Thymic Stromal Lymphopoietin Gene Expression Research Articles

Ghrelin Represses Thymic Stromal Lymphopoietin Gene Expression through Activation of Glucocorticoid Receptor and Protein Kinase C Delta in Inflamed Skin Keratinocytes.

Ghrelin, a peptide hormone secreted from enteroendocrine cells of the gastrointestinal tract, has anti-inflammatory activity in skin diseases, including dermatitis and psoriasis. However, the molecular mechanism underlying the beneficial effect of ghrelin on skin inflammation is not clear. In this study, we found that ghrelin alleviates atopic dermatitis (AD)-phenotypes through suppression of thymic stromal lymphopoietin (TSLP) gene activation. Knockdown or antagonist treatment of growth hormone secretagogue receptor 1a (GHSR1a), the receptor for ghrelin, suppressed ghrelin-induced alleviation of AD-like phenotypes and suppression of TSLP gene activation. We further found that ghrelin induces activation of the glucocorticoid receptor (GR), leading to the binding of GR with histone deacetylase 3 (HDAC3) and nuclear receptor corepressor (NCoR) NCoR corepressor to negative glucocorticoid response element (nGRE) on the TSLP gene promoter. In addition, ghrelin-induced protein kinase C δ (PKCδ)-mediated phosphorylation of p300 at serine 89 (S89), which decreased the acetylation and DNA binding activity of nuclear factor- κB (NF-κB) p65 to the TSLP gene promoter. Knockdown of PKCδ abolished ghrelin-induced suppression of TSLP gene activation. Our study suggests that ghrelin may help to reduce skin inflammation through GR and PKCδ-p300-NF-κB-mediated suppression of TSLP gene activation.

Thymic stromal lymphopoietin (TSLP) is a potent pro-inflammatory mediator which is epigenetically deregulated in endometriosis

ObjectiveEndometriosis is an estrogen-dependent disease characterized by the presence of endometriotic tissue outside the uterine cavity, the condition that immunological factors play important roles in its pathogenesis. Thymic stromal lymphopoietin (TSLP) is an interleukin 7–like cytokine that triggers dendritic cell–mediated T helper2 inflammatory responses. TSLP receptor, or cytokine receptor- like factor 2 (CRLF2), forms a functional heterodimeric complex with IL-7 receptor alpha (IL-7Rα) to bind with TSLP. The present study aimed to elucidate the expression and epigenetic alterations of TSLP gene parallel to TSLP receptor and IL-10 genes expression in endometrial tissues of patients with endometriosis compared to controls. Materials & methodsIn this case-control study, 45 women with and without endometriosis was enrolled. The relative expression of TSLP, TSLPR and IL-10 genes were examined using qPCR. Chromatin Immunoprecipitation (ChIP) was also used to monitor epigenetic marks of methylation and acetylation on lysine 9 of histone H3 (H3K9me/ac) and DNA methylation in TSLP promoter. Results and conclusionTSLP, TSLPR and IL-10 genes were overexpressed in ectopic endometriotic lesions compared to controls. In ectopic samples, significant H3K9 hyper-acetylation and hypo-methylation parallel to DNA hypo-methylation were detected in TSLP promoter compared to eutopic and control groups (p < 0.05). These epigenetic changes were aligned with TSLP gene expression profile. These data collectively identify TSLP and TSLPR as candidate genes critically involved in development of endometriosis beyond their role in promoting Th2 immune responses. In addition, acetylation and methylation of H3K9 may have effective roles in TSLP dysregulation in endometriosis.

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

Thymic stromal lymphopoietin (TSLP) plays a key role in the development of allergic inflammation. Little is known about possible triggers of equine TSLP expression. To investigate TSLP expression in equine insect bite hypersensitivity (IBH) skin lesions. The capacity of TLR 1-8 ligands (L) and of atopic cytokine milieu as potential triggers of TSLP and of interleukin (IL)-6 as a downstream effector molecule of TLR signalling, were examined in primary equine keratinocyte cultures. Lesional skin from IBH-affected and healthy skin from control-horses (n=9 each group) was sampled. Keratinocyte cultures were established from six healthy horses and stimulated with TLR 1-8-L, and with IL-4 and tumor necrosis factor-α, to mimic an atopic inflammation cytokine milieu. TSLP and IL-6 gene expression was assessed by quantitative real-time PCR. Expression of TSLP was significantly greater in IBH lesions compared to healthy skin. TLR 1-8-L significantly upregulated TSLP expression in keratinocytes. The strongest upregulation was induced by TLR 1/2-L and TLR 3-L. Combination of atopic cytokine milieu and TLR 1/2-L or TLR 3-L further increased TSLP expression. TLR-L 1-5 stimulation significantly upregulated IL-6 expression. The data herein suggest that the upregulation of TSLP expression in lesional skin of IBH-affected horses might play a role in IBH development. Moreover, TSLP expression is induced by TLR-L, in particular by TLR 1/2-L and TLR 3-L, and is further increased by atopic cytokine milieu, indicating a mechanism for TSLP-mediated exacerbation of IBH.

Protective effect of TSLP and IL-33 cytokines in ulcerative colitis

PurposeInflammatory bowel disease (IBD) primarily includes ulcerative colitis (UC) and Crohn’s disease (CD). Thymic stromal lymphopoietin (TSLP) is a cytokine produced by intestinal epithelial cells (IECs) with immunomodulatory properties that plays an important role in the development of regulatory T cell (Treg) responses and tolerance in the gut. On the other hand, IL-33 has been considered as a cytokine with two different properties, inflammatory and anti-inflammatory functions, the latter may play a protective role against chronic intestinal inflammation. In the present study, we investigated the relative gene expression levels of TSLP and IL-33 molecules in ulcerative colitis.MethodsPatients with clinical symptoms of colitis undergoing a routine diagnostic colonoscopy were included in this study. Biopsy specimens were collected and divided into two parts. One part was fixed and processed for routine histopathological examinations and the other part was stored for RNA extraction. TSLP and IL-33 gene expression were determined using the SYBR Green qRT-PCR.ResultsThe expression level of TSLP and IL-33 were significantly lower in UC patients compared with the control group. Moreover, the expressions of these cytokines were more down-regulated in severe UC patients compared with mild and moderate ones and the control group. We also showed a positive correlation between low expression of TSLP and IL-33 and the severity of UC disease.ConclusionsIn this study, we showed decreased mRNA expression levels of TSLP and IL-33 in UC patients and also a negative correlation between expression of TSLP and IL-33 and severity of UC disease.

Activation of Aryl Hydrocarbon Receptor Negatively Regulates Thymic Stromal Lymphopoietin Gene Expression via Protein Kinase Cδ-p300–NF-κB Pathway in Keratinocytes under Inflammatory Conditions

Epithelial-derived thymic stromal lymphopoietin (TSLP) plays an important role in pathogenesis in several types of dermatitis. Recently, the anti-inflammatory effects of aryl hydrocarbon receptor (AhR) have been reported in inflamed skin. In this study, keratinocytes were stimulated with tumor necrosis factor-α or flagellin in combination with AhR ligands or antagonist. TSLP gene expression and recruitment of transcriptional regulator to TSLP gene promoter were determined. The effects of AhR activation were also studied in DNFB-induced dermatitis model. We found that AhR activation suppressed upregulation of TSLP expression in keratinocytes treated with tumor necrosis factor-α or flagellin. In addition, AhR activation induced protein kinase Cδ-mediated phosphorylation of p300 at serine 89, leading to decreased acetylation and DNA binding activity of NF-κB p65 to the TSLP gene promoter. We also found that AhR activation alleviates dermatitis induced by DNFB treatment. Protein kinase Cδ depletion by small interfering RNA abolished the beneficial effect of AhR activation on dermatitis. Our study suggests that AhR activation may help to reduce inflammation in the dermatitis via downregulation of TSLP expression.

Effect of Alarmins on the Synthesis of Tissue Cytokines

A primary response of the innate immune system to a pathogen invasion or tissue damage is the synthesis of tissue cytokines. Interleukins (IL) 25 and 33 or thymic stromal lymphopoietin (TSLP) are produced by epithelial or muscle cells in response to pathogen fragments, i.e., pathogen associated molecular patterns (PAMPs) or endogenous stress factors (danger associated molecular patterns, DAMPs). The goal of this work is to compare the ability of the bacterial peptide N-formyl-met-leu-phe (fMLP) and an endogenous pruritus inducer, amino acid β-alanine, to stimulate the expression of tissue cytokines. It has been shown by quantitative PCR that fMLP stimulates the ex vivo gene expression of TSLP and IL-25 in murine trachea explants, and β-alanine also stimulates IL-33 gene expression. The in vivo level of TSLP and IL-33 has been evaluated by ELISA in lung homogenates 1 and 6 h after intratracheal injection of the stimulants. Both β‑alanine and fMLP induce the release of IL-33 and TSLP from the intracellular depot. It is shown for the first time that β-alanine and fMLP are activators of tissue cytokine synthesis.

Aryl hydrocarbon receptor activation by diesel exhaust particles mediates epithelium-derived cytokines expression in severe allergic asthma.

Exposure to environmental pollutants promotes Th2 cell responses. Aryl hydrocarbon receptor (AhR) activation aggravates allergic responses. Epithelium-derived thymic stromal lymphopoietin (TSLP), interleukin (IL)-25, and IL-33 are implicated in the dysregulation of Th2 immune responses in severe allergic asthma. Bronchial biopsies of 28 allergic severe asthma and 6 mild asthma subjects from highly polluted areas were analyzed for AhR nuclear translocation (NT), cytokine expression, and gene activation. Cultured primary epithelial cells were stimulated with diesel exhausted particles (DEP) to determine AhR-mediated IL-33, Il-25, and TSLP synthesis and release. Primary bronchial epithelial cells exposed to DEP showed upregulation of IL-33, IL-25, and TSLP. These effects were abolished by knockdown of AhR by siRNA. Increased AhR/ARNT binding to promoters of IL-33, IL-25, and TSLP was found using chromatin immunoprecipitation (ChIP) assay. Allergic severe asthma with high AhR NT had higher bronchial gene and protein expression of IL-33, IL-25, and TSLP. These patients derived clinical benefit from anti-IgE treatment. Aryl hydrocarbon receptor activation by DEP mediates upregulation of IL-33, IL-25, and TSLP with Th2 activation, potentially linking environmental pollution and allergic severe asthma.

Deficiency of KLF4 compromises the lung function in an acute mouse model of allergic asthma

Asthma is a chronic inflammatory disease of the airways and the mechanisms are not fully understood. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of monocytes, granulocyte and myeloid cells at early stage of differentiation. They possess phenotypic plasticity and regulate airway inflammation. We recently reported that Kruppel-like factor 4 (KLF4) regulates MDSC differentiation into fibrocytes, emerging effectors in chronic inflammation. However, the role of KLF4 in asthma is not known. Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine and a key initiator of allergic airway inflammation. Given the fact that TSLP promotes Th2 cytokine production that increases MDSC differentiation into fibrocytes, we postulate that KLF4 regulates asthma in a TSLP-dependent manner. In this study, we utilized a model of allergic asthma with ovalbumin challenge (OVA). We found that upon OVA treatment the wild type mice had increased MDSC infiltration into the lung, up-regulation of KLF4 and TSLP gene expression, and higher levels of Th2 cytokines including IL4 and IL13. Consistently, lack of KLF4 expression in monocytes and lung epithelial cells resulted in decreased TSLP expression and lower levels of Th2 cytokines in mice, and fibrocyte generation was compromised. KLF4 deficiency in these cells also led to decreased airway hyperresponsiveness (AHR), a cardinal feature of asthma, as assessed by whole body plethysmography. Moreover, lung fibrosis as measured by trichome staining was attenuated and the population of CD45 + COL1A1+ fibrocytes was diminished in this setting. Together, our results suggest that KLF4 regulates asthma development in a TSLP- and fibrocyte-dependent manner.

Dihomo-γ-linolenic acid prevents the development of atopic dermatitis through prostaglandin D1 production in NC/Tnd mice

BackgroundAtopic dermatitis (AD) is a chronic and relapsing skin disorder with pruritic skin symptoms. We previously reported that dihomo-γ-linolenic acid (DGLA) prevented the development of AD in NC/Tnd mice, though the mechanism remained unclear. ObjectiveWe attempted to investigate the mechanism of preventive effect of DGLA on AD development in NC/Tnd mice. MethodsThe clinical outcomes of NC/Tnd mice that were given diets containing DGLA, arachidonic acid, or eicosapentaenoic acid were compared. Lipid mediator contents in the skin in each group were also quantified. In addition, release of lipid mediators from RBL-2H3 mast cells treated with either DGLA or prostaglandin D1 (PGD1) was measured. Furthermore, effect of PGD1 on gene expression of thymic stromal lymphopoietin (TSLP) in PAM212 keratinocyte cells was determined. ResultsOnly DGLA containing diet suppressed the development of dermatitis in vivo. By quantifying the 20-carbon fatty acid-derived eicosanoids in the skin, the application of DGLA was found to upregulate PGD1, which correlated with a better outcome in NC/Tnd mice. Moreover, we confirmed that mast cells produced PGD1 after DGLA exposure, thereby exerting a suppressive effect on immunoglobulin E-mediated degranulation. PGD1 also suppressed gene expression of TSLP in keratinocytes. ConclusionThese results suggest that oral administration of DGLA causes preventive effects on AD development in NC/Tnd mice by regulating the PGD1 supply.

Evaluation of Gene Expression Using a Skin Tape Stripping Method

E S D A Y 848 Evaluation of Gene Expression Using a Skin Tape Stripping Method Byung Eui Kim, MD, PhD, Un Ha Lee, Peter Sang Kim, Donald Y. M. Leung, MD, PhD, FAAAAI; National Jewish Health, Denver, CO, Inje University, Paik Hospital, National Jewish Health. RATIONALE: Skin tape stripping is a non-invasive method used to evaluate epidermal protein expression. However, this technique has not been verified whether this skill is reliable to evaluate gene expression. METHODS: Skin tape stripping samples and skin punch biopsies were collected from 10 normal subjects and 10 patients with atopic dermatitis (AD). Total RNAwas isolated from the same donors for skin tape stripping samples and skin biopsies, and then real time RT-PCR was performed for filaggrin (FLG), thymic stromal lymphopoietin (TSLP) and loricrin (LOR). RESULTS: FLG gene expression was significantly decreased in lesional AD skin compared with skin from normal subjects in both tape stripping samples (P<0.05) and skin biopsies (P<0.05). LOR gene expression was also significantly decreased in lesional AD skin compared with skin from normal subjects in skin tape stripping samples (P<0.01) and skin biopsies (P<0.05). Additionally, LOR gene expression was significantly decreased (P<0.05) in nonlesional AD skin compared with normal subjects in tape stripping samples. TSLP gene expression from tape stripped samples was significantly increased in lesional AD skin compared with skin from normal subjects (P<0.05) and nonlesional AD (P<0.05). CONCLUSIONS: Using PCR data from both tape stripping samples and skin biopsies, we have found reduced filaggrin and loricrin, but increased TSLP, gene expression in AD. Skin tape stripping method may be used to examine gene expression in the skin since it is a non-invasive, and can be used for serial evaluation of the skin and protein expression. However, further study is required to validate this method.

Dominant Proportion of Staphylcoccus Aureus in the Skin of Atopic Dermatitis Patients through Metagenomic Analysis

E S D A Y 848 Evaluation of Gene Expression Using a Skin Tape Stripping Method Byung Eui Kim, MD, PhD, Un Ha Lee, Peter Sang Kim, Donald Y. M. Leung, MD, PhD, FAAAAI; National Jewish Health, Denver, CO, Inje University, Paik Hospital, National Jewish Health. RATIONALE: Skin tape stripping is a non-invasive method used to evaluate epidermal protein expression. However, this technique has not been verified whether this skill is reliable to evaluate gene expression. METHODS: Skin tape stripping samples and skin punch biopsies were collected from 10 normal subjects and 10 patients with atopic dermatitis (AD). Total RNAwas isolated from the same donors for skin tape stripping samples and skin biopsies, and then real time RT-PCR was performed for filaggrin (FLG), thymic stromal lymphopoietin (TSLP) and loricrin (LOR). RESULTS: FLG gene expression was significantly decreased in lesional AD skin compared with skin from normal subjects in both tape stripping samples (P<0.05) and skin biopsies (P<0.05). LOR gene expression was also significantly decreased in lesional AD skin compared with skin from normal subjects in skin tape stripping samples (P<0.01) and skin biopsies (P<0.05). Additionally, LOR gene expression was significantly decreased (P<0.05) in nonlesional AD skin compared with normal subjects in tape stripping samples. TSLP gene expression from tape stripped samples was significantly increased in lesional AD skin compared with skin from normal subjects (P<0.05) and nonlesional AD (P<0.05). CONCLUSIONS: Using PCR data from both tape stripping samples and skin biopsies, we have found reduced filaggrin and loricrin, but increased TSLP, gene expression in AD. Skin tape stripping method may be used to examine gene expression in the skin since it is a non-invasive, and can be used for serial evaluation of the skin and protein expression. However, further study is required to validate this method.

Short-Term Effect of Airborne Formaldehyde on Skin Barrier Function in Atopic Dermatitis

E S D A Y 848 Evaluation of Gene Expression Using a Skin Tape Stripping Method Byung Eui Kim, MD, PhD, Un Ha Lee, Peter Sang Kim, Donald Y. M. Leung, MD, PhD, FAAAAI; National Jewish Health, Denver, CO, Inje University, Paik Hospital, National Jewish Health. RATIONALE: Skin tape stripping is a non-invasive method used to evaluate epidermal protein expression. However, this technique has not been verified whether this skill is reliable to evaluate gene expression. METHODS: Skin tape stripping samples and skin punch biopsies were collected from 10 normal subjects and 10 patients with atopic dermatitis (AD). Total RNAwas isolated from the same donors for skin tape stripping samples and skin biopsies, and then real time RT-PCR was performed for filaggrin (FLG), thymic stromal lymphopoietin (TSLP) and loricrin (LOR). RESULTS: FLG gene expression was significantly decreased in lesional AD skin compared with skin from normal subjects in both tape stripping samples (P<0.05) and skin biopsies (P<0.05). LOR gene expression was also significantly decreased in lesional AD skin compared with skin from normal subjects in skin tape stripping samples (P<0.01) and skin biopsies (P<0.05). Additionally, LOR gene expression was significantly decreased (P<0.05) in nonlesional AD skin compared with normal subjects in tape stripping samples. TSLP gene expression from tape stripped samples was significantly increased in lesional AD skin compared with skin from normal subjects (P<0.05) and nonlesional AD (P<0.05). CONCLUSIONS: Using PCR data from both tape stripping samples and skin biopsies, we have found reduced filaggrin and loricrin, but increased TSLP, gene expression in AD. Skin tape stripping method may be used to examine gene expression in the skin since it is a non-invasive, and can be used for serial evaluation of the skin and protein expression. However, further study is required to validate this method.

House dust mite increases IL-33 and thymic stromal lymphopoietin (TSLP) gene expression in response to human rhinovirus 1B in murine bone marrow-derived macrophages. (HYP6P.276)

Abstract Acute viral infections are the most frequent cause of asthma exacerbations, and are therefore responsible for the majority of healthcare costs attributed to asthma. Human rhinovirus is the most common identified one in children and adults. It has been shown that IL-33- driven mechanism initiates TH2 responses to the clinically relevant allergens house dust mite (HDM). We have shown that TSLP is increased in asthma exacerbation. Alveolar macrophages have higher expression of IL-33 and TSLP in asthma. To determine whether HDM can have an effect on IL-33 and TSLP gene expression in response to human rhinovirus (RV), we treated bone marrow-derived macrophages (BMM) with HDM in the presence of M-CSF and infected them with RV1B. RV1B induced expression of IL-33 (2-fold, P-value&amp;lt;0.001) and TSLP (2-fold P-value&amp;lt;0.05) in HDM- treated macrophages after 24 hours compared to HDM non-treated BMM. RV1B infection caused an increase in IL-33 in IL-33 (P-value&amp;lt;0.01) and TSLP ( P-value&amp;lt;0.01) in HDM treated BMM compared to UV-treated RV1B group. There was no increase in IL-33 and TSLP gene expression in response to RV1B in the HDM-treated BMM at eight hours compared to UV-treated RV1B group, while HDM non-treated BMM showed increase in IL-33 (P-value&amp;lt;0.01) and TSLP (P-value=0.059 ) in response to RV1B compared to UV-treated RV1B. These results suggest that HDM increases IL-33 and TSLP gene expression in macrophages in response to RV1B which can play a role in asthma exacerbations.

Topical vitamin D analogue calcipotriol reduces skin fibrosis in experimental scleroderma

Vitamin D analogues can reduce TGF-β pro-fibrotic signaling in dermal fibroblasts, but they may also induce a potentially pro-fibrotic thymic stromal lymphopoietin (TSLP)-dependent Th2 cytokine local response. We have analyzed the net effect of topical vitamin D analogue calcipotriol (CPT) on the cytokine profile and the development of fibrosis in experimental model of bleomycin-induced fibrosis. Mice were simultaneously treated with topical CPT or vehicle cream and skin fibrosis was measured by collagen deposition, Masson's trichrome staining and hydroxyproline content. Cytokine and TSLP gene expression was evaluated by quantitative RT-PCR. We showed that in bleomycin injected skin, CPT administration significantly enhanced TSLP and IL-13 gene expression, but did not modify the expression of other cytokines. Skin fibrosis and hydroxyproline content were significantly reduced in CPT compared to vehicle-treated mice. In normal skin, topical administration of CPT lacked a direct pro-fibrotic effect. Our results demonstrate that topical CPT superinduces the expression of the TSLP/IL-13 Th2 axis in fibrotic skin, but it has a net anti-fibrotic effect. These data support the therapeutic use of topical vitamin D analogues for skin fibrosis.

Interleukin-1β stimulates the secretion of thymic stromal lymphopoietin (TSLP) from endometrioma stromal cells: possible involvement of TSLP in endometriosis

Is thymic stromal lymphopoietin (TSLP) involved in the pathophysiology of endometriosis? TSLP is up-regulated by interleukin (IL)-1β and may be involved in the development of endometriosis. Endometriosis is a chronic inflammatory disease in which the Th2 immune response is activated and has been suggested to promote the disease. TSLP is a master cytokine that drive Th2 immune response. A laboratory study. Primary cultures of endometrioma stromal cells (ESCs) were treated with IL-1β, a typical inflammatory cytokine associated with endometriosis. Gene expression of TSLP in ESCs and secretion of TSLP protein from ESCs were studied using quantitative PCR and a specific ELISA. Interferon γ (IFNγ), a typical Th1 cytokine, and IL-4, a typical Th2 cytokine, were added to the culture to evaluate their effect on the IL-1β-induced secretion of TSLP. Inhibitors of p38 mitogen-activated protein kinase (MAPK), p42/44 MAPK and stress-activated protein kinase/Jun amino-terminal kinase (SAPK/JNK) were added to the culture to examine intracellular signals involved in IL-1β-induced TSLP secretion. The expression of TSLP in endometrioma tissue was examined by immunohistochemistry. The concentration of TSLP in the serum and peritoneal fluid (PF) of women with or without endometriosis was measured with a specific ELISA. IL-1β stimulated the expression of TSLP mRNA and secretion of TSLP protein from ESCs. IL-4 enhanced the IL-1β-induced TSLP secretion from ESCs, while IFNγ reduced it. Inhibitors of p42/44 MAPK, p38 MAPK and SAPK/JNK suppressed the IL-1β-induced secretion of TSLP from ESCs. Positive immunostaining of TSLP was observed in the stroma of endometrioma tissue. TSLP concentrations in the serum and PF were both higher in women with endometriosis compared with those without endometriosis. The present study was only in vitro. The samples used for culture were endometrioma tissues, not including other types of endometriosis. Therefore, the present findings should be interpreted with caution. This study provided new insights in the Th2 immune response-related mechanism in endometriosis. This study is partly supported by grants from the Ministry of Health, Labour and Welfare, and the Ministry of Education, Culture, Sports, Science and Technology. The authors have no conflicts of interest to declare.

Long TSLP transcript expression and release of TSLP induced by TLR ligands and cytokines in human keratinocytes

Thymic stromal lymphopoietin (TSLP), highly expressed in keratinocytes in atopic dermatitis patients and bronchial epithelial cells in asthma patients, plays a key role in allergic diseases. Two forms of TSLP mRNA (long and short) have been reported. We compared the expression of the long-form and total TSLP transcripts in primary human keratinocytes. Primary human keratinocytes were stimulated with Toll-like receptor (TLR) ligands, cytokines, and vitamin D receptor agonists. Gene expression was analyzed by quantitative real-time PCR. The amount of TSLP released was measured by ELISA. PolyI:C (TLR3 ligand), FSL-1 (TLR2-TLR6 ligand) and flagellin (TLR5 ligand) upregulated long-form TSLP expression, which predominantly contributed to upregulation of total TSLP expression. A glucocorticoid or an endosomal acidification inhibitor inhibited the polyI:C-dependent upregulation of total TSLP and the decrease of the total TSLP was due to the decrease of the long-form. An atopic cytokine milieu (TNF-α+IL-4+IL-13) or TNF-α alone also upregulated the long-form. These stimuli also induced the release of TSLP. In contrast, a high concentration of calcitriol (1,25-dihydroxyvitamin D(3), the active form of vitamin D(3)) or its analog MC903 upregulated total TSLP significantly but not the long-form, and did not induce the release of TSLP. TLR ligands or cytokines predominantly upregulate the gene expression of the long TSLP form, which contributes to the TSLP protein production, in primary human keratinocytes. Specific measurement of the long-form rather than total TSLP should be useful for accurate detection of functional human TSLP gene expression.

Thymic stromal lymphopoietin: an immune cytokine gene associated with the metabolic syndrome and blood pressure in severe obesity

A previous expression profiling of VAT (visceral adipose tissue) revealed that the TSLP (thymic stromal lymphopoietin) gene was less expressed in severely obese men with (n=7) compared with without (n=7) the MetS (metabolic syndrome). We hypothesized that TSLP SNPs (single nucleotide polymorphisms) are associated with TSLP gene expression in VAT and with MetS phenotypes. Following validation of lower TSLP expression (P=0.003) in VAT of severely obese men and women with (n=70) compared with without (n=60) the MetS, a detailed genetic investigation was performed at the TSLP locus by sequencing its promoter, exons and intron-exon splicing boundaries using DNA of 25 severely obese subjects. Five tagging SNPs were genotyped in the 130 subjects from the expression analysis to test whether these SNPs contributed to TSLP expression variability (ANOVAs) and then genotyped in two independent samples of severely obese men (total, n=389) and women (total, n=894). In a sex-stratified multistage experimental design, ANOVAs were performed to test whether tagging SNPs were associated with MetS components treated as continuous variables. We observed that the non-coding SNP rs2289277 was associated with TSLP mRNA abundance (P=0.04), as well as with SBP [systolic BP (blood pressure)] (P=0.004) and DBP (diastolic BP) (P=0.0003) in men when adjusting for age, waist circumference, smoking and medication treating hypertension. These novel observations suggest that TSLP expression in VAT may partly explain the inter-individual variability for metabolic impairments in the presence of obesity and that specific SNPs (rs2289277 and/or correlating SNPs) may influence TSLP gene expression as well as BP in obese men.

Extracellular Double-Stranded RNA Induces TSLP via an Endosomal Acidification- and NF-κB-Dependent Pathway in Human Keratinocytes

Double-stranded RNA (dsRNA) causes keratinocytes to release thymic stromal lymphopoietin (TSLP), which plays a key role in allergic diseases. Endosomal Toll-like receptor 3 (TLR3) and cytosolic RIG-like receptors (RLRs) and PKR have been reported to recognize dsRNA. Here, we demonstrate that dsRNA induces TSLP in keratinocytes via an endosomal acidification-dependent and NF-κB-mediated pathway. After treatment with pharmacologic inhibitors or transfection with small interfering RNAs (siRNAs), primary human keratinocytes were stimulated. Bafilomycin A1, which inhibits endosomal acidification to block the TLR3 pathway, blocked the dsRNA-induced expression of TSLP, IL-8, IFN-β, and other molecules including the dsRNA sensors, whereas it did not inhibit diacyllipopeptide-induced expression of TSLP and IL-8. The dsRNA-induced gene expression of TSLP depended on RelA, a component of NF-κB, but not IRF3, similar to IL-8 but different from IFN-β, which depended on both IRF3 and RelA. The results indicate that endosomal acidification and the subsequent activation of NF-κB are necessary to sense extracellular dsRNA, suggesting the importance of the TLR3-NF-κB axis to trigger production of TSLP against the self dsRNA released from damaged cells or viral dsRNA, in the epidermis, relating to skin inflammation including atopic dermatitis (AD).

Increased expression of immunoreactive thymic stromal lymphopoietin in patients with severe asthma

Thymic stromal lymphopoietin (TSLP) is a cytokine implicated in the pathophysiology of asthma through 2 distinct pathways: a TSLP-OX40 ligand (OX40L)-T cell axis and a TSLP-mast cell axis. Whether these pathways are active in human asthma is unknown. We sought to investigate whether mucosal TSLP protein expression relates to asthma severity and distinct immunologic pathways. In healthy subjects and patients with mild-to-severe asthma, we immunostained bronchial biopsy specimens for TSLP, OX40, OX40L, T(H)2 cytokines, and inflammatory cell markers. We examined gene expression using RNA microarrays and quantitative RT-PCR. There was considerable heterogeneity in the levels of TSLP, IL-13, and IL-4 immunostaining across the cohort of asthmatic patients examined. Overall, TSLP protein expression was significantly increased in airway epithelium and lamina propria of asthmatic patients, particularly in patients with severe asthma. TSLP immunostaining in both compartments correlated with the severity of airflow obstruction. The majority of leukocytes expressing IL-13 were possibly nuocytes. Accounting for intersubject variability, the 55% of asthmatic patients with increased IL-13 immunostaining in the lamina propria also had increased IL-4 and TSLP expression. This was further substantiated by significant correlations between TSLP gene expression, a T(H)2 gene expression signature, and eosinophilic inflammation in bronchial biopsy specimens. Immunostaining for OX40, OX40L, and CD83 was sparse, with no difference between asthmatic patients and healthy subjects. TSLP expression is increased in a subset of patients with severe asthma in spite of high-dose inhaled or oral corticosteroid therapy. Targeting TSLP might only be efficacious in the subset of asthma characterized by increased TSLP expression and T(H)2 inflammation.

Expression of Toll-Like Receptors 2 and 3 on Esophageal Epithelial Cell Lines and on Eosinophils During Esophagitis

The chronic disease eosinophilic esophagitis may be mediated by the innate immune system. Activation of toll-like receptors (TLRs) in other tissues is known to initiate eosinophil infiltration, thus TLRs may be a potential mediator of esophageal eosinophilia. Little is known about TLRs in the esophagus. The purpose of this study was to identify the presence and activation of TLR2 and TLR3 on esophageal epithelial cell lines, primary epithelial cells and mucosal esophageal biopsies. TLR2 and TLR3 were identified by immunocytochemistry and immunoblot. PCR assessed alterations to gene expression by activation of TLR2 and TLR3. Immunohistochemistry co-localized eosinophils and TLR2/TLR3 on esophageal biopsies. TLR2 and TLR3 were expressed on the esophageal adenocarcinoma cell lines TE-1 and TE-7, but only TLR3 was present on the esophageal epithelial cell line HET-1A. Thymic stromal lymphopoietin gene expression was altered in response to ligands zymosan and polyI:C, demonstrating activation. Primary esophageal epithelial cells did not express TLR2 or TLR3. In esophageal biopsies, TLR2 and TLR3 expression was limited to eosinophils and other immune cells during esophagitis. TLR2 and TLR3 expression on cultured esophageal epithelial cells differs from TLR2 and TLR3 expression in esophageal biopsies, which is limited to immune cells during esophagitis.