The link between atopic dermatitis and asthma- immunological imbalance and beyond

Atopic diseases are multifactorial chronic disturbances which may evolve one into another and have overlapping pathogenetic mechanisms. Atopic dermatitis is in most cases the first step towards the development of the atopic march and represents a major socio-economic burden in the industrialized countries. The treatment of atopic diseases is often long-lasting and in some cases with lower effectiveness than expected.In order to prevent the development of the atopic march, the links between the atopic diseases have to be understood. The aim of this review is to present some major points outlining the link between atopic dermatitis and asthma, through a research in the medical literature from recent years.Stratifying patient populations according to the clinical phenotype of their disease and according to specific measurable values (biomarkers) can help to establish the main etiopathogenetic mechanisms of the disease in these populations. This will add predictive value for the evolution of the disease, and will allow the use and research of more targeted therapy in order to stop this evolution and comorbidities.

Current Insights into Atopic March

The incidence of allergic diseases is increasing, and research on their epidemiology, pathophysiology, and the prevention of onset is urgently needed. The onset of allergic disease begins in infancy with atopic dermatitis and food allergy and develops into allergic asthma and allergic rhinitis in childhood; the process is defined as “atopic march”. Atopic march is caused by multiple immunological pathways, including allergen exposure, environmental pollutants, skin barrier dysfunction, type 2 inflammation, and oxidative stress, which promote the progression of atopic march. Using recent evidence, herein, we explain the involvement of allergic inflammatory conditions and oxidative stress in the process of atopic march, its epidemiology, and methods for prevention of onset.

Epidermal Barrier Dysfunction in Atopic Dermatitis

Impaired skin barrier is one of the hallmarks of atopic dermatitis (AD), with abnormalities in the cornified envelope, lipid lamellae, tight junctions and cutaneous microbiome. These findings are also present in nonlesional skin of AD individuals, suggesting that epidermal barrier defects may be the initial step towards the development of AD and eventually other atopic diseases (atopic march). It is currently known that pathophysiology of AD involves an interplay between this dysfunctional skin barrier and a predominantly type 2 skewed innate and adaptive immune responses, which further disrupt the skin barrier through type 2 cytokines. In this setting, there is enhanced penetration of environmental and food allergens through a deficient barrier, leading to an increased susceptibility to sensitization. During the sensitization process, thymic stromal lymphopoietin (TSLP) polarizes skin dendritic cells to a T-helper 2 response, and TSLP seems to be a key cytokine in the sensitization of food allergy, allergic asthma and rhinitis. In this review, the authors describe the current knowledge of the pathophysiology of the epidermal barrier, its disruption in AD and how it may be involved in the development of atopic comorbidities and the role of barrier repair therapy on the prevention of the atopic march progression.

Anti-Interleukin Biologics for the treatment of the Atopic March Diseases

The atopic march refers to the natural history of allergic disorders as they develop from infancy to childhood. Classically, the atopic march begins with atopic dermatitis (AD), followed by food allergy, advancing to asthma, allergic rhinitis (AR), and finally to the fifth member eosinophilic esophagitis. The pathogenesis of the atopic march is complex, and involves genetic, immunological, and environmental factors. T helper type 2 (Th2) lymphocytes, and epithelial cells play a key role in the pathogenesis of the diseases in the atopic march. Th2 cells secrete cytokines, such as interleukin-5 (IL-5), IL-4, and IL-13, whereas, epithelial cell injury release alarmin cytokines, including IL-25, IL-33, and thymic stromal lymphopoietin (TSLP). Th2 cells and alarmin cytokines play an important role in the development of eczematous skin lesions, airway inflammation and remodeling, and oesophageal mucosal inflammation. Treatment of eosinophilic asthma and associated comorbid disorders is challenging, and requires a precision targeted approach with biologics. Dupilumab is a fully humanized IgG4 monoclonal antibody to the IL-4Rα, which mediates signaling to both IL-4 and IL-13, and blocks their immunopathological effects. Dupilumab is the only biologic that has been approved for the treatment of eosinophilic asthma, AD, and eosinophilic esophagitis. In patients with eosinophilic asthma treatment with dupilumab has been shown to improve asthma control, reduce exacerbations, and improve lung function. In patients with atopic dermatitis dupilumab has been demonstrated to improve the Eczema Area Severity Index (EASI) score, Investigator’s Global Assessment (IGA) response, SCORing Atopic Dermatitis (SCORAD) score, and the Peak Pruritus Numerical Rating (PNR) scale. Lebrikizumab and Tralokinumab (anti-IL-13) failed to show the expected results for the treatment of asthma, astoundingly, in several clinical trials they have been shown to significantly improvement EASI score, IGA response, SCORAD score, PNR scale, sleep architecture, and Dermatology Life Quality Index (DLQI). They have been granted First Tract Designation, and European Commission regulatory approval, respectively. Tezepelumab (anti-TSLP) is approved for the treatment of eosinophilic asthma, and has been shown to significantly reduce exacerbations, and improve asthma control, lung function, and HLQoL. However, tezepelumab did not meet the endpoints in phase II for the treatment of AD. Keywords: Atopic March; Atopic Dermatitis; Eosinophilic Asthma; Interleukin; Dupilumab; Tralokinumab

Melatonin prevents allergic airway inflammation in epicutaneously sensitized mice

Purpose: The pathological process of atopic dermatitis (AD) progressing into other types of allergic diseases such as asthma and allergic rhinitis during the first several years of life is often referred to as the atopic march. Although the phenomenon of atopic march has been recognized for decades, how asthma stems from AD is still not fully understood, confounding a universal strategy to effectively protect people from the atopic march. Methods: We established experimental atopic march mice by first inducing allergic dermatitis with 0.5% fluorescein isothiocyante applied to the skin, followed by an OVA airway challenge. In addition, by examining serum immunoglobulin concentrations, airway cytokines, the levels of oxidative stress markers, histopathological changes in lung tissue and airway hyperresponsiveness, we were able to validate the successful establishment of the model. Furthermore, by detecting the attenuating effects of melatonin (MT) and the levels of oxidative stress in the atopic march mice, we explored the potential molecular mechanisms involved in the development of atopic march. Results: By successfully establishing an experimental atopic march mouse model, we were able to demonstrate that overproduction of oxidative stress in the lung significantly upregulated the activation of NF-κB signaling pathways causing TSLP release, which further promotes the development of atopic march. Conclusions: To mitigate the development of the atopic march, antioxidants such as MT may be imperative to inhibit NF-κB activation in the lung, especially after the onset of AD.