TSLP expression: cellular sources, triggers, and regulatory mechanisms

Enhanced phenotype of calcipotriol-induced atopic dermatitis in filaggrin-deficient mice

Impaired function of filaggrin (FLG) is a major predisposing factor for atopic dermatitis (AD). Several studies on FLG-deficient (Flg^-/- ) mice have indicated an essential role for FLG in the skin barrier and the development of AD, but none of the studies have described the characteristics on Flg^-/- mice with calcipotriol (CPT)-induced atopic dermatitis, which restricts the comprehensive understanding of functions of FLG. The present study sought to generate Flg^-/- mice and applied CPT to produce AD-like dermatitis for in vivo analysis of the FLG functions. CPT was applied on the skin of Flg^-/- mice to establish the AD-like dermatitis mouse model. The lesion inflammation was evaluated by gross ear thickness, histopathology, immunofluorescence, and cytokine production. Also, mucopolysaccharide polysulfate (MPS) and ceramide were used to observe the therapeutic function in this model. The results showed that the inflammation of CPT-induced dermatitis in Flg^-/- mice was more severer than that of wild-type (WT) mice, as evident by the increased level of gross appearance, ear thickness, inflammatory cell infiltration (mast cells and CD3⁺ T cells), and inflammatory cytokine expression (interleukin (IL)-4, IL-6, IL-13, and thymic stromal lymphopoietin (TSLP)). The emollients MPS and ceramide partially restored the epidermal function and alleviated the skin inflammation in Flg^-/- mice with CPT-induced AD-like dermatitis. The current study demonstrated that skin barrier protein FLG is critical in the pathogenesis of AD. Also, the AD mouse model induced by CPT in Flg^-/- mice could be utilized to search for drug targets in AD.

Targeted Therapy for Chronıc Spontaneous Urtıcarıa: Ratıonale and Recent Progress

Chronic spontaneous urticaria (CSU) is characterized by the presence of wheals, angioedema, or both for at least 6 weeks. It may persist for a long time-up to 50% of the patients have been reported to be symptomatic 5 years after the onset. Some patients can suffer more than one episode of CSU during their lifetime. Considering the recurrences, disabling symptoms, and significant impact on quality of life, proper and effective treatment of CSU is critical. The use of antihistamines (AHs) is still the mainstay of treatment. However, given the low rates of response to AHs (38.6% and 63.2% to standard doses and higher doses, respectively), the complete control of symptoms seems difficult to attain. The use of omalizumab for CSU has been a major breakthrough in the care of patients with CSU. However, the partial response and lack of response to omalizumab in a subgroup of patients, as high as 70% in some studies, make the development of alternative treatments desirable. Ever-increasing knowledge on the pathogenesis is making new target molecules available and enabling drug development for CSU. In addition to drug repurposing as in anti-IL-4/13, IL-5, and IL-17 antibodies, novel targeted therapy options such as ligelizumab and Bruton's tyrosine kinase inhibitors are currently undergoing clinical trials and will be available in the near future. This article reviews the current challenges in the treatment of CSU, the pathogenesis and potential target molecules, and the rationale for novel treatments and their rapidly developing status.

Immunopharmacology in Vernal Keratoconjunctivitis: Current and Future Perspectives

Vernal keratoconjunctivitis (VKC) is a complex and chronic, multifactorial Th2 cell-mediated chronic ocular surface inflammatory condition that typically affects predominantly male children in hot or warm climates. The primary symptom is intense ocular pruritus, often significant enough to affect activities of daily living. Clinical features differ from simple forms of allergic conjunctivitis in that they are more-or-less confined to the superior tarsus and limbus. There is also a risk of corneal involvement, which leads to irreversible vision loss in approximately 6% of patients. Right now, there is no standardized treatment protocol, and many of the currently available options are not effective in severe and recurrent cases. As such, it is imperative to understand this complex allergic immune response in order to identify future therapeutic targets. This review will focus on potential drug targets in VKC, with particular emphasis on immunomodulators and immunobiologic agents.

The Implications of Pruritogens in the Pathogenesis of Atopic Dermatitis

Atopic dermatitis (AD) is a prototypic inflammatory disease that presents with intense itching. The pathophysiology of AD is multifactorial, involving environmental factors, genetic susceptibility, skin barrier function, and immune responses. A recent understanding of pruritus transmission provides more information about the role of pruritogens in the pathogenesis of AD. There is evidence that pruritogens are not only responsible for eliciting pruritus, but also interact with immune cells and act as inflammatory mediators, which exacerbate the severity of AD. In this review, we discuss the interaction between pruritogens and inflammatory molecules and summarize the targeted therapies for AD.

Chrysin Inhibits TNFα-Induced TSLP Expression through Downregulation of EGR1 Expression in Keratinocytes

Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine that acts as a critical mediator in the pathogenesis of atopic dermatitis (AD). Various therapeutic agents that prevent TSLP function can efficiently relieve the clinical symptoms of AD. However, the downregulation of TSLP expression by therapeutic agents remains poorly understood. In this study, we investigated the mode of action of chrysin in TSLP suppression in an AD-like inflammatory environment. We observed that the transcription factor early growth response (EGR1) contributed to the tumor necrosis factor alpha (TNFα)-induced transcription of TSLP. Chrysin attenuated TNFα-induced TSLP expression by downregulating EGR1 expression in HaCaT keratinocytes. We also showed that the oral administration of chrysin improved AD-like skin lesions in the ear and neck of BALB/c mice challenged with 2,4-dinitrochlorobenzene. We also showed that chrysin suppressed the expression of EGR1 and TSLP by inhibiting the extracellular signal-regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase (JNK) 1/2 mitogen-activated protein kinase pathways. Collectively, the findings of this study suggest that chrysin improves AD-like skin lesions, at least in part, through the downregulation of the ERK1/2 or JNK1/2-EGR1-TSLP signaling axis in keratinocytes.

Comparative Analysis of Cytokine Expression in Oral Keratinocytes and THP-1 Macrophages in Response to the Most Prevalent Serotypes of Aggregatibacter actinomycetemcomitans

BACKGROUND

Periodontitis is a chronic inflammatory disease associated with a dysbiotic biofilm. Many pathogens have been related with its progression and severity, one of which is Aggregatibacter actinomycetemcomitans, a Gram-negative bacteria with seven serotypes (a-g) according with the structure of its LPS, with serotype b defined as the most virulent compared with the other serotypes. The aim of this study was to evaluate the response of oral keratinocytes and macrophages to A. actinomycetemcomitans.

METHODS

Oral keratinocytes (OKF6/TERT2) and macrophages (THP-1) were infected with A. actinomycetemcomitans serotypes a, b and c. The expression of IL-1β, IL-6, IL-8, IL-18, TNF-α, MMP-9, RANKL, TLR-2, TLR-4, TLR-6, thymic stromal lymphopoietin (TSLP), and ICAM-1 was evaluated by qPCR at 2 and 24 h after infection.

RESULTS

An increase in the expression of these molecules was induced by all serotypes at both times of infection, with macrophages showing higher levels of expression at 24 h compared to epithelial cells in which the highest levels were observed in the first hours after infection.

CONCLUSIONS

Keratinocytes and macrophages contribute to the inflammation in periodontitis from the early stages of infection, producing the first waves of cytokines, acting as the first signal for professional immune cell recruitment and modulation of more specific immune responses.

Potential Targets to Mitigate Trauma- or Sepsis-Induced Immune Suppression

In sepsis and trauma, pathogens and injured tissue provoke a systemic inflammatory reaction which can lead to overwhelming inflammation. Concurrent with the innate hyperinflammatory response is adaptive immune suppression that can become chronic. A current key issue today is that patients who undergo intensive medical care after sepsis or trauma have a high mortality rate after being discharged. This high mortality is thought to be associated with persistent immunosuppression. Knowledge about the pathophysiology leading to this state remains fragmented. Immunosuppressive cytokines play an essential role in mediating and upholding immunosuppression in these patients. Specifically, the cytokines Interleukin-10 (IL-10), Transforming Growth Factor-β (TGF-β) and Thymic stromal lymphopoietin (TSLP) are reported to have potent immunosuppressive capacities. Here, we review their ability to suppress inflammation, their dynamics in sepsis and trauma and what drives the pathologic release of these cytokines. They do exert paradoxical effects under certain conditions, which makes it necessary to evaluate their functions in the context of dynamic changes post-sepsis and trauma. Several drugs modulating their functions are currently in clinical trials in the treatment of other pathologies. We provide an overview of the current literature on the effects of IL-10, TGF-β and TSLP in sepsis and trauma and suggest therapeutic approaches for their modulation.

Thymic stromal lymphopoietin production in DN32.D3 invariant natural killer T (iNKT) cell line and primary mouse liver iNKT cells

Background

Invariant natural killer T (iNKT) cells are known as the fast responder in allergic inflammation and the source of interleukin (IL)-4, IL-13, and interferon-gamma. Absence of iNKT cells down-regulated thymic stromal lymphopoietin (TSLP) production at the early stage of type 2 immune responses in the airway. However, it has not been reported whether iNKT cells are able to produce TSLP via stimulation of T-cell receptor (TCR).

Objective

We aimed to evaluate TSLP production from iNKT cells by TCR specific stimulations with anti-CD3/CD28 antibodies and α-galactoceramide (α-GalCer).

Methods

DN32.D3 iNKT cell line was stimulated with anti-CD3/CD28 antibodies, and TSLP production was measured in culture supernatants. Next, to confirm the TSLP production in primary mouse iNKT cells, the cells were sorted using α-GalCer-CD1d tetramer from mouse liver, and stimulated with anti-CD3/CD28 antibodies and α-GalCer. Then, cytokine productions were evaluated by enzyme-linked immunosorbent assay and quantitative polymerase chain reaction.

Results

TCR specific stimulation in DN32.D3 cells induced TSLP production as well as signature cytokines of iNKT cells. On the other hand, isolated primary mouse iNKT cells from liver did not show any induction of TSLP by TCR specific stimulations including anti-CD3/CD28 antibodies and α-GalCer, on the contrary to other cytokines.

Conclusion

This study suggested the possibility of TSLP production in iNKT cells, especially from DN32.D3 although primary mouse liver iNKT cells showed a different result.

The Protective HIV-1 Envelope gp41 Antigen P1 Acts as a Mucosal Adjuvant Stimulating the Innate Immunity

Mucosal nasal vaccine development, although ideal to protect from pathogens invading mucosally, is limited by the lack of specific adjuvant. We recently used P1, a conserved region of HIV-1 gp41-envelope glycoprotein, as efficient antigen in a prophylactic HIV-1 mucosal vaccine applied nasally. Herein, P1 immunomodulation properties were assessed on human nasal mucosal models by measuring induction of cytokine and chemokine production, intracellular signaling pathways, mucosal dendritic cell (DC) activation, and T cell proliferation. P1 adjuvant properties were evaluated by quantification of antigen-specific B cell responses against a model antigen in an in vitro immunization model. We now demonstrated that P1 has additional immunological properties. P1 initiates immune responses by inducing nasal epithelial cells to secrete the Th2-cytokine thymic stromal lymphopoietin (TSLP), a described mucosal adjuvant. Secreted TSLP activates, in turn, intracellular calcium flux and PAR-2-associated NFAT signaling pathway regulated by microRNA-4485. Thereafter, P1 induces mucosal dendritic cell maturation, secretion of TSLP in a TSLP-receptor (R)-dependent autocrine loop, but also IL-6, IL-10, IL-8, CCL20, CCL22, and MMP-9, and proliferation of CD4+ T cells. Finally, P1 acts as an adjuvant to stimulate antigen-specific B cell responses in vitro. Overall, P1 is a multi-functional domain with various immuno-modulatory properties. In addition to being a protective vaccine antigen for HIV prevention, P1 acts as adjuvant for other mucosal vaccines able to stimulate humoral and cellular antigen-specific responses.

Keratinocytes-Derived Reactive Oxygen Species Play an Active Role to Induce Type 2 Inflammation of the Skin: A Pathogenic Role of Reactive Oxygen Species at the Early Phase of Atopic Dermatitis

Background

Atopic dermatitis (AD) is characterized by chronic, relapsing skin inflammation (eczema) with itchy sensation. Keratinocytes, which are located at the outermost part of our body, are supposed to play important roles at the early phase of type 2 inflammation including AD pathogenesis.

Objective

The purpose of this study was to evaluate whether keratinocytes-derived reactive oxygen species (ROS) could be produced by the allergens or non-allergens, and the keratinocytes-derived ROS could modulate a set of biomarkers for type 2 inflammation of the skin.

Methods

Normal human epidermal keratinocytes (NHEKs) were treated with an allergen of house dust mites (HDM) or a non-allergen of compound 48/80 (C48/80). Then, biomarkers for type 2 inflammation of the skin including those for neurogenic inflammation were checked by reverse transcriptase-polymerase chain reaction and western immunoblot experiments.

Results

HDM or C48/80 was found to upregulate expression levels of our tested biomarkers, including type 2 T helper-driving pathway (KLK5, PAR2, and NFκB), epithelial-cell-derived cytokines (thymic stromal lymphopoietin, interleukin [IL]-25, IL-33), and neurogenic inflammation (NGF, CGRP). The HDM- or C-48/80-induced expression levels of the biomarkers could be blocked by an antioxidant treatment with 5 mM N-acetyl-cysteine. In contrast, pro-oxidant treatment with 1 mM H₂O₂ could upregulate expression levels of the tested biomarkers in NHEKs.

Conclusion

Our results reveal that keratinocytes-derived ROS, irrespective to their origins from allergens or non-allergens, have a potential to induce type 2 inflammation of AD skin.

Tezepelumab Pharmacokinetics, Safety, and Tolerability After Administration via Vial-and-syringe, Accessorized Prefilled Syringe, or Autoinjector: A Randomized Trial in Healthy Volunteers

PURPOSE

Tezepelumab is an anti-thymic stromal lymphopoietin monoclonal antibody therapeutic in development for patients with severe, uncontrolled asthma. In ongoing Phase III studies, tezepelumab is administered via subcutaneous (SC) injections using a vial-and-syringe (V-S). This study compared the pharmacokinetic (PK) parameters, safety, and tolerability of tezepelumab administered subcutaneously via V-S versus via an accessorized prefilled syringe (APFS) or autoinjector (AI).

METHODS

This single-center, randomized, open-label, parallel-group study was conducted in healthy volunteers aged 18-65 years. Participants, stratified according to weight (50 to <70 kg, 70 to <80 kg, or 80-90 kg), were randomized evenly to 9 groups representing injections to the abdomen, thigh, or upper arm via V-S, APFS, or AI. Tezepelumab PK parameters over 113 days were evaluated after a single 210-mg SC dose. The primary end points were comparison of C_max and AUC_0-∞ between device groups. Further PK parameters, immunogenicity, safety (including injection site reactions [ISRs] and injection site pain [visual analog scale]) were also assessed.

FINDINGS

A total of 315 adults were randomized to treatment. Geometric mean ratios for comparisons between device groups of C_max, AUC_0-∞, and AUC_0-last were close to 1, with 90% CIs all within the range of 0.8-1.25, meeting bioequivalence criteria. PK variables were also similar between devices across injection sites and weight categories. Across devices, thigh injection resulted in slightly higher exposure than upper arm injection, and abdomen injection resulted in exposure similar to or slightly lower than thigh injection; however, these differences were not clinically meaningful. Treatment-emergent anti-tezepelumab antibodies were present in 3 (2.9%), 1 (1.0%), and 0 participants in the V-S, APFS, and AI groups, respectively. Treatment-related adverse events were reported in 15.0% of participants overall (V-S, 10.7%; APFS, 18.1%; AI, 16.0%), including ISRs in 1 (1.0%), 3 (2.9%), and 3 (2.8%) participants in the V-S, APFS, and AI groups. Median visual analog scale pain score (0-100 mm scale) was 2 mm immediately after injection and was 0 mm at 30 min for all groups.

IMPLICATIONS

Tezepelumab PK parameters after a single 210-mg SC dose were comparable when administered via V-S, APFS, or AI. In all groups, immunogenicity rate and injection site pain were low, and ISRs were uncommon. These findings support administration of tezepelumab via APFS or AI, in addition to V-S, providing patients and physicians with greater choice and the potential convenience of at-home use. ClinicalTrials.gov identifier: NCT03989544.

miR-31 attenuates murine allergic rhinitis by suppressing interleukin-13-induced nasal epithelial inflammatory responses

The present study aimed to investigate whether microRNA (miR)-31 exerted therapeutic potential in allergic rhinitis (AR) and to explore its underlying mechanism. Firstly, the expression levels of miR-31 were detected by reverse transcription-quantitative PCR in the nasal mucosa of patients and mice. Subsequently, an ovalbumin (OVA)-induced animal model of AR was constructed. Allergic symptom score, histopathological characteristics, OVA-specific immunoglobulin E (IgE) titers, and T-helper (Th)1 and Th2 cell-related cytokine levels were analyzed in OVA-sensitized mice, miR-31-overexpressing mice, miR-negative control mice and control mice. Furthermore, interleukin (IL)-13-stimulated nasal epithelial cells (NECs) were used to assess the effects of miR-31 on the production of IL-13-induced inflammatory cytokines and mucin 5AC by performing western blotting and ELISA. The expression levels of miR-31 were significantly decreased in the nasal mucosa of the AR group compared with those in the control group. Moreover, upregulation of miR-31 markedly attenuated sneezing and nasal rubbing events, reduced nasal eosinophil infiltration and goblet cell hyperplasia, and decreased the levels of OVA-specific IgE and Th2-related cytokines. In addition, subsequent in vitro experiments showed that upregulation of miR-31 inhibited IL-13 receptor α1 chain expression and signal transducer and activator of transcription 6 phosphorylation in NECs. Furthermore, miR-31 suppressed IL-13-induced expression of thymic stromal lymphopoietin, granulocyte-macrophage colony-stimulating factor, eotaxin and mucin 5AC in NECs. In conclusion, these data revealed that miR-31 could ameliorate AR by suppressing IL-13-induced nasal epithelial inflammatory responses, and thus may serve as a novel therapeutic target for AR.

Role of IL-25, IL-33, and TSLP in triggering united airway diseases toward type 2 inflammation

Under the concept of "united airway diseases," the airway is a single organ wherein upper and lower airway diseases are commonly comorbid. The upper and lower airways are lined with respiratory epithelium that plays a vital role in immune surveillance and modulation as the first line of defense to various infective pathogens, allergens, and physical insults. Recently, there is a common hypothesis emphasizing epithelium-derived cytokines, namely IL-25, IL-33, and TSLP, as key regulatory factors that link in immune-pathogenic mechanisms of allergic rhinitis (AR), chronic rhinosinusitis (CRS), and asthma, mainly involving in type 2 inflammatory responses and linking innate and adaptive immunities. Herein, we review studies that elucidated the role of epithelium-derived triple cytokines in both upper and lower airways with the purpose of expediting better clinical treatments and managements of AR, CRS, asthma, and other associated allergic diseases via applications of the modulators of these cytokines.

An endothelial microRNA-1-regulated network controls eosinophil trafficking in asthma and chronic rhinosinusitis

BACKGROUND

Airway eosinophilia is a prominent feature of asthma and chronic rhinosinusitis (CRS), and the endothelium plays a key role in eosinophil trafficking. To date, microRNA-1 (miR-1) is the only microRNA known to be regulated in the lung endothelium in asthma models.

OBJECTIVE

We sought to determine the role of endothelial miR-1 in allergic airway inflammation.

METHODS

We measured microRNA and mRNA expression using quantitative RT-PCR. We used ovalbumin and house dust mite models of asthma. Endothelium-specific overexpression of miR-1 was achieved through lentiviral vector delivery or induction of a transgene. Tissue eosinophilia was quantified by using Congo red and anti-eosinophil peroxidase staining. We measured eosinophil binding with a Sykes-Moore adhesion chamber. Target recruitment to RNA-induced silencing complex was assessed by using anti-Argonaute2 RNA immunoprecipitation. Surface P-selectin levels were measured by using flow cytometry.

RESULTS

Serum miR-1 levels had inverse correlations with sputum eosinophilia, airway obstruction, and number of hospitalizations in asthmatic patients and sinonasal tissue eosinophilia in patients with CRS. IL-13 stimulation decreased miR-1 levels in human lung endothelium. Endothelium-specific overexpression of miR-1 reduced airway eosinophilia and asthma phenotypes in murine models and inhibited IL-13-induced eosinophil binding to endothelial cells. miR-1 recruited P-selectin, thymic stromal lymphopoietin, eotaxin-3, and thrombopoietin receptor to the RNA-induced silencing complex; downregulated these genes in the lung endothelium; and reduced surface P-selectin levels in IL-13-stimulated endothelial cells. In our asthma and CRS cohorts, miR-1 levels correlated inversely with its target genes.

CONCLUSION

Endothelial miR-1 regulates eosinophil trafficking in the setting of allergic airway inflammation. miR-1 has therapeutic potential in asthmatic patients and patients with CRS.

Regulators of thymic stromal lymphopoietin production by human adipocytes

Thymic stromal lymphopoietin (TSLP) is a cytokine that is known to play a role in inflammatory conditions, especially asthma and atopic dermatitis. It is also recognized to be expressed in human adipose tissue. TSLP production from human adipocytes is stimulated by thyroid-stimulating hormone (TSH). This study aimed to identify TSH-dependent signaling routes that regulate TSLP, to determine if TSLP production is stimulated by other cytokines (IL-1β and TNF-α), and to examine if TSLP production depends on the adipose depot. Human abdominal differentiated adipocytes were stimulated with TSH, IL-1β, or TNF-α. Activation of cell signaling kinases was measured by phospho-immunoblot analysis, and TSLP in medium was assessed by ELISA. TSLP responses from abdominal subcutaneous and omental adipocytes were compared. TSH-stimulated TSLP secretion from subcutaneous adipocytes was enhanced by IBMX (raises cAMP levels) and was blocked by UO126 (inhibitor of MEK1/2-ERK1/2). TSLP secretion was stimulated by IL-1β and by TNF-α. SC-514 (inhibitor of IKKβ/NF-κB) only reduced the former. There was no effect of SB203580 (p38 MAPK inhibitor) or SP600125 (JNK inhibitor) on the stimulation by TSH, IL-1β or TNF-α. Interferon-γ inhibited TSLP responses to TSH, IL-1β, and TNF-α; IL-4 only blocked the response to TNFα. Intra-abdominal omental adipocytes also release TSLP in response to TSH, IL-1β, and TNF-α. We conclude TSLP is produced by human differentiated adipocytes derived from subcutaneous or omental depots in response to a variety of agonists. Further studies will be needed to understand what role it may play in adipose biology.

Lipopolysaccharide regulates thymic stromal lymphopoietin expression via TLR4/MAPK/Akt/NF-κB-signaling pathways in nasal fibroblasts: differential inhibitory effects of macrolide and corticosteroid

BACKGROUND

Chronic rhinosinusitis (CRS) is an inflammatory disease of the sinonasal mucosa. Thymic stromal lymphopoietin (TSLP) is associated with T-helper 2 (Th2) response and induced by pathogen, allergen, toll-like receptor (TLR) ligands, and cytokines. Fibroblasts are known to be modulators of wound-healing, from inflammation to tissue remodeling. We examined effect of lipopolysaccharide (LPS) on TSLP production and the underlying mechanisms. We aimed to determine whether the effects of commonly used medications in CRS, namely corticosteroids, and macrolides, are related to LPS-induced TSLP in nasal fibroblasts.

METHODS

Fibroblasts were isolated from inferior turbinate tissues of CRS patients. TSLP and TLR4 expressions were determined by reverse transcript-polymerase chain reaction (RT-PCR), Western blot, enzyme-linked immunoassay, and immunofluorescence staining. Mitogen-activated protein kinase (MAPK), protein kinase B (Akt), and nuclear factor-kappaB (NF-κB) phosphorylation was determined by Western blot and/or luciferase assay.

RESULTS

LPS increased TSLP expression in a dose- and time-dependent manner. LPS antagonist and corticosteroids inhibited TLR4 expression in LPS-stimulated fibroblasts. LPS-RS, macrolides, corticosteroids, and specific inhibitors suppressed LPS-induced alterations. Ex vivo culture showed similar results.

CONCLUSION

LPS induces TSLP production via the TLR4, MAPK, Akt, and NF-κB pathways. The effects of corticosteroids and macrolides are related to LPS-induced TSLP expression. We explored new treatment modalities targeting LPS-induced TSLP production that could replace the currently used corticosteroid and macrolides for treatment of CRS.

Inhibition of thymic stromal lymphopoietin production to improve pruritus and quality of life in infants and children with atopic dermatitis

Background

Atopic dermatitis (AD) is an inflammatory pruritic chronic dermatosis involving the alarmin thymic stromal lymphopoietin (TSLP), which is directly implicated in AD pruritus.

Aims

To evaluate the efficacy of Tambourissa trichophylla leaf extract (TTLE) titrated in polyphenols and 18β‐glycyrrhetinic acid (GA) in vitro and in vivo for AD pruritus.

Patients/Methods

Initially, in vitro assessment of TSLP production in keratinocytes was undertaken. In normal human keratinocytes in vitro, TSLP was induced by polyinosinic:polycytidylic acid (Poly:IC), tumor necrosis factor (TNF)‐α, and interleukin (IL)‐4 and then quantified by ELISA in supernatants. Some cells were pretreated with TTLE and/or GA. Thereafter, an in vivo clinical study was performed including 48 infants and children with mild to severe AD flare‐ups, some of which were treated with topical corticosteroids. A topical spray containing TTLE and GA was applied. After 21 days of topical spray application, pruritus, sleeplessness, the SCORing Atopic Dermatitis (SCORAD) index, the Infant's Dermatitis Quality of Life index (IDQOL), and the Dermatitis Family Impact Questionnaire (DFIQ) were assessed.

Results

Thymic stromal lymphopoietin secretion was inhibited significantly in an AD environment by TTLE and GA by up to 57.2% and 73.3%, respectively. The use of the topical spray induced a significant reduction in pruritus and sleeplessness scores, as well as the SCORAD, IDQOL, and DFIQ indexes in the total group. Similar results were observed in patient subgroups with or without topical corticosteroid treatment.

Conclusions

A topical spray containing TTLE and GA, which inhibit TSLP secretion, efficiently decreases AD pruritus and improves the quality of life of AD patients.

An acid-hydrolyzed wheat protein activates the inflammatory and NF-κB pathways leading to long TSLP transcription in human keratinocytes

Hydrolyzed wheat proteins (HWPs) contained in cosmetics have occasionally caused immediate-type hypersensitivity following repeated skin exposure. Although the Cosmetic Ingredient Review Expert Panel concluded that < 3,500 Da HWP is safe for use in cosmetics, it remains biologically unknown how allergenic HWPs evoke immediate-type allergy percutaneously. Keratinocyte-derived thymic stromal lymphopoietin (TSLP) induces type 2 immune responses, which play an essential role in the pathogenesis of immediate-type allergy. Previously, we demonstrated that protein allergens in cultured human keratinocytes strongly induced long-form TSLP (loTSLP) transcription. However loTSLP-regulating signaling by HWP is poorly understood. In this study, we performed global gene expression analysis by microarray to investigate how the allergenic HWP acts on epidermal keratinocytes and the induction of loTSLP. Compared to human serum albumin (HSA), allergenic HWP induced a distinct gene expression pattern and preferentially activated various inflammatory pathways (High Mobility Group Box 1, Interleukin [IL]-6, IL-8, and acute phase response signaling). We identified 85 genes as potential nuclear factor-kappa B (NF-κB) target genes in GP19S-treated cells, compared with 29 such genes in HSA-treated cells. In addition, HWP specifically altered IL-17 signaling pathways in which transcription factors, NF-κB and activator protein-1, were activated. NF-κB signaling may be an important factor for HWP-induced inflammatory loTSLP transcription via inhibition assay. In conclusion, allergenic HWP caused an easily sensitizable milieu of activated inflammatory pathways and induced NF-κB-dependent loTSLP transcription in keratinocytes.

Abnormal thymic stromal lymphopoietin expression in the gastrointestinal mucosa of patients with eosinophilic gastroenteritis

OBJECTIVE

To investigate the differential expression of the thymic stromal lymphopoietin isoforms, short and long, and discern their biological implications under eosinophilic gastroenteritis.

METHODS

The expression of thymic stromal lymphopoietin and its two isoforms in tissues was assessed by quantitative RT-PCR in healthy controls (n=24) and patients with eosinophilic gastroenteritis (n=17).

RESULTS

Thymic stromal lymphopoietin mRNA was significantly reduced in eosinophilic gastroenteritis when compared with healthy controls (p<0.0001). A significantly lower amount of short thymic stromal lymphopoietin mRNA was observed in eosinophilic gastroenteritis when compared with controls (p<0.05), while a significantly higher amount of long thymic stromal lymphopoietin mRNA was observed in eosinophilic gastroenteritis when compared with controls (p<0.05). Peak eosinophilic count is significantly positively correlated with the expression of long thymic stromal lymphopoietin mRNA in the gastrointestinal mucosal of patients with eosinophilic gastroenteritis (r_s=0.623, p<0.005), while peak eosinophilic count is significantly negatively correlated with the expression of short thymic stromal lymphopoietin mRNA in the gastrointestinal mucosal of patients with eosinophilic gastroenteritis (r_s=-0.4474, p<0.05).

CONCLUSIONS

Abnormal mucosal thymic stromal lymphopoietin expression may contribute to gastrointestinal mucosa damage in eosinophilic gastroenteritis.

Thymic stromal lymphopoietin is a key cytokine for the immunomodulation of atherogenesis with Freund's adjuvant

Adaptive immune responses regulate the development of atherosclerosis, with a detrimental effect of type 1 but a protective role of type 2 immune responses. Immunization of Apolipoprotein E‐deficient (ApoE^−/−) mice with Freund's adjuvant inhibits the development of atherosclerosis. However, the underlying mechanisms are not fully understood. Thymic stromal lymphopoietin (TSLP) is an IL7‐like cytokine with essential impact on type 2 immune responses (Th2). Thymic stromal lymphopoietin is strongly expressed in epithelial cells of the skin, but also in various immune cells following appropriate stimulation. In this study, we investigated whether TSLP may be crucial for the anti‐atherogenic effect of Freund's adjuvant. Subcutaneous injection of complete Freund's adjuvant (CFA) rapidly led to the expression of TSLP and IL1β at the site of injection. In male mice, CFA‐induced TSLP occurred in immigrated monocytes—and not epithelial cells—and was dependent on NLRP3 inflammasome activation and IL1β‐signalling. In females, CFA‐induced TSLP was independent of IL1β and upon ovariectomy. CFA/OVA led to a more pronounced imbalance of the T cell response in TSLPR^−/− mice, with increased INFγ/IL4 ratio compared with wild‐type controls. To test whether TSLP contributes to the anti‐atherogenic effects of Freund's adjuvant, we treated ApoE^−/− and ApoE^−/−/TSLPR^−/− mice with either CFA/IFA or PBS. ApoE^−/− mice showed less atherogenesis upon CFA/IFA compared with PBS injections. ApoE^−/−/TSLPR^−/− mice had no attenuation of atherogenesis upon CFA/IFA treatment. Freund's adjuvant executes significant immune‐modulating effects via TSLP induction. TSLP‐TSLPR signalling is critical for CFA/IFA‐mediated attenuation of atherosclerosis.

Potential Biomarkers for Allergic Conjunctival Diseases

Allergic conjunctival diseases (ACDs) are a group of ocular allergies that include allergic conjunctivitis, atopic keratoconjunctivitis, vernal keratoconjunctivitis, and giant papillary conjunctivitis. Although a large body of information exists on the pathophysiology of ACDs, this has not yet lead to the development of clear recommendations and guidelines for the diagnosis of ACDs or development of conclusive and objective diagnostic tools. Identification of objectively measurable biomarkers that represent the molecular and cellular mechanisms associated with ACDs will be an important step toward achieving these aims. This is a comprehensive review of biological markers that have the potential to become "biomarker(s)" for ACDs and aid in the classification, diagnosis, and development of new therapeutic strategies for these group of allergic conditions.

Endocrine Disruptor Bisphenol A (BPA) Triggers Systemic Para-Inflammation and is Sufficient to Induce Airway Allergic Sensitization in Mice

Allergic airway diseases are accompanied by increased permeability and an inflammatory state of epithelial barriers, which are thought to be susceptible to allergen sensitization. Although exogenous drivers (proteases, allergens) of epithelial barrier disruption and sensitization are well studied, endogenous contributors (diet, xenobiotics, hormones, and metabolism) to allergic sensitization are much less understood. Xenoestrogens are synthetic or natural chemical compounds that have the ability to mimic estrogen and are ubiquitous in the food and water supply of developed countries. By interfering with the estrogen produced by the endocrine system, these compounds have the systemic potential to disrupt the homeostasis of multiple tissues. Our study examined the potential of prototypical xenoestrogen bisphenol A (BPA) to disrupt epithelial homeostasis in vitro and promote allergic responses in vivo. We found that BPA exposure in epithelial cultures in vitro significantly inhibited epithelial cell proliferation and wound healing, as well as promoted the expression of the innate alarmin cytokine TSLP in a time-and dose-dependent manner. In vivo, the exposure to BPA through water supply or inhalation induced a systemic para-inflammatory response by promoting the expression of innate inflammatory mediators in the skin, gut, and airway. In a murine tolerogenic antigen challenge model, chronic systemic exposure to BPA was sufficient to induce airway sensitization to innocuous chicken egg ovalbumin in the complete absence of adjuvants. Mechanistic studies are needed to test conclusively whether endocrine disruptors may play an upstream role in allergic sensitization via their ability to promote a para-inflammatory state.

Thymic stromal lymphopoietin protects in a model of airway damage and inflammation via regulation of caspase-1 activity and apoptosis inhibition

Thymic stromal lymphopoietin (TSLP), an epithelial cell-derived cytokine, exhibits both pro-inflammatory and pro-homeostatic properties depending on the context and tissues in which it is expressed. It remains unknown whether TSLP has a similar dual role in the airways, where TSLP is known to promote allergic inflammation. Here we show that TSLP receptor (TSLPR)-deficient mice (Tslpr^-/-) and mice treated with anti-TSLP antibodies exhibited increased airway inflammation and morbidity rates after bleomycin-induced tissue damage. We found that signaling through TSLPR on non-hematopoietic cells was sufficient for TSLP's protective function. Consistent with this finding, we showed that TSLP reduces caspase-1 and caspase-3 activity levels in primary human bronchial epithelial cells treated with bleomycin via Bcl-xL up-regulation. These observations were recapitulated in vivo by observing that Tslpr^-/- mice showed reduced Bcl-xL expression that paralleled increased lung caspase-1 and caspase-3 activity levels and IL-1β concentrations in the bronchial-alveolar lavage fluid. Our studies reveal a novel contribution for TSLP in preventing damage-induced airway inflammation.

Toll-like receptor-ligand induced thymic stromal lymphopoietin expression in primary equine keratinocytes

BACKGROUND

Thymic stromal lymphopoietin (TSLP) plays a key role in the development of allergic inflammation. Little is known about possible triggers of equine TSLP expression.

HYPOTHESIS/OBJECTIVES

To investigate TSLP expression in equine insect bite hypersensitivity (IBH) skin lesions. The capacity of TLR 1-8 ligands (L) and of atopic cytokine milieu as potential triggers of TSLP and of interleukin (IL)-6 as a downstream effector molecule of TLR signalling, were examined in primary equine keratinocyte cultures.

ANIMALS

Lesional skin from IBH-affected and healthy skin from control-horses (n = 9 each group) was sampled.

METHODS AND MATERIALS

Keratinocyte cultures were established from six healthy horses and stimulated with TLR 1-8-L, and with IL-4 and tumor necrosis factor-α, to mimic an atopic inflammation cytokine milieu. TSLP and IL-6 gene expression was assessed by quantitative real-time PCR.

RESULTS

Expression of TSLP was significantly greater in IBH lesions compared to healthy skin. TLR 1-8-L significantly upregulated TSLP expression in keratinocytes. The strongest upregulation was induced by TLR 1/2-L and TLR 3-L. Combination of atopic cytokine milieu and TLR 1/2-L or TLR 3-L further increased TSLP expression. TLR-L 1-5 stimulation significantly upregulated IL-6 expression.

CONCLUSIONS AND CLINICAL IMPORTANCE

The data herein suggest that the upregulation of TSLP expression in lesional skin of IBH-affected horses might play a role in IBH development. Moreover, TSLP expression is induced by TLR-L, in particular by TLR 1/2-L and TLR 3-L, and is further increased by atopic cytokine milieu, indicating a mechanism for TSLP-mediated exacerbation of IBH.

TSLP protects against liver I/R injury via activation of the PI3K/Akt pathway

Thymic stromal lymphopoietin (TSLP) is a cytokine mainly released by epithelial cells that plays important roles in inflammation, autoimmune disease, and cancer. While TSLP is expressed in the liver at high levels, the role of TSLP in liver ischemia/reperfusion (I/R) injury remains unknown. Experiments were carried out to determine the role of TSLP in liver I/R injury. Wild-type (WT) and TSLP receptor-knockout (TSLPR-/-) mice were subjected to liver partial warm I/R injury. Liver injury was assessed by measuring serum alanine aminotransferase (ALT) level, necrotic areas by liver histology, hepatocyte death, and local hepatic inflammatory responses. Signal pathways were explored in vivo and in vitro to identify possible mechanisms for TSLP in I/R injury. TSLP and TSLPR protein expression increased during liver I/R in vivo and following hepatocyte hypoxia/reoxygenation in vitro. Deletion of TSLPR or neutralization of TSLP with anti-TSLP antibody exacerbated liver injury in terms of serum ALT levels as well as necrotic areas in liver histology. Administration of exogenous recombinant mouse TSLP to WT mice significantly reduced liver damage compared with controls, but failed to prevent I/R injury in TSLPR-/- mice. TSLP induced autophagy in hepatocytes during liver I/R injury. Mechanistically, Akt was activated in WT mice during liver I/R injury. The opposite results were observed in TSLPR-/- mice. In addition, TSLP could directly induce Akt activation in hepatocytes independent of nonparenchymal cells in vitro. Furthermore, the Akt agonist, insulin-like growth factor-1 (IGF-1), prevented I/R injury in TSLPR-/- mice and an Akt inhibitor, LY294002, blocked the protective effects of TSLP in WT mice subjected to I/R. Our data indicate that TSLP protects against liver I/R injury via activation of the PI3K/Akt pathway. Through this pathway, TSLP induces autophagy in hepatocytes. Thus, TSLP is a potent inhibitor of stress-induced hepatocyte necrosis.

Atopic March: Collegium Internationale Allergologicum Update 2020

In recent decades, the worldwide prevalence of allergic disease has increased considerably. The atopic march is a model aimed at explaining the apparent progression of allergic diseases from atopic dermatitis (AD) to allergic asthma (AA) and to allergic rhinitis (AR). It hypothesizes that allergic disease begins, typically in children, with the development of AD, then AA, and finally progresses to AR. This theory has been widely studied in cross-sectional and long-term longitudinal studies and it has been found that as prevalence of AD declines, prevalence of AA increases. A similar relationship is reported between AA and AR. The legitimacy of the atopic march model is, however, currently debated. Epidemiological evidence and criticism of longitudinal studies point to an overstatement of the atopic march's prevalence and incorrect mechanisms, opening a discussion for alternative models to better explain the pathophysiological and epidemiological processes that promote this progression of allergic diseases. Albeit, risk factors for the development and progression of allergic disease, particularly AD, are critical in identifying disease progression. Investigating the role of age, severity, family history, phenotype, and genetic traits may give a better indication into the progression of allergic diseases. In addition, studies following patients from infancy into adulthood and a general increase in longitudinal studies would help broaden the knowledge of allergic disease progression and the atopic march.

Potential anti-inflammatory effect of Madi-Ryuk and its active ingredient tannic acid on allergic rhinitis

Madi-Ryuk (MDR) is a traditional Korean medicine and it has been widely used in Korea to treat arthritis and we previously reported the anti-allergic inflammatory effect of MDR in vitro model. However, therapeutic evidence of MDR on in vivo model of allergic inflammatory reaction has not yet been demonstrated. The research purpose was to investigate the efficacy of MDR and its active ingredient tannic acid (TA) in ovalbumin (OVA)-induced AR mice model. OVA-challenged AR mice orally medicated MDR or its active ingredient TA daily for ten days. In mice having a AR, MDR and TA prominently diminished number of rubs and levels of histamine, IgE, thymic stromal lymphopoietin, interleukin (IL)-1β, IL-4, IL-5, IL-13, IL-33, and tumor necrosis factor-α. In addition, protein expression levels and activities of caspase-1 were declined by oral medication of MDR and TA. Decline in levels of macrophage inflammatory protein-2 and intercellular adhesion molecules-1 and reduction in penetrations of inflammatory cells into inflamed tissue were also noted in MDR and TA groups. Taken together, identification of MDR effect in preclinical models suggests that MDR may be a therapeutic drug for the treatment and prevention of AR.

Thymic Stromal Lymphopoietin Interferes with the Apoptosis of Human Skin Mast Cells by a Dual Strategy Involving STAT5/Mcl-1 and JNK/Bcl-xL

Mast cells (MCs) play critical roles in allergic and inflammatory reactions and contribute to multiple pathologies in the skin, in which they show increased numbers, which frequently correlates with severity. It remains ill-defined how MC accumulation is established by the cutaneous microenvironment, in part because research on human MCs rarely employs MCs matured in the tissue, and extrapolations from other MC subsets have limitations, considering the high level of MC heterogeneity. Thymic stromal lymphopoietin (TSLP)-released by epithelial cells, like keratinocytes, following disturbed homeostasis and inflammation-has attracted much attention, but its impact on skin MCs remains undefined, despite the vast expression of the TSLP receptor by these cells. Using several methods, each detecting a distinct component of the apoptotic process (membrane alterations, DNA degradation, and caspase-3 activity), our study pinpoints TSLP as a novel survival factor of dermal MCs. TSLP confers apoptosis resistance via concomitant activation of the TSLP/ signal transducer and activator of transcription (STAT)-5 / myeloid cell leukemia (Mcl)-1 route and a newly uncovered TSLP/ c-Jun-N-terminal kinase (JNK)/ B-cell lymphoma (Bcl)-xL axis, as evidenced by RNA interference and pharmacological inhibition. Our findings highlight the potential contribution of TSLP to the MC supportive niche of the skin and, vice versa, highlight MCs as crucial responders to TSLP in the context of TSLP-driven disorders.

Prostaglandin E2 (PGE2)-EP2 signaling negatively regulates murine atopic dermatitis-like skin inflammation by suppressing thymic stromal lymphopoietin expression

BACKGROUND

Atopic dermatitis (AD) is a common and chronic inflammatory skin disease of type 2 immunity. Keratinocyte-derived cytokines, including thymic stromal lymphopoietin (TSLP) and IL-33, are considered to induce the development of AD. Production of prostanoids, a family of lipid mediators, is increased in AD lesions. However, their physiologic functions remain to be clarified.

OBJECTIVES

We sought to elucidate the functions of prostanoids in the development of AD.

METHODS

The roles of prostanoids were investigated in a mouse model of AD induced by repeated application of hapten and PAM212, a keratinocyte cell line.

RESULTS

Application of indomethacin, which blocks prostanoid synthesis, leads to enhanced TSLP and IL-33 production in the skin, increased serum IgE levels, and exacerbation of skin inflammation in this AD model. The skin inflammation was attenuated in TSLP receptor-deficient mice but not in IL-33-deficient mice, and the indomethacin-enhanced type 2 immune responses were abolished in TSLP receptor-deficient mice. Indomethacin increased protease-activated receptor 2-mediated TSLP production in keratinocytes in vitro, and prostaglandin E₂ reversed the increase in TSLP levels through its receptor, the prostaglandin E₂ receptor (EP2), by downregulating surface expression of protease-activated receptor 2. Administration of an EP2 agonist canceled indomethacin-enhanced TSLP production and type 2 immune responses in the skin, whereas an EP2 antagonist caused an enhancement of TSLP production and type 2 immune responses in the skin.

CONCLUSION

Prostaglandin E₂-EP2 signaling negatively regulates murine AD-like skin inflammation by suppressing TSLP expression.

TSLP promote M2 macrophages polarization and cardiac healing after myocardial infarction

Macrophages play an important role in inflammation and cardiac remodeling in response to myocardial infarction (MI). Earlier shift of inflammtory M1 macrophages to reparative M2 macrophages has demonstrated significant improvements in MI wound modeling and cardiac function. Here, we reported that TSLP could promote M1 to M2 macrophage polarization, and AngII skewed the macrophage phenotype towards M2 by inducing TSLP expression in vitro. Meanwhile, AngII could inhibit the expression of MMP2 and MMP9 in macrophages, which are engaged in ECM degradation and cardiac remodeling. In post-MI mice, TSLP expression were up-regulated in cardiac tissue and serum, probably induced by renin-angiotensin system activation and AngII level up-regulation following MI. Our study mapped the continuum of changes that occured in cardiac macrophages over the first week of MI, and found that rTSLP treatment promoted earlier phenotype shift of M1 to M2 macrophages, improving cardiac healing and ventricular function recovery. Taken together, this work identified a very promising therapeutic opportunity to manage macrophage phenotype and enhance resolution of inflammation in the post-MI heart.

Expression and allele frequencies of Thymic stromal lymphopoietin are a key factor of breast cancer risk

Background

Thymic stromal Lymphopoeitin (TSLP) is a key cytokine involved in inflammation and cancer progression. TSLP gene polymorphisms have been associated with increased susceptibility to cancer progression in different organs. We performed a control case study to examine the correlation of expression and polymorphisms of three nucleotides in TSLP with breast cancer (BC) risk in Saudi Arabian females.

Materials and methods

The study was conducted on 116 healthy control subjects and 127 female patients with BC for the purpose of genotyping. Ten matching tissues provided data on immunohistochemistry to evaluate TSLP expression. Three SNPs (rs10043985, rs2289276, and rs3806933) were genotyped with TaqMan allelic discrimination assay. The patients' ages and estrogen receptor statuses were used to investigate the potential correlations between the different variations of TSLP genotypes and BC risk.

Results

BC tissues expressed positive immuno‐staining for TSLP at a high rate compared to normal matching breast tissues. Malignant breast tumors exhibited higher TSLP expression than benign breast tumors. We also found that the rs3806933 (T) allele frequency decreased the risk of developing BC in the study population (OR = 0.356, p = 0.00027) significantly (0.356 times). Interestingly, statistical analysis revealed that the genotype mutant (AC) and the allele mutant (C) of rs10043985 within TSLP were significantly correlated with an increased BC risk (odds ratio [OR] = 4.762, confidence interval [CI] = 1.000–22.666, p = 0.03244; OR = 4.762, CI = 1.000–22.666, p = 0.03244; and OR = 4.575, CI = 0.975–21.464, p = 0.03516, respectively). In addition, the AC and AC + CC genotypes of TSLP rs10043985 were confirmed to be associated with an increased risk of BC risk in women aged above 48 years, compared with the AA genotype (AC and AC + CC vs. AA: OR = 9.468, CI = 0.493–181.768, p = 0.04537).

Conclusion

The results reveal significant correlation between SNPs in TSLP and BC progression in Saudi Arabian female patients.

Biomarkers of Inflammation in Obesity-Psoriatic Patients

Psoriasis is a common chronic inflammatory multisystemic disease with a complex pathogenesis consisting of genetic, immunological, and environmental components. It is associated with a number of comorbidities, including diabetes, metabolic syndrome, obesity, and myocardial infarction. In addition, the severity of psoriasis seems to be related to the severity of obesity. Patients with higher levels of obesity show poorer response to systemic treatments of psoriasis. Several studies have demonstrated that white adipose tissue is a crucial site of the formation of proinflammatory adipokines such as leptin, adiponectin, and resistin and classical cytokines such as interleukin- (IL-) 6 and tumour necrosis factor-α. In psoriasis, due to the proliferation of Th1, Th17, and Th22 cells, IL-22, among others, is produced in addition to the abovementioned cytokines. With respect to leptin and resistin, both of these adipokines are present in high levels in obese persons with psoriasis. Further, the plasma levels of leptin and resistin are related to the severity of psoriasis. These results strongly suggest that obesity, through proinflammatory pathways, is a predisposing factor to the development of psoriasis and that obesity aggravates existing psoriasis. Different inflammatory biomarkers link psoriasis and obesity. In this paper, the most important ones are described.

Generation of IL-3-Secreting CD4+ T Cells by Microbial Challenge at Skin and Mucosal Barriers

During Ag priming, naive CD4⁺ T cells differentiate into subsets with distinct patterns of cytokine expression that dictate to a major extent their functional roles in immune responses. We identified a subset of CD4⁺ T cells defined by secretion of IL-3 that was induced by Ag stimulation under conditions different from those associated with previously defined functional subsets. Using mouse models of bacterial and viral infections, we showed that IL-3–secreting CD4⁺ T cells were generated by infection at the skin and mucosa but not by infections introduced directly into the blood. Most IL-3–producing T cells coexpressed GM-CSF and other cytokines that define multifunctionality. Generation of IL-3–secreting T cells in vitro was dependent on IL-1 family cytokines and was inhibited by cytokines that induce canonical Th1 or Th2 cells. Our results identify IL-3–secreting CD4⁺ T cells as a potential functional subset that arises during priming of naive T cells in specific tissue locations.

Type 2 Innate Lymphoid Cells in Liver and Gut: From Current Knowledge to Future Perspectives

Innate lymphoid cells (ILCs) represent a heterogeneous population of recently discovered immune cells that mirror the functions of adaptive T lymphocytes. However, ILCs are devoid of specific antigen receptors and cellular activation depends on environmental cytokines, rendering them as early regulators of immune responses. Type 2 innate lymphoid cells (ILC2s) respond to alarmins, such as interleukin-25 and -33 and shape Th2-associated immunity by expressing IL-5 and IL-13 in a GATA3-dependent manner. In addition, ILC2s express the epidermal growth factor-like molecule Amphiregulin thereby promoting regeneration of injured tissue during inflammation. The gut and liver confer nutrient metabolism and bidirectional exchange of products, known as the gut-liver axis. Accordingly, both organs are continuously exposed to a large variety of harmless antigens. This requires avoidance of immunity, which is established by a tolerogenic environment in the gut and liver. However, dysregulations within the one organ are assumed to influence vitality of the other and frequently promote chronic inflammatory settings with poor prognosis. Intensive research within the last years has revealed that ILC2s are involved in acute and chronic inflammatory settings of gut and liver. Here, we highlight the roles of ILC2s in intestinal and hepatic inflammation and discuss a regulatory potential.

Microbiome of the Skin and Gut in Atopic Dermatitis (AD): Understanding the Pathophysiology and Finding Novel Management Strategies

Atopic dermatitis (AD) is a long-standing inflammatory skin disease that is highly prevalent worldwide. Multiple factors contribute to AD, with genetics as well as the environment affecting disease development. Although AD shows signs of skin barrier defect and immunological deviation, the mechanism underlying AD is not well understood, and AD treatment is often very difficult. There is substantial data that AD patients have a disturbed microbial composition and lack microbial diversity in their skin and gut compared to controls, which contributes to disease onset and atopic march. It is not clear whether microbial change in AD is an outcome of barrier defect or the cause of barrier dysfunction and inflammation. However, a cross-talk between commensals and the immune system is now noticed, and their alteration is believed to affect the maturation of innate and adaptive immunity during early life. The novel concept of modifying skin and gut microbiome by applying moisturizers that contain nonpathogenic biomass or probiotic supplementation during early years may be a preventive and therapeutic option in high risk groups, but currently lacks evidence. This review discusses the nature of the skin and gut flora in AD, possible mechanisms of skin-gut interaction, and the therapeutic implications of microbiome correction in AD.

Interactions of thymic stromal lymphopoietin with TLR2 and TLR4 regulate anti-fungal innate immunity in Aspergillus fumigatus-induced corneal infection

Thymic stromal lymphopoietin (TSLP) is an interleukin 7 (IL-7)-like four helix bundle cytokine that plays diverse roles in the regulation of immune responses. In fungal infection, pattern recognition receptors (PRRs), including the cell surface Toll-like receptors (TLRs) and cytoplasmic NOD-like receptors, recognize pathogen-associated molecular patterns to initiate downstream signal cascades to active immune responses. Our previous studies reported that, in vitro human cornea epithelium cells represented a novel target of TSLP and that TSLP/TSLPR/STAT5 signaling played an important role in the response to Aspergillus fumigatus challenge. TSLP downstream signaling molecules upregulated TLR2 and MyD88/NF kappa B-p65 signaling. This phenomenon suggested that TSLP had an impact on PRRs in antifungal immunity. In mouse fungal keratitis induced by A. fumigatus, TSLP was mainly expressed in the epithelium as well as in some infiltrated immune cells in a time-dependent manner. Exogenous TSLP with Aspergillus led to severe keratitis and worse corneal recovery with higher levels of TLR2, TLR4, IL-6, and IL-8 as well as increased neutrophil infiltration. By contrast, when TSLP was suppressed by siRNA, fungal keratitis was mild with higher levels of antimicrobial peptides such as human beta-defensin (hBD9). Taken together, our data revealed an unreported function of TSLP in mediating an anti-fungal inflammatory response and serving as a target to control tissue injury and infection in A. fumigatus keratitis.

Pathophysiology of atopic dermatitis: Clinical implications

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease. Genetic predisposition, epidermal barrier disruption, and dysregulation of the immune system are some of the critical components of AD. An impaired skin barrier may be the initial step in the development of the atopic march as well as AD, which leads to further skin inflammation and allergic sensitization. Type 2 cytokines as well as interleukin 17 and interleukin 22 contribute to skin barrier dysfunction and the development of AD. New insights into the pathophysiology of AD have focused on epidermal lipid profiles, neuroimmune interactions, and microbial dysbiosis. Newer therapeutic strategies focus on improving skin barrier function and targeting polarized immune pathways found in AD. Further understanding of AD pathophysiology will allow us to achieve a more precision medicine approach to the prevention and the treatment of AD.

IL-37 alleviates house dust mite-induced chronic allergic asthma by targeting TSLP through the NF-κB and ERK1/2 signaling pathways

Interleukin (IL)-37 has been described as a negative regulator of immune responses and is critical for asthma pathogenesis, but the mechanisms behind the protective role of IL-37 against allergic asthma are less well understood. We show here that IL-37 administered intranasally inhibited house dust mite (HDM)-induced chronic airway eosinophilic inflammation, goblet cell hyperplasia, peribronchial collagen deposition and airway hyperresponsiveness (AHR) to methacholine. In contrast to a weakened Th2 response in the lung that was characterized by the downregulation of Th2-associated cytokines and chemokines in IL-37-treated mice, IL-37 has no effect on relevant markers of systemic Th2 immune including serum immunoglobulins expression and in vitro production of Th2-associated cytokines by splenocytes on HDM recall. We demonstrated that the production of thymic stromal lymphopoietin (TSLP) in the lung tissue was associated with IL-37. Importantly, compared with IL-37 alone, TSLP coadministration with IL-37 restored HDM-induced airway inflammation and structural alterations, increased AHR to methacholine and promoted Th2-associated cytokine production. We further found that IL-37 inhibited the induction of TSLP expression by the main antigen of house dust mite, Der p1, by suppressing NF-κB and extracellular signal regulated kinase 1/2 (ERK1/2) activation in human bronchial epithelial (16-HBE) cells in vitro. These data highlight the importance of TSLP in IL-37-mediated protective role in asthma. IL-37 might represent a useful innovative and alternative therapy to control TSLP production in the airway.

A steroid alkaloid derivative 02F04 upregulates thymic stromal lymphopoietin expression slowly and continuously through a novel Gq/11-ROCK-ERK1/2 signaling pathway in mouse keratinocytes

Thymic stromal lymphopoietin (TSLP), a master switch of allergic inflammation, plays an important role in the pathogenesis of allergic diseases. Although many compounds upregulate TSLP expression in vivo or in vitro, most of them are pollutants or toxicants. In the previous study, for the first time, we found that a steroid alkaloid derivative 02F04, which has a unique skeletal structure compared with other TSLP-inducing chemicals, significantly induced TSLP production in mouse keratinocytes. However, it is not investigated thoroughly that how 02F04 produces TSLP and why. In this study, we did a detailed investigation on the inducible effect and underlying molecular mechanism of 02F04 on TSLP production. We found that the peak time of TSLP mRNA level induced by 02F04 at 48 h led to a slow and continuous TSLP production in PAM212 cells. Besides, 02F04-induced TSLP production was significantly suppressed by inhibitors of Rho-associated protein kinase (ROCK), guanine nucleotide-binding protein subunit alpha q/11 (Gq/11) and extracellular signal-regulated kinase 1/2 (ERK1/2) at not only protein but also mRNA levels, and by siRNA-mediated knockdown of Gq or G11. This suggested that ROCK, Gq/11 and ERK1/2 signaling pathways were involved in 02F04-induced TSLP production. Increase in the level of p-ERK1/2 induced by 02F04 was suppressed by both inhibitors of ROCK and Gq/11, indicating that ROCK and Gq/11 molecules were located at the upstream of ERK1/2 to regulate 02F04-induced TSLP production. Gq/11 was located at the upstream of ROCK because the specific Gq/11 inhibitor of YM-254890 significantly reduced 02F04-induced actin stress fiber formation. Taken together, 02F04 upregulates a slow and continuous TSLP production through a novel Gq/11-ROCK-ERK1/2 signaling pathway. The thorough understanding the effect and mechanism of 02F04 on TSLP production is expected to supply it as a novel TSLP-regulating compound and a potential new tool for investigating the role of TSLP in allergic disorders.

Airway epithelial TSLP production of TLR2 drives type 2 immunity in allergic airway inflammation

Epithelial cells (ECs)-derived cytokines are induced by different stimuli through pattern recognition receptors (PRRs) to mount a type-2-cell-mediated immune response; however, the underlying mechanisms are poorly characterized. Here, we demonstrated asthmatic features in both primary bronchial epithelial cells (pBECs) and mouse model using several allergens including ovalbumin (OVA), house dust mite (HDM), or Alternaria alternata. We found that toll-like receptor 2 (TLR2) was highly induced in ECs but not dendritic cells (DCs) by various allergens, leading to recruitment of circulating basophils into the lung via C-C chemokine ligand-2 (CCL2). TLR2 expression increased thymic stromal lymphopoietin (TSLP) production through the NF-κB and JNK signaling pathways to extend the survival of recruited basophils and resident DCs in the lung, predisposing a type-2-cell-mediated airway inflammation. Conversely, TLR2 deficiency impaired secretion of TSLP and CCL2, decreased infiltration of lung basophils, and increased resistance to Th2 response. Blocking TSLP also phenocopied these phenomena. Our findings reveal a pro-inflammatory role of airway ECs through a TLR2-dependent TSLP production, which may have implication for treating allergic asthma.

MicroRNA-31 Targets Thymic Stromal Lymphopoietin in Mucosal Infiltrated CD4+ T Cells: A Role in Achieving Mucosal Healing in Ulcerative Colitis?

BACKGROUND

Ulcerative colitis (UC) is characterized by disruption of the mucosal intestinal barrier. MicroRNAs, single-stranded noncoding RNAs of approximately 22nt, are dysregulated in UC. MicroRNAs targeting thymic stromal lymphopoietin (TSLP), a cytokine involved in T-cell maturation and polarization, may be involved in regulating UC inflammation and mucosal healing.

METHODS

Biopsy samples from non-UC (n = 38), inactive UC (n = 18), and active UC (n = 23) patients were analyzed for mRNA (real-time quantitative polymerase chain reaction) or TSLP protein expression (enzyme-linked immunosorbent assay). Flow cytometry was used to isolate CD4+ T cells from biopsies. The functional mechanism was shown using luciferase assays and antago-miR transfections. The TSLP/miR-31 association was analyzed on 196 subjects from a previous clinical trial that tested the anti-IL-13 drug tralokinumab, whereas mucosal healing effects were studied on a subset of patients (n = 13) from this trial.

RESULTS

We found that TSLP is reduced at both mRNA and protein levels in inflamed UC patients when compared with healthy subjects, in both whole biopsies and biopsy-isolated CD4+ CD25+ T cells. The expression of miR-31, predicted to target TSLP, inversely co-related to the levels of TSLP mRNA in T cells. Blocking miR-31 in vitro in T cells increased both TSLP mRNA expression and protein secretion. Luciferase assays showed that miR-31 directly targeted TSLP mRNA, suggesting a direct mechanistic link. We also found that TSLP is increased in patients who achieve mucosal healing, comparing biopsies before and after treatment from the tralokinumab trial.

CONCLUSIONS

Our data suggest a role for TSLP in promoting mucosal healing and regulating inflammation in UC, whereas miR-31 can directly block this effect.

Sentinels at the wall: epithelial-derived cytokines serve as triggers of upper airway type 2 inflammation

Recent evidence has demonstrated an expanding role of respiratory epithelial cells in immune surveillance and modulation. Studies have been focusing on the earliest events that link epithelial injury to downstream inflammatory responses. Cytokines produced by and released from respiratory epithelial cells are among these early trigger signals. Epithelial-derived cytokines, namely thymic stromal lymphopoietin (TSLP), interleukin (IL)-25, and IL-33, have come to the forefront of recent investigations. Each of these 3 cytokines has been implicated in chronic rhinosinusitis (CRS), asthma, and atopy. Herein we review studies elucidating the roles of epithelial-derived cytokines in the pathobiology of upper airway disease, with particular emphasis on type 2 inflammatory conditions.

Thymic stromal lymphopoietin in human pancreatic ductal adenocarcinoma: expression and prognostic significance

Thymic stromal lymphopoietin (TSLP) has emerged as an important, but contradictory, player conditioning tumor growth. In certain contexts, by driving T helper (h) 2 responses via tumor-associated OX40 Ligand (OX40L)⁺ dendritic cells (DCs), TSLP may play a pro-tumorigenic role. The study elucidates the importance of TSPL in pancreatic ductal adenocarcinoma (PDAC), by analyzing: i) TSLP levels in PDAC cell-line supernatants and plasma from patients with locally-advanced/metastatic PDAC, pre- and post-treatment with different chemotherapeutic protocols, in comparison with healthy donors; ii) TSLP and OX40L expression in PDAC and normal pancreatic tissues, by immunohistochemistry; iii) OX40L expression on ex vivo-generated normal DCs in the presence of tumor-derived TSLP, by flow cytometry; iv) clinical relevance in terms of diagnostic and prognostic value and influence on treatment modality and response.

Some PDAC cell lines, such as BxPC-3, expressed both TSLP mRNA and protein. Normal DCs, generated ex vivo in the presence of TSLP-rich-cell supernatants, displayed increased expression of OX40L, reduced by the addition of a neutralizing anti-TSLP polyclonal antibody. OX40L⁺ cells were detected in pancreatic tumor inflammatory infiltrates. Abnormally elevated TSLP levels were detected in situ in tumor cells and, systemically, in locally-advanced/metastatic PDAC patients. Of the chemotherapeutic protocols applied, gemcitabine plus oxaliplatin (GEMOX) significantly increased circulating TSLP levels. Elevated plasma TSLP concentration was associated with shorter overall survival and increased risk of poor outcome. Plasma TSLP measurement successfully discriminated PDAC patients from healthy controls.

These data show that TSLP secreted by pancreatic cancer cells may directly impact PDAC biology and patient outcome.

Antialarmins for treatment of asthma: future perspectives

PURPOSE OF REVIEW

Recent studies have highlighted the role of alarmins in asthma pathophysiology and tested the roles of these cytokines in asthmatic patients. This review will discuss the recent advances in the role of alarmins in asthma and the potential of future targeted therapies in asthma.

RECENT FINDINGS

Epithelial-derived cytokines can be released upon exposure to external stimuli, causing damage to the epithelial barrier and resulting in tissue inflammation. Of these cytokines, IL-25, IL-33 and thymic stromal lymphopoeitin (TSLP), have been associated with asthma. These alarmins are all not only overexpressed in asthmatic airways, particularly in airway epithelial cells, but also in other structural and immune cells. Furthermore, all three alarmins drive type-2 pro-inflammatory responses in several immune cells that have been identified as key players in the pathogenesis of asthma, including innate lymphoid type-2 cells. Clinical trials testing therapeutics that block pathways of the alarmins are in progress.

SUMMARY

To-date, only TSLP blockade has been reported in human clinical trials, and this approach has shown efficacy in asthmatic patients. Current body of evidence suggests that alarmins are useful upstream targets for treatment of asthma.

Type 2 immunity: Expanding our view

The classical vision of type 2 immune reactions is that they are characterized by a distinct cellular and cytokine repertoire that is critical for host resistance against helminthic worm infections but, when dysregulated, may cause atopic reactions that result in conditions such as asthma, rhinitis, dermatitis, and anaphylaxis. In this traditional view, the type 2 response is categorized as an adaptive immune response with differentiated T helper cells taking center stage, driving eosinophil recruitment and immunoglobulin production via the secretion of a distinct repertoire of cytokines that include interleukin-4 (IL-4), IL-5, and IL-13. The recent discovery of a group of innate cells that has the capacity to secrete copious amounts of type 2 cytokines, potentially in the absence of adaptive immunity, has reignited interest in type 2 biology. The discovery that these innate lymphoid cells and type 2 cytokines are involved in diverse biological processes-including wound healing, control of metabolic homeostasis, and temperature-has considerably changed our view of type 2 responses and the cytokines, chemokines, and receptors that regulate these responses.

Anticancer agent ABT-737 possesses anti-atopic dermatitis activity via blockade of caspase-1 in atopic dermatitis in vitro and in vivo models

OBJECTIVE

Previous studies reported that depletion of Bcl-2 has a protective effect against allergic diseases. Furthermore, recently our study showed that anticancer drug has antiallergic inflammatory effect. An anticancer agent ABT-737 is an inhibitor of Bcl-2 and has an anti-inflammatory effect. However, the antiallergic inflammatory activity of ABT-737 is still unknown. Here, we aimed to explore the anti-atopic dermatitis (AD) activity and the mechanism of ABT-737 in AD models.

MATERIALS AND METHODS

HaCaT cells were used for in vitro experiments. To evaluate the effect of ABT-737 in vivo model, BalB/c mice were orally administered ABT-737 for 6 weeks in 2,4-dinitrofluorobenzene (DNFB)-induced AD-like murine model. Major assays were enzyme-linked immunosorbent assay, reverse transcription-PCR, caspase-1 assay, histamine assay, and H&E staining.

RESULTS

ABT-737 significantly decreased thymic stromal lymphopoietin (TSLP) secretion and caspase-1 activity in activated HaCaT cells. In DNFB-induced AD mice, oral administration of ABT-737 alleviated clinical severity and scratching behavior. ABT-737 decreased levels of AD-related biomarkers including IgE, histamine, TSLP, and inflammatory cytokines. In addition, ABT significantly reduced caspase-1 activity in skin lesions of AD mice.

DISCUSSION AND CONCLUSIONS

ABT-737 elicited an anti-AD activity via suppression of caspase-1 activation in AD in vitro and in vivo models. Therefore, this study provides important information regarding the use of anticancer drugs for controlling allergic inflammatory diseases.

All along the watchtower: group 2 innate lymphoid cells in allergic responses

Group 2 innate lymphoid cells (ILC2) are a subset of innate lymphocytes that responds to local, tissue-derived signals and initiates allergic immune responses. ILC2 activation promotes the recruitment of eosinophils, polarization of alternatively activated macrophages, and tissue-remodeling, processes associated with the 'weep and sweep' response to helminthic worm colonization and infection. ILC2s also coordinate both physiologic and pathologic type 2 allergic immune responses, including promoting normal tissue development and remodeling and driving allergic pathology such as atopic dermatitis and allergic asthma. In this review we summarize recent advances in ILC2 biology, particularly focusing on how local cells and signals coordinately regulate ILC2s, how this may influence physiologic processes, and how ILC2 cooperate with adaptive T helper type 2 cells to drive pathologic allergic inflammation.

Interleukin-32 induced thymic stromal lymphopoietin plays a critical role in the inflammatory response in human corneal epithelium

Interleukin (IL)-32, a novel cytokine, participates in a variety of inflammatory disorders. Thymic stromal lymphopoietin (TSLP) plays important roles in mucosal epithelial cells, especially in allergy-induced inflammation, through the TSLP-TSLPR (thymic stromal lymphopoietin receptor) signalling pathway. However, the association of IL-32 with TSLP on the ocular surface remains unclear. The present work aimed to assess the functional association of IL-32 with TSLP in the control of pro-inflammatory cytokine levels in the corneal epithelium. Human corneal tissue specimens and human corneal epithelial cells (HCECs) were administered different concentrations of IL-32 in the presence or absence of various inhibitors to assess TSLP levels and localization, as well as the molecular pathways that control pro-inflammatory cytokine production. TSLP mRNA levels were determined by real time RT- PCR, while protein levels were quantitated by ELISA and immunohistochemical staining. TSLP protein expression was examined in donor corneal epithelium samples. IL-32 significantly upregulated TSLP and pro-inflammatory cytokines (TNFα and IL-6) in HCECs at the gene and protein levels. The production of pro-inflammatory molecules by IL-32 was increased by recombinant TSLP. Interestingly, both NF-κB (quinazoline) and caspase-1 (VX-765) inhibitors suppressed the IL-32-related upregulation of pro-inflammatory cytokines (TNFα and IL-6). These findings demonstrate that IL-32 and IL-32-induced-TSLP are critical cytokines that participate in inflammatory responses through the caspase-1 and NF-κB signalling pathways in the corneal epithelium, suggesting new molecular targets for inflammatory diseases of the ocular surface. The effects of IL-32 on cell proliferation and apoptosis were investigated by MTT assays and RT-PCR,respectively. The results demonstrated that IL-32 inhibits cells apoptosis in HCECs.

Exposure to a combination of formaldehyde and DINP aggravated asthma-like pathology through oxidative stress and NF-κB activation

Several epidemiological and experimental studies indicate a positive association between exposure to formaldehyde or phthalates and allergic asthma. However, nothing is yet known about the effects of exposure to formaldehyde and phthalates together, nor the role of each on allergic asthma. Here, we investigated the effects of a combined exposure to formaldehyde and diisononyl phthalate (DINP) on asthma-like pathology in mice, and determined the underlying mechanisms implicated in NF-κB and ROS. Mice were exposed to formaldehyde and/or DINP and sensitization with OVA. The results showed that exposure to 1.0 mg/m³ formaldehyde or 20 mg/kg·d DINP slightly aggravated the airway wall remodeling, promoted the production of IgE and IgG1, and induced the occurrence of airway hyperresponsiveness (AHR). However, these pathological responses and AHR were greatly exacerbated by the combined exposure to formaldehyde and DINP. Administering melatonin to block oxidative stress, alleviated the pathological responses and AHR induced by formaldehyde and DINP, and inhibited the activation of the NF-κB and the secretion of TSLP. Blocking NF-κB with Dehydroxymethylepoxyquinimicin, inhibited the elevation of TSLP expression and Th2/Th17 cytokine secretion, and effectively alleviated the allergic asthma-like symptoms. The results suggested that exposure to both formaldehyde and DINP aggravated hypersensitivity asthma symptoms by promoting oxidative stress and activating NF-κB. These findings expand our understanding of how formaldehyde and DINP exposure affect the development of allergic asthma.