IL-33: a novel danger signal system in atopic dermatitis

Promoting New Approach Methodologies (NAMs) for research on skin color changes in response to environmental stress factors: tobacco and air pollution

Aging is one of the most dynamic biological processes in the human body and is known to carry significant impacts on individuals' self-esteem. Skin pigmentation is a highly heritable trait made possible by complex, strictly controlled cellular and molecular mechanisms. Genetic, environmental and endocrine factors contribute to the modulation of melanin's amount, type and distribution in the skin layers. One of the hallmarks of extrinsic skin aging induced by environmental stress factors is the alteration of the constitutive pigmentation pattern clinically defined as senile lentigines and/or melasma or other pigmentary dyschromias. The complexity of pollutants and tobacco smoke as environmental stress factors warrants a thorough understanding of the mechanisms by which they impact skin pigmentation through repeated and long-term exposure. Pre-clinical and clinical studies demonstrated that pollutants are known to induce reactive oxygen species (ROS) or inflammatory events that lead directly or indirectly to skin hyperpigmentation. Another mechanistic direction is provided by Aryl hydrocarbon Receptors (AhR) which were shown to mediate processes leading to skin hyperpigmentation in response to pollutants by regulation of melanogenic enzymes and transcription factors involved in melanin biosynthesis pathway. In this context, we will discuss a diverse range of New Approach Methodologies (NAMs) capable to provide mechanistic insights of the cellular and molecular pathways involved in the action of environmental stress factors on skin pigmentation and to support the design of raw ingredients and formulations intended to counter their impact and of any subsequently needed clinical studies.

Crosstalk between Interleukin-1 Receptor-Like 1 and Transforming Growth Factor-β Receptor Signaling Promotes Renal Fibrosis

IL-33, a member of the IL-1 family, acts as an alarmin in immune response. Epithelial-mesenchymal transition and transforming growth factor-β (TGF-β)–induced fibroblast activation are key events in the development of renal interstitial fibrosis. The current study found increased expression of IL-33 and interleukin-1 receptor-like 1 (IL1RL1, alias ST2), the receptor for IL-33, in human fibrotic renal tissues. In addition, IL-33– or ST2-deficient mice showed significantly reduced levels of fibronectin, α-smooth muscle actin, and vimentin, and increased E-cadherin levels. In HK-2 cells, IL-33 promotes the phosphorylation of the TGF-β receptor (TGF-βR), Smad2, and Smad3, and the production of extracellular matrix (ECM), with reduced expression of E-cadherin. Blocking TGF-βR signaling or suppressing ST2 expression impeded Smad2 and Smad3 phosphorylation, thereby reducing ECM production, suggesting that IL-33–induced ECM synthesis requires cooperation between the two pathways. Mechanistically, IL-33 treatment induced a proximate interaction between ST2 and TGF-βRs, activating downstream Smad2 and Smad3 for ECM production in renal epithelial cells. Collectively, this study identified a novel and essential role for IL-33 in promoting TGF-β signaling and ECM production in the development of renal fibrosis. Therefore, targeting IL-33/ST2 signaling may be an effective therapeutic strategy for renal fibrosis.

Intrinsic Effects of Exposome in Atopic Dermatitis: Genomics, Epigenomics and Regulatory Layers

Atopic dermatitis (AD) or atopic eczema is an increasingly manifested inflammatory skin disorder of complex etiology which is modulated by both extrinsic and intrinsic factors. The exposome includes a person's lifetime exposures and their effects. We recently reviewed the extrinsic exposome's environmental risk factors that contribute to AD. The periods of pregnancy, infancy, and teenage years are recognized as crucial stages in the formation of AD, where the exposome leads to enduring impacts on the immune system. However, research is now focusing on the interactions between intrinsic pathways that are modulated by the extrinsic exposome, including genetic variation, epigenetic modifications, and signals, such as diet, stress, and microbiome interactions. As a result, immune dysregulation, barrier dysfunction, hormonal fluctuations, and skin microbiome dysbiosis are important factors contributing to AD development, and their in-depth understanding is crucial not only for AD treatment but also for similar inflammatory disorders.

The evolving landscape of biologic therapies for atopic dermatitis: Present and future perspective

Atopic dermatitis (AD) is one of the most common, chronic inflammatory skin diseases with a significant physical, emotional and socioeconomic burden. In recent years the understanding of AD pathogenesis has expanded from the Th2-centred perspective, with the recognition of the involvement of other immune axes. In different AD endotypes, influenced by environment, genetics and race, transcriptomic profiles have identified differing contributions of multiple immune axes such as, Th17, Th22 and Th1. The enriched pathogenic model of AD has catalysed the development of numerous biologic therapies targeting a range of key molecules implicated in disease progression. Currently, dupilumab and tralokinumab, which both target the Th2 pathway, are the only approved biologic therapies for AD in the United States and Europe. New biologic therapies in development, however, target different Th2-pathway molecules along with cytokines in other immune axes, including Th17 and Th22, offering promise for varied treatments for this heterogeneous disease. As the biologic pipeline advances, the integration into clinical practice and approval of these experimental biologics may provide more effective, tailored therapeutic solutions and illuminate on the pathologic processes of AD across a broader, more diverse patient population.

Astegolimab or Efmarodocokin Alfa in Patients With Severe COVID-19 Pneumonia: A Randomized, Phase 2 Trial

OBJECTIVES

Severe cases of COVID-19 pneumonia can lead to acute respiratory distress syndrome (ARDS). Release of interleukin (IL)-33, an epithelial-derived alarmin, and IL-33/ST2 pathway activation are linked with ARDS development in other viral infections. IL-22, a cytokine that modulates innate immunity through multiple regenerative and protective mechanisms in lung epithelial cells, is reduced in patients with ARDS. This study aimed to evaluate safety and efficacy of astegolimab, a human immunoglobulin G2 monoclonal antibody that selectively inhibits the IL-33 receptor, ST2, or efmarodocokin alfa, a human IL-22 fusion protein that activates IL-22 signaling, for treatment of severe COVID-19 pneumonia.

DESIGN

Phase 2, double-blind, placebo-controlled study (COVID-astegolimab-IL).

SETTING

Hospitals.

PATIENTS

Hospitalized adults with severe COVID-19 pneumonia.

INTERVENTIONS

Patients were randomized to receive IV astegolimab, efmarodocokin alfa, or placebo, plus standard of care. The primary endpoint was time to recovery, defined as time to a score of 1 or 2 on a 7-category ordinal scale by day 28.

MEASUREMENTS AND MAIN RESULTS

The study randomized 396 patients. Median time to recovery was 11 days (hazard ratio [HR], 1.01 d; p = 0.93) and 10 days (HR, 1.15 d; p = 0.38) for astegolimab and efmarodocokin alfa, respectively, versus 10 days for placebo. Key secondary endpoints (improved recovery, mortality, or prevention of worsening) showed no treatment benefits. No new safety signals were observed and adverse events were similar across treatment arms. Biomarkers demonstrated that both drugs were pharmacologically active.

CONCLUSIONS

Treatment with astegolimab or efmarodocokin alfa did not improve time to recovery in patients with severe COVID-19 pneumonia.

Phase 1 and 2 Randomized Clinical Studies Determine Lack of Efficacy for Anti-IL-17C Antibody MOR106 in Moderate-Severe Atopic Dermatitis

Interleukin 17C (IL-17C) modulates epithelial inflammation and has a possible role in atopic dermatitis (AD) pathology. Four randomized clinical studies (Phase 1 and 2) investigated the safety, tolerability, efficacy, and pharmacokinetic profile of the anti-IL-17C monoclonal antibody MOR106 for up to 12 weeks (NCT03568071: n = 207 adults with moderate-severe AD; NCT03689829 Part 1: n = 32 healthy males; NCT03689829 Part 2: n = 44 adults with moderate-severe AD; and NCT03864627: n = 76 adults with moderate-severe AD). In these studies, MOR106 was either administered intravenously (i.v.) every 2 or 4 weeks at doses between 1-10 mg/kg, or subcutaneously (s.c.), either as a single dose or doses every 2 weeks at 320 mg. Overall, MOR106 was well-tolerated, and the safety profile was consistent with monoclonal antibodies approved for AD. Bioavailability following s.c. dosing was 55%, and steady-state drug levels were reached at 2-4 weeks. Ongoing studies were terminated following a futility analysis of the Phase 2 placebo-controlled dose-finding study (NCT03568071) due to a low probability for achieving the primary efficacy endpoint. Cumulatively, MOR106 demonstrated ineffectiveness for the treatment of AD, but its safety and pharmacokinetic characteristics warrant further drug development in other indications. Funding: sponsored by Galapagos NV; funded by Novartis AG.

Phase 2 randomized clinical trial of astegolimab in patients with moderate to severe atopic dermatitis

BACKGROUND

The binding of IL-33 to its receptor ST2 (alias of IL1RL1) leads to the release of inflammatory mediators and may play a role in the pathogenesis of atopic dermatitis. Astegolimab is a fully human, IgG₂ mAb that binds to ST2 and inhibits IL-33 signaling.

OBJECTIVES

This study sought to assess the efficacy, safety, and pharmacokinetics of astegolimab in patients with atopic dermatitis.

METHODS

This was a randomized, placebo-controlled, phase 2 study in which adults with chronic atopic dermatitis were randomized 1:1 to receive astegolimab 490 mg every 4 weeks or placebo, for 16 weeks. The primary outcome was the percentage of change from baseline to week 16 of the Eczema Area and Severity Index score.

RESULTS

A total of 65 patients were enrolled in the study (placebo, n = 32; astegolimab, n = 33). The adjusted mean percentage of change from baseline to week 16 in the Eczema Area and Severity Index score was -51.47% for astegolimab compared with -58.24% for placebo, with a nonsignificant treatment difference of 6.77% (95% CI: -16.57-30.11; P = .5624). No differences were observed between treatment groups for secondary efficacy outcomes and in exploratory biomarkers (blood eosinophils, serum IL-5, serum CCL13). With the use of loading dose, pharmacokinetic exposure was sufficient from week 1. Astegolimab was well-tolerated, with a safety profile consistent with that observed in previous clinical trials.

CONCLUSIONS

In patients with atopic dermatitis, astegolimab did not show a significant difference compared to placebo for the primary or secondary outcomes.

IL-33/Regulatory T-Cell Axis Suppresses Skin Fibrosis

Fibrosis is a pathological hallmark of systemic sclerosis, a deadly autoimmune disease affecting the connective tissues of multiple organs. However, the immune mechanisms underlying fibrosis and systemic sclerosis remain unclear. To determine the initiating immune pathway in fibrosis, we investigated the role of type 2 alarmin cytokines in the mouse model of skin fibrosis. Wild-type mice that received subcutaneous bleomycin injections developed skin fibrosis accompanied by elevated IL-33 expression in the dermis. Likewise, we found IL-33 upregulation in human skin fibrosis. Mice with germline deletion of IL-33 receptor (ST2 knockout) showed markedly exacerbated skin fibrosis in association with significantly increased T helper 2 cell to regulatory T-cell ratio in the skin. Mice that lacked ST2 specifically on regulatory T cells (Foxp3Cre,ST2flox/flox) showed significantly worse skin fibrosis, increased T helper 2 to regulatory T cell ratio and IL-13 expression in the skin compared with wild-type mice. Our findings show that IL-33 cytokine signaling to regulatory T cells suppresses skin fibrosis and highlight a potential therapeutic axis to alleviate the debilitating manifestations of systemic sclerosis.

Critical Players and Therapeutic Targets in Chronic Itch

Chronic itch is one of the most prominent clinical characteristics of diverse systematic diseases. It is a devastating sensation in pathological diseases. Despite its importance, there are no FDA-labelled drugs specifically geared toward chronic itch. The associated complex pathogenesis and diverse causes escalate chronic itch to being one of the top challenges in healthcare. Humanized antibodies against IL-13, IL-4, and IL-31 proved effective in treatment of itch-associated atopic dermatitis but remain to be validated in chronic itch. There are still no satisfactory anti-itch therapeutics available toward itch-related neuropeptides including GRP, BNP, SST, CGRP, and SP. The newly identified potential itch targets including OSM, NMB, glutamate, periostin, and Serpin E1 have opened new avenues for therapeutic development. Proof-of-principle studies have been successfully performed on antagonists against these proteins and their receptors in itch treatment in animal models. Their translational interventions in humans need to be evaluated. It is of great importance to summarize and compare the newly emerging knowledge on chronic itch and its pathways to promote the development of novel anti-itch therapeutics. The goal of this review is to analyze the different physiologies and pathophysiologies of itch mediators, whilst assessing their suitability as new targets and discussing future therapeutic development.

AllergoOncology: Danger signals in allergology and oncology: A European Academy of Allergy and Clinical Immunology (EAACI) Position Paper

The immune system interacts with many nominal 'danger' signals, endogenous danger-associated (DAMP), exogenous pathogen (PAMP) and allergen (AAMP)-associated molecular patterns. The immune context under which these are received can promote or prevent immune activating or inflammatory mechanisms and may orchestrate diverse immune responses in allergy and cancer. Each can act either by favouring a respective pathology or by supporting the immune response to confer protective effects, depending on acuity or chronicity. In this Position Paper under the collective term danger signals or DAMPs, PAMPs and AAMPs, we consider their diverse roles in allergy and cancer and the connection between these in AllergoOncology. We focus on their interactions with different immune cells of the innate and adaptive immune system and how these promote immune responses with juxtaposing clinical outcomes in allergy and cancer. While danger signals present potential targets to overcome inflammatory responses in allergy, these may be reconsidered in relation to a history of allergy, chronic inflammation and autoimmunity linked to the risk of developing cancer, and with regard to clinical responses to anti-cancer immune and targeted therapies. Cross-disciplinary insights in AllergoOncology derived from dissecting clinical phenotypes of common danger signal pathways may improve allergy and cancer clinical outcomes.

Cell death in skin function, inflammation, and disease

Cell death is an essential process that plays a vital role in restoring and maintaining skin homeostasis. It supports recovery from acute injury and infection and regulates barrier function and immunity. Cell death can also provoke inflammatory responses. Loss of cell membrane integrity with lytic forms of cell death can incite inflammation due to the uncontrolled release of cell contents. Excessive or poorly regulated cell death is increasingly recognised as contributing to cutaneous inflammation. Therefore, drugs that inhibit cell death could be used therapeutically to treat certain inflammatory skin diseases. Programmes to develop such inhibitors are already underway. In this review, we outline the mechanisms of skin-associated cell death programmes; apoptosis, necroptosis, pyroptosis, NETosis, and the epidermal terminal differentiation programme, cornification. We discuss the evidence for their role in skin inflammation and disease and discuss therapeutic opportunities for targeting the cell death machinery.

Atopic dermatitis: Is innate or adaptive immunity in control? A clinical perspective

Atopic dermatitis (AD) is a chronic inflammatory skin disease with barrier defects and immune dysregulations. The pathogenesis of AD involves the physical barrier as well as epithelial cells, which are considered a vital part of the innate immunity of the skin. The importance of filaggrin mutations in the pathogenesis of AD has also been well-established with reproducible results around the world in multiple studies and ethnic groups. This protein plays an important role in skin barrier functions and further reaffirms barrier defects as one of the primary causes of AD. The main epithelial cells, keratinocytes, function as a major sentinel for the skin in detecting danger signals or microbial pathogens, and trigger downstream immune responses. In AD, these cells express TSLP, IL-33 and IL-25, which lead to downstream systemic production of type 2 cytokines. In spite of major advances in our understanding of the innate immunity of AD, recent success in the systemic therapeutics of AD have focused on targeting the products of the adaptive immunity, particularly cytokines produced by T cells. In addition to type 2 cytokines, type 17 cytokines have also been implicated in the pathogenesis of AD. The current review examines the implications of these cytokines in AD from clinical perspectives.

Molecular and cellular mechanisms of itch and pain in atopic dermatitis and implications for novel therapeutics

Atopic dermatitis is a chronic inflammatory skin disease. Patients with atopic dermatitis experience inflammatory lesions associated with intense itch and pain, which lead to sleep disturbance and poor mental health and quality of life. We review the molecular mechanisms underlying itch and pain symptoms in atopic dermatitis and discuss the current clinical development of treatments for moderate‐to‐severe atopic dermatitis. The molecular pathology of atopic dermatitis includes aberrant immune activation involving significant cross‐talk among the skin and immune and neuronal cells. Exogenous and endogenous triggers modulate stimulation of mediators including cytokine/chemokine expression/release by the skin and immune cells, which causes inflammation, skin barrier disruption, activation and growth of sensory neurons, itch and pain. These complex interactions among cell types are mediated primarily by cytokines, but also involve chemokines, neurotransmitters, lipids, proteases, antimicrobial peptides, agonists of ion channels or various G protein–coupled receptors. Patients with atopic dermatitis have a cytokine profile characterised by abnormal levels of interleukins 4, 12, 13, 18, 22, 31 and 33; thymic stromal lymphopoietin; and interferon gamma. Cytokine receptors mainly signal through the Janus kinase/signal transducer and activator of transcription pathway. Among emerging novel therapeutics, several Janus kinase inhibitors are being developed for topical or systemic treatment of moderate‐to‐severe atopic dermatitis because of their potential to modulate cytokine expression and release. Janus kinase inhibitors lead to changes in gene expression that have favourable effects on local and systemic cytokine release, and probably other mediators, thus successfully modulating molecular mechanisms responsible for itch and pain in atopic dermatitis.

Neuro-immune communication regulating pruritus in atopic dermatitis

Atopic dermatitis (AD) is a common, chronic-relapsing inflammatory skin disease with significant disease burden. Genetic and environmental trigger factors contribute to AD, activating two of our largest organs, the nervous and immune system. Dysregulation of neuro-immune circuits plays a key role in the pathophysiology of AD causing inflammation, pruritus, pain, and barrier dysfunction. Sensory nerves can be activated by environmental or endogenous trigger factors transmitting itch stimuli to the brain. Upon stimulation, sensory nerve endings also release neuromediators into the skin contributing again to inflammation, barrier dysfunction and itch. Additionally, dysfunctional peripheral and central neuronal structures contribute to neuroinflammation, sensitization, nerve elongation, neuropathic itch, thus chronification and therapy-resistance. Consequently, neuro-immune circuits in skin and central nervous system may be targets to treat pruritus in AD. Cytokines, chemokines, proteases, lipids, opioids, ions excite/sensitize sensory nerve endings not only induce itch but further aggravate/perpetuate inflammation, skin barrier disruption, and pruritus. Thus, targeted therapies for neuro-immune circuits as well as pathway inhibitors (e.g., kinase inhibitors) may be beneficial to control pruritus in AD either in systemic and/or topical form. Understanding neuro-immune circuits and neuronal signaling will optimize our approach to control all pathological mechanisms in AD, inflammation, barrier dysfunction and pruritus.

Role of Damage-Associated Molecular Patterns (DAMPs/Alarmins) in Severe Ocular Allergic Diseases

Severe ocular allergic diseases, such as atopic keratoconjunctivitis and vernal keratoconjunctivitis, cause severe allergic inflammation in the conjunctiva and corneal epithelial damage, resulting in visual disturbances. The involvement of damage (danger)-associated molecular patterns (DAMPs/alarmins) in the pathogenesis of these diseases has been recognized. Alarmins released from damaged corneal epithelial cells or eosinophils play a critical role in the induction of corneal lesions, vicious loop of corneal injury, and exacerbation of conjunctival allergic inflammation. Alarmins in the conjunctiva also play an essential role in the development of both allergic inflammation, based on the acquired immune system, and type 2 inflammation by innate immune responses in the ocular surface. Therefore, alarmins may be a potentially important therapeutic target in severe refractory ocular allergic diseases.

T cells in the skin: lymphoma and inflammatory skin disease

T cells are established contributors to the pathogenesis of atopic dermatitis (AD) and psoriasis, yet whether they are the key drivers or simply unwitting participants remains incompletely understood. Conversely, malignant T cells are the undisputed culprits of cutaneous T cell lymphoma (CTCL), a group of diseases that share key clinical, histopathological and molecular features with inflammatory skin disease (ISD). Here, we compare the pathogenesis of ISD and CTCL and discuss the resulting insights. Recurrent, skin-limited disease implicates skin-resident T cells (T_RM) in both ISD and CTCL. In CTCL, malignant T cells recruit benign T cells into inflammatory skin lesions, a disease-amplifying function also proposed for pathogenic T cells in ISD. Mechanistically, cytokines produced by malignant T cells in CTCL and by pathogenic T cells in ISD, respectively, are likely both necessary and sufficient to drive skin inflammation and pruritus, which in turn promotes skin barrier dysfunction and dysbiosis. Therapies for ISD target T cell effector functions but do not address the chronicity of disease while treatments for CTCL target malignant T cells but not primarily the symptoms of the disease. By integrating our understanding of ISD and CTCL, important insights into pathogenesis and therapy can be made which may improve the lives of sufferers of both disease groups.

Deacetylasperulosidic Acid Ameliorates Pruritus, Immune Imbalance, and Skin Barrier Dysfunction in 2,4-Dinitrochlorobenzene-Induced Atopic Dermatitis NC/Nga Mice

The prevalence of atopic dermatitis (AD), a disease characterized by severe pruritus, immune imbalance, and skin barrier dysfunction, is rapidly increasing worldwide. Deacetylasperulosidic acid (DAA) has anti-atopic activity in the three main cell types associated with AD: keratinocytes, mast cells, and eosinophils. Our study investigated the anti-atopic activity of DAA in 2,4-dinitrochlorobenzene-induced NC/Nga mice. DAA alleviated the symptoms of AD, including infiltration of inflammatory cells (mast cells and eosinophils), epidermal thickness, ear thickness, and scratching behavior. Furthermore, DAA reduced serum IgE, histamine, and IgG1/IgG2a ratio and modulated the levels of AD-related cytokines and chemokines, namely interleukin (IL)-1β, IL-4, IL-6, IL-9, IL-10, IL-12, tumor necrosis factor-α, interferon-γ, thymic stromal lymphopoietin, thymus and activation-regulated chemokine, macrophage-derived chemokine, and regulated on activation the normal T cell expressed and secreted in the serum. DAA restored immune balance by regulating gene expression and secretion of Th1-, Th2-, Th9-, Th17-, and Th22-mediated inflammatory factors in the dorsal skin and splenocytes and restored skin barrier function by increasing the expression of the pro-filaggrin gene and barrier-related proteins filaggrin, involucrin, and loricrin. These results suggest DAA as a potential therapeutic agent that can alleviate the symptoms of AD by reducing pruritus, modulating immune imbalance, and restoring skin barrier function.

Involvement of Alarmins in the Pathogenesis and Progression of Multiple Myeloma

OBJECTIVE

Multiple Myeloma (MM) is a haematological disease resulting from the neoplastic transformation of plasma cells. The uncontrolled growth of plasma cells in the bone marrow and the delivery of several cytokines causes bone erosion that often does not regress, even in the event of disease remission. MM is characterised by a multi-step evolutionary path, which starts with an early asymptomatic stage defined as monoclonal gammopathy of undetermined significance (MGUS) evolving to overt disease.

DATA SOURCES AND STUDY SELECTION

We have selected scientific publications on the specific topics "alarmis, MGUS, and MM", drawing from PubMed. The keywords we used were alarmines, MGUS, MM, and immune system.

RESULTS

The analysis confirms the pivotal role of molecules such as high-mobility group box-1, heat shock proteins, and S100 proteins in the induction of neoangiogenesis, which represents a milestone in the negative evolution of MM as well as other haematological and non-haematological tumours.

CONCLUSIONS

Modulation of the host immune system and the inhibition of neoangiogenesis may represent the therapeutic target for the treatment of MM that is capable of promoting better survival and reducing the risk of RRMM.

Anti-Inflammatory and Anti-Allergic Effects of Saponarin and Its Impact on Signaling Pathways of RAW 264.7, RBL-2H3, and HaCaT Cells

Saponarin{5-hydroxy-2-(4-hydroxyphenyl)-6-[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]-7-[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxychromen-4-one}, a flavone found in young green barley leaves, is known to possess antioxidant, antidiabetic, and hepatoprotective effects. In the present study, the anti-inflammatory, anti-allergic, and skin-protective effects of saponarin were investigated to evaluate its usefulness as a functional ingredient in cosmetics. In lipopolysaccharide-induced RAW264.7 (murine macrophage) cells, saponarin (80 μM) significantly inhibited cytokine expression, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, inducible nitric oxide synthase, and cyclooxygenase (COX)-2. Saponarin (80 μM) also inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 involved in the mitogen-activated protein kinase signaling pathway in RAW264.7 cells. Saponarin (40 μM) significantly inhibited β-hexosaminidase degranulation as well as the phosphorylation of signaling effectors (Syk, phospholipase Cγ1, ERK, JNK, and p38) and the expression of inflammatory mediators (tumor necrosis factor [TNF]-α, IL-4, IL-5, IL-6, IL-13, COX-2, and FcεRIα/γ) in DNP-IgE- and DNP-BSA-stimulated RBL-2H3 (rat basophilic leukemia) cells. In addition, saponarin (100 μM) significantly inhibited the expression of macrophage-derived chemokine, thymus and activation-regulated chemokine, IL-33, thymic stromal lymphopoietin, and the phosphorylation of signaling molecules (ERK, p38 and signal transducer and activator of transcription 1 [STAT1]) in TNF-α- and interferon (IFN)-γ-stimulated HaCaT (human immortalized keratinocyte) cells. Saponarin (100 μM) also significantly induced the expression of hyaluronan synthase-3, aquaporin 3, and cathelicidin antimicrobial peptide (LL-37) in HaCaT cells, which play an important role as skin barriers. Saponarin remarkably inhibited the essential factors involved in the inflammatory and allergic responses of RAW264.7, RBL-2H3, and HaCaT cells, and induced the expression of factors that function as physical and chemical skin barriers in HaCaT cells. Therefore, saponarin could potentially be used to prevent and relieve immune-related skin diseases, including atopic dermatitis.

Virtual discovery of a hetero-cyclic compound from the Universal Natural Product Database (UNPD36) as a potential inhibitor of interleukin-33: molecular docking and dynamic simulations

Interleukin (IL)-33 is a cytokine implicated in several inflammatory and autoimmune diseases. Upon binding to its receptor ST2, IL-33 activates allergic inflammatory responses. To block this protein-protein interaction with a potential anti-allergic agent, we screened Universal Natural Product Database (UNPD) using a combined approach of molecular docking and dynamic simulations. Six hundred compounds with high gastrointestinal absorption properties from the UNPD were retrieved and subjected to molecular docking using Autodock Vina, out of which four hetero-cyclic compounds (UNPD36, UNPD2045, UNPD8905, UNPD122514) were found to have binding energy score of < -7.0 Kcal/mol. Further analysis from 100 ns MD simulation of the best hit (UNPD36) revealed that IL-33_UNPD36 complex reached average stability at RMSD of 2.7 Å, and residues involved in the interaction showed lower fluctuations compared to the residues at the β4-β5 and β11-β12 loop region. Further molecular docking using Autodock 4.2 was carried out to determine the binding orientation of UNPD36. Using GROMACS, additional 50 ns MD simulations and MM-PBSA calculation were performed on this complex. Finally, chemoinformatic studies revealed that the UNPD36 had drug-like and pharmacokinetic profiles as well as potentials for oral and topical applications, in addition to good safety profile. Thus, it was concluded that a hetero-cyclic compound with chromone moiety (UNPD36) had a good and stable binding mode to serve as potential inhibitor of IL-33 and/or may provide a scaffold for further optimization toward the design of more potent inhibitors for application in the treatment of respiratory allergies.Communicated by Ramaswamy H. Sarma.

Diversified Stimuli-Induced Inflammatory Pathways Cause Skin Pigmentation

The production of melanin pigments by melanocytes and their quantity, quality, and distribution play a decisive role in determining human skin, eye, and hair color, and protect the skin from adverse effects of ultraviolet radiation (UVR) and oxidative stress from various environmental pollutants. Melanocytes reside in the basal layer of the interfollicular epidermis and are compensated by melanocyte stem cells in the follicular bulge area. Various stimuli such as eczema, microbial infection, ultraviolet light exposure, mechanical injury, and aging provoke skin inflammation. These acute or chronic inflammatory responses cause inflammatory cytokine production from epidermal keratinocytes as well as dermal fibroblasts and other cells, which in turn stimulate melanocytes, often resulting in skin pigmentation. It is confirmed by some recent studies that several interleukins (ILs) and other inflammatory mediators modulate the proliferation and differentiation of human epidermal melanocytes and also promote or inhibit expression of melanogenesis-related gene expression directly or indirectly, thereby participating in regulation of skin pigmentation. Understanding of mechanisms of skin pigmentation due to inflammation helps to elucidate the relationship between inflammation and skin pigmentation regulation and can guide development of new therapeutic pathways for treating pigmented dermatosis. This review covers the mechanistic aspects of skin pigmentation caused by inflammation.

Pruritus in psoriasis and atopic dermatitis: current treatments and new perspectives

Psoriasis and atopic dermatitis (AD) are two common chronic inflammatory skin diseases. Although showing different etiology and clinical manifestations, patients with either disease suffer from low health-related quality of life due to pruritus (dermal itch). Recent studies have revealed that more than 85% of psoriasis patients suffer from pruritus, and it is also the dominating symptom of AD. However, as this is a non-life treating symptom, it was partly neglected for years. In this review, we focus on current findings as well as the impact and potential treatments of pruritus in these two skin diseases. We first distinguish the type of itch based on involved mediators and modulators. This clear delineation between the types of pruritus based on involved receptors and pathways allows for precise treatment. In addition, insights into recent clinical trials aimed to alleviate pruritus by targeting these receptors are presented. We also report about novel advances in combinatorial treatments, dedicated to the type of pruritus linked to a causal disease. Altogether, we suggest that only a focused treatment tailored to the primary disease and the underlying molecular signals will provide fast and sustained relief of pruritus associated with psoriasis or AD.

Nuclear Alarmin Cytokines in Inflammation

Pathogen-associated molecular patterns (PAMPs) are some nonspecific and highly conserved molecular structures of exogenous specific microbial pathogens, whose products can be recognized by pattern recognition receptor (PRR) on innate immune cells and induce an inflammatory response. Under physiological stress, activated or damaged cells might release some endogenous proteins that can also bind to PRR and cause a harmful aseptic inflammatory response. These endogenous proteins were named damage-associated molecular patterns (DAMPs) or alarmins. Indeed, alarmins can also play a beneficial role in the tissue repair in certain environments. Besides, some alarmin cytokines have been reported to have both nuclear and extracellular effects. This group of proteins includes high-mobility group box-1 protein (HMGB1), interleukin (IL)-33, IL-1α, IL-1F7b, and IL-16. In this article, we review the involvement of nuclear alarmins such as HMGB1, IL-33, and IL-1α under physiological state or stress state and suggest a novel activity of these molecules as central initiators in the development of sterile inflammation.

Cellular context of IL-33 expression dictates impact on anti-helminth immunity

Interleukin-33 (IL-33) is a pleiotropic cytokine that can promote type 2 inflammation but also drives immunoregulation through Foxp3⁺T_reg expansion. How IL-33 is exported from cells to serve this dual role in immunosuppression and inflammation remains unclear. Here, we demonstrate that the biological consequences of IL-33 activity are dictated by its cellular source. Whereas IL-33 derived from epithelial cells stimulates group 2 innate lymphoid cell (ILC2)-driven type 2 immunity and parasite clearance, we report that IL-33 derived from myeloid antigen-presenting cells (APCs) suppresses host-protective inflammatory responses. Conditional deletion of IL-33 in CD11c-expressing cells resulted in lowered numbers of intestinal Foxp3⁺T_reg cells that express the transcription factor GATA3 and the IL-33 receptor ST2, causing elevated IL-5 and IL-13 production and accelerated anti-helminth immunity. We demonstrate that cell-intrinsic IL-33 promoted mouse dendritic cells (DCs) to express the pore-forming protein perforin-2, which may function as a conduit on the plasma membrane facilitating IL-33 export. Lack of perforin-2 in DCs blocked the proliferative expansion of the ST2⁺Foxp3⁺T_reg subset. We propose that perforin-2 can provide a plasma membrane conduit in DCs that promotes the export of IL-33, contributing to mucosal immunoregulation under steady-state and infectious conditions.

Novel therapies based on the pathophysiology of atopic dermatitis

Our understanding of the mechanisms underlying atopic dermatitis has been instrumental in the development of novel pharmacological agents. Worldwide, more than seventy companies are currently developing at least one new drug for the treatment of atopic dermatitis. Based on our current understanding of the pathophysiology of the disease, the present review article highlights the most important novel therapeutic strategies.

Cutaneous Immune Cell-Microbiota Interactions Are Controlled by Epidermal JunB/AP-1

Atopic dermatitis (AD) is a multi-factorial skin disease with a complex inflammatory signature including type 2 and type 17 activation. Although colonization by S. aureus is common in AD, the mechanisms rendering an organism prone to dysbiosis, and the role of IL-17A in the control of S. aureus-induced skin inflammation, are not well understood. Here, we show several pathological aspects of AD, including type 2/type 17 immune responses, elevated IgE, barrier dysfunction, pruritus, and importantly, spontaneous S. aureus colonization in JunB^Δep mice, with a large transcriptomic overlap with AD. Additionally, using Rag1^−/− mice, we demonstrate that adaptive immune cells are necessary for protection against S. aureus colonization. Prophylactic antibiotics, but not antibiotics after established dysbiosis, reduce IL-17A expression and skin inflammation, examined using Il17a-eGFP reporter mice. Mechanistically, keratinocytes lacking JunB exhibit higher MyD88 levels in vitro and in vivo, previously shown to regulate S. aureus colonization. In conclusion, our data identify JunB as an upstream regulator of microbiota-immune cell interactions and characterize the IL-17A response upon spontaneous dysbiosis.

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JunB^Δep mice display several defining features of atopic dermatitis

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Skin of JunB^Δep mice are colonized by human-derived S. aureus

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Adaptive immune system is necessary for protection against S. aureus

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JunB is an upstream regulator of the microbiota-immune cell interactions

Canine atopic dermatitis: Role of luteolin as new natural treatment

Background

Luteolin has been demonstrated to possess numerous biological effects. However, the effect of luteolin on LPS (Lipopolysaccharides) stimulation in CPEK cells has not been investigated.

Hypothesis/Objectives

An in vitro model of atopic canine dermatitis was used to identify the antioxidant effect of luteolin as a new treatment that is capable of improving the conditions of veterinary patients.

Methods

CPEK cells were treated with or without luteolin in the presence or absence of LPS. A cell viability assay was performed to test luteolin toxicity and the protective effect of luteolin after LPS stimulation. Additionally, enzyme‐linked immunosorbent assay (ELISA) kits were used to detect the levels of IL‐33, IL‐1β, IL‐6, and IL‐8.

Results

Luteolin was capable to significantly decrease levels expression of IL‐33, IL 1β, IL‐6, and IL‐8.

Conclusions and clinical importance

Luteolin could be a new pharmacological treatment for canine atopic dermatitis.

Adipose-derived stem cells attenuate atopic dermatitis-like skin lesions in NC/Nga mice

There is an unmet need in novel therapeutics for atopic dermatitis (AD). We examined the effects of autologous adipose-derived stem cells (ADSCs) on AD-like skin lesions induced by the application of 2,4-dinitrochlorobenzene (DNCB) in NC/Nga mice. Autologous ADSCs and ADSC-conditioned medium (ADSC-CM) were injected intralesionally three times. Clinical severity and histopathologic findings were compared in sham naïve control, saline-treated, ADSC-treated, ADSC-CM-treated and 2.5% cortisone lotion-applied animals. The severity index, skin thickness, mast cell number, as well as expression levels of thymic stromal lymphopoietin, CD45, chemoattractant receptor-homologous molecule, chemokine ligand 9 and chemokine ligand 20 were significantly lower in mice treated with ADSC, ADSC-CM, or 2.5% cortisone lotion. Tissue levels of interferon-γ as well as serum levels of interleukin-33 and immunoglobulin E levels were also decreased in those groups. We conclude that autologous ADSCs improved DNCB-induced AD-like skin lesions in NC/Nga mice by reducing inflammation associated with Th2 immune response and interferon-γ.

Neuro-Immunity Controls Obesity-Induced Pain

The prevalence of obesity skyrocketed over the past decades to become a significant public health problem. Obesity is recognized as a low-grade inflammatory disease and is linked with several comorbidities such as diabetes, circulatory disease, common neurodegenerative diseases, as well as chronic pain. Adipocytes are a major neuroendocrine organ that continually, and systemically, releases pro-inflammatory factors. While the exact mechanisms driving obesity-induced pain remain poorly defined, nociceptor hypersensitivity may result from the systemic state of inflammation characteristic of obesity as well as weight surplus-induced mechanical stress. Obesity and pain also share various genetic mutations, lifestyle risk factors, and metabolic pathways. For instance, fat pads are often found hyper-innervated and rich in immune cell types of multiple origins. These immunocytes release cytokines, amplifying nociceptor function, which, in turn, via locally released neuropeptides, sustain immunocytes' function. Here, we posit that along with mechanical stress stemming from extra weight, the local neuro-immune interplay occurring within the fat pads maintains the state of chronic low-grade inflammation and heightens sensory hypersensitivity. Overall, stopping such harmful neuro-immune crosstalk may constitute a novel pathway to prevent obesity-associated comorbidities, including neuronal hypersensitivity.

Exposure to diisononyl phthalate promotes atopic march by activating of NF-κB and p38 MAPK

What factors and underlying mechanisms influence the occurrence of the atopic march remain unclear. Recent studies suggest that exposure to diisononyl phthalate (DINP) might be associated with the occurrence of atopic dermatitis (AD) and asthma. However, little is known about the role of DINP exposure in the atopic march. In this study, we investigated the effect of DINP exposure on the progression from AD to asthma, and explored the potential mechanisms. We built an atopic march mouse model from AD to asthma, by exposure to DINP and sensitization with OVA. Pyrrolidine dithiocarbamate and SB203580 were used to block NF-κB and p38 MAPK respectively, to explore the possible molecular mechanisms. The data showed that DINP aggravated airway remodeling and airway hyperresponsiveness (AhR) in the progression from AD to asthma, induced a sharp increase in IL-33, IgE, Th2 and Th17 cytokines, and resulted in an increase in the expression of thymic stromal lymphopoietin (TSLP) and in the number of inflammatory cells. Blocking NF-κB inhibited AD-like lesions, and the production of IL-33 and TSLP in the progression of AD, while alleviating airway remodeling, AhR, and the expression of Th2 and Th17 cytokines in both the progression of AD and the asthmatic phenotype. Blocking p38 MAPK in the progression of asthma, inhibited airway remodeling, AhR, and the expression of Th2 and Th17 cytokines. The results demonstrated that exposure to DINP enhanced the immune response to memory CD4⁺ T helper cells through the NF-κB and p38 MAPK signaling pathways, leading to an aggravation of the atopic march.

IL-33 is associated with allergy in children sensitized to the cat

BACKGROUND

Several studies suggest that early-life exposure to animal allergens constitutes a relevant risk factor for the development of allergic sensitization.

OBJECTIVES

The aim of the present study was to determine the role of interleukin-33 in children sensitive to cat allergen with allergic rhinitis and/or asthma.

METHODS

The study included 51 children aged 5-18 years, both sexes, allergic to cats. Sensitization to cat allergen was confirmed by skin prick tests or specific IgE. Children were evaluated for the presence of bronchial asthma, atopic dermatitis, allergic rhinitis. A questionnaire evaluating the occurrence of allergic symptoms in children after contact with the cat and dog was performed. Mothers completed a questionnaire regarding cat exposure: during pregnancy and having a cat at home. A blood sample was taken from all children to measure the level of IL-33 in the serum.

RESULTS

Keeping a cat in the home, once in the past, or having a cat in the home during the mother's pregnancy, revealed a statistically significant relationship with IL-33 levels in the studied patients. Also, daily contact with a cat during pregnancy affected the level of IL-33. Higher levels of IL-33 were shown in people with hypersensitivity to cat and pollen allergens and cat and other animals. In patients with bronchial asthma higher levels of IL-33 were found than in patients without bronchial asthma.

CONCLUSIONS

Increased serum levels of IL-33 is related with keeping cats during pregnancy and in early childhood and can be associated with the development of asthma in children.

Eckol from Ecklonia cava ameliorates TNF-α/IFN-γ-induced inflammatory responses via regulating MAPKs and NF-κB signaling pathway in HaCaT cells

We investigated the protective effect of the bioactive compound eckol on inflammatory-related skin lesions in vitro. HaCaT cells were stimulated with tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) mixture, and treated with various concentration of eckol (25, 50, and 100 µg/ml). The expression of pro-inflammatory cytokines and chemokines were analyzed by enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR), respectively. Mitogen-activated protein kinase (MAPKs) and nuclear factor-kappa B (NF-κB) signaling pathways regulate immune and inflammation responses. Phosphorylation of MAPKs and NF-κB, indicating activation of respective signaling pathways, was examined by western blot analysis. Treatment of TNF-α and IFN-γ promoted the mRNA expression and production of pro-inflammatory cytokines and chemokines in HaCaT cells. However, eckol significantly suppressed the these mediators. Furthermore, activation of TNF-α/IFN-γ-induced MAPKs and NF-κB signaling pathway was inhibited by eckol treatment. Eckol also hampered the TNF-α/IFN-γ-mediated nuclear translocation of NF-κB p65 in HaCaT cells. Taken together, our findings demonstrate that eckol shows effective protective activity against TNF-α/IFN-γ-induced skin inflammation.

Immunoreactive Cells After Cerebral Ischemia

The immune system is rapidly activated after ischemic stroke. As immune cells migrate and infiltrate across the blood-brain barrier into the ischemic region, a cascade of cellular and molecular biological reactions occur, involving migrated immune cells, resident glial cells, and the vascular endothelium. These events regulate infarction evolution and thus influence the outcome of ischemic stroke. Most immune cells exert dual effects on cerebral ischemia, and some crucial cells may become central targets in ischemic stroke treatment and rehabilitation.

The relationship between Toxocara species seropositivity and allergic skin disorders: a systematic review and meta-analysis

We performed a systematic review and meta-analysis on observational studies to evaluate the possible associations between Toxocara species seropositivity and allergic skin disorders (ASDs). We searched the MEDLINE, ScienceDirect, Scopus, Web of Science and Google Scholar databases to 15 May 2018 to identify the relevant studies. We used a random effects meta-analysis model to generate the pooled odds ratio (OR) and 95% confidence intervals (CIs). Fifteen studies, including eight studies with a case-control design (735 patients and 1342 controls) and seven studies with a cross-sectional design (a total of 4804 participants, 1302 individuals with ASDs and 3502 without ASDs), were included in the meta-analysis. We found an increased risk for ASDs in individuals with Toxocara seropositivity (OR 1.75 [95% CI 1.16 to 2.64]). Subanalysis showed that Toxocara seropositivity was significantly associated with urticaria (OR 2.97 [95% CI 1.53 to 5.76]), however, it was not significantly associated with atopy (OR 1.08 [95% CI 0.55 to 2.15]) and eczema (OR 1.62 [95% CI 0.95 to 2.78]). Moreover, the pooled ORs were 2.34 (95% CI 1.32 to 4.15) and 1.27 (95% CI 0.69 to 2.35) for case-control and cross-sectional studies, respectively. The results of our study support hypotheses regarding the existence of a positive relationship between Toxocara infection and allergic disorders, although this association should be further investigated by longitudinal and mechanism studies.

The role of Interleukin-33 in the modulation of splenic T-cell immune responses after experimental ischemic stroke

The splenic T-cell immune response to stroke has been identified as an important role in the progression of brain injury following ischemic stroke. Interleukin (IL)-33 as a novel cytokine of IL-1 family has been found to be protective for ischemic brain injury. Here, we determined the contribution of IL-33 to the T-cell immune responses in the spleen after experimental ischemic stroke. Mice were subjected to 30 min of middle cerebral artery occlusion (MCAO) for ischemic stroke induction. Recombinant mouse IL-33 (100 μg/kg) was pre-treated intraperitoneally at 30 min prior to MCAO, then the percentages of T cell subsets, related cytokines and transcription factors in the spleen tissues were measured. Intraperitoneal IL-33 pre-treatment may attenuate neurological deficit scores and infarct volumes after MCAO, which was accompanied by reduced IFN-γ⁺ T cells and increased Foxp3⁺ T cells in the spleen tissues. Meanwhile, IL-33 pre-treatment could decrease the production of IFN-γ and increase the secretion of IL-4, IL-10 and TGF-β from the spleen at 24 h after MCAO. Additionally, the mRNA level of the transcription factor T-bet was downregulated by IL-33, and the levels of GATA-3 and Foxp3 mRNA were upregulated. These results showed that the long-term protective mechanism of IL-33 in ischemic stroke may be partly associated to its modulation role for splenic T-cell immune responses through inhibiting Th1 response and promoting Treg response, suggesting that IL-33 may be a candidate treatment for human stroke via modulating the peripheral immune system following stroke.

IL-27 signaling deficiency develops Th17-enhanced Th2-dominant inflammation in murine allergic conjunctivitis model

BACKGROUND

While most studies focus on pro-allergic cytokines, the protective role of immunosuppressive cytokines in allergic inflammation is not well elucidated. This study was to explore a novel anti-inflammatory role and cellular/molecular mechanism of IL-27 in allergic inflammation.

METHODS

A murine model of experimental allergic conjunctivitis (EAC) was induced in BALB/c, C57BL/6 or IL-27Rα-deficient (WSX-1^-/- ) mice by short ragweed pollen, with untreated or PBS-treated mice as controls. The serum, eyeballs, conjunctiva, cervical lymph nodes (CLNs) were used for study. Gene expression was determined by RT-qPCR, and protein production and activation were evaluated by immunostaining, ELISA and Western blotting.

RESULTS

Typical allergic manifestations and stimulated thymic stromal lymphopoietin (TSLP) signaling and Th2 responses were observed in ocular surface of EAC models in BALB/c and C57BL/6 mice. The decrease of IL-27 at mRNA (IL-27/EBI3) and protein levels were detected in serum, conjunctiva and CLN, as evaluated by RT-qPCR, immunofluorescent staining, ELISA and Western blotting. EAC induced in WSX-1^-/- mice showed aggravated allergic signs with higher TSLP-driven Th2-dominant inflammation, accompanied by stimulated Th17 responses, including IL-17A, IL-17F, and transcription factor RORγt. In contrast, Th1 cytokine IFNγ and Treg marker IL-10, with their respective transcription factors T-bet and foxp3, were largely suppressed. Interestingly, imbalanced activation between reduced phosphor (P)-STAT1 and stimulated P-STAT6 were revealed in EAC, especially WSX-1^-/- -EAC mice.

CONCLUSION

These findings demonstrated a natural protective mechanism by IL-27, of which signaling deficiency develops a Th17-type hyperresponse that further aggravates Th2-dominant allergic inflammation.

The Pro-tumorigenic IL-33 Involved in Antitumor Immunity: A Yin and Yang Cytokine

Interleukin-33 (IL-33), considered as an alarmin released upon tissue stress or damage, is a member of the IL-1 family and binds the ST2 receptor. First described as a potent initiator of type 2 immune responses through the activation of T helper 2 (T_H2) cells and mast cells, IL-33 is now also known as an effective stimulator of T_H1 immune cells, natural killer (NK) cells, iNKT cells, and CD8 T lymphocytes. Moreover, IL-33 was shown to play an important role in several cancers due to its pro and anti-tumorigenic functions. Currently, IL-33 is a possible inducer and prognostic marker of cancer development with a direct effect on tumor cells promoting tumorigenesis, proliferation, survival, and metastasis. IL-33 also promotes tumor growth and metastasis by remodeling the tumor microenvironment (TME) and inducing angiogenesis. IL-33 favors tumor progression through the immune system by inducing M2 macrophage polarization and tumor infiltration, and upon activation of immunosuppressive cells such as myeloid-derived suppressor cells (MDSC) or regulatory T cells. The anti-tumor functions of IL-33 also depend on infiltrated immune cells displaying T_H1 responses. This review therefore summarizes the dual role of this cytokine in cancer and suggests that new proposals for IL-33-based cancer immunotherapies should be considered with caution.

Soluble ST2 suppresses IL-5 production by human basophilic KU812 cells, induced by epithelial cell-derived IL-33

BACKGROUND

Epithelial cell-derived IL-33 has an important role in the initiation and activation of innate allergic inflammation. IL-33 acts as a cytokine through the ST2 receptor (ST2L) and it stimulates the production of Th2 cytokines. Soluble ST2 (sST2) may regulate Th2 responses by neutralizing the activity of IL-33. Basophils express ST2L and produce IL-5 in response to IL-33. However, the role of the epithelial cell-basophil interaction and sST2 in IL-5 production remains unclear.

METHODS

Cultured human bronchial epithelial (hBE33) cells, that contained the human IL-33 gene (i.e., hBE33 cells) and a human basophilic cell line, KU812 cells, were used to study the epithelial cell-basophil interaction in the production of IL-5 induced by HDM.

RESULTS

At 15 min after incubation, HDM stimulated the rapid release of IL-33 from cultured hBE33 cells. IL-33 and the supernatant of HDM-treated hBE33 cells stimulated IL-5 production from KU812 cells. Anti-IL-33 antibody and anti-ST2 antibody treatment of KU812 cells suppressed IL-5 production, which had been induced by the supernatant of HDM-treated hBE33 cells. The hBE33 cells secreted sST2 in a time-dependent manner. The production of sST2 by KU812 cells co-cultured with hBE33 cells was significantly increased, compared with KU812 cells cultured with the supernatant of hBE33 cells. Soluble ST2 suppressed IL-5 production by KU812 cells, which was induced by the supernatant of HDM-treated hBE33 cells.

CONCLUSIONS

Epithelial cell-derived IL-33 promoted IL-5 production by KU812 cells. The subsequently produced sST2 has important roles in regulating Th2 responses.

Interleukin-33: Its Emerging Role in Allergic Diseases

Allergic diseases, which include asthma, allergic rhinitis (AR), chronic rhinosinusitis (CRS), atopic dermatitis (AD), food allergy (FA), allergic keratoconjunctivitis, seriously affect the quality of life of people all over the world. Recently, interleukin-33 (IL-33) has been found to play an important role in these refractory disorders, mainly by inducing T helper (Th) 2 immune responses. This article reviews the mobilization and biological function of IL-33 in allergic disorders, providing novel insights for addressing these hypersensitive conditions.

Cytokine Signaling in the Development and Homeostasis of Regulatory T cells

Cytokine signaling is indispensable for regulatory T-cell (Treg) development in the thymus, and also influences the homeostasis, phenotypic diversity, and function of Tregs in the periphery. Because Tregs are required for establishment and maintenance of immunological self-tolerance, investigating the role of cytokines in Treg biology carries therapeutic potential in the context of autoimmune disease. This review discusses the potent and diverse influences of interleukin (IL)-2 signaling on the Treg compartment, an area of knowledge that has led to the use of low-dose IL-2 as a therapy to reregulate autoaggressive immune responses. Evidence suggesting Treg-specific impacts of the cytokines transforming growth factor β (TGF-β), IL-7, thymic stromal lymphopoietin (TSLP), IL-15, and IL-33 is also presented. Finally, we consider the technical challenges and knowledge limitations that must be overcome to bring other cytokine-based, Treg-targeted therapies into clinical use.

Optimization of Cytokine Milieu to Reproduce Atopic Dermatitis-related Gene Expression in HaCaT Keratinocyte Cell Line

Although atopic dermatitis (AD) is characterized by cytokine production predominantly mediated by T helper (Th) 2 cells, AD pathogenesis also involves innate immune and Th1 cells. To optimize the cytokine milieu required for accurate reproduction of AD-related gene expression profile in vitro, we evaluated the expression pattern of CCL22, CCL17, IL5, IL13, IL33, IL25, TSLP, FLG, and LOR in human lesional AD skin and cytokine-stimulated HaCaT cells. An increase in Th2 mediators (IL5, IL13, CCL22, CCL17, IL25, IL33, and TSLP) and a decrease in genes related to cornified cell envelope (filaggrin and loricrin) were observed in human AD lesions. Innate (tumor necrosis factor-α) and/or Th1/Th2 adaptive cytokines (interferon-γ/IL-4) were required for inducing these inflammatory changes in HaCaT cells, implying that a complex network of innate, Th1, and Th2 cytokines drives AD-like changes. Therefore, stimulation with various combinations of cytokines, beyond Th2 polarization, is necessary when HaCaT cell line is used to study genetic changes implicated in AD pathogenesis.

Infectious Complications in Atopic Dermatitis

Atopic dermatitis is characterized by the interplay of skin barrier defects with the immune system and skin microbiome that causes patients to be at risk for infectious complications. This article reviews the pathogenesis of atopic dermatitis and the mechanisms through which patients are at risk for infection from bacterial, viral, and fungal pathogens. Although these complications may be managed acutely, prevention of secondary infections depends on a multipronged approach in the maintenance of skin integrity, control of flares, and microbial pathogens.