Contribution of an impaired epithelial barrier to the atopic march

Trends (2007-2019) of major atopic diseases throughout the life span in a large Mexican population

Background

Major atopic diseases such as atopic dermatitis (AD), allergic rhinitis (AR), and asthma share the same atopic background, but they often show differences in their epidemiological behavior.

Objective

We aimed to report the profile of these atopic diseases in a large Mexican population, including their age-related incidences, male:female (M:F) ratios, recent time trends, and association with altitude.

Methods

Registries from the largest, nationwide health institution in Mexico (more than 34 million insured subjects), were reviewed. New cases of AD, AR, and asthma diagnosed each year by family physicians from 2007 to 2019 were adjusted by the corresponding insured population to estimate incidence rates.

Results

Incidences of the 3 atopic diseases were highest in the 0-4 years age-group and progressively decreased thereafter until adolescence. Asthma and AR, but not AD, were more frequent in males during childhood (M:F ratios of 1.5, 1.3, and 0.95, respectively), but predominated in females during adulthood (M:F ratios of 0.52, 0.68, and 0.73, respectively). Time trends showed an initial increasing trend of annual incidences, with a peak around 2009-2011, and a downward trend afterward. This decreasing trend was seen in all age-groups and was more evident for AD (∼50% drop) and asthma (∼40% drop) than for AR (∼20% drop). Geographical distribution suggested that incidences of asthma and AR, but not of AD, had an inverse association with altitude.

Conclusion

Annual incidences of the 3 major atopic diseases have declined in recent years in almost all age groups, and their epidemiological profile during the life span showed contrasting differences according to age, sex, and ecological association with altitude, mainly regarding AD.

Succinate and mitochondrial DNA trigger atopic march from atopic dermatitis to intestinal inflammation

BACKGROUND

Atopic march has long been recognized as the progression from atopic dermatitis (AD) to food allergy and asthma during infancy and childhood. However, effective blocking is hampered by the lack of specific biomarkers.

OBJECTIVES

We aimed to investigate the pathologic progression of atopic march trajectories from skin to gut.

METHODS

We built an atopic march mouse model by mechanical skin injury and percutaneous sensitization to peanut allergen. Anaphylaxis from the skin to the small intestine was then investigated by ELISA, RNA sequencing, quantitative real-time PCR, histopathologic analysis, and flow cytometry. The findings from the mice results were also verified by the serum samples of allergic pediatric patients.

RESULTS

After modeling, inflammation in the skin and small intestine manifested as a mixed type of T_H2 and T_H17. Further analysis identified elevated succinate in the circulation and expanded tuft cells with upregulated IL-25 in the small intestine, resulting in increased intestinal type 2 innate lymphoid cells and an enhanced type 2 inflammatory response. In addition, free mitochondrial DNA (mtDNA) released after tissue damage was also involved in inflammation march from injured skin to small intestine through the STING pathway. Analysis of clinical samples verified that serum concentrations of succinate and mtDNA were higher in AD allergic children than non-AD allergic children.

CONCLUSIONS

Succinate and mtDNA play key roles in skin-to-gut cross talk during the atopic march from AD to food allergy, and can be considered as biomarkers for risk assessment or targets for atopic march prevention strategies.

The Acari Hypothesis, III: Atopic Dermatitis

Atopic dermatitis is a chronic relapsing dermatopathology involving IgE against allergenic materials present on mammalian epithelial surfaces. Allergens are as diverse as pet danders, and polypeptides expressed by microbes of the mammalian microbiome, e.g., Malassezia spp. The Acari Hypothesis posits that the mammalian innate immune system utilizes pathogen-bound acarian immune effectors to protect against the vectorial threat posed by mites and ticks. Per The Hypothesis, IgE-mediated allergic disease is a specious consequence of the pairing of acarian gastrointestinal materials, e.g., allergenic foodstuffs, with acarian innate immune effectors that have interspecies operability. In keeping with The Hypothesis, the IgE profile of atopic patients should include both anti-acarian antibodies and specious antibodies responsible for specific allergy. Further, the profile should inform on the diet and/or environment of the acarian vector. In this regard, the prevalence of Demodex and Dermatophagoides on the skin of persons suffering from atopic dermatitis is increased. Importantly, the diets of these mites correspond well with the allergens of affected patients. In this report, roles for these specific acarians in the pathogenesis of atopic dermatitis are proposed and elaborated.

Longitudinal atopic dermatitis endotypes: An atopic march paradigm that includes Black children

BACKGROUND

The atopic march has been studied mostly in White populations, biasing our current paradigms.

OBJECTIVE

We sought to define the atopic march in Black and White children and explore mechanisms for racial differences.

METHODS

Utilizing the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children (MPAACH) cohort (n = 601), we assessed longitudinal sensitization, food allergy (FA), allergic rhinitis, risk of asthma development (through the Pediatric Asthma Risk Score), Scoring for Atopic Dermatitis (SCORAD), transepidermal water loss, skin filaggrin (FLG) expression, exposures, and genetic heritability to define AD progression endotypes in Black and White children.

RESULTS

White MPAACH children were more likely to be sensitized to aero and food allergens (P = .0001) and over 3 times more likely to develop FA and/or allergic rhinitis (AR) without asthma risk (P < .0001). In contrast, Black children were over 6 times more likely to proceed to high asthma risk without FA, sensitization, or AR (P < .0001). White children had higher lesional and nonlesional transepidermal water loss (both P < .001) as well as decreased nonlesional keratinocyte FLG expression (P = .02). Black children had increased genetic heritability for asthma risk and higher rates of exposures to secondhand smoke and traffic-related air pollution.

CONCLUSIONS

Black and White children with AD have distinct allergic trajectories defined by different longitudinal endotypes. Black children exhibit higher asthma risk despite a more intact skin barrier and less sensitization, FA, and AR. White children have less asthma risk, despite a more dysfunctional skin barrier, and more FA, AR, and sensitization. The observed racial differences are likely due in part to increased genetic heritability for asthma risk and harmful environmental exposures in Black children. Collectively, our findings provide a new paradigm for an atopic march that is inclusive of Black children.

Association of antibiotics use in preschool age with atopic and allergic skin diseases in young adulthood: a population-based retrospective cohort study

BACKGROUND

Overuse and misuse of antibiotics is a public health problem in low-income and middle-income countries. Although the association of antibiotics with atopic and allergic diseases has been established, most studies focused on prenatal exposure and the occurrence of disease in infants or young children.

OBJECTIVE

To investigate the association of preschool use of antibiotics with atopic and allergic skin diseases in young adulthood.

DESIGN

Population-based retrospective cohort.

SETTING AND PARTICIPANTS

The first-year college students (n=20 123) from five universities were investigated. The sampled universities are located in Changsha, Wuhan, Xiamen, Urumqi and Hohhot, respectively.

METHODS

We conducted a dermatological field examination and a questionnaire survey inquiring the participants about the frequency of upper respiratory tract infection (URTI) and the preschool antibiotics use (prior to 7 years old). The two-level probit model was used to estimate the associations, and adjusted risk ratio (aRR) and 95% CI were presented as the effect size.

RESULTS

A total of 20 123 participants with complete information was included in the final analysis. The frequent antibiotics use intravenously (aRR 1.36, 95% CI 1.14 to 1.62) and orally (aRR 1.18, 95% CI 1.01 to 1.38) prior to 7 years old was significantly associated with atopic dermatitis in young adulthood. Similar trends could be observed in allergic skin diseases among those who use antibiotics orally and intravenously, with RRs of 1.16 (95% CI 1.01 to 1.34) and 1.33 (95% CI 1.13 to 1.57), respectively.

CONCLUSIONS

Preschool URTI and antibiotics use significantly increases the risk of atopic and allergic skin diseases in young adulthood.

Thymic stromal lymphopoietin, skin barrier dysfunction, and the atopic march

OBJECTIVE

Atopic dermatitis often precedes the development of other atopic diseases, and the atopic march describes this temporal relationship in the natural history of these diseases. Although the pathophysiological mechanisms that underlie this relationship are poorly understood, epidemiologic and genetic data have suggested that the skin might be an important route of sensitization to allergens.

DATA SOURCES

Review of recent studies on the role of skin barrier defects in systemic allergen sensitization.

STUDY SELECTIONS

Recent publications on the relationship between skin barrier defects and expression of epithelial cell-derived cytokines.

RESULTS

Animal models have begun to elucidate on how skin barrier defects can lead to systemic allergen sensitization. Emerging data now suggest that epithelial cell-derived cytokines, such as thymic stromal lymphopoietin, drive the progression from atopic dermatitis to asthma and food allergy. Skin barrier defects can lead to induction of epithelial cell-derived cytokines, which in turn leads to the initiation and maintenance of allergic inflammation and the atopic march.

CONCLUSION

Development of new biologic drug targeting type 2 cytokines provides novel therapeutic interventions for atopic dermatitis.

Trajectories of early-onset rhinitis in the Singapore GUSTO mother-offspring cohort

BACKGROUND

The natural history of childhood rhinitis is not well described.

OBJECTIVE

This study aimed to identify different rhinitis trajectories in early childhood and their predictors and allergic associations.

METHODS

Rhinitis symptoms were ascertained prospectively from birth until 6 years using standardized questionnaires in 772 participants. Rhinitis was defined as one or more episodes of sneezing, runny and/or blocked nose >2 weeks duration. Latent trajectories were identified using group-based modelling, and their predictive risk factors and allergic associations were examined.

RESULTS

Three rhinitis trajectory groups were identified: 7.6% (n = 59) were termed early transient rhinitis, 8.6% (n = 66) late transient rhinitis, and 6.6% (n = 51) persistent rhinitis. The remaining 77.2% (n = 596) were classified as non-rhinitis/reference group. Early transient rhinitis subjects were more likely of Indian ethnicity, had siblings, reported childcare attendance, early wheezing and eczema in the first 3 years of life. Late transient rhinitis was associated with antenatal exposure to smoking, higher maternal education levels, and wheezing at age 36-72 months. Persistent rhinitis was associated with male gender, paternal and maternal history of atopy, eczema, and house dust mite sensitization.

CONCLUSIONS & CLINICAL RELEVANCE

Risk factors for early transient rhinitis involve a combination of genetic and early environmental exposures, whereas late transient rhinitis may relate to maternal factors and early respiratory infections independent of atopy. In contrast, persistent rhinitis is strongly associated with atopic risk and likely represents the typical trajectory associated with allergic disorders. Allergic rhinitis symptoms may commence as early as the first year of life and may inform development of early interventive strategies.

Epicutaneous sensitization to food allergens in atopic dermatitis: What do we know?

Atopic dermatitis (AD) is a chronic inflammatory skin disease mainly affecting children, which has no definitive curative therapy apart from natural outgrowing. AD is persistent in 30%-40% of children. Epithelial barrier dysfunction in AD is a significant risk factor for the development of epicutaneous food sensitization, food allergy, and other allergic disorders. There is evidence that prophylactic emollient applications from birth may be useful for primary prevention of AD, but biomarkers are needed to guide cost-effective targeted therapy for high-risk individuals. In established early-onset AD, secondary preventive strategies are needed to attenuate progression to other allergic disorders such as food allergy, asthma, and allergic rhinitis (the atopic march). This review aims to describe the mechanisms underpinning the development of epicutaneous sensitization to food allergens and progression to clinical food allergy; summarize current evidence for interventions to halt the progression from AD to food sensitization and clinical food allergy; and highlight unmet needs and directions for future research.

Efficacy and safety of So-Cheong-Ryong-Tang in patients with atopic dermatitis and respiratory disorders: Study protocol of a double-blind randomized placebo-controlled trial

BACKGROUND

Atopic dermatitis (AD, atopic eczema) is a pruritic, inflammatory, chronic skin disease. Since there is limitation of conventional treatment of AD, traditional herbal medicine can be an attractive therapeutic option in patients having AD for a long time. So-Cheong-Ryong-Tang (SCRT) has been found to inhibit histamine release and degranulation of mast cells, differentiation of basophils, and proliferation of eosinophils. We designed this clinical trial to evaluate the efficacy and safety of SCRT as compared to placebo in patients with AD and respiratory disorders.

METHODS/DESIGN

This study is a single-center, randomized, double-blind, placebo-controlled, and investigator-initiated clinical trial. A total of 60 patients between 7 and 65 years of age with AD and respiratory disorders who received a diagnosis of AD by Hanifin and Rajka criteria who scored 15 to 50 in a scoring atopic dermatitis (SCORAD) will be enrolled. Participants will be randomly assigned to the SCRT or placebo group in a ratio of 1:1 and they will have a visit schedule comprising 4 visits including a screening visit during 8 to 10 weeks. The participants will be administered SCRT or placebo 3 times a day for 4 weeks. The primary outcome will be measured by a change of the SCORAD index. The secondary outcomes will be measured by changes in the dose and frequency of usage of the AD ointment, dermatology life quality index scores, pruritus and sleep disorder in visual analog scale, skin moisture content, skin surface temperature, Hamilton anxiety rating scale scores, depression rating scale scores, stress/autonomic nervous function test, and attention deficit hyperactivity disorder survey scores at week 4 as compared to those at the baseline.

DISCUSSION

To the best of our knowledge, SCRT has rarely been reported for dermatologic diseases. This will be the first clinical trial to assess the efficacy and safety of SCRT in patients with AD and respiratory disorders. We hope that the results of this trial will provide evidence for the use of SCRT as a new treatment for AD with respiratory disorders.

TRIAL REGISTRATION

Korean National Clinical Trial Registry, Clinical Research Information Service. (KCT0004148) (https://cris.nih.go.kr/cris/search/search_result_st01_en.jsp?seq=14981<ype=&rtype=).

Filaggrin and atopic march

There is an increasing number of experimental, genetic and clinical evidence of atopic dermatitis expression as a pre-condition for later development of other atopic diseases such as asthma, food allergy and allergic rhinitis. Atopic dermatitis is a heterogeneous, recurrent childhood disease, also present in the adult age. It is increasingly attributed to systemic features and is characterized by immunological and skin barrier integrity and function dysregulation. To maintain the protective function of the skin barrier, in particular the maintenance of pH, hydration and antimicrobial functions, the filaggrin, among others, plays a significant role. Filaggrin is a multifunctional, histidine-rich, insoluble protein. The lack of filaggrin is associated with various cutaneous (e.g. ichthyosis vulgaris, allergic contact dermatitis) and non-cutaneous (e.g. diabetes, inflammatory conditions of the gastrointestinal tract) diseases and may be a result of genetic, immunological factors combined with environmental factors. In this review we summarised (emphasized) recent findings in understanding the role of filaggrin in atopic dermatitis and other diseases, participants in the atopic march.

Environmental exposures and mechanisms in allergy and asthma development

Environmental exposures interplay with human host factors to promote the development and progression of allergic diseases. The worldwide prevalence of allergic disease is rising as a result of complex gene-environment interactions that shape the immune system and host response. Research shows an association between the rise of allergic diseases and increasingly modern Westernized lifestyles, which are characterized by increased urbanization, time spent indoors, and antibiotic usage. These environmental changes result in increased exposure to air and traffic pollution, fungi, infectious agents, tobacco smoke, and other early-life and lifelong risk factors for the development and exacerbation of asthma and allergic diseases. It is increasingly recognized that the timing, load, and route of allergen exposure affect allergic disease phenotypes and development. Still, our ability to prevent allergic diseases is hindered by gaps in understanding of the underlying mechanisms and interaction of environmental, viral, and allergen exposures with immune pathways that impact disease development. This Review highlights epidemiologic and mechanistic evidence linking environmental exposures to the development and exacerbation of allergic airway responses.

Mechanisms by Which Atopic Dermatitis Predisposes to Food Allergy and the Atopic March

The Atopic march denotes the progression from atopic dermatitis (AD) to the development of other allergic disorders such as immunoglobulin (Ig) E-mediated food allergy, allergic rhinitis and asthma in later childhood. There is increasing evidence from prospective birth cohort studies that early-onset AD is a risk factor for other allergic diseases or is found in strong association with them. Animal studies now provide mechanistic insights into the pathways that may be responsible for triggering the progression from the skin barrier dysfunction seen in AD to epicutaneous sensitization, food allergy and allergic airway disorders. Recent large randomized controlled trials have demonstrated the efficacy of early interventions targeted at AD and food allergy prevention. These show great promise for research into future strategies aimed at prevention of the atopic march.