

BACKGROUND

This paper describes the background, aim, and design of a prospective birth-cohort study in Korea called the COhort for Childhood Origin of Asthma and allergic diseases (COCOA). COCOA objectives are to investigate the individual and interactive effects of genetics, perinatal environment, maternal lifestyle, and psychosocial stress of mother and child on pediatric susceptibility to allergic diseases.

METHODS/DESIGN

The participants in COCOA represents a Korean inner-city population. Recruitment started on 19 November, 2007 and will continue until 31 December, 2015. Recruitment is performed at five medical centers and eight public-health centers for antenatal care located in Seoul. Participating mother-baby pairs are followed from before birth to adolescents. COCOA investigates whether the following five environmental variables contribute causally to the development and natural course of allergic diseases: (1) perinatal indoor factors (i.e. house-dust mite, bacterial endotoxin, tobacco smoking, and particulate matters 2.5 and 10), (2) perinatal outdoor pollutants, (3) maternal prenatal psychosocial stress and the child's neurodevelopment, (4) perinatal nutrition, and (5) perinatal microbiome. Cord blood and blood samples from the child are used to assess whether the child's genes and epigenetic changes influence allergic-disease susceptibility. Thus, COCOA aims to investigate the contributions of genetics, epigenetics, and various environmental factors in early life to allergic-disease susceptibility in later life. How these variables interact to shape allergic-disease susceptibility is also a key aim.The COCOA data collection schedule includes 11 routine standardized follow-up assessments of all children at 6 months and every year until 10 years of age, regardless of allergic-disease development. The mothers will complete multiple questionnaires to assess the baseline characteristics, the child's exposure to environmental factors, maternal pre- and post-natal psychological stress, and the child's neurodevelopment, nutritional status, and development of allergic and respiratory illnesses. The child's microbiome, genes, epigenetics, plasma cytokine levels, and neuropsychological status, the microbiome of the residence, and the levels of indoor and outdoor pollutants are measured by standard procedures.

DISCUSSION

The COCOA study will improve our understanding of how individual genetic or environmental risk factors influence susceptibility to allergic disease and how these variables interact to shape the phenotype of allergic diseases.

Environmental changes, microbiota, and allergic diseases

During the last few decades, the prevalence of allergic disease has increased dramatically. The development of allergic diseases has been attributed to complex interactions between environmental factors and genetic factors. Of the many possible environmental factors, most research has focused on the most commonly encountered environmental factors, such as air pollution and environmental microbiota in combination with climate change. There is increasing evidence that such environmental factors play a critical role in the regulation of the immune response that is associated with allergic diseases, especially in genetically susceptible individuals. This review deals with not only these environmental factors and genetic factors but also their interactions in the development of allergic diseases. It will also emphasize the need for early interventions that can prevent the development of allergic diseases in susceptible populations and how these interventions can be identified.

Analysis of the prevalence of and risk factors for atopic dermatitis using an ISAAC questionnaire in 8,750 Korean children

BACKGROUND

Since 1995, epidemiologic studies of atopic disorders using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire have been performed in many countries, including the Republic of Korea. The prevalence, burden and risk factors of atopic dermatitis were surveyed in these studies, which helped to enhance their comparability among different areas and age groups, as well as to clarify the nature of atopic dermatitis and other atopic disorders.

METHODS

From 21 facilities, 8,750 children were enrolled in this cross-sectional study. The data were collected via the Internet using a questionnaire based on the Korean-language version of the ISAAC study format.

RESULTS

The prevalence of atopic dermatitis over the previous 12 months was 14.4%. The prevalence in preschool children was significantly higher than in elementary school children. Family history of atopic diseases, diagnosis of allergic conjunctivitis and diagnosis of food allergy were positively associated with atopic dermatitis in both preschool and elementary school children. In addition, raising pets was positively associated with atopic dermatitis in preschool children. In elementary school children, female gender, secondhand smoking, breastfeeding, changing the parents' house to a newly built one during the first year of life, diagnosis of asthma and diagnosis of allergic rhinitis were positively associated with atopic dermatitis.

CONCLUSION

The prevalence of atopic dermatitis in preschool and elementary school children in Korea is similar to that of children in other developing countries. The risk factors for atopic dermatitis are different in preschool and elementary school children. More detailed strategies will be necessary to reduce atopic dermatitis in both age groups.

Effects of Lactobacillus rhamnosus on asthma with an adoptive transfer of dendritic cells in mice

AIM

This study was designed to investigate whether the protective effects of Lactobacillus rhamnosus (Lcr35) on allergic asthma are associated with the adoptive transfer of dendritic cells (DCs) and regulatory T cells (Tregs), using a mouse experimental model of asthma.

METHODS AND RESULTS

BALB/c mice were orally administered Lcr35 or intravenously treated with in vivo Lcr35-treated DCs daily and were then sensitized and challenged with ovalbumin (OVA) in accordance with a model of asthma protocol. Both the oral application of Lcr35 and intravenous administration of Lcr35-treated DCs suppressed all aspects of the asthmatic response, including bronchial hyperresponsiveness (BHR), total cell counts in the bronchoalveolar lavage (BAL) fluid, the production of OVA-specificimmunoglobulin E (IgE), and pulmonary eosinophilic inflammation. The mechanism of action of Lcr35 is related to Tregs, which suppress the Th2 response in the respiratory organs, and this is mediated by DCs in the mouse model of asthma.

CONCLUSIONS

These results confirm that the mechanism underlying the effects of Lcr35 on asthma involves the adoptive transfer of DCs.

SIGNIFICANCE AND IMPACT OF THE STUDY

This finding broadens the possibility that Lcr35 has potential as an alternative therapeutic approach to the treatment of human asthma.

Effect of paracetamol use on the modification of the development of asthma by reactive oxygen species genes

BACKGROUND

Recent studies have identified an increase in the prevalence of asthma associated with paracetamol use.

OBJECTIVE

To identify the relationship among asthma, biomarkers, genes, and paracetamol use in preschool children.

METHODS

We undertook a population-based, cross-sectional survey of 933 preschool children. Asthma status was classified according to medical history and asthmatic symptoms. History of paracetamol use in infancy was recorded. Impulse oscillometry, blood tests for eosinophils and total IgE, and genotyping of NAT2, Nrf2, and GSTP1 polymorphisms by TaqMan assay were conducted.

RESULT

Paracetamol use in infancy was associated with an increased risk of treatment for asthma within the previous 12 months. Paracetamol use together with a family history of asthma increased the risk of asthma diagnosis ever, current asthma, and treatment for asthma within the previous 12 months. Gene polymorphisms in NAT2 (rs4271002), Nrf2 (rd6726395), and GSTP1 (rd1695) increased the risk of treatment for asthma within the last 12 months. Eosinophils were significantly elevated in the group with paracetamol use and a family history of asthma; however, the serum total IgE level and IOS did not show any significant difference.

CONCLUSION

Paracetamol use in infancy was significantly associated with increased risk of asthma. The association is more significant in genetically susceptible children, related to antioxidant genes, and the effect may be mediated by eosinophilic inflammation.

Gene-environment interactions in asthma and allergic diseases: challenges and perspectives

The concept of gene-environment (GxE) interactions has dramatically evolved in the last century and has now become a central theme in studies that assess the causes of human disease. Despite the numerous efforts to discover genes associated in asthma and allergy through various approaches, including the recent genome-wide association studies, investigation of GxE interactions has been mainly limited to candidate genes, candidate environmental exposures, or both. This review discusses the various strategies from hypothesis-driven strategies to the full agnostic search of GxE interactions with an illustration from recently published articles. Challenges raised by each piece of the puzzle (ie, phenotype, environment, gene, and analysis of GxE interaction) are put forward, and tentative solutions are proposed. New perspectives to integrate various types of data generated by new sequencing technologies and to progress toward a systems biology approach of disease are outlined. The future of a molecular network-based approach of disease to which GxE interactions are related requires space for innovative and multidisciplinary research. Assembling the various parts of a puzzle in a complex system could well occur in a way that might not necessarily follow the rules of logic.

Role of parental atopy in cow's milk allergy: a population-based study

BACKGROUND

A family history of atopy has been considered an independent risk factor for atopic diseases in children.

OBJECTIVE

To relate the risk of an infant developing IgE-mediated cow's milk allergy (IgE-CMA) to the atopic status of parents.

METHODS

Assessment of the parental atopic status of children with IgE-CMA (n = 66) previously identified in a large-scale prospective study was compared with the parental atopic status of a control group of healthy infants (n = 156). The atopic status was identified both by self-reporting and skin prick tests (SPTs).

RESULTS

Analysis for the risk for infants to develop IgE-CMA depended on the assessment method used. No significant differences were noted in self-reported parental atopic status between the IgE-CMA patients and the control group. However, among the subgroup of infants with persistent IgE-CMA (n = 25), maternal but not paternal self-reporting for atopy was more likely compared with parents of the control group (P = .04). In contrast, when analyzed by SPT, in both this persistent subgroup and the total allergic cohort, no significant differences were noted whether analyzed by single parent or both parents and whether the parent tested singly or multiply positive on the SPT.

CONCLUSION

In families with children with persistent IgE-CMA, self-reporting of atopy by parents may be biased. Furthermore, the demonstration of IgE-mediated responses to allergens in parents is insufficient by itself, in a general population cohort, to predict which infants are at greatest risk of developing IgE-CMA.