Characterization of P5, a novel NFAT/AP-1 site in the human IL-4 promoter

Generation of reporter mice for detecting the transcriptional activity of nuclear factor of activated T cells

Nuclear factor of activated T cells (NFAT) is a transcription factor essential for immunological and other biological responses. To develop analyzing system for NFAT activity in vitro and in vivo, we generated reporter mouse lines introduced with NFAT-driven enhanced green fluorescent protein (EGFP) expressing gene construct. Six tandem repeats of -286 to -265 of the human IL2 gene to which NFAT binds in association with its co-transcription factor, activator protein (AP)-1, was conjunct with thymidine kinase minimum promoter and following EGFP coding sequence. Upon introduction of the resulting reporter cassette into C57BL/6 fertilized eggs, the transgenic mice were obtained. Among 7 transgene-positive mice in 110 mice bone, 2 mice showed the designated reporter mouse character. Thus, the EGFP fluorescence of CD4+ and CD8+ T cells in these mice was enhanced by stimulation through CD3 and CD28. Each of phorbol 12-myristate 13-acetate (PMA) and ionomycin (IOM) stimulation weakly but their combined stimulation strongly enhanced EGFP expression. The stimulation-induced EGFP upregulation was also observed following T cell subset differentiation in a different manner. The EGFP induction by PMA + IOM stimulation was more potent than that by CD3/CD28 stimulation in helper T (Th)1, Th2, Th9, and regulatory T cells, while both stimulation conditions displayed the equivalent EGFP induction in Th17 cells. Our NFAT reporter mouse lines are useful for analyzing stimulation-induced transcriptional activation mediated by NFAT in cooperation with AP-1 in T cells.

Acute 4,4'-Methylene Diphenyl Diisocyanate Exposure-Mediated Downregulation of miR-206-3p and miR-381-3p Activates Inducible Nitric Oxide Synthase Transcription by Targeting Calcineurin/NFAT Signaling in Macrophages

Exposure to 4,4'-methylene diphenyl diisocyanate (MDI) in the occupational setting may lead to development of occupational asthma (OA), and the underlying molecular mechanisms of MDI-induced disease pathogenesis remain an active area of research. Using a nose-only mouse inhalation model, we find that circulating microRNA (miR)-206-3p and miR-381-3p are downregulated after MDI exposure; however, cellular miR-206-3p and miR-381-3p responses after MDI aerosol exposure and their pathophysiological roles in MDI-OA are unknown. We hypothesize that miR-206-3p and miR-381-3p-regulated mechanisms cause increased expression of the inducible nitric oxide synthase (iNOS) after MDI aerosol exposure. We examined cellular miR-206-3p and miR-381-3p, calcineurins, nuclear factors of activated T cells (NFATs), and iNOS levels from both nose-only exposed murine bronchoalveolar lavage cells (BALCs) and differentiated THP-1 macrophages treated with MDI-glutathione (GSH) conjugates. Both in vivo murine MDI aerosol exposure and in vitro MDI-GSH exposures in THP-1 macrophages result in downregulation of endogenous miR-206-3p and miR-381-3p and upregulation of PPP3CA and iNOS expression. Transfection of THP-1 macrophages with miR-inhibitor-206-3p and miR-inhibitor-381-3p resulted in the upregulation of PPP3CA and iNOS. Using RNA-induced silencing complex immunoprecipitation and translational reporter assays, we verified that PPP3CA, but not iNOS, is directly targeted by both miR-206-3p and miR-381-3p. Downregulation of miR-206-3p and miR-381-3p following by MDI exposure induces calcineurin/NFAT signaling-mediated iNOS transcription in macrophages and BALCs.

Circulating miRs-183-5p, -206-3p and -381-3p may serve as novel biomarkers for 4,4'-methylene diphenyl diisocyanate exposure

BACKGROUND

Occupational exposure to the most widely used diisocyanate, 4,4'-methylene diphenyl diisocyanate (MDI), is a cause of occupational asthma (OA). Early recognition of MDI exposure and sensitization is essential for the prevention of MDI-OA.

OBJECTIVE

Identify circulating microRNAs (miRs) as novel biomarkers for early detection of MDI exposure and prevention of MDI-OA.

MATERIALS AND METHODS

Female BALB/c mice were exposed to one of three exposure regimens: dermal exposure to 1% MDI in acetone; nose-only exposure to 4580 ± 1497 μg/m³ MDI-aerosol for 60 minutes; or MDI dermal exposure/sensitization followed by MDI-aerosol inhalation challenge. Blood was collected and miRCURY™ miRs qPCR Profiling Service was used to profile circulate miRs from dermally exposed mice. Candidate miRs were identified and verified from mice exposed to three MDI-exposure regimens by TaqMan^® miR assays.

RESULTS

Up/down-regulation patterns of circulating mmu-miRs-183-5p, -206-3p and -381-3p were identified and verified. Circulating mmu-miR-183-5p was upregulated whereas mmu-miRs-206-3p and -381-3p were downregulated in mice exposed via all three MDI exposure regimens.

DISCUSSION AND CONCLUSION

Upregulation of circulating miR-183-5p along with downregulation of circulating miRs-206-3p and -381-3p may serve as putative biomarkers of MDI exposure and may be considered as potential candidates for validation in exposed human worker populations.

The Role of BACH2 in T Cells in Experimental Malaria Caused by Plasmodium chabaudi chabaudi AS

BTB and CNC Homology 1, Basic Leucine Zipper Transcription Factor 2 (BACH2) is a transcription factor best known for its role in B cell development. More recently, it has been associated with T cell functions in inflammatory diseases, and has been proposed as a master transcriptional regulator within the T cell compartment. In this study, we employed T cell-specific Bach2-deficient (B6.Bach2^ΔT) mice to examine the role of this transcription factor in CD4⁺ T cell functions in vitro and in mice infected with Plasmodium chabaudi AS. We found that under CD4⁺ T cell polarizing conditions in vitro, Th2, and Th17 helper cell subsets were more active in the absence of Bach2 expression. In mice infected with P. chabaudi AS, although the absence of Bach2 expression by T cells had no effect on blood parasitemia or disease pathology, we found reduced expansion of CD4⁺ T cells in B6.Bach2^ΔT mice, compared with littermate controls. Despite this reduction, we observed increased frequencies of Tbet⁺ IFNγ⁺ CD4⁺ (Th1) cells and IL-10-producing Th1 (Tr1) cells in mice lacking Bach2 expression by T cells. Studies in mixed bone marrow chimeric mice revealed T cell intrinsic effects of BACH2 on hematopoietic cell development, and in particular, the generation of CD4⁺ and CD8⁺ T cell subsets. Furthermore, T cell intrinsic BACH2 was needed for efficient expansion of CD4⁺ T cells during experimental malaria in this immunological setting. We also examined the response of B6.Bach2^ΔT mice to a second protozoan parasitic challenge with Leishmania donovani and found similar effects on disease outcome and T cell responses. Together, our findings provide new insights into the role of BACH2 in CD4⁺ T cell activation during experimental malaria, and highlight an important role for this transcription factor in the development and expansion of T cells under homeostatic conditions, as well as establishing the composition of the effector CD4⁺ T cell compartment during infection.

Unique properties of TCR-activated p38 are necessary for NFAT-dependent T-cell activation

Nuclear factor of activated T cells (NFAT) transcription factors are required for induction of T-cell cytokine production and effector function. Although it is known that activation via the T-cell antigen receptor (TCR) results in 2 critical steps, calcineurin-mediated NFAT1 dephosphorylation and NFAT2 up-regulation, the molecular mechanisms underlying each are poorly understood. Here we find that T cell p38, which is activated by an alternative pathway independent of the mitogen-activated protein (MAP) kinase cascade and with different substrate specificities, directly controls these events. First, alternatively (but not classically) activated p38 was required to induce the expression of the AP-1 component c-Fos, which was necessary for NFAT2 expression and cytokine production. Second, alternatively (but not classically) activated p38 phosphorylated NFAT1 on a heretofore unidentified site, S79, and in its absence NFAT1 was unable to interact with calcineurin or migrate to the nucleus. These results demonstrate that the acquisition of unique specificities by TCR-activated p38 orchestrates NFAT-dependent T-cell functions.

The p38 MAP kinase, which is required for a large number of important biological responses, is activated by an enzymatic cascade that results in its dual phosphorylation on p38^T180Y182. T cells have evolved a unique pathway in which T-cell antigen receptor (TCR) ligation results in phosphorylation of p38^Y323 (the alternative pathway). Why T cells acquired this pathway is the subject of conjecture. In this study, we examine the activation of 2 members of the nuclear factor of activated T cells (NFAT) family, which, when dephosphorylated by calcineurin, migrate from the cytoplasm to the nucleus. In T cells with the alternative pathway ablated by a single amino acid substitution (p38^Y323F), NFAT1 remained in the cytoplasm after stimulation via the TCR. Studies identified NFAT1^S79 as a target for alternatively (but not classically) activated p38, and phosphorylation of this residue was required for binding calcineurin and nuclear translocation. Furthermore, although classically activated p38 induced NFAT1 translocation in the absence of NFAT1^S79 phosphorylation, unlike alternatively activated p38 it did not cause NFAT2 up-regulation. This paradox was resolved by the finding that only the latter induces c-Fos, which binds to the NFAT2 promoter and participates in its up-regulation. These T-cell-specific p38 activities provide a strong rationale for the acquisition of the alternative mechanism for activating p38.

Orai1 promotes tumor progression by enhancing cancer stemness via NFAT signaling in oral/oropharyngeal squamous cell carcinoma

Emerging evidence indicates that Orai1, a key calcium channel for store-operated Ca²⁺ entry, is associated with human cancer. However, the underlying mechanism by which Orai1 regulates cancer progression remains unknown. Here we report that intracellular level of Orai1 is increased in a stepwise manner during oral/oropharyngeal carcinogenesis and highly expressed in cancer stem-like cell (CSC)-enriched populations of human oral/oropharyngeal squamous cell carcinoma (OSCC). Ectopic Orai1 expression converted non-tumorigenic immortalized oral epithelial cells to malignant cells that showed CSC properties, e.g., self-renewal capacity, increased ALDH1^HIGH cell population, increased key stemness transcription factors, and enhanced mobility. Conversely, inhibition of Orai1 suppressed tumorigenicity and CSC phenotype of OSCC, indicating that Orai1 could be an important element for tumorigenicity and stemness of OSCC. Mechanistically, Orai1 activates its major downstream effector molecule, NFATc3. Knockdown of NFATc3 in the Orai1-overexpressing oral epithelial cells abrogates the effect of Orai1 on CSC phenotype. Moreover, antagonist of NFAT signaling also decreases CSC phenotype, implying the functional importance of Orai1/NFAT axis in OSCC CSC regulation. Our study identifies Orai1 as a novel molecular determinant for OSCC progression by enhancing cancer stemness, suggesting that inhibition of Orai1 signaling may offer an effective therapeutic modality against OSCC.

Aspirin induces IL-4 production: augmented IL-4 production in aspirin-exacerbated respiratory disease

Aspirin hypersensitivity is a hallmark of aspirin-exacerbated respiratory disease (AERD), a clinical syndrome characterized by the severe inflammation of the respiratory tract after ingestion of cyclooxygenase-1 inhibitors. We investigated the capacity of aspirin to induce interleukin-4 (IL-4) production in inflammatory cells relevant to AERD pathogenesis and examined the associated biochemical and molecular pathways. We also compared IL-4 production in peripheral blood mononuclear cells (PBMCs) from patients with AERD vs aspirin-tolerant asthma (ATA) upon exposure to aspirin. Aspirin induced IL-4 expression and activated the IL-4 promoter in a report assay. The capacity of aspirin to induce IL-4 expression correlated with its activity to activate mitogen-activated protein kinases, to form DNA-protein complexes on P elements in the IL-4 promoter and to synthesize nuclear factor of activated T cells, critical transcription factors for IL-4 transcription. Of clinical importance, aspirin upregulated IL-4 production twice as much in PBMCs from patients with AERD compared with PBMCs from patients with ATA. Our results suggest that IL-4 is an inflammatory component mediating intolerance reactions to aspirin, and thus is crucial for AERD pathogenesis.

IL-4 haplotype -590T, -34T and intron-3 VNTR R2 is associated with reduced malaria risk among ancestral indian tribal populations

Background

Interleukin 4 (IL-4) is an anti-inflammatory cytokine, which regulates balance between T_H1 and T_H2 immune response, immunoglobulin class switching and humoral immunity. Polymorphisms in this gene have been reported to affect the risk of infectious and autoimmune diseases.

Methods

We have analyzed three regulatory IL-4 polymorphisms; -590C>T, -34C>T and 70 bp intron-3 VNTR, in 4216 individuals; including: (1) 430 ethnically matched case-control groups (173 severe malaria, 101 mild malaria and 156 asymptomatic); (2) 3452 individuals from 76 linguistically and geographically distinct endogamous populations of India, and (3) 334 individuals with different ancestry from outside India (84 Brazilian, 104 Syrian, and 146 Vietnamese).

Results

The -590T, -34T and intron-3 VNTR R2 alleles were found to be associated with reduced malaria risk (P<0.001 for -590C>T and -34C>T, and P = 0.003 for VNTR). These three alleles were in strong LD (r²>0.75) and the TTR2 (-590T, -34T and intron-3 VNTR R2) haplotype appeared to be a susceptibility factor for malaria (P = 0.009, OR = 0.552, 95% CI = 0.356 –0.854). Allele and genotype frequencies differ significantly between caste, nomadic, tribe and ancestral tribal populations (ATP). The distribution of protective haplotype TTR2 was found to be significant (χ²₃ = 182.95, p-value <0.001), which is highest in ATP (40.5%); intermediate in tribes (33%); and lowest in caste (17.8%) and nomadic (21.6%).

Conclusions

Our study suggests that the IL-4 polymorphisms regulate host susceptibility to malaria and disease progression. TTR2 haplotype, which gives protection against malaria, is high among ATPs. Since they inhabited in isolation and mainly practice hunter-gatherer lifestyles and exposed to various parasites, IL-4 TTR2 haplotype might be under positive selection.

Coordinated regulation of IL-4 and IL-13 expression in human T cells: 3C analysis for DNA looping

Asthma is a chronic allergic disorder characterised by chronic inflammation. The balance of type I and type II (CD4+) T helper cells is of critical importance. In asthma there is an overexpression of T(H)2 cytokines, such as IL-4, IL-5 and IL-13. The genes encoding these cytokines are located together the same chromosomal region, 5q31.1 in humans. Here we confirm a central role for the transcription factors NFAT and GATA3 in the regulation of human IL-4 and IL-13. Chromatin Conformation Capture (3C) demonstrated the formation of specific ligation products containing spliced IL-4 and IL-13 DNA sequences in human T(H)2 polarised HuT-78 cells. This suggests that co-ordinate expression of T(H)2 cytokines, under the control of GATA3 and NFAT1 is due to the formation of a chromatin hub by DNA looping.

Characterization of cis-regulatory elements conferring mercury-induced interleukin-4 gene expression in rat mast cells: a role for signal transducer and activator of transcription 6 and TATA box binding sites

We have previously shown that oxidative stress is involved in the pathogenesis of a mercuric chloride (HgCl(2))-induced, T helper type 2 (Th2)-driven autoimmune syndrome in Brown Norway (BN) rats. In the context of the syndrome, the oxidative stress-induced mast cell response seems to determine the development of the early phase of vasculitis, while oxidative stress-mediated interleukin (IL)-4 production may contribute to the subsequent Th2-driven autoimmune response. However, the molecular basis of IL-4 gene transcription induced by HgCl(2) in mast cells remains unknown. In the present study, we dissect the critical regulatory mechanisms in the IL-4 gene promoter in the rat mast cell line RBL-2H3. Immunoprecipitation provided evidence that treatment with HgCl(2) increased phosphorylation of signal transducer and activator of transcription 6 (STAT6). Transient transfection reporter analyses with a series of 5' end deletions of the IL-4 promoter produced evidence that STAT6 and TATA box binding sites are important in HgCl(2)-induced IL-4 gene expression. Subsequent elimination of one or both sites by site-directed mutagenesis significantly inhibited IL-4 promoter activity. Our results provide evidence that STAT6 and TATA box regulatory elements play an important role in HgCl(2)-induced IL-4 transcription in rat mast cells.

Th2 cells as targets for therapeutic intervention in allergic bronchial asthma

Th2 cells play a central role in the pathogenesis of allergic bronchial asthma, since each of their characteristic cytokines such as IL-4, IL-5, IL-9 and IL-13 contributes to hallmarks of this disease, including airway eosinophilia, increased mucus production, production of allergen-specific IgE and development of airway hyper-responsiveness. Therefore, these cells are predisposed as target cells for therapeutic intervention. Experimental approaches targeted Th2-type effector cytokines, Th2-cell recruitment and Th2-cell development. Another strategy uses the immunomodulatory potential of tolerance-inducing cytokines such as IL-10 or of cytokines such as IL-12, IL-18 and IFN-gamma that are able to induce a counterbalancing Th1 immune response.

Runx3 inhibits IL-4 production in T cells via physical interaction with NFAT

Interleukin (IL)-4 plays a key role in T helper 2 (Th2) cell differentiation favoring humoral immune response. Regulation of IL-4 gene expression, therefore, is critically important for Th2 dependent responses and Th2 dominant disorders. In T cells, IL-4 gene expression is regulated positively or negatively by a combination of several transcription factors. Recently, enhanced IL-4 production was reported in Runx3 knockout mice; this implies negative regulation of IL-4 by Runx3. Runx proteins are transcription factors that have a Runt domain and have essential functions in development. In this study, the molecular mechanism that downregulates IL-4 expression was investigated. Runx3 inhibited IL-4 production in EL-4 T cells stimulated with PMA/ionomycin. Runx3-mediated IL-4 inhibition was NFAT-dependent, and Runx3 was physically associated with NFAT. Therefore, our results suggest that the interaction between NFAT and Runx3 is a mechanism that causes the negative regulation of IL-4, along with previously reported repression by T-bet.

Establishment of an in vitro test system to evaluate the down-regulatory activities of natural products on IL-4

Interleukin-4 (IL-4), a representative TH2 cytokine, plays a pathologic role in the onset of various allergic diseases including atopic dermatitis, atopic rhinitis, and asthma. Several drug candidates that down-regulate IL-4 expression have been studied for their possible use as antiallergic agents in clinical settings. Therefore, an in vitro test to evaluate IL-4 promoter activities might be useful for selecting candidates of novel natural therapeutics. The promoter region (-741 to +56) of IL-4 was cloned upstream of a luciferase gene in the plasmid pGL4.14 with a hygromycin resistance gene as a selection marker to generate pGL4.14-IL-4. Treatment with PMA and A23187 highly increased luciferase activity by approximately 10-fold compared with the control in both EL-4 thymoma and RBL-2H3 cells transiently transfected with pGL4.14-IL-4, as well as in stable cell lines constantly expressing pGL4.14-IL-4. Cyclosporin A and dexamethasone, well-known anti-allergic agents, significantly down-regulated the activity in a dose-dependent manner. The feasibility of this system was evaluated by measuring the down-regulatory activities of various extracts from the TBRC plant library on PMA- and A23187-induced luciferase activities of IL-4 promoter, and by measuring IL-4 production in cultured cells using ELISA assays. The results of this study suggest that this primary screening system is simple and time-saving, and might be suitable for the selection of natural therapeutic candidates for allergic disease by measuring the down-regulatory effects of natural products on the IL-4 promoter.

MHC class II transactivator represses human IL-4 gene transcription by interruption of promoter binding with CBP/p300, STAT6 and NFAT1 via histone hypoacetylation

In addition to its property of enhancing major histocompatibility complex (MHC) class II expression, the class II transactivator (CIITA) was recently demonstrated to be involved in T helper type 1/type 2 (Th1/Th2) differentiation by regulating interleukin-4 (IL-4) gene transcription. There was however, controversy regarding whether CIITA promotes or suppresses IL-4 expression in the experiments with transgenic mice. To clarify the discrepancy by using simpler experimental systems, human Jurkat T cells that express IL-4 but not interferon-gamma, even if stimulated with phorbol 12-myristate 13-acetate plus ionomycin, were used for CIITA transfection. Significant suppression of IL-4 gene expression was demonstrated. Simultaneously, histones H3 and H4 in the IL-4 promoter were hypoacetylated. The suppression could be totally reversed by the histone deacetylatase inhibitor trichostatin A. Furthermore, the IL-4 expression was determined in primarily established human Th1/Th2 cells to which CIITA small interference RNA (siRNA) had been introduced. A substantially increased level of IL-4 was recorded in the CIITA siRNA-transfected Th1 cells, which was in parallel with significantly enhanced acetylation in histone H3 of the IL-4 promoter. Chromatin immunoprecipitation analysis indicated that CIITA abrogated the binding of coactivator CBP/p300 and transcription factors STAT6/NFAT1 to IL-4 promoter in the CIITA-transfected cells. In conclusion, CIITA was active in the repression of transcription activation of human IL-4 gene in both the T-cell line and the primary human CD4 T cells by preventing transcription factors from binding to IL-4 promoter through histone hypoacetylation. Our data confirm a potential significant role of CIITA in controlling Th1/Th2 differentiation via modulation of IL-4 gene activation.

Characterization of a novel PMA-inducible pathway of interleukin-13 gene expression in T cells

Although interleukin 13 (IL-13) is an important mediator of asthma and allergic diseases, the molecular mechanisms regulating IL-13 gene expression are not well understood. This study was designed to define the molecular mechanisms governing IL-13 gene expression in T cells. IL-13 expression was examined in human peripheral blood T cells and in the EL-4 T-cell line by enzyme-linked immunosorbent assay and reverse-transcription polymerase chain reaction. An IL-13 promoter deletion analysis was performed using luciferase-based reporter plasmids transiently transfected into EL-4 cells by electroporation. DNA binding factors were investigated using electrophoretic mobility shift assays. In contrast to IL-4 expression, which required concomitant activation of calcium- and protein kinase C- (PKC-) dependent signalling pathways, PKC activation alone was sufficient for IL-13 protein secretion in mitogen-primed (but not resting) peripheral blood T cells, and for IL-13 mRNA expression and promoter activity in EL-4 T cells. Promoter deletion analysis localized a phorbol 12-myristate 13-acetate (PMA)-sensitive element to a proximal promoter region between -109 and -79 base pairs upstream from the IL-13 transcription start site. This promoter region supported the binding of both constitutive and PMA-inducible nuclear factors in gel shift assays.

Positive Selection on a Human-Specific Transcription Factor Binding Site Regulating IL4 Expression

A single nucleotide polymorphism in the promoter of the multifunctional cytokine Interleukin 4 (IL4) affects the binding of NFAT, a key transcriptional activator of IL4 in T cells. This regulatory polymorphism influences the balance of cytokine signaling in the immune system, with important consequences-positive and negative-for human health. We determined that the NFAT binding site is unique to humans; it arose by point mutation along the lineage separating humans from other great apes. We show that its frequency distribution among human subpopulations has been shaped by the balance of selective forces on IL4's diverse roles. New statistical approaches, based on parametric and nonparametric comparisons to neutral variants typed in the same individuals, indicate that differentiation among subpopulations at the IL4 promoter polymorphism is too great to be attributed to neutral drift. The allele frequencies of this binding site represent local adaptation to diverse pathogenic challenges; disease states associated with the common derived allele are side-effects of positive selection on other IL4 functions.

Regulation of IL4 gene expression by T cells and therapeutic perspectives

Interleukin-4 (IL-4) is crucial for the differentiation of naive T helper (T(H)) cells into the T(H)2 effector cells that promote humoral (antibody) immunity and provide protection against intestinal helminths. IL-4 also has a central role in the pathogenesis of allergic inflammation. Many transcription factors are involved in the regulation of expression of the gene encoding IL-4. Initiation of transcription of the gene encoding IL-4 in naive T(H) cells is regulated by the T(H)2-specific transcription factor GATA3, whereas acute expression of the gene encoding IL-4 in T(H)2 cells is mediated by inducible, ubiquitous transcription factors after antigen encounter. This review focuses on acute activation of the gene encoding IL-4 in T cells and discusses therapeutic perspectives at the transcriptional level.

Chemogenomic identification of Ref-1/AP-1 as a therapeutic target for asthma

Asthma is characterized by an oxidantantioxidant imbalance in the lungs leading to activation of redox-sensitive transcription factors, nuclear factor kappaB (NF-kappaB), and activator protein-1 (AP-1). To develop therapeutic strategies for asthma, we used a chemogenomics approach to screen for small molecule inhibitor(s) of AP-1 transcription. We developed a beta-strand mimetic template that acts as a reversible inhibitor (pseudosubstrate) of redox proteins. This template incorporates an enedione moiety to trap reactive cysteine nucleophiles in the active sites of redox proteins. Specificity for individual redox factors was achieved through variations in X and Y functionality by using a combinatorial library approach. A limited array (2 x 6) was constructed where X was either NHCH(3) or NHCH(2) Ph and Y was methyl, phenyl, m-cyanophenyl, m-nitrophenyl, m-acetylaniline, or m-methylbenzoate. These analogs were evaluated for their ability to inhibit transcription in transiently transfected human lung epithelial A549 cells from either an AP-1 or NF-kappaB reporter. A small-molecule inhibitor, PNRI-299, was identified that selectively inhibited AP-1 transcription (IC(50) of 20 microM) without affecting NF-kappaB transcription (up to 200 microM) or thioredoxin (up to 200 microM). The molecular target of PNRI-299 was determined to be the oxidoreductase, redox effector factor-1 by an affinity chromatography approach. The selective redox effector factor-1 inhibitor, PNRI-299, significantly reduced airway eosinophil infiltration, mucus hypersecretion, edema, and IL-4 levels in a mouse asthma model. These data validate AP-1 as an important therapeutic target in allergic airway inflammation.

Transcriptional regulation of the IL-5 gene in peripheral T cells of asthmatic patients

Mechanisms that underlie the regulation of IL-5 gene expression in human peripheral T cells remain incompletely defined because of the low efficiency of transfection of plasmid constructs into non-transformed T cells. To elucidate the cellular and molecular mechanisms of IL-5 production, concanavalin A (ConA)-stimulated blastocytes derived from peripheral blood lymphocytes of asthmatic patients were employed in this study. Transcriptional activity of the synthetic human IL-5 promoter in ConA-stimulated blastocytes correlated with the production of IL-5. Deletion analysis of the reporter gene showed that the cis-regulatory element located at - 119 to - 80 is critical for inducible IL-5 promoter activity. Electrophoretic mobility shift assay revealed that an oligonucleotide probe corresponding to the element (- 119 to - 90) gave two specific bands. The slower migrating band was absolutely dependent on stimulation and was composed of a co-operative complex of the transcription factors, nuclear factor of activated T cells (NFAT) and activating protein-1 (AP-1). The faster migrating band was also inducible and was identified as AP-1-less NFAT. Mutation of either the NFAT or AP-1 element abrogated the slower migrating band and at the same time abolished transcriptional activity of the human IL-5 promoter/enhancer gene. Cyclosporin A equivalently suppressed DNA-binding activity of the composite NFAT/AP-1 site, promoter activity and protein production of IL-5. In conclusion, these data suggests that the composite NFAT/AP-1 binding element (- 115 to - 100) plays a crucial role in IL-5 synthesis by peripheral T cells of asthmatic patients.

Autocrine IL-4 gene regulation at late phases of TCR activation in differentiated Th2 cells

IL-4 is a multifunctional cytokine whose secretion displays important immunomodulatory functions. Its expression is regulated at the level of transcription, and one of the main factors involved is NFAT. The IL-4-induced transcription factor Stat6 is required for the development of naive T cells into Th2 phenotype, capable of secreting IL-4. However, IL-4 production by differentiated Th2 cells is IL-4 independent; thus, it remains unclear whether Stat6 plays any role in the IL-4 expression by mature Th2 cells. We have analyzed in the Th2 clone D10.G4.1 the nuclear proteins able to bind the regulatory element P1 of the IL-4 promoter. Gel-shift assays show NFAT1 as the most abundant nuclear protein that binds to P1 after ionomycin plus PMA activation, whereas Stat6 accounts for the bulk of the P1 binding in the presence of exogenous IL-4. Reporter experiments agree with an inhibitory effect of Stat6 on the NFAT1-induced transcriptional activity directed by the P1 element. CD3 signaling leads to an early induction of NFAT1-P1 complexes correlating with a strong induction of the IL-4 gene. In later phases of CD3 activation, P1 is also bound by Stat6 and a fall in the IL-4 mRNA levels takes place. These two late events during CD3 activation were found to be sensible in experiments conducted with an anti-IL-4 Ab. These results suggest that IL-4 endogenously produced by Th2 cells under TCR triggering modulates its own expression through Stat6.

rVista for comparative sequence-based discovery of functional transcription factor binding sites

Identifying transcriptional regulatory elements represents a significant challenge in annotating the genomes of higher vertebrates. We have developed a computational tool, rVista, for high-throughput discovery of cis-regulatory elements that combines clustering of predicted transcription factor binding sites (TFBSs) and the analysis of interspecies sequence conservation to maximize the identification of functional sites. To assess the ability of rVista to discover true positive TFBSs while minimizing the prediction of false positives, we analyzed the distribution of several TFBSs across 1 Mb of the well-annotated cytokine gene cluster (Hs5q31; Mm11). Because a large number of AP-1, NFAT, and GATA-3 sites have been experimentally identified in this interval, we focused our analysis on the distribution of all binding sites specific for these transcription factors. The exploitation of the orthologous human-mouse dataset resulted in the elimination of > 95% of the approximately 58,000 binding sites predicted on analysis of the human sequence alone, whereas it identified 88% of the experimentally verified binding sites in this region.

Histone deacetylation inhibits IL4 gene expression in T cells

BACKGROUND

Dysregulated expression of IL-4 has been linked with allergic diseases. IL-4 expression is controlled at the level of gene transcription by the coordinated action of multiple factors that bind regulatory promoter elements. In addition, alterations in chromatin structure are thought to play a role in regulating the expression of cytokines in the T(H)2 gene cluster, although the biochemical basis for these alterations in human T cells is not well understood.

OBJECTIVE

We sought to define the role of histone acetylation in the regulation of IL4 gene expression in human T cells.

METHODS

IL-4 protein production was measured by means of ELISA. IL-4 promoter activity was measured with luciferase-based reporter constructs transiently transfected into Jurkat T cells. The acetylation status of histones associated with the IL4 gene was analyzed with chromatin immunoprecipitation assays.

RESULTS

IL-4 production from activated peripheral blood T cells was enhanced by the histone deacetylase inhibitor trichostatin A. Overexpression of the type 1 histone deacetylases 1, 2, and 3 inhibited transcription driven by the IL-4 promoter in Jurkat T cells, whereas cotransfection of the histone acetyltransferase CREB-binding protein potentiated IL-4 promoter activity. Using chromatin immunoprecipitation assays, we show that nucleosomes in the proximal IL-4 promoter are acetylated on T-cell activation.

CONCLUSION

Our results demonstrate that the acetylation state of histones associated with the IL-4 promoter is a key regulator of IL4 gene expression.

Yin-Yang 1 activates interleukin-4 gene expression in T cells

Interleukin-4 (IL-4) is a multifunctional cytokine that plays an important role in immune and inflammatory responses. Expression of the IL-4 gene is tightly controlled at the level of gene transcription by both positive and negative regulatory elements in the IL-4 promoter. Several constitutive nuclear factors have been identified that can interact with IL-4 promoter elements in DNA binding assays. Here we report that the zinc-finger protein YY-1 (Yin-Yang 1) can bind to multiple elements within the human IL-4 promoter. Cotransfection of Jurkat T cells with different IL-4 promoter/reporter constructs together with expression vectors encoding antisense, wild-type, or zinc finger-deleted mutant YY-1 suggested that YY-1 enhanced IL-4 promoter activity in a DNA-binding domain-dependent manner. Site-directed mutagenesis revealed that a proximal YY-1-binding site, termed Y0 ((-59)TCATTTT(-53)), was essential for YY-1-driven IL-4 promoter activity. In addition, cotransfected YY-1 enhanced both IL-4 promoter activity and endogenous IL-4 gene expression in nontransformed peripheral blood T cells. Thus, YY-1 positively regulates IL-4 gene expression in lymphocytes.

Partners in transcription: NFAT and AP-1

Combinatorial regulation is a powerful mechanism that enables tight control of gene expression, via integration of multiple signaling pathways that induce different transcription factors required for enhanceosome assembly. The four calcium-regulated transcription factors of the NFAT family act synergistically with AP-1 (Fos/Jun) proteins on composite DNA elements which contain adjacent NFAT and AP-1 binding sites, where they form highly stable ternary complexes to regulate the expression of diverse inducible genes. Concomitant induction of NFAT and AP-1 requires concerted activation of two different signaling pathways: calcium/calcineurin, which promotes NFAT dephosphorylation, nuclear translocation and activation; and protein kinase C (PKC)/Ras, which promotes the synthesis, phosphorylation and activation of members of the Fos and Jun families of transcription factors. A fifth member of the NFAT family, NFAT5, controls the cellular response to osmotic stress, by a mechanism that requires dimer formation and is independent of calcineurin or of interaction with AP-1. Pharmacological interference with theNFAT:AP-1 interaction may be useful in selective manipulation of the immune response. Balanced activation of NFAT and AP-1 is known to be required for productive immune responses, but the role of NFAT:AP-1 interactions in other cell types and biological processes remains to be understood.

Preferential activation of nuclear factor of activated T cells c correlates with mouse strain susceptibility to allergic responses and interleukin-4 gene expression

Dysregulated expression of the T helper 2 cytokine interleukin (IL)-4 is thought to play a fundamental role in the pathogenesis of allergic asthma. The molecular basis for dysregulated IL-4 production is not well understood. We analyzed in detail the molecular factors involved in regulating IL-4 transcription in a well-characterized mouse model. In this model, A/J mice developed allergen-induced IL-4 cytokine gene expression, airway inflammation, and hyperresponsiveness, whereas C3H/HeJ (C3H) mice did not. Here we report that isolated splenocytes from A/J and C3H mice stimulated ex vivo with concanavalin A reproduced the cytokine phenotype observed in the airway after antigen challenge. We hypothesized that differences in splenocyte IL-4 production involved either polymorphisms in regulatory IL-4 promoter regions, or the expression and activation of transcription factors necessary for promoter transactivation in a strain-dependent manner. To address these questions, we first sequenced ~ 700 base pairs containing well-characterized IL-4 promoter regulatory elements using genomic DNA obtained from C3H and A/J mice. Next, we used electrophoretic mobility shift assays with relevant IL-4 promoter sequences to screen nuclear extracts isolated from A/J and C3H splenocytes for functional transcriptional factor complexes. Here we show that susceptibility to antigen-induced airway hyperresponsiveness is not due to polymorphisms in the IL-4 promoter, but is associated with preferential expression of nuclear factor of activated T cells c in splenocyte nuclear extracts obtained from A/J mice. In conclusion, our data link dysregulated activation of a specific transcription factor with susceptibility to allergic airway inflammation.