Abstract Atopic dermatitis (AD) is a common skin condition, characterized by a complex, heterogeneous pathogenesis, including skin barrier dysfunctions, allergy/immunology, and pruritus. When the ...skin barrier is disrupted by, for example, the filaggrin gene mutation and/or environmental factors, the skin is predisposed to being penetrated by external stimuli. Foreign antigens can be subdivided into two subsets by size: haptens (including metals) and protein antigens. It is known that a single hapten challenge provokes Th1 initially, but that repeated elicitation with haptens results in a shift toward Th2-dominated responses. On the other hand, exposure to protein antigens directly induces Th2-dominant conditions via the thymic stromal lymphopoietin (TSLP) receptor on Langerhans cells. Recently, it has been revealed that Th2 cells produce IL-31, which provokes pruritus, and that Th2 cytokines decrease filaggrin expressions by keratinocytes. These findings suggest that Th2 conditions lead to pruritus and barrier dysfunctions. In this review, we will examine the highly complex interplay among skin barrier abnormality, allergy/immunology, and pruritus as a trinity in the development of AD.
Atopic dermatitis (AD) is the most common inflammatory skin disease in the industrialized world and has multiple causes. Over the past decade, data from both experimental models and patients have ...highlighted the primary pathogenic role of skin barrier deficiency in patients with AD. Increased access of environmental agents into the skin results in chronic inflammation and contributes to the systemic “atopic (allergic) march.” In addition, persistent skin inflammation further attenuates skin barrier function, resulting in a positive feedback loop between the skin epithelium and the immune system that drives pathology. Understanding the mechanisms of skin barrier maintenance is essential for improving management of AD and limiting downstream atopic manifestations. In this article we review the latest developments in our understanding of the pathomechanisms of skin barrier deficiency, with a particular focus on the formation of the stratum corneum, the outermost layer of the skin, which contributes significantly to skin barrier function.
Melanoma, a skin cancer associated with high mortality rates, is highly radio- and chemotherapy resistant but can also be very immunogenic. These circumstances have led to a recent surge in research ...into therapies aiming to boost anti-tumor immune responses in cancer patients. Among these immunotherapies, neutralizing antibodies targeting the immune checkpoints T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) are being hailed as particularly successful. These antibodies have resulted in dramatic improvements in disease outcome and are now clinically approved in many countries. However, the majority of advanced stage melanoma patients do not respond or will relapse, and the hunt for the "magic bullet" to treat the disease continues. This review examines the mechanisms of action and the limitations of anti-PD-1/PD-L1 and anti-CTLA-4 antibodies which are the two types of checkpoint inhibitors currently available to patients and further explores the future avenues of their use in melanoma and other cancers.
Key research advances in atopic dermatitis (AD) suggest the complexity of its endotypes. A comprehensive serum biomarker panel revealed at least 4 types of AD. Some represent classic TH2-dominant AD ...with filaggrin mutations commonly reported in Europeans, a simultaneously activated multipolar axis of cytokines often reported in Asian individuals, and an intrinsic type characterized by TH2 inferiority. Innate lymphoid cells, including natural killer cells, natural killer T cells, and fibroblasts, play a role in AD development and heterogeneity. Here, we discuss the endotypes of AD from the perspective of antigen types (hapten vs protein antigens), barrier function, and a novel set of immune cells. Endotypic stratification of AD may lead to the development of customized therapeutic strategies in the future.
Lipid mediators, such as prostanoids and leukotrienes (LTs), exert a range of actions through their own receptors on cell surfaces in various pathophysiological conditions. It has been reported that ...the production of prostanoids and LTs is significantly elevated in the skin lesions of some chronic inflammatory skin diseases, such as atopic dermatitis (AD) and psoriasis, showing the possible involvement of these lipid mediators in the development of those diseases. Although the actual significance of these lipid mediators in humans is still unclear, the findings from studies in mice suggest diverse roles of the lipid mediators in the progression or regulation of these diseases. For example, in a mouse AD model, prostaglandin D2 inhibits the induction of Th2 cells through DP receptor on Langerhans cells, while it promotes infiltration of Th2 cells through chemoattractant receptor-homologous molecule expressed on Th2 cells. In a psoriasis model, thromboxane A2-TP signaling promotes psoriatic dermatitis by facilitating IL-17 production from γδ T cells. In this short review, we summarize the current findings on the roles of prostanoids and LTs in AD and psoriasis as revealed by studies in mice, and discuss the potential of these lipid mediators as therapeutic targets in humans.
Barrier dysfunction in the skin allergy Egawa, Gyohei; Kabashima, Kenji
Allergology International,
January 2018, 20180101, 2018-Jan, 2018-01-00, 2018-01-01, Volume:
67, Issue:
1
Journal Article
Peer reviewed
Open access
The skin is continuously exposed to external pathogens, and its barrier function is critical for skin homeostasis. Previous studies have shown that the barrier dysfunction is one of the most ...predisposing factors for the development of skin allergic diseases such as atopic dermatitis. In this article, we summarize how the physical barrier of the skin is organized and review its link to the pathomechanism of skin allergic diseases. We describe the formation of the SC barrier in terms of the following five categories: 1) filaggrin metabolism; 2) cornified envelope; 3) intercellular lipids; 4) corneodesmosome; and 5) corneocyte desquamation. New approaches to restoring the skin barrier function are also discussed.
Abstract
Atopic dermatitis (AD) is a common T-cell-mediated inflammatory disease of the skin. Signatures of AD are characterized by an impaired skin barrier, aberrant Th2-type cytokine production and ...intensive pruritus. Transcriptomic analysis, however, has revealed a heterogeneous pathogenesis and the co-existence of multiple cytokine axes of Th17, Th22 and Th1 types, especially in intrinsic (a subtype of AD without skin barrier impairment), pediatric and Asian types of AD. Furthermore, the therapeutic effect of anti-IL-4 receptor α against AD was not as high as that of IL-17 blockage against psoriasis, which implies a modification of the disease spectrum by non-Th2-type cytokine axes in AD. These lines of evidence indicate a need for personalized or precision medicine appropriate for each subtype of AD.
Interleukin-31 may play a role in the pathobiologic mechanism of atopic dermatitis and pruritus. We wanted to assess the efficacy and safety of nemolizumab (CIM331), a humanized antibody against ...interleukin-31 receptor A, in the treatment of atopic dermatitis.
In this phase 2, randomized, double-blind, placebo-controlled, 12-week trial, we assigned adults with moderate-to-severe atopic dermatitis that was inadequately controlled by topical treatments to receive subcutaneous nemolizumab (at a dose of 0.1 mg, 0.5 mg, or 2.0 mg per kilogram of body weight) or placebo every 4 weeks or an exploratory dose of 2.0 mg of nemolizumab per kilogram every 8 weeks. The primary end point was the percentage improvement from baseline in the score on the pruritus visual-analogue scale (on which a negative change indicates improvement) at week 12. Secondary end points included changes in the score on the Eczema Area and Severity Index (EASI, on which a negative change indicates improvement), and body-surface area of atopic dermatitis.
Of 264 patients who underwent randomization, 216 (82%) completed the study. At week 12, among the patients who received nemolizumab every 4 weeks, changes on the pruritus visual-analogue scale were -43.7% in the 0.1-mg group, -59.8% in the 0.5-mg group, and -63.1% in the 2.0-mg group, versus -20.9% in the placebo group (P<0.01 for all comparisons). Changes on the EASI were -23.0%, -42.3%, and -40.9%, respectively, in the nemolizumab groups, versus -26.6% in the placebo group. Respective changes in body-surface area affected by atopic dermatitis were -7.5%, -20.0%, and -19.4% with nemolizumab, versus -15.7% with placebo. Among the patients receiving nemolizumab every 4 weeks, treatment discontinuations occurred in 9 of 53 patients (17%) in the 0.1-mg group, in 9 of 54 (17%) in the 0.5-mg group, and in 7 of 52 (13%) in the 2.0-mg group, versus in 9 of 53 (17%) in the placebo group.
In this phase 2 trial, nemolizumab at all monthly doses significantly improved pruritus in patients with moderate-to-severe atopic dermatitis, which showed the efficacy of targeting interleukin-31 receptor A. The limited size and length of the trial preclude conclusions regarding adverse events. (Funded by Chugai Pharmaceutical; XCIMA ClinicalTrials.gov number, NCT01986933 .).
Until the past year, our therapeutic armamentarium for treating atopic dermatitis (AD) was still primarily topical corticosteroids and, for more severe disease, systemic immunosuppressants. The ...pipeline of more targeted topical and systemic therapies is expanding based on our growing understanding of the mechanism for AD and is particularly focused on suppressing the skewed immune activation. Most agents are in phase 2 clinical trials. Crisaborole, a topical phosphodiesterase 4 (PDE4) inhibitor, became available in late 2016 in the United States for mild-to-moderate AD, with other PDE4 inhibitors, an agonist of the aryl hydrocarbon receptor, Janus kinase inhibitors, and commensal organisms also in trials for topical application. The first highly effective mAb for AD, dupilumab, targets the IL-4/IL-13 receptor and was approved in early 2017 in the United States for moderate-to-severe adult AD. Other biologics similarly inhibit TH2 cytokines (thymic stromal lymphopoietin, IL-4, IL-5, IL-13, and the itch-specific cytokine IL-31 and their receptors) or TH22/TH17 cytokines, levels of which are increased in lesional skin. Orally administered small-molecule inhibitors that suppress inflammation (targeting chemoattractant receptor–homologous molecules expressed on TH2 lymphocytes, PDE4, the histamine 4 receptor, and Janus kinase) or specifically itching (eg, NK1R inhibitors) are also being studied. Comparing biomarkers with individual responses to experimental agents will help to determine subphenotypes within AD that predict prognosis and treatment responses.
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