A20 (Tnfaip3) expressed in CD4+ T cells suppresses Th2 cell-mediated allergic airway inflammation in mice.

A20 (Tnfaip3), a ubiquitin-editing enzyme, inhibits NF-κB signaling pathways in response to pro-inflammatory cytokines. Previous studies have proved the anti-inflammatory roles of A20 in various cell types, including T cells, B cells, dendritic cells, and intestinal epithelial cells. Moreover, recent studies have shown that A20 expressed in lung epithelial cells is required for LPS-induced protection from asthma. In humans, a single-nucleotide polymorphism in TNFAIP3 is associated with asthma risk. However, the role of A20 expressed in T cells in asthmatic responses has not been elucidated. We addressed this point by generating mice lacking A20 expression in T cells (CD4-CreA20 fl/fl mice). We found that house dust mite (HDM)-induced allergic airway inflammation, mucus production, airway hyperresponsiveness, and Th2 cytokine production were significantly exacerbated in CD4-CreA20 fl/fl mice compared with those in control A20 fl/fl mice. In vitro differentiation of Th2 cells but not of Th1 cells or Th17 cells was enhanced in CD4+ T cells by the absence of A20. Consistently, enforced expression of A20 inhibited the differentiation of Th2 cells but not of Th1 cells or Th17 cells. Notably, the expression of GATA3 was significantly enhanced in A20-deficient CD4+ T cells, and the enhanced GATA3 expression was partly canceled by IL-2 neutralization. These results suggest that A20 functions as a stabilizing factor maintaining GATA3 levels during the induction of Th2 cells to prevent excessive Th2 cell differentiation.

Hierarchical control of interleukin 13 (IL-13) signals in lung fibroblasts by STAT6 and SOX11.

Interleukin (IL)-13 is a signature cytokine of type 2 inflammation important for the pathogenesis of various diseases, including allergic diseases. Signal transducer and activator of transcription (STAT) 6 is a critical transcriptional factor for the IL-13 signals; however, it remains unknown how expression of the IL-13-induced genes is differentiated by the transcriptional machineries. In this study, we identified IL-13-induced transcriptional factors in lung fibroblasts using DNA microarrays in which SOX11 was included. Knockdown of SOX11 down-regulated expression of periostin and CCL26, both of which are known to be downstream molecules of IL-13, whereas enforced expression of SOX11 together with IL-13 stimulation enhanced expression of periostin. Moreover, we found that in DNA microarrays combining IL-13 induction and SOX11 knockdown there exist both SOX11-dependent and -independent molecules in IL-13-inducible molecules. In the former, many inflammation-related and fibrosis-related molecules, including periostin and CCL26, are involved. These results suggest that SOX11 acts as a trans-acting transcriptional factor downstream of STAT6 and that in lung fibroblasts the IL-13 signals are hierarchically controlled by STAT6 and SOX11.

Discrete roles of STAT4 and STAT6 transcription factors in tuning epigenetic modifications and transcription during T helper cell differentiation.

Signal transducer and activator of transcription 4 (STAT4) and STAT6 are key factors in the specification of helper T cells; however, their direct roles in driving differentiation are not well understood. Using chromatin immunoprecipitation and massive parallel sequencing, we quantitated the full complement of STAT-bound genes, concurrently assessing global STAT-dependent epigenetic modifications and gene transcription by using cells from cognate STAT-deficient mice. STAT4 and STAT6 each bound over 4000 genes with distinct binding motifs. Both played critical roles in maintaining chromatin configuration and transcription of a core subset of genes through the combination of different epigenetic patterns. Globally, STAT4 had a more dominant role in promoting active epigenetic marks, whereas STAT6 had a more prominent role in antagonizing repressive marks. Clusters of genes negatively regulated by STATs were also identified, highlighting previously unappreciated repressive roles of STATs. Therefore, STAT4 and STAT6 play wide regulatory roles in T helper cell specification.

Dectin-1 Plays an Important Role in House Dust Mite-Induced Allergic Airway Inflammation through the Activation of CD11b+ Dendritic Cells.

It is well known that sensitization against fungi is closely associated with severity of asthma. Dectin-1 (gene symbol Clec7a), a C-type lectin receptor, recognizes the fungal cell wall component ß-glucan, as well as some component(s) in house dust mite (HDM) extract. However, the roles of Dectin-1 in HDM-induced allergic airway inflammation remain unclear. In this study, we used Dectin-1-deficient (Clec7a-/-) mice to examine whether Dectin-1 is involved in HDM-induced allergic airway inflammation. We found that HDM-induced eosinophil and neutrophil recruitment into the airways was significantly attenuated in Clec7a-/- mice compared with that in wild-type mice. In addition, HDM-induced IL-5, IL-13, and IL-17 production from mediastinum lymph node cells was reduced in HDM-sensitized Clec7a-/- mice. Dectin-1 was expressed on CD11b+ dendritic cells (DCs), an essential DC subset for the development of allergic inflammation, but not on CD103+ DCs, plasmacytoid DCs, or lung epithelial cells. Transcriptome analysis revealed that the expression of chemokine/chemokine receptors, including CCR7, which is indispensable for DC migration to draining lymph nodes, was decreased in Clec7a-/- DCs. In accordance with these results, the number of HDM-labeled CD11b+ DCs in mediastinum lymph nodes was significantly reduced in Clec7a-/- mice compared with wild-type mice. Taken together, these results suggest that Dectin-1 expressed on CD11b+ DCs senses some molecule(s) in HDM extract and plays a critical role in the induction of HDM-induced allergic airway inflammation by inducing the expression of chemokine/chemokine receptors in DCs.

T-bet inhibits innate lymphoid cell-mediated eosinophilic airway inflammation by suppressing IL-9 production.

BACKGROUND: Innate lymphoid cells (ILCs) are emerging subsets of immune cells that produce large amounts of cytokines upon cytokine and/or alarmin stimulation. Recent studies have shown that T-bet plays pivotal roles in the development of ILC3s and type 1 ILCs; however, the roles of T-bet in lung type 2 innate lymphoid cells (ILC2s) remain unknown. OBJECTIVE: We sought to determine the role of T-bet in ILC2-mediated airway inflammation. METHODS: The expression of T-bet in lung ILCs (defined as Thy1.2+ Lin- cells) was examined. The roles of T-bet in the development of lung ILC2s and airway inflammation induced by IL-33 administration were examined by using T-bet-deficient (T-bet-/-) mice. Gene expression profiles of T-bet-/- lung ILCs were analyzed by RNA sequencing. RESULTS: T-bet was expressed in lung ILC2s (defined as Thy1.2+ Lin- cells expressing ST2 or CD25) and IFN-γ enhanced its expression. Although the development of lung ILC2s at steady-state conditions was normal in T-bet-/- mice, IL-33-induced accumulation of lung ILC2s and eosinophilic airway inflammation were exacerbated in T-bet-/- mice. The exacerbated accumulation of ILC2s and eosinophilic airway inflammation by the absence of T-bet were evident even in a RAG2-/- background, suggesting that T-bet expressed in non-T/non-B population is involved in the suppression of IL-33-induced eosinophilic airway inflammation. Transcriptome analysis revealed that IL-9 expression in IL-33-stimulated lung ILCs was upregulated in T-bet-/- mice compared with that in wild-type mice. Importantly, neutralization of IL-9 markedly attenuated IL-33-induced accumulation of lung ILC2s and eosinophilic inflammation in T-bet-/- mice. CONCLUSIONS: T-bet suppresses IL-9 production from lung ILC2s and thereby inhibits IL-33-induced eosinophilic airway inflammation.

Role of p53 in systemic autoimmune diseases.

The tumor suppressor p53 has been shown to play a central role in tumor suppression by inducing apoptosis, cell cycle arrest, senescence, and DNA repair. In addition, recent observations indicate that the dysfunction of p53 is associated with the development of autoimmune diseases. In this review, we discuss the importance of p53 in various human and murine autoimmune diseases. We also discuss the role of p53 in controlling the balance between Th17 cells and Tregs, the alteration of which is shown to be involved in the development of autoimmunity. It is postulated that the selective restoration of p53 function in T cells could be applicable to the treatment of systemic autoimmune diseases.

Tumor suppressor p53 inhibits systemic autoimmune diseases by inducing regulatory T cells.

The tumor suppressor p53 plays a central role in tumor suppression by inducing apoptosis, cell cycle arrest, senescence, and DNA repair. In addition to the antitumor functions of p53, accumulating evidence using systemic p53-deficient mice suggests that p53 suppresses autoimmunity. However, it remains unknown how p53 suppresses autoimmunity. In this study, we generated T cell-specific p53-deficient mice (CD4-Cre p53(fl/fl) mice, or p53 conditional knockout [cKO] mice) and found that aged p53-cKO mice spontaneously developed inflammatory lesions in various organs, including lung, liver, stomach, thyroid gland, submandibular gland, and kidney. Additionally, anti-nuclear Abs and autoantibodies against gastric parietal cells were detected in p53-cKO mice but not in control p53(fl/fl) mice (p53 wild-type mice). Importantly, the number of Foxp3(+)CD4(+) regulatory T cells (Tregs) in the spleen and lung as well as in vitro differentiation of induced Tregs was significantly reduced in p53-cKO mice as compared with that in p53 wild-type mice. Regarding the mechanisms underlying p53-mediated Treg induction, p53 enhanced the transcription of Foxp3 by binding to the promoter and the conserved noncoding DNA sequence-2 of the Foxp3 gene. Taken together, these results suggest that p53 expressed in T cells functions as a suppressor for autoimmunity by inducing Treg differentiation.

Ultrasound can improve the accuracy of the 2010 American College of Rheumatology/European League against rheumatism classification criteria for rheumatoid arthritis to predict the requirement for methotrexate treatment.

OBJECTIVE: The 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria for rheumatoid arthritis (RA) refer to a possible use of ultrasound "for confirmation of the clinical findings." We undertook this study to determine the optimized definition of ultrasound-detected synovitis for the 2010 ACR/EULAR criteria and to assess the impact of its use on the accuracy of RA classification. METHODS: One hundred nine patients with musculoskeletal symptoms for ≤3 years were enrolled in the study. Patients underwent clinical, laboratory, radiographic, and comprehensive ultrasonographic assessments at baseline and received routine management from expert rheumatologists who were blinded to the ultrasound findings. RESULTS: Sensitivity and specificity of the 2010 ACR/EULAR criteria using different definitions of synovitis to identify patients who developed a disease requiring methotrexate (MTX) treatment within 1 year were 58.5% and 79.4%, respectively, for clinical synovitis (tenderness or swelling), 78.0% and 79.4%, respectively, for ultrasound-detected synovitis with a gray-scale (GS) imaging score≥1 (GS≥1 ultrasound synovitis), and 56.1% and 93.7%, respectively, for GS≥2 ultrasound synovitis or a synovial power Doppler (PD) signal score≥1 (GS≥2/PD≥1 ultrasound synovitis). Receiver operating characteristic curve analysis for the criteria scores revealed the largest area under the curve with GS≥2/PD≥1 ultrasound synovitis. CONCLUSION: Ultrasound assessment improves the accuracy of the 2010 ACR/EULAR criteria for identifying patients with a disease requiring MTX treatment. Our data provide preliminary but vital information for the methodology to confirm the presence of synovitis using ultrasound in the 2010 ACR/EULAR criteria.

Role of calcium ionophore A23187-induced activation of IkappaB kinase 2 in mast cells.

BACKGROUND: Mast cells are known to play a pivotal role in allergic diseases by releasing granules containing histamine and other preformed chemical mediators. Cross-linking of high-affinity receptors for IgE (FcεRI) on mast cells results in rapid increases in intracellular free calcium concentration [Ca(2+)]i and consequent activation of many transcription factors, including NFAT, NF-κB, JNK and CREB. Ca(2+) signaling is essential for many cellular activities such as proliferation, gene expression and degranulation in mast cells. In addition to Ca(2+) signaling, previous reports have shown that IkappaB kinase 2 (IKK2 or IKKß), a central component of the IKK complex mediating NF-κB activation, also plays a crucial role in FcεRI-mediated degranulation and cytokine production. Moreover, it has been demonstrated that activation of PKCß, a calcium-dependent PKC isoform, leads to IKK2 activation in many cell types. However, the roles of Ca(2+) signaling and PKCß in the activation of IKK2 in mast cells remain largely unknown. METHODS: We investigated the effect of PKC inhibitor Gö6976 on calcium ionophore A23187-induced activation of IKK2 in mast cells. We also examined the role of IKK2 in A23187-induced NF-κB-dependent gene induction, degranulation, proinflammatory cytokine production and extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation by using IKK2-deficient (IKK2(-/-)) fetal liver-derived mast cells (FLMCs). RESULTS: A23187 activated IKK2 and NF-κB even in the presence of Gö6976 in mast cells. A23187-induced degranulation, cytokine production and activation of ERK1/2 were diminished in IKK2(-/-) FLMCs compared to those in wild-type FLMCs. CONCLUSIONS: Ca(2+)-IKK2 signaling is involved in the degranulation and cytokine production in activated mast cells by a mechanism independent of PKCß.

Pre-dinner administration increases the efficacy of proton pump inhibitors on refractory GERD symptoms in connective tissue disease patients.

BACKGROUND: A significant proportion of patients with connective tissue disease (CTD) have gastric esophageal reflux disease (GERD) symptoms despite receiving proton pump inhibitors (PPIs). Although pre-meal administration of PPIs is recommended in Western countries, the benefit of this administration timing in Japanese CTD patients with refractory GERD symptoms has not been proven. OBJECTIVE: To determine whether pre-dinner administration of PPIs is more efficacious for refractory GERD symptoms in Japanese CTD patients. METHODS: CTD patients receiving oral PPIs were instructed to take PPIs 1 h before dinner. Gastrointestinal symptoms were evaluated with frequency scale for the symptoms of GERD (FSSG) and gastrointestinal symptom rating scale (GSRS) before and after the intervention. RESULTS: Pre-dinner administration of PPIs significantly improved FSSG total score, from a median of 8 to 6.5 (P = 0.005). Pre-dinner administration was more effective in patients with overt GERD symptoms (from median 18 to 10, P < 0.001) than in those with mild GERD symptoms (from median 2 to 2, P = 0.201). In addition to reflux syndrome, pre-dinner administration of PPIs significantly decreased abdominal pain syndrome and constipation syndrome of GSRS. CONCLUSION: Pre-dinner administration of PPIs may increase their efficacy in Japanese CTD patients with GERD, especially those with overt symptoms.

Prevalence and risk factors of osteonecrosis of the femoral head in patients with ANCA-associated vasculitis: a multicentre cohort study.

OBJECTIVE: We aimed to determine the prevalence and risk factors for osteonecrosis of the femoral head (ONFH) in a multicentre cohort of patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). METHODS: One hundred and eighty-six AAV patients who underwent radiographs and MRI screening of bilateral hip joints at more than 6 months after initial remission induction therapy (RIT) were retrospectively assessed for the presence of ONFH. RESULTS: Among 186 AAV patients, 33 (18%) were diagnosed with ONFH. Among the patients with ONFH, 55% were asymptomatic and 64% had bilateral ONFH. Seventy-six per cent of ONFH joints were in precollapse stages (stage ≤2), whereas 24% of ONFH joints were in collapse stages (stage ≥3). Moreover, 56% of the precollapse stage joints were already at risk of future collapse (type ≥C-1). Even in asymptomatic ONFH patients, 39% of the precollapse stage joints were type ≥C-1. Prednisolone dose of ≥20 mg/day on day 90 of RIT was an independent risk factor for ONFH in AAV patients (OR 1.072, 95% CI 1.017 to 1.130, p=0.009). Rituximab use was a significant beneficial factor against ONFH (p=0.019), but the multivariate analysis rejected its significance (p=0.257). CONCLUSION: Eighteen per cent of AAV patients developed ONFH, and two-thirds of the ONFH joints were already in collapse stages or at risk of future collapse. Prednisolone dose of ≥20 mg/day on day 90 of RIT was an independent risk factor for ONFH. A rapid reduction of glucocorticoids in RIT and early detection of precollapse ONFH by MRI may decrease and intervene ONFH development in AAV patients.

Overexpression of cell cycle regulator CDCA3 promotes oral cancer progression by enhancing cell proliferation with prevention of G1 phase arrest.

BACKGROUND: Cell division cycle associated 3 (CDCA3), part of the Skp1-cullin-F-box (SCF) ubiquitin ligase, refers to a trigger of mitotic entry and mediates destruction of the mitosis inhibitory kinase. Little is known about the relevance of CDCA3 to human malignancy including oral squamous cell carcinoma (OSCC). We aimed to characterize the expression state and function of CDCA3 in OSCC. METHODS: We evaluated CDCA3 mRNA and protein expression in both OSCC-derived cell lines and primary OSCCs and performed functional analyses of CDCA3 in OSCC-derived cells using the shRNA system. RESULTS: The CDCA3 expression at both the mRNA and protein levels was frequently up-regulated in all cell lines examined and primary tumors (mRNA, 51/69, 74 %; protein, 79/95, 83 %) compared to normal controls (p < 0.001). In contrast, no significant level of CDCA3 protein expression was seen in oral premalignant lesions (OPLs) (n = 20) compared with the expression in OSCCs. Among the clinical variables analyzed, the CDCA3 expression status was closely related to tumor size (p < 0.05). In addition, suppression of CDCA3 expression with shRNA significantly (p < 0.05) inhibited cellular proliferation compared with the control cells by arresting cell-cycle progression at the G1 phase. Further, there was up-regulation of the cyclin-dependent kinase inhibitors (p21(Cip1), p27(Kip1), p15(INK4B), and p16(INK4A)) in the knockdown cells. CONCLUSION: The current results showed that overexpression of CDCA3 occurs frequently during oral carcinogenesis and this overexpression might be associated closely with progression of OSCCs by preventing the arrest of cell-cycle progression at the G1 phase via decreased expression of the cyclin-dependent kinase inhibitors.

B and T lymphocyte attenuator suppresses IL-21 production from follicular Th cells and subsequent humoral immune responses.

We recently showed that mice lacking B and T lymphocyte attenuator (BTLA), a third inhibitory coreceptor expressed on B cells and T cells, exhibit an increased Ag-specific IgG response and gradually develop hyper-gamma-globulinemia and autoantibody production. Recent studies revealed that follicular Th (Tfh) cells, which are non-Th1, non-Th2 effector T cells that express CXCR5 and provide help for B cells to produce Ig, also express BTLA. However, the role of BTLA in Tfh cell function remains unknown. In this study, we examined the regulatory role of BTLA in the development and function of Tfh cells. We found that CXCR5(+) Tfh cells expressed higher levels of BTLA than did CXCR5(-) conventional CD4(+) T cells. We also found that adoptive transfer of BTLA(-/-) CD4(+) T cells, stimulated under Tfh cell-inducing conditions (Tfh-like cells), to wild-type (WT) mice induced more Ag-specific IgG2a and IgG2b production compared with that of WT Tfh-like cells. By contrast, another adoptive-transfer experiment using BTLA(-/-) mice as recipients showed that the expression of BTLA on B cells was not involved in the regulation of Tfh-like cell-mediated Ag-specific IgG responses. Moreover, the development of IL-21-producing CXCR5(+) Tfh-like cells was significantly increased in BTLA(-/-) CD4(+) T cells compared with WT CD4(+) T cells. Furthermore, Tfh-like cell-mediated IgG responses were abolished when IL-21R(-/-) mice were used as recipients. These results suggest that BTLA signaling suppresses IL-21 production from Tfh cells and subsequent Tfh cell-mediated IgG responses.

A case of methotrexate-associated Epstein-Barr virus-positive mucocutaneous ulcer.

Epstein-Barr virus-positive mucocutaneous ulcer (EBVMCU) is a B-cell proliferative disorder that has been designated as a provisional entity in the 2017 World Health Organization classification for lymphoid neoplasms. While EBVMCU may contain varying numbers of cells with Hodgkin and Reed-Sternberg cells-like morphology, the clinical course is benign and must be distinguished from lymphomas. Patients who develop EBVMCU are commonly immunocompromised, with methotrexate (MTX) as the leading cause. Most previously reported cases of EBVMCU describe mucosal ulcers with very little documentation on skin lesions and its course. Here, we report a case of MTX-associated EBVMCU of the lower leg that underwent spontaneous regression after MTX withdrawal, during which negative conversion of local Epstein-Barr virus activation was confirmed.

STAT4 is required for IFN-ß-induced MCP-1 mRNA expression in murine mast cells.

BACKGROUND: Mast cells are immunocompetent cells that are found in almost all tissues and function as sentinels of immune responses. Recently, it has been shown that mast cells play significant roles in innate immune responses. However, it is still largely unknown whether signal transducers and activators of transcription 4 (STAT4), one of the STAT proteins under type I IFN signaling, is involved in type I IFN-mediated gene expression in mast cells. METHODS: We investigated the role of STAT4 in IFN-ß-induced gene expression in mast cells by using STAT4-deficient (STAT4(-/-)) bone marrow-derived mast cells (BMMCs). RESULTS: STAT4 was expressed in BMMCs and activated in response to IFN-ß but not to IL-12 or IL-23. The development of BMMCs as well as IgE-induced degranulation of BMMCs was normal in STAT4(-/-) mice. On the other hand, while IFN-ß-induced mRNA expression of interferon-induced protein with tetratricopeptide repeats 1 (IFIT-1), protein kinase interferon-inducible double stranded RNA dependent (PKR), and myxovirus resistance 1 (Mx1) was similar between STAT4(-/-) BMMCs and wild-type (WT) BMMCs, IFN-ß-induced MCP-1 mRNA expression was severely diminished in STAT4(-/-) BMMCs as compared with WT BMMCs. CONCLUSIONS: STAT4 plays an essential role in IFN-ß-induced MCP-1 mRNA expression in mast cells.

Post-Transcriptional Regulation of Immune Responses and Inflammatory Diseases by RNA-Binding ZFP36 Family Proteins.

Post-transcriptional regulation is involved in the regulation of many inflammatory genes. Zinc finger protein 36 (ZFP36) family proteins are RNA-binding proteins involved in messenger RNA (mRNA) metabolism pathways. The ZFP36 family is composed of ZFP36 (also known as tristetraprolin, TTP), ZFP36L1, ZFP36L2, and ZFP36L3 (only in rodents). The ZFP36 family proteins contain two tandemly repeated CCCH-type zinc-finger motifs, bind to adenine uridine-rich elements in the 3'-untranslated regions (3' UTR) of specific mRNA, and lead to target mRNA decay. Although the ZFP36 family members are structurally similar, they are known to play distinct functions and regulate different target mRNAs, probably due to their cell-type-specific expression patterns. For instance, ZFP36 has been well-known to function as an anti-inflammatory modulator in murine models of systemic inflammatory diseases by down-regulating the production of various pro-inflammatory cytokines, including TNF-α. Meanwhile, ZFP36L1 is required for the maintenance of the marginal-zone B cell compartment. Recently, we found that ZFP36L2 reduces the expression of Ikzf2 (encoding HELIOS) and suppresses regulatory T cell function. This review summarizes the current understanding of the post-transcriptional regulation of immunological responses and inflammatory diseases by RNA-binding ZFP36 family proteins.

T-bet and STAT6 Coordinately Suppress the Development of IL-9-Mediated Atopic Dermatitis-Like Skin Inflammation in Mice.

T-bet and signal transducer and activator of transcription (STAT) 6 are critical factors for helper T-cell differentiation in humans and mice. Additionally, polymorphisms in TBX21 (T-bet) and STAT6 are associated with the susceptibility of allergic diseases. However, precise mechanisms of the reciprocal regulation between T-bet and STAT6 in allergy remain unclear. To determine the reciprocal regulation in vivo, we investigated the phenotype of T-bet/STAT6 double-deficient (T-bet-/- STAT6-/-) mice. Unexpectedly, T-bet-/- STAT6-/- mice but not T-bet-/- mice or STAT6-/- mice spontaneously developed severe dermatitis. Not only eosinophils and mast cells but also CD4+ T cells infiltrated into the skin of T-bet-/- STAT6-/- mice. Adoptive transfer of CD4+ T cells of T-bet-/- STAT6-/- mice into severe combined immunodeficient mice induced the accumulation of eosinophils and mast cells in the skin, whereas depletion of CD4+ T cells ameliorated the dermatitis in T-bet-/- STAT6-/- mice. Comprehensive transcriptome analyses revealed that IL-9 expression was enhanced in T-bet-/- STAT6-/- CD4+ T cells. Indeed, IL-9 neutralization ameliorated the dermatitis in T-bet-/- STAT6-/- mice. T-bet-/- STAT6-/- CD4+ T cells expressed functional thymic stromal lymphopoietin receptors and produced large amounts of IL-9 on thymic stromal lymphopoietin stimulation. These results indicate that T-bet and STAT6 coordinately suppress atopic dermatitis-like skin inflammation, possibly by inhibiting thymic stromal lymphopoietin-dependent IL-9 production in CD4+ T cells.

IL-4-Stat6 signaling induces tristetraprolin expression and inhibits TNF-alpha production in mast cells.

Increasing evidence has revealed that mast cell-derived tumor necrosis factor alpha (TNF-alpha) plays a critical role in a number of inflammatory responses by recruiting inflammatory leukocytes. In this paper, we investigated the regulatory role of interleukin 4 (IL-4) in TNF-alpha production in mast cells. IL-4 inhibited immunoglobulin E-induced TNF-alpha production and neutrophil recruitment in the peritoneal cavity in wild-type mice but not in signal transducers and activators of transcription 6 (Stat6)-deficient mice. IL-4 also inhibited TNF-alpha production in cultured mast cells by a Stat6-dependent mechanism. IL-4-Stat6 signaling induced TNF-alpha mRNA destabilization in an AU-rich element (ARE)-dependent manner, but did not affect TNF-alpha promoter activity. Furthermore, IL-4 induced the expression of tristetraprolin (TTP), an RNA-binding protein that promotes decay of ARE-containing mRNA, in mast cells by a Stat6-dependent mechanism, and the depletion of TTP expression by RNA interference prevented IL-4-induced down-regulation of TNF-alpha production in mast cells. These results suggest that IL-4-Stat6 signaling induces TTP expression and, thus, destabilizes TNF-alpha mRNA in an ARE-dependent manner.