Signal transduction by the atopy-associated human thymic stromal lymphopoietin (TSLP) receptor depends on Janus kinase function

The Role of the JAK-STAT Pathway in Childhood B-Cell Acute Lymphoblastic Leukemia

B-cell lymphoblastic leukemia is a hematologic neoplasm that poses a serious health concern in childhood. Genetic aberrations, such as mutations in the genes IL-7, IL7R, JAK1, JAK2, TLSP, CRLF2, and KTM2A or gene fusions involving BCR::ABL1, ETV6::RUNX1, and PAX5::JAK2, often correlate with the onset of this disease. These aberrations can lead to malfunction of the JAK-STAT signaling pathway, which is implicated in various important biological processes, including those related to immunology. Understanding the mechanisms underlying the malfunction of the JAK-STAT pathway holds potential for research on drugs targeting its components. Available drugs that interfere with the JAK-STAT pathway include fludarabine, ruxolitinib, and fedratinib.

Anti-chitinase-3-like 1 antibody attenuated atopic dermatitis-like skin inflammation through inhibition of STAT3-dependent CXCL8 expression

BACKGROUND AND PURPOSE

Chitinase-3-like 1 (CHI3L1) causes skin inflammation in the progression of atopic dermatitis. We investigated if anti-CHI3L1 antibody could prevent the development of atopic dermatitis and its mechanisms of action.

EXPERIMENTAL APPROACH

The effect of CHI3L1 antibody on phthalic anhydride-induced atopic dermatitis animal model and in vitro reconstructed human skin (RHS) model were investigated. Expression and release of atopic dermatitis-related cytokines were determined using an enzyme-linked immunosorbent assay, and RT-qPCR, STAT3 and CXCL8 signalling were measured by western blotting.

KEY RESULTS

Anti-CHI3L1 antibody suppressed phthalic anhydride-induced epidermal thickening, clinical score, IgE level and infiltration of inflammatory cells, and reduced phthalic anhydride-induced inflammatory cytokines concentration. In addition, CHI3L1 antibody treatment inhibited the expression of STAT3 activity in phthalic anhydride-treated skin. It was also confirmed that CHI3L1 antibody treatment alleviated atopic dermatitis-related inflammation in the RHS model. The inhibitory effects of CHI3L1 antibody was similar or more effective compared with that of the IL-4 antibody. We further found that CHI3L1 is associated with CXCL8 by protein-association network analysis. siRNA of CHI3L1 blocked the mRNA levels of CHI3L1, IL-1β, IL-4, CXCL8, TSLP, and the expression of CHI3L1 and p-STAT, and the level of CXCL8, whereas recombinant level of CXCL8 was elevated. Moreover, siRNA of STAT3 reduced the mRNA level of these cytokines. CHI3L1 and p-STAT3 expression correlated with the reduced CXCL8 level in the RHS in vitro model.

CONCLUSION AND IMPLICATIONS

Our data demonstrated that CHI3L1 antibody could be a promising effective therapeutic drug for atopic dermatitis.

Ruyong formula improves thymus function of CUMS-stimulated breast cancer mice

ETHNOPHARMACOLOGICAL RELEVANCE

Ruyong Formula (RYF) is a famous Chinese herbal formula composed of 10 traditional Chinese herbs. It has been used as a therapeutic agent for breast cancer patients with depressive symptoms in China. However, its underlying pharmacological mechanism remains unclear.

AIM OF THE STUDY

This study aimed to explore the mechanism of RYF on the changes of thymus immune function in breast cancer body under mood disorders such as depression/anxiety.

MATERIALS AND METHODS

The chronic unpredictable mild stress (CUMS) was used to stimulate 4T1 breast cancer mice. The behavioral changes, 5-hydroxytryptamine (5-HT) level in brain, cytokeratin 5 (CK5) and 8 (CK8) expression in thymus, the proportion of T cell subsets, the thymic output, phenotypic changes of thymus epithelial cells (TECs), the expression levels of immune-related factors and downstream proteins of TSLP were analyzed after RYF treatment.

RESULTS

In CUMS stimulated group, the level of 5-HT in brain was significantly increased after RYF treatment. The output function of the thymus was improved, and the number of TECs in the medulla (CK5+), the proportion of CD3+CD4-CD8- (Double negative) and CD3+CD4+CD8+ (Double positive) T cells were all increased. The mRNA level of TSLP in mouse thymus was significantly decreased, but increased for IL-7. The protein levels of TSLP and Vimentin were decreased, but increased for p-STAT3, p-JAK2, E-cadherin, and p-PI3K p55 in vivo. In vitro study was showed the levels of Snail 1, Zeb 1 and Smad increased significantly in TGF-β1 group, and RYF could reverse their expression.

CONCLUSIONS

RYF could restore the structure and function of the thymus in depressed breast cancer mice by reversing the phenotypic changes of TECs and activating the JAK2/STAT3/PI3K pathway.

An antibody fragment-decorated liposomal conjugate targets Philadelphia-like acute lymphoblastic leukemia

Philadelphia-like acute lymphoblastic leukemia (Ph-like ALL) is an aggressive B-ALL malignancy associated with high rates of relapse and inferior survival rate. While targeted treatments against the cell surface proteins CD22 or CD19 have been transformative in the treatment of refractory B-ALL, patients may relapse due to antigen loss, necessitating targeting alternative antigens. Cytokine receptor-like factor 2 (CRLF2) is overexpressed in half of Ph-like ALL cases conferring chemoresistance and enhancement of leukemia cell survival. Therefore, targeting CRLF2 may reduce the likelihood of relapse associated with antigen loss. We developed a CRLF2-targeting single-chain variable fragment modified by the fragment crystallizable region (CRLF2 scFv-Fc) conjugated to a drug maytansinoid 1 (DM1)-DOPC liposomal conjugate, creating homogeneous CRLF2-targeted liposomes (CRLF2-DM1 LIP). Cellular association and internalization studies in a Ph-like ALL cell line, MHH-CALL-4, compared to its lentivirally transduced CRLF2-knockdown counterpart (KD-CALL-4) revealed excellent CRLF2-targeting efficiency of CRLF2-DM1 LIP. Moreover, CRLF2-DM1 LIP showed selective association and internalization ex vivo using Ph-like ALL patient-derived xenograft (PDX) cells with minimal reactivity with non-target cells. Cell apoptosis assays demonstrated the CRLF2-dependent potency of CRLF2-DM1 LIP in Ph-like ALL cell lines. This study is the first to highlight the therapeutic potential of a CRLF2-directed scFv-Fc-liposomal conjugate for targeting Ph-like ALL.

The role of Janus kinase signaling in the pathology of atopic dermatitis

Atopic dermatitis (AD) is a heterogeneous, chronic, relapsing, inflammatory skin disease associated with considerable physical, psychological, and economic burden. The pathology of AD includes complex interactions involving abnormalities in immune and skin barrier genes, skin barrier disruption, immune dysregulation, microbiome disturbance, and other environmental factors. Many of the cytokines involved in AD pathology, including IL-4, IL-13, IL-22, IL-31, thymic stromal lymphopoietin, and IFN-γ, signal through the Janus kinase (JAK)-signal transducer and activation of transcription (STAT) pathway. The JAK family includes JAK1, JAK2, JAK3, and tyrosine kinase 2; the STAT family includes STAT1, STAT2, STAT3, STAT4, STAT5A/B, and STAT6. Activation of the JAK-STAT pathway has been implicated in the pathology of several immune-mediated inflammatory diseases, including AD. However, the exact mechanisms of JAK-STAT involvement in AD have not been fully characterized. This review aims to discuss current knowledge about the role of the JAK-STAT signaling pathway and, specifically, the role of JAK1 in the pathology and symptomology of AD.

The Use of JAK/STAT Inhibitors in Chronic Inflammatory Disorders

The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway plays a critical role in orchestrating immune and inflammatory responses, and it is essential for a wide range of cellular processes, including differentiation, cell growth, and apoptosis. Over the years, this pathway has been heavily investigated due to its key role in the pathogeneses of several chronic inflammatory conditions, e.g., psoriasis, atopic dermatitis (AD), and inflammatory bowel diseases (IBDs). Nevertheless, the impact of this pathway on the pathogenesis of inflammatory conditions remains unclear. This review describes the role of the JAK/STAT signaling pathway in the pathogenesis of inflammatory diseases such as psoriasis (Pso), psoriatic arthritis (PsA), AD, and IBD with a focus on ulcerative colitis (UC) and briefly resumes the use of JAK inhibitors in their clinical management.

TSLP as a Potential Therapy in the Treatment of CRLF2 B Cell Acute Lymphoblastic Leukemia

Cytokine receptor-like factor 2 B-cell acute lymphoblastic leukemia (CRLF2 B-ALL) is a high-risk subtype characterized by CRLF2 overexpression with poor survival rates in children and adults. CRLF2 and interleukin-7 receptor alpha (IL-7Rα) form a receptor for the cytokine thymic stromal lymphopoietin (TSLP), which induces JAK/STAT and PI3K/AKT/mTOR pathway signals. Previous studies from our group showed that low TSLP doses increased STAT5, AKT, and S6 phosphorylation and contributed to CRLF2 B-ALL cell survival. Here we investigated the role of TSLP in the survival and proliferation of CRLF2 B-ALL cells in vitro and in vivo. We hypothesized that high doses of TSLP increase CRLF2 signals and contribute to increased proliferation of CRLF2 B-ALL cells in vitro and in vivo. Interestingly, we observed the opposite effect. Specifically, high doses of TSLP induced apoptosis in human CRLF2 B-ALL cell lines in vitro, prevented engraftment of CRLF2 B-ALL cells, and prolonged the survival of +TSLP patient-derived-xenograft mice. Mechanistically, we showed that high doses of TSLP induced loss of its receptor and loss of CRLF2 signals in vitro. These results suggest that high doses of TSLP could be further investigated as a potential therapy for the treatment of CRLF2 B-ALL.

Infant consumption of microRNA miR-375 in human milk lipids is associated with protection from atopy

BACKGROUND

Human milk is thought to reduce infant atopy risk. The biologic mechanism for this protective effect is not fully understood.

OBJECTIVES

We tested the hypothesis that infant consumption of 4 microRNAs (miR-146b-5p, miR-148b-3p, miR-21-5p, and miR-375-3p) in human milk would be associated with reduced atopy risk.

METHODS

The Breast Milk Influence of the Microtranscriptome Profile on Atopy in Children over Time (IMPACT) study involved a cohort of mother-infant dyads who planned to breastfeed beyond 4 mo. Infant consumption of the 4 human milk microRNAs (miRNAs) in the first 6 mo was calculated as the product of milk miRNA concentration and the number of human milk feeds, across 3 lactation stages: early milk (0-4 wk), transitional milk (4-16 wk), and mature milk (16-24 wk). The primary outcome was infant atopy in the first year, defined as atopic dermatitis (AD), food allergies, or wheezing. The final analysis included 432 human milk samples and 7824 wk of longitudinal health data from 163 dyads.

RESULTS

Seventy-three infants developed atopy. Forty-one were diagnosed with AD (25%), 33 developed food allergy (20%), and 10 had wheezing (6%). Eleven developed >1 condition (7%). Infants who did not develop atopy consumed higher concentrations of miR-375-3p (d = 0.18, P = 0.022, adj P = 0.044) and miR-148b-3p (d = 0.23, P = 0.007, adj P = 0.028). The consumption of miR-375-3p (X2 = 5.7, P = 0.017, OR: 0.92, 95% CI: 0.86, 0.99) was associated with reduced atopy risk. Concentrations of miR-375-3p increased throughout lactation (r = 0.46, F = 132.3, P = 8.4 × 10-34) and were inversely associated with maternal body mass (r = -0.11, t = -2.1, P = 0.032).

CONCLUSIONS

This study provides evidence that infant consumption of miR-375-3p may reduce atopy risk.

Nonylphenol exacerbates ovalbumin-induced allergic rhinitis via the TSLP-TSLPR/IL-7R pathway and JAK1/2-STAT3 signaling in a mouse model

Nonylphenol (NP) can be widely used as a plasticizer, surfactant, antioxidant, textile printing, dyeing additive, and pesticide emulsifier. Animal studies have shown that NP aggravates ovalbumin (OVA)-induced allergic rhinitis (AR); however, the exact mechanism underlying its action has not yet been detailed. This study aimed to explore the aggravation of the AR inflammatory response following NP exposure and its possible mechanism. The AR mouse model was constructed using OVA. Under NP exposure, allergic nasal symptoms were observed, eosinophil infiltration was assessed by Sirius red staining, and the levels of IL-4, IL-5, and IL-13 in nasal mucosa samples were detected using cytometric bead array. The mRNA levels of OX40/OX40L and GATA3 in nasal mucosa were detected by qPCR, and the expression levels of the TSLP and JAK1/2-STAT3 signaling pathway components were also identified. Our results suggest that NP exposure exacerbated allergic nasal symptoms and that eosinophils accumulated in nasal mucosa after OVA challenge. The levels of the typical T helper 2 cytokines, as well as the mRNA levels of OX40/OX40L and GATA3, were elevated in the nasal mucosa of OVA-challenged mice exposed to NP. In addition, NP exposure elevated the TSLP, TSLPR, IL-7R, p-JAK1, p-JAK2, and p-STAT3 levels in the nasal mucosa after OVA stimulation. Overall, the present study suggests NP can exacerbate OVA-induced AR inflammatory responses; furthermore, this aggravating effect of NP may be related to the TSLP-TSLPR/IL-7R and JAK1/2-STAT3 signaling pathways.

Investigational approaches for unmet need in severe asthma

INTRODUCTION

Molecular antibodies (mAb) targeting inflammatory mediators are effective in T2-high asthma. The recent approval of Tezepelumab presents a novel mAb therapeutic option to those with T2-low asthma.

AREAS COVERED

We discuss a number of clinical problems pertinent to severe asthma which are less responsive to current therapies, such as persistent airflow obstruction and airway hyperresponsiveness. We discuss selected investigational approaches, including a number of candidate therapies under investigation in two adaptive platform trials currently in progress, with particular reference to this unmet need, as well as their potential in phenotypes such as neutrophilic asthma and obese asthma, which may or may not overlap with a T2-high phenotype.

EXPERT OPINION

The application of discrete targeting approaches to T2-low molecular phenotypes, including those phenotypes in which inflammation may not arise within the airway, has yielded variable results to date. Endotypes associated with T2-low asthma are likely to be diverse but await validation. Investigational therapeutic approaches must, likewise, be diverse if the goal of remission is to become attainable for all those living with asthma.

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

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

The Role of Airway Epithelial Cell Alarmins in Asthma

The airway epithelium is the first line of defense for the lungs, detecting inhaled environmental threats through pattern recognition receptors expressed transmembrane or intracellularly. Activation of pattern recognition receptors triggers the release of alarmin cytokines IL-25, IL-33, and TSLP. These alarmins are important mediators of inflammation, with receptors widely expressed in structural cells as well as innate and adaptive immune cells. Many of the key effector cells in the allergic cascade also produce alarmins, thereby contributing to the airways disease by driving downstream type 2 inflammatory processes. Randomized controlled clinical trials have demonstrated benefit when blockade of TSLP and IL-33 were added to standard of care medications, suggesting these are important new targets for treatment of asthma. With genome-wide association studies demonstrating associations between single-nucleotide polymorphisms of the TSLP and IL-33 gene and risk of asthma, it will be important to understand which subsets of asthma patients will benefit most from anti-alarmin therapy.

A recombinant antibody fragment directed to the thymic stromal lymphopoietin receptor (CRLF2) efficiently targets pediatric Philadelphia chromosome-like acute lymphoblastic leukemia

Antibody fragments are promising building blocks for developing targeted therapeutics, thus improving treatment efficacy while minimising off-target toxicity. Despite recent advances in targeted therapeutics, patients with Philadelphia-like acute lymphoblastic leukemia (Ph-like ALL), a high-risk malignancy, lack specific and effective targeted treatments. Cytokine receptor-like factor 2 (CRLF2) is overexpressed in 50% of Ph-like ALL cases, conferring the survival of leukemia blasts through activation of the JAK/STAT signalling pathway. Targeting such a vital cell-surface protein could result in potent anti-leukaemic efficacy and reduce the likelihood of relapse associated with antigen loss. Herein, we developed a novel single-chain variable fragment (scFv) against CRLF2 based on a monoclonal antibody raised against the recombinant extracellular domain of human TSLPRα chain. The scFv fragment demonstrated excellent binding affinity with CRLF2 protein in the nanomolar range. Cellular association studies in vitro using an inducible CRLF2 knockdown cell line and ex vivo using patient-derived xenografts revealed the selective association of the scFv with CRLF2. The fragment exhibited significant receptor antagonistic effects on STAT5 signalling, suggesting possible therapeutic implications in vivo. This study is the first to describe the potential use of a novel scFv for targeting Ph-like ALL.

Functional characterisation of two receptor interaction determinants in human thymic stromal lymphopoietin

Thymic stromal lymphopoietin (TSLP) is a pro-inflammatory cytokine with important pathological roles in Asthma bronchiale, malignant tumours and other diseases. The heterodimeric human TSLP receptor (hTSLPR) consists of the TSLP-binding subunit (TSLPRα) and the IL-7Rα-subunit. We studied the properties of hTSLP variants with mutations in their bipartite interaction interface towards IL-7Rα. One mutant (T46D/K101D) showed only mild impairment in receptor affinity but a massive reduction in biological activity. To facilitate the future development of hTSLP mutants with drug properties, we have devised a eukaryontic cytokine display assay with activity read-out and intrinsic genotype-phenotype coupling.

STAT3 maintains skin barrier integrity by modulating SPINK5 and KLK5 expression in keratinocytes

Skin barrier dysfunction induces skin inflammation. Signal transducer and activator of transcription 3 (STAT3) is known to be involved in Th17-mediated immune responses and barrier integrity in the cornea and intestine; however, its role in the skin barrier remains largely unknown. In this study, we elucidated the potential role of STAT3 in the skin barrier and its effect on kallikrein-related peptidase 5 (KLK5) and serine protease inhibitor Kazal-type 5 (SPINK5) expression using a mouse model with keratinocyte-specific ablation of STAT3. Keratinocyte-specific loss of STAT3 induced a cutaneous inflammatory phenotype with pruritus and intense scratching behaviour in mice. Transcriptomic analysis revealed that the genes associated with impaired skin barrier function, including KLK5, were upregulated. The effect of STAT3 on KLK5 expression in keratinocytes was not only substantiated by the increase in KLK5 expression following treatment with STAT3 siRNA but also by its decreased expression following STAT3 overexpression. Overexpression and IL-17A-mediated stimulation of STAT3 increased the expression of SPINK5, which was blocked by STAT3 siRNA. These results suggest that the expression of SPINK5 and KLK5 in keratinocytes could be dependent on STAT3 and that STAT3 might play an essential role in the maintenance of skin barrier homeostasis.

Skullcapflavone II Suppresses TNF-α/IFN-γ-Induced TARC, MDC, and CTSS Production in HaCaT Cells

Skullcapflavone II (SFII), a flavonoid derived from Scutellaria baicalensis, has been reported to have anti-inflammatory properties. However, its therapeutic potential for skin inflammatory diseases and its mechanism are unknown. Therefore, this study aimed to investigate the effect of SFII on TNF-α/IFN-γ-induced atopic dermatitis (AD)-associated cytokines, such as thymus- and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC). Co-stimulation with TNF-α/IFN-γ in HaCaT cells is a well-established model for induction of pro-inflammatory cytokines. We treated cells with SFII prior to TNF-α/IFN-γ-stimulation and confirmed that it significantly inhibited TARC and MDC expression at the mRNA and protein levels. Additionally, SFII also inhibited the expression of cathepsin S (CTSS), which is associated with itching in patients with AD. Using specific inhibitors, we demonstrated that STAT1, NF-κB, and p38 MAPK mediate TNF-α/IFN-γ-induced TARC and MDC, as well as CTSS expression. Finally, we confirmed that SFII significantly suppressed TNF-α/IFN-γ-induced phosphorylation of STAT1, NF-κB, and p38 MAPK. Taken together, our study indicates that SFII inhibits TNF-α/IFN-γ-induced TARC, MDC, and CTSS expression by regulating STAT1, NF-κB, and p38 MAPK signaling pathways.

Genetic Alterations and Therapeutic Targeting of Philadelphia-Like Acute Lymphoblastic Leukemia

Philadelphia-like (Ph-like) acute lymphoblastic leukemia (ALL) is a subgroup of B-cell precursor ALL which by gene expression analysis clusters with Philadelphia-positive ALL although lacking the pathognomonic BCR-ABL1 oncoprotein. Its prevalence increases with age and similar to BCR-ABL1-positive ALL, Ph-like ALL is characterized by IKZF1 or other B-lymphoid transcription factor gene deletions and by poor outcome to conventional therapeutic approaches. Genetic alterations are highly heterogenous across patients and include gene fusions, sequence mutations, DNA copy number changes and cryptic rearrangements. These lesions drive constitutively active cytokine receptor and kinase signaling pathways which deregulate ABL1 or JAK signaling and more rarely other kinase-driven pathways. The presence of activated kinase alterations and cytokine receptors has led to the incorporation of targeted therapy to the chemotherapy backbone which has improved treatment outcome for this high-risk subtype. More recently, retrospective studies have shown the efficacy of immunotherapies including both antibody drug-conjugates and chimeric antigen receptor T cell therapy and as they are not dependent on a specific genetic alteration, it is likely their use will increase in prospective clinical trials. This review summarizes the genomic landscape, clinical features, diagnostic assays, and novel therapeutic approaches for patients with Ph-like ALL.

Dibutyl phthalate induces allergic airway inflammation in rats via inhibition of the Nrf2/TSLP/JAK1 pathway

Dibutyl phthalate (DBP), an important plastic contaminant in the environment, is known to cause organ toxicity. Although current research has shown that DBP-induced organ toxicity is associated with oxidative stress, the toxic effect of DBP on the lungs have not been fully elucidated. Therefore, we investigated the potential mechanism by which DBP induces pulmonary toxicity using a model of DBP-induced allergic airway inflammation in rats. The results showed that chronic exposure to DBP induced histopathological damage, inflammation, oxidative stress, apoptosis, and increased the protein levels of thymic stromal lymphopoietin (TSLP) and its downstream protein Janus kinase 1 (JAK1) and signal transducer and activator of transcription 6 (STAT6). Moreover, DBP exposure inhibited nuclear factor-erythroid-2-related factor 2 (Nrf2) and levels of its target genes NAD(P)H quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1). Additionally, using in vitro experiments, we found that DBP induced oxidative stress, reduced cell viability, and inhibited the Nrf2/HO-1/NQO1 pathway in mouse alveolar type II epithelial cell line. Overall, these data demonstrate that DBP induces allergic airway inflammation in rats via inhibition of the Nrf2/TSLP/JAK1 pathway.

Modulation of Signaling Mediated by TSLP and IL-7 in Inflammation, Autoimmune Diseases, and Cancer

Thymic Stromal Lymphopoietin (TSLP) and Interleukin-7 (IL-7) are widely studied cytokines within distinct branches of immunology. On one hand, TSLP is crucially important for mediating type 2 immunity at barrier surfaces and has been linked to widespread allergic and inflammatory diseases of the airways, skin, and gut. On the other hand, IL-7 operates at the foundations of T-cell and innate lymphoid cell (ILC) development and homeostasis and has been associated with cancer. Yet, TSLP and IL-7 are united by key commonalities in their structure and the structural basis of the receptor assemblies they mediate to initiate cellular signaling, in particular their cross-utilization of IL-7Rα. As therapeutic targeting of TSLP and IL-7 via diverse approaches is reaching advanced stages and in light of the plethora of mechanistic and structural data on receptor signaling mediated by the two cytokines, the time is ripe to provide integrated views of such knowledge. Here, we first discuss the major pathophysiological roles of TSLP and IL-7 in autoimmune diseases, inflammation and cancer. Subsequently, we curate structural and mechanistic knowledge about receptor assemblies mediated by the two cytokines. Finally, we review therapeutic avenues targeting TSLP and IL-7 signaling. We envision that such integrated view of the mechanism, structure, and modulation of signaling assemblies mediated by TSLP and IL-7 will enhance and fine-tune the development of more effective and selective approaches to further interrogate the role of TSLP and IL-7 in physiology and disease.

Advances in Understanding the Initial Steps of Pruritoceptive Itch: How the Itch Hits the Switch

Pruritoceptive (dermal) itch was long considered an accompanying symptom of diseases, a side effect of drug applications, or a temporary sensation induced by invading pruritogens, as produced by the stinging nettle. Due to extensive research in recent years, it was possible to provide detailed insights into the mechanism of itch mediation and modulation. Hence, it became apparent that pruritus is a complex symptom or disease in itself, which requires particular attention to improve patients’ health. Here, we summarize recent findings in pruritoceptive itch, including how this sensation is triggered and modulated by diverse endogenous and exogenous pruritogens and their receptors. A differentiation between mediating pruritogen and modulating pruritogen seems to be of great advantage to understand and decipher the molecular mechanism of itch perception. Only a comprehensive view on itch sensation will provide a solid basis for targeting this long-neglected adverse sensation accompanying numerous diseases and many drug side effects. Finally, we identify critical aspects of itch perception that require future investigation.

Overexpression of miR-142-5p inhibits the progression of nonalcoholic steatohepatitis by targeting TSLP and inhibiting JAK-STAT signaling pathway

This study aimed to figure out the underlying mechanism of miR-142-5p in the non-alcoholic steatohepatitis (NASH). Bioinformatics, luciferase assay and Western blot were performed. The NASH mouse model was established through feeding a high fat diet (HFD). Relative expressions of miR-142-5p, thymic stromal lymphopoietin (TSLP), inflammatory factors were detected by qRT-PCR. The injury level of liver was assessed via measurement of serum alanine aminotransferase (ALT) and serum aspartate aminotransferase (AST). H&E staining and Masson's trichrome staining examine the liver fatty degeneration and fibrosis. MiR-142-5p and TSLP were differentially expressed and JAK-STAT signaling pathway was activated in the NASH group. Luciferase assay identified that TSLP was the downstream target of miR-142-5p. Through overexpression of miR-142-5p, ALT and AST in serum were inhibited, pro-inflammatory factors, liver fatty degeneration and fibrosis in liver tissues were decreased, while anti-inflammatory factors were increased. Overexpression of TSLP and JAK-STAT signaling pathway activation could reverse the effects of miR-142-5p on NASH. Taken together, overexpression of miR-142-5p could attenuate NASH progression via inhibiting TSLP and JAK-STAT pathway. MiR-142-5p might be a novel latent target for NASH therapy.

The Current Genomic and Molecular Landscape of Philadelphia-like Acute Lymphoblastic Leukemia

Philadelphia (Ph)-like acute lymphoblastic leukemia (ALL) is a high-risk B-cell Acute Lymphoblastic Leukemia (B-ALL) characterized by a gene expression profile similar to Ph-positive B-ALL but lacking the BCR-ABL1 translocation. The molecular pathogenesis of Ph-like B-ALL is heterogenous and involves aberrant genomics, receptor overexpression, kinase fusions, and mutations leading to kinase signaling activation, leukemogenic cellular proliferation, and differentiation blockade. Testing for the Ph-like signature, once only a research technique, is now available to the clinical oncologist. The plethora of data pointing to poor outcomes for this ALL subset has triggered investigations into the role of targeted therapies, predominantly involving tyrosine kinase inhibitors that are showing promising results.

The Potential Inhibitory Effects of miR-19b on Ocular Inflammation are Mediated Upstream of the JAK/STAT Pathway in a Murine Model of Allergic Conjunctivitis

Purpose

Thymic stromal lymphopoietin (TSLP) is a pro-allergic cytokine that initiates allergic inflammatory reaction between epithelial and dendritic cells (DCs). miR-19b was reported to suppress TSLP expression. The present study aimed to examine miR-19b expression, regulation, and function in allergic conjunctivitis (AC).

Methods

A murine model of experimental AC was induced in BALB/c mice by short ragweed pollen. The serum, eye balls, conjunctiva, and cervical lymph nodes (CLN) were used for the study. Gene expression was determined by RT-PCR, whereas protein production and activation were evaluated by immunostaining, ELISA, and Western blotting.

Results

In the murine AC model, miR-19b was aberrantly downregulated, whereas the levels of TSLP and p-STAT3, as well as the number of CD11c+ pSTAT3+ DCs were increased. Moreover, Th2 inflammatory cytokine expression was significantly increased. These severe phenotypes could be counteracted by either applying exogenous miR-19b mimic microRNAs or the JAK/STAT inhibitor CYT387. Moreover, overexpression of miR-19b repressed p-STAT3 expression and the number of CD11c+ cells in AC eye and CLN tissues.

Conclusions

These findings suggested that miR-19b reduced ocular surface inflammation by inhibiting Stat3 signaling via TSLP downregulation in a murine AC model. Moreover, the present study further demonstrated the clinical potential of applying miR-19b and anti-JAK/STAT therapies in the treatment of AC.

Molecular and Cellular Responses to the TYK2/JAK1 Inhibitor PF-06700841 Reveal Reduction of Skin Inflammation in Plaque Psoriasis

The IL-23/T helper type 17 cell axis is a target for psoriasis. The TYK2/Janus kinase 1 inhibitor PF-06700841 will directly suppress TYK2-dependent IL-12 and IL-23 signaling and Janus kinase 1-dependent signaling in cells expressing these signaling molecules, including T cells and keratinocytes. This clinical study sought to define the inflammatory gene and cellular pathways through which PF-06700841 improves the clinical manifestations of psoriasis. Patients (n = 30) with moderate-to-severe psoriasis were randomized to once-daily 30 mg (n = 14) or 100 mg (n = 7) PF-06700841 or placebo (n = 9) for 28 days. Biopsies were taken from nonlesional and lesional skin at baseline and weeks 2 and 4. Changes in the psoriasis transcriptome and genes induced by IL-17 in keratinocytes were evaluated with microarray profiling and reverse transcriptase-PCR. Reductions in IL-17A, IL-17F, and IL-12B mRNA were observed as early as 2 weeks and approximately 70% normalization of lesional gene expression after 4 weeks. Immunohistochemistry showed significant decreases in markers of keratinocyte activation, epidermal thickness, KRT16 and Ki-67 expression, and immune cell infiltrates CD3⁺/CD8⁺ (T cells) and CD11c (dendritic cells) after 2 weeks of treatment, corresponding with improvement in histologic score. PF-06700841 improves clinical symptoms of chronic plaque psoriasis by inhibition of proinflammatory cytokines that require TYK2 and Janus kinase 1 for signal transduction.

Tyrosine Kinases in Autoimmune and Inflammatory Skin Diseases

Tyrosine kinases relay signals from diverse leukocyte antigen receptors, innate immune receptors, and cytokine receptors, and therefore mediate the recruitment and activation of various leukocyte populations. Non-receptor tyrosine kinases of the Jak, Src, Syk, and Btk families play major roles in various immune-mediated disorders, and small-molecule tyrosine kinase inhibitors are emerging novel therapeutics in a number of those diseases. Autoimmune and inflammatory skin diseases represent a broad spectrum of immune-mediated diseases. Genetic and pharmacological studies in humans and mice support the role of tyrosine kinases in several inflammatory skin diseases. Atopic dermatitis and psoriasis are characterized by an inflammatory microenvironment which activates cytokine receptors coupled to the Jak-Stat signaling pathway. Jak kinases are also implicated in alopecia areata and vitiligo, skin disorders mediated by cytotoxic T lymphocytes. Genetic studies indicate a critical role for Src-family kinases and Syk in animal models of autoantibody-mediated blistering skin diseases. Here, we review the various tyrosine kinase signaling pathways and their role in various autoimmune and inflammatory skin diseases. Special emphasis will be placed on identification of potential therapeutic targets, as well as on ongoing preclinical and clinical studies for the treatment of inflammatory skin diseases by small-molecule tyrosine kinase inhibitors.

Topical Application of JAK1/JAK2 Inhibitor Momelotinib Exhibits Significant Anti-Inflammatory Responses in DNCB-Induced Atopic Dermatitis Model Mice

Atopic dermatitis (AD) is a chronic recurrent skin disease dominated by T-helper 2 inflammation. Momelotinib (MMB) is a novel JAK1/JAK2 inhibitor suppressing the signal transduction of multiple pro-inflammatory cytokines. Recent studies indicated that JAK inhibitor could play a therapeutic role in AD disease. In this study, we evaluated the efficacy of MMB as a novel JAK1/JAK2 inhibitor in DNCB-induced AD mice and TSLP-activated dendritic cells. Our data showed that topical application of MMB reduced the skin severity scores and total serum IgE levels, and alleviated the histological indexes including epidermal thickness measurement and mast cell number. Also, it was demonstrated that MMB down-regulated the mRNA expression of IL-4, IL-5, IFN-γ and TSLP, and inhibited the phosphorylation of STAT1, STAT3 and STAT5 in skin lesions. Moreover, MMB reduced the expression of CD80, CD86, MHCII and mRNA of OX40L in TSLP-activated dendritic cells. In general, our study suggests that MMB can improve the symptoms of AD and topical application of MMB can become a promising new therapy strategy for AD.

Biologic and small-molecule medications in the management of pyoderma gangrenosum

Pyoderma gangrenosum (PG) is an uncommon inflammatory skin disorder characterized by neutrophil dysfunction. There are currently no FDA-approved drugs for the treatment of this disease, and treatment has typically relied on traditional immunosuppressive medications such as prednisone or cyclosporine. The efficacy of biologics in the treatment of other pro-inflammatory conditions such as psoriasis, rheumatoid arthritis, and inflammatory bowel disease is well-documented in the literature. Therefore, the use of biologic medications for the treatment of rarer inflammatory skin conditions, such as PG, is a compelling topic for investigation. Biologic and small-molecule therapies allow physicians to target specific pro-inflammatory mediators that underlie PG pathogenesis. This review provides an update on the use of biologic and small-molecule medications for the treatment of PG and summarizes the latest data on the clinical efficacy and pharmacology of these treatments.

A versatile platform for activity determination of cytokines and growth factors based on the human TSLP (thymic stromal lymphopoietin) receptor

Cytokines and growth factors are signaling proteins involved in communication processes between cells. They are involved in the control of numerous essential physiological processes such as cell proliferation, gene transcription and differentiation; therefore being in the focus of basic and applied research. Many of them are also of relevance for human diseases. When observed as potential targets for pharmacological intervention and objects of structure/function studies, it is important to measure their biological activities, optionally along with potential inhibitors, in a convenient and rational manner. Such tests are frequently laborious to set up and their establishment is complicated by the necessity to employ problematic cell types and sophisticated assays. Here we present a robust and modular activity assay system which can be adapted to virtually all ligands that signal through dimerization of membrane receptors from different families. The technique rests on fusing ligand-binding domains of specific receptors to the transmembrane and intracellular components of the thymic stromal lymphopoietin (TSLP) receptor which translates signals into readily quantifiable luciferase expression in reporter cells. We show that the activation of various hematopoietic cytokine receptors, of receptor tyrosine kinases as well as of receptors bearing serine/threonine kinase domains by their respective ligands was faithfully reflected both upon transient and stable introduction of hybrid receptor and reporter gene constructs into the murine pro-B cell line Ba/F3. Moreover, we demonstrate the suitability of this platform for the functional characterization of cytokine/growth factor receptor inhibitors.

IL-17A+GM-CSF+ Neutrophils Are the Major Infiltrating Cells in Interstitial Lung Disease in an Autoimmune Arthritis Model

Objective

To gain a better understanding of the pathogenesis of autoimmune arthritis-associated interstitial lung disease (ILD), we sought to identify the characteristics of lung-infiltrating cells in SKG mice with ILD.

Methods

We injected curdlan in SKG mice at 8 weeks of age, and identified the presence of ILD by PET-MRI at 20 weeks post-injection and histological analysis at 22 weeks post-injection. Lung-infiltrating cells were examined by flow cytometry. Analysis of serum cytokines by the Luminex multiplex cytokine assay was performed at 14 and 22 weeks post-injection, and cytokine profiles before and after the development of ILD were compared. Opal multiplexed immunofluorescent staining of lung tissue was also performed.

Results

At 20 weeks post-injection, curdlan-treated SKG mice developed not only arthritis but also lung inflammation combined with fibrosis, which was identified by PET-MRI and histological analysis. The majority of inflammatory cells that accumulated in the lungs of curdlan-treated SKG mice were CD11b⁺Gr1⁺ neutrophils, which co-express IL-17A and GM-CSF, rather than TNF-α. Compared with 14 weeks post-injection, serum levels of GM-CSF, MCP1, IL-17A, IL-23, TSLP, and soluble IL-7Rα had increased at 22 weeks post-injection, whereas those of IFN-γ, IL-22, IL-6, and TNF-α remained unchanged. Furthermore, IL-23, CXCL5, IL-17A, and GM-CSF, but not TNF-α, were observed in immunofluorescent-stained lung tissue.

Conclusion

We found that IL-17A⁺GM-CSF⁺ neutrophils represented the major inflammatory cells in the lungs of curdlan-treated SKG mice. In addition, GM-CSF and IL-17A appear to play a more important role than TNF-α in ILD development.

Hypoxia and Local Inflammation in Pulmonary Artery Structure and Function

Hypoxia is recognized as a contributor to pulmonary vascular diseases such as pulmonary hypertension. Hypoxia-induced inflammatory changes can enhance structural and functional changes in pulmonary artery (PA) in the context of PH. Accordingly, understanding how hypoxia and inflammation are linked in the context of pulmonary artery structure and function could be relevant towards development of novel therapies for PH. In this regard, factors such as thymic stromal lymphopoietin (TSLP), an inflammatory cytokine, and brain-derived neurotrophic factor (BDNF), a neurotrophin, have been found critical for nonvascular systems such as airway and asthma. While TSLP canonically affects the immune system, in nonvascular systems, noncanonical effects such as altered [Ca²⁺]_i and cell proliferation have been noted: aspects also relevant to the PA, where there is currently little to no data. Similarly, better known in the nervous system, there is increasing evidence that BDNF is locally produced by structural cells of the airway and can contribute to asthma pathophysiology. In this chapter, we summarize the potential relevance of factors such as TSLP and BDNF to the PA and in the context of hypoxia influences towards development of PH. We focus on cell sources and targets such as PA endothelial cells (PAECs) and smooth muscle cells (PASMCs), and the effects of TSLP or BDNF on intracellular Ca²⁺ responses to vasoconstrictor agonist, cell proliferation, and potential signaling cascades involved.

Short Thymic Stromal Lymphopoietin Attenuates Toluene Diisocyanate-induced Airway Inflammation and Inhibits High Mobility Group Box 1-Receptor for Advanced Glycation End Products and Long Thymic Stromal Lymphopoietin Expression

Short thymic stromal lymphopoietin (short TSLP), one of TSLP variants, exerts anti-inflammatory activities in endotoxin shock and colitis mouse models. Our latest work reported that short TSLP prevented house dust mite-induced epithelial barrier disruption. Yet the role of short TSLP in toluene diisocyanate (TDI)-induced asthma is unknown. Male BALB/c mice were sensitized and challenged with TDI to generate a chemical-induced asthma model. Synthetic short TSLP peptides were given intranasally or intraperitoneally before each challenge. TDI significantly increased inflammation and hyperresponsiveness of airway, which were suppressed by short TSLP treatment. Levels of mouse TSLP, high mobility group box 1 (HMGB1), and receptor for advanced glycation end products (RAGE) in airway epithelium and whole lung tissues were markedly increased in TDI group compared with control mice, which were decreased after administration of short TSLP. Meanwhile, short TSLP also inhibited STAT5(Y694) phosphorylation, which was highly expressed in airways of TDI-exposure mice. In vitro, both TDI-human serum albumin (HSA) and recombinant human (rh) HMGB1 promoted long TSLP but not short TSLP gene production in human bronchial epithelial cells (16HBE). Cells pre-treated with short TSLP exhibited less expression of RAGE and long TSLP and lower phosphorylation of Akt(S473), p38 MAPK(T180/Y182), and STAT5(Y694) than stimulated with TDI-HSA or rhHMGB1 alone. Results suggest that short TSLP prevents airway inflammation in a chemical-induced asthma model, which might be associated with the inhibitions of HMGB1-RAGE and long TSLP expression and STAT5(Y694) phosphorylation.

Role of Transcription Factors in Pulmonary Artery Smooth Muscle Cells: An Important Link to Hypoxic Pulmonary Hypertension

Hypoxia, namely a lack of oxygen in the blood, induces pulmonary vasoconstriction and vasoremodeling, which serve as essential pathologic factors leading to pulmonary hypertension (PH). The underlying molecular mechanisms are uncertain; however, pulmonary artery smooth muscle cells (PASMCs) play an essential role in hypoxia-induced pulmonary vasoconstriction, vasoremodeling, and PH. Hypoxia causes oxidative damage to DNAs, proteins, and lipids. This damage (oxidative stress) modulates the activity of ion channels and elevates the intracellular calcium concentration ([Ca²⁺]_i, Ca²⁺ signaling) of PASMCs. The oxidative stress and increased Ca²⁺ signaling mutually interact with each other, and synergistically results in a variety of cellular responses. These responses include functional and structural abnormalities of mitochondria, sarcoplasmic reticulum, and nucleus; cell contraction, proliferation, migration, and apoptosis, as well as generation of vasoactive substances, inflammatory molecules, and growth factors that mediate the development of PH. A number of studies reveal that various transcription factors (TFs) play important roles in hypoxia-induced oxidative stress, disrupted PAMSC Ca²⁺ signaling and the development and progress of PH. It is believed that in the pathogenesis of PH, hypoxia facilitates these roles by mediating the expression of multiple genes. Therefore, the identification of specific genes and their transcription factors implicated in PH is necessary for the complete understanding of the underlying molecular mechanisms. Moreover, this identification may aid in the development of novel and effective therapeutic strategies for PH.

JAK3 as an Emerging Target for Topical Treatment of Inflammatory Skin Diseases

The recent interest and elucidation of the JAK/STAT signaling pathway created new targets for the treatment of inflammatory skin diseases (ISDs). JAK inhibitors in oral and topical formulations have shown beneficial results in psoriasis and alopecia areata. Patients suffering from other ISDs might also benefit from JAK inhibition. Given the development of specific JAK inhibitors, the expression patterns of JAKs in different ISDs needs to be clarified. We aimed to analyze the expression of JAK/STAT family members in a set of prevalent ISDs: psoriasis, lichen planus (LP), cutaneous lupus erythematosus (CLE), atopic dermatitis (AD), pyoderma gangrenosum (PG) and alopecia areata (AA) versus healthy controls for (p)JAK1, (p)JAK2, (p)JAK3, (p)TYK2, pSTAT1, pSTAT2 and pSTAT3. The epidermis carried in all ISDs, except for CLE, a strong JAK3 signature. The dermal infiltrate showed a more diverse expression pattern. JAK1, JAK2 and JAK3 were significantly overexpressed in PG and AD suggesting the need for pan-JAK inhibitors. In contrast, psoriasis and LP showed only JAK1 and JAK3 upregulation, while AA and CLE were characterized by a single dermal JAK signal (pJAK3 and pJAK1, respectively). This indicates that the latter diseases may benefit from more targeted JAK inhibitors. Our in vitro keratinocyte psoriasis model displayed reversal of the psoriatic JAK profile following tofacitinib treatment. This direct interaction with keratinocytes may decrease the need for deep skin penetration of topical JAK inhibitors in order to exert its effects on dermal immune cells. In conclusion, these results point to the important contribution of the JAK/STAT pathway in several ISDs. Considering the epidermal JAK3 expression levels, great interest should go to the investigation of topical JAK3 inhibitors as therapeutic option of ISDs.

Insight into the role of TSLP in inflammatory bowel diseases

Proinflammatory cytokines are thought to modulate pathogeneses of various inflammatory bowel diseases (IBDs). Thymic stromal lymphopoietin (TSLP), which has been studied in various allergic diseases such as asthma, atopic dermatitis (AD) and eosinophilic esophagitis (EoE), has been less considered to be involved in IBDs. However, mucosal dendritic cells (DCs) induced by various cytokines including TSLP were reported to cause polarization of T cell toward Th2 response, the differentiation of regulatory T-cell (Treg), and secretion of IgA by B cells. In this review, we discuss the concept that decreased TSLP has the potential to accelerate the development of Th1 response dominant diseases such as the Crohn's disease (CD) while increased TSLP has the potential to lead to a development of Th2 cell dominant diseases such the ulcerative colitis (UC). To examine TSLP's role as a potential determining factor for differentiating UC and CD, we analyzed the effects of other genes regulated by TSLP in regards to the UC and CD pathogeneses using data from online open access resources such as NetPath, GeneMania, and the String database. Our findings indicate that TSLP is a key mediator in the pathogenesis of IBDs and that further studies are needed to evaluate its role.

Thymic Stromal Chemokine TSLP Acts through Th2 Cytokine Production to Induce Cutaneous T-cell Lymphoma

Thymic stromal lymphopoietin (TSLP) activates dendritic cells to induce Th2-mediated inflammation. Periostin, an extracellular matrix protein produced by fibroblasts, induces chronic inflammation by stimulating TSLP production. Recently, a reinforcing cycle linking Th2-type immune responses with periostin-induced keratinocyte activation has been proposed in atopic dermatitis pathogenesis. In this study, we investigated the role of TSLP and periostin in the development of cutaneous T-cell lymphoma (CTCL), where Th2 cytokines and chemokines are also dominant. TSLP and periostin mRNA expression levels were elevated in CTCL lesional skin, both of which correlated with IL4 expression levels. In vitro and ex vivo, IL4 or IL13 stimulated periostin expression by dermal fibroblasts, and fibroblasts from CTCL lesional skin expressed higher levels of periostin than those from control skin. Serum periostin levels of CTCL patients were also significantly higher than those of healthy individuals. Hut78 and MJ, CTCL cell lines, and peripheral blood mononuclear cells from leukemic CTCL patients expressed the TSLP receptor. TSLP induced production of IL4 and IL13 by Hut78 and MJ cells through the activation of STAT5. Moreover, TSLP induced proliferation of CTCL cells both in vitro and in vivo These data suggest that periostin-mediated TSLP production by keratinocytes directly stimulates CTCL tumor cell growth in addition to inducing a Th2-dominant tumor environment in CTCL. Cancer Res; 76(21); 6241-52. ©2016 AACR.

A novel xenograft model to study the role of TSLP-induced CRLF2 signals in normal and malignant human B lymphopoiesis

Thymic stromal lymphopoietin (TSLP) stimulates in-vitro proliferation of human fetal B-cell precursors. However, its in-vivo role during normal human B lymphopoiesis is unknown. Genetic alterations that cause overexpression of its receptor component, cytokine receptor-like factor 2 (CRLF2), lead to high-risk B-cell acute lymphoblastic leukemia implicating this signaling pathway in leukemogenesis. We show that mouse thymic stromal lymphopoietin does not stimulate the downstream pathways (JAK/STAT5 and PI3K/AKT/mTOR) activated by the human cytokine in primary high-risk leukemia with overexpression of the receptor component. Thus, the utility of classic patient-derived xenografts for in-vivo studies of this pathway is limited. We engineered xenograft mice to produce human thymic stromal lymphopoietin (+T mice) by injection with stromal cells transduced to express the cytokine. Control (-T) mice were produced using stroma transduced with control vector. Normal levels of human thymic stromal lymphopoietin were achieved in sera of +T mice, but were undetectable in -T mice. Patient-derived xenografts generated from +T as compared to -T mice showed a 3-6-fold increase in normal human B-cell precursors that was maintained through later stages of B-cell development. Gene expression profiles in high-risk B-cell acute lymphoblastic leukemia expanded in +T mice indicate increased mTOR pathway activation and are more similar to the original patient sample than those from -T mice. +T/-T xenografts provide a novel pre-clinical model for understanding this pathway in B lymphopoiesis and identifying treatments for high-risk B-cell acute lymphoblastic leukemia with overexpression of cytokine-like factor receptor 2.

Blockade of thymic stromal lymphopoietin (TSLP) receptor inhibits TSLP-driven proliferation and signalling in lymphoblasts from a subset of B-precursor ALL patients

PURPOSE

The cytokine thymic stromal lymphopoietin (TSLP) and its receptor TSLPR are involved in intercellular communication in the course of allergic inflammation and have recently been implicated in the development of various malignancies including B cell precursor acute lymphoblastic leukemia (BCP-ALL). We studied TSLPR expression, TSLP-induced signal transduction and its antibody-mediated inhibition in long-term cultures of primary cells derived from B-precursor ALL patients.

METHODS

TSLPR expression was determined by flow cytometry and Western blot analysis, cell proliferation, signal transduction via the JAK/STAT pathway was analysed by Western blot detection of STAT tyrosine phosphorylation and by measuring TSLP-dependent activation of a STAT-specific reporter gene construct. For inhibition studies a recently introduced antagonistic antibody to the TSLPRα-subunit was used.

RESULTS

TSLPR surface expression was observed in leukemic lymphoblasts from two out of ten patients with BCP-ALL. Upon TSLP stimulation, the cells with the highest TSLPR expression level showed enhanced proliferation and JAK/STAT-mediated gene regulation in a dose-dependent manner. By employment of an inhibitory antibody to the TSLPR, both TSLP-triggered cell proliferation and STAT transcription factor activation were specifically inhibited.

CONCLUSIONS

These results suggest that blockade of the TSLPR might be a therapeutic option for a subset of BCP-ALL patients.

Activity of the Type II JAK2 Inhibitor CHZ868 in B Cell Acute Lymphoblastic Leukemia

A variety of cancers depend on JAK2 signaling, including the high-risk subset of B cell acute lymphoblastic leukemias (B-ALLs) with CRLF2 rearrangements. Type I JAK2 inhibitors induce paradoxical JAK2 hyperphosphorylation in these leukemias and have limited activity. To improve the efficacy of JAK2 inhibition in B-ALL, we developed the type II inhibitor CHZ868, which stabilizes JAK2 in an inactive conformation. CHZ868 potently suppressed the growth of CRLF2-rearranged human B-ALL cells, abrogated JAK2 signaling, and improved survival in mice with human or murine B-ALL. CHZ868 and dexamethasone synergistically induced apoptosis in JAK2-dependent B-ALLs and further improved in vivo survival compared to CHZ868 alone. These data support the testing of type II JAK2 inhibition in patients with JAK2-dependent leukemias and other disorders.

Mechanisms of pre-B-cell receptor checkpoint control and its oncogenic subversion in acute lymphoblastic leukemia

Pre-B cells within the bone marrow represent the normal counterpart for most acute lymphoblastic leukemia (ALL). During normal early B-cell development, survival and proliferation signals are dominated by cytokines, particularly interleukin-7 (IL-7) for murine developing B cells. With expression of a functional pre-B-cell receptor (BCR), cytokine signaling is attenuated and the tonic/autonomous pre-BCR signaling pathway provides proliferation as well as differentiation signals. In this review, we first describe checkpoint mechanisms during normal B-cell development and then discuss how genetic lesions in these pathways function as oncogenic mimicries and allow transformed pre-B cells to bypass checkpoint control. We focus on cytokine receptor signaling that is mimicked by activating lesions in receptor subunits or downstream mediators as well as aberrant activation of non-B lymphoid cytokine receptors. Furthermore, we describe the molecular switch from cytokine receptor to pre-BCR signaling, how this pathway is of particular importance for certain ALL subtypes, and how pre-BCR signaling is engaged by genetic lesions, such as BCR-ABL1. We discuss the transcriptional control mechanisms downstream of both cytokine- and pre-BCR signaling and how normal checkpoint control mechanisms are circumvented in pre-B ALL. Finally, we highlight new therapeutic concepts for targeted inhibition of oncogenic cytokine or pre-BCR signaling pathways.

The route to pathologies in chronic inflammatory diseases characterized by T helper type 2 immune cells

T helper type 2 (Th2)-characterized inflammatory responses are highly dynamic processes initiated by epithelial cell damage resulting in remodelling of the tissue architecture to prevent further harm caused by a dysfunctional epithelial barrier or migrating parasites. This process is a temporal and spatial response which requires communication between immobile cells such as epithelial, endothelial, fibroblast and muscle cells and the highly mobile cells of the innate and adaptive immunity. It is further characterized by a high cellular plasticity that enables the cells to adapt to a specific inflammatory milieu. Incipiently, this milieu is shaped by cytokines released from epithelial cells, which stimulate Th2, innate lymphoid and invariant natural killer (NK) T cells to secrete Th2 cytokines and to activate dendritic cells which results in the further differentiation of Th2 cells. This milieu promotes wound-healing processes which are beneficial in parasitic infections or toxin exposure but account for increasingly dysfunctional vital organs, such as the lung in the case of asthma and the colon in ulcerative colitis. A better understanding of the dynamics underlying relapses and remissions might lead ultimately to improved therapeutics for chronic inflammatory diseases adapted to individual needs and to different phases of the inflammation.

TSLP signaling pathway map: a platform for analysis of TSLP-mediated signaling

Thymic stromal lymphopoietin (TSLP) is a four-helix bundle cytokine that plays a critical role in the regulation of immune responses and in the differentiation of hematopoietic cells. TSLP signals through a heterodimeric receptor complex consisting of an interleukin-7 receptor α chain and a unique TSLP receptor (TSLPR) [also known as cytokine receptor-like factor 2 (CRLF2)]. Cellular targets of TSLP include dendritic cells, B cells, mast cells, regulatory T (Treg) cells and CD4+ and CD8+ T cells. The TSLP/TSLPR axis can activate multiple signaling transduction pathways including the JAK/STAT pathway and the PI-3 kinase pathway. Aberrant TSLP/TSLPR signaling has been associated with a variety of human diseases including asthma, atopic dermatitis, nasal polyposis, inflammatory bowel disease, eosinophilic eosophagitis and, most recently, acute lymphoblastic leukemia. A centralized resource of the TSLP signaling pathway cataloging signaling events is not yet available. In this study, we present a literature-annotated resource of reactions in the TSLP signaling pathway. This pathway map is publicly available through NetPath (http://www.netpath.org/), an open access signal transduction pathway resource developed previously by our group. This map includes 236 molecules and 252 reactions that are involved in TSLP/TSLPR signaling pathway. We expect that the TSLP signaling pathway map will provide a rich resource to study the biology of this important cytokine as well as to identify novel therapeutic targets for diseases associated with dysregulated TSLP/TSLPR signaling.

Database URL: http://www.netpath.org/pathways?path_id=NetPath_24

Protein tyrosine phosphatases as wardens of STAT signaling

Signaling by signal transducers and activators of transcription (STATs) is controlled at many levels of the signaling cascade. Protein tyrosine phosphatases (PTPs) regulate STAT activation at several layers, including direct pSTAT dephosphorylation in both cytoplasm and nucleus. Despite the importance of this regulation mode, many aspects are still incompletely understood, e.g., the identity of PTPs acting on certain members of the STAT family. After a brief introduction into the STAT and PTP families, we discuss here the current knowledge on PTP mediated regulation of STAT activity, focusing on the interaction of individual STATs with specific PTPs. Finally, we highlight open questions and propose important tasks of future research.

Evidence for a functional thymic stromal lymphopoietin signaling axis in fibrotic lung disease

Thymic stromal lymphopoietin (TSLP) recently has emerged as a key cytokine in the development of type 2 immune responses. Although traditionally associated with allergic inflammation, type 2 responses are also recognized to contribute to the pathogenesis of tissue fibrosis. However, the role of TSLP in the development of non-allergen-driven diseases, characterized by profibrotic type 2 immune phenotypes and excessive fibroblast activation, remains underexplored. Fibroblasts represent the key effector cells responsible for extracellular matrix production but additionally play important immunoregulatory roles, including choreographing immune cell recruitment through chemokine regulation. The aim of this study was to examine whether TSLP may be involved in the pathogenesis of a proto-typical fibrotic disease, idiopathic pulmonary fibrosis (IPF). We combined the immunohistochemical analysis of human IPF biopsy material with signaling studies by using cultured primary human lung fibroblasts and report for the first time, to our knowledge, that TSLP and its receptor (TSLPR) are highly upregulated in IPF. We further show that lung fibroblasts represent both a novel cellular source and target of TSLP and that TSLP induces fibroblast CCL2 release (via STAT3) and subsequent monocyte chemotaxis. These studies extend our understanding of TSLP as a master regulator of type 2 immune responses beyond that of allergic inflammatory conditions and suggest a novel role for TSLP in the context of chronic fibrotic lung disease.

The involvement of the JAK-STAT signaling pathway in chronic inflammatory skin disease atopic dermatitis

Atopic dermatitis (AD), a common chronic inflammatory skin disease, is characterized by inflammatory cell skin infiltration. The JAK-STAT pathway has been shown to play an essential role in the dysregulation of immune responses in AD, including the exaggeration of Th2 cell response, the activation of eosinophils, the maturation of B cells, and the suppression of regulatory T cells (Tregs). In addition, the JAK-STAT pathway, activated by IL-4, also plays a critical role in the pathogenesis of AD by upregulating epidermal chemokines, pro-inflammatroy cytokines, and pro-angiogenic factors as well as by downregulating antimicrobial peptides (AMPs) and factors responsible for skin barrier function. In this review, we will highlight the recent advances in our understanding of the JAK-STAT pathway in the pathogenesis of AD.

Role of transcription factors in the pathogenesis of asthma and COPD

Inflammation is a central feature of asthma and chronic obstructive pulmonary disease (COPD). Despite recent advances in the knowledge of the pathogenesis of asthma and COPD, much more research on the molecular mechanisms of asthma and COPD are needed to aid the logical development of new therapies for these common and important diseases, particularly in COPD where no effective treatments currently exist. In the future the role of the activation/repression of different transcription factors and the genetic regulation of their expression in asthma and COPD may be an increasingly important aspect of research, as this may be one of the critical mechanisms regulating the expression of different clinical phenotypes and their responsiveness to therapy, particularly to anti-inflammatory drugs.

Altered responses to homeostatic cytokines in patients with idiopathic CD4 lymphocytopenia

Idiopathic CD4 lymphocytopenia (ICL) is a rare immune deficiency characterized by a protracted CD4(+) T cell loss of unknown etiology and by the occurrence of opportunistic infections similar to those seen in AIDS. We investigated whether a defect in responses to cytokines that control CD4(+) T cell homeostasis could play a role in ICL. Immunophenotype and signaling responses to interleukin-7 (IL-7), IL-2, and thymic stromal lymphopoietin (TSLP) were analyzed by flow cytometry in CD4(+) T cells from 15 ICL patients and 15 healthy blood donors. The induction of phospho-STAT5 after IL-7 stimulation was decreased in memory CD4(+) T cells of some ICL patients, which correlated with a decreased expression of the IL-7Rα receptor chain (R = 0.74, p<0.005) and with lower CD4(+) T cell counts (R = 0.69, p<0.005). IL-2 responses were also impaired, both in the Treg and conventional memory subsets. Decreased IL-2 responses correlated with decreased IL-7 responses (R = 0.75, p<0.005), pointing to combined defects that may significantly perturb CD4(+) T cell homeostasis in a subset of ICL patients. Unexpectedly, responses to the IL-7-related cytokine TSLP were increased in ICL patients, while they remained barely detectable in healthy controls. TSLP responses correlated inversely with IL-7 responses (R = -0.41; p<0.05), suggesting a cross-regulation between the two cytokine systems. In conclusion, IL-7 and IL-2 signaling are impaired in ICL, which may account for the loss of CD4(+) T cell homeostasis. Increased TSLP responses point to a compensatory homeostatic mechanism that may mitigate defects in γc cytokine responses.

Expression analysis and specific blockade of the receptor for human thymic stromal lymphopoietin (TSLP) by novel antibodies to the human TSLPRα receptor chain

Thymic stromal lymphopoietin (TSLP) is an interleukin-7 (IL-7)-like cytokine with a pivotal role in development and maintenance of atopic diseases such as allergic asthma and atopic dermatitis. Moreover, recent studies show an involvement of TSLP in the progression of various cancers. TSLP signaling is mediated by the TSLP receptor (TSLPR), a heterodimeric type I cytokine receptor. It consists of the IL-7 receptor alpha chain (IL-7Rα), which is shared with the IL-7 receptor, and the TSLPRα chain as a specific subunit. Blocking signal release by TSLP without affecting IL-7 function is a potentially interesting option for the treatment of atopic diseases or certain tumors. By employing the extracellular domain of human TSLPRα chain (hTSLPRα(ex)) as an antigen, we generated a set of monoclonal antibodies. Several binders to native and/or denatured receptor protein were identified and characterized by cytometry and Western blot analysis. A screen based on a STAT3-driven reporter gene assay in murine pro-B cells expressing a functional hTSLPR yielded two hybridoma clones with specific antagonistic properties towards hTSLP, but not IL-7. Kinetic studies measuring blockade of hTSLP-dependent STAT phosphorylation in a TSLP-responsive cell line revealed an inhibitory constant in the nanomolar range.

Signaling cascades initiated by TSLP-mediated signals in different cell types

Thymic stromal lymphopoietin (TSLP) has been well characterized as a consequence of its ability to modulate allergic and neoplastic diseases. However, downstream signaling mediated by TSLP varies significantly between the cell type and species examined. Since this observation is often overlooked and in some cases ignored, this review aims to consolidate the molecular pathways activated by TSLP receptors expressed by various human and mouse cell types.