A role for TSLP in the development of inflammation in an asthma model

Critical Role of TSLP Receptor on CD4 T Cells for Exacerbation of Skin Inflammation

Thymic stromal lymphopoietin (TSLP) is a key cytokine that initiates and promotes allergic inflammation both in humans and mice. It is well known that TSLP is important in initial step of inflammation by stimulating dendritic cells to promote Th2 differentiation of naive T cells. However, TSLP is abundantly produced in the late phase of inflammation, as well; therefore, we focused on the function of TSLP in chronic Th2-type inflammation. By establishing a novel (to our knowledge) chronic allergic skin inflammation mouse model with repetitive challenges of hapten after sensitization, we demonstrated that CD4 T cell-specific deletion of TSLP receptor (TSLPR) resulted in near-complete ablation of ear swelling and infiltration of CD4 T cells and eosinophils, but after second challenge. Of note, TSLPR deletion on CD4 T cells did not affect acute inflammation. As expected, transfer of Ag-sensitized wild-type CD4T cells, but not of TSLPR-deficient CD4T cells, increased skin inflammation in the model upon challenge. Furthermore, production of IL-4 from TSLPR-deficient CD4T cells in inflamed ear lesions was markedly diminished, demonstrating that TSLP-dependent IL-4 production from CD4T cells was critical for the exacerbation of skin inflammation. Similar results were obtained in Th2-type allergic skin inflammation model using MC903. Collectively, these results indicate that TSLP acts directly on CD4 T cells to elicit pathogenesis of Th2 cells, thereby having a critical role in exacerbation of skin inflammation in the chronic phase.

Blockade of thymic stromal lymphopoietin and CRTH2 attenuates airway inflammation in a murine model of allergic asthma

BACKGROUND/AIMS

Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine that plays a key role in Th2-mediated inflammation, both directly by promoting the proliferation of naïve CD4 Th2 cells, and indirectly by activating dendritic cells (DCs). TSLP-activated DCs induce the expansion of chemoattractant receptor homologous molecule expressed on Th2 (CRTH2)+ CD4+ Th2 memory cells, which undergo a Th2 response and express prostaglandin D2 (PGD2) synthase. CRTH2, a PGD2 receptor, is a selective Th2-cell surface marker. We investigated the effects of an anti-TSLP antibody (Ab) and a CRTH2 antagonist, as well as their mechanisms of action, in a mouse model of acute asthma.

METHODS

BALB/c mice were sensitized and challenged with ovalbumin. We then evaluated the effects of the administration of an anti-TSLP Ab either alone or together with a CRTH2 antagonist on cell counts, Th2 cytokine levels in bronchoalveolar fluid, and the levels of epithelium-derived cytokines such as TSLP, interleukin (IL) 33, and IL-25 in lung homogenates, as well as airway hyper-responsiveness (AHR).

RESULTS

Anti-TSLP Ab and the CRTH2 antagonist significantly attenuated eosinophilic airway inflammation, AHR, and the expression of Th2 cytokines. The expression of GATA-3 and the levels of IL-33 and IL-25 in lung tissues were affected by the combined anti-TSLP and CRTH2 antagonist treatment.

CONCLUSION

These results suggest that the dual blockade of TSLP and CRTH2 may serve as an effective treatment target for eosinophilic asthma.

TSLP drives acute TH2-cell differentiation in lungs

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine that is important for the development of type 2 inflammatory responses at mucosal surfaces.

OBJECTIVE

In humans, TSLP level has been found to be elevated in the lungs of patients with asthma, and in mouse models, TSLP can promote type 2 airway inflammation, primarily through the activation of dendritic cells. However, the mechanisms underlying its role remain unclear. The objective of this study was to provide a mechanistic analysis of TSLP-mediated type 2 airway inflammation METHODS: To dissect the mechanisms of TSLP-mediated type 2 responses, mice were treated with TSLP and antigen to evaluate cellular immune responses. Flow cytometric analyses were used to follow responses in the airways, and conditional deletion of TSLP receptor and adoptive transfer were used to identify the cellular subsets involved in this inflammatory response.

RESULTS

We showed that TSLP can directly promote T_H2-cell differentiation in the lung, independent of the draining lymph nodes. We also identified a population of patrolling monocytes/interstitial macrophages (IMs) (CD11c-expressing IMs) that are both necessary and sufficient for TSLP-mediated T_H2-cell differentiation and airway inflammation. T_H2-cell-driven airway eosinophilia is attenuated by ablation of CD11c-expressing IMs or by selective deficiency of TSLP receptor signaling in these cells. More importantly, CD11c-expressing IMs are sufficient for the induction of acute T_H2-cell responses in the lungs that is independent of dendritic cells and T-cell priming in the draining lymph nodes.

CONCLUSION

These findings indicate a novel mechanistic role for TSLP and CD11c-expressing IMs in the development of acute T_H2-cell-dependent allergic airway inflammation. This work also demonstrates a new role for TSLP in promoting type 2 responses directly in the lung.

Anti-TSLP antibodies: Targeting a master regulator of type 2 immune responses

TSLP is an epithelial cell-derived cytokine synthesized in response to various stimuli, including protease allergens and microorganisms like viruses and bacteria. Biological functions of TSLP require heterodimer formation between the TSLP receptor (TSLPR) and IL-7 receptor-α, which polarize dendritic cells to induce type 2 inflammation and directly expand and/or activate Th2 cells, group 2 innate lymphoid cells, basophils, and other immune cells. TSLP is thus considered a master regulator of type 2 immune responses at the barrier surfaces of skin and the respiratory/gastrointestinal tract. Indeed, genetic, experimental, and clinical evidence suggests that the TSLP-TSLPR pathway is associated with the pathogenesis of allergic diseases such as atopic dermatitis (AD) and asthma. Tezepelumab (AMG-157/MEDI9929) is a human anti-TSLP antibody that prevents TSLP-TSLPR interactions. A phase 2 trial for moderate to severe AD showed that a greater but not statistically significant percentage of tezepelumab-treated patients showed clinical improvements compared to the placebo group. A phase 2 trial for uncontrolled, severe asthma showed significant decreases in asthma exacerbation rate and improved pulmonary function and asthma control for tezepelumab-treated patients. Levels of biomarkers of type 2 inflammation, such as blood/sputum eosinophil counts and fraction of exhaled nitric oxide decreased, however, clinical efficacy was observed irrespective of the baseline levels of these biomarkers. A blockade of the TSLP-TSLPR pathway likely will exert significant clinical effects on AD, asthma, and other allergic diseases. The efficacy of anti-TSLP antibodies compared to other biologics needs to be further examined.

ncRNAs in Type-2 Immunity

Immunological diseases, including asthma, autoimmunity and immunodeficiencies, affect a growing percentage of the population with significant unmet medical needs. As we slowly untangle and better appreciate these complex genetic and environment-influenced diseases, new therapeutically targetable pathways are emerging. Non-coding RNA species, which regulate epigenetic, transcriptional and translational responses are critical regulators of immune cell development, differentiation and effector function, and may represent one such new class of therapeutic targets. In this review we focus on type-2 immune responses, orchestrated by T_H2 cell-derived cytokines, IL-4, IL-5 and IL-13, which stimulate a variety of immune and tissue responses- commonly referred to as type-2 immunity. Evolved to protect us from parasitic helminths, type-2 immune responses are observed in individuals with allergic diseases, including Asthma, atopic dermatitis and food allergy. A growing number of studies have identified the involvement of various RNA species, including microRNAs (miRNA) and long non-coding (lncRNA), in type-2 immune responses and in both clinical and pre-clinical disease settings. We highlight these recent findings, identify gaps in our understanding and provide a perspective on how our current understanding can be harnessed for novel treat opportunities to treat type-2 immune-mediated diseases.

Transient receptor potential vanilloid-3 (TRPV3) channel induces dermal fibrosis via the TRPV3/TSLP/Smad2/3 pathways in dermal fibroblasts

BACKGROUND

Excessive wound healing can lead to hypertrophic scars, which are not only a cosmetic issue but could also be itchy or painful. Previously, we reported that, in comparison with normal tissue, thymic stromal lymphopoietin (TSLP) expression was increased in skin burn scars when the activation of transient receptor potential vanilloid-3 (TRPV3) of keratinocytes was increased. However, the functional role of TRPV3 in dermal fibrosis remains unclear.

OBJECTIVE

We aimed to determine whether TRPV3 affects the collagen production of human primary dermal fibroblasts (HPDFs) and to investigate the mechanism involved.

METHOD

Human primary dermal fibroblasts were cultured and transformed into myofibroblasts using TSLP and carvacrol. Expression levels of α-SMA, fibronectin, and COL1A1 were determined using qPCR, western blotting, and immunofluorescence staining. Ca²⁺ influx was measured using a calcium-sensitive fluorescent dye, Fura3-AM. Nuclear factor of activated T-cells (NFAT) and phosphorylated-Smad2/3 were determined by western blotting. Silencing of TRPV3 with TRPV3-specific small interference RNA was evaluated using qPCR and western blotting.

RESULTS

The expression levels of α-SMA, fibronectin, COL1A1, and TSLP were significantly increased in carvacrol-treated HPDFs. The expression levels of α-SMA, fibronectin, and COL1A1 were significantly increased by TSLP. The expression levels of TSLP and COL1A1 were significantly blocked by TRPV3 silencing in HPDFs. Regulation of Ca²⁺ influx and the expression levels of NFAT and p-Smad2/3 were significantly increased in carvacrol-treated HPDFs. ECM productions induced via the TRPV3/TSLP/Smad2/3 pathways.

CONCLUSIONS

The activation of the TRPV3 channels regulates dermal fibrosis by reducing extracellular matrix production via the TRPV3/TSLP/Smad2/3 pathways in dermal fibroblasts.

Intrauterine growth restriction induces skin inflammation, increases TSLP and impairs epidermal barrier function

Intrauterine growth restriction (IUGR) and low birth weight are risk factors for childhood asthma. Atopic march describes the progression from early dermatitis to asthma during life. Since inflammatory signaling is linked to increased airway resistance and lung remodeling in rats after IUGR, we queried if these findings are related to skin inflammatory response. Firstly, we induced IUGR in Wistar rats by isocaloric protein restriction during gestation. IUGR rats showed lower body weight at postnatal day 1 (P1), catch-up growth at P21, and similar body weight like controls at P90. At P1 and P90, mRNA of inflammatory as well as fibrotic markers and number of skin immune cells (macrophages) were increased after IUGR. Skin thymic stromal lymphopoietin (TSLP) mRNA at P1 and serum TSLP at P1 and P21 were elevated in IUGR. Moreover, IUGR impaired transepidermal water loss at P21 and P90. IUGR induced higher. Secondly, the increase of TEWL after Oxazolone treatment as a model of atopic dermatitis (AD) was greater in IUGR than in Co. Our data demonstrate an early inflammatory skin response, which is linked to persistent macrophage infiltration in the skin and impaired epidermal barrier function after IUGR. These findings coupled with elevated TSLP could underlie atopic diseases in rats after IUGR. KEY MESSAGES: • The present study shows that IUGR increases macrophage infiltration and induces an inflammatory and fibrotic gene expression pattern in the skin of newborn rats. • Early postnatal inflammatory response in the skin after IUGR is followed by impaired epidermal barrier function later in life. • IUGR aggravates transepidermal water loss in an experimental atopic dermatitis model, possibly through elevated TSLP in skin and serum. • Early anti-inflammatory treatment and targeting TSLP signaling could offer novel avenues for early prevention of atopic disorders and late asthma in high-risk infants.

Targeted deletion of the TSLP receptor reveals cellular mechanisms that promote type 2 airway inflammation

Thymic stromal lymphopoietin (TSLP) is a critical upstream cytokine inducing type 2 inflammation in various diseases, including asthma and atopic dermatitis. Accumulating evidence suggests that TSLP can directly stimulate a variety of immune cells, such as dendritic cells (DCs), basophils, T cells, and group 2 innate lymphoid cells (ILC2s). However, which cell types directly respond to TSLP in vivo and how TSLP initiates type 2 inflammation has remained controversial. To define the precise role of TSLP in vivo, for the first time we generated multiple cell lineage-specific TSLP receptor-deficient mice to systematically dissect the cell-intrinsic requirements for TSLP responsiveness in type 2 inflammation in the lung. In papain-induced innate immune-mediated type 2 airway inflammation, TSLP directly stimulated ILC2s, but not basophils, leading to enhanced type 2 inflammation. On the other hand, in OVA-induced adaptive immune-mediated type 2 airway inflammation, TSLP principally acted on DCs and CD4 + T cells during the sensitization phase, but not basophils or ILC2s, and facilitated the development of Th2 cell-mediated airway inflammation. Together, these findings reveal that TSLP activates distinct immune cell cascades in the context of innate and adaptive immune-mediated type 2 inflammation.

Distinct Chronic Post-Viral Lung Diseases upon Infection with Influenza or Parainfluenza Viruses Differentially Impact Superinfection Outcome

Chronic obstructive pulmonary disease (COPD) and asthma remain prevalent human lung diseases. Variability in epithelial and inflammatory components that results in pathologic heterogeneity complicates the development of treatments for these diseases. Early childhood infection with parainfluenza virus or respiratory syncytial virus is strongly associated with the development of asthma and COPD later in life, and exacerbations of these diseases correlate with the presence of viral RNA in the lung. Well-characterized animal models of postviral chronic lung diseases are necessary to study the underlying mechanisms of viral-related COPD and asthma and to develop appropriate therapies. In this study, we cross-analyzed chronic lung disease caused by infection with Sendai virus (SeV) or influenza A virus in mice. Differences were observed in lesion composition and inflammatory profiles between SeV- and influenza A virus-induced long-term lung disease. In addition, a primary SeV infection led to worsened pathologic findings on secondary heterologous viral challenge, whereas the reversed infection scheme protected against disease in response to a secondary viral challenge >1 month after the primary infection. These data demonstrate the differential effect of primary viral infections in the susceptibility to disease exacerbation in response to a different secondary viral infection and highlight the usefulness of these viral models as tools to understand the underlying mechanisms that mediate distinct chronic postviral lung diseases.

Tezepelumab: a novel biological therapy for the treatment of severe uncontrolled asthma

Introduction: Thymic stromal lymphopoietin (TSLP) is overexpressed in the airways of severe asthmatics and is an upstream cytokine that orchestrates inflammatory responses in asthma. TSLP exerts its effects by binding to a high affinity heteromeric receptor complex composed of TSLPR and IL-7Rα. An association of polymorphisms in TSLP with airway hyperresponsiveness, IgE, eosinophilia and asthma has been documented. TSLP has been implicated in asthma pathophysiology. Tezepelumab is a first-in-class human monoclonal antibody that binds to TSLP, thus inhibiting its interaction with TSLP receptor complex. Tezepelumab given as an add-on-therapy to patients with severe uncontrolled asthma has shown safety, tolerability and efficacy. Several trials are evaluating the long-term safety and the efficacy of tezepelumab in adults and adolescents with severe uncontrolled asthma.Areas covered: We provide an overview of the monoclonal antibody therapeutics market for severe uncontrolled asthma, examine the underlying pathophysiology that drives TSLP and discuss the use of tezepelumab for the treatment of severe uncontrolled asthma,Expert opinion: TSLP is a promising target for T2-high and perhaps some patients with T2-low asthma. The results of preliminary clinical trials are encouraging. Several unanswered questions concerning basic pathophysiological aspects of TSLP variants, the long-term safety and efficacy of tezepelumab with different phenotypes/endotypes of asthma should be addressed.

TSLP Exacerbates Septic Inflammation via Murine Double Minute 2 (MDM2) Signaling Pathway

Thymic stromal lymphopoietin (TSLP) is crucial for Th2-mediated inflammation. Sepsis is a serious systemic inflammatory reaction with organ dysfunction by infection. However, the function of TSLP during sepsis is poorly understood. Thus, we investigated a role and regulatory mechanism of TSLP during sepsis. Sepsis was induced by lipopolysaccharides (LPS) or Escherichia coli DH5α injection in mice. TSLP levels were measured in human subjects, mice, and macrophages. TSLP deficiency or murine double minute 2 (MDM2) deficiency was induced using siRNA or an MDM2 inhibitor, nutlin-3a. We found that TSLP levels were elevated in serum of patients and mice with sepsis. TSLP deficiency lowered liver damage and inflammatory cytokine levels in mice with sepsis. TSLP was produced by the MDM2/NF-κB signaling pathway in LPS-stimulated macrophages. TSLP downregulation by an MDM2 inhibitor, nutlin-3a, alleviated clinical symptoms and septic inflammatory responses. Pharmacological inhibition of TSLP level by cisplatin reduced the septic inflammatory responses. Altogether, the present results show that TSLP exacerbates septic inflammation via the MDM2 signaling pathway, suggesting that TSLP may be a potential target for the treatment of sepsis.

Rhinovirus Attributes that Contribute to Asthma Development

Early-life wheezing-associated infections with human rhinovirus (HRV) are strongly associated with the inception of asthma. The immune system of immature mice and humans is skewed toward a type 2 cytokine response. Thus, HRV-infected 6-day-old mice but not adult mice develop augmented type 2 cytokine expression, eosinophilic inflammation, mucous metaplasia, and airway hyperresponsiveness. This asthma phenotype depends on interleukin (IL)-13-producing type 2 innate lymphoid cells, the expansion of which in turn depends on release of the innate cytokines IL-25, IL-33, and thymic stromal lymphopoietin from the airway epithelium. In humans, certain genetic variants may predispose to HRV-induced childhood asthma.

Thymic stromal lymphopoietin production induced by skin irritation results from concomitant activation of protease-activated receptor 2 and interleukin 1 pathways

BACKGROUND

Thymic stromal lymphopoietin (TSLP) mediates proallergic T helper 2-type responses by acting on leucocytes. Endogenous pathways regulating TSLP production are poorly defined.

OBJECTIVES

To uncover the mechanisms by which skin barrier disruption elicits TSLP production and to delineate the level at which individual mechanistic components may converge.

METHODS

A combination of primary keratinocytes, skin explants and in vivo strategies was employed. Murine skin was tape stripped in the presence of neutralizing antibodies or antagonists. Cells and explants were stimulated with interleukin (IL)-1 and protease-activated receptor 2 agonist (PAR-2-Ag). TSLP levels were quantified by enzyme-linked immunosorbent assay and real-time quantitative polymerase chain reaction. Chromatin immunoprecipitation and promoter reporter assays were used to examine recruitment and functional activity of nuclear factor kappa B (NF-κB) at the TSLP promoter.

RESULTS

TSLP induction in mouse skin occurred in a PAR-2- and IL-1-dependent manner. This scenario was duplicated by exogenous IL-1 plus PAR-2-Ag vs. each stimulus alone. Joint activity of PAR-2 and IL-1 was also observed in human keratinocytes. The TSLP promoter was identified as the target of PAR-2/IL-1, whereby PAR-2 activation augmented the recruitment of NF-κB and transcriptional activation over IL-1 alone. Combined treatment showed activity at concentrations of IL-1 unable to elicit NF-κB activity on their own.

CONCLUSIONS

Skin barrier disruption activates the IL-1 and the PAR-2 pathways, which act in concert to activate the TSLP promoter and possibly other inflammatory genes. Awareness of this combined activity may permit a more flexible clinical management by selective targeting of either pathway individually or collectively. What's already known about this topic? Thymic stromal lymphopoietin (TSLP) is rapidly induced upon skin perturbation and mediates proallergic T helper 2-type responses by acting on leucocytes. Endogenous control of TSLP expression is poorly understood, but interleukin (IL)-1 is one regulator in the cutaneous environment In addition to IL-1, protease-activated receptor 2 (PAR-2) organizes central inflammatory pathways in the skin. What does this study add? IL-1 and PAR-2 pathways cooperate in driving TSLP production in mice and humans. Pathway integration occurs at the level of the TSLP promoter through enhanced recruitment and transcriptional activation of nuclear factor kappa B. When PAR-2 is co-stimulated, very low IL-1 levels (inactive by themselves) can induce biologically meaningful responses in the skin environment. What is the translational message? Physical skin irritation results in robust TSLP production by simultaneous activation of PAR-2 and IL-1 pathways.

TSLP and TSLP receptors variants are associated with smoking

Background

To search for new prevention markers for early detection of the diseases caused by tobacco, we aimed to investigate the polymorphisms in TSLP and TSLPRs associated with cigarette smoking in the Saudi population.

Materials and methods

Samples were collected from 177 smokers and 126 healthy controls. Three TSLP SNPs [rs3806933, rs2289276, and rs10043985], three TSLPR SNPs [rs36133495, rs36177645, and rs36139698], and two IL7R SNPs rs1053496 and rs12516866 were analyzed by genotyping.

Results

Two TSLP SNPs (rs10043985 and rs3806933) and one TSLPR SNP (rs36139698) showed significant correlations with smoking behavior, but not IL7R rs12516866 and rs1053496. rs10043985 showed a clear association with long‐term smoking regardless of daily cigarette consumption. rs2289276 was associated with short‐term smoking but not with daily cigarette consumption. rs3806933 was highly associated with different smoker subgroups. Rs36139698 was highly associated with long‐term smokers who consumed ≥20 cigarettes/day, and the “T” allele was associated only with individuals who smoked ≤20 cigarettes/day. Rs36139698 corresponds to a P195L substitution and produces a TSLPR mutant with a predicted ΔΔG increase of 2.15 kcal/mol and has a more stable structure than the wild‐type variant.

Conclusions

Investigating TSLP and TSLPR polymorphisms is crucial for elucidating the mechanisms underlying tobacco‐induced diseases.

Skin tissue expression and serum level of thymic stromal lymphopoietin in patients with psoriasis vulgaris

Thymic stromal lymphopoietin (TSLP) is known to be associated with allergic diseases. It is also suggested that TSLP has a role in autoimmune diseases such as psoriasis; however, the associated pathways remain unknown. There is currently little information on TSLP in psoriasis vulgaris. We investigated TSLP expressions on lesional and non-lesional skin of psoriasis vulgaris patients using reverse transcription- polymerase chain reaction. TSLP level was also investigated in serum from psoriasis vulgaris patients compared to healthy control using enzyme-linked immunosorbent assay. TSLP expression was higher in lesional skin (1.90) compared to non-lesional skin (1.76); however, the difference was not statistically significant (P>0.05). TSLP serum levels were significantly higher in psoriasis patients (287.40 pg/dL) as compared to controls (114.70 pg/dL) (P<0.05). This study concluded that TSLP levels in the serum of psoriasis vulgaris patients are higher than controls. TSLP was also found in keratinocyte of psoriasis patients, the expression was higher in the lesional compared to non-lesional skin; however, this difference is statistically insignificant. These findings suggest that TSLP may play a role in the pathogenesis of psoriasis vulgaris, but its exact role remains unclear.

Similar immune mechanisms control experimental airway eosinophilia elicited by different allergens and treatment protocols

Background

Mouse models have been extremely valuable in identifying the fundamental mechanisms of airway inflammation that underlie human allergic asthma. Several models are commonly used, employing different methods and routes of sensitisation, and allergens of varying clinical relevance. Although all models elicit similar hallmarks of allergic airway inflammation, including airway eosinophilia, goblet cell hyperplasia and cellular infiltration in lung, it is not established whether they do so by involving the same mechanisms.

Results

We compared the impact of inactivation of various innate or adaptive immune genes, as well as sex, in different models of allergic airway inflammation in mice of C57BL/6 background. Chicken ovalbumin (OVA) and house dust mite (HDM) were used as allergens in settings of single or multiple intranasal (i.n.) challenges, after sensitisation in adjuvant or in adjuvant-free conditions. Eosinophil numbers in the broncho-alveolar lavage and lung histopathology were assessed in each model. We found that Major Histocompatibility Complex Class II (MHCII) deficiency and lack of conventional CD4+ T cells had the most profound effect, essentially ablating airway eosinophilia and goblet cell hyperplasia in all models. In contrast, Thymic stromal lymphopoietin receptor (TSLPR) deficiency greatly reduced eosinophilia but had a variable effect on goblet cells. CD1d deficiency and lack of Natural Killer T (NKT) cells moderately impaired inflammation in OVA models but not HDM, whereas sex affected the response to HDM but not OVA. Lastly, defective Toll-like receptor (TLR)4 expression had only a relatively modest overall impact on inflammation.

Conclusion

All the models studied were comparably dependent on adaptive CD4+ T cell responses and TSLP. In contrast, sex, NKT cells and TLR4 appeared to play subtler and more variable roles that were dependent on the type of allergen and mode of immunization and challenge. These results are consistent with clinical data suggesting a key role of CD4+ T cells and TSLP in patients with allergic asthma.

Electronic supplementary material

The online version of this article (10.1186/s12865-019-0295-y) contains supplementary material, which is available to authorized users.

Mechanical Skin Injury Promotes Food Anaphylaxis by Driving Intestinal Mast Cell Expansion

Mast cell (MC) mediator release after crosslinking of surface-bound IgE antibody by ingested antigen underlies food allergy. However, IgE antibodies are not uniformly associated with food allergy, and intestinal MC load is an important determinant. Atopic dermatitis (AD), characterized by pruritis and cutaneous sensitization to allergens, including foods, is strongly associated with food allergy. Tape stripping mouse skin, a surrogate for scratching, caused expansion and activation of small intestinal MCs, increased intestinal permeability, and promoted food anaphylaxis in sensitized mice. Tape stripping caused keratinocytes to systemically release interleukin-33 (IL-33), which synergized with intestinal tuft-cell-derived IL-25 to drive the expansion and activation of intestinal type-2 innate lymphoid cells (ILC2s). These provided IL-4, which targeted MCs to expand in the intestine. Duodenal MCs were expanded in AD. In addition to promoting cutaneous sensitization to foods, scratching may promote food anaphylaxis in AD by expanding and activating intestinal MCs.

Epithelial cell-derived cytokines: more than just signaling the alarm

The epithelial cell-derived cytokines thymic stromal lymphopoietin (TSLP), IL-33, and IL-25 are central regulators of type 2 immunity, which drives a broad array of allergic responses. Often characterized as "alarmins" that are released by the barrier epithelium in response to external insults, these epithelial cell-derived cytokines were initially thought to act only early in allergic inflammation. Indeed, TSLP can condition dendritic cells to initiate type 2 responses, and IL-33 may influence susceptibility to asthma through its role in establishing the immune environment in the perinatal lungs. However, TSLP, IL-33, and IL-25 all regulate a broad spectrum of innate immune cell populations and are particularly potent in eliciting and activating type 2 innate lymphoid cells (ILC2s) that may act throughout allergic inflammation. Recent data suggest that a TSLP/ILC axis may mediate steroid resistance in asthma. Recent identification of memory Th2 cell subsets that are characterized by high receptor expression for TSLP, IL-33, and IL-25 further supports a role for these cytokines in allergic exacerbations. There is therefore growing interest in developing biologics that target TSLP, IL-33, and IL-25. This Review provides an overview of TSLP, IL-33, and IL-25 and the development of blocking antibodies that target these epithelial cell-derived cytokines.

Molecular basis and cellular mechanisms of eosinophilic esophagitis for the clinical practice

Eosinophilic esophagitis (EoE) is a chronic, allergen-driven inflammatory esophageal disease characterized by predominantly eosinophilic inflammation leading to esophageal dysfunction. Recent efforts to understand EoE have increased our knowledge of the disease. Areas covered: Multiple cells, molecules, and genes interplay with early life environmental factors in the pathophysiology of EoE to converge in the esophageal epithelium at the center of disease pathogenesis. Epithelial cells constitute a mayor cytokine source for TSLP and Calpain-14; an impaired epithelial barrier function allowing penetration of food and microbiota-derived antigens is involved in triggering and maintaining inflammation. Eosinophil and mast cell-derived products, including TGFβ, together with IL-1β and TNFα, promote epithelial mesenchymal transition in EoE, contributing to tissue remodeling by synthetizing and depositing extracellular matrix in subepithelial layers. This article aims to provide a state-of-the-art update on the pathophysiology of EoE applied to clinical practice, and latest research and developments with potential interest to improve the diagnosis and treatment of patients with EoE are revised. Expert commentary: Preliminary approaches have provided promising results toward incorporating minimally invasive methods for patient diagnosis and monitoring in clinical practice. Early diagnosis and optimized therapies will allow for personalized medicine in EoE.

Potential Role of Interleukin-25/Interleukin-33/Thymic Stromal Lymphopoietin-Fibrocyte Axis in the Pathogenesis of Allergic Airway Diseases

Objective:

Allergic airway diseases (AADs) are a group of heterogeneous disease mediated by T-helper type 2 (Th2) immune response and characterized with airway inflammation and remodeling, including allergic asthma, allergic rhinitis, and chronic rhinosinusitis with allergic background. This review aimed to discuss the abnormal epithelial-mesenchymal crosstalk in the pathogenesis of AADs.

Data Sources:

Articles referred in this review were collected from the database of PubMed published in English up to January 2018.

Study Selection:

We had done a literature search using the following terms “allergic airway disease OR asthma OR allergic rhinitis OR chronic sinusitis AND IL-25 OR IL-33 OR thymic stromal lymphopoietin OR fibrocyte”. Related original or review articles were included and carefully analyzed.

Results:

It is now believed that abnormal epithelial-mesenchymal crosstalk underlies the pathogenesis of AADs. However, the key regulatory factors and molecular events involved in this process still remain unclear. Epithelium-derived triple cytokines, including interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin (TSLP), are shown to act on various target cells and promote the Th2 immune response. Circulating fibrocyte is an important mesenchymal cell that can mediate tissue remodeling. We previously found that IL-25-circulating fibrocyte axis was significantly upregulated in patients with asthma, which may greatly contribute to asthmatic airway inflammation and remodeling.

Conclusions:

In view of the redundancy of cytokines and “united airway” theory, we propose a new concept that IL-25/IL-33/TSLP-fibrocyte axis may play a vital role in the abnormal epithelial-mesenchymal crosstalk in some endotypes of AADs. This novel idea will guide potential new intervention schema for the common treatment of AADs sharing common pathogenesis in the future.

Social Networking of Group Two Innate Lymphoid Cells in Allergy and Asthma

Allergic diseases including asthma, chronic rhinosinusitis, and atopic dermatitis are common conditions worldwide. While type 2 immune responses induced by T-cells significantly cause allergic inflammation, the recently identified group two innate lymphoid cells (ILC2s) are emerging as critical players in the development of allergy. Upon allergen exposure, ILC2s are rapidly activated by cytokines released by epithelial cells. Activated ILC2s release various effector cytokines altogether contributing to the pathogenesis of allergy and can even cause inflammation in the absence of T-cells, as observed in asthma. Although the factors inducing ILC2 activation have been identified, evidence suggests that multiple factors can enhance or repress ILC2 proliferation, trafficking, or secretion of effector cytokines upon allergic inflammation. In this review, we discuss the recent findings that influence ILC2 activation and the resulting effects on the pathogenesis of allergy. A better understanding of how ILC2s are modulated will open the door to the development of new therapeutic strategies against allergic diseases.

T Helper Cell Differentiation, Heterogeneity, and Plasticity

Naïve CD4 T cells, on activation, differentiate into distinct T helper (Th) subsets that produce lineage-specific cytokines. By producing unique sets of cytokines, effector Th subsets play critical roles in orchestrating immune responses to a variety of infections and are involved in the pathogenesis of many inflammatory diseases including autoimmunity, allergy, and asthma. The differentiation of Th cells relies on the strength of T-cell receptor (TCR) signaling and signals triggered by polarizing cytokines that activate and/or up-regulate particular transcription factors. Several lineage-specific master transcription factors dictate Th cell fates and functions. Although these master regulators cross-regulate each other, their expression can be dynamic. Sometimes, they are even coexpressed, resulting in massive Th-cell heterogeneity and plasticity. Similar regulation mediated by these master regulators is also found in innate lymphoid cells (ILCs) that are innate counterparts of Th cells.

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.

Design and characterization of Zweimab and Doppelmab, high affinity dual antagonistic anti-TSLP/IL13 bispecific antibodies

Patients with severe Th2 type asthma often have a steroid resistant phenotype and are prone to acute exacerbations. Current novel therapies have only marginal therapeutic effects. One of the hypotheses for lack of major efficacy in most patients is targeting only one redundant pathway leaving others active. Hence, we have designed and developed novel highly potent bispecific anti-TSLP/IL13 antibodies called Zweimabs (monovalent bispecific) and Doppelmabs (bivalent bispecific) that concurrently inhibits the signaling by these two cytokines.

Thymic Stromal Lymphopoietin Isoforms, Inflammatory Disorders, and Cancer

Thymic stromal lymphopoietin (TSLP) is a pleiotropic cytokine originally isolated from a murine thymic stromal cell line. TSLP exerts its biological effects by binding to a high-affinity heteromeric complex composed of thymic stromal lymphopoietin receptor chain and IL-7Rα. TSLP is primarily expressed by activated lung and intestinal epithelial cells, keratinocytes, and fibroblasts. However, dendritic cells (DCs), mast cells, and presumably other immune cells can also produce TSLP. Different groups of investigators have demonstrated the existence of two variants for TSLP in human tissues: the main isoform expressed in steady state is the short form (sf TSLP), which plays a homeostatic role, whereas the long form (lfTSLP) is upregulated in inflammatory conditions. In addition, there is evidence that in pathological conditions, TSLP can be cleaved by several endogenous proteases. Several cellular targets for TSLP have been identified, including immune (DCs, ILC2, T and B cells, NKT and Treg cells, eosinophils, neutrophils, basophils, monocytes, mast cells, and macrophages) and non-immune cells (platelets and sensory neurons). TSLP has been originally implicated in a variety of allergic diseases (e.g., atopic dermatitis, bronchial asthma, eosinophilic esophagitis). Emerging evidence indicates that TSLP is also involved in chronic inflammatory (i.e., chronic obstructive pulmonary disease and celiac disease) and autoimmune (e.g., psoriasis, rheumatoid arthritis) disorders and several cancers. These emerging observations greatly widen the role of TSLP in different human diseases. Most of these studies have not used tools to analyze the expression of the two TSLP isoforms. The broad pathophysiologic profile of TSLP has motivated therapeutic targeting of this cytokine. Tezepelumab is a first-in-class human monoclonal antibody (1) that binds to TSLP inhibiting its interaction with TSLP receptor complex. Tezepelumab given as an add-on-therapy to patients with severe uncontrolled asthma has shown safety and efficacy. Several clinical trials are evaluating the safety and the efficacy of tezepelumab in different inflammatory disorders. Monoclonal antibodies used to neutralize TSLP should not interact or hamper the homeostatic effects of sf TSLP.

The Hunt for the Source of Primary Interleukin-4: How We Discovered That Natural Killer T Cells and Basophils Determine T Helper Type 2 Cell Differentiation In Vivo

Interleukin (IL)-4 plays a central role in determining the phenotype of naïve CD4⁺ T cells by promoting their differentiation into IL-4-producing T helper type 2 (Th2) cells, which are crucial for the induction of allergic inflammation. However, to date, the potential sources of “primary IL-4” in vivo, as distinguished from IL-4 produced by Th2 cells, remain unclear. Here, I describe the research I carried out in collaboration with Dr. William E. Paul to identify “primary IL-4”-producing cells and Th2 cell differentiation in vivo.

Innate and adaptive type 2 immunity in lung allergic inflammation

Allergic inflammation is a type 2 immune disorder classically characterized by high levels of immunoglobulin E (IgE) and the development of Th2 cells. Asthma is a pulmonary allergic inflammatory disease resulting in bronchial hyper-reactivity. Atopic asthma is defined by IgE antibody-mediated mast cell degranulation, while in non-atopic asthma there is no allergen-specific IgE and more involvement of innate immune cells, such as basophils, group 2 innate lymphoid cells (ILC2), and eosinophils. Recently, protease allergens were shown to cause asthmatic responses in the absence of Th2 cells, suggesting that an innate cell network (IL-33/TSLP-basophil-ILC2-IL-5/IL-13 axis) can facilitate the sensitization phase of type 2 inflammatory responses. Recent evidence also indicates that in the chronic phase, these innate immune cells directly or indirectly contribute to the adaptive Th2 cell responses. In this review, we discuss the role of Th2 cytokines (IL-4 and IL-13) and innate immune cells (mast cells, basophils, ILC2s, and dendritic cells) in the cross-talk between innate and adaptive inflammatory responses.

TSLP signaling in CD4+ T cells programs a pathogenic T helper 2 cell state

Pathogenic T helper 2 (T_H2) cells, which produce increased amounts of the cytokines interleukin-5 (IL-5) and IL-13, promote allergic disorders, including asthma. Thymic stromal lymphopoietin (TSLP), a cytokine secreted by epithelial and innate immune cells, stimulates such pathogenic T_H2 cell responses. We found that TSLP signaling in mouse CD4⁺ T cells initiated transcriptional changes associated with T_H2 cell programming. IL-4 signaling amplified and stabilized the genomic response of T cells to TSLP, which increased the frequency of T cells producing IL-4, IL-5, and IL-13. Furthermore, the TSLP- and IL-4-programmed T_H2 cells had a pathogenic phenotype, producing greater amounts of IL-5 and IL-13 and other proinflammatory cytokines than did T_H2 cells stimulated with IL-4 alone. TSLP-mediated T_H2 cell induction involved distinct molecular pathways, including activation of the transcription factor STAT5 through the kinase JAK2 and repression of the transcription factor BCL6. Mice that received wild-type CD4⁺ T cells had exacerbated pathogenic T_H2 cell responses upon exposure to house dust mites compared to mice that received TSLP receptor-deficient CD4⁺ T cells. Transient TSLP signaling stably programmed pathogenic potential in memory T_H2 cells. In human CD4⁺ T cells, TSLP and IL-4 promoted the generation of T_H2 cells that produced greater amounts of IL-5 and IL-13. Compared to healthy controls, asthmatic children showed enhancement of such T cell responses in peripheral blood. Our data support a sequential cytokine model for pathogenic T_H2 cell differentiation and provide a mechanistic basis for the therapeutic targeting of TSLP signaling in human allergic diseases.

ITGB4 is essential for containing HDM-induced airway inflammation and airway hyperresponsiveness

Airway epithelial cells play a significant role in the pathogenesis of asthma. Although the structural and functional defects of airway epithelial cells have been postulated to increase asthma susceptibility and exacerbate asthma severity, the mechanism and implication of these defects remain uncertain. Integrin β4 (ITGB4) is a structural adhesion molecule that is downregulated in the airway epithelium of asthma patients. In this study, we demonstrated that ITGB4 deficiency leads to severe allergy-induced airway inflammation and airway hyper-responsiveness (AHR) in mice. After house dust mite (HDM) challenge, epithelial cell-specific ITGB4-deleted mice showed increased lymphocyte, eosinophil, and neutrophil infiltration into lung compared with that of the wild-type mice. ITGB4 deficiency also resulted in increased expression of the Th2 cytokine IL-4, IL-13, and the Th17 cytokine IL-17A in the lung tissue and in the T cells after HDM challenge. The aggravated inflammation in ITGB4 defect mice was partly caused by enhanced disrupted epithelial barrier integrity after HDM stress, which induced the increased thymic stromal lymphopoietin secretion from airway epithelial cells. This study therefore demonstrates that ITGB4 plays a pivotal role in containing allergen-mediated lung inflammation and airway hyper-responsiveness in allergic asthma.

Characterization of signaling pathways regulating the expression of pro-inflammatory long form thymic stromal lymphopoietin upon human metapneumovirus infection

Thymic stromal lymphopoietin (TSLP) is associated with several allergic diseases including asthma. Two isoforms of TSLP exist in humans, a long form (lfTSLP) and a short form (sfTSLP), displaying distinct immunological functions. Recently, TSLP was found to be upregulated in human airway cells upon human metapneumovirus (hMPV) infection, yet it remains unclear if the two isoforms are regulated differently during hMPV infection. Importantly, the molecular mechanisms underlying hMPV-mediated TSLP induction remain undescribed. In this study, we characterized the expression and regulation of TSLP in hMPV-infected human airway cells. We demonstrated that hMPV strongly induced the expression of pro-inflammatory lfTSLP in human airway epithelial cells and lung fibroblasts. Further, knockdown of pattern recognition receptors retinoic acid-inducible gene I (RIG-I) or Toll-like receptor 3 (TLR3), as well as downstream signal transducers, abrogated hMPV-mediated lfTSLP induction. Importantly, silencing of TANK-binding kinase 1 (TBK1) also impaired hMPV-mediated lfTSLP induction, which could be attributed to compromised NF-κB activation. Overall, these results suggest that TBK1 may be instrumental for hMPV-mediated activation of NF-κB downstream RIG-I and TLR3, leading to a specific induction of lfTSLP in hMPV-infected human airway cells.

TRPV3 Channel in Keratinocytes in Scars with Post-Burn Pruritus

Post-burn pruritus is a common and distressing sequela of burn scars. Empirical antipruritic treatments usually fail to have a satisfactory outcome because of their limited selectivity and possible side effects. Therefore, novel drug targets need to be identified. Here, we aimed to investigate the possible role of protease-activated receptor 2 (PAR2) and transient receptor potential vanniloid 3 (TRPV3), along with the relation of TRPV3 to thymic stromal lymphopoietin (TSLP). Specimens from normal (unscarred) or burn-scarred (with or without pruritus) tissue were obtained from burn patients for this study. In each sample, the keratinocytes were isolated and cultured, and the intracellular Ca²⁺ level at the time of stimulation of each factor was quantified and the interaction was screened. PAR2 function was reduced by antagonism of TRPV3. Inhibiting protein kinase A (PKA) and protein kinase C (PKC) reduced TRPV3 function. TSLP mRNA and protein, and TSLPR protein expressions, increased in scars with post-burn pruritus, compared to scars without it or to normal tissues. In addition, TRPV1 or TRPV3 activation induced increased TSLP expression. Conclusively, TRPV3 may contribute to pruritus in burn scars through TSLP, and can be considered a potential therapeutic target for post-burn pruritus.

Intelectin contributes to allergen-induced IL-25, IL-33, and TSLP expression and type 2 response in asthma and atopic dermatitis

The epithelial and epidermal innate cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) have pivotal roles in the initiation of allergic inflammation in asthma and atopic dermatitis (AD). However, the mechanism by which the expression of these innate cytokines is regulated remains unclear. Intelectin (ITLN) is expressed in airway epithelial cells and promotes allergic airway inflammation. We hypothesized that ITLN is required for allergen-induced IL-25, IL-33, and TSLP expression. In two asthma models, Itln knockdown reduced allergen-induced increases in Il-25, Il-33, and Tslp and development of type 2 response, eosinophilic inflammation, mucus overproduction, and airway hyperresponsiveness. Itln knockdown also inhibited house dust mite (HDM)-induced early upregulation of Il-25, Il-33, and Tslp in a model solely inducing airway sensitization. Using human airway epithelial cells, we demonstrated that HDM-induced increases in ITLN led to phosphorylation of epidermal growth factor receptor and extracellular-signal regulated kinase, which were required for induction of IL-25, IL-33, and TSLP expression. In two AD models, Itln knockdown suppressed expression of Il-33, Tslp, and Th2 cytokines and eosinophilic inflammation. In humans, ITLN1 expression was significantly increased in asthmatic airways and in lesional skin of AD. We conclude that ITLN contributes to allergen-induced Il-25, Il-33, and Tslp expression in asthma and AD.

The role of IL-25 in the reduction of oxidative stress and the apoptosis of airway epithelial cells with specific immunotherapy in an asthma mouse model

Oxidative stress and cell apoptosis play important roles in the pathogenesis of asthma. Specific immunotherapy (SIT) is the only curative approach for asthma and is effective at decreasing asthmatic oxidation and cell apoptosis, but the mechanisms remain unclear. In this study, by using in vivo and in vitro models, we indirectly demonstrated that SIT alleviated the apoptosis and oxidative stress of bronchial epithelial cells in an asthma model through regulating interleukin (IL)-25. Female BALB/c mice were used for an asthma model induced by exposure to house dust mite (HDM) extracts as allergens. Prior to the challenge, the mice were either given the SIT vaccine or N-Acetyl-L-cysteine (NAC).

RESULTS

Compared with that in asthma models, SIT administration decreased (1) airway hyper-responsiveness; (2) the production of cytokines, including IL-4, IL-5, IL-13, and IL-25, as well as serum HDM-specific IgE and IgG1, as shown by ELISA; and (3) lipid oxidative species, such as reactive oxidative species (ROS) and malondialdehyde (MDA), in the lung tissue. Moreover, TUNEL staining showed that SIT alleviated pulmonary cell apoptosis. In vitro, flow cytometry showed that human recombinant IL-25 (rIL-25) led to increased cell apoptosis and ROS in the human epithelial cell line 16HBE in a dose and time-dependent fashion. In conclusion, in vivo, SIT reduced asthmatic Th2 cytokine levels and the production of IL-25 and alleviated oxidative stress and cell apoptosis in the lung tissue. In vitro, IL-25 increased the number of apoptotic cells and the production of ROS in16HBE cells.

Preparation of recombinant human thymic stromal lymphopoietin protein

Human thymic stromal lymphopoietin (hTSLP) protein plays a central role in inflammation. Characterizing properties of hTSLP requires a recombinant overexpression system that produces correctly folded, active hTSLP. In this report, an efficient overexpression system for the production of hTSLP was developed. We constructed expression plasmids of the full-length hTslp gene with or without the signal peptide and transformed the plasmids into Escherichia coli. The design of the recombinant proteins included an N-terminal His-tag, which facilitated purification. An affinity gradient elution method was used to improve recovery and concentration levels of denatured hTSLP, with 90% purity observed following affinity chromatography. Refolding of the denatured hTSLP was tested using four different protein refolding approaches. The optimal refolding conditions involved stepwise buffer exchanges to reduce the urea concentration from 4 to 0 M in 50 mM Tris (pH 8.0), 1 mM EDTA, 50 mM NaCl, 10% glycerol, 400 mM L-Arg, 0.2 mM oxidized glutathione, and 2 mM reduced glutathione. The activity of the refolded recombinant hTSLP protein was measured by an ELISA assay. Interestingly, the presence of N-terminal signal peptide inhibited the overexpression of hTSLP in E. coli. The amount of recombinant hTSLP protein purified reached a level of 2.52 × 10^-3 mg/L.

Epithelial Cell Regulation of Allergic Diseases

Allergic diseases, which have escalated in prevalence in recent years, arise as a result of maladaptive immune responses to ubiquitous environmental stimuli. Why only certain individuals mount inappropriate type 2 immune responses to these otherwise harmless allergens has remained an unanswered question. Mounting evidence suggests that the epithelium, by sensing its environment, is the central regulator of allergic diseases. Once considered to be a passive barrier to allergens, epithelial cells at mucosal surfaces are now considered to be the cornerstone of the allergic diathesis. Beyond their function as maintaining barrier at mucosal surfaces, mucosal epithelial cells through the secretion of mediators like IL-25, IL-33, and TSLP control the fate of downstream allergic immune responses. In this review, we will discuss the advances in recent years regarding the process of allergen recognition and secretion of soluble mediators by epithelial cells that shape the development of the allergic response.

Protective effect of forsythiaside A on OVA-induced asthma in mice

Forsythiaside A (FSA), an active constituent isolated from the Chinese medicinal herb Forsythia suspensa, has been known to have anti-inflammatory effect. However, the effect of FSA on allergic airway inflammation remains unclear. The aim of this study was to investigate the effect of FSA on OVA-induced asthma in mice. Mice model of asthma was induced by OVA. OVA-induced airway hyperresponsiveness (AHR) and inflammatory cells in BALF were detected. The production of IgE, IL-4, IL-5, IFN-γ, and IL-13 were detected by ELISA. The effects of FSA on Nrf2 and NF-κB signaling pathways were detected by western blot analysis. The results showed that treatment of FSA significantly attenuated OVA-induced lung histopathological changes. FSA inhibited OVA-induced AHR and inflammatory cells in BALF. OVA-induced IgE, IL-4, IL-5, and IL-13 production were also inhibited by FSA. Western blot analysis showed that treatment of FSA inhibited OVA-induced NF-κB activation. Treatment of FSA dose-dependently up-regulated the expression of Nrf2 and HO-1. In addition, we found that FSA up-regulated the expression of Nrf2 and HO-1 both in A549 cells and MS-H cells. Taken together, FSA suppressed inflammatory responses in OVA-induced asthma through activating Nrf2/HO-1 signaling pathway. FSA may be a promising potential preventive agent for asthma treatment.

The Innate Cytokines IL-25, IL-33, and TSLP Cooperate in the Induction of Type 2 Innate Lymphoid Cell Expansion and Mucous Metaplasia in Rhinovirus-Infected Immature Mice

Early-life respiratory viral infection is a risk factor for asthma development. Rhinovirus (RV) infection of 6-d-old mice, but not mature mice, causes mucous metaplasia and airway hyperresponsiveness that are associated with the expansion of lung type 2 innate lymphoid cells (ILC2s) and are dependent on IL-13 and the innate cytokine IL-25. However, contributions of the other innate cytokines, IL-33 and thymic stromal lymphopoietin (TSLP), to the observed asthma-like phenotype have not been examined. We reasoned that IL-33 and TSLP expression are also induced by RV infection in immature mice and are required for maximum ILC2 expansion and mucous metaplasia. We inoculated 6-d-old BALB/c (wild-type) and TSLP receptor-knockout mice with sham HeLa cell lysate or RV. Selected mice were treated with neutralizing Abs to IL-33 or recombinant IL-33, IL-25, or TSLP. ILC2s were isolated from RV-infected immature mice and treated with innate cytokines ex vivo. RV infection of 6-d-old mice increased IL-33 and TSLP protein abundance. TSLP expression was localized to the airway epithelium, whereas IL-33 was expressed in epithelial and subepithelial cells. RV-induced mucous metaplasia, ILC2 expansion, airway hyperresponsiveness, and epithelial cell IL-25 expression were attenuated by anti-IL-33 treatment and in TSLP receptor-knockout mice. Administration of intranasal IL-33 and TSLP was sufficient for mucous metaplasia. Finally, TSLP was required for maximal ILC2 gene expression in response to IL-25 and IL-33. The generation of mucous metaplasia in immature RV-infected mice involves a complex interplay among the innate cytokines IL-25, IL-33, and TSLP.

MicroRNA-145 down-regulates mucin 5AC to alleviate airway remodeling and targets EGFR to inhibit cytokine expression

This study aims to explore how microRNA-145 (miR-145) affects airway remodeling and cytokine expression by targeting epidermal growth factor receptor (EGFR) to regulate mucin 5AC (MUC5AC).Mice alveolar epithelial cells (AECs) were divided into a control, blank, miR-145 mimics, mimic control, miR-145 inhibitors, inhibitor control, si-EGFR and miR-145 inhibitors + si-EGFR group. Asthma mice models with airway remodeling were induced with an Ovalbumin (OVA) solution and randomly divided into a normal, asthma, asthma + miR-145 mimics, asthma + miR-145 mimic control, asthma + si-EGFR or asthma + si-EGFR NC group. Airway remodeling degree and histomorphology was measured using hematoxylin-eosin (HE), Masson and periodic acid-Schiff (PAS) staining. Flow cytometry was used to detect Th2 and Th17 cells in peripheral blood, ELISA was used to measure inflammatory factors. qRT-PCR and western blotting was adapted to detect the expressions of EGFR and the relevant cytokines that are regulated by miR-145.The control, miR-145 mimics and si-EGFR groups showed a higher expression of miR-145 and a lower expression of EGFR and cytokines than the blank, mimic control, inhibitor control and miR-145 inhibitor + si-EGFR groups. Mice in the asthma + miR-145 mimics and asthma + si-EGFR groups showed lower WAt/Pbm, WAi/Pbm and WAm/Pbm, less inflammatory cells, less airway modeling and alleviated goblet cell hyperplasia and mucus obstruction than the asthma group. Furthermore, the expressions of EGFR and cytokines of transfected cells and lung tissues were negatively related to those of miR-145. MiR-145 can down-regulate MUC5AC by negatively targeting EGFR and thereby relieving airway remodeling.

Critical role of TSLP-responsive mucosal dendritic cells in the induction of nasal antigen-specific IgA response

Thymic stromal lymphopoietin (TSLP) is an interleukin-7 (IL-7)-like cytokine involved in T helper 2 type immune responses. The primary target of TSLP is myeloid dendritic cells (DCs), however, little is known about the mechanism by which TSLP elicits respiratory IgA immune responses upon mucosal immunization. Here, we found that the levels of TSLP and TSLPR were upregulated in the mucosal DCs of mice nasally immunized with pneumococcal surface protein A (PspA) plus cholera toxin (CT) compared with those immunized with PspA alone. PspA-specific IgA responses, but not IgG Ab responses were significantly reduced in both serum and mucosal secretions of TSLPR knockout mice compared with wild-type mice after nasal immunization with PspA plus CT. Furthermore, CD11c⁺ mucosal DCs isolated from TSLPR knockout mice nasally immunized with PspA plus CT were less activated and exhibited markedly reduced expression of IgA-enhancing cytokines (e.g., APRIL, BAFF, and IL-6) compared with those from equivalently immunized wild-type mice. Finally, exogenous TSLP promoted production of IgAs in an in vitro DC-B cell co-culture system as exhibited by enhanced IL-6 production. These results suggest that TSLP-TSLPR signaling is pivotal in the induction of nasal respiratory immunity against pathogenic pneumococcal infection.

New perspectives on the regulation of type II inflammation in asthma

Asthma is a chronic inflammatory disease of the lungs which has been thought to arise as a result of inappropriately directed T helper type-2 (Th2) immune responses of the lungs to otherwise innocuous inhaled antigens. Current asthma therapeutics are directed towards the amelioration of downstream consequences of type-2 immune responses (i.e. β-agonists) or broad-spectrum immunosuppression (i.e. corticosteroids). However, few approaches to date have been focused on the primary prevention of immune deviation. Advances in molecular phenotyping reveal heterogeneity within the asthmatic population with multiple endotypes whose varying expression depends on the interplay between numerous environmental factors and the inheritance of a broad range of susceptibility genes. The most common endotype is one described as "type-2-high" (i.e. high levels of interleukin [IL]-13, eosinophilia, and periostin). The identification of multiple endotypes has provided a potential explanation for the observations that therapies directed at typical Th2 cytokines (IL-4, IL-5, and IL-13) and their receptors have often fallen short when they were tested in a diverse group of asthmatic patients without first stratifying based on disease endotype or severity. However, despite the incorporation of endotype-dependent stratification schemes into clinical trial designs, variation in drug responses are still apparent, suggesting that additional genetic/environmental factors may be contributing to the diversity in drug efficacy. Herein, we will review recent advances in our understanding of the complex pathways involved in the initiation and regulation of type-2-mediated immune responses and their modulation by host factors (genetics, metabolic status, and the microbiome). Particular consideration will be given to how this knowledge could pave the way for further refinement of disease endotypes and/or the development of novel therapeutic strategies for the treatment of asthma .

HIV-Tat regulates macrophage gene expression in the context of neuroAIDS

Despite the success of cART, greater than 50% of HIV infected people develop cognitive and motor deficits termed HIV-associated neurocognitive disorders (HAND). Macrophages are the major cell type infected in the CNS. Unlike for T cells, the virus does not kill macrophages and these long-lived cells may become HIV reservoirs in the brain. They produce cytokines/chemokines and viral proteins that promote inflammation and neuronal damage, playing a key role in HIV neuropathogenesis. HIV Tat is the transactivator of transcription that is essential for replication and transcriptional regulation of the virus and is the first protein to be produced after HIV infection. Even with successful cART, Tat is produced by infected cells. In this study we examined the role of the HIV Tat protein in the regulation of gene expression in human macrophages. Using THP-1 cells, a human monocyte/macrophage cell line, and their infection with lentivirus, we generated stable cell lines that express Tat-Flag. We performed ChIP-seq analysis of these cells and found 66 association sites of Tat in promoter or coding regions. Among these are C5, CRLF2/TSLPR, BDNF, and APBA1/Mint1, genes associated with inflammation/damage. We confirmed the association of Tat with these sequences by ChIP assay and expression of these genes in our THP-1 cell lines by qRT-PCR. We found that HIV Tat increased expression of C5, APBA1, and BDNF, and decreased CRLF2. The K50A Tat-mutation dysregulated expression of these genes without affecting the binding of the Tat complex to their gene sequences. Our data suggest that HIV Tat, produced by macrophage HIV reservoirs in the brain despite successful cART, contributes to neuropathogenesis in HIV-infected people.

TSLP signaling blocking alleviates E-cadherin dysfunction of airway epithelium in a HDM-induced asthma model

Recent studies have indicated that Thymic stromal lymphopoietin (TSLP) plays an important role in the prevention and treatment of asthma. However the role of TSLP in dysfunction of airway epithelial adherens junctions E-cadherin in house dust mite (HDM)-induced asthma has not been addressed. We hypothesized that TSLP contributed to HDM-induced E-cadherin dysfunction in asthmatic BALB/c mice and 16HBE cells. In vivo, a HDM-induced asthma mouse model was set up for 8weeks. Mice inhaled an anti-TSLP monoclonal antibody (mAb) before HDM. The mice treated with the anti-TSLP mAb ameliorated airway inflammation, the decreasing and aberrant distribution of E-cadherin and β-catenin as well as phosphorylation(p)-AKT induced by HDM. In vitro, HDM increased the expression of TSLP and E-cadherin dysfunction by PI3K/Akt signaling pathway. The exposure of 16HBE to TSLP resulted in redistribution of E-cadherin. These results indicate that TSLP may be an important contributor in E-cadherin dysfunction of HDM-induced asthma. TSLP signaling blocking shows a protective effect in mice and that the PI3K/Akt pathway may play a role in this process.

Upregulation of interleukin-33 and thymic stromal lymphopoietin levels in the lungs of idiopathic pulmonary fibrosis

BACKGROUND

Innate T helper type 2 (Th2) immune responses mediated by interleukin (IL)-33, thymic stromal lymphopoietin (TSLP), and IL-25 have been shown to play an important role in pulmonary fibrosis of animal models; however, their clinical implications remain poorly understood.

METHODS

TSLP, IL-25, and IL-33 concentrations were measured in bronchoalveolar lavage fluids obtained from normal controls (NCs; n = 40) and from patients with idiopathic pulmonary fibrosis (IPF; n = 100), non-specific interstitial pneumonia (NSIP; n = 22), hypersensitivity pneumonitis (HP; n = 20), and sarcoidosis (n = 19).

RESULTS

The TSLP and IL-33 levels were significantly higher in patients with IPF relative to the NCs (p = 0.01 and p = 0.0001, respectively), NSIP (p = 4.95E - 7 and p = 0.0002, respectively), HP (p = 0.00003 and p = 0.000005, respectively), and sarcoidosis groups (p = 0.003 and p = 0.0001, respectively). However, the IL-25 levels were not significantly different between NC and IPF group (p = 0.432). Receiver operating characteristic curves of the TSLP and IL-33 levels revealed clear differences between the IPF and NC groups (AUC = 0.655 and 0.706, respectively), as well as between the IPF and the other lung disease groups (AUC = 0.786 and 0.781, respectively). Cut-off values of 3.52 pg/μg TSLP and 3.77 pg/μg IL-33 were shown to differentiate between the IPF and NC groups with 99.2 and 94.3% accuracy. Cut-off values of 4.66 pg/μg TSLP and 2.52 pg/μg IL-33 possessed 99.4 and 93.2% accuracy for differentiating among the IPF and other interstitial lung disease groups.

CONCLUSIONS

Innate immune responses may be associated with the development of IPF. Furthermore, the IL-33 and TSLP levels in BAL fluids may be useful for differentiating IPF from other chronic interstitial lung diseases.

Distinct roles of short and long thymic stromal lymphopoietin isoforms in house dust mite-induced asthmatic airway epithelial barrier disruption

Loss of airway epithelial integrity contributes significantly to asthma pathogenesis. Thymic stromal lymphopoietin (TSLP) may have dual immunoregulatory roles. In inflammatory disorders of the bowel, the long isoform of TSLP (lfTSLP) promotes inflammation while the short isoform (sfTSLP) inhibits inflammation. We hypothesize that lfTSLP contributes to house dust mite (HDM)-induced airway epithelial barrier dysfunction and that synthetic sfTSLP can prevent these effects. In vitro, airway epithelial barrier function was assessed by monitoring transepithelial electrical resistance, fluorescent-dextran permeability, and distribution of E-cadherin and β-catenin. In vivo, BALB/c mice were exposed to HDM by nasal inhalation for 5 consecutive days per week to establish an asthma model. sfTSLP and 1α,25-Dihydroxyvitamin D3 (1,25D3) were administered 1 h before HDM exposure. After 8 weeks, animal lung function tests and pathological staining were performed to evaluate asthma progression. We found that HDM and lfTSLP impaired barrier function. Treatment with sfTSLP and 1,25D3 prevented HDM-induced airway epithelial barrier disruption. Moreover, sfTSLP and 1,25D3 treatment ameliorated HDM-induced asthma in mice. Our data emphasize the importance of the different expression patterns and biological properties of sfTSLP and lfTSLP. Moreover, our results indicate that sfTSLP and 1,25D3 may serve as novel therapeutic agents for individualized treatment of asthma.

Th2 Cells and Th17 Cells in the Development of Endometriosis – Possible Roles of Interleukin-4 and Interleukin-17A

Endometriosis is recognized as an inflammatory disease in which inflammatory cytokines, such as interleukin (IL)-1β and TNFα, play important roles. Immunological factors are also suggested to be involved in the pathogenesis of endometriosis. This review provides comprehensive knowledge about helper T cell (Th cell) and its specific cytokines in endometriosis. A series of our studies demonstrated the presence of Th2 cells and Th17 cells in endometriotic tissues and revealed multiple effects of IL-4 and IL-17A, cytokines secreted from respective Th cells. IL-1β induces secretion of thymic stromal lymphopoietin (TSLP), a regulator for differentiation of inflammatory Th2 cells, in endometriotic stromal cells (ESCs). IL-4 stimulates proliferation of ESCs and production of 3β-hydroxysteroid dehydrogenase Type 2, an enzyme in an estrogen production pathway, in ESCs. IL-17A stimulates IL-8 and Gro-α secretion from ESCs and proliferation of ESCs. IL-17A-induced Gro-α promotes neutrophil migration, which may contribute to the presence of neutrophils in endometriotic tissues. IL-17A also increases secretion of CCL20, a chemokine for Th17 cells, from ESCs, which seems to induce migration of Th17 cells to the endometriotic tissues and enhance the effects of IL-17A further. TNFα in combination with IL-17A synergistically enhances secretion of IL-8 and CCL-20, suggesting cooperation of inflammation and Th17 immune response. These findings suggest that IL-4 and IL-17A promote the development of endometriosis through induction of cell proliferation, inflammation, and estrogen production. It is thus also suggested that IL-4 and IL-17A would be a target of treatment of the disease.

A TSLP-complement axis mediates neutrophil killing of methicillin-resistant Staphylococcus aureus

Community-acquired Staphylococcus aureus infections often present as serious skin infections in otherwise healthy individuals and have become a worldwide epidemic problem fueled by the emergence of strains with antibiotic resistance, such as methicillin-resistant S. aureus (MRSA). The cytokine thymic stromal lymphopoietin (TSLP) is highly expressed in the skin and in other barrier surfaces and plays a deleterious role by promoting T helper cell type 2 (TH2) responses during allergic diseases; however, its role in host defense against bacterial infections has not been well elucidated. We describe a previously unrecognized non-TH2 role for TSLP in enhancing neutrophil killing of MRSA during an in vivo skin infection. Specifically, we demonstrate that TSLP acts directly on both mouse and human neutrophils to augment control of MRSA. Additionally, we show that TSLP also enhances killing of Streptococcus pyogenes, another clinically important cause of human skin infections. Unexpectedly, TSLP mechanistically mediates its antibacterial effect by directly engaging the complement C5 system to modulate production of reactive oxygen species by neutrophils. Thus, TSLP increases MRSA killing in a neutrophil- and complement-dependent manner, revealing a key connection between TSLP and the innate complement system, with potentially important therapeutic implications for control of MRSA infection.

Epithelial-Derived Cytokines in Asthma

The interaction between the airway epithelium and the inhaled environment is crucial to understanding the pathobiology of asthma. Several studies have identified an important role of airway epithelial-derived cytokines, IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) in asthma pathogenesis. These cytokines have been described as epithelial-derived alarmins that activate and potentiate the innate and humoral arms of the immune system in the presence of actual or perceived damage. Each of the three epithelial-derived alarmins has been implicated in the pathobiology of inhaled allergen-induced airway responses. The best evidence to date exists for TSLP, in that a human monoclonal antibody, which binds TSLP and prevents its engagement with its receptor, resolves airway inflammation in patients with allergic asthma and attenuates allergen-induced airway responses. Better understanding the roles that the epithelial-derived alarmins play and how they influence airway immune response may allow the development of novel therapeutics for asthma treatment.

Lipopolysaccharide Attenuates Induction of Proallergic Cytokines, Thymic Stromal Lymphopoietin, and Interleukin 33 in Respiratory Epithelial Cells Stimulated with PolyI:C and Human Parechovirus

Epidemiological studies based on the "hygiene hypothesis" declare that the level of childhood exposure to environmental microbial products is inversely related to the incidence of allergic diseases in later life. Multiple types of immune cell-mediated immune regulation networks support the hygiene hypothesis. Epithelial cells are the first line of response to microbial products in the environment and bridge the innate and adaptive immune systems; however, their role in the hygiene hypothesis is unknown. To demonstrate the hygiene hypothesis in airway epithelial cells, we examined the effect of lipopolysaccharide (LPS; toll-like receptor 4 ligand) on the expression of the proallergic cytokines thymic stromal lymphopoietin (TSLP) and interleukin 33 (IL33) in H292 cells (pulmonary mucoepidermoid carcinoma cells). Stimulation with the TLR ligand polyI:C and human parechovirus type 1 (HPeV1) but not LPS-induced TSLP and IL33 through interferon regulatory factor 3 (IRF3) and NF-κB activity, which was further validated by using inhibitors (dexamethasone and Bay 11-7082) and short hairpin RNA-mediated gene knockdown. Importantly, polyI:C and HPeV1-stimulated TSLP and IL33 induction was reduced by LPS treatment by attenuating TANK-binding kinase 1, IRF3, and NF-κB activation. Interestingly, the basal mRNA levels of TLR signaling proteins were downregulated with long-term LPS treatment of H292 cells, which suggests that such long-term exposure modulates the expression of innate immunity signaling molecules in airway epithelial cells to mitigate the allergic response. In contrast to the effects of LPS treatment, the alarmin high-mobility group protein B1 acts in synergy with polyI:C to promote TSLP and IL33 expression. Our data support part of the hygiene hypothesis in airway epithelia cells in vitro. In addition to therapeutic targeting of TSLP and IL33, local application of non-pathogenic LPS may be a rational strategy to prevent allergies.

TSLP receptor is not essential for house dust mite-induced allergic rhinitis in mice

TSLP induces Th2 cytokine production by Th2 cells and various other types of cells, thereby contributing to Th2-type immune responses and development of allergic disorders. We found that house dust mite (HDM) extract induced TSLP production by nasal epithelial cells, suggesting that TSLP may be involved in development of HDM-induced allergic rhinitis (AR). To investigate that possibility in greater detail, wild-type and TSLP receptor-deficient (TSLPR-/-) mice on the C57BL/6J background were repeatedly treated intranasally with HDM extract. The frequency of sneezing, numbers of eosinophils and goblet cells, thickness of submucosal layers, serum levels of total IgE and HDM-specific IgG1, and levels of IL-4, IL-5 and IL-13 in the culture supernatants of HDM-stimulated LN cells were comparable in the two mouse strains. Those findings indicate that, in mice, TSLPR is not crucial for development of HDM-induced AR.