Identification of cis-acting regulatory elements controlling interleukin-4 gene expression in T cells: roles for NF-Y and NF-ATc

Bifidobacterium Strain-Specific Enhances the Efficacy of Cancer Therapeutics in Tumor-Bearing Mice

Colorectal cancer (CRC) is among the leading causes of cancer-related death in the world. The development of CRC is associated with smoking, diet, and microbial exposure. Previous studies have shown that dysbiosis of the gut microbiome affects cancer development, because it leads to inflammation and genotoxicity. Supplementation with specific microbiota induces anti-tumor effects by enhancing of anti-tumor immunity. Here, we observed that supplementation with either of two B. breve strains reduces tumor growth in MC38 colon carcinoma-bearing mice. Interestingly, only one B. breve strain boosted the efficacy of cancer therapeutics, including oxaliplatin and PD-1 blockade. Extensive immune profiling and transcriptomic analysis revealed that the boosting B. breve strain augments lymphocyte-mediated anti-cancer immunity. Our results suggest that supplementation with B. breve strains could potentially be used as a strategy to enhance the efficacy of CRC therapeutics.

The Hap Complex in Yeasts: Structure, Assembly Mode, and Gene Regulation

The CCAAT box-harboring proteins represent a family of heterotrimeric transcription factors which is highly conserved in eukaryotes. In fungi, one of the particularly important homologs of this family is the Hap complex that separates the DNA-binding domain from the activation domain and imposes essential impacts on regulation of a wide range of cellular functions. So far, a comprehensive summary of this complex has been described in filamentous fungi but not in the yeast. In this review, we summarize a number of studies related to the structure and assembly mode of the Hap complex in a list of representative yeasts. Furthermore, we emphasize recent advances in understanding the regulatory functions of this complex, with a special focus on its role in regulating respiration, production of reactive oxygen species (ROS) and iron homeostasis.

Kv1.3 channel blockade with the Vm24 scorpion toxin attenuates the CD4+ effector memory T cell response to TCR stimulation

BACKGROUND

In T cells, the Kv1.3 and the KCa3.1 potassium channels regulate the membrane potential and calcium homeostasis. Notably, during TEM cell activation, the number of Kv1.3 channels on the cell membrane dramatically increases. Kv1.3 blockade results in inhibition of Ca2+ signaling in TEM cells, thus eliciting an immunomodulatory effect. Among the naturally occurring peptides, the Vm24 toxin from the Mexican scorpion Vaejovis mexicanus is the most potent and selective Kv1.3 channel blocker known, which makes it a promissory candidate for its use in the clinic. We have shown that addition of Vm24 to TCR-activated human T cells inhibits CD25 expression, cell proliferation and reduces delayed-type hypersensitivity reactions in a chronic inflammation model. Here, we used the Vm24 toxin as a tool to investigate the molecular events that follow Kv1.3 blockade specifically on human CD4+ TEM cells as they are actively involved in inflammation and are key mediators of autoimmune diseases.

METHODS

We combined cell viability, activation, and multiplex cytokine assays with a proteomic analysis to identify the biological processes affected by Kv1.3 blockade on healthy donors CD4+ TEM cells, following TCR activation in the presence or absence of the Vm24 toxin.

RESULTS

The peptide completely blocked Kv1.3 channels currents without impairing TEM cell viability, and in response to TCR stimulation, it inhibited the expression of the activation markers CD25 and CD40L (but not that of CD69), as well as the secretion of the pro-inflammatory cytokines IFN-γ and TNF and the anti-inflammatory cytokines IL-4, IL-5, IL-9, IL-10, and IL-13. These results, in combination with data from the proteomic analysis, indicate that the biological processes most affected by the blockade of Kv1.3 channels in a T cell activation context were cytokine-cytokine receptor interaction, mRNA processing via spliceosome, response to unfolded proteins and intracellular vesicle transport, targeting the cell protein synthesis machinery.

CONCLUSIONS

The Vm24 toxin, a highly specific inhibitor of Kv1.3 channels allowed us to define downstream functions of the Kv1.3 channels in human CD4+ TEM lymphocytes. Blocking Kv1.3 channels profoundly affects the mRNA synthesis machinery, the unfolded protein response and the intracellular vesicle transport, impairing the synthesis and secretion of cytokines in response to TCR engagement, underscoring the role of Kv1.3 channels in regulating TEM lymphocyte function.

Quality of TCR signaling determined by differential affinities of enhancers for the composite BATF-IRF4 transcription factor complex

Variable strengths of T cell receptor (TCR) signaling can produce divergent outcomes, but the mechanism remains obscure. The abundance of the transcription factor IRF4 increases with TCR signal strength, but how this would induce distinct types of responses is unclear. We compared T_H2 gene expression with BATF/IRF4 enhancer occupancy at varying strengths of TCR stimulation. BATF/IRF4-dependent genes clustered into distinct TCR-sensitivities. Enhancers exhibited a spectrum of occupancy by BATF/IRF4 ternary complex that correlated with TCR-sensitivity of gene expression. DNA sequences immediately flanking the previously defined AICE motif controlled the affinity for BATF/IRF4 for direct binding to DNA. ChIP-exo analysis allowed identification of a novel high-affinity AICE2 motif at a human SNP of CTLA4 associated with resistance to autoimmunity. Thus, the affinity of different enhancers for the BATF-IRF4 complex may underlie divergent signaling outcomes in response to various strengths of TCR signaling.

Adipocyte SIRT1 controls systemic insulin sensitivity by modulating macrophages in adipose tissue

Adipose tissue inflammation, characterized by augmented infiltration and altered polarization of macrophages, contributes to insulin resistance and its associated metabolic diseases. The NAD⁺-dependent deacetylase SIRT1 serves as a guardian against metabolic disorders in multiple tissues. To dissect the roles of SIRT1 in adipose tissues, metabolic phenotypes of mice with selective ablation of SIRT1 in adipocytes and myeloid cells were monitored. Compared to myeloid-specific SIRT1 depletion, mice with adipocyte-selective deletion of SIRT1 are more susceptible to diet-induced insulin resistance. The phenotypic changes in adipocyte-selective SIRT1 knockout mice are associated with an increased number of adipose-resident macrophages and their polarization toward the pro-inflammatory M1 subtype. Mechanistically, SIRT1 in adipocytes modulates expression and secretion of several adipokines, including adiponectin, MCP-1, and interleukin 4, which in turn alters recruitment and polarization of the macrophages in adipose tissues. In adipocytes, SIRT1 deacetylates the transcription factor NFATc1 and thereby enhances the binding of NFATc1 to the Il4 gene promoter. These findings suggest that adipocyte SIRT1 controls systemic glucose homeostasis and insulin sensitivity via the cross talk with adipose-resident macrophages.

Compensatory dendritic cell development mediated by BATF-IRF interactions

The AP-1 transcription factor Batf3 is required for homeostatic development of CD8α⁺ classical dendritic cells that prime CD8 T-cell responses against intracellular pathogens. Here, we identify an alternative, Batf3-independent pathway for their development operating during infection with intracellular pathogens mediated by the cytokines IL-12 and IFN-γ. This alternative pathway results from molecular compensation for Batf3 provided by the related AP-1 factors Batf, which also functions in T and B cells, and Batf2 induced by cytokines in response to infection. Reciprocally, physiologic compensation between Batf and Batf3 also occurs in T cells for expression of IL-10 and CTLA-4. Compensation among BATF factors is based on the shared capacity of their leucine zipper domains to interact with non-AP-1 factors such as Irf4 and Irf8 to mediate cooperative gene activation. Conceivably, manipulating this alternative pathway of dendritic cell development could be of value in augmenting immune responses to vaccines.

Cyclosporine A suppresses immunoglobulin G biosynthesis via inhibition of cyclophilin B in murine hybridomas and B cells

Immunoglubulin G (IgG) is a major isotype of antibody, which is predominantly involved in immune response. The complete tetramer is needed to fold and assemble in endoplasmic reticulum (ER) prior to secretion from cells. Protein quality control guided by ER chaperons is most essential for full biological activity. Cyclophilin B (CypB) was initially identified as a high-affinity binding protein for the immunosuppressive drug Cyclosporine A (CsA). CsA suppresses organ rejection by halting productions of pro-inflammatory molecules in T cell and abolishes the enzymatic property of CypB that accelerates the folding of proteins by catalysing the isomerization of peptidyl-proline bonds in ER. Here, we reported that CsA significantly inhibited IgG biosynthesis at posttranslational level in antibody secreting cells. Moreover, CsA stimulated the extracellular secretion of CypB and induced ROS generation, leading to expressions of ER stress markers. In addition, the absence of intracellular CypB impaired the formation of ER multiprotein complex, which is most important for resisting ER stress. Interestingly, CsA interrupted IgG folding via occupying the PPIase domain of CypB in ER. Eventually, unfolded IgG is degraded via Herp-dependent ERAD pathway. Furthermore, IgG biosynthesis was really abrogated by inhibition of CypB in primary B cells. We established for the first time the immunosuppressive effect of CsA on B cells. Conclusively, the combined results of the current study suggest that CypB is a pivotal molecule for IgG biosynthesis in ER quality control.

Enhanced chromatin accessibility and recruitment of JUNB mediate the sustained IL-4 expression in NFAT1 deficient T helper 2 cells

Nuclear factor of activated T cells (NFAT) is a family of transcription factors composed of five proteins. Among them, NFAT1 is a predominant NFAT protein in CD4(+) T cells. NFAT1 positively regulates transcription of a large number of inducible cytokine genes including IL-2, IL-4, IL-5 and other cytokines. However, disruption of NFAT1 results in an unexpected increase of IL-4. In this study, we have investigated the role of NFAT1 in regulation of IL-4 gene expression in T helper 2 cells (Th2) from an epigenetic viewpoint. NFAT1 deficient Th2 cells showed a sustained IL-4 expression while wild type (WT) cells reduced its expression. We tested whether epigenetic maintenance and changes in the chromatin architecture of IL-4 promoter locus play a role in differential IL-4 transcription between in WT and NFAT1 deficient Th2 cells. Compared with WT, NFAT1 deficient CD4(+) Th2 cells exhibited enhanced chromatin accessibility with permissive histone modification and DNA demethylation in the IL-4 promoter region. Transcription factors bound to IL-4 promoter region in the absence of NFAT1 were identified by Micro-LC/LC-MS/MS analysis. Among the candidates, preferential recruitment of JUNB to the IL-4 promoter was confirmed by chromatin immunoprecipitation analysis. Overexpression of JUNB together with SATB1 synergistically upregulated IL-4 promoter activity, while knockdown JUNB significantly reduced IL-4 expression. Our results suggest that the prolonged IL-4 expression in NFAT1 deficient Th2 cells is mediated by preferential binding of JUNB/SATB1 to the IL-4 promoter with permissive chromatin architecture.

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.

Elevating calcium in Th2 cells activates multiple pathways to induce IL-4 transcription and mRNA stabilization

PMA and ionomycin cause T cell cytokine production. We report that ionomycin alone induces IL-4 and IFN-gamma, but not IL-2, from in vivo- and in vitro-generated murine Th2 and Th1 cells. Ionomycin-induced cytokine production requires NFAT, p38, and calmodulin-dependent kinase IV (CaMKIV). Ionomycin induces p38 phosphorylation through a calcium-dependent, cyclosporine A-inhibitable pathway. Knocking down ASK1 inhibits ionomycin-induced p38 phosphorylation and IL-4 production. Ionomycin also activates CaMKIV, which, together with p38, induces AP-1. Cooperation between AP-1 and NFAT leads to Il4 gene transcription. p38 also regulates IL-4 production by mRNA stabilization. TCR stimulation also phosphorylates p38, partially through the calcium-dependent pathway; activated p38 is required for optimal IL-4 and IFN-gamma.

Cholecystokinin activates pancreatic calcineurin-NFAT signaling in vitro and in vivo

Elevated endogenous cholecystokinin (CCK) release induced by protease inhibitors leads to pancreatic growth. This response has been shown to be mediated by the phosphatase calcineurin, but its downstream effectors are unknown. Here we examined activation of calcineurin-regulated nuclear factor of activated T-cells (NFATs) in isolated acinar cells, as well as in an in vivo model of pancreatic growth. Western blotting of endogenous NFATs and confocal imaging of NFATc1-GFP in pancreatic acini showed that CCK dose-dependently stimulated NFAT translocation from the cytoplasm to the nucleus within 0.5-1 h. This shift in localization correlated with CCK-induced activation of NFAT-driven luciferase reporter and was similar to that induced by a calcium ionophore and constitutively active calcineurin. The effect of CCK was dependent on calcineurin, as these changes were blocked by immunosuppressants FK506 and CsA and by overexpression of the endogenous protein inhibitor CAIN. Parallel NFAT activation took place in vivo. Pancreatic growth was accompanied by an increase in nuclear NFATs and subsequent elevation in expression of NFAT-luciferase in the pancreas, but not in organs unresponsive to CCK. The changes also required calcineurin, as they were blocked by FK506. We conclude that CCK activates NFATs in a calcineurin-dependent manner, both in vitro and in vivo.

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.

Dimer composition and promoter context contribute to functional cooperation between AP-1 and NFAT

The transcription factors activator protein 1 (AP-1) and nuclear factor of activated T-cells (NFAT) cooperate to induce the expression of cytokines during the immune response. While much is known about the signaling pathways and physical interactions between NFAT and AP-1 dimers following lymphocyte activation, few studies have addressed the role of AP-1 composition in modulating NFAT:AP-1-dependent transcription. We examined the function of specific AP-1 complexes using "tethered" AP-1 dimers with defined composition. We found that NFAT can functionally cooperate with all AP-1 dimers tested. Noteworthy, Jun approximately Jun-containing dimers, which are relatively inactive when tested on an AP-1-dependent promoter, are effective co-activators of an NFAT:AP-1-dependent promoter. Interestingly, specific AP-1 dimer combinations behave differently when tested on interleukin 2 (IL2) and interleukin 4 (IL4) gene regulatory regions. Moreover, the requirement for NFAT to activate each of the promoters is different. Our results suggest that higher NFAT levels are necessary to activate the IL4 promoter. Hence changes in AP-1 composition and the level of participating NFAT proteins can differentially influence cytokine gene expression, resulting in biological consequences for the modulation and dynamics of the immune response.

A distal conserved sequence element controls Ifng gene expression by T cells and NK cells

Chromatin dynamics that regulate Ifng gene expression are incompletely understood. By using cross-species comparative sequence analyses, we have identified conserved noncoding sequences (CNSs) upstream of the Ifng gene, one of which, located -22 kb from the transcriptional start site, contains clustered consensus binding sequences of transcription factors that function in T cell differentiation. CNS-22 was uniquely associated with histone modifications typical of accessible chromatin in both T helper 1 (Th1) and Th2 cells and demonstrated significant and selective T-bet (T-box transcription factor expressed in T cells, Tbx21)-dependent binding and enhancer activity in Th1 cells. Deletion of CNS-22 in the context of an Ifng reporter transgene ablated T cell receptor-dependent and -independent Ifng expression in Th1 effectors and similarly blocked expression by cytotoxic T lymphocytes and natural killer cells. Thus, a single distal element may be essential for Ifng gene expression by both innate and adaptive immune effector cell lineages.

Phosphoinositide-dependent kinase 1 targets protein kinase A in a pathway that regulates interleukin 4

CD28 plays a critical role in T cell immune responses. Although the kinase Akt has been shown to act downstream of CD28 in T helper (Th)1 cytokine induction, it does not induce Th2 cytokines such as interleukin 4 (IL-4). We recently reported that phosphoinositide-dependent kinase 1 (PDK1) partially corrects the defect in IL-4 production present in CD28-deficient T cells, suggesting that PDK1 regulates IL-4 independently of Akt. We now describe a signaling pathway in which PDK1 targets IL-4 in the murine Th2 cell line D10. PDK1-mediated activation of this pathway is dependent on protein kinase A (PKA) and the nuclear factor of activated T cells (NFAT) P1 transcriptional element in the IL-4 promoter. PDK1 localizes to the immune synapse in a phosphatidylinositol 3-kinase–dependent manner, partially colocalizes with PKA at the synapse, and physically interacts with PKA. In RNA interference knockdown experiments, PDK1 is necessary for phosphorylation of PKA in T cells, as well as for activation of the IL-4 NFAT P1 element by the T cell receptor (TCR) and CD28. Phosphorylation of the critical PKA threonine residue is stimulated by engagement of TCR/CD28 via a PDK1-dependent mechanism. These findings together define a pathway linking the kinases PDK1 and PKA in the induction of the Th2 cytokine IL-4.

Inhibition of interleukin-4 production in activated T cells via the downregulation of AP-1/NF-AT activation by N-lauroyl-D-erythro-sphingosine and N-lauroyl-D-erythro-C20-sphingosine

Allergic diseases are hypersensitivity disorders that are associated with the generation of specific immunoglobulin E (IgE) in response to environmental allergens. Interleukin (IL)-4, which is primarily produced by the CD4(+) T cells, is an important stimulus for the switching of the antibody isotype to IgE in both mice and humans. In a previous study, we demonstrated that ceramide derivatives coupled with a lauroyl group exerted strong inhibitory effects on IL-4 production in T cells. In this study, we attempted to characterize the mechanisms underlying the inhibition of IL-4 production in T cells. Two ceramide derivatives, N-lauroyl-D-erythro-sphingosine and N-lauroyl-D-erythro-C(20)-sphingosine (hereafter abbreviated as LES and LECS, respectively), were shown to significantly inhibit the production of IL-4 in both primary CD4(+) T cells and EL4 T thymoma cells in a dose-dependent manner. LES and LECS also inhibited the activity of the IL-4 gene promoter in EL4 cells transiently transfected with IL-4 gene promoter constructs, but this effect was impaired in EL4 cells that had been transfected with an IL-4 promoter construct deleted of a P4 site harboring the AP-1 and NF-AT binding sites. Furthermore, LES and LECS inhibited the DNA binding activities of both AP-1 and NF-AT transcription factors. In addition, LES and LECS were demonstrated to suppress PMA-stimulated PKC activity, although they exerted no significant effects on the protein levels of the conventional PKCs. These results indicate that the ceramides, LES and LECS, may inhibit the production of IL-4 in the activated T cells, via the downregulation of AP-1/NF-AT activation and PKC activity.

Transcription factor GATA-3 is involved in repression of promoter activity of the human interleukin-4 gene

GATA-3 was shown to bind to two sites of the IL-4 gene promoter in human T-cell lines PER-117 and Jurkat. A motif located in the region of position -860 and responsible for GATA-3 binding was detected for the first time. Mutation or deletion of this site increased the promoter activity. The findings suggest a direct involvement of GATA-3 in regulation of the human IL-4 gene transcription as a repressor of the promoter activity.

A cytokine promoter/yellow fluorescent protein reporter transgene serves as an early activation marker of lymphocyte subsets

A mouse containing an IL-4 promoter linked to the yellow fluorescent protein (YFP) reporter transgene was created to follow aspects of lymphocyte development and function. Following stimulation with phorbol 12-myristate 13-acetate and ionomycin, anti-CD3/CD28, antigen-specific peptide, or allogeneic cells, both CD4 and CD8 T cells expressed the transgene within 24h in a manner that was consistent with cellular activation markers. Transgene induction was inhibited by cyclosporine and FK506, suggesting that its activation occurs in an NFAT-dependent manner. B lymphocytes were also able to express the transgene when stimulated with LPS. This induction was inhibited in part by rapamycin. The results suggest that this transgene can function as an indicator of lymphocyte activation. Because YFP is not toxic and requires no preparation of the cells to view the reporter gene, this system provides a unique tool to follow lymphocyte activation in a number of model systems, such as those involving transplantation, allergy, and vaccine development.

Formononetin, a phyto-oestrogen, and its metabolites up-regulate interleukin-4 production in activated T cells via increased AP-1 DNA binding activity

Phyto-oestrogens are polyphenolic non-steroidal plant compounds with oestrogen-like biological activity. Phyto-oestrogens have many biological effects including oestrogen agonist/antagonist properties. However, the effect of phyto-oestrogens on allergic responses remains unclear. In this study we investigated whether formononetin, a phyto-oestrogen, and its metabolites, daidzein and equol, affect production of interleukin-4 (IL-4), a pro-inflammatory cytokine closely associated with allergic immune response, in primary CD4+ T cells and EL4 T lymphoma cells. Formononetin, daidzein and equol significantly enhanced IL-4 production from both CD4+ T cells and EL4 cells in a dose-dependent manner. Formononetin, daidzein and equol also enhanced IL-4 gene promoter activity in EL4 cells transiently transfected with IL-4 gene promoter constructs, but this effect was impaired in EL4 cells transfected with an IL-4 promoter construct deleted of P4 site carrying nuclear factor of activated T cells (NF-AT) and activator protein-1 (AP-1) binding sites. In addition, formononetin, daidzein and equol increased AP-1 DNA binding activities while did not affect NF-AT DNA binding activities. The enhancing effects on IL-4 production and AP-1 DNA binding activities were abrogated by specific inhibitors for phosphatidylinositol-3-kinase (PI3K), protein kinase C (PKC) and p38 mitogen-activated protein kinase (MAPK), indicating that formononetin, daidzein and equol might enhance IL-4 production by increased activation of AP-1 through the PI3-K/PKC/p38 MAPK signalling pathway. These results suggest that phyto-oestrogens and some of their metabolites may increase allergic responses via the enhancement of IL-4 production in T cells.

Inhibitory activity of a ceramide library on interleukin-4 production from activated T cells

Allergic diseases are hypersensitivity disorders associated with the production of specific immunoglobulin E (IgE) to environmental allergens. Interleukin (IL)-4, produced primarily by CD4(+) T cells, is an important stimulus for the switch of the antibody isotype to IgE in both mice and humans. In this study we investigated the inhibitory activity of IL-4 production in activated T cells by screening ceramide derivatives prepared by solid phase combinatorial chemistry. Many ceramide derivatives significantly inhibited IL-4 production in T cells. In particular, ceramide derivatives with a lauroyl group showed strong inhibitory activities on IL-4 production in both phorbol 12-myristate 13-acetate (PMA)-activated EL4 T cells and antigen-primed cells, suggesting that they can be used as compounds for the development of anti-allergic agents.

A critical control element for interleukin-4 memory expression in T helper lymphocytes

Naive T helper (Th) lymphocytes are induced to express the il4 (interleukin-4) gene by simultaneous signaling through the T cell receptor and the interleukin (IL)-4 receptor. Upon restimulation with antigen, such preactivated Th lymphocytes can reexpress the il4 gene independent of IL-4 receptor signaling. This memory for expression of the il4 gene depends on epigenetic modification of the il4 gene locus and an increased expression of GATA-3, the key transcription factor for Th2 differentiation. Here, we have identified a phylogenetically conserved sequence, the conserved intronic regulatory element, in the first intron of the il4 gene containing a tandem GATA-3 binding site. We show that GATA-3 binds to this sequence in a position- and orientation-dependent manner, in vitro and in vivo. DNA demethylation and histone acetylation of this region occurs early and selectively in differentiating, IL-4-secreting Th2 lymphocytes. Deletion of the conserved element by replacement of the first exon and part of the first intron of the il4 gene with gfp leads to a defect in the establishment of memory for expression of IL-4, in that reexpression of IL-4 still requires costimulation by exogenous IL-4. The conserved intronic regulatory element thus links the initial epigenetic modification of the il4 gene to GATA-3 and serves as a genetic control element for memory expression of IL-4.

Characterization of the first nonmammalian T2 cytokine gene cluster: the cluster contains functional single-copy genes for IL-3, IL-4, IL-13, and GM-CSF, a gene for IL-5 that appears to be a pseudogene, and a gene encoding another cytokinelike transcript, KK34

A genomics approach based on the conservation of synteny was used to develop a bacterial artificial chromosome (BAC) contig across the chicken T2 cytokine gene cluster. Sequencing of representative BACs showed that the chicken genome encodes genes for the homologs of mammalian interleukin-3 (IL-3), IL-4, IL-5, IL-13, and granulocyte-macrophage colony-stimulating factor (GM-CSF). These sequences represent the first T2 cytokines found outside of mammals, and their location demonstrates that the T2 cluster is ancient (at least 300 million years old). Four of these genes (IL-3, IL-4, IL-13, and GM-CSF) are expressed at the mRNA level and can be expressed as recombinant protein. In contrast to the other four genes, the chicken IL-5 (ChIL-5) gene we sequenced lacks a recognizable promoter and regulatory sequences in the predicted 3'-untranslated region (3'-UTR). Further, there is no evidence for its expression at the mRNA level. We, therefore, hypothesize that it is a pseudogene. Genomic analysis revealed that a recently characterized cytokinelike transcript, KK34, not identified in our initial analysis of the BAC sequence, is also encoded in this cluster. This gene may represent a duplication of an ancestral IL-5 gene and may encode the functional homolog of IL-5 in the chicken.

Essential role of LFA-1 in activating Th2-like responses by alpha-galactosylceramide-activated NKT cells

NKT cells produce large amounts of cytokines associated with both the Th1 (IFN-gamma) and Th2 (IL-4) responses following stimulation of their invariant Valpha14 Ag receptor. The role of adhesion molecules in the activation of NKT cells by the Valpha14 ligand alpha-galactosylceramide (alpha-GalCer) remains unclear. To address this issue, LFA-1-/- (CD11a-/-) mice were used to investigate IL-4 and IFN-gamma production by NKT cells following alpha-GalCer stimulation. Intriguingly, LFA-1-/- mice showed increased IL-4, IL-5, and IL-13 production and polarized Th2-type responses in response to alpha-GalCer in vitro and in vivo. Furthermore, the Th2-specific transcription factor GATA-3 was up-regulated in alpha-GalCer-activated NKT cells from LFA-1-/- mice. These results provide the first genetic evidence that the adhesion receptor LFA-1 has a crucial role in Th2-polarizing functions of NKT cells.

Mining microarray data to identify transcription factors expressed in naïve resting but not activated T lymphocytes

Transcriptional repressors controlling the expression of cytokine genes have been implicated in a variety of physiological and pathological phenomena. An unknown repressor that binds to the distal NFAT element of the interleukin-2 (IL-2) gene promoter in naive T-helper lymphocytes has been implicated in autoimmune phenomena and has emerged as a potentially important factor controlling the latency of HIV-1. The aim of this paper was the identification of this repressor. We resorted to public microarray databases looking for DNA-binding proteins that are present in naïve resting T cells but are downregulated when the cells are activated. A Bayesian data mining statistical analysis uncovered 25 candidate factors. Of the 25, NFAT4 and the oncogene ets-2 bind to the common motif AAGGAG found in the HIV-1 LTR and IL-2 probes. Ets-2 binding site contains the three G's that have been shown to be important for binding of the unknown factor; hence, we considered it the likeliest candidate. Electrophoretic mobility shift assays confirmed cross-reactivity between the unknown repressor and anti-ets-2 antibodies, and cotransfection experiments demonstrated the direct involvement of Ets-2 in silencing the IL-2 promoter. Designing experiments for transcription factor analysis using microarrays and Bayesian statistical methodologies provides a novel way toward elucidation of gene control networks.

Arginine Methylation of NIP45 Modulates Cytokine Gene Expression in Effector T Lymphocytes

Posttranslational modification of proteins within T cell receptor signaling cascades allows T lymphocytes to rapidly initiate an appropriate immune response. Here we report a role for arginine methylation in regulating cytokine gene transcription in the T helper lymphocyte. Inhibition of arginine methylation impaired the expression of several cytokine genes, including the signature type 1 and type 2 helper cytokines, interferon gamma, and interleukin-4. T cell receptor signaling increased expression of the protein arginine methyltransferase PRMT1, which in turn methylated the nuclear factor of activated T cells (NFAT) cofactor protein, NIP45. Arginine methylation of the amino terminus of NIP45 modulated its interaction with NFAT and resulted in augmented cytokine production, while T cells from mice lacking NIP45 had impaired expression of IFNgamma and IL-4. Covalent modification of NIP45 by arginine methylation is an important mechanism of regulating the expression of NFAT-dependent cytokine genes.

A distal region in the interferon-gamma gene is a site of epigenetic remodeling and transcriptional regulation by interleukin-2

Interferon-gamma (IFN-gamma) is a multifunctional cytokine that defines the development of Th1 cells and is critical for host defense against intracellular pathogens. IL-2 is another key immunoregulatory cytokine that is involved in T helper differentiation and is known to induce IFN-gamma expression in natural killer (NK) and T cells. Despite concerted efforts to identify the one or more transcriptional control mechanisms by which IL-2 induces IFN-gamma mRNA expression, no such genomic regulatory regions have been described. We have identified a DNase I hypersensitivity site approximately 3.5-4.0 kb upstream of the transcriptional start site. Using chromatin immunoprecipitation assays we found constitutive histone H3 acetylation in this distal region in primary human NK cells, which is enhanced by IL-2 treatment. This distal region is also preferentially acetylated on histones H3 and H4 in primary Th1 cells as compared with Th2 cells. Within this distal region we found a Stat5-like motif, and in vitro DNA binding assays as well as in vivo chromosomal immunoprecipitation assays showed IL-2-induced binding of both Stat5a and Stat5b to this distal element in the IFNG gene. We examined the function of this Stat5-binding motif by transfecting human peripheral blood mononuclear cells with -3.6 kb of IFNG-luciferase constructs and found that phorbol 12-myristate 13-acetate/ionomycin-induced transcription was augmented by IL-2 treatment. The effect of IL-2 was lost when the Stat5 motif was disrupted. These data led us to conclude that this distal region serves as both a target of chromatin remodeling in the IFNG locus as well as an IL-2-induced transcriptional enhancer that binds Stat5 proteins.

Exposure to 4-tert-octylphenol, an environmentally persistent alkylphenol, enhances interleukin-4 production in T cells via NF-AT activation

4-tert-Octylphenol (OP) is a representative endocrine disruptor that may have adverse effects on human health. The influence of this compound on allergic immune responses remains unclear. In this study, we have examined the effects of OP on production of interleukin-4 (IL-4), a pro-inflammatory cytokine closely associated with allergic immune responses. OP significantly enhanced IL-4 production in antigen-primed T cells in a dose-dependent manner. Treatment with OP in vivo resulted in significant increase of IL-4 production in T cells and of IgE levels in sera of antigen-primed mice. Furthermore, OP enhanced the activation of IL-4 gene promoter in EL4 T cells transiently transfected with IL-4 promoter/reporter constructs, and the enhancing effect mapped to a region in the IL-4 promoter containing binding sites for nuclear factor of activated T cell (NF-AT). Activation of T cells by phorbol-12-myristate-13-acetate (PMA) resulted in markedly enhanced binding activities to the NF-AT site, which significantly increased upon addition of OP, indicating that the transcription factor NF-AT was involved in the enhancing effect of OP on IL-4 production. The enhancement of IL-4 production by OP was blocked by FK506, a calcineurin inhibitor, but not by the estrogen receptor (ER) antagonist ICI 182780. FK506 inhibited the NF-AT-DNA binding activity and IL-4 gene promoter activity enhanced by OP in a dose-dependent manner. These findings demonstrate that OP enhances IL-4 production in T cells via the stimulation of calcineurin-dependent NF-AT activation.

Microbial-gut interactions in health and disease. Immune responses

The indigenous bacterial microflora colonize the gut at birth and remain there throughout life. Approximately 10(14) bacteria are present in the ileum and colon and they are clearly immunogenic. The evidence is strong that the vast majority of IgA plasma cells in normal human gut are responding to the antigens of the flora, and although the flora is also responsible for producing the large numbers of T cells which are present in the gut of healthy individuals, the types of T cell response which the flora elicits are less well understood. A major challenge for the immune system is to distinguish between the antigens of the flora and the antigens of pathogens. There is also a growing realization that the normal flora can also influence gene expression in antigen-presenting cells in the gut and so set the context in which T cells respond to food antigen and vaccines.

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.

Enhanced interleukin-4 production in CD4+ T cells and elevated immunoglobulin E levels in antigen-primed mice by bisphenol A and nonylphenol, endocrine disruptors: involvement of nuclear factor-AT and Ca2+

Bisphenol A (BPA) and p-nonylphenol (NP) are representative endocrine disruptors (EDs) that may have adverse effects on human health. The influence of these compounds on allergic immune responses remains unclear. In this study, we have examined the effects of BPA and NP on production of interleukin-4 (IL-4), a pro-inflammatory cytokine closely associated with allergic immune responses. Both BPA and NP significantly enhanced IL-4 production in keyhole limpet haemocyanin (KLH)-primed CD4+ T cells in a concentration-dependent manner. Treatment with BPA or NP in vivo resulted in significant increase of IL-4 production in CD4+ T cells and of antigen-specific immunoglobulin E (IgE) levels in the sera of KLH-primed mice. Furthermore, BPA and NP enhanced the activation of IL-4 gene promoter in EL4 T cells transiently transfected with IL-4 promoter/reporter constructs, and the enhancing effect mapped to a region in the IL-4 promoter containing binding sites for nuclear factor (NF)-AT. Activation of T lymphocytes by phorbol 12-myristate 13-acetate/ionomycin resulted in markedly enhanced binding activities to the NF-AT site, which significantly increased upon addition of BPA or NP, as demonstrated by the electrophoretic mobility shift assay, indicating that the transcription factor NF-AT was involved in the enhancing effect of BPA and NP on IL-4 production. The enhancement of IL-4 production by BPA or NP was significantly reduced by nitrendipine, a blocker of Ca2+ influx, and by FK506, a calcineurin inhibitor. FK506 inhibited the NF-AT-DNA binding activity and IL-4 gene promoter activity enhanced by BPA or NP. These results represent the first report describing possible enhancement of allergic response by EDs through increasing IL-4 production in CD4+ T cells and antigen-specific IgE levels in the sera via the stimulation of Ca2+/calcineurin-dependent NF-AT activation.

Modulation of T cell cytokine production by interferon regulatory factor-4

Production of cytokines is one of the major mechanisms employed by CD4(+) T cells to coordinate immune responses. Although the molecular mechanisms controlling T cell cytokine production have been extensively studied, the factors that endow T cells with their ability to produce unique sets of cytokines have not been fully characterized. Interferon regulatory factor (IRF)-4 is a lymphoid-restricted member of the interferon regulatory factor family of transcriptional regulators, whose deficiency leads to a profound impairment in the ability of mature CD4(+) T cells to produce cytokines. In these studies, we have investigated the mechanisms employed by IRF-4 to control cytokine synthesis. We demonstrate that stable expression of IRF-4 in Jurkat T cells not only leads to a strong enhancement in the synthesis of interleukin (IL)-2, but also enables these cells to start producing considerable amounts of IL-4, IL-10, and IL-13. Transient transfection assays indicate that IRF-4 can transactivate luciferase reporter constructs driven by either the human IL-2 or the human IL-4 promoter. A detailed analysis of the effects of IRF-4 on the IL-4 promoter reveals that IRF-4 binds to a site adjacent to a functionally important NFAT binding element and that IRF-4 cooperates with NFATc1. These studies thus support the notion that IRF-4 represents one of the lymphoid-specific components that control the ability of T lymphocytes to produce a distinctive array of cytokines.

Altered IL-4 mRNA stability correlates with Th1 and Th2 bias and susceptibility to hypersensitivity pneumonitis in two inbred strains of mice

Previously, we have shown in a model of hypersensitivity pneumonitis that Th1-biased C57BL/6 mice are susceptible and Th2-biased DBA/2 mice are resistant to disease. We also showed that this was explained in part by differential regulation of IL-12 by IL-4. For these reasons, we postulated that C57BL/6 and DBA/2 mice differentially express IL-4. In this study, we show that C57BL/6 immune cells express Th2 but not Th1 cytokines at lower levels than DBA/2 cells. We also found that C57BL/6 splenocytes exhibit decreased mRNA stability of Th2 cytokines, relative to DBA/2 splenocytes. Stability of IL-2 and IFN-gamma were similar in the two strains of mice. Differences in Th2 cytokine mRNA stability between C57BL/6 and DBA/2 cells were not due to sequence polymorphism at specific regions of the IL-4/IL-13 locus. Furthermore, expression of Th1- and Th2-specific transcription factors T-bet and GATA-3, as well as the nuclear factor of activated T cells transcription factor, NFATc, was not significantly different between the two mice. Our data suggest that decreased mRNA stability of Th2 cytokines in C57BL/6 splenocytes may underlie the differential susceptibility to hypersensitivity pneumonitis between C57BL/6 and DBA/2 mice. Moreover, our results indicate that regulation of mRNA stability may serve as an important mechanism underlying Th1/Th2 immune polarization.

Endothelial Cells Stimulate T Cell NFAT Nuclear Translocation in the Presence of Cyclosporin A: Involvement of the wnt/Glycogen Synthase Kinase-3β Pathway

T cells resistant to the immunosuppressive drug cyclosporin A (CsA) may be important mediators of chronic graft rejection. We previously reported that T cells activated in the presence of endothelial cells (EC) develop resistance to CsA, and initiate IL-2 secretion within 8-12 h of triggering. CsA normally blocks the phosphatase, calcineurin, thus preventing nuclear translocation of the transcription factor, NFAT. We find that in the presence but not the absence of EC, NFAT1 can be detected in the nuclei of CsA-treated T cells within 8 h of triggering, reaching a maximal level of 60% of control by 24 h. Glycogen synthase kinase-3beta (GSK-3beta), which rephosphorylates NFAT and promotes nuclear export, is inhibited by EC costimulation. GSK-3beta is a component of the wnt signaling pathway, and EC express wnt-5a and T cells express frizzled-5, a wnt-5a receptor. Wnt-5a promotes T cell NFAT nuclear accumulation in the presence of CsA, an effect mimicked by Li(+), a potent inhibitor of GSK-3beta. The protein kinase C agonist PMA dramatically synergizes with both EC and wnt-5a in stimulating T cell IL-2 synthesis, and inhibition of either protein kinase C by Ro-31-8425 or G-proteins by pertussis toxin effectively blocks the actions of wnt-5a on T cells. Finally, a secreted, dominant-negative form of frizzled-5 blocks EC-mediated CsA resistance. Thus, EC promote CsA-resistant nuclear localization of NFAT and subsequent IL-2 synthesis through a noncanonical wnt-dependent pathway.

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.

Hydroquinone, a reactive metabolite of benzene, enhances interleukin-4 production in CD4+ T cells and increases immunoglobulin E levels in antigen-primed mice

Exposure to cigarette smoke is known to increase the risk of the development of allergic disease. The mechanism is not well understood. In this study, we determined the effect of hydroquinone (HQ), a major metabolite of benzene present in large quantities in cigarette tar, on interleukin-4 (IL-4) production by CD4+ T cells. HQ significantly enhanced IL-4 production by keyhole limpet haemocyanin (KLH)-primed CD4+ T cells in a dose-dependent manner. The enhancing effect of HQ on IL-4 production was maximal at a concentration of 50 micro m. It increased the level of IL-4 production approximately 10-fold. HQ enhanced IL-4 mRNA expression and also IL-4 gene promoter activity, suggesting that the enhancing effect of HQ on IL-4 production may occur at the transcriptional level. Furthermore, the injection of KLH-primed mice with HQ resulted in a significant increase in the levels of IL-4 and immunoglobulin E. These findings provide evidence that HQ, a major component of cigarette tar, may enhance allergic immune responses by inducing the production of IL-4 in CD4+ T cells.

Induction of NFATc2 expression by interleukin 6 promotes T helper type 2 differentiation

Interleukin (IL)-6 is produced by professional antigen-presenting cells (APCs) such as B cells, macrophages, and dendritic cells. It has been previously shown that APC-derived IL-6 promotes the differentiation of naive CD4+ T cells into effector T helper type 2 (Th2) cells. Here, we have studied the molecular mechanism for IL-6-mediated Th2 differentiation. During the activation of CD4+ T cells, IL-6 induces the production of IL-4, which promotes the differentiation of these cells into effector Th2 cells. Regulation of IL-4 gene expression by IL-6 is mediated by nuclear factor of activated T cells (NFAT), as inhibition of NFAT prevents IL-6-driven IL-4 production and Th2 differentiation. IL-6 upregulates NFAT transcriptional activity by increasing the levels of NFATc2. The ability of IL-6 to promote Th2 differentiation is impaired in CD4+ T cells that lack NFATc2, demonstrating that NFATc2 is required for regulation of IL-4 gene expression by IL-6. Regulation of NFATc2 expression and NFAT transcriptional activity represents a novel pathway by which IL-6 can modulate gene expression.

Sustained NFAT signaling promotes a Th1-like pattern of gene expression in primary murine CD4+ T cells

T cell activation is known to be critically regulated by the extent and duration of TCR-induced signaling pathways. The NFAT family of transcription factors is believed to play an important role in coupling these quantitative differences in TCR-induced signaling events into changes in gene expression. In this study we have specifically investigated the effects of sustained NFAT signaling on T cell activation by introducing a constitutively active mutant version of NFATc1 (caNFATc1) into primary murine CD4(+) T cells and examining its effects on gene expression. We now report that ectopic expression of caNFATc1 partially mimics TCR signaling, resulting in enhanced expression of CD25 and CD40 ligand and down-regulation of CD62L. More importantly, we find that expression of caNFATc1 in T cells maintained under either nonpolarizing or Th1-skewing conditions leads to a marked selective increase in the number of cells expressing the prototypical Th1 cytokine, IFN-gamma. Furthermore, when expressed in Th2-skewed cells, caNFATc1 appears to attenuate Th2 differentiation by decreasing production of IL-4 and promoting the expression of IFN-gamma. Finally, we find that caNFATc1 enhances expression of functional P-selectin glycoprotein ligand-1, up-regulates Fas ligand expression, and increases susceptibility to activation-induced cell death, cellular traits that are preferentially associated with Th1 effector cells. Taken together, these results suggest that sustained NFAT signaling, mediated by ectopic expression of caNFATc1, acts to promote a Th1-like pattern of gene expression and thereby serves to highlight the important relationship between the degree of NFAT signaling and the qualitative pattern of gene expression induced during T cell activation.

Interferon regulatory factor 4 (IRF4) interacts with NFATc2 to modulate interleukin 4 gene expression

Proteins of the nuclear factor of activated T cells (NFAT) family of transcription factors are critical for lymphocyte activation in the immune system. In particular, NFATs are important regulators of inducible IL-4 gene expression. Interferon regulatory factor 4 (IRF4) is an immune system-restricted interferon regulatory factor that is required for lymphocyte activation, but its molecular functions in the T lineage remain to be elucidated. We demonstrate that IRF4 potently synergizes with NFATc2 to specifically enhance NFATc2-driven transcriptional activation of the IL-4 promoter. This function is dependent on the physical interaction of IRF4 with NFATc2. IRF4 synergizes with NFATc2 and the IL-4-inducing transcription factor, c-maf, to augment IL-4 promoter activity as well as to elicit significant levels of endogenous IL-4 production. Furthermore, naïve T helper cells from mice lacking IRF4 are compromised severely for the production of IL-4 and other Th2 cytokines. The identification of IRF4 as a partner for NFATc2 in IL-4 gene regulation provides an important molecular function for IRF4 in T helper cell differentiation.

1,25-dihydroxyvitamin D3 inhibits IFN-gamma and IL-4 levels during in vitro polarization of primary murine CD4+ T cells

Following their activation, naive CD4+ T cells can differentiate into one of two effector cell subsets, Th1 and Th2. These two subsets have different cytokine secretion patterns and thus mediate separate arms of the immune response. It has been established that the fat-soluble vitamin D(3) metabolite 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) and its nuclear receptor, the vitamin D receptor, play an important role in the immune system primarily through the transcriptional inhibition of cytokine genes that either are required for Th1 differentiation or are products of differentiated Th1 cells. Therefore, we wanted to test directly the ability of 1,25(OH)(2)D(3) to alter the Th differentiation process. Our results indicate that 1,25(OH)(2)D(3) inhibits not only the Th1 cytokine IFN-gamma but also the Th2 cytokine IL-4 in naive CD62 ligand+CD4+ T cells during their in vitro polarization. This effect is most dramatic when the ligand is present from the onset of the differentiation process. If the ligand is added after the polarization has ensued, the inhibition is significantly diminished. In activated (CD62 ligand-CD4+) T cells, 1,25(OH)(2)D(3) is still able to inhibit IFN-gamma but has no effect on IL-4 production. Our results also indicate that inhibition of these two cytokines in naive cells by vitamin D receptor and its ligand is neither a result of a cell cycle block nor an inhibition of Th1 or Th2 transcription factor expression but, rather, at least in the case of Th2 differentiation, an attenuation of IL-4 transcription by the receptor.

Tea pigments inhibit the production of type 1 (T(H1)) and type 2 (T(H2)) helper T cell cytokines in CD4(+) T cells

Tea pigments are oxidized products of polyphenols derived from tea leaves (Camellia sinensis). Theaflavins are constituents of tea pigments with antioxidant, antineoplastic and antiinflammatory properties similar to their parent compounds. The biological properties of polyphenols and theaflavins have been linked to their capacity to inhibit the activation of nuclear factor-kappaB (NF-kappaB), a transcription factor, which is critically involved in the molecular regulation of a number of proinflammatory cytokines. The current study examines the requirement for NF-kappaB in the immunosuppressive effects mediated by tea antioxidants. Specifically, we tested the hypothesis that cytokines produced by type 1 (T(H1)) CD4(+) T cells which require NF-kappaB for gene expression, such as interleukin-2 (IL-2) and interferon gamma (IFN gamma), are selectively inhibited by tea pigments. We found that tea pigments potently suppress IL-2 secretion, IL-2 gene expression and the activation of NF-kappaB in murine spleens enriched for CD4(+) T cells, as expected. Consistent with our hypothesis, tea pigments also inhibited the induction of IFNgamma mRNA. However, the expression of the T(H2) cytokines IL-4 and IL-5, which lack functional NF-kappaB sites within their promoters was unexpectedly suppressed by tea pigments, as well. The results indicate that NF-kappaB may be only one of multiple transcription factors inhibited by tea pigments.

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.

The IL-4 production capability of different strains of naive CD4(+) T cells controls the direction of the T(h) cell response

The qualitative nature of an immune response raised against infectious pathogens depends upon the phenotypes of T(h) cell subsets, which secrete distinct types of cytokines. Genetic background is known to greatly influence the nature of the T(h) cell response. However, the precise nature of this influence still remains unclear. In the present study, we demonstrate that CD62L(+), CD44(low) and CD4(+) naive T cells from BALB/c mice are capable of producing significant amounts of IL-4, while naive T cells from B10.D2 mice exhibit no IL-4 production. The addition of exogenous IL-4 into the B10.D2 induction culture recovered T(h)2 development, thereby indicating that the potential of naive T cells to secrete IL-4 at primary activation is likely to substantially influence development of T(h)2. Regulation of the IL-4 gene in naive T cells differs from that in cells committed towards becoming T(h)2 cells, based on the observation that naive T cells from STAT6-deficient mice having a BALB/c background produce detectable amounts of IL-4. The IL-4 promoter region was found to be equally histone acetylated in both BALB/c and B10.D2 naive T cells by primary TCR activation. Interestingly, the expression levels of transcription factors NF-AT and GATA-3, which regulate promoter activity, differ between BALB/c and B10.D2 cells. These results suggest that the differences in expression level between the two transcriptional factors may affect the potential of naive T cells to secrete IL-4, which may subsequently influence the development of T(h) cell phenotypes.

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.

Friend of GATA-1 represses GATA-3-dependent activity in CD4+ T cells

The development of naive CD4+ T cells into a T helper (Th) 2 subset capable of producing interleukin (IL)-4, IL-5, and IL-13 involves a signal transducer and activator of transcription (Stat)6-dependent induction of GATA-3 expression, followed by Stat6-independent GATA-3 autoactivation. The friend of GATA (FOG)-1 protein regulates GATA transcription factor activity in several stages of hematopoietic development including erythrocyte and megakaryocyte differentiation, but whether FOG-1 regulates GATA-3 in T cells is uncertain. We show that FOG-1 can repress GATA-3-dependent activation of the IL-5 promoter in T cells. Also, FOG-1 overexpression during primary activation of naive T cells inhibited Th2 development in CD4+ T cells. FOG-1 fully repressed GATA-3-dependent Th2 development and GATA-3 autoactivation, but not Stat6-dependent induction of GATA-3. FOG-1 overexpression repressed development of Th2 cells from naive T cells, but did not reverse the phenotype of fully committed Th2 cells. Thus, FOG-1 may be one factor capable of regulating the Th2 development.

Requirement of two NFATc4 transactivation domains for CBP potentiation

Recruitment of the coactivator CREB-binding protein (CBP) to transcription factors is important for gene expression. Various regions of CBP such as the KIX and CH3 domains have been shown to interact with numerous transcription factors. The NFAT group of transcription factors is involved in multiple biological processes. NFATc4/NFAT3 has been proposed to play an important role in heart hypertrophy, adipocyte differentiation, and learning and memory. We demonstrate here that two transactivation domains, located at the NH(2) and COOH termini of NFATc4, are critical for interacting with CBP. Each transactivation domain interacts with a distinct region of the CBP protein (the KIX and CH3 domains). Binding of CBP potentiates NFATc4-mediated transcription activity. Both transactivation domains of NFATc4 are required for CBP function. Removal of either NFATc4 transactivation domain abolishes CBP potentiation. Conversely, mutation of the KIX or CH3 domain prevents CBP-mediated potentiation of NFATc4 transcription activation. These data demonstrate that formation of a functional NFATc4.CBP transcription complex requires interactions at two distinct sites.

Deletion of a coordinate regulator of type 2 cytokine expression in mice

Mechanisms that underlie the patterning of cytokine expression in T helper (T(H)) cell subsets remain incompletely defined. An evolutionarily conserved approximately 400-bp noncoding sequence in the intergenic region between the genes Il4 and Il13, designated conserved noncoding sequence 1 (CNS-1), was deleted in mice. The capacity to develop T(H)2 cells was compromised in vitro and in vivo in the absence of CNS-1. Despite the profound effect in T cells, mast cells from CNS-1(-/-) mice maintained their capacity to produce interleukin 4. A T cell-specific element critical for the optimal expression of type 2 cytokines may represent the evolution of a regulatory sequence exploited by adaptive immunity.

Unexpected characteristics of the IFN-gamma reporters in nontransformed T cells

Analysis of the IFN-gamma promoter has primarily been conducted by transient expression of reporter constructs in transformed cells. However, the activity of cis elements may differ when expressed transiently compared with their activity within native chromatin. Furthermore, the transcription factors and signaling mechanisms in transformed cells may differ from those in normal T cells. To analyze IFN-gamma promoter regulation in normal T cells, we developed a novel retroviral bottom-strand reporter system to allow the chromatin integration of promoter regions in primary developing T cells. As controls, both the IL-2 and IL-4 promoters were inducible in this system, with the IL-4 reporter having Th2-specific activity. Strikingly, the IFN-gamma promoter exhibited constitutive activity in both Th1 and Th2 subsets, in contrast to the behavior of the endogenous IFN-gamma gene, which is inducible only in Th1 cells. In mapping this activity, we found that the AP-1/GM-CSF site in the distal promoter element is the most critical element for the constitutive activity. Transgenic reporter lines for the IFN-gamma promoter confirmed the constitutive behavior of the isolated IFN-gamma promoter. This constitutive activity was resistant to inhibition by cyclosporin A and was independent of Stat4 and p38 mitogen-activated protein kinase. These results suggest that IFN-gamma promoter regulation may require cis elements residing either downstream or >3.4 kb upstream of the transcriptional start site, involving repression of constitutive activity.